1

Organic LEDs ndash part 8

bull Exciton Dynamics in Disordered Organic Thin Films

bull Quantum Dot LEDs

Handout on QD-LEDs Coe et al Nature 420 800 (2002)

April 29 2003 ndash Organic Optoelectronics - Lecture 20b

2

Exciton Dynamics in Time Dependant PL

3

Dynamic Spectral Shifts of DCM2 in Alq3

bull Measurement performed on doped DCM2Alq3 filmsbull Excitation at λ=490 nm (only DCM2 absorbs)

~ DCM2 PL red shifts gt 20 nm over 6 ns ~

Wavelength [ nm ]

4

Time Evolution of 4 DCM2 in Alq3 PL Spectrum

5

Electronic Processes in Molecules

density of availableS1 or T1 states

6

Time Evolution of DCM2 Solution PL Spectra

7

Spectral Shift due to~ Exciton Diffusion ~

~ Intermolecular Solid State Interactions ~

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

2

Exciton Dynamics in Time Dependant PL

3

Dynamic Spectral Shifts of DCM2 in Alq3

bull Measurement performed on doped DCM2Alq3 filmsbull Excitation at λ=490 nm (only DCM2 absorbs)

~ DCM2 PL red shifts gt 20 nm over 6 ns ~

Wavelength [ nm ]

4

Time Evolution of 4 DCM2 in Alq3 PL Spectrum

5

Electronic Processes in Molecules

density of availableS1 or T1 states

6

Time Evolution of DCM2 Solution PL Spectra

7

Spectral Shift due to~ Exciton Diffusion ~

~ Intermolecular Solid State Interactions ~

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

3

Dynamic Spectral Shifts of DCM2 in Alq3

bull Measurement performed on doped DCM2Alq3 filmsbull Excitation at λ=490 nm (only DCM2 absorbs)

~ DCM2 PL red shifts gt 20 nm over 6 ns ~

Wavelength [ nm ]

4

Time Evolution of 4 DCM2 in Alq3 PL Spectrum

5

Electronic Processes in Molecules

density of availableS1 or T1 states

6

Time Evolution of DCM2 Solution PL Spectra

7

Spectral Shift due to~ Exciton Diffusion ~

~ Intermolecular Solid State Interactions ~

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

4

Time Evolution of 4 DCM2 in Alq3 PL Spectrum

5

Electronic Processes in Molecules

density of availableS1 or T1 states

6

Time Evolution of DCM2 Solution PL Spectra

7

Spectral Shift due to~ Exciton Diffusion ~

~ Intermolecular Solid State Interactions ~

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

5

Electronic Processes in Molecules

density of availableS1 or T1 states

6

Time Evolution of DCM2 Solution PL Spectra

7

Spectral Shift due to~ Exciton Diffusion ~

~ Intermolecular Solid State Interactions ~

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

6

Time Evolution of DCM2 Solution PL Spectra

7

Spectral Shift due to~ Exciton Diffusion ~

~ Intermolecular Solid State Interactions ~

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

7

Spectral Shift due to~ Exciton Diffusion ~

~ Intermolecular Solid State Interactions ~

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

8

Excitonic Energy Variations

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

9

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Exciton Thermalization ~

EXCITON DIFFUSION LEADS TO REDUCTION IN FWHM

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

10

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

11

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

12

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

13

Time Evolution of Peak PL in Neat Thin Films

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

14

Parameters for Simulating Exciton Diffusion

observed radiative lifetime (τ)Nor

malize

d Integ

rated Spe

ctral Int

ensity

Foumlrster radius (RF) Assign value for allowed transfers

Assume Gaussian shape of width wDOS Center at peak of initial bulk PL spectrum Molecular PL spectrum impliedhellip

excitonic density of states (gex(E))

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

15

Fitting Simulation to Experiment ndash Doped Films

bull Good fits possible for all data sets

bull RF decreases with increasing doping falling from 52 Aring to 22 Aring

bull wDOS also decreases with increasing doping ranging from 0146 eV to 0120 eV

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

16

Fitting Simulation ndash Neat Films

bull Spectral shift observed in each material system

bull Molecular dipole and wDOS are correllated lower dipoles correspond to less dispersion

bull Even with no dipole some dispersion exists

bull Experimental technique general and yields firstmeasurements of excitonic energy dispersionin amorphous organic solids

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

17

Temporal Solid State Solvation

upon excitation both magnitude and direction

of lumophore dipole moment can change

FOR EXAMPLE for DCM micro1 ndash micro0 gt 20 Debye ~ from 56 D to 263 D ~

following the excitation the environment surrounding the

excited molecule will reorganize to minimize the overall

energy of the system (maximize micro bull Eloc)

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

18

Exciton Distribution in the Excited State (S1 or T1)

~ Time Evolved Molecular Reconfiguration ~

DIPOLE-DIPOLE INTERACTIONLEADS TO ENERGY SHIFT IN DENSITY OF EXCITED STATES

log(Time)

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

19

Fusion of Two Material Sets Hybrid devicescould enableLEDs Solar CellsPhotodetectorsModulators and Laserswhich utilize thebest properties of each individual material

Efficient

OrganicSemiconductors

Flexible

Emissive

Fabrication ofrational

structureshas been the

mainobstacle to date

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

20

Inorganic Nanocrystals ndash Quantum Dots

Quantum Dot SIZE

Synthetic route of Murrayet al J Am Chem Soc115 8706 (1993)

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

21

Fusion of Two Material Sets

Quantum Dots Organic Molecules

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

22

Integration of Nanoscale MaterialsQuantum Dots and Organic Semiconductors

ZnS overcoating shell(0 to 5 monolayers)

Oleic Acid orTOPO capsSynthetic routes of Murray et

al J Am Chem Soc 1158706 (1993) and Chen et alMRS Symp Proc 691G102

Trioctylphosphine oxide

Tris(8-hydroxyquinoline)Aluminum (III)

3-(4-Biphenylyl)-4-phenyl-5-tert-butylphenyl-124-triazole

NN-Bis(naphthalen-1-yl)-NN-bis(phenyl)benzidine

NN-Bis(3-methylphenyl)-NN-bis-(phenyl)-benzidine

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

23

1 A solution of an organic material QDs and solventhellip2 is spin-coated onto a clean substrate3 During the solvent drying time the QDs rise to the surfacehellip4 and self-assemble into grains of hexagonally close packed spheres

Organic hosts that deposit as flat filmsallow for imaging via AFM despite theAFM tip being as large as the QDs

Phase segregation is driven by acombination of size and

chemistry

Phase Segregation and Self-Assembly

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

24

As the concentration ofQDs in the spin-castingsolution is increasedthe coverage of QDs onthe monolayer is alsoincreased

Monolayer Coverage ndash QD concentration

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

25

CdSe(ZnS)TOPO PbSeoleic acid

QD-LED Performance

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

26

Full Size Series of PbSe Nanocrystals

from 3 nm to 10 nm in Diameter

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

27

Design of Device StructuresQDs are poor chargetransport materials

Isolate layer functions of maximizedevice performance1 Generate excitons on organic

sites2 Transfer excitons to QDs via Foumlrster or Dexter energy transfer3 QD electroluminescence

Phase Segregation

But efficient emittershellip

Use organics for charge transport

Need a new fabrication method inorder to be able to make such doubleheterostructures

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

28

A general method

Phase segregation occurs for different1) organic hosts TPDNPD and poly-TPD2) solvents chloroformchlorobenzene andmixtures with toluene3) QD core materialsPbSe CdSe andCdSe(ZnS)4) QD capping moleculesoleic acid and TOPO5) QD core size 4-8nm6) substrates SiliconGlass ITO7) Spin parametersspeed accelerationand time

bull This process is robust but further exploration is needed to broadly generalize these findingsbull For the explored materials consistent description is possiblebull We have shown that the process is not dependent on any one material componentPhase segregation 1048774 QD-LED structures

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

29

EL RecombinationRegion Dependence

on Current

Coe et al Org Elect (2003)

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

30

Spectral Dependence on Current DensityTOP DOWN VIEW of the QD MONOLAYER

Exciton recombinationwidth far exceeds the QDmonolayer thickness athigh current densityTo achieve truemonochrome emissionnew exciton confinementtechniques are needed

CROSS-SECTIONAL VIEW of QD-LED

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31

31

Benefits of Quantum Dots in Organic LEDs

Demonstrated bullSpectrally Tunable ndash single material set can access most of visible range bullSaturated Color ndash linewidths of lt 35nm Full Width at Half of Maximum bullCan easily tailor ldquoexternalrdquo chemistry without affecting emitting core bullCan generate large area infrared sourcesPotential bullHigh luminous efficiency LEDs

possible even in red and blue bullInorganic ndash potentially more stable longer lifetimes

The ideal dye molecule

• Slide 1
• Slide 2
• Slide 3
• Slide 4
• Slide 5
• Slide 6
• Slide 7
• Slide 8
• Slide 9
• Slide 10
• Slide 11
• Slide 12
• Slide 13
• Slide 14
• Slide 15
• Slide 16
• Slide 17
• Slide 18
• Slide 19
• Slide 20
• Slide 21
• Slide 22
• Slide 23
• Slide 24
• Slide 25
• Slide 26
• Slide 27
• Slide 28
• Slide 29
• Slide 30
• Slide 31