Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV...

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Advancing Phosphor Science: Targeting high-efficiency phosphors via informatics Jakoah Brgoch, Ph.D. Department of Chemistry University of Houston Email: [email protected]

Transcript of Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV...

Page 1: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Advancing Phosphor Science: Targeting high-efficiency phosphors via informatics

Jakoah Brgoch, Ph.D. Department of Chemistry

University of Houston

Email: [email protected]

Page 2: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

λ

White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission and phosphor emission appear as white light. LED + Phosphor Radiation from LED (absorbed by phosphor) Radiation from phosphor down-conversion (emission from phosphor)

Phosphor converted solid-state white lighting

George, Denault, and Seshadri Annu. Rev. Mater. Sci, 2013, 43, 2.1:2.21 2

Page 3: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Phosphors consist of two components: activator ion (luminescent center) and a host lattice Emitted light can be tuned to desired wavelength by changing the CFS of the activator ion

Mechanism of phosphor emission in white LEDs

3 George, Denault, and Seshadri Annu. Rev. Mater. Sci, 2013, 43, 2.1:2.21

Page 4: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Phosphors consist of two components: activator ion (luminescent center) and a host lattice Emitted light can be tuned to desired wavelength by changing the CFS of the activator ion The photophysics occurs in the band gap o Need wide band-gap materials that can

accommodate the RE

Mechanism of phosphor emission in white LEDs

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Host Conduction Band

Host Valence Band

Page 5: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Cerium-substituted YAG: The prototypical phosphor

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(Y2.97Ce0.03)Al5O12

Cerium-substituted yttrium aluminum garnet (YAG:Ce3+) is a widely used phosphor because of its high photoluminescent quantum yield (PLQY= 80-95%)

Absorbs blue and then down converts to a yellow emission

Page 6: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

The need for new phosphors

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A better approach to develop new, efficient inorganic phosphors Develop phosphors that have enhanced thermal quenching properties for high-power LED and laser based lighting

Page 7: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Highly rigid structures improve photoluminescence efficiency This is well known in molecular chemistry …

How do we measure structural rigidity in a solid?

Y3Al5O12:Ce3+ BaMgAl10O17:Eu2+ Sr2Si5N8:Eu2+

Yellow Emission 90 % Efficient (Chem. Mater. 2009 21, 316)

Blue Emission 92 % Efficient (Chem. Mater. 2002 14, 5045)

Orange/Red Emission 80% Efficient (Appl. Phys. Lett. 2011 99, 241106)

vs. biphenyl fluorene

A more efficient method to identify new phosphor hosts

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Page 8: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Calculating Debye temperature from the elastic constants

V = unit cell volume n = number of atoms BH = bulk modulus M = molar mass σ = Poisson’s ratio f(σ) = function of Poisson's ratio

BH and Poisson’s ratio can be calculated from stress-strain relationships determined by first-principles (VASP)

Examples of phosphor hosts screened

Brgoch, DenBaars, and Seshadri J. Phys. Chem. C 2013, 117, 17955-17959. 8

Page 9: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Quantum yield (Φ) increases with Debye temperature Aluminates tend to have the highest Debye temperature and largest quantum yield of the compounds examined so far

Brgoch, DenBaars, and Seshadri J. Phys. Chem. C 2013, 117, 17955-17959.

Quantum yield of Ce3+ phosphors follow Debye temperature

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Φ

Page 10: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

A small gap can lead to emission quenching due to thermal population of the conduction band To use this approach as a screening tool compound must have a wide band gap

The band gap is accurately calculated using hybrid functional calculations (HSE06)

Host Conduction Band

Host Valence Band

Brgoch, DenBaars, and Seshadri J. Phys. Chem. C 2013, 117, 17955-17959.

Phosphor hosts need to have a wide band-gap for the RE orbitals

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Page 11: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Plotting Debye temperature against band-gap can be used to identify compounds that have the optimal properties o The most efficient materials fall in the top-right corner

Brgoch, DenBaars, and Seshadri J. Phys. Chem. C 2013, 117, 17955-17959.

Sorting diagram for efficient (Ce3+) phosphor hosts

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Page 12: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Searching structural through crystal structure databases, e.g., the ICSD, indicates the potential targets for synthetic consideration

Screening for efficient phosphor hosts

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Page 13: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Examining metadata provides an indication of where to focus the future search o Oxides are still a great place to focus – in particular borates

Learning from large data-sets – Compositional information

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Page 14: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Learning from large data-sets – Coordination environments

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Examining metadata provides an indication of where to focus the future search o Oxides are still a great place to focus – in particular borates o Higher coordination environments appear to be favorable in efficient phosphors

Effective coordination number

Page 15: Advancing Phosphor Science: Targeting high-efficiency ...White LEDs use a blue (450 nm) or near-UV (405 nm) that is partially converted by a phosphor. The combination of the LED emission

Advancing Phosphor Science: Targeting high-efficiency phosphors via informatics

Jakoah Brgoch, Ph.D. Department of Chemistry

University of Houston

Email: [email protected]

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Supporting Information · thickness of 4.0 and 2.5 nm. N/N Results WO3 nano-flake with thickness 4.0 nm WO3 nano-flake with thickness 2.5 nm 1 Bearing area 1,464.40 nm2 291,298 nm2

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Controlling LEDs with Arduino - WordPress.com...Controlling LEDs with Arduino (adapted from a document by Victor Gallego) Practice 1: Blinking LED We need: 1 protoboard 1 LED 1 resistor

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Cite as: X. Chi et al., Science · 2020. 6. 19. · 9A1 IS2 0.001 nM 200 400 600 80010001200 No mAb .13% — 1000 nM — 500 nM 250 nM 125 nM 62.5 nM 31.25 nM 15.63 nM - 7.81 nM ro

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