Nanopatterned Metallic Films for Use As...
1
Optimizing optical AND electrical properties Optimizing optical AND electrical properties Changing geometrical parameters, in general, affects both optical and electrical properties Constant-sheet-resistance transformation keeps electrical properties fixed Optical properties will vary 1 1 2 2 3 3 hw a hw a hw a = = a R wh ρ = Nano-patterned metal film 1D: Geometry and R Nano-patterned metal film 1D: Geometry and R current a R wh ρ = period width a w What are the optical properties? Nano-patterning enables new class of electrodes Nano-patterning enables new class of electrodes Nano-patterned metal J.-Y. Lee et al., Nano Letters 8, 689 (2008) ITO Physics governing performance are more involved Trade-off of optical (T) vs. electrical (R ) for ITO Trade-off of optical (T) vs. electrical (R ) for ITO (Courtesy of P. Peumans) Sheet Resistance (Ω/sq) R h ρ = thickness resistivity h ρ Thin film Thick film ITO Metal oxide films are often used as electrodes Metal oxide films are often used as electrodes Transparent metal oxides = incumbent technology Indium Tin Oxide (ITO): transparent, conductive expensive, brittle, sputtering damages active layers Fundamental trade-off between optical & electrical properties (Optical Films UK) Optoelectronics: Managing photons and electrons Optoelectronics: Managing photons and electrons Transparent conductive electrodes are critical for optoelectronic devices Electrodes: excellent optical and electrical properties Light emitting devices (electrons in, photons out) (SPIE Newsroom and Sigma Aldrich) Photovoltaic devices (photons in, electrons out) Abstract Nanopatterned Metallic Films for Use As Transparent Conductive Electrodes Peter B. Catrysse and Shanhui Fan E. L. Ginzton Laboratory, Stanford University, Stanford, CA, USA Transparent conductive electrodes are critical to the operation of optoelectronic devices, such as photovoltaic cells and light emitting diodes. Effective electrodes need to combine excellent electrical and optical properties. Metal oxides, such as indium tin oxide, are commonly used. There is substantial interest in replacing them, however, motivated by practical problems and recent discoveries regarding the optics of nano-patterned metals. When designing nano-patterned metallic films for use as electrodes, one needs to account for both optical and electrical properties. In general, it is insufficient to optimize nano-structured films based upon optical properties alone, since structural variations will also affect the electrical properties. In this work, we investigate the need for simultaneous optical and electrical performance by analyzing the optical properties of a class of nano-patterned metallic electrodes that is obtained by a constant-sheet-resistance transformation. Within such a class the electrical and optical properties can be separated, i.e., the sheet resistance can be kept constant and the transmittance can be optimized independently. For simple one-dimensional periodic patterns with constant sheet-resistance, we find a transmission maximum (polarization-averaged) when the metal sections are narrow (< 40 nm, ~ 10% metal fill-factor) and tall (> 100 nm). Our design approach results in an optimum for both normal and oblique transmission. Moreover, it carries over to more complex two-dimensional (2D) patterns. This is significant as there are no previous reports regarding numerical studies on the optical and electrical properties of 2D nano-patterns in the context of electrode design. Optical behavior governed by propagating modes (TE polarization), and by interference of propagating modes and coupled SPP modes (TM polarization) Transparent electrodes based on nano-patterned metallic films are designed and optimized based on a constant-sheet-resistance transformation Design rules favors nano-patterned metallic films consisting of tall and narrow wire geometries (over short and wide wire geometries) Design rules and broadband transmittance remain valid for oblique incidence and extends to 2D patterned metallic films Summary This work was supported by the Center for Advanced Molecular Photovoltaics (CAMP) under Award No KUSC1-015-21 made by the King Abdullah University of Science and Technology, and by DOE Grant No. DE-FG02-07ER46426. The computation is performed through the support of NSF-LRAC program. Transmittance of thick 1D patterned metal film Transmittance of thick 1D patterned metal film TE TM E H 400 nm 400 nm 80 nm a h w = = = 400 1000 nm → Sharp dip Large transmission Cutoff and evanescent tunneling Catrysse and Fan, Nano Lett. 10, 2944 (2010) Transmittance of thin 1D patterned metal electrode Transmittance of thin 1D patterned metal electrode 400 nm 10 nm 80 nm a h w = = = 400 1000 nm → TE TM E H Catrysse and Fan, Nano Lett. 10, 2944 (2010) TM behavior: mode in gap and surface modes TM behavior: mode in gap and surface modes TM H 400 nm 10 nm 80 nm a h w = = = Mode in gap: Large T Surface resonance: Dip in T Catrysse and Fan, Nano Lett. 10, 2944 (2010) R = cst design favors narrow and tall wires R = cst design favors narrow and tall wires 3.2 Ω 1.6 Ω 0.8 Ω Narrow Tall Wires! • Broadband T > 90% • Robust in w, h • Good off-axis Broadband Average T (VIS-NIR) Catrysse and Fan, Nano Lett. 10, 2944 (2010) Broadband transmission for 1D and 2D patterns Broadband transmission for 1D and 2D patterns a = 400 nm w = 40 nm h = 100 nm R = 1.6 Ω/ Catrysse and Fan, Nano Lett. 10, 2944 (2010) Narrow/tall wire designs optimal for 2D patterns Narrow/tall wire designs optimal for 2D patterns 3.2 Ω 1.6 Ω 0.8 Ω Catrysse and Fan, Nano Lett. 10, 2944 (2010) MotivationPhysicsEngineering
Transcript of Nanopatterned Metallic Films for Use As...
Optimizing optical AND electrical propertiesOptimizing optical AND electrical properties
Changing geometrical parameters, in general, affects both optical and electrical properties
Constant-sheet-resistance transformationkeeps electrical properties fixed
Optical properties will vary
1 1 2 2 3 3h w a h w a h w a= =
aRw hρ
=
Nano-patterned metal film 1D: Geometry and RNano-patterned metal film 1D: Geometry and R
current
aRw hρ
=periodwidth
aw
What are the optical properties?
Nano-patterning enables new class of electrodesNano-patterning enables new class of electrodes
Nano-patterned metal
J.-Y. Lee et al., Nano Letters 8, 689 (2008)
Ho group: R < 10 Ω/ and T > 80% (7756-21)
ITO
Physics governing performance are more involved
ITO
Trade-off of optical (T) vs. electrical (R ) for ITOTrade-off of optical (T) vs. electrical (R ) for ITO
(Courtesy of P. Peumans)
Sheet Resistance(Ω/sq)R hρ=
thicknessresistivity
hρ
Thinfilm
Thick film
ITO
Metal oxide films are often used as electrodesMetal oxide films are often used as electrodes
Transparent metal oxides= incumbent technology
Indium Tin Oxide (ITO):
transparent, conductive
expensive, brittle,sputtering damagesactive layers
Fundamental trade-offbetween optical & electricalproperties
(Optical Films UK)
Optoelectronics: Managing photons and electronsOptoelectronics: Managing photons and electrons
Transparent conductive electrodes are critical for optoelectronic devices
Electrodes: excellent optical and electrical properties
Light emitting devices(electrons in, photons out)
(SPIE Newsroom and Sigma Aldrich)
Photovoltaic devices(photons in, electrons out)
Abstract
Nanopatterned Metallic Films for Use As Transparent Conductive ElectrodesPeter B. Catrysse and Shanhui Fan
E. L. Ginzton Laboratory, Stanford University, Stanford, CA, USA
Transparent conductive electrodes are critical to the operation of optoelectronic devices, such as photovoltaic cells and light emitting diodes. Effective electrodes need to combine excellent electrical and optical properties. Metal oxides, such as indium tin oxide, are commonly used. There is substantial interest in replacing them, however, motivated by practical problems and recent discoveries regarding the optics of nano-patterned metals. When designing nano-patterned metallic films for use as electrodes, one needs to account for both optical and electrical properties. In general, it is insufficient to optimize nano-structured films based upon optical properties alone, since structural variations will also affect the electrical properties.
In this work, we investigate the need for simultaneous optical and electrical performance by analyzing the optical properties of a class of nano-patterned metallic electrodes that is obtained by a constant-sheet-resistance transformation. Within such a class the electrical and optical properties can be separated, i.e., the sheet resistance can be kept constant and the transmittance can be optimized independently. For simple one-dimensional periodic patterns with constant sheet-resistance, we find a transmission maximum (polarization-averaged) when the metal sections are narrow (< 40 nm, ~ 10% metal fill-factor) and tall (> 100 nm). Our design approach results in an optimum for both normal and oblique transmission. Moreover, it carries over to more complex two-dimensional (2D) patterns. This is significant as there are no previous reports regarding numerical studies on the optical and electrical properties of 2D nano-patterns in the context of electrode design.
Optical behavior governed by propagating modes (TE polarization), and by interference of propagating modes and coupled SPP modes (TM polarization)Transparent electrodes based on nano-patterned metallic films are designed and optimized based on a constant-sheet-resistance transformationDesign rules favors nano-patterned metallic films consisting of tall and narrow wire geometries (over short and wide wire geometries)Design rules and broadband transmittance remain valid for oblique incidence and extends to 2D patterned metallic films
Summary
This work was supported by the Center for Advanced Molecular Photovoltaics (CAMP) under Award No KUSC1-015-21 made by the King Abdullah University of Science and Technology, and by DOE Grant No. DE-FG02-07ER46426. The computation is performed through the support of NSF-LRAC program.
Transmittance of thick 1D patterned metal filmTransmittance of thick 1D patterned metal film
TE
TM
E
H
400 nm400 nm80 nm
ahw
===
400 1000 nm→
Sharp dip
Large transmission
Cutoff and evanescenttunneling
Catrysse and Fan, Nano Lett. 10, 2944 (2010)
Transmittance of thin 1D patterned metal electrodeTransmittance of thin 1D patterned metal electrode
400 nm10 nm80 nm
ahw
===
400 1000 nm→
TE
TM
E
H
Catrysse and Fan, Nano Lett. 10, 2944 (2010)
TM behavior: mode in gap and surface modesTM behavior: mode in gap and surface modes
TM H
400 nm10 nm80 nm
ahw
===
Mode in gap:Large TSurface
resonance:Dip in T
Catrysse and Fan, Nano Lett. 10, 2944 (2010)
R = cst design favors narrow and tall wiresR = cst design favors narrow and tall wires
3.2 Ω1.6 Ω0.8 Ω
NarrowTall
Wires!• Broadband T > 90%• Robust in w, h• Good off-axis
BroadbandAverage T(VIS-NIR)
Catrysse and Fan, Nano Lett. 10, 2944 (2010)
Broadband transmission for 1D and 2D patternsBroadband transmission for 1D and 2D patterns
a = 400 nmw = 40 nmh = 100 nm
R = 1.6 Ω/
Catrysse and Fan, Nano Lett. 10, 2944 (2010)
Narrow/tall wire designs optimal for 2D patternsNarrow/tall wire designs optimal for 2D patterns
3.2 Ω1.6 Ω0.8 Ω
Catrysse and Fan, Nano Lett. 10, 2944 (2010)
Motivation
Physics
Engineering
![Physical descriptions Meet the Robinsons. She is young She is tall [tɔ:l] She is thin [θɪn] She has got short black hair [heə ɼ ]](https://static.fdocument.org/doc/165x107/551a275b550346a4248b51be/physical-descriptions-meet-the-robinsons-she-is-young-she-is-tall-tl-she-is-thin-n-she-has-got-short-black-hair-he-.jpg)
