Transcript A brief overview of Plasmonic Nanostructure Design for
A brief overview of
Plasmonic Nanostructure Design for Efficient Light Coupling into Solar Cells
V.E. Ferry, L.A. Sweatlock, D. Pacifici, and H.A. Atwater,
Nano Letters
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4391 Douglas Detert EE235 Prof. Connie Chang March 2, 2009
Solar Cell Design/Material Considerations • Conventional solar cells (e.g. Silicon) require thick absorption layers for complete absorption • Thin film solar cells (e.g. CdTe, CIGS) decrease bulk recombination effects and allow for higher quality absorber materials • Problem: Thin film cells are limited by decreased absorption, carrier excitation, and photocurrent • Solution: Texture top/bottom surfaces to enhance light absorption Douglas Detert — EE235 — March 2, 2009
Surface Plasmon Polariton Enhanced Solar Cells • Surface Plasmon Polaritons (SPPs) are collective oscillations of free electrons at metal/dielectric boundaries • SPPs are highly localized to interfaces and propagate easily for microns. Energy in SPP modes enhances absorption • Momentum mismatch between incident light and SPPs does not allow for direct excitation of SPPs • Goal: Design a nanostructure back contact that scatters light into SPP mode Barnes. J Opt A-Pure Appl Op
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S87-S93 (2006) Douglas Detert — EE235 — March 2, 2009
Scattering From a Single Groove • Light energy is scattered into two key modes • Photonic (~semiconductor) • SPP (~interface) • Both enhance photoabsorption, but photonic modes are not supported in extremely thin structures Douglas Detert — EE235 — March 2, 2009 H y
Results: Scattering From a Single Groove • Finite-difference time-domain (FDTD) simulations paired with modal decomposition analysis • Three physical effects involved in incoupling efficiencies: • Fabry-Pérot resonance of thin film • Photonic mode excitation at SPP resonance wavelength • Polarization resonance of scatterer • Film thickness and scatterer geometry affect above properties Douglas Detert — EE235 — March 2, 2009
Effect of Groove Dimensions • Groove width: SPP modes break down at large groove sizes, photonic mode flattens out • Groove depth has little effect on incoupling efficiency • Ridge-like structure: enhances photonic mode Douglas Detert — EE235 — March 2, 2009
Conclusion & Outlook • Groove-like nanostructures improve photoabsorption in thin film solar cells by coupling light to various modes, including interfacial SPP modes.
• Incoupling to SPP modes allows for enhancement in thin film solar cells • To date, solar cells enhanced by SPPs have been fabricated with only top-layer patterning.
Douglas Detert — EE235 — March 2, 2009 Pillai et al. JAP 101 093105 (2007)