Extremely thin solar absorbers
Martijn de Sterke
ETAs
IPOS Institute of Photonics and Optical Science
› Current photovoltaics based on silicon, but
- Silicon is expensive to extract and to process
- Poor absorption (indirect bandgap); excellent electronic properties
› Possible alternative: “earth-abundant materials” eg FeS2, CuO2
- Good absorbers; poor electronic properties (short diffusion length)
- Get around this by Extremely Thin Absorbers (10’s of nanometers),
which yet need to absorb strongly
› Standard solution: highly convoluted surface, but large surface
area and associated recombination
ETAs (cont’d)
› Our approach (Catchpole & de Sterke + White, McP, Botten)
- Evanescent field enhancement—evanescent fields not subject to
energy conservation
- Plasmonic enhancement in metals (been rarely used in solar cells)
- Dielectric enhancement via evanescent grating orders
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Possible geometries
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Tools
› Electron beam lithography
› Nanoimprinting
› Nanoparticle fabrication
all in unusual materials
› Deposition and etching
› PL
› High-resolution microscopy
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Outlook
› Growing area with strong societal demand
› Two very strong groups already in this area (UNSW and ANU)
+ much other work elsewhere
› But on the other hand
- Solutions seem to require excellent theory/modeling expertise
- Funding from multiple sources available (cf Mary O’Kane’s
comments at 2011 IPOS workshop)
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