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Extremely thin solar absorbers
Martijn de Sterke
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
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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Scale bars are 1 μm
Tools
› Electron beam lithography› Nanoimprinting› Nanoparticle fabrication› Deposition and etching › PL› High-resolution microscopy
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all in unusual materials
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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