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 FeS 2, CuO 2 -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 3

Possible geometries 4

Tools ›Electron beam lithography ›Nanoimprinting ›Nanoparticle fabrication ›Deposition and etching ›PL ›High-resolution microscopy 5 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) 6