Greifswald 2024 – scientific programme
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SYEC: Symposium Lasers and Photonic Technologies for Environmental Challenges
SYEC 4: Photonics-Assisted Green Energy Production II
SYEC 4.2: Talk
Tuesday, February 27, 2024, 16:45–17:00, ELP 6: HS 4
Making ultra-thin silicon solar cells competitive through hyperuniform disordered light trapping. — •Alexander Lambertz1,2, Esther Alarcon-Llado1, and Jorik van de Groep2 — 1NWO-i AMOLF, Amsterdam, Netherlands — 2University of Amsterdam, Amsterdam, Netherlands
Current industrys crystalline silicon solar cells rely on fossil fuels for wafer production and require too much high-quality silicon per watt-peak and are thus unsuitable to meet climate goals. Substantially reducing the absorber thicknesses will not only allow to save silicon, but also to avoid the wasteful Czoralski process, use lower quality poly-silicon, expand the application of c-Si cells to light-weight, semi-transparent, flexible, and wearable photovoltaics.
In order to overcome the shortcoming of poor absorption in thin silicon layers, we present light-trapping patterns based on hyperspectral uniformity to achieve unprecedented absorptance values. We experimentally demonstrated beyond 65% sunlight absorption in one micron thick free-standing silicon membranes and developed an analytical model based on temporal coupled-mode theory to find optimum Fourier-space profiles.
We recently fabricated ultra-thin silicon solar cells of less than five micron thickness by molecular beam epitaxy that have shown over 15 % power conversion efficiencies when our patterns were applied, where flat silicon-nitride-coated references only achieved about 10%. We furthermore give reasonable indication that efficiencies beyond 20 % are achievable already below 10 micron silicon thicknesses.
Keywords: silicon solar cell; metasurface; nanophotonics; hyperuniformity; light-trapping