Optically-thick 300 nm GaAs solar cells using adjacent photonic crystals

Ultra-thin photovoltaics offer the potential for increasing efficiency while minimizing costs. However, a suitable light trapping strategy is needed to reach the optically thick regime for otherwise thin-film structures. III-V materials can benefit from simple adjacent light trapping structures, if correctly designed. Here we present three strategies for a 300 nm thick GaAs cell using front photonic crystals, back photonic crystals, and both front and back combined, predicting a maximum photocurrent, J_sc=29.9 mA/cm² under the radiative limit, including an enhanced absorption in the Urbach-tail. We analyze the increased absorption isolating the Fabry-Perot resonances, the single pass absorption and the scattered contribution from the incident light.