23.5% Efficiency GaAs Solar Cells Fabricated with Low-cost, Non-vacuum Processing

We report advances in low-cost GaAs photovoltaic device processing. First, we developed an open-tube zinc diffusion technique for forming p-type layers with sheet resistance less than 100 ohms per square on GaAs and InP. Second, we use this technique along with chemical surface passivation to fabricate GaAs solar cells that, uncertified, achieve Voc = 964 mV Voc, FF = 82% FF, Jsc, = 29.8 mAcm-2 Jsc, and 23.5% efficiency. Third, we discovered GaAs cells with long hole diffusion length can be made byfabricated from wafers growing obtained from GaAs ingots grown in a part of the phase diagram thate minimizes the EL2 defect. Fourth, we show an in-air, precious metal-free process for making ohmic contacts to n-type GaAs.