GaAs/InGaP core-multishell nanowire-array-based solar cells

Abstract

Semiconductor nanowires (NWs) are good candidate for light-absorbing material in next generation photovoltaic and III-V NW-based multiheterojunction solar cells using lattice-mismatched material system are expected as high energy-conversion efficiencies under concentrated light. Here we demonstrate core-shell GaAs NW arrays by using catalyst-free selective-area metal organic vapor phase epitaxy (SA-MOVPE) as a basis for multijunction solar cells. The reflectance of the NW array without any anti-reflection coating showed much lower reflection than that of a planar wafer. Next we then fabricated core-shell GaAs NW array solar cells with radial p-n junction. Despite the low reflectance, the energyconversion efficiency was 0.71% since a high surface recombination rate of photo-generated carriers and poor ohmic contact between the GaAs and transparent indium-tin-oxide (ITO) electrode. To avoid these degradations, we introduced an InGaP layer and a Ti/ITO electrode. As a result, we obtained a short-circuit current of 12.7mAcm-2, an open-circuit voltage of 0.5 V, and a fill factor of 0.65 for an overall efficiency of 4.01%. © 2013 The Japan Society of Applied Physics.