Sulfur passivation and contact methods for GaAs nanowire solar cells

Abstract

The effect of sulfur passivation on core–shell p–n junction GaAs nanowire (NW) solar cellshas been investigated. Devices of two types were investigated, consisting of indium tinoxide contact dots or opaque Au finger electrodes. Lateral carrier transport from the NWsto the contact fingers was achieved via a p-doped GaAs surface conduction layer. NWsbetween the opaque contact fingers had sidewall surfaces exposed for passivation by sulfur.The relative cell efficiency increased by 19% upon passivation. The contribution of thethin film grown between the NWs to the total cell efficiency was estimated byremoving the NWs using a sonication procedure. Mechanisms of carrier transport andphotovoltaic effects are discussed on the basis of spatially resolved laser scanningmeasurements.