Interface stoichiometry control in ZnO/Cu2O photovoltaic devices

Cu2O is a potential earth-abundant alternative to established thin photovoltaic materials (CIGS, CdTe, etc.) because of its low cost, high availability, and inexpensive processing, but Cu2O has seen limited development as a photovoltaic device material owing to challenges in measurement and control of interface stoichiometry and doping. We report measurements of Cu2O interface stoichiometry and the effect of interface composition on heterojunction device performance. ZnO/Cu2O interface stoichiometry was varied by adjusting the ZnO window layer deposition conditions and stoichiometry was measured by X-ray photoelectron spectroscopy. Current-voltage characteristics of ZnO/Cu2O heterojunctions indicate open circuit voltages of Voc ~ 530 mV for devices where the Cu2O layer is stoichiometric at the interface and Voc ~ 100 mV for devices where Cu2O is nonstoichiometric at the interface.