Effect of AZO film deposition conditions on the photovoltaic properties of AZO–Cu2O heterojunctions

This report describes the effect of ZnO:Al (AZO) film deposition conditions on the photovoltaic properties of AZO–Cu2O heterojunction devices. The devices were fabricated by depositing a transparent conducting AZO thin film on a Cu2O sheet that functions as the active layer as well as the substrate. The photovoltaic properties of these devices were considerably dependent on deposition temperature, irrespective of the deposition method used to fabricate them. Maximum efficiencies of 1.2 and 1.0% measured under AM2 solar illumination were obtained in AZO/Cu2O devices fabricated using AZO films deposited at a temperature around 200 8C by pulsed laser deposition (PLD) and r.f. magnetron sputtering (r.f.MS), respectively. The improvement in properties resulting from an increase in the deposition temperature up to about 200 8C is attributed to an improvement of crystallinity in the AZO films; the degradation resulting from an increase over 250 8C is related to an increase of resistivity in Cu2O.