Photovoltaic properties of low-damage magnetron-sputtered n-type ZnO thin film/p-type Cu2O sheet heterojunction solar cells

•Highest conversion efficiency of 3.22% was achieved.•Optimum conditions found for target-substrate distance and r.f.:d.c. power ratio.•Efficiency further improved by r.f. power superimposed DC magnetron sputtering. The photovoltaic properties of Cu2O-based heterojunction solar cells were improved using an n-type layer composed of thin films in a binary oxide semiconductor. This layer was prepared by a low-damage deposition method that applies a system for multi-chamber radio frequency (r.f.) power superimposed direct current (d.c.) magnetron sputtering. For an Al-doped ZnO (AZO)/n-ZnO/p-Cu2O heterojunction solar cell prepared using r.f. power superimposed d.c magnetron sputtering, we achieved the highest efficiency yet reported (3.22%) by optimizing sputtering conditions such as the substrate-target distance and the r.f.:d.c. power ratio. This value represents characteristics that exceed those of AZO/Cu2O solar cells having a similar structure based on r.f. power superimposed d.c magnetron sputtering.