Thin film deposition of Cu2O and application for solar cells

Deposition conditions of cuprous oxide (Cu2O) thin films on glass substrates and nitrogen doping into Cu2O were studied by using reactive radio-frequency magnetron sputtering method. The effects of defect passivation by crown-ether cyanide treatment, which simply involves immersion in KCN solutions containing 18-crown-6 followed by rinse, were also studied. By the crown-ether cyanide treatment, the luminescence intensity due to the near-band-edge emission of Cu2O at around 680 nm was enhanced, and the hole density was increased from 1016 to 1017 cm−3. Finally, polycrystalline p-Cu2O/n-ZnO heterojunctions were grown for use in solar cells. Two deposition sequences were studied, ZnO deposited on Cu2O and Cu2O deposited on ZnO. It was found that the crystallographic orientation and current–voltage characteristics of the heterojunction were significantly influenced by the deposition sequence, both being far superior for the heterojunction with structure Cu2O on ZnO than for the inverse structure. We successfully obtained a photoresponse for the first time in the deposited thin film of Cu2O/ZnO.