Fig. 4From: Nano-structured CuO-Cu2O Complex Thin Film for Application in CH3NH3PbI3 Perovskite Solar CellsFESEM images of CuO-Cu2O complex thin films fabricated using thermal oxidation at various temperatures. a Thermal treatment at 300 °C. b Thermal treatment at 350 °C. c Thermal treatment at 400 °CBack to article page