Effect of annealing temperature on the properties of electrodeposited Cu2O on FTO glass substrate

This study aimed to investigate the formation of Cu2O thin films on fluorine-doped tin oxide glass substrate by electrochemical deposition. The obtained Cu2O thin films were annealed in air at various temperatures from 300 to 500 degrees C. X-ray diffraction analysis shows that as-deposited and annealed thin films at 300 degrees C have a cubic structure with a Cu2O composition. The Cu2O films annealed at 400 and 500 degrees C were completely converted onto the monoclinic structure with CuO composition. On the other hand, atomic force microscope and scanning electron microscope images showed that the shape of Cu2O grains was changed significantly from cubic to grains upon annealing. Mott-Schottky and photoelectrochemical measurements indicate that Cu2O thin films exhibit p-type conductivity before and after annealing. Photoluminescence measurements indicated two peaks at around 523 and 355 nm, which confirmed the existence of Cu2O and CuO thin films, respectively. Finally, the CuO nanostructures obtained at 500 degrees C exhibited a high photocurrent enhancement and stability compared to as-deposited sample. As a consequence, the optical bandgap was reduced from 2.41 to 1.75 eV.