Effect of Thermal Annealing on the Optical Properties of 3D-Printed Nanostructured CuO Films for Flexible Photovoltaic Solar Cells

In this work, the effect of thermal annealing on the optical and structural properties of 3D-printed nanostructured copper oxide films deposited on polyimide substrates is investigated for the first time. It was shown that both asdeposited and annealed at T alpha = 160 C-degrees films have mainly monoclinic CuO phase. XRD and Raman results show that these films also contain a small amount of Cu2O phase, and possibly an amorphous CuO as well as a metastable CuO2-like phases. At the same time, films annealed at 300 C-degrees for 10 min are characterized by a pure CuO phase and have the best optical quality. The band gap of the investigated copper oxide films is equal to (1.53-1.64) eV, which is associated with indirect allowed optical transitions. The results obtained paves the way to the development of nanotechnologies for obtaining CuO films by the 3D printing method, suitable for flexible electronics, especially for solar energy.