Characterization of Cu2−xSe thin films synthesized from electrochemical deposition

•Cu2−xSe films were electrodeposited on Mo substrate with CuSO4 and H2SeO3.•The deposited films were near-stoichiometric Cu2−xSe with FCC structure.•The direct band gap for Cu2−xSe thin films are in the range of 2.14–2.18 eV.

Copper selenide (Cu2−xSe) thin films were potentiostatically deposited on molybdenum substrate with an aqueous solution of CuSO4 and H2SeO3. The effect of the deposition potential on the microstructure and electrical properties of the thin films were studied using FESEM, HRTEM, and two probe conducting measurements. The morphologies of the films changed from densely packed nanoparticles to the plate-like grains growing perpendicular to the substrate. In addition, these plates were composed of nanoparticles of about 100–200 nm in size. The nanoparticles were verified to be the face centered cubic (FCC) Cu2−xSe from XPS and HRTEM analysis. The direct band gap for the Cu2−xSe thin films was in the range of 2.14–2.18 eV measured from UV–vis absorption edge. The electrical conductivity of the thin films increased from 4.51 × 10−3 to 7.08 × 10−3 (Ω m)−1 as the Cu/Se ratio decreased from 1.92 to 1.89.