Characterization of Cu(In,Ga)Se2 films deposited by single-step electron beam evaporation for solar cell applications

CuInxGa(1−x)Se2 (CIGS) thin films have been prepared by a single step of electron beam evaporation of a mixed alloy power made of high purity elemental copper, indium, gallium and selenium. The crystalline quality of CIGS films increases with increasing the substrate temperature, and stoichiometric CuIn0.7Ga0.3Se2 with chalcopyrite phase and (1 1 2) preferential orientation can be obtained at a substrate temperature of 650 °C. X-ray diffractometer (XRD), scanning electron microscope (SEM) and absorption spectroscopy are used to characterize the obtained films. CuIn0.7Ga0.3Se2 films evaporated at 650 °C is found to have a bandgap of about ∼1.11 eV. In addition, two different acceleration voltages (5 kV and 10 kV) for the electron gun are also compared and a high acceleration voltage is found to be crucial in order to obtain stoichiometric CIGS films without Cu-deficiency. Our results suggest that the single-step electron beam evaporation at a high acceleration voltage could be potentially applied for fabrication of CIGS thin solar cells.