Optical and electrical characteristics of thermally evaporated Cu0.5Ag0.5InSe2 thin films

In this study, optical and electrical characteristics of the Cu0.5Ag0.5InSe2 (CAIS) polycrystalline thin films were investigated. They were deposited on soda lime glass substrates with the evaporation of pure elemental sources by using physical thermal evaporation technique at 200 °C substrate temperature. The thin films were characterized firstly in as-grown form, and then annealed under the nitrogen environment to deduce the effects of annealing on the optical and electrical properties of the deposited thin films related to their structural changes. In fact, these material properties of the CAIS thin films were studied by carrying out transmission, Hall Effect, and temperature dependent dark- and photo-conductivity measurements as a function of annealing temperature. From the optical analysis, the band gap energies were found between 1.44 and 1.51 eV for the as-grown and annealed films, respectively. The analysis of electrical conductivity showed that electrical properties of the films were dependent on the variable range hopping and thermionic emission conduction mechanisms at low temperature region and above the room temperature, respectively. Under different illumination intensities, the photo-conductivity properties of CAIS film samples were analyzed under the consideration of two-center model.