Optical and electrical properties of Cu-In-Te based thin films and solar cells

Cu-In-Te based thin films were grown onto soda-lime glass substrates at a substrate temperature of 200°C by co-evaporation using a molecular beam epitaxy system. The dependence of the optical and electrical properties of the films on the Cu/In atomic ratio was investigated. As the optical bandgap of the CuIn₃Te₅ thin films was 1.02 eV, the valence and conduction band offsets of the CdS/CuIn₃Te₅ interface were determined to be 1.54 eV and -0.14 eV, respectively. A solar cell with a ZnO/CdS/CuIn₃Te₅/Mo/SLG structure showed a total area (0.50 cm²) efficiency of 5.1% under AM1.5 illumination (100 mW/cm²) after light soaking. The recombination mechanisms in the CdS/CuIn₃Te₅ thin-film solar cells are suggested on the basis of the temperature dependence of the device properties.