Synthesis and characteristics of Cu(In,Ga)Se2 thin films from nanoparticles by solvothermal method and selenisation process

Abstract

Cu(In,Ga)Se2 (CIGS) thin films were successfully synthesised by a facile and low-cost non-vacuum process. First, the chalcopyrite CIGS nanoparticles with nanoplate-like shapes were synthesised by a mild solvothermal method using CuCl2·2H2O, Ga2Se3, In2Se3 and elemental selenium as original materials. Secondly, homogeneous CIGS nanoinks were prepared and then spin-coated onto soda–lime glass substrates. Subsequently, CIGS precursor films were formed by two-step preheating treatments in air. Lastly, CIGS films were fabricated by selenisation process using Se vapour at 500°C. The obtained CIGS films were of a typical chalcopyrite structure and indicated p-type semiconductor characteristics. The optical bandgap of the films was 1.19 eV with a high-absorption coefficient exceeding 104 cm−1. The quality of the CIGS films was significantly improved by post-selenisation process.