Photoluminescence Properties of Cu(InGa)Se2 Thin Films Prepared by Mechanochemical Process

Cu(InGa)Se2 (CIGS) thin films have been successfully grown by a mechanochemical process (MCP), which is a low-cost process, without any additional heating. In this study, we carried out low-temperature photoluminescence (PL) measurements for CIGS films prepared by the MCP. The CIGS films with Ga contents of 1 and 5% showed four radiative recombinations. The emission peaks of 0.97 and 0.90 eV were assigned to free-to-bound and donor–acceptor pair transitions, respectively. The other two peaks were the phonon replicas. The film which exhibited high conversion efficiency shows the emission of a free exciton. From the free exciton energy, we inferred that the acceptor and donor defects were VCu and VSe, respectively. These results suggested that the films grown by mechanical synthesis possess intrinsic defects identical to those in films deposited by a vacuum process.