Fabrication and characterization of Cu (In, Ga)Se₂ thin films

CuIn_1-xGa_xSe₂ (CIGS) is a promising direct band-gap semiconductor material for developing a new generation of high-efficiency and low-cost thin film solar cells due to its variable band-gap structure and high absorption coefficient in visible range. In this paper, a series of CIGS thin films were fabricated by combination of DC sputtering and selenizing processes. The effects of the sputtering power for deposition of CuIn_1-xGa_x (CIG) metal precursors and substrates on the microstructures and optical properties of the CIGS films were investigated. It was found that the film, deposited at 50 W sputtering power onto Mo-coated soda lime glass (SLG) substrate and then selenized at 550°C for 40 minutes, exhibited a single chalcopyrite phase, uniform and dense morphology, and columnar grains. It is also found that the optical band gaps of the films are in the range of 1.21~1.24 eV.