Cu(In, Ga)Se 2 thin films were deposited on Mo/soda-lime glass substrates by the one-stage co-evaporation process at the substrate temperatures (T sub ) from 350 • C to 550 • C. The structural and electrical properties of CIGS films have been studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) and Hall effect measurement. The experimental results indicate that a temperature of 450 • C is critical for CIGS films grown by the one-stage process. The (In, Ga) 2 Se 3 phase with high resistivity is found below this temperature. The higher T sub will lead to the formation of single-phase CIGS films with larger grain size and better electrical properties. A higher carrier concentration and lower resistivity of CIGS films are ascribed to sodium incorporation diffused from the glass substrate and the disappearance of the (In, Ga) 2 Se 3 phase in CIGS films. Additionally, the performance of the CIGS solar cells improves significantly with the increase of T sub . It can be attributed to the reduction of the grain-boundary recombination and the sufficient reaction between the additional (In, Ga) 2 Se 3 phase and the Cu x Se y binary phase at T sub above 500 • C.