CIGS thin film and device performance produced through a variation Ga concentration during three-stage growth process

In this study, Cu(In,Ga)Se2 (CIGS) absorber is grown on Mo-coated soda-lime glass substrates through co-evaporation deposition. Several types of Ga distribution in CIGS was examined by adjusting the [Ga]/([In]+[Ga]) ratio at the first and third stages. The electrical properties of the film were also determined. The carrier concentration increased with increasing Ga content. The highest carrier concentration of 8.46 × 1015 cm−3 were obtained when the [Ga]/([In]+[Ga]) ratio (0.36) was 0.4: 0.3 at the first and third stage. The best device conversion efficiency of 12.5% was achieved because the suitable [Ga]/([In]+[Ga] ratio, band-gap gradient distribution and low recombination rate.