Properties of different temperature annealed Cu(In,Ga)Se2 and Cu(In,Ga)2Se3.5 films prepared by RF sputtering

We have investigated the effect of annealing temperature on structural, compositional, electrical properties of the one-step RF sputtered Cu(In,Ga)Se2 and Cu(In,Ga)2Se3.5 films. After the annealing at various temperatures, loss of Se element is significant for the Cu(In,Ga)Se2 films and meanwhile composition of the annealed Cu(In,Ga)2Se3.5 films keeps almost constant. The as-deposited Cu(In,Ga)Se2 and Cu(In,Ga)2Se3.5 films show amorphous structure and they follow different transformation process to form chalcopyrite structure. Electrical conductivity of the annealed CIGS films related to their chemical composition. Cu(In,Ga)Se2 films annealed at 150 °C show unique electron transport mechanism for the formation of hexagonal CuSe phase. Electrical conductivity of the chalcopyrite structure films are dominated by the “variable range hopping” transport mechanism. The annealed Cu(In,Ga)2Se3.5 films present higher density of disorders than the annealed Cu(In,Ga)Se2 films for their significant Cu deficient composition.