Cu(In,Ga)Se2 films prepared by sputtering with a chalcopyrite Cu(In,Ga)Se2 quaternary alloy and In targets

This study reports the successful preparation of Cu(In,Ga)Se2 (CIGS) thin film solar cells by magnetron sputtering with a chalcopyrite CIGS quaternary alloy target. Bi-layer Mo films were deposited onto soda lime glass. A CIGS quaternary alloy target was used in combination with a stack indium target for compensating the loss of indium during annealing process. A one-stage annealing process was performed to form CIGS chalcopyrite phase. Experimental results show that the optimal adhesion strength, residual stress, and resistivity were obtained at a thickness ratio of 67% of bi-layer Mo films and a working pressure of 0.13 Pa. The CIGS precursor was layered through selenization at 798 K for 20 min. The stoichiometry ratios of the CIGS film were Cu/(In + Ga) = 0.91 and Ga/(In + Ga) = 0.23, which approached the device-quality stoichiometry ratio (Cu/(In + Ga) <0.95, and Ga/(In + Ga) <0.3). The resistivity of the sample was 11.8 Ωcm, with a carrier concentration of 3.6 × 1017 cm−3 and mobility of 1.45 cm2V−1s−1. The resulting film exhibited p-type conductivity.