13.6%-efficient Cu(In,Ga)Se2 solar cell with absorber fabricated by RF sputtering of (In,Ga)2Se3 and CuSe targets

A conversion efficiency of 13.6% has been achieved in Cu(In,Ga)Se2 (CIGS) thin film solar cell with absorber layer fabricated by sequentially RF sputtering (In,Ga)2Se3 and CuSe targets and further annealing in Se vapor. The significant improvement, comparing with the efficiency of 10.8% for CIGS solar cell sputtering from a quaternary CIGS target, was attributed to smoother surface, better crystallinity, and more compact structure of the CIGS film. The reaction pathway of (In,Ga)2Se3/CuSe bilayer was discussed, and such a bilayer design was demonstrated to be energetically favorable to form a better-crystallized CIGS film. ► 13.6%-efficient CIGS solar cell with absorber fabricated by sputtering (In,Ga)3Se2 and CuSe targets was reported. ► Efficiency improvement mainly aroused from smoother surface, and more compact microstructure. ► Significantly enhanced crystallinity of the two-target process could be attributed to the one-dimensional diffusion growth model and the CuSe-assist grain growth. ► Further improvements in the precursor structure and the selenization process were expected to enhance efficiency ever further.