10% efficiency Cu(In,Ga)Se2 solar cell with strongly (220)/(204) oriented Cu-poor absorber layers sputtered using single quaternary target

Cu-poor CIGS thin films were fabricated by RF magnetron sputtering from a single quaternary target with the composition of Cu0.7In0.7Ga0.3Se2, in an effort to improve the cell efficiency of CIGS solar cells. The Cupoor thin films with the ([Cul/[In]+[Ga]) composition ratios of 0.70-0.77 were obtained showing that the composition of the target can be transferred to the film. It was also observed that the strongly (220)/ (204) preferred orientation appeared at the substrate temperatures higher than 600 degrees C, which is known to be essential for achieving high-quality CIGS solar cells. This result indicates that the Cu-Se compounds present in trace amounts of CIGS films hinder the (112) orientation and promotes the growth of the (220) orientation. As a result, the CIGS absorber layer with the Cu-poor composition and the (220)/(204) preferred orientation exhibited a drastically improved cell efficiency of 10.02%. (C) 2019 Published by Elsevier B.V.