Defects in RbF-Treated Cu(In_xGa_1-x)Se₂ Solar Cells and Their Impact on V_OC

Cu(In,Ga)Se-2 solar cell efficiency is limited by V-OC due in large part to bulk defects limiting lifetime, but alkali treatments such as RbF recover some of the V-OC loss. In this work, defects in RbF-treated and untreated CIGS were quantitatively characterized using DLTS and DLOS, and three main defects were identified in each sample. The RbF-PDT resulted in a large decrease in the mid-gap trap concentration, which was accompanied by a large improvement in minority carrier lifetime. This lifetime improvement combined with a change in doping accounted for a significant portion of the V-OC improvement in the RbF CIGS.