Cu(In,Ga)Se2 thin film solar cells with buffer layer alternative to CdS

Progress in fabricating Cu(In,Ga)Se₂ (CIGS) solar cells with ZnS(O,OH) buffer layers prepared by chemical bath deposition (CBD) is discussed in this paper. Such buffer layers could potentially replace CdS in the CIGS solar cell. Total-area conversion efficiency of up to 18.6% has been reported previously using ZnS(O,OH) prepared by CBD. The reported 100 nm CBD ZnS(O,OH) layer was prepared by at least three consecutive depositions, which would make it a relatively expensive replacement for CdS. The recent development of a ZnS(O,OH) layer that enabled to obtain high-efficiency devices using a single-layer CBD is reported in this paper. A 14.4%-efficient device is obtained by using one-layer CBD ZnS(O,OH) on commercial-grade Shell Solar Cu(In,Ga)(S,Se)₂ (CIGSS) absorber and an up to 17.4% device is obtained by using two-layer CBD ZnS(O,OH) on an NREL CIGS absorber.