A Comparative Study of (Cd,Zn)S Buffer Layers for Cu(In,Ga)Se₂ Solar Panels Fabricated by Chemical Bath and Surface Deposition Methods

Scale-up to large-area Cu(In,Ga)Se₂ (CIGS) solar panels is proving to be much more complicated than expected. Particularly, the non-vacuum wet-chemical buffer layer formation step has remained a challenge and has acted as a bottleneck in industrial implementations for mass-production. This technical note deals with the comparative analysis of the impact on different methodologies for the buffer layer formation on CIGS solar panels. Cd(1-x)ZnxS ((Cd,Zn)S) thin films were prepared by chemical bath deposition (CBD), and chemical surface deposition (CSD) for 24-inch (37 cm × 47 cm) patterned CIGS solar panel applications. Buffer layers deposited by the CBD method showed a higher Zn addition level and transmittance than those prepared by the CSD technique due to the predominant cluster-by-cluster growth mechanism, and this induced a difference in the solar cell performance, consequently. The CIGS panels with (Cd,Zn)S buffer layer formed by the CBD method showed a 0.5% point higher conversion efficiency than that of panels with a conventional CdS buffer layer, owing to the increased current density and open-circuit voltage. The samples with the CSD (Cd,Zn)S buffer layer also increased the conversion efficiency with 0.3% point than conventional panels, but mainly due to the increased fill factor.