Cross-sectional Kelvin probe force microscopy on Cu(In,Ga)Se2 solar cells: Influence of RbF and KF post-deposition treatment on the surface potential of the absorber layer

Abstract

Post-deposition treatment (PDT) of the absorber layer with alkali fluorides has led to a significant increase in the efficiency of Cu(In,Ga)Se2 (CIGS) thin-film solar cells. In this contribution, we investigate the influence of alkali PDTs on the absorber's surface potential by means of Kelvin probe force microscopy (KPFM). To this end, we perform KPFM on cross sections of complete CIGS solar cells. To improve the reliability of the measurement procedure, we deposit a gold layer on top of the solar cell as a reference layer. Using this approach, we study the influence of RbF and KF PDT on the absorber's surface potential for CIGS solar cells with different absorber and buffer compositions. In all cases, an increased surface potential of the cross section of the absorber layer is measured for the cells with PDT.