Impact of a RbF post-deposition treatment on the chemical structure of wide-gap CuIn0.1Ga0.9Se2 thin-film solar cell absorber surfaces

A detailed characterization of the impact of a RbF post-deposition treatment (RbF-PDT) on the chemical structure of a wide-gap Cu(In, Ga)Se-2 thin-film solar cell absorber surface with a high Ga/(Ga + In) (GGI) ratio of 0.9 is presented. Using synchrotron- and lab-based x-ray photoelectron spectroscopy, as well as x-ray-excited Auger electron spectroscopy, we observe distinct differences to RbF-PDT on absorber surfaces with the common GGI of similar to 0.3. In particular, RbF-PDT reduces sodium and oxide content at the surface, while the copper concentration at the surface is not affected. We find no spectral evidence for the formation of a distinct Rb-In-Se surface layer. In addition, we observe that the GGI ratio at the surface is slightly decreased due to a reduction of the Ga and an increase in the In concentration, which may explain the observed improvement in the power conversion efficiency after the PDT (from 6.8% to 7.3%). (c) 2025 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).