Investigation of RbF post-deposition treatment onto $Cu(In,Ga)Se_2$ thin-films and solar cells

Abstract

The effects induced by alkali elements are responsible for the last decade of significant efficiency increase in CIGS world record cells. The last world record publication revealed that cells treated by RbF post-deposition treatment (PDT) outperform those treated with KF, which is the previous record cells. Nevertheless, little is known about the fundamentals of RbF-PDT on the material and electrical properties of the three-stage co-evaporated CIGS solar devices from the literature. In this work, we investigate the impact of RbF post-deposition treatment (PDT) on the material and device properties of $Cu(In,Ga)Se_2$ (CIGS) thin-film solar cells. An optimum of the PDT is found increasing the efficiency by about 0.8% compared to our Rb-free reference. We also investigate the compositional and morphological modifications due to RbF-PDT using Scanning electron microscopy (SEM), grazing incidence X-ray diffraction (GIXRD) and secondary ion mass spectrometry (SIMS). Moreover, we observe a enhancement of electrical properties by photoluminescence spectroscopy (PL) and drive-level capacitance profiling (DLCP).