Surface characterization of epitaxial Cu-rich CuInSe₂ absorbers

Abstract

We investigated the electrical properties of epitaxial Cu-rich CuInSe2 by Kelvin probe force microscopy (KPFM) under ambient and ultra-high vacuum conditions. We first measured the sample under ambient conditions before and after potassium cyanide (KCN) etching. In both cases, we do not see any substantial contrast in the surface potential data; furthermore, after the KCN etching we observed outgrowths with a height around 2nm over the sample surface. On the other hand, the KPFM measurements under ultra-high vacuum conditions show a work function dependence according to the surface orientation of the Cu-rich CuInSe2 crystal. Our results show the possibility to increase the efficiency of epitaxial Cu-rich CuInSe2 by growing the materials in the appropriated surface orientation where the variations in work function are reduced.

The impact of Kelvin probe force microscopy operation modes and environment on grain boundary band bending in perovskite and Cu(In,Ga)Se2 solar cells

“…In the FM-case (Fig. 4 (d)) some topographic features, namely, the (112) and (312) facets showed higher workfunction values compared to the other facets as reported previously [73]. In AM-KPFM (Fig.…”

“…5 shows topography (a-d) and workfunction maps (e-h) of the same single-crystal CISe absorber measured with different levels of surface contamination. The fresh sample exhibited the facet-dependent contrast, as discussed in the section 4.2 and detailed in Lanzoni et al [73]. After 20 months in UHV, this sample was measured again (Fig.…”