Valence band alignment with a small spike at the CuI/CuInS2 interface

Abstract

From the point of view of the “doping pinning rule,” application of p-type buffer layer materials for CuInS2 solar cells may lead to record levels of cell efficiency due to an optimal band offset at the interface. Under simplified simulation conditions, an increase in efficiency of up to about 18% was predicted. Evaluation of the valence band offset between CuI and single crystalline CuInS2 by photoelectron spectroscopy displays a spike height of (0.1±0.2) eV, optimal for solar cell applications. The positions of the valence band edge were determined by assuming a parabolic distribution of the density of states.