Band offsets at the CdS/CuInSe2 heterojunction

TLDR: In this article, first principles calculations yield for CdS/CuInSe2 ΔEc=+0.31 eV, hence, a type-I band alignment is assumed.

Abstract: The traditional explanation for the successful electron‐hole separation in CdS/CuInSe2 solar cells rests on the assumption of a type‐II band lineup: The conduction‐band minimum is assumed to be on the CdS window while the valence‐band maximum is assumed to be localized on the CuInSe2 absorber. This picture of negative conduction‐band offset ΔEc<0 was supported by the electron affinity rule, but was sharply contradicted by the more recent photoemission experiments of Nelson et al. for CdS/CuInSe2 yielding ΔEc=+1.08 eV. Our first principles calculations yield for CdS/CuInSe2 ΔEc=+0.31 eV, hence, a type‐I band alignment. We challenge the published experimental value as being in error and point to the need of revising current solar cell device models that assume ΔEc<0.