Title

KF Post-deposition Treatment of Industrial Cu(In, Ga)(S, Se)2 Thin-film Surfaces: Modifying the Chemical and Electronic Structure

Document Type

Article

Publication Date

1-1-2017

Publication Title

Applied Physics Letters

Volume

111

Issue

7

Abstract

The chemical and electronic structures of industrial chalcopyrite photovoltaic absorbers after KF post-deposition treatment (KF-PDT) are investigated using electron spectroscopies to probe the occupied and unoccupied electronic states. In contrast to a variety of recent publications on the impact of KF-PDT, this study focuses on industrial Cu(In,Ga)(S,Se)2 absorbers that also contain sulfur at the surface. We find that the KF-PDT removes surface adsorbates and oxides and also observe a change in the S/Se ratio. Furthermore, the KF-PDT leads to a Cu reduction at the surface but to a much lower degree than the strongly Cu-depleted or even Cu-free surfaces reported for (non-industrial) sulfur-free Cu(In,Ga)Se2 absorbers. The valence band maximum at the surface is found at a lower energy compared to the untreated absorber, and the conduction band minimum is found at a higher energy, overall revealing a widening of the bandgap in the surface region. © 2017 Author(s).

Language

english

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