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

Lorelle Mansfield, Michelle Mezher, Kimberly Horsley, Monika Blum, Robert Wieting, Lothar Weinhardt, Kannan Ramanathan, Clemens Heske

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21 Scopus Citations

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.

Original languageAmerican English
Article numberArticle No. 071601
Number of pages5
JournalApplied Physics Letters
Volume111
Issue number7
DOIs
StatePublished - 14 Aug 2017

Bibliographical note

Publisher Copyright:
© 2017 Author(s).

NREL Publication Number

  • NREL/JA-5K00-70059

Keywords

  • crystallography
  • deposition
  • electron spectroscopy
  • electronic structure
  • gallium
  • semiconducting selenium compounds

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