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Title: KF post-deposition treatment of industrial Cu(In, Ga)(S, Se) 2 thin-film surfaces: Modifying the chemical and electronic structure

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)Se 2 absorbers. Furthermore, 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.
Authors:
 [1] ; ORCiD logo [2] ;  [3] ;  [1] ;  [4] ;  [5] ;  [4] ; ORCiD logo [5]
  1. Univ. of Nevada, Las Vegas (UNLV), Las Vegas, NV (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. Univ. of Nevada, Las Vegas (UNLV), Las Vegas, NV (United States); Univ. of Hawaii at Manoa, Honolulu, HI (United States)
  4. STION, San Jose, CA (United States)
  5. Univ. of Nevada, Las Vegas (UNLV), Las Vegas, NV (United States); Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen (Germany); Karlsruhe Institute of Technology (KIT), Karlsruhe (Germany)
Publication Date:
Report Number(s):
NREL/JA-5K00-70059
Journal ID: ISSN 0003-6951
Grant/Contract Number:
AC36-08GO28308; ZEJ-2-22082-0.1
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 111; Journal Issue: 7; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Solar Energy Technologies Office (EE-4S), SunShot Foundational Program to Advance Cell Efficiency (F-PACE); USDOE
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; crystallography; deposition; electron spectroscopy; electronic structure; gallium; semiconducting selenium compounds
OSTI Identifier:
1379465
Alternate Identifier(s):
OSTI ID: 1374925