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Title: Band gap temperature-dependence and exciton-like state in copper antimony sulphide, CuSbS 2

The temperature-dependence of the band gap of the proposed photovoltaic absorber copper antimony sulphide (CuSbS 2) has been studied by Fourier-transform infrared spectroscopy. The direct gap rises from 1.608 to 1.694 eV between 300 and 4.2 K. Below 200 K an exciton-like feature develops above the absorption edge at 1.82 eV. First-principles calculations evaluate band structure, band symmetries, and dipole selection rules, suggesting distinctly enhanced absorption for certain excitonic optical transitions. Striking consistency is seen between predicted dielectric and absorption spectra and those determined by ellipsometry, which reveal rapidly strengthening absorption passing 105 cm-1 at 2.2 eV. Furthermore, these results suggest beneficial photovoltaic performance due to strong optical absorption arising from unusually strong electron-hole interactions in polycrystalline CuSbS 2 material.
 [1] ;  [2] ;  [3] ; ORCiD logo [4] ;  [1] ; ORCiD logo [1] ;  [5] ;  [6] ; ORCiD logo [5] ; ORCiD logo [7] ; ORCiD logo [1]
  1. Stephenson Institute for Renewable Energy, Liverpool (United Kingdom)
  2. Univ. College London, London (United Kingdom)
  3. Norwegian Univ. of Science and Technology, Trondheim (Norway)
  4. Wroclaw Univ. of Technology, Wroclaw (Poland)
  5. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  6. Univ. of Liverpool, Liverpool (United Kingdom)
  7. Univ. College London, London (United Kingdom); Diamond Light Source Ltd., Didcot (United Kingdom)
Publication Date:
Report Number(s):
Journal ID: ISSN 2166-532X
Grant/Contract Number:
Accepted Manuscript
Journal Name:
APL Materials
Additional Journal Information:
Journal Volume: 6; Journal Issue: 8; Journal ID: ISSN 2166-532X
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)
Country of Publication:
United States
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; dielectrics; excitons; absorption spectroscopy; electromagnetic transitions; optical absorption; band gap; band structure; solar energy
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1441077