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Title: Impact of Wide-Ranging Nanoscale Chemistry on Band Structure at Cu(In, Ga)Se 2 Grain Boundaries

The relative chemistry from grain interiors to grain boundaries help explain why grain boundaries may be beneficial, detrimental or benign towards device performance. 3D Nanoscale chemical analysis extracted from atom probe tomography (APT) (10’s of parts-per-million chemical sensitivity and sub-nanometer spatial resolution) of twenty grain boundaries in a high-efficiency Cu(In, Ga)Se 2 solar cell shows the matrix and alkali concentrations are wide-ranging. The concentration profiles are then related to band structure which provide a unique insight into grain boundary electrical performance. Fluctuating Cu, In and Ga concentrations result in a wide distribution of potential barriers at the valence band maximum (VBM) (-10 to -160 meV) and the conduction band minimum (CBM) (-20 to -70 meV). Furthermore, Na and K segregation is not correlated to hampering donors, (In, Ga) Cu and V Se, contrary to what has been previously reported. In addition, Na and K are predicted to be n-type dopants at grain boundaries. An overall band structure at grain boundaries is presented.
Authors:
 [1] ;  [2] ;  [3] ;  [3] ;  [3]
  1. Colorado School of Mines, Golden, CO (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States). National Center for Photovoltaics
  3. Colorado School of Mines, Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5K00-70450
Journal ID: ISSN 2045-2322
Grant/Contract Number:
AC36-08GO28308; 1040456
Type:
Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; electronic devices; mass spectrometry; photonic devices; solar cells
OSTI Identifier:
1407464