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Title: Nanoscale insight into the p-n junction of alkali-incorporated Cu(In,Ga)Se 2 solar cells

The effects of alkali diffusion and post-deposition treatment in three-stage processed Cu(In,Ga)Se 2 solar cells are examined by using atom probe tomography and electrical property measurements. Cells, for which the substrate was treated at 650 °C to induce alkali diffusion from the substrate prior to absorber deposition, exhibited high open-circuit voltage (758 mV) and efficiency (18.2%) and also exhibited a 50 to 100-nm-thick ordered vacancy compound layer at the metallurgical junction. Surprisingly, these high-temperature samples exhibited higher concentrations of K at the junction (1.8 at.%) than post-deposition treatment samples (0.4 at.%). A model that uses Ga/(Ga + In) and Cu/(Ga + In) profiles to predict bandgaps (+/-17.9 meV) of 22 Cu(In,Ga)Se2 solar cells reported in literature was discussed and ultimately used to predict band properties at the nanoscale by using atom probe tomography data. The high-temperature samples exhibited a greater drop in the valence band maximum (200 meV) due to a lower Cu/(Ga + In) ratio than the post-deposition treatment samples. There was an anticorrelation of K concentrations and Cu/(Ga + In) ratios for all samples, regardless of processing conditions. In conclusion, changes in elemental profiles at the active junctions correlate well with the electrical behaviour of these devices.
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [2] ;  [3] ;  [3]
  1. National Renewable Energy Lab. (NREL), Golden, CO (United States); Colorado School of Mines, Golden, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. Colorado School of Mines, Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5K00-68439
Journal ID: ISSN 1062-7995
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Progress in Photovoltaics
Additional Journal Information:
Journal Volume: 25; Journal Issue: 9; Journal ID: ISSN 1062-7995
Publisher:
Wiley
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 77 NANOSCIENCE AND NANOTECHNOLOGY; bandgap; alkali; chalcogenides; atom probe tomography
OSTI Identifier:
1375623
Alternate Identifier(s):
OSTI ID: 1374459

Stokes, Adam, Al-Jassim, Mowafak, Norman, Andrew, Diercks, David, and Gorman, Brian. Nanoscale insight into the p-n junction of alkali-incorporated Cu(In,Ga)Se2 solar cells. United States: N. p., Web. doi:10.1002/pip.2883.
Stokes, Adam, Al-Jassim, Mowafak, Norman, Andrew, Diercks, David, & Gorman, Brian. Nanoscale insight into the p-n junction of alkali-incorporated Cu(In,Ga)Se2 solar cells. United States. doi:10.1002/pip.2883.
Stokes, Adam, Al-Jassim, Mowafak, Norman, Andrew, Diercks, David, and Gorman, Brian. 2017. "Nanoscale insight into the p-n junction of alkali-incorporated Cu(In,Ga)Se2 solar cells". United States. doi:10.1002/pip.2883. https://www.osti.gov/servlets/purl/1375623.
@article{osti_1375623,
title = {Nanoscale insight into the p-n junction of alkali-incorporated Cu(In,Ga)Se2 solar cells},
author = {Stokes, Adam and Al-Jassim, Mowafak and Norman, Andrew and Diercks, David and Gorman, Brian},
abstractNote = {The effects of alkali diffusion and post-deposition treatment in three-stage processed Cu(In,Ga)Se2 solar cells are examined by using atom probe tomography and electrical property measurements. Cells, for which the substrate was treated at 650 °C to induce alkali diffusion from the substrate prior to absorber deposition, exhibited high open-circuit voltage (758 mV) and efficiency (18.2%) and also exhibited a 50 to 100-nm-thick ordered vacancy compound layer at the metallurgical junction. Surprisingly, these high-temperature samples exhibited higher concentrations of K at the junction (1.8 at.%) than post-deposition treatment samples (0.4 at.%). A model that uses Ga/(Ga + In) and Cu/(Ga + In) profiles to predict bandgaps (+/-17.9 meV) of 22 Cu(In,Ga)Se2 solar cells reported in literature was discussed and ultimately used to predict band properties at the nanoscale by using atom probe tomography data. The high-temperature samples exhibited a greater drop in the valence band maximum (200 meV) due to a lower Cu/(Ga + In) ratio than the post-deposition treatment samples. There was an anticorrelation of K concentrations and Cu/(Ga + In) ratios for all samples, regardless of processing conditions. In conclusion, changes in elemental profiles at the active junctions correlate well with the electrical behaviour of these devices.},
doi = {10.1002/pip.2883},
journal = {Progress in Photovoltaics},
number = 9,
volume = 25,
place = {United States},
year = {2017},
month = {4}
}