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Title: Physics of grain boundaries in polycrystalline photovoltaic semiconductors

Abstract

Thin-film solar cells based on polycrystalline Cu(In,Ga)Se 2 (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film polycrystalline solar cells can reach such high efficiencies despite containing a high density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this study, we review our atomistic theoretical understanding of the physics of grain boundaries in CIGS and CdTe absorbers. We show that intrinsic GBs with dislocation cores exhibit deep gap states in both CIGS and CdTe. Although, in each solar cell device, the GBs can be chemically modified to improve their photovoltaic properties. In CIGS cells, GBs are found to be Cu-rich and contain O impurities. Density-functional theory calculations reveal that such chemical changes within GBs can remove most of the unwanted gap states. In CdTe cells, GBs are found to contain a high concentration of Cl atoms. Cl atoms donate electrons, creating n-type GBs between p-type CdTe grains, forming local p-n-p junctions along GBs. This leads to enhanced current collections. In conclusion, chemical modification of GBs allows for high efficiency polycrystalline CIGS and CdTe thin-film solar cells.

Authors:
 [1];  [1];  [1];  [1];  [1];  [2];  [3];  [4];  [5];  [5];  [5];  [6];  [5]
  1. Univ. of Toledo, OH (United States). Wright Center for Photovoltaics Innovation and Commercialization (PVIC)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Science (CNMS)
  4. Univ. of Toledo, OH (United States). Wright Center for Photovoltaics Innovation and Commercialization (PVIC) ; National Renewable Energy Lab. (NREL), Golden, CO (United States)
  5. National Renewable Energy Lab. (NREL), Golden, CO (United States)
  6. Univ. of Tennessee, Knoxville, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1265414
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 117; Journal Issue: 11; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 14 SOLAR ENERGY

Citation Formats

Yan, Yanfa, Yin, Wan-Jian, Wu, Yelong, Shi, Tingting, Paudel, Naba R., Li, Chen, Poplawsky, Jonathan D., Wang, Zhiwei, Moseley, John, Guthrey, Harvey, Moutinho, Helio, Pennycook, Stephen J., and Al-jassim, Mowafak. Physics of grain boundaries in polycrystalline photovoltaic semiconductors. United States: N. p., 2015. Web. doi:10.1063/1.4913833.
Yan, Yanfa, Yin, Wan-Jian, Wu, Yelong, Shi, Tingting, Paudel, Naba R., Li, Chen, Poplawsky, Jonathan D., Wang, Zhiwei, Moseley, John, Guthrey, Harvey, Moutinho, Helio, Pennycook, Stephen J., & Al-jassim, Mowafak. Physics of grain boundaries in polycrystalline photovoltaic semiconductors. United States. doi:10.1063/1.4913833.
Yan, Yanfa, Yin, Wan-Jian, Wu, Yelong, Shi, Tingting, Paudel, Naba R., Li, Chen, Poplawsky, Jonathan D., Wang, Zhiwei, Moseley, John, Guthrey, Harvey, Moutinho, Helio, Pennycook, Stephen J., and Al-jassim, Mowafak. Mon . "Physics of grain boundaries in polycrystalline photovoltaic semiconductors". United States. doi:10.1063/1.4913833. https://www.osti.gov/servlets/purl/1265414.
@article{osti_1265414,
title = {Physics of grain boundaries in polycrystalline photovoltaic semiconductors},
author = {Yan, Yanfa and Yin, Wan-Jian and Wu, Yelong and Shi, Tingting and Paudel, Naba R. and Li, Chen and Poplawsky, Jonathan D. and Wang, Zhiwei and Moseley, John and Guthrey, Harvey and Moutinho, Helio and Pennycook, Stephen J. and Al-jassim, Mowafak},
abstractNote = {Thin-film solar cells based on polycrystalline Cu(In,Ga)Se2 (CIGS) and CdTe photovoltaic semiconductors have reached remarkable laboratory efficiencies. It is surprising that these thin-film polycrystalline solar cells can reach such high efficiencies despite containing a high density of grain boundaries (GBs), which would seem likely to be nonradiative recombination centers for photo-generated carriers. In this study, we review our atomistic theoretical understanding of the physics of grain boundaries in CIGS and CdTe absorbers. We show that intrinsic GBs with dislocation cores exhibit deep gap states in both CIGS and CdTe. Although, in each solar cell device, the GBs can be chemically modified to improve their photovoltaic properties. In CIGS cells, GBs are found to be Cu-rich and contain O impurities. Density-functional theory calculations reveal that such chemical changes within GBs can remove most of the unwanted gap states. In CdTe cells, GBs are found to contain a high concentration of Cl atoms. Cl atoms donate electrons, creating n-type GBs between p-type CdTe grains, forming local p-n-p junctions along GBs. This leads to enhanced current collections. In conclusion, chemical modification of GBs allows for high efficiency polycrystalline CIGS and CdTe thin-film solar cells.},
doi = {10.1063/1.4913833},
journal = {Journal of Applied Physics},
number = 11,
volume = 117,
place = {United States},
year = {Mon Mar 16 00:00:00 EDT 2015},
month = {Mon Mar 16 00:00:00 EDT 2015}
}

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