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Title: No Evidence for Passivation Effects of Na and K at Grain Boundaries in Polycrystalline Cu(In,Ga)Se2 Thin Films for Solar Cells

Abstract

Thin-film solar cells based on Cu(In,Ga)Se2 (CIGSe) absorber layers reach conversion efficiencies of above 20%. One key to this success is the incorporation of alkali metals, such as Na and K, into the surface and the volume of the CIGSe thin film. The present work discusses the impact of Na and K on the grain-boundary (GB) properties in CIGSe thin films, i.e., on the barriers for charge carriers, ..phi..b, and on the recombination velocities at the GBs, sGB. First, the physics connected with these two quantities as well as their impact on the device performance are revised, and then the values for the barrier heights and recombination velocities are provided from the literature. The sGB values are measured by means of a cathodoluminescence analysis of Na-/K-free CIGSe layers as well as on CIGSe layers on Mo/sapphire substrates, which are submitted to only NaF or only KF postdeposition treatments. Overall, passivating effects on GBs by neither Na nor K can be confirmed. The GB recombination velocities seem to remain on the same order of magnitude, in average about 10^3-10^4 cm s^-1, irrespective of whether CIGSe thin films are Na-/K-free or Na-/K-containing.

Authors:
 [1];  [1];  [1];  [1]; ORCiD logo [2];  [2];  [3];  [3]
  1. Helmholtz-Zentrum Berlin fur Materialien und Energie GmbH
  2. National Renewable Energy Laboratory (NREL), Golden, CO (United States)
  3. Martin-Luther-University Halle-Wittenberg
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1598130
Report Number(s):
NREL/JA-5K00-75990
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Journal Name:
Solar RRL
Additional Journal Information:
Journal Volume: 3; Journal Issue: 8
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 36 MATERIALS SCIENCE; Cu(In,Ga)Se2; grain boundaries; potassium; sodium; solar cells

Citation Formats

Abou-Ras, Daniel, Nikolaeva, Aleksandra, Caicedo Davila, Sebastian, Krause, Maximilian, Guthrey, Harvey L, Al-Jassim, Mowafak M, Morawski, Marcin, and Scheer, Roland. No Evidence for Passivation Effects of Na and K at Grain Boundaries in Polycrystalline Cu(In,Ga)Se2 Thin Films for Solar Cells. United States: N. p., 2019. Web. doi:10.1002/solr.201900095.
Abou-Ras, Daniel, Nikolaeva, Aleksandra, Caicedo Davila, Sebastian, Krause, Maximilian, Guthrey, Harvey L, Al-Jassim, Mowafak M, Morawski, Marcin, & Scheer, Roland. No Evidence for Passivation Effects of Na and K at Grain Boundaries in Polycrystalline Cu(In,Ga)Se2 Thin Films for Solar Cells. United States. doi:10.1002/solr.201900095.
Abou-Ras, Daniel, Nikolaeva, Aleksandra, Caicedo Davila, Sebastian, Krause, Maximilian, Guthrey, Harvey L, Al-Jassim, Mowafak M, Morawski, Marcin, and Scheer, Roland. Wed . "No Evidence for Passivation Effects of Na and K at Grain Boundaries in Polycrystalline Cu(In,Ga)Se2 Thin Films for Solar Cells". United States. doi:10.1002/solr.201900095.
@article{osti_1598130,
title = {No Evidence for Passivation Effects of Na and K at Grain Boundaries in Polycrystalline Cu(In,Ga)Se2 Thin Films for Solar Cells},
author = {Abou-Ras, Daniel and Nikolaeva, Aleksandra and Caicedo Davila, Sebastian and Krause, Maximilian and Guthrey, Harvey L and Al-Jassim, Mowafak M and Morawski, Marcin and Scheer, Roland},
abstractNote = {Thin-film solar cells based on Cu(In,Ga)Se2 (CIGSe) absorber layers reach conversion efficiencies of above 20%. One key to this success is the incorporation of alkali metals, such as Na and K, into the surface and the volume of the CIGSe thin film. The present work discusses the impact of Na and K on the grain-boundary (GB) properties in CIGSe thin films, i.e., on the barriers for charge carriers, ..phi..b, and on the recombination velocities at the GBs, sGB. First, the physics connected with these two quantities as well as their impact on the device performance are revised, and then the values for the barrier heights and recombination velocities are provided from the literature. The sGB values are measured by means of a cathodoluminescence analysis of Na-/K-free CIGSe layers as well as on CIGSe layers on Mo/sapphire substrates, which are submitted to only NaF or only KF postdeposition treatments. Overall, passivating effects on GBs by neither Na nor K can be confirmed. The GB recombination velocities seem to remain on the same order of magnitude, in average about 10^3-10^4 cm s^-1, irrespective of whether CIGSe thin films are Na-/K-free or Na-/K-containing.},
doi = {10.1002/solr.201900095},
journal = {Solar RRL},
number = 8,
volume = 3,
place = {United States},
year = {2019},
month = {5}
}

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