The effect of Na on the electronic properties of Cu(In,Ga)Se2 thin films: A local-probe study

D. Azulay; D. Abou-Ras; I. Popov; I. Balberg; O. Millo

doi:10.1002/pssr.201600058

The effect of Na on the electronic properties of Cu(In,Ga)Se₂ thin films: A local-probe study

D. Azulay^*, D. Abou-Ras, I. Popov, I. Balberg, O. Millo

^*Corresponding author for this work

Racah Institute of Physics

Research output: Contribution to journal › Article › peer-review

10 Scopus citations

Abstract

We investigated the effect of Na incorporation on the electronic properties of polycrystalline CuIn_0.7Ga_0.3Se₂ thin films using scanning tunneling microscopy and spectroscopy. The tunneling spectra indicate a reduced in-gap density of states at grain boundaries and reveal a downward band-bending in Na-rich grain boundaries with respect to the adjacent grains, in agreement with our conductive atomic force microscopy data. It thus appears that Na passivates deep-level defects at grain boundaries and induces a downward band-bending there. Moreover, we provide evidence that Na passivates mainly Cu vacancy related defects. We suggest that the grain-boundary passivation, which reduces the recombination rate of photogenerated carriers, is at least of major importance in the well known Na-induced improvement in the efficiency of the corresponding solar cells.

Original language	American English
Pages (from-to)	448-452
Number of pages	5
Journal	Physica Status Solidi - Rapid Research Letters
Volume	10
Issue number	6
DOIs	https://doi.org/10.1002/pssr.201600058
State	Published - 1 Jun 2016

Bibliographical note

Funding Information:
The authors are grateful to Thorsten Rissom, HZB, for providing the CIGSe solar cells, to Bianca Bunn, Carola Ferber, Michael Kirsch, Tim Münchenberg, and Jan Schniebs for their help with the solar-cell production. This work was supported in part by the Israel Science Foundation, the Harry de Jur Chair in Applied Science (O.M.) and the Enrique Berman Chair in Solar Energy Research (I.B.).

Publisher Copyright:
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Keywords

Cu(In,Ga)Se
electronic properties
grain boundaries
scanning tunneling spectroscopy

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10.1002/pssr.201600058

Cite this

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title = "The effect of Na on the electronic properties of Cu(In,Ga)Se2 thin films: A local-probe study",

abstract = "We investigated the effect of Na incorporation on the electronic properties of polycrystalline CuIn0.7Ga0.3Se2 thin films using scanning tunneling microscopy and spectroscopy. The tunneling spectra indicate a reduced in-gap density of states at grain boundaries and reveal a downward band-bending in Na-rich grain boundaries with respect to the adjacent grains, in agreement with our conductive atomic force microscopy data. It thus appears that Na passivates deep-level defects at grain boundaries and induces a downward band-bending there. Moreover, we provide evidence that Na passivates mainly Cu vacancy related defects. We suggest that the grain-boundary passivation, which reduces the recombination rate of photogenerated carriers, is at least of major importance in the well known Na-induced improvement in the efficiency of the corresponding solar cells.",

keywords = "Cu(In,Ga)Se, electronic properties, grain boundaries, scanning tunneling spectroscopy",

author = "D. Azulay and D. Abou-Ras and I. Popov and I. Balberg and O. Millo",

note = "Funding Information: The authors are grateful to Thorsten Rissom, HZB, for providing the CIGSe solar cells, to Bianca Bunn, Carola Ferber, Michael Kirsch, Tim M{\"u}nchenberg, and Jan Schniebs for their help with the solar-cell production. This work was supported in part by the Israel Science Foundation, the Harry de Jur Chair in Applied Science (O.M.) and the Enrique Berman Chair in Solar Energy Research (I.B.). Publisher Copyright: {\textcopyright} 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim",

year = "2016",

month = jun,

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doi = "10.1002/pssr.201600058",

language = "American English",

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T1 - The effect of Na on the electronic properties of Cu(In,Ga)Se2 thin films

T2 - A local-probe study

AU - Azulay, D.

AU - Abou-Ras, D.

AU - Popov, I.

AU - Balberg, I.

AU - Millo, O.

N1 - Funding Information: The authors are grateful to Thorsten Rissom, HZB, for providing the CIGSe solar cells, to Bianca Bunn, Carola Ferber, Michael Kirsch, Tim Münchenberg, and Jan Schniebs for their help with the solar-cell production. This work was supported in part by the Israel Science Foundation, the Harry de Jur Chair in Applied Science (O.M.) and the Enrique Berman Chair in Solar Energy Research (I.B.). Publisher Copyright: © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

PY - 2016/6/1

Y1 - 2016/6/1

N2 - We investigated the effect of Na incorporation on the electronic properties of polycrystalline CuIn0.7Ga0.3Se2 thin films using scanning tunneling microscopy and spectroscopy. The tunneling spectra indicate a reduced in-gap density of states at grain boundaries and reveal a downward band-bending in Na-rich grain boundaries with respect to the adjacent grains, in agreement with our conductive atomic force microscopy data. It thus appears that Na passivates deep-level defects at grain boundaries and induces a downward band-bending there. Moreover, we provide evidence that Na passivates mainly Cu vacancy related defects. We suggest that the grain-boundary passivation, which reduces the recombination rate of photogenerated carriers, is at least of major importance in the well known Na-induced improvement in the efficiency of the corresponding solar cells.

AB - We investigated the effect of Na incorporation on the electronic properties of polycrystalline CuIn0.7Ga0.3Se2 thin films using scanning tunneling microscopy and spectroscopy. The tunneling spectra indicate a reduced in-gap density of states at grain boundaries and reveal a downward band-bending in Na-rich grain boundaries with respect to the adjacent grains, in agreement with our conductive atomic force microscopy data. It thus appears that Na passivates deep-level defects at grain boundaries and induces a downward band-bending there. Moreover, we provide evidence that Na passivates mainly Cu vacancy related defects. We suggest that the grain-boundary passivation, which reduces the recombination rate of photogenerated carriers, is at least of major importance in the well known Na-induced improvement in the efficiency of the corresponding solar cells.

KW - Cu(In,Ga)Se

KW - electronic properties

KW - grain boundaries

KW - scanning tunneling spectroscopy

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