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Issue 29, 2012
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Soft X-ray characterization of Zn1−xSnxOy electronic structure for thin film photovoltaics

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Abstract

Zinc tin oxide (Zn1−xSnxOy) has been proposed as an alternative buffer layer material to the toxic, and light narrow-bandgap CdS layer in CuIn1−x,GaxSe2 thin film solar cell modules. In this present study, synchrotron-based soft X-ray absorption and emission spectroscopies have been employed to probe the densities of states of intrinsic ZnO, Zn1−xSnxOy and SnOx thin films grown by atomic layer deposition. A distinct variation in the bandgap is observed with increasing Sn concentration, which has been confirmed independently by combined ellipsometry-reflectometry measurements. These data correlate directly to the open circuit potentials of corresponding solar cells, indicating that the buffer layer composition is associated with a modification of the band discontinuity at the CIGS interface. Resonantly excited emission spectra, which express the admixture of unoccupied O 2p with Zn 3d, 4s, and 4p states, reveal a strong suppression in the hybridization between the O 2p conduction band and the Zn 3d valence band with increasing Sn concentration.

Graphical abstract: Soft X-ray characterization of Zn1−xSnxOy electronic structure for thin film photovoltaics

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Article information


Submitted
01 May 2012
Accepted
24 May 2012
First published
21 Jun 2012

Phys. Chem. Chem. Phys., 2012,14, 10154-10159
Article type
Paper

Soft X-ray characterization of Zn1−xSnxOy electronic structure for thin film photovoltaics

M. Kapilashrami, C. X. Kronawitter, T. Törndahl, J. Lindahl, A. Hultqvist, W. Wang, C. Chang, S. S. Mao and J. Guo, Phys. Chem. Chem. Phys., 2012, 14, 10154
DOI: 10.1039/C2CP41394A

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