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Point defects in Cu2ZnSnSe4 (CZTSe): Resonant X‐ray diffraction study of the low‐temperature order/disorder transition
The interest in Cu2ZnSn(S,Se)4 (CZTS) for photovoltaic applications is motivated by similarities to Cu(In,Ga)Se2 while being comprised of non‐toxic and earth abundant elements. However, CZTS suffers from a Voc deficit, where the Voc is much lower than expected based on the band gap, which may be the...
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Published in: | Physica Status Solidi B. Basic Solid State Physics 2017-09, Vol.254 (9), p.n/a |
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Main Authors: | , , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | The interest in Cu2ZnSn(S,Se)4 (CZTS) for photovoltaic applications is motivated by similarities to Cu(In,Ga)Se2 while being comprised of non‐toxic and earth abundant elements. However, CZTS suffers from a Voc deficit, where the Voc is much lower than expected based on the band gap, which may be the result of a high concentration of point‐defects in the CZTS lattice. Recently, reports have observed a low‐temperature order/disorder transition by Raman and optical spectroscopies in CZTS films and is reported to describe the ordering of Cu and Zn atoms in the CZTS crystal structure. To directly determine the level of Cu/Zn ordering, we have used resonant‐XRD, a site, and element specific probe of long range order. We used CZTSe films annealed just below and quenched from just above the transition temperature; based on previous work, the Cu and Zn should be ordered and highly disordered, respectively. Our data show that there is some Cu/Zn ordering near the low temperature transition but significantly less than high chemical order expected from Raman. To understand both our resonant‐XRD results and the Raman results, we present a structural model that involves antiphase domain boundaries and accommodates the excess Zn within the CZTS lattice.
This work reports a resonant X‐ray diffraction (REXD) study of Cu/Zn order in heat‐treated Cu2ZnSnSe4 thin films. Here differences in Cu/Zn ordering measured by Raman spectroscopy are discussed and a hypothesis for this discrepancy is presented. |
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ISSN: | 0370-1972 1521-3951 |
DOI: | 10.1002/pssb.201700156 |