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Compositional Dependence of Chemical and Electrical Properties in Cu sub(2)ZnSnS sub(4) Thin Films
Photovoltaic-grade thin-film solar cell absorber layers composed of Cu sub(2)ZnSnS sub(4) are most often prepared under nonstoichiometric compositions, in particular Cu-poor and Zn-rich conditions. The effects of compositional deviations on chemical and electrical properties of this material are und...
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Published in: | IEEE journal of photovoltaics 2016-07, Vol.6 (4), p.990-996 |
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Main Authors: | , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | Photovoltaic-grade thin-film solar cell absorber layers composed of Cu sub(2)ZnSnS sub(4) are most often prepared under nonstoichiometric compositions, in particular Cu-poor and Zn-rich conditions. The effects of compositional deviations on chemical and electrical properties of this material are under investigation and are expected to have a strong influence on final device performance. Herein, a study of variation in the cationic ratios (Cu/Zn, Cu/Sn) across a broad range and their effect on the properties of thin films is presented. After etching to remove the ZnS phase, the ratio of Cu/Zn is nearly constant between all the films, while there are significant variations in the ratio of Cu/Sn. This is correlated with changes in the chemical and electrical properties of these films, as determined by variable temperature conductivity measurements. The postetching composition and absence of Sn-S secondary phases points to multivalency of Sn in this material, in addition to other potential factors such as differences in grain size and defect formation. The Cu/Sn ratio is shown to strongly affect the electrical properties of films, in particular of the conductivity, grain boundary barriers, and localization length. |
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ISSN: | 2156-3403 |
DOI: | 10.1109/JPHOTOV.2016.2566888 |