Charge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}
Exploring the conduction mechanism in the chalcogenide perovskite BaZrS_{3} is of significant interest due to its potential suitability as a top absorber layer in silicon-based tandem solar cells and other optoelectronic applications. Theoretical and experimental studies anticipate native ambipolar...
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| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
American Physical Society
2025-07-01
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| Series: | PRX Energy |
| Online Access: | http://doi.org/10.1103/t7ns-99dk |
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| Summary: | Exploring the conduction mechanism in the chalcogenide perovskite BaZrS_{3} is of significant interest due to its potential suitability as a top absorber layer in silicon-based tandem solar cells and other optoelectronic applications. Theoretical and experimental studies anticipate native ambipolar doping in BaZrS_{3}, although experimental validation remains limited. This study reveals a transition from highly insulating behavior to n-type conductivity (approximately 100 S/cm) in BaZrS_{3} thin films through annealing in an S-poor environment. BaZrS_{3} thin films are synthesized via a two-step process: co-sputtering of Ba-Zr followed by sulfurization at 600^{∘}C, and subsequent annealing in high vacuum. Ultraviolet-visible spectroscopy measurements reveal a red shift of approximately 100 meV in the band gap concurrent with sample-color darkening after vacuum annealing. The increase in defect density from the order of 10^{17} to 10^{21}cm^{−3} with vacuum annealing, coupled with the low activation energy (approximately 8 meV), and the n-type character of the defects, strongly suggests that sulfur vacancies (V_{S}) are responsible for the n-type doping, in agreement with theoretical predictions. Temperature-dependent Hall measurement shows that phonon scattering governs charge transport at room temperature in BaZrS_{3} films and that S vacancies are shallow donor defects acting as a weak impurity metal. The shift of the valence-band maximum (VBM) with respect to the Fermi level, quantified by hard x-ray photoelectron spectroscopy (Ga Kα, 9.25 keV), further corroborates the induced n type of conductivity in annealed samples. Our findings indicate that vacuum annealing induces V_{S} defects that dominate charge transport, resulting in n-type conductivity in BaZrS_{3} under S-poor conditions. These discoveries will inform important design choices, such as selecting appropriate contact materials, for integrating BaZrS_{3} into solar cell structures or other devices. |
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| ISSN: | 2768-5608 |