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: Garima Aggarwal, Adeem Saeed Mirza, Stefania Riva, Corrado Comparotto, Robert J. W. Frost, Soham Mukherjee, Monica Morales-Masis, Håkan Rensmo, Jonathan Staaf Scragg
Format: Article
Language:English
Published: American Physical Society 2025-07-01
Series:PRX Energy
Online Access:http://doi.org/10.1103/t7ns-99dk
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author Garima Aggarwal
Adeem Saeed Mirza
Stefania Riva
Corrado Comparotto
Robert J. W. Frost
Soham Mukherjee
Monica Morales-Masis
Håkan Rensmo
Jonathan Staaf Scragg
author_facet Garima Aggarwal
Adeem Saeed Mirza
Stefania Riva
Corrado Comparotto
Robert J. W. Frost
Soham Mukherjee
Monica Morales-Masis
Håkan Rensmo
Jonathan Staaf Scragg
author_sort Garima Aggarwal
collection DOAJ
description 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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spelling doaj-art-9ea4d51448ef401c8361818ad968fd6c2025-08-20T03:50:16ZengAmerican Physical SocietyPRX Energy2768-56082025-07-014303300110.1103/t7ns-99dkCharge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}Garima AggarwalAdeem Saeed MirzaStefania RivaCorrado ComparottoRobert J. W. FrostSoham MukherjeeMonica Morales-MasisHåkan RensmoJonathan Staaf ScraggExploring 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.http://doi.org/10.1103/t7ns-99dk
spellingShingle Garima Aggarwal
Adeem Saeed Mirza
Stefania Riva
Corrado Comparotto
Robert J. W. Frost
Soham Mukherjee
Monica Morales-Masis
Håkan Rensmo
Jonathan Staaf Scragg
Charge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}
PRX Energy
title Charge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}
title_full Charge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}
title_fullStr Charge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}
title_full_unstemmed Charge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}
title_short Charge Transport and Defects in Sulfur-Deficient Chalcogenide Perovskite BaZrS_{3}
title_sort charge transport and defects in sulfur deficient chalcogenide perovskite bazrs 3
url http://doi.org/10.1103/t7ns-99dk
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