Electronic structure and defect states in bismuth and antimony sulphides identified by energy-resolved electrochemical impedance spectroscopy
One of the reasons chalcogenide-based photovoltaic solar cells do not yet meet the expected high-power conversion efficiencies is a lack of understanding of their electronic structure, and particularly the nature of the point defects in the absorber materials. We show that the density of states (DOS...
| Autores: | , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2025 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/432969 |
| Acceso en línea: | https://hdl.handle.net/2117/432969 https://dx.doi.org/10.1088/2515-7655/add59f |
| Access Level: | acceso abierto |
| Palabra clave: | Chalcogenides Electronic structure Density of states Valence band maximum Conduction band minimum Bandgap Defects Àrees temàtiques de la UPC::Enginyeria electrònica |
| Sumario: | One of the reasons chalcogenide-based photovoltaic solar cells do not yet meet the expected high-power conversion efficiencies is a lack of understanding of their electronic structure, and particularly the nature of the point defects in the absorber materials. We show that the density of states (DOS) of the characteristic features of the electronic structure, such as band edges and energy distribution of defects, can be obtained experimentally by energy-resolved electrochemical impedance spectroscopy (ER-EIS) in a technically simple and quick way. The ER-EIS data correlate well with theoretical density functional theory (DFT) calculations. The ER-EIS reveals that Bi2S3, has only shallow defects near the conduction band minimum (CBM). In Sb2S3, ER-EIS also shows deep defect states, which can be the cause of the low electrical conductivity of Sb2S3 and lower than theoretically possible power conversion efficiency of Sb2S3-based solar cells. A dominant sulphur vacancy defect was identified in Bi- and Sb-chalcogenides. In the (SbxBi(1-x))2S3 ternary alloy series, a gradual transformation of CBM and defect states in the band gap was observed. Notably, a 1:9 ratio of Bi:Sb cations already transforms the deep sulphur defects into shallow ones while keeping the band edges similar to those of the pristine Sb2S3. It can provide a novel strategy for healing the deep defect states in Sb2S3, a crucial step for boosting solar cell performance. |
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