Repercussion of sulfur-doping on surface morphology and charge transport in Cs₃Bi₂I₉ perovskite inverted solar cells
Author Identifier (ORCID)
Abstract
Lead-free cesium bismuth iodide (Cs₃Bi₂I₉) has emerged as a promising alternative to Pb-based perovskite absorbers; however, its photovoltaic potential remains constrained by a wide bandgap and unfavorable film morphology. Here, we report a novel mixed-anion engineering strategy for the fabrication of CsBiSI₂ thin films through the incorporation of dimethylammonium bismuth sulfide (DMABiS₂) as a sulfur precursor, combined with toluene-assisted antisolvent processing to promote controlled crystallization and structural reorganization. The resulting films, prepared via a simple spin-coating route, exhibit markedly improved surface coverage, enlarged grain size, and enhanced thickness uniformity relative to pristine Cs₃Bi₂I₉, as confirmed by AFM and FESEM analyses. X-ray diffraction and Raman spectroscopy further reveal the formation of Bi–S bonding and the evolution of a more interconnected lattice, evidencing successful anion substitution and a transition from a zero-dimensional framework toward higher structural connectivity. This structural modulation leads to a reduced optical bandgap from 2.08 to 1.76 eV and an extended absorption edge, thereby enhancing visible-light harvesting. When implemented in inverted solar cells with the architecture ITO/NiOₓ/perovskite/PC₆₁BM/BCP/Ag, the mixed-anion films deliver simultaneous improvements in current density, open-circuit voltage, fill factor, and power conversion efficiency, increasing from 2.25% to 3.40%. These findings demonstrate that sulfur incorporation represents an effective route to concurrently optimize the morphology, optoelectronic properties, and device performance of bismuth-based lead-free perovskite absorbers.
Keywords
0D structure, bandgap tuning, chalcohalide, lead-free perovskites, morphology, photovoltaic effect
Document Type
Journal Article
Date of Publication
9-15-2026
Article Number
110151
ISSN
24680230
Volume
97
Publication Title
Surfaces and Interfaces
Publisher
Elsevier
School
School of Science
RAS ID
101735
Funding Information
The authors gratefully acknowledge the contribution of the Ministry of Higher Education Malaysia by providing funds for the Fundamental Research Grant Scheme (FRGS/1/2023/TK08/UKM/01/2).
Copyright
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Recommended Citation
Sadek, S., Subbiah, J., Elsmani, M. I., Sobayel, K., Islam, M. T., Nur-E-Alam, M., Islam, M. A., Liang, Z., Teridi, M. a. M., Chelvanathan, P., & Ibrahim, M. A. (2026). Repercussion of sulfur-doping on surface morphology and charge transport in Cs₃Bi₂I₉ perovskite inverted solar cells. Surfaces and Interfaces, 97, Article 110151. https://doi.org/10.1016/j.surfin.2026.110151