Surface Physics of Low-Dimensional Pnictogen Chalcohalides and Its Impact on Photovoltaic Technologies
Abstract
Low-dimensional pnictogen chalcohalides (MChX; M = Bi, Sb; Ch = S, Se; X = I, Br) are promising non-toxic semiconductors for solar energy conversion, yet the power conversion efficiencies of MChX solar cells remain below 10%, far from their Shockley-Queisser limit of ∼30%. Efficient charge extraction depends critically on the band-edge alignment between the absorber and the charge-selective contacts, which is a surface property. Here, we combine first-principles calculations with device-level modelling to investigate the surface energetics and band alignments across the MChX family. An exhaustive sampling of crystal orientations, including low-symmetry facets, identifies the (011) and (010) surfaces as the most stable terminations in all eight compounds. Their formation energies differ by only ≈ 0.01-0.03J m−2, yet their band edges are shifted rigidly with respect to each other by up to $0.8$eV. Drift-diffusion simulations of BiSBr show that the coexistence of such facets can reduce the open-circuit voltage by up to $0.6$V, even in an otherwise ideal, defect-free absorber. Surface orientation thus emerges as a hidden design parameter for charge extraction. This study may help to explain the gap between the theoretical and experimental efficiencies of MChX solar cells, and it provides new design principles for MChX-based photovoltaic and photocatalytic technologies.
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BibTeX
@misc{lopez2026surface,
title = {{Surface Physics of Low-Dimensional Pnictogen Chalcohalides and Its Impact on Photovoltaic Technologies}},
author = {Cibrán López and David Rovira and Álex Jiménez-Arguijo and Zacharie Jehl and Edgardo Saucedo and Claudio Cazorla},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.10136},
eprint = {2610.10136},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.10136},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Surface Physics of Low-Dimensional Pnictogen Chalcohalides and Its Impact on Photovoltaic Technologies
AU - Cibrán López
AU - David Rovira
AU - Álex Jiménez-Arguijo
AU - Zacharie Jehl
AU - Edgardo Saucedo
AU - Claudio Cazorla
PY - 2026
DA - 2026/10/07
PB - arXiv
DO - 10.48550/arxiv.2610.10136
UR - https://arxiv.org/abs/2610.10136
AB - Low-dimensional pnictogen chalcohalides (MChX; M = Bi, Sb; Ch = S, Se; X = I, Br) are promising non-toxic semiconductors for solar energy conversion, yet the power conversion efficiencies of MChX solar cells remain below 10%, far from their Shockley-Queisser limit of ∼30%. Efficient charge extraction depends critically on the band-edge alignment between the absorber and the charge-selective contacts, which is a surface property. Here, we combine first-principles calculations with device-level modelling to investigate the surface energetics and band alignments across the MChX family. An exhaustive sampling of crystal orientations, including low-symmetry facets, identifies the (011) and (010) surfaces as the most stable terminations in all eight compounds. Their formation energies differ by only ≈ 0.01-0.03J m^−2, yet their band edges are shifted rigidly with respect to each other by up to $0.8$eV. Drift-diffusion simulations of BiSBr show that the coexistence of such facets can reduce the open-circuit voltage by up to $0.6$V, even in an otherwise ideal, defect-free absorber. Surface orientation thus emerges as a hidden design parameter for charge extraction. This study may help to explain the gap between the theoretical and experimental efficiencies of MChX solar cells, and it provides new design principles for MChX-based photovoltaic and photocatalytic technologies.
ER -