Stable lead-free bismuth perovskite solar cells via thermally activated bilayer conversion
Abstract
Lead-free bismuth-based metal halide perovskites are promising photovoltaic candidates due to their low toxicity, favorable bandgaps and intrinsic air stability. Scalable, reproducible fabrication remains challenging. We study post-deposition annealing of methylammonium bismuth iodide (MBI) bilayer films prepared by low-temperature thermal vapor deposition (LTTV), where BiI3 and MAI are sequentially evaporated at substrate temperatures as low as 40°C under moderate vacuum in ambient air. Unlike solution or high-vacuum co-evaporation routes, LTTV provides a practical dry pathway to crystalline, converted MBI absorbers. Annealing above 200°C drives thermally activated bilayer conversion to a monoclinic C2/c MBI phase with strong (111) texture and micrometer-scale grain growth, yielding power conversion efficiencies up to 0.53%, fill factor 0.63 and short-circuit current density 1.68 mA cm−2. Forward and reverse J–V scans are statistically indistinguishable across the device population, indicating hysteresis-free operation attributed to limited ionic disorder from the dry conversion pathway. Non-encapsulated devices retain stable photovoltaic performance during extended ambient dark storage, confirming the ambient storage stability of LTTV-deposited MBI absorbers. These results demonstrate LTTV as a scalable route to stable bismuth perovskite absorbers for solar energy applications.
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BibTeX
@article{jouane2026stable,
title = {{Stable lead-free bismuth perovskite solar cells via thermally activated bilayer conversion}},
author = {Youssef Jouane and Hesham Hawashin and Nicolas Parou and Sylvain Vedraine and Rémi Antony and Bernard Ratier and Dmitry Aldakov and Johann Bouclé},
journal = {Solar Energy},
year = {2026},
month = aug,
doi = {10.1016/j.solener.2026.114961},
url = {https://unilim.hal.science/hal-05734713v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Stable lead-free bismuth perovskite solar cells via thermally activated bilayer conversion
AU - Youssef Jouane
AU - Hesham Hawashin
AU - Nicolas Parou
AU - Sylvain Vedraine
AU - Rémi Antony
AU - Bernard Ratier
AU - Dmitry Aldakov
AU - Johann Bouclé
PY - 2026
DA - 2026/08/04
JO - Solar Energy
DO - 10.1016/j.solener.2026.114961
UR - https://unilim.hal.science/hal-05734713v1
AB - Lead-free bismuth-based metal halide perovskites are promising photovoltaic candidates due to their low toxicity, favorable bandgaps and intrinsic air stability. Scalable, reproducible fabrication remains challenging. We study post-deposition annealing of methylammonium bismuth iodide (MBI) bilayer films prepared by low-temperature thermal vapor deposition (LTTV), where BiI3 and MAI are sequentially evaporated at substrate temperatures as low as 40°C under moderate vacuum in ambient air. Unlike solution or high-vacuum co-evaporation routes, LTTV provides a practical dry pathway to crystalline, converted MBI absorbers. Annealing above 200°C drives thermally activated bilayer conversion to a monoclinic C2/c MBI phase with strong (111) texture and micrometer-scale grain growth, yielding power conversion efficiencies up to 0.53%, fill factor 0.63 and short-circuit current density 1.68 mA cm−2. Forward and reverse J–V scans are statistically indistinguishable across the device population, indicating hysteresis-free operation attributed to limited ionic disorder from the dry conversion pathway. Non-encapsulated devices retain stable photovoltaic performance during extended ambient dark storage, confirming the ambient storage stability of LTTV-deposited MBI absorbers. These results demonstrate LTTV as a scalable route to stable bismuth perovskite absorbers for solar energy applications.
SN - 0038-092X
SN - 1471-1257
ER -