An entropy-regulating molecular lock stabilizes formamidinium lead halide perovskite
- Tianyin Miao
- Sanwan Liu
- Xia Lei
- Yong Zhang
- Wenpei Li
- Qisen Zhou
- Jianan Wang
- Nikita A. Emelianov
- Victoria V. Ozerova
- Valeria S. Bolshakova
- Wenqiang Wang
- Zheng Zhou
- Zhongjie Zhu
- Lanlu Lu
- Zhenhua Chen
- Jingyuan Ma
- Erxiang Xu
- Luyao Wang
- Yunfei Li
- Zhengtian Tan
- Shijie Zheng
- Guilin Liu
- Lianbo Guo
- Jingbai Li
- Yang Shen
- Pavel A. Troshin
- Sergey M. Aldoshin
- Zonghao Liu
- Nam-Gyu Park
- Wei Chen
2026-05-14
A critical limitation of formamidinium lead iodide (FAPbI 3 ) perovskite solar cells (PSCs) lies in the intrinsic instability of the ionic–covalent Pb–I octahedral lattice, relative to the unfavorable hexagonal δ-phase under operating conditions. We report an entropy-regulating molecular-lock strategy using 1-pyridin-3-ylmethyl-piperazine hydrochloride (3-PMPCl). Strong interactions between the perovskite lattice surface and 3-PMPCl modulate the rotational freedom of organic cations and suppress the detrimental entropy increase associated with [PbI 6 ] 4− octahedra disorder or expansion. This entropy-favored environment intrinsically increases the phase transition energy barrier. The uniform distribution and strong adsorption of 3-PMPCl stabilize the α-phase under elevated temperature and humidity conditions. We achieved a certified power conversion efficiency (PCE) of 27.6% in FAPbI 3 -based PSCs. However, the operational stability of such champion devices remains below the state of the art. Adopting a stable bismuth electrode addresses this issue with a slight reduction in efficiency, yielding a device that retains 93.0% of its initial PCE (26.8%) after 1011 hours at 85°C under 1-sun illumination.