Tianyin Miao, Sanwan Liu, Xia Lei, Yong Zhang, Wenhua Li, Qisen Zhou, Yi-Xiang Wang, Nikita A. Emelianov, Victoria V. Ozerova, Valeria S. Bolshakova, W WANG, Zheng Zhou, Z G Zhu, Lanlu Lu, Z J Chen, Jingyuan Ma, Erxiang Xu, L S Wang, Li Yunfei, Zhengtian Tan, Shijie Zheng, Guilin Liu, Lianbo Guo, Jingbai Li, Yi Shen, Pavel A. Troshin, С. М. Алдошин, Zonghao Liu, Nam-Gyu Park, Wei Chen
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.