Phase‐Pure α‐FAPbI<sub>3</sub> Perovskite Solar Cells via Activating Lead–Iodine Frameworks
Tingting Niu, Lingfeng Chao, Yingdong Xia, Kaiyu Wang, Xueqin Ran, Xiao Huang, Changshun Chen, Jinpei Wang, Deli Li, Zhenhuang Su, Zhelu Hu, Xingyu Gao, Jing Zhang, Yonghua Chen
Abstract
Abstract Narrow bandgap cubic formamidine perovskite (α‐FAPbI 3 ) is widely studied for its potential to achieve record‑breaking efficiency. However, its high preparation difficulty caused by lattice instability is criticized. A popular strategy for stabilizing the α‐FAPbI 3 lattice is to replace intrinsic FA + or I − with smaller ions of MA + , Cs + , Rb + , and Br − , whereas this generally leads to broadened optical bandgap and phase separation. Studies show that ions substitution‐free phase‐pure α‐FAPbI 3 can achieve intrinsic phase stability. However, the challenging preparation of high‐quality films has hindered its further development. Here, a facile synthesis of high‐quality MA + , Cs + , Rb + , and Br − ‐free phase‐pure α‐FAPbI 3 perovskite film by a new solution modification strategy is reported. This enables the activation of lead–iodine (Pb─I) frameworks by forming the coated Pb⋯O network, thus simultaneously promoting spontaneous homogeneous nucleation and rapid phase transition from δ to α phase. As a result, the efficient and stable phase‐pure α‐FAPbI 3 PSC is obtained through a one‐step method without antisolvent treatment, with a record efficiency of 23.15% and excellent long‐term operating stability for 500 h under continuous light stress.