Localized Lattice Expansion of FAPbBr<sub>3</sub> to Design a 3D Hybrid Perovskite for Sensitive Near‐Infrared Photodetection
Chengmin Ji, Tingting Zhu, Yipeng Fan, Zhou Li, Xitao Liu, Lina Li, Zhihua Sun, Junhua Luo
Abstract
Abstract A mixed‐cation 3D lead bromide hybrid perovskite (NMDAP) 2 FAPb 4 Br 13 ( 1 , NMDAP 2+ = N‐methyl‐1,3‐diaminopropanium, FA + = formamidinium) is tailored by incorporating the large NMDAP 2+ cation with the small FA + ion into 3D FAPbBr 3 . Structurally, the small FA + ions occupy the prototypical cavities formed by distorted corner‐sharing PbBr 6 octahedra as in FAPbBr 3 , while the bulky NMDAP 2+ ions are confined to the expanded lattice which is defined by a new structural motif composed of eight corner‐sharing PbBr 6 octahedra and four edge‐sharing octahedra. This localized lattice expansion from FAPbBr 3 creates a new branch of the intriguing 3D hybrid perovskite family, breaking the limits of the conventional Goldschmidt tolerance factor rule. Moreover, a high two‐photon absorption (2AP) coefficient of 60.8 cm MW −1 was demonstrated to near‐infrared (NIR) 800 nm illumination, enabling sensitive NIR photoresponses with large on/off ratio (≈10 4 ) as well as favorable stability.