Studies of High-Membered Two-Dimensional Ruddlesden-Popper Cs7Pb6I19 Perovskite Nanosheets via Kinetically Controlled Reactions
Yi-Chia Chen, Kuan-Chang Wu, Hsin-An Chen, Wen-Hui Chu, Swathi M. Gowdru, Jou-Chun Lin, Bi-Hsuan Lin, Mau-Tsu Tang, Chia-Che Chang, Ying-Huang Lai, Tsung-Rong Kuo, Cheng-Yen Wen, Di-Yan Wang*
Mater. Horiz. 2022, just accepted.
Two-dimensional (2D) all-inorganic Ruddlesden-Popper (RP) perovskites Cs7Pb6I19 nanosheets (NSs) were successfully developed for the first time by employing a structural recrystallization process with additional passivation of small organic sulfide molecules. The structure of Cs7Pb6I19 NSs are confirmed by powder X-ray diffraction measurements, atomically-resolved STEM measurements and atomic force microscopic (AFM) studies. Cs7Pb6I19 NSs with a specific n value of 6 exhibit an unique absorption and emission spectra with intense excitons at 560 nm due to quantum confinement effects in 2D perovskite slabs. The formation mechanisms of 2D Cs7Pb6I19 NSs and 3D γ-CsPbI3 phases were investigated by in-situ photoluminescence (PL) spectroscopy and the activation energies of their formation reactions were calculated to be 151 kJ/mol and 95.3 kJ/mol, respectively. The phase stability of 2D Cs7Pb6I19 NSs can be maintained at temperatures below 14 oC for more than 4 weeks. The overall results indicate that 2D Cs7Pb6I19 NSs demonstrate unique optical properties and structural stability compared with other 3D perovskite materials. We have opened a new path to the future discovery of 2D perovskite structure with metastable phases by using this recrystallization method and the assistance of sulfur-derived organic molecules.