Ohmi Takuya, Oswald Iain W H, Neilson James R, Roth Nikolaj, Nishioka Shunta, Maeda Kazuhiko, Fujii Kotaro, Yashima Masatomo, Azuma Masaki, Yamamoto Takafumi
Laboratory for Materials and Structures, Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8503, Japan.
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523-1872, United States.
J Am Chem Soc. 2023 Sep 13;145(36):19759-19767. doi: 10.1021/jacs.3c05390. Epub 2023 Aug 30.
α-FAPbI (FA = CH(NH)) with a cubic perovskite structure is promising for photophysical applications. However, α-FAPbI is metastable at room temperature, and it transforms to the δ-phase at a certain period of time at room temperature. Herein, we report a thiocyanate-stabilized pseudo-cubic perovskite FAPbI with ordered columnar defects (α'-phase). This compound has a √5 × √5 × tetragonal unit cell (: cell parameter of primitive perovskite cell) with a band gap of 1.91 eV. It is stable at room temperature in a dry atmosphere. Furthermore, the presence of the α'-phase in a mixed sample with the δ-phase drastically reduces the δ-to-α transition temperature measured on heating, suggesting the reduction of the nucleation energy of the α-phase or thermodynamic stabilization of the α-phase through epitaxy. The defect-ordered pattern in the α'-phase forms a coincidence-site lattice at the twinned boundary of the single crystals, thus hinting at an epitaxy- or strain-based mechanism of α-phase formation and/or stabilization. In this study, we developed a new strategy to control defects in halide perovskites and provided new insight into the stabilization of α-FAPbI by pseudo-halide and grain boundary engineering.
具有立方钙钛矿结构的α-FAPbI（FA = CH(NH)）在光物理应用方面很有前景。然而，α-FAPbI在室温下是亚稳态的，并且在室温下经过一段时间会转变为δ相。在此，我们报道了一种具有有序柱状缺陷（α'相）的硫氰酸盐稳定的准立方钙钛矿FAPbI。该化合物具有一个√5×√5×的四方晶胞（：原始钙钛矿晶胞的晶胞参数），带隙为1.91 eV。它在干燥气氛中室温下稳定。此外，在与δ相的混合样品中α'相的存在显著降低了加热时测量的δ向α转变温度，这表明α相成核能量的降低或通过外延实现α相的热力学稳定。α'相中的缺陷有序图案在单晶的孪晶边界处形成了一个重合点阵，从而暗示了基于外延或应变的α相形成和/或稳定机制。在本研究中，我们开发了一种控制卤化物钙钛矿中缺陷的新策略，并为准卤化物和晶界工程对α-FAPbI的稳定作用提供了新的见解。
