Remarkable Black‐Phase Robustness of CsPbI<sub>3</sub> Nanocrystals Sealed in Solid SiO<sub>2</sub>/AlO<sub>x</sub> Sub‐Micron Particles
Yue Lin, Xiaotong Fan, Xiao Yang, Xi Zheng, Weizhi Huang, Zhibin Shangguan, Yuhan Wang, Hao‐Chung Kuo, Tingzhu Wu, Zhong Chen
Abstract
Abstract This work combines the high‐temperature sintering method and atomic layer deposition (ALD) technique, and yields SiO 2 /AlO x –sealed γ–CsPbI 3 nanocrystals (NCs). The black‐phase CsPbI 3 NCs, scattered and encapsulated firmly in solid SiO 2 sub‐micron particles, maintain in black phases against water soaking, ultraviolet irradiation, and heating, exhibiting remarkable phase stability. A new phase‐transition route, from γ via β to α phase without transferring into δ phase, has been discovered upon temperature increasing. The phase stability is ascribed to the high pressure exerted by the rigid SiO 2 encapsulations, and its condensed amorphous structures that prevent the permeation of H 2 O molecules. Nanoscale coating of Al 2 O 3 thin films, which are deposited on the surface of the CsPbI 3 ‐SiO 2 by ALD, enhances the protection against O 2 infiltration, greatly elevating the high‐temperature stability of CsPbI 3 NCs sealed inside, as the samples remain bright after 1‐h annealing in air at 400 ° C. These fabrication and encapsulation techniques effectively prevent the formation of δ–CsPbI 3 under harsh environment, bringing the high‐pressure preservation of black‐phase CsPbI 3 from laboratory to industry toward potential applications in both photovoltaic and fluorescent areas.