Remarkable Black-Phase Robustness of CsPbI 3 Nanocrystals Sealed in Solid SiO 2 /AlO x Sub-Micron Particles

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 50; p. e2103510
• Main Authors: Lin, Yue, Fan, Xiaotong, Yang, Xiao, Zheng, Xi, Huang, Weizhi, Shangguan, Zhibin, Wang, Yuhan, Kuo, Hao-Chung, Wu, Tingzhu, Chen, Zhong
• Format: Journal Article
• Language: English
• Published: Germany 01.12.2021
• Subjects: black phase CsPbI 3; pervoskite nanocrystal; phase stability
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202103510

This work combines the high-temperature sintering method and atomic layer deposition (ALD) technique, and yields SiO /AlO -sealed γ-CsPbI nanocrystals (NCs). The black-phase CsPbI NCs, scattered and encapsulated firmly in solid SiO 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 encapsulations, and its condensed amorphous structures that prevent the permeation of H O molecules. Nanoscale coating of Al O thin films, which are deposited on the surface of the CsPbI -SiO by ALD, enhances the protection against O infiltration, greatly elevating the high-temperature stability of CsPbI 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 under harsh environment, bringing the high-pressure preservation of black-phase CsPbI from laboratory to industry toward potential applications in both photovoltaic and fluorescent areas.