From Heterostructures to Solid‐Solutions: Structural Tunability in Mixed Halide Perovskites

• Published in: Advanced materials (Weinheim) Vol. 35; no. 11; pp. e2205923 - n/a
• Main Authors: Shin, Donghoon, Lai, Minliang, Shin, Yongjin, Du, Jingshan S., Jibril, Liban, Rondinelli, James M., Mirkin, Chad A.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01-03-2023
• Subjects: Anions; Composition; Crystallization; halide perovskites; Heterostructures; Ion migration; Materials science; Nanocrystals; nanolithography; Optoelectronics; Perovskites; robust heterostructures; solid‐solutions; structural tunability; suppressed photoinduced phase segregations; Synthesis; solid-solutions; suppressed photoinduced phase segregations; robust heterostructures; structural tunability; nanolithography; halide perovskites
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202205923

The stability, reliability, and performance of halide‐perovskite‐based devices depend upon the structure, composition, and particle size of the device‐enabling materials. Indeed, the degree of ion mixing in multicomponent perovskite crystals, although challenging to control, is a key factor in determining properties. Herein, an emerging method termed evaporation–crystallization polymer pen lithography is used to synthesize and systematically study the degree of ionic mixing of Cs0.5FA0.5PbX3 (FA = formamidinium; X = halide anion, ABX3) crystals, as a function of size, temperature, and composition. These experiments have led to the discovery of a heterostructure morphology where the A‐site cations, Cs and FA, are segregated into the core and edge layers, respectively. Simulation and experimental results indicate that the heterostructures form as a consequence of a combination of both differences in solubility of the two ions in solution and the enthalpic preference for Cs–FA ion segregation. This preference for segregation can be overcome to form a solid‐solution by decreasing crystal size (<60 nm) or increasing temperature. Finally, these tools are utilized to identify and synthesize solid‐solution nanocrystals of Cs0.5FA0.5Pb(Br/I)3 that significantly suppress photoinduced anion migration compared to their bulk counterparts, offering a route to deliberately designed photostable optoelectronic materials.
The degree of ion mixing in multicomponent perovskite crystals is a key factor for the stability and performance of optoelectronic devices but remains challenging to control. In this work, a new method, termed evaporation–crystallization polymer pen lithography, is used to synthesize and systematically study libraries of halide perovskite crystals (Cs1−xFAxPbX3, where X = halide anion) and reveals strategies for deliberately controlling ion segregation behavior in these materials.