From Heterostructures to Solid-Solutions: Structural Tunability in Mixed Halide Perovskites.
basic_science · Level V
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- Record sourced from PubMed, PMID 36205651.
- Also identified by DOI 10.1002/adma.202205923.
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Abstract
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 Cs<sub>0.5</sub> FA<sub>0.5</sub> PbX<sub>3</sub> (FA = formamidinium; X = halide anion, ABX<sub>3</sub> ) 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 Cs<sub>0.5</sub> FA<sub>0.5</sub> Pb(Br/I)<sub>3</sub> that significantly suppress photoinduced anion migration compared to their bulk counterparts, offering a route to deliberately designed photostable optoelectronic materials.