Excitation Intensity- and Size-Dependent Halide Photosegregation in CsPb(I<sub>0.5</sub>Br<sub>0.5</sub>)<sub>3</sub> Perovskite Nanocrystals.
basic_science · Level V
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- Record sourced from PubMed, PMID 36468911.
- Also identified by DOI 10.1021/acsnano.2c10781.
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Abstract
Although broad consensus exists that photoirradiation of mixed-halide lead perovskites leads to anion segregation, no model today fully rationalizes all aspects of this near ubiquitous phenomenon. Here, we quantitatively compare experimental, CsPb(I<sub>0.5</sub>Br<sub>0.5</sub>)<sub>3</sub> nanocrystal (NC) terminal anion photosegregation stoichiometries and excitation intensity thresholds to a band gap-based, thermodynamic model of mixed-halide perovskite photosegregation. Mixed-halide NCs offer strict tests of theory given physical sizes, which dictate local photogenerated carrier densities. We observe that mixed-anion perovskite NCs exhibit significant robustness to photosegregation, with photosegregation propensity decreasing with decreasing NC size. Observed size- and excitation intensity-dependent photosegregation data agree with model predicted size- and excitation intensity-dependent terminal halide stoichiometries. Established correspondence between experiment and theory, in turn, suggests that mixed-halide perovskite photostabilities can be predicted a priori using local gradients of (empirical) Vegard's law expressions of composition-dependent band gaps.