Atomic-Scale Polarization and Strain at the Surface of Lead Halide Perovskite Nanocrystals

Inorganic halide perovskite nanocrystals (NCs) are beingwidelyexplored as next-generation optoelectronic materials. Critical tounderstanding the optoelectronic properties and stability behaviorof perovskite NCs is the material's surface structure, wherethe local atomic configuration deviates from that of the bulk. Throughlow-dose aberration-corrected scanning transmission electron microscopyand quantitative imaging analysis techniques, we directly observedthe atomic structure at the surface of the CsPbBr3 NCs.CsPbBr3 NCs are terminated by a Cs-Br plane, andthe surface Cs-Cs bond length decreases significantly (& SIM;5.6%)relative to the bulk, imposing compressive strain and inducing polarization,which we also observed in CsPbI3 NCs. Density functionaltheory calculations suggest such a reconstructed surface contributesto the separation of holes and electrons. These findings enhance ourfundamental understanding of the atomic-scale structure, strain, andpolarity at the surface of inorganic halide perovskites and providevaluable insights into designing stable and efficient optoelectronicdevices.

Automated summary

Inorganic halide perovskite nanocrystals (NCs) are extensively studied as next-generation optoelectronic materials. The atomic structure at the surface of CsPbBr3 NCs is directly observed, revealing a Cs-Br terminated surface with a significantly decreased Cs-Cs bond length, inducing compressive strain and polarization. Density functional theory calculations suggest that this reconstructed surface contributes to the separation of holes and electrons. These findings enhance our understanding of the surface structure and provide insights for designing stable and efficient optoelectronic devices.