Light-Induced Transient Lattice Dynamics and Metastable Phase Transition in CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> Nanocrystals.
basic_science · Level V
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- Record sourced from PubMed, PMID 36916650.
- Also identified by DOI 10.1021/acsnano.2c06950.
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Abstract
Methylammonium lead iodide (MAPbI<sub>3</sub>) perovskite nanocrystals (NCs) offer desirable optoelectronic properties with prospective utility in photovoltaics, lasers, and light-emitting diodes (LEDs). Structural rearrangements of MAPbI<sub>3</sub> in response to photoexcitation, such as lattice distortions and phase transitions, are of particular interest, as these engender long carrier lifetime and bolster carrier diffusion. Here, we use variable temperature X-ray diffraction (XRD) and synchrotron-based transient X-ray diffraction (TRXRD) to investigate lattice response following ultrafast optical excitation. MAPbI<sub>3</sub> NCs are found to slowly undergo a phase transition from the tetragonal to a pseudocubic phase over the course of 1 ns under 0.02-4.18 mJ/cm<sup>2</sup> fluence photoexcitation, with apparent nonthermal lattice distortions attributed to polaron formation. Lattice recovery exceeds time scales expected for both carrier recombination and thermal dissipation, indicating meta-stability likely due to the proximal phase transition, with symmetry-breaking along equatorial and axial directions. These findings are relevant for fundamental understanding and applications of structure-function properties.