AI Article Synopsis
- Methylammonium lead iodide (MAPbI) perovskite nanocrystals exhibit excellent optoelectronic features, making them suitable for use in devices like solar cells, lasers, and LEDs.
- Through advanced techniques like variable temperature X-ray diffraction and synchrotron-based transient X-ray diffraction, it was discovered that these nanocrystals experience a phase transition from tetragonal to pseudocubic when exposed to light, occurring over 1 nanosecond.
- The study highlights that lattice recovery occurs more rapidly than anticipated under certain conditions, suggesting the material can maintain a state of meta-stability due to structural changes, which is important for enhancing device performance.
Article Abstract
Methylammonium lead iodide (MAPbI) perovskite nanocrystals (NCs) offer desirable optoelectronic properties with prospective utility in photovoltaics, lasers, and light-emitting diodes (LEDs). Structural rearrangements of MAPbI 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 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 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.
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