On-Chip Light-Incorporated In Situ Transmission Electron Microscopy of Metal Halide Perovskite Materials

We report an on-chip light-incorporated in situ transmission electron microscopy ((LIST)-S-2) approach forprobing metal halide perovskites (MHPs) at the nanoscale, realizingthe real-time, site-specific tracking of the light-triggered structuretransformation. This in situ platform is based ona specifically designed microelectromechanical systems (MEMS) chipthat offers the capability of light illumination with adjustable intensityand tailorable multiwavelength. The excellent operational reliabilityof the platform allows for the continuous observation of nanoscaleregions of interest, recording the morphological and structural evolutionsof perovskite grains and grain boundaries. A proof-of-concept demonstrationshows a polycrystalline MHP film undergoing decomposition upon continuouslight illumination. Counterintuitively, the decomposition starts andexpands within the intragrain regions rather than at the grain boundaries.This work demonstrates an unprecedented ability to reveal light-triggeredstructural-phase variation for illuminating the dynamic behaviorsof MHPs with implications for various energy applications.