Atomic-scale visualization of metallic lead leak related fine structure in CsPbBr quantum dots.

All-inorganic lead halide perovskites (AILHPs) quantum dots (QDs) have been widely investigated as promising materials for optoelectronic applications because of their outstanding luminescence properties. Lead leakage, a common impurity and environmental pollution source that majorly hinders the commercialization of lead halide perovskite devices, has lately attracted considerable attention. Its detrimental influence on the luminescence performance has been widely reported. However, an in-depth experimental study of the chemistry geometry relating to lead leakage in CsPbBr QDs has been rarely reported to date. Herein, combining real-time (scanning) transmission electron microscopy ((S)TEM) with density functional theory calculations, we showed detailed atomic and electronic structure study of the phase boundaries in CsPbBr QDs during the lead leakage process. A phenomenon of two-phase coexistence was reported to be linked with the lead precipitating in CsPbBr QDs. A phase boundary between the Ruddlesden-Popper (RP) phase and conventional orthorhombic perovskite was developed when the lead particle was aggregating in the QDs. Our results suggested that in considering the detrimental exciton quenching process not only the role of lead nanoparticles should be considered but also the influence of the phase boundary on electron-hole transport is worthy of attention. The direct visualization of the delicate atomic and electronic structures associated with lead aggregation in CsPbBr sheds light on how the leakage process influences the luminescence performance and provides a potential route for suppressing the generation of environmentally harmful byproducts for advanced devices.