Atomic Characterization of Byproduct Nanoparticles on Cesium Lead Halide Nanocrystals Using High-Resolution Scanning Transmission Electron Microscopy

Recent microstructural studies on lead halide perovskite nanocrystals have consistently reported the coexistence of byproduct nanoparticles (NPs). However, the nature of these NPs and their formation mechanism are still a matter of debate. Herein, we have investigated the structure and compositions of the NPs located on colloidal cesium lead bromide nanocrystals (CsPbBr3NCs), mainly through aberration-corrected transmission electron microscopy and spectroscopy. Our results show that these NPs can be assigned to PbBr2and CsPb2Br5. The new CsPb2Br5species are formed by reacting CsPbBr3NCs with the remaining PbBr2during the drying process. In addition, observation of the metallic Pb NPs are ascribed to the electron damage effect on CsPbBr3NCs during transmission electron microscopy imaging.Keywords:lead halide perovskite materials;colloidal cesium lead halide nanocrystals;scanning transmission electron microscopy and spectroscopy