Study of Electron Beam-Initiated Structure Damage and Recovery of Perovskite Thin Films

Perovskite light-emitting diodes (PeLEDs) are rising techniques that have attracted worldwide attention, and the community is increasingly considering vapor-phase deposition (VPD) as a promising route to realize reliable perovskite displays. Transmission electron microscopy (TEM) has been extensively applied to characterize the structural details of perovskites and related devices. However, under conventional imaging conditions, the high-energy electron beam is sufficient to cause collapse of the original crystal structure and the electron radiation effect on perovskites prepared by VPD has not been systematically studied. In this study, the damage and recovery processes of vacuum-deposited perovskite nanocrystalline structures are systematically studied by comprehensive transmission electron microscopy (TEM) techniques. It is observed that with prolonged electron beam irradiation, the CsPbBr3 nanocrystals surrounding the irradiation zone are gradually damaged, generating Pb nanoparticles, whereas the crystal structure within the irradiated region is not damaged. Further theoretical analysis reveals that a high-energy electric field is formed at the edge of the irradiation zone due to electron beam irradiation, which would lead to Br ion migration to the irradiation center and the breakdown of the CsPbBr3 nanocrystalline structure at the periphery regions. When the electron beam is shifted to the periphery region, the Pb nanoparticles gradually disappear with the regrowth of CsPbBr3 nanocrystals, which indicates that Br ions migrate back to the newly positively charged irradiation zone. The mechanism of the reversible transformation process is highly related to the electron beam-induced electric field, which would facilitate a deeper understanding of the electron beam irradiation effect on perovskite materials and help understand and enhance the stability of perovskites in devices.