Transformation and degradation of metal halide perovskites induced by energetic electrons and their practical implications

Transmission electron microscopy (TEM) has been used in the characterizations of the lattice and defect structures as well as electronic and chemical properties of various materials. When TEM analyses were performed on lead halide perovskites (LHPs) and related materials, it has often been found that transformation and damage were easily induced in the specimens by electron beam irradiation. As the structural and chemical instabilities of LHPs and related materials are the main obstacle that must be overcome for their practical large-scale applications in solar cells and other optoelectronic applications, we examine whether and how the TEM-based irradiation and analyses can serve the purpose of rapid evaluation of the instabilities of a LHP to stimuli such as light and electric field which are crucial to its optoelectronic applications. We first provide a brief overview of the basic physical properties of LHPs related to the instability and the current understanding of the general mechanisms of sample damages induced by energetic electrons, followed with an analysis of the distinctive vulnerability and damaging features of LHPs with respect to electron beam irradiation. Based on the analysis of the similarities in the mechanisms of the damages generated by different stimuli, proper conditions are outlined with which the TEM-based investigations can be employed as a speed-up tester for the instabilities of LHPs against photon (including visible, ultraviolet and x-ray) exposure and an applied electric field. Furthermore, the perspectives of employing TEM-based processes in the fabrication of nanostructures and directly carrying out subsequent in situ analysis are elaborated, which is key to acquiring knowledge for improving focused electron beam-based industrial micro- and nanofabrication technologies.