Electron‐Beam‐Related Studies of Halide Perovskites: Challenges and Opportunities

Abstract

Electron beam microscopy and related characterization techniques play an important role in revealing the microstructural, morphological, physical, and chemical information of halide perovskites and their impact on associated optoelectronic devices. However, electron beam irradiation usually causes damage to these beam-sensitive materials, negatively impacting their device performance, and complicating this interpretation. In this article, the electron microscopy and spectroscopy techniques are reviewed that are crucial for the understanding of the crystallization and microstructure of halide perovskites (e.g. MAPbI 3 , CsPbBr 3 ). In addition, special attention is paid to assessing and mitigating the electron beam-induced damage caused by these techniques during measurements of both organic-inorganic hybrid and all-inorganic halide perovskites. Since the halide perovskites are fragile, a protocol involving delicate control of both electron beam dose and dose rate, coupled with careful data analysis, is shown to be the key to enable the acquisition of reliable structural and compositional information such as atomic-resolution images, chemical elemental mapping and electron diffraction patterns. Limiting the electron beam dose is shown to be the critical parameter enabling the characterization of various halide perovskite materials. Novel methods to unveil the mechanisms of device operation, including charge carrier generation, diffusion, and extraction are presented in scanning electron microscopy studies combined with electron-beam induced current and cathodoluminescence mapping. Future opportunities for electron-beam related characterizations of halide perovskites are also discussed.

Nanometric Chemical Analysis of Beam‐Sensitive Materials: A Case Study of STEM‐EDX on Perovskite Solar Cells

“…However, this is very challenging when dealing with organic–inorganic nanocomposites, such as hybrid halide perovskites, as such materials are prone to beam damage when subjected to high‐intensity electron bombardment. [ 8–11 ] Previous research has shown that the primary beam damage mechanism for hybrid perovskites is radiolysis or ionization damage which causes bond breaking and disintegration of the perovskite crystal structure. [ 12,13 ] Possible results of radiolysis include formation of vacancies through atomic/ionic displacement and loss of volatile molecules.…”

“…[ 19 ] Further, it indicates that dose rate has minimum impact on beam damage, as previous works conducted with parallel beam TEM‐EDX also observed a similar decline of I/Pb ratio in MAPbI 3 . [ 9,10,14 ] We note that factors other than total dose may affect the extent of radiolysis, such as electron beam energy or sample thickness (or surface/volume ratio). [ 13 ] Here both are nominally constant, so have been disregarded from the analysis.…”

Electron-Beam Irradiation Induced Regulation of Surface Defects in Lead Halide Perovskite Thin Films

“…A focused electron beam (e-beam) provided in a scanning electron microscope (SEM) or transmission electron microscope (TEM) can also be used to regulate crystal structures, as well as optoelectronic properties of materials [39][40][41]. Although a single-crystal MAPbBr 3 microplate photodetector with increased photocurrent has been fabricated through direct e-beam exposure, it is widely accepted that e-beam irradiation can significantly degrade perovskite structures as well as the PL emission [42,43]. Therefore, how electrons affect or interact with OIHPs is still an open question.…”

Mitigating Damage to Hybrid Perovskites Using Pulsed-Beam TEM

“…[1][2][3] Structural, chemical, electronic, and dynamic properties at this scale are accessible with transmission electron microscopy (TEM), but the stability of HOIPs is such that electron-beam damage can be significant. [4][5][6][7] Indeed, sensitivity of HOIPs to even low dose rates may limit what can be learned about fundamental structure/function relationships. [8][9][10] This damage is thought to occur through a combination of charging, ionic excitation, and heating leading to ion migration and separation of the organic and inorganic constituents.…”

“…Beam-damage mechanisms in TEM are numerous and often synergistic, necessitating detailed design and systematic execution of experiments. 4,23 Conveniently, fs pulsed lasers in a stable lab environment afford high levels of control, enabling accurate and precise quantification of pulsed TEM beam damage. 17 An overview of the fs laser-driven approach used here, and the method for quantifying damage to MAPbI3 specimens, is shown in Figure 1.…”