J. Semicond. > 2022, Volume 43 > Issue 4 > 041106, doi: 10.1088/1674-4926/43/4/041106

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# Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors

Corresponding author: Xiaoxing Ke, kexiaoxing@bjut.edu.cn; Manling Sui, mlsui@bjut.edu.cn

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Abstract: Halide perovskites are strategically important in the field of energy materials. Along with the rapid development of the materials and related devices, there is an urgent need to understand the structure–property relationship from nanoscale to atomic scale. Much effort has been made in the past few years to overcome the difficulty of imaging limited by electron dose, and to further extend the investigation towards operando conditions. This review is dedicated to recent studies of advanced transmission electron microscopy (TEM) characterizations for halide perovskites. The irradiation damage caused by the interaction of electron beams and perovskites under conventional imaging conditions are first summarized and discussed. Low-dose TEM is then discussed, including electron diffraction and emerging techniques for high-resolution TEM (HRTEM) imaging. Atomic-resolution imaging, defects identification and chemical mapping on halide perovskites are reviewed. Cryo-TEM for halide perovskites is discussed, since it can readily suppress irradiation damage and has been rapidly developed in the past few years. Finally, the applications of in-situ TEM in the degradation study of perovskites under environmental conditions such as heating, biasing, light illumination and humidity are reviewed. More applications of emerging TEM characterizations are foreseen in the coming future, unveiling the structural origin of halide perovskite’s unique properties and degradation mechanism under operando conditions, so to assist the design of a more efficient and robust energy material.

Fig. 1.  (Color online) Schematic illustration of advanced TEM characterization for halide perovskites.

Fig. 2.  (Color online) (a) Electron beam irradiation damage observed in free-standing MAPbI3 films. (i, ii). TEM images recorded initially and after the irradiation (9870 e/(Å2·s) for ~2 min), respectively[47]. (b) Time-series of TEM images on MAPbI3 single crystal showing the electron beam damage from 0 to 50 s, where bubble-like morphology (colored arrows) emerged and grew[49]. (c) Time-series of TEM images obtained on BA2PbBr4 nanosheets[53]. (d) TEM images of the (i) CsPbCl3, (ii) CsPbBr3 and (iii) CsPbI3 QDs where "dark spots" present at the QD corners indicated irradiation damage[54]. (e) Schematic illustration of CsPbBr3 degradation pathway[56].

Fig. 3.  (Color online) (a) Degradation of MAPbI3 studied using SAED taken from a near-<1$\stackrel{-}{1}$0> t-oriented grain: i) the initial, pristine phase and ii) after 1 min (total dose per area of ≈1 × 102 e/Å2), iii) 2 min (total dose per area of ≈2 × 102 e/Å2), iv) 18 min (total dose per area of ≈2 × 103 e/Å2) of weak electron beam exposure (≈2 e/Å2)[46]. (b) Degradation in MAPbX3 by forming superstructured intermediate phase: i) atomistic structure of tetragonal MAPbI3; ii) electron diffraction (ED) pattern along the [001]c direction; iii) the observed ED of superstructure phase; iv) the simulated ED of superstructure phase MAPbI2.5; v) the corresponding atomistic structure; vi) atomistic structure of MAPbBr3; vii) ED pattern along the [001] direction; viii) the observed ED pattern with additional reflections; ix) the simulated ED of superstructure phase MAPbBr2.5; x) the corresponding atomistic structure with ordered bromine vacancies[69]. (c) TEM images and [110] oriented-SAED patterns taken from grain highlighted in yellow circles from FAPbI3 films with (i, ii) 10% MA, (iii, iv) 20% MA, (v, vi) 30% MA, (vii, viii) 40% MA[78]. (d) Stabilization of photoactive perovskites against degradation by tilted octahedral, as illustrated by structural model (i–vi), calculated energy difference (vii), AFM-IR characterization (viii–x), and TEM imaging (xi) with corresponding SAED (xii–l)[79].

Fig. 4.  (Color online) (a) HRTEM of CsPbBr3 nanocrystals (i) where the coexistence of cubic and orthorhombic phases were demonstrated by FFT patterns (ii, iii), simulated diffraction patterns (iv, v), and illustrated structure (vi, vii)[41]. (b) CTF-corrected denoised HRTEM image (i) of CH3NH3PbBr3 with different CH3NH3 orientations, where (ii, iii) the structural model (left) and the simulated projected potential map (right) corresponding to region 1 and 2 in (i), respectively[39]. (c) Ptychography reconstructed image of CsPbBr3, with the scale bar of 5Å[84]. (d) Atomic-scale structures of intragrain stacking-fault (i) and twinning interfaces (ii) obtained on orthorhombic FA0.5Cs0.5PbI3 grains along the [100] projection direction[86]. (e) Atomically resolved interface at the (2T)2 PbI4–(2T)2 PbI4–(2T)2 PbBr4 heterostructure[87]. (f) Butterworth-filtered LAADF-STEM images of grain boundaries (i), triple junctions (ii), grain boundary (iii) and aligned vacancy defects indicated by red circle (iv), obtained from a 30-nm-thick film of FAPbI3[67].

Fig. 5.  (Color online) (a, b) Atomically resolved HAADF-STEM images and corresponding EDX-mappings of CsPbBr3 nanoplates[92]. (c) STEM-EELS from a CsPbBr3 nanosheet to determine bandgap, where (i) demonstrates measured data and (ii) shows as-calculated bandgap value[93].

Fig. 6.  (Color online) (a) Stacking faults observed in a MAPbI3 with corresponding FFT patterns as inset (i), and corresponding magnified HRTEM (ii, v, vi) with structural model (iii) and (iv) the simulated HRTEM image[96]. (b) Atomically resolved-cryo-TEM image of aged MAPbI3 collected at a low dose condition (electron dose, ~5.96 e/Å2), with corresponding enlargement (ii, iv), structural model (iii) and polarization map (v)[40].

Fig. 7.  (Color online) (a) In-situ heating of MAPbI3 based PSCs up to 250 °C, where the temperature evolution of morphology change and elemental migration was monitored by HAADF-STEM images and EDX mappings. The same scale bar applies to all panels[42]. (b) In-situ electrical biasing on MAPbI3, where morphology and structure change was monitored by HAADF-STEM, TEM and SAED, respectively[109]. (c) In-situ TEM showing the impact of controlled humidity on the conversion of MAPbI3 into MAPbI3·H2O and finally PbI2, using liquid cell[112].

Fig. 8.  (Color online) Illustrated summary of safe dose and damage dose for different perovskite materials, plotted in coloured columns. Numbers in the figure correspond to the reference numbers as listed in the tables and references. Shade in each column indicates relatively-safe dose range versus damage-prone dose range. Generally speaking, 2D pvsk is suggested to be imaged below the dose of 50 e/(Å2·s), MAPbI3/ MAPbBr3 below ~100 e/(Å2·s), whereas CsPbBr3 can tolerate dose up to more than 1000 e/(Å2·s).

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Received: 28 February 2022 Revised: 25 March 2022 Online: Accepted Manuscript: 06 April 2022Uncorrected proof: 12 April 2022Published: 18 April 2022

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Xiaomei Wu, Xiaoxing Ke, Manling Sui. Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors[J]. Journal of Semiconductors, 2022, 43(4): 041106. doi: 10.1088/1674-4926/43/4/041106 X M Wu, X X Ke, M L Sui. Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors[J]. J. Semicond, 2022, 43(4): 041106. doi: 10.1088/1674-4926/43/4/041106Export: BibTex EndNote
 Citation: Xiaomei Wu, Xiaoxing Ke, Manling Sui. Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors[J]. Journal of Semiconductors, 2022, 43(4): 041106. X M Wu, X X Ke, M L Sui. Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors[J]. J. Semicond, 2022, 43(4): 041106. Export: BibTex EndNote

# Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors

##### doi: 10.1088/1674-4926/43/4/041106
• Author Bio:

Xiaomei Wu got her BS and master’s degrees in 2018 and 2021 at Beijing Technology and Business University. Now she is a doctoral student at Beijing University of Technology. Her research focuses on energy materials microstructure characterization using TEM

Xiaoxing Ke is an associate professor at Beijing University of Technology (BJUT), China. She received her Ph.D. degree from Physics Department, University of Antwerp, Belgium in 2010. After 4 years of postdoctoral fellowship in EMAT, University of Antwerp, she joined BJUT in 2014. Her research interests mainly focus on microstructure investigation on energy materials using advanced transmission electron microscopy (TEM), including aberration-corrected (S)TEM and 3D electron tomography

Manling Sui is a Distinguished Professor at Beijing University of Technology (BJUT). She received her Ph.D. in 1991 at Institute of Metal Research, Chinese Academy of Sciences, and successively worked at Northeastern University in China, University of Wisconsin-Madison in the United States, and Institute of Metal Research, Chinese Academy of Sciences. Then she joined BJUT as Distinguished Professor of Cheung Kong Scholars Programme in 2009. Her research is focused on the structure and property relationships of advanced materials at atomic scale, especially using in situ transmission electron microscopy with external stimuli such as thermal, electrical, mechanical, optical, and liquid/gas environments

• Corresponding author: kexiaoxing@bjut.edu.cnmlsui@bjut.edu.cn