Atomic-resolution transmission electron microscopy of electron beam–sensitive crystalline materials

Zhang, Daliang; Zhu, Yihan; Liu, Lingmei; Xiao, Ying; Hsiung, Chia-En; Sougrat, Rachid; Li, Kun; Han, Yu

doi:10.1126/science.aao0865

Cited by 426 publications

(504 citation statements)

References 38 publications

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“…Although TEM has been widely used for structure characterization of perovskite MAPbI 3 15–17 , the atomically resolved imaging remains elusive due to its electron beam-sensitive nature 18 . Thus, the electron diffraction (ED) or fast Fourier transform (FFT) pattern based on lattice fringes becomes a common preference to identify the phase of perovskite.…”

Section: Introductionmentioning

confidence: 99%

Atomic scale insights into structure instability and decomposition pathway of methylammonium lead iodide perovskite

et al. 2018

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Organic–inorganic hybrid perovskites are promising candidates for the next-generation solar cells. Many efforts have been made to study their structures in the search for a better mechanistic understanding to guide the materials optimization. Here, we investigate the structure instability of the single-crystalline CH3NH3PbI3 (MAPbI3) film by using transmission electron microscopy. We find that MAPbI3 is very sensitive to the electron beam illumination and rapidly decomposes into the hexagonal PbI2. We propose a decomposition pathway, initiated with the loss of iodine ions, resulting in eventual collapse of perovskite structure and its decomposition into PbI2. These findings impose important question on the interpretation of experimental data based on electron diffraction and highlight the need to circumvent material decomposition in future electron microscopy studies. The structural evolution during decomposition process also sheds light on the structure instability of organic–inorganic hybrid perovskites in solar cell applications.

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Section: Introductionmentioning

confidence: 99%

Atomic scale insights into structure instability and decomposition pathway of methylammonium lead iodide perovskite

et al. 2018

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“…[31,32] For this reason, traditional methodologies to achieve atomic-resolution are unsuitable, since it requires the use of the diffraction and imaging modes several times and it causes to reach a destructive total electron dose to the material. However, in addition to being sensitive to sample preparation, LHPs are also easily damaged by electron beams, and the high acceleration voltage causes knock-on damage, heating effects, and radiolysis.…”

Section: Wwwadvancedsciencenewscommentioning

confidence: 99%

“…The alloys started with the pure MAPbI 3 and subsequent transformation into the mixed compounds. 2019, 9,1900444 [32] The squares highlight two ordered domains with off-centered MA + that have different orientations. The authors claimed that an energy funnel was produced as consequence of the bandgap gradient in the NWs due to the Br-rich and Cl-rich regions.…”

Section: Energy-dispersive X-ray Spectroscopymentioning

confidence: 99%

“…The study shows the elemental maps for Pb, Br, and I measured by EDS, where it is shown that Pb and I are homogenously distributed, whereas Br shown clustering and a heterogenous distribution. [32] Copyright 2018 The American Association for the Advancement of Science. The authors also showed that charge carrier transport can be induced in one-way, creating anisotropy of the charges.…”

Section: Energy-dispersive X-ray Spectroscopymentioning

confidence: 99%

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Imaging and Mapping Characterization Tools for Perovskite Solar Cells

Hidalgo

Castro‐Méndez

Correa‐Baena

2019

Advanced Energy Materials

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define the perovskite structure, decreases below 0.8 and orthorhombic, rhombohedral, or tetragonal structures tend to form. For large A-cations, layered 2D [3] and 1D [4] chain structures can be formed, e.g., Ruddlesden-Popper, Aurivillius, and Dion-Jacobson phases. Both 3D and 2D perovskites have gained the attention of the solar cell community.Lead halide perovskites are outstanding semiconductors with impressive optoelectronic properties, such as high absorption coefficient, tunable band gap, and long charge carrier lifetimes. Despite having such impressive properties, there is still a need for deeper understanding of the degradation mechanisms of the perovskite materials in order to make PSCs viable for outdoor applications and commercialization. [5,6] Currently, a major challenge facing perovskites is their long-term stability, due to their sensitivity to temperature, moisture, oxygen, and ultraviolet (UV) light. [6] Furthermore, chemical and electronic stability, compositional, and crystal homogeneity in the absorber layer of PSCs are parameters that allow us to understand and ensure the maximum PCE and long-term durability of the devices.Imaging and mapping characterization techniques allow researchers to obtain insights of the nano-and microscale features related to their chemical and electronic properties, which in turn limit PSC performance and long-term durability. This review will focus on the progress of the imaging and mapping techniques that have been used understanding and designing perovskite materials. This comprehensive review will span from basic morphology characterization methods, such as scanning electron microscopy (SEM) to advanced, synchrotron-based characterization using X-ray microscopy, such as X-ray fluorescence for compositional mapping, and X-ray beam induced current (XBIC) for electric performance mapping. Different imaging and mapping tools allow for correlations of different physical, chemical, optical and electrical features in space and time. These characterization techniques have helped explain phenomena that govern perovskite materials, including chemical and electrical properties and how they relate to solar cell performance. The following table summarizes the different imaging and mapping characterization techniques and their use for PSCs research.Perovskite solar cells (PSCs) have attracted much attention as efficiencies have gone beyond 24%. To achieve these impressive numbers, the PSC scientific community is working to improve the perovskite optoelectronic properties. Imaging and mapping characterization techniques have been widely used to understand the fundamental properties that allow lead halide perovskites to achieve high performance. In this review, these techniques are evaluated, from simple tools, such as electron microscopy, to more complex systems that include atomic force microscopy, synchrotron-based X-ray mapping, and ultrafast and photoluminescence mapping. These tools have helped understand lead halide perovskites and their impressive optoelectronic prope...

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“…To make a fair comparison between these two images, we correct the "contrast inversion" (methods) introduced by the contrast transfer function (CTF) of the objective lens 32 . Here, the weak-phase object approximation applies to sample thicknesses up to ~100 nm owing to the low density of ZIF-8, which reduces its effective scattering thickness 13 . This standard image processing procedure (methods) generates CTF-corrected images of empty ZIF-8 ( Fig.…”

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confidence: 99%

Cryo-EM Structures of Atomic Surfaces and Host-Guest Chemistry in Metal-Organic Frameworks

Wang

Zhou

et al. 2020

Matter

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Host-guest interactions govern the chemistry of a broad range of functional materials. However, the weak bonding between host and guest prevents atomic-resolution studies of their structure and chemistry using transmission electron microscopy (TEM). This problem is exacerbated in metalorganic frameworks (MOF), in which the host framework is easily damaged by the electron beam.Here, we use cryogenic-electron microscopy (cryo-EM) to simultaneously address these two challenges and resolve the atomic surface structure of zeolitic imidazolate framework (ZIF-8) andits interaction with guest CO2 molecules. We image atomic step-edge sites on the ZIF-8 surface that provides possible insight to its growth behavior. Furthermore, we observe two distinct binding sites for CO2 within the ZIF-8 pore, which are both predicted by density functional theory (DFT) to be energetically favorable. This CO2 insertion induces an apparent ~3% lattice expansion along the <002> and <011> directions of the ZIF-8 unit cell. The ability to stabilize MOFs and preserve their host-guest chemistry opens a rich materials space for scientific exploration and discovery using cryo-EM. Main Text:Metal-organic frameworks (MOFs) are a large class of highly porous materials 1-3 whose chemistry and crystalline structure can be tuned for potential applications in gas storage 4-6 , separations 7 , and catalysis 8 . Interactions between the host framework and guest molecule are central to such applications but are poorly understood at the single particle level. Although transmission electron microscopy (TEM) has been used to study the empty MOF framework 9-13 , guest insertion within the MOFs could not be imaged. The weak bonding between the guest molecule and framework is easily damaged even under low electron doses 14,15 . Furthermore, guest molecules are likely to desorb from MOF pores under the high vacuum condition (~10 -6 mbar) of the TEM at room temperature (supplementary text). Therefore, current studies rely on ensemble measurements using X-ray/neutron diffraction 16,17 , nuclear magnetic resonance 18 , or theoretical simulations 19 .However, the structural information obtained by these methods is averaged over bulk particles.Direct observations of individual MOF particles and their interaction with guest species at high spatial resolution have not been possible.Recently, cryogenic-electron microscopy (cryo-EM) was shown to be a powerful tool beyond structural biology. For instance, reactive lithium battery materials have been successfully stabilized for imaging and spectroscopy [20][21][22][23][24] . Such cryogenic condition may also reduce radiation damage to the MOF framework (supplementary text). However, cryo-EM procedures developed for biological or battery materials are not necessarily compatible with MOFs. Here, we establish a new cryo-EM protocol to reveal atomic host-guest structures within MOFs, demonstrating that these entities, held together by weak interactions, can be preserved for high-resolution imaging at cryogenic condition (Fig. 1...

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Atomic-resolution transmission electron microscopy of electron beam–sensitive crystalline materials

Cited by 426 publications

References 38 publications

Atomic scale insights into structure instability and decomposition pathway of methylammonium lead iodide perovskite

Atomic scale insights into structure instability and decomposition pathway of methylammonium lead iodide perovskite

Imaging and Mapping Characterization Tools for Perovskite Solar Cells

Cryo-EM Structures of Atomic Surfaces and Host-Guest Chemistry in Metal-Organic Frameworks

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