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![(Color online) Phases characterization of MAPbI 3 under different temperature. Atomistic structures of (a) orthorhombic (below À111 °C), (b) tetragonal (À111 to 54 °C) and (c) cubic (over 54℃) MAPbI 3 . (d-f) SAED patterns of MAPbI 3 at À180, 25, 90 °C. (g-i) The corresponding simulated SAED patterns along the [1 0 0] direction of orthorhombic and tetragonal MAPbI 3 and [1 1 0] direction of cubic MAPbI 3.](profile/Jinjin-Zhao-2/publication/341594260/figure/fig1/AS:929708480937984@1598671183376/Color-online-Phases-characterization-of-MAPbI-3-under-different-temperature-Atomistic.png)
(Color online) Phases characterization of MAPbI 3 under different temperature. Atomistic structures of (a) orthorhombic (below À111 °C), (b) tetragonal (À111 to 54 °C) and (c) cubic (over 54℃) MAPbI 3 . (d-f) SAED patterns of MAPbI 3 at À180, 25, 90 °C. (g-i) The corresponding simulated SAED patterns along the [1 0 0] direction of orthorhombic and tetragonal MAPbI 3 and [1 1 0] direction of cubic MAPbI 3.
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Organic-inorganic hybrid perovskites (OIHPs) have attracted extensive research interest as a promising candidate for efficient and inexpensive solar cells. Transmission electron microscopy (TEM) characterizations that can benefit the fundamental understanding and the degradation mechanism are widely used for these materials. However, their sensitiv...
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... study the effect of temperature on the beam sensitivity, we first examine the phase of MAPbI 3 at different temperature, which is reported to be orthorhombic phase below À(111 ± 2) °C, tetragonal phase between À(111 ± 2) and (58 ± 5) °C and cubic phase over (58 ± 5) °C [26,27], as shown in Fig. 1a-c. The MAPbI 3 is grown to be a tetragonal phase (Fig. S1 online) [24], whose SAED pattern (Fig. 1e) matches with the simulated one (Fig. 1h). At À180 °C, the acquired SAED pattern (Fig. 1d) shows no superstucture diffraction spots of the orthorhombic phase, highlighted by the circle on the simulated ED pattern (Fig. 1g), suggesting ...
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... study the effect of temperature on the beam sensitivity, we first examine the phase of MAPbI 3 at different temperature, which is reported to be orthorhombic phase below À(111 ± 2) °C, tetragonal phase between À(111 ± 2) and (58 ± 5) °C and cubic phase over (58 ± 5) °C [26,27], as shown in Fig. 1a-c. The MAPbI 3 is grown to be a tetragonal phase (Fig. S1 online) [24], whose SAED pattern (Fig. 1e) matches with the simulated one (Fig. 1h). At À180 °C, the acquired SAED pattern (Fig. 1d) shows no superstucture diffraction spots of the orthorhombic phase, highlighted by the circle on the simulated ED pattern (Fig. 1g), suggesting that a low temperature in vacaum will not cause the transition from ...
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... sensitivity, we first examine the phase of MAPbI 3 at different temperature, which is reported to be orthorhombic phase below À(111 ± 2) °C, tetragonal phase between À(111 ± 2) and (58 ± 5) °C and cubic phase over (58 ± 5) °C [26,27], as shown in Fig. 1a-c. The MAPbI 3 is grown to be a tetragonal phase (Fig. S1 online) [24], whose SAED pattern (Fig. 1e) matches with the simulated one (Fig. 1h). At À180 °C, the acquired SAED pattern (Fig. 1d) shows no superstucture diffraction spots of the orthorhombic phase, highlighted by the circle on the simulated ED pattern (Fig. 1g), suggesting that a low temperature in vacaum will not cause the transition from tetragonl to orthorhombic phase for ...
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... of MAPbI 3 at different temperature, which is reported to be orthorhombic phase below À(111 ± 2) °C, tetragonal phase between À(111 ± 2) and (58 ± 5) °C and cubic phase over (58 ± 5) °C [26,27], as shown in Fig. 1a-c. The MAPbI 3 is grown to be a tetragonal phase (Fig. S1 online) [24], whose SAED pattern (Fig. 1e) matches with the simulated one (Fig. 1h). At À180 °C, the acquired SAED pattern (Fig. 1d) shows no superstucture diffraction spots of the orthorhombic phase, highlighted by the circle on the simulated ED pattern (Fig. 1g), suggesting that a low temperature in vacaum will not cause the transition from tetragonl to orthorhombic phase for the single crystal MAPbI 3 , which has ...
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... to be orthorhombic phase below À(111 ± 2) °C, tetragonal phase between À(111 ± 2) and (58 ± 5) °C and cubic phase over (58 ± 5) °C [26,27], as shown in Fig. 1a-c. The MAPbI 3 is grown to be a tetragonal phase (Fig. S1 online) [24], whose SAED pattern (Fig. 1e) matches with the simulated one (Fig. 1h). At À180 °C, the acquired SAED pattern (Fig. 1d) shows no superstucture diffraction spots of the orthorhombic phase, highlighted by the circle on the simulated ED pattern (Fig. 1g), suggesting that a low temperature in vacaum will not cause the transition from tetragonl to orthorhombic phase for the single crystal MAPbI 3 , which has also been observed in Diroll's study [28]. We also ...
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... 5) °C [26,27], as shown in Fig. 1a-c. The MAPbI 3 is grown to be a tetragonal phase (Fig. S1 online) [24], whose SAED pattern (Fig. 1e) matches with the simulated one (Fig. 1h). At À180 °C, the acquired SAED pattern (Fig. 1d) shows no superstucture diffraction spots of the orthorhombic phase, highlighted by the circle on the simulated ED pattern (Fig. 1g), suggesting that a low temperature in vacaum will not cause the transition from tetragonl to orthorhombic phase for the single crystal MAPbI 3 , which has also been observed in Diroll's study [28]. We also examine the phase at a high temperature and find the SAED pattern at 90 °C (Fig. 1f) indicates either a [1 1 0] direction of cubic ...
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... highlighted by the circle on the simulated ED pattern (Fig. 1g), suggesting that a low temperature in vacaum will not cause the transition from tetragonl to orthorhombic phase for the single crystal MAPbI 3 , which has also been observed in Diroll's study [28]. We also examine the phase at a high temperature and find the SAED pattern at 90 °C (Fig. 1f) indicates either a [1 1 0] direction of cubic phase (Fig. 1i) or a [1 0 0] direction of the tetragonal phase (Fig. 1h), thus making us unable to indentify the specific phase. Since the obtained SAED patterns can match with the pristine MAPbI 3 , it is concluded the structure of MAPbI 3 is not damaged under low and high temperature in ...
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... 1g), suggesting that a low temperature in vacaum will not cause the transition from tetragonl to orthorhombic phase for the single crystal MAPbI 3 , which has also been observed in Diroll's study [28]. We also examine the phase at a high temperature and find the SAED pattern at 90 °C (Fig. 1f) indicates either a [1 1 0] direction of cubic phase (Fig. 1i) or a [1 0 0] direction of the tetragonal phase (Fig. 1h), thus making us unable to indentify the specific phase. Since the obtained SAED patterns can match with the pristine MAPbI 3 , it is concluded the structure of MAPbI 3 is not damaged under low and high temperature in ...
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... cause the transition from tetragonl to orthorhombic phase for the single crystal MAPbI 3 , which has also been observed in Diroll's study [28]. We also examine the phase at a high temperature and find the SAED pattern at 90 °C (Fig. 1f) indicates either a [1 1 0] direction of cubic phase (Fig. 1i) or a [1 0 0] direction of the tetragonal phase (Fig. 1h), thus making us unable to indentify the specific phase. Since the obtained SAED patterns can match with the pristine MAPbI 3 , it is concluded the structure of MAPbI 3 is not damaged under low and high temperature in ...
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... also find a facet-dependent electron beam sensitivity for MAPbI 3 . Specifically, as shown in Fig. 4, the D t for a (1 0 0) exposed plane ranges from 210 to 500 e Å À2 which is about 10 times larger than a (0 0 1) exposed plane (30-41 e Å À2 ) for MAPbI 3 , obtained from Fig. S10 (online). This is because the migration barrier of iodine on (0 0 1) surface (0.32 eV) is smaller than that on (1 0 0) surface (0.45 eV), calculated by the first-principles study [37], suggesting an easier diffusion of iodine on (0 0 1) surface and relatively higher stability of (1 0 0) surface. In fact, the higher stability of (1 0 0) exposed ...
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... further study the effect of anion and compare the beam sensitivity of tetragonal MAPbI 3 and cubic MAPbBr 3 . The D t for MAPbI 3 ranges from 30 to 41 e Å À2 (Fig. S10a-c online) which is about half of MAPbBr 3 (63-113 e Å À2 ), acquired from Fig. S11 (online), suggesting that MAPbBr 3 is more stable than MAPbI 3 under electron beam iiradiation. The result is consistent with the conclution that MAPbBr 3 is more thermally and chemically stable than MAPbI 3 [39,40], further indicating it is reasonable to judge ...
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... further study the effect of anion and compare the beam sensitivity of tetragonal MAPbI 3 and cubic MAPbBr 3 . The D t for MAPbI 3 ranges from 30 to 41 e Å À2 (Fig. S10a-c online) which is about half of MAPbBr 3 (63-113 e Å À2 ), acquired from Fig. S11 (online), suggesting that MAPbBr 3 is more stable than MAPbI 3 under electron beam iiradiation. The result is consistent with the conclution that MAPbBr 3 is more thermally and chemically stable than MAPbI 3 [39,40], further indicating it is reasonable to judge the stability by comparing the D t values. OIHPs are extremely sensitive to electron ...
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... in Fig. 5c. When the summed dose increases to 24.9 e Å À2 , many additional superstructure diffraction spots appear (Fig. 5d,e), which is likely due to the ordered vacancies in MAPbI 2.5 , whose simulated ED (Fig. 5f) can match the FFT, as we reported previously [7]. In fact, a few dim additional diffraction spots have already appeared even at (Fig. S12 online), suggesting several e Å À2 is able to induce phase transition or damage for MAPbI 3 . Accordingly, on the one hand, extra attention should be paid to the dim additional superstructure spots that are easily ignored but indicating the phase transition when dealing with the atomic structure of MAPbI 3 . On the other hand, extremely low ...
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Organic–inorganic hybrid perovskites (OIHPs) have attracted extensive research interest as promising candidates for optoelectronic applications such as solar cells. Transmission electron microscopy (TEM)-based characterizations hold the key to revealing the morphological, microstructural, physical, and chemical information of OIHPs. However, their...
Citations
... Furthermore, it exceeds the Young's modulus values observed in other metal-free perovskites [27]. Typically, for perovskite crystal structures, the mechanical properties are predominantly determined by the metal center and coordination bonds [41][42][43][44]. In metal-free perovskites, the absence of a metallic core is compensated by hydrogen bonds within the A-site macromolecules and the surrounding network [28]. ...
... Nevertheless, the fundamental behaviors and effects of intragrain defects and impurities have been rarely studied, although they have been known essential to semiconductors in general 15,16 . One major hurdle in this research direction is to reliably image the microstructure and dynamics of intragrain defects and impurities in perovskites 3,[17][18][19][20] . Transmission electron microscopy (TEM) is a workhorse tool for materials characterization with high spatial resolution, which has been leveraged to demonstrate unambiguous observation of atomic-scale details of perovskites [21][22][23][24][25] . ...
... which are mainly contributed by the p orbitals of Pb and I atoms around the defect(Supplementary Figs. 17,18). For FA/Cs interstitials(Supplementary Figs. ...
Intragrain impurities can impart detrimental effects on the efficiency and stability of perovskite solar cells, but they are indiscernible to conventional characterizations and thus remain unexplored. Using in situ scanning transmission electron microscopy, we reveal that intragrain impurity nano-clusters inherited from either the solution synthesis or post-synthesis storage can revert to perovskites upon irradiation stimuli, leading to the counterintuitive amendment of crystalline grains. In conjunction with computational modelling, we atomically resolve crystallographic transformation modes for the annihilation of intragrain impurity nano-clusters and probe their impacts on optoelectronic properties. Such critical fundamental findings are translated for the device advancement. Adopting a scanning laser stimulus proven to heal intragrain impurity nano-clusters, we simultaneously boost the efficiency and stability of formamidinium-cesium perovskite solar cells, by virtual of improved optoelectronic properties and relaxed intra-crystal strain, respectively. This device engineering, inspired and guided by atomic-scale in situ microscopic imaging, presents a new prototype for solar cell advancement.
... In defective grain boundaries, even low doses of electrons change grain orientations [17] . Also, the degradation seems to be facet-dependent, indicating that the sample crystalline quality is crucial to the resilience to X-ray damage [18] . Interestingly, the cryogenic conditions do not avoid degradation but favor sample amorphization [19,20] . ...
Metal halide perovskites (MHP) suffer from photo-structural-chemical instabilities whose intricacy requires state-of-the-art tools to investigate their properties under various conditions. This study addresses the damage caused by focused X-ray beams on MHP through a correlative multi-technique approach. The damage after high-dose irradiation is noticeable in many ways: the loss of iodine and organic components, whose relative amount is reduced; the formation of an excavated area modifying the sample morphology; and an altered optical reflectivity indicating an optically inactive layer. The damage mechanism combines radiolysis and sputtering processes. Interestingly, the bulk underneath the excavated area maintains the initial halide proportion demonstrated by a stable photoluminescence emission energy. We also show that controlling the beam dose and environment is an excellent strategy to mitigate the dose harm. Hence, we combined a controlled X-ray dose with an inert N2 atmosphere to certify the conditions to probe MHP properties while mitigating damage efficiently. Finally, we applied optimized conditions in an X-ray ptychography experiment, reaching a 15-nm spatial resolution, an outcome that has never been attained in this class of materials.
... The existence of PAA in the CsPbI 3 film was evidenced by transmission electron microscopy (TEM). [43][44][45][46] Compared with control sample (Figure 2F), the PAA-treated CsPbI 3 sample is coated with an amorphous layer of several nanometers, which is due to the fact that the large-size PAA could not enter the lattice and aggregate between the grain boundaries. The formation of an amorphous layer may also contribute to the increase of device stability. ...
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... Since radiolysis is dominant at low electron-beam voltages, 42 higher electron beam voltages are less harmful to LHPs. 36,41 Furthermore, it is rather the total electron dose that is critical compared to the dose rate. 43 For organic as well as for inorganic LHPs, the decomposition into PbX 2 (X = I, Br, Cl) and metallic Pb has been reported by various authors. ...
Phase segregation in inorganic CsPb(BrxI1–x)3 nanoparticles (NPs) exhibiting originally a homogeneous [Br]:[I] mixture was investigated by means of in situ transmission electron microscopy (TEM) and evaluated by using multivariate analyses. The colloidal synthesis of the NPs offers good control of the halide ratios on the nanoscale. The spatially resolved TEM investigations were correlated with integral photoluminescence measurements. By this approach, the halide-segregation processes and their spatial distributions can be described as being governed by the interaction of three partial processes: electron- and photon-irradiation-induced iodide oxidation, local differences in band gap energy, and intrinsic lattice strain. Since the oxidation can be induced by both electron-beam and light irradiation, both irradiation types can induce phase segregation in CsPb(BrxI1–x)3 compounds. This makes in situ TEM a valuable tool to monitor phase transformation in corresponding NPs and thin films on the sub-nm scale.
... The structural degradation behaviors of perovskites under various experimental conditions were also investigated via low-dose electron diffraction and imaging techniques, which optimized the operating conditions of TEM for characterizing OIHPs [30]. As shown in Figure 5, a TEM cryogenic holder (Gatan 636) was employed to study the SAED patterns of MAPbI3 at different temperatures, which are reported to be orthorhombic phase below -(111 ± 2) °C, tetragonal phase between −(111 ± 2) and (58 ± 5) °C, and cubic phase over (58 ± 5) °C, as shown in Figure 5a-c [31]. The MAPbI3 is grown to be a tetragonal phase, whose SAED pattern ( Figure 5e) matches with the simulated one (Figure 5h). ...
... The structural instability of OIHP materials under various conditions (e.g., high temperature, oxygen, humid environment, light) becomes a vital issue to hamper the commercialization of PSCs [27][28][29]. By employing the SAED technique, Chen et al. investigated the decomposition mechanism of OIHPs under electron beam irradiations [30,31]. A possible decomposition way was thus proposed as shown in Figure 4. ...
... The structural degradation behaviors of perovskites under various experimental conditions were also investigated via low-dose electron diffraction and imaging techniques, which optimized the operating conditions of TEM for characterizing OIHPs [30]. As shown in Figure 5, a TEM cryogenic holder (Gatan 636) was employed to study the SAED patterns of MAPbI 3 at different temperatures, which are reported to be orthorhombic phase below −(111 ± 2) • C, tetragonal phase between −(111 ± 2) and (58 ± 5) • C, and cubic phase over (58 ± 5) • C, as shown in Figure 5a-c [31]. The MAPbI 3 is grown to be a tetragonal phase, whose SAED pattern (Figure 5e) matches with the simulated one (Figure 5h). ...
Transmission electron microscope (TEM) is thought as one powerful tool to imaging the atomic-level structure of organic inorganic hybrid perovskite (OIHP) materials, which provides valuable and essential guidance toward high performance OIHP-related devices. However, these OIHPs exhibit poor electron beam stability, severely limiting their practical applications in TEM. Here in this article, the application of TEM to obtain atomic-scale image of OIHPs, main obstacles in identifying the degradation product and future prospects of TEM in the characterization of OIHP materials are reviewed and presented. Three potential strategies (sample protection, low temperature technology, and low-dose technologies) are also proposed to overcome the current drawback of TEM technology.
... At 300 keV energy irradiation, their results suggested that impact displacement of H, C, N, and I can lead to the loss of both CH 3 NH 3 and I. Therefore, they believed that knock-on damage plays an important role in MAPbI 3 . On the contrary, Chen et al. 106 found that a higher accelerating voltage (300 kV) caused less damage to the films, and a lower accelerating voltage (80 kV) accelerated the damage to the films. As shown in Fig. 3(b), the authors obtained these four results with different experimental parameters from different regions of the sample on the same transmission electron microscopy grid. ...
... 93,94 In other words, their experimental results show that high accelerating voltages should be used in TEM characterization. Chen et al. 106 also investigated the effect of six exposed crystalline surfaces of perovskite on its stability, denoted #1-6 in Fig. 3(c). They found that MAPbI 3 (100) planes are more stable than (001) planes, possibly due to the high diffusion potential of iodide ions at the (100) facet, which makes diffusion difficult and stabilizes the crystal. ...
... Chen et al. 106 observed a similar phenomenon along the [001] and [100] directions of MAPbI 3 at À180 C, as illustrated in Figs. 12(e)-12(l). ...
In the last few years, organic–inorganic hybrid perovskites (OIHPs) have attracted immense research and industry attention for their application as light absorbers in solar cells and light-emitting diodes. Characterizing OIHP materials and optoelectronic devices using transmission electron microscopy (TEM)-based techniques has played a large role in understanding their structural, compositional, and electronic properties. However, the highly energetic and electrically charged electron beam radiation used in TEM can result in damage to the pristine structure, as OIHPs are unstable and highly sensitive to electron beams. This damage potentially obscures intrinsic information and leads to a serious misunderstanding of the microscopic structure–property–performance relationship for OIHP optoelectronic devices. To address this issue, we first review the electron and ion beam-induced degradation mechanism of OIHPs, followed by a review of the development of ultra-low-dose TEM techniques that can able to minimize this damage, thus can able to obtain reliable, intrinsic structural information about OIHPs from the atomic to micrometer length scales. Finally, we suggest a protocol for appropriate TEM specimen preparation and characterization techniques. This protocol can help ensure that future TEM studies of OIHPs give reliable information, thereby enabling a deeper understanding and optimization of the performance and long-term stability of OIHP optoelectronic devices.
... High-fidelity Kelvin-probe force microscopy (KPFM) demonstrated the distinct potential distribution of cross-sectional PSCs under dark and light illumination, which can be correlated to ion migrations and defect dynamics [13][14] . While beneficial, recent publications have reported the beam sensitivity of hybrid organic-inorganic perovskites 10,[15][16] . For instance, PSC lamellas in TEM displayed significant deterioration during data acquisition via chemical-bond breakage and local heating. ...
Focused ion beam (FIB) techniques have been frequently used to section metal-halide perovskites for microstructural investigations. However, the ion beams directly irradiated to the sample surface may alter the properties far different from pristine, potentially leading to modified deterioration mechanisms under aging stressors. Here, we combine complementary approaches to measure the subsurface characteristics of polished perovskite and identify the chemical species responsible for the measured properties. Analysis of the experimental results in conjunction with Monte Carlo simulations indicates that atomic displacements and local heating occur in the subsurface of methylammonium lead iodide (MAPbI3) by glazing Ar+ beam irradiation (15 nm by 4 kV at 3 degree). The lead-rich, iodine-deficient surface promotes rapid phase segregation under thermal aging conditions. On the other hand, despite the subsurface modification, our experiments confirm the rest of the MAPbI3 bulk retains the material integrity. Our observation supports that polished perovskites could serve in studying the properties of bulk or buried junctions far away from the altered subsurface with care.
... The same group of authors continued to study the degradation process of MAPbBr 3 by SAED and reported a similar degradation process, proposing a general degradation mechanism for MA-PbX 3 as halogen ion desorption → formation of ordered vacancies → formation of MAPbX 3-x mesophase → precipitation of PbX 2 ", as shown in Fig. 3(b) [69] . Similar degradation pathways had been generally recognized in oxide perovskites, but it was first proposed in halide perovskites [70,71] . More recently, similar degradation mechanism was reported in all-inorganic perovskite of γ-CsPbIBr 2 as well, where an intermediate phase [e.g., CsPb (1−x) (IBr) (3−y) ] with a superstructure of ordered vacancies was formed, followed by reduction from Pb 2+ to Pb 0 and thus precipitation of Pb nanoparticles [72] . ...
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.
... In addition, several other factors involved in our STEM approach may contribute to the minimization of ionization damage, which include enhancing the specimen conductivity due to carbon coating, thinning the FIBed crosssection specimen to below 50 nm, and applying a high electron accelerating voltage (300 kV). 42 All these enable maintaining the structure of device cross-section specimen even under the scanning electron probe with beam currents up to several pA, which is much higher than that in recent STEM characterization of MHPs by Rothmann et al. 13 Furthermore, we employed high angle annular dark-field (HAADF), rather than low angle annular dark-field (LAADF) mode for STEM imaging to acquire scattered electrons at a higher space angle. The higher electron dose rate enables the acquisition of highcontrast atomic-scale STEM-HAADF images with an acceptable signal to noise ratio (SNR), although LAADF is potentially superior in detecting a larger fraction of scattered electrons. ...
Deciphering the atomic and electronic structures of interfaces is key to developing state-of-the-art perovskite semiconductors. However, conventional characterization techniques have limited previous studies mainly to grain-boundary interfaces, whereas the intragrain-interface microstructures and their electronic properties have been much less revealed. Herein using scanning transmission electron microscopy, we resolved the atomic-scale structural information on three prototypical intragrain interfaces, unraveling intriguing features clearly different from those from previous observations based on standalone films or nanomaterial samples. These intragrain interfaces include composition boundaries formed by heterogeneous ion distribution, stacking faults resulted from wrongly stacked crystal planes, and symmetrical twinning boundaries. The atomic-scale imaging of these intragrain interfaces enables us to build unequivocal models for the ab initio calculation of electronic properties. Our results suggest that these structure interfaces are generally electronically benign, whereas their dynamic interaction with point defects can still evoke detrimental effects. This work paves the way toward a more complete fundamental understanding of the microscopic structure-property-performance relationship in metal halide perovskites.
