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Atomic-scale imaging of CH3NH3PbI3 structure and its decomposition pathway

Abstract

Understanding the atomic structure and structural instability of organic-inorganic hybrid perovskites is the key to appreciate their remarkable photoelectric properties and understand failure mechanism. Here, using low-dose imaging technique by direct-detection electron-counting camera in a transmission electron microscope, we investigate the atomic structure and decomposition pathway of CH3NH3PbI3 (MAPbI3) at the atomic scale. We successfully image the atomic structure of perovskite in real space under ultra-low electron dose condition, and observe a two-step decomposition process, i.e., initial loss of MA+ followed by the collapse of perovskite structure into 6H-PbI2 with their critical threshold doses also determined. Interestingly, an intermediate phase (MA0.5PbI3) with locally ordered vacancies can robustly exist before perovskite collapses, enlightening strategies for prevention and recovery of perovskite structure during the degradation. Associated with the structure evolution, the bandgap gradually increases from ~1.6 eV to ~2.1 eV. In addition, it is found that C-N bonds can be readily destroyed under irradiation, releasing NH3 and HI and leaving hydrocarbons. These findings enhance our understanding of the photoelectric properties and failure mechanism of MAPbI3, providing potential strategies into material optimization.

Introduction

Organic-inorganic hybrid perovskites (OIHPs) have attracted great research interests as promising materials for the next generation photovoltaic energy harvesting1,2, electro-optic detection3,4 and all-optical conversion5,6. Their remarkable properties are underpinned by atomic structures of hybrid perovskites7, ABX3, with organic species such as CH3NH3+ (MA+) and CH(NH2)2+ (FA+) occupying A-site and inorganic Pb2+ in B-site surrounded by X-octahedron formed by halogen elements like I and Br. In particular, the corner-sharing [PbI6]4− octahedron is believed to be beneficial for carrier diffusion8,9, while its distortion under chemical strain10 makes the band gap tunable, ideal for photovoltaic conversion. Moreover, the organic cations as well as the hydrogen bonding may lead to spontaneous polarization and ferroelectricity11, which promotes the separation of photoexcited electron-hole pairs, and thus reduces the recombination and improves the carrier lifetime12. These characteristics are responsible for the promising optoelectronic properties including high carrier mobility, long charge diffusion length and superior power conversion efficiency13. Nevertheless, the exact atomic structure of OIHPs is still unsettled, with two possible space groups, polar I4cm and nonpolar I4/mcm still hotly debated depending on the orientations of polar ions such as MA+14. While many perovskite oxides are polar with strong ferroelectricity, the polarity of OIHPs has yet to be firmly established15.

The lack of detailed understanding on atomic structure of OIHPs is largely due to the incapability to image OIHPs at the atomic scale16,17. It is well known that OIHPs are quite unstable and prone to decomposition under electron beam irradiation18,19,20,21. While much progress has been made in transmission electron microscopy (TEM) characterizations of OIHPs, direct visualization of atomic structure remains to be elusive. Initial TEM studies at low doses are mainly observing the morphology evolutions18 and structure transitions by reciprocal-space electron diffraction (ED) techniques19,20, and many of the earlier studies mislabeled the decomposition product PbI2 as MAPbI322,23,24. With the help of direct-detection electron-counting (DDEC) camera, high-resolution TEM (HRTEM) image of CH3NH3PbBr3 has been successfully obtained, which is much more stable than MAPbI3, though the observed off-centered MA+ with different orientations has not been well substantiated16. Recently, low-dose scanning transmission electron microscopy (STEM) technique provides atomic-scale insights into crystalline defects of CH(NH2)2PbI3 (FAPbI3), though the obtained atomic structures have already been damaged due to the large doses involved (53–221 e Å−2)25. Cryo-HRTEM has been used to image MAPbI3 at 100 e Å−2, yet the corresponding fast Fourier transform (FFT) pattern lacks (002) reflection, indicating substantial beam damage26. Furthermore, Li et al. found that superstructure reflections, a sign of structural transition due to beam damage, have already appeared at a dose as low as 7.6 e Å−2 (Ref. 27), and under Cryo-TEM, rapid amorphization has also been observed18,28. Indeed, the damage-free pristine structure of MAPbI3 has not been imaged at the atomic scale, and the corresponding real-space degradation pathway is yet to be established, thus motivating this study.

It is well known that STEM imaging introduces comparably larger dose and damage than low-dose HRTEM, while the contrast of HRTEM is sensitive to imaging condition, making it difficult to identify the specific atomic columns of MAPbI329. To overcome these difficulties, we adopted DDEC camera combined with an imaging technique using a negative value of the spherical-aberration coefficient30, and we have successfully captured the atomic structure of MAPbI3 in real space at a dose as low as 0.7 e Å−2, ensuring minimum beam damage if any. We further observed a two-step degradation pathway at the atomic scale, initiated with the loss of MA+ to form a superstructure MA0.5PbI3 with ordered MA+ vacancies (\({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\)), followed by the diffusion of I and Pb2+ to form the decomposed 6H-PbI2, with the corresponding critical doses also identified. During the process, C–N bonds can be destroyed under irradiation, releasing NH3 and HI and leaving hydrocarbons. The continuous structure transformations result in gradually increased bandgap, which is confirmed by scanning electron microscope cathodoluminescence (SEM-CL) experiments and validated by density functional theory (DFT) calculations. The direct visualization of the structure and degradation process at the atomic scale provides valuable sights into understanding the properties and stability of OIHPs. Furthermore, the emergence of superstructure before the collapse of perovskite framework also points toward a strategy for stabilizing the materials during the degradation.

Results

Identification of damage-free threshold dose

MAPbI3 nanocrystals with 10–20 nm size and good crystalline (Supplementary Fig. 1) are chosen for low-dose imaging. Using DDEC camera, HRTEM images of MAPbI3 can be acquired at low doses as shown in Fig. 1. It is noted that sufficient dose (Supplementary Fig. 2) is needed to obtain images with good quality and superstructure diffraction reflections appear due to the generation of intermediate phases when the dose is larger than 2.7 e Å−2 (Fig. 1b, g). Judging from the corresponding FFT patterns, the [001] MAPbI3 with intermediate phases gradually transforms at 13.6 e Å−2, and finally decomposes into [\(\bar{4}\)41] or [48\(\bar{1}\)] 6H-PbI2 (Supplementary Fig. 3) at 272.0 e Å−2. Such a 6H-PbI2 product has also been observed during the degradation of polycrystal MAPbI321. Thus the threshold dose for MAPbI3 without forming superstructures is determined to be 2.7 e Å−2 while 272.0 e Å−2 for the complete decomposition into PbI2. These determined doses can guide the future TEM characterizations of MAPbI3, especially for in situ ones such as under heat, electric field etc, for which the effect of electron beam irradiation is generally more significant due to the larger dose.

Fig. 1: Tracking structure evolution during the decomposition of MAPbI3.
figure1

ae Time-series HRTEM images during the degradation of MAPbI3 under electron beam irradiation. The corresponding doses are marked on each panel. Scale bar, 4 nm. fj The corresponding FFT patterns from MAPbI3 to 6H-PbI2. Circles indicate the superstructure diffraction reflections. Scale bar 2 nm−1.

Atomic-imaging of MAPbI3 structure and the intermediate phase

We then investigate the atomic structure via an imaging technique using a negative value of the spherical-aberration coefficient (Cs), which has enabled the successful observation of both light and heavy elements in oxide perovskite30. Figure 2a is the HRTEM image acquired at a negative Cs with an overfocus, wherein the brightest ‘I’ column, second brightest ‘II’ column and the darkest ‘III’ column can be distinguished. By comparing the atomic structure features of MAPbI3 (Fig. 2b) and HRTEM simulations (Supplementary Fig. 4), ‘I’, ‘II’ and ‘III’ columns are identified to be Pb2+-I, I and MA+, respectively. With increased dose, the intensity of MA+ is decreased at 10.5 e Å−2 as shown in Fig. 2c. The quantitative intensity analysis (Fig. 2d) further verifies that the intensity of MA+ progressively decreases within the initial 10.5 e Å−2, and then remains stable until 28.0 e Å−2 before subsequent gradual increase (Supplementary Fig. 5). The decreased intensity is caused by the formation of \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\)31 while the unchanged intensity is likely resulted from a relatively stable intermediate phase with the preserved perovskite framework. The subsequently increased intensity is resulted from the diffusion of I and Pb2+, as discussed in the following. Figure 2e and Supplementary Fig. 6 further show \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\) appears at every other ‘III’ column, as illustrated in Fig. 2f. Such a cation-vacancy-ordered structure with superstructure reflections (Supplementary Fig. 7) corresponds to MA0.5PbI3, whose stability is verified by molecular dynamic simulation (Supplementary Fig. 8). Accordingly, it is concluded that the loss of MA+ starts even at 1.0 e Å−2 and reaches a balanced state between ~10.5 and 28.0 e Å−2 to form ordered \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\), wherein the perovskite structure framework is preserved.

Fig. 2: Atomic-imaging of the loss of MA+ and intermediate phase.
figure2

a HRTEM image acquired at 0.7 e Å−2. ‘I’, ‘II’ and ‘III’ columns correspond to Pb2+-I, I, and MA+ columns respectively. Scale bar, 3 Å. b Structural model of tetragonal MAPbI3. c HRTEM image acquired at 10.5 e Å−2. d Intensity ratio of ‘III’ to ‘I’ column with increased doses. Nine data points of ‘III’ and ‘I’ type columns are used to obtain nine intensity ratios at each dose. The error bars represent standard deviations. e HRTEM image acquired at 28.0 e Å−2. f Structural model of MA0.5PbI3. The squares indicate \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\).

Evolution of the electronic structure and chemical bonding

The effect of ordered \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\) on its electronic structure is further investigated. Figure 3a, b show the calculated band structure of MAPbI3 and MA0.5PbI3. The band gap of MAPbI3 is 1.56 eV while it is 1.69 eV for MA0.5PbI3. The increased band gap is caused by the enhanced hybridization between I-5p and Pb2+-6p atomic orbitals and the conduct band minimum shifting about 0.1 eV to the high energy level, as explained in Supplementary Fig. 9. To confirm this analysis, we also carried out SEM CL experiments. Supplementary Fig. 10 shows the initial CL emission with a single excitonic peak at the photon energy of ~1.58 eV. Time-series CL emissions in Fig. 3c show that the observed peaks gradually become broader and shift to higher energy (2.05 eV) with the excitonic peak intensity decreasing. Such blue-shift is associated with the electron-beam-induced phase transformations32, i.e., forming the intermediate phases and decomposing into 6H-PbI2, considering that the calculated bandgaps of MAPbI3, MA0.5PbI3 and 6H-PbI2 are 1.56, 1.69, and 2.15 eV (Supplementary Fig. 11), respectively, in good agreement with the experimental observation.

Fig. 3: Electronic structure and chemical bonding evolutions during the degradation.
figure3

a, b Electronic structures of MAPbI3 and MA0.5PbI3. The Fermi level is set to zero. c Time-series CL spectra showing the bandgap gradually increases from 1.6 eV to 2.05 eV. The dashed lines show the calculated bandgaps at 1.56, 1.69 and 2.15 eV for MAPbI3, MA0.5PbI3 and 6H-PbI2, respectively. d Time-series vibrational spectra under ‘aloof’ mode with the electron probe ~30 nm away from MAPbI3. Black arrows indicate the peaks related with CH3-NH3+ rock, CH3 bend and NH3+ stretch. The background was subtracted by the power-law function. e Evolutions of normalized intensities of CH3 bending (cyan circles) and CH3-NH3+ rock (orange squares) during the degradation. Inset is the schematic diagram of ‘aloof’ mode showing the electron probe is ~30 nm away from MAPbI3 for the vibrational spectroscopy measurements.

In addition to electronic structure evolutions, it is worth investigating how the chemical bonding within organic components evolves (Fig. 3d, e) during the degradation. Vibrational electron energy loss spectroscopy operated at ‘aloof’ mode33 (inset of Fig. 3e), which enables the control of damage by changing the distance between electron beam and sample33, is used to obtain the characteristic vibrational modes of MAPbI3 (Fig. 3d). We can observe the vibrational signals of CH3-NH3+ rock at 113 meV, CH3 bend at 177 meV, and NH3+ stretch at 391 meV34. Time-series vibrational spectra show that the peaks of CH3-NH3+ rock and NH3+ stretch gradually disappear with increased time, suggesting the breakage of chemical bonds and/or escape of the certain gas. The extracted intensities of C–N and C–H bonds are shown in Fig. 3e and the processing details are shown in Supplementary Fig. 12. It is observed that the intensity of C–H bonds does not decrease during the degradation, suggesting the negligible release of carbonaceous gas. Such C–H bend signals can come from (–CH2–CH2–)35,36,37 or CH3I, while previous energy-dispersive spectroscopy19 and X-ray photoelectron spectroscopy38 results show that the atomic ratio of I to Pb for the beam-induced decomposition product is ~2, suggesting it to be PbI2 instead of CH3I. Thus, the C–H bend signal in the final byproduct likely comes from (–CH2–CH2–)35,36,37. In addition, the peak of CH3-NH3+ rock gradually disappears, suggesting its breakage, which leads to the formation and escape of volatile NH3, further explaining the gradually decreased intensity of the N–H bond (Fig. 3d) and the drop of N content to 0 (Ref. 38). Such degradation process has also been proposed in the previous study based on the exposure to moisture39, indicating similarities in degradation mechanism between the electron beam irradiation and other stimuli.

Atomic-scale observation of I and Pb2+ diffusion

Based on above study, we further investigate the atomic-scale decomposition pathway of MAPbI3. Figure 4a is the structure of perovskite with \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\), as illustrated in Fig. 4e. With increased doses, it is observed that the intensities of these three columns gradually change (Fig. 4b–d). A quantitative analysis of the intensity changes (Supplementary Fig. 13) shows that the intensities of ‘I’ columns initially increase and then gradually decrease while the intensities of ‘II’ columns continuously increase and the intensities of ‘III’ columns initially decrease and then gradually increase. Finally, intensities of all three type columns converge, indicating the formation of PbI2. The initial intensity decrease of MA+ column results from the formation of \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\), while the following increased intensity of MA+ column and decreased intensity of Pb2+-I column are believed to be caused by two kinds of I and Pb2+ diffusion as illustrated in Fig. 4f. One is the diffusion of I and Pb2+ into \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\) (Supplementary Fig. 14) while the other is caused by the [PbI6]4− octahedron slipping from corner sharing to edge sharing. Finally, the structure gradually evolves to PbI2. Figure 4e–g illustrate the atomic-scale structural evolution and the related ion migration during the decomposition from MAPbI3, MA0.5PbI3, to the final PbI2, mainly involving two processes, forming \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\,\)and the collapse of perovskite structure via the diffusion of Pb2+ and I. While previous literature21 proposed a two-step transformation of polycrystalline MAPbI3: Pb-related defects form at grain boundary and then phase transforms into PbI2, here we have observed an intermediate phase with locally ordered MA+ vacancies and revealed the atomic-scale decomposition pathway from MAPbI3 into PbI2, which enhances our understanding on the OHIPs’ degradation.

Fig. 4: Atomic-scale imaging of the decomposition pathway.
figure4

ad HRTEM images with increased doses during the degradation into PbI2. The corresponding doses are marked on each panel. Scale bar, 2 Å. e Atomic structure of MA0.5PbI3. Black squares indicate \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\). f Atomic structures to illustrate two kinds of I and Pb2+ diffusion. Left panel shows I and Pb2+ diffusing to \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\) while the right panel illustrates the [PbI6]4− octahedron slipping from corner sharing to edge sharing. g Atomic structure of PbI2.

Discussion

The extreme beam sensitivity of OIHPs hinders atomic-resolution imaging and thus the detailed investigations on their structure-property relationships. By DDEC camera, we have determined that the threshold dose for superstructure formation is about 2.7 e Å−2, and perovskite collapses into PbI2 within 272.0 e Å−2, both of which are smaller than those measured by ED19. This is mainly because ED pattern is obtained from a comparably larger region and represents the average information. These threshold conditions can guide future TEM characterizations and encourage more atomic-scale investigations about OIHPs.

Atomic-scale imaging of MAPbI3 and its degradation pathway allows us to better understand properties of OIHPs. For example, the observed off-center displacements (up to ~30 pm) between different atom columns likely indicate the polar nature of this material40, although further studies are needed to fully clarify this point, including determining MA+ configuration15 and quantifying the effects from possible mistilt and residual aberrations41. Furthermore, from the energetic point of view, the electron beam can transfer energy to the materials, enable ions to overcome the diffusion barrier and thus induce structure transformations, which is similar to heat- or light-induced phase transformations and degradation. For example, the decomposition of MAPbI3 into PbI2 with the release of NH3 and HI38 has also been observed under light illumination42 and moisture atmosphere39. In addition, the increase of bandgap during the degradation has also been observed under illumination43,44. Therefore, our investigation of electron beam-induced decomposition pathway can also help understand how the devices fail in practical working conditions. Besides, the superstructure phase with additional reflections has been previously reported to be likely related with octahedra tilts18 or ordered iodine vacancies19 based on reciprocal-space ED analysis, our atomic-resolution imaging, however, has suggested that cation-ordered vacancies are more likely. Such an intermediate phase (MA0.5PbI3) with locally ordered vacancies can stably exist before perovskite collapses, suggesting the degraded structure with partial formation of \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\) may be recovered. This likely sheds light into reversible photoinduced structural changes without forming PbI245. Such self-healing behavior under illumination has also been observed in MAPbI3-based solar cells46. In addition, the loss of MA+ causes the increase of bandgap, which provides a potentially new strategy to tune the bandgap in constructing tandem solar cells47. Also, the increased bandgap facilitates multiwave electroluminescence emission, adjusting various color luminescence under increasing bias voltage4,48.

Ion migration in OIHP-based electronic device is regarded as one of the most important processes, which contributes to the phase segregation, hysteresis in J-V curves and device degradation49. Previous studies about ion migration are either based on calculations or macro-measurements49 like time of flight secondary ion mass spectroscopy50, conductive atomic force microscopy51, and energy-dispersive X-ray mappings52,53, all without achieving the atomic-scale resolution in real space. Our atomic-resolution imaging provides direct evidence for the diffusion of MA+, I, and Pb2+ under electron beam irradiation, thus providing some insights into understanding ion-migration-induced phase transformations and degradation, and consequently the optimization of device performance. For example, since the gentle irradiation under illumination likely only causes the reversible formation of \({{{\mbox{V}}}}_{{{\mbox{MA}}}}^{-}\) with perovskite structure preserved, accordingly the device efficiency can be fully recovered at early degradation stages54. However, longer irradiation brings in I and Pb2+ diffusion to induce an irreversible transformation into PbI2, thus bringing in an irreversible device performance degradation. The irreversible performance decline has also been observed under elevated temperature55,56 and large bias57 due to the irreversible ion migration and structure degradation.

In summary, we have acquired the atomic structure of MAPbI3, determined the threshold doses during TEM characterizations, and clarified the atomic-scale ion migration during its degradation into PbI2. The degradation pathway is proposed to be a two-step, initialed by the loss of MA+ and followed by the diffusion of I and Pb2+ to form PbI2, during which C–N bonds can be destroyed under irradiation, releasing NH3 and HI and leaving hydrocarbons. Such degradation process leads to the gradual increase of bandgap. These findings can be used to guide the future TEM characterizations, enrich the understandings of the degradation mechanism and optimization strategies, and provide atomic-scale insights into understanding its fundamental properties.

Methods

MAPbI3 synthesis

MAPbI3 nanocrystals were bought from Xiamen Luman Technology Co., Ltd. Micro MAPbI3 was synthesized as previously reported58. Specifically, PbI2 and MAI were prepared in γ-butyrolactone (GBL) with molar ratio 1:1 and the concentration of 1.3 mol L−1. Then they were stirred at 70 °C for 12 h to obtain the precursor solution. After, the  precursor solution was filtered using polytetrafluoroethylene (PTFE) filter with 0.22 μm pore size. Two pieces of fluorine-doped tin oxide (FTO)/TiO2 substrates were clamped together and vertically and partially soaked in MAPbI3 precursor solution (10 ml) at 120 °C. Then the precursor solution was added twice one day in the nitrogen glove box. After several days, the substrates with single-crystal MAPbI3 film were brought out, and dried at 120 °C for 10 min in nitrogen.

Characterization and image analysis

ED patterns and HRTEM images were acquired at an aberration corrected FEI electron microscope (Titan Cubed Themis G2) operated at 300 kV. The Cs value is ~6.8 μm. Before acquiring images, the illumination range was set to be ~3 μm in diameter. To shorten the exposure time to electron beam, we adjusted the defocus and the astigmatism well in one ~3-μm region, then blanked beam, and moved to another ~3-μm region to acquire the HRTEM image. HRTEM images were acquired at a magnification of 77,000 by DDEC camera in electron-counting mode with the dose fractionation function. The correction of drift was achieved by using the DigitalMicrograph software by cross-correlation. The original image contains 40 subframes in 4 s and every 2 subframes were summed to enhance the contrast for a more accurate estimation of drift. Hanning window and Bandpass filters were combined to improve the accuracy of the cross correlation. HRTEM images in Figs. 12e, and 4, and Supplementary Figs. 2, 6, and 7 have been ABSF-filtered. HRTEM images in Fig. 2a, c have been first ABSF-filtered and then averaged from multiple regions using a home-made MATLAB code to reduce noise.

The morphology was characterized by SEM (FEI Quanta 200 F) and CL spectrum was acquired using Rainbow-CL of Beijing Goldenscope Technology Co., Ltd at 5 kV, spotsize 4. Each single CL spectrum was acquired using 4 s. Vibrational spectra characterizations were obtained under 30 kV using Nion U-HERMES200 electron microscope. Each spectrum was stacked from 200 single spectrum, obtained using 800 ms, and the processing details were shown in Supplementary Fig. 12. The simulated ED patterns were obtained by the SingleCrystal (Crystalmaker) software. Structural models were acquired using Vesta software.

DFT calculation

Our first-principles calculations were performed within the framework of DFT as implemented in the Vienna ab initio simulation package59,60. The ion-electron interaction was depicted by projector augmented-wave method61. The electron exchange correlation was treated by the generalized gradient approximation with Perdew–Bruke–Ernzerhof functional62. A kinetic cutoff energy was set as 500 eV for the Kohn–Sham orbitals being expanded in the plane-wave basis. The atomic positions were fully optimized with a conjugate gradient algorithm until the Hellman–Feynman force on each atom are less than 0.01 eV/Å63. The Monkhorst-Pack k- point meshes was sampled as 9 × 9 × 764.

Ab initio molecular dynamics simulation

We performed the ab initio molecular dynamic (AIMD) simulation. The plane-wave cutoff was set as 500 eV and the Brillouin zone is sampled at the Γ point. The AIMD was performed in the canonical ensemble at 300 K.

Data availability

The authors declare that all relevant data are included in the paper and Supplementary Information files and are available from the corresponding author upon reasonable request.

Code availability

Additional data including the codes are available from the corresponding author upon reasonable request.

References

  1. 1.

    Kojima, A., Teshima, K., Shirai, Y. & Miyasaka, T. Organometal halide perovskites as visible-light sensitizers for photovoltaic cells. J. Am. Chem. Soc. 131, 6050–6051 (2009).

    CAS  Article  Google Scholar 

  2. 2.

    Chen, W. et al. Efficient and stable large-area perovskite solar cells with inorganic charge extraction layers. Science 350, 944 (2015).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  3. 3.

    Cao, Y. et al. Perovskite light-emitting diodes based on spontaneously formed submicrometre-scale structures. Nature 562, 249–253 (2018).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  4. 4.

    Lin, K. et al. Perovskite light-emitting diodes with external quantum efficiency exceeding 20 per cent. Nature 562, 245–248 (2018).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  5. 5.

    Saouma, F. O., Stoumpos, C. C., Wong, J., Kanatzidis, M. G. & Jang, J. I. Selective enhancement of optical nonlinearity in two-dimensional organic-inorganic lead iodide perovskites. Nat. Commun. 8, 742 (2017).

    ADS  CAS  PubMed  PubMed Central  Article  Google Scholar 

  6. 6.

    Fan, Y. et al. Resonance-enhanced three-photon luminesce via lead halide perovskite metasurfaces for optical encoding. Nat. Commun. 10, 2085 (2019).

    ADS  PubMed  PubMed Central  Article  CAS  Google Scholar 

  7. 7.

    Huang, J., Yuan, Y., Shao, Y. & Yan, Y. Understanding the physical properties of hybrid perovskites for photovoltaic applications. Nat. Rev. Mater. 2, 17042 (2017).

    ADS  CAS  Article  Google Scholar 

  8. 8.

    Filip, M. R., Eperon, G. E., Snaith, H. J. & Giustino, F. Steric engineering of metal-halide perovskites with tunable optical band gaps. Nat. Commun. 5, 5757 (2014).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  9. 9.

    Milot, R. L., Eperon, G. E., Snaith, H. J., Johnston, M. B. & Herz, L. M. Temperature‐dependent charge‐carrier dynamics in CH3NH3PbI3 perovskite thin films. Adv. Funct. Mater. 25, 6218–6227 (2015).

    CAS  Article  Google Scholar 

  10. 10.

    Jiao, Y. et al. Strain engineering of metal halide perovskites on coupling anisotropic behaviors. Adv. Funct. Mater. 31, 2006243 (2021).

    CAS  Article  Google Scholar 

  11. 11.

    Li, W. et al. Chemically diverse and multifunctional hybrid organic–inorganic perovskites. Nat. Rev. Mater. 2, 16099 (2017).

    ADS  Article  Google Scholar 

  12. 12.

    Yan, W., Lu, G. & Liu, F. Effect of chlorine substitution on lattice distortion and ferroelectricity of CH3NH3PbI3. J. Phys. Chem. C. 120, 17972–17977 (2016).

    CAS  Article  Google Scholar 

  13. 13.

    National Renewable Energy Laboratory (NREL). Efficiency records chart. https://www.nrel.gov/pv/cell-efficiency.html. Accessed Aug 2021.

  14. 14.

    Frost, J. M. et al. Atomistic origins of high-performance in hybrid halide perovskite solar cells. Nano Lett. 14, 2584–2590 (2014).

    ADS  CAS  PubMed  PubMed Central  Article  Google Scholar 

  15. 15.

    Huang, B. et al. Polar or nonpolar? That is not the question for perovskite solar cells. Natl Sci. Rev. 8, nwab094 (2021).

    Article  Google Scholar 

  16. 16.

    Zhang, D. et al. Atomic-resolution transmission electron microscopy of electron beam-sensitive crystalline materials. Science 359, 675–679 (2018).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  17. 17.

    Song, K. et al. Atomic-resolution imaging of halide perovskites using electron microscopy. Adv. Energy Mater. 10, 1904006 (2020).

    ADS  CAS  Article  Google Scholar 

  18. 18.

    Rothmann, M. U. et al. Structural and chemical changes to CH3NH3PbI3 induced by electron and gallium ion beams. Adv. Mater. 30, 1800629 (2018).

    Article  CAS  Google Scholar 

  19. 19.

    Chen, S. et al. Atomic scale insights into structure instability and decomposition pathway of methylammonium lead iodide perovskite. Nat. Commun. 9, 4807 (2018).

    ADS  PubMed  PubMed Central  Article  CAS  Google Scholar 

  20. 20.

    Rothmann, M. U. et al. Direct observation of intrinsic twin domains in tetragonal CH3NH3PbI3. Nat. Commun. 8, 14547 (2017).

    ADS  CAS  PubMed  PubMed Central  Article  Google Scholar 

  21. 21.

    Alberti, A. et al. Pb clustering and PbI2 nanofragmentation during methylammonium lead iodide perovskite degradation. Nat. Commun. 10, 2196 (2019).

    ADS  PubMed  PubMed Central  Article  CAS  Google Scholar 

  22. 22.

    Chen, S. & Gao, P. Challenges, myths, and opportunities of electron microscopy on halide perovskites. J. Appl. Phys. 128, 10901 (2020).

    ADS  CAS  Article  Google Scholar 

  23. 23.

    Deng, Y. Perovskite decomposition and missing crystal planes in HRTEM. Nature 594, E6–E7 (2021).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  24. 24.

    Ning, Z. et al. Quantum-dot-in-perovskite solids. Nature 523, 324–328 (2015).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  25. 25.

    Rothmann, M. U. et al. Atomic-scale microstructure of metal halide perovskite. Science 370, 548 (2020).

    Article  CAS  Google Scholar 

  26. 26.

    Zhu, Y. et al. Direct atomic scale characterization of the surface structure and planar defects in the organic-inorganic hybrid CH3NH3PbI3 by Cryo-TEM. Nano Energy 73, 104820 (2020).

    CAS  Article  Google Scholar 

  27. 27.

    Li, Y. et al. Unravelling degradation mechanisms and atomic structure of organic-inorganic halide perovskites by cryo-EM. Joule 3, 2854–2866 (2019).

    CAS  PubMed  PubMed Central  Article  Google Scholar 

  28. 28.

    Chen, S. et al. Transmission electron microscopy of organic-inorganic hybrid perovskites: myths and truths. Sci. Bull. 65, 1643–1649 (2020).

    CAS  Article  Google Scholar 

  29. 29.

    Williams, D. B., Carter, C. B. & Microscopy, C. T. E. Transmission Electron Microscopy: A Textbook for Materials Science, 2nd ed. (Springer, New York, 2009).

  30. 30.

    Jia, C. L., Lentzen, M. & Urban, K. Atomic-resolution imaging of oxygen in perovskite ceramics. Science 299, 870 (2003).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  31. 31.

    Jia, C. L., Houben, L., Thust, A. & Barthel, J. On the benefit of the negative-spherical-aberration imaging technique for quantitative HRTEM. Ultramicroscopy 110, 500–505 (2010).

    CAS  Article  Google Scholar 

  32. 32.

    Xiao, C. et al. Mechanisms of electron-beam-induced damage in perovskite thin films revealed by cathodoluminescence spectroscopy. J. Phys. Chem. C. 119, 26904–26911 (2015).

    CAS  Article  Google Scholar 

  33. 33.

    Rez, P. et al. Damage-free vibrational spectroscopy of biological materials in the electron microscope. Nat. Commun. 7, 10945 (2016).

    ADS  CAS  PubMed  PubMed Central  Article  Google Scholar 

  34. 34.

    Glaser, T. et al. Infrared spectroscopic study of vibrational modes in methylammonium lead halide perovskites. J. Phys. Chem. Lett. 6, 2913–2918 (2015).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  35. 35.

    Luongo, J. P. Infrared study of polypropylene. J. Appl. Polym. Sci. 3, 302–309 (1960).

    CAS  Article  Google Scholar 

  36. 36.

    Gulmine, J. V., Janissek, P. R., Heise, H. M. & Akcelrud, L. Polyethylene characterization by FTIR. Polym. Test. 21, 557–563 (2002).

    CAS  Article  Google Scholar 

  37. 37.

    Van Helvoort, K., Knippers, W., Fantoni, R. & Stolte, S. The Raman spectrum of ethane from 600 to 6500 cm-1 stokes shifts. Chem. Phys. 111, 445–465 (1987).

    Article  Google Scholar 

  38. 38.

    Milosavljević, A. R., Huang, W., Sadhu, S. & Ptasinska, S. Low-energy electron-induced transformations in organolead halide perovskite. Angew. Chem. Int. Ed. 55, 10083–10087 (2016).

    Article  CAS  Google Scholar 

  39. 39.

    Li, Y. et al. Degradation by exposure of coevaporated CH3NH3PbI3 thin films. J. Phys. Chem. C. 119, 23996–24002 (2015).

    CAS  Article  Google Scholar 

  40. 40.

    Röhm, H. et al. Ferroelectric properties of perovskite thin films and their implications for solar energy conversion. Adv. Mater. 31, 1806661 (2019).

    Article  CAS  Google Scholar 

  41. 41.

    Gao, P. et al. Picometer-scale atom position analysis in annular bright-field STEM imaging. Ultramicroscopy 184, 177–187 (2018).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  42. 42.

    Song, Z. et al. Probing the origins of photodegradation in organic-inorganic metal halide perovskites with time-resolved mass spectrometry. Sustain. Energ. Fuels 2, 2460–2467 (2018).

    CAS  Article  Google Scholar 

  43. 43.

    Merdasa, A. et al. Super-resolution luminescence microspectroscopy reveals the mechanism of photoinduced degradation in CH3NH3PbI3 perovskite nanocrystals. J. Phys. Chem. C. 120, 10711–10719 (2016).

    CAS  Article  Google Scholar 

  44. 44.

    Ouafi, M., Jaber, B., Atourki, L., Bekkari, R. & Laânab, L. Improving UV stability of MAPbI3 perovskite thin films by bromide incorporation. J. Alloy. Compd. 746, 391–398 (2018).

    CAS  Article  Google Scholar 

  45. 45.

    Gottesman, R. et al. Photoinduced reversible structural transformations in free-standing CH3NH3PbI3 Perovskite Films. J. Phys. Chem. Lett. 6, 2332–2338 (2015).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  46. 46.

    Liu, X. et al. Light-induced degradation and self-healing inside CH3NH3PbI3-based solar cells. Appl. Phys. Lett. 116, 253303 (2020).

    ADS  CAS  Article  Google Scholar 

  47. 47.

    Hoke, E. T. et al. Reversible photo-induced trap formation in mixed-halide hybrid perovskites for photovoltaics. Chem. Sci. 6, 613–617 (2015).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  48. 48.

    Wang, N. et al. Perovskite light-emitting diodes based on solution-processed self-organized multiple quantum wells. Nat. Photon 10, 699–704 (2016).

    ADS  CAS  Article  Google Scholar 

  49. 49.

    Zhang, T., Hu, C. & Yang, S. Ion migration: a “double-edged sword” for halide-perovskite-based electronic devices. Small Methods 4, 1900552 (2020).

    ADS  Article  CAS  Google Scholar 

  50. 50.

    Li, J., Dong, Q., Li, N. & Wang, L. Direct evidence of ion diffusion for the silver-electrode-induced thermal degradation of inverted perovskite solar cells. Adv. Energy Mater. 7, 1602922 (2017).

    Article  CAS  Google Scholar 

  51. 51.

    Xia, G. et al. Nanoscale insights into photovoltaic hysteresis in triple‐cation mixed-halide perovskite: resolving the role of polarization and ionic migration. Adv. Mater. 31, 1902870 (2019).

    Article  CAS  Google Scholar 

  52. 52.

    Divitini, G. et al. In situ observation of heat-induced degradation of perovskite solar cells. Nat. Energy 1, 15012 (2016).

    ADS  CAS  Article  Google Scholar 

  53. 53.

    Yuan, Y. et al. Electric-field-driven reversible conversion between methylammonium lead triiodide perovskites and lead iodide at elevated temperatures. Adv. Energy Mater. 6, 1501803 (2016).

    Article  CAS  Google Scholar 

  54. 54.

    Khenkin, M. V. et al. Dynamics of photoinduced degradation of perovskite photovoltaics: from reversible to irreversible processes. ACS Appl. Energy Mater. 1, 799–806 (2018).

    CAS  Article  Google Scholar 

  55. 55.

    Tress, W. et al. Interpretation and evolution of open-circuit voltage, recombination, ideality factor and subgap defect states during reversible light-soaking and irreversible degradation of perovskite solar cells. Energ. Environ. Sci. 11, 151–165 (2018).

    CAS  Article  Google Scholar 

  56. 56.

    Mesquita, I., Andrade, L. & Mendes, A. Temperature impact on perovskite solar cells under operation. ChemSusChem 12, 2186–2194 (2019).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  57. 57.

    Bae, S. et al. Electric-field-induced degradation of methylammonium lead iodide perovskite solar cells. J. Phys. Chem. Lett. 7, 3091–3096 (2016).

    CAS  PubMed  Article  PubMed Central  Google Scholar 

  58. 58.

    Zhao, J. et al. Single crystalline CH3NH3PbI3 self-grown on FTO/TiO2 substrate for high efficiency perovskite solar cells. Sci. Bull. 62, 1173–1176 (2017).

    CAS  Article  Google Scholar 

  59. 59.

    Kresse, G. & Hafner, J. Ab initio molecular dynamics for open-shell transition metals. Phys. Rev. B 48, 13115 (1993).

    ADS  CAS  Article  Google Scholar 

  60. 60.

    Furthmüller, J. & Kresse, G. Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54, 11169–11186 (1996).

    ADS  Article  Google Scholar 

  61. 61.

    Blöchl, P. E. Projector augmented-wave method. Phys. Rev. B 50, 17953 (1994).

    ADS  Article  Google Scholar 

  62. 62.

    Perdew, J. P., Burke, K. & Ernzerhof, M. Generalized gradient approximation made simple. Phys. Rev. Lett. 77, 3865–3868 (1996).

    ADS  CAS  PubMed  Article  PubMed Central  Google Scholar 

  63. 63.

    Grimme, S., Antony, J., Ehrlich, S. & Krieg, H. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. J. Chem. Phys. 132, 154104 (2010).

    ADS  PubMed  Article  CAS  PubMed Central  Google Scholar 

  64. 64.

    Monkhorst, H. J. & Pack, J. D. Special points for Brillouin-zone integrations. Phys. Rev. B 13, 5188 (1976).

    ADS  MathSciNet  Article  Google Scholar 

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Acknowledgements

This work was supported by the National Natural Science Foundation of China (11974023, 52021006, 52125307, 11772207, U2130128, 22003074, 51575135, 51622503, U1537206 and 51621091), the Key R&D Program of Guangdong Province (2018B030327001, 2018B010109009), the “2011 Program” from the Peking-Tsinghua-IOP Collaborative Innovation Center of Quantum Matter, the Guangdong Provincial Key Laboratory Program from the Department of Science and Technology of Guangdong Province (2021B1212040001), Guangdong Basic and Applied Basic Research Foundation (2020A1515110580), the State Key Laboratory of Mechanics and Control of Mechanical Structures (Nanjing University of Aeronautics and astronautics) (MCMS-E-0420G01), SIAT Innovation Program for Excellent Young Researchers, the Shenzhen Science and Technology Innovation Committee (JCYJ20180507182257563), Natural Science Foundation of Heilongjiang Province of China (YQ2019E023), Natural Science Foundation of Hebei Province for distinguished young scholar (A2019210204) and Central guiding local science and technology development fund projects (216Z4302G). The authors gratefully acknowledge the Electron Microscopy Laboratory at Peking University for the use of electron microscopes and the support of the Center for Computational Science and Engineering at Southern University of Science and Technology. The authors also thank Mr. Yunkun Wang and Prof. Yu-nan Gao at Peking University for Raman test of MAPbI3, Prof. Yuan Yao at Institute of Physics, Chinese Academy of Sciences and Dr. Wenquan Ming at Hunan University for helpful discussions about the HRTEM data processing.

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P.G., J.L., J.Z. and S.C. conceived the project. P.G. and J.L. supervised the project. S.C. performed TEM experiments, analyzed experimental data and prepared the manuscript with the direction of P.G. and help from J.Q. and J.C. C.W. performed the calculations under the guidance of X.W. B.H. carried out vibrational spectroscopy and Z.L. performed CL measurements. Z.M. and W.H. grew MAPbI3 crystals under the guidance of J.Z. Q.Z, J.F., K.L. and D.Y. provided additional specimen. S.C., J.L. and P.G. wrote the manuscript and all authors participated in the revision.

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Correspondence to Jinjin Zhao, Xiao Wang, Jiangyu Li or Peng Gao.

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Chen, S., Wu, C., Han, B. et al. Atomic-scale imaging of CH3NH3PbI3 structure and its decomposition pathway. Nat Commun 12, 5516 (2021). https://doi.org/10.1038/s41467-021-25832-9

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