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Published November 15, 2017 | Supplemental Material
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Layer-by-Layer Degradation of Methylammonium Lead Tri-iodide Perovskite Microplates


The methylammonium lead iodide (MAPbI3) perovskite has attracted considerable interest for its high-efficiency, low-cost solar cells, but is currently plagued by its poor environmental and thermal stability. To aid the development of robust devices, we investigate here the microscopic degradation pathways of MAPbI3 microplates. Using in situ transmission electron microscopy to follow the thermal degradation process, we find that under moderate heating at 85°C the crystalline structure shows a gradual evolution from tetragonal MAPbI3 to trigonal lead iodide layered crystals with a fixed crystallographic direction. Our solid-state nudged elastic band calculations confirm that the surface-initiated layer-by-layer degradation path exhibits the lowest energy barrier for crystal transition. We further show experimentally and theoretically that encapsulation of the perovskites with boron nitride flakes suppresses the surface degradation, greatly improving its thermal stability. These studies provide mechanistic insight into the thermal stability of perovskites that suggests new designs for improved stability.

Additional Information

© 2017 Elsevier B.V. Received 15 June 2017, Revised 24 June 2017, Accepted 4 August 2017, Available online 20 September 2017. Published: September 20, 2017. X.D. acknowledges the support by National Science Foundation DMR1508144. Y.H. acknowledges the financial support from National Science Foundation EFRI-1433541. W.A.G. and H.X. acknowledge support by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award no. DE-SC0004993. Author Contributions: X.D., Y.H., and Z. Fan designed the research and experimental studies. W.A.G. and H.X. designed and conducted the theoretical studies. Z. Fan carried out the in situ HRTEM characterization. H.X. performed the theoretical calculations. Y.W., G.W., and Z.L. synthesized the material and conducted the XRD characterization. Z. Feng and Z.Z. analyzed the data. H.C.-C., S.-J.L., and Z. Fan prepared the hBN-perovskite-hBN heterostructure. X.D., Z. Fan, and H.X. wrote the manuscript. All the authors participated in discussions of the research.

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October 17, 2023