Fig. 1. Unit cell of an ideal cubic perovskite ABX₃ (left), and their extended crystalline structured connected by corner-sharing [BX₆]^4- octahedra (right). Reproduced with permission^[5]. Copyright 2016, Wiley-VCH

Fig. 2. The top layer atoms and simulated STM images^[33]. Copyright 2017, American Chemical Society

Fig. 3. TGA curve of CH₃NH₃PbI₃ decomposition^[48]. Copyright 2014, American Chemical Society

Fig. 4. The PL image of a large number of samples of MAPbI₃ excited by a commercial color camera at 458 nm before degradation, in which the pure MAPbI₃ structure is seen as red (left image); the right image is another image of the same area after degradation, in which green emission is observed, corresponding Launched on PbI^[52]₂.Copyright 2016, American Chemical Society

Fig. 5. Synthetic procedure for perovskite nanocrystals^[55]. Copyright 2016, Wiley-VCH

Fig. 6. The top-down synthetic method towards methylammonium lead halide perovskite nanocrystals^[58]. Copyright 2017, Wiley-VCH

Fig. 7. Schematic of the ABX₃ perovskite crystal structure (left); Elements that are used as ions in the mixed-metal perovskite materials (right)^[59].Copyright 2017, Royal Society of Chemistry

Fig. 8. Regular (PbI₆) octahedral chain in CH₃NH₃PbI₃ (left) and distorted chain in 12.5 at.% Cs-doped CH₃NH₃PbI₃ (right). (Gray/Purple/Brown/Blue/Pink/Turquoise sphere represents Pb/I/C/N/H/Cs atom)^[66]

Fig. 9. Schematic overview of contraction of octahedral after partially replacing Pb²⁺ by smaller Zn²⁺ ions^[72]

Fig. 10. The local geometry and the electron localization function (ELF) contour plots of MAPbI₃Cl_3-x before and after Zn doping^[69]. Copyright 2018，Elsevier

Fig. 11. Schematics formation of perovskite layer with and without addition of Ni²⁺ metal ions, scanning electron microscopy images of PbI₂ films with various NiCl₂:PbI₂ molar ratio, SEM images of corresponding perovskite films^[70]. Copyright 2018, Wiley-VCH

Fig. 12. The crystal structure of pristine MAPbI₃ (left) and MAPbI₃ (Ni) perovskite (right), in which Ni-I and Ni-N bonds are indicated with green lines^[70]. Copyright 2018, Wiley-VCH

Fig. 13. Perovskite structures of CH₃NH₃Pb (SCN)₂I (left) and CH₃NH₃PbI₃ (right) for comparison. Carbon gray, iodine red, lead pink, nitrogen blue, sulfur yellow^[80]. Copyright 2015, Wiley-VCH

Fig. 14. SEM images of CH₃NH₃Pb(SCN)_xI_3-x film prepared using DMF as the solvent of Pb(SCN)₂ and pure CH₃NH₃PbI₃ film (right)^[79]. Copyright 2019, American Chemical Society

Fig. 15. Schematic device structure of a MAPbI₃/UCns bilayer photodetector and scanning electron microscopy and transmission electron microscopy of the neat UCns layer, MAPbI₃ arrays and bilayer^[56]. Copyright 2017, American Chemical Society

Fig. 16. Detectivity and responsivity as a function of time showing long-term environmental stability for MAPbI₃/UCns bilayer and the neat MAPbI₃ photodetectors exposure under ambient condition with 30-40% relative humidity (RH)^[56]. Copyright 2017, American Chemical Society

Fig. 17. Water soaking showing strong water resistance of the MAPbI₃/UCns bilayer in contrast to the neat MAPbI₃ film^[56]. Copyright 2017, American Chemical Society

Fig. 18. Schematic configuration photodetector and cross-section SEM image of CH₃NH₃PbI₃/C8BTBT heterojunction thin films, and XRD spectra of CH₃NH₃PbI₃ (black) and CH₃NH₃PbI₃/C8BTBT heterojunction (red) thin films^[83]. Copyright 2017, Wiley-VCH

Fig. 19. Photocurrent and responsivity of CH₃NH₃PbI₃ and CH₃NH₃PbI₃/C8BTBT heterojunction photodetectors measured in ambient condition for 20 days^[83]. Copyright 2017, Wiley-VCH