Fig. 1. Range of X-ray photon energy and some applications^[26]

Fig. 2. Schematic diagram of photoelectric absorption process^[27]

Fig. 3. Two working modes of semiconductor X-ray detectors^[29]

Fig. 4. Linear absorption coefficients varying with photon energy for some representative semiconductors^[33]

Fig. 5. Basic process of indirect X-ray detection^[36]

Fig. 6. Three stages of indirect X-ray detection^[42]

Fig. 7. Schematic diagram of single pixel of FPXI^[30]

Fig. 8. X-ray image of sharp edge^[51]

Fig. 9. Two coupled methods between scintillator screen and camera chip. (a) Optical system of lens; (b) fiber optic plate

Fig. 10. Schematic diagram of X-ray CT system^[7]

Fig. 11. X-ray direct imaging based on a-Se^[30]. (a) AX-2430 type FPXI; (b) X-ray image of hand

Fig. 12. X-ray direct detection and imaging based on perovskite single crystal. (a) MAPbI₃ single crystal^[74]; (b) integration of MAPbI₃ single crystal and Si^[20]; (c) X-ray imaging of letter "N"^[20]

Fig. 13. X-ray direct detection based on double perovskite single crystal^[18]. (a) Cs₂AgBiBr₆ single crystal; (b) test results of lowest detection limit

Fig. 14. X-ray direct detection and imaging based on perovskite polycrystal. (a) Polycrystalline perovskite solar cells^[22]; (b) X-ray image of leaf^[22]; (c) perovskite FPXI^[21]; (d) X-ray image of hand^[21]

Fig. 15. Manufacturing technique of perovskite polycrystal film. (a) MAPbI₃ polycrystal wafer and structure of detector^[93];(b) Cs₂AgBiBr₆ polycrystal wafer^[83]; (c) imaging results^[83]

Fig. 16. Traditional indirect X-ray imaging system. (a) Chest X-ray imaging system^[7]; (b) acicular structure of CsI^[37]; (c) evaporation of CsI∶Tl crystals on TFT^[36]; (d) difference of scattering between two kinds of scintillators^[39]

Fig. 17. Other traditional scintillators. (a) Glass scintillators and detector array in CT system^[7]; (b) SrI₂∶Eu scintillators^[39]; (c) LuAG∶Ce scintillators^[39]

Fig. 18. Two-dimensional perovskite scintillators. (a) (Phe)₂PbBr₄ crystal^[108]; (b) sub-nanosecond time resolution^[109]; (c) imaging demonstration of lead-free two-dimensional perovskite scintillators^[121]

Fig. 19. Inorganic perovskite nanocrystal scintillators. (a) RL spectra of CsPbX₃ all-inorganic perovskite nanocrystal scintillators^[23]; (b) indirect X-ray imager based on perovskite nanocrystal scintillators^[23]; (c) comparison of imaging resolution between CsPbBr₃ and GOS films^[123]; (d) high-concent CsPbBr₃ nanosheet solution and large area film^[124]; (e) structural schematic of CsPbBr₃@Cs₄PbBr₆^[24]

Fig. 20. Improvement of inorganic perovskite nanocrystal scintillators. (a) Perovskite glass scintillators^[126]; (b) stability test of glass scintillators under high temperature and high humidity^[126]; (c) high resolution of glass scintillators (~15 lp/mm)^[126]; (d) schematic diagram of CsPbBr₃ liquid scintillators and corresponding imaging demonstration^[129]

Fig. 21. Self-absorption effect of CsPbBr₃ and corresponding solution. (a) Self-absorption effect of CsPbBr₃^[131]; (b) CsPbBr₃ is coupled with organic luminescent materials to form plastic scintillators^[133]

Fig. 22. Other perovskite or halide scintillators. (a) Crystal structure and powder photo of Cs₂NaTbCl₆^[135]; (b) lattice structure of Cs₂Ag_0.6Na_0.4In_1-yBi_yCl₆^[25]; (c) large Stokes shift of Cs₂Ag_0.6Na_0.4In_1-yBi_yCl₆^[25]; (d) comparison of decay lifetime between CsI∶Tl and Cs₂Ag_0.6Na_0.4In_1-yBi_yCl₆^[25]