Metal-Free Perovskites for X-Ray Detection and Imaging: Progress and Prospects

Abstract

X-ray detection is essential in a wide range of fields, including medical diagnostics, industrial nondestructive testing, and homeland security. Among the materials used for X-ray detection, metal-free perovskites (MFPs) have recently emerged as promising class materials. They not only retain the excellent optoelectronic properties of conventional perovskites but also offer advantages typical of organic materials, such as flexibility, light weight, and chemical diversity. Importantly, MFPs are nontoxic and water degradable, with a density similar to that of human tissues, making them effective tissue-equivalent materials. Owing to these unique attributes, MFPs have garnered attention for their potential in low-cost, environmentally friendly X-ray detection technologies. In this review, we provide a comprehensive overview of MFPs, focusing on their crystal structures, compositional design, and physical characteristics. We then highlight recent advancements in their application as X-ray detectors, emphasizing material optimization, device performance, and practical implementation. Finally, we discuss the current challenges in this field and offer perspectives on future directions for MFPs as competitive materials for X-ray detection.

Keywords

ferroelectric / imaging / metal-free / perovskites / X-ray detection

References

[1] L. Yi, B. Hou, H. Zhao, and X. Liu, “X-Ray-to-Visible Light-Field Detection Through Pixelated Colour Conversion,” Nature618, no. 7964 (2023): 281-286.

[2] X. Ou, X. Qin, B. Huang, et al., “High-Resolution X-Ray Luminescence Extension Imaging,” Nature590, no. 7846 (2021): 410-415.

[3] X. Hu, S. Luo, J. Leng, et al., “Density-Discriminating Chromatic X-Ray Imaging Based on Metal Halide Nanocrystal Scintillators,” Science Advances9, no. 37 (2023): eadh5081.

[4] Y. He, I. Hadar, and M. G. Kanatzidis, “Detecting Ionizing Radiation Using Halide Perovskite Semiconductors Processed Through Solution and Alternative Methods,” Nature Photonics16, no. 1 (2021): 14-26.

[5] H. Wei and J. Huang, “Halide Lead Perovskites for Ionizing Radiation Detection,” Nature Communications10, no. 1 (2019): 1066.

[6] H. Wu, Y. Ge, G. Niu, and J. Tang, “Metal Halide Perovskites for X-Ray Detection and Imaging,” Matter4, no. 1 (2021): 144-163.

[7] Z. Li, F. Zhou, H. Yao, Z. Ci, Z. Yang, and Z. Jin, “Halide Perovskites for High-Performance X-Ray Detector,” Materials Today48 (2021): 155-175.

[8] Y. Zhou, J. Chen, O. M. Bakr, and O. F. Mohammed, “Metal Halide Perovskites for X-Ray Imaging Scintillators and Detectors,” ACS Energy Letters6, no. 2 (2021): 739-768.

[9] X. He, Y. Deng, D. Ouyang, et al., “Recent Development of Halide Perovskite Materials and Devices for Ionizing Radiation Detection,” Chemical Reviews123, no. 4 (2023): 1207-1261.

[10] a) F. Zhou, Z. Li, W. Lan, Q. Wang, and Z. Jin, “Halide Perovskite, a Potential Scintillator for X-Ray Detection,” Small Methods4, no. 10 (2020): 2000506. b) Y. Xu, A. Ying, J. Peng, et al., “Hybrid Perovskite X-Ray Detectors With Enhanced Radioluminescence via Thermally Activated Delayed Fluorescence,” Science China Materials66, no. 2 (2022): 724-732.

[11] X. Wang, H. Shi, H. Ma, et al., “Organic Phosphors With Bright Triplet Excitons for Efficient X-Ray-Excited Luminescence,” Nature Photonics15, no. 3 (2021): 187-192.

[12] W. Ma, Y. Su, Q. Zhang, et al., “Thermally Activated Delayed Fluorescence (TADF) Organic Molecules for Efficient X-Ray Scintillation and Imaging,” Nature Materials21, no. 2 (2021): 210-216.

[13] P. Ran, L. Yang, T. Jiang, et al., “Multispectral Large-Panel X-Ray Imaging Enabled by Stacked Metal Halide Scintillators,” Advanced Materials34, no. 42 (2022): 2205458.

[14] F. Cao, D. Yu, W. Ma, et al., “Shining Emitter in a Stable Host: Design of Halide Perovskite Scintillators for X-Ray Imaging From Commercial Concept,” ACS Nano14, no. 5 (2019): 5183-5193.

[15] X. Li, C. Meng, B. Huang, D. Yang, X. Xu, and H. Zeng, “All-Perovskite Integrated X-Ray Detector With Ultrahigh Sensitivity,” Advanced Optical Materials8, no. 12 (2020): 2000273.

[16] Y. Wang, M. Li, Z. Chai, Y. Wang, and S. Wang, “Perovskite Scintillators for Improved X-Ray Detection and Imaging,” Angewandte Chemie International Edition62, no. 38 (2023): 2304638.

[17] J. Chen, G. Liu, F. Chen, et al., “Binaphthol Diimide Scintillators for X-Ray Imaging,” Science China Materials67, no. 8 (2024): 2583-2589.

[18] G.-H. Dun, H. Zhang, K. Qin, et al., “Wafer-Scale Photolithography-Pixeled Pb-Free Perovskite X-Ray Detectors,” ACS Nano16, no. 7 (2022): 10199-10208.

[19] J. Peng, Y. Xu, F. Yao, H. Huang, R. Li, and Q. Lin, “Ion-Exchange-Induced Slow Crystallization of 2D-3D Perovskite Thick Junctions for X-Ray Detection and Imaging,” Matter5, no. 7 (2022): 2251-2264.

[20] Y. Liu, Y. Zhang, X. Zhu, et al., “Triple-Cation and Mixed-Halide Perovskite Single Crystal for High-Performance X-Ray Imaging,” Advanced Materials33, no. 8 (2021): 2006010.

[21] L. Gao and Q. Yan, “Recent Advances in Lead Halide Perovskites for Radiation Detectors,” Solar RRL4, no. 2 (2019): 1900210.

[22] J.-W. Lee, S. Tan, S. I. Seok, Y. Yang, and N.-G. Park, “Rethinking the A Cation in Halide Perovskites,” Science375, no. 6583 (2022): eabj1186.

[23] Y. Li, Y. Lei, H. Wang, and Z. Jin, “Two-Dimensional Metal Halides for X-Ray Detection Applications,” Nano-Micro Letters15, no. 1 (2023): 128.

[24] L. Li, H. Chen, Z. Fang, et al., “An Electrically Modulated Single-Color/Dual-Color Imaging Photodetector,” Advanced Materials32, no. 24 (2020): 1907257.

[25] P. Shi, Y. Ding, B. Ding, et al., “Oriented Nucleation in Formamidinium Perovskite for Photovoltaics,” Nature620, no. 7973 (2023): 323-327.

[26] E. Ercan, C. L. Liu, and W. C. Chen, “Nano–Micro Dimensional Structures of Fiber-Shaped Luminous Halide Perovskite Composites for Photonic and Optoelectronic Applications,” Macromolecular Rapid Communications41, no. 21 (2020): 2000157.

[27] Z. Wang, S. Tie, H. Zhang, et al., “Supple Formamidinium-Based Low-Dimension Perovskite Derivative for Sensitive and Ultrastable X-Ray Detection,” ACS Nano17, no. 14 (2023): 13638-13647.

[28] P. Zhang, Y. Hua, Y. Xu, et al., “Ultrasensitive and Robust 120 keV Hard X-Ray Imaging Detector Based on Bixed-Halide Perovskite CsPbBr_3−nI_n Single Crystals,” Advanced Materials34, no. 12 (2022): 2106562.

[29] X. Zhang, T. Zhu, C. Ji, Y. Yao, and J. Luo, “In Situ Epitaxial Growth of Centimeter-Sized Lead-Free (BA)₂CsAgBiBr₇/Cs₂AgBiBr₆ Heterocrystals for Self-Driven X-Ray Detection,” Journal of the American Chemical Society143, no. 49 (2021): 20802-20810.

[30] X. Li, X. Lan, W. Liu, X. Cui, and Z. Cui, “Toxicity, Migration and Transformation Characteristics of Lead in Soil-Plant System: Effect of Lead Species,” Journal of Hazardous Materials395 (2020): 122676.

[31] A. Babayigit, A. Ethirajan, M. Muller, and B. Conings, “Toxicity of Organometal Halide Perovskite Solar Cells,” Nature Materials15, no. 3 (2016): 247-251.

[32] R. Vidal, J.-A. Alberola-Borràs, S. N. Habisreutinger, et al., “Assessing Health and Environmental Impacts of Solvents for Producing Perovskite Solar Cells,” Nature Sustainability4, no. 3 (2021): 277-285.

[33] N.-G. Park, “Green Solvent for Perovskite Solar Cell Production,” Nature Sustainability4, no. 3 (2020): 192-193.

[34] Y. Zhu and J. Zhang, “Antimony-Based Halide Perovskite Nanoparticles as Lead-Free Photocatalysts for Controlled Radical Polymerization,” Macromolecular Rapid Communications45, no. 9 (2024): 2300695.

[35] R. Nag and E. Cummins, “Human Health Risk Assessment of Lead (Pb) Through the Environmental-Food Pathway,” Science of the Total Environment810 (2022): 151168.

[36] H.-Y. Ye, Y.-Y. Tang, P.-F. Li, et al., “Metal-Free Three-Dimensional Perovskite Ferroelectrics,” Science361, no. 6398 (2018): 151-155.

[37] W. Li and L.-J. Ji, “Perovskite Ferroelectrics Go Metal Free,” Science361, no. 6398 (2018): 132.

[38] C. A. Bremner, M. Simpson, and W. T. A. Harrison, “New Molecular Perovskites: Cubic C₄N₂H₁₂·NH₄Cl₃·H₂O and 2-H Hexagonal C₆N₂H₁₄·NH₄Cl₃,” Journal of the American Chemical Society124, no. 37 (2002): 10960-10961.

[39] Z. Li, S. Shi, G. Peng, et al., “Metal-Free Hydrazinium Halide Perovskitoid Single Crystals for X-Ray Detection,” Nano Letters23, no. 21 (2023): 9972-9979.

[40] X. Song, Q. Li, J. Han, et al., “Highly Luminescent Metal-Free Perovskite Single Crystal for Biocompatible X-Ray Detector to Attain Highest Sensitivity,” Advanced Materials33, no. 36 (2021): 2102190.

[41] Z. Li, G. Peng, Z. Li, et al., “Hydrogen Bonds Strengthened Metal-Free Perovskite for Degradable X-Ray Detector With Enhanced Stability, Flexibility and Sensitivity,” Angewandte Chemie International Edition62, no. 10 (2023): e202218349.

[42] L. He, X. Yu, and W. Li, “Recent Progress and Trends in X-Ray-Induced Photodynamic Therapy With Low Radiation Doses,” ACS Nano16, no. 12 (2022): 19691-19721.

[43] N. Kimoto, H. Hayashi, C. Lee, T. Maeda, and A. Katsumata, Advanced X-Ray Radiation Detection: Medical Imaging and Industrial Applications, ed. K. Iniewski (Springer International Publishing, 2023), 75-106.

[44] X. Song, Q. Cui, Y. Liu, et al., “Metal-Free Halide Perovskite Single Crystals With Very Long Charge Lifetimes for Efficient X-Ray Imaging,” Advanced Materials32, no. 42 (2020): 2003353.

[45] Z. Li, Z. Li, G. Peng, et al., “PF₆⁻ Pseudohalides Anion Based Metal-Free Perovskite Single Crystal for Stable X-Ray Detector to Attain Record Sensitivity,” Advanced Materials35, no. 25 (2023): 2300480.

[46] H. Li, T. Li, C. Ma, et al., “‘One-Click Restart’ Recycling of Metal-Free Perovskite X-Ray Detectors,” Advanced Materials36, no. 26 (2024): 2400783.

[47] X. Song, H. Cohen, J. Yin, et al., “Low Dimensional, Metal-Free, Hydrazinium Halide Perovskite-Related Single Crystals and Their Use as X-Ray Detectors,” Small19, no. 30 (2023): 2300892.

[48] Y. Wu, Z. Li, Y. Lei, and Z. Jin, “Metal-Free Perovskites for X-Ray Detection,” Chemistry—A European Journal29, no. 56 (2023): e202301536.

[49] J. Bie, D.-B. Yang, M.-G. Ju, et al., “Molecular Design of Three-Dimensional Metal-Free A(NH₄)X₃ Perovskites for Photovoltaic Applications,” JACS Au1, no. 4 (2021): 475-483.

[50] X. Xu, Q. Zhou, Y. Wang, et al., “Expanding the Toolbox of Metal-Free Organic Halide Perovskite for X-Ray Detection,” Chinese Chemical Letters35, no. 9 (2023): 109272.

[51] L.-L. Chu, T. Zhang, W.-Y. Zhang, et al., “Three-Dimensional Metal-Free Molecular Perovskite With a Thermally Induced Switchable Dielectric Response,” Journal of Physical Chemistry Letters11, no. 5 (2020): 1668-1674.

[52] H. S. Choi, S. Li, I.-H. Park, et al., “Tailoring the Coercive Field in Ferroelectric Metal-Free Perovskites by Hydrogen Bonding,” Nature Communications13, no. 1 (2022): 794.

[53] P. Deng, X.-Y. Guo, H. Fang, R. Liu, and P.-W. Chen, “Combustion Behavior and Mechanism of Molecular Perovskite Energetic Material DAP-4-Based Composites With Metal Fuel Al,” Defence Technology27 (2023): 53-63.

[54] K. Li, L.-Y. Dong, H.-X. Xu, et al., “Electronic Structures and Elastic Properties of a Family of Metal-Free Perovskites,” Materials Chemistry Frontiers3, no. 8 (2019): 1678-1685.

[55] V. M. Goldschmidt, “Die Gesetze der Krystallochemie,” Naturwissenschaften14, no. 21 (1926): 477-485.

[56] Q. Cui, S. F. Liu, and K. Zhao, “Structural and Functional Insights Into Metal-Free Perovskites,” Journal of Physical Chemistry Letters13, no. 23 (2022): 5168-5178.

[57] B. Zhang, T. Zheng, J. You, et al., “Electron-Phonon Coupling Suppression by Enhanced Lattice Rigidity in 2D Perovskite Single Crystals for High-Performance X-Ray Detection,” Advanced Materials35, no. 7 (2023): 2208875.

[58] H. Zhang, Z.-K. Xu, Z.-X. Wang, et al., “Large Piezoelectric Response in a Metal-Free Three-Dimensional Perovskite Ferroelectric,” Journal of the American Chemical Society145, no. 8 (2023): 4892-4899.

[59] T. W. Kasel, Z. Deng, A. M. Mroz, C. H. Hendon, K. T. Butler, and P. Canepa, “Metal-Free Perovskites for Non Linear Optical Materials,” Chemical Science10, no. 35 (2019): 8187-8194.

[60] Y. Ai, X.-G. Chen, P.-P. Shi, et al., “Fluorine Substitution Induced High T_c of Enantiomeric Perovskite Ferroelectrics: (R)- and (S)-3-(Fluoropyrrolidinium)MnCl₃,” Journal of the American Chemical Society141, no. 10 (2019): 4474-4479.

[61] Y. Shang, R.-K. Huang, S.-L. Chen, et al., “Metal-Free Molecular Perovskite High-Energetic Materials,” Crystal Growth & Design20, no. 3 (2020): 1891-1897.

[62] H.-Y. Zhang, Y.-Y. Tang, P.-P. Shi, and R.-G. Xiong, “Toward the Targeted Design of Molecular Ferroelectrics: Modifying Molecular Symmetries and Homochirality,” Accounts of Chemical Research52, no. 7 (2019): 1928-1938.

[63] X. Li, M. Kepenekian, L. Li, et al., “Tolerance Factor for Stabilizing 3D Hybrid Halide Perovskitoids Using Linear Diammonium Cations,” Journal of the American Chemical Society144, no. 9 (2022): 3902-3912.

[64] H. Wang, J. Li, H. Lu, et al., “Chiral Hybrid Germanium(II) Halide With Strong Nonlinear Chiroptical Properties,” Angewandte Chemie International Edition62, no. 41 (2023): e202309600.

[65] Y. Shang, Z.-H. Yu, R.-K. Huang, et al., “Metal-Free Hexagonal Perovskite High-Energetic Materials With NH₃OH⁺/NH₂NH³⁺ as B-Site Cations,” Engineering6, no. 9 (2020): 1013-1018.

[66] Q. Cui, X. Liu, N. Li, et al., “A New Metal-Free Molecular Perovskite-Related Single Crystal With Quantum Wire Structure for High-Performance X-Ray Detection,” Small20, no. 13 (2023): 2308945.

[67] P. Dong, C. Lin, N. Ye, and M. Luo, “Dimensional Regulation in Metal-Free Perovskites by Compositional Engineering to Achieve Record Low X-Ray Detection Limits,” Angewandte Chemie International Edition63, no. 30 (2024): e2407048.

[68] H. S. Choi, J. Lin, G. Wang, et al., “Molecularly Thin, Two-Dimensional All-Organic Perovskites,” Science384, no. 6691 (2024): 60-66.

[69] Y. Lei, M. Yin, C. Shi, et al., “npj Flexible Electron,” npj Flexible Electronics8, no. 1 (2024): 46.

[70] Y. Huang, L. Qiao, Y. Jiang, et al., “A-Site Cation Engineering for Highly Efficient MAPbI₃ Single-Crystal X-Ray Detector,” Angewandte Chemie International Edition58, no. 49 (2019): 17834-17842.

[71] W. Li, X. Feng, K. Guo, et al., “Prominent Free Charges Tunneling Through Organic Interlayer of 2D Perovskites,” Advanced Materials35, no. 18 (2023): 2211808.

[72] W.-X. Zhang, S.-L. Chen, Y. Shang, Z.-H. Yu, and X.-M. Chen, “Molecular Perovskites as a New Platform for Designing Advanced Multi-Component Energetic Crystals,” Energetic Materials Frontiers1, no. 3–4 (2020): 123-135.

[73] M.-J. Sun, C. Zheng, Y. Gao, et al., “Linear Electro-Optic Modulation in Highly Polarizable Organic Perovskites,” Advanced Materials33, no. 4 (2021): 2006368.

[74] H.-S. Wu, B. T. Murti, J. Singh, P.-K. Yang, and M.-L. Tsai, “Prospects of Metal-Free Perovskites for Piezoelectric Applications,” Advanced Science9, no. 12 (2022): 2104703.

[75] Q. Cui, X. Song, Y. Liu, et al., “Halide-Modulated Self-Assembly of Metal-Free Perovskite Single Crystals for Bio-Friendly X-Ray Detection,” Matter4, no. 7 (2021): 2490-2507.

[76] H. Morita, R. Tsunashima, S. Nishihara, and T. Akutagawa, “Doping of Metal-Free Molecular Perovskite With Hexamethylenetetramine to Create Non-Centrosymmetric Defects,” CrystEngComm22, no. 13 (2020): 2279-2282.

[77] Q. Li, S. Li, M. Qu, and J. Xiao, “Anisotropic Impact Sensitivity of Metal-Free Molecular Perovskite High-Energetic Material (C₆H₁₄N₂)(NH₂NH₃)(ClO₄)₃ by First-Principles Study,” ACS Omega7, no. 20 (2022): 17185-17191.

[78] V. F. Dvoryankin, G. G. Dvoryankina, A. A. Kudryashov, A. G. Petrov, V. D. Golyshev, and S. V. Bykova, “X-Ray Sensitivity of Cd0.9Zn0.1Te Detectors,” Technical Physics55, no. 2 (2010): 306-308.

[79] M. Li, H. Li, W. Li, et al., “Oriented 2D Perovskite Wafers for Anisotropic X-Ray Detection Through a Fast Tableting Strategy,” Advanced Materials34, no. 8 (2022): 2108020.

[80] Z. Wang, H. Lu, W. Zhao, et al., “Against the Wallach’s Rule Through Rational Design of Metal-Free Chiral Perovskites Toward Efficient Red Circularly Polarized Phosphorescence,” Angewandte Chemie International Edition64, no. 19 (2025): 2501360.

[81] Z. Wang, X. Qiu, H. Wang, et al., “Chiral Metal-Free Anti-Perovskite With Strong Chiroptical Nonlinearity,” Angewandte Chemie International Edition64, no. 6 (2024): 2420249.

[82] M. G. Ehrenreich, Z. Zeng, S. Burger, et al., “Mechanical Properties of the Ferroelectric Metal-Free Perovskite [MDABCO](NH₄)I₃,” Chemical Communications55, no. 27 (2019): 3911-3914.

[83] T. Handa, R. Hashimoto, G. Yumoto, T. Nakamura, A. Wakamiya, and Y. Kanemitsu, “Metal-Free Ferroelectric Halide Perovskite Exhibits Visible Photoluminescence Correlated With Local Ferroelectricity,” Science Advances8, no. 25 (2022): eabo1621.

[84] Z.-H. Yu, D.-X. Liu, Y.-Y. Ling, et al., “Periodate-Based Molecular Perovskites as Promising Energetic Biocidal Agents,” Science China Materials66, no. 4 (2022): 1641-1648.

[85] Y. Feng, J. Zhang, W. Cao, J. Zhang, and J. n. M. Shreeve, “A Promising Perovskite Primary Explosive,” Nature Communications14, no. 1 (2023): 7765.

[86] J.-J. Wang, D. Fortino, B. Wang, X. Zhao, and L.-Q. Chen, “Extraordinarily Large Electrocaloric Strength of Metal-Free Perovskites,” Advanced Materials32, no. 7 (2020): 1906224.

[87] K. D. G. I. Jayawardena, H. M. Thirimanne, S. F. Tedde, et al., “Millimeter-Scale Unipolar Transport in High Sensitivity Organic–Inorganic Semiconductor X-Ray Detectors,” ACS Nano13, no. 6 (2019): 6973-6981.

[88] Y. He, W. Ke, G. C. B. Alexander, et al., “Resolving the Energy of γ-Ray Photons With MAPbI₃ Single Crystals,” ACS Photon5, no. 10 (2018): 4132-4138.

[89] Y. Liu, Z. Xu, Z. Yang, et al., “Inch-Size 0D-Structured Lead-Free Perovskite Single Crystals for Highly Sensitive Stable X-Ray Imaging,” Matter3, no. 1 (2020): 180-196.

[90] Q. Wei, X. Fan, P. Xiang, et al., “Cs₃Cu₂I₅ Single Crystal for Efficient Direct X-Ray Detection,” Advanced Optical Materials11, no. 19 (2023): 2300247.

[91] Q. Wang, Q. Zhou, M. Nikl, et al., “Highly Resolved X-Ray Imaging Enabled by In(I) Doped Perovskite-Like Cs₃Cu₂I₅ Single Crystal Scintillator,” Advanced Optical Materials10, no. 11 (2022): 2200304.

[92] A. Li, M. Yang, P. Tang, et al., “Composition Engineering Growth of Cs₃Bi₂I₉ Single Crystals With Low Defect Density for X-Ray Detectors,” ACS Applied Materials and Interfaces15, no. 19 (2023): 23390-23401.

[93] Q. Fan, H. Xu, S. You, et al., “Centimeter-Sized Single Crystals of Dion-Jacobson Phase Lead-Free Double Perovskite for Efficient X-Ray Detection,” Small19, no. 34 (2023): 2301594.

[94] M. Chen, X. Dong, D. Chu, et al., “Interlayer-Spacing Engineering of Lead-Free Perovskite Single Crystal for High-Performance X-Ray Imaging,” Advanced Materials35, no. 18 (2023): 2211977.

[95] J. G. Yukta, M. A. Afroz, S. Alghamdi, P. J. Sellin, and S. Satapathi, “Wide-band-gap Metal-free Perovskite for Third-order Nonlinear Optics,” ACS Photon9, no. 11 (2022): 3529-3539.

[96] C. Ma, H. Li, M. Chen, Y. Liu, K. Zhao, and S. Liu, “Water-Resistant Lead-Free Perovskitoid Single Crystal for Efficient X-Ray Detection,” Advanced Functional Materials32, no. 30 (2022): 2202160.

[97] W. Yuan, G. Niu, Y. Xian, et al., “In Situ Regulating the Order–Disorder Phase Transition in Cs₂AgBiBr₆ Single Crystal Toward the Application in an X-Ray Detector,” Advanced Functional Materials29, no. 20 (2019): 1900234.

[98] J. A. Steele, W. Pan, C. Martin, et al., “Perovskite-Based Devices: Photophysical Pathways in Highly Sensitive Cs₂AgBiBr₆ Double-Perovskite Single-Crystal X-Ray Detectors (Adv. Mater. 46/2018),” Advanced Materials30, no. 46 (2018): 1804450.

[99] H. Li, Y. Lei, G. Peng, et al., “Low-Temperature Melt Processing Monolithic Integration of Organic Manganese (II) Bromide Wafers With Pixelated Substrate for High Sensitivity X-Ray Imaging,” Advanced Functional Materials32, no. 48 (2022): 2208199.

[100] J. Di, H. Li, J. Su, et al., “Reveal the Humidity Effect on the Phase Pure CsPbBr₃ Single Crystals Formation at Room Temperature and Its Application for Ultrahigh Sensitive X-Ray Detector,” Advanced Science9, no. 2 (2021): 2103482.

[101] X. Du, Y. Liu, W. Pan, et al., “Chemical Potential Diagram Guided Rational Tuning of Electrical Properties: A Case Study of CsPbBr₃ for X-Ray Detection,” Advanced Materials34, no. 17 (2022): 2110252.

[102] D. Xin, S. Dong, M. Zhang, et al., “Nucleation Engineering in Sprayed MA₃Bi₂I₉ Films for Direct-Conversion X-Ray Detectors,” Journal of Physical Chemistry Letters13, no. 1 (2022): 371-377.

[103] Y. Zhang, Y. Liu, Z. Xu, et al., “Nucleation-Controlled Growth of Superior Lead-Free Perovskite Cs3Bi2I9 Single-Crystals for High-Performance X-Ray Detection,” Nature Communications11, no. 1 (2020): 2304.

[104] X. Song, T. Li, H. Li, S. Lin, J. Yin, and K. Zhao, “High Hardness Metal-Free Perovskite Based on Hexamethylenetetramine for Efficient X-Ray Detection,” Science China Materials67, no. 4 (2024): 1348-1355.

[105] X. Li, X. Du, P. Zhang, et al., “Lead-Free Halide Perovskite Cs₃Bi₂Br₉ Single Crystals for High-Performance X-Ray Detection,” Science China Materials64, no. 6 (2021): 1427-1436.

[106] X. Li, P. Zhang, Y. Hua, et al., “Ultralow Detection Limit and Robust Hard X-Ray Imaging Detector Based on Inch-Sized Lead-Free Perovskite Cs₃Bi₂Br₉ Single Crystals,” ACS Applied Materials and Interfaces14, no. 7 (2022): 9340-9351.

[107] Y. He, C. C. Stoumpos, I. Hadar, et al., “Demonstration of Energy-Resolved γ-Ray Detection at Room Temperature by the CsPbCl₃ Perovskite Semiconductor,” Journal of the American Chemical Society143, no. 4 (2021): 2068-2077.

[108] Y. He, I. Hadar, M. C. De Siena, et al., “Sensitivity and Detection Limit of Spectroscopic-Grade Perovskite CsPbBr₃ Crystal for Hard X-Ray Detection,” Advanced Functional Materials32, no. 24 (2022): 2112925.

[109] S. Johnsen, Z. Liu, J. A. Peters, et al., “Thallium Chalcohalides for X-Ray and γ-Ray Detection,” Journal of the American Chemical Society133, no. 26 (2011): 10030-10033.

[110] NIST, X-Ray Mass Attenuation Coefficients, accessed October 5, 2020, https://www.nist.gov/pml/x-ray-mass-attenuation-coefficients.

[111] Y. Su, W. Ma, and Y. M. Yang, “Perovskite Semiconductors for Direct X-Ray Detection and Imaging,” Journal of Semiconductors41, no. 5 (2020): 051204.

[112] Z. Wang, S. Heshka, J. Wang, L. Wielopolski, and S. B. Heymsfield, “Magnitude and Variation of Fat-Free Mass Density: A Cellular-Level Body Composition Modeling Study,” American Journal of Physiology-Endocrinology and Metabolism284, no. 2 (2003): E267-E273.

[113] R. A. Brooks and G. D. Chiro, “Beam Hardening in X-ray Reconstructive Tomography,” Physics in Medicine and Biology21, no. 3 (1976): 390.

[114] I. Fratelli, L. Basiricò, A. Ciavatti, et al., “Trap States Ruling Photoconductive Gain in Tissue-equivalent, Printed Organic X-ray Detectors,” Advanced Materials Technologies8, no. 3 (2022): 2200769.

[115] X. He, M. Xia, H. Wu, et al., “Quasi-2D Perovskite Thick Film for X-Ray Detection With Low Detection Limit,” Advanced Functional Materials32, no. 7 (2021): 2109458.

[116] A. Hadi, R. L. Schlichtmann, M. I. Milot, et al., “Melt-Processed Halide Perovskite Thin Films From a Two-Dimensional Ruddlesden–Popper Phase Precursor,” Journal of Physical Chemistry Letters14, no. 22 (2023): 5194-5202.

[117] J. Zhang, H. Ma, X. Zhang, and Y. Ma, “Light-Induced Degradation of Metal-Free Organic Perovskites,” Journal of Physical Chemistry Letters13, no. 42 (2022): 9848-9854.

[118] B. Yang, W. Pan, H. Wu, et al., “Heteroepitaxial Passivation of Cs2AgBiBr6 Wafers With Suppressed Ionic Migration for X-Ray Imaging,” Nature Communications10, no. 1 (2019): 1989.

[119] H. Wei, Y. Fang, P. Mulligan, et al., “Sensitive X-Ray Detectors Made of Methylammonium Lead Tribromide Perovskite Single Crystals,” Nature Photonics10, no. 5 (2016): 333-339.

[120] N. Li, Y. Li, S. Xie, et al., “High-Performance and Self-Powered X-Ray Detectors Made of Smooth Perovskite Microcrystalline Films With 100 μm Grains,” Angewandte Chemie International Edition62, no. 19 (2023): e202302435.

[121] J. Jiang, M. Xiong, K. Fan, et al., “Synergistic Strain Engineering of Perovskite Single Crystals for Highly Stable and Sensitive X-Ray Detectors With Low-Bias Imaging and Monitoring,” Nature Photonics16, no. 8 (2022): 575-581.

[122] W. Pan, H. Wu, J. Luo, et al., “Cs2AgBiBr6 Single-Crystal X-Ray Detectors With a Low Detection Limit,” Nature Photonics11 (2017): 726-732.

[123] S. Kasap, J. B. Frey, G. Belev, et al., “Amorphous and Polycrystalline Photoconductors for Direct Conversion Flat Panel X-Ray Image Sensors,” Sensors11, no. 5 (2011): 5112-5157.

[124] F. Lappe, “The Energy of Electron-Hole Pair Formation by X-Rays in PbO,” Journal of Physics and Chemistry of Solids20, no. 3–4 (1961): 173-176.

[125] R. Devanathan, L. R. Corrales, F. Gao, and W. J. Weber, “Signal Variance in Gamma-Ray Detectors—A Review,” Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment565, no. 2 (2006): 637-649.

[126] C. A. Klein, “Bandgap Dependence and Related Features of Radiation Ionization Energies in Semiconductors,” Journal of Applied Physics39, no. 4 (1968): 2029-2038.

[127] Y. Zhou, L. Zhao, Z. Ni, et al., “Heterojunction Structures for Reduced Noise in Large-Area and Sensitive Perovskite X-Ray Detectors,” Science Advances7, no. 36 (2021): eabg6716.

[128] E. C. Lin, “Radiation Risk From Medical Imaging,” Mayo Clinic Proceedings85, no. 12 (2010): 1142-1146.

[129] R. Zhuang, X. Wang, W. Ma, et al., “Highly Sensitive X-Ray Detector Made of Layered Perovskite-Like (NH4)3Bi2I9 Single Crystal With Anisotropic Response,” Nature Photonics13, no. 9 (2019): 602-608.

[130] H. Li, J. Song, W. Pan, et al., “Sensitive and Stable 2D Perovskite Single-Crystal X-Ray Detectors Enabled by a Supramolecular Anchor,” Advanced Materials32, no. 40 (2020): 2003790.

[131] C. Ji, Y. Li, X. Liu, et al., “Monolayer-to-Multilayer Dimensionality Reconstruction in a Hybrid Perovskite for Exploring the Bulk Photovoltaic Effect Enables Passive X-Ray Detection,” Angewandte Chemie International Edition60, no. 38 (2021): 20970-20976.

[132] M. Xia, Z. Song, H. Wu, et al., “Compact and Large-Area Perovskite Films Achieved via Soft-Pressing and Multi-Functional Polymerizable Binder for Flat-Panel X-Ray Imager,” Advanced Functional Materials32, no. 16 (2022): 2110729.

[133] H. Morita, R. Tsunashima, S. Nishihara, et al., “Ferroelectric Behavior of a Hexamethylenetetramine-Based Molecular Perovskite Structure,” Angewandte Chemie International Edition58, no. 27 (2019): 9184-9187.

[134] J. Wang, X.-X. Chen, L. Ye, Y.-P. Gong, Y. Shang, and W.-X. Zhang, “A Room-Temperature Moisture-Stabilized Metal-Free Energetic Ferroelectric Material for Piezoelectric Generation,” Materials Chemistry Frontiers7, no. 11 (2023): 2251-2259.

[135] Z. Li, Y. Pang, G. Peng, et al., “Aminoazanium of A-Site Cations in Metal-Free Halide Perovskite Single Crystals to Reduce Thermal Expansion for Efficient X-Ray Detection,” Journal of Physical Chemistry Letters15, no. 16 (2024): 4375-4383.

[136] X. Liu, Q. Cui, H. Li, et al., “Biocompatible Metal-Free Perovskite Membranes for Wearable X-Ray Detectors,” ACS Applied Materials and Interfaces16, no. 13 (2024): 16300-16308.

[137] A. L. Semrau, S. V. Dummert, C. Eckel, S. Mackewicz, R. T. Weitz, and G. Kieslich, “Synthetic Approaches Targeting Metal-Free Perovskite [HMDABCO](NH₄)I₃ Thin Films,” Crystal Growth & Design22, no. 1 (2021): 406-413.

[138] D. Sirbu, H. C. L. Tsui, N. Alsaif, et al., “Wide-Band-Gap Metal-Free Perovskite for Third-Order Nonlinear Optics,” ACS Photon8 (2021): 2450-2458.

[139] J. Zhao, L. Zhao, Y. Deng, et al., “Perovskite-Filled Membranes for Flexible and Large-Area Direct-Conversion X-Ray Detector Arrays,” Nature Photonics14, no. 10 (2020): 612-617.

[140] R. M. F. Baptista, G. Moreira, B. Silva, et al., “Lead-Free MDABCO-NH₄I₃ Perovskite Crystals Embedded in Electrospun Nanofibers,” Materials15, no. 23 (2022): 8397.

[141] H.-S. Wu, S.-M. Wei, S.-W. Chen, et al., “Metal-Free Perovskite Piezoelectric Nanogenerators for Human–Machine Interfaces and Self-Powered Electrical Stimulation Applications,” Advanced Science9, no. 18 (2022): 2105974.

[142] Z. Li, G. Peng, H. Chen, C. Shi, Z. Li, and Z. Jin, “Metal-Free PAZE-NH₄X₃⋅H₂O Perovskite for Flexible Transparent X-Ray Detection and Imaging,” Angewandte Chemie International Edition61, no. 36 (2022): 202207198.

[143] Q. Cui, N. Bu, X. Liu, et al., “Efficient Eco-Friendly Flexible X-Ray Detectors Based on Molecular Perovskite,” Nano Letters22, no. 14 (2022): 5973-5981.

[144] W. Pan, B. Yang, G. Niu, et al., “Hot-Pressed CsPbBr₃ Quasi-Monocrystalline Film for Sensitive Direct X-Ray Detection,” Advanced Materials31, no. 44 (2019): 1904405.

[145] C. Li, S. Zhou, J. Nie, J. Huang, X. Ouyang, and Q. Xu, “Durable Flexible Polymer-Encapsulated Cs₄PbI₆ Thin Film for High Sensitivity X-ray Detection,” Nano Letters21, no. 24 (2021): 10279-10283.

[146] J. Zhao, X. Wang, Y. Ding, et al., “A Flexible Perovskite Homojunction With Metallic Ion Doping for Large-Scale and High Sensitivity X-Ray Detection,” Journal of Materials Chemistry A11, no. 16 (2023): 9049-9056.

[147] C. Liang, S. Zhang, L. Cheng, et al., “Thermoplastic Membranes Incorporating Semiconductive Metal–Organic Frameworks: An Advance on Flexible X-Ray Detectors,” Angewandte Chemie International Edition59, no. 29 (2020): 11856-11860.

[148] Z. Li, S. Chang, H. Zhang, et al., “Flexible Lead-Free X-ray Detector From Metal–Organic Frameworks,” Nano Letters21, no. 16 (2021): 6983-6989.

[149] L. Basirico, A. Ciavatti, T. Cramer, P. Cosseddu, A. Bonfiglio, and B. Fraboni, “Direct X-Ray Photoconversion in Flexible Organic Thin Film Devices Operated Below 1 V,” Nature Communications7, no. 1 (2016): 13063.

[150] X. Liu, H. Li, Q. Cui, et al., “Molecular Doping of Flexible Lead-Free Perovskite-Polymer Thick Membranes for High-Performance X-Ray Detection,” Angewandte Chemie International Edition134, no. 41 (2022): e202209320.

[151] Y. Shi, B. Zhang, J. Zhao, et al., “A Deformation Mismatch Strategy Enables Over 120% Stretchability of Encapsulated Serpentine Silicon Strips for Stretchable Electronics,” FlexMat1, no. 2 (2024): 150-159.

[152] H. Chen, B. Liu, J. Cao, et al., “Flexible UV Photodetector Based on Copper Tetraiodogallate (CuGaI₄) Film,” FlexMat1 (2024): 54-58.

[153] G.-Z. Liu, J. Zhang, and L.-Y. Wang, “A Novel Molecular Cubic Perovskite Built From Charge-Assisted Hydrogen Bond Linkages,” Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry41, no. 9 (2011): 1091-1094.

[154] X. Song, G. Hodes, K. Zhao, and S. Liu, “Metal-Free Organic Halide Perovskite: A New Class for Next Optoelectronic Generation Devices,” Advanced Energy Materials11 (2021): 2003331.

[155] T. Kim, S. Jeong, K.-H. Kim, H. Shim, D. Kim, and H.-J. Kim, “Engineered Surface Halide Defects by Two-Dimensional Perovskite Passivation for Deformable Intelligent Photodetectors,” ACS Applied Materials and Interfaces14, no. 22 (2022): 26004-26013.

[156] R. Zhuang, S. Cai, Z. Mei, et al., “Solution-Grown BiI/BiI₃ van der Waals Heterostructures for Sensitive X-Ray Detection,” Nature Communications14, no. 1 (2023): 1621.

[157] Y. Song, L. Li, M. Hao, et al., “Elimination of Interfacial-Electrochemical-Reaction-Induced Polarization in Perovskite Single Crystals for Ultrasensitive and Stable X-Ray Detector Arrays,” Advanced Materials33, no. 52 (2021): 2103078.

[158] H. Yao, S. Shi, Z. Li, et al., “Strategies From Small-Area to Scalable Fabrication for Perovskite Solar Cells,” Journal of Energy Chemistry57 (2020): 567-586.

[159] C. Ji, S. Wang, Y. Wang, et al., “2D Hybrid Perovskite Ferroelectric Enables Highly Sensitive X-Ray Detection With Low Driving Voltage,” Advanced Functional Materials30, no. 5 (2019): 1905529.

[160] J. Zheng, Y. Zeng, J. Wang, et al., “Hydrogen-Rich 2D Halide Perovskite Scintillators for Fast Neutron Radiography,” Journal of the American Chemical Society143, no. 50 (2021): 21302-21311.

[161] W. Shao, Q. Li, T. He, et al., “Synergy of Organic and Inorganic Sites in 2D Perovskite for Fast Neutron and X-Ray Imaging,” Advanced Functional Materials33, no. 40 (2023): 2301767.

[162] M. Xia, G. Niu, L. Liu, et al., “Back Cover Image,” InfoMat4, no. 9 (2022): e12325.

[163] Q. Sun, Z. Hao, J. Li, et al., “Dual Discrimination of Fast Neutrons From Strong γ Noise Using Organic Single-Crystal Scintillator,” Matter6, no. 1 (2023): 274-284.

[164] G. Peng, Z. Li, Y. Xu, Y. Lei, H. Wang, and Z. Jin, “Evidence of Cation Symmetry Reduction Induced Bulk Photovoltaic Effect in Metal-Free Perovskite for Efficient Self-Powered X-Ray Detection,” Advanced Materials37, no. 26 (2025): 2502335.

[165] H. C. L. Tsui, D. Sirbu, N. Alsaif, et al., “Few-Mode Metal-Free Perovskite Optical Fiber With Second-Order Optical Nonlinearity,” APL Photonics9, no. 3 (2024): 036106.

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