採用噴塗法製備無鉛 AgBi₂I₇多晶膜層，並探討其作為 X 光感測材料之製程條件與暗電流特性。近年來，鹵化物鈣鈦礦材料因具有高原子序、可調控能隙及低溫溶液製程等優勢，於直接式 X 光感測領域展現良好性能；然而，含鉛鹵化物鈣鈦礦之毒性與離子遷移問題，促使研究方向逐漸轉向鉍系等無鉛替代材料。AgBi₂I₇ 作為 Ag–Bi–I 系無鉛鹵化物材料之一，其單晶元件已展現良好之 X 光衰減能力與元件性能。然而，單晶成長製程耗時且不利於大面積化；相較之下，溶液製程之多晶膜層具有製程溫度低、可大面積化等優勢，但目前應用於 AgBi₂I₇ 之相關研究仍相對有限，尤其以噴塗製程製備 AgBi₂I₇ 多晶膜層之系統性研究更為少見。
系統性探討手動氣壓噴塗與超音波噴塗兩種製程中，溶劑系統、製程溫度、噴塗間隔時間及熱退火溫度對 AgBi₂I₇ 膜層形貌、結晶特性及其暗電流之影響。DMF:DMSO 溶劑系統則分別於超音波噴塗與手動氣壓噴塗製程下，建立膜層形貌與暗電流表現較佳之製程條件。
以手動氣壓噴塗製備之 AgBi₂I₇ 膜層為基礎，進一步比較 MoOₓ、NiOₓ 及 MoOₓ/NiOₓ 雙層阻擋層對元件暗電流之影響。由暗電流量測可知，MoOₓ 單層於負偏壓下具有最低且最穩定之暗電流表現。依據溶劑系統與噴塗方式之比較結果，DMF:DMSO = 4:1 可作為 AgBi₂I₇ 膜層製備之主要溶劑系統；在兩種噴塗方式各自較佳條件下，超音波噴塗樣品於負電場範圍內呈現較低之暗電流密度。另一方面，阻擋層整合結果顯示，於手動氣壓噴塗樣品中加入 MoOₓ 阻擋層可進一步降低元件暗電流。所建立之 AgBi₂I₇ 膜層噴塗製程與界面調控結果，可作為後續 Ag–Bi–I 系無鉛 X 光感測元件開發之參考。

Lead-free AgBi₂I₇ polycrystalline films were fabricated by spray coating, focusing on process development and electrical characterization for potential X-ray sensing applications. Bismuth-based halides have attracted attention as alternatives to lead-based halide perovskites because of their lower toxicity and improved environmental stability. Although AgBi₂I₇ single crystals have shown favorable X-ray attenuation and device performance, their time-consuming growth process limits large-area fabrication. Solution-processed polycrystalline films therefore provide a more scalable route, while systematic studies of spray-coated AgBi₂I₇ films remain limited.
Manual pneumatic spray coating and ultrasonic spray coating were used to investigate the effects of solvent system, substrate temperature, spray interval, and annealing temperature on film morphology, crystallinity, and electrical properties. Among the solvent systems examined, DMF:DMSO = 4:1 provided more complete film morphology and was used as the main solvent system for subsequent process studies. Under the selected conditions for each spray method, the ultrasonic spray-coated sample exhibited lower dark current density in the negative electric field region. The effects of MoOₓ, NiOₓ, and MoOₓ/NiOₓ blocking layers were further compared using manually spray-coated AgBi₂I₇ films. The MoOₓ single layer exhibited the lowest and most stable dark current under reverse bias. These results indicate that spray-coating conditions and blocking-layer structures both affect the dark-current behavior of AgBi₂I₇ devices, providing a processing basis for future Ag–Bi–I-based direct X-ray sensing devices.

1. Tie, S., et al., Efficient X-ray Attenuation Lead-Free AgBi2I7 Halide Rudorffite Alternative for Sensitive and Stable X-ray Detection. Journal of Physical Chemistry Letters, 2020. 11: p. 7939-7945.
2. Xiao, Z., W. Meng, D.B. Mitzi, and Y. Yan, Crystal Structure of AgBi2I7 Thin Films. Journal of Physical Chemistry Letters, 2016. 7: p. 3903-3907.
3. Zhu, H., et al., Progress and Applications of (Cu–)Ag–Bi–I Semiconductors, and Their Derivatives, as Next-Generation Lead-Free Materials for Photovoltaics, Detectors and Memristors. International Materials Reviews, 2024. 69(1): p. 19-62.
4. Kim, Y., et al., Pure Cubic-Phase Hybrid Iodobismuthates AgBi2I7 for Thin-Film Photovoltaics. Angewandte Chemie International Edition, 2016. 55: p. 9586-9590.
5. Kulkarni, A., et al., Performance Enhancement of AgBi2I7 Solar Cells by Modulating a Solvent-Mediated Adduct and Tuning Remnant BiI3 in One-Step Crystallization. Chemical Communications, 2019. 55(28): p. 4031-4034.
6. Gutmann, V., Empirical Parameters for Donor and Acceptor Properties of Solvents. Electrochimica Acta, 1976. 21(9): p. 661-670.
7. Lusic, H. and M.W. Grinstaff, X-ray-Computed Tomography Contrast Agents. Chemical Reviews, 2013. 113: p. 1641-1666.
8. Chen, Y.-T., et al., Inorganic Cs3Bi2I9 Lead-Free Halide Perovskite Film for Large-Area X-ray Detector via Low-Cost Ambient Spray Coating. NPG Asia Materials, 2024. 16: p. 34.
9. Haruta, Y., et al., Columnar Grain Growth of Lead-Free Double Perovskite Using Mist Deposition Method for Sensitive X-ray Detectors. Crystal Growth & Design, 2021. 21: p. 4030-4037.
10. Haruta, Y., et al., Fabrication of (101)-Oriented CsPbBr3 Thick Films with High Carrier Mobility Using a Mist Deposition Method. Applied Physics Express, 2019. 12: p. 085505.
11. Abbas, M., et al., A Critical Review on Crystal Growth Techniques for Scalable Deposition of Photovoltaic Perovskite Thin Films. Materials, 2020. 13: p. 4851.
12. Zhou, C., et al., Lead-Free Perovskites and Derivatives Enable Direct and Scintillation-Type X-ray Detection. Materials Science & Engineering R, 2023. 156: p. 100756.
13. Ghosh, J., et al., Progress and Opportunities in Bismuth-Based Materials for X-ray Detection. MRS Energy & Sustainability, 2025. 12: p. 233-253.
14. Li, Z., et al., Halide Perovskite for High-Performance X-ray Detector. Materials Today, 2021. 48: p. 155-175.
15. He, X., et al., Recent Development of Halide Perovskite Materials and Devices for Ionizing Radiation Detection. Chemical Reviews, 2023. 123(4): p. 1207-1261.
16. Dudipala, V., et al., Halide Perovskites and Their Derivatives for Efficient, High-Resolution Direct Radiation Detection: Design Strategies and Applications. Advanced Materials, 2024. 36: p. 2304523.
17. Xu, X., et al., Halide Perovskites: A Dark Horse for Direct X-ray Imaging. EcoMat, 2020. 2: p. e12064.
18. Zhang, Y., et al., Nucleation-Controlled Growth of Superior Lead-Free Perovskite Cs3Bi2I9 Single-Crystals for High-Performance X-ray Detection. Nature Communications, 2020. 11: p. 2304.
19. Zhang, J., et al., Top-Seed Solution-Based Growth of Perovskite Cs3Bi2I9 Single Crystal for High Performance X-ray Detection. ACS Photonics, 2022. 9: p. 641-651.
20. Yang, Y., et al., Annealing Induced Re-crystallization in CH3NH3PbI3₋ₓClₓ for High Performance Perovskite Solar Cells. Scientific Reports, 2017. 7: p. 46724.
21. Kumar, J., et al., Advanced Strategies to Tailor the Nucleation and Crystal Growth in Hybrid Halide Perovskite Thin Films, 2022. 10: p. 842924.
22. Howard, I.A., et al., Coated and Printed Perovskites for Photovoltaic Applications. Advanced Materials, 2019. 31: p. 1806702.
23. Patidar, R., et al., Slot-Die Coating of Perovskite Solar Cells: An Overview. Materials Today Communications, 2020. 22: p. 100808.
24. Bishop, J.E., J.A. Smith, and D.G. Lidzey, Development of Spray-Coated Perovskite Solar Cells. ACS Applied Materials & Interfaces, 2020. 12: p. 48237-48245.
25. Chen, T., et al., Oleic Acid-Assisted Nucleation Growth of Highly Luminescent CsCu2I3 Single Crystals and Their Films for Flexible and Dynamic High-Resolution X-Ray Imaging. Advanced Optical Materials, 2023. 11: p. 2301072.
26. Sakhatskyi, K., et al., Characterizing Emerging Detector Materials for Low-Dose X-Ray Imaging. Advanced Materials, 2025: p. e12795.
27. Starkholm, A., et al., Green Fabrication of Sulfonium-Containing Bismuth Materials for High-Sensitivity X-Ray Detection. Advanced Materials, 2025. 37: p. 2418626.
28. Liu, R., et al., Halide Perovskite X-ray Detectors: Fundamentals, Progress, and Outlook. Applied Physics Reviews, 2024. 11: p. 021327.
29. Kumaresan, S., et al., Inorganic Hole Transport Layer for Lead Free Bismuth Halide Perovskite for Photovoltaic Device. Optical Materials, 2024. 154: p. 115722.
30. Zhao, Y., A.M. Nardes, and K. Zhu, Effective Hole Extraction Using MoOₓ-Al Contact in Perovskite CH3NH3PbI3 Solar Cells. Applied Physics Letters, 2014. 104: p. 213906.
31. Pan, W., et al., Cs2AgBiBr6 Single-Crystal X-ray Detectors with a Low Detection Limit. Nature Photonics, 2017. 11: p. 726-732.
32. Wei, H., et al., Sensitive X-ray Detectors Made of Methylammonium Lead Tribromide Perovskite Single Crystals. Nature Photonics, 2016. 10: p. 333-339.
33. Tie, S., et al., Robust Fabrication of Hybrid Lead-Free Perovskite Pellets for Stable X-ray Detectors with Low Detection Limit. Advanced Materials, 2020. 32: p. 2001981.
34. Wei, W., et al., Monolithic Integration of Hybrid Perovskite Single Crystals with Heterogenous Substrate for Highly Sensitive X-ray Imaging. Nature Photonics, 2017. 11: p. 315-321.
35. Song, Y., et al., Elimination of Interfacial-Electrochemical-Reaction-Induced Polarization in Perovskite Single Crystals for Ultrasensitive and Stable X-Ray Detector Arrays. Advanced Materials, 2021. 33: p. 2103078.
36. Zhuang, R., et al., Highly Sensitive X-ray Detector Made of Layered Perovskite-Like (NH4)3Bi2I9 Single Crystal with Anisotropic Response. Nature Photonics, 2019. 13: p. 602-608.
37. Liu, H., et al., Large-Area Flexible Perovskite Light-Emitting Diodes Enabled by Inkjet Printing. Advanced Materials, 2024. 36: p. 2309921.
38. Ichwani, R., et al., Using Machine Learning for Prediction of Spray Coated Perovskite Solar Cells Efficiency: From Experimental to Theoretical Models. Materials & Design, 2023. 233: p. 112161.
39. Weerasinghe, H.C., et al., The First Demonstration of Entirely Roll-to-Roll Fabricated Perovskite Solar Cell Modules under Ambient Room Conditions. Nature Communications, 2024. 15: p. 1656.
40. Lee, J.-W., D.-K. Lee, and N.-G. Park, Control of Crystal Growth toward Scalable Fabrication of Perovskite Solar Cells. Advanced Functional Materials, 2019. 29: p. 1807047.
41. Liu, C., Y.-B. Cheng, and Z. Ge, Understanding of Perovskite Crystal Growth and Film Formation in Scalable Deposition Processes. Chemical Society Reviews, 2020. 49(6): p. 1653-1687.
42. Worsley, C., et al., Green Solvent Engineering for Enhanced Performance and Reproducibility in Printed Carbon-Based Mesoscopic Perovskite Solar Cells and Modules. Materials Advances, 2022. 3: p. 1125-1138.
43. Wu, X., et al., Green-Solvent-Processed Formamidinium-Based Perovskite Solar Cells with Uniform Grain Growth and Strengthened Interfacial Contact via a Nanostructured Tin Oxide Layer. Materials Horizons, 2023. 10: p. 122-135.
44. Sánchez, R.S., et al., Crystallization Dynamics in Metal Halide Perovskite Thin Films. Chemical Society Reviews, 2021. 50(12): p. 7108-7146.
45. Chung et al., Engineering Perovskite Precursor Inks for Scalable Production of High-Efficiency Perovskite Photovoltaic Modules. Advanced Energy Materials, 2023. 13: p. 2300595.
46. Yun et al., Intermediate Phase-Free Process for Methylammonium Lead Iodide Thin Film for High-Efficiency Perovskite Solar Cells. Advanced Science, 2021. 8: p. 2102492.
47. Dangudubiyyam, U.K., et al., Eco-Friendly Solvent System for Inkjet Deposition of Wide Bandgap Perovskite Solar Cells Enabling Tandem Integration. Advanced Science, 2026. 0: p. e76463.
48. Zeng, L., et al., A Safer Sodium-Ion Battery Based on Nonflammable Organic Phosphate Electrolyte. Advanced Science, 2016. 3: p. 1600066.
49. SDBSWeb, National Institute of Advanced Industrial Science and Technology (AIST), Spectral Database for Organic Compounds, DMF (SDBS No. 324), DMSO (SDBS No. 2459).
50. Shanmugam, R., K. Ramya, R.K. Sankaranarayanan, and G. Arivazhagan, Carbonyl stretching bands of N,N-dimethylformamide. Chemical Physics, 2026. 610: p. 113353.
51. Wallace, V.M., N.R. Dhumal, F.M. Zehentbauer, H.J. Kim, and J. Kiefer, Revisiting the Aqueous Solutions of Dimethyl Sulfoxide by Spectroscopy in the Mid- and Near-Infrared: Experiments and Car-Parrinello Simulations. The Journal of Physical Chemistry B, 2015. 119: p. 14780-14789.
52. Hossain, M.I., et al., Advancing MoOx and NiOx as hole transport layers for perovskite solar cells: Experimental and theoretical insights. Next Energy, 2025. 9: p. 100463.
53. Nandi, P., et al., NiO as Hole Transporting Layer for Inverted Perovskite Solar Cells: A Study of X-Ray Photoelectron Spectroscopy. Advanced Materials Interfaces, 2024. 11(8): p. 2300751.
54. Kanai, K., et al., Electronic structure of anode interface with molybdenum oxide buffer layer. Organic Electronics, 2010. 11: p. 188-194.
55. White, R.T., E.S. Thibau, and Z.-H. Lu, Interface Structure of MoO3 on Organic Semiconductors. Scientific Reports, 2016. 6: p. 21109.
56. Matsushima, T., et al., Interfacial charge transfer and charge generation in organic electronic devices. Organic Electronics, 2011. 12: p. 520-528.