Green Fabrication of Sulfonium-Containing Bismuth Materials for High-Sensitivity X-Ray Detection

Organic-inorganic hybrid materials based on lead and bismuth have recently been proposed as novel X- and gamma-ray detectors for medical imaging, non-destructive testing, and security, due to their high atomic numbers and facile preparation compared to traditional materials like amorphous selenium and Cd(Zn)Te. However, challenges related to device operation, excessively high dark currents, and long-term stability have delayed commercialization. Here, two novel semiconductors incorporating stable sulfonium cations are presented, [(CH₃CH₂)₃S]₆Bi₈I₃₀ and [(CH₃CH₂)₃S]AgBiI₅, synthesized via solvent-free ball milling and fabricated into dense polycrystalline pellets using cold isostatic compression, two techniques that can easily be upscaled, for X-ray detection application. The fabricated detectors exhibit exceptional sensitivities (14 100-15 190 µC Gy_air ^-1 cm^-2) and low detection limits (90 nGy_air s^-1 for [(CH₃CH₂)₃S]₆Bi₈I₃₀ and 78 nGy_air s^-1 for [(CH₃CH₂)₃S]AgBiI₅), far surpassing current commercial detectors. Notably, they maintain performance after 9 months of ambient storage. The findings highlight [(CH₃CH₂)₃S]₆Bi₈I₃₀ and [(CH₃CH₂)₃S]AgBiI₅ as scalable, cost-effective and highly stable alternatives to traditional semiconductor materials, offering great potential as X-ray detectors in medical and security applications.