One-Dimensional 3-Fluorobenzylamine Bismuth Iodide with Enhanced Inter-Chain Coupling: Achieving High External...

Developing efficient, lead-free materials for deep-ultraviolet (UVC) photodetection remains a critical challenge for energy-efficient applications. Here, we report bis(3-fluorobenzylammonium)pentaiodobismuthate(III) (3FBABI), a one-dimensional hybrid bismuth halide that achieves high photodetector performance through optimized structural design. Single-crystal x-ray diffraction reveals highly ordered zig-zag [BiI₅]^2- chains with short inter-chain I···I contacts (3.87 Å), enabling enhanced electronic coupling and a direct bandgap of 2.09 eV. Photodetectors fabricated in planar FTO/3FBABI/FTO configuration operate at ultra-low voltages starting from 0.01 V, significantly lower than typical perovskite photodetectors. At 0.2 V bias, the device delivers notable performance metrics: responsivity of 9.65 A/W, specific detectivity of 2.3 × 10^{1 2} Jones, and external quantum efficiency of 4710% at 254 nm. The device demonstrates robust environmental stability, maintaining performance after prolonged exposure to air, water, and continuous UV illumination. Comparative analysis with literature shows 3FBABI among the top-performing lead-free UVC photodetectors, with operating voltages 50-100 times lower than conventional devices. These results establish 3FBABI as a promising lead-free alternative for next-generation low-power optoelectronic systems, addressing both performance and sustainability requirements for practical UV sensing applications.