Crystal structure, optical properties, mobility, and photoelectric performance of [PEA]3[Bi2I9]

Lead halide-based salts exhibit good photoelectric properties; however, the use, leakage, and recovery of toxic lead require careful consideration. Therefore, developing a lead-free optoelectronic material conveniently and quickly is very important. Moreover, there is relatively little research on the salts of bismuth halides. In this study, we synthesized [PEA]₃[Bi₂I₉] single crystals (SC) by volatilizing N,N-dimethylformamide (DMF) solvent at 70°C. The crystal system and spatial group of [PEA]₃[Bi₂I₉] are monoclinic and P2₁/n, respectively. The Tauc plot reveals the optical band gap of the [PEA]₃[Bi₂I₉] SC at 2.048 eV. The carrier mobility of [PEA]₃[Bi₂I₉] SC is 47.4 cm² V⁻¹ s⁻¹. Steady-state fluorescence and time-resolved fluorescence spectrum indicate that there are four fluorescence peaks and about 7 μs lifetime, respectively. The photodetector based on [PEA]₃[Bi₂I₉] SC under different voltages (0.5, 1, 1.5, 2, and 2.5 V) exhibits stability and regularity with turning-on/off of the light. In addition, thermogravimetric analysis (TGA) tests indicate that [PEA]₃[Bi₂I₉] SC has considerable thermal stability at temperatures up to 260°C, showing promise for becoming a high temperature resistant and nontoxic sensor with good application prospects.