Bismuth-based lead-free perovskite film for highly sensitive detection of ammonia gas

Lead halide perovskite materials have received increased attention for sensing applications, due to their environmental sensitivity. However, the lead toxicity represents a potential obstacle to their practical sensing application. Here, we report a lead-free (phenethylammonium)₃Bi₂Br₉-based sensor for ammonia (NH₃) gas detection. The sensor exhibits high gas response (R₀/R_g = 1.76, at 30 ppm NH₃), short response/recovery time (39/130 s), low detection limit (0.2 ppm), and good reversibility. The NH₃ sensing mechanism is established using a combination of X‐ray diffraction (XRD), absorption spectra, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy and differential thermal analysis (DTA) measurements. The results demonstrate that the electron-donating NH₃ molecules may first absorb onto the surface of the (phenethylammonium)₃Bi₂Br₉ film for electron-injection, and then infiltrate it to dissociate the Bi₂Br₉³⁻ bi-octahedra. It will form a new NH₄Br substance, different from an NH₃-induced phase transformation in perovskite CH₃NH₃PbI₃. This work reveals that it is feasible to design high-performance gas sensors based on environmentally-friendly Bi-based perovskites.