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

Abstract 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/Rg = 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.