Lead-Free Halide Double Perovskite Cs2AgBiCl6 for H2S Trace Detection at Room Temperature

Hydrogen sulfide (H2S) is an important respiratory biomarker of many diseases, and thus, developing H2S gas sensors with low detection limits at low operating temperatures is essential for the early diagnosis of diseases in low-resource environments. Although lead halide perovskites have unique electronic and optical properties, the high toxicity of lead has prompted the development of alternative materials. In this study, Cs2AgBiCl6 was synthesized using a simple method. The sensor based on Cs2AgBiCl6 showed excellent sensing of H2S gas at room temperature over a wide humidity range, with high response (90.6 vs 10 ppm of H2S) and fast response speed (99.6 s vs 400 ppb H2S). The detection limit was low (5 ppb H2S), and the selectivity at room temperature was excellent. Small changes in H2S concentration (<100 ppb) were detected as a fully reversible resistance signal. Additionally, sum frequency vibration spectroscopy and DFT calculations showed that the high gas sensitivity was attributed to the physical adsorption of H2S at Cl vacancies on the surface of Cs2AgBiCl6, as well as efficient charge transfer. This work provides an avenue for developing high-performance gas sensors based on nontoxic, wide band gap, halide double perovskite semiconductors operating at room temperature.