Stable and sensitive tin-lead perovskite photodetectors enabled by azobenzene derivative for near-infrared acousto-optic conversion communications

Hybrid tin (Sn)-lead (Pb) halide perovskite materials with narrow bandgap and low toxicity play an irreplaceable role in near-infrared (NIR) photodetectors. However, the unsustainable device performance and stability, caused by abundant trap states and the easy oxidation of Sn2+ to Sn4+, have been hindering the development of Sn–Pb perovskite photodetectors. Herein, an azobenzene derivative was employed in Sn-Pb perovskite photodetectors as a multifunctional additive to dramatically improve device performance and stability. X-ray photoelectron spectroscopy indicated that the N˭N in azobenzene can effectively passivate the under-coordinated Pb ions at the film surface, which led to dark current reduction by almost two orders of magnitude. Noise current was dominated by shot noise converted from 1/f noise previously, which provided direct evidence that trap-induced recombination has been effectively inhibited by N˭N. As a result, it contributes a noise current of 0.42 pA Hz−1/2, as well as an ultrafast response speed of 42.9 ns. Furthermore, Sn–Pb perovskite photodetectors remain 90% of original responsivity after almost 300 h in ambient air, which can be attributed to hydrophobic carbon chains of azobenzene derivative. To the best of our knowledge, it is one of the most stabilized Sn-Pb perovskite photodetectors in ambient air so far. Finally, Sn–Pb perovskite photodetectors successfully transmitted audio signal without obvious distortion as NIR light receivers in an acousto-optic conversion communication, exhibiting a potential application in enciphered data transmission. It is believed that azobenzene derivative provides a universal strategy to achieve stable and sensitive Sn–Pb perovskite photodetectors.