LAUSR

Low‐bandgap tin (Sn)‐lead (Pb) halide perovskites can achieve near‐infrared response for photodetectors. However, the Sn‐based devices suffer from notorious instability and high defect densities due to the oxidation propensity of Sn2+. Herein, a multifunctional additive 4‐amino‐2,3,5,6‐tetrafluorobenzoic acid (ATFBA) is presented, which can passivate surface defects and inhibit the oxidation of Sn2+ through hydrogen bonds and chelation coordination from the terminal amino and carboxyl groups. The perfluorinated benzene ring structure of ATFBA affords the passivator assembled at the grain boundaries to enhance the water resistance. With the synergistical passivation of these functional groups, the Sn–Pb perovskite photodetector exhibits a remarkable responsivity of 0.52 A W‐1 and an excellent specific detectivity of 5.34 × 1012 Jones at 850 nm, along with remaining 97% of its initial responsivity over 450 days. Benefitting from high sensitivity, the photodetector is integrated into a pulse oximetry sensor visualization system, yielding accurate blood oxygen saturation and heart rate with less than 2% error. This work paves the avenue toward constructing high‐performance and stable Sn–Pb perovskite photodetectors for practical applications.