Highly Sensitive Tin-Lead Perovskite Photodetectors with Over 450 Days Stability Enabled by Synergistic Engineering for Pulse Oximetry System.

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 Sn 2+ . Herein, we present a multifunctional additive 4-amino-2,3,5,6-tetrafluorobenzoic acid (ATFBA), which can passivate surface defects and inhibit the oxidation of Sn 2+ 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, our Sn-Pb perovskite photodetector exhibits a remarkable responsivity of 0.52 A W -1 and an excellent specific detectivity of 5.34 × 10 12 Jones at 850 nm, along with remaining 97% of its initial responsivity over 450 days. Benefitting from high sensitivity, the photodetector was integrated into a pulse oximetry sensor visualization system, yielding accurate blood oxygen saturation and heart rate with less than 2% error. Our work paves the avenue towards constructing high-performance and stable Sn-Pb perovskite photodetectors for practical applications. This article is protected by copyright. All rights reserved.