Stable Near-Infrared Sn−Pb Perovskite Photodetectors Enabled by Synergistic Solvent−Additive Engineering

Abstract Tin−lead (Sn−Pb) mixed perovskites have emerged as promising candidates for near-infrared photodetection owing to their narrow bandgaps and outstanding optoelectronic properties. However, the facile oxidation of Sn2+ and the high defect density within the perovskite films severely limit the detection sensitivity and environmental stability of the resulting devices. Herein, we propose a combined modification strategy integrating DMPU-based solvent engineering with guanidinosuccinic acid (GSA) additive engineering to improve the crystallization quality and surface chemical stability of Sn−Pb perovskite films. Mechanistic insights indicate that the strong Lewis base DMPU effectively regulates the crystallization kinetics through coordination with inorganic components in the precursor, yielding compact and smooth films. Meanwhile, GSA molecules introduce strong coordination with undercoordinated surface ions through their functional groups, suppressing the oxidation of Sn2+ to Sn4+. Consecutively, the modified photodetectors exhibit superior electrical and photoresponse performance. At zero bias, the optimized device yields a low dark current density of 1.49 × 10−9 A cm−2, a broad spectral response from 350 to 850 nm, a peak responsivity of 0.362 A W−1 at 830 nm, and a specific detectivity of 1.28 × 1012 Jones. In addition, the device shows an expanded linear dynamic range of 89 dB and fast response/recovery times of 86/112 μs. Stability tests further demonstrate that the unencapsulated device retains 80% and 78% of its initial performance after being maintained in the dark under nitrogen at 85 °C for 700 h and stored in the dark in a nitrogen-filled glovebox at 25 ± 2 °C for 2500 h, respectively. This work provides an effective strategy for developing high-performance near-infrared perovskite photodetectors.