Achieving High-Performance Photodetectors through Defect Passivation Enabled by Additive Engineering of Pb–Sn Mixed Perovskites

Pb–Sn mixed perovskites possess a broad absorption spectrum extending into the near-infrared (NIR) region (∼1000 nm), rendering them as suitable candidates for NIR photodetectors. However, the rapid crystallization process of Pb–Sn mixed perovskites can lead to uneven surface properties, while the swift oxidation of Sn²⁺ increases the defect density, which in turn can trap photogenerated charges and degrade the photodetector performance. Therefore, regulating the crystallization process and preventing Sn-oxidation are critical steps in developing high-performance Pb–Sn mixed perovskite photodetectors. Herein, GuSCN (GS) additive engineering was utilized to enhance the performance of Pb–Sn mixed perovskite photodetectors. The GS additive effectively suppresses Sn-oxidation, resulting in a reduced defect density. Furthermore, it enhances the lateral charge transport properties by promoting an increase in the grain size of the perovskite film. As a result, the GS-assisted photodetector achieves a remarkable responsivity of 2.82 × 10⁴ A·W^–1 and an excellent specific detectivity of 3.67 × 10¹⁴ Jones. Furthermore, the GS-assisted Pb–Sn mixed perovskite photodetector demonstrates strong NIR responsiveness, facilitating its application in photoplethysmography sensors for detecting vital biological signals. This study provides important insights for advancing next-generation optoelectronic devices based on perovskite materials.