Highly efficient and stable near-infrared photodetectors enabled from passivated tin-lead hybrid perovskites

Tin-lead perovskite-based photodetectors have a wide light-absorption wavelength range, which spans 1000 nm. However, the preparation of the mixed tin-lead perovskite films faces two great obstacles, namely easy oxidation of Sn²⁺to Sn⁴⁺and fast crystallization from tin-lead perovskite precursor solutions, thus further resulting in poor morphology and high density of defects in tin-lead perovskite films. In this study, we demonstrated a high-performance of near-infrared photodetectors prepared from a stable low-bandgap (MAPbI₃)_0.5(FASnI₃)_0.5film modified with 2-fluorophenethylammonium iodide (2-F-PEAI). The addition engineering can efficiently improve the crystallization of (MAPbI₃)_0.5(FASnI₃)_0.5films through the coordination binding between Pb²⁺and N atom in 2-F-PEAI, and resulting in a uniform and dense (MAPbI₃)_0.5(FASnI₃)_0.5film. Moreover, 2-F-PEAI suppressed Sn²⁺oxidation and effectively passivated defects in the (MAPbI₃)_0.5(FASnI₃)_0.5film, thereby significantly reducing the dark current in the PDs. Consequently, the near-infrared photodetectors showed a high responsivity with a specific detectivity of over 10¹²Jones at 800 to near-1000 nm. Additionally, the stability of PDs incorporated with 2-F-PEAI has been significantly improved under air conditions, and the device with the 2-F-PEAI ratio of 400:1 retained 80% of its initial efficiency after 450 h storage in air without encapsulation. Finally, 5 × 5 cm²photodetector arrays were fabricated to demonstrate the potential utility of the Sn-Pb perovskite photodetector in optical imaging and optoelectronic applications.