Silicon/Perovskite Core–Shell Heterojunctions with Light-Trapping Effect for Sensitive Self-Driven Near-Infrared Photodetectors

In this article, we fabricated a sensitive near-infrared (NIR) light detector by directly coating a layer of Cs-doped FAPbI 3 perovskite film onto vertical Si nanowire (SiNW) array. The as-assembled SiNW array/perovskite core–shell heterojunction exhibits a typical rectifying characteristic in darkness and distinct photoresponse characteristics under light illumination. Owning to the remarkable photovoltaic effect, the heterojunction can work as a self-driven NIR detector without an exterior energy supply. Further photoresponse investigation reveals that the photodetector is sensitive in a wide wavelength range with maximum sensitivity at ∼850 nm. The responsivity ( R ) and specific detectivity ( D *) are estimated to be 14.86 mA W –1 and 2.04 × 10 10 Jones at 0 V bias, respectively, which can be improved to 844.33 mA W –1 and 3.2 × 10 11 Jones at a bias voltage of −0.9 V. In addition, the present device also possesses distinct advantages of a large I light / I dark ratio exceeding 10 4, swift response rate with rise/decay times of 4/8 μs, and relatively good ambient stability. According to our numerical simulation based on finite element method, the superior device performance is associated with strong light-trapping effect in such unique core–shell heterojunction array.