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 FAPbI3 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 × 1010 Jones at 0 V bias, respectively, which can be improved to 844.33 mA W–1 and 3.2 × 1011 Jones at a bias voltage of −0.9 V. In addition, the present device also possesses distinct advantages of a large Ilight/Idark ratio exceeding 104, 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.