Van der Waals MoS₂/Two-Dimensional Perovskite Heterostructure for Sensitive and Ultrafast Sub-Band-Gap Photodetection

Two-dimensional (2D) hybrid perovskites have been extensively studied as the promising light-sensitive materials in the photodetectors owing to their improved structural stability over that of their three-dimensional counterparts. However, the application of the 2D perovskite-based photodetector in the near-infrared (NIR) region is obstructed by the large intrinsic optical band gap. Herein, we develop a novel van der Waals heterostructure composed of few-layer 2D perovskite/MoS₂ nanoflakes, which exhibits high-sensitivity detection performance over a broad spectral region, from the visible region to the telecommunication wavelength (i.e., 1550 nm). In particular, the photoresponsivity and specific detectivity under an 860 nm laser reach 121 A W^-1 and 4.3 × 10¹⁴ Jones, respectively, whereas the individual nanoflakes show no response under the same wavelength. Meanwhile, the response time at the microsecond (μs) level is obtained, shortened by around 3 orders of magnitude compared to that of the constituting layers. The sensitive and ultrafast photoresponse at the NIR wavelength stems from the strong interlayer transition of sub-band-gap photons and the rapid separation of the photogenerated carriers by the built-in field within the heterojunction area. Our results not only provide an effective approach to achieve sub-band-gap photodetection in 2D perovskite-based structures but also suggest a universal strategy to fabricate high-performance optoelectronic devices.