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.

inevitable, which reduces the reliability in high-density integration. Furthermore, uncontrollable interface is detrimental to the retention time and operation speed of the memory device. 2D van der Waals (vdW) crystals manifest ultra-thin layered structure, highly anisotropic in-and outof-plane conductivity and superior carrier migration, [6] which are promising to solve the above problems. Over the past decade, 2D vdW atomic crystals, such as graphene, MoS 2 , ReS 2 , etc., are widely used as the composed elements in FGNVM, [7][8][9][10][11] and extended device structures are proposed to improve the performance. [12,13] It has been demonstrated that the FGNVM based on vdW heterostructure could enable atomically sharp interface for ultrafast operation at tens of nanosecond. [14][15][16] Nonetheless, the investigation is still in the initial stage and much research work has to be carried out before the commercialization of the vdW-heterostructure-based nonvolatile memory. In conventional FGNVM, the program/erase operations are accomplished by electrical stimuli. The repetitive voltage drives not only increase the power consumption, but also deteriorate the reliability and stability of the device. [17] Light, as an efficient non-contact signal, has a small energy dissipation when traveling through the free space. Therefore, using light illumination as an auxiliary programming method is beneficial to realize long-distance quantum communication, while effectively minimizing the power consumption, so as to improve the reliability The development of floating-gate nonvolatile memory (FGNVM) is limited by the charge storage, retention and transfer ability of the charge-trapping layer.Here, it is demonstrated that due to the unique alternate inorganic/organic chain structure and superior optical sensitivity, an insulating 2D Ruddlesden-Popper perovskite (2D-RPP) layer can function both as an excellent chargestorage layer and a photosensitive layer. Optoelectronic memory composed of a MoS 2 /hBN/2D-RPP (MBR) van der Waals heterostructure is demonstrated. The MBR device exhibits unique light-controlled charge-storage characteristics, with maximum memory window up to 92 V, high on/off ratio of 10 4 , negligible degeneration over 10 3 s, >1000 program/erase cycles, and write speed of 500 µs. Dependent on the initial states, the MBR optoelectronic memory can be programmed in both positive photoconductivity (PPC) and negative photoconductivity (NPC) modes, with up to 11 and 22 distinct resistance states, respectively. The optical program power for each bit is as low as 36/10 pJ for PPC/NPC. The results not only reveal the potential of 2D-RPP as a superior charge-storage medium in floating-gate memory, but also provides an effective strategy toward fast, low-power and stable optical multi-bit storage and neuromorphic computing.

Van der Waals (vdW) integration of two-dimensional (2D) nanosheets provides the possibility to design optoelectronic devices with extended functionality in a controllable manner. Here, by leveraging the appropriate energy band alignment and the high-efficiency charge transfer at the junction, we construct the MoS2/graphene/2D-perovskite vdW heterostructure, which realizes the highly sensitive and broadband photodetection. Particularly, at the near-infrared (NIR) wavelength (λ = 1550 nm), the heterostructure photodetector shows a balanced trade-off between the high responsivity (>3000 A/W) and fast response time (<1 ms), outperforming the previously reported NIR photodetectors based on all-inorganic vdW heterostructures. Our work not only extends the response wavelength of the 2D hybrid perovskite-based photodetector to the NIR range, but also offers additional insight into optoelectronic devices via vdW integration engineering.