Photodetectors capable of detecting light in a wide spectrum is central to diversified optoelectronic applications in spectroscopy, remote sensing, imaging and optical communication. [1] Two-dimensional (2D) transition metal dichalcogenides (TMDs) provide a tremendous potential for broadband optoelectronics due to their relatively high mobility, appropriate bandgaps, and flexibility. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In particular, TMD layers of different bandgaps and doping (p or n types) can be stacked together into van der 2D atomic sheets of transition metal dichalcogenides (TMDs) have a tremendous potential for next-generation optoelectronics since they can be stacked layer-by-layer to form van der Waals (vdW) heterostructures. This allows not only bypassing difficulties in heteroepitaxy of lattice-mismatched semiconductors of desired functionalities but also providing a scheme to design new optoelectronics that can surpass the fundamental limitations on their conventional semiconductor counterparts. Herein, a novel 2D h-BN/p-MoTe 2 / graphene/n-SnS 2 /h-BN p-g-n junction, fabricated by a layer-by-layer dry transfer, demonstrates high-sensitivity, broadband photodetection at room temperature. The combination of the MoTe 2 and SnS 2 of complementary bandgaps, and the graphene interlayer provides a unique vdW heterostructure with a vertical built-in electric field for high-efficiency broadband light absorption, exciton dissociation, and carrier transfer. The graphene interlayer plays a critical role in enhancing sensitivity and broadening the spectral range. An optimized device containing 5−7-layer graphene has been achieved and shows an extraordinary responsivity exceeding 2600 A W −1 with fast photoresponse and specific detectivity up to ≈10 13 Jones in the ultraviolet-visible-near-infrared spectrum. This result suggests that the vdW p-g-n junctions containing multiple photoactive TMDs can provide a viable approach toward future ultrahigh-sensitivity and broadband photonic detectors.

Ternary two‐dimensional (2D) semiconductors with controllable wide bandgap, high ultraviolet (UV) absorption coefficient, and critical tuning freedom degree of stoichiometry variation have a great application prospect for UV detection. However, as‐reported ternary 2D semiconductors often possess a bandgap below 3.0 eV, which must be further enlarged to achieve comprehensively improved UV, especially deep‐UV (DUV), detection capacity. Herein, sub‐one‐unit‐cell 2D monolayer BiOBr nanoflakes (≈0.57 nm) with a large size of 70 µm are synthesized for high‐performance DUV detection due to the large bandgap of 3.69 eV. Phototransistors based on the 2D ultrathin BiOBr nanoflakes deliver remarkable DUV detection performance including ultrahigh photoresponsivity (Rλ, 12739.13 A W−1), ultrahigh external quantum efficiency (EQE, 6.46 × 106%), and excellent detectivity (D*, 8.37 × 1012 Jones) at 245 nm with a gate voltage (Vg) of 35 V attributed to the photogating effects. The ultrafast response (τrise = 102 µs) can be achieved by utilizing photoconduction effects at Vg of −40 V. The combination of photocurrent generation mechanisms for BiOBr‐based phototransistors controlled by Vg can pave a way for designing novel 2D optoelectronic materials to achieve optimal device performance.

InSe (bandgap of ~1.20 to 1.80 eV depended on thickness reduction from bulk to monolayer). Specifically, the uncooled SWIR detectivity is up to ~10 14 Jones at 1064 nm and ~10 12 Jones at 1550 nm, respectively. This result indicates that the 2DLMs vdW heterostructures with type-II band alignment produce an interlayer exciton transition, and this adventage can offer a viable strategy for devising high-performance optoelectronics in SWIR or even longer wavelengths beyond the individual limitations of the bandgaps and heteroepitaxy of the constituent atomic layers.

In article number https://doi.org/10.1002/adma.201805656, Rui Chen, Liyuan Zhang, Youpin Gong, and co‐workers develop an h‐BN/MoTe2/graphene/SnS2/h‐BN van der Waals heterostructure to realize an ultrahigh‐sensitivity broadband (405–1550 nm) photodetector, due to its unique advantages for high‐efficiency light absorption and exciton dissociation. Graphene plays a key role in enhancing the sensitivity and broadening the spectral range, providing a viable approach toward future ultrahigh sensitivity and broadband photodetectors.