Room‐temperature‐operating highly sensitive mid‐wavelength infrared (MWIR) photodetectors are utilized in a large number of important applications, including night vision, communications, and optical radar. Many previous studies have demonstrated uncooled MWIR photodetectors using 2D narrow‐bandgap semiconductors. To date, most of these works have utilized atomically thin flakes, simple van der Waals (vdW) heterostructures, or atomically thin p–n junctions as absorbers, which have difficulty in meeting the requirements for state‐of‐the‐art MWIR photodetectors with a blackbody response. Here, a fully depleted self‐aligned MoS2‐BP‐MoS2 vdW heterostructure sandwiched between two electrodes is reported. This new type of photodetector exhibits competitive performance, including a high blackbody peak photoresponsivity up to 0.77 A W−1 and low noise‐equivalent power of 2.0 × 10−14 W Hz−1/2, in the MWIR region. A peak specific detectivity of 8.61 × 1010 cm Hz1/2 W−1 under blackbody radiation is achieved at room temperature in the MWIR region. Importantly, the effective detection range of the device is twice that of state‐of‐the‐art MWIR photodetectors. Furthermore, the device presents an ultrafast response of ≈4 µs both in the visible and short‐wavelength infrared bands. These results provide an ideal platform for realizing broadband and highly sensitive room‐temperature MWIR photodetectors.
Reaction of L(0)NiBr(2) with 2 equiv of NaH yielded the Ni(II) hydride complex [(L(•-))Ni(μ-H)(2)Ni(L(•-))] (1) (L = [(2,6-iPr(2)C(6)H(3))NC(Me)](2); L(0) represents the neutral ligand, L(•-) is its radical-anionic form, and L(2-) denotes the dianion) in good yield. Stepwise reduction of complex 1 led to a series of nickel hydrides. Reduction of 1 with 1 equiv of sodium metal afforded a singly reduced species [Na(DME)(3)][(L(•-))Ni(μ-H)(2)Ni(L(•-))] (2a) (DME = 1,2-dimethoxyethane), which contains a mixed-valent core [Ni(μ-H)(2)Ni](+). With 2 equiv of Na a doubly reduced species [Na(DME)](2)[L(2-)Ni(μ-H)(2)NiL(2-)] (3a) was obtained, in which each monoanion (L(•-)) in the precursor 1 has been reduced to L(2-). By using potassium as the reducing agent, two analogous species [K(DME)(4)][(L(•-))Ni(μ-H)(2)Ni(L(•-))] (2b) and [K(DME)](2)[L(2-)Ni(μ-H)(2)NiL(2-)] (3b) were obtained. Further treatment of 3b with 2 equiv of K led to a trinuclear complex [K(DME)(THF)](2)K(2)[L(2-)Ni(μ-H)(2)Ni(μ-H)(2)NiL(2-)] (4), which contains one Ni(II) and two Ni(I) centers with a triplet ground state. When 1 and 3a were warmed in toluene or benzene, respectively, three reverse-sandwich dinickel complexes, [(L(•-))Ni(μ-η(3):η(3)-C(7)H(8))Ni(L(•-))] (5) and [Na(DME)](2)[L(2-)Ni(μ-η(3):η(3)-C(6)H(5)R)NiL(2-)] (6: R = CH(3); 7: R = H), were isolated. Reaction of 1 with Me(3)SiN(3) gave the N(3)-bridged complex [(L(•-))Ni(μ-η(1)-N(3))(2)Ni(L(•-))] (8). The crystal structures of complexes 1-8 have been determined by X-ray diffraction, and their electronic structures have been fully studied by EPR/NMR spectroscopy.
Metal phosphorous tri-chalcogenides are a category of new ternary 2D layered materials with a wide range of tuneable bandgaps (1.2-3.5 eV). These wide-bandgap semiconductors exhibit great potential applications in solar-blind ultraviolet (SBUV) photodetection. However, these 2D solarblind photodetectors suffer from low photoresponsivity, slow photoresponse speed, and narrow operation spectral region, thereby limiting their practical applications. Here, an ultra-broadband photodetection based on a FePSe 3 / MoS 2 heterostructure with coverage ranging from solar-blind ultraviolet 265 nm to longwave infrared (LWIR) 10.6 µm is reported. Notably, the device exhibits excellent weak light detection capability. A high photoresponsivity of 33 600 A W −1 and an external quantum efficiency of 1.57 × 10 7 % are demonstrated. A noise-equivalent power as low as 5.7 × 10 -16 W Hz −1/2 and a specific detectivity up to 1.51 × 10 13 cm Hz 1/2 W −1 are realized in the SBUV region. The room temperature LWIR photoresponsivity of 0.12 A W −1 is realized. This work opens a route to design high-performance SBUV photo detectors and wide spectral photoresponse applications.
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