Photodetectors with excellent detecting properties over a broad spectral range have advantages for the application in many optoelectronic devices. Introducing imperfections to the atomic lattices in semiconductors is a significant way for tuning the bandgap and achieving broadband response, but the imperfection may renovate their intrinsic properties far from the desire. Here, by controlling the deviation from the perfection of the atomic lattice, ultrabroadband multilayer MoS photodetectors are originally designed and realized with the detection range over 2000 nm from 445 nm (blue) to 2717 nm (mid-infrared). Associated with the narrow but nonzero bandgap and large photoresponsivity, the optimized deviation from the perfection of MoS samples is theoretically found and experimentally achieved aiming at the ultrabroadband photoresponse. By the photodetection characterization, the responsivity and detectivity of the present photodetectors are investigated in the wavelength range from 445 to 2717 nm with the maximum values of 50.7 mA W and 1.55 × 10 Jones, respectively, which represent the most broadband MoS photodetectors. Based on the easy manipulation, low cost, large scale, and broadband photoresponse, this present detector has significant potential for the applications in optoelectronics and electronics in the future.

grown as the white laser gains [12][13][14][15] and some approaches have been developed for constructing the prerequisite optical feedback "cavity" with the goal of simultaneous RGB or RYGB lasing. [10,11,13,14] However, constrained by the compactness, difficulty in growth or wavelength control, or the environment friendly, the white lasers are still underdeveloped, and the available materials and approaches are still being extensively sought.In recent years, an emerging family of 2D nanomaterials, group of early transition metal carbides and/or carbonitrides labeled MXenes, was developed by selectively etching MAX phases, [16,17] where M represents an early transition metal, A denotes a main group of 3 or 4 elements, and X is either carbon or nitrogen. They have exhibited super chemical, physical, and environmental properties distinguishing from traditional 2D materials, e.g., they possess hydrophilic surface with metallic conductivity, excellent chemical stability, superior electrical conductivity, environmentally friendly characteristics, etc. [18][19][20][21][22] Unfortunately, their intrinsic photoluminescence response is low, which limits their optical and even further biological applications. The formation of quantum dots (QDs) would generally enhance their photoluminescence by means of the quantum confinement and edge effects, which has been recently experimentally realized in Ti 3 C 2 MXene QDs with the wavelength range from about 350 nm (violet) to 600 nm (orange-red). [23,24] Therefore, it can be believed that the 2D MXenes should be excellent white laser gain medium if the gain can be further enhanced especially in the red range and a broadband optical feedback "cavity" can be constructed. Associated with the theory of a finite atomic system, the sensitivity of the electronic states density of the QDs, corresponding to their photoluminescence, is dependent on their sizes due to the Coulomb blockade effect, [25][26][27] which indicated that the MXene quantum systems with fewer atom layers structure should be more susceptible to the same external passivation and should have better passivation effect than those MXenes with more atom layers structure. For MXene materials, their unique structural characteristics determine that they have at least three-atom layered structure, which indicates that the V 2 C MQDs with fewest atom layers should possess enhanced and broadened photoluminescence after passivation. Considering the optical feedback, effective Multicolor photoluminescence over the full visible color spectrum is critical in many modern science and techniques, such as full-color lighting, displays, biological and chemical monitoring, multiband communication, etc., but the ultimate white lasing especially on the nanoscale is still a challenge due to its exacting requirements in the balance of the gain and optical feedback at different wavelengths. Recently, 2D transition metal carbides (MXenes) have emerged, with some superior chemical, physical, and environmental properties distinguishing them from tr...

Mid- and even long-infrared photodetection is highly desired for various modern optoelectronic devices, and photodetectors that operate at room temperature (RT) remain challenging and are being extensively sought. Recently, the Weyl semimetal has attracted much interest, and its Lorentz invariance can be broken to have tilted chiral Weyl cones around the Fermi level, which indicates that the photocurrent can be generated by the incident photons at arbitrarily long wavelengths. Furthermore, the atypical linear dispersion bands in Weyl cones result in high carrier mobility and quadratic energy dependence of the density of states, which can enhance the efficiency of the photocurrent and suppress thermal carriers, in addition to its favorable large absorption coefficient. In this study, a Weyl semimetal TaAs photodetecting prototype is reported, which operates at RT with an outstanding response that ranges from the visible to the long-infrared range. This study indicates that the Weyl semimetal TaAs should boost the development of modern optoelectronics and photonics.

space. By selecting and arranging these components, the electronic structuresincluding the bandgap and the density of states (DOS) dispersion relation-can be tailored, and desirable effects, such as the photovoltaic effect, [1] quantum Hall effect, [2] and Anderson localization, [3] can be generated and optimized. The detection of light in optoelectronic semiconductors, which exploits the photoelectric effect and involves the conversion of light into an electrical signal, has become indispensable to optoelectronic devices that are used in an array of applications today, such as safety monitoring, biological sensors, remote optical communication, and so on. [4,5] The possible photodetection range is determined by the bandgap of the semiconductor. For UV, visible, and near-IR regimes, photodetectors are typically made from commercial semiconductors with relatively large bandgaps such as silicon, [6] gallium nitride, [7] and indium phosphide. [8,9] However, the fabrication of high-performance mid-IR (3-8 µm) and far-IR (>8 µm) photodetectors remains a major challenge as a result of the intrinsic competition between narrow bandgaps, which give rise to broad wavelength responsivity, and small dark currents, which correspond to highly responsive capacity and large shot noise. [10][11][12][13] This conditions above undoubtedly constrain the development of modern technologies and systems associated with broadband photodetection including the safety monitoring, multiwavelength photodetection, remote optical communication, etc.Generally, the intensity of the dark current depends on the temperature-dependent Fermi-Dirac distribution function, [14] , where E − E F is the energy position, k is the Boltzmann constant), as well as the electronic state density, N c , of the conduction band. The primary calculation shows the f E at 150 K (low temperature) is three orders of magnitude smaller than that at room temperature (RT) when the energy levels correspond to mid-IR region (3-8 µm) corresponding to the narrow bandgap of semiconductors (≈0.4-0.15 eV). To date, researchers have focused mainly on suppressing the dark current by lowering the operating temperature of narrow-bandgap semiconductors which reduces the population of the Fermi-Dirac distribution. [15,16] For instance, state-of-the-art mid-IR photodetectors in the market based on HgCdTe demand the operating temperature as low as about 70 K [15] besides its Photodetection using semiconductors is critical for capture, identification, and processing of optical information. Nowadays, broadband photodetection is limited by the underdeveloped mid-IR photodetection at room temperature (RT), primarily as a result of the large dark currents unavoidably generated by the Fermi-Dirac distribution in narrow-bandgap semiconductors, which constrains the development of some modern technologies and systems. Here, an electronic-structure strategy is proposed for designing ultrabroadband covering mid-and even far-IR photodetection materials operating at RT and a layered MoS 2 is manifested ...

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Two-dimensional (2D) materials have exotic intrinsic electronic band structures and are considered as revolutionary foundations for novel nanodevices. Band engineering of 2D materials may pave a new avenue to overcome numerous challenges in modern technologies, such as room temperature (RT) photodetection of light with photon energy below their band gaps. Here, we reported the pioneering RT MoS 2 -based photodetection in the terahertz (THz) region via introducing Mo 4+ and S 2− vacancies for rational band gap engineering. Both the generation and transport of extra carriers, driven by THz electromagnetic radiations, were regulated by the vacancy concentration as well as the resistivity of MoS 2 samples. Utilizing the balance between the carrier concentration fluctuation and carrier-scattering probability, a high RT photoresponsivity of 10 mA/W at 2.52 THz was realized in an Mo-vacancy-rich MoS 2.19 sample. This work overcomes the challenge in the excessive dark current of RT THz detection and offers a convenient way for further optoelectronic and photonic devices based on band gap-engineered 2D materials.

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