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2D semiconductors are regarded as the potential channel materials for high‐performance integrated optoelectronics. However, the absence of an effective photoconductive gain mechanism and the adverse effects from traditional SiO2 substrate prevent the further breakthrough of the photosensitivity of 2D semiconductors‐based photodetectors. Here, an ingenious out‐of‐plane heterostructure is proposed for boosting the photosensitivity. Sub‐millimeter scale (>700 µm) tri‐layer WSe2 with high quality and uniformity is robustly deposited and integrated with 2D photosensitive channels for gate‐tunable photodetection. The WSe2 with naturally passivated surface can not only serve as a substrate passivation layer to mitigate the detrimental substrate effects, but also introduces vertical built‐in fields, which efficiently separates the photogenerated carriers and produces high photoconductive gain. Under gate voltage modulation, the proposed InSe photodetector exhibits a series of excellent performances, including responsivity of 112 A W−1, detectivity of 8.6 × 1012 Jones, light on/off ratio of 1.3 × 104 and rise/decay time of 29.1/15.3 ms. More inspiringly, this heterostructure scheme is universally applicable to 2D WS2 photodetector and also significantly improves its photosensitivity, demonstrating broad applicability. This research will provide helpful guidance for the design and optimization of customizable optoelectronic devices based on 2D semiconductors. [ABSTRACT FROM AUTHOR]

The excellent semiconducting properties and ultrathin morphological characteristics allow van der Waals (vdW) heterostructures based on 2D materials to be promising channel materials for the next‐generation optoelectronic devices, especially in photodetectors. Although various 2D heterostructure‐based photodetectors have been developed, the unavoidable trade‐off between responsivity and detectivity remains a critical issue for these devices. Here, an ingenious phototransistor based on WSe2/WS2/WSe2 dual‐vdW heterostructures is constructed, performing both high responsivity and detectivity. In the charge neutrality point (gate voltage of −15 V and bias voltage of 1 V), this device demonstrates a pronounced photosensitivity, accompanying with high detectivity of 1.9 × 1014 Jones, high responsivity of 35.4 A W−1, and fast rise/fall time of 3.2/2.5 ms at 405 nm with power density of 60 µW cm−2. Density functional theory calculations, energy band profiles, and optoelectronic characteristics jointly verify that the high performance is ascribed to the distinctive device design, which not only facilitates the separation of photogenerated carriers but also produces a strong photogating effect. As a feasible application, an automotive radar system is demonstrated, proving that the device has considerable potential for application in vehicle intelligent assisted driving. [ABSTRACT FROM AUTHOR]

Photodetectors, essential for a wide range of optoelectronic applications in both military and civilian sectors, face challenges in balancing responsivity, detectivity, and response time due to their inherent unidirectional carrier transport mechanism. Multifunctional photodetectors that address these trade-offs are highly sought after for their potential to reduce costs, simplify system design, and surpass Moore's Law limitations. Herein, we present a multimodal phototransistor based on a 2D MoTe 2 /In 2 S 3 heterostructure. Through dual electrical modulation employing bias voltage and gate voltage, we engineer the energy band to achieve switchable photoresponse mechanisms between photoconductive and photovoltaic modes. In photoconductive mode, the device exhibits a responsivity of 320 A/W and a specific detectivity of 1.2 × 10 13 Jones. Meanwhile, in photovoltaic mode, it exhibits a light on/off ratio of 2 × 10 5 and response speed of 0.68/0.60 ms. These capabilities enable multifunctional applications such as high-resolution imaging across various wavelengths, a conceptual optoelectronic logic gate, and dual-channel optical communication. This work makes an advancement in the development of future multifunctional optoelectronic devices.

Next-generation imaging systems require photodetectors with high sensitivity, polarization sensitivity, miniaturization, and integration. By virtue of their intriguing attributes, emerging 2D materials offer innovative avenues to meet these requirements. However, the current performance of 2D photodetectors is still below the requirements for practical application owing to the severe interfacial recombination, the lack of photoconductive gain, and insufficient photocarrier collection. Here, a tunneling dominant imaging photodetector based on WS 2 /Te heterostructure is reported. This device demonstrates competitive performance, including a remarkable responsivity of 402 A W -1 , an outstanding detectivity of 9.28 × 10 13 Jones, a fast rise/decay time of 1.7/3.2 ms, and a high photocurrent anisotropic ratio of 2.5. These outstanding performances can be attributed to the type-I band alignment with carrier transmission barriers and photoinduced tunneling mechanism, allowing reduced interfacial trapping effect, effective photoconductive gains, and anisotropic collection of photocarriers. Significantly, the constructed photodetector is successfully integrated into a polarized light imaging system and an ultra-weak light imaging system to illustrate the imaging capability. These results suggest the promising application prospect of the device in future imaging systems., (© 2023 Wiley-VCH GmbH.)

Two-dimensional (2D) material-based van der Waals (vdW) heterostructures with exotic semiconducting properties have shown tremendous potential in next-generation photovoltaic photodetectors. Nevertheless, these vdW heterostructure devices inevitably suffer from a compromise between high sensitivity and fast response. Herein, an ingenious photovoltaic photodetector based on a WSe 2 /WS 2 /p-Si dual-vdW heterojunction is demonstrated. First-principles calculations and energy band profiles consolidate that the photogating effect originating from the bottom vdW heterojunction not only strengthens the photovoltaic effect of the top vdW heterojunction, but also suppresses the recombination of photogenerated carriers. As a consequence, the separation of photogenerated carriers is facilitated and their lifetimes are extended, resulting in higher photoconductive gain. Coupled with these synergistic effects, this WSe 2 /WS 2 /p-Si device exhibits both high sensitivity (responsivity of 340 mA W -1 , a light on/off ratio greater than 2500, and a detectivity of 3.34 × 10 11 Jones) and fast response time (rise/decay time of 657/671 μs) under 405 nm light illumination in self-powered mode. Finally, high-resolution visible-light and near-infrared imaging capabilities are demonstrated by adopting this dual-heterojunction device as a single pixel, indicating its great application prospects in future optoelectronic systems., Competing Interests: The authors declare no competing financial interests., (This journal is © The Royal Society of Chemistry.)