Bulk-like molybdenum disulfide (MoS2) thin films were deposited on the surface of p-type Si substrates using dc magnetron sputtering technique and MoS2/Si p-n junctions were formed. The vibrating modes of E12g and A1g were observed from the Raman spectrum of the MoS2 films. The current density versus voltage (J-V) characteristics of the junction were investigated. A typical J-V rectifying effect with a turn-on voltage of 0.2 V was shown. In different voltage range, the electrical transporting of the junction was dominated by diffusion current and recombination current, respectively. Under the light illumination of 15 mW cm−2, the p-n junction exhibited obvious photovoltaic characteristics with a short-circuit current density of 3.2 mA cm−2 and open-circuit voltage of 0.14 V. The fill factor and energy conversion efficiency were 42.4% and 1.3%, respectively. According to the determination of the Fermi-energy level (∼4.65 eV) and energy-band gap (∼1.45 eV) of the MoS2 films by capacitance-voltage curve and ultraviolet-visible transmission spectra, the mechanisms of the electrical and photovoltaic characteristics were discussed in terms of the energy-band structure of the MoS2/Si p-n junctions. The results hold the promise for the integration of MoS2 thin films with commercially available Si-based electronics in high-efficient photovoltaic devices.

Using nanomaterials to develop multimodal systems has generated cutting-edge biomedical functions. Herein, we develop a simple chemical-vapor-deposition method to fabricate graphene-isolated-Au-nanocrystal (GIAN) nanostructures. A thin layer of graphene is precisely deposited on the surfaces of gold nanocrystals to enable unique capabilities. First, as surface-enhanced-Raman-scattering substrates, GIANs quench background fluorescence and reduce photocarbonization or photobleaching of analytes. Second, GIANs can be used for multimodal cell imaging by both Raman scattering and near-infrared (NIR) two-photon luminescence. Third, GIANs provide a platform for loading anticancer drugs such as doxorubicin (DOX) for therapy. Finally, their NIR absorption properties give GIANs photothermal therapeutic capability in combination with chemotherapy. Controlled release of DOX molecules from GIANs is achieved through NIR heating, significantly reducing the possibility of side effects in chemotherapy. The GIANs have high surface areas and stable thin shells, as well as unique optical and photothermal properties, making them promising nanostructures for biomedical applications.

Two‐dimensional‐material‐based self‐driven photodetectors show high sensitivity, fast and broadband response under built‐in electric field in a P–N junction configuration. However, the methods, including doping and multiple transfer processes, for constructing the heterostructures is complex and time‐costing. On the other hand, asymmetric Schottky barrier heights caused by metal electrodes scale, kinds, contact area and thickness can lead to zero‐bias driven photo‐response. In this work, a metal–semiconductor–metal irregular WS2 photodetector with symmetric electrodes are achieved by wet‐transfer. A high zero‐bias photo‐responsivity of 777 mA W−1, a fast response speed of 7.8/37.2 ms, a Ilight/Idark ratio of 104 and a high detectivity of 4.94 × 1011 Jones under 405 nm light are obtained because of a Schottky barrier height difference of ≈50.2 mV through Fermi‐level pinning effect and different contact area. The responsivity at −2 V is stable in the range of 2.23 to 3.45 A W−1 and the empirical factor reaches to 0.99 by the efficient carrier generation process. The WS2 asymmetric Schottky photodetectors outperform most heterostructure based photodiodes. This paper provides a facile route toward self‐powered photodetectors with high performance, easy processing and simple architecture for future applications.

In-plane anisotropic two-dimensional (2D) materials offer great opportunities for developing novel polarization sensitive photodetectors without in conjunction of filters and polarizers. However, owing to low linear dichroism ratio and insufficient...

A solar cell based on the n-MoS2/i-SiO2/p-Si heterojunction is fabricated. The device exhibits a high power-conversion efficiency of 4.5% due to the incorporation of a nano-scale SiO2 buffer into the MoS2/Si interface. The present device architectures are envisaged as potentially valuable candidates for high-performance photovoltaic devices.

Silicon‐based electronic devices, especially graphene/Si photodetectors (Gr/Si PDs), have triggered tremendous attention due to their simple structure and flexible integration of the Schottky junction. However, due to the relatively poor light–matter interaction and mobility of silicon, these Gr/Si PDs typically suffer an inevitable compromise between photoresponsivity and response speed. Herein, a novel strategy for coupling 2D In2S3 with Gr/Si PDs is demonstrated. The introduction of the double‐heterojunction design not only strengthens the light absorption of graphene/Si but also combines the advantages of the photogating effect and photovoltaic effect, which suppresses the dark current, accelerates the separation of photogenerated carriers, and brings photoconductive gain. As a result, In2S3/graphene/Si devices present an ultrahigh photoresponsivity of 4.53 × 104 A W−1 and fast response speed less than 40 µs, simultaneously. These parameters are an order of magnitude higher than pristine Gr/Si PDs and among the best values compared with reported 2D materials/Si heterojunction PDs. Furthermore, the In2S3/graphene/Si PD expresses outstanding long‐term stability, with negligible performance degradation even after 1 month in air or 1000 cycles of operation. These findings highlight a simple and novel strategy for constructing high‐sensitivity and ultrafast Gr/Si PDs for further optoelectronic applications.

Alloy engineering and heterostructures designing are two efficient methods to improve the photosensitivity of two-dimensional (2D) material-based photodetectors. Herein, we report the first-principle calculation about the band structure of SnS1–x Se x (0 ≤ x ≤ 1) and synthesize these alloy nanosheets. Systematic measurements indicate that SnS0.25Se0.75 exhibits the highest hole mobility (0.77 cm2·V–1·s–1) and a moderate photoresponsivity (4.44 × 102 A·W–1) with fast response speed (32.1/57.5 ms) under 635 nm irradiation. Furthermore, to reduce the dark current and strengthen the light absorption, a self-driven SnS0.25Se0.75/n-Si device has been fabricated. The device achieved a preeminent photo-responsivity of 377 mA·W–1, a detectivity of ∼1011 Jones and I light/I dark ratio of ∼4.5 × 102. In addition, the corresponding rising/decay times are as short as 4.7/3.9 ms. Moreover, a broadband sensitivity from 635 to 1200 nm is obtained and the related photoswitching curves are stable and reproducibility. Noticeably, the above parameters are comparable or superior to the most of reported group IVA layered materials-based self-driven photodetectors. Last, the synergistic effects between the SnS0.25Se0.75 nanosheets and the n-Si have been discussed by the band alignment. These brilliant results will pave a new pathway for the development of next generation 2D alloy-based photoelectronic devices.

The ability to detect linearly polarized light is essential in the field of angle‐dependent optoelectronics and polarization optical applications. To date, most polarization‐sensitive photodetectors are mainly based on single 2D anisotropic materials, which still suffer from the large dark current, from being external bias driven, and from low anisotropy ratio. To address these obstacles, we fabricated a van der Waals (vdW) GeAs/InSe heterojunction with type‐II band alignment achieving a high‐performance self‐driven polarization‐sensitive photodetector. The heterojunction exhibits excellent rectifying characteristics with a current rectification ratio exceeding 103. By operating in photovoltaic mode at zero bias, the device shows a very low dark current of ∼0.1 picoampere, high photoresponsivity of 357 mA/W, and large photo‐switching ratio of 103, yielding a high specific detectivity of 2 × 1011 Jones and photoelectric conversion efficiency (PCE) up to 8%. Benefiting from the anisotropic structure of the GeAs components, the heterojunctions also exhibit self‐driven polarization‐sensitive photodetection with superior anisotropic photocurrent ratio of ∼18 which surpasses state‐of‐the‐art 2D based polarization‐dependent detectors. This work proposes an effective strategy utilizing the anisotropic/isotropic vdW heterojunctions to enable self‐powered and high‐performance polarization‐sensitive photodetectors, opening a new avenue towards the promising potential applications in polarization‐resolved electronics and photonics.