The discovery of graphene has triggered the research on 2D layer structured materials. Among many 2D materials, semiconducting transition metal dichalcogenides (TMDs) are widely considered to be the most promising ones due to their excellent electrical and optoelectronic characteristics. Tungsten disulfide (WS2) is a kind of such TMDs with fascinating properties, such as the high carrier mobility, appropriate band gap, strong light–matter interaction with the large light absorption coefficient, very large exciton binding energy, large spin splitting, and polarized light emission. All these interesting properties can make the 2D WS2 being highly favorable for applications in memristors, light‐emitting devices, optical modulators, and many others. Here, the comprehensive review on the properties, vapor phase synthesis, electronic and optoelectronic applications of 2D WS2 is presented. This review does not only serve as a design guideline to elevate the material quality of 2D WS2 films via enhanced synthesis approaches, but also provides valuable insights to various strategies to improve their device performances. With the fast development of wafer‐scale synthesis methods and novel device structures, 2D WS2 can undoubtedly be a rising star for the next‐generation devices in the near future.

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For conventional polycrystalline Ni‐rich cathode material consisting of numerous primary particles in disordered orientation, the crystal anisotropy in charge/discharge process results in the poor rate capability and rapid capacity degradation. In this work, highly‐dispersed submicron single‐crystal LiNi0.8Co0.15Al0.05O2 (SC‐NCA) cathode is efficiently prepared by spray pyrolysis (SP) technique followed by a simple solid‐state lithiation reaction. Porous Ni0.8Co0.15Al0.05Ox precursor prepared via SP exhibits high chemical activity for lithiation reaction, enabling the fabrication of single‐crystal cathode at a relatively low temperature. In this way, the contradiction between high crystallinity and cation disordering is well balanced. The resulted optimized SC‐NCA shows polyhedral single‐crystal morphology with moderate grain size (≈1 μm), which are beneficial to shortening the Li+ diffusion path and improving the structural stability. As cathode for lithium ion batteries, SC‐NCA delivers a high discharge capacity of 202 and 140 mAh g−1 at 0.1 and 10 C, respectively, and maintains superior capacity retention of 161 mAh g−1 after 200 cycles at 1C. No micro‐crack is observed in the cycled SC‐NCA particles, indicating such single‐crystal morphology can greatly relieve the anisotropic micro‐strain. This effective, continuous and adaptable strategy for preparing single‐crystal Ni‐rich cathode without any additive may accelerate their practical application.

An electro-absorption optical modulator based on dual-graphene-on-graphene configuration is presented and investigated. Four graphene layers are embedded in a silicon-on-insulator (SOI) waveguide, the total metal-graphene contact resistance of this structure is reduced 50% by the graphene layers co-electrode design. By optimizing the position of each graphene-on-graphene (GOG) layer in the waveguide, a strong interaction between graphene layers and light is obtained, which leads to a significant change of the effective mode index (EMI) in the waveguide. Calculations show that an electro-absorption optical modulator can achieve 34 dB extinction ratio (ER) and 100 GHz modulation bandwidth with 5 µm-long active region and 17.6 fJ/bit consumption.