Since monolayer graphitic film was successfully exfoliated by using scotch tape in 2004, [3] 2D materials like carbon group, transition metal dichalcogenides (TMDs), and layered metal oxides have received considerable attention and provided brand-new potential in nano-scale electronic devices. [4][5][6][7] Differ from 3D materials, 2D materials possess strong chemical bonds in each layer and weak van der Waals (vdW) forces between the adjacent layers. [8] The monolayer and fewlayer sheets of 2D layered materials can be obtained via various synthesis methods such as micromechanical exfoliation, [9] liquid exfoliation, [10] and chemical vapor deposition (CVD). [7] Due to the weak vdW force, the thermal and lattice mismatches between different materials become insignificant, which is conducive to construct heterostructure. [11][12][13] Additionally, there are no dangling bands on the 2D material surface owing to the sheet structure, thus such an excellent feature allows carrier scattering to be largely eliminated compared to bulk semiconductors. Besides, the inherent ultrathin properties enable the enhanced gate modulation effect, mitigating SCEs. All these remarkable merits of 2D materials render them promising candidates for sub-10 nm FETs. [14][15][16] Furthermore, 2D layered structure materials with high surface area, flexibility, unique optical and electronic properties are also potentially feasible for application in micro-electromechanical systems (MEMS), optoelectronics, biosensors, super capacitors, and solar cells. [7,[17][18][19][20][21] Van der Waals layered indium selenide (InSe) is an emerging star of the 2D semiconducting materials because of its excellent fundamental properties, such as ultrahigh carrier mobility, layer-tunable bandgap, large elastic deformability, and rich polytypes. In addition, 2D layered indium selenide has demonstrated outstanding device performance including photodetector, fieldeffect transistor, memory and synapse, mechanical and gas sensor, which has offered a new chance to next-generation electrical and optoelectronic devices. This review presents a comprehensive summary of recent progress in 2D layered indium selenide. The novel fundamental properties and synthetic methods are summarized. Also, the indium selenide-based stateof-the-art electronic/optoelectronic devices, such as a functional field-effect transistor, photodetector, and mechanical and gas sensors are systematically summarized. The techniques to enhance the performances of devices are also discussed. Finally, a brief discussion on the challenges and future opportunities as a guideline for this field is provided.

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Recently, researchers have focused on optoelectronics based on two-dimensional van der Waals materials to realize multifunctional memory and neuron applications. Layered indium selenide (InSe) semiconductors satisfy various requirements as photosensitive channel materials, and enable the realization of intriguing optoelectronic applications. Herein, we demonstrate InSe photonic devices with different trends of output currents rooted in the carrier capture/release events under various gate voltages. Furthermore, we reported an increasing/flattening/decreasing synaptic weight change index (∆Wn) via a modulated gate electric field, which we use to imitate medicine-acting metaplasticity with effective/stable/ineffective features analogous to the synaptic weight change in the nervous system of the human brain. Finally, we take advantage of the low-frequency noise (LFN) measurements and the energy-band explanation to verify the rationality of carrier capture-assisted optoelectronics applied to neural simulation at the device level. Utilizing optoelectronics to simulate essential biomedical neurobehaviors, we experimentally demonstrate the feasibility and meaningfulness of combining electronic engineering with biomedical neurology.