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The development of optoelectronic devices requires breakthroughs in new material systems and novel device mechanisms, and the demand recently changes from the detection of signal intensity and responsivity to the exploration of sensitivity of polarized state information. Two-dimensional (2D) materials are a rich family exhibiting diverse physical and electronic properties for polarization device applications, including anisotropic materials, valleytronic materials, and other hybrid heterostructures. In this review, we first review the polarized-light-dependent physical mechanism in 2D materials, then present detailed descriptions in optical and optoelectronic properties, involving Raman shift, optical absorption, and light emission and functional optoelectronic devices. Finally, a comment is made on future developments and challenges. The plethora of 2D materials and their heterostructures offers the promise of polarization-dependent scientific discovery and optoelectronic device application.

Substitutional doping of two-dimensional (2D) transition metal dichalcogenides (TMDs) has been recognized as a promising strategy to tune their optoelectronic properties for a wide array of applications. However, controllable doping of TMDs remains a challenging issue due to the natural doping of these materials. Here, we demonstrate the controllable growth of indium-doped p-type WS 2 monolayers with various doping concentrations via chemical vapor deposition (CVD) of a host tungsten (W) source and indium (In) dopant. Scanning transmission electron microscopy confirmed that In atoms successfully substitute the W atoms in the WS 2 lattice. Intriguingly, the photoluminescence of the doped sample experiences strong intensity modulation by the doping concentration, which first increases remarkably with an enhancement factor up to~35 and then decreases gradually when further increasing the doping concentration. Such a phenomenon is attributed to the progressive change of the exciton to trion ratio as well as the defect concentration in the doped samples. The assignment was further verified by the electric behavior of the fabricated In-doped WS 2 field effect transistors, which changes regularly from n-type to bipolar and finally to p-type behavior with increasing doping concentration. The successful growth of p-type monolayer WS 2 and the dual control of its optical and electrical properties by In doping may provide a promising method to engineer the opto-electronic properties of 2D materials.

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A p-type semiconductor candidate of nickel oxide (NiO) desires longer carrier lifetimes with suitable conduction band edge, which holds a unique advantage to drive the hydrogen evolution toward efficient water splitting. However, a relatively large band gap (∼4 eV) greatly hinders its practical applications. We thus theoretically explore the band edge tailoring of NiO by doping electron-poor S on the sites of O. With the increase of incorporated S density, the electronic band gap (E g) of p-type-doped NiO is reduced with the improved valance band maximum (VBM), which is dominated by the emerged S 3p orbital hybridized with Ni t2g states. Accordingly, the hole transportation might be enhanced due to the enlarged VBM offset between the active layer and NiO1–x S x . Furthermore, the magnetic momentum per Ni atom increases with the increase of S densities, owing to the p-type-doping-induced majority and minority spin mismatch. It is confirmed that the VBM of NiO with S density lower than 2.08% consists of S 3p and Ni t2g states with majority spin. Moreover, as a turning point, the special quasirandom structure (SQS) with S density as high as 2.78% shows a balanced spin feature, while the states with minority spin play a predominant role in the VBM with S density higher than 8.33%.

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