This review systematically summarizes the electronic band structures, optical properties and device applications of 2D anisotropic semiconductors.

Harvesting energy through light radiation is an attractive solution for powering wireless devices in the future. In particular, self-driven optoelectronic devices are especially attractive for low-energy devices on the Internet of Things. Two-dimensional (2D) materials at atomic scale thicknesses are very attractive for future self-powered optoelectronic devices due to not only their unique electronic and optical properties, but also the feasibility to fabricate desirable heterostructures, which differ from their bulk counterparts and conventional optoelectronic materials. In this review, we mainly summarized the mechanism and performance of self-powered optoelectronic devices based on 2D materials. The figure of merit and mechanism of self-driving optoelectronic devices including the interface-junction effect, bulk photovoltaic effect, and photothermoelectric effect are discussed in detail. In addition, the recent progress on the performance of self-powered optoelectronic devices based on 2D materials is compared, followed by the perspective of this field. This review is aimed to give a generalized knowledge of 2D self-powered optoelectronic devices, and thus prompt the exploration and development of novel functional devices based on 2D materials.

Quasi-two-dimensional (quasi-2D) perovskites show great potential in light-emitting diodes. The use of additives plays a key role in the passivation of defects and the suppression of low-dimensional phases. However, the effects of additives vary greatly in different perovskite formulations/films with different light-emitting bands. In this paper, the universal utility of additives was achieved through sodium hexafluorophosphate (NaPF₆). Benefitting from the neutral environment of the additives and the hydrogen bonds formed by PF₆ ⁻/PEA⁺ (F⋯H–N), the low-dimensional phases are effectively reduced, and the distribution of the medium/high-dimensional phases is more balanced. Meanwhile, the PF₆ ⁻ anionic group can passivate the uncoordinated Pb²⁺, and reduce the defect density of the film. Finally, a maximum EQE of 16.8% was achieved in quasi-2D PEA₂Cs_n−1Pb_nBr_3n+1 green PeLEDs (514 nm), which was significantly higher than that of the pristine device (a maximum EQE of 10%). Correspondingly, the maximum EQE of sky blue PeLEDs (490 nm) based on the mixed halogen [(PEA)_0.75(GA)_0.25]₂CsPb₂X₇ (X = Br and Cl) component can be increased from 5.6% to 9.6%. The maximum EQE of pure blue PeLEDs (474 nm) can be increased from 3% to 4%. This class of neutral additives provides a solution for high-performance quasi-2D perovskite electroluminescence.