Mid-infrared (MIR) light-emitting devices play a key role in optical communications, thermal imaging, and material analysis applications. Two-dimensional (2D) materials offer a promising direction for next-generation MIR devices owing to their exotic optical properties, as well as the ultimate thickness limit. More importantly, van der Waals heterostructures—combining the best of various 2D materials at an artificial atomic level—provide many new possibilities for constructing MIR light-emitting devices of large tuneability and high integration. Here, we introduce a simple but novel van der Waals heterostructure for MIR light-emission applications built from thin-film BP and transition metal dichalcogenides (TMDCs), in which BP acts as an MIR light-emission layer. For BP–WSe2 heterostructures, an enhancement of ~200% in the photoluminescence intensities in the MIR region is observed, demonstrating highly efficient energy transfer in this heterostructure with type-I band alignment. For BP–MoS2 heterostructures, a room temperature MIR light-emitting diode (LED) is enabled through the formation of a vertical PN heterojunction at the interface. Our work reveals that the BP–TMDC heterostructure with efficient light emission in the MIR range, either optically or electrically activated, provides a promising platform for infrared light property studies and applications.
to the photon-assisted oxygen desorption from the nanostructure surface, resulting in a decrease of hole concentration. [2] Also, in the case of n-type InAs nanowires, the hot carrier trapping process at the surface gives the reduction of photoexcited charge carriers. [3] Therefore, additional electronic states are always required to compensate photoexcited charge carriers for accessing NPC situation. Nanostructured materials with plenteous surface sites can potentially generate a high density of localized energy states to trap photoexcited charge carriers, which are promising for constructing optoelectronic devices with high-speed frequency response and low power consumption. [3,4] 2D materials have proved to be one of the most promising materials of which the focus has expanded beyond graphene to other layered van der Waals materials with a variety of distinct properties. [5][6][7][8][9][10] A burgeoning research direction goes toward the newly emerged metal phosphorus trichalcogenides (MPTs). [11][12][13][14] MPTs have many fascinating properties as featured in photoelectronic and electronic fields, such as a wide range of indirect bandgap from 1.3 to 3.5 eV, [11] and high carrier mobility. [15] In addition, the introduction of magnetic metal atoms can bring new physical phases, such as antiferromagnetic or ferromagnetic order. [16,17] With these advantages, some works have demon strated that MPTs obtain a remarkable photo response under ultraviolet (UV) illumination 2D materials have aroused tremendous attention in the last decade, and magnetic materials of the 2D scale are rising to prominence in recent years, which may revolutionize current optical and electronic applications. Photoconductivity is a well-known optical and electrical property, which should be positive as the conductivity of material increases typically upon the absorption of electromagnetic radiation. Here, a controllable switch from negative to positive photoconductivity effect of FePS 3 nanosheets is enabled by the modulation of the excitation wavelengths. These effects originate from an ultrafast process of hot carrier trapping, as visualized and investigated by the transient absorption microscopy at a quantitative level. This hot carrier trapping process is about 1.25 ps resulting in a lower diffusion constant state (≈3.5 cm 2 s −1 ), which provides deep insight into the intrinsic properties of 2D FePS 3 for further study. The results demonstrate experimentally the possibility to tune the electronic properties of 2D magnetic materials by an optical way, which not only induces the change in the magnitude but also in the sign, leading to more understandings and possibilities in 2D optoelectronic devices with many unexpected and multifunctional properties.
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