Stacking single layers of atoms on top of each other provides a fundamental way to achieve novel material systems and engineer their physical properties, which offers opportunities for exploring fundamental physics and realizing next-generation optoelectronic devices. Among the two-dimensional (2D)-stacked systems, transition metal dichalcogenide (TMDC) heterostructures are particularly attractive because they host tightly-bonded interlayer excitons which possess various novel and appealing properties. These interlayer excitons have drawn significant research attention and hold high potential for the application in unique optoelectronic devices, such as polarization- and wavelength-tunable single photon emitters, valley Hall transistors, and possible high-temperature superconductors. The development of these devices requires a comprehensive understanding of the fundamental properties of these interlayer excitons and the impact of electric fields on their behaviors. In this review, we summarize the recent advances on the understanding of interlayer exciton dynamics under electric fields in TMDC heterostructures. We put emphasis on the electrical modulation of interlayer excitons’ emission, the valley Hall transport of charge carriers after the separation of interlayer excitons by an electric field, and the correlation physics of interlayer excitons and charges under electrical doping and tuning. Challenges and perspectives are finally discussed for the application of TMDC heterostructures in future optoelectronics.

Artificial van der Waals (vdWs) heterostructures offer unprecedented opportunities to explore and reveal novel synergistic electronic and optical phenomena, which are beneficial for the development of novel optoelectronic devices at atomic limits. However, due to the damage caused by the device fabrication process, their inherent properties such as carrier mobility are obscured, which hinders the improvement of device performance and the incorporation of vdWs materials into next-generation integrated circuits. Herein, combining pump-probe spectroscopic and scanning probe microscopic techniques, the intrinsic optoelectronic properties of PtSe₂/MoSe₂ heterojunction were nondestructively and systematically investigated. The heterojunction exhibits a broad-spectrum optical response and maintains ultrafast carrier dynamics (interfacial charge transfer ~ 0.8 ps and carrier lifetime ~ 38.2 ps) simultaneously. The in-plane exciton diffusion coefficient of the heterojunction was extracted (19.4 ± 7.6 cm²∙s⁻¹), and its exciton mobility as high as 756.8 cm²∙V⁻¹∙s⁻¹ was deduced, exceeding the value of its components. This enhancement was attributed to the formation of an n-type Schottky junction between PtSe₂ and MoSe₂, and its built-in electric field assisted the ultrafast transfer of photogenerated carriers from MoSe₂ to PtSe₂, enhancing the in-plane exciton diffusion of the heterojunction. Our results demonstrate that PtSe₂/MoSe₂ is suitable for the development of broad-spectrum and sensitive optoelectronic devices. Meanwhile, the results contribute to a fundamental understanding of the performance of various optoelectronic devices based on such PtSe₂ two-dimensional (2D) heterostructures.

Two-dimensional (2D) materials hold great potential for the development of next-generation integrated circuits (ICs) at the atomic limit. However, it is still very challenging to build high performance devices. One of the main factors that limit the incorporation of 2D materials into IC technology is their relatively low carrier mobility. Thus, the engineering strategies that focus on optimizing performance continue to emerge. Herein, using a spatiotemporal resolved pump-probe setup, the carrier transport performance and relaxation process of few-layer and bulk MoSe₂ under pressure were investigated nondestructively and simultaneously. Our results show that pressure can tune the transport performance effectively. In particular, under pressure regulation, the carrier mobility of the bulk MoSe₂ increases by ~ 4 times; meanwhile, the carrier lifetimes of the samples become shorter. Although the processes almost return to their initial state after the pressure release, it is still surprising to see that the carrier mobilities of few-layer and bulk MoSe₂ are still ~ 1.5 and 2 times enhanced, and carrier lifetimes are still shorter than the initial state. Combined with the Raman spectra under pressure, we consider that it is caused by the enhanced layer coupling and lattice compression. The combination of enhanced mobility and shortened lifetime in MoSe₂ under pressure holds great potential for optoelectronic applications under the deep ocean and deep earth.