Researchers have demonstrated a two-dimensional material device that uses an applied voltage to switch between two distinct exciton states, controlling whether energy carriers can move through the material or remain localized. The work, led by Dehui Li at Huazhong University of Science and Technology, uses a hybrid perovskite-tungsten disulfide heterostructure and represents a practical advance toward excitonic and valleytronic circuits.
Excitons are bound electron-hole pairs created when a material absorbs light. They occupy an intermediate position between light and electrical charge, and researchers have long explored them as a third channel for transporting information alongside electrons in conventional computing and photons in photonic devices. The obstacle is lifetime: excitons typically recombine quickly, either emitting light or dissipating energy through non-radiative processes, which limits how far they can travel.
One established solution is to separate the electron and hole across two different material layers, forming an interlayer exciton that can transport energy over longer distances. Previous efforts have relied on stacked transition-metal dichalcogenides such as MoSe₂/WSe₂ or WS₂/WSe₂. Those systems require extremely precise rotational alignment between layers — a twist-angle engineering challenge — to produce prominent interlayer exciton emission.
The new device avoids that constraint. By pairing a hybrid perovskite with WS₂, the researchers created a heterostructure that does not demand careful rotational alignment. Applying a voltage switches the device between interlayer excitons and intralayer excitons, allowing the team to control whether excitons move through the material or stay localized. The mechanism hinges on a voltage-driven transition between Type-II and Type-I band alignment, which governs charge transfer dynamics at the interface.
The researchers also used voltage to toggle the device between low and high valley-polarization states across the two exciton regimes. Valley polarization describes how strongly carriers favor one of two equivalent energy minima, known as valleys, in a material's electronic structure. That ability to electrically control valley states points toward valleytronics, a field that aims to use valleys rather than charge or spin to encode and process information.
Polarization-resolved photoluminescence spectra, collected under circularly polarized laser excitation at opposite voltages, confirmed the switching behavior. The results show that a single device can electrically govern both energy transport and information states in a 2D material system — two functions that had previously been addressed separately.
The findings were published in Reports on Progress in Physics by Yingying Chen and colleagues. More broadly, the research offers a route to electrically tunable exciton transport in hybrid 2D systems, bringing excitonic and valleytronic circuit concepts closer to practical implementation. The work also highlights hybrid perovskite–transition-metal dichalcogenide heterostructures as a platform that sidesteps the stringent alignment requirements of all-TMD stacks, potentially simplifying device fabrication for future optoelectronic and information-processing technologies.
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