Designer charge-transfer van der Waals heterostructures.

Interlayer charge transfer in two-dimensional van der Waals (vdW) heterostructures underpins a wide range of emergent quantum phenomena, ranging from excitonic dynamics and light-matter interactions to various correlated electron states. The ability to manipulate interlayer charge transfer on demand offers a powerful knob to control and functionalize these emergent phenomena. In this review, we discuss the recently emerging strategies for assembling and engineering charge-transfer vdW heterostructures in a programmable fashion. We first discuss various static control knobs for programming interlayer charge transfer, including interfacial band alignment and symmetry breaking interfaces. We next discuss strategies to dynamically modify interlayer charge transfer using light and pressure to perturb charge-transfer heterostructures, with an emphasis on interlayer excitons in transition-metal dichalcogenides. We further highlight new applications that emerge out of these charge-transfer heterostructures, ranging from polaritonic devices to novel transistor architectures and photo- and electro-chemical cells. Finally, we conclude with an outlook and future prospects for a new generation of charge-transfer heterostructures.