Hybrid Heterostructures to Generate Long-Lived and Mobile Photocarriers in Graphene.

We report the generation of long-lived and highly mobile photocarriers in hybrid van der Waals heterostructures that are formed by monolayer graphene, few-layer transition metal dichalcogenides, and the organic semiconductor FZnPc. Samples are fabricated by dry transfer of mechanically exfoliated MoS or WS few-layer flakes on a graphene film, followed by deposition of FZnPc. Transient absorption microscopy measurements are performed to study the photocarrier dynamics. In heterostructures of FZnPc/few-layer-MoS/graphene, electrons excited in FZnPc can transfer to graphene and thus be separated from the holes that reside in FZnPc. By increasing the thickness of MoS, these electrons acquire long recombination lifetimes of over 100 ps and a high mobility of 2800 cm V s. Graphene doping with mobile holes is also demonstrated with WS as the middle layers. These artificial heterostructures can improve the performance of graphene-based optoelectronic devices.