Large-area flexible photodetector based on atomically thin MoS2/graphene film

Highlights: • Morphology evolution of the MoS₂ film was investigated, and the grain boundaries were clearly illustrated. • Continuous MoS₂ film (2~3 mm) with high quality single crystalline grains (20~100 μm) was achieved. • Polymer electrolyte (PEO: LiClO₄ =8:1) was introduced to form the side-gated FET. • The highly transparent flexible photodetector demonstrated high responsivity (33.3A/W) and good stability. In this paper, we demonstrate a large-area flexible photodetector based on vertically stacked atomically thin MoS₂/graphene film. The MoS₂ film is grown by CVD method. We have realized the growth of several square millimeter continuous monolayer MoS₂ film via precisely control the atmosphere and temperature in the tube furnace. In experiment, the MoS₂ and graphene film was transferred on PET substrate successively. Polymer electrolyte composed of PEO and LiClO₄ was introduced to fabricate the side-gated flexible photodetector. The devices exhibit high performance at low operation voltage. External responsivity is about 3.5 A/W at V_gs = −1 V, V_ds = 1 V with incident power of 60 μW (520 nm). Noteworthy is that the transmittance of the heterostructure at 520 nm is only about 10.5%, the internal responsivity even reaches to about 33.3 A/W, which is higher than most of the flexible photodetectors based on nanomaterials. Besides, the devices display high stability during transient on/off test. We believe the MoS₂/graphene photodetector would be a promising candidate in flexible electronic system. Besides, such hybrid film design is also portable and meaningful for future photodetector investigation.