Graphene-WS2 Nanotube Film for Photodetection

We present a fully water-processed, lithography-free photodetector that combines few-layer graphene (Gr) flakes with multi-walled tungsten disulfide (WS2) nanotubes in a single ecofriendly dispersion. Two sequential drop-casts of Gr/WS2 solution onto 100 μm polyethylene-terephthalate form a percolating hybrid film. Under illumination the devices exhibit linear photoconductive behaviour; the photocurrent rises from 2.0 nA at 1 V to 13.4 nA at 3 V, yielding a bias tunable responsivity of 0.05-0.22 μA W-1 and fast response times of about 200 ms. The results are consistent with a distributed, network-level mechanism in which photocarriers generated in WS2 nanotubes are extracted across numerous Gr/WS2 nanojunctions via the graphene scaffold, yielding a predominantly photoconductive response with minor photogating and bolometric contributions. The low bias operation, mechanical flexibility and absence of toxic solvents indicate that Gr/WS2 nanotube dispersions are a viable route toward roll-to-roll fabrication of large-area, bias-controllable photodetectors for wearable or disposable optoelectronic platforms.