Oxygen-incorporated and layer-by-layer stacked WS nanosheets for broadband, self-driven and fast-response photodetection.

Two-dimensional (2D) layered WS2 nanosheets have been regarded as exciting and emerging candidate materials in constructing high performance photodetectors. In this work, we develop a facile solvothermal method to synthesize oxygen-doped WS2 microrods composed of layer-by-layer stacked nanosheets. The WS2 microrods exhibit an obvious bandgap of 1.2 eV, together with a broad near-infrared (NIR) absorption after 1100 nm. The unique absorption can be ascribed to the oxygen-incorporation-induced localized surface plasmon resonance (LSPR) effect. A hybrid WS2/Si heterojunction, which allows the combination of the WS2 microrods with a mature silicon platform, is then constructed by a facile spin-coating fabrication process to investigate the photoresponse properties. Benefitting from the remarkable photovoltaic performance, the WS2/Si heterojunction acts as a self-driven photodetector with outstanding characteristics. The photodetector exhibits a decent responsivity (R) of 1.5 A W-1, a high specific detectivity (D*) of ∼2 × 1012 Jones, fast response speeds with rise/fall times of 2.0/7.2 μs, and good ambient stability (2 months) at zero bias. Notably, the photodetector is still sensitive at a broadband wavelength in the NIR region (1100-2000 nm). The broadband response is attributed to the LSPR effect of the oxygen-incorporated WS2. These results suggest great potential of the oxygen-incorporated WS2/Si heterojunctions in NIR light detection.