A new self-powered broadband photodetector was fabricated by coating an n-silicon nanowire (n-Si NW) array with a layer of p-cupric oxide (CuO) nanoflakes through a new simple solution synthesis method. The p-n heterojunction shows excellent rectification characteristics in the dark and distinctive photovoltaic behavior under broadband light illumination. The photoresponse of the detector at zero bias voltage shows that this self-powered photodetector is highly sensitive to visible and near-infrared light illuminations, with excellent stability and reproducibility. Ultrafast response rise and recovery times of 60 and 80 μs, respectively, are shown by the CuO based nanophotodetector. In addition, the broadband photodetector can also provide a rapid binary response, with current changing from positive to negative upon illumination under a small bias. The binary response arises from the photovoltaic behavior and the low turn-on voltage of the CuO/Si NW device. These properties make the CuO/Si NW broadband photodetector suitable for applications that require high response speeds and self-sufficient functionality.

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High-performance broadband photodetectors have recently attracted signifi cant interest [1][2][3][4][5] because of their importance to a variety of applications, including imaging, remote sensing, environmental monitoring, astronomical detection, photometers and analytical applications. Graphene is a promising material for broadband photodetection applications because of its ability to absorb incident light over a wide wavelength range, from at least the visible (VIS) spectrum to the infrared. [ 6 ] Recent works have demonstrated that zerobandgap single-or few-layer graphene-based photodetectors based on a fi eld-effect transistor (FET) structure could operate in the near-infrared (NIR) and VIS parts of the electromagnetic spectrum. [ 7,8 ] However, no working spectra have been demonstrated for these zero-bandgap graphene photodetectors in longer wavelength ranges. Theoretical calculations indicated that opening and varying the bandgap of