Photodetectors based on a hybrid structure of graphene sensitized with lead selenide (PbSe) colloidal quantum dots (QDs) effective in the near-infrared (NIR) region with high responsivity were investigated. Colloidal PbSe nanocrystals were synthesized via a hot injection method. The bandgap of the synthesized nanocrystals was determined to be 0.68 eV by measuring their optical absorbance spectrum. Photodetectors based on PbSe QDs were investigated to examine their functionality. These devices were characterized by measuring the current-voltage curves in the dark and light and the spectral response spectrum. A photodetector was fabricated using a multilayer mechanically exfoliated graphene on a Si/SiO2 substrate with a PbSe QDs layer on top. A responsivity and detectivity of 1265A/W and 3.4 *1010cm.Hz0.5/W respectively were calculated based on current-voltage measurements.

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A few layers graphene-based phototransistor was fabricated and investigated. Graphene layers were mechanically exfoliated and transferred into a p-doped Si/SiO2 substrate to fabricate a graphene field effect transistor. Gold electrodes were deposited to create a drain and source to the graphene and a back contact gate to the p-doped silicon. The device performance was examined by measuring the current-voltage characteristics in the dark and under illumination. At zero drain voltage bias and room temperature, the device operated and achieved high responsivity and detectivity on the order of 2.7 × 104 A W−1 and 5 × 1012 cm·Hz0.5/W, respectively. A ratio of 29 between the photocurrent and the dark current was achieved. The device shows an excellent tunable photoresponse as a function of the applied back-gate voltage, which indicates the domination of a photogating effect produced by the Si/SiO2 substrate.