Abstract
Lightweight, simple and flexible self-powered photodetectors are urgently required for the development and application of advanced optical systems for the future of wearable electronic technology. Here, using a low-temperature reduction process, we report a chemical approach for producing freestanding monolithic reduced graphene oxide papers with different gradients of the carbon/oxygen concentration ratio. We also demonstrate a novel type of freestanding monolithic reduced graphene oxide self-powered photodetector based on a symmetrical metal–semiconductor–metal structure. Upon illumination by a 633-nm continuous wave laser, the lateral photovoltage is observed to vary linfearly with the laser position between two electrodes on the reduced graphene oxide surface. This result may suggest that the lateral photovoltaic effect in the reduced graphene oxide film originates from the built-in electric field by the combination of both the photothermal electric effect and the gradient of the oxygen-to-carbon composition. These results represent substantial progress toward novel, chemically synthesized graphene-based photosensors and suggest one-step integration of graphene-based optoelectronics in the future.
Highlights
A material is problematic due to its increased complexity as well as destroying their original high flexibility and integrity[13,14], excluding polymer composites
The characteristic 2θpeak of thick graphene oxide film (TGOF) appearing at 10.68° corresponds to a d-spacing of approximately 0.83 nm for the AB-stacked graphene oxide (GO), which is consistent with the interlayer spacing of GO sheets reported in the literature, because of the existence of the numerous oxygen functional groups on both sides/edges of the sheets and the water molecules trapped between them[16,17]
The TrGOF showed a distinct, broad peak at approximately 23.9° (FWHM = 1.54°) corresponding to a d-spacing of 0.37 nm, which indicates the removal of oxygen functional groups from GO sheets and the subsequent restoration of the sp[2] carbon network by a hydriodic acid vapor-assisted process
Summary
A material is problematic due to its increased complexity as well as destroying their original high flexibility and integrity[13,14], excluding polymer composites. The “gradient-reduction depth” between the interior and exterior of the GO paper can be used to create different electrical and chemical properties along the direction of gravity Both p-type and n-type interiors of rGO paper are roughly determined by the type of residual functional groups, such as electron-donating (EDG: sp2-bonded hydroxyl, ether and epoxy groups) or electron-withdrawing groups (EWG: carboxyl, carbonyl and sp3-bonded hydroxyl, ether and epoxide groups)[15]. We present the simple design and preparation of a flexible micrometer-thick rGO membrane (∼1.4 μm thick) using hydriodic acid vapor at low temperature. This freestanding rGO membrane is a highly flexible, lightweight and electrically conductive three-dimensional foam with an open porous and interconnected graphene network. The TrGOF was cut by operating scissors into rectangular strips of approximately 6 × 25 mm[2] with an active length of 20 mm
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