Functionalized graphene quantum dot (GQD) based materials play an important role in the development of high-performance, low-cost, large-area optoelectronic devices. The progress, however, is impeded by the poor understanding of the physical mechanism for GQDs in these devices. In this paper, chlorine doped GQD (Cl-GQD) based photovoltaic photodetectors have been fabricated using a solution process, and it was found that the presence of Cl-GQDs can significantly enhance the performance of the device. The improved performance of Cl-GQD based devices has been investigated by systematically studying the structural, morphological, optical, electrical, electrochemical and photoelectrical properties. The important photovoltaic detectors parameters such as the saturation current densities (J 0 ), barrier heights (F b ), built-in potentials (V bi ), carrier concentrations (N) and depletion layer widths (W d ) have been calculated and discussed by studying the I-V and C-V characteristics under different illuminations. The frequency dependent capacitance and conductance have also been discussed. The results provide guidance for developing high-performance graphene based optoelectronic devices.

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Reduction in dark current using resonant tunneling barriers in quantum dots-in-a-well long wavelength infrared photodetector Appl. Phys. Lett. 93, 131115 (2008); 10.1063/1.2996410Bias and temperature dependence of the escape processes in quantum dots-in-a-well infrared photodetectors Graphene quantum dots (GQDs) are becoming one of the hottest advanced functional materials because of the opening of the bandgap due to quantum confinement effect, which shows unique optical and electrical properties. The chlorine doped GQDs (Cl-GQDs) have been fabricated by chemical exfoliation of HCl treated carbon fibers (CFs), which were prepared from degreasing cotton through an annealing process at 1000 C for 30 min. Raman study shows that both G and 2D peaks of GQDs may be redshifted (softened) by chlorine doping, leading to an n-type doping. The first vertical (Cl)-GQDs based photovoltaic detectors have been demonstrated, both the light absorbing and electron-accepting roles for (Cl)-GQDs in photodetection have been found, resulting in an exceptionally big ratio of photocurrent to dark current as high as $10 5 at room temperature using a 405 nm laser irradiation under the reverse bias voltage. The study expands the application of (Cl)-GQDs to the important optoelectronic detection devices. V C 2014 AIP Publishing LLC.

Ultraviolet (UV) photodetector has attracted extensive interests due to its wide-ranging applications from defense technology to optical communications. The use of wide bandgap metal oxide semiconductor materials is of great interest in the development of UV photodetector due to their unique electronic and optical properties. In this work, deep UV photodetector based on NiO/β-Ga 2 O 3 heterojunction was developed and investigated. The β-Ga 2 O 3 layer was prepared by magnetron sputtering and exhibited selective orientation along the family of (2 01) crystal plane after annealing. The photodetector demonstrated good performance with a high responsivity (R) of 27.43 AW −1 under a 245-nm illumination (27 μWcm −2) and the maximum detectivity (D*) of 3.14 × 10 12 cmHz 1/2 W −1 , which was attributed to the p-NiO/n-β-Ga 2 O 3 heterojunction.