Browsing by Author "Wang, J. X."

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    ItemOpen Access
    An efficient non-Lambertian organic light-emitting diode using imprinted submicron-size zinc oxide pillar arrays
    (AIP, 2013) Liu, S. W.; Wang, J. X.; Divayana, Y.; Dev, K.; Tan S.T.; Demir, Hilmi Volkan; Sun, X. W.
    We report phosphorescent organic light-emitting diodes with a substantially improved light outcoupling efficiency and a wider angular distribution through applying a layer of zinc oxide periodic nanopillar arrays by pattern replication in non-wetting templates technique. The devices exhibited the peak emission intensity at an emission angle of 40° compared to 0° for reference device using bare ITO-glass. The best device showed a peak luminance efficiency of 95.5 ± 1.5 cd/A at 0° emission (external quantum efficiency - EQE of 38.5 ± 0.1%, power efficiency of 127 ± 1 lm/W), compared to that of the reference device, which has a peak luminance efficiency of 68.0 ± 1.4 cd/A (EQE of 22.0 ± 0.1%, power efficiency of 72 ± 1 lm/W). © 2013 American Institute of Physics.
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    Free-standing ZnO-CuO composite nanowire array films and their gas sensing properties
    (IOP Publishing, 2011-07-19) Wang, J. X.; Sun, X. W.; Yang, Y.; Kyaw, A. K. K.; Huang, X. Y.; Yin, J. Z.; Wei, J.; Demir, Hilmi Volkan
    A modified hydrothermal method was developed to synthesize ZnO-CuO composite nanostructures. A free-standing film made of ZnO-CuO nanostructures was assembled on the surface of the hydrothermal solution with a smooth surface on one side and a spherical surface on the other side. The structure, growth mechanism and the optical properties of the composite nanostructures were studied. Structural characterizations indicate that the composite nanostructure mainly consisted of two single-crystal phases of CuO and ZnO. The sensitivity for CO gas detection was significantly improved for the composite CuO-ZnO nanostructure film. This method offers a possible route for the fabrication of free-standing nanostructure films of different functional composite oxides.
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    Top-illuminated dye-sensitized solar cells with a room-temperature-processed ZnO photoanode on metal substrates and a Pt-coated Ga-doped ZnO counter electrode
    (IOP Publishing, 2011-01-11) Kyaw, A. K. K.; Sun, X. W.; Zhao, J. L.; Wang, J. X.; Zhao, D. W.; Wei, X. F.; Liu, X. W.; Demir, Hilmi Volkan; Wu, T.
    We report on top-illuminated, fluorine tin oxide/indium tin oxide-free (FTO/ITO-free), dye-sensitized solar cells (DSCs) using room-temperature- processed ZnO layers on metal substrates as the working electrodes and Pt-coated Ga-doped ZnO layers (GZO) as the counter electrodes. These top-illuminated DSCs with GZO render comparable efficiency to those employing commercial FTO counter electrodes. Despite a lower current density, the top-illuminated DSCs result in a higher fill factor than conventional DSCs due to a low ohmic loss at the electrode/semiconductor interface. The effect of metal substrate on the performance of the resulting top-illuminated DSCs is also studied by employing various metals with different work functions. Ti is shown to be a suitable metal to be used as the working electrode in the top-illuminated device architecture owing to its low ohmic loss at the electrode/semiconductor interface, minimum catalytic activity on redox reactions and high resistance to corrosion by liquid electrolytes.