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Author: search.filters.author.Pratontep, SirapatSubject: search.filters.subject.Morphology

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    Morphology-controlled seed-assisted hydrothermal ZnO nanowires via critical concentration for nucleation and their photoluminescence properties
    (2015-01-01)
    Kasamechonchung, Panita
    ;
    Horprathum, Mati
    ;
    Boonpavanitchakul, Kanittha
    ;
    Supaka, Nuttapun
    ;
    Prompinit, Panida
    Here we demonstrate the controllability on morphology of hydrothermal ZnO nanowires through the critical concentration for nucleation. When Zn ion concentration is relatively low, the nucleation process preferentially occurs on the (0001) plane, promoting nanowire growth. In contrast, for relatively high Zn ion concentration, the (10-10) plane emerges, suppressing nanowire growth. The occurrence of this nucleation competition on the crystal planes as a function of concentration is caused by differences in the critical nucleation sizes between the (0001) plane and the (1010) plane. Furthermore, we found that the density of ZnO nanowires trend to decrease with increasing the growth time due to the lateral growth effect. Photoluminescence measurement of ZnO nanowires exhibited that the near band emission peak of 380nm decreased with decreasing nanowire diameter while the broad emission peak below band gap appears the opposite trend because of surface to volume ratio effect.
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    Effects of tetramethylene sulfone solvent additives on conductivity of PEDOT:PSS film and performance of polymer photovoltaic cells
    (2013-01-01)
    Keawprajak, Anusit
    ;
    Koetniyom, Wantana
    ;
    Piyakulawat, Phimwipha
    ;
    Jiramitmongkon, Kanpitcha
    ;
    Pratontep, Sirapat
    A solvent additive in PEDOT:PSS solution is one of many methods to improve the conductivity of the poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films. We explore a new type of the solvent additive, namely tetramethylene sulfone (TMS), for the fabrication of the PEDOT:PSS conductive layer in the ITO/PEDOT:PSS/P3HT:PCBM/TiO<inf>x</inf>/Al polymer photovoltaic cells, in comparison to a more common dimethyl sulfoxide (DMSO) solvent additive. At optimal conditions, the TMS additive at 10 wt.% has been found to enhance the conductivity of pristine PEDOT:PSS films from 0.04 S/cm up to approximately 189 S/cm, compared with the highest conductivity for the case of the DMSO additive at 15 wt.% of 117 S/cm. Possible mechanisms of this conductivity enhancement, relating to the polymer conformation and the film morphology, have been investigated by Raman spectroscopy, X-ray diffraction, atomic force microscopy, and transmission electron microscopy. The performance of the polymer photovoltaic cells fabricated with the solvent additives PEDOT:PSS films follows a similar trend to the conductivity of the films as a function of the additive concentration. The additives mainly lead to greater short circuit current density (J<inf>sc</inf>) of the photovoltaic cells. The highest power conversion efficiency (PCE) of 2.24% of the device has been obtained with the 10 wt.% TMS additive of, compared to the PCE of 1.48% for the standard device without solvent additive. © 2012 Elsevier B.V. All rights reserved.