| Summary: | 碩士 === 大葉大學 === 電機工程學系 === 102 === In the present study, a sol-gel NiOx overlayer layer was employed to suppress the dark current of the TiO2 photoanode (electrode a) for the dye-sensitized solar cell (DSSC). The content of NiOx was controlled by the spin-coated layers (1 ~ 4 layers) and the as-prepared electrodes were designated as electrode b ~ e with structures of TiO2/NiOx(1L), TiO2/NiOx(2L), TiO2/NiOx(3L) and TiO2/NiOx(4L), respectively.
SEM micrographs revealed that the profile of NiOx overlayer is not a well-defined thin film, instead, they are evenly distributed onto TiO2 films as nanorod-like bundles. X-ray diffractograms for electrode b ~ e exhibit two distinct diffraction peaks, ascribing to NiO and Ni2O3 phases, respectively whose chemical states are confirmed by the XPS analysis. The onset voltage of the dark current is blue shifted over 100mV by employing electrodes with a NiOx overlayer. Electrochemical impedance analysis confirms that a NiOx overlayer has effectively suppressed the transport of photoelectrons from TiO2 to the electrolyte by the larger impedance values measured at middle frequencies. The amount of dye leached from electrode b was dramatically increased by 47%, compared to that from a bare TiO2 electrode. It is reasoned that the basic NiOx-coated surface favors dye attachment through its carboxylic acid groups. In addition, the morphology of NiOx nanostructures also renders additional surface area for dye attachment. The cell conversion efficiency () was enhanced substantially for electrode d by which the best of 6.64% with Jsc and Voc of 19.48 mAcm-2 and 0.646 V, respectively.
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