| Summary: | 碩士 === 國立高雄應用科技大學 === 化學工程與材料工程系博碩士班 === 103 === This study is divided into two parts. The first part is to modify the porous TiO2 photoanode with a compact TiO2 layer by anodic pulse deposition for dye-sensitized solar cells (DSSCs). The TiO2 photoanode could be successfully modified by adjusting sintering temperature, current density, and deposition time. The impact of surface modification on the material properties of TiO2 film and their photovoltaic properties were investigated. The photoanodes modified under different conditions were constructed with a platinum counter electrode to form DSSC. The electrochemical impedance analysis showed that the charge-transfer resistance of DSSC with modified photoanode by a compact TiO2 layer became smaller than that of DSSC without modification. The transmitted light intensity modulation spectroscopy (IMPS/IMVS) analysis revealed that the photoanode after surface modification has better transition time, electron lifetime, electron diffusion length, and electron collection rate. The photoelectron conversion efficiency of DSSC employing the photoanode modified under optimal condition was considerably increased by 18.1% (from 7.18 to 8.48%). The second part is to prepare the nickel hexacyanoferrate (NiHCF) nanoparticles by coprecipitation method and carbonize the NiHCF under argon gas at high temperature for 5 h. After carbonization, the powder was acid-treated with HCl or HNO3 to remove the metal traces such as Ni and Fe. Scanning electron microscope and transmission electron microscope images revealed that after carbonization in 550 and 750C, the cleavage of CN bond on Fe and Ni catalysts led to the formation of the carbon nanospheres and carbon nanotubes, respectively. X-ray diffraction and energy dispersive spectroscopic analysis revealed that the diffraction peak of graphite appeared and the peak of NiFe alloy decreased after the acid treatment. In addition, the specific surface area of carbon nanospheres and nanotubes was significantly increased after acid treatment due to the removal of NiFe cores. Carbon nanotube/sphere films were coated on conductive glass substrate by electrophoretic deposition as the counter electrodes and compared with Pt counter electrode. The cyclic voltammetry indicated that the anodic (3.727 mA cm-2) and cathodic (-3.707 mA cm-2) peak current densities occurred at 0.19 and -0.17 V vs. Pt. The photoelectron conversion efficiency of DSSC employing the carbon counter electrode was significantly increased to 7.40 %. The nanotube counter electrode also showed a stable performance towards I-/I3- redox couple. After 1000 cyclic voltammetry tests, its anodic and cathodic peak current densities remained as high as 97.9 and 97.8 % compared with those at the first cycle.
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