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Improvement in performances of dye-sensitized solar cell based on nanostructured rutile-phased Ti02

Ahmad, Mohd Khairul (2012) Improvement in performances of dye-sensitized solar cell based on nanostructured rutile-phased Ti02. PhD thesis, Shizuoka University.


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Renewable energy has been extensively studied nowadays by many researchers around the world. Among this renewable energy, there is solar cell which is one of the promising candidates to overcome the energy crisis in the future. With low cost production and simple fabrication of Dye-sensitized solar cell (DSC), DSC is one of the best solar cell which could overcome the energy problem in the future. Anatase-phased Ti02 film is the conventional material for photoelectrode semiconductor layer of the DSC, even though rutile-phased Ti02 gives same characteristics such as band gap property. It may be due to the preparation condition for the rutile phase, which needs higher temperature than 900 OC for preparation. The rutile-phased Ti02 has good electron transportation compared to the anatase phase. Because of this, the rutile-phased Ti02 has been applied to some electronic devices. Nanostructures play main roles in electron transportation in any electronic devices. By preparing the rutile-phased Ti02 and applying nanostructures in the fabrication, DSC performances should be improved. The rutile-phased Ti02, therefore, is also strong candidate for high performance DSCs. In the present study, DSCs based on the rutile-phased Ti02 have been successfully prepared and their performances have been improved by applying two kinds of nanostructures; aligned rutile-phased Ti02 nanorods and rutile-phased TiOz nanoflowers. Both nanostructures were prepared using hydrothermal method at 150 OC for different reaction times. The nanostructures were grown directly on a fluorine doped tin oxide glass (FTO coated glass). As for the growth mechanism, the aligned rutile-phased Ti02 nanorods were firstly grown on the FTO coated glass. Then, through chemical reaction and pressure inside an autoclave, the rutile-phased TiOa nanoflowers were synthesized and deposited on top of the aligned nanorods. Mixture of titanium butoxide, hydrochloric acid, cetyltrimethylammonium bromide (CTAB) and deionized water was prepared and put into the 300 ml autoclave made by Teflon. The FTO plates were put in horizontally with FTO surface facing upwards. After the hydrothermal process, the plates were rinsed with deionzed water and annealed at 450 "C for 30 min. Field emission scanning electron microscopy (FE-SEM) was carried out to observe a surface morphology and a thickness of the prepared rutile-phased Ti02 films. X-ray diffractions (XRD) characterization was taken to examine and determine the Ti02 crystalline phases in prepared films. Solar simulator was used to measure the performances of Dye-sensitized solar cell based on the rutile-phased Ti02. For the dye adsorption property, UV-Vis-NIR spectrophotometer measure an amount of dye adsorption in the film. Electrochemical Impedance Spectroscopy (EIS) was also used to determine a conductivity of the DSCs. In early stage of the study, influence of TBOT concentration on the surface morphology, structural properties and solar cell efficiency were investigated for the rutile-phased Ti02 films and the DSCs based on the films. The highest energy conversion efficiency, 0.4 % was achieved using different solution concentration for the preparation under the solar light illumination 100 r n ~ c r n(-1~.5 AM). Low dye adsorption in the film was the reason for low energy conversion efficiency. By growing the rutile-phased Ti02 nanoflowers on top of the aligned Ti02 nanorods, the dye adsorption is increased. This is due to an increase in surface area of Ti02 layer for dye to adsorb. Cetyltrimethylarnrnonium bromide (CTAB) is introduced to control and enhance the growth of rutile-phased Ti02 nanoflowers. As a result, the best efficiency of 3.11 % is obtained and the improvement is mainly attributed to an introduction of Ti02 nanoflowers for more dye adsorption. Energy conversion efficiency as high as 4.27 % is achieved through some improvement on the DSC based on rutile-phased Ti02 layer. Two steps of hydrothermal process are conducted. First step is to prepare only the aligned rutile-phased Ti02 nanorods. At this step, very dense and aligned nanorods are obtained with 3 pm in length. In the second step, the rutile-phased TiOz nanoflowers are synthesized. By preparing new solution with some modification, a large amount of Ti02 nanoflowers with smaller sizes are obtained. The thickness is about 15 pm. Energy conversion efficiency of 4.27 % for nanostructured rutile-phased Ti02 based DSC is the highest record nowadays.

Item Type: Thesis (PhD)
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK1001-1841 Production of electric energy or power. Powerplants. Central stations
Depositing User: Normajihan Abd. Rahman
Date Deposited: 24 Dec 2013 08:16
Last Modified: 24 Dec 2013 08:16
URI: http://eprints.uthm.edu.my/id/eprint/4667
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