Photoanode and counter electrode modification for more efficient dye sensitized solar cells

dc.contributor.authorZheng, Yichen
dc.date.accessioned2014-06-11T16:42:51Z
dc.date.available2014-06-11T16:42:51Z
dc.date.graduationmonthAugust
dc.date.issued2014-06-11
dc.date.published2014
dc.description.abstractWith the increasing consumption of energy and the depletion of fossil fuels, finding an alternative energy source is critical. Solar energy is one of the most promising energy sources and solar cells are the devices that convert solar radiation into electricity. Currently, the most widely used solar cell is based on p-n junction formed with crystalline silicon materials. While showing high efficiency, the high fabrication cost limits its broad applications. Dye sensitized solar cell (DSSC) is a promising low-cost alternative to the Si solar cell, but its efficiency is much lower. Improvements in materials and interfaces are needed to increase the DSSC efficiency while maintain the low cost. In this thesis, three projects were investigated to optimize the DSSC efficiency and reduce the cost. The first project is to optimize the TiO[subscript]2 barrier layers on Fluorine-doped Tin Dioxide (FTO) surface. Two preparation methods, i.e. TiCl[subscript]4 solution treatment and thermal oxidation of sputtered Ti metal films, were employed and systematically studied in order to minimize electron-hole recombination and electron backflow during photovoltaic processes of DSSCs. TiCl[subscript]4 solution treatment method was found to create a porous TiO[subscript]2 barrier layer. Ti sputtering method created a very compact TiO[subscript]2 blocking layer. Two methods showed different characteristics and may be used for different DSSC studies. The second project is to reduce the DSSC cost while maintaining the efficiency by replacing the expensive Pt counter electrode with a novel vertically aligned carbon nanofiber (VACNF) electrode. A large specific electrode surface area (~125 cm[superscript]2 over 1 cm[superscript]2 geometric area) was obtained by using VACNFs. The relatively high surface area, good electric conductivity and the large numbers of active graphitic edges existed in cone-like microstructure of VACNFs were employed to improve redox reaction rate of I[subscript]3[superscript]-/I[superscript]- mediators in the electrolyte. Faster electron transfer and good catalytic activities were obtained with such counter electrodes. The third project is to develop a metal organic chemical vapor deposition (MOCVD) method to coat TiO[subscript]2 shells on VACNF arrays as potential photoanodes in the DSSC system in order to improve the electron transfer. Fabrication processes were demonstrated and preliminary materials were characterized with scanning electron microscopy and transmission electron microscopy. MOCVD at 300 mTorr vapor pressure at 550° C for 120 min was found to be the optimal condition.
dc.description.advisorJun Li
dc.description.degreeMaster of Science
dc.description.departmentDepartment of Chemistry
dc.description.levelMasters
dc.description.sponsorshipChemistry department
dc.identifier.urihttp://hdl.handle.net/2097/17841
dc.language.isoen_US
dc.publisherKansas State University
dc.rights© the author. This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectDye-sensitized solar cells
dc.subjectPhotovoltaic
dc.subjectPhotoanode
dc.subjectCounter electrode
dc.subjectTiO2
dc.subject.umiChemistry (0485)
dc.subject.umiMaterials Science (0794)
dc.titlePhotoanode and counter electrode modification for more efficient dye sensitized solar cells
dc.typeThesis

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