Studies on photoelectrode optimization for energy efficiencyenhancement in nanostructured Zinc Oxide Dye-Sensitized solar cells | |
| Author | Pichanan Teesetsopon |
| Call Number | AIT Diss. no.ET-12-03 |
| Subject(s) | Nanostructures Energy efficiency Photoelectrode Optimization |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Energy |
| Publisher | Asian Institute of Technology |
| Abstract | A Dye-sensitized solar cell (DSSC) is a photoelectrochemical cell consisting mainly of photoelectrode, dye and counter electrode that are immersed in a redox electrolyte. Though the highest efficiency of DSSC was obtained from nanoparticulate titania (TiO2) photoelectrodes, zinc oxide (ZnO) shows potential advantages in electron transport due to its 2-3 orders of magnitude higher electron mobility than anatase TiO2. Moreover, a variety of nanostructured ZnO provide a good opportunity for improvementof ZnO based DSSC efficiency. However, very little knowledge exists regarding the photoelectrode interface effects on ZnO-DSSC’s performance. Therefore, in this work, the photoelectrode interface optimization by thermal treatment, external reverse biasing and semiconductor-semiconductor contact on ZnO-DSSC performance were studied.The charge transfer through individual interface in DSSC cell was investigated via electrochemical impedance analysis (EIS). Through modeling of experimental data, each internal interface characteristic was determined in terms of resistance and capacitance existing at the particular interface. The model was used to examinethe effectoftypical photoelectrode treatment through annealing at moderate temperatureson the photoelectrode properties and the internal electrical characteristics of DSSC. By comparing the morphology of the electrode surfaces, dye adsorption and current-voltage characteristics,it was demonstrated that annealingin the air can improve DSSC efficiencydue to the enhancement ofcharge collection, contributed by better ZnOcrystallinity and reduction of interfacial charge transfer resistance at the ZnO/dye/electrolyte interface.The optimum annealing temperature was found at 400°C.Moreover, the electron recombination between transparent conducting oxide substrate and the electrolyte was also revealed for the first timein this work.Interfacial characteristics of ZnO-DSSC under various reverse biasing conditions were also determined in this study. The revere biasing of solar cell normally occurs when the cell is under shade and it was found that fill factor and cell efficiency increased, influenced by the increment of internal interface resistances. This leads to lower charge recombination through all internal interfaces in the cell and so, higher conversion efficiencies could be achieved.The photoelectrode interface properties also depend on the type of semiconductor contact. The comparison between homojunction and heterojunction semiconductor photoelectrode on ZnO-DSSC performance was investigated. The homojunction photoelectrode was prepared based on the optimized fluorine doped zinc oxide substrate (FZO) fabricated by Pyrosol technique withzinc oxide nanoparticles. The results were compared with the heterojunction photoelectrode based on commercial fluorine doped tin oxide substrate (FTO). The potential enhancement of ZnO-DSSC performance was observed for homojunction photoelectrode due to the reduction of charge recombination at photoelectrode substrate-semiconductor interface. |
| Year | 2012 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Kumar, Sivanappan ;Dutta, Joydeep (Co-Chairperson) |
| Examination Committee(s) | Weerakorn Ongsakul |
| Scholarship Donor(s) | National Science and Technology DevelopmentAgency(NSTDA), Thailand |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2012 |