published_or_final_version / Physics / Doctoral / Doctor of Philosophy

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24975号 / エネ博第471号 / 新制||エネ||88(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー変換科学専攻 / (主査)教授 長﨑 百伸, 教授 田中 仁, 教授 稲垣 滋 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

Dye sensitized solar cells (DSSCs) have typically been produced using organic liquids such as acetonitrile as the electrolyte solvent. In real world situations water can permeate into the cell through sealing materials and is also likely to be introduced during the fabrication process. This is a problem as the introduction of water into cells optimized to use an organic solvent tends to be detrimental to cell performance. In this work DSSCs which are optimized to use water as the main electrolyte solvent are produced and characterized. Optimization of aqueous DSSCs resulted in cells with efficiencies up to 3.5% being produced. In terms of characterization, it is generally seen in this work that aqueous DSSCs produce a lower photocurrent but similar photovoltage compared to DSSCs made using acetonitrile and reasons for this are examined in detail. The decreased ability of the aqueous electrolyte to wet the nanoporous TiO2 compared to an acetonitrile electrolyte is found to be a key difficulty and several possible solutions to this problem are examined. By measuring the photocurrent output of aqueous cells as a function of xy position it can be seen that there is some dye dissolution near to the electrolyte filling holes. This is thought to be linked to pH and the effect of 4-tert-butylpyridine and may also decrease the photocurrent. It is found that there is little difference between the two types of cells in terms of the conduction band position and the reaction of electrons in the semiconductor with triiodide in the electrolyte, explaining the similarity in photovoltage. By altering the pH of the electrolyte in an aqueous cell it is found to be possible to change the TiO2 conduction band position in the DSSC. This has a significant effect on the open circuit voltage and short circuit current of the cell, though the pH range available is limited by the fact that dye desorbs at high pH values.