Dye sensitized solar cells (DSSCs) have typically been produced usingorganic liquids such as acetonitrile as the electrolyte solvent. In real worldsituations water can permeate into the cell through sealing materials and isalso likely to be introduced during the fabrication process. This is a problemas the introduction of water into cells optimized to use an organic solventtends to be detrimental to cell performance. In this work DSSCs which areoptimized to use water as the main electrolyte solvent are produced andcharacterized. Optimization of aqueous DSSCs resulted in cells withefficiencies up to 3.5% being produced.In terms of characterization, it is generally seen in this work that aqueousDSSCs produce a lower photocurrent but similar photovoltage compared toDSSCs made using acetonitrile and reasons for this are examined in detail.The decreased ability of the aqueous electrolyte to wet the nanoporous TiO2compared to an acetonitrile electrolyte is found to be a key difficulty andseveral possible solutions to this problem are examined. By measuring thephotocurrent output of aqueous cells as a function of xy position it can beseen 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 andmay also decrease the photocurrent. It is found that there is little differencebetween the two types of cells in terms of the conduction band position andthe 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 bepossible to change the TiO2 conduction band position in the DSSC. This hasa significant effect on the open circuit voltage and short circuit current of thecell, though the pH range available is limited by the fact that dye desorbs athigh pH values.
|Date of Award||31 Oct 2013|
|Supervisor||Petra Cameron (Supervisor) & Laurie Peter (Supervisor)|
- aqueous dye sensitized solar cells
- water based dye sensitized solar cells
- photocurrent mapping
- mesoporous titanium dioxide wetting
- infra red electron density measurement