Overcoming the Mass Transport Limitations of Dye-Sensitised Solar Cells : Towards highly efficient and robust alternative redox mediator electrolyte DSSCs

Dye-sensitised solar cells (DSSCs) have been subject to decadelong research interest, and may have some potential niche market applications. Recently, major advances in power conversion efficiencies have been achieved following the transition to cobalt polypyridine based redox mediators. Unfortunately, these champion devices remained unfeasible for commercialisation due to heavy reliance on flammable volatile acetonitrile electrolytes. Overcoming this issue has been a challenge due to increased mass transport limitations, which are especially exacerbated in more stable albeit viscous electrolytes. The overall aim of this thesis is to better understand the contributing factors to mass transport, and then to develop practical solutions to overcome these limitations. In particular, specific mass transport limitations pertaining to the bulk electrolyte medium and electrolyte-infiltrated TiO2 medium, are investigated. The effect of non-uniform photogeneration profile across the photoanode is explored with respect to mass transport using photocurrent transient techniques. Practical devices engineering for optimal mass transport is explored in terms of minimising the inter-electrode spacing and maximising light absorption towards the electrolyte-electrode side. Alternative devices based on more practical electrolytes with higher viscosity are optimised for high efficiency