SPECTROSCOPIC INVESTIGATIONS OF PHOTOINDUCED ELECTRON TRANSFER PROCESSES AT INTERFACES AND IN SOLUTION

Photoinduced electron transfer is an essential reaction in artificial solar energy conversionapplications. The challenge for decades of research has been to demonstrate a long-lived charge separated state with high energy that in principle can be used for chemical or solar-to-electric energy conversion.[1] For example, the primary energy conversion process in a dye-sensitized solar cell (DSC) is a photoinduced charge separation at the metal oxide-dye interface, making the formation and decay lifetime of the charge separated state an important aspect of these systems.[2, 3] Upon photon absorption, a surface-bound chromophore is promoted to a higher energy excited state, whereby it can undergo forward electron transfer (electron injection) to the conduction band or acceptor states in TiO2. The resultant charge separation consists of the injected electron and the oxidized dye. Following the initial charge separation step, DSCs are reliant upon regeneration of the oxidized dye by a soluble reductant present in the electrolyte. This reaction is often termed dye regeneration and is typically not optimized under operational conditions. However, pre-organized interactions between the immobilized dye and redox-active species in the electrolyte offer a method for enhancing the regeneration reaction in DSCs. Within this dissertation, several synthetic design approaches are introduced, and the corresponding electron dynamics are explored