Taking control of charge transfer : strategic design for solar cells

The thesis is focused on the investigation of the electron transfer mechanisms leading to solar fuel production and to the identification of engineering principles that can be used to design materials able to improve charge separation. Molecular systems composed of three or more subunits arranged in a Donor-Antenna-Acceptor design are required to achieve efficient photoinduced charge separation. It is shown how structural changes in the systems design can be used to systematically optimize the energy gradients and electronic coupling between the molecular subunits, necessary to achieve controlled unidirectional charge transfer. To gain insight into the mechanisms governing the charge transfer processes within a molecular system, the process of photoinduced heterogeneous electron injection is investigated through nonadiabatic dynamics simulations. Coherent electron-nuclear vibrational effects are found to drive the electron transfer process by promoting the coherent superposition of the exciton and the charge transfer quantum state. A photoanode for solar water splitting comprising the functions of light-harvesting, charge separation and catalysis is also investigated. It is observed that, following a fast heterogeneous electron injection, the system catalytic activity is driven by a proton-coupled electron transfer mechanism in which the role of the solvent is crucial.UBL - phd migration 201