Dye-Sensitized Photoelectrochemical Cells are promising devices in solar energy conversion. However, several limitations still have to be addressed, such as the major loss pathway through charge... Show moreDye-Sensitized Photoelectrochemical Cells are promising devices in solar energy conversion. However, several limitations still have to be addressed, such as the major loss pathway through charge recombination at the dye-semiconductor interface. Charge separating dyes constructed as push-pull systems can increase the spatial separation of electron and hole, decreasing the recombination rate. Here, we in silico investigate a family of dyes, consisting of polyphenylamine donors, fluorene bridges and perylene monoimide acceptors using a combination of semi-empirical nuclear dynamics and a quantum propagation of photoexcited electron and hole. To optimize the charge separation, several molecular design strategies are investigated, including modifying the donor molecule, increasing the π-bridge length and decoupling the molecular components through steric effects. It is found that the combination of a triphenylamine donor, using an extended 2-fluorene π-bridge and decoupling the different components by steric hindrance from side groups results in a dye with significantly improved charge separation properties in comparison to the original supramolecular complex. Show less
With increasing carbon dioxide levels in the atmosphere and their detrimental effect on the global climate, modern society needs to push for more renewable energy sources. Storing widely accessible... Show moreWith increasing carbon dioxide levels in the atmosphere and their detrimental effect on the global climate, modern society needs to push for more renewable energy sources. Storing widely accessible and abundant solar energy in chemical bonds in the form of molecular fuel via artificial photosynthesis can support this endeavour. Dye-sensitized Photoelectrochemical Cells are promising candidates for Solar-to-fuel conversion; however, their efficiency is still lacking and needs further improvement. Computational Simulations can provide insight in fundamental mechanisms and guide the search for suitable molecular components and interfaces to improve the performance of such devices. In this thesis, a wide range of computational tools are applied to investigate the photoinduced processes and catalytic intermediates involved in dye-sensitized photoanodes for water oxidation. Through combination of semi-empirical methods with DFT and quantum-classical approaches, large scale molecular simulations of extended photoanode systems including electrode, dye and water oxidation catalyst become feasible. The insights gained from these fundamental processes are used to evaluate and optimize molecular components in silico. Show less
Electron-nuclear (vibronic) coupling has emerged as an important factor in determining the efficiency of energy transfer and charge separation in natural and artificial photosynthetic systems. Here... Show moreElectron-nuclear (vibronic) coupling has emerged as an important factor in determining the efficiency of energy transfer and charge separation in natural and artificial photosynthetic systems. Here we investigate the photoinduced charge-transfer process in a hydrogen-bonded donor-acceptor molecular complex. By using real-time quantum-classical simulations based on time-dependent Kohn-Sham equations, we follow in detail the relaxation from the Franck-Condon point to the region of strong nonadiabatic coupling where electron transfer occurs. We elucidate how the charge transfer is coupled to specific vibrational modes and how it is affected by isotope substitution. The importance of resonance in nuclear and electron dynamics and the role of dynamic symmetry breaking are emphasized. Using the dipole moment as a descriptive parameter, exchange of angular momentum between nuclear and electronic subsystems in an electron-nuclear resonant process is inferred. The performed simulations support a nonadiabatic conversion via adiabatic passage process that was recently put forward. These results are relevant in deriving rational design principles for solar-to-fuel conversion devices. Show less
