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
Menzel, J.P.; Kloppenburg, M.; Belić, J.; Groot, H.J.M. de; Visscher, L.; Buda, F. 2021
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
