Abstract
The present work aims at a better and deeper insight into the forces that govern the intramolecular charge transfer (ICT) and photo injection processes in dyes for dye sensitized solar cells (DSSC). The geometry, electronic structure, electron density distribution, and absorption spectra, for a selected donor-pi-acceptor (D-pi-A) dye for DSSC were computed and analyzed at a high level of DFT theory. The coplanar geometry of the studied dye (D1) indicates a strong conjugation which facilitates ICT. NBO analyses reveal that this ICT amounts to 0.8e, which is localized on the acceptor and anchoring groups resulting in a marked total delocalization interaction energy. The origin of this stabilization is two-fold; first the pi-charge transfer (CT) interaction from donor to acceptor orbitals and the hyperconjugative interactions involving Rydberg states. The effect of fluorine substituents, in the pi-spacer, on the quantum effciency of DSSCs was investigated. Gibb's free energy values, redox potentials, excited state life time, non-linear optical properties (NLO) and driving forces for D1 and its fluorinated derivatives were computed.