Theoretical characterization of highly efficient porphyrazin dye sensitized solar cells

Density functional theory (DFT) and time-dependent DFT (TD-DFT) methodologies have been applied in an attempt to improve the performance of the dye YD2-o-C8 which is characterized by 11.9-12.7% efficiencies. We aimed at narrowing the band gap of YD2-o-C8 to extend the light harvesting region to near IR. This was done through replacing the porphyrin macrocycle by the tetraazaporphyrin (porphyrazin) macrocycle, so that the performances of the suggested cells could be improved with Ti38O76, (TiO2) 60, SiC, ZrO2, and GaP semiconductor electrodes. The effects of modifying the central macrocycle on cell performance are confirmed in terms of FMOs, energy gaps, electrode (VB and CB) edges, density of states (DOS), MEPs, dipole moments, IP, EA, reorganization energies, UV-Vis absorption, Phi(LHE), Phi(injection), and life times of the excited states. Replacing porphyrin macrocycle by porphyrazin macrocycle resulted in charge separated states, unidirectional charge transfer, narrower band gaps, increase of DOS nearby Fermi levels, asymmetric polarization, delocalization of the negative charges near the anchoring groups, efficient electron injection, suppressing macrocycle aggregation, active dye regeneration, longer life times of the excited states, and inhibited dye recombination. Co-sensitizers are suggested for near IR sensitization to improve the photo-to-current conversion efficiency. Size ranges: for dyes (0.1-1 nm), and for pore diameters of a dye sensitized mesoporous film of TiO2 (2-50 nm).