Molecular modeling and simulation for the design of dye sensitizers with mono- and di-substituted donor moieties

In the present work, eight donor–bridge–acceptor (D-b-A) moieties with one- and two-electron donor species with different electron acceptor anchoring groups were modeled using density functional theory. A thiophene molecular bridge was used to separate the electron donor moiety from the electron acceptor anchoring group. After the ground-state geometry optimization of these molecular species with a density functional theory-based method, time-dependent density functional theory was employed to investigate the optoelectronic properties. To comprehensively analyze the performance of these modeled dye sensitizers, the absorption wavelength, light-harvesting efficiency, HOMO energy, LUMO energy, open-circuit photovoltage, short-circuit photocurrent density, energy of intramolecular charge transfer, and electron injection efficiency were computed. Based on the computation of these optoelectronic parameters, the performance of mono- and di-substituted D-b-A sensitizers with different electron acceptor anchoring groups was compared. The present investigation indicates that the di-substituted donor moiety may enhance light-harvesting efficiency, short-circuit photocurrent density, and open-circuit photovoltage, resulting in better light-to-power conversion efficiency in dye-sensitized solar cells.