Theoretical design of porphyrazine derivatives as promising sensitizers for dye-sensitized solar cells

Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations have been carried out on the electronic structure and optical properties of a set of heterocycle-fused zinc porphyrazine (ZnPz) derivatives, aiming at screening efficient sensitizers for dye-sensitized solar cells (DSSCs). Our results show that the absorption spectra of the designed dyes shift to longer wavelengths and the light harvesting efficiencies are much higher than isolated ZnPz. Moreover, the designed dyes have larger contributions of the anchoring group to the lowest unoccupied molecular orbitals (LUMOs) compared with the currently best sensitizer YD2-o-C8, indicating enhanced electron injection ability from the sensitizer to the semi-conductor. Furthermore, the designed dyes exhibit good performance in terms of the charge transfer characteristics, the driving force of electron injection and dye regeneration, and the excited-state lifetime. Overall, the designed dyes, especially indigo blue fused ZnPz and acridine fused ZnPz, are revealed to be promising sensitizers for high-efficiency DSSCs.