A Promising Candidate with D-A-A-A Architecture as an Efficient Sensitizer for Dye-Sensitized Solar Cells

A series of metal-free organic dyes with electron-rich (D) and electron-deficient units (A) as linkers have been studied theoretically by means of density functional theory (DFT) and time-dependent DFT calculations to explore the effects of spacers on the optical and electronic properties of triphenylamine dyes. The results show that Dye1 with a structure of D-A-A-A is superior to the typical C218 dye in various key aspects, including the maximum absorption ((max)=511 nm), the charge-transfer characteristics (D/q/t is 5.49 angstrom/0.818 e(-)/4.41 angstrom), the driving force for charge-carrier injection (G(inject)=1.35 eV)/dye regeneration (G(regen)=0.27 eV), and the lifetime of the first excited state (=3.1 ns). It is thus proposed to be a promising candidate in dye-sensitized solar cell applications.