A Promising Candidate with D-A-A-A architecture as an efficient sensitizer for dye-densitized solar cells

A series of metal-free organic dyes with electron-rich (D) and electron-deficient units (A) as π linkers have been studied theoretically by means of density functional theory (DFT) and time-dependent DFT calculations to explore the effects of π 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 (λ_max = 511 nm), the charge-transfer characteristics (D/Δq/t is 5.49 Å/0.818 e^-/ 4.41 Å), the driving force for charge-carrier injection (ΔG_inject= 1.35 eV)/dye regeneration (ΔG_regen = 0.27 eV), and the lifetime of the first excited state (τ = 3.1 ns). It is thus proposed to be a promising candidate in dye-sensitized solar cell applications.