Structural engineering of dipolar organic dyes with an electron-deficient diphenylquinoxaline moiety for efficient dye-sensitized solar cells

A series of new organic dyes containing an electron-deficient diphenylquinoxaline moiety was synthesized and employed as the photosensitizers in dye-sensitized solar cells (DSSCs). The multiple phenyl rings in the peripheral positions of the dye structure provide a hydrophobic barrier to slow down the charge recombination. The photophysical and electrochemical properties of these dyes were investigated in detail. The cell performance and the associated photophysical and electrochemical properties can be easily tuned by the modification of the aromatic fragments within the π spacer. Dye CR204-based DSSC reached the best energy conversion efficiency of 6.49% with an open-circuit voltage of 666 mV, a short-circuit photocurrent density of 14.9 mA cm^-2, and a fill factor of 0.66. The IPCE of CR204-based DSSC covers the light-harvesting to NIR region.