Molecular engineering of quinoxaline dyes toward more efficient sensitizers for dye-sensitized solar cells

D-A-π-A-featured organic dyes incorporating diphenylquinoxaline unit (such as IQ4) have shown great potential in anti-aggregation and broadening spectral response in the field of dye-sensitized solar cells (DSSCs). The crucial restriction for quinoxaline-based cell to attain higher efficiency is the relatively low photocurrent density (J_SC). In the present work, three novel push-pull dyes only differing in electron donors, have been designed based on the IQ4 backbone, in order to further improve the light-harvesting capability of quinoxaline dyes and to examine the donor influence on dye performance. Theoretical analysis of the factors correlated with the J_SC and open-circuit photovoltage (V_OC) demonstrate that, relative to the parent IQ4 dye, the NIQ4 dye bearing the elegant N-annulated perylene donor shows a good performance in light harvesting, electron injection, and dye regeneration, indicating an increased J_SC potential for the related cell. Furthermore, despite possessing a smaller vertical dipole moment, the improved blocking effect of NIQ4 not only prevents unfavorable self-aggregation, but also effectively inhibits the parasitic back-recombination. Therefore, the NIQ4 is proposed to be a potential dye in DSSC applications.