D-A-π-A Motif Quinoxaline-Based Sensitizers with High Molar Extinction Coefficient for Quasi-Solid-State Dye-Sensitized Solar Cells

To meet the requirement of high molar extinction coefficient, broad absorption spectrum, and photo/thermal stability for sensitizers of quasi-solid-state dye-sensitized solar cells (Qs-DSSCs) with reduced film thickness, a novel D-A-π-A configuration organic sensitizer IQ22 was specifically designed, in which the conjugation bridge of cyclopentadithiophene (CPDT) unit was incorporated to widen the light response and enhance molar coefficients for increasing the short-circuit current density (J_SC), and the octane chain on CPDT was targeted for suppressing the charge recombination and improving the open-circuit voltage (V_OC). As a result, the Qs-DSSC based on IQ22 exhibits very promising conversion efficiency as high as 8.76%, with a J_SC of 18.19 mA cm^-2, a V_OC of 715 mV, and a fill factor (FF) of 0.67 under AM 1.5 illumination (100 mW cm^-2), standing out in the Qs-DSSCs utilizing metal-free organic sensitizers.