Effect of electron-withdrawing groups in conjugated bridges: molecular engineering of organic sensitizers for dye-sensitized solar cells

Four organic sensitizers containing quinoxaline or benzoxadiazole as an auxiliary electron acceptor in conjugated bridge were synthesized and utilized for dye-sensitized solar cells (DSSCs). It was found that the incorporation of different electron-withdrawing moieties can affect the absorption spectra, electronic properties, the interfacial interactions and then the overall conversion efficiencies significantly. Therefore, the appropriate selection of the auxiliary acceptor was important to optimize the photovoltaic performance of solar cells. Among these sensitizers, LI-44 based solar cell showed the best photovoltaic performance: a shortcircuit photocurrent density (J sc) of 13.90 mA/cm2, an open-circuit photovoltage (V oc) of 0.66 V, and a fill factor (FF) of 0.66, corresponding to an overall conversion efficiency of 6.10% under standard global AM 1.5 solar light conditions.