Three new metal-free organic sensitizers containing 11,12-bis(hexyloxy) dibenzo[a,c]phenazine (BPz) units were synthesized and used for dye-sensitized solar cells (DSSCs). The broad absorption spectra indicate that the light harvesting abilities were enhanced by the introduction of the BPz unit in the p-conjugated space, which can also cause an anti-aggregation effect and the suppression of charge recombination. Among these sensitizers, LI-39 showed the best photovoltaic performance: a shortcircuit photocurrent density (Jsc) of 14.40 mA cm-2, an open-circuit photovoltage (Voc) of 0.74 V, and a fill factor (ff) of 0.67, corresponding to an overall conversion efficiency of 7.18% under standard global AM 1.5 solar light conditions. The result shows that the organic sensitizers based on this bulky fused aromatic rings as well as the auxiliary acceptor are the promising candidates for improvement of the performance of DSSCs.
