Three novel phenothiazine dyes (JY31-33) featured oligothiophene pi-bridge have been designed, synthesized and applied as photosensitizers for highly efficient dye-sensitized solar cells (DSSCs). The introduction of alkyl chains on oligothiophene pi-bridge is found to significantly improve the open-circuit voltage of the resultant device. Phenothiazine bearing a 4-butoxyphenyl group as the secondary donor exhibits a stronger electron-donating ability and a positive acceleration on the short-circuit current density and open-circuit voltage. The dye JY33 containing a secondary donor and two alkyl chains finally gives a high efficiency of 7.48% under the 100 mW cm(-2) simulated AM1.5 sunlight, with a short-circuit photocurrent density (J(sc)) of 17.18 mA cm(-2), an open-circuit photovoltage (V-oc) of 742 mV and a fill factor (FF) of 0.59. (C) 2016 Elsevier B.V. All rights reserved.