In order to develop efficient phenothiazine organic dyes for dye-sensitized solar cells.(DSSCs), four new phenothiazine organic dyes (W21-24) containing dithieno[3,2-b:2',3'-dlpyrrole (DTP) units have been designed and synthesized. W21-23 contains diverse DTP blocks on the terminal part of the dyes, which allow us to understand the effect of the DTP substituent on the performance organic dyes. Results reveal that the substituent of DTP unit affects the light harvesting capability of dyes as well as interfacial charge transfer and recombination in devices. In addition, electrochemical, photophysical and photovoltaic performance of W23 have been investigated and compared to those of W24, which has a different conjugation order of phenothiazine and DTP unit. W24 sensitized electrode exhibits a better light absorption due to a strong ICT charge transition and high dye loading amount, which contributes to the higher photocurrent of devices. Particularly, W24 displays a significantly decreased charge recombination rates. Thus, W24 shows the best photovoltaic efficiency of 7.7% under the standard global AM 1.5 solar conditions. (C) 2017 Elsevier Ltd. All rights reserved.