Effects of meta or para connected organic dyes for dye-sensitized solar cell

Two novel phenothiazine-based organic dyes have been designed and synthesized as sensitizers for dye-sensitized solar cell (DSSC). In these dyes, we have employed carbazole as donor, phenothiazine as pi-bridge, and rhodanine acetic acid as acceptor. For comparison, a benzene group has been introduced as the pi-linker between carbazole donor and phenothiazine pi-bridge with meta or para connection mode. Using the dye with the para connected method, the DSSC devices exhibited higher power conversion efficiency of 5.57% than those based on dye with meta-connection mode (4.56%). The improved performance mainly came from better short-circuit photocurrent current. Photophysical, electrochemical, theoretical calculations and electrochemical impedance spectroscopy have been further investigated to disclose corresponding device mechanisms.