2,6-Conjugated Bodipy sensitizers for high-performance dye-sensitized solar cells

• Phenothiazine was used as the donor in Bodipy dye based DSSCs.
• Bodipy-furan as the π-conjugated bridge and cyanoacetic acid as electron acceptor are favorable to improve the efficiency.
• The best reported conversion efficiency of 5.31% was achieved with the DSSCs based on UY7.

A series of novel 2,6-conjugated Bodipy metal-free organic dyes (UY5–8) with phenothiazine (PTZ) moiety as electron donor for the dye-sensitized solar cells (DSSCs) have been designed and synthesized. The optical, electrochemical properties and photovoltaic performances are extensively investigated. The structure–property relationship shows that the introduction of various auxiliary conjugated spacers and anchoring groups are favorable to changing the efficiency of DSSCs. Among these dyes, UY7 comprised of furan with lower resonance energy as linker and cyanoacetic acid unit as electron acceptor possesses a flatter structure and longer electron recombination lifetime. Hence, a DSSCs using UY7 showing best photovoltaic performance with a short-circuit photocurrent density (Jsc) of 13.64 mA cm−2, an open-circuit photovoltage (Voc) of 590 mV and a fill factor (ff) of 0.66, corresponding to an overall conversion efficiency (η) of 5.31% under 100 mW cm−2 simulated AM 1.5 G solar irradiation. This is the best reported result in the solar cell with a Bodipy dye as photosensitizer.

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