Highly efficient light-harvesting boradiazaindacene sensitizers for dye-sensitized solar cells featuring phenothiazine donor antenna.

A series of novel 2,6-disubstituted boradiazaindacene (BODIPY) metal-free organic dyes (UY1-4) with phenothiazine (PTZ) moiety as electron donor for the dye-sensitized solar cells (DSSCs) have been designed and synthesized. Their photophysical, electrochemical and photovoltaic properties are extensively investigated. The structure-property relationship shows that the introduction of double donor-acceptor (D-A) branch and BODIPY-thiophene as the π-conjugated bridge is favorable to improve the efficiency of DSSCs. Among these dyes, UY4 comprised of double D-A branch with PTZ units as electron donor, a BODIPY-thiophene unit as bridge and 2-cyanoacrylic acid unit as electron acceptor possesses a stronger donating ability and longer absorption band. Hence, a DSSCs using UY4 showing best photovoltaic performance with a short-circuit photocurrent density (Jsc) of 12.16 mA cm-2, an open-circuit photovoltage (Voc) of 0.59 V and a fill factor (ff) of 0.68, corresponding to an overall conversion efficiency (η) of 4.89% under AM 1.5 irradiation (100 mW cm-2). This is the best reported result in the solar cell with a BODIPY dye as photosensitizer. [ABSTRACT FROM AUTHOR]