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

Abstract

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.