A novel series of metal-free organic photosensitizers based on D-π-A or D-A1-π-A structure motif namely, BD-n, (where n = 1–5) bearing a high hole-transporting benzodithienothiophene as the π-bridge for the first time, carbazole or triarylamine as the electron-donor and benzothiadiazole or quinoxaline as the auxiliary electron-deficient unit was synthesized and investigated for DSSC applications. DSSCs based on these five photosensitizers were also fabricated which exhibited efficiencies ranging from 3.92% to 5.46%. Among these DSSCs, devices based on D-A1-π-A type dye, BD-3 and bidenate dye, BD-5 as a photosensitizer afforded the best efficiencies of 5.34%–5.46%. Our results suggested that an incorporation of a proper auxiliary accepting group (A1) into the D-π-A conjugation system to enhance light harvesting and charge transfer as well as the use of V-shaped di-anchoring strategy to suppress aggregation on the TiO2 surface were found to be useful and effective strategies to enhance the photovoltaic performance of a DSSC. These devices exhibited relatively long electron lifetimes suggesting the slow charge recombination kinetics and thus better DSSC performance. Our findings also suggest that benzodithienothiophene is a promising π-bridge to construct organic photosensitizers for high-efficiency DSSCs.
Scopus Subject Areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Materials Chemistry
- Electrical and Electronic Engineering
- Organic photosensitizers