Novel D-A-π-A organic dyes based on 3-dimensional triarylamine and benzothiadiazole derivatives for high-performance dye-sensitized solar cells

Organic dyes with a 3-dimensional (3D) structure is helpful for retarding dyes aggregation and charge recombination as well as improving the power conversion efficiency (PCE) of dye-sensitized solar cells (DSSCs). In this contribution, a novel 3D triarylamine derivative (IDTTPA) featuring an inden-othiophenene unit has been designed, synthesized, and applied to develop a 3D organic dyes. Two novel D-A-pi-A organic dyes (CD1 and CD2) based on IDTTPA as the electron donors, 2,1,3-benzothiadiazole derivatives as the auxiliary acceptors, and formic acid as the anchoring groups have been successfully synthesized and applied in DSSCs. The effects of the fluoro substitute groups on the photophysical, electrochemical, and photovoltaic properties are investigated. The results indicate that the fluoro containing dye CD2 exhibits higher molar extinction coefficient, stronger light-capturing ability, and better photovoltaic performance than those of CD1 dye without fluoro substitute. Investigation of the DSSCs performance shows that CD2-based DSSCs exhibit a high PCE value of 7.91%, higher than that of CD1-based DSSCs (6.29%), even higher than that of the reference DSSCs based on N719 (7.49%). This works has demonstrated that this kind of 3D unit (IDTTPA) is a strong and promising electron donor unit to develop high efficiency metal-free organic dyes. (C) 2016 Elsevier B.V. All rights reserved.