Synthesis and Characterization of 2D-D-π-A-Type Organic Dyes Bearing Bis(3,6-di-tert-butylcarbazol-9-ylphenyl)aniline as Donor Moiety for Dye-Sensitized Solar Cells

A series of novel 2D-D--A-type organic dyes, namely CCTTnA (n = 13), bearing bis(3,6-di-tert-butylcarbazol-9-ylphenyl)aniline as an electron-donor moiety (2D-D), oligothiophene segments with a number of thiophene units from one to three units as -conjugated spacers (), and cyanoacrylic acid as the electron acceptor (A) were synthesized and characterized as dye sensitizers for dye-sensitized solar cells (DSSCs). These compounds exhibit high thermal and electrochemical stability. Detailed investigations of these dyes reveal that both peripheral carbazole donors (2D) have beneficial influence on the red-shifted absorption spectrum of the dye in solution and dye adsorbed on TiO2 film, and the broadening of the incident monochromatic photon-to-current conversion efficiency (IPCE) spectra of the DSSCs, leading to enhanced energy conversion efficiency (). Among these dyes, CCTT3A shows the best photovoltaic performance, and a maximal incident monochromatic photon-to-current conversion efficiency (IPCE) value of 80%, a short-circuit photocurrent density (Jsc) of 9.98 mAcm2, open-circuit voltage (Voc) of 0.70 V, and fill factor (FF) of 0.67, corresponding to an overall conversion efficiency of 4.6% were achieved. This work suggests that organic dyes based on this type of donor moiety or donor molecular architecture are promising candidates for improved performance DSSCs.