Monoanchoring (D-D-π-A) and Dianchoring (D-D-(π-A)₂) Organic Dyes Featuring Triarylamine Donors Composed of Fluorene and Carbazole

Organic dyes containing carbazole as an auxiliary donor, oligothiophene linkers, and cyanoacrylic acid acceptors with two different architectures (D-D-π-A and D-D-(π-A)₂) were synthesized and characterized by optical and electrochemical measurements. The charge-transfer transitions of the monoanchoring dyes with a D-D-π-A configuration are intense whereas the π-π* transitions of the dianchoring dyes with D-D-(π-A)₂ architecture are promising. Incorporation of bithiophene into the conjugation slightly lowers the LUMO level of the dyes. The optical and electrochemical properties of these dyes are better than diphenylamine-based dyes. The TDDFT calculations were performed to rationalize the trends in the optical and electrochemical properties of the dyes. The efficiency of dye-sensitized solar cells based on the monoanchoring dyes is two to fivefold larger than the corresponding cells based on dianchoring congeners. Also, the use of chenodeoxycholic acid as an additive increases the efficiency of the devices reasonably.