Effect of a pi-bridging unit in triphenylamine-benzothiadiazole based donor acceptor chromophores for dye-sensitized solar cells

• Published in: Electrochimica acta 2014-11, Vol.147, p.617-625
• Main Authors: Yigit, Mesude Zeliha, Bilgili, Hakan, Sefer, Emre, Demic, Serafettin, Zafer, Ceylan, Can, Mustafa, Koyuncu, Sermet
• Format: Article
• Language: English
• Subjects: donor-acceptor dyes; dye sensitized solar cells; π-bridge effect
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2014.09.138

[Display omitted] •Effect of pi bridge unit based on triphenylamine-benzothiadiazole metal free sensitizers were synthesized and used in dye sensitized solar cells (DSSCs).•The power conversion efficiencies η were increased from 3.16% to 3.81% by using thiophene instead of phenylene as a π-bridge unit when an ionic liquid electrolyte (0.5M LiI (99,9%) and 0.05M I2 (99,9%) in 3- methoxypropionitrile) was used in this system. Two new metal free sensitizers based on triphenylamine-benzothiadiazole were synthesized and used in dye sensitized solar cells (DSSCs). Electrochemical and optical properties of the dyes were studied by cyclic voltammetry, UV-vis absorption and fluorescence spectroscopy. A red shift was observed by the attachment of a thiophene (MZ-259) instead of a phenylene (MZ-255) bridge. The reverse effect was observed in the electrochemical properties because of the more electron-donating thiophene incorporated into the cyanoacrylic acid as an anchoring-acceptor unit in this system resulted in a higher LUMO level. The charge distribution of the dyes was also proved by DFT calculations using the Spartan10 program with the parameters of B3LYP and 6-31G** basis set. Finally the photovoltaic performances were investigated under standard AM 1.5 illumination with a power of 100mW/cm2 using an ionic liquid based electrolyte. The power conversion efficiencies, η, were increased from 3.16% to 3.81% by using thiophene instead of phenylene as a π-bridge unit.