Substituent effect of fluorine atom on benzothiadiazole bridging unit in dye sensitized solar cells

Abstract

Dye sensitized solar cells performances using two organic dyes with fluorinated-benzothiadiazole spacer, 3-{5-[7-(5-{4-[Bis(9,9-dimethyl-9H-fluoren-2-yl)-amino]-5-fluoro-phenyl}thiophen-2-yl)benzo-[1,2,5] thiadiazol-4-yl]thiophen-2-y1}-2-cyano acrylic acid (JIC-311) and 3454 7-(5-0-1Bis(9,9-dimethyl-9Hfluoren-2-yl)-aminol-5,6-difluorophe-nyl)thiophen-2-yl)benzo-11,2,51thiadiazol-4-yllthiophen-2-yl)-2- cyano acrylic acid (JK-312), were systematically investigated by solar simulation equipment, stepped light-induced transient measurements of photocurrent and voltage, and electrochemical impedance spectroscopy. To investigate substituent effect of fluorine atom on benzothiadiazole, molecular orbital calculations of two dyes using a time dependent density functional theory model with B3LYP/3-31G* were also carried out. JK-312 showed a unique electronic transition from HOMO-1 to LUMO. Short circuit current and open-circuit voltage in DSSCs performances were increased by the introduction of fluorine atom into spacer segment, compared to fluorine-free dyes. (C) 2013 Elsevier Ltd. All rights reserved.