title: Organic dyes containing fluorene decorated with imidazole units for dye-sensitized solar cells.
abstract: New organic dyes containing fluorene functionalized with two imidazole chromophores as donors and cyanoacrylic acid acceptors have been synthesized and successfully demonstrated as sensitizers in nanocrystalline TiO2-based dye-sensitized solar cells (DSSCs). The monoimidazole analogues were also synthesized for comparison. The Sommelet reaction of bromomethylated 2-bromo-9,9-diethyl-9H-fluorene produced the key precursor 7-bromo-9,9-diethyl-9H-fluorene-2,4-dicarbaldehyde required for the preparation of imidazole-functionalized fluorenes. Since the dyes possess weak donor segment, the electron-richness of the conjugation pathway dictated the optical, electrochemical, and photovoltaic properties of the dyes. The dyes served as sensitizers in DSSC and exhibited moderate efficiency up to 3.44%. The additional imidazole present on the fluorene has been found to retard the electron recombination due to the bulkier hydrophobic environment and led to high open-circuit voltage in the devices.
authors.affiliation: Organic Materials Laboratory, Department of Chemistry, Indian Institute of Technology Roorkee , Roorkee 247 667, India.
authors.forename: Dhirendra
authors.initials: D
authors.lastname: Kumar
authors.forename: K R Justin
authors.initials: KR
authors.lastname: Thomas
authors.forename: Chuan-Pei
authors.initials: CP
authors.lastname: Lee
authors.forename: Kuo-Chuan
authors.initials: KC
authors.lastname: Ho