title: Effect of Substituents in Catechol Dye Sensitizers on Photovoltaic Performance of Type II Dye-Sensitized Solar Cells.
abstract: In order to provide a direction in molecular design of catechol (Cat) dyes for type II dye-sensitized solar cells (DSSCs), the dye-to-TiO2 charge-transfer (DTCT) characteristics of Cat dyes with various substituents and their photovoltaic performance in DSSCs are investigated. The Cat dyes with electron-donating or moderately electron-withdrawing substituents exhibit a broad absorption band corresponding to DTCT upon binding to TiO2 films, whereas those with strongly electron-withdrawing substituents exhibit weak DTCT. This study indicates that the introduction of a moderately electron-withdrawing substituent on the Cat moiety leads to not only an increase in the DTCT efficiency, but also the retardation of back electron transfer. This results in favorable conditions for the type II electron-injection pathway from the ground state of the Cat dye to the conduction band of the TiO2 electrode by the photoexcitation of DTCT bands.
authors: Department of Applied Chemistry, Graduate School of Engineering Hiroshima University, Higashi-Hiroshima 739-8527 (Japan). yooyama@hiroshima-u.ac.jp.
authors: Yousuke
authors: Y
authors: Ooyama
authors: Department of Applied Chemistry, Graduate School of Engineering Hiroshima University, Higashi-Hiroshima 739-8527 (Japan).
authors: Masahiro
authors: M
authors: Kanda
authors: Department of Applied Chemistry, Graduate School of Engineering Hiroshima University, Higashi-Hiroshima 739-8527 (Japan).
authors: Koji
authors: K
authors: Uenaka
authors: Department of Applied Chemistry, Graduate School of Engineering Hiroshima University, Higashi-Hiroshima 739-8527 (Japan).
authors: Joji
authors: J
authors: Ohshita
keywords: catechols; charge transfer; dyes; sensitizers; solar cells