title: Oligothiophene-containing coumarin dyes for efficient dye-sensitized solar cells.
abstract: We have developed oligothiophene-containing coumarin dyes fully functionalized for dye-sensitized nanocrystalline TiO(2) solar cells (DSSCs). DSSCs based on the dyes gave good performance in terms of incident photon-to-current conversion efficiency (IPCE) in the range of 400-800 nm. A solar energy-to-electricity conversion efficiency (eta) of 7.4% was obtained with a DSSC based on 2-cyano-3-[5'-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)-[2,2']bithiophenyl-5-yl]acrylic acid (NKX-2677) under simulated AM 1.5G irradiation (100 mW cm(-2)) with a mask: short-circuit current density (J(sc)) = 13.5 mA cm(-2); open-circuit voltage (V(oc)) = 0.71 V; fill factor (FF) = 0.77. Transient absorption spectroscopy measurements indicated that electron injection from NKX-2677 to the conduction band of TiO(2) is very rapid (<100 fs), which is much faster than the emission lifetime of the dye (1.0 ns), giving a highly efficient electron injection yield of near unity.
authors.affiliation: National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan. k.hara@aist.go.jp
authors.forename: Kohjiro
authors.initials: K
authors.lastname: Hara
authors.forename: Zhong-Sheng
authors.initials: ZS
authors.lastname: Wang
authors.forename: Tadatake
authors.initials: T
authors.lastname: Sato
authors.forename: Akihiro
authors.initials: A
authors.lastname: Furube
authors.forename: Ryuzi
authors.initials: R
authors.lastname: Katoh
authors.forename: Hideki
authors.initials: H
authors.lastname: Sugihara
authors.forename: Yasufumi
authors.initials: Y
authors.lastname: Dan-Oh
authors.forename: Chiaki
authors.initials: C
authors.lastname: Kasada
authors.forename: Akira
authors.initials: A
authors.lastname: Shinpo
authors.forename: Sadaharu
authors.initials: S
authors.lastname: Suga