title: Photophysical and (photo)electrochemical properties of a coumarin dye.
abstract: A new coumarin dye, cyano-{5,5-dimethyl-3-[2-(1,1,6,6-tetramethyl-10-oxo-2,3,5,6-tetrahydro-1H,4H,10H-11-oxa-3a-aza-benzo[de]anthracen-9-yl)vinyl]cyclohex-2-enylidene}-acetic acid (NKX-2753), was prepared and characterized with respect to photophysical and electrochemical properties. It was employed as a dye sensitizer in dye-sensitized solar cells and showed efficient photon-to-electron conversion properties. The photocurrent action spectrum exhibited a broad feature with a maximum incident photon-to-electron conversion efficiency (IPCE) of 84% at 540 nm, which is comparable to that for the famous red dye RuL2(NCS)2 (known as N3), where L stands for 2,2'-bipyridyl-4,4'-dicarboxylic acid. The sandwich-type solar cell with NKX-2753, under illumination of full sun (AM1.5, 100 mW cm(-2)), produced 16.1 mA cm(-2) of short-circuit photocurrent, 0.60 V of open-circuit photovoltage, and 0.69 of fill factor, corresponding to 6.7% of overall energy conversion efficiency using 0.1 M LiI, 0.05 M I2, 0.1 M guanidinium thiocyanate, and 0.6 M 1,2-dimethyl-3-n-propyl-imidazolium iodide in dry acetonitrile as redox electrolyte. In comparison with its analogue NKX-2586 (Langmuir 2004, 20, 4205), NKX-2753 with an extra side ring on the alkene chain produced much higher IPCE values at the same conditions. The side ring acted as a spacer to efficiently prevent dye aggregation when adsorbed on the TiO2 surface, resulting in significant improvements of short-circuit photocurrent, open-circuit photovoltage, and fill factor compared with NKX-2586 that aggregated on the TiO2 surface.
authors.affiliation: Solar Light Energy Conversion Team, Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Higashi, Tsukuba, Ibaraki 305-8565, Japan. zs.wang@aist.go.jp
authors.forename: Zhong-Sheng
authors.initials: ZS
authors.lastname: Wang
authors.forename: Kohjiro
authors.initials: K
authors.lastname: Hara
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
authors.forename: Hironori
authors.initials: H
authors.lastname: Arakawa
authors.forename: Hideki
authors.initials: H
authors.lastname: Sugihara
mesh_terms: D004396:Coloring Agents / Q000737:chemistry*; D003374:Coumarins / Q000737:chemistry*; D004563:Electrochemistry; D010777:Photochemistry; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D004396:Coloring Agents; D003374:Coumarins; C030123:coumarin