title: Molecular engineering of organic sensitizers for dye-sensitized solar cell applications.
abstract: Novel unsymmetrical organic sensitizers comprising donor, electron-conducting, and anchoring groups were engineered at a molecular level and synthesized for sensitization of mesoscopic titanium dioxide injection solar cells. The unsymmetrical organic sensitizers 3-(5-(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D5), 3-(5-bis(4-(diphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D7), 5-(4-(bis(4-methoxyphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D9), and 3-(5-bis(4,4'-dimethoxydiphenylamino)styryl)thiophen-2-yl)-2-cyanoacrylic acid (D11) anchored onto TiO2 and were tested in dye-sensitized solar cell with a volatile electrolyte. The monochromatic incident photon-to-current conversion efficiency of these sensitizers is above 80%, and D11-sensitized solar cells yield a short-circuit photocurrent density of 13.90 +/- 0.2 mA/cm(2), an open-circuit voltage of 740 +/- 10 mV, and a fill factor of 0.70 +/- 0.02, corresponding to an overall conversion efficiency of 7.20% under standard AM 1.5 sun light. Detailed investigations of these sensitizers reveal that the long electron lifetime is responsible for differences in observed open-circuit potential of the cell. As an alternative to liquid electrolyte cells, a solid-state organic hole transporter is used in combination with the D9 sensitizer, which exhibited an efficiency of 3.25%. Density functional theory/time-dependent density functional theory calculations have been employed to gain insight into the electronic structure and excited states of the investigated species.
authors.affiliation: Organic Chemistry and Physical Chemistry, Center of Molecular Devices, Royal Institute of Technology, Teknikringen 30, 10044 Stockholm, Sweden.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Hagberg
authors.forename: Jun-Ho
authors.initials: JH
authors.lastname: Yum
authors.forename: Hyojoong
authors.initials: H
authors.lastname: Lee
authors.forename: Filippo
authors.initials: F
authors.lastname: De Angelis
authors.forename: Tannia
authors.initials: T
authors.lastname: Marinado
authors.forename: Karl Martin
authors.initials: KM
authors.lastname: Karlsson
authors.forename: Robin
authors.initials: R
authors.lastname: Humphry-Baker
authors.forename: Licheng
authors.initials: L
authors.lastname: Sun
authors.forename: Anders
authors.initials: A
authors.lastname: Hagfeldt
authors.forename: Michael
authors.initials: M
authors.lastname: Grätzel
authors.forename: Md K
authors.initials: MK
authors.lastname: Nazeeruddin