title: Rhodanine dyes for dye-sensitized solar cells : spectroscopy, energy levels and photovoltaic performance.
abstract: Three new sensitizers for photoelectrochemical solar cells were synthesized consisting of a triphenylamine donor, a rhodanine-3-acetic acid acceptor and a polyene connection. The conjugation length was systematically increased, which resulted in two effects: first, it led to a red-shift of the optical absorption of the dyes, resulting in an improved spectral overlap with the solar spectrum. Secondly, the oxidation potential decreased systematically. The excited state levels were, however, calculated to be nearly stationary. The experimental trends were in excellent agreement with density functional theory (DFT) computations. The photovoltaic performance of this set of dyes as sensitizers in mesoporous TiO2 solar cells was investigated using electrolytes containing the iodide/triiodide redox couple. The dye with the best absorption characteristics showed the poorest solar cell efficiency, due to losses by recombination of electrons in TiO2 with triiodide. Addition of 4-tert butylpyridine to the electrolyte led to a strongly reduced photocurrent for all dyes due to a reduced electron injection efficiency, caused by a 0.15 V negative shift of the TiO2 conduction band potential.
authors.affiliation: Center of Molecular Devices, Royal Institute of Technology, School of Chemical Science and Engineering, Physical Chemistry, 100 44, Stockholm, Sweden.
authors.forename: Tannia
authors.initials: T
authors.lastname: Marinado
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Hagberg
authors.forename: Maria
authors.initials: M
authors.lastname: Hedlund
authors.forename: Tomas
authors.initials: T
authors.lastname: Edvinsson
authors.forename: Erik M J
authors.initials: EM
authors.lastname: Johansson
authors.forename: Gerrit
authors.initials: G
authors.lastname: Boschloo
authors.forename: Håkan
authors.initials: H
authors.lastname: Rensmo
authors.forename: Tore
authors.initials: T
authors.lastname: Brinck
authors.forename: Licheng
authors.initials: L
authors.lastname: Sun
authors.forename: Anders
authors.initials: A
authors.lastname: Hagfeldt