title: Exciton diffusion controlled quantum efficiency in hybrid dye sensitized solar cells.
abstract: Well-ordered and uniform titania nanoparticle arrays were synthesized using diblock copolymers as structure directing agents. High molecular weight copolymers of polystyrene-b-polyethylene oxide and poly(methylmethacrylate)-b-polyethylene oxide were used to control the distance between titania nanoparticles in the range of 20-60 nm. Using these titania nanoparticle arrays and regioregular poly(3-hexylthiophene), models for a dye sensitized photovoltaic cell were assembled, in which the interparticle spacing was systematically varied. In these simplified solar cells, the titania nanocrystals were surrounded by a continuous regioregular poly(3-hexylthiophene) phase. The spacing between the titania nanoparticles was chosen as to provide enough space for the hole transfer material-regioregular poly(3-hexylthiophene)-to assemble as pi stacks. The external quantum efficiency showed a clear dependence on the distance between titania nanoparticles and reached 12% at an excitation wavelength of 515 nm in the best case. This demonstrates that the regioregular poly(3-hexylthiophene) phase acts as the locus of excition generation while the dye layer prevents charge recombination at the heterointerface. Thus control of the exciton diffusion is a key issue for present solid-state dye sensitized solar cells.
authors.affiliation: Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Mainz, Germany.
authors.forename: Zaicheng
authors.initials: Z
authors.lastname: Sun
authors.forename: Yajun
authors.initials: Y
authors.lastname: Cheng
authors.forename: Maria
authors.initials: M
authors.lastname: Lechmann
authors.forename: Jiaoli
authors.initials: J
authors.lastname: Li
authors.forename: Jixue
authors.initials: J
authors.lastname: Li
authors.forename: Jishan
authors.initials: J
authors.lastname: Wu
authors.forename: Andrew
authors.initials: A
authors.lastname: Grimsdale
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Butt
authors.forename: Jochen S
authors.initials: JS
authors.lastname: Gutmann