title: Hyperbranched quasi-1D nanostructures for solid-state dye-sensitized solar cells.
abstract: In this work we demonstrate hyperbranched nanostructures, grown by pulsed laser deposition, composed of one-dimensional anatase single crystals assembled in arrays of high aspect ratio hierarchical mesostructures. The proposed growth mechanism relies on a two-step process: self-assembly from the gas phase of amorphous TiO2 clusters in a forest of tree-shaped hierarchical mesostructures with high aspect ratio; oriented crystallization of the branches upon thermal treatment. Structural and morphological characteristics can be optimized to achieve both high specific surface area for optimal dye uptake and broadband light scattering thanks to the microscopic feature size. Solid-state dye sensitized solar cells fabricated with arrays of hyperbranched TiO2 nanostructures on FTO-glass sensitized with D102 dye showed a significant 66% increase in efficiency with respect to a reference mesoporous photoanode and reached a maximum efficiency of 3.96% (among the highest reported for this system). This result was achieved mainly thanks to an increase in photogenerated current directly resulting from improved light harvesting efficiency of the hierarchical photoanode. The proposed photoanode overcomes typical limitations of 1D TiO2 nanostructures applied to ss-DSC and emerges as a promising foundation for next-generation high-efficiency solid-state devices comprosed of dyes, polymers, or quantum dots as sensitizers.
authors.affiliation: Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia , Via Giovanni Pascoli, 70/3, 20133 Milano, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Passoni
authors.forename: Farbod
authors.initials: F
authors.lastname: Ghods
authors.forename: Pablo
authors.initials: P
authors.lastname: Docampo
authors.forename: Agnese
authors.initials: A
authors.lastname: Abrusci
authors.forename: Javier
authors.initials: J
authors.lastname: Martí-Rujas
authors.forename: Matteo
authors.initials: M
authors.lastname: Ghidelli
authors.forename: Giorgio
authors.initials: G
authors.lastname: Divitini
authors.forename: Caterina
authors.initials: C
authors.lastname: Ducati
authors.forename: Maddalena
authors.initials: M
authors.lastname: Binda
authors.forename: Simone
authors.initials: S
authors.lastname: Guarnera
authors.forename: Andrea
authors.initials: A
authors.lastname: Li Bassi
authors.forename: Carlo Spartaco
authors.initials: CS
authors.lastname: Casari
authors.forename: Henry J
authors.initials: HJ
authors.lastname: Snaith
authors.forename: Annamaria
authors.initials: A
authors.lastname: Petrozza
authors.forename: Fabio
authors.initials: F
authors.lastname: Di Fonzo