title: Mesoporous tin-doped indium oxide thin films: effect of mesostructure on electrical conductivity.
abstract: We present a versatile method for the preparation of mesoporous tin-doped indium oxide (ITO) thin films via dip-coating. Two poly(isobutylene)-b-poly(ethyleneoxide) (PIB-PEO) copolymers of significantly different molecular weight (denoted as PIB-PEO 3000 and PIB-PEO 20000) are used as templates and are compared with non-templated films to clarify the effect of the template size on the crystallization and, thus, on the electrochemical properties of mesoporous ITO films. Transparent, mesoporous, conductive coatings are obtained after annealing at 500 °C; these coatings have a specific resistance of 0.5 Ω cm at a thickness of about 100 nm. Electrical conductivity is improved by one order of magnitude by annealing under a reducing atmosphere. The two types of PIB-PEO block copolymers create mesopores with in-plane diameters of 20-25 and 35-45 nm, the latter also possessing correspondingly thicker pore walls. Impedance measurements reveal that the conductivity is significantly higher for films prepared with the template generating larger mesopores. Because of the same size of the primary nanoparticles, the enhanced conductivity is attributed to a higher conduction path cross section. Prussian blue was deposited electrochemically within the films, thus confirming the accessibility of their pores and their functionality as electrode material.
authors.affiliation: Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
authors.forename: Till
authors.initials: T
authors.lastname: von Graberg
authors.affiliation: Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
authors.forename: Pascal
authors.initials: P
authors.lastname: Hartmann
authors.affiliation: Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Rein
authors.affiliation: ISTM-CNR, Dipartimento di Scienze Chimiche, Universita'degli Studi di Padova, via Marzolo 1, 5131-Padova, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Gross
authors.affiliation: Institut für Physikalische Chemie und Elektrochemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 3A, D-30167 Hannover, Germany.
authors.forename: Britta
authors.initials: B
authors.lastname: Seelandt
authors.affiliation: BASF SE, D-67056 Ludwigshafen, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Röger
authors.affiliation: BASF SE, D-67056 Ludwigshafen, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Zieba
authors.affiliation: BASF SE, D-67056 Ludwigshafen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Traut
authors.affiliation: Institut für Physikalische Chemie und Elektrochemie, Gottfried Wilhelm Leibniz Universität Hannover, Callinstraße 3A, D-30167 Hannover, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Wark
authors.affiliation: Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Janek
authors.affiliation: Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 58, D-35392 Giessen, Germany.
authors.forename: Bernd M
authors.initials: BM
authors.lastname: Smarsly
keywords: ITO; electrical properties; functionalization; porous materials; thin films