On the Relation between Morphology and FET Mobility of Poly(3‐alkylthiophene)s at the Polymer/SiO2 and Polymer/Air Interface. (27th November 2013)

• Record Type: Journal Article
• Authors: Oosterbaan, Wibren D.; Bolsée, Jean‐Christophe; Wang, Linjun; Vrindts, Veerle; Lutsen, Laurence J.; Lemaur, Vincent; Beljonne, David; McNeill, Christopher R.; Thomsen, Lars; Manca, Jean V.; Vanderzande, Dirk J. M.
• Is Part Of: Advanced functional materials. Volume 24:Number 14(2014)
• Page Start: 1994
• Page End: 2004
• Publication Date: 2013-11-27
• Subjects: Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201303298
• Languages: English
• ISSNs: 1616-301X

Abstract

<abstract abstract-type="main" xml:lang="en"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The influence of the interface of the dielectric SiO<sub>2</sub> on the performance of bottom‐contact, bottom‐gate poly(3‐alkylthiophene) (P3<italic>A</italic>T) field‐effect transistors (FETs) is investigated. In particular, the operation of transistors where the active polythiophene layer is directly spin‐coated from chlorobenzene (CB) onto the bare SiO<sub>2</sub> dielectric is compared to those where the active layer is first spin‐coated then laminated via a wet transfer process such that the film/air interface of this film contacts the SiO<sub>2</sub> surface. While an apparent alkyl side‐chain length dependent mobility is observed for films directly spin‐coated onto the SiO<sub>2</sub> dielectric (with mobilities of ≈10<sup>−3</sup> cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup> or less) for laminated films mobilities of 0.14 ± 0.03 cm<sup>2</sup> V<sup>−1</sup> s<sup>−1</sup> independent of alkyl chain length are recorded. Surface‐sensitive near edge X‐ray absorption fine structure (NEXAFS) spectroscopy measurements indicate a strong out‐of‐plane orientation of the polymer backbone at the original air/film interface while much lower average tilt angles of the polymer backbone are observed at the SiO<sub>2</sub>/film interface. A comparison with NEXAFS on crystalline P3<italic>A</italic>T nanofibers, as well as molecular mechanics and electronic structure calculations on ideal P3<italic>A</italic>T crystals suggest a close to crystalline polymer organization at the P3<italic>A</italic>T/air interface of films from CB. These results emphasize the negative influence of wrongly oriented polymer on charge carrier mobility and highlight the potential of the polymer/air interface in achieving excellent "out‐of‐plane" orientation and high FET mobilities.</p> </abstract>