One-Step Macroscopic Alignment of Conjugated Polymer Systems by Epitaxial Crystallization during Spin-Coating
Journal article, 2013

The one-step preparation of highly anisotropic polymer semiconductor thin films directly from solution is demonstrated. The conjugated polymer poly(3-hexylthiophene) (P3HT) as well as P3HT:fullerene bulk–heterojunction blends can be spin-coated from a mixture of the crystallizable solvent 1,3,5-trichlorobenzene (TCB) and a second carrier solvent such as chlorobenzene. Solidification is initiated by growth of macroscopic TCB spherulites followed by epitaxial crystallization of P3HT on TCB crystals. Subsequent sublimation of TCB leaves behind a replica of the original TCB spherulites. Thus, highly ordered thin films are obtained, which feature square-centimeter-sized domains that are composed of one spherulite-like structure each. A combination of optical microscopy and polarized photoluminescence spectroscopy reveals radial alignment of the polymer backbone in case of P3HT, whereas P3HT:fullerene blends display a tangential orientation with respect to the center of spherulite-like structures. Moreover, grazing-incidence wide-angle X-ray scattering reveals an increased relative degree of crystallinity and predominantly flat-on conformation of P3HT crystallites in the blend. The use of other processing methods such as dip-coating is also feasible and offers uniaxial orientation of the macromolecule. Finally, the applicability of this method to a variety of other semi-crystalline conjugated polymer systems is established. Those include other poly(3-alkylthiophene)s, two polyfluorenes, the low band-gap polymer PCPDTBT, a diketopyrrolopyrrole (DPP) small molecule as well as a number of polymer:fullerene and polymer:polymer blends.

nucleation

bulk–heterojunction

spherulite

fullerene

epitaxy

polymer semiconductors

Author

Christian Müller

Chalmers, Chemical and Biological Engineering, Polymer Technology

M. Aghamohammadi

Universitat Autonoma de Barcelona (UAB)

Scott Himmelberger

Stanford University

P. Sonar

Agency for Science, Technology and Research (A*STAR)

M. Garriga

Universitat Autonoma de Barcelona (UAB)

Alberto Salleo

Stanford University

M. Campoy-Quiles

Universitat Autonoma de Barcelona (UAB)

Advanced Functional Materials

1616-301X (ISSN) 16163028 (eISSN)

Vol. 23 19 2368-2377

Subject Categories

Polymer Technologies

DOI

10.1002/adfm.201202983

More information

Latest update

4/14/2022