One-step macroscopic alignment of conjugated polymer systems by epitaxial crystallization during spin-coating
Müller, Christian, Aghamohammadi, Mahdieh, Himmelberger, Scott, Sonar, Prashant, Garriga, Miquel, Salleo, Alberto, & Campoy-Quiles, Mariano (2013) One-step macroscopic alignment of conjugated polymer systems by epitaxial crystallization during spin-coating. Advanced Functional Materials, 23(19), pp. 2368-2377.
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. Macroscopic spherulite-like structures of the conjugated polymer poly(3-hexylthiophene) (P3HT) grow directly during spin-coating. This is achieved by processing P3HT or P3HT:fullerene bulk heterojunction blends from a mixture of the crystallizable solvent 1,3,5-trichlorobenzene and a second carrier solvent such as chlorobenzene. Epitaxial growth of the polymer on solidified solvent crystals gives rise to circular-symmetric, spherulite-like structures that feature a high degree of anisotropy.
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|Item Type:||Journal Article|
|Keywords:||bulk-heterojunction, epitaxy, fullerene, nucleation, polymer semiconductors, spherulite, 1 , 3 , 5-Trichlorobenzene, Bulk heterojunction, Epitaxial crystallization, Poly(3-alkylthiophene), Relative degree of crystallinity, Wide angle X-ray scattering, Alignment, Anisotropy, Carrier mobility, Epitaxial growth, Fullerenes, Heterojunctions, Optical microscopy, Photoluminescence spectroscopy, Polymer blends, Polypropylenes, Solvents, Thin films, Plastic coatings|
|Divisions:||Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
|Copyright Owner:||Copyright © 2013 WILEY-VCH Verlag GmbH & Co.|
|Deposited On:||09 Oct 2014 00:09|
|Last Modified:||09 Oct 2014 22:01|
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