Effects of Confinement on Microstructure and Charge Transport in High Performance Semicrystalline Polymer Semiconductors

Type
Article

Authors
Himmelberger, Scott
Dacuña, Javier
Rivnay, Jonathan
Jimison, Leslie H.
McCarthy-Ward, Thomas
Heeney, Martin
McCulloch, Iain
Toney, Michael F.
Salleo, Alberto

KAUST Grant Number
KUS-C1-015-21

Online Publication Date
2012-11-23

Print Publication Date
2013-04-25

Date
2012-11-23

Abstract
The film thickness of one of the most crystalline and highest performing polymer semiconductors, poly(2,5-bis(3-tetradecylthiophen-2-yl)thieno[3,2-b] thiophene) (PBTTT), is varied in order to determine the effects of interfaces and confinement on the microstructure and performance in organic field effect transistors (OFETs). Crystalline texture and overall film crystallinity are found to depend strongly on film thickness and thermal processing. The angular distribution of crystallites narrows upon both a decrease in film thickness and thermal annealing. These changes in the film microstructure are paired with thin-film transistor characterization and shown to be directly correlated with variations in charge carrier mobility. Charge transport is shown to be governed by film crystallinity in films below 20 nm and by crystalline orientation for thicker films. An optimal thickness is found for PBTTT at which the mobility is maximized in unannealed films and where mobility reaches a plateau at its highest value for annealed films. The effects of confinement on the morphology and charge transport properties of poly(2,5-bis(3-tetradecylthiophen-2-yl) thieno[3,2-b]thiophene) (PBTTT) are studied using quantitative X-ray diffraction and field-effect transistor measurements. Polymer crystallinity is found to limit charge transport in the thinnest films while crystalline texture and intergrain connectivity modulate carrier mobility in thicker films. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Citation
Himmelberger S, Dacuña J, Rivnay J, Jimison LH, McCarthy-Ward T, et al. (2012) Effects of Confinement on Microstructure and Charge Transport in High Performance Semicrystalline Polymer Semiconductors. Advanced Functional Materials 23: 2091–2098. Available: http://dx.doi.org/10.1002/adfm.201202408.

Acknowledgements
Portions of this research were carried out at the Stanford Synchrotron Radiation Lightsource, a national user facility operated by Stanford University on behalf of the US Department of Energy, Office of Basic Energy Sciences. A.S. and S.H. gratefully acknowledge financial support from the National Science Foundation. This publication was partially based on work supported by the Center for Advanced Molecular Photovoltaics (Award No. KUS-C1-015-21), made by King Abdullah University of Science and Technology (KAUST).

Publisher
Wiley

Journal
Advanced Functional Materials

DOI
10.1002/adfm.201202408

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