The Effect of Interfacial Roughness on the Thin Film Morphology and Charge Transport of High-Performance Polythiophenes

Published

March 11, 2008

Author(s)

Y S. Jung, Regis J. Kline, Daniel A. Fischer, Eric K. Lin, Martin Heeney, Iain McCulloch, Dean DeLongchamp

Abstract

We control and vary the roughness of a dielectric upon which a high-performance polymer semiconductor, poly(2,5-bis(3-alkylthiophen-2-yl)thieno[3,2-b]thiophene) (pBTTT) is cast, to determine the effects of roughness on thin-film microstructure and the performance of organic field-effect transistors (OFETs). pBTTT forms large, well-oriented terraced domains with high carrier mobility after it is cast upon flat, low-surface-energy substrates and heated to a mesophase. Upon dielectrics with root-mean square (RMS) roughness greater than 0.5 nm, we find significant morphological changes in the pBTTT active layer and significant reductions in its charge carrier mobility. The pBTTT films on rough dielectrics exhibit significantly less order than those on smooth dielectrics through characterization with atomic force microscopy and X-ray diffraction. This critical RMS roughness implies that there exists a condition at which the pBTTT domains no longer conform to the local nanometer-scale curvature of the substrate.

Citation

Advanced Functional Materials

Pub Type

Journals

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Keywords

dielectric roughness, OFET, organic electronics, OTFT, polythiophene

Citation

Jung, Y. , Kline, R. , Fischer, D. , Lin, E. , Heeney, M. , McCulloch, I. and DeLongchamp, D. (2008), The Effect of Interfacial Roughness on the Thin Film Morphology and Charge Transport of High-Performance Polythiophenes, Advanced Functional Materials, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852764 (Accessed October 9, 2025)