Scalable manufacturing of small-molecule organic thin film transistors (OTFTs) with performance approaching single crystals requires extraordinary control over microstructures and morphologies of organic semiconductors (OSCs). Here, contact-induced nucleation in the context of small-molecule OSCs and OSC:polymer blends prepared by blade coating, a printing process capable of mimicking large area batch and roll-to-roll manufacturing, is investigated. Using polarized optical microscopy, microbeam grazing incidence wide angle X-ray scattering, and energy-filtered transmission electron microscopy, it is revealed that previous design rules drawn from spin coating of OSCs and contact-induced nucleation may have to be revisited in the context of blade coating. It is shown that blade coating achieves texture purity in case of 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene (diF-TES-ADT), irrespective of whether the contact is chemically treated with a halogenated self-assembled monolayer (SAM) or not, in contrast to spin coating which requires an SAM. Here, it is demonstrated that OSC-contact interactions increase the nucleation density and can disrupt the vertical stratification in polymer:OSC blends with great detrimental effects on carrier transport. Using these lessons, we demonstrate bottom-contact bottom-gate OTFTs without chemical surface modification achieving hole mobilities of 4.6 and 3.6 cm2 V-1 s-1, using 6,13-bis(triisopropylsilylethynyl)pentacene and diF-TES-ADT, respectively, blended with an insulating polymer. Contact-induced nucleation, normally a desirable effect when spin-coating organic semiconductors (OSC), is shown to disrupt the crystallization of large OSC domains and to alter the vertical stratification of otherwise high-performance polymer:OSC blends.
|Number of pages||8|
|Journal||Advanced Functional Materials|
|State||Published - Apr 12 2016|
Bibliographical noteFunding Information:
This work was supported by the Office of Competitive Research Funds under the Competitive Research Grant (round 1). A.A. is grateful to SABIC for the Presidential SABIC Chair. The authors acknowledge use of the D1 beam line at the Cornell High Energy Synchrotron Source supported by the National Science Foundation and the National Institutes of Health and General Medical Sciences via NSF awards DMR-0936384 and DMR-1332208. The authors thank Jake Mohin (Carnegie-Mellon University) and Dave Schuller (MacCHESS) for their help with the micrograph metrology software as well as Sterling Cornaby, Tom Szebenyi, and Don Bilderback (CHESS) for providing the high-quality X-ray-focusing capillary.
© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
- blade coating
- contact-induced nucleation
- organic semiconductors
- organic thin film transistors
- polymer:molecule blends
ASJC Scopus subject areas
- Chemistry (all)
- Materials Science (all)
- Condensed Matter Physics