Journal
ORGANIC ELECTRONICS
Volume 29, Issue -, Pages 88-93Publisher
ELSEVIER
DOI: 10.1016/j.orgel.2015.11.033
Keywords
Organic thin-film transistors; Bar-coating; Conjugated polymers; Benzothiadiazole; Molecular weight; Solution process
Funding
- National Research Foundation of Korea (NRF) grant - Korean Government (MSIP) [NRF-2014R1A2A2A01007159]
- National Research Foundation of Korea Grant - Korean Government (MSIP)
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We report high-performance organic thin-film transistors (OTFTs) with an ultrathin active layer of difluorobenzothiadiazole-dithienosilole copolymer (PDFDT) form by using the wire bar-coating process. The top-gate/bottom contact (TG/BC) OTFTs based on bar-coated PDFDT polymer as channel material and poly(methyl methacrylate) (PMMA) as gate dielectric show a hole mobility of up to 2.2 cm(2) V-1 s(-1) with a current ON/OFF ratio (I-on/I-off) of 10(4)-10(5), with the mobility being two times larger than that of the spincoated PDFDT based OTFTs. The higher mobility of the bar-coated PDFDT polymer films can be attributed to the well-organized fibril structures of the polymer chains. Importantly, two different molecular weight polymers (M-n = 23 and 34 kDa) were employed to conduct these experiments and both batches showed about the same performance, which mitigates the typical batch-to-batch variation in OTFT performance. Furthermore, we explored the operational stability of the bar-coated OTFTs in ambient air and nitrogen environments. The bias-stress and cycling tests between the ON/OFF states of the bar-coated devices showed high stability in both nitrogen and air. Conclusively, here we demonstrate that (i) a simple barcoating process is a better method to control and obtain good polymer morphology in comparison to spin-coating, and (ii) the PDFDT polymer has great potential to provide good reproducibility and stability in large-area OTFT devices. (C) 2015 Elsevier B.V. All rights reserved.
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