Charge transport enhancement via air-mediated self-organization in polymer semiconductors
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Charge transport enhancement via air-mediated self-organization in polymer semiconductors Takashi Kushida1, Takashi Nagase2, 3, and Hiroyoshi Naito2, 3 1
Integrative Technology Research Institute, Teijin Limited, Hino, Tokyo 191-8512, Japan Department of Physics and Electronics, Osaka Prefecture University, Sakai 599-8531, Japan 3 The Research Institute for Molecular Electronics Devices, Osaka Prefecture University, Sakai 599-8531, Japan 2
ABSTRACT Air-mediated molecular ordering in self-organized polymer semiconductors of regioregular poly(3-hexylthiophene) (P3HT) and poly[(9,9′-dioctylfluorenyl-2,7-diyl)-(2,2′bithiophene-5,5′-diyl)] (F8T2) was investigated using organic field-effect transistors (OFETs) fabricated by transfer-printing using poly(dimethylsiloxane) stamps with various surface energies. OFET measurements revealed that the charge transport in the polymer semiconductors via the air interface layer was better than that via the substrate interface layer. The results indicated that the formation of a highly ordered microstructure at the polymer/air interface through air-mediated self-organization occurs in many polymer semiconductors. This airmediated self-organization was weaker than substrate-mediated self-organization, whose influence appeared in OFETs with thin semiconductor films. INTRODUCTION Organic field-effect transistors (OFETs) have attracted considerable attention as a promising alternative to amorphous silicon-based inorganic thin-film transistors for large-area electronic devices, including active-matrix flat-panel displays and radio-frequency identification tags [1-5]. Solution-processable OFETs [6] based on soluble organic materials have recently attracted interest as a key device for realizing printed organic electronics because they allow the fabrication of large-area, flexible electronic circuits at low temperatures using low-cost printing processes such as ink-jet printing, microcontact printing (μCP) [7-11], and screen printing. The field-effect mobility of soluble organic semiconductors has been improved remarkably in recent years by improving the intermolecular π-electron coupling utilizing self-organizing behavior on hydrophobic, low-energy surfaces. Field-effect mobility comparable to that of hydrogenated amorphous silicon (~1 cm2 V–1 s–1) has recently been achieved in OFETs based on polymer semiconductors [12,13] and soluble molecular semiconductors [14,15]. In a previous study, we reported a new approach for improving the field-effect mobility of solution-processable OFETs by utilizing the air-mediated self-organization of polymer semiconductors. We showed that charge mobility in a regioregular poly(3-hexylthiophene) (P3HT) film is significantly increased at the film surface by enhancing the self-organization at the P3HT/air interface and that such air-mediated self-organization is not strongly affected by self-organization at the P3HT/substrate interface in 100-nm thick P3HT films using a transferprinting method [16].
In this study, we investigated the air-mediated self-orga
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