ION MODULATED ORGANIC TRANSISTORS - Doria

Nikolai Kaihovirta2. EXPERIMENTALstructure [46-48]. For OFETs, the measured mobility and on/off ratio ofwell-ordered P3HT has been reported higher than 0.1 cm 2 /Vs and 10 6respectively [49-51], which are comparable to the inorganic a-SiMOSFETs.C 6 H 13SnS C 6 H 13Chart 2.3. The chemical structure for the (regioregular) P3HT.In this thesis, the P3HT semiconductor was used for all transistors(with exception for the all-polymer membrane based ECT in Paper 3).Two P3HT materials (Rieke Metals, Inc. and Plexcore, Inc.), supplied bySigma-Aldrich Inc., was used. The P3HT was dissolved in eitheranhydrous chloroform (when spin-coated) or in a 1:1 mixture of tolueneand p-xylene (when coated by reverse gravure). The P3HT was spincoated,except for the all-printed HIFET in Paper 1. For the all-printedHIFET, the P3HT was applied in air by the reverse gravure coatingtechnique. The reverse gravure coater was a tabletop Mini-Labo testcoater (Yasui Seiki Co.).For the membrane based ECTs in Paper 3, the redox-active polymerwas PEDOT/PSS (Baytron P). It was printed by flexography using aFlexiproof 100 (R K Print Coat Instruments Ltd) flexographic printingunit.2.1.4 InsulatorsPolymeric dielectric insulators are soluble and often processable at lowtemperatures and, hence, suitable for plastic electronics. Moreover, unlikethe frequently used SiO 2-insulator, all four transistor geometries can beemployed (Figure 1.1). Polymeric insulators are, however, low-κinsulators and their break-down voltages are usually low. Therefore, andas discussed in Section 1.2.3, it has been popular to add a cross-linkingagent in order to fabricate “sub-100 nanometer” robust polymericinsulators for low-voltage OFETs. On the other hand, the problem withsubstrate roughness becomes more significant. In Paper 1, a noncrosslinkedpoly(methyl methacrylate) (PMMA) (Sigma-Aldrich, Inc.)dielectric insulator was used for fabricating OFETs on different plasticsubstrates. The chemical structure is shown in Chart 2.4 a). The PMMA16