ION MODULATED ORGANIC TRANSISTORS - Doria

Nikolai Kaihovirta3. RESULTS AND DISCUSSIONS3.3 All-Polymer Low-Voltage ECTs on Patterned Ion-Conducting MembranesPatterning of the membrane, as shown in Figure 3.5, is a simple andversatile method of controlling the ionic conductivity in the membrane. Inthis work, the technique was further elaborated and utilized fordemonstrating all-polymer ECTs manufactured on patterned ionconductingPVDF:PSSA membranes. The rather simple device structureand the low-voltage and stable operation that has been earlierdemonstrated with the PEDOT/PSS based ECTs [38, 40, 41], attracts theion-conducting membranes as suitable platforms for manufacturing ECTsby roll-to-roll manufacturing techniques.Figure 3.8. (a) The patterned PVDF:PSSA membrane. (b) Flexography is a rollto-rollsuitable printing technique. (c) A photograph of the printed ECTs on thepatterned PVDF:PSSA membrane. (d) A schematic figure of the ECT structure.The source, drain and the gate are denoted by S, D and G respectively. (e) Thetransistor channel and the gate are coupled via the PVDF:PSSA. Thus they forman electrochemical cell, as schematically shown.The membranes were prepared by the EB technique described inScheme 2.1. Besides the PVDF:PSSA, the whole ECT structure consists ofPEDOT/PSS, which is printed by flexography, as illustrated in Figure 3.8.Due to the redox-mechanism, the ECT can be fabricated in a lateralgeometry, unlike OFETs. Therefore, all three electrodes can be placed onthe same printing plate, and the device structure printed in one step.Naturally, this also reduces the issues related to electrode alignment. Inthis work, two modifications of the water-based PEDOT/PSS dispersionwere done to improve the printed structure. Firstly, the viscosity of thedispersion was adjusted by partially removing water by evaporation.Hence, the resolution of the print pattern was improved. Additionally the30