Fabrication and characterization of liquid electrolyte gated polymer field effect transistor for basic circuit applications

Abstract

In this thesis, a simple polymer field effect transistor structure is designed and fabricated. To decrease the operating voltage of the transistor, electrolyte solutions are used as gate material. Using electrolyte at the gate increased the capacitance of the induced channel by the effect called electrical double layer formation which allowed transistor to operate under 1V. In the first step DI water is used as electrolyte solution because of its application simplicity. In order to stabilize the gate electrode and create a solid structure for the circuit design a novel electrode framework which is named planar gate electrode structure is implemented. Then, length of the channel is adjusted to be able to analyze the functional polymers that has been synthesized Chemistry Department of the Project. Comparison of different transistor designs has shown that a certain extent of ionic concentration results in higher ionization rate, so increase in the transconductance of the transistor. After the comparison of transistors which are prepared by commercial P3HT and P3HT with hydrophilic functionalization (P3HT-co-P3PEGT), it has also been observed that hydrophilicity of the polymer increases the effect of electrical double layer capacitance. In the last section, a high gain inverter is achieved by integration of P3HT-co-P3PEGT and 100mm NaCl solution. Thus, it is proved that the fabricated OFETs in this study can drive basic digital circuit applications.