Development of Polymer Blend Systems for High Performance Organic Field-Effect Transistors

Abstract

Organic materials have numerous advantages over other materials because of their toughness, light weight, resistance to corrosion, colorability, fast productivity and low cost. For these reasons, in the present generation, organic materials have become an indattain new characteristics. However, the studies conducted for the development of electrical and physical properties of organic semiconductors by synthesis and engineering have been limited to a single component. This thesis is dedicated to the development of polymer blend electronics for applications in multi-functional semiconducting materials with unprecedented properties; these include simultaneous improvement of optical transmittance and field-effect mobility or operability of organic field-effect transistor (OFET) and polymer light emitting diode (PLED).Further, this study aims at the investigation of processing methods and characteristics of these materials to demonstrate prototype applications. Chapter 1 provides a general and fundamental overview of organic electronics; this includes conjugated organic systems to be utilized as charge transporting materials and device principles for organic field-effect transistors. Polymer blend electronics for novel organic devices composed of various types of blends have also been reviewed in this chapter. Chapter 2 describes a strategy for the simultaneously improvement of optical transparency and charge carrier mobility without an inverse trade-off in semiconducting polymers (SPs) by using a semiconducting/insulating polymer blend system. The detailed mechanisms underlying the excellent optical and electrical properties of our polymer blend system have been elucidated in this chapter. Furthermore, the fundamental issues related to the charge transport physics and molecular stacking structures of various polymeric semiconductors have been addressed. Consequently, optically transparent, deformable, and high-mobility polymer blend composite systems and their applications in prototypes of next-generation transparent and flexible electronics have also been demonstrated. Chapter 3 describes an important strategy of a novel method that is used to generate a dual functionality of polymers in semiconductors; this is achieved by blending a charge transport material of an OFET device and light-emitting materials of a PLED device. The dual functional polymeric semiconductors simultaneously ensure high field-effect mobility as well as light emitting properties. The working mechanisms have been thoroughly examined using various analytical measurements. The new approach enables the first demonstration of the OFET-PLED integrated device, which has been fabricated with a single semiconducting layer structure using printing.