신축성 전자 소자를 위한 유기물 반도체의 미세 구조 제어

Abstract

Research on intrinsic stretchable organic semiconductor is receiving a lot of attention in recent years to develop of next generation electronics. However, most of studies have fatal drawbacks, particularly in charge carrier mobility degradation and inconstant microstructure by phase separation. By this motivation, I have done the research on effectively maintaining the charge carrier transport properties and universally applicable to develop of stretchability without phase separation. These results were achieved by controlling the microstructure of the organic semiconductor. In chapter 1, I summarized the research trend of the stretchable electronics and current status of stretchable organic semiconductor. And I introduce the basic concept of organic field-effect transistors (OFETs) about operational principle and device configurations. After that, the principle of mechanical properties of organic semiconductor were reviewed. Finally, the objective and motivation of this thesis are introduced. In chapter 2, the effect on mechanical and electrical correlation of isolated thiophene rings and fused thiophene rings have been studied. It is found that the polymer composed of isolated thiophene moiety (DPP-3T, DPP-4T) is more ductile than the polymer composed of fused thiophene moiety (DPP-DTT, DPP-TVT). The isolated thiophene units can rotate freely that results in a low glass transition temperature of the polymer backbone, and highly entangled with each polymer segments. Detailed microstructure analysis suggests that flexible backbone polymer show alignment in the strain direction but brittle backbone polymer show fracture at low strain. Crystallography evidences suggest that the isolated thiophene moiety polymers had low relative crystallinity ratio. And strain induced OFETs based on isolated thiophene moiety polymers had high charge carrier mobility compared to fused thiophene moiety polymers. Therefore, the isolated ring moiety polymers are more stretchable than fused ring moiety polymers. In chapter 3, I proposed a system to develop of stretchable organic semiconductor through crosslinking with low crystalline polymer (IDT-BT) and azide terminated crosslinker. After crosslinking these two components resulted in superior mechanical and electrical properties at a high strain. Microstructure analysis suggests that crosslinked polymer show a low aggregation of polymer backbone with relatively low content of crystallinity ratio compared to non-crosslinked polymer. Based on these studies, the mechanism of stretchable organic semiconductor through crosslinking was suggested comparing with various crystallinity polymer (regiorandom-P3HT, regioregular-P3HT, DPP-DTT). Therefore, it is a strategy to improve stretchability through crosslinked low crystalline polymer.