키랄 유기 반도체를 이용한 고성능 전자 소자 개발에 관한 연구

Abstract

Recently, social and industrial interests about chiral electronics are increasing because of a variety of potential applications in electronics including devices for circularly polarized light (CPL) detection and biomedical fields for chiral chemical or drug sensing. However, there are only few reported studies on these fields and the device performances for the detection of chiral components are not enough to be applied to practical applications. Herein, this thesis is dedicated to understanding of the supramolecular chirality via molecular design of chiral organic semiconductors and their self-assembly for chiral organic electronics applications such as CPL phototransistors and chiral biomedical sensors. In chapter 2, novel chiral organic semiconductors (OSCs), N,N-bis-(1-phenylethyl)perylene-3,4,9,10-tetracarboxyldiimide (CPDI-Ph), were designed and synthesized. Interestingly, homochiral nanowires (NWs) exhibited distinct circular dichroism (CD) spectra with a much higher dissymmetry factor (g factor) than the solution and thin film states did because of their supramolecular chirality. Moreover, heterochiral NWs showed chiral discrimination. Compared with heterochiral NWs, homochiral NWs displayed higher n-channel transistor performance, consistent with their short π-plane distances and large overlap for better charge transport. (S)-CPDI-Ph homochiral NWs presented an electron mobility of 0.058 cm2V-1s-1 in single NW-based phototransistor (OPT), surpassing reported values for p-channel organic chiral materials by two to three orders of magnitude. In addition, the resulting photoresponsivity (R) exceeded previous data obtained for phototransistors involving single NWs consisting of perylene diimides (PDIs) derivatives. Owing to their enhanced supramolecular chirality and photoresponsivity of the homochiral nanostructures, (R)- and (S)-CPDI-Ph NWs exhibited higher selectivity than their thin films in OPTs for circularly polarized light (CPL) sensing, which demonstrates that these newly developed chiral OSC nanostructures are highly promising for chiroptical sensing. In chapter 3, tuning of supramolecular chirality and optoelectronic properties in self-assembly of chiral organic semiconductors were investigated. We have systematically investigated the morphogenesis of chiral supramolecular self-assemblies of CPDI-Ph in different aggregation states using a binary solvent system of tetrahydro furan (THF) and water. Their dynamic aggregation processes have been analyzed by time-dependent in-situ UV-visible (UV-vis) spectroscopy, CD spectroscopy, and scanning electron microscopy (SEM). Due to the polarity of the solvent and the hydrophobic effect, the binary solvent system has yielded different morphologies depending on the DI water ratio (fw), which correspond well to their differing performance in OFETs. In addition, we have also utilized vibrational circular dichroism (VCD) to effectively discriminate the chiral PDI derivatives. In chapter 4, organic-inorganic hybrid chiral coordination polymers (CPs) were synthesized and their supramolecular chirality were investigated for chiral biomedical sensor applications. We introduce amino-acid functionalized naphthanelene diimides (NDIs) as organic linkers to construct novel multi-functional homochiral and heterochiral supramolecular biocoordination polymers (SBCPs) (i.e., AlaNDI-Zn) and use them as a platform to characterize chirality transcription of amino acids in biocoordination polymers. Unlike previous photoswitchable CPs that use reversible structural or geometrical changes of the ligands upon light irradiation, we developed photochromic and photoswitchable SBCPs with redox NDI ligands. The mechanism can be assigned to the formation of radical anions in SBCPs upon exposure to UV light. Besides, SBCPs have been applied for photoluminescence (PL) sensing of a trace amount of the harmful chemical hydrazines with a concentration of 10−7 M, which is two orders of magnitude lower than the detection limit in previous reports. This simple and feasible method can be used to sense a low concentration of electron-rich amines. Furthermore, we used insulating SBCPs for chemiresistive sensing of common alcohols, such as methanol and ethanol, which supports the use of CPs with low conductivity for future sensing applications.