서강대학교

초록

Since the first demonstration of electrogenerated chemiluminescence or electrochemiluminescence (ECL) from organic molecules in the 1960s, considerable scientific effort has been devoted to utilizing this phenomenon, particularly in the field of chemical/bioanalytical analysis and sensors. Several ECL-based analytical techniques for clinical analysis, environmental monitoring, food analysis, bioanalysis, and chemical detection have been proposed. This benefit comes from the sensitivity of the ECL process. The ECL process exhibits high reaction selectivity because only the reaction amount can be controlled by adjusting the electrode potential. Additionally, because ECL-based analysis and sensing techniques operate without the usage of an external light source, a simple system with a very low background noise level can be produced. As a result, ECL has been widely used with high utilization as a probe technology for detecting a very small amount of analytes. Recently, research has been actively conducted to propose an alternative device platform using ECL for lighting or display devices. The trend of future device technology is soft electronics, with deformable (follderable, bendable, etc.). In this respect, ion-based electronics has an advantage in that it enables a device having a new architecture that may not be realized by conventional electronic devices, and based on this, it can be proposed as a new display technology. To improve this concept, this thesis comprehensively studied the electrochemiluminescent systems for light-emitting devices composed of ionic liquids. To begin, Chapter 1 discusses the fundamental ECL theory and the material properties of ionic liquids, which constitute the title. The ECL phenomenon, in which light is generated as a consequence of an electrochemical reaction, is a pretty classic concept. Although the reaction mechanism is well-known, it is briefly reviewed herein. Ionic liquids, another component of the title, are indeed a liquid phase at room temperature despite being contained entirely of ions only. Notably, it is emerging as an alternative to conventional chemical solvents. Moreover, it might replace an organic solvent-based electrolyte solution as a revolutionary electrolyte. At the closing of the chapter, the reasons for adopting ECL and ionic liquids throughout the entire Ph.D. period are discussed, so establishing and enhancing the necessity for electrochemical systems to be used as light sources. The following section, Chapter 2, delves into the operations of the ECL devices. Obviously, ECL is a well-known process in bio-applications, and it employs ECL as an ultra-sensitive technology with low-intense dim light. However, it may be processed to make intense light based on a massive amount of chemical reactions and even in the form of a device. In this scenario, it is essential to understand not only the reaction mechanism inside the circumstance but also the operating mechanism as a device. To this goal, we explain the operating mechanism of ECLD that distinguishes "ionic transfer" from other types of electronics. This recommends applying the pulsed method for more intelligent operation of ECLD. The frequency dependency of AC-pulse driving was explained from the perspective of thermodynamics(mass transports) and kinetics(reaction rates). On the basis of an explanation of the galvanostatic mode in which the electrochemical system is controlled by current, a strategy for enhancing the device's lifetime is suggested. Furthermore, Chapter 3 covers gel-type luminescent active layers incorporating polymer matrix. Leakage is the most significant flaw of liquid-based systems. Due to leakage concerns, it is inevitably more challenging to organize a liquid phase into a device than a solid state. So, it can be effectively solved by enclosing the ionic liquid in the polymer matrix of the organo-gel. In addition, based on the proof results that effective mass transfer occurs even in such a gel-type medium, the previous section about the device operating mechanism is still appropriate. At the end of the chapter, the results of using a gel-type active layer formed of thermoplastic polyurethane with excellent mechanical properties to make an ECL gel that can be stretched and deformable will be described. Finally, in Chapter 4, the ECLD will be shown using a novel device architecture. An electrochemical-based device can also be driven even in a device structure that is not currently implemented in a commonly utilized electronic device. As an example, the ECLD could be configured in parallel in some kind of a coplanar electrode structure, and with this advance, a light-emitting device without a transparent electrode that could not be realized in a conventional light-emitting device could be done. Furthermore, device operating stability may be improved by using a revolutionary device architecture with a floating electrode, which is a third electrode that is not coupled to an external power source. Overall, through a study undertaken over the Ph.D. course, it is possible to help clarify a device operating mechanism of an electrochemistry-based device, optimize device characteristics based on the operating mechanism, and introduce unique materials for a deformable device that retains electrochemical characteristics and demonstrates a superior response to mechanical stimuli. Moreover, utilizing a novel device architecture suited for operating an electrochemically-based device can improve the operating characteristics. We hope that the results of this comprehensive research will contribute in a minor but meaningful direction to the widespread acceptance of several electrochemically-based electronics.