인쇄전자 및 광전자 소자 응용을 위한 직접 패터닝 된 고성능 플렉시블 전극 제작 및 특성평가

Abstract

Printed electronics is a key technology for realizing next generation of wearable electronics that are expected to be miniaturization, light-weight, and low-cost. Furthermore, the demand and development of printing and coating techniques has explosively increased in the scientific and technological fields. In general, the printed electronics includes not only a printing technique capable of patterning in a specific area such as inkjet printing, screen printing, or gravure printing but also a coating technique capable of quick deposition in a overall area such as meyer rod bar coating, spin coating, blade coating, or slot casting. The main focus of printed electronics is the production of functional ink or paste materials for the applications. Functional inks and pastes are specifically synthesized and formulated to meet the requirements (viscosity, solid contents, and size) of the printing or coating process. Next, it is important to select a printing or coating techniques appropriate for the properties of formulated inks and pastes. Lastly, the design of patterns and structures is necessary for the applications. The developed materials, printing or coating techniques, and designs can be easily applied to many areas including logic/memory devices of transistor, memory, and resistor; chemical sensor of gas sensor, bio-sensor, and vapor sensor; display of light emitted diode (LED), electrochromic, and backlight; energy of solar cell, battery, and supercapacitor. The overarching objectives of this dissertation are (1) to fabricate an inkjet-printed conductive tracks formed on the various flexible substrates using the developed Cu complex ion inks, (2) synthesis of p-typed copper sulfide nanoparticles (Cu2-xS NPs) with interesting optical properties and development of thermal shielding films utilizing a doctor blade coating, (3) to manufacture a transparent electrode of Ag nanowire network by a meyer rod bar coating. The synthesized Cu complex ion ink of metal organic decomposition (MOD) type could be lower the sintering temperature than the nanoparticle-based inks since the ligand-decomposed Cu atoms in Cu ion and organic complex were sintered. The printed Cu conductive features showed an excellent electrical and mechanical properties after sintering process. The Cu conductive tracks of various line width were easily fabricated by adjusting the droplet size ejected in inkjet printer. Additionally, the printed Cu conductive patterns were formed at low temperature and for short time using the hydrogen plasma and intense pulsed light (IPL) methods. The mechanical properties between the Cu conductive patterns and flexible substrates increased using the surface engineering of self-assembled monolayer (SAM). The copper sulfide nanoparticles absorb near-infrared (NIR, 800 - 2400 nm) region by a localized surface plasmon resonance (LSPR) property and ultraviolet (UV, 200 - 400 nm) region by a band gap. Because the above 52% of thermal energy to increase the temperature is concentrated in UV/NIR, the thermal shielding property of copper sulfide nanoparticles is remarkable. These nanoparticles have different optical property depending on the dispersibility, and the intensity of LSPR absorption and thermal shielding was dramatically reduced. In addition, it was confirmed that the different phases of Cu2-xS NPs has various carrier (hole) concentration and LSPR peak, and the actual thermal effect was systematically measured by a simulated experiment. In the transparent electrodes of optoelectronics, Ag nanowires with the diameter of 27 nm and the length 22 µm were synthesized and formulated the inks suitable for meyer rod coater. It is also fabricated the transparent conductive electrodes via the self-assembly of Ag nanowires network with a cell shape. The cell network of Ag nanowires with high optical transmittance and low sheet resistance was simply achieved on flexible polymer films. At last, the figure of merit between the cell shaped- and random Ag nanowires network (general method) was studied and demonstrated. In this dissertation, the work was divided into five chapters. Chapter 1 describes printed copper conductive electrode, thermal shielding material and transparent electrodes for optoelectronics. Chapter 2 describes the fabrication of Cu conductive features with excellent electrical conductivity and superior mechanical stability. Chapter 3 describes the synthesis of Cu2-xS NPs and analyses the thermal shielding properties. In this chapter, the silica on the surface of Cu2-xS NPs are coated for photo and disperse stability. Chapter 4 describes the development of superb transparent electrodes with Ag nanowires network of cell shape and explains the mechanism of cell structure. Chapter 5 summarizes this research.