SeungCheol Yang

Desalination via a new membrane capacitive deionization process utilizing flow-electrodes

A capacitive deionization process utilizing flow-electrodes (FCDI) was designed and evaluated for use in seawater desalination. The FCDI cell exhibited excellent removal efficiency (95%) with respect to an aqueous NaCl solution (salt concentration: 32.1 g L−1), demonstrating that the FCDI process could effectively overcome the limitations of typical CDI processes.

Ion storage and energy recovery of a flow-electrode capacitive deionization process

The ion storage and extraction (or the ion charge and discharge) of a continuous capacitive deionization system were investigated using novel flow-electrode capacitive deionization (FCDI). The flow-electrode, charged by constant voltage, generated about 20% of the supplied energy in an FCDI cell during constant current discharge with NaCl solution (concentration: 35.0 g L−1).

Rollable transparent glass-fabric reinforced composite substrate for flexible devices.

Recently, there has been considerable interest in fl exible displays, as they facilitate the fabrication of displays that are thin, lightweight, robust, conformable, and fl exible. [ 1 ] To enable a fl exible display, a fl exible substrate must be used as the fundamental starting component in place of a conventional glass substrate. In general, metal foils, ultra-thin glasses, and plastic fi lms are considered candidates for a fl exible substrate. [ 2 ] In particular, fl exible displays using plastic substrates based on organic polymers have been a major topic not only because these show outstanding fl exibility and optical clarity at the same time, but also because they offer the possibility of a reduction in cost, coupled with a roll-to-roll process and ink-jet printing technology. [ 3 ] Common examples of commercially available polymers are polyethylene terephthalate (PET), polyether sulfone (PES), polyethylene naphthalate (PEN), polycarbonate (PC), and polyimide (PI). [ 1 , 4 ] To replace conventionally used glass substrates, a plastic substrate must be equipped with the properties of glass, such as optical transparency, thermal/chemical stability, O 2 /H 2 O permeability, low birefringence (or retardation), dimensional stability, and a low coeffi cient of thermal expansion (CTE). [ 1 ] Among these properties, the low CTE of plastic substrates coupled with dimensional stability is arguably the most important requirement, as it is directly related to compatibility with all other necessary display layers to be integrated onto them. [ 1 ] Although there have been extensive studies of fl exible devices built on polymer substrates, such as electrophoretic displays and organic thin-fi lm transistors (OTFTs), little progress have been made even with high-temperature processed devices such as active-matrix liquid crystal displays (AMLCDs). [ 5 ] Major obstacles include the high CTEs of polymers insuffi cient for the display layer integrations. Moreover, polymers usually have low glass transition temperatures ( T g s) where abrupt CTE changes are accompanied. This greatly limits their practical application in terms of the process temperature. Even polymers with a high T g , e.g., PES, are known to have a CTE of ∼ 50 ppm K − 1 , much higher than the typically required level (less than 20 ppm K − 1 ). [ 1 ] Other highT g polymers such as polytetrafl uoroethylene (PTFE) and poly(ether ether ketone) (PEEK) also have signifi cant drawbacks for implementation into large-area plastic electronics, as they are unfavorable in terms of cost. PI has a low CTE of ∼ 20 ppm K − 1 and a high

Thermally Stable, Dye-Bridged Nanohybrid-Based White Light-Emitting Diodes

Thermally stable red and green light-emitting nanohybrids are introduced as an organic luminescent converter with broad color tunability and a high color rendering index for white light-emitting diodes (LEDs). Nanohybrid-based white LEDs are thermally stable and the color coordination is not changed by heat exposure.

High-performance hybrid plastic films: a robust electrode platform for thin-film optoelectronics

We report a novel flexible hybrid plastic film that can be used as a robust electrode platform for typical thin-film optoelectronic devices. Silver nanowires (AgNWs) were embedded on the surface of a glass-fabric reinforced transparent composite (GFRHybrimer) film to form a flexible transparent conducting substrate with excellent opto-electrical properties, superior thermal stability, and impressive mechanical flexibility. A highly efficient and flexible inverted organic solar cell with a power conversion efficiency (PCE) of 5.9% under 100 mW cm−2 AM 1.5G illumination was fabricated on the AgNW–GFRHybrimer film. The AgNW–GFRHybrimer film exhibits potential as an excellent transparent electrode for low cost flexible optoelectronic devices.

Thermally resistant UV-curable epoxy–siloxane hybrid materials for light emitting diode (LED) encapsulation

A UV-curable epoxy–siloxane hybrid material (epoxy hybrimer) was fabricated by photo-cationic polymerization of a sol–gel derived cyclo-aliphatic epoxy oligosiloxane (CAEO) blended with oxetane cross-linker in the presence of an onium salt. Antioxidants for fabrication of the UV-curable epoxy hybrimer with high thermal resistance against yellowing were incorporated in the UV-curable epoxy hybrimer. The UV-curable epoxy hybrimer with the antioxidants showed high thermal resistance without yellowing during 120 °C thermal aging. High thermal resistance of the UV-curable epoxy hybrimer was similar and higher compared to those of commercial thermally curable silicone and UV-curable epoxy LED encapsulants, respectively. The thermally resistant UV-curable epoxy hybrimer was successfully encapsulated on a LED without any cracking or delamination, and maintained a flat surface on the LED without distortion of the designed flat shape. Before/after thermal and blue light aging, the performance of the LED encapsulated by the UV-curable epoxy hybrimer was not changed. On the basis of its excellent properties as a LED encapsulant, the UV-curable epoxy hybrimer can be utilized as a UV-curable LED encapsulant for white LEDs.

Flow-Electrode Capacitive Deionization Using an Aqueous Electrolyte with a High Salt Concentration

Flow-electrode capacitive deionization (FCDI) is novel capacitive deionization (CDI) technology that exhibits continuous deionization and a high desalting efficiency. A flow-electrode with high capacitance and low resistance is required for achieving an efficient FCDI system with low energy consumption. For developing high-performance flow-electrode, studies should be conducted considering porous materials, conductive additives, and electrolytes constituting the flow-electrode. Here, we evaluated the desalting performances of flow-electrodes with spherical activated carbon and aqueous electrolytes containing various concentrations of NaCl in the FCDI unit cell for confirming the effect of salt concentration on the electrolyte of a flow-electrode on desalting efficiency. We verified the necessity of a moderate amount of salt in the flow-electrode for compensating for the reduction in the performance of the flow-electrode, attributed to the resistance of water used as the electrolyte. Simultaneously, we confirmed the potential use of salt water with a high salt concentration, such as seawater, as an aqueous electrolyte for the flow-electrode.

Highly Condensed Fluorinated Methacrylate Hybrid Material for Transparent Low-k Passivation Layer in LCD-TFT

Photocurable and highly condensed fluorinated methacrylate oligosiloxane, with a low dielectric constant (kappa = 2.54), was prepared by a nonhydrolytic sol-gel condensation reaction. The oligosiloxane resin was then spin-coated, photocured, and thermally baked in order to fabricate a fluorinated methacrylate hybrid material (FM hybrimer) thin film. This study investigated the application of this FM hybrimer film as a low-kappa passivation layer in LCD-based thin film transistors (TFT). It was found that a dielectric constant as low as kappa = 2.54 could be obtained, without introducing pores in the dense FM hybrimer films. This study compares FM hybrimer film characteristics with those required for passivation layers in LCD-TFTs, including thermal stability, optical transmittance, hydrophobicity, gap fill, and planarization effects as well as electrical insulation.

Photo-curable siloxane hybrid material fabricated by a thiol–ene reaction of sol–gel synthesized oligosiloxanes

The thiol-ene reaction of a sol-gel synthesized oligosiloxane thiol-ene mixture was processed through UV irradiation, resulting in transparency, high refractive index, good thermal stability and especially excellent electrical insulation materials. It provides new strong potential of the thiol-ene system for application in dielectric materials.

Highly Condensed Epoxy−Oligosiloxane-Based Hybrid Material for Transparent Low-k Dielectric Coatings

A highly condensed epoxy-oligosiloxane resin was synthesized using a sol-gel condensation reaction of (3-glycidoxypropyl)trimethoxysilane and diphenylsilanediol in the presence of solvent. A higher degree of condensation and a larger molecular size of oligosiloxanes were achieved compared to a condensation reaction without the addition of a solvent. The epoxy-hybrimer coating film was fabricated by the spin coating and thermal curing of the synthesized oligosiloxane resin. The leakage current density and the dielectric constant decreased from 25.9 to 7.6 nA cm(-2) and from 3.16 to 3.03, respectively, by using the solvent in the preparation. The hybrimer coating film of a highly condensed oligosiloxane resin had a high transmittance of over 90% in a wavelength between 300 and 800 nm. Thus, the epoxy-hybrimer coating film can be utilized as the passivation layer in the thin-film transistor.