김세현 교수

Here we summarize recent progress in the development of electrolyte-gated transistors (EGTs) for organic and printed electronics. EGTs employ a high capacitance electrolyte as the gate insulator; the high capacitance increases drive current, lowers operating voltages, and enables new transistor architectures. Although the use of electrolytes in electronics is an old concept going back to the early days of the silicon transistor, new printable, fast-response polymer electrolytes are expanding the

We report performance optimization and stability analysis of aerosol-jet-printed electrolyte-gated transistors (EGTs) based on the polymer semiconductor poly(3-hexylthiophene) (P3HT). EGTs were optimized with respect to printed P3HT thickness and the completed device annealing temperature. EGTs with relatively thin P3HT films (∼50 nm) annealed at 120 °C have the best performance and display an unusual combination of metrics including sub-1-V operation, ON/OFF current ratios of 10(6), OFF current

Abstract An eco‐friendly biodegradable starch paper is introduced for use in next‐generation disposable organic electronics without the need for a planarizing layer. The starch papers are formed by starch gelatinization using a very small amount of 0.5 wt% polyvinyl alcohol (PVA), a polymer that bound to the starch, and 5 wt% of a crosslinker that bound to the PVA to improve mechanical properties. This process minimizes the additions of synthetic materials. The resultant starch paper provides a

Dual-function electrochromic supercapacitors (ECSs) that indicate their real-time charge capacity in color are fabricated using tungsten trioxide (WO₃) and Li-doped ion gels containing hydroquinone (HQ). The ECSs can simultaneously serve as either electrochromic devices or supercapacitors. The coloration/bleaching and charging/discharging characteristics are investigated between 0 and -1.5 V. At the optimal HQ concentration, large transmittance contrast (∼91%), high coloration efficie

Abstract A chemically coupled polymer layer is introduced onto inorganic oxide dielectrics from a dilute chlorosilane‐terminated polystyrene (PS) solution. As a result of this surface modification, hydrophilic‐oxide dielectrics gain hydrophobic, physicochemically stable properties. On such PS‐coupled SiO 2 or AlO x dielectrics, various vacuum‐ and solution‐processable organic semiconductors can develop highly ordered crystalline structures that provide higher field‐effect mobilities ( μ FET s) t

Low-operating-voltage organic field-effect transistor has been realized by using the cross-linked cyanoethylated poly(vinyl alcohol) (CR-V) as a gate dielectric. The cross-linked CR-V dielectric was found to have a high dielectric constant of 12.6 and good insulating properties, resulting in a high capacitance (92.9nF∕cm2 at 20Hz) for a dielectric thickness of 120nm. A pentacene field-effect transistor fabricated with the cross-linked CR-V dielectric was found to exhibit a high carrier mobility

Tuning of the energetic barriers to charge transfer at the semiconductor/dielectric interface in organic field-effect transistors (OFETs) is achieved by varying the dielectric functionality. Based on this, the correlation between the magnitude of the energy barrier and the gate-bias stress stability of the OFETs is demonstrated, and the origin of the excellent device stability of OFETs employing fluorinated dielectrics is revealed.

In this study, we propose low power consumption, all-in-one type electrochromic devices (ECDs) for effective heat shutters. Considering diffusion-controlled device operation, polymeric viologens (poly-viologens) are synthesized to lower the diffusivity of EC chromophores and to minimize self-bleaching. In comparison with devices based on mono-viologens corresponding to the monomer of poly-viologens, poly-viologen-containing ECDs exhibit advantages of lower coloration voltage (ca, -0.55 V) and hi

Electrohydrodynamic jet printing is a promising technology for high-resolution direct printing. This review provides a comprehensive summary of the fabrication and printing methods of various functional materials (and inks) for practical devices.

We demonstrate the origin and mechanism of the hysteresis behavior that is frequently observed during the operation of organic field-effect transistors (OFETs) based on polymer gate dielectrics. Although polar functionalities, such as hydroxyl groups, present in the polymer gate dielectrics are known to induce hysteresis, there have only been a few detailed investigations examining how the presence of such end functionalities both at the polymer surface—forming an interface with the semiconducto

Abstract MXenes are interesting 2D materials that have been considered as attractive frontier materials for potential applications in the fields of energy and electronic devices due to their excellent optoelectronic properties including metallic conductivity and high optical transparency. However, it is still challenging to achieve compatibility for the as‐synthesized MXene nanosheets with simple solution‐deposition and patterning processes because of their limited solubility in many solvents. H

Low-voltage tungsten trioxide (WO₃)-based electrochromic devices (ECDs) are successfully demonstrated.

Flexible electrochromic devices (ECDs) based on Li-doped ion gels and tungsten trioxide (WO3) are demonstrated. Colored ECDs cannot be produced using conventional ion gels comprised of copolymers and room temperature ionic liquids (RTILs) due to a lack of cations that can be inserted into WO3. Based on considerations of the coloration mechanism, we developed Li-doped ion gels and applied these to devices. The effects of Li salt concentration are systematically examined, with respect to device dy