Yonsang Kim

Transfer characteristics of ZnO thin-film transistors (TFTs) based on ZnO doped with various alkali metals. A new doping method is demonstrated by employing alkali metals to achieve high-performance and solution-processed ZnO TFTs with a low processing temperature (∼300 °C), which is applicable to flexible plastic substrates.

We demonstrated a new water motion active transducer (WMAT) without any external bias-voltage sources or additional processes, which critically limit the use of conventional passive capacitive transducers that convert mechanical motion into electric energy. From a simple structure, we successfully turned on an LED using various kinds of natural water motion. The WMAT, which has wide applicability, has good potential to be a candidate for generating sustainable electric energy.

An all-solution-processed flexible thin film piezoelectric nanogenerator is demonstrated using reactive zinc hydroxo-condensation and a screen-printing method. The highly elastic thin film allows the piezoelectric energy to be generated through the mechanical rolling and muscle stretching of the piezoelectric unit. This flexible all solution-processed nanogenerator is promising for use in future energy harvesters such as wearable human patches and mobile electronics. Detailed facts of importance

We have developed soft molding as a method for meso-scale-area fabrication of three-dimensional structures. The soft molding, which is a form of soft lithography, involves placing an elastomeric mold on the surface of a spin-coated polymer film with a slight pressure (<1 N/cm2), allowing the mold to absorb solvent, releasing the pressure, and then letting the mold and the substrate remain undisturbed for a period of time. The three-dimensional structure thus formed is robust in that the p

Solution-processed and alkali metals, such as Li and Na, are introduced in doped amorphous zinc tin oxide (ZTO) semiconductor TFTs, which show better electrical performance, such as improved field effect mobility, than intrinsic amorphous ZTO semiconductor TFTs. Furthermore, by using spectroscopic UV-visible analysis we propose a comprehensive technique for monitoring the improved electrical performance induced by alkali metal doping in terms of the change in optical properties. The change in th

Evaporation-induced electricity generation, harnessing natural vaporization of water, is spotlighted as a promising energy conversion system with showing off remarkable characteristics such as continuous generation without artificial water motions. However, the vague origin and mechanism of this phenomenon are obstacles for practical application. Herein, the origin of the evaporation-induced electricity generation was verified in terms of the "ionovoltaic" effect, ionic motion-induced charge car

Solution‐processed oxide semiconductors (OSs) used as channel layer have been presented as a solution to the demand for flexible, cheap, and transparent thin‐film transistors (TFTs). In order to produce high‐performance and long‐sustainable portable devices with the solution‐processed OS TFTs, the low‐operational voltage driving current is a key issue. Experimentally, increasing the gate‐insulator capacitances by high‐ k dielectrics in the OS TFTs has significantly improved the field‐effect mobi

A super-hydrophobic and highly transparent nanostructured film was fabricated via imprinting and conformally uniform chemical anchoring of poly(dimethylsiloxane) on a controlled nanoscopic dimension.

Recently, various energy transducers driven by the relative motion of solids and liquids have been demonstrated. However, in relation to the energy transducer, a proper understanding of the dynamic behavior of ions remains unclear. Moreover, the energy density is low for practical usage mainly due to structural limitations, a lack of material development stemming from the currently poor understanding of the mechanisms, and the intermittently generated electricity given the characteristics of the

Oxidation-resistant copper nanowires (Cu NWs) are synthesized by a polyol reduction method. These Cu NWs show excellent oxidation resistance, good dispersibility, and have a low sintering temperature. A Cu NW-based flexible, foldable, and free-standing electrode is fabricated by filtration and a sintering process. The electrode also exhibits high electrical conductivity even bending, folding, and free-standing.

In this work, a whole manufacturing process of the curved copper nanowires (CCNs) based flexible transparent conductive electrode (FTCE) is reported with all solution processes, including synthesis, coating, and networking. The CCNs with high purity and good quality are designed and synthesized by a binary polyol coreduction method. In this reaction, volume ratio and reaction time are the significant factors for the successful synthesis. These nanowires have an average 50 nm in width and 25-40 μ

We verified the origin of water-infiltration-induced electricity generation by an ionovoltaic effect, specifically, ion–surface interaction induced potential asymmetry in a porous CuO nanowire film.

Here we present an alternative, new, unconventional lithographic technique developed to create dense and multilevel nanostructure pattern transfer using a highly accurate polyurethane acrylate (PU, MINS101m, Minuta Tech.) mold and a polyelectrolyte multilayer as the adhesion promotion layer. Specifically, we demonstrate the pattern transfer of periodic 80 nm lines with 400 nm height and complex and multilevel nanostructures to a polymer layer on various substrates, such as Si or SiO2 wafers, gla

Solution-processed high-K dielectrics for oxide thin-film transistors (TFTs) have been widely studied with the objective of achieving high performance and low-cost TFTs for next-generation displays. In this study, we introduce an amorphous hafnium-lanthanum oxide (HfLaOx) gate insulator with high electrical permittivity which was fabricated by the simple spin-coating method. In particular, the solution-processed HfLaOx dielectric layer, which was achieved by a mixture of two Hf and La metal hydr