Jun Hee Han

Highly conductive and flexible color filter electrode using multilayer film structure

In this paper, a high performance flexible component that serves as a color filter and an electrode simultaneously is suggested. The suggested highly conductive and flexible color filter electrode (CFE) has a multilayer film structure composed of silver (Ag) and tungsten trioxide (WO3). The CFE maintained its color filtering capability even when the films were bent on a polyethylene terephthalate (PET) film. Low sheet resistance of the CFE was obtained using WO3 as a bridge layer that connects two Ag layers electrically. The sheet resistance was less than 2 Ω/sq. and it was negligibly changed after bending the film, confirming the flexibility of the CFE. The CFE can be easily fabricated using a thermal evaporator and is easily patterned by photolithography or a shadow mask. The proposed CFE has enormous potential for applications involving optical devices including large area devices and flexible devices.

Highly Conductive Transparent and Flexible Electrodes Including Double-Stacked Thin Metal Films for Transparent Flexible Electronics

To keep pace with the era of transparent and deformable electronics, electrode functions should be improved. In this paper, an innovative structure is suggested to overcome the trade-off between optical and electrical properties that commonly arises with transparent electrodes. The structure of double-stacked metal films showed high conductivity (<3 Ω/sq) and high transparency (∼90%) simultaneously. A proper space between two metal films led to high transmittance by an optical phenomenon. The principle of parallel connection allowed the electrode to have high conductivity. In situ fabrication was possible because the only materials composing the electrode were silver and WO3, which can be deposited by thermal evaporation. The electrode was flexible enough to withstand 10 000 bending cycles with a 1 mm bending radius. Furthermore, a few μm scale patterning of the electrode was easily implemented by using photolithography, which is widely employed industrially for patterning. Flexible organic light-emitting diodes and a transparent flexible thin-film transistor were successfully fabricated with the proposed electrode. Various practical applications of this electrode to new transparent flexible electronics are expected.

Microcavity effect using nanoparticles to enhance the efficiency of organic light-emitting diodes.

In this paper, in contrast with previously reported approaches, we suggest exploiting a microcavity effect using nanoparticles to improve the optical efficiency of organic light-emitting diodes (OLED). The method to input the nanoparticles inside the OLED device is simple and cost effective by virtue of employing a solution process using a spin coating fabrication method. Titanium dioxide (TiO2) nanoparticles were used to improve the reflection by its high refractive index. In tandem with optimized heights of the organic layers, the increased light reflectance at the anode side, which includes the TiO2 nanoparticle layer, improved the optical efficiency of the OLED device via the microcavity effect. In order to prove that the enhancement of the optical efficiency was due to an enhanced microcavity effect caused by TiO2 nanoparticles, a microcavity simulation was conducted. The electrical characteristics were not affected by the nanoparticles and a clear pixel image was maintained. The results in this paper show that a nanoparticle based microcavity effect can be exploited to enhance the optical efficiency of OLEDs.