Seok-Beom Yoon

A Development of Creative Capstone Design Education

This paper discusses the creative capstone design education in Kongju N ational University and introduce a new operational capstone design education m ethod. T he result products are evaluated by self-evaluation and perform ance assessment that is based on the operational m ethod and procedure of the project. The capstone design teams are comprised of 2~ 3 students w ith a individual major accomplishm ents. A ll team s are satisfied the criteria of evaluation. A nd theirs self-satisfaction and questionaries are totally 3.88~ 4.44 point out of 5. Compared w ith the conduct of previous capstone design project that w as not the industry affiliate, it provides students w ith industrial experience in design and developm ent of industrial solution. And industrial partner must provide funds for student team to desig n, fabrication and test in next time.

Fabrication of Geometric Sapphire Shaped InGaN/Al2O3 (S) LED Scribed by Using Wet Chemical Etching

The wet chemical etching method for etching V-grooves into sapphire substrates is used as scribing technique, and a geometric sapphire shaped InGaN/Al2O3 (S) light-emitting diode (LED) chip is fabricated. The V-groove is formed on the backside of a 150-µ-thick sapphire substrate by wet etching in a 3H2SO4:1H3PO4 chemical solution. The fabricated wet scribed geometric sapphire shaped LED exhibits a 15.86% enhancement in the light output power at 60-mA compared to the laser-stealth-scribed conventional rectangular LED. In addition, a ray-tracing simulation using “Light Tools” is performed on shaped geometric sapphire samples to investigate the enhancement of the light extracted from the substrate. The enhancement of the light output power for the wetscribed geometric sapphire shaped LED is thought to be due to the elimination of thermal damage and to an increase in light extraction from geometric sapphire shaped structure.

Fabrication of a White Organic Light Emitting Diode By Synthesizing a Novel Non-conjugated Blue Emitting Material PPPMA-co-DTPM Copolymer

To fabricate a single layer white organic light emitting diode (OLED), a novel non-conjugated blue emitting material PPPMA-co-DTPM copolymer was synthesized containing a perylene moiety unit with hole transporting and blue emitting ability and a triazine moiety unit with electron transporting ability. The devices were fabricated using PPPMA-co-DTPM copolymer by varying the doping concentrations of each red, green and blue fluorescent dye, by molecular-dispersing into Toluene solvent with spin coating method. In case of ITO/PPPMA-co-DTPM:TPB structure, as they were molecular-dispersing into 30 mg/ml Toluene solvent, nearly-pure white light was obtained both (0.325, 0.339) in the CIE coordinates at 18 V and (0.335, 0.345) at 15 V. The turn-on voltage was 3 V, the light-emitting turn-on voltage was 4 V, and the maximum external quantum efficiency was at 24.5 V. Also, in case of using 40 mg/ml Toluene solvent, the CIE coordinate was (0.345, 0.342) at 20 V.

Enhanced Luminous Intensity in LEDs with Current Blocking Layer

Abstract Inserting a SiO 2 layer underneath the p-pad electrode as the current blocking layer (CBL) structure and extending p-metal finger patterns, the GaN LEDs using an indium–tin-oxide (ITO) layer show the improved light output intensity, resulting from better current spreading and reduced light loss on the surface of p-pad metal. The LEDs with an oxide layer of 100 μm-pad-width and 6 μm-finger-width have better light output intensities than those with an oxide layer of 105 μm-pad-width and 12 μm-finger-width. Using the ATLAS device simulator from Silvaco Corporation, the current density distributions on the active layer in CBL LEDs have been investigated. Key Words : GaN LED, Current Blocking Layer, SiO 2 Layer, Current Spreading, Simulation Received 2 June 2014, Revised 4 July 2014Accepted 20 July 2014Corresponding Author: Kee-Young Kwon (Kongju National University) Email: kky@kongju.ac.krⒸ The Society of Digital Policy & Management. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is ISSN: 1738-1916 properly cited.

Analysis of the Characteristics of a White OLED using the Newly Synthesized Blue Emitting Material nitro-DPVT by Varying the Doping Concentrations of Fluorescent Dye and the Thickness of the NPB Layer

A stacked white organic light-emitting diode (OLED) having a blue/orange emitting layer was fabricated by synthesizing nitro-DPVT, a new derivative of the blue-emitting material DPVBi on the market. The white-emission of the two-wavelength type was successfully obtained by using both nitro-DPVT for blue~emitting material, orange emission as a host material and Rubrene for orange emission as a guest material. The basic structure of the fabricated white OLED is glass/ITO/NPB/nitro-DPVT/nitro-DPVT:. To evaluate the. characteristics of the devices, firstly, we varied the doping concentrations of fluorescent dye Rubrene from 0.5 % to 0.8 % to 1.3 % to 1.5 % to 3.0 % by weight. A nearly pure white-emission was obtained in CIE coordinates of (0.3259, 0.3395) when the doping concentration of Rubrene was 1.3 % at an applied voltage of 18 V. Secondly, we varied the thickness of the NPB layer from by fixing doping with of Rubrene at 1.3 %. A nearly pure white-emission was also obtained in CIE coordinates of (0.3304, 0.3473) when the NPB layer was thick at an applied voltage of 16 V. The two devices started to operate at 4 V and to emit light at 4.5 V. The external quantum efficiency was above 0.4 % when almost all of the current was injected.