• Transactions on Electrical and Electronic Materials
• /
• v.15 no.1
• /
• pp.45-48
• /
• 2014

We have investigated the effects of an Ag capping layer on the emission characteristics of transparent organic light-emitting devices with Ca/Ag double-layer cathodes. The thickness of the Ag layer was varied from 10 to 30 nm, whereas the Ca was fixed to be a 10 nm in the Ca/Ag structure. The luminance and current efficiency on the cathode and anode sides are significantly dependent on the Ag thickness. For example, the current efficiency on the anode side increases from 8.4 to 11.7 cd/A, whereas, on the cathode side, it decreases from 3.2 to 0.2 cd/A as the Ag thickness increases from 10 to 30 nm. These changes in emission characteristics were investigated by measuring electroluminescence, transmission, and reflection spectra.

• Korean Journal of Materials Research
• /
• v.27 no.6
• /
• pp.312-317
• /
• 2017

In the construction of a white LED, the region of the red emission is a very important factor. Red light emitting materials play an important role in improving the color rendering index of commercial lighting. These materials also increase the color gamut of display products. Therefore, the development of novel phosphors with red emission and the study of color tuning are actively underway to improve product quality. In the present study, heuristic algorithms were used to search for phosphors capable of increasing the color rendering index and color gamut. Using a heuristic algorithm, the phosphors that were identified were $SrGe_4O_9:Mn^{4+}$ and $BaGe_4O_9:Mn^{4+}$. Emission spectra study confirmed that these phosphors emit light in the deep red wavelength region, which can fulfill the requirement for the improvement in color rendering index and color gamut for a white LED.

• Journal of the Korean Applied Science and Technology
• /
• v.25 no.2
• /
• pp.265-268
• /
• 2008

Among the efforts to increase the efficiency of organic light-emitting device (OLED), there is a way: doping phosphorescent materials. As a phosphorescent material, complexes of heavy transition metal, platinum, were synthesized. $Cl^-$ ion and phenyl group were used as ancillary ligands with 2-(2-pyridyl)benzimidazole (pbi) as a chromophore. The complexes were analysed by FAB-mass spectrometer and absorption and emission spectra were obtained. A phenyl group was able to shift the emission band of the complex even if it's not a chromorphore.

• Proceedings of the KIEE Conference
• /
• 1999.11d
• /
• pp.997-999
• /
• 1999

We fabricated white light-emitting organic electroluminescent device which have a mixed single emitting layer containing poly(N-vinylcarbazole)[PVK], tris(8-hydroxyquinoline)aluminum[Alq3] and poly(3-hexylthiophene)[P3HT] and investigated the emission properties of it. We expect to obtain a blue light from PVK, green light from Alq3 and red light from P3HT The fabricated device emits white light over 18V with slight orange light. We think that the energy transfer in a mixed layer occurred from PVK to $Alq_3$ and P3HT resulted in decreasing the blue light intensity from PVK. With mixing of N, N'-diphenyl-N, N'-(3-methylphenyl)-[1,1'-biphenyl]-4, 4'-diamine[TPD], hole transport material, to the emitting layer, the luminance intensity of device was increased 50 times than that of the device which not contain TPD. We find that the efficiency of the white light electroluminescent device can be improved by injecting electron more effectively and blue light need to improve the color purity of white light.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.16 no.1
• /
• pp.8-13
• /
• 2008

Emissions from automobiles have long been considered a prime source of pollutants involved in smog formation and ozone production. Especially VOCs are associated with serious environmental problems such as photo-chemical smog as well as human health effects. Since motor vehicles are a major source of VOCs, estimating of emission from mobile source is the most important factor to control VOCs. VOCs are emitted from various pollution like motor vehicles, mobile and stationary source that has characteristics of toxicity, cancer-causing, bio-accumulation, durability in air and diffusion can exert a bad influence upon human health and environment. However we don't have any standard or regulation about VOCs emissions. This study is summarized as VOCs emission characteristics from in-use light-duty diesel and LPG fueled vehicles. The vehicle exhaust-gas test mode is CVS cycle and nier-10 cycles that developed on EPA and National Institute of Environmental Research. TO-14 method (Toxic Organic) was chosen for VOCs analysis from EPA in USA. This study results will be useful when make a emission factor and rule making of emission standard about domestic VOCs emission for the improve to air condition.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.12 no.4
• /
• pp.467-472
• /
• 2012

In this paper, we present a finite element method (FEM) study on the space charge effects in organic light emitting diodes. The physical model covers all the key physical processes in OLEDs, namely charge injection, transport and recombination, exciton diffusion, transfer and decay as well as light coupling, and thin-film-optics. The exciton model includes generation, diffusion, and energy transfer as well as annihilation. We assumed that the light emission originates from oscillation which thus is embodied as exciton in a stack of multilayer. We discuss the accumulation of charges at internal interfaces and their signature in the transient response as well as the electric field distribution. We also report our investigation on the influence of the insertion of the emission layer (EML) in the bilayer structure.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.4
• /
• pp.190-196
• /
• 2001

We measured 3-dimensional images of the light emitted from plasma display panel(PDP) by using newly proposed scanned point detecting method(SPDM). The SPDM has the point detector with pinhole. The light emitted from PDP cell at the in-focus position can pass through the pinhole and be collected by detector. On the contrary, the light emitted from PDP cell at the out-of-focus positions is focused on the front of or the behind of the pinhole. We could analyze the characteristic of 3-dimensional light emission distribution by SPDM. From 3-dimensional measurement of 828[nm], the efficient design of PDP cell, the importance of opening ration, and the relations between BUS electrode position and discharge intensity are obtained. Also, the relationship between discharge characteristics and sustain electrode structures in AC-PDP are studied by measuring luminance, current, and discharge voltage.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.577-580
• /
• 2000

We measured 3-dimensional images of the light emitted from plasma display panel(PDP) by using newly proposed scanned point detecting method(SPDM). The SPDM has the point detector with pinhole. The light emitted from PDP cell at the in-focus position can pass through the pinhole and be collected by detector. On the contrary, the light emitted from PDP cell at the out-of-focus positions is focused on the front of or the behind of the pinhole. We could analyze the characteristic of 3-dimensional light emission distribution by SPDM. From 3-dimensional measurement of 828nm, we found that the efficient design of PDP cell, the importance of opening ratio, and the relations between BUS electrode position and discharge intensity are obtained.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.8 no.6
• /
• pp.87-100
• /
• 2000

HC and CO emissions during the cold start contribute the majority of the total emissions in the legislated driving cycles. Therefore, in order to minimize the cold-start emissions, the fast light-off techniques have been developed and presented in the literature. One of the most encouraging strategies for reducing start-up emissions is to place the light-off catalyst, in addition to the main under-body catalyst, near the engine exhaust manifold. This study numerically consider three-dimensional, unsteady compressible reacting flow in the light-off and under body catalyst to examine the impact of a light-off catalyst on thermal response of the under body catalyst and tail pipe emission. The effect of flow distribution on the temperature distribution and emission performance have also been examined. The present results show that flow distribution has a great influence on the temperature distribution in the monolith at the early stage of warm-up process and the ultimate conversion efficiency of light-off catalyst is severly deteriorated when the space velocity is above $100,000hr^{-1}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.299-300
• /
• 2009

We have studied an organic layer and semitransparent Al cathode thickness dependent optical properties for top-emission organic light-emitting diodes. Device structure is ITO(170nm)/TPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/Al(100nm) and Al(100nm)/TPD(xnm)/$Alq_3$(ynm)/LiF(0.5nm)/Al(25nm). While a thickness of total, organic layer was varied from 85nm to 165nm, a ratio of those two layers was kept to be about 2:3. Then it was compared with that of bottom devices. And a thickness of semitransparent Al cathode was varied from 20nm to 30nm for the device with an organic layer thickness of 140nm. We were able to control the emission spectra from the top-emission organic light-emitting diodes.