• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.174-177
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• 2001

We have seen the effects of buffer layer in organic light-emitting diodes using poly(N-vinylcarbazole)(PVK). Polymer PVK buffer layer was made using spin casting techniques. Two different types of spin casting have been applied; static coating and dynamic coating. Two device structures were fabricated; one is ITO/TPD/Alq$_3$/Al as a reference, and the other is ITO/PVK/TPD/Alq$_3$/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage characteristics and luminous efficiency were measured with a variation of spin-casting methods and rpm speeds. We have obtained an improvement of luminous efficiency by a factor of two and half when the PVK buffer layer is used.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2000년도 제1회 학술대회 논문집
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• pp.115-116
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• 2000

Influence of sustain pulse-width on electro-luminous efficiency is experimentally investigated for surface discharge of AC-PDP. It is found that the firing voltage is decreased as the pulse-width is increased from $2\;{\mu}s$ to $8\;{\mu}s$ with sweeping frequency range of 10 kHz to 50 kHz. It has been found that the optimal sustain pulse-width is in the range of $3{\sim}4\;{\mu}s$ under driving frequency range of 30 kHz and 50 kHz, based on observations of memory coefficient, wall charge, and wall voltage as well as luminous efficiency.

• KIEE International Transactions on Electrophysics and Applications
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• 제11C권2호
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• pp.37-41
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• 2001

In this study, organic electroluminescent devices with the ITO/TPD/Alq$_3$/cathode structure, using various materials of Al, Mg:Ag, Al:Li, MgF$_2$/Al, and LiF/Al as cathodes, were fabricated. We investigated the electrical and optical properties of the devices as follow: current density-voltage(J-V), luminance-voltage(L-V) and luminous efficiency-voltage curves. The bilayer cathodes with LiF/Al and MgF$_2$/Al exhibited better device performance than the other cathodes. It is considered that the improved performance of the organic electroluminescent devices is attributable to the lowering of driving voltage caused by the enhanced electron injection. The alkaline-earth fluorides are desirable materials to improve the performance of the EL devices with the Al cathode, and high luminous efficiency was achieved.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.1815-1817
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• 2000

Plasma display Panels(PDPs) are one of the leading technologies currently under development for large-area high-brightness flat panel displays. However, the luminance and luminous efficiency of at PDPs should be improved. Especially, one of the main factors affecting on the luminance and luminous efficiency of ac PDP may be the phosphor thickness and size of discharge space. In this study, we examined into addressing time, electrical and optical properties as a parameter of the phosphor thickness and the size of discharge space during the display period of ac PDP. It is found out that the optimum phosphor thickness was $50{\mu}m$ and height of discharge space was about $100{\mu}m$.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권9호
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• pp.436-442
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• 2002

Recently color AC PDP(plasma display panel) technology is rapidly improved. However, the luminous efficiency improvement is a key issue for making plasma display into a large-area flat display. In this paper, we suggest a new concentration of Xe in He-Ne-Xe gas mixture in order to achieve a high luminous efficiency of color AC PDPs. We calculated the densities of 25 species as a function of the time zero dimensional simulation using CVODE solver and we compared the results of zero dimensional simulation with a measurement of photo wave brightness and luminous efficiency, in order to find the optimum mixing condition of He-Ne-Xe gas in color plasma display panel. We obtained a high discharge speed under Xe mixing ratio of 1% by simulation and confirmed that through measuring photo wave.

• 조명전기설비학회논문지
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• 제24권10호
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• pp.13-20
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• 2010

Until now, dimmable fluorescent luminaires has been widely used for dimming systems, and LED is currently attracting attentions as a alternative lamp due to environmental problem issues. LED, one of eco-friendly high efficiency lamp, has advantage that dimming is easy than fluorescent luminaire. But there have been not enough research on technical development and application for LED dimming. Therefore, to analyze luminous quantity of dimmable LED, the illuminance, color temperature, luminance, and current were measured in the whole range of dimming. In the results of this study, the dimmable LED of various types showed a similar trend in the changed luminous quantity by dimming.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
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• pp.59-62
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• 2004

We investigated the effect of Xe content variation on the luminous efficiency of two different sub-pixel types, i.e., segmented electrode in delta color arrayed enclosed sub-pixel (SDE) and conventional stripe barrier type, in an ac plasma display panel through three-dimensional numerical simulations. The conventional cell type was found to have higher VUV generation efficiency as compared with that of SDE structure, but as the Xe content increased, the SDE type showed higher improvements in efficiency due to the lower plasma loss to the barrier walls.

• KIEE International Transactions on Electrophysics and Applications
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• 제2C권5호
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• pp.253-257
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• 2002

A new Current-Controlled Driving Method that can drive AC PDPs with low voltage and high luminous efficiency for the sustaining period is presented. In this driving method, the voltage source is connected to a storage capacitor and the stored voltage is delivered to the panel through LC resonance. Thus, this driving method can drive the panel with a voltage source as low as about half of the voltage necessary in the conventional driving methods. The discharge current flowing into the AC PDP is limited in this method. Thus, the power consumption for the discharge is reduced and the discharge input power to output luminance efficiency is improved. Experimental results using this driving method showed that we could drive an AC PDP with a voltage source as low as 146V and that high luminous efficiency of 1.33 1m／W can be achieved.

• Journal of Information Display
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• 제5권4호
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• pp.7-11
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• 2004

Effects of base vacuum level on the electrical and optical characteristics of the plasma display panel (PDP) were investigated. The relationship between efficiency and base vacuum level before filling discharge gas was analyzed. For the base vacuum level of $1{\times}10^{-4}$ torr, firing voltage of a 2-inch diagonal PDP panel was 232 V at the discharge gas pressure of 400 torr and luminous efficiency was 1.5 lm/W at 180V sustaining pulse. On the other hand for $1{\times}10^{-6}$torr, the firing voltage was reduced to 215 V and luminous efficiency was improved considerably to 2.5 lm/W. We successfully demonstrated the smooth operation of tip-less PDP fabricated using vacuum in-line sealing method.

• Transactions on Electrical and Electronic Materials
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• 제17권1호
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• pp.37-40
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• 2016

Performance enhancement of organic light-emitting diodes (OLEDs) is investigated in a device structure of ITO/TPD/Alq₃/LiF/Al and ITO/TPD/Alq₃/BCP/LiF/Al. Here, bathocuproine (BCP) is used as an electron-transport layer. Current density-voltage-luminance characteristics of the OLEDs show that the performance of the device is better with BCP layer than without BCP layer. The current density, luminance, luminous efficiency, and external-quantum efficiency are improved by approximately 22%, 50%, 2%, and 18%, respectively. Since the BCP layer lowers the electron energy barrier, electron transport is facilitated and the movement of hole is blocked as the applied voltage increases. This results in an increased recombination rate of holes and electrons.