• KIEE International Transactions on Electrophysics and Applications
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• 제2C권6호
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• pp.292-296
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• 2002

A new sustain driving method for the AC PDP is presented. In this driving method, the voltage source is connected to a storage capacitor, this storage capacitor charges an intermediate capacitor through LC resonance, and the panel is charged from the intermediate capacitor indirectly. In this way, the current flowing into the AC PDP when the sustain discharge occurs is reduced because the current is indirectly supplied from a capacitor, a limited source of charge. Thus, the input power to the output luminance efficiency is improved. Since the voltage supplied to the storage capacitor is doubled through LC resonance, this method call drive an AC PDP with a voltage source of about half of the voltage necessary in the conventional driving methods. The experiments showed that this charge-controlled driving method could drive ail AC PDP with a voltage source of as low as 107V. Using a panel of the conventional structure, luminous efficiency of 1.28 lm/W was achieved.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.1070-1073
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• 2003

We have studied the characteristics of organic light-emitting diodes(OLEDs) with the PTFE buffer layer. The OLEDs have been based on the molecular compounds, N,N'-diphenyl-N,N'-bis (3-methylphenyl)-1, 1'- biphenyl-4, 4'-diamine (TPD) as a hole transport, tris(8-hydroxyquinolinoline) aluminum (III) ($Alq_3$) as an electron transport and the Polytetrafluoroethylene (PTFE) as a buffer layer. The devices of structure were fabricated ITO/PTFE/TPD(40nm)/$Alq_3$(60nm)/Al( 150nm) to see the effects of the PTFE buffer layer in organic EL devices. The thickness of the PTFE layer varied from 0.5 to 10[nm]. We were measured Current-Voltage-Luminance Characteristics and Luminance efficiency due to the variation of PTFE thickness. the PTFE layer was reported that helped to enhance the hole tunneling injection and effectively impede induim diffusion from the ITO electrode. We have obtained an improvement of luminance efficiency when the PTFE thickness is 0.5[nm] is used. The improvement of efficiency of is expected due to a function of hole-blocking of PTFE in OLEDs.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.427-428
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• 2008

New high efficiency green light emitting phosphorescent devices with emission layers of [TCTA/TCTA:TAZ/TAZ]:Ir$(ppy)_3$ have been fabricated and evaluated in this paper. Among the devices having different thicknesses of TCTA:TAZ mixed layer in the total 300$\AA$-thick host of TCTA(80$\AA$)/TCTA:TAZ (50~100$\AA$)/TAZ, the device with host of TCTA(80$\AA$)/TCTA:TAZ(90$\AA$)/TAZ(130$\AA$) showed the best electroluminescent characteristics with the current density of 95 mA/$cm^2$ and luminance of 25,000 cd/$m^2$ at an applied voltage of 10V. The maximum current efficiency was 52 cd/A under the luminance of 400 cd/$m^2$.

• 한국표면공학회지
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• 제50권5호
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• pp.398-404
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• 2017

In order to study the AC driving mechanism for OLED lighting, the fluorescent OLEDs were fabricated and the electroluminescent characteristics of the OLEDs by AC forward bias were analyzed. In the case of the driving method of OLED by AC forward bias under the same voltage and the same current density, degradation of luminescent characteristics for elapsed time progressed faster than in the case of the driving method by DC bias. These phenomena were caused by the peak voltage of AC forward bias which is ${\sqrt{2}}$ times higher than the DC voltage. In addition, the degradation of the OLED was accelerated because the AC forward bias had come close to the upper limit of the allowable voltage range even though the peak voltage didn't exceed the allowable range of the OLED. However, the fabricated fluorescent OLED showed little degradation of OLED characteristics due to AC forward bias from 0 V to 6.04 V. Therefore, OLED lighting by AC driving will become commercialized if sufficient luminance is realized at a voltage at which the characteristics of the OLED are not degradation by the AC driving method.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.229.1-229.1
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• 2016

본 연구에서는 Hole Transporting Layer(HTL)와 Electron Transporting Layer(ETL)의 두께에 의한 특성을 비교해보기 위해서 각각 0, 10, 20 nm로 HTL, ETL 두께를 달리한 형광 OLED소자를 제작하였다. ETL의 두께가 얇아질수록 $V_{TH}$ 값은 2.5V에서 0.9 V로 낮게 나타났고 소자의 전체 두께와 on voltage는 비례한다는 특성을 발견할 수 있었다. HTL과 ETL이 두꺼울수록 각 layer에서 carrier들의 이동에 delay가 생기고 emission layer에서 표면까지 거리가 생기기 때문이다. ETL의 두께가 두꺼울수록 높은 luminance 값을 나타내는 차이를 보여주고 있다. Hole에 비해 이동도가 작은 electron은 emission layer까지 늦게 전달되어, EML내에서 비교적 cathode쪽에 가까운 곳에서 exciton이 형성되기 때문이다. CE에도 더 두꺼운 ETL을 가진 소자가 더 높은 CE값 가짐을 확인할 수 있다. 모든 소자가 $200mA/cm^2$에서 가장 높은 CE값을 나타낸 이유는 $200mA/cm^2$에서 electron-hole 결합이 만들어내는 exciton형성이 가장 많기 때문이다. PE, QE도 ETL 두께가 두꺼울수록 특성을 향상이다. 결론적으로 ETL의 두꺼울수록 current density값이 감소함을 보이고 있는 반면 turn on voltage, luminance, efficiency 증가함을 볼 수 있다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권6호
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• pp.261-266
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• 2003

We investigated the effect of oxygen plasma treatment of indium-tin oxide(ITO) surface on the performance of electroluminescence(EL) devices. ITO surface treated oxygen plasma has been analyzed using atomic force microscope(AFM) and X-ray photoelectron spectroscopy(XPS), to investigate the relations between the properties of the ITO surface and the properties of the current-voltage-luminance(I-V-L) characteristics of the fabricated OLED with the structure of ITO(plasma treatment) / TPD / Alq$_3$/ Al. It is found that the oxygen plasma treatment of ITO anode improve the hole injection of the OLED due to the modification of the surface states. The treated ITO anode nay be low voltage with high luminance efficiency.

• 한국전기전자재료학회논문지
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• 제18권12호
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• pp.1143-1147
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• 2005

In this study, we report an improved efficiency of Organic light emitting diodes(OLEDs), using $UV/O_3$ treated anode and different cathode. We investigated the efficiency of OLEDs by $UV/O_3$ treatment of ITO surface. We Performed $UV/O_3$ treatment and found that $UV/O_3$ treatment enhanced the performance of OLEDs. The fundamental structure of the OLEDs was ITO $anode/{\alpha}-NPD/Alq_3/Al$ or Li:Al cathode. The Li:Al can improve the OLEDs efficiency dramatically in cathode because it has lower work function than Al. Current-voltage, Luminance-voltage characteristics and luminance efficiency were measured at room temperature.

• Journal of Information Display
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• 제2권4호
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• pp.39-45
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• 2001

The voltage controlled ramp(VCR) waveform has recently been introduced in the reset period prior to addressing for plasma display. However, this method results in the oscillation of the gap voltage when the ramp rate is increased so as to reduce reset period. In this paper a current controlled ramp(CCR) waveform method in the reset period is suggested. This method can suppress the oscillation of gap voltage under the condition of shorter ramp time. Moreover, the reset time can be reduced by about 30 % compared with the VCR method under the same background luminance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
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• pp.1890-1892
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• 2005

Recently, high luminance and high efficiency were realized in OLEDs with multilayer structure including emitting materials such as metal-chelate complexes. New luminescent materials, [2- (2-hydroxyphenyl)-quinoline] (Zn(HPB)q), [(1,10-phenanthroline)- (8-hydroxyquinoline)] Zn(Phen)q was synthesized. Zn-Complexes have low molecular compound and thermal stability. The ionization potential(IP) and electron affinity(EA) of Zn-complexes were measured by cyclic-voltammetry(CV). The fundamental structure of the OLEDs was $ITO/{\alpha}$-NPD/Zn-Complex/Al and then we made device structure rightly in energy band gap. We using Zn(Phen)q as emitting layer and Zn(HPB)q as electron transport layer. We measured current density-voltage, luminance-voltage characteristics.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제53권2호
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• pp.91-96
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• 2004

In darkroom condition, it was observed that a white picture pattern lasted several minutes leaves a recognizable trace in subsequent black background picture. Although this is not a serious problem for the most current public display or home TV applications, the image sticking should be minimized for future high quality multimedia display applications. In order to characterize this picture memory effect having relatively long time scale, spatially resolved luminance measurement and light waveform measurement have been performed. Pixels located at the outer boundary of white pattern previously displayed shows highest luminance. These cells also shows fastest ignition at the ramp up reset sequence. The luminance and ignition voltage differences between boundary cells and the other cells are increased with display duration and number of sustain-pulse. It is speculated that image sticking observed at the boundary cell is originated from the transport of charged particles and re-deposition of reactive species such as Mg, O provided from strong sustain discharge region.