• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.67-68
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• 2006

Organic light-emitting devices (OLEDs) with the high efficiency and long lifetime are of growing interest in next-generation displays. Among the factors influencing OLEDs properties, one of unstable factor is $Alq_3$ cationic species caused by the excess holes resided in $Alq_3$ layer. Therefore, we suppressed the accumulation of excess holes by using the mixed-hole transporting layer (MHTL) of NPB and CBP in multilayer green OLEDs. The devices with MHTL showed improved characteristics in the luminance efficiency and lifetime. More characteristics and the carrier transport mechanism will be discussed.

• International journal of advanced smart convergence
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• 제12권4호
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• pp.1-7
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• 2023

Large-size, organic light-emitting device (OLED) panels based on highly reliable gate driver circuits integrated using InGaZnO thin film transistors (TFTs) were developed to achieve ultra-high resolution TVs. These large-size OLED panels were driven by using a novel gate driver circuit not only for displaying images but also for sensing TFT characteristics for external compensation. Regardless of the negative threshold voltage of the TFTs, the proposed gate driver circuit in OLED panels functioned precisely, resulting from a decrease in the leakage current. The falling time of the circuit is approximately 0.9 ㎲, which is fast enough to drive 8K resolution OLED displays at 120 Hz. 120 Hz is most commonly used as the operating voltage because images consisting of 120 frames per second can be quickly shown on the display panel without any image sticking. The reliability tests showed that the lifetime of the proposed integrated gate driver is at least 100,000 h.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.1591-1594
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• 2006

In this work, we fabricated efficient white organic light emitting device (WOLED) by the stack of complementary fluorescent dye-doped layers, Effect of dye-doping ratio and thickness of each layers on WOLED efficiency and emission spectrum was investigated. Moreover, out-coupling efficiency enhancement using microlens array was analyzed for bottom and top-emitting device architecture, leading to higher light extraction properties.

• Proceedings of the KIEE Conference
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• 대한전기학회 1998년도 하계학술대회 논문집 D
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• pp.1358-1360
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• 1998

In this paper, organic thin film LED(light emitting diode) having ITO glass/$Alq_3$/Al structure using an $Alq_3$ was fabricated by the vacuum evaporation and the absorbance, wave length, 1-V characteristics were investigated. Electroluminescence of green and wavelength of 510[nm] were observed in this device. We observed absorbance form 320[nm] to 430[nm] and knew unstability of $Alq_3$ material as light emitting device.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.439-442
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• 1998

In this paper, organic thin film LED(light emitting diode) having ITO glass/Alq$_3$/Al structure using an Alq$_3$ was fabricated by the vacuum evaporation and the absorbance, wave length, I-V characteristics were investigated, Electroluminescence of green and wavelength of 510[nm] were observed in this device. We observed absorbance form 320[nm] to 430[nm] and knew unstability of Alq$_3$ material as light emitting device.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제23권8호
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• pp.638-644
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• 2010

We have carry out numerical simulation of the electric-optical characteristics of organic light emitting diodes with gradient-doped emitting layer which were reported to be effective in improving luminous efficiency and lifetime. In this paper, the basic structure is comprised of ITO/NPB/$Alq_3$:C545T[%]/$Alq_3$/LiF/Al, six devices by separating the emitting layer of $Alq_3$:C545T[%] were studied. As the result, the uniformly-doped devices exhibited superior luminous efficiency-current density characteristics over conventional undoped device. In the case of gradient-doped devices, electric-optical characteristics were improved similar to uniformed-doped devices, unusually the distribution of traped-charge density in the OLED devices was shown as the staircase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.277-278
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• 2009

We have studied an angular dependence of emission pattern of top-emssion organic light-emitting diodes (TEOLED). Device structure is Al(100nm)/TPD(40nm)/$Alq_3$(60nm)/LiF(0.5nm)/Al(2nm)/Ag(30nm). N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) and tris-(8-hydroxyquinoline) aluminium ($Alq_3$)were used as a hole transport layer and emission layer, respectively. Organic layers and cathode were thermally evaporated at $2\times10^{-5}$torr. The evaporation rate of the organic material was maintained to be $1.5\sim2.0{\AA}/s$, and that of metal layer to be $0.5\sim5{\AA}/s$. A transmittance of a cathode electrode(Al/Ag) in visible region is about 25~30%. In order to measure view-angle dependent intensity, electroluminenscence spectra of the device at each angle were integrated. Angle dependent emission spectra of the device do not show blue shift. Emission intensity of the device that the going straight characteristic is stronger the bottom-emission organic light-emitting diodes is shown.

• Transactions on Electrical and Electronic Materials
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• 제10권1호
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• pp.28-30
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• 2009

We have studied organic layer-thickness dependent electrical and optical properties of bottom- and top-emission devices. Bottom-emission device was made in a structure of ITO(170 nm)/TPD(x nm)/$Alq_3$(y nm)/LiF(0.5 nm)/Al(100 nm), and a top-emission device in a structure of glass/Al(100 nm)/TPD(x nm)/$Alq_3$(y nm)/LiF(0.5 nm)/Al(25 nm). A hole-transport layer of TPD (N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine) was thermally deposited in a range of 35 nm and 65 nm, and an emissive layer of $Alq_3$ (tris-(8-hydroxyquinoline) aluminum) was successively deposited in a range of 50 nm and 100 nm. Thickness ratio between the hole-transport layer and the emissive layer was maintained to be 2:3, and a whole layer thickness was made to be in a range of 85 and 165 nm. From the current density-luminance-voltage characteristics of the bottom-emission devices, a proper thickness of the organic layer (55 nm thick TPD and 85 nm thick $Alq_3$ layer) was able to be determined. From the view-angle dependent emission spectrum of the bottom-emission device, the peak wavelength of the spectrum does not shift as the view angle increases. However, for the top-emission device, there is a blue shift in peak wavelength as the view angle increases when the total layer thickness is thicker than 140 nm. This blue shift is thought to be due to a microcavity effect in organic light-emitting diodes.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제22권4호
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• pp.323-326
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• 2009

We have developed blue-emitting phosphorescent organic light emitting diodes (OLEDs) using 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and tris (8-quinolinolato)aluminum ($Alq_3$) electron transport layers. As blue dopant and host materials, bis[(4,6-di-fluorophenyl)-pyridinate-N,C2']picolinate (FIrpic) and N,N'-dicarbazolyl-3,5-benzene (mCP) were used, respectively. The driving voltage, current efficiency and emission characteristics of devices were investigated. While the driving voltage was about $1{\sim}2$ V lower in the device with an $Alq_3$ layer, the current efficiency was about 66 % higher in the device with BCP electron transport layer. the blue phosphorescent OLED with BCP layer exhibited higher purity of color, resulting from a relatively weak electroluminescence intensity at 500 nm.

• Proceedings of the KIEE Conference
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1281-1282
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• 2008

Low cost TCO(Transparent Conductive oxide) thin films were prepared by 3" DC/RF magnetron sputtering systems. For the AZO preparation processes a 99.99% AZO target (Zn: 98 wt.%, $Al_2O_3$: 2 wt.%) was used. In order to verify feasibility of the AZO thin films to organic light emitting device (OLED) application, test organic light emitting device was fabricated based on AZO as TCO, TPD as hole transporting layer (HTL), Alq3 as both emitting layer (EML) and electron transporting layer (ETL), and aluminium as cathode, where the both ITO and AZO surfaces were treated using $O_2$ RF plasma. The I-V characteristics of the AZO/TPD/Alq3/Al OLEDs were evaluated. As the results, the performance of the OLEDs with AZO as transparent conducting anode could be useable.