• Journal of the Semiconductor & Display Technology
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• v.3 no.3
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• pp.31-35
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• 2004

A blue light emitting diode with 8 periods InGaN/GaN multi-quantum well structure grown by metal-organic chemical vapor deposition was fabricated with the inclusion of the metal-interconnection process in order to integrate the chips for light lamp. The quantum well structure provides the blue light photoluminescence peaked at 479.2 nm at room temperature. As decreasing the temperature to 20 K, the main peak was shifted to 469.7 nm and a minor peak at 441.9 nm appeared indicating the quantum dot formation in quantum wells. The current-voltage measurement for the fabricated LED chips shows that the metal-interconnection provides good current path with ohmic resistance of 41 $\Omega$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.153-156
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• 2005

In this study, we have investigated transient properties of top emission organic light emitting diode (OLED) with a red electrophosphorescent dopant. The emission spectrum shows a strong peak at 620 nm accompanied with a small peak at 675 nm in the red region. Time evolution of electrophosphorescence reveals a decay time of 703 ms at a voltage pulse of 5 V in a device with an emitting area of 20 $mm^2$. Rise and delay times vary from 450 to 14 ms and 73 to 3 ms, respectively, as the voltage amplitude increases from 4.5 to 10 V. These results are compared with the red emitting device without an electron injection layer.

• Journal of Information Display
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• v.7 no.4
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• pp.21-23
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• 2006

We developed a 4.5" 192${\times}$64 active matrix organic light-emitting diode display on a glass using organic thin-film transistor (OTFT) switching-arrays with two transistors and a capacitor in each sub-pixel. The OTFTs has bottom contact structure with a unique gate insulator and pentacene for the active layer. The width and length of the switching OTFT is 800${\mu}m$ and lO${\mu}m$ respectively and the driving OTFT has 1200${\mu}m$ channel width with the same channel length. On/off ratio, mobility, on-current of switching OTFT and on-current of driving OTFT were $10^6,0.3{\sim}0.5$ $cm^2$/V·sec, order of 10 ${\mu}A$ and over 100 ${\mu}A$, respectively. AMOLEDs composed of the OTFT switching arrays and OLEDs made using vacuum deposition method were fabricated and driven to make moving images, successfully.

• Advanced Industrial SCIence
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• v.1 no.1
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• pp.16-22
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• 2022

Starting with cathode ray tubes, displays are forming markets in the order of active marix organic light emitting diode (AMOLED) after PDP (Plasma Display Panel) and LCD (Liquid Crystal Display). OLED is recognized as a key field for the development of each country preparing for the fourth industrial revolution, and especially Samsung Display and LG Display, which are the top industries in Korea, are leading the market with more than 90% of OLED shares. Currently, AMOLED has moved to the area that can be folded or bent. This technology is possible because TFT (Thin Film Transistor) and OLED may be formed on a flexible substrate. In the future, the technology will move to stretchable displays, and for this, the development of substrate materials is first, and then TFT and OLED devices should also be implemented with stretchable materials.

• Proceedings of the KIEE Conference
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• 1998.07d
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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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• 1998.06a
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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 Information Display
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• v.9 no.3
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• pp.23-27
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• 2008

This paper reports that well-balanced white emission with three primary colors can be achieved with a simple white organic light-emitting diode (WOLED) structure of ITO / $\alpha$-NPD (50 nm) / $\alpha$-NPD: Btp2Ir(acac) (8 wt%, 6 nm) / $\alpha$-NPD (5 nm) / BCP (3 nm) / $Alq_3$: C545T (0.5 wt%, 10 nm) / $Alq_3$ (40 nm) / LiF (0.5 nm) / Al (100 nm). The external quantum efficiency of the device reached 3.8% at a current density (luminance) of 4.6 mA/$cm^2$ (310 cd/$m^2$), and the maximal luminance of the device reached 19,000 cd/$m^2$ at 11.5 V. The insignificant blue shift of the emitting color with an increasing current density can be attributed to the narrowing of the exciton formation zone width.

• Journal of Information Display
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• v.7 no.2
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• pp.26-30
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• 2006

Insertion of a thin lithium fluoride (TLF) layer between an emitting layer (EML) and an electron transporting layer has resumed in the developement of a highly efficient and bright organic light-emitting diode (OLED). Comparing with the performance of the device as a function of position with the TLF layer in tris-(8-hydroxyquinoline) aluminum $(Alq_{3})$, we propose the optimal position for the TLF layer in the stacked structure. The fabricated OLED shows a luminance efficiency of more than 20 cd/A, a power efficiency of 12 Im/W (at 20 mA/$cm^{2}$), and a luminance of more than 22 000 cd/$m^{2}$ (at 100 mA/$cm^{2}$), respectively. We suggest that the enhanced performance of the OLED is probably attributed to the improvement of carrier balance to achieve a high level of recombination efficiency in an EML.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.95-96
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• 2008

A new voltage-driven pixel circuit using soluble-processed organic thin film transistors (OTFTs) for an active matrix organic light emitting diode (AMOLED) is proposed. The proposed circuit is composed of four switching TFTs, one driving TFT and one storage capacitor. The proposed circuit can compensate for the degradation of OLED current caused by the threshold voltage shift of the OTFT. The simulation results show that the variation of OLED current corresponding to a 3V threshold voltage shift is decreased by 30% compared to the conventional 2TlC structure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.4
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• pp.379-385
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• 2006

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$(200{\AA})$/nitro-DPVT$(100{\AA})$/nitro-DPVT:$Rubrene(100{\AA})/BCP(70{\AA})/Alq_3(150{\AA})/Al(600{\AA})$. 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 $150{\AA}\;to\;200{\AA}\;to\;250{\AA}\;to\;300{\AA}$ 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 $250-{\AA}$ 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.