• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.936-940
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• 2005

IMML(Inorganic metal multi-layer) was used as cathode in the OLED devices to reduce the reflectance or ITO and increase the contrast ratio. Device structure was $ITO/{\alpha}-NPD/Alq_3:DCJTB/Alq_3/IMML/Al$. $Alq_3$ and DCJTB (4 - (dicyanomethylene) - 2 - ( 1 - propyls) 6 - methy 4H - pyrans) as host material lot red emission and red emitting guest material. IMML made three different layer: thin aluminum layer, aluminum layer doped with silicon monoxide, thick aluminum layer. The red OLED device with IMML showed the average reflectance of $4.97\%$, and then normal OLED with or without polarizer showed the average reflectance of $4.55\%$, $46\%$ at visible range from 380 nm to 780 nm. The brightness of OLED with IMML at 13 V was 5557 $cd/m^2$, and that of normal OLED with polarizer was 4872 $cd/m^2$. IMML could be the substitution for polarizer with same reflection, low cost, easy process in flat panel display market.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.10
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• pp.941-944
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• 2005

In this experiment, OLEDs(Organic Light Emitting Diodes) was fabricated to confirm effect of Plasma treatment which increase the hole injection characteristic from anode. Device structure was $ITO/2-TNATA/{\alpha}-NPD/DPVBi/BAlq/Alq_3/Al:Li$. We used DPVBi (4, 4 - Bis (2,2-diphenylethen-1-yls) - Biphenyl) as a blue emitting material. To optimize the process condition of plasma treatment, we used 2 gases of the oxygen and nitrogen gas under 120 mTorr with 100 W, 200 W, and 400 W plasma power. The current efficiency of $N_2$ plasma is more efficient than that of $O_2$ plasma. At $1000 cd/m^2$, we obtained the maximum current efficiency of 6.45 cd/A using $N_2$ gas with 200 W plasma power.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.939-942
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• 2001

We fabricated Red Organic light-emitting devices(OLED). The Basic Device Structure is ITO/hole transfer layer, TPD(50nm)/red emitting layer, Alq3 doped with DCM2 or DCM2:rubrene(xnm)/electorn transfer layer, Alq3(50-xnm)/LiF(0.8nm)/Al(8nm) . The thickness of emitting layer(xnm) changed 5, 10, 20nm. we demonstrate red emitting OLED with dependent on the thickness and concentrators of Alq3 layer doped with DCM2 or co-doped with DCM2:ruberene. The Emission color and Brightness are changed with doping or co-doping condition, dopant concentarton. In the case of rubrene:DCM2 co-doped layer structure, the red color Purity and device efficiency is improved. The CIE index of rubrene co-doped OLED is x=0.67, y=0.31. By co-doping the Alq3 layer with DCM2, rubrene, EL efficiency improved from 0.38cd/A to 0.44cd/A in comparison whit DCM2 doped Alq3 layer.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.1
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• pp.83-88
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• 2004

BAlq was fabricated as for hole blocking layer in the OLED devices to investigate its electrical and optical characteristics. Device structure was ITO/$\alpha$ -NPD/EML/BAlq/Alq3/Al:Li using TYG-201, DPVBi (4, 4 - Bis (2, 2 - diphenylethen-1 - yls) - Biphenyl), Alq and DCJTB (4-(dicyanomethylene)-2- (1-propyls)6-methy 4H-pyrans) as green emitting material, blue emitting material, host material for red emission and red emitting guest material respectively. The OLED device showed optimum working voltage and electron density at 600 cd/$m^2$ when thickness of BAlq is 25$\AA$ for RGB OLED devices while their efficiencies are better at 50$\AA$ of BAlq. Red and blue color OLEDs also fabricated using 30$\AA$ thickness of BAlq and compared with those without BAlq layer. BAlq was more effective in electrical properties such as working voltage, current density and efficiency of red OLED than blue and green ones. This study describes that 30$\AA$ is optimum thickness of BAlq for best performance of full color OLED devices when using BAlq as a hole blocking material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.1038-1041
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• 2002

We have investigated the effects of cathode in organic light-emitting diodes of ITO/TPD/$Alq_3$/Cathodes(Al, LiF/Al, Ca/Al, and LiAl) by measuring current-voltage-luminance characteristics. The device with cathodes other than Al cathode shows the efficiency by an oder of one compared with Al cathode only. This improvement is due to a reduction of barrier height in cathode side.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.309-310
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• 2006

We studied dielectric properties of OLEDs(Organic Light-emitting Diodes) depending on applied voltage (AC) of PTFE(Polytetrafluoroethylene), material of hole injection layer in structure of ITO/hole injection layer (PTFE)/emitting layer, Alq3(Tris(8-hydroxyquinolibe) Alumin)/Al. PTFE is deposited 2 [nm] as rate of 0.2~03 [${\AA}/s$] and $Alq_3$ is deposited 100 [nm] as rate of 1.3~1.5 [${\AA}/s$] m high vacuum ($5{\times}10^{-6}$[torr]). In result of these studies, we can know dielectric properties of OLEDs. Impedance is decreased depending on applied voltage variation, dielectric loss showed peak in specified voltage and showed cole-cole plot of a specimen.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1134-1139
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• 2006

Electrical, optical, and structural properties of indium zinc oxide (IZO) anode films grown by a RF magnetron sputtering were investigated as functions of RF power and working pressure in pure Ar ambient. To investigate electrical, optical and structural properties of IZO anode films, 4-point probe and UV/VIS spectrometry, and X-ray diffraction (XRD) were performed, respectively. A sheet resistance of $15.2{\Omega}/{\square}$, average transmittance above 80 % in visible range, expecially above 85 % in 550 nm, and root mean square roughness of 1.13 nm were obtained from optimized IZO anode films grown in oxygen free ambient. All samples show amorphous structure regardless of RF power and working pressure due to low substrate temperature. In addition, XPS depth profile obtained from IZO/PES exhibits that there is no obvious evidence of interfacial reaction between IZO and PES substrate. Furthermore, current-voltage-luminance of the flexible phosphorescent flexible OLEDs fabricated on IZO anode shows dependence on sheet resistance of the IZO anode. These results indicate that the IZO anode is a promising candidate to substitute conventional ITO anode for high-quality flexible displays.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.103-106
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• 2004

We have studied a conduction mechanism and equivalent circuit analysis in $Alq_3$ based Organic Light Emitting Diode. The conduction mechanism in organic light emitting diode can be classified into three regions; ohmic region, space-charge-limited current (SCLC) region and trap-charge-limited current (TCLC) region depending on the region of applied voltage. Equivalent circuit model of organic light emitting diode can be established using a parallel combination of resistance $R_p$ and capacitance $C_p$ with a small series resistance $R_s$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1015-1018
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• 2004

We investigate the influence of the New Electron Injection Layers (EIL) on the performance of the Alkali Metal Complex vapor-deposited Organic Light Emitting Diodes(OLED). Two different Alkali Metal Complex were used; Lithium Quinolate (Liq), and Sodium Quinolate (Naq). In all cases, $Alq_3$ was the Electron Transporting Layer (ETL). We measure and compare the current density-voltage (J-V) and luminance-voltage (L-V) characteristics. We concluded that the turn-on voltage, and luminance efficiency are controlled by the type of EIL material used. We show the longer life-time OLED with Alkali Metal Complex EIL than OLED with LiF EIL. And we show the Optimized Alkali Metal Complex thickness is 3nm. Existent LiF to because is inorganic material, there is trouble to do epitaxy into thin layers but regulates the thickness in case of Alkali Metal Complex matter characteristic that is easy be. Alkali Metal Complex also appeared by sensitive thing in thickness than LiF If utilize this material, It is thought much advantages may be at common use of OLED.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.53-56
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• 2002

The effect of $\alpha$-septithiophene (${\alpha}-7T$) layers on the organic light emitting diode(OLED) was studied. The ${\alpha}-7T$ was used for a buffer layer in OLED. Hole injection was investigated and improved emission efficiency. The OLEDs structure can be described as indium tin oxide(ITO)/ buffer layer / hole transporting layer / emitting layer / electron transporting layer / LiF / Al. The hole transporting layer were composed of N,N-diphenyl-N,N-di(3-methylphenyl)-1,1-biphenyl-4,4-diamine(TPD), and N,N-di(naphthalene-1-ly)-N,N-diphenyl-benzidine( ${\alpha}$-NPD). The emitting layer, and electron transporting layer consist of tris(8-hydroxyquinolinato) aluminum($Alq_3$). All organic layer were deposited at a background pressure of less than $10^{-6}$ torr using ultra high vacuum (UHV) system. The ${\alpha}-7T$ layer can substitute the hole blocking layer, and improve hole injection properties.