• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.8
• /
• pp.775-779
• /
• 2006

In this study, sputtered $Al_2O_3$ thin films were evaluated as a passivation layer in the process of InGaN-based blue LEDs in order to improve the brightness of LED lamps. In terms of packaged LED lamps, lamps with $Al_2O_3$ passivation layer emanated higher brightness than those with $SiO_2$ passivation layer, and LED lamps with 90 nm $Al_2O_3$ passivation layer were the brightest among four kinds of lamps. Although lamps with $Al_2O_3$ passivation had a slight increase in operating voltage, their brightness was improved about 13.6 % compare to the lamps made of conventional LEDs without the changes of emitting wavelength.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08a
• /
• pp.679-682
• /
• 2007

We have developed low voltage operating OLEDs with new electron transport layer. The device having a structure of ITO/2TNATA/HTL:Rubrene(1%)/HTL /new ETL/LiF/Al have been used. The voltage for achieving $1,000\;cd/m^2$ was 4.1 V, whereas the turn on voltage for the brightness of $1\;cd/m^2$ was 2.8 V. This high luminance at low operating voltage is caused by the high current density, resulting from high electron conduction property of the new electron transport layer.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08a
• /
• pp.1023-1026
• /
• 2007

Highly efficient inverted bottom emission organic light emitting device (IBOLED) with a structure of ITO/EIL/Alq3/NPB/WO3/Al was investigated. To enhance electron injection from ITO cathode to Alq3 EML layer, we introduced ultra thin Al layer and Liq layer between ITO and Alq3. The device characteristics showed tune on voltage of 4.5V, the maximum luminance of 21100 Cd/m2 and current efficiencies of 3.56 Cd/A.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.3
• /
• pp.332-335
• /
• 1998

An alternating copolymer of PPV and PTV, poly[2-methoxy-5-(3,7-dimethyl)octyloxy-1,4-phenylenevinylene-alt-2,5-thienylenevinylene] (DAPPV-PTV) has been synthesized and light-emitting properties of the polymer have been studied. A single layer EL device using DAPPV-PTV as an emitting layer between ITO and Al electrodes (ITO/DAPPV-PTV/Al) has been fabricated, and light emission of the device becomes visible at 3 V. The EL emission maximum of the device is about 620 nm. Double layer EL device using DAPPV-PTV and Alq3 (ITO/DAPPV-PTV/Alq3/Al) has also been fabricated. The double layer EL device shows two-color emission depending on the applied voltage. The device emits a pale green color from 8 V, and then the color turns to red at about 18 V.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.250-250
• /
• 2012

Organic light-emitting diodes (OLED) and polymer light emitting diodes (PLED) have been regarded as the candidate for the next generation light source and flat panel display. Currently, the most common OLED industrial fabrication technology used in producing real products utilizes a fine shadow mask during the thermal evaporation of small molecule materials. However, due to high potential including low cost, easy process and scalability, various researches about solution process are progressed. Since polymer has some disadvantages such as short lifetime and difficulty of purifying, small molecule OLED (SMOLED) can be a good alternative. In this work, we have demonstrated high efficient solution-processed OLED with small molecule. We use CBP (4,4'-N,N'-dicarbazolebiphenyl) as a host doped with green dye (Ir(ppy)3 (fac-tris(2-phenyl pyridine) iridium)). PBD (2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole) and TPD (N,N'diphenyl-N,N'-Bis (3-methylphenyl)-[1,1-biphenyl]-4,4'-diamine) are employed as an electron transport material and a hole transport material. And TPBi (2,2',2''-(1,3,5-phenylene) tris (1-phenyl-1H-benzimidazole)) is used as an hole blocking layer for proper hole and electron balance. With adding evaporated TPBi layer, the current efficiency was very improved. Among various parameters, we observed the property of OLED device by changing the thickness of hole transporting layer and solvent which can dissolve organic material. We could make small molecule OLED device with finding proper conditions.

• Journal of the Korean Applied Science and Technology
• /
• v.30 no.2
• /
• pp.244-250
• /
• 2013

We investigated green phosphorescent organic light-emitting diodes (PHOLEDs) with charge control layer (CCL) to produce high efficiency. The CCL and host material which was 4,4,N,N'-dicarbazolebiphenyl (CBP) of bipolar property can control the carrier movement in emitting layer (EML). The performance improvement by the insertion of CCL was realized to the well confined exciton and the reduced triplet exciton quenching effect in EML. Five types of devices (Device A, B, C, D, and E) were fabricated following the thickness of CCL within EML. The properties of device D using optimized thickness of CCL showed external quantum efficiency of 16.22% and luminous efficiency of 55.76 cd/A, respectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.3
• /
• pp.827-834
• /
• 2010

We have performed numerical simulations of the electrical characteristics for multi-layer organic light emitting diode devices with doped emitting layer using a commercial simulation program. In this paper, the basic structure consists of the ITO/NPB/$Alq_3$:C545T(%)/$Alq_3$/LiF/Al, four devices that were composed of $Alq_3$ as the host and C545T as the green dopant with different concentration, were studied. As the result, the variations of the doping concentration rate of C545T have a effect on the voltage-current density characteristics. The voltage-current characteristics are quite consistent with the results which were experimentally determined in a previous reference paper. In addition, the voltage-luminance characteristics were greatly improved, and the luminous efficiency was improved three times. In order to analyze these driving mechanism, we have investigated the distribution of electric field, charge density of the carriers, and recombination rates in the inner of the OLED devices.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1451-1453
• /
• 2007

The electrical and the optical properties of organic light-emitting devices (OLEDs) with or without multiple heterostructures acting as a hole transport layer were investigated. The efficiency enhancement mechanism in the OLEDs with multiple heterostructures is described on the basis of the electrical and the optical results.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.609-612
• /
• 2008

Characteristics of indium-zinc-oxide (IZO)-Ag-IZO multilayer grown on a PET substrate were investigated for flexible organic emitting diodes. By inserting very thin Ag layer between amorphous IZO, IZO-Ag-IZO (IAI) multilayer anode exhibited remarkably reduced sheet resistance and high transmittance due to the surface plasmon resonance effect and Ag layer.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.424-427
• /
• 2008

We make performance simulations of three different organic light-emitting diodes (OLEDs), one of which is based on a conventional layered structure and the others on a blended structure where an emitting layer (EML) is either uniformly or stepwise mixed with an electron transport layer (ETL), Tris-(8-hydroxyquinoline) aluminum ($Alq_3$).