• Journal of the Semiconductor & Display Technology
• /
• v.21 no.1
• /
• pp.91-94
• /
• 2022

Top emission organic light-emitting diode is commonly used because of high efficiency and good color purity than bottom - emission organic light-emitting device. Unlike BEOLED, TEOLED contain semi-transparent metal cathode. Because of semi-transparent cathode, micro cavity effect occurs in TEOLED. We optimized this effect by changing the thickness of hole injection layer. Device consists of is indium-tin-oxide / N,N'-Di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl-4,4'-diamine (x nm) / tris-(8-hydroxyquinoline) aluminum (50nm) / LiF(0.5nm) / Mg:Ag (1:9), and we changed NPB thickness which is used as HTL in our device in order to study how micro cavity effects are changed by optical path. As the results, NPB thickness at 35nm showed the current efficiency of 8.55Cd/A.

• Transactions on Electrical and Electronic Materials
• /
• v.12 no.2
• /
• pp.84-87
• /
• 2011

We fabricated phosphorescent organic light-emitting devices with a 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) host layer. Two kinds of devices, one of ITO/TAPC/TAPC:FIrpic/TAZ/LiF/Al (device A) and one of ITO/TAPC:FIrpic/TAPC/TAZ/LiF/Al (device B), were prepared to investigate electrical and optical properties. Iridium(III) bis[(4,6-difluorophenyl)-pyridinato-N,$C^{2'}$]picolinate (FIrpic) and 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole (TAZ) were used as a blue phosphorescent guest material and an electron transport layer, respectively. The TAPC layer in device B strongly contributes to whitish emission, higher driving voltage, and lower current efficiency characteristics compared with device A. The mechanisms of these electrical and optical characteristics of the devices were investigated.

• Transactions on Electrical and Electronic Materials
• /
• v.6 no.1
• /
• pp.25-28
• /
• 2005

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using poly(3,4-ethylenedioxythiophene):poly(stylenesulfonate)(PEDOT:PSS) in a device structure of $ITO/PEDOT:PSS/TPD/Alq_{3}/cathode$. Polymer PEDOT:PSS buffer layer was made by spin casting method. Current-voltage, luminance-voltage characteristics and efficiency of device were measured at room temperature with a variation of cathode materials; Al, LiF/Al, LiAl, and Ca/Al. The device with LiF/Al cathode shows an improvement of external quantum efficiency approximately by a factor of ten compared to that of Al cathode only device. Our observation shows that cathode is important in improving the efficiency of the organic light-emitting diodes.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.139-139
• /
• 2010

Ionic Transition Metal Complex based (iTMC) Light-emitting electrochemical cells (LEECs) have been drawn attention for cheap and easy-to-fabricate light-emitting device. LEEC is one of the promising candidate for next generation display and solid-state lighting applications which can cover the defects of current commercial OLEDs like complicated fabrication process and strong work-function dependent sturucture. We have investigated the performance characteristics of LEECs based on poly (3, 4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)-incorporated transition metal complex, which is tris(2, 2'-bipyridyl)ruthenium(II) hexafluorophosphate in this study. There are advantages using conductive polymer-incorporated luminous layer to prevent light disturbance and absorbance while light-emitting process between light-emitting layer and transparent electrode like ITO. The devices were fabricated as sandwiched structure and light-emitting layer was deposited approximately 40nm thickness by spin coating and aluminum electrode was deposited using thermal evaporation process under the vacuum condition (10-3Pa). Current density and light intensity were measured using optical spectrometer, and surface morphology changes of the luminous layer were observed using XRD and AFM varying contents of PEDOT:PSS in the Ruthenium(II) complex solution. To observe enhanced ionic conductivity of PEDOT:PSS and luminous layer, space-charge-limited-currents model was introduced and it showed that the performances and stability of LEECs were improved. Main discussions are the followings. First, relationship between film thickness and performance characteristics of device was considered. Secondly, light-emitting behavior when PEDOT:PSS layer on the ITO, as a buffer, was introduced to iTMC LEECs. Finally, electrical properties including carrier mobility, current density-voltage, light intensity-voltage, response time and turn-on voltages were investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.10
• /
• pp.850-853
• /
• 2009

We have optimized the device structure by using the dielectric layer such as anti-reflection thin film to improve the emitting efficiency of white organic light emitting device (WOLED). Basically, dielectric layer with anti-reflection characteristics can enhance the emitting efficiency of WOLED by compensating the refractive index of organic layer, ITO, and Glass. Here, WOLED was designed and optimized by Macleod simulator. The refractive index of 1.74 was calculated for Dielectric layer and was selected as $TiO_2$. The optimal thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively, at the wavelength of 600 nm. The transmittance of ITO was measured with the thickness variation of dielectric layer and ITO in Organic layer/ITO/Dielectric layer structure. The transmittance of ITO was 95.17% and thicknesses of $TiO_2$ and ITO were 119.3 and 166.6 nm, respectively. This result, calculated and measured values were coincided.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2010.06a
• /
• pp.132-132
• /
• 2010

In a previous report, we demonstrated that poly (3,4-ethylenedioxythiophene) derived from poly (ionic liquid) (PEDOT:PIL) constitutes a polymeric hole-injecting material capable of improving device lifetime in organic light-emitting diodes (OLEDs).was attributed to aprotection characteristic of PEDOT:PIL for the indium extraction from ITO electrodes, which frequently occurrs in the OLED device with the conventional PEDOT materials. In this study, we report the OLED device lifetime as well asvice efficiencycan be further improved with the modified PEDOT:PIL in whichorganic compounds are incorporated. The deviced performance will be presented in terms of device lifetime and efficiencies.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.118.3-118
• /
• 2001

CLED (Contact Light Emitting Device) has three layers consisting of a transparent electrode, a light emitting layer and a substrate. When the substrate of the CLED comes in contact with a fingerprint under AC input voltage, it makes an electric field between the fingerprint and the device. Due to the electric field, the light is emitted along the ridgeline of the fingerprint. The intensity along the ridge on the surface of the CLED increase in proportion to the electric field. To achieve uniform performance of fingerprint verification devices, inspection system of CLED for quality control were required. In this research, we proposed the factors for quality controls such as dimensions of the CLED, uniformity ...

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.26 no.10
• /
• pp.745-753
• /
• 2013

Performance of organic light-emitting diodes incorporating microlens array was simulated using a Light Tools software. Use of microlens array can help the light to escape out of the device. We simulated a reference device that is consisted of reflection layer, emissive layer, and flat transparent substrate. And in this reference device, outcoupled efficiency of 22% was obtained. Several shapes of microlens were applied such as hemisphere, trapezoid, cone, and rectangular parallelepiped. The results showed the improvement of outcoupled efficiency of the device with microlens compared to that of the reference one. And from the analyses of the simulated data, the obtained appropriate shape of microlens is hemisphere, and the improvement of the device with hemispherical lens is 57% higher than that of the reference one.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.28-31
• /
• 2003

We have investigated the electrical characteristics of the organic light emitting diodes (OLEDs) using the numerical device simulation. The current-voltage characteristics, the charge carrier concentrations, and the recombination rate profiles are presented. The simulation results of the effects of the various device parameters on the device characteristics are discussed.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.1148-1151
• /
• 2009

A self-designed, written in labview, Organic Light-Emitting Diode junction temperature measuring program was used to calculate the internal junction temperature for devices during operation, and an infrared thermometer was used to measure the backside temperature of the device substrate, to discuss the effects of the junction and substrate temperature difference to the characteristics of the device.