• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.37 no.6
• /
• pp.17-23
• /
• 2000

In this study, we prepared red organic light-emitting-diode(OLED) with a fluorescent dye(Sq)-doped and inserted between emission and cathode layer 1,3-bis(5-p-t-butylphenyl)-1,3,4-oxadiazol-2-yl)benzene (OXD7) or/and tris(8-hydroxyquinoline) aluminum ($Alq_3$) layers for increasing electroluminescent(EL) efficiency. This inserting effect has been observed and EL mechanism characteristics have been examined. The hole transfer layer is a N,N'-diphenyl-N,N'-bis-(3-methyl phenyl)-1,1'-diphenyl-4,4'-diamine (TPD), and the host and guest materials of emission layer is $Alq_3$ and bis[1-methyl-3,3'-dimethyl-2-indorindiylmethyl] squaraine (Sq), respectively. For the inserting of $Alq_3$, emission efficiency increased. But we can not obtained highly pure red emission owing to the emission of inserting $Alq_3$ layer. The inserting of OXD7 makes hole block and accumulate. Because of increasing recombination probability of electron and hole, highly pure red color can be held. Simultaneously brightness characteristics and emission efficiency could improve.

• Korean Journal of Optics and Photonics
• /
• v.3 no.2
• /
• pp.111-116
• /
• 1992

ZnS:Sm, F TFEL devices with double insulating layer are prepared by e-beam evaporation method. Electroluminescence and luminous efficiency of the device fabricated at various conditions are investigated. The main transitions on the emission spectra for ZnS:Sm, F TFEL device occur at$^4G_{5/2}\to^6H_{9/2}^4G_{5/2}\to^6H_{7/2}, \;^4G_{5/2}\to^6H_{5/2}\to$.Among them, the dominant spectral line and its corresponding transition occur at $^4G_{5/2}\to^6H_{9/2}$(650 nm) and results in an orange-red emission color. The optimum concentration and substrate temperature for the ZnS:Sm, F TFEL device are around 1 wt% and $200^{\circ}C$. Luminous efficiency for the device is the largest at optimum condition.

• Journal of the Korean Chemical Society
• /
• v.56 no.2
• /
• pp.264-273
• /
• 2012

Five derivatives of phenylthiourea namely: 1-(4-methoxyphenyl)-3-phenylthiourea (1), 1-(4-methylphenyl)-3- phenylthiourea (2), 1-(4-bromophenyl)-3-phenylthiourea (3), 1-(4-chlorophenyl)-3-phenylthiourea (4) and 1-phenylthiourea (5) have been evaluated as new inhibitors for the corrosion of carbon steel in 2 M HCl solution using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Potentiodynamic polarization measurements showed that these derivatives are mixed-type inhibitors. The inhibition efficiency was found to increase with inhibitor concentration and decreases with rise in temperature. The thermodynamic parameters of adsorption and activation were determined and discussed. Nyquist plots showed depressed semicircles with their centre below real axis. The adsorption process of studied derivatives on carbon steel surface obeys Temkin adsorption isotherm. The synergistic effect of these derivatives and some anions is discussed from the viewpoint of adsorption models. The electrochemical results are in good agreement with the calculated quantum chemical HOMO and LUMO energies of the tested molecules.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.52 no.6
• /
• pp.261-266
• /
• 2003

We investigated the effect of oxygen plasma treatment of indium-tin oxide(ITO) surface on the performance of electroluminescence(EL) devices. ITO surface treated oxygen plasma has been analyzed using atomic force microscope(AFM) and X-ray photoelectron spectroscopy(XPS), to investigate the relations between the properties of the ITO surface and the properties of the current-voltage-luminance(I-V-L) characteristics of the fabricated OLED with the structure of ITO(plasma treatment) / TPD / Alq$_3$/ Al. It is found that the oxygen plasma treatment of ITO anode improve the hole injection of the OLED due to the modification of the surface states. The treated ITO anode nay be low voltage with high luminance efficiency.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07b
• /
• pp.972-975
• /
• 2002

Electroluminescence(EL) devices based on organic thin layers have attracted lot of interests because of their application as display. One of the problems is red material. It offered a short life and poor emission efficiency to boot. In this study, this problem can be solved by using a multi-layer device structure. Organic electroluminescent devices which are composed of organic thin multi-layer films are fabricated. The basic structure is ITO / Emitting layer / LiP / Al EL device in which Hole transport/Electron blocking PVK layer was blending. We demonstrate the enhancement of eletroluminescence (EL) from blends of poly(3-hexylthiophene) in poly(N-vinylcarvazole). The emitting layer is consisted of a host material(PVK) and a guest emitting material(P3HT). It was showed higher EL intensity and their electro-optical properties were investigated.

• Journal of the Korean Applied Science and Technology
• /
• v.16 no.1
• /
• pp.41-44
• /
• 1999

Recently, high luminance and efficiency were realize in organic thin film electroluminescence (EL) cells with multilayer structures including an emitting layer (EML), hole transporting layer (HTL), and an electron transporting layer (ETL). In this study, Bis(10-hydroxybenzo[h]quinolinato)beryllium (Bebq2) was synthesized. PL and EL characteristics of their thin film were investigated by fabricating the devices having a structure of ITO/PVK/Bebq2/Al, ITO/PVK dispersed with TPD/Bebq2/Al. The EL color of these device was greenish and the wavelength of their EL peaks was located, respectly, at 495nm, and 492.5nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.10
• /
• pp.897-902
• /
• 1998

We prepared Organic LED with a two layer structure by vacuum evaporation. The diode consisted of hole transfer layer (thickness of 30, 50, 70 nm) and electron transfer layer (thickness of 70, 50, 30 nm) material, which was N, N'-diphenyl- N, N'-bis-(3-methyl phenyl)-1,1'-diphenyl-4,4'-diamine)(TPD) and tris(8-hydroxy quinoline) aluminum(Alq3), respectively. We investigated EL properties of the LED with various thickness and cathode electrode. The best results were obtained when thickness of the electron layer is equal to that of emission layer and when AlLi alloy was used as a cathode. The EL intensity, luminance and efficiency of organic LED with equal of layer thick were improved seven, three and two times, respectively. Alq3 was ionized by carrier injection from cathode and could produce exitons. After electron-hole pairs were formed by combination of the electrons and holes at the emission layer, Alq3 layer emitted light.

• Electrical & Electronic Materials
• /
• v.8 no.6
• /
• pp.752-758
• /
• 1995

Red emitting CaS:Eu,S electroluminescent(EL) device prepared at 550.deg. C by an electron-beam evaporation technique, demonstrated luminance of 175cd/m$\^$2/ and efficiency of 0.311m/W with 3kHz drive. Luminance was increased with the increase of applied voltage and frequency. From the results of the PL spectrum and the EL spectrum, the CaS:Eu, S device showed emission peak near 640nm resulted from the transition of EU$\^$2+/ 4f$\^$6/5d.rarw.4f$\^$7/. The capacitance of the phosphor layer from the Sawyer-Tower circuit was 10.5nF/cm$\^$2/.

• International Journal of Computer Science & Network Security
• /
• v.21 no.12
• /
• pp.75-80
• /
• 2021

In this paper, a dual-band Koch Snowflake antenna is proposed for wireless communication systems. Fractal geometry, CPW-feed and stepped ground planes are used to improve the impedance bandwidth. By properly introducing a hexagonal split-ring slot to radiating element, a lower frequency band is generated. The proposed structure is fabricated and tested. Experiment results exhibit dual-band of 0.73-0.98 GHZ and 1.6-3.1 GHz which makes this antenna suitable candidate for GSM900, GSM1800, UTMS2100, Wi-Fi 2400 and LTE2600 bands. In addition, a good radiation pattern, a satisfactory peak gain and a radiation efficiency, which reaches 95%, are achieved.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1411-1414
• /
• 2007

We have developed a top-emitting white organic electroluminescent device (TWOLED) incorporating a low-reflectivity molybdenum (Mo) anode and doped transport layers as well as a dual-layer architecture of doped blue and yellow emitters with the same blue host. The EL efficiency and operational lifetime of TWOLED can be enhanced by a factor of 1.2 and 3.4 than that of standard TWOLED, respectively, with a co-doping technology in yellow emitter by doping another blue dopant. The enhancement in device performances can be attributed to improve the energy transfer efficiency from blue host to yellow dopant through a blue dopant as medium in yellow emitter.