New three emitting compounds, AK-1, AK-2 and AK-3 including diazocine moiety were synthesized through Suzuki-coupling reaction. Physical properties such as optical, electroluminescent properties were investigated. UV-visible spectrum of AK-1, AK-2 and AK-3 in film state showed maximum 392, 393 and 401 nm. PL spectrum of AK-1, AK-2 and AK-3 showed maximum emission wavelength of 472, 473 and 435 nm. Three compounds were used as EML in OLED device: ITO/2-TNATA (60 nm)/NPB (15 nm)/EML (35 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm). AK-3 OLED device showed C.I.E value of (0.18, 0.26) and luminance efficiency of 0.51 cd/A at 10 mA/cm2. New derivatives including diazocine moiety were introduced as OLED emitting material and the EL efficiency was increased by the proper combination of core and side group.

4-methyl-7-(10-(pyren-1-yl)anthracen-9-yl)-2H-chromen-2-one (PAC), 7,7’-(anthracene-9,10-diyl)bis(4- methyl-2H-chromen-2-one) (CAC), 7-Anthracen-9-yl-4-methyl-chromen-2-one(AC), and 7-(naphthalen-1-yl)-2Hchromen-2-one (NC) were synthesized through Suzuki aryl-aryl coupling reaction. Optical and electroluminescence (EL) properties were evaluated by UV-visible absorption, photoluminescence (PL) spectra, and EL devices. Synthesized compounds were used as an emitting layer (EML) in non-doped device with the following structures: ITO/2-TNATA (60 nm)/NPB (15 nm)/synthesized compounds (35 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm). Non-doped devices showed luminance efficiency (L.E.) of 1.38, 1.03, 1.12, and 0.39 cd/A at a current density of 10 mA/cm2.

Quantum dots(QDs) with their tunable luminescence properties are uniquely suited for use as lumophores in light emitting device. We investigate the microstructural effect on the electroluminescence(EL). Here we report the use of inorganic semiconductors as robust charge transport layers, and demonstrate devices with light emission. We chose mechanically smooth and compositionally amorphous films to prevent electrical shorts. We grew semiconducting oxide films with low free-carrier concentrations to minimize quenching of the QD EL. The hole transport layer(HTL) and electron transport layer(ETL) were chosen to have carrier concentrations and energy-band offsets similar to the QDs so that electron and hole injection into the QD layer was balanced. For the ETL and the HTL, we selected a 40-nm-thick ZnSnOx with a resistivity of 10Ω·cm, which show bright and uniform emission at a 10 V applied bias. Light emitting uniformity was improved by reducing the rpm of QD spin coating.At a QD concentration of 15.0 mg/mL, we observed bright and uniform electroluminescence at a 12 V applied bias. The significant decrease in QD luminescence can be attributed to the non-uniform QD layers. This suggests that we should control the interface between QD layers and charge transport layers to improve the electroluminescence.

New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis(α-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd m-2 at an applied voltage of 10 V and current density of 680 mA/cm2. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.

Zinc complexes with bis[2-(o-hydroxyphenyl) naphtol [1,2] oxazolato ligands (ZnPBO-4) and its derivatives (ZnPBO-S) were synthesized, and luminescent properties of these materials were investigated. Both the fluorescent emission band and electroluminescent emission band were discussed based on their ligand structure differences. The emission band found that it strongly depends on the molecular structure of introduced ligand. It was tuned from 446 nm to 491 nm by changing the ligand structures. Spreading of the π-conjugation in 2-(o-hydroxyphenyl) group gives rise to a blue shift. The EL properties also showed good consistency with their differences of ligand structure. Bright-blue EL emission with a maximum luminance of 3,100 cd/m2 at 12V, current density, 575 mA/m2 was obtained from the organic light-emitting diodes (OLEDs) using ZnPBO-4 as emitting layer. It was also found that the newly synthesized materials were suitable to be used as emitting materials in organic EL device.

ZnS:Cu,Cl 형광체를 이용하여 ITO/glaas 기판위에 스크린인쇄법으로 적층형과 혼합형 구조로된 2종류의 교류전계 발광소자를 제작한 후 인가전압과 주파수에 따른 광학적, 전기적 특성을 조사, 비교하였다. 적층헝의 경우 발광휘도는 400Hz, 200V 구동전압에서 약 55 cd/m2를 나타내었다. 인가전압의 주파수를 400Hz에서 30Hz로 증가시킬 경우 휘도는 420 cd/m2로 크게 향상되었다. 혼합형의 경우 400Hz의 주파수에서 문턱전압은 45V이었고, 200V, 30KHz 주파수의 동작조건에서 최대휘도는 670 cd/m2 이었다. 휘도-전압 특성 측정결과 적층형구조 보다 혼합형 소자구조에서 발광강도가 약 1.5배 증가하였다. 주파수에 따른 주발광 파장의 변화는 양쪽시료 모두 유사하게 나타났다. 1KHz이하의 저주파에서는 652 nm의 청녹색 발광과장을 나타내었으며 5KHz이상에서는 452 nm과장의 청색발광을 나타내었다.

White emission is important for applying organic EL devices to full-color flat panel display and backlight for liquid crystal display. In order to obtain white emission, the use of a light-emitting material which shows the white emission by itself is advantageous for these applications because of its high reliability and productivity. A chelate-metal complex such as zinc bis(2-(2-hydroxyphenyl) benzothiazolate) (Zn(BTZ)2 was known to emit white light with a broad electroluminescence. In this study, the electroluminescent characteristics of Be(BTZ)2 and Mg(BTZ)2, as well as Zn(BTS)2 were investigated using organic electroluminescent devices with the structure of ITO/TPD/ Be(BTZ)2, Mg(BTZ)2, or Zn(BTZ)2/Al. It was found that the device containing Be(BTZ)2 showed the highest power efficiency.

The tfTZ(4,4',4"-trifluoro-triazine) was used as a hole blocking material for the electroluminescent devices(ELDs) in this study. In general, the holes are outnumbered the electrons in hole transport and emitting layers because the hole transport is more efficient in most organic ELDs. The hole blocking layer are expected to control the excess holes to increase the recombination of holes and electrons and to decrease current density. The former study using the 2,4,6-triphenyl-1,3,5-triazine(TTA) as hole blocking layer showed that the TTA did not form stable films with vapor deposition technique. The tfTZ can generate stable evaporated films, moreover the fluorine group can lower the highest occupied molecular orbital(HOMO) level, which produces the energy barrier for the holes. The tfTZ has high electron affinities according to the data by the Cyclic-Voltammety(CV) method, which is developed for the measurement of HOMO and lowest occupied molecular orbital(LUMO) level of organic thin films. The lowered HOMO level is made the tfTZ to be applied for a hole blocking layer in ELDs. We fabricated multilayer ELDs with a structure of ITO/hole blocking layer(HBL)/hole transporting layer(HTL)/emitting layer/electrode. The hole blocking properties of this devices is confirmed from the lowered current density values compared with that without hole blocking layer.

Organic Electroluminescent devices(OELD) consisted of multilayer structures have been studied for the application the application to flat-panel display. Metal-chelate complexes, zinc bis(2-(2-hydroxyphenyl)benzoxazolate) (Zn(BOX)2) and zinc bis(2-(2-hydroxyphenyl)benzothiazolate) (Zn(BOX)2), have been intensively investigated as an white-light emitting layer and recognized to have good electroluminescent(EL) properties. In this study, (Zn(BOX)2) and (Zn(BTZ)2) were synthesized and characterized by FT-IR, 1H-NMR, UV-VIS and PL. Their EL properties were also studied and their ionization potential(IP) and electron affinity(EA) were also measured by cyclic voltammetry(CV).

New electroluminescent materials base on anthracene chromophore, [9.10-bis(α-naph -thylethenyl) anthracene (α-BNA)] were newly synthesized. The anthracene derivatives with bulky substituent possessed high melting point and they gave stable amorphous films through vacuum - sublimation methods. Three types of electroluminescent devices were fabricated with double layer and triple layer structure : ITO/TPD/emission layer/MgAg, ITO/emission layer/ OXD-7 and ITO/ TPD/ emission layer/OXD-7/MgAg, respectively. In three types of devices with the emissive layer of α-BNA, efficient orange electroluminescence was observed. In the triple layer device whit a emitting layer of 20 nm thickness , maximum luminance was about 10000 cd/ m2 at an applied voltage of 10v and maximum external quantum efficiency was 1.0%.

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.

Tris(8-hydroxyquinoline)-aluminum complex(AlQ3) having greenish luminescent characteristics was synthesized and it was confirmed with UV-Vis absorption spectroscopy, elemental analysis, and FT-IR spectroscopy that AlQ3 was successfully synthesized. Thin films of AlQ3 having multilayer structure were prepared by spin coating method and vacuum evaporation technique. Photopluminescent characteristics of these films were investigated by Luminescence spectroscopy and Current-Voltage(I-V) characteristics of these films were also investigated.