Single OLED and tandem OLED was manufactured to analyze the electroluminescence characteristics of DC driving, AC driving, and full-wave rectification driving. The threshold voltage of OLED was the highest in DC driving, and the lowest in full-wave rectification driving due to an improvement of current injection characteristics. The luminance at a driving voltage lower than 10.5 V (8,534 cd/m2) of single OLED and 20 V (7,377 cd/m2) of a tandem OLED showed that the full-wave rectification drive is higher than that of DC drive. The luminous efficiency of OLED is higher in full-wave rectification driving than in DC driving at low voltage, but decrease at high voltage. The full-wave rectification power source may obtain higher current density, higher luminance, and higher current efficiency than the AC power source. In addition, it was confirmed that the characteristics of AC driving and full-wave rectification driving can be predicted from DC driving characteristics by comparing the measured values and calculated values of AC driving and full-wave rectification driving emission characteristics. From the above results, it can be seen that OLED lighting with improved electroluminescence characteristics compared to DC driving is possible using full-wave rectification driving and tandem OLED.

7,8,10-triphenylfluoranthene [TP-F], 7,10-diphenyl-8-p-tolylfluoranthene [DPT-F] and 7,10-diphenyl-8-p-cyanophenlyfluoranthene [DPC-F] were synthesized by using the Knoevenagel condensation and Diels–Alder addition. Multilayered EL devices were fabricated using these materials as non-doped blue emitting layers. DPT-F device including a methyl group has better thermal properties, a better luminance efficiency, a lower operating voltage, and a higher power efficiency than the TP-F device. TP-F showed skyblue CIE value of (0.192, 0.269) and 3.27cd/A at 10mA/cm2. DPT-F also showed sky-blue CIE value of (0.185, 0.252) and 2.31cd/A at 10mA/cm2.

Two emitting compounds, 9,10-bis-[1,1;3,1]terphenyl-5-yl-1,5-di-o-tolyl- anthracene [TP-DTA-TP] and 9,10-bis-phenyl[1,1;3,1]triphenyl-5-yl-1,5-di-o- tolylanthracene[ TPB-DTA-TPB] based on newtwisted core moiety were synthesized through boration, Suzuki reaction, and Sandmeyer reactions. EL performance was improved by varying the chemical structure of the side group. Physical properties such as optical, electrochemical, and electroluminescent properties were investigated. Synthesized compounds were used as an EML in OLED device: ITO/2-TNATA (60 nm)/NPB (15 nm)/TP-DTA-TP or TPB-DTA-TPB (35 nm)/Alq3 (20 nm)/LiF (1 nm)/Al (200 nm). It was found that TPB-DTA-TPB showed higher luminance efficiency and better C.I.E. value than TP-DTA-TP device.

The organic light-emitting diodes are fabricated with six anthracene derivatives containing simple substituents such as phenyl or naphthyl group. The device structure is as in the following: Indium tin oxide (ITO) (180 nm)/4,4-4,4`,4``-tris[N-(1-naphthyl)-Nphenylamino] triphenylamine (2-TNATA) (30 nm)/4,4`-bis[N-(1-naphthyl)-N-phenyl-1-amino] biphenyl (NPB) (20 nm)/Emitting compound (30 nm)/2,2′,2"- (1,3,5-Benzinetriyl)-tris (1-phenyl-1-H–benz-imidazole) TPBi (40 nm)/lithium quinolate (Liq) (2 nm)/Al (100 nm). In the emitting layer the anthracene derivatives are used without any dopant. All the six devices show blue emissions. Among the tested diodes, the one with 9-(2-naphthyl)-10-(p-tolyl) anthracene (2-NTA) exhibited luminous efficiency, power and external quantum efficiencies of 3.26 cd/A, 0.98 lm/A, 2.8 % at 20 mA/cm .

투명한 교류 분말형 전계발광 소자는 Electroluminescence (EL) 용 ZnS계 형광체와 시아노 에틸 유기바인더의 첨가량을 달리하여 제작하였다. 전면전극 indium thin oxide(ITO) glass 위에 약 3 μm 크기 의 형광체로 발광층을 형성하여 silver nanowire(Ag NW)를 스핀코팅으로 후면전극 형성 후 연구를 진행 하였다. 본 연구에 제작된 소자의 발광휘도와 투과도을 통해 등황색 계열의 약 585 nm의 주파장 스펙트 럼을 확인하였고 형광체의 첨가량이 낮아질수록 발광휘도가 약 80 %로 감소, 투과도는 약 30 % 증가하 는 것을 알 수 있었다.

스크린 인쇄 방식을 통해 ZnS기반의 AC 분산형 EL 소자를 제작하였다. 유전체층 재료로 BaTiO3를 사용하였다. 소자의 경우는 쉽게 변수를 조정할 수 있는 수동 스크린 인쇄 방식을 사용하여 최적의 조건으로 제작하였다. TiO2는 내산성, 내알칼리성이 좋아 인체에 무해하기 때문에 광촉매제로 많이사용되고 있다. 기판은 투명전극인 ITO glass와 유연한 ITO PET film의 두가지 방식으로 제작하였다. 본연구에서는 형광체층에 TiO2의 첨가량을 변화시킨 EL소자를 SEM과 XRD를 통하여 구조를 분석하고, 발광 스펙트럼을 통하여 분석하였다. 그리고 TiO2의 첨가량이 증가할수록, 발광효율이 증가하는 것을 알 수 있었다.

스크린 인쇄 방식을 통해 Cu,Al 형광체와 BaTiO3를 혼합한 층의 무기 전계 발광소자를 제작하였다. 혼합층의 두깨는 60㎛로 제작하였다. 형광층의 비율이 유전층보다 높아질수록 발광효율은 증가하였으나. 안정성을 떨어졌다. 가장 높은 효율을 보인 비율은 형광층 3: 유전층 1의 비율이었다.

We investigated the effect of electron injection layer on the performance of organic light emitting devices (OLEDs). As an electron injection layer, the quinolate metal complexes were used. We optimized the device efficiency by varying the thickness of the quinolate metal complexes layer. The device with 1 nm of the quinolate metal complexes layer showed significant enhancement of the device performance and device lifetime. We also compared the effect of 8-hydroxyquinolinolatolithium (Liq) with that of bis(8-quinolinolato)-zinc (Znq2) and 8-hydroxyquinolinolatosodium (Naq) as an electron injection layer. As a result, Liq is considered as a better materials for the electron injection layer than Znq2 and Naq.

Organic-based electroluminescent devices have attracted lots of interests because of their possible application as a large-area flat panel display. Polyimides have been used for photo-alignment in LCD(Liquid Crystal Display). However, the devices used in this study were fabricated with polyimide doped with N,N'-Diphenyl-N,N'-di(m-tolyl)-benzidine(TPD) (3, 10, 30wt%) for electroluminescent hole tranforting layer(EHTL). The photochemical and physical properties of EHTL was studied. The film thicknesses were reduced under illumination with UV light. Polyimide films doped with TPD(3wt%) was irradiated and the electrical properties of the films were studied.