• Journal of the Semiconductor & Display Technology
• /
• v.11 no.3
• /
• pp.33-37
• /
• 2012

Simple and high efficiency blue organic light-emitting diodes with three organic layers of N, N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolylamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD]/1,1-bis-(di-4-polya-minophenyl)cyclohexane[TAPC]/electron transport material [ET-137] were fabricated and their electroluminescent characteristics were evaluated according to the TAPC thickness variation in a range of $50{\sim}300{\AA}$. Electroluminescence spectra of the devices with structure of DNTPD/TAPC/ET-137 showed all the same central emission wavelengths of 455 nm under an applied voltage of 7V, which were similar with that of the device with ET-137 only. On the other hand, the electroluminescence spectra of the device with structure of DNTPD/ET-137 without TAPC layer showed double emission peaks at the wavelengths of 455 nm and 561 nm under an applied voltage of 7V. In the devices with structure of DNTPD/TAPC/ET-137, single peak blue emission was not maintained in the device with $50{\AA}$-thick TAPC above 8V by the formation of exciplex. In the device with $300{\AA}$-thick TAPC, however, single peak blue emission was maintained until 10 V. According to the thickness increase of TAPC in the fabricated devices, the current density and luminance decreased, but the luminous efficiency and roll-off characteristics were improved.

• Elastomers and Composites
• /
• v.59 no.1
• /
• pp.1-7
• /
• 2024

Nanorod graphitic carbon nitride (g-C₃N₄) was synthesized by reacting melamine (C₃H₆N₆) with trithiocyanuric acid (C₃H₃N₃S₃) in distilled water for 10 h at room temperature. The resulting mixture was calcined at 550℃ for 2 h in an electric furnace under an air atmosphere. Nanorod g-C₃N₄/Ag₃PO₄ composites were prepared by adding nanorod graphitic carbon nitride (g-C₃N₄) powder, silver nitrate (AgNO₃), ammonia (NH₃·H₂O, 25.0-30.0%), and sodium hydrogen phosphate (Na₃HPO₄) to distilled water. The samples were characterized via X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy. The photocatalytic activities of the nanorod g-C₃N₄/Ag₃PO₄ composites were demonstrated via the degradation of organic dyes, such as methylene blue and methyl orange, under blue light-emitting diode irradiation and evaluated using UV-vis spectrophotometry.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1236_1237
• /
• 2009

Organic light emitting diode (OLED) is currently the focus of intense interest in the field of photonics. It is attractive for the in low-operating voltage, low power consumption, easy fabrication and low cost. A typical OLED consists of one or more organic layers sandwiched between a high work function anode, such as indium tin oxide (ITO), and a low work function cathode such as Ca, Mg:Ag, and Al. Tris-(8-hydroxy)quinolinealuminum ($Alq_3$) has taken a prominent position in the development of OLED due to its relative stability as an electron transporting and emitting material. We investigated an efficiency improvement of the OLED depending on thickness variation of $Alq_3$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.06a
• /
• pp.281-281
• /
• 2009

Electrical analysis of red, green and blue (RGB) organic light emitting diode (OLED), which were measured at various temperatures from 230K to 370K by steps of 20K, were investigated using current-voltage(I-V) characteristics. Ideality factor and series resistance were obtained from the thermionic emission theory. Experimental results showed that the ideality factors were 2.12 for red, 3.80 for green, and 6.03 for blue OLED at 290K, respectively. The series resistance were 1960, 2190, 2630$\Omega$ for red, green and blue OLED at the same temperature. It was found that the OLED ideality factors were much higher than near unity for well-behaved silicon diodes, because of the organic material and multi-layer fabrication diode. In addition, the series resistance was near 2k$\Omega$ range. More researches are required to reduce both ideality factors and series resistance to increase the efficiency of OLEDs.

• Proceedings of the Polymer Society of Korea Conference
• /
• 2006.10a
• /
• pp.194-194
• /
• 2006

Polymer light-emitting diodes(PLEDs) have great potential application in large area flat panel displays and general lighting so intense academic and industrial research, and impressive scientific and technological progress has been achieved in this field. However, the efficiency and stability of PLEDs till need to be improved in order to fully realize the advantages of low cost and ease of fabrication provided by organic materials. Here, we report our effort to enhance the PLED' s performance in two approaches : 1) Utilizing nano-structured materials such as nano particles, clay, nano porous silica in active layer 2) Modifying the device structure in nano scale to improve not only the device efficiency but also its stability.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.1418-1420
• /
• 2008

In this paper, the light emitting efficiency, spectrum, and the lifetime of the phosphorescent devices, whose emission characteristics are strongly dominated not only by the energy transfer but also by the charge carrier trapping induced by the emissive dopant, are explained by differences in the energy levels of the host, dopant, and nearby transport layers. On the basis of our finding on device performance and photocurrent measurement data by time-of-flight (TOF), we investigated the effect of the difference of carrier trapping dopant and properties of the host materials on the efficiency roll-off of phosphorescent organic light emitting diode (OLED), along with a physical interpretation and practical design scheme, such as a multiple host system, for improving the efficiency and lifetime of devices.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2002.08a
• /
• pp.336-339
• /
• 2002

Fluorenevinylene-based EL polymers, poly(9,9-dioctylfluorene-2,7-vinylene) (PFV) and poly[(9,9-dioctylfluorene-2,7-vinylene)-co-{2-methoxy-5-(2 ethylhexyloxy)-1,4-phenylenevinylene}] (PFV-co-MEH-PPV), have been synthesized by Gilch polymerization method. The resulting polymers were soluble in common organic solvents and easily spin cast onto the indium-tin oxide (ITO) substrate. The weight average molecular weight and polydispersity of PFV and PFV-co-MEH-PPV were in the range of 22.2 - 43.2 x $10^4$ and 1.9 - 3.0, respectively. Double-layer light-emitting diodes with ITO/PEDOT/Polymer/Al configuration were fabricated. PFV-co-MEH-PPV showed better EL properties than those of PFV and MEH-PPV The turn-on voltage of poly(9,9dialkylfluorene) derivatives were dramatically decreased to the 2.5 V compared to fluorene-based EL polymers. The maximum brightness and luminescence efficiency were up 7 to 1350 cd/$m^2$ and 0.51 Cd/A.

• Journal of the Korean Vacuum Society
• /
• v.21 no.1
• /
• pp.12-16
• /
• 2012

Although silver is used for T-OLED (Top emitting organic Light-Emitting Diode) as reflective anode, it is not an ideal material due to its low work function. Thus, we study the effect of annealing and atmospheric pressure plasma treatment on Ag film that increases its work function by forming the thin silver oxide layer on its surface. In this study, we deposited silver on glass substrate using RF sputtering. Then we treated the Ag samples annealing at $300^{\circ}C$ for 30 minutes in atmosphere or treating the atmospheric plasma treatment for 30, 60, 90, 120s, respectively. We measured the change of the mechanical properties and the potential value of surface with each one at a different treatment type and time. We used nano-indenter system and KPFM (Kelvin Probe Force Microscopy). KPFM method can be measured the change of surface potential. The nanoindenter results showed that the plasma treatment samples for 30s, 120s had very low elastic modulus, hardness and Weibull modulus. However, annealed sample and plasma treated samples for 60s and 90s had better mechanical properties. Therefore, plasma treatment increases the uniformity thin film and the surface potential that is very effective for the performace of T-OLED.

• Journal of Information Display
• /
• v.12 no.3
• /
• pp.141-144
• /
• 2011

To improve the performance of blue fluorescent and green phosphorescent organic light-emitting diode devices, Merck developed novel green phosphorescent host and electron-transporting materials. The newly developed electron-transporting material improves the external quantum efficiency of blue fluorescent devices up to 8.7%, with an excellent lifetime. In combination with the newly developed host materials, the efficiency of green phosphorescent devices can be improved by a factor of 1.7, and the lifetime by a factor of 7.

• Information Display
• /
• v.7 no.3
• /
• pp.4-17
• /
• 2006

차세대 디스플레이로서, 특히 휴대기기를 위한 플레깃블 디스플레이에 대한 관심이 증가되고 있다. 지난 몇 년간 계속적으로 연구가 이루어져 왔음에도 불구하고, 플렉시블 디스플레이는 아직 하나의 '제품'으로서 시장에 진입하지 못하고 있다. 플렉시블 디스플레이는 플라스틱이나 메탈 호일, 플렉시블 유리와 같은 플렉시블 기판이 쓰이는데, 이것은 가벼우면서 얇고 강하며 제조 측면에서 높은 생산성을 가질뿐만 아니라 착용이 가능할 정도의 자유로운 디자인이 가능하다는 장점을 가지고 있다. 이러한 많은 장점으로 인해 플렉시블 디스플레이의 연구와 개발이 빠르게 진행되고 있다. 지난 몇 년 동안 개발된 전기영동(electrophoretic), 유기전계발광(OLED, organic light-emitting diode), 액정(liquid-crystal)과 관련된 플렉시블 디스플레이에 대해 성능 등을 알아보고, 플렉시블 디스플레이용으로 개발된 플라스틱 기판과 그 위에 형성된 유기박막트랜지스터(OTFTs, organic thin film transistors)의 특성을 분석한다. 그리고 oTFTs의 성능과 제작공정의 이해를 위해 self organized process에 대해 설명하고 마지막으로 중요 연구 과제를 제시한다.