• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 추계학술대회 논문집
• /
• pp.380-381
• /
• 2007

This paper reports on the deposition conditions and properties of ITO films used as electrode layer in a organic light emitting diodes on a PET substrate. The deposition technique employed was specially designed roll-to-roll sputtering. The oxide was deposited at room temperature in an argon and oxygen plasma on a transparent conducting ITO layer on a PET film. The influence of deposition parameters such as DC power, working pressure and oxygen partial pressure has been investigated, in order to obtain the best compromise between a high deposition rate and adequate electro-optical properties. Electrical and optical properties of ITO films were analyzed by Hall measurement examinations with van der pauw geometry at room temperature and UV/Vis spectrometer analysis, respectively. In addition, the structural properties and surface smoothness were measured by x-ray diffraction and scaning electron microscopy, respectively. From optimized ITO films grown by roll-to-roll sputter system, good electrical$(6.44{\times}10^{-4}\;{\Omega}-cm)$ and optical(above 86 % at 550 nm) properties were obtained. Also, the ITO films exhibited amorphous structure and very flat surface beacause of low deposition temperature.

• 문화기술의 융합
• /
• 제7권1호
• /
• pp.564-569
• /
• 2021

본 연구에서는 일반적인 구조의 LED와 경사진 구조의 LED에 대하여, 전극이 없을 때와 전극에서 20%의 흡수(80% 반사)가 발생할 때, 그리고 전극에서 60%의 흡수(40% 반사)가 발생할 때로 구분하여, 전극에서의 흡수와 활성 영역의 높이가 광추출 효율 및 평균 광자 진행 거리에 미치는 영향을 조사하고, 활성 영역의 적절한 높이를 제안하였다. 일반적인 LED에서 전극의 흡수가 증가할수록, 광추출 효율은 18%에서 15%, 13%로 낮아지고, 활성 영역의 높이가 두 전극 사이의 정 중앙에 위치할 때 가장 광 추출 효율이 높다. 경사진 구조의 LED에서는 전극의 흡수가 증가할수록, 광추출 효율은 38%에서 33%, 25%로 낮아지고, 활성 영역의 높이가 두 전극 사이의 정 중앙에 위치할 때 가장 광 추출 효율이 높다. 경사진 구조의 LED는 일반적인 LED 보다 광추출 효율을 두 배 이상 높일 수 있다. 이는 전반사에 의해 광자가 칩 내부에 갇히는 현상을 줄여주기 때문이다.

• 한국표면공학회지
• /
• 제45권1호
• /
• pp.15-19
• /
• 2012

Tris(8-quinolinolato)aluminum(III); $Alq_3$ has been frequently used as an electron transporting layer in organic light-emitting diodes. Either Ba with a low work function or Au with a high work function was deposited on $Alq_3$ layer in vacuum. And then, the behaviors of electron transition at the $Alq_3$/Ba and $Alq_3$/Au interfaces were investigated by using the near edge x-ray absorption fine structure (NEXAFS) spectroscopy. In the each interface, the energy levels of unoccupied obitals were assigned as ${\pi}^*$(LUMO, LUMO+1, LUMO+2 and LUMO+3) and ${\sigma}^*$. And the relative intensities of these peaks were investigated. In an oxygen atom composing $Alq_3$ molecule, the relative intensities for a transition from K-edge to LUMO+2 were largely increased as Ba coverage (${\Theta}_{Ba}$, 2.7 eV) with a low work function was in-situ sequentially increased on $Alq_3$ layer. In contrast, the relative intensities for the LUMO+2 peak were reduced as Au coverage (${\Theta}_{Au}$, 5.1 eV) with a high work function were increased on $Alq_3$ layer. This means that the electron transition by photon in oxygen atom which consists in the unoccupied orbitals in $Alq_3$ molecule, largely depends on work function of a metal. Meanwhile, in the case of electron transition in a carbon atom, as ${\Theta}_{Ba}$ was increased on $Alq_3$, the relative intensity from K-edge to ${\pi}_1{^*}$ (LUMO and LUMO+1) was slightly decreased, and from K-edge to ${\pi}_2{^*}$ (LUMO+2 and LUMO+3) was somewhat increased. This rising of the energy state from ${\pi}_1{^*}$ to ${\pi}_2{^*}$ exhibits that electrons provided by Ba would contribute to the process of electron transition in the $Alq_3$/Ba interfaces. As shown in above observation, the analyses of NEXAFS spectra in each interface could be important as a basic data to understand the process of electron transition by photon in pure organic materials.

• 한국재료학회지
• /
• 제26권3호
• /
• pp.117-122
• /
• 2016

White organic light-emitting diodes with a structure of indium-tin-oxide [ITO]/N,N-diphenyl-N,N-bis-[4-(phenylm-tolvlamino)-phenyl]-biphenyl-4,4-diamine [DNTPD]/[2,3-f:2, 2-h]quinoxaline-2,3,6,7,10,11-hexacarbonitrile [HATCN]/1,1-bis(di-4-poly-aminophenyl) cyclo -hexane [TAPC]/emission layers doped with three color dopants/4,7-diphenyl-1,10-phenanthroline [Bphen]/$Cs_2CO_3$/Al were fabricated and evaluated. In the emission layer [EML], N,N-dicarbazolyl-3,5-benzene [mCP] was used as a single host and bis(2-phenyl quinolinato)-acetylacetonate iridium(III) [Ir(pq)2acac]/fac-tris(2-phenylpyridinato) iridium(III) $[Ir(ppy)_3]$/iridium(III) bis[(4,6-di-fluoropheny)-pyridinato-N,C2] picolinate [FIrpic] were used as red/green/blue dopants, respectively. The fabricated devices were divided into five types (D1, D2, D3, D4, D5) according to the structure of the emission layer. The electroluminescence spectra showed three peak emissions at the wavelengths of blue (472~473 nm), green (495~500 nm), and red (589~595 nm). Among the fabricated devices, the device of D1 doped in a mixed fashion with a single emission layer showed the highest values of luminance and quantum efficiency at the given voltage. However, the emission color of D1 was not pure white but orange, with Commission Internationale de L'Eclairage [CIE] coordinates of (x = 0.41~0.45, y = 0.41) depending on the applied voltages. On the other hand, device D5, with a double emission layer of $mCP:[Ir(pq)_2acac(3%)+Ir(ppy)_3(0.5%)]$/mCP:[FIrpic(10%)], showed a nearly pure white color with CIE coordinates of (x = 0.34~0.35, y = 0.35~0.37) under applied voltage in the range of 6~10 V. The luminance and quantum efficiency of D5 were $17,160cd/m^2$ and 3.8% at 10 V, respectively.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 하계학술대회 논문집 C
• /
• pp.1703-1705
• /
• 2004

New luminescent material, 6.11-dihydoxy-5.12-naphtacene-dione $Alq_3$ complex($Alq_2$-Ncd), 1.4-dihydoxy-5.8-naphtaquinone $Alq_3$ complex ($Al_2Nq_4$) was synthesized. The $Alq_2-$ Ncd and $Al_2Nq_4$ has big molecular weight and many ${\pi}$-electrons more than widely known $Alq_3$. And extended efforts have been made to obtain high-performance electro luminescent(EL) devices. We used hole transfer layer of powdered TPD to improve hole transfer and characteristics of interface in OLED. This study indicates not only the sterical effect but also some other effects that would be responsible for the change of the emission wavelength. improvement of luminance and etc.

• 한국재료학회지
• /
• 제13권3호
• /
• pp.191-194
• /
• 2003

The influence of on ion beam irradiation to the indium tin oxide (ITO) substrate on the performance of the organic light-emitting diodes (OLEDs) was studied. ITO films were used as the transparent anode of OLEDs with poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) as a hole-injection/transport layer. Oxygen and argon plasma treatment of ITO resulted in a change in the work function and the chemical composition. For plasma treated ITO anodes, the device efficiency clearly correlated with the value of the work function. We also discussed the implications of our experimental study in relation to the modification of the ITO surface composition, transmittance, reflectance, and water contact angle (WCA).

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2005년도 추계종합학술대회
• /
• pp.773-776
• /
• 2005

In the fabrication of high performance Blue organic light emitting diode, 2-TNATA[4,4',4"-tris(2-naphthylphenyl-phenylamino)-triphenylamine] as hole injection material and NPB[N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine] as hole transport material were deposited on the ITO (Indium Tin Oxide)/Glass substrate by vacuum evaporation. And then, Blue color emission layer was deposited using GDI602 as a host material and GDI691 as a dopant. Finally, small molecule OLED with the structure of ITO/2-TNATA/NPB/GDI602+GDI691/Alq3/LiF/Al was obtained by in-situ deposition of Alq3, LiF and Al as electron transport material, electron injection material and cathode, respectively. Blue OLED fabricated in our experiments showed the color coordinate of CIE(0.14, 0.16) and the maximum luminescence efficiency of 1.06 lm/W at 11 V with the peak emission wavelength of 464 nm.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.34-35
• /
• 2009

We have studied the electrical and optical of organic light-emitting diodes depending on hole size of crucible boat using BCP materials. The thickness of TPD, $Alq_3$ and BCP was manufactured 40 nm, 60 nm and 5 nm under a base pressure of $5\times10^{-6}$ Torr using at thermal evaporation, respectively. In order to investigate the optimal surface roughness of BCP, the BCP was thermally evaporated to be 0.8 nun, 1.0 mm, 1.2 mm and 1.5 mm as a hole size of crucible boat, respectively. As the experimental results, we found that the luminous efficiency and the external quantum efficiency of the device is superior to others when hole size of crucible boat using BCP is 1.2 mm. Also, compared to the ones from the devices having the hole size of crucible boat is 1.0 mm and 1.5mm layer, the external quantum efficiency were improved by 2.5 and 2.4 times.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• 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.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 하계학술대회 논문집
• /
• pp.292-292
• /
• 2009

OLED(Organic Light Emitting Device)는 LCD(Liquid Crystal Display)의 뒤를 잇는 차세대 디스플레이의 선두주자로서 자체발광형이기 때문에 백라이트 등의 보조광원이 불필요하며, 구동전압이 낮고 넓은 시야각과 빠른 응답속도 등의 특징을 가지고 있다. 또한 플렉서블 기판을 사용할 수 있어 차세대 디스플레이인 플렉서블 디스플레이에 적합하다. 플렉서블한 디스플레이를 만들기 위해서 플라스틱 기판에 OLED 물질을 사용하여 기존에 무겁고, 깨지기 쉬우며, 변형이 불가능한 유리로 만든 소자 보다 더 가볍고 깨지지 않고 변형이 가능한 플렉서블 디스플레이를 제작 할 수 있다. 그러나 플라스틱 기판은 매우 큰 투습율을 가지고 있어 OLED소자에 적용시키면 공기 중의 수분이나 산소와 접촉이 많아져 쉽게 산화되어 소자의 효율 및 수명이 짧아진다. 또한 OLED에 사용되는 유기물도 산소나 수분에 의해 특성이 급격히 저하되기 때문에 산소 및 수분의 차단은 필수적이다. 이러한 단점을 최소화하기 위해서 PECVD(Plasma Enhanced Chemical Vapor Deposition)로 만든 SiON(Silicon Oxynitride) 박막을 차단막(Passivation layer)으로 사용하였다. PECVD를 이용하여 SiON 박막을 증착시킬 때 RF Power, 공정압력, Distance의 변화에 따른 박막의 결정화도, 수분투습도, 광투과도 등의 특성을 FT-IR(Fourier Transform Infrared Spectroscopy), Ellipsometer, UV-visible Spectrophotometer, MOCON를 이용하여 SiON 박막의 특성을 고찰하였다.