• 한국재료학회지
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• 제15권8호
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• pp.543-547
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• 2005

Organic electroluminescence devices were made from 1,4-bis-(9-anthrylvinyl)benzene (AVB) and 1,4-bis-(9-aminoanthryl)benzene (AAB) anthracene derivatives. Device structure was ITO/AVB/PANI(EB)/Al (multi-layer device) and ITO/AAB:DCM/Al(single-layer device). In these devices, AVB, polyaniline(emeraldine base) (PANI(EB)) and AAB were used as the emitting material. 4-(dicyanomethylene)-2-methyl-6-p-(dimethylamino)styryl-4H -pyran(DCM) was used as red fluorescent dopant. We studied change of fluorescence wavelength with concentration of DCM doped in AAB. The ionization potential (IP) and optical band gap (Eg) were measured by cyclic voltammetry and UV-visible spectrum. We compared with difference of emitting wavelength between photoluminescence and electroluminescence spectrum. In case of the multi-layer device, PANI and AVB EL spectra have similar wave pattern to each PL spectrum and when PAM and AVB were used at the same time, and multi-layer device showed that a balanced recombination and radiation kom PANI and AVB. In case of the single-layer device, with the increase of DCM concentration, the blue emission decreases and red emission increases. This indicates that DCM was excited by the energy transfer from AAB to DCM or the direct recombination at the dopant sites due to carrier trapping, or both. The device with $1.0wt\%$ DCM concentration gave white light.

• Transactions on Electrical and Electronic Materials
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• 제16권3호
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• pp.124-129
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• 2015

Organic electronics are the domain in which the components and circuits are made of organic materials. This new electronics help to realize electronic and optoelectronic devices on flexible substrates. In recent years, organic materials have replaced conventional semiconductors in many electronic components such as, organic light-emitting diodes (OLEDs), organic field-effect transistors (OFETs) and organic photovoltaic (OPVs). It is well known that organic light emitting diodes (OLEDs) have many advantages in comparison with inorganic light-emitting diodes LEDs. These advantages include the low price of manufacturing, large area of electroluminescent display, uniform emission and lower the requirement for power. The aim of this paper is to model polymer LEDs and OLEDs made with small molecules for studying the electrical and optical characteristics. The purpose of this modeling process is, to obtain information about the running of OLEDs, as well as, the injection and charge transport mechanisms. The first simulation structure used in this paper is a mono layer device; typically consisting of the poly (2-methoxy-5(2'-ethyl) hexoxy-phenylenevinylene) (MEH-PPV) polymer sandwiched between an anode with a high work function, usually an indium tin oxide (ITO) substrate, and a cathode with a relatively low work function, such as Al. Electrons will then be injected from the cathode and recombine with electron holes injected from the anode, emitting light. In the second structure, we replaced MEH-PPV by tris (8-hydroxyquinolinato) aluminum (Alq₃). This simulation uses, the Poole-Frenkel -like mobility model and the Langevin bimolecular recombination model as the transport and recombination mechanism. These models are enabled in ATLAS- SILVACO. To optimize OLED performance, we propose to change some parameters in this device, such as doping concentration, thickness and electrode materials.

• 센서학회지
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• 제30권5호
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• pp.309-313
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• 2021

Organic semiconductors have received tremendous attention for their research because of their tunable electrical and optical properties that can be achieved by changing their molecular structure. However, organic materials are inherently unstable in the presence of oxygen and moisture. Therefore, it is necessary to develop moisture and air stable semiconducting materials that can replace conventional organic semiconductors. In this study, we developed a NiO_x thin film through a solution process. The electrical characteristics of the NiO_x thin film, depending on the thermal annealing temperature and UV-ozone treatment, were determined by applying them to the hole injection layer of an organic light-emitting diode. A high annealing temperature of 500 ℃ and UV-ozone treatment enhanced the conductivity of the NiO_x thin films. The optimized NiO_x exhibited beneficial hole injection properties comparable those of 1,4,5,8,9,11-hexaazatriphenylene hexacarbonitrile (HAT-CN), a conventional organic hole injection layer. As a result, both devices exhibited similar power efficiencies and the comparable electroluminescent spectra. We believe that NiO_x could be a potential solution which can provide robustness to conventional organic semiconductors.

• 한국정밀공학회지
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• 제30권6호
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• pp.589-595
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• 2013

Solution processed conjugated molecules enable to manufacture various electronic devices by unconventional and cost effective patterning methods as screen or gravure printing. Spin-coating is the most popularly used method to form conjugated polymeric film for various electronic devices. The coating method has certain disadvantages such as a large amount of unwanted wastes, difficulty forming a film with a large area, and impossible to apply roll-to-roll manufacturing. We present here a promising alternative coating method, bar-coating for conjugated polymer film and OLED with the bar coated light emitting layer. In this papers, we show atomic force microscope images of spin- and bar-coated Poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,8-diyl)] (F8BT) films on substrate. The bar-coated film showed a slight lower RMS roughness (1.058 [nm]) than spin-coated film (1.767 [nm]). It means the bar-coating is suitable method to form light emitting layers in OLEDs. By using bar-coating process, an OLED obtained with 4.7 [cd/A] in maximum current efficiency.

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2955-2960
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• 2010

Spiro-type orange phosphorescent host materials, 9-diphenylphosphine oxide-spiro[fluorene-7,9'-benzofluorene] (OPH-1P) and 5-diphenylphosphine oxide-spiro[fluorene-7,9'-benzofluorene] (OPH-2P) were successfully prepared by a lithiation reaction followed by a phosphination reaction with diphenylphosphinic chloride. The EL characteristics of OPH-1P and OPH-2P as orange host materials doped with iridium(III) bis(2-phenylquinoline)acetylacetonate ($Ir(pq)_2acac$) were evaluated. The electroluminescence spectra of the ITO (150 nm)/DNTPD (60 nm)/NPB (30 nm)/OPH-1P or OPH-2P: $Ir(pq)_2acac$ (30 nm)/BCP (5 nm)/$Alq_3$ (20 nm)/LiF (1 nm)/Al (200 nm) devices show a narrow emission band with a full width at half maximum of 75 nm and $\lambda_{max}$ = 596 nm. The device obtained from OPH-1P doped with 3% $Ir(pq)_2acac$ showed an orange color purity of (0.580, 0.385) and an efficiency of (14 cd/A at 7.0 V). The ability of the OPH-P series to combine a high triple energy with a low operating voltage is attributed to the inductive effect of the P=O moieties and subsequent energy lowering of the LUMO, resulting in the enhancement of both the electron injection and transport in the device. The overall result is a device with an EQE > 8% at high brightness, but operating voltage of less than 6.4 V, as compared to the literature voltages of ~10 V.

• 폴리머
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• 제32권4호
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• pp.372-376
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• 2008

유기발광소자(OLED)에서 정공 주입층으로 사용되는 4,4',4"-tris(N-(2-naphthyl)-N-phenylamino)-triphenylamine(2-TNATA)가 전극으로 사용되는 ITO(indium tin oxide)와 홀 수송층(hole transport layer, HTL)사이에 박막으로 진공 증착되었다. 공증착에 의해 C60이 약 20 wt% 도핑된 2-TNATA:C60 층을 제조하였으며, AFM과 XRD를 이용하여 2-TNATA:C60 박막의 분자 배향성 및 토폴로지를 관찰하였다. 또한, 다층 소자의 J-V, L-V 및 전류 효율 특성이 고찰되었다. C60은 분자 배향성을 가지고 있으나, 2-TNATA:C60 박막은 C60 분자의 균일한 분산에 의해 분자 배향성이 확인되지 않았다. C60의 도핑에 의해서 2-TNATA 박막이 더욱 조밀해지고 균일해지는 것을 확인하였으며, 이로 인하며 박막 내의 전류 밀도가 증가됨을 확인하였다. 2-TNATA:C60 하이브리드 박막을 이용하여 ITO/2-TNATA:C60/NPD/$Alq_3$/LiF/Al 다층 소자를 제조하였을 때 소자의 휘도가 향상되었으며 소자 효율도 약 4.7에서 약 6.7 cd/A로 증가하였다.

• 폴리머
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• 제33권5호
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• pp.407-412
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• 2009

유기발광소자(OLED)에서 정공 수송층(hole injection layer, HIL)으로 사용되는 N,N'-di-1-naphthyl-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPD)가 정공 주입층(hole injection layer HIL)으로 사용된 PEDOT-PSS 층 위로 진공 증착되었다. PEDOT-PSS 층은 ITO 유리 위에 스핀 코팅되어 제조되었다. 또한, NPD와 $C_{60}$의 공증착에 의해 $C_{60}$이 약 10 wt% 도핑된 NPD-$C_{60}$ 층을 제조하였으며, AFM과 XRD를 이용하여 NPD-$C_{60}$ 박막의 모폴로지 특성을 관찰하였다. 다층 소자를 제조하여 J-Y, L-V 및 전류 효율 특성이 고찰되었다. $C_{60}$박막은 국부적인 결정성 구조를 가지고 있으나, NPD-$C_{60}$ 박막에서는 $C_{60}$ 분자가 균일하게 분산되어 $C_{60}$의 결정성 구조가 확인되지 않았다. 또한, $C_{60}$의 도핑에 의해서 박막의 표면이 균일해지는 것을 확인하였으며, 박막 내의 전류 밀도가 증가됨을 확인하였다. NPD-$C_{60}$ 박막을 이용하여 ITO/PEDOT-PSS/NPD-$C_{60}/Alq_3$/LiF/Al 다층 소자를 제조하였을 때, 소자의 휘도 측면에서 약 80% 향상 효과가 있었으며, 소자 효율 측면에서도 약 25%의 향상을 기대할 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.781-783
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• 2009

We achieved high efficiency and long lifetime in small-molecule organic light-emitting diodes using a blend of polyaniline-based conducting polymer and a perfluorinated ionomer as a hole injection layer (HIL). The HIL formed by single spin coating greatly enhanced the surface work function and thus the hole injection from the anode, which resulted in great improvement in device luminous efficiency. We find that the solution processed HIL outperforms the conventional vacuum-deposited small molecule HIL in terms of the device performance.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.675-679
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• 2004

The existing conjugated blue emitting material polymer which has been used for the two-wavelength method white-emission has good stability and low operating voltage as merits, but the imbalanced carrier transport has been indicated as problem area. We have introduced a novel blue emitting material having perylene moiety unit with hole transporting ability and blue emitting property and triazine moiety unit with electron transporting ability into the same host chain. We have synthesized N-[p-(perylen-3-y1)pheny1]methacry1 amide (PPMA) monomer and [N-(2,4-dipheny1-1,3,5-triazine)pheny1 methacry1 amide] (DTPM) monomer having blue light-emitting unit and electron transport unit, respectively by three steps. A novel non-conjugated blue emitting material Poly[N -[p­(perylene-3-y1) pheny1] methacry1 amide-co-N-[P-(4,6-dipheny1-1,3,5-triazine-2-y1]pheny1]methacry1 amide] (PPPMA-co-DTPM) copolymer having electron transporting unit was synthesized by the solution polymerization of PPMA and DTPM monomers with an AIBN initiator and showed high yield of $75{\%}$. It was very soluble in common organic solvents, and the fabrication of the thin film using a spin coating method was very simple. The PPPMA exhibited a good thermal stability.

• 한국전기전자재료학회논문지
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• 제20권9호
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• pp.798-801
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• 2007

Multilayer transparent electrodes, having a much lower electrical resistance than the widely used transparent conducting oxide electrodes, were prepared by using radio frequency magnetron sputtering. The multilayer structure consisted of five layers, indium tin oxided (ITO)/zinc oxide (ZnO)/Ag/zinc oxide (ZnO)/ITO. With about 50 nm thick ITO films, the multilayer showed a high optical transmittance in the visible range of the spectrum and had color neutrality. The electrical and optical properties of ITO/ZnO/Ag/ZnO/ITO multilayer were changed mainly by Ag film properties, which were affected by the deposition process of the upper layer. Especially ZnO layer was improved to adhesion of Ag and ITO. A high quality transparent electrode, having a resistance as low as and a high optical transmittance of 91% at 550 nm, was obtained. It could satisfy the requirement for the flexible OLED and LCD.