• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.1
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• pp.8-17
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• 2023

In conventional liquid crystal display(LCD) manufacturing process, Indium Tin Oxide(ITO) as transparent electrode and rubbing process of polyimide as alignment layer are essential process to apply electric field and align liquid crystal molecules. However, there are some limits that deposition of ITO requires high vacuum state, and rubbing process might damage the device with tribolectric discharge. In this paper, we made nanocomposite with PEDOT:PSS and MWNT to replace ITO and constructed alignment layer by nano imprint lithography with nano wrinkle pattern, to replace rubbing process. These replacement made that only one PEDOT:PSS/MWNT film can function as two layers of ITO and polyimide alignment layer, which means simplification of process. Transferred nano wrinkle patterns functioned well as alignment layer, and we found out lowered threshold voltage and shortened response time as MWNT content increase, which is related to increment of electric conductivity of the film. Through this study, it may able to contribute to process simplification, reducing process cost, and suggesting a solution to disadvantage of rubbing process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.2
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• pp.69-73
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• 2018

The power law is very important in gas sensing for the determination of gas concentration. In this study, the resistance of a gas sensor based on poly (3, 4-ethylenedioxythiophene) polystyrene sulfonate+graphene oxide composite was found to exhibit a power law dependence on hydrogen concentration at $150^{\circ}C$. Experiments were carried out in the gas concentration range of 30~180 ppm at which the sensor showed a sensitivity of 6~9% with a response and recovery time of 30s.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.184-184
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• 2010

ITO의 전극 패턴에 따른 유기 광기전력 소자의 전기적 특성에 대해서 연구하였다. 소자의 구조는 ITO/PEDOT:PSS(90nm)/CuPc(20nm)/$C_{60}$(40nm)/LiF(0.5nm)/Al(100nm)이고, PEDOT:PSS는 스핀 코팅한 후 $120^{\circ}C$에서 20분간 건조시켰으며, 유기물은 열증착을 하여 제작하였다. ITO 전극의 패턴을 corss-bar type과 island type으로 하여 소자의 특성을 비교하였다. 광원은 500W xenon lamp를 사용하였고, optical density filter로 광원의 세기를 조절하였으며, AM 1.5G의 스펙트럼을 조사하였다. PEDOT:PSS 층을 사용함으로서 유기 광기전력 소자의 효율, 단락 전류, 그리고 개방 전압의 향상을 얻을 수 있었다. ITO 전극 패턴에 따른 광기전력 소자의 특성은 cross-bar type에 비하여 island type의 구조에서 유기 광기전력 소자의 효율이 34% 감소하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.193-194
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• 2008

$Orgacon^{TM}$ products, based on the conducting polymer PEDOT/PSS, are very promising materials in cost-effective R2R production of large area electronics. This presentation will show both the progress in the surface resistance/VLT and progress in the stability (T/R.H. and light stability). A new generation of films, coating formulations and inks will be presented.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.4
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• pp.37-42
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• 2007

We fabricated the polymer light emitting diodes (PLEDs) with ITO/PEDOT:PSS/PVK/PFO:MEH-PPV/LiF/Al structures. The effect of the thickness of PEDOT:PSS hole injection layer(HIL) on the electrical and optical properties of PLEDs was investigated. In addition, PVK hole transport layer(HTL) was introduced in the PLED device, and compared the properties of the PLEDS with and without PVX layer. All organic film layers were prepared by the spin coating method on the plasma treated ITO/glass substrates. As the thickness of PEDOT:PSS film layer decreased from about 80 nm to 50 nm, the luminance of PLED device increased from $220cd/m^2$에서 $450cd/m^2$. This may be ascribed to the increased transportation efficiency of the holes into the emission layer of PLED. The maximum current density and luminance were obtained fir the PLED device with PVX hole transport layer, showing that the current density and luminance were $268mA/cm^2\;and\;540cd/m^2$ at 12V, respectively. This values were improved by about 14% and 22% in current density and luminance compared with the PLED device without PVK layer.

• Journal of the Microelectronics and Packaging Society
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• v.12 no.2 s.35
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• pp.155-159
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• 2005

In this report, Polymer light emitting diodes (PLEDs) with an ITO/PEDOT:PSS/MEH-PPV/Al structure were prepared by spin coating method on the glass substrate patterned ITO (indium tin oxide), using PEDOT:PSS(poly(3,4=ethylenedioxythiophene):poly(styrene sulfolnate)) as the hole transfer material and MEH-PPV(poly(2-methoxy-5-(2-ethyhexoxy)-1,4-phenylenvinylene)) having a different concentration (0.1, 0.3, 0.5, 0.7, 0.9, 1.5 wt$\%$) as the emitting material. The electrical and optical properties of the prepared PLED samples were investigated. The good electrical and optical properties were observed for the PLED samples with a MEH-PPV concentration ranging from 0.5 to $0.9 wt\%$. However, the current and luminance values for PLED sample with $1.5 wt\%$ of MEH-PPV decreased greatly. The maximum luminance and light efficiency for the PLEDs with concentration of $0.5 wt\%$ MEH-PPV were $409 cd/m^2$ and 4.90 Im/W at 9 V, respectively. The emission spectrums were found to be $560{\~}585 nm$ in wavelength showing orange color.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.100-104
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• 2019

We have investigated the feasibility of fabricating fine stripes using needle coating for potential applications in solution-processed organic light-emitting diodes (OLEDs). To this end, we have employed an aqueous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solution that has been widely used as a hole injection layer (HIL) of OLEDs and performed needle coatings by varying the process parameters such as the coating gap and coating speed. As expected, the stripe width is reduced with increasing coating speed. However, the central thickness of the stripe is rather increased as the coating speed increases, which is different from other coating processes such as slot-die and blade coatings. It is due to the fact that the meniscus formed between the needle tip and the substrate varies depending sensitively on the coating speed. It is also found that the stripe width and thickness are reduced with increasing coating gap. To demonstrate its applicability to OLEDs, we have fabricated a red OLED stripe and obtained light emission with the width of about 90㎛.

• Journal of Information Display
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• v.4 no.1
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• pp.29-33
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• 2003

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine (CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) in a device structure of $ITO/bufferr/TPD/Alq_3/Al$. Polymer PVK and PEDOT:PSS buffer layer were produced using the spin casting method where as the CuPc layer was produced using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature at various a thickness of the buffer layer. We observed an improvement in the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer were used, respectively. The enhancement of the efficiency is assumed to be attributed to the improved balance of holes and elelctrons resulting from the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer function as a hole-injection supporter and the PVK layer as a hole-blocking one.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.139-139
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• 2010

Ionic Transition Metal Complex based (iTMC) Light-emitting electrochemical cells (LEECs) have been drawn attention for cheap and easy-to-fabricate light-emitting device. LEEC is one of the promising candidate for next generation display and solid-state lighting applications which can cover the defects of current commercial OLEDs like complicated fabrication process and strong work-function dependent sturucture. We have investigated the performance characteristics of LEECs based on poly (3, 4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS)-incorporated transition metal complex, which is tris(2, 2'-bipyridyl)ruthenium(II) hexafluorophosphate in this study. There are advantages using conductive polymer-incorporated luminous layer to prevent light disturbance and absorbance while light-emitting process between light-emitting layer and transparent electrode like ITO. The devices were fabricated as sandwiched structure and light-emitting layer was deposited approximately 40nm thickness by spin coating and aluminum electrode was deposited using thermal evaporation process under the vacuum condition (10-3Pa). Current density and light intensity were measured using optical spectrometer, and surface morphology changes of the luminous layer were observed using XRD and AFM varying contents of PEDOT:PSS in the Ruthenium(II) complex solution. To observe enhanced ionic conductivity of PEDOT:PSS and luminous layer, space-charge-limited-currents model was introduced and it showed that the performances and stability of LEECs were improved. Main discussions are the followings. First, relationship between film thickness and performance characteristics of device was considered. Secondly, light-emitting behavior when PEDOT:PSS layer on the ITO, as a buffer, was introduced to iTMC LEECs. Finally, electrical properties including carrier mobility, current density-voltage, light intensity-voltage, response time and turn-on voltages were investigated.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.168.1-168.1
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• 2014

We developed poly (3,4-ethylene dioxylene thiophene):poly (styrene sulfonic acid) (PEDOT:PSS)-free organic solar cells (OSCs) using buffer and anode combined Ta doped $In_2O_3$ (ITaO) electrodes. To optimize the ITaO electrodes, we investigated the effect of $Ta_2O_5$ doping power on the electrical, optical, and structural properties of the co-sputtered ITaO films. The optimized ITaO film doped with 20 W $Ta_2O_5$ radio frequency power showed sheet resistance of 17.11 Ohm/square, a transmittance of 93.45%, and a work function of 4.9 eV, all of which are comparable to the value of conventional ITO electrodes. The conventional bulk heterojunction OSC with ITaO anode showed a power conversion efficiency (PCE) of 3.348% similar to the OSCs (3.541%) with an ITO anode. In addition, OSCs fabricated on an ITaO electrode successfully operated without an acidic PEDOT:PSS buffer layer and showed a PCE of 2.634%, which was much higher than the comparable no buffer OSC with an ITO anode. Therefore, co-sputtered ITaO electrodes simultaneously acting as a buffer and an anode layer can be considered promising transparent electrodes for cost-efficient and reliable OSCs because they can eliminate the use of an acidic PEDOT:PSS buffer layer.