• Title, Summary, Keyword: OTFT

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유기박막트랜지스터의 플렉시블 디스플레이 패널 적용 연구

  • Lee, Myeong-Won;Ryu, Gi-Seong;Song, Jeong-Geun
    • Information Display
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    • v.8 no.3
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    • pp.12-17
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    • 2007
  • 유기박막트랜지스터(OTFT)는 지난 십 수년 간 개발되어 상용화의 단계에 도달하여 우선적으로 플렉시블 디스플레이에 적용될 것으로 예상된다. 본 논문에서는 EPD와 OLED의 구동소자로서 OTFT를 사용한 플렉시블 디스플레이 패널 제작에 대해서 살펴본다. EPD와 OLED는 소자의 구조와 특성이 다르기 ��문에 OTFT 어레이와 집적화 시 고려해야 할 요소들도 다르다. EPD는 문턱전압이 없으므로 스위칭 소자로서 OTFT가 반드시 필요하다. 또한 전압구동소자이고 동작이 느리기 ��문에 OTFT의 이동도가 $0.01cm^2/V.sec$ 이상만 되어도 사용 가능하고 쌍안정 소자임에도 불구하고 저장 캐패시터를 사용하여야 한다. 그리고 OTFT 패널과 EPD 패널을 상호 부착해야 하므로 OTFT 어레이에 영향을 주지 않는 중간층이 중요한 요소이다. OLED는 전류구동소자이므로 OTFT의 이동도가 최소 $0.1cmcm^2/V.sec$ 이상이어야 하고, OTFT 어레이와 동일한 패널을 사용하므로 제조 공정의 호환성이 필수 요건이다.

Study on OTFT-Backplane for Electrophoretic Display Panel (전기영동 디스플레이 패널용 OTFT-하판 제작 연구)

  • Lee, Myung-Won;Ryu, Gi-Sung;Song, Chung-Kun
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.45 no.7
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    • pp.1-8
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    • 2008
  • We fabricated flexible electrophoretic display(EPD) driven by organic thin film transistors(OTFTs) on plastic substrate. We designed the W/L of OTFT to be 15, considering EPD's transient characteristics. The OTFTs employed bottom contact structure and used Al for gate electrode, the cross-linked polyvinylphenol for gate insulator, pentacene for active layer. The plastic substrate was coated by PVP barrier layer in order to remove the islands which were formed after pre-shrinkage process and caused the electrical short between bottom scan and top data metal lines. Pentacene active layer was confined within the gate electrodes so that the off current was controlled and reduced by gate electrodes. Especially, PVA/Acryl double layers were inserted between EPD panel and OTFT-backplane in order to protect OTFT-backplane from the damages created by lamination process of EPD panel on the backplane and also accommodate pixel electrodes through via holes. From the OTFT-backplane the mobility was $0.21cm^2/V.s$, Ion/Ioff current ratio $10^5$. The OTFT-EPD panel worked successfully and demonstrated to display some patterns.

The Fabrication of OTFT-OLED Array Using Ag-paste for Source and Drain Electrode (Ag 페이스트를 소스와 드레인 전극으로 사용한 OTFT-OLED 어레이 제작)

  • Ryu, Gi-Seong;Kim, Young-Bae;Song, Chung-Kun
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.45 no.5
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    • pp.12-18
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    • 2008
  • Ag paste was employed for source and drain electrode of OTFTs and for the data metal lines of OTFT-OLED array on PC(polycarbonate) substrate. We tested two kinds of Ag-pastes such as pastes for 325 mesh and 500 mesh screen mask to examine the pattern ability and electrical performance for OTFTs. The minimum feature size was 60 ${\mu}m$ for 325 mesh screen mask and 40 ${\mu}m$ for 500 mesh screen mask. The conductivity was 60 $m{\Omega}/\square$ for 325 mesh and 133.1 $m{\Omega}/\square$ for 500 mesh. For the OTFT performance the mobility was 0.35 $cm^2/V{\cdot}sec$ and 0.12 $cm^2/V{\cdot}sec$, threshold voltage was -4.7 V and 0.9 V, respectively, and on/off current ratio was ${\sim}10^5$, for both screen masks. We applied the 500 mash Ag paste to OTFT-OLED array because of its good patterning property. The pixel was composed of two OTFTs and one capacitor and one OLED in the area of $2mm{\times}2mm$. The panel successfully worked in active mode operation even though there were a few bad pixels.

Self-Assembled $TiO_2$ and Polyelectrolyte Multilayer as OTFT Gate Insulator

  • Moon, Zi-Su;Kim, Hong-Doo
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1422-1424
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    • 2009
  • Modified self-assembled $TiO_2$ and polyelectrolyte multilayer film have been used as OTFT insulator. Both films were used as gate insulator and their thickness were reduced to the order of 10nm. The operating voltage of OTFT was substantially reduced due to nanoscale thickness of titanium oxide and polyelectrolyte multilayer. Pentacene-based OTFT characteristics will be discussed.

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High resolution flexible e-paper driven by printed OTFT

  • Hu, Tarng-Shiang;Wang, Yi-Kai;Peng, Yu-Rung;Yang, Tsung-Hua;Chiang, Ko-Yu;Lo, Po-Yuan;Chang, Chih-Hao;Hsu, Hsin-Yun;Chou, Chun-Cheng;Hsieh, Yen-Min;Liu, Chueh-Wen;Hu, Jupiter
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.421-427
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    • 2009
  • We successfully fabricated 4.7-inch organic thin film transistors array with $640{\times}480$ pixels on flexible substrate. All the processes were done by photolithography, spin coating and ink-jet printing. The OTFT-Electrophoretic (EP) pixel structure, based on a top gate OTFT, was fabricated. The mobility, ON/OFF ratio, subthreshold swing and threshold voltage of OTFT on flexible substrate are: 0.01 ^2/V-s, 1.3 V/dec, 10E5 and -3.5 V. After laminated the EP media on OTFT array, a panel of 4.7-inch $640{\times}480$ OTFT-EPD was fabricated. All of process temperature in OTFT-EPD is lower than $150^{\circ}C$. The pixel size in our panel is $150{\mu}m{\times}150{\mu}m$, and the aperture ratio is 50 %. The OTFT channel length and width is 20 um and 200um, respectively. We also used OTFT to drive EP media successfully. The operation voltages that are used on the gate bias are -30 V during the row data selection and the gate bias are 0 V during the row data hold time. The data voltages that are used on the source bias are -20 V, 0 V, and 20 V during display media operation.

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Development of the Printed Top Gate Organic Thin Film Transistor (OTFT)

  • Kang, H.S.;Kang, H.C.;Lee, M.H.;Park, S.Y.;Kim, M.J.;Heo, J.S.;Kim, D.W.;Noh, Y.H.;Lee, S.;Kim, J.Y.;Kim, C.D.;Kang, I.B.
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.113-116
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    • 2008
  • The active layer thickness and curing condition dependent performance of an organic thin film transistor (OTFT) with inkjetted organic semiconductor (OSC) layer is studied The best performance of the OTFT was found when the thickness of ose was ~120 nm cured at $60^{\circ}C$. The performance enhancement of the OTFT with inkjetted OSC layer was discussed by comparing the OTFT with spin-coated ose layer.

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Passivation Layer (Thermosetting Film)가 형성된 유기박막 트랜지스터의전기적 특성 변화에 대한 연구

  • Seong, Si-Hyeon;Kim, Gyo-Hyeok;Jeong, Il-Seop
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.380-380
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    • 2013
  • 본 논문에서는 외기 환경 요인 중에서 H2O와 O2의 영향으로 성능이 저하되는 유기박막트랜지스터(OTFT)의 수명시간 향상을 위하여 필요한 passivation layer의 효과에 대하여 알아 보았다. OTFT에 기존의 액상 공정이나 증착 공정으로 단일 passivation layer또는 다층 passivation layer를 형성하는 방식과는 다르게 향후에 산업 전반에 적용이 기대되는 것을 고려하여 제작 공정의 간편성을 위하여 film 형태로 되어 있는 열경화성 epoxy resin film으로 passivation layer를 구현하는 방법을 사용하여 OTFT의 storage stability를 평가하였다. passivation layer가 없는 OTFT와 열경화성 epoxy resin film으로 passivation된 OTFT의 전기적 특성이 서로 비교 평가되었으며 또한 30일 동안 온도 $25^{\circ}C$ 상대습도 40%의 환경을 갖는 Desicator 안에서 소자를 보관하여 시간에 따른 전기적 특성 변화를 검증하여 epoxy resin film의 passivation layer으로의 적용가능성을 검증하였다. 결과적으로 30일 후의 passivation layer가 없는 OTFT의 전기적 특성은 매우 낮게 떨어진 반면에 epoxy resin film으로 passivation layer가 구현된 OTFT의 mobility는 $0.060cm^2$/Vs, VT는 -0.18 V, on/off ratio는 $3.7{\times}10^3$으로 초기의 소자 특성이 잘 유지되는 결과를 얻었다. OTFT는 Flexible한 polyethersulfone (PES)기판에 게이트 전극이 하부에 있는 Bottom gate 구조로 제작되었고 채널 형성을 위한 유기반도체 재료로 6,13-bis (triisopropylsilylethynyl) (TIPS) pentacene이 사용되었고 spin coating된 Poly-4-vinylphenol (PVP)가 게이트 절연체로 사용되었다. 이때 Au전극은 Shadow mask를 이용하여 증착하였다. 또한 OTFT의 채널 길이 $100{\mu}m$, 채널 폭 $300{\mu}m$의 영역에 Drop casting법을 사용하여 채널을 형성하였다. 물리적 특성은 scanning electron microscopy (SEM), scanning probe microscopy (SPM), x-ray diffraction (XRD)를 사용하여 분석하였고, 전기적 특성은 Keithley-4200을 사용하여 추출하였다.

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Fabrication of Organic Thin Film Transistor(OTFT) for Flexible Display by using Microcontact Printing Process (미세접촉프린팅공정을 이용한 플렉시블 디스플레이 유기박막구동소자 제작)

  • Kim K.Y.;Jo Jeong-Dai;Kim D.S.;Lee J.H.;Lee E.S.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.595-596
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    • 2006
  • The flexible organic thin film transistor (OTFT) array to use as a switching device for an organic light emitting diode (OLED) was designed and fabricated in the microcontact printing and low-temperature processes. The gate, source, and drain electrode patterns of OTFT were fabricated by microcontact printing which is high-resolution lithography technology using polydimethylsiloxane(PDMS) stamp. The OTFT array with dielectric layer and organic active semiconductor layers formed at room temperature or at a temperature tower than $40^{\circ}C$. The microcontact printing process using SAM(self-assembled monolayer) and PDMS stamp made it possible to fabricate OTFT arrays with channel lengths down to even nano size, and reduced the procedure by 10 steps compared with photolithography. Since the process was done in low temperature, there was no pattern transformation and bending problem appeared. It was possible to increase close packing of molecules by SAM, to improve electric field mobility, to decrease contact resistance, and to reduce threshold voltage by using a big dielecric.

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Fabrication of Flexible OTFT Array with Printed Electrodes by using Microcontact and Direct Printing Processes

  • Jo, Jeong-Dai;Lee, Taik-Min;Kim, Dong-Soo;Kim, Kwang-Young;Esashi, Masayoshi;Lee, Eung-Sug
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.155-158
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    • 2007
  • Printed organic thin-film transistor(OTFT) to use as a switching device for an organic light emitting diode(OLED) were fabricated in the microcontact printing and direct printing processes at room temperature. The gate electrodes($5{\mu}m$, $10{\mu}m$, and $20{\mu}m$) of OTFT was fabricated using microcontact printing process, and source/drain electrodes ($W/L=500{\mu}m/5{\mu}m$, $500{\mu}m/10{\mu}m$, and $500{\mu}m/20{\mu}m$) was fabricated using direct printing process with hard poly(dimethylsiloxane)(h-PDMS) stamp. Printed OTFT with dielectric layer was formed using special coating system and organic semiconductor layer was ink-jet printing process. Microcontact printing and direct printing processes using h-PDMS stamp made it possible to fabricate printed OTFT with channel lengths down to $5{\mu}m$, and reduced the process by 20 steps compared with photolithography. As results of measuring he transfer characteristics and output characteristics of OTFT fabricated with the printing process, the field effect characteristic was verified.

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Fabrication of OTFT-backplane with solution process for Electrophoretic Display panel

  • Lee, Myung-Won;Lee, Mi-Young;Park, Jong-Seung;Song, Chung-Kun
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.428-430
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    • 2009
  • We fabricated flexible OTFT-backplanes with combining printing technique and conventional photolithography process for the electrophoretic display(EPD). The active area size of backplane was 6" in diagonal direction and consisted of $192{\times}150$ pixels, containing 1 OTFT employed bottom contact structure and 1 capacitance in each pixel.

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