• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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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.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.12
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• pp.13-18
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• 2005

In this paper, we fabricated a pixel array in which each pixel was consisted of Organic Thin Film Transistor (OTFT) serially connected with Organic Light Emitting Diode (OLED) on Poly-ethylene-terephthalate (PET) substrate and the number of pixels was 64 x 64. As a gate insulator of OTFT, the thermally cross-linked PVP was used and the organic semiconductor, Pentacene, is deposited for an active layer of OTFT considering the compatibility with PET substrate. The mobility of OTFT is $1.0\;cm^2/V{\cdot}sec$ as a discrete device, but it was reduced to $0.1\~0.2\;cm^2/V{\codt}sec$ in the array. We analyzed the operation of the array and confirmed the current driving ability of OTFTs for the OLEDs.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.186-189
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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 room temperature process. The gate, source, and drain electrode patterns of OTFT were fabricated by microcontact printing process. The OTFT array with dielectric layer and organic active semiconductor layer formed at room temperature or at a temperature lower than $40^{\circ}C$. The microcontact printing process using SAM and PDMS stamp made it possible to fabricate OTFT arrays with channel lengths down to even submicron size, and reduced the fabrication process by 10 steps compared with photolithography. Since the process was done in room temperature, there was no pattern shrinkage, transformation, and bending problem appeared. Also, it was possible to improve electric field mobility, to decrease contact resistance, to increase close packing of molecules by SAM, and to reduce threshold voltage by using a big dielectric.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.45-48
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• 2002

Poly(3-hexylthiophene) or P3HT based organic thin film transistor (OTFT) array was fabricated on flexible poly carbonate substrates and the electrical characteristics were investigated. As the gate dielectric, a dual layer structure of polyimide-$SiO_2$ was used to improve the roughness of $SiO_2$ surface and further enhancing the device performance and also source-drain electrodes were $O_2$ plasma treated for improvement of the electrical properties, such as drain current and field effect mobility. For the active layer, polymer semiconductor, P3HT layer was printed by contact-printing and spin-coating method. The electrical properties of OTFT devices printed by both methods were evaluated for the comparison. Based on the experiments, P3HT-based OTFT array with field effect mobility of 0.02~0.025 $cm^{2}/V{\cdot}s$ and current modulation (or $I_{on}/I_{off}$ ratio) of $10^{3}\sim10^{4}$ was fabricated.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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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.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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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.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.889-892
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• 2004

We developed a high performance bottom contact, organic thin-film transistor (OTFT) array on plastic using a self-organized process. The effect of OTS treatment on the PVP gate insulator for the performance of OTFT on plastic has been studied The OTFT without OTS exhibited a field-effect mobility of 0.1 $cm^2$/Vs on/off current ratio of > $10^7$. On the other hand, OTFT with OTS, exhibited a field-effect mobility of 1.3 $cm^2$/Vs and on/off current ratio of>$10^8$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.64-67
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• 2005

We fabricated an array consisting of organic TFTs(OTFT) and organic LEDs (OLED) in order to demonstrate the possible application of OTFTs to flexible active matrix OLED (AMOLED). The panel was composed of $64{\times}64$ pixels on 4 inch size polyethylene-terephehalate (PET) substrate in which each pixel had one OTFT integrated with one green OLED. The panel successfully displayed some letters and pictures by emitting green light with a luminance of $1.5\;cd/m^2$ at 6 V, which was controlled by the gate voltage of OTFT.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.3
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• pp.7-11
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• 2011

In this paper, we proposed a simple and high-yield printing process for source and drain electrodes of organic thin film transistor (OTFT). The surface energy of PVP (poly 4-vinylphenol) gate dielectric was decreased from 56 $mJ/m^2$ to 45 $mJ/m^2$ by adding fluoride of 3000ppm into it. Meanwhile the surface energy of source and drain (S/D) electrodes area on the PVP was increased to 87 $mJ/m^2$ by treating the areas, which was patterned by photolithography, with oxygen plasma, maximizing the surface energy difference from the other areas. A conductive polymer, G-PEDOT:PSS, was deposited on the S/D electrode areas by brushing painting process. With such a simple process we could obtain a high yield of above 90 % in $16{\times}16$ arrays of OTFTs. The performance of OTFTs with the fluoride-added PVP was similar to that of OTFTs with the ordinary PVP without fluoride, generating the mobility of 0.1 $cm^2/V.sec$, which was sufficient enough to drive electrophoretic display (EPD) sheet. The EPD panel employing the OTFT-backpane successfully demonstrated to display some patterns on it.