• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1002-1004
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• 2009

Solution-processed indium-gallium-zinc-oxide thin-film transistors were fabricated by sol-gel method. By a combinatorial study of InGaZnO multi-component system, optimum molar ratio of In, Ga, and Zn has been selected. By adjusting the In:Ga:Zn molar ratio, TFTs with field-effect mobility of 0.5 ~ 1.5 $cm^2$/V-s, threshold voltage of -5 ~ 5 V, and subthreshold slope of 1.5 ~ 2.5 V/decade were achieved.

• 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.568-570
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• 2009

Octadecyltrichlorosilane (OTS) self-assembled monolayer was selectively patterned by deep ultraviolet exposure, resulting in differential surface state, hydrophilic area with OTS hydrophobic surroundings. High-resolution (<10 ${\mu}m$) nanoparticulate Ag electrodes and organic semiconductors were patterned from simple dip-casting and ink-jetting on the pre-patterned hydrophilic surface, forming all solution-processed organic thin film transistors. The devices typically have shown a mobility of 0.065 $cm^2/V{\cdot}s$ and on-off current ratio of $8{\times}10^5$.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.6
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• pp.491-495
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• 2014

We developed a compact high-precision slot-die coating machine for thin-film deposition on a flexible substrate. For smooth and precise coating, air-bearing and linear motor system were employed to minimize velocity ripple. The gap control mechanism is specially designed to have repeatability of gap between nozzle and substrate under 1 ${\mu}m$. Due to extremely precise gap control, the machine can coat thin-films down to 50 nm with $200mm{\times}100mm$ size. A thin film of Ag nano-particle ink is coated for demonstration.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.67-70
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• 2009

Printed electronics are emerging technology to realize various microelectronic devices via a cost-effective method. Here we introduce high performance inkjet printed polymer field-effect transistors and application to complementary integrated circuits with p-type and n-type conjugated polymers. The performance of devices highly depends on the selection of dielectrics, printing condition and device architecture. The device optimization and performances of various integrated circuits, e.g., complementary inverters and ring oscillators will be mainly discussed in this talk.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.917-919
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• 2009

Effects of nano-silver contents(15~50wt%) on screen printed-etched gate electrodes and electrical characteristics of OTFTs were investigated. As Ag contents increased, the screen-printed film was transferred exactly without spreading and obtained the densely-packed layer with a stable and excellent conductivity but, its thickness was increased and surface became rougher. It was found that the leakage current of MIM devices and off-state currents of OTFTs became larger due to poor step coverage of PVP dielectric layer on the thick and rough gate electrodes for nano-Ag inks with Ag contents more than 30wt%.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.142-144
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• 2009

We demonstrated narrow and good aspect-ratio inkjet-printed silver lines with multi-time over-printing methods. By using this strategy, narrow silver lines were obtained with 200 nm thickness and their width and gap between printed lines of uniform narrow silver lines were 30 ${\mu}m$ and 17 ${\mu}m$, respectively. It also had good conductivity, sheet resistacne of 0.36 ${\Omega}/{\square}$ and specific resistance of $8{\mu}{\Omega}{\cdot}cm$. In current stress test, narrow silver line with 30 ${\mu}m$ width was able to a current flow up to 50 mA (2.1A/$cm^2$). Using surface treatment on poly-arylate substrate with $UVO_3$, we obtained clean-edge narrow line without any edge waviness.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.239-242
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• 2009

$Sr_2Si_5N_8:Eu^{2+}$, one of the most recently developed phosphors for use in white light emitting diodes, exhibits a two-peak emission. Namely, the emission band of $Sr_2Si_5N_8:Eu^{2+}$ is deconvoluted into two Gaussian peaks irrespective of the $Eu^{2+}$ concentration. We examined the two-peak emission of $Sr_2Si_5N_8:Eu^{2+}$ by analyzing the time-resolved photoluminescence spectra. We revealed that the two-peak emission was closely associated with the energy transfer taking place between $Eu^{2+}$ activators located at two different crystallographic sites in the $Sr_2Si_5N_8$ structure. The experimental results coincided well with the rate equation model involving the crystallographic information of the host.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1571-1572
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• 2009

Polymer solar cells were fabricated with gravure printing process and the effect of thermal annealing of gravure printed organic layer was investigated. The layer structure of polymer solar cells is glass / ITO / hole transfer layer / active layer / Al structure was fabricated. For the active layer, 1:1 ratio of poly-3-hexylthiophene (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) mixture was applied. The P3HT/PCBM blend was gravure printed onto the substrates. The effect of thermal annealing was investigated by changing annealing time and the number of printing. Maximum 3.6% of power conversion efficiency was achieved with gravure printing of organic layer and thermal annealing in this work.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.730-732
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• 2007

We fabricated a coplanar type organic thin-film transistors using ink-jet printed silver source/drain electrodes and ${\alpha},{\omega}-dihexylquaterthiophene$ (DH4T) which is an active layer. Use of ink-jet printed silver nanoparticle-based metal electrode assists the energetic mismatch with p-type organic semiconductor via modification of their interfacial properties to enable ohmic contact formation.