• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.469.2-469.2
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• 2014

All-solid-state solar cell based on Chloride doped organometallic halide perovskite, (CH3NH3)PbIxCl3-x, has achieved a highly power conversion efficiency (PCE) to over 15% [1] and further improvements are expected up to 20% [2]. In this way, solar cells using novel light absorbing perovskite material are actively being studied as a next generation solar cells. However, making solution-process require high temperature up to $500^{\circ}C$ to form compact hole blocking layer and sinter the mesoporous oxide scaffold layer. Because of this high temperature process, fabrication of flexible solar cells on plastic substrate is still troubleshooting. In this study, we fabricated highly efficient flexible perovskite solar cells with PCE in excess of 11%. Atomic layer deposition (ALD) is used to deposit dense $TiO_2$ as hole blocking layer on ITO/PEN substrate. The all fabrication process is done at low temperature below $150^{\circ}C$. This work shows that one of the important blueprint for commercial use of perovskite solar cells.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.319-319
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• 2010

Dye-sensitized solar cells (DSSCs) based on plastic substrates have attracted much attention mainly due to extensive applications such as ubiquitous powers, as well as the practical reasons such as light weight, flexibility and roll-to-roll process. However, conventional high temperature fabrication technology for glass based DSSCs, cannot be applied to flexible devices because polymer substrates cannot withstand the heat more than $150^{\circ}C$. Therefore, low temperature fabrication process, without using a polymer binder or thermal sintering, was required to fabricate necked $TiO_2$. In this presentation, we proposed polymer-inorganic composite photoelectrode, which can be fabricated at low temperature. The concept of composite electrode takes an advantage of utilizing elastic properties of polymers, such as good impact strength. As an elastic material, poly(methyl methacrylate) (PMMA) is selected because of its optical transparency and good adhesive properties. In this work, a polymer-inorganic composite electrode was constructed on FTO/glass substrate under low temperature sintering condition, from the mixture of PMMA and $TiO_2$ colloidal solution. The effect of PMMA composition on the photovoltaic property was investigated. Then, the enhanced mechanical stability of this composite electrode on ITO/PEN substrate was also demonstrated from bending test.

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.168-171
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• 2013

A reflective flexible display was fabricated by placing a thermochromic pigment on a polyethylene naphthalate (PEN) substrate coated with an indium tin oxide (ITO) film, and its thermo-optical characteristics were investigated. The reflective thermochromic display showed good image quality with a reflectance of approximately 65%. As a flexible display, the display showed reliability without damage to the image even after the display was bent strongly. The reflective display cell exhibits continuously the gray level according to the temperature controlled by applied voltage. This low cost display is expected be used in outdoor poster applications where information needs to be presented clearly.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1443-1444
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• 2011

플렉시블 OLED 소자에서 주요한 역할을 하는 기판은 디스플레이의 성능, 신뢰성과 가격을 결정한다. 플렉시블 OLED소자의 기판으로는 PET, PC, PES, PEN과 같은 고분자 계열의 기판이 많이 사용되고 있지만 거칠기 등의 문제가 있는 것으로 알려져 있다. 본 논문에서는 셀룰로오스 종이를 사용하는 투명 플렉시블 OLED 소자를 개발하였다. 본 논문에서는 개발한 셀룰로오스 종이의 표면 거칠기는 $3.1{\AA}$이었으며, 투과도는 97.6%로서 PET기판 보다 우수한 특성을 보여주었다. 셀룰로오스 종이를 기판위에 양극으로 Ni을 이용하는 녹색 발광 플렉시블 OLED소자를 구현하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.469-469
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• 2013

Flexible display는 미래의 평판디스플레이 시장으로 꼽히고 있는 대표적인 분야이다. PET, PEN, PI 등의 polymer substrate는 접거나 구부리는 형태로 변형이 가능하기 때문에 차세대 기술로 평가되어지는 Flexible display, Solar cell, OLED 등 다방면에 응용이 가능하다. 또한 ITO는 지금까지 개발된 재료 중에서 가장 투명하고 전기가 잘 통하며, 생산성도 좋기 때문에 이것을 투명전극의 재료로 사용한다. 디스플레이에 사용되는 투명 전도막의 경우, 가시광 영역에서의 투과 및 반사와 같은 광학적 특성은 중요한 요소 중의 하나이다. 투명 전도막의 광흡수, 반사 및 투과즉성은 박막 내에 존재하는 전공밴드의 전자, 자유전자, polar optical phonon 등의 빛과의 반응에 의해 결정된다고 알려져 있다. 본 연구에서는 저온 증착된 ITO 박막의 광학적 특성을 향상시킬 수 있는 방법을 모색하고 기계적, 화학적 특성을 분석하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08b
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• pp.1680-1682
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• 2007

The integrated circuits such as inverters, ring oscillators, NAND and NOR gates, and rectifiers were fabricated on PEN substrate by using pentacene TFTs. The OTFTs used bottom contact structure and produced the average mobility of $0.26\;cm^2/V.sec$ and on/off current ratio of $10^5$. All circuits worked successfully like the simulation results. Especially, the rectifier was able to operate up to 1 MHz input signals, and ring oscillator exhibited oscillation frequency of 1MHz at-40V.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.383-383
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• 2011

We fabricated thermal annealing-free polymer solar cells (PSC) by processing with additive and applied to flexible substrates. The 1, 8-Diiodooctane of 3 vol% blended with active solution resulted in enhancement of $J_{SC}$ due to increase of light absorption and hole mobility as improving the crystallinity of P3HT. In addition, the $V_{OC}$ of PSCs with additive was improved by inserting $TiO_2$ layer without any treatment. The $TiO_2$ layer prevented the direct contact between active layer and Al electrode and reduced the charge recombination near Active/Al interface. It was confirmed by calculation of J0 and photo-voltage transient measurement. The power conversion efficiencies of annealing-free PSCs using additive for ITO glass and flexible (ITO PEN) substrate were obtained 3.03% and 2.45%, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.637-637
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• 2013

We develop single-crystal poly(3,4-ethylenedioxythiopene nanowires using liquid-bridge-mediated nanotransfer printing via vapor phase polymerization. This direct printing method can simultaneously enable the synthesis, alignment and patterning of the nanowires from molecular ink solutions. Twoor three-dimensional complex structures of various single-crystal organic nanowires were directly fabricated over a large area using many types of molecular inks. This method is capable of generating several optoelectronic devices. LB-nTM is based on the direct transfer of various materials from a mold to a substrate via a liquid bridge between them. To demonstrate its usefulness, we used LB-nTM to fabricate nanowire field-effect transistors and arrays of 6,13-bis (triisopropyl- silylethynyl) pentacene (TIPS-PEN) nanowire field-effect transistors.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.255-256
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• 2007

A A4 size black and white reflective plastic display was developed for out door application. For document readability, high resolution of 180ppi plastic TFT backplane and high reflectance electrophoretic front panel sheet was used. Preparation of display was held near $100^{\circ}C$ process on PEN substrate.

• Journal of the Optical Society of Korea
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• v.17 no.5
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• pp.428-432
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• 2013

This research presents a flexible reflective thermochromic display (TCD) comprised of thermochromic pigments and a patterned indium tin oxide (ITO) film coated on a polyethylene naphthalate (PEN) substrate, and the display's thermo-optical characteristics. The display showed maximum red, green, and blue reflectances of 30%, 38%, and 29%, respectively. Furthermore, the display exhibited a continuous grey color when the temperature was changed continuously. As a flexible display, the display showed reliable thermo-optical performance without image damage even when highly bent. We expect the proposed TCD will be used in outdoor information display applications where low cost is a key factor.