• 대한기계학회논문집B
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• 제36권10호
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• pp.1049-1054
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• 2012

유기전자재료의 발전으로 박막화, 유연화, 경량화가 가능하면서, 저가의 생산비용으로 제조 될 수 있는 유기반도체의 개발 및 상용화에 대한 연구가 활발히 이루어지고 있다. 하지만, 유기반도체를 구성하는 유기재료 및 전극재료가 미량의 수분과 반응으로 성능이 저하되는 문제로 상용화의 큰 걸림돌이 되고 있다. 따라서 유기재료 및 전극을 동작환경의 수분으로부터 보호할 수 있는 고성능 투습 방지막 개발에 대한 연구가 많이 진행되고 있다. 본 연구에서는 $SiO_x$/parylene 및 $SiN_x$/parylene 구조를 이용한 다중 구조의 고성능 박막 봉지막을 개발하고, 개발된 박막을 Ca-corrosion test를 이용하여 수분투과율을 측정하였다. 또한 박막 봉지재를 유기태양전지에 적용하여 유기태양전지의 수명과 투습특성과의 관계를 확인하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.126-126
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• 2016

Understanding adsorption behavior organic molecules at oxide surfaces is very important for the application of organic-inorganic hybrid materials. Recently, monoethanolamine (MEA) adsorbed on $TiO_2$ surface has received great interests because it can lower the work function of $TiO_2$ in photo-electronic devices such as OLED and solar cells. In this study, we investigated the role of surface defects in adsorption behaviors of MEA at the rutile $TiO_2$ (110) surface by combined study of scanning tunneling microscopy and density functional theory calculations. Our results revealed that oxygen vacancy is the most stable adsorption site for MEA on $TiO_2$ (110) surface at low coverage. As coverage increases, the oxygen vacancies are occupied with the molecules and MEA molecules start to adsorb at Ti rows at higher coverages. Our results show that the defects at oxide surfaces and the intermolecular interactions are important factors for determining stable adsorption structure of MEA at $TiO_2$ (110) surfaces.

• Bulletin of the Korean Chemical Society
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• 제31권1호
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• pp.116-119
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• 2010

Adsorption structures of the self-assembled thin films of $\alpha$-cyano-4-hydroxycinnamic acid (CHCA) anchoring on $TiO_2$ surfaces have been studied by using temperature-dependent diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopy. From the presence of the strong $\nu(COO^-)$ band at ~1390 $cm^{-1}$ along with the disappearance of the OH bands in the carboxylic acid group in the DRIFT spectra at room temperature, CHCA appeared to adsorb onto $TiO_2$ surfaces as a carboxylate form. The absence of the out-of-plane benzene ring modes of CHCA in the DRIFT spectra suggests a rather vertical orientation of CHCA on $TiO_2$. Above ~220$ ^{\circ}C$, CHCA seemed to start to thermally degrade on $TiO_2$ surfaces referring from the disappearance of most vibrational modes in the DRIFT spectra, whereas the $\nu$(C ≡ N) bands were found to remain relatively conspicuous as the temperature increased even up to ~460$^{\circ}C$.

• ETRI Journal
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• 제36권4호
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• pp.654-661
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• 2014

We develop accurate finite-difference time-domain (FDTD) modeling of polymer bulk heterojunction solar cells containing Ag nanoparticles between the hole-transporting layer and the transparent conducting oxide-coated glass substrate in the wavelength range of 300 nm to 800 nm. The Drude dispersion modeling technique is used to model the frequency dispersion behavior of Ag nanoparticles, the hole-transporting layer, and indium tin oxide. The perfectly matched layer boundary condition is used for the top and bottom regions of the computational domain, and the periodic boundary condition is used for the lateral regions of the same domain. The developed FDTD modeling is employed to investigate the effect of geometrical parameters of Ag nanospheres on electromagnetic fields in devices. Although negative plasmonic effects are observed in the considered device, absorption enhancement can be achieved when favorable geometrical parameters are obtained.

• 한국전기전자재료학회논문지
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• 제31권1호
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• pp.55-60
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• 2018

Transparent conductive thin films (TCFs) are essential materials for solar cells, organic light-emitting diodes, and display panels. Indium tin oxide (ITO) is one of the most widely used commercial materials to create TCFs'; however, new materials that can possibly replace ITO at a lower cost and/or those possessing mechanical flexibility are urgently needed. Silver nanowire (AgNW) is one of those promising materials, as it is less expensive and possesses superior mechanical flexibility as compared to ITO. We used AgNW and sol-gel ZnO to fabricate composite thin films by spray coating. We propose two spray-coating methods: the 'metal-organic chemical vapor deposition (MOCVD)/AgNW' method and the Mixture method. These two methods are expected to be commercialized for high-quality and low-cost products, respectively.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2279-2285
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• 2011

The geometries, electronic structures and absorption spectra of the two organic triphenylamine-based dyes TA-St-CA and TA-DM-CA, containing identical electron donors and acceptors but the different conjugated bridges, were studied by density functional theory (DFT) at the B3LYP and PBE1PBE levels, respectively. The influence of para-orientating methoxyl units on the electronic structures and light absorption properties of the dyes and the consequent photovoltaic performance of the dye-sensitized solar cells (DSSCs) were investigated in detail. The results indicate that the introduction of the para-orientating methoxyl units into the conjugated bridge induces the increased absorption wavelength as well as the more negative EHOMO corresponding to the bigger driving force $(E_{I^-/I^-_3}-E_{HOMO})$ for dye reduction, which together improve the photovoltaic performance of TA-DM-CA, although there is a decline of the open circuit voltage caused by the more negative $E_{LUMO}$.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.163-163
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• 2012

We observed strain evolution of P3HT crystals in P3HT:PCBM films and the effect of Al electrode on the evolution during real time annealing process. Based on simple assumptions, both relaxed lattice parameters and thermal expansion coefficient could be quantitatively determined. P3HT:PCBM films displayed tensile strain in as-prepared samples regardless of the presence of an Al layer. In the absence of Al layer, P3HT crystals showed only strain relaxation at an annealing temperature of $180^{\circ}C$. Meanwhile In the presence of an Al layer, the strain was relaxed and changed to compressive strain at around 120C annealing temperature, which indicated a tightening of the thiophene ring packing. These behaviors support the improved performance of devices fabricated by post annealing process.

• Bulletin of the Korean Chemical Society
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• 제33권9호
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• pp.2897-2902
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• 2012

New photovoltaic donor materials, 4,4'-(2,2'-bithiazole-5,5'-diyl)bis(N,N-diphenylbenzenamine) (BDT) and 4-(2,2'-bithiazol-5-yl)-N,N-diphenylbenzenamine (BT), were synthesized. A solution processable triphenylamine-containing bithiazole (BDT and BT) was blended with a [6,6]-phenyl $C_{61}$ butyric acid methyl ester (PCBM) acceptor to study the performance of small-molecule-based bulk heterojunction (BHJ) photovoltaic devices. Optimum device performance was achieved after annealing, for device with a BDT/PCBM ratio of 1:4. The open-circuit voltage, short-circuit current, and power conversion efficiency of the device with the aforementioned BDT/PCBM ratio were 0.51 V, 4.10 $mA\;cm^{-2}$, and 0.68%, respectively, under simulated AM 1.5 solar irradiation (100 $mW\;cm^{-2}$).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1068_1069
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• 2009

$TiO_2$의 계면적을 넓힘으로써 태양전지의 특성을 향상시키기 위해 정렬도가 높은 나노 기공 (nanopore, NP) 이산화티타늄 ($TiO_2$)을 이용하여 복합 태양전지를 제작하였다. Polymethyl methacrylate (PMMA)를 사용한 nanoimprinting lithography (NIL) 기술을 이용하여 NP $TiO_2$를 제작하였으며. 광활성층으로는 poly(3-hexylthiophene) (P3HT)와 [6,6]-phenyl $C_{61}$ butyric acid methyl ester (PCBM)을 사용하였다. NP $TiO_2$를 이용한 태양전지의 전력변환효율이 1.49%로 표면이 고른 소자의 효율인 1.18%에 비해 26% 가량 증가하였다. 이와 같은 효율 향상의 원인은 $TiO_2$와 광활성층의 계면이 증가되어 전하의 생성과 분리가 용이해졌기 때문인 것으로 사료된다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.246-249
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• 2007

현재까지 $P3HT:C_{60}-PCBM$계는 고분자 유기 태양전지에서 가장 좋은 효율을 보여주고 있다. 그러나 보다 고효율의 소자 제작을 위해 신재료에 대한 연구들이 활발히 진행되고 있으며, 본 연구에서는 $C_{60}-PCBM$ 대신 $C_{70}-PCBM$을 합성하여 소자를 제작하였다. $C_{70}-PCBM$은 $C_{60}-PCBM$에 비하여 가시광선 영역에서 상대적으로 높은 광흡수율을 보여 주었으며, 이것은 광전류의 향상을 가져왔다. 소자제작의 주요 변수로 $P3HT:C_{70}-PCBM$ 광활성층의 처리 조건, 즉, 용매, 조성비, 열처리 조건, 광활성층의 두께 등을 조절하였는데, buffer층(LiF 층) 등이 도입되지 않은 간단한 제작조건 하에서도 본 $C_{70}-PCBM$는 $C_{60}-PCBM$계에 버금가는 3.5% (AM 1.5G, 100 $mW/cm^{2}$ 조건) 이상의 효율을 나타내었다.