• Current Photovoltaic Research
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• 제2권3호
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• pp.84-87
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• 2014

Protection of solar cell surface is important to prevent from dust, pollen, sand, etc. Therefore, development of large area antifouling film is urgent for high performance of solar cells. The surface of silica spheres was modified to fabricate large area antifouling film. The surface of monodisperse silica spheres has been modified with 3-(trimethoxysilyl) propylmethacrylate (TMSPM) to fabricate large area photonic crystal. Although the surface modification of silica spheres with TMSPM has been failed for the base catalyst, the second trial using acid catalyst showed the following results. The FTIR absorption peak at $1721cm^{-1}$ representing C=O stretching vibration indicates that the TMSPM was attached on the surface of silica spheres. The methanol solution comprised of the surface modified silica spheres (average diameter of 380 nm) and a photoinitiator was poured in the patterned silicon wafer with the dimension of 10 cm x 10 cm and irradiated UV-light during the self-assembly process. The result showed large area crack and defect free nanostructures.

• 한국광학회지
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• 제21권5호
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• pp.200-205
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• 2010

본 논문에서는 포토닉 밴드갭 광섬유(Photonic Bandgap Fiber: PBGF) 사이에 중공광섬유(Hollow Optical Fiber: HOF)를 융착 접속시켜 만든 광섬유 간섭계와 넓은 모드 면적을 가지는 광자결정 광섬유(Large Mode Area-Photonic Crystal Fiber: LMA-PCF)사이에 HOF를 융착접속시켜 만든 광섬유 간섭계의 온도 및 스트레인에 대한 광학적 특성을 분석하였다. PBGF 또는 LMA-PCF와 HOF의 융착접속시 광섬유내 공기구멍을 최대한 유지하도록 융착조건을 최적화하여 접속 손실을 줄였다. PBGF와 HOF로 구성된 광섬유 간섭계의 온도 및 스트레인에 대한 민감도는 각각 15.4 pm/$^{\circ}C$와 0.24 pm/${\mu}\varepsilon$으로 측정되었으며, LMA-PCF와 HOF로 구성된 광섬유 간섭계의 온도 및 스트레인에 대한 민감도는 각각 17.4 pm/$^{\circ}C$와 0.2 pm/${\mu}\varepsilon$으로 측정되었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.134.2-134.2
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• 2014

Photonic crystal solar cells have the potential for addressing the disparate length scales in polymer photovoltaic materials, thereby confronting the major challenge in solar cell technology: efficiency. One must achieve simultaneously an efficient absorption of photons with effective carrier extraction. Unfortunately the two processes have opposing requirements. Efficient absorption of light calls for thicker PV active layers whereas carrier transport always benefits from thinner ones, and this dichotomy is at the heart of an efficiency/cost conundrum that has kept solar energy expensive relative to fossil fuels. This dichotomy persists over the entire solar spectrum but increasingly so near a semiconductor's band edge where absorption is weak. We report a 2-D, photonic crystal morphology that enhances the efficiency of organic photovoltaic cells relative to conventional planar cells. The morphology is developed by patterning an organic photoactive bulk heterojunction blend of Poly(3-(2-methyl-2-hexylcarboxylate) thiophene-co-thiophene) and PCBM via PRINT, a nano-embossing method that lends itself to large area fabrication of nanostructures. The photonic crystal cell morphology increases photocurrents generally, and particularly through the excitation of resonant modes near the band edge of the organic PV material. The device performance of the photonic crystal cell showed a nearly doubled increase in efficiency relative to conventional planar cell designs. Photonic crystals can also enhance performance of other optoelectronic devices including organic laser.

• Journal of the Optical Society of Korea
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• 제19권1호
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• pp.63-68
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• 2015

A one-step fabrication of a photonic crystal (PC) with functional defects is demonstrated. Using multi-beam phase-controlled holographic lithography with a diffracting optical element, large area one dimensional (1D) and two dimensional (2D) PCs with periodic defects were fabricated. The uniform area is up to $2mm^2$, and tens of defect channels have been introduced in the 1D and 2D PC structure. This technique gives rise to substantial reduction in the fabrication complexity and significant improvement in the spatial accuracy of introducing functional defects in photonic crystals. This method can also be used to design and fabricate three dimensional (3D) PCs with periodic defects.

• Journal of the Optical Society of Korea
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• 제9권4호
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• pp.140-144
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• 2005

In this paper we have investigated the guiding properties of photonic crystal fibers (PCFs) with a square-lattice of air-holes in the cladding. We have shown numerical results of PCFs with various air hole sizes and hole-to-hole spacings over a wide wavelength range. The group velocity dispersion, effective area and effective refractive index of PCF have been calculated numerically. The waveguide dispersion has greatly affected the group velocity dispersion when hole-to-hole spacing is about $1{\mu}m$. The effective area is quite flat over the wide spectral range whether the hole-to-hole spacing is large or ratio of diameter to pitch is large. From the field distribution, we found that the field is tightly confined within the core region of PCF when the pitch is $3{\mu}m$ and the air-filling fraction is 0.9.

• 한국광학회:학술대회논문집
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• 한국광학회 2008년도 동계학술발표회 논문집
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• pp.351-351
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• 2008

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.183-184
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• 2006

• Macromolecular Research
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• 제12권2호
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• pp.189-194
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• 2004

When water is evaporated quickly from a water-based colloidal suspension, colloidal particles protrude from the water surface, distorting it and generating lateral capillary forces between the colloidal particles. The protruded colloidal particles are then assembled into ordered colloidal crystalline domains that float on the water surface on account of their having a lower effective density than water. These colloidal crystal domains then assemble together by lateral capillary force and convective flow; the generated colloidal crystal has grain boundaries. The single domain size of the colloidal crystal could be controlled, to some extent, by changing the rate of water evaporation, but it seems very difficult to fabricate a single crystal over a large area of the water's surface without reorienting each colloidal crystal domain. To reorient such colloidal crystal domains, a glass plate was dipped into the colloidal suspension at a tilted angle because the meniscus (airwaterglass plate interface) is pinned and thinned by further water evaporation. The thinning meniscus generated a shear force and reoriented the colloidal crystalline domains into a single domain.

• 한국전기전자재료학회논문지
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• 제23권3호
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• pp.245-249
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• 2010

Two dimensional(2D) pair-photonic crystals (pair-PCs) have been fabricated by a multiple-exposure nanosphere lithography (MENSL) method using the self-assembled nanospheres as lens-mask patterns and the collimated laser beam as a multiple-exposing source. The arrays of the 2D pair-PCs exhibited variable lattice structures and shape the control of rotating angle (${\Theta}$), tilting angle (${\gamma}$) and the exposure conditions. In addition, the base period or filling factor of pair-PCs as well as their shapes could be changed by experimental conditions and nanosphere size. A 1.18-${\mu}m$-thick resist was spincoated on Si substrate and the multiple exposure was carried out at change of ${\gamma}$ and ${\Theta}$. Images of prepared 2D pair-PCs were observed by SEM. We believe that the MENSL method is a suitable useful tool to realize the pair-periodic arrays of large area.

• 한국전기전자재료학회논문지
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• 제20권8호
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• pp.726-730
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• 2007

Two dimensional photonic crystals (2D PCs) have been fabricated by a double exposure holographic method using a He-Cd laser with a wavelength of 442nm. The arrays of the 2D PCs exhibit variable lattice structures from square to triangle according to a change of rotating angle $({\gamma})$ for double exposure beams. In addition, the period and filling factor of PCs as well as the forms (dot or antidot) could be controlled by experimental conditions. $A l.18-{\mu}m-thick$ resist was spin-coated on Si substrate and the 1st holographic exposure was carried out at incident angle $({\theta})$ of $11^{\circ}$. Then the sample was rotated to ${\gamma}=45^{\circ}{\sim}90^{\circ}$ and the 2nd holographic process was performed at ${\theta}=11^{\circ}$. The variation of diffraction efficiency during the exposure process was observed using a He-Ne laser in real time. The images of 2D PCs prepared were analyzed by SEM and AFM. We believe that the double holographic method is a tool suitable to realize the 2D PCs with a periodic array of large area.