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Plasmonic nanograting design for inverted polymer solar cells.
Kim, Inho,Jeong, Doo Seok,Lee, Taek Seong,Lee, Wook Seong,Lee, Kyeong-Seok Optical Society of America 2012 Optics express Vol.20 No.5
<P>Plasmonic nanostructures for effective light trapping in a variety of photovoltaics have been actively studied. Metallic nanograting structures are one of promising architectures. In this study, we investigated numerically absorption enhancement mechanisms in inverted polymer photovoltaics with one dimensional Ag nanograting in backcontact. An optical spacer layer of TiO<sub>2</sub>, which also may act as an electron transport layer, was introduced between nanograting pillars. Using a finite-difference-time domain method and performing a modal analysis, we explored correlations between absorption enhancements and dimensional parameters of nanograting such as period as well as height and width. The optimal design of nanograting for effective light trapping especially near optical band gap of an active layer was discussed, and 23% of absorption enhancement in a random polarization was demonstrated numerically with the optimally designed nanograting. In addition, the beneficial role of the optical spacer in plasmonic light trapping was also discussed.</P>
Kim, Inho,Lee, Taek Seong,Jeong, Doo Seok,Lee, Wook Seong,Kim, Won Mok,Lee, Kyeong-Seok Optical Society of America 2013 Optics express Vol.21 No.4
<P>Transparent metal grid combining with plasmonic absorption enhancement is a promising replacement to indium tin oxide thin films. We numerically demonstrate metal grids in one or two dimension lead to plasmonic absorption enhancements in ultrathin organic solar cells. In this paper, we study optical design of metal grids for plasmonic light trapping and identify different plasmonic modes of the surface plasmon polaritons excited at the interfaces of glass/metal grids, metal grids/active layers, and the localized surface plasmon resonance of the metal grids using numerical calculations. One dimension metal grids with the optimal design of a width and a period lead to the absorption enhancement in the ultrathin active layers of 20 nm thickness by a factor of 2.6 under transverse electric polarized light compared to the case without the metal grids. Similarly, two dimensional metal grids provide the absorption enhancement by a factor of 1.8 under randomly polarized light.</P>
Asymmetric back contact nanograting design for thin c-Si solar cells
Inho Kim,Doo Seok Jeong,Wook Seong Lee,Won Mok Kim,Kyeong-Seok Lee,Taek-Sung Lee 한국물리학회 2016 Current Applied Physics Vol.16 No.5
Texturing of silicon wafers with periodic gratings in submicron scale is one of effective light trapping routes especially for thin crystalline silicon solar cells. The grating can be very effective for trapping of photons near band gap of crystalline silicon when its period is suitably chosen. The asymmetric gratings provide higher light trapping efficiency than symmetric ones because the asymmetric one suppress the escape of internally reflected light in the silicon wafers. In this study, we conceptually show that asymmetric grating can be fabricated by simple stacking of a dielectric layer onto the symmetric silicon grating structures. Optical simulations were performed to calculate optical absorptions in thin crystalline silicon of a 5 mm thickness with symmetric and asymmetric grating structures.We demonstrate that with the asymmetric grating structures combined with highly efficient antireflection coating, optical absorptions in the thin silicon wafers can reach over 97% of the Lambertian absorption limit.
관절경으로 확인한 슬내장의 진단에서 SPECT와 MRI의 비교
성상철,이명철,손영진,김태균,성인호,정준기,소영,강흥식 대한슬관절학회 1998 대한슬관절학회지 Vol.10 No.2
Bone single photon emission computed tomography(SPECT) of the knees has been shown to be of diagnostic value for the investigation of intemal derangement of knees(IDK). This study compared bone SPECT and magnetic resonance image(MRI) with arthroscopic findings for the diagnosis of IDK. Fifty patients who had been performed arthroscopy in Seoul National University Hospital from January 1997 to September 1997 were studied with both the modalities preoperatively. There were 38 meniscal injuries, 26 cruciate ligament injuries and 8 cases of patellofemoral joint problems. In view of SPECT, the most remarkable results were from meniscal tears. In meniscal tears, the diagnostic values of SPECT were 89.5% of sensitivity, 66.7% of specificity, 84% of diagnostic accuracy, which were comparable to those of MRI, 97.4%, 91.7% and 96%, respectively. But SPECT showed inferior diagnostic values in cruciate ligament injuries. For anterior knee pain, SPECT was more sensitive than MRI for the detection of pathology. And for functionally related cases, such as ACL impingement to intercondylar notch, SPECT was far more valuable than MRI. Bone SPECT will not provide the anatomical detail of MRI but seems to be a useful tool for the detection of wide range of knee disorders including IDK. Further research is justified to investigate the precise role of bone SPECT in clinical practice and its value in relation to MRI.