• Proceedings of the Korean Magnestics Society Conference
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• 2008.12a
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• pp.145.1-145.1
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• 2008

• Current Photovoltaic Research
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• v.2 no.4
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• pp.152-156
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• 2014

We report hybrid solar cells fabricated with polymer/fullerene bulk heterojunction layers that contain inorganic nanocrystals synthesized by in-situ reaction in the presence of polymer chains. The inorganic (cadmium sulfide) nanocrystal ($CdS_{NC}$) was generated by the reaction of cadmium acetate and sulfur by varying the reaction time up to 30 min. The synthesized $CdS_{NC}$ showed a rectangular flake shape, while the size of $CdS_{NC}$ reached ca. 150 nm when the reaction time was 10 min. The performance of hybrid solar cells with $CdS_{NC}$ synthesized for 10 min was better than that of a control device, whereas poor performances were measured for other hybrid solar cells with $CdS_{NC}$ synthesized for more than 10 min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.28-28
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• 2008

We have demonstrated the combinatorial synthesis of a variety of transparent conducting oxides using a combinatorial sputter system. The effects of a wide range of Nb or Zn doping rate on the optical and electrical properties of Indium-tin oxides (ITO) films were investigated. The Nb or Zn doped ITO films were fabricated on glass substrates, using combinatorial sputtering system which yields a linear composition spread of Nb or Zn concentration in ITO films in a controlled manner by co-sputtering two targets of ITO and $Nb_2O_5$ or ITO and ZnO. We have examined the work-function, resistivity, and optical properties of the Nb or Zn-doped ITO films. Furthermore, the effects of Hz plasma treatment on the physical properties of Ga or Zn doped ITO films synthesized by combinatorial sputter system were investigated.

• Current Photovoltaic Research
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• v.4 no.2
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• pp.48-53
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• 2016

We report the effect of physical load on the stability of organic solar cells under physical loads. The active layers in organic solar cells were fabricated with bulk heterojunction films (BHJ) films of poly (3-hexylthiophene) and phenyl-$C_{61}$-butyric methyl ester. The loading time was varied up to 60 s by keeping the physical load constant. Results showed that the open circuit voltage was not influenced by the physical load but other solar cell parameters were sensitive to the loading time. The fill factor was very slightly increased at 15 s, while short circuit current density was well kept for 30 s. The power conversion efficiency was reasonably maintained for 45 s but became significantly decreased by the continuous loading for 60 s.

• Current Optics and Photonics
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• v.7 no.5
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• pp.496-503
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• 2023

We present a detailed analysis of the light extraction efficiency (LEE) of a core-shell nanorod light emitting diode (LED) using finite-difference time-domain (FDTD) simulations. We found that the LEE has a deep dependence on source positions and polarization directions based on the calculated LEE results for every x and z position inside the core-shell nanorod structure. The LEEs are different for the upper part (pyramid) and the lower part (sidewall) of the core-shell nanorod owing to total internal reflection (TIR) and the generated optical modes in the structure. As a result, the LEE of sidewall is much larger than that of pyramid. The averaged LEE of the core-shell nanorod LED is also investigated with variable p-GaN thickness, n-GaN thickness, and height for the design guidelines for the optimized LEE of core-shell nanorod LEDs.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.5.2-5.2
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• 2009

Carbon based nanoelctronic materials such as buckyball, CNT, and graphene have been active field of research because of their superior electronic prperties and potential application to flexible electronics. Still the difficulty of fabrication and spatial control prevent them from practical applications. Here I introduce a novel growth method of CNTs, known as surface assisted growth, that can answer the challenge. Various device examples from as-grown CNTs will prove the importance of this method for future nanoelectronics.

• Korean Journal of Chemical Engineering
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• v.35 no.12
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• pp.2496-2503
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• 2018

The short-term stability of high efficiency polymer : nonfullerene solar cells was investigated by employing a quick (ten cycles) current density-voltage (J-V) cycling method. Polymer : nonfullerene solar cells with initial power conversion efficiency (PCE) of >10% were fabricated using bulk heterojunction (BHJ) films of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1,2-b:4,5b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5,7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(2-methylene-((3-(1,1-dicyanomethylene)-6/7-methyl)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M). One set of the BHJ (PBDB-T : IT-M) films was thermally annealed at $160^{\circ}C$ for 30min, while another set was used without any thermal treatment after spin-coating. The quick J-V scan (cycling) measurement disclosed that the PCE decay was relatively slower for the annealed BHJ layers than the unannealed (as-cast) BHJ layers. As a result, after ten cycles, the annealed BHJ layers delivered higher PCE than the unannealed BHJ layers due to higher and more stable trend in fill factor. The present quick J-V cycling method is simple but expected to be useful for the prediction of short-term stability in organic solar cells.

• Current Photovoltaic Research
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• v.7 no.3
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• pp.55-60
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• 2019

Polymer:nonfullerene solar cells with an inverted-type device structure were fabricated by employing the bulk heterojunction (BHJ) active layers, which are composed of poly[(2,6-(4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione))] (PBDB-T) and 3,9-bis(6-methyl-2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2',3-d']-s-indaceno[1,2-b:5,6-b']dithiophene (IT-M). The BHJ layers were formed on a pre-patterned indium-tin oxide (ITO)-coated glass substrate by spin-coating using the blend solutions of PBDB-T and IT-M. The solar cell performances were investigated with respect to the cell position on the ITO-glass substrates. In addition, the short-term shelf lifetime of solar cells was tested by storing the PBDB-T:IT-M solar cells in a glovebox filled with inert gas. The results showed that the performance of solar cells was relatively higher for the cells close to the center of substrates, which was maintained even after storage for 24 h. In particular, the PCE of PBDB-T:IT-M solar cells was marginally decreased after storage for 24 h owing to the slightly reduced fill factor, even though the open circuit voltage was unchanged after 24 h.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.11
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• pp.56-64
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• 2007

We developed the first automatic design system targeting a promising hybrid CMOS-Nanoelectronics Architecture called CMOL. The CMOL architecture uses NOR gates to implement combinational logic. In this hybrid CMOS-nanoelectronics architecture, logical functions and the interconnections share the nanoelectronics hardware resource. Towards automating the CMOL physical design process, we developed a model for the CMOL architecture, formulated the placement and routing problems for the CMOL architecture subject to the unique CMOL specific constraints, and solved it by combining a placement algorithm with a gate assignment algorithm in a loop. We validated the proposed approach by implementing several industrial strength designs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04c
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• pp.41-41
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• 2008

Al-doped ZnO (AZO) thin films have been fabricated by vertical in-line dc magnetron sputtering for transparent conducting oxides (TCOs) applications. The effects of substrate temperature and dc power on the characteristics of AZO thin films are investigated and also optimized the process conditions to get the best electrical and optical properties. The fabricated thin films show a good electrical and optical uniformity within ${\pm}5%$ over the whole area of substrate ($200mm\;{\times}\;200mm$) ; the minimum resistivity of $8\;{\times}\;10^{-4}\;{\Omega}cm$ and the average transmittance of 90% within the visible wavelength range. We have found that the band gap ($E_g$) increases with increasing substrate temperature and dc power, whereas the crystallinity is getting improved with increasing substrate temperature. The binding energy of Zn $2p_{3/2}$ and O 1s is observed to decrease as the substrate temperature increases.