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  1. Article ; Online: Special Issue on “Selected Papers from GPVC Conferences”

    Hongsub Jee / Jaehyeong Lee

    Applied Sciences, Vol 12, Iss 8564, p

    2022  Volume 8564

    Abstract: At the core of the climate crisis lies excessive carbon emissions from the continued use of fossil fuels [.] ...

    Abstract At the core of the climate crisis lies excessive carbon emissions from the continued use of fossil fuels [.]
    Keywords n/a ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Language English
    Publishing date 2022-08-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  2. Article ; Online: Amplification of Chirality in Photopatterned 3D Nanostructures of Chiral/Achiral Mixtures

    Hongsub Jee / Guanying Chen / Jaehyeong Lee

    Applied Sciences, Vol 12, Iss 8702, p

    2022  Volume 8702

    Abstract: The dispersion of a chiral polymer in a polymerizable matrix can amplify the chirality of the material, and a helical conformation of the chiral material within the polymerized SU-8 excessively increased the circular dichroism. Here, we demonstrate the ... ...

    Abstract The dispersion of a chiral polymer in a polymerizable matrix can amplify the chirality of the material, and a helical conformation of the chiral material within the polymerized SU-8 excessively increased the circular dichroism. Here, we demonstrate the fabrication of three-dimensional nanostructures of chiral/achiral mixtures by two-photon lithography. The irradiation of light and annealing caused local changes in the chiral material and finally led to the enhancement of the optical properties. The demonstration of a photopatternable chiral material could expand the usage of optical materials for various applications.
    Keywords chiral ; achiral ; circular dichroism ; optical activity ; two-photon lithography ; photopatterning ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Language English
    Publishing date 2022-08-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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  3. Article ; Online: Photo-Sintered Silver Thin Films by a High-Power UV-LED Module for Flexible Electronic Applications

    Minha Kim / Hongsub Jee / Jaehyeong Lee

    Nanomaterials, Vol 11, Iss 2840, p

    2021  Volume 2840

    Abstract: In recent printed electronics technology, a photo-sintering technique using intense pulsed light (IPL) source has attracted attention, instead of conventional a thermal sintering process with long time and high temperature. The key principle of the photo- ...

    Abstract In recent printed electronics technology, a photo-sintering technique using intense pulsed light (IPL) source has attracted attention, instead of conventional a thermal sintering process with long time and high temperature. The key principle of the photo-sintering process is the selective heating of a thin film with large light absorption coefficients, while a transparent substrate does not heat by the IPL source. Most research on photo-sintering has used a xenon flash lamp as a light source. However, the xenon flash lamp requires instantaneous high power and is unsuitable for large area applications. In this work, we developed a new photo-sintering system using a high-power ultraviolet light emitting diode (UV-LED) module. A LED light source has many merits such as low power consumption and potential large-scale application. The silver nanoparticles ink was inkjet-printed on a polyethylene terephthalate (PET) and photo-sintered by the UV-LED module with the wavelength of 365 and 385 nm. The electrical resistivity as low as 5.44 × 10 −6 Ω·cm (just about three times compared to value of bulk silver) was achieved at optimized photo-sintering conditions (wavelength of 365 nm and light intensity of 300 mW/cm 2 ).
    Keywords silver thin film ; photo-sintering ; ultraviolet light emitting diode (UV-LED) ; low temperature process ; flexible substrate ; Chemistry ; QD1-999
    Subject code 620
    Language English
    Publishing date 2021-10-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  4. Article ; Online: Simulation-Based Shading Loss Analysis of a Shingled String for High-Density Photovoltaic Modules

    Jaesung Bae / Hongsub Jee / Yongseob Park / Jaehyeong Lee

    Applied Sciences, Vol 11, Iss 11257, p

    2021  Volume 11257

    Abstract: Shingled photovoltaic (PV) modules with increased output have attracted growing interest compared to conventional PV modules. However, the area per unit solar cell of shingled PV modules is smaller because these modules are manufactured by dividing and ... ...

    Abstract Shingled photovoltaic (PV) modules with increased output have attracted growing interest compared to conventional PV modules. However, the area per unit solar cell of shingled PV modules is smaller because these modules are manufactured by dividing and bonding solar cells, which means that shingled PV modules can easily have inferior shading characteristics. Therefore, analysis of the extent to which the shadow affects the output loss is essential, and the circuit needs to be designed accordingly. In this study, the loss resulting from the shading of the shingled string used to manufacture the shingled module was analyzed using simulation. A divided cell was modeled using a double-diode model, and a shingled string was formed by connecting the cell in series. The shading pattern was simulated according to the shading ratio of the vertical and horizontal patterns, and in the case of the shingled string, greater losses occurred in the vertical direction than the horizontal direction. In addition, it was modularized and compared with a conventional PV module and a shingled PV module. The results confirmed that the shingled PV module delivered higher shading output than the conventional PV module in less shade, and the result of the shading characteristic simulation of the shingled PV module was confirmed to be accurate within an error of 1%.
    Keywords simulation ; photovoltaic ; shingled ; shading ; PSpice ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Subject code 600
    Language English
    Publishing date 2021-11-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  5. Article ; Online: In Situ Polymerization of Chiral Poly(fluorene-alt-benzothiadiazole) Nanocomposites with Enhanced Chirality

    Hongsub Jee / Hyeong-Sub Oh / Jaehyeong Lee

    Applied Sciences, Vol 10, Iss 23, p

    2020  Volume 8740

    Abstract: Poly(fluorene-alt-benzothiadiazole) (PFBT) is a promising chiral polymer for use in metamaterials and other photonic applications, due to its large chiral optical activity at visible wavelengths. However, its usages are very limited, since it is not ... ...

    Abstract Poly(fluorene-alt-benzothiadiazole) (PFBT) is a promising chiral polymer for use in metamaterials and other photonic applications, due to its large chiral optical activity at visible wavelengths. However, its usages are very limited, since it is not readily patternable into microstructures and challenging to apply to applications. In this paper, we demonstrate photo patterning of chiral PFBT/Achiral SU-8 photoresist to produce high quality structures while retaining the extraordinary chiral optical activity of our previously-reported PFBT/SU8 nanocomposite films. The ability to produce cleanly patterned microfeatures with high chirality may enable wider use of PFBT in chiral metamaterials and other photonic applications.
    Keywords polymerization ; fabrication ; chirality ; nanocomposites ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Language English
    Publishing date 2020-12-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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    Inter-library loan at ZB MED

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  6. Article ; Online: Fabrication of Large Area, Ordered Nanoporous Structures on Various Substrates for Potential Electro-Optic Applications

    Hongsub Jee / Kiseok Jeon / Min-Joon Park / Jaehyeong Lee

    Applied Sciences, Vol 11, Iss 12136, p

    2021  Volume 12136

    Abstract: Nanoporous structures have attracted great attention in electronics, sensor and storage devices, and photonics because of their large surface area, large volume to surface ratio, and potential for high-sensitivity sensor applications. Normally, electron ... ...

    Abstract Nanoporous structures have attracted great attention in electronics, sensor and storage devices, and photonics because of their large surface area, large volume to surface ratio, and potential for high-sensitivity sensor applications. Normally, electron or ion beam patterning can be used for nanopores fabrication by direct writing. However, direct writing is a rather expensive and time-consuming method due to its serial nature. Therefore, it may not translate to a preferred manufacturing process. In this research, a perfectly ordered large-area periodic pattern in an area of approximately 1 cm 2 has been successfully fabricated on various substrates including glass, silicon, and polydimethylsiloxane, using a two-step process comprising visible light-based multibeam interference lithography and subsequent pattern transfer processes of reactive ion etching and nanomolding. Additionally, the multibeam interference lithography templated anodized aluminum oxide process has been described. Since the fabrication area in multibeam interference lithography can be extended by using a larger beam size, it is highly cost effective and manufacturable. Furthermore, although not described here, an electrodeposition process can be utilized as a pattern transfer process. This large-area perfectly ordered nanopore array will be very useful for high-density electronic memory and photonic bandgap and metamaterial applications.
    Keywords multibeam interference lithography (MIL) ; reactive ion etching (RIE) ; large area ; nanopore ; transfer ; pattern ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Subject code 620
    Language English
    Publishing date 2021-12-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

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    Inter-library loan at ZB MED

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  7. Article ; Online: Fabrication of the Cu 2 ZnSnS 4 Thin Film Solar Cell via a Photo-Sintering Technique

    Vu Minh Han Cao / Jaesung Bae / Joongpyo Shim / Byungyou Hong / Hongsub Jee / Jaehyeong Lee

    Applied Sciences, Vol 12, Iss 38, p

    2022  Volume 38

    Abstract: Alternative photo-sintering techniques for thermal annealing processes are used to improve the morphology, layer properties, and enhance solar cell performance. The fast, nontoxic, low cost, and environmentally friendly characteristics of Cu 2 ZnSnS 4 ... ...

    Abstract Alternative photo-sintering techniques for thermal annealing processes are used to improve the morphology, layer properties, and enhance solar cell performance. The fast, nontoxic, low cost, and environmentally friendly characteristics of Cu 2 ZnSnS 4 have led to its consideration as an alternative potential absorber layer in copper indium gallium diselenide thin film solar cells. This work investigates the photo-sintering process for the absorber layer of Cu 2 ZnSnS 4 solar cells. A Cu 2 ZnSnS 4 layer was grown by hot-injection and screen-printing techniques, and the characteristics of the photo-sintered Cu 2 ZnSnS 4 layer were evaluated by X-ray Diffraction, Raman spectroscopy, Energy dispersive X-ray analysis, Ultraviolet-visible spectroscopy, and field emission scanning electron microscopes. Overall, the optimal composition was Cu-poor and Zn-rich, without a secondary phase, estimated optical band-gap energy of approximately 1.6 eV, and enhanced morphology and kesterite crystallization. Using an intensity pulse light technique to the CZTS layer, fabrication of the solar cell device demonstrated successfully, and the efficiency of 1.01% was achieved at 2.96 J/cm 2 .
    Keywords CZTS solar cell ; hot-injection ; photo-sintering ; Intense Pulse Light System ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Subject code 620
    Language English
    Publishing date 2022-12-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  8. Article ; Online: Surface Passivation of Crystalline Silicon Wafer Using H 2 S Gas

    Jian Lin / Hongsub Jee / Jangwon Yoo / Junsin Yi / Chaehwan Jeong / Jaehyeong Lee

    Applied Sciences, Vol 11, Iss 8, p

    2021  Volume 3527

    Abstract: We report the effects of H 2 S passivation on the effective minority carrier lifetime of crystalline silicon (c-Si) wafers. c-Si wafers were thermally annealed under an H 2 S atmosphere at various temperatures. The initial minority carrier lifetime (6.97 ...

    Abstract We report the effects of H 2 S passivation on the effective minority carrier lifetime of crystalline silicon (c-Si) wafers. c-Si wafers were thermally annealed under an H 2 S atmosphere at various temperatures. The initial minority carrier lifetime (6.97 μs) of a c-Si wafer without any passivation treatments was also measured for comparison. The highest minority carrier lifetime gain of 2030% was observed at an annealing temperature of 600 °C. The X-ray photoelectron spectroscopy analysis revealed that S atoms were bonded to Si atoms after H 2 S annealing treatment. This indicates that the increase in minority carrier lifetime originating from the effect of sulfur passivation on the silicon wafer surface involves dangling bonds.
    Keywords crystalline silicon ; H 2 S ; minority carrier lifetime ; passivation ; dangling bonds ; Technology ; T ; Engineering (General). Civil engineering (General) ; TA1-2040 ; Biology (General) ; QH301-705.5 ; Physics ; QC1-999 ; Chemistry ; QD1-999
    Language English
    Publishing date 2021-04-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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  9. Article ; Online: In Situ Ultraviolet Polymerization Using Upconversion Nanoparticles

    Hongsub Jee / Guanying Chen / Paras N. Prasad / Tymish Y. Ohulchanskyy / Jaehyeong Lee

    Nanomaterials, Vol 10, Iss 2054, p

    Nanocomposite Structures Patterned by Near Infrared Light

    2020  Volume 2054

    Abstract: In this paper, we report an approach to polymerization of a nanocomposite containing UV-polymerizable organic material and inorganic, NaYbF 4 :Tm 3+ core-based nanoparticles (NPs), which are optimized for upconversion of near infrared (NIR) to ... ...

    Abstract In this paper, we report an approach to polymerization of a nanocomposite containing UV-polymerizable organic material and inorganic, NaYbF 4 :Tm 3+ core-based nanoparticles (NPs), which are optimized for upconversion of near infrared (NIR) to ultraviolet (UV) and blue light. Our approach is compatible with numerous existing UV-polymerizable compositions and the NaYF 4 : Yb, Tm 3+ core-based NPs are much more stable against harsh conditions than NIR organic photo-initiators proposed earlier. The use of a core-shell design for the NPs can provide a suitable method for binding with organic constituents of the nanocomposite, while maintaining efficient NIR-to-UV/blue conversion in the NaYbF 4 core. The prepared photopolymerized transparent polymer nanocomposites display upconversion photoluminescence in UV, visible and NIR ranges. We also demonstrate a successful fabrication of polymerized nanocomposite structure with millimeter/submillimeter size uniformly patterned by 980 nm irradiation of inexpensive laser diode through a photomask.
    Keywords upconversion ; core-shell nanoparticles ; photopatterning ; ultraviolet ; polymerization ; near-infrared ; Chemistry ; QD1-999
    Subject code 620
    Language English
    Publishing date 2020-10-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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