http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Simple and rapid cleaning of graphenes with a ‘bubble-free’ electrochemical treatment
Park, Byoungchoo,Huh, Jun Nyeong,Lee, Won Seok,Bae, In-Gon The Royal Society of Chemistry 2018 Journal of Materials Chemistry C Vol.6 No.9
<P>We herein report a remarkably simple and fast bubble-free electrochemical (EC) treatment process to clean single-layer graphenes (SLGs) that become unintentionally doped during their transfer process. For the EC-treatment process, linear sweeping voltages with respect to a Ag/AgCl reference electrode are applied to the SLG used as a working electrode within non-faradaic regions in a non-aqueous electrolyte. In the EC treatment, we adjust the sweeping voltage ranges and find that treatment at negative voltages for 10 min induces the desorption of not only the polymer scaffold residue but also the etchant residues remaining on the SLG surface <I>via</I> the Coulombic repulsion mechanism between the residues and the SLG electrode. Accordingly, the EC-treated SLG is de-doped and begins to recover its intrinsic electrical properties, showing a Dirac point energy of ∼4.4 eV, a work function of ∼4.6 eV, and high carrier mobility levels, comparable to the intrinsic properties of graphene monolayers. This study shows the potential to revolutionise the cleaning technique of residue on SLGs and demonstrates that bubble-free EC-treated SLGs can be used to fabricate reliable and controllable transparent SLGs for advanced graphene-based electronic devices.</P>
Surfactant additives for improved photovoltaic effect of polymer solar cells
Park, Byoungchoo,Huh, Yoon Ho,Kim, Mina The Royal Society of Chemistry 2010 Journal of materials chemistry Vol.20 No.48
<p>We herein report on the photovoltaic (PV) effect of a polymer bulk-heterojunction (BHJ) layer consisting of poly(3-hexylthiophene) : methanofullerene mixed with a surfactant additive. The mixed surfactant is poly(oxyethylene tridecyl ether) (PTE). Excellent performance was achieved by using the surfactant as an additive in the PV layer, thereby increasing the short-circuit current density and fill factor. These increases led to a power conversion efficiency of 4.51 ± 0.16%, which was higher than that (3.89 ± 0.08%) of the reference device without the surfactant. This improvement can be attributed to the increased dissociation efficiency of the bound <I>e</I>–<I>h</I> pairs, which may be due to the oriented PTE surfactant molecules at interfaces between the phase-separated BHJ domains. These results suggest that a PV layer mixed with a PTE surfactant additive is a promising functional composite material for use in polymer PV cells.</p> <P>Graphic Abstract</P><P>A polymer photovoltaic system mixed with a nonionic ‘surfactant additive’ is proposed for the realization of efficient exciton dissociation. <img src='http://pubs.rsc.org/ej/JM/2010/c0jm02091e/c0jm02091e-ga.gif'> </P>
Park, Byoungchoo,Kim, Mina,Kim, Sun Woong,Kim, In Tae The Optical Society 2009 Optics express Vol.17 No.15
<P>We present the results of a study of highly circularly polarized unidirectional lasing emission from an organic lasing device that consisted of a dye-doped cholesteric liquid crystal (CLC) layer on a 1-dimensional (1-D) photonic crystal (PC) reflecting mirror substrate. Unidirectional lasing was demonstrated successfully for this device structure at the wavelength of the high-energy band edge of the CLC layer. It was also shown that circularly polarized lasing emission was produced from the lasing device at a low lasing threshold of 2.5 mJ/pulse. The handedness of lasing light corresponds to the handedness of the used CLC layer with a high ratio of intensity between right- and left-handed circularly polarized lasing light over of up to 3.7. These results show that the CLC / 1-D PC device enables unidirectional lasing with highly circularly polarized laser emission..</P>
Polarized electroluminescence from organic light-emitting devices using photon recycling
Park, Byoungchoo,Huh, Yoon Ho,Jeon, Hong Goo The Optical Society 2010 Optics express Vol.18 No.19
<P>We present results that show highly polarized electroluminescence (EL) from an organic light-emitting device (OLED) by using a quarter-wave (관/4) retardation plate (QWP) film and a giant birefringent optical (GBO) photonic reflective polarizer. Polarized EL light of 13,400 cd/m(2) with high peak efficiencies (greater than 10 cd/A and 3.5 lm/W) was obtained from an OLED in this way. These values are almost double those of a polarized OLED that only uses a polarizer. The direction of polarization of the emitted EL light from the polarized OLED corresponded to the passing axis of the GBO reflective polarizer. Furthermore, the degree of linear polarization obtained, i.e. the ratio between the brightness of two linearly polarized EL emissions parallel and perpendicular to the passing axis, is greater than 40 over the whole range of emitted luminance.</P>
Park, Byoungchoo,Kim, Mina,Kim, Sun Woong,Jang, Wongun,Takezoe, Hideo,Kim, Yunki,Choi, Eun Ha,Seo, Yoon Ho,Cho, Guang Sup,Kang, Seung Oun WILEY-VCH Verlag 2009 Advanced Materials Vol.21 No.7
<B>Graphic Abstract</B> <P>A liquid-crystal/polymer composite is used to produce a photonic bandgap system. Films of the composite show a large field-induced reversible color shift of the reflection band of over 150 nm. Intensity-controllable laser emission at relatively low lasing thresholds is generated from composite films doped with dye. Moreover, the laser exhibits omnidirectional emission propagation on application of an electric field. <img src='wiley_img/09359648-2009-21-7-ADMA200800729-content.gif' alt='wiley_img/09359648-2009-21-7-ADMA200800729-content'> </P>
Photovoltaic characteristics of polymer solar cells fabricated by pre-metered coating process
Park, Byoungchoo,Han, Mi-young The Optical Society 2009 Optics express Vol.17 No.16
<P>We present the results of a study of flat and uniform poly(3-hexylthiophene):methanofullerene bulk-heterojunction photovoltaic (PV) layers that were produced by a simple pre-metered horizontal-dipping process for the fabrication of polymer solar cells (PSCs). It is shown that this process can produce high quality and thin films by utilizing the downstream meniscus of the solution, which can be controlled by adjusting experimental parameters of the gap height and the carrying speed. It is also shown that the produced PV film exhibits high power conversion efficiency of ca. 4.2% with a large active area. It was demonstrated that this pre-metered process for solution coating may be promising for achieving highly efficient, reliable, and large-area PSCs.</P>
Park, Byoungchoo,Park, Chan Hyuk,Kim, Mina,Han, Mi-young The Optical Society 2009 Optics express Vol.17 No.12
<P>We present the results of a study of highly linear polarized light emissions from an Organic Light-Emitting Device (OLED) that consisted of a flexible Giant Birefringent Optical (GBO) multilayer polymer reflecting polarizer substrate. Luminous Electroluminescent (EL) emissions over 4,500 cd/m(2) were produced from the polarized OLED with high peak efficiencies in excess of 6 cd/A and 2 lm/W at relatively low operating voltages. The direction of polarization for the emitted EL light corresponded to the passing (ordinary) axis of the GBO-reflecting polarizer. Furthermore, the estimated polarization ratio between the brightness of two linearly polarized EL emissions parallel and perpendicular to the passing axis could be as high as 25 when measured over the whole emitted luminance range.</P>