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RISS 인기검색어
- 검색키워드
- 저자 : Henry Opoku (검색결과 6 건)
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Opoku, Henry,Nketia-Yawson, Benjamin,Shin, Eun Sol,Noh, Yong-Young Elsevier 2017 Organic electronics Vol.41 No.-
<P><B>Abstract</B></P> <P>We investigate the effect of a binary solvent blend as a solvent for poly{[<I>N</I>,<I>N</I>′-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} P(NDI2OD-T2) on the characteristics of n-channel organic field-effect transistors (OFETs). To make the binary solvent blend, the low-boiling-point non-solvent propylene glycol methyl ether acetate (PGMEA, b.p ∼146 °C) is added to the high-boiling-point good solvent 1,2-dichlorobenzene (O-DCB, b.p ∼180 °C) at various mixing ratio from 0 to 40 v%. UV–vis spectra of P(NDI2OD-T2) solution dissolved in the binary solvent clearly show the formation of polymer aggregates through a gradual red shift of the intramolecular charge transfer band with the addition of high concentrations of non-solvent PGMEA. Higher edge-on oriented crystallinity is observed for P(NDI2OD-T2) films spin-coated from the binary solvent with 5–10 v% PGMEA by out-of-order x-ray diffraction. P(NDI2OD-T2) films are applied as the active layer in top-gate/bottom-contact OFETs. Improved n-type field-effect mobility of the P(NDI2OD-T2) semiconducting layer up to 0.59 cm<SUP>2</SUP>/Vs was achieved for on-center spin coated films compared to 1.03 cm<SUP>2</SUP>/Vs for off-center (parallel alignment) spin-coated films respectively employing the binary solvent with 10 v% PGMEA.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Investigate the binary solvent effect on characteristics of organic transistors. </LI> <LI> Low-boiling-point non-solvent and the high-boiling-point good solvent is optimized. </LI> <LI> P(NDI2OD-T2) OFETs show an improved mobility of 1.03 cm<SUP>2</SUP>/Vs by binary solvent. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Opoku, Henry,Nketia-Yawson, Benjamin,Shin, Eun-Sol,Noh, Yong-Young The Royal Society of Chemistry 2018 Journal of materials chemistry. C, Materials for o Vol.6 No.3
<P>Chlorinated solvents exhibit excellent solubility characteristics for common conjugated molecules and superior physical properties such as adequate viscosity, surface tension and high boiling point, so they are the preferred processing solvent option for realizing high-performance organic devices by cost-effective graphic art printing, despite their known adverse environmental impact. Based on Hansen solubility parameter analysis, this study employed a non-halogenated binary solvent blend of mesitylene and acetophenone to closely mimic the efficiency of dichlorobenzene, a well-known chlorinated solvent for widely used conjugated polymers used in organic field-effect transistors (OFETs) such as poly{[<I>N</I>,<I>N</I>′-bis(2-octyldodecyl)-1,4,5,8-naphthalenediimide-2,6-diyl]-<I>alt</I>-5,5′-(2,2′-bithiophene)} (P(NDI2OD-T2)), 3,6-bis-(5bromo-thiophen-2-yl)-<I>N</I>,<I>N</I>-bis(2-octyl-1-dodecyl)-1,4-dioxo pyrrolo[3,4-<I>c</I>]pyrrole (DPPT-TT) and indacenodithiophene-<I>co</I>-benzothiadiazole (IDT-BT). We tuned the solvent quality of the non-halogenated binary blend in various ratios and studied their effect on polymer pre-aggregation in the solution state, polymer microstructure, and morphological evolution of polymer thin films cast from the solvent blends. High-performance top-gate/bottom-contact OFETs were demonstrated with field-effect mobility values of up to ∼0.574, ∼0.634 and ∼0.785 cm<SUP>2</SUP> V<SUP>−1</SUP> s<SUP>−1</SUP> for P(NDI2OD-T2), DPPT-TT, and IDT-BT polymers, respectively, employing a mesitylene and acetophenone blend (95 : 5 vol%) as a processing solvent.</P>
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Henry Opoku,Chinna Bathula,Melaku Dereje Mamo,Nabeen K Shrestha,이태권,노용영 한국고분자학회 2019 Macromolecular Research Vol.27 No.1
Two narrow band gap triisopropylsilyl substituted benzo[1,2-b:4,5-b] dithiophene (TIPS-BDT) derivatives, P1 (1.65 eV) and P2 (1.46 eV) are synthesized for ambipolar organic field-effect transistors and complementary inverters. Two electron acceptor units, heptadecanyl substituted thieno[3,4-c]pyrrole-4,6-dione (TPD) and ethylhexyl substituted diketopyrrolo[3,4-c]pyrrole (DPP) are incorporated to tune the structure and resulting properties of the donor-acceptor type copolymers. Structural modification based on the acceptor unit variation, resulted in comparable electrochemical, optical, microstructural, and charge transporting properties, as well as environmental and operational stability. TIPS-BDT copolymers with TPD acceptor units show comparatively superior performance, with field effect mobility ~10-3 cm2V-1s-1 for both holes and electrons and inverter gain ~18 with poly(methyl methacrylate) gate dielectric.
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Bui, Hoa Thi,Shrestha, Nabeen K.,Cho, Keumnam,Bathula, Chinna,Opoku, Henry,Noh, Yong-Young,Han, Sung-Hwan Elsevier 2018 Journal of electroanalytical chemistry Vol.828 No.-
<P><B>Abstract</B></P> <P>The present work reports on the morphological influence of catalyst on oxygen reduction reaction (ORR). As a catalyst, Prussian blue analog structured nickel hexacyanoferrate (Ni-HCF) with two distinct morphologically controlled frameworks, <I>viz.</I> granular crystalline bulk film and rose-petal like structured thin film having smooth surface, are synthesized <I>via</I> controlled anodization route, and their morphological influence on the ORR is investigated. In addition, the influence of addition of carbon black, which is commonly used as catalytic dispersing support, is also studied on the catalytic mechanism for the ORR. Based on the hydrodynamic voltammetry of the electrocatalytic films on rotating disk electrode, the number of electrons involved in the reduction of an O<SUB>2</SUB> molecule, and the kinetic current density of the reaction are estimated. While the pristine Ni-HCF frameworks based catalyst, regardless of their morphology, demonstrates the direct reduction of O<SUB>2</SUB> with participation of 4 electrons, the frameworks when mixed with carbon black as support diverts the reduction <I>via</I> two steps with participation of 2 electrons at each step. A larger kinetic current density is, however, obtained in the case of granular crystalline bulk film of the Ni-HCF frameworks.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Morphologically controlled Ni-HCF frameworks are synthesized <I>via</I> anodization route. </LI> <LI> Electrocatalytic behavior of the frameworks towards ORR is studied. </LI> <LI> The pristine frameworks show the direct 4e<SUP>−</SUP> reduction of O<SUB>2</SUB> into OH<SUP>−</SUP>. </LI> <LI> After mixing with carbon black support, the ORR path is diverted to 2 + 2e<SUP>−</SUP> process. </LI> <LI> Compared to thin film, the bulk film of the frameworks reveals faster rate of ORR. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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