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Jeong S.,Daegu Gyeongbuk Institute of Science and Technology | Han Y.S.,Daegu Gyeongbuk Institute of Science and Technology | Kwon Y.,Daegu University | Choi M.-S.,Konkuk University | And 3 more authors.
Synthetic Metals | Year: 2010

The synthesized n-type perylene derivative, N,N′-bis-(5- bromopyridine-2-yl)-1,6,7,12-tetrakis(4-n-butoxyphenoxy)-3,4,9,10-perylene tetracarboxydiimide (PPyB), was applied to polymer solar cells as an additive in P3HT [poly(3-hexylthiophene)]:PCBM [[6,6]-phenyl C61-butyric acid methyl ester] blend films. The addition of 1 wt% PPyB into a P3HT:PCBM layer led to a considerable improvement of over 70% in power conversion efficiency due to the enhanced short circuit current when compared with that of reference cell without an additive. Photoluminescence, X-ray measurements and carrier mobility studies revealed that the perylene additives increased electron mobility and contributed to more effective exciton dissociation due to the presence of the additive, PPyB, in the interfaces between the P3HT and PCBM domains. © 2010 Elsevier B.V. All rights reserved. Source

Park B.C.,University of Ulsan | Hong I.K.,University of Ulsan | Jang H.D.,University of Ulsan | Tran V.D.N.,University of Ulsan | And 2 more authors.
Materials Letters | Year: 2010

Effects of Cu doping on the ferroelectric and piezoelectric properties of 0.0038 mol K5.4Cu1.3Ta10O29 modified (K0.5Na0.5)NbO3 ceramics have been investigated. On the basis of analyses on crystal structure and polarization hysteresis, it is suggested that Cu ions reveal amphoteric doping behavior in KNN ceramics. At doping levels up to 1 mol%, the Cu ions substitute pentavalent B-site cations, acting as acceptors that generate O-vacancies to resultantly harden the ceramics. At doping levels above 1.5 mol%, however, Cu ions play a role as donors by replacing monovalent A-site cations. A specimen doped with 0.5 mol% CuO shows an extremely high mechanical quality factor of 3053, which is higher than those of any other reports on KNN-based ceramics. © 2010 Elsevier B.V. All rights reserved. Source

Jeong M.,University of Ulsan | Lee Y.M.,Ulsan Fine Chemical Industry Center | Hong S.H.,University of Ulsan | Park S.Y.,Chungbuk National University | And 2 more authors.
Biotechnology Letters | Year: 2010

Methyl (R)-2-chloromandelate, a key intermediate in the synthesis of clopidogrel, was obtained by the reduction of methyl-2-chlorobenzoylformate using whole cells of Saccharomyces cerevisiae. A 100% conversion and 96.1% of enantiomeric excess (ee) value was obtained when 17 methyl-2-chlorobenzoylformate/l was reacted with 8 g S. cerevisiae/l and 83g glucose/l at pH 7. © 2010 Springer Science+Business Media B.V. Source

Do N.B.,University of Ulsan | Jang H.D.,University of Ulsan | Hong I.,University of Ulsan | Han H.S.,University of Ulsan | And 3 more authors.
Ceramics International | Year: 2012

Effect of excess CuO additive on the sintering behavior and piezoelectric properties of Bi 0.5(Na 82K 0.18) 0.5TiO 3 ceramics was investigated. The addition of small amount of excess CuO as low as 1 mol% was quite effective to lower the sintering temperature (T s) of BNKT ceramics down to 975°C while their piezoelectric properties were degraded by Cu doping. However, the electric field-induced strain was markedly enhanced by further addition of Nb 2O 5 with CuO without elevating T s. The normalized strain S max/E max of 427 pm/V was obtained with a specimen sintered with 0.02 mol CuO and 0.03 mol Nb 2O 5 in excess. © 2011 Elsevier Ltd and Techna Group S.r.l. Source

Do N.B.,University of Ulsan | Lee H.-B.,University of Ulsan | Le D.T.,University of Ulsan | Jeong S.-K.,University of Ulsan | And 3 more authors.
Current Applied Physics | Year: 2011

The phase diagram of ternary (1-x-y) Bi 0.5Na 0.5TiO 3-x Bi 0.5K 0.5TiO 3-yLiTaO 3 (BNT-BKT-LT) ceramics was investigated within the range of x = 0-0.4 and y = 0-0.1 via analyses on their crystal structure, dielectric and field-induced strain properties. BNT-rich compositions revealed ferroelectric rhombohedral symmetry (FE R: x < 0.18 and y < 0.04) while BKT modified BNT ceramics transformed into ferroelectric tetragonal symmetry (FE T; x > 0.18 and y < 0.02). However, LT modification of BNT-BKT ceramics induced a phase transition to nonpolar pseudocubic symmetry (NP PC; x = 0-0.4 and y > 0.04). At phase boundaries between these three regions, the coexistence of two or three phases was observed. Interestingly, the electric field-induced strain was markedly enhanced at the ferroelectric-nonpolar phase boundary. © 2011 Elsevier B.V. All rights reserved. Source

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