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Kim B.,Ulsan National Institute of Science and Technology | Yeom H.R.,Ulsan National Institute of Science and Technology | Choi W.-Y.,Gangneung - Wonju National University | Kim J.Y.,Ulsan National Institute of Science and Technology | And 2 more authors.
Tetrahedron | Year: 2012

We report the synthesis, characterization, and electrochemical properties of bis-PCBM dyad containing 4-nitro-α-cyanostilbene units for potential usage in efficient organic solar cells. The bis-PCBM dyad is fully characterized by NMR, UV-vis absorption, and electrochemical cyclic voltammetry. It is found that the presence of 4-nitro-α-cyanostilbenes affects the cyclic voltammetry and absorption spectrum very little. Whereas the 56 π-electron system in the bis-functionalized fullerene cage significantly influences on the electrochemical and photophysical properties, resulting in up-shifted LUMO and wider absorption compared to PCBM. Although the efficiencies of both conventional and the inverted cells based on P3HT/bis-PCBM dyad as the preliminary results are low in comparison with the optimized high-performance PSCs, it is believed that the efficiency would be improved through successful device optimization of P3HT/bis-PCBM dyad cells. © 2012 Elsevier Ltd. All rights reserved.


Lee J.D.,Daegu Gyeongbuk Institute of Science and Technology | Yun W.S.,Daegu Gyeongbuk Institute of Science and Technology | Park N.,Low Dimensional Carbon Materials Center
Physical Review Letters | Year: 2016

Investigating a theoretical model of the optical-field-induced current in dielectrics driven by strong few-cycle laser pulses, we propose an asymmetric conducting of the current by forming a heterojunction made of two distinct dielectrics with a low hole mass (mh∗me∗) and low electron mass (me∗mh∗), respectively. This proposition introduces the novel concept of a petahertz (1015 Hz) diode to rectify the current in the petahertz domain, which should be a key ingredient for the electric signal manipulation of future light-wave electronics. Further, we suggest the candidate dielectrics for the heterojunction. © 2016 American Physical Society.


Kim G.,UNIST gil | Kim G.,Low Dimensional Carbon Materials Center | Lim H.,UNIST gil | Lim H.,Korea Basic Science Institute | And 14 more authors.
Nano Letters | Year: 2015

Heterostructures of hexagonal boron nitride (h-BN) and graphene have attracted a great deal of attention for potential applications in 2D materials. Although several methods have been developed to produce this material through the partial substitution reaction of graphene, the reverse reaction has not been reported. Though the endothermic nature of this reaction might account for the difficulty and previous absence of such a process, we report herein a new chemical route in which the Pt substrate plays a catalytic role. We propose that this reaction proceeds through h-BN hydrogenation; subsequent graphene growth quickly replaces the initially etched region. Importantly, this conversion reaction enables the controlled formation of patterned in-plane graphene/h-BN heterostructures, without needing the commonly employed protecting mask, simply by using a patterned Pt substrate. © 2015 American Chemical Society.


Sa Y.J.,Ulsan National Institute of Science and Technology | Sa Y.J.,Advanced Center for Energy | Park C.,Ulsan National Institute of Science and Technology | Jeong H.Y.,Low Dimensional Carbon Materials Center | And 7 more authors.
Angewandte Chemie - International Edition | Year: 2014

A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom-doped carbon (CNT/HDC) core-sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom-containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom-containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom-doped nanocarbon catalysts in terms of half-wave potential and kinetic current density. The four-electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long-term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites. A facile, scalable route for the synthesis of new nanocomposites that are based on carbon nanotubes/heteroatom- doped carbon (CNT/HDC) core-sheath nanostructures has been developed. The CNT/HDC nanostructures exhibit excellent electrocatalytic activity, kinetics, and durability for the oxygen reduction reaction, and they also performed well as the cathode catalysts in alkaline fuel cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kim K.,Low Dimensional Carbon Materials Center | Kim I.-H.,Low Dimensional Carbon Materials Center | Yoon K.-Y.,Low Dimensional Carbon Materials Center | Lee J.,Low Dimensional Carbon Materials Center | Jang J.-H.,Low Dimensional Carbon Materials Center
Journal of Materials Chemistry A | Year: 2015

Patterned FTO was fabricated via a facile method as an efficient current collector in a photoelectrochemical water splitting system. The photocurrent density of α-Fe2O3 on patterned FTO exhibited a 1.7 times increase relative to α-Fe2O3 on FTO due to the light scattering and rapid transfer of excited electrons. © The Royal Society of Chemistry 2015.

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