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Featured researches published by Yun-Hwa Hwang.


Advanced Materials | 2013

SnO2/Graphene Composites with Self‐Assembled Alternating Oxide and Amine Layers for High Li‐Storage and Excellent Stability

S.J. Richard Prabakar; Yun-Hwa Hwang; Eun‐Gyoung Bae; Sangdeok Shim; Dongwook Kim; Myoung Soo Lah; Kee-Sun Sohn; Myoungho Pyo

An alternating stack (SG/GN) consisting of SnO₂-functionalized graphene oxide (SG) and amine-functionalized GO (GN) is prepared in solution. The thermally reduced SG/GN (r(SG/GN)) with decreased micro-mesopores and completely eliminated macropores, results in a high reversible capacity and excellent capacity retention (872 mA h g⁻¹ after 200 cycles at 100 mA g⁻¹) when compared to a composite without GN.


Journal of Materials Chemistry | 2012

Genetic Algorithm-assisted optimization of partially dyed-TiO2 for room-temperature printable photoanodes of dye-sensitized solar cells

Eun Gyoung Bae; Hyunho Kim; Yun-Hwa Hwang; Kee-Sun Sohn; Myoungho Pyo

The processing parameters for photoanodes that are printable in a room-temperature (RT) continuous process for dye-sensitized solar cells (DSCs) were optimized by the use of Genetic Algorithm (GA). The photoanodes were prepared at RT from mixtures of partially dyed-TiO2 (PDT) with various sizes and dye-loadings and were subsequently compressed for the fabrication of PDT films with different compositions, nanoporous structures, and thicknesses. According to our decision parameter design, there were 220 different cases, from which only 30 chromosomes for each generation were selected for the testing of photovoltaic performance to determine the global optimal point in power conversion efficiency (η). After 7 generations (i.e., only 210 chromosomes tested out of 220), η reached 6.02%, which was 22% higher than the value reported previously without the aid of a GA. The photoanode composed of a mixture of 14, 21, and 40 nm TiO2 with different dye-loadings and compressed to a thickness of 8.0 μm under 94 MPa showed the highest η (short circuit current = 12.03 mA cm−2, open circuit voltage = 685 mV, fill factor = 72.8%). A comparison of the photovoltaic parameters and characteristic charge transport properties revealed that sparsely dyed small TiO2 provided an efficient electron transport route to increase the short circuit current. The role of large TiO2 dyed up to monolayer coverage, on the other hand, was also disclosed to partially increase the short circuit current by light scattering. We hope that the GA-assisted photoanode optimization, presented here, will encourage new directions in research while providing an efficient RT printing process for the continuous fabrication of DSCs.


Journal of The Electrochemical Society | 2011

PCBM-Grafted MWNT for Enhanced Electron Transport in Polymer Solar Cells

Youn Su Jung; Yun-Hwa Hwang; Ali Javey; Myoungho Pyo

1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C 61 (PCBM) grafted to multi-walled carbon nanotubes (MWNTs) was for the first time synthesized and utilized for enhancing the electron transport in bulk-heterojunction solar cells. Minimal interaction between poly(3-hexylthiophene) (P3HT) and PCBM-grafted MWNT (PCBM-g-MWNT) reduced the chance for MWNT to function as a hole transporter. The comparison of charge carrier mobilities revealed that the electron moves ca. twice faster in a device containing 0.3 wt % PCBM-g-MWNT than in devices with 0.1 wt % MWNT or no MWNT. PCBM-g-MWNT, blended with P3HT and PCBM for polymer solar cells, enhanced the cell efficiency (η) by 39% at 0.3 wt %.


Carbon | 2013

Graphene oxide as a corrosion inhibitor for the aluminum current collector in lithium ion batteries

S.J. Richard Prabakar; Yun-Hwa Hwang; Eun Gyoung Bae; Dong Kyu Lee; Myoungho Pyo


Journal of Power Sources | 2013

SnO2 nanoparticles confined in a graphene framework for advanced anode materials

Yun-Hwa Hwang; Eun Gyoung Bae; Kee-Sun Sohn; Sangdeok Shim; Xiaokai Song; Myoung Soo Lah; Myoungho Pyo


Journal of The Electrochemical Society | 2013

Graphene-Sandwiched LiNi0.5Mn1.5O4 Cathode Composites for Enhanced High Voltage Performance in Li Ion Batteries

S.J. Richard Prabakar; Yun-Hwa Hwang; Bichna Lee; Kee-Sun Sohn; Myoungho Pyo


Journal of The Electrochemical Society | 2012

Gadolinium-Doped LiMn2O4 Cathodes in Li Ion Batteries: Understanding the Stabilized Structure and Enhanced Electrochemical Kinetics

Su Cheol Han; Satendra Pal Singh; Yun-Hwa Hwang; Eun Gyoung Bae; Byung Kyu Park; Kee-Sun Sohn; Myoungho Pyo


Synthetic Metals | 2011

Synthesis of selenopheno[3,2-c]thiophene derivatives and (opto)electrochemical properties of new low bandgap conjugated polymers

Yu-Ra Jo; Soo-Hyoung Lee; Youn-Sik Lee; Yun-Hwa Hwang; Myoungho Pyo; Kyukwan Zong


Bulletin of The Korean Chemical Society | 2013

Binder-free Sn/Graphene Nanocomposites Prepared by Electrophoretic Deposition for Anode Materials in Lithium Ion Batteries

Eun Gyoung Bae; Yun-Hwa Hwang; Myoungho Pyo


Journal of Nanoscience and Nanotechnology | 2012

TiO2-grafted multi-walled carbon nanotubes for dye-sensitized solar cells.

Yun-Hwa Hwang; Hyunho Kim; Kyukwan Zong; Myoungho Pyo

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Myoungho Pyo

Sunchon National University

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Eun Gyoung Bae

Sunchon National University

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Myoung Soo Lah

Ulsan National Institute of Science and Technology

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Sangdeok Shim

Sunchon National University

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Soo-Hyoung Lee

Chonbuk National University

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Youn-Sik Lee

Chonbuk National University

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Yu-Ra Jo

Chonbuk National University

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