Bon-Ryul Koo

Chemical properties of electrosprayed antimony tin oxide thin film/Ag nanowire multilayer for transparent conductive electrodes

An antimony tin oxide (ATO) thin film/Ag nanowire (NW) multilayer was fabricated by spin-coating and electrospray deposition. To investigate the optimum thickness of the ATO thin layer deposited on Ag NWs, its deposition time was varied in the range of 0–15 min. The multilayer nanostructure with an ATO thin layer deposited for 3 min exhibited excellent sheet resistance (~27.9 Ω/), high optical transmittance (~81.9%), good haze value (~4.7%), excellent thermal stability under microwave annealing at 300 °C, and excellent chemical stability for 4 weeks because of the optimized ATO thin layer and excellent electrical conductivity of the Ag NWs.

Improvement of Transparent Conducting Performance on Oxygen-Activated Fluorine-Doped Tin Oxide Electrodes Formed by Horizontal Ultrasonic Spray Pyrolysis Deposition

In this study, highly transparent conducting fluorine-doped tin oxide (FTO) electrodes were fabricated using the horizontal ultrasonic spray pyrolysis deposition. In order to improve their transparent conducting performances, we carried out oxygen activation by adjusting the ratio of O2/(O2+N2) in the carrier gas (0%, 20%, and 50%) used during the deposition process. The oxygen activation on the FTO electrodes accelerated the substitution concentration of F (FO•) into the oxygen sites in the FTO electrode while the oxygen vacancy (VO••) concentration was reduced. In addition, due to growth of pyramid-shaped crystallites with (200) preferred orientations, this oxygen activation caused the formation of a uniform surface structure. As a result, compared to others, the FTO electrode prepared at 50% O2 showed excellent electrical and optical properties (sheet resistance of ∼4.0 ± 0.14 Ω/□, optical transmittance of ∼85.3%, and figure of merit of ∼5.09 ± 0.19 × 10-2 Ω-1). This led to a superb photoconversion efficiency (∼7.03 ± 0.20%) as a result of the improved short-circuit current density. The photovoltaic performance improvement can be defined by the decreased sheet resistance of FTO used as a transparent conducting electrode in dye-sensitized solar cells (DSSCs), which is due to the combined effect of the high carrier concentration by the improved FO• concentration on the FTO electrodes and the fasted Hall mobility by the formation of a uniform FTO surface structure and distortion relaxation on the FTO lattices resulting from the reduced VO••• concentration.

Synthesis and Characterization of SnO 2 -CoO/carbon-coated CoO Core/shell Nanowire Composites

/carbon-coated CoO core/shell nanowire composites were synthesized by using electrospinning and hydrothermal methods. In order to obtain /carbon-coated CoO core/shell nanowire composites, nanowire composites and /polygonal core/shell nanowire composites are also synthesized. To demonstrate their structural, chemical bonding, and morphological properties, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were carried out. These results indicated that the morphologies and structures of the samples were changed from nanowires having cylindrical structures to core/shell nanowires having polygonal structures after a hydrothermal process. At last, /carbon-coated CoO core/shell nanowire composites having irregular and high surface area are formed after carbon coating using a polypyrrole (PPy). Also, there occur phases transformation of cobalt phases from to CoO during carbon coating using a PPy under a argon atmosphere.

Spindle-shaped Fe 2 O 3 Nanoparticle Coated Carbon Nanofiber Composites for Low-cost Dye-sensitized Solar Cells

Carbon nanofiber (CNF) composites coated with spindle-shaped nanoparticles (NPs) are fabricated by a combination of an electrospinning method and a hydrothermal method, and their morphological, structural, and chemical properties are measured by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. For comparison, CNFs and spindle-shaped NPs are prepared by either an electrospinning method or a hydrothermal method, respectively. Dye-sensitized solar cells (DSSCs) fabricated with the composites exhibit enhanced open circuit voltage (0.70 V), short-circuit current density (), fill factor (61.30%), and power conversion efficiency (5.52%) compared to those of the CNFs (0.66 V, , 51.96%, and 3.97%) and spindle-shaped NPs (0.67 V, , 50.17%, and 3.86%). This performance improvement can be attributed to a synergistic effect of a superb catalytic reaction of spindle-shaped NPs and efficient charge transfer relative to the one-dimensional nanostructure of the CNFs. Therefore, spindle-shaped -NP-coated CNF composites may be proposed as a potential alternative material for low-cost counter electrodes in DSSCs.

Electrical and Optical Properties of F-Doped SnO 2 Thin Film/Ag Nanowire Double Layers

Fluorine-doped SnO2 (FTO) thin film/Ag nanowire (NW) double layers were fabricated by means of spin coating and ultrasonic spray pyrolysis. To investigate the optimum thickness of the FTO thin films when used as protection layer for Ag NWs, the deposition time of the ultrasonic spray pyrolysis process was varied at 0, 1, 3, 5, or 10 min. The structural, chemical, morphological, electrical, and optical properties of the double layers were examined using X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, the Hall effect measurement system, and UV-Vis spectrophotometry. Although pure Ag NWs formed isolated droplet-shaped Ag particles at an annealing temperature of 300 oC, Ag NWs covered by FTO thin films maintained their high-aspect-ratio morphology. As the deposition time of the FTO thin films increased, the electrical and optical properties of the double layers degraded gradually. Therefore, the double layer fabricated with FTO thin films deposited for 1 min exhibited superb sheet resistance (~14.9Ω/□), high optical transmittance (~88.6 %), the best FOM (~19.9 × 10−3 Ω−1), and excellent thermal stability at an annealing temperature of 300 oC owing to the good morphology maintenance of the Ag NWs covered by FTO thin films.

Improvement of Triboelectric Efficiency using SnO 2 Friction Layer for Triboelectric Generator

The triboelectric property of a material is important to improve an efficiency of triboelectric generator (TEG) in energy harvesting from an ambient energy. In this study, we have studied the TEG property of a semiconducting which has yet to be explored so far. As a counter triboelectric material, PET and glass are used. Vertical contact mode is utilized to evaluate the TEG efficiency. thin film is deposited by atomic layer deposition on bare Si wafer for various thicknesses from 5.2 nm to 34.6 nm, where the TEG output is increased from 13.9V to 73.5V. Triboelectric series are determined by comparing the polarity of output voltage of 2 samples among , PET, and glass. In conclusion, , as an intrinsic n-type material, has the most strong tendency to be positive side to lose the electron and PET has the most strong tendency to be negative side to get the electron, and glass to be between them. Therefore, the -PET combination shows the highest TEG efficiency.

Fabrication of Uniform TiO2 Blocking Layers for Prevention of Electron Recombination in Dye-Sensitized Solar Cells

Uniform

전기방사법을 이용하여 제조된 Sb-Doped SnO2 투명전도막의 전기적 및 광학적 특성

TiO_2

복합 전기방사법을 이용한 Fe-doped TiO2/α-Fe2O3 이중구조 나노와이어의 합성 및 자성 특성

blocking layers (BLs) are fabricated using ultrasonic spray pyrolysis deposition (USPD) method. To improve the photovoltaic performance of dye-sensitized solar cells (DSSCs), the BL thickness is controlled by using USPD times of 0, 20, 60, and 100 min, creating

Activated mesoporous carbon nanofibers fabricated using water etching-assisted templating for high-performance electrochemical capacitors

TiO_2