Eun-Sung Lee

Synthesis and Electrochemical Investigations of Ni1 − x O Thin Films and Ni1 − x O on Three-Dimensional Carbon Substrates for Electrochemical Capacitors

Nickel oxide/carbon nanotube (Ni 1 - x O/CNT) film nanocomposite electrodes for electrochemical capacitors were prepared by electrochemically precipitating nickel hydroxide onto a CNT film substrate and heating it in air at 300°C. For comparison, nickel oxide thin film and nickel oxide/carbon paper (Ni 1 - x O/C paper) electrodes were also prepared via electrochemical route. The nickel oxide layers (∼5 nm thickness) in the Ni 1 - x O/CNT film electrode were coated uniformly on the surface of the individual CNTs, constructing a 3D nanoporous network structure through the entire thickness of the film. In comparison to the thin film and Ni 1 - x O/C paper electrodes, the Ni 1 - x O/CNT film electrode showed a very high specific capacitance of ∼ 1000 F g - 1 with a high rate capability in 1 M KOH. The Ni 1 - x O/CNT film electrode also showed a good cycle life during 100 cycles in 1 M KOH. The high specific capacitance and good power characteristics of the Ni 1 - x O/CNT nanocomposite electrode can be attributed to the construction of an electrode with a very thin film of electroactive materials with a nanometer thickness on a CNT film substrate with a 3D nanoporous network structure.

Capillary flow of amorphous metal for high performance electrode

Metallic glass (MG) assists electrical contact of screen-printed silver electrodes and leads to comparable electrode performance to that of electroplated electrodes. For high electrode performance, MG needs to be infiltrated into nanometer-scale cavities between Ag particles and reacts with them. Here, we show that the MG in the supercooled state can fill the gap between Ag particles within a remarkably short time due to capillary effect. The flow behavior of the MG is revealed by computational fluid dynamics and density funtional theory simulation. Also, we suggest the formation mechanism of the Ag electrodes, and demonstrate the criteria of MG for higher electrode performance. Consequently, when Al85Ni5Y8Co2 MG is added in the Ag electrodes, cell efficiency is enhanced up to 20.30% which is the highest efficiency reported so far for screen-printed interdigitated back contact solar cells. These results show the possibility for the replacement of electroplating process to screen-printing process.

Enhancement of electrical conductivity of thick silver electrode using a tailored amorphous alloy

Metallic glass (MG) can be a promising additive for the screen-printed silver electrode, when the composition of MG is properly tailored. When Cu-Zr-Al MG is used as an additive, the contact resistance between the Ag electrode and the Si emitter significantly decreases down to 5.39u2009mΩu2009cm2 on 100u2009Ω/sq of emitter, while when Cu-Zr Mg is used, the contact resistance is 31.28u2009mΩu2009cm2. Wider supercooled-liquid region and high reactivity with silver of Cu-Zr-Al MG lead to wider contact area of the Ag electrode and higher density of Ag crystallites, resulting in such a low contact resistance.

Thermal decomposition of silver acetate in silver paste for solar cell metallization: An effective route to reduce contact resistance

A screen printed silver/metallic glass (MG) paste formulated with Ag acetate resulted in a specific contact resistance in the range of 0.6–0.7u2009mΩ·cm2 on both the n- and p-type Si emitters of interdigitated back-contact solar cells. Silver nanocrystallites resulting from thermally decomposed Ag acetate prevented the Al MG frits from directly interacting with the Si emitter, thus reducing the amount of Al diffused into the Si emitters, and subsequently, the contact resistance. A photovoltaic conversion efficiency of 20.3% was achieved using this technique.

Evaluation of E-government Systems with Cognitive Mapping Simulation

E-Government system performance must be measured by an exporting company prior to implementation in other countries. However, it is extremely difficult to perform this task due to the existence of a large number of factors to consider and analyze. The motivation of this study was to propose a new method to reduce this difficulty in measuring e-Government system performance. We adopted a cognitive mapping approach for this purpose, where a set of relevant factors that affect e-Government system performance were collected and the causal relationships among them were identified and analyzed to investigate the equilibrium results given certain input conditions. The e-Government system used for handling intellectual property in South Korea was used as a test-bed. Experiment results revealed that cognitive mapping simulation can yield statistically sound and practically rich results.

Who’s More Powerful? King vs. Knight: Relative Influence of CEO vs. Team Leader on Emotional Contagion and Performance

Organizations are neither isolated nor insulated from emotional display. This paper examines the emotional contagion between a leader and followers and its impact on performance, and tries to answer the question of “What should leaders do, express positive emotions or negative emotions?”. I test the emotional contagion effects of leader-follower relationship, using two contextual variables – organizational and team performance – and take the different hierarchical position of leaders into consideration. Moreover, this paper determines in which circumstance among four scenarios described in the paper the followers converge emotionally more to CEO vs team leader.