Myeong Jun Kim

Enhanced quantum efficiency of amorphous silicon thin film solar cells with the inclusion of a rear-reflector thin film

We investigated the growth mechanism of amorphous silicon thin films by implementing hot-wire chemical vapor deposition and fabricated thin film solar cell devices. The fabricated cells showed efficiencies of 7.5 and 8.6% for the samples without and with the rear-reflector decomposed by sputtering, respectively. The rear-reflector enhances the quantum efficiency in the infrared spectral region from 550 to 750 nm. The more stable quantum efficiency of the sample with the inclusion of a rear-reflector than the sample without the rear-reflector due to the bias effect is related to the enhancement of the short circuit current.

Enhancement effect of short-circuit currents of Si solar cells with inclusion of indium tin oxide layers on metal–semiconductor interfaces

We investigated the enhancement effect on short-circuit currents by indium tin oxide contact layers imbedded in metal–semiconductor interfaces in Si solar cells. Both samples that incorporate the thin film layer and the crossed finger lines of indium tin oxide exhibit an enhancement of p–n junction photocurrents and depletion capacitances with enhanced bulk donor concentrations at the emitter contacts. The indium tin oxide layer provides the passivation layer on the Si emitter surface with reduced trap states and the carrier transport layer for charge collection. The Si solar cells with indium tin oxide showed improved performance in shunt resistance and short-circuit current.

Conductive property of carbon-nanotube dispersed nanocomposite coatings for steel

Nanostructured modification of polymers has opened up new perspective for multifunctional materials. Carbon-nanotubes have the potential to increase the conductivity of their composite, with improved or retaining mechanical performance. This study focuses on the evaluation of the thermal and electrical conductivities of carbonnanotube filled alkyd resins for steel coatings. Polymer/Carbon-nanotube nanocomposites have been prepared by mixing commercial multiwall carbon-nanotubes with alkyd resins and by curing. The thermal and electrical conductivities of carbon-nanotubes filled nanocomposite was found to be increased comparing with the original resin without any fillers or with the resin with carbon-black or carbon-nanofiber.

Preparation and Characterization of Epoxy/Clay Nanocomposites

Epoxy/clay nanocomposites have been prepared using montmorillonite (MMT) ionexchanged with various organic cations ; hexadecyltributyl phosphonium ion, octadecyltrimethyl ammonium ion, methyl tallow bis-2-hydroxyethyl ammonium ion and dimethyl hydrogenatedtallow (2-ethylhexyl) ammonium ion. The resulting nanocomposites were found to show exfoliated clay structure by using transmission electron microscopy (TEM) and X-ray diffractometry (XRD). The flame retarding property of 5wt% clay/epoxy nanocomposites was found to be enhanced when compared with that of the original epoxy without clay.