Byung Keun Hwang

Characterization of chemical-vapor-deposited low-k thin films using x-ray porosimetry

Trimethylsilane-based carbon-doped silica films prepared with varying chemical-vapor-deposition process conditions were characterized using x-ray reflectivity and porosimetry to measure the film thickness, average film density, density depth profile, wall density, and porosity. Samples deposited under single or dual frequency conditions with either N2O or O2 as an oxidant were compared. The structural parameters were correlated with the chemical bond structure measured by Fourier transform infrared spectroscopy. The density profiles of the porous films were uniform with a slight densification at the film surface. The distribution of pores was also uniform through the film. Films prepared under a single frequency and/or N2O atmosphere had the lowest film density, wall density, and dielectric constant. The porosities of the films were similar and the pore sizes were less than 10 A.

Improved spectral response of silicone encapsulanted photovoltaic modules

In this work the benefit of using optically superior silicone encapsulant materials over the incumbent ethylene vinyl acetate is demonstrated. Optical characterization of the two materials demonstrates improved transmission in the UV region of the solar spectrum. Single cell mini-modules were prepared using two different manufacturers of screen printed textured monocrystalline Si PV cells. Spectral response measurements demonstrate a 0.74–1.03% relative increase in short circuit current density when silicones are used rather than ethylene vinyl acetate, clearly in the region of improved UV transparency. IV measurements demonstrate a 0.31–1.45% improvement in current for silicone.