Effects of Interelectrode Spacing on the Properties of Microcrystalline Silicon Absorber and Solar Cells

Abstract

We study the effect of the spacing between electrodes in very high frequency plasma enhanced chemical vapor deposition on the properties of microcrystalline silicon films and their related n-i-p solar cells. We vary the spacing from 0.2 to 1.0 cm to deposit microcrystalline silicon at 67.8 MHz while maintaining other growth parameters. The spacing between the electrodes significantly changes the plasma conditions, which govern film precursor chemistry as well as introduce etching and ion bombardment to the film; thereby, influencing nucleation and growth of the microcrystalline Si films. The resulting films were characterized by UV-Vis spectrometry, atomic force microscopy, X-ray diffraction, and transmission electron microscopy. We found that deposition rate decreases, while surface roughness and short circuit current density increase with smaller spacing.