Electronic properties of low temperature epitaxial silicon thin film photovoltaic devices grown by HWCVD

Abstract

This study addresses the correlation of the electrical, surface, and structural evolution of HWCVD crystalline Si thin films with temperature, thickness, and hydrogen dilution. Scanning electron microscopy and atomic force microscopy reveal an increase with surface roughness with hydrogen dilution, as expected, while showing increasing surface roughness with substrate temperature, in contrast to previous studies of crystalline Si growth. This suggests that H desorption enables more contaminant absorption of the growing surface with increasing temperature, in turn increasing roughness. The open-circuit voltage of these films is shown to increase significantly over time, 50 mV over one week, due to the decrease in surface recombination velocity associated with the growth of a native oxide layer. This indicates the importance of post-deposition treatments for surface passivation.