Improvement of a-Si Solar Cell Fabricated by Mercury-Sensitized Photochemical Vapor Deposition Using H2 Dilution Technique

Abstract

The fabrication of hydrogen-diluted amorphous silicon (a-Si) film by the mercury-sensitized photochemical vapor deposition (photo-CVD) method has been performed. The hydrogen content in the film along with the optical bandgap was found to increase with the hydrogen/silane dilution ratio, while the dihydride/monohydride bond ratio decreased at the substrate temperature of 150° C. As a result, a decrease in the defect density was observed. Moreover, the photo- and dark conductivities were maintained in the range of 3×10^-5 and 1×10^-10 S/cm, respectively, in spite of the fact that the optical bandgap widened. The solar cells with hydrogen diluted i-layers were fabricated and showed improvement in the open-circuit voltage and fill factor (FF), resulting in the increase of both initial and stabilized efficiencies. The forward- and reverse-bias dark I-V characteristics measurement of solar cells revealed improvement in quality and stability of the hydrogen-diluted i-layers.