High-Performance Hydrogenated Amorphous Silicon-Germanium Solar Cells Fabricated by Photochemical Vapor Deposition

Abstract
High-quality a-SiGe:H films have been prepared by photochemical vapor deposition (photo-CVD) with a high dilution ratio of H2. Films with a bandgap of 1.55 eV has a photoconductivity of 1.6×10-4 S/cm (AM1, 100 mW/cm2). Solar cells of the p-i-n type were fabricated by applying such high-quality a-SiGe:H films to the i-layer. The performance of a-SiGe:H solar cells has been drastically improved by introducing graded-bandgap layers at the p/i and i/n hetero-interfaces. At present, a conversion efficiency of 8.65% with high collection efficiencies in the long-wavelength region has been achieved with 1.57 eV bandgap material.