Post-hydrogen treatment of boron-doped hydrogenated amorphous silicon carbide (a-SiC:H) film using a mercury-sensitized photochemical vapor deposition (photo-CVD) method was proposed as a novel method to improve film quality. The activation energy of the hydrogen-treated him decreased from 0.467 eV to 0.441 eV and its conductivity increased from 3.7 x 10(-7) Scm(-1) to 6.5 x 10(-7) Scm(-1) as the hydrogen treatment time increased from 0 (without hydrogen treatment) to 30 minutes. These film changes are thought to occur in the bulk of the boron-doped a-SiC:H him. When this method was applied to the boron-doped a-SiC:H layer of pin-type amorphous silicon solar cells, the open circuit voltage and fill factor increased without causing a decrease in the short circuit current, resulting in a conversion efficiency enhancement of about 7%. This improvement in the cell performance can be explained by an increase in the built-in potential of the cell due to a decrease in the activation energy of the p-layer.