The effect of hydrogen dilution on the light degradation behavior of amorphous silicon (a‐Si:H)p‐i‐nsolar cells fabricated by mercury‐sensitized photochemical vapor deposition has been systematically investigated. In the case of solar cells with nop/ibuffer layer, the open‐circuit voltage (Voc) of the cells with theilayer prepared by H2‐diluted SiH4was found to increase with the light‐soaking time, while theVocof the cell withilayer prepared from pure SiH4decreased. Moreover, the single junction solar cell with theVocof 1.001 V and fill factor of 0.72 has been achieved by optimizing H2dilution ratio inilayer and employing the wide band gappand buffer layer. ©1995 American Institute of Physics.