We discuss a new molecular dynamics approach for investigating the light‐induced degradation in a‐Si:H. In this approach Si‐Si and newly developed Si‐H interatomic potential have been utilized to describe a 60‐atom a‐Si:H model containing 10% H, similar to device‐quality material. Molecular dynamics schemes for investigating hydrogen‐induced defects and bond‐breaking models of the Staebler‐Wronski effect are discussed.