Amorphous diamond-like carbon films (a:DLC) were used as anti-reflecting coatings and as hard protecting materials for silicon solar cells. The dependence of a:DLC film thickness (t) on the short circuit current and on the efficiency of the solar cells was examined theoretically and experimentally. A good correlation exists between the experimental and theoretical values. A maximum efficiency of the solar cell was obtained for t = 55 nm of the a:DLC film, corresponding to an improvement of the efficiency by 30%. These solar cells were also examined under mechanical abrasive conditions using a powder abrasive system. The property of a:DLC films to protect solar cells was demonstrated.