It is demonstrated that multijunctiona‐Si:H‐based solar cells are more stable than their single‐junction counterparts and that the stability improves as the number of junctions increases. It is further shown that the rate of degradation of multijunction devices can be explained in terms of the rates of degradation of their individualilayers. It is thus possible to predict the amount of photodegradation of multijunction devices after prolonged light soaking, knowing only the rates of degradation of single‐junction cells in terms of thei‐layer thicknesses and the intensity of the illumination to which they are exposed.