Hydrogenated amorphous silicon solar cells have been realised in both a p-i-n configuration on a Corning glass substrate as well as in a n-i-p configuration on stainless-steel substrate. The performance degradation of the two kinds of cell under solar illumination has been examined for a 140 h period. During degradation, the two devices were kept under load in the maximum power condition that is normally used in a solar plant. The performance of the Corning glass deposited device exhibited a higher rate of degradation with respect to the other cell. A discussion on the possible reasons for this behaviour is given. (C) 2002 Elsevier Science B.V. All rights reserved.