In this study, the indoor evaluation of amorphous silicon modules was conducted using extended visual inspection and various electrical characterisation tools. The visual inspection, which included low-magnification optical microscopy, revealed several defects resulting from physical damage and bad scribing. These defects, as well as poor material quality, are likely contributors to the degradation in performance observed during the measurement of current-voltage characteristics under standard conditions, as well as at different temperature and irradiance levels. The observed degradation is carefully analysed in this paper. (c) 2006 Elsevier B.V. All rights reserved.