A decrease of surface passivation quality is observed in FZ, Cz, and mc-Si lifetime samples during light-induced degradation (LID) treatments. It is shown that this degradation occurs not only in samples with single SiN x :H layers but also when using layer stacks consisting of SiO x /SiN x :H or AlO x :H/SiN x :H. Time-resolved calculation of the surface saturation current density J 0 s is shown to be a reliable method to separate changes in the bulk and at the surface of samples during LID treatments. The impact of the observed changes in passivation quality on the outcome and interpretation of LID experiments aiming at changes in the bulk of Cz or mc-Si is investigated and discussed.