It was shown that the photo-induced defect population growth of an optically thick film could exhibit a stretched exponential time dependence if the defect did not decay or diffuse within the time scale of the experiment. After formulating a simple model, the low-temperature photo-induced absorption of polyaniline was used as an example.

K.Kim, A.J.Epstein: Applied Physics Letters, 1995, 67[19], 2786-8