AbstractTo understand the direct relation among photodarkening (PD), photoinduced volume change (PVC), and photoinduced defect creation (PDC), we perform in‐situ simultaneous measurements of all three phenomena, i.e. optical absorption coefficient (for PD), surface height (for PVC), and photocurrent which monitors PDC, in amorphous As2Se3 films. The time evolution of PDC during light excitation is empirically described by a stretched exponential function: 1 ‐ exp[‐(t /τ)β], where τ is the effective response time and β (< 1.0) the dispersion parameter, while we have found that the PVC and PD were essentially given by a simple exponential function (β = 1). The value of τ for the PDC is very much smaller than those for the PVC and PD. As the time evolutions for all three phenomena are independent of each others, there may be no direct relationship among them. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)