Every semiconductor device contains as grown and process induced defects even though the techniques to minimize the density of defects are known. Conventional DLTS methods are used to identify the trapping defects in the device. However, the activity of the traps could be suppressed or enhanced by the operating conditions of the device such as temperature, current through the device or light directed onto the device. We studied the DLTS spectra of silicon polycrystaline solar cells, as well as silicon and GaAs photodetectors in the dynamic regime, namely under light and at elevated temperature. Significant change in the resulting spectra were observed when compared to the spectra obtained by conventional DLTS methods.