The measured internal spectral response and open-circuit voltage of two silicon solar cells were modeled with the simulation program PC1D version 4.4 by both applying and not applying the depletion approximation (DA). A comparison between the results from the two modeling approaches shows that dividing the device under exam into regions according to the DA is preferable in order to get both modeling reliability and physical insight into the device operation. Not using the DA leads in fact to both overestimate the bulk lifetime and neglect the optical properties of highly doped regions. (C) 2002 Elsevier Science B.V. All rights reserved.