Deep level transient spectroscopy has been used to measure the electrical activity of deep levels in n (+) p junctions applied in solar cells based on Si. Due to the asymmetry of the diode structures the investigation was focused on defects present in p-type Si. We report the presence of several levels. Interpreting the data we notice that some of the revealed traps involve metallic impurities, simultaneously showing properties characteristic for extended defects. Based upon both these facts, we suggest that extended defects are probably generated during device processing and control the electrical activity, which depends on the degree of metal contamination of the Si material. (C) 2002 Elsevier Science B.V. All rights reserved.