The surface photovoltage (SPV) technique adapted to thin samples was used to monitor solar cell technology. The relatively short minority carrier diffusion length from 70 to 80 mu m found in p-bulk of the cells results from the presence of a layer with structural defects near the surface. The measurement of successively etched samples reveals that freshly cut off silicon wafers are already strongly destroyed to a depth of at least 35 mu m. A diffusion length of about 300 mu m was evaluated in the samples after removing the disturbed layer. (c) 2005 Elsevier B.V. All rights reserved.