The surface photovoltage (SPV) measurements of CdS/CdT solar cells, prepared by electrodeposition technique, is presented. Minority carrier diffusion length (L) and lifetime (tau) along with the surface space-charge width (W) in the polycrystalline CdTe absorber layers were estimated. A simple modification of the existing theory of surface photovoltage (SPV) measurements is considered to include the effect of grain boundaries in the polycrystalline material. It was observed that the value of the diffusion length, derived from the Goodman＇s expression, was much higher (almost double) than the value obtained by considering the effect of barrier height at the grain boundaries of the polycrystalline absorber layer. This indicated that for SPV measurements in polycrystalline material the consideration of the effect of grain boundaries becomes essential. The use of Goodman＇s simplified expression may not yield unambiguous results, (C) 2000 Elsevier Science B.V. All rights reserved.