This study investigates defect passivation in fine-grained polycrystalline silicon layers by means of hydrogenation. The polycrystalline silicon layers are deposited on oxidized Si wafers using high-temperature chemical vapour deposition. The hydrogenation treatment is performed in a direct plasma enhanced chemical vapour deposition system. The samples are characterized by resistivity vs. temperature measurements of p-type layers and by quasi-steady state open-circuit voltage measurements of p-n diodes made in the material. The results show a large increase of the measured open-circuit voltage by the hydrogenation treatment, with the open-circuit voltage of the samples at a light intensity of 1 Sun rising from 180 mV without hydrogenation to values up to 380 mV. This corresponds to a defect concentration decrease by a factor of three. (C) 2005 Elsevier B.V. All rights reserved.