Here we investigated the effects of hydrogen treatment on highly defected polycrystalline silicon solar cells in terms of defects passivation and surface etching. The poly-Si films were formed by high-temperature chemical vapour deposition. The hydrogen treatment was carried out through deposition of a-SiNx:H layer followed by a thermal treatment or by direct hydrogen plasma. The deposition of silicon nitride layers on polysilicon cells led to a slight increase in the open-cirCUit voltage without damage to the surface. In contrast, after plasma hydrogenation. the results revealed an etching process of the emitter simultaneously with an important increase of the measured open-circuit voltage by a factor 2, reaching 420 mV. (c) 2006 Elsevier B.V. All rights reserved.