Conventional and electromagnetically casted multicrystalline silicon solar cells are fabricated following different passivation schemes. Thin layers (∼100 A˚) of thermal dry and plasma‐enhanced chemical‐vapor‐deposition (PECVD) SiO2are implemented for surface oxide passivation of multicrystalline silicon solar cells and compared. It is found that growing thin layers of thermal dry oxide results in efficient surface passivation. However, for thin PECVD SiO2layers it is necessary to perform low‐temperature forming gas anneal, postdeposition, in order to observe the surface passivation effect. In addition, hydrogen plasma passivation has been optimized for achieving deep penetration of atomic hydrogen in the material (≳30 &mgr;m) and as a consequence very effective bulk passivation of multicrystalline silicon solar cells. By combining front and back thermal dry SiO2passivation with hydrogen remote plasma treatment, a cell efficiency of 17% (independently confirmed) on 4 cm2area and 180 &mgr;m thickness is realized without any Al gettering. On the other hand, the cell efficiencies obtained using thin layers of PECVD SiO2are found to be very comparable to the efficiency of the cells fabricated with thermal dry SiO2layers provided that PECVD Si3N4/SiO2are used as a double‐layer antireflection coating. ©1995 American Institute of Physics.