The invention relates to a method for producing passivation layers on crystalline silicon by a) coating the silicon with a solution containing at least one polysilazane of the general formula (1): —(SiR′R″—NR′″)-n, wherein R′, R″, R′″ are the same or different and stand independently of each other for hydrogen or a possibly substituted alkyl, aryl, vinyl, or (trialkoxysilyl)alkyl group, wherein n is an integer and n is chosen such that the polysilazane has a number average molecular weight of 150 to 150,000 g/mol, b) subsequently removing the solvent by evaporation, whereby polysilazane layers of 50-500 nm thickness remain on the silicon wafer, and c) heating the polysilazane layer at normal pressure to 200-1000° C. in the presence of air or nitrogen, wherein upon tempering the ceramic layers release hydrogen for bulk passivation of the silicon.