Preparation method of silicon dioxide passivation film of crystalline silicon solar cell

The invention provides a preparation method of a silicon dioxide passivation film of a crystalline silicon solar cell. The method comprises: (1) performing cleaning texturing and diffusion-type PN junction processing on a surface of a silicon wafer, and removing an edge junction and surface layer phosphorosilicate glass; (2) performing first oxidation processing on the silicon wafer after the processing of the step (1); (3) performing second oxidation processing on the silicon wafer after the processing of the step (2); and (4) depositing at least two layers of silicon nitride films, which have different refractive indexes and thicknesses, on the surface of the silicon wafer after the processing of the step (3). The preparation method is applied to a polycrystalline silicon cell, and can play a good role in passivation of the surface of the cell and reduce efficiency loss, caused by a recombination, of the cell; a leak current of the cell can also be effectively reduced at a cell process end, and the anti-PID capability of the cell is improved; and anti-corrosion and moistureproof performance of the cell can also be enhanced, and the service life of the cell is prolonged.