The invention relates to a
solar battery diffusion method which is characterized by comprising a step I of first oxidation, a step II of
diffusion and a step III of second oxidation. The step II of
diffusion comprises primary diffusion, the secondary diffusion and
tertiary diffusion. In the
solar battery diffusion method provided by the invention, a P-type
silicon wafer is used as a diffusion source substrate; through three sub-steps of diffusion in the diffusion stage, the
inlet flow of
nitrogen and
oxygen turns from large to small, and the inletting time turns from long to short; in the step III, the concentration of a
phosphorus source is driven into the substrate from high to low, thus the
surface concentration is gradually reduced, and the surface recombination and defect concentration is reduced; gradient
doping is formed, the P-N
junction area is widened, and the open-circuit
voltage is increased; and meanwhile, through the relatively deep junction, the series resistance can be reduced, and the conversion efficiency of a
solar battery is improved. The solar battery diffusion method does not need an additional process, is relatively low in cost and can be used for improving the conversion efficiency of the
crystalline silicon solar battery.