Solar cell and preparation method thereof

The invention provides a solar cell and a preparation method thereof. The preparation method comprises the following steps: respectively depositing a first intrinsic amorphous silicon layer and a second intrinsic amorphous silicon layer on the front surface and the back surface of a monocrystalline silicon substrate; depositing an n-type doped amorphous silicon layer on the first intrinsic amorphous silicon layer; depositing a p-type doped amorphous silicon layer on the second intrinsic amorphous silicon layer; depositing an n-type doped microcrystalline silicon layer on the n-type doped amorphous silicon layer; depositing a p-type doped microcrystalline silicon layer on the p-type doped amorphous silicon layer; the gas pressure for depositing the n-type doped microcrystalline silicon layer and the p-type doped microcrystalline silicon layer is 3-5 Torr, the flow ratio of SiH4 to doped gas to H2 is 1: (1-1.5): (150-200), the starting power is 2000-3500 W, and the starting time is 100-230 s; and alkali polishi