Preparation method of full back contact photovoltaic cell

The invention discloses a preparation method of a full back contact photovoltaic cell, and belongs to the field of photovoltaic cells. A tunneling oxide layer and a doped poly layer are deposited on the back surface of an N-type texturing silicon wafer, then high-temperature annealing is carried out to activate doped doping elements, meanwhile, silicon oxide layers are formed on the two surfaces, p-region graphical film opening is carried out on the poly layer on the back surface by using laser to form a second region, and the second region is oxidized after film opening, so that the silicon oxide layers are formed on the two surfaces of the N-type texturing silicon wafer. Then laser is carried out on the second area to remove part of the oxide layer (at the moment, an isolation area is formed through protection of the oxide layer between the first area and the third area to prevent reverse doping electric leakage during boron expansion) to form a third area, boron expansion is carried out after secondary tex