Solar cell, method for preparing solar cell, and solar cell production line

A solar cell comprising:

• an N-type silicon substrate comprising a first surface and a second surface opposite to the first surface, wherein a boron-doped polycrystalline silicon layer is in the N-type silicon substrate at a depth close to the first surface;
• a tunnel oxide layer in contact with the second surface;
• a phosphorus-doped polycrystalline silicon layer on a surface of the tunnel oxide layer away from the N-type silicon substrate;
• grooves extending through the phosphorus-doped polycrystalline silicon layer and the tunnel oxide layer and partially extending into the N-type silicon substrate;
• front grid lines in contact with the boron-doped polycrystalline silicon layer;
• and
• back grid lines in contact with the phosphorus-doped polycrystalline silicon layer, wherein in a thickness direction of the N-type silicon substrate, projections of contact regions between the back grid lines and the phosphorus-doped polycrystalline silicon layer do not overlap with projections of the grooves.

A solar cell production line comprising sequentially connected:

• a texturing equipment configured for texturing an N-type silicon substrate;
• a boron doping equipment configured for boron doping the N-type silicon substrate to form a boron-doped polycrystalline silicon layer in the N-type silicon substrate close to a first surface;
• a first chain-type acid polishing equipment configured for removing a borosilicate glass layer on a second surface of the N-type silicon substrate, the second surface being opposite to the first surface;
• a first tank-type polishing equipment configured for polishing the second surface of the N-type silicon substrate;
• a phosphorus doping equipment configured for forming a tunnel oxide layer, a phosphorus-doped polycrystalline silicon layer, and a mask layer on the second surface of the N-type silicon substrate;
• a first laser equipment configured for performing laser ablation on the mask layer to form through holes each exposing the phosphorus-doped polycrystalline silicon layer;
• a second chain-type acid polishing equipment configured for removing a phosphosilicate glass layer on the first surface of the N-type silicon substrate;
• a second tank-type polishing equipment comprising an alkaline solution tank configured for containing an alkaline solution and a hydrofluoric acid tank configured for containing a hydrofluoric acid solution, so as to etch and remove the phosphorus-doped polycrystalline silicon layer, the tunnel oxide layer, and part of the N-type silicon substrate corresponding to the through holes using the alkaline solution, thereby forming grooves extending through the phosphorus-doped polycrystalline silicon layer and the tunnel oxide layer and partially extending into the N-type silicon substrate, and to remove the mask layer using the hydrofluoric acid solution;
• a deposition equipment configured for forming a front passivation layer and/or a front anti-reflection layer on the first surface of the N-type silicon substrate, and/or forming a back passivation layer and/or a back anti-reflection layer on the second surface of the N-type silicon substrate;
• a printing equipment configured for forming front grid lines on the first surface of the N-type silicon substrate and forming back grid lines on the second surface of the N-type silicon substrate;
• and
• a second laser equipment configured for assisting sintering of the front grid lines and the back grid lines.