Method for repairing laser grooving damage of back film of PERC solar cell

Abstract

The invention discloses a method for repairing the laser grooving damage of the back film of a PERC solar cell. According to the method, after the back surface of the back film is grooved, a silicon wafer is arranged into heat treatment equipment; the heat treatment equipment comprises a high-temperature activation area and a low-temperature repair area; the silicon wafer is subjected to high-temperature thermal annealing treatment in the high-temperature activation area, so that the overall lattice thermal motion of a silicon substrate can be increased; and low-temperature thermal annealing treatment is performed on the low-temperature repair area, so that the silicon substrate can be recrystallized. After the substrate silicon is subjected to the high-temperature activation and low-temperature recrystallization processes, the laser damage area of the substrate silicon is obviously repaired, so that composite loss caused by laser damage is reduced, and therefore, open-circuit voltageVoc is increased, and the conversion efficiency of the PERC solar cell is thus improved.

Description

Technical field [0001] The invention relates to the manufacturing field of solar cells, and in particular to a method for repairing PERC solar cell back film laser slotting damage. Background technique [0002] PERC solar cells are currently one of the most popular high-efficiency cells on the market. The back-side partial contact back passivation technology (PERC) significantly reduces the back-side recombination loss of solar cells and greatly improves the efficiency of solar cells. However, the current passivation film structure commonly used in PERC technology is Al 2 O 3 / SiN x Laminated, due to Al 2 O 3 / SiN x The laminated properties are stable, and the conventional back aluminum paste cannot be etched through. Therefore, in order to ensure the contact between the aluminum paste and the silicon substrate, laser grooving is required; however, laser grooving will inevitably cause certain damage to the silicon substrate, because The high temperature generated by the laser wil...

AI Technical Summary

Problems solved by technology

However, the passivation film structure commonly used in PERC technology is Al 2 o 3 / SiN x stack, due to the Al 2 o 3 / SiN x The properties of the laminate are stable, and the conventional back aluminum paste cannot be etched through, so laser grooving is required to ensure the contact between the aluminum paste and the silicon substrate; however, laser grooving will inevitably cause certain damage to the silicon substrate, because The high temperature generated by the laser will cause lattice defects to form on the surface of the silicon substrate, resulting in additional recombination centers, which will reduce the conversion efficiency of the final cell

Generally, the area of ​​the laser groove on the back of the PERC solar cell accounts for 0.5% to 3%, and the implied_Voc loss due to laser damage is about 2 to 5mV, which is reflected in the efficiency of the solar cell, and its efficiency loss is 0.1% to 0.25%.

[0003] The prior art with the publication number CN109616556A discloses "A method for integrating back annealing and front coating of a silicon wafer and a method for preparing a battery sheet". , using the heating process required for the front coating to repair the damage caused by the laser grooving. The advantage of this method is that it does not need to add any additional processes, but also because it uses the heat required for the positive film deposition process, its temperature is lower and Due to the nature of the positive film, it is impossible to adjust the heat treatment parameters, which greatly limits the effect of thermal annealing repair; at the same time, during the laser slotting process, since the front side of the cell is not coated, the substrate silicon will inevitably directly contact the conveyor belt and slotting Countertops are prone to scratches and dirt

[0004] The prior art with the publication number CN105470347A discloses "A Manufacturing Method for PERC Cells", the annealing step used is located after the deposition of aluminum oxide on the back side and before the deposition of silicon nitride on the back side, and the annealing temperature is set at 400-500°C , which is used to eliminate the residual stress generated after the deposition of alumina, that is, it is an annealing scheme for the alumina film, which cannot repair lattice defects well

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