A method for repairing laser grooving damage of perc solar cell back film

Abstract

The invention discloses a method for repairing laser groove damage on the back film of a PERC solar cell. After grooves are made on the back, the silicon wafer is put into heat treatment equipment, and the heat treatment equipment includes a high-temperature activation area and a low-temperature repair area. The wafer is subjected to high-temperature thermal annealing treatment in the high-temperature activation region to increase the overall lattice thermal movement of the silicon substrate; and then a low-temperature thermal annealing treatment is performed in the low-temperature repair region to recrystallize the silicon substrate. After the substrate silicon undergoes a high-temperature activation-low-temperature recrystallization process, the laser-damaged area of ​​the substrate silicon is significantly repaired, thereby reducing the recombination loss caused by laser damage, increasing the open-circuit voltage Voc, and improving the conversion efficiency of PERC solar cells.

Description

technical field [0001] The invention relates to the field of manufacturing solar cells, in particular to a method for repairing laser groove damage on the back film of PERC solar cells. Background technique [0002] PERC solar cells are currently one of the most popular high-efficiency cells on the market. The rear partial contact back passivation technology (PERC) can significantly reduce the recombination loss on the back of the solar cell and greatly improve the efficiency of the solar cell. 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 wi...

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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