A method for reducing double laser cutting damage of P-IBC battery

Abstract

The application provides a method for reducing damage of P-IBC cell caused by two-pass laser cutting, and the method further comprises coating a cooling liquid on the periphery of a two-pass laser slotting area before two-pass laser slotting is performed. In the method provided by the application, the cooling liquid can effectively block the horizontal conduction of the thermal energy of the laser, thereby reducing the damage of the horizontal thermal conduction of the laser to the lateral passivation layer. Meanwhile, since the cooling liquid does not exist in the laser slotting area, the vertical energy of the laser is not affected, thereby avoiding the deterioration of the slotting effect. The method provided by the application can reduce the damage of the passivation effect caused by laser slotting and improve the overall efficiency of the cell.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology, specifically relating to a method for reducing damage from two-stage laser cutting of P-IBC cells. Background Technology

[0002] With the rapid development of photovoltaic technology, the conversion efficiency of crystalline silicon solar cells has been improving year by year. Currently, the mainstream P-type bifacial PERC (Passivated Emitter Rear Cell) cells have encountered efficiency bottlenecks, and various manufacturers have begun research on more efficient cells with different structures. Among them, P-IBC (P-Interdigitated Back Contact) cells have stood out due to their high efficiency improvement and high compatibility with PERC production lines, and many manufacturers in the industry have begun to increase their investment in the research and development and production of P-type IBC cells.

[0003] Currently, the fabrication process of P-IBC solar cells requires two laser processes. The second laser process is mainly for mold opening, where the laser is used to open the silicon nitride and aluminum oxide films on the P-region of the back of the cell, allowing for aluminum paste printing and contact. However, the mold opening process often significantly impairs the passivation effect, leading to a substantial reduction in the minority carrier lifetime of the solar cell and further affecting its efficiency. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a method for reducing damage from two-stage laser cutting of P-IBC cells. The method provided by the present invention can reduce the passivation effect damage caused by laser mold opening and improve the overall efficiency of the cell.

[0005] This invention provides a method for reducing damage from two-stage laser cutting of P-IBC batteries, which further includes coating the outer periphery of the two-stage laser grooving area with a coolant before performing the two-stage laser grooving.

[0006] Preferably, the area coated with coolant is an annular area located at the perimeter of the two laser-grooved areas.

[0007] Preferably, the ring width of the annular region is 0.1 to 8 μm.

[0008] Preferably, the ring width of the annular region is 0.1 to 4 μm.

[0009] Preferably, the annular region is a circular annular region or a square region resembling a square.

[0010] Preferably, there is no coolant in the two-stage laser grooving area.

[0011] Preferably, the coating method includes printing, spraying, or wet chemical methods.

[0012] This invention also provides a P-IBC battery fabrication process, comprising the following steps:

[0013] The silicon substrate is sequentially polished, subjected to LPCVD (Low Pressure Chemical Vapor Deposition), phosphorus diffusion, laser treatment, cleaning, double-sided alumina preparation, front and back SiNx single-layer / multilayer film preparation, coolant coating on the outer periphery of the second laser grooving area, second laser grooving and printing sintering to obtain the P-IBC cell.

[0014] Preferably, the laser source for the dual-laser grooving is nanosecond green light, picosecond violet light, or picosecond green light, and the laser frequency is 500K to 2000K.

[0015] Compared with existing technologies, this invention provides a method for reducing damage from double laser cutting of P-IBC cells. Before performing the double laser grooving, a coolant is coated onto the outer periphery of the laser grooving area. In this method, the coolant effectively blocks the horizontal conduction of laser heat energy, thereby reducing the damage to the transverse passivation layer caused by laser heat conduction. Simultaneously, since there is no coolant in the laser grooving area, the vertical energy of the laser is not affected, thus preventing a deterioration in the grooving effect. The method provided by this invention can reduce passivation damage caused by laser molding and improve the overall efficiency of the cell. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the P-IBC battery prepared according to the present invention. Detailed Implementation

[0017] This invention provides a method for reducing damage from two-stage laser cutting of P-IBC batteries, which further includes coating the outer periphery of the two-stage laser grooving area with a coolant before performing the two-stage laser grooving.

[0018] In this invention, the area coated with coolant is an annular area located at the periphery of the two-stage laser grooving area.

[0019] The annular region has a width of 0.1–8 μm, preferably 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, or 8 μm, or any value between 0.1 and 8 μm. More preferably, the annular region has a width of 0.1–4 μm.

[0020] In some specific embodiments of the present invention, the annular region is a circular annular region or a square region resembling a square.

[0021] The present invention does not impose any particular limitations on the method of coating the outer periphery of the double-laser grooving area with coolant. Once the area to be coated with coolant is determined, a coating method known to those skilled in the art can be used. In some specific embodiments of the present invention, the coating method includes printing, spraying, and wet chemical methods.

[0022] This invention does not impose any particular limitation on the specific type of coolant; any laser coolant known to those skilled in the art for use in industrial laser applications is acceptable, or a coolant with a low carbon content that readily volatilizes or vaporizes under laser energy. The coolant is a fluid with a certain degree of plasticity; preferably, it is a plastic fluid. In this invention, the coolant does not introduce an additional dielectric layer under laser irradiation.

[0023] In some specific embodiments of the present invention, the coolant includes:

[0024] 70-75 parts by weight of deionized water;

[0025] 20-25 parts by weight of surfactant;

[0026] 3-5 parts by weight of wetting and penetrating agent;

[0027] 0.2 parts by weight of defoamer.

[0028] The surfactant is selected from one or more of polyether, fatty alcohol polyoxyethylene ether, polyethylene glycol, and polypropylene glycol.

[0029] The wetting and penetrating agent is selected from one or more of alkynyl alcohols and alkynyl alcohol polyoxyethylene ethers;

[0030] The defoamer is selected from end-capped polyethers.

[0031] In this invention, the coating thickness of the coolant is 0.1 to 2 μm, preferably 0.1, 0.5, 1, 1.5, 5, or any value between 0.1 and 2 μm.

[0032] In this invention, the coolant can effectively block the conduction of laser heat energy in the horizontal direction, thereby reducing the damage of laser heat conduction to the transverse passivation layer.

[0033] In this invention, there is no coolant in the dual-laser grooving area, the purpose of which is not to affect the energy of the laser in the vertical direction, thereby avoiding a deterioration in the grooving effect.

[0034] When applying coolant in this invention, the entire area is not coated. Instead, the coolant is applied to the outer periphery of the area where the second laser grooving is performed. The main reason is that this invention has found through experiments that the magnitude of the laser energy in the vertical direction has no significant impact on the passivation effect, but has a great impact in the horizontal direction. Therefore, the damage caused by the laser to the passivation is in the horizontal direction.

[0035] This invention also provides a P-IBC battery fabrication process, comprising the following steps:

[0036] The silicon substrate is sequentially polished, LPCVD deposited, phosphorus diffused, laser-cut, cleaned, double-sided alumina prepared, front and back SiNx single-layer / multilayer film prepared, coolant coated on the outer periphery of the second laser grooving area, second laser grooving and printing sintering to obtain the P-IBC cell.

[0037] In this invention, the silicon substrate is selected from a P-type single-crystal silicon substrate. The silicon substrate is first polished. This invention does not impose any particular limitation on the polishing method; any polishing method known to those skilled in the art is acceptable.

[0038] Next, a tunneling oxide layer and a poly layer are deposited on the surface of the silicon substrate using LPCVD.

[0039] Then, phosphorus diffusion is performed to prepare a pn junction. After phosphorus diffusion is completed, a laser treatment, cleaning, double-sided alumina preparation, and front and back SiNx single-layer / multilayer film preparation are performed. This invention does not impose any special limitations on the specific methods for the laser treatment, cleaning, double-sided alumina preparation, and front and back SiNx single-layer / multilayer film preparation; methods known to those skilled in the art are acceptable.

[0040] Then, coolant is applied to the outer periphery of the second laser-grooved area. This step is as described above and will not be repeated here.

[0041] After coating is completed, a second laser grooving is performed. The laser source for the second laser grooving is nanosecond green light, picosecond violet light or picosecond green light, and the laser frequency is 500K to 2000K, preferably 500, 1000, 1500, 2000, or any value between 500K and 2000K.

[0042] Finally, printing and sintering are performed. This invention does not impose any particular limitation on the specific method of printing and sintering; any printing and sintering method known to those skilled in the art is acceptable. Ultimately, a P-IBC battery is obtained.

[0043] See Figure 1 , Figure 1 This is a schematic diagram of the structure of the P-IBC battery prepared according to the present invention.

[0044] Figure 1In the diagram, 1 is the silicon substrate, 2 is the tunneling oxide layer, 3 is the aluminum oxide layer, 4 is the doped Poly layer, 5 is the SiNx single-layer / multilayer film, 6 is the Ag electrode, and 7 is the Al electrode.

[0045] In the method provided by this invention, the coolant can effectively block the horizontal conduction of laser heat energy, thereby reducing the damage to the transverse passivation layer caused by laser heat conduction. Simultaneously, since there is no coolant in the laser grooving area, the vertical energy of the laser is not affected, thus preventing a deterioration in the grooving effect. The method provided by this invention can reduce passivation damage caused by laser molding and improve the overall efficiency of the solar cell.

[0046] To further understand the present invention, the following description, in conjunction with embodiments, illustrates a method for reducing damage from two-stage laser cutting of P-IBC batteries provided by the present invention. The scope of protection of the present invention is not limited by the following embodiments.

[0047] Examples 1-3

[0048] 1) A P-type single-crystal silicon substrate is selected and then polished. Next, a tunneling oxide layer and a poly layer are deposited on the surface of the silicon substrate using LPCVD. Then, phosphorus diffusion is performed to prepare a pn junction. After phosphorus diffusion is completed, a laser treatment, cleaning, double-sided alumina preparation, and front and back SiNx single-layer / multilayer film preparation are performed.

[0049] 2) Apply coolant to the outer periphery of the second laser grooving area. The composition of the coolant is shown in Table 1. The area to which the coolant is applied is an annular area located at the periphery of the second laser grooving area. The shape and width of the annular area are shown in Table 1. The coating thickness or surface load of the coolant is shown in Table 1.

[0050] Table 1 Coolant, Coating Parameters, and Second-Stage Laser Parameters

[0051]

[0052] 3) After coating is completed, a second laser grooving is performed. The laser source and laser frequency parameters for the second laser grooving are shown in Table 1.

[0053] Finally, printing and sintering are performed to obtain the P-IBC battery.

[0054] Comparative Example 1

[0055] 1) Same as Examples 1-3

[0056] 2) Perform double laser grooving. The laser source and laser frequency parameters for the double laser grooving are shown in Table 1.

[0057] Finally, printing and sintering are performed to obtain the P-IBC battery.

[0058] The results show that the coolant provided by this invention can effectively block the horizontal conduction of laser heat energy, thereby reducing the damage to the transverse passivation layer caused by laser heat conduction. Furthermore, since there is no coolant in the laser grooving area, no additional dielectric layer is introduced. The method provided by this invention can reduce the passivation effect damage caused by laser molding and improve the overall efficiency of the solar cell. In contrast, in Comparative Example 1, the two laser grooving processes often cause significant damage to the passivation effect, leading to a substantial reduction in the minority carrier lifetime of the solar cell and further affecting the cell efficiency.

[0059] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for reducing damage from two-stage laser cutting of P-IBC batteries, characterized in that, Before performing the second laser grooving, a coolant is applied to the outer periphery of the second laser grooving area; the area coated with coolant is an annular area located at the periphery of the second laser grooving area, and there is no coolant in the second laser grooving area.

2. The method according to claim 1, characterized in that, The ring width of the annular region is 0.1–8 μm.

3. The method according to claim 1, characterized in that, The ring width of the annular region is 0.1 to 4 μm.

4. The method according to claim 1, characterized in that, The annular region can be a circular annular region or a square region resembling a square.

5. The method according to claim 1, characterized in that, The coating methods include printing, spraying, and wet chemical methods.

6. A P-IBC battery manufacturing process, characterized in that, Includes the following steps: The silicon substrate is sequentially polished, LPCVD deposited, phosphorus diffused, laser-cut, cleaned, double-sided alumina prepared, front and back SiNx single-layer / multilayer film prepared, coolant coated on the outer periphery of the second laser grooving area, second laser grooving and printing sintering to obtain the P-IBC cell.

7. The preparation process according to claim 6, characterized in that, The laser source for the dual-laser grooving is nanosecond green light, picosecond violet light, or picosecond green light, and the laser frequency is 500K to 2000K.

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