DBR (Distributed Bragg Reflector) mask structure for reducing laser damage and manufacturing method of back contact battery

Abstract

The invention discloses a DBR mask structure capable of reducing laser damage and a manufacturing method of a back contact battery, and relates to the technical field of batteries. The DBR mask structure comprises multiple sets of DBR unit structures which are arranged in an overlapped mode, each set of DBR unit structure is composed of a silicon oxide film layer and a silicon nitride film layer, in the DBR mask structure, the silicon oxide film layers and the silicon nitride film layers are alternately arranged, the refractive index of the silicon oxide film layers is 1.5 + / -0.045, the optical thickness of the silicon oxide film layers is 59.2 + / -1.8 nm or 88.6 + / -2.5 nm, the refractive index of the silicon nitride film layers is 1.9 + / -0.057, and the optical thickness of the silicon nitride film layers is 59.2 + / -1.8 nm or 88.6 + / -2.5 nm. The optical thickness is 46.7 + / -1.35 nm or 70 + / -2.0 nm; most of laser energy is reflected by using the DBR mask structure, the film layer structure below the mask layer is protected in the laser patterning process, and secondary distribution of a doping source, reduction of the passivation characteristic of the surface and influence on the conversion efficiency of the battery are avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a DBR mask structure capable of reducing laser damage and a method for manufacturing a back-contact battery. Background Art

[0002] As early as 1975, Schwartz and Lammert proposed the concept of back-contact solar cells. Sunpower, an American company, was the first in the world to commercialize back-contact solar cells by combining TOPCon cell technology with back-contact cell structural design. However, the cell process is complex, involving multiple mask lithography processes, and the cost of cell production is extremely high, so it has never been mass-produced. In recent years, with the rapid development of laser technology, some domestic and foreign manufacturers have applied laser technology to the patterning of BC cells. Laser patterning technology will be the mainstream technology for the industrialization of XBC cells in the future. However, in the process of grooving (holes) using laser patterning technology, due to the high laser energy, it is inevitable that the laser will damage the crystalline silicon surface or the nano (micro) doped layer on the crystalline silicon surface, resulting in a higher interface state density, increased recombination, and a loss of some cell conversion efficiency.

[0003] In passivated back-contact solar cells, the conventional mask layer structure generally utilizes a single layer of silicon oxide or silicon nitride film, and optical parameters such as refractive index and thickness are not strictly designed. The mask layer structure is simply to meet the need to protect the area from damage during the wet cleaning process or to change the doping concentration or doping type in the protected area under high-temperature diffusion conditions. There are no reports on the design of the mask layer that considers the damage of the laser light wave to the film layer under the mask layer during the grooving process. During the laser patterning process, most of the laser light wave energy can pass through the mask layer, and the laser energy is relatively high, thus reaching the surface of the film layer under the mask layer structure, either causing laser damage or forming a secondary distribution of the dopant source of the film structure under the mask layer, reducing the surface passivation characteristics and affecting the conversion efficiency of the cell. Summary of the Invention

[0004] The present invention aims to solve the technical problem that laser patterning causes damage to the crystalline silicon surface or doping layer, resulting in increased recombination, secondary distribution of doping sources, reduced surface passivation characteristics, and decreased battery conversion efficiency. The purpose is to provide a DBR (Distributed Bragg Reflector) mask structure that reduces laser damage and a method for manufacturing a back-contact battery. The DBR mask structure is used to reflect most of the laser energy, effectively protecting the underlying film layer during the laser patterning process, preventing it from reaching the surface of the film layer below the mask layer and causing laser damage. At the same time, it can avoid the formation of a secondary distribution of the doping sources of the film layer structure below the mask layer, avoid reducing the surface passivation characteristics, and thus ensure the efficiency of the manufactured battery.

[0005] The present invention is achieved through the following technical solutions:

[0006] A first object of the present invention is to provide a DBR mask structure that reduces laser damage, comprising a plurality of overlapping DBR unit structures, each DBR unit structure being composed of a silicon oxide film layer and a silicon nitride film layer, wherein the silicon oxide film layer and the silicon nitride film layer are alternately arranged in the DBR mask structure;

[0007] The refractive index of the silicon oxide film layer is 1.5±0.045, and the optical thickness is 59.2±1.8nm or 88.6±2.5nm;

[0008] The refractive index of the silicon nitride film layer is 1.9±0.057, and the optical thickness is 46.7±1.35 nm or 70±2.0 nm.

[0009] Furthermore, the DBR unit structure is provided in 1 to 10 groups.

[0010] A second object of the present invention is to provide a method for manufacturing a back-contact battery, comprising the following steps:

[0011] A first tunneling oxide layer, a first doped polysilicon or amorphous silicon layer, and a mask layer are sequentially grown on the backlight surface of the silicon substrate, wherein the mask layer adopts the DBR mask structure according to claim 1;

[0012] A first laser patterning process is performed to remove the mask layer and the first doped polysilicon or amorphous silicon layer in a local area;

[0013] The first alkali solution treatment completely exposes the surface of the silicon substrate in the local area;

[0014] A second tunneling oxide layer and a second doped polysilicon or amorphous silicon layer are sequentially grown on the backlight surface of the silicon substrate and activated to form a first region, a gap region, and a second region;

[0015] A second laser patterning process is performed to remove the film layer grown on the mask layer in the second region and in the gap region;

[0016] The second alkali solution treatment makes the gap area completely leak out of the surface of the silicon substrate;

[0017] Texturing treatment is performed to form a textured structure on both the gap area and the front surface of the silicon substrate, while removing the mask layer and the film layer on the surface of the second doped polysilicon layer;

[0018] A dielectric passivation film layer and an anti-reflection passivation film are grown on both the backlight surface and the front surface;

[0019] A first metal electrode is formed in the first region, and a second metal electrode is formed in the second region, thereby completing the fabrication of a back-contact battery.

[0020] Furthermore, the alkali solution used in the alkali solution treatment is a KOH or NaOH solution with a mass fraction of 10% to 30%.

[0021] Furthermore, during the first alkaline solution treatment, the remaining first tunneling oxide layer and the first doped polysilicon or amorphous silicon layer need to be completely removed.

[0022] Furthermore, the second doped polysilicon or amorphous silicon layer has a doping type opposite to that of the first doped polysilicon or amorphous silicon layer.

[0023] Furthermore, during the second alkaline solution treatment, the second tunneling oxide layer and the second doped polycrystalline layer remaining on the mask layer in the second region and in the gap region need to be completely removed.

[0024] Furthermore, the mask layer and the film layer on the surface of the second doped polysilicon layer are removed using an HF solution with a mass fraction of 1% to 2%.

[0025] Furthermore, growing a dielectric passivation film layer and an anti-reflection passivation film on both the backlight surface and the front surface includes:

[0026] A first dielectric passivation film layer and a first anti-reflection passivation film layer are sequentially grown on the backlight surface, and a second dielectric passivation film layer and a second anti-reflection film layer are sequentially grown on the light-absorbing surface.

[0027] The third object of the present invention is to provide a back contact battery prepared by the above method.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. In the process of manufacturing back-contact batteries in the present invention, the mask layer adopts the mask structure provided by the present invention. During the laser patterning process, it can effectively protect the film layer below, reflect most of the laser energy, and avoid reaching the surface of the film layer below the mask layer and causing laser damage. At the same time, it can avoid the formation of a secondary distribution of the doping source of the film layer structure below the mask layer, avoid reducing the passivation characteristics of the surface, and thus ensure the efficiency of the manufactured battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0031] Figure 1 Schematic diagram of the structure of the DBR mask structure of the present invention;

[0032] Figure 2 This is a schematic diagram of the product structure obtained in step 1 of Example 1;

[0033] Figure 3 This is a schematic diagram of the product structure obtained in step 2 of Example 1;

[0034] Figure 4 This is a schematic diagram of the product structure obtained in step 3 of Example 1;

[0035] Figure 5 This is a schematic diagram of the product structure obtained in step 4 of Example 1;

[0036] Figure 6 This is a schematic diagram of the product structure obtained in step 5 of Example 1;

[0037] Figure 7 This is a schematic diagram of the product structure obtained in step 6 of Example 1;

[0038] Figure 8 This is a schematic diagram of the product structure obtained in step 7 of Example 1;

[0039] Figure 9 This is a schematic diagram of the product structure obtained in step eight of Example 1;

[0040] Figure 10 This is a schematic diagram of the product structure obtained in step nine of Example 1;

[0041] Figure 11 This is a schematic diagram of the product structure finally obtained in Example 1.

[0042] Markings and corresponding parts names in the accompanying drawings:

[0043] 1-silicon substrate, 101-first region, 102-gap region, 103-second region, 2-first tunneling oxide layer, 3-first doped polysilicon or amorphous silicon layer, 4-mask layer, 40-DBR unit structure, 41-silicon oxide film layer, 42-silicon nitride film layer, 5-second tunneling oxide layer, 6-second doped polysilicon or amorphous silicon layer, 7-PSG or BSG layer, 8-first dielectric passivation film layer, 9-first anti-reflection passivation film layer, 10-second dielectric passivation film layer, 11-second anti-reflection film layer, 12-first metal electrode, 13-second metal electrode. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the embodiments and drawings. Obviously, the schematic implementation methods of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0045] The following describes in detail, with appropriate reference to the accompanying drawings, embodiments of the present invention's DBR mask structure for reducing laser damage and a method for fabricating a back-contact solar cell. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions may be omitted. This is done to avoid unnecessary redundancy and to facilitate understanding by those skilled in the art.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all steps of the present application can be performed sequentially or randomly, but are preferably performed sequentially.

[0047] Currently, conventional mask layer structures basically use a single-layer silicon oxide film or silicon nitride film structure, and there is no strict design for optical parameters such as refractive index and thickness. The mask layer structure is simply to meet the need to protect the area from being damaged by the wet cleaning process or to change the doping concentration or doping type of the protected area under high-temperature diffusion conditions. There are no reports on considering the damage of laser light waves to the film layer under the mask layer during the grooving process from the perspective of mask layer design. During the laser patterning process, most of the energy of the laser light wave can pass through the mask layer, and the laser energy is relatively high, thereby reaching the surface of the film layer under the mask layer structure, or causing laser damage, or forming a secondary distribution of the doping source of the film layer structure under the mask layer, reducing the passivation characteristics of the surface and affecting the conversion efficiency of the battery.

[0048] To solve this problem, the present invention provides a DBR mask structure that reduces laser damage, including multiple sets of overlapping DBR unit structures 40. Each set of DBR unit structures 40 is composed of a silicon oxide film layer 41 and a silicon nitride film layer 42. In the DBR mask structure, the silicon oxide film layer 41 and the silicon nitride film layer 42 are arranged alternately.

[0049] The refractive index of the silicon oxide film layer 41 is 1.5±0.045, and the optical thickness is 59.2±1.8 nm or 88.6±2.5 nm;

[0050] The refractive index of the silicon nitride film layer 42 is 1.9±0.057, and the optical thickness is 46.7±1.35 nm or 70±2.0 nm.

[0051] The DBR mask structure of the present invention can significantly reflect the laser energy entering the mask layer 4 structure, thereby reducing damage to the surface of the film layer below the mask layer 4 structure, reducing surface recombination, and also reducing the formation of secondary distribution of the doping source of the film layer structure below the mask layer 4, thereby avoiding reducing the passivation characteristics of the surface, thereby ensuring the conversion efficiency of the battery.

[0052] If the patterning laser is an ultraviolet laser with a wavelength of 355 nm, the refractive index of the silicon oxide film layer 41 is 1.5±0.045, and the optical thickness is 59.2±1.8 nm; the refractive index of the silicon nitride film layer 42 is 1.9±0.057, and the optical thickness is 46.7±1.35 nm.

[0053] If the patterning laser is a green laser with a wavelength of 532 nm, the refractive index of the silicon oxide film 41 is 1.5±0.045, and the optical thickness is 88.6±2.5 nm; the refractive index of the silicon nitride film 42 is 1.9±0.057, and the optical thickness is 70±2.0 nm.

[0054] The main reason the above mask layer structure requires strict control of the film's refractive index and optical thickness is that when light from a medium with a refractive index of n1 enters a medium with a refractive index of n2, the first-order reflected light interferes with the second-order, third-order, and finally the nth-order reflected light. When the phase difference between the reflected light of each order satisfies 2kπ (k is a positive integer), constructive interference occurs, and the medium's reflectivity reaches its maximum value. Based on this principle, if n1 is less than n2, when light from the n1 medium enters the n2 medium, the reflected light has a phase difference of π with the original incident light. It can be deduced that to keep the first-order and second-order reflected light in phase, the phase condition required for light incident on the n2 medium is an odd multiple of π, and the dielectric film thickness d2 satisfies (2k+1)·λ0 / 4n2, where λ0 is the design wavelength (corresponding to the laser wavelength in this document). Based on this principle, applying this result to multilayer film interference yields the DBR film structure of the present invention. Therefore, the present invention strictly controls the refractive index and optical thickness. Compared with the prior art which does not strictly control the refractive index and optical thickness, it can effectively reflect the laser and protect the underlying film layer from damage to the greatest extent.

[0055] It should be noted that the DBR mask structure designed in the present invention is suitable for ultraviolet lasers with a wavelength of 355nm and green lasers with a wavelength of 532nm. Although other wavelengths of lasers exist in the prior art, such as the 1064nm red laser, their deeper penetration into silicon materials hinders patterning. For example, shorter wavelength ultraviolet lasers, such as 248nm, are extremely expensive and are rarely used in the production of crystalline silicon solar cells. The wavelengths of 355 and 532nm are commonly used in crystalline silicon cell patterning. Therefore, the present invention provides specific parameter designs for the DBR mask structure for these two wavelengths.

[0056] As a further technical solution, the DBR unit structures 40 are provided in 1 to 10 groups. More preferably, the DBR unit structures 40 are provided in 2 to 10 groups. Experiments have shown that providing one group of DBR unit structures 40 can reflect 64% of the laser energy, providing five groups of DBR unit structures 40 can reflect 80% of the laser energy, and providing 2 to 10 groups achieves a better effect.

[0057] Based on the above DBR mask structure, a method for manufacturing a back contact cell is proposed, comprising the following steps:

[0058] (1) An N-type or P-type silicon substrate 1 is selected as a substrate, and both sides of the silicon substrate 1 are polished.

[0059] (2) growing a first tunneling oxide layer 2, a first doped polysilicon or amorphous silicon layer 3, and a mask layer 4 in sequence on the backlight surface of the silicon substrate 1, wherein the mask layer 4 adopts a DBR mask structure;

[0060] (3) The first laser patterning process is to remove the mask layer 4 and the first doped polysilicon or amorphous silicon layer 3 in a local area.

[0061] (4) The alkaline solution used is a KOH or NaOH solution with a mass fraction of 10% to 30% for the first alkaline solution treatment to completely remove the remaining first tunneling oxide layer 2 and the first doped polysilicon or amorphous silicon layer 3, so that the surface of the silicon substrate 1 is completely exposed in a local area.

[0062] (5) growing a second tunneling oxide layer 5 and a second doped polysilicon or amorphous silicon layer 6 on the backlight side of the silicon substrate 1 in sequence, wherein the second doped polysilicon or amorphous silicon layer 6 has a doping type opposite to that of the first doped polysilicon or amorphous silicon layer 3;

[0063] The first doped polysilicon or amorphous silicon layer 3 and the second doped polysilicon or amorphous silicon layer 6 are activated, and a PSG or BSG layer 7 is grown on the surface of the second doped polysilicon or amorphous silicon layer 6. At this time, a first region 101, a gap region 102 and a second region 103 are formed on the backlight surface.

[0064] Here, PSG stands for phosphosilicate glass, and BSG stands for borosilicate glass.

[0065] (6) A second laser patterning process is performed to remove the film layers grown on the mask layer 4 in the second region 103 and the gap region 102; the specific film layers include the second doped polysilicon or amorphous silicon layer 6, PSG or BSG layer 7 on the mask layer 4 in the second region 103, and the second doped polysilicon or amorphous silicon layer 6, PSG or BSG layer 7 grown in the gap region 102.

[0066] (7) A second alkaline solution treatment is performed using a KOH or NaOH solution with a mass fraction of 10% to 30% to remove the second tunneling oxide layer 5 and the second doped polysilicon or amorphous silicon layer 6 remaining on the mask layer 4 in the second region 103 and the gap region 102, so that the gap region 102 is completely exposed to the surface of the silicon substrate 1.

[0067] (8) A mixed solution of a KOH or NaOH solution with a mass fraction of 1% to 3% and an isopropyl alcohol or a texturing additive with a volume fraction of 0.5% to 1% is used for texturing treatment, so that a velvet structure is formed on both the gap area 102 and the front surface of the silicon substrate 1. At the same time, a HF solution with a mass fraction of 1% to 2% is used to remove the mask layer 4 and the PSG or BSG layer 7 grown on the surface of the second doped polysilicon layer.

[0068] (9) A first dielectric passivation film layer 8 and a first anti-reflection passivation film layer 9 are sequentially grown on the backlight surface of the silicon substrate 1, and a second dielectric passivation film layer 10 and a second anti-reflection film layer 11 are sequentially grown on the light-absorbing surface.

[0069] Among them, the first dielectric passivation film layer 8 is aluminum oxide, the first anti-reflection passivation film layer 9 is silicon nitride, the second dielectric passivation film layer 10 is aluminum oxide or silicon oxide, the second anti-reflection film layer 11 is silicon nitride, and the second anti-reflection film layer 11 can be a composite film layer of a multilayer silicon nitride film.

[0070] (10) Metal electrodes are fabricated, forming a first metal electrode 12 in the first region 101 and a second metal electrode 13 in the second region 103, so that the first metal electrode 12 contacts the first doped polysilicon or amorphous silicon layer 3, and the second metal electrode 13 contacts the second doped polysilicon or amorphous silicon layer 6, thereby completing the fabrication of a back-contact battery.

[0071] In the process of manufacturing the back-contact battery of the present invention, the mask layer 4 adopts the DBR mask structure provided by the present invention. During the laser patterning process, it can effectively protect the film layer below, reflect most of the laser energy, and avoid reaching the surface of the film layer below the mask layer 4 and causing laser damage. At the same time, it can avoid the formation of a secondary distribution of the doping source of the film layer structure below the mask layer 4, avoid reducing the passivation characteristics of the surface, and thus ensure the efficiency of the manufactured battery.

[0072] The technical solution of the present invention is further described in detail below with reference to the embodiments.

[0073] It should be noted that the experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art, unless otherwise specified, and can be obtained from commercial channels by those skilled in the art.

[0074] Example 1

[0075] A method for manufacturing a back-contact battery comprises the following steps:

[0076] Step 1: Select an N-type CZ original silicon wafer as the silicon substrate 1, first immerse the original silicon wafer in a mixed solution of KOH or NaOH with a mass fraction of 2-5% and H2O2 with a mass fraction of 2-6% at a temperature of 65℃~85℃ to remove the damaged layer, and then use a KOH or NaOH solution with a mass fraction of 10%~30% to perform double-sided polishing to obtain Figure 2 The structure shown.

[0077] Step 2: On one polished surface (defined as the back surface), a first tunnel oxide layer 2 with a thickness of 1 to 3 nm and a phosphorus-doped n-type polysilicon layer or amorphous silicon layer with a thickness of 100 to 200 nm are sequentially deposited on one side in sequence by LPCVD, PECVD or PVD to obtain a first doped polysilicon or amorphous silicon layer 3. Figure 3The structure shown.

[0078] Step 3: A mask layer 4 is grown on the back surface of the first doped polysilicon or amorphous silicon layer 3 by PECVD; wherein the mask layer 4 is composed of two groups of DBR unit structures, each group of DBR unit structures is composed of a silicon oxide film layer and a silicon nitride film layer, and the mask layer 4 grown in this way is formed by alternating and repeated growth of silicon oxide film layers and silicon nitride film layers; the refractive index of the silicon oxide film layer is 1.5, and the growth thickness is 59.2nm; the refractive index of the silicon nitride film layer is 1.9, and the growth thickness is 46.7nm, and the obtained Figure 4 The structure shown.

[0079] Step 4: Use an ultraviolet picosecond laser to partially remove the first doped polysilicon or amorphous silicon layer 3 and the mask layer 4 thereon, wherein the laser spot size is selected to be a square spot of 100 to 120 μm, the total width of a unit structure (1 pitch structure) is set to 600 to 1200 μm, and the width of the first doped polysilicon or amorphous silicon layer 3 removed in 1 pitch unit is 500 to 1000 μm, and the Figure 5 The structure shown.

[0080] Step 5: Polishing is performed using a KOH or NaOH solution with a mass fraction of 10% to 30% to completely remove the first tunneling oxide layer 2 and the first doped polysilicon or amorphous silicon layer 3 remaining in the local laser processing area of ​​step 4, so that the local laser processing area exposes the surface of the silicon substrate, and obtains Figure 6 The structure shown.

[0081] Step 6: On the backlight side of the battery, a second tunneling oxide layer 5 and a second doped polysilicon or amorphous silicon layer 6 are grown in sequence by LPCVD or PECVD. The thickness of the second tunneling oxide layer 5 is 1 to 2 nm, and the second doped polysilicon or amorphous silicon layer 6 is a boron-doped polysilicon layer with a thickness of 150 to 300 nm. Then, the phosphorus source of the first doped polysilicon or amorphous silicon layer and the boron source of the second doped polysilicon or amorphous silicon layer are activated at a temperature of 850°C to 1000°C. During the activation process, 6000 to 10000 sccm of oxygen is introduced, and a BSG layer is grown on the surface of the second doped polysilicon layer 6. The obtained structure is as shown in FIG. Figure 7 As shown; at this time, three areas are formed on the backlight surface, namely the first area 101, the gap area 102 and the second area 103.

[0082] Step 7: Use ultraviolet laser to perform local patterning again to remove the BSG layer and the second doped polysilicon or amorphous silicon layer 6 grown on the mask layer 4 in the second region 103 and in the gap region 102, and then use a KOH or NaOH solution with a mass fraction of 10% to 30% to remove the second tunneling oxide layer 5 and the second doped polysilicon or amorphous silicon layer 6 remaining on the mask layer 4 and in the gap region 102. The obtained structure is as follows: Figure 8 shown.

[0083] Step 8: Use a mixed solution of KOH or NaOH solution with a mass fraction of 1% to 3% and isopropyl alcohol or a texturing additive with a volume fraction of 0.5% to 1% to perform texturing treatment, so that the gap area 102 and the front surface both form a velvet structure; at the same time, use a HF solution with a mass fraction of 1% to 2% to remove the mask layer 4 grown on the surface of the first doped polysilicon or amorphous silicon layer 3 and the BSG layer on the surface of the second doped polysilicon or amorphous silicon layer 6, and the treated structure is as shown below. Figure 9 shown.

[0084] Step 9: On the backlight side of the battery, the first dielectric passivation film layer 8 (aluminum oxide) and the first anti-reflection passivation film layer 9 (silicon nitride) are grown in sequence by atomic layer deposition and PECVD respectively. The thickness of the first dielectric passivation film layer 8 is 5 to 20 nm, and the thickness of the first anti-reflection passivation film layer 9 is 80 to 100 nm of SiNx:H film. The flow ratio of SiH4 to NH3 during the coating process is about 1:5, and the coating temperature is set to 490°C to 550°C. The light-absorbing side of the battery is also coated by atomic layer deposition. The second dielectric passivation film layer 10 (aluminum oxide or silicon oxide) and the second anti-reflection film layer 11 (silicon nitride) are grown in sequence by the layer deposition method and the PECVD method. The thickness of the second dielectric passivation film layer 10 is 3 to 15 nm. The second anti-reflection film layer 11 can be a composite film layer of a multilayer silicon nitride film. The second anti-reflection film layer 11 is a SiNx:H film layer with a thickness of 70 to 80 nm. The flow ratio of SiH4 to NH3 during the coating process is about 1:4, and the coating temperature is set to 450°C to 480°C. The obtained battery structure is as follows Figure 10 shown.

[0085] Step 10: Form the first metal electrode 12 and the second metal electrode 13 respectively by screen printing and superimposing sintering, so that the first metal electrode 12 contacts the first doped polysilicon or amorphous silicon layer 3, and the second metal electrode 13 contacts the second doped polysilicon or amorphous silicon layer 6, and finally complete the production of the entire back contact battery structure. The final battery structure is as follows: Figure 11 shown.

[0086] Example 2

[0087] The difference between this embodiment and embodiment 1 is that:

[0088] The mask layer 4 is composed of five groups of DBR unit structures, each of which is composed of a silicon oxide film layer and a silicon nitride film layer. The mask layer 4 grown in this way is formed by alternating and repeated growth of silicon oxide film layers and silicon nitride film layers; the silicon oxide film layer has a refractive index of 1.5 and a growth thickness of 59.2 nm; the silicon nitride film layer has a refractive index of 1.9 and a growth thickness of 46.7 nm.

[0089] Example 3

[0090] The difference between this embodiment and embodiment 1 is that:

[0091] The mask layer 4 is composed of 10 groups of DBR unit structures, each of which is composed of a silicon oxide film layer and a silicon nitride film layer. The mask layer 4 grown in this way is formed by alternating and repeated growth of silicon oxide film layers and silicon nitride film layers; the silicon oxide film layer has a refractive index of 1.5 and a growth thickness of 59.2nm; the silicon nitride film layer has a refractive index of 1.9 and a growth thickness of 46.7nm.

[0092] Example 4

[0093] The difference between this embodiment and embodiment 1 is that:

[0094] The mask layer 4 is composed of two groups of DBR unit structures, each group of DBR unit structures is composed of a silicon oxide film layer and a silicon nitride film layer. The mask layer 4 grown in this way is formed by alternating and repeated growth of silicon oxide film layers and silicon nitride film layers; the silicon oxide film layer has a refractive index of 1.5 and a growth thickness of 88.6nm; the silicon nitride film layer has a refractive index of 1.9 and a growth thickness of 70nm.

[0095] Correspondingly, a green laser is used.

[0096] Example 5

[0097] The difference between this embodiment and embodiment 1 is that:

[0098] The mask layer 4 is composed of five groups of DBR unit structures, each of which is composed of a silicon oxide film layer and a silicon nitride film layer. The mask layer 4 grown in this way is formed by alternating and repeated growth of silicon oxide film layers and silicon nitride film layers; the silicon oxide film layer has a refractive index of 1.5 and a growth thickness of 88.6 nm; the silicon nitride film layer has a refractive index of 1.9 and a growth thickness of 70 nm.

[0099] Correspondingly, a green laser is used.

[0100] Example 6

[0101] The difference between this embodiment and embodiment 1 is that:

[0102] The mask layer 4 is composed of 10 groups of DBR unit structures, each of which is composed of a silicon oxide film layer and a silicon nitride film layer. The mask layer 4 grown in this way is formed by alternating and repeated growth of silicon oxide film layers and silicon nitride film layers; the silicon oxide film layer has a refractive index of 1.5 and a growth thickness of 88.6nm; the silicon nitride film layer has a refractive index of 1.9 and a growth thickness of 70nm.

[0103] Correspondingly, a green laser is used.

[0104] Comparative Example 1

[0105] The difference between this comparative example and Example 1 is that the structure of the mask layer 4 is a single-layer silicon oxide film.

[0106] Comparative Example 2

[0107] The difference between this comparative example and Example 1 is that the structure of the mask layer 4 is a single-layer silicon nitride film layer.

[0108] In order to demonstrate the technical effect of the mask structure of the present invention, passivation tests were carried out on the battery samples made based on the mask structure of the present invention in Examples 1-6, and the battery samples made based on the conventional mask layer structure in Comparative Examples 1 and 2. The results are shown in Table 1.

[0109] Table 1. Passivation test results of batteries made in Examples 1-6 and Comparative Examples 1 and 2

[0110] Mask layer structure Laser type iVoc(mV) average <![CDATA[J0(fA / cm 2 )Mean]]> Example 1 2 sets of DBR unit structure UV laser 732 2.65 Example 2 5 groups of DBR unit structure UV laser 733 2.60 Example 3 10 groups of DBR unit structure UV laser 733 2.61 Example 4 2 sets of DBR unit structure Green laser 729 4.16 Example 5 5 groups of DBR unit structure Green laser 730 4.17 Example 6 10 groups of DBR unit structures Green laser 730.5 4.07 Comparative Example 1 Single-layer silicon oxide film UV laser 725 5.5 Comparative Example 2 Single-layer silicon nitride film violet laser 720 10.01

[0111] From the experimental results in Table 1, it can be seen that the iVoc (hidden open circuit voltage) value obtained by the battery sample produced by the method of the embodiment of the present invention is significantly higher than that of the comparative example, and a lower J0 (composite current density) value is obtained, which has a better passivation effect.

[0112] It can be seen that the conventional mask layer structure causes the laser energy to damage the structure of the film layer underneath the mask layer, thereby reducing the passivation of the film layer structure underneath, which will reduce the open circuit voltage of the battery at the battery end, thereby losing battery efficiency; while the mask layer structure of the present invention greatly reduces the damage to the crystalline silicon surface during the laser patterning process, reduces surface recombination, and effectively protects the film layer underneath. The film layer structure has better passivation performance, which is conducive to achieving higher battery conversion efficiency.

[0113] Finally, it should be noted that the above specific embodiments are only used to explain in detail the purpose, technical solutions and beneficial effects of the present invention. It should be understood that the above is only a specific implementation method of the present invention and is not used to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the above specific embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions described in the above embodiments, or to replace or improve some or all of the technical features therein. These modifications, equivalent replacements, and improvements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and description of the present invention.

Claims

1. A DBR mask structure for reducing laser damage, characterized in that: It comprises a plurality of overlapping DBR unit structures, each of which is composed of a silicon oxide film layer and a silicon nitride film layer, and in the DBR mask structure, the silicon oxide film layer and the silicon nitride film layer are arranged alternately; The refractive index of the silicon oxide film layer is 1.5±0.045, and the optical thickness is 59.2±1.8nm or 88.6±2.5nm; The refractive index of the silicon nitride film layer is 1.9±0.057, and the optical thickness is 46.7±1.35 nm or 70±2.0 nm.

2. A DBR mask structure for reducing laser damage according to claim 1, characterized in that: The DBR unit structure is arranged in 1 to 10 groups.

3. A method for manufacturing a back contact battery, characterized in that: The following steps are involved: A first tunneling oxide layer, a first doped polysilicon or amorphous silicon layer, and a mask layer are sequentially grown on the backlight surface of the silicon substrate, wherein the mask layer adopts the DBR mask structure as claimed in claim 1; A first laser patterning process is performed to remove the mask layer and the first doped polysilicon or amorphous silicon layer in a local area; The first alkali solution treatment completely exposes the surface of the silicon substrate in the local area; A second tunneling oxide layer and a second doped polysilicon or amorphous silicon layer are sequentially grown on the backlight surface of the silicon substrate, and activated to form a first region, a gap region, and a second region; A second laser patterning process is performed to remove the film layer grown on the mask layer in the second region and in the gap region; The second alkali solution treatment makes the gap area completely leak out of the surface of the silicon substrate; Texturing treatment is performed to form a velvet structure on both the gap area and the front surface of the silicon substrate, and the mask layer and the film layer on the surface of the second doped polysilicon layer are removed at the same time; A dielectric passivation film layer and an anti-reflection passivation film are grown on both the backlight surface and the front surface; A first metal electrode is formed in the first region, and a second metal electrode is formed in the second region, thereby completing the fabrication of a back contact battery.

4. The method for manufacturing a back contact battery according to claim 3, characterized in that: The alkali solution used in the alkali solution treatment is a KOH or NaOH solution with a mass fraction of 10% to 30%.

5. The method for manufacturing a back contact battery according to claim 3, characterized in that: During the first alkaline solution treatment, the remaining first tunneling oxide layer and the first doped polysilicon or amorphous silicon layer need to be completely removed.

6. The method for manufacturing a back contact battery according to claim 3, characterized in that: The second doped polysilicon or amorphous silicon layer has a doping type opposite to that of the first doped polysilicon or amorphous silicon layer.

7. The method for manufacturing a back contact battery according to claim 3, characterized in that: During the second alkaline solution treatment, the second tunneling oxide layer and the second doped polycrystalline layer remaining on the mask layer in the second region and in the gap region need to be completely removed.

8. The method for manufacturing a back contact battery according to claim 3, characterized in that: The film layer on the surface of the mask layer and the second doped polysilicon layer is removed by using an HF solution with a mass fraction of 1% to 2%.

9. The method for manufacturing a back contact battery according to claim 3, characterized in that: The dielectric passivation film layer and the anti-reflection passivation film are grown on both the backlight surface and the front surface, including: A first dielectric passivation film layer and a first anti-reflection passivation film layer are sequentially grown on the backlight surface, and a second dielectric passivation film layer and a second anti-reflection film layer are sequentially grown on the light-absorbing surface.

10. A back contact battery, characterized in that: The method is prepared by any one of claims 3 to 9.

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