Front structure of solar cell, solar cell and its manufacturing method, and photovoltaic module

Abstract

The present application provides a front structure of a solar cell, the solar cell and a preparation method thereof, and a photovoltaic module. The front structure of the solar cell includes a boron emitter layer; a passivation film layer; and front busbars. Direct physical contact is formed between the front busbars and the boron emitter layer in some regions, and indirect physical contact is formed through the passivation film layer in some regions. The total doping concentration of the boron emitter layer is 2.8×10<supgt;18< / supgt>atoms / cm<supgt;3< / supgt> to 4.0×10<supgt;18< / supgt>atoms / cm<supgt;3< / supgt>, which can improve the performance of the solar cell.

Description

Technical Field

[0001] This application relates to the field of solar cells, and in particular, to a front structure of a solar cell, a solar cell, a preparation method thereof, and a photovoltaic module. Background Art

[0002] In the front structure of current solar cells, the boron emitter layer introduces more defects due to the high-temperature boron source diffusion process. Especially in the boron emitter layer corresponding to the metallization region and the boron emitter layer corresponding to the light absorption region, it is necessary to take into account the Schottky contact resistivity in the metallization region and the spectral response and carrier recombination damage in the light absorption region, which have an impact on the photoelectric conversion efficiency of solar cells. This has become a technical problem that urgently needs to be solved in the industry to develop high-efficiency solar cell technology. Summary of the Invention

[0003] To solve the above technical problems, this application discloses a solar cell, a preparation method thereof, and a photovoltaic module to reduce the recombination loss in the contact region between the boron emitter layer and the front busbar in the front structure and improve the performance of the solar cell.

[0004] In a first aspect, this application provides a front structure of a solar cell, including:

[0005] A boron emitter layer;

[0006] A passivation film layer;

[0007] A front busbar, wherein the front busbar forms a direct physical contact with the boron emitter layer in some regions and an indirect physical contact with the boron emitter layer through the passivation film layer in some regions;

[0008] The total doping concentration of the boron emitter layer is 2.8×10 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 .

[0009] In some embodiments of this application, the total doping concentration of the boron emitter layer is 2.8×10 18 atoms / cm 3 ~3.2×10 18 atoms / cm 3 .

[0010] In some embodiments of this application, the junction depth of the boron emitter layer is 0.5 μm to 2.0 μm;

[0011] And / or,

[0012] The sheet resistance of the boron emitter layer is 300 Ω / sq to 1500 Ω / sq.

[0013] In some embodiments of the present application, the sheet resistance of the boron emitter layer is 500 Ω / sq to 1000 Ω / sq.

[0014] In some embodiments of the present application, the junction depth of the boron emitter layer is 0.5 μm to 0.8 μm.

[0015] In some embodiments of the present application, the junction depth of the boron emitter layer is 0.8 μm to 1.5 μm.

[0016] In some embodiments of the present application, the region of direct physical contact has a silver-silicon eutectic matrix and a silver-silicon eutectic overflow, and the region of direct physical contact further has a silver crystal that is electrically connected to the silver-silicon eutectic matrix and the silver-silicon eutectic overflow.

[0017] In some embodiments of the present application, the silver crystal includes a crystallization main chain and crystallization side chains extending from the crystallization main chain in a growth direction different from that of the crystallization main chain.

[0018] In some embodiments of the present application, the region of indirect physical contact has a conductive aggregate, and a passivation film layer is located between the conductive aggregate and the boron emitter layer; wherein, the conductive aggregate includes a glass phase material and metal conductive particles, and the metal conductive particles have the same type of metal element as the silver crystal.

[0019] In a second aspect, the present application provides a solar cell, including the front structure of the solar cell described in the second aspect.

[0020] In a third aspect, the present application provides a method for manufacturing a solar cell as described in the second aspect, including the following steps:

[0021] Provide a textured silicon wafer as a silicon substrate, place the silicon substrate in a boron diffusion furnace, and prepare a boron emitter layer on the front of the silicon substrate through a boron diffusion process;

[0022] Sequentially form a tunneling passivation layer and a phosphorus-doped polysilicon layer on the back of the silicon substrate;

[0023] Sequentially form a passivation film layer on the boron emitter layer, and form a back passivation layer on the phosphorus-doped polysilicon layer;

[0024] Print electrode paste on the passivation film layer and the back passivation layer;

[0025] High-temperature pre-sintering causes the electrode paste printed on the passivation film layer to form a front current collection grid line precursor, and causes the electrode paste printed on the back passivation layer to form a back electrode;

[0026] The front current collecting grid line precursor is subjected to laser-induced contact treatment to form a front current collecting grid line.

[0027] In some embodiments of the present application, a boron emitter layer is prepared on the front surface of the silicon substrate by a boron diffusion process, including:

[0028] Pre-oxidation process: The temperature of the boron diffusion furnace is T 1 , and the pressure in the furnace tube is P 1 . Oxygen and nitrogen are introduced into the boron diffusion furnace, wherein, 750 °C ≤ T 1 ≤ 850 °C, 230 mPa ≤ P 1 ≤ 270 mPa, the oxygen flow rate is 800 sccm to 2000 sccm, and the nitrogen flow rate is 200 sccm to 1000 sccm;

[0029] Multi-stage deposition process: The temperature of the boron diffusion furnace is T 2 , and the pressure in the furnace tube is P 2 . Oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace in stages, and the temperature in the furnace is increased stage by stage for each stage, wherein, 750 °C ≤ T 2 ≤ 850 °C, the oxygen flow rate is 200 sccm to 600 sccm, 230 mPa ≤ P 2 ≤ 270 mPa, the nitrogen flow rate is 3000 sccm to 5000 sccm, and the boron source gas flow rate is 80 sccm to 150 sccm;

[0030] Multi-stage PN junction advancement process: The temperature of the boron diffusion furnace is T 3 , and the pressure in the furnace tube is P 3 . Nitrogen is introduced into the boron diffusion furnace, wherein, 850 °C ≤ T 3 ≤ 950 °C, 580 mPa ≤ P 3 ≤ 620 mPa, and the nitrogen flow rate is 3000 sccm to 5000 sccm;

[0031] Post-oxidation process: The temperature of the boron diffusion furnace is T 4 , and the pressure in the furnace tube is P 4 . Oxygen is introduced into the boron diffusion furnace to form a silicon oxide mask layer with a thickness of 50 nm to 120 nm, wherein, 950 °C ≤ T 4 ≤ 1050 °C, 780 mPa ≤ P 4 ≤ 820 mPa, and the oxygen flow rate is 10000 sccm to 30000 sccm.

[0032] In some embodiments of the present application, P 4 > P 3 ;

[0033] and / or, P 4 > P2 ;

[0034] and / or, P 4 > P 1 ;

[0035] and / or, P 3 > P 2 ;

[0036] and / or, P 3 > P 1 .

[0037] In some embodiments of the present application, T 2 > T 1 ;

[0038] and / or, T 3 > T 2 ;

[0039] and / or, T 4 > T 3 .

[0040] In some embodiments of the present application, in the multi-stage deposition process, the number of deposition stages is 2 to 5.

[0041] In some embodiments of the present application, the multi-stage deposition process includes:

[0042] The first deposition stage: the temperature of the boron diffusion furnace is T 21 , the pressure of the furnace tube is P 21 , oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace, wherein, 750°C ≤ T 21 ≤ 850°C, 230 mPa ≤ P 21 ≤ 270 mPa, the oxygen flow rate is 200 sccm to 600 sccm, the nitrogen flow rate is 3000 sccm to 5000 sccm, and the boron source gas flow rate is 80 sccm to 150 sccm;

[0043] The second deposition stage: the temperature of the boron diffusion furnace is T 22 , the pressure of the furnace tube is P 22 , oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace, wherein, 750°C ≤ T 22 ≤ 850°C, and T 22 > T 21 , 230 mPa ≤ P 22 ≤ 270 mPa, the oxygen flow rate is 200 sccm to 600 sccm, the nitrogen flow rate is 3000 sccm to 5000 sccm, and the boron source gas flow rate is 80 sccm to 150 sccm;

[0044] The third deposition stage: the temperature of the boron diffusion furnace is T23 The pressure of the furnace tube is P 23 , oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace, where 750°C ≤ T 23 ≤ 850°C, and T 23 > T 22 , 230 mPa ≤ P 23 ≤ 270 mPa, the oxygen flow rate is 200 sccm to 600 sccm, the nitrogen flow rate is 3000 sccm to 5000 sccm, and the boron source gas flow rate is 80 sccm to 150 sccm.

[0045] In some embodiments of the present application, the process of performing laser-induced contact treatment on the front current collecting grid line precursor includes:

[0046] Performing laser-induced contact treatment on the front current collecting grid line precursor on the front side of the silicon substrate.

[0047] Fourthly, the present application provides a photovoltaic module, which includes the solar cell as described in the second aspect, or the photovoltaic module includes the solar cell prepared by the preparation method as described in the third aspect.

[0048] Compared with the prior art, the present application has at least the following beneficial effects:

[0049] The present application provides a front structure of a solar cell, a solar cell and its preparation method, and a photovoltaic module. Among them, by controlling the total doping concentration of the boron emitter layer to be 2.8×10 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 , it is beneficial to reduce the recombination loss of the boron emitter layer in the front structure, and it will not cause the decline of the thin film carrier transport ability of the boron emitter layer due to the too low total doping concentration of the boron emitter layer, thereby improving the photoelectric conversion performance of the solar cell; in addition, by using the laser-induced sintering technology to form a metal-semiconductor contact structure with a low resistivity in the metallization area, thereby reducing the resistance loss at the metal-semiconductor contact structure, and to a certain extent reducing the corrosion area of the glass phase in the silver paste in the metallization area on the surface passivation film layer, improving the open circuit voltage of the solar cell, and further improving the photoelectric conversion efficiency of the solar cell. Description of the Drawings

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1 Schematic diagram of the front structure of a solar cell according to an embodiment of the present application;

[0052] Figure 2 Schematic diagram of the contact area between the front current collecting grid line and the boron emitter layer according to an embodiment of the present application;

[0053] Figure 3 Schematic diagram of the electrochemical capacitance - voltage (ECV) curve according to an embodiment of the present application;

[0054] Figure 4 Schematic diagram of the morphology of the silver crystal according to an embodiment of the present application;

[0055] Figure 5 Schematic diagram of the structure of a solar cell according to an embodiment of the present application.

[0056] Explanation of reference numerals: silicon substrate - 1, boron emitter layer - 2, passivation film layer - 3, front current collecting grid line - 4, tunneling passivation layer - 5, phosphorus - doped polysilicon layer - 6, back passivation layer - 7, back electrode - 8, first gold - semiconductor contact region - 41, second gold - semiconductor contact region - 42, silver - silicon eutectic matrix - 411, silver - silicon eutectic overflow - 412, silver crystal - 413, conductive aggregate - 421, crystallization main chain - 4131, crystallization side chain - 4132. Detailed implementation manners

[0057] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0058] In the present application, the orientation or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. are based on the orientation or positional relationships shown in the accompanying drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation.

[0059] Moreover, in addition to being able to represent orientation or positional relationships, some of the above - mentioned terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to specific situations.

[0060] In addition, the terms "installed", "set up", "provided with", "connected", and "linked" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0061] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, components, or parts (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, components, or parts. Unless otherwise specified, the meaning of "a plurality" is two or more.

[0062] The technical solution of this application will be further described below in conjunction with embodiments and drawings.

[0063] In a first aspect, this application provides a front structure of a solar cell. As Figure 1 shown, the front structure of the solar cell includes a boron emitter layer 2, a passivation film layer 3, and a front busbar 4. Among them, the boron emitter layer 2 is located on the front of the silicon substrate 1, and the passivation film layer 3 is located on the front of the boron emitter layer 2. There is a Schottky contact region between the front busbar 4 and the boron emitter layer 2. As Figure 2 shown, a direct physical contact is formed between the front busbar 4 and the boron emitter layer 2 in some regions, and this direct physical contact region includes Figure 2 the Schottky contact first region 41 shown; an indirect physical contact is formed between the front busbar 4 and the boron emitter layer 2 in some regions through the passivation film layer 3, and this indirect physical contact region includes Figure 2 the Schottky contact second region 42 shown. The Schottky contact first region 41 and the Schottky contact second region 42 constitute the above-mentioned Schottky contact region.

[0064] The total doping concentration of the boron emitter layer 2 is 2.8×10 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 . For example, the total doping concentration of the boron emitter layer is 2.8×10 18 atoms / cm 3 , 3.0×10 18 atoms / cm 3 , 3.2×10 18 atoms / cm 3 、3.5×10 18atoms / cm 3 and 4.0×10 18 atoms / cm 3 or any value between the above two numerical ranges.

[0065] In this application, the total doping concentration C total of the boron emitter layer refers to: the integral area of the ECV curve of the boron emitter layer. Exemplarily, referring to Figure 3 , for the first target test point to the xth target test point, the integral area is the area enclosed by the ECV curve, the abscissa value (L 1 ) of the first target test point, the abscissa value (L x ) of the xth target test point, and the horizontal axis. Among them, the target test point refers to the specific boron atom doping concentration corresponding to a specific junction depth when obtaining the single-point value of the ECV curve; since the resistivity of the currently used N-type silicon substrate is 0.6 Ω·cm to 16 Ω·cm, in order to reasonably limit the upper limit of the ECV curve test points, the upper limit doping concentration of the ECV curve test points is defined as greater than 1.0×10 17 atoms / cm 3 , that is, the test points with a doping concentration less than 1.0×10 17 atoms / cm 3 do not belong to the selection range of the ECV curve test points.

[0066] The total doping concentration C total of the boron emitter layer can be calculated by the following expression:

[0067] C total = D 1 *L 1 + D 2 *(L 2 - L 1 ) + D 3 *(L 3 - L 2 ) + …… + D x *(L x - L x-1 ) (1)

[0068] In formula (1), D 1 represents the doping concentration corresponding to the first target test point, L 1 represents the junction depth corresponding to the first target test point, D x represents the doping concentration corresponding to the xth target test point, and L x represents the junction depth corresponding to the xth target test point.

[0069] It should be noted that the total doping concentration C totalIn this application, it is used to characterize the overall doping level of the boron emitter layer. When sunlight shines on the front of the solar cell, the short-wave photons with higher energy will be preferentially absorbed on the front of the solar cell, and the boron emitter layer corresponds to the short-wave spectral response band in the solar spectrum. In order to fully absorb the photons in the short-wave spectral band, using a boron emitter layer with a lower doping concentration is beneficial to improving the short-wave spectral response of the boron emitter layer, and the lower the doping concentration, the more beneficial it is to improving the short-wave spectral response of the boron emitter layer. However, the doping concentration in the boron emitter layer also needs to have the carrier transport ability to transport photo-generated carriers from the generation site to the front current collection grid line, that is, the sheet resistance of the boron emitter layer in the light-receiving area affects the current loss of photo-generated carriers before they are transported to the front current collection grid line. In order to achieve the best balance between the short-wave spectral response and the sheet resistance transmission loss of the boron emitter layer, the total doping concentration C of the boron emitter layer total needs to be controlled within a reasonable range.

[0070] The front structure of the solar cell provided by this application. In this front structure, by controlling the total doping concentration of the boron emitter layer to be 2.8×10 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 , keeping the total doping concentration of the boron emitter layer within a suitable range is beneficial to reducing the recombination loss in the contact area between the boron emitter layer and the front current collection grid line in the front structure, and will not cause the decline of the sheet carrier transport ability of the boron emitter layer due to the too low total doping concentration of the boron emitter layer, thereby improving the performance of the solar cell; in addition, by using the laser-induced sintering technology to form a Schottky contact structure with a lower resistivity in the metallization area, thereby reducing the resistance loss at the Schottky contact structure, and to a certain extent reducing the corrosion area of the glass phase in the silver paste in the metallization area on the surface passivation film layer, improving the open-circuit voltage of the solar cell, and further improving the photoelectric conversion efficiency of the solar cell.

[0071] In some embodiments of this application, the total doping concentration of the boron emitter layer is 2.8×10 18 atoms / cm 3 ~3.2×10 18 atoms / cm 3 . For example, the total doping concentration of the boron emitter layer is 2.8×10 18 atoms / cm 3 、2.9×10 18 atoms / cm 3 、3.0×10 18 atoms / cm 3 、3.1×10 18 atoms / cm3 、 3.2×10 18 atoms / cm 3 or any value between the above two numerical ranges. By adjusting the total doping concentration of the boron emitter layer within the above range, an optimal balance can be achieved between the short-wavelength spectral response and the sheet resistance transmission loss of the boron emitter layer. Especially after laser-induced sintering treatment of the front metallization area or adding a denser current collector grid line design on the front, on the basis of sacrificing part of the carrier transport loss, a boron emitter layer with a more moderate doping concentration range can be used to further improve the short-wavelength spectral response of the boron emitter layer.

[0072] In some embodiments of the present application, the junction depth of the boron emitter layer is 0.5 μm to 2.0 μm; and / or, the sheet resistance of the boron emitter layer is 300 Ω / sq to 1500 Ω / sq. For example, the junction depth of the boron emitter layer is 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.5 μm or 2.0 μm; the sheet resistance of the boron emitter layer is 300 Ω / sq, 500 Ω / sq, 800 Ω / sq, 1000 Ω / sq, 1200 Ω / sq or 1500 Ω / sq. By adjusting the junction depth and / or sheet resistance of the boron emitter layer within the above range, the sheet resistance loss of the photo-generated carriers transported to the front current collector grid line can be reduced.

[0073] In some embodiments of the present application, the sheet resistance of the boron emitter layer is 500 Ω / sq to 1000 Ω / sq. For example, the sheet resistance of the boron emitter layer is 500 Ω / sq, 600 Ω / sq, 700 Ω / sq, 800 Ω / sq, 900 Ω / sq or 1000 Ω / sq. By adjusting the sheet resistance of the boron emitter layer within the above range, while reducing the sheet resistance loss of the photo-generated carriers transported to the front current collector grid line, the short-wavelength spectral response of the boron emitter layer can be taken into account, and a relatively better balance can be achieved between the two.

[0074] In some embodiments of the present application, the junction depth of the boron emitter layer is 0.5 μm to 0.8 μm. For example, the junction depth of the boron emitter layer is 0.5 μm, 0.6 μm, 0.7 μm or 0.8 μm. By adjusting the junction depth of the boron emitter layer within the above range, while reducing the sheet resistance loss of the photo-generated carriers transported to the front current collector grid line, the short-wavelength spectral response of the boron emitter layer can be taken into account, and a relatively better balance can be achieved between the two.

[0075] In some embodiments of the present application, the junction depth of the boron emitter layer is 0.8 μm to 1.5 μm. For example, the junction depth of the boron emitter layer is 0.8 μm, 1.0 μm, 1.3 μm, or 1.5 μm. By controlling the junction depth of the boron emitter layer within the above range, the sheet resistance loss of photo-generated carriers transported to the front current collection grid lines can be minimized.

[0076] In some embodiments of the present application, referring to Figure 4 , in the directly physically contacted region, that is, the first Au-Semiconductor contact region 41 has a Ag-Si eutectic matrix 411 and a Ag-Si eutectic overflow 412. The directly physically contacted region also has a Ag crystal 413 electrically connected to the Ag-Si eutectic matrix 411 and the Ag-Si eutectic overflow 412. The front structure of the solar cell of the present application includes the Ag crystal 413 with higher conductivity, as well as the Ag-Si eutectic matrix 411 and the Ag-Si eutectic overflow 412 for improving the conductivity of the boron emitter layer, thereby significantly increasing the conductivity of the Au-Semiconductor contact conductive structure for photo-generated carriers to output. Thus, the contact performance between the front current collection grid lines and the boron emitter layer is effectively improved by optimizing the conductive structure. It can be seen that by making the above improvements and optimizations to the front structure of the solar cell, the contact performance between the boron emitter layer and the front current collection grid lines can be improved, the contact resistance can be reduced, the transport ability of carriers can be increased, and thus the open-circuit voltage and the photoelectric conversion efficiency of the solar cell can be effectively improved.

[0077] In some embodiments of the present application, referring to Figure 4 , the Ag crystal 413 includes a crystal main chain 4131 and crystal side chains 4132 extending from the crystal main chain 4131 in a growth direction different from that of the crystal main chain 4131, such that the Ag crystal 413 as a whole has a dendritic structure. This Ag crystal formed after the crystallization of silver element has the characteristics of higher purity and higher conductivity, thereby reducing the series resistance of the solar cell and improving the photoelectric conversion efficiency.

[0078] In some embodiments of the present application, referring to Figure 2 , in the indirectly physically contacted region, that is, the second Au-Semiconductor contact region 42 has a conductive aggregate 421, and there is also a passivation film layer 3 with a relatively high dielectric constant between the conductive aggregate 421 and the boron emitter layer 2. Among them, the conductive aggregate includes a glass phase material and metal conductive particles, and the metal conductive particles have the same type of metal element as the Ag crystal, such as silver element.

[0079] In a second aspect, the present application provides a solar cell, which includes the front structure of the solar cell described in any of the above embodiments.

[0080] In some embodiments of the present application, the solar cell is a TOPCon cell, such as Figure 5As shown in the figure, the solar cell includes: a silicon substrate 1; on the front side of the silicon substrate 1, a boron emitter layer 2, a passivation film layer 3, and a front current collecting grid line 4 are sequentially provided in a direction away from the front side; on the back side of the silicon substrate 1, a tunneling passivation layer 5, a phosphorus-doped polysilicon layer 6, a back passivation layer 7, and a back electrode 8 are sequentially provided in a direction away from the back side.

[0081] Among them, the material of the tunneling passivation layer may include a variety of dielectric materials, such as at least one of silicon oxide, amorphous silicon, polysilicon, and silicon carbide. Specifically, the tunneling passivation layer may be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation performance, can minimize the recombination loss of carriers on the surface of the semiconductor substrate, and is a film with excellent durability for subsequent high-temperature processes. The tunneling passivation layer may also have a pinhole channel structure, enabling the free movement of carriers in the solar cell, and generating selective passage of majority carriers through heavily doped polysilicon, which is beneficial to reducing the recombination loss of minority carriers. Among them, the phosphorus-doped polysilicon layer is a phosphorus-doped polysilicon layer, and the back passivation layer is a passivation layer, and its material may be selected from any one material or any combination of materials among silicon oxide, aluminum oxide, silicon carbide, silicon nitride, or silicon oxynitride layers.

[0082] The above is an introduction to the structural film layers on the front side of the solar cell. It can be understood that according to the structural characteristics of different types of solar cells, film layers with other structural characteristics may also be provided on the front and back sides of the solar cell, such as an antireflection layer. In addition, the method of forming the structural film layer can also adopt the conventional practices of the existing technology. For example, a silicon substrate with a textured surface structure is obtained through texturing, and the passivation film layer and antireflection layer are obtained through atomic layer deposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD) processes, etc. In addition, this application can also adopt conventional practices such as polishing and cleaning according to the situation of forming a wrap-around plating layer, a borosilicate glass layer, or a phosphosilicate glass layer during the formation of each structural film layer. This application does not limit this.

[0083] In the third aspect, this application provides a method for manufacturing a solar cell, including the following steps:

[0084] Step A: Provide a textured silicon wafer as the silicon substrate, place the silicon substrate in a boron diffusion furnace, and prepare a boron emitter layer on the front side of the silicon substrate through a boron diffusion process;

[0085] Step B: Sequentially form a tunneling passivation layer and a phosphorus-doped polysilicon layer on the back side of the silicon substrate;

[0086] Step C: Sequentially form a passivation film layer on the boron emitter layer and form a back passivation layer on the phosphorus-doped polysilicon layer;

[0087] Step D: Print electrode paste on the passivation film layer and the back passivation layer;

[0088] Step E: High-temperature pre-sintering causes the electrode paste printed on the passivation film layer to form a front current collection grid line precursor, and the electrode paste printed on the back passivation layer forms a back electrode.

[0089] Step F: Laser-induced contact treatment is performed on the front current collection grid line precursor to form the front current collection grid line.

[0090] In step A, the front surface of the silicon substrate can be pre-textured to form a pyramidal texture structure, which is beneficial to reducing the reflectivity of the silicon substrate surface and increasing the refraction and scattering of light inside the silicon substrate. The boron diffusion process of the present application can be based on a dry oxygen process or, alternatively, on a wet oxygen process. When the wet oxygen process is used, the growth rate of the silicon oxide mask layer by wet oxygen is relatively fast, and the temperature for forming the silicon oxide mask layer (i.e., the post-oxidation process) can be controlled at about 1000 °C, which is lower than the post-oxidation process temperature of the dry oxygen process. The lower temperature can significantly extend the service life of the quartz tube in the diffusion furnace. Moreover, the pre-oxidation process, the multi-stage deposition process, the multi-stage PN junction pushing process, and the post-oxidation process can be completed in one diffusion furnace, reducing the number of equipment used and lowering the production cost. And although the growth rate of the silicon oxide mask by the wet oxygen process is relatively fast, when applied to TOPCon cells, since the silicon oxide mask formed during the boron diffusion stage of TOPCon cells is only used as a mask, the requirement for its denseness is not high. Based on this, the wet oxygen process of the present application is more suitable for the boron diffusion process of TOPCon cells.

[0091] In addition, in step A, a silicon oxide mask layer is also formed on the surface of the boron emitter layer. The silicon substrate can be an N-type silicon substrate, and the thickness range of the silicon substrate is 100 μm to 200 μm, which is not particularly limited in the present application.

[0092] In step B, the tunneling passivation layer and the phosphorus-doped polysilicon layer can be prepared by a tube-type PECVD device, which is not particularly limited in the present application.

[0093] In step C, an alumina layer can be deposited on the boron emitter layer as the front passivation film layer using an ALD device; a silicon oxynitride layer can be deposited on the phosphorus-doped polysilicon layer as the back passivation layer using a PECVD device;

[0094] In step D, electrode paste can be printed on the passivation film layer on the front and the back passivation layer on the back by screen printing to form electrode grid lines. The electrode grid lines of the present application can include main grid lines and sub-grid lines. The electrode paste of the present application includes, but is not limited to, pure silver electrode paste and silver-aluminum electrode paste.

[0095] In step E, the high-temperature pre-sintering temperature can be 650°C to 780°C. There is no special limitation in this application as long as the front current collector grid line precursor and the back electrode can be formed.

[0096] In step F, by performing laser-induced contact treatment on the front current collector grid line precursor, it is beneficial to form a silver-silicon eutectic matrix and silver crystal grains electrically connected to the silver-silicon eutectic matrix in the region of direct physical contact between the front current collector grid line and the boron emitter layer, thereby significantly improving the conductivity of the hole or electron output conductive structure of the solar cell. Thus, the contact performance between the front current collector grid line and the boron emitter layer is effectively improved by optimizing the conductive structure.

[0097] A method for manufacturing a solar cell provided in this application includes preparing the boron emitter layer of this application on the front side of a silicon substrate based on a boron diffusion process, and performing laser-induced contact treatment on the front current collector grid line precursor to form the front current collector grid line, thereby forming the boron emitter layer of this application. It is beneficial to form a silver-silicon eutectic matrix and silver crystal grains electrically connected to the silver-silicon eutectic matrix in the region of direct physical contact between the front current collector grid line and the boron emitter layer, improving the contact performance between the front current collector grid line and the boron emitter layer, and thus improving the performance of the solar cell.

[0098] In some embodiments of this application, preparing a boron emitter layer on the front side of a silicon substrate through a boron diffusion process includes:

[0099] Pre-oxidation process: The temperature of the boron diffusion furnace is T 1 , and the pressure of the furnace tube is P 1 . Oxygen and nitrogen are introduced into the boron diffusion furnace. Among them, 750°C ≤ T 1 ≤ 850°C, 230 mPa ≤ P 1 ≤ 270 mPa, the oxygen flow rate is 800 sccm to 2000 sccm, and the nitrogen flow rate is 200 sccm to 1000 sccm;

[0100] Multi-stage deposition process: The temperature of the boron diffusion furnace is T 2 , and the pressure of the furnace tube is P 2 . Oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace in stages, and the temperature inside the furnace is increased gradually in each stage. Among them, 750°C ≤ T 2 ≤ 850°C, the oxygen flow rate is 200 sccm to 600 sccm, 230 mPa ≤ P 2 ≤ 270 mPa, the nitrogen flow rate is 3000 sccm to 5000 sccm, and the boron source gas flow rate is 80 sccm to 150 sccm;

[0101] Multi-stage PN junction advancement process: The temperature of the boron diffusion furnace is T 3 , and the pressure of the furnace tube is P3 , introduce nitrogen gas into the boron diffusion furnace, where 850°C ≤ T 3 ≤ 950°C, 580 mPa ≤ P 3 ≤ 620 mPa, and the nitrogen gas flow rate is 3000 sccm to 5000 sccm;

[0102] Post-oxidation process: The temperature of the boron diffusion furnace is T 4 , and the furnace tube pressure is P 4 , introduce oxygen gas into the boron diffusion furnace to form a silicon oxide mask layer with a thickness of 50 nm to 120 nm, where 950°C ≤ T 4 ≤ 1050°C, 780 mPa ≤ P 4 ≤ 820 mPa, and the oxygen gas flow rate is 10000 sccm to 30000 sccm.

[0103] During the pre-oxidation process, T 1 can be 750°C, 770°C, 800°C, 820°C or 850°C, P 1 can be 230 mPa, 240 mPa, 250 mPa, 260 mPa or 270 mPa, the oxygen gas flow rate can be 800 sccm, 1000 sccm, 1300 sccm, 1500 sccm or 2000 sccm, and the nitrogen gas flow rate can be 200 sccm, 400 sccm, 600 sccm, 700 sccm or 1000 sccm; The pre-oxidation process takes 220 s to 260 s. By regulating the temperature T of the boron diffusion furnace 1 , the furnace tube pressure P 1 , the oxygen gas flow rate, the nitrogen gas flow rate and the time of the pre-oxidation process within the above ranges, a thin oxide layer (with a thickness of about 1 nm to 3 nm) is grown on the surface of the silicon substrate as a barrier layer, which can slow down the diffusion rate of boron atoms in the next step and at the same time make the diffusion of boron atoms more uniform.

[0104] The inventors have found through research that introducing a large amount of boron source at one time will cause waste because the boron source cannot be used up completely, and will also cause the temperature at the gas inlet end of the diffusion furnace to be too low, resulting in too large a temperature difference in the boron diffusion furnace and affecting the deposition effect. Based on this, the present application adopts a multi-stage deposition process, that is, divides the deposition process into multiple stages, adjusts the temperature of the boron diffusion furnace, the furnace tube pressure, and the flow rates of oxygen, nitrogen and boron source gas in each deposition stage, and makes the furnace temperature increase gradually in each stage, which can improve the utilization rate of the boron source and prevent too large a temperature difference in the boron diffusion furnace, which is beneficial to obtaining the boron emitter layer of the present application.

[0105] In some embodiments of the present application, P 4 > P 3 ; and / or, P 4 > P 2; and / or, P 4 > P 1 ; and / or, P 3 > P 2 ; and / or, P 3 > P 1 This application controls the furnace tube pressure P 1 , P 2 , P 3 , P 4 in the above-mentioned pre-oxidation process, multi-stage deposition process, multi-stage PN junction advancement process, and post-oxidation process to satisfy the above relationships. On the one hand, as the furnace tube pressure increases, the internal and external pressure difference of the furnace tube made of quartz gradually decreases, thereby reducing the pressure of the furnace tube and the risk of hidden cracks in the furnace tube; on the other hand, for the wet oxygen process, the furnace tube pressure is higher in the post-oxidation process, which can increase the concentration of wet oxygen, thereby increasing the oxidation rate and reducing the oxidation time.

[0106] In the multi-stage PN junction advancement process, T 3 can be 850 °C, 870 °C, 900 °C, 920 °C or 950 °C, P 3 can be 580 mPa, 590 mPa, 600 mPa, 610 mPa or 620 mPa, and the nitrogen flow rate can be 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm or 5000 sccm. Oxygen and boron source gases are not introduced in this process.

[0107] The multi-stage PN junction advancement process of this application can include at least two advancement stages. Among them, the time of the first advancement stage is 350 s to 400 s, and the time of the second advancement stage is 300 s to 340 s.

[0108] In the post-oxidation process, T 4 can be 950 °C, 980 °C, 1000 °C, 1040 °C or 1050 °C, P 4 can be 780 mPa, 790 mPa, 800 mPa, 810 mPa or 820 mPa, and the oxygen flow rate can be 10000 sccm, 15000 sccm, 20000 sccm, 25000 sccm or 30000 sccm; the time used in the post-oxidation process is 4000 s to 8000 s.

[0109] In some embodiments of this application, T 2 > T 1 ; and / or, T 3 > T 2 ; and / or, T 4 > T 3. In this application, by regulating the temperatures T of the above-mentioned pre-oxidation process, multi-stage deposition process, multi-stage PN junction advancement process, and post-oxidation process in the boron diffusion furnace 1 、T 2 、T 3 、T 4 to satisfy the above relationships is conducive to achieving more uniform effective doping of boron atoms on the front side of the silicon substrate and activating boron atoms to reduce the formation probability of the boron-doped dead layer.

[0110] In some embodiments of this application, in the multi-stage deposition process of this application, the number of deposition stages is 2 to 5. For example, the deposition stage may include 2 stages, 3 stages, 4 stages, or 5 stages.

[0111] In some embodiments of this application, the multi-stage deposition process includes:

[0112] The first deposition stage: The temperature of the boron diffusion furnace is T 21 , the furnace tube pressure is P 21 , oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace. Among them, 750°C ≤ T 21 ≤ 850°C, 230 mPa ≤ P 21 ≤ 270 mPa, the oxygen flow rate is 200 sccm to 600 sccm, the nitrogen flow rate is 3000 sccm to 5000 sccm, and the boron source gas flow rate is 80 sccm to 150 sccm; the time used for the first deposition stage is 100 s to 140 s;

[0113] The second deposition stage: The temperature of the boron diffusion furnace is T 22 , the furnace tube pressure is P 22 , oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace. Among them, 750°C ≤ T 22 ≤ 850°C, and T 22 > T 21 , 230 mPa ≤ P 22 ≤ 270 mPa, the oxygen flow rate is 200 sccm to 600 sccm, the nitrogen flow rate is 3000 sccm to 5000 sccm, and the boron source gas flow rate is 80 sccm to 150 sccm; the time used for the second deposition stage is 200 s to 250 s;

[0114] The third deposition stage: The temperature of the boron diffusion furnace is T 23 , the furnace tube pressure is P 23 , oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace. Among them, 750°C ≤ T 23 ≤ 850°C, and T 23 > T 22 , 230 mPa ≤ P 23≤270mPa, oxygen flow rate is 200sccm~600sccm, nitrogen flow rate is 3000sccm~5000sccm, boron source gas flow rate is 80sccm~150sccm; the third deposition stage takes 200s~250s.

[0115] In some embodiments of the present application, the process of performing laser induced contact treatment on the front current collecting grid line precursor includes:

[0116] Laser induced contact treatment is performed on the front side of the silicon substrate for the front current collector gate line precursor (a reverse bias voltage of 10V to 25V is applied during this process). On the one hand, the reverse bias voltage is used to further enhance the built-in electric field of the solar cell at the contact interface between the boron emitter layer and the front current collector gate line precursor. On the other hand, a large number of photogenerated carriers are generated through the laser induced contact treatment. Through the combined effect of these two aspects, electron carriers and hole carriers are sorted by the electric field, and one type of carrier with an electric charge is rapidly transported to the boron emitter layer under the acceleration of the electric field. These carriers will generate a large amount of heat when passing through the glass phase material with a large resistivity, which is conducive to the formation of a silver-silicon eutectic matrix and a silver-silicon eutectic overflow in the area of ​​direct physical contact between the front current collector gate line and the boron emitter layer, as well as silver crystals conductively connected to the silver-silicon eutectic matrix and the silver-silicon eutectic overflow.

[0117] In some embodiments of the present application, after forming the passivation film layer, a silicon oxynitride layer may be deposited on the passivation film layer using a PECVD device as a front anti-reflection layer.

[0118] In a third aspect, the present application provides a photovoltaic module, wherein the photovoltaic module comprises a solar cell prepared by the preparation method as described in the first aspect, or the photovoltaic module comprises the solar cell as described in the second aspect.

[0119] The present application also provides a photovoltaic module, which is used to convert received light energy into electrical energy and transmit it to an external load. The photovoltaic module includes: at least one battery string, which is formed by connecting a plurality of the above-mentioned solar cells; a packaging film, which is used to cover the surface of the battery string; and a cover plate, which is used to cover the surface of the packaging film away from the battery string.

[0120] The present application will be further described below in conjunction with more specific embodiments. In addition, the electrode paste and the like used in the following embodiments can be obtained through commercial purchase. For example, the front current collector grid line paste uses a commercially available silver electrode paste of the Guangda T129 model, and the Al content in the electrode paste accounts for 0.05 wt% to 0.10 wt%, and the oxygen content accounts for 1.0 wt% to 5.0 wt%. Among them, the elemental content ratio in the silver electrode paste can be tested by an energy dispersive spectrometer (EDS).

[0121] Example 1

[0122] This embodiment provides a solar cell with a front structure, and its post-oxidation process is based on a wet oxygen process. The preparation method is as follows:

[0123] <Pre-oxidation process>

[0124] Provide a textured silicon wafer as the silicon substrate (thickness 125 μm), and place the silicon substrate in a boron diffusion furnace. The temperature T of the boron diffusion furnace 1 is 820 °C, and the furnace tube pressure P 1 is 250 mPa. The oxygen flow rate is 1000 sccm, and the nitrogen flow rate is 500 sccm. An oxide layer with a thickness of 1 nm to 3 nm is formed on the surface of the silicon substrate;

[0125] <Multi-stage deposition process>

[0126] <First deposition stage>

[0127] The temperature T of the boron diffusion furnace 21 is 825 °C, and the furnace tube pressure P 21 is 250 mPa. Oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace. The oxygen flow rate is 300 sccm, the nitrogen flow rate is 4000 sccm, the boron source gas flow rate is 100 sccm, and the time is 120 s, and then purging is carried out;

[0128] <Second deposition stage>

[0129] The temperature T of the boron diffusion furnace 22 is 835 °C, and the furnace tube pressure P 22 is 250 mPa. Oxygen, nitrogen, and boron source gas are introduced into the boron diffusion furnace. The oxygen flow rate is 300 sccm, the nitrogen flow rate is 4000 sccm, the boron source gas flow rate is 100 sccm, and the time is 210 s, and then purging is carried out;

[0130] <Third deposition stage>

[0131] The temperature T of the boron diffusion furnace 23 is 845 °C, and the furnace tube pressure P 23The temperature of the boron diffusion furnace is 885°C, the pressure in the furnace tube is 250 mPa. Oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace. The flow rate of oxygen is 300 sccm, the flow rate of nitrogen is 4000 sccm, the flow rate of boron source gas is 100 sccm, and the time is 210 s. Then purging is carried out;

[0132] <Multi-stage PN junction propulsion>

[0133] <The first propulsion stage>

[0134] The temperature T of the boron diffusion furnace 31 is 885°C, the pressure P in the furnace tube 31 is 600 mPa. Nitrogen is introduced into the boron diffusion furnace. The flow rate of nitrogen is 4000 sccm, and the time is 360 s;

[0135] <The second propulsion stage>

[0136] The temperature T of the boron diffusion furnace 32 is 885°C, the pressure P in the furnace tube 32 is 600 mPa. Nitrogen is introduced into the boron diffusion furnace. The flow rate of nitrogen is 4000 sccm, and the time is 330 s to form a boron emitter layer;

[0137] <Post-oxidation process>

[0138] The temperature T of the boron diffusion furnace 4 is 1020°C, the pressure P in the furnace tube 4 is 800 mPa. Nitrogen is bubbled into a water vapor bottle so that nitrogen carries water molecules. At the same time, oxygen is introduced into the boron diffusion furnace. The flow rate of oxygen is 18000 sccm, and the time is 5900 s to form a silicon oxide mask layer with a thickness of 100 nm to 150 nm on the boron emitter layer.

[0139] <Alkaline etching>

[0140] A chain HF equipment is used to remove the borosilicate glass on the back of the silicon substrate due to boron diffusion, and then a tank-type alkaline etching machine is used to remove the P-N junction on the back and edge of the silicon substrate.

[0141] <Preparing a tunneling passivation layer>

[0142] A tube-type PECVD equipment is used to deposit a silicon oxide tunneling passivation layer on the back of the silicon substrate.

[0143] <Preparing a phosphorus-doped amorphous silicon layer>

[0144] A tube-type PECVD equipment is used to deposit a phosphorus-doped polysilicon layer on the tunneling passivation layer.

[0145] <Annealing>

[0146] A tube-type annealing furnace is used for annealing;

[0147] <RCA Cleaning>

[0148] First, pass through a chain-type device and use hydrofluoric acid with a mass concentration of 5% to remove the phosphorus-doped polysilicon layer and its silicon oxide mask layer that are wrapped around to the front side, and then transfer to a tank-type alkali polishing machine to remove the front-side wrap-around coating;

[0149] <Depositing a Passivation Layer>

[0150] Use an ALD device to deposit an aluminum oxide layer on the boron emitter layer as the front-side passivation film layer; use a PECVD device to deposit a silicon oxynitride layer on the phosphorus-doped polysilicon layer as the back-side passivation layer; among them, both the front-side passivation film layer and the back-side passivation layer can be understood as the passivation layer provided on the boron emitter layer.

[0151] <Printing Electrode Paste>

[0152] Screen-print electrode paste on the front-side passivation film layer and the second passivation layer respectively.

[0153] <High-Temperature Presintering>

[0154] At 740 °C, high-temperature presintering causes the electrode paste printed on the passivation film layer to form a front-side current collector grid line precursor, and causes the electrode paste printed on the back-side passivation layer to form a back-side electrode.

[0155] <Laser-Induced Contact Treatment>

[0156] Perform laser-induced contact treatment on the front-side current collector grid line precursor to form a front-side current collector grid line.

[0157] Example 2

[0158] Except that the post-oxidation process is carried out based on a dry oxygen process, the rest is the same as in Example 1.

[0159] <Post-Oxidation Process>

[0160] The temperature T of the boron diffusion furnace 4 is 1030 °C, the furnace tube pressure P 4 is 800 mPa, oxygen is introduced into the boron diffusion furnace, the oxygen flow rate is 18000 sccm, and the time is 5900 s to form a silicon oxide mask layer with a thickness of 100 nm to 150 nm on the boron emitter layer.

[0161] The front structure of a solar cell, the solar cell and its manufacturing method, and a photovoltaic module disclosed in the present application have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the technical solution and the core inventive point of the embodiments of the present application. At the same time, for those of ordinary skill in the art, according to the idea of the present application, there will be changes in the specific implementation manner and the application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A front structure of a solar cell, characterized in that: include: Boron emitter layer; Passivation film layer; A front current collecting gate line, wherein the front current collecting gate line forms direct physical contact with the boron emitter layer in a partial area, and forms indirect physical contact with the boron emitter layer in a partial area through the passivation film layer; The total doping concentration of the boron emitter layer is 2.8×10 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 , the total doping concentration of the boron emitter layer refers to: the integral area of ​​the ECV curve of the boron emitter layer, and the total doping concentration of the boron emitter layer is determined by the following expression: <h2 style=";text-align:left;direction:ltr">C<h2 style=";text-align:left;direction:ltr"> total <h2 style=";text-align:left;direction:ltr"> =D1*L1+D2*(L2-L1)+D3*(L3-L2)+……+D<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> *(L<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> -L<h2 style=";text-align:left;direction:ltr"> x-1 <h2 style=";text-align:left;direction:ltr"> ) Where D1 represents the doping concentration corresponding to the first target test point, L1 represents the junction depth corresponding to the first target test point, and D x Indicates the doping concentration corresponding to the xth target test point, L x Indicates the junction depth corresponding to the xth target test point.

2. The front structure of the solar cell according to claim 1, characterized in that: The total doping concentration of the boron emitter layer is 2.8×10 18 atoms / cm 3 ~3.2×10 18 atoms / cm 3 .

3. The front structure of the solar cell according to claim 1, characterized in that: The junction depth of the boron emitter layer is 0.5 μm to 2.0 μm; and / or, The sheet resistance of the boron emitter layer is 300Ω / sq to 1500Ω / sq.

4. The front structure of the solar cell according to claim 2, characterized in that: The sheet resistance of the boron emitter layer is 500Ω / sq to 1000Ω / sq.

5. The front structure of the solar cell according to claim 2, characterized in that: The junction depth of the boron emitter layer is 0.5 μm to 0.8 μm.

6. The front structure of the solar cell according to claim 2, characterized in that: The junction depth of the boron emitter layer is 0.8 μm to 1.5 μm.

7. The front structure of the solar cell according to claim 1, characterized in that: The region of direct physical contact has a silver-silicon eutectic matrix and a silver-silicon eutectic overflow, and the region of direct physical contact also has a silver crystal conductively connected to the silver-silicon eutectic matrix and the silver-silicon eutectic overflow.

8. The front structure of the solar cell according to claim 7, characterized in that: The silver crystals include a crystalline main chain and crystalline side chains extending from the crystalline main chain in a growth direction different from that of the crystalline main chain.

9. The front structure of the solar cell according to claim 7, characterized in that: The indirect physical contact area has a conductive aggregate, and the passivation film layer is located between the conductive aggregate and the boron emitter layer; wherein the conductive aggregate includes a glass phase material and metal conductive particles, and the metal conductive particles have the same type of metal elements as the silver crystals.

10. A solar cell, characterized in that: The solar cell comprises the front structure of the solar cell according to any one of claims 1 to 9.

11. A method for preparing a solar cell as claimed in claim 10, characterized in that: The following steps are involved: Providing a textured silicon wafer as a silicon substrate, placing the silicon substrate into a boron diffusion furnace, and preparing a boron emitter layer on the front side of the silicon substrate by a boron diffusion process; forming a tunnel passivation layer and a phosphorus-doped polysilicon layer in sequence on the back side of the silicon substrate; forming a passivation film layer on the boron emitter layer and a back passivation layer on the phosphorus-doped polysilicon layer in sequence; Printing electrode slurry on the passivation film layer and the back passivation layer; Pre-sintering at high temperature causes the electrode paste printed on the passivation film layer to form a front current collecting grid line precursor, and causes the electrode paste printed on the back passivation layer to form a back electrode; The front current collecting grid line precursor is subjected to laser induced contact treatment to form the front current collecting grid line.

12. The preparation method according to claim 11, characterized in that: The method of preparing a boron emitter layer on the front side of the silicon substrate by a boron diffusion process comprises: Pre-oxidation process: the temperature of the boron diffusion furnace is T1, the furnace tube pressure is P1, oxygen and nitrogen are introduced into the boron diffusion furnace, wherein 750°C≤T1≤850°C, 230mPa≤P1≤270mPa, the oxygen flow rate is 800sccm~2000sccm, and the nitrogen flow rate is 200sccm~1000sccm; Multi-stage deposition process: the temperature of the boron diffusion furnace is T2, the furnace tube pressure is P2, oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace in stages, and the furnace temperature of each stage is increased step by step, wherein 750°C≤T2≤850°C, the oxygen flow rate is 200sccm~600sccm, 230mPa≤P2≤270mPa, the nitrogen flow rate is 3000sccm~5000sccm, and the boron source gas flow rate is 80sccm~150sccm; Multi-stage PN junction process: the temperature of the boron diffusion furnace is T3, the furnace tube pressure is P3, and nitrogen is introduced into the boron diffusion furnace, wherein 850°C≤T3≤950°C, 580mPa≤P3≤620mPa, and the nitrogen flow rate is 3000sccm~5000sccm; Post-oxidation process: the temperature of the boron diffusion furnace is T4, the furnace tube pressure is P4, oxygen is introduced into the boron diffusion furnace to form a silicon oxide mask layer with a thickness of 50nm~120nm, wherein 950℃≤T4≤1050℃, 780mPa≤P4≤820mPa, and the oxygen flow rate is 10000sccm~30000sccm.

13. The preparation method according to claim 12, characterized in that: P4>P3; and / or, P4>P2; and / or, P4>P1; and / or, P3>P2; And / or, P3>P1.

14. The preparation method according to claim 12, characterized in that: T2>T1; and / or, T3>T2; And / or, T4>T3.

15. The preparation method according to claim 12, characterized in that: In the multi-stage deposition process, the number of deposition stages is 2-5.

16. The preparation method according to claim 12, characterized in that: The multi-stage deposition process includes: First deposition stage: Boron diffusion furnace temperature is T 21 , the furnace tube pressure is P 21 , oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace, where 750℃≤T 21 ≤850℃,230mPa≤P 21 ≤270mPa, oxygen flow rate is 200sccm~600sccm, nitrogen flow rate is 3000sccm~5000sccm, and boron source gas flow rate is 80sccm~150sccm; Second deposition stage: Boron diffusion furnace temperature is T 22 , the furnace tube pressure is P 22 , oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace, where 750℃≤T 22 ≤850℃, and T 22 >T 21 , 230mPa≤P 22 ≤270mPa, oxygen flow rate is 200sccm~600sccm, nitrogen flow rate is 3000sccm~5000sccm, and boron source gas flow rate is 80sccm~150sccm; The third deposition stage: the temperature of the boron diffusion furnace is T 23 , the furnace tube pressure is P 23 , oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace, where 750℃≤T 23 ≤850℃, and T 23 >T 22 , 230mPa≤P 23 ≤270mPa, oxygen flow rate is 200sccm~600sccm, nitrogen flow rate is 3000sccm~5000sccm, and boron source gas flow rate is 80sccm~150sccm.

17. The preparation method according to claim 11, characterized in that: The process of performing laser induced contact treatment on the front current collecting grid line precursor includes: The front current collecting gate line precursor is subjected to laser induced contact treatment on the front side of the silicon substrate.

18. A photovoltaic module, characterized in that: The photovoltaic module comprises the solar cell according to claim 10, or the photovoltaic module comprises the solar cell prepared by the preparation method according to any one of claims 11 to 17.

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