Front-side structure of solar cell, solar cell and preparation method therefor, and photovoltaic module

Abstract

Provided in the present disclosure are a front-side structure of a solar cell, a solar cell and a preparation method therefor, and a photovoltaic module. The front-side structure of a solar cell comprises: a boron emitter layer; a passivation film layer; and front-side current collection grid lines, wherein the front-side current collection grid lines and the boron emitter layer form direct physical contact in some areas, and form indirect physical contact in some areas by means of the passivation film layer; and the total doping concentration of the boron emitter layer ranges from 2.8×1018atoms / cm3 to 4.0×1018atoms / cm3. Therefore, the performance of the solar cell can be improved.

Description

Front structure of solar cells, solar cells and their fabrication methods, photovoltaic modules

[0001] Related cross-references

[0002] This disclosure claims priority to Chinese Patent Application No. 202411189196.3, filed on August 28, 2024, entitled "Front-side structure of solar cell, solar cell and method of preparation thereof, photovoltaic module", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of solar cells, and more particularly to a front-side structure of a solar cell, a solar cell and its fabrication method, and a photovoltaic module. Background Technology

[0004] In the current front structure of solar cells, the boron emitter layer has many defects due to the high-temperature boron source diffusion process. In particular, the boron emitter layer corresponding to the metallization region and the boron emitter layer corresponding to the light absorption region need to take into account the impact of the gold half-contact resistivity of the metallization region and the spectral response and carrier recombination damage of the light absorption region on the photoelectric conversion efficiency of the solar cell. This has become a technical problem that the industry urgently needs to solve in order to develop high-efficiency solar cell technology. Summary of the Invention

[0005] To address the aforementioned technical issues, this disclosure provides a solar cell and its fabrication method, as well as a photovoltaic module, to reduce recombination losses in the contact area between the boron emitter layer and the front current collector grid in the front structure, thereby improving the performance of the solar cell.

[0006] In a first aspect, this disclosure provides a front-side structure for a solar cell, comprising:

[0007] Boron emitter layer;

[0008] Passivation film;

[0009] The front current collector line forms direct physical contact with the boron emitter layer in some areas and indirect physical contact through the passivation film layer in other areas.

[0010] The total doping concentration of the boron emitter layer is 2.8 × 10⁻⁶. 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 .

[0011] In some embodiments of this disclosure, the total doping concentration of the boron emitter layer is 2.8 × 10⁻⁶. 18 atoms / cm3 ~3.2×10 18 atoms / cm 3 .

[0012] In some embodiments of this disclosure, the junction depth of the boron emitter layer is 0.5 μm to 2.0 μm;

[0013] And / or,

[0014] The sheet resistance of the boron emitter layer is 300Ω / sq to 1500Ω / sq.

[0015] In some embodiments of this disclosure, the sheet resistance of the boron emitter layer is 500 Ω / sq to 1000 Ω / sq.

[0016] In some embodiments of this disclosure, the junction depth of the boron emitter layer is 0.5 μm to 0.8 μm.

[0017] In some embodiments of this disclosure, the junction depth of the boron emitter layer is 0.8 μm to 1.5 μm.

[0018] In some embodiments of this disclosure, the region of direct physical contact has a silver-silicon eutectic substrate and a silver-silicon eutectic overflow, and the region of direct physical contact also has a silver crystal electrically connected to the silver-silicon eutectic substrate and the silver-silicon eutectic overflow.

[0019] In some embodiments of this disclosure, the silver crystal includes a crystalline backbone and crystalline side chains extending from the crystalline backbone in a growth direction different from that of the crystalline backbone.

[0020] In some embodiments of this disclosure, the region of indirect physical contact has a conductive aggregate, and the passivation film layer is located between the conductive aggregate and the boron emitter layer; wherein the conductive aggregate comprises a glass phase material and metallic conductive particles, and the metallic conductive particles have the same type of metal element as the silver crystal.

[0021] In a second aspect, this disclosure provides a solar cell including the front structure of the solar cell described in the second aspect.

[0022] Thirdly, this disclosure provides a method for fabricating a solar cell as described in the second aspect, comprising the following steps:

[0023] A texturized silicon wafer is provided as a silicon substrate. The silicon substrate is placed in a boron diffusion furnace, and a boron emitter layer is prepared on the front side of the silicon substrate by a boron diffusion process.

[0024] A tunneling passivation layer and a phosphorus-doped polycrystalline silicon layer are sequentially formed on the back side of the silicon substrate;

[0025] A passivation film layer is sequentially formed on the boron emitter layer, and a back passivation layer is formed on the phosphorus-doped polycrystalline silicon layer;

[0026] Electrode paste is printed on the passivation film layer and the back passivation layer;

[0027] High-temperature pre-sintering causes the electrode paste printed on the passivation film layer to form a front current collector precursor, and causes the electrode paste printed on the back passivation layer to form a back electrode.

[0028] The front current collector line precursor is subjected to laser-induced contact treatment to form the front current collector line.

[0029] In some embodiments of this disclosure, a boron emitter layer is fabricated on the front side of the silicon substrate using a boron diffusion process, including:

[0030] Pre-oxidation process: The temperature of the boron diffusion furnace is T1, the pressure of the furnace tube is P1, and oxygen and nitrogen are introduced into the boron diffusion furnace. Among them, 750℃≤T1≤850℃, 230mPa≤P1≤270mPa, oxygen flow rate is 800sccm~2000sccm, and nitrogen flow rate is 200sccm~1000sccm.

[0031] Multi-stage deposition process: The temperature of the boron diffusion furnace is T2, the pressure of the furnace tube is P2, oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace in stages, and the temperature inside the furnace in each stage is increased step by step. Among them, 750℃≤T2≤850℃, oxygen flow rate is 200sccm~600sccm, 230mPa≤P2≤270mPa, nitrogen flow rate is 3000sccm~5000sccm, and boron source gas flow rate is 80sccm~150sccm.

[0032] Multi-stage PN junction process: The temperature of the boron diffusion furnace is T3, the pressure of the furnace tube is P3, and nitrogen gas is introduced into the boron diffusion furnace. Among them, 850℃≤T3≤950℃, 580mPa≤P3≤620mPa, and the nitrogen gas flow rate is 3000sccm~5000sccm.

[0033] Post-oxidation process: The temperature of the boron diffusion furnace is T4, the pressure of the furnace tube is P4, oxygen is introduced into the boron diffusion furnace to form a silicon oxide mask layer with a thickness of 50nm to 120nm, wherein 950℃≤T4≤1050℃, 780mPa≤P4≤820mPa, and the oxygen flow rate is 10000sccm~30000sccm.

[0034] In some embodiments of this disclosure, P4 > P3;

[0035] And / or, P4 > P2;

[0036] And / or, P4 > P1;

[0037] And / or, P3>P2;

[0038] And / or, P3>P1.

[0039] In some embodiments of this disclosure, T2 > T1;

[0040] And / or, T3 > T2;

[0041] And / or, T4 > T3.

[0042] In some embodiments of this disclosure, the number of deposition stages in the multi-stage deposition process is 2 to 5.

[0043] In some embodiments of this disclosure, the multi-stage deposition process includes:

[0044] First deposition stage: the 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, wherein 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;

[0045] 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, wherein 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;

[0046] 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, wherein 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.

[0047] In some embodiments of this disclosure, the process of laser-induced contact treatment of the front current collector line precursor includes:

[0048] Laser-induced contact processing is performed on the front side of the silicon substrate to the front current collector line precursor.

[0049] Fourthly, this disclosure provides a photovoltaic module, the photovoltaic module comprising the solar cell as described in the second aspect, or the photovoltaic module comprising the solar cell prepared by the preparation method as described in the third aspect.

[0050] Compared with the prior art, this disclosure has at least the following beneficial effects:

[0051] This disclosure provides a front-side structure of a solar cell, a solar cell and its fabrication method, and a photovoltaic module, wherein the total doping concentration of the boron emitter layer is controlled to be 2.8 × 10⁻⁶. 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 This approach not only helps reduce recombination losses in the boron emitter layer of the front structure but also prevents the thin-layer carrier transport capacity of the boron emitter layer from decreasing due to excessively low total doping concentration, thereby improving the photoelectric conversion performance of the solar cell. Furthermore, by employing laser-induced sintering technology to form a gold-semiconductor contact structure with low resistivity in the metallized region, the resistance loss at the gold-semiconductor contact structure is reduced, and the corrosion area of ​​the glass-to-surface passivation film in the silver paste of the metallized region is reduced to a certain extent, thereby increasing the open-circuit voltage of the solar cell and ultimately improving the photoelectric conversion efficiency of the solar cell. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 is a schematic diagram of the front structure of a solar cell according to one embodiment of the present disclosure;

[0054] Figure 2 is a schematic diagram of the contact area between the front current collector grid line and the boron emitter layer in one embodiment of this disclosure;

[0055] Figure 3 is a schematic diagram of the electrochemical capacitance-voltage (ECV) curve of one embodiment of the present disclosure;

[0056] Figure 4 is a schematic diagram of the morphology of silver crystals according to one embodiment of the present disclosure;

[0057] Figure 5 is a schematic diagram of the structure of a solar cell according to one embodiment of the present disclosure.

[0058] Explanation of reference numerals in the attached figures: Silicon substrate-1, Boron emitter layer-2, Passivation film layer-3, Front current collector line-4, Tunneling passivation layer-5, Phosphorus-doped polycrystalline silicon layer-6, Back passivation layer-7, Back electrode-8, Gold-semiconductor contact first region-41, Gold-semiconductor contact second region-42, Silver-silicon eutectic substrate-411, Silver-silicon eutectic overflow-412, Silver crystal-413, Conductive aggregate-421, Crystalline main chain-4131, Crystalline side chain-4132. Detailed Implementation

[0059] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0060] In this disclosure, the terms “upper,” “lower,” “left,” “right,” “front,” “rear,” “top,” “bottom,” “inner,” “outer,” “vertical,” “horizontal,” “lateral,” and “longitudinal” indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. These terms are primarily for the purpose of better describing this disclosure and its embodiments and are not intended to limit the indicated devices, elements, or components to having a specific orientation or to be constructed and operated in a specific orientation.

[0061] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain circumstances to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this disclosure according to the specific circumstances.

[0062] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection via an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this disclosure according to the specific circumstances.

[0063] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.

[0064] The technical solutions of this disclosure will be further described below with reference to the embodiments and accompanying drawings.

[0065] In a first aspect, this disclosure provides a front-side structure for a solar cell. As shown in FIG1, the front-side structure of the solar cell includes a boron emitter layer 2, a passivation film layer 3, and a front-side current collector 4, wherein the boron emitter layer 2 is located on the front side of a silicon substrate 1, and the passivation film layer 3 is located on the front side of the boron emitter layer 2. A gold-semiconductor contact region is formed between the front-side current collector 4 and the boron emitter layer 2. As shown in FIG2, the front-side current collector 4 and the boron emitter layer 2 form a direct physical contact in a portion of the region, including the first gold-semiconductor contact region 41 shown in FIG2; the front-side current collector 4 and the boron emitter layer 2 also form an indirect physical contact through the passivation film layer 3 in a portion of the region, including the second gold-semiconductor contact region 42 shown in FIG2. The first gold-semiconductor contact region 41 and the second gold-semiconductor contact region 42 constitute the aforementioned gold-semiconductor contact region.

[0066] The total doping concentration of boron emitter layer 2 is 2.8 × 10⁻⁶. 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 × 10⁻⁶. 18 atoms / cm 3 3.0×10 18 atoms / cm 3 3.2×10 18 atoms / cm 3 3.5×10 18 atoms / cm 3 4.0×10 18 atoms / cm 3 Or any value between the two ranges mentioned above.

[0067] In this disclosure, the total doping concentration C of the boron emitter layer is... totalThis refers to the integrated area of ​​the ECV curve of the boron emitter layer. For example, referring to Figure 3, for the first target test point to the xth target test point, the integrated area is the ECV curve, the abscissa value of the first target test point (L1), and the abscissa value of the xth target test point (L...). x The area enclosed by the x-axis and y-axis. The target test point refers to the specific boron atom doping concentration at a specific junction depth when obtaining a single-point value on the ECV curve. Since the resistivity of the currently used N-type silicon substrate is 0.6 Ω·cm to 16 Ω·cm, to reasonably limit the upper limit of the ECV curve test point, the upper limit doping concentration of the ECV curve test point is defined as greater than 1.0 × 10⁻⁶. 17 atoms / cm 3 That is, the doping concentration is less than 1.0 × 10 17 atoms / cm 3 The test points are not within the range of test points selected for the ECV curve.

[0068] The total doping concentration C of the boron emitter layer can be calculated using the following expression. total :

[0069] C total =D1*L1+D2*(L2-L1)+D3*(L3-L2)+……+D x *(L x -L x-1 (1)

[0070] In equation (1), 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 L represents the doping concentration corresponding to the x-th target test point. x This represents the knot depth corresponding to the x-th target test point.

[0071] It should be noted that the total doping concentration C of the boron emitter layer totalIn this disclosure, the overall doping level of the boron emitter layer is used to characterize the solar cell. When sunlight shines on the front side of a solar cell, high-energy short-wavelength photons are preferentially absorbed on the front side. The boron emitter layer corresponds to the short-wavelength spectral response band in the solar spectrum. To fully absorb photons in the short-wavelength spectral band, using a boron emitter layer with a lower doping concentration is beneficial to improving the short-wavelength spectral response of the boron emitter layer, and the lower the doping concentration, the better the short-wavelength spectral response of the boron emitter layer. However, the doping concentration in the boron emitter layer also needs to have the carrier transport capability to transport photogenerated carriers from the generation point to the front current collector line. That is, the thin-film resistance of the boron emitter layer in the light-receiving region affects the current loss of photogenerated carriers before they are transported to the front current collector line. To achieve the optimal balance between the short-wavelength spectral response and the thin-film resistance transport loss of the boron emitter layer, the total doping concentration C of the boron emitter layer is... total It needs to be kept within a reasonable range.

[0072] The solar cell front-side structure disclosed herein is wherein the total doping concentration of the boron emitter layer is controlled to be 2.8 × 10⁻⁶. 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 This approach maintains the total doping concentration of the boron emitter layer within a suitable range. This not only helps reduce recombination losses in the contact area between the boron emitter layer and the front current collector in the front structure, but also prevents the thin-layer carrier transport capacity of the boron emitter layer from decreasing due to excessively low total doping concentration, thereby improving the performance of the solar cell. In addition, by using laser-induced sintering technology to form a gold-semiconductor contact structure with low resistivity in the metallized region, the resistance loss at the gold-semiconductor contact structure is reduced, and the corrosion area of ​​the glass-to-surface passivation film in the silver paste of the metallized region is reduced to a certain extent, thereby increasing the open-circuit voltage of the solar cell and thus improving the photoelectric conversion efficiency of the solar cell.

[0073] In some embodiments of this disclosure, the total doping concentration of the boron emitter layer is 2.8 × 10⁻⁶. 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 × 10⁻⁶. 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 Alternatively, any value between the two ranges mentioned above. 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 thin-film resistance transport loss of the boron emitter layer. In particular, after laser-induced sintering of the front metallization region or by adding a denser current collector grid design on the front side, the short-wavelength spectral response of the boron emitter layer can be further improved by using a boron emitter layer with a more suitable doping concentration range, while sacrificing some carrier transport loss.

[0074] In some embodiments of this disclosure, 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; and 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 ranges, the thin-film transport resistance loss of photogenerated carriers transported to the front-side collector gate line can be reduced.

[0075] In some embodiments of this disclosure, 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, the thin-film transport resistance loss of photogenerated carriers to the front current collector grid line can be reduced while taking into account the short-wavelength spectral response of the boron emitter layer, achieving a relatively good balance between the two.

[0076] In some embodiments of this disclosure, 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, it is possible to reduce the thin-film transport resistance loss of photogenerated carriers to the front current collector grid line while taking into account the short-wavelength spectral response of the boron emitter layer, achieving a relatively good balance between the two.

[0077] In some embodiments of this disclosure, 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 adjusting the junction depth of the boron emitter layer within the above range, the thin-film transport resistance loss of photogenerated carriers transported to the front current collector line can be minimized.

[0078] In some embodiments of this disclosure, referring to Figure 4, the region of direct physical contact, i.e., the first region 41 of the gold-silicon contact, has a silver-silicon eutectic substrate 411 and a silver-silicon eutectic overflow 412. The region of direct physical contact also has a silver crystal 413 electrically connected to the silver-silicon eutectic substrate 411 and the silver-silicon eutectic overflow 412. The front structure of the solar cell of this disclosure includes a silver crystal 413 with higher conductivity, and a silver-silicon eutectic substrate 411 and a silver-silicon eutectic overflow 412 for improving the conductivity of the boron emitter layer. This significantly improves the conductivity of the gold-silicon contact conductive structure for photogenerated carrier output, thereby effectively improving the contact performance between the front current collector and the boron emitter layer through optimization of the conductive structure. It is evident that by improving and optimizing the front structure of the solar cell as described above, the contact performance between the boron emitter layer and the front current collector can be improved, the contact resistance reduced, and the carrier transport capacity increased, thereby effectively improving the open-circuit voltage and photoelectric conversion efficiency of the solar cell.

[0079] In some embodiments of this disclosure, referring to Figure 4, the silver crystal 413 includes a crystalline main chain 4131 and crystalline side chains 4132 extending from the crystalline main chain 4131 in a growth direction different from that of the crystalline main chain 4131, so that the silver crystal 413 as a whole has a dendritic structure. This silver crystal, formed after the silver element is crystallized, has the characteristics of higher purity and higher electrical conductivity, thereby reducing the series resistance of the solar cell and improving the photoelectric conversion efficiency.

[0080] In some embodiments of this disclosure, referring to FIG2, the region of indirect physical contact, namely the second region 42 of the gold-semiconductor contact, has a conductive aggregate 421, and the conductive aggregate 421 is separated from the boron emitter layer 2 by a passivation film layer 3 with a high dielectric constant. 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, such as silver.

[0081] Secondly, this disclosure provides a solar cell that includes the front structure of the solar cell described in any of the above embodiments.

[0082] In some embodiments of this disclosure, the solar cell is a TOPCon cell, as shown in FIG5. 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 collector line 4 are sequentially disposed 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 polycrystalline silicon layer 6, a back passivation layer 7 and a back electrode 8 are sequentially disposed in a direction away from the back side.

[0083] The material of the tunneling passivation layer can include a variety of dielectric materials, such as at least one of silicon oxide, amorphous silicon, polycrystalline silicon, and silicon carbide. Specifically, the tunneling passivation layer can be composed of a silicon oxide layer containing silicon oxide. This is because silicon oxide layers have excellent passivation properties, which can minimize the recombination loss of charge carriers on the semiconductor substrate surface, and are thin films with excellent durability for subsequent high-temperature processes. The tunneling passivation layer can also have a pinhole channel structure, allowing charge carriers within the solar cell to move freely. The selective passage of majority charge carriers through heavily doped polycrystalline silicon helps reduce the recombination loss of minority charge carriers. The phosphorus-doped polycrystalline silicon layer is a phosphorus-doped polycrystalline silicon layer, and the back passivation layer is a passivation layer whose material can be selected from any one or any combination of silicon oxide, aluminum oxide, silicon carbide, silicon nitride, or silicon oxynitride.

[0084] The above describes the structural film layers on the front side of a solar cell. It is understood that, depending on the structural characteristics of different types of solar cells, other structural film layers, such as anti-reflection layers, can be applied to the front and back sides of the solar cell. Furthermore, the methods for forming these structural film layers can also employ conventional practices of the prior art. For example, a textured silicon substrate can be obtained through texturing, and passivation films, anti-reflection layers, etc., can be obtained through atomic layer deposition (ALD) or plasma-enhanced chemical vapor deposition (PECVD) processes. In addition, this disclosure may also employ conventional methods such as polishing and cleaning, depending on the formation of the coating layer, borosilicate glass layer, or phosphosilicate glass layer during the formation of each structural film layer; this disclosure does not impose any limitations on these methods.

[0085] Thirdly, this disclosure provides a method for fabricating a solar cell, comprising the following steps:

[0086] Step A: 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 side of the silicon substrate through a boron diffusion process;

[0087] Step B: A tunneling passivation layer and a phosphorus-doped polycrystalline silicon layer are sequentially formed on the back side of the silicon substrate;

[0088] Step C: A passivation film layer is sequentially formed on the boron emitter layer, and a back passivation layer is formed on the phosphorus-doped polycrystalline silicon layer;

[0089] Step D: Print electrode paste on the passivation film layer and the back passivation layer;

[0090] Step E: High-temperature pre-sintering causes the electrode paste printed on the passivation film layer to form the front current collector line precursor, and causes the electrode paste printed on the back passivation layer to form the back electrode.

[0091] Step F: Perform laser-induced contact treatment on the front current collector line precursor to form the front current collector line.

[0092] In step A, the front side of the silicon substrate can be pre-textured to form a pyramidal textured structure, which helps reduce the reflectivity of the silicon substrate surface and increases the refraction and scattering of light inside the silicon substrate. The boron diffusion process disclosed herein can be based on a dry oxidation process or a wet oxidation process. When using a wet oxidation process, the growth rate of the silicon oxide mask layer is faster, and the temperature for forming the silicon oxide mask layer (i.e., the post-oxidation process) can be controlled at around 1000°C, which is lower than the post-oxidation temperature of the dry oxidation process. The lower temperature can significantly extend the lifespan of the quartz tube in the diffusion furnace. Furthermore, the pre-oxidation process, multi-stage deposition process, multi-stage PN junction advancement process, and post-oxidation process can be combined into a single diffusion furnace, reducing the number of equipment used and lowering production costs. Although the silicon oxide mask growth rate of the wet oxidation process is faster, 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 density is not high. Therefore, the wet oxygen process disclosed herein is more suitable for the boron diffusion process of TOPCon cells.

[0093] 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 of the silicon substrate ranges from 100 μm to 200 μm, which is not particularly limited in this disclosure.

[0094] In step B, a tunneling passivation layer and a phosphorus-doped polycrystalline silicon layer can be prepared using a tubular PECVD device, without any particular limitation in this disclosure.

[0095] In step C, an aluminum oxide layer can be deposited on the boron emitter layer using an ALD device as a passivation film layer on the front side; and a silicon oxynitride layer can be deposited on the phosphorus-doped polycrystalline silicon layer using a PECVD device as a passivation layer on the back side.

[0096] In step D, electrode paste can be screen-printed onto the passivation film layer on the front side and the back passivation layer on the back side to form electrode grid lines. The electrode grid lines of this disclosure may include main grid lines and sub-grid lines. The electrode pastes of this disclosure include, but are not limited to, pure silver electrode paste and silver-aluminum electrode paste.

[0097] In step E, the high-temperature pre-sintering temperature can be 650℃~780℃. This disclosure does not have any particular limitations, as long as the front current collector precursor and the back electrode can be formed.

[0098] In step F, laser-induced contact treatment of the front current collector precursor facilitates the formation of a silver-silicon eutectic matrix and a silver crystal electrically connected to the silver-silicon eutectic matrix in the region of direct physical contact between the front current collector and the boron emitter layer. This significantly improves the conductivity of the hole or electron output conductive structure of the solar cell, thereby effectively improving the contact performance between the front current collector and the boron emitter layer through optimization of the conductive structure.

[0099] This disclosure provides a method for fabricating a solar cell. A boron emitter layer of this disclosure is prepared on the front side of a silicon substrate using a boron diffusion process. A laser-induced contact treatment is then performed on the front current collector precursor to form the front current collector, thereby forming the boron emitter layer. This method facilitates the formation of a silver-silicon eutectic matrix and silver crystals electrically connected to the silver-silicon eutectic matrix in the region of direct physical contact between the front current collector and the boron emitter layer. This improves the contact performance between the front current collector and the boron emitter layer, thereby enhancing the performance of the solar cell.

[0100] In some embodiments of this disclosure, a boron emitter layer is fabricated on the front side of a silicon substrate using a boron diffusion process, including:

[0101] Pre-oxidation process: The temperature of the boron diffusion furnace is T1, the pressure of the furnace tube is P1, and oxygen and nitrogen are introduced into the boron diffusion furnace. Among them, 750℃≤T1≤850℃, 230mPa≤P1≤270mPa, oxygen flow rate is 800sccm~2000sccm, and nitrogen flow rate is 200sccm~1000sccm.

[0102] Multi-stage deposition process: The temperature of the boron diffusion furnace is T2, the pressure of the furnace tube is P2, oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace in stages, and the temperature inside the furnace in each stage is increased step by step. Among them, 750℃≤T2≤850℃, oxygen flow rate is 200sccm~600sccm, 230mPa≤P2≤270mPa, nitrogen flow rate is 3000sccm~5000sccm, and boron source gas flow rate is 80sccm~150sccm.

[0103] Multi-stage PN junction process: The temperature of the boron diffusion furnace is T3, the pressure of the furnace tube is P3, and nitrogen gas is introduced into the boron diffusion furnace. Among them, 850℃≤T3≤950℃, 580mPa≤P3≤620mPa, and the nitrogen gas flow rate is 3000sccm~5000sccm.

[0104] Post-oxidation process: The temperature of the boron diffusion furnace is T4, the pressure of the furnace tube is P4, oxygen is introduced into the boron diffusion furnace to form a silicon oxide mask layer with a thickness of 50nm to 120nm, wherein 950℃≤T4≤1050℃, 780mPa≤P4≤820mPa, and the oxygen flow rate is 10000sccm~30000sccm.

[0105] During the pre-oxidation process, T1 can be 750℃, 770℃, 800℃, 820℃, or 850℃; P1 can be 230mPa, 240mPa, 250mPa, 260mPa, or 270mPa; oxygen flow rate can be 800sccm, 1000sccm, 1300sccm, 1500sccm, or 2000sccm; and nitrogen flow rate can be 200sccm, 400sccm, 600sccm, 700sccm, or 1000sccm. The pre-oxidation process takes 220s to 260s. By adjusting the boron diffusion furnace temperature T1, furnace tube pressure P1, oxygen flow rate, nitrogen flow rate, and pre-oxidation process time within the above ranges, a thin oxide layer (approximately 1nm to 3nm thick) is grown on the silicon substrate surface as a barrier layer. This slows down the diffusion rate of boron atoms in the next step and also makes the diffusion of boron atoms more uniform.

[0106] The inventors discovered that introducing a large amount of boron source at once leads to incomplete use and waste, and also causes the inlet temperature of the diffusion furnace to be too low, resulting in excessive temperature differences in the boron diffusion furnace and affecting the deposition effect. Based on this, this disclosure employs a multi-stage deposition process, dividing the deposition process into multiple stages. By adjusting the temperature of the boron diffusion furnace, the furnace tube pressure, and the flow rates of oxygen, nitrogen, and boron source gases in each deposition stage, and by gradually increasing the furnace temperature in each stage, the utilization rate of the boron source can be improved, and excessive temperature differences in the boron diffusion furnace can be prevented, which is beneficial for obtaining the boron emitter layer of this disclosure.

[0107] In some embodiments of this disclosure, P4>P3; and / or, P4>P2; and / or, P4>P1; and / or, P3>P2; and / or, P3>P1. This disclosure satisfies the above relationships by regulating the furnace tube pressures P1, P2, P3, and P4 during the pre-oxidation process, multi-stage deposition process, multi-stage PN junction advancement process, and post-oxidation process. On the one hand, as the furnace tube pressure increases, the pressure difference between the inside and outside of the quartz furnace tube gradually decreases, thereby reducing the furnace tube pressure and lowering the risk of microcracks in the furnace tube. On the other hand, for the wet oxidation process, the furnace tube pressure is higher during the post-oxidation process, which can increase the concentration of wet oxygen, thereby increasing the oxidation rate and reducing the oxidation time.

[0108] In the multi-stage PN junction advancement process, T3 can be 850℃, 870℃, 900℃, 920℃ or 950℃, P3 can be 580mPa, 590mPa, 600mPa, 610mPa or 620mPa, and nitrogen flow rate can be 3000sccm, 3500sccm, 4000sccm, 4500sccm or 5000sccm. No oxygen or boron source gas is introduced in this process.

[0109] The multi-stage propulsion process of the PN junction disclosed herein may include at least two propulsion stages, wherein the duration of the first propulsion stage is 350s to 400s and the duration of the second propulsion stage is 300s to 340s.

[0110] In the post-oxidation process, T4 can be 950℃, 980℃, 1000℃, 1040℃ or 1050℃, P4 can be 780mPa, 790mPa, 800mPa, 810mPa or 820mPa, and oxygen flow rate can be 10000sccm, 15000sccm, 20000sccm, 25000sccm or 30000sccm; the post-oxidation process takes 4000s to 8000s.

[0111] In some embodiments of this disclosure, T2 > T1; and / or, T3 > T2; and / or, T4 > T3. This disclosure, by controlling the boron diffusion furnace temperatures T1, T2, T3, and T4 in the aforementioned pre-oxidation process, multi-stage deposition process, multi-stage PN junction advancement process, and post-oxidation process to satisfy the above relationships, facilitates more uniform and effective doping of boron atoms on the front side of the silicon substrate and activates boron atoms to reduce the probability of boron-doped dead layers forming.

[0112] In some embodiments of this disclosure, the number of deposition stages in the multi-stage deposition process is 2 to 5. For example, the deposition stages may include 2 stages, 3 stages, 4 stages, or 5 stages.

[0113] In some embodiments of this disclosure, the multi-stage deposition process includes:

[0114] First deposition stage: the 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, wherein 750℃≤T 21 ≤850℃, 230mPa≤P 21 ≤270mPa, oxygen flow rate of 200sccm~600sccm, nitrogen flow rate of 3000sccm~5000sccm, boron source gas flow rate of 80sccm~150sccm; the first deposition stage takes 100s~140s;

[0115] 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, wherein 750℃≤T 22 ≤850℃, and T 22 >T 21 230mPa≤P 22 ≤270mPa, oxygen flow rate of 200sccm~600sccm, nitrogen flow rate of 3000sccm~5000sccm, boron source gas flow rate of 80sccm~150sccm; the second deposition stage takes 200s~250s;

[0116] 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, wherein 750℃≤T 23 ≤850℃, and T 23 >T 22 230mPa≤P 23 ≤270mPa, oxygen flow rate of 200sccm~600sccm, nitrogen flow rate of 3000sccm~5000sccm, boron source gas flow rate of 80sccm~150sccm; the third deposition stage takes 200s~250s.

[0117] In some embodiments of this disclosure, the process of laser-induced contact treatment of the front current collector precursor includes:

[0118] Laser-induced contact treatment is performed on the front current collector precursor of the silicon substrate (a reverse bias voltage of 10V to 25V is applied during this process). On the one hand, the reverse bias voltage further enhances the built-in electric field of the solar cell at the contact interface between the boron emitter layer and the front current collector precursor. On the other hand, the laser-induced contact treatment generates a large number of photogenerated carriers. Through the combined effect of these two aspects, electron carriers and hole carriers are sorted by the electric field. One type of charge carrier is accelerated by the electric field and rapidly transported to the boron emitter layer. When these carriers pass through the glass phase material with high resistivity, they generate a lot of heat, which is conducive to the formation of silver silicon eutectic matrix and silver silicon eutectic overflow in the region of direct physical contact between the front current collector and the boron emitter layer, as well as silver crystals that are electrically connected to the silver silicon eutectic matrix and silver silicon eutectic overflow.

[0119] In some embodiments of this disclosure, after the passivation film is formed, a silicon oxynitride layer can be deposited on the passivation film as a front antireflection layer using a PECVD device.

[0120] Thirdly, this disclosure provides a photovoltaic module, the photovoltaic module comprising a solar cell prepared by the preparation method described in the first aspect, or the photovoltaic module comprising a solar cell as described in the second aspect.

[0121] This disclosure also provides a photovoltaic module for converting received light energy into electrical energy and transmitting it to an external load. The photovoltaic module includes: at least one cell string, which is composed of a plurality of the aforementioned solar cells connected together; an encapsulating film for covering the surface of the cell string; and a cover plate for covering the surface of the encapsulating film facing away from the cell string.

[0122] The present disclosure will be further described below with reference to more specific embodiments. Furthermore, the electrode pastes used in the following embodiments are all commercially available. For example, the front current collector paste uses commercially available Guangda T129 silver electrode paste, with an Al content of 0.05wt% to 0.10wt% and an oxygen content of 1.0wt% to 5.0wt%. The elemental content percentages in the silver electrode paste can be measured using an energy dispersive spectroscopy (EDS) instrument.

[0123] Example 1

[0124] This embodiment provides a solar cell with a front-side structure, wherein the subsequent oxidation process is based on a wet oxidation process, and the preparation method is as follows:

[0125] <Pre-oxidation process>

[0126] A texturized silicon wafer (125 μm thick) is provided as a silicon substrate. The silicon substrate is placed in a boron diffusion furnace with a temperature T1 of 820°C, a furnace tube pressure P1 of 250 mPa, an oxygen flow rate of 1000 sccm, and a nitrogen flow rate of 500 sccm to form an oxide layer with a thickness of 1 nm to 3 nm on the surface of the silicon substrate.

[0127] <Multi-stage sedimentation process>

[0128] <First Depositional Stage>

[0129] Boron diffusion furnace temperature T 21 The temperature is 825℃, and the pressure P in the furnace tube is... 21 The pressure was 250 mPa. Oxygen, nitrogen and boron source gas were introduced into the boron diffusion furnace at a flow rate of 300 sccm, a flow rate of 4000 sccm and a flow rate of 100 sccm for 120 seconds, followed by purging.

[0130] <Second Depositional Stage>

[0131] Boron diffusion furnace temperature T22 The temperature is 835℃, and the pressure P in the furnace tube is... 22 The pressure was 250 mPa. Oxygen, nitrogen and boron source gas were introduced into the boron diffusion furnace at a flow rate of 300 sccm, a flow rate of 4000 sccm and a flow rate of 100 sccm for 210 s, and then purged.

[0132] <Third Depositional Stage>

[0133] Boron diffusion furnace temperature T 23 The temperature is 845℃, and the pressure P in the furnace tube is... 23 The pressure was 250 mPa. Oxygen, nitrogen and boron source gas were introduced into the boron diffusion furnace at a flow rate of 300 sccm, a flow rate of 4000 sccm and a flow rate of 100 sccm for 210 s, and then purged.

[0134] <Multi-stage advancement of PN junction>

[0135] <First Phase of Advancement>

[0136] Boron diffusion furnace temperature T 31 The temperature is 885℃, and the pressure P in the furnace tube is... 31 The pressure is 600 mPa. Nitrogen gas is introduced into the boron diffusion furnace at a flow rate of 4000 sccm for 360 s.

[0137] <Second Phase of Advancement>

[0138] Boron diffusion furnace temperature T 32 The temperature is 885℃, and the pressure P in the furnace tube is... 32 At a pressure of 600 mPa, nitrogen gas is introduced into the boron diffusion furnace at a flow rate of 4000 sccm for 330 s to form a boron emitter layer.

[0139] <Post-oxidation process>

[0140] The temperature T4 of the boron diffusion furnace is 1020℃, and the pressure P4 of the furnace tube is 800mPa. Nitrogen gas is bubbled into the steam bottle so that the nitrogen carries water molecules. At the same time, oxygen is introduced into the boron diffusion furnace at a flow rate of 18000sccm for 5900s. A silicon oxide mask layer with a thickness of 100nm to 150nm is formed on the boron emitter layer.

[0141] <Alkali Polishing>

[0142] A chain-type HF equipment is used to remove the borosilicate glass on the back side of the silicon substrate due to boron expansion, and then a tank-type alkaline polishing machine is used to remove the PN junction on the back side and edge of the silicon substrate.

[0143] <Preparation of Tunneling Passivation Layer>

[0144] Deposit a silicon oxide tunneling passivation layer on the back side of the silicon substrate using a tube-type PECVD equipment.

[0145] <Prepare a phosphorus-doped amorphous silicon layer>

[0146] Deposit a phosphorus-doped polysilicon layer on the tunneling passivation layer using a tube-type PECVD equipment.

[0147] <Annealing>

[0148] Perform annealing using a tube-type annealing furnace;

[0149] <RCA cleaning>

[0150] First, pass through a chain-type equipment, 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 deposited on the front side, and then transfer to a tank-type alkali polishing machine to remove the front-side deposited layer;

[0151] <Deposit a passivation layer>

[0152] Use an ALD equipment to deposit an aluminum oxide layer on the boron emitter layer as the front-side passivation film layer; use a PECVD equipment 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.

[0153] <Print electrode paste>

[0154] Screen-print electrode paste on the front-side passivation film layer and the second passivation layer respectively.

[0155] <High-temperature pre-sintering>

[0156] At 740 °C, high-temperature pre-sintering makes the electrode paste printed on the passivation film layer form a front-side current collector grid line precursor, and makes the electrode paste printed on the back-side passivation layer form a back-side electrode.

[0157] <Laser-induced contact treatment>

[0158] Perform laser-induced contact treatment on the front-side current collector grid line precursor to form a front-side current collector grid line.

[0159] Example 2

[0160] Except that the post-oxidation process is carried out based on a dry oxygen process, the rest is the same as in Example 1.

[0161] <Post-oxidation process>

[0162] The temperature T4 of the boron diffusion furnace is 1030℃, the pressure P4 of the furnace tube is 800mPa, oxygen is introduced into the boron diffusion furnace at a flow rate of 18000sccm for 5900s, and a silicon oxide mask layer with a thickness of 100nm to 150nm is formed on the boron emitter layer.

[0163] The foregoing has provided a detailed description of the front structure of a solar cell, the solar cell and its fabrication method, and the photovoltaic module disclosed herein. Specific examples have been used to illustrate the principles and implementation methods of this disclosure. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this disclosure. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this disclosure. Therefore, the content of this specification should not be construed as a limitation of this disclosure.

Claims

1. A front-side structure of a solar cell, characterized in that, include: Boron emitter layer; Passivation film; The front current collector line forms direct physical contact with the boron emitter layer in some areas and indirect physical contact through the passivation film layer in other areas. The total doping concentration of the boron emitter layer is 2.8 × 10⁻⁶. 18 atoms / cm 3 ~4.0×10 18 atoms / cm 3 .

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 × 10⁻⁶. 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-side 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 in direct physical contact has a silver-silicon eutectic matrix and a silver-silicon eutectic overflow, and the region in direct physical contact also has a silver crystal that is electrically 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 crystal includes a main crystal chain and crystalline side chains extending from the main crystal chain in a growth direction different from that of the main crystal chain.

9. The front structure of the solar cell according to claim 7, characterized in that, The region of indirect physical contact has conductive aggregates, and the passivation film layer is located between the conductive aggregates and the boron emitter layer; wherein, the conductive aggregates include glass phase material and metal conductive particles, and the metal conductive particles have the same type of metal element as the silver crystal.

10. A solar cell, characterized in that, The solar cell includes the front-side structure of the solar cell as described in any one of claims 1 to 9.

11. A method for preparing a solar cell as described in claim 10, characterized in that, Includes the following steps: A texturized silicon wafer is provided as a silicon substrate. The silicon substrate is placed in a boron diffusion furnace, and a boron emitter layer is prepared on the front side of the silicon substrate by a boron diffusion process. A tunneling passivation layer and a phosphorus-doped polycrystalline silicon layer are sequentially formed on the back side of the silicon substrate; A passivation film layer is sequentially formed on the boron emitter layer, and a back passivation layer is formed on the phosphorus-doped polycrystalline silicon layer; Electrode paste is printed on the passivation film layer and the back passivation layer; High-temperature pre-sintering causes the electrode paste printed on the passivation film layer to form a front current collector precursor, and causes the electrode paste printed on the back passivation layer to form a back electrode. The front current collector line precursor is subjected to laser-induced contact treatment to form the front current collector line.

12. The preparation method according to claim 11, characterized in that, The process of fabricating a boron emitter layer on the front side of the silicon substrate using a boron diffusion process includes: Pre-oxidation process: The temperature of the boron diffusion furnace is T1, the pressure of the furnace tube is P1, and oxygen and nitrogen are introduced into the boron diffusion furnace. Among them, 750℃≤T1≤850℃, 230mPa≤P1≤270mPa, oxygen flow rate is 800sccm~2000sccm, and nitrogen flow rate is 200sccm~1000sccm. Multi-stage deposition process: The temperature of the boron diffusion furnace is T2, the pressure of the furnace tube is P2, oxygen, nitrogen and boron source gas are introduced into the boron diffusion furnace in stages, and the temperature inside the furnace in each stage is increased step by step. Among them, 750℃≤T2≤850℃, oxygen flow rate is 200sccm~600sccm, 230mPa≤P2≤270mPa, nitrogen flow rate is 3000sccm~5000sccm, and boron source gas flow rate is 80sccm~150sccm. Multi-stage PN junction process: The temperature of the boron diffusion furnace is T3, the pressure of the furnace tube is P3, and nitrogen gas is introduced into the boron diffusion furnace. Among them, 850℃≤T3≤950℃, 580mPa≤P3≤620mPa, and the nitrogen gas flow rate is 3000sccm~5000sccm. Post-oxidation process: The temperature of the boron diffusion furnace is T4, the pressure of the furnace tube is P4, oxygen is introduced into the boron diffusion furnace to form a silicon oxide mask layer with a thickness of 50nm to 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 to 5.

16. The preparation method according to claim 12, characterized in that, The multi-stage deposition process includes: First deposition stage: the 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, wherein 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: 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, wherein 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; 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, wherein 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 laser-induced contact treatment on the front current collector line precursor includes: Laser-induced contact processing is performed on the front side of the silicon substrate to the front current collector line precursor.

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

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