Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to the field of solar cells, and discloses a solar cell, a preparation method thereof and a photovoltaic module. The solar cell comprises a cell substrate and an electrode arranged on the cell substrate, a plurality of pore structures are arranged in the electrode, the electrode has an electrode cross section perpendicular to the length direction of the electrode, the total area of the plurality of pore structures on the electrode cross section is S1, the area of the electrode cross section is S2, s1 and S2 meet the condition that S1 / S2 is more than 1% and less than or equal to 15%. The carrier transmission capability in the electrode of the solar cell is high, and the structural stability of the electrode is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a solar cell, a preparation method of the solar cell, a solar cell and a photovoltaic module. BACKGROUND

[0002] In a solar cell, an electrode contacts a cell substrate, thereby realizing collection of carriers. The pore structure in the electrode not only affects the transmission performance of the carriers in the electrode, but also affects the structural stability of the electrode. Therefore, how to optimize the transmission performance of the carriers in the electrode while improving the structural stability of the electrode is a problem to be solved at present. SUMMARY

[0003] Embodiments of the present application disclose a solar cell, a preparation method of the solar cell and a photovoltaic module. The solar cell has high carrier transmission capacity in the electrode and good structural stability of the electrode.

[0004] In a first aspect, the present application discloses a solar cell, which comprises a cell substrate and an electrode arranged on the cell substrate, the electrode has a plurality of pore structures, the electrode has an electrode cross section perpendicular to the length direction of the electrode, the total area of the plurality of pore structures on the electrode cross section is S1, the area of the electrode cross section is S2, and the S1 and the S2 satisfy: 1% < S1 / S2 ≤ 15%.

[0005] Further, the S1 is 1.5 μm 2 ~10 μm 2 ; and / or, the S2 is 55 μm 2 ~80 μm 2 .

[0006] Further, the pore diameter of any of the pore structures is 0.05 μm ~ 0.60 μm.

[0007] Further, the electrode on the cell substrate has m1 test points, the average resistivity of the m1 test points is 0.5 Ω·cm 2 ~2.0 Ω·cm 2 , wherein the m1 is a positive integer greater than or equal to 2.

[0008] Further, the difference between the resistivity of the test point and the average resistivity is x1, the number of the test points satisfying the x1 is n1, the ratio of the n1 to the m1 is 55% ~ 99%, and the x1 is -0.2 Ω·cm 2 ~0.2 Ω·cm 2 .

[0009] Further, a ratio of a thickness and an average width of any one of the electrode sections is 55% to 99%.

[0010] Further, the thickness of the electrode is 5.5 μm to 8.5 μm; and / or, the average width of the electrode is 7 μm to 13 μm; and / or, a spacing between two adjacent electrodes is 0.75 μm to 1.25 μm; and / or, the electrode section is a circular arc structure.

[0011] Further, the battery substrate includes a first region where the electrode is arranged and a second region outside the first region. Any one of the 1 μm x 1 μm regions has m2 pyramid structures, and the m2 is a positive integer greater than or equal to 2. In any one of the 1 μm x 1 μm regions, the truncated mean of the heights of the m2 pyramid structures is a, the difference between the height of any one of the pyramid structures and the truncated mean is x2, the number of the pyramid structures satisfying the x2 is n2, and a ratio of the n2 to the m2 is 60% to 99%, where the x2 is 0.05 μm to 0.5 μm.

[0012] Further, the battery substrate includes a first region where the electrode is arranged and a second region outside the first region.

[0013] Further, the solar cell is a passivated contact solar cell, the electrode includes a first electrode and a second electrode, and the battery substrate includes: a substrate including a light-receiving surface and a back surface arranged opposite to each other; a diffusion doped layer, a first functional layer, and the first electrode are sequentially arranged on the light-receiving surface of the substrate; a passivated contact structure, a second functional layer, and the second electrode are sequentially arranged on the back surface of the substrate, and the passivated contact structure includes a dielectric layer and a doped silicon layer sequentially stacked on the back surface; The first functional layer is a first passivation layer and / or a first anti-reflection layer, the second functional layer is a second passivation layer and / or a second anti-reflection layer, the first electrode is in ohmic contact with the diffusion doped layer, and the second electrode is in ohmic contact with the doped silicon layer.

[0014] In a second aspect, the embodiments of the present application disclose a preparation method of a solar cell, and the preparation method includes the following steps: printing an electrode paste on a battery substrate; heating the electrode paste to a peak temperature, and then decreasing the peak temperature to a preset temperature to obtain the electrode, wherein the electrode has a plurality of pore structures, the electrode has an electrode cross section perpendicular to the length direction of the electrode, the total area of the plurality of pore structures on the electrode cross section is S1, the area of the electrode cross section is S2, and the S1 and the S2 satisfy: 1% < S1 / S2 ≤ 15%; and the solar cell according to any one of the first aspect.

[0015] Further, in the step of then decreasing the peak temperature to a preset temperature, the rate of temperature decrease is 350 ℃ / min ~ 600 ℃ / min.

[0016] Further, the ratio of the temperature increase time to the temperature decrease time is 1 ~ 1.5; and / or, the temperature increase time is 25 s ~ 50 s, and the temperature decrease time is 20 s ~ 50 s; and / or, the difference between the peak temperature and the preset temperature is 250 ℃ ~ 500 ℃; and / or, when preparing the electrode on the back light surface of the battery substrate, the peak temperature is 600 ℃ ~ 750 ℃; and / or, when preparing the electrode on the light receiving surface of the battery substrate, the peak temperature is 670 ℃ ~ 800 ℃; and / or, the preset temperature is 250 ℃ ~ 500 ℃.

[0017] Further, the battery substrate comprises a substrate, and the step of preparing a pyramid structure on the substrate comprises: etching the substrate by using an alkali and a texturing additive to prepare the pyramid structure on the substrate, wherein the ratio of the mass percentage content of the alkali to the mass percentage content of the additive is 1.4 ~ 2.2, and the time is 440 s ~ 700 s.

[0018] Further, the mass percentage content of the alkali is 1.5 wt% ~ 6.0 wt%, and the mass percentage content of the texturing additive is 1.1 wt% ~ 4.2 wt%; and / or, the mass of the substrate before preparing the pyramid structure is a, and the mass of the substrate after preparing the pyramid structure is b, and the a and the b satisfy: a-b = 0.25 g ~ 0.5 g; and / or, the reflectivity of the substrate after preparing the pyramid structure is 5.5% ~ 9.0%; and / or, the alkali is sodium hydroxide.

[0019] In a third aspect, the embodiments of the present application disclose a photovoltaic module, comprising the solar cell of any one of the first aspect; or the solar cell prepared by the preparation method of any one of the second aspect.

[0020] Compared with the prior art, the present application has the beneficial effects that: The present application discloses a solar cell, a preparation method thereof and a photovoltaic module. By controlling the ratio of the hole structure area S1 in the electrode to the area S2 of the electrode cross section within a specific range, the transmission capacity of the carriers in the electrode is improved, and the structural stability of the electrode is also improved.

[0021] Specifically, when S1 and S2 satisfy 1% < S1 / S2 ≤ 15%, the compactness of the electrode material is appropriate, thereby effectively reducing the bulk resistance of the electrode, improving the conductivity of the electrode, reducing the transmission barrier of the carriers in the electrode, reducing the diffusion difficulty of the carriers, and improving the photoelectric conversion efficiency of the solar cell. In addition, when S1 and S2 satisfy 1% < S1 / S2 ≤ 15%, the electrode can provide appropriate space to respond to the expansion or contraction of the electrode material caused by temperature changes, thereby helping to reduce the internal stress of the electrode to a higher degree and improving the structural stability of the electrode; the above range also enables the electrode to form a stable support structure, avoids the phenomenon of structural cracking and collapse of the electrode during solder strip welding, and further ensures the structural stability of the electrode. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings used in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0023] Figure 1 is a structural schematic diagram of an electrode provided by the embodiments of the present application; Figure 2 is a scanning electron microscope image of an electrode provided by the embodiments of the present application; Figure 3 is a scanning electron microscope image of the contact interface between the electrode and the pyramid structure provided by the embodiments of the present application; Figure 4 is a structural schematic diagram of a solar cell provided by the embodiments of the present application; Figure 5 is a distribution schematic diagram of the resistivity of a plurality of test points on a solar cell provided by the embodiments of the present application.

[0024] Icons: 1. Battery substrate; 1a. Pyramid structure; 11. Substrate; 11a. Light-receiving surface; 11b. Backlight-receiving surface; 12. Diffusion-doped layer; 13. First functional layer; 131. First passivation layer; 132. First antireflection layer; 14. Passivation contact structure; 141. Dielectric layer; 142. Doped silicon layer; 15. Second functional layer; 2. Electrode; 21. Hole structure; 2a. First electrode; 2b. Second electrode. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] In this application, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.

[0027] 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 some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0028] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (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, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0029] The technical solutions provided in this application will be further described below with reference to the embodiments and accompanying drawings.

[0030] In solar cells, electrodes are used to transport charge carriers generated in the cell substrate to external circuits. The transport capacity of charge carriers in the cell substrate affects the photoelectric conversion efficiency of the solar cell. Specifically, the transport efficiency of charge carriers within the electrodes is related to the pore structure of the electrodes. Excessive pores can significantly reduce the conductivity of the electrodes, increase the transport barrier for charge carriers, and weaken the structural stability of the electrodes. Therefore, adopting a low-porosity electrode design can effectively reduce the difficulty of charge carrier transport and enhance the structural stability of the electrodes themselves.

[0031] However, the applicant discovered that low-porosity electrodes exacerbate the accumulation of internal stress within the electrodes, affecting their long-term stability. This is because solar cells operate outdoors for extended periods, where temperatures fluctuate significantly. In high-temperature environments, electrode materials expand due to heat, while in low-temperature environments, they contract due to cold. Low-porosity electrodes struggle to effectively cope with these expansions and contractions caused by temperature changes, resulting in higher internal stress and consequently lower structural stability during long-term use.

[0032] Based on the above problems, this application provides a solar cell and its preparation method, as well as a photovoltaic module. Using this solar cell can effectively optimize the diffusion ability of charge carriers in the electrode and improve the structural stability of the electrode.

[0033] This application provides a solar cell, such as... Figure 1 and Figure 2 As shown, the solar cell includes a cell substrate 1 and an electrode 2 disposed on the cell substrate 1. The electrode 2 has multiple hole structures 21 and an electrode cross section perpendicular to the length direction of the electrode 2. The total area of ​​the multiple hole structures 21 on the electrode cross section is S1, and the area of ​​the electrode cross section is S2. S1 and S2 satisfy: 1% < S1 / S2 ≤ 15%.

[0034] Here, pore structure 21 refers to a structure that has cavities and gaps inside; that is, in the electrode cross-section, pore structure 21 refers to the black area in the electrode cross-section diagram (see...). Figure 2 (As indicated by the red circle in the image). Furthermore, the area of ​​the electrode cross-section refers to the sum of the total area of ​​the hole structures 21 on that cross-section and the total area of ​​the electrode material, that is, the area of ​​the pattern formed by the contour lines in the electrode cross-section (see [reference]). Figure 2 The red line at the outline of the middle electrode 2.

[0035] Additionally, electrode 2 includes a main grid and a sub-grid connected to the main grid. The sub-grid is a structure used to form an ohmic contact with the battery substrate 1. The electrode cross-section can be rectangular or arc-shaped. Preferably, when the electrode cross-section is arc-shaped, the narrower top helps to reduce shading and improve the absorption and utilization rate of sunlight, while the wider bottom makes the contact surface between electrode 2 and battery substrate 1 larger, thereby helping to reduce contact resistance and improve carrier transport performance.

[0036] The battery substrate 1 refers to the semi-finished product to be sintered, in which each functional film layer has been prepared and electrode paste has been printed on the functional film layer. The functional film layer refers to the film layer structure with specific electrical or optical properties deposited on the substrate, and the film layer type of the functional film layer is related to the solar cell type. For example, when the solar cell is a heterojunction solar cell, its corresponding functional film layer includes a passivation layer, a doped silicon layer, and a transparent conductive layer.

[0037] Furthermore, this application employs focused ion beam (FIB) to cut electrode 2, exposing electrode cross-sections at different locations. This is further combined with scanning electron microscopy (SEM) to obtain cross-sectional images. Finally, image processing software (imageJ) is used to calculate the total area of ​​the pore structure 21 in these cross-sectional images and the area of ​​the electrode cross-section, thus obtaining their area ratio. Specifically, this application first uses focused ion beam and scanning electron microscopy to obtain multiple cross-sectional images of electrode 2 at different locations along its length. Then, image processing software is used to calculate the ratio of the total area of ​​the pore structure 21 to the area of ​​the electrode cross-section in these multiple images, and the average of these multiple ratios is obtained. For example, the area ratios of the two ends and the middle portion along the length of electrode 2 can be obtained separately, and their average value can be calculated.

[0038] Alternatively, the corresponding area ratio can be obtained using three-dimensional reconstruction techniques of focused ion beam scanning electron microscopy (FIB-SEM). This application does not limit the specific method for obtaining the area ratio, as long as it achieves the desired effect.

[0039] This application controls S1 and S2 to satisfy: 1% < S1 / S2 ≤ 15%, which ensures suitable density of the electrode material. This effectively reduces the bulk resistance of electrode 2, improves its conductivity, lowers the transport barrier for charge carriers in electrode 2, thereby reducing the difficulty of charge carrier diffusion and improving the photoelectric conversion efficiency of the solar cell. Furthermore, when S1 and S2 satisfy the range of 1% < S1 / S2 ≤ 15%, electrode 2 not only provides suitable space to cope with the expansion or contraction of the electrode material caused by temperature changes, thus helping to significantly reduce the internal stress of electrode 2 and improve its structural stability, but also forms a stable support structure, preventing structural cracking and collapse of electrode 2 during welding, further ensuring the structural stability of electrode 2.

[0040] When S1 / S2 ≤ 1%, the electrode material becomes too dense, making it difficult for electrode 2 to cope with the contraction or expansion caused by external temperature changes. This exacerbates the accumulation of internal stress in electrode 2, leading to a sharp decline in the long-term stability of electrode 2. When S1 / S2 > 15%, the proportion of pore structures 21 in electrode 2 is too high, making it more prone to cracking or collapse under external forces. This makes it difficult for electrode 2 to form a stable support structure, resulting in decreased structural stability of electrode 2. In addition, it also reduces the conductivity of electrode 2, increases the transition barrier for charge carriers in electrode 2, and hinders the diffusion of charge carriers in electrode 2.

[0041] Furthermore, more preferably, when S1 and S2 are controlled to satisfy 3% ≤ S1 / S2 ≤ 10%, it is more conducive to improving the diffusion ability of charge carriers in electrode 2 while improving the structural stability of electrode 2, thereby helping to further improve the photoelectric efficiency of the solar cell. For example, S1 / S2 is 1.2%, 3%, 8%, 8%, 10%, or 15%, etc.

[0042] In summary, this application controls S1 / S2 to satisfy 1% < S1 / S2 ≤ 15%, which helps to improve the structural stability of electrode 2 and reduce the diffusion difficulty of charge carriers in electrode 2, thereby helping to improve the photoelectric conversion efficiency of solar cells.

[0043] Furthermore, S1 is 1.5 μm 2 ~10 μm 2 S2 is 55 μm 2 ~80 μm 2 By controlling S1 and S2 within the aforementioned ranges, the density of the electrode material becomes more suitable, thereby enhancing the diffusion capacity of charge carriers within electrode 2 while better ensuring its structural stability, ultimately contributing to further improving the photoelectric conversion efficiency of the solar cell. For example, S1 is 1.5 μm.2 4.6 μm 2 6 μm 2 8 μm 2 or 10 μm 2 etc.; S1 is 55 μm 2 62 μm 2 70 μm 2 76 μm 2 or 80 μm 2 wait.

[0044] Furthermore, the pore size of any pore structure 21 is between 0.05 μm and 0.60 μm. When the pore size of the pore structure 21 is within this range, it helps to further reduce the difficulty of carrier diffusion and enables the pore structure 21 to better cope with the shrinkage and expansion properties of the electrode material under temperature changes, thereby helping to further improve the structural stability of the electrode 2. For example, the pore size is 0.05 μm. 2 0.15 μm 2 0.3 μm 2 0.45 μm 2 or 0.60 μm 2 wait.

[0045] Here, the aperture refers to the maximum distance between two relative boundary points in the hole structure 21. For example, when the hole structure 21 is elliptical, the aperture refers to the major axis of the ellipse; when the hole structure 21 is circular, the aperture refers to the diameter of the circle. The aperture value of the hole structure 21 can be directly measured using image processing software in the electrode cross-sectional image obtained by scanning electron microscopy. This application does not limit the specific method for measuring the aperture; any method that achieves the desired effect is acceptable.

[0046] Furthermore, electrode 2 has m1 test points, and the average resistivity of the m1 test points is 0.5 Ω·cm. 2 ~2.0Ω·cm 2 Where m1 is a positive integer greater than or equal to 2. When the average resistivity of electrode 2 is within the above range, it indicates that the contact performance between electrode 2 and battery substrate 1 is high, which is more conducive to promoting carrier transport. For example, the average resistivity is 0.5 Ω·cm. 2 0.8Ω·cm 2 1.2Ω·cm 2 1.6Ω·cm 2 or 2.0Ω·cm 2 wait.

[0047] Furthermore, the difference between the resistivity of the test point and the average resistivity is x1, the number of test points satisfying x1 is n1, the ratio of n1 to m1 is 55%~99%, and x1 is -0.2 Ω·cm. 2 ~0.2 Ω·cm 2 When the ratio of n1 to m1 of x1 is within the above range, it indicates that the contact performance between the electrode 2 and the cell substrate 1 in different regions of the solar cell is good, thereby ensuring the carrier transport performance in different regions and further improving the photoelectric conversion efficiency of the solar cell. For example, the ratio is 55%, 70%, 80%, 90%, or 99%, etc.

[0048] Furthermore, the ratio of the thickness to the average width of any electrode cross-section is 55% to 99%.

[0049] Thickness H refers to the thickness direction along electrode 2 (see [reference]). Figure 1 The vertical distance between the highest and lowest points of the electrode cross-section (in the Y direction); the average width refers to the average width of the electrode cross-section at different locations, such as the average of the top width, middle width, and bottom width of the electrode cross-section.

[0050] When the ratio is within the above range, it can effectively reduce the shading area of ​​electrode 2, reduce its obstruction of sunlight, and thus help improve the absorption and utilization rate of sunlight; furthermore, it also helps to reduce the resistance of electrode 2, improve carrier transport efficiency, reduce series resistance loss, and ultimately improve the photoelectric conversion efficiency of the solar cell. For example, the ratio is 55%, 65%, 75%, 85%, or 99%, etc.

[0051] The thickness of electrode 2 is 5.5 μm to 8.5 μm. Controlling the thickness of electrode 2 within this range helps to further ensure the conductivity of electrode 2; and the aforementioned thickness also helps to reduce the difficulty of solder strip welding and improve the performance of solder strip welding. For example, the thickness of electrode 2 is 5.5 μm, 6.2 μm, 7.0 μm, 7.8 μm, or 8.5 μm, etc.

[0052] Furthermore, the average width of electrode 2 is 7 μm to 13 μm. When the average width of electrode 2 is within the above range, it helps to reduce the blocking effect of electrode 2 on sunlight, and further improves the absorption and utilization rate of sunlight. For example, the average width is 7 μm, 8.5 μm, 10 μm, 11.5 μm, or 13 μm, etc.

[0053] Furthermore, the spacing between two adjacent electrodes 2 is 0.75μm~1.25μm.

[0054] The spacing refers to the vertical distance between two adjacent electrodes 2. For example, when electrode 2 includes a sub-gate, the spacing refers to the vertical distance between two adjacent sub-gates.

[0055] When the spacing between two adjacent electrodes 2 is within the aforementioned range, it not only further ensures the carrier collection capability of the electrodes 2, but also helps to further improve the absorption and utilization rate of sunlight. For example, the spacing is 0.75μm, 0.9μm, 1.0μm, 1.1μm, or 1.25μm, etc.

[0056] Furthermore, the battery substrate 1 includes a first region and a second region located outside the first region, the first region being the region where the electrode 2 is disposed; The first region includes multiple 1μm×1μm regions, and each 1μm×1μm region contains m2 pyramid structures 1a, where m2 is a positive integer greater than or equal to 2. Within any 1μm×1μm region, the truncated mean of the heights of m2 pyramid structures 1a is a, the difference between the height of any pyramid structure 1a and the truncated mean is x2, and the number of pyramid structures 1a satisfying x2 is n2, the ratio of n2 to m2 is 60%~99%, where x2 is 0.05μm~0.5μm.

[0057] The truncated mean refers to the average of the remaining data after removing the maximum and minimum values ​​from a dataset to eliminate the influence of extreme values ​​(or outliers).

[0058] When the ratio is within the above range, it indicates that the height uniformity of the pyramid structure 1a in the first region is good, which helps to increase the contact area between the electrode 2 and the pyramid structure 1a, thereby further improving the charge carrier collection capability of the electrode 2. For example, the ratio is 60%, 70%, 80%, 90%, or 99%.

[0059] In addition, combined Figure 3 It can be seen that, Figure 3 The left area in the middle (i.e. Figure 3 The pyramid structure 1a in region A has high height uniformity, so the contact area between electrode 2 and battery substrate 1 in this region is large, which helps to further improve the photoelectric conversion efficiency of solar cells.

[0060] Furthermore, the surface roughness value in the first region is higher than that in the second region. By setting the first region with lower roughness, the contact performance between the electrode 2 and the battery substrate 1 can be further optimized, and the contact resistance can be reduced; by setting the second region with higher roughness, it is more conducive to utilizing the light-trapping effect of the pyramid structure 1a in the second region, thereby further improving the absorption and utilization rate of sunlight.

[0061] Furthermore, the solar cell includes a back-contact solar cell, a PERC solar cell, or a passivated contact solar cell.

[0062] Among them, such as Figure 4 As shown, when the solar cell is a passivated contact solar cell, electrode 2 includes a first electrode 2a and a second electrode 2b, and the cell substrate 1 includes: Substrate 11, which includes a light-receiving surface 11a and a backlight surface 11b disposed opposite to each other; A diffusion doped layer 12, a first functional layer 13, and a first electrode 2a are sequentially disposed on the light-receiving surface 11a of the substrate 11. A passivation contact structure 14, a second functional layer 15, and a second electrode 2 are sequentially disposed on the backlight surface 11b of the substrate 11. The passivation contact structure 14 includes a dielectric layer 141 and a doped silicon layer 142 sequentially stacked on the backlight surface 11b. The first functional layer 13 is a first passivation layer 131 and / or a first antireflection layer 132, the second functional layer 15 is a second passivation layer and / or a second antireflection layer, the first electrode 2a is in ohmic contact with the diffused doped layer 12, and the second electrode 2b is in ohmic contact with the doped silicon layer 142.

[0063] This application discloses a method for fabricating a solar cell, the method comprising the following steps: Electrode paste is printed onto the battery substrate; First, the electrode slurry is heated to a peak temperature, and then cooled to a preset temperature to obtain an electrode. The electrode has multiple pore structures and an electrode cross-section perpendicular to its length direction. The total area of ​​the multiple pore structures on the electrode cross-section is S1, and the area of ​​the electrode cross-section is S2. S1 and S2 satisfy: 1% < S1 / S2 ≤ 15%; the above-mentioned solar cell is obtained.

[0064] In the subsequent step of reducing the peak temperature to the preset temperature, the cooling rate is 350 ℃ / min to 600 ℃ / min.

[0065] This application limits the cooling rate within the aforementioned range, which helps avoid the phenomenon of increased number and area of ​​pore structures caused by thermal stress concentration or incomplete gas emission. This further helps control S1 and S2 to satisfy 1% < S1 / S2 ≤ 15%, thereby improving the photoelectric conversion efficiency of the solar cell to a greater extent. For example, the cooling rate is 350 ℃ / min, 400 ℃ / min, 450 ℃ / min, 500 ℃ / min, 550 ℃ / min, or 600 ℃ / min, etc.

[0066] Furthermore, the ratio of heating time to cooling time is 1 to 1.5. By controlling the ratio of heating time to cooling time within the above range, the electrode sintering effect is good, the amount of gas generated is appropriate, and it is easier to discharge the gas from the electrode during cooling, thereby helping to ensure that S1 / S2 is within the scope of this application. For example, the ratio is 1, 1.1, 1.2, 1.3, 1.4, or 1.5, etc.

[0067] The heating time is 25 s to 50 s, and the cooling time is 20 s to 50 s. Controlling the heating and cooling times within these ranges effectively controls the curing rate of the electrode slurry, ensuring good contact performance with the battery substrate. It also effectively controls the amount of gas generated and the degree of thermal stress accumulation, allowing sufficient time for gas release and thermal stress relief during cooling, thus contributing to a significant improvement in electrode performance. For example, the heating time can be 25 s, 30 s, 35 s, 40 s, 45 s, or 50 s; and the cooling time can be 20 s, 30 s, 35 s, 40 s, 45 s, or 50 s.

[0068] The difference between the peak temperature and the preset temperature is 250℃ to 500℃. By controlling the difference between the peak temperature and the preset temperature within this range, the generation of thermal stress can be effectively suppressed, thereby helping to improve the structural stability of the electrode to a greater extent. For example, the difference can be 250℃, 300℃, 350℃, 400℃, 450℃, or 500℃, etc.

[0069] When preparing the electrode on the back surface of the battery substrate, the peak temperature is 600℃~750℃; when preparing the electrode on the light-receiving surface of the battery substrate, the peak temperature is 670℃~800℃; the preset temperature is 250℃~500℃.

[0070] Controlling the peak temperature and preset temperature parameters of the electrode preparation within the above range helps to improve the sintering effect of the electrode slurry, effectively suppresses the generation of thermal stress, and thus improves the structural stability and carrier transport performance of the electrode to a greater extent.

[0071] In addition, the battery substrate includes a base, and the steps for fabricating the pyramid structure on the base include: A pyramid structure was fabricated on a substrate by etching with an alkali and a texturing additive, wherein the mass percentage ratio of the alkali to the additive was 1.4 to 2.2, and the etching time was 440 s to 700 s.

[0072] The type of the texturing additive is TS57V12; the alkali is sodium hydroxide.

[0073] By controlling the mass percentage ratio of the reagents and the time within the above-mentioned range, the height of the prepared pyramid structure is more uniform, which helps to improve the contact performance between the electrode and the battery substrate and enhance the carrier transport capacity. For example, the ratios are 1.4, 1.6, 1.8, 2.0, or 2.2, etc.; and the times are 440 s, 500 s, 550 s, 600 s, 650 s, or 700 s, etc.

[0074] Furthermore, the alkali content ranges from 1.5 wt% to 6.0 wt%, and the texturing additive content ranges from 1.1 wt% to 4.2 wt%. By controlling the alkali and texturing additive content within these ranges, the uniformity of substrate corrosion is improved, which helps to ensure a higher degree of uniformity in the height of the prepared pyramid structure and further helps to ensure the contact performance between the electrode and the battery substrate. For example, the alkali content is 1.5 wt%, 2.5 wt%, 3.5 wt%, 5.5 wt%, or 6.0 wt%, and the texturing additive content is 1.1 wt%, 2.0 wt%, 2.5 wt%, 3.5 wt%, or 4.2 wt%, etc.

[0075] Furthermore, the mass of the substrate before the pyramid structure is fabricated is m1, and the mass of the substrate after the pyramid structure is fabricated is m2. m1 and m2 satisfy the condition: m1 - m2 = 0.25 g ~ 0.5 g. By controlling the mass difference within this range, the structural stability of the fabricated solar cell is effectively ensured, preventing problems such as cell cracking and improving the long-term stability of the solar cell. For example, the mass difference can be 0.25 g, 0.3 g, 0.35 g, 0.4 g, or 0.5 g, etc.

[0076] The reflectivity of the substrate after fabricating the pyramid structure is 5.5% to 9.0%. By controlling the reflectivity within this range, it is easier to improve the absorption and utilization rate of sunlight, thereby improving the photoelectric conversion efficiency of the solar cell.

[0077] This application discloses a photovoltaic module, which includes: the solar cell described above; or a solar cell prepared by the above-described preparation method.

[0078] This application discloses a photovoltaic module, which includes the aforementioned solar cell.

[0079] The technical solution of this application will be further explained below with reference to more specific embodiments and experimental test results.

[0080] Example 1: This embodiment provides a method for fabricating a solar cell: Preparation of battery substrate: Pyramid structure fabrication on N-type silicon substrate: The silicon substrate was etched using 3% sodium hydroxide and 1.5% texturing additive to fabricate the pyramid structure. The etching time was 550 s. The difference between the mass 'a' of the silicon substrate before and after pyramid structure fabrication was 4 g. The reflectivity of the substrate was 7%, and the ratio of n2 to m2 was 80%.

[0081] The prepared pyramid-shaped silicon substrate is placed in a boron diffusion furnace, and boron trichloride gas is diffused at 1000℃~1080℃ to form a diffusion layer on the light-receiving surface of the silicon substrate.

[0082] The back surface of the silicon substrate is polished using a chain-type HF device.

[0083] A dielectric layer with a thickness of 1 nm was prepared on the gate line region and non-gate line region of the backlight surface of a silicon substrate. The silicon substrate was placed in a PECVD device, and N2O with a flow rate of 12000 sccm was introduced. The power was 12000 W and the reaction time was 80 s. A 40 nm thick doped silicon layer was fabricated on the dielectric layer: A first functional layer is sequentially fabricated from the inside to the outside on the side of the diffusion layer away from the silicon substrate. The first functional layer includes an aluminum oxide layer with a thickness of 5 nm and a silicon nitride layer with a thickness of 10 nm. A second functional layer is fabricated on the conductive layer. The second functional layer includes a silicon nitride functional layer with a thickness of 10 nm.

[0084] The first electrode is fabricated on the first functional layer: Electrode paste is printed onto the battery substrate; The electrode slurry was first heated to a peak temperature, then cooled to a preset temperature to obtain the first electrode. The cooling rate was 500 °C / min, the peak temperature was 700 °C, the preset temperature was 350 °C, the heating time was 35 s, and the cooling time was 35 s. The resulting first electrode had an S1 / S2 ratio of 5% and an S1 particle size of 3.5 μm. 2 S2 is 70 μm 2 The pore size of any given pore structure ranges from 0.10 μm to 0.45 μm, and the average resistivity of the 30 test points is 1.7 Ω·cm. 2 The ratio of electrode cross-section thickness to average width is 80%, electrode thickness is 6.5 μm, spacing between adjacent electrodes is 1 μm, average electrode width is 10 μm, and ratio of n1 to m1 is 80%.

[0085] The second electrode is fabricated on the second functional layer: Electrode paste is printed onto the battery substrate; The electrode slurry was first heated to a peak temperature, then cooled to a preset temperature to obtain a second electrode. The cooling rate was 500 °C / min, the peak temperature was 700 °C, the preset temperature was 350 °C, the heating time was 35 s, and the cooling time was 35 s. The resulting second electrode had an S1 / S2 ratio of 5%, with S1 having a particle size of 3. μm. 2 S2 is 75 μm 2 The pore size of any given pore structure ranges from 0.15 μm to 0.50 μm, and the average resistivity of the 30 test points is 1.7 Ω·cm. 2 The ratio of electrode cross-section thickness to average width is 75%, the electrode thickness is 6.5 μm, the spacing between adjacent electrodes is 1 μm, the average electrode width is 10 μm, and the ratio of n1 to m1 is 80%.

[0086] Example 2: The only difference between this embodiment and Embodiment 1 is that S1 / S2 equals 10%.

[0087] Example 3: The only difference between this embodiment and Embodiment 1 is that S1 / S2 equals 0.8%.

[0088] Example 4: The only difference between this embodiment and Embodiment 1 is that S1 / S2 equals 15%.

[0089] Example 5: The only difference between this embodiment and Embodiment 1 is that the pore diameter of any pore structure is greater than 1.0 μm.

[0090] Example 6: The only difference between this embodiment and Embodiment 1 is that the ratio of n2 to m2 is 60%.

[0091] Example 7: The only difference between this embodiment and Embodiment 1 is that the ratio of n2 to m2 is 50%.

[0092] Comparative Example 1: The difference between this comparative example and Example 1 is that S1 / S2 equals 0.5%.

[0093] Comparative Example 2: The difference between this comparative example and Example 1 is that S1 / S2 equals 17%.

[0094] Performance testing: Resistivity test: like Figure 5 As shown, Figure 5This diagram illustrates the resistivity distribution on the electrode at different test points provided in Example 1. A TLM testing machine (model: TLM-SCAN, manufacturer: Shanghai Shunmiao Optoelectronic Technology Co., Ltd.) was used to perform probe pressing tests on the solar cells of each example and comparative example to obtain the contact resistivity of the solar cells. Furthermore, 30 test points were used. As shown in the diagram, the resistivity at these 30 points is mainly concentrated at 1.0 Ω·cm. 2 ~1.4Ω·cm 2 Within a certain range, it indicates that the electrode has high resistivity uniformity, which is more conducive to the electrode collecting charge carriers from the battery substrate.

[0095] Testing of solar cell performance: The solar cells prepared in Examples 1 to 7 and Comparative Examples 1 to 2 were subjected to the following related tests: This application describes the performance testing of a solar cell using the Wavelabs solar simulator, including open-circuit voltage, short-circuit current, and fill factor. The Wavelabs simulator is a device that simulates sunlight, and when combined with electronic loads, data acquisition, and computing equipment, it is used to test the electrical performance of photovoltaic devices (including solar cells), such as Eta, Voc, Jsc, and FF, which reflect the performance of the solar cell. Test conditions: AM1.5, 1000 W / m 2 The test environment temperature was 25℃, and the effective battery area was 20.38 cm². 2 The experimental test results are as follows, where Voc represents the open-circuit voltage, Jsc represents the short-circuit current density, FF represents the fill factor, and Eta represents the photoelectric conversion efficiency.

[0096] Table 1 Performance test results of solar cells

[0097] Analysis of the data from Examples 1 to 4 and Comparative Examples 1 and 2 shows that the photoelectric conversion efficiency of Examples 1 to 4 is superior to that of Comparative Examples 1 and 2. It is evident that controlling S1 and S2 to satisfy 1% < S1 / S2 ≤ 15% results in suitable electrode compactness, reduces the transport barrier of charge carriers in the electrode, lowers the diffusion difficulty of charge carriers, and improves the photoelectric conversion efficiency of the solar cell. Furthermore, the electrode provides suitable space to cope with the expansion or contraction of the electrode material caused by temperature changes, thereby helping to reduce the internal stress of the electrode to a greater extent and improve the structural stability of the electrode.

[0098] Analysis of Examples 1 to 4 shows that the photoelectric conversion efficiency of Examples 1 and 2 is better than that of Examples 3 and 4. This indicates that the ratio of S1 to S2 in Examples 1 and 2 is more suitable, and a more suitable ratio is more conducive to improving the carrier transport capability and the structural stability of the electrode.

[0099] Analysis of the data from Examples 1 and 5 shows that the photoelectric conversion efficiency of Example 1 is better than that of Example 5. This indicates that the pore size of the pore structure in Example 1 is more suitable. A more suitable pore size can further ensure the carrier transport capability and further improve the structural stability of the electrode.

[0100] Analysis of the data from Examples 1, 6, and 7 shows that the photoelectric conversion efficiency of Examples 1 and 6 is better than that of Example 7. This indicates that the pyramid structure in Examples 1 and 6 has better height uniformity. Better uniformity helps to increase the contact area between the electrode and the pyramid structure, thereby further improving the electrode's ability to collect charge carriers.

[0101] The solar cells, their preparation methods, and photovoltaic modules disclosed in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the solar cells, their preparation methods, and photovoltaic modules. 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 application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A solar cell, characterized by, The solar cell comprises a cell substrate and an electrode arranged on the cell substrate, the electrode has a plurality of hole structures therein, the electrode has an electrode section perpendicular to the length direction of the electrode, the total area of the plurality of hole structures on the electrode section is S1, the area of the electrode section is S2, and the S1 and the S2 satisfy: 1% < S1 / S2 ≤ 15%.

2. The solar cell according to claim 1, characterized in that, S1 is 1.5 μm 2 10 μm 2 ; and / or, S2 is 55 μm 2 ~80 μm 2 .

3. The solar cell according to claim 1, characterized in that, The aperture of any one of the hole structures is 0.05 μm to 0.60 μm.

4. The solar cell according to claim 1, characterized in that, The electrode on the battery base has m1 test points, and the average resistivity of the m1 test points is 0.5 Ω·cm 2 ~2.0 Ω·cm 2 wherein the m1 is a positive integer greater than or equal to 2.

5. The solar cell according to claim 4, characterized in that, The difference between the resistivity of the test point and the average resistivity is x1, the number of test points satisfying x1 is n1, the ratio of n1 to m1 is 55% to 99%, and x1 is -0.2 Ω·cm 2 -0.2 Ω·cm 2 .

6. The solar cell according to claim 1, characterized in that, The ratio of the thickness to the average width of any one of the electrode sections is 55% to 99%.

7. The solar cell according to claim 1, characterized in that, The thickness of the electrode is 5.5 μm to 8.5 μm; and / or, The average width of the electrode is 7 μm to 13 μm; and / or, The spacing between two adjacent electrodes is 0.75 μm to 1.25 μm; and / or, The electrode section is a circular arc structure.

8. The solar cell according to claim 1, characterized in that, The cell substrate comprises a first region and a second region outside the first region, and the first region is a region where the electrode is arranged; The first region comprises a plurality of 1 μm×1 μm regions, any one of the 1 μm×1 μm regions has m2 pyramid structures, and the m2 is a positive integer greater than or equal to 2; In any one of the 1 μm×1 μm regions, the truncated mean of the heights of the m2 pyramid structures is a, the difference between the height of any one of the pyramid structures and the truncated mean is x2, the number of the pyramid structures satisfying the x2 is n2, the ratio of the n2 to the m2 is 60% to 99%, and the x2 is 0.05 μm to 0.5 μm.

9. The solar cell according to claim 1, characterized in that, The cell substrate comprises a first region and a second region outside the first region, and the surface roughness value at the first region is higher than that at the second region.

10. The solar cell according to any one of claims 1 to 9, characterized in that The solar cell is a passivated contact solar cell, the electrode comprises a first electrode and a second electrode, and the cell substrate comprises: a substrate comprising a light-receiving surface and a back surface arranged oppositely; a diffusion doped layer, a first functional layer, and the first electrode are sequentially arranged on the light-receiving surface of the substrate; a passivated contact structure, a second functional layer, and the second electrode are sequentially arranged on the back surface of the substrate, and the passivated contact structure comprises a dielectric layer and a doped silicon layer which are sequentially arranged on the back surface; The first functional layer is a first passivation layer and / or a first anti-reflection layer, the second functional layer is a second passivation layer and / or a second anti-reflection layer, the first electrode is in ohmic contact with the diffusion doped layer, and the second electrode is in ohmic contact with the doped silicon layer.

11. A method of producing a solar cell, characterized by, The preparation method comprises the following steps: printing an electrode paste on a cell substrate; The electrode paste is heated to a peak temperature, and then reduced from the peak temperature to a preset temperature to obtain the electrode, wherein the electrode has a plurality of pore structures, the electrode has an electrode cross section perpendicular to the length direction of the electrode, the total area of the plurality of pore structures on the electrode cross section is S1, the area of the electrode cross section is S2, and the S1 and the S2 satisfy: 1% < S1 / S2 ≤ 15%; and the solar cell of any one of claims 1 to 10 is obtained.

12. The method of claim 11, wherein, In the step of then reducing from the peak temperature to a preset temperature, the cooling rate is 350 ℃ / min ~ 600 ℃ / min.

13. The method of claim 12, wherein, The ratio of the heating time to the cooling time is 1 ~ 1.5; and / or, The heating time is 25 s ~ 50 s, and the cooling time is 20 s ~ 50 s; and / or, The difference between the peak temperature and the preset temperature is 250 ℃ ~ 500 ℃; and / or, When the electrode of the back light surface of the battery substrate is prepared, the peak temperature is 600 ℃ ~ 750 ℃; and / or, When the electrode of the light receiving surface of the battery substrate is prepared, the peak temperature is 670 ℃ ~ 800 ℃; and / or, The preset temperature is 250 ℃ ~ 500 ℃.

14. The method of claim 11, wherein, The battery substrate comprises a substrate, and the step of preparing a pyramid structure on the substrate comprises: The substrate is etched by using an alkali and a texturing additive to prepare the pyramid structure on the substrate, wherein the mass percentage content ratio of the alkali and the additive is 1.4 ~ 2.2, and the time is 440 s ~ 700 s.

15. The preparation method according to claim 14, characterized in that, The mass percentage content of the alkali is 1.5 wt% ~ 6.0 wt%, and the mass percentage content of the texturing additive is 1.1 wt% ~ 4.2 wt%; and / or, The mass of the substrate before the pyramid structure is prepared is a, and the mass of the substrate after the pyramid structure is prepared is b, and the a and the b satisfy: a-b = 0.25 g ~ 0.5 g; and / or, The reflectivity of the substrate after the pyramid structure is prepared is 5.5% ~ 9.0%; and / or, The alkali is sodium hydroxide.

16. A photovoltaic module, characterized by The photovoltaic module comprises the solar cell of any one of claims 1 to 10; or comprises the solar cell prepared by the preparation method of any one of claims 11 to 15.

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