Conductive silver paste, electrodes, solar cells and their fabrication methods

Abstract

This application relates to a conductive silver paste, an electrode, a solar cell, and a method for preparing the same. The conductive silver paste comprises a composite glass frit and conductive powder. The composite glass frit comprises lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide, wherein the mass ratio α of silicon dioxide to aluminum oxide ranges from 1.5 to 2.5. The conductive powder comprises first conductive silver powder, second conductive silver powder, and conductive silver wire, wherein the size of the first conductive silver powder is less than 1 μm, and the size of the second conductive silver powder is larger than the size of the first conductive silver powder. The electrode formed by the conductive silver paste exhibits good bonding performance with the substrate, meeting the requirements for long-term stable operation of the solar cell.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, specifically to a conductive silver paste, an electrode, a solar cell, and a method for preparing the same. Background Technology

[0002] Currently, mass-produced N-type TOPCon solar cells generally employ screen-printed silver paste combined with high-temperature sintering to fabricate the back electrode. Existing silver paste formulations and processes are not specifically designed for the ultra-thin polycrystalline silicon layer on the back of the cell, resulting in insufficient adhesion between the fine grid and the polycrystalline silicon. These issues directly cause grid line desiccation, detachment, and cracking, leading to increased contact resistance and decreased photoelectric conversion efficiency in the solar cell. During production handling, lamination welding, and in outdoor humid and corrosive environments, the grid lines are prone to detachment and failure, significantly reducing cell reliability and lifespan, while also increasing the defect rate and mass production costs, making it difficult to meet the long-term stable operation requirements of solar cells. Summary of the Invention

[0003] In view of this, this application provides a conductive silver paste, an electrode, a solar cell, and a method for preparing the same. The electrode formed by the conductive silver paste has good bonding performance with the substrate, meeting the requirements for long-term stable operation of the solar cell.

[0004] This application provides a conductive silver paste, which includes a composite glass material and conductive powder. The composite glass material includes lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide, wherein the mass ratio α of silicon dioxide to aluminum oxide is in the range of 1.5 ≤ α ≤ 2.5. The conductive powder includes a first conductive silver powder, a second conductive silver powder, and conductive silver wire, wherein the size of the first conductive silver powder is less than 1 μm, and the size of the second conductive silver powder is larger than the size of the first conductive silver powder.

[0005] Furthermore, the mass ratio β of the conductive powder to the composite glass material is in the range of 34 ≤ β ≤ 61.33.

[0006] Furthermore, in the composite glass material, the mass fraction a1 of silicon dioxide ranges from 8% to 12%; the mass fraction a2 of aluminum oxide ranges from 4% to 6%.

[0007] Furthermore, in the composite glass material, the mass fraction a3 of lead monoxide ranges from 55% to 65%; and the mass fraction a4 of boron trioxide ranges from 15% to 22%.

[0008] Furthermore, in the conductive powder, the mass fraction b1 of the first conductive silver powder is in the range of 15% ≤ b1 ≤ 25%; the mass fraction b2 of the second conductive silver powder is in the range of 70% ≤ b2 ≤ 80%; and the mass fraction b3 of the conductive silver wire is in the range of 3% ≤ b3 ≤ 8%.

[0009] Further, the conductive powder satisfies at least one of the following conditions: the average particle size d1 of the first conductive silver powder is in the range of 50nm≤d1≤200nm; the average particle size d2 of the second conductive silver powder is in the range of 1μm≤d2≤3μm; the sphericity of the second conductive silver powder is greater than or equal to 95%; the radial dimension d3 of the conductive silver wire is in the range of 20nm≤d3≤50nm; the length d4 of the conductive silver wire is in the range of 10μm≤d4≤30μm; and the aspect ratio of the conductive silver wire is greater than or equal to 200.

[0010] Furthermore, in the conductive silver paste, the mass fraction A1 of the composite glass material ranges from 1.5% to 2.5%; or, the mass fraction A2 of the conductive powder ranges from 85% to 92%.

[0011] This application provides an electrode made using the conductive silver paste provided in this application.

[0012] This application provides a solar cell, which includes a substrate and an electrode provided in this application, wherein the electrode is disposed on the surface of the substrate.

[0013] Furthermore, the substrate includes a silicon substrate, a tunneling oxide layer and a polysilicon layer stacked together, and the electrode is located on the side of the polysilicon layer away from the silicon substrate and connected to the polysilicon layer; wherein the thickness h of the polysilicon layer is in the range of 70nm≤h≤100nm.

[0014] This application provides a method for preparing a solar cell, the method comprising: providing a substrate; providing a conductive silver paste provided in this application, printing the conductive silver paste onto the substrate, and drying it; and sintering and curing the substrate and the conductive silver paste to obtain an electrode.

[0015] Further, the sintering and curing of the substrate and the conductive silver paste includes: heating to a first preset temperature at a preset heating rate for sintering, and then cooling to a second preset temperature at a preset cooling rate for curing after sintering; wherein the preset heating rate v1 is in the range of 15℃ / s≤v1≤20℃ / s, the first preset temperature T1 is in the range of 740℃≤T1≤760℃, the preset cooling rate v2 is in the range of 10℃ / s≤v2≤15℃ / s, and the second preset temperature T2 is in the range of 200℃≤T2≤240℃.

[0016] In the conductive silver paste provided in this application, in a first aspect, the composite glass material includes lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide. Lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide work synergistically to make the activity of the conductive silver paste mild and controllable, thereby enabling it to form a stable chemical bond with the polycrystalline silicon layer and improve the adhesion of the electrode formed by the conductive silver paste to the polycrystalline silicon layer. Specifically, lead monoxide lowers the softening point of the composite glass material, allowing it to fully melt at the sintering temperature and corrode and wet the dielectric layer, thus achieving contact bonding between the conductive silver paste and the polycrystalline silicon layer. Boron trioxide adjusts the rheological properties, i.e., fluidity, of the composite glass material, improving its wettability and bonding ability with the polycrystalline silicon layer. Silica increases the melting point and structural stability of the composite glass material; if its mass proportion in the composite glass material is too high, it will lead to an increased melting point and decreased activity, resulting in insufficient corrosion of the dielectric layer and consequently, insufficient bonding between the electrode formed by the conductive silver paste and the polycrystalline silicon layer. Alumina enhances the weather resistance of the composite glass material and improves the stability of the conductive silver paste in humid, hot, and acetic acid environments, thereby extending the service life of the electrode formed by the conductive silver paste in humid, hot, and acetic acid environments and preventing the electrode from deteriorating after long-term use.

[0017] Secondly, in the composite glass material, the mass ratio α of silicon dioxide to alumina satisfies the range of 1.5 ≤ α ≤ 2.5. This ensures that both the mass fractions of silicon dioxide and alumina are within a reasonable range, achieving good adhesion and long-term bonding between the electrode formed by the conductive silver paste and the polycrystalline silicon layer. Silicon dioxide fully enhances the activity of the conductive silver paste, while alumina fully enhances its weather resistance. This effectively avoids the problems of excessive silicon dioxide content leading to increased melting point, decreased activity, and insufficient corrosion of the dielectric layer, resulting in insufficient electrode bonding. Conversely, it avoids the problems of excessive alumina content leading to decreased weather resistance, easy failure in humid and acetic acid environments, and poor electrode adhesion after long-term use. Thus, the two components synergistically regulate the activity and stability of the composite glass material.

[0018] Thirdly, the conductive powder includes a first conductive silver powder and a second conductive silver powder. The size of the first conductive silver powder is less than 1 μm, and the size of the second conductive silver powder is larger than that of the first conductive silver powder. The larger second conductive silver powder is the main phase in the conductive powder, used to construct a stable conductive framework and ensure efficient current transmission. Furthermore, the nano-sized first charged silver powder fills the gaps formed by the second conductive silver powder, thereby increasing the density of the silver film and increasing the contact area between the conductive silver paste and the polycrystalline silicon layer, which helps to reduce contact resistance. Moreover, the first conductive silver powder can penetrate deep into the tiny gaps on the surface of the polycrystalline silicon layer, strengthening the adhesion between the electrode and the polycrystalline silicon layer and preventing local delamination. Furthermore, the conductive powder also includes conductive silver wires, which can form a three-dimensional mesh support structure within the silver film, thereby significantly improving the mechanical strength, flexural toughness, friction resistance, and extrusion resistance of the electrode, reducing stress cracking, and indirectly strengthening the adhesion between the electrode and the polycrystalline silicon layer. By combining the first conductive silver powder, the second conductive silver powder, and the conductive silver wire, the density and mechanical strength of the silver film are significantly improved. This reduces the interfacial resistance between the electrode and the polycrystalline silicon layer while simultaneously increasing the bonding strength between them. The electrode exhibits better resistance to production line and packaging stresses, which is beneficial for improving the performance of the solar cell. Compared to solutions using only a single type of silver powder, the conductive silver paste provided in this application results in a silver film with higher density and better toughness after sintering. When subjected to external stresses (such as flipping friction or lamination compression), the electrode is less prone to cracking or powder detachment, maintaining good structural integrity and bonding strength with the substrate.

[0019] In summary, this application improves the bonding and adhesion between the conductive silver paste and the ultrathin polycrystalline silicon layer by optimizing the composition and ratio of the composite glass material and compounding conductive silver powder of different sizes with one-dimensional conductive silver wires. When the conductive silver paste forms electrodes after printing and sintering, the electrodes are firmly bonded to the polycrystalline silicon layer, the electrodes are not prone to powder detachment, and the contact electrode between the electrodes and the polycrystalline silicon layer is low, thereby giving the solar cell better conductivity and long-term reliability. Furthermore, the electrodes are less prone to detachment and failure under production handling, lamination welding, and outdoor humid and corrosive environments, significantly improving the reliability and lifespan of the solar cell, while increasing production yield, reducing mass production costs, and meeting the long-term stable operation requirements of the solar cell. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the implementation will be briefly introduced below. Obviously, the drawings described below are some implementations of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of a solar cell according to an embodiment of this application; Figure 2 This is a partial cross-sectional structural diagram of a solar cell according to an embodiment of this application; Figure 3 This is a schematic flowchart illustrating a method for fabricating a solar cell according to an embodiment of this application.

[0022] Explanation of reference numerals in the attached figures: 100 - Electrode, 200 - Solar cell, 210 - Substrate, 211 - Silicon substrate, 212 - Tunneling oxide layer, 213 - Polycrystalline silicon layer, 214 - Dielectric layer. Detailed Implementation

[0023] 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 of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0024] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0025] In this document, references to "embodiment" or "implementation" mean that a particular feature, structure, or characteristic described in connection with an embodiment or implementation may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0026] Currently, mass-produced N-type TOPCon solar cells generally employ screen-printed silver paste combined with high-temperature sintering to prepare the back electrode. The core reason for insufficient adhesion between the grid and polycrystalline silicon is that existing silver paste formulations and processes are not specifically designed for the ultra-thin polycrystalline silicon layer on the back of the cell. Firstly, conventional silver pastes have a high glass frit system with a single composition, making it difficult to form stable chemical bonds with the ultra-thin polycrystalline silicon layer, resulting in weak interfacial adhesion after sintering. Secondly, the conductive phase of the silver paste is mostly single-particle silver powder, leading to low film density and poor mechanical strength after sintering, making it prone to cracking and detachment under external forces. These problems directly cause grid line powder shedding, detachment, and cracking, resulting in increased cell contact resistance and decreased photoelectric conversion efficiency. In production handling, lamination welding, and outdoor humid and corrosive environments, the grid lines are prone to detachment and failure, significantly reducing cell reliability and lifespan, while also increasing the production defect rate and mass production costs, making it difficult to meet the long-term stable operation requirements of solar cells.

[0027] In this application, the N-type TOPCon (Tunnel Oxide Passivated Contact) solar cell is a high-efficiency N-type silicon-based cell. Its core structure involves fabricating an ultrathin tunneling oxide layer and a doped polycrystalline silicon layer on the surface of a silicon substrate. The tunneling oxide layer is used to achieve passivation and selective carrier transport, thereby significantly reducing carrier recombination and improving the open-circuit voltage and photoelectric conversion efficiency of the solar cell. Because it integrates an ultrathin polycrystalline silicon passivation structure on the back side, it places extremely high demands on the sintering activity and interfacial bonding characteristics of the electrode materials. Conventional silver paste is difficult to adapt and is prone to problems such as insufficient adhesion and burn-through of the passivation layer.

[0028] Please see Figure 1 and Figure 2 This application provides a conductive silver paste, which includes a composite glass material and conductive powder. The composite glass material includes lead monoxide (PbO), boron trioxide (B2O3), silicon dioxide (SiO2), and aluminum oxide (Al2O3), wherein the mass ratio α of silicon dioxide to aluminum oxide is in the range of 1.5≤α≤2.5. The conductive powder includes a first conductive silver powder, a second conductive silver powder, and conductive silver wire, wherein the size of the first conductive silver powder is less than 1μm, and the size of the second conductive silver powder is larger than the size of the first conductive silver powder.

[0029] Specifically, the mass ratio α of silicon dioxide to aluminum oxide can be, but is not limited to, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4 and 2.5.

[0030] Optionally, in one specific embodiment, the composite glass material is composed of lead monoxide, boron trioxide, silicon dioxide and aluminum oxide; in other words, the composite glass material is a quaternary composite glass material of lead monoxide, boron trioxide, silicon dioxide and aluminum oxide.

[0031] Understandably, the size of the first conductive silver powder is at the nanometer level, and the size of the second conductive silver powder is at the micrometer level.

[0032] Understandably, after the conductive silver paste provided in this application is printed on the substrate 210, the substrate 210 and the conductive silver paste are sintered and cured so that the conductive silver paste forms the electrode 100.

[0033] Optionally, the solar cell 200 includes a substrate 210 and an electrode 100. The substrate 210 includes a silicon substrate 211, a tunneling oxide layer 212, and a polycrystalline silicon layer 213 stacked together. The electrode 100 is located on the side of the polycrystalline silicon layer 213 away from the silicon substrate 211 and is connected to the polycrystalline silicon layer 213, so that when an external electrical signal is applied to the electrode 100, the electrode 100 and the polycrystalline silicon layer 213 are electrically connected.

[0034] Optionally, the solar cell 200 further includes a dielectric layer 214 disposed on the surface of the polycrystalline silicon layer 213 opposite to the silicon substrate 211. The electrode 100 passes through the dielectric layer 214 and is connected to the polycrystalline silicon layer 213, with the electrode 100 at least partially exposed on the surface of the dielectric layer 214 opposite to the polycrystalline silicon layer 213. In some optional embodiments, the dielectric layer 214 is a silicon nitride layer.

[0035] Optionally, the first conductive silver powder and the second conductive silver powder are conductive particles, belonging to zero-dimensional materials, while the conductive silver wire is a one-dimensional material.

[0036] In the conductive silver paste provided in this embodiment, in a first aspect, the composite glass material includes lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide. Lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide work together to make the activity of the conductive silver paste mild and controllable, thereby forming a stable chemical bond with the polycrystalline silicon layer 213 and improving the adhesion of the electrode 100 formed by the conductive silver paste to the polycrystalline silicon layer 213. Specifically, lead monoxide can lower the softening point of the composite glass material, allowing it to fully melt at the sintering temperature and corrode and wet the dielectric layer 214, thereby achieving contact connection between the conductive silver paste and the polycrystalline silicon layer 213. Boron trioxide can adjust the rheological properties, i.e., fluidity, of the composite glass material, improving the wettability and bonding ability between the composite glass material and the polycrystalline silicon layer 213. Silica can increase the melting point and structural stability of the composite glass material. If its mass proportion in the composite glass material is too large, it will lead to an increase in the melting point and a decrease in activity, thus failing to fully corrode the dielectric layer 214, resulting in insufficient bonding between the electrode 100 formed by the conductive silver paste and the polycrystalline silicon layer 213. Alumina can enhance the weather resistance of the composite glass material and improve the stability of the conductive silver paste in humid and hot and acetic acid environments, thereby extending the service life of the electrode 100 formed by the conductive silver paste in humid and hot and acetic acid environments and preventing the adhesion of the electrode 100 from deteriorating after long-term use.

[0037] Secondly, in the composite glass material, the mass ratio α of silicon dioxide to alumina satisfies the range of 1.5 ≤ α ≤ 2.5. This ensures that both the mass fractions of silicon dioxide and alumina are within a reasonable range, achieving good bonding and long-term adhesion between the electrode 100 formed by the conductive silver paste and the polycrystalline silicon layer 213. Silicon dioxide fully enhances the activity of the conductive silver paste, while alumina fully enhances its weather resistance. This effectively avoids the problems of excessive silicon dioxide content leading to increased melting point, decreased activity, and insufficient corrosion of the dielectric layer 214, resulting in insufficient bonding of the electrode 100. Conversely, it avoids the problems of excessive alumina content leading to decreased weather resistance, easy failure in humid and acetic acid environments, and poor adhesion of the electrode 100 after long-term use. Thus, the two components synergistically regulate the activity and stability of the composite glass material.

[0038] Thirdly, the conductive powder includes a first conductive silver powder and a second conductive silver powder. The size of the first conductive silver powder is less than 1 μm, and the size of the second conductive silver powder is larger than the size of the first conductive silver powder. The larger second conductive silver powder is the main phase in the conductive powder, used to construct a stable conductive framework and ensure efficient current transmission. Furthermore, the nano-sized first charged silver powder fills the gaps formed by the second conductive silver powder, thereby increasing the density of the silver film and increasing the contact area between the conductive silver paste and the polycrystalline silicon layer 213, which helps to reduce contact resistance. Moreover, the first conductive silver powder can penetrate deep into the tiny gaps on the surface of the polycrystalline silicon layer 213, strengthening the adhesion between the electrode 100 and the polycrystalline silicon layer 213 and preventing local delamination. Furthermore, the conductive powder also includes conductive silver wires, which can form a three-dimensional mesh support structure within the silver film, thereby significantly improving the mechanical strength, flexural toughness, friction resistance, and extrusion resistance of the electrode 100, reducing stress cracking, and indirectly strengthening the adhesion between the electrode 100 and the polycrystalline silicon layer 213. Through the synergistic effect of the first conductive silver powder, the second conductive silver powder, and the conductive silver wires, the density and mechanical strength of the silver film are fully enhanced. While reducing the interfacial resistance between the electrode 100 and the polycrystalline silicon layer 213, the bonding strength between the electrode 100 and the polycrystalline silicon layer 213 is also improved. The electrode 100 has better resistance to production line and packaging stress, which is beneficial to improving the performance of the solar cell 200. Compared with the solution that only uses a single silver powder, the conductive silver paste provided in this application forms a silver film with higher density and better toughness after sintering. When subjected to external stress (such as flipping friction and lamination extrusion), the electrode 100 is not prone to cracking or powder detachment, and can still maintain good structural integrity and its bonding strength with the substrate 210.

[0039] In summary, this application improves the bonding and adhesion between the conductive silver paste and the ultra-thin polycrystalline silicon layer 213 by optimizing the composition and ratio of the composite glass material and compounding conductive silver powder of different sizes with one-dimensional conductive silver wires. When the conductive silver paste forms the electrode 100 after printing and sintering, the electrode 100 is firmly bonded to the polycrystalline silicon layer 213, the electrode 100 is not prone to powder detachment, and the contact electrode 100 between the electrode 100 and the polycrystalline silicon layer 213 is low, thereby giving the solar cell 200 better conductivity and long-term reliability. Furthermore, the electrode 100 is less likely to detach and fail under production handling, lamination welding, and outdoor humid and corrosive environments, significantly improving the reliability and service life of the solar cell 200, while increasing production yield, reducing mass production costs, and meeting the long-term stable operation requirements of the solar cell 200.

[0040] Understandably, in the terminology of this application, "weather resistance" refers to the ability of a material to withstand the combined effects of climatic factors such as sunlight, temperature changes, wind and rain erosion in an outdoor environment.

[0041] Understandably, in the terminology of this application, "silver film" refers to a dense and continuous silver film formed on the surface of substrate 210 after the silver paste is sintered at high temperature. The silver film is the core part of electrode 100 and is the core carrier for electrode 100 to achieve conductivity and to be combined with polycrystalline silicon layer 213.

[0042] Preferably, the mass ratio α of silicon dioxide to aluminum oxide is 2, and the composite glass material has better overall performance, so that the electrode 100 formed by the conductive silver paste has better bonding force with the polycrystalline silicon layer 213 of the substrate 210.

[0043] In some optional embodiments, the mass ratio β of the conductive powder to the composite glass material is in the range of 34 ≤ β ≤ 61.33.

[0044] Specifically, the mass ratio β of the conductive powder to the composite glass material can be, but is not limited to, 34, 35, 38, 40, 42, 44, 45, 48, 50, 52, 53, 54, 55, 58, 60, 61, and 61.33.

[0045] In this embodiment, when the mass ratio β of the conductive powder to the composite glass material satisfies the range of 34 ≤ β ≤ 61.33, the mass fractions of both the conductive powder and the composite glass material in the conductive silver paste are within a reasonable range. During sintering, the composite glass material can melt, flow, and etch the dielectric layer 214 with a depth within a reasonable range, thus achieving effective electrical contact between the conductive silver paste and the polycrystalline silicon layer 213. Simultaneously, this enhances the bonding ability between the conductive silver paste and the polycrystalline silicon layer 213, thereby improving the adhesion between them. Furthermore, the conductive powder can form a continuous, dense, and unobstructed conductive network within the conductive silver paste, ensuring excellent conductivity of the electrode 100, thereby enabling the solar cell 200 to possess good electrical performance and long-term stability. When the value of β is too large, the mass fraction of the conductive powder is too high or the mass fraction of the composite glass material is too low, weakening the etching effect of the conductive silver paste on the dielectric layer 214. This makes it difficult for the conductive silver paste to form a good ohmic contact with the polycrystalline silicon layer 213, and also reduces the bonding force between the electrode 100 and the polycrystalline silicon layer 213, easily leading to problems such as poor adhesion and easy detachment of the electrode 100, thus affecting the photoelectric conversion efficiency and long-term reliability of the solar cell 200. When the value of β is too small, the mass fraction of the conductive powder is too small or the mass fraction of the composite glass material is too high. If the mass fraction of the conductive powder is too small, it is difficult for the conductive powder to form a continuous and complete conductive path in the conductive silver paste, resulting in insufficient conductivity and increased contact resistance of the electrode 100, thereby reducing the fill factor and photoelectric conversion efficiency of the solar cell 200. If the mass fraction of the composite glass material is too large, the etching effect of the conductive silver paste will be too strong, which may result in excessive etching on the surface of the substrate 210, or even erosion and damage to the underlying functional layers such as the polycrystalline silicon layer 213 and the silicon substrate 210, thereby increasing the leakage current and reducing the photoelectric conversion efficiency of the solar cell 200.

[0046] Understandably, in the terminology of this application, "leakage current" refers to the abnormal stray current generated by the solar cell 200 under reverse bias or dark conditions, which is not conducted through the normal PN junction, but through paths such as defect channels, interface damage, and edge breakdown.

[0047] In some optional embodiments, the mass fraction A1 of the composite glass material in the conductive silver paste ranges from 1.5% to 2.5%.

[0048] Specifically, in the conductive silver paste, the mass fraction A1 of the composite glass material can be, but is not limited to, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, and 2.5%.

[0049] In the conductive silver paste provided in this embodiment, when the mass fraction A1 of the composite glass material meets the range of 1.5% ≤ A1 ≤ 2.5%, the mass fraction of the composite glass material is within a reasonable range. During sintering, the composite glass material can melt, flow, and etch the dielectric layer 214, with the etching depth within a reasonable range, thereby achieving effective electrical contact between the conductive silver paste and the polycrystalline silicon layer 213. Simultaneously, it enhances the bonding ability between the conductive silver paste and the polycrystalline silicon layer 213, thus improving the adhesion between them. When the mass fraction of the composite glass material is too high, the etching effect of the conductive silver paste is too strong, potentially etching too deeply onto the surface of the substrate 210, or even eroding and damaging the underlying functional layers such as the silicon substrate 210, thereby increasing leakage current and reducing the photoelectric conversion efficiency of the solar cell 200. When the mass fraction of the composite glass material is too small, it is difficult to fully etch the dielectric layer 214 during sintering. This prevents the conductive silver paste from reaching and contacting the polycrystalline silicon layer 213, thus failing to form a good ohmic contact. Consequently, the contact resistance of the solar cell 200 increases significantly, the conductivity of the electrode 100 deteriorates, and the photoelectric conversion efficiency of the solar cell 200 is affected. Furthermore, it reduces the adhesion between the conductive silver paste and the polycrystalline silicon layer 213, making the electrode 100 formed by the conductive silver paste prone to powder shedding and reducing the electrical performance of the electrode 100.

[0050] In some optional embodiments, the mass fraction A2 of the conductive powder in the conductive silver paste is in the range of 85% ≤ A2 ≤ 92%.

[0051] Specifically, in the conductive silver paste, the mass fraction A2 of the conductive powder can be, but is not limited to, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, 88.5%, 89%, 89.5%, 90%, 90.5%, 91%, 91.5%, and 92%.

[0052] In the conductive silver paste provided in this embodiment, when the mass fraction A2 of the conductive powder meets the range of 85%≤A2≤92%, the mass fraction of the conductive powder is within a reasonable range. The first conductive silver powder, the second conductive silver powder, and the conductive silver wire in the conductive powder work together to form a continuous, dense, and unobstructed conductive network within the conductive silver paste, ensuring the excellent conductivity of the electrode 100. When the mass fraction of the conductive powder is too large, the proportion of other components in the conductive silver paste, such as the composite glass material, decreases accordingly, weakening the etching effect of the conductive silver paste on the dielectric layer 214. This makes it difficult for the conductive silver paste to form a good ohmic contact with the polycrystalline silicon layer 213, and also reduces the bonding force between the electrode 100 and the polycrystalline silicon layer 213, easily leading to problems such as poor adhesion and easy detachment of the electrode 100, thereby affecting the photoelectric conversion efficiency and long-term reliability of the solar cell 200. When the mass fraction of the conductive powder is too small, the conductive powder is difficult to form a continuous and complete conductive path in the conductive silver paste, resulting in insufficient conductivity and increased contact resistance of the electrode 100, thereby reducing the fill factor and photoelectric conversion efficiency of the solar cell 200.

[0053] Understandably, in the terminology of this application, "fill factor" refers to the ratio of the maximum output power of the solar cell 200 to the product of the open-circuit voltage and the short-circuit current. The larger the value of the fill factor, the higher the photoelectric conversion efficiency of the solar cell 200.

[0054] In some optional embodiments, the mass fraction a1 of silica in the composite glass frit is in the range of 8% ≤ a1 ≤ 12%.

[0055] Specifically, in the composite glass material, the mass fraction a1 of silicon dioxide can be, but is not limited to, 8%, 8.5%, 8.8%, 9%, 9.5%, 9.6%, 10%, 10.5%, 10.8%, 11%, 11.5%, 11.8%, and 12%.

[0056] In the composite glass material provided in this embodiment, when the mass fraction of silicon dioxide a1 meets the range of 8%≤a1≤12%, and the mass fraction of silicon dioxide is within a reasonable range, the composite glass material has a suitable softening temperature, moderate fluidity, and controllable etching ability. This allows the conductive silver paste to fully etch the dielectric layer 214 and form a good ohmic contact with the polycrystalline silicon layer 213 during the sintering process, without causing excessive erosion of the polycrystalline silicon layer 213. At the same time, it improves the adhesion and connection reliability between the electrode 100 and the polycrystalline silicon layer 213, which is beneficial to improving the electrical performance and long-term stability of the solar cell 200. If the mass fraction a1 of silicon dioxide is too high, the softening temperature and viscosity of the composite glass material will be too high, reducing its activity and etching ability. During the sintering process of the conductive silver paste, the conductive silver paste will be difficult to effectively melt and etch the dielectric layer 214, resulting in the conductive silver paste failing to form a good ohmic contact with the polycrystalline silicon layer 213, increasing the contact resistance of the solar cell 200, and simultaneously reducing the interfacial bonding force between the electrode 100 and the polycrystalline silicon layer 213. If the mass fraction a1 of silicon dioxide is too low, the softening temperature of the composite glass material will be too low, its chemical stability will be poor, and its etching activity will be too strong. During the sintering process of the conductive silver paste, the conductive silver paste may over-etch the dielectric layer 214 and the polycrystalline silicon layer 213, causing erosion damage, increasing the leakage current of the solar cell 200, and reducing the parallel resistance and photoelectric conversion efficiency.

[0057] In some optional embodiments, the mass fraction a2 of alumina in the composite glass material is in the range of 4% ≤ a2 ≤ 6%.

[0058] Specifically, in the composite glass material, the mass fraction a2 of alumina can be, but is not limited to, 4%, 4.2%, 4.5%, 4.6%, 4.8%, 5%, 5.2%, 5.4%, 5.5%, 5.6%, 5.8%, 5.9%, and 6%.

[0059] In the composite glass material provided in this embodiment, when the mass fraction a2 of alumina meets the range of 4% ≤ a2 ≤ 6%, the mass fraction of alumina is within a reasonable range. Alumina, as a modifier and stabilizer of the glass network in the composite glass material, can stabilize the structure of the composite glass material and give it good weather resistance. At the same time, it can adjust the softening temperature, melt flow and etching activity of the composite glass material to ensure that the etching of the dielectric layer 214 is uniform and controllable during the sintering process, thereby giving the conductive silver paste and polycrystalline silicon layer 213 good interface reliability and long-term adhesion. If the mass fraction a2 of alumina is too large, the alumina exceeds the carrying capacity of the glass network and cannot be completely integrated into the glass network. The excess alumina exists in a free state, resulting in uneven internal structure and increased defects in the composite glass material. This may lead to a decrease in the weather resistance of the composite glass material, making it prone to failure in humid and hot and acetic acid environments. After long-term use, the adhesion between the electrode 100 and the substrate 210 deteriorates, reducing the performance of the solar cell 200. If the mass fraction a2 of alumina is too small, the alumina will not adequately enhance the weather resistance of the composite glass material. Specifically, the alumina will not effectively support the glass network in the composite glass material, resulting in poor stability and loose structure of the composite glass material. Under corrosive environments such as humid heat and acetic acid, the structure will easily deteriorate and the weather resistance will decrease.

[0060] In some optional embodiments, the mass fraction a3 of lead monoxide in the composite glass frit is in the range of 55% ≤ a3 ≤ 65%.

[0061] Specifically, in the composite glass material, the mass fraction a3 of lead monoxide can be, but is not limited to, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, and 65%.

[0062] In the composite glass material provided in this embodiment, when the mass fraction of lead monoxide a3 is within the range of 55%≤a3≤65%, the mass fraction of lead monoxide is within a reasonable range. Lead monoxide can effectively reduce the softening temperature and melting temperature of the composite glass material, so that the composite glass material can be fully melted and spread at conventional sintering temperatures and has good fluidity. This enables effective etching and interface wetting of the dielectric layer 214, ensuring good ohmic contact between the conductive silver paste and the polycrystalline silicon layer 213, which helps to reduce contact resistance and improve the performance of the solar cell 200.

[0063] In some optional embodiments, the mass fraction a4 of boron trioxide in the composite glass material is in the range of 15% ≤ a4 ≤ 22%.

[0064] Specifically, in the composite glass material, the mass fraction a4 of boron trioxide can be, but is not limited to, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, 18.5%, 19%, 20%, 21%, and 22%.

[0065] In the composite glass material provided in this embodiment, when the mass fraction a4 of boron trioxide is within the range of 15% ≤ a4 ≤ 22%, the mass fraction of boron trioxide is within a reasonable range. As an important rheological modifying component in the composite glass material, boron trioxide can effectively adjust the melt viscosity and high-temperature rheological behavior of the composite glass material, enabling it to possess suitable softening characteristics and flow spreading performance during sintering and heating, ensuring its uniform distribution in the interface region. Simultaneously, boron trioxide can significantly improve the interfacial wettability between the composite glass material and the polycrystalline silicon layer 213, promoting the full spreading and tight adhesion of the composite glass material on the polycrystalline silicon surface, enhancing the interfacial bonding force, and improving the bonding strength between the electrode 100 and the polycrystalline silicon layer 213, thereby ensuring good interfacial contact stability and mechanical adhesion.

[0066] In some optional embodiments, the mass fraction b1 of the first conductive silver powder in the conductive powder ranges from 15% to 25%.

[0067] Specifically, in the conductive powder, the mass fraction b1 of the first conductive silver powder can be, but is not limited to, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, and 25%.

[0068] In the conductive powder provided in this embodiment, when the mass fraction b1 of the first conductive silver powder meets the range of 15%≤b1≤25%, the mass fraction of the first conductive silver powder is within a reasonable range. The first conductive silver powder can fully utilize the gap-filling effect and interface anchoring effect of nano-sized particles. Without affecting the stability of the main conductive framework structure constructed by the large-particle-size second conductive silver powder, it effectively fills the microscopic gaps between silver powder particles, significantly improves the overall density and uniformity of the silver film, significantly optimizes the internal microstructure of the electrode 100, and improves the interface adhesion and contact characteristics between the electrode 100 and the polycrystalline silicon layer 213, laying a structural foundation for achieving low contact resistance and high interface bonding. When the mass fraction of the first conductive silver powder is too large, it may increase the sintering shrinkage rate of the conductive silver paste, easily causing the electrode 100 to warp, crack, or even partially delaminate from the polycrystalline silicon layer 213, reducing the structural stability of the electrode 100 disposed on the substrate 210. When the mass fraction of the first conductive silver powder is too small, it is difficult for the first conductive silver powder to fully fill the gaps between the larger second conductive silver powder particles, resulting in a low density of the silver film. This leads to insufficient effective contact area between the electrode 100 and the polycrystalline silicon layer 213, increasing interfacial contact resistance and thus reducing the photoelectric conversion efficiency of the solar cell 200. Furthermore, the first conductive silver powder is difficult to fully embed into the surface gaps of the polycrystalline silicon layer 213, making it difficult to effectively improve the interfacial bonding force between the conductive silver paste and the polycrystalline silicon layer 213, thereby reducing the long-term stability of the electrode 100.

[0069] In some optional embodiments, the mass fraction b2 of the second conductive silver powder in the conductive powder ranges from 70% to 80%.

[0070] Specifically, in the conductive powder, the mass fraction b2 of the second conductive silver powder can be, but is not limited to, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, and 80%.

[0071] In the conductive powder provided in this embodiment, when the mass fraction b2 of the second conductive silver powder meets the range of 70%≤b2≤80%, the mass fraction of the second conductive silver powder is within a reasonable range. As the main phase of the conductive powder, the second conductive silver powder can fully build a continuous, dense, and stable conductive framework within the conductive silver paste, ensuring efficient and low-loss transport of current within the electrode 100, significantly reducing the series resistance and contact resistance of the electrode 100, thereby improving the fill factor and photoelectric conversion efficiency of the solar cell 200. When the mass fraction of the second conductive silver powder is too large, correspondingly, the mass fraction of other components in the conductive powder, such as the first conductive silver powder and / or the mass proportion of the conductive silver wire, is too small. The first conductive silver powder cannot fully play its role in filling the gaps between the second conductive silver powder, thereby reducing the packing density of the conductive powder. The electrode 100 will have insufficient density after sintering, which will also increase the contact resistance and reduce the bonding force between the electrode 100 and the substrate 210, affecting the structural stability and long-term reliability of the electrode 100. Alternatively, the conductive silver wires may be insufficient to support the formed three-dimensional network, resulting in poor mechanical strength and flexural toughness of the electrode 100. Under external stresses such as lamination friction or extrusion, it is prone to cracking, indirectly reducing the adhesion between the electrode 100 and the polycrystalline silicon layer 213. When the mass fraction of the second conductive silver powder is too small, it is difficult for the second conductive silver powder to form a complete and continuous conductive framework within the conductive silver paste, leading to decreased conductivity of the conductive silver paste, increased series resistance, and ultimately a decrease in the fill factor and photoelectric conversion efficiency of the solar cell 200.

[0072] In some optional embodiments, the mass fraction b3 of the conductive silver wire in the conductive powder ranges from 3% to 8%.

[0073] Specifically, in the conductive powder, the mass fraction b3 of the conductive silver wire can be, but is not limited to, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.2%, 4.5%, 4.8%, 5%, 5.2%, 5.5%, 6%, 6.5%, 6.8%, 7%, 7.2%, 7.5%, 7.8%, and 8%.

[0074] In the conductive powder provided in this embodiment, when the mass fraction b3 of the conductive silver wire meets the range of 3% ≤ b3 ≤ 8%, the mass fraction of the conductive silver wire is within a reasonable range. The conductive silver wires interlock and intertwine within the sintered electrode 100, forming a continuous and stable three-dimensional mesh support structure. This structure effectively distributes external forces and internal thermal stress, significantly improving the overall mechanical strength, bending toughness, friction resistance, and extrusion resistance of the electrode 100, reducing stress cracking and warping deformation during preparation, module lamination, and use. Simultaneously, the conductive silver wire itself possesses excellent conductivity, and the three-dimensional network it forms can synergize with the conductive pathways constructed by the first and second conductive silver powders. This enhances mechanical properties while ensuring the electrode 100 has excellent and stable conductivity, ultimately improving the fill factor and photoelectric conversion efficiency of the solar cell 200. When the mass fraction of the conductive silver wire is too high, the corresponding mass fractions of other components in the conductive powder, such as the first conductive silver powder and / or the second conductive silver powder, are too low. This results in an overly loose accumulation of conductive particles within the conductive silver paste, reducing the density of the electrode 100. Consequently, this increases the conductive pathways within the electrode 100, raises the contact resistance, and weakens the tight bond between the electrode 100 and the substrate 210. When the mass fraction of the conductive silver wire is too low, it is difficult for the conductive silver wire to form an effective and continuous three-dimensional support network in the silver film. This makes it difficult to improve the mechanical strength, flexural toughness, friction resistance, and extrusion resistance of the electrode 100. Under stress, the electrode 100 is prone to stress cracking, warping, and other problems, weakening the bond between the electrode 100 and the polycrystalline silicon layer 213.

[0075] Preferably, in a specific embodiment of the conductive powder, the mass fraction b1 of the first conductive silver powder is 20%, the mass fraction b2 of the second conductive silver powder is 75%, and the mass fraction b3 of the conductive silver wire is 5%.

[0076] In some optional embodiments, the conductive powder satisfies the following condition: the average particle size d1 of the first conductive silver powder is in the range of 50nm≤d1≤200nm.

[0077] Specifically, the average particle size d1 of the first conductive silver powder can be, but is not limited to, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, and 200nm.

[0078] In this embodiment, when the average particle size d1 of the first conductive silver powder meets the range of 50nm≤d1≤200nm, the average particle size of the first conductive silver powder is within a reasonable range. The first conductive silver powder can fully utilize the filling, penetration, and low-resistance sintering properties of nano-silver powder, embedding itself in the gaps of the conductive framework constructed by the second conductive silver powder, significantly improving the density and continuity of the silver film, thereby reducing the resistance of the electrode 100. Simultaneously, the first conductive silver powder can also smoothly penetrate into the micro-grooves, gaps, and defects on the surface of the polycrystalline silicon layer 213, achieving multi-point anchoring between the electrode 100 and the polycrystalline silicon layer 213, significantly increasing the effective contact area between the electrode 100 and the polycrystalline silicon layer 213, thereby reducing contact resistance. Furthermore, it avoids excessively high surface energy due to the small average particle size of the first conductive silver powder, preventing agglomeration of the first conductive silver powder. The first conductive silver powder can be uniformly dispersed within the conductive silver paste, improving the uniformity of the conductive silver paste.

[0079] In some optional embodiments, the conductive powder satisfies the following condition: the average particle size d2 of the second conductive silver powder is in the range of 1μm≤d2≤3μm.

[0080] Specifically, the average particle size d2 of the second conductive silver powder can be, but is not limited to, 1μm, 1.1μm, 1.3μm, 1.5μm, 1.6μm, 1.8μm, 2μm, 2.2μm, 2.3μm, 2.5μm, 2.6μm, 2.7μm, 2.9μm, and 3μm.

[0081] In this embodiment, when the average particle size d2 of the second conductive silver powder satisfies the range of 1μm≤d2≤3μm, the average particle size of the second conductive silver powder is within a reasonable range, and there is sufficient overlap contact area between adjacent particles of the second conductive silver powder, so that the second conductive silver powder can construct a smooth electron transport channel, achieve efficient and low-loss current conduction, effectively reduce the series resistance of the electrode 100, and improve the fill factor of the solar cell 200. In addition, the second conductive silver powder has a suitable specific surface area and sintering characteristics. The second conductive silver powder shrinks uniformly and has low stress during sintering, which makes the electrode 100 have a flat morphology and a solid structure, avoiding insufficient contact points due to excessively large particle size or insufficient skeleton support due to excessively small particle size. This balances the high conductivity, high density, and good mechanical stability of the electrode 100, and ensures reliable interface bonding between the electrode 100 and the polycrystalline silicon layer 213.

[0082] In some optional embodiments, the conductive powder satisfies the following condition: the sphericity of the second conductive silver powder is greater than or equal to 95%.

[0083] Understandably, in the terminology of this application, "sphericity" refers to a geometric parameter characterizing how close the particle morphology is to an ideal sphere. The higher the sphericity, the smoother the particle surface, the more rounded the shape, and the less obvious the sharp edges and burrs.

[0084] Specifically, the sphericity value of the second conductive silver powder can be, but is not limited to, 95%, 95.2%, 95.5%, 95.6%, 96%, 96.5%, 97%, 97.5%, 98%, 98.2%, 98.5%, and 99%.

[0085] In this embodiment, when the sphericity of the second conductive silver powder is greater than or equal to 95%, the surface of the second conductive silver powder is relatively smooth and the shape is relatively round. It has the characteristics of good fluidity, dense packing, uniform dispersion and low sintering shrinkage in the conductive silver paste. This is beneficial to improving the packing density and sintering density of the conductive powder, thereby forming a dense, flat and stable electrode 100. While improving the conductivity of the electrode 100, it also enhances the interfacial adhesion between the electrode 100 and the polycrystalline silicon layer 213.

[0086] In some optional embodiments, the conductive powder satisfies the following condition: the radial dimension d3 of the conductive silver wire is in the range of 20nm≤d3≤50nm.

[0087] Understandably, the radial dimension of the conductive silver wire is the same as the diameter of the conductive silver wire.

[0088] Specifically, the radial dimension d3 of the conductive silver wire can be, but is not limited to, 20nm, 22nm, 25nm, 26nm, 28nm, 30nm, 32nm, 35nm, 38nm, 40nm, 42nm, 45nm, 46nm, 48nm, and 50nm.

[0089] In this embodiment, when the radial dimension d3 of the conductive silver wire satisfies the range of 20nm≤d3≤50nm, the radial dimension of the conductive silver wire is within a reasonable range. In the conductive skeleton constructed by the second conductive silver powder, the conductive silver wire can freely interweave and overlap at multiple points in the gaps, forming a continuous, uninterrupted three-dimensional mesh support structure. In addition, the conductive silver wire has excellent structural flexibility and can form a multi-dimensional stress dispersion network inside the sintered silver film, effectively absorbing the thermal and mechanical stress generated during sintering, curing, and long-term outdoor use. This significantly improves the flexural toughness, friction resistance, and extrusion resistance of the electrode 100, inhibiting the initiation and propagation of microcracks from the root, avoiding problems such as cracking and warping of the electrode 100, and strengthening the interfacial adhesion and long-term bonding stability between the electrode 100 and the polycrystalline silicon layer 213.

[0090] In some optional embodiments, the conductive powder satisfies the following condition: the length d4 of the conductive silver wire is in the range of 10μm≤d4≤30μm.

[0091] Specifically, the length d4 of the conductive silver wire can be, but is not limited to, 10μm, 12μm, 15μm, 16μm, 18μm, 20μm, 22μm, 23μm, 25μm, 26μm, 28μm and 30μm.

[0092] In this embodiment, when the length d4 of the conductive silver wire meets the range of 10μm≤d4≤30μm, the length of the conductive silver wire is within a reasonable range. The conductive silver wire can effectively span multiple larger second conductive silver powders, forming a continuous and stable three-dimensional overlapping network within the conductive silver paste. This not only provides structural support but also enhances the mechanical strength, flexural toughness, and stress crack resistance of the electrode 100, thereby improving the interfacial adhesion and long-term bonding stability between the electrode 100 and the polycrystalline silicon layer 213. Furthermore, it avoids problems such as entanglement, knotting, and uneven dispersion within the conductive silver paste due to excessively long conductive powders, thus improving the performance of the conductive silver paste.

[0093] In some optional embodiments, the conductive powder satisfies the following condition: the aspect ratio of the conductive silver wire is greater than or equal to 200.

[0094] Specifically, the aspect ratio of the conductive silver wire can be, but is not limited to, 200, 210, 225, 230, 235, 240, 260, 280, 300, 320, etc.

[0095] In this embodiment, when the aspect ratio of the conductive silver wire is greater than or equal to 200, the aspect ratio of the conductive silver wire is within a reasonable range. The conductive silver wire can give full play to the long-range structural advantages of one-dimensional materials and form a highly compatible conductive enhancement system with the first conductive silver powder and the second conductive silver powder. At the same time, it can realize the stable construction of the three-dimensional network structure of the silver film, effectively improve the structural toughness of the silver film, thereby optimizing the conductive channels of the conductive powder and improving the interface bonding reliability between the electrode 100 and the polycrystalline silicon layer 213.

[0096] Optionally, the conductive silver paste further includes an organic carrier, which includes an organic solvent, a resin, and a thickener. In the organic carrier, the organic solvent has a mass fraction of 4% to 7%, the resin has a mass fraction of 1.5% to 3%, and the thickener has a mass fraction of 0.3% to 1%.

[0097] Understandably, the organic solvent is used to dissolve the resin and adjust its viscosity to improve the smoothness of the printing process. If the mass fraction of the organic solvent is too high, it will lead to slow drying and excessive residue, thereby reducing the adhesion between the electrode 100 and the polycrystalline silicon layer 213. If the mass fraction of the organic solvent is too low, it will cause the conductive silver paste to be too thick, making it prone to line breakage during printing and reducing the molding performance of the conductive silver paste.

[0098] Optionally, the mass fraction of the organic solvent can be, but is not limited to, 4%, 4.2%, 4.5%, 4.6%, 4.8%, 5%, 5.2%, 5.5%, 5.6%, 5.8%, 6%, 6.2%, 6.5%, 6.6%, 6.8%, and 7%, etc. Optionally, the organic solvent includes at least one of terpineol, butyl carbitol acetate, and ethylene glycol monobutyl ether.

[0099] Understandably, the resin is used to enhance the strength of the silver film and improve the printability and initial adhesion of the conductive silver paste. If the mass fraction of the resin is too high, excessive residual carbon may occur during sintering, thereby increasing the contact resistance between the electrode 100 and the polycrystalline silicon layer 213. If the mass fraction of the resin is too low, it is difficult to improve the structural strength of the silver film, thereby increasing the probability of powder shedding and breakage of the electrode 100 and reducing the performance of the electrode 100.

[0100] Optionally, the mass fraction of the resin can be, but is not limited to, 1.5%, 1.6%, 1.8%, 2%, 2.1%, 2.2%, 2.5%, 2.6%, 2.8%, 2.9%, and 3%.

[0101] Optionally, the resin includes at least one of ethyl cellulose, acrylic resin, and phenolic resin.

[0102] Understandably, the thickener is used to prevent the conductive powder from settling in the conductive silver paste, which helps to improve the clarity of the printing and maintain the shape of the electrode 100.

[0103] Optionally, the mass fraction of the thickener may be, but is not limited to, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, and 1%.

[0104] Optionally, the thickener includes at least one of hydrogenated castor oil, organobentonite, and fumed silica.

[0105] In this embodiment, the organic solvent, the resin, and the thickener work together to enable the conductive silver paste to form a high-strength silver film, thereby achieving good cohesion of the silver film. This improves the printability of the conductive silver paste and its initial adhesion to the substrate 210, while ensuring that the printed conductive silver paste is complete, without ink overflow or false printing, laying the foundation for the formation of a clearly structured electrode 100 after sintering. In addition, it can also improve the surface wettability of the conductive silver paste and the substrate 210, further enhancing the bonding performance between the conductive silver paste and the substrate 210.

[0106] This application provides an electrode 100, which is made using the conductive silver paste provided in this application.

[0107] Understandably, the electrode 100 has a grid structure. This grid structure includes fine grids, which are the metal electrode 100 grid lines on the front or back of the solar cell 200 that collect charge carriers and are a key structure for current collection and transmission.

[0108] In this embodiment, the conductive silver paste is sintered and cured to form the electrode 100. The conductive silver paste has good weather resistance and chemical stability. When the conductive silver paste is coated on the surface of the substrate 210, the electrode 100 and the substrate 210 have good bonding performance and long-term stability. At the same time, the electrode 100 has good structural toughness and conductivity, and can still function stably after a period of time. The electrode 100 has good performance in use.

[0109] This application provides a solar cell 200, which includes a substrate 210 and an electrode 100 provided in this application, wherein the electrode 100 is disposed on the surface of the substrate 210.

[0110] Understandably, the solar cell 200 is an N-type TOPCon cell.

[0111] In this embodiment, the electrode 100 is formed from the conductive silver paste provided in this application. The electrode 100 is disposed on the surface of the substrate 210 to achieve electrical connection between the electrode 100 and the substrate 210. The electrode 100 and the substrate 210 have good interfacial adhesion and long-term bonding stability, which allows the electrode 100 to be firmly disposed on the surface of the substrate 210 and to perform circuit conduction. Even under complex working conditions such as long-term humid and hot environment, high and low temperature cycle and mechanical vibration, the interfacial bonding can still be maintained tightly, and it is not easy to fall off, warp or local delamination. At the same time, the electrode 100 formed by the conductive silver paste has high internal density and continuous and stable conductive path, which can effectively reduce series resistance and contact resistance, and ensure efficient and low-loss collection and transmission of photogenerated carriers, thereby enabling the solar cell 200 to have a high fill factor and photoelectric conversion efficiency.

[0112] Optionally, the peel force between the electrode 100 and the substrate 210 ranges from 4N to 5.5N, and the electrode 100 and the substrate 210 have good bonding strength. Specifically, the peel force between the electrode 100 and the substrate 210 can be, but is not limited to, 4N, 4.1N, 4.3N, 4.5N, 4.6N, 4.8N, 5N, 5.1N, 5.3N, and 5.5N.

[0113] In some optional embodiments, the substrate 210 includes a silicon substrate 211, a tunneling oxide layer 212 and a polysilicon layer 213 stacked together, and the electrode 100 is disposed on the surface of the polysilicon layer 213; wherein the thickness h of the polysilicon layer 213 is in the range of 70nm≤h≤100nm.

[0114] Understandably, the silicon substrate 211 has excellent photoelectric conversion characteristics and can absorb photon energy under illumination to generate photogenerated electron-hole pairs, providing the core power source for the solar cell 200.

[0115] Understandably, the tunneling oxide layer 212 serves as an insulating barrier to effectively separate the silicon substrate 211 from the polycrystalline silicon layer 213, preventing unnecessary current leakage between the two, ensuring directional transport of photogenerated carriers, and improving the photoelectric conversion efficiency of the solar cell 200.

[0116] Understandably, the polycrystalline silicon layer 213 is used to receive photogenerated carriers generated by the silicon substrate 211 and efficiently transmit them to the electrode 100, thereby achieving effective current conduction and reducing carrier transmission loss.

[0117] Specifically, the thickness h of the polycrystalline silicon layer 213 can be, but is not limited to, 70nm, 72nm, 75nm, 78nm, 80nm, 82nm, 85nm, 88nm, 90nm, 92nm, 95nm, 96nm, 98nm, and 100nm.

[0118] In this embodiment, by improving and optimizing the conductive silver paste, the electrode 100 prepared from the conductive silver paste can perfectly adapt to the structure of the ultra-thin polycrystalline silicon layer 213. It can not only fit tightly against the surface of the polycrystalline silicon layer 213 to achieve stable adhesion, but also form a firm bond with the polycrystalline silicon layer 213, effectively avoiding problems such as electrode 100 falling off and poor contact due to the thinness of the polycrystalline silicon layer 213. Meanwhile, the electrode 100 structure adapted to the ultra-thin polycrystalline silicon layer 213 reduces compression damage to the polycrystalline silicon layer 213, preventing breakage due to the weight or structure of the electrode 100. This ensures both the structural integrity of the polycrystalline silicon layer 213 and the stability of the electrical connection between the electrode 100 and the polycrystalline silicon layer 213, thereby guaranteeing that the conductivity of the electrode 100 remains unaffected. This achieves a dual improvement in the conductivity and structural stability of the electrode 100, while also ensuring the structural safety of the polycrystalline silicon layer 213, further enhancing the overall operational reliability and photoelectric conversion efficiency of the solar cell 200. Furthermore, the moderate thickness of the polycrystalline silicon layer 213 allows for stable chemical bonding and mechanical anchoring with the electrode 100, resulting in stronger adhesion and preventing the solar cell 200 from failing due to burn-through during sintering caused by an excessively thin polycrystalline silicon layer 213.

[0119] Optionally, the solar cell 200 further includes a dielectric layer 214 disposed on the surface of the polycrystalline silicon layer 213 opposite to the silicon substrate 211. The electrode 100 passes through the dielectric layer 214 and is connected to the polycrystalline silicon layer 213, with the electrode 100 at least partially exposed on the surface of the dielectric layer 214 opposite to the polycrystalline silicon layer 213. In some optional embodiments, the dielectric layer 214 is a silicon nitride layer.

[0120] Please see Figure 3 This application provides a method for fabricating a solar cell 200, the method comprising: S101 provides substrate 210.

[0121] Understandably, the substrate 210 includes a silicon substrate 211, a tunneling oxide layer 212, a polysilicon layer 213, and a dielectric layer 214 stacked together.

[0122] S102, Provide the conductive silver paste provided in this application, print the conductive silver paste on the substrate 210, and dry it.

[0123] Understandably, the conductive silver paste is printed on the surface of the dielectric layer 214 opposite to the silicon substrate 211.

[0124] S103, the substrate 210 and the conductive silver paste are sintered and solidified to obtain the electrode 100.

[0125] Understandably, after the substrate 210 and the conductive silver paste are sintered and cured, the conductive silver paste forms the electrode 100.

[0126] Understandably, during the sintering process of the substrate 210 and the conductive silver paste, the conductive silver paste corrodes a portion of the dielectric layer 214 in contact with it and penetrates into the dielectric layer 214 to achieve contact connection between the conductive silver paste and the polycrystalline silicon layer 213.

[0127] In the method for preparing the solar cell 200 provided in this embodiment, the conductive silver paste is modified by improving the composite glass material and conductive powder so that the conductive silver paste can fully melt at the sintering temperature and achieve corrosion and wetting of the dielectric layer 214. Furthermore, after contacting the polycrystalline silicon layer 213, the conductive silver paste can form a stable chemical bond with the surface of the polycrystalline silicon, improving the adhesion between the conductive silver paste and the polycrystalline silicon layer 213, and ultimately improving the bonding force between the electrode 100 and the polycrystalline silicon layer 213. In addition, the conductive silver paste also has good weather resistance, which extends the service life of the electrode 100 in humid and hot environments and acetic acid environments, preventing the adhesion of the electrode 100 from deteriorating after long-term use. Furthermore, the conductive powder is composed of the first conductive silver powder, the second conductive silver powder, and the conductive silver wire. The three-dimensional network structure formed by the first conductive silver powder, the second conductive silver powder, and the conductive silver wire is dense and has good mechanical strength. Simultaneously, it can penetrate into the tiny gaps on the surface of the polycrystalline silicon layer 213, thereby enabling the electrode 100 to possess both good electrical properties and flexural toughness, and to have good bonding strength with the polycrystalline silicon layer 213. The solar cell 200 prepared by the above method has low internal resistance and structural stability.

[0128] In some optional embodiments, the sintering and curing of the substrate 210 and the conductive silver paste includes: heating to a first preset temperature at a preset heating rate for sintering, and then cooling to a second preset temperature at a preset cooling rate for curing after sintering; wherein the preset heating rate v1 is in the range of 15℃ / s≤v1≤20℃ / s, the first preset temperature T1 is in the range of 740℃≤T1≤760℃, the preset cooling rate v2 is in the range of 10℃ / s≤v2≤15℃ / s, and the second preset temperature T2 is in the range of 200℃≤T2≤240℃.

[0129] Specifically, the preset heating rate v1 can be, but is not limited to, 15℃ / s, 15.5℃ / s, 16℃ / s, 16.5℃ / s, 17℃ / s, 17.5℃ / s, 18℃ / s, 18.5℃ / s, 19℃ / s, 19.5℃ / s, and 20℃ / s.

[0130] Specifically, the value of the first preset temperature T1 can be, but is not limited to, 740℃, 742℃, 744℃, 745℃, 746℃, 748℃, 750℃, 752℃, 754℃, 755℃, 756℃, 758℃, and 760℃.

[0131] Specifically, the preset cooling rate v2 can be, but is not limited to, 10℃ / s, 10.5℃ / s, 11℃ / s, 11.5℃ / s, 12℃ / s, 12.5℃ / s, 13℃ / s, 13.5℃ / s, 14℃ / s, 14.5℃ / s, and 15℃ / s.

[0132] Specifically, the value of the second preset temperature T2 can be, but is not limited to, 200℃, 202℃, 205℃, 208℃, 210℃, 215℃, 218℃, 220℃, 222℃, 225℃, 230℃, 232℃, 235℃, 238℃, and 240℃.

[0133] In this embodiment, sintering is performed by heating to a first preset temperature at a preset heating rate, and then curing is performed by cooling to a second preset temperature at a preset cooling rate after sintering. The preset heating rate and the preset cooling rate are relatively large. In other words, during the sintering process of the substrate 210 and the conductive silver paste, rapidly heating to the first preset temperature allows the organic carrier in the silver paste to volatilize quickly, preventing residual organic carrier from affecting the density of the silver film. Simultaneously, it shortens the residence time of the conductive powder in the medium-low temperature range, effectively inhibiting excessive growth of the conductive powder and ensuring its uniform dispersion, laying the foundation for forming a continuous and stable conductive path. Furthermore, rapid heating quickly crosses the medium-low temperature stage, reducing excessive oxidation of the tunneling oxide layer 212 and preventing structural damage. It also ensures that the composite glass material in the conductive silver paste is fully melted, strengthening the bond between the electrode 100 and the substrate 210, and avoiding high contact resistance due to insufficient melting of the composite glass material. Furthermore, rapidly cooling to the second preset temperature for curing after sintering reduces the difference in thermal expansion between the substrate 210 and the silver paste, reduces thermal stress accumulation, and avoids problems such as silver film cracking and damage to the functional layer of the substrate 210. This ensures a highly efficient and stable sintering process, improving production efficiency while guaranteeing the conductivity and structural stability of the electrode 100. When the solar cell 200 is cured at the second preset temperature, the interfacial thermal stress between the electrode 100 and the polycrystalline silicon layer 213 is fully released, residual trace amounts of organic carrier are cured, and the interfacial bonding force between the electrode 100 and the polycrystalline silicon layer 213 is further strengthened. Ultimately, the electrode 100 can be stably disposed on the substrate 210. The solar cell 200 prepared by the method provided in this application has better performance.

[0134] When the first preset temperature T1 meets the range of 740℃≤T1≤760℃, it is within a reasonable range to ensure that the organic carrier in the conductive silver paste fully volatilizes and that the conductive powder forms a stable sintering neck during sintering, constructing a continuous conductive network and effectively reducing the contact resistance between the electrode 100 and the substrate 210. Furthermore, the softening point of the composite glass material closely matches the sintering curve, allowing the composite glass material in the conductive silver paste to fully melt and wet the dielectric layer 214, thereby etching the dielectric layer 214 and achieving contact with the polycrystalline silicon layer 213, which is beneficial for improving the bonding force between the electrode 100 and the polycrystalline silicon layer 213. Moreover, it avoids burning through the polycrystalline silicon layer 213 due to excessively high first preset temperature and avoids insufficient melting of the composite glass material due to excessively low first preset temperature, thus allowing the composite glass material to fully exert its effect of improving the bonding force between the conductive silver paste and the polycrystalline silicon layer 213.

[0135] When the second preset temperature T2 is within the range of 200℃≤T2≤240℃, the internal stress of the solar cell 200 can be effectively eliminated without damaging its structure, while simultaneously curing the residual organic carrier. If the second preset temperature is too low, the stress elimination and curing effects will be weak. If the second preset temperature is too high, new thermal stress will be introduced, affecting the structural stability of the solar cell 200.

[0136] The technical solution of this application will be further described below with reference to several embodiments: Example 1: The conductive silver paste of Example 1 includes composite glass material, conductive powder and organic carrier.

[0137] (1) Preparation of composite glass material and corresponding test results: The composite glass material includes lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide. In the composite glass material, the mass fraction a1 of silicon dioxide is 10%, the mass fraction a2 of aluminum oxide is 5%, the mass fraction a3 of lead monoxide is 60%, and the mass fraction a4 of boron trioxide is 25%.

[0138] Corresponding tests and results: After a 6-hour acetic acid corrosion test, the cell efficiency degradation of the solar cell 200 in this embodiment was reduced by about 21% compared with the traditional PbO-B2O3 binary glass silver paste, and the long-term adhesion was significantly improved.

[0139] (2) Preparation of conductive powder and corresponding test results: In the conductive silver paste, the mass fraction A2 of the composite glass material is 2%.

[0140] The conductive powder comprises a first conductive silver powder, a second conductive silver powder, and a conductive silver wire. The mass fraction b1 of the first conductive silver powder is 20%, the mass fraction b2 of the second conductive silver powder is 75%, and the mass fraction b3 of the conductive silver wire is 5%.

[0141] Corresponding tests and results: The density of the silver film increased by more than 15% after sintering, and the friction resistance and extrusion resistance of the electrode 100 were significantly enhanced.

[0142] (3) Preparation of organic carriers: The organic carrier includes an organic solvent, a resin, and a thickener. In the organic carrier, the organic solvent has a mass fraction of 5.5%, the resin has a mass fraction of 2%, and the thickener has a mass fraction of 0.5%.

[0143] The resin system and solvent ratio of the organic carrier are optimized, and a resin material with a high thixotropic index is selected to make the conductive silver paste have both good printability and molding properties. After printing, the outline of the electrode 100 is clear and there is no ink overflow. After drying at 300-400℃, a silver film with high cohesive strength is formed. Its initial adhesion can withstand the friction during the flipping and transfer process on the production line, avoiding premature damage of the electrode 100 in subsequent processes.

[0144] Example 2: Example 2, based on the conductive silver paste of Example 1, precisely controls the parameters of the entire process of printing, drying, and sintering, forming a process synergy control chain to ensure that the conductive silver paste is fully bonded to the substrate 210, while avoiding structural damage caused by improper processes.

[0145] (1) Printing process control: A high-tension screen printing plate is used, the squeegee pressure is controlled to be greater than 80N, the printing speed ranges from 400mm / s to 550mm / s, and the printing gap ranges from 0.1 to 0.15mm; this ensures that the wet grid lines (i.e., conductive silver paste) have uniform thickness (deviation ≤5μm), no grid breaks, and no ink overflow, laying the foundation for subsequent drying and sintering.

[0146] (2) Drying process control: An infrared drying oven is used for constant temperature drying, with process parameters of 350℃±20℃ for no less than 20 seconds; this ensures that the organic solvent in the organic carrier evaporates completely and stably, leaving no residual bubbles, and forming a dense silver film. The initial adhesion of the silver film can withstand the friction of routine flipping on the production line.

[0147] (3) Sintering process control: The optimal sintering process is a rapid sintering curve with a first preset temperature T1 ranging from 740℃ to 760℃ (preset heating rate ranging from 15℃ / s to 20℃ / s, preset cooling rate ranging from 10℃ / s to 15℃ / s); the rapid sintering curve can effectively inhibit the excessive growth of conductive powder and avoid harmful interface reactions.

[0148] (4) Immediately after sintering, the solar cell 200 is placed in a constant temperature furnace at 220°C for low-temperature post-curing treatment (10 to 15 minutes). The core function is to release the thermal stress between the electrode 100 and the substrate 210, cure the trace organic matter remaining in the silver film, and further strengthen the interfacial bonding force.

[0149] Experimental data: After post-curing treatment, the average adhesion of the back electrode 100 of the solar cell 200 increased from 3.5N to 4.2N, an increase of 20%.

[0150] Example 3: Example 3 is based on the conductive silver paste of Example 1 and the parameter design of the entire process of printing, drying and sintering based on Example 2. It establishes a matching principle with the substrate 210 to ensure that the thickness of the conductive silver paste is adapted to the thickness of the polycrystalline silicon layer 213. While obtaining good ohmic contact, it protects the passivation structure and maintains strong interface bonding.

[0151] (1) Surface treatment of substrate 210: Before printing the conductive silver paste, the substrate 210 is cleaned using a plasma cleaning process to remove surface oil, dust and other contaminants, ensuring good wettability of the conductive silver paste on the surface of the substrate 210 and ensuring full contact between the conductive silver paste and the substrate 210.

[0152] (2) Matching criteria for the thickness of conductive silver paste and polycrystalline silicon layer 213: When the thickness of the polycrystalline silicon layer 213 is greater than 100 nm, conventional conductive silver paste can be used.

[0153] When the thickness of the polysilicon layer 213 is less than or equal to 100 nm, the conductive silver paste provided in this application should be used. The conductive silver paste can be adapted to a thinner polysilicon layer 213 and is tightly bonded to the polysilicon layer 213.

[0154] Based on the above, the conductive silver paste provided in this application, after being printed, sintered, and cured, forms the electrode 100 on the surface of the substrate 210, which has the following beneficial effects: Firstly, the electrode 100 and the substrate 210 have good adhesion, and the solar cell 200 has long-term reliability. By improving the conductive silver paste, the mechanical anchoring and chemical bonding of the interface between the electrode 100 and the substrate 210 are strengthened from the source. The peel force of the electrode 100 of the solar cell 200 prepared by this method can reach 4.0N to 5.5N under normal conditions, with a preferred range of 4.2N to 5.0N. After being placed in a humid heat environment of 85℃ / 85%RH for 1000 hours, the peel force retention rate is greater than or equal to 85%, and the peel force is still maintained at 3.4N to 4.7N. After 6 hours of acetic acid corrosion test, the peel force retention rate is greater than or equal to 90%, with no powdering or peeling. In the harsh stress environment of module encapsulation (lamination, welding) and long-term outdoor operation (humid heat, acetic acid corrosion), the risk of electrode 100 powder shedding / detachment of the solar cell 200 is greatly reduced. After accelerated aging test, the efficiency degradation of the solar cell 200 is less than or equal to 5%, which is far superior to the existing technology.

[0155] Secondly, it improves production yield and the average photoelectric conversion efficiency of solar cells 200: it effectively reduces the hidden efficiency loss and scrap rate caused by electrode 100 powder shedding and detachment, and the production yield of solar cells 200 is improved by 3% to 5% in mass production tests; at the same time, the optimized bonding characteristics of the conductive silver paste and the substrate 210 interface make the contact resistance lower and more stable, which makes a positive contribution to improving the average photoelectric conversion efficiency of the solar cells 200, and the average efficiency of mass-produced solar cells 200 is improved by 0.1% to 0.2%.

[0156] Third, the conductive silver paste provided in this application has strong compatibility with the process and is easy to implement in mass production: the customized silver paste of this invention can be adapted to the screen printing equipment of existing production lines. The process parameter adjustment can be completed on the existing equipment without the need to add large-scale production equipment. The transformation cost is low and it is easy to promote and apply in the industry.

[0157] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form yet another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0158] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A conductive silver paste, characterized in that, The conductive silver paste comprises: A composite glass material comprising lead monoxide, boron trioxide, silicon dioxide, and aluminum oxide, wherein the mass ratio α of silicon dioxide to aluminum oxide ranges from 1.5 to 2.5; and The conductive powder comprises a first conductive silver powder, a second conductive silver powder, and conductive silver wires, wherein the size of the first conductive silver powder is less than 1 μm, and the size of the second conductive silver powder is larger than the size of the first conductive silver powder.

2. The conductive silver paste according to claim 1, characterized in that, The mass ratio β of the conductive powder to the composite glass material is in the range of 34≤β≤61.

33.

3. The conductive silver paste according to claim 1, characterized in that, In the composite glass material, the mass fraction a1 of silicon dioxide ranges from 8% to 12%; the mass fraction a2 of aluminum oxide ranges from 4% to 6%.

4. The conductive silver paste according to claim 1, characterized in that, In the composite glass material, the mass fraction a3 of lead monoxide ranges from 55% to 65%; the mass fraction a4 of boron trioxide ranges from 15% to 22%.

5. The conductive silver paste according to claim 1, characterized in that, In the conductive powder, the mass fraction b1 of the first conductive silver powder ranges from 15% to 25%; the mass fraction b2 of the second conductive silver powder ranges from 70% to 80%; and the mass fraction b3 of the conductive silver wire ranges from 3% to 8%.

6. The conductive silver paste according to claim 1, characterized in that, The conductive powder satisfies at least one of the following conditions: The average particle size d1 of the first conductive silver powder is in the range of 50nm≤d1≤200nm; The average particle size d2 of the second conductive silver powder is in the range of: 1μm≤d2≤3μm; The sphericity of the second conductive silver powder is greater than or equal to 95%; The radial dimension d3 of the conductive silver wire is in the range of: 20nm≤d3≤50nm; The length d4 of the conductive silver wire is in the range of: 10μm≤d4≤30μm; The aspect ratio of the conductive silver wire is greater than or equal to 200.

7. The conductive silver paste according to any one of claims 1 to 6, characterized in that, In the conductive silver paste, the mass fraction A1 of the composite glass material ranges from 1.5% to 2.5%; or, the mass fraction A2 of the conductive powder ranges from 85% to 92%.

8. An electrode, characterized in that, The electrode is made using the conductive silver paste described in any one of claims 1 to 7.

9. A solar cell, characterized in that, The solar cell includes: a substrate and the electrode as described in claim 8, wherein the electrode is disposed on the surface of the substrate.

10. The solar cell according to claim 9, characterized in that, The substrate includes a silicon substrate, a tunneling oxide layer and a polysilicon layer stacked together, and the electrode is located on the side of the polysilicon layer away from the silicon substrate and connected to the polysilicon layer. The thickness h of the polycrystalline silicon layer is in the range of 70nm≤h≤100nm.

11. A method for preparing a solar cell, characterized in that, The method for preparing the solar cell includes: Provide substrate; Provide the conductive silver paste according to any one of claims 1 to 7, print the conductive silver paste onto the substrate, and dry it; The substrate and the conductive silver paste are sintered and cured to obtain the electrode.

12. The preparation method according to claim 11, characterized in that, The sintering and curing of the substrate and the conductive silver paste includes: heating to a first preset temperature at a preset heating rate for sintering, and cooling to a second preset temperature at a preset cooling rate after sintering for curing. The preset heating rate v1 is in the range of 15℃ / s ≤ v1 ≤ 20℃ / s, the first preset temperature T1 is in the range of 740℃ ≤ T1 ≤ 760℃, the preset cooling rate v2 is in the range of 10℃ / s ≤ v2 ≤ 15℃ / s, and the second preset temperature T2 is in the range of 200℃ ≤ T2 ≤ 240℃.

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