Back contact solar cell and photovoltaic module

Abstract

The application provides a back contact solar cell and a photovoltaic module. The back contact solar cell comprises a cell body and a grid line arranged on the back of the cell body. The grid line comprises, in sequence along a first direction, a metal seed layer, a conductive transfer layer and a metal protective layer. The metal seed layer is in conductive contact with the cell body. The orthographic projection of the conductive transfer layer on the cell body is located within the orthographic projection of the metal protective layer on the cell body, and the orthographic projection of the conductive transfer layer on the cell body covers the orthographic projection of the metal seed layer on the cell body. The material of the metal seed layer comprises a first metal. The material of the conductive transfer layer comprises a second metal, and the second metal is a base metal with an electrical conductivity not less than 2*10 7 S / m. The material of the metal protective layer comprises a third metal. Through the improvement of the structure and the material, the grid line has good conductive performance, and the manufacturing cost of the back contact solar cell is reduced.

Description

Technical Field

[0001] This application relates to the field of solar cells, and more particularly to a back-contact solar cell and photovoltaic module. Background Technology

[0002] Back-contact solar cells are solar cells with no grid lines on the front and the grid lines in the P and N regions are interlaced on the back of the cell. However, silver is expensive and its resources are limited, which is not conducive to reducing the manufacturing cost of solar cells.

[0003] In related technologies, copper grid lines are used to partially or completely replace silver in the manufacture of grid lines. However, copper is prone to oxidation in air, and the conductivity of copper grid lines is still not as good as that of silver grid lines. Therefore, it is difficult to apply them on a large scale in the current manufacturing of back contact solar cells. Summary of the Invention

[0004] To address the aforementioned technical issues, this application discloses a back-contact solar cell and photovoltaic module, which enables the grid lines to have good conductivity while reducing manufacturing costs.

[0005] In one aspect, this application provides a back-contact solar cell, including a cell body and grid lines disposed on the back side of the cell body. Along a first direction of the cell body, the grid lines sequentially include a metal seed layer, a conductive transport layer and a metal protective layer. The metal seed layer is in conductive contact with the cell body. The first direction is the direction from the front side to the back side of the cell body. The orthographic projection of the conductive transport layer on the battery body is located within the orthographic projection of the metal protective layer on the battery body, and the orthographic projection of the conductive transport layer on the battery body covers the orthographic projection of the metal seed layer on the battery body. The material of the metal seed layer includes a first metal, which has silicon inward diffusion stability; The conductive transport layer is made of a second metal, wherein the second metal has a conductivity of not less than 2 × 10⁻⁶. 7 Base metals with S / m; The material of the metal protective layer includes a third metal, which has oxidation stability.

[0006] In some embodiments of this application, the metal protective layer extends beyond the edge of the conductive transport layer by a dimension D1, where 0.5 μm ≤ D1 ≤ 50 μm.

[0007] In some embodiments of this application, the width of the metal seed layer is W1, the width of the conductive transport layer is W2, and the width of the metal protective layer is W3, satisfying: W3>W2≥W1.

[0008] In some embodiments of this application, 4μm≤W1≤450μm, 4μm≤W2≤450μm, and 5μm≤W3≤500μm.

[0009] In some embodiments of this application, the orthographic projection of the metal seed layer onto the battery body lies within the orthographic projection of the conductive transport layer onto the battery body.

[0010] In some embodiments of this application, the dimension of the conductive transport layer extending beyond the edge of the metal seed layer is D2, where 0 μm ≤ D2 ≤ 10 μm.

[0011] In some embodiments of this application, the metal protective layer, the conductive transport layer, and the metal seed layer form an inverted step structure along the first direction.

[0012] In some embodiments of this application, the metal seed layer includes a first main body layer and a first embedding segment, the first main body layer being spread on the surface of the battery body, and the first embedding segment being embedded in the battery body and in conductive contact with the battery body.

[0013] In some embodiments of this application, the conductive transport layer includes a second body layer and a second embedded segment, the second body layer being spread on the surface of the metal seed layer and the second embedded segment being embedded in the metal seed layer.

[0014] In some embodiments of this application, the thickness of the first main layer is H1, the thickness of the second main layer is H2, and the thickness of the metal protective layer is H3, where H1 < H3 ≤ H2.

[0015] In some embodiments of this application, 20nm≤H1≤1μm, 0.5μm≤H2≤10μm, and 0.5μm≤H3≤10μm.

[0016] In some embodiments of this application, the battery body includes a silicon substrate, and the back side of the silicon substrate includes alternately arranged N-type regions and P-type regions, wherein the N-type regions include an N-type doped layer and the P-type regions include a P-type doped layer; In the N-type region, the first embedded segment penetrates other functional film layers on the back side of the silicon substrate and contacts the N-type doped layer; In the P-type region, the first embedded segment penetrates other functional film layers on the back side of the silicon substrate and contacts the P-type doped layer; The other functional films include a second interface passivation layer and a back antireflection layer.

[0017] In some embodiments of this application, the first metal includes at least one selected from silver, nickel, aluminum, molybdenum, titanium, and tungsten; The second metal includes at least one of copper and aluminum; The third metal includes at least one of tin, nickel, aluminum, titanium, and tungsten.

[0018] In some embodiments of this application, the metal seed layer is a single-layer structure or a multi-layer composite structure.

[0019] In some embodiments of this application, the gate lines include main gates and fine gates.

[0020] Secondly, this application provides a photovoltaic module, which includes a back-contact solar cell as described in the first aspect.

[0021] Compared with the prior art, this application has at least the following beneficial effects: This application provides a back-contact solar cell and a photovoltaic module. The back-contact solar cell includes a cell body and grid lines disposed on the back side of the cell body. Along a first direction, the grid lines sequentially include a metal seed layer, a conductive transport layer, and a metal protective layer. The metal seed layer is in conductive contact with the cell body. The orthographic projection of the conductive transport layer on the cell body lies within the orthographic projection of the metal protective layer on the cell body, thereby allowing the upper surface of the conductive transport layer to be covered by the metal protective layer. Furthermore, the metal seed layer below the conductive transport layer is also indirectly covered by the metal protective layer, protecting and preventing oxidation of the metal in the conductive transport layer and the metal seed layer due to contact with the external environment. This effectively protects the underlying conductive transport layer and the metal seed layer. Moreover, the orthographic projection of the conductive transport layer on the cell body overlaps the orthographic projection of the metal seed layer on the cell body, ensuring close contact between the upper surface of the metal seed layer and the conductive transport layer, thus improving the ability of charge carriers to transport from the metal seed layer to the conductive transport layer. The metal seed layer of this application comprises a first metal, which has silicon inward diffusion stability and is not easily migrated into the inner silicon substrate, thus preventing metal atoms from diffusing into the interior of the battery body and increasing the recombination probability of charge carriers, thereby improving the functional stability of the metal seed layer; the conductive transport layer comprises a second metal, which has a conductivity of not less than 2 × 10⁻⁶. 7 The base metal with a S / m ratio achieves good carrier transport while reducing the consumption of precious metals, thereby lowering manufacturing costs. The metal protective layer material includes a third metal, which has oxidation stability and is not easily oxidized or deteriorated in the external environment, thus preventing water vapor and oxygen from entering the back contact solar cell through the metal protective layer and corroding the conductive transport layer and metal seed layer. In summary, this application improves both the structure and materials of the back contact solar cell grid lines, achieving good conductivity while reducing the manufacturing cost of the back contact solar cell. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of a back-contact solar cell in one embodiment of this application; Figure 2 This is a schematic diagram of the grid line structure in one embodiment of this application; Figure 3 This is a top view of the grid lines in one embodiment of this application; Figure 4 This is a schematic diagram of the grid line structure in another embodiment of this application; Figure 5 This is a schematic diagram of the grid line structure in another embodiment of this application; Figure 6 This is a schematic diagram of the structure of the metal seed layer in another embodiment of this application; Figure 7 This is a schematic diagram of the structure of a back-contact solar cell semi-finished product according to one embodiment of this application; Figure 8 This is a schematic diagram illustrating the opening treatment in one embodiment of this application; Figure 9 This is a schematic diagram of a metal seed layer deposited in one embodiment of this application; Figure 10 This is a schematic diagram of a conductive transport layer deposited in one embodiment of this application; Figure 11 This is a schematic diagram of a deposited metal protective layer in one embodiment of this application; Figure 12 This is a schematic diagram illustrating the fabrication of a mask layer in one embodiment of this application; Figure 13 This is a schematic diagram illustrating etching in one embodiment of this application; Figure 14 This is a schematic diagram illustrating the removal of the mask layer in one embodiment of this application; Figure 15 This is a micrograph of the grid lines in one embodiment of this application.

[0024] Explanation of reference numerals in the attached figures: 1-Silicon substrate, 2-First interface passivation layer, 3-N-type doped layer, 4-P-type doped layer, 5-Front-side passivation layer, 6-Front-side antireflection layer, 7-Second interface passivation layer, 8-Back-side antireflection layer, 9-Gate line, 10-Isolation region, 12-Mask layer, 91-Metal seed layer, 92-Conductive transport layer, 93-Metal protective layer, 911-First main layer, 912-First embedding segment, 921-Second main layer, 922-Second embedding segment. Detailed Implementation

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

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

[0027] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0028] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.

[0029] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0030] The technical solution of this application will be further described below with reference to the embodiments and accompanying drawings.

[0031] Firstly, this application provides a back-contact solar cell. (Reference) Figure 1 The back-contact solar cell includes a cell body and grid lines 9 disposed on the back side of the cell body. Along a first direction of the cell body, the grid lines 9 sequentially include a metal seed layer 91, a conductive transport layer 92, and a metal protective layer 93. The metal seed layer 91 is in conductive contact with the cell body. Specifically, the metal seed layer 91 penetrates the second interface passivation layer 7 and the back anti-reflection layer 8 and contacts the N-type doped layer 3. The orthographic projection of the conductive transport layer 92 onto the cell body lies within the orthographic projection of the metal protective layer 93 onto the cell body, and the orthographic projection of the conductive transport layer 92 onto the cell body covers the orthographic projection of the metal seed layer 91 onto the cell body. For example, refer to... Figure 2 and Figure 3 The width of the conductive transport layer 92 is greater than the width of the metal seed layer 91, and the projected area of ​​the conductive transport layer 92 on the battery body can be greater than the projected area of ​​the metal seed layer 91 on the battery body; or, refer to Figure 4 The width of the conductive transport layer 92 is equal to the width of the metal seed layer 91, and the projected area of ​​the conductive transport layer 92 on the battery body can be equal to the projected area of ​​the metal seed layer 91 on the battery body. The metal seed layer is made of a first metal, which has silicon-in-semiconductor stability and is not easily migrated to the inner silicon substrate. The conductive transport layer is made of a second metal, which has a conductivity of not less than 2 × 10⁻⁶. 7 Base metals with a conductivity of S / m have the advantages of good electrical conductivity and relatively low price. Materials for the metal protective layer include tertiary metals, which have oxidation stability and are not easily oxidized.

[0032] In this application, the first direction refers to the direction from the front to the back of the battery body. The battery body can be the body structure of a back-contact solar cell, excluding the grid lines.

[0033] This application provides a back-contact solar cell, wherein the orthographic projection of the conductive transport layer on the cell body lies within the orthographic projection of the metal protective layer on the cell body, thereby allowing the upper surface of the conductive transport layer to be covered by the metal protective layer. Furthermore, the metal seed layer beneath the conductive transport layer is also indirectly covered by the metal protective layer, protecting and preventing oxidation of the metals in the conductive transport layer and metal seed layer due to contact with the external environment, thus achieving effective protection for the underlying conductive transport layer and metal seed layer. Moreover, the orthographic projection of the conductive transport layer on the cell body overlaps the orthographic projection of the metal seed layer on the cell body, ensuring close contact between the upper surface of the metal seed layer and the conductive transport layer, improving the ability of charge carriers to transport from the metal seed layer to the conductive layer. The metal seed layer in this application is made of a first metal, which possesses silicon inward diffusion stability and is not easily migrated into the inner silicon substrate, improving the functional stability of the metal seed layer. The conductive transport layer is made of a second metal, which has a conductivity of not less than 2 × 10⁻⁶. 7 The base metal with a S / m ratio achieves good carrier transport while reducing the consumption of precious metals, thereby lowering manufacturing costs. The metal protective layer material includes a third metal, which has oxidation stability and is not easily oxidized or deteriorated in the external environment, thus preventing water vapor and oxygen from entering the back contact solar cell through the metal protective layer and corroding the conductive transport layer and metal seed layer. In summary, this application improves both the structure and materials of the back contact solar cell grid lines, achieving good conductivity while reducing the manufacturing cost of the back contact solar cell.

[0034] In some embodiments of this application, reference is made to Figure 2 The metal protective layer 93 extends beyond the edge of the conductive transport layer 92 by a dimension D1, where 0.5 μm ≤ D1 ≤ 50 μm. That is, the portion of the metal protective layer extending beyond the edge forms an outrigger structure. For example, D1 can be 0.5 μm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm. Within this range, the metal protective layer effectively covers the upper surface of the conductive transport layer, and the outrigger structure also covers at least a portion of the side surface of the conductive transport layer. For example, the outrigger structure covers a portion of the side surface of the conductive transport layer, or it covers the entire side surface of the conductive transport layer, thereby protecting the side surface of the conductive transport layer and preventing the metal protective layer from blocking light and affecting the solar cell efficiency due to an excessively long outrigger portion.

[0035] The expenditure structure of this application can exist in the width direction of the back contact solar cell or in the length direction of the back contact solar cell.

[0036] In some embodiments of this application, reference is made to Figure 2The width of the metal seed layer is W1, the width of the conductive transport layer is W2, and the width of the metal protective layer is W3, satisfying the condition: W3>W2≥W1. The fact that W1, W2, and W3 satisfy the above relationship facilitates the formation of the multilayer composite gate structure of this application, thereby achieving effective protection of the underlying conductive transport layer and metal seed layer through the metal protective layer.

[0037] In some embodiments of this application, reference is made to Figure 2 , 4μm≤W1≤450μm, 4μm≤W2≤450μm, 5μm≤W3≤500μm. For example, W1 is 4μm, 10μm, 50μm, 100μm, 200μm, 300μm, 400μm or 450μm, W2 is 4μm, 5μm, 10μm, 15μm, 50μm, 80μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm or 450μm, W3 is 5μm, 10μm, 15μm, 50μm, 80μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm or 500μm. Within the aforementioned range, W1, W2, and W3 facilitate the formation of the multilayer composite structure gate lines of this application, thereby achieving effective protection of the underlying conductive transport layer and metal seed layer through the metal protective layer.

[0038] In some embodiments of this application, reference is made to Figure 2 The orthographic projection of the metal seed layer 91 onto the battery body lies within the orthographic projection of the conductive transport layer 92 onto the battery body. Thus, the edge of the conductive transport layer extends beyond the edge of the metal seed layer, allowing the upper surface of the metal seed layer to be completely covered by the conductive transport layer. This ensures close contact between the upper surface of the metal seed layer and the conductive transport layer, improving the ability of charge carriers to transport from the metal seed layer to the conductive transport layer. Furthermore, the conductive transport layer also provides protection for the metal seed layer beneath it.

[0039] In some embodiments of this application, reference is made to Figure 2 The conductive transport layer 92 extends beyond the edge of the metal seed layer 91 by a dimension D2, where 0 μm ≤ D2 ≤ 10 μm. For example, D2 can be 0 μm, 1 μm, 3 μm, 5 μm, 7 μm, 8 μm, or 10 μm. Within the above range, the conductive transport layer can extend beyond the edge of the metal seed layer, or the edge of the conductive transport layer can be flush with the edge of the metal seed layer. The upper surface of the metal seed layer can be covered by the conductive transport layer, ensuring close contact between the upper surface of the metal seed layer and the conductive transport layer, thereby improving the ability of charge carriers to transport from the metal seed layer to the conductive transport layer.

[0040] In some embodiments of this application, reference is made to Figure 5The metal protective layer 93, the conductive transport layer 92, and the metal seed layer 91 form an inverted step structure along a first direction. Specifically, along the first direction, the length and / or width of the metal protective layer 93, the conductive transport layer 92, and the metal seed layer 91 increase sequentially, thereby forming an inverted step structure. The metal protective layer, the conductive transport layer, and the metal seed layer form an inverted step structure along the length and / or width direction of the back contact solar cell, and this inverted step structure has at least two inverted steps on each side of the grid line. Figure 5 The reflection path of the light is also shown with arrows. (Reference) Figure 5 Each step has the ability to reflect light emitted from the back of the solar cell back to the back-contact solar cell. In one scenario, light escaping from the front of the cell is reflected back onto the cell by the step structure, gaining a second absorption opportunity. In another scenario, light reflected from the back of the cell onto the step structure is also reflected onto the cell surface, gaining a second absorption opportunity. This increases the light absorption capacity of the back-contact solar cell's back area, improves the short-circuit current, and thus improves the photoelectric conversion efficiency of the back-contact solar cell.

[0041] In some embodiments of this application, reference is made to Figure 2 The metal seed layer 91 includes a first main layer 911 and a first embedding segment 912. The first main layer 911 is spread on the surface of the battery body. Specifically, the first main layer 911 is spread on the surface of the back antireflection layer 8 of the battery body, increasing the contact area between the metal seed layer and the battery body, thereby improving the bonding strength between the metal seed layer and the battery body. The first embedding segment 912 is embedded in the battery body and makes conductive contact with the battery body. Specifically, the first embedding segment 912 penetrates and embeds into the second interface passivation layer 7 and the back antireflection layer 8 of the battery body, and then contacts the N-type doped layer 3. The first embedding segment of the metal seed layer not only further improves the bonding strength between the metal seed layer and the battery body, but also improves the carrier transport capability of the gate line.

[0042] In some embodiments of this application, reference is made to Figure 2 The conductive transport layer 92 includes a second main layer 921 and a second embedded segment 922. The second main layer 921 is spread on the surface of the metal seed layer 91. Specifically, the second main layer 921 spreads on the surface of the first main layer 911 of the metal seed layer 91, increasing the contact area between the conductive transport layer and the metal seed layer, thereby improving the bonding strength between the conductive transport layer and the metal seed layer. The second embedded segment 922 is embedded in the metal seed layer 91, specifically, the second embedded segment 922 is embedded inside the first embedded segment 912. The second embedded segment of the conductive transport layer not only further improves the bonding strength between the conductive transport layer and the metal seed layer, but also improves the carrier transport capacity between the conductive transport layer and the metal seed layer.

[0043] In some embodiments of this application, reference is made to Figure 2 The thickness of the first main layer 911 is H1, the thickness of the second main layer 921 is H2, and the thickness of the metal protective layer 93 is H3, where H1 < H3 ≤ H2. H2 ≥ H3 is because the second main layer 921 is the primary conductive layer, and its greater thickness improves the conductivity of the grid lines. H3 > H1 is because the metal protective layer requires a larger thickness to isolate external moisture and oxygen, protecting the underlying conductive transport layer and metal seed layer, thus ensuring the conductivity of the grid lines. A smaller thickness of H1 reduces the amount of expensive metal used, thereby lowering the manufacturing cost of the grid lines and consequently reducing the manufacturing cost of the back contact solar cell.

[0044] In some embodiments of this application, reference is made to Figure 2 The specified values ​​are: 20nm ≤ H1 ≤ 1μm, 0.5μm ≤ H2 ≤ 10μm, and 0.5μm ≤ H3 ≤ 10μm. For example, H1 can be 20nm, 50nm, 100nm, 200nm, 500nm, 800nm, or 1μm; H2 can be 0.5μm, 0.8μm, 1μm, 3μm, 5μm, 7μm, 9μm, or 10μm; and H3 can be 0.5μm, 1μm, 3μm, 5μm, 7μm, or 10μm. The inclusion of H1, H2, and H3 within these ranges allows the gate line to have good conductivity while reducing its manufacturing cost.

[0045] In some embodiments of this application, reference is made to Figure 1 and Figure 2 The battery body includes a silicon substrate 1. A first interface passivation layer 2 is disposed on the back side of the silicon substrate 1. The back side of the silicon substrate 1 includes alternately arranged N-type regions and P-type regions. The N-type regions include an N-type doped layer 3 located on the surface of the first interface passivation layer 2 in the N-type regions. The P-type regions include a P-type doped layer 4 located on the surface of the first interface passivation layer 2 in the P-type regions. In the N-type regions, a first embedding segment 912 penetrates other functional film layers on the back side of the silicon substrate 1 and contacts the N-type doped layer 3. In the P-type regions, the first embedding segment 912 penetrates other functional film layers on the back side of the silicon substrate 1 and contacts the P-type doped layer 4. The other functional film layers include a second interface passivation layer 7 and a back anti-reflection layer 8. In addition, an isolation region 10 is provided between the N-type regions and the P-type regions. The grid structure of this application is applied to back contact solar cells, reducing the manufacturing cost of back contact solar cells.

[0046] In some embodiments of this application, the first metal includes at least one of silver, nickel, aluminum, molybdenum, titanium, and tungsten. The aforementioned metals have silicon inward diffusion stability and are not easily migrated to the inner silicon substrate, thereby improving the functional stability of the metal seed layer. The second metal includes at least one of copper and aluminum. The aforementioned metals reduce the consumption of precious metals while achieving good carrier transport capability, thereby reducing manufacturing costs. The third metal includes at least one of tin, nickel, aluminum, titanium, and tungsten. The aforementioned metals have oxidation stability and are not easily oxidized and deteriorated in the external environment, thereby preventing water vapor and oxygen from entering the back contact solar cell through the metal protective layer and corroding the conductive transport layer and the metal seed layer.

[0047] In some embodiments of this application, the metal seed layer can be a single-layer structure or a multi-layer composite structure. (Reference) Figure 2 The metal seed layer can be a single-layer structure formed from a first metallic material, which has the advantage of simple preparation; or, refer to Figure 6 The metal seed layer can be a multilayer composite structure formed by two or more first metal materials, such as a multilayer composite structure formed by silver and nickel. By replacing a portion of the silver with nickel, the manufacturing cost of the gate line can be further reduced.

[0048] In some embodiments of this application, the grid lines include a main grid and fine grids. The grid line structure of this application can be applied not only to the fine grids but also to the main grids, replacing expensive metals such as silver in the original main grids and fine grids, thereby further reducing the manufacturing cost of back-contact solar cells.

[0049] In some embodiments of this application, reference is made to Figure 1 The front side of the back contact solar cell also includes a front passivation layer 5 and a front anti-reflection layer 6, and the front side of the silicon substrate 1 has a front textured structure.

[0050] The material of the first interface passivation layer in this application can include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Specifically, the first interface passivation layer can be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent interface passivation performance, which can minimize the recombination loss of minority carriers on the semiconductor substrate surface, and is a thin film with excellent reliability and durability for subsequent high-temperature processes. To better provide interface passivation for the substrate, the thickness of the first interface passivation layer can be 0.8 nm to 5 nm. For example, the thickness of the first interface passivation layer can be 0.8 nm, 1.0 nm, 1.2 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm, etc. However, this application is not limited to these values, and the thickness of the first interface passivation layer can have various values. The first interface passivation layer can also have a pinhole channel function, allowing carriers in the crystalline silicon solar cell to move freely. The selective passage of majority carriers is generated by heavily doped polycrystalline silicon, which helps to reduce the recombination loss of minority carriers.

[0051] In this application, the material of the front passivation layer includes aluminum oxide; the material of the antireflection layer includes, but is not limited to, silicon nitride, silicon oxynitride, and silicon oxide.

[0052] This application does not impose any particular restrictions on the thickness of each functional film layer. Technicians can set and adjust the thickness of each functional film layer according to the structural characteristics of the back contact solar cell.

[0053] This application does not impose any particular limitation on the method for fabricating the grid lines, as long as the grid line structure of this application can be achieved. In some embodiments of this application, taking the process of forming a fine grid as an example, the method for fabricating the back contact solar cell and the grid lines may include the following steps: Step A, Reference Figure 7 We provide semi-finished back-contact solar cells; Step B, Reference Figure 8 An opening is made in the second interface passivation layer 7 of the N-type region and the P-type region and the back anti-reflection layer 8, so that the N-type doped layer 3 and the P-type doped layer 4 are exposed at the opening. Step C, Reference Figure 9 A metal seed layer 91 is deposited on the back side of the back contact solar cell semi-finished product; Step D, Reference Figure 10 A conductive transport layer 92 is deposited on the surface of the metal seed layer 91; Step E, Reference Figure 11 A metal protective layer 93 is deposited on the surface of the conductive transport layer 92; Step F, Reference Figure 12A mask layer 12 is fabricated on the surface of the metal protective layer 93, and the position of the mask layer corresponds to the position where the fine grid is to be formed, that is, the opening position. Step G, Reference Figure 13 The metal protective layer, conductive transport layer and metal seed layer are etched using an etching solution. The metal protective layer, conductive transport layer and metal seed layer at the opening are not etched away under the protection of the mask. Step H, Reference Figure 14 The mask layer is removed to form the fine gate structure of this application.

[0054] In step A, the back-contact solar cell semi-finished product includes a silicon substrate 1. A first interface passivation layer 2 is disposed on the back side of the silicon substrate 1. The back side of the silicon substrate 1 includes alternately arranged N-type and P-type regions. The N-type regions include an N-type doped layer 3 located on the surface of the first interface passivation layer 2 in the N-type regions; the P-type regions include a P-type doped layer 4 located on the surface of the first interface passivation layer 2 in the P-type regions. A second interface passivation layer 7 and a back anti-reflection layer 8 are also stacked on the back side of the back-contact solar cell semi-finished product. Furthermore, an isolation region 10 is provided between the N-type and P-type regions. The front side of the back-contact solar cell semi-finished product is provided with a front passivation layer 5 and a front anti-reflection layer 6, and the front side of the silicon substrate 1 has a textured surface structure.

[0055] In step B, the opening process can specifically remove the second interface passivation layer (specifically, an aluminum oxide film layer) and the back antireflection layer (specifically, a silicon nitride film layer) of the area to be formed by laser, exposing the underlying P-type doped layer, which facilitates the subsequent formation of ohmic or Schottky contacts between the P-type doped layer and the metal seed layer.

[0056] In steps C to E, the deposition process of the metal seed layer, conductive transport layer, and metal protective layer includes, but is not limited to, magnetron sputtering, vapor deposition, electroless plating, or electroplating.

[0057] In step F, the mask layer material includes epoxy resin or acrylic resin. The width of the gate lines can be adjusted by controlling the width of the mask.

[0058] In step G, during the formation of the gate lines with the expenditure structure of this application, the different etching capabilities of different metals in different solutions can be utilized for fabrication, allowing direct etching in the same etching solution. The etching rate of the metal protective layer is lower than that of the conductive transport layer, thus preserving the metal protective layer beneath the mask. The etching solution may include a mixture of 1 wt% to 5 wt% sulfuric acid and 1 wt% to 5 wt% hydrogen peroxide.

[0059] In the back-contact solar cell of this application, the fabrication principle of the main grid is the same as that of the fine grid, and will not be repeated here.

[0060] Figure 15 This is a micrograph of a gate line in one embodiment of this application, specifically a micrograph of one side of the gate line. From Figure 15 As can be seen, the metal protective layer, conductive transport layer, and metal seed layer are stacked, and their widths gradually decrease, exhibiting a distinct outward structure. The other side of the gate line also has the above structure.

[0061] Thirdly, this application provides a photovoltaic module, which includes a back-contact solar cell as described in the first aspect.

[0062] This application also provides a photovoltaic module for converting received light energy into electrical energy and transmitting it to an external load. The photovoltaic module includes: at least one cell string, which is composed of multiple solar cells connected together; an encapsulating film for covering the surface of the cell string; and a cover plate for covering the surface of the encapsulating film facing away from the cell string.

[0063] The foregoing has provided a detailed description of a back-contact solar cell and photovoltaic module disclosed in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core inventive points of the embodiments of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A back-contact solar cell, characterized in that, The battery includes a battery body and grid lines disposed on the back of the battery body. Along a first direction of the battery body, the grid lines sequentially include a metal seed layer, a conductive transport layer and a metal protective layer. The metal seed layer is in conductive contact with the battery body. The first direction is the direction from the front to the back of the battery body. The orthographic projection of the conductive transport layer on the battery body is located within the orthographic projection of the metal protective layer on the battery body, and the orthographic projection of the conductive transport layer on the battery body covers the orthographic projection of the metal seed layer on the battery body. The material of the metal seed layer includes a first metal, which has silicon inward diffusion stability; The conductive transport layer is made of a second metal, wherein the second metal has a conductivity of not less than 2 × 10⁻⁶. 7 Base metals with S / m; The material of the metal protective layer includes a third metal, which has oxidation stability.

2. The back-contact solar cell according to claim 1, characterized in that, The metal protective layer extends beyond the edge of the conductive transport layer by a dimension D1, where 0.5μm≤D1≤50μm.

3. The back-contact solar cell according to claim 1, characterized in that, The width of the metal seed layer is W1, the width of the conductive transport layer is W2, and the width of the metal protective layer is W3, satisfying: W3>W2≥W1.

4. The back-contact solar cell according to claim 3, characterized in that, 4μm≤W1≤450μm, 4μm≤W2≤450μm, 5μm≤W3≤500μm.

5. The back-contact solar cell according to claim 1, characterized in that, The orthographic projection of the metal seed layer onto the battery body lies within the orthographic projection of the conductive transport layer onto the battery body.

6. The back-contact solar cell according to claim 4, characterized in that, The conductive transport layer extends beyond the edge of the metal seed layer by a dimension D2, where 0 μm ≤ D2 ≤ 10 μm.

7. The back-contact solar cell according to claim 4, characterized in that, The metal protective layer, the conductive transport layer, and the metal seed layer form an inverted step structure along the first direction.

8. The back-contact solar cell according to claim 1, characterized in that, The metal seed layer includes a first main body layer and a first embedded segment. The first main body layer is spread on the surface of the battery body, and the first embedded segment is embedded in the battery body and makes conductive contact with the battery body.

9. The back-contact solar cell according to claim 8, characterized in that, The conductive transport layer includes a second main layer and a second embedded segment. The second main layer is spread on the surface of the metal seed layer, and the second embedded segment is embedded in the metal seed layer.

10. The back-contact solar cell according to claim 9, characterized in that, The thickness of the first main body layer is H1, the thickness of the second main body layer is H2, and the thickness of the metal protective layer is H3, where H1 < H3 ≤ H2.

11. The back-contact solar cell according to claim 10, characterized in that, 20nm≤H1≤1μm, 0.5μm≤H2≤10μm, 0.5μm≤H3≤10μm.

12. The back-contact solar cell according to claim 8, characterized in that, The battery body includes a silicon substrate, and the back side of the silicon substrate includes alternately arranged N-type regions and P-type regions, wherein the N-type regions include an N-type doped layer and the P-type regions include a P-type doped layer; In the N-type region, the first embedded segment penetrates other functional film layers on the back side of the silicon substrate and contacts the N-type doped layer; In the P-type region, the first embedded segment penetrates other functional film layers on the back side of the silicon substrate and contacts the P-type doped layer; The other functional films include a second interface passivation layer and a back antireflection layer.

13. The back-contact solar cell according to claim 1, characterized in that, The first metal includes at least one of silver, nickel, aluminum, molybdenum, titanium, and tungsten; The second metal includes at least one of copper and aluminum; The third metal includes at least one of tin, nickel, aluminum, titanium, and tungsten.

14. The back-contact solar cell according to claim 1, characterized in that, The metal seed layer can be a single-layer structure or a multi-layer composite structure.

15. The back-contact solar cell according to claim 1, characterized in that, The grid lines include main grids and fine grids.

16. A photovoltaic module, characterized in that, The photovoltaic module includes the back-contact solar cell as described in any one of claims 1 to 15.

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