Solar cell and preparation thereof

Abstract

A solar cell, comprising a silicon substrate. The silicon substrate comprises a first doped region in a front surface of the silicon substrate and a second doped region in a back surface of the silicon substrate. The first doped region and the second doped region have opposite conductivity types. The concentration of a second element in the second doped region is more than 10 times the concentration of a first element in the first doped region. The second element passes through a layered structure on the back surface side of the silicon substrate and is doped into the second doped region. The layered structure on the back surface side of the silicon substrate comprises an interface passivation layer and a doped passivation layer which are sequentially stacked on the surface of the side of the second doped region away from the silicon substrate. The second element is doped in the doped passivation layer.

Description

A solar cell and its preparation

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on September 27, 2023, with application number 202311269609.4, entitled “A solar cell and its preparation”, and the Chinese patent application filed with the China Patent Office on February 8, 2024, with application number 202410176821.4, entitled “A solar cell and its preparation”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to devices used in the photovoltaic field, and in particular to a solar cell, a cell string, and a solar module. Background Art

[0004] The TOPCon cell is a solar cell based on the principle of selective carriers. It passivates the contacts through a tunneling oxide layer, and its unit structure is an N-type silicon substrate unit. An ultra-thin silicon oxide layer is prepared on the back of the cell, and then a thin doped silicon layer is deposited. The two layers together form a tunneling passivation contact structure, which effectively reduces surface recombination and metal contact recombination, providing more room for further improving the conversion efficiency of the cell. The TOPCon cell retains and utilizes existing traditional cell equipment and processes to the maximum extent. It only requires the addition of thin film deposition equipment, without the need for back-side openings and alignment, which greatly simplifies the cell production process and reduces the difficulty of mass production. Although the TOPCon cell has many advantages as mentioned above, in existing TOPCon type cells, if there is a heavily doped area on the front surface of the cell, severe Auger recombination may occur, resulting in severe light absorption and affecting cell efficiency.

[0005] Summary of the Invention

[0006] In view of the above problems, this application is intended to improve the problems involved in the above related technologies.

[0007] This application involves the following solutions:

[0008] A solar cell includes a silicon substrate, wherein the silicon substrate includes a first doped region within a front surface of the silicon substrate and a second doped region within a back surface of the silicon substrate, wherein the first doped region and the second doped region have opposite conductivity types, wherein the concentration of a second element in the second doped region is more than 10 times the concentration of a first element in the first doped region,

[0009] The second element is doped into the second doping region through the layer structure on the back side of the silicon substrate. The layer structure on the back side of the silicon substrate includes an interface passivation layer and a doping passivation layer stacked in sequence on the surface of the second doping region away from the silicon substrate, and the second element is doped in the doping passivation layer.

[0010] Optionally, the concentration of the first element is 10-1000 times the concentration of the doping element in the silicon substrate; the concentration of the first element in the first doping region is optionally in the range of 1E+15cm -3 to 1E+19cm -3 .

[0011] Optionally, in a direction from the front side to the back side of the solar cell, the silicon substrate includes a first doping region, a silicon substrate, and a second doping region;

[0012] The concentration of the second element is 100-10000 times the concentration of the doping element in the silicon substrate; the concentration of the second element in the optional second doping region is in the range of 1E+17cm -3 to 1E+20cm -3 .

[0013] Optionally, in the direction from the front to the back of the solar cell, the first doped region sequentially comprises a first element heavily doped region and a first element lightly doped region, wherein the first element is a Group III element and the second element is a Group V element.

[0014] Optionally, the concentration of the first element in the first element heavily doped region is 100 to 1000 times the concentration of the doping element in the silicon substrate, and the multiple between the maximum and minimum values ​​of the concentration of the first element in the first element heavily doped region is less than or equal to 20.

[0015] Optionally, the concentration of the first element in the first element heavily doped region is 1E+18 cm -3 to 1E+19cm -3 .

[0016] Optionally, the sum of the thicknesses of the first element heavily-doped region and the first element lightly-doped region is less than or equal to 100 nm.

[0017] Optionally, the thickness of the first element lightly doped region is 20 to 90 nm, optionally 30 to 70 nm, and the concentration of the first element in the first element lightly doped region is 10 to 50 times the concentration of the doping element in the silicon substrate.

[0018] Optionally, the second element concentration of the second doping region is greater than the first element concentration of the first element heavily doped region; optionally, the second element concentration of the second doping region is more than 10 times the first element concentration of the first element heavily doped region.

[0019] Optionally, in the direction from the front side to the back side of the solar cell, the solar cell has a first doping region, a silicon substrate and a second doping region in sequence, wherein the first element is a Group V element and the second element is a Group III element.

[0020] Optionally, the doping element in the silicon matrix is ​​antimony; and

[0021] The concentration of antimony in the silicon matrix ranges from 4E+14cm -3 to 2E+16cm -3 , optional 4.3E+14cm -3 to 1.9E+16cm -3 and / or

[0022] The resistivity of the silicon substrate is 0.3 to 10 Ω·cm, and can be optionally 0.4 to 8 Ω·cm; or 0.5 to 6 Ω·cm.

[0023] Optionally, the sum of the concentration of the first element and the concentration of the silicon matrix doping element is less than or equal to 2E+19cm -3 ;or

[0024] The sum of the concentration of the second element and the concentration of the silicon matrix doping element is less than or equal to 1E+21cm -3 .

[0025] Optionally, in the doped passivation layer, the concentration of the second element at a first preset depth from the surface of the doped passivation layer away from the silicon substrate is greater than the concentration of the first element at a first preset depth from the surface of the first doped region, the thickness of the doped passivation layer ranges from 100 to 400 nm, and the first preset depth is less than or equal to the thickness of the doped passivation layer.

[0026] Optionally, a second element is doped into the interface passivation layer,

[0027] In the direction from the doped passivation layer to the interface passivation layer, in the interface passivation layer, the concentration of the second element at a second preset depth from the surface of the doped passivation layer away from the silicon substrate is greater than the concentration of the first element at a second preset depth from the surface of the first doped region, the thickness of the interface passivation layer ranges from 0.5 to 5 nm, and the second preset depth is less than or equal to the sum of the thicknesses of the doped passivation layer and the interface passivation layer.

[0028] Optionally, in the direction from the doped passivation layer to the second doped region, in the second doped region, the concentration of the second element at a third preset depth from the surface of the doped passivation layer away from the silicon substrate is greater than the concentration of the first element at a third preset depth from the surface of the first doped region, the thickness range of the second doped region is 30 to 100 nm, and the third preset depth is less than or equal to the sum of the thicknesses of the doped passivation layer, the interface passivation layer and the second doped region.

[0029] Optionally, the battery includes a front electrode and a back electrode, the front electrode includes a first electrode body and a first contact portion in contact with the first doping region, the back electrode includes a second electrode body and a second contact portion in contact with the second doping region, and the concentration of the first element in the first contact portion is less than the concentration of the second element in the second contact portion.

[0030] Optionally, the mechanical strength of the battery is greater than or equal to 50 MPa.

[0031] A cell string comprises a plurality of aforementioned solar cells interconnected by conductive interconnectors.

[0032] Optionally, the curvature of the solar cell is less than or equal to 2 mm.

[0033] Optionally, the conductive interconnect is bonded to the solar cell by soldering or conductive bonding.

[0034] Optionally, welding includes a heating step.

[0035] Optionally, the temperature range of the heating step is 100-160 degrees Celsius, and the curvature of the solar cell is less than or equal to 1.5 mm.

[0036] Optionally, the temperature range of the heating step is 165-200 degrees Celsius, and the curvature of the solar cell is less than or equal to 2 mm.

[0037] Optionally, the conductive interconnect comprises an electrical contact portion contacting an electrode of the solar cell, and the electrical contact portion comprises antimony.

[0038] A solar cell assembly comprises a plurality of cells, an encapsulation layer, a cover plate and a back plate, wherein the encapsulation layer seals the plurality of cells and is located between the cover plate and the back plate; the cells are the aforementioned solar cells.

[0039] Optionally, the curvature of the battery is less than or equal to 1.2 mm.

[0040] Optionally, the solar module further includes a frame, and edges of the cover plate and / or back plate are embedded in a mounting portion of the frame.

[0041] Optionally, the cover plate and / or the back plate are transparent plates.

[0042] Optionally, the back plate is a non-transparent plate.

[0043] Optionally, the battery protrudes toward the cover plate to form a curved shape.

[0044] Optionally, the plurality of cells are interconnected via a conductive interconnect, the conductive interconnect comprising an electrical contact portion contacting an electrode of the solar cell, the electrical contact portion comprising antimony.

[0045] Effects of the Invention

[0046] The solar cell described in the present application can suppress Auger recombination caused by high doping, improve light absorption, and enhance cell efficiency because the concentration of the first element in the first doping region is lower than the concentration of the second element in the second doping region.

[0047] The solar cell of the present application can overcome the crystalline silicon lattice distortion caused by single element doping and avoid the many defects in the heavily doped area because the silicon substrate itself contains the Sb element and is further doped with the third main group and the fifth main group to form a co-doped first doping region and a second doping region. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] FIG1 is a schematic diagram of a battery structure (TOPCon structure) provided in this application.

[0049] Figure 2 Schematic diagram of the battery stringing process.

[0050] Figure 3 is another schematic diagram of the battery stringing process.

[0051] FIG4 is a schematic diagram of a specific structure of a battery assembly.

[0052] FIG5 is another specific structural diagram of a battery assembly.

[0053] FIG6 is a schematic diagram of another structure of the battery structure (TOPCon structure) provided in this application.

[0054] Explanation of symbols

[0055] Among them, 1-silicon substrate, 2-first element lightly doped region, 3-first element heavily doped region, 4-second doped region, 5-tunneling layer, 6-doped polysilicon layer, 7-second contact portion, 8-second electrode body, 9-first element doped region. DETAILED DESCRIPTION

[0056] The following embodiments of the present application are intended only to illustrate specific implementation methods for implementing the present application and are not to be construed as limiting the present application. Any other changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principles of the present application are deemed equivalent replacements and fall within the scope of protection of the present application.

[0057] The specific embodiments of the present application will be described in more detail below. However, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0058] It should be noted that certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that technicians may use different nouns to refer to the same component. This specification and claims do not use the difference in nouns as a way to distinguish components, but use the difference in the functions of the components as the criterion for distinction. As mentioned throughout the specification and claims, "including" or "comprising" is an open term, so it should be interpreted as "including but not limited to". The subsequent description of the specification is a preferred embodiment of the present application, but the description is based on the general principles of the specification and is not intended to limit the scope of the present application. The scope of protection of this application shall be as defined by the attached claims.

[0059] As used herein, "substantially free" with respect to a particular component is used herein to mean that the particular component is not purposefully formulated into the composition and / or is present only as a contaminant or in trace amounts. Thus, the total amount of the particular component resulting from any unintentional contamination of the composition is less than 0.05%, optionally less than 0.01%. Most preferably, the composition is one in which the amount of the particular component is undetectable by standard analytical methods.

[0060] As used in this specification, "a" or "an" may mean one or more. As used in the claims, when used with the word "comprising", the word "a" or "an" may mean one or more than one.

[0061] The term "or" is used in the claims to mean "and / or" unless explicitly stated to refer only to alternatives or the alternatives are mutually exclusive, although this disclosure supports a definition referring only to alternatives and "and / or." As used herein, "another" can mean at least a second or more.

[0062] In the present application, the silicon wafer itself involved in the following content of the present application does not need further definition. For example, the silicon wafer can be a silicon wafer obtained after machining and slicing after the silicon rod is drawn (also called a bare silicon wafer); the silicon wafer can also be a partial battery structure including a silicon substrate and a layer structure formed on the silicon substrate, wherein the implementation method of the partial battery structure can be an intermediate product formed during the preparation process of the battery, or it can be obtained after recovering and peeling off other layer structures from the battery or component. The partial battery structure is, for example, a structure including a silicon substrate, at least part of the first doping region and at least part of the second doping region. As long as the partial battery structure can have a certain shape and can be in the form of a sheet, that is, the size of the bare silicon wafer, the silicon substrate or the partial battery structure on one surface is larger than the size of the other surface perpendicular to it, and it can be flat or plate-shaped. In addition, those skilled in the art will understand that when peeling the battery or component, even if the first doping region or the second doping region is partially destroyed, as long as the partial doping region still exists, it should be understood as the aforementioned partial battery structure. For example, in a specific embodiment, the length of at least one side of the partial battery structure of the present application comprising a silicon substrate, at least a portion of the first doped region and at least a portion of the second doped region is greater than 156 mm, for example, it can be 158 ± 2 mm, (160 ± 2) mm, (165 ± 2) mm, (170 ± 2) mm, (175 ± 2) mm, (180 ± 2) mm, (185 ± 2) mm, 190 ± 2 mm, (195 ± 2) mm, (200 ± 2) mm, (205±2) mm, (210±2) mm, (215±2) mm, (220±2) mm, (225±2) mm, (230±2) mm, (235±2) mm, (240±2) mm, (245±2) mm, (250±2) mm, (255±2) mm, (260±2) mm, (265±2) mm, (270±2) mm, (275±2) mm, and any ranges therebetween. In a specific embodiment, the thickness of the silicon substrate or the portion of the battery structure comprising the silicon substrate, at least a portion of the first doped region and at least a portion of the second doped region of the present application is at least 70 to 170 μm, for example, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, or 160 μm. In a specific embodiment, the size of the partial battery structure obtained by stripping the battery or component, which includes a silicon substrate, at least a portion of the first doping region and at least a portion of the second doping region, can be smaller than the aforementioned thickness, as long as the doping concentrations of the first element, the second element, the silicon substrate doping element, and the resistivity of the silicon substrate detected therefor meet the limitations involved in this application.

[0063] In the present application, the silicon substrate itself can be undoped and have substantially the same performance as the raw material, a bare silicon wafer. Thus, the first doped region and the second doped region can be doped layers formed within the silicon substrate, with properties and parameters substantially identical to those of the silicon substrate except for the doping elements. They can also be other materials with different materials, crystallinity, and performance than the silicon substrate.

[0064] In the present application, the silicon substrate itself can be actively doped, that is, the silicon substrate itself has a doping element (the doping element is referred to as the silicon substrate doping element in this article). The doping element is usually added during the crystal pulling process when preparing the bare silicon wafer, so the silicon substrate doping element is evenly distributed in all parts of the silicon substrate, that is, the initial concentration of the silicon substrate doping element is the same. For example, in the following embodiment of a silicon wafer comprising three parts, namely, a silicon substrate, a first doping region, and a second doping region, the initial concentration of the silicon substrate doping element is the same in the silicon substrate, the first doping region, and the second doping region. Or in the following embodiment of a silicon wafer comprising three parts, namely, a silicon substrate, a first doping region including a heavily doped region of the first element and a lightly doped region of the first element, and a second doping region, the initial concentration of the silicon substrate doping element is the same in the silicon substrate, the heavily doped region of the first element, the lightly doped region of the first element, and the second doping region.

[0065] When the doping element of the silicon substrate is antimony, the concentration range of antimony in the silicon substrate is 4E+14cm -3 to 2E+16cm -3 , optional 4.3E+14cm -3 to 1.9E+16cm -3 .

[0066] When the silicon substrate is doped with phosphorus, the concentration of phosphorus in the silicon substrate is in the range of 4E+14 cm -3 to 2E+17cm -3 , optional 4.3E+14cm -3 to 1.9E+17cm -3 .

[0067] When the silicon substrate is doped with gallium, the concentration of gallium in the silicon substrate is in the range of 4E+14 cm -3 to 2E+16cm -3 , optional 4.3E+14cm -3 to 1.9E+16cm -3 .

[0068] When the silicon substrate is doped with germanium, the concentration of germanium in the silicon substrate is in the range of 4E+14 cm -3 to 2E+17cm -3 , optional 4.3E+14cm-3 to 1.9E+17cm -3 .

[0069] In the present application, the silicon substrate includes a silicon substrate, a first doping region and a second doping region. The first doping region and the second doping region are located on both sides of the silicon substrate, and the first doping region and the second doping region are located inside the silicon substrate.

[0070] In this application, the front side of the silicon substrate refers to the surface facing the sunlight under normal working conditions of the cell, and the back side refers to the surface on the other side of the silicon substrate opposite to the front side.

[0071] In the present application, the concentration of the silicon matrix doping element in the silicon matrix, the concentration of the silicon matrix doping element in the first doping region, and the concentration of the silicon matrix doping element in the second doping region can be detected by any method known to those skilled in the art. Those skilled in the art can choose based on demand, for example, by SIMS, ICP-MS, GDMS and other methods, preferably by ICP-MS method. Those skilled in the art will understand that the concentration of the silicon matrix doping element in the silicon matrix, the first doping region, and the second doping region can refer to the concentration of the silicon matrix doping element at any point on the surface, middle or inside of one or more of the silicon matrix, the first doping region, and the second doping region. Of course, it can also be the average value of the silicon matrix doping element concentration at multiple positions, or the average value of the silicon matrix doping element concentration in the entire silicon matrix, the first doping region, and the second doping region. Those skilled in the art can select any of the above-mentioned points for detection based on actual conditions based on the detection conditions and the instruments used, or can calculate the average value of multiple points after detecting multiple points as the concentration of the silicon matrix doping element. In a specific embodiment, the concentration of the silicon matrix doping element refers to the average value detected over the thickness of the silicon matrix. For example, the concentration of the silicon matrix doping element in the silicon matrix, the first doping region, and the second doping region is detected in a thickness direction using the SIMS method, and the average value in this thickness direction is calculated.

[0072] In the present application, in one embodiment, the doping element in the silicon substrate is antimony. At this time, the concentration of the antimony element in the silicon substrate, as well as the concentration of the antimony element in the silicon substrate, the first doping region, and the second doping region can be detected by any method known to those skilled in the art. Those skilled in the art can make a choice based on demand, for example, by SIMS, ICP-MS, GDMS and other methods, preferably by ICP-MS method. Those skilled in the art will understand that the concentration of the antimony element in the silicon substrate, the first doping region, and the second doping region can refer to the concentration of the antimony element at any site on the surface, in the middle or inside of one or more of the silicon substrate, the first doping region, and the second doping region. Of course, it can also be the average value of the antimony element concentration at multiple locations, or the average value of the antimony element concentration in one or more of the entire silicon substrate, the first doping region, and the second doping region. Those skilled in the art can select the above-mentioned arbitrary sites for detection based on actual conditions based on the detection conditions and the instruments used, or can calculate the average value of multiple sites after detecting multiple sites as the concentration of the antimony element. In a specific embodiment, the concentration of antimony element refers to the average value detected over the thickness of the silicon substrate. For example, the concentration of antimony element in the silicon substrate, the first doping region, and the second doping region is detected in a thickness direction using the SIMS method, and the average value in this thickness direction is calculated.

[0073] Similarly, when the doping elements in the silicon substrate are phosphorus, germanium, or gallium, the same method can be used for detection.

[0074] In the present application, the concentration of the first element or the second element in the doping region can be detected by any method known to those skilled in the art. Those skilled in the art can select based on demand, for example, by SIMS, ICP-MS, GDMS and other methods, preferably by ICP-MS method. Those skilled in the art will understand that the concentration of the first element or the second element in the doping region can refer to the concentration of the first element or the second element at any site on the surface or in the middle of the first doping region or the second doping region on one side of the silicon substrate. Of course, it can also be the average value of the concentration of the first element or the second element at multiple locations, or the average value of the concentration of the first element or the second element in the entire first doping region or the second doping region. Those skilled in the art can select the above-mentioned arbitrary sites for detection based on actual conditions based on the detection conditions and the instruments used, or calculate the average value of multiple sites after detecting multiple sites to serve as the concentration of the first element or the second element. In a specific embodiment, the concentration of the first element or the second element refers to the average value detected on the thickness of the first doping region or the second doping region. For example, the concentration of the first element or the second element in the doping region is detected in a thickness direction using the SIMS method, and the average value in this thickness direction is obtained.

[0075] In the present application, the resistivity of the silicon substrate can be detected by any method known to those skilled in the art, and those skilled in the art can make a choice based on demand, for example, by a four-probe tester test, or by a non-contact eddy current method or other methods (for example, a terahertz offline two-dimensional imaging device (FalconWave-S) can be used for detection), or by a four-probe tester test. Those skilled in the art will understand that the resistivity of the silicon wafer can refer to the resistivity detection data of any site on the surface of the silicon substrate, in the middle of the silicon substrate or inside the silicon substrate, and of course it can also be the average value of the resistivity detection data of multiple locations or the average value of the resistivity on the entire silicon substrate. Those skilled in the art can select the above-mentioned arbitrary sites for detection based on the actual situation based on the detection conditions and the instruments used, or can calculate the average value of multiple sites after detecting multiple sites to serve as the resistivity of the silicon substrate. In a specific embodiment, the resistivity of the silicon substrate refers to the average value of the resistivity detected on the thickness of the silicon substrate, for example, the resistivity of each site of the silicon substrate is detected in a thickness direction using a four-probe tester, and the average value in this thickness direction is obtained.

[0076] Those skilled in the art can fully understand that the inspection of the silicon substrate in the solar cell can be carried out on a silicon substrate of any size, and can be a partial cell structure obtained after recovering it from the cell or component and peeling off other layer structures. As long as the inspection results obtained after the inspection is carried out according to the method described in this application fall within the limitations involved in this application, it should be considered to meet the silicon substrate of the solar cell defined in this application.

[0077] In this application, the method for detecting whether a certain element is contained in the silicon substrate and the doped region can be detected by SIMS, ICP-MS, GDMS and the like, preferably by ICP-MS to detect metal elements. In this application, solar cells are also referred to as batteries.

[0078] In a specific embodiment of the present application, only antimony is actively doped as the fifth main group doping element in the silicon substrate of the present application. In this case, those skilled in the art will understand that depending on the different sources of silicon wafer raw materials, the silicon wafer or silicon substrate itself may contain other elements, such as any one, two or three of phosphorus, gallium and germanium, but only antimony is actively doped as the fifth main group doping element. Usually, in a silicon substrate, the crystalline silicon lattice is distorted due to the doping of a single element, resulting in many defects in the heavily doped area; but in a specific embodiment of the present application, since the silicon substrate itself contains the Sb element, and is further doped with the third main group and the fifth main group to form a co-doped first doping area and a second doping area, the crystalline silicon lattice distortion caused by the doping of a single element can be overcome, and the many defects in the heavily doped area can be avoided.

[0079] In a specific embodiment of the present application, phosphorus is doped into the silicon substrate of the present application as a fifth main group doping element.

[0080] In a specific embodiment of the present application, gallium is doped into the silicon substrate of the present application as a third main group doping element.

[0081] In a specific embodiment of the present application, bismuth is doped into the silicon substrate of the present application as a fifth main group doping element.

[0082] The present application provides a solar cell, as shown in FIG1 , which includes a silicon substrate 1, a first doped region on the front side of the silicon substrate 1, and a second doped region 4 on the back side of the silicon substrate 1. The first doped region and the second doped region 4 have opposite conductivity types, wherein the concentration of the first element in the first doped region is less than the concentration of the second element in the second doped region 4 of the silicon substrate. Those skilled in the art will understand that the cell shown in FIG1 refers to a TOPCon structure cell. FIG1 merely schematically shows the structure of a TOPCon cell and is not intended to limit the structure of the cell. The structure of the cell shall be subject to the structure claimed for protection in the claims of this application. The silicon substrate 1, the first doped region, and the second doped region constitute a silicon substrate.

[0083] In a specific embodiment of a TOPCon battery, the first element is an element of Group III, and the second element is an element of Group V. Group III elements include boron, aluminum, gallium, indium, and thallium, and Group V elements include nitrogen, phosphorus, arsenic, antimony, and bismuth.

[0084] In a specific embodiment, the first element is boron, and the second element is phosphorus.

[0085] In a specific embodiment of a TOPCon cell, the first doped region is a boron doped region, and the second doped region 4 is a phosphorus doped region. The first doped region is formed by direct doping, while the second doped region is formed by doping the doped passivation layer in the solar cell into the silicon substrate via an interface passivation layer.

[0086] In a specific embodiment, the interface passivation layer refers to a layer that has a passivation effect and allows doping elements to pass through, for example, it may be a tunneling layer.

[0087] In a specific embodiment, the doped passivation layer may be doped polysilicon.

[0088] For TOPCon cells, in the silicon substrate of the present application, the concentration of the first element in the first doping region is less than the concentration of the second element in the second doping region 4. Since the doping concentrations of the first doping regions 2 and 3 are low, the Auger recombination caused by high doping is effectively suppressed, and light absorption can also be improved, thereby improving cell efficiency.

[0089] In the present application, the concentration of the second element in the second doping region 4 is more than 10 times the concentration of the first element in the first doping region, for example, 10 times to 10,000 times, for example, 100 to 10,000 times. Since the light intensity is weak on the back side, the effects of Auger recombination and the like are small. At this time, a higher concentration of doping is used, which is beneficial to provide energy for the drift process of free carriers, promote the migration of free carriers, and perform carrier extraction. In addition, at least the concentration of the second element in the second doping region 4 is controlled to be more than 10 times the concentration of the first element in the first doping region. This can ensure that Auger recombination caused by high doping is effectively suppressed, and can also improve light absorption, especially for the light-receiving surface, thereby improving battery efficiency. In a specific embodiment, the concentration of the phosphorus element in the second doping region 4 is more than 10 times the concentration of the boron element in the first doping region, for example, 10 times to 10,000 times.

[0090] In a specific embodiment, the concentration of the phosphorus element in the second doping region 4 is a multiple of the concentration of the boron element in the first doping region, which can be 10 times, 20 times, 30 times, 40 times, 50 times, 60 times, 70 times, 80 times, 90 times, 100 times, 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, 1000 times, 5000 times, 10000 times, etc.

[0091] In a specific embodiment, the concentration of the second element (eg, phosphorus) in the second doping region 4 is in the range of 1E+17 cm -3 to 1E+20cm -3 , for example, it can be 1E+17cm -3 、2E+17cm -3 、3E+17cm -3 、4E+17cm -3 、5E+17cm -3 、6E+17cm -3 、7E+17cm -3 、8E+17cm -3 、9E+17cm -3 、1E+18cm -3 、2E+18cm -3 、3E+18cm -3 、4E+18cm -3 、5E+18cm -3 、6E+18cm -3 、7E+18cm -3 、8E+18cm -3 、9E+18cm -3 、1E+19cm -3、2E+19cm -3 、3E+19cm -3 、4E+19cm -3 、5E+19cm -3 、6E+19cm -3 、7E+19cm -3 、8E+19cm -3 、9E+19cm -3 or 1E+20cm -3 .

[0092] In the present application, the concentration of the first element is 10-1000 times the concentration of the doping element in the silicon substrate.

[0093] In a specific embodiment, the doping element of the silicon substrate 1 may be Sb element (antimony element).

[0094] In a specific embodiment, the concentration of the first element is 10-1000 times the concentration of the silicon substrate doping element of the silicon substrate 1. For example, it can be 10 times, 100 times, 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, or 1000 times.

[0095] In a specific embodiment, the concentration of the boron element is 10-1000 times the concentration of the Sb element in the silicon substrate 1. For example, it can be 10 times, 100 times, 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, or 1000 times. The advantages of doping the silicon substrate 1 with the Sb element are: low concentration doping, few defects, can improve the charge mobility of the silicon substrate and reduce the resistivity of the silicon substrate; secondly, the Sb element can reduce the band edge energy level differentiation of crystalline silicon caused by doping, and the Sb element doping has a high ionization rate.

[0096] In traditional silicon wafers, B or P elements are used for doping and subsequent heavy doping processes. Because the atomic ratio of B / Si is 0.7 and the atomic ratio of P / Si is 0.94, single-atom doping in heavily doped regions can cause significant crystalline silicon lattice distortion. In this application, Sb is used to dope the silicon wafer, forming a low-concentration first doping region on the front and a high-concentration second doping region on the back. This solves the problem of charge recombination caused by high doping on the front side of the silicon substrate, achieving a low-concentration front side and a thinner PN junction, thereby reducing light absorption.

[0097] The concentration of the first element in the first doping region is in the range of 1E+15 cm -3 to 1E+19cm -3 ; or 1E+16cm -3 to 1E+19cm -3In a specific embodiment, for example, the concentration of the first element in the first doping region may be 1E+15 cm -3 、2E+15cm -3 、3E+15cm -3 、4E+15cm -3 、5E+15cm -3 、6E+15cm -3 、7E+15cm -3 、8E+15cm -3 、9E+15cm -3 、1E+16cm -3 、2E+16cm -3 、 3E+16cm -3 、4E+16cm -3 、5E+16cm -3 、6E+16cm -3 、7E+16cm -3 、8E+16cm -3 、9E+16cm -3 、1E+17cm -3 、2E+17cm -3 、3E+17cm -3 、4E+17cm -3 、5E+17cm -3 、6E+17cm -3 、7E+17cm -3 、8E+17cm -3 、9E+17cm -3 、1E+18cm -3 、2E+18cm -3 、3E+18cm -3 、4E+18cm -3 、5E+18cm -3 、6E+18cm -3 、7E+18cm -3 、8E+18cm -3 、9E+18cm -3 or 1E+19cm -3 .

[0098] In the present application, the first doping region includes a first element heavily doped region 3 and a first element lightly doped region 2. In the direction from the front to the back of the solar cell, the solar cell has the first element heavily doped region 3, the first element lightly doped region 2, the silicon substrate 1 and the second doping region 4 in sequence.

[0099] The concentration of the boron element in the first element heavily doped region 3 is greater than the concentration of the boron element in the first element lightly doped region 2 .

[0100] The concentration of the first element in the first element heavily doped region 3 is 100 to 1000 times the concentration of the doping element in the silicon substrate 1 , and the multiple between the maximum and minimum values ​​of the first element concentration in the first element heavily doped region 3 is less than or equal to 20.

[0101] In a specific embodiment, the concentration of the boron element in the first heavily doped region 3 is 100 to 1000 times the concentration of the doping element in the silicon substrate 1, for example, 100 times, 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, or 1000 times. In a specific embodiment, the concentration of the boron element in the first heavily doped region 3 is 100 to 1000 times the concentration of the Sb element in the silicon substrate 1, for example, 100 times, 200 times, 300 times, 400 times, 500 times, 600 times, 700 times, 800 times, 900 times, or 1000 times.

[0102] The multiple of the maximum and minimum boron concentrations in the first heavily doped region 3 is less than or equal to 20, for example, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11 or 10.

[0103] Since the first element of the first element heavily doped region 3 is uniformly doped and the doping elements of the silicon substrate 1 are uniformly doped, such a design has a better carrier separation effect on the silicon wafer, which is beneficial to improving the open circuit voltage and efficiency of the solar cell.

[0104] In a specific embodiment, the thickness of the first element heavily doped region 3 is 10-50 nm, preferably 15-35 nm. In a specific embodiment, the thickness of the first element heavily doped region 3 can be 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm or 50 nm.

[0105] The heavily doped region of the first element can play a selective contact role, but a larger concentration (generally greater than 1E+20cm -3 ) will cause greater light absorption, so the Auger recombination is serious, and the localized processing will be limited to the lateral transmission of charges in the PN junction region. The concentration relationship between the first element heavily doped region and the doping element of the silicon substrate 1 in this application can ensure excellent charge selective transmission while reducing Auger recombination.

[0106] In this application, the concentration of the first element in the first element heavily doped region 3 is 1E+18cm -3 to 1E+19cm -3 .

[0107] Specifically, the concentration of the boron element in the first heavily doped region 3 may be 1E+18 cm -3 、2E+18cm -3 、3E+18cm -3 、4E+18cm -3 、5E+18cm -3 、6E+18cm -3 、7E+18cm -3 、8E+18cm -3 、9E+18cm -3 or 1E+19cm -3 .

[0108] In the present application, the sum of the thicknesses of the first element heavily doped region 3 and the first element lightly doped region 2 is less than or equal to 100 nm. When the thickness of the first doped region is large, a PN junction with excessive concentration and large thickness will be generated, which will cause the light absorption on the front side of the silicon wafer (the first doped region) to account for an increased proportion compared to the light absorption of the silicon substrate 1, and the concentration of free carriers is too large, which in turn leads to a large charge recombination effect. When the thickness of the first doped region is small, a thinned PN junction region and a low concentration are generated, and at low concentrations, the boron element in the first doped region and the Sb element in the silicon substrate 1 work together to reduce lattice distortion, thereby helping to reduce the charge recombination effect.

[0109] Specifically, the sum of the thicknesses of the first element heavily doped region 3 and the first element lightly doped region 2 may be 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, or the like.

[0110] In the present application, the thickness of the first element lightly doped region 2 is 20 to 90 nm, optionally 30 to 70 nm, and the concentration of the first element in the first element lightly doped region 2 is 10 to 50 times the concentration of the doping element in the silicon substrate 1 .

[0111] Specifically, the thickness of the first element lightly doped region 2 can be 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, etc.

[0112] The concentration of boron in the first lightly doped region 2 may be 10 times, 15 times, 20 times, 25 times, 30 times, 35 times, 40 times, 45 times or 50 times the concentration of the doping element (eg, Sb) in the silicon substrate 1 .

[0113] The thickness of the first element lightly doped region 2 is greater than the thickness of the first element heavily doped region 3 .

[0114] In the present application, the multiple between the maximum value and the minimum value of the concentration of the first element in the first element lightly doped region 2 is less than or equal to 40.

[0115] Specifically, the multiple of the maximum value and the minimum value of the boron element concentration in the first lightly doped region 2 is less than or equal to 40, for example, it can be 40, 35, 30, 25, 20, etc.

[0116] The boron element in the first lightly doped region 2 is uniformly doped.

[0117] The doping amount of the Sb element doped in the first element lightly doped region 2 and the first element heavily doped region 3 is the same as the doping amount of the Sb element doped in the silicon substrate 1 .

[0118] In the present application, the concentration of the second element in the second doping region 4 is greater than the concentration of the first element in the first element heavily doped region 3;

[0119] The concentration of the second element in the second doping region 4 is more than 10 times that of the first element in the first heavily doped region 3 . Specifically, the concentration of phosphorus in the second doping region 4 is greater than that of boron in the first heavily doped region 3 .

[0120] The concentration of phosphorus in the second doping region 4 is more than 10 times the concentration of boron in the first heavily doped region 3 , for example, it may be 10 times to 1000 times.

[0121] Specifically, the concentration of phosphorus in the second doping region 4 can be 10 times, 15 times, 20 times, 25 times, 30 times, 35 times, 40 times, 45 times, 50 times, 55 times, 60 times, 65 times, 70 times, 75 times, 80 times, etc., which is a multiple of the concentration of boron in the first heavily doped region 3.

[0122] In this application, the concentration range of the doping element in the silicon substrate is 4E+14cm -3 to 2E+16cm -3 , optional 4.30E+14cm -3 to 1.9E+16cm -3 .

[0123] In this application, the concentration of antimony in the silicon matrix is ​​in the range of 4E+14 cm -3 to 2E+16cm -3 , optional 4.30E+14cm -3 to 1.9E+16cm -3 ;

[0124] Specifically, the concentration of antimony in the silicon matrix can be 4E+14 cm -3 、4.30E+14cm -3 、5E+14cm -3 、6E+14cm -3 、7E+14cm -3 、8E+14cm -3、9E+14cm -3 、1E+15cm -3 、2E+15cm -3 、3E+15cm -3 、4E+15cm -3 、5E+15cm -3 、6E+15cm -3 、7E+15cm -3 、8E+15cm -3 、9E+15cm -3 、1E+16cm -3 、1.9E+16cm -3 or 2E+16cm -3 .

[0125] The resistivity of the silicon substrate is 0.3 to 10 Ω·cm, and can be optionally 0.4 to 80 Ω·cm; or 0.5 to 60 Ω·cm.

[0126] Specifically, the resistivity of the silicon substrate may be 0.3Ω·cm, 0.4Ω·cm, 0.5Ω·cm, 0.6Ω·cm, 0.7Ω·cm, 0.8Ω·cm, 0.9Ω·cm, 1.9Ω·cm, 2.9Ω·cm, 3.9Ω·cm, 4.9Ω·cm, 5.9Ω·cm, 6.9Ω·cm, 7.9Ω·cm, 8.9Ω·cm, 9.9Ω·cm or 109Ω·cm.

[0127] In the application, since the antimony element in the silicon substrate, the antimony element and / or the doping element in the doping region are all uniformly doped, the resistivity of the overall structure or silicon substrate as a battery including the silicon substrate, at least part of the first doping region and at least part of the second doping region is very uniform, the resistivity change rate is small, and the average resistivity offset rate is small, which can effectively reduce the lateral transmission resistance of the carriers and improve the battery efficiency.

[0128] In the present application, the second element is doped into the doped region through the layer structure on the back side of the silicon substrate. The layer structure on the back side of the silicon substrate includes a tunneling layer 5 and a doped polysilicon layer 6 stacked in sequence on the surface of the second doped region 4 on the side away from the silicon substrate 1, and the second element is doped in the doped polysilicon layer 6.

[0129] Specifically, phosphorus is doped into the doped polysilicon layer 6 , and the phosphorus in the doped polysilicon layer 6 passes through the tunneling layer 5 , thereby forming the second doped region 4 in a region of the silicon substrate close to the tunneling layer 5 .

[0130] The tunneling layer 5 is an ultra-thin silicon oxide layer, which may be a non-dense thin film, and has a thickness of 1-1.3 nm, for example, 1 nm, 1.1 nm, 1.2 nm or 1.3 nm.

[0131] The doped polysilicon layer 6 is an N-type polysilicon layer.

[0132] The thickness of the second doping region 4 is 3-300 nm, and may be 5-200 nm, for example, 3 nm, 5 nm, 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, etc.

[0133] In the present application, in the doped polysilicon layer 6, the concentration of the second element at a depth x (i.e., a first preset depth) from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 is greater than the concentration of the first element at a depth x (i.e., a first preset depth) from the surface of the first doped region, and the thickness of the doped polysilicon layer 6 ranges from 100 to 400 nm, where x is less than or equal to the thickness of the doped polysilicon layer 6.

[0134] Specifically, the thickness of the doped polysilicon layer 6 may be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm.

[0135] In the doped polysilicon layer 6 , the depth x from the surface of the doped polysilicon layer 6 away from the silicon substrate 1 refers to the distance x extending from the surface of the doped polysilicon layer 6 away from the silicon substrate 1 toward the silicon substrate 1 .

[0136] The depth x from the surface of the first doped region refers to the distance x extending from the side surface of the first element heavily doped region 3 away from the silicon substrate 1 in the direction close to the silicon substrate 1. The value of x is less than 400nm. For example, the value of x can be 300nm, 200nm, 100nm, 90nm, 80nm, 70nm, 60nm, 50nm, etc. When x is 300nm, the thickness of the doped polysilicon layer 6 can be 300nm-400nm, excluding 300nm. When x is 200nm, the thickness of the doped polysilicon layer 6 can be 200nm-400nm, excluding 200nm. When x is 100nm, the thickness of the doped polysilicon layer 6 can be 100nm-400nm, excluding 100nm. When x is less than 100nm, the thickness of the doped polysilicon layer 6 can be 100nm-400nm.

[0137] In the present application, a second element is doped in the tunneling layer 5. In the direction from the doped polysilicon layer 6 to the tunneling layer 5, in the tunneling layer 5, the concentration of the second element at a depth y from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 (i.e., the second preset depth) is greater than the concentration of the first element at a depth y from the surface of the first doped region (i.e., the second preset depth). The thickness of the tunneling layer 5 ranges from 0.5 to 5 nm, and y is less than or equal to the sum of the thicknesses of the doped polysilicon layer 6 and the tunneling layer 5.

[0138] Specifically, the thickness of the tunneling layer 5 may be 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm or 3 nm.

[0139] In the tunneling layer 5 , the depth y from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 refers to the distance y extending from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 toward the silicon substrate 1 , and the end point of this distance is located inside the tunneling layer 5 .

[0140] The depth y from the surface of the first doped region refers to the distance y extending from the side surface of the first element heavily doped region 3 away from the silicon substrate 1 in the direction close to the silicon substrate 1. The value of y is 100.5nm-403nm. For example, the value of y can be 403nm, 400nm, 350nm, 300nm, 250nm, 200nm, 150nm, 110nm, 100.5nm, etc. When the value of y is 400nm, the sum of the thicknesses of the doped polysilicon layer 6 and the tunneling layer 5 can be 400nm-403nm. When the value of y is 350nm, the sum of the thicknesses of the doped polysilicon layer 6 and the tunneling layer 5 can be 350nm-403nm. When the value of y is 300nm, the sum of the thicknesses of the doped polysilicon layer 6 and the tunneling layer 5 can be 300nm-403nm. When the value of y is 200 nm, the sum of the thicknesses of the doped polysilicon layer 6 and the tunneling layer 5 may be 200 nm-403 nm.

[0141] In the present application, in the direction from the doped polysilicon layer 6 to the second doping region 4, the concentration of the second element in the second doping region 4 at a depth z from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 (i.e., the third preset depth) is greater than the concentration of the first element at a depth z from the surface of the first doping region (i.e., the third preset depth), and the thickness of the second doping region 4 ranges from 30 to 100 nm, and z is less than or equal to the sum of the thicknesses of the doped polysilicon layer 6, the tunneling layer 5, and the second doping region 4.

[0142] Specifically, the thickness of the second doping region 4 is in the range of 30 to 100 nm, for example, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, etc.

[0143] In the second doping region 4 , the depth z from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 refers to the distance z extending from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 toward the direction close to the silicon substrate 1 , and the end point of this distance is located within the second doping region 4 .

[0144] The depth z from the surface of the first doped region refers to the distance z extending from the surface of the first element heavily doped region 3 away from the silicon substrate 1 toward the silicon substrate 1. The value of z is 130.5nm-503nm, and can be, for example, 130.5nm, 140nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, or 503nm. When the value of z is 500nm, the sum of the thicknesses of the doped polysilicon layer 6, the tunneling layer 5, and the second doped region 4 can be 500nm-503nm. When the value of z is 400nm, the sum of the thicknesses of the doped polysilicon layer 6, the tunneling layer 5, and the second doped region 4 can be 400nm-503nm. When the value of z is 300nm, the sum of the thicknesses of the doped polysilicon layer 6, the tunneling layer 5, and the second doped region 4 can be 300nm-503nm. When the value of z is 200 nm, the sum of the thicknesses of the doped polysilicon layer 6 , the tunneling layer 5 and the second doped region 4 may be 200 nm-503 nm.

[0145] The present application also provides a solar cell, as shown in Figure 6, in the direction from the front to the back of the solar cell, the solar cell has a first doping region 9, a silicon substrate 1 and a second doping region 4 in sequence, wherein the first doping region 9 is doped with a first element, and the second doping region 4 is doped with a second element, the first element is a fifth main group element, and the second element is a third main group element.

[0146] Specifically, the first element is an element of the fifth main group, and the second element is an element of the third main group. The third main group elements include boron, aluminum, gallium, indium, and thallium, and the fifth main group elements include nitrogen, phosphorus, arsenic, antimony, and bismuth.

[0147] The concentration of the first element in the first doping region and the concentration of the second element in the second doping region described in the battery structure shown in FIG. 1 for the first embodiment are also applicable to the embodiment described in FIG. 6 .

[0148] In a specific embodiment, when the doping element of the silicon substrate is Sb doping, the first element is phosphorus and the second element is boron.

[0149] In a specific embodiment of a TOPCon cell, the first doped region 9 is a phosphorus-doped region, and the second doped region 4 is a boron-doped region. The first doped region 9 is formed by direct doping, while the second doped region 4 is formed by doping the doped passivation layer in the solar cell into the silicon substrate via an interface passivation layer.

[0150] In one specific embodiment, phosphorus is doped into the first doped region 9 by direct doping, and the boron doped region 4 is formed by doping the silicon substrate via the interfacial passivation layer through the doped passivation layer in the solar cell. The doped passivation layer contains boron. Specifically, the doped polysilicon layer 6 is doped with boron, and the boron in the doped polysilicon layer 6 passes through the tunneling layer 5, thereby forming the second doped region 4 in the silicon substrate near the tunneling layer 6.

[0151] The tunneling layer 5 is an ultra-thin silicon oxide layer, which may be a non-dense thin film, and has a thickness of 1-1.3 nm, for example, 1 nm, 1.1 nm, 1.2 nm or 1.3 nm.

[0152] The doped polysilicon layer 6 is an N-type polysilicon layer.

[0153] The thickness of the second doping region 4 is 3-300 nm, and may be 5-200 nm, for example, 3 nm, 5 nm, 10 nm, 50 nm, 100 nm, 150 nm, 200 nm, etc.

[0154] The thickness of the first element doping region 9 can be 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, etc.

[0155] In the present application, in the doped polysilicon layer 6, the concentration of the second element at a depth x (i.e., a first preset depth) from the surface of the doped polysilicon layer 6 on the side away from the silicon substrate 1 is greater than the concentration of the first element at a depth x (i.e., a first preset depth) from the surface of the first doped region, and the thickness of the doped polysilicon layer 6 ranges from 100 to 400 nm, where x is less than or equal to the thickness of the doped polysilicon layer 6.

[0156] Specifically, the thickness of the doped polysilicon layer 6 may be 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, or 400 nm.

[0157] In the doped polysilicon layer 6 , the depth x from the surface of the doped polysilicon layer 6 away from the silicon substrate 1 refers to the distance x extending from the surface of the doped polysilicon layer 6 away from the silicon substrate 1 toward the silicon substrate 1 .

[0158] In a specific embodiment, the concentration of the boron element in the second doping region 4 is more than 10 times the concentration of the phosphorus element in the first doping region 9 , for example, 10 times to 10,000 times.

[0159] The doping amount of the Sb element doped in the first element doping region 9 is the same as that of the Sb element doped in the silicon substrate 1 .

[0160] In this application, the concentration range of Sb element in the silicon matrix is ​​4E+14cm -3 to 2E+16cm-3 , optional 4.30E+14cm -3 to 1.9E+16cm -3 .

[0161] In this application, since the concentration of the first element is less than that of the second element, Auger recombination of free carriers can be further reduced, further improving short-circuit current. Furthermore, Auger recombination of free carriers can be reduced without reducing the passivation effect of the tunneling layer, further improving short-circuit current, open-circuit voltage, and battery efficiency.

[0162] In the present application, if the type of doping element in the silicon substrate itself is consistent with the type of the first element (for example, belonging to the third or fifth main group), it usually has a first doping region; that is, as shown in FIG. 6 of the present application.

[0163] Specifically, in one embodiment, the silicon substrate itself is doped with phosphorus as a fifth main group doping element. At this time, as shown in Figure 6, it includes a silicon substrate 1, a first doping region 9 on the front side of the silicon substrate 1, and a second doping region 4 on the back side of the silicon substrate 1. The first doping region 9 is doped with phosphorus, and the second doping region 4 is doped with boron. At this time, the concentration of the second element in the second doping region 4 is more than 10 times the concentration of the first element in the first doping region, for example, 10 times to 10,000 times.

[0164] In one embodiment, the silicon substrate itself is doped with gallium as a third main group doping element. At this time, as shown in Figure 6, it includes a silicon substrate 1, a first doping region 9 on the front side of the silicon substrate 1, and a second doping region 4 on the back side of the silicon substrate 1. The first doping region 9 is doped with phosphorus, and the second doping region 4 is doped with boron. At this time, the concentration of the second element in the second doping region 4 is more than 10 times the concentration of the first element in the first doping region, for example, 10 times to 10,000 times.

[0165] In one embodiment, the silicon substrate itself is doped with bismuth as a fifth main group doping element. At this time, as shown in Figure 6, it includes a silicon substrate 1, a first doping region 9 on the front side of the silicon substrate 1, and a second doping region 4 on the back side of the silicon substrate 1. The first doping region 9 is doped with phosphorus, and the second doping region 4 is doped with boron. At this time, the concentration of the second element in the second doping region 4 is more than 10 times the concentration of the first element in the first doping region, for example, 10 times to 10,000 times.

[0166] In the present application, if the type of doping element of the silicon substrate itself is inconsistent with the type of the first element (for example, the silicon substrate itself is doped with a third main group element, and the first element is a fifth main group element; for another example, the silicon substrate itself is doped with a fifth main group element, and the first element is a third main group element), it is necessary to control the first doping region to have a first lightly doped region and a first heavily doped region; that is, the situation shown in Figure 1 of the present application.

[0167] In one embodiment, the silicon substrate itself is doped with phosphorus as a Group V doping element. As shown in FIG1 , the silicon substrate sequentially comprises a heavily doped region 3 with the first element, a lightly doped region 2 with the first element, a silicon substrate 1, and a second doped region 4. The first doped region comprises the heavily doped region 3 with the first element and the lightly doped region 2 with the first element. Both the heavily doped region 3 with the first element and the lightly doped region 2 with the first element are doped with boron, while the second doped region 4 is doped with phosphorus. In this case, the concentration of the second element in the second doped region 4 is more than 10 times the concentration of the first element in the heavily doped region 3 with the first element, for example, 100 to 10,000 times.

[0168] In one embodiment, the silicon substrate itself is doped with gallium as a Group III doping element. As shown in FIG1 , the substrate sequentially comprises a heavily doped region 3 with the first element, a lightly doped region 2 with the first element, a silicon substrate 1, and a second doped region 4. The first doped region comprises the heavily doped region 3 with the first element and the lightly doped region 2 with the first element. Both the heavily doped region 3 with the first element and the lightly doped region 2 with the first element are doped with boron, and the second doped region 4 is doped with phosphorus. In this case, the concentration of the second element in the second doped region 4 is more than 10 times the concentration of the first element in the heavily doped region 3 with the first element, for example, 100 to 10,000 times.

[0169] In one embodiment, the silicon substrate itself is doped with bismuth as a Group V doping element. As shown in FIG1 , the silicon substrate sequentially comprises a heavily doped region 3 with the first element, a lightly doped region 2 with the first element, a silicon substrate 1, and a second doped region 4. The first doped region comprises the heavily doped region 3 with the first element and the lightly doped region 2 with the first element. Both the heavily doped region 3 with the first element and the lightly doped region 2 with the first element are doped with boron, and the second doped region 4 is doped with phosphorus. In this case, the concentration of the second element in the second doped region 4 is more than 10 times the concentration of the first element in the heavily doped region 3 with the first element, for example, 100 to 10,000 times.

[0170] In addition, except that the doping element of the silicon substrate is not Sb, the remaining descriptions of Figures 1 and 2 above also apply to the case where the silicon substrate is doped with other elements. The battery of the present application can suppress Auger recombination caused by high doping, achieve improved light absorption, promote carrier migration and extraction, and obtain a battery component with high battery efficiency.

[0171] In the present application, the solar cell also includes a front electrode and a back electrode, the front electrode includes a first electrode body (not shown in the figure) and a first contact portion (not shown in the figure) in contact with the first doping region, and the back electrode includes a second electrode body 8 and a second contact portion 7 in contact with the second doping region 4, and the concentration of the first element of the first contact portion is less than the concentration of the second element of the second contact portion 7.

[0172] Specifically, the front electrode includes a first electrode body and a first contact portion, the first contact portion is stacked with the first element heavily doped region 3, and the first electrode body and the first contact portion are stacked together on the side surface facing away from the first element heavily doped region 3.

[0173] The back electrode also includes a second electrode body 8 and a second contact portion 7. The second contact portion 7 is stacked with the surface of the doped polysilicon layer 6 facing away from the tunneling layer 5, and the surface of the second contact portion 7 facing away from the doped polysilicon layer 6 is stacked with the second electrode body 8.

[0174] The first contact portion and the second contact portion 7 can both be silver-silicon alloy layers with a thickness of 5nm-100nm, for example, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm or 100nm.

[0175] In the present application, the mechanical strength of the solar cell is greater than or equal to 70 MPa, for example, it can be 70 MPa-1000 MPa, for example, it can be 70 MPa, 80 MPa, 90 MPa, 100 MPa, 110 MPa, etc.

[0176] In a specific embodiment, the contact portion contains a silicon matrix doping element, such as antimony, thereby reducing the contact resistance of the solar cell and further reducing the contact resistance of the battery assembly.

[0177] The present application also provides a battery assembly comprising the aforementioned solar cell. For a description of the solar cell, reference may be made to the aforementioned description. The solar cell comprises a front electrode and a back electrode, wherein the front electrode forms a first electrical connection with a first conductive interconnect, and the back electrode forms a second electrical connection with a second conductive interconnect, wherein the concentration of the first element in the first electrical connection is less than the concentration of the second element in the second electrical connection. In this embodiment, it is possible to reduce Auger recombination while ensuring that the contact resistance is controlled within a relatively small range.

[0178] In a specific embodiment, at least one of the first electrical connection portion and the second electrical connection portion includes a silicon matrix doping element, such as antimony.

[0179] In a specific embodiment, the conductive interconnects include, for example, conductive connecting lines (sometimes also referred to as connecting lines, metal ribbons) and a conductive backplane (sometimes also referred to as a bonding layer).

[0180] The solar cell includes a front electrode and a back electrode. The front electrode and a first conductive interconnect form a first electrical connection portion, and the back electrode and a second conductive interconnect form a second electrical connection portion. The concentration of a first element in the first electrical connection portion is lower than the concentration of a second element in the second electrical connection portion. At least one of the first electrical connection portion and the second electrical connection portion includes a silicon matrix doping element, such as antimony.

[0181] In this application, the conductive interconnect can refer to a metal soldering ribbon used to electrically connect the batteries of this application; it can also refer to a conductive interconnect compatible with the backplane of the battery assembly described below, through which the batteries of this application are electrically connected. Typically, a metal soldering ribbon is used, with direct contact between the front electrode and the conductive interconnect, or between the back electrode and the conductive interconnect. In this case, the concentration of the first element in the first electrical connection portion is less than the concentration of the second element in the second electrical connection portion.

[0182] In a specific embodiment, metal welding ribbons are used as connecting wires to realize electrical connection of the battery of the present application.

[0183] In a specific embodiment, the battery of the present application is connected to the conductive interconnects (such as wiring patterns and conductive through-holes) on the backplane through, for example, a conductive adhesive, thereby achieving electrical connection of the battery of the present application.

[0184] In some embodiments, the first electrical connection portion includes a silicon matrix doping element, such as antimony, and the second electrical connection portion does not include a silicon matrix doping element. In some embodiments, the first electrical connection portion does not include a silicon matrix doping element, and the second electrical connection portion includes a silicon matrix doping element, such as antimony. In some embodiments, both the first electrical connection portion and the second electrical connection portion include a silicon matrix doping element, such as antimony.

[0185] In the present application, since the first electrical connection part and / or the second electrical connection part contains silicon matrix doping elements, such as antimony elements, the contact resistance between the first electrical connection part and / or the second electrical connection part and the battery can also be reduced, thereby further reducing the contact resistance of the solar cell assembly.

[0186] The present application also relates to a solar cell assembly, comprising: an encapsulation layer, a cover plate and a back plate, wherein the encapsulation layer seals at least one cell string, and the encapsulation layer is located between the cover plate and the back plate, wherein the cell string comprises a plurality of cells (e.g., TOPCon cells) as described above in the present application, interconnected by conductive interconnects.

[0187] In this application, the conductive interconnect can refer to a metal soldering ribbon used to electrically connect the battery of this application; it can also refer to a conductive interconnect provided on a backplane, through which the battery of this application is electrically connected. In this case, the battery includes a front electrode and a back electrode, the front electrode and the first conductive interconnect directly or indirectly form a first electrical connection, and the back electrode and the second conductive interconnect directly or indirectly form a second electrical connection, and the concentration of the first element in the first electrical connection is less than the concentration of the second element in the second electrical connection.

[0188] The present application also includes a cell string structure, comprising a plurality of the above-mentioned solar cells of the present application interconnected by conductive interconnectors.

[0189] In a specific embodiment, the conductive interconnects include, for example, conductive connecting lines (sometimes also referred to as connecting lines, metal ribbons) and a conductive backplane (sometimes also referred to as a bonding layer).

[0190] Specifically, before forming a photovoltaic module, the battery needs to go through a stringing (or string welding) step, specifically referring to Figure 2, where multiple batteries are connected by multiple connecting wires, for example, they can be connected in series. The connecting wire can be a metal wire structure (welding strip), and its cross-section can be a circular cross-section, a triangular cross-section, etc., which can be composed of a substrate and a bonding layer wrapped outside the substrate. In addition, the conductive interconnection can also be achieved through a conductive adhesive. For example, the batteries can be bonded by a conductive adhesive on the backplane, and the wiring pattern and the conductive through-holes on the backplane form mutual electrical connections.

[0191] In a specific embodiment, in the present application, whether the connection is made using a metal welding ribbon or a bonding layer formed on the backplane, as long as the battery contacts the conductive interconnection on the metal welding ribbon or the bonding layer through the electrode, and the contact portion contains antimony elements, such a structure can further reduce the contact resistance of the battery string.

[0192] In the stringing step, welding is used for electrical connection, and the welding process requires a heating operation, the main purpose of which is to melt the bonding layer of the connecting wire to form an electrical connection with the battery. However, in the heating step, the stress of the battery may be uneven in the upper and lower directions, and this uneven stress will cause bending. However, the greater the bending in the stringing process, the greater the risk of hidden cracks and fragments in the battery during lamination. The mechanical strength of the battery involved in this application is greater than 50Mpa, and its mechanical strength is relatively large, which can suppress excessive bending of the battery cells when stringing, and can improve the yield of the component to a certain extent. Generally speaking, the curvature of the back-contact battery will be larger than that of the double-sided battery. This is because the stress difference between the upper and lower surfaces of the back-contact battery will be larger.

[0193] Specifically, the curvature of the back-contact battery after being heated at 165-200 degrees Celsius and strung together is less than or equal to 2mm, and the curvature after being heated at a low temperature of 100-160 degrees Celsius and strung together is less than or equal to 1.5mm; and the curvature of the bifacial battery after being heated at 165-200 degrees Celsius and strung together is less than or equal to 1.2mm, and the curvature after being heated at a low temperature of 100-160 degrees Celsius and strung together is less than or equal to 1mm. It can be seen that the curvature of the specially doped battery of the present application is small, which can well control the problems of hidden cracks and fragments during lamination. It should be noted that the curvature involved in the present application refers to the height or depth of the bulge or depression generated on the surface of the battery when the battery is bent, which can be obtained by measuring the curvature radius of the battery edge.

[0194] The present application also relates to a solar cell assembly, comprising a plurality of cells, an encapsulation layer, a cover plate and a back plate as described above. The encapsulation layer seals the plurality of cells and is located between the cover plate and the back plate.

[0195] The battery strings of the present application are formed into battery assemblies through typesetting, stacking, lamination and other processes. The formed battery assembly is shown in Figure 4. Among them, during the lamination process, it is necessary to apply pressure and heat so that the encapsulation layer melts and seals the battery string and bonds the cover plate and the back plate, and the encapsulation layer is located between the cover plate and the back plate. In the lamination process, due to the above-mentioned pressure application and heating operations, part of the stress of the battery is released and suppressed. For back-contact batteries, the curvature of the battery in the battery assembly after lamination is less than or equal to 1.2 mm, and for double-sided batteries, the curvature of the battery in the battery assembly after lamination is less than or equal to 0.8 mm. It has been verified that the hidden cracks and fragmentation problems of the laminated batteries are significantly controlled. As can be seen from Figure 2, the bending direction of the battery is toward the cover plate, that is, the battery protrudes toward the direction of the cover plate to form a curved shape.

[0196] Specifically, referring to Figure 2, the curvature of the back-contact battery after being heated at 165-200 degrees Celsius and strung together is less than or equal to 2mm, and the curvature after being heated at a low temperature of 100-160 degrees Celsius and strung together is less than or equal to 1.5mm; referring to Figure 3, the curvature of the bifacial battery after being heated at 165-200 degrees Celsius and strung together is less than or equal to 1.2mm, and the curvature after being heated at a low temperature of 100-160 degrees Celsius and strung together is less than or equal to 1mm. It can be seen that the curvature of the specially doped battery of the present application is small, which can well control the problems of hidden cracks and fragments during lamination. It should be noted that the curvature involved in the present application refers to the height or depth of the bulge or depression generated on the surface of the battery when the battery is bent, which can be obtained by measuring the curvature radius of the battery edge.

[0197] The present application also relates to a solar cell assembly, comprising a plurality of cells, an encapsulation layer, a cover plate and a back plate as described above. The encapsulation layer seals the plurality of cells and is located between the cover plate and the back plate.

[0198] The battery strings of the present application are formed into battery assemblies through typesetting, stacking, lamination and other processes, and the formed battery assemblies are shown in Figures 4 and 5. Among them, during the lamination process, it is necessary to apply pressure and heat so that the encapsulation layer melts and seals the battery strings and bonds the cover plate and the back plate, and the encapsulation layer is located between the cover plate and the back plate. In the lamination process, due to the above-mentioned pressure application and heating operations, part of the stress of the battery is released and suppressed. For the back-contact battery, see Figure 4, the curvature of the battery in the laminated battery assembly is less than or equal to 1.2 mm, and for the double-sided battery, see Figure 5, the curvature of the battery in the laminated battery assembly is less than or equal to 0.8 mm. It has been verified that the hidden cracks and fragmentation problems of the laminated batteries are significantly controlled. It can be seen from Figures 4 and 5 that the bending direction of the battery is toward the cover plate, that is, the battery protrudes toward the direction of the cover plate to form a curved shape.

[0199] Specifically, the encapsulation layer can be at least one of EVA, POE, silicone, and PVB. The cover plate is close to the light-receiving surface of the battery and is made of a transparent organic or inorganic material. Preferably, it can be low-iron embossed glass, and its thickness is preferably 2.0 or 3.2 mm. The back plate can be transparent or non-transparent. For double-glass modules, the back plate is a transparent material, which is preferably glass, while for single-glass modules, the back plate can be non-transparent, such as a TPC board. Furthermore, the battery module also includes a frame, which has a groove-shaped mounting portion for accommodating the laminate, and the edges of the cover plate and the back plate are embedded in the mounting portion of the frame.

[0200] In a specific embodiment, in this application, whether the connection is made using a metal connecting wire (metal welding ribbon) or a bonding layer formed on the backplane, as long as the battery is in contact with the conductive interconnection on the metal welding ribbon or the bonding layer through the electrode, and the contact part contains antimony element, such a structure can further reduce the contact resistance of the component.

[0201] In some embodiments, the contact resistance between the first electrical connection portion, the second electrical connection portion and the battery can be effectively reduced, thereby further reducing the contact resistance of the solar cell assembly.

[0202] Example

[0203] This application provides general and / or specific descriptions of the materials and experimental methods used in the experiments. In the following examples, unless otherwise specified, % represents wt%, i.e., percentage by weight. All reagents or instruments used without manufacturer indication are commercially available conventional reagents.

[0204] Example 1

[0205] The polysilicon block is loaded into the quartz crucible. For example, the solid silicon raw material is first piled into the quartz crucible, and then the quartz crucible filled with solid silicon is placed in the single crystal furnace.

[0206] The single crystal furnace is vacuumed and argon is introduced. After reaching the set furnace pressure of 11 Tor, the heater of the single crystal furnace is turned on to gradually melt the solid silicon in the quartz crucible into a molten state.

[0207] After the solid silicon material in the quartz crucible is heated and melted, its actual volume decreases. The melted silicon material does not reach the maximum capacity of the quartz crucible. Therefore, the quartz crucible needs to be filled with silicon material twice using an external feeder, such as a quartz tube feeding cylinder. In this embodiment, the quartz tube feeding cylinder is used to fill the quartz crucible four times. During the filling process, the heater simultaneously melts the silicon material in the quartz crucible.

[0208] During the process of charging the silicon material with the quartz tube charging barrel, the Sb-containing dopant is buried in the silicon material in the quartz tube charging barrel.

[0209] After all the silicon material in the quartz crucible is melted, the temperature adjustment stage begins, the seed crystal is inserted into the liquid surface, and the critical crystallization temperature of the liquid surface temperature is reached by controlling power parameters, etc.

[0210] After the seed crystal and the liquid level reach the crystallization point, the seed crystal is subjected to the following crystal pulling process.

[0211] During the crystal pulling process, the constant diameter power was controlled at 45 kW; the argon flow rate was 100 slm; the furnace pressure was 5 Torr; the crucible speed was 4 rpm; and the crystal speed was 6 rpm. The silicon rod pulling process was completed by reducing the diameter of the silicon rod. The silicon rod was then cut to a suitable length by a cutting machine and transferred to a squarer to be processed into a square rod. The square rod was polished by a polishing machine and then transferred to a slicer to be cut into silicon wafers by diamond wire. The detection showed that the Sb concentration of the silicon wafer in Example 1 was 1E+16 cm -3 .

[0212] Experimental Example 1

[0213] The TOPCon cell was prepared by using the Sb-doped silicon wafer prepared in Example 1. During the preparation process, the concentration of boron in the first heavily doped region was controlled to be 1E+18 cm -3 , its thickness is 30nm, and the concentration of boron in the first element lightly doped region is 1E+17cm -3 , its thickness is 70nm, the total thickness of the first doping layer is 100nm, and the concentration of phosphorus in the second doping region is 1E+19cm -3The battery performance of TOPCon battery is shown in Table 1.

[0214] J detected in Table 1 SC 、V OC The specific conditions for FF and Eff are as follows. At 25°C, air mass 1.5G, and 1 sun equivalent lighting conditions, current-voltage (IV) measurements were performed on each completed cell using a solar simulator. Cell parameters J were extracted from these IV curves. SC 、V OC , FF and Eff, the following experimental examples and comparative examples were all tested using the same method.

[0215] Experimental Example 2

[0216] The TOPCon cell in Experimental Example 2 differs from the TOPCon cell in Experimental Example 1 in that the boron concentration in the first heavily doped region is higher, while all other parameters are the same. The cell performance of the TOPCon cell in this experimental example is shown in Table 1.

[0217] Experimental Example 3

[0218] The TOPCon cell in Experimental Example 3 differs from the TOPCon cell in Experimental Example 1 in terms of the thickness of the lightly doped first element region and the total thickness of the first doped layer. All other parameters are the same. The cell performance of the TOPCon cell in this experimental example is shown in Table 1.

[0219] Experimental Example 4

[0220] The TOPCon cell in Experimental Example 4 differs from the TOPCon cell in Experimental Example 1 in that the thicknesses of the lightly doped region and the heavily doped region are different. The total thickness of the first doped layer is the same, and all other parameters are the same. The cell performance of the TOPCon cell in this experimental example is shown in Table 1.

[0221] Experimental Example 5

[0222] The TOPCon cell in Experimental Example 5 is different from the TOPCon cell in Experimental Example 1 in that the Sb-doped silicon wafer prepared in Example 1 is not used for preparation, but a conventional phosphorus-doped silicon wafer is used for preparation (wherein the phosphorus doping concentration in the silicon substrate is 1E+17 cm -3 The battery performance of the TOPCon battery of this experimental example is shown in Table 1.

[0223] Comparative Example 1

[0224] The TOPCon cell in Comparative Example 1 is a conventional TOPCon cell in the prior art, and is prepared using the silicon wafer prepared in Example 1. The cell performance of the TOPCon cell in this comparative example is shown in Table 1.

[0225] Experimental Example 6

[0226] The Sb-doped silicon wafer prepared in Example 1 was used to prepare a battery. During the preparation process, the concentration of phosphorus in the first element doping region was controlled to be 5E+17 cm -3 , its thickness is 70nm, and the concentration of boron in the second doping region is 1E+20cm -3 , its thickness is about 150nm, and the structure of the battery is shown in Figure 6. The battery performance of the TOPCon battery of this experimental example is shown in Table 2.

[0227] Comparative Example 2

[0228] The Sb-doped silicon wafer prepared in Example 1 was used to prepare a battery. During the preparation process, the concentration of phosphorus in the first element doping region was controlled to be 1E+20 cm -3 , its thickness is 70nm, and the concentration of boron in the second doping region is 1E+17cm -3 , its thickness is about 150nm, and the structure of the battery is shown in Figure 6. The battery performance of the TOPCon battery of this comparative example is shown in Table 2.

[0229] Table 1 is a comparison of parameters of Experimental Examples 1-5 and Comparative Example 1

[0230] Table 2 is a comparison of the parameters of Experimental Example 6 and Comparative Example 2

[0231] Through the above embodiments, it can be found that under the conditions of meeting the concentration and doping region thickness required by this solution, the battery performance can be effectively optimized and the battery efficiency can be improved. By comparing the experimental examples with the comparative examples, it is found that the reduction of the concentration and thickness of the light-receiving surface does not affect the battery performance, because the optimization of the concentration and thickness reduces the carrier recombination and improves the battery efficiency. By comparing Experimental Examples 1, 3, and 4, it can be found that when the thickness of the doping region on the light-receiving surface is 100nm, due to the thinner doping region on the light-receiving surface, the carrier recombination area on the front surface of the battery can be reduced, and the short-circuit current density of the battery can be effectively improved, thereby improving the battery efficiency. Comparing Experimental Example 1 with Experimental Example 2, the battery efficiencies of the two are almost the same. Experimental Example 2 is slightly lower in short-circuit current density and fill factor, mainly because the concentration of the heavily doped region is slightly higher than that of Experimental Example 1, which will result in a slightly stronger carrier recombination effect than that of Experimental Example 1.

[0232] In summary, the restrictive conditions proposed in this solution can effectively reduce the carrier recombination efficiency in the light-receiving area of ​​the TOPCon cell's front surface. Furthermore, due to factors such as the atomic radius of elements B, P, and Sb, the lattice distortion stress caused by doping can be effectively reduced, further improving cell performance. Furthermore, Experimental Example 5, in which the silicon substrate is doped with phosphorus, also similarly reduces carrier recombination and improves cell efficiency.

[0233] In addition, if the conductivity type of the first doping region and the second doping region is changed, the same effect can be obtained as long as the concentration of the first element in the first doping region is controlled to be less than the concentration of the second element in the second doping region, and the concentration of the second element in the second doping region is more than 10 times the concentration of the first element in the first doping region, as shown in Experimental Example 6.

[0234] This application also provides the following solutions:

[0235] 1. A solar cell comprising a silicon substrate, a first doped region on a front side of the silicon substrate, and a second doped region on a back side of the silicon substrate, wherein the first doped region and the second doped region have opposite conductivity types, wherein a first element concentration in the first doped region is less than a second element concentration in the second doped region.

[0236] 2. The solar cell according to item 1, wherein

[0237] The concentration of the second element in the second doping region is more than 10 times the concentration of the first element in the first doping region.

[0238] 3. The solar cell according to item 1 or 2, wherein

[0239] The concentration of the first element is 10-1000 times the concentration of the doping element in the silicon substrate; the concentration of the first element in the optional first doping region is in the range of 1E+15cm -3 to 1E+19cm -3 .

[0240] 4. A solar cell according to any one of items 1 to 3, wherein the first doping region includes a first element heavily doped region and a first element lightly doped region, and in the direction from the front side to the back side of the solar cell, the solar cell has the first element heavily doped region, the first element lightly doped region, the silicon substrate and the second doping region in sequence.

[0241] 5. The solar cell according to item 4, wherein the concentration of the first element in the first element heavily doped region is 100 to 1000 times the concentration of the doping element in the silicon substrate, and the multiple between the maximum and minimum values ​​of the concentration of the first element in the first element heavily doped region is less than or equal to 20.

[0242] 6. The solar cell according to item 4 or 5, wherein the concentration of the first element in the first element heavily doped region is 1E+18 cm -3 to 1E+19cm -3 .

[0243] 7. The solar cell according to any one of items 4 to 6, wherein the sum of the thicknesses of the region heavily doped with the first element and the region lightly doped with the first element is less than or equal to 100 nm.

[0244] 8. A solar cell according to any one of items 4 to 7, wherein the thickness of the first element lightly doped region is 20 to 90 nm, optionally 30 to 70 nm, and the concentration of the first element in the first element lightly doped region is 10 to 50 times the concentration of the doping element in the silicon substrate.

[0245] 9. A solar cell according to any one of items 4 to 8, wherein the concentration of the second element in the second doping region is greater than the concentration of the first element in the first element heavily doped region; optionally, the concentration of the second element in the second doping region is more than 10 times the concentration of the first element in the first element heavily doped region.

[0246] 10. The solar cell according to any one of items 4 to 9, wherein

[0247] The doping element in the silicon matrix is ​​antimony; and

[0248] The concentration of antimony in the silicon matrix ranges from 4E+14cm -3 to 2E+16cm -3 , optional 4.3E+14cm -3 to 1.9E+16cm -3 and / or

[0249] The resistivity of the silicon substrate is 0.3 to 10 Ω·cm, and can be optionally 0.4 to 8 Ω·cm; or 0.5 to 6 Ω·cm.

[0250] 11. The solar cell according to any one of items 1 to 10, wherein

[0251] The sum of the concentration of the first element and the concentration of the silicon matrix doping element is less than or equal to 2E+19; or

[0252] The sum of the concentration of the second element and the concentration of the silicon matrix doping element is less than or equal to 1E+21.

[0253] 12. The solar cell according to any one of items 4 to 11, wherein

[0254] The second element is doped into the doped region through the layer structure on the back side of the silicon substrate,

[0255] The layer structure on the back side of the silicon substrate includes an interface passivation layer and a doping passivation layer stacked in sequence on the surface of the second doping region away from the silicon substrate.

[0256] doping the doped passivation layer with a second element,

[0257] The first element is an element selected from the third main group; the second element is an element selected from the fifth main group.

[0258] 13. The solar cell according to item 12, wherein

[0259] In the doped passivation layer, the concentration of the second element at a first preset depth from the surface of the doped passivation layer on the side away from the silicon substrate is greater than the concentration of the first element at a first preset depth from the surface of the first doped region. The thickness of the doped passivation layer ranges from 100 to 400 nm, and the first preset depth is less than or equal to the thickness of the doped passivation layer.

[0260] 14. The solar cell according to item 12, wherein

[0261] Doping the second element in the interface passivation layer,

[0262] In the direction from the doped passivation layer to the interface passivation layer, in the interface passivation layer, the concentration of the second element at a second preset depth from the surface of the doped passivation layer away from the silicon substrate is greater than the concentration of the first element at a second preset depth from the surface of the first doped region, the thickness of the interface passivation layer ranges from 0.5 to 5 nm, and the second preset depth is less than or equal to the sum of the thicknesses of the doped passivation layer and the interface passivation layer.

[0263] 15. The solar cell according to item 12, wherein

[0264] In the direction from the doped passivation layer to the second doped region, in the second doped region, the concentration of the second element at a third preset depth from the surface of the doped passivation layer away from the silicon substrate is greater than the concentration of the first element at a third preset depth from the surface of the first doped region, the thickness range of the second doped region is 30 to 100 nm, and the third preset depth is less than or equal to the sum of the thicknesses of the doped passivation layer, the interface passivation layer and the second doped region.

[0265] 16. A solar cell according to any one of items 1 to 15, wherein the cell includes a front electrode and a back electrode, the front electrode includes a first electrode body and a first contact portion that is in direct or indirect contact with the first doping region, the back electrode includes a second electrode body and a second contact portion that is in direct or indirect contact with the second doping region, and the concentration of the first element in the first contact portion is less than the concentration of the second element in the second contact portion.

[0266] 17. The solar cell according to any one of items 1 to 16, wherein the mechanical strength of the solar cell is greater than or equal to 50 MPa.

[0267] 18. A cell string comprising a plurality of solar cells according to any one of items 1 to 17 interconnected by conductive interconnectors.

[0268] 19. The cell string according to item 18, wherein the curvature of the solar cells is less than or equal to 2 mm.

[0269] 20. The cell string according to item 19, wherein the conductive interconnect is bonded to the solar cell by welding or conductive bonding.

[0270] 21. The battery string according to item 20, wherein the welding comprises a heating step.

[0271] 22. According to the cell string of item 21, the temperature range of the heating step is 100-160 degrees Celsius, and the curvature of the solar cell is less than or equal to 1.5 mm.

[0272] 23. According to the battery string of item 21, the temperature range of the heating step is 165-200 degrees Celsius, and the curvature of the solar cell is less than or equal to 2 mm.

[0273] 24. The cell string according to any one of items 18 to 23, wherein the conductive interconnect comprises an electrical contact portion that contacts an electrode of the solar cell, the electrical contact portion comprising antimony.

[0274] 25. A solar module comprising: an encapsulation layer, a cover plate, and a back plate, wherein the encapsulation layer seals at least one cell string and is located between the cover plate and the back plate.

[0275] The cell string comprises a plurality of solar cells according to any one of items 1 to 17 interconnected by conductive interconnectors.

[0276] 26. According to the solar module of item 25, the solar cell includes a front electrode and a back electrode, the front electrode directly or indirectly forms a first electrical connection part with the first conductive interconnection, and the back electrode directly or indirectly forms a second electrical connection part with the second conductive interconnection, and the concentration of the first element in the first electrical connection part is less than the concentration of the second element in the second electrical connection part.

[0277] 27. The solar module according to item 26, at least one of the first electrical connection part and the second electrical connection part comprises antimony.

[0278] Although the embodiments of the present application are described above, the present application is not limited to the above-mentioned specific embodiments and application fields. The above-mentioned specific embodiments are merely illustrative and instructive, and not restrictive. A person of ordinary skill in the art, under the guidance of this specification and without departing from the scope of protection of the claims of this application, can also make many forms, all of which fall within the scope of protection of this application.

Claims

1. A solar cell comprising a silicon substrate, wherein the silicon substrate comprises a first doped region in the front side of the silicon substrate and a second doped region in the back side of the silicon substrate, wherein the first doped region and the second doped region have opposite conductivity types, wherein: The concentration of the second element in the second doping region is more than 10 times the concentration of the first element in the first doping region, The second element is doped into the second doping region through the layer structure on the back side of the silicon substrate, and the layer structure on the back side of the silicon substrate includes an interface passivation layer and a doping passivation layer stacked in sequence on the surface of the second doping region away from the silicon substrate, and the second element is doped in the doping passivation layer.

2. The solar cell according to claim 1, wherein: The concentration of the first element is 10-1000 times the concentration of the doping element in the silicon substrate; the concentration of the first element in the first doping region can be in the range of 1E+15cm -3 To 1E+19cm -3 .

3. The solar cell according to claim 1, wherein: In the direction from the front side to the back side of the solar cell, the silicon substrate comprises the first doping region, the silicon substrate, and the second doping region; The concentration of the second element is 100-10000 times the concentration of the doping element in the silicon substrate; the concentration of the second element in the second doping region can be in the range of 1E+17cm -3 To 1E+20cm -3 .

4. The solar cell according to any one of claims 1 to 3, wherein In the direction from the front side to the back side of the solar cell, the first doping region sequentially comprises a first element heavily doped region and a first element lightly doped region, wherein the first element is a third main group element and the second element is a fifth main group element.

5. The solar cell according to claim 4, wherein: The concentration of the first element in the first element heavily doped region is 100 to 1000 times the concentration of the doping element in the silicon substrate, and the multiple between the maximum value and the minimum value of the concentration of the first element in the first element heavily doped region is less than or equal to 20.

6. The solar cell according to claim 4, wherein: The concentration of the first element in the first element heavily doped region is 1E+18cm -3 To 1E+19cm -3 .

7. The solar cell according to claim 4, wherein: The sum of the thicknesses of the first element heavily-doped region and the first element lightly-doped region is less than or equal to 100 nm.

8. The solar cell according to claim 4, wherein: The thickness of the first element lightly doped region is 20 to 90 nm, and can be optionally 30 to 70 nm, and the concentration of the first element in the first element lightly doped region is 10 to 50 times the concentration of the doping element in the silicon substrate.

9. The solar cell according to claim 4, wherein: The concentration of the second element in the second doping region is greater than the concentration of the first element in the region heavily doped with the first element; optionally, the concentration of the second element in the second doping region is more than 10 times the concentration of the first element in the region heavily doped with the first element.

10. The solar cell according to any one of claims 1 to 3, wherein In the direction from the front side to the back side of the solar cell, the solar cell has the first doping region, a silicon substrate and the second doping region in sequence, wherein the first element is a fifth main group element and the second element is a third main group element.

11. The solar cell according to claim 2 or 3, wherein: The doping element in the silicon substrate is antimony; and The concentration range of antimony in the silicon matrix is ​​4E+14cm -3 To 2E+16cm -3 , optional 4.3E+14cm -3 To 1.9E+16cm -3 ; and / or The resistivity of the silicon substrate is 0.3-10Ω·cm, and can be optionally 0.4-8Ω·cm; or 0.5-6Ω·cm.

12. The solar cell according to claim 2 or 3, wherein: The sum of the concentration of the first element and the concentration of the silicon substrate doping element is less than or equal to 2E+19cm -3 ;or The sum of the concentration of the second element and the concentration of the silicon substrate doping element is less than or equal to 1E+21cm -3 .

13. The solar cell according to any one of claims 1 to 3, wherein In the doped passivation layer, the concentration of the second element at a first preset depth from the surface of the doped passivation layer on a side away from the silicon substrate is greater than the concentration of the first element at a first preset depth from the surface of the first doping region, the thickness of the doped passivation layer ranges from 100 to 400 nm, and the first preset depth is less than or equal to the thickness of the doped passivation layer.

14. The solar cell according to any one of claims 1 to 3, wherein doping the second element in the interface passivation layer, In the direction from the doped passivation layer to the interface passivation layer, in the interface passivation layer, the concentration of the second element at a second preset depth from the surface of the doped passivation layer on a side away from the silicon substrate is greater than the concentration of the first element at a second preset depth from the surface of the first doped region, the thickness of the interface passivation layer ranges from 0.5 to 5 nm, and the second preset depth is less than or equal to the sum of the thicknesses of the doped passivation layer and the interface passivation layer.

15. The solar cell according to any one of claims 1 to 3, wherein In the direction from the doped passivation layer to the second doped region, in the second doped region, the concentration of the second element at a third preset depth from the surface of the doped passivation layer away from the silicon substrate is greater than the concentration of the first element at a third preset depth from the surface of the first doped region, the thickness of the second doped region ranges from 30 to 100 nm, and the third preset depth is less than or equal to the sum of the thicknesses of the doped passivation layer, the interface passivation layer and the second doped region.

16. The solar cell according to any one of claims 1 to 3, wherein The solar cell includes a front electrode and a back electrode, the front electrode includes a first electrode body and a first contact portion in contact with the first doping region, the back electrode includes a second electrode body and a second contact portion in contact with the second doping region, and the concentration of the first element in the first contact portion is less than the concentration of the second element in the second contact portion. 17 . The solar cell according to claim 1 , wherein the mechanical strength of the solar cell is greater than or equal to 50 MPa.

18. A cell string comprising a plurality of solar cells according to any one of claims 1 to 17 interconnected by conductive interconnectors.

19. The battery string according to claim 18, wherein: The curvature of the solar cell is less than or equal to 2 mm. 20 . The cell string according to claim 19 , wherein the conductive interconnector is bonded to the solar cell by welding or conductive bonding.

21. The battery string of claim 20, wherein the welding comprises a heating step.

22. The battery string according to claim 21, wherein the temperature range of the heating step is 100-160 degrees Celsius, and the curvature of the solar cell is less than or equal to 1.5 mm.

23. The battery string according to claim 21, wherein the temperature range of the heating step is 165-200 degrees Celsius, and the curvature of the solar cell is less than or equal to 2 mm.

24. The cell string according to any one of claims 18 to 23, wherein the conductive interconnect comprises an electrical contact portion contacting an electrode of the solar cell, the electrical contact portion comprising antimony element.

25. A solar cell assembly, comprising a plurality of cells, a packaging layer, a cover plate and a back plate, wherein the packaging layer seals the plurality of cells and the packaging layer is located between the cover plate and the back plate; the cell is a solar cell according to any one of claims 1 to 17.

26. The solar module of claim 25, wherein: The curvature of the battery is less than or equal to 1.2 mm.

27. The solar energy assembly according to claim 25, further comprising a frame, wherein the edges of the cover plate and / or the back plate are embedded in the mounting portion of the frame.

28. The solar module according to any one of claims 25 to 27, wherein the cover plate and / or the back plate is a transparent plate.

29. The solar module according to any one of claims 25 to 27, wherein the back sheet is a non-transparent sheet.

30. The solar module according to any one of claims 25 to 27, wherein the cell protrudes toward the cover plate to form a curved shape.

31. The solar module according to any one of claims 25 to 27, wherein the plurality of cells are interconnected by a conductive interconnector, the conductive interconnector comprising an electrical contact portion contacting an electrode of the solar cell, the electrical contact portion comprising antimony element.

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