Heterojunction solar cell and method for manufacturing the same

Abstract

The present invention provides a heterojunction solar cell and a manufacturing method thereof. The heterojunction solar cell involved has a first doped layer disposed on the light-receiving surface of a silicon substrate and a second doped layer disposed on the backlight surface. At least one of the first doped layer and the second doped layer includes at least two doped films stacked. Among two adjacent doped films, the doping concentration of the doped film farther from the silicon substrate is greater than that of the doped film closer to the silicon substrate. In the present invention, since the doped film closer to the silicon substrate in the first doped layer or / and the second doped layer has a lower doping concentration, it can minimize the entry of doped atoms into the corresponding intrinsic amorphous layer, thereby reducing the defect density of the corresponding intrinsic amorphous layer. Since the doped film farther from the silicon substrate in the first doped layer or / and the second doped layer has a higher doping concentration, it is beneficial for field passivation and can also reduce the contact resistance between the first doped layer or / and the second doped layer and the corresponding outer layer.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic manufacturing, and particularly to a heterojunction solar cell and a manufacturing method thereof. Background Art

[0002] The heterojunction solar cell is a relatively efficient crystalline silicon solar cell at present. It combines the characteristics of crystalline silicon cells and silicon-based thin film cells, and has advantages such as a short manufacturing process, a low process temperature, a high conversion efficiency, and a large power generation. Figure 1 The following shows a schematic structural diagram of a heterojunction solar cell involved in the prior art, which sequentially includes a first collector 51', a first transparent conductive film layer 41', a first doped layer 31', a first intrinsic amorphous layer 21', a silicon substrate 10', a second intrinsic amorphous layer 22', a second doped layer 32', a second transparent conductive film layer 42', and a second collector 52' from top to bottom.

[0003] In the prior art, there are the following problems: when the doping concentrations in the first doped layer 31' and the second doped layer 32' involved are too high, the doped atoms will enter the first intrinsic amorphous layer 21' and the second intrinsic amorphous layer 22', and further increase the defect density of the first intrinsic amorphous layer 21' and the second intrinsic amorphous layer 22', affecting the passivation effect on the silicon substrate 10'; while when the doping concentrations in the first doped layer 31' and the second doped layer 32' involved are too low, the resistivity of the first doped layer 31' and the second doped layer 32' is relatively high, which is not conducive to current transmission.

[0004] In view of this, it is necessary to provide an improved technical solution to solve the above problems. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To achieve the above-mentioned invention purpose, the present invention provides a heterojunction solar cell, and its specific design is as follows.

[0006] A heterojunction solar cell includes: a silicon substrate, a first intrinsic amorphous layer and a first doped layer sequentially stacked on the light-receiving surface of the silicon substrate, a second intrinsic amorphous layer and a second doped layer with a doping type opposite to that of the first doped layer sequentially stacked on the backlight surface of the silicon substrate; at least one of the first doped layer and the second doped layer includes at least two stacked doped films, and among adjacent two of the doped films, the doping concentration of the doped film far from the silicon substrate is greater than that of the doped film close to the silicon substrate.

[0007] Further, the doped film is a doped amorphous silicon film, a doped amorphous silicon oxide film, a doped microcrystalline silicon film or a doped microcrystalline silicon oxide film.

[0008] Furthermore, the average doping concentration of the first doping layer is less than that of the second doping layer.

[0009] Furthermore, the number of doping films in the second doping layer is not greater than that in the first doping layer.

[0010] Furthermore, the thickness of the first doping layer is less than or equal to that of the second doping layer.

[0011] Furthermore, the doping film constituting the first doping layer is a phosphorus-doped film, and the phosphorus-doped film includes a first phosphorus-doped film, a second phosphorus-doped film, and a third phosphorus-doped film that are sequentially stacked outside the first intrinsic amorphous layer. The phosphorus doping concentrations in the first phosphorus-doped film, the second phosphorus-doped film, and the third phosphorus-doped film are 50 - 150 ppm, 100 - 300 ppm, and 200 - 400 ppm, respectively.

[0012] Furthermore, the thicknesses of the first phosphorus-doped film, the second phosphorus-doped film, and the third phosphorus-doped film are 2 - 4 nm, 2 - 4 nm, and 1 - 3 nm, respectively.

[0013] Furthermore, the doping film constituting the second doping layer is a boron-doped film, and the boron-doped film includes a first boron-doped film, a second boron-doped film, and a third boron-doped film that are sequentially stacked outside the second intrinsic amorphous layer. The boron doping concentrations in the first boron-doped film, the second boron-doped film, and the third boron-doped film are 100 - 300 ppm, 200 - 500 ppm, and 400 - 600 ppm, respectively.

[0014] Furthermore, the thicknesses of the first boron-doped film, the second boron-doped film, and the third boron-doped film are 2 - 5 nm, 2 - 5 nm, and 1 - 3 nm, respectively.

[0015] Furthermore, the first intrinsic amorphous layer and the second intrinsic amorphous layer each include at least two stacked intrinsic films, and each of the intrinsic films is composed of one of an intrinsic amorphous silicon film, an intrinsic amorphous silicon oxide film, and an intrinsic amorphous silicon carbide film.

[0016] Furthermore, the intrinsic film farthest from the silicon substrate in the first intrinsic amorphous layer and / or the second intrinsic amorphous layer is an intrinsic amorphous silicon oxide film.

[0017] Furthermore, the number of intrinsic films in the second intrinsic amorphous layer is not greater than that in the first intrinsic amorphous layer.

[0018] Furthermore, among two adjacent intrinsic films, the hydrogen content of the intrinsic film closer to the silicon substrate is greater than that of the intrinsic film farther from the silicon substrate.

[0019] Further, the first intrinsic amorphous layer and the second intrinsic amorphous layer each include three stacked intrinsic films. In the direction from the inner intrinsic film to the outer intrinsic film, the hydrogen content ranges of the three intrinsic films in the first intrinsic amorphous layer and the second intrinsic amorphous layer are successively 20%-40%, 10%-25%, and 8%-20%.

[0020] Further, in the direction from the inner intrinsic film to the outer intrinsic film, the thicknesses of the three intrinsic films in the first intrinsic amorphous layer are successively 1-3 nm, 2-4 nm, and 1-3 nm, and the thicknesses of the three intrinsic films in the second intrinsic amorphous layer are successively 1-5 nm, 3-10 nm, and 0-5 nm.

[0021] The present invention also provides a method for manufacturing a heterojunction solar cell, which includes the following steps:

[0022] Providing a silicon substrate;

[0023] Successively forming a first intrinsic amorphous layer and a first doped layer on the light-receiving surface of the silicon substrate;

[0024] Successively forming a second intrinsic amorphous layer and a second doped layer on the backlight surface of the silicon substrate, and the doping type of the second doped layer is opposite to that of the first doped layer;

[0025] At least one of the step of forming the first doped layer and the step of forming the second doped layer includes successively forming at least two doped films, and in two adjacent doped films formed successively, the doping concentration of the doped film far from the silicon substrate is greater than that of the doped film close to the silicon substrate.

[0026] Further, the step of forming the first doped layer includes successively forming three phosphorus-doped films on the surface of the first intrinsic amorphous layer. In the direction away from the silicon substrate, the range of the PH3 / SiH4 flow ratio values when forming the three phosphorus-doped films is successively 50-150 ppm, 100-300 ppm, and 200-400 ppm.

[0027] Further, the step of forming the second doped layer includes successively forming three boron-doped films on the surface of the second intrinsic amorphous layer. In the direction away from the silicon substrate, the range of the B2H6 / SiH4 flow ratio values when forming the three boron-doped films is successively 50-150 ppm, 100-250 ppm, and 200-300 ppm.

[0028] Further, at least one of the step of forming the first intrinsic amorphous layer and the step of forming the second intrinsic amorphous layer includes successively forming at least two intrinsic films, and in two adjacent intrinsic films formed successively, the hydrogen content of the intrinsic film close to the silicon substrate is greater than that of the intrinsic film far from the silicon substrate.

[0029] Further, both the first intrinsic amorphous layer forming step and the second intrinsic amorphous layer forming step include sequentially forming three intrinsic films. In the direction from the inner intrinsic film to the outer intrinsic film, the H2 / SiH4 flow rate ratio ranges for forming the three intrinsic films in the first intrinsic amorphous layer and the second intrinsic amorphous layer are 0, 3 - 10, and 10 - 20 in sequence.

[0030] Further, in the first intrinsic amorphous layer forming step and the second intrinsic amorphous layer forming step, it also includes: after forming one intrinsic film, introducing pure H2 or H2-diluted SiH4 onto the surface of the corresponding intrinsic film for plasma treatment; wherein, the H2 / SiH4 dilution ratio in the H2-diluted SiH4 is greater than 100.

[0031] Advantages of the present invention: Based on the specific structure of the heterojunction solar cell involved in the present invention, the doped film close to the silicon substrate in the first doping layer or / and the second doping layer has a low doping concentration, which can minimize the entry of doped atoms into the corresponding intrinsic amorphous layer, thereby reducing the defect density of the corresponding intrinsic amorphous layer; the doped film far from the silicon substrate in the first doping layer or / and the second doping layer has a high doping concentration, which is beneficial for field passivation and can also reduce the contact resistance between the first doping layer or / and the second doping layer and the corresponding outer layer. Description of the Drawings

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0033] Figure 1 The figure shows a schematic structural diagram of a heterojunction solar cell in the prior art;

[0034] Figure 2 The figure shows a schematic diagram of the first implementation structure of the heterojunction solar cell of the present invention;

[0035] Figure 3 The figure shows a schematic diagram of the second implementation structure of the heterojunction solar cell of the present invention.

[0036] In the figure, 10 is a silicon substrate, 21 is a first intrinsic amorphous layer, 31 is a first doped layer, 311 is a first phosphorus-doped film, 312 is a second phosphorus-doped film, 313 is a third phosphorus-doped film, 41 is a first transparent conductive film layer, 51 is a first collector, 22 is a second intrinsic amorphous layer, 32 is a second doped layer, 321 is a first boron-doped film, 322 is a second boron-doped film, 323 is a third boron-doped film, 42 is a second transparent conductive film layer, and 52 is a second collector. Detailed implementation mode

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] Reference Figure 2 As shown, the heterojunction solar cell involved in the present invention includes: a silicon substrate 10, a first intrinsic amorphous layer 21 and a first doped layer 31 sequentially stacked on the light-receiving surface of the silicon substrate 10, and a second intrinsic amorphous layer 22 and a second doped layer 32 sequentially stacked on the backlight surface of the silicon substrate 10. Among them, the doping types of the first doped layer 31 and the second doped layer 32 are opposite, one of which is n-type doping, that is, phosphorus doping is used; the other is p-type doping, that is, boron doping is used.

[0039] More specifically, reference Figure 2 As shown, in this specific embodiment, the heterojunction solar cell involved includes: a first transparent conductive film layer 41 and a first collector 51 sequentially stacked outside the first doped layer 31, and a second transparent conductive film layer 42 and a second collector 52 sequentially stacked outside the second doped layer 32.

[0040] In the specific implementation process, the light-receiving surface of the silicon substrate 10 involved is the surface of the heterojunction solar cell that directly receives sunlight, and the backlight surface is the surface of the heterojunction solar cell that does not directly receive sunlight, that is, the surface opposite to the light-receiving surface.

[0041] In the present invention, at least one of the first doped layer 31 and the second doped layer 32 includes at least two stacked doped films. Among the adjacent two doped films, the doping concentration of the doped film farther from the silicon substrate 10 is greater than that of the doped film closer to the silicon substrate 10.

[0042] Based on the specific structure of the heterojunction solar cell involved in the present invention, the doped film near the silicon substrate 10 in the first doped layer 31 or / and the second doped layer 32 has a lower doping concentration, which can minimize the entry of doped atoms into the corresponding intrinsic amorphous layer (i.e., the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22), thereby reducing the defect density of the corresponding intrinsic amorphous layer. The doped film far from the silicon substrate 10 in the first doped layer 31 or / and the second doped layer 32 has a higher doping concentration, which is beneficial for field passivation and can also reduce the contact resistance between the first doped layer 31 or / and the second doped layer 32 and the corresponding outer layer (in this specific embodiment, including the first transparent conductive film layer 41 and the second transparent conductive film layer 42).

[0043] In the specific implementation process of the present invention, the doped film involved is a doped amorphous silicon film, a doped amorphous silicon oxide film, a doped microcrystalline silicon film or a doped microcrystalline silicon oxide film. Generally, for the convenience of fabrication, the multiple doped films constituting the first doped layer 31 are of the same material, for example, all are doped amorphous silicon films; the multiple doped films constituting the second doped layer 32 are also of the same material, for example, all are doped amorphous silicon oxide films; the multiple doped films constituting the first doped layer 31 and the multiple doped films constituting the second doped layer 32 can be the same or different.

[0044] Preferably, in some embodiments of the present invention, the average doping concentration of the first doped layer 31 is less than that of the second doped layer 32. For a heterojunction solar cell, its light-receiving surface is the main surface of the photocurrent. Since the first doped layer 31 has a relatively low average concentration, it can have a higher mobility, which is beneficial for the transmission of the photocurrent on the light-receiving surface of the heterojunction solar cell; while on the backlight side of the heterojunction solar cell, since the average doping concentration of the second doped layer 32 is relatively high, the resistance of the heterojunction solar cell can be reduced.

[0045] In still other preferred embodiments of the present invention, the number of doped films in the second doped layer 32 is not greater than that in the first doped layer 31. For a heterojunction solar cell, its light-receiving surface is the main surface of the photocurrent, and higher performance requirements are imposed on the first doped layer 31. By setting more doped films, the comprehensive performance of the first doped layer 31 can be better optimized.

[0046] Furthermore, the thickness of the first doped layer 31 is less than or equal to the thickness of the second doped layer 32, and preferably, the thickness of the first doped layer 31 is less than the thickness of the second doped layer 32. Generally, the thickness of the first doped layer 31 is 5 - 11 nm, and the thickness of the second doped layer 32 is 5 - 13 nm.

[0047] For a heterojunction solar cell, the light absorption effect on the light-receiving surface has a much greater impact on the photoelectric conversion efficiency of the cell than the light absorption effect on the backlight surface. A relatively small thickness of the first doping layer 31 can effectively reduce the loss of sunlight on the light-receiving surface when passing through the first doping layer 31, improve the short-circuit current of the heterojunction solar cell, and enable the heterojunction solar cell to have better photoelectric conversion efficiency. For the backlight surface, the light absorption problem does not need to be considered too much. A relatively thick thickness of the second doping layer 32 can have better conductivity, thereby reducing the contact resistance between it and the second transparent conductive film 42.

[0048] The silicon substrate 10 involved in the present invention can specifically select a p-type single-crystalline silicon substrate or an n-type single-crystalline silicon substrate; however, as a preferred embodiment of the present invention, the single-crystalline silicon substrate 10 is an n-type single-crystalline silicon substrate. When the single-crystalline silicon substrate 10 is an n-type single-crystalline silicon substrate, the first doping layer 31 is n-type doping, that is, phosphorus doping is used; the second doping layer 32 is p-type doping, that is, boron doping is used.

[0049] In some more specific embodiments, in combination with Figure 2 As shown, in this embodiment, the doping film constituting the first doping layer 31 is a phosphorus doping film. Specifically, the phosphorus doping film includes a first phosphorus doping film 311, a second phosphorus doping film 312, and a third phosphorus doping film 313 that are sequentially stacked outside the first intrinsic amorphous layer 21. Among them, the phosphorus doping concentrations in the first phosphorus doping film 311, the second phosphorus doping film 312, and the third phosphorus doping film 312 are 50 - 150 ppm, 100 - 300 ppm, and 200 - 400 ppm, respectively.

[0050] Preferably, the thicknesses of the first phosphorus doping film 311, the second phosphorus doping film 312, and the third phosphorus doping film 313 are 2 - 4 nm, 2 - 4 nm, and 1 - 3 nm, respectively.

[0051] Furthermore, in Figure 2 As shown in the embodiment, the doping film constituting the second doping layer 32 is a boron doping film. The boron doping film includes a first boron doping film 321, a second boron doping film 322, and a third boron doping film 323 that are sequentially stacked outside the second intrinsic amorphous layer 22. Among them, the boron doping concentrations in the first boron doping film 321, the second boron doping film 322, and the third boron doping film 323 are 100 - 300 ppm, 200 - 500 ppm, and 400 - 600 ppm, respectively. Since the boron doping concentrations in the first boron doping film 321, the second boron doping film 322, and the third boron doping film 323 are greater than the phosphorus doping concentrations in the first phosphorus doping film 311, the second phosphorus doping film 312, and the third phosphorus doping film 312 in sequence, the average doping concentration of the first doping layer 31 can be made less than the average doping concentration of the second doping layer 32.

[0052] Preferably, the thicknesses of the first boron-doped film 321, the second boron-doped film 322, and the third boron-doped film 323 are 2-5 nm, 2-5 nm, and 1-3 nm, respectively.

[0053] As a preferred embodiment of the present invention, the first intrinsic amorphous layer 31 and the second intrinsic amorphous layer 32 each include at least two layers of stacked intrinsic films, where each intrinsic film is composed of one of an intrinsic amorphous silicon film, an intrinsic amorphous silicon oxide film, and an intrinsic amorphous silicon carbide film. Refer to Figure 3 As shown, in this specific embodiment, both the first intrinsic amorphous layer 31 and the second intrinsic amorphous layer 32 include three layers of stacked intrinsic films. Specifically, the first intrinsic amorphous layer 21 includes a first intrinsic film 211, a second intrinsic film 212, and a third intrinsic film 213 that are sequentially stacked on the light-receiving surface of the silicon substrate 10; the second intrinsic amorphous layer 22 includes a fourth intrinsic film 221, a fifth intrinsic film 222, and a sixth intrinsic film 223 that are sequentially stacked on the backlight surface of the silicon substrate 10.

[0054] Since both the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 include at least two layers of stacked intrinsic films, in the specific implementation process, it is convenient to form the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 with better comprehensive performance by controlling the characteristics of each layer of film.

[0055] As a preference of the present invention, in the specific implementation process, the intrinsic film farthest from the silicon substrate 10 in the first intrinsic amorphous layer 21 and / or the second intrinsic amorphous layer 22 is set as an intrinsic amorphous silicon oxide film. Refer to Figure 3 As shown, in this embodiment, the third intrinsic film 213 is the intrinsic film farthest from the single-crystalline silicon substrate 10 in the first intrinsic amorphous layer 21, and the third intrinsic film 213 in this embodiment is preferably an intrinsic amorphous silicon oxide film. It can be understood that in some other embodiments of the present invention, the intrinsic film farthest from the single-crystalline silicon substrate 10 in the second intrinsic amorphous layer 22 can also be set as an intrinsic amorphous silicon oxide film, that is, the Figure 3 sixth intrinsic film 223 farthest from the silicon substrate 10 in the shown embodiment can also be set as an intrinsic amorphous silicon oxide film.

[0056] The passivation effect of the intrinsic amorphous silicon oxide film is worse than that of the intrinsic amorphous silicon film and the intrinsic amorphous silicon carbide film, but it has better light transmittance than the intrinsic amorphous silicon film and the intrinsic amorphous silicon carbide film. In the heterojunction solar cell, the intrinsic film farthest from the silicon substrate 10 in the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 has limited passivation effect on the silicon substrate 10 due to the distance. Setting it as the intrinsic amorphous silicon oxide film with the best light transmittance can increase the light transmittance of the corresponding intrinsic layer and optimize the photoelectric conversion efficiency of the heterojunction solar cell to a certain extent.

[0057] In addition, in some further preferred embodiments of the present invention, the number of intrinsic films in the second intrinsic amorphous layer 22 is not greater than the number of intrinsic films in the first intrinsic amorphous layer 21. For a heterojunction solar cell, its light-receiving surface serves as the main surface for generating photocurrent, and higher performance requirements are imposed on the first intrinsic amorphous layer 21. By setting a greater number of intrinsic films, the comprehensive performance of the first intrinsic amorphous layer 21 can be better optimized.

[0058] Furthermore, the thickness of the first intrinsic amorphous layer 21 is less than or equal to the thickness of the second intrinsic amorphous layer 22, and preferably, the thickness of the first intrinsic amorphous layer 21 is less than the thickness of the second intrinsic amorphous layer 22. Generally, the thickness of the first intrinsic amorphous layer 21 is 4 - 10 nm, and the thickness of the second intrinsic amorphous layer 22 is 4 - 20 nm. For the specific reasons, reference can be made to the description of the thickness configuration of the first doped layer 31 and the second doped layer 32, which will not be elaborated here.

[0059] As a further preference of the present invention, among two adjacent intrinsic films, the hydrogen content of the intrinsic film closer to the silicon substrate 10 is greater than that of the intrinsic film farther from the silicon substrate 10. Specifically, as shown in Figure 3 In this embodiment, the hydrogen content of the first intrinsic film 211, the second intrinsic film 212, and the third intrinsic film 213 in the first intrinsic amorphous layer 21 decreases in sequence, and the hydrogen content of the fourth intrinsic film 221, the fifth intrinsic film 222, and the sixth intrinsic film 223 in the second intrinsic amorphous layer 22 also decreases in sequence.

[0060] It is relatively easy to understand that the closer the intrinsic film in the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 is to the silicon substrate 10, the more obvious its passivation effect is. The first intrinsic film 211 and the fourth intrinsic film 221 are both directly attached to the silicon substrate 10, and their highest hydrogen content can enable the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 to have an optimal passivation effect on the silicon substrate 10. Specifically, the higher hydrogen content of the first intrinsic film 211 and the fourth intrinsic film 221 can better passivate the dangling bonds at the surface position of the silicon substrate 10.

[0061] As a preference of the present invention, when the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 each include three stacked intrinsic films, in the direction from the inner intrinsic film to the outer intrinsic film, the hydrogen content ranges of the three intrinsic films in the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 are all 20% - 40%, 10% - 25%, and 8% - 20% in sequence. That is, the hydrogen content ranges of the first intrinsic film 201 and the fourth intrinsic film 204 are 20% - 40%, the hydrogen content ranges of the second intrinsic film 212 and the fifth intrinsic film 222 are 10% - 25%, and the hydrogen content ranges of the third intrinsic film 213 and the sixth intrinsic film 223 are 8% - 20%.

[0062] Further preferably, in Figure 3 In the embodiments, the hydrogen content ranges of the first intrinsic film 211 and the fourth intrinsic film 221 are 24% - 30%, the hydrogen content ranges of the second intrinsic film 212 and the fifth intrinsic film 222 are 12% - 18%, and the hydrogen content ranges of the third intrinsic film 213 and the sixth intrinsic film 223 are 10% - 15%.

[0063] As a further preference for the embodiments Figure 3 shown in the present invention, in the direction from the inner - layer intrinsic film to the outer - layer intrinsic film, the thicknesses of the three intrinsic films in the first intrinsic amorphous layer are 1 - 3 nm, 2 - 4 nm, and 1 - 3 nm in sequence, and the thicknesses of the three intrinsic films in the second intrinsic amorphous layer are 1 - 5 nm, 3 - 10 nm, and 0 - 5 nm in sequence. Specifically, the thickness ranges of the first intrinsic film 211, the second intrinsic film 212, and the third intrinsic film 213 in the first intrinsic amorphous layer 21 are 1 - 3 nm, 2 - 4 nm, and 1 - 3 nm in sequence, and the thickness ranges of the fourth intrinsic film 221, the fifth intrinsic film 222, and the sixth intrinsic film 223 in the second intrinsic amorphous layer 22 are 1 - 5 nm, 3 - 10 nm, and 0 - 5 nm in sequence.

[0064] The present invention further provides a manufacturing method for a heterojunction solar cell. It specifically includes the following steps:

[0065] Provide a silicon substrate 10;

[0066] Form a first intrinsic amorphous layer 21 and a first doping layer 31 on the light - receiving surface of the silicon substrate 10 in sequence;

[0067] Form a second intrinsic amorphous layer 22 and a second doping layer 32 on the back - light surface of the silicon substrate in sequence, and the doping type of the second doping layer 32 is opposite to that of the first doping layer 31.

[0068] In the above steps, at least one of the steps of forming the first doping layer 31 and the step of forming the second doping layer 32 includes sequentially forming at least two doping films, and in two adjacent doping films formed in sequence, the doping concentration of the doping film farther from the silicon substrate 10 is greater than that of the doping film closer to the silicon substrate.

[0069] Among them, a specific implementation of the step of providing the silicon substrate 10 is: select an n - type single - crystal silicon wafer, use a 15% volume ratio KOH aqueous solution to remove the damaged layer, then use a KOH and anisotropic texturing additive solution to form a pyramid - shaped textured surface structure on the surface of the n - type single - crystal silicon wafer, then use an ozone aqueous solution with a concentration of 10 - 50 ppm to treat the n - type single - crystal silicon wafer with a pyramid - shaped textured surface, and use a 2% HF solution to remove the surface oxide layer of the n - type single - crystal silicon wafer, and finally wash and dry to obtain the silicon substrate 10. Usually, the height of the pyramid in the pyramid structure is 0.5 - 3 um, and the surface reflectivity of the textured surface is about 10%.

[0070] The first intrinsic amorphous layer 21, the first doped layer 31, the second intrinsic amorphous layer 22, and the second doped layer 32 in the present invention are all formed by the PECVD process.

[0071] Among them, for Figure 2 the heterojunction solar cell with the shown implementation structure, the formation step of the first doped layer 31 includes sequentially forming three layers of phosphorus-doped films on the surface of the first intrinsic amorphous layer 21. In the direction away from the silicon substrate, the range of the PH3 / SiH4 flow ratio values when forming the three layers of phosphorus-doped films is 50 - 150 ppm, 100 - 300 ppm, and 200 - 400 ppm in sequence. The formation step of the second doped layer 32 includes sequentially forming three layers of boron-doped films on the surface of the second intrinsic amorphous layer 22. In the direction away from the silicon substrate, the range of the B2H6 / SiH4 flow ratio values when forming the three layers of boron-doped films is 50 - 150 ppm, 100 - 250 ppm, and 200 - 300 ppm in sequence.

[0072] More specifically, a specific formation step of the first doped layer 31 is as follows: Heat the PECVD coating chamber to 180 °C, and control the pressure at 30 - 200 Pa; Introduce PH3, SiH4, and H2 towards the surface of the first intrinsic amorphous layer 21, control the PH3 / SiH4 flow ratio value at 50 - 150 ppm, and deposit to form the first phosphorus-doped film 311; Then adjust the PH3 / SiH4 flow ratio value to 100 - 300 ppm, and deposit to form the second phosphorus-doped film 312; Finally, adjust the PH3 / SiH4 flow ratio value to 200 - 400 ppm, and deposit to form the third phosphorus-doped film 313. All the doped films in the first doped layer 31 formed by this step are doped amorphous silicon films. During the formation of the first doped layer 31, keep the SiH4 flow rate unchanged, and maintain the chamber pressure unchanged by adjusting the H2 flow rate.

[0073] In still other embodiments of the present invention, when all the doped films of the first doped layer 31 are doped amorphous silicon oxide films, a specific formation step of the first doped layer 31 is as follows: heat the PECVD coating chamber to 180 °C and control the pressure at 30 - 200 Pa; introduce PH3, SiH4, CO2, and H2 facing the surface of the first intrinsic amorphous layer 21, control the flow ratio value of PH3 / SiH4 to be 50 - 150 ppm, and the flow ratio value of CO2 / SiH4 to be 0.5 - 2, and deposit to form the first phosphorus-doped film 311; then adjust the flow ratio value of PH3 / SiH4 to 100 - 300 ppm and the flow ratio value of CO2 / SiH4 to be 0.5 - 2, and deposit to form the second phosphorus-doped film 312; finally, adjust the flow ratio value of PH3 / SiH4 to 200 - 400 ppm and the flow ratio value of CO2 / SiH4 to be 0.5 - 2, and deposit to form the third phosphorus-doped film 313. During the process of forming the first doped layer 31 through this step, keep the SiH4 flow rate unchanged and maintain the chamber pressure unchanged by adjusting the H2 flow rate.

[0074] Correspondingly, a specific formation step of the second doped layer 32 is as follows: heat the PECVD coating chamber to 180 °C and control the pressure at 30 - 200 Pa; introduce B2H6, SiH4, and H2 facing the surface of the second intrinsic amorphous layer 22, control the flow ratio value of B2H6 / SiH4 to be 50 - 150 ppm, and deposit to form the first boron-doped film 321; then adjust the flow ratio value of B2H6 / SiH4 to 100 - 250 ppm and deposit to form the second boron-doped film 322; finally, adjust the flow ratio value of B2H6 / SiH4 to 200 - 300 ppm and deposit to form the third boron-doped film 323. All the doped films of the second doped layer 32 formed through this step are doped amorphous silicon films. During the formation process of the second doped layer 32, keep the SiH4 flow rate unchanged and maintain the chamber pressure unchanged by adjusting the H2 flow rate.

[0075] In still other embodiments of the present invention, when all the doped films of the second doped layer 32 are doped amorphous silicon oxide films, a specific formation step of the second doped layer 32 is as follows: heat the PECVD coating chamber to 180 °C and control the pressure at 30 - 200 Pa; introduce B2H6, SiH4, CO2 and H2 towards the surface of the second intrinsic amorphous layer 22, control the flow ratio value of B2H6 / SiH4 to be 50 - 150 ppm, and the flow ratio value of CO2 / SiH4 to be 0.5 - 2, and deposit to form the first boron-doped film 321; then adjust the flow ratio value of B2H6 / SiH4 to 100 - 250 ppm, and the flow ratio value of CO2 / SiH4 to be 0.5 - 2, and deposit to form the second boron-doped film 322; finally, adjust the flow ratio value of B2H6 / SiH4 to 200 - 300 ppm, and the flow ratio value of CO2 / SiH4 to be 0.5 - 2, and deposit to form the third boron-doped film 323. During the process of forming the second doped layer 32 through this step, keep the SiH4 flow rate unchanged, and adjust the H2 flow rate to maintain the chamber pressure unchanged.

[0076] It can be understood that in the specific implementation process, by controlling the forming time of each doped film, the thickness of each doped film can be controlled.

[0077] For Figure 3 the heterojunction solar cell shown, at least one of the formation steps of the first intrinsic amorphous layer 21 and the formation step of the second intrinsic amorphous layer 22 includes sequentially forming at least two intrinsic films, and in two adjacent intrinsic films formed in sequence, the hydrogen content of the intrinsic film closer to the silicon substrate 10 is greater than the hydrogen content of the intrinsic film farther from the silicon substrate 10.

[0078] In some specific embodiments of the present invention, as combined with Figure 3 shown, both the formation step of the first intrinsic amorphous layer 21 and the formation step of the second intrinsic amorphous layer 22 include sequentially forming three intrinsic films. To make the hydrogen content of the intrinsic film closer to the silicon substrate 10 greater than the hydrogen content of the intrinsic film farther from the silicon substrate 10, during the implementation of this embodiment, in the direction from the inner intrinsic film to the outer intrinsic film, the H2 / SiH4 flow ratio ranges for forming the three intrinsic films in the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 are 0, 3 - 10, and 10 - 20 in sequence.

[0079] As a specific implementation manner, when all the intrinsic modes constituting the first intrinsic amorphous layer 21 are intrinsic amorphous silicon films, the specific formation steps of the first intrinsic amorphous layer 21 include: heating the PECVD coating chamber to 180 °C and controlling the pressure at 30 - 200 Pa; first introducing pure SiH4 towards the light-receiving surface of the silicon substrate 10 to deposit and form the first intrinsic layer film 211. It can be understood that pure SiH4 is equivalent to an H2 / SiH4 flow rate ratio of 0; then, introducing SiH4 diluted with H2 to deposit and form the second intrinsic layer film 212 on the first intrinsic layer film 211. At this time, the flow rate ratio range of H2 / SiH4 is 3 - 10; continue to introduce SiH4 diluted with H2 to deposit and form the third intrinsic layer film 213 on the second intrinsic layer film 212. At this time, adjust the flow rate ratio range of H2 / SiH4 to 10 - 20.

[0080] The first intrinsic amorphous layer 21 is deposited by introducing pure SiH4, which can form an intrinsic layer with a high hydrogen content (i.e., more bonded hydrogen) and can inhibit the growth of epitaxial silicon at the interface. However, in the first intrinsic amorphous layer 21 with a high hydrogen content, loose structures such as micropores are easily formed, and the quality of the thin film body is poor. While the second intrinsic layer film 212 and the third intrinsic layer film 213 use SiH4 diluted with H2. Although the bonded hydrogen content in the corresponding intrinsic layer is reduced, a dense structure can be formed. The film thicknesses of the second intrinsic layer film 212 and the third intrinsic layer film 213 are dense, which can prevent the doping atoms in the first doping layer 31 from entering the first intrinsic amorphous layer 21, thereby avoiding reducing the passivation effect of the first intrinsic amorphous layer 21.

[0081] In Figure 3 In the illustrated embodiment, when all the intrinsic modes constituting the second intrinsic amorphous layer 22 are intrinsic amorphous silicon films, the specific formation steps of the second intrinsic amorphous layer 22 can refer to the specific formation steps of the above first intrinsic amorphous layer 21, and will not be elaborated here specifically.

[0082] In some other embodiments of the present invention, when the intrinsic mode is an intrinsic amorphous silicon oxide film, the gas introduced also adds CO2 on the basis of the gas components for making the intrinsic amorphous silicon film; and preferably, the flow rate ratio range of SiH4 / CO2 is 0.5 - 2. Correspondingly, when the intrinsic mode is an intrinsic amorphous silicon carbide film, the gas introduced also adds CH4 on the basis of the gas components for making the intrinsic amorphous silicon film; and preferably, the flow rate ratio range of SiH4 / CH4 is 0.5 - 2.

[0083] Furthermore, in the formation steps of the first intrinsic amorphous layer 21 and the formation steps of the second intrinsic amorphous layer 22, it further includes: after forming one intrinsic film, introducing pure H2 or SiH4 diluted with H2 towards the surface of the corresponding intrinsic film for plasma treatment; wherein, the dilution ratio of H2 / SiH4 in the SiH4 diluted with H2 is greater than 100.

[0084] Specifically, in combination with Figure 3 As shown, in the specific implementation process of some embodiments of the present invention, during the formation step of the first intrinsic amorphous layer 21, after the formation of the first intrinsic film 211, after the formation of the second intrinsic film 212, and after the formation of the third intrinsic film 213, a plasma treatment with pure H2 or SiH4 diluted with H2 can be added once. Among them, preferably, a plasma treatment with pure H2 or SiH4 diluted with H2 is added once after the formation of each intrinsic film; second preferably, a plasma treatment with pure H2 or SiH4 diluted with H2 is added only after the formation of the third intrinsic film 213.

[0085] Correspondingly, during the formation step of the second intrinsic amorphous layer 22, after the formation of the fourth intrinsic film 221, after the formation of the fifth intrinsic film 222, and after the formation of the sixth intrinsic film 223, a plasma treatment with pure H2 or SiH4 diluted with H2 can also be added once. Among them, preferably, a plasma treatment with pure H2 or SiH4 diluted with H2 is added once after the formation of each intrinsic film; second preferably, a plasma treatment with pure H2 or SiH4 diluted with H2 is added only after the formation of the sixth intrinsic film 223.

[0086] In this embodiment, by adding a plasma treatment with pure H2 or SiH4 diluted with H2, the hydrogen content of the corresponding intrinsic film can be further increased, and the passivation effect of the first intrinsic amorphous layer 21 and the second intrinsic amorphous layer 22 on the silicon substrate 10 can be further improved.

[0087] It can be understood that the method for manufacturing a heterojunction solar cell involved in the present invention further includes:

[0088] Transparent conductive film manufacturing step: The first transparent conductive film layer 41 and the second transparent conductive film layer 42 are respectively manufactured on the surfaces of the first doped layer 31 and the second doped layer 32 by using PVD deposition, RPD deposition, or magnetron sputtering deposition process.

[0089] Collector manufacturing step: A layer of low-temperature conductive silver paste is respectively printed on the first transparent conductive film layer 41 and the second transparent conductive film layer 42 by screen printing, and then sintered at a low temperature of 150 - 300 °C to form a good ohmic contact, thereby forming the first collector 51 and the second collector 52.

[0090] Among them, a specific implementation manner of the first transparent conductive film 41 and the second transparent conductive film 42 is as follows: heat the deposition chamber of the PVD device to 190°C; place the silicon substrate 10 on which the first doping layer 31 and the second doping layer 32 are completed on a carrier plate and send it into the deposition chamber; use an ITO (In2O3:SnO2 = 97:3) target to coat the surface of the first doping layer 31 to deposit a first transparent conductive film layer 41 with a thickness of 70 - 100 nm; use an ITO (In2O3:SnO2 = 90:10) target to coat the surface of the second doping layer 32 to deposit a second transparent conductive film layer 42 with a thickness of 70 - 100 nm.

[0091] It can be understood that the ITO (In2O3:SnO2 = 97:3) target means that the mass ratio of In2O3 to SnO2 in the ITO target material is 97:3, and the ITO (In2O3:SnO2 = 90:10) target means that the mass ratio of In2O3 to SnO2 in the ITO target material is 90:10. The relatively low content of the doped oxide SnO2 in the first transparent conductive film layer 41 makes the first transparent conductive film layer 41 have better light transmittance, which is beneficial to the light collection effect of the light-receiving surface of the heterojunction solar cell; the relatively high content of the doped oxide SnO2 in the second transparent conductive film layer 42 makes the second transparent conductive film layer 42 have better conductivity, and can optimize the contact resistance between the second transparent conductive film layer 42 and the second collector.

[0092] It should be understood that although this specification is described according to the embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0093] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not used to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A heterojunction solar cell, comprising: A silicon substrate, a first intrinsic amorphous layer and a first doped layer which are sequentially stacked on the light-receiving surface of the silicon substrate, a second intrinsic amorphous layer and a second doped layer with a doping type opposite to that of the first doped layer which are sequentially stacked on the light-shielding surface of the silicon substrate; characterized in that at least one of the first doped layer and the second doped layer contains at least two stacked doped films, and among two adjacent doped films, the doping concentration of the doped film farther from the silicon substrate is greater than that of the doped film closer to the silicon substrate, the average doping concentration of the first doped layer is less than that of the second doped layer, and the doping type of the first doped layer is the same as that of the silicon substrate; the thickness of the first doped layer is less than or equal to that of the second doped layer, and the heterojunction solar cell further includes a first transparent conductive film layer disposed outside the first doped layer and a second transparent conductive film layer disposed outside the second doped layer.

2. The heterojunction solar cell according to claim 1, wherein, The doped film is a doped amorphous silicon film, a doped amorphous silicon oxide film, a doped microcrystalline silicon film or a doped microcrystalline silicon oxide film.

3. The heterojunction solar cell according to claim 1, wherein, The number of doped films in the second doped layer is not greater than that in the first doped layer.

4. The heterojunction solar cell according to any one of claims 1-3, wherein, The silicon substrate is an n-type single-crystalline silicon substrate, the doped film constituting the first doped layer is a phosphorus-doped film, and the phosphorus-doped film includes a first phosphorus-doped film, a second phosphorus-doped film and a third phosphorus-doped film which are sequentially stacked outside the first intrinsic amorphous layer, and the phosphorus doping concentrations in the first phosphorus-doped film, the second phosphorus-doped film and the third phosphorus-doped film are 50-150 ppm, 100-300 ppm and 200-400 ppm respectively.

5. The heterojunction solar cell according to claim 4, wherein, The thicknesses of the first phosphorus-doped film, the second phosphorus-doped film and the third phosphorus-doped film are 2-4 nm, 2-4 nm and 1-3 nm respectively.

6. The heterojunction solar cell according to any one of claims 1-3, wherein, The silicon substrate is an n-type single-crystalline silicon substrate, the doped film constituting the second doped layer is a boron-doped film, and the boron-doped film includes a first boron-doped film, a second boron-doped film and a third boron-doped film which are sequentially stacked outside the second intrinsic amorphous layer, and the boron doping concentrations in the first boron-doped film, the second boron-doped film and the third boron-doped film are 100-300 ppm, 200-500 ppm and 400-600 ppm respectively.

7. The heterojunction solar cell according to claim 6, wherein, The thicknesses of the first boron-doped film, the second boron-doped film and the third boron-doped film are 2-5 nm, 2-5 nm and 1-3 nm respectively.

8. The heterojunction solar cell according to any one of claims 1-3, wherein, The first intrinsic amorphous layer and the second intrinsic amorphous layer each include at least two stacked intrinsic films, and each intrinsic film is composed of one of an intrinsic amorphous silicon film, an intrinsic amorphous silicon oxide film and an intrinsic amorphous silicon carbide film.

9. The heterojunction solar cell according to claim 8, wherein, The outermost intrinsic film of the first intrinsic amorphous layer and / or the second intrinsic amorphous layer away from the silicon substrate is an intrinsic amorphous silicon oxide film.

10. The heterojunction solar cell according to claim 8, wherein, The number of intrinsic films in the second intrinsic amorphous layer is not greater than that in the first intrinsic amorphous layer.

11. The heterojunction solar cell according to claim 8, wherein, Among two adjacent intrinsic films, the hydrogen content of the intrinsic film closer to the silicon substrate is greater than that of the intrinsic film farther from the silicon substrate.

12. The heterojunction solar cell according to claim 11, wherein, The first intrinsic amorphous layer and the second intrinsic amorphous layer respectively include three intrinsic films arranged in a stacked manner, and in the direction from the inner intrinsic film to the outer intrinsic film, the hydrogen content ranges of the three intrinsic films in the first intrinsic amorphous layer and the second intrinsic amorphous layer are successively 20%-40%, 10%-25%, and 8%-20%.

13. The heterojunction solar cell according to claim 12, wherein, In the direction from the inner intrinsic film to the outer intrinsic film, the thicknesses of the three intrinsic films in the first intrinsic amorphous layer are successively 1-3 nm, 2-4 nm, and 1-3 nm, and the thicknesses of the three intrinsic films in the second intrinsic amorphous layer are successively 1-5 nm, 3-10 nm, and 0-5 nm.

14. A method for manufacturing a heterojunction solar cell, comprising the following steps: Provide a silicon substrate; Form a first intrinsic amorphous layer and a first doped layer on the light-receiving surface of the silicon substrate in sequence; Form a second intrinsic amorphous layer and a second doped layer on the backlight surface of the silicon substrate in sequence, and the doping type of the second doped layer is opposite to that of the first doped layer; It is characterized in that at least one of the step of forming the first doped layer and the step of forming the second doped layer includes successively forming at least two doped films, and in two adjacent doped films formed in sequence, the doping concentration of the doped film far from the silicon substrate is greater than that of the doped film close to the silicon substrate, the average doping concentration of the first doped layer is less than that of the second doped layer, and the doping type of the first doped layer is the same as that of the silicon substrate; the thickness of the first doped layer is less than or equal to that of the second doped layer; The method for manufacturing the heterojunction solar cell further includes: respectively manufacturing a first transparent conductive film layer and a second transparent conductive film layer on the surfaces of the first doped layer and the second doped layer.

15. The method for manufacturing a heterojunction solar cell according to claim 14, wherein, The silicon substrate is an n-type single-crystalline silicon substrate, and the step of forming the first doped layer includes successively forming three phosphorus-doped films on the surface of the first intrinsic amorphous layer. In the direction away from the silicon substrate, the range of the PH3 / SiH4 flow ratio values when forming the three phosphorus-doped films is successively 50-150 ppm, 100-300 ppm, and 200-400 ppm.

16. The method for manufacturing a heterojunction solar cell according to claim 14, wherein, The silicon substrate is an n-type single-crystalline silicon substrate, and the step of forming the second doped layer includes successively forming three boron-doped films on the surface of the second intrinsic amorphous layer. In the direction away from the silicon substrate, the range of the B2H6 / SiH4 flow ratio values when forming the three boron-doped films is successively 50-150 ppm, 100-250 ppm, and 200-300 ppm.

17. The manufacturing method of the heterojunction solar cell according to any one of claims 14 - 16, characterized in that, At least one of the step of forming the first intrinsic amorphous layer and the step of forming the second intrinsic amorphous layer includes successively forming at least two intrinsic films, and in two adjacent intrinsic films formed in sequence, the hydrogen content of the intrinsic film close to the silicon substrate is greater than that of the intrinsic film far from the silicon substrate.

18. The manufacturing method of the heterojunction solar cell according to claim 17, characterized in that, Both the step of forming the first intrinsic amorphous layer and the step of forming the second intrinsic amorphous layer include successively forming three intrinsic films. In the direction from the inner intrinsic film to the outer intrinsic film, the range of the H2 / SiH4 flow ratio values when forming the three intrinsic films in the first intrinsic amorphous layer and the second intrinsic amorphous layer is successively 0, 3-10, and 10-20.

19. The manufacturing method of the heterojunction solar cell according to claim 18, characterized in that, In the formation step of the first intrinsic amorphous layer and the formation step of the second intrinsic amorphous layer, it further includes: after forming an intrinsic film, introducing pure H2 or H2-diluted SiH4 onto the surface of the corresponding intrinsic film for plasma treatment; wherein, the dilution ratio of H2 / SiH4 in the H2-diluted SiH4 is greater than 100.

Images