Solar cell and preparation method thereof
By setting a differentiated textured surface structure on the back of the solar cell substrate, the problem of carrier recombination was solved, the efficiency and light utilization of the solar cell were improved, the fabrication process was simplified, and the production cost was reduced.
Patent Information
- Application Number
- CN202410135492.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-30
- Publication Date
- 2025-08-01
AI Technical Summary
The problem of carrier recombination is serious in existing solar cells, which limits the improvement of solar cell efficiency, especially in cells with electrodes on the back.
Differentiated first and third regions are set on the back side of the solar cell substrate to form a first textured structure and a second textured structure with different specific surface areas. By adjusting the density, area and height of the protrusions, carrier recombination is reduced and light absorption is improved.
It significantly improves the carrier recombination problem, increases the efficiency of solar cells, reduces the electrode contact area, and enhances the utilization of light from the back side.
Smart Images
Figure CN120417583A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor technology, and particularly to a solar cell and a method for manufacturing the same. Background Art
[0002] A solar cell is a semiconductor device that converts light energy into electrical energy through the photovoltaic effect. Solar cells are increasingly widely used in current production and life. For a solar cell with electrodes disposed on the back surface, compared with a traditional solar cell having electrodes designed on the front and back surfaces respectively, a higher short-circuit current and a higher front-side conversion efficiency can be obtained. However, the problem of carrier recombination in the above-mentioned solar cell is relatively serious, which also limits the further improvement of the efficiency of the solar cell. Summary of the Invention
[0003] Based on this, in view of the problems in the above background art, it is necessary to provide a solar cell to improve the problem of carrier recombination in the solar cell and further improve the efficiency of the solar cell.
[0004] According to some embodiments of the present disclosure, a solar cell is provided, which includes: a substrate, a first doping structure, a first electrode, a second doping structure, and a second electrode; the back surface of the substrate has a first region, a second region, and a third region, and the third region is disposed between the first region and the second region;
[0005] The first doping structure is disposed on the first region, the first electrode is in contact with the first doping structure, the second doping structure is disposed on the second region, the second electrode is electrically connected to the second doping structure, and the doping types of the first doping structure and the second doping structure are different;
[0006] The surface of the first region has a first texture structure, the surface of the third region has a second texture structure, and the surface area of the first texture structure per unit bottom area is smaller than the specific surface area of the second texture structure per unit bottom area.
[0007] In some embodiments of the present disclosure, the first texture structure includes a plurality of first protrusions, the second texture structure includes a plurality of second protrusions, and the first texture structure and the second texture structure satisfy at least one of the conditions a to c:
[0008] a: The distribution density of the first protrusions on the first region is less than the distribution density of the second protrusions on the third region;
[0009] b: The sum of the bottom areas of all the first protrusions is less than the sum of the bottom areas of all the second protrusions;
[0010] c: The height of the first raised portion is less than the height of the second raised portion.
[0011] In some embodiments of the present disclosure, the height of the first raised portion ≤ 1 μm.
[0012] In some embodiments of the present disclosure, the height of the second raised portion is 1 μm to 4.5 μm.
[0013] In some embodiments of the present disclosure, the distribution density of the first raised portion on the first region is less than 10%.
[0014] In some embodiments of the present disclosure, the distribution density of the second raised portion on the third region is more than 90%.
[0015] In some embodiments of the present disclosure, the surface of the first region protrudes from the surface of the third region, and the surface of the second region protrudes from the surface of the first region.
[0016] In some embodiments of the present disclosure, the height difference between the second region and the first region < 1 μm.
[0017] In some embodiments of the present disclosure, the height difference between the second region and the third region > 1 μm.
[0018] In some embodiments of the present disclosure, the width of the first region is 250 μm to 350 μm.
[0019] In some embodiments of the present disclosure, the width of the second region is 500 μm to 650 μm.
[0020] In some embodiments of the present disclosure, the width of the third region is 200 μm to 300 μm.
[0021] In some embodiments of the present disclosure, relative to the total area of the first region, the second region, and the third region, the area ratio of the first region > 15%.
[0022] In some embodiments of the present disclosure, the first doping structure is disposed in the substrate and exposed from the surface of the first region, and the doping element in the first doping structure includes the element of the first electrode.
[0023] In some embodiments of the present disclosure, the second doping structure includes a dielectric layer and a doped polycrystalline layer stacked, and the dielectric layer and the doped polycrystalline layer are sequentially stacked on the substrate.
[0024] Further, the present disclosure also provides a method for manufacturing a solar cell as described in any one of the above embodiments, which includes the following steps:
[0025] Provide a substrate;
[0026] Form the second doping structure on the second region of the substrate and form a mask layer covering the second doping structure;
[0027] Perform differential laser treatment on the first region and the third region, and perform texturing treatment on the substrate, so that a first textured structure is formed on the surface of the first region, and a second textured structure is formed on the surface of the third region; and,
[0028] Prepare the first electrode and the second electrode and form the first doping structure.
[0029] In some embodiments of the present disclosure, the step of performing differential laser treatment on the first region and the third region includes: performing laser treatment on the first region with a first laser and performing laser treatment on the third region with a second laser, and the average power of the first laser is lower than the average power of the second laser.
[0030] In some embodiments of the present disclosure, before forming the second doping structure, a step of polishing the substrate is further included.
[0031] In some embodiments of the present disclosure, the step of preparing the first electrode and the second electrode and forming the first doping structure includes: preparing a first electrode paste on the first region, and performing heat treatment on the first electrode paste so that elements in the first electrode paste diffuse into the substrate to form the first electrode and the first doping structure located in the substrate.
[0032] The back surface of the substrate in the solar cell provided by the present disclosure has a first region, a second region, and a third region. The surface of the first region has a first textured structure, and the surface of the third region has a second textured structure. The second textured structure separates the first textured structure and the second region, and the specific surface area of the first textured structure is smaller than the specific surface area of the second textured structure. Among them, by setting the specific surface area of the second textured structure to be larger, it is possible to ensure that the back surface of the solar cell still has a relatively high light absorption rate as much as possible. By setting the specific surface area of the first textured structure to be smaller, the contact area between the first electrode and the first doping structure can be reduced, thereby significantly improving the problem of carrier recombination in the solar cell and effectively improving the efficiency of the solar cell.
[0033] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following describes in detail with reference to the preferred embodiments of the present invention and the accompanying drawings. Description of the Drawings
[0034] Figure 1 Schematic structural diagram of a solar cell provided by the present disclosure;
[0035] Figure 2 is Figure 1 Schematic diagram of the back structure of the solar cell shown in
[0036] Figure 3 Schematic structural diagram of a substrate;
[0037] Figure 4 is Figure 3 Schematic structural diagram of forming a second doping structure and a mask layer on the basis of the structure shown in
[0038] Figure 5 is Figure 4 Schematic structural diagram after differential laser treatment and texturing treatment on the basis of the structure shown in
[0039] Figure 6 Surface topography map of the first region of the substrate in Example 1;
[0040] Figure 7 Surface topography map of the third region of the substrate in Example 1;
[0041] Among them, the meanings of the respective reference numerals are as follows:
[0042] 100, substrate; 101, first region; 102, second region; 103, third region; 1010, first textured surface structure; 1030, second textured surface structure; 110, first doping structure; 120, second doping structure; 121, dielectric layer; 122, doped polycrystalline layer; 130, first electrode; 140, second electrode; 150, back passivation layer; 160, front passivation layer; 210, mask layer. Detailed implementation manners
[0043] To facilitate the understanding of the present disclosure, the present disclosure will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present disclosure more thorough and comprehensive.
[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs. The terms used in the specification of the present disclosure herein are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.
[0045] It should be understood that when an element or layer is referred to as being "on", "adjacent to", "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on", "directly adjacent to", "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers and / or portions, these elements, components, regions, layers and / or portions should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or portion from another element, component, region, layer or portion. Thus, without departing from the teachings of the present disclosure, the first element, component, region, layer or portion discussed below may be referred to as the second element, component, region, layer or portion.
[0046] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. are used herein for convenience in describing the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms are intended to include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then an element or feature described as "under" or "beneath" or "below" other elements or features will be oriented "on" the other elements or features. Thus, the exemplary terms "under" and "beneath" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are to be interpreted accordingly.
[0047] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present disclosure. As used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.
[0048] The disclosed embodiments are described with reference to cross-sectional views that are schematic illustrations of ideal embodiments (and intermediate structures) of the present disclosure. As such, variations from the shapes as shown are to be expected due to, for example, manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present disclosure should not be limited to the particular shapes of the regions shown herein, but include shape deviations resulting from, for example, manufacturing. The regions shown in the figures are substantially schematic, and their shapes are not intended to show the actual shape of the regions of the device and are not intended to limit the scope of the present disclosure.
[0049] Figure 1 Schematic structural diagram of a solar cell provided for the present disclosure, with reference to Figure 1 As shown, the solar cell includes: a substrate 100, a first doping structure 110, a first electrode 130, a second doping structure 120, and a second electrode 140; the back surface of the substrate 100 has a first region 101, a second region 102, and a third region 103, and the third region 103 is disposed between the first region 101 and the second region 102; the first doping structure 110 is disposed on the first region 101, the first electrode 130 is electrically connected to the first doping structure 110, the second doping structure 120 is disposed on the second region 102, the second electrode 140 is electrically connected to the second doping structure 120, and the doping types of the first doping structure 110 and the second doping structure 120 are different; the surface of the first region 101 has a first textured structure 1010, the surface of the third region 103 has a second textured structure 1030, and the specific surface area of the first textured structure 1010 is smaller than the specific surface area of the second textured structure 1030.
[0050] The back surface of the substrate 100 in the solar cell provided by the present disclosure has a first region 101, a second region 102, and a third region 103. The surface of the first region 101 has a first textured structure 1010, and the surface of the third region 103 has a second textured structure 1030. The second textured structure 1030 separates the first textured structure 1010 from the second region 102, and the specific surface area of the first textured structure 1010 is smaller than the specific surface area of the second textured structure 1030. Among them, by setting the specific surface area of the second textured structure 1030 to be relatively large, it is possible to ensure that the back surface of the solar cell still has a relatively high light absorption rate as much as possible. By setting the specific surface area of the first textured structure 1010 to be relatively small, the contact area between the first electrode 130 and the first doping structure 110 can be reduced, thereby significantly improving the problem of carrier recombination of the solar cell and effectively increasing the efficiency of the solar cell.
[0051] In the present disclosure, the "surface area per unit bottom area" refers to the surface area of the first textured structure 1010 or the second textured structure 1030 on the bottom surface of a unit area. It can be understood that both the first textured structure 1010 and the second textured structure 1030 may have a fluctuating surface, and depending on the degree of fluctuation and the specific shape, the surface areas of the first textured structure 1010 and the second textured structure 1030 on the bottom surface of a unit area are also different.
[0052] In this solar cell, the first doping structure 110 can be shaped after the first region 101. Further, the first doping structure 110 can be a structure stacked on the substrate 100, or can be disposed in the substrate 100 and flush with the surface of the first region 101.
[0053] In some examples of this embodiment, the ratio of the surface area per unit bottom area of the first textured structure 1010 to the specific surface area per unit bottom area of the second textured structure 1030 is 50% or less. Further, the ratio of the surface area per unit bottom area of the first textured structure 1010 to the specific surface area per unit bottom area of the second textured structure 1030 is 30% or less. Still further, the ratio of the surface area per unit bottom area of the first textured structure 1010 to the specific surface area per unit bottom area of the second textured structure 1030 is 10% or less.
[0054] Referring to Figure 1 As shown, in some examples of this embodiment, the first textured structure 1010 includes a plurality of first protrusions, and the second textured structure 1030 includes a plurality of second protrusions. It can be understood that the first protrusions and the second protrusions can be regular shapes or irregular shapes. In some examples of this embodiment, both the first protrusions and the second protrusions can be pyramid-shaped.
[0055] In some examples of this embodiment, the distribution density of the first protrusions on the first region 101 is less than the distribution density of the second protrusions on the third region 103.
[0056] In some examples of this embodiment, the sum of the bottom areas of all the first protrusions is less than the sum of the bottom areas of all the second protrusions.
[0057] In some examples of this embodiment, the height of the first protrusions is less than the height of the second protrusions.
[0058] It can be understood that by setting the distribution density of the first protrusions on the first region 101 to be small, the bottom area of the first protrusions to be small, and the height of the first protrusions to be small, the surface area of the first textured structure 1010 can be made small.
[0059] In some examples of this embodiment, the height of the first protrusion is ≤ 1 μm. For example, the height of the first protrusion can be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 800 nm, or the height of the first protrusion can also be within the range between any two of the above heights.
[0060] In some examples of this embodiment, the height of the second protrusion is 1 μm to 4.5 μm. For example, the height of the second protrusion can be 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or 4.5 μm, or the height of the second protrusion can also be within the range between any two of the above heights.
[0061] In some examples of this embodiment, the distribution density of the first protrusions on the first region 101 is below 10%. Among them, the distribution density of the first protrusions on the first region 101 refers to the ratio of the total bottom area occupied by all the first protrusions to the bottom area occupied by the first region 101. Further, the distribution density of the first protrusions on the first region 101 can be 1%, 2%, 3%, 4%, 5%, 7%, 9% or 10%, or the distribution density of the first protrusions on the first region 101 can also be within the range between any two of the above ratios.
[0062] In some examples of this embodiment, the distribution density of the second protrusions on the third region 103 is above 90%. Among them, the distribution density of the second protrusions on the third region 103 refers to the ratio of the total bottom area occupied by all the second protrusions to the bottom area occupied by the third region 103. Further, the distribution density of the second protrusions on the third region 103 can be 91%, 92%, 93%, 94%, 95%, 97%, 99% or 100%, or the distribution density of the second protrusions on the third region 103 can also be within the range between any two of the above ratios.
[0063] In some examples of this embodiment, the surface reflectivity of the first region 101 is higher than that of the third region 103.
[0064] In some examples of this embodiment, the surface reflectivity of the second region 102 is higher than that of the first region 101.
[0065] Refer to Figure 1 As shown, in some examples of this embodiment, the surface of the second region 102 can be a flat surface to minimize the surface area of the second region 102 as much as possible, thereby improving the surface reflectivity of the second region 102. Among them, the surface of the second region 102 can be a flat surface formed after polishing.
[0066] Refer toFigure 1 As shown, in some examples of this embodiment, the surface of the first region 101 protrudes from the surface of the third region 103, and the surface of the second region 102 protrudes from the surface of the first region 101. Among them, the surface of the first region 101 protrudes from the surface of the third region 103, so that there is a height difference between the first region 101 and the third region 103, and the surface of the second region 102 protrudes from the surface of the first region 101, so that there is a height difference between the second region 102 and the third region 103. By setting this height difference, the first region 101 and the second region 102 can be further spaced apart to improve the recombination of carriers.
[0067] Referring to Figure 1 As shown, in some examples of this embodiment, the height difference between the second region 102 and the first region 101 is < 1 μm. For example, the height difference between the second region 102 and the first region 101 can be 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 650 nm, 800 nm or 950 nm, or the height difference between the second region 102 and the first region 101 can also be within the range between any two of the above height differences.
[0068] Referring to Figure 1 As shown, in some examples of this embodiment, the height difference between the second region 102 and the third region 103 is > 1 μm. For example, the height difference between the second region 102 and the third region 103 can be 1.1 μm to 10 μm. Further, the height difference between the second region 102 and the third region 103 can be 1.1 μm, 2 μm, 3 μm, 4 μm, 1.1 μm, 5 μm, 6.5 μm, 8 μm or 10 μm, or the height difference between the second region 102 and the third region 103 can also be within the range between any two of the above height differences.
[0069] Figure 2 is Figure 1 a schematic diagram of the back structure of the solar cell shown in
[0070] Referring to Figure 2 As shown, in some examples of this embodiment, the width of the first region 101 can be 250 μm to 350 μm. For example, the width of the first region 101 can be 250 μm, 260 μm, 280 μm, 300 μm, 320 μm, 340 μm or 350 μm, or the width of the first region 101 can also be within the range between any two of the above widths.
[0071] Referring to Figure 2As shown, in some examples of this embodiment, the width of the second region 102 can be 500 μm to 650 μm. For example, the width of the second region 102 can be 500 μm, 520 μm, 550 μm, 580 μm, 600 μm, 620 μm, or 650 μm. Alternatively, the width of the second region 102 can also be within the range between any two of the above widths.
[0072] Referring to Figure 2 As shown, in some examples of this embodiment, the width of the third region 103 can be 200 μm to 300 μm. For example, the width of the third region 103 can be 200 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm, or 300 μm. Alternatively, the width of the third region 103 can also be within the range between any two of the above widths.
[0073] Referring to Figure 2 As shown, in some examples of this embodiment, with respect to the total area of the first region 101, the second region 102, and the third region 103, the area ratio of the first region 101 > 15%. Setting the area ratio of the first region 101 > 15% can further improve the problem of carrier recombination in this solar cell and improve the efficiency of the solar cell.
[0074] In some examples of this embodiment, the doping type of the first doping structure 110 is the same as that of the substrate 100, and the doping type of the second doping structure 120 is different from that of the substrate 100. It can be understood that the doping types include P-type and N-type. In this embodiment, the substrate 100 can be P-type doped, the first doping structure 110 can also be P-type doped, and the second doping structure 120 can be N-type doped.
[0075] Referring to Figure 1 As shown, in some examples of this embodiment, the first doping structure 110 can be disposed in the substrate 100 and exposed from the surface of the first region 101. The doping elements in the first doping structure 110 can include the elements of the first electrode 130. It can be understood that in the actual preparation process, the material of the first electrode 130 can be directly contacted with the substrate 100 and heat-treated, so that the elements of the first electrode 130 can diffuse into the substrate 100 to form the first doping structure 110 located in the substrate 100. Further, the first electrode 130 can also be directly contacted with the first doping structure 110.
[0076] Referring to Figure 1As shown, in some examples of this embodiment, the second doping structure 120 may include a dielectric layer 121 and a doped polycrystalline layer 122 arranged in a stacked manner. The dielectric layer 121 and the doped polycrystalline layer 122 are sequentially stacked on the substrate 100. By providing the dielectric layer 121 and the doped polycrystalline layer 122, a passivated contact structure can be formed, further improving the efficiency of the solar cell.
[0077] In some examples of this embodiment, the material of the dielectric layer 121 may include a dielectric material, and the dielectric material may be selected from at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, and titanium oxide. Further, the dielectric layer 121 may include silicon oxide. For example, the dielectric layer 121 may be a silicon oxide layer. Silicon oxide has relatively excellent passivation performance, which can minimize the recombination loss of minority carriers on the surface of the substrate 100, and silicon oxide also has excellent durability in high-temperature treatment processes.
[0078] In some examples of this embodiment, the material of the substrate 100 may include a silicon material, and the material of the doped polycrystalline layer 122 may include doped polycrystalline silicon.
[0079] In some examples of this embodiment, in order to better provide interface passivation for the substrate 100, the thickness of the dielectric layer 121 may be 0.1 nm - 5 nm. For example, the thickness of the dielectric layer 121 may be 0.1 nm, 0.5 nm, 1 nm, 1.5 nm, 2 nm, 3 nm, 4 nm, 5 nm. However, the present invention is not limited thereto, and the thickness of the dielectric layer 121 may also have various values.
[0080] In this embodiment, the dielectric layer 121 may serve as a barrier for electrons and holes and cooperate with the doped polycrystalline layer 122 to prevent minority carriers from passing through. Moreover, the dielectric layer 121 may also have the function of pinhole channels, enabling the carriers in the solar cell to move freely. By allowing the majority carriers to selectively pass through the doped polycrystalline layer 122, the recombination loss of minority carriers can be reduced. Furthermore, the dielectric layer 121 can also separate the substrate 100 from the doped polycrystalline layer 122 and prevent the doping elements in the doped polycrystalline layer 122 from diffusing into the substrate 100.
[0081] In some other examples, the second doping structure 120 may be arranged similar to the first doping structure 110. For example, the second doping structure 120 may also be disposed in the substrate 100 and exposed from the surface of the second region 102. At this time, in the actual preparation process, the second doping structure 120 can be obtained by doping the surface of the second region 102.
[0082] Refer to Figure 1As shown, in some examples of this embodiment, the solar cell may further include a back passivation layer 150, and the back passivation layer 150 may cover at least a part of the back surface of the substrate 100. For example, the back passivation layer 150 may cover the first region 101, the second region 102, and the third region 103.
[0083] In some examples of this embodiment, the back passivation layer 150 may include a stacked structure formed of multiple materials.
[0084] In some examples of this embodiment, the material of the back passivation layer 150 may be a material having a passivation effect on the substrate 100. For example, the material of the back passivation layer 150 may include one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, amorphous silicon, and transparent conductive metal oxide.
[0085] Refer to Figure 1 As shown, in some examples of this embodiment, the back passivation layer 150 may cover the first doping structure 110 and the second doping structure 120. Further, the first electrode 130 may pass through the back passivation layer 150 and directly contact the first doping structure 110, and the second electrode 140 may pass through the back passivation layer 150 and directly contact the second doping structure 120.
[0086] Refer to Figure 1 As shown, in some examples of this embodiment, the material of the first electrode 130 may include a metal. For example, the material of the first electrode 130 may include aluminum. Further, the material of the first electrode 130 may also include other elements of the third main group such as boron.
[0087] Refer to Figure 1 As shown, in some examples of this embodiment, the material of the second electrode 140 may also include a metal. Further, the material of the second electrode 140 may include one or more of silver, copper, aluminum, and nickel. In this embodiment, the material of the second electrode 140 may be conductive silver paste.
[0088] Refer to Figure 1 As shown, in some examples of this embodiment, the solar cell may further include a front passivation layer 160, and the front passivation layer 160 may cover at least a part of the front surface of the substrate 100. Further, the front passivation layer 160 may cover the entire front surface of the substrate 100.
[0089] In some examples of this embodiment, the front passivation layer 160 may include a stacked structure formed of multiple materials.
[0090] In some examples of this embodiment, the material of the front passivation layer 160 can be a material that passivates the substrate 100. For example, the material of the front passivation layer 160 can include one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, amorphous silicon, and transparent conductive metal oxides.
[0091] Referring to Figure 1 As shown, in some examples of this embodiment, the front surface of the substrate 100 of the solar cell may further have a front surface texture structure. The front surface texture structure can reduce the front surface reflectivity of the solar cell and improve the conversion efficiency. Further, the front surface reflectivity of the substrate 100 of the solar cell can be the same as the surface reflectivity of the third region 103.
[0092] In addition, the back surface of the P-type solar cell in the traditional technology usually adopts a full polishing design, which results in low light utilization rate on the back surface of the solar cell. However, the solar cell provided by the present disclosure has a differential texture structure on the back surface, which can effectively improve the back surface efficiency of the solar cell and further significantly improve the overall efficiency of the solar cell.
[0093] Further, the present disclosure also provides a method for manufacturing a solar cell as Figure 1 shown, which includes the following steps S1 to S5.
[0094] Step S1, providing a substrate.
[0095] Figure 3 FIG. is a schematic structural diagram of a substrate 100. In some examples of this embodiment, the material of the substrate 100 can include a semiconductor material. Further, the material of the substrate 100 can include a silicon material, and the silicon material can be monocrystalline silicon.
[0096] In some examples of this embodiment, it may further include the steps of polishing and cleaning the substrate 100. Among them, an alkaline solution can be used for polishing. It can be understood that by polishing and cleaning the substrate 100, a flat surface can be formed on the front and / or back surfaces of the substrate 100. After polishing and cleaning, flat surfaces can be formed on the first region 101, the second region 102, and the third region 103 on the back surface.
[0097] Step S2, forming a second doping structure and a mask layer on the second region of the substrate.
[0098] Figure 4 For Figure 3 FIG. is a schematic structural diagram of forming a second doping structure 120 and a mask layer 210 on the basis of the structure shown. Referring to Figure 4As shown, in some examples of this embodiment, the second doping structure 120 may include a dielectric layer 121 and a doped polycrystalline layer 122 arranged in a stacked manner. The dielectric layer 121 and the doped polycrystalline layer 122 are sequentially stacked on the substrate 100, and the second doping structure 120 may be fabricated on a preset second region 102. The mask layer 210 may be disposed on the doped polycrystalline layer 122 to cover the doped polycrystalline layer 122.
[0099] Further, referring to Figure 4 As shown, in some examples of this embodiment, the second doping structure 120 and the mask layer 210 may also cover the first region 101 and the third region 103 together.
[0100] In some examples of this embodiment, the step of fabricating the dielectric layer 121 may include: depositing the material of the dielectric layer 121 on the surface of the substrate 100 to form the dielectric layer 121. Among them, the method of depositing the material of the dielectric layer 121 on the surface of the substrate 100 may be chemical vapor deposition, such as low-pressure chemical vapor deposition or plasma-enhanced chemical vapor deposition.
[0101] In some other examples, the step of fabricating the dielectric layer 121 may also include: oxidizing the substrate 100 to form the dielectric layer 121 covering the substrate 100.
[0102] In some examples of this embodiment, the step of fabricating the doped polycrystalline layer 122 may include: depositing a doped polycrystalline material on the surface of the substrate 100 and performing an annealing treatment to form the doped polycrystalline layer 122, or depositing an intrinsic polycrystalline material on the surface of the substrate 100 and then doping the intrinsic polycrystalline material to form the doped polycrystalline layer 122. Among them, the method of depositing the doped polycrystalline material or the intrinsic polycrystalline material may be chemical vapor deposition, such as low-pressure chemical vapor deposition or plasma-enhanced chemical vapor deposition.
[0103] In some examples of this embodiment, the step of fabricating the mask layer 210 may include: depositing a mask material on the surface of the substrate 100 to form the mask layer 210. Further, the method of depositing the mask material may be chemical vapor deposition. The mask layer 210 is used to protect the second doping structure 120 covered by the mask layer 210 in subsequent etching processes.
[0104] Further, in the step of depositing an intrinsic polycrystalline material on the surface of the substrate 100 and then doping the intrinsic polycrystalline material, an oxidation material may be formed on the doped polycrystalline layer 122, and this oxidation material may also be used as the material of the mask layer 210, thus eliminating the need for additional deposition of the mask material.
[0105] Step S3, perform differential laser treatment on the first region and the third region.
[0106] Among them, the differential laser treatment refers to different treatment conditions when performing laser treatment on the first region 101 and the third region 103, so that there are differences in the surfaces of the first region 101 and the third region 103. By performing differential laser treatment on the first region 101 and the third region 103, it is possible to form different first textured structures 1010 and second textured structures 1030 on the first region 101 and the third region 103 respectively in the subsequent texturing process.
[0107] Further, in some examples of this embodiment, the steps of performing differential laser treatment on the first region 101 and the third region 103 include: performing laser treatment on the first region 101 with a first laser and performing laser treatment on the third region 103 with a second laser, and the average power of the first laser is lower than that of the second laser. By setting the average power of the first laser to be lower, it is possible to make the etching amount of the first region 101 relatively smaller than that of the third region 103 in the same time, so that the first region 101 and the third region 103 form a differential surface structure.
[0108] In some examples of this embodiment, the pulse time of the first laser can be shorter than that of the second laser. For example, the first laser can be a picosecond or femtosecond laser, and the second laser can be a nanosecond laser. This can make the second laser have a higher average power.
[0109] In some examples of this embodiment, the pulse time of the first laser can be the same as that of the second laser, wherein the frequency of the second laser is lower than that of the first laser, and / or the energy of the second laser is higher than that of the first laser, and / or the overlap rate of the second laser is higher than that of the first laser.
[0110] In some examples of this embodiment, in the steps of performing differential laser treatment, the mask layer 210 located on the first region 101 and the third region 103 can be removed, and the removal amount of the first doping structure 110 located on the first region 101 is less than the removal amount of the first doping structure 110 located on the third region 103.
[0111] Step S4, perform texturing treatment on the substrate.
[0112] Figure 5 For Figure 4 a schematic diagram of the structure after differential laser treatment and texturing treatment on the basis of the shown structure. Referring to Figure 5 as shown, after texturing treatment, the surface of the first region 101 has a first textured structure 1010, and the surface of the third region 103 has a second textured structure 1030.
[0113] In some examples of this embodiment, a texturing agent can be used to texture the substrate 100. Among them, the mask layer 210 is used to block the texturing agent. Since the second region 102 is shielded by the mask layer 210, a textured surface structure will not be formed on the surface of the second region 102. The first region 101 and the third region 103 form different surfaces in the step of differential laser treatment. Therefore, the first region 101 and the third region 103 can have different removal amounts during the texturing process, so as to form the first textured surface structure 1010 and the second textured surface structure 1030 respectively.
[0114] In some examples of this embodiment, in the step of texturing treatment, a front textured surface structure can also be formed on the front surface of the substrate 100.
[0115] Step S5, prepare the first electrode and the second electrode and form the first doping structure.
[0116] In some examples of this embodiment, before preparing the first electrode 130 and the second electrode 140, it further includes the step of preparing a back passivation layer 150 on the back surface of the substrate 100. The back passivation layer 150 can cover at least part of the back surface of the substrate 100. For example, the back passivation layer 150 can cover the first region 101, the second region 102, and the third region 103.
[0117] In some examples of this embodiment, the back passivation layer 150 can include a stacked structure formed by multiple materials. The method of preparing the back passivation layer 150 can be chemical vapor deposition.
[0118] In some examples of this embodiment, the material of the back passivation layer 150 can be a material that has a passivation effect on the substrate 100. For example, the material of the back passivation layer 150 can include one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, amorphous silicon, and transparent conductive metal oxide.
[0119] In some examples of this embodiment, before preparing the first electrode 130 and the second electrode 140, it further includes the step of preparing a front passivation layer 160 on the front surface of the substrate 100. The front passivation layer 160 can cover at least part of the front surface of the substrate 100. Further, the front passivation layer 160 can cover the entire front surface of the substrate 100.
[0120] In some examples of this embodiment, the front passivation layer 160 can include a stacked structure formed by multiple materials. The method of preparing the front passivation layer 160 can be chemical vapor deposition.
[0121] In some examples of this embodiment, the material of the front passivation layer 160 can be a material that passivates the substrate 100. For example, the material of the front passivation layer 160 can include one or more of silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, silicon carbide, amorphous silicon, and transparent conductive metal oxides.
[0122] In some examples of this embodiment, the back passivation layer 150 and the front passivation layer 160 can be prepared separately. For example, the back passivation layer 150 can include an aluminum oxide layer and a silicon nitride layer laminated on the substrate 100 in sequence. Among them, the thickness of the aluminum oxide layer can be 10 nm to 30 nm, and the thickness of the silicon nitride layer can be 70 nm to 110 nm. The back passivation layer 150 can also have an antireflection effect. The front passivation layer 160 can include an aluminum oxide layer and a silicon nitride layer laminated on the substrate 100 in sequence. Among them, the thickness of the aluminum oxide layer can be 5 nm to 10 nm, and the thickness of the silicon nitride layer can be 65 nm to 85 nm. The front passivation layer 160 can also have an antireflection effect.
[0123] In some examples of this embodiment, the back passivation layer 150 and the front passivation layer 160 can be prepared simultaneously. For example, both the back passivation layer 150 and the front passivation layer 160 can include an aluminum oxide layer and a silicon nitride layer laminated on the substrate 100 in sequence. Among them, the thickness of the aluminum oxide layer can be 3 nm to 6 nm, and the thickness of the silicon nitride layer can be 65 nm to 85 nm.
[0124] It can be understood that before preparing the first electrode 130 and the second electrode 140, an opening process can be performed on the corresponding regions of the back passivation layer 150 first, so that the first electrode 130 and the second electrode 140 can pass through the back passivation layer 150 and be electrically connected to the corresponding doping structures.
[0125] In some examples of this embodiment, the steps of preparing the first electrode 130 can include: preparing the first electrode 130 paste on the first region 101, and performing a heat treatment on the first electrode 130 paste so that the elements in the first electrode 130 paste diffuse into the substrate 100 to form the first electrode 130 and the first doping structure 110 located in the substrate 100. Further, the first electrode 130 paste can be a conductive aluminum paste, and the heat treatment temperature can be 600 °C to 800 °C.
[0126] In some examples of this embodiment, the steps of preparing the second electrode 140 can include: preparing the second electrode 140 paste on the second region 102, and performing a sintering treatment on the second electrode 140 paste to form the second electrode 140.
[0127] After the above steps S1 to step S5, a solar cell as shown in Figure 1 can be prepared.
[0128] In the conventional technology, limited by the actual preparation process, the surface textures formed on the substrate are often the same, which makes the surface textures in different regions have the same surface area and it is difficult to prepare different surface textures on the same substrate.
[0129] In the preparation method of the present disclosure, by forming a mask layer and adopting a differential laser treatment method, not only can different first surface texture structures and second surface texture structures be formed to improve the efficiency of the solar cell, but also this preparation process is particularly suitable for a P-type substrate, which only needs to use a mask once to complete the preparation of the solar cell, effectively simplifying the preparation process of the cell. In addition, this preparation process can also use metallic aluminum as the first electrode. Compared with the conventional technology in which both electrodes use silver materials, this preparation process can also significantly reduce the production cost of the solar cell.
[0130] Furthermore, the present disclosure also provides the following specific examples and comparative examples. Through the specific descriptions of the following examples and comparative examples, the advantages of the present disclosure will also be obvious.
[0131] Example 1
[0132] Provide a P-type monocrystalline silicon wafer as the substrate, and perform polishing treatment and cleaning treatment on it;
[0133] Deposit a layer of silicon oxide layer as the dielectric layer on the substrate by low-pressure chemical vapor deposition method, then deposit a layer of intrinsic polysilicon layer and perform phosphorus diffusion treatment to form a doped polysilicon layer and a phosphosilicate glass layer on the doped polysilicon layer, and use this phosphosilicate glass layer as the mask layer;
[0134] Use picosecond laser to perform laser treatment on the first region, and use nanosecond laser to perform laser treatment on the third region, remove the mask layer and etch the doped polysilicon layer and the dielectric layer;
[0135] Perform texturing treatment on the substrate so that a front surface texture structure is formed on the front surface of the substrate, a first surface texture structure is formed on the first region of the back surface, and a second surface texture structure is formed on the third region of the back surface;
[0136] Deposit an aluminum oxide layer with a thickness of 5 nm and a silicon nitride layer with a thickness of 70 nm on the front and back surfaces of the substrate respectively as the front surface passivation layer and the back surface passivation layer;
[0137] Use laser to perform opening treatment on the back surface passivation layer to expose the first region and the second region, screen-print conductive aluminum paste on the first region, screen-print conductive silver paste on the second region, and then perform sintering treatment.
[0138] Comparative Example 1
[0139] Provide a P-type monocrystalline silicon wafer as a substrate, and perform polishing treatment and cleaning treatment on it;
[0140] Deposit a layer of silicon oxide layer on the substrate as a dielectric layer by low-pressure chemical vapor deposition method, then deposit a layer of intrinsic polysilicon layer and perform phosphorus diffusion treatment to form a doped polysilicon layer and a phosphosilicate glass layer on the doped polysilicon layer, remove the phosphosilicate glass layer, and prepare a photosensitive resin layer covering the second region as a mask, with the first region and the third region exposed from the photosensitive resin;
[0141] Remove the doped polysilicon layer and the dielectric layer on the first region and the third region, and perform texturing treatment on the front side of the substrate so that a front surface texture structure is formed on the front side of the substrate, and perform polishing treatment on the back side of the substrate;
[0142] Deposit an aluminum oxide layer with a thickness of 5 nm and a silicon nitride layer with a thickness of 70 nm on the front and back sides of the substrate in sequence as the front passivation layer and the back passivation layer respectively;
[0143] Use a laser to perform opening treatment on the back passivation layer to expose the first region and the second region, screen-print conductive aluminum paste on the first region, screen-print conductive silver paste on the second region, and then perform sintering treatment.
[0144] Comparative Example 2
[0145] Provide a P-type monocrystalline silicon wafer as a substrate, and perform polishing treatment and cleaning treatment on it;
[0146] Deposit a layer of silicon oxide layer on the substrate as a dielectric layer by low-pressure chemical vapor deposition method, then deposit a layer of intrinsic polysilicon layer and perform phosphorus diffusion treatment to form a doped polysilicon layer and a phosphosilicate glass layer on the doped polysilicon layer, and use the phosphosilicate glass layer as a mask layer;
[0147] Use picosecond laser with the same process parameters to perform laser treatment on the first region and the third region, remove the mask layer and etch the doped polysilicon layer and the dielectric layer;
[0148] Perform texturing treatment on the substrate so that a front surface texture structure is formed on the front side of the substrate, and the same back surface texture structure is formed on the first region and the third region on the back side;
[0149] Deposit an aluminum oxide layer with a thickness of 5 nm and a silicon nitride layer with a thickness of 70 nm on the front and back sides of the substrate in sequence as the front passivation layer and the back passivation layer respectively;
[0150] Use a laser to perform opening treatment on the back passivation layer to expose the first region and the second region, screen-print conductive aluminum paste on the first region, screen-print conductive silver paste on the second region, and then perform sintering treatment.
[0151] Experiment 1: The back surface of the substrate after texturing treatment in Example 1 was observed using a scanning electron microscope. The surface topography map of the first region can be seen in Figure 6 , and the surface topography map of the third region can be seen in Figure 7 .
[0152] Experiment 2: The front efficiency, back efficiency, bifaciality, overall cell efficiency, and open-circuit voltage of the solar cells prepared as in Example 1, Comparative Example 1, and Comparative Example 2 were measured. The results can be seen in Table 1, where the bifaciality is the ratio of the back efficiency to the front efficiency.
[0153] Table 1
[0154]
[0155] Referring to Figure 6 and Figure 7 shown, in Example 1, the first region has a first textured surface structure on its surface, and the third region has a second textured surface structure. The first textured surface structure includes a plurality of first protrusions, and the second textured surface structure includes a plurality of second protrusions. The distribution density of the first protrusions in the first textured surface structure on the first region is significantly smaller, and the sum of the bottom areas of the first protrusions is also smaller. Additionally, the height of the first protrusions is relatively smaller. The second textured surface structure is similar to the commonly used pyramid texture, while the first textured surface structure is a "micro-texture structure", such that the surface area per unit bottom area of the first textured surface structure is smaller than the specific surface area per unit bottom area of the second textured surface structure.
[0156] Compared with Example 1, in Comparative Example 1, the first region and the third region were polished instead of textured, that is, no textured surface structure was formed on the first region and the third region. Referring to Table 1, the back efficiency of Comparative Example 1 is significantly lower than that of Example 1, mainly because the back surface of the cell in Comparative Example 1 does not have a textured surface structure and has poor light absorption ability, which also results in a significantly lower overall efficiency of Comparative Example 1. Compared with Example 1, in Comparative Example 2, the same textured surface structure was formed on the first region and the third region. Although this makes the back surface have a stronger light absorption ability, there are relatively serious carrier recombination problems, resulting in significantly lower open-circuit voltage and front efficiency, and thus a significantly lower overall efficiency of Comparative Example 2. The solar cell of Example 1 can significantly improve the carrier recombination problem while taking into account the back light absorption ability by setting different first and second textured surface structures, thereby enabling the solar cell to have a significantly higher overall efficiency.
[0157] Please note that the above examples are for illustrative purposes only and do not imply any limitation to the present disclosure.
[0158] It should be understood that, unless otherwise clearly stated herein, there is no strict order restriction for the execution of steps, and these steps can be executed in other orders. Moreover, at least a part of the steps in the preparation process may include multiple sub-steps or multiple stages. These sub-steps or stages do not necessarily need to be completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or sub-steps or stages of other steps.
[0159] Each embodiment in this specification is described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the embodiments, reference can be made to each other.
[0160] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.
Claims
1. A solar cell, characterized in that, include: A P-type substrate, a first doping structure, a first electrode, a second doping structure, and a second electrode; The back surface of the substrate has a first area, a second area and a third area, and the third area is arranged between the first area and the second area; The first doping structure is disposed on the first region, the first electrode is in contact with the first doping structure, the second doping structure is disposed on the second region, the second electrode is electrically connected to the second doping structure, and the first doping structure and the second doping structure have different doping types; The surface of the first region has a first velvet structure, and the surface of the third region has a second velvet structure. The surface area per unit bottom area of the first velvet structure is smaller than the specific surface area per unit bottom area of the second velvet structure.
2. The solar cell according to claim 1, characterized in that The first velvet structure includes a plurality of first protrusions, the second velvet structure includes a plurality of second protrusions, and the first velvet structure and the second velvet structure satisfy at least one of conditions a to c: a: the distribution density of the first protrusions on the first area is less than the distribution density of the second protrusions on the third area; b: the sum of the bottom areas of all the first protrusions is smaller than the sum of the bottom areas of all the second protrusions; c: The height of the first protrusion is smaller than the height of the second protrusion.
3. The solar cell according to claim 2, characterized in that The height of the first protrusion is ≤1 μm; and / or, The height of the second protrusion is 1 μm to 4.5 μm; and / or, The distribution density of the first protrusions in the first area is less than 10%; and / or, The distribution density of the second protrusions in the third area is greater than 90%.
4. The solar cell according to any one of claims 1 to 3, characterized in that, The surface of the first region is arranged to protrude from the surface of the third region, and the surface of the second region is arranged to protrude from the surface of the first region; Optionally, the height difference between the second region and the first region is less than 1 μm; Optionally, a height difference between the second region and the third region is greater than 1 μm.
5. The solar cell according to claim 4, characterized in that, The width of the first region is 250 μm to 350 μm; and / or, The width of the second region is 500 μm to 650 μm; and / or, The width of the third region is 200 μm to 300 μm.
6. The solar cell according to claim 5, wherein With respect to the total area of the first region, the second region, and the third region, the area of the first region accounts for more than 15%.
7. The solar cell according to any one of claims 1 to 3 and 5 to 6, characterized in that The first doping structure is disposed in the substrate and exposed from the surface of the first region, and the doping elements in the first doping structure include elements of the first electrode; and / or, The second doping structure includes a dielectric layer and a doped polycrystalline layer which are stacked together. The dielectric layer and the doped polycrystalline layer are stacked together in sequence on the substrate.
8. A method for preparing a solar cell according to any one of claims 1 to 7, characterized in that, The steps include: providing a substrate; forming the second doping structure and a mask layer covering the second doping structure on the second region of the substrate; Differentially laser process the first region and the third region, and texture the substrate so that a first textured surface structure is formed on the surface of the first region and a second textured surface structure is formed on the surface of the third region; and, Fabricate the first electrode and the second electrode and form the first doping structure.
9. The preparation method according to claim 8, characterized in that, The step of differentially laser processing the first region and the third region includes: laser processing the first region with a first laser and laser processing the third region with a second laser, wherein the average power of the first laser is lower than that of the second laser.
10. The preparation method according to claim 8 or 9, characterized in that, Before forming the second doping structure, a step of polishing the substrate is further included; and / or The step of fabricating the first electrode and the second electrode and forming the first doping structure includes: preparing a first electrode paste on the first region and performing heat treatment on the first electrode paste so that the elements in the first electrode paste diffuse into the substrate to form the first electrode and the first doping structure located in the substrate.