Solar cell, preparation method thereof and photovoltaic module
By forming a borosilicate glass layer and a phosphorus silicon glass layer on the polysilicon layer, and using laser action to diffuse boron and phosphorus doped atoms into the polysilicon layer to form the first and second polar regions, the problems of multiple high-temperature steps in the preparation of TBC cells are solved, and the effects of cost reduction, process time reduction and efficiency improvement are achieved.
Patent Information
- Application Number
- CN202510124418.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-26
- Publication Date
- 2025-04-29
AI Technical Summary
When preparing the P-type polar region and N-type polar region of TBC batteries, multiple high-temperature steps are required, resulting in complex and expensive equipment, complex process flow and long time.
By forming a borosilicate glass layer and a phosphorus silicon glass layer on the polysilicon layer, and using laser action to diffuse boron and phosphorus doped atoms into the polysilicon layer, the first and second polar regions are formed, and the first and second electrodes are formed, respectively, to reduce the high temperature step.
This method reduces high-temperature steps, reduces costs, shortens process time, improves preparation efficiency, and simplifies battery process flow.
Smart Images
Figure CN119907341A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of photovoltaic technology, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art
[0002] TBC (TOPCon-BC, back-junction back-contact high-efficiency cell) technology combines the efficient TOPCon (Tunnel Oxide Passivated Contact solar cell) technology with the back-junction / back-contact technology. It utilizes the excellent passivation contact structure of TOPCon cell technology, but sets all electrodes on the back of the cell to avoid light energy loss caused by grid line shading on the front side, maximizes the use of incident photons, and helps improve cell conversion efficiency.
[0003] However, when preparing the P-type polar region and the N-type polar region of the TBC battery, multiple high-temperature steps are usually required, the equipment required is complicated and expensive, and the process flow is complicated and the process time is long. Summary of the invention
[0004] The embodiments of the present application provide a solar cell and a method for preparing the same, and a photovoltaic module, which can reduce high-temperature steps, lower costs, shorten process time, and improve preparation efficiency.
[0005] The first aspect of the present application provides a method for preparing a solar cell, comprising:
[0006] Providing a substrate, a tunneling layer and a polysilicon layer are formed on the back side of the substrate, the polysilicon layer is located on a side of the tunneling layer away from the substrate, and the polysilicon layer includes alternating first and second regions;
[0007] forming a borosilicate glass layer on the polysilicon layer, applying a laser to a portion of the borosilicate glass layer located in the first region so that boron in the borosilicate glass layer diffuses into the first region of the polysilicon layer to form a first polarity region, and removing the remaining borosilicate glass layer on the polysilicon layer;
[0008] forming a phosphosilicate glass layer on the polysilicon layer, applying a laser to a portion of the phosphosilicate glass layer located in the second region so that phosphorus in the phosphosilicate glass layer diffuses into the second region of the polysilicon layer to form a second polarity region, and removing the remaining phosphosilicate glass layer on the polysilicon layer;
[0009] A first electrode is formed in the first polarity region, and a second electrode is formed in the second polarity region.
[0010] In one embodiment, the laser acts on the portion of the borosilicate glass layer located in the first region, so that the boron in the borosilicate glass layer diffuses into the first region of the polysilicon layer to form a first polarity region, including:
[0011] The laser acts on the portion of the borosilicate glass layer located in the first region, so that the surface of the polysilicon layer located in the first region away from the substrate is liquefied, so that the portion of the borosilicate glass layer covering the first region is melted from a preset interface toward a direction away from the substrate, and the preset interface is an interface between the borosilicate glass layer and the polysilicon layer;
[0012] During the liquefaction of the polysilicon layer and the melting of the borosilicate glass layer, boron in the borosilicate glass layer diffuses into the polysilicon layer, so that the first region forms a first polarity region.
[0013] In one embodiment, the polysilicon layer is liquefied and the borosilicate glass layer is melted, so that the borosilicate glass layer is ablated to remove the portion of the borosilicate glass layer located in the first region.
[0014] In one embodiment, the laser acts on the portion of the phosphosilicate glass layer located in the second region, so that phosphorus in the phosphosilicate glass layer diffuses into the second region of the polysilicon layer to form a second polarity region, including:
[0015] The laser acts on the portion of the phosphosilicate glass layer located in the second region, so that the surface of the polysilicon layer located in the second region away from the substrate is liquefied, so that the portion of the phosphosilicate glass layer covering the second region is melted from a preset interface toward a direction away from the substrate, and the preset interface is an interface between the phosphosilicate glass layer and the polysilicon layer;
[0016] During the liquefaction of the polysilicon layer and the melting of the phosphosilicate glass layer, phosphorus in the phosphosilicate glass layer diffuses into the polysilicon layer, so that the second region forms a second polarity region.
[0017] In one embodiment, the polysilicon layer is liquefied and the borosilicate glass layer is melted, so that the borosilicate glass layer is ablated to remove the portion of the borosilicate glass layer located in the first region.
[0018] In one embodiment, removing the remaining borosilicate glass layer on the polysilicon layer comprises:
[0019] removing the area of the borosilicate glass layer not affected by the laser by a wet chemical method; and / or
[0020] The step of removing the remaining phosphosilicate glass layer on the polysilicon layer comprises:
[0021] The areas of the phosphosilicate glass layer not acted upon by the laser are removed by a wet chemical method.
[0022] In one embodiment, the method for preparing a solar cell further comprises:
[0023] After forming the first polarity region, removing laser damage in the area acted upon by the laser using a wet chemical method; and / or
[0024] After the second polarity region is formed, laser damage on the area acted upon by the laser is removed by a wet chemical method.
[0025] In one embodiment, the first region and the second region are spaced apart.
[0026] In one embodiment, the first region and the second region are adjacent to each other; before the step of forming the first electrode and the second electrode, the method for preparing a solar cell further includes:
[0027] Using a laser process to remove a portion of the boundary between the first polarity region and the second polarity region, so as to at least expose the polarity region corresponding to the boundary inside the polysilicon layer;
[0028] The active area of the laser process is removed by wet chemical method to expose the substrate corresponding to the interface position.
[0029] In one embodiment, the method for preparing a solar cell further comprises:
[0030] forming a back passivation layer on the polysilicon layer forming the first polarity region and the second polarity region;
[0031] The first electrode and the second electrode penetrate the back passivation layer to the polysilicon layer.
[0032] In one embodiment, the method for preparing a solar cell further comprises:
[0033] A front passivation layer is formed on the front side of the substrate.
[0034] A second aspect of the present application provides a solar cell, which is prepared by the method for preparing a solar cell as described above.
[0035] A third aspect of the present application provides a photovoltaic assembly, comprising a battery string, wherein the battery string is formed by connecting a plurality of solar cells as described above.
[0036] The above-mentioned solar cell and its preparation method, photovoltaic module, wherein the preparation method includes providing a substrate, forming a tunneling layer and a polysilicon layer on the back of the substrate, the polysilicon layer including an alternating first region and a second region; forming a borosilicate glass layer on the polysilicon layer, and applying a laser to the portion of the borosilicate glass layer located in the first region, so that the boron in the borosilicate glass layer diffuses into the polysilicon layer, so that the first region forms a first polarity region; forming a phosphosilicate glass layer on the polysilicon layer, and applying a laser to the portion of the phosphosilicate glass layer located in the second region, so that the phosphorus in the phosphosilicate glass layer diffuses into the polysilicon layer, so that the second region forms a second polarity region; removing the remaining borosilicate glass layer and the phosphosilicate glass layer on the polysilicon layer respectively; forming a first electrode in the first polarity region, and forming a second electrode in the second polarity region. Compared with the related art, the preparation process can reduce the high temperature step, thereby reducing the required equipment, reducing the cost, and shortening the process time, which is helpful to improve the production capacity of solar cells and photovoltaic modules; in addition, the preparation process has simple steps, which can simplify the battery process flow and improve the preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0038] Figure 1 One of the flow charts of a method for preparing a solar cell according to an embodiment;
[0039] Figure 2 One of the structural block diagrams of a solar cell according to an embodiment;
[0040] Figure 3 The second structural block diagram of a solar cell according to an embodiment;
[0041] Figure 4 The third structural block diagram of a solar cell according to an embodiment;
[0042] Figure 5 This is a fourth structural block diagram of a solar cell according to an embodiment;
[0043] Figure 6 This is a fifth structural block diagram of a solar cell according to an embodiment;
[0044] Figure 7 This is a sixth structural block diagram of a solar cell according to an embodiment;
[0045] Figure 8 The second flowchart of the method for preparing a solar cell according to an embodiment;
[0046] Fig. 9 The seventh structural block diagram of a solar cell according to an embodiment;
[0047] Fig.10 The eighth structural block diagram of a solar cell according to an embodiment;
[0048] Fig.11 A ninth structural block diagram of a solar cell according to an embodiment;
[0049] Fig.12 This is a tenth structural block diagram of a solar cell according to an embodiment;
[0050] Fig.13 The eleventh structural block diagram of a solar cell according to an embodiment;
[0051] Fig.14 The twelfth structural block diagram of a solar cell according to an embodiment;
[0052] Fig.15 This is the thirteenth structural block diagram of a solar cell according to an embodiment.
[0053] Reference numerals:
[0054] Substrate: 110; tunneling layer: 120; polysilicon layer: 130; borosilicate glass layer: 140;
[0055] Phosphorus silicon glass layer: 150; first electrode: 160; second electrode: 170; back passivation layer: 180;
[0056] Front passivation layer: 190; first electrode region: P region; second electrode region: N region. DETAILED DESCRIPTION
[0057] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0058] It is understood that the terms "first", "second", etc. used in this application can be used to describe various elements in this article, but these elements are not limited by these terms. These terms are only used to distinguish the first element from another element, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. It should be noted that when an element is referred to as "arranged on" another element, it can be directly on another element or there can also be a centered element. When an element is considered to be "connected" to another element, it can be directly connected to another element or there may be a centered element at the same time.
[0059] Figure 1 This is a flow chart of a method for preparing a solar cell provided in an embodiment of the present application. Figure 1 , a method for preparing a solar cell includes: steps 102 to 108.
[0060] Step 102 , providing a substrate, a tunnel layer and a polysilicon layer are formed on the back side of the substrate, the polysilicon layer is located on a side of the tunnel layer away from the substrate, and the polysilicon layer includes alternating first regions and second regions.
[0061] Please refer to Figure 2 The substrate 110 is used to receive incident light and generate photogenerated carriers, and has a front side and a back side opposite to each other. The front side can be understood as the surface facing the sunlight, also called the light-receiving side; the back side can be understood as the surface facing away from the sunlight, also called the backlight side. The substrate 110 includes but is not limited to a doped semiconductor substrate 110 made of silicon or germanium, or a doped compound semiconductor substrate 110 made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, or gallium oxide. The doping element type of the substrate 110 can be N-type, and the N-type element can be, for example, any one of phosphorus, arsenic, or antimony; the doping element type of the substrate 110 can also be P-type, and the P-type element can be, for example, boron and gallium.
[0062] The tunneling layer 120 is located on the back side of the substrate 110. The tunneling layer 120 can be combined with the dangling bonds on the back side of the substrate 110 to reduce the defects on the back side of the substrate 110 and improve the photoelectric conversion efficiency of the solar cell. The material of the tunneling layer 120 can be a dielectric material, for example, at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. The polysilicon layer 130 is located on the side of the tunneling layer 120 away from the substrate. The polysilicon layer 130 includes alternating first and second regions. The first region is used to form a first polarity region after diffusing boron doping atoms in a subsequent step, and the second region is used to form a second polarity region after diffusing phosphorus doping atoms in a subsequent step.
[0063] Step 104, forming a borosilicate glass layer on the polysilicon layer, applying laser to a portion of the borosilicate glass layer located in the first region, so that boron in the borosilicate glass layer diffuses into the first region of the polysilicon layer to form a first polarity region, and removing the remaining borosilicate glass layer on the polysilicon layer.
[0064] Please refer to Figure 3 The borosilicate glass layer 140 is located on a side of the polysilicon layer 130 away from the substrate 110 and covers at least a first region ( Figure 3 Take the complete coverage of the polysilicon layer 130 as an example). The borosilicate glass layer 140 is rich in boron-doped atoms. When the laser acts on the portion of the borosilicate glass layer 140 located in the first region, the laser energy not only acts on the borosilicate glass layer 140, but also acts on the polysilicon layer 130 because the borosilicate glass layer 140 almost transmits light, and the laser energy can be absorbed by the polysilicon layer 130. Therefore, by utilizing the difference in light absorption of different materials of the borosilicate glass layer 140 and the polysilicon layer 130, the laser acts on the back of the cell, so that the polysilicon layer 130 absorbs the laser energy, and then indirectly heats the borosilicate glass layer 140, so that the boron-doped atoms are heated and diffused into the polysilicon layer 130, forming a first polarity region (P region). The first polarity region can be understood as the projection coverage area of the first electrode on the polysilicon layer 130, which is the main region for establishing and maintaining the flow of current in the solar cell structure.
[0065] Please refer to Figure 4After forming the first polarity region, the borosilicate glass layer 140 remaining after the diffusion of the boron-doped atoms on the polysilicon layer 130 can be removed. Optionally, the remaining borosilicate glass layer 140 may include the borosilicate glass layer 140 that may exist on the first region after the polysilicon layer 130 absorbs energy after the laser action, and may also include the borosilicate glass layer 140 that is not acted on by the laser and is located on the second region. It can be understood that in other embodiments, when the borosilicate glass layer 140 only covers the first region, and after the laser action, no borosilicate glass layer 140 remains on the first region, the step of removing the remaining borosilicate glass layer 140 on the polysilicon layer 130 can be omitted.
[0066] Therefore, through the action of laser, the boron-doped atoms in the borosilicate glass layer 140 can be diffused into the polysilicon layer 130, thereby reducing the high-temperature steps in the boron diffusion process and the required equipment.
[0067] Step 106, forming a phosphosilicate glass layer on the polysilicon layer, applying laser to the portion of the phosphosilicate glass layer located in the second region, so that phosphorus in the phosphosilicate glass layer diffuses into the second region of the polysilicon layer to form a second polarity region, and removing the remaining phosphosilicate glass layer on the polysilicon layer.
[0068] Please refer to Figure 5 The phosphosilicate glass layer 150 is located on a side of the polysilicon layer 130 away from the substrate 110 and covers at least the second region ( Figure 5 Take the complete coverage of the polysilicon layer 130 as an example). The phosphosilicate glass layer 150 is rich in phosphorus-doped atoms. When the laser acts on the portion of the phosphosilicate glass layer 150 located in the second region, the laser energy not only acts on the phosphosilicate glass layer 150, but also acts on the polysilicon layer 130 because the phosphosilicate glass layer 150 almost transmits light, and the laser energy can be absorbed by the polysilicon layer 130. Therefore, by utilizing the difference in light absorption of different materials of the phosphosilicate glass layer 150 and the polysilicon layer 130, the laser acts on the back of the cell, so that the polysilicon layer 130 absorbs the laser energy, and then indirectly heats the phosphosilicate glass layer 150, so that the phosphorus-doped atoms are heated and diffused into the polysilicon layer 130, forming a second polarity region (N region). The second polarity region can be understood as the projection coverage area of the second electrode on the polysilicon layer 130, which is the main region for establishing and maintaining the flow of current in the solar cell structure.
[0069] Please refer to Figure 6After forming the second polarity region, the phosphosilicate glass layer 150 remaining after the diffusion of phosphorus-doped atoms on the polysilicon layer 130 can be removed. Optionally, the remaining phosphosilicate glass layer 150 may include the phosphosilicate glass layer 150 that may exist on the second region after the polysilicon layer 130 absorbs energy after the laser action, and may also include the phosphosilicate glass layer 150 that is not laser-actuated and is located on the first region. It can be understood that in other embodiments, when the phosphosilicate glass layer 150 only covers the second region, and after the laser action, no phosphosilicate glass layer 150 remains on the second region, the step of removing the remaining phosphosilicate glass layer 150 on the polysilicon layer 130 can be omitted.
[0070] Therefore, through the action of laser, the boron-doped atoms in the phosphosilicate glass layer 150 can be diffused into the polysilicon layer 130, thereby reducing the high-temperature steps in the phosphorus diffusion process and the required equipment.
[0071] It can be understood that step 106 can be performed before step 104 or after step 104, and the present application does not limit this.
[0072] Step 108 , forming a first electrode in the first polarity region, and forming a second electrode in the second polarity region.
[0073] Please refer to Figure 7 , the first electrode 160 and the second electrode 170 are formed in the first polarity region and the second polarity region respectively. The first electrode 160 and the second electrode 170 have opposite conductivity types. Optionally, the first electrode 160 and the second electrode 170 can be metal electrodes formed by screen printing, laser transfer or electroplating, and further, can be realized by screen printing, laser transfer of low-temperature silver paste / low-temperature copper paste / silver-coated copper paste, or can be formed into a patterned electrode by electroplating one or more alloys of Al / Ti / Ni / Co / Ag / Cu / Sn, etc.
[0074] In the related art, the process of preparing the first polarity region and the second polarity region usually requires interleaving of laser / wet chemical etching processes, and the steps involved are, for example: high-temperature boron diffusion after depositing the polysilicon layer 130, followed by deposition of an additional mask layer, laser film opening, wet chemical etching; high-temperature phosphorus diffusion after depositing the polysilicon layer 130 again, laser isolation, deposition of front and back passivation films, and screen printing. In the aforementioned process, multiple high-temperature steps are involved, the equipment required is complex and expensive, and the process flow is complicated and the process time is long.
[0075] The method for preparing a solar cell provided in the present embodiment comprises providing a substrate 110, forming a tunneling layer 120 and a polysilicon layer 130 on the back side of the substrate 110, wherein the polysilicon layer 130 includes an alternating first region and a second region; forming a borosilicate glass layer 140 on the polysilicon layer 130, applying a laser to a portion of the borosilicate glass layer 140 located in the first region so that the boron in the borosilicate glass layer 140 diffuses into the polysilicon layer 130, so that the first region forms a first polarity region; forming a phosphosilicate glass layer 150 on the polysilicon layer 130, applying a laser to a portion of the phosphosilicate glass layer 150 located in the second region so that the phosphorus in the phosphosilicate glass layer 150 diffuses into the polysilicon layer 130, so that the second region forms a second polarity region; removing the remaining borosilicate glass layer 140 and the phosphosilicate glass layer 150 on the polysilicon layer 130 respectively; forming a first electrode 160 in the first polarity region, and forming a second electrode 170 in the second polarity region. Compared with related technologies, this preparation process can reduce the high-temperature boron step and the high-temperature phosphorus step, thereby reducing the required equipment, reducing costs, and shortening the process time, which helps to increase production capacity; in addition, the preparation process has simple steps, which can simplify the battery process flow and improve preparation efficiency.
[0076] In one embodiment, a laser is applied to a portion of the borosilicate glass layer 140 located in the first region, so that the boron in the borosilicate glass layer 140 diffuses into the polysilicon layer 130, so that the first region forms a first polarity zone, including: a laser is applied to a portion of the borosilicate glass layer 140 located in the first region, so that the surface of the polysilicon layer 130 located in the first region away from the substrate 110 is liquefied, so that the portion of the borosilicate glass layer 140 covering the first region is melted from a preset interface toward a direction away from the substrate 110, and the preset interface is the interface between the borosilicate glass layer 140 and the polysilicon layer 130.
[0077] When the laser acts on the portion of the borosilicate glass layer 140 located in the first area, due to the difference in light absorption of different materials of the borosilicate glass layer 140 and the polysilicon layer 130, the surface of the polysilicon layer 130 away from the substrate 110 absorbs the laser energy and begins to liquefy, and conducts heat in two directions close to the substrate 110 and away from the substrate 110. In the direction close to the substrate 110, the liquefaction depth of the polysilicon layer 130 increases, that is, the doping depth increases (in the liquid state, the diffusion coefficient of heteroatoms is several orders of magnitude higher than that in the solid state); in the direction away from the substrate 110, the borosilicate glass layer 140 is in direct contact with the liquefied polysilicon layer 130 and is indirectly heated, so that the portion of the borosilicate glass layer 140 covering the first area melts from the interface between the borosilicate glass layer 140 and the polysilicon layer 130 toward the direction away from the substrate 110.
[0078] In the process of liquefying the polysilicon layer 130 and melting the borosilicate glass layer 140, the boron-doped atoms in the borosilicate glass layer 140 diffuse into the polysilicon layer 130, so that the first region forms a first polarity zone. Specifically, in the process of liquefying the polysilicon layer 130 and melting the borosilicate glass layer 140, the polysilicon layer 130 forms a polysilicon melt, and the boron-doped atoms in the borosilicate glass layer 140 diffuse from the melted borosilicate glass layer 140 into the polysilicon melt to form a first polarity zone.
[0079] Optionally, during the diffusion process, the diffusion depth of the boron doping atoms can reach the micrometer level within 1 us, with a fast diffusion speed and high diffusion efficiency. Optionally, the thickness of the borosilicate glass layer 140 can be 30nm-80nm, further ensuring that the boron doping atoms diffuse from the molten borosilicate glass layer 140 to the doping depth in the polysilicon melt.
[0080] In one embodiment, during the liquefaction of the polysilicon layer 130 and the melting of the borosilicate glass layer 140 , ablation is performed between the borosilicate glass layer 140 and the phosphosilicate glass layer 150 to remove the portion of the borosilicate glass layer 140 located in the first region.
[0081] During the liquefaction of the polysilicon layer 130 and the melting of the borosilicate glass layer 140, the borosilicate glass layer 140 is indirectly ablated due to the evaporation of silicon in the polysilicon layer 130 and the expansion of the gas in the later process. On the one hand, this can prevent the remaining small number of boron-doped atoms from further diffusing from the borosilicate glass layer 140 to the polysilicon layer 130. On the other hand, when the gas expands to a certain extent, the borosilicate glass layer 140 will explode from the inside in a direction away from the substrate 110, so that the borosilicate glass layer 140 on the first area can be directly removed.
[0082] In one of the embodiments, a laser is applied to a portion of the phosphosilicate glass layer 150 located in the second region, so that phosphorus in the phosphosilicate glass layer 150 diffuses into the polysilicon layer 130, so that the second region forms a second polarity zone, including: a laser is applied to a portion of the phosphosilicate glass layer 150 located in the second region, so that a surface of the polysilicon layer 130 located in the second region away from the substrate 110 is liquefied, so that a portion of the phosphosilicate glass layer 150 covering the second region is melted from a preset interface toward a direction away from the substrate 110, and the preset interface is the interface between the phosphosilicate glass layer 150 and the polysilicon layer 130.
[0083] When the laser acts on the portion of the phosphosilicate glass layer 150 located in the second region, due to the difference in light absorption of different materials of the phosphosilicate glass layer 150 and the polysilicon layer 130, the surface of the polysilicon layer 130 away from the substrate 110 absorbs the laser energy and begins to liquefy, and conducts heat in two directions, close to the substrate 110 and away from the substrate 110. In the direction close to the substrate 110, the liquefaction depth of the polysilicon layer 130 increases, that is, the doping depth increases (in the liquid state, the diffusion coefficient of heteroatoms is several orders of magnitude higher than that in the solid state); in the direction away from the substrate 110, the phosphosilicate glass layer 150 is in direct contact with the liquefied polysilicon layer 130 and is indirectly heated, so that the portion of the phosphosilicate glass layer 150 covering the second region melts from the interface between the phosphosilicate glass layer 150 and the polysilicon layer 130 toward the direction away from the substrate 110.
[0084] In the process of liquefying the polysilicon layer 130 and melting the phosphosilicate glass layer 150, the phosphorus-doped atoms in the phosphosilicate glass layer 150 diffuse into the polysilicon layer 130, so that the second region forms a second polarity zone. Specifically, in the process of liquefying the polysilicon layer 130 and melting the phosphosilicate glass layer 150, the polysilicon layer 130 forms a polysilicon melt, and the phosphorus-doped atoms in the phosphosilicate glass layer 150 diffuse from the melted phosphosilicate glass layer 150 into the polysilicon melt to form a second polarity zone.
[0085] Optionally, during the diffusion process, the phosphorus-doped atoms can diffuse to a depth of micrometers within 1 us, with a fast diffusion speed and high diffusion efficiency. Optionally, the thickness of the phosphorus-silicate glass layer 150 can be 30 μm-80 μm, further ensuring that the phosphorus-doped atoms diffuse from the molten phosphorus-silicate glass layer 150 to a doping depth in the polysilicon melt.
[0086] In one embodiment, during the liquefaction of the polysilicon layer 130 and the melting of the phosphosilicate glass layer 150 , the phosphosilicate glass layer 150 is ablated to remove the portion of the phosphosilicate glass layer 150 located in the second region.
[0087] During the liquefaction of the polysilicon layer 130 and the melting of the phosphosilicate glass layer 150, the phosphosilicate glass layer 150 is indirectly ablated due to the evaporation of silicon in the polysilicon layer 130 and the expansion of the gas in the later process. On the one hand, this can prevent the remaining small number of phosphorus-doped atoms from further diffusing from the phosphosilicate glass layer 150 to the polysilicon layer 130. On the other hand, when the gas expands to a certain extent, the phosphosilicate glass layer 150 will explode from the inside in a direction away from the substrate 110, so that the phosphosilicate glass layer 150 on the second area can be directly removed.
[0088] In one embodiment, removing the remaining borosilicate glass layer 140 on the polysilicon layer 130 includes: using a wet chemical method to remove the area of the borosilicate glass layer 140 that is not acted on by the laser; and / or removing the remaining phosphosilicate glass layer 150 on the polysilicon layer 130 includes: using a wet chemical method to remove the area of the phosphosilicate glass layer 150 that is not acted on by the laser. Removing the remaining silicon glass layer on the back polysilicon layer 130 by a wet chemical method is simpler and more efficient, and the removal speed can be flexibly controlled, which is conducive to improving the preparation efficiency of the battery.
[0089] In other embodiments, the borosilicate glass layer 140 remaining on the back side can be removed by laser process after the boron doping atoms are diffused, and / or the phosphosilicate glass layer 150 remaining on the back side can be removed by laser process after the phosphorus doping atoms are diffused. By using the laser process, the depth and range of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 to be removed can be accurately controlled, thereby reducing the impact on the polysilicon layer 130.
[0090] In one embodiment, the method for preparing a solar cell further includes: after forming the first polarity region, removing the laser damage in the region acted on by the laser by a wet chemical method; and / or, after forming the second polarity region, removing the laser damage in the region acted on by the laser by a wet chemical method. Removing the laser damage in the region acted on by the laser by wet chemical method can further improve the stability of the cell.
[0091] It can be understood that after the first polarity zone is formed, the step of removing laser damage in the area acted by the laser using a wet chemical method can be performed before or after removing the borosilicate glass layer 140; after the second polarity zone is formed, the step of removing laser damage in the area acted by the laser using a wet chemical method can be performed before or after removing the phosphosilicate glass layer 150.
[0092] In one of the embodiments, the first region and the second region are spaced apart, so that the first polarity region and the second polarity region that are finally formed are also spaced apart, avoiding direct contact between the first polarity region and the second polarity region. The process is simple and the production capacity is higher. In addition, there is no need to set an isolation region outside the polysilicon material in the polysilicon layer 130, and it is not affected by the passivation effect of the isolation region.
[0093] It can be understood that before the corresponding doping atoms are diffused into the first region and the second region, they can only be virtually defined regions in the polysilicon layer 130. The two virtually defined regions are spaced apart, which can be understood as the regions where the laser is acted on twice during the boron doping process and the phosphorus doping process, so that the first polarity region and the second polarity region formed are spaced apart, and the spaced region is a region that is not doped with boron and phosphorus.
[0094] In one embodiment, if Figure 8As shown, the first region and the second region are adjacent to each other; before the step of forming the first electrode 160 and the second electrode 170, the method for preparing the solar cell further includes: step 802 to step 804.
[0095] Step 802: using a laser process to remove a portion of the boundary between the first polarity region and the second polarity region, so as to at least expose the polarity region at the corresponding boundary inside the polysilicon layer.
[0096] Among them, after the first polarity zone and the second polarity zone are formed, part of the area at the junction of the first polarity zone and the second polarity zone can be removed, and the removed part at least exposes a part of the inner layer of the polysilicon layer 130, that is, the polarity zone at the corresponding junction inside the polysilicon layer 130, so that the first polarity zone and the second polarity zone are at least partially separated.
[0097] Optionally, a laser device may be used to remove a portion of the interface between the first polarity region and the second polarity region. Optionally, a mask layer may be provided at the interface between the first polarity region and the second polarity region away from the surface of the substrate 110, and then the mask layer may be removed at the interface between the first polarity region and the second polarity region using a laser device to expose a portion of the first polarity region and the second polarity region. Optionally, a mask layer may be formed by a high temperature deposition method or a printing method, and the mask layer may be a single or multiple composite thin films such as silicon nitride, aluminum oxide, titanium oxide, silicon oxide, silicon oxynitride, or an anti-corrosion slurry / ink.
[0098] Step 804, using a wet chemical method to remove the active area of the laser process, exposing the substrate at the corresponding junction position. Phase isolation between the first polarity region and the second polarity region is achieved, while avoiding the influence caused by lateral doping that may exist between the first polarity region and the second polarity region. Optionally, after exposing the substrate 110 at the corresponding junction position, a polished surface or a pyramid-shaped velvet surface randomly distributed at the micrometer level can be formed on the back surface of the substrate 110, and the damage caused by the laser is eliminated.
[0099] In one embodiment, at least the polarity region at the corresponding junction position inside the polysilicon layer 130 is exposed, including: exposing the polarity region at the corresponding junction position inside the polysilicon layer 130; or exposing the tunneling layer 120 at the corresponding junction position; or exposing the substrate 110 at the corresponding junction position. By selectively removing part of the first polarity region and the second polarity region, the polarity region at the corresponding junction position inside the polysilicon layer 130 can be exposed; or, completely removing the first polarity region and the second polarity region at the junction position can expose part of the tunneling layer 120; or on the basis of the former, partially / completely removing the tunneling layer 120 at this position can expose the semiconductor substrate 110. The method is simple, and multiple feasible embodiments make the preparation process more flexible, and can match different subsequent wet chemical method parameters to finally remove the active area of the laser process. It can be understood that different exposure positions only affect the matching between the two-step process of laser and wet chemical method. After the two-step process is completed, the final effect can be consistent, which improves reliability.
[0100] In one embodiment, the method for preparing a solar cell further includes: forming a back passivation layer 180 on the polysilicon layer 130 forming the first polarity region and the second polarity region; wherein the first electrode 160 and the second electrode 170 penetrate the back passivation layer 180 to the polysilicon layer 130 (please refer to Fig. 9 The structure shown in the figure) is formed by forming a back passivation layer 180 to reduce light reflection, improve the light absorption efficiency of the battery, and prevent the recombination loss of carriers; wherein the first electrode 160 and the second electrode 170 penetrate the back passivation layer 180 to the polysilicon layer 130 to ensure that the current can be effectively collected. Optionally, the back passivation layer 180 can be a single or multiple composite films such as silicon nitride, aluminum oxide, titanium oxide, silicon oxide, and silicon oxynitride.
[0101] In one embodiment, the method for preparing a solar cell further includes: forming a front passivation layer 190 on the front side of the substrate 110 (please continue to refer to Fig. 9 The front passivation layer 190 can effectively reduce the defects on the silicon surface. Optionally, the front passivation layer 190 can be a single or multiple composite films such as silicon nitride, aluminum oxide, titanium oxide, silicon oxide, and silicon oxynitride.
[0102] The preparation process of each layer in the solar cell structure is further described below with some optional specific implementations:
[0103] 1. Provide a substrate 110, including crystalline silicon, with an N-type or P-type doping type.
[0104] 2. Perform wet chemical etching on the front surface of the substrate 110, and the front surface after etching has a pyramid-shaped velvet surface with random distribution at the micron level.
[0105] 3. References Fig.10 In the structure shown, an ultra-thin tunneling layer 120 is prepared on the back side of the substrate 110 , and a polysilicon layer 130 is deposited on the surface of the ultra-thin tunneling layer 120 away from the substrate 110 .
[0106] 4. References Fig.10 In the structure shown, a layer of BSG is deposited on the surface of the polysilicon layer 130 away from the substrate 110 .
[0107] 5. References Fig.11 The structure shown is processed on the back surface by laser equipment, so that the boron in the BSG layer located in the first area diffuses into the polysilicon layer 130. The laser acts on the back of the battery, and the difference in light absorption of different materials is used to make the polysilicon layer 130 absorb the laser heat, liquefy the surface of the polysilicon layer 130 away from the substrate 110, and conduct the heat in two directions close to and away from the substrate 110, wherein the BSG layer is in direct contact with the liquefied polysilicon layer 130 and is indirectly heated, and the BSG layer melts from the polysilicon-BSG layer interface to the direction of the BSG layer away from the substrate 110, wherein the doped atoms diffuse from the liquefied doped glass into the polysilicon melt, and the diffusion depth can reach the micron level within 1us, forming the first polarity zone. Subsequently, silicon evaporation and gas expansion will cause indirect ablation of the glass layer, preventing the dopant from further diffusing from the BSG layer to the polysilicon layer 130, and further, blasting from the inside away from the substrate 110 to remove the BSG layer in the first area.
[0108] 6. References Fig.11 In the structure shown, the BSG layer in the second area on the back side that has not been lasered is removed by wet chemical method. The laser damage removal step can be selectively added by wet chemical method. The laser damage step can be performed before or after the BSG layer removal step.
[0109] 7. References Fig.12 In the structure shown, a layer of PSG is deposited on the surface of the polysilicon layer 130 away from the substrate 110.
[0110] 8. References Fig.13The structure shown is processed on the back surface by laser equipment, so that the phosphorus in the PSG layer of the second area diffuses into the polysilicon layer 130. The laser acts on the back of the battery, and the difference in light absorption of different materials is used to make the polysilicon layer 130 absorb the laser heat, liquefy the surface of the polysilicon layer 130 away from the substrate 110, and conduct the heat in two directions close to and away from the substrate 110, wherein the PSG layer is in direct contact with the liquefied polysilicon layer 130 and is indirectly heated, and the PSG layer melts from the polysilicon-PSG layer interface to the direction of the PSG layer away from the substrate 110, wherein the doped atoms diffuse from the liquefied doped glass into the polysilicon melt, and the diffusion depth can reach the micron level within 1us, forming a second polarity zone. The second polarity zone can be separated from the first polarity zone by a remaining polysilicon layer 130 ( Fig.13 Taking this as an example); there may be no polysilicon layer 130 remaining, and the first polarity region is in direct contact with the second polarity region.
[0111] Subsequently, silicon evaporation and gas expansion may cause indirect ablation of the glass layer, preventing further diffusion of dopants from the PSG layer into the polysilicon layer 130 , and further, blasting away from the substrate 110 from the inside to remove the PSG layer in the second region.
[0112] 9. References Fig.13 In the structure shown, the PSG layer in the first area on the back side that has not been lasered is removed by wet chemical method. The laser damage removal step can be selectively added by wet chemical method. The laser damage step can be performed before or after the PSG layer removal step.
[0113] 10. References Fig.14 In the structure shown, a back passivation layer 180 is disposed on the back surface, and the back passivation layer 180 may be silicon nitride.
[0114] 9. References Fig.14 In the structure shown, a front passivation layer 190 is provided on the front side of the substrate 110 , and the front passivation layer 190 may be silicon nitride.
[0115] 10. References Fig.15 In the structure shown, a first electrode 160 is disposed in a first polarity region, and a second electrode 170 is disposed in a second polarity region. The first electrode 160 and the second electrode 170 have opposite conductivity types.
[0116] In the above embodiment, BSG and PSG are deposited on the polysilicon layer 130 in steps, and then laser doping and ablation processes are performed on the BSG in the first region and the PSG in the second region in steps to complete the preparation of the P and N type polarity regions. Compared with the related art, the high temperature steps of boron doping and phosphorus doping can be reduced, thereby reducing the required equipment, reducing costs, shortening the process time, and helping to increase production capacity; in addition, the preparation process has simple steps, which can simplify the battery process flow and improve preparation efficiency.
[0117] It can be understood that, in addition to the relevant steps of the method for preparing the solar cell structure involved in the above embodiment, other existing preparation steps may be included according to actual needs to obtain corresponding process effects, which will not be further limited here.
[0118] It should be understood that, although the steps in the flowcharts involved in the above embodiments are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages, and these steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the steps or stages in other steps.
[0119] The present application also provides a solar cell, which is prepared by the method for preparing a solar cell according to any one of the above embodiments or a combination of the above embodiments. Since the preparation method can reduce costs, shorten process time, and improve preparation efficiency, the solar cell can be mass-produced.
[0120] The embodiment of the present application further provides a photovoltaic assembly, including a battery string, wherein the battery string is formed by connecting a plurality of solar cells of the above embodiment.
[0121] The embodiment of the present application also provides a photovoltaic system, including the photovoltaic components in any of the above embodiments. The photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. It can be understood that the application scenarios of the photovoltaic system are not limited to this, that is to say, the photovoltaic system can be applied in all fields where solar energy is required to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array may be an array combination of multiple photovoltaic components. For example, multiple photovoltaic components can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. After the convergence, the current flows through the inverter and is converted into the alternating current required by the mains power grid, and then connected to the mains network to realize solar power supply.
[0122] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, 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, they should be considered to be within the scope of this specification.
[0123] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.
Claims
1. A method for preparing a solar cell, characterized in that: include: Providing a substrate, a tunneling layer and a polysilicon layer are formed on the back side of the substrate, the polysilicon layer is located on a side of the tunneling layer away from the substrate, and the polysilicon layer includes alternating first and second regions; forming a borosilicate glass layer on the polysilicon layer, applying a laser to a portion of the borosilicate glass layer located in the first region so that boron in the borosilicate glass layer diffuses into the first region of the polysilicon layer to form a first polarity region, and removing the remaining borosilicate glass layer on the polysilicon layer; forming a phosphosilicate glass layer on the polysilicon layer, applying a laser to a portion of the phosphosilicate glass layer located in the second region so that phosphorus in the phosphosilicate glass layer diffuses into the second region of the polysilicon layer to form a second polarity region, and removing the remaining phosphosilicate glass layer on the polysilicon layer; A first electrode is formed in the first polarity region, and a second electrode is formed in the second polarity region.
2. The method for preparing a solar cell according to claim 1, characterized in that: The laser acts on a portion of the borosilicate glass layer located in the first region, so that boron in the borosilicate glass layer diffuses into the first region of the polysilicon layer to form a first polarity region, including: The laser acts on the portion of the borosilicate glass layer located in the first region, so that the surface of the polysilicon layer located in the first region away from the substrate is liquefied, so that the portion of the borosilicate glass layer covering the first region is melted from a preset interface toward a direction away from the substrate, and the preset interface is an interface between the borosilicate glass layer and the polysilicon layer; During the liquefaction of the polysilicon layer and the melting of the borosilicate glass layer, boron in the borosilicate glass layer diffuses into the polysilicon layer, so that the first region forms a first polarity region.
3. The method for preparing a solar cell according to claim 2, characterized in that: The polysilicon layer is liquefied and the borosilicate glass layer is melted, so that the borosilicate glass layer is ablated to remove a portion of the borosilicate glass layer located in the first region.
4. The method for preparing a solar cell according to claim 1, characterized in that: The laser acts on the portion of the phosphosilicate glass layer located in the second region, so that phosphorus in the phosphosilicate glass layer diffuses into the second region of the polysilicon layer to form a second polarity region, including: The laser acts on the portion of the phosphosilicate glass layer located in the second region, so that the surface of the polysilicon layer located in the second region away from the substrate is liquefied, so that the portion of the phosphosilicate glass layer covering the second region is melted from a preset interface toward a direction away from the substrate, and the preset interface is an interface between the phosphosilicate glass layer and the polysilicon layer; During the liquefaction of the polysilicon layer and the melting of the phosphosilicate glass layer, phosphorus in the phosphosilicate glass layer diffuses into the polysilicon layer, so that the second region forms a second polarity region.
5. The method for preparing a solar cell according to claim 4, characterized in that: The polysilicon layer is liquefied and the borosilicate glass layer is melted, so that the borosilicate glass layer is ablated to remove a portion of the borosilicate glass layer located in the first region.
6. The method for preparing a solar cell according to claim 1, characterized in that: The step of removing the remaining borosilicate glass layer on the polysilicon layer comprises: removing the area of the borosilicate glass layer not affected by the laser by a wet chemical method; and / or The step of removing the remaining phosphosilicate glass layer on the polysilicon layer comprises: The areas of the phosphosilicate glass layer not acted upon by the laser are removed by a wet chemical method.
7. The method for preparing a solar cell according to claim 1, characterized in that: The method for preparing the solar cell further comprises: After forming the first polarity region, removing laser damage in the area acted upon by the laser using a wet chemical method; and / or After the second polarity region is formed, laser damage on the area acted upon by the laser is removed by a wet chemical method.
8. The method for preparing a solar cell according to claim 1, characterized in that: The first region and the second region are spaced apart.
9. The method for preparing a solar cell according to claim 1, characterized in that: The first area and the second area are adjacent to each other; Before the step of forming the first electrode and the second electrode, the method for preparing a solar cell further includes: Using a laser process to remove a portion of the boundary between the first polarity region and the second polarity region, so as to at least expose the polarity region corresponding to the boundary inside the polysilicon layer; The active area of the laser process is removed by wet chemical method to expose the substrate corresponding to the interface position.
10. The method for preparing a solar cell according to any one of claims 1 to 9, characterized in that: The method for preparing the solar cell further comprises: forming a back passivation layer on the polysilicon layer forming the first polarity region and the second polarity region; The first electrode and the second electrode penetrate the back passivation layer to the polysilicon layer.
11. The method for preparing a solar cell according to any one of claims 1 to 9, characterized in that: The method for preparing the solar cell further comprises: A front passivation layer is formed on the front side of the substrate.
12. A solar cell, characterized in that: The solar cell is prepared by the method for preparing a solar cell according to any one of claims 1 to 11.
13. A photovoltaic module, characterized in that: The invention comprises a battery string, wherein the battery string is formed by connecting a plurality of solar cells as claimed in claim 12.