Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to a solar cell, a preparation method thereof and a photovoltaic module, a substrate is provided, a tunneling layer, a polycrystalline silicon layer, a borosilicate glass layer and a phosphorosilicate glass layer which are laminated are formed on the back surface of the substrate along a direction far away from the substrate, and the polycrystalline silicon layer comprises first areas and second areas which are alternated; laser acts on the borosilicate glass layer and the part, located in the first area, of the phosphorosilicate glass layer, so that boron in the borosilicate glass layer is diffused into the polycrystalline silicon layer, and a first polarity area is formed in the first area; the preset temperature acts on the borosilicate glass layer and the part, located in the second area, of the phosphorosilicate glass layer, so that phosphorus in the phosphorosilicate glass layer is diffused into the polycrystalline silicon layer, and a second polarity area is formed in the second area; removing the residual borosilicate glass layer and phosphorosilicate glass layer on the polycrystalline silicon layer; a first electrode is formed in the first polar region, and a second electrode is formed in the second polar region. According to the preparation method, the high-temperature step can be reduced, the cost can be reduced, the process time can be shortened, and the productivity can be improved.

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, wherein a stacked tunneling layer, a polysilicon layer, a borosilicate glass layer and a phosphosilicate glass layer are formed on the back side of the substrate in a direction away from the substrate, wherein the polysilicon layer includes alternating first and second regions;

[0007] Applying laser to the borosilicate glass layer and the phosphosilicate glass layer at the first region, so that boron in the borosilicate glass layer diffuses into the polysilicon layer, so that the first region forms a first polarity region;

[0008] A preset temperature acts on the borosilicate glass layer and the phosphosilicate glass layer located in the second region, so that phosphorus in the phosphosilicate glass layer diffuses into the polysilicon layer, so that the second region forms a second polarity region;

[0009] removing the borosilicate glass layer and the phosphosilicate glass layer remaining on the polysilicon layer;

[0010] A first electrode is formed in the first polarity region, and a second electrode is formed in the second polarity region.

[0011] In one embodiment, the laser acts on the borosilicate glass layer and the phosphosilicate 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, including:

[0012] The laser acts on the portions of the borosilicate glass layer and the phosphosilicate 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;

[0013] In the process of liquefying the polysilicon layer and melting the borosilicate glass layer, the boron-doped atoms in the borosilicate glass layer diffuse into the polysilicon layer, so that the first region forms a first polarity region.

[0014] In one embodiment, during the liquefaction of the polysilicon layer and the melting of the borosilicate glass layer, ablation is performed between the borosilicate glass layer and the phosphosilicate glass layer to remove portions of the borosilicate glass layer and the phosphosilicate glass layer located in the first region.

[0015] In one embodiment, the preset temperature range includes 850°C-900°C.

[0016] In one embodiment, the formation process of the second polar region is performed in an inert gas environment.

[0017] In one embodiment, before the step of forming the first polarity region and the second polarity region, the method for preparing a solar cell further includes:

[0018] Partial regions of the borosilicate glass layer and the phosphosilicate glass layer are removed to expose a preset region of the polysilicon layer, where the preset region is used to separate the first region from the second region.

[0019] In one embodiment, before the step of forming the first electrode and the second electrode, the method for preparing a solar cell further includes:

[0020] 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;

[0021] The active area of ​​the laser process is removed by wet chemical method to expose the substrate corresponding to the interface position.

[0022] In one embodiment, the step of exposing at least the polarity region inside the polysilicon layer corresponding to the boundary position includes:

[0023] exposing a polarity region inside the polysilicon layer corresponding to the boundary position; or

[0024] exposing the tunneling layer at a position corresponding to the interface; or

[0025] The substrate at a position corresponding to the interface is exposed.

[0026] In one embodiment, the method for preparing a solar cell further comprises:

[0027] forming a back passivation layer on the polysilicon layer forming the first polarity region and the second polarity region;

[0028] The first electrode and the second electrode penetrate the back passivation layer to the polysilicon layer.

[0029] In one embodiment, the method for preparing a solar cell further comprises:

[0030] A front passivation layer is formed on the front side of the substrate.

[0031] 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.

[0032] A second 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.

[0033] The solar cell and its preparation method and photovoltaic module are provided by providing a substrate, the back side of the substrate is formed with a stacked tunneling layer, a polysilicon layer, a borosilicate glass layer and a phosphosilicate glass layer in a direction away from the substrate, and the polysilicon layer includes an alternating first region and a second region; a laser acts on the part of the borosilicate glass layer and the phosphosilicate 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; a preset temperature acts on the part of the borosilicate glass layer and 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; the remaining borosilicate glass layer and the phosphosilicate glass layer on the polysilicon layer are removed; a first electrode is formed in the first polarity region, and a second electrode is formed in the second polarity region. Compared with the related art, the preparation method 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; in addition, the preparation process is simple in steps, which can simplify the battery process flow and improve the preparation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] 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.

[0035] Figure 1 A flow chart of a method for preparing a solar cell structure according to an embodiment;

[0036] Figure 2 is a structural block diagram of a solar cell structure according to an embodiment;

[0037] Figure 3 is a structural block diagram of a solar cell structure according to an embodiment;

[0038] Figure 4 is a structural block diagram of a solar cell structure according to an embodiment;

[0039] Figure 5 is a structural block diagram of a solar cell structure according to an embodiment;

[0040] Figure 6 is a structural block diagram of a solar cell structure according to an embodiment;

[0041] Figure 7 A flow chart of a method for preparing a solar cell structure according to an embodiment;

[0042] Figure 8 is a structural block diagram of a solar cell structure according to an embodiment;

[0043] Fig. 9 is a structural block diagram of a solar cell structure according to an embodiment;

[0044] Fig.10 is a structural block diagram of a solar cell structure according to an embodiment;

[0045] Fig.11 is a structural block diagram of a solar cell structure according to an embodiment;

[0046] Fig.12 is a structural block diagram of a solar cell structure according to an embodiment;

[0047] Fig.13 is a structural block diagram of a solar cell structure according to an embodiment;

[0048] Fig.14 is a structural block diagram of a solar cell structure according to an embodiment;

[0049] Fig.15is a structural block diagram of a solar cell structure according to an embodiment;

[0050] Fig.16 is a structural block diagram of a solar cell structure according to an embodiment;

[0051] Fig.17 is a structural block diagram of a solar cell structure according to an embodiment;

[0052] Fig.18 is a structural block diagram of a solar cell structure according to an embodiment;

[0053] Fig.19 is a structural block diagram of a solar cell structure according to an embodiment;

[0054] Fig. 20 FIG. 4 is a structural block diagram of a solar cell structure according to an embodiment of the present invention.

[0055] Reference numerals:

[0056] Substrate: 110; tunneling layer: 120; polysilicon layer: 130; borosilicate glass layer: 140;

[0057] Phosphorus silicon glass layer: 150; first electrode: 160; second electrode: 170;

[0058] Back passivation layer: 180; front passivation layer: 190; mask layer: 200;

[0059] The first electrode region is a P region; the second electrode region is an N region. DETAILED DESCRIPTION

[0060] 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.

[0061] 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.

[0062] 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 110.

[0063] Step 102, providing a substrate, a back side of the substrate having a stacked tunneling layer, a polysilicon layer, a borosilicate glass layer and a phosphosilicate glass layer formed in a direction away from the substrate, and the polysilicon layer includes alternating first regions and second regions.

[0064] 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.

[0065] Among them, 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, such as at least one of magnesium fluoride, silicon oxide, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide.

[0066] Please refer to Figure 2 , a stacked polysilicon layer 130, a borosilicate glass layer 140 (BSG) and a phosphosilicate glass layer 150 (PSG) are sequentially formed on the tunneling layer 120 in a direction away from the substrate 110. The polysilicon layer 130 includes alternating first and second regions, the borosilicate glass layer 140 is located on the polysilicon layer 130, and the phosphosilicate glass layer 150 is located on the borosilicate glass layer 140. The orthographic projections of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 on the polysilicon layer 130 can cover the first region and the second region respectively.

[0067] It can be understood that a substrate 110 is provided, and a stacked tunneling layer 120, a polysilicon layer 130, a borosilicate glass layer 140 and a phosphosilicate glass layer 150 are formed on the back side of the substrate 110 in a direction away from the substrate 110. This may include that, when the substrate 110 is provided, a stacked structure of the tunneling layer 120, the polysilicon layer 130, the borosilicate glass layer 140 and the phosphosilicate glass layer 150 is formed; it may also include that, after the substrate 110 is provided, a stacked structure of the tunneling layer 120, the polysilicon layer 130, the borosilicate glass layer 140 and the phosphosilicate glass layer 150 is sequentially formed on the substrate 110.

[0068] Step 104 , laser acts on the borosilicate glass layer and the phosphosilicate glass layer located in the first region, so that boron in the borosilicate glass layer diffuses into the polysilicon layer, so that the first region forms a first polarity region.

[0069] The first polarity region (P region) can be understood as the projection coverage area of ​​the first electrode on the polysilicon layer 130 , and is the main region for establishing and maintaining the flow of current in the solar cell structure.

[0070] The borosilicate glass layer 140 is rich in boron-doped atoms. When the laser acts on the borosilicate glass layer 140 and the phosphosilicate glass layer 150 located in the first region, the laser energy acts not only on the outer phosphosilicate glass layer 150, but also on the borosilicate glass layer 140. At the same time, since the borosilicate glass layer 140 and the phosphosilicate glass layer 150 almost transmit light, the laser energy also acts on the polysilicon layer 130, 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, the phosphosilicate glass layer 150 and the polysilicon layer 130, the laser can be applied to the back of the battery to make the polysilicon layer 130 absorb the laser energy, thereby indirectly heating the borosilicate glass layer 140, so that the boron-doped atoms are diffused into the polysilicon layer 130 by heat, forming a first polarity region (refer to Figure 3 as shown).

[0071] 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.

[0072] Step 106 , applying a preset temperature to the portions of the borosilicate glass layer and the phosphosilicate glass layer located in the second region, so that phosphorus in the phosphosilicate glass layer diffuses into the polysilicon layer, so that the second region forms a second polarity region.

[0073] The second polarity region (N region) can be understood as the projection coverage area of ​​the second electrode 170 on the polysilicon layer 130 , and is the main region for establishing and maintaining the flow of current in the solar cell structure.

[0074] The borosilicate glass layer 140 is rich in boron doping atoms, and the phosphosilicate glass layer 150 is rich in phosphorus doping atoms. Under the action of a preset temperature, the diffusion rate of phosphorus doping atoms in the borosilicate glass layer 140 is different from the diffusion rate of boron doping atoms in the borosilicate glass layer 140, and the diffusion rate of phosphorus doping atoms in the polysilicon layer 130 is different from the diffusion rate of boron doping atoms in the polysilicon layer 130. The phosphorus diffusion is performed by utilizing the different diffusivities of the phosphorus doping atoms and the boron doping atoms to form a second polarity zone in the second region. The different diffusivities of phosphorus doping atoms and boron doping atoms include that at the preset temperature, the diffusion rate of phosphorus doping atoms in polysilicon is much faster than the diffusion rate of boron doping atoms; and at the preset temperature, the boron content in the borosilicate glass layer 140 will reduce the glass transition point and increase the permeability to phosphorus doping atoms. Therefore, the diffusion of phosphorus doping atoms occupies an absolute dominant position in the diffusion process, thereby forming a second polarity zone (reference Figure 4 as shown).

[0075] Optionally, an annealing process can be selectively added during the diffusion of phosphorus-doped atoms to eliminate damage caused by the previous laser process and further improve the stability of the battery.

[0076] Step 108, removing the remaining borosilicate glass layer and phosphosilicate glass layer on the polysilicon layer (please refer to Figure 5 structure shown).

[0077] Among them, the remaining borosilicate glass layer 140 and the phosphosilicate glass layer 150 may include the borosilicate glass layer 140 and the phosphosilicate glass layer 150 that may remain on the first polarity zone of the polysilicon layer 130 after the laser action. It can be understood that since the polysilicon layer 130 absorbs energy and indirectly heats the borosilicate glass layer 140, during the laser action, part or even all of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 on the first polarity zone may be removed or may remain; the remaining borosilicate glass layer 140 and the phosphosilicate glass layer 150 may also include the borosilicate glass layer 140 and the phosphosilicate glass layer 150 on the second polarity zone after the preset temperature is applied.

[0078] Optionally, the remaining borosilicate glass layer 140 and phosphosilicate glass layer 150 on the back side may be removed by wet chemical method. This method is simpler and more efficient to operate, and the removal speed can be flexibly controlled, which is beneficial to improving the preparation efficiency of the battery.

[0079] Optionally, the remaining borosilicate glass layer 140 and phosphosilicate glass layer 150 on the back side may be removed by a laser process. This method can accurately control the depth and range of the borosilicate glass layer 140 and phosphosilicate glass layer 150 to be removed, thereby reducing the impact on the polysilicon layer 130.

[0080] Step 110, forming a first electrode in the first polarity region and forming a second electrode in the second polarity region (please refer to Figure 6 structure shown).

[0081] 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 can be realized by screen printing, laser transfer of low-temperature silver paste / low-temperature copper paste / silver-coated copper paste, or can be patterned electrodes formed by electroplating one or more alloys of Al / Ti / Ni / Co / Ag / Cu / Sn, etc.

[0082] 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.

[0083] The method for preparing a solar cell provided in the present embodiment comprises providing a substrate 110, wherein a stacked tunneling layer 120, a polysilicon layer 130, a borosilicate glass layer 140 and a phosphosilicate glass layer 150 are formed on the back side of the substrate 110 in a direction away from the substrate 110, wherein the polysilicon layer 130 comprises alternating first and second regions; a laser is applied to the portions of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 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; a preset temperature is applied to the portions of the borosilicate glass layer 140 and 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; the remaining borosilicate glass layer 140 and the phosphosilicate glass layer 150 on the polysilicon layer 130 are removed; a first electrode 160 is formed in the first polarity region, and a second electrode 170 is formed in the second polarity region. Compared with related technologies, this preparation process can reduce high-temperature steps, thereby reducing the required equipment, reducing costs, and shortening process time, which helps to increase production capacity. In addition, this preparation process has simple steps, which can simplify the battery process flow and improve preparation efficiency.

[0084] In one embodiment, a laser is applied to portions of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 located in the first region, so that the boron in the borosilicate glass layer 140 diffuses into the polysilicon layer 130, so that a first polarity zone is formed in the first region, including: a laser is applied to portions of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 located in the first region, so that a surface of the polysilicon layer 130 located in the first region away from the substrate 110 is liquefied, so that a 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, wherein the preset interface is the interface between the borosilicate glass layer 140 and the polysilicon layer 130.

[0085] When the laser acts on the portions of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 located in the first area, due to the difference in light absorption of different materials of the borosilicate glass layer 140, 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 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.

[0086] 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.

[0087] Optionally, during the diffusion process, the diffusion depth of the boron-doped atoms can reach the micron level within 1us, with a fast diffusion speed and high diffusion efficiency. Optionally, the thickness of the borosilicate glass layer 140 can be 40 nm-100 nm, which can further ensure that during laser heating, during the diffusion of the boron-doped atoms to the polysilicon layer 130, the phosphorus-doped atoms in the phosphorus-doped glass layer 150 can diffuse without being affected by the energy generated by the heat of the polysilicon layer 130, reducing or even preventing the phosphorus-doped atoms from diffusing into the polysilicon layer, thereby achieving the single diffusion of the boron-doped atoms during the laser heating process; Optionally, the thickness of the borosilicate glass layer 140 can be 40 nm-80 nm, further ensuring the doping depth of the boron-doped atoms diffused from the molten borosilicate glass layer 140 to the polysilicon melt.

[0088] It can be understood that in the actual process, the laser heating process can also allow phosphorus doping atoms to exist at a lower concentration, and the electrical properties of the first polarity region should be mainly boron doping atoms. The presence of the lower concentration of phosphorus doping atoms will not affect the carrier concentration, mobility and conductivity of the first polarity region. In one embodiment, during the liquefaction of the polysilicon layer 130 and the melting of the borosilicate glass layer 140, the space between the borosilicate glass layer 140 and the phosphosilicate glass layer 150 is ablated to remove the portions of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 located in the first region.

[0089] 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, it can prevent the remaining small number of boron-doped atoms and phosphorus-doped atoms in the phosphosilicate glass layer 150 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, and the borosilicate glass layer 140 and the phosphosilicate glass layer 150 on the first area can be directly removed (please refer to Figure 3 ).

[0090] In one embodiment, the preset temperature range includes 850°C-900°C. Within the temperature range of 850°C-900°C, for example, when the preset temperature is any one of 850°C, 890°C, 900°C, etc., in the stacked structure of the borosilicate glass layer 140 and the phosphosilicate glass layer 150, the phosphorus-doped atoms can diffuse into the polysilicon layer 130, while the boron-doped atoms will not diffuse into the polysilicon layer 130, thereby achieving a single diffusion of phosphorus-doped atoms in the preset temperature heating process.

[0091] It can be understood that in the actual process, the preset temperature heating process can also allow boron-doped atoms to exist in a lower concentration. Finally, the electrical properties of the second polarity region should be dominated by phosphorus-doped atoms. The presence of this lower concentration of boron-doped atoms will not affect the carrier concentration, mobility and conductivity of the second polarity region.

[0092] In one embodiment, the formation process of the second polar region is carried out in an inert gas environment. The inert gas environment includes but is not limited to a nitrogen environment. In the inert gas environment, it is possible to maintain an oxygen-free, water-free or other active molecule-free environment, prevent the phosphorus doping atoms from reacting with other substances at a preset temperature, reduce losses, and avoid diffusion barriers caused by oxidation, hydrolysis or other chemical reactions.

[0093] In one embodiment, before the step of forming the first polarity region and the second polarity region, the method for preparing a solar cell further includes: removing a portion of the borosilicate glass layer 140 and the phosphosilicate glass layer 150 to expose a preset region of the polysilicon layer 130, wherein the preset region is used to separate the first region and the second region.

[0094] Before the first polarity zone and the second polarity zone are formed, part of the borosilicate glass layer 140 and the phosphorus silicon glass layer 150 can be removed, and the position of the removed part corresponds to the preset area of ​​the polysilicon layer 130, and the preset area is located between the first area and the second area of ​​the polysilicon layer 130, thereby isolating the two areas, and then the first polarity zone and the second polarity zone formed subsequently are spaced apart, avoiding direct contact between the first polarity zone and the second polarity zone, and the process is simple, the production capacity is higher, and there is no need to set an isolation area in the polysilicon layer 130, and it is not affected by the passivation effect of the isolation area. Optionally, a laser device can be used to remove part of the borosilicate glass layer 140 and the phosphorus silicon glass layer 150.

[0095] In one embodiment, if Figure 7 As shown, before the step of forming the first electrode 160 and the second electrode 170 , the method for preparing a solar cell further includes: step 702 to step 704 .

[0096] Step 702: Use a laser process to remove a portion of the interface between the first polarity region and the second polarity region, so as to at least expose the polarity region at the corresponding interface inside the polysilicon layer.

[0097] 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.

[0098] 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.

[0099] Step 704, using a wet chemical method to remove the active area of ​​the laser process, exposing the substrate at the corresponding junction position, thereby achieving phase isolation between the first polarity region and the second polarity region, 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 micron-scale randomly distributed pyramid-shaped velvet surface can be formed on the back surface of the substrate 110, and the damage caused by the laser can be eliminated.

[0100] 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.

[0101] 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 Figure 8 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.

[0102] 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 Figure 8 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.

[0103] The preparation process of each layer in the solar cell structure is further described below with some optional specific implementations:

[0104] Embodiment 1:

[0105] 1. Provide a substrate 110, including crystalline silicon, with an N-type or P-type doping type.

[0106] 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.

[0107] 3. References Fig. 9 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 .

[0108] 4. References Fig. 9 In the structure shown, a layer of BSG is deposited on the surface of the polysilicon layer 130 away from the substrate 110 , and a layer of PSG is deposited on the surface of the BSG layer away from the substrate 110 .

[0109] 5. References Fig.10 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 and the PSG layer.

[0110] 6. References Fig.11The structure shown can be used in an inert gas environment, but not limited to a nitrogen environment, at a temperature of 850°C, using the different diffusivities of phosphorus-doped atoms and boron-doped atoms in polysilicon and the high diffusivity of phosphorus in BSG to diffuse phosphorus-doped atoms in the second region. Specifically, at this temperature, the diffusion rate of phosphorus in polysilicon is much faster than the diffusion rate of boron-doped atoms; the boron content in BSG will reduce the glass transition point and increase the permeability to phosphorus-doped atoms. Therefore, the diffusion of phosphorus-doped atoms occupies an absolute dominant position in the diffusion process, thereby forming a second polarity zone. In this diffusion process, an annealing process can be selectively added to eliminate the damage caused by the previous laser process.

[0111] 7. References Fig.12 In the structure shown, the remaining PSG and BSG on the back side are removed using a wet chemical method.

[0112] 8. References Fig.13 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.

[0113] 9. References Fig.13 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.

[0114] 10. References Fig.13 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.

[0115] Embodiment 2:

[0116] 11. Provide a substrate 110, including crystalline silicon, with an N-type or P-type doping type.

[0117] 12. 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.

[0118] 13. References Fig. 9 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 .

[0119] 14. References Fig. 9 In the structure shown, a layer of BSG is deposited on the surface of the polysilicon layer 130 away from the substrate 110 , and a layer of PSG is deposited on the surface of the BSG layer away from the substrate 110 .

[0120] 15. References Fig.10The structure shown is processed on the back surface by laser equipment, so that the boron doped atoms in the BSG layer located in the first area diffuse 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 and the PSG layer.

[0121] 16. References Fig.11 The structure shown can be used in an inert gas environment, but not limited to a nitrogen environment, at a temperature of 900°C, using the different diffusivities of phosphorus-doped atoms and boron-doped atoms in polysilicon and the high diffusivity of phosphorus-doped atoms in BSG to diffuse phosphorus in the second region. At 900°C, the diffusion rate of phosphorus-doped atoms in polysilicon is much faster than that of boron-doped atoms; the boron content in BSG will reduce the glass transition point and increase the permeability to phosphorus. Therefore, the diffusion of phosphorus-doped atoms occupies an absolute dominant position in the diffusion process, thereby forming a second polarity region. In this diffusion process, an annealing process can be selectively added to eliminate the damage caused by the previous laser process.

[0122] 17. References Fig.12 In the structure shown, the remaining PSG and BSG on the back side are removed using a wet chemical method.

[0123] 18. References Fig.14 In the structure shown, a mask layer (refer to 200 in the figure) is provided in the first polarity region and the second polarity region away from the surface of the substrate 110, which can be deposited by a high-temperature deposition method or a printing method. Specifically, it can be a single or multiple composite films such as silicon nitride, aluminum oxide, titanium oxide, silicon oxide, silicon oxynitride, or anti-corrosion slurry / ink.

[0124] 19. References Fig.15 The structure shown in FIG. 1 is a structure in which a mask layer is removed at the interface between the first polarity region and the second polarity region by using a laser device to expose a portion of the first polarity region and the second polarity region ( Fig.15Taking this as an example), the first / second polarity region may be selectively removed, or the first / second polarity region at that location may be completely removed to expose part of the tunneling layer 120, or the tunneling layer 120 at that location may be partially / completely removed to expose the substrate 110.

[0125] 20. References Fig.16 In the structure shown, the first / dipolar regions and the tunneling layer 120 in the laser action area are completely removed by wet chemical method, and a polished surface or micrometer-scale randomly distributed pyramids are formed on the back surface of the substrate 110.

[0126] 21. References Fig.17 In the structure shown, a back passivation layer 180 is disposed on the back surface, and the back passivation layer 180 may be aluminum oxide.

[0127] 22. References Fig.17 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 titanium oxide.

[0128] 23. References Fig.17 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.

[0129] Embodiment 3:

[0130] 24. Provide a substrate 110, including crystalline silicon, with an N-type or P-type doping type.

[0131] 25. References Fig. 9 In the structure shown, wet chemical etching is performed on the front side of the substrate 110, and the front surface after etching has a pyramid-shaped velvet surface with random distribution at the micron level.

[0132] 26. References Fig. 9 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 .

[0133] 27. References Fig. 9 In the structure shown, a layer of BSG is deposited on the surface of the polysilicon layer 130 away from the substrate 110 , and a layer of PSG is deposited on the surface of the BSG layer away from the substrate 110 .

[0134] 28. References Fig.18 In the structure shown, the BSG layer and the PSG layer on a partial area are removed using a laser device.

[0135] 29. References Fig.19The structure shown is processed on the back surface by laser equipment, so that the boron doped atoms in the BSG layer located in the first area diffuse 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 and the PSG layer.

[0136] 30. References Fig.19 The structure shown can be used in an inert gas environment, but not limited to a nitrogen environment, at a temperature of 875°C, using the different diffusivities of phosphorus-doped atoms and boron-doped atoms in polysilicon and the high diffusivity of phosphorus in BSG to diffuse phosphorus in the second region. At 875°C, the diffusion rate of phosphorus-doped atoms in polysilicon is much faster than that of boron; the boron content in BSG will reduce the glass transition point and increase the permeability to phosphorus. Therefore, the diffusion of phosphorus-doped atoms occupies an absolute dominant position in the diffusion process, thereby forming a second polarity region. In this diffusion process, an annealing process can be selectively added to eliminate the damage caused by the previous laser process.

[0137] 31. References Fig.19 In the structure shown, the remaining PSG and BSG on the back side are removed using a wet chemical method.

[0138] 32. References Fig. 20 In the structure shown, a back passivation layer 180 is disposed on the back surface, and the back passivation layer 180 may be a silicon oxynitride film.

[0139] 33. References Fig. 20 In the structure shown, a front passivation layer 190 is provided on the front side of the substrate 110. The front passivation layer 190 may be a composite film of silicon nitride, aluminum oxide, titanium oxide, silicon oxide, or silicon oxynitride.

[0140] 34. References Fig. 20 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.

[0141] In the above embodiments, BSG and PSG are deposited on the back to form a mixed film layer, and then laser doping and ablation processes are performed, and then a high-temperature phosphorus diffusion process is performed to complete the preparation of P and N type polarity regions. Compared with related technologies, a high-temperature step can be reduced, 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.

[0142] 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.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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, wherein a stacked tunneling layer, a polysilicon layer, a borosilicate glass layer and a phosphosilicate glass layer are formed on the back side of the substrate in a direction away from the substrate, wherein the polysilicon layer includes alternating first and second regions; Applying laser to the borosilicate glass layer and the phosphosilicate glass layer at the first region, so that boron in the borosilicate glass layer diffuses into the polysilicon layer, so that the first region forms a first polarity region; A preset temperature acts on the borosilicate glass layer and the phosphosilicate glass layer located in the second region, so that phosphorus in the phosphosilicate glass layer diffuses into the polysilicon layer, so that the second region forms a second polarity region; removing the borosilicate glass layer and the phosphosilicate glass layer remaining 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 the borosilicate glass layer and the phosphosilicate glass layer at 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, including: The laser acts on the portions of the borosilicate glass layer and the phosphosilicate 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; In the process of liquefying the polysilicon layer and melting the borosilicate glass layer, the boron-doped atoms in the borosilicate glass layer diffuse 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: During the liquefaction of the polysilicon layer and the melting of the borosilicate glass layer, ablation is performed between the borosilicate glass layer and the phosphosilicate glass layer to remove portions of the borosilicate glass layer and the phosphosilicate glass layer located in the first region.

4. The method for preparing a solar cell according to claim 1, characterized in that: The preset temperature ranges from 850°C to 900°C.

5. The method for preparing a solar cell according to claim 1, characterized in that: The formation process of the second polar region is carried out in an inert gas environment.

6. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: Before the step of forming the first polarity region and the second polarity region, the method for preparing the solar cell further includes: Partial regions of the borosilicate glass layer and the phosphosilicate glass layer are removed to expose a preset region of the polysilicon layer, where the preset region is used to separate the first region from the second region.

7. The method for preparing a solar cell according to any one of claims 1 to 5, characterized in that: 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.

8. The method for preparing a solar cell according to claim 7, characterized in that: The step of at least exposing the polarity region at the interface position inside the polysilicon layer includes: exposing a polarity region inside the polysilicon layer corresponding to the boundary position; or exposing the tunneling layer at a position corresponding to the interface; or The substrate at a position corresponding to the interface is exposed.

9. The method for preparing a solar cell according to any one of claims 1 to 5, 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.

10. The method for preparing a solar cell according to any one of claims 1 to 5, 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.

11. 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 10.

12. 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 11.

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