Photovoltaic cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to a photovoltaic cell, a preparation method thereof and a photovoltaic module. The photovoltaic cell comprises a silicon substrate, a doped silicon layer, a composite barrier layer and a metal electrode, the silicon substrate is provided with a first surface and a second surface which are oppositely arranged, the first surface comprises a first area and a second area, and the second surface comprises a third area and a fourth area; the doped silicon layer is arranged on at least one of the first surface and the second surface; a composite barrier layer and a metal electrode are arranged on the surface, far away from the silicon substrate, of the doped silicon layer in the first region and / or the third region, and the metal electrode is electrically connected with the doped silicon layer; the composite barrier layer is arranged between the metal electrode and the doped silicon layer, and the material of the composite barrier layer comprises TiOx and TiN. According to the photovoltaic cell, the risk that silver penetrates through the doped silicon layer can be reduced, electric leakage is reduced, and then high conversion efficiency can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic, in particular to a photovoltaic cell, a preparation method thereof and a photovoltaic module. BACKGROUND

[0002] TOPCon cell is the abbreviation of Tunnel Oxide Passivated Contact photovoltaic cell, which is one of the mainstream technologies of high-efficiency crystalline silicon photovoltaic cells at present. With high conversion efficiency and good industrialization prospect, it has become a research and application hotspot in the photovoltaic industry. However, in the preparation method of the traditional TOPCon photovoltaic cell, when the printed conductive silver paste is sintered at high temperature to prepare the electrode, silver is easy to penetrate the doped silicon layer, causing leakage. SUMMARY

[0003] Therefore, it is necessary to provide a photovoltaic cell, a preparation method thereof and a photovoltaic module. The photovoltaic cell of the present application can reduce the risk of silver penetrating the doped silicon layer, reduce leakage, and thus achieve high conversion efficiency.

[0004] In a first aspect, the present application provides a photovoltaic cell, comprising a silicon substrate, a doped silicon layer, a composite barrier layer and a metal electrode; the silicon substrate has a silicon substrate with oppositely arranged first and second surfaces, the first surface includes a first region and a second region, and the second surface includes a third region and a fourth region; the doped silicon layer is arranged on at least one of the first surface and the second surface; the surface of the doped silicon layer away from the silicon substrate in the first region and / or the third region is provided with the composite barrier layer and the metal electrode, and the metal electrode and the doped silicon layer are electrically connected; the composite barrier layer is arranged between the metal electrode and the doped silicon layer, and the material of the composite barrier layer includes TiO x and TiN.

[0005] In some embodiments, the thickness of the composite barrier layer is 5-8 nm.

[0006] In some embodiments, the atomic ratio of N element to O element in the composite barrier layer is (3-7):7.

[0007] In some embodiments, the thickness of the doped silicon layer is 70-90 nm.

[0008] In some embodiments, the percentage of the depth of the composite barrier layer into the doped silicon layer to the thickness of the doped silicon layer is 15-20%.

[0009] In some embodiments, the depth of the composite barrier layer into the doped silicon layer is 12-18 nm.

[0010] In some embodiments, the doped silicon layer comprises a first doped silicon layer on the first surface and a second doped silicon layer on the second surface, the first doped silicon layer and the second doped silicon layer are oppositely doped; the composite barrier layer comprises a first composite barrier layer and a second composite barrier layer; the metal electrode comprises a first metal electrode and a second metal electrode.

[0011] The first composite barrier layer and the first metal electrode are sequentially stacked on the surface of the first doped silicon layer in the first region away from the silicon substrate; the second composite barrier layer and the second metal electrode are sequentially stacked on the surface of the second doped silicon layer in the third region away from the silicon substrate.

[0012] In some embodiments, the photovoltaic cell further comprises a tunneling oxide layer and an aluminum oxide layer; the tunneling oxide layer is between the silicon substrate and the second doped silicon layer; the aluminum oxide layer is between the tunneling oxide layer and the second doped silicon layer.

[0013] In some embodiments, the thickness of the aluminum oxide layer is 0.2 nm to 0.5 nm.

[0014] In a second aspect, the present application provides a method for preparing a photovoltaic cell, the photovoltaic cell being any one of the above-mentioned photovoltaic cells, comprising the following steps:

[0015] Providing the silicon substrate;

[0016] Preparing a doped silicon layer on at least one of the first surface and the second surface;

[0017] Coating an electrode paste on the surface of the doped silicon layer in the first region and / or the third region, the electrode paste comprising an organic carrier, glass powder, Ag particles and TiN particles;

[0018] Sintering the electrode paste to form the metal electrode and the composite barrier layer.

[0019] In some embodiments, the mass percentage of the TiN particles in the electrode paste is 3% to 8%.

[0020] In some embodiments, the particle size of the TiN particles is 20 nm to 50 nm.

[0021] In some embodiments, the highest temperature of the sintering process is 700°C to 750°C.

[0022] In some embodiments, the doped silicon layer includes a first doped silicon layer on the first surface and a second doped silicon layer on the second surface, the first doped silicon layer and the second doped silicon layer have opposite doping types; the recombination barrier layer includes a first recombination barrier layer and a second recombination barrier layer; the metal electrode includes a first metal electrode and a second metal electrode;

[0023] The first recombination barrier layer and the first metal electrode are sequentially stacked on a surface of the first doped silicon layer in the first region away from the silicon substrate; the second recombination barrier layer and the second metal electrode are sequentially stacked on a surface of the second doped silicon layer in the third region away from the silicon substrate;

[0024] The photovoltaic cell further includes a tunneling oxide layer and an aluminum oxide layer; the tunneling oxide layer is between the silicon substrate and the first doped silicon layer; the aluminum oxide layer is between the tunneling oxide layer and the first doped silicon layer;

[0025] The method for preparing the aluminum oxide layer includes the following steps:

[0026] An aluminum oxide atomic layer is prepared on the surface of the tunneling oxide layer by an aluminum precursor and an oxygen precursor, and the number of layers of the aluminum oxide atomic layer is 2-5.

[0027] In some embodiments, the method further includes the following steps:

[0028] A second doped silicon layer is prepared on the second surface of the silicon substrate by boron diffusion using a boron source;

[0029] The boron diffusion includes a preheating process, a diffusion process, and a relaxation process performed in sequence;

[0030] The temperature of the diffusion process is higher than the temperature of the preheating process, and the temperature of the relaxation process is between the temperature of the diffusion process and the temperature of the preheating process.

[0031] In a third aspect, the present application provides a photovoltaic module, comprising:

[0032] A cover plate;

[0033] At least one cell string, the cell string including the photovoltaic cell of any one of the above or the photovoltaic cell prepared by the method for preparing the photovoltaic cell of any one of the above;

[0034] And a packaging layer, the packaging layer being between the cover plate and the cell string, the cover plate being connected with the cell string through the packaging layer.

[0035] The composite barrier layer is arranged between the metal electrode and the doped silicon layer in the region where the metal electrode is arranged, and the material of the composite barrier layer includes TiO x and TiN, which can control the diffusion depth of metal atoms in the process of preparing the metal electrode, thereby reducing the risk of metal atoms penetrating the doped silicon layer, reducing the leakage current, and further realizing a higher conversion efficiency of the photovoltaic cell. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A structure diagram of a photovoltaic cell according to an embodiment of the present application is provided.

[0037] Figure 2 A structure diagram of sequentially preparing a tunneling oxide layer, an aluminum oxide layer, and a second doped silicon layer on the second surface of the silicon substrate is provided.

[0038] Figure 3 A structure diagram of sequentially preparing a first doped silicon layer on the basis of the structure shown in Figure 2

[0039] Figure 4 A structure diagram of sequentially preparing a first passivation layer and a second passivation layer on the basis of the structure shown in Figure 3

[0040] Figure 5 A structure diagram of sequentially preparing a first metal electrode and a first composite barrier layer on the basis of the structure shown in Figure 4

[0041] BRIEF DESCRIPTION OF DRAWINGS

[0042] 10-silicon substrate; 11-first region; 12-second region; 13-third region; 14-fourth region; 21-first doped silicon layer; 22-second doped silicon layer; 30-first passivation layer; 41-first composite barrier layer; 42-second composite barrier layer; 50-first metal electrode; 60-tunneling oxide layer; 70-aluminum oxide layer; 80-second passivation layer; 90-second metal electrode. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application are described in detail below. In the following description, a large number of specific details are set forth in order to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0044] ​​​Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0045] In the description of the application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0046] In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0047] In this application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, it can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0048] Reference Figure 1As shown, an embodiment of the present application provides a photovoltaic cell, comprising a silicon substrate 10, a doped silicon layer, a recombination barrier layer and a metal electrode; the silicon substrate 10 has a silicon substrate 10 with oppositely arranged first and second surfaces, the first surface includes a first region 11 and a second region 12, and the second surface includes a third region 13 and a fourth region 14; the doped silicon layer is arranged on at least one of the first and second surfaces; the doped silicon layer located in the first region 11 and / or the third region 13 is provided with a recombination barrier layer and a metal electrode on the surface away from the silicon substrate 10, the metal electrode and the doped silicon layer are electrically connected; the recombination barrier layer is arranged between the metal electrode and the doped silicon layer, and the material of the recombination barrier layer includes TiO x and TiN.

[0049] In the above photovoltaic cell, the recombination barrier layer is arranged between the metal electrode and the doped silicon layer in the region provided with the metal electrode, and the material of the recombination barrier layer includes TiO x and TiN, which can control the diffusion depth of metal atoms in the process of preparing the metal electrode, thereby reducing the risk of metal atoms penetrating the doped silicon layer and reducing the leakage current, and thus realizing a higher conversion efficiency of the photovoltaic cell.

[0050] In some embodiments, the material of the recombination barrier layer is a composite material formed by TiO x and TiN.

[0051] In some embodiments, the thickness of the recombination barrier layer is 5nm-8nm.

[0052] Optionally, the thickness of the recombination barrier layer is 5nm, 5.2nm, 5.5nm, 5.8nm, 6nm, 6.2nm, 6.5nm, 6.8nm, 7nm, 7.2nm, 7.5nm, 7.8nm or 8nm, or the thickness of the recombination barrier layer can also be within a range between any two of the above thicknesses.

[0053] In some embodiments, the atomic ratio of N element to O element in the recombination barrier layer is (3-7):7.

[0054] Optionally, the atomic ratio of N element to O element in the recombination barrier layer is 3:7, 3.5:7, 4:7, 4.5:7, 5:7, 5.5:7, 6:7, 6.5:7 or 7:7, or the atomic ratio of N element to O element in the recombination barrier layer can also be within a range between any two of the above atomic ratios.

[0055] In some embodiments, the thickness of the doped silicon layer is 70nm-90nm.

[0056] Optionally, the thickness of the doped silicon layer is 70 nm, 72 nm, 74 nm, 76 nm, 78 nm, 80 nm, 82 nm, 84 nm, 86 nm, 88 nm, or 90 nm, or the thickness of the doped silicon layer can also be within a range between any two of the above thicknesses.

[0057] In some embodiments, the depth of the composite barrier layer into the doped silicon layer accounts for 15% to 20% of the thickness of the doped silicon layer.

[0058] In the conventional sintering of conductive silver paste to prepare a metal electrode, the diffusion depth of silver is usually 80% to 90% of the thickness of the doped silicon layer. In the technical solution of the present application, the diffusion depth of silver is reduced by at least 60% through the blocking of silver diffusion by the composite barrier layer. Referring again to FIG. 1, it can be understood that the depth of the composite barrier layer into the doped silicon layer refers to the distance between the surface of the composite barrier layer close to the silicon substrate 10 and the surface of the doped silicon layer away from the silicon substrate 10. Exemplarily, Figure 1 Figure 1 In the technical solution of the present application, the diffusion depth of silver is reduced by at least 60% through the blocking of silver diffusion by the composite barrier layer. Referring again to FIG. 1, it can be understood that the depth of the composite barrier layer into the doped silicon layer refers to the distance between the surface of the composite barrier layer close to the silicon substrate 10 and the surface of the doped silicon layer away from the silicon substrate 10. Exemplarily,

[0059] In some embodiments, the depth of the composite barrier layer into the doped silicon layer is 12 nm to 18 nm.

[0060] Optionally, the depth of the composite barrier layer into the doped silicon layer is 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, or 18 nm, or the depth of the composite barrier layer into the doped silicon layer can also be within a range between any two of the above depths.

[0061] In some embodiments, the doped silicon layer includes a first doped silicon layer 21 on the first surface and a second doped silicon layer 22 on the second surface, the doping types of the first doped silicon layer 21 and the second doped silicon layer 22 are opposite; the composite barrier layer includes a first composite barrier layer 41 and a second composite barrier layer 42; the metal electrode includes a first metal electrode 50 and a second metal electrode 90;

[0062] The surface of the first doped silicon layer 21 away from the silicon substrate 10 in the first region 11 is sequentially stacked with the first composite barrier layer 41 and the first metal electrode 50; the surface of the second doped silicon layer 22 away from the silicon substrate 10 in the third region 13 is sequentially stacked with the second composite barrier layer 42 and the second metal electrode 90.

[0063] ​In some embodiments, the photovoltaic cell further comprises a tunneling oxide layer 60 and an aluminum oxide layer 70; the tunneling oxide layer 60 is located between the silicon substrate 10 and the first doped silicon layer 21; and the aluminum oxide layer 70 is located between the tunneling oxide layer 60 and the first doped silicon layer 21.

[0064] The aluminum oxide layer 70 is arranged between the tunneling oxide layer 60 and the first doped silicon layer 21, which can fill the oxygen vacancy defects and reduce the interface state density to 5x10 10 cm -2 eV -1 In a conventional TOPCon cell, the interface recombination defects are high, and the interface state density between the doped silicon layer and the tunneling oxide layer 60 is usually greater than 1x10 11 cm -2 eV -1 In the present application, the interface state density between the doped silicon layer and the tunneling oxide layer 60 can be reduced by the aluminum oxide layer 70, thereby improving Voc and conversion efficiency.

[0065] In some embodiments, the thickness of the aluminum oxide layer 70 is 0.2nm-0.5nm.

[0066] It can be understood that the aluminum oxide layer 70 with the above thickness can be prepared by 2-5 cycles of atomic layer deposition. If only one atomic layer is prepared, i.e., an aluminum oxide layer 70 with a thickness of only about 0.11nm is prepared, it is easy to cause the surface dangling bonds and oxygen vacancies of the tunneling oxide layer 60 to be not completely covered. When the thickness of the aluminum oxide layer 70 is too large, it can cause the band structure to deteriorate, form a carrier transport barrier, thereby affecting the transport of carriers, and cause the conversion efficiency to decrease. Within the above range of the thickness of the aluminum oxide layer 70, the conversion efficiency of the photovoltaic cell can be improved. At the same time, the aluminum oxide layer 70 with too large thickness is also easy to cause interface cracks in the subsequent processing process due to the high coefficient of thermal expansion, thereby causing the fragment rate to increase. Alternatively, the thickness of the aluminum oxide layer 70 is 0.2nm, 0.22nm, 0.25nm, 0.28nm, 0.3nm, 0.32nm, 0.35nm, 0.38nm, 0.4nm, 0.42nm, 0.45nm, 0.48nm or 0.5nm, or the thickness of the aluminum oxide layer 70 can also be within the range between any two of the above thicknesses.

[0067] It should be noted that the positions of the aluminum oxide layer 70 and the recombination barrier layer in the present application are relatively independent, but the two can have a synergistic effect in effect. The aluminum oxide layer 70 is used to reduce the interface recombination, so that more carriers can reach the contact area of the photovoltaic cell, at the same time, the recombination barrier layer can reduce the metal recombination and improve the collection efficiency of the carriers, thereby improving the conversion efficiency of the photovoltaic cell. Further, the compressive stress of the aluminum oxide layer 70 can also be used to offset the tensile stress of the sintering of the slurry for preparing the recombination barrier layer in the present application, thereby reducing the fragmentation rate of the wafer. At the same time, since the recombination barrier layer reduces the penetration of metal atoms, the structure of the present application can be used to prepare a lower thickness of the doped silicon layer in the thin silicon wafer, and at the same time, the thinner doped silicon layer produces a high field passivation effect through the aluminum oxide layer 70 and the tunneling oxide layer 60, which can offset the potential risk of the increase of the contact resistance caused by the thin layer. That is, although the recombination barrier layer and the aluminum oxide layer 70 of the present application are respectively optimized for contact and passivation, they can achieve a synergistic effect of structure and effect, and can improve the electrical performance of the photovoltaic cell.

[0068] In some embodiments, the thickness of the tunneling oxide layer 60 is 1 nm to 2 nm.

[0069] Optionally, the thickness of the tunneling oxide layer 60 is 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm or 2 nm, or the thickness of the tunneling oxide layer 60 can also be within a range between any two thicknesses mentioned above.

[0070] In some embodiments, the material of the tunneling oxide layer 60 includes SiO2.

[0071] In some embodiments, the photovoltaic cell further comprises a first passivation layer 30 disposed on the surface of the first doped silicon layer 21 away from the silicon substrate 10, and the first metal electrode 50 and the first doped silicon layer 21 are electrically connected.

[0072] In some embodiments, the material of the first passivation layer 30 includes at least one of aluminum oxide, silicon nitride and silicon oxynitride.

[0073] In some embodiments, the photovoltaic cell further comprises a second passivation layer 80 disposed on the surface of the second doped silicon layer 22 away from the silicon substrate 10, and the second metal electrode 90 and the second doped silicon layer 22 are electrically connected.

[0074] In some embodiments, the material of the second passivation layer 80 includes at least one of aluminum oxide, silicon nitride and silicon oxynitride.

[0075] In some embodiments, the thickness of the silicon substrate 10 is 100 µm to 150 µm.

[0076] It can be understood that the probability of breakage is higher during the manufacturing process when using thin wafer silicon substrate 10. The solar cell structure and manufacturing method of the present application can be applied to a silicon substrate 10 with a thinner thickness, reducing the probability of breakage during the manufacturing process of the photovoltaic cell. It can be understood that an N-type silicon wafer can be used as the silicon substrate 10, and the doping elements include at least one of P, As, Sb and Bi. A P-type silicon wafer can also be used as the silicon substrate 10, and the doping elements include at least one of B, Al, Ga and In.

[0077] A further embodiment of the present application provides a manufacturing method of a photovoltaic cell, the photovoltaic cell being any one of the photovoltaic cells described above, comprising the following steps:

[0078] providing a silicon substrate 10;

[0079] forming a doped silicon layer on at least one of the first surface and the second surface;

[0080] applying an electrode paste on the surface of the doped silicon layer located in the first region 11 and / or the third region 13, the electrode paste comprising an organic carrier, glass powder, Ag particles and TiN particles;

[0081] sintering the electrode paste to form a metal electrode and a composite barrier layer.

[0082] In the present application, the sintering process of the electrode paste with TiN particles can form a composite barrier layer in the area where the electrode is prepared, without the need to add an additional process step to prepare the barrier layer in advance to block the diffusion of silver atoms. During the sintering process, the TiN nanoparticles will react with the natural oxide layer on the silicon surface to form TiO x When the sintering temperature is above 700°C, TiN and TiO x can form a chemical-bonded heterostructure, thereby forming a continuously distributed TiN / TiO x composite barrier layer. It can be understood that the TiN / TiO x composite barrier layer refers to a composite material formed by TiN and TiO x two materials. At the same time, the TiN nanoparticles form a three-dimensional penetration barrier network in the electrode paste, which can increase the tortuosity of the diffusion path of Ag atoms and make Ag atoms preferentially diffuse horizontally along the surface of the TiN nanoparticles rather than vertically penetrate. That is, the manufacturing method of the electrode of the present application can form a composite barrier layer, reducing the risk of silver atoms penetrating the doped silicon layer.

[0083] In some embodiments, the mass percentage of TiN particles in the electrode paste is 3% to 8%.

[0084] Optionally, the TiN particles are present in the electrode slurry in a mass percentage of 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or 8%, or the TiN particles are present in the electrode slurry in a mass percentage within a range between any two of the aforementioned mass percentages.

[0085] In some embodiments, the organic vehicle is present in the electrode slurry in a mass percentage of 10% to 25%.

[0086] Optionally, the organic vehicle is present in the electrode slurry in a mass percentage of 10%, 12%, 15%, 18%, 20%, 22%, or 25%, or the organic vehicle is present in the electrode slurry in a mass percentage within a range between any two of the aforementioned mass percentages.

[0087] In some embodiments, the organic vehicle includes a film former, a solvent, a plasticizer, and a surfactant.

[0088] In some embodiments, the film former includes at least one of ethyl cellulose, nitrocellulose, polyvinylidene, polyvinyl alcohol, polymethylstyrene, polymethyl methacrylate, acrylic resin, and polyvinyl butyral.

[0089] In some embodiments, the solvent includes at least one of terpineol, butyl carbitol acetate, ethylene glycol ethyl ether acetate, tri-butyl citrate, lecithin, diethylene glycol butyl ether acetate, and tri-butyl citrate.

[0090] In some embodiments, the plasticizer includes at least one of dibutyl phthalate, diethylene glycol dibutyl ether, and dioctyl adipate.

[0091] In some embodiments, the surfactant includes at least one of toluene, ethanol, cyclohexanone, dibutyl phthalate, and dioctyl adipate.

[0092] In some embodiments, the glass powder is present in the electrode slurry in a mass percentage of 1% to 5%.

[0093] Optionally, the glass powder is present in the electrode slurry in a mass percentage of 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or the glass powder is present in the electrode slurry in a mass percentage within a range between any two of the aforementioned mass percentages.

[0094] In some embodiments, the glass powder includes SiO2.

[0095] In some embodiments, the glass powder further includes at least one of B2O3 and P2O5.

[0096] In some embodiments, the glass powder further comprises at least one of PbO, ZnO, Bi2O3, Li2O, Al2O3, ZrO2, TiO2, NaF, and CaF2.

[0097] In some embodiments, the Ag particles account for 70% to 90% of the mass percentage of the electrode slurry.

[0098] Optionally, the Ag particles account for 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, or 90% of the mass percentage of the electrode slurry, or the Ag particles can account for a mass percentage within a range between any two of the above mass percentages.

[0099] In some embodiments, the TiN particles have a particle size of 20 nm to 50 nm.

[0100] Optionally, the TiN particles have a particle size of 20 nm, 22 nm, 25 nm, 28 nm, 30 nm, 32 nm, 35 nm, 38 nm, 40 nm, 42 nm, 45 nm, 48 nm, or 50 nm, or the TiN particles can have a particle size within a range between any two of the above particle sizes.

[0101] In some embodiments, the sintering process has a maximum temperature of 700°C to 750°C.

[0102] Optionally, the sintering process has a maximum temperature of 700°C, 705°C, 710°C, 715°C, 720°C, 725°C, 730°C, 735°C, 740°C, 745°C, or 750°C, or the sintering process can have a maximum temperature within a range between any two of the above temperatures.

[0103] In some embodiments, the method for preparing the aluminum oxide layer 70 comprises the following steps:

[0104] The aluminum oxide atomic layers are prepared layer by layer on the surface of the tunneling oxide layer 60 by an aluminum precursor and an oxygen precursor, and the number of the aluminum oxide atomic layers is 2 to 5.

[0105] Optionally, the number of the aluminum oxide atomic layers is 2, 3, 4, or 5.

[0106] In some embodiments, the atomic layer deposition has a temperature of 190°C to 210°C.

[0107] Optionally, the atomic layer deposition has a temperature of 190°C, 192°C, 194°C, 196°C, 198°C, 200°C, 202°C, 204°C, 206°C, 208°C, or 210°C, or the atomic layer deposition can have a temperature within a range between any two of the above temperatures.

[0108] In some embodiments, the oxygen precursor comprises trimethylaluminum.

[0109] In some embodiments, the oxygen precursor comprises water.

[0110] In some embodiments, the pulse ratio of the aluminum precursor and the oxygen precursor is 1:1.

[0111] In some embodiments, the method further comprises the following steps:

[0112] preparing a second doped silicon layer 22 on the second surface of the silicon substrate 10 by boron diffusion using a boron source;

[0113] The boron diffusion comprises a preheating process, a diffusion process and a relaxation process in sequence.

[0114] The temperature of the diffusion process is higher than the temperature of the preheating process, and the temperature of the relaxation process is between the temperature of the diffusion process and the temperature of the preheating process.

[0115] The segmented boron diffusion method of the present application can achieve higher boron diffusion uniformity and reduce the sheet resistance of the boron-doped silicon layer on the back surface of the silicon substrate 10. It should be noted that there is a correlation between the segmented boron diffusion method of the present application and the interface stability of the aluminum oxide layer 70. During the preheating process, the interfacial thermal stress of the tunnel oxide layer 60 and the aluminum oxide layer 70 can be reduced, and the mismatch rate thereof can be reduced. At the same time, it can also avoid the crystallization of the aluminum oxide layer 70 at the initial high temperature stage when the diffusion process is directly performed. The relaxation process can also repair the silicon lattice damage caused by boron diffusion, and reduce the density of the aluminum oxide layer 70 / silicon interface dangling bond. Further, the above-mentioned boron diffusion process can also achieve a relatively gentle doping effect, thereby optimizing the contact band of the composite barrier layer obtained by subsequent slurry sintering treatment. That is, the boron diffusion method of the present application can serve as a key to interface passivation of the aluminum oxide layer 70 and optimization of the electrode structure, and through temperature time sequence control, interface defect repair and metal contact optimization can be simultaneously achieved. The three work together to improve the conversion efficiency of the photovoltaic cell.

[0116] In some embodiments, the holding temperature of the relaxation process is 3.8 times to 4 times the temperature of the atomic layer deposition.

[0117] The relaxation treatment has a better effect of reducing the density of the dangling bonds of the aluminum oxide layer 70 / silicon interface when the holding temperature of the relaxation treatment is in the range of a multiple of the temperature of the atomic layer deposition. Alternatively, the holding temperature of the relaxation treatment is 3.8 times, 3.82 times, 3.84 times, 3.86 times, 3.88 times, 3.9 times, 3.92 times, 3.94 times, 3.96 times, 3.98 times or 4 times of the temperature of the atomic layer deposition, or the holding temperature of the relaxation treatment can also be in the range between any two of the above multiples.

[0118] In some embodiments, the holding temperature of the preheating treatment is 600-700℃, the holding time is 3-7min, and the volume concentration of the boron source is 0.08%-0.12%.

[0119] Alternatively, the holding temperature of the preheating treatment is 600℃, 620℃, 640℃, 660℃, 680℃ or 700℃, or the holding temperature of the preheating treatment can also be in the range between any two of the above holding temperatures.

[0120] Alternatively, the holding time of the preheating treatment is 3min, 3.5min, 4min, 4.5min, 5min, 5.5min, 6min, 6.5min or 7min, or the holding time of the preheating treatment can also be in the range between any two of the above holding times.

[0121] Alternatively, the volume concentration of the boron source of the preheating treatment is 0.08%, 0.085%, 0.09%, 0.095%, 0.1%, 0.105%, 0.11%, 0.115% or 0.12%, or the volume concentration of the boron source of the preheating treatment can also be in the range between any two of the above volume concentrations.

[0122] In some embodiments, the holding temperature of the diffusion treatment is 820-900℃, the holding time is 12-18min, and the volume concentration of the boron source is 0.3%-0.8%.

[0123] Alternatively, the holding temperature of the diffusion treatment is 820℃, 840℃, 860℃, 880℃ or 900℃, or the holding temperature of the diffusion treatment can also be in the range between any two of the above holding temperatures.

[0124] Alternatively, the holding time of the diffusion treatment is 12min, 13min, 14min, 15min, 16min, 17min or 18min, or the holding time of the diffusion treatment can also be in the range between any two of the above holding times.

[0125] Optionally, the volume concentration of the boron source in the diffusion treatment is 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, or 0.8%, or the volume concentration of the boron source in the diffusion treatment can be within the range of any two of the above volume concentrations.

[0126] In some embodiments, the relaxation treatment is held at a temperature of 760°C to 800°C for 6 min to 10 min, and the volume concentration of the boron source is 0.03% to 0.08%.

[0127] Optionally, the relaxation treatment insulation temperature is 760℃, 765℃, 770℃, 775℃, 780℃, 785℃, 790℃, 795℃ or 800℃, or the relaxation treatment insulation temperature can be within the range of any two of the above insulation temperatures.

[0128] Optionally, the holding time for relaxation treatment is 6 min, 7 min, 8 min, 9 min or 10 min, or the holding time for relaxation treatment can be within the range of any two of the above holding times.

[0129] Optionally, the volume concentration of the boron source undergoing relaxation treatment is 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, or 0.08%, or the volume concentration of the boron source undergoing relaxation treatment may be within the range of any two of the above volume concentrations.

[0130] In some embodiments, the method for preparing a photovoltaic cell includes the following steps:

[0131] S10: Provide a silicon substrate 10; sequentially prepare a tunneling oxide layer 60, an aluminum oxide layer 70 and a second doped silicon layer 22 on the second surface;

[0132] Reference Figure 2 As shown, Figure 2 This is a schematic diagram of a structure in which a tunneling oxide layer, an aluminum oxide layer, and a second doped silicon layer are sequentially stacked on the second surface of a silicon substrate.

[0133] S20: A first doped silicon layer 21 is prepared on the first surface;

[0134] Reference Figure 3 As shown, Figure 3 In order to be in Figure 2 A schematic diagram of the structure for fabricating the first doped silicon layer based on the structure shown.

[0135] S30: A first passivation layer 30 is formed on the first doped silicon layer 21, and a second passivation layer 80 is formed on the second doped silicon layer 22;

[0136] Reference Figure 4 As shown,Figure 4 As shown in Figure 3 Structure diagram for preparing the first passivation layer and the second passivation layer based on the structure shown in

[0137] S40: coating electrode paste on the first passivation layer 30 located in the first region 11, and performing sintering treatment on the electrode paste to form the first metal electrode 50 and the first composite barrier layer 41;

[0138] Referring to Figure 5 As shown in Figure 5 As shown in Figure 4 Structure diagram for preparing the first metal electrode 50 and the first composite barrier layer 41 based on the structure shown in

[0139] S50: coating electrode paste on the second passivation layer 80 located in the third region 13, and performing sintering treatment on the electrode paste to form the second metal electrode 90 and the second composite barrier layer 42.

[0140] Referring to Figure 1 As shown in Figure 1 As shown in Figure 5 Structure diagram for preparing the second metal electrode 90 and the second composite barrier layer 42 based on the structure shown in

[0141] In some embodiments, the first doped silicon layer 21 is a P-type doped silicon layer.

[0142] In some embodiments, the material of the P-type doped silicon layer includes at least one of P-type doped amorphous silicon and P-type doped polycrystalline silicon.

[0143] In some embodiments, the doping element of the P-type doped silicon layer includes at least one of B, Al, Ga and In.

[0144] In some embodiments, the second doped silicon layer 22 is an N-type doped silicon layer.

[0145] In some embodiments, the material of the N-type doped silicon layer includes at least one of N-type doped amorphous silicon and N-type doped polycrystalline silicon.

[0146] In some embodiments, the doping element of the N-type doped silicon layer includes at least one of P, As, Sb and Bi.

[0147] Another embodiment of the present application provides a photovoltaic module, comprising:

[0148] a cover plate;

[0149] at least one cell string, the cell string comprising the photovoltaic cell of any one of the above or the photovoltaic cell prepared by the preparation method of the photovoltaic cell of any one of the above;

[0150] and a packaging layer, the packaging layer being between the cover plate and the battery string, the cover plate being connected with the battery string through the packaging layer.

[0151] The following is a specific embodiment:

[0152] Embodiment 1

[0153] A method for preparing a photovoltaic cell:

[0154] (1) providing an N-type silicon substrate 10 with a thickness of 130 µm;

[0155] (2) preparing a 1.2 nm tunneling oxide layer 60 on the second surface, depositing 2 cycles of aluminum oxide atomic layers on the tunneling oxide layer 60 through trimethylaluminum and water atomic layer deposition, obtaining an aluminum oxide layer 70 with a thickness of 0.22 nm, the atomic layer deposition temperature being 200 ℃; depositing a phosphorus-doped polysilicon layer on the aluminum oxide layer 70 through LPCVD;

[0156] (3) preparing a boron-doped silicon layer on the first surface, the preheating treatment having a holding temperature of 650 ℃, a holding time of 5 min, a volume concentration of the boron source of 0.1%, the diffusion treatment having a holding temperature of 850 ℃, a holding time of 15 min, and a volume concentration of the boron source of 0.5%, the relaxation treatment having a holding temperature of 780 ℃, a holding time of 8 min, and a volume concentration of the boron source of 0.05%;

[0157] (4) preparing a first passivation layer 30 on the boron-doped silicon layer and a second passivation layer 80 on the phosphorus-doped silicon layer;

[0158] (5) applying electrode paste to the first passivation layer 30 located in the first region 11, the electrode paste containing 6% glass powder and 5% TiN nanoparticles by mass percentage, and having a viscosity of 35 Pa·s, and performing sintering treatment on the electrode paste, the sintering treatment having a peak temperature of 730 ℃, a duration of 3 s, and a cooling rate of 80 ℃ / s, to form a first metal electrode 50 and a first composite barrier layer 41;

[0159] (6) applying electrode paste to the second passivation layer 80 located in the third region 13, the electrode paste containing 6% glass powder and 5% TiN nanoparticles by mass percentage, and having a viscosity of 35 Pa·s, and performing sintering treatment on the electrode paste, the sintering treatment having a peak temperature of 730 ℃, a duration of 3 s, and a cooling rate of 80 ℃ / s, to form a second metal electrode 90 and a second composite barrier layer 42.

[0160] Embodiment 2

[0161] The method for preparing the photovoltaic cell in Example 2 is basically the same as that in Example 1, with the difference that: in step (2), the aluminum oxide layer 70 is not prepared; in step (3), the diffusion temperature of the boron-doped silicon layer is 850°C, and the holding time is 23 min.

[0162] Comparative Example 1

[0163] The method for preparing the photovoltaic cell in Comparative Example 1 is basically the same as that in Example 1, with the difference that: in step (2), the aluminum oxide layer 70 is not prepared; in step (3), the diffusion temperature of the boron-doped silicon layer is 850°C, and the holding time is 23 min; in steps (5) and (6), the electrode slurry does not contain TiN nanoparticles.

[0164] Comparative Example 2

[0165] The method for preparing the photovoltaic cell in Comparative Example 2 is basically the same as that in Example 1, with the difference that: in steps (5) and (6), the electrode slurry does not contain TiN nanoparticles.

[0166] The photovoltaic cells prepared in Example 1 and Comparative Example 1 are tested, and the test results are shown in Table 1 below. It can be understood that the following test results are the average values of 200 samples.

[0167] Table 1

[0168]

[0169] As can be seen from the test results, the photovoltaic cells prepared in Example 1 and Example 2 have a composite barrier layer between the metal electrode and the doped silicon layer in the region provided with the metal electrode, and the material of the composite barrier layer includes TiO x and TiN, which can control the diffusion depth of metal atoms in the process of preparing the metal electrode, thereby reducing the risk of metal atoms penetrating the doped silicon layer and reducing the leakage current.

[0170] Further, the electrode slurry in Comparative Example 2 does not contain TiN nanoparticles, which can significantly improve the open-circuit voltage, but still has the problem of metal contact, resulting in a large contact resistance and leakage current. In Example 2, compared with Comparative Example 1, only the electrode slurry is improved, which can effectively inhibit the penetration of Ag and improve the contact effect, but cannot improve the bulk passivation and interface passivation, and the improvement of Voc is limited.

[0171] From the test data of Comparative Example 1 and Example 2, Comparative Example 1 and Comparative Example 2, it can be seen that the photovoltaic cell in Example 1 has comprehensively improved performance, including lower contact resistance, leakage current, and higher Voc, average conversion efficiency, compared to the photovoltaic cells in Example 2, Comparative Example 1 and Comparative Example 2. That is, the different improvement points in the present application have a synergistic effect. Further, through the synergistic effect of each improvement point, the wafer breakage rate in Example 1 is also significantly reduced compared to Example 2, Comparative Example 1 and Comparative Example 2.

[0172] The technical features of the above-described embodiments can be combined in any manner. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described, but it should be considered that any combination of the technical features is within the scope of the present disclosure as long as the combination does not result in contradictions.

[0173] The above-described embodiments only express several implementation manners of the present application, and the description is specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the scope of the present application. Therefore, the scope of protection of the patent of the present application should be subject to the appended claims, and the description and drawings can be used to explain the content of the claims.

Claims

1. A photovoltaic cell, characterized by, The application relates to a silicon substrate, a doped silicon layer, a composite barrier layer and a metal electrode; the silicon substrate has a silicon substrate with oppositely arranged first and second surfaces, the first surface comprises a first region and a second region, and the second surface comprises a third region and a fourth region; the doped silicon layer is arranged on at least one of the first and second surfaces; the doped silicon layer in the first and / or third region is provided with the composite barrier layer and the metal electrode on the surface away from the silicon substrate, the metal electrode is electrically connected with the doped silicon layer; the composite barrier layer is arranged between the metal electrode and the doped silicon layer, and the material of the composite barrier layer comprises TiO x and TiN.

2. The photovoltaic cell of claim 1, wherein, The thickness of the composite barrier layer is 5-8 nm.

3. The photovoltaic cell of claim 1, wherein, In the composite barrier layer, the atomic ratio of N element and O element is (3-7):

7.

4. The photovoltaic cell of claim 1, wherein, The thickness of the doped silicon layer is 70-90 nm.

5. The photovoltaic cell of claim 1, wherein, The depth of the composite barrier layer into the doped silicon layer accounts for 15-20% of the thickness of the doped silicon layer.

6. The photovoltaic cell of claim 1, wherein, The depth of the composite barrier layer into the doped silicon layer is 12-18 nm.

7. The photovoltaic cell according to any one of claims 1 to 6, wherein, The doped silicon layer comprises a first doped silicon layer on the first surface and a second doped silicon layer on the second surface, the doping types of the first doped silicon layer and the second doped silicon layer are opposite; the composite barrier layer comprises a first composite barrier layer and a second composite barrier layer; the metal electrode comprises a first metal electrode and a second metal electrode; The surface of the first doped silicon layer in the first region away from the silicon substrate is sequentially stacked with the first composite barrier layer and the first metal electrode; the surface of the second doped silicon layer in the third region away from the silicon substrate is sequentially stacked with the second composite barrier layer and the second metal electrode.

8. The photovoltaic cell of claim 7, wherein, The photovoltaic cell further comprises a tunneling oxide layer and an aluminum oxide layer; the tunneling oxide layer is between the silicon substrate and the second doped silicon layer; the aluminum oxide layer is between the tunneling oxide layer and the second doped silicon layer.

9. The photovoltaic cell of claim 8, wherein, The thickness of the aluminum oxide layer is 0.2-0.5 nm.

10. A method for producing a photovoltaic cell, the photovoltaic cell being the photovoltaic cell according to any one of claims 1 to 9, characterized by, The method comprises the following steps: Providing the silicon substrate; Preparing a doped silicon layer on at least one of the first surface and the second surface; Coating an electrode slurry on the surface of the doped silicon layer in the first region and / or the third region, the electrode slurry comprising an organic carrier, glass powder, Ag particles and TiN particles; Sintering the electrode slurry to form the metal electrode and the composite barrier layer.

11. The method of claim 10, wherein the method further comprises: The mass percentage of the TiN particles in the electrode slurry is 3-8%; and / or, The particle size of the TiN particles is 20-50 nm.

12. The method of claim 10, wherein the method further comprises: The highest temperature of the sintering process is 700-750℃.

13. The method of claim 10, wherein the method further comprises: The doped silicon layer comprises a first doped silicon layer on the first surface and a second doped silicon layer on the second surface, the doping types of the first doped silicon layer and the second doped silicon layer are opposite; the composite barrier layer comprises a first composite barrier layer and a second composite barrier layer; the metal electrode comprises a first metal electrode and a second metal electrode; The surface of the first doped silicon layer in the first region away from the silicon substrate is sequentially stacked with the first composite barrier layer and the first metal electrode; the surface of the second doped silicon layer in the third region away from the silicon substrate is sequentially stacked with the second composite barrier layer and the second metal electrode; The photovoltaic cell further comprises a tunneling oxide layer and an aluminum oxide layer; the tunneling oxide layer is between the silicon substrate and the first doped silicon layer; the aluminum oxide layer is between the tunneling oxide layer and the first doped silicon layer; The preparation method of the aluminum oxide layer comprises the following steps: An aluminum oxide atomic layer is prepared on the surface of the tunneling oxide layer by atomic layer deposition using an aluminum precursor and an oxygen precursor, and the number of layers of the aluminum oxide atomic layer is 2-5 layers.

14. The method of claim 13, wherein the method further comprises: Further comprising the following steps: A second doped silicon layer is prepared on the second surface of the silicon substrate by boron diffusion using a boron source; The boron diffusion comprises a preheating process, a diffusion process and a relaxation process performed in sequence; The temperature of the diffusion process is higher than the temperature of the preheating process, and the temperature of the relaxation process is between the temperature of the diffusion process and the temperature of the preheating process.

15. A photovoltaic module, characterized by, Comprise: A cover plate; At least one battery string comprising the photovoltaic cell of any one of claims 1-9, or the photovoltaic cell prepared by the method of any one of claims 10-14; And a packaging layer between the cover plate and the battery string, the cover plate being connected with the battery string through the packaging layer.

Images