Back contact solar cell, photovoltaic module and photovoltaic system

Abstract

The invention is applicable to the technical field of back contact solar cells, and provides a back contact solar cell, a photovoltaic module and a photovoltaic system.The back contact solar cell comprises a silicon substrate, a first doped region, a second doped region and a passivation layer, the first electrode penetrates through the passivation layer and is in contact with the first doped region, the second electrode penetrates through the passivation layer and is in contact with the second doped region, each of the first electrode and the second electrode comprises a first region and a second region, the first region is close to the silicon substrate, and the second region is far away from the silicon substrate; the metal crystal density of the first region is smaller than that of the second region, and the metal doping concentration of the first region is smaller than that of the second region. Through the arrangement, the first region with low metal crystal density and low metal doping concentration is formed at the part, close to the substrate, of the metal electrode, so that the slurry concentration of silver slurry in the passivation layer is reduced, the formation of a composite center is reduced or even avoided, and the open voltage of the solar cell is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of back-contact solar cells, and in particular relates to a back-contact solar cell, a photovoltaic module and a photovoltaic system. Background Art

[0002] Since the back-contact solar cell has no main grid line on the front, the positive and negative electrodes are arranged on the back of the battery, which reduces shading and effectively increases the short circuit of the battery, thereby improving the energy conversion efficiency of the solar cell and thus has broad application prospects.

[0003] At present, in the production and preparation process of back-contact solar cells, silver paste is printed on the back of the back-contact solar cell, and metal electrodes are prepared by high-temperature sintering. The silver paste contains a certain amount of glass, which will corrode the passivation layer, so that the metal silver in the silver paste passes through the passivation layer and contacts the doped layer on the back of the back-contact solar cell. At the same time, the silver crystals will be burned into the passivation layer along with the glass. However, the existing silver paste concentration in the passivation layer is too high, which will cause paste damage, form a large number of composite centers, and lead to low opening voltage. Summary of the invention

[0004] The embodiment of the present invention provides a back-contact solar cell, aiming to solve the problem that a large number of recombination centers are formed during the preparation of metal electrodes in the existing back-contact solar cells, resulting in a low opening voltage.

[0005] The embodiment of the present invention is implemented as follows: a back contact solar cell, comprising:

[0006] A silicon substrate, wherein a plurality of first doping regions and a plurality of second doping regions are arranged alternately in sequence along a first direction on the back side of the silicon substrate, and the polarities of the first doping regions and the second doping regions are opposite;

[0007] A passivation layer is disposed on a side of the first doped region and the second doped region away from the silicon substrate;

[0008] A first electrode passing through the passivation layer and contacting the first doped region; and

[0009] a second electrode passing through the passivation layer and contacting the second doped region;

[0010] The first electrode and the second electrode both include a first region and a second region, the first region is close to the silicon substrate, the second region is far from the silicon substrate, the metal crystal density of the first region is smaller than the metal crystal density of the second region, and the metal doping concentration of the first region is smaller than the metal doping concentration of the second region.

[0011] Furthermore, the metal crystal density of the first region is C1, 1 / 10 -6 mm 2 ≤C1≤20 / 10 -6 mm2 , the metal crystal density in the second region is C2,7 / 10 -6 mm 2 ≤C2≤50 / 10 -6 mm 2 .

[0012] Furthermore, the metal doping concentration of the first region is D1, 1.0E19≤D1≤8.0E19, and the metal doping concentration of the second region is D2, 1.0E20≤D2≤9.0E20.

[0013] Furthermore, the first electrode and the second electrode include the following components in percentage by mass:

[0014] Silver powder 90%-95%, glass 0.5%-1% and organic carrier 4%-9.5%.

[0015] Furthermore, the glass body comprises the following components in percentage by weight:

[0016] Bismuth trioxide 90% to 96%, cerium oxide 1% to 2%, silicon oxide 1% to 5% and metal tungsten 2% to 3%.

[0017] Furthermore, the silver powder is at least one of fine spherical and flaky silver powders.

[0018] Furthermore, the particle size of the silver powder is 0.4 to 5 μm.

[0019] Furthermore, the silicon substrate is an N-type silicon wafer or a P-type silicon wafer.

[0020] Furthermore, the back side of the silicon substrate is a polished surface or a textured surface.

[0021] In a second aspect, the present application also provides a photovoltaic module, comprising the back-contact solar cell as described above.

[0022] In a third aspect, the present application also provides a photovoltaic system, comprising the photovoltaic assembly as described above.

[0023] Beneficial effects of the present application: The back-contact solar cell provided by the present application includes a silicon substrate, and the back side of the silicon substrate is provided with a plurality of first doping regions and a plurality of second doping regions arranged alternately in sequence along a first direction, the polarities of the first doping regions and the second doping regions are opposite, a passivation layer is provided on a side of the first doping region and the second doping region away from the silicon substrate, a first electrode passing through the passivation layer and contacting the first doping region, and a second electrode passing through the passivation layer and contacting the second doping region, the first electrode and the second electrode both include a first region and a second region, the first region is close to the silicon substrate, the second region is far from the silicon substrate, the metal crystal density of the first region is less than the metal crystal density of the second region, and the metal doping concentration of the first region is less than the metal doping concentration of the second region. Through the above-mentioned arrangement, a first region with low metal crystal density and low metal doping concentration is formed through the part of the metal electrode close to the substrate, and the slurry concentration of the silver paste in the passivation layer is reduced, thereby reducing or even avoiding the formation of recombination centers, and improving the opening voltage of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of an embodiment of a back contact solar cell provided by the present application;

[0025] Figure 2 It is a schematic diagram of the microstructure of an embodiment of a back-contact solar cell provided in the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] In the description of the present invention, it is necessary to understand that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0029] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or mutual communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0031] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference values ​​and / or reference letters in different examples, and this repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the examples of various specific processes and materials provided by the present invention, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0032] The back-contact solar cell provided by the present application includes a silicon substrate, and the back side of the silicon substrate is provided with a plurality of first doping regions and a plurality of second doping regions arranged alternately in sequence along a first direction, the polarities of the first doping regions and the second doping regions are opposite, a passivation layer is provided on a side of the first doping region and the second doping region away from the silicon substrate, a first electrode passing through the passivation layer and contacting the first doping region, and a second electrode passing through the passivation layer and contacting the second doping region, the first electrode and the second electrode both include a first region and a second region, the first region is close to the silicon substrate, the second region is far from the silicon substrate, the metal crystal density of the first region is less than the metal crystal density of the second region, and the metal doping concentration of the first region is less than the metal doping concentration of the second region. Through the above-mentioned arrangement, a first region with low metal crystal density and low metal doping concentration is formed through the part of the metal electrode close to the substrate, and the slurry concentration of the silver paste in the passivation layer is reduced, thereby reducing or even avoiding the formation of recombination centers, and improving the opening voltage of the solar cell.

[0033] Embodiment 1

[0034] like Figure 1 to Figure 2 As shown, one embodiment of the present application provides a back contact solar cell, comprising:

[0035] A silicon substrate 100, wherein a plurality of first doping regions 110 and a plurality of second doping regions 120 are arranged alternately in sequence along a first direction on the back side of the silicon substrate 100, wherein the polarities of the first doping regions 110 and the second doping regions 120 are opposite;

[0036] A passivation layer 200 disposed on a side of the first doping region 110 and the second doping region 120 away from the silicon substrate 100;

[0037] A first electrode 300 passing through the passivation layer 200 and contacting the first doping region 110; and

[0038] A second electrode 400 passing through the passivation layer 200 and contacting the second doping region 120;

[0039] The first electrode 300 and the second electrode 400 both include a first region and a second region, the first region is close to the silicon substrate 100, the second region is far away from the silicon substrate 100, the metal crystal density of the first region is less than the metal crystal density of the second region, and the metal doping concentration of the first region is less than the metal doping concentration of the second region.

[0040] During implementation, the silicon substrate 100 can be an N-type silicon wafer or a P-type silicon wafer, wherein the N-type silicon wafer is obtained by adding pentavalent elements (such as phosphorus or arsenic) to the silicon raw material, and these pentavalent elements provide additional free electrons; the P-type silicon wafer is obtained by adding trivalent elements (such as boron or gallium) to the silicon raw material, and these trivalent elements control the diffusion of electron holes, which will not be elaborated.

[0041] The silicon substrate 100 has a front side and a back side, wherein the front side of the silicon substrate 100 corresponds to the light-receiving side of the solar cell, and similarly, the back side of the silicon substrate 100 corresponds to the backlight side of the solar cell. Optionally, the silicon substrate 100 may be a single crystal silicon wafer, which is a single crystal formed by slowly cooling the silicon raw material after melting, and has a compact and orderly crystal structure, and has high conversion efficiency, stability and life. Optionally, the silicon substrate 100 may be a polycrystalline silicon wafer, which is a form of single-substance silicon, in which when the molten single-substance silicon solidifies under supercooling conditions, the silicon atoms are arranged in the form of a diamond lattice into many crystal nuclei, and if these crystal nuclei grow into grains with different crystal plane orientations, these grains are combined to crystallize into polycrystalline silicon.

[0042] Optionally, the surface of the silicon substrate 100 can be a polished surface or a textured surface, without limitation. The textured surface is obtained by performing a texture process on the surface of the silicon substrate 100 to produce an uneven pyramid structure on the surface of the silicon substrate 100, and the light trapping effect of the uneven textured surface is utilized to increase the absorption of sunlight, reduce the reflectivity, increase the short-circuit current, and improve the photoelectric conversion efficiency of the solar cell.

[0043] Optionally, the texturing process includes but is not limited to acid texturing, alkali texturing, mechanical texturing, electrochemical texturing, reactive ion etching texturing, laser texturing and mask texturing, etc., which will not be elaborated herein.

[0044] A plurality of first doping regions 110 and a plurality of second doping regions 120 are arranged on the back side of the silicon substrate 100 . The first doping regions 110 and the second doping regions 120 are alternately arranged in sequence along the first direction. That is, a second doping region 120 is arranged between two adjacent first doping regions 110 . Similarly, a first doping region 110 is arranged between two adjacent second doping regions 120 .

[0045] In implementation, the first direction refers to a direction parallel to the thin grid of the solar cell. Exemplarily, when the thin grid of the solar cell extends horizontally, the first doping region 110 and the second doping region 120 are alternately arranged and distributed in the horizontal direction, and a spacing groove is provided between the first doping region 110 and the second doping region 120, and the spacing groove extends in the vertical direction. Similarly, when the thin grid of the solar cell extends vertically, the first doping region 110 and the second doping region 120 are alternately arranged and distributed in the vertical direction, and a spacing groove is provided between the first doping region 110 and the second doping region 120, and the spacing groove extends in the horizontal direction.

[0046] The polarities of the first doping region 110 and the second doping region 120 are opposite, that is, when the first doping region 110 is an anode region, the second doping region 120 is a cathode region, and when the first doping region 110 is a cathode region, the second doping region 120 is an anode region.

[0047] A passivation layer 200 is also provided on the back of the solar cell. During implementation, the passivation layer 200 is a passivation film provided on the back of the solar cell. The passivation film is used to improve the photoelectric conversion efficiency and stability of the solar cell, reduce surface damage and oxidation reaction of the solar cell, and extend the service life of the solar cell.

[0048] In some possible embodiments, the passivation film includes titanium dioxide, aluminum oxide, ferric oxide, etc., without limitation. Preferably, the passivation film can be made of aluminum oxide to ensure light absorption rate.

[0049] The solar cell further includes a first electrode 300 and a second electrode 400, which are fine grids of the solar cell, and the polarities of the first electrode 300 and the second electrode 400 are related to the polarities of the first doping region 110 and the second doping region 120. For example, when the first doping region 110 is a positive electrode region, the first electrode 300 is a positive electrode, the second doping region 120 is a negative electrode region, and the second electrode 400 is a negative electrode; when the first doping region 110 is a negative electrode region, the first electrode 300 is a negative electrode, the second doping region 120 is a positive electrode region, and the second electrode 400 is a positive electrode.

[0050] The first electrode 300 and the second electrode 400 are made by printing silver paste and sintering at high temperature. The silver paste includes the following components in mass percentage:

[0051] Silver powder 90%-95%, glass 0.5%-1% and organic carrier 4%-9.5%.

[0052] Silver powder is a conductive phase and its main function is to conduct electricity. The quality of silver powder directly affects the volume resistance and contact resistance of the electrode material.

[0053] The glass body is a bonding phase, and its function is to be a conductive film layer medium, connecting the conductive phase and the silicon substrate 100. If its own component ratio and overall content in the silver paste are too high, the conductivity of the silver paste will deteriorate, and if it is too low, it cannot penetrate into the passivation layer 200 and the silicon substrate 100 to form a conductive contact.

[0054] The organic carrier is composed of organic matter and part of liquid. Its main function is to transport the conductive phase and the adhesive phase and control the fluidity of the slurry.

[0055] In some possible embodiments, the silver paste consists of 90% silver powder, 0.5% glass and 9.5% organic vehicle.

[0056] As a possible embodiment, the silver paste is composed of 91% silver powder, 1% glass and 8% organic vehicle.

[0057] As a possible embodiment, the silver paste is composed of 92% silver powder, 1% glass and 7% organic vehicle.

[0058] As a possible embodiment, the silver paste is composed of 95% silver powder, 0.6% glass and 4.4% organic vehicle.

[0059] As a possible embodiment, the silver paste is composed of 93% silver powder, 1% glass and 4% organic vehicle.

[0060] It should be noted that the above-mentioned embodiments list the mass percentage of each component in the silver paste as an example of the embodiments of the present application, rather than a specific limitation of the present application. In some other embodiments, the mass percentage of each component in the silver paste may also use other values ​​without limitation.

[0061] During implementation, the preparation process of the first electrode 300 and the second electrode 400 includes:

[0062] The silver paste is placed in a drying area for drying. The drying process can evaporate the organic matter in the silver paste and remove impurities in the silver paste to ensure the quality of the sintered electrode.

[0063] The silver paste after drying is pre-sintered, that is, the silver paste is heated to raise the temperature to about 500°.

[0064] The silver paste is sintered by raising the temperature to about 700 degrees, so that the glass body and the passivation layer 200 react and corrode, and the metal silver and silicon react to generate a silicon-silver compound, thereby forming a good ohmic contact.

[0065] In some embodiments, after the silver paste is sintered at high temperature, the battery cell needs to be cooled. On the one hand, the silver paste is cooled and solidified to form a metal electrode. On the other hand, the battery cell can be cooled to room temperature before subsequent process steps can be performed.

[0066] After the first electrode 300 and the second electrode 400 are prepared, the first electrode 300 passes through the passivation layer 200 to contact the first doping region 110, and the second electrode 400 passes through the passivation layer 200 to contact the second doping region 120. The first electrode 300 can be divided into a first region and a second region, and similarly, the second electrode 400 can also be divided into a first region and a second region. Compared with the first region and the second region, the first region is close to the silicon substrate 100, while the second region is far away from the silicon substrate 100.

[0067] For ease of understanding, illustratively, the first electrode 300 may be divided into a first region 310 and a second region 320, and the second electrode 400 may be divided into a first region 410 and a second region 420, as shown in FIG. Figure 1 As shown, no further elaboration is given.

[0068] It should be noted that the above Figure 1 The proportions of the first region and the second region in the metal electrode and the boundary between the two are illustrative of an embodiment of the present application, rather than a specific limitation of the present application. In other embodiments, other methods may be used to set the proportions of the first region and the second region in the metal electrode and the boundary between the two, as long as the first region is close to the silicon substrate 100 and the second region is far from the silicon substrate 100, without limitation.

[0069] During the sintering process, the glass body reacts with the passivation layer 200 to corrode the passivation layer 200, so that the metallic silver in the silver paste passes through the passivation layer 200 and contacts the doping layer on the back of the back-contact solar cell. At the same time, the silver crystals are burned into the passivation layer 200 along with the glass body, so that the metal crystal density in the first region is less than that in the second region, and the metal doping concentration in the first region is less than that in the second region.

[0070] In some embodiments, the metal crystal density of the first region is C1, 1 / 10 -6 mm 2 ≤C1≤20 / 10 -6 mm 2 For example, the metal crystal density in the first region is 2 / 10 -6 mm 2 , 3 / 10 -6 mm 2 , 4 / 10 -6 mm 2 , 5 / 10 -6 mm 2 , 8 / 10 -6 mm 2 , 10 / 10 -6 mm 2 , 11 / 10 -6 mm 2 , 12 / 10 -6 mm 2 , 15 / 10 -6 mm 2 , 17 / 10 -6 mm 2 、19 / 10 -6 mm 2 or 1 / 10 -6 mm 2 Until 20 / 10 - 6 mm 2 Any numerical value in is not specifically limited.

[0071] The metal crystal density in the second region is C2, 7 / 10-6 mm 2 ≤C2≤50 / 10 -6 mm 2 For example, the metal crystal density in the second region is 8 / 10 -6 mm 2 , 9 / 10 -6 mm 2 , 10 / 10 -6 mm 2 , 11 / 10 -6 mm 2 , 12 / 10 -6 mm 2 , 15 / 10 -6 mm 2 、16 / 10 - 6 mm 2 , 18 / 10 -6 mm 2 、19 / 10 -6 mm 2 , 20 / 10 -6 mm 2 , 25 / 10 -6 mm 2 , 30 / 10 -6 mm 2 , 35 / 10 -6 mm 2 , 40 / 10 -6 mm 2 , 45 / 10 -6 mm 2 or 7 / 10 -6 mm 2 Up to 50 / 10 -6 mm 2 Any numerical value in is not specifically limited.

[0072] Further, the metal doping concentration of the first region is D1, 1.0E19≤D1≤8.0E19. Exemplarily, the metal doping concentration of the first region is 1.0E19, 1.5E19, 1.6E19, 1.7E19, 1.8E19, 2.0E19, 3.0E19, 4.0E19, 5.0E19, 6.0E19, 7.0E19 or any value from 1.0E19 to 8.0E19, without specific limitation.

[0073] The metal doping concentration of the second region is D2, 1.0E20≤D2≤9.0E20. E20 refers to 10 20 , which means that there are 10 20 metal atoms or molecules, and similarly, E19 refers to 10 19, which means that there are 10 19 Metal atoms or molecules, the unit area is usually cubic centimeters.

[0074] Exemplarily, the metal doping concentration of the second region is 1.0E20, 1.2E20, 1.3E20, 1.4E20, 1.8E20, 2.0E20, 3.0E20, 4.0E20, 5.0E20, 6.0E20, 7.0E20, 8.0E20 or any value from 1.0E20 to 9.0E20, without specific limitation.

[0075] The back contact solar cell provided in the present application includes a silicon substrate 100, and the back side of the silicon substrate 100 is provided with a plurality of first doping regions 110 and a plurality of second doping regions 120 arranged alternately in sequence along a first direction, the polarities of the first doping regions 110 and the second doping regions 120 are opposite, a passivation layer 200 is provided on a side of the first doping region 110 and the second doping region 120 away from the silicon substrate 100, a first electrode 300 passing through the passivation layer 200 and contacting the first doping region 110, and a second electrode 400 passing through the passivation layer 200 and contacting the second doping region 120, the first electrode 300 and the second electrode 400 both include a first region and a second region, the first region is close to the silicon substrate 100, the second region is far away from the silicon substrate 100, the metal crystal density of the first region is less than the metal crystal density of the second region, and the metal doping concentration of the first region is less than the metal doping concentration of the second region. Through the above-mentioned configuration, a first region with low metal crystal density and low metal doping concentration is formed by the part of the metal electrode close to the substrate, and the slurry concentration of the silver paste in the passivation layer 200 is reduced, thereby reducing or even avoiding the formation of the recombination center, and improving the opening voltage of the solar cell.

[0076] In some optional embodiments, the glass body includes the following components in percentage by weight:

[0077] Bismuth trioxide 90% to 96%, cerium oxide 1% to 2%, silicon oxide 1% to 5% and metal tungsten 2% to 3%.

[0078] In some embodiments, the glass body is composed of 90% bismuth trioxide, 2% cerium oxide, 5% silicon oxide, and 3% metallic tungsten.

[0079] As a possible implementation, the glass body is composed of 91% bismuth trioxide, 2% cerium oxide, 4% silicon oxide and 3% metal tungsten.

[0080] As a possible implementation, the glass body is composed of 92% bismuth trioxide, 3% cerium oxide, 2% silicon oxide and 3% metal tungsten.

[0081] As a possible implementation, the glass body is composed of 93% bismuth trioxide, 2% cerium oxide, 3% silicon oxide and 2% metal tungsten.

[0082] As a possible implementation, the glass body is composed of 94% bismuth trioxide, 1% cerium oxide, 2% silicon oxide and 3% metal tungsten.

[0083] It should be noted that the mass percentages of the components of the glass body listed in the above-mentioned embodiments are illustrative examples of the embodiments of the present application, and are not specific limitations of the present application. In some other embodiments, the mass percentages of the components of the glass body may also use other values ​​without limitation.

[0084] In some optional embodiments, the silver powder is at least one of fine spherical and flaky silver powder. In practice, when the silver powder is fine spherical, it can be regarded as spherical silver powder. Spherical silver powder is a silver powder with a spherical or nearly spherical structure, with high roundness and uniform particle distribution, which is conducive to improving the fluidity and coating properties of the conductive silver paste. In addition, the surface of the spherical silver powder particles is relatively smooth, which is conducive to reducing the contact resistance between particles and improving the conductive performance and reliability.

[0085] As a possible implementation method, the particle size of the spherical silver powder is generally between 400 nanometers and 5 micrometers, and the particle size can be controlled to meet different application requirements.

[0086] Optionally, the particle size of the flaky silver powder is usually between several microns and more than ten microns, and has a large specific surface area, which can provide more contact area and enhance the conductive performance.

[0087] Optionally, the average thickness of the flaky silver powder is generally between tens and one hundred nanometers, which makes it have good conductivity and plasticity, and can effectively reduce resistance and improve conductivity efficiency.

[0088] In some possible embodiments, since flaky silver powder has good stability in the conductive silver paste, can maintain its conductive properties for a long time, and is not easily oxidized or deteriorated, flaky silver powder is preferably used.

[0089] Embodiment 2

[0090] In some optional embodiments, the present application provides a photovoltaic module, comprising the back-contact solar cell as described above.

[0091] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the structure and implementation principle of the photovoltaic assembly described above can refer to the corresponding structure and implementation principle in the aforementioned embodiment 1, and will not be repeated here.

[0092] The back contact solar cell provided in the present application includes a silicon substrate 100, and the back side of the silicon substrate 100 is provided with a plurality of first doping regions 110 and a plurality of second doping regions 120 arranged alternately in sequence along a first direction, the polarities of the first doping regions 110 and the second doping regions 120 are opposite, a passivation layer 200 is provided on a side of the first doping region 110 and the second doping region 120 away from the silicon substrate 100, a first electrode 300 passing through the passivation layer 200 and contacting the first doping region 110, and a second electrode 400 passing through the passivation layer 200 and contacting the second doping region 120, the first electrode 300 and the second electrode 400 both include a first region and a second region, the first region is close to the silicon substrate 100, the second region is far away from the silicon substrate 100, the metal crystal density of the first region is less than the metal crystal density of the second region, and the metal doping concentration of the first region is less than the metal doping concentration of the second region. Through the above-mentioned configuration, a first region with low metal crystal density and low metal doping concentration is formed by the part of the metal electrode close to the substrate, and the slurry concentration of the silver paste in the passivation layer 200 is reduced, thereby reducing or even avoiding the formation of the recombination center, and improving the opening voltage of the solar cell.

[0093] Embodiment 3

[0094] In some optional embodiments, the present application provides a photovoltaic system, including the photovoltaic component as described above.

[0095] Those skilled in the art can clearly understand that, for the convenience and simplicity of description, the structure and implementation principle of the photovoltaic system described above can refer to the corresponding structure and implementation principle in the aforementioned embodiments one and two, and will not be repeated here.

[0096] The back contact solar cell provided in the present application includes a silicon substrate 100, and the back side of the silicon substrate 100 is provided with a plurality of first doping regions 110 and a plurality of second doping regions 120 arranged alternately in sequence along a first direction, the polarities of the first doping regions 110 and the second doping regions 120 are opposite, a passivation layer 200 is provided on a side of the first doping region 110 and the second doping region 120 away from the silicon substrate 100, a first electrode 300 passing through the passivation layer 200 and contacting the first doping region 110, and a second electrode 400 passing through the passivation layer 200 and contacting the second doping region 120, the first electrode 300 and the second electrode 400 both include a first region and a second region, the first region is close to the silicon substrate 100, the second region is far away from the silicon substrate 100, the metal crystal density of the first region is less than the metal crystal density of the second region, and the metal doping concentration of the first region is less than the metal doping concentration of the second region. Through the above-mentioned configuration, a first region with low metal crystal density and low metal doping concentration is formed by the part of the metal electrode close to the substrate, and the slurry concentration of the silver paste in the passivation layer 200 is reduced, thereby reducing or even avoiding the formation of the recombination center, and improving the opening voltage of the solar cell.

[0097] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A back contact solar cell, characterized in that: include: A silicon substrate, wherein a plurality of first doping regions and a plurality of second doping regions are arranged alternately in sequence along a first direction on the back side of the silicon substrate, and the polarities of the first doping regions and the second doping regions are opposite; A passivation layer disposed on a side of the first doped region and the second doped region away from the silicon substrate; a first electrode passing through the passivation layer and contacting the first doped region; as well as a second electrode passing through the passivation layer and contacting the second doped region; The first electrode and the second electrode each include a first region and a second region, the first region is close to the silicon substrate, the second region is far from the silicon substrate, the metal crystal density of the first region is smaller than the metal crystal density of the second region, and the metal doping concentration of the first region is smaller than the metal doping concentration of the second region.

2. The back contact solar cell according to claim 1, characterized in that The metal crystal density of the first region is C1,1 / 10 -6 mm 2 ≤C1≤20 / 10 -6 mm 2 , the metal crystal density of the second region is C2,7 / 10 -6 mm 2 ≤C2≤50 / 10 -6 mm 2 .

3. The back contact solar cell according to claim 1, characterized in that The metal doping concentration of the first region is D1, 1.0E19≤D1≤8.0E19, and the metal doping concentration of the second region is D2, 1.0E20≤D2≤9.0E20.

4. The back contact solar cell according to claim 1, characterized in that: The first electrode and the second electrode include the following components in percentage by mass: Silver powder 90%-95%, glass 0.5%-1% and organic carrier 4%-9.5%.

5. The back contact solar cell according to claim 4, characterized in that The glass body comprises the following components in percentage by weight: Bismuth trioxide 90% to 96%, cerium oxide 1% to 2%, silicon oxide 1% to 5% and metal tungsten 2% to 3%.

6. The back contact solar cell according to claim 4, characterized in that: The silver powder is at least one of fine spherical and flaky silver powders.

7. The back contact solar cell according to claim 4, characterized in that: The particle size of the silver powder is 0.4-5 μm.

8. The back-contact solar cell according to any one of claims 1 to 7, characterized in that The silicon substrate is an N-type silicon wafer or a P-type silicon wafer.

9. The back-contact solar cell according to any one of claims 1 to 7, characterized in that The back side of the silicon substrate is a polished surface or a textured surface.

10. A photovoltaic module, characterized in that: A back-contact solar cell comprising the method of any one of claims 1 to 9.

11. A photovoltaic system, characterized in that: Comprising the photovoltaic module as claimed in claim 10.

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