Solar cell

Abstract

The utility model discloses a solar cell, which comprises a silicon substrate, and a first dielectric layer, a first doping layer, a second dielectric layer and a second doping layer which are sequentially arranged on a first surface of the silicon substrate, the doping type of the first doping layer is the same as that of the second doping layer, and the doping concentration of the second doping layer is greater than that of the first doping layer. And the doping concentration of the second doping layer is sequentially reduced from the second surface to the first surface. According to the solar cell, the contact resistivity of metal and a semiconductor can be reduced, and the conversion efficiency of the solar cell is improved. In addition, the possibility of diffusion of doped elements from low concentration to high concentration can be reduced, and the passivation effect is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of photovoltaic power generation, in particular to a solar cell. Background Art

[0002] Passivated contact cell is a solar cell that uses an ultra-thin dielectric layer as the passivation layer structure. The substrate of the passivated contact cell is usually based on an N-type silicon substrate. An ultra-thin silicon oxide dielectric layer is prepared on the back of the cell, and a doped polysilicon thin layer is deposited. The two together form a passivated contact structure.

[0003] In the related technology, as the concentration of the doping layer increases, it helps to reduce the contact resistivity of the metal and semiconductor and improve the battery conversion efficiency. However, further increasing the concentration of the doping layer will increase the ability to penetrate the dielectric layer, causing the doping elements in the doping layer to diffuse into the dielectric layer and silicon, affecting the passivation effect. Utility Model Content

[0004] The utility model discloses a solar cell, which can improve the passivation performance and enhance the conversion efficiency of the cell.

[0005] In order to achieve the above object, the utility model discloses a solar cell, comprising:

[0006] A silicon substrate having a first surface and a second surface disposed opposite to each other;

[0007] A first dielectric layer, a first doping layer, a second dielectric layer and a second doping layer are sequentially arranged on the first surface;

[0008] The first doping layer and the second doping layer have the same doping type, and the doping concentration of the second doping layer is greater than the doping concentration of the first doping layer. The doping concentration of the second doping layer decreases in sequence along the direction from the second surface to the first surface.

[0009] As an optional implementation, the doping concentration of the second doping layer is 5.0E 20 cm -3 -1.0E 21 cm -3 , and the thickness of the second doping layer is 90nm-150nm.

[0010] As an optional implementation, the number of the second doping layers is three, and in the direction from the second surface to the first surface, the doping concentrations of the three second doping layers are 8.0E 20 cm -3 -1.0E 21 cm -3 , 6.0E 20 cm-3 -8.0E 20 cm -3 , 5.0E 20 cm -3 -7.0E 20 cm -3 .

[0011] As an optional implementation, along the direction from the second surface to the first surface, the thicknesses of the three second doping layers are 40 nm-60 nm, 30 nm-50 nm, and 20 nm-40 nm, respectively.

[0012] As an optional implementation manner, the thickness of the first doping layer is 30nm-50nm, and / or the doping concentration of the first doping layer is 1E 20 cm -3 -5E 20 cm -3 .

[0013] As an optional implementation manner, the silicon substrate is N-type, and the first doped layer and the second doped layer are n-type polysilicon layers.

[0014] As an optional implementation, the thickness of the first dielectric layer is 1 nm-2 nm, and / or the thickness of the second dielectric layer is 0.5 nm-1 nm.

[0015] As an optional implementation, the radio frequency power during the preparation of the first dielectric layer and the second dielectric layer is 12.5 kW-15 kW.

[0016] As an optional implementation, the solar cell further includes a first passivation layer and a second passivation layer, the first passivation layer is arranged on a side of the second doped layer away from the first surface, and the second passivation layer is arranged on the second surface;

[0017] The solar cell also includes a first electrode and a second electrode, the first electrode is arranged on the first passivation layer, and one end of the first electrode penetrates the first passivation layer, the second doping layer and the second dielectric layer to be connected to the first doping layer, the second electrode is arranged on the second passivation layer, and one end of the second electrode penetrates the second passivation layer to be connected to the silicon substrate.

[0018] As an optional implementation manner, the first passivation layer is a first silicon nitride layer;

[0019] The second passivation layer includes an aluminum oxide layer and a second silicon nitride layer. Along a direction from the first surface to the second surface, the aluminum oxide layer and the second silicon nitride layer are sequentially arranged on the second surface.

[0020] Compared with the related art, the beneficial effects of the present invention are:

[0021] The solar cell disclosed in the utility model comprises a silicon substrate, a first dielectric layer, a first doping layer, a second dielectric layer, and a second doping layer sequentially arranged on the first surface of the silicon substrate, the first doping layer and the second doping layer have the same doping type, and the doping concentration of the second doping layer is greater than the doping concentration of the first doping layer, and the doping concentration of the second doping layer decreases in sequence along the direction from the second surface to the first surface. By superimposing the first doping layer, the second dielectric layer, and the second doping layer on the first dielectric layer, the doping concentration of the second doping layer is greater than the doping concentration of the first doping layer, the contact resistivity of the metal and the semiconductor can be reduced, and the battery conversion efficiency can be improved. In addition, the doping concentration of the second doping layer is set to gradually decrease along the direction from the second surface to the first surface, so that a concentration gradient can be formed, reducing the possibility of diffusion of doping elements from low concentration to high concentration, thereby avoiding the penetration of the second doping layer into the dielectric layer, not affecting the interface recombination between the dielectric layer and the doping layer, and being more conducive to improving the passivation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0023] Figure 1 This is a schematic diagram of the structure of a solar cell disclosed in an embodiment of the utility model;

[0024] Figure 2 The figure is a schematic diagram of the internal structure of a solar cell disclosed in an embodiment of the utility model.

[0025] Icon: 100, solar cell; 10, silicon substrate; 11, first surface; 12, second surface; 20, first dielectric layer; 30, first doped layer; 40, second dielectric layer; 50, second doped layer; 60, first passivation layer; 70, second passivation layer; 71, aluminum oxide layer; 72, second silicon nitride layer; 80, first electrode; 90, second electrode. DETAILED DESCRIPTION

[0026] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0027] In the present invention, the directions or positional relationships indicated by the terms "upper", "lower", "outer", etc. are based on the directions or positional relationships shown in the accompanying drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific direction, or to be constructed and operated in a specific direction.

[0028] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in this utility model can be understood according to specific circumstances.

[0029] In addition, the terms "disposed" and "provided with" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements or components. For ordinary technicians in this field, the specific meanings of the above terms in this utility model can be understood according to specific circumstances.

[0030] In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise specified, "plurality" means two or more.

[0031] A passivated contact cell is a solar cell that uses an ultra-thin dielectric layer as a passivation layer structure. The substrate of the passivated contact cell is usually based on an N-type silicon substrate. An ultra-thin silicon oxide dielectric layer is prepared on the back of the cell, and a doped polysilicon thin layer is deposited. The two together form a passivated contact structure. When the phosphorus doping concentration in the polysilicon layer increases, it helps to reduce the contact resistivity of metals and semiconductors and improve ohmic contact, but it will lead to an increase in the extinction coefficient, intensified parasitic absorption in the long-wave band, and greater current loss. At the same time, the increase in the amount of phosphorus doping will increase the ability to penetrate the dielectric layer.

[0032] In the related art, a first dielectric layer, a first n-type polysilicon doped layer, a second dielectric layer, and a second n-type polysilicon doped layer are sequentially deposited on the back of a silicon wafer, and the thickness of the second dielectric layer is greater than the thickness of the first dielectric layer, and the thickness of the second n-type polysilicon doped layer is greater than the thickness of the first n-type polysilicon doped layer. By introducing two dielectric layers and two n-type polysilicon doped layers on the back of the battery, the internal diffusion of phosphorus atoms inside the silicon wafer during the phosphorus diffusion process can be effectively reduced, and the interface passivation effect on the back side can be effectively improved. However, the inventors have found through research that further increasing the concentration of the doping layer will lead to an increase in the ability to penetrate the dielectric layer, causing the doping elements in the doping layer to diffuse into the dielectric layer and the silicon, affecting the passivation effect.

[0033] Based on this, the utility model discloses a solar cell, including a silicon substrate and a first dielectric layer, a first doping layer, a second dielectric layer, and a second doping layer, which are sequentially arranged on a first surface of the silicon substrate. The first doping layer and the second doping layer have the same doping type, and the doping concentration of the second doping layer is greater than the doping concentration of the first doping layer. The doping concentration of the second doping layer decreases sequentially along the second surface toward the first surface.

[0034] The solar cell of the present application can reduce the contact resistivity of metals and semiconductors and improve the conversion efficiency of the cell by making the doping concentration of the second doping layer greater than the doping concentration of the first doping layer. In addition, the second doping layer is provided, and its doping concentration is gradually reduced along the direction from the second surface to the first surface, so that a concentration gradient can be formed, reducing the possibility of diffusion of doping elements from low concentration to high concentration, thereby avoiding the penetration of the second doping layer into the dielectric layer, not affecting the interface recombination between the dielectric layer and the doping layer, and being more conducive to improving the passivation effect.

[0035] The technical solution of the utility model will be further described below in conjunction with embodiments and drawings.

[0036] See also Figure 1 to Figure 2 The utility model discloses a solar cell 100, comprising a silicon substrate 10, the silicon substrate 10 having a first surface 11 and a second surface 12 disposed opposite to each other, and a first dielectric layer 20, a first doping layer 30, a second dielectric layer 40 and a second doping layer 50 disposed sequentially on the first surface 11. The first doping layer 30 and the second doping layer 50 have the same doping type, and the doping concentration of the second doping layer 50 is greater than the doping concentration of the first doping layer 30, and the doping concentration of the second doping layer 50 decreases sequentially along the direction from the second surface 12 to the first surface 11. It should be noted that the first surface 11 is the back side of the solar cell 100, and the second surface 12 is the front side of the solar cell 100, that is, the above dielectric layer and doping layer are both disposed on the back side of the solar cell 100.

[0037] The solar cell 100 disclosed in the utility model comprises a silicon substrate 10, a first dielectric layer 20, a first doping layer 30, a second dielectric layer 40, and a second doping layer 50 sequentially arranged on the first surface 11 of the silicon substrate 10, wherein the doping concentration of the second doping layer 50 is greater than the doping concentration of the first doping layer 30, and the doping concentration of the second doping layer 50 decreases sequentially along the second surface 12 pointing to the first surface 11. By superimposing the first doping layer 30, the second dielectric layer 40, and the second doping layer 50 on the first dielectric layer 20, the doping concentration of the second doping layer 50 is greater than the doping concentration of the first doping layer 30, so that the contact resistivity of the metal and the semiconductor can be reduced and the battery conversion efficiency can be improved. In addition, the doping concentration of the second doping layer 50 is set to gradually decrease along the direction from the second surface 12 to the first surface 11, so that a concentration gradient can be formed, reducing the possibility of diffusion of doping elements from low concentration to high concentration, thereby avoiding the penetration of the second doping layer 50 into the dielectric layer, not affecting the interface recombination between the dielectric layer and the doping layer, and being more conducive to improving the passivation effect.

[0038] It should be noted that the material of the dielectric layer may include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. Specifically, the dielectric layer may be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation properties, can minimize the recombination loss of minority carriers on the surface of the semiconductor substrate, and is a film with excellent durability for subsequent high-temperature processes.

[0039] It is understood that the dielectric layer, as a barrier to electrons and holes, can be combined with the polysilicon layer to prevent minority carriers from passing through. The dielectric layer can also have a pinhole channel effect, allowing the carriers in the solar cell 100 to move freely, and the selective passage of majority carriers through the heavily doped polysilicon is beneficial to reduce the recombination loss of minority carriers. In addition, the dielectric layer can be used as a diffusion barrier to prevent the dopant of the doped polysilicon layer from diffusing into the semiconductor substrate.

[0040] In some embodiments, the doping concentration of the second doping layer 50 is 5.0E 20 cm -3 -1.0E 21 cm -3 , and the thickness of the second doping layer 50 is 90nm-150nm. By designing the concentration of the second doping layer 50 to be 5.0E 20 cm -3 -1.0E 21 cm -3, while increasing the doping concentration of the second doping layer 50, reducing the contact resistivity of the metal and the semiconductor, and improving the battery conversion efficiency, it also limits the situation where the penetration ability of the second doping layer 50 into the dielectric layer increases due to excessive doping concentration. When the electrode is formed, a too thin thickness will burn through the second doping layer 50 and the dielectric layer will directly contact the silicon substrate 10, while a too thick second doping layer 50 will lead to an increase in the extinction coefficient of the solar cell 100, aggravated parasitic absorption in the long-wave band, and thus lead to a large current loss. Based on this, the present application also limits the thickness of the second doping layer 50, which is conducive to controlling the metal recombination during printing of the electrode area and improving the passivation effect.

[0041] Furthermore, the number of the second doping layer 50 may be three, and in the direction from the second surface 12 to the first surface 11, the doping concentrations of the three second doping layers 50 are 8.0E 20 cm -3 -1.0E 21 cm -3 , 6.0E 20 cm -3 -8.0E 20 cm -3 , 5.0E 20 cm -3 -7.0E 20 cm -3 For example, the doping concentrations of the three second doping layers 50 are 9E 20 cm -3 , 7E 20 cm -3 , 6E 20 cm -3 . By making the doping concentration of the three layers of the second doping layer 50 form a decreasing gradient in the direction from the second surface 12 to the first surface 11, that is, the concentration of the second doping layer 50 farther away from the first dielectric layer 20 is lower, so that the doping elements of the low-concentration second doping layer 50 are difficult to diffuse to the high-concentration second doping layer 50, which can not only maintain the second doping layer 50 with a high doping concentration, reduce the contact resistivity of the metal and the semiconductor, and improve the battery conversion efficiency, but also weaken the ability of the doping elements to diffuse into the dielectric layer, which is beneficial to optimize the passivation performance. It can be understood that in other embodiments, the second doping layer 50 can also be two layers, four layers or more layers.

[0042] Correspondingly, along the direction from the second surface 12 to the first surface 11, the thicknesses of the three second doping layers 50 are 40nm-60nm, 30nm-50nm, and 20nm-40nm, respectively. For example, the thicknesses of the three second doping layers 50 are 50nm, 40nm, and 30nm, respectively. By making the thicknesses of the three second doping layers 50 also change in a decreasing gradient, even if a small amount of doping elements diffuse into the silicon substrate 10, it can further play a blocking role and maintain the overall concentration of the doping elements in the second doping layer 50.

[0043] Optionally, the thickness of the first doping layer 30 is 30 nm-50 nm, for example, 35 nm, 40 nm, 45 nm, etc., and / or the doping concentration of the first doping layer 30 is 1E 20 cm -3 -5E 20 cm -3 , for example, it can be 2E 20 cm -3 , 3E 20 cm -3 , 4E 20 cm -3 In this way, the concentration of the first doping layer 30 can be prevented from being too high, so that the penetration ability of the first doping layer 30 into the first dielectric layer 20 is enhanced, and the doping elements diffuse inward, resulting in an increase in the interface recombination of the first dielectric layer 20, and at the same time affecting the pinhole density of the first dielectric layer 20, thereby affecting the passivation effect of the solar cell 100.

[0044] In one example, the silicon substrate 10 may be N-type, and the first doping layer 30 and the second doping layer 50 are n-type polysilicon layers. Optionally, the doping elements of the first doping layer 30 and the second doping layer 50 may be phosphorus, and the material of the first dielectric layer 20 and the second dielectric layer 40 may be silicon oxide.

[0045] It is understandable that the N-type silicon substrate 10 has a lower cell temperature coefficient, is less affected in a high temperature environment, has stable performance, and can greatly improve the open circuit voltage of the solar cell 100, resulting in a higher conversion efficiency of the solar cell 100.

[0046] In another example, the silicon substrate 10 may be of P type, in which case the first doping layer 30 and the second doping layer 50 are p-type polysilicon layers, and the doping elements of the first doping layer 30 and the second doping layer 50 may be boron.

[0047] It should be noted that a too thick dielectric layer is difficult to tunnel, thereby increasing the contact resistance, and ultimately affecting the efficiency of the solar cell 100. The thinner, more uniform, and more defect-free the dielectric layer is, the stronger the tunnel effect is, the better the selective collection of carriers will be, the smaller the recombination loss will be, and the higher the photoelectric conversion rate of the solar cell 100 will be. However, the dielectric layer cannot be too thin, otherwise it will lead to an increase in interface density and a decrease in passivation effect.

[0048] In order to better provide the interface passivation effect, in some embodiments, the thickness of the first dielectric layer 20 is 1nm-2nm, for example, 1.2nm, 1.5nm, 1.8nm, and / or the thickness of the second dielectric layer 40 is 0.5nm-1nm, for example, 0.6nm, 0.7nm, 0.8nm. In this way, on the one hand, the dielectric layer will not be too thin, resulting in an increase in interface density, thereby affecting the passivation effect; on the other hand, the dielectric layer can have a good tunneling effect, thereby improving the efficiency of the solar cell 100. In addition, the thickness of the second dielectric layer 40 is less than the first dielectric layer 20, and is maintained at 0.5nm-1nm, which can make the solar cell 100 have a higher open circuit voltage, which is more conducive to improving the overall performance of the solar cell 100.

[0049] In some embodiments, the RF power during the preparation of the first dielectric layer 20 and the second dielectric layer 40 is 12.5kW-15kW, for example, 13kW, 13.5kW, or 14kW. It should be noted that the first dielectric layer 20 and the second dielectric layer 40 can be gradually formed on the first surface 11 of the silicon substrate 10 by using LPCVD (Low Pressure Chemical Vapor Deposition) equipment or PECVD (Plasma Enhanced Chemical Vapor Deposition) equipment. By controlling the RF power of the equipment to 12.5kW-15kW, it is beneficial to improve the uniformity and density of the first dielectric layer 20 and the second dielectric layer 40, thereby enhancing the blocking ability of the doped elements and further improving the passivation performance of the solar cell 100.

[0050] In some embodiments, the solar cell 100 further includes a first passivation layer 60 and a second passivation layer 70, wherein the first passivation layer 60 is disposed on the side of the second doping layer 50 away from the first surface 11, and the second passivation layer 70 is disposed on the second surface 12. By further forming the passivation layer on the first surface 11 and the second surface 12 of the solar cell 100, on the one hand, the absorption of light is increased, and on the other hand, a passivation effect is played.

[0051] Furthermore, the solar cell 100 further includes a first electrode 80 and a second electrode 90, wherein the first electrode 80 is disposed on the first passivation layer 60, and one end of the first electrode 80 penetrates the first passivation layer 60, the second doping layer 50 and the second dielectric layer 40 to connect with the first doping layer 30, and the second electrode 90 is disposed on the second passivation layer 70, and one end of the second electrode 90 penetrates the second passivation layer 70 to connect with the silicon substrate 10. Specifically, the first electrode 80 penetrates the first passivation layer 60, the second doping layer 50 and the second dielectric layer 40, and penetrates the first doping layer 30 to connect with the inside thereof, so that the first electrode 80 does not directly contact with the silicon substrate 10, reducing metal recombination and contact resistance, thereby improving the efficiency of the solar cell 100. One end of the second electrode 90 is directly connected to the second surface 12 of the silicon substrate 10, which is more conducive to the conductive performance of the two.

[0052] It is understandable that, during the preparation process, the first electrode 80 can be sintered through the first passivation layer 60, the second doping layer 50, the second dielectric layer 40 and connected to the interior of the first doping layer 30. Similarly, the second electrode 90 can be sintered through the second passivation layer 70 and connected to the silicon substrate 10.

[0053] In some embodiments, the first passivation layer 60 is a first silicon nitride layer, that is, the material of the first passivation layer 60 is silicon nitride. The second passivation layer 70 includes an aluminum oxide layer 71 and a second silicon nitride layer 72. The aluminum oxide layer 71 and the second silicon nitride layer 72 are sequentially arranged on the second surface 12 along the direction from the first surface 11 to the second surface 12. Correspondingly, the aluminum oxide layer 71 is directly in contact with the second surface 12, and the second silicon nitride layer 72 is located at the top. Using aluminum oxide layer and silicon nitride layer as passivation layers, on the one hand, the aluminum oxide layer can increase the absorption of light, and at the same time, the hydrogen atoms generated during the formation of the silicon nitride layer have a passivation effect on the silicon substrate 10; on the other hand, the aluminum oxide layer is thin and easily damaged in the subsequent production of battery components, and the formation of the silicon nitride layer also has a protective effect on the aluminum oxide layer.

[0054] Of course, in some other embodiments, the first passivation layer 60 may also be any one of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer, or a stacked layer of multiple layers.

[0055] The test results of the solar cells in this embodiment are shown in Table 1 below.

[0056] Table 1

[0057]

[0058] The solar cell of the present application is used as an experimental group, and the passivated contact cell in the related art is used as a control group. The open circuit voltage, short circuit current and conversion efficiency of the solar cell are mainly tested from the aspects of fill factor, series resistance, parallel resistance, reverse current, etc. According to the test data in Table 1, it can be seen that the solar cell in this embodiment is sequentially provided with a first dielectric layer 20, a first doping layer 30, a second dielectric layer 40, and a second doping layer 50 on the first surface 11 of the silicon substrate 10. The first doping layer 30 and the second doping layer 50 have the same doping type, and the doping concentration of the second doping layer 50 is greater than the doping concentration of the first doping layer 30. The doping concentration of the second doping layer 50 decreases in sequence along the direction from the second surface 12 to the first surface 11, and finally achieves the effect of comprehensively improving the open circuit voltage and conversion efficiency of the solar cell 100.

[0059] The following is a brief description of the preparation method of the solar cell 100 provided by the present invention. The preparation method may include the following steps:

[0060] a) First, the silicon substrate 10 is cleaned and subjected to microstructure morphology treatment. This step is mainly to remove organic dirt and metal impurities on the surface of the silicon substrate 10 and to remove the mechanical damage layer generated during the wire cutting process of the silicon substrate 10.

[0061] b) Prepare PN junction by high temperature diffusion.

[0062] c) Cleaning and polishing the first surface 11 of the silicon substrate 10.

[0063] d) A first dielectric layer 20 is prepared on the first surface 11 using an LPCVD device or a PECVD device, the radio frequency power of the device is 12.5 kW-15 kW, and the thickness of the first dielectric layer is 1 nm-2 nm.

[0064] e) depositing a first doping layer 30 on the first dielectric layer 20, with a thickness of 30nm-50nm and a doping concentration of 1E 20 cm -3 -5E 20 cm -3 .

[0065] f) depositing a second dielectric layer 40 on the first doped layer 30, the radio frequency power of the device is 12.5 kW-15 kW, and the thickness of the first dielectric layer is 0.5 nm-1 nm.

[0066] g) Three second doping layers 50 are sequentially formed on the second dielectric layer 40, with doping concentrations of 8.0E 20 cm -3 -1.0E 21 cm -3 , 6.0E 20 cm-3 -8.0E 20 cm -3 , 5.0E 20 cm -3 -7.0E 20 cm -3 The thicknesses are 40nm-60nm, 30nm-50nm, and 20nm-40nm respectively.

[0067] h) depositing a silicon oxide layer on the second doping layer 50, wherein the silicon oxide layer is a protective layer.

[0068] i) The above structure layer is subjected to high temperature annealing and crystallization. The annealing process converts amorphous silicon into polycrystalline silicon in order to activate the passivation performance. The annealing temperature is 900°C-950°C, for example, 910°C, 930°C, 940°C, etc. The annealing time is 40min-50min, for example, 42min, 45min, 47min, etc. The above silicon oxide layer plays a protective role in annealing. After annealing, the test square resistance of the above structure layer is 20Ω / sq-25Ω / sq, and the test surface concentration is 5.0E 20 cm -3 -7.0E 20 cm -3 , indicating that the dielectric layer, doping layer and other structural layers after annealing meet the test standards.

[0069] j) Cleaning the silicon oxide layer, then depositing a silicon nitride layer on the first surface 11, and depositing an aluminum oxide layer and a silicon nitride layer on the second surface 12, respectively, and screen-printing gate lines to form a first electrode 80 and a second electrode 90.

[0070] Except for the preparation of the dielectric layer and the doping layer on the first surface 11 of the solar cell 100, the other structures are conventional processes and will not be described in detail here.

[0071] The solar cell disclosed in the embodiment of the utility model is introduced in detail above. The principle and implementation mode of the utility model are explained in this article by using specific examples. The description of the above embodiments is only used to help understand the solar cell of the utility model and its core concept. At the same time, for those skilled in the art, according to the concept of the utility model, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as a limitation on the utility model.

Claims

1. A solar cell, characterized in that: include: A silicon substrate having a first surface and a second surface disposed opposite to each other; A first dielectric layer, a first doping layer, a second dielectric layer and a second doping layer are sequentially arranged on the first surface; The first doping layer and the second doping layer have the same doping type, and the doping concentration of the second doping layer is greater than the doping concentration of the first doping layer. The second doping layer includes multiple layers, and the doping concentration and thickness of the multiple layers of the second doping layer decrease successively along the direction from the second surface to the first surface.

2. The solar cell according to claim 1, characterized in that: The thickness of the second doping layer is 90nm-150nm.

3. The solar cell according to claim 2, characterized in that: The number of the second doping layers is three.

4. The solar cell according to claim 3, characterized in that: In the direction from the second surface to the first surface, the thicknesses of the three second doping layers are 40nm-60nm, 30nm-50nm, and 20nm-40nm, respectively.

5. The solar cell according to claim 1, characterized in that: The thickness of the first doping layer is 30nm-50nm.

6. The solar cell according to claim 1, characterized in that: The silicon substrate is N-type, and the first doping layer and the second doping layer are n-type polysilicon layers.

7. The solar cell according to any one of claims 1 to 6, characterized in that: The thickness of the first dielectric layer is 1 nm-2 nm, and / or the thickness of the second dielectric layer is 0.5 nm-1 nm.

8. The solar cell according to any one of claims 1 to 6, characterized in that: The radio frequency power during the preparation of the first dielectric layer and the second dielectric layer is 12.5 kW to 15 kW.

9. The solar cell according to any one of claims 1 to 6, characterized in that: The solar cell further comprises a first passivation layer and a second passivation layer, wherein the first passivation layer is arranged on a side of the second doping layer away from the first surface, and the second passivation layer is arranged on the second surface; The solar cell also includes a first electrode and a second electrode, the first electrode is arranged on the first passivation layer, and one end of the first electrode penetrates the first passivation layer, the second doping layer and the second dielectric layer to be connected to the first doping layer, the second electrode is arranged on the second passivation layer, and one end of the second electrode penetrates the second passivation layer to be connected to the silicon substrate.

10. The solar cell according to claim 9, characterized in that: The first passivation layer is a first silicon nitride layer; The second passivation layer includes an aluminum oxide layer and a second silicon nitride layer. Along a direction from the first surface to the second surface, the aluminum oxide layer and the second silicon nitride layer are sequentially arranged on the second surface.

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