Solar cells and photovoltaic modules

Abstract

The present application relates to a solar cell and a photovoltaic module, comprising: a semiconductor substrate, the semiconductor substrate comprising a front side and a back side arranged oppositely; an emitter and a front side passivation layer located on the front side of the semiconductor substrate; a tunneling layer, a doped conductive layer and a back side passivation layer located on the back side of the semiconductor substrate, wherein the doped conductive layer comprises a first doped conductive layer corresponding to the back side metallization region and a second doped conductive layer corresponding to the back side non-metallization region, and the oxygen content of the first doped conductive layer is less than the oxygen content of the second doped conductive layer; a front side electrode in contact with the emitter and a back side electrode in contact with the first doped conductive layer. The present application can reduce metal recombination centers and improve passivation effects by controlling the oxygen content of the first doped conductive layer to be less than the oxygen content of the second doped conductive layer, and at the same time, make the polysilicon doped in the metal region have better conductivity, thereby improving the conversion efficiency of the solar cell.

Description

[Technical field]

[0001] The present application relates to the technical field of solar photovoltaic modules, and in particular to a solar cell and a photovoltaic module. [Background technology]

[0002] TOPCon is a tunnel oxide passivated contact (Tunnel Oxide Passivated Contact) solar cell technology based on the principle of selective carriers. Its cell structure is an N-type silicon substrate cell. An ultra-thin layer of silicon oxide is prepared on the back of the cell, and then a thin layer of doped silicon is deposited. The two together form a passivated contact structure, which effectively reduces surface recombination and metal contact recombination, providing greater room for further improving cell conversion efficiency.

[0003] Although the conversion efficiency of TOPCon cells is relatively high, the preparation process of TOPCon cells is relatively complicated due to the preparation of the passivated contact structure, which makes the preparation cost of TOPCon cells high and the improvement of conversion efficiency is limited. Therefore, how to improve the conversion efficiency of TOPCon cells puts higher requirements on the preparation of solar cells and has become an urgent problem to be solved in the photovoltaic industry. [Summary of the invention]

[0004] In order to overcome the above-mentioned defects, the present application provides a solar cell and a photovoltaic module, which can ensure the passivation performance of the metallized area, reduce the metal contact of the battery while ensuring the open circuit voltage, thereby improving the battery efficiency and performance.

[0005] In a first aspect, an embodiment of the present application provides a solar cell, comprising:

[0006] A semiconductor substrate, the semiconductor substrate comprising a front side and a back side arranged opposite to each other;

[0007] An emitter and a front passivation layer located on the front side of the semiconductor substrate;

[0008] A tunneling layer, a doped conductive layer and a back passivation layer located on the back side of the semiconductor substrate, wherein the doped conductive layer includes a first doped conductive layer corresponding to the back metallization area and a second doped conductive layer corresponding to the back non-metallization area, the oxygen content of the first doped conductive layer is less than the oxygen content of the second doped conductive layer; the first doped conductive layer and the second doped conductive layer are both phosphorus doped layers, and the concentration of phosphorus in the first doped conductive layer is greater than the concentration of phosphorus in the second doped conductive layer;

[0009] A front electrode in contact with the emitter and a back electrode in contact with the first doped conductive layer. In combination with the first aspect, the tunneling layer comprises a first tunneling layer corresponding to a back metallized region and a second tunneling layer corresponding to the back non-metallized region, and the oxygen content of the first tunneling layer is greater than the oxygen content of the second tunneling layer.

[0010] In combination with the first aspect, the concentration of phosphorus in the first doped conductive layer is 1E20 cm -3 ~1E21cm -3 , and / or the concentration of phosphorus in the second doped conductive layer is 8E19 cm -3 ~5E20 cm -3 .

[0011] In combination with the first aspect, the sheet resistance of the first doped conductive layer is 30Ω / sq to 80Ω / sq, and / or the sheet resistance of the second doped conductive layer is 60Ω / sq to 400Ω / sq.

[0012] In combination with the first aspect, the thickness of the first doped conductive layer is 30 nm to 300 nm, and / or the thickness of the second doped conductive layer is 30 nm to 300 nm.

[0013] In combination with the first aspect, the oxygen content in the second doped conductive layer is 27% to 28%.

[0014] In combination with the first aspect, the nitrogen content of the first doped conductive layer is greater than the nitrogen content of the second doped conductive layer, and the mass proportion of nitrogen in the second doped conductive layer is 1% to 2%.

[0015] In combination with the first aspect, the thickness of the tunneling layer is 0.8 nm to 2 nm.

[0016] In combination with the first aspect, the tunneling layer includes a first tunneling layer corresponding to the back metallization area and a second tunneling layer corresponding to the back non-metallization area, and the oxygen content in the second tunneling layer is 17% to 19%.

[0017] In combination with the first aspect, the thickness of the back passivation layer is 70 nm to 120 nm.

[0018] In a second aspect, an embodiment of the present application provides a photovoltaic component, which includes a cover plate, a packaging material layer, and a solar cell string, and the solar cell string includes a plurality of solar cells described in the first aspect.

[0019] Compared with the prior art, this application has the following improvements:

[0020] The present application controls the oxygen content of the first doped conductive layer to be smaller than the oxygen content of the second doped conductive layer, so that the doped conductive layer on the back of the solar cell has a selective structure. The larger oxygen content of the second doped conductive layer can reduce the metal recombination center and improve the passivation effect. The smaller oxygen content of the first doped conductive layer also makes the doped polysilicon in the metal area have better conductivity, thereby reducing the metal contact while ensuring the open circuit voltage, thereby improving the cell performance and conversion efficiency of the solar cell.

[0021] Other features and advantages of the embodiments of the present application will be described in the subsequent description, and partly become apparent from the description, or understood by practicing the embodiments of the present application. The purpose and other advantages of the embodiments of the present application are realized and obtained by the structures specifically pointed out in the description and the drawings.

Brief Description of the Drawings

[0022] In order to more clearly illustrate the technical solutions of 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 the solar cell of this application;

[0024] Figure 2 The preparation flow chart of the solar cell of this application;

[0025] Figure 3 A schematic diagram of the structure after preparing the emitter for this application;

[0026] Figure 4 This is a schematic diagram of the structure after the conductive layer is doped and partially laser treated in this application;

[0027] Figure 5 This is a schematic diagram of the structure of forming a front passivation layer and a back passivation layer on the front and back of a semiconductor substrate in the present application;

[0028] Figure 6 This is a schematic diagram of the structure of the photovoltaic module of this application.

[0029] Reference numerals:

[0030] 1- semiconductor substrate;

[0031] 2-Emitter;

[0032] 3- Tunneling layer;

[0033] 31-first tunneling layer;

[0034] 32-second tunneling layer;

[0035] 4- doped conductive layer;

[0036] 41- a first doped conductive layer;

[0037] 42- a second doped conductive layer;

[0038] 5-front passivation layer;

[0039] 6- back passivation layer;

[0040] 7-front electrode;

[0041] 8- back electrode;

[0042] 1000-PV panels;

[0043] 100-Solar cell;

[0044] 200-first cover plate;

[0045] 300-first packaging glue layer;

[0046] 400- second encapsulation adhesive layer;

[0047] 500- Second cover plate. [Specific implementation method]

[0048] In order to better understand the technical solution of the present invention, the embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0049] It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0051] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0052] It should be noted that the directional words such as "upper", "lower", "left", and "right" described in the embodiments of the present invention are described based on the angles shown in the accompanying drawings and should not be understood as limiting the embodiments of the present application. In addition, in the context, it should also be understood that when it is mentioned that an element is connected to another element "upper" or "lower", it can not only be directly connected to another element "upper" or "lower", but also indirectly connected to another element "upper" or "lower" through an intermediate element.

[0053] It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, the order of the steps of each embodiment is not limited to being performed in the order arranged in this specification. In some cases, the implementation steps can be adjusted according to specific needs to perform the steps shown or described in a different order from that shown here.

[0054] TOPCon cells rely on the "tunneling effect" to achieve rear surface passivation. The existing rear surface structure of TOPCon cells is, from the inside to the outside, a semiconductor substrate, a tunneling oxide layer, a doped polysilicon layer, a rear surface passivation layer and a rear surface metal electrode. The metal electrode forms an ohmic contact with the semiconductor, and the tunneling oxide layer and the doped polysilicon layer form a tunneling oxide layer passivation contact structure. In order to further improve the conversion efficiency and performance of solar cells, how to reduce the contact resistance of the metallized area has become an urgent problem to be solved in the photovoltaic industry.

[0055] Furthermore, people began to improve the preparation process of solar cells, mainly by forming heavy doping in the metallized area through laser doping, thereby reducing the contact resistance of the metallized area and improving the conversion efficiency of solar cells. However, in the process of laser processing, it is inevitable that a certain amount of damage will occur to the battery film layer, resulting in a decrease in battery performance.

[0056] Therefore, in order to improve the conversion efficiency and battery performance of solar cells, the present application proposes a solar cell, such as Figure 1 As shown, including:

[0057] A semiconductor substrate 1, wherein the semiconductor substrate 1 comprises a front surface and a back surface that are arranged opposite to each other;

[0058] An emitter 2 and a front passivation layer 5 located on the front side of the semiconductor substrate 1;

[0059] A tunneling layer 3, a doped conductive layer 4 and a back passivation layer 6 are located on the back side of the semiconductor substrate 1, wherein the doped conductive layer 4 includes a first doped conductive layer 41 corresponding to the back metallization area and a second doped conductive layer 42 corresponding to the back non-metallization area, and the oxygen content of the first doped conductive layer 41 is less than the oxygen content of the second doped conductive layer 42;

[0060] A front electrode 7 in contact with the emitter 2 and a back electrode 8 in contact with the first doped conductive layer 41 .

[0061] In the above scheme, the present application controls the oxygen content of the first doped conductive layer 41 to be less than the oxygen content of the second doped conductive layer 42, so that the doped conductive layer 4 on the back of the solar cell has a selective structure. The larger oxygen content of the second doped conductive layer 42 can reduce the metal recombination center and improve the passivation effect. The smaller oxygen content of the first doped conductive layer 41 also makes the doped polysilicon in the metal area have better conductivity, thereby reducing the metal contact while ensuring the open circuit voltage, thereby improving the battery performance and conversion efficiency of the solar cell.

[0062] Here, the front side of the semiconductor substrate 1 is the surface facing the sun (i.e., the light-receiving side), and the back side of the semiconductor substrate 1 is the surface facing away from the sun (i.e., the backlight side). In some embodiments, the semiconductor substrate 1 is an N-type N semiconductor substrate, and the N-type semiconductor substrate can be a crystalline silicon substrate (silicon substrate), for example, a polycrystalline silicon substrate, a single crystal silicon substrate, a microcrystalline silicon substrate, or a silicon carbide substrate. The specific type of the semiconductor substrate is not limited in the embodiments of the present application. The doping element of the semiconductor substrate can be phosphorus, nitrogen, etc.

[0063] In some embodiments, the N-type semiconductor substrate is an N-type crystalline silicon substrate (or silicon wafer), and the thickness of the N-type semiconductor substrate is 60 μm to 240 μm, specifically 60 μm, 80 μm, 90 μm, 100 μm, 120 μm, 150 μm, 200 μm or 240 μm, etc., which is not limited here.

[0064] In some embodiments, the emitter 2 is a P-type emitter, and the P-type emitter is a boron-doped diffusion layer. The boron-doped diffusion layer is a P-type emitter (i.e., a P+ layer) formed by diffusing boron atoms to a certain depth from the front surface using a boron source through a diffusion process. For example, the boron source can be liquid boron tribromide or boron trichloride.

[0065] In some embodiments, the tunneling layer 3 is a thin oxide layer, for example, it can be silicon oxide or metal oxide, and can contain other additional elements, such as nitrogen. Exemplarily, the tunneling layer 3 can be a stacked structure of one or more of a silicon oxide layer, an aluminum oxide layer, a silicon oxynitride layer, a molybdenum oxide layer, and a hafnium oxide layer. In other embodiments, the tunneling layer 3 can also be an oxygen-containing silicon nitride layer, an oxygen-containing silicon carbide layer, etc. The tunneling layer may not have a perfect tunnel barrier in actual effect, because, for example, it contains defects such as pinholes, which can cause other charge carrier transport mechanisms (such as drift, diffusion) to dominate relative to the tunneling effect.

[0066] In some embodiments, the thickness of the tunneling layer 3 is 0.8nm to 2nm. Specifically, the thickness of the tunneling layer 3 is 0.8nm, 0.9nm, 1.0nm, 1.2nm, 1.4nm, 1.6nm, 1.8nm or 2nm, etc. The thickness of the tunneling layer 3 refers to the thickness of the tunneling layer relative to the formation surface. The thickness of the tunneling layer 3 is too large, which is not conducive to reducing the contact resistance of the tunneling layer. By controlling the thickness of the tunneling layer, the reduction of the fill factor caused by the contact resistance can be suppressed. The present application can improve the open circuit voltage of the solar cell and enhance the efficiency of the solar cell by forming a tunneling layer on the back side of the semiconductor substrate 1.

[0067] In some embodiments, the content of oxygen in the first doped conductive layer 41 is 19% to 22%. Specifically, the content of oxygen in the first doped conductive layer 41 can be, for example, 19%, 19.5%, 19.7%, 20.5%, 20.8%, 21%, 21.3%, 21.5%, 21.8% and 22%; the content of oxygen in the second doped conductive layer 42 is 27% to 28%. Specifically, the content of oxygen in the second doped conductive layer 42 can be, for example, 27%, 27.02%, 27.5%, 27.85% and 28%.

[0068] In some embodiments, the tunneling layer 3 includes a first tunneling layer 31 corresponding to the back metallization region and a second tunneling layer 32 corresponding to the back non-metallization region, the oxygen content of the first tunneling layer 31 is greater than the oxygen content of the second tunneling layer 32, the oxygen content in the first tunneling layer 31 is 25% to 30%, the oxygen content in the first tunneling layer 31 can be, for example, 25%, 26%, 27%, 28%, 29% and 30%, and the oxygen content in the second tunneling layer 32 can be, for example, 17%, 17.5%, 18%, 18.3% and 19%. In the present application, the oxygen content of the first tunneling layer 31 is controlled to be greater than the oxygen content of the second tunneling layer 32, that is, the number of bridging oxygen in the first tunneling layer 31 is large, so that the compactness of the first tunneling layer 31 is increased, and the presence of holes in the tunneling layer is avoided. At the same time, the second tunneling layer 32 with a lower oxygen content ensures the tunneling effect, thereby improving the passivation effect of the battery.

[0069] In some embodiments, the oxygen content at the interface between the first doped conductive layer 41 and the first tunneling layer 31 is greater than the oxygen content at the interface between the second doped conductive layer 42 and the second tunneling layer 32. By controlling the oxygen content at the interface between the doped conductive layer 4 and the tunneling layer 3, the film quality of the tunneling layer 3 in the metallization area can be improved, and the passivation effect of the battery can be further improved.

[0070] In some embodiments, the oxygen content at the interface between the first doped conductive layer 41 and the back passivation layer 6 is greater than the oxygen content at the interface between the second doped conductive layer 42 and the back passivation layer 6. The present application can improve the film quality of the tunneling layer in the metallization region by controlling the oxygen content at the interface between the doped conductive layer 4 and the back passivation layer 6, and can further enhance the passivation effect of the battery.

[0071] In some embodiments, the oxygen content of the first doped conductive layer 41 is less than that of the first tunnel layer 31 . The higher oxygen content of the first tunnel layer 31 increases the compactness of the first tunnel layer 31 , thereby improving the safety of the semiconductor substrate 1 and the first tunnel layer 31 .

[0072] In some embodiments, the nitrogen content of the first doped conductive layer 41 is greater than the nitrogen content of the second doped conductive layer 42 .

[0073] In some embodiments, the mass percentage of nitrogen in the first doped conductive layer 41 is 3% to 5%. Specifically, the mass percentage of nitrogen in the first doped conductive layer 41 may be, for example, 3%, 3.5%, 4%, 4.5% and 5%.

[0074] In some embodiments, the mass proportion of nitrogen in the second doped conductive layer 42 is 1% to 2%. Specifically, the mass proportion of nitrogen in the second doped conductive layer 42 can be, for example, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9% and 2%.

[0075] In some embodiments, the doped conductive layer 4 includes at least one of silicon carbide and polysilicon, that is, the doped conductive layer 4 can be a doped polysilicon layer, a silicon carbide layer, or a composite layer of a doped polysilicon layer and a silicon carbide layer. Specifically, the dopant of the first doped conductive layer 41 and the second doped conductive layer is an n-type dopant, and the n-type dopant can be, for example, an n-type impurity of a group V element (including P, As, Bi, Sb, etc.).

[0076] In some embodiments, when the doped conductive layer 4 is doped with a polysilicon layer, the doping element in the doped polysilicon layer 4 is phosphorus, that is, the first doped conductive layer 41 and the second doped conductive layer 42 are both phosphorus-doped polysilicon layers, and the concentration of phosphorus in the first doped conductive layer 41 is greater than the concentration of phosphorus in the second doped conductive layer 42, so that the first doped conductive layer 41 is a heavily doped area in the metallization area, thereby improving the passivation effect of the metallization area.

[0077] In some embodiments, the concentration of phosphorus in the first doped conductive layer 41 is 1E20 cm -3 ~1E21cm -3Specifically, the concentration of phosphorus in the first doped conductive layer 41 may be, for example, 1E20 cm -3 , 2E20 cm -3 、3E20 cm -3 、4E20 cm -3 、5E20 cm -3 、6E20 cm -3 、7E20 cm -3 、8E20 cm -3 、9E20 cm -3 and 1E21cm -3 .

[0078] In some embodiments, the concentration of phosphorus in the second doped conductive layer 42 is 8E19 cm -3 ~5E20 cm -3 Specifically, the concentration of phosphorus in the second doped conductive layer 42 may be, for example, 8E19 cm -3 、9E19cm -3 , 1E20 cm -3 、2E20cm -3 、3E20 cm -3 、4E20 cm -3 and 5E20 cm -3 .

[0079] It can be understood that by controlling the concentration of phosphorus in the first doped conductive layer 41 and the second doped conductive layer 42 within the above range, a selective structure is formed on the back of the solar cell, that is, the first doped conductive layer 41 located in the metallized area is an n++ heavily doped area, and the second doped conductive layer 42 located in the non-metallized area is an n+ polycrystalline silicon layer, thereby reducing the contact resistance of the metallized area, improving the fill factor of the battery, and further improving the battery performance.

[0080] In some embodiments, the square resistance of the first doped conductive layer 41 is 30Ω / sq to 80Ω / sq. Specifically, the square resistance of the first doped conductive layer 41 may be, for example, 30Ω / sq, 40Ω / sq, 50Ω / sq, 60Ω / sq, 70Ω / sq, and 80Ω / sq.

[0081] In some embodiments, the square resistance of the second doped conductive layer 42 is 60Ω / sq to 400Ω / sq. Specifically, the square resistance of the second doped conductive layer 42 can be, for example, 60Ω / sq, 80Ω / sq, 100Ω / sq, 150Ω / sq, 200Ω / sq, 300Ω / sq and 400Ω / sq.

[0082] In some embodiments, the thickness of the first doped conductive layer 41 is 30 nm to 300 nm. Specifically, the thickness of the first doped conductive layer 41 may be, for example, 30 nm, 50 nm, 70 nm, 90 nm, 110 nm, 150 nm, 200 nm, 250 nm and 300 nm.

[0083] In some embodiments, the thickness of the second doped conductive layer 42 is 30 nm to 300 nm. Specifically, the thickness of the second doped conductive layer 42 may be, for example, 30 nm, 50 nm, 70 nm, 90 nm, 110 nm, 150 nm, 200 nm, 250 nm and 300 nm.

[0084] It can be understood that the thickness of the first doped conductive layer 41 and the second doped conductive layer 42 can be the same, that is, the present application can improve the passivation effect of the battery, improve the conductivity and fill factor, and thus improve the battery performance of the solar cell by only changing the distribution of heavy elements in the first doped conductive layer 41 and the second doped conductive layer 42.

[0085] In some embodiments, the front passivation layer 5 may include, but is not limited to, at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc., or any combination thereof. The front passivation layer 5 can produce a good passivation effect on the semiconductor substrate 1, which helps to improve the conversion efficiency of the battery. It should be noted that the front passivation layer 5 can also play a role in reducing the reflection of incident light, and in some instances, it can also be called an anti-reflection layer.

[0086] In some embodiments, the thickness of the front passivation layer 5 is in the range of 10 nm to 120 nm, specifically 10 nm, 20 nm, 30 nm, 42 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or 120 nm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0087] In some embodiments, the back passivation layer 6 may include, but is not limited to, at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc., or any combination thereof. When the back passivation layer 6 is a stacked silicon nitride layer and a silicon oxide layer or a stacked silicon nitride layer and a silicon oxynitride layer, the silicon nitride layer is located on the surface of the doped conductive layer 4, and the silicon oxide layer or the silicon oxynitride layer is located on the surface of the silicon nitride layer.

[0088] In some embodiments, the thickness of the back passivation layer 6 is in the range of 70 nm to 120 nm, and specifically may be 70 nm, 80 nm, 90 nm, 100 nm or 120 nm, etc. Of course, it may also be other values ​​within the above range, which is not limited here.

[0089] In some embodiments, the front electrode 7 and the back electrode 8 are both metal gate electrodes, and the material of the metal gate electrodes includes at least one of copper, silver, aluminum, and nickel. When the metal gate electrodes are made of copper, silver, aluminum, and nickel, they are all easily corroded.

[0090] The metal grid line electrode includes a main grid line and a secondary grid line. The secondary grid line is connected to the main grid line. The secondary grid line is used to gather the current generated by the solar cell, and the main grid line is used to collect the current on the secondary grid line.

[0091] As an optional technical solution of the present application, multiple main grid lines are distributed at equal intervals, so that the current collected by each main grid line is more uniform.

[0092] This application also provides a method for preparing the above solar cell, please refer to Figure 2 , is a flow chart of a method for preparing a solar cell of the present application, comprising the following steps:

[0093] An emitter 2 is formed on the front surface of the textured semiconductor substrate 1;

[0094] A tunneling layer 3 and a conductive layer are formed on the back side of the semiconductor substrate 1, and the conductive layer is doped and partially laser treated to form a doped conductive layer 4, wherein the doped conductive layer 4 includes a first doped conductive layer 41 corresponding to the back metallized area and a second doped conductive layer 42 corresponding to the back non-metallized area, and the oxygen content of the first doped conductive layer 41 is less than the oxygen content of the second doped conductive layer 42;

[0095] A back passivation layer 6 is formed on the surface of the first doped conductive layer 41 and the second doped conductive layer 42 and a front passivation layer 5 is formed on the surface of the emitter 2;

[0096] A back electrode 8 penetrates through the back passivation layer 6 to form contact with the first doped polysilicon layer, and a front electrode 7 penetrates through the surface of the front passivation layer 5 to form contact with the emitter 2 .

[0097] In some embodiments, the front side of the semiconductor substrate 1 is the surface facing the sun (ie, the light-receiving side), and the back side of the semiconductor substrate 1 is the surface facing away from the sun (ie, the backlight side).

[0098] Specifically, the method for manufacturing a solar cell provided in the embodiment of the present application can be used to manufacture an N-type solar cell, and can further be used to manufacture an N-type TOPCon cell. Below, the method for manufacturing the N-type TOPCon cell of the present application will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0099] Step S100, see Figure 3 , forming an emitter 2 on the front side of the semiconductor substrate 1 after texturing;

[0100] In some embodiments, the semiconductor substrate 1 is an N-type semiconductor substrate, which may be a crystalline silicon substrate (silicon substrate), such as a polycrystalline silicon substrate, a single crystal silicon substrate, a microcrystalline silicon substrate, or a silicon carbide substrate. The specific type of the semiconductor substrate is not limited in the embodiments of the present application. The doping element of the semiconductor substrate may be phosphorus, nitrogen, etc.

[0101] In some embodiments, the front and rear surfaces of the semiconductor substrate 1 may be textured to form a velvet surface or surface texture structure (e.g., a pyramid structure). The texture treatment may be performed by chemical etching, laser etching, mechanical etching, plasma etching, etc., which are not limited here. Exemplarily, the front and rear surfaces of the semiconductor substrate 1 may be textured using a NaOH solution. Since the corrosion of the NaOH solution is anisotropic, a pyramid velvet surface structure may be prepared.

[0102] It can be understood that the surface of the semiconductor substrate 1 has a velvet structure through the texturing process, which produces a light trapping effect, increases the amount of light absorbed by the solar cell, and thus improves the conversion efficiency of the solar cell.

[0103] In some embodiments, before the texturing process, a step of cleaning the N-type semiconductor substrate 1 may be included to remove metal and organic pollutants on the surface.

[0104] In some embodiments, the emitter 2 can be formed on the front side of the semiconductor substrate 1 by any one or more methods of high temperature diffusion, slurry doping or ion implantation. Specifically, the emitter 2 is formed by diffusing boron atoms through a boron source. In some embodiments, the emitter 2 is designed as a selective emitter structure. The boron source can be, for example, treated with boron tribromide for diffusion, so that the microcrystalline silicon phase of the crystalline silicon is transformed into a polycrystalline silicon phase. Since the surface of the semiconductor substrate 1 has a high concentration of boron, a borosilicate glass layer (BSG) is usually formed. This borosilicate glass layer has a metal gettering effect, which will affect the normal operation of the solar cell and needs to be removed later.

[0105] Step 200, please refer to Figure 4 A tunneling layer 3 and a conductive layer are formed on the back side of the semiconductor substrate 1, and the conductive layer is doped and locally laser treated to form a doped conductive layer 4, wherein the doped conductive layer 4 includes a first doped conductive layer 41 corresponding to the back metallized area and a second doped conductive layer 42 corresponding to the back non-metallized area, and the oxygen content of the first doped conductive layer 41 is less than the oxygen content of the second doped conductive layer 42.

[0106] In some embodiments, a tunneling layer 3 may be first formed on the back side of the semiconductor substrate 1 , and then a doped polysilicon layer 4 may be formed on the surface of the tunneling layer 3 .

[0107] In some implementations, the specific operation method for forming the oxide layer is not limited in the present application. For example, the rear surface of the semiconductor substrate 1 can be oxidized by any one of ozone oxidation, high temperature thermal oxidation and nitric acid oxidation.

[0108] In some embodiments, the specific operation method of forming the conductive layer is not limited in the embodiments of the present application. For example, any one of low-pressure chemical vapor deposition, plasma-enhanced chemical vapor deposition and atmospheric pressure chemical vapor deposition can be used to deposit a conductive layer on the surface of the tunneling layer to protect the oxide layer. Secondly, the conductive layer is doped to form a high-low junction (n / n + -Si), which can effectively reduce the recombination rate of carriers on the back of the battery and further improve the conversion efficiency of solar cells.

[0109] In some embodiments, an in-situ doping treatment can be performed while depositing the conductive layer to form a doped conductive layer 4, and the doped conductive layer 4 includes at least one of silicon carbide and polycrystalline silicon, that is, the doped conductive layer 4 can be a doped polycrystalline silicon layer, a silicon carbide layer, or a composite layer of a doped polycrystalline silicon layer and a silicon carbide layer.

[0110] In some embodiments, when the doped conductive layer 4 is a phosphorus-doped polysilicon layer, the phosphorus doping source may be prepared by any one or more methods of high-temperature diffusion, slurry doping or ion implantation.

[0111] In some embodiments, the metallized region refers to the region where the back electrode 8 penetrates the back passivation layer 6 to form contact with the doped polysilicon layer, and the non-metallized region refers to other regions on the doped polysilicon layer. It can be understood that the doped polysilicon layer 4 is composed of a first doped polysilicon layer 41 and a second doped polysilicon layer 42 that are spaced apart.

[0112] In some embodiments, when the doped conductive layer 4 is a phosphorus-doped polysilicon layer, the doping source for the local laser treatment is the phosphosilicate glass on the surface of the doped polysilicon layer and the unactivated phosphorus in the polysilicon layer, and these phosphors are activated by laser to form a heavily doped polysilicon layer with a higher phosphorus concentration.

[0113] In some embodiments, the laser for local laser treatment includes green light with a wavelength of 532 nm. Of course, it can also be laser light with other wavelength ranges, which is not limited here.

[0114] In some embodiments, the pulse width of the local laser treatment is 15ns to 40ns. Specifically, the pulse width of the local laser treatment may be, for example, 15ns, 18ns, 20ns, 25ns, 26ns, 29ns, 30ns, 32ns, 35ns and 40ns.

[0115] In some embodiments, the laser frequency of the local laser treatment is 100 KHz to 400 KHz. Specifically, the laser frequency of the local laser treatment may be, for example, 100 KHz, 150 KHz, 200 KHz, 250 KHz, 300 KHz, 350 KHz and 400 KHz.

[0116] In some embodiments, the total laser energy of the local laser treatment is 0.1 J*cm -2 ~0.2J*cm -2 Specifically, the comprehensive laser energy of the local laser treatment may be, for example, 0.1 J*cm -2 、0.13J*cm -2 、0.15J*cm -2 、0.18J*cm -2 and 0.2J*cm -2 .

[0117] The applicant has found that controlling the pulse width, laser frequency and comprehensive laser energy of the local laser treatment within the above-defined ranges can ensure the formation of a heavily doped region in the metallized region.

[0118] In some embodiments, the conductive layer is doped, and the concentration of the doped conductive layer 4 obtained after the doping treatment is 8E19 cm -3 ~5E20 cm -3 Then, the doped conductive layer 4 in the metallized region is locally laser treated. During the local laser treatment, the laser acts on the doped conductive layer 4, causing the polysilicon in the metallized region to melt and recrystallize. In this process, more phosphorus elements occupy the silicon lattice, increasing the concentration of phosphorus elements in the doped conductive layer (i.e., the first doped conductive layer 41) in the metallized region, thereby forming a heavily doped region. The concentration of phosphorus elements in the first doped conductive layer 41 is 1E20cm -3 ~1E21cm -3 Specifically, the concentration of phosphorus in the first doped conductive layer 41 may be, for example, 1E20 cm -3 、2E20cm -3 、3E20 cm -3 、4E20 cm -3 、5E20 cm -3 、6E20 cm -3 、7E20 cm -3 、8E20 cm -3 、9E20 cm -3 and 1E21cm -3The concentration of phosphorus in the doped conductive layer (i.e., the second doped conductive layer 42) in the non-metallized region remains the same, i.e., the concentration of phosphorus in the second doped conductive layer 42 is 8E19 cm -3 ~5E20 cm -3 Specifically, the concentration of phosphorus in the second doped conductive layer 42 may be, for example, 8E19 cm -3 、9E19cm -3 , 1E20 cm -3 , 2E20 cm -3 、3E20 cm -3 、4E20cm -3 and 5E20 cm -3 .

[0119] In some embodiments, due to laser heavy doping of the doped conductive layer in the metallized region, the film layer elements in the doped conductive layer in the metallized region change, wherein the nitrogen element in the doped conductive layer in the metallized region increases, that is, the nitrogen content of the first doped conductive layer 41 is greater than the nitrogen content of the second doped conductive layer 42, specifically, the mass proportion of the nitrogen element in the first doped conductive layer 41 is 3% to 5%, and the mass proportion of the nitrogen element in the second doped conductive layer 42 is 1% to 2%. The oxygen content in the doped conductive layer in the metallized region decreases, the oxygen content of the first doped conductive layer 41 is less than the oxygen content of the second doped conductive layer 42, the oxygen content of the first doped conductive layer 41 is 19% to 22%, and the oxygen content of the second doped conductive layer 42 is 27% to 28%. The present application controls the oxygen content of the first doped conductive layer 41 to be less than the oxygen content of the second doped conductive layer 42, thereby reducing the recombination center on the back side of the solar cell and compensating for the mechanical damage caused by laser treatment of the metallized area. At the same time, the nitrogen content of the first doped conductive layer 41 is controlled to be greater than the nitrogen content of the second doped conductive layer 42, so that the prepared solar cell has excellent passivation effect and good conductivity, thereby improving the cell performance of the solar cell.

[0120] In some embodiments, due to laser heavy doping of the doped conductive layer in the metallized area, the oxygen content of the tunneling layer 3 in the metallized area is increased, that is, the oxygen content of the first tunneling layer 31 is greater than the oxygen content of the second tunneling layer 32, so that the number of bridging bond oxygen in the tunneling layer 3 is increased, thereby increasing the density of the tunneling layer 3, thereby ensuring the tunneling effect of the tunneling layer 3 while effectively improving the problem of increased holes in the tunneling layer caused by the laser, ensuring the passivation performance of the laser heavy doping area, ensuring the open circuit voltage while reducing the metal contact of the battery, and improving the battery efficiency.

[0121] In some embodiments, due to the laser heavy doping of the doped conductive layer in the metallized region, the oxygen content at the interface between the doped conductive layer and the tunneling layer 3 in the metallized region is increased, that is, the oxygen content at the interface between the first doped conductive layer 41 and the first tunneling layer 31 is greater than the oxygen content at the interface between the second doped conductive layer 42 and the second tunneling layer 32. The increase in the oxygen content at the interface between the doped conductive layer and the tunneling layer 3 in the metallized region can improve the film quality of the tunneling layer 3 in the metallized region, and can further enhance the passivation effect of the battery.

[0122] Step S300, see Figure 5 A back passivation layer 6 is formed on the surface of the first doped conductive layer 41 and the second doped conductive layer 42 , and a front passivation layer 5 is formed on the surface of the emitter 2 .

[0123] In some embodiments, due to the laser heavy doping of the doped conductive layer in the metallized area, the oxygen content at the interface between the doped conductive layer and the back passivation layer 6 in the metallized area is increased, that is, the oxygen content at the interface between the first doped conductive layer 41 and the back passivation layer 6 is greater than the oxygen content at the interface between the second doped conductive layer 42 and the back passivation layer 6. The increase in the oxygen content at the interface between the doped conductive layer and the back passivation layer 6 in the metallized area can improve the film quality of the back passivation layer 6 in the metallized area, and can further enhance the passivation effect of the battery.

[0124] In some embodiments, a back passivation layer 6 is formed on the surfaces of the first doped conductive layer 41 and the second doped conductive layer 42. The back passivation layer 6 may include but is not limited to at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc. or any combination thereof.

[0125] For example, the back passivation layer 6 is composed of silicon nitride. The silicon nitride thin film layer can play the role of an anti-reflection film, and the silicon nitride thin film has good insulation, density, stability and masking ability for impurity ions. The silicon nitride thin film layer can have a passivation effect on the semiconductor substrate 1, significantly improving the photoelectric conversion efficiency of the solar cell.

[0126] In some embodiments, the thickness of the back passivation layer 6 is in the range of 70 nm to 120 nm, and specifically may be 70 nm, 80 nm, 90 nm, 100 nm or 120 nm, etc. Of course, it may also be other values ​​within the above range, which is not limited here.

[0127] In some embodiments, when the back passivation layer 6 is a stacked silicon nitride layer and a silicon oxide layer or a stacked silicon nitride layer and a silicon oxynitride layer, the silicon nitride layer is located on the surface of the doped conductive layer 4, and the silicon oxide layer or the silicon oxynitride layer is located on the surface of the silicon nitride layer.

[0128] In some embodiments, the front passivation layer 5 may include, but is not limited to, at least one of silicon oxide, silicon nitride, silicon oxynitride, aluminum oxide, etc., or any combination thereof. The front passivation layer 5 can produce a good passivation effect on the semiconductor substrate 1, which helps to improve the conversion efficiency of the battery. It should be noted that the front passivation layer 5 can also play a role in reducing the reflection of incident light, and in some instances, it can also be called an anti-reflection layer.

[0129] In some embodiments, the thickness of the front passivation layer 5 is in the range of 10 nm to 120 nm, specifically 10 nm, 20 nm, 30 nm, 42 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or 120 nm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0130] Step S400, see Figure 1 , penetrating the back passivation layer 6 to form a back electrode 8 in contact with the first doped polysilicon layer 41 , and penetrating the front passivation layer 5 to form a front electrode 7 in contact with the emitter 2 .

[0131] In some embodiments, a front main grid and a front sub-grid are printed on the front side of the semiconductor substrate 1 using a slurry, and the slurry is dried to form a corresponding front electrode 7. A back main grid and a back sub-grid are printed on the back side of the semiconductor substrate 1 using a slurry, and the slurry is dried to form a corresponding back electrode 8. Finally, the dried cell is sintered to obtain a solar cell.

[0132] The embodiment of the present invention does not limit the specific materials of the front electrode 7 and the back electrode 8. For example, the front electrode 7 is a silver electrode or a silver / aluminum electrode, and the back electrode 8 is a silver electrode or a silver / aluminum electrode.

[0133] It should be noted that, in the present application, unless otherwise specified, each operation step may be performed in sequence or not. The present application embodiment does not limit the sequence of steps for preparing a solar cell, and may be adjusted according to the actual production process.

[0134] In a third aspect, a photovoltaic assembly 1000 includes a cell string formed by electrically connecting the aforementioned solar cells.

[0135] Specifically, see Figure 6 The photovoltaic assembly 1000 includes a first cover plate 200 , a first packaging adhesive layer 300 , a solar cell string, a second packaging adhesive layer 400 and a second cover plate 500 .

[0136] In some embodiments, a solar cell string includes a plurality of solar cells 100 as described above connected by conductive ribbons, and the solar cells 100 may be connected by partial stacking or splicing.

[0137] In some embodiments,

[0138] The first cover plate 200 and the second cover plate 500 may be transparent or opaque cover plates, such as glass cover plates or plastic cover plates.

[0139] The two sides of the first encapsulation adhesive layer 300 are respectively in contact with the first cover plate 200 and the battery string, and the two sides of the second encapsulation adhesive layer 400 are respectively in contact with the second cover plate 500 and the battery string. The first encapsulation adhesive layer 300 and the second encapsulation adhesive layer 400 can be ethylene-vinyl acetate copolymer (EVA) film, polyethylene octene co-elastomer (POE) film or polyethylene terephthalate (PET) film.

[0140] The photovoltaic module 1000 may also be packaged in a side-enclosed manner, that is, the sides of the photovoltaic module 1000 are completely encapsulated by a packaging tape to prevent lamination deviation of the photovoltaic module 1000 during the lamination process.

[0141] The photovoltaic module 1000 also includes an edge sealing component, which is fixedly packaged on a part of the edge of the photovoltaic module 1000. The edge sealing component can be fixedly packaged on the edge near the corner of the photovoltaic module 1000. The edge sealing component can be a high temperature resistant tape. The high temperature resistant tape has excellent high temperature resistance, will not decompose or fall off during the lamination process, and can ensure reliable packaging of the photovoltaic module 1000. Among them, the two ends of the high temperature resistant tape are respectively fixed to the second cover plate 500 and the first cover plate 200. The two ends of the high temperature resistant tape can be bonded to the second cover plate 500 and the first cover plate 200 respectively, and the middle part can realize the limitation of the side of the photovoltaic module 1000 to prevent the photovoltaic module 1000 from lamination deviation during the lamination process.

[0142] In some embodiments, the photovoltaic assembly 1000 further includes a frame (the frame is Figure 6 The frame can be made of aluminum alloy or stainless steel. When the frame is made of aluminum alloy, the strength and corrosion resistance of the frame are very good. The frame can support and protect the entire solar panel. The photovoltaic module can also be connected to the external photovoltaic bracket through the frame. Multiple photovoltaic modules can be connected to each other to form a photovoltaic power station.

[0143] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A solar cell, characterized in that: include: A semiconductor substrate, the semiconductor substrate comprising a front side and a back side arranged opposite to each other; An emitter and a front passivation layer located on the front side of the semiconductor substrate; A tunneling layer, a doped conductive layer and a back passivation layer located on the back side of the semiconductor substrate, wherein the doped conductive layer includes a first doped conductive layer corresponding to the back metallization area and a second doped conductive layer corresponding to the back non-metallization area, the oxygen content of the first doped conductive layer is less than the oxygen content of the second doped conductive layer, the oxygen content of the first doped conductive layer is 19% to 22%, and the oxygen content of the second doped conductive layer is 27% to 28%; the first doped conductive layer and the second doped conductive layer are both phosphorus-doped layers, and the concentration of phosphorus in the first doped conductive layer is greater than the concentration of phosphorus in the second doped conductive layer; A front electrode in contact with the emitter and a back electrode in contact with the first doped conductive layer.

2. The solar cell according to claim 1, characterized in that The concentration of phosphorus in the first doped conductive layer is 1E20 cm -3 ~1E21cm -3 , and / or the concentration of phosphorus in the second doped conductive layer is 8E19 cm -3 ~5E20cm -3 .

3. The solar cell according to claim 1, characterized in that The sheet resistance of the first doped conductive layer is 30Ω / sq to 80Ω / sq, and / or the sheet resistance of the second doped conductive layer is 60Ω / sq to 400Ω / sq.

4. The solar cell according to claim 1, characterized in that The thickness of the first doped conductive layer is 30 nm to 300 nm, and / or the thickness of the second doped conductive layer is 30 nm to 300 nm.

5. The solar cell according to claim 1, characterized in that: The oxygen content in the second doped conductive layer is 27%-28%.

6. The solar cell according to claim 1, characterized in that The nitrogen content of the first doped conductive layer is greater than the nitrogen content of the second doped conductive layer, and the mass proportion of nitrogen in the second doped conductive layer is 1% to 2%.

7. The solar cell according to claim 1, characterized in that The thickness of the tunneling layer is 0.8 nm to 2 nm.

8. The solar cell according to claim 1 or 7, characterized in that: The tunneling layer includes a first tunneling layer corresponding to a back metallization region and a second tunneling layer corresponding to a back non-metallization region, and an oxygen content in the second tunneling layer is 17% to 19%.

9. The solar cell according to claim 1, characterized in that: The thickness of the back passivation layer is 70nm-120nm.

10. A photovoltaic module, characterized in that: The photovoltaic assembly comprises a cover plate, a packaging material layer, and a solar cell string, wherein the solar cell string comprises a plurality of solar cells according to any one of claims 1 to 9.

Images