Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention relates to the technical field of photovoltaic power generation, in particular to a solar cell, a preparation method thereof and a photovoltaic module. The solar cell comprises a substrate, wherein the surface of the substrate is provided with a first region and a second region outside the first region; the patterned doping layer is located on the substrate, and the position of the doping layer corresponds to the first area; the height difference between the surface, away from the substrate, of the doped layer and the surface, located in the second area, of the substrate is delta H, and delta H is larger than or equal to 0.5 micrometer and smaller than or equal to 7 micrometers. The functional layer is arranged on the doping layer and on the surface of the substrate in the second area; and the grid line passes through the functional layer and is in ohmic contact with the doping layer.

Description

TECHNICAL FIELD

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

[0002] It is difficult to improve the efficiency of a solar cell, and although the film layer structure can be optimized to reduce non-ideal optical loss, the substrate is more damaged and difficult to clean due to the optimization of the film layer structure, and these damages exist in the final solar cell product, which brings more recombination loss problems. Therefore, the above-mentioned contradictions make it difficult to effectively improve the efficiency of the solar cell as expected. SUMMARY

[0003] To solve the above technical problems, the present application discloses a solar cell, a preparation method thereof, and a photovoltaic module, so as to reduce the non-ideal optical loss of the solar cell, ensure the quality of the film layer structure in the solar cell, and further ensure that the efficiency of the solar cell can be effectively improved.

[0004] In a first aspect, the present application provides a solar cell, which comprises:

[0005] a substrate, a surface of the substrate having a first region and a second region outside the first region;

[0006] a patterned doped layer, the doped layer being located on the substrate, and a position of the doped layer corresponding to the first region; wherein a height difference between a surface of the doped layer away from the substrate and a surface of the substrate located in the second region is ΔH, 0.5 μm≤ΔH≤7 μm;

[0007] a functional layer, the functional layer being provided on the doped layer and on the surface of the substrate located in the second region;

[0008] a grid line, the grid line being in ohmic contact with the functional layer and the doped layer.

[0009] Preferably, 2 μm≤ΔH≤7 μm.

[0010] Further, the surface of the substrate located in the first region has a plurality of first pyramid base microstructures, an average base side length of the first pyramid base microstructures being L1, 4 μm≤L1≤16 μm;

[0011] the surface of the substrate located in the second region has a plurality of second pyramid base microstructures, an average base side length of the second pyramid base microstructures being L2, 5 μm≤L2≤35 μm, and L2>L1.

[0012] Further, the width of the doped layer along a preset direction is D, 100 μm≤D≤450 μm, and the preset direction is perpendicular to the length direction of the gate line.

[0013] Preferably, 100 μm≤D≤200 μm.

[0014] Further, the thickness of the doped layer is 35 nm-135 nm.

[0015] Further, the sheet resistance of the doped layer is 10 Ω·sq -1 -75 Ω·sq -1 .

[0016] Further, the thickness of the functional layer is 0.5 nm-10 nm.

[0017] Further, the doped layer comprises a first doped sub-layer, a barrier layer and a second doped sub-layer in sequence in a direction from the substrate to the gate line, the barrier layer comprises at least one of a silicon oxide layer or a silicon oxynitride layer, and the gate line is in ohmic contact with the second sub-layer through the functional layer.

[0018] In one embodiment, the thickness of the first doped sub-layer is 10 nm-25 nm, the doping concentration of the first doped sub-layer is 1×10 19 cm 3 -1×10 21 cm 3 , the thickness of the barrier layer is 1.0 nm-5.0 nm, the thickness of the second doped sub-layer is 60 nm-130 nm, the doping concentration of the second doped sub-layer is 1×10 20 cm 3 -9×10 21 cm 3 , and the doping concentration of the second doped sub-layer is greater than that of the first doped sub-layer.

[0019] In another embodiment, the thickness of the first doped sub-layer is 5 nm-15 nm, the doping concentration of the first doped sub-layer is 5×10 18 cm 3 -1×10 21 cm 3 , the thickness of the barrier layer is 1.0 nm-5.0 nm, the thickness of the second doped sub-layer is 20 nm-50 nm, the doping concentration of the second doped sub-layer is 1×10 20 cm 3 -9×10 21 cm 3, and a doping concentration of the second dopant sub-layer is greater than a doping concentration of the first dopant sub-layer.

[0020] Further, the solar cell further comprises a patterned dielectric layer, the patterned dielectric layer is arranged between the substrate and the doped layer, the dielectric layer corresponds to the position of the doped layer, and the thickness of the dielectric layer is 1 nm to 4 nm; and an inner extension doped layer, the inner extension doped layer is arranged between the substrate and the dielectric layer.

[0021] Optionally, the substrate is a silicon substrate.

[0022] Optionally, the doped layer comprises at least one of a doped polysilicon layer, a doped microcrystalline silicon layer, and a doped amorphous silicon layer.

[0023] Optionally, the doped layer is of an N-type or a P-type, when the doped layer is of the N-type, the doping element in the doped layer comprises at least one of phosphorus, arsenic, and antimony, and when the doped layer is of the P-type, the doping element in the doped layer comprises at least one of boron and gallium.

[0024] Optionally, the functional layer comprises at least one of a passivation layer and an anti-reflection layer.

[0025] Optionally, the functional layer comprises at least one of a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, and an aluminum oxide layer.

[0026] Optionally, the gate line comprises at least one of a silver gate line, a silver-aluminum gate line, a copper gate line, and a nickel gate line.

[0027] Further, the surface of the substrate comprises a light-receiving surface and a back surface arranged oppositely, and the doped layer is arranged on the side of the back surface of the substrate.

[0028] The solar cell further comprises the dielectric layer arranged between the substrate and the doped layer.

[0029] The substrate is an N-type silicon substrate, and the doped layer is an N-type doped polysilicon layer.

[0030] The functional layer is a back surface passivation layer.

[0031] In a second aspect, the present application provides a method for preparing a solar cell, the method comprising the following steps:

[0032] providing a substrate with a mask layer and a doped layer, wherein the doped layer is arranged between the mask layer and the substrate, the substrate has a middle region and an edge region located at the periphery of the middle region, and the thickness of the mask layer and the doped layer corresponding to the middle region is greater than the thickness corresponding to the edge region.

[0033] laser opening the mask layer to form a first region with a pattern difference and a second region outside the first region; wherein the second region is a laser opening region, and in the second region corresponding to the edge region, the surface of the doped layer is exposed and forms an oxide layer;

[0034] pre-cleaning to clean the oxide layer;

[0035] RCA cleaning to expose the surface of the substrate in the second region and expose the surface of the doped layer in the first region, and the height difference between the surface of the doped layer away from the substrate and the back surface of the substrate in the second region is ΔH, 0.5 μm≤ΔH≤7 μm;

[0036] post-processing to form a functional layer on the side of the patterned doped layer away from the substrate and the substrate not covered by the doped layer, and form a gate line on the functional layer, so that the gate line is in ohmic contact with the functional layer and the doped layer.

[0037] Further, the pre-cleaning conditions include: using an alkali agent with a concentration of 0.1wt%-0.5wt% and hydrogen peroxide with a concentration of 1wt%-10wt% for pre-cleaning, the temperature is 65°C-80°C, and the time is 50s-150s; wherein the alkali agent includes sodium hydroxide solution or potassium hydroxide solution.

[0038] Further, in the step of providing the substrate with the mask layer and the doped layer, the mask layer includes: a silicon nitride mask layer arranged close to the doped layer and a silicon oxide mask layer arranged away from the doped layer.

[0039] Optionally, the laser opening conditions include: using a green light source, the laser power is 20W-60W, the laser overlap rate is 5%-70%, and the laser opening depth is 3nm-35nm.

[0040] Optionally, the laser opening conditions include: the laser power is 20W-55W, and the laser overlap rate is 45%-70%.

[0041] Alternatively, the laser opening conditions include: the laser power is 30W-55W, and the laser overlap rate is 10%-35%.

[0042] In a third aspect, the embodiments of the present application provide a photovoltaic module, which includes the solar cell of the first aspect or the solar cell prepared by the preparation method of the second aspect.

[0043] Compared with the prior art, the present application has at least the following beneficial effects:

[0044] The solar cell provided by the application has a height difference AH between the surface of the doped layer, such as the doped polysilicon layer, away from the substrate and the surface of the substrate without the grid line area within a specific range, which can reduce optical loss, laser damage residue and oxidation layer residue, and ensure the film quality of the back surface functional layer, thereby solving the above new problems caused by the patterned doped layer, such as the doped polysilicon layer, and effectively improving the performance of the solar cell. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0046] Figure 1 is a structural schematic diagram of a solar cell in an embodiment of the application;

[0047] Figure 2 is a structural schematic diagram of a substrate in a solar cell in an embodiment of the application;

[0048] Figure 3 is a structural schematic diagram of another solar cell in an embodiment of the application;

[0049] Figure 4 is an ECV diagram of a doped layer in a solar cell in an embodiment of the application;

[0050] Figure 5 is a structural schematic diagram of another solar cell in an embodiment of the application;

[0051] Figure 6 is a process flow diagram of a preparation method of a solar cell in an embodiment of the application;

[0052] Figure 7 is a topographic diagram of the junction between the first region and the second region of the edge region of a substrate after RCA cleaning of a solar cell in an embodiment of the application;

[0053] Figure 8 is a topographic diagram of the junction between the first region and the second region of the edge region of a substrate after RCA cleaning of a solar cell in the prior art.

[0054] Explanation of reference signs:

[0055] 1, substrate; 11, light-receiving surface; 12, back surface; 1A, first region; 1B, second region; 111, first pyramid base microstructure; 112, second pyramid base microstructure;

[0056] 2, doped layer; 21, first sub-doped layer; 22, barrier layer; 23, second sub-doped layer;

[0057] 3, functional layer; 4, gate line; 5, dielectric layer; 6, inner extension doped layer. DETAILED DESCRIPTION

[0058] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0059] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not intended to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0060] In addition, in addition to indicating the orientation or positional relationship, the above-mentioned part of the terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. For those skilled in the art, the specific meaning of these terms in the present application can be understood according to the specific situation.

[0061] In addition, the terms "mount", "set", "provided with", "connect", "connected" should be broadly understood. For example, it can be fixedly connected, detachably connected, or integrally constructed; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or internal communication between two devices, elements or components. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific situation.

[0062] In addition, the terms "first", "second" and the like are mainly used to distinguish different devices, elements or components (the specific type and structure may be the same or different), and are not intended to indicate or imply the relative importance and quantity of the indicated devices, elements or components. Unless otherwise stated, the meaning of "multiple" is two or more.

[0063] To improve the photoelectric conversion efficiency of a solar cell, the non-ideal optical loss of the back surface of the solar cell can be considered. For example, the passivated contact solar cell has a doped polysilicon layer arranged on the back surface, and the parasitic absorption of the doped polysilicon layer is relatively obvious. Therefore, the optical loss caused by the parasitic absorption can be reduced by arranging the doped polysilicon layer in a patterned structure, the current advantage is released, the short-circuit current is improved, and the efficiency of the solar cell is promoted.

[0064] However, this structure needs to perform a patterning operation on the entire doped polysilicon layer, and ensure that the doped polysilicon layer in the area without the gate line is completely removed, that is, the substrate in the area without the gate line is exposed. However, the applicant found that this would cause new problems: when performing the above-mentioned patterning operation by means of laser, laser damage would be caused to the doped polysilicon layer and even the substrate, especially the doped polysilicon layer and the substrate in the edge region around the substrate, not only the laser damage exists (because the doped polysilicon layer itself has the problem of uneven distribution), but also an oxide layer caused by laser would be formed on the surface of the doped polysilicon layer in the edge region around the substrate. The residual of this oxide layer would eventually adversely affect the efficiency improvement of the solar cell again, offsetting the current advantage released by the patterned doped layer, resulting in that the performance of the solar cell cannot be effectively improved.

[0065] The present application has found that, when the height difference ΔH between the surface of the doped polysilicon layer or other doped layer away from the substrate and the surface of the substrate in the area without the gate line is within a certain range, the optical loss, the laser damage and the oxide layer residue can be reduced, and the film quality of the functional layer on the back surface can be ensured, thereby solving the above-mentioned new problems caused by the patterned doped polysilicon layer or other doped layer. Thus, the performance of the solar cell can be effectively improved.

[0066] Referring to Figure 1 The solar cell provided by the embodiment of the present application comprises:

[0067] A substrate 1, the surface of the substrate 1 has a first area 1A and a second area 1B located outside the first area 1A;

[0068] A patterned doped layer 2, the doped layer 2 is located on the substrate 1, and the position of the doped layer 2 corresponds to the first area 1A; wherein the height difference between the surface of the doped layer 2 away from the substrate 1 and the surface of the substrate 1 in the second area 1B is ΔH, and 0.5 μm≤ΔH≤7 μm;

[0069] A functional layer 3, the functional layer 3 is arranged on the doped layer 2 and on the surface of the substrate 1 in the second area 1B;

[0070] A gate line 4, the gate line 4 is in ohmic contact with the functional layer 3 and the doped layer 2.

[0071] The first region 1A and the second region 1B of the substrate 1 can be divided into a metal region and a non-metal region by whether the gate line 4 is arranged. Since the position of the patterned doped layer 2 corresponds to the first region 1A, and the gate line 4 is in ohmic contact with the doped layer 2 through the functional layer 3, the position of the gate line 4 also corresponds to the first region 1A. The first region 1A is a metal region for arranging the gate line 4, and the second region 1B is a non-metal region without arranging the gate line 4. Preferably, the substrate 1 can be a silicon substrate 1.

[0072] The patterned doped layer 2 refers to that the doped layer 2 is not arranged on the substrate 1 in an integral film layer structure, but is arranged on part of the substrate 1 in a patterned local film layer structure. Specifically, the doped layer 2 is arranged on the first region 1A of the substrate 1, and the second region 1B does not have the doped layer 2. In this way, the patterned doped layer 2 only exists in the first region 1A corresponding to the arrangement of the gate line 4, which can maximize the reduction of the area of the doped layer 2 on the basis of ensuring the ohmic contact between the doped layer 2 and the gate line 4, thereby reducing the optical loss problem caused by the parasitic absorption of the doped layer 2. Optionally, the doped layer 2 includes at least one of a doped polysilicon layer, a doped microcrystalline silicon layer, and a doped amorphous silicon layer. In addition, the doped layer 2 is of N-type or P-type. When the doped layer 2 is of N-type, the doped elements in the doped layer 2 include at least one of phosphorus, arsenic, or antimony. When the doped layer 2 is of P-type, the doped elements in the doped layer 2 include at least one of boron or gallium. It can be understood that other film layers such as a dielectric layer 5 can also be arranged between the doped layer 2 and the substrate 1, which is not limited in the present application.

[0073] The functional layer 3 is arranged on the doped layer 2 and on the surface of the substrate 1 in the second region 1B, that is, the functional layer 3 is arranged in an integral layer, covering the doped layer 2 and the substrate 1 without the doped layer 2. In the embodiments of the present application, the functional layer 3 can be at least one of a passivation layer or an anti-reflection layer. Optionally, the functional layer 3 includes at least one of a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, and an aluminum oxide layer.

[0074] The gate line 4 is in ohmic contact with the doped layer 2 through the functional layer 3, so the positions of the gate line 4 and the doped layer 2 both correspond to the first region 1A of the substrate 1. Since the gate line 4 is metal, light is difficult to enter the substrate 1 from the position of the gate line 4. Therefore, the doped layer 2 is arranged in this part of the region, and the doped layer 2 is not arranged in other regions, which can more effectively utilize the area of the doped layer 2 and reduce its parasitic absorption. Optionally, the gate line 4 includes at least one of a silver gate line 4, a silver-aluminum gate line 4, a copper gate line 4, or a nickel gate line 4.

[0075] As to the problem that the substrate 1 is more damaged and difficult to be cleaned due to the patterning of the doping layer 2 by means of laser, etc., the present inventors have found that, when the height difference ΔH between the surface of the doping layer 2 away from the substrate 1 and the surface of the substrate 1 in the second region 1B is controlled within the range of 0.5 μm to 7 μm, the oxidation layer residue caused by laser can be effectively cleaned, the damage of the substrate 1 can be repaired, and the obvious secondary texturing on the surface of the substrate 1 in the second region 1B can be avoided.

[0076] It can be understood that the above ΔH can be obtained by observing the cross-sectional view (longitudinal cross-section along the direction perpendicular to the substrate 1) of the solar cell in the specified region using a Zeta 3D microscope, and then measuring and calculating. For example, a 64 μm x 32 μm cross-sectional range is selected for shooting, and the height difference ΔH between the surface of the doping layer 2 away from the substrate 1 and the surface of the substrate 1 in the second region 1B is measured. Specifically, five different 64 μm x 32 μm regions can be selected, and the ΔH in the corresponding cross-sectional range is measured and calculated. The ΔH of these different positions is averaged. The measurement method of ΔH is not limited in the present application.

[0077] When ΔH is less than 0.5 μm, the oxidation layer residue caused by the laser patterning of the doping layer 2 cannot be effectively cleaned, and there are still more residues. Finally, the photoelectric conversion efficiency of the solar cell is not significantly improved. However, the height difference is not the larger the better. When ΔH is greater than 7 μm, the contact performance between the doping layer 2 and the grid line 4 in the first region 1A is poor, the fill factor of the solar cell is significantly reduced, and the substrate 1 surface in the second region 1B is obviously second textured. This leads to poor contact performance between the substrate 1 and the functional layer 3 in the second region 1B, and the functional layer 3 is prone to quality problems such as film explosion. Therefore, the height difference ΔH is controlled within the above range, which can more comprehensively solve the problems of cleaning the oxidation layer residue, the secondary texturing after the repair of the substrate 1 and the film explosion caused thereby, and thus more effectively improve the performance of the solar cell such as the photoelectric conversion efficiency.

[0078] For example, 0.5 μm ≤ ΔH ≤ 7 μm includes any point value within the height difference range, for example, ΔH is 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm or 7 μm.

[0079] Preferably, 2 μm ≤ ΔH ≤ 7 μm. When the height difference ΔH between the surface of the doping layer 2 away from the substrate 1 and the surface of the substrate 1 in the second region 1B is further controlled within the range of 2 μm to 7 μm, the effect of improving the photoelectric conversion efficiency of the solar cell is more optimal.

[0080] Further, in combination withFigure 2 as shown, Figure 2 is a structural schematic diagram of a substrate 1 of a solar cell according to an embodiment of the present application, and is a clear schematic diagram of the first pyramid base microstructure 111 on the surface of the substrate 1, Figure 2 The surface of the substrate 1 in the first region 1A has a plurality of first pyramid base microstructures 111, and the average base edge length of the first pyramid base microstructure 111 is L1, 4 μm≤L1≤16 μm. The surface of the substrate 1 in the second region 1B has a plurality of second pyramid base microstructures 112, and the average base edge length of the second pyramid base microstructure 112 is L2, 5 μm≤L2≤35 μm, and L2>L1.

[0081] It can be understood that the average base edge lengths L1 and L2 can be obtained by observing the substrate 1 (top view) of the specified region using a Zeta measuring instrument, and then measuring and calculating. For example, five 64 μm×32 μm regions at different positions can be selected, the base edge lengths of a plurality of different first pyramid base microstructures 111 are measured and calculated, and the average value of the base edge lengths is taken as the average base edge length L1 of the first pyramid base microstructure 111. L2 is measured in the same way, and the measurement method of L1 and L2 is not limited in the present application.

[0082] The preparation method of the first pyramid base microstructure 111 and the second pyramid base microstructure 112 is not limited in the present application. The pyramid base microstructure can be obtained by the following method, for example: first, texturing the substrate 1 to make the surface of the substrate 1 have a plurality of pyramid microstructures, and then polishing the substrate 1 to make the pyramid tips of the pyramid microstructures be corroded away, and the remaining structure forms the shape of the pyramid base microstructure.

[0083] On the basis of controlling the height difference ΔH between the surface of the substrate 1 away from the doped layer 2 and the surface of the substrate 1 in the second region 1B to be within the range of 0.5 μm-7 μm, and further controlling the average base edge lengths of the pyramid base microstructures in the first region 1A and the second region 1B to be within the above range and the size relationship, it is beneficial to better ensure the contact performance, the cleaning effect of the laser damage residue, and the texturing degree of the second region 1B. The average base edge length of the first pyramid base microstructure 111 in the first region 1A reflects the size of the base after normal RCA cleaning, and is controlled to be within 4 μm-15 μm, which can better ensure the contact performance between the doped layer 2 and the grid line 4 in the first region 1A. The average base edge length of the second pyramid base microstructure 112 in the second region 1B reflects the size of the base after the pre-cleaning and the normal RCA cleaning, and is controlled to be within 5 μm-35 μm and L2>L1, which can better ensure that the laser damage residue is cleaned, but at the same time, it will not be too large to cause the secondary texturing phenomenon.

[0084] 4pm≤L1≤16pm includes any point value in the numerical range, for example, L1 is 4pm, 5pm, 8pm, 10pm, 12pm, 15pm or 16pm. 5pm≤L2≤35pm includes any point value in the numerical range, for example, L2 is 5pm, 8pm, 10pm, 12pm, 15pm, 20pm, 25pm or 30pm. It can be understood that although the numerical ranges of L1 and L2 overlap, since L2>L1, those skilled in the art can determine appropriate L1 and L2 from the above numerical ranges, which meet the respective numerical ranges and the relationship L2>L1. For example, when L1 is 5pm, L2 can be 7pm. For example, when L1 is 16pm, L2 can be 24pm.

[0085] Further, the width of the doped layer 2 along the preset direction is D, 100pm≤D≤450pm, and the preset direction is perpendicular to the length direction of the gate line 4. Controlling the width D of the doped layer 2 in the above range is beneficial to better release the current advantage. Compared with the case where the width range of the doped layer 2 is greater than 450pm, further controlling the width of the doped layer 2 in the range of 100pm to 450pm can further reduce the setting area of the doped layer 2, and thus less parasitic absorption, thereby further releasing the current advantage. 100pm≤D≤450pm includes any point value in the numerical range, for example, D is 100pm, 150pm, 180pm, 200pm, 250pm, 300pm, 350pm, 400pm or 450pm.

[0086] It can be understood that the width D of the doped layer can be observed by using a Zeta measuring instrument on the doped layer (top view) of the specified area, and then measured and calculated. For example, five different 64pm×32pm areas can be selected, and the width D of the doped layer is measured and calculated, and the average of the widths is taken, which reflects the width D of the doped layer. The measurement method of the width D of the doped layer is not limited in the present application.

[0087] It can be understood that when the width D of the doped layer 2 is narrowed to 100pm to 450pm, the manufacturing precision of the patterned doped layer 2 can be improved by adjusting the grabbing point mode of the laser light source. For example, the laser light source can be adjusted to be the light source of the PERC cell.

[0088] Preferably, the width D of the doped layer 2 is 100pm to 200pm. When the width D of the doped layer 2 is controlled in the range, the area of the doped layer 2 on the entire substrate 1 is smaller, and the non-ideal optical loss such as parasitic absorption is less.

[0089] Further, the thickness of the doped layer 2 is 35 nm to 135 nm. In the embodiment of the present application, the thickness of the doped layer 2 can be achieved in two ways, one is greater than 90 nm, for example, 91 nm to 135 nm, and the other is that the thickness of the doped layer 2 is thinned to 35 nm to 90 nm. Among them, the doped layer 2 with a thickness greater than 90 nm can better ensure the effect of manufacturing the grid line 4 on the doped layer 2 and the functional layer 3, reduce the risk of electrode paste burning of the grid line 4, and also effectively reduce the problem of film explosion in the process of advancing the doped elements in the doped layer 2 to the direction of the substrate 1, which further helps to improve the photoelectric conversion efficiency of the solar cell from the above aspects. Among them, the doped layer 2 with a thickness of 35 nm to 90 nm is more beneficial to reduce the parasitic absorption caused by the doped layer 2. Among them, the thickness of the doped layer 2 is 35 nm to 135 nm, including any point value in the numerical range, for example, the thickness of the doped layer 2 is 35 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm or 135 nm.

[0090] Further, the sheet resistance of the doped layer 2 is 10 Ω·sq -1 to 75 Ω·sq -1 . Among them, the sheet resistance of the doped layer 2 is 10 Ω·sq -1 to 75 Ω·sq -1 , including any point value in the numerical range, for example, the sheet resistance of the doped layer 2 is 10 Ω·sq -1 , 15 Ω·sq -1 , 20 Ω·sq -1 , 25 Ω·sq -1 , 30 Ω·sq -1 , 40 Ω·sq -1 , 50 Ω·sq -1 , 60 Ω·sq -1 or 75 Ω·sq -1 . When the sheet resistance of the doped layer 2 is further controlled within the above range, it is beneficial to improve the transmission capacity of the carrier in the doped layer, optimize the contact performance between the doped layer and the grid line, and avoid the recombination of the photo-generated carrier in the doped layer. When the solar cell further includes a medium layer 5 arranged between the substrate 1 and the doped layer 2, the above sheet resistance range of the doped layer 2 is also beneficial to improve the tunneling efficiency of the carrier tunneling through the medium layer, and avoid affecting the open circuit voltage and the fill factor of the solar cell.

[0091] Further, the thickness of the functional layer 3 is 0.5 nm to 10 nm. Among them, the thickness of the functional layer 3 is 0.5 nm to 10 nm, including any point value in the numerical range, for example, the thickness of the functional layer 3 is 0.5 nm, 1 nm, 2 nm, 3 nm, 5 nm, 8 nm or 10 nm.

[0092] It is understandable that the thickness of the aforementioned functional layer can be measured using an ellipsometer. For example, by measuring the film thickness at different locations of the functional layer and averaging these thicknesses, the thickness of the functional layer can be obtained.

[0093] Further reading Figure 3 , Figure 3 This is a schematic diagram of another solar cell structure according to an embodiment of this application. Following the direction from the substrate 1 towards the grid line 4, the doped layer 2 sequentially includes a first doped sublayer 21, a barrier layer 22, and a second doped sublayer 23. The barrier layer 22 includes at least one layer of silicon oxide or silicon oxynitride. By setting the doped layer 2 as a composite structure of the above-mentioned sublayers, the barrier layer 22 can be used to prevent excessive diffusion of doped elements from the second doped sublayer 23 into the substrate 1, ensuring a high surface doping concentration level of the second doped sublayer 23 and guaranteeing carrier transport capability. Preferably, the barrier layer 22 can be a silicon oxide layer.

[0094] See further Figure 4 , Figure 4 This is an electrochemical capacitance-voltage (ECV) diagram of the doped layer 2 in the solar cell of this application embodiment. The doped layer 2 is a doped polycrystalline silicon layer. The diagram shows the distribution of carrier concentration in the doped layer 2. Specifically, in the first region 1A (i.e., the metallization region), the doping concentration of the doped layer 2 decreases with increasing doping depth. However, a high doping concentration, approximately 9 × 10⁻⁶, is observed near the surface of the doped layer 2. 21 pcs / cm 3 The deeper the doping and the lower the doping concentration, the more ideal the overall doping trend appears. This doping trend indicates that the embodiments of this application do indeed have a high doping concentration level on the surface of the doped layer 2, while the doping concentration expanding into the substrate 1 is relatively small. Therefore, the solar cell has both good carrier transport capability and good passivation performance, and will not have problems such as obvious film bursting leading to interface defects.

[0095] In one optional embodiment, the overall thickness of the doped layer 2 is a conventional thickness, and the thickness and doping concentration of each layer in the doped layer 2 are set as follows: the thickness of the first doped sublayer 21 is 10 nm to 25 nm, and the doping concentration of the first doped sublayer 21 is 1 × 10⁻⁶. 19 pcs / cm 3 ~1×10 21 pcs / cm 3 The thickness of the barrier layer 22 is 1.0 nm to 5.0 nm; the thickness of the second doped sublayer 23 is 60 nm to 130 nm, and the doping concentration of the second doped sublayer 23 is 1 × 10⁻⁶. 20 pcs / cm3 ~9x10 21 cm-2 3 , and the doping concentration of the second dopant layer 23 is greater than the doping concentration of the first dopant layer 21.

[0096] In the above composite structure of the doping layer 2, the first dopant layer 21 is a film layer with a relatively thin thickness and a relatively low doping concentration, which is conducive to ensuring that a small amount of doping elements enter the substrate 1, thereby reducing the composite and enhancing the passivation effect; on this basis, the thickness of the barrier layer 22 is controlled to be relatively thin within the above range, which can play a certain blocking effect on the doping elements from the second dopant layer 23, reduce the probability of film explosion caused by the diffusion of a large amount of doping elements in the direction of the substrate 1, and maintain a higher doping concentration of more doping elements in the second dopant layer 23; further, the second dopant layer 23 is a film layer with a relatively thick thickness and a relatively high doping concentration, which can reduce the contact resistance between the grid line 4 and the second dopant layer 23, and promote the improvement of the opening voltage and filling performance of the cell sheet.

[0097] In this way, through the cooperative arrangement of the two layers of dopant layers with different thicknesses and different doping concentrations and the barrier layer 22, the overall thickness of the doping layer 2 in the first region 1A and the high surface doping concentration can be taken into account, which ensures that there is no problem of burning through or film explosion during subsequent sintering of the grid line 4, and also ensures good contact performance between the grid line 4 and the doping layer 2.

[0098] The thickness of the first dopant layer 21 is 10 nm to 25 nm, including any point value within the range, for example, the thickness of the first dopant layer 21 is 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm or 25 nm. The doping concentration of the first dopant layer 21 is 1x10 19 cm-2 3 to 1x10 21 cm-2 3 , including any point value within the range, for example, the doping concentration of the first dopant layer 21 is 1x10 19 cm-2 3 , 5x10 19 cm-2 3 , 1x10 20 cm-2 3 , 5x10 20 cm-2 3 or 1x10 21 cm-2 3The thickness of the barrier layer 22 is 1.0 nm to 5.0 nm, including any value within this range. For example, the thickness of the barrier layer 22 may be 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 4.0 nm, or 5.0 nm. The thickness of the second doped sublayer 23 is 60 nm to 130 nm, including any value within this range. For example, the thickness of the second doped sublayer 23 may be 60 nm, 70 nm, 75 nm, 80 nm, 90 nm, 100 nm, 110 nm, or 130 nm. The doping concentration of the second doped sublayer 23 is 1 × 10⁻⁶. 20 pcs / cm 3 ~9×10 21 pcs / cm 3 This includes any point within this range, for example, the doping concentration of the second doped sublayer 23 is 1 × 10⁻⁶. 20 pcs / cm 3 5×10 20 pcs / cm 3 1×10 21 pcs / cm 3 5×10 21 pcs / cm 3 1×10 22 pcs / cm 3 5×10 22 pcs / cm 3 Or 9×10 22 pcs / cm 3 .

[0099] In another optional embodiment, the overall thickness of the doped layer 2 is reduced, and the thickness and doping concentration of each layer in the doped layer 2 are set as follows: the thickness of the first doped sublayer 21 is 5nm to 15nm, and the doping concentration of the first doped sublayer 21 is 5×10⁻⁶. 18 pcs / cm 3 ~1×10 21 pcs / cm 3 The thickness of the barrier layer 22 is 1.0 nm to 5.0 nm; the thickness of the second doped sublayer 23 is 20 nm to 50 nm, and the doping concentration of the second doped sublayer 23 is 1 × 10⁻⁶. 20 pcs / cm 3 ~9×10 21 pcs / cm 3 Furthermore, the doping concentration of the second doped sublayer 23 is greater than that of the first doped sublayer 21.

[0100] Compared with the previous method of setting the overall thickness of the doped layer 2 to a conventional thickness, when the overall thickness of the doped layer 2 is reduced, and the thickness and doping concentration of each film layer are set as described above, in addition to enhancing the passivation effect and reducing film bursting, it also has the characteristics of less parasitic absorption and more significant advantages in releasing current.

[0101] The thickness of the first doped sublayer 21 is 5 nm to 15 nm, including any value within this range. For example, the thickness of the first doped sublayer 21 is 5 nm, 8 nm, 10 nm, 12 nm, or 15 nm. The doping concentration of the first doped sublayer 21 is 5 × 10⁻⁶. 18 pcs / cm 3 ~1×10 21 pcs / cm 3 This includes any point within this numerical range, for example, the doping concentration of the first doped sublayer 21 is 5 × 10⁻⁶. 18 pcs / cm 3 1×10 19 pcs / cm 3 5×10 19 pcs / cm 3 1×10 20 pcs / cm 3 5×10 20 pcs / cm 3 Or 1×10 21 pcs / cm 3 The thickness of the barrier layer 22 is 1.0 nm to 5.0 nm, including any value within this range. For example, the thickness of the barrier layer 22 may be 1.0 nm, 1.5 nm, 2.0 nm, 2.5 nm, 3.0 nm, 4.0 nm, or 5.0 nm. The thickness of the second doped sublayer 23 is 20 nm to 50 nm, including any value within this range. For example, the thickness of the second doped sublayer 23 may be 20 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm. The doping concentration of the second doped sublayer 23 is 1 × 10⁻⁶. 20 pcs / cm 3 ~9×10 21 pcs / cm 3 This includes any point within this range, for example, the doping concentration of the second doped sublayer 23 is 1 × 10⁻⁶. 20 pcs / cm 3 5×10 20 pcs / cm 3 1×10 21 pcs / cm 3 5×10 21 pcs / cm 3 1×10 22 pcs / cm 3 5×10 22 pcs / cm3 or 9 x 10 22 cm-2 3

[0102] In addition to the above-mentioned film layers, the solar cell of the embodiments of the present application can further include other film layers.

[0103] In one embodiment, the solar cell further comprises a functional layer 3, which is disposed on the light-receiving surface 11 of the substrate 1. Figure 5 Figure 5 Fig. 4 is a structural schematic diagram of another solar cell according to the embodiments of the present application. The solar cell further comprises a patterned dielectric layer 5 disposed between the substrate 1 and the doped layer 2. The dielectric layer 5 corresponds to the position of the doped layer 2, and the thickness of the dielectric layer 5 is 1 nm to 4 nm. The dielectric layer 5 acts as a potential barrier for electrons and holes, and can be combined with the polysilicon layer to prevent the minority carriers from passing through. The dielectric layer 5 can also have a pinhole channel effect, allowing the carriers in the solar cell to move freely, and the selective passing of the majority carriers through the heavily doped polysilicon layer, which is conducive to reducing the recombination loss of the minority carriers. In addition, the dielectric layer 5 can be used as a diffusion barrier to prevent the diffusion of the doping elements of the doped polysilicon layer into the semiconductor substrate, and cooperates with the barrier layer 22 to play a certain blocking effect, ensuring that only a small amount of doping elements reaches the substrate 1. The material of the dielectric layer 5 can include a variety of dielectric materials, such as at least one of silicon oxide, magnesium fluoride, amorphous silicon, polysilicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide or titanium oxide. Specifically, the dielectric layer 5 can be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation performance, can maximize the reduction of the recombination loss of the minority carriers on the surface of the semiconductor substrate, and is a thin film with excellent durability to subsequent high-temperature processes.

[0104] In one embodiment, the solar cell further comprises an inner diffusion doped layer 6, which is located between the substrate 1 and the dielectric layer 5. The inner diffusion doped layer 6 can be formed by a small amount of doping elements from the first doped sub-layer 21 passing through the dielectric layer 5 and diffusing inwardly to the surface of the substrate 1.

[0105] Further, the surface of the substrate 1 includes the light-receiving surface 11 and the back surface 12 disposed opposite to each other, and the doped layer 2 is disposed on the back surface 12 side of the substrate 1. When the dielectric layer 5 is also disposed on the back surface 12, specifically, the dielectric layer 5 is disposed between the substrate 1 and the doped layer 2, and the dielectric layer 5 and the doped layer 2 together form a passivation contact structure. In addition, preferably, the substrate 1 is an N-type silicon substrate 1, the doped layer 2 is a P-type doped polysilicon layer, and the functional layer 3 is a back surface 12 passivation layer. The back surface 12 passivation layer can be a single layer or a composite layer of one or more of a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer.

[0106] ​​It can be understood that a film layer (such as an emitter, a passivation layer, an anti-reflection layer, etc.) can also be arranged on the light-receiving surface 11 side of the solar cell, and the embodiments of the present application do not limit this. For example, when the back surface 12 of the solar cell is sequentially provided with a dielectric layer 5, a P-type doped polysilicon layer, and a silicon nitride passivation anti-reflection layer, the light-receiving surface 11 of the solar cell can be sequentially provided with a boron diffusion layer, an aluminum oxide light-receiving surface passivation layer, a silicon nitride layer anti-reflection layer, and a light-receiving surface grid line 4, etc.

[0107] The embodiments of the present application also provide a preparation method of a solar cell. It can be understood that the preparation method is one method for obtaining the solar cell of the embodiments of the present application, but is not limited to the only method. That is, the solar cell of the embodiments of the present application can also be prepared by other methods, and the present application does not limit this, so it should not be understood as the preparation method provided by the embodiments of the present application being a limitation on the solar cell.

[0108] Further combining Figure 6 As shown in the drawings, the preparation method of the solar cell of the embodiments of the present application includes the following steps:

[0109] A substrate with a mask layer and a doped layer is provided; wherein the doped layer is arranged between the mask layer and the substrate, the substrate has a middle region and an edge region located at the periphery of the middle region, and the thickness of the mask layer and the doped layer corresponding to the middle region is greater than the thickness corresponding to the edge region;

[0110] The mask layer is laser opened to form a first region with a pattern difference and a second region located outside the first region; wherein the second region is the laser opening region, and in the second region corresponding to the edge region, the surface of the doped layer is exposed and formed into an oxide layer;

[0111] Pre-cleaning, cleaning the oxide layer;

[0112] RCA cleaning, so that the surface of the substrate located in the second region is exposed, and the surface of the doped layer located in the first region is exposed, and the height difference between the surface of the doped layer away from the substrate and the back surface of the substrate located in the second region is H, 0.5 μm≤H≤7 μm;

[0113] Post-processing, forming a functional layer on the side of the patterned doped layer away from the substrate and the substrate not covered by the doped layer, and forming a grid line on the functional layer, so that the grid line is in ohmic contact with the doped layer through the functional layer, to obtain the above-mentioned solar cell.

[0114] The doping layer and the mask layer can be formed on the substrate by PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition) or the like, for example, by PECVD or LPCVD to sequentially deposit the doping layer and the mask layer on the surface of the substrate. When the solar cell further comprises a dielectric layer, the dielectric layer, the doping layer and the mask layer can be sequentially deposited on the surface of the substrate.

[0115] For example, when the doping layer and the mask layer are formed on the substrate by the PECVD process, the doping layer and the mask layer inevitably have poor uniformity, specifically, the doping layer corresponding to the middle region of the substrate is thicker, and the doping layer corresponding to the edge region of the substrate is thinner, and the mask layer also has the same problem of poor uniformity. Such poor uniformity of the film thickness can further cause a series of problems, including:

[0116] Firstly, for the mask layer, due to the thicker middle region and the thinner edge region, in the subsequent laser opening process of the mask layer to make a pattern difference, the following situation occurs: only a part of the mask layer corresponding to the middle region is removed (that is, the mask layer in the middle region is not completely opened), but the mask layer in the edge region is completely removed, and the doping layer in the edge region is exposed and forms an oxide layer due to the laser treatment. That is, after the laser opening process, the film layer state corresponding to the middle region is different from the film layer state corresponding to the edge region, especially the film layer state of the region corresponding to the edge region and treated by the laser changes significantly. The film layer state includes not only the difference in film thickness (the mask layer and the doping layer in the middle region are thicker, and only the doping layer in the edge region is thinner), but also the difference in film surface properties (the mask layer remains in the middle region, and the doping layer is exposed and oxidized to an oxide layer in the edge region, or the mask layer in the middle region is completely opened to expose the doping layer, and the doping layer in the edge region is thinner and more damaged.

[0117] Therefore, the thickness of the mask layer and the doping layer corresponding to the middle region is greater than the thickness of the mask layer and the doping layer corresponding to the edge region in the embodiments of the present application. When the mask layer is laser opened, the second region is the laser opening region, and the surface of the doping layer corresponding to the edge region is exposed and forms an oxide layer.

[0118] Secondly, in the RCA cleaning stage, if the substrate after the laser opening is directly cleaned, due to the different film layer states of the middle region and the edge region, the oxide layer in the edge region is difficult to clean completely, and there is a residue problem, and this residue finally exists in the finished solar cell, which affects the performance of the solar cell.

[0119] Therefore, the embodiment of the present application solves a series of problems caused by the uneven thickness of the doped layer by using the preparation method.

[0120] Specifically, although the film layer distribution of the doped layer and the mask layer on the substrate inevitably has uneven problems, resulting in that the area corresponding to the edge region and subjected to laser opening of the film has exposed the doped layer and is oxidized into an oxide layer, the embodiment of the present application adds a pre-cleaning step for cleaning the oxide layer after laser opening of the mask layer and before RCA cleaning, so that the film layer properties of the edge region are more close to and consistent with the film layer state of the middle region.

[0121] On this basis, after normal RCA cleaning, since the oxide layer has been removed relatively clean, the film layer state of the middle region is relatively close to that of the edge region, so that the RCA cleaning can effectively remove the remaining mask layer and laser damage layer, and there is no obvious oxide layer residue. It can be understood that the laser damage layer refers to the fact that the laser energy is relatively high during laser opening of the film, which can penetrate the mask layer and cause damage to the surface of the doped layer below. The damaged area formed in this way is the laser damage layer. That is, the laser damage layer is still the doped layer, which can be easily cleaned by RCA cleaning. However, the oxide layer is different. The oxide layer is formed on the exposed doped layer under the joint action of laser and air after the mask layer in the edge region is completely opened to expose the doped layer during the laser opening of the mask layer. The film layer properties determine that it is not easy to be removed by normal RCA cleaning. Therefore, the pre-cleaning of the oxide layer is performed before the RCA cleaning, so that a better removal effect of the mask layer and the laser damage layer can be achieved.

[0122] After RCA cleaning, the surface of the substrate in the second region and the surface of the doped layer in the first region are exposed, and the height difference ΔH between the surface of the substrate in the second region and the surface of the doped layer in the first region is controlled to be 0.5 μm-7 μm, to obtain a patterned doped layer. In this way, the cleaning effect can be ensured, there is no large amount of oxide layer residue, the surface of the substrate in the second region is not significantly re-textured, parasitic absorption is reduced, the current advantage is truly released, and the purpose of effectively improving the performance of the solar cell is achieved.

[0123] Further referring to the comparison of Figure 7 and Figure 8 , it can be seen that Figure 7 After pre-cleaning and then RCA cleaning, the oxide layer and the laser damage layer are both cleaned relatively clean. However, Figure 8 is the prior art in which RCA cleaning is directly performed after laser opening of the mask layer, and the topography of the junction between the first region (i.e., the metal region) and the second region (i.e., the non-metal region) of the edge region of the substrate is photographed, from which it can be seen thatFigure 8 It can be obviously seen that the junction of the first region and the second region still has obvious damage residues which will remain in the solar cell after the solar cell product is prepared and will bring adverse effects. The embodiment of the present application can better solve this problem.

[0124] In addition, after the pre-cleaning and the RCA cleaning, when the functional layer is formed, the functional layer can not only improve the performance of the solar cell (for example, when the functional layer is a passivation layer, it is beneficial to further improve the passivation performance of the solar cell), but also can play the following roles:

[0125] First, it can assist in filling the positions of the concave damage which are not removed completely after the RCA cleaning. Although most of the laser damage layer is cleaned after the RCA cleaning, the laser damage layer formed in the edge region can still remain, and the functional layer will be deposited at the remaining laser damage layer during the deposition process to saturate the dangling bonds of the concave damage position and further reduce the recombination defects.

[0126] Second, it can provide auxiliary support for the RCA cleaning, reduce the cleanliness requirement of the RCA cleaning, and widen the process window. Since the functional layer is deposited after the RCA cleaning, the dangling bonds of the laser damage layer can be passivated, and the deposition of the functional layer can effectively compensate the cleaning effect of the RCA, saturate the remaining dangling bonds, thereby reducing the strict requirement of the RCA cleaning degree (i.e., allowing a certain degree of incomplete cleaning), relaxing the process control window, and making the preparation method more suitable for large-scale production.

[0127] It can be understood that, in addition to sequentially arranging the doped layer and the mask layer on the substrate, the preparation method of the solar cell of the embodiment of the present application can also arrange other film layers on the substrate. In addition to the laser opening film, pre-cleaning, RCA cleaning and other treatments, the preparation method of the solar cell of the embodiment of the present application can also include conventional operations such as texturing, polishing, and removing the wrap plating, which can be implemented by those skilled in the art as needed, and the embodiment of the present application does not limit this. Taking the back light surface of the substrate having the mask layer and the doped layer as an example, before preparing the doped layer and the mask layer on the back light surface of the substrate, the preparation method of the solar cell of the embodiment of the present application can also include:

[0128] First, the light receiving surface of the substrate is textured;

[0129] The diffusion of the doped element is performed on the light receiving surface of the textured substrate to form a diffusion layer with a different conductivity type from the substrate as an emitter on the light receiving surface of the substrate; for example, when the doped layer of the back light surface is a phosphorus doped layer, the diffusion layer of the light receiving surface can be a boron diffusion layer;

[0130] The back light surface of the substrate with the emitter is polished;

[0131] Then, a doping layer and a mask layer are prepared on the back surface of the substrate in sequence, so that the substrate becomes a substrate with a mask layer and a doping layer.

[0132] Further, the pre-cleaning condition includes: using an alkali agent with a concentration of 0.1wt%-0.5wt% and hydrogen peroxide with a concentration of 1wt%-10wt% for pre-cleaning, the temperature is 65°C-80°C, and the time is 50s-150s; wherein the alkali agent includes sodium hydroxide solution or potassium hydroxide solution.

[0133] In the above pre-cleaning condition, a low-concentration alkali agent is used, and hydrogen peroxide with increased strong oxidizing property is used. Such conditions can more effectively remove the residual oxide layer, better reduce the difference in film properties between the edge region and the middle region caused by laser opening film operation, thereby leveling the film state of the edge region and the middle region, facilitating the cleaning effect of subsequent normal RCA cleaning, and reducing the problem of residual oxide layer in the edge region after RCA cleaning.

[0134] Further, in the step of providing the substrate with the mask layer and the doping layer, the mask layer includes: a silicon nitride mask layer arranged close to the doping layer and a silicon oxide mask layer arranged away from the doping layer.

[0135] The above-mentioned composite structure of the mask layer has the following effects: on the one hand, the silicon oxide layer has a strong blocking effect on phosphorus, and the silicon nitride layer has a weaker blocking effect on phosphorus than the silicon oxide layer, and the combination of the two is conducive to promoting the doping layer to have a high surface doping concentration, thereby reducing the contact resistance of the doping layer and the gate line, and better alleviating the problem of film explosion and avoiding the inward diffusion of excessive doping elements to the substrate direction. On the other hand, the mask layer formed by the combination of the two materials can reduce the damage threshold of the substrate by laser and reduce the occurrence of recombination at the interface of the substrate. Therefore, especially when the doping layer includes a first dopant layer, a barrier layer and a second dopant layer, and the doping layer is a phosphorus doping layer, the mask layer with the above-mentioned composite structure has more excellent effects.

[0136] Further, the condition of laser opening film includes: using a green light source, the laser power is 20W-60W, the laser overlap rate is 5%-70%, and the depth of laser opening film is 3nm-35nm.

[0137] The depth of laser opening film is controlled within the above-mentioned range, which is conducive to improving the effect of subsequent RCA cleaning and reducing the requirements of RCA cleaning. On the one hand, it is conducive to ensuring the removal effect of the doping layer in the second region by RCA cleaning, and will not affect the removal effect of the doping layer in the second region due to too shallow opening film depth; on the other hand, it can appropriately reduce the degree of laser damage to the doping layer, so that the effect of removing the laser damage layer by RCA cleaning is better.

[0138] Compared with a red light source (wavelength of 600nm-750nm), the green light source is a short-wave light source (wavelength of about 532nm), the doped layer (especially the doped layer is a doped polysilicon layer) has a strong absorption coefficient for light of 0-650nm wavelength, and under the same laser intensity, the doped layer (especially the doped layer is a doped polysilicon layer) has better absorption of green light, which can further reduce the laser power, thereby reducing the damage to the substrate caused by high laser power.

[0139] In addition, the laser power and the laser overlap rate can reflect the influence of laser energy on the substrate. The greater the power and the higher the overlap rate, the greater the damage to the substrate, and the more difficult it is to clean under the same cleaning condition. Controlling the laser power and the laser overlap rate within the above range can help reduce the damage of the laser to the substrate, reduce the cleaning difficulty, and improve the passivation performance of the non-metallized area. The laser overlap rate refers to the degree of overlap between adjacent laser pulses or scanning paths. Taking a square laser spot as an example, when two laser spots are used in succession, if the second laser spot completely covers the area of the first laser spot, the overlap rate is 100%, and if the two laser spots are completely staggered and do not overlap, the overlap rate is 0%.

[0140] Optionally, the laser opening film condition includes that the laser power is 20W-55W and the laser overlap rate is 45%-70%. When the doped layer is set to a conventional thickness, the above laser opening film condition can better match the thickness of the doped layer, thereby helping to reduce the damage of the laser to the substrate, reduce the cleaning difficulty, and improve the passivation performance of the non-metallized area.

[0141] Optionally, the laser opening film condition includes that the laser power is 30W-55W and the laser overlap rate is 10%-35%. When the doped layer is set to a thinned thickness (for example, the doped layer is 35nm-90nm), the above laser opening film condition can better match the thickness of the doped layer, thereby helping to reduce the damage of the laser to the substrate, reduce the cleaning difficulty, and improve the passivation performance of the non-metallized area.

[0142] The embodiment of the present application also provides a photovoltaic module, which includes the above-mentioned solar cell or the solar cell prepared by the above-mentioned preparation method.

[0143] The embodiment of the present application will be further described below in combination with specific examples and test results.

[0144] Example 1

[0145] The embodiment provides a solar cell, which includes:

[0146] The substrate is an N-type silicon substrate, and the back surface of the substrate comprises a first region and a second region outside the first region; wherein the surface of the substrate in the first region has a plurality of first pyramid base microstructures, the average base length L1 of the first pyramid base microstructures is 4.5 μm, and the surface of the substrate in the second region has a plurality of second pyramid base microstructures, the average base length L2 of the second pyramid base microstructures is 7 μm;

[0147] The light-receiving surface of the substrate is sequentially provided with a boron diffusion layer with a thickness of 0.85 μm, an aluminum oxide passivation layer with a thickness of 4.5 nm, and a silicon nitride anti-reflection layer with a thickness of 80 nm;

[0148] The back surface of the substrate is sequentially provided with a patterned silicon oxide dielectric layer with a thickness of 1.4 nm, a patterned doped layer, and a silicon nitride passivation anti-reflection layer with a thickness of 75 nm;

[0149] The first electrode is in ohmic contact with the boron diffusion layer after passing through the silicon nitride anti-reflection layer and the aluminum oxide passivation layer;

[0150] The second electrode is in ohmic contact with the doped layer after passing through the silicon nitride passivation anti-reflection layer;

[0151] The positions of the patterned silicon oxide dielectric layer, the patterned doped layer, and the second electrode correspond to the first region, the doped layer is a phosphorus-doped polysilicon layer, the sheet resistance of the doped layer is 35 Ω·sq -1 , the width D of the doped layer is 120 μm, and the doped layer comprises a first doped sublayer with a thickness of 5.5 nm, a silicon oxide barrier layer with a thickness of 2 nm, and a second doped sublayer with a thickness of 75 nm, which are sequentially arranged on the surface of the silicon oxide dielectric layer away from the substrate, the doping concentration of the first doped sublayer is 6×10 19 cm -3 -1 20 , and the doping concentration of the second doped sublayer is 3.5×10 -3 cm

[0152] The height difference ΔH between the surface of the second doped sublayer away from the substrate and the surface of the substrate in the second region is 0.5 μm.

[0153] Embodiment 2

[0154] The difference between this embodiment and Embodiment 1 is that the height difference ΔH between the surface of the doped layer away from the substrate and the back surface of the substrate in the second region in the solar cell is 1.5 μm.

[0155] Embodiment 3

[0156] This example differs from Example 1 in that the height difference ΔH between the surface of the doped layer facing away from the substrate and the back surface of the substrate in the second region is 2 μm in the solar cell.

[0157] Example 4

[0158] This example differs from Example 1 in that the height difference ΔH between the surface of the doped layer facing away from the substrate and the back surface of the substrate in the second region is 5 μm in the solar cell.

[0159] Example 5

[0160] This example differs from Example 1 in that the height difference ΔH between the surface of the doped layer facing away from the substrate and the back surface of the substrate in the second region is 7 μm in the solar cell.

[0161] Comparative Example 1

[0162] This comparative example differs from Example 1 in that the height difference ΔH between the surface of the doped layer facing away from the substrate and the back surface of the substrate in the second region is 0.4 μm in the solar cell.

[0163] Comparative Example 2

[0164] This comparative example differs from Example 1 in that the height difference ΔH between the surface of the doped layer facing away from the substrate and the back surface of the substrate in the second region is 8 μm in the solar cell.

[0165] Performance Test

[0166] Photoelectric conversion efficiency, open-circuit voltage, short-circuit current, fill factor test:

[0167] The performance test of photoelectric conversion efficiency, open-circuit voltage (Voc), short-circuit current (Isc), fill factor (FF) and the like was performed using a halm test sorting device, which is a device for simulating sunlight, and further equipped with an electronic load, a data acquisition and calculation device, and the like, for testing the electrical performance of photovoltaic devices (including solar cells). The silicon wafer of the solar cell for control test was 210 mm in size, and the calibrated light intensity was 1000 ± 5 W / m 2 . The test results are shown in Table 1.

[0168] Table 1: Performance test results of the solar cells of the examples and comparative examples

[0169]

[0170] From the experimental results of the examples and the comparative examples, it can be seen that the comprehensive photoelectric performance of the solar cell of the examples of the present application is superior to that of the comparative examples. Especially when ΔH in the solar cell is controlled to be 2 μm to 7 μm, the photoelectric conversion efficiency of the solar cell has exceeded 26.5%, which has a more obvious efficiency improvement effect compared with comparative example 1 and comparative example 2.

[0171] The above has introduced the technical solutions disclosed by the examples of the present application in detail, and the principles and implementation manners of the present application have been described by applying specific examples. The above example explanations are only for helping to understand the technical solutions and core invention points of the examples of the present application. Meanwhile, for the general technical personnel in the art, according to the idea of the present application, the specific implementation manners and application ranges will have changes, and on the basis of the above, the content of the specification should not be understood as a limitation on the present application.

Claims

1. A solar cell, characterized by, The solar cell comprises: a substrate, a surface of the substrate having a first region and a second region outside the first region; a patterned doped layer, the doped layer being on the substrate, and a position of the doped layer corresponding to the first region; wherein a height difference between the surface of the substrate facing away from the doped layer and the surface of the substrate at the second region is ΔH, 0.5 μm≤ΔH≤7 μm; a functional layer, the functional layer being on the doped layer and on the surface of the substrate at the second region; a gate line, the gate line being in ohmic contact with the functional layer and the doped layer.

2. The solar cell according to claim 1, characterized in that, 2 μm≤ΔH≤7 μm.

3. The solar cell according to claim 1, characterized in that, The surface of the substrate at the first region has a plurality of first pyramid base microstructures, an average base side length of the first pyramid base microstructures being L1, 4 μm≤L1≤16 μm; The surface of the substrate at the second region has a plurality of second pyramid base microstructures, an average base side length of the second pyramid base microstructures being L2, 5 μm≤L2≤35 μm, and L2>L1.

4. The solar cell according to claim 1, characterized in that, A width of the doped layer in a preset direction is D, 100 μm≤D≤450 μm, the preset direction being perpendicular to a length direction of the gate line.

5. The solar cell according to claim 4, characterized in that, 100 μm≤D≤200 μm.

6. The solar cell according to claim 1, characterized in that, A thickness of the doped layer is 35 nm-135 nm; and / or, The sheet resistance of the doped layer is 10 Ω sq -1 ~ 75 Ω sq -1 ; and / or, A thickness of the functional layer is 0.5 nm-10 nm.

7. The solar cell according to claim 1, characterized in that, In a direction from the substrate toward the gate line, the doped layer sequentially comprises a first dopant layer, a barrier layer, and a second dopant layer, the barrier layer comprising at least one of a silicon oxide layer or a silicon oxynitride layer, the gate line being in ohmic contact with the functional layer and the second dopant layer.

8. The solar cell according to claim 7, characterized in that, The thickness of the first doped sub-layer is 10-25 nm, and the doping concentration of the first doped sub-layer is 1x10 19 3 ~1x10 21 3 cm-2.​​ A thickness of the barrier layer is 1.0 nm-5.0 nm; The thickness of the second doped sub-layer is 60-130 nm, the doping concentration of the second doped sub-layer is 1x10 20 3 9x10 21 cm 3 -2, and the doping concentration of the second doped sub-layer is greater than the doping concentration of the first doped sub-layer.​ 9. The solar cell of claim 7, wherein The thickness of the first doped sub-layer is 5-15 nm, and the doping concentration of the first doped sub-layer is 5x10 18 3 ~1x10 21 3 cm-2.​​ A thickness of the barrier layer is 1.0 nm-5.0 nm; The thickness of the second sub-doped layer is 20-50 nm, the doping concentration of the second sub-doped layer is 1×10 20 3 9×10 21 cm 3 -2, and the doping concentration of the second sub-doped layer is greater than the doping concentration of the first sub-doped layer.​ 10. The solar cell according to any one of claims 1 to 9, characterized in that, The solar cell further comprises: a patterned dielectric layer, the patterned dielectric layer being between the substrate and the doped layer, a position of the dielectric layer corresponding to a position of the doped layer, a thickness of the dielectric layer being 1 nm-4 nm; an inner extension doped layer, the inner extension doped layer being between the substrate and the dielectric layer; and / or, The substrate is a silicon substrate; and / or, The doped layer comprises at least one of a doped polysilicon layer, a doped microcrystalline silicon layer, and a doped amorphous silicon layer; and / or, A doping type of the doped layer is N-type or P-type, when the doping type of the doped layer is N-type, a doping element in the doped layer comprises at least one of a phosphorus element, an arsenic element, or an antimony element, when the doping type of the doped layer is P-type, a doping element in the doped layer comprises at least one of a boron element or a gallium element; and / or, The functional layer comprises at least one of a passivation layer and an anti-reflection layer; and / or, The functional layer comprises at least one of a silicon nitride layer, a silicon oxynitride layer, a silicon oxide layer, and an aluminum oxide layer; and / or, The gate line comprises at least one of a silver gate line, a silver-aluminum gate line, a copper gate line, or a nickel gate line.

11. The solar cell according to claim 10, characterized in that The surface of the substrate comprises a light-receiving surface and a back light surface arranged oppositely, and the doped layer is arranged on the back light surface side of the substrate; The solar cell further comprises the medium layer arranged between the substrate and the doped layer; The substrate is an N-type silicon substrate, and the doped layer is an N-type doped polysilicon layer. The functional layer is a back light surface passivation layer.

12. A method of producing a solar cell, characterized by, The preparation method comprises the following steps: providing a substrate with a mask layer and a doped layer; wherein the doped layer is arranged between the mask layer and the substrate, the substrate has a middle region and an edge region located at the periphery of the middle region, the thickness of the mask layer and the doped layer corresponding to the middle region is greater than the thickness corresponding to the edge region; laser opening the mask layer to form a first region with a pattern difference and a second region outside the first region; wherein the second region is a laser opening region, in the second region corresponding to the edge region, the surface of the doped layer is exposed and formed into an oxide layer; pre-cleaning to clean the oxide layer; RCA cleaning to expose the surface of the substrate located in the second region and the surface of the doped layer located in the first region, and the height difference between the surface of the doped layer away from the substrate and the back light surface of the substrate located in the second region is ΔH, 0.5 μm≤ΔH≤7 μm; post-processing to form a functional layer on the side of the patterned doped layer away from the substrate and the substrate not covered by the doped layer, and to form a gate line on the functional layer, so that the gate line is in ohmic contact with the functional layer and the doped layer.

13. The method of claim 12, wherein, The pre-cleaning conditions comprise: using an alkali agent with a concentration of 0.1wt%-0.5wt% and hydrogen peroxide with a concentration of 1wt%-10wt% for pre-cleaning, the temperature is 65°C-80°C, and the time is 50s-150s; wherein the alkali agent comprises sodium hydroxide solution or potassium hydroxide solution.

14. The method of claim 12, wherein, In the step of providing a substrate with a mask layer and a doped layer, the mask layer comprises: a silicon nitride mask layer arranged close to the doped layer and a silicon oxide mask layer arranged away from the doped layer.

15. The preparation method according to claim 12, characterized in that, The laser opening conditions comprise: using a green light source, the laser power is 20W-60W, the laser overlap rate is 5%-70%, and the laser opening depth is 3nm-35nm.

16. The method of claim 15, wherein, The laser opening conditions comprise: the laser power is 20W-55W, and the laser overlap rate is 45%-70%. Alternatively, the laser opening conditions comprise: the laser power is 30W-55W, and the laser overlap rate is 10%-35%.

17. A photovoltaic module, characterized by, The photovoltaic module comprises the solar cell according to any one of claims 1-11, or the solar cell prepared by the preparation method according to any one of claims 12-16.

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