Solar cell, preparation method thereof and photovoltaic module

Abstract

The invention discloses a solar cell, a preparation method thereof and a photovoltaic module, and relates to the technical field of solar cells. The solar cell includes: a substrate; the doping structure is located on the substrate and comprises a plurality of doping layers which are arranged in a stacked mode in the first direction perpendicular to the substrate and have the same conduction type; the grid electrode is positioned on one side, far away from the substrate, of the doping structure and extends into the doping structure along the first direction; wherein the doping concentration of the doping layer far away from the substrate is larger than that of the doping layer close to the substrate, and the projection area of the doping layer far away from the substrate on the substrate is smaller than that of the doping layer close to the substrate on the substrate. Movement of minority carriers is reduced while migration of multiple carriers is promoted, surface recombination is reduced, the open voltage and filling factors of the battery are improved, and the efficiency of the battery is improved.

Description

Technical Field

[0001] The embodiments of the present disclosure relate to the technical field of solar cells, and in particular to a solar cell and a preparation method thereof, and a photovoltaic module. Background Art

[0002] The core structure of TOPCon (Tunnel Oxide Passivated Contact) cells consists of a tunnel oxide layer and a doped polysilicon layer on the surface of the tunnel oxide layer. The doped polysilicon layer can protect the tunnel oxide layer and form an additional field passivation effect with the tunnel oxide layer to promote the separation of majority carriers and minority carriers. The highly doped polysilicon layer can provide good conductivity, which is conducive to reducing contact resistance and improving carrier transmission efficiency. However, the doped polysilicon layer covering the metal contact area and the non-metal contact area increases the carrier recombination rate of the solar cell, affecting the performance of the solar cell. Summary of the invention

[0003] The embodiments of the present disclosure provide a solar cell and a method for preparing the same, and a photovoltaic module, which can reduce the recombination rate of carriers and improve the performance of the solar cell.

[0004] A solar cell, comprising:

[0005] substrate;

[0006] A doping structure, located on the substrate, comprising a plurality of doping layers of the same conductivity type stacked and arranged along a first direction perpendicular to the substrate;

[0007] a gate, located at a side of the doping structure away from the substrate, and extending into the doping structure along the first direction;

[0008] The doping concentration of the doping layer far from the substrate is greater than the doping concentration of the doping layer close to the substrate, and the projection area of ​​the doping layer far from the substrate on the substrate is smaller than the projection area of ​​the doping layer close to the substrate on the substrate.

[0009] In one embodiment, the substrate includes a first region and a second region, the first region and the second region are adjacent to each other along a second direction parallel to the substrate, and extend along a third direction parallel to the substrate, and the third direction intersects with the second direction; the doping structure includes a bottom doping layer, a middle doping layer and a top doping layer stacked in sequence in the first region, the bottom doping layer covers the first region and the second region, the middle doping layer extends along the second direction to cover a portion of the second region, and the top doping layer covers the first region.

[0010] In one embodiment, there are multiple middle doped layers and they are stacked along the first direction; the size of the middle doped layer close to the bottom doped layer extending to the second region is larger than the size of the middle doped layer far from the bottom doped layer extending to the second region.

[0011] In one embodiment, the gate comprises:

[0012] The main gate is located on the surface of the top doped layer, extends along the third direction, and extends along the first direction to penetrate the middle doped layer.

[0013] In one embodiment, the gate further comprises:

[0014] A fine gate is located on the doping structure, extends along the second direction, and extends into the doping structure along the first direction.

[0015] A method for preparing a solar cell, comprising:

[0016] providing a substrate;

[0017] forming a doping structure on the substrate, wherein the doping structure comprises a plurality of doping layers of the same conductivity type stacked and arranged along a first direction perpendicular to the substrate;

[0018] forming a gate on a side of the doped structure away from the substrate, wherein the gate extends into the doped structure along the first direction;

[0019] The doping concentration of the doping layer far from the substrate is greater than the doping concentration of the doping layer close to the substrate, and the projection area of ​​the doping layer far from the substrate on the substrate is smaller than the projection area of ​​the doping layer close to the substrate on the substrate.

[0020] In one embodiment, the substrate includes a first region and a second region, the first region and the second region are adjacent to each other along a second direction parallel to the substrate, and extend along a third direction parallel to the substrate, the third direction intersecting with the second direction; the step of forming a doping structure on the substrate includes:

[0021] forming a bottom doped layer on the substrate, wherein the bottom doped layer covers the first region and the second region;

[0022] Selectively depositing on the surface of the bottom doped layer to form a middle doped layer, wherein the middle doped layer covers the first region and extends along the second direction to cover a portion of the second region;

[0023] selectively depositing on the middle doped layer to form a top doped layer covering the first region;

[0024] Wherein, the doping structure includes the bottom doping layer, the middle doping layer and the top doping layer.

[0025] In one embodiment, the middle doped layer and the top doped layer are formed by an atomic layer deposition process.

[0026] In one embodiment, the step of selectively depositing on the surface of the bottom doped layer to form the middle doped layer includes:

[0027] Performing multiple selective depositions on the surface of the bottom doped layer respectively to form a plurality of middle doped layers stacked along the first direction;

[0028] The dimension of the middle doped layer close to the bottom doped layer extending to the second region is greater than the dimension of the middle doped layer far from the bottom doped layer extending to the second region.

[0029] In one embodiment, the substrate includes a first region and a second region, the first region and the second region are adjacent to each other along a second direction parallel to the substrate, and extend along a third direction parallel to the substrate, the third direction intersecting with the second direction; the step of forming a doping structure on the substrate includes:

[0030] forming a bottom doping layer, a middle doping material layer and a top doping material layer stacked along the first direction on the substrate;

[0031] removing the top doped material layer in the second region to form a top doped layer covering the first region;

[0032] removing a portion of the middle doping material layer in the second region to form a middle doping layer, wherein the middle doping layer covers the first region and extends along the second direction to cover a portion of the second region;

[0033] The doping concentration of the top doping material layer is greater than the doping concentration of the middle doping material layer, and the doping concentration of the middle doping material layer is greater than the doping concentration of the bottom doping layer.

[0034] In one embodiment, a plurality of middle doping material layers stacked along the first direction are formed on the surface of the bottom doping layer, and the removing of part of the middle doping material layer in the second region to form the middle doping layer includes:

[0035] Using multiple laser etching processes to correspondingly etch the plurality of middle doped material layers to form a plurality of middle doped layers;

[0036] Wherein, along the second direction, the size of the middle doping material layer close to the bottom doping layer that is etched away is smaller than the size of the middle doping material layer far from the bottom doping layer that is etched away.

[0037] In one embodiment, forming a gate on a side of the doped structure away from the substrate includes:

[0038] A main gate is formed on the surface of the top doped layer. The main gate extends along the third direction and extends along the first direction to penetrate the middle doped layer.

[0039] In one embodiment, forming a gate on a side of the doping structure away from the substrate further comprises:

[0040] A fine gate is formed on the doped structure, wherein the fine gate extends along the second direction and extends into the doped structure along the first direction.

[0041] A photovoltaic assembly comprises a plurality of solar cells as described above, and / or a plurality of solar cells manufactured by the method for manufacturing a solar cell as described above.

[0042] In the above solar cell, the doping concentration of the doping layer far from the substrate in the doping structure is greater than the doping concentration of the doping layer close to the substrate, so that the doping concentration of the doping layer gradually decreases along the direction close to the substrate, increasing the longitudinal electric field of the solar cell in the first direction, promoting the migration of majority carriers while reducing the movement of minority carriers; and the difference in doping concentration makes the work function of the two adjacent doping layers different, further increasing the migration of majority carriers and inhibiting the movement of minority carriers. The projection area of ​​the doping layer far from the substrate on the substrate is smaller than the projection area of ​​the doping layer close to the substrate on the substrate, forming a transverse electric field in the doping structure, and the transverse electric field is parallel to the surface of the substrate. Under the action of the transverse electric field, carriers gather in the doping structure in the area where the doping layer far from the substrate is located. The formation of a gate in the doping structure in the area where the doping layer far from the substrate is located can realize the collection of carriers, reduce the number of gates, reduce the amount of gate materials, and reduce the cost of solar cells. Reduce surface recombination, increase the battery opening voltage and fill factor, and improve the efficiency of the battery.

[0043] In the above-mentioned method for preparing solar cells, the doping structure formed on the substrate includes a plurality of doping layers of the same conductive type stacked in a first direction perpendicular to the substrate, and the doping concentration of the doping layer far from the substrate is greater than the doping concentration of the doping layer close to the substrate, so that the doping concentration of the doping layer gradually decreases along the direction close to the substrate, increasing the longitudinal electric field of the solar cell in the first direction, promoting the migration of majority carriers while reducing the movement of minority carriers; and the difference in doping concentrations makes the work functions of the two adjacent doping layers different, further increasing the migration of majority carriers and inhibiting the movement of minority carriers. The projection area of ​​the doping layer far from the substrate on the substrate is smaller than the projection area of ​​the doping layer close to the substrate on the substrate, forming a transverse electric field in the doping structure, and the transverse electric field is parallel to the surface of the substrate. Under the action of the transverse electric field, carriers gather in the doping structure in the area where the doping layer far from the substrate is located, and a gate is formed in the doping structure in the area where the doping layer far from the substrate is located to realize the collection of carriers, reduce the number of gates, reduce the amount of gate materials, and reduce the cost of solar cells. Reduce surface recombination, increase the battery opening voltage and fill factor, and improve the efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or related technologies, the drawings required for use in the embodiments or related technical descriptions will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] FIG1 is a schematic diagram of a process for preparing a solar cell in some embodiments;

[0046] FIG2 is a schematic cross-sectional view of a solar cell after a gate is formed in some embodiments;

[0047] Figure 3 is a schematic cross-sectional view of a solar cell after a middle doping layer is formed in some embodiments;

[0048] Figure 4 is a cross-sectional schematic diagram of a solar cell after the middle doping layer 204 is formed in some other embodiments;

[0049] Figure 5 is a schematic cross-sectional view of a solar cell after a top doping material layer is formed in some embodiments;

[0050] Figure 6 is a schematic cross-sectional view of a solar cell after a top doping layer is formed in some embodiments;

[0051] Figure 7 is a schematic top view of a solar cell after a middle doping layer is formed in some embodiments;

[0052] Figure 8 In some embodiments Figure 7 A schematic cross-sectional view of a solar cell along the AA direction;

[0053] Fig. 9 FIG. 4 is a schematic cross-sectional view of a solar cell after a gate is formed in some embodiments.

[0054] Description of reference numerals:

[0055] First region 1, second region 2, second sub-region 21, second sub-region 22, second sub-region 23, second sub-region 24, substrate 102, doping structure 104, gate 106, tunneling layer 108, bottom doped layer 202, middle doped layer 204, top doped layer 206, middle doped material layer 302, top doped material layer 304, front doped layer 402, front carrier transport layer 404, protective layer 406, front electrode 408, main gate 1061, fine gate 1062, middle doped layer 2041, middle doped layer 2042, middle doped layer 2043. DETAILED DESCRIPTION

[0056] In order to facilitate understanding of the embodiments of the present disclosure, the embodiments of the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the embodiments of the present disclosure are shown in the drawings. However, the embodiments of the present disclosure can be implemented in many different forms and are not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the embodiments of the present disclosure more thorough and comprehensive.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the disclosed embodiments belong. The terms used herein in the specification of the disclosed embodiments are only for the purpose of describing specific embodiments and are not intended to limit the disclosed embodiments. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0058] In the description of the embodiments of the present disclosure, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "inside", "outside", etc. indicating orientations or positional relationships are based on the methods or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present disclosure and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present disclosure.

[0059] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. In the description of the present disclosure, the meaning of "several" is at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0060] As used herein, the terms "substrate" and "base" refer to and include the base material or structure of the material of the transistor introduced in the present disclosure. The substrate can be a semiconductor substrate, a base semiconductor layer on a support structure, a metal electrode, or a semiconductor substrate having one or more layers, structures or regions formed thereon. The substrate can be a conventional silicon substrate or other bulk substrate including a semiconductor material layer.

[0061] FIG1 is a schematic flow chart of a method for preparing a solar cell in some embodiments, and FIG2 is a schematic cross-sectional view of a solar cell after a gate is formed in some embodiments. By way of example, the X direction shown in FIG2 is a first direction perpendicular to a substrate, the Y direction is a second direction parallel to the substrate, and the Z direction is a third direction parallel to the substrate, and the third direction intersects with the second direction.

[0062] As shown in FIG. 1 and FIG. 2 , in this embodiment, a method for preparing a solar cell is provided, comprising:

[0063] S102, providing a substrate.

[0064] A substrate 102 for preparing a solar cell is provided, and the material of the substrate 102 includes a doped semiconductor substrate made of silicon or germanium, or a doped compound semiconductor substrate made of silicon carbide, silicon germanium, gallium arsenide, indium phosphide, zinc oxide, gallium oxide, etc. As an example, in this embodiment, the constituent material of the substrate 102 is doped single crystal silicon.

[0065] S104, forming a doping structure on the substrate.

[0066] A doping structure 104 is formed on a substrate 102, wherein the doping structure 104 includes a plurality of doping layers of the same conductive type stacked along a first direction X perpendicular to the substrate 102; wherein the conductive types include N-type and P-type with opposite conductive types, the doping concentration of the doping layer away from the substrate 102 is greater than the doping concentration of the doping layer close to the substrate 102, and the projection area of ​​the doping layer away from the substrate 102 on the substrate 102 is smaller than the projection area of ​​the doping layer close to the substrate 102 on the substrate 102.

[0067] 2 is used for exemplary explanation. When the conductivity type of the doping structure 104 is all N-type, the direction of the longitudinal electric field generated by the difference in doping concentration of each doping layer in the doping structure 104 is: from the doping layer in the doping structure 104 far away from the substrate 102 to the substrate 102, as shown by the dotted line 1 in FIG2 , and the direction of the arrow is the direction of the longitudinal electric field. The direction of the lateral electric field generated by the difference in doping concentration and the difference in projection area of ​​each doping layer in the doping structure 104 is: from the area with thick thickness of the doping structure 104 to the area with thin thickness of the doping structure 104, as shown by the dotted line 2 in FIG2 , and the direction of the arrow is the direction of the lateral electric field. That is, when the conductivity type of the doping structure 104 is all N-type, the longitudinal electric field generated by the doping structure 104 is shown by the dotted line 1, and the lateral electric field is shown by the dotted line 2. When the conductivity type of the doping structure 104 is all P-type, the direction of the longitudinal electric field generated by the difference in doping concentration of each doping layer in the doping structure 104 is: from the substrate 102 to the doping layer in the doping structure 104 away from the substrate 102, as shown by the solid line 3 in Figure 2, and the direction of the arrow is the direction of the longitudinal electric field. The direction of the lateral electric field generated by the difference in doping concentration and the difference in projection area of ​​each doping layer in the doping structure 104 is: from the area with thin thickness of the doping structure 104 to the area with thick thickness of the doping structure 104, as shown by the solid line 4 in Figure 2, and the direction of the arrow is the direction of the lateral electric field. That is, when the conductivity type of the doping structure 104 is all P-type, the longitudinal electric field generated by the doping structure 104 is as shown by the solid line 2, and the lateral electric field is as shown by the solid line 4.

[0068] As shown in FIG2 , when the doping structure 104 includes more than two doping layers, the more than two doping layers are divided into a bottom doping layer 202, a middle doping layer 204 (two middle doping layers 204 are used as an example in FIG2 ), and a top doping layer 206 which are stacked sequentially in a direction away from the substrate 102. The doping concentration increases sequentially from the bottom doping layer 202 to the top doping layer 206, and the projection area of ​​the doping layer in a plane parallel to the substrate 102 (the plane where the second direction Y and the third direction Z are located) decreases sequentially.

[0069] It is understandable that when the doping structure 104 includes two doping layers, the doping layer close to the substrate 102 is the bottom doping layer 202 , and the doping layer away from the substrate 102 is the top doping layer 206 , and there is no middle doping layer 204 between the top doping layer 206 and the bottom doping layer 202 .

[0070] S106, forming a gate on a side of the doping structure away from the substrate.

[0071] A gate 106 is formed on a side of the doping structure 104 away from the substrate 102 . The gate 106 extends into the doping structure 104 along the first direction X. The gate 106 is electrically connected to the doping layer in the doping structure 104 .

[0072] In the above-mentioned method for preparing the solar cell, the doping structure 104 formed on the substrate 102 includes a plurality of doping layers of the same conductive type stacked in a first direction X perpendicular to the substrate 102, and the doping concentration of the doping layer away from the substrate 102 is greater than the doping concentration of the doping layer close to the substrate 102, so that the doping concentration of the doping layer gradually decreases along the direction close to the substrate 102, thereby increasing the longitudinal electric field of the solar cell in the first direction X, promoting the migration of majority carriers while reducing the movement of minority carriers; and, the difference in doping concentrations results in differences in the work functions of two adjacent doping layers, further increasing the migration of majority carriers and suppressing the movement of minority carriers. The projection area of ​​the doping layer far from the substrate 102 on the substrate 102 is smaller than the projection area of ​​the doping layer near the substrate 102 on the substrate 102, and a transverse electric field is formed in the doping structure 104, and the transverse electric field is parallel to the surface of the substrate 102, that is, the transverse electric field is parallel to the plane where the second direction Y and the third direction Z are located. Under the action of the transverse electric field, the carriers gather in the doping structure 104 in the area where the doping layer far from the substrate 102 is located, and the gate 106 is formed in the doping structure 104 in the area where the doping layer far from the substrate 102 is located to collect the carriers, reduce the number of gates 106, reduce the amount of gate materials, and reduce the cost of solar cells. Reduce surface recombination, increase the battery opening voltage and fill factor, and improve the efficiency of the battery.

[0073] In some embodiments, the substrate 102 includes a light-receiving surface and a backlight surface that are relatively arranged in a first direction X perpendicular to the substrate 102. The light-receiving surface is the surface of the solar cell facing the sunlight (the light-facing surface), and the backlight surface is the surface of the solar cell facing away from the sunlight. The doping structure 104 is located on at least one of the light-receiving surface and the backlight surface.

[0074] As shown in FIG2 , in some embodiments, before forming the doping structure 104 on the substrate 120, the method for preparing a solar cell further includes: forming a tunneling layer 108 on the surface of the substrate 102; wherein the doping structure 104 is located on the surface of the tunneling layer 108 away from the substrate 102, and the opposite surfaces of the tunneling layer 108 are in contact with the substrate 102 and the doping structure 104, respectively. The doping structure 104 and the tunneling layer 108 together form a field passivation effect, promote the separation of majority carriers and minority carriers, and the lateral electric field formed in the doping structure 104 increases the effect of field passivation. Exemplarily, the material of the tunneling layer 108 includes silicon dioxide.

[0075] Exemplarily, a plasma enhanced chemical deposition process is used, for example, the process gas includes silane and nitric oxide gas, to form a tunneling layer 108 on the first surface of the substrate 102. As an example, the thickness of the tunneling layer 108 in the first direction X is 1.5 nm-2 nm.

[0076] Figure 3 is a schematic cross-sectional view of a solar cell after forming a middle doping layer in some embodiments, Figure 4 is a cross-sectional schematic diagram of a solar cell after forming the middle doping layer 204 in some other embodiments, such as Figure 3 , Figure 4 As shown, in one embodiment, the substrate 102 includes a first region 1 and a second region 2, the first region 1 and the second region 2 are adjacent along a second direction Y parallel to the substrate 102, and the first region 1 and the second region 2 both extend along a third direction Z parallel to the substrate 102, the third direction Z intersects with the second direction Y, and further, the third direction Z is perpendicular to the second direction Y. The step of forming the doping structure 104 on the substrate 102 includes: steps S202-S206.

[0077] S202 , forming a bottom doping layer 202 on the substrate 102 , wherein the bottom doping layer 202 covers the first region 1 and the second region 2 .

[0078] Specifically, a deposition process, such as an atomic layer deposition process or a plasma enhanced chemical vapor deposition process, is used to form a bottom doping layer 202 covering the first region 1 and the second region 2 on the substrate 102. Further, the bottom doping layer 202 has a thickness of 65nm-75nm.

[0079] S204 , selectively depositing on the surface of the bottom doping layer to form a middle doping layer, wherein the middle doping layer covers the first region and extends along the second direction to cover a portion of the second region.

[0080] like Figure 3 As shown, in some embodiments, the step of selectively depositing on the surface of the bottom doping layer 202 to form the middle doping layer 204 includes: performing a selective deposition on the surface of the bottom doping layer 202 to form the middle doping layer 204 located on the surface of the bottom doping layer, wherein the middle doping layer 204 covers the first region 1 and extends along the second direction Y to cover a portion of the second region 2. The process is simple and easy to operate.

[0081] Specifically, a deposition process, such as an atomic layer deposition process, is used to selectively deposit the surface of the bottom doping layer 202 away from the substrate 102 to form a middle doping layer 204, the middle doping layer 204 covers the first region 1 and a portion of the second region 2 close to the first region 1, the doping concentration of the middle doping layer 204 is less than the doping concentration of the bottom doping layer 202, the middle doping layer 204 covers a portion of the top surface of the bottom doping layer 202 away from the substrate 102, and the bottom doping layer 202 exposed by the middle doping layer 204 is located in the second region 2 away from the first region 1. Exemplarily, a deposition process is performed using a mask as a mask to form the middle doping layer 204 on the surface of the bottom doping layer 202 away from the substrate 102, the mask exposes the portion of the bottom doping layer 202 where the middle doping layer 204 needs to be formed, and covers the portion where the middle doping layer 204 does not need to be formed.

[0082] like Figure 4 As shown, in one embodiment, the step of selectively depositing on the surface of the bottom doping layer 202 to form the middle doping layer 204 includes: performing multiple selective depositions on the surface of the bottom doping layer 202 to form multiple middle doping layers 204 stacked along the first direction X; wherein the size of the middle doping layer 204 close to the bottom doping layer 202 extending to the second region 2 is larger than the size of the middle doping layer 204 far from the bottom doping layer 202 extending to the second region 2. The process is simple and easy to operate.

[0083] Specifically, a deposition process, such as an atomic layer deposition process, is used to perform multiple selective depositions on the surface of the bottom doping layer 202 away from the substrate 102, the first selective deposition is performed on the surface of the bottom doping layer 202, and the subsequent selective deposition is performed on the surface of the middle doping layer 204 formed in the previous time, so as to obtain a plurality of middle doping layers 204 stacked along the first direction X, each layer of the middle doping layer 204 covers the first region 1 and a portion of the second region 2 close to the first region 1, the area of ​​the first region 2 close to the first region 1 covered by the middle doping layer 204 away from the bottom doping layer 202 is smaller than the area of ​​the first region 2 close to the first region 1 covered by the middle doping layer 204 close to the bottom doping layer 202, and the doping concentration of the middle doping layer 204 away from the bottom doping layer 202 is greater than the doping concentration of the middle doping layer 204 close to the bottom doping layer 202.

[0084] Exemplarily, a deposition process is performed using the mask as a mask, and a middle doped layer 204 is formed on a surface of the bottom doped layer 202 away from the substrate 102, and the mask exposes a portion where the middle doped layer 204 needs to be formed, and covers a portion where the middle doped layer 204 does not need to be formed. The portion exposed by the mask corresponding to the latter deposition process is smaller than the portion exposed by the mask corresponding to the former deposition process.

[0085] The size of the middle doped layer 204 close to the bottom doped layer 202 extending to the second region 2 is larger than the size of the middle doped layer 204 far from the bottom doped layer 202 extending to the second region 2. Figure 6 L1, L2 and L3 are used to characterize the size of each middle doping layer 204 covering the second region 2, L1 is larger than L2, and L2 is larger than L3.

[0086] S206 , selectively depositing on the middle doped layer to form a top doped layer covering the first region.

[0087] A deposition process, such as an atomic layer deposition process, is used to selectively deposit on the middle doping layer 204 to form a top doping layer 206 covering the first region, wherein the doping concentration of the top doping layer 206 is greater than the doping concentration of the middle doping layer 204. The doping structure 104 includes the bottom doping layer 202, the middle doping layer 204, and the top doping layer 206.

[0088] Figure 5 is a schematic cross-sectional view of a solar cell after a top doping material layer is formed in some embodiments, Figure 6 is a schematic cross-sectional view of a solar cell after a top doping layer is formed in some embodiments, Figure 7 is a schematic top view of a solar cell after a middle doping layer is formed in some embodiments, Figure 8 In some embodiments Figure 7 A schematic cross-sectional view of a solar cell along the AA direction is shown in FIG. Figure 5-Figure 8 As shown, in one embodiment, the substrate 102 includes a first region 1 and a second region 2, the first region 1 and the second region 2 are adjacent to each other along a second direction Y parallel to the substrate 102, and extend along a third direction Z parallel to the substrate 102, and the third direction Z intersects with the second direction Y; the step of forming the doping structure 104 on the substrate 102 includes: S302-S306.

[0089] S302, forming a bottom doping layer, a middle doping material layer and a top doping material layer stacked along the first direction on the substrate.

[0090] like Figure 5As shown, an atomic layer deposition process or a plasma chemical vapor deposition process is used to sequentially form a bottom doping layer 202, a middle doping material layer 302, and a top doping material layer 304 stacked along a first direction X on a substrate 102, and the bottom doping layer 202, the middle doping material layer 302, and the top doping material layer 304 all cover the first area 1 and the second area 2. The doping concentration of the top doping material layer 304 is greater than the doping concentration of the middle doping material layer 302, and the doping concentration of the middle doping material layer 302 is greater than the doping concentration of the bottom doping layer 202.

[0091] S304, removing the top doping material layer in the second region to form a top doping layer covering the first region.

[0092] like Figure 6 As shown, an etching process is adopted to etch away the top doping material layer 304 located in the second region 2 to form a top doping layer 204 composed of the top doping material layer 304 of the first region 1 , exposing the middle doping material layer 302 of the second region 2 .

[0093] S306, removing a portion of the middle doping material layer in the second region to form a middle doping layer, wherein the middle doping layer covers the first region and extends along the second direction to cover a portion of the second region.

[0094] like Figure 7 , Figure 8 As shown, an etching process is used to etch away the top doping layer 204 to expose the portion of the middle doping material layer 302 located in the second region 2 , thereby forming a middle doping layer 204 consisting of the first region 1 and the portion of the middle doping material layer 302 of the second region 2 close to the first region 1 .

[0095] In some embodiments, a middle doping material layer 302 is formed on the surface of the bottom doping layer 202, and the removing of part of the middle doping material layer 302 in the second region 2 to form the middle doping layer 204 includes: using a single laser etching process to etch and remove part of the middle doping material layer 302 to form the middle doping layer 204 covering the first region 1 and part of the second region 2 close to the first region 1, and the middle doping layer 204 exposes the bottom doping layer 202 covering part of the second region 2 away from the first region 1. In the process of etching to form the middle doping layer 204, no mask is required, the process is simple, easy to operate, and the cost is low.

[0096] like Figure 5-8As shown, in one embodiment, a plurality of middle doping material layers 302 stacked along the first direction X are formed on the surface of the bottom doping layer 202, and the removing of part of the middle doping material layer 302 in the second region 2 to form the middle doping layer 204 comprises: etching the plurality of middle doping material layers 302 correspondingly using multiple laser etching processes to form the plurality of middle doping layers 204; wherein, along the second direction Y, the size of the middle doping material layer 302 etched away close to the bottom doping layer 202 is smaller than the size of the middle doping material layer 302 etched away from the bottom doping layer 202. In the process of etching the plurality of middle doping layers 204 of different sizes stacked in the first direction X, no mask is required, the process is simple, the operation is convenient, and the cost is low.

[0097] The size of the middle doping material layer 302 etched away near the bottom doping layer 202 is smaller than the size of the middle doping material layer 302 etched away away from the bottom doping layer 202. Figure 7 D1, D2 and D3 are used to characterize the size of each middle doping material layer 302 that has been etched away, and D1 is larger than D2, and D2 is larger than D3.

[0098] Figure 5-Figure 8 Taking the bottom doping layer 202 surface having three middle doping material layers 302 stacked along the first direction X as an example, forming the middle doping layer 204 by multiple laser etching is illustrated, and the number of laser etching processes is the same as the number of layers of the middle doping material layers 302 . First, a first laser etching process is used to etch a portion of the first middle doping material layer 302 located in region 2-1 close to the top doping layer 204, exposing the second middle doping material layer 302 below, and forming the first middle doping layer 204 close to the top doping layer 204, and the size of region 2-1 in the second direction Y is D1; ​​secondly, a second laser etching process is used to etch a portion of the second middle doping material layer 302 located in region 2-2 exposed by the first middle doping layer 204, exposing the third middle doping material layer 302 below, and forming the second middle doping layer 204, and the size of region 2-2 in the second direction Y is D2, and D2 is smaller than D1; thirdly, a third laser etching process is used to etch a portion of the third middle doping material layer 302 located in region 2-3 close to the bottom doping layer 202, exposing the bottom doping layer 202 below, and forming the third middle doping layer 204, and the size of region 2-3 in the second direction Y is D3, and D3 is smaller than D2.

[0099] like Figure 7 , Figure 8As shown, in one embodiment, the gate 106 is formed on the side of the doped structure 104 away from the substrate 102, including: forming a main gate 1061 on the surface of the top doped layer 206, the main gate 1061 extends along the third direction Z, and extends along the first direction X to penetrate the middle doped layer 204, and the main gate 1061 can collect carriers gathered in the doped structure 104 in the area (first area 1) where the top doped layer 206 is located. Further, a plurality of main gates 1061 are arranged at intervals along the second direction Y.

[0100] In one embodiment, the forming of the gate 106 on the side of the doping structure 104 away from the substrate 102 further includes: forming a fine gate 1062 on the doping structure 104, the fine gate 1062 extending along the second direction Y and extending into the doping structure 104 along the first direction Z. Further, a plurality of fine gates 1062 are arranged at intervals along the third direction Z.

[0101] It can be understood that, in the second direction Y, along the direction pointing from the second region 2 to the first region 1, the number of stacked doping layers of different parts of the doping structure 104 increases successively, so that the doping structure 104 is stepped, and in the parts with the same number of stacked doping layers, the fine gate line 1062 stops in the same doping layer in the doping structure 104, and in the parts with the same number of stacked doping layers but different numbers of stacked doping layers, the fine gate line 1062 stops in different doping layers in the doping structure 104.

[0102] Illustratively, the material of the main grid line 1061 and the material of the thin grid line 1062 include metal silver.

[0103] Exemplarily, a screen printing process is used to print silver paste to form the gate line 106 .

[0104] In some embodiments, the material of the doping layer includes doped non-polycrystalline silicon. After forming the doping structure 104 on the substrate 102 , the process further includes: crystallizing the doping structure 104 using an annealing process to convert the doped amorphous silicon into doped polycrystalline silicon and activating doping ions in the doping structure 104 .

[0105] Fig. 9 is a schematic cross-sectional view of a solar cell after a gate is formed in some embodiments. Fig. 9 As an example, a method for preparing a solar cell is described below.

[0106] The present disclosure provides a first embodiment, which includes the following steps:

[0107] In the first step, a substrate 102 of a first conductive type (N type is used as an example) is provided, wherein the substrate 102 includes a first region 1 and a second region 2 adjacent to each other along a second direction Y and extending along a third direction Z; the second region 2 is divided into a second sub-region 21, a second sub-region 22, a second sub-region 23, and a second sub-region 24 adjacent to each other in sequence along a direction close to the first region 1; illustratively, the thickness of the substrate 102 in the first direction X is 130 um, and the dimensions of the substrate 102 in the second direction Y and the third direction Z are both 210 mm, and the ratio of the dimensions of the second sub-region 21, the second sub-region 22, the second sub-region 23, the second sub-region 24 and the first region 1 in the second direction Y is 1:1:1:1:2.

[0108] In the second step, a double-sided texturing process is performed to form pyramid texturing surfaces on the light-facing side and the backlight side of the substrate 102 .

[0109] In the third step, a diffusion process is used to form a front doped layer 402 of the second conductivity type (P type, such as boron) on the light-facing surface of the substrate 102, and oxidation is performed. Exemplarily, the thickness of the front doped layer 402 in the first direction X is 200 nm.

[0110] In the fourth step, a back polishing and cleaning process is used to remove the front doping layer 402 plated on the backlight surface, and to remove surface contamination and impurities.

[0111] In the fifth step, a tunneling layer 108 (silicon dioxide) is formed on the backlight surface by using a plasma chemical vapor deposition process with silane and nitric oxide as process gases.

[0112] In the sixth step, a plasma chemical vapor deposition process is used to form a bottom doped layer 202 of the first conductivity type on the surface of the tunneling layer 108, and the bottom doped layer 202 covers the first area 1 and the second area 2; illustratively, the material of the bottom doped layer 202 is phosphorus-doped amorphous silicon, the process gas is silane and phosphine, and the thickness of the bottom doped layer 202 in the first direction X is 65nm-75nm.

[0113] In the seventh step, an atomic layer deposition process is used to selectively deposit on the surface of the bottom doped layer 202 to form a middle doped layer 2041 of the first conductivity type, a middle doped layer 2042 of the first conductivity type, a middle doped layer 2043 of the first conductivity type and a top doped layer 206 of the first conductivity type stacked in the first direction X, wherein the doping concentrations of the middle doped layer 2041, the middle doped layer 2042, the middle doped layer 2043 and the top doped layer 206 increase in sequence and are greater than the doping concentration of the bottom doped layer 202; wherein the bottom doped layer 202, the middle doped layer 2041, the middle doped layer 2042, the middle doped layer 2043 and the top doped layer 206 constitute a doping structure 104; the middle doped layer 2041 is located on the surface of the bottom doped layer 202 away from the substrate 102, and covers the second sub-region 22, The sizes of the second sub-area 23, the second sub-area 24 and the first area 1 in the second direction Y and the third direction Z are 175 mm and 210 mm respectively; the middle doping layer 2042 is located on the surface of the middle doping layer 2041 away from the substrate 102, and covers the second sub-area 23, the second sub-area 24 and the first area 1, and the sizes in the second direction Y and the third direction Z are 140 mm and 210 mm respectively; the middle doping layer 2043 is located on the surface of the middle doping layer 2042 away from the substrate 102, and covers the second sub-area 24 and the first area 1, and the sizes in the second direction Y and the third direction Z are 105 mm and 210 mm respectively; the top doping layer 206 is located on the surface of the middle doping layer 2043 away from the substrate 102, and covers the first area 1, and the sizes in the second direction Y and the third direction Z are 70 mm and 210 mm respectively. Exemplarily, the materials of the middle doping layer 2041, the middle doping layer 2042, the middle doping layer 2043 and the top doping layer 206 are all phosphorus-doped amorphous silicon, and the process gases of the atomic layer deposition process are all silicon tetrachloride, water and phosphine, and the thickness in the first direction X is the same, for example, the thickness is 7nm. The directions of the longitudinal electric field perpendicular to the substrate 102 and the lateral electric field parallel to the substrate 102 increased by the doping structure 104 are as follows: Fig. 9 As shown by the arrows in , the longitudinal electric field promotes the movement of electrons to the backlight side while suppressing the movement of holes. The transverse electric field causes the carriers to gather in the doping structure 104 covering the first region 1, reducing surface recombination, increasing the battery opening voltage and fill factor, and improving the efficiency of the battery.

[0114] In the eighth step, an annealing process is used to perform crystallization treatment to convert the doped amorphous silicon in the doping structure 104 into doped polysilicon and activate the doping ions.

[0115] In the ninth step, RCA cleaning technology is used to remove the doping structure 104 plated on the light-facing surface, and to remove contamination and impurities on the light-facing surface.

[0116] In the tenth step, an atomic layer deposition process is used to form a front carrier transport layer 404 on the surface of the front doped layer 402 away from the substrate 102 to protect the PN junction in the solar cell and passivate the light-facing surface. Exemplarily, the material of the front carrier transport layer 404 is aluminum oxide, and the thickness of the front carrier transport layer 404 in the first direction X is 7nm-10nm.

[0117] In the eleventh step, a protective layer 406 is formed on the surface of the front carrier transport layer 404 away from the substrate 102 and the surface of the doping structure 104 away from the substrate 102 by using a plasma enhanced chemical vapor deposition process; wherein the surface of the doping structure 104 away from the substrate 102 is stepped. Exemplarily, the material of the protective layer 406 is silicon nitride, and the thickness of the protective layer 406 in the first direction X is 75nm-85nm.

[0118] In the twelfth step, a screen printing process using silver paste is used to form spaced front electrodes 408 on the surface of the protective layer 406 on the light-facing side of the substrate 102 away from the substrate 102 . The front electrodes 408 penetrate the protective layer 406 and the front carrier transport layer 404 , and are electrically connected to the front doping layer 402 .

[0119] Step 12: Using a screen printing process with silver paste as the material, a gate 106 is formed on the surface of the protective layer 406 on the backlight side of the substrate 102 away from the substrate 102, wherein the gate 106 includes a main gate 1061 and a fine gate. The main gate 1061 is a plurality of strips, located on the surface of the protective layer 406 in the first area 1, extending along the third direction Z, and extending in the first direction X to penetrate the middle doping layer 204, and electrically connected to the bottom doping layer 202. The main gate 1061 can collect carriers gathered in the doping structure 104 in the first area 1. The main gate 1061 is located in the first area 1, and the number of gate lines is reduced without affecting the carrier collection, the amount of silver paste is reduced, the manufacturing cost is reduced, and the surface recombination of carriers is reduced. Further, a plurality of main gates 1061 are arranged at intervals along the second direction Y. The fine gate extends along the second direction Y, is arranged at intervals along the third direction Z, and extends to the doping structure 104 in the first direction X. It can be understood that in the first direction X, the fine gate line in the second sub-region 21 at least extends to contact with the bottom doping layer 202, the fine gate line in the second sub-region 22 at least extends to contact with the middle doping layer 2041, the fine gate line in the second sub-region 23 at least extends to contact with the middle doping layer 2042, the fine gate line in the second sub-region 24 at least extends to contact with the middle doping layer 2043, and the fine gate line in the first region 1 at least extends to contact with the top doping layer 206. The fine gate line is formed once, and the depth of the process conditions in the first direction X is limited.

[0120] The present disclosure provides a second embodiment, and the difference between the second embodiment and the first embodiment lies in that the sixth step and the seventh step are different. The sixth step of the second embodiment is: using a plasma chemical vapor deposition process to form a doping material structure on the surface of the tunneling layer 108, the doping material structure includes a bottom doping layer 202, a first middle doping material layer, a second middle doping material layer, a third middle doping material layer and a top doping material layer stacked in the first direction X, wherein the bottom doping layer 202, the first middle doping material layer, the second middle doping material layer, the third middle doping material layer and the top doping material layer all cover the first area 1 and the second area 2, and are all of the first conductivity type, and the doping concentration increases in sequence. Exemplarily, the process gases of the plasma chemical vapor deposition process are silane and phosphine, the overall thickness of the doping material structure in the first direction X is 105nm-115nm, and the thicknesses of the first middle doping material layer, the second middle doping material layer, the third middle doping material layer and the top doping material layer are the same, for example, all are 7nm.The seventh step is: first, using a laser etching process, etching away the top doping material layer covering the second sub-region 21, the second sub-region 22, the second sub-region 23 and the second sub-region 24 to form a top doping layer 206 composed of the top doping material layer of the first region 1, the etching removal dimensions in the second direction Y and the third direction Z are 140 mm and 210 mm respectively, the etching depth in the first direction X is the same as the thickness of the top doping material layer, and the etching depth is the distance between the place where the etching stops and the surface of the doping material structure away from the substrate 102; secondly, using a laser etching process, The third middle doping material layer covering the second sub-region 21, the second sub-region 22 and the second sub-region 23 is etched away to form a middle doping layer 2043 composed of the third middle doping material layer of the first region 1 and the second sub-region 24. The etching removal dimensions in the second direction Y and the third direction Z are 105 mm and 210 mm, respectively. The etching depth in the first direction X is the same as the sum of the thicknesses of the third middle doping material layer and the top doping material layer. Again, a laser etching process is used to etch away the second middle doping material layer covering the second sub-region 21 and the second sub-region 22 to form a middle doping layer 2043 composed of the third middle doping material layer of the first region 1 and the second sub-region 24. The middle doped layer 2042 composed of the second middle doped material layer of the first sub-region 1, the second sub-region 23 and the second sub-region 24 is etched and removed by 70 mm and 210 mm in the second direction Y and the third direction Z, respectively, and the etching depth in the first direction X is the same as the sum of the thicknesses of the second middle doped material layer, the third middle doped material layer and the top doped material layer; then, a laser etching process is used to etch and remove the first middle doped material layer covering the second sub-region 21, so as to form a first middle doped material layer composed of the first region 1, the second sub-region 22, the second sub-region 23 and the second sub-region 24. The middle doping layer 2041 is etched and removed by 35 mm and 210 mm in the second direction Y and the third direction Z, respectively. The etching depth in the first direction X is the same as the sum of the thicknesses of the first middle doping material layer, the second middle doping material layer, the third middle doping material layer and the top doping material layer. The remaining doping material structure is the bottom doping layer 202, and a doping structure 104 is obtained, wherein the doping structure 104 includes a bottom doping layer 202, a middle doping layer 2041, a middle doping layer 2042, a middle doping layer 2043 and a top doping layer 206.

[0121] It should be understood that, although the various steps in the flowchart of FIG. 1 are shown in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence according to the order indicated by the arrows. Unless there is a clear explanation in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a part of the steps in FIG. 1 may include a plurality of sub-steps or a plurality of stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a part of the sub-steps or stages of other steps.

[0122] As shown in FIG2 , the present disclosure provides a solar cell, and the parts that are the same or corresponding to the embodiments in the above-mentioned method for preparing the solar cell will not be described in detail below. In this embodiment, the solar cell includes: a substrate 102, a doping structure 104 and a gate 106; the doping structure 104 is located on the substrate 102, and includes a plurality of doping layers of the same conductive type stacked along a first direction X perpendicular to the substrate 102; the gate 106 is located on the side of the doping structure 104 away from the substrate 102, and extends into the doping structure 104 along the first direction X; wherein the doping concentration of the doping layer away from the substrate 102 is greater than the doping concentration of the doping layer close to the substrate 102, and the projection area of ​​the doping layer away from the substrate 102 on the substrate 102 is smaller than the projection area of ​​the doping layer close to the substrate 102 on the substrate 102.

[0123] In the above solar cell, the doping concentration of the doping layer far from the substrate 102 in the doping structure 104 is greater than the doping concentration of the doping layer close to the substrate 102, so that the doping concentration of the doping layer gradually decreases along the direction close to the substrate 102, increasing the longitudinal electric field of the solar cell in the first direction X, promoting the migration of majority carriers while reducing the movement of minority carriers; and the difference in doping concentration makes the work function of the two adjacent doping layers different, further increasing the migration of majority carriers and inhibiting the movement of minority carriers. The projection area of ​​the doping layer far from the substrate 102 on the substrate 102 is smaller than the projection area of ​​the doping layer close to the substrate 102 on the substrate 102, forming a transverse electric field in the doping structure 104, the transverse electric field is parallel to the surface of the substrate 102, under the action of the transverse electric field, the carriers gather in the doping structure in the area where the doping layer far from the substrate 102 is located, and the gate 106 is formed in the doping structure 104 in the area where the doping layer far from the substrate 102 is located to realize the collection of carriers, reduce the number of gates 106, reduce the amount of gate materials, and reduce the cost of solar cells. Reduce surface recombination, increase the battery opening voltage and fill factor, and improve the efficiency of the battery.

[0124] like Figure 3 , Figure 4 As shown, in one embodiment, the substrate 102 includes a first region 1 and a second region 2, the first region 1 and the second region 2 are adjacent to each other along a second direction Y parallel to the substrate 102, and extend along a third direction Z parallel to the substrate 102, and the third direction Z intersects with the second direction Y; the doping structure 104 includes a bottom doping layer 202, a middle doping layer 204 and a top doping layer 206 which are sequentially stacked in the first region 1, the bottom doping layer 202 covers the first region 1 and the second region 2, the middle doping layer 204 extends along the second direction Y to cover a portion of the second region 2, and the top doping layer 206 covers the first region 1.

[0125] like Figure 4 As shown, in one embodiment, the number of the middle doping layers 204 is multiple and they are stacked along the first direction X; the size of the middle doping layer 204 close to the bottom doping layer 202 extending to the second region 2 is larger than the size of the middle doping layer 204 away from the bottom doping layer 202 extending to the second region 2.

[0126] like Figure 7 , Figure 8 As shown, in one embodiment, the gate 106 includes: a main gate 1061, the main gate 1061 is located on the surface of the top doped layer 202, extends along the third direction Z, and extends along the first direction X to penetrate the middle doped layer 204. The main gate 1061 can collect carriers gathered in the doping structure 104 in the area (first area 1) where the top doped layer 206 is located. Further, a plurality of main gates 1061 are arranged at intervals along the second direction Y.

[0127] like Figure 7 , Figure 8 As shown, in one embodiment, the gate 106 further includes: a fine gate 1062, which is located on the doped structure 104, extends along the second direction Y, and extends into the doped structure 104 along the first direction X. Further, a plurality of fine gates 1062 are arranged at intervals along the third direction Z.

[0128] The present disclosure also provides a photovoltaic assembly, comprising a plurality of solar cells as described above, and / or a plurality of solar cells manufactured using the method for manufacturing a solar cell as described above.

[0129] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0130] The above-mentioned embodiments only express several implementation methods of the embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the embodiments of the present disclosure, and these all belong to the protection scope of the embodiments of the present disclosure.

Claims

1. A solar cell, characterized in that: include: substrate; A doping structure, located on the substrate, comprising a plurality of doping layers of the same conductivity type stacked and arranged along a first direction perpendicular to the substrate; a gate, located at a side of the doping structure away from the substrate, and extending into the doping structure along the first direction; The doping concentration of the doping layer far from the substrate is greater than the doping concentration of the doping layer close to the substrate, and the projection area of ​​the doping layer far from the substrate on the substrate is smaller than the projection area of ​​the doping layer close to the substrate on the substrate.

2. The solar cell according to claim 1, characterized in that The substrate includes a first region and a second region, the first region and the second region are adjacent to each other along a second direction parallel to the substrate, and extend along a third direction parallel to the substrate, and the third direction intersects with the second direction; the doping structure includes a bottom doping layer, a middle doping layer and a top doping layer stacked in sequence in the first region, the bottom doping layer covers the first region and the second region, the middle doping layer extends along the second direction to cover a portion of the second region, and the top doping layer covers the first region.

3. The solar cell according to claim 2, characterized in that: There are multiple middle doped layers stacked along the first direction; the size of the middle doped layer close to the bottom doped layer extending to the second region is larger than the size of the middle doped layer far from the bottom doped layer extending to the second region.

4. The solar cell according to claim 2, characterized in that: The gate comprises: The main gate is located on the surface of the top doped layer, extends along the third direction, and extends along the first direction to penetrate the middle doped layer.

5. The solar cell according to claim 4, characterized in that: The gate further comprises: A fine gate is located on the doping structure, extends along the second direction, and extends into the doping structure along the first direction.

6. A method for preparing a solar cell, characterized in that: include: providing a substrate; forming a doping structure on the substrate, wherein the doping structure comprises a plurality of doping layers of the same conductivity type stacked and arranged along a first direction perpendicular to the substrate; forming a gate on a side of the doped structure away from the substrate, wherein the gate extends into the doped structure along the first direction; The doping concentration of the doping layer far from the substrate is greater than the doping concentration of the doping layer close to the substrate, and the projection area of ​​the doping layer far from the substrate on the substrate is smaller than the projection area of ​​the doping layer close to the substrate on the substrate.

7. The method for preparing a solar cell according to claim 6, characterized in that: The substrate comprises a first region and a second region, the first region and the second region are adjacent to each other along a second direction parallel to the substrate and extend along a third direction parallel to the substrate, the third direction intersecting the second direction; The step of forming a doping structure on the substrate comprises: forming a bottom doped layer on the substrate, wherein the bottom doped layer covers the first region and the second region; Selectively depositing on the surface of the bottom doped layer to form a middle doped layer, wherein the middle doped layer covers the first region and extends along the second direction to cover a portion of the second region; selectively depositing on the middle doped layer to form a top doped layer covering the first region; Wherein, the doping structure includes the bottom doping layer, the middle doping layer and the top doping layer.

8. The method for preparing a solar cell according to claim 7, characterized in that: The middle doping layer and the top doping layer are formed by an atomic layer deposition process.

9. The method for preparing a solar cell according to claim 7, characterized in that: The step of selectively depositing on the surface of the bottom doped layer to form the middle doped layer comprises: Performing multiple selective depositions on the surface of the bottom doped layer respectively to form a plurality of middle doped layers stacked along the first direction; The dimension of the middle doped layer close to the bottom doped layer extending to the second region is greater than the dimension of the middle doped layer far from the bottom doped layer extending to the second region.

10. The method for preparing a solar cell according to claim 6, characterized in that: The substrate comprises a first region and a second region, the first region and the second region are adjacent to each other along a second direction parallel to the substrate and extend along a third direction parallel to the substrate, the third direction intersecting the second direction; The step of forming a doping structure on the substrate comprises: forming a bottom doping layer, a middle doping material layer and a top doping material layer stacked along the first direction on the substrate; removing the top doped material layer in the second region to form a top doped layer covering the first region; removing a portion of the middle doping material layer in the second region to form a middle doping layer, wherein the middle doping layer covers the first region and extends along the second direction to cover a portion of the second region; The doping concentration of the top doping material layer is greater than the doping concentration of the middle doping material layer, and the doping concentration of the middle doping material layer is greater than the doping concentration of the bottom doping layer.

11. The method for preparing a solar cell according to claim 10, characterized in that: The bottom doped layer has a plurality of middle doped material layers stacked along the first direction formed on the surface thereof, and the middle doped material layers in the second region are removed to form the middle doped layer, comprising: Using multiple laser etching processes to correspondingly etch the plurality of middle doped material layers to form a plurality of middle doped layers; Wherein, along the second direction, the size of the middle doping material layer close to the bottom doping layer that is etched away is smaller than the size of the middle doping material layer far from the bottom doping layer that is etched away.

12. The method for preparing a solar cell according to any one of claims 7 to 11, characterized in that: The step of forming a gate on a side of the doping structure away from the substrate comprises: A main gate is formed on the surface of the top doped layer. The main gate extends along the third direction and extends along the first direction to penetrate the middle doped layer.

13. The method for preparing a solar cell according to claim 12, characterized in that: The method further comprises forming a gate on a side of the doping structure away from the substrate, and further comprising: A fine gate is formed on the doped structure, wherein the fine gate extends along the second direction and extends into the doped structure along the first direction.

14. A photovoltaic module, characterized in that: The invention comprises a plurality of solar cells according to any one of claims 1 to 5, and / or a plurality of solar cells manufactured by the method for manufacturing a solar cell according to any one of claims 6 to 13.

Images