Photovoltaic cell piece preparation method, photovoltaic cell piece and photovoltaic module

Abstract

The invention relates to a preparation method of a photovoltaic cell, the photovoltaic cell and a photovoltaic module, and the preparation method comprises the steps: providing a substrate which comprises a to-be-doped part, the to-be-doped part comprises a plurality of pyramid structures, and each pyramid structure comprises a tower top and a tower bottom; placing slurry on the top of the tower, wherein the slurry comprises doped impurities; drying the slurry, wherein the slurry becomes a solidified body fixedly connected to the top of the tower; annealing the substrate and the cured body so that the average concentration of the doped impurities at the top of the tower is greater than the average concentration of the doped impurities at the bottom of the tower; and forming a metal electrode in ohmic contact with the top of the tower. On one hand, the compounding rate of electrons and holes in the pyramid structure is low, and on the other hand, the contact resistance between the tower top and the metal electrode is low, so that the preparation method can improve the photoelectric conversion efficiency of the prepared photovoltaic cell.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a method for preparing a photovoltaic cell, a photovoltaic cell and a photovoltaic module. Background Art

[0002] The photovoltaic cell of the related art has low photoelectric conversion efficiency. Summary of the invention

[0003] In view of this, the present application provides a method for preparing a photovoltaic cell, a photovoltaic cell and a photovoltaic module, wherein the preparation method of the present application can improve the photoelectric conversion efficiency of the prepared photovoltaic cell.

[0004] In a first aspect, the present application provides a method for preparing a photovoltaic cell sheet, the preparation method comprising: providing a substrate, wherein the substrate comprises a portion to be doped, the portion to be doped comprises a plurality of pyramid structures, the pyramid structures comprise a tower top and a tower bottom; placing a slurry on the tower top, wherein the slurry comprises doping impurities, the doping impurities comprise at least one third main group element, or the doping impurities comprise at least one fifth main group element; drying the slurry so that the slurry becomes a solidified body fixed to the tower top; annealing the substrate and the solidified body so that the average concentration of the doping impurities diffused to the tower top is greater than the average concentration of the doping impurities diffused to the tower bottom; removing the solidified body; forming a passivation layer; and forming a metal electrode in ohmic contact with the tower top.

[0005] The photovoltaic cell prepared according to the preparation method of the present application has the following advantages: in the pyramid structure in ohmic contact with the metal electrode, the average concentration of doped impurities in the top of the tower is greater than the average concentration of doped impurities in the bottom of the tower. On the one hand, the arrangement allows a high-low junction to be formed between the top of the tower and the bottom of the tower, and the type of the high-low junction can be N+ / N, or the type of the high-low junction can be P+ / P, and the rate of recombination of electrons and holes in the pyramid structure in ohmic contact with the metal electrode is low. On the other hand, the arrangement also allows a low contact resistance between the top of the tower and the metal electrode, and good conductivity between the top of the tower and the metal electrode. Therefore, the preparation method of the present application can improve the photoelectric conversion efficiency of the prepared photovoltaic cell.

[0006] Optionally, the method of placing the slurry on the top of the tower includes at least one of: coating the slurry on the top of the tower using a spin coating process, printing the slurry on the top of the tower using a screen printing process, and spraying the slurry on the top of the tower using a spray coating process.

[0007] Optionally, the method of applying the slurry on the top of the tower using a spin coating process satisfies at least one of the following settings: Setting 1): first rotate the substrate, and then drip the slurry onto the surface of the substrate having the portion to be doped; Setting 2): make the spin coating speed n within the range of 2000r / min to 5000r / min.

[0008] Optionally, the method of dripping the slurry onto the surface of the substrate having the portion to be doped includes: dripping the slurry onto at least two spaced-apart locations on the surface of the substrate having the portion to be doped.

[0009] Optionally, the method of printing slurry on the top of the tower using a screen printing process satisfies at least one of the following settings: Setting a: making the printing pressure F in the range of 40N to 80N; Setting b: making the printing speed v in the range of 200mm / s to 400mm / s.

[0010] Optionally, a slurry satisfying at least one of the following settings is used: Setting i: using a slurry having a Brookfield viscosity in the range of 20 cps to 50 cps; Setting ii: using a slurry having a surface tension in the range of 22N to 42N.

[0011] After removing the solidified body and before forming the passivation layer, the method of the present application may further include: masking the pyramid structure. Alternatively, after annealing the substrate and the solidified body and before removing the solidified body, the method of the present application may further include: depositing an outer mask layer on the solidified body.

[0012] In a second aspect, the present application provides a photovoltaic cell, which can be prepared by the preparation method described above, the photovoltaic cell comprising a stacked silicon substrate, a diffusion layer and a passivation layer, the side of the diffusion layer facing the passivation layer comprising a plurality of pyramid structures, the pyramid structures comprising tower tops and tower bottoms; the photovoltaic cell also comprises a metal electrode corresponding to the diffusion layer, at least a portion of the tower tops of the diffusion layer are in ohmic contact with the metal electrode; the average concentration of doped impurities at the tower tops in ohmic contact with the metal electrode is greater than the average concentration of doped impurities at the tower bottoms in the same pyramid structure.

[0013] The present application provides another photovoltaic cell, which can be prepared by the preparation method described above, the photovoltaic cell includes a stacked silicon substrate, a tunneling layer, a doped conductive layer and a passivation layer, the side of the doped conductive layer facing the passivation layer includes a plurality of pyramid structures, the pyramid structure includes a tower top and a tower bottom; the photovoltaic cell also includes a metal electrode corresponding to the doped conductive layer, at least a portion of the tower tops of the doped conductive layer are in ohmic contact with the metal electrode; the average concentration of doped impurities at the tower tops in ohmic contact with the metal electrode is greater than the average concentration of doped impurities at the tower bottoms in the same pyramid structure.

[0014] The photovoltaic cell of the present application has a relatively high photoelectric conversion efficiency, which will not be described in detail here.

[0015] In a third aspect, the present application provides a photovoltaic module, the photovoltaic module includes a battery string, the battery string includes at least two electrically connected photovoltaic cells, and the photovoltaic cell is the photovoltaic cell described above. The photovoltaic module of the present application also includes the technical effects of the photovoltaic cell, which will not be repeated here.

[0016] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 is a schematic diagram of a local structure of a substrate in a specific embodiment;

[0019] Figure 2 It is a schematic diagram of a local structure of a pyramid structure in a specific embodiment;

[0020] Figure 3 is a schematic diagram of a partial structure of a substrate and a slurry in a specific embodiment;

[0021] Figure 4 It is a schematic diagram of the local structure of the pyramid structure and the slurry in a specific embodiment;

[0022] Figure 5 It is a schematic diagram of the partial structure of the pyramid structure and the solidified body in a specific embodiment;

[0023] Figure 6 is a schematic diagram of a partial structure of a pyramid structure and a solidified body in a specific embodiment, wherein the pyramid structure is doped with doping impurities;

[0024] Figure 7 is a schematic diagram of the structure of the substrate in a top-down perspective;

[0025] Figure 8 is a schematic diagram of the structure of the substrate and the slurry from a top view, wherein the slurry has been fully coated on the surface of the substrate;

[0026] Fig. 9 is a schematic diagram of the structure of the substrate and the slurry from a top view, wherein the slurry does not completely coat the surface of the substrate;

[0027] Fig.10 It is a schematic diagram of the state of the slurry during the rotation process;

[0028] Fig.11 is a schematic diagram of the structure of the substrate in a top view, wherein the portion to be doped is located in the area to be metallized and the non-metallized area;

[0029] Fig.12 is a schematic diagram of the structure of the substrate in a top view, wherein the portion to be doped is located in the area to be metallized;

[0030] Fig.13 It is a schematic diagram of the structure of the substrate and the slurry from a top-down perspective;

[0031] Fig.14 is a schematic diagram of a partial structure of a pyramid structure in another specific embodiment;

[0032] Fig.15 is a schematic diagram of a partial structure of a substrate and a slurry in a specific embodiment;

[0033] Fig.16 It is a schematic diagram of the structure of the pyramid structure and the inner mask layer;

[0034] Fig.17 It is a schematic diagram of the structure of the pyramid structure and the outer mask layer;

[0035] Figure 18 to Figure 27 Schematic diagram of the structure of the photovoltaic cell provided in this application in various specific embodiments.

[0036] Description of reference numerals:

[0037] 1- substrate;

[0038] 1a-area to be metallized;

[0039] 1b-non-metallized area;

[0040] 11-part to be doped;

[0041] 111-Pyramid structure;

[0042] 111a - top of the tower;

[0043] 111b - bottom of the tower;

[0044] 111c - middle part of the tower;

[0045] 2- slurry;

[0046] 2a-cured body;

[0047] 21-Contact part;

[0048] 22- surface connection part;

[0049] 3-Inner mask layer;

[0050] 4-outer mask layer;

[0051] 100-photovoltaic cells;

[0052] 100a-metallization area;

[0053] 100b-non-metallized area;

[0054] 10-silicon substrate;

[0055] 20- diffusion layer;

[0056] 30- tunneling layer;

[0057] 40-doped conductive layer;

[0058] 60-positive metal electrode;

[0059] 70 - negative metal electrode;

[0060] 80-aluminum oxide passivation layer;

[0061] 90-Silicon nitride passivation layer. DETAILED DESCRIPTION

[0062] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0063] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the protection scope of the present application.

[0064] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0065] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0066] In the figures of this document, directions X, Y and Z are perpendicular, wherein direction Y represents the direction from the backlight side of the photovoltaic cell to the light-receiving side of the photovoltaic cell, and the light-receiving side refers to the side of the photovoltaic cell directly illuminated by sunlight.

[0067] In a first aspect, the present application provides a method for preparing a photovoltaic cell, the method comprising the following contents:

[0068] Provide a substrate, wherein, please refer to Figure 1 As shown, the substrate 1 includes a portion to be doped 11, and the portion to be doped 11 includes a plurality of pyramid structures 111. Figure 2 As shown, the pyramid structure 111 may include a tower top 111 a and a tower bottom 111 b .

[0069] It should be noted that the substrate refers to a sheet structure that includes at least a silicon base (also known as a silicon substrate). Of course, the substrate may include a tunneling layer and an intrinsic layer in addition to the silicon base. The portion to be doped 11 refers to a portion of the substrate that needs to be doped with doping impurities later. The doping impurities may include at least one P-type element (the third main group element in the periodic table) or at least one N-type element (the fifth main group element in the periodic table). The multiple pyramid structures 111 refer to the structure formed after a velvet surface (with multiple micron-sized grooves and protrusions) is made on the surface of the portion to be doped 11.

[0070] Please refer to Figure 3 As shown, slurry 2 is placed on substrate 1, please refer to Figure 4 As shown, taking a single pyramid structure 111 as an example, the slurry 2 is mainly placed at the top 111a of the pyramid, wherein the slurry 2 includes the doping impurities and auxiliary materials described in this article.

[0071] It should be noted that the placement in “placing slurry 2 at the tower top 111a” is an action of bringing the slurry that was not originally in contact with the tower top into contact with the tower top. The subsequent content of this article will specifically introduce how to place the slurry at the tower top.

[0072] It should be noted that, as a source material including doped impurities, the state of the slurry may include a liquid state or a solid-liquid mixed state. If the slurry includes a liquid state, the slurry may also be referred to as a liquid or ink containing doped impurities. If the slurry includes a solid-liquid mixed state, the slurry may also be referred to as a colloid containing doped impurities or a paste containing doped impurities. Further, in a classification system in which the material state classification includes solid, liquid, gaseous, and a mixed state of at least two of the first three, the state of the slurry may be a state that does not include a gaseous state. Accordingly, the slurry can be placed at the top of the tower, and the slurry is not easy to quickly leave the top of the tower.

[0073] In such Figure 4 Based on the above, the slurry 2 is dried to make the slurry 2 as shown in FIG. Figure 5 The solidified body 2a shown is fixed to the tower top 111a, that is, the solidified body 2a has no fluidity, and the position of the solidified body 2a is fixed relative to the position of the tower top 111a.

[0074] After annealing the substrate 1 and the solidified body 2a, the impurities in the solidified body 2a will diffuse into the pyramid structure 111. Since the top 111a of the pyramid is in contact with the solidified body 2a, the bottom 111b of the pyramid is not in contact with the solidified body 2a, and the top 111a of the pyramid is closer to the solidified body 2a than the bottom 111b of the pyramid. After the diffusion is completed, please refer to Figure 6 As shown, the average concentration of the doping impurities diffused in the tower top 111 a is greater than the average concentration of the doping impurities diffused in the tower bottom 111 b.

[0075] It should be noted that among the multiple pyramid structures 111 in contact with the slurry 2, the tower bottoms 111b in most of the pyramid structures 111 do not contact the slurry 2, and the tower bottoms 111b in a few of the pyramid structures 111 may contact a small amount of slurry 2. Even so, the degree of influence on the result of "the average concentration of doping impurities in the tower top 111a is greater than the average concentration of doping impurities in the tower bottom 111b" to be formed is relatively small. Therefore, the few tower bottoms 111b that contact a small amount of slurry 2 can also be regarded as not contacting the slurry 2.

[0076] It should be noted that in Figure 6 In the structure shown, the concentration of the doping impurities in the tower top 111a is distributed in a gradient, for example, along the reverse direction Y, the concentration of the doping impurities in the tower top 111a gradually decreases. Figure 6 In the structure shown, the concentration of the doping impurities in the tower bottom 111b is also distributed in a gradient, for example, along the reverse direction Y, the concentration of the doping impurities in the tower bottom 111a gradually decreases. Figure 6 In the structure shown, the concentration of doping impurities gradually decreases along a direction from the surface of the pyramid structure 111 to the inside of the pyramid structure 111 (a direction perpendicular to the surface of the pyramid structure).

[0077] After annealing the substrate 1 and the solidified body 2a, the solidified body is removed, a passivation layer is formed, and a metal electrode is formed to make an ohmic contact (also known as a metallized contact) with the top of the tower to prepare the desired photovoltaic cell. The following content of this article will further introduce in detail the content after annealing the substrate 1 and the solidified body 2a in the method of this application.

[0078] According to the above content, in the pyramid structure 111 in ohmic contact with the metal electrode, the average concentration of the doping impurities in the top 111a of the tower is greater than the average concentration of the doping impurities in the bottom 111b of the tower. On the one hand, this arrangement allows a high-low junction to be formed between the top 111a of the tower and the bottom 111b of the tower. If the doping impurities include at least one N-type element, the type of the high-low junction can be N + / N, a built-in electric field E1 is formed between the top 111a and the bottom 111b of the tower, and the direction of the built-in electric field E1 is from the top 111a of the tower to the bottom 111b of the tower. The built-in electric field E1 can attract the electrons at the bottom 111b of the tower to migrate to the top 111a of the tower, and the built-in electric field E1 can repel the holes at the bottom 111b of the tower, thereby reducing the possibility of the electrons that need to migrate to the metal electrode (negative metal electrode) being recombined by the holes. Similarly, if the doped impurities include at least one P-type element, the type of the high-low junction can be P + / P, a built-in electric field E2 will be formed between the tower top 111a and the tower bottom 111b, and the direction of the built-in electric field E2 is from the tower bottom 111b to the tower top 111a. The built-in electric field E2 can attract holes located at the tower bottom 111b to migrate to the tower top 111a, and the built-in electric field E2 can repel electrons located at the tower bottom 111b, thereby reducing the possibility of holes moving toward the metal electrode (positive metal electrode) being recombined by electrons. On the other hand, this setting also makes the contact resistance between the tower top 111a and the metal electrode lower, and the conductivity between the tower top 111a and the metal electrode is better. Therefore, the preparation method of the photovoltaic cell provided in the embodiment of the present application can improve the photoelectric conversion efficiency of the prepared photovoltaic cell.

[0079] In the preparation method of the related art, all surfaces of the pyramid structure of the to-be-doped part need to be in contact with the diffusion source (containing the element to be doped with impurities). Taking a single pyramid structure as an example, the difference between the doping concentrations at any part of the pyramid structure surface is small, and the difference between the doping concentrations at any part of the pyramid structure is also small. It can also be said that the difference between the average doping concentration at the top of the pyramid structure and the average doping concentration at the bottom of the pyramid structure is small. After diffusion, the surface of the bottom of the tower needs to be selectively removed to reduce the average doping concentration at the bottom of the tower, so that the average doping concentration at the bottom of the tower is less than the average doping concentration at the top of the tower, thereby forming the required high-low junction. However, "selectively removing the surface of the bottom of the tower" causes a large degree of damage to the pyramid structure, which is likely to cause more microscopic defects on the surface of the pyramid structure and introduce more impurities, and is likely to cause more recombination centers on the surface of the pyramid structure. More recombination centers are likely to increase the rate of recombination of electrons and holes inside the pyramid structure.

[0080] Compared with the related art, the preparation method of the present application does not need to remove the surface of the bottom of the pyramid structure after diffusing the pyramid structure, and the degree of damage to the pyramid structure is relatively small. It is not easy to produce more microscopic defects on the surface of the pyramid structure and introduce more impurities, and it is not easy to produce more recombination centers on the surface of the pyramid structure. Accordingly, it is not easy to increase the recombination rate of electrons and holes inside the pyramid structure.

[0081] Optionally, if the substrate includes a silicon substrate with a velvet surface, the portion to be doped may be located on a side portion of the silicon substrate with the velvet surface, and the slurry may be placed on the top of the pyramid structure of the portion to be doped of the silicon substrate. After the doping impurities diffuse into the portion to be doped, the portion to be doped becomes a diffusion layer. If the silicon substrate includes a high concentration of N-type elements, the diffusion layer may include a high concentration of P-type elements, or if the silicon substrate includes a high concentration of P-type elements, the diffusion layer may include a high concentration of N-type elements, and the diffusion layer and the silicon substrate form a PN junction.

[0082] Optionally, if the substrate may include a stacked silicon substrate, a tunneling layer and an intrinsic layer, the side of the intrinsic layer away from the tunneling layer has a velvet surface, the part to be doped may be located on the side with the velvet surface in the intrinsic layer, and the slurry may be placed at the top of the pyramid structure of the part to be doped in the intrinsic layer. After the doping impurities diffuse into the part to be doped, the part to be doped becomes a doped medium layer. It should be noted that a part of the intrinsic layer may be the part to be doped, or the entire intrinsic layer may be the part to be doped, but the part to be doped is in contact with the tunneling layer, so that the formed doped medium layer is also in contact with the tunneling layer. It should be noted that the silicon substrate and the doped medium layer may include the same N-type element or P-type element, or either of the silicon substrate and the doped medium layer includes an N-type element and the other includes a P-type element. It should be noted that although the diffusion layer and the doped medium layer are both formed by diffusion, the originally doped parts are different. For the sake of distinction, the part formed by the diffusion of the part to be doped of the silicon substrate is referred to as the diffusion layer, and the part formed by the diffusion of the part to be doped of the intrinsic layer is referred to as the doped medium layer.

[0083] It should be noted that the doped dielectric layer needs to be annealed later to increase the volume ratio of polysilicon in the doped dielectric layer to improve the conductivity of the doped dielectric layer. Therefore, the doped dielectric layer after annealing can be called a doped conductive layer.

[0084] If the silicon substrate and the doped conductive layer include the same N-type element or P-type element, the average concentration of the doped impurities in the doped conductive layer needs to be greater than the average concentration of the doped impurities in the silicon substrate. This setting is conducive to the formation of a high-low junction. The role of the high-low junction has been described above and will not be repeated here.

[0085] Alternatively, if the paste includes a P-type element, the paste may include at least one of a boron element, an aluminum element, and a gallium element. More specifically, the paste may include at least one of C4H9NBO3, GACL3, and ALCL3.

[0086] Alternatively, if the slurry includes an N-type element, the slurry may include at least one of a phosphorus element, an arsenic element, and an antimony element. More specifically, the slurry may include C5H 16 O 16 P4.

[0087] Optionally, the auxiliary material of the slurry may include at least one of water, resin, glass frit and thickener, and the auxiliary material may serve as a carrier for doping impurities.

[0088] Optionally, the method of placing the slurry on the top of the tower includes: coating the slurry on the top of the tower using a spin coating process. For details, please refer to Figure 7 As shown, the substrate 1 can be rotated counterclockwise along direction j. The slurry (not shown in the figure) on the substrate 1 and not yet fully coated on the surface of the substrate 1 is difficult to rotate synchronously with the substrate 1 in time due to inertia. On the one hand, the slurry on the substrate 1 will deform along the surface of the substrate. During the continuous rotation of the substrate 1, the slurry does not have time to fall into the gully between two adjacent pyramid structures and is dispersed along the surface of the substrate. Please refer to Figure 8 As shown, the dispersed slurry 2 will gradually cover the surface of the substrate 1. On the other hand, since the slurry itself has a certain surface tension, there is a certain amount of gas in the gully between two adjacent pyramid structures, which can provide support for the slurry, so that the slurry is mainly in contact with the top of the pyramid structure, and the slurry is not easy to flow to the bottom of the tower. In addition, the slurry itself has a certain viscosity, so that the slurry is not easy to flow to the bottom of the tower, and the surface viscosity of the slurry will also reduce the fluidity of the gas in the gully between two adjacent pyramid structures, so that the gas in the gully between two adjacent pyramid structures can provide good support for the slurry. Therefore, under the spin coating process, the slurry is mainly in contact with the top of the pyramid structure.

[0089] The rotation axis of the substrate for rotational motion may be parallel to the Y direction.

[0090] Alternatively, the substrate may be spun using a spin coater or a spin coating device.

[0091] In other embodiments, the substrate may also be rotated clockwise.

[0092] Optionally, the method of coating the slurry on the top of the tower using a spin coating process also satisfies the following setting 1) and / or setting 2).

[0093] Setting 1): Please refer to Figure 7 As shown, first rotate the substrate 1, please refer to Fig. 9 As shown, the slurry 2 is dripped onto the surface of the rotating substrate 1 (the surface having the doped portion), please refer to Fig.10 As shown, the slurry 2 is immediately dispersed relative to the surface of the substrate (not shown in the figure) under the action of inertia, please refer to Figure 8 As shown, the slurry 2 covers the surface of the substrate 1. Under this setting, when the slurry 2 drips onto the surface of the substrate 1, it does not have time to contact the bottom of the tower and spreads along the surface of the substrate 1, so that the slurry 2 mainly contacts the top of the tower.

[0094] In other embodiments, the substrate may be rotated and the slurry may be dripped onto the substrate simultaneously.

[0095] In other embodiments, the slurry may be dripped onto the substrate first, and then the substrate may be rotated.

[0096] Setting 2): Make the spin coating speed n in the range of 2000r / min to 5000r / min. The spin coating speed n can be specifically 2000r / min, 2500r / min, 3000r / min, 3500r / min, 4000r / min, 4500r / min or 5000r / min. If the spin coating speed n is too small, for example, the spin coating speed n is less than 2000r / min, it takes a long time to coat the surface of the substrate 1 (the surface with the part to be doped) with the slurry 2, and the coating efficiency is low. In addition, it is easy for a part of the slurry 2 to have more time to flow to the bottom 111b of the tower. If the spin coating speed n is too large, for example, the spin coating speed n is greater than 5000 r / min, after the slurry 2 is fully coated on the surface of the substrate 1, the slurry 2 at the edge of the substrate 1 is easily thrown off the substrate 1, and most of the slurry 2 at the center of the surface of the substrate 1 is also easily moved to the edge of the substrate 1, that is, it is difficult to evenly coat the surface of the substrate 1 with the slurry 2. Therefore, it is better to make the spin coating speed n within the range of 2000 r / min to 5000 r / min.

[0097] Optionally, the rotation speed of the substrate 1 can be increased to a preset value, and then the slurry 2 can be dripped onto the surface of the substrate 1 (the surface with the portion to be doped) which has the preset rotation speed. Under this setting, the slurry dripped onto the substrate 1 is not easy to flow to the bottom 111b of the tower, and the slurry 2 dripped onto the substrate 1 can be better maintained at the top 111a of the tower.

[0098] Optionally, the rotation speed of the substrate 1 can be increased first, and the slurry 2 can be dripped onto the surface (the surface with the portion to be doped) of the substrate 1 during the process of increasing the rotation speed of the substrate 1. Under this setting, the slurry dripped onto the substrate 1 is not easily rebounded by the rotating substrate 1, reducing the possibility of the slurry 2 being splashed to a position other than the substrate 1, thereby achieving the effect of saving the slurry 2.

[0099] Optionally, the method of dripping the slurry onto the surface of the substrate 1 (the surface having the portion to be doped) includes: Fig. 9 As shown, the slurry 2 is dripped on at least two spaced-apart locations on the surface of the substrate 1. On the one hand, the areas around at least two locations where the slurry 2 is dripped can be coated with the slurry 2 at the same time. This method has the advantage of a higher coating speed. On the other hand, the weight of the slurry 2 carried by any location where the slurry 2 is dripped will not be too large, thereby reducing the possibility that the tower bottom 111b of any location where the slurry 2 is dripped will easily contact the slurry 2.

[0100] Optionally, see Fig.10 As shown, at least two locations spaced apart in direction Z (locations for dripping slurry 2) have a set distance d1 therebetween, satisfying 20mm≤d1≤30mm, and the distance d1 can specifically be 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm or 30mm.

[0101] Optionally, at least two locations spaced apart in direction X (locations for dripping slurry 2) have a set distance d2 between them, satisfying 20 mm ≤ d2 ≤ 30 mm, and the distance d2 can specifically be 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm or 30 mm.

[0102] The number of the locations in the substrate 1 for dripping the slurry 2 may be two, three, four or more.

[0103] In other embodiments (not shown in the figure), the slurry can be dripped along a preset circular trajectory on the surface of the substrate, and the number of the preset circular trajectory can be one, two or more. If the number of the circular trajectory is two or more, the diameters of the circular trajectory can be different.

[0104] In other embodiments (not shown in the figure), the slurry can be dripped along a preset rectangular track line on the surface of the substrate, and the number of the preset rectangular track lines can be one, two or more. If the number of the rectangular track lines is two or more, the sizes of the rectangular track lines can be different.

[0105] In other embodiments (not shown in the figures), the slurry may also be dripped onto the surface of the substrate along a preset flat spiral trajectory.

[0106] Please refer to Figure 11-Figure 12 As shown, the substrate 1 may include a region to be metallized 1a and a non-metallized region 1b. The region to be metallized 1a is a region where a metal electrode needs to be set later, and the non-metallized region 1b is a region where a metal electrode does not need to be set later. Fig.11 and Fig.12 The dot-dash line is used to indicate the boundary between the area to be metallized 1a and the non-metallized area 1b.

[0107] Optionally, see Fig.11 As shown, the portion to be doped 11 of the substrate 1 may be located in the area to be metallized 1a and the non-metallized area 1b. Fig.11The surface of the substrate 1 shown (the surface with the part to be doped) may not be masked. After the surface of the substrate 1 is coated with the slurry, after drying and annealing, the doping impurities in the solidified body can diffuse to the part located in the metallized area 1a and the part located in the non-metallized area 1b in the part to be doped 11. Under this setting, the area of ​​the diffusion layer or doped conductive layer for transmitting carriers (electrons or holes) in the prepared photovoltaic cell is relatively large, and the photoelectric conversion efficiency of the prepared photovoltaic cell is high.

[0108] in, Fig.11 The portion to be doped 11 of the substrate 1 shown can be located in the area to be metallized 1a and the non-metallized area 1b, the multiple pyramid structures included in the portion to be doped 11 are at least in the area to be metallized 1a, some other pyramid structures included in the portion to be doped 11 can be located in the non-metallized area 1b, or the portion to be doped 11 does not include the pyramid structures located in the non-metallized area 1b.

[0109] Optionally, see Fig.12 As shown, the portion to be doped 11 of the substrate 1 may be located in the area to be metallized 1a, but not in the non-metallized area 1b. Fig.12 The portion of the substrate 1 shown in the figure located in the non-metallized area 1b has been masked (covered by a mask layer). After the substrate 1 is coated with the slurry, and after the drying and annealing treatments, the doping impurities in the solid body diffuse to the pyramid structure of the to-be-doped portion 11, but the doping impurities in the solid body are blocked by the mask layer, so that the doping impurities in the solid body cannot diffuse to the portion of the substrate 1 located in the non-metallized area 1b. Under this setting, the area of ​​the silicon substrate covered by the diffusion layer or doped conductive layer of the prepared photovoltaic cell is relatively small, the degree of parasitic absorption (the phenomenon that light is absorbed by the diffusion layer or doped conductive layer but does not generate electrons and holes) is relatively small, the silicon substrate can absorb more sunlight and can effectively convert the absorbed sunlight into more electrons and more holes, and the prepared photovoltaic cell has a high photoelectric conversion efficiency.

[0110] The mask layer may include photoresist, silicon oxide or silicon nitride.

[0111] It should be noted that after the diffusion, the mask layer needs to be removed so as to facilitate the subsequent formation of a passivation layer on the portion of the substrate 1 located in the non-metallized area 1 b.

[0112] It should be noted that, in the spin coating, the device for dripping the slurry can be a dripping gun or a dripping machine. Regarding the use of the dripping gun, the dripping gun can be manually controlled or electrically controlled to drip the slurry onto the substrate.

[0113] It should be noted that during spin coating, the slurry can be dripped on the area to be metallized on the substrate and / or on the non-metallized area of ​​the substrate. Fig.11 The embodiment shown is still Fig.12 In the illustrated embodiment, the portion to be doped 11 is coated with the slurry.

[0114] Optionally, the slurry can be printed on the top of the tower using a screen printing process. Fig.13 As shown, the substrate 1 may include a region to be metallized 1a and a non-metallized region 1b, and the portion to be doped is in the region to be metallized 1a, so the slurry can be selectively printed on the top of the towers of the multiple pyramid structures of the portion to be doped in the region to be metallized 1a using a screen printing process. After drying and annealing, the doping impurities in the solidified body can diffuse to the top of the tower in the region to be metallized 1a, while the top of the tower in the non-metallized region 1b that is not in contact with the solidified body will not be diffused, and the parasitic absorption of the prepared photovoltaic cell is small, and the silicon substrate of the prepared photovoltaic cell can absorb more sunlight and can effectively convert the absorbed sunlight into more electrons and more holes, and the photoelectric conversion efficiency of the prepared photovoltaic cell is high.

[0115] In other embodiments (not shown in the figure), the screen printing process can also be used to print the slurry not only on the top of the tower in the area to be metallized, but also on the top of the tower in the local position adjacent to the area to be metallized in the non-metallized area, so that the area of ​​the diffusion layer or doped conductive layer used to transmit carriers (electrons or holes) in the prepared photovoltaic cell is relatively large, and the degree of parasitic absorption of the prepared photovoltaic cell is small, and the photoelectric conversion efficiency of the prepared photovoltaic cell is high. Accordingly, the concentration of doped impurities in the slurry printed on the top of the tower in the non-metallized area can be less than the concentration of doped impurities in the slurry printed on the top of the tower in the area to be metallized, which is conducive to the formation of high-low junctions. The role of the high-low junction has been described above and will not be repeated here.

[0116] It should be noted that the screen printing process requires the use of a screen and a scraper. The principle of the screen printing process is to use the mesh holes on the screen to penetrate the slurry rather than the principle that the mesh holes are not impermeable to the slurry. When printing, the screen needs to be placed with slurry, and a certain pressure is applied to the screen with a scraper while the scraper is moved. During the movement of the scraper, the slurry is squeezed and printed on the substrate through the mesh holes.

[0117] Optionally, the method of printing the slurry on the top of the tower using a screen printing process satisfies the following setting a and / or setting b.

[0118] Setting a: Make the printing pressure F within the range of 40N to 80N. The printing pressure F can be 40N, 45N, 50N, 55N, 60N, 65N, 70N, 75N or 80N. If the printing pressure F is too small, for example, the printing pressure F is less than 40N, the effect of the slurry penetrating the mesh is poor, and the top of the tower where the slurry needs to be printed is likely not to be printed. If the printing pressure F is too large, for example, the printing pressure F is greater than 80N, on the one hand, it is easy for more slurry to be printed to the bottom of the tower, and on the other hand, it is easy to wear the scraper and the screen, and even easy to crush the substrate. Therefore, it is better to have the printing pressure F within the range of 40N to 80N.

[0119] Setting b: making the printing speed v in the range of 200 mm / s to 400 mm / s. The printing speed v can specifically be 200 mm / s, 210 mm / s, 220 mm / s, 230 mm / s, 240 mm / s, 250 mm / s, 260 mm / s, 270 mm / s, 280 mm / s, 290 mm / s, 300 mm / s, 310 mm / s, 320 mm / s, 330 mm / s, 340 mm / s, 350 mm / s, 360 mm / s, 370 mm / s, 380 mm / s, 390 mm / s or 400 mm / s. If the printing speed v is too small, for example, the printing speed v is less than 200mm / s, on the one hand, the time for printing the slurry is long, and before the slurry becomes a solid body, more of the previously printed slurry may have flowed to the bottom of the tower. On the other hand, there will be too much slurry printed on the pyramid structure at the same part, and too much slurry is easy to flow to the bottom of the tower. If the printing speed v is too large, for example, the printing speed v is greater than 400mm / s, the slurry does not have time to penetrate the mesh, so that the top of the tower that needs to be printed with slurry can contact less slurry, which is easy to make the subsequent diffusion effect poor, so that the concentration of doped impurities in the top of the tower is easy to be lower than the preset concentration, and the concentration of doped impurities in the bottom of the tower is also easy to be lower than the preset concentration. Therefore, it is better to have a printing speed v in the range of 200mm / s to 400mm / s.

[0120] Of course, factors that affect whether the slurry is better printed on the top of the tower may also include the scraper angle, which refers to the angle between the substrate surface and the side of the scraper. The scraper angle can be in the range of 40° to 80°, and the scraper angle can be specifically 40°, 45°, 50°, 55°, 60°, 65°, 70°, 75° or 80°. When the scraper angle is in the range of 40° to 80°, the slurry is better printed on the top of the tower.

[0121] Optionally, the slurry can also be sprayed on the top of the tower using a spraying process. A set first angle can be provided between the spraying direction and the substrate surface, and the first angle can be in the range of 30° to 60°, and the first angle can specifically be 30°, 35°, 40°, 45°, 50°, 55° or 60°. Under this setting, a set second angle can be provided between the spraying direction and the side of the top of the tower, and the second angle can be in the range of 80° to 100°, and the second angle can specifically be 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°, 89°, 90°, 91°, 92°, 93°, 94°, 95°, 96°, 97°, 98°, 99° or 100°. The sprayed slurry is ejected toward the side of the tower top in a direction nearly perpendicular to the side of the tower top. When the slurry collides with the side of the tower top, due to the inelastic collision, the kinetic energy of the slurry is lost to a large extent, and the possibility of the slurry flowing from the tower top to the tower bottom is small.

[0122] The spraying process can also have the technical effect of selectively placing the slurry at the target position (such as the area to be metallized) of the screen printing process described above, which will not be described in detail here.

[0123] Optionally, a slurry satisfying setting i and / or setting ii as follows is used.

[0124] Setting i: Use a slurry with a Brookfield viscosity in the range of 20cps to 50cps. The Brookfield viscosity of the slurry can specifically be 20cps, 25cps, 30cps, 35cps, 40cps, 45cps or 50cps. If the Brookfield viscosity of the slurry used is less than 20cps, the slurry will easily flow from the top of the tower to the bottom of the tower. If the Brookfield viscosity of the slurry used is greater than 50cps, it is difficult for the slurry to be quickly and evenly dispersed on the substrate, which may easily result in too much slurry at some locations and too little slurry at some other locations. In the subsequent diffusion process, it is easy to cause the doping concentration at some locations to be too high and the doping concentration at some other locations to be too low, resulting in poor diffusion effect. Therefore, it is better that the Brookfield viscosity of the slurry used is in the range of 20cps to 50cps.

[0125] It should be noted that the Brookfield viscosity is a viscosity value measured using a Brookfield viscometer. The Brookfield viscometer is a rotational viscometer, which is mainly used to measure viscosity.

[0126] Setting ii: Use a slurry with a surface tension in the range of 22N to 42N. The surface tension of the slurry can specifically be 22N, 23N, 24N, 25N, 26N, 27N, 28N, 29N, 30N, 31N, 32N, 33N, 34N, 35N, 36N, 37N, 38N, 39N, 40N, 41N or 42N. If the surface tension of the slurry is less than 22N, the surface tension of the slurry is too small, and the slurry easily flows from the top of the tower to the bottom of the tower. If the surface tension of the slurry is greater than 42N, the surface tension of the slurry is too large, the slurry easily floats on the top of the tower, the slurry is not easy to flow to the top of the tower, and the contact area between the slurry and the side of the top of the tower is relatively small. In the subsequent diffusion process, it is easy to make the concentration of doped impurities in the top of the tower lower than the preset concentration, and it is easy to make the concentration of doped impurities in the bottom of the tower lower than the preset concentration. Therefore, the surface tension of the slurry is preferably in the range of 22N to 42N.

[0127] It should be noted that in Figure 2 In the pyramid structure 111 shown in , the height of the tower top 111a in the direction Y and the height of the tower bottom 111b in the direction Y can be the same, or the height of the tower top 111a in the direction Y can be greater than the height of the tower bottom 111b in the direction Y, or the height of the tower top 111a in the direction Y can be less than the height of the tower bottom 111b in the direction Y.

[0128] In other embodiments, the distribution of the pyramid structures 111 in the direction Y may also be as follows: Fig.14 As shown, the pyramid structure 111 may include a tower top 111a, a tower middle 111c and a tower bottom 111b, wherein the tower middle 111c is located between the tower top 111a and the tower bottom 111b.

[0129] If in Fig.14 The slurry is placed on the pyramid structure 111 shown, please refer to Fig.15 As shown, the slurry 2 can contact the tower top 111a and the tower middle 111c respectively, but the volume of the slurry 2 contacted by the tower top 111a is larger, while the volume of the slurry 2 contacted by the tower middle 111c is smaller. After diffusion, the concentration of doping impurities in the tower top 111a is greater than the concentration of doping impurities in the tower middle 111c, and the concentration of doping impurities in the tower middle 111c is greater than the concentration of doping impurities in the tower bottom 111b.

[0130] In other embodiments, the slurry may also be placed in Fig.14 In the tower top 111a shown, the slurry does not contact the tower middle 111c and the tower bottom 111b.

[0131] Please note that, please refer to Figure 4As shown, the slurry 2 placed at the tower top 111a may include a contact portion 21 and a surface connection portion 22 distributed along the direction Y, wherein the contact portion 21 mainly contacts the tower top 111a, and the surface connection portion 22 is used to connect the contact portions 21 located on both sides of each tower top 111a, and the surface connection portion 22 is higher than the contact portion 21 and the tower top 111a. Under the action of the surface tension of the slurry 2 and the influence of the viscosity of the slurry 2, the contact portion 21 is not easy to flow away from the surface connection portion 22 to the tower bottom 111b, and the suspended portion of the surface connection portion 22 is not easy to fall to the tower bottom 111b. After the slurry becomes a solidified body, as shown in FIG. Figure 5 As shown, the cured body 2 a includes a cured contact portion 21 and a cured surface layer connecting portion 22 .

[0132] Optionally, after placing the slurry at the top of the tower, it is necessary to dry it in a short time to reduce the possibility of the slurry flowing to the bottom of the tower. The interval between placing the slurry at the top of the tower and drying the slurry can be in the range of 0 to 30 seconds, and the interval can specifically be 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 seconds.

[0133] Optionally, the method of drying the slurry includes placing the substrate and the slurry on a heating table, the heating table generates heat, and the heat is transferred to the slurry through the substrate, so that the slurry dries and becomes a solidified body.

[0134] The heating temperature of the heating stage may be in the range of 200°C to 350°C, and the heating temperature may specifically be 200°C, 250°C, 300°C or 350°C.

[0135] In addition, the heating time of the heating stage can be 1 minute to 3 minutes, and the heating temperature can be specifically 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes or 3 minutes.

[0136] In other embodiments, the method of drying the slurry may also include irradiating the slurry with a high-power lamp. The high-power lamp generates a large amount of heat when emitting light, and the heat is transferred to the slurry through air convection to dry the slurry and turn it into a solidified body.

[0137] In other embodiments, the method of drying the slurry may also include heating the slurry with microwaves to dry the slurry and form a solidified body.

[0138] Optionally, the method of annealing the substrate and the cured body includes placing the substrate and the cured body in an environment with a temperature of at least 800°C. The annealing temperature may specifically be 800°C, 850°C, 900°C, 950°C or 1000°C.

[0139] Optionally, the method for annealing substrate and cured body comprises annealing time in the range of 15 minutes to 30 minutes. Specifically, the annealing time can be 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes or 30 minutes.

[0140] Both the drying process and the annealing process are to apply heat to the substrate and the slurry to raise the temperature of the substrate and the slurry, but the temperature of the drying process is relatively low, and the temperature of the annealing process is relatively high. In some embodiments, the same device can be used for the drying process first and then the annealing process, that is, the heating temperature of the device is first set to the temperature required for the drying process, and then the heating temperature of the device is set to the temperature required for the annealing process. In some embodiments, a dedicated device (such as a heating table) can be used for the drying process, and another dedicated device (such as a high-temperature device such as a tubular diffusion furnace) can be used for the annealing process.

[0141] Optionally, after removing the solidified body and before forming the passivation layer, the method of the embodiment of the present application further includes masking the pyramid structure to form a mask layer that can protect the pyramid structure doped with dopant impurities, thereby reducing the possibility of the pyramid structure doped with dopant impurities being damaged by subsequent alkaline polishing (polishing a certain part of the substrate with alkaline solution), and reducing the possibility of the pyramid structure doped with dopant impurities being contaminated by other dopant impurities to be diffused subsequently.

[0142] Methods for masking the top of the tower may include oxidation treatment of the pyramid structure, see Fig.16 As shown, an inner mask layer 3 is formed in the pyramid structure 111. The inner mask layer 3 may include silicon oxide, which can better protect the doped pyramid structure.

[0143] It should be noted that the oxidation treatment is to place the substrate in an atmosphere including oxygen and heat it to diffuse oxygen into the pyramid structure. Fig.16 As shown, the required inner mask layer 3 is formed from the surface of the pyramid structure 111 to the inside of the pyramid structure 111 .

[0144] It should be noted that after the subsequent alkali polishing and diffusion of other doping impurities, the inner mask layer 3 needs to be removed so as to form a passivation layer on the surface of the doped pyramid structure 111 .

[0145] The method for masking the top of the tower can also include utilizing a vapor deposition process such as Fig.17 An outer mask layer 4 is deposited on the surface of the pyramid structure 111 as shown. The outer mask layer 4 may include silicon oxide and / or silicon nitride. Silicon oxide and / or silicon nitride may better protect the doped pyramid structure 111 .

[0146] It should be noted that the vapor deposition process forms the required outer mask layer 4 on the surface of the pyramid structure 111 toward the outside of the pyramid structure 111. Therefore, even if the outer mask layer 4 needs to be removed later, the damage to the doped pyramid structure 111 is relatively small.

[0147] The vapor deposition process may include chemical vapor deposition and physical vapor deposition. Chemical vapor deposition may include low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD) or atmospheric pressure chemical vapor deposition (APCVD).

[0148] It should be noted that after the subsequent alkali polishing and diffusion of other doping impurities, the outer mask layer 4 needs to be removed so as to form a passivation layer on the surface of the doped pyramid structure 111 .

[0149] It should be noted that the method for removing the solidified body before the mask treatment tower top may include using hydrofluoric acid, sulfuric acid, hydrochloric acid or other acidic solutions to remove the solidified body, and after removing the solidified body, washing with alkaline solution and water to achieve the purpose of neutralizing the pH.

[0150] Optionally, after annealing the substrate and the solidified body and before removing the solidified body, the method of the embodiment of the present application may further include: depositing an outer mask layer on the solidified body, using the solidified body and the outer mask layer to protect the doped pyramid structure, reducing the possibility of the pyramid structure doped with doping impurities being damaged by subsequent alkali polishing (polishing a certain part of the substrate with alkali solution), and reducing the possibility of the pyramid structure doped with doping impurities being contaminated by other doping impurities to be diffused subsequently. The outer mask layer may include silicon oxide and / or silicon nitride, and the process of depositing the outer mask layer may include chemical vapor deposition or physical vapor deposition.

[0151] It should be noted that after the subsequent alkali polishing and diffusion of other doping impurities, the solidified body and the outer mask layer need to be removed so as to form a passivation layer on the surface of the doped pyramid structure 111 .

[0152] Optionally, the method of forming the passivation layer includes forming an aluminum oxide passivation layer and / or a silicon nitride passivation layer, and the process of forming the passivation layer may include chemical vapor deposition or physical vapor deposition.

[0153] Optionally, the method of forming the metal electrode may include screen printing, laser transfer or inkjet printing.

[0154] According to the above content, this article provides a specific embodiment of the preparation method, the content is as follows:

[0155] 1) Alkaline solution is used to form a velvet surface on one side of the silicon substrate, that is, to form multiple pyramid structures.

[0156] 2) Placing slurry on the top of multiple pyramid structures using a spin coating process or a screen printing process.

[0157] 3) The slurry is heated using a heating table to dry the slurry into a solidified body.

[0158] 4) Annealing the silicon substrate and the solidified body to form a diffusion layer on the silicon substrate.

[0159] 5) Use hydrofluoric acid to remove the solidified body, and wash with alkali solution and water.

[0160] 6) Oxidation treatment to form borosilicate glass (including silicon oxide) on the surface of the pyramid structure.

[0161] 7) The borosilicate glass on the other side of the silicon substrate is removed by using hydrofluoric acid, and the other side of the silicon substrate is polished by using alkaline solution.

[0162] 8) A tunneling layer and a doped dielectric layer are sequentially formed on the other side of the silicon substrate.

[0163] 9) Remove phosphosilicate glass, coating (amorphous silicon and / or polycrystalline silicon) and borosilicate glass.

[0164] 10) Deposit an aluminum oxide passivation layer on the diffusion layer and deposit a silicon nitride passivation layer on both sides.

[0165] 11) Metal electrodes are prepared using screen printing and sintering processes.

[0166] In the second aspect, the embodiment of the present application provides a photovoltaic cell, which can be prepared by the preparation method described above, the photovoltaic cell comprises a stacked silicon substrate, a diffusion layer and a passivation layer, the side of the diffusion layer facing the passivation layer comprises a plurality of pyramid structures, the pyramid structure comprises a tower top and a tower bottom, the photovoltaic cell also comprises a metal electrode corresponding to the diffusion layer, at least a portion of the tower tops of the diffusion layer are in ohmic contact with the metal electrode (also known as metallization contact), and the concentration of doped impurities at the tower tops in ohmic contact with the metal electrode is greater than the concentration of doped impurities at the bottom of the tower in the same pyramid structure. Under this setting, the rate of recombination of electrons and holes in the pyramid structure is low, and the contact resistance between the ohmically contacted metal electrode and the tower top is low. Therefore, the photovoltaic cell of the embodiment of the present application has a high photoelectric conversion efficiency. The relevant specific technical effects have been described above and will not be repeated here.

[0167] Optionally, see Fig.18 As shown, one side of the silicon substrate 10 is entirely provided with a diffusion layer 20, and the diffusion layer 20 has a plurality of pyramid structures 111. The concentration of doped impurities at the top of each pyramid structure 111 is greater than the concentration of doped impurities at the bottom of the pyramid structure 111. Some pyramid structures 111 are located in the metallized area 100a of the photovoltaic cell 100, and some pyramid structures 111 are located in the non-metallized area 100b of the photovoltaic cell 100. The top of the pyramid structure 111 located in the metallized area 100a is in ohmic contact with the corresponding metal electrode.

[0168] The average concentration of doping impurities in the pyramid structure 111 located in the non-metallized region 100b may be equal to or less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a. If the average concentration of doping impurities in the pyramid structure 111 located in the non-metallized region 100b is less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a, a high-low junction may be formed, and the function of the high-low junction has been described above and will not be repeated here.

[0169] Optionally, see Fig.19 As shown, a diffusion layer 20 is disposed on one side of the silicon substrate 10, and the diffusion layer 20 has a plurality of pyramid structures 111 located in the metallized area 100a of the photovoltaic cell 100, and the concentration of doping impurities at the top of each pyramid structure 111 is greater than the concentration of doping impurities at the bottom of the pyramid structure, and the diffusion layer 20 also includes a portion that does not have a pyramid structure and is located in the non-metallized area 100b of the photovoltaic cell 100. The top of the pyramid structure 111 is in ohmic contact with the corresponding metal electrode.

[0170] The average concentration of doping impurities in the portion of the diffusion layer 20 located in the non-metallized region 100b may be equal to or less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a. If the average concentration of doping impurities in the portion of the diffusion layer 20 located in the non-metallized region 100b is less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a, a high-low junction may be formed, and the function of the high-low junction has been described above and will not be repeated here.

[0171] Optionally, see Figure 20-21 As shown, a diffusion layer 20 is partially provided on one side of the silicon substrate 10, and the diffusion layer 20 is located in the metallization area 100a of the photovoltaic cell 100, and the diffusion layer 20 includes a plurality of pyramid structures 111, and the concentration of doping impurities at the top of each pyramid structure 111 is greater than the concentration of doping impurities at the bottom of the pyramid structure 111. The top of the pyramid structure 111 is in ohmic contact with the corresponding metal electrode.

[0172] Please refer to Fig. 20 As shown, the silicon substrate 10 may also have a pyramid structure 111 , but the pyramid structure 111 of the silicon substrate 10 is located in the non-metallized area 100 b of the photovoltaic cell 100 .

[0173] Please refer to Fig.21 As shown, the portion of the silicon substrate 10 located in the non-metallized area 100 b may not have the pyramid structure.

[0174] Please note that, please refer to Figure 18-Figure 21 As shown, the term "corresponding to" in "the photovoltaic cell includes a metal electrode corresponding to the diffusion layer" means "corresponding to" in an ohmic contact relationship. For example, under the condition that the diffusion layer 20 includes a P-type element, the metal electrode corresponding to the diffusion layer 20 may be a positive metal electrode 60. Of course, in addition to the metal electrode corresponding to the diffusion layer 20, the photovoltaic cell 100 may also include other metal electrodes, and the other metal electrodes are in ohmic contact with the silicon substrate, or the other metal electrodes are in ohmic contact with the doped conductive layer, for example, the other metal electrodes may be negative metal electrodes.

[0175] Please refer to Figure 18-Figure 21As shown, if the doping impurities of the diffusion layer 20 include P-type elements, the top of the pyramid structure 111 located in the metallization area 100a is in ohmic contact with the positive metal electrode 60. Correspondingly, if the doping impurities of the diffusion layer 20 include P-type elements, the photovoltaic cell 100 may also include an aluminum oxide passivation layer 80 and a silicon nitride passivation layer 90. The aluminum oxide passivation layer 80 mainly plays a field passivation role, reducing the rate of recombination of electrons and holes in the diffusion layer 20, and the silicon nitride passivation layer 90 mainly plays a role in reducing reflected light, so that the silicon substrate 10 can absorb more light, which is conducive to the silicon substrate generating more electrons and holes, thereby helping to improve the photoelectric conversion efficiency of the photovoltaic cell.

[0176] In other embodiments (not shown in the figure), if the doping impurities of the diffusion layer include N-type elements, the top of the pyramid structure located in the metallization region is in ohmic contact with the negative metal electrode.

[0177] Please refer to Figure 18-Figure 21 As shown, the diffusion layer 20 may be located on the light-receiving side of the photovoltaic cell 100 .

[0178] In other embodiments, the diffusion layer may also be located on the backlight side of the photovoltaic cell.

[0179] The photovoltaic cell 100 of the embodiment of the present application can be specifically as follows Fig. 22 As shown, the photovoltaic cell 100 may also include a tunneling layer 30 and a doped conductive layer 40. The tunneling layer 30 is located on the side of the silicon substrate 10 away from the diffusion layer 20, and the doped conductive layer 40 is located on the side of the tunneling layer 30 away from the silicon substrate 10. The tunneling layer 30 may include at least one of silicon oxide, silicon nitride and silicon oxynitride. The doped conductive layer 40 may include polycrystalline silicon, and of course the doped conductive layer 40 may also include amorphous silicon. In the doped conductive layer 40, the volume proportion of polycrystalline silicon is greater than the volume proportion of amorphous silicon, so that the doped conductive layer 40 has good conductivity. The thickness dimension of the tunneling layer 30 in the direction Y is 1nm to 5nm, and the thickness dimension may specifically be 1nm, 2nm, 3nm, 4nm or 5nm. If the diffusion layer 20 includes P-type elements, and the silicon substrate 10 and the doped conductive layer 40 both include N-type elements, the electrons in the silicon substrate 10 can use the tunneling effect to pass through the tunneling layer 30 and migrate to the doped conductive layer 40. Therefore, as Fig. 22 The photovoltaic cell 100 shown may be a tunnel passivated contact solar cell (TOPcon).

[0180] Please refer to Fig. 22As shown, the photovoltaic cell 100 may also include a silicon nitride passivation layer 90 located on the side of the doped conductive layer 40 away from the tunneling layer 30, and the silicon nitride passivation layer 90 also has the function of reducing reflected light. It should be noted that although the backlight side of the photovoltaic cell 100 is not directly irradiated by sunlight, there is also a lot of ambient light in the environment. The silicon nitride passivation layer 90 can reduce the loss of ambient light, so that more ambient light is incident from the backlight side of the photovoltaic cell 100 into the silicon substrate 10, so that the silicon substrate 10 absorbs more light and generates more electrons and holes, thereby improving the photoelectric conversion efficiency of the photovoltaic cell 100.

[0181] The embodiment of the present application provides another photovoltaic cell sheet, which can be prepared by the preparation method described above, the photovoltaic cell sheet includes a stacked silicon substrate, a tunneling layer, a doped conductive layer and a passivation layer, at least one side of the doped conductive layer facing the passivation layer includes a plurality of pyramid structures, the pyramid structure includes a tower top and a tower bottom, the photovoltaic cell sheet also includes a metal electrode corresponding to the doped conductive layer, at least a portion of the tower tops of the doped conductive layer are in ohmic contact with the metal electrode, and the concentration of doped impurities at the tower tops in ohmic contact with the metal electrode is greater than the concentration of doped impurities at the bottom of the tower in the same pyramid structure. Under this setting, the rate of recombination of electrons and holes in the pyramid structure is low, and the contact resistance between the ohmically contacted metal electrode and the tower top is low. Therefore, the photovoltaic cell sheet of the embodiment of the present application has a high photoelectric conversion efficiency. The relevant specific technical effects have been described above and will not be repeated here.

[0182] Optionally, see Fig.23 As shown, the side of the tunneling layer 30 facing away from the silicon substrate 10 is entirely provided with a doped conductive layer 40, and the doped conductive layer 40 has a plurality of pyramid structures 111, and the concentration of doped impurities at the top of each pyramid structure 111 is greater than the concentration of doped impurities at the bottom of the pyramid structure 111, some pyramid structures 111 are located in the metallized area 100a of the photovoltaic cell 100, and some pyramid structures 111 are located in the non-metallized area 100b of the photovoltaic cell 100, and the top of the pyramid structure 111 located in the metallized area 100a is in ohmic contact with the corresponding metal electrode.

[0183] The average concentration of doping impurities in the pyramid structure 111 located in the non-metallized region 100b may be equal to or less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a. If the average concentration of doping impurities in the pyramid structure 111 located in the non-metallized region 100b is less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a, a high-low junction may be formed, and the function of the high-low junction has been described above and will not be repeated here.

[0184] Optionally, see Fig.24 As shown, the side of the tunneling layer 30 facing away from the silicon substrate 10 is entirely provided with a doped conductive layer 40, the doped conductive layer 40 has a plurality of pyramid structures 111 located in the metallized area 100a of the photovoltaic cell 100, the concentration of doped impurities at the top of each pyramid structure 111 is greater than the concentration of doped impurities at the bottom of the pyramid, and the doped conductive layer 40 also includes a portion that does not have a pyramid structure and is located in the non-metallized area 100b of the photovoltaic cell 100. The top of the pyramid structure 111 is in ohmic contact with the corresponding metal electrode.

[0185] The average concentration of doping impurities in the portion of the doped conductive layer 40 located in the non-metallized region 100b may be equal to or less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a. If the average concentration of doping impurities in the portion of the doped conductive layer 40 located in the non-metallized region 100b is less than the average concentration of doping impurities in the pyramid structure 111 located in the metallized region 100a, a high-low junction may be formed, and the function of the high-low junction has been described above and will not be repeated here.

[0186] Optionally, see Fig.25 As shown, a tunneling layer 30 is partially provided on one side of the silicon substrate 10, and a doped conductive layer 40 is provided on one side of the tunneling layer 30 away from the silicon substrate 10. The tunneling layer 30 and the doped conductive layer 40 are both located in the metallization area 100a of the photovoltaic cell 100, and the doped conductive layer 40 includes a plurality of pyramid structures 111, and the concentration of doped impurities at the top of each pyramid structure 111 is greater than the concentration of doped impurities at the bottom of the pyramid structure 111. The top of the pyramid structure 111 is in ohmic contact with the corresponding metal electrode.

[0187] The material, size and function of the tunneling layer 30 have been introduced above and will not be repeated here. The material, size and function of the doped conductive layer 40 have been introduced above and will not be repeated here. Figure 23-Figure 25 The photovoltaic cell 100 shown may be a tunnel passivated contact cell (TOPcon).

[0188] Please note that, please refer to Figure 23-Figure 25As shown, the term "corresponding to" in "the photovoltaic cell includes a metal electrode corresponding to the doped conductive layer" means "corresponding to" in an ohmic contact relationship. For example, under the condition that the doped conductive layer 40 includes an N-type element, the metal electrode corresponding to the doped conductive layer 40 may be a negative metal electrode 70. Of course, in addition to the metal electrode corresponding to the doped conductive layer 40, the photovoltaic cell 100 may also include other metal electrodes, and the other metal electrodes are in ohmic contact with the diffusion layer. For example, the other metal electrodes may be positive metal electrodes.

[0189] Please refer to Figure 23-Figure 25 As shown, if the doping impurities of the doped conductive layer 40 include N-type elements, the top of the pyramid structure 111 located in the metallization area 100a is in ohmic contact with the negative metal electrode 70. Correspondingly, if the doping impurities of the doped conductive layer 40 include N-type elements, the photovoltaic cell 100 may also include a silicon nitride passivation layer 90, and the silicon nitride passivation layer 90 mainly plays a role in reducing reflected light. Although the backlight side of the photovoltaic cell 100 is not directly irradiated by sunlight, there is also a lot of ambient light in the environment. The silicon nitride passivation layer 90 can reduce the loss of ambient light, so that more ambient light is incident from the backlight side of the photovoltaic cell 100 into the silicon substrate 10, so that the silicon substrate 10 absorbs more light and generates more electrons and holes, thereby improving the photoelectric conversion efficiency of the photovoltaic cell 100.

[0190] It should be noted that Figure 18-Figure 21 Any of the structural solutions for the photovoltaic cell 100 shown in Figure 23-Figure 25 Any of the structural solutions for the photovoltaic cell 100 shown in the figures can be combined to form multiple solutions for the specific structure of the photovoltaic cell 100.

[0191] The present application embodiment provides another photovoltaic cell sheet, such as Figure 26-Figure 27 As shown, the photovoltaic cell is a back contact photovoltaic cell (Back Contact solar cell), the positive metal electrode 60 and the negative metal electrode 70 are both on the backlight side of the photovoltaic cell 100, and no metal electrode is provided on the light-receiving side of the photovoltaic cell 100. Therefore, the area of ​​the photovoltaic cell 100 directly illuminated by sunlight is relatively large, and the photovoltaic cell 100 has a greater photoelectric conversion efficiency.

[0192] Among them, the average concentration of doped impurities at the top of the tower in the pyramid structure 111 in ohmic contact with the positive metal electrode 60 is greater than the average concentration of doped impurities at the bottom of the tower in the same pyramid structure 111. Under this setting, the rate of recombination of electrons and holes in the pyramid structure 111 is low, and the contact resistance between the metal electrode in ohmic contact and the top of the tower is low. Therefore, the photovoltaic cell of the embodiment of the present application has a high photoelectric conversion efficiency. The relevant specific technical effects have been described above and will not be repeated here.

[0193] about Figure 26-Figure 27 The other structures of the photovoltaic cell 100 shown can be understood by referring to the relevant contents above, which will not be described again here.

[0194] In a third aspect, an embodiment of the present application provides a photovoltaic module, which includes a laminate and a frame, and the frame is installed at the edge of the laminate. The laminate includes a stacked photovoltaic glass, a first encapsulation film, a battery string, a second encapsulation film and a backplane. Alternatively, the laminate includes a stacked first photovoltaic glass, a first encapsulation film, a battery string, a second encapsulation film and a second photovoltaic glass. Wherein, the battery string is formed by electrically connecting a plurality of photovoltaic cells described above.

[0195] The photovoltaic module of the embodiment of the present application also includes the technical effects of the photovoltaic cell in the above content, which will not be repeated here.

[0196] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a photovoltaic cell, characterized in that: The method comprises: Providing a substrate, wherein the substrate comprises a portion to be doped, the portion to be doped comprises a plurality of pyramid structures, and the pyramid structures comprise a tower top and a tower bottom; Placing a slurry at the top of the tower, wherein the slurry includes doping impurities, the doping impurities include at least one element of the third main group, or the doping impurities include at least one element of the fifth main group; Drying the slurry to make it a solidified body fixed to the top of the tower; Annealing the substrate and the solidified body so that the average concentration of the doping impurities diffused toward the top of the tower is greater than the average concentration of the doping impurities diffused toward the bottom of the tower; removing the solidified body; forming a passivation layer; A metal electrode is formed in ohmic contact with the top of the tower.

2. The method for preparing a photovoltaic cell according to claim 1, characterized in that: The method of placing slurry at the top of the tower comprises: At least one of the following methods is used: coating the slurry on the top of the tower by a spin coating process, printing the slurry on the top of the tower by a screen printing process, and spraying the slurry on the top of the tower by a spray coating process.

3. The method for preparing a photovoltaic cell according to claim 2, characterized in that: The method of coating the slurry on the top of the tower by spin coating technology satisfies at least one of the following settings: Setting 1): first rotating the substrate, and then dripping the slurry onto the surface of the substrate having the portion to be doped; Setting 2): Make the spin coating speed n in the range of 2000r / min to 5000r / min.

4. The method for preparing a photovoltaic cell according to claim 3, characterized in that: The method of dripping the slurry onto the surface of the substrate having the portion to be doped comprises: The slurry is dripped onto at least two locations spaced apart from each other on the surface of the substrate having the portion to be doped.

5. The method for preparing a photovoltaic cell according to claim 2, characterized in that: The method of printing the slurry on the top of the tower by screen printing technology satisfies at least one of the following settings: Setting a: Make the printing pressure F within the range of 40N to 80N; Setting b: Make the printing speed v within the range of 200 mm / s to 400 mm / s.

6. The method for preparing a photovoltaic cell according to any one of claims 1 to 5, characterized in that: Use a slurry that meets at least one of the following settings: Setting i: using the slurry having a Brookfield viscosity in the range of 20 cps to 50 cps; Setting ii: Use the slurry with a surface tension in the range of 22N to 42N.

7. The method for preparing a photovoltaic cell according to any one of claims 1 to 5, characterized in that: After removing the solidified body and before forming the passivation layer, the method further comprises: masking the pyramid structure; Alternatively, after the annealing treatment of the substrate and the solidified body and before the removing of the solidified body, the method further comprises: depositing an outer mask layer on the solidified body.

8. A photovoltaic cell, characterized in that: The photovoltaic cell sheet comprises a stacked silicon substrate, a diffusion layer and a passivation layer, wherein a side of the diffusion layer facing the passivation layer comprises a plurality of pyramid structures, and the pyramid structures comprise a tower top and a tower bottom; The photovoltaic cell further comprises a metal electrode corresponding to the diffusion layer, and at least a portion of the tower tops of the diffusion layer are in ohmic contact with the metal electrode; An average concentration of doping impurities at the top of the tower in ohmic contact with the metal electrode is greater than an average concentration of doping impurities at the bottom of the tower in the same pyramid structure.

9. A photovoltaic cell, characterized in that: The photovoltaic cell comprises a stacked silicon substrate, a tunneling layer, a doped conductive layer and a passivation layer, wherein a side of the doped conductive layer facing the passivation layer comprises a plurality of pyramid structures, and the pyramid structures comprise a tower top and a tower bottom; The photovoltaic cell further comprises a metal electrode corresponding to the doped conductive layer, and at least a portion of the tower tops of the doped conductive layer are in ohmic contact with the metal electrode; An average concentration of doping impurities at the top of the tower in ohmic contact with the metal electrode is greater than an average concentration of doping impurities at the bottom of the tower in the same pyramid structure.

10. A photovoltaic module, characterized in that: The photovoltaic module comprises a battery string, and the battery string comprises at least two electrically connected photovoltaic cells, and the photovoltaic cell is the photovoltaic cell according to claim 8 or 9.

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