Photovoltaic module, and solar cell and preparation method therefor

Abstract

The present application discloses a photovoltaic module, and a solar cell and a preparation method therefor. The solar cell comprises: a substrate, wherein the substrate has a first surface and a second surface which are oppositely arranged; a first doped region, located in the substrate and extending from the first surface into the substrate; a second doped region, comprising a tunneling layer and a second silicon-containing doped layer which are sequentially stacked on the first surface, wherein one side surface of the tunneling layer is stacked on the first surface of the substrate. The first doped region and the second doped region are alternately arranged, the conductive type of the second doped region and the conductive type of the first doped region are opposite, and a gap is present between the first doped region and the second doped region. The first doped region contains boron as a doping element.

Description

Photovoltaic module, solar cell and method for manufacturing the same TECHNICAL FIELD

[0001] The present application relates to the field of photovoltaics, in particular to a photovoltaic module, a solar cell and a method for manufacturing the same. BACKGROUND

[0002] Improving photoelectric conversion efficiency and reducing production cost is the eternal goal of mass production of solar cells, aiming to reduce the degree of photovoltaic power generation. At present, the tunneling passivation structure is widely used in the field of solar cells, but the doping concentration of the doping element in the tunneling passivation structure needs to be large enough to achieve effective passivation of the substrate and to ensure the efficiency of the cell. Moreover, the preparation of the tunneling passivation layer in the prior art is divided into a tunneling layer and a passivation layer, and subsequent doping preparation, which inevitably brings about a long manufacturing time, and various steps need to be matched with each other, the process window is narrow, the manufacturing difficulty is great, and the yield is difficult to control, especially it cannot match with the new electrode preparation LECO process.

[0003] At the same time, the existing back contact cell usually sets the tunneling passivation structure as a back junction structure, for example, the TBC structure sets a tunneling layer and a p-type doped polysilicon on the tunneling layer as a back emitter on the back surface of an N-type substrate, and sets a tunneling layer and an n-type doped polysilicon on the tunneling layer as a back field layer. Also, for example, a tunneling layer and an n-type doped polysilicon on the tunneling layer are set as a back emitter on the back surface of a P-type substrate, and aluminum is doped as a back field region on the back surface of the P-type substrate. The above-mentioned back contact cells are difficult to effectively utilize the LECO process to improve the efficiency. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a solar cell, which has a lower doping element in the first doped region and also has good cell performance.

[0005] Specifically, the present application relates to the following aspects:

[0006] According to the first aspect, the application provides a solar cell, comprising a substrate having a first surface and a second surface arranged oppositely, a first doped region is located at the first surface, in the first doped region, the doping concentration of non-activated elements is 1E19-1E22, the doping concentration of activated elements is 1E17-8E18, and in the first doped region, the doping concentration of the activated elements first increases and then decreases in the direction from the first surface to the substrate, and the difference between the maximum doping concentration of the activated elements and the doping concentration of the activated elements at the first surface is 1E18-7E18. Compared with the prior art, the cell of the application reduces the doping concentration of activated elements and the doping concentration of non-activated elements while maintaining the electrical performance of the cell in the prior art. The lower the doping concentration, the smaller the recombination of doped elements, and the better the passivation effect of the cell. The higher the open circuit voltage of the corresponding cell. The conventional cell in the prior art requires high doping concentration to match the conventional screen printing to form good metal-semiconductor contact to collect the current generated by the substrate, while the application adopts the LECO process to form good contact (metal-semiconductor contact) between the first electrode and the first doped region on the first doped region with lower doping concentration. Therefore, the solar cell of the application matches the corresponding LECO process, which takes into account both low-complexity low-surface-doping-concentration samples and good contact to increase the open circuit voltage of the cell, while the fill factor remains essentially the same or even slightly improves.

[0007] In some embodiments, a first electrode is arranged on the side surface of the substrate away from the first doped region, and the first electrode partially extends into the first doped region; the contact resistivity between the first electrode and the first doped region is 0.1-3 mΩ / cm 2 . Because the cell uses the LECO process during preparation, the contact resistivity between the first electrode and the first doped region is reduced compared with the prior art, thereby reducing the doping concentration of activated elements and the doping concentration of non-activated elements in the first doped region while maintaining the performance of the cell.

[0008] In some embodiments, the first surface of the first doped region has a first pedestal-like texture structure; the first pedestal-like texture structure includes a plurality of first pedestals; under 20 times magnification, the number of first pedestals whose orthographic projection on the substrate within an area of 650 μm x 650 μm is a quadrilateral is 1-10; and / or the height of the first pedestals is 0-0.3 μm, and does not include 0; and / or the sheet resistance of the first doped region is 200 ohm-500 ohm, the first doped region has the maximum doping concentration of the active element within a depth range of 0.1-0.4 μm from the first surface; the junction depth of the first doped region is 1-1.5 μm; too high first pedestals and too many first pedestals will cause the roughness of the first surface to increase, the surface to be uneven, and affect the quality of the film layer subsequently stacked thereon; too small first pedestals will cause the density of the first pedestals to increase, thereby affecting the quality of the film layer subsequently stacked thereon, and meanwhile, a suitable pedestal size correspondingly reduces the doping concentration of the active element and the doping concentration of the non-active element in the first doped region, thereby more matching the corresponding LECO process.

[0009] The difference between the depth of the maximum doping concentration of the active element from the first surface and the depth of the junction depth from the first surface is 0.9-1.3 μm. The closer the position of the maximum doping concentration of the active element is to the first surface, the closer the non-active element is to the first surface; the higher the doping concentration of the non-active element at the first surface, the easier it is to form a strong recombination region, and it is not easy to remove, thereby causing the battery performance to decrease. In the present application, the position of the maximum doping concentration of the active element can achieve the best passivation effect and contact effect.

[0010] In some embodiments, the first surface corresponding to the first doped region has a first pyramid-shaped texture structure, the height of the first pyramid-shaped texture structure is 0.5-3 μm; during the preparation of the battery, at the height, the influence of the diffusion of the doped element on the first pyramid-shaped texture structure is minimal during the preparation of the first doped region, the first pyramid-shaped texture structure can take into account the reflectivity, and can bring smaller tip regions and smaller high-combination regions of metal contact during the subsequent contact process of preparing the first electrode, and at the same time, the appropriate pyramid size correspondingly reduces the doping concentration of the activated element and the doping concentration of the non-activated element in the first doped region, so as to more match the corresponding LECO process. In the depth range of 0.05-0.3 μm from the first surface, the first doped region has a maximum doping concentration of the activated element; the junction depth of the first doped region is 0.8-1.2 μm; the maximum doping concentration of the activated element plays a major role in the subsequent contact process of forming the first electrode and the first doped region, and in the depth range where the maximum doping concentration of the activated element is located, the first electrode and the first doped region reach the best contact resistivity, which is beneficial to the collection of photo-generated current.

[0011] The difference between the depth of the maximum doping concentration of the activated element from the first surface and the depth of the junction depth from the first surface is 0.5-0.8 μm. The position where the maximum doping concentration of the activated element is located to the first surface and the position where the maximum doping concentration of the activated element is located to the substrate are the two main regions participating in conduction, but the region from the position where the maximum doping concentration of the activated element is located to the first surface has the greatest impact on recombination, therefore, the ratio of the depth from the position where the maximum doping concentration of the activated element is located to the first surface to the entire junction depth is adjusted, so as to minimize the impact of surface recombination while ensuring contact.

[0012] In some embodiments, a first passivation layer and a first electrode are arranged on the side surface of the first doped region away from the substrate, the first passivation layer covers the first doped region, the first electrode includes current collecting electrodes extending along a second direction and arranged at intervals along a first direction, part of the current collecting electrodes contact the first doped region through the first passivation layer along the second direction, and the second direction intersects the first direction.

[0013] In some embodiments, the first electrode further comprises interconnecting portions electrically connected to the current collecting electrode, the interconnecting portions are arranged in the second direction and arranged in the first direction; the interconnecting portions are located on the surface of the first passivation layer facing away from the first doped region, the current collecting electrode comprises a current collecting electrode portion, which is adjacent to the junction of the interconnecting portion and the current collecting electrode in the second direction, and which is located on the surface of the first passivation layer facing away from the first doped region or is located in the first passivation layer, in the second direction, the size of the current collecting electrode portion is less than or equal to one third of the distance between adjacent interconnecting portions. The interconnecting portion can prevent more first electrodes at the intersection from damaging the contact between the first passivation layer and the underlying first doped region, causing more serious metal recombination.

[0014] In some embodiments, the battery further comprises a second doped region located on the first surface, the first doped region and the second doped region are arranged alternately, and the second doped region is opposite in conductivity type to the first doped region; the first surface corresponding to the first doped region has a first tower base-like texture structure; the first surface corresponding to the second doped region has a second tower base-like texture structure; the second tower base-like texture structure comprises a plurality of second tower bases;

[0015] The one-dimensional size of the second tower base is greater than or equal to the one-dimensional size of the first tower base;

[0016] The one-dimensional size of the second tower base is the size of the surface of the side of the second tower base away from the substrate;

[0017] The height of the second tower base is less than or equal to the height of the first tower base.

[0018] The first tower base and the second tower base have different film layers formed on the surfaces, so different requirements are made on the topography of the tower base. For the second doped region, the size of the second tower base needs to be as small as possible to ensure that the tunneling layer prepared on this topography has higher quality, but for the first doped region, the first tower base with certain undulations can increase the area of the first doped region, and the topography of the first tower base will affect the topography of the second tower base. The first tower base is prepared first, and the second tower base corresponding to the second doped region is prepared on the basis of the first tower base.

[0019] In some embodiments, the battery further comprises a second doped region located on the first surface, the first doped region and the second doped region are arranged alternately; the second doped region is opposite in conductivity type to the first doped region; the first surface corresponding to the first doped region has a first pyramid-like texture structure, and the first surface corresponding to the second doped region has a second tower base-like texture structure; the second tower base-like texture structure comprises a plurality of second tower bases;

[0020] The one-dimensional size of the second tower base is smaller than the one-dimensional size of the tower base of the first pyramid-shaped texture structure; the one-dimensional size of the second tower base is the size of the side surface of the second tower base away from the base;

[0021] Under the matching, in the preparation of the first doped region, the influence of the diffusion process of the doped element on the first pyramid-shaped texture structure is minimal, the first pyramid-shaped texture structure can take into account the reflectivity, and in the subsequent contact process of preparing the first electrode, it brings smaller tip area and smaller high recombination area of metal contact, and at the same time, the appropriate pyramid size correspondingly reduces the doping concentration of the active element and the doping concentration of the non-active element in the first doped region, so as to more match the corresponding LECO process, the second doped region adopts the second tower base structure, and the second tower base is too high, which causes the roughness of the first surface corresponding to the second doped region to be large, the surface is uneven, and the quality of the film layer stacked thereon is affected; the second tower base is too small, which will cause the density of the second tower base to increase, thereby affecting the quality of the film layer stacked thereon.

[0022] The height of the second tower base is smaller than the height of the first pyramid-shaped texture structure, which is beneficial to the preparation of the gap region which is easy to passivate.

[0023] In some embodiments, the battery further comprises a second doped region and a first passivation layer, the second doped region is located on the first surface, and the first doped region and the second doped region are arranged alternately; the second doped region is opposite to the first doped region in the conductive type; the first doped region and the second doped region have a gap region; the roughness of the first surface corresponding to the gap region is 0-1 μm; and the first passivation layer covers the gap region. The passivation of the first surface of the gap region is the joint action of field passivation and hydrogen passivation of the first passivation layer (aluminum oxide and silicon nitride), but the roughness is too large, which causes the film quality of the first passivation layer to be poor.

[0024] In some embodiments, the battery further comprises a second doped region and a first passivation layer, the second doped region is located on the first surface, and the first doped region and the second doped region are arranged alternately; the second doped region is opposite to the first doped region in the conductive type; the first doped region and the second doped region have a gap region; and the first passivation layer covers the gap region.

[0025] The first surface corresponding to the first doped region has a first tower base-like texture structure; the height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region is 0.5-6 μm; or the first surface corresponding to the first doped region has a first pyramid-like texture structure; the height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region is 0.5-8 μm. The passivation of the first surface of the gap region is realized by the joint action of field passivation and hydrogen passivation of the first passivation layer (aluminum oxide and silicon nitride), the first surface of the gap region is lower than the first surface of the first doped region, thereby forming a pit in the gap region, which can increase the contact area of the first surface of the gap region with aluminum oxide and hydrogen, passivate the surface dangling bonds, and thereby strengthen the passivation of the first surface. When the pit is too deep, the corresponding aluminum oxide in the region will also be relatively thin, so that the passivation effect of the aluminum oxide will be poor; when the pit is too shallow, the original first doped region in the pit cannot be completely removed clean during the preparation of the battery, and the residue will form high-strength recombination centers with the new diffusion layer during the preparation of the second doped region.

[0026] In some embodiments, the active element and the non-active element of the first doped region are both third main group elements, the battery further comprises a second doped region, the second doped region is located on the first surface, and the first doped region and the second doped region are arranged alternately; the second doped region comprises a tunneling layer and a second silicon-containing doped layer; one side surface of the tunneling layer is laminated to the first surface of the substrate, and the other side surface of the tunneling layer is laminated to the second silicon-containing doped layer; the roughness of the first surface corresponding to the second doped region is less than or equal to 0.5 μm. Low roughness is conducive to growing a more dense tunneling layer, so that the tunneling layer has more excellent chemical passivation and transmission effect.

[0027] In some embodiments, the battery further comprises a second doped region, the second doped region is located on the second surface, the second surface has a third tower base-like texture structure, the second doped region comprises a tunneling layer and a second silicon-containing doped layer which are sequentially laminated in the direction from close to the second surface to away from the second surface, and the conductive type of the first doped region is opposite to that of the second doped region, the first pyramid-like texture structure can not only take into account the reflectivity, but also bring smaller tip region and smaller high recombination area of metal contact in the subsequent contact process of preparing the first electrode, and at the same time, the appropriate pyramid size correspondingly reduces the doping concentration of the active element and the doping concentration of the non-active element in the first doped region, so as to be more matched with the corresponding LECO process, the second surface has a third tower base-like texture structure, the third tower base is too high, which leads to the roughness of the first surface corresponding to the second doped region being large, the surface being uneven, and affecting the quality of the film layer laminated thereon subsequently; the third tower base is too small, which leads to the density of the third tower base being increased, thereby affecting the quality of the film layer laminated thereon subsequently.

[0028] According to a second aspect, the present application also provides a method for manufacturing a solar cell, comprising the following steps:

[0029] providing a substrate; the substrate has a first surface and a second surface arranged oppositely;

[0030] doping elements enter the substrate from the first surface of the substrate, thereby forming a first doped region;

[0031] In the first doped region, the doping concentration of the non-activated elements is 1E19-1E22, the doping concentration of the activated elements is 1E17-8E18, and in the first doped region, in the direction from the first surface to the substrate, the doping concentration of the activated elements first increases and then decreases, and the difference between the maximum doping concentration of the activated elements and the doping concentration of the activated elements at the first surface is 1E18-7E18.

[0032] In some embodiments, after the first doped region is formed, a first electrode is formed on the first doped region, and the first electrode at least partially extends into the first doped region.

[0033] In some embodiments, forming the first electrode comprises the following steps:

[0034] forming a first electrode precursor;

[0035] treating the first electrode precursor and the first doped region by using a LECO process.

[0036] In some embodiments, when the first surface corresponding to the first doped region has a first pyramid-shaped texture structure, the diameter of the spot of the laser used in the LECO process is less than or equal to the distance between the highest points of adjacent tower tips in the first pyramid-shaped texture structure; or

[0037] When the first surface corresponding to the first doped region has a first tower base-shaped texture structure, and the first tower base-shaped texture structure comprises a plurality of first tower bases, the diameter of the spot of the laser used in the LECO process is less than or equal to the distance between the geometric centers of adjacent first tower bases in the polished surface.

[0038] In some embodiments, the solar cell manufactured is the aforementioned solar cell.

[0039] According to a third aspect, the present application also provides a photovoltaic module comprising the aforementioned solar cell, or the solar cell manufactured by the aforementioned manufacturing method.

[0040] According to a fourth aspect, the present application provides a solar cell, comprising: a substrate having a first surface and a second surface oppositely arranged; a first doped region located in the substrate and extending from the first surface into the substrate; and a second doped region comprising a tunneling layer and a second silicon-containing doped layer stacked in sequence on the first surface, one side surface of the tunneling layer being stacked on the first surface of the substrate, wherein the first doped region and the second doped region are alternately arranged, the second doped region is opposite in conductivity type to the first doped region, and a gap region is provided between the first doped region and the second doped region, and wherein the first doped region contains a doping element boron.

[0041] In some embodiments, a first electrode is provided on a side surface of the first doped region away from the substrate, and a partial area of the first electrode extends into the first doped region; the contact resistivity between the first electrode and the first doped region is 0.1-3 mΩ / cm2. 2 .

[0042] In some embodiments, a first passivation layer and a first electrode are provided on a side surface of the first doped region away from the substrate, the first passivation layer covers the first doped region, the first electrode comprises current collecting electrodes extending along a second direction and arranged at intervals along a first direction, a partial area of the current collecting electrodes contacts the first doped region through the first passivation layer, and the second direction intersects the first direction.

[0043] In some embodiments, the first electrode further comprises body electrodes extending along the first direction and arranged at intervals along the second direction.

[0044] In some embodiments, the first electrode further comprises interconnection portions electrically connected to the current collecting electrodes, the body electrodes are connected to the current collecting electrodes through the interconnection portions, the interconnection portions are arranged at intervals along the second direction and arranged at intervals along the first direction; the interconnection portions are located on a surface of the first passivation layer away from the first doped region, the current collecting electrodes comprise current collecting electrode portions adjacent to the junctions of the interconnection portions and the current collecting electrodes along the second direction, and located on the surface of the first passivation layer away from the first doped region or located in the first passivation layer; along the second direction, the size of the current collecting electrode portions is less than or equal to one third of the interval between adjacent interconnection portions.

[0045] In some embodiments, the first passivation layer covers the gap region; the roughness of the first surface corresponding to the gap region is 0-1 μm.

[0046] In some embodiments, the second doped region corresponds to a roughness of the first surface less than or equal to 0.5 μm.

[0047] In some embodiments, the doped elements in the first doped region include non-activated elements and activated elements, the doped concentration of the non-activated elements is 1E19-1E22, the doped concentration of the activated elements is 1E17-8E18, and in the first doped region, the doped concentration of the activated elements increases first and then decreases in the direction from the first surface to the substrate, and the difference between the maximum doped concentration of the activated elements and the doped concentration of the activated elements at the first surface is 1E18-7E18.

[0048] In some embodiments, the first doped region corresponds to a first pyramid-shaped texture structure of the first surface, and the second doped region corresponds to a second tower base-shaped texture structure of the first surface; the second tower base-shaped texture structure includes a plurality of second tower bases; the one-dimensional size of the second tower base is less than the one-dimensional size of the tower bottom of the first pyramid-shaped texture structure, wherein the one-dimensional size of the second tower base is the size of the side surface of the second tower base away from the substrate; and the height of the second tower base is less than the height of the first pyramid-shaped texture structure.

[0049] In some embodiments, the doped concentration of the first surface corresponding to the gap region has a first concentration difference with the doped concentration of the first surface corresponding to the first doped region; and / or the doped concentration within a certain depth range of the first surface corresponding to the gap region has a second concentration difference with the doped concentration within the depth range of the first surface corresponding to the first doped region, wherein the first concentration difference and the second concentration difference are both more than 10 times.

[0050] In some embodiments, the height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region is 0.5-8 μm; and / or the height difference between the first surface corresponding to the gap region and the first surface corresponding to the second doped region is 0.2-4 μm.

[0051] In some embodiments, the substrate is a silicon substrate.

[0052] According to a fifth aspect, the present application further provides a method for preparing a solar cell, comprising:

[0053] A substrate having a first surface and a second surface disposed opposite to each other is provided. A dopant element is introduced into the substrate from the first surface of the substrate to form a bulk doped region. A first patterning is performed to pattern the bulk doped region to form a plurality of first doped regions spaced apart on the first surface of the substrate, while the first surface of the substrate without the first doped regions forms a polished surface. The first doped regions are located within the substrate and extend from the first surface into the substrate. A bulk tunneling layer and a bulk second silicon-containing doped layer are sequentially formed on the first doped regions and the first surface of the substrate without the first doped regions. A second patterning is performed to pattern the tunneling layer and the second silicon-containing doped layer to form a plurality of second doped regions spaced apart as a patterned layered tunneling layer and second silicon-containing doped layer, such that the second doped regions are arranged alternately with the first doped regions and have a gap region between the first doped regions and the second doped regions. The second doped regions have a conductivity type opposite to that of the first doped regions. The first doped regions have a dopant element boron.

[0054] In some embodiments, after the first doped regions are formed, a first electrode is formed on the first doped regions. Forming the first electrode includes forming a first electrode precursor on a side surface of the first doped regions facing away from the substrate, and processing the first electrode precursor and the first doped regions using a LECO process to form the first electrode partially extending into the first doped regions.

[0055] In some embodiments, after the second doped regions are formed, a second electrode is formed on the second doped regions. Forming the second electrode includes forming a second electrode precursor on a side surface of the second doped regions facing away from the substrate, and processing the second electrode precursor and the second doped regions using a LECO process to form the second electrode extending into the second doped regions.

[0056] In some embodiments, the method further includes forming a first passivation layer on a side surface of the first doped regions and the second doped regions facing away from the substrate. Forming the first electrode precursor on the first doped regions includes forming the first electrode precursor on a side surface of the first doped regions corresponding to the side surface of the first passivation layer facing away from the substrate. Forming the second electrode precursor on the second doped regions includes forming the second electrode precursor on a side surface of the second doped regions corresponding to the side surface of the first passivation layer facing away from the substrate. The first electrode extends through the first passivation layer to contact the first doped regions, and the second electrode extends through the first passivation layer to contact the second silicon-containing doped layer.

[0057] In some embodiments, the doping concentration at the first surface corresponding to the gap region has a first concentration difference with the doping concentration at the first surface corresponding to the first doped region; and / or the doping concentration within a certain depth range of the first surface corresponding to the gap region has a second concentration difference with the doping concentration within the depth range of the first surface corresponding to the first doped region, wherein the first concentration difference and the second concentration difference are both more than 10 times; or wherein the height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region is 0.5-8 μm; and / or the height difference between the first surface corresponding to the gap region and the first surface corresponding to the second doped region is 0.2-4 μm.

[0058] In some embodiments, when the first surface corresponding to the first doped region has a first pyramid-shaped texture structure, the diameter of the spot of the laser employed in the LECO process is less than or equal to the distance between the highest points of adjacent peaks in the first pyramid-shaped texture structure; or when the first surface corresponding to the first doped region has a first pedestal-shaped texture structure, the first pedestal-shaped texture structure comprises a plurality of first pedestals, the diameter of the spot of the laser employed in the LECO process is less than or equal to the distance between the geometric centers of adjacent first pedestals in the first pedestal-shaped texture structure.

[0059] In some embodiments, the substrate is a silicon substrate wafer.

[0060] According to a sixth aspect, the present application also provides a photovoltaic module comprising the aforementioned solar cell, or the solar cell prepared by the aforementioned preparation method.

[0061] The technical effects achieved by the corresponding technical features in the solutions provided by the fourth aspect and the fifth aspect of the present application can refer to the technical effects described with respect to the corresponding technical features of the first aspect and the second aspect, which will not be described herein again.

[0062] The solar cell provided by the present application has the first doped region doped with boron and the tunneling layer and the second silicon-containing doped layer stacked in sequence on the back surface of the cell, which can effectively match the LECO process and improve the contact between the first doped region and the first electrode, thereby improving the overall efficiency of the cell. Further, on the basis of taking into account the performance of the cell, the doping concentration of the activated elements and the doping concentration of the non-activated elements in the first doped region are correspondingly reduced, and thus the solar cell of the present application not only has a low surface doping concentration of the first doped region for low recombination, but also can achieve good contact between the first doped region and the first electrode, so that the open-circuit voltage of the cell is increased, the fill factor is basically the same, or even slightly improved. BRIEF DESCRIPTION OF DRAWINGS

[0063] The accompanying drawings are used to help understand the present application and are not intended to limit the present application unduly. Of the drawings:

[0064] Fig. 1 is a structural diagram of a solar cell provided by the present application.

[0065] Fig. 2 is a partial structural diagram of a solar cell provided by the present application.

[0066] Fig. 3 is a partial structural diagram of a solar cell provided by the present application.

[0067] Legend of reference signs 1 - silicon substrate, 2 - first doped region, 3 - first electrode, 4 - second silicon-containing doped layer, 5 - tunneling layer, 6 - second electrode, 7 - passivation layer, 8 - bulk electrode, 9 - collector electrode, 10 - interconnection. DETAILED DESCRIPTION

[0068] The exemplary embodiments of the present application are described below with reference to the accompanying drawings, in which various details of the embodiments of the present application are set forth in order to provide a thorough understanding of the present application. It will be apparent, however, to those skilled in the art that various changes and modifications can be made without departing from the scope and spirit of the present application. Also, the description below is merely illustrative of the principles of the present application, and does not limit the scope of the present application.

[0069] The present application provides a solar cell, which includes a substrate having a first surface and a second surface disposed opposite to each other, and a first doped region 2 formed by diffusing a doping element into the substrate and located at the first surface. In the first doped region 2, a doping concentration of a non-activated element is 1E19 to 1E22, and a doping concentration of an activated element is 1E17 to 8E18. In the first doped region 2, the doping concentration of the activated element increases first and then decreases in a direction from the first surface to the substrate. A difference between a maximum doping concentration of the activated element and a doping concentration of the activated element at the first surface is 1E18 to 7E18. The lower the doping concentration of the activated element and the doping concentration of the non-activated element, the smaller the recombination of the doping element, and the better the passivation effect of the cell. The higher the open circuit voltage of the cell, and the higher doping concentration is required for a conventional cell to match a conventional screen printing to form a good metal semiconductor contact to collect the current generated by the substrate. However, the present application uses a LECO process to form a good contact (metal semiconductor contact) between the first electrode and the first doped region at a lower doping concentration, and thus the solar cell of the present application matches the corresponding LECO process, and can achieve a low recombination of a low surface doping concentration sample and a good contact to increase the open circuit voltage of the cell, and the fill factor is basically the same, or even slightly improved.

[0070] In the present application, the first surface of the substrate is a back light surface, and the second surface is a light surface.

[0071] The first doped region 2 is located within the substrate and is a region proximate to the first surface (including the first surface), i.e. the first doped region 2 is a region extending a certain depth into the substrate from the first surface.

[0072] In some embodiments, in the first doped region 2, the doping concentration of the non-activating element can be 5E19 to 5E21.

[0073] In some embodiments, in the first doped region 2, the doping concentration of the non-activating element can be 5E19 to 1E21.

[0074] In some embodiments, in the first doped region 2, the doping concentration of the activating element is 1E17 to 7E18.

[0075] In some embodiments, in the first doped region 2, the doping concentration of the activating element is 1E17 to 5E18.

[0076] In some embodiments, in the first doped region 2, the doping concentration of the activating element is 1E17 to 3E18.

[0077] In some embodiments, the difference between the maximum doping concentration of the activating element and the doping concentration of the activating element at the first surface is 1E18 to 3E18.

[0078] In some embodiments, the difference between the maximum doping concentration of the activating element and the doping concentration of the activating element at the first surface is 1E18 to 5E18.

[0079] Specifically, in the first doped region 2, the doping concentration of the non-activating element can be 1E19, 2E19, 3E19, 4E19, 5E19, 6E19, 7E19, 8E19, 9E19, 1E20, 2E20, 3E20, 4E20, 5E20, 6E20, 7E20, 8E20, 9E20, 1E21, 2E21, 3E21, 4E21, 5E21, 6E21, 7E21, 8E21, 9E21 or 1E22.

[0080] Specifically, in the first doped region 2, the doping concentration of the activating element is 1E17, 2E17, 3E17, 4E17, 5E17, 6E17, 7E17, 8E17, 9E17, 1E18, 2E18, 3E18, 4E18, 5E18, 6E18, 7E18 or 8E18.

[0081] Specifically, in the first doped region 2, the difference between the maximum doping concentration of the activating element and the doping concentration of the activating element at the first surface can be 1E18, 2E18, 3E18, 4E18, 5E18, 6E18 or 7E18.

[0082] The skilled person can understand that the doping concentration of the non-activated element / the doping concentration of the activated element in the first doped region 2 can refer to the doping concentration of the non-activated element / the doping concentration of the activated element at the surface of the first doped region 2, at any random site in the first doped region 2, or the average of the doping concentration of the non-activated element / the doping concentration of the activated element at multiple sites, or the average of the doping concentration of the non-activated element / the doping concentration of the activated element in the first doped region 2. The skilled person can select any random site for detection based on the detection conditions and the instrument used, or can calculate the average of multiple sites after detecting multiple sites, and use the average as the doping concentration of the non-activated element / the doping concentration of the activated element. In a specific embodiment, the doping concentration of the non-activated element / the doping concentration of the activated element refers to the average value detected in the thickness of the non-activated element / the activated element, for example, the concentration of the non-activated element / the activated element in the first doped region 2 is detected in a thickness direction by the SIMS method, and the average value in the thickness direction is calculated.

[0083] Herein, the doping concentration of the non-activated element in the first doped region refers to the concentration value detected at any random site in the first doped region, and the doping concentration of the non-activated element is 1E19-1E22, which means that any detected concentration is within the range of 1E19-1E22.

[0084] Herein, the doping concentration of the activated element in the first doped region refers to the concentration value detected at any random site in the first doped region, and the doping concentration of the activated element is 1E17-8E18, which means that any detected concentration is within the range of 1E17-8E18.

[0085] In this context, the activated element is generally tested by the ECV differential capacitance voltage method. The doping element of the non-activated element is tested by the ECV differential capacitance voltage method and the SIMS secondary ion mass spectrometry method. The ECV differential capacitance voltage method can measure the concentration of the doping element involved in conduction, which is compared with the doping element composition test by the SEMS secondary ion mass spectrometry test. The SIMS secondary ion mass spectrometry test measures the total concentration of the element as A under the condition that the doping element is phosphorus or boron. The ECV differential capacitance voltage method can test the concentration of the doping element involved in conduction as B (i.e. the doping concentration of the activated element), and the non-activated impurity concentration C is A-B.

[0086] In this paper, the activated element is the activated state of the doped element, and the non-activated element is the non-activated state of the doped element. The doped element itself has two effects, one is to participate in conduction (the role of the activated element), and the other is the role of the complex electron or hole of the doped element itself (the role of the non-activated element). The non-activated element is a complex center, that is, it captures carriers and hinders the movement of carriers. Therefore, the greater the doping concentration of the non-activated doped element, the more carriers are captured, and the greater the decline in battery performance, mainly reflected in the open pressure, that is, as the concentration of the non-activated doped element increases, the open circuit voltage of the battery will continue to decrease. Therefore, while meeting the conductivity, the smaller the doping concentration of the activated element and the non-activated element, the better the battery passivation effect, and the higher the open circuit voltage of the battery.

[0087] As shown in FIG. 2, the first electrode 3 is arranged on the side surface of the first doped region 2 away from the substrate, and part of the first electrode 3 extends into the first doped region 2.

[0088] The contact resistivity of the first electrode 3 and the first doped region 2 is 0.1-5 mΩ / cm 2 In some embodiments, the contact resistivity is 0.1-3 mΩ / cm 2 In some embodiments, the contact resistivity is 0.1-1.5 mΩ / cm 2 .

[0089] Specifically, the contact resistivity of the first electrode 3 and the first doped region 2 can be 0.1 mΩ / cm 2 , 0.2 mΩ / cm 2 , 0.3 mΩ / cm 2 , 0.4 mΩ / cm 2 , 0.5 mΩ / cm 2 , 1 mΩ / cm 2 , 1.1 mΩ / cm 2 , 1.2 mΩ / cm 2 , 1.3 mΩ / cm 2 , 1.4 mΩ / cm 2 , 1.5 mΩ / cm 2 , 1.6 mΩ / cm 2 , 1.7 mΩ / cm 2 , 1.8 mΩ / cm 2 , 1.9 mΩ / cm 2 , 2 mΩ / cm 2 , 2.1 mΩ / cm 2 , 2.2 mΩ / cm 2 , 2.3 mΩ / cm 2 , 2.4 mΩ / cm 2 , 2.5 mΩ / cm 2 , 2.6 mΩ / cm 22.7 mQ / cm 2 2.8 mQ / cm 2 2.9 mQ / cm 2 3 mQ / cm 2 3.1 mQ / cm 2 3.2 mQ / cm 2 3.3 mQ / cm 2 3.4 mQ / cm 2 3.5 mQ / cm 2 3.6 mQ / cm 2 3.7 mQ / cm 2 3.8 mQ / cm 2 3.9 mQ / cm 2 4 mQ / cm 2 4.1 mQ / cm 2 4.2 mQ / cm 2 4.3 mQ / cm 2 4.4 mQ / cm 2 4.5 mQ / cm 2 4.6 mQ / cm 2 4.7 mQ / cm 2 4.8 mQ / cm 2 4.9 mQ / cm 2 5 mQ / cm 2 .

[0090] In this context, the contact resistivity of the first electrode 3 with the first doped region 2 is tested using the TLM test method, whose test principle is based on the TLM (Transfer Length Method) technology, which is to prepare a series of electrodes of different lengths on the material, and then measure the resistance between the electrodes to infer the conductive performance of the material. The working principle of the TLM tester is to use the fact that the current will be affected by the resistance during transmission between the electrodes. By measuring the resistance value, the conductive performance of the material can be obtained. When the current is transmitted between the electrodes, it will be affected by the contact resistance of the electrodes and the bulk resistance of the material itself, and the TLM tester can separate the effects of these two parts by measuring the resistance value between the electrodes.

[0091] Since the battery uses the LECO technology in the preparation process, the contact resistivity of the first electrode 3 with the first doped region 2 is reduced compared with the prior art, thereby reducing the doping concentration of the active elements and the doping concentration of the non-active elements in the first doped region 2 while the performance of the battery remains unchanged.

[0092] In the present application, the ratio of the contact area of the first electrode 3 with the first doped region 2 to the area of the normal projection of the first doped region 2 on the substrate is (0.5-2):1, which can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, etc.

[0093] This can ensure the contact of the first electrode 3 with the first doped region 2, i.e., reduce the above contact resistivity, so that the battery has a good metal-semiconductor contact and is conducive to current collection.

[0094] The area of the normal projection of the first doped region 2 on the substrate can be calculated by testing the one-dimensional size of the first doped region 2 under a microscope, and the one-dimensional size can be length and width.

[0095] The contact area of the first electrode 3 with the first doped region 2 is the sum of the effective contact area and the ineffective contact area, which can be calculated by removing the first electrode through acid etching, and then scanning by 3D to calculate the contact area (i.e., the total area) of the first electrode 3 with the first doped region 2. The surface area of the irregular region after removing the first electrode is the ineffective contact area, and the total area minus the ineffective contact area is the effective contact area.

[0096] The ratio of the effective contact area of the first electrode 3 with the first doped region 2 to the contact area of the first electrode 3 with the first doped region 2 is (0.5-0.9):1, which can be 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, etc. The larger the effective contact area, i.e., the smaller the ineffective contact area, the less the metal recombination, thereby improving the passivation effect of the battery to improve the open-circuit voltage.

[0097] In some embodiments of the present application, the first surface corresponding to the first doped region 2 is a polished surface, and the polished surface has a first tower base-like texture structure; the first tower base-like texture structure includes a plurality of first tower bases.

[0098] The shape of the first tower base can be a circular truncated cone or a prismatic truncated cone, and the normal projection of the first tower base on the first surface has a circular shape, a triangular shape, a quadrilateral shape, a pentagonal shape, a hexagonal shape, and an n-gon shape.

[0099] When the first tower base is a circular truncated cone, the diameter of the side surface of the first tower base close to the first surface is 0.5-1.5 μm, and the diameter of the side surface away from the first surface is 1-5 μm, and the diameter of the tower base can be measured by 3D scanning.

[0100] The number of the first tower bases in the form of quadrilateral in the area of 650 μm x 650 μm under 20 times microscope is 1-10. In the process of preparing the battery, the polishing process of the first surface corresponding to the first doped region 2 is non-specular polishing. The different etching rates of silicon in alkaline solution in different crystal directions form the tower base texture structure. The size of the tower base can be controlled by controlling the concentration, temperature, etching time and different additives of the alkaline solution, reducing the activity of the alkaline solution and the size and speed of the bubbles to control the size of the tower base.

[0101] The height of the first tower base is 0-0.3 μm, and 0 is not included, for example, it can be 0.3 μm, 0.29 μm, 0.28 μm, 0.27 μm, 0.26 μm, 0.25 μm, 0.24 μm, 0.23 μm, 0.22 μm, 0.21 μm, 0.2 μm, 0.19 μm, 0.18 μm, 0.17 μm, 0.16 μm, 0.15 μm, 0.14 μm, 0.13 μm, 0.12 μm, 0.11 μm, 0.1 μm, 0.09 μm, 0.08 μm, 0.07 μm, 0.06 μm, 0.05 μm, 0.04 μm, 0.03 μm, 0.02 μm, 0.01 μm, etc.

[0102] The first tower base is too high and the number of the first tower base is too much, which will cause the roughness of the first surface to be large, the surface to be uneven, and the quality of the film layer stacked on the top of the first surface to be affected. If the first tower base is too small, the density of the first tower base will increase, which will affect the quality of the film layer stacked on the top of the first tower base. At the same time, the appropriate size of the first tower base reduces the doping concentration of the activated elements and the doping concentration of the non-activated elements in the first doped region, so as to match the corresponding LECO process.

[0103] The sheet resistance of the first doped region 2 is 200 ohm-500 ohm, for example, it can be 200 ohm, 250 ohm, 300 ohm, 350 ohm, 400 ohm, 450 ohm, 500 ohm, etc.

[0104] The sheet resistance is also called film resistance, which is a measurement value for indirectly representing the thermal infrared performance of vacuum coating on the sample of film layer, glass coated film layer, etc. The value can be directly converted into thermal infrared emissivity. The size of the sheet resistance is independent of the size of the sample, and its unit is Siements / sq, which is increased by ohm / sq representation. The unit is directly translated into sheet resistance or surface resistance, which is also called film layer resistance for film layer measurement.

[0105] The first doped region 2 has a maximum doping concentration of the active element in a depth range of 0.1-0.4 μm from the first surface; that is, the position of the maximum doping concentration of the active element in the first doped region 2 is 0.1-0.4 μm, for example, 0.1 μm, 0.12 μm, 0.15 μm, 0.17 μm, 0.2 μm, 0.22 μm, 0.25 μm, 0.27 μm, 0.3 μm, 0.32 μm, 0.35 μm, 0.37 μm, 0.4 μm, etc., away from the first surface.

[0106] The closer the position of the maximum doping concentration of the active element is to the first surface, the closer the non-active element is to the first surface; the higher the doping concentration of the non-active element on the first surface, the easier it is to form a strong recombination region, and it is not easy to remove, thereby causing the battery performance to decline. In the present application, the position of the maximum doping concentration of the active element can achieve the best passivation effect and contact effect.

[0107] The junction depth of the first doped region 2 is 1-1.5 μm, for example, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, etc.

[0108] The difference between the depth of the position of the maximum doping concentration from the first surface and the depth of the junction depth from the first surface is 0.9-1.3 μm, for example, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, etc.

[0109] The doping concentration of the active element on the first surface corresponding to the first doped region 2 is 1E18-7E18, for example, 1E18, 2E18, 3E18, 4E18, 5E18, 6E18, or 7E18, etc.

[0110] In some embodiments of the present application, as shown in FIG. 1, the first surface corresponding to the first doped region 2 has a textured structure, which has a first pyramidal texture structure with a height of 0.5-3 μm, for example, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, etc. During the preparation of the cell, the height of the first pyramidal texture structure is 0.5-3 μm, at which height the influence of the diffusion process of the doping element on the first pyramidal texture structure is minimal during the preparation of the first doped region, and the first pyramidal texture structure can both take into account the reflectivity and bring about smaller tip regions and smaller high-combination regions of metal contact during the subsequent contact process of preparing the first electrode.

[0111] The first doped region 2 has a maximum doping concentration of the active element within a depth range of 0.05-0.3 μm from the first surface, i.e., the position of the maximum doping concentration of the active element within the first doped region 2 is 0.05-0.3 μm from the first surface, for example, 0.05 μm, 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, 0.2 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm, 0.3 μm, etc.

[0112] The maximum doping concentration of the active element plays a major role in the subsequent formation of the first electrode and the contact process of the first doped region, and within the depth range of the maximum doping concentration of the active element, the first electrode and the first doped region achieve the best contact resistivity, which is beneficial to the collection of photo-generated current, and the position of the maximum doping concentration within the first doped region 2 is 0.05-0.3 μm from the first surface, within which depth range the transmission gain of the active element is maximum and the near-surface recombination loss caused by the non-active element is minimum.

[0113] The junction depth of the first doped region 2 is 0.8-1.2 μm, for example, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, etc.

[0114] The depth of the position where the maximum doping concentration of the activation element is located from the first surface and the depth of the junction from the first surface are 0.5-0.8 μm, for example, 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.75 μm, 0.8 μm, etc.

[0115] The position where the maximum doping concentration of the activation element is located from the first surface and the position where the maximum doping concentration of the activation element is located from the substrate are the two main regions participating in conduction, but the region where the position where the maximum doping concentration of the activation element is located from the first surface has the greatest impact on recombination, so the proportion of the depth of the position where the maximum doping concentration of the activation element is located from the first surface and the entire junction depth is adjusted, so that the impact of surface recombination can be minimized while ensuring contact.

[0116] The doping concentration of the activation element on the first surface corresponding to the first doped region 2 is 1E18-7E18, for example, 1E18, 2E18, 3E18, 4E18, 5E18, 6E18, or 7E18, etc.

[0117] In the present application, as shown in FIG. 3, a first passivation layer and a first electrode 3 are arranged on the side surface of the first doped region 2 away from the substrate, the first passivation layer covers the first doped region 2, and the first electrode 3 includes collector electrodes 9 extending along the second direction and arranged at intervals along the first direction, part of the collector electrodes 9 along the second direction passes through the first passivation layer and contacts the first doped region 2, the second direction intersects the first direction, and the second direction and the first direction define a plane perpendicular to the thickness direction of the substrate, and in some embodiments, the first direction is perpendicular to the second direction. Such a design can block too much metal in the first electrode from entering the substrate, spreading downward or to both sides, and causing greater metal recombination loss.

[0118] The first electrode 3 further includes interconnection portions 10, the interconnection portions 10 are electrically connected with the collector electrodes 9, and the interconnection portions 10 are arranged at intervals along the second direction and arranged at intervals along the first direction; the interconnection portions 10 are located on the surface of the first passivation layer away from the first doped region 2, and the collector electrodes 9 include collector electrode portions which are immediately adjacent to the junction of the collector electrodes 9 and the interconnection portions 10 along the second direction, which are located on the surface of the first passivation layer away from the first doped region 2, or are located in the first passivation layer; along the second direction, the size of the collector electrode portion is less than or equal to one third of the interval between adjacent interconnection portions 10. The interconnection portion can prevent too much first electrode at the intersection from damaging the contact between the first passivation layer and the underlying first doped region, causing more serious metal recombination.

[0119] The first electrode 3 further comprises body electrodes 8 extending along the first direction and arranged at intervals along the second direction, and the body electrodes 8 are connected to the current collecting electrodes 9 through interconnections 10. The size of the interconnections can be greater than or equal to the size of the current collecting electrodes. In the case where the size of the interconnections 10 is equal to the size of the current collecting electrodes 9, a non-welding process can be used to realize the interconnection of the back contact battery, such as a film coating process, in which a carrier film with conductive interconnections is directly attached to the surface of the back contact battery and is pressed to form electrical interconnections. For example, the interconnections 10 can be bus electrodes, or interconnections arranged on the bus electrodes.

[0120] In this document, the size of the interconnections can be the length, width or diameter thereof. The size of the current collecting electrodes can be the length, width or diameter thereof. For example, the width of the interconnections can be greater than the width of the current collecting electrodes. For example, the length of the interconnections can be equal to the length of the current collecting electrodes.

[0121] In this application, the active element and the inactive element are both Group IIIA elements or Group VA elements.

[0122] The active element and the inactive element are the same doping element.

[0123] In some embodiments, the active element and the inactive element are both boron elements.

[0124] In some embodiments of the application, the battery further comprises a second doped region on the first surface, the first doped regions 2 and the second doped regions are arranged alternately, and the second doped regions are opposite in conductivity type to the first doped regions 2; the first surface corresponding to the first doped regions 2 has a first tower base-like texture structure; the first surface corresponding to the second doped regions has a second tower base-like texture structure; and the second tower base-like texture structure comprises a plurality of second tower bases.

[0125] In the process of preparing the battery, the polishing process of the first surface corresponding to the second doped regions is non-specular polishing, and different etching rates of silicon in alkaline solution in different crystal directions form a tower base-like texture structure. The concentration, temperature, etching time and different additives of the alkaline solution can be controlled to reduce the activity of the alkaline solution and the size and speed of the gas bubbles generated to control the size of the tower base.

[0126] The number and size of the second tower bases per unit area can be determined according to actual needs. Too many second tower bases per unit area will result in a larger roughness of the first surface, uneven surface and affect the quality of the subsequent film layers stacked thereon. Too few second tower bases will result in an increased density of the second tower bases, which will affect the quality of the subsequent film layers stacked thereon.

[0127] The one-dimensional size of the second tower base is greater than or equal to the one-dimensional size of the first tower base.

[0128] The one-dimensional size of the second tower base is the size of the side surface of the second tower base away from the base;

[0129] Under the matching, in the preparation of the first doped region, the influence of the diffusion process of the doped element on the first tower base-like texture structure is minimal, the first tower base-like texture structure can take into account the reflectivity, and can bring smaller tip regions and smaller high-combination regions of metal contacts in the subsequent contact process of preparing the first electrode, and at the same time, the appropriate pyramid size correspondingly reduces the doping concentration of the activated element and the doping concentration of the non-activated element in the first doped region, so as to more match the corresponding LECO process, the second doped region adopts the second tower base structure, and the second tower base is too high, which causes the roughness of the first surface corresponding to the second doped region to be large, the surface is uneven, and the quality of the film layer stacked thereon is affected; the second tower base is too small, which will cause the density of the second tower base to increase, thereby affecting the quality of the film layer stacked thereon. In this article, the one-dimensional size can be determined according to the orthographic projection shape of the second tower base on the base. For example, when the orthographic projection of the second tower base on the base is circular, the one-dimensional size refers to the diameter of the circle; when the orthographic projection of the second tower base on the base is rectangular, the one-dimensional size can be the diagonal length or length of the rectangle.

[0130] The height of the second tower base is less than or equal to the height of the first tower base.

[0131] The film layers formed by the surfaces of the first tower base and the second tower base are different, so the topography of the tower base has different requirements. For the second doped region, the size of the second tower base needs to be as small as possible to ensure that the tunneling layer prepared on the topography has higher quality, but for the first doped region, the first tower base with a certain fluctuation can increase the area of the first doped region, and the topography of the first tower base will affect the topography of the second tower base. The first tower base is prepared first, and the second tower base corresponding to the second doped region is prepared on the basis of the first tower base.

[0132] The first tower base needs to consider reducing the current loss caused by reflection to the greatest extent, and the second tower base needs to consider the recombination loss in the transmission process to the greatest extent, because the etching process is not very uniform, and thus in actual effect, the height of the second tower base is less than or equal to the height of the first tower base, at this time, the number of tower bases is reduced, and the recombination loss in the transmission process is minimized.

[0133] In some embodiments of the present application, the battery further comprises a second doped region located on the first surface, the first doped regions 2 and the second doped regions are arranged alternately; the second doped regions are opposite in conductive type to the first doped regions 2; the first surface corresponding to the first doped regions 2 has a first pyramid-shaped texture structure, and the first surface corresponding to the second doped regions has a second tower base-shaped texture structure; the second tower base-shaped texture structure comprises a plurality of second tower bases. The first pyramid-shaped texture structure is conducive to light trapping and improves the overall bifaciality of the battery. At the same time, the first pyramid-shaped texture structure is conducive to contact with the first electrode 3, and when the LECO process is used, the surface of the first electrode 3 is in better contact with the first doped regions 2.

[0134] In the process of preparing the battery, the polishing process of the first surface corresponding to the second doped regions is non-specular polishing, and different etching rates of silicon in alkaline solution in different crystal directions form a tower base-shaped texture structure. The concentration, temperature, etching time and different additives of the alkaline solution can be controlled to reduce the activity of the alkaline solution and the size and speed of the bubbles generated to control the size of the tower base.

[0135] The number and size of the second tower bases per unit area can be determined according to actual needs. Too many second tower bases per unit area will cause the roughness of the first surface to increase, the surface to be uneven, and the quality of the film layers subsequently stacked thereon to be affected. Too few second tower bases will cause the density of the second tower bases to increase, thereby affecting the quality of the film layers subsequently stacked thereon.

[0136] The one-dimensional size of the second tower base is smaller than the one-dimensional size of the tower base of the first pyramid-shaped texture structure; the one-dimensional size of the second tower base is the size of the surface of the second tower base away from the substrate;

[0137] The one-dimensional size of the tower base of the first pyramid-shaped texture structure is the one-dimensional size of the figure of the orthogonal projection of the tower base of the first pyramid-shaped texture structure on the substrate.

[0138] The height of the second tower base is smaller than the height of the first pyramid-shaped texture structure, which is conducive to the preparation of an easily passivated gap region.

[0139] In the present application, the battery further comprises a second doped region and a first passivation layer, the second doped region is located on the first surface, and the first doped region 2 and the second doped region are arranged alternately; the second doped region is opposite to the first doped region 2 in the conduction type; there is a gap region between the first doped region 2 and the second doped region; the roughness of the first surface corresponding to the gap region is 0-1 μm, for example, it can be 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm; the first passivation layer covers the gap region. The passivation of the first surface of the gap region is the joint action of field passivation and hydrogen passivation of the first passivation layer (aluminum oxide and silicon nitride), but the roughness is too large to cause the first passivation layer to have poor film quality.

[0140] The width of the gap region is 10 μm-60 μm, for example, it can be 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, etc.

[0141] In some embodiments, the first surface corresponding to the first doped region 2 has a first mesa-like texture structure; the height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region 2 is 0.5-6 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, etc. In addition, the first surface of the substrate corresponding to the second doped region and the first surface corresponding to the gap region can also have a height difference, and the first surface corresponding to the gap region is lower than the first surface of the substrate corresponding to the second doped region, i.e. in the thickness direction of the substrate, the first surface corresponding to the gap region is closer to the second surface of the substrate than the first surface of the substrate corresponding to the second doped region. The height difference between the first surface of the substrate corresponding to the second doped region and the first surface corresponding to the gap region can enhance the effective isolation between the first doped region 2 and the second doped region, and reduce the recombination of photo-generated carriers in the gap region. The height difference between the first surface of the substrate corresponding to the second doped region and the first surface corresponding to the gap region is 0.2-4 μm, for example, it can be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.5 μm, 4 μm.

[0142] In some embodiments, the first surface corresponding to the first doped region 2 has a first pyramidal texture structure; the height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region 2 is 0.5-8 μm, for example, it can be 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 6 μm, 7 μm, 7.5 μm, 8 μm, etc. In addition, the height difference can also exist between the first surface of the substrate corresponding to the second doped region and the first surface corresponding to the gap region, and the first surface corresponding to the gap region is lower than the first surface of the substrate corresponding to the second doped region, i.e. in the thickness direction of the substrate, the first surface corresponding to the gap region is closer to the second surface of the substrate than the first surface of the substrate corresponding to the second doped region. The height difference between the first surface of the substrate corresponding to the second doped region and the first surface corresponding to the gap region can enhance the effective isolation between the first doped region 2 and the second doped region, and reduce the recombination of photo-generated carriers in the gap region. The height difference between the first surface of the substrate corresponding to the second doped region and the first surface corresponding to the gap region is 0.2-4 μm, for example, it can be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, 3.5 μm, 4 μm.

[0143] In some embodiments, the first doped region 2 has either a first pyramidal texture structure or a first tower base texture structure. The impurity doping concentration at the first surface corresponding to the gap region, or within a certain depth range of the first surface corresponding to the gap region, is lower than the doping concentration at the first surface corresponding to the first doped region, or within a certain depth range of the first surface corresponding to the first doped region. This doping concentration difference further enhances the isolation between the first doped region and the second doped region, while reducing the carrier recombination and parasitic absorption of light in the gap region. For example, the surface doping concentration of the first surface corresponding to the gap region is lower than the surface doping concentration of the first surface corresponding to the first doped region, preferably with a concentration difference of more than 10 times; the average doping concentration within a 20 nm depth range of the first surface corresponding to the gap region is lower than the average doping concentration within a 20 nm depth range of the first surface corresponding to the first doped region 2, preferably with a concentration difference of more than 10 times; the average doping concentration within a 50 nm depth range of the first surface corresponding to the gap region is lower than the average doping concentration within a 50 nm depth range of the first surface corresponding to the first doped region 2, preferably with a concentration difference of more than 10 times; the maximum doping concentration within a 20 nm depth range of the first surface corresponding to the gap region is lower than the maximum doping concentration within a 20 nm depth range of the first surface corresponding to the first doped region 2, preferably with a concentration difference of more than 10 times; the maximum doping concentration within a 50 nm depth range of the first surface corresponding to the gap region is lower than the maximum doping concentration within a 50 nm depth range of the first surface corresponding to the first doped region 2, preferably with a concentration difference of more than 10 times.

[0144] In some embodiments, the first surface corresponding to the first doped region 2 has either a first pyramidal texture or a first tower base texture. The impurity doping concentration at the first surface corresponding to the gap region, or within a certain depth range of the first surface corresponding to the gap region, is lower than the doping concentration at the first surface corresponding to the second doped region, or within a certain depth range of the first surface corresponding to the second doped region. This doping concentration difference further enhances the isolation between the first doped region and the second doped region, while reducing the carrier recombination and parasitic absorption of light in the gap region. For example, the surface doping concentration of the first surface corresponding to the gap region is lower than the surface doping concentration of the first surface corresponding to the second doped region, preferably with a concentration difference of more than 10 times; the average doping concentration within a 20 nm depth range of the first surface corresponding to the gap region is lower than the average doping concentration within a 20 nm depth range of the first surface corresponding to the second doped region, preferably with a concentration difference of more than 10 times; the average doping concentration within a 50 nm depth range of the first surface corresponding to the gap region is lower than the average doping concentration within a 50 nm depth range of the first surface corresponding to the second doped region, preferably with a concentration difference of more than 10 times; the maximum doping concentration within a 20 nm depth range of the first surface corresponding to the gap region is lower than the maximum doping concentration within a 20 nm depth range of the first surface corresponding to the second doped region 2, preferably with a concentration difference of more than 10 times; the maximum doping concentration within a 50 nm depth range of the first surface corresponding to the gap region is lower than the maximum doping concentration within a 50 nm depth range of the first surface corresponding to the second doped region, preferably with a concentration difference of more than 10 times.

[0145] The passivation of the first surface of the gap region is achieved through the combined action of field passivation and hydrogen passivation of the first passivation layer (aluminum oxide and silicon nitride). The first surface of the gap region is lower than the first surface of the first doped region 2, forming a recess in the gap region, which can increase the contact area of the first surface of the gap region with aluminum oxide and hydrogen, passivate the surface dangling bonds, and thus enhance the passivation of the first surface. When the recess is too deep, the corresponding aluminum oxide in this region will also be relatively thin, so its aluminum oxide passivation effect will be poor; when the recess is too shallow, the original first doped region in the recess cannot be completely removed during the preparation of the battery, and the residue will form high-strength recombination centers with the new diffusion layer during the preparation of the second doped region.

[0146] In this application, the second doped region includes a tunneling layer 5 and a second silicon-containing doped layer; one side surface of the tunneling layer 5 is laminated to the first surface of the substrate, and the other side surface is laminated to one side surface of the second silicon-containing doped layer.

[0147] The second silicon-containing doped layer can be one of an n-type doped polysilicon layer, an n-type doped amorphous silicon layer, an n-type doped microcrystalline silicon layer, and an n-type doped silicon carbide layer, including but not limited to these.

[0148] The thickness of the second silicon-containing doped layer is 50 nm-400 nm, for example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, or the like.

[0149] The roughness of the first surface corresponding to the second doped region is less than or equal to 0.5 μm, that is, the roughness of the silicon substrate 1 at the joint with the tunneling layer 5 is less than or equal to 0.5 μm, for example, it can be 0.5 μm, 0.49 μm, 0.48 μm, 0.47 μm, 0.46 μm, 0.45 μm, 0.44 μm, 0.43 μm, 0.42 μm, 0.41 μm, 0.40 μm, 0.39 μm, or the like. In some embodiments, the roughness of the first surface corresponding to the second doped region is less than or equal to 0.45 μm; the roughness of the first surface corresponding to the second doped region is less than or equal to 0.4 μm. A low roughness is conducive to growing a more dense tunneling layer thereon, so that the tunneling layer has more excellent chemical passivation and transport effects.

[0150] In this context, the roughness refers to the difference between the highest point and the lowest point. The roughness can be measured by 3D scanning.

[0151] Specifically, the solar cell is a BC cell, and the second doped region is arranged on the first surface of the substrate alternately with the first doped region 2. The second doped region includes the tunneling layer 5 and the second silicon-containing doped layer 4 stacked in sequence on the first surface, the tunneling layer 5 is stacked with the substrate, and the second electrode 6 is arranged on the second silicon-containing doped layer 4; the second silicon-containing doped layer 4 is opposite in conductivity type to the first doped region 2, the doping element in the first doped region 2 is boron, and the doping element in the second silicon-containing doped layer 4 is phosphorus. The substrate is a silicon substrate 1.

[0152] The second passivation layer is stacked on the second surface of the silicon substrate 1, the first passivation layer covering the second silicon-containing doped layer 4 and the first doped region 2 is stacked on the side surface of the second silicon-containing doped layer 4 away from the silicon substrate 1, and the first electrode 3 penetrates through the second passivation layer and extends into the first doped region 2, and the second electrode 6 penetrates through the second passivation layer and contacts the second silicon-containing doped layer 4.

[0153] The first doped region 2 and the second doped region have a gap region therebetween, and the width of the gap region is 10 μm-60 μm.

[0154] The roughness of the first surface of the silicon substrate 1 in the gap region is 0-1 μm, for example, 0, 0.2 μm, 0.4 μm, 0.6 μm, 0.8 μm, 1 μm, etc.

[0155] The roughness of the first surface of the silicon substrate 1 in which the tunneling layer 5 is laminated is 0-0.5 μm, for example, 0 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, etc.

[0156] The silicon substrate 1 can be an n-type silicon substrate 1 or a p-type silicon substrate 1.

[0157] In some embodiments, the light-receiving surface of the silicon substrate 1 has a textured structure, and the back surface is a polished surface.

[0158] In some embodiments, both the light-receiving surface and the back surface of the silicon substrate 1 have a textured structure.

[0159] In some embodiments, part of the back surface of the silicon substrate 1 has a textured structure, and part of the back surface is a polished surface.

[0160] The thickness of the first doped region 2 is 400 nm-3 μm, for example, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, 900 nm, 950 nm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, etc.

[0161] The second silicon-containing doped layer 4 can be one of an n-type doped polysilicon layer, an n-type doped amorphous silicon layer, an n-type doped microcrystalline silicon layer, and an n-type doped silicon carbide layer, including but not limited to the above.

[0162] The thickness of the second silicon-containing doped layer 4 is 50 nm-400 nm.

[0163] The tunneling layer 5 is a silicon oxide layer, and the thickness thereof is 1-2 nm.

[0164] The first passivation layer includes a silicon nitride layer (SiNx, x can be any value) and an aluminum oxide layer (AlOx, x is any value) laminated in sequence, wherein the side surface of the silicon nitride layer away from the aluminum oxide layer is laminated together with the silicon substrate 1.

[0165] The thickness of the silicon nitride layer is 50 nm-130 nm, and the thickness of the aluminum oxide layer is 2 nm-15 nm.

[0166] The second passivation layer comprises a silicon nitride layer (SiNx, x can be any value) and an aluminum oxide layer (AlOx, x is any value) stacked in sequence, wherein the side surface of the silicon nitride layer away from the aluminum oxide layer is stacked together with the first doped region 2 and the second silicon-containing doped layer 4.

[0167] The thickness of the silicon nitride layer is 50-130 nm, and the thickness of the aluminum oxide layer is 2-15 nm.

[0168] The first electrode 3 and the second electrode 6 can each be silver, copper, aluminum, or an alloy thereof. The first electrode 3 and the second electrode 6 can be the same or different.

[0169] In the present application, the battery further comprises a second doped region located on the second surface, the second doped region comprises a tunneling layer 5 and a second silicon-containing doped layer 4 stacked in sequence from the direction close to the second surface to the direction away from the second surface, and the conductive type of the first doped region 2 is opposite to that of the second doped region.

[0170] Specifically, when the solar cell is a TOPcon cell, the second surface of the substrate has a tunneling layer 5, a second silicon-containing doped layer 4, and a second electrode 6 stacked in sequence from the direction close to the second surface to the direction away from the second surface, the second surface has a third base-of-pyramid texture structure, and the doping type of the first doped region 2 is opposite to that of the second silicon-containing doped layer 4. The first surface of the substrate has the first doped region 2, the first electrode 3 is arranged on the first doped region 2, the first passivation layer is stacked on the side surface of the first doped region 2 away from the substrate, the second passivation layer is stacked on the side surface of the second silicon-containing doped layer 4 away from the substrate, the first electrode 3 penetrates through the first passivation layer and is connected with the first doped region 2, and the second electrode 6 penetrates through the second passivation layer and is connected with the second silicon-containing doped layer 4.

[0171] The first pyramid texture structure not only takes into account the reflectivity, but also brings smaller tip regions and smaller high-combination regions of metal contact in the subsequent contact process of preparing the first electrode, and the appropriate pyramid size correspondingly reduces the doping concentration of the activated elements and the doping concentration of the non-activated elements in the first doped region, so as to more match the corresponding LECO process. The second surface has a third base-of-pyramid texture structure, and the third base-of-pyramid is too high, which causes the roughness of the first surface corresponding to the second doped region to be large, the surface is uneven, and the quality of the film layer stacked thereon subsequently is affected. The third base-of-pyramid is too small, which causes the density of the third base-of-pyramid to increase, thereby affecting the quality of the film layer stacked thereon subsequently.

[0172] The descriptions of the substrate, the second silicon-containing doped layer 4, the first passivation layer and the second passivation layer, the first electrode 3, and the second electrode 6 can refer to the descriptions in the foregoing BC cell.

[0173] The application provides a preparation method of a solar cell, comprising the following steps:

[0174] providing a substrate; the substrate has oppositely arranged first and second surfaces;

[0175] doping elements enter the substrate from the first surface of the substrate, thereby forming a first doped region 2;

[0176] In the first doped region 2, the doping concentration of the non-activated elements is 1E19-1E22, and the doping concentration of the activated elements is 1E17-8E18; and in the first doped region 2, in the direction from the first surface to the inside of the substrate, the doping concentration of the activated elements first increases and then decreases, and the difference between the maximum doping concentration of the activated elements and the doping concentration of the activated elements at the first surface is 1E18-7E18.

[0177] After the first doped region 2 is formed, a first electrode 3 is formed on the first doped region 2, and the first electrode 3 at least partially extends into the first doped region 2.

[0178] In the step of forming the first electrode 3, a first electrode precursor is first formed, and then a LECO process is used to treat the first electrode precursor and the first doped region 2.

[0179] LECO (Laser-enhanced contact optimization) is also known as laser-enhanced contact optimization, which is an advanced laser sintering technology. The technology can locally destroy the passivation layer in a very precise manner and promote the electron transmission between the metal electrode and the silicon. The LECO process locally applies high-intensity laser pulses on the front or back surface of the solar cell and maintains a constant reverse voltage. The local current generated thereby can significantly reduce the contact resistivity between the semiconductor and the metal electrode.

[0180] When the first surface corresponding to the first doped region 2 has a first pyramid-shaped texture structure, the diameter of the laser spot used in the LECO process is less than or equal to the distance between the highest points of two adjacent towers in the first pyramid-shaped texture structure.

[0181] When the first surface corresponding to the first doped region 2 has a first tower base-shaped texture structure, the diameter of the laser spot used in the LECO process is less than or equal to the distance between the geometric centers of two adjacent first tower bases in the first tower base-shaped texture structure.

[0182] Specifically, when the solar cell is a BC cell, the preparation method of the solar cell comprises the following steps:

[0183] Step 1: providing a silicon substrate 1; the silicon substrate 1 has oppositely arranged first and second surfaces;

[0184] Step two: polish or texturize the first surface (backlight surface) of the silicon substrate 1, and diffuse the doping elements to form the first doped region 2.

[0185] Step three: first patterning, forming the patterned first doped region 2.

[0186] The first patterning is performed by a conventional method, which is not specifically limited, for example, laser grooving or mask method.

[0187] When laser grooving is used for patterning, the unit energy density of the laser can be adjusted, the power, frequency, speed and type of the laser light source are adjusted, the energy density is adjusted to 0.3 J / m3-2 J / m 3 The reflectivity of the laser wavelength on the battery structure is adjusted, the reflectivity on the textured surface is 1%-5%, and the reflectivity on the polished surface is 5%-25%, at this time the best film removal effect and low damage effect are achieved, and the judgment standard is PL test, the PL measurement after laser is reduced by 1%-5%.

[0188] When the mask method is used, the mask is an oxide with a thickness of 5 nm-100 nm, the main component of the oxide is silicon oxide, and the proportion of boron in the oxide is 0-20%, or other masking films are used, such as commonly used wax printing or gum printing, etc. The main advantage of this composition of the masking film is that it can be completely removed in low-concentration HF (1%-5%) in 120S or in low-concentration NaOH or KOH (2%-10%) in 240S, and no additives are used, and no other impurities are introduced.

[0189] After the first patterning is completed, the first doped region 2 is arranged on the first surface of the silicon substrate 1, and the exposed silicon substrate forms a polished surface.

[0190] Step four: form an integral tunneling layer 5 and a second silicon-containing doped layer 4 on the surface of the first doped region 2 away from the silicon substrate 1 and the exposed silicon substrate 1.

[0191] The preparation process of the tunneling layer 5 and the second silicon-containing doped layer 4 is a conventional way, which is not limited further, for example, the tunneling layer 5 can be formed by POLY method, and the second silicon-containing doped layer 4 can be formed by LPCVD method.

[0192] Step five: second patterning: forming the patterned tunneling layer 5 and the second silicon-containing doped layer 4.

[0193] The second patterning is performed by a conventional method, which is not specifically limited, for example, laser grooving + cleaning or mask method.

[0194] In the second patterning process, the tunneling layer 5 and the second silicon-containing doped layer 4 located on the first doped region 2 are removed, and the tunneling layer 5 and the second silicon-containing doped layer 4 in the gap region between the first doped region 2 and the second silicon-containing doped layer 4 are removed.

[0195] Step six: a passivation layer 7 is formed on the second surface (light-facing surface) of the silicon substrate 1 and the side surface of the second silicon-containing doped layer 4 away from the silicon substrate 1. The passivation layer 7 on the light-facing surface of the silicon substrate 1 is a second passivation layer, and the passivation layer 7 on the first doped region 2 and the second silicon-containing doped layer 4 is a first passivation layer. The preparation process of the passivation layer 7 is a conventional method, which is not limited here, for example, the passivation layer can be formed by a pecvd method.

[0196] Step seven: forming the first electrode 3 and the second electrode 6.

[0197] First, a screen printing process is used to form a first electrode precursor on the side surface of the first passivation layer away from the first doped region, and a second electrode is formed on the side surface of the first passivation layer away from the second doped region; then a LECO process is used to treat the first electrode 3 and the first doped region 2, thereby forming the first electrode 3 and the second electrode 6 penetrating through the first passivation layer on the first passivation layer. The first electrode 3 penetrates through the first passivation layer and partially extends into the first doped region 2, and the second electrode 6 penetrates through the first passivation layer and contacts the second silicon-containing doped layer 4.

[0198] The laser in the LECO process is green light or infrared light, the reverse bias is between 2V-15V, and the scanning method is front scanning or back scanning.

[0199] When the first surface corresponding to the first doped region 2 has a first pyramid-shaped texture structure, the diameter of the laser spot used in the LECO process is less than or equal to the distance between the highest points of two tower tips in the first pyramid-shaped texture structure.

[0200] When the first surface corresponding to the first doped region 2 has a first tower base-shaped texture structure, the diameter of the laser spot used in the LECO process is less than or equal to the distance between the geometric centers of two adjacent first tower bases in the first tower base-shaped texture structure. The LECO process can improve the contact performance of the first electrode 3 and the first doped region 2, thereby improving the electrical performance of the battery. Compared with the prior art without LECO process treatment, the series resistance of the solar cell of the present application is reduced, the FF is improved, the open circuit voltage is improved, and the battery efficiency is improved.

[0201] Specifically, when the solar cell is a TOPcon cell, the preparation method of the solar cell comprises the following steps:

[0202] Step one: providing a silicon substrate 1; the silicon substrate 1 has a first surface and a second surface arranged oppositely;

[0203] Step two: diffusing a doping element on the first surface (light-facing surface) of the silicon substrate 1 to form a first doped region 2;

[0204] Step three: sequentially forming a tunneling layer 5 and a second silicon-containing doped layer 4 on the second surface (backlight surface) of the silicon substrate 1 from the side close to the second surface to the side away from the second surface;

[0205] Step four: forming a first passivation layer on the side surface of the first doped region 2 away from the silicon substrate 1, and forming a second passivation layer on the side surface of the second silicon-containing doped layer 4 away from the silicon substrate 1.

[0206] Step five: forming a second electrode 6 on the side surface of the second passivation layer away from the silicon substrate 1, and the second electrode 6 is connected to the second silicon-containing doped layer 4 through the second passivation layer; and forming a first electrode precursor on the side surface of the first passivation layer away from the first doped region 2 by using a screen printing process, and then treating the first electrode 3 and the first doped region 2 by using a LECO process,

[0207] The LECO process can improve the contact performance of the first electrode 3 and the first doped region 2, thereby improving the electrical performance of the battery. Compared with the prior art without using the LECO process, the series resistance of the solar cell of the present application is reduced, the FF is improved, the open circuit voltage is improved, and the battery efficiency is improved.

[0208] When the first surface corresponding to the first doped region 2 has a first pyramid-shaped texture structure, the diameter of the laser spot used in the LECO process is less than or equal to the distance between the highest points of two towers in the first pyramid-shaped texture structure.

[0209] When the first surface corresponding to the first doped region 2 has a first tower base-shaped texture structure, the diameter of the laser spot used in the LECO process is less than or equal to the distance between the geometric centers of two adjacent first tower bases in the first tower base-shaped texture structure. The LECO process can improve the contact performance of the first electrode 3 and the first doped region 2, thereby improving the electrical performance of the battery. Compared with the prior art without using the LECO process, the series resistance of the solar cell of the present application is reduced, the FF is improved, the open circuit voltage is improved, and the battery efficiency is improved.

[0210] The preparation method of the present application, and the solar cell prepared by the method is the aforementioned solar cell.

[0211] The present application provides a photovoltaic module comprising the aforementioned solar cell.

[0212] The present application provides a photovoltaic system comprising the aforementioned photovoltaic module.

[0213] Embodiment

[0214] The experimental methods used in the following examples are conventional methods unless otherwise specified.

[0215] The materials, reagents, etc. used in the following examples can be obtained from commercial channels unless otherwise specified.

[0216] Example 1

[0217] The BC solar cell of the present embodiment includes the following steps:

[0218] Step one: providing a silicon substrate 1; the silicon substrate has a first surface and a second surface arranged oppositely;

[0219] The monocrystalline silicon wafer is an N-type silicon wafer, and a double-sided texturing and cleaning process is performed on the N-type silicon wafer to form a first pyramid-shaped texture structure on the first surface, and the height of the first pyramid-shaped texture structure is 1-3 μm.

[0220] Step two: diffusing boron elements on the first surface (back surface) of the silicon substrate 1 to form a full-layer doped region. In the doped region, the minimum doping concentration of the non-activated boron elements is 1E19, the maximum doping concentration is 1E22 within a depth range of 0.3 μm from the first surface, the doping concentration at the first surface is 5E20, the minimum doping concentration of the activated boron elements is 1E17, the maximum doping concentration is 8E18 within a depth range of 0.3 μm from the first surface, the doping concentration at the first surface is 5E18, and in the doped region, the doping concentration of the activated boron elements first increases and then decreases in the direction from the first surface to the substrate, and the difference between the maximum doping concentration of the activated boron elements and the doping concentration of the activated elements at the first surface is 3E18; the junction depth of the doped region is 0.8 μm; and the sheet resistance of the doped region is 200 ohm.

[0221] Step three: first patterning to form a patterned first doped region 2.

[0222] When laser grooving is used for patterning, a first laser is used to irradiate the first surface except the doped region to be reserved, and the doped region except the doped region to be reserved is etched to expose the silicon substrate. The first laser is a picosecond laser, and the energy density of the laser is 200 MJ / m 3 After the first patterning is completed, the first surface of the silicon substrate 1 has a plurality of first doped regions 2 arranged at intervals. The width of the first doped region 2 is 250 μm, and the exposed silicon substrate has a second pyramid-shaped texture structure.

[0223] Step four: form a whole layer of tunneling layer 5 and second silicon-containing doped layer 4 on the side surface of first doped region 2 away from silicon substrate 1. Tunneling layer 5 can be formed by POLY method, and second silicon-containing doped layer 4 can be formed by LPCVD method. Tunneling layer 5 is a silicon oxide layer with a thickness of 2 nm. Second silicon-containing doped layer 4 is a phosphorus-doped polysilicon layer with a thickness of 100 nm.

[0224] Step five: second patterning: form patterned tunneling layer 5 and second silicon-containing doped layer 4.

[0225] The second laser irradiates the first doped region 2 and the second silicon-containing doped layer directly above the gap region, and the laser instantaneously high temperature plays a role of film opening. Then, the second silicon-containing doped layer, the tunneling layer directly above the first doped region, and the second silicon-containing doped layer, the tunneling layer of the gap region are etched away, thereby forming patterned tunneling layer 5 and second silicon-containing doped layer 4.

[0226] The second laser is a picosecond laser, and the energy density of the laser is 200 MJ / m 3 .

[0227] The width of the second silicon-containing doped layer 4 and the tunneling layer 5 is 250 μm.

[0228] The height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region 2 is 2 μm; the height difference between the first surface corresponding to the tunneling layer 5 and the first surface corresponding to the first doped region 2 is 3 μm;

[0229] The roughness of the first surface corresponding to the gap region is 1 μm;

[0230] The roughness of the first surface corresponding to the second doped region is 0.5 μm.

[0231] Step six: form passivation layer 7 on the second surface (light-facing surface) of silicon substrate 1 and the side surface of second silicon-containing doped layer 4 away from silicon substrate 1. The passivation layer on the light-facing surface of silicon substrate 1 is a second passivation layer, and the passivation layer on the first doped region 2 and the second silicon-containing doped layer 4 is a first passivation layer. The passivation layer can be formed by pecvd method. The passivation layer is a silicon nitride layer and an aluminum oxide layer, the thickness of the silicon nitride layer is 100 nm, and the thickness of the aluminum oxide layer is 5 nm. In the first passivation layer, the side surface of the silicon nitride layer away from the aluminum oxide layer is laminated with the silicon substrate 1. In the second passivation layer, the side surface of the silicon nitride layer away from the aluminum oxide layer is laminated with the first doped region 2 and the second silicon-containing doped layer 4.

[0232] Step seven: form first electrode 3 and second electrode 6.

[0233] Firstly, a first electrode precursor is formed on the surface of the first passivation layer away from the first doped region by screen printing process, and a second electrode is formed on the surface of the first passivation layer away from the second doped region; then, the first electrode 3 and the first doped region 2 are treated by LECO process, so as to form the first electrode 3 and the second electrode 6, the first electrode 3 penetrates through the first passivation layer and partially extends into the first doped region 2, and the second electrode 6 penetrates through the first passivation layer and is connected with the second doped layer 4 containing silicon. The first electrode is silver paste, and the second electrode is silver paste.

[0234] The laser in the LECO process is green light, the reverse bias is 15V, the reverse current is 8A, and the diameter of the laser spot in the front scanning or back scanning is the distance between the two tower tips in the first pyramid-shaped texture structure. The LECO process can improve the contact performance of the first electrode 3 and the first doped region 2, thereby improving the electrical performance of the battery. Compared with the prior art without LECO process treatment, the series resistance of the solar cell of the present application is reduced, the FF is improved, the open circuit voltage is improved, and the battery efficiency is improved.

[0235] The performance of the solar cell of the present embodiment is shown in Table 1.

[0236] The solar cells of Examples 2-4 and the solar cell of Example 1 differ only in that the parameters in the LECO process are different, specifically the reverse bias is different.

[0237] The performance of the solar cell of the present embodiment is shown in Table 1.

[0238] The solar cells of Example 5 and Comparative Examples 3-4 and the solar cell of Example 1 differ only in that the maximum doping concentration of the activated element in the first doped region is different.

[0239] The performance of the solar cell of the present embodiment is shown in Table 1.

[0240] The solar cells of Example 6 and Comparative Example 5 and the solar cell of Example 1 differ only in that the difference between the maximum doping concentration of the activated element in the first doped region and the doping concentration of the activated element at the first surface is different.

[0241] The performance of the solar cell of the present embodiment is shown in Table 1.

[0242] Example 7 and the solar cell of Example 1 differ only in that steps one and two, the steps one and two of the present embodiment are as follows:

[0243] Step one: providing a silicon substrate 1; the silicon substrate has a first surface and a second surface arranged opposite to each other;

[0244] The single crystal silicon wafer is an N-type silicon wafer, and the two surfaces of the N-type silicon wafer are polished to make the first surface have a first tower base-shaped texture structure; in a region with an area of 650 μm×650 μm under a 20-fold microscope, the number of quadrilaterals of the orthographic projection of the first tower base on the base is 1-10, and the height of the first tower base is 0-0.3 μm;

[0245] In step two, the first surface (backlight surface) of the silicon substrate 1 is doped with boron elements to diffuse the doped elements, thereby forming a first doped region 2. In the first doped region 2, the minimum doping concentration of the non-activated boron elements is 1E19, the maximum doping concentration in the depth range of 0.35 μm from the first surface is 1E22, the doping concentration at the first surface is 5E20, the minimum doping concentration of the activated boron elements is 1E17, the maximum doping concentration in the depth range of 0.35 μm from the first surface is 8E18, the doping concentration at the first surface is 5E18, and in the first doped region 2, the doping concentration of the activated boron elements first increases and then decreases in the direction from the first surface to the base, and the difference between the maximum doping concentration of the activated boron elements and the doping concentration of the activated elements at the first surface is 3E18; the junction depth of the first doped region 2 is 1.4 μm; and the sheet resistance of the first doped region 2 is 200 ohm.

[0246] The performance of the solar cell of the present embodiment is shown in Table 1.

[0247] Comparative Example 1

[0248] The solar cell of the present comparative example 1 is different from the solar cell of the present embodiment only in that the LECO process is not performed. The performance of the solar cell of the present comparative example is shown in Table 1.

[0249] Comparative Example 2

[0250] The solar cell of the present comparative example 2 is different from the solar cell of the present embodiment only in that the first doped region 2, the structure of the first doped region 2 of the solar cell in the present comparative example 2 is a first tunneling layer + a first doped layer, the first tunneling layer 5 is silicon oxide with a thickness of 2 nm, and the first doped layer is a p-type polysilicon doped layer with a thickness of 100 nm.

[0251] The performance of the solar cell of the present comparative example is shown in Table 1.

[0252] Each electrical performance parameter in Table 1 is obtained by IV tester testing.

[0253] Table 1 is the parameters of each embodiment and comparative example

[0254] Summary: From the above table, it can be seen that the solar cell of the present application uses LECO technology, changes the contact between the first electrode and the first doped region, thereby reducing the contact resistance between the first electrode and the first doped region. On the basis of taking into account the performance of the cell, the doping concentration of the activated elements and the doping concentration of the non-activated elements in the first doped region can be correspondingly reduced. The doping concentration of the activated elements can be as low as 1E17-1E19. In Comparative Example 1-Comparative Example 3, the contact resistance between the first electrode and the first doped region is high, so the performance of the cell is low. In Comparative Example 4, although the cell efficiency is high, the Voc value is lower than that of Example 1, so it cannot be used to make a high-efficiency cell. In Comparative Example 5 and Comparative Example 6, although the cell efficiency is high, the recombination is larger and the Voc value is lower than that of Example 1, so it cannot be used to make a high-efficiency cell.

[0255] Although the embodiments of the present application are described above in conjunction with the drawings, the present application is not limited to the above-described specific embodiments and application fields, and the above-described specific embodiments are merely illustrative and instructive, but not restrictive. Those skilled in the art can make many forms under the guidance of the present specification and without departing from the scope of the claims of the present application, which are all within the protection scope of the present application.

Claims

1. A solar cell comprising: a substrate having a first surface and a second surface disposed opposite to each other; a first doped region located within the substrate and extending from the first surface into the substrate; a second doped region including a tunneling layer and a second silicon-containing doped layer stacked in order on the first surface, one side surface of the tunneling layer being stacked on the first surface of the substrate, wherein the first doped region and the second doped region are alternately arranged, the second doped region has a conductivity type opposite to that of the first doped region, and a gap region is provided between the first doped region and the second doped region, wherein the first doped region contains a doping element boron.

2. The solar cell of claim 1, wherein, a first electrode is provided on a side surface of the first doped region away from the substrate, and a partial region of the first electrode extends into the first doped region; The contact resistivity of the first electrode to the first doped region is 0.1-3 mΩ / cm 2 .

3. The solar cell of claim 1, wherein, a first passivation layer and a first electrode are provided on a side surface of the first doped region away from the substrate, the first passivation layer covers the first doped region, the first electrode includes current collecting electrodes extending in a second direction and arranged at intervals in a first direction, a partial region of the current collecting electrodes is in contact with the first doped region through the first passivation layer, and the second direction intersects the first direction.

4. The solar cell of claim 3, wherein, the first electrode further includes body electrodes extending in the first direction and arranged at intervals in the second direction.

5. The solar cell of claim 4, wherein, the first electrode further includes interconnection portions electrically connected to the current collecting electrodes, the body electrodes are connected to the current collecting electrodes through the interconnection portions, the interconnection portions are arranged at intervals in the second direction and arranged at intervals in the first direction, the interconnection portions are located on a surface of the first passivation layer facing away from the first doped region, the current collecting electrodes include current collecting electrode portions adjacent to the junctions of the interconnection portions and the current collecting electrodes in the second direction, and the current collecting electrode portions are located on the surface of the first passivation layer facing away from the first doped region or are located within the first passivation layer; in the second direction, a size of the current collecting electrode portion is less than or equal to one third of a spacing between adjacent interconnection portions.

6. The solar cell of claim 3, wherein, the first passivation layer covers the gap region; a roughness of the first surface corresponding to the gap region is 0-1 μm. 7.The solar cell according to claim 1, wherein a roughness of the first surface corresponding to the second doped region is less than or equal to 0.5 μm.

8. The solar cell of claim 1, wherein, the doping element in the first doped region includes a non-activated element and an activated element, a doping concentration of the non-activated element is 1E19-1E22, a doping concentration of the activated element is 1E17-8E18, and in the first doped region, in a direction from the first surface into the substrate, the doping concentration of the activated element first increases and then decreases, and a difference between a maximum doping concentration of the activated element and a doping concentration of the activated element at the first surface is 1E18-7E18.

9. The solar cell of claim 8, wherein, The first surface corresponding to the first doped region has a first pyramid-shaped texture structure, and the first surface corresponding to the second doped region has a second tower base-shaped texture structure; the second tower base-shaped texture structure comprises a plurality of second tower bases; The one-dimensional size of the second tower base is smaller than the one-dimensional size of the tower bottom of the first pyramid-shaped texture structure, wherein the one-dimensional size of the second tower base is the size of the side surface of the second tower base away from the substrate; The height of the second tower base is smaller than the height of the first pyramid-shaped texture structure.

10. The solar cell of claim 9, wherein, The doping concentration at the first surface corresponding to the gap region has a first concentration difference with the doping concentration at the first surface corresponding to the first doped region; And / or The doping concentration within a certain depth range of the first surface corresponding to the gap region has a second concentration difference with the doping concentration within the depth range of the first surface corresponding to the first doped region, Wherein the first concentration difference and the second concentration difference are both more than 10 times.

11. The solar cell of claim 9, wherein, The height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region is 0.5-8 μm; And / or The height difference between the first surface corresponding to the gap region and the first surface corresponding to the second doped region is 0.2-4 μm.

12. The solar cell of claim 1, wherein, The substrate is a silicon substrate.

13. A method for preparing a solar cell, comprising: providing a substrate, the substrate having a first surface and a second surface arranged oppositely; allowing a doping element to enter the substrate from the first surface of the substrate, thereby forming a whole-layer doped region; first patterning, comprising: patterning the whole-layer doped region to form a plurality of first doped regions arranged at intervals at the first surface of the substrate, while the first surface of the exposed substrate without the first doped regions forms a polished surface, wherein the first doped regions are located in the substrate and extend from the first surface into the substrate; forming a whole-layer tunneling layer and a whole-layer second silicon-containing doped layer on the side surface of the first doped regions away from the substrate and the first surface of the exposed substrate in sequence; second patterning, comprising: patterning the tunneling layer and the second silicon-containing doped layer to form a patterned layered tunneling layer and a second silicon-containing doped layer as a plurality of second doped regions, so that the second doped regions and the first doped regions are arranged alternately, and the first doped regions and the second doped regions have gap regions therebetween, wherein the second doped regions have a conductive type opposite to that of the first doped regions, wherein the first doped region has a doping element boron.

14. The production method according to claim 13, wherein After the first doped region is formed, a first electrode is formed on the first doped region, and the formation of the first electrode comprises: forming a first electrode precursor on the side surface of the first doped region away from the substrate; treating the first electrode precursor and the first doped region by using a LECO process to form a first electrode partially extending into the first doped region.

15. The method of making according to claim 14, wherein, After the second doped region is formed, a second electrode is formed on the second doped region, and the formation of the second electrode comprises: forming a second electrode precursor on the second doped region on a side surface facing away from the substrate; treating the second electrode precursor and the second doped region by a LECO process to form a second electrode extending into the second doped region.

16. The method of making of claim 15, further comprising: forming a first passivation layer on a side surface of the first doped region and the second doped region facing away from the substrate, wherein forming the first electrode precursor on the first doped region comprises forming the first electrode precursor on a side surface of the first doped region corresponding to the side surface of the first passivation layer facing away from the substrate; and forming the second electrode precursor on the second doped region comprises forming the second electrode precursor on a side surface of the second doped region corresponding to the side surface of the first passivation layer facing away from the substrate, wherein the first electrode extends through the first passivation layer to contact the first doped region, and the second electrode extends through the first passivation layer to contact the second doped region.

17. The method of making according to claim 16, wherein, a first concentration difference between a doping concentration at the first surface corresponding to the gap region and a doping concentration at the first surface corresponding to the first doped region; and / or a second concentration difference between a doping concentration within a depth range of the first surface corresponding to the gap region and a doping concentration within the depth range of the first surface corresponding to the first doped region, wherein the first concentration difference and the second concentration difference are both more than 10 times; or wherein a height difference between the first surface corresponding to the gap region and the first surface corresponding to the first doped region is 0.5-8 μm; and / or a height difference between the first surface corresponding to the gap region and the first surface corresponding to the second doped region is 0.2-4 μm.

18. The method of making according to claim 14, wherein, when the first surface corresponding to the first doped region has a first pyramid-shaped texture structure, a diameter of a spot of a laser used in the LECO process is less than or equal to a distance between highest points of adjacent peaks in the first pyramid-shaped texture structure; or when the first surface corresponding to the first doped region has a first pedestal-shaped texture structure, a diameter of a spot of a laser used in the LECO process is less than or equal to a distance between geometric centers of adjacent pedestals in the first pedestal-shaped texture structure.

19. The method of making according to claim 18, wherein, the substrate is a silicon substrate.

20. A photovoltaic module comprising the solar cell according to any one of claims 1-12, or the solar cell prepared according to the preparation method of any one of claims 13-19.

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