Solar cell, cell assembly and photovoltaic system
By setting the first and second type doping layers on the back of the silicon substrate and contacting them at the junction, the diffusion characteristics of the dopant are used to reduce the doping concentration at the junction, which solves the problem of recombination in the contact area of the solar cell and improves the performance and efficiency of the cell.
Patent Information
- Application Number
- CN202421795983.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-26
- Publication Date
- 2025-10-21
- Estimated Expiration
- 2034-07-26
AI Technical Summary
The contact area of a solar cell is where photogenerated carriers easily recombine, resulting in a drop in open-circuit voltage and a reduction in short-circuit current, affecting cell efficiency.
The first type and second type doping layers are arranged on the back of the silicon substrate and are in contact at the junction. The diffusion characteristics of the dopant are utilized to reduce the doping concentration at the junction and reduce the recombination effect.
It effectively reduces interface defects, improves the performance of solar cells, and significantly increases the output power and efficiency of the cells.
Smart Images
Figure CN223463285U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model belongs to photovoltaic technology field especially relates to a solar cell, battery assembly and photovoltaic system. BACKGROUND
[0002] The contact area of the solar cell is the place where the photo-generated carriers (electrons and holes) are easily recombined. The recombination in the contact area reduces the number of effective carriers, resulting in a decrease in the open-circuit voltage of the cell. The open-circuit voltage is an important parameter of the output voltage of the solar cell, and its decrease directly affects the overall efficiency of the cell. The recombination phenomenon reduces the photo-generated carriers that can reach the electrode, thereby reducing the short-circuit current. The reduction in the short-circuit current means a decrease in the collection efficiency of the photo-generated current, which affects the output power of the cell. SUMMARY
[0003] The utility model provides a solar cell, battery assembly and photovoltaic system, aims at reducing the problem of recombination in the contact area of the solar cell.
[0004] The utility model is realized in this way. A solar cell comprises:
[0005] A silicon substrate has a back surface and a front surface arranged oppositely;
[0006] A first-type doped layer is located in a first region of the back surface of the silicon substrate;
[0007] A second-type doped layer is located in a second region of the back surface of the silicon substrate;
[0008] The first-type doped layer and the second-type doped layer intersect at the intersection of the first region and the second region;
[0009] The doping concentration of the first-type doped layer at the intersection of the first-type doped layer and the second-type doped layer is less than the doping concentration of the first-type doped layer at the non-intersection, and the doping concentration of the second-type doped layer at the intersection of the first-type doped layer and the second-type doped layer is less than the doping concentration of the second-type doped layer at the non-intersection;
[0010] The first-type doped layer is a P-type doped layer or an N-type doped layer.
[0011] The second-type doped layer is a P-type doped layer or an N-type doped layer, and is of a different type from the first-type doped layer.
[0012] Optionally, the second region partially overlaps with the first region, the second type of doped layer comprises a stacked portion, a non-stacked portion, and a connecting portion connecting the stacked portion and the non-stacked portion, the stacked portion is disposed in the overlapping region of the second region and the first region, and is stacked on the first type of doped layer, and the connecting portion is in contact with the first type of doped layer.
[0013] Optionally, the distance between the first type of doped layer and the front surface of the silicon substrate is greater than the distance between the non-stacked portion and the front surface of the silicon substrate.
[0014] Optionally, the doping concentration of the N-type doped layer is 3e20 cm -3 .
[0015] Optionally, the doping concentration of the P-type doped layer is 5e19 cm -3 .
[0016] Optionally, an insulating layer is disposed between the first type of doped layer and the stacked portion.
[0017] Optionally, a first tunneling layer is disposed on the bottom surface of the first type of doped layer, the first tunneling layer comprises a first dopant, a second tunneling layer is disposed on the bottom surface of the stacked portion and the non-stacked portion, and the inner side surface of the connecting portion, the second tunneling layer comprises a second dopant.
[0018] Optionally, the doping concentration of the first dopant in the first tunneling layer is less than the doping concentration of the first type of doped layer at the junction of the first type of doped layer and the second type of doped layer, and the doping concentration of the second dopant in the second tunneling layer is less than the doping concentration of the second type of doped layer at the junction of the first type of doped layer and the second type of doped layer.
[0019] Optionally, the thickness of the first tunneling layer and the second tunneling layer is 0.5 nm to 20 nm.
[0020] Optionally, the intersection of the first tunneling layer and the silicon substrate is a first type of inner expansion layer, and the intersection of the second tunneling layer and the silicon substrate is a second type of inner expansion layer.
[0021] Optionally, the doping concentration of the first dopant at each position is:
[0022] The doping concentration of the first type of inner expansion layer < the doping concentration of the first tunneling layer < the doping concentration at the junction of the first type of doped layer and the second type of doped layer < the doping concentration at the non-junction of the first type of doped layer;
[0023] Optionally, the doping concentration of the second dopant at each position is:
[0024] The doping concentration of the second type inner expansion layer is < the doping concentration of the second tunneling layer < the doping concentration at the joint of the first type doping layer and the second type doping layer < the doping concentration at the non-joint of the second type doping layer.
[0025] The utility model also provides a battery assembly, including above-mentioned solar cell.
[0026] The utility model also provides a photovoltaic system, including above-mentioned battery assembly.
[0027] The utility model discloses reach the beneficial effect, because the first type doping layer and the second type doping layer are arranged at the back of the first area and the second area of silicon base, and make the first type doping layer and the second type doping layer contact at the joint of the first area and the second area, utilize the diffusion characteristic of dopant to make the first dopant and the second dopant reduce the doping concentration at the joint, can effectively reduce the recombination effect, reduce interface defect, thereby significantly improve the performance of solar cell. BRIEF DESCRIPTION OF DRAWINGS
[0028] Figure 1 It is the partial structure schematic drawing of the first solar cell that the utility model provides;
[0029] Figure 2 It is the partial structure schematic drawing of the second solar cell that the utility model provides;
[0030] Figure 3 It is the partial structure schematic drawing of the third solar cell that the utility model provides;
[0031] Figure 4 It is the partial structure schematic drawing of the fourth solar cell that the utility model provides;
[0032] Figure 5 It is the partial structure schematic drawing of the fifth solar cell that the utility model provides.
[0033] BRIEF DESCRIPTION OF DRAWINGS
[0034] 100, solar cell; 110, first area; 111, first type doping layer; 120, second area; 121, second type doping layer; 1211, laminated part; 1212, connecting part; 1213, non-laminated part; 130, insulating layer; 140, first tunneling layer; 150, silicon base; 160, second tunneling layer. DETAILED DESCRIPTION
[0035] In order to make the purpose, technical scheme and advantages of the utility model more clearly, the following will be further described in detail by combining with the drawings and examples. The examples of the examples are shown in the drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The examples described below by referring to the drawings are exemplary and are only used to explain the utility model, and cannot be understood as limiting the utility model. In addition, it should be understood that the specific examples described herein are only used to explain the utility model, and are not used to limit the utility model.
[0036] In the description of the utility model, it should be understood that the terms "length", "width", "upper", "lower", "left", "right", "horizontal", "top", "bottom" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the utility model and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore, it cannot be understood as limiting the utility model.
[0037] In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include one or more of the features. In the description of the utility model, the meaning of "multiple" is two or more than two, unless otherwise specifically limited.
[0038] In the description of the utility model, it should be noted that unless otherwise specifically specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the communication or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.
[0039] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature, which can include that the first and second features are in direct contact, or the first and second features are not in direct contact but are in contact through another feature between them.
[0040] The disclosure below provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application. In addition, the present application can repeatedly refer to numbers and / or letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art can realize that other processes and / or materials can be used without departing from the scope of the present application.
[0041] The present application sets the first type of doped layer and the second type of doped layer on the first area and the second area of the back surface of the silicon substrate, and makes the first type of doped layer and the second type of doped layer contact at the junction of the first area and the second area. The diffusion characteristics of the dopant are used to reduce the doping concentration of the first dopant and the second dopant at the junction, which can effectively reduce the recombination effect and reduce the interface defect, thereby significantly improving the performance of the solar cell.
[0042] Example One
[0043] As shown in Figure 1 and Figure 2 The present application provides a solar cell 100, comprising:
[0044] A silicon substrate 150, the silicon substrate 150 has a back surface and a front surface arranged oppositely;
[0045] A first type of doped layer 111 is located on the first area 110 of the back surface of the silicon substrate 150;
[0046] A second type of doped layer 121 is located on the second area 120 of the back surface of the silicon substrate 150;
[0047] The first type of doped layer 111 and the second type of doped layer 121 are in contact at the junction of the first area 110 and the second area 120;
[0048] The doping concentration of the first type of doped layer 111 at the junction with the second type of doped layer 121 is less than the doping concentration of the first type of doped layer 111 at the non-junction position, and the doping concentration of the second type of doped layer 121 at the junction with the first type of doped layer 111 is less than the doping concentration of the second type of doped layer 121 at the non-junction position.
[0049] The first type of doped layer 111 is a P-type doped layer or an N-type doped layer.
[0050] The second type of doped layer 121 is a P-type doped layer or an N-type doped layer, and is of a different type from the first type of doped layer 111.
[0051] The first type of doped layer 111 is located in the first region 110, and the second type of doped layer 121 is located in the second region 120. Both the first region 110 and the second region 120 are located on the back surface of the silicon substrate 150. Specifically, a plurality of first regions 110 and a plurality of second regions 120 can be arranged at intervals. The first region 110 and the second region 120 have a junction. The first region 110 and the second region 120 can be arranged adjacent to each other, or can partially overlap. This means that the specific layout of the first type of doped layer 111 and the second type of doped layer 121 at the junction can have two cases:
[0052] The first type of doped layer 111 and the second type of doped layer 121 are adjacent but do not overlap at the junction, as shown in FIG. 1B. Figure 2
[0053] The first type of doped layer 111 and the second type of doped layer 121 have a certain overlapping region at the junction, as shown in FIG. 1C. Figure 1
[0054] Because the dopants have the characteristic of diffusion, in the region where the first type of doped layer 111 and the second type of doped layer 121 are adjacent or partially overlap, the P-type dopants and the N-type dopants will penetrate each other during the high-temperature diffusion process. This mutual penetration leads to a decrease in the doping concentration at the junction, because the two different types of dopants will dilute each other at the junction, reducing their respective concentrations.
[0055] The mutually penetrating dopants form a gradient region at the junction. In this region, the concentration of the first dopant in the first type of doped layer 111 gradually decreases, and the concentration of the second dopant gradually increases; while in this region, the concentration of the second dopant in the second type of doped layer 121 gradually decreases, and the concentration of the first dopant gradually increases. The existence of this gradient region causes the overall doping concentration at the junction to decrease.
[0056] In semiconductor materials, high doping concentrations can cause strain and deformation in the lattice structure. The introduction of dopant atoms can lead to lattice distortion, which is particularly pronounced at high doping concentrations. Lattice distortion can lead to the formation of more defects within the crystal, and these defects are precisely the main source of recombination centers. By reducing the doping concentration, the lattice distortion can be reduced, thereby reducing the formation of defects. In areas of high doping concentration, the interaction between dopant atoms is enhanced, and this interaction leads to changes in energy levels and the formation of local electric fields. These changes may generate additional energy levels that can act as "traps" for recombination centers, capturing free carriers and promoting their recombination. Reducing the doping concentration reduces the interaction between dopant atoms, thereby reducing the formation of such recombination centers.
[0057] It can be understood that the first-type doping layer 111 and the second-type doping layer 121 are of different types. When the first-type doping layer 111 is a P-type doping layer, the second-type doping layer 121 is an N-type doping layer; when the first-type doping layer 111 is an N-type doping layer, the second-type doping layer 121 is a P-type doping layer.
[0058] In the present application, a first-type doping layer 111 and a second-type doping layer 121 are provided in the first region 110 and the second region 120 on the back side of the silicon substrate 150, and the first-type doping layer 111 and the second-type doping layer 121 are made to contact each other at the junction of the first region 110 and the second region 120. By utilizing the diffusion characteristics of the dopant to reduce the doping concentration of the first dopant and the second dopant at the junction, the recombination effect can be effectively reduced, the interface defects can be reduced, and the performance of the solar cell 100 can be significantly improved.
[0059] Example Two
[0060] like Figure 3 As shown, based on the first embodiment, the second region 120 partially overlaps with the first region 110, and the second type doped layer 121 includes a stacked portion 1211, a non-stacked portion 1213, and a connecting portion 1212 connecting the stacked portion 1211 and the non-stacked portion 1213. The stacked portion 1211 is placed in the overlapping area of the second region 120 and the first region 110, and is stacked on the first type doped layer 111. The connecting portion 1212 is in contact with the first type doped layer 111.
[0061] In this embodiment, N and P need to be doped twice on the back side of the silicon substrate 150. N may be doped first and then P, or P may be doped first and then N. Assume that the first type doping layer 111 is a P-type doping layer, the second type doping layer 121 is an N-type doping layer, and P-type doping is performed first and then N-type doping.
[0062] Doping is performed in two steps. The first step involves P-type doping in the first region 110 on the back side of the silicon substrate 150. Dopants such as boron are introduced into the silicon substrate 150, forming a P-type doped layer. The second step involves N-type doping in the second region 120 on the back side of the silicon substrate 150. Dopants such as phosphorus are introduced into the silicon substrate 150, forming an N-type doped layer. Because the second region 120 partially overlaps with the first region 110, during the N-type doping step, the N-type dopant partially overlaps the P-type doped layer, forming a step surface.
[0063] The stacked portion 1211 is located in the overlapping region between the second region 120 and the first region 110, and is stacked on the P-type doped layer. The non-stacked portion 1213 is located in the portion of the second region 120 that does not overlap with the first region 110, forming a pure N-type doped region. The connecting portion 1212 connects the stacked portion 1211 and the non-stacked portion 1213, and contacts the P-type doped layer to ensure electrical contact between the doped layers.
[0064] By performing the doping process in two steps and controlling the doping area and concentration during the doping process, the process is relatively simple and controllable. This method does not require complex doping masks or multiple doping processes, and only requires reasonable area control and doping concentration adjustment during the doping process.
[0065] Example Three
[0066] like Figure 1 As shown, based on the second embodiment, the distance between the first-type doped layer 111 and the front surface of the silicon substrate 120 is greater than the distance between the non-laminated portion 1213 and the front surface of the silicon substrate.
[0067] In this embodiment, the first-type doped layer 111 and the non-laminated portion 1213 are not on the same plane, and there is a height difference between the first-type doped layer 111 and the non-laminated portion 1213. A good isolation effect is achieved between the first-type doped layer 111 and the non-laminated portion 1213, with good electrical isolation and lower risk of short circuit or leakage. The height difference can be flexibly set according to actual needs and is not limited here. Among them, the height difference can be flexibly set according to actual needs and is not limited here.
[0068] Example Four
[0069] Based on the first embodiment, the doping concentration of the N-type doping layer is 3e20cm -3 .
[0070] The doping concentration of the N-type doping layer is 3×10 20 cm -3, meaning there are a large number of electrons as the primary charge carriers. This high concentration of electrons helps improve the conductivity of the doped layer, reducing internal resistance, thereby increasing the output power of the solar cell 100. Combined with a reasonable PN junction structure design, this can significantly improve the efficiency and performance of the solar cell 100.
[0071] In the actual production process, high N-type doping concentration can be achieved through the following methods: ion implantation, chemical vapor deposition, thermal diffusion, etc., all of which can achieve control of doping concentration.
[0072] Example Five
[0073] Based on the first embodiment, the doping concentration of the P-type doping layer is 5e19cm -3 .
[0074] The doping concentration of the P-type doping layer is 5×10 19 cm -3 , meaning there are a large number of electrons as the primary charge carriers. This high concentration of electrons helps improve the conductivity of the doped layer, reducing internal resistance, thereby increasing the output power of the solar cell 100. Combined with a reasonable PN junction structure design, this can significantly improve the efficiency and performance of the solar cell 100.
[0075] In the actual production process, high P-type doping concentration can be achieved through the following methods: ion implantation, chemical vapor deposition, thermal diffusion, etc., all of which can achieve control of doping concentration.
[0076] Example Six
[0077] like Figure 4 As shown, based on the second embodiment, an insulating layer 130 is provided between the first-type doped layer 111 and the stacked portion 1211 .
[0078] The insulating layer 130 is disposed between the two dissimilarly doped layers and serves as a physical barrier to prevent diffusion of dopant atoms during high-temperature processing, maintaining the stability and uniformity of the doping concentration. The insulating layer 130 can improve the interface quality between the first-type doped layer 111 and the stacked portion 1211, reduce interface defects, and improve current transmission efficiency at the interface.
[0079] The performance of the solar cell 100 can be significantly improved by disposing the insulating layer 130 between the first-type doped layer 111 and the stacked portion 1211. Specifically, the insulating layer can be a BSG layer (Boron Silicate Glass).
[0080] Example Seven
[0081] like Figure 5As shown, on the basis of embodiment two, a first tunneling layer 140 containing a first dopant is arranged on the bottom surface of the first type doped layer 111, and a second tunneling layer 160 containing a second dopant is arranged on the bottom surface of the stacked portion and the non-stacked portion and the inner side surface of the connecting portion.
[0082] The first tunneling layer 140 is arranged between the silicon substrate 150 and the first type doped layer 111, and the second tunneling layer 160 is arranged between the second type doped layer 121 and the adjacent layers. The first tunneling layer 140 and the second tunneling layer 160 have a blocking effect, reducing the interface defects and recombination centers between the doped layers and the silicon substrate 150, and improving the lifetime and collection efficiency of the photo-generated carriers. The first tunneling layer contains a first dopant, and the second tunneling layer contains a second dopant, reducing the potential barrier and enhancing the quantum tunneling effect, so that electrons and holes can more efficiently cross the interface between different doped layers, improving the transmission efficiency of the carriers.
[0083] It can be understood that the first tunneling layer 140 and the second tunneling layer 160 can use the same material or different materials. Common materials used for tunneling layers include SiO, AlO, SiNx, etc.
[0084] Example Eight
[0085] On the basis of embodiment seven, the doping concentration of the first dopant in the first tunneling layer 140 is less than the doping concentration of the first type doped layer 111 at the junction of the first type doped layer 111 and the second type doped layer 121, and the doping concentration of the second dopant in the second tunneling layer 160 is less than the doping concentration of the second type doped layer 121 at the junction of the first type doped layer 111 and the second type doped layer 121.
[0086] The lower doping concentration in the first tunneling layer 140 and the second tunneling layer 160 forms a thin and smooth barrier region, which helps the occurrence of quantum tunneling effect. The lower doping concentration allows electrons and holes to easily cross the tunneling layer through tunneling effect, improving the transmission efficiency of the carriers.
[0087] Example Nine
[0088] On the basis of embodiment seven, the thickness of the first tunneling layer 140 and the second tunneling layer 160 is 0.5nm-20nm.
[0089] The thickness of the tunneling layer has strict requirements. If it is too thick, P or N cannot diffuse into the tunneling layer, and if it is too thin, it cannot play a passivation role. Within the thickness range of 0.5nm-20nm, the tunneling layer can effectively realize quantum tunneling effect, allowing electrons and holes to more efficiently cross the interface between different doped layers, improving the transmission efficiency of the carriers.
[0090] Example Ten
[0091] In the embodiment seven, the intersection of the first tunneling layer 140 and the silicon substrate 150 is a first type of inner extension layer, and the intersection of the second tunneling layer 160 and the silicon substrate 150 is a second type of inner extension layer.
[0092] In the case that the dopants have diffusion characteristics, the P-type dopants and the N-type dopants will penetrate into the silicon substrate 150 during the high-temperature diffusion process in the regions adjacent to the first tunneling layer 140 and the second tunneling layer 160.
[0093] Example Eleven
[0094] In the embodiment ten, the doping concentration of the first dopant at each position is:
[0095] The doping concentration of the first type of inner extension layer < the doping concentration of the first tunneling layer 140 < the doping concentration at the intersection of the first type of doped layer 111 and the second type of doped layer 121 < the doping concentration at the non-intersection of the first type of doped layer 111.
[0096] The doping concentration of the second dopant at each position is:
[0097] The doping concentration of the second type of inner extension layer < the doping concentration of the second tunneling layer 160 < the doping concentration at the intersection of the first type of doped layer 111 and the second type of doped layer 121 < the doping concentration at the non-intersection of the second type of doped layer 121.
[0098] The gradual change of the doping concentration of the inner extension layer, the tunneling layer 140, and the adjacent regions helps to form a smooth potential transition and improve the separation and transmission efficiency of the carriers. The design of the doping concentration gradient can optimize the electrical characteristics inside the battery by controlling the transmission path of the carriers and the electric field distribution.
[0099] Example Twelve
[0100] The embodiment provides a battery assembly, which comprises the solar cell 100 in the above embodiments.
[0101] The battery assembly of the embodiment has the same beneficial effects as the above-mentioned solar cell 100, which will not be repeated here.
[0102] Example Thirteen
[0103] The embodiment provides a photovoltaic system, which comprises the battery assembly in the above embodiments.
[0104] The photovoltaic system of the embodiment has the same beneficial effects as the above-mentioned battery assembly, which will not be repeated here.
[0105] The above merely preferred embodiments of the present application are not used to limit the present application, any modification, equivalent replacement and improvement etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.
Claims
1. A solar cell, characterized by, The solar cell comprises: a silicon substrate having a back surface and a front surface arranged oppositely; a first-type doped layer located at a first region of the back surface of the silicon substrate; a second-type doped layer located at a second region of the back surface of the silicon substrate; the first-type doped layer and the second-type doped layer meet at a meeting region of the first region and the second region; a doping concentration of the first-type doped layer at the meeting region of the first-type doped layer and the second-type doped layer is less than a doping concentration of the first-type doped layer at a non-meeting region of the first-type doped layer, and a doping concentration of the second-type doped layer at the meeting region of the first-type doped layer and the second-type doped layer is less than a doping concentration of the second-type doped layer at a non-meeting region of the second-type doped layer; wherein the first-type doped layer is a P-type doped layer or an N-type doped layer; the second-type doped layer is a P-type doped layer or an N-type doped layer, and is of a different type from the first-type doped layer.
2. The solar cell of claim 1, wherein, The second region partially overlaps the first region, the second-type doped layer comprises a stacked portion, a non-stacked portion, and a connecting portion connecting the stacked portion and the non-stacked portion, the stacked portion is arranged in an overlapping region of the second region and the first region, and is arranged on the first-type doped layer, and the connecting portion is in contact with the first-type doped layer.
3. The solar cell according to claim 2, characterized in that, A distance between the first-type doped layer and the front surface of the silicon substrate is greater than a distance between the non-stacked portion and the front surface of the silicon substrate.
4. The solar cell of claim 2, wherein the first and second doped regions are formed by implanting dopants into the first and second surfaces of the substrate. An insulating layer is arranged between the first-type doped layer and the stacked portion.
5. The solar cell of claim 2, wherein the first and second doped regions are formed by implanting dopants into the first and second surfaces of the substrate. A first tunneling layer is arranged on a bottom surface of the first-type doped layer, the first tunneling layer comprises a first dopant, a second tunneling layer is arranged on a bottom surface of the stacked portion and the non-stacked portion, and an inner side surface of the connecting portion, the second tunneling layer comprises a second dopant.
6. The solar cell of claim 5, wherein the first and second doped regions are formed by implanting dopants into the first and second surfaces of the substrate. A doping concentration of the first dopant in the first tunneling layer is less than the doping concentration of the first-type doped layer at the meeting region of the first-type doped layer and the second-type doped layer, and a doping concentration of the second dopant in the second tunneling layer is less than the doping concentration of the second-type doped layer at the meeting region of the first-type doped layer and the second-type doped layer.
7. The solar cell of claim 5, wherein the first and second doped regions are formed by implanting dopants into the first and second surfaces of the substrate. A thickness of the first tunneling layer and the second tunneling layer is 0.5 nm to 20 nm.
8. The solar cell of claim 5, wherein the first and second doped regions are formed by implanting ions of phosphorus into the first and second surfaces of the substrate. An intersection of the first tunneling layer and the silicon substrate is a first-type inner expansion layer, and an intersection of the second tunneling layer and the silicon substrate is a second-type inner expansion layer.
9. The solar cell of claim 8, wherein the first and second doped regions are formed by implanting dopants into the first and second surfaces of the substrate. The doping concentration of the first dopant at each position is: the doping concentration of the first-type inner expansion layer < the doping concentration of the first tunneling layer < the doping concentration at the meeting region of the first-type doped layer and the second-type doped layer < the doping concentration at the non-meeting region of the first-type doped layer. The doping concentration of the second dopant at each position is: the doping concentration of the second-type inner expansion layer < the doping concentration of the second tunneling layer < the doping concentration at the meeting region of the first-type doped layer and the second-type doped layer < the doping concentration at the non-meeting region of the second-type doped layer.
10. A battery assembly characterized by, The solar cell comprises any one of claims 1 to 9.
11. A photovoltaic system characterized by, The battery assembly comprises claim 10.