Back contact cell, cell assembly and photovoltaic system

Abstract

The invention relates to the technical field of solar cells, and provides a back contact cell, a cell assembly and a photovoltaic system, in the back contact cell, a groove is formed in a third region of a silicon substrate, the back contact cell further comprises a first connection region located between the groove and a first region, a first doped layer is located on the first region, a second doped layer is located on the second region, and the second doped layer is located on the second region. The third doped layer is located in the first connection region, the third doped layer comprises a first body part and a first transition part located between the first body part and the first doped layer, and the doping concentration of a first doped element in the first doped layer is larger than or equal to 100 times of the doping concentration of the first doped element in the first body part. Therefore, the carrier recombination rate of the region near the groove can be reduced while the excellent insulation isolation effect is realized, the surface recombination loss is reduced, and the efficiency of the back contact battery is further improved.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and more particularly to a back-contact cell, a cell module, and a photovoltaic system. Background Technology

[0002] Back-contact solar cells integrate both the emitter and base contact electrodes on the back of the cell, completely eliminating the obstruction of light-receiving surfaces by metal electrodes, thereby significantly improving light-harvesting capabilities and short-circuit current output.

[0003] In back-contact solar cells of relevant technologies, a common process for achieving electrical isolation between the p-type and n-type regions is etching trenches on a silicon substrate. During trench fabrication, microstructures form on the lateral surfaces of the etched p- and n-type regions, creating defect aggregation areas. These lateral surfaces are directly exposed at the trenches, leading to significant recombination losses and severely limiting the efficiency improvement of back-contact solar cells. Therefore, improving the efficiency of back-contact solar cells while ensuring effective electrical isolation has become a key technical challenge for researchers. Summary of the Invention

[0004] This application provides a back-contact battery, a battery module, and a photovoltaic system.

[0005] This application is implemented as follows: the back contact battery in the embodiments of this application includes: A silicon substrate having opposing front and back sides, the back side including a first region and a second region spaced apart and a third region located between the first region and the second region, the third region having a trench recessed toward the inside of the silicon substrate, the third region including a first connection region located between the trench and the first region; A first doped layer is stacked on the first region, and the first doped layer is doped with a first doping element; A second doped layer is stacked on the second region, the second doped layer being doped with a second dopant element, and the polarity of the second doped layer being opposite to that of the first doped layer; and A third doped layer is stacked on the first connection region and connected to the first doped layer. The third doped layer is doped with a first doping element and the polarity of the third doped layer is the same as that of the first doped layer. The third doped layer includes a first body portion and a first transition portion located between the first body portion and the first doped layer, wherein the doping concentration of the first doped element in the first doped layer is greater than or equal to 100 times the doping concentration of the first doped element in the first body portion.

[0006] In some embodiments, the doping concentration of the first doped element in the first doped layer is greater than or equal to 1000 times the doping concentration of the first doped element in the first body portion.

[0007] In some embodiments, the doping concentration of the first dopant element in the first doped layer is 1E19 / cm³. 3 -8E20 / cm 3 The doping concentration of the first doped element in the first body part is less than or equal to 1E17 / cm3.

[0008] In some embodiments, the doping concentration of the first doped element in the first body portion is 1E12 / cm3-1E16 / cm3.

[0009] In some embodiments, the doping concentration of the first doped element in the first transition portion is greater than the doping concentration of the first doped element in the first body portion, and the doping concentration of the first doped element in the first transition portion is less than the doping concentration of the first doped element in the first doped layer. In the direction from the first doped layer toward the body portion, the doping concentration of the first doped element in the first transition portion gradually decreases.

[0010] In some embodiments, the width of the third doped layer is 10 μm-600 μm.

[0011] In some embodiments, the width of the first body portion is 5μm-590μm.

[0012] In some embodiments, the width of the first transition portion is 0.2 μm-10 μm.

[0013] In some embodiments, the ratio between the width of the first body portion and the overall width of the third doped layer is 0.5-0.998, and the ratio between the width of the first transition portion and the overall width of the third doped layer is 0.002-0.5.

[0014] In some embodiments, the width of the trench is 5μm-600μm.

[0015] In some embodiments, the depth of the trench is less than one-quarter of the thickness of the silicon substrate.

[0016] In some embodiments, a first dielectric layer is provided between the first doped layer and the silicon substrate, and a second dielectric layer is provided between the third doped layer and the silicon substrate, wherein both the first dielectric layer and the second dielectric layer are doped with a first doping element; The doping concentration of the first doped element in the second dielectric layer is less than the doping concentration of the first doped element in the first dielectric layer.

[0017] In some embodiments, the silicon substrate has a first inner expansion layer formed at the contact interface with the first dielectric layer, and the first inner expansion layer is doped with a first doping element. The silicon substrate does not have an inner expansion layer at the interface with the second dielectric layer, or the silicon substrate has a second inner expansion layer at the interface with the second dielectric layer, wherein the second inner expansion layer is doped with a first doping element, and the doping concentration of the first doping element in the second inner expansion layer is less than the doping concentration of the first doping element in the first inner expansion layer.

[0018] In some embodiments, the thickness of the second inner expansion layer is less than the thickness of the first inner expansion layer.

[0019] In some embodiments, the thickness of the first inner expansion layer is 5nm-150nm, and the thickness of the second inner expansion layer is less than or equal to 30nm.

[0020] In some embodiments, the thickness of the second inner expansion layer is less than or equal to 0.2 times the thickness of the first inner expansion layer.

[0021] In some embodiments, the second inner expansion layer includes a first portion located below the first body portion and a second portion located below the first transition portion, wherein the thickness of the first portion is less than the thickness of the second portion.

[0022] In some embodiments, the doping concentration of the first doped element in the first portion is less than the doping concentration of the first doped element in the second portion.

[0023] In some embodiments, the third region includes a second connection region located between the trench and the second region, wherein the first connection region and the second connection region are located on opposite sides of the trench; The back contact battery further includes a fourth doped layer, which is stacked on the second connection region and connected to the second doped layer. The polarity of the fourth doped layer is the same as that of the second doped layer. The fourth doped layer includes a second body portion and a second transition portion located between the second body portion and the second doped layer. The doping concentration of the second doped element in the second doped layer is greater than or equal to 100 times the doping concentration of the second doped element in the second body portion.

[0024] In some embodiments, the doping concentration of the second doped element in the second doped layer is greater than or equal to 1000 times the doping concentration of the second doped element in the second body portion.

[0025] In some embodiments, the doping concentration of the second dopant element in the second doped layer is 5E19 / cm³. 3 -8E20 / cm 3 The doping concentration of the second doped element in the second body portion is less than or equal to 5E17 / cm³. 3 .

[0026] In some embodiments, the doping concentration of the second doped element in the second body portion is 1E12 / cm³. 3 -E16 / cm 3 .

[0027] In some embodiments, the doping concentration of the second doped element in the second transition portion is greater than the doping concentration of the second doped element in the second body portion, and the doping concentration of the second doped element in the second transition portion is less than the doping concentration of the second doped element in the second doped layer. In the direction from the second doped layer toward the body portion, the doping concentration of the second doped element in the second transition portion gradually decreases.

[0028] In some embodiments, the width of the fourth doped layer is 10 μm-500 μm.

[0029] In some embodiments, the width of the second transition portion is 0.2 μm-10 μm.

[0030] In some embodiments, the width of the second body portion is 5μm-498μm.

[0031] In some embodiments, the ratio between the width of the second body portion and the overall width of the fourth doped layer is 0.5-0.997, and the ratio between the width of the second transition portion and the overall width of the fourth doped layer is 0.001-0.4.

[0032] In some embodiments, a third dielectric layer is provided between the second doped layer and the silicon substrate, and a fourth dielectric layer is provided between the fourth doped layer and the silicon substrate, wherein the third dielectric layer and the fourth dielectric layer are both doped with a second doping element; The doping concentration of the second doped element in the fourth dielectric layer is less than the doping concentration of the second doped element in the third dielectric layer.

[0033] In some embodiments, the silicon substrate has a third inner expansion layer formed at the contact interface with the third dielectric layer, and the third inner expansion layer is doped with a second doping element. The silicon substrate does not have an inner extension layer at the contact interface with the fourth dielectric layer, or the silicon substrate has a fourth inner extension layer at the contact interface with the fourth dielectric layer, wherein the fourth inner extension layer is doped with a second doping element, and the doping concentration of the second doping element in the fourth inner extension layer is less than the doping concentration of the second doping element in the third inner extension layer.

[0034] In some embodiments, the thickness of the fourth inner expansion layer is less than the thickness of the third inner expansion layer.

[0035] In some embodiments, the thickness of the third inner expansion layer is 5nm-100nm, and the thickness of the fourth inner expansion layer is less than or equal to 40nm.

[0036] In some embodiments, the thickness of the fourth inner expansion layer is less than or equal to 0.4 times the thickness of the third inner expansion layer.

[0037] In some embodiments, the fourth inner expansion layer includes a third portion located below the second body portion and a fourth portion located below the second transition portion, wherein the thickness of the third portion is less than the thickness of the fourth portion.

[0038] In some embodiments, the doping concentration of the second doped element in the third portion is less than the doping concentration of the second doped element in the fourth portion.

[0039] This application also provides a battery assembly comprising a plurality of back contact batteries as described in any of the preceding claims.

[0040] This application also provides a photovoltaic system, which includes the aforementioned battery components.

[0041] In the back-contact battery, battery module, and photovoltaic system of this application embodiment, a trench is formed on a third region of the silicon substrate, which also includes a first connection region located between the trench and the first region. A first doped layer is located on the first region, a second doped layer is located on the second region, and a third doped layer is located on the first connection region. The third doped layer includes a first body portion and a first transition portion located between the first body portion and the first doped layer. The doping concentration of the first doped element in the first doped layer is greater than or equal to 100 times the doping concentration of the first doped element in the first body portion. Thus, by simultaneously employing trenches and a lightly doped third doped layer in the third region, the higher resistance of the third doped layer, combined with the trenches, achieves better electrical isolation between the first and second doped layers, thereby improving the leakage resistance of the back contact battery and ensuring its efficiency. Simultaneously, the doping concentration of the first body portion is at least two orders of magnitude lower than that of the first doped layer, providing a lightly doped region near the trenches. Due to the low-doping characteristics of the first body portion, its doping concentration is far lower than that of the first doped layer. Even if the sides of the first body portion are exposed at the trenches, this optimized design reduces the carrier recombination rate near the trenches, lowers surface recombination losses, and thus reduces the loss of photogenerated carriers, improving carrier collection efficiency and ultimately enhancing the efficiency of the back contact battery.

[0042] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of a photovoltaic system module provided in an embodiment of this application; Figure 2 This is a schematic diagram of a battery assembly provided in an embodiment of this application; Figure 3 This is a schematic diagram of the back side structure of the silicon wafer of the back contact battery provided in the embodiments of this application; Figure 4 yes Figure 3 A schematic diagram of the cross-sectional structure of the back contact battery along line IV-IV. Figure 5 yes Figure 4 A magnified schematic diagram of the back contact battery at point V; Figure 6 yes Figure 4 A magnified structural diagram of the back contact battery at point VI; Figure 7 yes Figure 3 Another cross-sectional view of the back contact battery along line IV-IV is shown in the diagram.

[0044] Explanation of key component symbols: A photovoltaic system 1000, a battery module 200, a back contact battery 100, a silicon substrate 10, a front side 11, a back side 12, a first region 121, a second region 122, a third region 123, a trench 1231, a first connection region 1232, a second connection region 1233, a first doped layer 20, a second doped layer 30, a third doped layer 40, a first body portion 41, a first transition portion 42, a first dielectric layer 51, a second dielectric layer 52, a first inner expansion layer 61, a second inner expansion layer 62, a first portion 621, a second portion 622, a fourth doped layer 70, a second body portion 71, a second transition portion 72, a third dielectric layer 81, a fourth dielectric layer 82, a third inner expansion layer 91, a fourth inner expansion layer 92, a third portion 921, a fourth portion 922, a passivation film layer 110, a first electrode 120, and a second electrode 130. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. Examples of embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Furthermore, it should be understood that the specific embodiments described herein are merely for explaining this application and are not intended to limit this application.

[0046] In the description of this application, it should be understood that the terms "upper", "lower", "left", "right", "lateral", "longitudinal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "several" means two or more, unless otherwise explicitly specified.

[0048] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0049] The following disclosure provides numerous different embodiments or examples for implementing various structures of this application. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the scope of this application. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, various specific examples of processes and materials are provided in this application, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0050] Please see Figure 1 and Figure 2 The photovoltaic system 1000 in this application embodiment may include the battery module 200 in this application embodiment, and the battery module 200 in this application embodiment may include a plurality of back contact batteries 100 in this application embodiment.

[0051] In embodiments of this application, multiple back-contact batteries 100 in the battery assembly 200 can be connected in series to form multiple battery strings. Each battery string can be connected in series, in parallel, or in a series-parallel combination to achieve current collection and output. For example, the connection between individual battery cells can be achieved by welding solder strips, or the connection between individual battery strings can be achieved by busbars. In some embodiments, the individual battery strings can form a battery cell array, and then be packaged together by a front plate, a front adhesive film, a rear adhesive film, and a back plate to form the battery assembly 200.

[0052] In the embodiments of this application, please refer to Figures 3-6 The back contact battery 100 in this embodiment may include a silicon substrate 10, a first doped layer 20, a second doped layer 30 and a third doped layer 40.

[0053] like Figure 3 and Figure 4As shown, the silicon substrate 10 has a front side 11 and a back side 12. The back side 12 of the silicon substrate 10 includes a first region 121 and a second region 122 arranged at intervals, and a third region 123 located between the first region 121 and the second region 122.

[0054] Specifically, such as Figure 3 As shown, in some embodiments, the back surface 12 of the silicon substrate 10 may include a plurality of first regions 121, a plurality of second regions 122 and a plurality of third regions 123. The plurality of first regions 121 and the plurality of second regions 122 may be arranged alternately along a first direction and both may extend along a second direction. The third region 123 is located between adjacent first regions 121 and second regions 122. That is, the third region 123 is located between any two adjacent first regions 121 and second regions 122. The first direction and the second direction may be the longitudinal direction and the transverse direction of the back contact battery 100, respectively, and no specific limitation is made here.

[0055] like Figure 4 As shown, a trench 1231 recessed toward the inside of the silicon substrate 10 is formed on the third region 123. The third region 123 also includes a first connection region 1232 located between the trench 1231 and the first region 121. That is, the third region 123 includes a trench region and a first connection region 1232. The first connection region 1232 is located between the trench region and the first region 121 and is adjacent to the first region 121. The first connection region 1232 can be understood as a connection transition region between the edge of the trench 1231 and the first region 121. The trench 1231 is recessed toward the inside of the silicon substrate 10 compared to the first region 121, the second region 122 and the first connection region 1232.

[0056] like Figure 4 and Figure 5 As shown, a first doped layer 20 is stacked on the first region 121, and the first doped layer 20 is doped with a first doping element. A second doped layer 30 is stacked on the second region 122, and the second doped layer 30 is doped with a second doping element. The polarity of the second doped layer 30 is opposite to that of the first doped layer 20. That is, the second doped layer 30 and the first doped layer 20 have different conductivity types, one of which is n-type and the other is p-type.

[0057] The third doped layer 40 is stacked on the first connection region 1232 and connected to the first doped layer 20. The third doped layer 40 is also doped with the first doping element, and the polarity of the third doped layer 40 is the same as that of the first doped layer 20. That is to say, when the conductivity type of the first doped layer 20 is p-type, the conductivity type of the third doped layer 40 is also p-type, and when the conductivity type of the first doped layer 20 is n-type, the conductivity type of the third doped layer 40 is also n-type.

[0058] Among them, such as Figure 4 and Figure 5 The third doped layer 40 may include a first body portion 41 and a first transition portion 42 located between the first body portion 41 and the first doped layer 20. The doping concentration of the first doped element in the first doped layer 20 is greater than or equal to 100 times the doping concentration of the first doped element in the first body portion 41, such as 100 times, 110 times, 120 times, 130 times, 140 times, 150 times, 200 times, etc.

[0059] It should be noted that in this document, "first dopant element" and "second dopant element" refer to Group 3 and Group 5 elements, respectively. For example, in some embodiments, the first dopant element may be a Group 3 element, such as boron or gallium, while the second dopant element may be a Group 5 element, such as phosphorus, arsenic, or antimony. Of course, in some embodiments, the first dopant element may be a Group 5 element and the second dopant element may be a Group 3 element; no specific limitation is made here. That is to say, in the embodiments of this application, one of the first dopant element and the second dopant element is a Group 3 element, and the other is a Group 5 element.

[0060] In some embodiments, the third group element is boron and the fifth group element is phosphorus. In the following description, boron is used as the first dopant and phosphorus is used as the second dopant, but this should not be construed as a limitation of this application.

[0061] It should also be noted that, in this paper, the doping concentrations of the first dopant element and the second main group element in each layer structure can be obtained by means of ECV testing, etc. The ECV testing method is a well-known testing method in the field, and will not be described in detail here to avoid being too lengthy.

[0062] In the back contact battery 100, battery module 200 and photovoltaic system 1000 of the present application embodiments, a trench 1231 is formed on the third region 123 of the silicon substrate 10, which also includes a first connection region 1232 located between the trench 1231 and the first region 121. A first doped layer 20 is located on the first region 121, a second doped layer 30 is located on the second region 122, and a third doped layer 40 is located on the first connection region 1232. The third doped layer 40 includes a first body portion 41 and a first transition portion 42 located between the first body portion 41 and the first doped layer 20. The doping concentration of the first doped element in the first doped layer 20 is greater than or equal to 100 times the doping concentration of the first doped element in the first body portion 41.

[0063] Thus, by simultaneously employing trench 1231 and a lightly doped third doped layer 40 in the third region 123, the third doped layer 40 has a higher resistance. Through its cooperation with trench 1231, better electrical isolation between the first doped layer 20 and the second doped layer 30 can be achieved, thereby improving the leakage resistance of the back contact battery 100 and ensuring the efficiency of the back contact battery 100. At the same time, the doping concentration of the first body portion 41 is at least two orders of magnitude lower than that of the first doped layer 20, providing a lightly doped region near trench 1231. Due to the low doping characteristics of the first body portion 41, the doping concentration of the first body portion 41 is much lower than that of the first doped layer 20 (at least two orders of magnitude lower). Even if the side of the first body portion 41 is exposed at trench 1231, this optimized design can reduce the carrier recombination rate of the first body portion 41 near trench 1231, reduce surface recombination loss, thereby reducing the loss of photogenerated carriers, improving carrier collection efficiency, and thus improving the efficiency of the back contact battery 100. Furthermore, by introducing the third doped layer 40, the lateral electric field generated by the low-doped first body portion 41 and the high-doped first doped layer 20 can achieve a good field passivation effect. At the same time, setting the doping concentration of the first body portion 41 to a lower level can reduce interface defects below the first body portion 41 and improve the passivation effect.

[0064] In other words, in the embodiments of this application, by opening a trench 1231 in the third region 123 and providing a first body portion 41 with a doping concentration much lower than that of the first doped layer 20 in the region adjacent to the trench 1231, it is possible to reduce the carrier recombination rate in the region near the trench 1231 while achieving excellent insulation and isolation effects, thereby reducing surface recombination losses and improving the efficiency of the back contact battery 100.

[0065] Specifically, in the embodiments of this application, the silicon substrate 10 can be a p-type silicon substrate or an n-type silicon substrate, and there is no specific limitation herein. The first doped layer 20, the second doped layer 30, and the third doped layer 40 can all be at least one of polycrystalline silicon, microcrystalline silicon, amorphous silicon, and nanocrystalline silicon, and there is no specific limitation herein.

[0066] In the silicon substrate 10, the back surface 12 can be either textured or polished, and the specific type is not limited here. In some embodiments, the first region 121, the first connection region 1232, and the second region 122 can be substantially flush, that is, on the silicon substrate 10, the back surface 12 is a complete textured or polished surface, the area where the trench 1231 is formed is a recessed area, and the other areas remain substantially flush. Of course, in some embodiments, the surfaces of the first region 121, the first connection region 1232, the second region 122, and the bottom surface of the trench 1231 region can all be polished or textured surfaces, or some areas can be textured and some areas can be polished, and the specific type is not limited here. For example, in some possible embodiments, the surfaces of the first region 121, the first connection region 1232, and the second region 122 can be polished surfaces, and the area where the trench 1231 (including the bottom surface and the side surface of the trench) is located is textured.

[0067] like Figure 4 As shown, in some embodiments, the back contact battery 100 may further include a passivation film layer 110 covering the entire back surface 12. In other words, the passivation film layer 110 is stacked and covers the first doped layer 20, the second doped layer 30, and the third doped layer 40, and also covers the trench 1231. In the back contact battery 100, a first electrode 120 is disposed on a first region 121, and a second electrode 130 is disposed on a second region 122. The first electrode 120 at least partially penetrates the passivation film layer 110 and is in conductive contact with the first doped layer 20, and the second electrode 130 at least partially penetrates the passivation film layer 110 and is in conductive contact with the second doped layer 30.

[0068] In some embodiments, the doping concentration of the first doped element in the first doped layer 20 is greater than or equal to 1000 times the doping concentration of the first doped element in the first body portion 41, for example, 1000 times, 1200 times, 1400 times, 1600 times, 1800 times, or 2000 times.

[0069] Thus, by setting the concentration of the first doped element in the first body portion 41 to be less than or equal to one-thousandth of the concentration of the first doped element in the first doped layer 20, the built-in electric field strength at the interface between the first doped layer 20 and the first body portion 41 can be significantly enhanced to improve the carrier collection efficiency. At the same time, the doping concentration of the first body portion 41 is less than or equal to 0.1% of the doping concentration of the first doped layer 20, which can keep the doping concentration of the first body portion 41 at an extremely low level, thereby further suppressing the recombination loss of carriers on the surface of the first body portion 41 exposed at the trench 1231, further improving the carrier collection efficiency, and further improving the overall photoelectric conversion efficiency of the battery.

[0070] In some embodiments, the doping concentration of the first dopant element in the first doped layer 20 may be 1E19 / cm³. 3 -8E20 / cm 3 For example, 1E19cm 3 5E19 / cm 3 1E20 / cm 3 2E20 / cm 3 5E20 / cm 3 8E20 / cm 3 Or 1E19 / cm 3 -8E20 / cm 3 Other values ​​are not limited here. The doping concentration of the first doped element in the first body part 41 may be less than or equal to 1E17 / cm³. 3 For example, 1E17cm 3 5E16 / cm 3 1E16 / cm 3 5E15 / cm 3 1E15 / cm 3 5E14 / cm 3 wait.

[0071] Thus, on the one hand, the doping concentration of the first doped element in the first doped layer 20 is set to 1E19 / cm. 3 -8E20 / cm 3 Within this range, it is possible to avoid excessively low sheet resistance due to excessively low concentration of the first doped layer 20, resulting in low carrier collection efficiency, and to avoid excessively high series resistance. Simultaneously, it ensures good ohmic contact with the external electrode, reduces contact resistance, and provides an efficient collection channel for photogenerated carriers. It also avoids excessively high doping concentration of the first doped layer 20, which could lead to intensified Auger recombination and the formation of dead layers on the surface, thus intensifying surface recombination. On the other hand, the doping concentration of the first doped element in the first body portion 41 is set to be less than or equal to 1E17 / cm³. 3 This can significantly reduce the composite loss caused by the exposure of low concentration of the first body part 41 at the trench 1231.

[0072] Furthermore, in some embodiments, the doping concentration of the first doped element in the first body portion 41 is preferably 1E12 / cm³. 3 -1E16 / cm 3 For example, 1E12 / cm 3 5E12 / cm 3 1E13 / cm 3 5E13 / cm 3 5E14 / cm 3 1E15 / cm 35E15 / cm 3 1E16 / cm 3 Or 1E12 / cm 3 -1E16 / cm 3 Other values ​​in this context are not restricted.

[0073] Thus, the doping concentration of the first doped element in the first body portion 41 is optimized and limited to 1E12 / cm. 3 -1E16 / cm 3 Within the range, with a maximum of 1E19 / cm in the first doped layer 20. 3 -8E20 / cm 3 The doping concentration forms a gradient, and this optimized concentration control can maintain the recombination loss of the cross section of the first body part 41 exposed at the trench 1231 at a low level. At the same time, such a concentration range also provides effective passivation for the first connection region 1232 and helps to form a suitable built-in electric field, promote carrier separation and transport, improve carrier collection efficiency, avoid excessive recombination loss due to excessively high doping concentration, and also avoid poor passivation and low carrier collection efficiency due to excessively low doping concentration.

[0074] In some embodiments, the doping concentration of the first doped element in the first transition portion 42 may be greater than the doping concentration of the first doped element in the first body portion 41, and the doping concentration of the first doped element in the first transition portion 42 may be less than the doping concentration of the first doped element in the first doped layer 20. In the direction from the first doped layer 20 toward the first body portion 41, the doping concentration of the first doped element in the first transition portion 42 gradually decreases.

[0075] Thus, by providing a first transition portion 42 with a higher doping concentration than the first body portion 41 between the first doped layer 20 and the first body portion 41, and by optimizing the design of the first transition portion 42 to have a gradient doping concentration that gradually decreases in the direction extending from the first doped layer 20 to the first body portion 41, a smooth potential transition region can be established between the first doped layer 20 and the first body portion 41, thereby improving carrier transport and avoiding carrier recombination loss that may be caused by abrupt changes in doping concentration.

[0076] Please see Figure 5 In some embodiments, the width of the third doped layer 40 (i.e., the dimension in the first direction, i.e.) Figure 5The sum of the width L1 of the first body portion 41 and the width L2 of the first transition portion can be 10μm-600μm, for example, 10μm, 20μm, 40μm, 60μm, 80μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 600μm or other values ​​between 10μm and 600μm.

[0077] Thus, optimizing the width of the third doped layer 40 within the reasonable range of 10μm-600μm effectively avoids the situation where an excessively small overall width of the third doped layer 40 would cause the space charge region formed at the interface of the first body portion 41 at the junction of trenches 1231 to affect the area covered by the first doped layer 20, thereby exacerbating recombination losses. Conversely, it also avoids the situation where an excessively large width of the third doped layer 40 would affect the coverage area of ​​the first doped layer 20, leading to a decrease in carrier collection efficiency. In other words, through this optimized design, the relationship between recombination loss and carrier collection efficiency can be balanced, maintaining low recombination loss while ensuring carrier collection efficiency.

[0078] Please see Figure 5 In some embodiments, the width L1 (i.e., the dimension in the first direction) of the first body portion 41 may be 5μm-590μm, for example, 5μm, 10μm, 20μm, 40μm, 60μm, 80μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, 550μm, 590μm or other values ​​between 5μm and 590μm.

[0079] Thus, by optimizing the width L1 of the first body portion 41 within a reasonable range of 5μm-590μm, it is possible to avoid the space charge region formed at the interface of the first body portion 41 at the junction of the trenches 1231 being too small, which would affect the first transition portion 42 or even the area covered by the first doped layer 20 and lead to increased recombination loss. It is also possible to avoid the carrier collection efficiency being reduced due to the width L1 of the first body portion 41 being too large.

[0080] Please see Figure 5 In some embodiments, the width L2 (i.e., the dimension in the first direction) of the first transition portion 42 may be 0.2μm-10μm, for example, 0.2μm, 0.4μm, 0.8μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or other values ​​between 0.2μm and 10μm.

[0081] Thus, by optimizing and limiting the width L2 of the first transition portion 42 to the range of 0.2μm-5μm, the electrical connection performance between the first doped layer 20 and the first body portion 41 can be effectively optimized, improving the electrical performance of the back contact cell 100. This optimized width ensures that an ideal doping concentration gradient and built-in electric field are formed between the first doped layer 20 and the first body portion 41, thereby effectively reducing the lateral recombination loss of charge carriers through the transition region and improving the collection efficiency of photogenerated charge carriers.

[0082] Specifically, the width of the first transition portion 42, which is a region where the doping concentration changes from high to low, directly determines the steepness of the doping concentration gradient and the resulting built-in electric field strength. When the width L2 of the first transition portion 42 is too small, the doping concentration gradient may be too steep, resulting in an excessively strong local electric field with a narrow range of influence and a high overall recombination rate in that region. Conversely, when the width L2 of the first transition portion 42 is too large, the doping concentration gradient is too gentle, and the built-in electric field strength is insufficient to effectively separate and guide carriers, thereby reducing carrier collection efficiency and increasing bulk recombination loss. Based on this, by precisely controlling the width L2 of the first transition portion 42 within the range of 0.2 μm to 5 μm, a moderate doping concentration gradient can be ensured, thereby establishing a stable and effective built-in electric field between the first doped layer 20 and the first body portion 41, thus optimizing carrier collection efficiency.

[0083] In some embodiments, the ratio between the width L1 of the first body portion 41 and the overall width (i.e., L1+L2) of the third doped layer 40 is 0.5-0.998, for example, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.97, 0.99, 0.998, or other values ​​between 0.5 and 0.998. The ratio between the width L2 of the first transition portion 42 and the overall width (i.e., L1+L2) of the third doped layer 40 is 0.002-0.5, for example, 0.002, 0.004, 0.006, 0.008, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, or other values ​​between 0.002 and 0.5.

[0084] Thus, by optimizing the width ratio of the first body portion 41 in the third doped layer 40 and the width of the first transition portion 42 in the third doped layer 40, the width L1 of the first body portion 41 and the width L2 of the first transition portion 42 can be within a reasonable range, thereby keeping the recombination loss of the back contact battery 100 at a low level and achieving the best carrier collection efficiency.

[0085] In some embodiments, the width of the groove 1231 (i.e., the dimension in the first direction) may be 5μm-600μm, such as 5μm, 10μm, 50μm, 100μm, 200μm, 300μm, 400μm, 500μm, 600μm or other values ​​between 5μm and 600μm.

[0086] Thus, by optimizing the width of trench 1231 within a small range of 5μm-600μm, trench 1231 can achieve effective isolation, while avoiding excessive width of trench 1231 which would occupy too much effective area and thus affect the carrier collection effect in the area where trench 1231 is located. At the same time, it can also prevent excessive width of trench 1231 from causing a significant decrease in the mechanical performance of the battery.

[0087] Specifically, in conventional technical solutions, trenches 1231 are typically made quite wide to ensure electrical isolation. This results in lower carrier collection efficiency in the area where trenches 1231 are located and a decrease in the mechanical performance of the battery. However, in the embodiments of this application, since the doping concentration of the first body portion 41 adjacent to trenches 1231 in the third doped layer 40 is low, it can itself provide a certain degree of isolation between the first doped layer 20 and the second doped layer 30. Therefore, based on this, the isolation effect between the first doped layer 20 and the second doped layer 30 can be maintained while narrowing the width of trenches 1231. Based on this, the inventors of this application have discovered through research and verification that setting the width of trenches 1231 within a reasonable range of 5μm-600μm can achieve better carrier collection efficiency while ensuring the isolation effect between the first doped layer 20 and the second doped layer 30.

[0088] In some embodiments, the depth of the trench 1231 is less than one-quarter of the thickness of the silicon substrate 10.

[0089] In this way, the depth of the trench 1231 can be avoided, which would cause a significant decrease in the mechanical strength of the back contact battery 100, and reduce the risk of cracking and microcracks caused by stress during manufacturing, transportation and use.

[0090] Please see Figure 4 and Figure 5 In some embodiments, a first dielectric layer 51 is provided between the first doped layer 20 and the silicon substrate 10, and a second dielectric layer 52 is provided between the third doped layer 40 and the silicon substrate 10. Both the first dielectric layer 51 and the second dielectric layer 52 are doped with a first doping element, and the doping concentration of the first doping element in the second dielectric layer 52 is less than the doping concentration of the first doping element in the first dielectric layer 51.

[0091] Thus, the first dielectric layer 51 and the second dielectric layer 52 enhance the interface passivation of the back contact cell 100. Simultaneously, they effectively block the diffusion of the first doped elements in the first doped layer 20 and the third doped layer 40 into the silicon substrate 10, effectively preventing excessive penetration of the first doped elements into the silicon substrate 10 and the formation of Auger recombination centers in the bulk region. Furthermore, a higher doping concentration in the first doped layer 20 reduces the contact resistance of the first electrode 120, ensuring efficient carrier collection. A lower doping concentration in the third doped layer 40 significantly reduces parasitic light absorption in this region, thereby increasing the short-circuit current. In other words, this configuration ensures efficient carrier collection while reducing Auger recombination and parasitic absorption losses.

[0092] Specifically, in some embodiments, both the first dielectric layer 51 and the second dielectric layer 52 have tunneling functionality. That is, the first dielectric layer 51 and the second dielectric layer 52 can be tunneling layers. The first dielectric layer 51 and the second dielectric layer 52 can be, for example, at least one of silicon oxide layer, silicon nitride layer, and silicon oxynitride layer. No specific limitation is made here.

[0093] In some embodiments, the thickness of the first dielectric layer 51 and the second dielectric layer 52 may be 0.3nm-4nm, such as 0.3nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm or other values ​​between 0.3nm and 4nm, and no specific limitation is made here.

[0094] Please see Figure 5 In some embodiments, the silicon substrate 10 has a first inner expansion layer 61 (i.e., a first inner expansion layer 61 at the first connection region 1232) formed at the contact interface with the first dielectric layer 51, and the first inner expansion layer 61 is doped with a first doping element.

[0095] In some embodiments, the silicon substrate 10 does not have an inner extension layer at the contact interface with the second dielectric layer 52.

[0096] Thus, there is no inner expansion layer below the second dielectric layer 52, and the presence of the inner expansion layer will not cause the inner expansion layer to be exposed at the interface of the trench 1231, thus preventing an increase in recombination loss.

[0097] Of course, such as Figure 5 As shown, in some embodiments, a second inner expansion layer 62 may also be formed at the contact interface between the silicon substrate 10 and the second dielectric layer 52 (i.e., a second inner expansion layer 62 is present at the first connection region 1232). The second inner expansion layer 62 is doped with a first doping element, and the doping concentration of the first doping element in the second inner expansion layer 62 is less than the doping concentration of the first doping element in the first inner expansion layer 61.

[0098] Thus, even though there is a second inner expansion layer 62 at the first connection region 1232, since the doping concentration of the second inner expansion layer 62 is lower than that of the first inner expansion layer 61, the recombination loss will not be too large even if the second inner expansion layer 62 is included at the cross section of the trench 1231.

[0099] In some embodiments, the doping concentration of the first doped element in the second inner layer 62 is less than or equal to 10% of the doping concentration of the first doped element in the first inner layer 61, for example, 10%, 0.8%, 0.6%, 0.4%, 0.2%, or 0.1%.

[0100] Thus, by setting the doping concentration of the second inner layer 62 to be less than or equal to 10% of the doping concentration of the first dopant element in the first inner layer 61, the first dopant element in the second inner layer 62 can be kept at an extremely low level, thereby maintaining the bulk recombination loss at an extremely low level.

[0101] Please see Figure 5 In some embodiments, the thickness of the second inner expansion layer 62 is less than the thickness of the first inner expansion layer 61.

[0102] Thus, by setting the thickness of the second inner expansion layer 62 to be less than the thickness of the first inner expansion layer 61, even if the second inner expansion layer 62 is exposed at the cross-sectional position of the trench 1231, the influence range of the space charge region formed is smaller due to its smaller thickness, which can reduce the volume recombination loss caused by the space charge region.

[0103] In some embodiments, the thickness of the first inner layer 61 may be 5nm-150nm, such as 5nm, 10nm, 20nm, 40nm, 80nm, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, or other values ​​between 5nm and 150nm.

[0104] The thickness of the second inner layer 62 can be less than or equal to 30nm, for example, 30nm, 20nm, 10nm, 5nm, 3nm, 2nm, 1nm, or 0.5nm.

[0105] Thus, by optimizing the thickness of the first inner expansion layer 61 and the second inner expansion layer 62, the recombination loss in the bulk region can be maintained at a low level, and the overall interface recombination can be reduced while ensuring effective carrier separation, thereby guaranteeing the efficiency of the back contact battery 100.

[0106] In some embodiments, the thickness of the second inner expansion layer 62 may be less than or equal to 0.2 times the thickness of the first inner expansion layer 61, such as 0.2 times, 0.15 times, 0.1 times, 0.05 times, 0.03 times, 0.02 times, 0.01 times, 0.005 times, 0.002 times, 0.0002 times, 0.0001 times, etc.

[0107] Thus, by setting the thickness of the second inner expansion layer 62 to be less than or equal to 0.2 times the thickness of the first inner expansion layer 61, the thickness of the second inner expansion layer 62 can be positioned within a relatively thin range. Even if the second inner expansion layer 62 is exposed at the cross-sectional position of the trench 1231, the influence range of the space charge region on the bulk region can be reduced, and the recombination loss of the bulk region can be maintained at a low level.

[0108] Please see Figure 5 In some embodiments, the second inner expansion layer 62 may include a first portion 621 located below the first body portion 41 and a second portion 622 located below the first transition portion 42, wherein the thickness of the first portion 621 is less than the thickness of the second portion 622.

[0109] Thus, since the exposure of the first part 621 at the cross section of the groove 1231 will increase the composite loss of the body region, setting the thickness of the first part 621 to be smaller can reduce the composite loss of the body region.

[0110] In some embodiments, the doping concentration of the first dopant element in the first portion 621 is less than the doping concentration of the first dopant element in the second portion 622.

[0111] Thus, by setting the doping concentration in the first part 621 to a low level, even if the first part 621 is exposed at the cross-section of the trench 1231, the recombination loss of the battery can be maintained at a low level.

[0112] Please see Figure 4 and Figure 6 In some embodiments, the third region 123 may include a second connection region 1233 located between the trench 1231 and the second region 122, with the first connection region 1232 and the second connection region 1233 located on opposite sides of the trench 1231. The back contact battery 100 may also include a fourth doped layer 70, which is stacked on the second connection region 1233 and connected to the second doped layer 30. The fourth doped layer 70 is doped with a second doping element, and the polarity of the fourth doped layer 70 is the same as that of the second doped layer 30.

[0113] The fourth doped layer 70 may include a second body portion 71 and a second transition portion 72 located between the second body portion 71 and the second doped layer 30. The doping concentration of the second doped element in the second doped layer 30 is greater than or equal to 100 times the doping concentration of the second doped element in the second body portion 71, such as 100 times, 110 times, 120 times, 130 times, 140 times, 150 times, 200 times, etc.

[0114] Thus, by simultaneously employing trench 1231 and a lightly doped fourth doped layer 70 in the fourth region, the fourth doped layer 70 has a higher resistance. Through the cooperation of the third doped layer 40, the fourth doped layer 70, and the trench 1231, the optimal electrical isolation effect between the first doped layer 20 and the second doped layer 30 can be achieved, thereby improving the leakage resistance of the back contact battery 100 and ensuring the efficiency of the back contact battery 100. At the same time, the doping concentration of the second body portion 71 is relatively low, providing a lightly doped region near the trench 1231. Due to the low doping characteristics of the second body portion 71, the doping concentration of the second body portion 71 is at least two orders of magnitude lower than the doping concentration of the second doped layer 30. Even if the side of the second body portion 71 is exposed at the trench 1231, this optimized design can reduce the carrier recombination rate of the second body portion 71 near the trench 1231, reduce surface recombination loss, thereby reducing the loss of photogenerated carriers, improving the carrier collection efficiency, and thus improving the efficiency of the back contact battery 100. Furthermore, by introducing the fourth doped layer 70, the lateral electric field generated by the low-doped second body portion 71 and the high-doped second doped layer 30 can achieve a good field passivation effect. At the same time, setting the doping concentration of the second body portion 71 to a lower level can reduce interface defects beneath the second body portion 71 and improve the passivation effect.

[0115] Of course, it should be noted that, such as Figure 7 As shown, in some possible embodiments, the back contact battery 100 may not have the second connection region 1233 and the fourth doped layer 70. In such a case, the second region 122 is adjacent to the trench 1231 of the third region 123, and the second doped layer 30 can cover the entire second region 122. No specific limitation is made here.

[0116] In some embodiments, the doping concentration of the second doped element in the second doped layer 30 is greater than or equal to 1000 times the doping concentration of the second doped element in the second body portion 71, for example, 1000 times, 1200 times, 1400 times, 1600 times, 1800 times, or 2000 times.

[0117] Thus, by setting the concentration of the second doped element in the second body portion 71 to be less than or equal to one-thousandth of the concentration of the second doped element in the second body portion 71, the built-in electric field strength at the interface between the second doped layer 30 and the second body portion 71 can be significantly enhanced to improve the carrier collection efficiency. At the same time, the doping concentration of the second body portion 71 is less than or equal to 0.1% of the doping concentration of the second doped layer 30, which can keep the doping concentration of the second body portion 71 at an extremely low level, thereby further suppressing the recombination loss of carriers at the surface of the second body portion 71 exposed in the trench 1231 region, further improving the carrier collection efficiency, and further improving the overall photoelectric conversion efficiency of the battery.

[0118] In some embodiments, the doping concentration of the second dopant element in the second doped layer 30 may be 5E19 / cm³. 3 -8E20 / cm 3 For example, 5E19 / cm 3 1E20 / cm 3 2E20 / cm 3 5E20 / cm 3 8E20 / cm 3 Or 5E19 / cm 3 -8E20 / cm 3 Other values ​​are not limited here. The doping concentration of the second doped element in the second body part 71 may be less than or equal to 5E17 / cm³. 3 For example, 5E17cm 3 1E17cm 3 5E16 / cm 3 1E16 / cm 3 5E15 / cm 3 1E15 / cm 3 5E14 / cm 3 wait.

[0119] Thus, on the one hand, the doping concentration of the second doped element in the second doped layer 30 is set at E19 / cm². 3 -8E20 / cm 3 Within this range, it is possible to avoid excessively low sheet resistance due to excessively low concentration of the second doped layer 30, resulting in low carrier collection efficiency, and to avoid excessively high series resistance. Simultaneously, it ensures good ohmic contact with the external electrode, reduces contact resistance, and provides an efficient collection channel for photogenerated carriers. It also avoids excessively high doping concentration of the second doped layer 30, which could lead to intensified Auger recombination and the formation of dead layers on the surface, thus intensifying surface recombination. On the other hand, the doping concentration of the second doped element in the second body portion 71 is set to be less than or equal to E17 / cm³. 3This can significantly reduce the composite loss caused by the exposure of low concentration of the second body part 71 at the trench 1231.

[0120] Furthermore, in some embodiments, the doping concentration of the second doped element in the second body portion 71 is preferably 1E12 / cm³. 3 -1E16 / cm 3 For example, 1E12 / cm 3 5E12 / cm 3 1E13 / cm 3 5E13 / cm 3 5E14 / cm 3 1E15 / cm 3 5E15 / cm 3 1E16 / cm 3 Or 1E12 / cm 3 -1E16 / cm 3 Other values ​​in this context are not restricted.

[0121] Thus, the doping concentration of the second doped element in the second body portion 71 is optimized and limited to 1E12 / cm. 3 -1E16 / cm 3 Within the range, with a maximum E19 / cm in the second doped layer 30. 3 -8E20 / cm 3 The doping concentration forms a gradient, and this optimized concentration control can maintain the recombination loss of the cross section of the second body 71 exposed at the trench 1231 at a low level. At the same time, such a concentration range also provides effective passivation for the second connection region 1233 and helps to form a suitable built-in electric field, promote carrier separation and transport, improve carrier collection efficiency, avoid excessive recombination loss due to excessively high doping concentration, and also avoid poor passivation and low carrier collection efficiency due to excessively low doping concentration.

[0122] In some embodiments, the doping concentration of the second doped element in the second transition portion 72 may be greater than the doping concentration of the second doped element in the second body portion 71, and the doping concentration of the second doped element in the second transition portion 72 may be less than the doping concentration of the second doped element in the second doped layer 30. In the direction from the second doped layer 30 toward the second body portion 71, the doping concentration of the second doped element in the second transition portion 72 gradually decreases.

[0123] Thus, by providing a second transition portion 72 with a higher doping concentration than the second body portion 71 between the second doped layer 30 and the second body portion 71, and by optimizing the design of the second transition portion 72 to have a gradient doping concentration that gradually decreases in the direction extending from the second doped layer 30 to the second body portion 71, a smooth potential transition region can be established between the second doped layer 30 and the second body portion 71, thereby improving carrier transport and avoiding carrier recombination loss that may be caused by abrupt changes in doping concentration.

[0124] Please see Figure 6 In some embodiments, the width of the fourth doped layer 70 (i.e., the dimension in the first direction, i.e.) Figure 6 The sum of the width L3 of the second body portion 71 and the width L4 of the second transition portion can be 10μm-500μm, for example, 10μm, 20μm, 40μm, 60μm, 80μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 500μm, or other values ​​between 10μm and 500μm. Thus, optimizing the width of the fourth doped layer 70 within the reasonable range of 10μm-500μm effectively avoids the situation where an excessively small overall width of the fourth doped layer 70 would cause the space charge region formed at the interface of the second body portion 71 at the junction of trenches 1231 to affect the area covered by the second doped layer 30, thereby exacerbating recombination losses. Conversely, it also avoids the situation where an excessively large width of the fourth doped layer 70 would affect the coverage area of ​​the second doped layer 30, leading to a decrease in carrier collection efficiency. In other words, through this optimized design, the relationship between recombination loss and carrier collection efficiency can be balanced, maintaining low recombination loss while ensuring carrier collection efficiency.

[0125] Please see Figure 6 In some embodiments, the width L3 of the second body portion 71 (i.e., the dimension in the first direction) may be 5μm-498μm, for example, 5μm, 10μm, 20μm, 40μm, 60μm, 80μm, 100μm, 150μm, 200μm, 250μm, 300μm, 350μm, 400μm, 450μm, 490μm, 495μm, 498μm or other values ​​between 5μm and 498μm.

[0126] Thus, by optimizing the width L3 of the second body portion 71 within a reasonable range of 5μm-498μm, it is possible to avoid the space charge region formed at the interface of the second body portion 71 at the junction of the trenches 1231 being too small, which would affect the second transition portion 72 or even the area covered by the second doped layer 30 and lead to increased recombination loss. It is also possible to avoid the carrier collection efficiency being reduced due to the width L3 of the second body portion 71 being too large.

[0127] Please see Figure 6 In some embodiments, the width L4 of the second transition portion 72 (i.e., the dimension in the first direction) may be 0.2μm-10μm, for example, 0.2μm, 0.4μm, 0.8μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm or other values ​​between 0.2μm and 10μm.

[0128] Thus, by optimizing and limiting the width L4 of the second transition portion 72 to the range of 0.2μm-5μm, the electrical connection performance between the second doped layer 30 and the second body portion 71 can be effectively optimized, improving the electrical performance of the back contact cell 100. This optimized width ensures that an ideal doping concentration gradient and built-in electric field are formed between the second doped layer 30 and the second body portion 71, thereby effectively reducing the recombination loss of charge carriers in the transition region and improving the collection efficiency of photogenerated charge carriers.

[0129] Specifically, the width of the second transition portion 72, which is a region where the doping concentration changes from high to low, directly determines the steepness of the doping concentration gradient and the resulting built-in electric field strength. When the width L4 of the second transition portion 72 is too small, the doping concentration gradient may be too steep, resulting in an excessively strong local electric field with a narrow range of influence and a high overall recombination rate in that region. Conversely, when the width L4 of the second transition portion 72 is too large, the doping concentration gradient is too gentle, and the built-in electric field strength is insufficient to effectively separate and guide carriers, thereby reducing carrier collection efficiency and increasing bulk recombination loss. Based on this, by precisely controlling the width L4 of the second transition portion 72 within the range of 0.2 μm to 5 μm, a moderate doping concentration gradient can be ensured, thereby establishing a stable and effective built-in electric field between the second doped layer 30 and the second body portion 71, thus optimizing carrier collection efficiency.

[0130] In some embodiments, the ratio between the width L3 of the second body portion 71 and the overall width (i.e., L3+L4) of the fourth doped layer 70 is 0.5-0.997, for example, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.97, 0.99, 0.997, or other values ​​between 0.5-0.997. The ratio between the width L4 of the second transition portion 72 and the overall width (i.e., L3+L4) of the fourth doped layer 70 is 0.001-0.4, for example, 0.001, 0.002, 0.004, 0.006, 0.008, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or other values ​​between 0.001-0.4.

[0131] Thus, by optimizing the width ratio of the second body portion 71 in the fourth doped layer 70 and the width of the second transition portion 72 in the fourth doped layer 70, the width L3 of the second body portion 71 and the width L4 of the second transition portion 72 can be within a reasonable range, thereby keeping the recombination loss of the back contact cell 100 at a low level and achieving the best carrier collection efficiency.

[0132] Please see Figure 4 and Figure 6 In some embodiments, a third dielectric layer 81 is provided between the second doped layer 30 and the silicon substrate 10, and a fourth dielectric layer 82 is provided between the fourth doped layer 70 and the silicon substrate 10. Both the third dielectric layer 81 and the fourth dielectric layer 82 are doped with a second doping element, and the doping concentration of the second doping element in the fourth dielectric layer 82 is less than the doping concentration of the second doping element in the third dielectric layer 81.

[0133] Thus, the third dielectric layer 81 and the fourth dielectric layer 82 enhance the interface passivation effect of the back contact cell 100. Simultaneously, they effectively block the second dopant elements in the second doped layer 30 and the fourth doped layer 70, suppressing their diffusion into the silicon substrate 10. This effectively prevents excessive penetration of the second dopant elements into the silicon substrate 10, which could lead to the formation of more Auger recombination centers in the bulk region. Furthermore, a higher doping concentration in the second doped layer 30 reduces the contact resistance of the first electrode 120, ensuring efficient carrier collection. A lower doping concentration in the fourth doped layer 70 significantly reduces optical parasitic absorption in this region, thereby increasing the short-circuit current. In other words, this configuration ensures efficient carrier collection while reducing Auger recombination and parasitic absorption losses.

[0134] Specifically, in some embodiments, both the third dielectric layer 81 and the fourth dielectric layer 82 have tunneling functionality. That is, the third dielectric layer 81 and the fourth dielectric layer 82 can be tunneling layers, and the third dielectric layer 81 and the fourth dielectric layer 82 can be, for example, at least one of silicon oxide layer, silicon nitride layer, and silicon oxynitride layer, without any specific limitation.

[0135] In some embodiments, the thickness of the third dielectric layer 81 and the fourth dielectric layer 82 may be 0.3nm-4nm, such as 0.3nm, 0.5nm, 1nm, 1.5nm, 2nm, 2.5nm, 3nm, 3.5nm, 4nm or other values ​​between 0.3nm and 4nm, and no specific limitation is made here.

[0136] Please see Figure 6 In some embodiments, the silicon substrate 10 has a third inner expansion layer 91 formed at the contact interface with the third dielectric layer 81 (i.e., the third inner expansion layer 91 is present at the second connection region 1233), and the third inner expansion layer 91 is doped with a second doping element.

[0137] In some embodiments, the silicon substrate 10 does not have an inner extension layer at the contact interface with the fourth dielectric layer 82.

[0138] Thus, there is no inner expansion layer below the fourth dielectric layer 82, and the presence of the inner expansion layer will not cause the inner expansion layer to be exposed at the interface of the trench 1231, thus preventing an increase in recombination loss.

[0139] Of course, such as Figure 6 As shown, in some embodiments, a fourth inner expansion layer 92 may also be formed at the contact interface between the silicon substrate 10 and the fourth dielectric layer 82 (i.e., a fourth inner expansion layer 92 is present at the second connection region 1233). The fourth inner expansion layer 92 is doped with a second doping element, and the doping concentration of the second doping element in the fourth inner expansion layer 92 is less than the doping concentration of the second doping element in the third inner expansion layer 91.

[0140] Thus, even though there is a fourth inner expansion layer 92 at the second connection region 1233, since the doping concentration of the fourth inner expansion layer 92 is lower than that of the third inner expansion layer 91, the recombination loss will not be too large even if the fourth inner expansion layer 92 is included at the cross section of the trench 1231.

[0141] In some embodiments, the doping concentration of the second doped element in the fourth inner layer 92 is less than or equal to 10% of the doping concentration of the second doped element in the third inner layer 91, for example, 10%, 0.8%, 0.6%, 0.4%, 0.2%, or 0.1%.

[0142] Thus, by setting the doping concentration of the fourth inner layer 92 to be less than or equal to 10% of the doping concentration of the second doping element in the third inner layer 91, the second doping element in the fourth inner layer 92 can be kept at an extremely low level, thereby maintaining the bulk recombination loss at an extremely low level.

[0143] Please see Figure 6 In some embodiments, the thickness of the fourth inner expansion layer 92 is less than the thickness of the third inner expansion layer 91.

[0144] Thus, by setting the thickness of the fourth inner expansion layer 92 to be less than that of the third inner expansion layer 91, even if the fourth inner expansion layer 92 is exposed at the cross-sectional position of the trench 1231, the influence range of the space charge region formed is smaller due to its smaller thickness, which can reduce the volume recombination loss caused by the space charge region.

[0145] In some embodiments, the thickness of the third inner layer 91 may be 5nm-100nm, such as 5nm, 10nm, 20nm, 40nm, 80nm, 100nm or other values ​​between 5nm and 100nm.

[0146] The thickness of the fourth inner layer 92 can be less than or equal to 40nm, for example, 40nm, 30nm, 20nm, 10nm, 5nm, 3nm, 2nm, 1nm, or 0.5nm.

[0147] Thus, by optimizing the thickness of the third inner expansion layer 91 and the fourth inner expansion layer 92, the recombination loss in the bulk region can be kept at a low level, thereby ensuring the efficiency of the back contact battery 100.

[0148] In some embodiments, the thickness of the fourth inner expansion layer 92 may be less than or equal to 0.4 times the thickness of the third inner expansion layer 91, such as 0.4 times, 0.35 times, 0.3 times, 0.25 times, 0.2 times, 0.15 times, 0.1 times, 0.05 times, 0.03 times, 0.02 times, 0.01 times, 0.005 times, 0.002 times, 0.0002 times, 0.0001 times, etc.

[0149] Thus, by setting the thickness of the fourth inner expansion layer 92 to be less than or equal to 0.4 times the thickness of the third inner expansion layer 91, the thickness of the fourth inner expansion layer 92 can be located within a relatively thin range. Even if the fourth inner expansion layer 92 is exposed at the cross-sectional location of the trench 1231, the influence range of the space charge region on the bulk region can be reduced, and the recombination loss of the bulk region can be maintained at a low level.

[0150] Please see Figure 6In some embodiments, the fourth inner expansion layer 92 may include a third portion 921 located below the second body portion 71 and a fourth portion 922 located below the second transition portion 72, wherein the thickness of the third portion 921 is less than the thickness of the fourth portion 922.

[0151] Thus, since the exposure of the third part 921 at the cross section of the groove 1231 will increase the composite loss of the body region, setting the thickness of the third part 921 to be smaller can reduce the composite loss of the body region.

[0152] In some embodiments, the doping concentration of the second doped element in the third part 921 is less than the doping concentration of the second doped element in the fourth part 922.

[0153] Thus, by setting the doping concentration in the third part 921 to a low level, even if the third part 921 is exposed at the cross-section of the trench 1231, the recombination loss of the battery can be maintained at a low level.

[0154] In the description of this specification, the references to terms such as "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0155] Furthermore, the above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A back-contact battery, characterized in that, include: A silicon substrate having opposing front and back sides, the back side including a first region and a second region spaced apart and a third region located between the first region and the second region, the third region having a trench recessed toward the inside of the silicon substrate, the third region including a first connection region located between the trench and the first region; A first doped layer is stacked on the first region, and the first doped layer is doped with a first doping element; A second doped layer is stacked on the second region, the second doped layer is doped with a second doping element, and the polarity of the second doped layer is opposite to that of the first doped layer; and A third doped layer is stacked on the first connection region and connected to the first doped layer. The third doped layer is doped with a first doping element and the polarity of the third doped layer is the same as that of the first doped layer. The third doped layer includes a first body portion and a first transition portion located between the first body portion and the first doped layer, wherein the doping concentration of the first doped element in the first doped layer is greater than or equal to 100 times the doping concentration of the first doped element in the first body portion.

2. The back contact battery according to claim 1, characterized in that, The doping concentration of the first doped element in the first doped layer is greater than or equal to 1000 times the doping concentration of the first doped element in the first body portion.

3. The back contact battery according to claim 1, characterized in that, The doping concentration of the first doped element in the first doped layer is 1E19 / cm³. 3 -8E20 / cm 3 The doping concentration of the first doped element in the first body portion is less than or equal to 1E17 / cm³. 3 .

4. The back contact battery according to claim 3, characterized in that, The doping concentration of the first doped element in the first body section is 1E12 / cm³. 3 -1E16 / cm 3 .

5. The back contact battery according to claim 1, characterized in that, The doping concentration of the first doped element in the first transition portion is greater than the doping concentration of the first doped element in the first body portion, and the doping concentration of the first doped element in the first transition portion is less than the doping concentration of the first doped element in the first doped layer. In the direction from the first doped layer toward the body portion, the doping concentration of the first doped element in the first transition portion gradually decreases.

6. The back contact battery according to claim 1, characterized in that, The width of the third doped layer is 10μm-600μm.

7. The back contact battery according to claim 1, characterized in that, The width of the first body part is 5μm-590μm.

8. The back contact battery according to claim 1, characterized in that, The width of the first transition portion is 0.2μm-10μm.

9. The back contact battery according to any one of claims 1-8, characterized in that, The ratio between the width of the first body portion and the overall width of the third doped layer is 0.5-0.998, and the ratio between the width of the first transition portion and the overall width of the third doped layer is 0.002-0.

5.

10. The back contact battery according to claim 1, characterized in that, The width of the groove is 5μm-600μm.

11. The back contact battery according to claim 1, characterized in that, The depth of the trench is less than one-quarter of the thickness of the silicon substrate.

12. The back contact battery according to claim 1, characterized in that, A first dielectric layer is provided between the first doped layer and the silicon substrate, and a second dielectric layer is provided between the third doped layer and the silicon substrate. Both the first dielectric layer and the second dielectric layer are doped with a first doping element. The doping concentration of the first doped element in the second dielectric layer is less than the doping concentration of the first doped element in the first dielectric layer.

13. The back contact battery according to claim 12, characterized in that, The silicon substrate has a first inner expansion layer formed at the contact interface with the first dielectric layer, and the first inner expansion layer is doped with a first doping element. The silicon substrate does not have an inner expansion layer at the interface with the second dielectric layer, or the silicon substrate has a second inner expansion layer at the interface with the second dielectric layer, wherein the second inner expansion layer is doped with a first doping element, and the doping concentration of the first doping element in the second inner expansion layer is less than the doping concentration of the first doping element in the first inner expansion layer.

14. The back contact battery according to claim 13, characterized in that, The thickness of the second inner expansion layer is less than the thickness of the first inner expansion layer.

15. The back contact battery according to claim 14, characterized in that, The thickness of the first inner expansion layer is 5nm-150nm, and the thickness of the second inner expansion layer is less than or equal to 30nm.

16. The back contact battery according to claim 14, characterized in that, The thickness of the second inner expansion layer is less than or equal to 0.2 times the thickness of the first inner expansion layer.

17. The back contact battery according to any one of claims 13-16, characterized in that, The second inner expansion layer includes a first portion located below the first body portion and a second portion located below the first transition portion, wherein the thickness of the first portion is less than the thickness of the second portion.

18. The back contact battery according to claim 17, characterized in that, The doping concentration of the first doped element in the first part is less than the doping concentration of the first doped element in the second part.

19. The back contact battery according to claim 1, characterized in that, The third region includes a second connecting region located between the trench and the second region, wherein the first connecting region and the second connecting region are located on both sides of the trench; The back contact battery further includes a fourth doped layer, which is stacked on the second connection region and connected to the second doped layer. The polarity of the fourth doped layer is the same as that of the second doped layer. The fourth doped layer includes a second body portion and a second transition portion located between the second body portion and the second doped layer. The doping concentration of the second doped element in the second doped layer is greater than or equal to 100 times the doping concentration of the second doped element in the second body portion.

20. The back contact battery according to claim 19, characterized in that, The doping concentration of the second doped element in the second doped layer is greater than or equal to 1000 times the doping concentration of the second doped element in the second body portion.

21. The back contact battery according to claim 19, characterized in that, The doping concentration of the second doped element in the second doped layer is 5E19 / cm³. 3 -8E20 / cm 3 The doping concentration of the second doped element in the second body portion is less than or equal to 5E17 / cm³. 3 .

22. The back contact battery according to claim 21, characterized in that, The doping concentration of the second doped element in the second body section is 1E12 / cm². 3 -1E16 / cm 3 .

23. The back contact battery according to claim 19, characterized in that, The doping concentration of the second doped element in the second transition portion is greater than the doping concentration of the second doped element in the second body portion, and the doping concentration of the second doped element in the second transition portion is less than the doping concentration of the second doped element in the second doped layer. In the direction from the second doped layer toward the body portion, the doping concentration of the second doped element in the second transition portion gradually decreases.

24. The back contact battery according to claim 19, characterized in that, The width of the fourth doped layer is 10μm-500μm.

25. The back contact battery according to claim 19, characterized in that, The width of the second transition section is 0.2μm-10μm.

26. The back contact battery according to claim 19, characterized in that, The width of the second body portion is 5μm-498μm.

27. The back contact battery according to any one of claims 19-26, characterized in that, The ratio between the width of the second body portion and the overall width of the fourth doped layer is 0.5-0.997, and the ratio between the width of the second transition portion and the overall width of the fourth doped layer is 0.001-0.

4.

28. The back contact battery according to claim 19, characterized in that, A third dielectric layer is provided between the second doped layer and the silicon substrate, and a fourth dielectric layer is provided between the fourth doped layer and the silicon substrate. Both the third dielectric layer and the fourth dielectric layer are doped with the second doping element. The doping concentration of the second doped element in the fourth dielectric layer is less than the doping concentration of the second doped element in the third dielectric layer.

29. The back contact battery according to claim 28, characterized in that, The silicon substrate has a third inner expansion layer formed at the contact interface with the third dielectric layer, and the third inner expansion layer is doped with a second doping element. The silicon substrate does not have an inner extension layer at the contact interface with the fourth dielectric layer, or the silicon substrate has a fourth inner extension layer at the contact interface with the fourth dielectric layer, wherein the fourth inner extension layer is doped with a second doping element, and the doping concentration of the second doping element in the fourth inner extension layer is less than the doping concentration of the second doping element in the third inner extension layer.

30. The back contact battery according to claim 29, characterized in that, The thickness of the fourth inner expansion layer is less than the thickness of the third inner expansion layer.

31. The back contact battery according to claim 30, characterized in that, The thickness of the third inner expansion layer is 5nm-100nm, and the thickness of the fourth inner expansion layer is less than or equal to 40nm.

32. The back contact battery according to claim 30, characterized in that, The thickness of the fourth inner expansion layer is less than or equal to 0.4 times the thickness of the third inner expansion layer.

33. The back contact battery according to any one of claims 29-32, characterized in that, The fourth inner expansion layer includes a third portion located below the second body portion and a fourth portion located below the second transition portion, wherein the thickness of the third portion is less than the thickness of the fourth portion.

34. The back contact battery according to claim 33, characterized in that, The doping concentration of the second doped element in the third part is less than the doping concentration of the second doped element in the fourth part.

35. A battery assembly, characterized in that, Includes the back contact battery as described in any one of claims 1-34.

36. A photovoltaic system, characterized in that, Includes the battery assembly as described in claim 35.

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