Solar cell, cell module and photovoltaic system

Abstract

The invention is applicable to the field of photovoltaic technology, and provides a solar cell, a cell assembly and a photovoltaic system, the solar cell comprises a silicon substrate, the silicon substrate is provided with a backlight surface and a light facing surface which are oppositely arranged, the backlight surface of the silicon substrate is provided with first areas and second areas, and the first areas and the second areas are alternately arranged; the N-type doped layer is arranged on the first region in a stacked manner; the first electrode is in ohmic contact with the N-type doped layer and partially penetrates into the N-type doped layer; the P-type doped layer is arranged on the second region in a stacked manner; the second electrode is in ohmic contact with the P-type doped layer and partially penetrates into the P-type doped layer; the N-type doping layer is provided with a first contact surface in contact with the first electrode, and the first contact surface is provided with a plurality of holes; the P-type doping layer is provided with a second contact surface in contact with the second electrode, and the second contact surface is provided with dendritic dents. The dents have irregular shapes, so that the contact between the P-type doping layer and the second electrode is firmer, the conductivity of the P region is improved, and the photoelectric conversion efficiency of the solar cell is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaics, and particularly relates to solar cells, battery modules, and photovoltaic systems. Background Art

[0002] As one of the most abundant renewable energy sources, solar energy has great development potential and application prospects. A solar cell is the core device that directly converts solar energy into electrical energy and is a key technology for the efficient utilization of solar energy. The photoelectric conversion efficiency refers to the proportion of incident light energy converted into electrical energy by a solar cell and is the core index for measuring the performance of a solar cell. Improving the photoelectric conversion efficiency can increase the electrical energy output per unit area and reduce the power generation cost.

[0003] Currently, the photoelectric conversion efficiency of commercial silicon-based solar cells is about 20% - 25%. Improving the photoelectric conversion efficiency of solar cells is an important part of solar cell research and development. Improving the photoelectric conversion efficiency can increase the electrical energy output per unit area, reduce the power generation cost, thereby shortening the investment recovery period, enhancing market competitiveness, and promoting the rapid development of the photovoltaic industry. Therefore, improving the photoelectric conversion efficiency of solar cells not only has important economic, environmental, and technical significance but also is the key to promoting the sustainable development of the photovoltaic industry. Summary of the Invention

[0004] Embodiments of the present invention provide a solar cell, a battery module, and a photovoltaic system, aiming to improve the photoelectric conversion efficiency of the solar cell and solve the problem of low photoelectric conversion efficiency of the solar cell.

[0005] Embodiments of the present invention are implemented as follows. A solar cell includes:

[0006] A silicon substrate having a backlight surface and a light-facing surface disposed opposite to each other. A first region and a second region are disposed on the backlight surface of the silicon substrate, and the first region and the second region are alternately arranged;

[0007] An N-type doped layer stacked on the first region;

[0008] A first electrode in ohmic contact with the N-type doped layer, and the first electrode partially penetrates into the N-type doped layer;

[0009] A P-type doped layer stacked on the second region;

[0010] A second electrode in ohmic contact with the P-type doped layer, and the second electrode partially penetrates into the P-type doped layer;

[0011] The N-type doped layer has a first contact surface in contact with the first electrode, and a plurality of holes are formed on the first contact surface;

[0012] The P-type doping layer has a second contact surface in contact with the second electrode, and the second contact surface has dendritic indentations.

[0013] Optionally, the second contact surface has a number of convex hull-like structures, and the indentations are provided on the convex hull-like structures.

[0014] Optionally, the first contact surface has a number of pyramid-like structures, and the holes are provided on the pyramid-like structures.

[0015] Optionally, the area of the region where the first electrode portion penetrates into the N-type doping layer per unit area is smaller than the area of the region where the second electrode portion penetrates into the P-type doping layer.

[0016] Optionally, the degree of penetration of the edges on both sides of the first electrode into the N-type doping layer is greater than the degree of penetration of the edges on both sides of the second electrode into the P-type doping layer.

[0017] Optionally, the depth of penetration of the first electrode portion into the N-type doping layer is smaller than the depth of penetration of the second electrode portion into the P-type doping layer.

[0018] Optionally, adjacent pyramid-like structures partially overlap.

[0019] Optionally, the shapes of a number of the convex hull-like structures are different.

[0020] Optionally, the second electrode portion penetrates through the P-type doping layer and contacts the silicon substrate.

[0021] Optionally, the adjacent first region and second region are separated by a trench region.

[0022] This embodiment provides a battery assembly, including the above-mentioned solar cell.

[0023] This embodiment provides a photovoltaic system, including the above-mentioned battery assembly.

[0024] The beneficial effects achieved by the present invention are as follows. Since the first region and the second region are alternately arranged on the backlight surface, an N-type doping layer is stacked on the first region and is in ohmic contact with the first electrode that partially penetrates, and a P-type doping layer is stacked on the second region and is in ohmic contact with the second electrode that partially penetrates. At the same time, the first contact surface between the N-type doping layer and the first electrode has a number of holes, and the second contact surface between the P-type doping layer and the second electrode has dendritic indentations, making the contact between the P-type doping layer and the second electrode more firm, which is beneficial to improving the conductivity of the P region, and further improving the photoelectric conversion efficiency of the solar cell. Description of the Drawings

[0025] Figure 1 It is an enlarged schematic structural diagram of the first region provided by an embodiment of the present invention;

[0026] Figure 2 It is a further enlarged structural schematic diagram of the first region provided by an embodiment of the present invention;

[0027] Figure 3 It is a structural schematic diagram of the first contact surface provided by an embodiment of the present invention from a first perspective;

[0028] Figure 4 It is a structural schematic diagram of the first contact surface provided by an embodiment of the present invention from a second perspective;

[0029] Figure 5 It is an enlarged structural schematic diagram of the second region provided by an embodiment of the present invention;

[0030] Figure 6 It is a further enlarged structural schematic diagram of the second region provided by an embodiment of the present invention;

[0031] Figure 7 It is a structural schematic diagram of the second contact surface provided by an embodiment of the present invention from a first perspective;

[0032] Figure 8 It is a structural schematic diagram of the second contact surface provided by an embodiment of the present invention from a second perspective.

[0033] Explanation of reference numerals:

[0034] 10. First region; 100. First contact surface; 101. Hole; 102. Pyramidal structure;

[0035] 20. Second region; 200. Second contact surface; 201. Dimple; 202. Convex structure. Detailed implementation manners

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0037] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "left", "right", "horizontal", "top", "bottom", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention.

[0038] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, the meaning of "a plurality of" is two or more unless otherwise specifically defined.

[0039] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected" and "coupled" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection or an integral connection; it may be a mechanical connection, an electrical connection or a connection capable of mutual communication; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In the present invention, unless otherwise clearly specified and defined, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through additional features therebetween. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is lower than that of the second feature.

[0041] The following disclosure provides many different embodiments or examples for implementing different structures of the present invention. To simplify the disclosure of the present invention, the components and settings of specific examples are described below. Of course, they are only examples and are not intended to limit the present invention. In addition, the present invention may repeat reference numerals and / or reference letters in different examples. Such repetition is for the purpose of simplification and clarity, and does not itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides examples of various specific processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0042] In the present invention, a first region and a second region are alternately arranged on the backlight surface. An N-type doped layer is stacked on the first region and is in ohmic contact with a partially penetrating first electrode. A P-type doped layer is stacked on the second region and is in ohmic contact with a partially penetrating second electrode. At the same time, there are a number of holes in the first contact surface between the N-type doped layer and the first electrode, and dendritic indentations on the second contact surface between the P-type doped layer and the second electrode, making the contact between the P-type doped layer and the second electrode more firm, which is beneficial to improving the conductivity of the P region and further improving the photoelectric conversion efficiency of the solar cell.

[0043] Embodiment 1

[0044] As Figures 1 to 8 shown, this embodiment provides a solar cell, which is characterized by including:

[0045] A silicon substrate having a backlight surface and a light-facing surface arranged opposite to each other. A first region 10 and a second region 20 are arranged on the backlight surface of the silicon substrate, and the first region 10 and the second region 20 are alternately arranged;

[0046] An N-type doped layer stacked on the first region 10;

[0047] A first electrode in ohmic contact with the N-type doped layer, and the first electrode partially penetrates into the N-type doped layer;

[0048] A P-type doped layer stacked on the second region 20;

[0049] A second electrode in ohmic contact with the P-type doped layer, and the second electrode partially penetrates into the P-type doped layer;

[0050] The N-type doped layer has a first contact surface 100 in contact with the first electrode, and there are a number of holes 101 on the first contact surface 100;

[0051] The P-type doped layer has a second contact surface 200 in contact with the second electrode, and dendritic indentations 201 are on the second contact surface 200.

[0052] The silicon substrate has two main surfaces: the light-facing side and the backlight side. The light-facing side directly faces the sunlight, while the backlight side is the other side. The two surfaces are placed opposite each other.

[0053] Two different areas are arranged on the backlight surface of the silicon substrate, a first area 10 and a second area 20, and the two areas are arranged alternately. Specifically, a plurality of first areas 10 and a plurality of second areas 20 are arranged alternately along a first direction, and both the first areas 10 and the second areas 20 extend along a second direction, which intersects the first direction. The first areas 10 and the second areas 20 can be arranged alternately along the lateral direction of the silicon substrate and both extend along the longitudinal direction, that is, the first direction can be the lateral direction of the back-contact battery, and the second direction can be the longitudinal direction of the back-contact battery, and the two are perpendicular to each other. Of course, in other embodiments, the first direction and the second direction can also be other directions. For example, both can be diagonal directions of the silicon substrate, which is not limited here. The first area 10 and the second area 20 do not overlap with each other, and the first area 10 and the second area 20 are arranged adjacent to each other.

[0054] An N-type doped layer is disposed in the first region 10, and a P-type doped layer is disposed in the second region 20. The N-type doped layer and the P-type doped layer have different polarities. The N-type doped layer and the P-type doped layer form regions with different electrical properties, supporting the formation of a PN junction and the separation of carriers.

[0055] The first electrode is disposed on the N-type doped layer and is in ohmic contact with the N-type doped layer. Both the N-type doped layer and the first electrode are conductive media. When the N-type doped layer and the first electrode are in contact, an electrical channel is opened, enabling current conduction.

[0056] The second electrode is disposed on the P-type doped layer and is in ohmic contact with the P-type doped layer. Both the P-type doped layer and the second electrode are conductive media. When the P-type doped layer and the second electrode are in contact, an electrical channel is opened, enabling current conduction.

[0057] The first electrode partially penetrates into the N-type doped layer, and the second electrode partially penetrates into the P-type doped layer. That is, there are some gaps on both the N-type doped layer and the P-type doped layer, allowing the electrode paste to penetrate into the gaps.

[0058] The formation of the gap may be that, in the process of preparing the N-type doped layer and the P-type doped layer, some semiconductor processes are usually adopted, such as chemical vapor deposition (CVD), diffusion and other methods. Taking chemical vapor deposition as an example, in the process of depositing the doped layer, atoms or molecules are deposited onto the surface of the silicon substrate one by one. Due to the influence of factors such as thermal motion and surface energy during the deposition process, the atoms or molecules cannot be arranged completely tightly and uniformly. They may form some tiny voids at certain positions, and these voids constitute the gaps for the subsequent electrodes to penetrate. For example, during the high-temperature diffusion doping process, when impurity atoms diffuse in the silicon lattice, they interact with silicon atoms, which may cause local distortion of the lattice, thus generating some interstitial spaces.

[0059] It can be understood that the "penetration" in this embodiment means that the depth of the electrode entering the gap of the doped layer is relatively deep, not just staying on the surface layer of the gap, but entering the interior of the gap along the depth of the gap, filling all or most of the gaps.

[0060] Moreover, when performing N-type and P-type doping, the distribution of impurity atoms in the silicon substrate is not completely uniform. In some regions, the impurity concentration is relatively high, and in some regions, the impurity concentration is relatively low. In the regions with a relatively low impurity concentration, the binding force between silicon atoms is relatively weak, and in the subsequent process, it is easier to form gaps. For example, during ion implantation doping, the energy and dose distribution of ion implantation may be uneven to some extent, resulting in uneven impurity distribution in the doped layer, thus forming gaps.

[0061] As Figure 3 shown, the N-type doped layer has a first contact surface 100 in contact with the first electrode, and there are several holes 101 on the first contact surface 100. The holes 101 are circular holes or approximately circular holes. Specifically, the approximately circular holes can be elliptical holes, or polygonal holes with rounded tips, such as triangular holes with rounded tips, or other holes with a smooth contour and no sharp inflection points. It can be understood that the first contact surface 100 includes the surface part (the surface facing away from the silicon substrate, which may be a flat surface or a surface with unevenness), and the holes 101. The holes 101 have hole walls. The first electrode is in contact with the first contact surface 100, that is, the first electrode is in contact with the surface part and penetrates into the holes 101, and is also in contact with the hole walls of the holes 101.

[0062] As Figure 7As shown, the P-type doping layer has a second contact surface 200 in contact with the second electrode, and dendritic indentations 201 are present on the second contact surface 200. It can be understood that the second contact surface 200 includes a non-indentation part (the surface facing away from the silicon substrate, which may be a flat surface or a surface with unevenness), and the indentations 201. The indentations 201 have sidewalls. The second electrode is in contact with the second contact surface 200, that is, the second electrode is in contact with the non-indentation part, and the first electrode is recessed into the indentations 201 and is also in contact with the sidewalls of the indentations 201.

[0063] In a semiconductor, the mobility of carriers is one of the important factors for measuring its conductivity. Electrons and holes, as the two types of carriers in a semiconductor, have different mobilities. Generally, the mobility of electrons is higher than that of holes.

[0064] In the N-type doping layer, the main carriers are electrons. The mass of electrons is relatively small, and the scattering effect on the semiconductor lattice is relatively weak, enabling them to move relatively freely in the lattice, so they have a higher mobility. In the P-type doping layer, the main carriers are holes. Holes are essentially the vacancies left after electrons in the valence band transition to the conduction band. Their equivalent mass is relatively large, and the scattering effect is stronger when moving in the lattice, resulting in a lower mobility of holes. The lower carrier mobility makes the conductivity of the P region relatively poor.

[0065] The distribution of the holes 101 is relatively regular. The regular holes 101 have relatively regular shapes and distributions, and this regularity makes the bonding between the electrode and the doping layer have a certain symmetry and stability. The irregular structure of the dendritic indentations 201 is more complex. The directions and lengths of their branches are different, and they can be inter-embedded with the second electrode from multiple angles and directions. The dendritic indentations 201 are more suitable for dealing with complex and changing stress environments. Due to their irregular structure, they can disperse and resist stress in multiple directions. When the battery is subjected to external forces from different directions, the tight bonding between the electrode and the P-type doping layer can still be maintained. The dendritic indentations 201 enable the second electrode to be embedded in the P-type doping layer like tree roots taking root in the soil, and this structure provides a strong mechanical anchoring effect.

[0066] A firm connection can ensure that during the current transmission process, there will be no loosening or separation between the electrode and the doping layer due to factors such as external forces and thermal stress. If the connection is not firm, there may be tiny gaps or areas with poor contact during use. These places will hinder the normal transmission of carriers, causing carriers to accumulate or scatter in these areas, thus affecting the overall conductivity. A firm connection can maintain the stability of the carrier transmission path, enabling carriers to continuously and stably transfer from one conductor to another, thereby improving the photoelectric conversion efficiency of the solar cell.

[0067] Specifically, for the observation of the first surface and the second surface, an appropriate pickling solution can be selected to first pickle and remove the first grid line and the second grid line on the solar cell. For example, if the grid line is silver, dilute nitric acid can be selected as the pickling solution. Calculate and prepare enough volume of the pickling solution to ensure that the cell sample can be completely immersed. After washing off the first grid line and the second grid line, observing their original positions is the first surface and the second surface.

[0068] In this embodiment, a first region 10 and a second region 20 are alternately arranged on the backlight surface of the silicon substrate. An N-type doping layer is stacked on the first region 10 and is in ohmic contact with a partially penetrating first electrode. A P-type doping layer is stacked on the second region 20 and is in ohmic contact with a partially penetrating second electrode. And the first contact surface 100 has a plurality of holes 101, and the second contact surface 200 has dendritic indentations 201. Since the conductivity of the P region is poorer than that of the N region, and the dendritic irregular indentations 201 on the second contact surface 200 can make the contact between the P-type doping layer and the second electrode more firm, it is beneficial to improve the conductivity of the P region, and thus improve the photoelectric conversion efficiency of the solar cell.

[0069] Embodiment 2

[0070] As Figure 8 shown, in some embodiments, the second contact surface 200 has a plurality of convex bump-like structures 202, and the indentations 201 are arranged on the convex bump-like structures 202.

[0071] In the preparation process of the solar cell, for the contact surface (the second contact surface 200) between the P-type doping layer and the second electrode, photolithography and etching techniques can be used to form the convex bump-like structures 202. First, a photoresist is coated on the surface of the P-type doping layer, and the pre-designed convex bump pattern is transferred to the photoresist through a photolithography process. Then, using an etching process, the unprotected areas by the photoresist are etched, so as to form convex bump-like structures 202 on the surface of the P-type doping layer. After that, through further micro-nano processing techniques, dendritic indentations 201 are etched on the convex bump-like structures 202. For example, plasma etching technology is used to precisely control the etching parameters to form the required indentations 201 on the convex bump surface.

[0072] The setting of the convex bump-like structures 202 greatly increases the contact area. The convex bump-like structures 202 themselves increase the surface area of the second contact surface 200, and the setting of the indentations 201 on the convex bumps further increases the contact area at the micro level. A larger contact area means that there are more regions between the P-type doping layer and the second electrode for carrier exchange. As the contact area increases, the contact resistance decreases, thereby improving the conductivity of the solar cell and enhancing the photoelectric conversion efficiency of the cell.

[0073] Enhanced mechanical bonding force: The combination of the convex hull-like structure 202 and the indentations 201 forms a complex three-dimensional interlocking structure. The second electrode material can be filled into the gaps between the indentations 201 and the convex hulls, just like tree roots penetrating into the soil and tightly bonding with the surrounding soil, making the connection between the second electrode and the P-type doped layer more firm. This firm connection can resist the influence of factors such as thermal stress and mechanical vibration during the use of the battery, reduce the risk of separation between the electrode and the doped layer, and improve the stability and reliability of the battery.

[0074] Example 3

[0075] As Figure 4 shown, in some examples, there are several pyramid-like structures 102 on the first contact surface 100, and the holes 101 are arranged on the pyramid-like structures 102.

[0076] For the contact surface between the N-type doped layer and the first electrode (the first contact surface 100), methods such as chemical etching or reactive ion etching can be used to prepare the pyramid-like structures 102. Taking chemical etching as an example, the N-type doped silicon wafer is placed in a specific etching solution. Due to the different etching rates of different crystal planes of the silicon crystal, pyramid-like structures 102 will be formed on the surface of the silicon wafer. Then, holes 101 are formed on the pyramid-like structures 102 through processes such as ion implantation or photolithographic etching. For example, the positions of the holes 101 are defined by photolithography first, and then these areas are etched using etching gas to form the required holes 101.

[0077] The setting of the pyramid-like structures 102 significantly increases the contact area. The pyramid-like structures 102 have inclined surfaces, which greatly increase the surface area of the first contact surface 100 compared with the planar structure. The existence of the holes 101 further increases the contact area at the microscale, enabling the first electrode and the N-type doped layer to make more sufficient contact. This helps to reduce the contact resistance, improve the transmission efficiency of electrons from the N-type doped layer to the first electrode, and thus enhance the overall performance of the solar cell.

[0078] The combination of the pyramid-like structures 102 and the holes 101 is beneficial to improving the light trapping and carrier collection efficiency. The pyramid-like structures 102 can cause the incident light to undergo multiple reflections and refractions on the surface of the battery, increasing the propagation path of the light inside the battery and improving the light absorption efficiency. At the same time, the holes 101 can serve as carrier collection channels, enabling electrons to be collected from the N-type doped layer to the first electrode more quickly, reducing the probability of carrier recombination, and improving the photoelectric conversion efficiency of the battery.

[0079] In this embodiment, the inclined surface of the pyramid-like structure 102 changes the propagation direction of light, causing the light to be reflected multiple times inside the battery, increasing the interaction time between the light and the semiconductor material, and improving the generation efficiency of photo-generated carriers. The existence of the holes 101 provides a more direct transmission path for electrons, reducing the diffusion distance of electrons in the N-type doped layer and lowering the probability of electron-hole recombination. From a mechanical perspective, the combination of the pyramid 102 and the holes 101 forms a physically locking structure between the electrode and the doped layer, increasing the friction and bonding force between the two and improving the mechanical stability of the battery.

[0080] Embodiment Four

[0081] In some instances, the area of the region where the first electrode portion penetrates deeply into the N-type doped layer per unit area is smaller than the area of the region where the second electrode portion penetrates deeply into the P-type doped layer.

[0082] In the manufacture of solar cells, silver paste is usually printed on the cell surface as the electrode material. During the high-temperature sintering process, the organic components in the silver paste decompose and volatilize, while the silver particles begin to melt and diffuse into the doped layer. During the process of the silver paste burning through, silver atoms interact with silicon atoms. Under suitable temperature and time conditions, silver atoms will aggregate at specific positions and form a crystal structure. These silver crystals have a certain regular arrangement, which is an ordered structure spontaneously formed by silver atoms during the diffusion and cooling processes. Also, due to the certain mutual solubility of silver and silicon at high temperatures, some silver atoms will combine with silicon atoms to form a silver-silicon alloy. The formation of this alloy changes the original chemical properties and physical structures of silver and silicon, playing a role in connecting and improving the electrical properties between the electrode and the doped layer.

[0083] As Figure 1 、 Figure 2 、 Figure 5 and Figure 6 shown, specifically, the verification method can be to observe the solar cell after pickling with an acid cleaning solution. The silver crystals and the silver-silicon alloy have relatively high chemical stability and are not easily dissolved by chemical reactions in the acid cleaning solution. Therefore, the silver crystals and the silver-silicon alloy will remain in place. In this way, the distribution of the silver crystals and the silver-silicon alloy formed in the doped layer after the silver paste burns through can be visually observed, and then the sizes of the areas where the first electrode portion and the second electrode portion penetrate deeply into the N-type doped layer and the P-type doped layer can be determined.

[0084] The second electrode part penetrates deep into the P-type doped layer to form a large-area silver crystal or silver-silicon alloy, which can reduce the contact resistance between the electrode and the P-type doped layer, improve the hole collection efficiency, and thus enhance the current output ability of the battery. Although the silver crystal or silver-silicon alloy formed by the first electrode part in the N-type doped layer has a smaller area, it can also ensure the effective transmission of electrons and maintain the overall electrical performance balance of the battery.

[0085] In this embodiment, a suitable distribution of silver crystals and silver-silicon alloys helps to improve the reliability and stability of the battery. The silver crystals and silver-silicon alloys can enhance the bonding force between the electrode and the doped layer, prevent the electrode from falling off or having poor contact during long-term use, and extend the service life of the battery.

[0086] Embodiment Five

[0087] In some instances, the penetration degree of the edges on both sides of the first electrode into the N-type doped layer is greater than that of the edges on both sides of the second electrode into the P-type doped layer.

[0088] Both sides of the electrode refer to the two sides in the extending direction of the electrode. The penetration degree of the edges on both sides of the first electrode into the N-type doped layer is greater than that of the edges on both sides of the second electrode into the P-type doped layer, that is, the depth of the edges on both sides of the first electrode penetrating into the N-type doped layer is greater than that of the edges on both sides of the second electrode penetrating into the P-type doped layer. Specifically, it can be that the depth of the edges on both sides of the first electrode penetrating into the N-type doped layer is greater than the depth of the edges on both sides of the second electrode penetrating into the P-type doped layer, or it can be that the area of the edges on both sides of the first electrode penetrating into the N-type doped layer is greater than the area of the edges on both sides of the second electrode penetrating into the P-type doped layer, or it can also be that both the depth and area of the edges on both sides of the first electrode penetrating into the N-type doped layer are greater than the depth and area of the edges on both sides of the second electrode penetrating into the P-type doped layer.

[0089] When the solar cell is working, the current distribution is not uniform. The current density in the edge region of the electrode is relatively high. If the contact resistance in the edge region is large, it will lead to more uneven current distribution and problems such as local overheating. By increasing the penetration degree of the edges on both sides of the first electrode into the N-type doped layer, the current transmission in the edge region can be made smoother, the current distribution inside the battery can be improved, and the efficiency loss and battery damage caused by current concentration can be avoided.

[0090] Embodiment Six

[0091] In some instances, the depth of the first electrode part penetrating into the N-type doped layer is less than the depth of the second electrode part penetrating into the P-type doped layer.

[0092] The contact surface between the N-type doped layer and the first electrode is the first contact surface 100, and the contact surface between the P-type doped layer and the second electrode is the second contact surface 200. The depth at which the first electrode penetrates into the N-type doped layer on the first contact surface 100 is less than the depth at which the second electrode penetrates into the P-type doped layer on the second contact surface 200. It can be understood that the above characteristics are described at the average level. There may be some positions where the depth of the first electrode penetrating into the N-type doped layer is greater than the depth of the second electrode penetrating into the P-type doped layer, but the area of such positions accounts for a relatively small proportion in the entire cell area and is ignored here.

[0093] The electron mobility in the N-type doped layer is usually high, and a relatively shallow penetration depth is sufficient to meet the rapid collection of electrons, avoiding excessive penetration and affecting the electrical properties of the N-type doped layer. The hole mobility in the P-type doped layer is relatively low, and a relatively deep penetration depth can increase the collection area and efficiency of holes, improve the cell's ability to collect holes, and thus enhance the overall photoelectric conversion efficiency. Moreover, the relatively shallow penetration of the first electrode can reduce the interference with the internal carrier distribution in the N-type doped layer and lower the probability of electron-hole recombination. The relatively deep penetration of the second electrode can more effectively collect holes and reduce the recombination loss of holes in the P-type doped layer.

[0094] Example Seven

[0095] As Figure 2 and Figure 4 shown, in some examples, adjacent pyramidal structures 102 partially overlap.

[0096] When light is reflected and refracted on the surface of the pyramidal structure 102, the partially overlapping pyramidal structures 102 increase the number of reflections and refractions of light on the cell surface, extend the propagation path of light inside the cell, enable more light to be absorbed, improve the light utilization efficiency of the cell, and thus increase the generation amount of photo-generated carriers.

[0097] Example Eight

[0098] As Figure 6 and Figure 8 shown, in some examples, the shapes of several convex hull structures 202 are different.

[0099] The convex hull structure 202 is in a convex shape. The heights of the protrusions of the convex hull structure 202 are different, and the protruding shapes and sizes of the convex hull structure 202 are also different. That is, the shape of the convex hull structure 202 is random and varies.

[0100] Convex hull structures 202 with different shapes can scatter light at different angles and wavelengths, making the light more evenly distributed on the cell surface, increasing the interaction area and time between light and cell materials, and improving the light absorption efficiency.

[0101] The convex hull-like structures 202 with various shapes also increase the complexity and diversity of the bonding between the second electrode and the P-type doped layer, enabling the electrode material to better fill the gaps between the convex hulls, enhancing the mechanical bonding force, and also being beneficial to the transport and collection of holes.

[0102] Example Nine

[0103] In some instances, the second electrode partially penetrates the P-type doped layer and contacts the silicon substrate.

[0104] The direct contact between the second electrode and the silicon substrate provides a more direct transport path for carriers, reduces the transport resistance of carriers in the P-type doped layer, decreases the series resistance of the battery, and improves the fill factor and photoelectric conversion efficiency of the battery. And directly contacting the silicon substrate can more effectively collect the holes generated from the silicon substrate and diffused to the P-type doped layer, reducing the recombination loss of holes in the P-type doped layer and improving the hole collection efficiency.

[0105] Example Ten

[0106] In some instances, adjacent first regions 10 and second regions 20 are separated by a trench region.

[0107] The trench region can effectively isolate the adjacent first regions 10 (related to the first electrode and the N-type doped layer) and second regions 20 (related to the second electrode and the P-type doped layer), reduce the electrical interference between different regions, prevent the lateral diffusion of carriers and the leakage phenomenon, and improve the open-circuit voltage and photoelectric conversion efficiency of the battery.

[0108] Example Eleven

[0109] This embodiment also provides a battery module, including the solar cell in the above embodiment.

[0110] The battery module may include a plurality of back-contact solar cell wafers. The plurality of back-contact solar cell wafers in the battery module can be connected in series in sequence to form a battery string. Each battery string can be connected in series, in parallel, or in a series-parallel combination to achieve the current collection and output. For example, the connection between each cell can be realized by welding solder tapes, and the connection between each battery string can be realized by a bus bar.

[0111] The battery module may further include a metal frame, a backsheet, a photovoltaic glass, and an encapsulant (not shown in the figures). The encapsulant can be filled between the light-facing surface of the solar cell and the photovoltaic glass, the backlight-facing surface and the backsheet, and adjacent cells, etc. As a filler, it can be a transparent colloid with good light-transmitting performance and aging resistance. For example, the encapsulant can adopt an EVA encapsulant or a POE encapsulant, and can be specifically selected according to the actual situation, which is not limited here.

[0112] The photovoltaic glass can be covered on the glue film on the light-facing surface of the solar cell. The photovoltaic glass can be ultra-white glass, which has high light transmittance, high transparency, and excellent physical, mechanical, and optical properties. For example, the light transmittance of the ultra-white glass can reach more than 92%, and it can protect the solar cell without affecting the efficiency of the solar cell as much as possible. At the same time, the glue film can bond the photovoltaic glass and the solar cell together, and the presence of the glue film can seal and insulate the solar cell and prevent water and moisture.

[0113] The backsheet can be attached to the glue film on the backlight surface of the solar cell. The backsheet can protect and support the solar cell, and has reliable insulation, water resistance, and aging resistance. The backsheet can have multiple options, usually it can be tempered glass, plexiglass, aluminum alloy TPT composite glue film, etc., and its specific settings can be determined according to specific circumstances and are not limited here. The whole composed of the backsheet, the solar cell, the glue film, and the photovoltaic glass can be set on the metal frame. The metal frame is the main external support structure of the entire battery module, and can stably support and install the battery module. For example, the battery module can be installed at the required installation position through the metal frame.

[0114] The beneficial effects of the battery module in this embodiment are the same as those of the above-mentioned solar cell, and will not be elaborated here.

[0115] Example Twelve

[0116] This embodiment also provides a photovoltaic system, including the battery module in the above embodiment.

[0117] The photovoltaic system can be applied in photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to devices or apparatuses that use solar energy for power generation, such as user solar power supplies, solar street lights, solar cars, solar buildings, and so on. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is to say, the photovoltaic system can be applied in all fields that require solar power generation. Taking the photovoltaic power generation system network as an example, the photovoltaic system can include a photovoltaic array, a busbar box, and an inverter. The photovoltaic array can be an array combination of multiple battery modules. For example, multiple battery modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the busbar box, and the busbar box can collect the current generated by the photovoltaic array. After the collected current flows through the inverter and is converted into alternating current required by the mains power grid, it is connected to the mains network to achieve solar power supply.

[0118] The beneficial effects of the photovoltaic system in this embodiment are the same as those of the above-mentioned battery module, and will not be elaborated here.

[0119] It is understandable that those skilled in the art can, under the guidance of the above embodiments, combine various implementation manners in the above embodiments to obtain technical solutions of various implementation manners.

[0120] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A solar cell, characterized in that, Comprising: A silicon substrate having a backlight surface and a light-facing surface disposed opposite to each other. A first region and a second region are disposed on the backlight surface of the silicon substrate, and the first region and the second region are alternately arranged; An N-type doped layer stacked on the first region; A first electrode in ohmic contact with the N-type doped layer, and a part of the first electrode penetrates into the N-type doped layer; A P-type doped layer stacked on the second region; A second electrode in ohmic contact with the P-type doped layer, and a part of the second electrode penetrates into the P-type doped layer; The N-type doped layer has a first contact surface in contact with the first electrode, and a plurality of holes are formed on the first contact surface; The P-type doped layer has a second contact surface in contact with the second electrode, and dendritic indentations are formed on the second contact surface.

2. The solar cell according to claim 1, wherein, A plurality of convex hull-like structures are formed on the second contact surface, and the indentations are formed on the convex hull-like structures.

3. The solar cell according to claim 1, wherein A plurality of pyramid-like structures are formed on the first contact surface, and the holes are formed on the pyramid-like structures.

4. The solar cell according to claim 1, characterized in that, The area of the region where the first electrode penetrates into the N-type doped layer per unit area is smaller than the area of the region where the second electrode penetrates into the P-type doped layer.

5. The solar cell according to claim 1, characterized in that, The penetration degree of the edges on both sides of the first electrode into the N-type doped layer is greater than the penetration degree of the edges on both sides of the second electrode into the P-type doped layer.

6. The solar cell according to claim 1, characterized in that, The depth of the part of the first electrode penetrating into the N-type doped layer is smaller than the depth of the part of the second electrode penetrating into the P-type doped layer.

7. The solar cell according to claim 3, characterized in that, The adjacent pyramid-like structures partially overlap.

8. The solar cell according to claim 2, wherein, The shapes of a plurality of the convex hull-like structures are different.

9. The solar cell according to claim 1, wherein, The second electrode partially penetrates through the P-type doped layer and contacts the silicon substrate.

10. The solar cell according to claim 1, characterized in that, The adjacent first region and second region are separated by a trench region.

11. A battery assembly, characterized in that, A solar cell according to claims 1-10.

12. A photovoltaic system, characterized in that, A battery module according to claim 11.

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