Back contact solar cells, tandem cells, photovoltaic modules

Abstract

This application relates to back-contact solar cells, tandem solar cells, and photovoltaic modules. The back-contact solar cell includes: a substrate having a front surface and a rear surface disposed opposite to each other; the rear surface of the substrate having a first region and a second region; the first region having a planar structure and the second region having a textured structure; a first electrode in contact with the textured structure; the textured structure including a plurality of first substructures with gaps between adjacent first substructures; and a second electrode in contact with the planar structure. The first and second electrodes each include spherical metal particles, comprising first spherical metal particles with a diameter ≤1µm and second spherical metal particles with a diameter >1µm, at least a portion of the first spherical metal particles being located within the gaps, and at least a portion of the second spherical metal particles being in contact with the top of the first substructures. The solar cell provided by this application can improve the structural stability of the cell and reduce current output loss.

Description

Technical Field

[0001] This application relates to the field of photovoltaic technology, and in particular to back-contact solar cells, tandem cells, and photovoltaic modules. Background Technology

[0002] Fully back-electrode (BC) batteries integrate both positive and negative electrodes on the back of the battery. This eliminates light loss due to grid lines on the front, resulting in extremely high efficiency potential. Furthermore, the absence of metal electrodes on the front makes them more aesthetically pleasing than conventional double-sided contact batteries. BC batteries have attracted widespread attention. Extensive research has been conducted to optimize the battery's microstructure in order to further improve efficiency.

[0003] Traditional solar cell conductive pastes contain metal particles. During sintering, the poor adhesion between these particles and the silicon substrate can easily lead to electrode detachment. Furthermore, during printing, the paste is prone to grid breakage or edge diffusion, affecting electrode uniformity and electrical performance. This is especially true for textured solar cells, where the high surface unevenness and large contact area create gaps between metal particles, resulting in decreased electrode contact stability and increased contact resistance. Summary of the Invention

[0004] This application provides back-contact solar cells, tandem cells, and photovoltaic modules. The back-contact solar cells have metal particles of different sizes interlocked within the electrodes, which can improve electrode connection stability, reduce electrode contact resistance, improve cell structural stability, and reduce current output loss.

[0005] In a first aspect, this application provides a back-contact solar cell, comprising: A substrate having a front surface and a rear surface disposed opposite to each other, the rear surface of the substrate having a first region and a second region, the first region having a textured structure and the second region having a planar structure; A first electrode is in contact with the texture structure; the texture structure includes a plurality of first substructures, with a gap between two adjacent first substructures; The second electrode is in contact with the planar structure; The first electrode and the second electrode each include spherical metal particles. The spherical metal particles include first spherical metal particles with a particle size ≤ 1µm and second spherical metal particles with a particle size > 1µm. At least a portion of the first spherical metal particles are located within the gap, and at least a portion of the second spherical metal particles are in contact with the top of the first substructure.

[0006] In some implementations, the proportion of the first spherical metal particles is greater than the proportion of the second spherical metal particles.

[0007] In some embodiments, the first substructure includes a top portion away from the front surface of the substrate, a bottom portion near the front surface of the substrate, and a sidewall connecting the top portion and the bottom portion; at least a portion of the first spherical metal particle is in contact with the sidewall and / or the bottom portion.

[0008] In some implementations, the distance between the tops of two adjacent first substructures is 0.2µm to 3.5µm.

[0009] In some embodiments, the first electrode and the second electrode further include disc-shaped metal particles with a thickness of 0.3µm to 2.5µm and a particle size of 2µm to 6µm.

[0010] In some embodiments, the first electrode and the second electrode further include strip-shaped metal particles with a thickness of 20 nm to 200 nm and a length of 2 µm to 50 µm.

[0011] In some embodiments, at least a portion of the disc-shaped metal particles are in contact with the top of the first substructure.

[0012] In some embodiments, at least a portion of the top surface of the first substructure has a one-dimensional dimension of 5 nm to 240 nm, and the disc-shaped metal particle or the second spherical metal particle is in contact with the top surface of the first substructure.

[0013] In some embodiments, the distance between the top and bottom of the first substructure is less than or equal to 5 μm in a direction away from and perpendicular to the front surface.

[0014] In some implementations, the first substructure is a pyramid-shaped microstructure.

[0015] In some embodiments, the raw materials for the first electrode and the second electrode are conductive pastes. The conductive pastes include an organic carrier and metal particles dispersed within the organic carrier. The metal particles include spherical metal particles, disc-shaped metal particles, and ribbon-shaped metal particles. The spherical metal particles account for more than or equal to 50% of the total mass of all metal particles, the disc-shaped metal particles account for less than 40% of the total mass of all metal particles, and the ribbon-shaped metal particles account for less than 10% of the total mass of all metal particles.

[0016] In some embodiments, the back-contact solar cell further includes: A first amorphous silicon layer is located on the surface of the textured structure of the substrate; A P-type doped layer is located on the side of the first amorphous silicon layer away from the substrate; the first electrode is electrically connected to the P-type doped layer. A tunneling layer, the tunneling layer being located on the surface of the planar structure of the substrate; An N-type doped layer is located on the side of the tunneling layer away from the substrate; the second electrode is electrically connected to the N-type doped layer.

[0017] In some embodiments, the back-contact solar cell further includes: A first transparent conductive layer is located on the side of the P-type doped layer away from the substrate; the first electrode is electrically connected to the first transparent conductive layer. A second transparent conductive layer is located on the side of the N-type doped layer away from the tunneling layer; the second electrode is electrically connected to the second transparent conductive layer.

[0018] In some embodiments, the first region accounts for 50%-80% of the distribution on the rear surface of the substrate; the second region accounts for 20%-50% of the distribution on the rear surface of the substrate.

[0019] Secondly, this application provides a tandem solar cell, including a crystalline silicon bottom cell and a perovskite top cell, wherein the crystalline silicon bottom cell includes the aforementioned back-contact solar cell, and the perovskite top cell is electrically connected to the crystalline silicon bottom cell.

[0020] Thirdly, this application provides a photovoltaic module, which includes the aforementioned back-contact solar cells, and the back-contact solar cells are electrically connected to form a solar cell string.

[0021] The back-contact solar cell provided in this application embodiment has at least the following technical effects: In this application, the electrodes of the back-contact solar cell contain spherical metal particles. On one hand, smaller first spherical metal particles are embedded in the gaps between the first substructures. The distribution of multiple first spherical metal particles in the gaps increases the number and area of ​​contact points between the electrode and the cell film, significantly increasing the connection stability of the electrode. On the other hand, larger second spherical metal particles contact the top of the first substructure, forming a stable electrical conduction. The larger particle size of the second spherical metal particles also restricts the detachment of the first spherical metal particles in the gaps, effectively increasing the contact area between the textured structure and the electrode, and improving the conductivity of the electrode. In summary, the combined effect of the first and second spherical metal particles significantly improves the connection stability of the textured structure between the first electrode and the substrate, effectively reduces the contact resistance of the electrode, and makes the conductive path smoother. The interlocking connection of the metal particles with the textured structure can improve the structural stability of the cell and reduce current output loss.

[0022] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the back-contact solar cell structure provided in Embodiment 1 of this application; Figure 2 This is a cross-sectional schematic diagram of the electrode located on the textured structure in the back-contact solar cell provided in Embodiment 1 of this application; Figure 3 This is a magnified view of a partial structure of a back-contact solar cell provided in an embodiment of this application; Figure 4a , Figure 4b These are electron microscope images of the first electrode on the textured structure of the back-contact solar cell provided in the embodiments of this application; Figure 4c Another electron microscope image of the first electrode on the textured structure of the back-contact solar cell provided in the embodiments of this application; Figure 5 Electron microscope images of the planar structure of a back-contact solar cell provided in the embodiments of this application; Figure 6a , Figure 6b These are electron microscope images of the first electrode on the planar structure of the back-contact solar cell provided in the embodiments of this application; Figure 7 This is a schematic diagram of the structure of the back-contact solar cell provided in Embodiment 2 of this application; Figure 8 This is a schematic diagram of the structure of a solar tandem battery provided in an embodiment of this application; Figure 9This is a schematic diagram of the structure of a photovoltaic module provided in an embodiment of this application.

[0024] Figure label: 100 - Back contact solar cell; A - Region 1; B - Region 2; 10-Base; 101 - Front surface; 102 - Rear surface; 11 - Front surface passivation layer; 12 - Anti-reflective layer; 110 - Texture structure; 111 - First substructure; 111a - Top; 111b - Bottom; 111c - Sidewall; 120 - Planar structure; 121 - Second substructure; 122 - Third substructure; 130 - Passivated contact structure; 131 - Tunneling layer; 132 - N-type doped layer; 141 - First amorphous silicon layer; 142 - Second amorphous silicon layer; 150-P type doped layer; 160-doped conductive layer; 170 - First transparent conductive layer; 180 - Second transparent conductive layer; 20 - First electrode; 30 - Second electrode; 31-Spherical metal particle; 311-First spherical metal particle; 312-Second spherical metal particle; 32-Disc-shaped metal particles; 33-Ribbon-shaped metal particles; 40-Perovskite Top Cell; 41-First Transport Layer; 42-Perovskite layer; 43-Second Transport Layer; 44 - Transparent conductive layer; 45 - Third electrode; 50-Composite layer; 60-battery string; 61 - Encapsulating film; 62-Cover plate.

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. Detailed Implementation

[0026] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0027] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0028] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0029] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0030] It should be noted that the directional terms such as "upper," "lower," "left," and "right" described in the embodiments of this application are used to describe the angles shown in the accompanying drawings and should not be construed as limiting the embodiments of this application. Furthermore, in the context, it should be understood that when it is mentioned that an element is connected "upper" or "lower" to another element, it can be directly connected to the other element "upper" or "lower," or indirectly connected to the other element "upper" or "lower" through an intermediate element.

[0031] In related technologies, the conductive paste of traditional solar cells contains metal particles. During the sintering process, the poor adhesion between the metal particles and the silicon substrate can easily lead to electrode detachment. Furthermore, the paste is prone to grid breakage or edge diffusion during printing, affecting electrode uniformity and electrical performance. This is especially true for textured solar cells, where the high surface unevenness and large contact area can create gaps between metal particles, resulting in decreased electrode contact stability and increased contact resistance.

[0032] Figure 1 This is a schematic diagram of the back-contact solar cell structure provided in Embodiment 1 of this application; Figure 2 This is a cross-sectional schematic diagram of the electrode located on the textured structure in the back-contact solar cell provided in Embodiment 1 of this application; see reference. Figures 1 to 2 As shown, the back contact solar cell 100 includes a substrate 10, the substrate 10 having a front surface 101 and a rear surface 102 disposed opposite to each other, the rear surface 102 of the substrate 10 having a first region A and a second region B, the first region A having a textured structure 110, and the second region B having a planar structure 120. The first electrode 20 is in contact with the texture structure 110; the texture structure 110 includes a plurality of first substructures 111, and there is a gap between two adjacent first substructures 111. The second electrode 30 is in contact with the planar structure 120; The first electrode 20 and the second electrode 30 each include spherical metal particles 31. The spherical metal particles 31 include first spherical metal particles 311 with a particle size ≤ 1µm and second spherical metal particles 312 with a particle size > 1µm. At least a portion of the first spherical metal particles 311 are located in the gap, and at least a portion of the second spherical metal particles 312 are in contact with the top of the first substructure 111.

[0033] In this application, the electrodes of the back-contact solar cell contain spherical metal particles. On one hand, smaller first spherical metal particles are embedded in the gaps between the first substructures. The distribution of multiple first spherical metal particles in the gaps increases the number and area of ​​contact points between the electrode and the cell film, significantly increasing the connection stability of the electrode. On the other hand, larger second spherical metal particles contact the top of the first substructure, forming a stable electrical conduction. The larger particle size of the second spherical metal particles also restricts the detachment of the first spherical metal particles in the gaps, effectively increasing the contact area between the textured structure and the electrode, and improving the conductivity of the electrode. In summary, the combined effect of the first and second spherical metal particles significantly improves the connection stability of the textured structure between the first electrode and the substrate, effectively reduces the contact resistance of the electrode, and makes the conductive path smoother. The interlocking connection of the metal particles with the textured structure can improve the structural stability of the cell and reduce current output loss.

[0034] According to the embodiments of this application, the solar cell type of this application can be applied to bifacial cells, such as PERC (Passivated Emitter Rear Cell) cells, TOPCon (Tunnel Oxide Passivated Contact solar cell) cells, or can be applied to back contact cells, such as hybrid HBC cells, such as hybrid cells combining TBC (TopCon-Back Contact) and HJT, etc. As long as the cell has a textured surface structure and a planar structure, it should be applicable.

[0035] Please continue reading. Figure 1The substrate 10 can be an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type dopant element, which can be at least one of group V elements such as phosphorus (P), bismuth (Bi), antimony (Sb), or arsenic (As). The P-type semiconductor substrate is doped with a P-type dopant element, which can be at least one of group III elements such as boron (B), aluminum (Al), gallium (Ga), or indium (In).

[0036] The material of the substrate 10 may include monocrystalline silicon, polycrystalline silicon, amorphous silicon, and microcrystalline silicon, etc., and is not limited here.

[0037] The substrate 10 includes a front surface 101 and a rear surface 102 disposed opposite to each other along a first direction Z, where Z can be the thickness direction of the back contact solar cell. The front surface 101 can be the front side of the substrate 10, i.e., the surface of the substrate 10 that can be directly exposed to sunlight; the rear surface 102 can be the back side of the substrate 10, i.e., the surface of the substrate 10 that is not directly exposed to sunlight. Both the front surface 101 and the rear surface 102 can receive sunlight and convert light energy into electrical energy.

[0038] The rear surface 102 of the substrate 10 has a first region A and a second region B. It should be noted that the first region A and the second region B are artificially divided regions, and there is actually no substantial dividing line between the first region A and the second region B.

[0039] In some embodiments, a texturing process may be performed on at least one of the front surface 101 and the rear surface 102 to form a textured structure 110 on at least one of the front surface 101 and the rear surface 102, thereby enhancing the absorption and utilization rate of incident light on the front surface 101 and / or the rear surface 102.

[0040] In some embodiments, the first region A has a textured structure 110, and the second region B has a planar structure 120. The planar structure 120 and the textured structure 110 are located in different types of conductive regions (i.e., the first region and the second region), respectively. The first electrode 20 is in contact with the first region A, and the second electrode 30 is in contact with the second region B.

[0041] The first region A has a texture structure 110. The texture structure 110 refers to a micro-nano-sized structure that can scatter or reflect light to enhance light absorption. The texture structure 110 of this application can be formed by chemical etching, laser etching, mechanical etching or plasma etching on the substrate 10.

[0042] like Figure 2As shown, specifically, the texture structure 110 includes multiple first substructures 111, which can be pyramidal microstructures or non-pyramidal microstructures. Non-pyramidal microstructures can be understood as base / frustum-shaped or stepped morphologies formed due to the destruction of the main body of the pyramidal microstructure. The texture structure 110 of this application enables the screen-printed metal paste to better fill the electrode during electrode formation, especially the first spherical metal particles 311 can be stacked and filled within the gaps, thereby achieving better electrode contact, higher open-circuit voltage, and a higher fill factor.

[0043] In some specific embodiments, the first substructure 111 is a pyramid-shaped microstructure. At least a portion of the top of the first substructure 111 is laser-crystallized to form a platform, for example, by laser ablation of the pyramid tip. The one-dimensional dimension of the top surface of at least a portion of the first substructure 111 is 5nm to 240nm, specifically 5nm, 10nm, 50nm, 80nm, 100nm, 150nm, 180nm, 200nm, 220nm, or 240nm, etc., and is not limited herein. The bottom surface morphology of the first substructure 111 includes at least one of rhombus, square, trapezoid, approximately rhombus, approximately square, and approximately trapezoid.

[0044] It should be noted that the "~" between two values ​​in this application represents the endpoint value including both values. The one-dimensional dimension of the top surface of the first substructure 111 can be the length, width, diagonal length, diameter of the circle, etc., and is not limited here.

[0045] Figure 3 This is a magnified view of a partial structure of the back-contact solar cell provided in the embodiments of this application. Please refer to it. Figure 2 and Figure 3 As shown, the distance L between the tops of two adjacent first substructures 111 is 0.2µm to 3.5µm, specifically 0.2µm, 0.5µm, 0.8µm, 1.0µm, 1.5µm, 1.8µm, 2.0µm, 2.5µm, 3.0µm, 3.5µm, etc., or other values ​​within the above range, which are not limited here. Optionally, the distance between the tops of two adjacent first substructures 111 is 1.5µm to 3.5µm, and more preferably, the distance between the tops of two adjacent first substructures 111 is 2µm to 3µm.

[0046] In some embodiments, the first substructure 111 includes a top 111a away from the front surface of the substrate, a bottom 111b near the front surface of the substrate, and a sidewall 111c connecting the top 111a and the bottom 111b; at least a portion of the first spherical metal particles 311 are in contact with the sidewall 111c and / or the bottom 111b. It is understood that after the smaller-diameter first spherical metal particles 311 are embedded in the gap between the two first substructures 111, they can contact the sidewall 111c and / or the bottom 111b of the first substructure 111. During subsequent sintering, these small-diameter first spherical metal particles 311 can form a stable connection with the battery, and the second spherical metal particles 312 located at the top of the first substructure 111 can form a stable conductive connection with the first spherical metal particles 311 filling the gap.

[0047] In some specific embodiments, such as Figure 3 As shown, in a direction away from and perpendicular to the front surface, the distance H between the top 111a and the bottom 111b of the first substructure 111 is less than or equal to 5 μm. Specifically, it can be 0.5 µm, 0.8 µm, 1.0 µm, 1.5 µm, 1.8 µm, 2.0 µm, 2.5 µm, 3.0 µm, 3.5 µm, 4 µm, 5 µm, etc., or other values ​​within the above range, which are not limited here. Optionally, the distance H is 0.5 µm to 5 µm. Further optionally, the distance H between the top 111a and the bottom 111b of the first substructure 111 is 1 µm to 3 µm.

[0048] In some instances, when measuring the one-dimensional dimensions of the top surface of a pyramid-shaped microstructure, the spacing L between the tops, and the height H, the surface calibration of the film layer can be directly measured using testing instruments (optical microscope, atomic force microscope, scanning electron microscope, transmission electron microscope, etc.).

[0049] Figure 4a , Figure 4b These are electron microscope (EM) images of the first electrode on the textured structure of the back-contact solar cell provided in the embodiments of this application, as shown below. Figure 4a and Figure 4b As shown, small-diameter first spherical metal particles 311 are embedded in the gap between two adjacent first substructures 111, with some of the first spherical metal particles 311 contacting the sidewalls 111c and / or the bottom 111b of the first substructure 111. Some of the second spherical metal particles 312 contact the top 111a of the first substructure 111. The spherical metal particles of different diameters can adapt to the size of the textured structure, contacting the top, body, and bottom of the pyramid-shaped microstructure, enabling the electrode to form effective contact with the textured structure from all directions. This improves the stability of the conductive connection between the electrode and the textured structure and reduces contact resistance.

[0050] Figure 4c Another electron microscope image of the first electrode on the textured structure of the back-contact solar cell provided in the embodiments of this application, as shown below. Figure 4c As shown, both the first and second electrodes include spherical metal particles 31, disc-shaped metal particles 32, and strip-shaped metal particles 33. The combination of these three different types of metal particles can make the electrode have a more complete conductive network inside, thereby improving the mechanical strength of the electrode.

[0051] Please continue reading. Figure 2 ,like Figure 2 As shown, the second region B has a planar structure 120, which can be formed by polishing the back surface of the substrate with an alkaline solution. The planar structure 120 formed by polishing is essentially the base portion of a pyramid-shaped microstructure or a non-pyramid-shaped microstructure, and is not a completely flat surface. The planar structure 120 has a low surface roughness, which is beneficial for achieving greater flatness during the deposition of the tunneling layer and the N-type doped layer. This allows for better morphology and stability of the contact interface between the passivation contact structure and the substrate 10, improving the mobility of photogenerated carriers and thus increasing the carrier concentration, thereby improving the photoelectric conversion performance of the solar cell.

[0052] Figure 5 An electron microscope image of the planar structure of the rear surface of the back contact solar cell provided in the embodiments of this application, as shown below. Figure 5 As shown, the planar structure 120 includes two or more second substructures 121 arranged adjacently but not stacked, and two or more third substructures 122 that are at least partially stacked. The second substructures 121 and third substructures 122 partially overlap, which can reduce the roughness of the back surface of the substrate 10. The planar structure in the first region of this application has a lower roughness, which is beneficial to the contact of the conductive paste in the first region and can also control the light absorption effect of the back surface of the substrate.

[0053] In some embodiments, at least two or more third substructures 122 are partially stacked, and the one-dimensional dimension L2 of the top surface of the third substructure 122 away from the rear surface is greater than or equal to 5 μm and less than or equal to 12 μm.

[0054] Figure 6a , Figure 6b The images shown are electron microscope (EM) images of electrodes on the planar structure of the back-contact solar cell provided in the embodiments of this application, as follows: Figure 6a and Figure 6b As shown, due to the low roughness of the planar structure 120 on the back contact surface of the solar cell, the metal particles in the conductive paste are laid flat on its surface.

[0055] Figure 7 This is a schematic diagram of the structure of the back-contact solar cell provided in Embodiment 2 of this application, as shown below. Figure 7As shown, in this embodiment, the first region A is doped with P-type doping, and the substrate 10 and the second region B are doped with N-type doping.

[0056] In some implementations, such as Figure 7 As shown, the back-contact solar cell also includes a first amorphous silicon layer 141 and a P-type doped layer 150 stacked in the first region A. The first amorphous silicon layer 141 is located in the texture structure 110 of the substrate 10. The P-type doped layer 150 is located on the side of the first amorphous silicon layer 141 away from the substrate 10, and the first electrode 20 is electrically connected to the P-type doped layer 150 located in the first region A.

[0057] In some embodiments, the material of the P-type doped layer 150 may include doped amorphous silicon, doped microcrystalline silicon, and doped nanocrystalline silicon. For example, the P-type doped layer 150 may be doped amorphous silicon with P-type dopant elements or doped nanocrystalline silicon with P-type dopant elements.

[0058] Please continue reading. Figure 7 The back-contact solar cell also includes a tunneling layer 131 and an N-type doped layer 132 stacked in the second region B. The tunneling layer 131 and the N-type doped layer 132 form a passivation contact structure 130, further improving the passivation effect on the back surface of the substrate 10. The doping elements in the N-type doped layer 132 are the same as those in the substrate 10, and a concentration difference is formed between them, thereby forming a high-low junction. This allows the N-type doped layer 132 to form good contact with the second electrode 30 and to form band bending on the surface of the substrate 10, achieving selective carrier transport and reducing recombination losses.

[0059] In some embodiments, the tunneling layer 131 is located on the surface of the planar structure 120 of the substrate; the N-type doped layer 132 is located on the side of the tunneling layer 131 away from the substrate 10.

[0060] The tunneling layer 131 serves to form dangling bonds on the saturated rear surface 102, reducing the defect state density and carrier recombination rate. It also helps to create band bending, enabling selective carrier transport and improving the carrier collection efficiency of the second electrode 30. The tunneling layer 131 can be made of a dielectric material, such as silicon oxide, silicon nitride, or silicon oxynitride. The thickness of the tunneling layer 131 is generally between 1 nm and 2 nm, and can be set according to actual needs without limitation. In some feasible embodiments, the tunneling layer 131 can be formed on the rear surface 102 of the substrate 10 using ozone oxidation, high-temperature thermal oxidation, nitric acid oxidation, chemical vapor deposition, or low-pressure chemical vapor deposition.

[0061] In some embodiments, the N-type doped layer 132 may be made of doped polycrystalline silicon, doped amorphous silicon, doped microcrystalline silicon, or doped nanocrystalline silicon. For example, the N-type doped layer 132 may be doped polycrystalline silicon with an N-type dopant element.

[0062] In some embodiments, the second electrode 30 is electrically connected to the N-type doped layer 132.

[0063] In some embodiments, the back-contact solar cell further includes a second amorphous silicon layer 142 and a doped conductive layer 160 located on the surface of the passivated contact structure 130.

[0064] In some embodiments, the N-type doped layer 132, the P-type doped layer 150, and the doped conductive layer 160 can be a single-layer film structure or a stacked structure including multiple films.

[0065] In some embodiments, the back-contact solar cell further includes a first transparent conductive layer 170 located in a first region A and a second transparent conductive layer 180 located in a second region B. The first transparent conductive layer 170 is located on the side of the P-type doped layer 150 away from the substrate, and the first electrode 20 is electrically connected to the first transparent conductive layer 170. The second transparent conductive layer 180 is located on the side of the N-type doped layer 132 away from the tunneling layer 131, and the second electrode 30 is electrically connected to the second transparent conductive layer 180.

[0066] The first transparent conductive layer 170 can reduce the contact resistance between the first electrode 20 and the P-type doped layer 150, thereby improving the efficiency of the first electrode 20 in collecting charge carriers. The material of the first transparent conductive layer 170 may include at least one of fluorine-doped tin oxide, aluminum-doped zinc oxide, tin-doped indium oxide, tungsten-doped indium oxide, molybdenum-doped indium oxide, cerium-doped indium oxide, and indium hydroxide.

[0067] The second transparent conductive layer 180 can reduce the contact resistance between the second electrode 30 and the N-type doped layer 132, thereby improving the efficiency of the second electrode 30 in collecting charge carriers. The material of the second transparent conductive layer 180 may include at least one of fluorine-doped tin oxide, aluminum-doped zinc oxide, tin-doped indium oxide, tungsten-doped indium oxide, molybdenum-doped indium oxide, cerium-doped indium oxide, and indium hydroxide.

[0068] In the embodiments of this application, the first electrode 20 and the second electrode 30 are formed by screen printing of conductive paste.

[0069] Specifically, the conductive paste includes an organic carrier and metal particles dispersed within the organic carrier, such as... Figure 4cAs shown, the metal particles include spherical metal particles 31, disc-shaped metal particles 32, and strip-shaped metal particles 33. The metal particles can be made of copper. The combination of these three different types of metal particles can make the electrode have a more complete conductive network inside, thereby improving the mechanical strength of the electrode.

[0070] Among them, the spherical metal particles 31 have low rolling resistance, which can improve the flow performance during the screen printing process. Furthermore, the first spherical metal particles 311 with a particle size ≤1µm can fill the gaps between the first substructures 111 of the textured structure, so that the spherical metal particles 31 can fully contact the textured structure 110. The first spherical metal particles 311 distributed in the gaps can increase the contact points and significantly increase the connection stability of the electrodes.

[0071] At least some of the disc-shaped metal particles 32 can contact the top of the first substructure 111, which can enhance the surface contact. This surface-to-surface contact method can effectively increase the contact area and reduce the resistivity. Furthermore, the disc-shaped metal particles 32 can also improve the lateral transport of charge carriers and enhance the current collection efficiency of the sub-gate and the main gate. In addition, the disc-shaped metal particles 32 and the second spherical metal particles 312 cooperate with each other to prevent the first spherical metal particles 311 in the gap from detaching from the gap, reduce the oxidation area, and improve the conductivity stability under humid and hot environments.

[0072] The strip-shaped metal particles 33 can construct long-range electrical channels. These strip-shaped particles can form an interwoven network within the organic carrier, similar to beads, creating a complete conductive network. This reduces the risk of breakage within the network and, after sintering, helps improve the electrode's resistance to bending and reduces the risk of electrode cracking and detachment.

[0073] In some embodiments, the spherical metal particles 31 include a first spherical metal particle 311 with a particle size ≤ 1µm and a second spherical metal particle 312 with a particle size > 1µm. Exemplarily, the particle size of the first spherical metal particle 311 can be 1µm, 0.8µm, 0.5µm, 0.4µm, 0.3µm, 0.2µm, 0.1µm, 0.05µm, etc., or other values ​​within the above range, which are not limited here. Optionally, the particle size of the first spherical metal particle 311 is 400nm~900nm. The particle size of the second spherical metal particle 312 can be 1.1µm, 1.2µm, 1.5µm, 1.8µm, 2.0µm, 2.2µm, 2.5µm, 3.0µm, etc., or other values ​​within the above range, which are not limited here. Optionally, the particle size of the second spherical metal particle 312 is 1.1µm~1.5µm.

[0074] In some embodiments, the proportion of first spherical metal particles 311 in the conductive paste is greater than that of second spherical metal particles 312, meaning a higher proportion of smaller particles. This facilitates the embedding of smaller particles into the gaps of the textured structure during screen printing. The accumulation of these smaller particles within the gaps helps fill the voids between the first substructures, contributing to the formation of a dense, low-resistance electrode and resulting in a more stable connection between the electrode and the battery cell. Specifically, the ratio of first spherical metal particles 311 to second spherical metal particles 312 in the conductive paste can be (6~9):(1:4), specifically 6:4, 7:3, 7.5:2.5, 8:2, 8.5:1.5, 9:1, etc., or other values ​​within the aforementioned range, which are not limited here. By controlling the proportion of spherical metal particles of different sizes in the conductive paste, a more stable metal-silicon contact interface can be formed after sintering, helping to reduce resistance, improve electrode conductivity and durability, reduce carrier recombination rate inside the battery, and improve charge transport efficiency.

[0075] In some embodiments, the thickness of the disc-shaped metal particles 32 is 0.3µm to 2.5µm. Exemplarily, the thickness of the disc-shaped metal particles 32 can be 0.3µm, 0.5µm, 0.8µm, 1.0µm, 1.5µm, 1.8µm, 2.0µm, 2.5µm, etc., or other values ​​within the above range, which are not limited here. The particle size of the disc-shaped metal particles 32 is 2µm to 6µm. Exemplarily, the particle size of the disc-shaped metal particles 32 can be 2µm, 2.5µm, 3µm, 3.5µm, 4µm, 4.5µm, 5µm, 5.5µm, 6µm, etc., or other values ​​within the above range, which are not limited here. Roughening the surface of the disc-shaped metal particles 32 can improve the contact between the disc-shaped metal particles and film layers with different structures, thereby improving the conductivity of the electrode.

[0076] In some embodiments, the thickness of the strip metal particle 33 is 20nm to 200nm. For example, the thickness of the strip metal particle 33 can be 20nm, 50nm, 80nm, 100nm, 130nm, 150nm, 180nm, 200nm, etc., or other values ​​within the above range, which are not limited here. The length of the strip metal particle 33 is 2µm to 50µm. For example, the length of the strip metal particle 33 can specifically be 2µm, 5µm, 7µm, 10µm, 15µm, 20µm, 25µm, 30µm, 35µm, 40µm, 45µm, 50µm, etc., or other values ​​within the above range, which are not limited here.

[0077] In some embodiments, the spherical metal particles 31 account for more than or equal to 50% of the total mass of all metal particles. Specifically, this could be 50%, 55%, 60%, 65%, 70%, 75%, 80%, or other values ​​within the aforementioned range, which are not limited here. The disc-shaped metal particles 32 account for less than 40% of the total mass of all metal particles. Specifically, this could be 40%, 35%, 30%, 25%, 20%, 15%, 10%, or other values ​​within the aforementioned range, which are not limited here. The strip-shaped metal particles 33 account for less than 10% of the total mass of all metal particles. Specifically, this could be 10%, 8%, 7%, 6%, 5%, 4%, 2%, or other values ​​within the aforementioned range, which are not limited here.

[0078] To better achieve high conductivity of the electrodes simultaneously, the mass percentages of spherical metal particles 31, disc-shaped metal particles 32, and ribbon-shaped metal particles 33 are 55%~80%, 10%~35%, and 2%~10%, respectively. Further optionally, the mass percentages of spherical metal particles, disc-shaped metal particles, and ribbon-shaped metal particles are 60%~70%, 20%~30%, and 5%~10%, respectively.

[0079] In some specific embodiments, the conductive paste also includes an organic carrier, which may include ethyl cellulose, terpineol, and a dispersant. Dispersing metal particles in the organic carrier can make the viscosity, thixotropy, and drying speed of the conductive paste more suitable for high-precision screen printing.

[0080] In some embodiments, the distribution ratio of the first region A on the rear surface 102 of the substrate 10 is 50%-80%, specifically it can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, etc., or other values ​​within the above range, which are not limited here. The distribution ratio of the second region B on the rear surface 102 of the substrate 10 is 20%-50%; specifically it can be 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc., or other values ​​within the above range, which are not limited here.

[0081] This application, by limiting the spacing between two adjacent first regions or two adjacent second regions on the substrate 10 and limiting the distribution ratio of the first and second regions on the rear surface of the substrate, can form a PN junction with excellent conductivity on the substrate 10 during the fabrication of solar cells, thereby improving the photoelectric performance of the fabricated solar cells.

[0082] This application provides a tandem solar cell, including a crystalline silicon bottom cell and a perovskite top cell. The crystalline silicon bottom cell includes the aforementioned back contact solar cell 100, and the perovskite top cell is electrically connected to the crystalline silicon bottom cell.

[0083] like Figure 8 As shown, in some embodiments, a composite layer 50 is disposed between the perovskite top cell 40 and the back-contact solar cell 100 (i.e., the crystalline silicon bottom cell). The composite layer 50 can be a transparent conductive oxide, such as ITO (indium tin oxide), AZO (aluminum-doped zinc oxide), FTO (fluorine-doped tin oxide), or ATO (antimony-doped tin oxide). The perovskite top cell 40 has a wider bandgap than the crystalline silicon bottom cell. Therefore, stacking the perovskite top cell 40 on top of the crystalline silicon bottom cell can give the tandem cell a wider spectral response range, thereby maximizing the utilization of solar energy and improving the efficiency of the solar cell.

[0084] The perovskite top solar cell 40 includes a first transport layer 41, a perovskite layer 42, a second transport layer 43, a transparent conductive layer 44, and a third electrode 45 arranged along a first direction Z. One of the first transport layer 41 and the second transport layer 43 is an electron transport layer, and the other is a hole transport layer. The electron transport layer can be a metal oxide or a fullerene derivative, and the hole transport layer can be a metal oxide or a self-assembled molecular layer (SAM). The transparent conductive layer 44 can be IZO (indium zinc oxide), a transparent conductive oxide. The third electrode 45 is disposed on the transparent conductive layer 44 and electrically connected to it. The third electrode 45 can be sintered from a metal paste, which can include at least one of silver, aluminum, copper, tin, gold, lead, or nickel.

[0085] The perovskite material in the perovskite top cell 40 has a high light absorption coefficient and a long carrier diffusion distance. After the photons absorbed by the perovskite material are converted into electrons, they are easily collected by the electrodes with low loss. Therefore, it can generate high photogenerated voltage and current, making the perovskite exhibit high photoelectric conversion efficiency.

[0086] Figure 9 This is a schematic diagram of the structure of a photovoltaic module provided in an embodiment of this application, such as... Figure 9 As shown, the photovoltaic module includes: The battery string 60 is formed by connecting multiple cell sub-cells of solar cells formed by the preparation method provided in the foregoing embodiments; Encapsulating film 61 is used to cover the surface of the battery string; Cover plate 62 is used to cover the surface of the encapsulating film 61 that is away from the battery string.

[0087] It should be noted that solar cells are electrically connected to form multiple cell strings, which are connected in series and / or parallel. Since solar cells consist of sub-cells, and these sub-cells are formed by dividing a whole solar cell into sections, the decrease in current through the sub-cells can improve the power loss of the photovoltaic module, thereby increasing the photoelectric conversion efficiency of the photovoltaic module.

[0088] In one or more embodiments, reference is made to Figure 9 As shown, multiple battery strings can be electrically connected via solder ribbons. The electrodes of the battery sub-cells with the same polarity are arranged in the same direction, or in other words, the positive electrode of each battery sub-cell faces the same side, so that the solder ribbons connect different sides of two adjacent battery sub-cells respectively. In some embodiments, the battery sub-cells can also be arranged with electrodes of different polarities facing the same side, that is, the electrodes of multiple adjacent battery sub-cells are arranged in the order of first polarity, second polarity, and first polarity respectively, then the solder ribbons connect two adjacent battery sub-cells on the same side.

[0089] In one or more embodiments, there is no gap between the battery sub-cells, that is, the battery sub-cells overlap each other.

[0090] In one or more embodiments, the encapsulating film includes a first encapsulating layer and a second encapsulating layer. The first encapsulating layer covers one of the front or back sides of the solar cell, and the second encapsulating layer covers the other of the front or back sides of the solar cell. Specifically, at least one of the first encapsulating layer or the second encapsulating layer can be an organic encapsulating film such as polyvinyl butyral (PVB) film, ethylene-vinyl acetate copolymer (EVA) film, polyvinyl octene elastomer (POE) film, or polyethylene terephthalate (PET) film.

[0091] In some cases, the first encapsulation layer and the second encapsulation layer still have a boundary line before lamination. After lamination, the photovoltaic module no longer has the concept of a first encapsulation layer and a second encapsulation layer, that is, the first encapsulation layer and the second encapsulation layer have formed an integral encapsulation film.

[0092] In one or more embodiments, the cover plate can be a glass cover plate, a plastic cover plate, or other cover plate with light-transmitting function. Specifically, the surface of the cover plate facing the encapsulating film can be an uneven surface, thereby increasing the utilization rate of incident light. The cover plate includes a first cover plate and a second cover plate, the first cover plate being opposite to the first encapsulation layer, and the second cover plate being opposite to the second encapsulation layer.

[0093] The present application is further illustrated below through embodiments, accompanying drawings, and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present application. However, it is apparent that one or more embodiments may be implemented without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0094] Example 1 The specific steps in fabricating a back-contact solar cell include: Step 1: Provide substrate 10, and perform texturing and oxidation treatments on substrate 10 in sequence.

[0095] Step 2: A front surface passivation layer 11 and an anti-reflection layer 12 are sequentially stacked on the front surface of the substrate 10 in a direction away from the substrate 10.

[0096] Step 3: After acid washing, the back surface of the substrate 10 is polished with an alkaline solution to form a planar structure on the back surface of the substrate 10.

[0097] Step 4: A tunneling layer 131 is formed on the planar structure of the back surface of the substrate 10; a polycrystalline silicon thin film layer is deposited on the surface of the tunneling layer 131, and the polycrystalline silicon thin film layer is doped to form an N-type doped layer 132, wherein the tunneling layer 131 and the N-type doped layer 132 constitute a passivation contact structure 130.

[0098] Step 5: Laser etching is used to define and form the first region A, and the region with the planar structure 120 is designated as the second region B. Then, an alkaline solution is used to etch the first region A on the back surface of the substrate, resulting in a textured structure 110 in the first region A. The textured structure includes multiple first substructures, with the distance between the tops of two adjacent first substructures ranging from 0.2µm to 3.5µm, and at least some of the top surfaces of the first substructures having a one-dimensional dimension of 5nm to 240nm.

[0099] Step six: deposit an amorphous silicon layer on the back surface of the substrate 10, including a first amorphous silicon layer 141 located in the first region A and a second amorphous silicon layer 142 located in the second region; perform doping treatment on the amorphous silicon layer to form a P-type doped layer 150 and a doped conductive layer 160.

[0100] Step 7: A transparent conductive layer is fabricated on the entire surface of the P-type doped layer 150 and the doped conductive layer 160, and a groove is made in the transparent conductive layer to obtain the battery body, so that the first transparent conductive layer 170 located in the first region of the battery body and the second transparent conductive layer 180 located in the second region are electrically isolated.

[0101] Step 8: Conductive paste is printed on the first transparent conductive layer 170 and the second transparent conductive layer 180 respectively. After drying and sintering, the first electrode 20 and the second electrode 30 are obtained, thus obtaining a solar cell.

[0102] In this embodiment, the metal particles in the conductive paste include spherical metal particles, disc-shaped metal particles, and ribbon-shaped metal particles. The spherical metal particles account for approximately 68% of the total mass of all metal particles. The spherical metal particles include first spherical metal particles with a particle size ≤ 1µm and second spherical metal particles with a particle size > 1µm. The disc-shaped metal particles account for approximately 25% of the total mass of all metal particles, and the ribbon-shaped metal particles account for approximately 7% of the total mass of all metal particles.

[0103] In this embodiment, the solar cell exhibits significantly improved stability of the textured connection between the first electrode and the substrate due to the combined action of the first and second spherical metal particles. The interlocking textured structure of the spherical metal particles forms a mechanical bond, resulting in a significantly higher peeling force compared to solar cells fabricated with conductive paste containing only single spherical metal particles (particle size > 1µm). The electrode is less prone to peeling or delamination. Furthermore, it effectively reduces the contact resistance of the electrode, ensuring stable interlocking particles maintain low contact resistance and smoother conductive pathways. The interlocking textured structure of the metal particles enhances the structural stability of the cell and reduces current output loss.

[0104] The above are merely optional embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A back-contact solar cell, characterized in that, include: A substrate having a front surface and a rear surface disposed opposite to each other, the rear surface of the substrate having a first region and a second region, the first region having a textured structure and the second region having a planar structure; A first electrode is in contact with the texture structure; the texture structure includes a plurality of first substructures, with a gap between two adjacent first substructures; The second electrode is in contact with the planar structure; The first electrode and the second electrode each include spherical metal particles. The spherical metal particles include first spherical metal particles with a particle size ≤ 1µm and second spherical metal particles with a particle size > 1µm. At least a portion of the first spherical metal particles are located within the gap, and at least a portion of the second spherical metal particles are in contact with the top of the first substructure.

2. The back-contact solar cell according to claim 1, characterized in that, The proportion of the first spherical metal particles is greater than the proportion of the second spherical metal particles.

3. The back-contact solar cell according to claim 1, characterized in that, The first substructure includes a top portion away from the front surface of the substrate, a bottom portion close to the front surface of the substrate, and a sidewall connecting the top portion and the bottom portion; At least a portion of the first spherical metal particle is in contact with the sidewall and / or the bottom.

4. The back-contact solar cell according to claim 1, characterized in that, The distance between the tops of two adjacent first substructures is 0.2µm to 3.5µm.

5. The back-contact solar cell according to claim 1, characterized in that, The first electrode and the second electrode also include disc-shaped metal particles with a thickness of 0.3µm to 2.5µm and a particle size of 2µm to 6µm.

6. The back-contact solar cell according to claim 1, characterized in that, The first electrode and the second electrode further include strip-shaped metal particles with a thickness of 20 nm to 200 nm and a length of 2 µm to 50 µm.

7. The back-contact solar cell according to claim 5, characterized in that, At least a portion of the disc-shaped metal particles are in contact with the top of the first substructure.

8. The back-contact solar cell according to claim 5, characterized in that, At least a portion of the top surface of the first substructure has a one-dimensional dimension of 5nm to 240nm, and the disc-shaped metal particle or the second spherical metal particle is in contact with the top surface of the first substructure.

9. The back-contact solar cell according to claim 3, characterized in that, In a direction away from and perpendicular to the front surface, the distance between the top and bottom of the first substructure is less than or equal to 5 μm.

10. The back-contact solar cell according to any one of claims 1 to 9, characterized in that, The first substructure is a pyramid-shaped microstructure.

11. The back-contact solar cell according to any one of claims 1 to 9, characterized in that, The raw materials for the first electrode and the second electrode are conductive pastes. The conductive pastes include an organic carrier and metal particles dispersed in the organic carrier. The metal particles include spherical metal particles, disc-shaped metal particles, and ribbon-shaped metal particles. The spherical metal particles account for more than or equal to 50% of the total mass of all metal particles, the disc-shaped metal particles account for less than 40% of the total mass of all metal particles, and the ribbon-shaped metal particles account for less than 10% of the total mass of all metal particles.

12. The back-contact solar cell according to any one of claims 1 to 9, characterized in that, The back-contact solar cell also includes: A first amorphous silicon layer is located on the surface of the textured structure of the substrate; A P-type doped layer is located on the side of the first amorphous silicon layer away from the substrate; the first electrode is electrically connected to the P-type doped layer. A tunneling layer, the tunneling layer being located on the surface of the planar structure of the substrate; An N-type doped layer is located on the side of the tunneling layer away from the substrate; the second electrode is electrically connected to the N-type doped layer.

13. The back-contact solar cell according to claim 12, characterized in that, The back-contact solar cell also includes: A first transparent conductive layer is located on the side of the P-type doped layer away from the substrate; the first electrode is electrically connected to the first transparent conductive layer. A second transparent conductive layer is located on the side of the N-type doped layer away from the tunneling layer; the second electrode is electrically connected to the second transparent conductive layer.

14. The back-contact solar cell according to any one of claims 1 to 9, characterized in that, The first region accounts for 50%-80% of the distribution on the rear surface of the substrate; the second region accounts for 20%-50% of the distribution on the rear surface of the substrate.

15. A stacked battery, characterized in that, It includes a crystalline silicon bottom cell and a perovskite top cell, wherein the crystalline silicon bottom cell includes a back-contact solar cell according to any one of claims 1 to 14, and the perovskite top cell is electrically connected to the crystalline silicon bottom cell.

16. A photovoltaic module, characterized in that, The photovoltaic module includes a back-contact solar cell according to any one of claims 1 to 14, wherein the back-contact solar cells are electrically connected to form a solar cell string.

Images