Solar cell and photovoltaic module

Abstract

Solar cell, featuring: a substrate; a passivation layer that is formed over an area of ​​the substrate; Fingers arranged in a first direction and extending in a second direction, the fingers penetrating the passivation layer to be electrically connected to the substrate, and having first fingers and second fingers arranged alternately; Connecting electrodes, wherein each of the connecting electrodes is in electrical contact with end sections of at least two adjacent first fingers on the same side and has one of the following features: at least one first connecting section and one second connecting section connected to each other, wherein the first connecting section is connected to an end section of each finger of the at least two adjacent first fingers, the first connecting section and the respective finger have an included angle that is not equal to 180°, and the first connecting section and the second connecting section have an included angle that is not equal to 180°; and a curved, wave-like structure.

Description

TECHNICAL FIELD

[0001] Embodiments of this disclosure relate generally to the field of photovoltaics, and more particularly to a solar cell and a photovoltaic module. BACKGROUND

[0002] Due to the gradual depletion of fossil energy sources, solar cells, which convert the sun's light energy into electrical energy, are increasingly being used as a new energy alternative. Solar cells utilize the principle of photovoltaics to generate charge carriers and then use electrodes to extract the charge carriers, enabling efficient use of electrical energy.

[0003] Conventional solar cells mainly include interfinger back contact (IBC) cells, passivated tunnel oxide contact (TOPCON) cells, passivated emitter real cells (PERC), heterojunction cells, etc. The photovoltaic conversion efficiency of solar cells is improved by reducing optical losses and photogenerated recombination of charge carriers on the surface and in the body of a silicon substrate through various film layer settings and functional constraints.

[0004] In conventional solar cells, the current generated by the cell is collected and output through finger electrodes and busbars, and the current generated by the cell is transferred to one end of the module through pads on the busbars. However, the solar cells in existing technology have a weak current collection capacity, which hinders the improvement of the photoelectric conversion efficiency of the solar cells. SUMMARY

[0005] Some embodiments of this disclosure provide a solar cell and a photovoltaic module that at least contribute to improving the weak current collection capability of edge grid lines in the solar cell.

[0006] Some embodiments of this disclosure provide a solar cell comprising: a substrate; a passivation layer formed over a surface of the substrate; fingers comprising rows of first fingers and rows of second fingers arranged alternately along a first direction, each of the fingers extending in a second direction, each row of first fingers comprising a corresponding set of first fingers arranged at intervals in the second direction, and each row of second fingers comprising a corresponding set of second fingers arranged at intervals in the second direction, each row of first fingers being located between two adjacent rows of second fingers, and wherein the fingers penetrate the passivation layer to be electrically connected to the substrate;Connecting electrodes, each of the connecting electrodes being in electrical contact with end portions of at least two adjacent first fingers on one side of the rows of first fingers and having either a cross-sectional structure or a curved wave-like structure; wherein the cross-sectional structure comprises at least a first connecting portion and a second connecting portion connected to each other, and wherein the first connecting portion is connected to an end portion of a respective one of the at least two adjacent first fingers, the first connecting portion and the respective finger having an included angle that is not equal to 180°, and the first connecting portion and the second connecting portion having an included angle that is not equal to 180°.

[0007] In some embodiments, the substrate has a first boundary, a second boundary, a third boundary, and a fourth boundary that are adjacent to each other, the first boundary being opposite the third boundary in the first direction and the second boundary being opposite the fourth boundary in the second direction; wherein the solar cell further comprises edge rails adjacent the second boundary; and wherein the edge rails are in electrical contact with the second fingers arranged in the first direction.

[0008] In some embodiments, the solar cell further comprises solder pads provided on the passivation layer, wherein each of the solder pads is electrically connected to a respective edge bar, and wherein each of the solder pads and the second boundary have a first distance that is greater than a second distance between one of the edge bars and the second boundary.

[0009] In some embodiments, each of the connecting electrodes and the second boundary have a third distance that is greater than the second distance.

[0010] In some embodiments, each of the edge rails comprises a first interconnection line extending in the first direction, at least one electrical interconnection line, and an interconnection structure; wherein the at least one electrical interconnection line is provided between the first interconnection line and the interconnection structure and extends in a direction intersecting the first direction, the interconnection structure is provided on and in electrical contact with some of the second fingers, and the first interconnection line is provided on a side of the at least one electrical interconnection line proximate the second boundary; and wherein a respective solder joint is provided on the interconnection structure.

[0011] In some embodiments, the interconnect structure includes a hollow region, and the respective solder joint partially overlaps the hollow region.

[0012] In some embodiments, each of the connecting electrodes comprises a plurality of groups of first and second connecting portions arranged alternately.

[0013] In some embodiments, the connecting electrodes comprise the same material as the fingers.

[0014] In some embodiments, the curved wave-like structure comprises a plurality of arcs, each having a radian in the range of 0.1 rad to π.

[0015] In some embodiments, each of the connecting electrodes has a width of less than 30 µm.

[0016] Some embodiments of this disclosure further provide a photovoltaic module comprising: at least one cell string, each formed by connecting a plurality of solar cells according to any one of the above embodiments; at least one solder strip, each configured to electrically connect the plurality of solar cells to each form the at least one cell string; at least one encapsulating adhesive film, each configured to cover a surface of a respective cell string; and at least one cover plate, each configured to cover a surface of a respective encapsulating adhesive film facing away from the plurality of cell strings.

[0017] In some embodiments, the at least one solder strip is soldered to the solder pads of each of the plurality of solar cells, and each of the at least one solder strip has an orthographic projection on the substrate that does not overlap with an orthographic projection of a corresponding one of the edge rails on the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] One or more embodiments are described by way of example with corresponding figures in the accompanying drawings, which are not intended to be limiting of these embodiments. Unless otherwise stated, the figures in the accompanying drawings do not represent scale limitations. To better illustrate the technical solutions in the embodiments of this disclosure or conventional technologies, the accompanying drawings that must be used in the embodiments are briefly described below, and it is obvious that the drawings in the following description are only some embodiments of this disclosure. For a person skilled in the art, further drawings can also be made after these drawings. Fig. 1 is a schematic structural diagram of a first solar cell according to an embodiment of this disclosure. Fig. 2 is a cross-sectional view of Fig. 1 along the section line A1-A2. Fig. 3 is a schematic structural diagram of a second solar cell according to an embodiment of this disclosure. Fig. 4 is a schematic structural diagram of a connection electrode in the second solar cell according to an embodiment of this disclosure. Fig. 5 is a schematic structural diagram of a third solar cell according to an embodiment of this disclosure. Fig. 6 is an enlarged partial view of section B in Fig. 5. Fig. 7 is a schematic structural diagram of a connection electrode in the third solar cell according to an embodiment of this disclosure. Fig. 8 is a schematic structural diagram of a fourth solar cell according to an embodiment of this disclosure. Fig. 9 is an enlarged partial view of section C in Fig. 8. Fig. 10 is a schematic structural diagram of a photovoltaic module according to an embodiment of this disclosure. Fig. 11 is a cross-sectional view of Fig. 10 along the section line M1-M2. Fig. 12 is a partial schematic structural diagram of a cell and a solder strip in a photovoltaic module according to an embodiment of this disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] On this basis, it can be seen that the current collection capacity of the edge electrodes in conventional solar cells is weak.

[0020] It is found that one of the reasons for the weak current collection ability of the edge electrodes of the conventional solar cell is due to a peculiarity of the IBC cell in the conventional solar cells, that is, a back surface of the cell has electrodes (fingers) of the first polarity and electrodes (fingers) of the second polarity, a gap on the electrode of the first or the second polarity needs to be arranged to allow a solder strip or a bus bar connected to the electrode of the other of the first and second polarities to pass through, so portions of the fingers near the edges of the cell may not be able to collect the current.

[0021] In the embodiments of this disclosure, the connecting electrodes are provided, wherein each connecting electrode is in electrical contact with the end portions of at least two adjacent first fingers on the same side, and a hollow square electrode is formed by the connecting electrode and the fingers, so that an area of ​​a portion of the electrode at the edge is increased and the current collection capability is improved.

[0022] In addition, the connecting electrode has a curved, wave-like shape. In the conventional process for manufacturing the connecting electrode, the scraper must press the paste into the holes of the screen plate in a direction parallel to the arrangement direction of the fingers and perpendicular to the extension direction of the fingers and the substrate, so that the paste covers an area of ​​the passivation layer. Since the total area of ​​the holes on the same horizontal line is small, the paste can quickly fill the holes, allowing the holes on different horizontal lines to communicate with each other, thus ensuring good continuity of the connecting electrode to avoid gaps, and the connecting electrode can fully fulfill the function of current collection.The connection electrode has a curved, wave-like shape, compared with a straight, linear shape, a contact area between an end portion of the connection electrode and an end portion of the first finger connected to the connection electrode is large, so that the problem of the gap between the connection electrode and the first finger is avoided, and the contact area between the connection electrode and the first finger is large, so that the contact resistance between the connection electrode and the first finger is small, which improves the photoelectric conversion efficiency of the solar cell.

[0023] The connection electrode includes at least a first connection portion and a second connection portion connected to each other, wherein an included angle between the first connection portion and the finger is not equal to 180°, and an included angle between the first connection portion and the second connection portion is not equal to 180°. When manufacturing the connection electrode with the first connection portion and the second connection portion, less paste filling is required for the connection electrodes on the same horizontal line, so that the paste can be continuous on the surface of the passivation layer and no gap is formed between the first finger and the first connection portion.

[0024] Embodiments of this disclosure are described in detail below with reference to the accompanying drawings. Those skilled in the art will understand that many technical details are set forth in the embodiments of this disclosure to enable readers to better understand this disclosure. However, the technical solutions set forth in this disclosure can be implemented without these technical details and various changes and modifications based on the following embodiments.

[0025] Fig. 1 is a schematic structural diagram of a first solar cell according to an embodiment of this disclosure, and Fig. 2 is a schematic cross-sectional diagram of Fig. 1 along the section line A1-A2.

[0026] With reference to Fig. 1 and Fig. 2, the solar cell comprises a substrate 100, a passivation layer 123 formed over a surface of the substrate 100, and fingers comprising rows of first fingers 121 and rows of second fingers 122 arranged alternately along a first direction Y, each of the fingers extending in a second direction X, each row of first fingers 121 comprising a corresponding set of first fingers 121 arranged at intervals in the second direction, and each row of second fingers 122 comprising a corresponding set of second fingers 122 arranged at intervals in the second direction X, each row of first fingers 121 being located between two adjacent rows of second fingers 122. The fingers penetrate the passivation layer 123 and are electrically connected to the substrate 100.

[0027] In some embodiments, the solar cell may be an IBC cell, ie, it comprises first fingers 121 having first polarities and second fingers 122 having second polarities on the same side of the substrate 100.

[0028] In some embodiments, the material of substrate 100 comprises an elemental semiconductor material. Specifically, the elemental semiconductor material is made of a single element, e.g., silicon or germanium. The elemental semiconductor material may be in a monocrystalline state, a polycrystalline state, an amorphous state, or a microcrystalline state (simultaneously comprising the monocrystalline state and the amorphous state). For example, silicon may be at least one of monocrystalline silicon, polycrystalline silicon, amorphous silicon, or microcrystalline silicon.

[0029] In some embodiments, the material of substrate 100 comprises a compound semiconductor material. Common compound semiconductor materials include, but are not limited to, silicon germanium, silicon carbide, gallium arsenide, indium gallium, perovskite, cadmium telluride, copper indium selenium, etc. Substrate 100 may also be a sapphire substrate, a silicon substrate on an insulator, or a germanium substrate on the insulator.

[0030] In some embodiments, the substrate 100 comprises an N-type semiconductor substrate or a P-type semiconductor substrate. The N-type semiconductor substrate is doped with an N-type dopant, and the N-type dopant can be any Group V element, such as phosphorus (P), bismuth (Bi), antimony (Sb), arsenic (As), etc. The P-type semiconductor substrate is doped with a P-type dopant, and the P-type dopant can be any Group III element, such as boron (B), aluminum (Al), gallium (Ga), indium (In), etc.

[0031] In some embodiments, the substrate 100 includes first and second surfaces that are opposite to each other. In some embodiments, the first surface of the substrate 100 is a front surface and the second surface is a back surface. In some embodiments, the first surface of the substrate 100 is a back surface and the second surface is a front surface. That is, the solar cell is a single-sided cell, and the front surface can be used as a light-receiving surface for receiving incident light, and the back surface can be used as a backlight surface. In some embodiments, the solar cell is a double-sided cell, meaning both the first and second surfaces of the substrate 100 can be used as light-receiving surfaces for receiving incident light. For example, in some embodiments of this disclosure, the fingers are formed on the second surface of the substrate, and the second surface of the substrate is the back surface.

[0032] In some embodiments, the first surface of the substrate 100 has a textured structure, and the textured structure includes a regularly shaped pyramidal textured structure and an irregularly shaped black silicon. A sloped surface of the textured structure can increase the internal reflection of incident light, thereby improving the absorption and utilization rate of the substrate for incident light and further increasing the efficiency of the solar cell.

[0033] In some embodiments, the first surface of the substrate 100 has a front surface field (FSF) in which doped ions have a conductivity type that matches the conductivity type of the doped ions in the substrate, and the area minority concentration is reduced by utilizing the field passivation effect, so that the area recombination rate is reduced, while the series resistance is reduced and the electron transfer capability is improved.

[0034] In some embodiments, the first surface of the substrate 100 is the front surface and the second surface is the back surface. The second surface of the substrate 100 is a polishing surface. The polishing surface refers to a flat surface formed by a polishing solution or laser etching to remove the patterned structure of the surface. After polishing, the flatness of the second surface is increased, the reflection of long-wavelength light is enhanced, and the secondary absorption of projection light is promoted, thereby improving the short-circuit current. By reducing the specific surface area of ​​the second surface, recombination on the second surface is reduced and the passivation effect of the second surface is improved.

[0035] In some embodiments, the second surface comprises first doped regions 108 and second doped regions 109 spaced apart and arranged alternately, wherein the first doped regions 108 are doped with dopant ions of a conductivity type the same as that of the substrate 100, and the second doped regions 109 are doped with dopant ions of a conductivity type different from that of the substrate 100. For example, the substrate is an N-type substrate, the first doped regions 108 are N-type regions, the second doped regions 109 are P-type regions, PN junctions are formed between the second doped regions 109 and the substrate 100, and charge carriers are effectively conducted therethrough.

[0036] In some embodiments, the doping concentration of the doping ions in a first doping region 108 is greater than the doping concentration of the doping ions in the substrate 100, a high-low junction is formed between the first doping region 108 and the substrate 100, and the ability to conduct charge carriers is improved.

[0037] A gap or isolation structure is provided between a first doped region 108 and a second doped region 109 to achieve automatic isolation between regions of different conductivity types, thereby preventing heavily doped P-type regions and N-type regions at the back of the IBC cell from forming tunnel junctions that cause electrical leakage and degrade cell efficiency.

[0038] In some embodiments, the passivation layer 123 is formed on the first doped regions 108 and the second doped regions 109.

[0039] The passivation layer 123 may comprise a single-layer film layer structure or a laminated film layer structure, and a material of the passivation layer 123 includes at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon oxide carbonitride, titanium oxide, hafnium oxide, aluminum oxide, etc.

[0040] In some embodiments, the first fingers 121 penetrate the passivation layer 123 to be electrically connected to the first doped regions 108, and the second fingers 122 penetrate the passivation layer 123 to be electrically connected to the second doped regions 109.

[0041] The first fingers 121 and the second fingers 122 serve to collect and combine the current of the solar cell. Each of the first fingers 121 and the second fingers 122 is sintered from a burn-through paste. One method of forming the first fingers 121 or the second fingers 122 includes printing a metal paste onto a portion of a surface of the passivation layer 123 or an anti-reflective layer using a screen printing process. The metal paste may comprise at least one of the elements silver, aluminum, copper, tin, gold, lead, or nickel. In some embodiments, the metal paste comprises a material with a highly corrosive component, such asGlass powder, so that the corrosive component attacks the passivation layer 123 or the anti-reflection layer in the sintering process, whereby the metal paste penetrates into the passivation layer 123 or the non-reflective layer so that it is in electrical contact with the first doped regions 108 or the second doped regions 109.

[0042] In some embodiments, the solar cell includes a front passivation layer 124 formed over the first surface (i.e., the front surface). The front passivation layer 124 may be a single-layer structure or a laminated structure, and the material of the front passivation layer 124 comprises at least one of silicon oxide, silicon nitride, silicon oxynitride, silicon oxide carbonitride, titanium oxide, hafnium oxide, aluminum oxide, etc.

[0043] In some embodiments, the solar cell further comprises anti-reflective layers, each formed on a side of the passivation layer facing away from the substrate and on a side of the front passivation layer facing away from the substrate. Each of the first fingers penetrates the anti-reflective layer and the passivation layer to be in electrical contact with a corresponding first doped region, and each of the second fingers penetrates the anti-reflective layer and the passivation layer to be in electrical contact with a corresponding second doped region. The refractive index of the anti-reflective layer is high, thus reducing reflection damage at the backside of the cell, and the material of the anti-reflective layer can be silicon nitride or silicon oxynitride, or both.

[0044] In some embodiments, the fingers extend in the second direction X, the first direction Y and the second direction X may be perpendicular to each other, or an included angle between the first direction Y and the second direction X may be less than 90 degrees, e.g., 60 degrees, 45 degrees, 30 degrees, etc., as long as the first direction Y and the second direction X are not the same direction. To simplify the description and improve understanding, the first direction Y and the second direction X are illustrated as perpendicular to each other as an example. In a specific application, the included angle between the first direction Y and the second direction X may be adjusted according to actual needs and application scenarios, which is not limited in the embodiments of this disclosure.

[0045] In some embodiments, the substrate 100 includes a first boundary 101, a second boundary 102, a third boundary 103, and a fourth boundary 104 arranged adjacent to each other. The first boundary 101 is opposite the third boundary 103 in the first direction Y, and the second boundary 102 is opposite the fourth boundary 104 in the second direction X.

[0046] In some embodiments, a junction between the first boundary 101 and the second boundary 102, a junction between the second boundary 102 and the third boundary 103, a junction between the third boundary 103 and the fourth boundary 104, and a junction between the fourth boundary 104 and the first boundary 101 include chamfers. The reason for forming the chamfers 105 is that a monocrystalline silicon rod can only be made round due to the extraction limitation of the monocrystalline silicon process for preparing the substrate in conventional solar cells. The silicon rod is sliced ​​after coming out, i.e.The cross section of the silicon rod is cut into the appearance of a monocrystalline silicon wafer (after calculating the area, an illumination area is maximized in one unit, the material of the silicon rod is saved as much as possible, and it is also convenient for the production of cells and modules), and the chamfers are often added at various interfaces of the substrate to reduce the external stress on the silicon wafer and avoid micro-damage at the corners of the silicon wafer.

[0047] Fig. 3 is a schematic structural diagram of a second solar cell according to an embodiment of this disclosure, and Fig. Figure 4 is a schematic structural diagram of a connection electrode in the second solar cell according to an embodiment of this disclosure. The second solar cell also has a cross-sectional structure as shown in Fig. 2, and a corresponding drawing can be found on Fig. 2.

[0048] With reference to Fig. 3 and Fig. 4, the solar cell comprises a substrate, a passivation layer formed on a surface of the substrate, fingers, and connecting electrodes 230. The fingers comprise rows of first fingers 221 and rows of second fingers 222 arranged alternately along a first direction Y, each of the fingers extending in a second direction X, each row of first fingers 221 comprising a corresponding set of first fingers 221 arranged at intervals in the second direction, and each row of second fingers 222 comprising a corresponding set of second fingers 222 arranged at intervals in the second direction X, each row of first fingers 221 being located between two adjacent rows of second fingers 222. The fingers penetrate the passivation layer and are electrically connected to the substrate.Each of the connecting electrodes 230 is in electrical contact with end portions of at least two adjacent first fingers 221 on one side of the rows of first fingers 221.

[0049] In some embodiments, the connecting electrodes 230 are provided to improve the collection rate for the current generated by portions of the electrodes at the edge and a portion of the substrate at the edge. Each connecting electrode 230 is in electrical contact with end portions of at least two adjacent first fingers 221 on the same side, so that the current generated by a finger at the second boundary 202 or the fourth boundary 204 of the substrate can be collected by another finger of the same polarity as that finger if that finger provides a gap for a bus bar of a different polarity than that finger, thus improving the collection efficiency and the photoelectric conversion efficiency of the solar cell.

[0050] In some embodiments, the connecting electrode 230 is a whole electrode connecting the adjacent first fingers 221, and an extending direction of the connecting electrode 230 is perpendicular to an extending direction of the first finger 221, so that a printing pattern of existing fingers can be partially changed or the connecting electrodes 230 can be reprinted to reduce the improvement of the current process, which improves the compatibility and applicability of the device.

[0051] In some embodiments, the extension direction of the connection electrode 230 is perpendicular to the extension direction of the first finger 221, and the extension direction of the connection electrode 230 is the first direction Y. The extension direction of the connection electrode 230 is parallel to an extension direction of the second boundary 202, which occupies a small portion of a region of the substrate at the edge, so that the electrodes can be provided at a short distance from the second boundary 202, that is, longer first fingers 221 can be formed and larger regions can be used for the formation of the busbars, thereby reducing the process difficulty.

[0052] In some embodiments, the material of the connecting electrodes 230 is the same as the material of the fingers. The paste of the connecting electrodes 230 is the same as the paste of the fingers, i.e., the connecting electrodes 230 are formed by the burn-through paste, and the connecting electrodes 230 also penetrate the passivation layer to be electrically connected to the corresponding first doped regions. In this way, the connecting electrodes 230 can not only collect the current of the first fingers 221, but also collect the current on a portion of the surface of the substrate adjacent to the second boundary 202 or the fourth boundary 204, thereby enlarging the collection paths and increasing the current collection efficiency.

[0053] In some embodiments, the paste of the connection electrodes 230 is the same as the paste of the bus bars, that is, the connection electrodes 230 are formed by a non-burn-through paste, and the connection electrodes 230 are formed on the surface of the passivation layer, so that the first doped regions and the second doped regions do not need to be set on the surface of the substrate under the connection electrodes 230 to prevent a short circuit caused by electrical contact between the connection electrodes 230 and the second doped regions of a different polarity.Furthermore, the connection electrodes 230 must not damage the passivation layer, thus ensuring the integrity of the film layer of the passivation layer, which improves the passivation effect of the passivation layer on the substrate and contributes to reducing the optical loss of the solar cell, thus improving the photoelectric conversion efficiency of the solar cell. Furthermore, since the non-burn-through paste does not contain excessive glass powder that could damage the PN junction, metal recombination is effectively reduced, the open-circuit voltage of the solar cell is improved, and the conversion efficiency of the solar cell is increased.

[0054] Conventional paste comprises a mixture of metal powder, glass powder, and an organic charge carrier. Non-burn-through paste refers to pastes that contain a lower proportion of glass powder than conventional pastes, exhibit weak burn-through capability during the sintering process, and do not need or cannot burn the passivation layer paste. Burn-through paste is a paste that has strong burn-through capability and is capable of burning through the passivation layer during the sintering process.

[0055] In some embodiments, the width of the connection electrode 230 in the second direction X is less than 30 µm. For example, the width of the connection electrode 230 is less than 28 µm, 26 µm, 23 µm, 20 µm, 18.3 µm, 15 µm, 12 µm, or 10 µm. When the width of the connection electrode 230 is within one of the above-mentioned ranges, the connection electrode 230 has a sufficient width to collect the charge carriers of the substrate, and the cross-sectional area of ​​the connection electrode 230 itself is large, resulting in lower electrical loss. The connecting electrode 230 also occupies a small area, so that it occupies a small area of ​​the region at the boundary, whereby the second fingers 222 are able to further collect the current at the edge, thereby reducing the enlargement of an area for collecting the current by the second fingers 222.

[0056] In some embodiments, the chamfers 205, the first boundary 201, the second boundary 202, the third boundary 203, the fourth boundary 204, the first fingers 221, and the second fingers 222 may refer to the descriptions of the chamfers 105, the first boundary 101, the second boundary 102, the third boundary 103, the fourth boundary 104, the first fingers 121, and the second fingers 122 in the above embodiments, and details will not be described again here.

[0057] Fig. 5 is a schematic structural diagram of a third solar cell according to an embodiment of this disclosure, Fig. 6 is an enlarged partial view of section B in Fig. 5 and Fig. Figure 7 is a schematic structural diagram of a connection electrode in a third solar cell according to an embodiment of this disclosure. The third solar cell also has a cross-sectional structure as shown in Fig. 2, and a corresponding drawing can be found on Fig. 2.

[0058] With reference to Fig. 5 and Fig. 6, some embodiments of this disclosure provide a solar cell comprising a substrate, a passivation layer formed over a surface of the substrate, fingers, and connection electrodes 330. The fingers comprise rows of first fingers 321 and rows of second fingers 322 arranged alternately along a first direction Y, with each of the fingers extending in a second direction X, each row of first fingers 321 comprising a corresponding set of first fingers 321 arranged at intervals in the second direction, and each row of second fingers 322 comprising a corresponding set of second fingers 322 arranged at intervals in the second direction X, each row of first fingers 321 being between two adjacent rows of second fingers 322. The fingers penetrate the passivation layer and are electrically connected to the substrate.Each connecting electrode 330 is in electrical contact with end portions of at least two adjacent first fingers 321 on one side of the rows of first fingers 321, and each connecting electrode 330 has a curved wave-like structure, ie, the connecting electrode 330 has a curved wave-like shape.

[0059] In some embodiments, the connecting electrode 330 has a curved, wave-like shape. In the conventional process for manufacturing the connecting electrode 330, the scraper moves in a direction parallel to an arrangement direction of the fingers and perpendicular to an extension direction of the fingers. Since the scraper must press the paste for filling holes of the screen plate in a direction perpendicular or inclined to a surface of the substrate in order to make the paste cover an area of ​​the passivation layer, a total area of ​​holes on the same horizontal line is small, the paste can quickly fill the holes, so that the holes on different horizontal lines communicate with each other, so the continuity of the connecting electrode is good to avoid the gap, and the connecting electrode 330 can fully fulfill the function of collecting the current.

[0060] Furthermore, since the width of the connection electrode in the second direction is narrow, such as less than 30 μm, the length of the first finger in the second direction, the length of the second finger in the second direction, and the length of the bus bar in the second direction are increased, so that the current collection capacity of the cell is improved, and the problem that the paste cannot fill the holes due to the narrow connection electrode is avoided by having the connection electrode 330 in a curved, wave-like shape. However, if the width of the connection electrode in the second direction is large, the paste can easily fill the holes, and the connection electrode is designed to have a curved, wave-like shape, so that the current collection capacity of the cell at the edge is improved.

[0061] In some examples, the holes on the same horizontal line refer to a horizontal line formed by connecting multiple holes in the first direction.

[0062] In some embodiments, the connecting electrode 330 has a curved, wave-like shape, compared to a straight, linear shape, a contact area between an end portion of the connecting electrode 330 and an end portion of the first finger 321 connected to the connecting electrode 330 is large, so that the problem of the gap between the connecting electrode 330 and the first finger 321 is avoided, and the contact area between the connecting electrode 330 and the first finger 321 is large, so that the contact resistance between the connecting electrode 330 and the first finger 321 is small, which improves the photoelectric conversion efficiency of the solar cell.

[0063] In some embodiments, the radian θ of any arc of the curved wave-like structure is in a range from 0.1 rad to π. The radian θ may be in a range from 0.1 rad to 0.3 rad, 0.3 rad to 0.6 rad, 0.6 rad to 1.1 rad, 1.1 rad to 1.5 rad, 1.5 rad to 1.9 rad, 1.9 rad to 2.2 rad, 2.2 rad to 2.9 rad, or 2.8 rad to π. Thus, the number of holes on the same horizontal line of the connecting electrode 330 with the curved wave-like shape is appropriate, and the paste can completely fill each hole on the mesh plate, ensuring the continuity of the connecting electrode 330.

[0064] Since the radian θ of each arc of the curved wave-like structure is in a range from 0.1 rad to π, in some embodiments, each arc of the curved wave-like structure has a relatively small width in the second direction X, and larger regions can be provided to increase the distance between the bus bar and the second boundary 302, thereby reducing the risk of damage to the second boundary 302, and the lengths of the first finger 321 and the second finger 322 in the second direction X are longer, so that the collection of charge carriers at the edge is more sufficient.

[0065] With reference to Fig. 7, each connecting electrode 330 has a cross-sectional structure. The cross-sectional structure includes at least a first connecting portion 331 and a second connecting portion 332 that are connected to each other. The first connecting portion 331 is in electrical contact with an end portion of the connecting electrode 330, an included angle α between the first connecting portion 331 and the finger is not equal to 180°, and an included angle β between the first connecting portion 331 and the second connecting portion 332 is not equal to 180°.

[0066] In some embodiments, the included angle α between the first connecting portion 331 and the finger is 20°, 30°, 49°, 68°, 90°, 108°, 120°, 150°, 175°, 197°, 210°, 260°, 300°, 310°, or 350°. The included angle β between the first connecting portion 331 and the second connecting portion 332 is 18°, 32°, 47°, 60°, 90°, 107°, 120°, 149°, 168°, 220°, 260°, or 349°.

[0067] When the included angle α between the first connecting portion 331 and the finger is not equal to 180° and the included angle β between the first connecting portion 331 and the second connecting portion 332 is not equal to 180°, or when the included angle α and the included angle β are within any of the above-mentioned ranges, for the connecting electrode of the same horizontal line when manufacturing the connecting electrode including the first connecting portion 331 and the second connecting portion 332, less paste is used to fill the holes so that the paste can be continuously placed on the surface of the passivation layer and there is no gap between the first finger 321 and the first connecting portion 331.

[0068] In some embodiments, a connecting electrode between two adjacent first fingers 321 includes a plurality of groups of first connecting portions 331 and second connecting portions 332 arranged alternately. The connecting electrode is divided into a plurality of first connecting portions 331 and second connecting portions 332 arranged alternately, thereby increasing the length of the connecting electrode, thereby increasing a region in which the connecting electrode collects charge carriers.

[0069] In some embodiments, the first connecting portions 331 of different groups are staggered along the second direction X, that is, an extension line in the first direction Y of a first connecting portion 331 in one group does not overlap with an extension line in the first direction Y of a first connecting portion in another group, so that the number of first connecting portions of the same horizontal line in the process of forming the connecting electrode is small and a total area of ​​the paste required to fill the holes on the same horizontal line is small, so that the continuity of the connecting electrodes is ensured.

[0070] In some embodiments, the lengths of the second connecting portions 332 of different groups may be the same or different.

[0071] In some embodiments, the solder strip is in contact with the finger, eliminating the bus bars in a conventional solar cell, reducing the cost of manufacturing the bus bars and shielding the bus bars, and thereby improving the photoelectric conversion efficiency of the solar cell.

[0072] Accordingly, embodiments of this disclosure provide a solar cell including bus bars in electrical contact with the solder strips, and the current at the fingers is collected with the bus bars, thereby avoiding the problem of gaps or pseudo-solder joints between the solder strips and the fingers, thereby improving the current collection efficiency of the cell.

[0073] Fig. 8 is a schematic structural diagram of a fourth solar cell according to an embodiment of this disclosure, and Fig. 9 is an enlarged partial view of section C in Fig. 8. The fourth solar cell also has a cross-sectional structure as shown in Fig. 2, and a corresponding drawing can be found on Fig. 2.

[0074] In some embodiments relating to Fig. 8 and Fig. 9, the solar cell further includes busbars 340, including first busbars 341 and second busbars 342 arranged alternately in the second direction X. The first busbars 341 are electrically connected to the first fingers 321, and the second busbars 342 are electrically connected to the second fingers 322.

[0075] In some embodiments, bus bars 340 may be made from the unburned paste. Bus bars 340 are configured to collect, combine, and transmit the current collected by the fingers to the solder strips.

[0076] In some embodiments, each bus bar 340 includes a connecting line 343 and a plurality of connecting pads 344, wherein the connecting line 343 is electrically connected to the fingers, and the connecting pads 344 are configured to be electrically connected to the solder strips. That is, the bus bar here is not a bus bar in the traditional sense, but forms a connected bridge with each finger through the connecting line and is connected to the solder strips through the connecting pads for collecting the current. Thus, the width of the connecting line can be made thinner, which reduces the effective light-shielding area and resistance loss, thereby improving the overall performance of the module. The connecting lines are placed more densely to shorten the current path through the finger and thus improve the photoelectric conversion efficiency of the solar cell.The thinner interconnect line and the thinner interconnect pad can also avoid the risk of hidden cracks and microcracks in the silicon wafer, so the interconnect line is attached to the edge of the solar cell with the risk of hidden cracks and microcracks, thereby improving the current collection ability at the edge and the current collection or current conduction path.

[0077] In some embodiments, the busbars adjacent to the second boundary 302 or the fourth boundary 304 are defined as edge bars. If the number of busbars is an even number, i.e., the edge bars adjacent to the second boundary 302 or the fourth boundary 304 have different polarities, one of the edge bars is in electrical contact with the plurality of second fingers 322 arranged in the first direction, the other of the edge bars is in electrical contact with the plurality of first fingers 321 arranged in the first direction, and the connection electrodes 330 are connected to the end portions of the second fingers 322 near the fourth boundary 304. If the number of busbars is an odd number, i.e., the edge bars adjacent to the second boundary 302 or the fourth boundary 304 have different polarities,If the edge rails adjacent to the fourth boundary 304 have the same polarity, the two edge rails are in electrical contact with the plurality of second fingers 322 arranged in the first direction. For example, an edge rail 350 is in electrical contact with the plurality of second fingers 322.

[0078] In some embodiments, with reference to Fig. 9, the edge rail 350 comprises a first connecting line 351 extending in the first direction, at least one electrical connecting line 352, and a connecting structure 353. The at least one electrical connecting line 352 is provided between the first connecting line 351 and the connecting structure 353, and an extending direction of the electrical connecting line 352 intersects with the first direction Y. The connecting structure 353 is provided on the second fingers 322 and is in electrical contact with the second fingers 322, and the first connecting line 351 is provided on the side of the electrical connecting line 352 adjacent to the second boundary 302.Thus, a soldering effect is ensured when soldering is performed on the connecting structure 353 to avoid a solder joint being too close to the edge of the back surface, which would lead to solder cracks at the end of the module when using the back-contact solar cell, as well as a poor appearance due to a final soldering position deviating from a cell region caused by solder stripe misalignment during soldering. The connecting structure 353 is connected via the at least one electrical connection line 352 through the first connection line 351 to ensure that the module formed from soldered back-contact solar cells can receive photogenerated charge carriers collected on the second fingers 322 and the edge bar 350 at the edges, thereby ensuring the charge carrier utilization rate.

[0079] That the boundaries extending in the second direction X of the connecting structure 353 are aligned with the second fingers 322, as in Fig. 9 is merely an example. In an actual solar cell, the interconnect structure may be in contact with a side surface of the second finger, the interconnect structure may be in contact with a portion of a top surface of the second finger, or the interconnect structure may completely cover a portion of the top surface of the second finger and extend between adjacent second fingers (i.e., the interconnect structure traverses a portion of the top surface of the second finger).

[0080] In some embodiments, the solar cell further comprises solder pads 306. The solder pads 306 are provided on the passivation layer, and each solder pad 306 is electrically connected to the edge bar 350. The solder pad 306 is placed on the connection structure 351. The solder pad 306 is configured to be electrically connected to a solder strip. In some embodiments, the solder pad 306 belongs to a portion of the edge bar.

[0081] That the solder joint is aligned with boundaries extending in the first direction Y of the interconnect structure, as in Fig. 9 is only one example. In an actual solar cell, the solder joint may be in contact with an inner side surface of the interconnect structure, the solder joint may be in contact with a portion of a top surface of the interconnect structure, or the solder joint may completely cover a portion of the top surface of the interconnect structure and extend to the electrical connection line, the second fingers, or a surface of the passivation layer (i.e., the solder joint traverses a portion of the top surface of the interconnect structure).

[0082] In some embodiments, a first distance between the solder joint 306 and the second boundary 302 is greater than a second distance between the edge rail 350 and the second boundary 302, where the second distance may be a distance between the first connection line and the second boundary. A third distance between the connection electrode 330 and the second boundary 302 is greater than the second distance between the edge rail 350 and the second boundary 302, so that the edge rail 350 can collect current at the edge and the connection electrode 330 is relatively far from the second boundary 302, thereby avoiding process damage to the edge.

[0083] In some embodiments, the third distance between the connecting electrode 330 and the second boundary 302 is greater than the second distance. That is, the connecting electrode 330 is placed between the connecting structure 353 and the first connecting line 351, so that the length of the first finger 321 can be increased in the second direction X, and the first fingers 321 can collect the current near the second boundary 302, thereby improving the current collection capability at the edge.

[0084] The connection electrode 330 is placed between the connection structure 353 and the first connection line 351, and the connection electrode 330 can collect the current generated by the first fingers 321 near the second boundary 302 having gaps for forming the connection structure 353, thereby improving the current collection ability at the edge.

[0085] The first distance may be defined as a vertical distance between a center of the solder joint and the second boundary, or as a vertical distance between an outer side of the solder joint near the second boundary and the second boundary. Similarly, the second distance is defined as a vertical distance between an axis of the first connection line and the second boundary, or as a vertical distance between an outer side of the first connection line near the second boundary and the second boundary. The third distance is defined as a vertical distance between the axis of the connection electrode 330 and the second boundary 302, or as a vertical distance between an outer side of the connection electrode 330 near the second boundary and the second boundary 302.

[0086] In some embodiments, the interconnect structure 353 includes a hollow region 307, and the solder joint 306 partially overlaps the hollow region 307. Because the interconnect structure adopts a hollow design, the paste consumption of the edge bar is reduced, thus saving paste and reducing the production and preparation costs of the cell. Furthermore, the height of the hollowed region of the interconnect structure is the smallest for a solder joint region required by the solder strip, and a height difference is formed between the edge bar and the hollow region, as well as between the solder joint and the hollow region, which promotes contact between the solder strip and the solder joint, as well as the edge bar and the soldering of the module, thereby improving the production yield of the module.

[0087] In the embodiments of this disclosure, the connecting electrodes 330 are provided, wherein each connecting electrode 330 is in electrical contact with the end portions of at least two adjacent first fingers 321 on the same side, and a hollow square electrode is formed by the connecting electrode 330 and the fingers, so that an area of ​​a portion of the electrode at the edge is increased and the current collection capability is improved.

[0088] In addition, the connecting electrode 330 has a curved, wave-like shape. In the conventional process for manufacturing the connecting electrode 330, the scraper moves in a direction parallel to an arrangement direction of the fingers and perpendicular to an extension direction of the fingers. Since the scraper must press the paste for filling holes of the screen plate in a direction perpendicular or inclined to a surface of the substrate in order to make the paste cover an area of ​​the passivation layer, a total area of ​​holes on the same horizontal line is small, the paste can quickly fill the holes, so that the holes on different horizontal lines communicate with each other, so the continuity of the connecting electrode is good to avoid the gap, and the connecting electrode 330 can fully fulfill the function of collecting the current.The connection electrode 330 has a curved, wave-like shape, compared with a straight, linear shape, a contact area between an end portion of the connection electrode 330 and an end portion of the first finger 321 connected to the connection electrode 330 is large, so that the problem of the gap between the connection electrode 330 and the first finger 321 is avoided, and the contact area between the connection electrode 330 and the first finger 321 is large, so that the contact resistance between the connection electrode 330 and the first finger 321 is small, which improves the photoelectric conversion efficiency of the solar cell.

[0089] The connection electrode 330 includes at least the first connection portion 331 and the second connection portion 332, which are connected to each other. The first connection portion 331 is in electrical contact with the end portion of the connection electrode 330, the included angle α between the first connection portion 331 and the finger is not equal to 180°, and the included angle β between the first connection portion 331 and the second connection portion 332 is not equal to 180°. For the connection electrode of the same horizontal line, when forming the connection electrode 330 including the first connection portion and the second connection portion, less paste is used to fill the holes, so that the paste can be continuously applied to the surface of the passivation layer, and there is no gap between the first finger 321 and the first connection portion 331.

[0090] In some embodiments, the chamfers 305, the first boundary 301, the second boundary 302, the third boundary 303, the fourth boundary 304, the first fingers 321, and the second fingers 322 may refer to the descriptions of the chamfers 105, the first boundary 101, the second boundary 102, the third boundary 103, the fourth boundary 104, the first fingers 121, and the second fingers 122 in the above embodiments.

[0091] Fig. 10 is a schematic structural diagram of a photovoltaic module according to an embodiment of this disclosure, Fig. 11 is a schematic cross-sectional view of Fig. 10 along the section line M1-M2, and Fig. 12 is a partial schematic structural diagram of a cell and a solder strip in a photovoltaic module according to an embodiment of this disclosure.

[0092] According to some embodiments of this disclosure with reference to Fig. 10 to Fig. 12, some embodiments of this disclosure further provide a photovoltaic module comprising: at least one cell string, each formed by connecting a plurality of solar cells 40 of any of the above embodiments, at least one solder strip 418, each configured to electrically connect the plurality of solar cells 40 to form at least one cell string, at least one encapsulating adhesive film 41, each configured to cover a surface of a respective cell string, and a cover plate 42, each configured to cover a surface of a respective encapsulating adhesive film 41 facing away from the plurality of cell strings.

[0093] In some embodiments, no gap is provided between the cells, meaning the cells overlap each other. The solar cell is referred to as a cell for short.

[0094] In some embodiments, reference is made to Fig. 12, the solder strip 418 is soldered to the solder joint 306 of the solar cell 40. An orthographic projection of the solder strip 418 on the substrate does not overlap with an orthographic projection of the edge bar 350 on the substrate. This allows the solder strip for the bus bar at the edge to collect the current through the solder joint 306, preventing damage to the edge of the cell and thus improving the yield of the photovoltaic module.

[0095] In some embodiments, the at least one encapsulation adhesive film 41 comprises a first encapsulation layer and a second encapsulation layer, wherein the first encapsulation layer covers either the front or the back of the solar cell 40, and the second encapsulation layer covers the other side of the front or the back of the solar cell 40. Specifically, at least one of the first or second encapsulation layer may be an organic encapsulation adhesive film, such as a polyvinyl butyral adhesive film (PVB adhesive film), an ethylene-vinyl acetate copolymer adhesive film (EVA adhesive film), a polyethylene-octene coelastomer adhesive film (POA adhesive film), or a polyethylene terephthalate adhesive film (PET adhesive film).

[0096] It is understood that the first encapsulation layer and the second encapsulation layer have a boundary before lamination, and the photovoltaic module formed after lamination does not have the so-called first encapsulation layer and second encapsulation layer, that is, the first encapsulation layer and the second encapsulation layer have formed an integral encapsulation layer 41.

[0097] In some embodiments, the at least one cover plate 42 may be a cover plate with a light-transmitting function, e.g., a glass cover plate or a plastic cover plate. Specifically, a surface of the cover plate 42 facing the encapsulation layer 41 may be a concave-convex surface, thereby increasing the utilization rate of the incident light. The at least one cover plate 42 comprises a first cover plate and a second cover plate, with the first cover plate facing the first encapsulation layer and the second cover plate facing the second encapsulation layer.

[0098] Although some embodiments of this disclosure are mentioned above, these embodiments are not intended to limit the claims. Those skilled in the art can make certain possible changes and modifications without departing from the spirit of this disclosure. Therefore, the scope of this disclosure is to be understood subject to the scope defined in the claims of this disclosure. Furthermore, the embodiments in the description and accompanying drawings of this disclosure are merely illustrative examples and are not intended to cover the entire scope of the claims of this disclosure.

[0099] Anyone skilled in the art will understand that the above embodiments are specific embodiments for implementing this disclosure, and that various changes in form and details may be made in practice without departing from the scope of this disclosure. Anyone skilled in the art may make various changes and modifications without departing from the scope of this disclosure, and therefore, the scope of this disclosure is subject to the scope defined in the claims.

[0100] A solar cell is provided, comprising: a substrate; a passivation layer formed over a surface of the substrate; fingers arranged in a first direction and extending in a second direction, the fingers penetrating the passivation layer to be electrically connected to the substrate and comprising first fingers and second fingers arranged alternately;Connecting electrodes, each of the connecting electrodes being in electrical contact with end portions of at least two adjacent first fingers on a same side, and comprising one of the following elements: at least a first connecting portion and a second connecting portion connected to each other, the first connecting portion being connected to an end portion of a respective one of the at least two adjacent first fingers, the first connecting portion and the respective finger having an included angle that is not equal to 180°, and the first connecting portion and the second connecting portion having an included angle that is not equal to 180°; and a curved wave-like structure;

Claims

[1] Solar cell, comprising: a substrate; a passivation layer formed over a surface of the substrate; Fingers arranged in a first direction and extending in a second direction, the fingers penetrating the passivation layer to be electrically connected to the substrate and having first fingers and second fingers arranged alternately; Connecting electrodes, each of the connecting electrodes being in electrical contact with end portions of at least two adjacent first fingers on the same side and having one of the following features: at least a first connecting portion and a second connecting portion connected to each other, wherein the first connecting portion is connected to an end portion of a respective finger of the at least two adjacent first fingers, the first connecting portion and the respective finger have an included angle that is not equal to 180°, and the first connecting portion and the second connecting portion have an included angle that is not equal to 180°; and a curved wave-like structure. [2] The solar cell of claim 1, wherein the substrate has a first boundary, a second boundary, a third boundary, and a fourth boundary adjacent to each other, the first boundary being opposite to the third boundary in the first direction and the second boundary being opposite to the fourth boundary in the second direction. [3] The solar cell of claim 2, further comprising: edge rails adjacent to the second boundary, the edge rails being in electrical contact with the second fingers arranged in the first direction. [4] The solar cell of claim 3, further comprising: solder pads provided on the passivation layer, wherein each of the solder pads is electrically connected to a corresponding one of the edge bars, and wherein each of the solder pads and the second boundary have a first distance that is greater than a second distance between one of the edge bars and the second boundary. [5] The solar cell of claim 4, wherein each of the connection electrodes and the second boundary has a third distance greater than the second distance. [6] The solar cell of claim 4, wherein each of the edge bars comprises a first interconnection line extending in the first direction, at least one electrical interconnection line, and an interconnection structure; wherein the at least one electrical interconnection line is provided between the first interconnection line and the interconnection structure and extends in a direction intersecting the first direction, the interconnection structure is provided on and in electrical contact with some of the second fingers, and the first interconnection line is provided on a side of the at least one electrical interconnection line proximate the second boundary; and wherein a corresponding one of the solder pads is provided on the interconnection structure. [7] The solar cell according to claim 6, wherein the connecting structure has a hollow region and the respective solder joint partially overlaps the hollow region. [8] The solar cell according to claim 1, wherein each of the connecting electrodes has a plurality of groups of first connecting portions and second connecting portions arranged alternately. [9] The solar cell according to claim 1, wherein the connecting electrodes comprise the same materials as the fingers. [10] The solar cell of claim 1, wherein the curved wave-like structure has a plurality of arcs each having a radian in the range of 0.1 rad to π. [11] The solar cell of claim 1, wherein each of the connection electrodes has a width of less than 30 µm. [12] The solar cell of claim 1, wherein the solar cell comprises an inter-finger back contact (IBC) cell. [13] The solar cell of claim 1, wherein each of the first fingers has a first polarity and each of the second fingers has a second polarity. [14] Photovoltaic module, comprising: at least one cell string, each formed by connecting a plurality of solar cells according to one of claims 1 to 13; at least one solder strip, each configured to electrically connect a plurality of solar cells to form at least one cell string; at least one encapsulating adhesive film, each adapted to cover an area of ​​a respective cell strand; and at least one cover plate, each of which is arranged to cover a surface of a corresponding encapsulating adhesive film facing away from the plurality of cell strands. [15] The photovoltaic module of claim 14, wherein the at least one solder strip is soldered to the solder pads of each of the plurality of solar cells, respectively, and each of the at least one solder strip has an orthographic projection on the substrate that does not overlap an orthographic projection of a corresponding one of the edge rails on the substrate.

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