A solar cell, a photovoltaic module, and a method for manufacturing a solar cell

Abstract

The present invention relates to a solar cell, a photovoltaic module, and a method for manufacturing a solar cell. The solar cell includes a silicon substrate, a transport layer, and a first electrode; the transport layer is located on one side of the silicon substrate, and metal crystals are provided in the transport layer; the first electrode is located on the side of the transport layer away from the silicon substrate, and the first electrode is electrically connected to the transport layer and the metal crystals; along the width direction of the first electrode, the number of metal crystals distributed at both end portions of the first electrode is less than the number of metal crystals distributed at the remaining positions of the first electrode. The metal crystals are located below the first electrode and are distributed near the middle of the first electrode, which can reduce the transport path of carriers in the first electrode, facilitate the direct extraction of carriers by the first electrode, and improve the collection efficiency of the first electrode for carriers.

Description

Technical Field

[0001] The present invention relates to the technical field of solar photovoltaics, and particularly relates to a solar cell, a photovoltaic module, and a method for manufacturing a solar cell. Background Art

[0002] A solar cell is a thin optoelectronic semiconductor sheet that directly generates electricity using sunlight. Under a certain illumination condition, the solar cell can instantaneously output a voltage and generate a current in the presence of a circuit, and it is a device that directly converts light energy into electrical energy through the photovoltaic effect or the photochemical effect. Among them, the electrode in the solar cell is one of the important components of the cell, and the main function of the electrode is to collect the carriers generated by sunlight irradiation. However, current solar cells have the defect of slow carrier collection rate by the electrode. Summary of the Invention

[0003] In view of this, the present invention provides a solar cell, a photovoltaic module, and a method for manufacturing a solar cell, aiming to partially or completely solve the technical problem that the existing solar cells have a slow carrier collection rate by the electrode.

[0004] To achieve the above object, the technical solution of the present invention is realized as follows:

[0005] In a first aspect, an embodiment of the present invention provides a solar cell, the solar cell includes a silicon substrate, a transport layer, and a first electrode; the transport layer is located on one side of the silicon substrate, and metal crystals are provided in the transport layer; the first electrode is located on the side of the transport layer away from the silicon substrate, and the first electrode is electrically connected to the transport layer and the metal crystals; along the width direction of the first electrode, the number of metal crystals distributed at both ends of the first electrode is less than the number of metal crystals distributed at the remaining positions of the first electrode.

[0006] Optionally, along the width direction of the first electrode, the width of the end portion of the first electrode where the number of metal crystals is less accounts for 8%-22% of the width of the first electrode.

[0007] Optionally, along the width direction of the first electrode, a preset width L2 is selected within the first electrode, and the total width of a plurality of the metal crystals within the preset width range is L1, and the range of L1 / L2 is 50%-90%.

[0008] Optionally, along the width direction of the first electrode, the width of the first electrode is L4; the total width of a plurality of the metal crystals connected to the first electrode is L3, and the range of L3 / L4 is 70%-85%.

[0009] Optionally, along the width direction of the first electrode, the width range of the metal crystals is 100nm - 600nm.

[0010] Optionally, the metal crystal includes a first metal crystal and a second metal crystal; along the width direction of the first electrode, the width range of the first metal crystal is 100 nm - 200 nm, and the width range of the second metal crystal is 300 nm - 600 nm.

[0011] Optionally, the number of the first metal crystals is greater than the number of the second metal crystals.

[0012] Optionally, along the thickness direction of the silicon substrate, the thickness range of the metal crystal is 50 nm - 300 nm.

[0013] Optionally, the solar cell further includes a second electrode, and the melting point of the first electrode is greater than that of the second electrode.

[0014] In a second aspect, an embodiment of the present invention provides a photovoltaic module, which includes the solar cell as described above.

[0015] In a third aspect, an embodiment of the present invention further provides a method for manufacturing a solar cell, the method including: disposing a transmission layer on one side of a silicon substrate; disposing a first paste on a side of the transmission layer away from the silicon substrate; performing a first sintering on the first paste at a temperature lower than the melting point of the first paste to form a first electrode; performing a second sintering on the first electrode to form metal crystals in the transmission layer; and electrically connecting the first electrode and the metal crystals.

[0016] Optionally, the solar cell further includes a second electrode, and the melting point of the second electrode is lower than that of the first electrode; the manufacturing method includes disposing a transmission layer on one side of a silicon substrate; disposing a first paste and a second paste on a side of the transmission layer away from the silicon substrate; performing a first sintering on the first paste and the second paste at a temperature lower than or equal to the melting point of the second paste to respectively form a first electrode and a second electrode; performing a second sintering on the first electrode to form metal crystals in the transmission layer; and electrically connecting the first electrode and / or the second electrode and the metal crystals.

[0017] Optionally, the step of performing a second sintering on the first electrode to form metal crystals in the transmission layer includes applying a reverse voltage to the first electrode and the second electrode; and performing a laser scan on the first electrode to form metal crystals in the transmission layer.

[0018] In the solar cell of the present invention, along the width direction of the first electrode, the number of metal crystals distributed at the two end portions of the first electrode is less than the number of those distributed at the remaining positions of the first electrode. The metal crystals are located below the first electrode and are distributed near the middle of the first electrode, which can reduce the carrier transmission path in the first electrode, facilitate the direct extraction of carriers from the first electrode, and improve the carrier collection efficiency of the first electrode.

[0019] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable, the following specifically gives the specific embodiments of the present invention. Brief Description of the Drawings

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments.

[0021] Figure 1 It is a schematic structural diagram of a solar cell in an embodiment of the present invention;

[0022] Figure 2 It is a schematic structural diagram of another solar cell in an embodiment of the present invention;

[0023] Figure 3 It is a test image of a transmission electron microscope of a solar cell in an embodiment of the present invention;

[0024] Figure 4 It is a schematic diagram of the electrode sintering temperature curve of a solar cell in an embodiment of the present invention;

[0025] Figure 5 It is a schematic flow chart of a preparation method of a solar cell in an embodiment of the present invention;

[0026] Figure 6 It is a schematic flow chart of another preparation method of a solar cell in an embodiment of the present invention.

[0027] Description of the Reference Numerals in the Drawings:

[0028] 10 - silicon substrate;

[0029] 21 - dielectric layer; 22 - doped conductive layer; 23 - first passivation layer; 24 - transport layer; 25 - tunneling oxide layer; 26 - doped polysilicon layer;

[0030] 31 - first electrode; 32 - second electrode;

[0031] 40 - metal crystal;

[0032] 50 - The fifth passivation layer and the second antireflection layer. Detailed implementation manners

[0033] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present invention can be more thoroughly understood and the scope of the present invention can be completely conveyed to those skilled in the art.

[0034] An embodiment of the present invention discloses a solar cell, which includes a silicon substrate 10, a transmission layer 24, and a first electrode 31; the transmission layer 24 is located on one side of the silicon substrate 10, and a metal crystal 40 is provided in the transmission layer 24; the first electrode 31 is located on the side of the transmission layer 24 away from the silicon substrate 10, and the first electrode 31 is electrically connected to the transmission layer 24 and the metal crystal 40; along the width direction of the first electrode 31, the number of metal crystals 40 distributed at both end portions of the first electrode 31 is less than the number of metal crystals 40 distributed at the remaining positions of the first electrode 31.

[0035] In a solar cell, the functions of the first electrode 31 and the second electrode 32 include collecting carriers (the carriers include free electrons and holes) generated by light irradiation and guiding them into an external circuit to form a current. The first electrode 31 and the second electrode 32 have high conductivity, good chemical stability, and appropriate mechanical strength, and at the same time, they should be able to effectively collect and transport carriers, reduce resistance loss, and improve the efficiency of the solar cell. Among them, the width direction of the first electrode 31 is Figure 1 the second direction B in

[0036] In some embodiments, the width range of the first electrode 31 is 10 μm - 80 μm.

[0037] In an embodiment of the present application, the metal crystal 40 is located in the transmission layer 24, and the metal crystal 40 is electrically connected to a part of the surface of the first electrode 31 facing the silicon substrate 10. The metal crystal 40 can form a carrier flow channel, which can improve the efficiency of the solar cell.

[0038] In an embodiment of the present application, along the width direction of the first electrode 31, the number of metal crystals 40 distributed at both end portions of the first electrode 31 is less than the number of metal crystals 40 distributed at the remaining positions of the first electrode 31. The metal crystal 40 is located below the first electrode 31 and is distributed at a position close to the middle of the first electrode 31, which can reduce the transmission path of carriers in the first electrode 31, facilitate the direct derivation of carriers by the first electrode 31, and improve the collection efficiency of the first electrode 31 for carriers.

[0039] In some embodiments, along the width direction of the first electrode 31, the width of the end portion where the number of metal crystals 40 distributed in the first electrode 31 is relatively small accounts for 8%-22% of the width of the first electrode 31.

[0040] In the embodiments of the present application, with reference to Figure 1 As shown, along the second direction B, the number of metal crystals 40 distributed at the left end and the right end of the first electrode 31 is relatively small. Among them, the width of the left end where the number of metal crystals 40 distributed in the first electrode 31 is relatively small accounts for 8%-22% of the width of the first electrode 31, and the width of the right end where the number of metal crystals 40 distributed in the first electrode 31 is relatively small accounts for 8%-22% of the width of the first electrode 31. The proportion sizes of the widths of the left and right ends can be the same or different.

[0041] In some embodiments, the specific value of the ratio of the end portion where the number of metal crystals 40 distributed in the first electrode 31 to the width of the first electrode 31 is set according to the usage requirements. The size of the ratio is, for example, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, but is not limited to the listed values. The size of the ratio may also be a value between the exemplified point values.

[0042] In some embodiments, along the width direction of the first electrode 31, a preset width L2 is selected within the first electrode 31, and the total width of a plurality of metal crystals 40 within the preset width range is L1. The range of L1 / L2 is 50%-90%.

[0043] Among them, the preset width L2 selected within the first electrode 31 is selected according to the usage requirements, and the preset width L2 is less than the width of the first electrode 31. For example, along the second direction B, a region with a width of 1 um - 5 um is selected below the first electrode 31, and the sum of the horizontal widths of a plurality of metal crystals 40 along the second direction B therein is calculated, and this sum is L1.

[0044] In the embodiments of the present application, along the width direction of the first electrode 31, a preset width L2 is selected within the first electrode 31, and the total width of a plurality of metal crystals 40 within the preset width range is L1. When L1 / L2 is within the above range, the ratio of the total width of a plurality of metal crystals 40 within the preset width range to the preset width is relatively large. The metal crystals 40 can form a high-efficiency carrier flow channel. A relatively large number of metal crystals is beneficial for carriers to move to the first electrode 31, accelerating the carrier transmission rate, thereby shortening the time required for carriers to pass through the transport layer 24 and effectively improving the efficiency of the solar cell.

[0045] In practical applications, the specific value of L1 / L2 is set according to the usage requirements. For example, L1 / L2 is 50%, 53%, 55%, 58%, 60%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, 83%, 85%, 87%, 90%, but is not limited to the listed values, and the proportion may also be a value between the exemplified point values.

[0046] In some embodiments, the metal crystal 40 contains the same elements as the first electrode 31, such as Ag.

[0047] In some embodiments, along the width direction of the first electrode 31, the width of the first electrode 31 is L4, and the total width of the multiple metal crystals 40 connected to the first electrode 31 is L3. The range of L3 / L4 is 70% - 85%.

[0048] In the embodiments of the present application, when L3 / L4 is within the above range, the ratio range of the total width of the multiple metal crystals 40 to the width of the first electrode 31 is relatively appropriate, that is, a high-efficiency carrier flow channel can be formed, which is beneficial for carriers to move to the first electrode 31, accelerating the carrier transmission rate, forming a high-efficiency metal-semiconductor contact structure, effectively improving the efficiency of the solar cell; and it can also be beneficial to reduce the risk of the metal crystal 40 damaging the passivation effect of the transmission layer 24, which is a consideration taking into account both the contact and passivation performance of the solar cell.

[0049] In some embodiments, the specific value of L3 / L4 is set according to the usage requirements. For example, L3 / L4 is 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 85%, but is not limited to the listed values, and the proportion may also be a value between the exemplified point values.

[0050] In some embodiments, along the width direction of the first electrode 31, the width range of the metal crystal 40 is 100 nm - 600 nm. When the width of the metal crystal 40 is within the above range along the width direction of the first electrode 31, the width of the metal crystal 40 is relatively large, and the contact area between the metal crystal 40 and the first electrode 31 and the transmission layer 24 is large, thereby forming a relatively wide carrier transmission channel, which is beneficial for carriers to move to the first electrode 31, accelerating the carrier transmission rate, and making the current transmission more effective.

[0051] It can be understood that along the width direction of the first electrode 31, the width of the metal crystal 40 is set according to the usage requirements. The width of the metal crystal 40 is, for example, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, but is not limited to the listed values, and the proportion may also be a value between the exemplified point values.

[0052] In some embodiments, the metal crystal 40 includes a first metal crystal and a second metal crystal; along the width direction of the first electrode 31, the width range of the first metal crystal is 100 nm - 200 nm, and the width range of the second metal crystal is 300 nm - 600 nm.

[0053] It can be understood that along the width direction of the first electrode 31, the width of the first metal crystal is set according to the usage requirements. The width of the first metal crystal is, for example, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, but is not limited to the listed values, and the proportion may also be a value between the example point value ranges.

[0054] Similarly, along the width direction of the first electrode 31, the width of the second metal crystal is set according to the usage requirements. The width of the second metal crystal is, for example, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, 400 nm, 420 nm, 440 nm, 460 nm, 480 nm, 500 nm, 520 nm, 540 nm, 560 nm, 580 nm, 600 nm, but is not limited to the listed values, and the proportion may also be a value between the example point value ranges.

[0055] In the embodiments of the present application, when the width of the first metal crystal is within the above range and the width of the second metal crystal is within the above range, carrier flow channels with various widths can be formed, which is more conducive to the movement of carriers to the first electrode 31, further accelerating the carrier transmission rate, and further shortening the time required for carriers to pass through the transmission layer 24.

[0056] Compared with the prior art, the second metal crystal has a larger width in the width direction of the first electrode 31, which can provide a better transmission channel for carriers, improve the longitudinal transmission efficiency of carriers in the transmission layer 24, and provide a larger space for the lateral transmission of carriers in terms of width, further improving the contact performance of the electrode on the transmission layer 24 with the same thickness.

[0057] In some embodiments, the number of the first metal crystals is greater than the number of the second metal crystals, which can prevent the second metal crystal from piercing the tunneling oxide layer, can form a high-efficiency carrier flow channel, and can reduce the contact resistance between the first electrode 31 and the transmission layer 24.

[0058] In some embodiments, the first metal crystal and the second metal crystal are arranged at intervals. And the distance between the intervals cannot be too large, so that electrons can be transmitted between adjacent first metal crystals and second metal crystals, thereby improving the extraction efficiency of the photocurrent of the solar cell.

[0059] In some other embodiments, there is a connected part between the first metal crystal and the second metal crystal.

[0060] In some embodiments, along the thickness direction of the silicon substrate 10, the thickness range of the metal crystal 40 is 50 nm - 300 nm.

[0061] The metal crystal 40 is a doped conductive layer 22 disposed in the transport layer 24. The thickness range of the doped conductive layer 22 is 50 nm - 300 nm. The metal crystal 40 has the above dimensions to match the thickness of the doped conductive layer 22 and avoid piercing the doped conductive layer 22.

[0062] In practical applications of the embodiments of the present application, the specific value of the thickness of the metal crystal 40 is set according to the usage requirements. For example, along the thickness direction of the silicon substrate 10, the thickness of the metal crystal 40 is 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, but not limited to the listed values, and the proportion may also be a value between the exemplified point value ranges.

[0063] In some embodiments, the width range of the second metal crystal is 300 nm - 600 nm, and the thickness range of the second metal crystal is 50 nm - 300 nm. At this time, the width of the second metal crystal is greater than the thickness of the second metal crystal, which can provide a space for the lateral transport of carriers, improve the transport efficiency of the doped conductive layer 22, and is beneficial to the improvement of the battery efficiency.

[0064] In some embodiments, the solar cell further includes a second electrode 32. The transport layer 24 includes a doped conductive layer 22. The side of the doped conductive layer 22 facing away from the silicon substrate 10 is connected to the first electrode 31 and / or the second electrode 32; the first metal crystal has a first end and a second end in opposite directions. The first end is connected to the first electrode 31 and / or the second electrode 32, and the second end is located in the doped conductive layer 22.

[0065] In the embodiments of the present application, the transmission layer 24 includes a doped conductive layer 22 and an ultra-thin dielectric layer 21 arranged in a stacked manner. The ultra-thin dielectric layer 21 is connected to the silicon substrate 10. The doped conductive layer 22 is connected to the first electrode 31 and the second electrode 32, or the doped conductive layer 22 is connected to the first electrode 31, or the doped conductive layer 22 is connected to the second electrode 32. The second end of the first metal crystal is located in the doped conductive layer 22, and the first metal crystal does not penetrate through the ultra-thin dielectric layer 21 into the silicon substrate 10, which can not only ensure that the ultra-thin dielectric layer 21 is not damaged, so as to ensure that the function of the ultra-thin dielectric layer 21 is not affected. That is, it ensures the good chemical passivation and tunneling effect of the ultra-thin dielectric layer 21. At the same time, it can also reduce the influence on the turn-on voltage to avoid damage to the silicon substrate 10 and ensure that the function of the silicon substrate 10 is not affected, thereby ensuring the performance of the solar cell.

[0066] In some embodiments, the solar cell further includes a second electrode 32. The transmission layer 24 includes a doped conductive layer 22. The side of the doped conductive layer 22 facing away from the silicon substrate 10 is connected to the first electrode 31 and / or the second electrode 32. The second metal crystal has a first end and a second end in opposite directions. The first ends are respectively connected to the first electrode 31 and the second electrode 32, and the second end is connected to the surface of the doped conductive layer 22 close to the silicon substrate.

[0067] In the embodiments of the present application, the second end is connected to the surface of the doped conductive layer 22 close to the silicon substrate, and the second metal crystal also does not penetrate through the ultra-thin dielectric layer 21 into the silicon substrate 10, which can not only ensure that the ultra-thin dielectric layer 21 is not damaged, so as to ensure that the function of the ultra-thin dielectric layer 21 is not affected. That is, it ensures the good chemical passivation and tunneling effect of the ultra-thin dielectric layer 21. At the same time, it can also reduce the influence on the turn-on voltage to avoid damage to the silicon substrate 10 to ensure that the function of the silicon substrate 10 is not affected, thereby ensuring the performance of the solar cell.

[0068] In some embodiments, the thickness of the doped conductive layer 22 is greater than or equal to 50 nm and less than or equal to 300 nm.

[0069] It can be understood that the thickness of the doped conductive layer 22 is set according to the usage requirements. The thickness of the doped conductive layer 22 is, for example, 50 nm, 70 nm, 90 nm, 110 nm, 130 nm, 150 nm, 170 nm, 190 nm, 210 nm, 220 nm, 240 nm, 250 nm, 270 nm, 290 nm, 300 nm, but is not limited to the listed values, and the proportion may also be a value between the example point value ranges.

[0070] As a possible implementation, the above solar cell may be a back-contact solar cell. The following describes the back-contact solar cell as an example. It should be understood that the following description is only for understanding and is not used for specific limitation. Specifically, referring to Figure 1 and Figure 3 As shown, the solar cell includes a silicon substrate 10, a first electrode 31, and a second electrode 32. Along the thickness direction of the solar cell, that is, in the first direction C, the silicon substrate 10 has two surfaces, which are respectively the backlight surface and the light-receiving surface of the silicon substrate 10. Both the first electrode 31 and the second electrode 32 are located on the backlight surface side of the silicon substrate 10. Among them, the doping type of the silicon substrate 10 can be N doping or P doping.

[0071] In some embodiments, referring to Figure 1 As shown, the transport layer 24 includes an ultra-thin dielectric layer 21 and a doped conductive layer 22. The dielectric layer 21 and the doped conductive layer 22 are stacked. The dielectric layer 21 is connected to the backlight surface of the silicon substrate 10; the first electrode 31 is connected to the doped conductive layer 22, and the second electrode 32 is connected to the backlight surface of the silicon substrate 10; the metal crystal 40 is disposed on a partial surface of the first electrode 31 facing the silicon substrate 10, and the metal crystal 40 is disposed within the doped conductive layer 22.

[0072] In the above structure of the embodiment of the present application, the solar cell is a back-contact cell, and the metal crystal 40 is located within the doped conductive layer 22, and the metal crystal 40 is in full contact with the doped conductive layer 22. Under the action of the metal crystal 40, the solar cell is conducive to the movement of carriers to the first electrode 31, accelerating the carrier transport rate, and further shortening the time required for carriers to pass through the doped conductive layer 22, which can improve the cell efficiency of the back-contact cell. The metal crystal 40 is located within the doped conductive layer 22, and the metal crystal 40 does not damage the function of the dielectric layer 21. While ensuring the passivation effect and tunneling effect of the dielectric layer 21, the cell efficiency is increased.

[0073] Further, one transport layer includes an ultra-thin dielectric layer 21 and a doped conductive layer 22, and the doped conductive layer 22 is a doped polysilicon layer; the other transport layer includes a doped conductive layer, the top surface of the doped conductive layer is coplanar with the surface of the silicon substrate 10, and the doped conductive layer is a diffusion layer formed on the surface of the silicon substrate 10.

[0074] The metal crystal 40 is located within the doped conductive layer 22, and the metal crystal 40 does not damage the function of the dielectric layer 21. While ensuring the passivation effect and tunneling effect of the dielectric layer 21, the solar cell efficiency is increased. When the metal crystal 40 is located within the diffusion layer, the metal crystal 40 can also provide a carrier transport path, reducing the time required for carriers to be transported to the second electrode 32. However, compared with the case where the metal crystal 40 is located in the doped polysilicon layer, the risk of the metal crystal 40 damaging the silicon substrate is greater.

[0075] In some embodiments, referring to Figure 1 as shown, the solar cell further includes a fifth passivation layer and a second antireflection layer 50, and the fifth passivation layer and the second antireflection layer 50 are disposed on the light-receiving surface of the silicon substrate 10.

[0076] Among them, the material of the antireflection layer is a single-layer or stacked structure of one or more of silicon nitride, silicon oxynitride, and aluminum oxide. The passivation layer is used to reduce charge recombination and surface reflection inside the solar cell, thereby improving the efficiency and performance of the cell. The material of the passivation layer is one or more of silicon oxide, silicon nitride, and aluminum oxide.

[0077] In some embodiments, referring to Figure 1 as shown, the solar cell further includes a first passivation layer 23, and the first passivation layer 23 is disposed on the backlight surface of the silicon substrate 10 and is connected to the side of the silicon substrate 10 and the transport layer 24 facing away from the silicon substrate 10. The first passivation layer 23 includes a single-layer or stacked structure of one or more materials such as aluminum oxide and silicon nitride.

[0078] In some embodiments, referring to Figure 2 as shown, the transport layer 24 includes a first transport layer (the first transport layer includes a dielectric layer 21 and a doped conductive layer 22 stacked) and a second transport layer (the second transport layer includes a tunneling oxide layer 25 and a doped polysilicon layer 26 stacked); the backlight surface of the silicon substrate 10 is respectively provided with the first transport layer and the second transport layer, and the first transport layer and the second transport layer are spaced apart; the first electrode 31 is connected to the surface of the first transport layer facing away from the silicon substrate 10, and the second electrode 32 is connected to the surface of the second transport layer facing away from the silicon substrate 10; the metal crystal 40 is disposed on a partial surface of the first electrode 31 facing the silicon substrate 10, and the metal crystal 40 is disposed inside the first transport layer; the metal crystal 40 is disposed on a partial surface of the second electrode 32 facing the silicon substrate 10, and the metal crystal 40 is disposed inside the second transport layer.

[0079] In the embodiments of the present application, the solar cell is a back-contact cell, the metal crystal 40 is located inside the first transport layer, and the metal crystal 40 is in full contact with the first transport layer. Under the action of the metal crystal 40, it is beneficial for carriers to move to the first electrode 31, accelerating the carrier transport rate, and can improve the cell efficiency of the back-contact cell.

[0080] The metal crystal 40 is located inside the second transport layer, and the metal crystal 40 is in full contact with the second transport layer. Under the action of the metal crystal 40, it is beneficial for carriers to move to the second electrode 32, accelerating the carrier transport rate, and can also improve the cell efficiency of the back-contact cell.

[0081] Further, in the embodiments of the present application, the materials of the dielectric layer 21 and the doped conductive layer 22 can be specifically selected according to the type of the solar cell. For example, the dielectric layer 21 includes a tunneling oxide layer, an intrinsic amorphous silicon layer, etc., and the doped conductive layer 22 includes a doped amorphous silicon layer, a doped polycrystalline silicon layer, etc.

[0082] A first transport layer and a second transport layer are respectively provided on the backlight surface of the silicon substrate 10. The first transport layer and the second transport layer are arranged at intervals. The interval arrangement is as follows: One is in the extending direction of the backlight surface of the silicon substrate 10, that is, in the second direction B, the first transport layer and the second transport layer are alternately arranged at intervals on the backlight surface of the silicon substrate 10, and they are in contact or non-contact in the extending direction of the backlight surface of the silicon substrate 10. The other is in the extending direction of the backlight surface of the silicon substrate 10, that is, in the second direction B, the first transport layer and the second transport layer are alternately arranged at intervals on the backlight surface of the silicon substrate 10, and they partially overlap in the thickness direction of the silicon substrate 10, that is, in the first direction C. The types of the first transport layer and the second transport layer are different. One of the first transport layer and the second transport layer is an electron transport layer, and the other of the first transport layer and the second transport layer is a hole transport layer.

[0083] In some embodiments, the back transport layer 24 includes a third passivation layer and a third doping layer. The third passivation layer and the third doping layer are stacked. The third passivation layer is connected to the backlight surface of the silicon substrate 10; the front transport layer 24 includes a doped conductive layer. The top surface of the doped conductive layer and the light-receiving surface of the silicon substrate 10 are coplanar. The doped conductive layer is a diffusion layer formed on the surface of the silicon substrate. A fourth passivation layer and a first antireflection layer are stacked on the diffusion layer; the first electrode 31 is connected to the surface of the third doping layer facing away from the silicon substrate 10, and the second electrode 32 is connected to the surface of the first antireflection layer facing away from the silicon substrate 10; the metal crystal 40 is disposed on a part of the surface of the first electrode 31 facing the silicon substrate 10, and the metal crystal 40 is disposed in the third doping layer.

[0084] In the embodiments of the present application, the solar cell is a Topcon (Tunnel Oxide Passivated Contact) cell. The metal crystal 40 is located in the third doping layer, and the metal crystal 40 is in full contact with the third doping layer. Under the action of the metal crystal 40, this Topcon cell is conducive to the movement of carriers to the first electrode 31, accelerating the transport rate of carriers, and can improve the cell efficiency of this Topcon cell.

[0085] In some embodiments, the first electrode 31 is silver, and the second electrode 32 is silver or aluminum.

[0086] In the embodiments of the present application, the materials of the first electrode 31 and the second electrode 32 can be set according to usage requirements. Among them, both silver and aluminum are materials with high electrical conductivity and good chemical stability. In practical applications, other materials can also be used to fabricate the first electrode 31 and the second electrode 32.

[0087] In some embodiments, the metal crystal 40 can be formed by the LECO (Laser-enhanced contact optimization) technology. The metal crystal can also be formed by other electrode sintering methods, which are not specifically limited herein.

[0088] Among them, the LECO technology is a process for optimizing the local and microscopic metal-semiconductor contacts based on laser induction. The LECO technology, in combination with special pastes, can reduce the contact resistance between silicon and metal while not increasing the recombination in the contact area, thereby improving the passivation of the solar cell and greatly enhancing the efficiency of the solar cell. Moreover, it can also improve the defects such as haze and blackening in the solar cell, and significantly increase the yield of the solar cell.

[0089] In some embodiments, the melting point of the first electrode 31 is greater than that of the second electrode 32. After the first electrode 31 and the second electrode 32 are sintered, the LECO technology causes the first electrode 31 to form the metal crystal 40.

[0090] In a solar cell, the first electrode 31 and the second electrode 32 are sintered. During the sintering process, there may be under-sintering or over-sintering situations (for example, the first electrode 31 includes Ag, the second electrode 32 includes Al, the melting point of Ag is 961 °C, the melting point of Al is 660 °C. When selecting an appropriate temperature for sintering, this temperature is lower than the melting temperature for Ag and higher than the melting temperature for Al. Therefore, the sintering temperatures for both Ag and Al are not the optimal temperatures, and there may be under-sintering or over-sintering situations). Neither under-sintering nor over-sintering meets the ideal sintering requirements of the solar cell. During under-sintering, the ohmic contact is not fully formed, the series resistance is relatively large, and the fill factor is relatively low; over-sintering will increase the probability of carrier recombination, and the open-circuit voltage is relatively low.

[0091] In the embodiments of the present application, when the first electrode 31 and the second electrode 32 are sintered, sintering can be carried out at a temperature lower than or equal to the temperature suitable for sintering the second electrode 32. At this time, the first electrode 31 is in an under-sintered state. Then, the laser-enhanced contact optimization technology is used for secondary sintering of the first electrode 31 to form the metal crystal 40 on a partial surface of the first electrode 31 facing the silicon substrate 10.

[0092] For example, it is described that the first electrode 31 includes Ag and the second electrode 32 includes Al. Ensure that the Al paste maintains an ideal process temperature range during sintering (this ideal process temperature range is lower than the sintering temperature of the original conventional sintering process. For specific reference, see Figure 4 , which shows a schematic diagram of the sintering time and sintering temperature curves of the conventional sintering process and the LECO sintering process). At this time, the Ag paste is in an under-sintered state. Through the LECO process, the Ag paste forms metal crystals 40 with the local micro-region of the silicon substrate 10 in a short time to form a contact. At the same time, due to the Al paste with a relatively low melting point being in the ideal process temperature range during sintering and being combined with the local LECO process, the composite loss caused in the production process is also greatly reduced, enhancing the performance of the metal-semiconductor contact structure and improving the efficiency of the solar cell; moreover, it can also improve defects such as fog and black, and greatly improve the product yield.

[0093] In the LECO sintering process, after the sintering process, an LECO process step is added. See Figure 2 As shown, a laser D with a specific wavelength is used to scan the grid line surface of the solar cell. The specific scanning area can be in the positive or negative electrode area of the grid line surface of the solar cell, or both the positive electrode area and the negative electrode area are irradiated simultaneously. The irradiation time and the laser scanning method are determined by the process requirements. At the same time, a reverse voltage is applied to the positive and negative electrodes of the solar cell.

[0094] The LECO process is applied to the manufacturing process of the solar cell. The role of the laser is to highly energize and short-time excite carriers. Then, under the action of the reverse voltage, the carriers will form a local current transmission channel to form a metal-semiconductor contact. In a solar cell, the reverse voltage applied to the LECO process needs to be within a certain range (for example, 0V to 20V), and the laser power is within a certain range (for example, 10% to 90% P max ), and at the same time, maintaining an appropriate laser scanning speed determines the scanning time. Through this LECO process, the efficiency of the solar cell is significantly improved; at the same time, since the LECO process can further improve the contact, it has a better improvement in low-efficiency chips and EL fog and black caused by poor contact.

[0095] In the embodiment of the present application, along the width direction of the first electrode 31, the number of metal crystals 40 distributed at both end portions of the first electrode 31 is less than the number distributed at the remaining positions of the first electrode 31. The metal crystals 40 are located below the first electrode 31 and are distributed at positions close to the middle of the first electrode 31, which can reduce the carrier transmission path in the first electrode 31, facilitating the direct extraction of carriers from the first electrode 31 and improving the carrier collection efficiency of the first electrode 31.

[0096] An embodiment of the present invention discloses a photovoltaic module, which includes a cover plate, a back plate, and a solar cell disposed between the cover plate and the back plate; the solar cell includes the solar cell as described above.

[0097] The embodiments of the present application do not specifically limit whether the photovoltaic module further includes other structures. For example, the photovoltaic module may further include: a first encapsulation film disposed between the cover plate and the solar cell, and a second encapsulation film disposed between the back plate and the solar cell.

[0098] The photovoltaic module and the solar cell can be referred to each other, and have the same or similar beneficial effects as any of the foregoing solar cells. To avoid repetition, it will not be elaborated here.

[0099] The present invention will be further elaborated in detail below with reference to specific embodiments.

[0100] Embodiment

[0101] Refer to Figure 1 As shown, in the solar cell, a dielectric layer 21 and a doped conductive layer 22 are provided on the backlight surface of the silicon substrate 10. The dielectric layer 21 and the doped conductive layer 22 are stacked, and the dielectric layer 21 is connected to the backlight surface of the silicon substrate 10. A fifth passivation layer and a second antireflection layer 50 are provided on the light-receiving surface of the silicon substrate 10.

[0102] The first electrode 31 is connected to the doped conductive layer 22, and the second electrode 32 is connected to the light-receiving surface of the silicon substrate 10; the metal crystal 40 is disposed on a partial surface of the first electrode 31 facing the silicon substrate 10, and the metal crystal 40 is disposed within the doped conductive layer 22.

[0103] The metal crystal 40 includes a first metal crystal and a second metal crystal, and the first metal crystal and the second metal crystal are arranged at intervals; along the width direction of the first electrode 31, the width range of the first metal crystal is 100 nm - 200 nm, and the width range of the second metal crystal is 300 nm - 600 nm.

[0104] Comparative Example

[0105] The difference from the above embodiment is that the metal crystal 40 only includes a third metal crystal. Along the width direction of the first electrode 31, the width range of the third metal crystal is 5 nm - 50 nm, and the rest is the same as the above embodiment.

[0106] For 1000 solar cells formed by the above embodiment and 1000 solar cells formed by the above comparative example, under the same test conditions, different process parameters are set for performance testing, and the test results are shown in Table 1 below.

[0107] Table 1

[0108] Group V - Bias P - Power v - Sweep Rate Eta Uoc Isc FF BSL - - - 0 0 0 0 SY1 V1 0.75*P v1 0.130 -0.0001 0.05 0.14 SY2 V2 0.875*P v2 0.100 -0.0001 0.04 0.09 SY3 V3 P v3 0.047 -0.0008 0.03 0.09

[0109] In Table 1, the data of the examples (group numbers SY1, SY2, and SY3) are the results obtained by taking the arithmetic mean of the test results of 1000 solar cells corresponding to the above examples. In Table 1, the bias voltage V, power P, and sweep rate v are all process parameters during testing. Eta characterizes the conversion efficiency of the solar cell, Uoc characterizes the open-circuit voltage of the solar cell, Isc characterizes the short-circuit current of the solar cell, and FF characterizes the fill factor of the solar cell.

[0110] It can be seen from Table 1 above that the efficiency of the examples is higher than that of the comparative example (group number BSL). The main reason is that in the examples, the metal crystal 40 simultaneously includes the first metal crystal and the second metal crystal. Along the width direction of the first electrode 31, the width range of the first metal crystal is 100 nm - 200 nm, and the width range of the second metal crystal is 300 nm - 600 nm. Multiple-width carrier flow channels can be formed in the solar cell, which is more conducive to the carriers moving to the first electrode 31, accelerating the carrier transmission rate, further shortening the time required for the carriers to pass through the transport layer 24, and thus effectively improving the efficiency of the solar cell.

[0111] The embodiment of the present invention also discloses a preparation method of a solar cell. Referring to Figure 5 as shown, the preparation method includes the following steps:

[0112] S11, a transport layer 24 is provided on one side of the silicon substrate 10.

[0113] In this step, the transport layer 24 can be deposited and formed on one side of the silicon substrate 10 by using equipment such as low-pressure chemical vapor deposition.

[0114] S12, a first paste is provided on the side of the transport layer 24 away from the silicon substrate 10.

[0115] In this step, the first paste can be printed on the surface of the side of the transport layer 24 away from the silicon substrate 10 by using a printing method.

[0116] S13, the first paste is sintered for the first time at a temperature lower than the melting point of the first paste to form the first electrode 31.

[0117] In this step, the first paste is sintered for the first time at a temperature lower than the melting point of the first paste to form the first electrode 31. At this time, the formed first electrode 31 has an underfired situation, and underfiring will cause the ohmic contact not to be fully formed, and the series resistance will be relatively large.

[0118] S14. Perform a second sintering on the first electrode 31 to form metal crystals 40 within the transport layer 24; the first electrode 31 is electrically connected to the metal crystals 40.

[0119] In this step, perform a second sintering on the first electrode 31 that was underfired in step S13 to form metal crystals 40 within the transport layer 24, enhance the performance of the metal-semiconductor contact structure, and improve the efficiency of the solar cell.

[0120] In the method for preparing a solar cell according to an embodiment of the present application, a two-step sintering method is adopted. In the first sintering, the first paste is sintered at a temperature equal to the melting point of the first paste, which can avoid overfiring but may result in underfiring. In the second sintering, metal crystals 40 are formed within the transport layer 24. These metal crystals 40 can form a high-efficiency carrier flow channel, facilitating the movement of carriers to the first electrode 31, accelerating the carrier transfer rate, thereby shortening the time required for carriers to pass through the transport layer 24 and effectively improving the efficiency of the solar cell.

[0121] An embodiment of the present invention also discloses another method for preparing a solar cell. The solar cell further includes a second electrode 32, and the melting point of the second electrode 32 is lower than that of the first electrode 31; refer to Figure 6 As shown, this preparation method includes the following steps:

[0122] S21. Provide a transport layer 24 on one side of the silicon substrate 10.

[0123] This step refers to step S11 above, and the embodiments of the present application will not elaborate further.

[0124] S22. Provide the first paste and the second paste on the side of the transport layer 24 away from the silicon substrate 10.

[0125] In this step, the first paste and the second paste can be printed on the surface of the transport layer 24 on the side away from the silicon substrate 10 by printing.

[0126] S23. Perform a first sintering on the first paste and the second paste at a temperature lower than or equal to the melting point of the second paste to form the first electrode 31 and the second electrode 32 respectively.

[0127] In this step, after performing a first sintering on the first paste and the second paste at a temperature lower than or equal to the melting point of the second paste, the second electrode 32 has a good sintering structure, while the first electrode 31 is underfired.

[0128] S24. Perform a second sintering on the first electrode 31 to form metal crystals 40 within the transport layer 24; the first electrode 31 and / or the second electrode 32 is electrically connected to the metal crystals 40.

[0129] In some embodiments, referring to Figure 2 As shown, step S24 further includes the following steps: applying a reverse voltage V to the first electrode 31 and the second electrode 32; performing a laser D scan on the first electrode 31 to form metal crystals 40 within the transport layer 24. At this time, when the first electrode 31 is scanned by the laser D, carriers can be excited with high energy for a short time, and then under the action of the reverse voltage, the carriers will form a local current transmission channel to form a metal-semiconductor contact, that is, metal crystals 40 are formed.

[0130] The method for preparing a solar cell according to an embodiment of the present application uses the method of simultaneously printing the first paste and the second paste and sintering twice to fabricate the first electrode 31 and the second electrode 32, which can not only reduce the processing procedures and improve the processing efficiency, but also avoid the influence of over-sintering or under-sintering on the efficiency of the solar cell.

[0131] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the said element.

[0132] Each embodiment in this specification is described in a related manner. The same or similar parts among the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. For the embodiments of the device, electronic device, computer-readable storage medium and computer program product including instructions, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0133] The above is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A solar cell, characterized in that, The solar cell includes a silicon substrate (10), a transport layer (24), a first electrode (31), and a first passivation layer (23); The transport layer (24) is located on one side of the silicon substrate (10), and metal crystals (40) are provided in the transport layer (24); The first passivation layer (23) is connected to the side of the transport layer (24) facing away from the silicon substrate (10); The first electrode (31) is located on the side of the transport layer (24) away from the silicon substrate (10), and the first electrode (31) is electrically connected to the transport layer (24) and the metal crystals (40); Along the width direction of the first electrode (31), the number of metal crystals (40) distributed at both end portions of the first electrode (31) is less than the number of those distributed at the remaining positions of the first electrode (31).

2. The solar cell according to claim 1, characterized in that, Along the width direction of the first electrode (31), the width of the end portion of the first electrode (31) where the number of metal crystals (40) is less accounts for 8%-22% of the width of the first electrode (31).

3. The solar cell according to claim 1, characterized in that Along the width direction of the first electrode (31), a preset width L2 is selected within the first electrode (31), and the total width of a plurality of the metal crystals (40) within the preset width range is L1, and the range of L1 / L2 is 50%-90%.

4. The solar cell according to claim 3, characterized in that, Along the width direction of the first electrode (31), the width of the first electrode (31) is L4; the total width of a plurality of the metal crystals (40) connected to the first electrode (31) is L3, and the range of L3 / L4 is 70%-85%.

5. The solar cell according to any one of claims 1-4, characterized in that, Along the width direction of the first electrode (31), the width range of the metal crystals (40) is 100 nm - 600 nm.

6. The solar cell according to claim 1, characterized in that, The metal crystals (40) include first metal crystals and second metal crystals; Along the width direction of the first electrode (31), the width range of the first metal crystals is 100 nm - 200 nm, and the width range of the second metal crystals is 300 nm - 600 nm.

7. The solar cell according to claim 6, characterized in that, The number of the first metal crystals is greater than the number of the second metal crystals.

8. The solar cell according to claim 1, characterized in that, Along the thickness direction of the silicon substrate (10), the thickness range of the metal crystals (40) is 50 nm - 300 nm.

9. The solar cell according to claim 1, wherein The solar cell further includes a second electrode (32), and the melting point of the first electrode (31) is greater than the melting point of the second electrode (32).

10. A photovoltaic module, characterized in that, The photovoltaic module includes the solar cell according to any one of claims 1 to 9.

11. A method for manufacturing a solar cell, characterized in that a transport layer (24) is provided on one side of a silicon substrate (10); a first paste is provided on the side of the transport layer (24) away from the silicon substrate (10); the first paste is subjected to a first sintering at a temperature lower than the melting point of the first paste to form a first electrode (31); The first electrode (31) is subjected to a second sintering to form metal crystals (40) within the transport layer (24); the first electrode (31) is electrically connected to the metal crystals (40); and along the width direction of the first electrode (31), the number of the metal crystals (40) distributed at two end portions of the first electrode (31) is less than the number of those distributed at the remaining positions of the first electrode (31).

12. The manufacturing method of the solar cell according to claim 11, characterized in that, The solar cell further includes a second electrode (32), and the melting point of the second electrode (32) is lower than that of the first electrode (31); the preparation method includes providing a transport layer (24) on one side of a silicon substrate (10); providing a first paste and a second paste on a side of the transport layer (24) away from the silicon substrate (10); performing a first sintering on the first paste and the second paste at a temperature lower than or equal to the melting point of the second paste to respectively form a first electrode (31) and a second electrode (32); performing a second sintering on the first electrode (31) to form metal crystals (40) within the transport layer (24); the first electrode (31) and / or the second electrode (32) is electrically connected to the metal crystals (40).

13. The manufacturing method of a solar cell according to claim 12, characterized in that, The step of performing a second sintering on the first electrode (31) to form metal crystals (40) within the transport layer (24) includes applying a reverse voltage to the first electrode (31) and the second electrode (32); performing laser scanning on the first electrode (31) to form metal crystals (40) within the transport layer (24).

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