Solar cell, photovoltaic module and preparation method of solar cell

Abstract

The invention relates to a solar cell, a photovoltaic module and a preparation method of the solar cell. The solar cell comprises a silicon substrate, a transmission layer and a first electrode, the transmission layer is located on one side of the silicon substrate, and a metal crystal is arranged in the transmission layer; the first electrode is located on the side, away from the silicon substrate, of the transmission layer, and the first electrode is electrically connected with the transmission layer and the metal crystal; in the width direction of the first electrode, the number of the metal crystals distributed at the two ends of the first electrode is smaller than the number of the metal crystals distributed at the other positions of the first electrode. The metal crystal is located below the first electrode and is distributed at a position close to the middle of the first electrode, so that the transmission path of carriers in the first electrode can be reduced, the carriers can be directly led out from the first electrode, and the collection efficiency of the first electrode on the carriers is improved.

Description

Technical Field

[0001] The present invention relates to the field of solar photovoltaic technology, and in particular to a solar cell, a photovoltaic module, and a method for preparing the solar cell. Background Art

[0002] Solar cells are photoelectric semiconductor sheets that use sunlight to generate electricity directly. When the illumination meets certain illumination conditions, solar cells can instantly output voltage and generate current in the presence of a circuit. They are devices that directly convert light energy into electrical energy through the photoelectric effect or photochemical effect. Among them, the electrodes in solar cells are one of the important components of the battery. The main function of the electrodes is to collect carriers generated by sunlight. However, current solar cells have the defect that the electrodes collect carriers at a slow rate. Summary of the invention

[0003] In view of this, the present invention proposes a solar cell, a photovoltaic module, and a method for preparing a solar cell, aiming to partially or completely solve the technical problem of slow carrier collection rate of electrodes in existing solar cells.

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

[0005] In a first aspect, an embodiment of the present invention provides a solar cell, comprising a silicon substrate, a transmission layer and a first electrode; the transmission layer is located on one side of the silicon substrate, and metal crystals are provided in the transmission layer; the first electrode is located on a side of the transmission layer away from the silicon substrate, and the first electrode is electrically connected to the transmission layer and the metal crystals; along the width direction of the first electrode, the number of the metal crystals distributed at the two ends of the first electrode is less than the number distributed at the rest 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 in the first electrode, the total width of the plurality of 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 the plurality of 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 of the metal crystal ranges from 100 nm to 600 nm.

[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 100nm-200nm, and the width range of the second metal crystal is 300nm-600nm.

[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 of the metal crystals ranges from 50 nm to 300 nm.

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

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

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

[0016] Optionally, the solar cell also includes a second electrode, and the melting point of the second electrode is lower than the melting point of the first electrode; the preparation method includes: setting a transmission layer on one side of the silicon substrate; setting a first slurry and a second slurry on a side of the transmission layer away from the silicon substrate; sintering the first slurry and the second slurry for a first time at a temperature lower than or equal to the melting point of the second slurry to form a first electrode and a second electrode respectively; sintering the first electrode for a second time to form metal crystals in the transmission layer; the first electrode and / or the second electrode are electrically connected to 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 laser scanning 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 ends of the first electrode is less than the number distributed at the rest of the first electrode. The metal crystals are located below the first electrode and distributed near the middle of the first electrode, which can reduce the transmission path of carriers in the first electrode, facilitate the direct extraction of carriers from the first electrode, and improve the collection efficiency of the first electrode for carriers.

[0019] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for describing the embodiments are briefly introduced below.

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

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

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

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

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

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

[0027] Description of reference numerals:

[0028] 10-silicon substrate;

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

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

[0031] 40-metal crystals;

[0032] 50 - a fifth passivation layer and a second anti-reflection layer. DETAILED DESCRIPTION

[0033] The 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 accompanying drawings, it should be understood that the present invention can also be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present invention and to enable the scope of the present invention to be fully communicated to those skilled in the art.

[0034] An embodiment of the present invention discloses a solar cell, which comprises 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 a 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 the metal crystals 40 distributed at the two ends of the first electrode 31 is less than the number distributed at the rest of the first electrode 31.

[0035] In a solar cell, the first electrode 31 and the second electrode 32 have the functions of collecting carriers (carriers include free electrons and holes) generated by light and guiding them to 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 can effectively collect and transmit carriers, reduce resistance loss, and improve the efficiency of the solar cell. The first electrode 31 has a width direction of 1. Figure 1 The second direction B in .

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

[0037] In the 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 the portion of the surface of the first electrode 31 facing the silicon substrate 10. The metal crystal 40 can form a carrier flow channel to improve the efficiency of the solar cell.

[0038] In the embodiment of the present application, along the width direction of the first electrode 31, the number of metal crystals 40 distributed at the two ends of the first electrode 31 is less than the number distributed at the rest of the first electrode 31. The metal crystals 40 are located below the first electrode 31 and are distributed near the middle of the first electrode 31, which can reduce the transmission path of carriers in the first electrode 31, facilitate the direct extraction of carriers from 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 of the first electrode 31 where the number of metal crystals 40 is less is 8%-22% of the width of the first electrode 31 .

[0040] In the embodiments of this application, refer to Figure 1 As shown, along the second direction B, the number of metal crystals 40 distributed at the left and right ends of the first electrode 31 is relatively small, wherein the width of the left end of the first electrode 31 where the number of metal crystals 40 distributed is relatively small accounts for 8%-22% of the width of the first electrode 31, and the width of the right end of the first electrode 31 where the number of metal crystals 40 distributed is relatively small accounts for 8%-22% of the width of the first electrode 31, and the proportions of the widths at the left and right ends may be the same or different.

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

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

[0043] The preset width L2 selected in the first electrode 31 is selected according to the use requirements, and the preset width L2 is smaller than the width of the first electrode 31. For example, along the second direction B, a region with a width of 1um-5um is selected below the first electrode 31, and the sum of the horizontal widths of the plurality of metal crystals 40 along the second direction B is calculated, and the sum is L1.

[0044] In the embodiment of the present application, along the width direction of the first electrode 31, a preset width L2 is selected in the first electrode 31, and the total width of the 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 the plurality of metal crystals 40 within the preset width range to the preset width is large, and the metal crystals 40 can form a highly efficient carrier flow channel. A larger number of metal crystals is conducive to the movement of carriers to the first electrode 31, thereby accelerating the carrier transmission rate, thereby shortening the time required for the carriers to pass through the transmission layer 24, and effectively improving the efficiency of the solar cell.

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

[0046] In some embodiments, the metal crystal 40 includes the same element 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 , the total width of the plurality of metal crystals 40 connected to the first electrode 31 is L3 , and the range of L3 / L4 is 70%-85%.

[0048] In the embodiment of the present application, when L3 / L4 is in the above range, the ratio range of the total width of the multiple metal crystals 40 and the width of the first electrode 31 is relatively suitable, that is, a high-efficiency carrier flow channel can be formed, which is beneficial for the movement of carriers to the first electrode 31, accelerates the carrier transmission rate, forms a high-efficiency metal-semiconductor contact structure, and effectively improves the efficiency of the solar cell; it can also help reduce the risk of the metal crystals 40 destroying the passivation effect of the transmission layer 24, taking into account the contact and passivation performance of the solar cell.

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

[0050] In some embodiments, the width of the metal crystal 40 is in the range of 100nm-600nm along the width direction of the first electrode 31. When the width of the metal crystal 40 is in 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, the first electrode 31 and the transmission layer 24 is large, thereby forming a wider carrier transmission channel, which is conducive to the movement of carriers to the first electrode 31, speeding up the transmission rate of carriers, and making current transmission more efficient.

[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 use requirements. The width of the metal crystal 40 is, for example, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, but is not limited to the listed values. The proportion may also be a value between the example point value range.

[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 of the first metal crystal ranges from 100 nm to 200 nm, and the width of the second metal crystal ranges from 300 nm to 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 usage requirements, and the width of the first metal crystal is, for example, 100nm, 110nm, 120nm, 130nm, 140nm, 150nm, 160nm, 170nm, 180nm, 190nm, 200nm, but is not limited to the listed values, and the proportion may also be a value between the example point value range.

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

[0055] In the embodiment 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 of 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 is wider 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 width, further improving the contact performance of the electrode on the transmission layer 24 of the same thickness.

[0057] In some embodiments, the number of first metal crystals is greater than the number of second metal crystals, which can prevent the second metal crystals from piercing the tunnel oxide layer and form efficient carrier flow channels, thereby reducing 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 spaced apart from each other, and the distance between the spaced apart cannot be too large, so that electrons can be transmitted between adjacent first metal crystals and second metal crystals, thereby improving the efficiency of extracting photocurrent from the solar cell.

[0059] In some other embodiments, the first metal crystal and the second metal crystal have a connected portion therebetween.

[0060] In some embodiments, along the thickness direction of the silicon substrate 10 , the thickness of the metal crystal 40 ranges from 50 nm to 300 nm.

[0061] The metal crystal 40 is a doped conductive layer 22 disposed in the transmission layer 24 . The thickness of the doped conductive layer 22 ranges from 50 nm to 300 nm. The metal crystal 40 has the above size to match the thickness of the doped conductive layer 22 to avoid puncturing the doped conductive layer 22 .

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

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

[0064] In some embodiments, the solar cell also includes a second electrode 32, the transmission layer 24 includes a doped conductive layer 22, and the doped conductive layer 22 is connected to the first electrode 31 and / or the second electrode 32 on the side facing away from the silicon substrate 10; 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 embodiment of the present application, the transmission layer 24 includes a doped conductive layer 22 and an ultra-thin dielectric layer 21 which are stacked, 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 pass 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, but also ensure that the function of the ultra-thin dielectric layer 21 is not affected. That is, the good chemical passivation and tunneling effect of the ultra-thin dielectric layer 21 are guaranteed. At the same time, the impact on the opening voltage can also be reduced to avoid the silicon substrate 10 from being damaged, ensure that the function of the silicon substrate 10 is not affected, and then ensure the performance of the solar cell.

[0066] In some embodiments, the solar cell also includes a second electrode 32, the transmission layer 24 includes a doped conductive layer 22, and 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 end is respectively connected to the first electrode 31 and the second electrode 32, and the second end is connected to a side of the doped conductive layer 22 close to the silicon substrate.

[0067] In the embodiment of the present application, the second end is connected to the side of the doped conductive layer 22 close to the silicon substrate, and the second metal crystal also does not pass 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, but also ensure that the function of the ultra-thin dielectric layer 21 is not affected. That is, the good chemical passivation and tunneling effect of the ultra-thin dielectric layer 21 are guaranteed. At the same time, the impact on the opening voltage can also be reduced to avoid the silicon substrate 10 from being damaged, so as 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 usage requirements, and the thickness of the doped conductive layer 22 is, for example, 50nm, 70nm, 90nm, 110nm, 130nm, 150nm, 170nm, 190nm, 210nm, 220nm, 240nm, 250nm, 270nm, 290nm, 300nm, but is not limited to the listed values, and the proportion may also be a value within the range of the example point values.

[0070] As a possible implementation, the solar cell may be a back-contact solar cell. The following description is made by taking a back-contact solar cell as an example. It should be understood that the following description is only for understanding and is not intended to be a specific limitation. 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 the backlight surface of the silicon substrate 10 and the light-receiving surface of the silicon substrate 10. The first electrode 31 and the second electrode 32 are both located on the backlight side of the silicon substrate 10. The doping type of the silicon substrate 10 can be N-doped or P-doped.

[0071] In some embodiments, reference Figure 1 As shown, the transmission 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 arranged on the partial surface of the first electrode 31 facing the silicon substrate 10, and the metal crystal 40 is arranged in 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, the metal crystal 40 is located in 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, which speeds up the transmission rate of carriers, thereby shortening the time required for carriers to pass through the doped conductive layer 22, and can improve the cell efficiency of the back contact cell. The metal crystal 40 is located in the doped conductive layer 22, and the metal crystal 40 does not destroy the function of the dielectric layer 21. While ensuring the passivation and tunneling effects of the dielectric layer 21, the cell efficiency is increased.

[0073] Furthermore, one transmission 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 transmission 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 in the doped conductive layer 22, and the metal crystal 40 does not damage the function of the dielectric layer 21. The efficiency of the solar cell is increased while ensuring the passivation and tunneling effects of the dielectric layer 21. When the metal crystal 40 is located in the diffusion layer, the metal crystal 40 can also provide a carrier transmission path to reduce the time required for the carrier to be transmitted 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, reference Figure 1 As shown, the solar cell further includes a fifth passivation layer and a second anti-reflection layer 50 , and the fifth passivation layer and the second anti-reflection layer 50 are disposed on the light-receiving surface of the silicon substrate 10 .

[0076] The material of the anti-reflection layer is a single layer or a stacked layer 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, reference Figure 1 As shown, the solar cell further includes a first passivation layer 23, which is disposed on the backlight side of the silicon substrate 10 and connected to the silicon substrate 10 and the side of the transmission layer 24 facing away from the silicon substrate 10. The first passivation layer 23 includes a single layer or a stacked structure of one or more materials such as aluminum oxide and silicon nitride.

[0078] In some embodiments, reference Figure 2 As shown, the transmission layer 24 includes a first transmission layer (the first transmission layer includes a dielectric layer 21 and a doped conductive layer 22 arranged in a stacked manner) and a second transmission layer (the second transmission layer includes a tunneling oxide layer 25 and a doped polysilicon layer 26 arranged in a stacked manner); the backlight surface of the silicon substrate 10 is respectively provided with a first transmission layer and a second transmission layer, and the first transmission layer and the second transmission layer are arranged at intervals; the first electrode 31 is connected to the surface of the first transmission layer away from the silicon substrate 10, and the second electrode 32 is connected to the surface of the second transmission layer away from the silicon substrate 10; the metal crystal 40 is arranged on the partial surface of the first electrode 31 facing the silicon substrate 10, and the metal crystal 40 is arranged in the first transmission layer; the metal crystal 40 is arranged on the partial surface of the second electrode 32 facing the silicon substrate 10, and the metal crystal 40 is arranged in the second transmission layer.

[0079] In the embodiment of the present application, the solar cell is a back contact cell, the metal crystal 40 is located in the first transmission layer, and the metal crystal 40 is in full contact with the first transmission layer. Under the action of the metal crystal 40, the solar cell is conducive to the movement of carriers to the first electrode 31, speeds up the transmission rate of carriers, and can improve the cell efficiency of the back contact cell.

[0080] The metal crystal 40 is located in the second transmission layer, and the metal crystal 40 is in full contact with the second transmission layer. Under the action of the metal crystal 40, the solar cell is conducive to the movement of carriers to the second electrode 32, speeding up the carrier transmission rate, and also improving the cell efficiency of the back contact cell.

[0081] Furthermore, in the embodiment 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 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] The backlight surface of the silicon substrate 10 is provided with a first transmission layer and a second transmission layer, respectively. The first transmission layer and the second transmission layer are arranged at intervals, and the intervals are arranged as follows: one is that in the extension direction of the backlight surface of the silicon substrate 10, that is, in the second direction B, the first transmission layer and the second transmission layer are alternately arranged at intervals on the backlight surface of the silicon substrate 10, and the two are in contact or non-contact in the extension direction of the backlight surface of the silicon substrate 10. The other is that in the extension direction of the backlight surface of the silicon substrate 10, that is, in the second direction B, the first transmission layer and the second transmission layer are alternately arranged at intervals on the backlight surface of the silicon substrate 10, and the two are partially overlapped in the thickness direction of the silicon substrate 10, that is, in the first direction C. The first transmission layer and the second transmission layer are of different types, one of the first transmission layer and the second transmission layer is an electron transmission layer, and the other of the first transmission layer and the second transmission layer is a hole transmission layer.

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

[0084] In the embodiment of the present application, the solar cell is a Topcon (Tunnel Oxide Passivated Contact) cell, and 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, the Topcon cell is conducive to the movement of carriers to the first electrode 31, speeds up the transmission rate of carriers, and can improve the cell efficiency of the Topcon cell.

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

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

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

[0088] Among them, LECO technology is a laser-induced local and microscopic metal-semiconductor contact optimization process. LECO technology is combined with special slurry to reduce the contact resistance between silicon and metal without increasing the recombination of the contact area, thereby improving the passivation of solar cells and greatly improving the efficiency of solar cells. In addition, it can also improve defects such as fogging and blackening in solar cells, greatly improving the yield of solar cells.

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

[0090] In the solar cell, the first electrode 31 and the second electrode 32 are formed by sintering, and under-burning or over-burning may occur during the sintering process (for example, the first electrode 31 includes Ag, and the second electrode 32 includes Al. The melting point of Ag is 961°C, and the melting point of Al is 660°C. When the sintering temperature is to be selected at an appropriate temperature, the temperature is lower than the melting temperature for Ag and higher than the melting temperature for Al. Therefore, the sintering temperatures of Ag and Al are not optimal temperatures, and under-burning or over-burning may occur). Neither under-burning nor over-burning meets the ideal sintering requirements of solar cells. When under-burning occurs, the ohmic contact is not fully formed, the series resistance will be too large, and the fill factor will be too low; over-burning will increase the probability of carrier recombination and the opening voltage will be too low.

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

[0092] For example, 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 (the ideal process temperature range is lower than the sintering temperature of the original conventional sintering process, see Figure 4 , which shows a schematic diagram of the curve of the sintering time and sintering temperature of the conventional sintering process and the LECO sintering process), at this time, the Ag paste is in an under-sintered state, and 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 contact. At the same time, since the Al paste with a relatively low melting point is in an ideal process temperature range during sintering and is combined with the local LECO process, the composite loss caused in the production process is also greatly reduced, the performance of the metal-semiconductor contact structure is enhanced, and the efficiency of the solar cell is improved; and 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, add the LECO process, refer to Figure 2 As shown, a laser of a specific wavelength is used to 3D scan the grid line surface of a solar cell. The specific scanning area can be the positive or negative electrode area of ​​the grid line surface of the solar cell, or the positive electrode area and the negative electrode area can be irradiated at the same time. 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 used in the manufacturing process of solar cells. The role of the laser is to excite the carriers with high energy for a short time. Then, under the action of the reverse voltage, the carriers will form a local current transmission channel and form a metal-semiconductor contact. In solar cells, the reverse voltage applied by 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 the scanning time is determined by maintaining an appropriate laser scanning speed. The LECO process significantly improves the efficiency of solar cells; at the same time, since the LECO process can further improve the contact, it can improve the inefficient sheets and EL fogging 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 the two ends of the first electrode 31 is less than the number distributed at the rest of the first electrode 31. The metal crystals 40 are located below the first electrode 31 and are distributed near the middle of the first electrode 31, which can reduce the transmission path of carriers in the first electrode 31, facilitate the direct extraction of carriers from the first electrode 31, and improve the collection efficiency of the first electrode 31 for carriers.

[0096] An embodiment of the present invention discloses a photovoltaic module, which includes a cover plate, a back plate, and a solar cell arranged 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 includes other structures. For example, the photovoltaic module may also include: a first packaging film disposed between the cover plate and the solar cell, and a second packaging film disposed between the back plate and the solar cell.

[0098] Photovoltaic modules and solar cells can refer to each other and have the same or similar beneficial effects as any of the aforementioned solar cells. In order to avoid repetition, they are not described here.

[0099] The present invention is further described in detail below with reference to specific embodiments.

[0100] Example

[0101] Reference Figure 1 As shown, in the solar cell, a dielectric layer 21 and a doped conductive layer 22 are provided on the backlight side 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 side of the silicon substrate 10. A fifth passivation layer and a second anti-reflection layer 50 are provided on the light-receiving side 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 portion of the surface of the first electrode 31 facing the silicon substrate 10 , and the metal crystal 40 is disposed in 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 100nm-200nm, and the width range of the second metal crystal is 300nm-600nm.

[0104] Comparative Example

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

[0106] The 1000 solar cells formed in the above embodiment and the 1000 solar cells formed in the above comparative example were subjected to performance tests under the same test conditions with different process parameters set. The test results are shown in Table 1 below.

[0107] Table 1

[0108] Group V-Bias P - Power v-sweep speed 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 embodiments (groups SY1, SY2, and SY3) are the results obtained by arithmetic averaging the test results of 1000 solar cells corresponding to the above embodiments. In Table 1, bias voltage V, power P, and scan rate v are all process parameters during the test. Eta represents the conversion efficiency of the solar cell, Uoc represents the open circuit voltage of the solar cell, Isc represents the short circuit current of the solar cell, and FF represents the fill factor of the solar cell.

[0110] It can be concluded from Table 1 above that the efficiency of the embodiment is higher than that of the comparative example (group BSL). The main reason is that in the embodiment, the metal crystal 40 includes both 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 100nm-200nm, and the width range of the second metal crystal is 300nm-600nm. A variety of carrier flow channels of various widths can be formed in the solar cell, which is more conducive to the movement of carriers to the first electrode 31, speeding up the transmission rate of carriers, further shortening the time required for carriers to pass through the transmission layer 24, thereby shortening the time required for carriers to pass through the transmission layer 24, and effectively improving the efficiency of the solar cell.

[0111] The present invention also discloses a method for preparing a solar cell. Figure 5 As shown, the preparation method comprises the following steps:

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

[0113] In this step, a transmission layer 24 may be deposited on one side of the silicon substrate 10 by using equipment such as low pressure chemical vapor deposition.

[0114] S12 , disposing a first slurry on a side of the transmission layer 24 away from the silicon substrate 10 .

[0115] In this step, the first slurry may be printed on the surface of the transmission layer 24 which is away from the silicon substrate 10 in a printing manner.

[0116] S13 , performing a first sintering on the first slurry at a temperature lower than the melting point of the first slurry to form the first electrode 31 .

[0117] In this step, the first slurry is sintered for the first time at a temperature lower than the melting point of the first slurry to form the first electrode 31. The first electrode 31 formed at this time is under-fired, which may result in incomplete formation of ohmic contact and large series resistance.

[0118] S14 , performing a second sintering on the first electrode 31 to form a metal crystal 40 in the transmission layer 24 ; the first electrode 31 is electrically connected to the metal crystal 40 .

[0119] In this step, the under-fired first electrode 31 in step S13 is sintered for the second time to form metal crystals 40 in the transmission layer 24, thereby enhancing the performance of the metal-semiconductor contact structure and improving the efficiency of the solar cell.

[0120] The method for preparing the solar cell of the embodiment of the present application adopts a two-time sintering method. The first sintering uses the temperature of the melting point of the first slurry to sinter the first slurry, which can avoid over-burning, but under-burning may occur. The second sintering forms metal crystals 40 in the transmission layer 24 during the second sintering. The metal crystals 40 can form a highly efficient carrier flow channel, which is conducive to the movement of carriers to the first electrode 31, speeding up the carrier transmission rate, thereby shortening the time required for the carriers to pass through the transmission layer 24, and effectively improving the efficiency of the solar cell.

[0121] The embodiment of the present invention also discloses another method for preparing a solar cell, wherein the solar cell further comprises a second electrode 32, wherein the melting point of the second electrode 32 is lower than the melting point of the first electrode 31; Figure 6 As shown, the preparation method comprises the following steps:

[0122] S21 , disposing a transmission layer 24 on one side of the silicon substrate 10 .

[0123] This step refers to the above-mentioned step S11, and the embodiment of the present application will not be traced back.

[0124] S22 , disposing a first slurry and a second slurry on a side of the transmission layer 24 away from the silicon substrate 10 .

[0125] In this step, the first slurry and the second slurry may be printed on the surface of the transmission layer 24 which is away from the silicon substrate 10 by printing.

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

[0127] In this step, after the first slurry and the second slurry are sintered for the first time at a temperature lower than or equal to the melting point of the second slurry, the second electrode 32 has a better sintered structure, while the first electrode 31 is under-sintered.

[0128] S24 , performing a second sintering on the first electrode 31 to form a metal crystal 40 in the transmission layer 24 ; the first electrode 31 and / or the second electrode 32 are electrically connected to the metal crystal 40 .

[0129] In some embodiments, reference Figure 2 As shown, step S24 also includes the following steps: applying a reverse voltage V to the first electrode 31 and the second electrode 32; performing laser D scanning on the first electrode 31 to form a metal crystal 40 in the transmission layer 24. At this time, when the laser D scans the first electrode 31, the 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 and then form a metal-semiconductor contact, that is, the metal crystal 40 is formed.

[0130] The method for preparing a solar cell in the embodiment of the present application adopts the method of printing the first slurry and the second slurry at the same time and sintering twice to prepare the first electrode 31 and the second electrode 32, which can reduce the processing steps and improve the processing efficiency, and can also avoid the influence of over-firing or under-firing on the efficiency of the solar cell.

[0131] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0132] Each embodiment in this specification is described in a related manner, and the same or similar parts between 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 products containing 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 description 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 comprises 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 metal crystals (40) are arranged in the transmission layer (24); The first electrode (31) is located on a 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 the metal crystals (40) distributed at the two ends of the first electrode (31) is smaller than the number distributed at other 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 relatively small accounts for 8% to 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 in the first electrode (31), the total width of the plurality of 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 the plurality of 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 to 4, characterized in that: Along the width direction of the first electrode (31), the width of the metal crystal (40) ranges from 100 nm to 600 nm.

6. The solar cell according to claim 1, characterized in that The metal crystal (40) comprises a first metal crystal and a second metal crystal; Along the width direction of the first electrode (31), the width of the first metal crystals ranges from 100 nm to 200 nm, and the width of the second metal crystals ranges from 300 nm to 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 of the metal crystal (40) ranges from 50 nm to 300 nm.

9. The solar cell according to claim 1, characterized in that: The solar cell further comprises 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 comprises the solar cell according to any one of claims 1 to 9.

11. A method for preparing a solar cell, characterized in that: A transmission layer (24) is provided on one side of the silicon substrate (10); Disposing a first slurry on a side of the transmission layer (24) away from the silicon substrate (10); Sintering the first slurry for the first time at a temperature lower than the melting point of the first slurry to form a first electrode (31); The first electrode (31) is sintered for a second time to form metal crystals (40) in the transmission layer (24); the first electrode (31) is electrically connected to the metal crystals (40).

12. The method for preparing a solar cell according to claim 11, characterized in that: The solar cell further comprises a second electrode (32), the melting point of the second electrode (32) being lower than the melting point of the first electrode (31); the preparation method comprises: A transmission layer (24) is provided on one side of the silicon substrate (10); Disposing a first slurry and a second slurry on a side of the transmission layer (24) away from the silicon substrate (10); Sintering the first slurry and the second slurry for the first time at a temperature lower than or equal to the melting point of the second slurry to form a first electrode (31) and a second electrode (32) respectively; The first electrode (31) is sintered for a second time to form metal crystals (40) in the transmission layer (24); the first electrode (31) and / or the second electrode (32) are electrically connected to the metal crystals (40).

13. The method for preparing 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) in the transmission layer (24) comprises: applying a reverse voltage to the first electrode (31) and the second electrode (32); The first electrode (31) is laser scanned to form metal crystals (40) in the transmission layer (24).

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