Solar cell, preparation method thereof and photovoltaic module
By depositing an insulating layer as a mask on the surface of a solar cell and combining laser thinning and wet etching methods, the high cost and complex process of fabricating narrow metal electrodes in existing technologies have been solved, achieving low-cost and high-yield metal electrode fabrication.
Patent Information
- Application Number
- CN202411433204.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2025-11-25
Smart Images
Figure CN121013443A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of solar cell technology, and in particular to a solar cell and its preparation method, and a photovoltaic module. Background Technology
[0002] Electroplating is one method of fabricating metal electrodes for solar cells. Narrower metal electrodes are beneficial for improving the efficiency of solar cells; however, electroplating methods for fabricating narrower metal electrodes face challenges such as increased manufacturing costs, complex and cumbersome processes, and poor quality. More specifically, electroplating methods cannot simultaneously achieve low cost, simple processes, and stable yield. Summary of the Invention
[0003] This application discloses a solar cell and its preparation method, as well as a photovoltaic module. It can maintain a low cost while manufacturing a narrow metal electrode, and also has the advantages of simple process and stable yield.
[0004] To achieve the above objectives, in a first aspect, embodiments of this application disclose a method for fabricating a solar cell, comprising the following steps:
[0005] A solar cell precursor is provided; wherein the solar cell precursor includes a silicon substrate and a doped layer disposed on the surface of the silicon substrate, the doped layer having an electrode placement region;
[0006] A metal seed layer is formed on the side of the doped layer that is opposite to the silicon substrate;
[0007] An insulating layer is deposited on the side of the metal seed layer that is opposite to the silicon substrate;
[0008] The insulating layer corresponding to the electrode setting area is removed; wherein the metal seed layer corresponding to the electrode setting area is exposed, and the insulating layer outside the electrode setting area is retained;
[0009] Metal electrodes are formed by electroplating on the exposed metal seed layer.
[0010] In a possible implementation of the first aspect, after the step of depositing an insulating layer on the side of the metal seed layer opposite to the silicon substrate, the deposited insulating layer has a first thickness;
[0011] The step of removing the insulating layer corresponding to the electrode setting area includes:
[0012] The insulating layer corresponding to the electrode placement area is thinned using physical methods; wherein the thinned insulating layer has a second thickness, the second thickness being less than the first thickness;
[0013] The insulating layer is wet-etched, and etching stops after the thinned insulating layer is removed.
[0014] In a possible implementation of the first aspect, the step of thinning the insulating layer corresponding to the electrode placement region includes:
[0015] The insulating layer corresponding to the electrode setting area is thinned using a laser.
[0016] And / or, the second thickness is 30% to 50% of the first thickness.
[0017] In one possible implementation of the first aspect, the solar cell precursor further includes a functional film disposed on the side of the doped layer facing away from the silicon substrate;
[0018] Before the step of forming a metal seed layer on the side of the doped layer facing away from the silicon substrate, the method for fabricating the solar cell further includes the following steps:
[0019] The functional film corresponding to the electrode setting area is removed; wherein the functional film outside the electrode setting area is retained.
[0020] In a possible implementation of the first aspect, the step of removing the functional film corresponding to the electrode setting region includes:
[0021] A groove is formed by removing the functional film corresponding to the electrode setting area using a laser.
[0022] After the step of forming a metal seed layer on the side of the doped layer away from the silicon substrate, the metal seed layer corresponding to the electrode setting region is formed on the surface of the doped layer through the groove, and the metal seed layer outside the electrode setting region is formed on the side of the functional film away from the doped layer.
[0023] In a possible implementation of the first aspect, the step of depositing an insulating layer on the side of the metal seed layer opposite to the silicon substrate includes:
[0024] An insulating layer is deposited on the side of the metal seed layer opposite to the silicon substrate using magnetron sputtering.
[0025] In a possible implementation of the first aspect, the step of forming a metal seed layer on the side of the doped layer opposite to the silicon substrate includes:
[0026] A metal seed layer is fabricated on the side of the doped layer opposite to the silicon substrate using magnetron sputtering; wherein the metal seed layer and the insulating layer are deposited sequentially in the same magnetron sputtering apparatus.
[0027] In a possible implementation of the first aspect, in the step of depositing an insulating layer on the side of the metal seed layer opposite to the silicon substrate using magnetron sputtering, the sputtering chamber temperature is 100°C to 150°C, and the sputtering power density is 2 W / cm². 2 ~8W / cm 2 The argon flow rate is 500 sccm to 1000 sccm, the substrate temperature is 200℃ to 300℃, the sputtering pressure is 0.3 Pa to 0.5 Pa, the argon to oxygen flow ratio is (2.5 to 3.5): 1, the target material is an aluminum target and / or a silicon target, and the sputtering time is 5 min to 20 min.
[0028] And / or, the step of fabricating a metal seed layer on the side of the doped layer facing away from the silicon substrate using magnetron sputtering includes:
[0029] A diffusion barrier layer is fabricated on the side of the doped layer facing away from the silicon substrate using magnetron sputtering; wherein the thickness of the deposited diffusion barrier layer is 5 nm to 20 nm.
[0030] A copper seed layer is formed on the side of the diffusion barrier layer facing away from the doped layer; the thickness of the deposited copper seed layer is 100 nm to 400 nm.
[0031] In a possible implementation of the first aspect, after the step of electroplating to form a metal electrode on the exposed metal seed layer, the electroplated metal electrode has a third thickness;
[0032] Following the step of electroplating a metal electrode onto the exposed metal seed layer, the method for fabricating the solar cell further includes the following steps:
[0033] The remaining insulating layer is removed by wet etching;
[0034] The exposed metal seed layer is removed by wet etching; wherein the metal electrode after wet etching has a fourth thickness, which is less than the third thickness.
[0035] In one possible implementation of the first aspect, the thickness of the insulating layer is 100 nm to 400 nm;
[0036] And / or, the insulating layer is an oxide insulating layer;
[0037] And / or, the material of the insulating layer is selected from at least one of silicon oxide or aluminum oxide;
[0038] And / or, the metal seed layer includes a diffusion barrier layer and a copper seed layer, the diffusion barrier layer and the copper seed layer being sequentially stacked on the side of the doped layer opposite to the silicon substrate along a direction away from the silicon substrate;
[0039] And / or, the metal electrode is a copper electrode, and the end of the copper electrode facing away from the silicon substrate is also electroplated with a tin protective layer; the thickness of the copper electrode is 3μm to 5μm, and the thickness of the tin protective layer is 1μm to 2μm.
[0040] Secondly, embodiments of this application disclose a solar cell, which is prepared by the solar cell preparation method described in the first aspect;
[0041] The solar cell includes a silicon substrate, a plurality of doped layers, a plurality of metal seed layers, and a plurality of metal electrodes. The doped layers are disposed on the surface of the silicon substrate, the metal seed layers are disposed on the doped layers and are in ohmic contact with the doped layers, and the metal electrodes are disposed on the side of the metal seed layers facing away from the doped layers.
[0042] In a possible implementation of the second aspect, the solar cell further includes a plurality of first dielectric layers, a plurality of second dielectric layers, and a functional film; the first dielectric layers and the second dielectric layers are alternately disposed on the back side of the silicon substrate; a trench region is formed between adjacent first dielectric layers and second dielectric layers;
[0043] The doped layer is of two types: an N-type doped polysilicon layer and a P-type doped polysilicon layer. Each N-type doped polysilicon layer is disposed on the side of each first dielectric layer facing away from the silicon substrate, and each P-type doped polysilicon layer is disposed on the side of each second dielectric layer facing away from the silicon substrate. The trench region separates adjacent N-type doped polysilicon layers and P-type doped polysilicon layers.
[0044] The functional film is disposed on the side of the N-type doped polycrystalline silicon layer facing away from the silicon substrate and on the side of the P-type doped polycrystalline silicon layer facing away from the silicon substrate;
[0045] There are two types of metal electrodes, namely a first metal electrode and a second metal electrode. The first metal electrode passes through the functional film and makes ohmic contact with the N-type doped polycrystalline silicon layer, and the second metal electrode passes through the functional film and makes ohmic contact with the P-type doped polycrystalline silicon layer.
[0046] Thirdly, embodiments of this application disclose a photovoltaic module, including a plurality of solar cells connected in series and / or in parallel, wherein at least one of the solar cells is the solar cell described in the second aspect.
[0047] Compared with existing technologies, the advantages of this application are as follows: The method for fabricating this solar cell involves depositing an insulating layer as a mask on the side of the metal seed layer facing away from the silicon substrate. Compared to methods that obtain masks through coating, the mask deposition method of this application avoids problems such as adhesive leakage, misalignment, and contamination inherent in coating methods, and the process is simpler. Furthermore, compared to methods using photosensitive dry films as masks, the mask deposition method of this application can maintain lower costs while fabricating narrower metal electrodes. In summary, the fabrication method of this application can maintain lower costs while fabricating narrower metal electrodes, and also has the advantages of simple processes and stable yield. Attached Figure Description
[0048] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0049] Figure 1 This is a schematic diagram of the structure of a solar cell provided in an embodiment of this application;
[0050] Figure 2 This is a flowchart of a method for fabricating a solar cell disclosed in Embodiment 1 of this application;
[0051] Figure 3 This is a schematic diagram of the structure of the solar cell precursor of Embodiment 1 of this application after step S2;
[0052] Figure 4 This is a schematic diagram of the structure of the solar cell precursor of Embodiment 1 of this application after step S3;
[0053] Figure 5 This is a schematic diagram of the structure of the solar cell precursor of Embodiment 1 of this application after step S4;
[0054] Figure 6 This is a schematic diagram of the structure of the solar cell precursor of Embodiment 1 of this application after step S5;
[0055] Figure 7 This is a schematic diagram of the structure of the solar cell precursor of Embodiment 1 of this application after step S6;
[0056] Figure 8 This is a schematic diagram of the structure of the solar cell precursor of Embodiment 1 of this application after step S7.
[0057] Explanation of reference numerals in the attached figures:
[0058] 100, Solar cell; 110, Silicon substrate; 111, Back side; 120, First dielectric layer; 130, Second dielectric layer; 140, N-type doped polycrystalline silicon layer; 150, P-type doped polycrystalline silicon layer; 160, Functional film; 161, Trench; A1, Electrode placement area; A2, Trench area; 170, Metal seed layer; 180a, Insulating layer with first thickness; 180b, Thinned insulating layer; 180c, Remaining insulating layer; 190, Metal electrode; 191, Tin protective layer. Detailed Implementation
[0059] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0060] In this application, the terms "upper," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing this application and its embodiments, and are not intended to limit the indicated device, element, or component to having a specific orientation, or to be constructed and operated in a specific orientation.
[0061] Furthermore, in addition to indicating location or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in some cases to indicate a certain dependency or connection relationship. Those skilled in the art can understand the specific meaning of these terms in this application based on the specific circumstances.
[0062] Furthermore, the term "setup" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection via an intermediate medium, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0063] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, elements, or components (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, elements, or components. Unless otherwise stated, "a plurality of" means two or more.
[0064] Electroplating can produce lower-cost metal electrodes to replace silver paste sintered electrodes, making it a major direction for cost reduction and efficiency improvement in solar cells. The electroplating process first requires forming a metal seed layer on the surface of the solar cell. Then, a mask is fabricated based on the pattern of the metal seed layer. Finally, metal is electroplated onto the metal seed layer to thicken it, forming a metal electrode with a certain thickness and width.
[0065] The aforementioned mask fabrication methods include photosensitive dry film and wet film. Photosensitive dry film is a polymer compound that undergoes a polymerization reaction upon exposure to ultraviolet light, forming a stable substance that adheres to the surface of the metal seed layer, thus blocking electroplating and etching. The resolution of the photosensitive dry film is related to its thickness. Specifically, the thicker the photosensitive dry film, the more severe the light refraction during exposure, resulting in lower resolution. In other words, the thinner the photosensitive dry film, the higher the resolution, which is more advantageous for fabricating narrower metal electrodes. However, the disadvantage of photosensitive dry film is that thinner films are more expensive. In other words, it is difficult to maintain a low cost when fabricating narrower metal electrodes. The minimum linewidth of metal electrodes achievable with photosensitive dry film is only 20 μm.
[0066] Wet films, such as photoresist and ink, have low viscosity and a certain degree of liquid fluidity. They are typically applied uniformly to the surface of solar cells using methods such as spraying, slot coating, blade coating, or screen printing. Although wet films offer improved resolution compared to photosensitive films, they still require drying after coating, making the process complex, cumbersome, and lengthy. Furthermore, issues such as adhesive leakage, misalignment, and contamination can occur during coating, leading to poor quality.
[0067] In summary, the above-mentioned mask fabrication methods cannot simultaneously achieve the advantages of low-cost fabrication of fine metal electrodes, simple process, and stable yield.
[0068] Based on the above analysis, this application provides a fabrication method in which an insulating layer is deposited as a mask on the side of a metal seed layer facing away from the silicon substrate. Compared to the method of obtaining a mask by coating, the mask deposition method of this application avoids problems such as resist leakage, misalignment, and contamination that exist in the coating method, and the process of mask deposition is simpler. On the other hand, compared to the method of using photosensitive dry film as a mask, the mask deposition method of this application can maintain a low cost while fabricating metal electrodes with a relatively narrow width. In summary, the fabrication method of this application can maintain a low cost while fabricating metal electrodes with a relatively narrow width, and also has the advantages of simple process and stable yield.
[0069] The technical solution of the present invention will now be described in conjunction with the embodiments and accompanying drawings.
[0070] In a first aspect, embodiments of this application disclose a method for fabricating a solar cell, comprising the following steps:
[0071] A solar cell precursor is provided; wherein the solar cell precursor includes a silicon substrate and a doped layer disposed on the surface of the silicon substrate, and the doped layer has an electrode placement region.
[0072] A metal seed layer is fabricated on the side of the doped layer that faces away from the silicon substrate;
[0073] An insulating layer is deposited on the side of the metal seed layer that is away from the silicon substrate;
[0074] The insulating layer corresponding to the electrode setting area is removed; the metal seed layer corresponding to the electrode setting area is exposed, while the insulating layer outside the electrode setting area is retained.
[0075] Metal electrodes are formed by electroplating on the exposed metal seed layer.
[0076] It should be noted that, in the above, the solar cell precursor refers to a semi-finished solar cell, such as a semi-finished product obtained after fabricating a doped layer on a silicon substrate. In this solar cell precursor, the doped layer can be disposed on the front and / or back sides of the silicon substrate. The method of depositing the insulating layer can be physical vapor deposition or chemical vapor deposition, but physical vapor deposition is preferred. The term "electrode placement region" refers to the region on the doped layer where a metal electrode is to be fabricated, such as a local region on the side of the doped layer facing away from the silicon substrate. Generally, the electrode placement region can be any region on the side of the doped layer facing away from the silicon substrate. The term "correspondence" refers to the correspondence in the thickness direction of the silicon substrate. The insulating layer corresponding to the electrode placement region can be understood as: a local insulating layer opposite to the electrode placement region in the thickness direction of the silicon substrate.
[0077] The preparation method of this application uses the deposited insulating layer as a mask. Compared with the above-mentioned photosensitive dry film, which requires exposure and development to complete patterning etching, the deposited insulating layer is easier to achieve high-precision patterning etching and has a lower manufacturing cost. This is beneficial to fabricate metal electrodes with a finer width while maintaining low cost.
[0078] Compared to the aforementioned wet film, the insulating layer does not require drying after deposition, nor does it require exposure and development, making the overall process simpler. This deposited insulating layer, used as an electroplating mask, also avoids defects such as adhesive leakage, misalignment, and contamination inherent in the wet film process, resulting in a more stable yield.
[0079] In summary, the preparation method of this application can maintain a low cost while fabricating metal electrodes with a narrow width, and also has the advantages of simple process and stable yield.
[0080] In some embodiments, after the step of depositing an insulating layer on the side of the metal seed layer facing away from the silicon substrate, the deposited insulating layer has a first thickness.
[0081] The step of removing the insulating layer corresponding to the electrode setting area includes:
[0082] The insulating layer corresponding to the electrode placement area is thinned using physical methods; wherein the thinned insulating layer has a second thickness, which is less than the first thickness. It should be noted that since the deposition thickness of the insulating layer is not uniform everywhere, the first thickness and the second thickness refer to the average thickness of the insulating layer.
[0083] The insulating layer is etched using a wet etching process, and etching stops once the thinned insulating layer is removed.
[0084] The aforementioned physical methods, such as laser thinning or ion thinning, avoid defects like adhesive leakage, misalignment, and contamination caused by patterned paste etching compared to methods using patterned paste. However, physical methods can affect the performance of the metal seed layer. For example, if a laser penetrates the insulating layer to irradiate the surface of the metal seed layer, the high temperature generated by the laser will cause oxidation, forming an oxide layer. This oxide layer affects the conductivity of the metal seed layer, thus impacting subsequent electroplating. Because the degree and depth of oxidation caused by the laser are uncontrollable, even subsequent wet cleaning to remove the oxide layer is difficult, potentially leading to incomplete oxide removal or an excessively thin metal seed layer, thus affecting subsequent processes.
[0085] To avoid the above situations, the preparation method of this application first uses physical methods to thin the insulating layer, that is, without penetrating the insulating layer, and then performs wet etching. During the wet etching process, the thinned insulating layer is selectively removed by utilizing the thickness difference of the insulating layer, so that the thinned insulating layer is penetrated. This preparation method can not only complete the patterning of the insulating layer, but also reduce the impact of physical methods on the performance of the metal seed layer.
[0086] Preferably, the step of thinning the insulating layer corresponding to the electrode placement area includes:
[0087] Laser is used to thin the insulating layer corresponding to the electrode setting area.
[0088] Laser thinning is relatively easy to achieve high-precision patterning. This fabrication method removes the insulating layer in the electrode area by first laser thinning and then wet etching. The purpose is to prevent the laser from penetrating the insulating layer and directly ablating the metal seed layer, which would cause oxidation of the metal seed layer.
[0089] It is understandable that the insulating layer outside the electrode area is not thinned by laser, thus maintaining the first thickness. Since the second thickness is less than the first thickness, the etching rate is consistent throughout the insulating layer during wet etching. When the etching depth reaches the second thickness, the insulating layer corresponding to the electrode area is removed. Although the insulating layer outside the electrode area sacrifices some thickness, it is still retained as an electroplating mask. Using the above method can both avoid oxidation of the metal seed layer and achieve patterned etching of the insulating layer.
[0090] The ratio of the second thickness to the first thickness should not be too low, otherwise the laser processing time will be difficult to control during laser thinning, and the insulating layer will be easily penetrated by the laser. The ratio of the second thickness to the first thickness should not be too high, otherwise the subsequent wet etching time will be too long, and the remaining insulating layer thickness after wet etching will be insufficient. Preferably, the second thickness is 30% to 50% of the first thickness, including any value within this range, such as 30%, 40%, or 50%. This can effectively prevent the laser from penetrating the insulating layer, shorten the wet etching time, and ensure that the remaining insulating layer thickness after wet etching is thick enough to effectively block electroplating.
[0091] In some embodiments, the solar cell precursor further includes a functional film disposed on the side of the doped layer facing away from the silicon substrate. The functional film is, for example, a passivation film and / or an antireflection film.
[0092] Before the step of fabricating a metal seed layer on the side of the doped layer facing away from the silicon substrate, the method for fabricating this solar cell further includes the following steps:
[0093] The functional film corresponding to the electrode setting area is removed; however, the functional film outside the electrode setting area is retained.
[0094] This preparation method removes the functional film corresponding to the electrode setting area, which can improve the performance of solar cells by adding functional films, and also allows the subsequently fabricated metal seed layer to pass through the functional film and contact the doped layer.
[0095] Preferably, the step of removing the functional film corresponding to the electrode setting area includes:
[0096] A groove is formed by removing the functional film corresponding to the electrode setting area using a laser.
[0097] After the step of forming a metal seed layer on the side of the doped layer away from the silicon substrate, the metal seed layer corresponding to the electrode setting area is formed on the surface of the doped layer through a groove, and the metal seed layer outside the electrode setting area is formed on the side of the functional film away from the doped layer.
[0098] This preparation method uses laser to pattern and groove the functional film, which has the advantages of high processing accuracy and simple operation.
[0099] In some embodiments, the step of depositing an insulating layer on the side of the metal seed layer facing away from the silicon substrate includes:
[0100] An insulating layer is deposited on the side of the metal seed layer facing away from the silicon substrate using magnetron sputtering.
[0101] Magnetron sputtering is a physical vapor deposition (PVD) method with advantages such as low deposition temperature, fast deposition rate, good uniformity of deposited films, and composition close to that of the target material. Using magnetron sputtering to deposit insulating layers avoids the formation of a wrap-around coating, thus eliminating the need for a wrap-around removal operation and simplifying the process.
[0102] Further, the step of fabricating a metal seed layer on the side of the doped layer facing away from the silicon substrate includes:
[0103] A metal seed layer is fabricated on the side of the doped layer facing away from the silicon substrate using magnetron sputtering; wherein the metal seed layer and the insulating layer are deposited sequentially in the same magnetron sputtering apparatus.
[0104] Since both the metal seed layer and the insulating layer are deposited using magnetron sputtering, they can be deposited sequentially in the same magnetron sputtering equipment. This simplifies the process and reduces equipment costs, allowing the metal seed layer and the insulating layer to be fabricated using a single magnetron sputtering device.
[0105] Preferably, in the step of depositing an insulating layer on the side of the metal seed layer facing away from the silicon substrate using magnetron sputtering, the sputtering chamber temperature is 100°C to 150°C, including any value within this temperature range, such as 100°C, 125°C, and 150°C. Depositing the insulating layer within this temperature range reduces oxidation of the metal seed layer. The sputtering power density is 2 W / cm². 2 ~8W / cm 2 This includes any point within that power density range, for example, 2 W / cm². 2 6W / cm 2 Or 8W / cm 2The argon flow rate is 500 sccm to 1000 sccm, including any value within this flow rate range, such as 500 sccm, 750 sccm, or 1000 sccm; the substrate temperature is 200℃ to 300℃, including any value within this temperature range, such as 200℃, 250℃, or 300℃; the sputtering pressure is 0.3 Pa to 0.5 Pa, including any value within this pressure range, such as 0.3 Pa, 0.4 Pa, or 0.5 Pa; the argon to oxygen flow ratio is (2.5 to 3.5):1, including any value within this flow ratio range, such as 2.5:1, 3:1, or 3.5:1; the target material is an aluminum target and / or a silicon target; and the sputtering time is 5 min to 20 min, including any value within this time range, such as 5 min, 15 min, or 20 min.
[0106] Preferably, the step of fabricating a metal seed layer on the side of the doped layer facing away from the silicon substrate using magnetron sputtering includes:
[0107] A diffusion barrier layer is fabricated on the side of the doped layer away from the silicon substrate using magnetron sputtering; wherein the thickness of the deposited diffusion barrier layer is 5 nm to 20 nm, including any value within this thickness range, such as 5 nm, 10 nm or 20 nm.
[0108] A copper seed layer is fabricated on the side of the diffusion barrier layer facing away from the doped layer; the thickness of the deposited copper seed layer is 100 nm to 400 nm, including any value within this thickness range, such as 100 nm, 250 nm or 400 nm.
[0109] More specifically, the target material used in the diffusion barrier layer includes at least one of the following: Ni, Cr, W, Ti, NiCr, NiW, TiW, NiMo, with a sputtering power density of 2 W / cm². 2 ~8W / cm 2 The argon flow rate was 500 sccm to 1000 sccm, the substrate temperature was <200℃, the sputtering pressure was 0.3 Pa to 0.5 Pa, and the sputtering time was 5 min to 20 min. Then, a copper seed layer with a thickness of 100 nm to 400 nm was deposited by magnetron sputtering on the diffusion barrier layer, wherein the copper seed layer was sputtered using a copper target with a purity >99.99%.
[0110] The diffusion barrier layer is used to prevent copper from the copper seed layer from diffusing into the silicon substrate and to increase the adhesion between the copper seed layer and the silicon substrate.
[0111] In some embodiments, after the step of electroplating to form a metal electrode on a bare metal seed layer, the electroplated metal electrode has a third thickness.
[0112] Following the step of electroplating a metal electrode onto the exposed metal seed layer, the fabrication method of this solar cell further includes the following steps:
[0113] Wet etching removes the remaining insulating layer;
[0114] Wet etching removes the exposed metal seed layer; wherein, the metal electrode after wet etching has a fourth thickness, which is less than the third thickness.
[0115] Removing the metal seed layer can prevent excess metal seed layer from affecting the performance of solar cells. Taking a back-contact solar cell as an example, after the metal seed layer is deposited, it covers the entire back side of the silicon substrate and may cause two doped layers with opposite conductivity types to connect and leak current. In order to avoid leakage current, the metal seed layer outside the metal electrode must be removed.
[0116] To remove the excess metal seed layer, the insulating layer used as a mask must first be removed, followed by wet etching to remove the metal seed layer. Wet etching avoids affecting the properties of the metal electrode. It is understandable that although the etching solution used to remove the metal seed layer generally corrodes the metal electrode, the metal electrode with the third thickness is thicker than the metal seed layer. Therefore, after wet etching removes the metal seed layer, the metal electrode sacrifices some thickness, becoming the fourth thickness.
[0117] The thickness of the insulating layer should not be too thin, to avoid uneven deposition resulting in undeposited areas and short circuits in the gate lines after subsequent electroplating. The thickness of the insulating layer should also not be too thick, to avoid prolonged deposition time and high manufacturing costs. Preferably, the thickness of the insulating layer is 100nm to 400nm, including any value within this range, such as 100nm, 250nm, or 400nm. This thickness specifically refers to a first thickness. Depositing an insulating layer within this thickness range can avoid the aforementioned undeposited areas and complete the deposition in a relatively short time.
[0118] Preferably, the insulating layer is an oxide insulating layer. Oxide insulating layers are readily obtained using deposition methods.
[0119] Preferably, the insulating layer is made of at least one of silicon oxide or aluminum oxide. Silicon oxide and aluminum oxide are low-cost materials with good insulation properties.
[0120] Preferably, the metal seed layer includes a diffusion barrier layer and a copper seed layer, which are sequentially stacked on the side of the doped layer away from the silicon substrate along the direction away from the silicon substrate.
[0121] Preferably, the metal electrode is a copper electrode, and a tin protective layer is electroplated on the end of the copper electrode facing away from the silicon substrate; the thickness of the copper electrode is 3μm to 5μm, including any value within this thickness range, such as 3μm, 4μm or 5μm, and the thickness of the tin protective layer is 1μm to 2μm, including any value within this thickness range, such as 1μm, 1.5μm or 2μm.
[0122] Secondly, this application discloses a solar cell 100, which is prepared by the solar cell preparation method described in the first aspect.
[0123] The solar cell 100 includes a silicon substrate 110, several doped layers, several metal seed layers 170, and several metal electrodes 190. The doped layers are disposed on the surface of the silicon substrate 110, the metal seed layers 170 are disposed on the doped layers and in ohmic contact with the doped layers, and the metal electrodes 190 are disposed on the side of the metal seed layers 170 facing away from the doped layers.
[0124] Preferably, the solar cell 100 further includes a plurality of first dielectric layers 120, a plurality of second dielectric layers 130, and a functional film 160. The first dielectric layers 120 and the second dielectric layers 130 are alternately disposed on the back surface 111 of the silicon substrate 110. A trench region A2 is formed between adjacent first dielectric layers 120 and second dielectric layers 130.
[0125] The materials of the first dielectric layer 120 and the second dielectric layer 130 may include a variety of dielectric materials, such as at least one selected from silicon oxide, magnesium fluoride, amorphous silicon, polycrystalline silicon, silicon carbide, silicon nitride, silicon oxynitride, aluminum oxide, or titanium oxide. Specifically, the first dielectric layer 120 and the second dielectric layer 130 may be composed of a silicon oxide layer containing silicon oxide. This is because the silicon oxide layer has excellent passivation properties, can minimize the recombination loss of minority carriers on the semiconductor substrate surface, and is a thin film with excellent durability for subsequent high-temperature processes.
[0126] The first dielectric layer 120 and the second dielectric layer 130 can also function as pinhole channels, allowing charge carriers within the solar cell 100 to move freely. The first dielectric layer 120 and the second dielectric layer 130 also selectively allow charge carriers to pass through the N-type doped polysilicon layer 140 and the P-type doped polysilicon layer 150, respectively, which helps reduce carrier recombination losses. Furthermore, the first dielectric layer 120 and the second dielectric layer 130 can respectively act as diffusion barriers to prevent the dopants from the N-type doped polysilicon layer 140 and the P-type doped polysilicon layer 150 from diffusing into the silicon substrate 110.
[0127] There are two types of doped layers: an N-type doped polysilicon layer 140 and a P-type doped polysilicon layer 150. Each N-type doped polysilicon layer 140 is disposed on the side of each first dielectric layer 120 facing away from the silicon substrate 110, and each P-type doped polysilicon layer 150 is disposed on the side of each second dielectric layer 130 facing away from the silicon substrate 110. The trench region A2 separates adjacent N-type doped polysilicon layers 140 and P-type doped polysilicon layers 150.
[0128] Functional films 160 are disposed on the side of N-type doped polysilicon layer 140 facing away from silicon substrate 110 and on the side of P-type doped polysilicon layer 150 facing away from silicon substrate 110. Functional films 160 are, for example, passivation films and / or antireflection films, and the material of functional films 160 can be oxides, nitrides or oxynitrides.
[0129] There are two types of metal electrodes 190, namely a first metal electrode and a second metal electrode. The first metal electrode passes through the functional film 160 and makes a 140-ohm contact with the N-type doped polycrystalline silicon layer, and the second metal electrode passes through the functional film 160 and makes a 150-ohm contact with the P-type doped polycrystalline silicon layer.
[0130] The solar cell 100 is a back-contact solar cell with no metal electrodes on its front side, which eliminates the light loss caused by the metal electrodes and can further improve the conversion efficiency of the solar cell 100.
[0131] It should be noted that this solar cell can also be other types of solar cells, such as heterojunction solar cells.
[0132] Thirdly, embodiments of this application disclose a photovoltaic module, including a plurality of solar cells connected in series and / or in parallel, wherein at least one solar cell is the solar cell described in the second aspect.
[0133] The technical solution of the present invention will be described below with reference to the embodiments.
[0134] Example 1
[0135] See Figure 2 This embodiment discloses a method for fabricating a solar cell, including the following steps:
[0136] S1. Provide solar cell precursors: See [link] Figure 3The solar cell precursor includes a silicon substrate 110, a first dielectric layer 120, a second dielectric layer 130, two doped layers, and a functional film 160. The first dielectric layer 120 and the second dielectric layer 130 are alternately disposed on the back surface 111 of the silicon substrate 110. A trench region A2 is formed between adjacent first dielectric layers 120 and second dielectric layers 130. The two doped layers are N-type doped polycrystalline silicon layers 140 and P-type doped polycrystalline silicon layers 150. Each N-type doped polycrystalline silicon layer 140 is disposed on the side of each first dielectric layer 120 facing away from the silicon substrate 110, and each P-type doped polycrystalline silicon layer 150 is disposed on the side of each second dielectric layer 130 facing away from the silicon substrate 110. The trench region A2 separates adjacent N-type doped polycrystalline silicon layers 140 and P-type doped polycrystalline silicon layers 150. The functional film 160 is disposed on the side of the N-type doped polysilicon layer 140 facing away from the silicon substrate 110, the side of the P-type doped polysilicon layer 150 facing away from the silicon substrate 110, and the surface of the trench region A2. The functional film 160 is a passivation film.
[0137] S2. Removal of the functional film corresponding to the electrode setting area: The functional film 160 corresponding to the electrode setting area A1 is removed using a laser to form a groove 161. The width of the groove 161 is 100 μm. For the structure of the solar cell precursor after step S2, please refer to [link to relevant documentation]. Figure 3 .
[0138] S3. Fabricate a metal seed layer on the side of the doped layer that faces away from the silicon substrate: Please refer to... Figure 3 and Figure 4 First, a diffusion barrier layer is fabricated on the side of the doped layer facing away from the silicon substrate 110 using magnetron sputtering. Then, a copper seed layer is fabricated on the side of the diffusion barrier layer facing away from the doped layer. The target material used for the diffusion barrier layer includes at least one of the following: Ni, Cr, W, Ti, NiCr, NiW, TiW, NiMo, with a sputtering power density of 4 W / cm³. 2 The argon flow rate was 800 sccm, the substrate temperature was <200℃, the sputtering pressure was 0.3 Pa, and the sputtering time was 20 min. Then, a copper seed layer with a thickness of 200 nm was deposited by magnetron sputtering on the diffusion barrier layer, wherein the copper seed layer was sputtered using a copper target with a purity >99.99%. The resulting diffusion barrier layer and copper seed layer were stacked to form a metal seed layer 170. The metal seed layer 170 corresponding to the electrode setting region A1 was formed on the surface of the N-type doped polysilicon layer 140 and the P-type doped polysilicon layer 150 through a groove 161. The metal seed layer 170 outside the electrode setting region A1 was formed on the side of the functional film 160 facing away from the N-type doped polysilicon layer 140 and the P-type doped polysilicon layer 150.
[0139] S4. Deposit an insulating layer on the side of the metal seed layer facing away from the silicon substrate: Please refer to... Figure 4 and Figure 5 An insulating layer was deposited on the side of the metal seed layer 170 facing away from the silicon substrate 110 using magnetron sputtering at a sputtering power density of 4 W / cm². 2 The argon flow rate was 800 sccm, the substrate temperature was 200℃, the sputtering pressure was 0.3 Pa, the argon to oxygen flow ratio was 3:1, the target materials were aluminum and silicon targets, and the sputtering time was 20 min. An insulating layer 180a with a first thickness of 200 nm was obtained.
[0140] S5. Using a laser to thin the insulating layer corresponding to the electrode setting area: Please refer to... Figure 5 and Figure 6 The insulating layer corresponding to the electrode setting area A1 is thinned using a laser, while the insulating layer 180a with a first thickness remains outside the electrode setting area A1. The thinned insulating layer 180b has a second thickness, which is 50% of the first thickness.
[0141] S6. Wet etching of the insulating layer: Etching stops after the thinned insulating layer is removed. Please refer to... Figure 6 and Figure 7 The insulating layer is etched using hydrofluoric acid or hydrochloric acid wet etching. Etching stops after the thinned insulating layer 180b is removed. The remaining insulating layer 180c covers the side of the functional film 160 facing away from the silicon substrate 110 and the surface of the trench region A2, thereby preventing subsequent metal plating on these surfaces. The metal seed layer 170 of the electrode placement region A1 is exposed through the groove 161.
[0142] S7. Electroplating to form a metal electrode on the exposed metal seed layer: Please refer to... Figure 7 and Figure 8 A 5 μm thick copper electrode and a 1 μm thick tin protective layer 191 are grown on the exposed metal seed layer 170 through the groove 161. The copper electrode is the metal electrode 190.
[0143] S8. Remove the remaining insulation layer: See Figure 8 The remaining insulating layer 180c is removed using hydrofluoric acid / hydrochloric acid. After the remaining insulating layer 180c is removed, the metal seed layer 170 covered by the remaining insulating layer 180c is exposed.
[0144] S9. Removal of exposed metal seed layer: Remove the exposed metal seed layer 170 using sulfuric acid, retaining the metal electrode 190, the tin protective layer 191 on the metal electrode 190, and the metal seed layer 170 covered by the metal electrode 190. The structure of the resulting solar cell 100 is referenced in the previous section. Figure 1 .
[0145] Example 2
[0146] The difference between this embodiment and embodiment 1 is that in step S5, the second thickness of the insulating layer after thinning is 20% of the first thickness.
[0147] Example 3
[0148] The difference between this embodiment and embodiment 1 is that in step S5, the second thickness of the insulating layer after thinning is 60% of the first thickness.
[0149] The solar cells of each embodiment were tested, and the test results are shown in Table 1.
[0150] Table 1. Test results of solar cells
[0151] Sample number Open circuit voltage (%) Short-circuit current (A) Fill factor (%) Conversion efficiency (%) Example 1 0.7450 14.06 82.78 25.90 Example 2 0.7444 14.03 82.68 25.79 Example 3 0.7445 14.04 82.84 25.87
[0152] As shown in Table 1, comparing the test results of Example 1 and Example 2, it can be seen that in Example 2, the second thickness of the insulating layer after thinning is only 20% of the first thickness, resulting in greater laser thinning of the insulating layer. Since some areas of the insulating layer are relatively thin, excessive thinning can lead to partial exposure of the metal seed layer, which is then oxidized by the laser, affecting the conductivity of the metal seed layer and consequently impacting the fabrication quality of the metal electrode. Consequently, the open-circuit voltage, short-circuit current, fill factor, and conversion efficiency of Example 2 are all lower than those of Example 1.
[0153] Comparing the test results of Examples 1 and 3, it can be seen that in Example 3, because the second thickness of the insulating layer after thinning is only 60% of the first thickness, the laser thinning of the insulating layer is less. After subsequent wet etching, the remaining insulating layer is thinner, resulting in poor insulation performance and affecting the fabrication quality of the metal electrode. Consequently, the open-circuit voltage, short-circuit current, fill factor, and conversion efficiency of Example 3 are all lower than those of Example 1.
[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A method for fabricating a solar cell, characterized in that, Includes the following steps: A solar cell precursor is provided; wherein the solar cell precursor includes a silicon substrate and a doped layer disposed on the surface of the silicon substrate, the doped layer having an electrode placement region; A metal seed layer is formed on the side of the doped layer that is opposite to the silicon substrate; An insulating layer is deposited on the side of the metal seed layer that is opposite to the silicon substrate; The insulating layer corresponding to the electrode setting area is removed; wherein the metal seed layer corresponding to the electrode setting area is exposed, and the insulating layer outside the electrode setting area is retained; Metal electrodes are formed by electroplating on the exposed metal seed layer.
2. The method for preparing a solar cell according to claim 1, characterized in that, After the step of depositing an insulating layer on the side of the metal seed layer opposite to the silicon substrate, the deposited insulating layer has a first thickness; The step of removing the insulating layer corresponding to the electrode setting area includes: The insulating layer corresponding to the electrode placement area is thinned using physical methods; wherein the thinned insulating layer has a second thickness, the second thickness being less than the first thickness; The insulating layer is wet-etched, and etching stops after the thinned insulating layer is removed.
3. The method for preparing a solar cell according to claim 2, characterized in that, The step of thinning the insulating layer corresponding to the electrode setting area includes: The insulating layer corresponding to the electrode setting area is thinned using a laser. And / or, the second thickness is 30% to 50% of the first thickness.
4. The method for preparing a solar cell according to claim 1, characterized in that, The solar cell precursor also includes a functional film, which is disposed on the side of the doped layer opposite to the silicon substrate. Before the step of forming a metal seed layer on the side of the doped layer facing away from the silicon substrate, the method for fabricating the solar cell further includes the following steps: The functional film corresponding to the electrode setting area is removed; wherein the functional film outside the electrode setting area is retained.
5. The method for preparing a solar cell according to claim 4, characterized in that, The step of removing the functional film corresponding to the electrode setting area includes: A groove is formed by removing the functional film corresponding to the electrode setting area using a laser. After the step of forming a metal seed layer on the side of the doped layer away from the silicon substrate, the metal seed layer corresponding to the electrode setting region is formed on the surface of the doped layer through the groove, and the metal seed layer outside the electrode setting region is formed on the side of the functional film away from the doped layer.
6. The method for preparing a solar cell according to claim 1, characterized in that, The step of depositing an insulating layer on the side of the metal seed layer opposite to the silicon substrate includes: An insulating layer is deposited on the side of the metal seed layer opposite to the silicon substrate using magnetron sputtering.
7. The method for preparing a solar cell according to claim 6, characterized in that, The step of forming a metal seed layer on the side of the doped layer opposite to the silicon substrate includes: A metal seed layer is fabricated on the side of the doped layer opposite to the silicon substrate using magnetron sputtering; wherein the metal seed layer and the insulating layer are deposited sequentially in the same magnetron sputtering apparatus.
8. The method for preparing a solar cell according to claim 7, characterized in that, In the step of depositing an insulating layer on the side of the metal seed layer opposite to the silicon substrate using magnetron sputtering, the sputtering chamber temperature is 100℃~150℃ and the sputtering power density is 2W / cm². 2 ~8W / cm 2 The argon flow rate is 500 sccm to 1000 sccm, the substrate temperature is 200℃ to 300℃, the sputtering pressure is 0.3 Pa to 0.5 Pa, the argon to oxygen flow ratio is (2.5 to 3.5): 1, the target material is an aluminum target and / or a silicon target, and the sputtering time is 5 min to 20 min. And / or, the step of fabricating a metal seed layer on the side of the doped layer facing away from the silicon substrate using magnetron sputtering includes: A diffusion barrier layer is fabricated on the side of the doped layer facing away from the silicon substrate using magnetron sputtering; wherein the thickness of the deposited diffusion barrier layer is 5 nm to 20 nm. A copper seed layer is formed on the side of the diffusion barrier layer facing away from the doped layer; the thickness of the deposited copper seed layer is 100 nm to 400 nm.
9. The method for preparing a solar cell according to claim 1, characterized in that, After the step of electroplating to form a metal electrode on the exposed metal seed layer, the electroplated metal electrode has a third thickness; Following the step of electroplating a metal electrode onto the exposed metal seed layer, the method for fabricating the solar cell further includes the following steps: The remaining insulating layer is removed by wet etching; The exposed metal seed layer is removed by wet etching; wherein the metal electrode after wet etching has a fourth thickness, which is less than the third thickness.
10. The method for preparing a solar cell according to any one of claims 1 to 9, characterized in that, The thickness of the insulating layer is 100nm to 400nm; And / or, the insulating layer is an oxide insulating layer; And / or, the material of the insulating layer is selected from at least one of silicon oxide or aluminum oxide; And / or, the metal seed layer includes a diffusion barrier layer and a copper seed layer, the diffusion barrier layer and the copper seed layer being sequentially stacked on the side of the doped layer opposite to the silicon substrate along a direction away from the silicon substrate; And / or, the metal electrode is a copper electrode, and the end of the copper electrode facing away from the silicon substrate is also electroplated with a tin protective layer; the thickness of the copper electrode is 3μm to 5μm, and the thickness of the tin protective layer is 1μm to 2μm.
11. A solar cell, characterized in that, The solar cell is prepared by the method described in any one of claims 1 to 10. The solar cell includes a silicon substrate, a plurality of doped layers, a plurality of metal seed layers, and a plurality of metal electrodes. The doped layers are disposed on the surface of the silicon substrate, the metal seed layers are disposed on the doped layers and are in ohmic contact with the doped layers, and the metal electrodes are disposed on the side of the metal seed layers facing away from the doped layers.
12. The solar cell according to claim 11, characterized in that, The solar cell further includes a plurality of first dielectric layers, a plurality of second dielectric layers, and a functional film; the first dielectric layers and the second dielectric layers are alternately disposed on the back side of the silicon substrate; a trench region is formed between adjacent first dielectric layers and second dielectric layers; The doped layer is of two types: an N-type doped polysilicon layer and a P-type doped polysilicon layer. Each N-type doped polysilicon layer is disposed on the side of each first dielectric layer facing away from the silicon substrate, and each P-type doped polysilicon layer is disposed on the side of each second dielectric layer facing away from the silicon substrate. The trench region separates adjacent N-type doped polysilicon layers and P-type doped polysilicon layers. The functional film is disposed on the side of the N-type doped polycrystalline silicon layer facing away from the silicon substrate and on the side of the P-type doped polycrystalline silicon layer facing away from the silicon substrate; There are two types of metal electrodes, namely a first metal electrode and a second metal electrode. The first metal electrode passes through the functional film and makes ohmic contact with the N-type doped polycrystalline silicon layer, and the second metal electrode passes through the functional film and makes ohmic contact with the P-type doped polycrystalline silicon layer.
13. A photovoltaic module, characterized in that, It includes several solar cells connected in series and / or in parallel, and at least one of the solar cells is the solar cell described in claim 11 or 12.