A process for the preparation of a solar cell, and a solar cell, module and system

Abstract

The application discloses a preparation process of a solar cell, the cell, an assembly and a system. The preparation process comprises the following steps: preparing a doped layer; preparing a seed metal for the first time; performing first heat treatment, so that the seed metal is partially oxidized on the back surface, and the seed metal and the doped layer form a seed metal silicide layer at the interface; preparing the seed metal for the second time; locally preparing an outer metal; performing second heat treatment, so that the seed metal and the outer metal form a seed metal-outer metal alloy body at the interface, the seed metal-outer metal alloy body and the oxidized seed metal oxide form a mixed conductive layer at the interface, the seed metal oxide far from the mixed conductive layer forms a seed metal oxide thin layer, the outer metal far from the mixed conductive layer forms an outer metal layer, and the seed metal oxide not covered by the outer metal forms a passivation scratch-resistant layer. The preparation process does not need to additionally prepare a passivation film and perform laser slotting, the obtained solar cell is not easy to be scratched, has lower contact resistivity, better current transmission performance, better metal burn-through prevention performance, and can reduce the cost of the cell.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a solar cell fabrication process, as well as solar cells, modules, and systems. Background Technology

[0002] Solar cells, also known as photovoltaic cells, are batteries that directly convert sunlight into electrical energy. They can be classified into monocrystalline silicon, polycrystalline silicon, and amorphous silicon solar cells. Among existing photovoltaic cell technologies, crystalline silicon solar cells are relatively mature and have the widest application. However, existing crystalline silicon solar cells still have some drawbacks. For example, current industrialized crystalline silicon solar cells generally use screen-printed silver paste combined with a high-temperature sintering process to complete the metallization process and form electrodes; however, this process requires a large amount of expensive silver paste, increasing the material cost of crystalline silicon solar cells.

[0003] Therefore, in order to reduce the cost of solar cells, researchers are gradually improving the structure of solar cells. For example, CN113629155A discloses a crystalline silicon solar cell whose grid electrode includes a first metal layer (such as titanium silicide paste) formed on a doped conductive layer, a dielectric conductive layer (such as titanium nitride paste) formed on the first metal layer, and a second metal layer (such as aluminum paste) formed on the dielectric conductive layer. This grid electrode does not require the use of expensive silver paste, which can reduce its raw material cost and achieve better conductivity. However, the metal diffusion blocking and current transport performance of this crystalline silicon solar cell still need improvement. Moreover, the passivation dielectric layer of this crystalline silicon solar cell is a silicon nitride passivation film, which is easily scratched by mechanical equipment. This greatly reduces the production yield of the solar cell and will further increase the production cost of the solar cell. In the fabrication process of this crystalline silicon solar cell, in order to achieve the passivation and anti-reflection effect, it is necessary to add the preparation of silicon nitride passivation film and laser grooving before the preparation of grid electrodes. This obviously increases the number of fabrication steps and prolongs the fabrication cycle of the cell, which will further affect the production cost of the cell. Summary of the Invention

[0004] One of the objectives of this invention is to overcome the shortcomings of the prior art and provide a process for preparing solar cells. This process does not require additional preparation of passivation films and laser grooving, has fewer steps, and the resulting solar cells are less prone to scratches, have a high production yield, lower contact resistivity, better current transmission performance, better resistance to metal burn-through, and can also reduce battery costs.

[0005] The second objective of this invention is to overcome the shortcomings of the prior art and provide a solar cell prepared by the above-mentioned process, so that the cell has the advantages of being less prone to scratches, having lower contact resistivity, better current transmission performance, better resistance to metal burn-through, and lower cost.

[0006] The third objective of this invention is to provide a solar cell module.

[0007] The fourth objective of this invention is to provide a solar cell system.

[0008] Based on this, the present invention discloses a process for fabricating a solar cell, comprising the following steps:

[0009] Step S1: Prepare a doped layer on the back side of the silicon substrate;

[0010] Step S2: Seed metal is prepared for the first time on the back side of the doped layer;

[0011] Step S3: Perform a first heat treatment on the seed metal after the first preparation to oxidize the back part of the seed metal into a seed metal oxide and to react the seed metal with the doped layer at the interface to form a seed metal silicide layer.

[0012] Step S4: Prepare seed metal a second time on the back side of the seed metal oxide;

[0013] Step S5: Locally prepare an outer metal on the back side of the seed metal prepared in the second step, and then perform a second heat treatment so that the seed metal prepared in the second step reacts with the outer metal at the interface to form a seed metal-outer metal alloy body, and the remaining seed metal is completely oxidized into seed metal oxide. Then, the seed metal-outer metal alloy body and the seed metal oxide diffuse into each other at the interface to form a mixed conductive layer, while the seed metal oxide far away from the mixed conductive layer forms a seed metal oxide thin layer, the outer metal far away from the mixed conductive layer forms an outer metal layer, and the seed metal oxide not covered by the outer metal forms a passivation anti-scratch layer.

[0014] The seed metal is an alloy formed from one or more of titanium, nickel, and molybdenum.

[0015] Preferably, the seed metal-outer metal alloy is a compound of the seed metal and the outer metal; or, the seed metal-outer metal alloy is a composite formed by the compound of the seed metal and the outer metal and the outer metal; or, the seed metal-outer metal alloy is a composite formed by the compound of the seed metal and the outer metal, the outer metal and the seed metal.

[0016] The outer metal is an alloy of one or more of copper, aluminum, and silver; the outer metal layer is a copper layer, an aluminum layer, a silver layer, or an alloy layer thereof.

[0017] Preferably, the thickness of the seed metal oxide thin layer is less than or equal to 20 nm.

[0018] Preferably, the seed metal silicide layer, the seed metal oxide thin layer, the mixed conductive layer, and the passivation and scratch-resistant layer are integrally formed.

[0019] More preferably, the outer metal layer is a copper layer, an aluminum layer, or an alloy layer thereof.

[0020] Preferably, the thickness of the seed metal silicide layer is less than or equal to 30 nm; the thickness of the mixed conductive layer is 10-130 nm; the thickness of the outer metal layer is 5-20 μm; and the thickness of the passivation and scratch-resistant layer is 10-150 nm.

[0021] Preferably, the doped layer comprises a tunneling oxide layer and a doped polycrystalline silicon layer sequentially stacked on the back side of the silicon substrate.

[0022] Preferably, the first and second heat treatments are carried out in an oxygen-containing atmosphere at a temperature of 700-900°C.

[0023] Preferably, before step S1, the back side of the silicon substrate is pretreated to form a planar structure on the back side of the silicon substrate.

[0024] The present invention also discloses a solar cell, comprising a silicon substrate and a doped layer stacked on the back side of the silicon substrate, the doped layer having a back electrode; the back electrode comprising a seed metal silicide layer covering the entire back side of the doped layer and a seed metal oxide thin layer, a mixed conductive layer, and an outer metal layer sequentially stacked in a local area on the back side of the seed metal silicide layer, wherein the seed metal silicide layer is one or more layers of nickel silicide, titanium silicide, and molybdenum silicide; the seed metal oxide thin layer is a thin layer structure formed by one or more layers of nickel oxide, titanium oxide, and molybdenum oxide; the mixed conductive layer is a structure formed by the interdiffusion of seed metal oxide and seed metal-outer metal alloy; the back side region of the seed metal silicide layer without an outer metal layer also has a passivation anti-scratch layer.

[0025] Preferably, the solar cell further includes a front electrode located on the front side of the silicon substrate.

[0026] The present invention also discloses a solar cell, comprising a silicon substrate and a doped layer stacked on the back side of the silicon substrate, the doped layer having a back electrode; the back electrode comprising a seed metal silicide layer covering the entire back side of the doped layer and a seed metal oxide thin layer, a mixed conductive layer, and an outer metal layer sequentially stacked on a local area of ​​the back side of the seed metal silicide layer, wherein the seed metal silicide layer is an alloy layer formed of at least two of nickel silicide, titanium silicide, and molybdenum silicide, the seed metal oxide thin layer is an alloy thin layer formed of at least two of nickel oxide, titanium oxide, and molybdenum oxide, and the mixed conductive layer is a structure formed by the interdiffusion of seed metal oxide and seed metal-outer metal alloy; the back side region of the seed metal silicide layer without an outer metal layer also has a passivation anti-scratch layer.

[0027] This invention also discloses a solar cell, comprising a silicon substrate and a doped layer stacked on the back side of the silicon substrate. The doped layer includes alternating P-type doped regions and N-type doped regions, with an isolation region between the P-type and N-type doped regions. The P-type doped regions have a positive electrode, and the N-type doped regions have a negative electrode. The positive electrode includes a seed metal silicide layer disposed on the back side of the doped layer and a seed metal oxide thin layer, a mixed conductive layer, and an outer metal layer sequentially stacked on a localized area of ​​the back side of the seed metal silicide layer corresponding to the P-type doped region. The negative electrode includes the seed metal silicide layer and the sequentially stacked... The seed metal silicide layer, corresponding to the N-type doped region, comprises a seed metal oxide thin layer, a mixed conductive layer, and an outer metal layer in a localized area on the back side. The seed metal silicide layer is formed by stacking one or more layers of nickel silicide, titanium oxide, and molybdenum silicide. The seed metal oxide thin layer is formed by stacking one or more layers of nickel oxide, titanium oxide, and molybdenum oxide. The mixed conductive layer is formed by the interdiffusion of the seed metal oxide and the seed metal-outer metal alloy. The back side region of the seed metal silicide layer without an outer metal layer also has a passivation anti-scratch layer.

[0028] The present invention also discloses a solar cell module, comprising a front layer, an encapsulation layer, a cell, and a photovoltaic backsheet stacked sequentially, wherein the cell is a solar cell as described above, or the cell is a solar cell manufactured using the process described above for manufacturing a solar cell.

[0029] The present invention also discloses a solar cell system, comprising one or more solar cell modules, wherein the solar cell module is one of the aforementioned solar cell modules.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] (1) In the preparation process of the present invention, only the seed metal, the first heat treatment, the preparation of the outer metal and the second heat treatment are required in sequence to obtain the back electrode with the seed metal silicide layer, the seed metal oxide thin layer, the mixed conductive layer and the outer metal layer, and at the same time, the passivation anti-scratch layer can be formed. That is, only the above two preparation steps and two heat treatments are required to obtain the passivation anti-scratch layer and the back electrode with the above four-layer structure at the same time. Compared with the existing crystalline silicon solar cells, the solar cell of the present invention does not need to add the preparation of passivation film and laser grooving to obtain the passivation anti-scratch layer at the same time as obtaining the back electrode, which significantly simplifies the battery preparation process, shortens the battery preparation cycle and greatly reduces the battery production cost.

[0032] (2) In the obtained solar cell, the passivation anti-scratch layer not only has the effect of passivation and anti-reflection, but also makes the solar cell less susceptible to scratches by mechanical equipment, greatly improving the production yield of the cell and further reducing the production cost of the cell; (3) The back electrode includes a four-layer structure consisting of a seed metal silicide layer, a seed metal oxide thin layer, a mixed conductive layer and an outer metal layer stacked sequentially. This is a new back electrode. Compared with the grid electrode of the existing crystalline silicon solar cell such as CN113629155A (where the first metal layer and the doped conductive layer are only in local contact in the grid line area), in this new back electrode, since the seed metal silicide layer and the doped layer are in full-surface contact, the contact area is larger, which has better electrical contact capability and electron collection capability, and can better reduce the contact resistivity. Moreover, the seed metal silicide layer, the mixed conductive layer and the outer metal layer are all conductive layers, and all have good conductivity. In particular, compared with the structure formed by the mutual diffusion of seed metal oxide and outer metal, the mixed conductive layer is formed by the use of seed metal oxide. The structure formed by the interdiffusion of oxide and seed metal-outer metal alloy has better conductivity, which can improve the conductivity of the back electrode; (4) The seed metal silicide layer near the doped layer and the mixed conductive layer near the outer metal layer can also separate the doped layer and the outer metal layer to prevent the outer metal layer from burning through the doped layer and contaminating the silicon substrate during heat treatment, thus reducing metal recombination loss; Compared with the seed metal silicide layer and the mixed conductive layer, the seed metal oxide thin layer is a room temperature insulating layer with better metal burn-through performance. Setting this room temperature insulating seed metal oxide thin layer between the seed metal silicide layer and the mixed conductive layer, together with the seed metal silicide layer and the mixed conductive layer, can greatly improve the separation effect between the doped layer and the outer metal layer, and further reduce metal recombination loss; (5) Moreover, the study found that when the thickness of the seed metal oxide thin layer is thin (such as less than or equal to 20nm), it can also perform normal current transmission performance without affecting the current transmission effect of the battery.

[0033] (6) In addition, the seed metal is an alloy formed from one or more of nickel, titanium and molybdenum. Therefore, neither the seed metal silicide layer nor the seed metal oxide thin layer contains expensive silver, thus reducing the raw material cost of the electrode. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of the structure of a solar cell in Example 1.

[0035] Figure 2 This is a schematic diagram of the structure of the silicon substrate after step 1 in a solar cell fabrication process of Example 1.

[0036] Figure 3 This is a schematic diagram of the structure of the silicon substrate after step 2 in a solar cell fabrication process of Example 1.

[0037] Figure 4 This is a schematic diagram of the structure of the silicon substrate after step 3 in a solar cell fabrication process of Example 1.

[0038] Figure 5 This is a schematic diagram of the structure of the silicon substrate after step 4 in a solar cell fabrication process of Example 1.

[0039] Figure 6 This is a schematic diagram of the structure of the silicon substrate after step 5 in a solar cell fabrication process of Example 1.

[0040] Figure 7 This is a schematic diagram of the structure of a solar cell in Example 2.

[0041] Explanation of reference numerals: 1. Silicon substrate; 2. Doped layer; 21. P-type doped region; 22. Isolation region; 23. N-type doped region; 3. Passivation and scratch-resistant layer; 4. Seed metal silicide layer; 5. Seed metal oxide thin layer; 6. Mixed conductive layer; 7. Outer metal layer; 8. Seed metal; 9. Seed metal oxide. Detailed Implementation

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0043] Example 1

[0044] One embodiment of the solar cell, referring to... Figure 1The battery includes a silicon substrate 1 and a doped layer 2 stacked on the back side of the silicon substrate 1. In practical applications, the doped layer 2 is stacked on the back side of the silicon substrate 1, and a back electrode is formed on the doped layer 2 on the back side of the silicon substrate 1. Alternatively, depending on the design requirements of different battery structures, a doped layer 2 can also be stacked on the front side of the silicon substrate 1, and a front electrode can be formed on the doped layer 2 on the front side of the silicon substrate 1. The structure and fabrication process of the back electrode are described in detail below. Of course, the following structure and fabrication process of the back electrode can also be applied to the front electrode.

[0045] The back electrode comprises a seed metal silicide layer 4 stacked over the entire back side of the doped layer 2, and a seed metal oxide thin layer 5, a mixed conductive layer 6, and an outer metal layer 7 sequentially stacked in a local area (i.e., electrode region) of the back side of the seed metal silicide layer 4; this is a novel back electrode. In one example of this embodiment, the seed metal silicide layer 4 in this novel back electrode is one or more layers of nickel silicide, titanium silicide, and molybdenum silicide; in another example of this embodiment, the seed metal silicide layer 4 may be an alloy layer formed from at least two of nickel silicide, titanium silicide, and molybdenum silicide (such as an alloy layer formed from titanium silicide and nickel silicide). The thickness of the seed metal silicide layer 4 is preferably less than or equal to 30 nm, more preferably 0.1-20 nm, for example, the thickness of the seed metal silicide layer 4 is 0.1 nm, 0.5 nm, 1 nm, 3 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm or 30 nm; compared with the grid electrode of the existing crystalline silicon solar cell such as CN113629155A (in which the first metal layer and the doped conductive layer in the grid electrode only make local contact in the grid area), in this new back electrode, the seed metal silicide layer 4 and the doped layer 2 are in full-surface contact, with a larger contact area, better electrical contact capability and electron collection capability, and can better reduce contact resistivity.

[0046] Furthermore, the ratio of the projected area of ​​the outer metal layer 7 on the silicon substrate 1 to the area of ​​the silicon substrate 1 is preferably greater than 1:10000; the outer metal layer 7 is a copper layer, an aluminum layer, a silver layer, or an alloy layer thereof (such as a copper-aluminum alloy layer), and the thickness of the outer metal layer 7 is preferably 5-20 μm, for example, the thickness of the outer metal layer 7 is 5 μm, 8 μm, 10 μm, 15 μm, or 20 μm. In one example of this embodiment, the seed metal oxide thin layer 5 is one or more layers of nickel oxide thin layer, titanium oxide thin layer, and molybdenum oxide thin layer stacked together; in another example of this embodiment, the seed metal oxide thin layer 5 is an alloy thin layer formed of at least two of nickel oxide, titanium oxide, and molybdenum oxide (such as an alloy thin layer formed of titanium oxide and nickel oxide). The thickness of the seed metal oxide thin layer 5 is less than or equal to 20 nm, for example, the thickness of the seed metal oxide thin layer 5 is 0.1 nm, 0.5 nm, 3 nm, 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, or 20 nm. The mixed conductive layer 6 is a structure formed by the interdiffusion of a seed metal oxide 9 and a seed metal-outer metal alloy. Specifically, the mixed conductive layer 6 is formed by the interdiffusion of the seed metal oxide 9 and the seed metal-outer metal alloy at the interface during a high-temperature heat treatment process, such as at 700-900°C. The seed metal 8 is nickel, titanium, molybdenum, or an alloy thereof (such as a titanium-nickel alloy). The seed metal oxide 9 is an alloy formed from one or more of nickel oxide, titanium oxide, and molybdenum oxide, more preferably titanium oxide, molybdenum oxide, or an alloy thereof (such as an alloy formed from titanium oxide and molybdenum oxide). The outer metal is copper, aluminum, silver, or an alloy thereof (such as a copper-aluminum alloy). The thickness of the mixed conductive layer 6 is 10-130 nm, for example, the thickness of the mixed conductive layer 6 is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, or 130 nm. In one example of this embodiment, the seed metal-outer metal alloy is a composite formed by a compound of seed metal 8 and an outer metal, and the outer metal itself (such as a composite formed by TiAl3 and Al). In another example of this embodiment, the seed metal-outer metal alloy is a composite formed by a compound of seed metal 8 and an outer metal, the outer metal itself, and seed metal 8 (such as a composite formed by TiAl3, Al, and Ti). In other examples of this embodiment, the seed metal-outer metal alloy is preferably a compound of seed metal 8 and an outer metal (such as TiAl3) to facilitate current transmission, thereby reducing the interfacial contact resistance of the back electrode and improving its conductivity.The seed metal silicide layer 4, the mixed conductive layer 6, and the outer metal layer 7 are all conductive layers with good conductivity. In particular, compared with the structure formed by the interdiffusion of seed metal oxide 9 and outer metal, the mixed conductive layer 6 has better conductivity because it is formed by the interdiffusion of seed metal oxide 9 and seed metal-outer metal alloy. Furthermore, the conductivity of this new back electrode is further improved by the full-surface contact between the seed metal silicide layer 4 and the doped layer 2.

[0047] Furthermore, the outer metal layer 7 is preferably a copper layer, an aluminum layer, or an alloy layer thereof (such as a copper-aluminum alloy layer), so that the back electrode does not contain expensive silver at all, which can further reduce the raw material cost of the electrode.

[0048] In this embodiment of the solar cell, the seed metal silicide layer 4 near the doped layer 2 and the mixed conductive layer 6 near the outer metal layer 7 not only conduct electricity but also separate the doped layer 2 from the outer metal layer 7, preventing the outer metal layer 7 from burning through the doped layer 2 and contaminating the silicon substrate 1 during heat treatment, thus reducing metal recombination loss. The seed metal oxide thin layer 5, being one or more layers of nickel oxide, titanium oxide, and molybdenum oxide, provides better protection against metal burn-through at room temperature compared to the seed metal silicide layer 4 and the mixed conductive layer 6. Placing this insulating seed metal oxide thin layer 5 between the seed metal silicide layer 4 and the mixed conductive layer 6, in conjunction with the seed metal silicide layer 4 and the mixed conductive layer 6, significantly enhances the separation effect between the doped layer 2 and the outer metal layer 7, further reducing metal recombination loss. Furthermore, research has found that even when the seed metal oxide thin layer 5 is thin (e.g., less than or equal to 20 nm), it still exhibits normal current transport performance without affecting the cell's current transport efficiency. Therefore, in this embodiment, the back electrode of the above four-layer structure is placed on the doped layer 2, which can not only better reduce the contact resistivity and further improve the current transmission performance, but also significantly improve its anti-metal burn-through performance, greatly reduce metal recombination loss, and reduce electrode cost. This provides a new idea for the setting of electrode structure, that is, to set a room temperature insulating layer, such as the seed metal oxide thin layer 5, in the electrode structure to improve electrode performance and reduce cost.

[0049] The seed metal silicide layer 4, in its non-electrode region (the area on the back side without the outer metal layer 7), also has a passivation and scratch-resistant layer 3. The thickness of the passivation and scratch-resistant layer 3 is 10-150 nm, for example, 10 nm, 20 nm, 30 nm, 50 nm, 60 nm, 80 nm, 100 nm, 110 nm, 120 nm, 130 nm, or 150 nm. This passivation and scratch-resistant layer 3 not only replaces the existing silicon nitride passivation film to achieve passivation and anti-reflection effects, but also makes the solar cell less susceptible to scratches from mechanical equipment, greatly improving the cell's production yield and further reducing its production cost.

[0050] The passivation and scratch-resistant layer 3 can be a material layer that simultaneously provides passivation, anti-reflection, and scratch resistance. Preferably, it is a seed metal oxide layer 9, namely a nickel oxide layer, a titanium oxide layer, a molybdenum oxide layer, or an alloy oxide layer thereof (such as an alloy layer of titanium oxide and nickel oxide), more preferably a nickel oxide layer, a titanium oxide layer, or an alloy oxide layer thereof. This type of seed metal oxide layer 9 can adhere well to the back side of the doped layer 2, and its mechanical properties are better than those of the silicon nitride film, exhibiting superior scratch resistance and significantly improving the battery production yield.

[0051] This embodiment also provides a fabrication process for the above-mentioned solar cell, including the following steps performed sequentially:

[0052] Step 1: Pre-process the back side of the silicon substrate 1. Preferably, the silicon substrate 1 is an N-type silicon substrate.

[0053] One example of this embodiment is that the back side of the silicon substrate 1 is pre-treated to form a planar structure on the back side of the silicon substrate 1, such as... Figure 2 As shown.

[0054] Step 2: Prepare a doped layer 2 on the back side of the planar structure of silicon substrate 1, such as... Figure 3 As shown. In order to improve the passivation contact performance of the solar cell, the doped layer 2 preferably includes a tunneling oxide layer and a doped polycrystalline silicon layer (such as an n+ doped polycrystalline silicon layer) sequentially stacked on the back side of the silicon substrate 1.

[0055] Step 3: For the first time, seed metal 8 is prepared on the entire back side of doped layer 2, such as... Figure 4 As shown. The thickness of the seed metal 8 prepared in the first step is preferably 5-80 nm, and the seed metal 8 is prepared by screen printing or deposition, preferably by deposition using a PVD device.

[0056] Step 4: The seed metal 8 prepared in the first step is subjected to a first heat treatment in an oxygen-containing atmosphere at 700-900℃, so that the back side of the seed metal 8 is oxidized to seed metal oxide 9, and the seed metal 8 reacts with the doped layer 2 at the interface to form a seed metal silicide layer 4, such as... Figure 5 As shown. The temperature of the first heat treatment is 700℃, 730℃, 750℃, 770℃, 800℃, 830℃, 860℃ or 900℃.

[0057] Step 5: Prepare seed metal 8 a second time on the back side of seed metal oxide 9, as follows: Figure 6 As shown. The thickness of the seed metal 8 prepared in the second step is preferably 1-80 nm, and the seed metal 8 is prepared by screen printing or deposition, preferably by deposition using a PVD device.

[0058] Step 6: Prepare an outer metal locally on the back side of the second-prepared seed metal 8, and then perform a second heat treatment in an oxygen-containing atmosphere at 700-900℃ (e.g., the temperature of the second heat treatment is 700℃, 720℃, 750℃, 780℃, 800℃, 830℃, 850℃, 880℃ or 900℃). During the second heat treatment, the second-prepared seed metal 8 and the outer metal react at the interface to form a seed metal-outer metal alloy, and the remaining seed metal 8 is completely oxidized to seed metal oxide 9. Then, the seed metal-outer metal alloy and the seed metal oxide 9 diffuse into each other at the interface to form a mixed conductive layer 6. The seed metal oxide 9 in the back electrode region that is far away from the mixed conductive layer 6 forms a seed metal oxide thin layer 5, the outer metal that is far away from the mixed conductive layer 6 forms an outer metal layer 7, and the seed metal oxide 9 that is not covered by the outer metal (i.e., the non-back electrode region) forms a passivation anti-scratch layer 3, thus obtaining the back electrode. Through steps 1-6 above, the fabrication of a solar cell according to this embodiment is completed, and its structure is as follows: Figure 1 As shown. The outer metal is prepared by screen printing, deposition, or other methods such as vapor deposition, preferably screen printing.

[0059] In the fabrication process of this solar cell, only the first preparation of seed metal 8, the first heat treatment, the second preparation of seed metal 8, the preparation of outer metal, and the second heat treatment are required sequentially to simultaneously obtain the passivation and scratch-resistant layer 3 and the back electrode with a four-layer structure. Furthermore, the seed metal silicide layer 4, the seed metal oxide thin layer 5, the mixed conductive layer 6, and the passivation and scratch-resistant layer 3 are integrally formed. That is, the passivation and scratch-resistant layer 3, along with the seed metal silicide layer 4, the seed metal oxide thin layer 5, and the mixed conductive layer 6 in the back electrode, are all transformed from seed metal 8 through the aforementioned steps. This simplifies the structure and fabrication process of the cell. Specifically, compared to existing crystalline silicon solar cells such as CN113629155A, the solar cell of this invention can obtain the passivation and scratch-resistant layer 3 simultaneously with the back electrode without the need for additional passivation film preparation and laser grooving, significantly simplifying the cell fabrication process, shortening the cell fabrication cycle, and greatly reducing cell production costs.

[0060] In summary, the fabrication process of this solar cell not only enables the resulting solar cell to have advantages such as being less prone to scratches, high production yield, lower contact resistivity, better current transmission performance, better resistance to metal burn-through, less metal recombination loss, and low cost; it also eliminates the steps of preparing the passivation film and laser grooving, requiring only the above three metal preparation steps and two heat treatment steps to simultaneously produce the back electrode and the passivation anti-scratch layer 3, greatly reducing the battery production cost. This fabrication process is stable and reliable and suitable for large-scale production.

[0061] This embodiment also discloses a solar cell module, including a front layer, an encapsulation layer, a cell, and a photovoltaic backsheet stacked in sequence, wherein the cell is one of the aforementioned solar cells.

[0062] This embodiment also discloses a solar cell system, including one or more solar cell modules, wherein the solar cell module is one of the solar cell modules described above.

[0063] Example 2

[0064] This embodiment of a solar cell, whose structure, fabrication process, components, and system are all the same as in Embodiment 1, see [link to Embodiment 1]. Figure 7 The difference between it and Example 1 is that:

[0065] In this embodiment, the silicon substrate 1 of the solar cell has no electrodes on its front side. The doped layer 2 on the back side of the silicon substrate 1 includes alternating P-type doped regions 21 and N-type doped regions 23, with an isolation region 22 between the P-type doped regions 21 and N-type doped regions 23. The P-type doped region 21 of the doped layer 2 has a positive electrode, and the N-type doped region 23 of the doped layer 2 has a negative electrode. The positive electrode includes a seed metal silicide layer 4 stacked on the back side of the doped layer 2 and a seed metal oxide thin layer 5, a mixed conductive layer 6, and an outer metal layer 7 stacked sequentially on a local area of ​​the back side of the seed metal silicide layer 4 corresponding to the P-type doped region 21. The negative electrode includes the seed metal silicide layer 4 and a seed metal oxide thin layer 5, a mixed conductive layer 6, and an outer metal layer 7 stacked sequentially on a local area of ​​the back side of the seed metal silicide layer 4 corresponding to the N-type doped region 23. That is, the seed metal silicide layer 4 covers the entire back side of the doped layer 2, and the positive and negative electrodes share this seed metal silicide layer 4. Both the positive and negative electrodes refer to the back electrode of Example 1 above, so they will not be described again.

[0066] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

[0067] The technical solution provided by the present invention has been described in detail above. Specific examples have been used to illustrate the principle and implementation of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A process for the production of a solar cell, characterized in that, The method comprises the following steps: Step S1, preparing a doped layer on the back surface of a silicon substrate; Step S2, preparing a seed metal on the back surface of the doped layer for the first time; Step S3, performing a first heat treatment on the seed metal prepared for the first time, so that the back surface part of the seed metal is oxidized into seed metal oxide, and the seed metal reacts with the doped layer at the interface to form a seed metal silicide layer; Step S4, preparing a seed metal on the back surface of the seed metal oxide for the second time; Step S5, locally preparing an outer metal on the back surface of the seed metal prepared for the second time, and then performing a second heat treatment, so that the seed metal prepared for the second time reacts with the outer metal at the interface to form a seed metal-outer metal alloy body, and the rest of the seed metal is completely oxidized into seed metal oxide, and then the seed metal-outer metal alloy body and the seed metal oxide diffuse at the interface to form a mixed conductive layer, the seed metal oxide away from the mixed conductive layer forms a seed metal oxide thin layer, the outer metal away from the mixed conductive layer forms an outer metal layer, and the seed metal oxide not covered by the outer metal forms a passivation scratch-resistant layer; The seed metal is an alloy formed by one or more of titanium, nickel and molybdenum.

2. The process for preparing a solar cell according to claim 1, wherein The seed metal-outer metal alloy body is a compound of the seed metal and the outer metal; or the seed metal-outer metal alloy body is a composite formed by the compound of the seed metal and the outer metal and the outer metal; or the seed metal-outer metal alloy body is a composite formed by the compound of the seed metal and the outer metal, the outer metal and the seed metal. The outer metal layer is a copper layer, an aluminum layer, a silver layer or an alloy layer thereof.

3. The process for preparing a solar cell according to claim 1, wherein The thickness of the seed metal oxide thin layer is less than or equal to 20 nm.

4. The process for preparing a solar cell according to claim 1, wherein The seed metal silicide layer, the seed metal oxide thin layer, the mixed conductive layer and the passivation scratch-resistant layer are integrally formed.

5. The process for preparing a solar cell according to claim 2, wherein The outer metal layer is a copper layer, an aluminum layer or an alloy layer thereof.

6. The process for preparing a solar cell according to any one of claims 1 to 5, wherein the process is performed in a vacuum chamber. The thickness of the seed metal silicide layer is less than or equal to 30 nm; the thickness of the mixed conductive layer is 10-130 nm; the thickness of the outer metal layer is 5-20 um; and the thickness of the passivation scratch-resistant layer is 10-150 nm.

7. The process of claim 1, wherein the process is performed at a temperature of 300- 600 °C. The doped layer comprises a tunneling oxide layer and a doped polysilicon layer stacked on the back surface of the silicon substrate in sequence.

8. The process of claim 1, wherein the process is performed at a temperature of 300- 600 °C. The first heat treatment and the second heat treatment are performed in an oxygen-containing atmosphere at a temperature of 700-900℃.

9. The process of claim 1, wherein the process is performed at a temperature of 300- 600 °C. Before the step S1, a step of pretreating the back surface of the silicon substrate to form a planar structure on the back surface of the silicon substrate is further included.

10. A solar cell produced by the production process according to any one of claims 1 to 9, characterized in that The solar cell comprises a silicon substrate and a doped layer stacked on the back surface of the silicon substrate, wherein the doped layer is provided with a back electrode; the back electrode comprises a seed metal silicide layer covering the back surface of the entire doped layer and a seed metal oxide thin layer, a mixed conductive layer and an outer metal layer stacked in sequence on the back surface of the seed metal silicide layer in a local region; the seed metal silicide layer is one or more layers of nickel silicide layer, titanium silicide layer and molybdenum silicide layer stacked in sequence; the seed metal oxide thin layer is a thin layer structure formed by one or more layers of nickel oxide thin layer, titanium oxide thin layer and molybdenum oxide thin layer stacked in sequence; the mixed conductive layer is a structure formed by mutual diffusion of the seed metal oxide and a seed metal-outer metal alloy body; and the back surface region of the seed metal silicide layer without the outer metal layer is further provided with a passivation scratch-resistant layer.

11. A solar cell according to claim 10, wherein, The solar cell further comprises a front electrode on the front surface of the silicon substrate.

12. A solar cell produced according to the production process of any one of claims 1-9, characterized in that, The solar cell comprises a silicon substrate and a doped layer stacked on the back surface of the silicon substrate, wherein the doped layer is provided with a back electrode; the back electrode comprises a seed metal silicide layer covering the back surface of the entire doped layer and a seed metal oxide thin layer, a mixed conductive layer and an outer metal layer stacked in sequence on the back surface of the seed metal silicide layer in a local region; the seed metal silicide layer is an alloy layer formed by at least two of nickel silicide, titanium silicide and molybdenum silicide; the seed metal oxide thin layer is an alloy thin layer formed by at least two of nickel oxide, titanium oxide and molybdenum oxide; and the mixed conductive layer is a structure formed by mutual diffusion of the seed metal oxide and a seed metal-outer metal alloy body.

13. A solar cell produced by the production process according to any one of claims 1 to 9, characterized in that The solar cell comprises a silicon substrate and a doped layer stacked on the back surface of the silicon substrate, wherein the doped layer comprises P-type doped regions and N-type doped regions arranged in sequence and alternately; the P-type doped regions and the N-type doped regions are provided with isolation regions; the P-type doped regions are provided with a positive electrode; and the N-type doped regions are provided with a negative electrode; the positive electrode comprises a seed metal silicide layer on the back surface of the doped layer and a seed metal oxide thin layer, a mixed conductive layer and an outer metal layer stacked in sequence on the back surface of the seed metal silicide layer in a local region corresponding to the P-type doped region; the negative electrode comprises the seed metal silicide layer and a seed metal oxide thin layer, a mixed conductive layer and an outer metal layer stacked in sequence on the back surface of the seed metal silicide layer in a local region corresponding to the N-type doped region; the seed metal silicide layer is one or more layers of nickel silicide layer, titanium silicide layer and molybdenum silicide layer stacked in sequence; the seed metal oxide thin layer is a thin layer structure formed by one or more layers of nickel oxide thin layer, titanium oxide thin layer and molybdenum oxide thin layer stacked in sequence; and the mixed conductive layer is a structure formed by mutual diffusion of the seed metal oxide and a seed metal-outer metal alloy body; and the back surface region of the seed metal silicide layer without the outer metal layer is further provided with a passivation scratch-resistant layer.

14. A solar cell module comprising a front layer, an encapsulation layer, a cell and a photovoltaic back sheet which are sequentially stacked, characterized in that, The solar cell is prepared by the preparation process of any one of claims 1-9.

15. A solar cell system comprising one or more solar cell modules, characterized by: The solar cell module is the solar cell module of claim 14.

Images