Method for processing a solar cell and solar cell

Abstract

This invention discloses a method for processing solar cells and a solar cell. The method includes: oxidizing a silicon wafer to be processed, including: ablating or reducing the size of adhering particles on the second surface of the silicon wafer; growing an additional oxide layer to solidify the adhering particles on the second surface of the silicon wafer; and removing the additional oxide layer. By introducing a substance that reacts with the particles adhering to the silicon wafer, a chemical reaction is achieved, thereby removing or reducing the size of the particles. The growth of the additional oxide layer quickly fixes the particles within it. When the additional oxide layer is removed, the particles adhering to the silicon wafer are removed along with it, thus improving the problem of cross-shaped black spots caused by adhering particles on the second surface of the silicon wafer and improving the quality of the solar cell.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and more specifically, to a method for processing solar cells and a solar cell. Background Technology

[0002] In recent years, solar cell technology has been continuously advancing. For example, Topcon cells, which have emerged in recent years, have gained popularity due to their excellent passivation performance. Topcon (tunnel oxide passivation contact) cells are characterized by an ultra-thin tunnel oxide layer on the back and a heavily doped polycrystalline silicon layer. This effectively improves the passivation of crystalline silicon cells, reduces metal recombination on the back of the cell, and also effectively reduces the back contact resistivity, thereby improving the cell's conversion efficiency.

[0003] In addition to traditional Topcon cell technology, the Selective Emitter (SE) structure is one of the methods to achieve high efficiency in the manufacturing process of crystalline silicon solar cells. The fabrication of Topcon cells has begun to incorporate selective emitter technology. By heavily doping the grid line region to form a highly doped, deep diffusion region, and lightly doping the non-grid line region to form a low-doped, shallow diffusion region, the emitter region is optimized. This reduces recombination in the diffusion layer, lowers the contact resistance of the metallization, and increases the open-circuit voltage, short-circuit current, and fill factor, thereby improving the photoelectric conversion efficiency of the solar cell.

[0004] Currently, Topcon solar cells with selective emitter structures are gradually being mass-produced. However, various defects are easily introduced during the production process, leading to poor electroluminescence testing and a decrease in yield. Among these defects, cross-shaped black spots are one of the main electroluminescence defects in solar cells. The main cause of these defects is the adhesion of particles of a certain size (≥5μm) and hardness to the back surface of the solar cell. Research has found that before the high-temperature diffusion (oxidation) process, the tolerance of the silicon wafer back surface to particles is extremely low. For silicon wafers after wet etching but before high-temperature diffusion (oxidation), the worse the cleanliness of the external environment, the longer the exposure time of the silicon wafer, and the larger the size of the adhered particles, the more severe the impact on cross-shaped black spot defects.

[0005] Therefore, there is an urgent need to provide a method for processing solar cells and a solar cell to improve the problem of frequent occurrence of cross-shaped black spot defects. Summary of the Invention

[0006] In view of this, the present invention provides a method for processing a solar cell and a solar cell.

[0007] On one hand, the present invention provides a method for processing solar cells, comprising:

[0008] A silicon substrate is provided, the silicon substrate including a first surface and a second surface disposed opposite to each other along a first direction;

[0009] The first surface is texturized and diffused to form a doped layer on the first surface;

[0010] The doped layer is laser-doped to obtain a silicon wafer to be processed;

[0011] The oxidation treatment of the silicon wafer to be processed includes:

[0012] The silicon wafer to be processed is loaded into a quartz boat;

[0013] The quartz boat is transported into the furnace tube;

[0014] The furnace tubes were evacuated.

[0015] To ablate or reduce the size of the adhering particles on the second surface of the silicon wafer to be treated;

[0016] An additional oxide layer is grown to solidify the adhering particles on the second surface of the silicon wafer to be treated onto the additional oxide layer;

[0017] Remove the additional oxide layer.

[0018] On the other hand, the present invention also provides a solar cell, which is processed using the solar cell processing method described above.

[0019] Compared with the prior art, the solar cell processing method provided by the present invention achieves at least the following beneficial effects:

[0020] The present invention provides a method for processing solar cells, comprising: providing a silicon substrate, the silicon substrate including a first surface and a second surface disposed opposite to each other along a first direction; texturing and diffusion processing of the first surface to form a doped layer on the first surface; laser doping of the doped layer to obtain a silicon wafer to be processed; and oxidizing the silicon wafer to be processed, comprising: loading the silicon wafer to be processed into a quartz boat; conveying the quartz boat into a furnace tube; evacuating the furnace tube; dissolving or reducing the size of the attached particles on the second surface of the silicon wafer to be processed by introducing a substance that can react with the particles attached to the silicon wafer to be processed, thereby achieving the removal of particles or reduction of particle size through a chemical reaction; growing an additional oxide layer to solidify the attached particles on the second surface of the silicon wafer to be processed into the additional oxide layer; and removing the additional oxide layer, wherein the growth of the additional oxide layer can quickly lock the particles within the additional oxide layer, and when the additional oxide layer is removed, the particles attached to the silicon wafer to be processed can be removed along with the additional oxide layer, thereby improving the problem of cross-shaped black spots caused by the attached particles on the second surface of the silicon wafer to be processed and improving the quality of the solar cell.

[0021] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time.

[0022] Other features and advantages of the invention will become clear from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. Attached Figure Description

[0023] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the invention and, together with their description, serve to explain the principles of the invention.

[0024] Figure 1 This is a flowchart of a method for processing solar cells provided by the present invention;

[0025] Figure 2 This is a schematic diagram of a solar cell structure provided by the present invention. Detailed Implementation

[0026] Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention.

[0027] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use.

[0028] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0029] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0031] In some alternative embodiments, refer to Figure 1 , Figure 1 This is a flowchart illustrating a method for processing solar cells provided by the present invention, specifically a particular embodiment of the method, including:

[0032] S101: A silicon substrate is provided, the silicon substrate including a first surface and a second surface disposed opposite to each other along a first direction;

[0033] S102: Texturing and diffusion treatment is performed on the first surface to form a doped layer on the first surface;

[0034] S103: Laser doping of the doped layer yields the silicon wafer to be processed;

[0035] S104: Oxidation treatment of the silicon wafer to be processed, including:

[0036] S1041: Load the silicon wafer to be processed into the quartz boat;

[0037] S1042: Convey the quartz boat into the furnace tube;

[0038] S1043: Vacuum treatment of furnace tubes;

[0039] S1044: Absorb or reduce the size of adhering particles on the second surface of the silicon wafer to be treated.

[0040] S1045: Growing an additional oxide layer to solidify the adhering particles on the second surface of the silicon wafer to be treated onto the additional oxide layer;

[0041] S1046: Remove additional oxide layer.

[0042] It is understandable that if the silicon substrate is an N-type silicon substrate, boron diffusion is performed after texturing the first surface in step S102. Conversely, if the silicon substrate is a P-type silicon substrate, phosphorus diffusion is performed after texturing the first surface in step S102. The choice of diffusion treatment can be based on the type of silicon substrate, and this embodiment does not impose specific limitations on this. In step S104, the silicon wafer to be processed still exposes the second surface of the silicon substrate. Oxidation treatment is performed to remove or reduce the particles attached to the second surface, reducing their impact on the solar cell and thus improving the cross-shaped black spot defects. Since the oxidation process needs to be carried out inside the process furnace tube, the silicon wafer to be processed needs to be loaded first (step S1041), followed by step S1042 (shipping). In step S1043, the furnace tube is evacuated, typically using a vacuum pump. In step S1044, the particles attached to the second surface of the silicon wafer to be processed are dissolved or the size of the particles is reduced. The size of the particles attached to the surface is determined by introducing a substance into the furnace tube that can react with the particles attached to the silicon wafer to be treated, so that the particles are chemically reacted to achieve particle removal or reduction in particle size. In steps S1045 and S1046, an additional oxide layer is grown to solidify the particles attached to the second surface of the silicon wafer to be treated onto the additional oxide layer. The removal of the additional oxide layer is achieved by quickly fixing the particles within the additional oxide layer, reducing the diffusion range of the impact of the attached particles on the silicon substrate. When the additional oxide layer is removed, the particles attached to the silicon wafer to be treated can be removed along with the additional oxide layer, thereby further removing the particles attached to the second surface.

[0043] The solar cell processing method provided in this embodiment has at least the following advantages:

[0044] The solar cell processing method provided in this embodiment includes: providing a silicon substrate, the silicon substrate including a first surface and a second surface disposed opposite to each other along a first direction; texturing and diffusion processing of the first surface to form a doped layer on the first surface; laser doping of the doped layer to obtain a silicon wafer to be processed; oxidizing the silicon wafer to be processed, including: loading the silicon wafer to be processed into a quartz boat; conveying the quartz boat into a furnace tube; evacuating the furnace tube; dissolving or reducing the size of the attached particles on the second surface of the silicon wafer to be processed by introducing a substance that can react with the particles attached to the silicon wafer to be processed, so that the particles are chemically reacted to achieve particle removal or particle size reduction; growing an additional oxide layer to solidify the attached particles on the second surface of the silicon wafer to be processed into the additional oxide layer; removing the additional oxide layer, wherein the growth of the additional oxide layer can quickly lock the particles into the additional oxide layer, and when the additional oxide layer is removed, the particles attached to the silicon wafer to be processed can be removed along with the additional oxide layer, thereby improving the problem of cross-shaped black spots caused by the attached particles on the second surface of the silicon wafer to be processed, and improving the quality of the solar cell.

[0045] In some alternative embodiments, reference continues to be made to... Figure 1 To ablate or reduce the size of adhering particles on the second surface of the silicon wafer to be treated, including:

[0046] Under a temperature range of 900℃ to 1050℃, nitrogen gas at a rate of 5000 sccm to 20000 sccm and reactants at a rate of 100 sccm to 300 sccm are introduced into the furnace tube. The reactants contain chlorine. The introduction time is 1000 s to 1500 s.

[0047] Understandably, the furnace tube is equipped with a heating and temperature control system, which can automatically raise the temperature to 900℃ to 1050℃. Of course, it is not limited to this. Setting the temperature range of 900℃ to 1050℃ is mainly for N-type silicon substrates. Within the temperature range of 900℃ to 1050℃, it is conducive to the rapid diffusion of boron and can also avoid the diffusion of boron to the silicon substrate due to excessively low temperature. Nitrogen gas is introduced, and its fluidity is used to balance the temperature distribution in the furnace tube until each temperature zone is constant at the set temperature. The reactants are introduced to react with the attached particles, dissolving and reducing the attached particles and lowering their hardness. Under the conditions of high-temperature extrusion, there will be no large-sized, high-hardness particles forming pits on the second surface of the silicon substrate, which would cause the pits to appear as cross-shaped black spots in the cell light emission test.

[0048] In some alternative embodiments, the reactants are dichloroethylene or chlorine gas.

[0049] It is understood that this embodiment only discloses that the reactants are dichloroethylene or chlorine gas. The chloride ions in the reactants can remove some of the attached particles and reduce the size and hardness of the attached particles. Of course, it is not limited to this. It can also be other chlorine-containing compounds or any substance that can dissolve or reduce the attached particles without affecting the silicon wafer to be treated. This embodiment does not impose specific limitations on this.

[0050] In some alternative embodiments, reference continues to be made to... Figure 1 The growth of an additional oxide layer includes an isothermal oxidation process, which includes:

[0051] While maintaining a temperature range of 900℃ to 1050℃, nitrogen or oxygen at a rate of 5000 sccm to 10000 sccm, oxygen carrying water vapor at a rate of 3000 sccm to 6000 sccm, and reactants at a rate of 200 sccm to 500 sccm are introduced into the furnace tube for a duration of 1000 s to 2400 s.

[0052] Understandably, under high-temperature conditions, over time, a relatively dense and uniform silicon dioxide layer, i.e., an additional oxide layer, will gradually form on the second surface of the silicon substrate. The introduced nitrogen or oxygen serves as the carrier gas, increasing the gas flow rate within the furnace cavity, facilitating faster and more uniform distribution of the oxygen carrying water vapor throughout the furnace. Using oxygen carrying water vapor, i.e., wet oxygen, can accelerate the growth rate of the silicon dioxide layer, rapidly growing a thicker layer on the second surface of the silicon substrate. This allows for the rapid containment of attached particles within the silicon dioxide layer, reducing their diffusion range and impact on the silicon substrate. Subsequent... The silica layer needs to be removed along with the other particles. The silica layer should be thicker than 90 nanometers. A thicker silica layer can completely encapsulate the attached particles. Of course, if moist oxygen cannot be provided, dry oxygen at 10,000 sccm-30,000 sccm can be introduced. Since the reaction rate of moist oxygen is faster than that of dry oxygen, the flow rate of dry oxygen needs to be increased to achieve rapid growth of the silica layer. Reactants can be introduced to continue reacting with the attached particles, further dissolving and reducing the size of the attached particles, thereby reducing the impact of the cross-shaped black spots.

[0053] In some optional embodiments, the isothermal oxidation process is followed by a cooling oxidation process, which includes:

[0054] After the isothermal oxidation process, the temperature is reduced to 800°C to 900°C, and oxygen is introduced into the furnace tube at a rate of 10,000 sccm to 20,000 sccm for 1,000 to 3,000 seconds.

[0055] Understandably, during the cooling oxidation process, the heating and temperature control system inside the furnace tube stops heating and lowers the temperature. Oxygen continues to be introduced during the cooling process to ensure complete oxidation and further thicken the additional oxide layer. The thicker additional oxide layer can also play a buffering role.

[0056] In some alternative embodiments, the water vapor temperature in the oxygen carrying water vapor is 70°C to 95°C.

[0057] It is understandable that steam at 70°C to 95°C can enter the furnace tube with oxygen as a carrier to facilitate the rapid formation of an oxide layer. If the steam temperature is less than 70°C, the amount of steam will be relatively small. If the steam temperature is greater than 95°C, the amount of oxygen as a carrier will be relatively small.

[0058] In some alternative embodiments, reference continues to be made to... Figure 1 After growing the additional oxide layer, the process also includes:

[0059] Nitrogen gas at 5000 sccm to 20000 sccm is introduced into the furnace tube, and the quartz boat is removed from the furnace tube at a speed of 120 mm / s to 220 mm / s.

[0060] Understandably, introducing nitrogen gas can serve to cool down and purge the air.

[0061] In some alternative embodiments, reference continues to be made to... Figure 1 The process of conveying the quartz boat into the furnace tube includes:

[0062] Nitrogen gas at a rate of 1000 sccm to 10000 sccm is introduced into the furnace tube, and the quartz boat is transported into the furnace tube at a speed of 120 mm / s to 220 mm / s.

[0063] It is understandable that nitrogen gas is introduced during the process of transporting the quartz boat into the furnace tube. Nitrogen gas can blow away the particulate matter attached to the second surface of the silicon wafer to be treated, thereby removing some of the particulate matter attached to the second surface of the silicon wafer to be treated, avoiding cross-shaped black spot defects that would affect the efficiency of the solar cell and prevent them from being mistaken for microcracks.

[0064] In some alternative embodiments, reference continues to be made to... Figure 1 Vacuuming of the furnace tubes includes:

[0065] Nitrogen gas at a rate of 5000 sccm to 20000 sccm is introduced into the furnace tube, and the evacuation time ranges from 120 s to 360 s.

[0066] Understandably, nitrogen gas is introduced during the vacuuming process of the furnace tube. Nitrogen gas can blow away particulate matter attached to the second surface of the silicon wafer to be treated, thereby removing some of the particulate matter attached to the second surface of the silicon wafer to be treated and improving the problem of cross-shaped black spots.

[0067] In some alternative embodiments, reference continues to be made to... Figure 1 The process involves ablating or reducing the size of adhering particles on the second surface of the silicon wafer to be treated, and / or growing an additional oxide layer, under pressure ranging from 600 mbar to 800 mbar.

[0068] Understandably, a pressure range of 600 mbar to 800 mbar, i.e. a slightly negative pressure state, can utilize the pumping speed control of the diaphragm vacuum pump to accelerate the flow of reaction gas, remove reaction byproducts, maintain sufficient reaction gas in the furnace cavity, and sustain the forward reaction.

[0069] Based on the same inventive concept, this invention also provides a specific embodiment of a solar cell 100, which is processed using any of the solar cell processing methods described in the above embodiments. After processing using any of the solar cell processing methods described in the above embodiments, the process may further include steps such as tunneling oxide layer deposition, doped polycrystalline silicon layer deposition, front-side etching, film coating, printing + sintering annealing, and testing and sorting; however, it is not limited to these steps. Please refer to [reference needed]. Figure 2 , Figure 2 This is a schematic diagram of a solar cell structure provided by the present invention. Figure 2 Taking an N-type solar cell as an example, the solar cell 100 includes a silicon substrate 01, a doped layer 02 on one side of the silicon substrate 01, a tunneling oxide layer 03 on the side of the silicon substrate 01 away from the doped layer 02, a doped polycrystalline silicon layer 04 on the side of the tunneling oxide layer 03 away from the silicon substrate 01, and a passivation film layer 05 on the side of the doped polycrystalline silicon layer 04 away from the tunneling oxide layer 03. Of course, it is not limited to this. It can be understood that the solar cell 100 provided in this embodiment has the beneficial effects of the solar cell processing method provided by the present invention. This embodiment will not be described in detail here.

[0070] As can be seen from the above embodiments, the solar cell processing method provided by the present invention achieves at least the following beneficial effects:

[0071] The present invention provides a method for processing solar cells, comprising: providing a silicon substrate, the silicon substrate including a first surface and a second surface disposed opposite to each other along a first direction; texturing and diffusion processing of the first surface to form a doped layer on the first surface; laser doping of the doped layer to obtain a silicon wafer to be processed; and oxidizing the silicon wafer to be processed, comprising: loading the silicon wafer to be processed into a quartz boat; conveying the quartz boat into a furnace tube; evacuating the furnace tube; dissolving or reducing the size of the attached particles on the second surface of the silicon wafer to be processed by introducing a substance that can react with the particles attached to the silicon wafer to be processed, thereby achieving the removal of particles or reduction of particle size through a chemical reaction; growing an additional oxide layer to solidify the attached particles on the second surface of the silicon wafer to be processed into the additional oxide layer; and removing the additional oxide layer, wherein the growth of the additional oxide layer can quickly lock the particles within the additional oxide layer, and when the additional oxide layer is removed, the particles attached to the silicon wafer to be processed can be removed along with the additional oxide layer, thereby improving the problem of cross-shaped black spots caused by the attached particles on the second surface of the silicon wafer to be processed and improving the quality of the solar cell.

[0072] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. A method for processing solar cells, characterized in that, include: A silicon substrate is provided, the silicon substrate including a first surface and a second surface disposed opposite to each other along a first direction; The first surface is texturized and diffused to form a doped layer on the first surface; The doped layer is laser-doped to obtain a silicon wafer to be processed; The oxidation treatment of the silicon wafer to be processed includes: The silicon wafer to be processed is loaded into a quartz boat; The quartz boat is transported into the furnace tube; The furnace tubes were evacuated. A substance that can react with the particles attached to the silicon wafer to be treated is introduced into the furnace tube to dissolve the particles attached to the second surface of the silicon wafer to be treated or to reduce the size of the particles attached to the second surface of the silicon wafer to be treated. An additional oxide layer is grown to solidify the adhering particles on the second surface of the silicon wafer to be treated onto the additional oxide layer; Remove the additional oxide layer.

2. The method for processing solar cells according to claim 1, characterized in that, The process of ablating or reducing the size of adhering particles on the second surface of the silicon wafer to be treated includes: Under a temperature range of 900℃ to 1050℃, nitrogen gas at a rate of 5000 sccm to 20000 sccm and reactants at a rate of 100 sccm to 300 sccm are introduced into the furnace tube. The reactants contain chlorine. The introduction time is 1000 s to 1500 s.

3. The method for processing solar cells according to claim 2, characterized in that, The reactants are dichloroethylene or chlorine gas.

4. The method for processing solar cells according to claim 2, characterized in that, The growth of the additional oxide layer includes an isothermal oxidation process, which includes: While maintaining a temperature range of 900°C to 1050°C, nitrogen or oxygen at 5000 sccm to 10000 sccm, oxygen carrying water vapor at 3000 sccm to 6000 sccm, and the reactants at 200 sccm to 500 sccm are introduced into the furnace tube for a duration of 1000 s to 2400 s.

5. The method for processing solar cells according to claim 4, characterized in that, The isothermal oxidation process is followed by a cooling oxidation process, which includes: After the isothermal oxidation process, the temperature is reduced to 800°C to 900°C, and oxygen is introduced into the furnace tube at a rate of 10,000 sccm to 20,000 sccm for 1,000 to 3,000 seconds.

6. The method for processing solar cells according to claim 4, characterized in that, The water vapor temperature in the oxygen carrying water vapor is between 70°C and 95°C.

7. The method for processing solar cells according to claim 1, characterized in that, Following the growth of the additional oxide layer, the process further includes: Nitrogen gas at 5000 sccm to 20000 sccm is introduced into the furnace tube, and the quartz boat is removed from the furnace tube at a speed of 120 mm / s to 220 mm / s.

8. The method for processing solar cells according to claim 1, characterized in that, The step of conveying the quartz boat into the furnace tube includes: Nitrogen gas at a rate of 1000 sccm to 10000 sccm is introduced into the furnace tube, and the quartz boat is transported into the furnace tube at a speed of 120 mm / s to 220 mm / s.

9. The method for processing solar cells according to claim 1, characterized in that, The process of evacuating the furnace tube includes: Nitrogen gas at a rate of 5000 sccm to 20000 sccm is introduced into the furnace tube, and the vacuuming time ranges from 120 s to 360 s.

10. The method for processing solar cells according to claim 1, characterized in that, The ablation of adhering particles on the second surface of the silicon wafer to be treated or the reduction of the size of adhering particles on the second surface of the silicon wafer to be treated, and / or the growth of the additional oxide layer, are carried out under pressure conditions ranging from 600 mbar to 800 mbar.

11. A solar cell, characterized in that, The solar cell is processed using the processing method described in any one of claims 1-10.

Images