Preparation method of solar cell

Abstract

The invention relates to the technical field of solar cells, in particular to a preparation method of a solar cell, which can improve the compactness of a silicon oxide mask and the crystallization uniformity of a doped polycrystalline silicon layer while saving procedures, thereby improving the cell efficiency on the whole. The preparation method of the solar cell comprises the following steps: sequentially forming a first amorphous silicon film and a silicon oxide mask layer on one side of a first surface of a substrate; annealing the substrate on which the first amorphous silicon thin film and the silicon oxide mask layer are formed; annealing comprises a first stage, a second stage and a third stage which are carried out in sequence, the first stage adopts a stepped heating mode for heating, the second stage adopts heat preservation in the presence of oxygen-containing gas, and the third stage adopts a stepped cooling mode for cooling; in the first stage, the air pressure in the annealing furnace is controlled to be 200-300 Pa higher than the air pressure in the annealing furnace in the second stage, and in the third stage, the air pressure in the annealing furnace is controlled to be 100-150 Pa lower than the air pressure in the annealing furnace in the second stage.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and particularly to a method for preparing a solar cell. Background Art

[0002] Currently, in silicon-based solar cells, the TOPCon (Tunnel Oxide Passivated Contact) technology is to prepare a tunneling oxide layer and a doped polysilicon layer on the back surface of the cell, which can achieve the selective passage of carriers and block the recombination of minority carriers (holes). The chemical passivation of the tunneling oxide layer and the field passivation effect of the doped polysilicon layer can greatly improve the open-circuit voltage and short-circuit current of the solar cell.

[0003] Among many preparation routes, plasma-enhanced chemical vapor deposition (PECVD) and annealing processes are favored by investors due to their high process integration and mature technology. For example, a tunneling oxide layer and an in-situ doped amorphous silicon layer are first prepared by PECVD, then SiH4 and N2O are introduced to prepare a silicon oxide mask on the surface of the in-situ doped amorphous silicon layer, and then, the doped amorphous silicon layer is crystallized into a doped polysilicon layer by high-temperature annealing.

[0004] However, the silicon oxide mask prepared by the above process has poor compactness and weak protection ability for the underlying doped polysilicon layer, which leads to the easy corrosion of the doped polysilicon layer, thus affecting the cell efficiency. At the same time, there are problems such as uneven heating of the doped amorphous silicon layer during high-temperature annealing, which is not conducive to improving the crystallization uniformity of the doped polysilicon layer and further reduces the cell efficiency. Summary of the Invention

[0005] Based on this, some embodiments of the present application provide a method for preparing a solar cell, which can improve the compactness of the silicon oxide mask and the crystallization uniformity of the doped polysilicon layer while saving processes, thereby improving the cell efficiency as a whole.

[0006] In a first aspect, a method for preparing a solar cell is provided, including:

[0007] Providing a substrate, the substrate having a first surface and a second surface oppositely disposed along its thickness direction;

[0008] Sequentially forming a first amorphous silicon thin film and a silicon oxide mask layer on one side of the first surface of the substrate;

[0009] Annealing the substrate on which the first amorphous silicon thin film and the silicon oxide mask layer are formed;

[0010] The annealing includes: a first stage, a second stage, and a third stage carried out in sequence. The first stage is heated in a stepped temperature increase manner, the second stage is kept warm in the presence of an oxygen-containing gas, and the third stage is cooled in a stepped temperature decrease manner;

[0011] In the first stage, the air pressure in the annealing furnace is controlled to be 200 Pa to 300 Pa higher than the air pressure in the annealing furnace in the second stage. In the third stage, the air pressure in the annealing furnace is controlled to be 100 Pa to 150 Pa lower than the air pressure in the annealing furnace in the second stage.

[0012] Optionally, the air pressure in the annealing furnace in the second stage is 200 Pa to 300 Pa.

[0013] Optionally, the oxygen-containing gas includes oxygen. In the second stage, the flow rate ratio of the carrier gas to the oxygen-containing gas is (1 to 22.5):1.

[0014] Optionally, the flow rate ratio of the carrier gas to the oxygen-containing gas is (1 to 9):1.

[0015] Optionally, the temperature increase at least includes: a first temperature increase stage, a second temperature increase stage, and a third temperature increase stage carried out in sequence. The target temperature in the first temperature increase stage is 70°C to 80°C lower than the temperature in the second stage, the target temperature in the second temperature increase stage is 50°C to 60°C lower than the temperature in the second stage, and the target temperature in the third temperature increase stage is 30°C to 40°C lower than the temperature in the second stage.

[0016] Optionally, the preparation method further includes:

[0017] After the first stage and before the second stage, a first evacuation treatment is performed on the gas in the annealing furnace; and / or,

[0018] After the second stage and before the third stage, a second evacuation treatment is performed on the gas in the annealing furnace.

[0019] Optionally, after the first evacuation treatment, the air pressure in the annealing furnace is 100 Pa to 200 Pa; and / or,

[0020] After the second evacuation treatment, the air pressure in the annealing furnace is 100 Pa to 200 Pa.

[0021] Optionally, the temperature reduction at least includes: a first temperature reduction stage, a second temperature reduction stage, and a third temperature reduction stage that are carried out in sequence. The target temperature of the first temperature reduction stage is 30°C to 50°C lower than the temperature of the second stage, the target temperature of the second temperature reduction stage is 60°C to 80°C lower than the temperature of the second stage, and the target temperature of the third temperature reduction stage is 130°C to 150°C lower than the temperature of the second stage.

[0022] Optionally, the preparation method further includes: a furnace pressure recovery stage. The target temperature of the furnace pressure recovery stage is the same as the target temperature of the third temperature reduction stage. The furnace pressure recovery stage includes a first furnace pressure recovery stage and a second furnace pressure recovery stage that are carried out in sequence;

[0023] In the first furnace pressure recovery stage, control the air pressure in the annealing furnace to be 300 Pa to 600 Pa. In the second furnace pressure recovery stage, control the air pressure in the annealing furnace to be 600 Pa to 900 Pa.

[0024] Optionally, in the first furnace pressure recovery stage, the flow rate of the carrier gas introduced into the annealing furnace is 15,000 sccm to 20,000 sccm, and the pumping flow rate of the annealing furnace is adjusted to 8,000 sccm to 20,000 sccm to control the air pressure in the annealing furnace to be 300 Pa to 600 Pa. In the second furnace pressure recovery stage, the flow rate of the carrier gas introduced into the annealing furnace is 15,000 sccm to 20,000 sccm, and the pumping flow rate of the annealing furnace is adjusted to 0 sccm to 6,000 sccm to control the air pressure in the annealing furnace to be 600 Pa to 900 Pa.

[0025] The beneficial technical effects of the preparation method of the solar cell provided by this application are as follows:

[0026] In the presence of an oxygen-containing gas, annealing the substrate on which the first amorphous silicon thin film and the silicon oxide mask layer are formed can enable the oxygen-containing gas to continue to oxidize the surface of the silicon oxide mask layer at a higher annealing temperature, thereby improving the density of the silicon oxide mask layer and realizing the densification treatment of the silicon oxide mask layer. At the same time, high-temperature annealing can also convert the first amorphous silicon thin film into a first polycrystalline silicon thin film, synchronize the densification treatment of the silicon oxide mask layer and the crystallization of amorphous silicon, save processes, and is beneficial for the dense silicon oxide mask to protect the underlying first polycrystalline silicon thin film, reduce the corrosion of the first polycrystalline silicon thin film in subsequent wet processes, and improve the battery efficiency.

[0027] In addition, in the first stage, the temperature is increased in a stepped manner, which can make the temperatures of each temperature zone as consistent as possible, and the uniformity of the whole boat is good. At the same time, during this process, by controlling the changes in the flow rate of the carrier gas introduced and the pumping flow rate, for example, controlling both the flow rate of the carrier gas introduced and the pumping flow rate to be relatively low, and using the heat-carrying and heat-preserving effect of the carrier gas to increase the stability of the temperature rise of the temperature field while adjusting the pressure in the annealing furnace to be relatively high. In the third stage, the temperature is decreased in a stepped manner, which can also keep the temperatures of each temperature zone as consistent as possible. At the same time, during this process, by controlling the changes in the flow rate of the carrier gas introduced and the pumping flow rate, for example, controlling both the flow rate of the carrier gas introduced and the pumping flow rate to be relatively high, and using the heat-carrying and heat-dissipating effect of the carrier gas to maintain the consistency of the temperature drop of each temperature zone while adjusting the pressure in the annealing furnace to be relatively low, thereby reducing problems such as crystallization differences in each temperature zone.

[0028] Furthermore, the inventors also found that: by adjusting the pressure in the annealing furnace in the first stage to be 200 Pa - 300 Pa higher than that in the second stage, and the pressure in the annealing furnace in the third stage to be 100 Pa - 150 Pa lower than that in the second stage, the temperature differences in each temperature zone of the annealing furnace can be kept small, thereby reducing the crystallization differences in different temperature zones and improving the uniformity of the whole boat.

[0029] In summary, in the method for preparing a solar cell provided in the embodiments of the present application, while saving processes, the denseness of the silicon oxide mask layer can be improved, and the crystallization uniformity of the doped polysilicon layer can be improved, thereby overall enhancing the battery efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic flow chart of a method for preparing a solar cell provided in the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In order to make the above objects, features, and advantages of the present application more obvious and understandable, the following detailed description of the specific embodiments of the present application is made with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0032] Unless the context requires otherwise, throughout the specification and claims, the term "comprising" is to be construed in an open, inclusive sense, i.e., "including, but not limited to". In the description of the specification, terms such as "one embodiment", "some embodiments", "exemplary embodiments", "exemplarily", or "some examples" are intended to indicate that specific features, structures, materials, or characteristics related to the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials, or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0033] Exemplary embodiments are described herein with reference to cross-sectional views and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and regions is exaggerated for clarity. Accordingly, variations in the shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Thus, exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include shape deviations caused by, for example, manufacturing. For example, an etched region shown as rectangular will typically have curved features. Thus, the regions shown in the drawings are schematic in nature, and their shapes are not intended to show the actual shape of the regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0034] "A and / or B" includes the following three combinations: only A, only B, and the combination of A and B.

[0035] In this document, unless otherwise specified, "one or more" means one or greater than or equal to two.

[0036] In this document, terms such as "for example", "such as", "example", "for illustration" are used for descriptive purposes, indicating an association in the covered content between different technical solutions before and after, but should not be construed as a limitation on the previous technical solution, nor should it be construed as a limitation on the scope of protection of this document. In this document, unless otherwise stated, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0037] In this document, "optionally", "optional", "option", mean optional, that is, it means any one of the two alternative options of "having" or "not having". If "optional" appears multiple times in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction relationship, each "optional" is independent of each other.

[0038] In this document, descriptions such as "optionally contain", "optionally include", etc., mean "contain or not contain". "Optional component X" means that component X is present or absent, or means containing or not containing this component X.

[0039] In this text, in "the first aspect", "the second aspect", etc., the terms "first", "second", etc. are only for descriptive purposes and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features.

[0040] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this text are only for illustrative purposes and do not represent the only implementation.

[0041] Unless otherwise defined, all technical and scientific terms used in this text have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the description of this application in this text are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0042] In this text, among the technical features described in an open-ended manner, it includes a closed technical solution composed of the listed features, and also includes an open technical solution containing the listed features.

[0043] In this text, the meaning of "at least one" is more than one, such as one, two or more. The meaning of "multiple" or "several" is at least two, such as two, three, etc., and the meaning of "multiple layers" is at least two layers, such as two layers, three layers, etc., unless otherwise specifically defined. In the description of this application, the meaning of "several" is at least one, such as one, two, etc., unless otherwise specifically defined.

[0044] In this text, regarding a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values within this numerical interval is considered continuous and includes the two numerical endpoints (i.e., the minimum value and the maximum value) of this numerical interval, as well as each numerical value between these two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within this numerical interval, it includes the two endpoint integers of this numerical range, as well as each integer between the two endpoints, which is equivalent to directly listing each integer. When providing multiple numerical ranges to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed in this text should be understood to include any and all sub-ranges subsumed therein. The "numerical value" in this numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. The "numerical interval" allows for a broad inclusion of numerical interval types such as percentage intervals, ratio intervals, ratio value intervals, etc.

[0045] In this article, regarding percentage content, unless otherwise specified, for solid-liquid mixtures and solid-solid mixtures, it refers to mass percentage, and for liquid-liquid mixtures, it refers to volume percentage.

[0046] In this article, regarding percentage concentration, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after adding this component.

[0047] In this article, %(w / w) and wt% both represent weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass-volume percentage.

[0048] In this article, regarding temperature parameters, unless otherwise specified, it is allowed to be a constant temperature treatment or a treatment within a certain temperature range. The constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument.

[0049] In this article, the term "room temperature" or "ambient temperature" generally refers to 4°C to 35°C, such as 20°C ± 5°C. In some embodiments of this article, "room temperature" or "ambient temperature" refers to 10°C to 30°C. In some embodiments of this article, "room temperature" or "ambient temperature" refers to 20°C to 30°C.

[0050] The fill factor (FF) used in this article refers to the ratio of the actual maximum achievable power (Pm or Vmp * Jmp) to the theoretical (not actually achievable) power (Jsc * Voc). Therefore, FF can be determined by the following formula:

[0051] FF = (Vmp * Jmp) / (Jsc * Voc)

[0052] Where Jmp and Vmp represent the current density and voltage at the maximum power point (Pm) respectively, and this point is obtained by changing the resistance in the circuit until J * V is the maximum; Jsc and Voc represent the short-circuit current and open-circuit voltage respectively. The fill factor is a key parameter for evaluating solar cells. Commercial solar cells usually have a fill factor of about 60% or more.

[0053] The open-circuit voltage (Voc) used in this article is the potential difference between the anode and cathode of the device under the condition of no connected external load.

[0054] The power conversion efficiency (PCE) of the solar cell used in this article refers to the percentage of the power converted from absorbed light into electrical energy. The power conversion efficiency (PCE) of the solar cell can be obtained through the incident light irradiance (E: W / m 2 ), and the surface area of the solar cell (Ac: m 2) is calculated except for the maximum power point (Pm). STC usually refers to the spectrum at a temperature of 25 °C, a radiation irradiance of 1000 W / m 2 , and an air mass of 1.5 (AM1.5).

[0055] In view of the problems in the related art that the compactness of the silicon oxide mask is poor, the protection ability for the underlying doped polysilicon layer is weak, resulting in the doped polysilicon layer being easily corroded, thus affecting the battery efficiency, and there is uneven heating of the doped amorphous silicon layer during high-temperature annealing, further reducing the battery efficiency, etc., the specific implementation manners of the present application are as follows:

[0056] In a first aspect, some embodiments of the present application provide a method for manufacturing a solar cell, as Figure 1 shown, the manufacturing method includes the following steps S11 to S13:

[0057] S11. Provide a substrate, which has a first surface and a second surface oppositely arranged along its thickness direction;

[0058] Among them, taking this solar cell as a silicon-based solar cell as an example, the substrate can be a silicon wafer after texturing and alkaline polishing, and a PN junction is formed on the silicon wafer.

[0059] S12. Sequentially form a first amorphous silicon thin film and a silicon oxide mask layer on one side of the first surface of the substrate;

[0060] The first amorphous silicon thin film can be a doped amorphous silicon thin film or an undoped amorphous silicon thin film, and no specific limitation is made here.

[0061] In some embodiments, the first amorphous silicon thin film is a doped amorphous silicon thin film. At this time, before S12, the manufacturing method may further include: forming a tunneling oxide layer on one side of the first surface of the substrate, and the tunneling oxide layer is between the substrate and the first amorphous silicon thin film. At this time, this solar cell can be a TOPCon cell.

[0062] S13. Anneal the substrate on which the first amorphous silicon thin film and the silicon oxide mask layer are formed;

[0063] The annealing includes: a first stage, a second stage, and a third stage carried out in sequence. The first stage is heated by a stepwise temperature increase method, the second stage is kept warm in the presence of an oxygen-containing gas, and the third stage is cooled by a stepwise temperature decrease method;

[0064] In the first stage, control the air pressure in the annealing furnace to be 200 Pa to 300 Pa higher than the air pressure in the annealing furnace in the second stage. In the third stage, control the air pressure in the annealing furnace to be 100 Pa to 150 Pa lower than the air pressure in the annealing furnace in the second stage.

[0065] Among them, in the presence of an oxygen-containing gas, annealing the substrate on which the first amorphous silicon thin film and the silicon oxide mask layer are formed enables the oxygen-containing gas to continue to oxidize the surface of the silicon oxide mask layer at a higher annealing temperature, thereby improving the density of the silicon oxide mask layer and achieving densification treatment of the silicon oxide mask layer. At the same time, high-temperature annealing can also convert the first amorphous silicon thin film into the first polycrystalline silicon thin film, synchronizing the densification treatment of the silicon oxide mask layer and the crystallization of amorphous silicon, saving processes, and being beneficial for the dense silicon oxide mask to protect the underlying first polycrystalline silicon thin film, reducing the corrosion of the first polycrystalline silicon thin film in subsequent wet processes and improving the battery efficiency.

[0066] Among them, the stepwise heating method does not directly raise the annealing temperature to the target temperature, but instead, like climbing stairs, raises the temperature in several stages, gradually increasing the temperature according to a predetermined stage and rate. Each stage has a specific temperature range and residence time, enabling more precise control of the heating process.

[0067] Similarly, the stepwise cooling method does not directly lower the annealing temperature to the furnace opening temperature, but instead, like going down stairs, lowers the temperature in several stages, gradually decreasing the temperature according to a predetermined stage and rate. Each stage has a specific temperature range and residence time, enabling more precise control of the cooling process.

[0068] During the research process, the inventors found that: during the above heating and cooling processes, the heating rates at various locations in the annealing furnace are inconsistent. In particular, a large amount of heat is lost in the area near the furnace door during the process of loading and unloading the boat, and the heating rate is slower compared to the area at the furnace tail, causing crystallization differences in each temperature zone and resulting in poor convergence of the final efficiency.

[0069] On the basis above, the inventor further found that: in the first stage, by means of stepwise heating, the temperature of each temperature zone can be made as consistent as possible, and the uniformity of the whole boat is good. At the same time, in this process, by controlling the changes in the flow rate of the carrier gas introduced and the pumping flow rate, for example, by controlling both the flow rate of the carrier gas introduced and the pumping flow rate to be relatively low, while using the heat-carrying and heat-preserving effect of the carrier gas to increase the temperature stability of the temperature field while adjusting the air pressure in the annealing furnace to be relatively high. In the third stage, by means of stepwise cooling, the temperature of each temperature zone can also be kept as consistent as possible. At the same time, in this process, by controlling the changes in the flow rate of the carrier gas introduced and the pumping flow rate, for example, by controlling both the flow rate of the carrier gas introduced and the pumping flow rate to be relatively high, while using the heat-carrying and heat-dissipating effect of the carrier gas to maintain the consistency of temperature reduction in each temperature zone while adjusting the air pressure in the annealing furnace to be relatively low, thereby reducing problems such as crystallization differences in each temperature zone. At the same time, the inventor also found that: by adjusting the air pressure in the annealing furnace in the first stage to be 200 Pa to 300 Pa higher than that in the second stage, and the air pressure in the annealing furnace in the third stage to be 100 Pa to 150 Pa lower than that in the second stage, the temperature difference between each temperature zone in the annealing furnace can be kept small, thereby reducing the crystallization difference in different temperature zones and improving the uniformity of the whole boat.

[0070] In summary, in the method for preparing a solar cell provided in the embodiment of the present application, while saving processes, the compactness of the silicon oxide mask layer can be improved, and the crystallization uniformity of the doped polysilicon layer can be improved, thereby overall enhancing the battery efficiency.

[0071] In some embodiments, the air pressure in the annealing furnace in the second stage is 200 Pa to 300 Pa. Exemplarily, the air pressure in the annealing furnace in the second stage can be controlled at 200 Pa, 210 Pa, 220 Pa, 230 Pa, 240 Pa, 250 Pa, 260 Pa, 270 Pa, 280 Pa, 290 Pa or 300 Pa, etc.

[0072] In these embodiments, in the first stage, the air pressure in the annealing furnace can be 300 Pa to 600 Pa, and in the third stage, the air pressure in the annealing furnace can be 50 Pa to 200 Pa.

[0073] For example, when the air pressure in the annealing furnace in the second stage is 200 Pa, since the air pressure in the annealing furnace in the first stage is 200 Pa - 300 Pa higher than that in the annealing furnace in the second stage, in the first stage, the air pressure in the annealing furnace can be 400 Pa, 410 Pa, 420 Pa, 430 Pa, 440 Pa, 450 Pa, 460 Pa, 470 Pa, 480 Pa, 490 Pa or 500 Pa, etc. When the air pressure in the annealing furnace in the second stage is 250 Pa, since the air pressure in the annealing furnace in the first stage is 200 Pa - 300 Pa higher than the air pressure in the annealing furnace during annealing, in the first stage, the air pressure in the annealing furnace can be 450 Pa, 460 Pa, 470 Pa, 480 Pa, 490 Pa, 500 Pa, 510 Pa, 520 Pa, 530 Pa, 540 Pa or 550 Pa, etc.; when the air pressure in the annealing furnace in the second stage is 300 Pa, since the air pressure in the annealing furnace in the first stage is 200 Pa - 300 Pa higher than that in the annealing furnace in the second stage, in the first stage, the air pressure in the annealing furnace can be 500 Pa, 510 Pa, 520 Pa, 530 Pa, 540 Pa, 550 Pa, 560 Pa, 570 Pa, 580 Pa, 590 Pa or 600 Pa, etc.

[0074] In some embodiments, the oxygen-containing gas described above includes oxygen. During the annealing process, the flow rate ratio of the carrier gas to the oxygen-containing gas is (1 - 22.5):1.

[0075] In some embodiments, the flow rate ratio of the carrier gas to the oxygen-containing gas is (1 - 9):1, and further preferably 3:1.

[0076] In these embodiments, the density of the silicon oxide mask layer can be increased as much as possible.

[0077] In some embodiments, when the flow rate ratio of the carrier gas to the oxygen-containing gas is (1 - 9):1, the flow rate of the carrier gas can be 1500 sccm - 4500 sccm, and the flow rate of oxygen can be 500 sccm - 1500 sccm.

[0078] In these embodiments, by controlling the flow rates of the carrier gas and oxygen within the above ranges respectively, the temperature fluctuations in different temperature zones can be minimized to the greatest extent, and a relatively high density of the silicon oxide mask layer can be maintained.

[0079] In some embodiments, the above temperature increase at least includes: a first temperature increase stage, a second temperature increase stage, and a third temperature increase stage that are sequentially performed. The target temperature of the first temperature increase stage is 70°C to 80°C lower than the temperature of the second stage, the target temperature of the second temperature increase stage is 50°C to 60°C lower than the temperature of the second stage, and the target temperature of the third temperature increase stage is 30°C to 40°C lower than the temperature of the second stage.

[0080] In these embodiments, the inventors found that: by controlling the differences between the target temperatures of the first temperature increase stage, the second temperature increase stage, and the third temperature increase stage and the temperature of the second stage within the above ranges respectively, it is possible to combine with the gas pressure in the annealing furnace as much as possible to maximize the temperature consistency of each temperature zone and the temperature increase stability of the temperature field.

[0081] In some embodiments, the temperature of the second stage can be 910°C to 930°C.

[0082] In these embodiments, the denseness of the silicon oxide mask and the crystallization degree of the first polysilicon layer can be maximally improved, and the battery efficiency can be increased; meanwhile, the target temperature of the first temperature increase stage can be 830°C to 860°C, the target temperature of the second temperature increase stage can be 850°C to 880°C, and the target temperature of the third temperature increase stage can be 870°C to 900°C.

[0083] In some embodiments, the preparation method further includes:

[0084] After the first stage and before the second stage, perform a first evacuation treatment on the gas in the annealing furnace; and / or,

[0085] After the second stage and before the third stage, perform a second evacuation treatment on the gas in the annealing furnace.

[0086] In these embodiments, after the first stage and before the second stage, by performing a first evacuation process on the gas in the annealing furnace, it is convenient to subsequently fill the reaction gases such as oxygen-containing gas and carrier gas in the annealing furnace, which is beneficial to the uniform reaction of the reaction gases with the surface of the first amorphous silicon film facing away from the substrate, and further improves the density and uniformity of the first mask. At the same time, through the first evacuation process, the carrier gas in the annealing furnace after heating can also be quickly evacuated, so that when the oxygen-containing gas and carrier gas are subsequently introduced, the temperature consistency of each temperature zone can be maintained as much as possible, and the low-temperature oxygen-containing gas and carrier gas during the introduction of the oxygen-containing gas and carrier gas can be reduced from causing different degrees of disturbance to the temperatures of different temperature zones, resulting in temperature fluctuations in different temperature zones, and the temperature stability and uniformity of the temperature field during the annealing process can be further improved. After the second stage and before the third stage, by performing a second evacuation process on the gas in the annealing furnace, it is convenient to quickly evacuate the remaining reaction gases during the heat preservation process, so that the temperatures of each temperature zone in the subsequent third stage can be as consistent as possible, and the low-temperature carrier gas during the introduction of the carrier gas can also be reduced from causing different degrees of disturbance to the temperatures of different temperature zones, resulting in temperature fluctuations in different temperature zones, and the cooling stability and uniformity of the temperature field can be further improved.

[0087] In some embodiments, after the first evacuation process, the air pressure in the annealing furnace is 100 Pa to 200 Pa; and / or,

[0088] After the second evacuation process, the air pressure in the annealing furnace is 100 Pa to 200 Pa.

[0089] In these embodiments, the inventors found that by controlling the air pressure in the annealing furnace to be 100 Pa to 200 Pa after the first evacuation process, the reaction uniformity of the subsequent reaction gases can be improved as much as possible, thereby improving the density and uniformity of the first mask as much as possible, and at the same time improving the temperature stability and uniformity of the temperature field during the subsequent second-stage heat preservation process as much as possible. By controlling the air pressure in the annealing furnace to be 100 Pa to 200 Pa after the second evacuation process, the cooling stability and uniformity of the temperature field can be improved as much as possible.

[0090] In some embodiments, the above cooling at least includes: a first cooling stage, a second cooling stage, and a third cooling stage that are sequentially performed. The target temperature of the first cooling stage is 30°C to 50°C lower than the temperature of the second stage, the target temperature of the second cooling stage is 60°C to 80°C lower than the temperature of the second stage, and the target temperature of the third cooling stage is 130°C to 150°C lower than the temperature of the second stage.

[0091] In these embodiments, the inventors found that by controlling the target temperature in the first temperature reduction stage, the target temperature in the second temperature reduction stage, and the difference between the target temperature in the third temperature reduction stage and the temperature in the second stage within the above ranges respectively, it is possible to combine with the air pressure in the annealing furnace as much as possible to maximize the temperature consistency of each temperature zone and the temperature reduction stability of the temperature field.

[0092] In some embodiments, the temperature in the second stage can be 910 °C. At this time, the target temperature in the first temperature reduction stage can be 860 °C to 880 °C, the target temperature in the second temperature reduction stage can be 830 °C to 850 °C, and the target temperature in the third temperature reduction stage can be 760 °C to 780 °C.

[0093] In some embodiments, the preparation method further includes: a furnace pressure recovery stage, where the target temperature in the furnace pressure recovery stage is the same as the target temperature in the third temperature reduction stage, and the furnace pressure recovery stage includes a first furnace pressure recovery stage and a second furnace pressure recovery stage that are carried out in sequence;

[0094] In the first furnace pressure recovery stage, control the air pressure in the annealing furnace to be 300 Pa to 600 Pa. In the second furnace pressure recovery stage, control the air pressure in the annealing furnace to be 600 Pa to 900 Pa.

[0095] In these embodiments, by controlling the target temperature in the furnace pressure recovery stage to be the same as the target temperature in the third temperature reduction stage, it is possible to reduce temperature fluctuations as much as possible, maintain the temperature consistency of each temperature zone, and keep the temperature distribution in each temperature zone relatively uniform and lasting at a higher temperature, which is convenient for improving the crystallization effect of the first polysilicon thin film. By dividing the furnace pressure recovery stage into a first furnace pressure recovery stage and a second furnace pressure recovery stage that are carried out in sequence, it is possible to achieve gradient pressure increase at a higher temperature, which is convenient for maintaining better temperature uniformity and holding time in each temperature zone at a higher temperature, and can further stabilize the temperature reduction stability and uniformity of the temperature field and improve the annealing effect.

[0096] In some embodiments, in the first furnace pressure recovery stage, the flow rate of the carrier gas introduced into the annealing furnace is 15000 sccm to 20000 sccm, and the pumping flow rate of the annealing furnace is adjusted to 8000 sccm to 20000 sccm to control the air pressure in the annealing furnace to be 300 Pa to 600 Pa. In the second furnace pressure recovery stage, the flow rate of the carrier gas introduced into the annealing furnace is 15000 sccm to 20000 sccm, and the pumping flow rate of the annealing furnace is adjusted to 0 sccm to 6000 sccm to control the air pressure in the annealing furnace to be 600 Pa to 900 Pa.

[0097] In these embodiments, by controlling the pressure in the annealing furnace within the above range, the rapid replacement of the gas in the annealing furnace under low pressure can help the annealing furnace cool down rapidly, and at the same time, the temperature uniformity of each temperature zone is maintained through the gradient cooling setting.

[0098] In a second aspect, some embodiments of the present application provide a solar cell, which is prepared by the preparation method as described in the first aspect.

[0099] In a third aspect, some embodiments of the present application provide a photovoltaic module, which includes: a plurality of solar cells connected in series and / or in parallel;

[0100] At least one of the solar cells is the solar cell as described in the second aspect.

[0101] In a fourth aspect, some embodiments of the present application provide a photovoltaic system, including the photovoltaic module as described in the third aspect.

[0102] The photovoltaic system can be applied in photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to devices or apparatuses that use solar energy for power generation, such as user solar power supplies, solar street lights, solar cars, solar buildings, and so on. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is to say, the photovoltaic system can be applied in all fields that require solar power generation. Taking the photovoltaic power generation system network as an example, the photovoltaic system can include a photovoltaic array, a busbar trunking box, and an inverter. The photovoltaic array can be an array combination of multiple solar cells. For example, multiple solar cells can form multiple photovoltaic arrays. The photovoltaic arrays are connected to the busbar trunking box, and the busbar trunking box can collect the current generated by the photovoltaic arrays. After the collected current flows through the inverter and is converted into alternating current required by the commercial power grid, it is connected to the commercial power grid to achieve solar power supply.

[0103] In order to objectively evaluate the technical effects of the embodiments of the present application, the present application will be described in detail and exemplarily through the following embodiments and comparative examples.

[0104] In the following embodiments and comparative examples, all raw materials can be obtained through commercial channels. And in order to maintain the reliability of the experiment, the raw materials used in the following embodiments and comparative examples have the same physical and chemical parameters or are prepared by the same treatment method.

[0105] Example 1

[0106] The preparation method of the solar cell provided in Example 1 is as follows:

[0107] Step S1), cleaning and texturing the N-type silicon wafer;

[0108] Step S2): Boron diffusion is carried out on the front side of the cleaned and textured N-type silicon wafer, and oxidation is carried out to prepare a PN junction and a borosilicate glass layer;

[0109] Step S3): Remove the borosilicate glass on the back side of the silicon wafer and perform alkaline polishing on the back side;

[0110] Step S4): Through PECVD (Plasma Enhanced Chemical Vapor Deposition), introduce N2O to prepare a tunneling oxide layer on the back side;

[0111] Step S5): After evacuating and purging the reaction chamber after the reaction in Step S4 is completed, introduce SiH4 with a flow rate of 2950 sccm, PH3 with a flow rate of 850 sccm, and H2 with a flow rate of 9800 sccm into the reaction chamber. Deposit a doped amorphous silicon layer on the surface of the tunneling oxide layer under the conditions of a pressure of 2650 Torr and a temperature of 440 °C. Then introduce SiH4 with a flow rate of 2000 sccm and N2O with a flow rate of 9800 sccm, and deposit a silicon oxide mask layer on the surface of the doped amorphous silicon layer under the conditions of a pressure of 1700 mTorr and a temperature of 440 °C;

[0112] Step S6): Gradually increase the temperature of the annealing furnace to 920 °C. This gradient temperature increase includes: a first temperature increase stage, a second temperature increase stage, and a third temperature increase stage in sequence. Among them, in the first temperature increase stage, the flow rate of nitrogen introduced is 3000 sccm, the target temperature is set to 845 °C, the pressure in the annealing furnace is maintained at 500 Pa, and the time is 600 s. In the second temperature increase stage, the flow rate of nitrogen introduced is 3000 sccm, the target temperature is set to 865 °C, the pressure in the annealing furnace is maintained at 500 Pa, and the time is 600 s. In the third temperature increase stage, the flow rate of nitrogen introduced is 3000 sccm, the target temperature is set to 885 °C, the pressure in the annealing furnace is maintained at 500 Pa, and the time is 600 s;

[0113] Step S7): Set the target temperature of the annealing furnace to 920 °C, evacuate the gas in the annealing furnace until the pressure in the annealing furnace is 150 Pa, and the time is 60 s. Then, introduce nitrogen and oxygen into the annealing furnace, where the flow rate of nitrogen is 3000 sccm and the flow rate of oxygen is 1000 sccm. The pressure in the annealing furnace is maintained at 250 Pa, and heat preservation is completed after 1440 s;

[0114] Step S8): Set the target temperature of the annealing furnace to 920 °C, evacuate the gas in the annealing furnace until the pressure in the annealing furnace is 150 Pa for 60 s. Then, cool the annealing furnace down to 780 °C in a gradient manner. This gradient cooling includes: a first cooling stage, a second cooling stage, and a third cooling stage that are carried out in sequence. Among them, in the first cooling stage, the flow rate of nitrogen introduced is 20000 sccm, the target temperature is set to 880 °C, the pressure in the annealing furnace is maintained at 100 Pa for 400 s. In the second cooling stage, the flow rate of nitrogen introduced is 20000 sccm, the target temperature is set to 850 °C, the pressure in the annealing furnace is maintained at 100 Pa for 400 s. In the third cooling stage, the flow rate of nitrogen introduced is 20000, the target temperature is set to 780 °C, the pressure in the annealing furnace is maintained at 100 Pa for 400 s;

[0115] Step S9): The annealing furnace pressure recovery stage includes a first furnace pressure recovery stage and a second furnace pressure recovery stage that are carried out in sequence. In the first furnace pressure recovery stage, the target temperature of the annealing furnace is set to 780 °C, continue to introduce nitrogen into the annealing furnace, the flow rate of nitrogen is 20000 sccm, and set the target pressure in the annealing furnace to 500 Pa for 500 s. In the second furnace pressure recovery stage, the target temperature of the annealing furnace is set to 780 °C, continue to introduce nitrogen into the annealing furnace, the flow rate of nitrogen is 20000 sccm, and set the target pressure in the annealing furnace to 800 Pa for 400 s to complete the furnace pressure recovery and then open the furnace door;

[0116] Step S10): Perform wet etching on the front side of the silicon wafer. Use HF to etch the phosphosilicate glass layer that has been deposited on the front edge and side, then use NaOH to remove the doped polysilicon in the deposited area, and finally use HF to remove the remaining borosilicate glass layer on the front side;

[0117] Step S11): Deposit a passivation and antireflection film on both the front side and the back side of the silicon wafer. First, deposit a 16 nm AlO film layer on the front side by ALD method, and then deposit a 75 nm SiN film layer by PECVD method. Deposit a 75 nm SiN film layer on the back side; x film layer 16nm, and then deposit SiN x film layer 75nm by PECVD method. Deposit SiN x film layer 75nm on the back side;

[0118] Step S12): Perform metallization screen printing on the silicon wafer, and then perform sintering and light injection to form a first grid line pattern and a second grid line pattern.

[0119] Example 2

[0120] The preparation method of the solar cell in Example 2 is basically the same as that of the solar cell in Example 1, except that:

[0121] In step S6), the annealing furnace is heated to 910°C in a gradient manner. In the first heating stage, the flow rate of nitrogen gas is 3000 sccm, the target temperature is set to 830°C, the pressure inside the annealing furnace is maintained at 500 Pa, and the time is 600 s. In the second heating stage, the flow rate of nitrogen gas is 20000 sccm, the target temperature is set to 850°C, the pressure inside the annealing furnace is maintained at 500 Pa, and the time is 600 s. In the third heating stage, the flow rate of nitrogen gas is 3000 sccm, the target temperature is set to 870°C, the pressure inside the annealing furnace is maintained at 500 Pa, and the time is 600 s.

[0122] In step S7), the target temperature of the annealing furnace is set to 910°C. The gas inside the annealing furnace is evacuated until the pressure inside the annealing furnace is 100 Pa, and the time is 60 s. Then, nitrogen gas and oxygen gas are introduced into the annealing furnace. The flow rate of nitrogen gas is 1500 sccm, the flow rate of oxygen gas is 1500 sccm, the pressure inside the annealing furnace is maintained at 250 Pa, and heat preservation is carried out for 1440 s.

[0123] In step S8), the target temperature of the annealing furnace is set to 910°C. The gas inside the annealing furnace is evacuated until the pressure inside the annealing furnace is 100 Pa, and the time is 60 s. Then, the annealing furnace is cooled in a gradient manner to 760°C. In this gradient cooling process, in the first cooling stage, the flow rate of nitrogen gas is 20000 sccm, the target temperature is set to 860°C, the pressure inside the annealing furnace is maintained at 100 Pa, and the time is 400 s. In the second cooling stage, the flow rate of nitrogen gas is 20000 sccm, the target temperature is set to 830°C, the pressure inside the annealing furnace is maintained at 100 Pa, and the time is 400 s. In the third cooling stage, the flow rate of nitrogen gas is 20000 sccm, the target temperature is set to 760°C, the pressure inside the annealing furnace is maintained at 100 Pa, and the time is 400 s.

[0124] In step S9), in the first furnace pressure recovery stage, the target temperature of the annealing furnace is set to 760°C, the flow rate of nitrogen gas is 20000 sccm, the target pressure inside the annealing furnace is 300 Pa, and the time is 500 s. In the second furnace pressure recovery stage, the target temperature of the annealing furnace is set to 760°C, the flow rate of nitrogen gas is 20000 sccm, the target pressure inside the annealing furnace is 600 Pa, and the time is 400 s.

[0125] Example 3

[0126] The preparation method of the solar cell in Example 3 is basically the same as that of the solar cell in Example 1, except that:

[0127] In step S6), the annealing furnace is heated to 930°C in a gradient manner. In the first heating stage, the flow rate of nitrogen is 3000 sccm, the target temperature is set to 860°C, the pressure inside the annealing furnace is maintained at 500 Pa, and the time is 600 s. In the second heating stage, the flow rate of nitrogen is 3000 sccm, the target temperature is set to 880°C, the pressure inside the annealing furnace is maintained at 500 Pa, and the time is 600 s. In the third heating stage, the flow rate of nitrogen is 3000 sccm, the target temperature is set to 900°C, the pressure inside the annealing furnace is maintained at 500 Pa, and the time is 600 s.

[0128] In step S7), the target temperature of the annealing furnace is set to 930°C. The gas inside the annealing furnace is evacuated until the pressure inside the annealing furnace reaches 200 Pa, and the time is 60 s. Then, nitrogen and oxygen are introduced into the annealing furnace. The flow rate of nitrogen is 4500 sccm, the flow rate of oxygen is 200 sccm, the pressure inside the annealing furnace is maintained at 300 Pa, and the time is 1440 s for heat preservation.

[0129] In step S8), the target temperature of the annealing furnace is set to 930°C. The gas inside the annealing furnace is evacuated until the pressure inside the annealing furnace reaches 200 Pa, and the time is 60 s. Then, the annealing furnace is cooled in a gradient manner to 800°C. In this gradient cooling process, in the first cooling stage, the flow rate of nitrogen is 20000 sccm, the target temperature is set to 900°C, the pressure inside the annealing furnace is maintained at 100 Pa, and the time is 400 s. In the second cooling stage, the flow rate of nitrogen is 20000 sccm, the target temperature is set to 870°C, the pressure inside the annealing furnace is maintained at 100 Pa, and the time is 400 s. In the third cooling stage, the flow rate of nitrogen is 20000 sccm, the target temperature is set to 800°C, the pressure inside the annealing furnace is maintained at 100 Pa, and the time is 800 s.

[0130] In step S9), in the first furnace pressure recovery stage, the target temperature of the annealing furnace is set to 800°C, the flow rate of nitrogen is 20000 sccm, the target pressure inside the annealing furnace is 600 Pa, and the time is 500 s. In the second furnace pressure recovery stage, the target temperature of the annealing furnace is set to 800°C, the flow rate of nitrogen is 20000 sccm, the target pressure inside the annealing furnace is 900 Pa, and the time is 400 s.

[0131] Example 4

[0132] The preparation method of the solar cell in Example 4 is basically the same as that of the solar cell in Example 1, except that:

[0133] In step S7), the gas inside the annealing furnace is not evacuated, and nitrogen and oxygen are directly introduced into the annealing furnace;

[0134] In step S8), the gas in the annealing furnace is not evacuated, and the annealing furnace is directly cooled at a gradient to 780 °C.

[0135] Example 5

[0136] The preparation method of the solar cell in Example 5 is basically the same as that of the solar cell in Example 1, except that:

[0137] In step S7), the gas in the annealing furnace is not evacuated, and nitrogen and oxygen are directly introduced into the annealing furnace.

[0138] Example 6

[0139] The preparation method of the solar cell in Example 6 is basically the same as that of the solar cell in Example 5, except that:

[0140] In step S8), the gas in the annealing furnace is not evacuated, and the annealing furnace is directly cooled at a gradient to 780 °C.

[0141] Example 7

[0142] The preparation method of the solar cell in Example 7 is basically the same as that of the solar cell in Example 5, except that:

[0143] In step S9), during the pressure recovery stage of the annealing furnace, the target temperature of the annealing furnace is directly set to 780 °C, the flow rate of nitrogen introduced into the annealing furnace is 20,000 sccm, the target air pressure in the annealing furnace is 800 Pa, and after 800 s, the furnace door is opened.

[0144] Comparative Example 1

[0145] The preparation method of the solar cell in Comparative Example 1 is basically the same as that of the solar cell in Example 1, except that:

[0146] In step S6), the annealing furnace is heated to the target temperature of 920 °C at a heating rate of 5 °C / min;

[0147] In step S7), the gas in the annealing furnace is not evacuated, and nitrogen with a flow rate of 4000 sccm is directly introduced into the annealing furnace, and the air pressure in the annealing furnace is maintained at 250 Pa for 1440 s for heat preservation;

[0148] In step S8), the gas in the annealing furnace is not evacuated, and nitrogen with a flow rate of 20,000 sccm is directly introduced into the annealing furnace, and the air pressure of the annealing furnace is maintained at 250 Pa for 1880 s to complete the cooling, and the target temperature of the cooling is 780 °C;

[0149] In step S9), the target temperature of the annealing furnace is set to 780 °C. Nitrogen with a flow rate of 20,000 sccm is directly introduced into the annealing furnace until the target pressure in the annealing furnace reaches 1000 Pa, and then the furnace door is opened.

[0150] Test example

[0151] The performance of the solar cells provided in Examples 1 to 7 and Comparative Example 1 was tested. The specific test results are shown in Table 1 below:

[0152] Table 1

[0153]

[0154] It can be seen from Table 1 that the efficiency of the solar cells provided in the examples of the present application is significantly better than that of the solar cells provided in Comparative Example 1, especially in terms of the open-circuit voltage and fill factor. Among them, Example 1 has the highest efficiency. The holding temperature of annealing in Examples 2 to 3 is different from that in Example 1, and the efficiency decreases slightly. In Examples 4 to 6, the evacuation step is not carried out compared with Example 1, which causes differences in the gas fields of various parts of the annealing furnace during the holding stage and the cooling stage, resulting in a decrease in the uniformity of some cells and a reduction in the average efficiency. In Example 7, the step-by-step backpressure step is not carried out compared with Example 1, which is not conducive to the stability in the annealing furnace and also affects the uniformity of the whole group, resulting in a slight decrease in the overall efficiency.

[0155] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0156] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A method for preparing a solar cell, characterized in that, Including: Providing a substrate having a first surface and a second surface oppositely disposed along its thickness direction; Successively forming a first amorphous silicon thin film and a silicon oxide mask layer on one side of the first surface of the substrate; Annealing the substrate on which the first amorphous silicon thin film and the silicon oxide mask layer are formed; The annealing includes: a first stage, a second stage, and a third stage carried out in sequence. The first stage is heated by a stepped temperature increase method, the second stage is kept warm in the presence of an oxygen-containing gas, and the third stage is cooled by a stepped temperature decrease method; In the first stage, controlling the air pressure in the annealing furnace to be 200 Pa to 300 Pa higher than the air pressure in the annealing furnace in the second stage. In the third stage, controlling the air pressure in the annealing furnace to be 100 Pa to 150 Pa lower than the air pressure in the annealing furnace in the second stage.

2. The manufacturing method of the solar cell according to claim 1, wherein, The air pressure in the annealing furnace in the second stage is 200 Pa to 300 Pa.

3. The preparation method of the solar cell according to claim 1 or 2, characterized in that, The oxygen-containing gas includes oxygen. In the second stage, the flow rate ratio of the carrier gas to the oxygen-containing gas is (1 to 22.5):

1.

4. The manufacturing method of the solar cell according to claim 3, characterized in that, The flow rate ratio of the carrier gas to the oxygen-containing gas is (1 to 9):

1.

5. The manufacturing method of the solar cell according to claim 1 or 2, characterized in that, The temperature increase at least includes: a first temperature increase stage, a second temperature increase stage, and a third temperature increase stage carried out in sequence. The target temperature in the first temperature increase stage is 70°C to 80°C lower than the temperature in the second stage, the target temperature in the second temperature increase stage is 50°C to 60°C lower than the temperature in the second stage, and the target temperature in the third temperature increase stage is 30°C to 40°C lower than the temperature in the second stage.

6. The method for preparing a solar cell according to claim 1 or 2, characterized in that, The preparation method further includes: After the first stage and before the second stage, performing a first evacuation treatment on the gas in the annealing furnace; and / or, After the second stage and before the third stage, performing a second evacuation treatment on the gas in the annealing furnace.

7. The manufacturing method of the solar cell according to claim 6, characterized in that, After the first evacuation treatment, the air pressure in the annealing furnace is 100 Pa to 200 Pa; and / or, After the second evacuation treatment, the air pressure in the annealing furnace is 100 Pa to 200 Pa.

8. The method for preparing a solar cell according to claim 1 or 2, characterized in that, The temperature decrease at least includes: a first temperature decrease stage, a second temperature decrease stage, and a third temperature decrease stage carried out in sequence. The target temperature in the first temperature decrease stage is 30°C to 50°C lower than the temperature in the second stage, the target temperature in the second temperature decrease stage is 60°C to 80°C lower than the temperature in the second stage, and the target temperature in the third temperature decrease stage is 130°C to 150°C lower than the temperature in the second stage.

9. The manufacturing method of the solar cell according to claim 8, characterized in that, The preparation method further includes: a furnace pressure recovery stage. The target temperature in the furnace pressure recovery stage is the same as the target temperature in the third temperature decrease stage. The furnace pressure recovery stage includes a first furnace pressure recovery stage and a second furnace pressure recovery stage carried out in sequence; In the first furnace pressure recovery stage, controlling the air pressure in the annealing furnace to be 300 Pa to 600 Pa. In the second furnace pressure recovery stage, controlling the air pressure in the annealing furnace to be 600 Pa to 900 Pa.

10. The preparation method of the solar cell according to claim 9, wherein, In the first furnace pressure recovery stage, the flow rate of the carrier gas introduced into the annealing furnace is 15,000 sccm to 20,000 sccm, and the pumping flow rate of the annealing furnace is adjusted to 8,000 sccm to 20,000 sccm to control the pressure in the annealing furnace to be 300 Pa to 600 Pa. In the second furnace pressure recovery stage, the flow rate of the carrier gas introduced into the annealing furnace is 15,000 sccm to 20,000 sccm, and the pumping flow rate of the annealing furnace is adjusted to 0 sccm to 6,000 sccm to control the pressure in the annealing furnace to be 600 Pa to 900 Pa.

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