Method for preparing passivation film of photovoltaic cell, photovoltaic cell and preparation method thereof

Abstract

Embodiments of the present application relate to the technical field of batteries, and provide a preparation method of a passivation film of a photovoltaic cell, a photovoltaic cell and a preparation method thereof. The preparation method of the passivation film comprises: when a carrier plate reaches a specified position in a reaction cavity, alternately introducing H2O and TMA into the reaction cavity, and only introducing TMA after all the surfaces of target silicon wafers on the carrier plate have adsorbed H2O, and only introducing H2O again after the H2O adsorbed on all the target silicon wafers on the carrier plate has reacted with TMA; setting one reaction cycle as one time of sequentially introducing H2O and TMA, and after a preset number of reaction cycles, H2O and TMA are introduced simultaneously until the reaction is completed, and a target silicon wafer with a passivation film deposited on the surface is obtained. The present application can not only avoid atomic arrangement faults on the silicon wafer and obtain a deposition film with good uniformity, but also ensure a certain production efficiency, and has the effect of simultaneously considering the quality and capacity of the passivation film.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic cells, and in particular to a method for preparing a passivation film of a photovoltaic cell, a photovoltaic cell and a method for preparing the same. Background Art

[0002] Currently, photovoltaic cells are one of the hottest energy sources. How to improve the efficiency of photovoltaic cells is the main problem people face. Crystalline silicon surface passivation is an effective method to improve the photoelectric conversion efficiency of cells, especially Al2O3 films grown by ALD (atomic layer deposition). Since they are grown layer by layer, the film has better uniformity and the film thickness can be precisely controlled, so it is more widely used.

[0003] In the related art, atomic layer deposition (ALD) primarily involves alternately introducing two precursors into a reaction chamber, where they are adsorbed and reacted on the substrate surface to form a thin film. This method introduces only one precursor at a time. Once the precursor is saturated with adsorption on the substrate surface, the remaining precursor is removed from the reaction chamber using a carrier gas. A second precursor is then introduced and reacts with the chemically adsorbed first precursor on the substrate surface until the second precursor completely covers the entire surface. The excess second precursor is then removed from the reaction chamber using a carrier gas. This entire process constitutes a reaction cycle. The thickness of the film can be controlled by controlling the number of reaction cycles. However, this method results in a slow growth rate for deposited films because the time required for each cycle includes the injection of the two precursors and the time required to evacuate the excess precursor twice, resulting in low production efficiency. To increase the speed of ALD, a spatially separated ALD method has been proposed, using a plate-type ALD apparatus. This method spatially separates the two precursors and controls their simultaneous introduction into the reaction chamber, allowing the precursors to react simultaneously across the entire plate surface during each cycle, significantly improving production efficiency.

[0004] However, the inventors realized that in actual use, the plate-type ALD device has the following defects: since two precursors are introduced at the same time, mixing is inevitable, resulting in the deposited film being not dense enough, and there are atomic arrangement faults in the deposited layer, resulting in poor film uniformity, which affects the passivation effect. Summary of the Invention

[0005] One or more embodiments of the present application provide a method for preparing a photovoltaic cell passivation film, a cell and its preparation method, so as to solve or at least partially alleviate the quality problem in the related art of using atomic layer deposition to prepare a passivation film, which is that the production capacity and film uniformity, density and other factors that affect the passivation effect cannot be well taken into account.

[0006] In a first aspect of the present application, a method for preparing a photovoltaic cell passivation film is provided, which adopts the following technical solution:

[0007] A method for preparing a photovoltaic cell passivation film is based on a plate-type ALD device, wherein the plate-type ALD device includes a reaction chamber, wherein a carrier is disposed in the reaction chamber, the carrier is used to place a target silicon wafer, and the carrier is used to reciprocate in the reaction chamber;

[0008] The method includes: when the carrier reaches a designated position in the reaction chamber, alternately introducing water vapor and trimethylaluminum into the reaction chamber, and introducing the trimethylaluminum only after the surfaces of all the target silicon wafers on the carrier have adsorbed the water vapor, and introducing the water vapor again only after the water vapor adsorbed on all the target silicon wafers on the carrier has reacted with the trimethylaluminum; setting the introduction of the water vapor and the trimethylaluminum once in sequence as one reaction cycle, and after a preset number of reaction cycles, introducing the water vapor and the trimethylaluminum simultaneously until the reaction is completed, thereby obtaining the target silicon wafers with a passivation film deposited on the surface.

[0009] In one embodiment, the ventilation flow rate of the water vapor is 1700-2700 sccm, and the ventilation temperature is 210-310°C.

[0010] In one embodiment, the trimethylaluminum has a ventilation flow rate of 1700-2700 sccm and a ventilation temperature of 210-310°C.

[0011] In one embodiment, after the surfaces of all the target silicon wafers on the carrier have adsorbed the water vapor, the method further includes: obtaining a first cycle number of the carrier, rounding up the first cycle number to obtain a first preset cycle number, and introducing trimethylaluminum into the reaction chamber when the carrier has run the first preset cycle number;

[0012] And / or, after the water vapor adsorbed on all the target silicon wafers reacts with the trimethylaluminum, it also includes: obtaining a second cycle number of the carrier plate, rounding up the second cycle number to obtain a second preset cycle number, and when the carrier plate runs the second preset cycle number, introducing the water vapor into the reaction chamber again.

[0013] In one embodiment, the preset number is greater than or equal to 1.

[0014] In one embodiment, when the water vapor and the trimethylaluminum are ventilated simultaneously, the ventilation flow rate of the water vapor remains unchanged, and / or when the water vapor and the trimethylaluminum are ventilated simultaneously, the ventilation flow rate of the trimethylaluminum remains unchanged.

[0015] In one embodiment, the thickness of the passivation film is 4-12 nm.

[0016] By adopting the above technical solution, the present invention changes the simultaneous introduction of TMA and H2O gases to first introducing them sequentially and then introducing them synchronously, thereby changing the ventilation method during the growth of the passivation film. This can not only avoid the problem of atomic arrangement faults caused by uneven deposition on the silicon wafer, but also improve production efficiency and ensure high production capacity, thereby achieving the purpose of taking into account both the quality and production capacity of the passivation film. Among them, during the sequential ventilation process, when all target silicon wafers have adsorbed water vapor, TMA is controlled to be introduced into the reaction chamber. When the introduced TMA reacts with the water vapor adsorbed on all target silicon wafers, water vapor is controlled to be introduced into the reaction chamber. Thus, on the one hand, it is ensured that each silicon wafer and each area of ​​the silicon wafer has undergone sufficient reaction, while at the same time, subsequent reactions can be carried out in a timely manner, without wasting gas, and the time required for the reaction process is shortened, thereby improving production efficiency.

[0017] The second aspect of the present application provides a method for preparing a photovoltaic cell, which adopts the following technical solution:

[0018] A method for preparing a photovoltaic cell, comprising: performing texturing on an initial silicon wafer, performing a first boron diffusion, performing a patterning process, performing a second boron diffusion, etching, and preparing a tunneling oxide layer and a polysilicon layer to obtain a target silicon wafer;

[0019] Prepare a passivation film on the front side of the target silicon wafer using the above-mentioned method for preparing a photovoltaic cell passivation film;

[0020] An anti-reflection film is prepared on the back side of the target silicon wafer, and front and rear electrodes are prepared on the front and back sides of the target silicon wafer to obtain a photovoltaic cell.

[0021] In one embodiment, the preparation of the tunneling oxide layer and the polysilicon layer includes: growing the tunneling oxide layer with a thickness of 1-2 nm on the back side of the etched silicon wafer, and then growing a film layer of doped polysilicon, and after annealing and cleaning to remove the oxide layer and borosilicate glass, obtaining the target silicon wafer.

[0022] In a third aspect of the present application, a battery is provided, which is manufactured using the above-mentioned method for preparing a photovoltaic cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, a brief introduction to the drawings of the embodiments will be given below. Obviously, the drawings described below only relate to some embodiments of the present application, and are not intended to limit the present application.

[0024] Figure 1 Schematic diagram of film deposition when two precursors are introduced simultaneously in plate-type ALD in the related art.

[0025] Figure 2Schematic diagram of controlling ventilation of the first inlet cavity in plate-type ALD according to some embodiments of the present application.

[0026] Figure 3 Schematic diagram of controlling ventilation of the second inlet cavity in plate-type ALD according to some embodiments of the present application.

[0027] Figure 4 Schematic diagram of controlling simultaneous ventilation of a first gas inlet cavity and a second gas inlet cavity in plate-type ALD according to some embodiments of the present application.

[0028] Figure 5 Schematic diagram of a battery structure according to some embodiments of the present application.

[0029] In the figure: 1. Carrier; 2. Target silicon wafer; 3. First air inlet cavity; 4. Second air inlet cavity; 5. Isolation gas cavity; 6. Exhaust cavity; 10. Initial silicon wafer; 20. Tunneling oxide layer; 30. Polysilicon film layer; 40. Passivation film; 50. Anti-reflection film; 60. Silver-aluminum electrode; 70. Silver electrode. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions, and advantages of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the accompanying drawings showing multiple embodiments of this application. It should be understood that the described embodiments are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments described in this application, all other embodiments obtained by ordinary technicians in this field without expending creative work will fall within the scope of protection of this application.

[0031] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as commonly understood by one skilled in the art to which this application belongs. The terms used in this application's specification and claims are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including," "comprising," "having," "having," "containing," and "containing" in the specification and claims of this application and the accompanying drawings are open-ended terms. Thus, "including," "comprising," and "having" refer, for example, to a method or apparatus having one or more steps or elements, but are not limited to having only those one or more elements. The terms "first," "second," and "first" in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, not to describe a specific order or priority. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed to indicate or imply relative importance or to implicitly specify the number of the technical features indicated. Thus, a feature designated "first" or "second" may explicitly or implicitly include one or more of the features. Throughout this application, unless otherwise specified, "plurality" means two or more.

[0032] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments.

[0033] The term "and / or" in this application is merely a description of the association relationship between associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0034] Traditional atomic layer deposition is to alternately introduce precursors into the reaction chamber or reaction tube. The corresponding equipment is called tubular ALD. This method and equipment have low production efficiency. In order to improve production capacity, people have developed plate ALD, which has a flat substrate carrier. Two precursors are introduced into the reaction chamber at the same time, and the two are spatially separated by an isolation gas such as nitrogen. The silicon wafer is placed on a carrier, and the carrier swings back and forth in the reaction chamber. The silicon wafer reacts when it swings below the TMA and when it swings below the water. Since the two precursors are introduced simultaneously and continuously, the precursors of each step of the ALD cycle react simultaneously on the entire plate surface, which greatly improves the deposition speed. This method has higher production efficiency and is especially suitable for the needs of large-scale production.

[0035] However, thin film deposition involves sequential reactions. For example, when depositing Al2O3 thin films using ALD, the two precursors can be trimethylaluminum (TMA) and water, where TMA provides the aluminum source and water provides the oxygen source. This means the silicon wafer surface first reacts with water vapor and then with the TMA precursor.

[0036] The overall reaction equation for TMA (Al(CH3)3) reacting with water on the silicon wafer surface to form aluminum oxide is:

[0037] 2Al(CH3)3+3 H2O→Al2O3+6CH4; (1)

[0038] The two half reactions of the reaction process are:

[0039] AlOH*+Al(CH3)3 →AlOAl(CH3)2* +CH4; (2)

[0040] AlCH3* +H2O →AlOH*+CH4; (3)

[0041] Among them, the items with * represent groups attached to the surface of the silicon wafer. When the silicon wafer moves below TMA, a half-reaction as shown in formula (2) occurs. When the silicon wafer moves below H2O, a half-reaction as shown in formula (3) occurs.

[0042] For ease of description, Figure 1 As shown, the two precursors are marked as A and B respectively. The reaction order on the silicon wafer is adsorption of A first and then adsorption of B. It should be noted that in actual production, there may be multiple air pipes / cavities above the silicon wafer, and the two precursor outlets are arranged alternately. Figure 1 For illustrative purposes only, it shows that there are three air pipes / air cavities above a silicon wafer, which are the air pipes / air cavities for the precursors A, B, and A. Therefore, when multiple silicon wafers are placed on the carrier, and the carrier moves to a certain position before ventilation begins, both A and B enter the same silicon wafer. Since it is a sequential reaction, the area below A begins to adsorb A, but the area below B does not adsorb B at this time. During the reciprocating motion of the carrier, when the silicon wafer originally below A swings to below B, A and B can react in this area, and B is adsorbed on the surface of A. At this time, A and B are already adsorbed on the surface of this area, and a deposition layer is generated through the reaction. However, the area originally below B only begins to adsorb A on the silicon wafer when it swings to below A. At this time, no deposition layer is generated in the area originally below B. It should be noted that Figure 1 In the figure, A and B represent the precursors H2O and TMA, respectively. The light-colored filled blocks represent the adsorption of A on the silicon wafer, and the dark-colored filled blocks represent the deposited layer or deposit Al2O3 obtained by the reaction between the adsorbed A on the silicon wafer and the further adsorbed B.

[0043] For example, Figure 1 The middle carrier moves rightward from state (a) to state (b). At this time, area (1) on the silicon wafer moves from below A to below B. Since A is already adsorbed on it, it can continue to adsorb B. However, adsorption has not yet occurred on area (2). Area (3) has also adsorbed A because it has passed A. It can be seen that different areas on the silicon wafer begin to have different adsorption situations. When the carrier continues to move rightward from state (b) to state (c), at this time, area (2) that has not adsorbed A begins to adsorb A, the same as area (3), while area (1) can continue to adsorb A. Therefore, at this time, area (1) has already adsorbed ABA, and the adsorbed A and B have reacted to form a deposition layer, and A continues to adsorb on the deposition layer, while other areas except area (1) only adsorb A. Subsequently, as the carrier moves back and forth, there are always differences in the adsorption and deposition layer formation on the silicon wafer, such as states (d), (e) and (f). Therefore, when two precursors are introduced at the same time, some areas on the silicon wafer begin to adsorb and generate a deposition layer, while others have not yet adsorbed or generated a deposition layer; some areas generate thicker deposition layers, while some areas generate thinner deposition layers. This will lead to a fault in the atomic arrangement on the silicon wafer and poor uniformity in thin film growth. The unevenness of the passivation film on the silicon wafer is not conducive to improving the passivation effect.

[0044] In addition, for the simultaneous ventilation method, although the two gases are separated by an isolation gas, it is inevitable that the isolation gas cannot be completely separated, resulting in the mixing of the two gases. For example, when adsorbing A, B may not be completely separated by the isolation gas, causing B to escape to A, resulting in a mixed gas, causing the gas to be impure and deposited on the surface of the silicon wafer, resulting in problems such as the deposition layer not being dense enough.

[0045] In order to solve the quality problems of poor film uniformity and density that affect the passivation effect in plate-type ALD due to the film-forming method and equipment structure of the simultaneous introduction of precursors, and also to ensure high production efficiency, an embodiment of the present invention provides a method for preparing a photovoltaic cell passivation film.

[0046] Figure 2 Schematic diagram of controlling ventilation of the first gas inlet cavity in plate-type ALD according to some embodiments of the present application;

[0047] Figure 3 Schematic diagram of controlling ventilation of the second inlet cavity in plate-type ALD according to some embodiments of the present application;

[0048] Figure 4 Schematic diagram of controlling simultaneous ventilation of a first gas inlet cavity and a second gas inlet cavity in plate-type ALD according to some embodiments of the present application.

[0049] One or more embodiments of the present application disclose a method for preparing a photovoltaic cell passivation film based on a plate-type ALD device, wherein the plate-type ALD device includes a reaction chamber, wherein a carrier is disposed in the reaction chamber, the carrier being used to place a target silicon wafer, and the carrier being used to reciprocate in the reaction chamber;

[0050] The method includes: when the carrier 1 reaches a designated position in the reaction chamber, alternately introducing water vapor and trimethylaluminum into the reaction chamber, and introducing trimethylaluminum only after the surfaces of all the target silicon wafers 2 on the carrier 1 have adsorbed the water vapor, and introducing water vapor again only after the water vapor adsorbed on all the target silicon wafers 2 on the carrier 1 has reacted with the trimethylaluminum; setting the introduction of the water vapor and the trimethylaluminum once in sequence as one reaction cycle, and after a preset number of reaction cycles, introducing the water vapor and the trimethylaluminum simultaneously until the reaction is completed, thereby obtaining the target silicon wafer 2 with a passivation film 40 deposited on the surface.

[0051] In the process of growing the passivation film, this embodiment changes the ventilation method, changing the simultaneous introduction of the two gases to first introducing them in sequence and then introducing them synchronously. This can not only avoid the problem of uneven atomic arrangement faults in the deposition layer on the silicon wafer, but also give full play to the advantages of the plate-type ALD equipment in improving production efficiency and ensuring high production capacity, thereby achieving the goal of taking into account both the quality and production capacity of the passivation film.

[0052] For the plate-type ALD equipment, it can be understood that a first air inlet cavity, a second air inlet cavity, an isolation gas cavity and an exhaust cavity are arranged above the carrier plate. The first air inlet cavity is used to introduce the water vapor, and the second air inlet cavity is used to introduce trimethylaluminum (TMA). The first air inlet cavity and the second air inlet cavity are alternately arranged along the extension direction of the carrier plate. The isolation gas cavity is provided between the first air inlet cavity and the second air inlet cavity, and the exhaust cavity is provided between the isolation gas cavity and the first air inlet cavity and between the isolation gas cavity and the second air inlet cavity.

[0053] The method of this embodiment is based on a plate-type ALD device. The silicon wafer is placed on a carrier, which moves back and forth. Two types of air inlet cavities are alternately arranged above the carrier. The two air inlet cavities are separated by an isolation gas cavity, and an exhaust cavity is also provided between the air inlet cavity and the isolation gas cavity. The exhaust cavity is used to discharge waste gas in a timely manner. Therefore, when the carrier reaches the designated position in the reaction chamber, the first air inlet chamber can be controlled to be ventilated and the second air inlet chamber closed, or the first air inlet chamber can be controlled to be closed and the second air inlet chamber can be ventilated, so that water vapor and trimethylaluminum can be alternately introduced into the reaction chamber. When the water vapor is adsorbed on the surfaces of all the target silicon wafers on the carrier, the first air inlet chamber is controlled to stop ventilating and the second air inlet chamber is ventilated. When the water vapor adsorbed on all the target silicon wafers reacts with the trimethylaluminum, the second air inlet chamber is controlled to stop ventilating and the first air inlet chamber is ventilated. This is a reaction cycle, that is, the period between two ventilations of the first air inlet chamber is a reaction cycle. After a preset number of reaction cycles, the first air inlet chamber and the second air inlet chamber are controlled to be ventilated at the same time until the reaction is completed to obtain the target silicon wafer with a passivation film deposited on the surface.

[0054] Specifically, this embodiment first introduces A, and through the reciprocating motion of the carrier plate, A is adsorbed on each silicon wafer. A is then closed and B is opened, allowing the reaction between A and B (i.e., H2O reacts with TMA to form Al2O3). Through the reciprocating motion of the carrier plate, B is deposited on the A layer on each silicon wafer and the reaction proceeds. By sequentially introducing A and B, A and B are uniformly adsorbed on the silicon wafer. The isolation gas chamber between A and B further isolates them during gas switching, preventing gas mixing that could affect the density of the deposited layer. Once uniform deposition is achieved on the silicon wafer surface, simultaneous ventilation is then employed to leverage the advantages of plate-type ALD in improving production efficiency. It should be noted that although subsequent simultaneous ventilation will also produce uneven film formation, the uniformity of the underlying deposits in contact with the silicon wafer has been guaranteed during the sequential ventilation, and the uniformity of the underlying deposits has the greatest impact on the passivation effect, and the uniformity of the deposited layer away from the silicon wafer has a weaker impact on the passivation effect. Therefore, this embodiment ensures the uniformity of the underlying deposits through sequential ventilation, and ensures improved production efficiency through synchronous ventilation, thereby taking into account both film formation quality and production capacity.

[0055] In addition, in this embodiment, the timing of switching between the two precursors is to start the switching mechanism only after ensuring that the required layers are deposited on all silicon wafers. That is, when A is adsorbed on all silicon wafers, the adsorption of B is started, and when B is adsorbed on all silicon wafers, it is switched to A. In this way, the uniformity of the deposited layer is guaranteed, and production time and gas usage are not wasted, thereby ensuring production efficiency. The technical problems of the original alumina structure being not dense enough and the existence of atomic arrangement faults in the swing position are solved, and the purpose of improving the passivation effect is achieved. At the same time, the technical effects of improving the conversion efficiency of photovoltaic cells and maintaining production advantages are achieved.

[0056] In some embodiments, the ventilation flow rate of the first air inlet cavity (i.e., the ventilation flow rate of the water vapor) is 1700-2700 sccm, and the ventilation temperature is 210-310° C. The ventilation flow rate of the second air inlet cavity (i.e., the ventilation flow rate of the trimethylaluminum) is 1700-2700 sccm, and the ventilation temperature is 210-310° C. The above ventilation flow rate and temperature settings ensure smooth film formation reaction.

[0057] In some embodiments, after the surfaces of all the target silicon wafers on the carrier have adsorbed the water vapor, the method further includes: obtaining a first cycle number of the carrier operation, rounding up the first cycle number to obtain a first preset cycle number, and when the carrier has run the first preset cycle number, introducing trimethylaluminum into the reaction chamber, that is, controlling the first air inlet chamber to stop ventilation and allowing the second air inlet chamber to ventilate;

[0058] And / or, after the water vapor adsorbed on all the target silicon wafers reacts with the trimethylaluminum, it also includes: obtaining a second cycle number of the carrier plate operation, rounding up the second cycle number to obtain a second preset cycle number, and when the carrier plate runs the second preset cycle number, introducing the water vapor into the reaction chamber again, that is, controlling the second air inlet chamber to stop ventilation and the first air inlet chamber to ventilate.

[0059] It should be noted that, since the carrier plate is a reciprocating motion, the carrier plate is moved back and forth once for a cycle, and the number of cycles of the carrier plate operation is the number of times the carrier plate reciprocates. In the present embodiment, since the two precursors are first passed in sequence, the switching timing of the two precursors is very important, the number of times the carrier plate operates when the surfaces of all target silicon wafers are reacted with water vapor or all target silicon wafers are reacted with TMA, then the number is rounded up to obtain a preset number of cycles, and the start and stop of the two precursors are controlled according to the preset number of cycles. So-called rounding up, its rule is that, regardless of the rule of rounding up, as long as there is a decimal behind, the integer in front is added by 1. For example, if it is obtained that the carrier plate has run 4.3 cycles, the preset number of cycles is 5. By rounding up to obtain the preset number of cycles, it is ensured that each silicon wafer and each region of the silicon wafer have been fully reacted, while being able to promptly carry out subsequent reactions, without wasting gas, and shortening the time required for the reaction process, thereby improving production efficiency.

[0060] For example, taking the adsorption of water vapor on the target silicon wafers as an example, it is assumed that after the carrier plate reciprocates five times, 99% of the target silicon wafers on the carrier plate have adsorbed water vapor, and the remaining target silicon wafers on the way to the next reciprocating motion of the carrier plate have also completed the adsorption of water vapor. For example, the carrier plate moves to the right once and then returns to the left once as one cycle, and the carrier plate only moves to the right once as half a cycle. Then, after the carrier plate cycles five times, during the rightward movement at the beginning of the sixth cycle, the remaining 1% of the target silicon wafers on the carrier plate also adsorb water vapor. As a result, all the target silicon wafers on the carrier plate have adsorbed water vapor. Assuming that the actual number of cycles run by the carrier plate at this time is 5.4, that is, the first cycle number is 5.4, then wait until the carrier plate completes the sixth cycle before introducing trimethylaluminum into the reaction chamber. On the one hand, it ensures that all the target silicon wafers on the carrier plate are adsorbed with water vapor. On the other hand, the entire cycle switching is also easy to operate. For example, switching the gas channel after obtaining that the carrier plate has run six cycles is simple and convenient.

[0061] It should also be noted that in this embodiment, the first and second preset cycle numbers are used to control the switching between water vapor and trimethylaluminum. That is, the introduction of trimethylaluminum begins after the first preset cycle number, and the introduction of water vapor begins after the second preset cycle number. The preset number is used to control the switching between the alternating introduction of water vapor and trimethylaluminum to the simultaneous introduction of water vapor and trimethylaluminum. That is, after the preset number of reaction cycles, the simultaneous introduction of water vapor and trimethylaluminum begins.

[0062] In some embodiments, the preset number is greater than or equal to 1. That is, after one or more reaction cycles, the uniformity of the bottom deposition layer in contact with the silicon wafer is ensured, and the synchronous ventilation method can be used to improve production efficiency.

[0063] The deposited layer in contact with the silicon wafer is referred to as the bottom layer. Since the bottom layer has the greatest impact on the passivation effect, ensuring uniformity in this layer is essential. Therefore, this embodiment employs sequential introduction of TMA and H2O into the reaction chamber, while maintaining synchronized ventilation above the bottom layer. This approach addresses the issue of poor uniformity in the deposited layer while maintaining the throughput advantages of plate-type ALD.

[0064] In some embodiments, when the water vapor and trimethylaluminum are ventilated simultaneously, the ventilation flow rate of the water vapor remains unchanged, that is, it remains consistent with the flow rate when only the water vapor ventilation is controlled, and / or when the water vapor and trimethylaluminum are ventilated simultaneously, the ventilation flow rate of the trimethylaluminum remains unchanged, that is, it remains consistent with the flow rate when only the trimethylaluminum ventilation is controlled. That is, when the first air inlet cavity and the second air inlet cavity are ventilated simultaneously, the ventilation flow rate of the first air inlet cavity remains consistent with the flow rate when only the first air inlet cavity is ventilated, and / or when the first air inlet cavity and the second air inlet cavity are ventilated simultaneously, the ventilation flow rate of the second air inlet cavity remains consistent with the flow rate when only the second air inlet cavity is ventilated.

[0065] In this embodiment, during the sequential ventilation and synchronous ventilation stages, the air flow rate of the first air inlet chamber remains unchanged, and / or the air flow rate of the second air inlet chamber remains unchanged, thereby avoiding gas fluctuations caused by switching the gas flow back and forth, thereby affecting the uniformity of the deposition layer.

[0066] In some embodiments, the thickness of the passivation film is 4-12 nm. In this embodiment, the thickness of the passivation film is controlled within this range to meet the required thickness and passivation effect, while saving production time and improving production efficiency.

[0067] One or more embodiments of the present application also disclose a method for preparing a photovoltaic cell, referring to Figure 5 Shown, including:

[0068] The initial silicon wafer 10 is subjected to texturing, first boron diffusion, patterning, second boron diffusion, etching, and preparation of a tunnel oxide layer 20 and a polysilicon layer to obtain a target silicon wafer;

[0069] A passivation film 40 is prepared on the front surface of the target silicon wafer using the above-mentioned method for preparing a photovoltaic cell passivation film;

[0070] An anti-reflection film 50 is prepared on the back surface of the target silicon wafer, and front and rear electrodes are prepared on the front and back surfaces of the target silicon wafer to obtain a photovoltaic cell.

[0071] In some embodiments, the preparation of the tunneling oxide layer 20 and the polysilicon layer includes: growing the tunneling oxide layer 20 with a thickness of 1-2 nm on the back side of the etched silicon wafer, and then growing a film layer of doped polysilicon, and after annealing and cleaning to remove the oxide layer and borosilicate glass, obtaining the target silicon wafer.

[0072] Specifically, if Figure 5 As shown in Figure 2, the preparation process of photovoltaic cells is as follows:

[0073] 1. Texturing the N-type silicon wafer to obtain a pyramid structure to increase the utilization rate of incident light;

[0074] 2. Carry out the first boron expansion;

[0075] 3. Use laser for patterning process;

[0076] 4. Perform boron diffusion annealing again;

[0077] 5. After step 4, the silicon wafer is removed from the back side of the BSG (boron silicate glass) using a chain HF laser. The silicon wafer is then placed in a mixture of KOH and additives to remove the back side and edge wraparound.

[0078] 6. Grow a tunnel oxide layer on the back of the silicon wafer after step 5. The tunnel oxide layer has a thickness of 1-2 nm, and then grow a doped polysilicon film layer 30;

[0079] 7. Place the silicon wafer after step 6 in a tube furnace for annealing to allow the doped a-Si film to crystallize into doped poly-Si;

[0080] 8. Post-clean the silicon wafer after step 7 to remove the oxide layer and BSG;

[0081] 9. After step 8, the silicon wafer is subjected to AlO passivation on the front side using a plate-type ALD device to generate a better film structure, thereby obtaining a passivation film 40. The specific operation method is as follows: the silicon wafer is loaded on a carrier plate, and then sequentially enters the feed chamber, the heating chamber, the process chamber, and the discharge chamber. The silicon wafer enters the process chamber in sequence, and the system starts working. In the first step, see Figure 2 : Water vapor is introduced into the gas pipeline at the top with a flow rate of 1700-2700 sccm and a temperature of 210-310°C; the water vapor is adsorbed on the surface of the silicon wafer; the second step is to see Figure 3 : Stop the water vapor, open the TMA pipeline, and introduce TMA at a flow rate of 1700-2700 sccm and a temperature of 210-310°C. TMA reacts with the water vapor adsorbed on the surface of the silicon wafer. The reaction includes two half reactions. For subsequent steps, see Figure 4: Water and TMA gas are ventilated simultaneously, with the gas flow rate remaining the same as before. During the entire process, the motion system drives the carrier to reciprocate, ensuring uniform contact between the silicon wafer and the reaction gas. The exhaust system continuously removes the exhaust gas and maintains a constant reaction pressure. Inert gas is introduced into the isolation gas to prevent mixing of the reaction gases. The above process is repeated to complete the deposition of aluminum oxide, where the aluminum oxide thickness ranges from 4 to 12 nm.

[0082] 10. Use PECVD to form passivation and anti-reflection layers on the front and back of the silicon wafer after step 9;

[0083] 11. After step 10, the silicon wafer is screen-printed with silver-aluminum paste to form contacts on the front side and silver paste to form contacts on the back side, respectively making front and rear electrodes, namely, silver-aluminum electrode 60 and silver electrode 70, to obtain a photovoltaic cell.

[0084] One or more embodiments of the present application further disclose a photovoltaic cell, which is manufactured using the photovoltaic cell manufacturing method described above.

[0085] The photovoltaic cell prepared in this embodiment was tested and compared with the comparative example. The results are shown in Table 1. The difference between the comparative example and this embodiment is that during the ALD deposition of the passivation film, trimethylaluminum and water vapor are introduced simultaneously, i.e. Figure 1 As shown in Table 1, it can be seen that the photovoltaic conversion efficiency and minority carrier lifetime of the cell of this embodiment are higher than those of the comparative example.

[0086] Table 1:

[0087] Film thickness / nm Minority carrier lifetime / μs efficiency / % Comparative Example 8 1340 24.7 This embodiment 6 1739 27.92

[0088] The above describes the basic principles, main features, and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above-described embodiments. The above-described embodiments and the specification merely illustrate the principles of the present application. Various changes and improvements may be made to the present application without departing from the spirit and scope of the present application. These changes and improvements fall within the scope of the present application for which protection is sought. The scope of protection claimed by the present application is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a photovoltaic cell passivation film, characterized in that: Based on a plate-type ALD device, the plate-type ALD device comprises a reaction chamber, a carrier plate (1) is provided in the reaction chamber, the carrier plate (1) is used to place a target silicon wafer (2), and the carrier plate (1) is used to reciprocate in the reaction chamber; The method comprises: when the carrier (1) reaches a designated position in the reaction chamber, alternately introducing water vapor and trimethylaluminum into the reaction chamber, and introducing trimethylaluminum only after the surfaces of all the target silicon wafers (2) on the carrier (1) have adsorbed the water vapor, and introducing water vapor again only after the water vapor adsorbed on all the target silicon wafers (2) on the carrier (1) has reacted with the trimethylaluminum; setting the introduction of the water vapor and the trimethylaluminum once in sequence as one reaction cycle, and after a preset number of reaction cycles have passed, introducing water vapor and trimethylaluminum simultaneously until the reaction is completed, thereby obtaining the target silicon wafer (2) with a passivation film (40) deposited on the surface; After the surfaces of all the target silicon wafers (2) on the carrier (1) have adsorbed the water vapor, the method further includes: obtaining a first cycle number of the carrier (1), rounding up the first cycle number to obtain a first preset cycle number, and when the carrier (1) has run the first preset cycle number, introducing the trimethylaluminum into the reaction chamber; After the water vapor adsorbed on all the target silicon wafers (2) reacts with the trimethylaluminum, the method further includes: obtaining a second cycle number of the carrier (1), rounding up the second cycle number to obtain a second preset cycle number, and when the carrier (1) has run the second preset cycle number, introducing the water vapor into the reaction chamber again.

2. The method for preparing a photovoltaic cell passivation film according to claim 1, wherein The ventilation flow rate of the water vapor is 1700-2700 sccm, and the ventilation temperature is 210-310°C.

3. The method for preparing a photovoltaic cell passivation film according to claim 1, wherein The trimethylaluminum has a ventilation flow rate of 1700-2700 sccm and a ventilation temperature of 210-310°C.

4. The method for preparing a photovoltaic cell passivation film according to claim 1, wherein The preset number is greater than or equal to 1.

5. The method for preparing a photovoltaic cell passivation film according to claim 1, wherein: When the water vapor and the trimethylaluminum are ventilated simultaneously, the ventilation flow rate of the water vapor remains unchanged; when the water vapor and the trimethylaluminum are ventilated simultaneously, the ventilation flow rate of the trimethylaluminum remains unchanged.

6. The method for preparing a photovoltaic cell passivation film according to claim 1, wherein: The thickness of the passivation film is 4-12 nm.

7. A method for preparing a photovoltaic cell, characterized in that: include: The initial silicon wafer (10) is subjected to texturing, first boron diffusion, patterning, second boron diffusion, etching, and preparation of a tunneling oxide layer (20) and a polysilicon layer to obtain a target silicon wafer (2); A passivation film (40) is prepared on the front surface of the target silicon wafer (2) using the method for preparing a photovoltaic cell passivation film according to any one of claims 1 to 6; An anti-reflection film (50) is prepared on the back side of the target silicon wafer (2), and front and rear electrodes are prepared on the front and back sides of the target silicon wafer (2) to obtain a photovoltaic cell.

8. The method for preparing a battery according to claim 7, wherein: The preparation of the tunneling oxide layer (20) and the polysilicon layer comprises: growing the tunneling oxide layer (20) with a thickness of 1-2 nm on the back side of the etched silicon wafer, then growing a film layer of doped polysilicon, and after annealing and cleaning to remove the oxide layer and borosilicate glass, obtaining the target silicon wafer (2).

9. A photovoltaic cell, characterized in that: The photovoltaic cell is prepared by the method for preparing the photovoltaic cell according to claim 7 or 8.

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