Solar cell and method of manufacturing the same

Abstract

The application relates to the field of photoelectric technology, in particular to a solar cell and a preparation method thereof, so as to improve the passivation performance and the ultraviolet-induced decay resistance of the solar cell. The solar cell comprises a substrate, the substrate has a first surface and a second surface oppositely arranged along the thickness direction thereof, the first surface of the substrate is formed with an emitter, and the doping type of the emitter is opposite to the doping type of the substrate; a first passivation layer is arranged on the first surface side of the substrate; the first passivation layer comprises a first aluminum oxide layer; and the H content in the first aluminum oxide layer gradually decreases in the direction gradually away from the substrate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optoelectronics, and in particular to a solar cell and a preparation method thereof. BACKGROUND

[0002] In the field of solar cells, especially in silicon-based solar cells, ultraviolet-induced degradation (UVID) is relatively common. For example, for N-type TOPCon cells, ultraviolet-induced degradation is particularly evident, mainly manifested as a gradual decline in cell performance under ultraviolet irradiation. The main reasons for ultraviolet-induced degradation are: first, in a long-term ultraviolet irradiation environment, the energy of ultraviolet light can cause an increase in lattice defects in crystalline silicon, affecting the transport and collection of carriers, thereby causing a decrease in cell efficiency; second, ultraviolet light can break some chemical bonds in silicon materials, thereby changing their electrical properties.

[0003] In related technologies, an ultraviolet absorption layer or an ultraviolet blocking layer is usually introduced into a solar cell to improve its ability to resist ultraviolet-induced degradation, however, the current ultraviolet absorption layer or ultraviolet blocking layer has limited ability to resist ultraviolet-induced degradation, limiting the improvement of the photoelectric conversion efficiency of the solar cell. SUMMARY

[0004] Therefore, it is necessary to provide a solar cell and a preparation method thereof to improve the passivation performance and the ability to resist ultraviolet-induced degradation of the solar cell.

[0005] In a first aspect, a solar cell is provided, comprising:

[0006] a substrate having a first surface and a second surface oppositely arranged along a thickness direction thereof, the first surface of the substrate forming an emitter, the doping type of the emitter being opposite to the doping type of the substrate;

[0007] a first passivation layer arranged on one side of the first surface of the substrate;

[0008] The first passivation layer comprises: a first aluminum oxide layer; along a direction gradually away from the substrate, the content of H in the first aluminum oxide layer decreases.

[0009] Optionally, along the direction gradually away from the substrate, the content of H in the first aluminum oxide layer decreases from 5×10 21 cm -3 to 4×10 19 cm -3 .

[0010] Optionally, in each region of the first aluminum oxide layer, the difference between the thickness of the maximum thickness position and the minimum thickness position is less than 0.3 nm.

[0011] Optionally, the first aluminum oxide layer has an average thickness of 4-15 nm.

[0012] Optionally, the first passivation layer further comprises a first silicon oxide layer.

[0013] The first silicon oxide layer is disposed on a side of the first aluminum oxide layer close to the substrate.

[0014] Optionally, the solar cell further comprises a second passivation layer disposed on a side of the second surface of the substrate.

[0015] The second passivation layer comprises a second aluminum oxide layer, and the content of H in the second aluminum oxide layer decreases gradually away from the substrate.

[0016] Optionally, the second passivation layer further comprises a second silicon oxide layer, and the second silicon oxide layer is disposed on a side of the second aluminum oxide layer close to the substrate.

[0017] In a second aspect, a method for manufacturing a solar cell is provided, comprising:

[0018] Providing a substrate having a first surface and a second surface oppositely disposed along a thickness direction thereof;

[0019] Forming an emitter on the first surface of the substrate, the emitter having a doping type opposite to that of the substrate;

[0020] Forming a first passivation layer on a side of the first surface of the substrate; the first passivation layer comprises a first aluminum oxide layer, and the content of H in the first aluminum oxide layer decreases gradually away from the substrate.

[0021] Optionally, the content of H in the first aluminum oxide layer decreases from 5×10 21 cm -3 to 4×10 19 cm -3 ; and the forming of the first passivation layer on the side of the first surface of the substrate comprises:

[0022] Introducing water vapor into an ALD cavity at a preset temperature and a preset pressure to perform water pretreatment on the side of the first surface of the substrate;

[0023] Sequentially depositing a hydrogen-containing aluminum oxide film layer and a hydrogen-free aluminum oxide film layer on the side of the first surface of the substrate after the water pretreatment;

[0024] Performing annealing on the hydrogen-containing aluminum oxide film layer and the hydrogen-free aluminum oxide film layer to manufacture the first aluminum oxide layer.

[0025] In some embodiments, water vapor is introduced into the ALD cavity at a preset temperature and a preset pressure to perform water pre-treatment on the first surface side of the substrate, including:

[0026] The water vapor is introduced into the ALD cavity at least 5 times at the preset temperature and the preset pressure, so that the water vapor is adsorbed on the first surface side of the substrate; and after each time of introducing the water vapor, inert gas is used to purge the water vapor that is not adsorbed on the first surface side of the substrate; wherein the flow rate of the water vapor introduced each time is 23 sccm ~ 35 sccm, and the time is 6.5 s ~ 15 s.

[0027] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0028] (1) the preset temperature is 250 °C ~ 300 °C, and the preset pressure is 0.01 mbar ~ 0.03 mbar;

[0029] (2) the annealing temperature is 525 °C ~ 575 °C, and the time is 10 min ~ 30 min.

[0030] In some embodiments, the first surface side of the substrate after water pre-treatment sequentially deposits a hydrogen-containing aluminum oxide film layer and an aluminum oxide film layer without hydrogen, including:

[0031] A first aluminum source is introduced into the ALD cavity, and the first aluminum source reacts with the first surface of the substrate after water pre-treatment to generate a first aluminum oxide film layer;

[0032] A first oxygen source and the first aluminum source are alternately introduced into the ALD cavity, the first oxygen source reacts with the side surface of the jth aluminum oxide film layer away from the substrate to generate an ith oxide film layer, and the first aluminum source reacts with the ith oxide film layer to generate an ith aluminum oxide film layer, thereby preparing the hydrogen-containing aluminum oxide film layer; wherein i is an integer of 2 ~ n, n is an integer greater than or equal to 2, j = i-1, the first oxygen source is a hydrogen-containing oxygen source; and

[0033] A second oxygen source and a second aluminum source are alternately introduced into the ALD cavity, the second oxygen source reacts with the side surface of the hydrogen-containing aluminum oxide layer away from the substrate to generate an oxide first film layer, and the second aluminum source reacts with the oxide first film layer to generate an aluminum oxide first film layer;

[0034] In the kth alternating inputting of the second oxygen source and the second aluminum source, the second oxygen source reacts with the s th aluminum oxide film layer to form the kth oxide film layer, and the second aluminum source reacts with the kth oxide film layer to form the kth aluminum oxide film layer, thereby preparing the hydrogen-free aluminum oxide film layer; wherein k is an integer of 2-m, m is an integer greater than or equal to 2, and s=k-1.

[0035] Optionally, the preparation method satisfies at least one of the following conditions:

[0036] (1) the first oxygen source comprises water vapor; and / or, the second oxygen source comprises ozone;

[0037] (2) the first aluminum source and the second aluminum source are the same or different in kind, and / or the first aluminum source and the second aluminum source are the same or different in flow rate;

[0038] (3) the flow rate of the first aluminum source is 23 sccm-35 sccm, and the time is 6.5 s-15 s; the flow rate of the first oxygen source is 23 sccm-35 sccm, and the time is 6.5 s-15 s;

[0039] (4) the flow rate of the second aluminum source is 23 sccm-35 sccm, and the time is 6.5 s-15 s; the flow rate of the second oxygen source is 23 sccm-35 sccm, and the time is 6.5 s-15 s;

[0040] (5) n is an integer of 12-35;

[0041] (6) m is an integer of 12-35.

[0042] Optionally, the preparation method further comprises:

[0043] Before each time the first oxygen source is input into the ALD cavity, the residual gas source after the previous step of reaction is first purged with an inert gas; and / or,

[0044] Before each time the first aluminum source is input into the ALD cavity, the residual gas source after the previous step of reaction is second purged with an inert gas; and / or,

[0045] Before each time the second oxygen source is input into the ALD cavity, the residual gas source after the previous step of reaction is third purged;

[0046] Before each time the second aluminum source is input into the ALD cavity, the residual gas source after the previous step of reaction is fourth purged.

[0047] Optionally, the first passivation layer further comprises a first silicon oxide layer; before the water pre-treatment of the first surface side of the substrate under a preset temperature and a preset pressure by introducing water vapor into the ALD cavity, the preparation method further comprises:

[0048] forming the first silicon oxide layer on the first surface side of the substrate.

[0049] Optionally, the solar cell further comprises a second passivation layer arranged on the second surface side of the substrate, the second passivation layer comprising: a second aluminum oxide layer; the H content in the second aluminum oxide layer gradually decreases in a direction gradually away from the substrate; the preparation method further comprises:

[0050] forming the second passivation layer on the second surface of the substrate by using the same process as the first passivation layer.

[0051] The solar cell and the preparation method thereof have the following beneficial effects:

[0052] Since the H content in the first aluminum oxide layer gradually decreases in a direction gradually away from the substrate, on the one hand, the H content at the position close to the substrate in the first aluminum oxide layer is relatively high, which facilitates the excess H at the position close to the substrate in the first aluminum oxide layer to enter the substrate to saturate the dangling bonds, thereby improving the passivation effect; on the other hand, the H content at the position away from the substrate in the first aluminum oxide layer is relatively low, which can block the H at the position close to the substrate in the substrate and the first aluminum oxide layer, and the H at the position close to the substrate in the substrate and the first aluminum oxide layer will not be ionized out of the surface of the substrate under the irradiation of ultraviolet light, thereby effectively enhancing the anti-ultraviolet-induced decay capability. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 A cross-sectional structure schematic diagram of a solar cell provided by an embodiment of the present application.

[0054] Reference signs:

[0055] 11, substrate; 12, first passivation layer; 111, emitter; 121, first aluminum oxide layer; 122, first silicon oxide layer; 13, second passivation layer; 131, second aluminum oxide layer; 132, second silicon oxide layer; 14, tunnel oxide layer; 15, doped polysilicon layer; 16, first antireflection layer; 17, second antireflection layer; 18, first electrode; 19, second electrode. DETAILED DESCRIPTION

[0056] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the detailed description of the specific embodiments of the present application is made below in conjunction with the accompanying drawings. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many different ways other than those described herein, and one of ordinary skill in the art can make similar improvements without departing from the spirit of the present application, and therefore the present application is not limited to the specific embodiments disclosed below.

[0057] Unless otherwise required by context, in the description and claims of the application, the term "comprises" is to be construed as an open, inclusive, meaning, i.e. "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "an exemplary embodiment", "exemplary embodiments", or "some examples" are intended to mean that a particular feature, structure, material, or characteristic is included in at least one embodiment or example of the present disclosure. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the particular features, structures, materials, or characteristics described can be included in any suitable way in any one or more embodiments or examples.

[0058] Exemplary embodiments are described herein with reference to cross-sectional and / or plan view illustrations that are schematic illustrations of idealized embodiments. In the drawings, the thickness of layers and regions are exaggerated for clarity. Accordingly, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, the exemplary embodiments should not be construed as limited to the particular shapes of regions as illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etched region illustrated as a rectangle will typically have rounded or curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the exemplary embodiments.

[0059] Herein, "for example", "for instance", "such as", "like", "illustrate" and the like are used for descriptive purposes only and are not intended to be limiting in any way. In the present document, A (such as B) means B is one non-limiting example of A, and A can be understood as not limited to B.

[0060] Herein, "optionally", "optional", "alternatively" means either of the two parallel solutions "have" or "have not", that is, selected from either of the two parallel solutions. If there are multiple "options" in a technical solution, and there is no special description, and there is no contradictory relationship or mutual restriction, each "option" is independent.

[0061] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having" or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the presence of additional elements of the same type in the composition or process.

[0062] As used herein, the terms "first", "second", etc. are used only to describe the purpose of the embodiments, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the technical features indicated.

[0063] It should be noted that when an element is referred to as being "fixed" or "set" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element. The terms "vertical", "horizontal", "upper", "lower", "left", "right", and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0065] In the technical features described in an open manner herein, both the closed technical solution consisting of the listed features and the open technical solution containing the listed features are included.

[0066] In the present text, "at least one" means one or more, such as one, two or more. "Plural" or "several" means at least two, such as two, three or more.

[0067] In the present text, in relation to numerical intervals (i.e. numerical ranges), the distribution of optional values within the numerical interval is considered to be continuous, and includes both numerical end points of the numerical interval (i.e. the minimum and maximum values), and every value between the two numerical end points, unless otherwise specified. When a numerical interval is directed only to integers within the numerical interval, including both end point integers and every integer between the two end points, it is equivalent to listing each integer directly, unless otherwise specified. When multiple numerical ranges are provided to describe a feature or a property, these numerical ranges can be combined. In other words, unless otherwise indicated, numerical ranges disclosed herein are to be understood as including any and all sub-ranges subsumed therein. A "value" in a numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. A "numerical interval" is intended to broadly include percentage intervals, ratio intervals, value intervals of the same type, etc.

[0068] In this context, reference to a percentage concentration, unless otherwise specified, refers to a final concentration. The final concentration refers to the proportion of the added ingredient in the system after the ingredient has been added.

[0069] As used herein, the fill factor (FF) refers to the ratio of the actual maximum obtainable power (Pm or Vmp * Imp) to the theoretical (non-actual obtainable) power (Isc * Voc). Thus, FF can be determined by the following equation:

[0070] FF = (Vmp * Imp) / (Isc * Voc)

[0071] where Imp and Vmp represent the current density and voltage at the maximum power point (Pm), which is obtained by varying the resistance in the circuit until I * V is maximized; and Isc 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 generally have a fill factor of about 60% or more.

[0072] As used herein, the open-circuit voltage (Voc) refers to the potential difference between the anode and cathode of a device under the condition of no connected external load.

[0073] As used herein, the power conversion efficiency (PCE) of a solar cell refers to the percentage of power converted from absorbed light to electrical energy. The power conversion efficiency (PCE) of a solar cell can be calculated by dividing the maximum power point (Pm) by the incident light radiation intensity (E: W / m 2 ) and the surface area (Ac: m 2 ) of the solar cell under standard test conditions (STC). STC generally refers to a spectrum with a temperature of 25°C, a radiation intensity of 1000 W / m 2 , and an air mass of 1.5 (AM1.5).

[0074] In this context, the steps involved in the method flow are not strictly limited in order unless otherwise specified in this context. They can be executed in other orders described. Moreover, any step can include multiple sub-steps or multiple stages, which do not necessarily be executed at the same time, but can be executed at different times, and the execution order is not necessarily sequential, but can be executed alternately or simultaneously with other steps or other steps or part of the sub-steps or stages.

[0075] In the related art, according to different preparation processes, silicon-based solar cells mainly include: PERC (Passivated Emitter and Rear Cell), TOPCon (Tunnel Oxide Passivated Contact solar cell), HJT (Hereto-junction with Intrinsic Thin-layer) and IBC (Interdigitated Back Contact).

[0076] For silicon-based solar cells, the minority carrier lifetime in the silicon wafer is largely affected by the surface state of the silicon wafer, such as the surface dangling bond of the silicon wafer, the defects and lattice distortion left by the slicing process of the silicon wafer, etc., which will all become carrier recombination centers, thereby causing the recombination of carriers on the surface of the silicon-based solar cell.

[0077] In order to improve the conversion efficiency of the cell, whether it is PERC (Passivated Emitter and Rear Cell), TOPCon (Tunnel Oxide Passivated Contact solar cell) or HJT (Hereto-junction with Intrinsic Thin-layer) and IBC (Interdigitated Back Contact) technology, more and more attention is paid to the passivation of the surface of the cell.

[0078] Especially for PERC (Passivated Emitter and Rear Cell), TOPCon (Tunnel Oxide Passivated Contact solar cell) and IBC (Interdigitated Back Contact), in order to improve the photoelectric conversion efficiency of the solar cell, a front passivation layer and a back passivation layer are usually made on the front and back surfaces of the solar cell respectively, however, the current front passivation layer and back passivation layer are both focused on passivating the dangling bond, defects and lattice distortion on the surface of the silicon wafer, etc., reducing the recombination of carriers on the surface of the solar cell.

[0079] In order to improve the ability of the solar cell to resist ultraviolet-induced degradation, an ultraviolet absorption layer or an ultraviolet blocking layer is usually additionally introduced in the solar cell. However, the passivation performance and the ability to resist ultraviolet-induced degradation of the current solar cell cannot be effectively improved. In particular, ultraviolet-induced degradation (UVID) is a high challenge for N-type TOPCon cells which are increasingly produced and applied.

[0080] Based on the above technical problems, the specific embodiments of the present application are described as follows:

[0081] In a first aspect, some embodiments of the present application provide a solar cell, as shown in the accompanying drawings, the solar cell comprises a substrate 11 and a first passivation layer 12; wherein the substrate 11 has a first surface and a second surface oppositely arranged along the thickness direction thereof, the first surface of the substrate 11 is formed with an emitter 111, and the first passivation layer 12 is arranged on the side of the first surface of the substrate 11. Figure 1

[0082] The solar cell can be a PERC (Passivated Emitter and Rear Cell), a TOPCon (Tunnel Oxide Passivated Contact solar cell) or an IBC (Interdigitated Back Contact).

[0083] When the solar cell is a PERC or a TOPCon, the first surface of the substrate 11 can be a light-receiving surface of the solar cell, and the emitter 111 is formed on the light-receiving surface of the solar cell, i.e. the front surface. At this time, the first passivation layer 12 can be arranged on the front surface of the solar cell and cover the first surface of the substrate 11 and the emitter 111; when the solar cell is an IBC, the first surface of the substrate can be a non-light-receiving surface of the solar cell, and the emitter and the back field are both formed on the non-light-receiving surface of the solar cell, i.e. the back surface. At this time, the first passivation layer can be arranged on the back surface of the solar cell and cover the emitter and the back field.

[0084] In the following embodiments, the solar cell will be taken as an N-type TOPCon for illustration, and those skilled in the art can understand that the present application is also applicable to the cases where the solar cell is a PERC and an IBC, which does not affect the protection scope of the present application.

[0085] In some embodiments, the doping type of the emitter 111 and the doping type of the substrate 11 are opposite, so as to form a PN junction of the solar cell.

[0086] ​In some embodiments, the substrate 11 can be an N-type silicon substrate, and the emitter 111 is a P-type emitter; or the substrate 11 can be a P-type silicon substrate, and the emitter 111 is an N-type emitter.

[0087] In some embodiments, the first passivation layer 12 comprises a first aluminum oxide layer 121. The H content in the first aluminum oxide layer 121 decreases gradually away from the substrate 11.

[0088] It should be noted that the first aluminum oxide layer 121 in the first passivation layer 12 contains hydrogen, which can passivate the silicon dangling bonds on the surface of the substrate 11 and the emitter 111, thereby playing a chemical passivation role to improve the photoelectric conversion efficiency of the solar cell. In addition, the fixed charge density of the first aluminum oxide layer 121 can reach 10 12 cm -3 Therefore, the first aluminum oxide layer 121 can also play a field passivation role, thereby further improving the photoelectric conversion efficiency of the solar cell.

[0089] However, under long-term ultraviolet light, the ultraviolet light can destroy the Si-H bonds on the surface of the substrate 11 and the emitter 111, thereby changing the distribution of hydrogen on the interface between the substrate 11 and the emitter 111 and the first passivation layer 12, affecting the passivation performance, and thus reducing the photoelectric conversion efficiency of the solar cell.

[0090] In the solar cell provided in the embodiments of the present application, the H content in the first aluminum oxide layer 121 decreases gradually away from the substrate 11. On the one hand, the H content near the substrate 11 in the first aluminum oxide layer 121 is relatively high, which facilitates the excess H near the substrate 11 in the first aluminum oxide layer 121 to enter the substrate 11 to saturate the dangling bonds, thereby improving the passivation effect; on the other hand, the H content away from the substrate 11 in the first aluminum oxide layer 121 is relatively low, which can block the H near the substrate 11 in the first aluminum oxide layer 121. Under the irradiation of ultraviolet light, the H near the substrate 11 in the first aluminum oxide layer 121 will not escape from the surface of the substrate 11, thereby effectively enhancing the anti-ultraviolet-induced degradation capability.

[0091] In some embodiments, the H content in the first aluminum oxide layer decreases from 5×10 21 cm -3 to 4×10 19 cm -3 .

[0092] In these embodiments, the surface of the first alumina layer 121 near the substrate 11 has more H to passivate the silicon dangling bonds in the substrate 11. As the H content in the first alumina layer 121 gradually decreases, the H in the first alumina layer 121 near the substrate 11 can be effectively suppressed from leaving the surface of the substrate 11, thereby effectively enhancing the resistance of the first passivation layer 12 to UV-induced degradation.

[0093] In some embodiments, the thickness difference between the maximum thickness location and the minimum thickness location in each region of the first alumina layer 121 is less than 0.3 nm.

[0094] In these embodiments, the first alumina layer 121 has better thickness uniformity and density, thereby further improving the resistance of the first passivation layer 12 to UV-induced degradation.

[0095] In some embodiments, the average thickness of the first alumina layer 121 is 4 nm to 15 nm. Here, the average thickness refers to the fact that the thickness of the first alumina layer 121 varies at different locations, and is obtained by measuring the thickness at multiple different locations and then averaging the thicknesses of these multiple different locations.

[0096] In some embodiments, the first passivation layer 12 further includes a first silicon oxide layer 122; the first silicon oxide layer 122 is disposed on the side of the first aluminum oxide layer 121 near the substrate 11.

[0097] In these embodiments, the oxygen in the first silicon oxide layer 122 can bond with the silicon on the first surface of the substrate 11, thereby forming Si-O bonds at the interface between the first passivation layer 12 and the substrate 11 and the emitter 111. This effectively passivates the dangling bonds on the surfaces of the substrate 11 and the emitter 111, further reducing carrier recombination, lowering the interface defect density on the surfaces of the substrate 11 and the emitter 111, further improving the passivation effect, and enhancing the resistance to UV-induced degradation.

[0098] In some embodiments, such as Figure 1 As shown, the solar cell further includes a second passivation layer 13 disposed on one side of the second surface of the substrate 11; the second passivation layer 13 includes a second aluminum oxide layer 131, and the H content in the second aluminum oxide layer 131 decreases along the direction gradually away from the substrate 11.

[0099] In these embodiments, the second passivation layer 13 can be a back passivation layer. Similar to the first passivation layer 12, firstly, the H content in the second alumina layer 131 included in the second passivation layer 13 near the substrate 11 is relatively high, which facilitates the entry of excess H in the second alumina layer 131 near the substrate 11 into the saturated dangling bonds in the substrate 11, thereby improving the passivation effect; secondly, the H content in the second alumina layer 131 far from the substrate 11 is relatively low, which can block the H in the substrate 11 and the second alumina layer 131 near the substrate 11. Under ultraviolet light irradiation, the H in the substrate 11 and the second alumina layer 131 near the substrate 11 will not be released from the surface of the substrate 11, thereby effectively enhancing the resistance to ultraviolet-induced degradation.

[0100] In some embodiments, the second passivation layer 13 further includes a second silicon oxide layer 132, which is disposed on the side of the second aluminum oxide layer 131 near the substrate 11.

[0101] In these embodiments, the second silicon oxide layer 132 can also passivate the dangling bonds on one side of the second surface of the substrate 11, thereby further improving the passivation effect and enhancing the resistance to UV-induced degradation.

[0102] It should be noted that, taking the N-type TOPCon solar cell as an example, as follows... Figure 1 As shown, the solar cell further includes a tunneling oxide layer 14 and a doped polycrystalline silicon layer 15 sequentially disposed on the second surface of the substrate 11, and a second passivation layer 13 disposed on the side of the doped polycrystalline silicon layer 15 facing away from the substrate 11. The tunneling oxide layer 14 and the doped polycrystalline silicon layer 15 together constitute a passivation contact structure, which allows majority carriers to tunnel into the doped polycrystalline silicon layer 15 while blocking minority carrier recombination, thereby improving the open-circuit voltage and short-circuit current of the solar cell.

[0103] The second silicon oxide layer 132 can passivate the surface dangling bonds of the doped polycrystalline silicon layer 15 on the side away from the substrate, thereby improving its passivation performance and resistance to UV-induced degradation.

[0104] In some embodiments, such as Figure 1 As shown, the solar cell further includes: a first antireflection layer 16 disposed on the side of the first passivation layer 12 away from the substrate 11, and / or a second antireflection layer 17 disposed on the side of the second passivation layer 13 away from the substrate 11.

[0105] In some embodiments, such as Figure 1 As shown, the solar cell further includes: a first electrode 18 disposed on the side of the first antireflection layer 16 away from the substrate 11, and / or a second electrode 19 disposed on the side of the second antireflection layer 17 away from the substrate 11.

[0106] In a second aspect, some embodiments of the present application provide a method for manufacturing a solar cell, the method comprising:

[0107] S21), providing a substrate having a first surface and a second surface oppositely arranged along a thickness direction of the substrate;

[0108] In some embodiments, the substrate is an N-type silicon substrate, and the first surface is a light-receiving surface of the substrate, and the second surface is a non-light-receiving surface of the substrate.

[0109] S22), forming an emitter on the first surface of the substrate, the emitter having a doping type opposite to a doping type of the substrate;

[0110] In some embodiments, the emitter is a P-type emitter.

[0111] S23), forming a first passivation layer on a side of the first surface of the substrate; the first passivation layer comprises a first aluminum oxide layer; and a content of H in the first aluminum oxide layer decreases gradually away from the substrate.

[0112] In some embodiments, the content of H in the first aluminum oxide layer decreases from 5x10 21 cm -3 to 4x10 19 cm -3 In some embodiments, forming the first passivation layer on the side of the first surface of the substrate comprises:

[0113] introducing water vapor into the ALD cavity at a preset temperature and a preset pressure to perform water pretreatment on the side of the first surface of the substrate;

[0114] sequentially depositing a hydrogen-containing aluminum oxide film layer and a hydrogen-free aluminum oxide film layer on the side of the first surface of the substrate after the water pretreatment;

[0115] performing annealing on the hydrogen-containing aluminum oxide film layer and the hydrogen-free aluminum oxide film layer to prepare the first aluminum oxide layer.

[0116] The ALD method is a technique for depositing thin films on the surface of a substrate through layer-by-layer atomic reactions. Specifically, taking the deposition of a hydrogen-containing aluminum oxide film layer and a non-hydrogen-containing aluminum oxide film layer on the first surface side of the substrate as an example, when the first oxygen source and the first aluminum source are alternately introduced into the ALD cavity and the first oxygen source and the first aluminum source are used as the reaction precursors of the hydrogen-containing aluminum oxide film layer, the first oxygen source undergoes chemical adsorption (such as hydroxyl reaction adsorption) on the first surface side of the substrate to form a first oxide film layer (which can be regarded as a first oxygen source adsorption layer), and then the first aluminum source reacts with the first oxygen source that has been adsorbed on the first surface side of the substrate, thereby generating the hydrogen-containing aluminum oxide film layer.

[0117] In these embodiments, by introducing water vapor into the ALD cavity at a preset temperature and a preset pressure to perform water pretreatment on the first surface side of the substrate, the reactivity and the uniformity of hydroxyl adsorption on the first surface side of the substrate can be improved, thereby improving the hydrogen-containing aluminum oxide film layer. Through annealing, the hydrogen in the hydrogen-containing aluminum oxide film layer diffuses into the non-hydrogen-containing aluminum oxide film layer, thereby obtaining a first aluminum oxide layer with a gradually decreasing hydrogen content in the direction gradually away from the substrate.

[0118] In some embodiments, the water pretreatment on the first surface side of the substrate by introducing water vapor into the ALD cavity at a preset temperature and a preset pressure includes:

[0119] In some embodiments, the water pretreatment on the first surface side of the substrate by introducing water vapor into the ALD cavity at a preset temperature and a preset pressure includes:

[0120] In these embodiments, by introducing water vapor into the ALD cavity at least 5 times to make the water vapor adsorb on the first surface side of the substrate, and using an inert gas to purge the water vapor that does not adsorb on the first surface side of the substrate after each time the water vapor is introduced, wherein the flow rate of the water vapor introduced each time is 23sccm ~ 35sccm and the time is 6.5 s ~ 15s, it can be ensured that the water vapor reaches the adsorption saturation degree on the first surface side of the substrate, thereby facilitating the activation of the first surface of the substrate and improving the uniformity of hydroxyl adsorption, and further facilitating the deposition of a more dense and uniform hydrogen-containing aluminum oxide film layer on the first surface side of the substrate, thereby a more dense and uniform first aluminum oxide layer can be prepared.

[0121] In some embodiments, the preset temperature is 250-300 DEG C, and the preset pressure is 0.01-0.03 mbar. The preset temperature is the deposition temperature, and the preset pressure is the bottom pressure, i.e., the ALD cavity is first vacuumed to the bottom pressure and preheated to the deposition temperature before water vapor is introduced into the ALD cavity, so as to facilitate the deposition of the first aluminum oxide layer.

[0122] In some embodiments, the annealing temperature is 525-575 DEG C, and the annealing time is 10-30 min.

[0123] In some embodiments, the hydrogen-containing aluminum oxide film layer and the hydrogen-free aluminum oxide film layer are sequentially deposited on the first surface side of the substrate after water pretreatment, including:

[0124] The first aluminum source is introduced into the ALD cavity, and the first aluminum source reacts with the first surface of the substrate after water pretreatment to form the first aluminum oxide film layer; and

[0125] The first oxygen source and the first aluminum source are alternately introduced into the ALD cavity, the first oxygen source reacts with the side surface of the jth aluminum oxide film layer away from the substrate to form the ith oxide film layer, the first aluminum source reacts with the ith oxide film layer to form the ith aluminum oxide film layer, thereby preparing the hydrogen-containing aluminum oxide film layer; wherein i is an integer of 2-n, n is an integer greater than or equal to 2, j=i-1, and the first oxygen source is a hydrogen-containing oxygen source; and

[0126] The second oxygen source and the second aluminum source are alternately introduced into the ALD cavity, the second oxygen source reacts with the side surface of the hydrogen-containing aluminum oxide layer away from the substrate to form the first oxide film layer, and the second aluminum source reacts with the first oxide film layer to form the first aluminum oxide film layer.

[0127] In the case of the kth alternately introducing the second oxygen source and the second aluminum source, the second oxygen source reacts with the side surface of the kth aluminum oxide film layer away from the substrate to form the kth oxide film layer, and the second aluminum source reacts with the kth oxide film layer to form the kth aluminum oxide film layer, thereby preparing the hydrogen-free aluminum oxide film layer; wherein k is an integer of 2-m, m is an integer greater than or equal to 2, and s=k-1.

[0128] In the embodiments, the first aluminum source is introduced into the ALD cavity to react with the water vapor adsorbed on the first surface side of the substrate to form a first aluminum oxide film layer. Since the water vapor adsorbed on the first surface side of the substrate has good uniformity, the first surface of the substrate can be uniformly activated, and thus the first aluminum oxide film layer is more dense and uniform. On the basis of the first aluminum oxide film layer, the first oxygen source and the first aluminum source are introduced into the ALD cavity for multiple cycles to form an aluminum oxide film layer containing hydrogen with a certain thickness, and surface conformality is achieved to improve the density and uniformity of the aluminum oxide film layer containing hydrogen. Then, the second oxygen source and the second aluminum source are alternately introduced into the ALD cavity. The second oxygen source is adsorbed on the surface of the aluminum oxide film layer containing hydrogen away from the substrate to form an oxide first film layer, and the second aluminum source reacts with the oxide first film layer to form an aluminum oxide first film layer. The second oxygen source and the second aluminum source are introduced into the ALD cavity for multiple cycles to form an aluminum oxide film layer not containing hydrogen with a certain thickness, and surface conformality is achieved to improve the density and uniformity of the aluminum oxide film layer not containing hydrogen.

[0129] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0130] (1) The first oxygen source comprises water vapor, and / or the second oxygen source comprises ozone;

[0131] (2) The first aluminum source and the second aluminum source are the same or different in type, and / or the first aluminum source and the second aluminum source are the same or different in flow rate;

[0132] (3) In the process of depositing the aluminum oxide film layer containing hydrogen, the flow rate of the first aluminum source introduced is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s; the flow rate of the first oxygen source introduced is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s;

[0133] (4) In the process of depositing the aluminum oxide film layer not containing hydrogen, the flow rate of the second aluminum source introduced is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s; the flow rate of the second oxygen source introduced is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s;

[0134] (5) n is an integer of 12 to 35;

[0135] (6) m is an integer of 12 to 35.

[0136] In the embodiments, by controlling the values of n and m, the thicknesses of the aluminum oxide film layer containing hydrogen and the aluminum oxide film layer not containing hydrogen can be accurately controlled.

[0137] In some embodiments, the first aluminum source and the second aluminum source each independently comprises TMA.

[0138] In the case of depositing the hydrogen-containing aluminum oxide film layer, not all of the first oxygen source can react in the case that the first oxygen source reacts with the first surface of the substrate or the first surface of the jth aluminum oxide film layer away from the silicon substrate, which is related to the adsorption saturation degree. Therefore, in the case of excess first oxygen source, the first oxygen source is often left over. Similarly, in the case that the first aluminum source reacts with the first surface of the substrate or the first surface of the ith oxide film layer after water pretreatment, the first aluminum source is also left over, and by-products are generated.

[0139] Based on this, in some embodiments, the preparation method further comprises:

[0140] Before each time the first oxygen source is introduced into the ALD cavity, the gas source left over after the previous reaction is first purged with an inert gas; and / or,

[0141] Before each time the first aluminum source is introduced into the ALD cavity, the gas source left over after the previous reaction is second purged with an inert gas.

[0142] In these embodiments, the excess gas source can be removed in time, thereby reducing the generation of by-products and improving the uniformity and density of the hydrogen-containing aluminum oxide film layer.

[0143] In some embodiments, the first purging time is 11 s ~ 23 s, and / or the second purging time is 11 s ~ 23 s.

[0144] Similarly to the deposition of the hydrogen-containing aluminum oxide film layer, not all of the second oxygen source can react in the case that the second oxygen source reacts with the first surface of the hydrogen-containing aluminum oxide film layer away from the substrate or the first surface of the sth aluminum oxide film layer away from the substrate, which is related to the adsorption saturation degree. Therefore, in the case of excess second oxygen source, the second oxygen source is often left over. Similarly, in the case that the second aluminum source reacts with the first oxide film layer or the kth oxide film layer, the second aluminum source is also left over, and by-products are generated.

[0145] Based on this, in some embodiments, the preparation method further comprises:

[0146] Before each time the second oxygen source is introduced into the ALD cavity, the gas source left over after the previous reaction is third purged with an inert gas; and / or,

[0147] Before each time the second aluminum source is introduced into the ALD cavity, the gas source left over after the previous reaction is fourth purged with an inert gas.

[0148] In these embodiments, the excess gas source can be removed in time, thereby reducing the generation of by-products and improving the uniformity and density of the hydrogen-containing aluminum oxide film layer.

[0149] In some embodiments, the third purging time is 11s~23s, and / or the fourth purging time is 11s~23s.

[0150] In some embodiments, the first passivation layer further comprises a first silicon oxide layer; in the same ALD cavity, the first oxygen source and the second oxygen source are sequentially opened, and before the at least one first sub-layer and the at least one second sub-layer are sequentially formed on the first surface side of the base with the emitter by the ALD method, the preparation method further comprises:

[0151] The first silicon oxide layer is formed on the first surface side of the base with the emitter.

[0152] In these embodiments, the first silicon oxide layer can passivate the first surface of the base, thereby further improving the passivation performance and the anti-ultraviolet-induced decay ability.

[0153] In some embodiments, the first silicon oxide layer can be formed on the first surface side of the base with the emitter by PECVD.

[0154] In some embodiments, the solar cell further comprises a second passivation layer arranged on the second surface side of the base, the second passivation layer comprising: a second aluminum oxide layer; the H content in the second aluminum oxide layer gradually decreases in the direction gradually away from the base; and the preparation method further comprises:

[0155] The second passivation layer is formed on the second surface of the base by the same process as the first passivation layer.

[0156] In these embodiments, the second passivation layer can be a back passivation layer, and at this time, the second passivation layer is formed on the second surface of the base by the same process as the first passivation layer, so that the front passivation layer and the back passivation layer can be formed synchronously.

[0157] The first aluminum oxide layer included in the first passivation layer and the second aluminum oxide layer included in the second passivation layer can be deposited in the same tubular ALD cavity.

[0158] In some embodiments, the second passivation layer further comprises a second silicon oxide layer arranged on the side of the second aluminum oxide layer close to the base; and the second silicon oxide layer and the first silicon oxide layer can be prepared by the same process.

[0159] In some embodiments, taking a TOPCon cell as an example, after the doped amorphous silicon layer on the back surface is prepared, when the doped amorphous silicon layer is converted into a doped polycrystalline silicon layer by annealing, a first silicon oxide layer can be formed on the first surface of the substrate having an emitter, and a second silicon oxide layer can be formed on the surface of the doped polycrystalline silicon layer by introducing an oxygen source into the reaction cavity.

[0160] The annealing temperature can be 900-1100°C, and the annealing time can be 35-65 min. At the annealing temperature and time, a dense first silicon oxide layer and a second silicon oxide layer can be formed on the first surface of the substrate and the surface of the doped polycrystalline silicon layer. In particular, when the H concentration is low, the bonding affinity between oxygen and silicon is strong, the Si-O bond formed at the interface can effectively passivate dangling bonds, maximize carrier recombination, reduce interface defect density, and the passivation effect of the Si-O bond is good and not easily affected by UV.

[0161] Here, the first silicon oxide layer can be formed at the interface between the first aluminum oxide layer and the substrate, and the second silicon oxide layer can be formed at the interface between the doped polycrystalline silicon layer and the second aluminum oxide layer on the back surface. The Si-O bond at the interface can effectively passivate dangling bonds, thereby further improving the ability to resist UV-induced decay.

[0162] In order to objectively evaluate the technical effects of the embodiments of the present application, the present application will be described in detail by the following examples and comparative examples.

[0163] In the following examples and comparative examples, all raw materials can be purchased in commercial form, and in order to maintain the reliability of the experiment, the raw materials used in the following examples and comparative examples all have the same physical and chemical parameters or are prepared by the same treatment method.

[0164] Example 1

[0165] The preparation method of the solar cell in Example 1 is as follows:

[0166] Step 1), select a 130 mm thick n-type single crystal silicon wafer, and form a reverse pyramid structure by texturing;

[0167] Step 2), form a P emitter by boron diffusion on the textured surface; + An emitter; the back surface is deposited with a 1.5 nm thick tunneling oxide layer (gas source: laughing gas), and a 90 nm thick doped amorphous silicon layer (gas source: silane and phosphine), and the amorphous silicon is converted into polycrystalline silicon by annealing at 900°C for 45 min, and oxygen is introduced into the reaction cavity during the annealing process, and a 2 nm thick silicon oxide layer is deposited on both surfaces;

[0168] Step 3), 10 nm thick aluminum oxide is deposited on both sides of the silicon wafer obtained in Step 2) by the following method: the ALD chamber is vacuumed to a vacuum degree of 0.01 mbar in the ALD chamber, and the preheating time is 700 s to make the temperature in the ALD chamber reach 280°C; water vapor is introduced into the ALD chamber for 5 times, and nitrogen is used to purge the unabsorbed water vapor after each time of water vapor introduction, the flow rate of water vapor is 30 sccm, the time is 10 s, TMA is introduced into the ALD chamber, the flow rate of TMA is 30 sccm, the time is 10 s; then water vapor and TMA are alternately introduced into the ALD chamber, the flow rate of water vapor is 30 sccm, the flow rate of TMA is 30 sccm, the time of water vapor and TMA introduction is 10 s respectively, the circulation is 24 times, and nitrogen is used to purge the excess water vapor for 20 s when the water vapor is saturated after being absorbed on both sides of the silicon wafer, and nitrogen is used to purge the excess TMA and waste gas for 15 s after the TMA reacts with the water vapor absorbed on the surface of the silicon wafer; then, ozone and TMA are alternately introduced into the ALD chamber, the flow rate of ozone is 30 sccm, the flow rate of TMA is 30 sccm, the time of ozone and TMA introduction is 10 s respectively, the circulation is 20 times, and nitrogen is used to purge the excess ozone for 15 s when the ozone is saturated after being absorbed on both sides of the silicon wafer, and nitrogen is used to purge the excess TMA and waste gas for 15 s after the TMA reacts with the ozone absorbed on the surface of the silicon wafer, and the gas leakage rate is <0.02 mbar / min during the process;

[0169] Step 4), after the deposition is completed, annealing is performed at 525°C for 20 min;

[0170] Step 5), about 70 nm of silicon nitride is deposited on both sides by PECVD (the gas sources are selected to be silane and ammonia); finally, the double-sided grid lines are printed to make a solar cell.

[0171] Example 2

[0172] The preparation method of the solar cell in Example 2 is basically the same as that in Example 1, and the only difference is that:

[0173] In Step 2), the thickness of the tunneling oxide layer formed on the back surface is 2.5 nm, and the thickness of the doped amorphous silicon layer is 120 nm, the doped amorphous silicon layer is converted into a doped polysilicon layer by annealing at 1100°C for 35 min, and oxygen is introduced into the reaction chamber during the annealing process, and a 20 nm thick silicon oxide layer is deposited on both sides;

[0174] In step 3), 15 nm thick aluminum oxide layer is deposited on both sides of the silicon wafer obtained in step 2), specifically, the tube ALD cavity is vacuumed, and nitrogen is introduced into the ALD cavity until the vacuum degree in the ALD cavity is 0.03 mbar, the preheating time is 700 s, and the temperature in the ALD cavity is 250°C; water vapor is introduced into the ALD cavity for 6 times, and nitrogen is used to purge the water vapor that does not adsorb after each time of water vapor introduction, the flow rate of water vapor introduced into the ALD cavity is 23 sccm, and the time is 6.5 s; then TMA is introduced into the ALD cavity, the flow rate of TMA is 23 sccm, and the time is 6.5 s; then water vapor and TMA are alternately introduced into the ALD cavity, the flow rate of water vapor is 23 sccm, the flow rate of TMA is 23 sccm, the introduction time of water vapor and TMA is 6.5 s respectively, and the circulation introduction is performed for 34 times, and nitrogen is used to purge the excess water vapor for 11 s when the water vapor is introduced so that the water vapor is saturatedly adsorbed on both sides of the silicon wafer, and nitrogen is used to purge the excess TMA and waste gas for 11 s after the TMA is introduced so that the TMA reacts with the water vapor adsorbed on the surface of the silicon wafer; then, ozone and TMA are alternately introduced into the ALD cavity, the flow rate of ozone is 23 sccm, the flow rate of TMA is 23 sccm, the introduction time of ozone and TMA is 6.5 s respectively, and the circulation introduction is performed for 35 times, and nitrogen is used to purge the excess ozone for 11 s when the ozone is introduced so that the ozone is saturatedly adsorbed on both sides of the silicon wafer, and nitrogen is used to purge the excess TMA and waste gas for 11 s after the TMA is introduced so that the TMA reacts with the ozone adsorbed on the surface of the silicon wafer, and the gas leakage rate is <0.02 mbar / min during the process;

[0175] In step 4), the annealing temperature is 575°C, and the annealing time is 30 min;

[0176] In step 5), 60 nm thick silicon nitride layer is deposited.

[0177] Example 3

[0178] In example 3, the preparation method of the solar cell is basically the same as that in example 1, and the difference is only that:

[0179] In step 2), the thickness of the tunneling oxide layer formed on the back surface is 2 nm, and the thickness of the doped amorphous silicon layer is 100 nm, the doped amorphous silicon layer is converted into a doped polysilicon layer by annealing at 1000°C for 65 min, and oxygen is introduced into the reaction cavity during the annealing process, and 10 nm thick silicon oxide layer is deposited on both sides;

[0180] In step 3), 4nm-thick aluminum oxide layers are deposited on both sides of the silicon wafer obtained in step 2) as follows: the ALD chamber is evacuated and nitrogen is introduced into the ALD chamber to a vacuum degree of 0.02mbar; the preheating time is 700s and the temperature in the ALD chamber is 300℃; water vapor is introduced into the ALD chamber for 7 times, and nitrogen is used to purge the water vapor that does not adsorb after each time of water vapor introduction; the flow rate of the water vapor introduced into the ALD chamber is 35sccm and the time is 15s; TMA is introduced into the ALD chamber, and the flow rate of the TMA is 35sccm and the time is 15s; then water vapor and TMA are alternately introduced into the ALD chamber, the flow rate of the water vapor is 35sccm, the flow rate of the TMA is 35sccm, the time of the water vapor introduction is 15s, and the time of the TMA introduction is 15s; the cycle of the water vapor and TMA introduction is 11 times, and nitrogen is used to purge the excess water vapor for 23s when the water vapor is saturated on both sides of the silicon wafer, and nitrogen is used to purge the excess TMA and waste gas for 23s after the TMA reacts with the water vapor adsorbed on the surface of the silicon wafer; then, ozone and TMA are alternately introduced into the ALD chamber, the flow rate of the ozone is 35sccm, the flow rate of the TMA is 35sccm, the time of the ozone introduction is 15s, and the time of the TMA introduction is 15s; the cycle of the ozone and TMA introduction is 12 times, and nitrogen is used to purge the excess ozone for 23s when the ozone is saturated on both sides of the silicon wafer, and nitrogen is used to purge the excess TMA and waste gas for 23s after the TMA reacts with the ozone adsorbed on the surface of the silicon wafer; in this process, the gas leakage rate is <0.02mbar / min.

[0181] In step 4), the annealing temperature is 550℃, and the annealing time is 10min.

[0182] In step 5), a 90nm-thick silicon nitride layer is deposited.

[0183] Comparative Example 1

[0184] The preparation method of the solar cell in Comparative Example 1 is basically the same as that in Example 1, and the only difference is that:

[0185] In step 3), water vapor is directly used as the oxygen source to prepare the aluminum oxide layer during the deposition of the aluminum oxide layer, and the substrate is not pre-treated with water, that is, the water vapor and TMA are alternately introduced into the ALD chamber for 45 times when the vacuum degree in the ALD chamber reaches 0.01mbar and the temperature reaches 280℃, and the other conditions are the same as those in Example 1.

[0186] Comparative Example 2

[0187] The preparation method of the solar cell in Comparative Example 2 is basically the same as that in Example 1, and the only difference is that:

[0188] In the process of depositing the aluminum oxide layer in step 3), ozone is used as the oxygen source to prepare the aluminum oxide layer, and the substrate is not subjected to water pretreatment, i.e., the ALD cavity is alternately filled with ozone and TMA for 45 times when the vacuum degree reaches 0.01 mbar and the temperature reaches 280°C, and the remaining conditions are the same as those in Example 1.

[0189] Test Example

[0190] The step 3) of Examples 1-3 and Comparative Examples 1-2 was simulated by uniformly inserting the alkali-etched pieces (silicon pieces subjected to alkali etching) into the grooves of the aluminum boat, and the thickness uniformity of the aluminum oxide layer after depositing the aluminum oxide layer was measured.

[0191] The specific test method is as follows: the five-point test method is selected, the center point and the four corner points (the four points on the corners are 20 mm away from the edge) of the silicon piece are selected, the thickness of the aluminum oxide layer corresponding to each point is measured, and the within-wafer uniformity is calculated, the calculation formula is: the difference between the maximum thickness and the minimum thickness of the same aluminum oxide layer; at the same time, the maximum thickness and the minimum thickness of the same batch of aluminum oxide layers prepared under the same conditions are measured, and the inter-wafer uniformity is calculated according to the formula (max-min) / (2*mean), wherein max represents the maximum thickness of the same batch of aluminum oxide layers, min represents the minimum thickness of the same batch of aluminum oxide layers, and mean represents the average thickness of the same batch of aluminum oxide layers, and the test results are shown in Table 1.

[0192] Table 1

[0193]

[0194] As shown in Table 1, compared with Comparative Examples 1-2, the within-wafer uniformity and the inter-wafer uniformity of Examples 1-3 are greatly improved, and the within-wafer uniformity and the inter-wafer uniformity of Comparative Example 1 and Comparative Example 2 are poor.

[0195] 2. The solar cell modules prepared by the solar cells provided in Examples 1-3 and Comparative Examples 1-2 were subjected to UV60 ultraviolet attenuation test, and the test results are shown in Table 2.

[0196] Table 2

[0197]

[0198] The test method of the UV60 ultraviolet attenuation test is: test the Voc, Isc, Vmp, Imp, Pmax and FF of the battery assembly before and after ultraviolet light irradiation respectively, and calculate the attenuation rate of each by using (the value after ultraviolet light irradiation-the value before ultraviolet light irradiation) / the value before ultraviolet light irradiation; wherein Vmp represents the voltage generated by the battery assembly at the maximum power point, Imp represents the current generated by the battery assembly at the maximum power point, and Pm represents the maximum power point.

[0199] The ultraviolet light irradiation condition of the UV60 ultraviolet attenuation test is: the front and back of the assembly are respectively exposed to a total UV irradiance of 60 kWh / m2 in the wavelength range of 280 nm to 400 nm, and the temperature of the assembly is maintained at 60±5℃ during the ultraviolet light irradiation. 2

[0200] As can be seen from Table 2, the power attenuation rate of the assemblies of Examples 1-3 is not more than 1%, while the power of the assemblies of Comparative Examples 1 and 2 has a large degree of attenuation.

[0201] The technical features of the above-described embodiments can be combined arbitrarily, and in order to make the description simple, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present disclosure.

[0202] The above-described embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent protection of the present application should be subject to the appended claims.​

Claims

1. A method for producing a solar cell, characterized by, The application relates to a preparation method of an aluminum oxide film layer. The application provides a substrate having a first surface and a second surface arranged oppositely along the thickness direction of the substrate; An emitter is formed on the first surface of the substrate, and the doping type of the emitter is opposite to the doping type of the substrate; Water vapor is introduced into an ALD cavity at a preset temperature and a preset pressure to perform water pretreatment on one side of the first surface of the substrate; A first aluminum source is introduced into the ALD cavity, the first aluminum source reacts with the first surface of the substrate after the water pretreatment to generate a first aluminum oxide film layer; A first oxygen source and the first aluminum source are alternately introduced into the ALD cavity, the first oxygen source reacts with the side surface of the jth aluminum oxide film layer away from the substrate to generate an ith oxide film layer, the first aluminum source reacts with the ith oxide film layer to generate an ith aluminum oxide film layer, and a hydrogen-containing aluminum oxide film layer is prepared; wherein i is an integer between 2 and n, n is an integer greater than or equal to 2, j = i-1, and the first oxygen source is a hydrogen-containing oxygen source; and A second oxygen source and a second aluminum source are alternately introduced into the ALD cavity, the second oxygen source reacts with the side surface of the hydrogen-containing aluminum oxide layer away from the substrate to generate an oxide first film layer, and the second aluminum source reacts with the oxide first film layer to generate an aluminum oxide first film layer; In the case that the second oxygen source and the second aluminum source are alternately introduced into the ALD cavity for the kth time, the second oxygen source reacts with the side surface of an aluminum oxide s-th film layer away from the substrate to generate an oxide k-th film layer, and the second aluminum source reacts with the oxide k-th film layer to generate an aluminum oxide k-th film layer, so as to prepare an aluminum oxide film layer without hydrogen; wherein k is an integer between 2 and m, m is an integer greater than or equal to 2, and s = k-1. The hydrogen-containing alumina film layer and the hydrogen-free alumina film layer are annealed to form a first passivation layer on the first surface side of the substrate; the first passivation layer comprises: a first alumina layer; the H content in the first alumina layer gradually decreases in a direction gradually away from the substrate, and the H content in the first alumina layer decreases from 5*10 21 cm -3 to 4*10 19 cm -3 .

2. The method of producing a solar cell according to claim 1, wherein Water vapor is introduced into the ALD cavity at a preset temperature and a preset pressure to perform water pretreatment on one side of the first surface of the substrate, including: The water vapor is introduced into the ALD cavity for at least 5 times at the preset temperature and the preset pressure, so that the water vapor is adsorbed on one side of the first surface of the substrate; and after each time of introducing the water vapor, inert gas is used to purge the water vapor which is not adsorbed on one side of the first surface of the substrate; wherein the flow rate of the water vapor is 23 sccm-35 sccm, and the time is 6.5 s-15 s.

3. The method of claim 1, wherein the method further comprises: The preparation method satisfies at least one of the following conditions: (1) the preset temperature is 250 DEG C-300 DEG C, and the preset pressure is 0.01 mbar-0.03 mbar; (2) the temperature of the annealing is 525 DEG C-575 DEG C, and the time is 10 min-30 min.

4. The method of producing a solar cell according to claim 1, wherein The preparation method satisfies at least one of the following conditions: (1) the first oxygen source comprises water vapor, and / or the second oxygen source comprises ozone; (2) the first aluminum source and the second aluminum source are the same or different in kind, and / or the first aluminum source and the second aluminum source are the same or different in flow rate; (3) the first aluminum source is introduced at a flow rate of 23-35 sccm for 6.5-15 s, and the first oxygen source is introduced at a flow rate of 23-35 sccm for 6.5-15 s; (4) the second aluminum source is introduced at a flow rate of 23-35 sccm for 6.5-15 s, and the second oxygen source is introduced at a flow rate of 23-35 sccm for 6.5-15 s; (5) n is an integer of 12-35; (6) m is an integer of 12-35.

5. The method of producing a solar cell according to any one of claims 1 to 4, characterized in that, The preparation method further comprises: before each time the first oxygen source is introduced into the ALD cavity, the residual gas source after the previous reaction is first purged with an inert gas; and / or, before each time the first aluminum source is introduced into the ALD cavity, the residual gas source after the previous reaction is second purged with an inert gas; and / or, before each time the second oxygen source is introduced into the ALD cavity, the residual gas source after the previous reaction is third purged; and / or, before each time the second aluminum source is introduced into the ALD cavity, the residual gas source after the previous reaction is fourth purged.

6. The method of producing a solar cell according to any one of claims 1 to 4, wherein The first passivation layer further comprises a first silicon oxide layer; before the first surface side of the substrate is water pretreated by introducing water vapor into the ALD cavity at a preset temperature and a preset pressure, the preparation method further comprises: forming the first silicon oxide layer on the second surface side of the substrate.

7. The method of producing a solar cell according to claim 6, wherein The solar cell further comprises a second passivation layer disposed on the second surface side of the substrate, the second passivation layer comprising: a second aluminum oxide layer; the content of H in the second aluminum oxide layer gradually decreases in a direction gradually away from the substrate; the preparation method further comprises: forming the second passivation layer on the second surface of the substrate using the same process as the first passivation layer.

8. A solar cell, characterized by, The solar cell is prepared using the preparation method of any one of claims 1-7.

9. The solar cell of claim 8, wherein, In each region of the first aluminum oxide layer, the difference between the maximum thickness position and the minimum thickness position is less than 0.3 nm.

10. The solar cell of claim 8, wherein, The average thickness of the first aluminum oxide layer is 4-15 nm.

11. The solar cell according to any one of claims 8 to 10, wherein The solar cell comprises a second passivation layer disposed on the second surface side of the substrate, the second passivation layer comprising a second aluminum oxide layer and a second silicon oxide layer, the second silicon oxide layer being disposed on the side of the second aluminum oxide layer close to the substrate.

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