Solar cell and preparation method thereof

Abstract

The invention relates to the technical field of photoelectricity, in particular to a solar cell and a preparation method thereof, and aims to improve the passivation performance and ultraviolet induced degradation resistance of the solar cell. The solar cell comprises a substrate, the substrate is provided with a first surface and a second surface which are oppositely arranged in 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 that of the substrate; the first passivation layer is arranged on one side of the first surface of the substrate; the first passivation layer comprises a first aluminum oxide layer; the H content in the first aluminum oxide layer is gradually reduced in the direction gradually away from the substrate.

Description

Technical Field

[0001] The present application relates to the field of optoelectronic technology, and in particular to a solar cell and a method for preparing the same. Background Art

[0002] Ultraviolet-Induced Degradation (UVID) is common in the field of solar cells, especially in silicon-based solar cells. For example, for N-type TOPCon cells, UVID is particularly obvious, mainly manifested as the gradual decline of cell performance under ultraviolet irradiation. The main reasons for UVID are: First, in a long-term ultraviolet irradiation environment, the energy of ultraviolet rays may cause an increase in lattice defects in crystalline silicon, affecting the transmission and collection of carriers, thereby reducing cell efficiency; second, ultraviolet rays can destroy some chemical bonds in silicon materials, thereby changing their electrical properties.

[0003] In the related art, a UV absorption layer or a UV blocking layer is usually introduced into a solar cell to improve its ability to resist UV-induced degradation. However, the current UV absorption layer or UV blocking layer has limited ability to resist UV-induced degradation, which limits the improvement of the photoelectric conversion efficiency of the solar cell. Summary of the invention

[0004] Based on this, it is necessary to provide a solar cell and a preparation method thereof to improve the passivation performance and anti-ultraviolet induced degradation capability of the solar cell.

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

[0006] A substrate, the substrate having a first surface and a second surface arranged opposite to each other along a thickness direction thereof, an emitter being formed on the first surface of the substrate, and a doping type of the emitter being opposite to a doping type of the substrate;

[0007] A first passivation layer, wherein the first passivation layer is disposed on one side of the first surface of the substrate;

[0008] The first passivation layer includes: a first aluminum oxide layer; and the H content in the first aluminum oxide layer decreases gradually in a direction away from the substrate.

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

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

[0011] Optionally, the average thickness of the first aluminum oxide layer is 4 nm to 15 nm.

[0012] Optionally, the first passivation layer further includes: 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 one side of the second surface of the substrate;

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

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

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

[0018] Providing a substrate having a first surface and a second surface disposed opposite to each other along a thickness direction of the substrate;

[0019] forming an emitter on the first surface of the substrate, wherein the doping type of the emitter is opposite to the doping type of the substrate;

[0020] A first passivation layer is formed on one side of the first surface of the substrate; the first passivation layer comprises: a first aluminum oxide layer; and the H content in the first aluminum oxide layer decreases gradually in a direction away from the substrate.

[0021] Optionally, in a direction gradually away from the substrate, the H content in the first aluminum oxide layer increases from 5×10 21 cm -3 Reduced to 4×10 19 cm -3 ; The forming of a first passivation layer on one side of the first surface of the substrate comprises:

[0022] At a preset temperature and a preset pressure, water vapor is introduced into the ALD chamber to perform water pretreatment on one side of the first surface of the substrate;

[0023] Depositing a hydrogen-containing aluminum oxide film layer and a non-hydrogen-containing aluminum oxide film layer in sequence on one side of the first surface of the substrate after water pretreatment;

[0024] The hydrogen-containing aluminum oxide film layer and the hydrogen-free aluminum oxide film layer are annealed to prepare the first aluminum oxide layer.

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

[0026] At the preset temperature and the preset pressure, the water vapor is introduced into the ALD chamber at least 5 times so that the water vapor is adsorbed on the first surface side of the substrate; and after each introduction of the water vapor, the water vapor that is not adsorbed on the first surface side of the substrate is purged with an inert gas; wherein the flow rate of each introduction of the water vapor 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 to 300°C, and the preset pressure is 0.01mbar to 0.03mbar;

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

[0030] In some embodiments, a hydrogen-containing aluminum oxide film layer and a non-hydrogen-containing aluminum oxide film layer are sequentially deposited on one side of the first surface of the substrate after water pretreatment, comprising:

[0031] A first aluminum source is introduced into the ALD chamber, wherein the first aluminum source reacts with the first surface of the substrate after water pretreatment to generate a first aluminum oxide film layer;

[0032] The first oxygen source and the first aluminum source are alternately introduced into the ALD chamber, the first oxygen source reacts with the surface of the j-th aluminum oxide film layer facing away from the substrate to generate the i-th oxide film layer, and the first aluminum source reacts with the i-th oxide film layer to generate the i-th aluminum oxide film layer, thereby preparing the hydrogen-containing aluminum oxide film layer; wherein i is an integer from 2 to 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

[0033] Alternately introducing a second oxygen source and a second aluminum source into the ALD chamber, the second oxygen source reacting with a surface of the hydrogen-containing aluminum oxide layer facing away from the substrate to form a first oxide film layer, and the second aluminum source reacting with the first oxide film layer to form a first aluminum oxide film layer;

[0034] When the second oxygen source and the second aluminum source are alternately introduced for the kth time, the second oxygen source reacts with the surface of the sth aluminum oxide film layer facing away from the substrate to generate a kth oxide film layer, and the second aluminum source reacts with the kth oxide film layer to generate a kth aluminum oxide film layer, thereby preparing the hydrogen-free aluminum oxide film layer; wherein k is an integer from 2 to 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 includes: water vapor; and / or, the second oxygen source includes: ozone;

[0037] (2) The first aluminum source and the second aluminum source are of the same or different types, and / or the flow rates of the first aluminum source and the second aluminum source are the same or different;

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

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

[0040] (5) n is an integer from 12 to 35;

[0041] (6) m is an integer from 12 to 35.

[0042] Optionally, the preparation method further comprises:

[0043] Before each introduction of the first oxygen source into the ALD chamber, a first purge of the gas source remaining after the previous step of reaction is performed using an inert gas; and / or,

[0044] Before each introduction of the first aluminum source into the ALD chamber, a second purge of the gas source remaining after the previous step of reaction is performed using an inert gas; and / or,

[0045] Before each introduction of the second oxygen source into the ALD chamber, a third purge is performed on the gas source remaining after the previous step of reaction; and / or,

[0046] Before the second aluminum source is introduced into the ALD chamber each time, a fourth purge is performed on the gas source remaining after the previous step of reaction.

[0047] Optionally, the first passivation layer further includes a first silicon oxide layer; before introducing water vapor into the ALD chamber at a preset temperature and a preset pressure and performing water pretreatment on one side of the first surface of the substrate, the preparation method further includes:

[0048] The first silicon oxide layer is formed on one side of the first surface of the substrate.

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

[0050] The second passivation layer is formed on the second surface of the substrate by adopting the same process as that of the first passivation layer.

[0051] The beneficial effects of the above-mentioned solar cell and its preparation method are as follows:

[0052] Since the H content in the first aluminum oxide layer decreases gradually in the direction away from the substrate, on the one hand, the H content in the first aluminum oxide layer near the substrate is relatively high, which makes it easier for excess H in the first aluminum oxide layer near the substrate to enter the saturated dangling bonds in the substrate, thereby improving the passivation effect; on the other hand, the H content in the first aluminum oxide layer far from the substrate is relatively low, which can block the H in the substrate and the first aluminum oxide layer near the substrate. Under the irradiation of ultraviolet light, the H in the substrate and the first aluminum oxide layer near the substrate will not be released from the surface of the substrate, thereby effectively enhancing the ability to resist ultraviolet induced attenuation. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0054] Reference numerals:

[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. tunneling oxide layer; 15. doped polysilicon layer; 16. first anti-reflection layer; 17. second anti-reflection layer; 18. first electrode; 19. second electrode. DETAILED DESCRIPTION

[0056] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0057] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as an open, inclusive meaning, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "exemplarily" or "some examples" and the like are intended to indicate that specific features, structures, materials or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representation of the above terms does not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0058] Exemplary embodiments are described herein with reference to cross-sectional views and / or plan views that are idealized exemplary drawings. In the drawings, the thickness of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are conceivable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but include shape deviations due to, for example, manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device, and are not intended to limit the scope of the exemplary embodiments.

[0059] In this document, "for example", "such as", "example", "for example", etc. are used for descriptive purposes, indicating that the previous and subsequent different technical solutions are related in terms of the content covered, but should not be understood as limiting the previous technical solution, nor can they be understood as limiting the scope of protection of this document. In this document, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0060] In this article, "optionally", "optional", and "optional" mean optional, that is, any one of the two parallel options of "yes" or "no". If there are multiple "options" in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "option" is independent.

[0061] Herein, descriptions such as "optionally contain", "optionally include", etc., mean "contain or not contain". "Optional component X" means component X exists or does not exist, or means containing or not containing the component X.

[0062] In this document, the terms "first", "second", etc. in "the first aspect", "the second aspect", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features.

[0063] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. 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 method.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0065] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0066] In this document, "at least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc.

[0067] Herein, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered to be continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval only refers to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be combined. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows broadly including numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0068] In this article, when it comes to percentage concentration, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of the component.

[0069] As used in this article, fill factor (FF) refers to the ratio of the actual maximum achievable power (Pm or Vmp * Imp) to the theoretical (not actually achievable) power (Isc * Voc). Therefore, FF can be determined by the following formula:

[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 changing the resistance in the circuit until I * V is the maximum value; Isc and Voc represent the short-circuit current and open-circuit voltage, respectively. Fill factor is a key parameter for evaluating solar cells. Commercial solar cells usually have a fill factor of about 60% or more.

[0072] As used herein, open circuit voltage (Voc) is the potential difference between the anode and cathode of the device with no external load connected.

[0073] The power conversion efficiency (PCE) of a solar cell used in this article refers to the percentage of power converted from absorbed light to electrical energy. The power conversion efficiency (PCE) of a solar cell can be measured by the incident light irradiance (E: W / m 2 ) and the surface area of ​​the solar cell (Ac:m 2 ) divided by the maximum power point (Pm). STC usually refers to the temperature of 25℃ and the irradiance of 1000 W / m 2 , the spectrum of air quality 1.5 (AM1.5).

[0074] In this article, if there are multiple steps involved in the method flow, unless there is a clear different description in this article, there is no strict order restriction for the execution of these steps, and they can be executed in other orders than described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and their execution order is not necessarily sequential, but can be executed in turn, alternating or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0075] In the related technologies, 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 silicon wafers is largely affected by the surface state of the silicon wafers, such as surface dangling bonds on the silicon wafers, defects and lattice distortion left by the silicon wafers during the slicing process, which can all become carrier recombination centers, causing carrier recombination on the surface of silicon-based solar cells.

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

[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 solar cells, front passivation layer and back passivation layer are usually made on the front and back of the solar cell respectively. However, the current front passivation layer and back passivation layer are focused on passivating dangling bonds, defects and lattice distortion on the surface of silicon wafers to reduce the recombination of carriers on the surface of solar cells.

[0079] In order to improve the UV-induced degradation capability of solar cells, an additional UV absorption layer or UV blocking layer is usually introduced into the solar cell. However, the current solar cells have the problem that the passivation performance and UV-induced degradation resistance cannot be effectively improved. In particular, UV-induced degradation (UVID) is a high challenge for N-type TOPCon cells, which are increasingly widely produced and applied.

[0080] Based on the above technical problems, the specific implementation methods of this application are described as follows:

[0081] In a first aspect, some embodiments of the present application provide a solar cell, such as Figure 1 As shown, the solar cell includes: a substrate 11 and a first passivation layer 12; wherein the substrate 11 has a first surface and a second surface arranged opposite to each other along its thickness direction, an emitter 111 is formed on the first surface of the substrate 11, and the first passivation layer 12 is arranged on one side of the first surface of the substrate 11.

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

[0083] In the case where the solar cell is PERC or TOPCon, the first surface of the substrate 11 can be the light-receiving surface of the solar cell, and the emitter 111 is formed on the light-receiving surface of the solar cell, that is, the front side. In this case, the first passivation layer 12 can be arranged on the front side of the solar cell and cover the first surface of the substrate 11 and the emitter 111; in the case where the solar cell is IBC, the first surface of the substrate can be the 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, that is, the back side. In this case, the first passivation layer can be arranged on the back side of the solar cell and cover the emitter and the back field.

[0084] In the following embodiments, the solar cell is an N-type TOPCon as an example for explanation. Those skilled in the art will understand that the present application is also applicable to the case where the solar cell is PERC and IBC, and this does not affect the protection scope of the present application.

[0085] In some embodiments, the doping type of the emitter 111 is opposite to the doping type of the substrate 11 , thereby forming a PN junction of the solar cell.

[0086] In some embodiments, the substrate 11 may be an N-type silicon substrate, in which case the emitter 111 is a P-type emitter; or the substrate 11 may be a P-type silicon substrate, in which case the emitter 111 is an N-type emitter.

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

[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 and improving the photoelectric conversion efficiency of the solar cell. At the same time, since the fixed charge density in the first aluminum oxide layer 121 can reach 10 12 cm -3 As described above, therefore, the first aluminum oxide layer 121 can also play a field passivation effect, thereby further improving the photoelectric conversion efficiency of the solar cell.

[0089] However, under long-term ultraviolet light, ultraviolet rays will 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, thereby reducing the photoelectric conversion efficiency of the solar cell.

[0090] In the solar cell provided in the embodiment of the present application, since the H content in the first aluminum oxide layer 121 decreases gradually in the direction away from the substrate 11, on the one hand, the H content at the position of the first aluminum oxide layer 121 close to the substrate 11 is relatively high, which facilitates the excess H at the position of the first aluminum oxide layer 121 close to the substrate 11 to enter the saturated dangling bonds in the substrate 11, thereby improving the passivation effect; on the other hand, the H content at the position of the first aluminum oxide layer 121 far from the substrate 11 is relatively low, which can block the substrate 11 and the H at the position of the first aluminum oxide layer 121 close to the substrate 11. Under the irradiation of ultraviolet light, the H at the substrate 11 and the position of the first aluminum oxide layer 121 close to the substrate 11 will not be released from the surface of the substrate 11, thereby effectively enhancing the ability to resist ultraviolet induced attenuation.

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

[0092] In these embodiments, the surface of the first aluminum oxide layer 121 close to the substrate 11 has more H to passivate the silicon dangling bonds in the substrate 11, and as the H content in the first aluminum oxide layer 121 gradually decreases, the H at a position close to the substrate 11 in the first aluminum oxide layer 121 can be effectively inhibited from being liberated from the surface of the substrate 11, thereby effectively enhancing the anti-ultraviolet induced attenuation capability of the first passivation layer 12.

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

[0094] In these embodiments, the first aluminum oxide layer 121 has better thickness uniformity and compactness, thereby further improving the UV induced degradation resistance of the first passivation layer 12 .

[0095] In some embodiments, the average thickness of the first aluminum oxide layer 121 is 4 nm to 15 nm. The average thickness here means that the thickness of the first aluminum oxide layer 121 at different locations is different, and the average value is obtained by measuring the thickness at multiple locations and then adding the thicknesses of the multiple different thicknesses.

[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 a side of the first aluminum oxide layer 121 close to 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, thereby effectively passivating the dangling bonds on the surfaces of the substrate 11 and the emitter 111, thereby further reducing carrier recombination, reducing the interface defect density on the surfaces of the substrate 11 and the emitter 111, further improving the passivation effect, and enhancing the ability to resist UV induced decay.

[0098] In some embodiments, 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 gradually in a direction away from the substrate 11.

[0099] In these embodiments, the second passivation layer 13 can be a back passivation layer. Similar to the above-mentioned first passivation layer 12, on the first aspect, the H content at the position close to the substrate 11 in the second aluminum oxide layer 131 included in the second passivation layer 13 is relatively high, so that there is excess H at the position close to the substrate 11 in the second aluminum oxide layer 131 to enter the saturated dangling bonds in the substrate 11, thereby improving the passivation effect; on the second aspect, the H content at the position far from the substrate 11 in the second aluminum oxide layer 131 is relatively low, which can block the H at the substrate 11 and the second aluminum oxide layer 131 close to the substrate 11. Under the irradiation of ultraviolet light, the H at the position close to the substrate 11 in the substrate 11 and the second aluminum oxide layer 131 will not be freed from the surface of the substrate 11, thereby effectively enhancing the ability to resist ultraviolet induced attenuation.

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

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

[0102] It should be noted that, taking the solar cell as an N-type TOPCon as an example, Figure 1 As shown, the solar cell further includes: a tunneling oxide layer 14 and a doped polysilicon 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 polysilicon layer 15 away from the substrate 11. The tunneling oxide layer 14 and the doped polysilicon layer 15 together constitute a passivation contact structure, which can allow majority carriers to tunnel into the doped polysilicon layer 15 while blocking minority carriers from 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 polysilicon layer 15 on the side away from the substrate, thereby improving its passivation performance and anti-ultraviolet induced degradation performance.

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

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

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

[0107] S21), providing a substrate, wherein the substrate has a first surface and a second surface arranged opposite to each other along a thickness direction thereof;

[0108] In which, taking the solar cell as an N-type TOPCon cell as an example, the substrate is an N-type silicon substrate. The first surface may be a light-receiving surface of the substrate, and the second surface may be a non-light-receiving surface of the substrate.

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

[0110] Since the doping type of the emitter is opposite to the doping type of the substrate, the substrate is still taken as an N-type silicon substrate for example, and the emitter is a P-type emitter.

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

[0112] In some embodiments, the H content in the first aluminum oxide layer increases from 5×10 21 cm -3 Reduced to 4×10 19 cm -3 ; forming a first passivation layer on one side of the first surface of the substrate, comprising:

[0113] At a preset temperature and a preset pressure, water vapor is introduced into the ALD chamber to perform water pretreatment on one side of the first surface of the substrate;

[0114] Depositing a hydrogen-containing aluminum oxide film layer and a non-hydrogen-containing aluminum oxide film layer in sequence on one side of the first surface of the substrate pretreated with water;

[0115] The aluminum oxide film layer containing hydrogen and the aluminum oxide film layer containing no hydrogen are annealed to prepare a first aluminum oxide layer.

[0116] ALD is a technique for depositing thin films on the surface of a substrate through layer-by-layer atomic reactions. Specifically, taking the example of sequentially depositing a hydrogen-containing aluminum oxide film layer and a non-hydrogen-containing aluminum oxide film layer on one side of the first surface of the substrate, when the first oxygen source and the first aluminum source are alternately introduced into the ALD chamber and the first oxygen source and the first aluminum source are used as reaction precursors of the hydrogen-containing aluminum oxide film layer, the first oxygen source undergoes chemical adsorption (such as hydroxyl reaction adsorption) on one side of the first surface of the substrate to generate a first oxide film layer (the first oxide film layer can be regarded as a first oxygen source adsorption layer), and then the first aluminum source reacts with the first oxygen source adsorbed on one side of the first surface of the substrate to generate a hydrogen-containing aluminum oxide film layer.

[0117] In these embodiments, water pretreatment is performed on the first surface side of the substrate by introducing water vapor into the ALD chamber at a preset temperature and a preset pressure, so that the reaction activity and hydroxyl adsorption uniformity 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 will diffuse into the hydrogen-free aluminum oxide film layer, thereby obtaining a first aluminum oxide layer with a decreasing H content in a direction gradually away from the substrate.

[0118] In some embodiments, water vapor is introduced into the ALD chamber at a preset temperature and a preset pressure to perform water pretreatment on the first surface side of the substrate, including:

[0119] At a preset temperature and a preset pressure, water vapor is introduced into the ALD chamber at least five times so that the water vapor is adsorbed on the first surface side of the substrate, and after each introduction of water vapor, the water vapor that is not adsorbed on the first surface side of the substrate is purged with an inert gas; wherein the flow rate of each water vapor introduction is 23 sccm ~35 sccm, and the time is 6.5 s ~15 s.

[0120] In these embodiments, water vapor is introduced into the ALD chamber at least five times so that the water vapor is adsorbed on the first surface side of the substrate, and after each introduction of water vapor, the water vapor that is not adsorbed on the first surface side of the substrate is purged with an inert gas, wherein the flow rate of each water vapor introduction is 23 sccm~35 sccm, and the time is 6.5 s~15 s, which can ensure that the water vapor reaches adsorption saturation 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 denser and uniform hydrogen-containing aluminum oxide film layer on the first surface side of the substrate, thereby preparing a denser and uniform first aluminum oxide layer.

[0121] In some embodiments, the preset temperature is 250°C to 300°C, and the preset pressure is 0.01 mbar to 0.03 mbar. The preset temperature is the deposition temperature, and the preset pressure is the bottom pressure, that is, before introducing water vapor into the ALD chamber, it is necessary to first evacuate the chamber to the bottom pressure, and preheat the ALD chamber to the deposition temperature to facilitate the subsequent deposition of the first aluminum oxide layer.

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

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

[0124] A first aluminum source is introduced into the ALD chamber, and the first aluminum source reacts with the first surface of the substrate pretreated with water to form a first aluminum oxide film layer; and

[0125] Alternately introducing a first oxygen source and a first aluminum source into the ALD chamber, the first oxygen source reacts with a surface of the j-th aluminum oxide film layer facing away from the substrate to generate an i-th oxide film layer, and the first aluminum source reacts with the i-th oxide film layer to generate an i-th aluminum oxide film layer, thereby preparing a hydrogen-containing aluminum oxide film layer; wherein i is an integer from 2 to 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] Alternately introducing a second oxygen source and a second aluminum source into the ALD chamber, the second oxygen source reacts with a surface of the hydrogen-containing aluminum oxide layer facing away from the substrate to form a first oxide film layer, and the second aluminum source reacts with the first oxide film layer to form a first aluminum oxide film layer;

[0127] When the second oxygen source and the second aluminum source are alternately introduced for the kth time, the second oxygen source reacts with the surface of the sth aluminum oxide film layer facing away from the substrate to generate the kth oxide film layer, and the second aluminum source reacts with the kth oxide film layer to generate the kth aluminum oxide film layer, thereby preparing a hydrogen-free aluminum oxide film layer; wherein k is an integer from 2 to m, m is an integer greater than or equal to 2, and s=k-1.

[0128] In these embodiments, by introducing a first aluminum source into the ALD chamber, the first aluminum source can react with water vapor adsorbed on one side of the first surface of the substrate to generate a first aluminum oxide film layer. Since the water vapor adsorbed on one side of the first surface of the substrate has good uniformity, the first surface of the substrate can be uniformly activated. Therefore, the first aluminum oxide film layer is more dense and uniform. On the basis of the first aluminum oxide film layer, by cyclically introducing the first oxygen source and the first aluminum source for multiple times, a hydrogen-containing aluminum oxide film layer with a certain thickness can be formed, and surface conformality can be achieved, thereby improving the density and uniformity of the hydrogen-containing aluminum oxide film layer. Then, by alternately introducing the second oxygen source and the second aluminum source into the ALD chamber, the second oxygen source is adsorbed on the surface of the side of the hydrogen-containing aluminum oxide film layer away from the substrate to form 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. By cyclically introducing the second oxygen source and the second aluminum source for multiple times, a hydrogen-free aluminum oxide film layer with a certain thickness can be formed, and surface conformality can be achieved, thereby improving the density and uniformity of the hydrogen-free aluminum oxide film layer.

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

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

[0131] (2) The first aluminum source and the second aluminum source are of the same or different types, and / or the flow rates of the first aluminum source and the second aluminum source are the same or different;

[0132] (3) During the deposition of the hydrogen-containing aluminum oxide film, the first aluminum source is introduced at a flow rate of 23 sccm to 35 sccm for a period of 6.5 s to 15 s, and the first oxygen source is introduced at a flow rate of 23 sccm to 35 sccm for a period of 6.5 s to 15 s;

[0133] (4) During the deposition of the hydrogen-free aluminum oxide film, the flow rate of the second aluminum source is 23 sccm to 35 sccm, the time is 6.5 s to 15 s, and the flow rate of the second oxygen source is 23 sccm to 35 sccm, the time is 6.5 s to 15 s;

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

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

[0136] In these embodiments, by controlling the values ​​of n and m, the thicknesses of the hydrogen-containing aluminum oxide film layer and the non-hydrogen-containing aluminum oxide film layer can be precisely controlled.

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

[0138] Among them, in the case of the above-mentioned deposition of the hydrogen-containing aluminum oxide film layer, when the first oxygen source reacts with the surface of the j-th aluminum oxide film layer facing away from the silicon substrate, not all of the first oxygen source can react, which is related to the degree of adsorption saturation. Therefore, when an excessive amount of the first oxygen source is introduced, some of the first oxygen source will often remain. Similarly, when the first aluminum source reacts with the first surface of the substrate after water pretreatment or the i-th oxide film layer, some of the first aluminum source will also remain and by-products will be produced.

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

[0140] Before each introduction of the first oxygen source into the ALD chamber, an inert gas is used to perform a first purge of the gas source remaining after the previous step of reaction; and / or,

[0141] Before the first aluminum source is introduced into the ALD chamber each time, an inert gas is used to perform a second purge on the gas source remaining after the previous step of reaction.

[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 purge time is 11 s to 23 s, and / or the second purge time is 11 s to 23 s.

[0144] Similar to the above-mentioned deposition of the hydrogen-containing aluminum oxide film layer, when the second oxygen source reacts with the surface of the hydrogen-containing aluminum oxide film layer facing away from the substrate or the surface of the sth aluminum oxide film layer facing away from the substrate, not all of the second oxygen source can react. This is related to the degree of adsorption saturation. Therefore, when an excess of the second oxygen source is introduced, some of the second oxygen source will often remain. Similarly, when the second aluminum source reacts with the first oxide film layer or the kth oxide film layer, some of the second aluminum source will also remain and by-products will be produced.

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

[0146] Before each introduction of the second oxygen source into the ALD chamber, the residual gas source after the previous step reaction is purged for the third time with an inert gas; and / or,

[0147] Before each time the second aluminum source is introduced into the ALD chamber, the gas source remaining after the previous step of reaction is purged for the fourth time 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 purge time is 11 s to 23 s, and / or the fourth purge time is 11 s to 23 s.

[0150] In some embodiments, the first passivation layer further includes a first silicon oxide layer; in the same ALD chamber, the first oxygen source and the second oxygen source are controlled to be turned on sequentially, and before at least one first sublayer and at least one second sublayer are sequentially formed on one side of the first surface of the substrate on which the emitter is formed by the ALD method, the preparation method further includes:

[0151] A first silicon oxide layer is formed on the first surface side of the substrate where the emitter is formed.

[0152] In these embodiments, the first silicon oxide layer can passivate the first surface of the substrate, thereby further improving the passivation performance and the ability to resist ultraviolet induced degradation.

[0153] In some embodiments, PECVD may be used to form a first silicon oxide layer on the first surface of the substrate on which the emitter is formed.

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

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

[0156] In these embodiments, the second passivation layer may be a back passivation layer. In this case, the second passivation layer is formed on the second surface of the substrate using the same process as the first passivation layer, and the front passivation layer and the back passivation layer may be formed simultaneously.

[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 chamber.

[0158] In some embodiments, the second passivation layer further includes 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; the second silicon oxide layer and the first silicon oxide layer can be prepared by the same process.

[0159] In some embodiments, taking the solar cell as a TOPCon cell as an example, after preparing the doped amorphous silicon layer on the back side, when the doped amorphous silicon layer is converted into a doped polycrystalline silicon layer by annealing, an oxygen source is introduced into the reaction chamber to form a first silicon oxide layer on the first surface of the substrate where the emitter is formed, and a second silicon oxide layer is formed on the surface of the doped polycrystalline silicon layer.

[0160] The annealing temperature can be 900°C to 1100°C, and the time can be 35min to 65min. 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 polysilicon layer. Especially when the H concentration is low, the bonding affinity between oxygen and silicon is very strong, and the Si-O bonds formed at the interface can effectively passivate dangling bonds, minimize carrier recombination, and reduce interface defect density. The passivation effect of the Si-O bonds is good and is 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 is formed at the interface between the doped polysilicon layer and the second aluminum oxide layer on the back. The Si-O bonds at the interface can effectively passivate the dangling bonds, thereby further improving the ability to resist UV-induced attenuation.

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

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

[0164] Example 1

[0165] The method for preparing the solar cell in Example 1 is as follows:

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

[0167] Step 2), Boron diffusion is performed on the velvet surface to form P + Emitter; a 1.5nm thick tunneling oxide layer (nitrous oxide is selected as the gas source) and a 90nm thick doped amorphous silicon layer (silane and phosphine are selected as the gas source) are deposited on the back surface by PECVD. The amorphous silicon is converted into polycrystalline silicon by annealing at 900℃ for 45min. Oxygen is introduced into the reaction chamber during the annealing process to deposit a 2nm thick silicon oxide layer on both sides.

[0168] Step 3), depositing aluminum oxide with a thickness of 10 nm on both sides of the silicon wafer obtained in step 2), the specific method is as follows: evacuate the tubular ALD chamber to a vacuum degree of 0.01 mbar in the ALD chamber, preheat for 700 s until the temperature in the ALD chamber is 280°C; introduce water vapor into the ALD chamber 5 times, and purge the unadsorbed water vapor with nitrogen after each water vapor introduction, each time the water vapor is introduced at a flow rate of 30 sccm and the time is 10 s, introduce TMA into the ALD chamber at a flow rate of 30 sccm and the time is 10 s; then continue to alternately introduce water vapor and TMA into the ALD chamber, the water vapor flow rate is 30 sccm, the TMA flow rate is 30 sccm, the water vapor and TMA introduction time are 10 s respectively, the introduction is cycled 24 times, and during the introduction When water vapor is introduced so that the water vapor is adsorbed on both sides of the silicon wafer to saturation, nitrogen is used to purge excess water vapor for 20 seconds, and after TMA is introduced so that TMA reacts with water vapor adsorbed on the surface of the silicon wafer, nitrogen is used to purge excess TMA and waste gas for 15 seconds; then, ozone and TMA are alternately introduced into the ALD chamber, the ozone flow rate is 30sccm, the TMA flow rate is 30sccm, the ozone and TMA introduction time are 10 seconds respectively, and the introduction is cycled 20 times, and when ozone is introduced so that the ozone adsorption on both sides of the silicon wafer is saturated, nitrogen is used to purge excess ozone for 15 seconds, and after TMA is introduced so that TMA reacts with ozone adsorbed on the surface of the silicon wafer, nitrogen is used to purge excess TMA and waste gas for 15 seconds, during this process, the gas leakage rate is less than 0.02mbar / min;

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

[0170] Step 5), deposit about 70nm of silicon nitride on both sides by PECVD (silane and ammonia are selected as gas sources); finally, print double-sided grid lines to make solar cells.

[0171] Example 2

[0172] The method for preparing the solar cell in Example 2 is substantially the same as the method for preparing the solar cell in Example 1, except that:

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

[0174] In step 3), a 15 nm thick aluminum oxide layer is deposited on both sides of the silicon wafer obtained in step 2), specifically, the tubular ALD chamber is evacuated, and nitrogen is introduced until the vacuum degree in the ALD chamber is 0.03 mbar, and the preheating time is 700 s until the temperature in the ALD chamber is 250°C; water vapor is introduced into the ALD chamber 6 times, and after each water vapor is introduced, the unadsorbed water vapor is purged with nitrogen, and the flow rate of each water vapor is 23 sccm, and the time is 6.5 s, TMA is introduced into the ALD chamber, and 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 chamber, the flow rate of water vapor is 23 sccm, the flow rate of TMA is 23 sccm, and the introduction time of water vapor and TMA is 6.5 s respectively, and the cycle is introduced 34 times, and When water vapor is introduced so that the water vapor is adsorbed on both sides of the silicon wafer to saturation, nitrogen is used to purge excess water vapor for 11 seconds, and after TMA is introduced so that TMA reacts with water vapor adsorbed on the surface of the silicon wafer, nitrogen is used to purge excess TMA and exhaust gas for 11 seconds; then, ozone and TMA are alternately introduced into the ALD chamber, the ozone flow rate is 23sccm, the TMA flow rate is 23sccm, the ozone and TMA introduction time are 6.5s respectively, and the cycle is introduced 35 times, and when ozone is introduced so that the ozone adsorption on both sides of the silicon wafer is saturated, nitrogen is used to purge excess ozone for 11 seconds, and after TMA is introduced so that TMA reacts with ozone adsorbed on the surface of the silicon wafer, nitrogen is used to purge excess TMA and exhaust gas for 11 seconds, during this process, the gas leakage rate is less than 0.02mbar / min;

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

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

[0177] Example 3

[0178] The method for preparing the solar cell in Example 3 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0179] In step 2), the thickness of the tunneling oxide layer formed on the back surface is 2 nm, the thickness of the doped amorphous silicon layer is 100 nm, and the doped amorphous silicon layer is annealed at 1000° C. for 65 min to convert the doped amorphous silicon layer into a doped polysilicon layer. During the annealing process, oxygen is introduced into the reaction chamber to deposit a 10 nm thick silicon oxide layer on both sides.

[0180] In step 3), a 4 nm thick aluminum oxide layer is deposited on both sides of the silicon wafer obtained in step 2), specifically, the tubular ALD chamber is evacuated, and nitrogen is introduced until the vacuum degree in the ALD chamber is 0.02 mbar, and the preheating time is 700 s until the temperature in the ALD chamber is 300°C; water vapor is introduced into the ALD chamber 7 times, and after each water vapor is introduced, the unadsorbed water vapor is purged with nitrogen, and the flow rate of each water vapor is 35 sccm, and the time is 15 s, TMA is introduced into the ALD chamber, and the flow rate of TMA is 35 sccm, and the time is 15 s; then water vapor and TMA are alternately introduced into the ALD chamber, the flow rate of water vapor is 35 sccm, the flow rate of TMA is 35 sccm, and the introduction time of water vapor and TMA is 15 s respectively, and the introduction is cycled 11 times, and in When water vapor is introduced so that the adsorption of water vapor on both sides of the silicon wafer reaches saturation, nitrogen is used to purge excess water vapor for 23 seconds, and after TMA is introduced so that TMA reacts with water vapor absorbed on the surface of the silicon wafer, nitrogen is used to purge excess TMA and waste gas for 23 seconds; then, ozone and TMA are alternately introduced into the ALD chamber, the ozone flow rate is 35sccm, the TMA flow rate is 35sccm, the ozone and TMA introduction time are 15 seconds respectively, and the cycle is introduced 12 times, and when ozone is introduced so that the adsorption of ozone on both sides of the silicon wafer reaches saturation, nitrogen is used to purge excess ozone for 23 seconds, and after TMA is introduced so that TMA reacts with ozone absorbed on the surface of the silicon wafer, nitrogen is used to purge excess TMA and waste gas for 23 seconds, during this process, the gas leakage rate is less than 0.02mbar / min;

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

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

[0183] Comparative Example 1

[0184] The method for preparing the solar cell in Comparative Example 1 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0185] During the deposition of the aluminum oxide layer in step 3), water vapor is directly used as the oxygen source to prepare the aluminum oxide layer, and the substrate is not subjected to water pretreatment. That is, it can be regarded as that when the vacuum degree in the ALD chamber reaches 0.01 mbar and the temperature reaches 280°C, water vapor and TMA are alternately introduced into the ALD chamber for a total of 45 times, and the other conditions are the same as in Example 1.

[0186] Comparative Example 2

[0187] The method for preparing the solar cell in Comparative Example 2 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0188] During the deposition of 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. That is, it can be regarded as that when the vacuum degree in the ALD chamber reaches 0.01 mbar and the temperature reaches 280°C, ozone and TMA are alternately introduced into the ALD chamber for a total of 45 times, and the other conditions are the same as in Example 1.

[0189] Test Case

[0190] Alkali-polished wafers (silicon wafers after alkali polishing) were uniformly inserted into the grooves of the aluminum boat to simulate step 3) of Examples 1 to 3 and Comparative Examples 1 to 2, and the thickness uniformity of the aluminum oxide layer after the aluminum oxide layer was deposited was measured.

[0191] The specific test method is: select the five-point test method, select the center point and four corner points of the silicon wafer respectively (the four corner points are 20mm away from the edge), measure the thickness of the aluminum oxide layer corresponding to each point, and calculate the uniformity within the wafer. The calculation formula is: the difference between the maximum thickness and the minimum thickness of the same aluminum oxide layer; at the same time, measure the maximum thickness and minimum thickness of the aluminum oxide layer of the same batch prepared under the same conditions, and calculate the uniformity between wafers according to the formula (max-min) / (2*mean), where max represents the maximum thickness of the aluminum oxide layer of the same batch, min represents the minimum thickness of the aluminum oxide layer of the same batch, and mean represents the average thickness of the aluminum oxide layer of the same batch. The test results are shown in Table 1 below.

[0192] Table 1

[0193]

[0194] It can be seen from Table 1 that, compared with Comparative Examples 1-2, the intra-sheet uniformity and inter-sheet uniformity of Examples 1-3 are greatly improved, while the intra-sheet uniformity and inter-sheet uniformity of Comparative Examples 1 and 2 are relatively poor.

[0195] 2. The cell assemblies prepared from the solar cells provided in Examples 1 to 3 and Comparative Examples 1 to 2 were subjected to UV60 ultraviolet attenuation tests. The test results are shown in Table 2 below.

[0196] Table 2

[0197]

[0198] The test method of UV60 ultraviolet attenuation test is: test the Voc, Isc, Vmp, Imp, Pmax and FF of the battery component before and after ultraviolet light irradiation respectively, and use (value after ultraviolet light irradiation - value before ultraviolet light irradiation) / value before ultraviolet light irradiation to calculate their respective attenuation rates; where Vmp represents the voltage generated by the battery component at the maximum power point, Imp represents the current generated by the battery component at the maximum power point, and Pm represents the maximum power point.

[0199] The UV60 UV attenuation test was conducted under the following UV irradiation conditions: the front and back sides of the module were exposed to a total UV irradiation of 60 kWh / m2 with a wavelength range of 280 nm to 400 nm. 2 Under the conditions, the component temperature is maintained within the range of 60±5℃ for ultraviolet light irradiation.

[0200] It can be seen from Table 2 that the power attenuation rate of the components of Examples 1 to 3 does not exceed 1%, while the power of the components of Comparative Examples 1 and 2 has a greater degree of attenuation.

[0201] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0202] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A solar cell, characterized in that: include: A substrate, the substrate having a first surface and a second surface arranged opposite to each other along a thickness direction thereof, an emitter being formed on the first surface of the substrate, and a doping type of the emitter being opposite to a doping type of the substrate; A first passivation layer, wherein the first passivation layer is disposed on one side of the first surface of the substrate; The first passivation layer comprises: a first aluminum oxide layer; In a direction gradually away from the substrate, the H content in the first aluminum oxide layer decreases.

2. The solar cell according to claim 1, characterized in that In the direction away from the substrate, the H content in the first aluminum oxide layer increases from 5×10 21 cm -3 Reduced to 4×10 19 cm -3 .

3. The solar cell according to claim 1, characterized in that In each region of the first aluminum oxide layer, the difference in thickness between a maximum thickness position and a minimum thickness position is less than 0.3 nm.

4. The solar cell according to claim 1, characterized in that The average thickness of the first aluminum oxide layer is 4nm-15nm.

5. The solar cell according to claim 1, characterized in that: The first passivation layer further comprises: a first silicon oxide layer; The first silicon oxide layer is disposed on a side of the first aluminum oxide layer close to the substrate.

6. The solar cell according to any one of claims 1 to 5, characterized in that: The solar cell further comprises: a second passivation layer disposed on one side of the second surface of the substrate; The second passivation layer includes: a second aluminum oxide layer, and the H content in the second aluminum oxide layer decreases gradually in a direction away from the substrate.

7. The solar cell according to claim 6, characterized in that: The second passivation layer further includes: a second silicon oxide layer, and the second silicon oxide layer is arranged on a side of the second aluminum oxide layer close to the substrate.

8. A method for preparing a solar cell, characterized in that: include: Providing a substrate having a first surface and a second surface disposed opposite to each other along a thickness direction of the substrate; forming an emitter on the first surface of the substrate, wherein the doping type of the emitter is opposite to the doping type of the substrate; forming a first passivation layer on one side of the first surface of the substrate; The first passivation layer comprises: a first aluminum oxide layer; In a direction gradually away from the substrate, the H content in the first aluminum oxide layer decreases.

9. The method for preparing a solar cell according to claim 8, characterized in that: In the direction away from the substrate, the H content in the first aluminum oxide layer increases from 5×10 21 cm -3 Reduced to 4×10 19 cm -3 ; The step of forming a first passivation layer on one side of the first surface of the substrate comprises: At a preset temperature and a preset pressure, water vapor is introduced into the ALD chamber to perform water pretreatment on one side of the first surface of the substrate; Depositing a hydrogen-containing aluminum oxide film layer and a non-hydrogen-containing aluminum oxide film layer in sequence on one side of the first surface of the substrate after water pretreatment; The hydrogen-containing aluminum oxide film layer and the hydrogen-free aluminum oxide film layer are annealed to prepare the first aluminum oxide layer.

10. The method for preparing a solar cell according to claim 9, characterized in that: At a preset temperature and a preset pressure, water vapor is introduced into the ALD chamber to perform water pretreatment on one side of the first surface of the substrate, including: At a preset temperature and a preset pressure, the water vapor is introduced into the ALD chamber at least 5 times so that the water vapor is adsorbed on the first surface side of the substrate; and after each introduction of the water vapor, the water vapor that is not adsorbed on the first surface side of the substrate is purged with an inert gas; wherein the flow rate of each introduction of the water vapor is 23 sccm ~35 sccm, and the time is 6.5 s ~15 s.

11. The method for preparing a solar cell according to claim 9, characterized in that: The preparation method satisfies at least one of the following conditions: (1) The preset temperature is 250°C to 300°C, and the preset pressure is 0.01 mbar to 0.03 mbar; (2) The annealing temperature is 525°C to 575°C, and the annealing time is 10 min to 30 min.

12. The method for preparing a solar cell according to claim 9, characterized in that: Sequentially depositing a hydrogen-containing aluminum oxide film layer and a hydrogen-free aluminum oxide film layer on one side of the first surface of the substrate after water pretreatment, comprising: A first aluminum source is introduced into the ALD chamber, wherein the first aluminum source reacts with the first surface of the substrate after water pretreatment to generate a first aluminum oxide film layer; The first oxygen source and the first aluminum source are alternately introduced into the ALD chamber, the first oxygen source reacts with the surface of the j-th aluminum oxide film layer facing away from the substrate to generate the i-th oxide film layer, and the first aluminum source reacts with the i-th oxide film layer to generate the i-th aluminum oxide film layer, thereby preparing the hydrogen-containing aluminum oxide film layer; wherein i is an integer from 2 to 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 Alternately introducing a second oxygen source and a second aluminum source into the ALD chamber, the second oxygen source reacting with a surface of the hydrogen-containing aluminum oxide layer facing away from the substrate to form a first oxide film layer, and the second aluminum source reacting with the first oxide film layer to form a first aluminum oxide film layer; When the second oxygen source and the second aluminum source are alternately introduced for the kth time, the second oxygen source reacts with the surface of the sth aluminum oxide film layer facing away from the substrate to generate a kth oxide film layer, and the second aluminum source reacts with the kth oxide film layer to generate a kth aluminum oxide film layer, thereby preparing the hydrogen-free aluminum oxide film layer; wherein k is an integer from 2 to m, m is an integer greater than or equal to 2, and s=k-1.

13. The method for preparing a solar cell according to claim 12, characterized in that: The preparation method satisfies at least one of the following conditions: (1) The first oxygen source includes: water vapor; and / or, the second oxygen source includes: ozone; (2) The first aluminum source and the second aluminum source are of the same or different types, and / or the flow rates of the first aluminum source and the second aluminum source are the same or different; (3) The flow rate of the first aluminum source is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s; the flow rate of the first oxygen source is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s; (4) The flow rate of the second aluminum source is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s; the flow rate of the second oxygen source is 23 sccm to 35 sccm, and the time is 6.5 s to 15 s; (5) n is an integer from 12 to 35; (6) m is an integer from 12 to 35.

14. The method for preparing a solar cell according to claim 12, characterized in that: The preparation method further comprises: Before each introduction of the first oxygen source into the ALD chamber, a first purge of the gas source remaining after the previous step of reaction is performed using an inert gas; and / or, Before each introduction of the first aluminum source into the ALD chamber, a second purge of the gas source remaining after the previous step of reaction is performed using an inert gas; and / or, Before each introduction of the second oxygen source into the ALD chamber, a third purge is performed on the gas source remaining after the previous step of reaction; and / or, Before the second aluminum source is introduced into the ALD chamber each time, a fourth purge is performed on the gas source remaining after the previous step of reaction.

15. The method for preparing a solar cell according to claim 9, characterized in that: The first passivation layer further includes a first silicon oxide layer; before introducing water vapor into the ALD chamber at a preset temperature and a preset pressure and performing water pretreatment on one side of the first surface of the substrate, the preparation method further includes: The first silicon oxide layer is formed on one side of the first surface of the substrate.

16. The method for preparing a solar cell according to any one of claims 8 to 15, characterized in that: The solar cell further comprises a second passivation layer disposed on one side of the second surface of the substrate, the second passivation layer comprising: a second aluminum oxide layer; the H content in the second aluminum oxide layer decreases gradually in a direction away from the substrate; the preparation method further comprises: The second passivation layer is formed on the second surface of the substrate by adopting the same process as that of the first passivation layer.

Images