Solar cell and preparation method thereof

Abstract

The invention relates to the technical field of solar cells, in particular to a solar cell and a preparation method thereof, which can improve the passivation performance, the light utilization rate and the antireflection performance of the solar cell to the greatest extent while giving consideration to the ultraviolet attenuation resistance of the solar cell. A solar cell includes a substrate and a first optical adjustment layer; the first optical adjustment layer comprises a first sub-layer, a second sub-layer, a third sub-layer, a silicon oxynitride layer and a first silicon oxide layer which are sequentially stacked in the direction gradually away from the substrate; the refractive index of the first sub-layer is 2.3-2.42, the refractive index of the second sub-layer is 2.12-2.2, the refractive index of the third sub-layer is 2.0-2.1, and the thickness ratio of the first sub-layer to the second sub-layer to the third sub-layer is (10-15): (6-10): (16-24); the refractive index of the silicon oxynitride layer is 1.75-2.0, the refractive index of the first silicon oxide layer is 1.54-1.75, and the thickness ratio of the silicon nitride layer to the silicon oxynitride layer to the first silicon oxide layer is (32-49): (18-26): (10-15).

Description

Technical Field

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

[0002] UV (Ultraviolet) attenuation, especially in the field of photovoltaic cell technology, mainly refers to the phenomenon that the performance of solar cells deteriorates after exposure to ultraviolet radiation. This attenuation can be caused by a variety of factors, including aging of materials in solar cells, damage to surface passivation layers, etc. For example, in N-type cell technology, such as TOPCon (Tunnel Oxide Passivated Contact) cells, they show strong sensitivity to ultraviolet-induced degradation (UVID). Specifically, the EL (Electroluminescence) imaging of TOPCon components will have light and dark patches. Even components with better imaging will have a significant attenuation of power performance over time, far below expectations.

[0003] A research report shows that: At present, some mass-produced TOPCon modules may experience a power attenuation of 10% to 16% in the first three years. Relevant experiments have shown that in the case of unpackaged, the attenuation rate of TOPCon cells can reach -1% to -3% in the efficiency attenuation after ultraviolet exposure. This fully verifies the strong destructiveness of UV (Ultraviolet) to solar cells.

[0004] In order to reduce UV attenuation, it is currently mainly achieved by increasing the silicon-nitrogen ratio in the anti-reflection layer. However, studies have found that as the silicon-nitrogen ratio increases, although the anti-UV attenuation performance will be improved to a certain extent, the increase in the silicon-nitrogen ratio will cause a decrease in the field passivation performance. At the same time, unreasonable settings of the anti-reflection layer will also cause a decrease in light utilization and anti-reflection performance, which is not conducive to the effective improvement of the comprehensive performance of solar cells. Summary of the invention

[0005] Based on this, some embodiments of the present application provide a solar cell that can maximize the passivation performance, light utilization and anti-reflection performance of the solar cell while taking into account the solar cell's anti-ultraviolet attenuation ability, thereby effectively improving the overall performance of the solar cell.

[0006] In a first aspect, a solar cell is provided, comprising:

[0007] 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;

[0008] A passivation layer is disposed on one side of the first surface of the substrate;

[0009] A first optical adjustment layer is disposed on a side of the passivation layer away from the substrate, the first optical adjustment layer comprising: a silicon nitride layer, a silicon oxynitride layer and a first silicon oxide layer stacked in sequence in a direction gradually away from the substrate;

[0010] In a direction gradually away from the substrate, the silicon nitride layer includes: a first sublayer, a second sublayer and a third sublayer stacked in sequence;

[0011] The refractive index of the first sublayer is 2.3-2.42, the refractive index of the second sublayer is 2.12-2.2, the refractive index of the third sublayer is 2.0-2.1, and the thickness ratio of the first sublayer, the second sublayer and the third sublayer is (10-15): (6-10): (16-24);

[0012] The refractive index of the silicon oxynitride layer is 1.75-2.0, the refractive index of the first silicon oxide layer is 1.54-1.75, and the thickness ratio of the silicon nitride layer, the silicon oxynitride layer and the first silicon oxide layer is (32-49):(18-26):(10-15).

[0013] Optionally, the thickness of the silicon nitride layer is 32 nm to 49 nm, and the thickness of the first optical adjustment layer is 60 nm to 90 nm.

[0014] Optionally, the silicon-nitrogen ratio in the first sub-layer is 1:(3-4), the silicon-nitrogen ratio in the second sub-layer is 1:(5-6.2), and the silicon-nitrogen ratio in the third sub-layer is 1:(8-10).

[0015] Optionally, the silicon oxynitride layer includes: a fourth sublayer and a fifth sublayer sequentially stacked in a direction gradually away from the substrate;

[0016] The refractive index of the fourth sublayer is 1.85-2.0, the refractive index of the fifth sublayer is 1.75-1.86, and the thickness ratio of the fourth sublayer to the fifth sublayer is (6-10):(12-16).

[0017] Optionally, the thickness of the fourth sublayer is 6 nm to 10 nm, and the thickness of the fifth sublayer is 12 nm to 16 nm.

[0018] Optionally, the silicon-nitrogen ratio of the fourth sublayer is 1:(4-5), and the silicon-oxygen ratio is 1:(4.5-6); the silicon-nitrogen ratio of the fifth sublayer is 1:(6-7), and the silicon-oxygen ratio is 1:(9-11).

[0019] In a second aspect, a method for preparing a solar cell is provided, comprising:

[0020] Providing a substrate having a first surface and a second surface disposed opposite to each other along a thickness direction of the substrate;

[0021] 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;

[0022] forming a first optical adjustment layer on one side of the first surface of the substrate, wherein the first optical adjustment layer comprises a silicon nitride layer, a silicon oxynitride layer and a first silicon oxide layer stacked in sequence in a direction gradually away from the substrate;

[0023] In a direction gradually away from the substrate, the silicon nitride layer includes: a first sublayer, a second sublayer and a third sublayer stacked in sequence;

[0024] The refractive index of the first sublayer is 2.3-2.42, the refractive index of the second sublayer is 2.12-2.2, the refractive index of the third sublayer is 2.0-2.1, and the thickness ratio of the first sublayer, the second sublayer and the third sublayer is (10-15): (6-10): (16-24);

[0025] The refractive index of the silicon oxynitride layer is 1.75-2.0, the refractive index of the first silicon oxide layer is 1.54-1.75, and the thickness ratio of the silicon nitride layer, the silicon oxynitride layer and the first silicon oxide layer is (32-49):(18-26):(10-15).

[0026] Optionally, forming a silicon nitride layer on one side of the first surface of the substrate comprises:

[0027] introducing silane and ammonia into the reaction chamber;

[0028] The flow ratio of the silane and the ammonia is controlled to change from 1: (3-4) to 1: (5-6.2), and then to 1: (8-10), and the time for introducing the silane and the ammonia is controlled to change from 80s-100s to 120s-150s, and then to 180s-220s, and the temperature and pressure in the reaction chamber are controlled to remain unchanged, and the power in the reaction chamber is controlled to increase first and then decrease, so as to deposit the silicon nitride layer on one side of the first surface of the substrate.

[0029] Optionally, in the case of forming a silicon nitride layer,

[0030] When the flow ratio of the silane to the ammonia is 1:(3-4), the flow rate of the silane is 2000 sccm-2800 sccm, the flow rate of the ammonia is 6000 sccm-11200 sccm, the pressure in the reaction chamber is 1500 mTorr-1800 mTorr, the temperature is 480°C-550°C, and the RF power is 11000W-14000W;

[0031] When the flow ratio of the silane to the ammonia is 1:(5-6.2), the flow rate of the silane is 1100 sccm-1800 sccm, the flow rate of the ammonia is 5500 sccm-10800 sccm, the pressure in the reaction chamber is 1500 mTorr-1800 mTorr, the temperature is 480°C-550°C, and the RF power is 12000W-15000W;

[0032] When the flow ratio of the silane to the ammonia is 1:(8~10), the flow rate of the silane is 1000 sccm~1500 sccm, the flow rate of the ammonia is 8000 sccm~15000 sccm, the pressure in the reaction chamber is 1500mTorr~1800mTorr, the temperature is 480℃~550℃, and the RF power is 11000W~14000W.

[0033] Optionally, the silicon oxynitride layer includes a fourth sublayer and a fifth sublayer; forming the silicon oxynitride layer on one side of the first surface of the substrate includes:

[0034] introducing silane, ammonia and laughing gas into the reaction chamber;

[0035] The flow ratio of the silane, the ammonia and the laughing gas is controlled to change from 1: (4-5): (4.5-6) ​​to 1: (6-7): (9-11), and the time for introducing the silane, the ammonia and the laughing gas is controlled to change from 50s-80s to 150s-200s, and the temperature, pressure and power in the reaction chamber are controlled to remain unchanged, so as to deposit the silicon oxynitride layer on one side of the first surface of the substrate.

[0036] Optionally, when forming the silicon oxynitride layer,

[0037] When the flow ratio of the silane, the ammonia and the laughing gas is 1:(4-5):(4.5-6), the flow rate of the silane is 900 sccm-1200 sccm, the flow rate of the ammonia is 3600 sccm-6000 sccm, the flow rate of the laughing gas is 4050 sccm-7200 sccm, the pressure in the reaction chamber is 1200 mTorr-1500 mTorr, the temperature is 480°C-550°C, and the RF power is 12000W-15000W;

[0038] When the flow ratio of the silane, the ammonia and the laughing gas is 1: (6~7): (9~11), the flow rate of the silane is 700 sccm~1000 sccm, the flow rate of the ammonia is 4200 sccm~7000 sccm, the flow rate of the laughing gas is 6300 sccm~11000 sccm, the pressure in the reaction chamber is 1200mTorr~1500 mTorr, the temperature is 480℃~550℃, and the RF power is 12000W~15000W.

[0039] Optionally, forming a first silicon oxide layer on one side of the first surface of the substrate comprises:

[0040] introducing silane and laughing gas into the reaction chamber;

[0041] The flow ratio of the silane and the laughing gas is controlled to be 1:(12-15) and the time is 100s-150s.

[0042] Optionally, when forming the first silicon oxide layer, the flow rate of the silane is 700 sccm ~1000 sccm, the flow rate of the nitrous oxide is 8400 sccm ~15000 sccm, the pressure in the reaction chamber is 900 mTorr ~1200 mTorr, the temperature is 480°C ~550°C, and the RF power is 11000W ~14000W.

[0043] The beneficial technical effects of the solar cell and the preparation method thereof provided by the present application are as follows:

[0044] By reasonably setting the refractive index and thickness of the first sublayer, the second sublayer and the third sublayer, the absorptivity, reflectivity and light transmittance of light in different bands of sunlight passing through the first sublayer, the second sublayer and the third sublayer can be adjusted, so that the first sublayer, the second sublayer and the third sublayer can reduce the absorption and reflection of light in other bands except UV light while maximizing the absorption of UV light, thereby maximizing the incident light in other bands except UV light, improving the utilization rate of sunlight, and at the same time maintaining the appropriate silicon-nitrogen ratio of the first sublayer, the second sublayer and the third sublayer as much as possible, and balancing the dangling bond passivation effect and the field passivation effect on the substrate surface through the first sublayer, the second sublayer and the third sublayer with different thicknesses and different silicon-nitrogen ratios, thereby maximizing the passivation effect of the battery. Similarly, by reasonably setting the refractive index and thickness of the silicon oxynitride layer and the first silicon oxide layer, it is also possible to reduce the amount of UV light reaching the passivation layer as much as possible, and to increase the amount of incident light in other bands except UV light as much as possible, thereby maximizing the anti-reflection effect. This can take into account the anti-ultraviolet attenuation ability of the solar cell while maximizing the passivation performance, light utilization rate and anti-reflection performance of the solar cell, so that the solar cell has good comprehensive performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 A schematic diagram of the cross-sectional structure of a solar cell provided in an embodiment of the present application. DETAILED DESCRIPTION

[0046] 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.

[0047] 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.

[0048] 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.

[0049] “A and / or B” includes the following three combinations: A only, B only, and a combination of A and B.

[0050] Herein, unless otherwise specified, "one or more" means one or more than or equal to two.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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., and "multilayer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0059] 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.

[0060] In this article, the percentage content, unless otherwise specified, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and volume percentage for liquid-liquid mixing.

[0061] 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.

[0062] Herein, %(w / w) and wt% both refer to weight percentage, %(v / v) refers to volume percentage, and %(w / v) refers to mass volume percentage.

[0063] In this article, when it comes to temperature parameters, unless otherwise specified, both constant temperature treatment and treatment within a certain temperature range are allowed. The constant temperature treatment allows the temperature to fluctuate within the accuracy range of instrument control.

[0064] As used in this article, fill factor (FF) refers to the ratio of the actual maximum achievable power (Pm or Vmp * Jmp) to the theoretical (not actually achievable) power (Jsc * Voc). Therefore, FF can be determined by the following formula:

[0065] FF = (Vmp * Jmp) / (Jsc * Voc)

[0066] Where Jmp 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 J * V is the maximum value; Jsc 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.

[0067] As used herein, open circuit voltage (Voc) is the potential difference between the anode and cathode of the device with no external load connected.

[0068] As used herein, the power conversion efficiency (PCE) of a solar cell refers to the percentage of power converted from absorbed light into electrical energy.

[0069] In view of the problem that the improvement of the anti-ultraviolet attenuation ability of solar cells in the related art may cause the light utilization rate, anti-reflection performance and passivation performance of solar cells to decrease, thereby being unfavorable for the effective improvement of the comprehensive performance of solar cells, the specific implementation methods of the present application are described as follows:

[0070] 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, a passivation layer 12 and a first optical adjustment layer 13; 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, the passivation layer 12 is arranged on one side of the first surface of the substrate 11, and the first optical adjustment layer 13 is arranged on the side of the passivation layer 12 away from the substrate 11.

[0071] The solar cell may be a silicon-based solar cell. For example, 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) cell.

[0072] 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. At this time, the passivation layer 12 and the first optical adjustment layer 13 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 an IBC cell, 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. At this time, the passivation layer 12 and the first optical adjustment layer 13 can be arranged on the back side of the solar cell and cover the emitter and the back field.

[0073] In the following embodiments, the solar cell is an N-type TOPCon as an example. Those skilled in the art will understand that the present application is also applicable to the case where the solar cell is a PERC and IBC cell, and this does not affect the protection scope of the present application.

[0074] 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.

[0075] In some embodiments, the substrate 11 may be an N-type substrate, and in this case, the emitter 111 is a P-type emitter.

[0076] In some embodiments, the first optical adjustment layer 13 includes: a silicon nitride layer 131 , a silicon oxynitride layer 132 , and a first silicon oxide layer 133 , which are sequentially stacked in a direction gradually away from the substrate 11 .

[0077] It should be noted that, in the silicon nitride layer 131 , as the Si content increases, the refractive index of the silicon nitride layer 131 increases, and the UV absorption capacity becomes stronger, which can reduce the UV light reaching the passivation layer 12 , increase UV stability, and improve the ability to resist UV attenuation.

[0078] At the same time, from the perspective of surface passivation, as the Si content increases, the Si-Si bonds and Si-H bonds increase, which is conducive to saturating the dangling bonds inside and on the surface of the substrate 11, thereby facilitating H to enter the substrate 11 for body passivation under subsequent annealing conditions. However, if the silicon nitride layer 131 is too silicon-rich, there will be a transition from N as the back bond in the Si-H bond to silicon as the back bond, and the dangling bonds of Si with N as the back bond form positively charged defect centers (K + ), the weakening of N back bonds in the silicon-rich silicon nitride layer will reduce K + , the fixed charge is reduced, thereby weakening the surface field passivation effect of the silicon nitride layer 131.

[0079] At the same time, different thicknesses of the silicon nitride layer 131 with a certain refractive index will also have different effects on the absorption and reflection of UV light and light in other bands except UV light. Therefore, the silicon nitride layer 131's absorption capacity for UV light, absorption and reflection capacity for light in other bands except UV light, and passivation performance are all related to the structure of the silicon nitride layer, its refractive index, silicon-nitrogen ratio, etc., and there is a contradiction between the optimal performance.

[0080] Similar to the above-mentioned silicon nitride layer 131, the silicon oxynitride layer 132 and the first silicon oxide layer 133 included in the first optical adjustment layer 13 also have the above-mentioned contradiction. Therefore, how to set the structure of the first optical adjustment layer 13 and match the refractive index and thickness of each layer to maximize the passivation performance, light utilization rate and anti-reflection performance of the solar cell while taking into account the anti-ultraviolet attenuation ability of the solar cell, has become a technical problem that needs to be solved urgently.

[0081] Based on the above, in some embodiments of the present application, along a direction gradually away from the substrate 11, the silicon nitride layer 131 includes: a first sublayer 131a, a second sublayer 131b and a third sublayer 131c stacked in sequence;

[0082] The refractive index of the first sublayer 131a is 2.3-2.42, the refractive index of the second sublayer 131b is 2.1-2.2, the refractive index of the third sublayer 131c is 2.0-2.1, and the thickness ratio of the first sublayer, the second sublayer and the third sublayer is (10-15): (6-10): (16-24);

[0083] The refractive index of the silicon oxynitride layer 132 is 1.75-2.0, the refractive index of the first silicon oxide layer 133 is 1.6-1.75, and the thickness ratio of the silicon nitride layer, the silicon oxynitride layer and the first silicon oxide layer is (32-49):(18-26):(10-15).

[0084] In the solar cell provided in the embodiment of the present application, by reasonably setting the refractive index and thickness of the first sublayer 131a, the second sublayer 131b, and the third sublayer 131c, the absorptivity, reflectivity, and light transmittance of light of different wavelength bands of sunlight passing through the first sublayer 131a, the second sublayer 131b, and the third sublayer 131c can be adjusted, so that the first sublayer 131a, the second sublayer 131b, and the third sublayer 131c can reduce the absorption of UV light while maximizing the absorption of UV light. The absorption and reflection of light in other bands except UV light can increase the incident light in other bands except UV light as much as possible, improve the utilization rate of sunlight, and at the same time maintain the appropriate silicon-nitrogen ratio of the first sublayer 131a, the second sublayer 131b and the third sublayer 131c as much as possible. The dangling bond passivation effect and the field passivation effect on the surface of the substrate 11 are balanced by the first sublayer 131a, the second sublayer 131b and the third sublayer 131c with different thicknesses and different silicon-nitrogen ratios, so as to improve the passivation effect of the battery as much as possible.

[0085] Similarly, by reasonably setting the refractive index and thickness of the silicon oxynitride layer 132 and the first silicon oxide layer 133, it is also possible to reduce the amount of UV light reaching the passivation layer 12 as much as possible, and increase the amount of incident light in other bands except UV light as much as possible, thereby maximizing the anti-reflection effect. This can take into account the anti-ultraviolet attenuation ability of the solar cell while maximizing the passivation performance, light utilization rate and anti-reflection performance of the solar cell, so that the solar cell has good comprehensive performance.

[0086] In some embodiments, the thickness of the silicon nitride layer 131 is 32 nm to 49 nm, and the thickness of the first optical adjustment layer 13 is 60 nm to 90 nm.

[0087] In these embodiments, by setting the thickness of the silicon nitride layer 131 to 32nm~49nm, the silicon nitride layer 131 can absorb UV light to the maximum extent while minimizing the absorption and reflection of light in other bands except UV light, thereby maximizing the utilization rate of sunlight. Similarly, by setting the thickness of the first optical adjustment layer 13 to 60nm~90nm, and combining the thickness ratios of the silicon nitride layer 131, the silicon oxynitride layer 132 and the first silicon oxide layer 133, the entire first optical adjustment layer 13 can absorb UV light to the maximum extent while minimizing the absorption and reflection of light in other bands except UV light, thereby maximizing the utilization rate of sunlight.

[0088] In some embodiments, the silicon-nitrogen ratio in the first sub-layer 131 a is 1:(3-4), the silicon-nitrogen ratio in the second sub-layer 131 b is 1:(5-6.2), and the silicon-nitrogen ratio in the third sub-layer 131 c is 1:(8-10).

[0089] In these embodiments, the silicon-nitrogen ratio in the first sublayer 131a is within the range of 1:(3-4), which can balance the surface passivation performance and field passivation performance of the first sublayer 131a to the greatest extent, and maximize the passivation effect of the first sublayer 131a on the substrate 11. At the same time, by reasonably setting the silicon-nitrogen ratios of the first sublayer 131a, the second sublayer 131b, and the third sublayer 131c, the dangling bond passivation effect and the field passivation effect of each layer on the surface of the substrate 11 can be balanced, and the passivation effect of the silicon nitride layer on the solar cell can be maximized. By reasonably setting the silicon-nitrogen ratio of the first sublayer 131a, the second sublayer 131b and the third sublayer 131c, the first sublayer 131a, the second sublayer 131b and the third sublayer 131c can be kept within their respective refractive index ranges, which makes it easy for the first sublayer 131a, the second sublayer 131b and the third sublayer 131c to adjust the absorption and reflection of sunlight at the atomic level, thereby achieving the technical effect of absorbing UV light to the greatest extent while minimizing the absorption and reflection of light in other bands except UV light, thereby maximizing the utilization rate of sunlight.

[0090] In some embodiments, the silicon oxynitride layer 132 includes: a fourth sublayer 132 a and a fifth sublayer 132 b sequentially stacked in a direction gradually away from the substrate 11 ;

[0091] The refractive index of the fourth sublayer 132a is 1.85-2.0, the refractive index of the fifth sublayer 132b is 1.75-1.86, and the thickness ratio of the fourth sublayer to the fifth sublayer is (6-10):(12-16).

[0092] In these embodiments, by setting the silicon oxynitride layer 132 as a fourth sublayer 132a and a fifth sublayer 132b with a gradient refractive index and reasonably setting their respective thicknesses, the absorption and reflection of light in different bands of sunlight passing through the silicon oxynitride layer 132 can be adjusted to the greatest extent, so that the silicon oxynitride layer 132 can maximize the absorption and adjust the absorption rate of UV light while minimizing the absorption and reflection of light in other bands except UV light, thereby maximizing the utilization rate of sunlight.

[0093] In some embodiments, the thickness of the fourth sublayer 132a is 6 nm to 10 nm, and the thickness of the fifth sublayer 132b is 12 nm to 16 nm.

[0094] In these embodiments, by setting the thickness of the fourth sublayer 132a and the fifth sublayer 132b within the above range, the absorption and reflection of light in different bands can be further adjusted, thereby maximizing the absorption rate of UV light and minimizing the absorption and reflection of light in other bands except UV light, thereby maximizing the utilization rate of sunlight.

[0095] In some embodiments, the silicon-nitrogen ratio of the fourth sublayer 132 a is 1:(4-5), and the silicon-oxygen ratio is 1:(4.5-6), and the silicon-nitrogen ratio of the fifth sublayer 132 b is 1:(6-7), and the silicon-oxygen ratio is 1:(9-11).

[0096] In these embodiments, similar to the corresponding relationship between the silicon-nitrogen ratio of the first sublayer 131a, the second sublayer 131b and the third sublayer 131c and their respective refractive indices and passivation effects, the silicon-nitrogen ratio and silicon-oxygen ratio in the fourth sublayer 132a and the fifth sublayer 132b also have a regulating effect on their respective refractive indices and passivation effects. By limiting the silicon-nitrogen ratio and silicon-oxygen ratio of the fourth sublayer 132a and the fifth sublayer 132b, the passivation performance of the solar cell and the absorption and reflection performance of the solar light in different wavelength bands can be balanced to the greatest extent, thereby maximizing the passivation performance, UV attenuation resistance and sunlight utilization rate of the solar cell.

[0097] In some embodiments, the passivation layer 12 includes: a second silicon oxide layer 121 and a first aluminum oxide layer 122 which are sequentially stacked in a direction gradually away from the substrate 11 .

[0098] In these embodiments, the second silicon oxide layer 121 can passivate the silicon dangling bonds on the surface of the substrate 11, thereby improving the passivation effect of the solar cell. The H in the first aluminum oxide layer 122 can diffuse to the surface of the substrate 11 and into the body of the substrate 11 during the annealing process, thereby passivating the silicon dangling bonds on the surface and in the body of the substrate 11 and improving the passivation effect.

[0099] In some embodiments, the solar cell may be an N-type TOPCon cell. In this case, the solar cell further comprises: a tunneling oxide layer 14, a doped polysilicon layer 15 and a second optical adjustment layer 16 sequentially arranged on the second surface of the substrate 11. The tunneling oxide layer 14 and the doped polysilicon layer 15 together constitute a passivation contact structure, which can allow the majority carriers to tunnel into the doped polysilicon layer 15 while blocking the minority carriers from recombination, thereby increasing the open circuit voltage and short circuit current of the solar cell. The second optical adjustment layer 16 may include a plurality of silicon nitride layers with gradually decreasing refractive indexes stacked in sequence in a direction gradually away from the substrate 11, and the second optical adjustment layer 16 plays the role of passivation and anti-reflection.

[0100] In some embodiments, Figure 1 As shown, the solar cell may further include: a first electrode 17 disposed on the side of the first optical adjustment layer 13 away from the substrate 11, the first electrode 17 passing through the first optical adjustment layer 13 and the passivation layer 12 and electrically connected to the emitter, and / or, a second electrode 18 disposed on the side of the second optical adjustment layer 16 away from the substrate 11, the second electrode 18 passing through the second optical adjustment layer 16 and electrically connected to the doped polysilicon layer 15.

[0101] In a second aspect, some embodiments of the present application provide a method for preparing a solar cell, the method comprising:

[0102] S11), providing a substrate, wherein the substrate has a first surface and a second surface arranged opposite to each other along a thickness direction thereof;

[0103] 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.

[0104] S12), 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;

[0105] 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.

[0106] S13), a passivation layer and a first optical adjustment layer are sequentially formed on one side of the first surface of the substrate, the first optical adjustment layer comprises a silicon nitride layer, a silicon oxynitride layer and a first silicon oxide layer sequentially stacked in a direction gradually away from the substrate; in a direction gradually away from the substrate, the silicon nitride layer comprises: a first sublayer, a second sublayer and a third sublayer sequentially stacked; wherein the refractive index of the first sublayer is 2.3~2.42, the refractive index of the second sublayer is 2.1~2.2, the refractive index of the third sublayer is 2.0~2.1, and the ratio of the thickness of the first sublayer, the second sublayer and the third sublayer is (10~15):(6~10):(16~24); the refractive index of the silicon oxynitride layer is 1.75~2.0, the refractive index of the first silicon oxide layer is 1.6~1.75, and the ratio of the thickness of the first sublayer, the second sublayer and the third sublayer is (10~15):(6~10):(16~24).

[0107] The silicon nitride layer, silicon oxynitride layer and first silicon oxide layer may be prepared in the same cavity by the same process, or may be prepared in different cavities by different processes, which is not specifically limited here.

[0108] In some embodiments, forming a silicon nitride layer on the first surface side of the substrate includes:

[0109] introducing silane and ammonia into the reaction chamber;

[0110] The flow ratio of silane and ammonia is controlled to change from 1: (3-4) to 1: (5-6.2), and then to 1: (8-10), and the time for introducing silane and ammonia is controlled to change from 70s-100s to 45s-75s, and then to 130s-190s, and the temperature and pressure in the reaction chamber are controlled to remain unchanged, and the power in the reaction chamber is controlled to increase first and then decrease, so as to deposit a silicon nitride layer on one side of the first surface of the substrate.

[0111] In these embodiments, PECVD (Plasma Enhanced Chemical Vapor Deposition) can be used to form a silicon nitride layer; wherein, by controlling the flow ratio and introduction time of silane and ammonia, the silicon-nitrogen ratio and thickness in the silicon nitride layer can be adjusted, thereby obtaining a first sublayer, a second sublayer, and a third sublayer with silicon-nitrogen ratios, refractive indexes, and thicknesses that change in sequence. For example, when the deposition starts, the flow ratio of silane and ammonia is controlled to be 1: (3-4) for 70s-100s, and the first sublayer can be deposited, and then, the flow ratio of silane and ammonia is adjusted to 1: (5-6.2) for 45s-75s, and the second sublayer can be deposited on the first sublayer, and then, the flow ratio of silane and ammonia is adjusted to 1: (8-10) for 130s-190s, and the third sublayer can be deposited on the second sublayer.

[0112] By controlling the temperature and pressure in the reaction chamber to remain constant, and controlling the power in the reaction chamber to first increase and then decrease, it is also possible to effectively improve the deposition uniformity and density of the first, second and third sublayers while appropriately increasing the deposition rate of the second sublayer to improve efficiency.

[0113] In some embodiments, the difference between the power when depositing the second sublayer and the power when depositing the first sublayer may be 1000W-2000W, and the power when depositing the third sublayer and the power when depositing the first sublayer may be the same.

[0114] In some embodiments, when the flow ratio of silane to ammonia is 1:(3-4), the flow rate of silane is 2000 sccm-2800 sccm, the flow rate of ammonia is 6000 sccm-11200 sccm, the pressure in the reaction chamber is 1500 mTorr-1800 mTorr, the temperature is 480°C-550°C, and the RF power is 11000W-14000W;

[0115] When the flow ratio of silane to ammonia is 1:(5~6.2), the flow rate of silane is 1100sccm~1800sccm, the flow rate of ammonia is 5500sccm~10800sccm, the pressure in the reaction chamber is 1500mTorr~1800mTorr, the temperature is 480℃~550℃, and the RF power is 12000W~15000W;

[0116] When the flow ratio of silane to ammonia is 1:(8~10), the flow rate of silane is 1000 sccm~1500 sccm, the flow rate of ammonia is 8000 sccm~15000 sccm, the pressure in the reaction chamber is 1500mTorr~1800 mTorr, the temperature is 480℃~550℃, and the RF power is 11000W~14000W.

[0117] In some embodiments, the silicon oxynitride layer includes a fourth sublayer and a fifth sublayer; forming the silicon oxynitride layer on one side of the first surface of the substrate includes:

[0118] introducing silane, ammonia and laughing gas into the reaction chamber;

[0119] The flow ratio of silane, ammonia and nitrous oxide is controlled to change from 1: (4-5): (4.5-6) ​​to 1: (6-7): (9-11), and the time for introducing silane, ammonia and nitrous oxide is controlled to change from 45s-75s to 100s-130s, and the temperature, pressure and power in the reaction chamber are controlled to remain unchanged to deposit a silicon oxynitride layer on one side of the first surface of the substrate.

[0120] In these embodiments, PECVD (Plasma Enhanced Chemical Vapor Deposition) can be used to form a silicon nitride layer; wherein, by controlling the flow ratio and introduction time of silane, ammonia and nitrous oxide, the silicon-nitrogen ratio, silicon-oxygen ratio and thickness in the silicon oxynitride layer can be adjusted, thereby obtaining a fourth sublayer and a fifth sublayer in which the silicon-nitrogen ratio, silicon-oxygen ratio, refractive index and thickness change sequentially.

[0121] For example, at the beginning of deposition, the flow ratio of silane, ammonia and nitrous oxide is controlled to be 1: (4~5): (4.5~6) and the time is 45s~75s, so that the fourth sublayer can be deposited. Then, the flow ratio of silane, ammonia and nitrous oxide is adjusted to 1: (6~7): (9~11) and the time is controlled to be 100s~130s, so that the fifth sublayer can be deposited on the fourth sublayer.

[0122] In some embodiments, when the above-mentioned silicon oxynitride layer is formed, when the flow ratio of silane, ammonia and laughing gas is 1: (4-5): (4.5-6), the flow rate of silane is 900 sccm ~ 1200 sccm, the flow rate of ammonia is 3600 sccm ~ 6000 sccm, the flow rate of laughing gas is 4050 sccm ~ 7200 sccm, the pressure in the reaction chamber is 1200mTorr ~ 1500mTorr, the temperature is 480 ° C ~ 550 ° C, and the RF power is 12000W ~ 15000W; when the flow ratio of silane, ammonia and laughing gas is 1: (6-7): (9-11), the flow rate of silane is 700 sccm ~ 1000 sccm, the flow rate of ammonia is 4200 sccm ~ 7000 sccm, and the flow rate of laughing gas is 6300 sccm ~ 11000 sccm. sccm, the pressure in the reaction chamber is 1200mTorr~1500mTorr, the temperature is 480℃~550℃, and the RF power is 12000W~15000W.

[0123] In some embodiments, forming a first silicon oxide layer on a first surface side of a substrate includes:

[0124] introducing silane and laughing gas into the reaction chamber;

[0125] The flow ratio of silane and nitrous oxide was controlled to be 1:(12~15) and the time was 80s~125s.

[0126] In these embodiments, PECVD (Plasma Enhanced Chemical Vapor Deposition) can be used to form a silicon nitride layer; wherein, by controlling the flow ratio and introduction time of silane and nitrous oxide, the silicon-oxygen ratio, refractive index and thickness of the first silicon oxide layer can be controlled, thereby obtaining a first silicon oxide layer with a thickness of 10nm~15nm and a refractive index of 1.54~1.75.

[0127] In some embodiments, when forming a first silicon oxide layer, the flow rate of silane is 700 sccm ~1000 sccm, the flow rate of nitrous oxide is 8400 sccm ~15000 sccm, the pressure in the reaction chamber is 900 mTorr ~1200 mTorr, the temperature is 480℃~550℃, and the RF power is 11000W~14000W.

[0128] In some embodiments, forming a passivation layer on the first surface side of the substrate includes:

[0129] forming a stacked second silicon oxide layer and an aluminum oxide layer in sequence on one side of the first surface of the substrate;

[0130] Among them, PECVD (Plasma Enhanced Chemical Vapor Deposition) or ALD (Atomic Layer Deposition) can be used to deposit the second silicon oxide layer and the aluminum oxide layer on one side of the first surface of the substrate, and the specific preparation method is not limited here.

[0131] In some embodiments, PECVD (Plasma Enhanced Chemical Vapor Deposition) may be used to sequentially form a stacked second silicon oxide layer and an aluminum oxide layer on one side of the first surface of the substrate.

[0132] 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.

[0133] 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.

[0134] Example 1

[0135] The method for preparing the solar cell provided in Example 1 is as follows:

[0136] (1) Clean and texture the N-type silicon wafer, form a P-type emitter on the front side of the N-type silicon wafer, and form a tunneling oxide layer and an N-type doped polysilicon layer on the back side of the N-type silicon wafer;

[0137] (2) depositing a second silicon oxide layer and an aluminum oxide layer on the front side of the N-type silicon wafer on which the tunneling oxide layer and the polysilicon layer are formed; specifically, introducing silane and laughing gas into the PECVD chamber to deposit the second silicon oxide layer, and introducing trimethylaluminum and laughing gas to deposit the aluminum oxide layer, the deposition temperature is 350° C., the deposition time of the second silicon oxide layer is 70 seconds, the thickness is 2 nm, and the deposition time of the aluminum oxide layer is 100 seconds, the thickness is 5 nm;

[0138] (3) Depositing a high refractive index silicon nitride layer on an N-type silicon wafer having a second silicon oxide layer and an aluminum oxide layer deposited thereon; specifically, introducing silane and ammonia into the PECVD chamber, the flow rate of ammonia is 8000 sccm, the flow rate of silane is 2500 sccm, the pressure in the chamber is 1700 mTorr, the RF power is 13000 W, the refractive index of the film layer is 2.39, the thickness is 12 nm, and the time is 80 s;

[0139] (4) Depositing a silicon nitride layer with a second-highest refractive index on the surface of the silicon nitride layer with a high refractive index. Specifically, introducing silane and ammonia into the PECVD chamber, the flow rate of ammonia is 9300sccm, the flow rate of silane is 1500sccm, the pressure in the chamber is 1700mTorr, the RF power is 14000W, the refractive index of the film layer is 2.13, the thickness is 8nm, and the time is 60s;

[0140] (5) Depositing a silicon nitride layer with a lower refractive index on the surface of the silicon nitride layer with the second highest refractive index. Specifically, introducing silane and ammonia into the PECVD chamber, the flow rate of ammonia is 11700sccm, the flow rate of silane is 1300sccm, the pressure in the chamber is 1700mTorr, the RF power is 13000W, the refractive index of the film layer is 2.06, the thickness is 20nm, and the time is 160s;

[0141] (6) Depositing a silicon oxynitride layer with a higher refractive index on the surface of the silicon nitride layer with a lower refractive index. Specifically, introducing silane, ammonia and nitrous oxide into the PECVD chamber, the flow rate of ammonia is 4950 sccm, the flow rate of silane is 1100 sccm, the flow rate of nitrous oxide is 6600 sccm, the pressure in the chamber is 1400 mTorr, the RF power is 14000 W, the refractive index of the film layer is 1.9, the thickness is 8 nm, and the time is 60 s;

[0142] (7) depositing a silicon oxynitride layer with a lower refractive index on the surface of the silicon oxynitride layer with a higher refractive index. Specifically, introducing silane, ammonia and nitrous oxide into the PECVD chamber, the flow rate of ammonia is 5400 sccm, the flow rate of silane is 800 sccm, the flow rate of nitrous oxide is 8000 sccm, the pressure in the chamber is 1400 mTorr, the RF power is 14000 W, the refractive index of the film layer is 1.8, the thickness is 14 nm, and the time is 110 s;

[0143] (8) depositing a first silicon oxide layer on the surface of the silicon oxynitride layer with a lower refractive index. Specifically, introducing silane and nitrous oxide into the PECVD chamber, the flow rate of silane is 800 sccm, the flow rate of nitrous oxide is 10400 sccm, the pressure in the chamber is 1100 mTorr, the RF power is 13000 W, the refractive index of the film layer is 1.6, the thickness is 12 nm, and the time is 100 s;

[0144] (9) Depositing a silicon nitride film layer with a reduced refractive index gradient on the back side of the N-type silicon wafer forming the tunnel oxide layer and the polysilicon layer, with a thickness of 80 nm;

[0145] (10) After the deposition is completed, the metal electrode is screen printed.

[0146] Example 2

[0147] 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:

[0148] In step (3), the flow rate of ammonia is 6000 sccm, the flow rate of silane is 2000 sccm, the gas pressure is 1500 mTorr, the RF power is 11000 W, the refractive index is 2.42, the thickness is 10 nm, and the time is 70 s;

[0149] In step (4), the flow rate of ammonia is 5500 sccm, the flow rate of silane is 1100 sccm, the gas pressure is 1500 mTorr, the RF power is 12000 W, the refractive index is 2.2, the thickness is 6 nm, and the time is 45 s;

[0150] In step (5), the flow rate of ammonia is 8000 sccm, the flow rate of silane is 1000 sccm, the gas pressure is 1500 mTorr, the RF power is 11000 W, the refractive index is 2.1, the thickness is 16 nm, and the time is 130 s;

[0151] In step (6), the flow rate of ammonia is 3600 sccm, the flow rate of silane is 900 sccm, the flow rate of nitrous oxide is 4050 sccm, the pressure in the chamber is 1200 mTorr, the RF power is 12000 W, the refractive index of the film is 2.0, the thickness is 6 nm, and the time is 45 s;

[0152] In step (7), the flow rate of ammonia is 4200 sccm, the flow rate of silane is 700 sccm, the flow rate of nitrous oxide is 6300 sccm, the pressure in the chamber is 1200 mTorr, the RF power is 12000 W, the refractive index of the film is 1.86, the thickness is 12 nm, and the time is 100 s;

[0153] In step (8), the flow rate of ammonia is 700 sccm, the flow rate of nitrous oxide is 8400 sccm, the pressure in the chamber is 900 mTorr, the RF power is 11000 W, the refractive index of the film is 1.75, the thickness is 10 nm, and the time is 80 s.

[0154] Example 3

[0155] 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:

[0156] In step (3), the flow rate of ammonia is 11200 sccm, the flow rate of silane is 2800 sccm, the pressure in the chamber is 1800 mTorr, the RF power is 14000 W, the refractive index of the film is 2.3, the thickness is 15 nm, and the time is 100 s;

[0157] In step (4), the flow rate of ammonia is 10800 sccm, the flow rate of silane is 1800 sccm, the gas pressure is 1800 mTorr, the RF power is 15000 W, the refractive index is 2.12, the thickness is 10 nm, and the time is 75 s;

[0158] In step (5), the flow rate of ammonia is 15000 sccm, the flow rate of silane is 1500 sccm, the gas pressure is 1800 mTorr, the RF power is 14000 W, the refractive index is 2.0, the thickness is 24 nm, and the time is 190 s;

[0159] In step (6), the flow rate of ammonia is 6000 sccm, the flow rate of silane is 1200 sccm, the flow rate of nitrous oxide is 7200 sccm, the pressure in the chamber is 1500 mTorr, the RF power is 15000 W, the refractive index of the film is 1.85, the thickness is 10 nm, and the time is 75 s;

[0160] In step (7), the flow rate of ammonia is 7000 sccm, the flow rate of silane is 1000 sccm, the flow rate of nitrous oxide is 11000 sccm, the pressure in the chamber is 1500 mTorr, the RF power is 15000 W, the refractive index of the film is 1.75, the thickness is 16 nm, and the time is 130 s;

[0161] In step (8), the flow rate of ammonia is 1000 sccm, the flow rate of nitrous oxide is 15000 sccm, the pressure in the chamber is 1200 mTorr, the RF power is 14000 W, the refractive index of the film is 1.54, the thickness is 15 nm, and the time is 125 s;

[0162] Example 4

[0163] The method for preparing the solar cell in Example 4 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0164] In step (3), the film thickness is 10 nm;

[0165] In step (4), the film thickness is 10 nm;

[0166] In step (5), the film thickness is 24 nm;

[0167] In step (6), the film thickness is 10 nm;

[0168] In step (7), the film thickness is 16 nm;

[0169] In step (8), the film thickness is 15 nm.

[0170] Example 5

[0171] The method for preparing the solar cell in Example 5 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0172] In step (3), the film thickness is 15 nm;

[0173] In step (4), the film thickness is 6 nm;

[0174] In step (5), the film thickness is 16 nm;

[0175] In step (6), the film thickness is 6 nm;

[0176] In step (7), the film thickness is 12 nm;

[0177] In step (8), the film thickness is 10 nm.

[0178] Comparative Example 1

[0179] 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:

[0180] In step (4), the film thickness is 5 nm;

[0181] In step (5), the film thickness is 14 nm.

[0182] Comparative Example 2

[0183] 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:

[0184] In step (4), the film thickness is 12 nm;

[0185] In step (5), the film thickness is 14 nm.

[0186] Comparative Example 3

[0187] The method for preparing the solar cell in Comparative Example 3 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0188] In step (4), the film thickness is 5 nm;

[0189] In step (5), the film thickness is 26 nm.

[0190] Comparative Example 4

[0191] The method for preparing the solar cell in Comparative Example 4 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0192] In step (4), the film thickness is 12 nm;

[0193] In step (5), the film thickness is 26 nm.

[0194] Comparative Example 5

[0195] The method for preparing the solar cell in Comparative Example 5 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0196] In step (3), the film thickness is 8 nm.

[0197] Comparative Example 6

[0198] The method for preparing the solar cell in Comparative Example 6 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0199] In step (3), the film thickness is 17 nm.

[0200] Comparative Example 7

[0201] The method for preparing the solar cell in Comparative Example 7 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0202] In step (6), the film thickness is 4 nm;

[0203] In step (7), the film thickness is 11 nm.

[0204] Comparative Example 8

[0205] The method for preparing the solar cell in Comparative Example 8 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0206] In step (6), the film thickness is 6 nm;

[0207] In step (7), the film thickness is 10 nm.

[0208] Comparative Example 9

[0209] The method for preparing the solar cell in Comparative Example 9 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0210] In step (6), the film thickness is 12 nm;

[0211] In step (7), the film thickness is 18 nm.

[0212] Comparative Example 10

[0213] The method for preparing the solar cell in Comparative Example 10 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0214] In step (6), the film thickness is 6 nm;

[0215] In step (7), the film thickness is 10 nm;

[0216] In step (8), the film thickness is 8 nm.

[0217] Comparative Example 11

[0218] The method for preparing the solar cell in Comparative Example 11 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0219] In step (6), the film thickness is 10 nm;

[0220] In step (7), the film thickness is 18 nm;

[0221] In step (8), the film thickness is 18 nm.

[0222] Test Case

[0223] 1. The performance of the solar cells provided in Examples 1 to 5 and Comparative Examples 1 to 11 was tested. The specific test results are shown in Table 1 below:

[0224] Table 1

[0225]

[0226] In Table 1, ΔPCE represents the relative value of PCE of each embodiment and comparative example compared with Comparative Example 8 under the same test conditions, which is numerically equal to the difference between PCE of each embodiment and comparative example and PCE of Comparative Example 8, ΔVoc represents the relative value of Voc of each embodiment and comparative example compared with Comparative Example 8 under the same test conditions, which is numerically equal to the difference between Voc of each embodiment and comparative example and Voc of Comparative Example 8, ΔJsc represents the relative value of Jsc of each embodiment and comparative example compared with Comparative Example 8 under the same test conditions, which is numerically equal to the difference between Jsc of each embodiment and comparative example and Jsc of Comparative Example 8, ΔFF represents the relative value of FF of each embodiment and comparative example compared with Comparative Example 8 under the same test conditions, which is numerically equal to the difference between FF of each embodiment and comparative example and FF of Comparative Example 8.

[0227] It can be seen from Table 1 that: taking Comparative Example 8 as a variation reference, as the thickness of each silicon nitride layer with different refractive indices, the thickness of the silicon oxynitride layer and the thickness of the first silicon oxide layer increase or decrease, the efficiency, open circuit voltage, short circuit current and fill factor of the solar cell will be affected. This shows that the efficiency, open circuit voltage, short circuit current and fill factor of the solar cell are all related to the refractive index, nitrogen-silicon ratio and thickness of each film layer.

[0228] Through research, it was found that: when the refractive index of the silicon nitride layer, the silicon oxynitride layer and the first silicon oxide layer is controlled to be 2.39, 2.13, 2.06, 1.9, 1.8 and 1.6 in the direction gradually approaching the N-type silicon wafer, as the thickness of each film layer changes within a certain range, the photoelectric conversion efficiency of the solar cell can be effectively improved; and as the thickness of each film layer exceeds its respective thickness range, the photoelectric conversion efficiency of the solar cell decreases. This shows that when the refractive index of each film layer is constant, by adjusting the thickness of each film layer to match, the light utilization rate, anti-reflection performance and passivation performance of the solar cell can be comprehensively adjusted while taking into account the UV resistance of the solar cell, thereby improving the efficiency of the solar cell as a whole, especially improving the comprehensive performance of the solar cell under long-term illumination.

[0229] 2. The solar cells provided in Examples 1 to 5 and Comparative Examples 1 to 11 were subjected to UV30 ultraviolet attenuation tests. The test results are shown in Table 2 below.

[0230] Table 2

[0231]

[0232] In Table 2, the PCE after attenuation is relative to the PCE before attenuation. The PCE before attenuation is shown as ΔPCE in Table 1, which is a relative value relative to the actual PCE of Comparative Example 8 before attenuation. The PCE after attenuation is also calculated based on the actual PCE of Comparative Example 8 before attenuation, which is a relative value relative to the actual PCE of Comparative Example 8 before attenuation, and is numerically equal to the difference between the actual PCE after attenuation and the actual PCE of Comparative Example 8 before attenuation. The attenuation rate can be calculated using (actual PCE after attenuation-actual PCE before attenuation) / actual PCE before attenuation.

[0233] The PCE values ​​before and after attenuation of each embodiment and comparative example 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).

[0234] In Table 2, the test method of UV30 ultraviolet attenuation test is: the PCE, Voc, Jsc and FF of the solar cell before and after ultraviolet light irradiation are tested respectively, and the respective attenuation rates are calculated using (value after ultraviolet light irradiation - value before ultraviolet light irradiation) / value before ultraviolet light irradiation.

[0235] The UV30 UV attenuation test was conducted under the following UV irradiation conditions: the front side of the solar cell was exposed to a total UV irradiation of 30 kWh / m2 with a wavelength range of 280 nm to 400 nm. 2 Under the conditions, the temperature of the solar cell is maintained in the range of 60±5℃ for ultraviolet light irradiation.

[0236] It can be seen from Table 2 that after the solar cells provided by Examples 1 to 5 and Comparative Examples 1 to 11 were subjected to UV30 ultraviolet attenuation tests, it was found that the PCE after attenuation of Example 1 and Examples 3 to 5 was positive compared with the PCE after attenuation of Comparative Examples 1 to 11, and only Example 2 was negative, and the attenuation rates of Examples 1 to 2 were all relatively small, indicating that the embodiments of the present application can maximize the comprehensive performance of solar cells while maintaining a relatively high anti-ultraviolet attenuation performance, and can extend the service life of solar cells.

[0237] 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.

[0238] 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 passivation layer is disposed on one side of the first surface of the substrate; A first optical adjustment layer is disposed on a side of the passivation layer away from the substrate, the first optical adjustment layer comprising: a silicon nitride layer, a silicon oxynitride layer and a first silicon oxide layer stacked in sequence in a direction gradually away from the substrate; In a direction gradually away from the substrate, the silicon nitride layer includes: a first sublayer, a second sublayer and a third sublayer stacked in sequence; The refractive index of the first sublayer is 2.3-2.42, the refractive index of the second sublayer is 2.12-2.2, the refractive index of the third sublayer is 2.0-2.1, and the thickness ratio of the first sublayer, the second sublayer and the third sublayer is (10-15): (6-10): (16-24); The refractive index of the silicon oxynitride layer is 1.75-2.0, the refractive index of the first silicon oxide layer is 1.54-1.75, and the thickness ratio of the silicon nitride layer, the silicon oxynitride layer and the first silicon oxide layer is (32-49):(18-26):(10-15).

2. The solar cell according to claim 1, characterized in that: The thickness of the silicon nitride layer is 32nm-49nm, and the thickness of the first optical adjustment layer is 60nm-90nm.

3. The solar cell according to claim 1, characterized in that The silicon-nitrogen ratio in the first sub-layer is 1:(3-4), the silicon-nitrogen ratio in the second sub-layer is 1:(5-6.2), and the silicon-nitrogen ratio in the third sub-layer is 1:(8-10).

4. The solar cell according to claim 1, characterized in that The silicon oxynitride layer comprises: a fourth sublayer and a fifth sublayer sequentially stacked in a direction gradually away from the substrate; The refractive index of the fourth sublayer is 1.85-2.0, the refractive index of the fifth sublayer is 1.75-1.86, and the ratio of the thickness of the fourth sublayer to that of the fifth sublayer is (6-10):(12-16).

5. The solar cell according to claim 4, characterized in that: The thickness of the fourth sublayer is 6 nm to 10 nm, and the thickness of the fifth sublayer is 12 nm to 16 nm.

6. The solar cell according to claim 4, characterized in that: The silicon-nitrogen ratio of the fourth sublayer is 1:(4-5), and the silicon-oxygen ratio is 1:(4.5-6). The silicon-nitrogen ratio of the fifth sublayer is 1:(6-7), and the silicon-oxygen ratio is 1:(9-11).

7. 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; A passivation layer and a first optical adjustment layer are sequentially formed on one side of the first surface of the substrate, wherein the first optical adjustment layer comprises a silicon nitride layer, a silicon oxynitride layer and a first silicon oxide layer which are sequentially stacked in a direction gradually away from the substrate; In a direction gradually away from the substrate, the silicon nitride layer includes: a first sublayer, a second sublayer and a third sublayer stacked in sequence; The refractive index of the first sublayer is 2.3-2.42, the refractive index of the second sublayer is 2.12-2.2, the refractive index of the third sublayer is 2.0-2.1, and the thickness ratio of the first sublayer, the second sublayer and the third sublayer is (10-15): (6-10): (16-24); The refractive index of the silicon oxynitride layer is 1.75-2.0, the refractive index of the first silicon oxide layer is 1.54-1.75, and the thickness ratio of the silicon nitride layer, the silicon oxynitride layer and the first silicon oxide layer is (32-49): (18-26): (10-15).

8. The preparation method according to claim 7, characterized in that: Forming a silicon nitride layer on one side of the first surface of the substrate comprises: introducing silane and ammonia into the reaction chamber; The flow ratio of the silane and the ammonia is controlled to change from 1: (3-4) to 1: (5-6.2), and then to 1: (8-10), and the time for introducing the silane and the ammonia is controlled to change from 70s-100s to 45s-75s, and then to 130s-190s, and the temperature and pressure in the reaction chamber are controlled to remain unchanged, and the power in the reaction chamber is controlled to increase first and then decrease, so as to deposit the silicon nitride layer on one side of the first surface of the substrate.

9. The preparation method according to claim 8, characterized in that: In the case of forming a silicon nitride layer, When the flow ratio of the silane to the ammonia is 1:(3-4), the flow rate of the silane is 2000 sccm-2800 sccm, the flow rate of the ammonia is 6000 sccm-11200 sccm, the pressure in the reaction chamber is 1500 mTorr-1800 mTorr, the temperature is 480°C-550°C, and the RF power is 11000W-14000W; When the flow ratio of the silane to the ammonia is 1:(5-6.2), the flow rate of the silane is 1100 sccm-1800 sccm, the flow rate of the ammonia is 5500 sccm-10800 sccm, the pressure in the reaction chamber is 1500 mTorr-1800 mTorr, the temperature is 480°C-550°C, and the RF power is 12000W-15000W; When the flow ratio of the silane to the ammonia is 1:(8~10), the flow rate of the silane is 1000 sccm~1500 sccm, the flow rate of the ammonia is 8000 sccm~15000 sccm, the pressure in the reaction chamber is 1500mTorr~1800mTorr, the temperature is 480℃~550℃, and the RF power is 11000W~14000W.

10. The preparation method according to claim 7, characterized in that: The silicon oxynitride layer includes a fourth sublayer and a fifth sublayer; and the silicon oxynitride layer is formed on one side of the first surface of the substrate, including: introducing silane, ammonia and laughing gas into the reaction chamber; The flow ratio of the silane, the ammonia and the laughing gas is controlled to change from 1: (4-5): (4.5-6) ​​to 1: (6-7): (9-11), and the time for introducing the silane, the ammonia and the laughing gas is controlled to change from 45s-75s to 100s-130s, and the temperature, pressure and power in the reaction chamber are controlled to remain unchanged, so as to deposit the silicon oxynitride layer on one side of the first surface of the substrate.

11. The preparation method according to claim 10, characterized in that: In the case of forming the silicon oxynitride layer, When the flow ratio of the silane, the ammonia and the laughing gas is 1:(4-5):(4.5-6), the flow rate of the silane is 900 sccm-1200 sccm, the flow rate of the ammonia is 3600 sccm-6000 sccm, the flow rate of the laughing gas is 4050 sccm-7200 sccm, the pressure in the reaction chamber is 1200 mTorr-1500 mTorr, the temperature is 480°C-550°C, and the RF power is 12000W-15000W; When the flow ratio of the silane, the ammonia and the laughing gas is 1: (6~7): (9~11), the flow rate of the silane is 700 sccm~1000 sccm, the flow rate of the ammonia is 4200 sccm~7000 sccm, the flow rate of the laughing gas is 6300 sccm~11000 sccm, the pressure in the reaction chamber is 1200mTorr~1500 mTorr, the temperature is 480℃~550℃, and the RF power is 12000W~15000W.

12. The preparation method according to claim 7, characterized in that: Forming a first silicon oxide layer on one side of the first surface of the substrate comprises: introducing silane and laughing gas into the reaction chamber; The flow ratio of the silane and the laughing gas is controlled to be 1:(12-15) and the time is 80s-125s.

13. The preparation method according to claim 12, characterized in that: When forming the first silicon oxide layer, the flow rate of the silane is 700 sccm ~1000 sccm, the flow rate of the nitrous oxide is 8400 sccm ~15000 sccm, the pressure in the reaction chamber is 900 mTorr ~1200 mTorr, the temperature is 480°C ~550°C, and the RF power is 11000W ~14000W.

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