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 an aluminum oxide layer, the fixed negative charge density of the aluminum oxide layer is larger than or equal to 4.0 * 10 < 12 > Qf / cm < 2 >, and the surface defect state density of the aluminum oxide layer is smaller than or equal to 0.9 * 10 < 12 > eV / cm < 2 >.

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] UV degradation, especially in photovoltaic cell technology, mainly refers to the phenomenon that the performance of solar cells degrades after exposure to ultraviolet (UV) radiation. This degradation 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 technologies, such as TOPCon cells, they show strong sensitivity to ultraviolet induced degradation (UVID). This means that there may be performance risks in the early adoption of these technologies, especially when the cells are exposed to high-intensity UV environments. UV will degrade the cell passivation performance and seriously damage the power of the cell components.

[0003] The damage of UV to the battery mainly lies in the damage to the passivation performance of the battery. However, how to further improve the passivation performance of solar cells to resist the attenuation caused by UV light has become a technical problem that needs to be solved urgently. Summary of the invention

[0004] Based on this, some embodiments of the present application provide a solar cell and a method for preparing the same, so as 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 comprises: an aluminum oxide layer, wherein the fixed negative charge density of the first aluminum oxide layer is greater than or equal to 4.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer is less than or equal to 0.9×10 12 eV / cm 2 .

[0009] Optionally, the fixed negative charge density of the aluminum oxide layer is 4.2×10 12 Qf / cm 2 ~7.0×10 12 Qf / cm 2, and the surface defect state density of the aluminum oxide layer is 0.5×10 12 eV / cm 2 ~0.9×10 12 eV / cm 2 .

[0010] Optionally, the solar cell further comprises: a first anti-reflection layer disposed on a side of the first passivation layer away from the substrate;

[0011] The first anti-reflection layer comprises a silicon nitride layer, and the silicon-nitrogen ratio of the silicon nitride layer decreases gradually in a direction away from the substrate.

[0012] Optionally, the silicon nitride layer includes: a first sublayer closest to the substrate and a second sublayer farthest from the substrate;

[0013] The refractive index of the first sublayer is 2.4-2.5, and the thickness is 32 nm-38 nm; the refractive index of the second sublayer is 1.9-2.0, and the thickness is 12 nm-18 nm.

[0014] Optionally, the silicon nitride layer further includes: a third sublayer disposed between the first sublayer and the second sublayer;

[0015] The refractive index of the third sublayer is 2.1-2.3, and the thickness is 22 nm-36 nm.

[0016] Optionally, the thickness uniformity of the silicon nitride layer satisfies: D even Less than 5%;

[0017] Among them, D even =(D max -D min ) / (D max +D min ), D max represents the thickness of the silicon nitride layer at the maximum position, D min It represents the thickness of the silicon nitride layer at the minimum thickness position.

[0018] Optionally, the thickness uniformity of the silicon nitride layer satisfies: D even It is 2.5%~3.8%.

[0019] Optionally, for the silicon nitride layer, a difference between a thickness at a maximum thickness position and a thickness at a minimum thickness position is 5 nm to 10 nm.

[0020] Optionally, the first anti-reflection layer further includes a silicon oxynitride layer and a first silicon oxide layer stacked in sequence on a side of the silicon nitride layer away from the substrate; a carrier recombination velocity of a surface of the first silicon oxide layer away from the substrate is less than or equal to 40 cm / s.

[0021] Optionally, a carrier recombination velocity of a surface of the first silicon oxide layer facing away from the substrate is 25 cm / s to 35 cm / s.

[0022] In a second aspect, a method for preparing a solar cell is provided, comprising:

[0023] Providing a substrate, the substrate comprising a first surface and a second surface disposed opposite to each other along a thickness direction thereof;

[0024] 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;

[0025] A first passivation layer is formed on one side of the first surface of the substrate, wherein the first passivation layer comprises: an aluminum oxide layer, wherein the fixed negative charge density of the aluminum oxide layer is greater than or equal to 4.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer is less than or equal to 0.9×10 12 eV / cm 2 ;

[0026] The step of forming a first passivation layer on one side of the first surface of the substrate comprises:

[0027] Depositing an aluminum oxide film layer on one side of the first surface of the substrate;

[0028] Under the protection of inert gas, the aluminum oxide film layer is annealed to prepare the aluminum oxide layer; wherein the annealing temperature is 550° C. to 590° C. and the annealing time is 15 min to 20 min.

[0029] Optionally, the solar cell further comprises a first anti-reflection layer disposed on a side of the first passivation layer away from the substrate, the first anti-reflection layer comprising: a silicon nitride layer, wherein a silicon-nitrogen ratio of the silicon nitride layer decreases gradually in a direction away from the substrate; the preparation method further comprises:

[0030] A silicon source and a nitrogen source are introduced into the reaction chamber, and the flow ratio of the silicon source to the nitrogen source is controlled to gradually decrease, and the silicon nitride layer is deposited on a side of the first passivation layer away from the substrate.

[0031] Optionally, the silicon nitride layer includes a first sublayer closest to the substrate and a second sublayer farthest from the substrate, the silicon source is selected from silane, and the nitrogen source is selected from ammonia;

[0032] When depositing the first sublayer, the flow ratio of the silicon source to the nitrogen source is 1:3.5~1:4, and the introduction time is 80 s~150 s; when depositing the second sublayer, the flow ratio of the silicon source to the nitrogen source is 1:10~1:10.5, and the introduction time is 110 s~160 s.

[0033] Optionally, the preparation method satisfies at least one of the following conditions:

[0034] (1) When depositing the first sub-layer, the flow rate of the silicon source is 2000 sccm~3000 sccm, and the flow rate of the nitrogen source is 8000 sccm~11000 sccm; when depositing the second sub-layer, the flow rate of the silicon source is 1000 sccm~1500 sccm, and the flow rate of the nitrogen source is 10000 sccm~16000 sccm;

[0035] (2) When depositing the first sublayer, the deposition temperature is 510°C~530°C, the deposition pressure is 800mTor~1000mTorr, and the deposition power is 7000W~9000W; when depositing the second sublayer, the deposition temperature is 510°C~530°C, the deposition pressure is 1400 mTorr~1800mTorr, and the deposition power is 11000W~15000W.

[0036] Optionally, the silicon nitride layer further comprises a third sublayer disposed between the first sublayer and the second sublayer, the silicon source is selected from silane, and the nitrogen source is selected from ammonia;

[0037] When depositing the third sub-layer, the flow ratio of the silicon source to the nitrogen source is 1:6-1:7, and the introduction time is 60s-110s.

[0038] Optionally, the preparation method satisfies at least one of the following conditions:

[0039] (1) When depositing the third sub-layer, the flow rate of the silicon source is 2000 sccm to 3000 sccm, and the flow rate of the nitrogen source is 12000 sccm to 18000 sccm;

[0040] (2) When depositing the third sub-layer, the deposition temperature is 510° C. to 530° C., the deposition pressure is 1500 mTorr to 1800 mTorr, and the deposition power is 13000 W to 15000 W.

[0041] The beneficial effects of the solar cell and the preparation method thereof are as follows:

[0042] By controlling the fixed negative charge density of the aluminum oxide layer to be greater than or equal to 4.0×10 12 Qf / cm 2 , the surface defect state density is less than or equal to 0.9×10 12 eV / cm 2 , while taking into account the high fixed negative charge density of the aluminum oxide layer, its surface defect state density can be reduced, the aluminum oxide layer can be given better field passivation and chemical passivation effects, and the performance stability of the solar cell can be improved, thereby generally improving the passivation effect and anti-ultraviolet induced degradation ability of the aluminum oxide layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 A schematic diagram of the cross-sectional structure of a solar cell provided in an embodiment of the present application.

[0044] Reference numerals:

[0045] 11. substrate; 12. first passivation layer; 111-emitter; 121. aluminum oxide layer; 13. first anti-reflection layer; 131. first sublayer; 132. second sublayer; 133. third sublayer; 134. silicon oxynitride layer; 135. first silicon oxide layer; 122. second silicon oxide layer; 14. second passivation layer; 15. second anti-reflection layer; 16. tunneling oxide layer; 17. doped polysilicon layer; 18. first electrode; 19. second electrode. 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] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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:

[0060] FF = (Vmp * Jmp) / (Jsc * Voc)

[0061] 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.

[0062] As used herein, open circuit voltage (Voc) is the potential difference between the anode and cathode of the device with no external load connected.

[0063] 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).

[0064] 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.

[0065] In view of the technical problem that the passivation performance of solar cells in the related art cannot resist the attenuation caused by UV light, the specific implementation methods of the present application are described as follows:

[0066] 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.

[0067] 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.

[0068] 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 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. In this case, the first passivation layer 12 can be arranged on the back side of the solar cell and cover the emitter and the back field.

[0069] 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.

[0070] 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.

[0071] In some embodiments, the substrate 11 may be an N-type silicon substrate, and in this case, the emitter 111 is a P-type emitter.

[0072] In some embodiments, the first passivation layer 12 includes an aluminum oxide layer 121. The fixed negative charge density of the aluminum oxide layer 121 is greater than or equal to 4.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer 121 is less than or equal to 0.9×10 12 eV / cm 2 .

[0073] Fixed negative charge density refers to the amount of fixed negative charge per unit volume or unit area in a certain substance. Here, it refers to the amount of fixed negative charge per unit area in the aluminum oxide layer. The greater the fixed negative charge density, the stronger the aluminum oxide layer can repel minority electrons, causing them to gather in a specific area, thereby effectively adjusting the electric field distribution in the aluminum oxide layer and enhancing the field passivation effect.

[0074] In addition, the increase in fixed negative charge density helps promote the separation of photogenerated carriers. In photocatalytic or photovoltaic materials, electron-hole pairs are generated when light shines on the material. Fixed negative charges can repel photogenerated electrons, separate them from holes, and reduce the recombination probability of carriers, thereby improving the photocatalytic activity or photoelectric conversion efficiency of the material, which is also a manifestation of enhanced field passivation effect.

[0075] Surface defect state density refers to the number of defect states per unit area and per unit energy on the surface of a material. These defect states can include dangling bonds, vacancies, impurities, etc. They can have a significant impact on the physical and chemical properties of the (substrate) material.

[0076] For example, as the surface defect state density increases, the carrier recombination centers in the aluminum oxide layer can be increased, because: the surface defect state can capture carriers, increase the probability of carrier recombination, and thus reduce the carrier mobility and conductivity of the (substrate) material. For example, in solar cells, high surface defect state density may lead to a decrease in solar cell performance, such as a decrease in the photoelectric conversion efficiency of the solar cell.

[0077] In addition, this surface defect state can also form a potential barrier on the material surface, affecting the injection and extraction of carriers, thereby affecting the turn-on voltage, current-voltage characteristics, etc. of the solar cell.

[0078] At the same time, surface defects can also serve as active sites to promote the separation and transfer of photogenerated carriers, improve photocatalytic activity, and change the surface chemical activity of the aluminum oxide layer to promote chemical reactions, which can easily lead to a reduction in material stability.

[0079] Among them, the fixed negative charge density can be measured by using the Corona probe corona electret technology. Specifically, the fixed negative charge density can be measured by using the capacitance measurement method. The capacitance change of the electret material (here refers to the aluminum oxide layer 121) before and after the electret is measured, and the fixed negative charge density of the aluminum oxide layer 121 can be calculated based on the relationship formula between capacitance and charge density and the measured capacitance change value.

[0080] The surface defect state density can be measured and calculated using the light absorption spectrum. For example, the light absorption spectrum can measure the absorption intensity of a material to light of different wavelengths. Surface defect states will cause changes in light absorption. Information on the surface defect state density can be obtained by analyzing the light absorption spectrum.

[0081] In the solar cell provided in the embodiment of the present application, by controlling the fixed negative charge density of the aluminum oxide layer 121 to be greater than or equal to 4.0×10 12 Qf / cm 2 , the surface defect state density is less than or equal to 0.9×10 12 eV / cm 2 , while taking into account the high fixed negative charge density of the aluminum oxide layer 121, its surface defect state density can be reduced, and the aluminum oxide layer 121 can be given better field passivation effect and chemical passivation effect, thereby improving the performance stability of the solar cell, thereby generally improving the passivation effect and anti-ultraviolet induced degradation capability of the aluminum oxide layer 121.

[0082] It is found through testing that the aluminum oxide layer 121 has a high ability to resist UV attenuation and can effectively reduce the UV attenuation of the solar cell.

[0083] In some embodiments, the fixed negative charge density of the aluminum oxide layer 121 is 4.2×10 12 Qf / cm 2 ~7.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer 121 is 0.5×10 12 eV / cm 2 ~0.9×10 12 eV / cm 2 .

[0084] In these embodiments, the fixed negative charge density of the aluminum oxide layer 121 is moderate, which can effectively improve the field passivation performance and will not attract holes to cause recombination, thereby not having an adverse effect on the number of effective carriers and the photoelectric performance of the solar cell. The surface defect state density of the aluminum oxide layer 121 is low, which can effectively improve the chemical passivation effect of the aluminum oxide layer 121.

[0085] In some embodiments, the solar cell further includes: a first anti-reflection layer 13 disposed on the side of the first passivation layer 12 away from the substrate; the first anti-reflection layer 13 includes a silicon nitride layer, and the silicon-nitrogen ratio of the silicon nitride layer decreases gradually in a direction away from the substrate.

[0086] In these embodiments, since the first anti-reflection layer 13 includes a silicon nitride layer, the silicon-nitrogen ratio in the silicon nitride layer decreases gradually in the direction away from the substrate 11. Therefore, the closer the silicon nitride layer is to the substrate 11, the more silicon-hydrogen bonds there are, which can effectively reduce silicon dangling bonds and improve the passivation effect. At the same time, the silicon-nitrogen ratio in the silicon nitride layer close to the substrate 11 is relatively high, which can give the silicon nitride layer close to the substrate 11 a higher refractive index, thereby improving the absorption effect of UV light and reducing the impact of UV light reaching the aluminum oxide layer 121 on the passivation performance of the aluminum oxide layer 121. As the distance from the substrate 11 increases, the silicon-nitrogen ratio in the silicon nitride layer decreases, and a nitrogen-rich silicon nitride film with a relatively low refractive index can be formed. By effectively controlling the refractive index of the entire silicon nitride layer, the absorption of short waves (such as UV light) by the silicon nitride layer can be increased, thereby reducing UV attenuation.

[0087] In some embodiments, the silicon nitride layer includes: a first sublayer 131 closest to the substrate 11 and a second sublayer 132 farthest from the substrate; wherein the first sublayer 131 has a refractive index of 2.4~2.5 and a thickness of 32 nm~38nm, and the second sublayer 132 has a refractive index of 1.9~2.0 and a thickness of 12 nm~18nm.

[0088] In these embodiments, by controlling the refractive index of the first sublayer 131 to be 2.4-2.5 and the thickness to be 32 nm-38 nm, the silicon nitride layer can absorb UV better and reduce the absorption and reflection of light in other bands, thereby increasing the probability of light in other bands reaching the substrate 11 and reducing the probability of UV reaching the aluminum oxide layer, thereby increasing the utilization rate of sunlight of the solar cell and reducing UV attenuation. By controlling the refractive index of the second sublayer 132 to be 1.9-2.0 and the thickness to be 12-18 nm, the absorption of light by the second sublayer 132 can be effectively reduced, thereby facilitating more sunlight to enter the lower substrate 11, thereby increasing the utilization rate of light by the solar cell.

[0089] Among them, there is no specific limitation on the number of sublayers and the refractive index values ​​between the first sublayer 131 and the second sublayer 132. All sublayer numbers and refractive indices that can absorb UV in sunlight passing through the second sublayer 132 and allow light of other bands to pass through are within the protection scope of this application.

[0090] For example, there may be multiple sublayers between the first sublayer 131 and the second sublayer 132, and the thickness of each layer is relatively thin. By controlling the refractive index of each layer to change in a certain proportion, UV light in sunlight can be absorbed and light of other bands can be allowed to pass as much as possible, thereby maximizing the ultraviolet absorption of the silicon nitride layer and minimizing the absorption of light of other bands by the silicon nitride layer, thereby maximizing the sunlight utilization rate of the solar cell and reducing UV attenuation.

[0091] In some embodiments, the silicon nitride layer further includes: a third sublayer 133 disposed between the first sublayer 131 and the second sublayer 132. The third sublayer 133 has a refractive index of 2.1 to 2.3 and a thickness of 22 nm to 36 nm.

[0092] In these embodiments, by controlling the refractive index and thickness of the third sublayer 133 within the above range, the absorption of UV by the silicon nitride layer can be maximized while reducing the absorption and reflection of light in other bands while ensuring fewer process steps, thereby improving the utilization of light by the solar cell while minimizing UV attenuation.

[0093] In some embodiments, the thickness uniformity of the silicon nitride layer satisfies: even Less than 5%; among them, D even =(D max -D min ) / (D max +D min ), D max Denotes the thickness of the silicon nitride layer at the maximum position, D min Indicates the thickness of the silicon nitride layer at the location where the thickness is minimum.

[0094] In some embodiments, the thickness uniformity of the silicon nitride layer satisfies: even It is 2.5%~3.8%.

[0095] In these embodiments, the silicon nitride layer is more dense and uniform, thereby further improving the anti-UV attenuation capability of the solar cell and improving the UV reliability of the solar cell.

[0096] In some embodiments, for the silicon nitride layer, a difference between a thickness at a maximum thickness position and a thickness at a minimum thickness position is 5 nm-10 nm.

[0097] In these embodiments, the silicon nitride layer is more dense and uniform, and its UV resistance can be improved.

[0098] In some embodiments, the first anti-reflection layer 13 further includes a silicon oxynitride layer 134 and a first silicon oxide layer 135 which are sequentially stacked and disposed on a side of the silicon nitride layer away from the substrate 11 .

[0099] In these embodiments, the refractive index of the silicon oxynitride layer 134 can be smaller than the refractive index of the second sublayer 132, and the refractive index of the first silicon oxide layer 135 is smaller than the refractive index of the silicon oxynitride layer 134, so as to improve the anti-reflection effect of the first anti-reflection layer 13 and improve the light utilization rate.

[0100] In some embodiments, the silicon oxynitride layer 134 has a thickness of 5 nm to 8 nm and a refractive index of 1.7 to 1.8.

[0101] In these embodiments, the silicon oxynitride layer 134 can further play an anti-reflection effect.

[0102] In some embodiments, the first silicon oxide layer 135 has a thickness of 10 nm to 12 nm and a refractive index of 1.5 to 1.6.

[0103] In some embodiments, a carrier recombination velocity of a surface of the first silicon oxide layer 135 facing away from the substrate 11 is less than or equal to 40 cm / s.

[0104] Among them, the carrier recombination rate is a physical quantity that indicates how fast electrons and holes recombine on the surface of semiconductor materials. The greater the carrier recombination rate, the easier it is for electrons and holes to recombine on the surface, which will affect the performance of solar cells, such as reducing the photoelectric conversion efficiency. In general, the greater the surface defect state density, the greater the surface carrier recombination rate. The measurement of the carrier recombination rate can also be used as a means of characterizing the size of the surface defect state density.

[0105] In the present application, the minority carrier lifetime measurement method can be used to measure the minority carrier lifetime of the surface of the first silicon oxide layer 135 away from the substrate 11, and then the surface carrier recombination rate is calculated according to the relevant theoretical model to obtain the carrier recombination rate of the surface of the first silicon oxide layer 135 away from the substrate 11.

[0106] The minority carrier lifetime measurement method may be a photoconductivity decay method, which uses laser irradiation to generate photogenerated carriers in a sample, and then measures the decay time of the photogenerated carriers to determine the minority carrier lifetime. When the photoconductivity decay method is used to measure the minority carrier lifetime of the surface of the first silicon oxide layer 135 away from the substrate 11, the solar cell with the first silicon oxide layer 135 prepared may be placed under a laser, and the laser may be used to irradiate the surface side of the first silicon oxide layer 135 away from the substrate 11.

[0107] In these embodiments, the carrier recombination rate of the surface of the first silicon oxide layer 135 facing away from the substrate 11 is less than or equal to 40 cm / s, which can effectively reduce the carrier recombination of the solar cell, thereby effectively improving the photoelectric conversion efficiency.

[0108] In some embodiments, a carrier recombination velocity of the first silicon oxide layer 135 at a surface facing away from the substrate 11 is 25 cm / s to 35 cm / s.

[0109] In these embodiments, the carrier recombination rate of the surface of the silicon oxide layer 135 facing away from the substrate 11 is relatively low, which can effectively improve the photoelectric conversion efficiency of the solar cell.

[0110] In some embodiments, the first passivation layer 12 further includes: a second silicon oxide layer 122 ; the second silicon oxide layer 122 is disposed on a side of the aluminum oxide layer 121 close to the substrate 11 .

[0111] In these embodiments, the oxygen in the second 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.

[0112] In some embodiments, Figure 1 As shown, the solar cell further includes: a second passivation layer 14 and a second anti-reflection layer 15 disposed on one side of the second surface of the substrate 11 .

[0113] In these embodiments, the second passivation layer 14 may be a back passivation layer, and the second anti-reflection layer 15 may be a back anti-reflection layer. The back passivation layer and the back anti-reflection layer may be prepared simultaneously or sequentially with the front passivation layer and the front anti-reflection layer using the same process, or may be formed separately using different processes.

[0114] 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 16 and a doped polysilicon layer 17 sequentially disposed on the second surface of the substrate 11, and a second passivation layer 14 disposed on the side of the doped polysilicon layer 17 away from the substrate 11. The tunneling oxide layer 16 and the doped polysilicon layer 17 together constitute a passivation contact structure, which can allow majority carriers to tunnel into the doped polysilicon layer 17 while blocking minority carriers from recombination, thereby improving the open circuit voltage and short circuit current of the solar cell.

[0115] In some embodiments, Figure 1 As shown, the solar cell may further include: a first electrode 18 disposed on the side of the first anti-reflection layer 13 away from the substrate 11 , and / or a second electrode 19 disposed on the side of the second anti-reflection layer 15 away from the substrate 11 .

[0116] In a second aspect, some embodiments of the present application provide a method for preparing a solar cell, the method comprising:

[0117] S11), providing a substrate, the substrate comprising a first surface and a second surface arranged opposite to each other along a thickness direction thereof;

[0118] 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.

[0119] 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;

[0120] 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.

[0121] S13), forming a first passivation layer on one side of the first surface of the substrate, the first passivation layer comprising: an aluminum oxide layer, the fixed negative charge density of the aluminum oxide layer is greater than or equal to 4.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer is less than or equal to 0.9×10 12 eV / cm 2 .

[0122] In some embodiments, S12), forming a first passivation layer on one side of the first surface of the substrate, comprising:

[0123] S121), depositing an aluminum oxide film layer on one side of the first surface of the substrate;

[0124] The aluminum oxide film layer may be deposited on one side of the first surface of the substrate by using PECVD (Plasma Enhanced Chemical Vapor Deposition) or ALD (Atomic Layer Deposition), and the specific preparation method is not limited here.

[0125] PECVD uses active substances generated by plasma to promote chemical reactions, causing precursor gases to decompose and deposit into thin films on the substrate. High-energy electrons in the plasma can excite and decompose precursor molecules, reducing the temperature required for the reaction.

[0126] ALD is based on self-limiting surface reactions. Precursor gases are alternately introduced into the reaction chamber, depositing only one layer of atoms or molecules at a time. The precursor reacts with the active sites on the substrate surface to form chemical bonds, and then the excess precursor and reaction byproducts are exhausted from the reaction chamber.

[0127] Both PECVD and ALD methods can be used to deposit an aluminum oxide film layer on the first surface of the substrate.

[0128] S122), under the protection of inert gas, annealing the aluminum oxide film layer to prepare the aluminum oxide layer; wherein the annealing temperature is 550° C. to 590° C., and the annealing time is 15 min to 20 min.

[0129] It should be noted that, microscopically, defects in the first passivation layer, such as vacancies, dislocations, impurity atoms, etc., will affect the distribution and density of fixed negative charges, and defects can serve as charge capture centers to attract or fix negative charges. Therefore, by optimizing the process conditions of the first passivation layer, such as temperature, pressure, deposition rate, etc., the generation of defects can be reduced, thereby optimizing and balancing the surface defect state density and fixed negative charge density of the first passivation layer.

[0130] In these embodiments, after the aluminum oxide layer is deposited, the surface defect state density of the aluminum oxide layer can be effectively reduced by controlling the annealing temperature to 550°C~590°C and the time to 15min~20min, while at the same time increasing the fixed negative charge density on the surface of the aluminum oxide layer. This can optimize and adjust the chemical passivation caused by the surface defect state density and the field passivation effect caused by the fixed negative charge density to a certain extent, thereby improving the passivation performance and resistance to UV induced attenuation.

[0131] In some embodiments, when annealing the aluminum oxide film layer, the preparation method further includes introducing hydrogen into the reaction chamber.

[0132] In these embodiments, the aluminum oxide film layer can be hydrogenated by introducing hydrogen during high-temperature annealing, and the H content of the aluminum oxide layer can be adjusted under the condition of an annealing temperature of 550°C to 590°C, thereby achieving a better passivation effect. For example, at this annealing temperature, it can also promote the formation of Si-H bonds on the substrate surface and reduce dangling bonds on the substrate surface.

[0133] In some embodiments, the solar cell further comprises a first anti-reflection layer disposed on a side of the first passivation layer away from the substrate, the first anti-reflection layer comprising: a silicon nitride layer, wherein the silicon-nitrogen ratio of the silicon nitride layer decreases gradually in a direction away from the substrate; the preparation method further comprises:

[0134] A silicon source and a nitrogen source are introduced into the reaction chamber, and the flow ratio of the silicon source and the nitrogen source is controlled to gradually decrease, and a silicon nitride layer is deposited on the side of the first passivation layer away from the substrate.

[0135] In these embodiments, PECVD can be used to deposit a silicon nitride layer. By controlling the flow ratio of the silicon source and the nitrogen source, a silicon nitride layer with a silicon-nitrogen ratio that gradually decreases in a direction away from the substrate can be prepared, thereby obtaining a first anti-reflection layer with a refractive index that gradually decreases in a direction away from the substrate.

[0136] In some embodiments, the silicon nitride layer includes a first sublayer closest to the substrate and a second sublayer farthest from the substrate, the silicon source is selected from silane, and the nitrogen source is selected from ammonia;

[0137] When depositing the first sublayer, the flow ratio of the silicon source to the nitrogen source is 1:3.5~1:4, and the introduction time is 80s~150s; when depositing the second sublayer, the flow ratio of the silicon source to the nitrogen source is 1:10~1:10.5, and the introduction time is 110s~160s.

[0138] In these embodiments, the silicon-nitrogen ratio can be adjusted by controlling the flow ratio of the silicon source and the nitrogen source, and the thickness of the first sublayer and the second sublayer can be adjusted by controlling the introduction time, so that the UV absorption capacity and anti-reflection capacity of the silicon nitride layer and the absorption capacity of light in other bands can be adjusted, thereby minimizing the absorption of light in other bands by the silicon nitride layer and improving the UV absorption capacity and anti-reflection capacity.

[0139] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0140] (1) When depositing the first sub-layer, the flow rate of the silicon source is 2000 sccm ~3000 sccm, and the flow rate of the nitrogen source is 8000 sccm ~11000 sccm. When depositing the second sub-layer, the flow rate of the silicon source is 1000 sccm ~1500 sccm, and the flow rate of the nitrogen source is 10000 sccm ~16000 sccm;

[0141] (2) When depositing the first sublayer, the deposition temperature is 510°C~530°C, the deposition pressure is 800mTor~1000mTorr, and the deposition power is 7000W~9000W; when depositing the second sublayer, the deposition temperature is 510°C~530°C, the deposition pressure is 1400 mTorr~1800mTorr, and the deposition power is 11000W~15000W.

[0142] In these embodiments, by controlling the flow rates of the silicon source and the nitrogen source, the molar ratio of silicon and nitrogen can be limited, so that the silicon-nitrogen ratio in the first sublayer and the second sublayer can be controlled, and then the refractive index of the first sublayer and the second sublayer can be controlled. By controlling the deposition temperature of the first sublayer to 510-530°C, the compactness of the first sublayer can be effectively improved, while too high a temperature will reduce the compactness of the silicon nitride film (such as the first sublayer). At the same time, by controlling the deposition power of the first sublayer to 7000W-9000W, low-power ion bombardment can reduce damage to the aluminum oxide layer and avoid a reduction in the passivation effect. By controlling the deposition pressure of the first sublayer to 800 mTorr-1000mTorr, low-pressure deposition can balance the increased deposition rate caused by high-temperature deposition, thereby improving the thickness uniformity of the first sublayer, and then improving the thickness uniformity of the entire silicon nitride layer.

[0143] In some embodiments, the silicon nitride layer also includes a third sublayer disposed between the first sublayer and the second sublayer. In this case, the silicon source is selected from silane and the nitrogen source is selected from ammonia. When depositing the third sublayer, the flow ratio of the silicon source and the nitrogen source is 1:6~1:7, and the introduction time is 60s~110s.

[0144] In these embodiments, by adjusting the flow ratio of the silicon source and the nitrogen source to 1:6~1:7, the silicon-nitrogen ratio of the third sub-layer can be adjusted, thereby adjusting the refractive index of the third sub-layer, and by controlling the introduction time of the silicon source and the nitrogen source to 60s~110s, the thickness of the third sub-layer can be adjusted, thereby adjusting the ultraviolet light absorption and the ability of the third sub-layer to allow light in other bands to pass through, thereby increasing the UV absorption capacity of the silicon nitride layer as much as possible and reducing the light loss in other bands.

[0145] In some embodiments, the preparation method satisfies at least one of the following conditions:

[0146] (1) When depositing the third sub-layer, the flow rate of the silicon source is 2000 sccm to 3000 sccm, and the flow rate of the nitrogen source is 12000 sccm to 18000 sccm;

[0147] (2) When depositing the third sublayer, the deposition temperature is 510°C~530°C, the deposition pressure is 1500 mTorr~1800 mTorr, and the deposition power is 13000W~15000W.

[0148] In these embodiments, by controlling the flow rates of the silicon source and the nitrogen source, the molar ratio of silicon and nitrogen can be limited, so that the silicon-nitrogen ratio in the first sublayer and the second sublayer can be controlled, and then the refractive index of the first sublayer and the second sublayer can be controlled. By controlling the deposition temperature of the third sublayer to 510-530°C, the compactness of the third sublayer can be effectively improved, while too high a temperature will reduce the compactness of the silicon nitride film (such as the third sublayer). At the same time, by controlling the deposition pressure of the third sublayer to 1500 mTorr-1800 mTorr and the deposition power to 13000W-15000W, the deposition rate can be increased as much as possible while maintaining a high thickness uniformity of the silicon nitride layer, thereby improving the preparation efficiency.

[0149] In some embodiments, the first anti-reflection layer further comprises a silicon oxynitride layer and a first silicon oxide layer stacked in sequence on a side of the silicon nitride layer away from the substrate. The preparation method further comprises:

[0150] A silicon oxynitride layer and a first silicon oxide layer are sequentially deposited on the side of the silicon nitride layer away from the substrate. For example, PECVD can be used to sequentially deposit the silicon oxynitride layer and the first silicon oxide layer on the side of the silicon nitride layer away from the substrate.

[0151] In some embodiments, sequentially depositing a silicon oxynitride layer and a first silicon oxide layer on a side of the silicon nitride layer facing away from the substrate may include:

[0152] A silicon source, a nitrogen source and an oxygen source are introduced into the reaction chamber, and a silicon oxynitride layer is deposited on the side of the silicon nitride layer facing away from the substrate by using PECVD;

[0153] A silicon source and an oxygen source are introduced into the reaction chamber, and a first silicon oxide layer is deposited on a side of the silicon oxynitride layer away from the substrate by using PECVD;

[0154] Wherein, the silicon source can be selected from silane, the nitrogen source can be selected from ammonia, and the oxygen source can be selected from laughing gas. At this time, when depositing the silicon oxynitride layer, the flow rate of silane is 1000 sccm~2000 sccm, the flow rate of ammonia is 5000 sccm~7000 sccm, and the flow rate of laughing gas is 4000 sccm~6000 sccm, and the introduction time is 60 s~100 s. The ratio of silicon element, nitrogen element and oxygen element can be adjusted to obtain a silicon oxynitride layer with a refractive index of 1.7~1.8. When depositing the first silicon oxide layer, the flow rate of silane is 1000 sccm~2000 sccm, the flow rate of laughing gas is 10000 sccm~12000 sccm, and the introduction time is 110 s~160 s.

[0155] In some embodiments, when depositing the silicon oxynitride layer and the first silicon oxide layer, the deposition temperature may be 510° C. to 530° C., the pressure may be 1400 mTorr to 1800 mTor, and the power may be 11000 W to 15000 W.

[0156] In these embodiments, a silicon oxynitride layer with high density and thickness uniformity can be obtained, and because the silicon oxynitride layer has a low interface state density, the passivation effect of the entire first passivation layer and the first anti-reflection layer can be improved as much as possible, and UV attenuation can be reduced, thereby improving the photoelectric conversion efficiency of the solar cell as much as possible.

[0157] 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.

[0158] 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.

[0159] Example 1

[0160] The method for preparing the solar cell in Example 1 is as follows:

[0161] Step 1), placing the cell after the second silicon oxide layer and the aluminum oxide layer are deposited in a PECVD furnace tube for high temperature annealing treatment, the temperature of the high temperature annealing treatment is 550°C, the time is 18 minutes, and the annealing atmosphere is a mixed atmosphere of nitrogen and hydrogen.

[0162] Step 2), after the annealing process is completed, the furnace tube is purged with nitrogen, the furnace tube is evacuated to a vacuum, silane and ammonia are introduced to prepare the first silicon nitride layer: the flow rate of silane is 2500sccm, the flow rate of ammonia is: 9000sccm, the introduction time is 100s, and the temperature in the reaction chamber is 520°C, the pressure is 900mTorr, and the power is 8000W during the whole process. Finally, the thickness of the first silicon nitride layer is 35nm and the refractive index is 2.4.

[0163] Step 3), changing the flow rates of silane and ammonia to prepare a second silicon nitride layer: the flow rate of silane is 2500 sccm, the flow rate of ammonia is 16000 sccm, the introduction time is 90 s, the temperature in the reaction chamber is 520°C, the pressure is 1600 mTorr, and the power is 14000 W during the whole process. Finally, the thickness of the second silicon nitride layer is 30 nm and the refractive index is 2.3.

[0164] Step 4), continue to change the flow rate of silane and ammonia to prepare the third silicon nitride layer: the flow rate of silane is 1200sccm, the flow rate of ammonia is 12000sccm, the introduction time is 130s, the temperature in the reaction chamber is 520°C, the pressure is 1600m Torr, and the power is 14000W during the whole process. Finally, the thickness of the third silicon nitride layer is 15nm and the refractive index is 2.0.

[0165] Step 5), depositing a silicon oxynitride layer: the flow rate of silane is 1500 sccm, the flow rate of ammonia is 6000 sccm, the flow rate of nitrous oxide is 5000 sccm, the introduction time is 80 s, the temperature in the reaction chamber is 520°C, the pressure is 1600 mTorr, and the power is 14000 W during the whole process. Finally, the thickness of the silicon oxynitride layer is 6 nm and the refractive index is 1.8.

[0166] Step 6), depositing the first silicon oxide layer, the flow rate of silane is 1500 sccm, the flow rate of nitrous oxide is 11000 sccm, the introduction time is 130 s, the temperature in the reaction chamber is 520°C, the pressure is 1600 mTorr, the power is 14000 W, and the thickness of the silicon oxide layer is 11 nm.

[0167] Step 7), after the deposition is completed, the back anti-reflection layer is deposited, and the preparation method is the same as that of the front passivation layer and the front anti-reflection layer, and finally the metal electrode is screen-printed.

[0168] Example 2

[0169] 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:

[0170] In step 1), the temperature of the high temperature annealing treatment is 560°C.

[0171] Example 3

[0172] 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:

[0173] In step 1), the temperature of the high temperature annealing treatment is 570°C.

[0174] Example 4

[0175] 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:

[0176] In step 1), the temperature of the high temperature annealing treatment is 580°C.

[0177] Example 5

[0178] 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:

[0179] In step 1), the temperature of the high temperature annealing treatment is 590°C.

[0180] Comparative Example 1

[0181] 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:

[0182] The temperature of the medium-high temperature annealing treatment in step 1) is 610°C.

[0183] Comparative Example 2

[0184] 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:

[0185] The temperature of the medium-high temperature annealing treatment in step 1) is 620°C.

[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] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 450° C. for 18 minutes;

[0189] In step 2), when depositing the first silicon nitride layer, the deposition pressure is 1400 mTorr and the deposition power is 12500W.

[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 Comparative Example 3, except that:

[0192] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 460° C. for 18 minutes.

[0193] Comparative Example 5

[0194] The method for preparing the solar cell in Comparative Example 5 is substantially the same as the method for preparing the solar cell in Comparative Example 3, except that:

[0195] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 470° C. for 18 minutes.

[0196] Comparative Example 6

[0197] The method for preparing the solar cell in Comparative Example 6 is substantially the same as the method for preparing the solar cell in Comparative Example 3, except that:

[0198] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 480° C. for 18 minutes.

[0199] Comparative Example 7

[0200] The method for preparing the solar cell in Comparative Example 7 is substantially the same as the method for preparing the solar cell in Comparative Example 3, except that:

[0201] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 490° C. for 18 minutes.

[0202] Comparative Example 8

[0203] The method for preparing the solar cell in Comparative Example 8 is substantially the same as the method for preparing the solar cell in Comparative Example 3, except that:

[0204] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 500° C. for 18 minutes.

[0205] Comparative Example 9

[0206] The method for preparing the solar cell in Comparative Example 9 is substantially the same as the method for preparing the solar cell in Comparative Example 3, except that:

[0207] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 520° C. for 18 minutes.

[0208] Comparative Example 10

[0209] The method for preparing the solar cell in Comparative Example 10 is substantially the same as the method for preparing the solar cell in Comparative Example 3, except that:

[0210] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 530° C. for 18 minutes.

[0211] Comparative Example 11

[0212] The method for preparing the solar cell in Comparative Example 11 is substantially the same as the method for preparing the solar cell in Comparative Example 3, except that:

[0213] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 540° C. for 18 minutes.

[0214] Comparative Example 12

[0215] The method for preparing the solar cell in Comparative Example 12 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0216] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 450° C. for 18 minutes.

[0217] Comparative Example 13

[0218] The method for preparing the solar cell in Comparative Example 13 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0219] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 460° C. for 18 minutes.

[0220] Comparative Example 14

[0221] The method for preparing the solar cell in Comparative Example 14 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0222] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 470° C. for 18 minutes.

[0223] Comparative Example 15

[0224] The method for preparing the solar cell in Comparative Example 15 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0225] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 480° C. for 18 minutes.

[0226] Comparative Example 16

[0227] The method for preparing the solar cell in Comparative Example 16 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0228] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 490° C. for 18 minutes.

[0229] Comparative Example 17

[0230] The method for preparing the solar cell in Comparative Example 17 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0231] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 500° C. for 18 minutes.

[0232] Comparative Example 18

[0233] The method for preparing the solar cell in Comparative Example 18 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0234] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 520° C. for 18 minutes.

[0235] Comparative Example 19

[0236] The method for preparing the solar cell in Comparative Example 19 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0237] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 530° C. for 18 minutes.

[0238] Comparative Example 20

[0239] The method for preparing the solar cell in Comparative Example 20 is substantially the same as the method for preparing the solar cell in Example 1, except that:

[0240] After the second silicon oxide layer and the aluminum oxide layer are deposited in step 1), annealing is performed directly at a temperature of 540° C. for 18 minutes.

[0241] Test Case

[0242] 1. The front and back sides of the battery modules prepared from the solar cells provided in Examples 1 to 5, Comparative Examples 1 to 12 and Comparative Examples 18 to 20 were respectively subjected to UV60 ultraviolet attenuation tests, and the test results are shown in Table 1 below.

[0243] Table 1

[0244]

[0245] In Table 1, the test method of UV60 ultraviolet attenuation test is: testing the Voc, Jsc, Vmp, Jmp, Pmax and FF of the battery assembly before and after ultraviolet light irradiation respectively, and using (value after ultraviolet light irradiation - value before ultraviolet light irradiation) / value before ultraviolet light irradiation to calculate the respective attenuation rates; wherein, Vmp represents the voltage generated by the battery assembly at the maximum power point, Jmp represents the current generated by the battery assembly at the maximum power point, and Pmax represents the maximum power point.

[0246] 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.

[0247] The reason why the attenuation rates of the front and back sides under ultraviolet light are different is that after being made into components, the front and back film layers are different, and the absorption and reflection of the solar cells are quite different. At the same time, there will be certain errors in the test, which will also cause the attenuation rates of the front and back sides under ultraviolet light to be different.

[0248] As shown in Table 1, compared with Comparative Examples 1-12 and Comparative Examples 18-20, the attenuation rates of Vmp (V), Jmp (A), Pmax (W) and FF (%) on the front and back sides of Examples 1-5 under ultraviolet light irradiation are greatly reduced, which can effectively improve the anti-ultraviolet attenuation ability of the battery assembly, indicating that by controlling the annealing temperature at 550°C to 590°C and by controlling the deposition pressure and power of the first silicon nitride layer, the anti-ultraviolet attenuation ability of the battery assembly can be improved to the greatest extent. Compared with Examples 1-5 and Comparative Examples 1-2, as the annealing temperature continues to increase, it is not conducive to improving the anti-ultraviolet attenuation ability of the battery assembly. By comparing Examples 1 to 5 with Examples 1 to 12 and Examples 18 to 20, it can be seen that: when the deposition pressure and power of the first silicon nitride layer are the same, by controlling the annealing temperature to be lowered, such as when the annealing temperature is 450°C or even slightly higher such as 530°C or 540°C, it is still not enough to improve the anti-ultraviolet attenuation capability of the battery assembly. By comparing Example 12 with Example 3, and Examples 18 to 20 with Examples 9 to 11, it can be seen that when the deposition pressure and power of the first silicon nitride layer are large, the Pmax of the battery assembly is reduced to a certain extent, indicating that the anti-ultraviolet attenuation capability of the battery assembly is reduced.

[0249] In summary, when the annealing temperature provided in the embodiment of the present application is 550°C~590°C and the deposition pressure and power of the first silicon nitride layer are controlled within a suitable range, the anti-ultraviolet attenuation ability of the battery assembly can be maximized, thereby maximizing the performance stability of the battery assembly. As shown in Table 3 below, by testing the film thickness uniformity of Examples 1~5 and Comparative Examples 1~20, it was found that the film thickness uniformity of the silicon nitride layer in the battery assembly provided by Examples 1~5 is better, while the film thickness uniformity of Comparative Examples 1~20 is poor, indicating that the anti-ultraviolet attenuation ability is affected by both the passivation performance and the film thickness uniformity.

[0250] 2. The photoelectric performance of the solar cells prepared in Examples 1 to 5 and Comparative Examples 1 to 20 was tested, and the test results are shown in Table 2 below.

[0251] Table 2

[0252]

[0253] It can be seen from Table 2 that by setting the annealing temperature to 550°C~590°C, the photoelectric conversion efficiency of the solar cell can be effectively improved. By increasing or decreasing the annealing temperature, the photoelectric conversion efficiency of the battery assembly decreases. By adopting high power and high pressure to deposit the first silicon nitride layer, when the annealing temperature is low, the fill factor and photoelectric conversion efficiency of the battery assembly decrease significantly, indicating that the annealing temperature provided in the embodiment of the present application is 550°C~590°C, and when the deposition pressure and power of the first silicon nitride layer are controlled within a suitable range, the photoelectric conversion efficiency of the solar cell can be maximized, indicating that the solar cell provided in the embodiment of the present application has better passivation performance.

[0254] 3. The fixed negative charge density, interface defect state density of the aluminum oxide layer in the solar cells prepared in Examples 1 to 5 and Comparative Examples 1 to 20, as well as the carrier surface recombination rate and thickness uniformity of the silicon nitride layer of the solar cells were tested. The test results are shown in Table 3 below.

[0255] Table 3

[0256]

[0257] Combining Table 1, Table 2 and Table 3, it can be seen that: compared with the traditional annealing method, by annealing at 550℃~590℃, the fixed negative charge density of the aluminum oxide layer can be effectively increased, and the surface defect state density of the aluminum oxide layer can be reduced, thereby improving the passivation performance of the aluminum oxide layer. At the same time, by testing the carrier recombination rate on the surface of the first silicon oxide layer, it is found that: annealing at 550℃~590℃ can reduce the surface carrier recombination rate of the battery component to the greatest extent, thereby improving the photoelectric conversion efficiency and anti-ultraviolet attenuation ability.

[0258] As the annealing temperature continues to increase to 610°C and 620°C, the fixed negative charge density of the aluminum oxide layer shows a downward trend, and the surface defect state density of the aluminum oxide layer shows an upward trend. The surface carrier recombination rate of the battery component also shows an upward trend. This shows that as the annealing temperature continues to increase, it is not conducive to the improvement of the passivation performance and the ability to resist UV attenuation.

[0259] When the annealing temperature is low, if the pressure and power during the deposition of the first silicon nitride layer are equivalent to those in the embodiment of the present application, then the fixed negative charge density of the aluminum oxide layer is between 4.7×10 12 Qf / cm 2 ~5.5×10 12 Qf / cm 2The surface defect state density is relatively large, and the passivation performance and UV resistance are reduced to a certain extent. When the annealing temperature is low and the pressure and power during the deposition of the first silicon nitride layer are relatively large, the fixed negative charge density of the aluminum oxide layer is between 3.0×10 12 Qf / cm 2 ~7.0×10 12 Qf / cm 2 At the same time, the surface defect state density increases greatly, the surface carrier recombination rate of the battery components also increases to varying degrees, and the passivation performance and anti-ultraviolet attenuation ability are reduced to a greater extent.

[0260] It can be seen that by controlling the annealing temperature within the range of 550℃~590℃, the fixed negative charge density of the aluminum oxide layer can be effectively increased while reducing the surface defect state density of the aluminum oxide layer. By adjusting the film deposition conditions of each layer, the surface carrier recombination rate of the battery component and the film uniformity of the silicon nitride layer can be minimized, thereby maximizing the passivation performance and anti-ultraviolet attenuation ability.

[0261] By measuring the uniformity of the film thickness of the silicon nitride layer, it is found that the film deposition conditions provided in the embodiment of the present application can effectively improve the uniformity of the film thickness of the silicon nitride layer, thereby further improving the anti-ultraviolet attenuation capability of the battery assembly. However, as the annealing temperature decreases, even if the silicon nitride layer is adjusted to be deposited under the same conditions as in the embodiment of the present application, it is also not conducive to improving the uniformity of the film thickness. This may be because the annealing temperature is too low, the hydrogen in the aluminum oxide layer is not released enough, and accumulates in the aluminum oxide layer. When the silicon nitride layer is subsequently deposited, a local film explosion will occur, resulting in poor uniformity of the film thickness.

[0262] 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.

[0263] 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: an aluminum oxide layer, wherein the fixed negative charge density of the aluminum oxide layer is greater than or equal to 4.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer is less than or equal to 0.9×10 12 eV / cm 2 .

2. The solar cell according to claim 1, characterized in that The fixed negative charge density of the aluminum oxide layer is 4.2×10 12 Qf / cm 2 ~7.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer is 0.5×10 12 eV / cm 2 ~0.9×10 12 eV / cm 2 .

3. The solar cell according to claim 1, characterized in that Also includes: A first anti-reflection layer disposed on a side of the first passivation layer away from the substrate; The first anti-reflection layer comprises a silicon nitride layer, and the silicon-nitrogen ratio of the silicon nitride layer decreases gradually in a direction away from the substrate.

4. The solar cell according to claim 3, characterized in that: The silicon nitride layer comprises: a first sublayer closest to the substrate and a second sublayer farthest from the substrate; The refractive index of the first sublayer is 2.4-2.5, and the thickness is 32 nm-38 nm; the refractive index of the second sublayer is 1.9-2.0, and the thickness is 12 nm-18 nm.

5. The solar cell according to claim 4, characterized in that: The silicon nitride layer further includes: a third sublayer disposed between the first sublayer and the second sublayer; The refractive index of the third sublayer is 2.1-2.3, and the thickness is 22 nm-36 nm.

6. The solar cell according to claim 3, characterized in that: The thickness uniformity of the silicon nitride layer satisfies: D even Less than 5%; Among them, D even =(D max -D min ) / (D max +D min ), D max represents the thickness of the silicon nitride layer at the maximum position, D min It represents the thickness of the silicon nitride layer at the minimum thickness position.

7. The solar cell according to claim 6, characterized in that: The thickness uniformity of the silicon nitride layer satisfies: D even It is 2.5%~3.8%.

8. The solar cell according to claim 3, characterized in that: For the silicon nitride layer, the difference between the thickness at the maximum thickness position and the thickness at the minimum thickness position is 5 nm to 10 nm.

9. The solar cell according to claim 3, characterized in that: The first anti-reflection layer further includes a silicon oxynitride layer and a first silicon oxide layer disposed on a side of the silicon nitride layer away from the substrate; a carrier recombination velocity of a surface of the first silicon oxide layer away from the substrate is less than or equal to 40 cm / s.

10. The solar cell according to claim 9, characterized in that: The carrier recombination velocity of the surface of the first silicon oxide layer facing away from the substrate is 25 cm / s to 35 cm / s.

11. A method for preparing a solar cell, characterized in that: include: Providing a substrate, the substrate comprising a first surface and a second surface disposed opposite to each other along a thickness direction thereof; 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 first passivation layer is formed on one side of the first surface of the substrate, wherein the first passivation layer comprises: an aluminum oxide layer, wherein the fixed negative charge density of the aluminum oxide layer is greater than or equal to 4.0×10 12 Qf / cm 2 , and the surface defect state density of the aluminum oxide layer is less than or equal to 0.9×10 12 eV / cm 2 ; The step of forming a first passivation layer on one side of the first surface of the substrate comprises: Depositing an aluminum oxide film layer on one side of the first surface of the substrate; Under the protection of inert gas, the aluminum oxide film layer is annealed to prepare the aluminum oxide layer; wherein the annealing temperature is 550° C. to 590° C. and the annealing time is 15 min to 20 min.

12. The method for preparing a solar cell according to claim 11, characterized in that: The solar cell further comprises a first anti-reflection layer disposed on a side of the first passivation layer away from the substrate, the first anti-reflection layer comprising: a silicon nitride layer, wherein the silicon-nitrogen ratio of the silicon nitride layer decreases gradually in a direction away from the substrate; the preparation method further comprises: A silicon source and a nitrogen source are introduced into the reaction chamber, and the flow ratio of the silicon source to the nitrogen source is controlled to gradually decrease, and the silicon nitride layer is deposited on a side of the first passivation layer away from the substrate.

13. The method for preparing a solar cell according to claim 12, characterized in that: The silicon nitride layer comprises a first sublayer closest to the substrate and a second sublayer farthest from the substrate, the silicon source is selected from silane, and the nitrogen source is selected from ammonia; When depositing the first sublayer, the flow ratio of the silicon source to the nitrogen source is 1:3.5~1:4, and the introduction time is 80s~150s; when depositing the second sublayer, the flow ratio of the silicon source to the nitrogen source is 1:10~1:10.5, and the introduction time is 110s~160s.

14. The method for preparing a solar cell according to claim 13, characterized in that: The preparation method satisfies at least one of the following conditions: (1) When depositing the first sub-layer, the flow rate of the silicon source is 2000 sccm~3000 sccm, and the flow rate of the nitrogen source is 8000 sccm~11000 sccm; when depositing the second sub-layer, the flow rate of the silicon source is 1000 sccm~1500 sccm, and the flow rate of the nitrogen source is 10000 sccm~16000 sccm; (2) When depositing the first sublayer, the deposition temperature is 510°C~530°C, the deposition pressure is 800mTor~1000mTorr, and the deposition power is 7000W~9000W; when depositing the second sublayer, the deposition temperature is 510°C~530°C, the deposition pressure is 1400 mTorr~1800mTorr, and the deposition power is 11000W~15000W.

15. The method for preparing a solar cell according to claim 14, characterized in that: The silicon nitride layer further comprises a third sublayer disposed between the first sublayer and the second sublayer, the silicon source is selected from silane, and the nitrogen source is selected from ammonia; When depositing the third sub-layer, the flow ratio of the silicon source to the nitrogen source is 1:6-1:7, and the introduction time is 60s-110s.

16. The method for preparing a solar cell according to claim 15, characterized in that: The preparation method satisfies at least one of the following conditions: (1) When depositing the third sub-layer, the flow rate of the silicon source is 2000 sccm to 3000 sccm, and the flow rate of the nitrogen source is 12000 sccm to 18000 sccm; (2) When depositing the third sub-layer, the deposition temperature is 510° C. to 530° C., the deposition pressure is 1500 mTorr to 1800 mTorr, and the deposition power is 13000 W to 15000 W.

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