Back contact solar cell, preparation method thereof, cell module and photovoltaic system

Abstract

The invention relates to the technical field of solar cells, and particularly discloses a back contact solar cell and a preparation method thereof, a cell assembly and a photovoltaic system, the back contact solar cell comprises a silicon substrate, the silicon substrate is provided with a first surface, a second surface and a side surface, the first surface and the second surface are oppositely arranged, and the side surface is respectively connected with the first surface and the second surface; the anti-reflection passivation composite layer comprises a first branch part arranged on the first surface and a second branch part extending from the edge of the first branch part to the outside of the side surface; the anti-reflection passivation composite layer comprises an ultrathin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer and a silicon oxide layer which are sequentially arranged in the direction away from the silicon substrate, and the refractive indexes of the silicon nitride layer, the silicon oxynitride layer and the silicon oxide layer are sequentially decreased. Influences brought by defects on the side face of the silicon substrate can be effectively solved, parasitic absorption on the edge of the cell can be reduced, the anti-reflection and passivation effects of the anti-reflection and passivation composite layer can be effectively improved through mutual cooperation of the multiple material layers, the stress problem can be improved, the conversion efficiency of the cell can be integrally and effectively improved, and the service life of the cell can be prolonged. And the long-term reliability of the battery is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular, to a back-contact solar cell, a preparation method thereof, a battery module, and a photovoltaic system. Background Art

[0002] A back-contact battery is a new type of solar cell structure. Different from the layout of traditional solar cells where the positive and negative electrodes are distributed on the front and back sides of the battery, the back-contact battery integrates both the positive and negative electrodes on the back side of the battery, so that there is no electrode blockage on the front side of the battery, thereby increasing the light absorption and effectively improving the photoelectric conversion efficiency.

[0003] In order to maximize the utilization of sunlight, a front surface composite film layer is usually deposited on the front surface of the existing back-contact battery. For example, the front surface composite film layer is composed of multiple film layers with different refractive indexes to increase the passivation effect and reduce the reflection loss. However, the current technical system still has limitations:

[0004] On the one hand, there are a large number of defects such as dangling bonds on the side walls of the silicon wafer. These defects cause the edges of the silicon wafer to become high-incidence regions of carrier recombination, increasing the parasitic absorption. Currently, back-contact batteries often focus on improving the passivation and anti-reflection effects on the front side of the battery, while ignoring the influence brought by the defects on the side walls of the silicon wafer, resulting in limited battery conversion efficiency of the existing back-contact batteries. On the other hand, due to poor matching of material properties such as the coefficient of thermal expansion and light characteristics between adjacent film layers of the existing front surface film layer, the overall passivation and reflection effects of the front surface film layer of the crystalline silicon battery are poor, and stress problems are likely to occur. The overall mechanical stability and adhesion of the film layer are poor, affecting the conversion efficiency and reliability of the battery. Summary of the Invention

[0005] The purpose of the present invention is to provide a back-contact solar cell, a preparation method thereof, a battery module, and a photovoltaic system in view of the existing technical status.

[0006] The present invention effectively solves the influence brought by the defects on the side of the silicon substrate by providing an optimized anti-reflection and passivation composite layer on the first surface and the side of the silicon substrate, reduces the parasitic absorption at the edge of the battery, and through the mutual cooperation between multiple material layers, effectively improves the anti-reflection and passivation effects of the anti-reflection and passivation composite layer, and improves the stress problem, thereby effectively improving the conversion efficiency of the battery as a whole and ensuring the long-term reliability of the battery, and improving the comprehensive performance of the battery.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] First, the present invention provides a back-contact solar cell, comprising:

[0009] A silicon substrate having a first surface, a second surface and side surfaces, the first surface and the second surface being disposed opposite to each other, and the side surfaces being respectively connected to the first surface and the second surface;

[0010] An antireflection passivation composite layer including a first part disposed on the first surface and a second part extending from the edge of the first part to the outside of the side surface;

[0011] The antireflection passivation composite layer includes an ultrathin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer and a silicon oxide layer disposed in sequence along a direction away from the silicon substrate, and the refractive indices of the silicon nitride layer, the silicon oxynitride layer and the silicon oxide layer decrease in sequence.

[0012] In some embodiments, the silicon nitride layer includes a first sublayer, a second sublayer, a third sublayer and a fourth sublayer disposed in sequence along a direction away from the silicon substrate, the refractive indices of the first sublayer, the second sublayer, the third sublayer and the fourth sublayer decrease in sequence, and the thicknesses of the sublayers are the same.

[0013] In some embodiments, the difference in refractive index between the first sublayer and the fourth sublayer is greater than or equal to 0.2, the difference in refractive index between the first sublayer and the second sublayer is less than or equal to 0.3, and between the second sublayer, the third sublayer and the fourth sublayer, the difference in refractive index between adjacent sublayers is less than or equal to 0.2.

[0014] In some embodiments, the refractive index of the first sublayer is 2.15 - 2.35, the refractive index of the second sublayer is 2.05 - 2.15, the refractive index of the third sublayer is 1.95 - 2.05, and the refractive index of the fourth sublayer is 1.85 - 1.95.

[0015] In some embodiments, the difference in refractive index between the silicon oxynitride layer and the fourth sublayer is less than or equal to 0.2, and the difference in refractive index between the silicon oxide layer and the silicon oxynitride layer is less than or equal to 0.4.

[0016] In some embodiments, the refractive index of the silicon oxynitride layer is 1.75 - 1.85, and the refractive index of the silicon oxide layer is 1.45 - 1.6.

[0017] In some embodiments, the thickness of the ultrathin silicon oxide layer is less than 2 nm, and the thickness of the aluminum oxide layer is greater than the thickness of the ultrathin silicon oxide layer.

[0018] In some embodiments, the thickness of the ultrathin silicon oxide layer is 0.3 nm - 0.8 nm, and the thickness of the aluminum oxide layer is 3 nm - 10 nm.

[0019] In some embodiments, the total thickness of the silicon nitride layer is 5 nm to 30 nm, the thickness of the silicon oxynitride layer is 20 nm to 60 nm, and the thickness of the silicon oxide layer is 5 nm to 30 nm.

[0020] In some embodiments, the thickness of the silicon oxynitride layer is greater than the total thickness of the silicon nitride layer.

[0021] In some embodiments, the thickness of the second part decreases in the direction from the first surface towards the second surface.

[0022] In some embodiments, the side surface includes a first side wall, a second side wall, a third side wall, and a fourth side wall connected in sequence, and the second part is disposed on at least one of the first side wall, the second side wall, the third side wall, and the fourth side wall.

[0023] In some embodiments, a doping layer is provided on the second surface, and a back surface antireflection passivation layer is provided on a side of the doping layer facing away from the silicon substrate. The back surface antireflection passivation layer includes an ultra-thin SiO2 layer, an Al2O3 layer, and a SiN x layer provided in sequence along a direction away from the silicon substrate.

[0024] Second, the present invention provides a method for manufacturing a back contact solar cell, including:

[0025] Providing a silicon substrate, the silicon substrate having a first surface, a second surface, and a side surface, the first surface and the second surface being oppositely disposed, and the side surface being respectively connected to the first surface and the second surface;

[0026] Depositing an antireflection passivation composite layer on the silicon substrate, the antireflection passivation composite layer including a first part disposed on the first surface and a second part extending from an edge of the first part to the outside of the side surface;

[0027] The step of depositing the antireflection passivation composite layer on the silicon substrate includes:

[0028] Sequentially depositing an ultra-thin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer on the first surface and outside the side surface, and making the refractive indices of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer decrease in sequence.

[0029] In some embodiments, both the ultra-thin silicon oxide layer and the aluminum oxide layer are obtained by using a modified ALD device. The modified ALD device includes a process chamber and an ozone generator, and a communication pipeline is provided between the ozone generator and the process chamber.

[0030] In some embodiments, the deposition step of the ultra-thin silicon oxide layer includes:

[0031] Transfer the silicon substrate into the process chamber, and alternately circulate and introduce a mixed gas of N2 / O3 and a purge gas into the process chamber. In the N2 / O3 mixed gas, the flow rate ratio of O3 is 5% - 50%, the deposition temperature is 50°C - 400°C, the pressure is 0.3 mbar - 0.8 mbar, and circulate N times until the thickness of the ultrathin silicon oxide layer reaches 0.3 nm - 0.8 nm;

[0032] The deposition step of the aluminum oxide layer includes:

[0033] After the deposition of the ultrathin silicon oxide layer is completed, maintain the same deposition temperature and pressure, and complete N growth cycles until the thickness of the aluminum oxide layer reaches 3 nm - 10 nm. Wherein, a single growth cycle is to sequentially introduce TMA, a purge gas, H2O vapor, and a purge gas into the process chamber, and the purge gas is nitrogen.

[0034] In some embodiments, the deposition step of the silicon nitride layer includes:

[0035] Transfer the silicon substrate deposited with the aluminum oxide layer into the PECVD chamber, introduce ammonia and silane, and deposit the first sub-layer, the second sub-layer, the third sub-layer, and the fourth sub-layer in sequence.

[0036] The refractive indices of the first sub-layer, the second sub-layer, the third sub-layer, and the fourth sub-layer decrease in sequence, and the thicknesses of each sub-layer are the same.

[0037] In some embodiments, during the deposition of the first sub-layer, the second sub-layer, the third sub-layer, and the fourth sub-layer, the ratio of the ammonia flow rate to the silane flow rate increases layer by layer, and the ratios of the ammonia flow rate to the silane flow rate of each sub-layer are 5 - 8, 8 - 11, 11 - 15, and 16 - 20 in sequence.

[0038] In some embodiments, the refractive index of the first sub-layer is 2.15 - 2.35, the refractive index of the second sub-layer is 2.05 - 2.15, the refractive index of the third sub-layer is 1.95 - 2.05, and the refractive index of the fourth sub-layer is 1.85 - 1.95.

[0039] In some embodiments, the refractive index of the silicon oxynitride layer is 1.75 - 1.85, and the refractive index of the silicon oxide layer is 1.45 - 1.6.

[0040] Third, the present invention provides a battery assembly, including the back contact solar cell described above; or,

[0041] Including the back contact solar cell prepared by the preparation method described above.

[0042] Fourth, the present invention also provides a photovoltaic system, including the above-mentioned battery assembly.

[0043] The beneficial effects of the present invention are as follows:

[0044] In the present invention, an antireflection and passivation composite layer is provided both on the first surface and the side surface of the silicon substrate. Among them, the part of the antireflection and passivation composite layer located on the first surface is the first part, and the part located outside the side surface is the second part. Both the first part and the second part include an ultrathin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer arranged in sequence along the direction away from the silicon substrate. Moreover, the refractive indices of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer decrease in sequence. On the one hand, the antireflection and passivation composite layer of the present invention can effectively passivate the first surface and the side surface of the silicon substrate and effectively reduce reflection loss. Specifically: an ultrathin silicon oxide layer is provided between the silicon substrate and the aluminum oxide layer in the antireflection and passivation composite layer of the present invention. The ultrathin silicon oxide layer can reduce the density of dangling bonds on the surface of the silicon substrate (the first surface and the side surface), reduce lattice defects, construct an ordered interface structure on the surface of the silicon substrate, reduce the recombination probability of carriers. At the same time, the ultrathin silicon oxide layer provides a good growth surface for the subsequent aluminum oxide layer, making the subsequently grown aluminum oxide layer more uniform. The ultrathin silicon oxide layer and the aluminum oxide layer as a whole exhibit better chemical passivation effects. Subsequently, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer with decreasing refractive indices are sequentially deposited on the basis of the aluminum oxide layer. The silicon nitride layer has a better field passivation effect. Combining with the chemical passivation effects of the aforementioned ultrathin silicon oxide layer and the aluminum oxide layer, the overall passivation effect of the antireflection and passivation composite layer is effectively improved. At the same time, the refractive indices of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer are set to decrease. The silicon nitride layer transitions to the silicon oxide layer through the silicon oxynitride layer, and the matching degree between adjacent materials is higher. Overall cooperation can provide a better antireflection effect, and light of different wavelengths is more likely to enter the battery interior, reducing reflection loss and effectively improving light utilization efficiency. On the other hand, the antireflection and passivation composite layer of the present invention not only has good antireflection and passivation effects, but also has a better matching degree between the material layers of the film, and can effectively improve the stress problem. Specifically: by setting an ultrathin silicon oxide layer with a relatively thin thickness, a buffer can be formed between the silicon substrate and the aluminum oxide layer, which can reduce the thermal stress between adjacent layers. At the same time, the silicon nitride layer adjacent to the aluminum oxide layer has a lower elastic modulus and has a better ability to adapt to deformation, which can buffer stress transmission. Combining with the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer with a relatively high material matching degree, the stress is dispersed layer by layer. Thus, through the mutual cooperation between multiple material layers, the mechanical stability and adhesion of the antireflection and passivation composite layer are effectively improved.

[0045] Thus, the present invention effectively solves the influence brought by the defects on the side surface of the silicon substrate by providing an optimized antireflection and passivation composite layer on the first surface and the side surface of the silicon substrate, reduces the parasitic absorption at the battery edge, and through the mutual cooperation between multiple material layers, effectively improves the antireflection and passivation effects of the antireflection and passivation composite layer and improves the stress problem, thereby effectively improving the conversion efficiency of the battery as a whole, ensuring the long-term reliability of the battery, and enhancing the comprehensive performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 FIG. is a schematic structural diagram of the back-contact solar cell of the present invention.

[0047] Figure 2 is Figure 1 a partial enlarged view of...

[0048] Figure 3 FIG. is a schematic structural diagram of another embodiment of the back-contact solar cell of the present invention.

[0049] Figure 4 is Figure 3 a partial enlarged view of part A of...

[0050] Figure 5 FIG. is a schematic partial structure diagram of the first part of the antireflection and passivation composite layer (the silicon nitride layer includes sub-layers) of the present invention.

[0051] Figure 6 FIG. is a flowchart of the preparation method of the back-contact solar cell of the present invention.

[0052] Figure 7 FIG. is a flowchart of the preparation method of the antireflection and passivation composite layer of the present invention.

[0053] Figure 8 FIG. is a schematic structural diagram of the improved ALD device of the present invention.

[0054] Figure 9 FIG. is a comparison chart of the reflectivity curves of Example 1 and Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0055] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the drawings and embodiments. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation to the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] In the description of the present invention, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of the said features. In the description of the present invention, the meanings of "a plurality" and "several" are two or more, unless otherwise specifically defined.

[0057] In the description of the present invention, unless otherwise clearly specified and defined, the first feature being "above" or "below" the second feature may include the first feature and the second feature being in direct contact, or may include the first feature and the second feature not being in direct contact but being in contact through additional features therebetween.

[0058] First, as shown in Figures 1 to 2 the present invention provides a back-contact solar cell, comprising:

[0059] a silicon substrate 1 having a first surface 11, a second surface 12 and side surfaces 13, the first surface 11 and the second surface 12 being oppositely arranged, and the side surfaces 13 being respectively connected to the first surface 11 and the second surface 12;

[0060] an anti-reflection passivation composite layer 2, comprising a first part 2A provided on the first surface 11 and a second part 2B extending from the edge of the first part 2A to the outside of the side surface 13;

[0061] The anti-reflection passivation composite layer 2 comprises a ultra-thin silicon oxide layer 21, an aluminum oxide layer 22, a silicon nitride layer 23, a silicon oxynitride layer 24 and a silicon oxide layer 25 which are sequentially arranged along the direction away from the silicon substrate 1, and the refractive indices of the silicon nitride layer 23, the silicon oxynitride layer 24 and the silicon oxide layer 25 decrease in sequence.

[0062] It can be understood that the silicon substrate 1 has a first surface 11 and a second surface 12 which are oppositely arranged. Among them, one is the light-receiving surface (usually correspondingly called the front side of the silicon substrate 1), and the other is the backlight surface (usually correspondingly called the back side of the silicon substrate 1). The side walls at the four peripheral edges of the silicon substrate 1 are the side surfaces 13. In this specification, the first surface 11 is used as the light-receiving surface and the second surface 12 is used as the backlight surface. Among them, the light-receiving surface generally refers to the side that receives light. In some embodiments, the light-receiving surface can also be set as a matte surface. It should be noted that in some embodiments, the light incident through the backlight surface can also be absorbed, thereby generating a photocurrent. In addition, in the actual application process, the present invention embodiment does not make specific limitations on the material and conductivity type of the silicon substrate 1. Exemplarily, the material of the silicon substrate 1 can be single crystal silicon, microcrystalline silicon, polycrystalline silicon or amorphous silicon, but not limited thereto, and its conductivity can be N-type or P-type.

[0063] In the present invention, an antireflection passivation composite layer 2 is provided both on the first surface 11 and outside the side surface 13 of the silicon substrate 1. Among them, the part of the antireflection passivation composite layer 2 located on the first surface 11 is the first sub-layer 2A, and the part located outside the side surface 13 is the second sub-layer 2B. Both the first sub-layer 2A and the second sub-layer 2B include a ultrathin silicon oxide layer 21, an aluminum oxide layer 22, a silicon nitride layer 23, a silicon oxynitride layer 24, and a silicon oxide layer 25 arranged in sequence along the direction away from the silicon substrate 1. Moreover, the refractive indices of the silicon nitride layer 23, the silicon oxynitride layer 24, and the silicon oxide layer 25 decrease in sequence. On the one hand, the antireflection passivation composite layer 2 of the present invention can effectively passivate the first surface 11 and the side surface 13 of the silicon substrate 1 and effectively reduce the reflection loss. Specifically: The ultrathin silicon oxide layer 21 is provided between the silicon substrate 1 and the aluminum oxide layer 22 in the antireflection passivation composite layer 2 of the present invention. The ultrathin silicon oxide layer 21 can reduce the density of dangling bonds on the surface of the silicon substrate 1 (the first surface 11 and the side surface 13), reduce lattice defects, construct an ordered interface structure on the surface of the silicon substrate 1, reduce the recombination probability of carriers. At the same time, the ultrathin silicon oxide layer 21 provides a good growth surface for the subsequent aluminum oxide layer 22, making the subsequently grown aluminum oxide layer 22 more uniform. The ultrathin silicon oxide layer 21 and the aluminum oxide layer 22 as a whole exhibit a better chemical passivation effect. Subsequently, on the basis of the aluminum oxide layer 22, a silicon nitride layer 23, a silicon oxynitride layer 24, and a silicon oxide layer 25 with decreasing refractive indices are deposited in sequence. The silicon nitride layer 23 has a better field passivation effect. Combining with the chemical passivation effect of the ultrathin silicon oxide layer 25 and the aluminum oxide layer 22 mentioned above, the overall passivation effect of the antireflection passivation composite layer 2 is effectively improved. At the same time, the refractive indices of the silicon nitride layer 23, the silicon oxynitride layer 24, and the silicon oxide layer 25 are set to decrease. The silicon nitride layer 23 transitions to the silicon oxide layer 25 through the silicon oxynitride layer 24, and the matching degree between adjacent materials is higher. As a whole, it can provide a better antireflection effect, and light of different wavelengths is more likely to enter the battery interior, reducing the reflection loss and effectively improving the light utilization rate. On the other hand, the antireflection passivation composite layer 2 of the present invention not only has good antireflection and passivation effects, but also has a better matching degree between the material layers of the film, and can effectively improve the stress problem. Specifically: By setting the ultrathin silicon oxide layer 21 with a relatively thin thickness, a buffer can be formed between the silicon substrate 1 and the aluminum oxide layer 22, which can reduce the thermal stress between adjacent layers. At the same time, the silicon nitride layer 23 adjacent to the aluminum oxide layer 22 has a lower elastic modulus and has a better ability to adapt to deformation, which can buffer the stress transmission. Combining the silicon nitride layer 23, the silicon oxynitride layer 24, and the silicon oxide layer 25 with a relatively high material matching degree, the stress is dispersed layer by layer. Thus, through the mutual cooperation between multiple material layers, the mechanical stability and adhesion of the antireflection passivation composite layer 2 are effectively improved.

[0064] Thus, by providing an optimized antireflection passivation composite layer 2 on the first surface 11 and the side surface 13 of the silicon substrate 1, the present invention effectively addresses the impact caused by the defects on the side surface 13 of the silicon substrate 1, reduces the parasitic absorption at the battery edge, and through the mutual cooperation between multiple material layers, effectively improves the antireflection and passivation effects of the antireflection passivation composite layer 2 and alleviates the stress problem, thereby overall effectively improving the conversion efficiency of the battery and ensuring the long-term reliability of the battery, enhancing the comprehensive performance of the battery.

[0065] In some embodiments, referring to Figure 3 and Figure 5 as shown, the silicon nitride layer 23 includes a first sub-layer 231, a second sub-layer 232, a third sub-layer 233, and a fourth sub-layer 234 arranged in sequence along the direction away from the silicon substrate 1. The refractive indices of the first sub-layer 231, the second sub-layer 232, the third sub-layer 233, and the fourth sub-layer 234 decrease in sequence, and the thicknesses of each sub-layer are the same.

[0066] Through the design of sub-layers with decreasing refractive indices in multiple layers, on the one hand, it further disperses and buffers stress, improves the cooperation degree between adjacent material layers, and further enhances the overall mechanical stability and adhesion of the antireflection passivation composite layer 2. At the same time, a highly matched refractive index and thickness are formed between adjacent material layers, better forming an interlayer optical transition, reducing the reflection loss of light at the interface, thereby overall effectively improving the conversion efficiency of the battery and ensuring the long-term reliability of the battery.

[0067] In some embodiments, the difference in refractive index between the first sub-layer 231 and the fourth sub-layer 234 is greater than or equal to 0.2, the difference in refractive index between the first sub-layer 231 and the second sub-layer 232 is less than or equal to 0.3, and between the second sub-layer 232, the third sub-layer 233, and the fourth sub-layer 234, the difference in refractive index between adjacent sub-layers is less than or equal to 0.2.

[0068] To enable the silicon nitride layer 23 to form a good optical transition between the alumina layer 22 and the silicon oxynitride layer 24 with a relatively large difference in refractive index, in the present invention, the difference in refractive index between the first sub-layer 231 and the fourth sub-layer 234 of the silicon nitride layer 23 is set to be greater than or equal to 0.2. At the same time, to ensure better optical property matching between the sub-layers of the silicon nitride layer 23, in the present invention, the difference in refractive index between the first sub-layer 231 and the second sub-layer 232 of the silicon nitride layer 23 is set to be less than or equal to 0.3, and between the second sub-layer 232, the third sub-layer 233, and the fourth sub-layer 234, the difference in refractive index between adjacent sub-layers is set to be less than or equal to 0.2. Thereby, the antireflection passivation composite layer 2 of the present invention has a better antireflection effect, and further effectively improves the battery conversion efficiency.

[0069] In some embodiments, the refractive index of the first sub-layer 231 is 2.15 to 2.35, the refractive index of the second sub-layer 232 is 2.05 to 2.15, the refractive index of the third sub-layer 233 is 1.95 to 2.05, and the refractive index of the fourth sub-layer 234 is 1.85 to 1.95.

[0070] Within this range, the silicon nitride layer 23 can form a good optical transition between the alumina layer 22 and the silicon oxynitride layer 24 with a relatively large difference in refractive index, and the anti-reflection passivation composite layer 2 as a whole has a better anti-reflection effect, thereby effectively improving the battery conversion efficiency.

[0071] Exemplarily, the refractive index of the first sub-layer 231 is 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.21, 2.22, 2.23, 2.24, 2.25, 2.26, 2.27, 2.28, 2.29, 2.30, 2.31, 2.32, 2.33, 2.34 or 2.35, but not limited thereto.

[0072] Exemplarily, the refractive index of the second sub-layer 232 is 2.05, 2.06, 2.07, 2.08, 2.09, 2.10, 2.11, 2.12, 2.13, 2.14 or 2.15, but not limited thereto.

[0073] Exemplarily, the refractive index of the third sub-layer 233 is 1.95, 1.96, 1.97, 1.98, 1.99, 2.00, 2.01, 2.02, 2.03, 2.04 or 2.05, but not limited thereto.

[0074] Exemplarily, the refractive index of the fourth sub-layer 234 is 1.85, 1.86, 1.87, 1.88, 1.89, 1.90, 1.91, 1.92, 1.93, 1.94 or 1.95, but not limited thereto.

[0075] In some embodiments, the difference in refractive index between the silicon oxynitride layer 24 and the fourth sub-layer 234 is less than or equal to 0.2, and the difference in refractive index between the silicon oxide layer 25 and the silicon oxynitride layer 24 is less than or equal to 0.4.

[0076] Within this range, the silicon nitride layer 23 can form a good optical transition between the alumina layer 22 and the silicon oxynitride layer 24 with a relatively large difference in refractive index, and the anti-reflection passivation composite layer 2 as a whole has a better anti-reflection effect, thereby effectively improving the battery conversion efficiency.

[0077] In some embodiments, the refractive index of the silicon oxynitride layer 24 is 1.75 to 1.85, and the refractive index of the silicon oxide layer 25 is 1.45 to 1.6.

[0078] Exemplarily, the refractive index of the silicon oxynitride layer 24 is 1.75, 1.76, 1.78, 1.79, 1.80, 1.81, 1.82, 1.83, 1.84 or 1.85, but not limited thereto.

[0079] Exemplarily, the refractive index of the silicon oxide layer 25 is 1.45, 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59 or 1.60, but not limited thereto.

[0080] In the present invention, by setting the refractive indices between the above-mentioned material layers, the optical property matching degree between adjacent material layers in the antireflection and passivation composite layer 2 is effectively improved, the absorption of sunlight by the battery is effectively increased, the reflection loss is reduced, and the conversion efficiency of the battery is improved.

[0081] In some embodiments, the thickness of the ultra-thin silicon oxide layer 21 is less than 2 nm, and the thickness of the aluminum oxide layer 22 is greater than the thickness of the ultra-thin silicon oxide layer 21.

[0082] When the thickness of the ultra-thin silicon oxide layer 21 is too thick, it is difficult to play a good stress buffering role between the aluminum oxide layer 22 and the silicon substrate 1, which affects the mechanical stability and adhesion of the antireflection and passivation composite layer 2. At the same time, it will also affect the passivation effect of the subsequent material layers. Aluminum oxide has excellent passivation performance. By combining a thinner ultra-thin silicon oxide layer 21 with a thicker aluminum oxide layer 22, the density of dangling bonds on the surface of the silicon substrate 1 can be effectively reduced, carrier recombination can be reduced, and more sufficient passivation can be provided, which helps to improve the open circuit voltage and fill factor of the battery, and thus improve the conversion efficiency of the battery.

[0083] In some embodiments, the thickness of the ultra-thin silicon oxide layer 21 is 0.3 nm to 0.8 nm, and the thickness of the aluminum oxide layer 22 is 3 nm to 10 nm.

[0084] Within this thickness range, the bonding degree between the ultra-thin silicon oxide layer 21, the aluminum oxide layer 22 and the silicon substrate 1 is better. The ultra-thin silicon oxide layer 21 can play a good stress buffering role, and at the same time, the passivation effect of the antireflection and passivation composite layer 2 is better.

[0085] Exemplarily, the thickness of the ultra-thin silicon oxide layer 21 is 0.3 nm, 0.35 nm, 0.4 nm, 0.45 nm, 0.5 nm, 0.55 nm, 0.6 nm, 0.65 nm, 0.7 nm, 0.75 nm or 0.8 nm, but not limited thereto.

[0086] Exemplarily, the thickness of the alumina layer 22 is 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm or 10 nm, but not limited thereto.

[0087] In some embodiments, the total thickness of the silicon nitride layer 23 is 5 nm to 30 nm, the thickness of the silicon oxynitride layer 24 is 20 nm to 60 nm, and the thickness of the silicon oxide layer 25 is 5 nm to 30 nm.

[0088] Within this thickness range, combined with the refractive index decreasing setting among the material layers of the silicon nitride layer 23, the silicon oxynitride layer 24, and the silicon oxide layer 25, the refractive index and thickness matching degree among the silicon nitride layer 23, the silicon oxynitride layer 24, and the silicon oxide layer 25 is higher. The antireflection passivation composite layer 2 as a whole can exhibit better optical property matching degree, effectively increasing the absorption of sunlight by the battery, reducing reflection loss, and improving the battery conversion efficiency.

[0089] Exemplarily, the total thickness of the silicon nitride layer 23 is 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm or 30 nm, but not limited thereto.

[0090] Exemplarily, the thickness of the silicon oxynitride layer 24 is 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm or 60 nm, but not limited thereto.

[0091] Exemplarily, the thickness of the silicon oxide layer 25 is 5 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 28 nm or 30 nm, but not limited thereto.

[0092] In some embodiments, preferably, the thickness of the silicon oxynitride layer 24 is greater than the total thickness of the silicon nitride layer 23, which is beneficial to further reducing reflection loss and improving stress distribution.

[0093] In some embodiments, the thickness of the second division 2B is set to decrease along the direction from the first surface 11 towards the second surface 12, which is beneficial to improving the stress distribution at the edge of the battery, effectively reducing stress concentration, and thus improving the overall performance of the antireflection passivation composite layer 2.

[0094] In some embodiments, the side surface 13 includes a first side wall, a second side wall, a third side wall, and a fourth side wall that are sequentially connected, and the second sub-portion 2B is provided on at least one of the first side wall, the second side wall, the third side wall, and the fourth side wall.

[0095] Preferably, the second sub-portion 2B is provided on the first side wall, the second side wall, the third side wall, and the fourth side wall.

[0096] In some embodiments, referring to Figure 1 and Figure 3 as shown, a doping layer 3 is provided on the second surface 12, and a back surface antireflection and passivation layer 5 is provided on the side of the doping layer 3 facing away from the silicon substrate 1. The back surface antireflection and passivation layer 5 includes an ultra-thin SiO2 layer 51, an Al2O3 layer 52, and a SiN x layer 53 arranged in sequence along the direction away from the silicon substrate 1.

[0097] By providing the back surface antireflection and passivation layer 5, the antireflection and passivation effects of the back surface of the battery are improved, and the conversion efficiency of the battery is further improved.

[0098] In some embodiments, the doping layer 3 includes a first doping layer 31 and a second doping layer 32 with opposite polarities. In some embodiments, the first doping layer 31 and the second doping layer 32 are arranged alternately; in another embodiment, a partial region of the second doping layer 32 may be stacked on a partial region of the first doping layer 31. At this time, an insulating protection layer exists in the stacked region between the first doping layer 31 and the second doping layer 32.

[0099] It can be understood that in terms of the conduction type, the polarities of the first doping layer 31 and the second doping layer 32 can be the same as or opposite to the polarity of the silicon substrate 1, and it is only necessary to ensure that the polarities of the first doping layer 31 and the second doping layer 32 are opposite. The material of any one of the first doping layer 31 and / or the second doping layer 32 is single-crystalline silicon, polycrystalline silicon, or amorphous silicon doped with group III element (such as B, Ga, or In) impurities, and the material of the other is single-crystalline silicon, microcrystalline, polycrystalline silicon, or amorphous silicon doped with group V element (such as P, As, Sb) impurities.

[0100] In some embodiments, a passivation layer 4 may also be provided between the doping layer 3 and the silicon substrate 1 to improve the passivation effect and the carrier transport effect. The passivation layer 4 may be an intrinsic amorphous silicon layer or a tunneling oxide layer (such as silicon oxide, titanium oxide, etc.). Exemplarily, when the doping layer 3 is made of polycrystalline silicon, the passivation layer 4 may be a tunneling oxide layer, but it is not limited thereto.

[0101] Second, referring to Figure 6 and Figure 7 as shown, the present invention provides a method for manufacturing a back-contact solar cell, including:

[0102] S100. Provide a silicon substrate 1, the silicon substrate 1 having a first surface 11, a second surface 12 and a side surface 13, the first surface 11 and the second surface 12 being disposed opposite to each other, and the side surface 13 being respectively connected to the first surface 11 and the second surface 12;

[0103] S200. Deposit an antireflection and passivation composite layer 2 on the silicon substrate 1, the antireflection and passivation composite layer 2 including a first portion 2A disposed on the first surface 11 and a second portion 2B extending from the edge of the first portion 2A to the outside of the side surface 13;

[0104] The step of depositing the antireflection and passivation composite layer 2 on the silicon substrate 1 includes:

[0105] Deposit an ultrathin silicon oxide layer 21, an aluminum oxide layer 22, a silicon nitride layer 23, a silicon oxynitride layer 24 and a silicon oxide layer 25 in sequence on the first surface 11 and outside the side surface 13, and make the refractive indices of the silicon nitride layer 23, the silicon oxynitride layer 24 and the silicon oxide layer 25 decrease in sequence.

[0106] Specifically, refer to Figure 7 As shown, the step of depositing the antireflection and passivation composite layer 2 on the silicon substrate 1 in step S200 includes:

[0107] S210. Deposit an ultrathin silicon oxide layer 21 on the first surface 11 and outside the side surface 13;

[0108] S220. Deposit an aluminum oxide layer 22 on the ultrathin silicon oxide layer 21;

[0109] S230. Deposit a silicon nitride layer 23 on the aluminum oxide layer 22;

[0110] S240. Deposit a silicon oxynitride layer 24 on the silicon nitride layer 23;

[0111] S250. Deposit a silicon oxide layer 25 on the silicon oxynitride layer 24.

[0112] In some embodiments, refer to Figure 8 As shown, both the ultrathin silicon oxide layer 21 and the aluminum oxide layer 22 are prepared by using a modified ALD device, and the modified ALD device includes a process chamber and an ozone generator, and a communication pipeline is provided between the ozone generator and the process chamber.

[0113] By continuously preparing the ultrathin silicon oxide layer 21 and the aluminum oxide layer 22 by using the modified ALD device, ozone provided by the ozone generator can be used to treat the silicon substrate 1 before depositing the aluminum oxide layer 22, clean and oxidize it, thereby forming the ultrathin silicon oxide layer 21 between the silicon substrate 1 and the aluminum oxide layer 22, which can not only improve the passivation performance of the aluminum oxide layer 22, but also play a good stress buffering role, and the antireflection and passivation composite layer 2 as a whole exhibits better passivation performance and mechanical stability.

[0114] Preferably, in this preparation method, a modified ALD device is used to prepare the ultra-thin silicon oxide layer 21 and the aluminum oxide layer 22, and PECVD is used to prepare the silicon nitride layer 23, the silicon oxynitride layer 24 and the silicon oxide layer 25.

[0115] In some embodiments, referring to Figure 1 、 Figure 3 、 Figure 7 and Figure 8 as shown, the deposition step (step S210) of the ultra-thin silicon oxide layer 21 includes:

[0116] Transfer the silicon substrate 1 to the process chamber, and alternately circulate and introduce the N2 / O3 mixed gas and the purge gas into the process chamber. In the N2 / O3 mixed gas, the flow rate ratio of O3 is 5% - 50%, the deposition temperature is 50°C - 400°C, the pressure is 0.3 mbar - 0.8 mbar, and circulate N times until the thickness of the ultra-thin silicon oxide layer 21 reaches 0.3 nm - 0.8 nm;

[0117] The deposition step (step S220) of the aluminum oxide layer 22 includes:

[0118] After the deposition of the ultra-thin silicon oxide layer 21 is completed, keep the same deposition temperature and pressure, and complete N growth cycles until the thickness of the aluminum oxide layer 22 reaches 3 nm - 10 nm. Among them, a single growth cycle is to sequentially introduce TMA, purge gas, H2O vapor and purge gas into the process chamber, and the purge gas is nitrogen.

[0119] Specifically, in step S210, place the silicon substrate 1 in the process chamber, evacuate, turn on the ozone generator at 5% - 100% power, and introduce the N2 / O3 mixed gas into the chamber for 1 s - 300 s at a temperature range of 50°C - 400°C and a pressure of 0.3 mbar - 0.8 mbar. Control the flow rate ratio of O3 in the N2 / O3 mixed gas to be 5% - 50%, and then purge the process chamber with high-purity nitrogen for 1 s - 300 s. This process is cycled 1 - 10 times to complete the preparation of the ultra-thin silicon oxide.

[0120] Specifically, in step S220, after the deposition of the ultra-thin silicon oxide layer 21 is completed, keep the same deposition temperature and pressure, first introduce TMA for a duration of 1 s - 20 s, then introduce nitrogen for purging for 1 s - 10 s, then introduce H2O vapor for 1 s - 30 s, and then introduce nitrogen for purging for 1 s - 10 s. This process is cycled 25 - 45 times to complete the deposition of the aluminum oxide film.

[0121] In some embodiments, the deposition step (step S230) of the silicon nitride layer 23 includes:

[0122] Transfer the silicon substrate 1 deposited with the alumina layer 22 into the PECVD chamber, introduce ammonia and silane, and deposit the first sub-layer 231, the second sub-layer 232, the third sub-layer 233, and the fourth sub-layer 234 in sequence.

[0123] The refractive indices of the first sub-layer 231, the second sub-layer 232, the third sub-layer 233, and the fourth sub-layer 234 decrease in sequence, and the thicknesses of each sub-layer are the same.

[0124] In some embodiments, during the deposition of the first sub-layer 231, the second sub-layer 232, the third sub-layer 233, and the fourth sub-layer 234, the ratio of the ammonia flow rate to the silane flow rate increases layer by layer, and the ratios of the ammonia flow rate to the silane flow rate of each sub-layer are 5-8, 8-11, 11-15, and 16-20 in sequence.

[0125] By controlling the ratio of the ammonia flow rate to the silane flow rate of each sub-layer to increase layer by layer, the N content in each sub-layer is increased, and the refractive index is increased layer by layer.

[0126] In some embodiments, the deposition step (step S230) of the silicon nitride layer 23 includes:

[0127] S231. Deposit the first sub-layer 231 on the alumina layer 22:

[0128] The temperature is controlled at 450°C - 550°C, the ratio of the ammonia flow rate to the silane flow rate is 5-8, the silane flow rate is 1500 sccm - 2000 sccm, the ammonia flow rate is 7500 sccm - 16000 sccm, the pressure is 1000 Torr - 2000 mTorr, the duty cycle is (2-5):(60-90), the RF power is 6000 W - 30000 W, and the duration is 150 s - 300 s.

[0129] S232. Deposit the second sub-layer 232 on the first sub-layer 231:

[0130] The temperature is controlled at 450°C - 550°C, the ratio of the ammonia flow rate to the silane flow rate is 8-11, the silane flow rate is 1000 sccm - 1500 sccm, the ammonia flow rate is 8000 sccm - 16500 sccm, the pressure is 1000 Torr - 2000 mTorr, the duty cycle is (2-5):(60-90), the RF power is 6000 W - 30000 W, and the duration is 150 s - 300 s.

[0131] S233. Deposit the third sub-layer 233 on the second sub-layer 232:

[0132] The temperature is controlled at 450°C to 550°C, the ratio of ammonia flow rate to silane flow rate is 11 to 15, the silane flow rate is 500 sccm to 1000 sccm, the ammonia flow rate is 5500 sccm to 15000 sccm, the pressure is 1000 Torr to 2000 mTorr, the duty cycle is (2 to 5):(60 to 90), the RF power is 6000 W to 30000 W, and the duration is 150 s to 300 s.

[0133] Deposit the fourth sub-layer 234 on the third sub-layer 233:

[0134] The temperature is controlled at 450°C to 550°C, the ratio of ammonia flow rate to silane flow rate is 16 to 20, the silane flow rate is 300 sccm to 900 sccm, the ammonia flow rate is 4800 sccm to 18000 sccm, the pressure is 1000 Torr to 2000 mTorr, the duty cycle is (2 to 5):(60 to 90), the RF power is 6000 W to 30000 W, and the duration is 150 s to 300 s.

[0135] In some embodiments, the steps (step S240) of preparing the silicon oxynitride layer 24 by PECVD include:

[0136] The temperature is controlled at 450°C to 550°C, the flow rate ratio among nitrous oxide, ammonia and silane is (15 to 18):(2 to 4):1, the silane flow rate is 300 sccm to 1000 sccm, the ammonia flow rate is 600 sccm to 4000 sccm, the nitrous oxide flow rate is 4500 sccm to 18000 sccm, the pressure is 1000 Torr to 2000 mTorr, the duty cycle is (2 to 5):(60 to 90), the RF power is 6000 W to 3000 W, and the duration is 150 s to 300 s.

[0137] In some embodiments, the steps (step S250) of preparing the silicon oxide layer 25 by PECVD include:

[0138] The temperature is controlled at 450°C to 550°C, the flow rate ratio between nitrous oxide and silane is (15 to 20):1, the silane flow rate is 300 sccm to 1000 sccm, the nitrous oxide flow rate is 4500 sccm to 20000 sccm, the pressure is 1000 Torr to 2000 mTorr, the duty cycle is (2 to 5):(60 to 90), the RF power is 6000 W to 3000 W, and the duration is 150 s to 300 s.

[0139] In some embodiments, the refractive index of the first sub-layer 231 is 2.15 to 2.35, the refractive index of the second sub-layer 232 is 2.05 to 2.15, the refractive index of the third sub-layer 233 is 1.95 to 2.05, and the refractive index of the fourth sub-layer 234 is 1.85 to 1.95.

[0140] In some embodiments, the refractive index of the silicon oxynitride layer 24 is 1.75 to 1.85, and the refractive index of the silicon oxide layer 25 is 1.45 to 1.6.

[0141] Third, the present invention provides a battery assembly, including the above-mentioned back-contact solar cell; or,

[0142] including the back-contact solar cell prepared by the above-mentioned preparation method.

[0143] Fourth, the present invention further provides a photovoltaic system, including the above-mentioned battery assembly.

[0144] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0145] Embodiment 1

[0146] See Figures 3 to 5 As shown, this embodiment discloses a back-contact solar cell, including:

[0147] A silicon substrate, having a first surface, a second surface, and side surfaces, the first surface and the second surface being oppositely arranged, and the side surfaces being respectively connected to the first surface and the second surface;

[0148] An antireflection passivation composite layer, including a first part disposed on the first surface and a second part extending from the edge of the first part to the outside of the side surface;

[0149] The antireflection passivation composite layer includes a ultrathin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer sequentially arranged in a direction away from the silicon substrate, and the refractive indices of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer decrease sequentially.

[0150] In this embodiment, the silicon nitride layer includes a first sub-layer, a second sub-layer, a third sub-layer, and a fourth sub-layer sequentially arranged in a direction away from the silicon substrate, the refractive indices of the first sub-layer, the second sub-layer, the third sub-layer, and the fourth sub-layer decrease sequentially, and the thicknesses of each sub-layer are the same.

[0151] In this embodiment, the refractive index difference between the first sub-layer and the fourth sub-layer is greater than or equal to 0.2, the refractive index difference between the first sub-layer and the second sub-layer is less than or equal to 0.3, and between the second sub-layer, the third sub-layer, and the fourth sub-layer, the refractive index difference between adjacent sub-layers is less than or equal to 0.2.

[0152] In this embodiment, the refractive index of the first sub-layer is 2.2, the refractive index of the second sub-layer is 2.15, the refractive index of the third sub-layer is 2.05, and the refractive index of the fourth sub-layer is 1.95.

[0153] In this embodiment, the refractive index difference between the silicon oxynitride layer and the fourth sub-layer is less than or equal to 0.2, and the refractive index difference between the silicon oxide layer and the silicon oxynitride layer is less than or equal to 0.4.

[0154] In this embodiment, the refractive index of the silicon oxynitride layer is 1.85, and the refractive index of the silicon oxide layer is 1.6.

[0155] In this embodiment, the thickness of the ultra-thin silicon oxide layer is less than 2 nm, and the thickness of the aluminum oxide layer is greater than the thickness of the ultra-thin silicon oxide layer.

[0156] In this embodiment, the thickness of the ultra-thin silicon oxide layer is 0.5 nm, and the thickness of the aluminum oxide layer is 5 nm.

[0157] In this embodiment, the total thickness of the silicon nitride layer is 15 nm, the thickness of the silicon oxynitride layer is 40 nm, and the thickness of the silicon oxide layer is 15 nm.

[0158] In this embodiment, the thickness of the silicon oxynitride layer is greater than the total thickness of the silicon nitride layer.

[0159] In this embodiment, the side surface includes a first side wall, a second side wall, a third side wall, and a fourth side wall connected in sequence, and the second part is disposed on the first side wall, the second side wall, the third side wall, and the fourth side wall.

[0160] In this embodiment, a doping layer is provided on the second surface, and a back surface antireflection passivation layer is provided on a side of the doping layer facing away from the silicon substrate. The back surface antireflection passivation layer includes an ultra-thin SiO2 layer, an Al2O3 layer, and a SiN x layer arranged in sequence along the direction away from the silicon substrate.

[0161] Second, this embodiment discloses a method for manufacturing a back contact solar cell, including:

[0162] S100. Provide a silicon substrate having a first surface, a second surface, and a side surface, where the first surface and the second surface are oppositely arranged, and the side surface is respectively connected to the first surface and the second surface;

[0163] S200. Deposit an antireflection passivation composite layer on the silicon substrate. The antireflection passivation composite layer includes a first part disposed on the first surface and a second part extending from the edge of the first part to the outside of the side surface;

[0164] The step of depositing the antireflection passivation composite layer on the silicon substrate includes:

[0165] An ultrathin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer are sequentially deposited on the first surface and outside the side surface, and the refractive indices of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer decrease in sequence.

[0166] Specifically, the step S200 of depositing an antireflection passivation composite layer on the silicon substrate includes:

[0167] S210. Deposit an ultrathin silicon oxide layer on the first surface and outside the side surface;

[0168] S220. Deposit an aluminum oxide layer on the ultrathin silicon oxide layer;

[0169] S230. Deposit a silicon nitride layer on the aluminum oxide layer;

[0170] S240. Deposit a silicon oxynitride layer on the silicon nitride layer;

[0171] S250. Deposit a silicon oxide layer on the silicon oxynitride layer.

[0172] In this embodiment, both the ultrathin silicon oxide layer and the aluminum oxide layer are prepared by a modified ALD device. The modified ALD device includes a process chamber and an ozone generator, and there is a communication pipeline between the ozone generator and the process chamber.

[0173] In this embodiment, the deposition step of the ultrathin silicon oxide layer (step S210) includes:

[0174] Place the silicon substrate in the process chamber, evacuate, turn on 50% of the power of the ozone generator, introduce an N2 / O3 mixed gas into the chamber for 30 s at a temperature range of 400 °C and a pressure of 0.8 mbar, control the flow ratio of O3 in the N2 / O3 mixed gas to be 10%, and then purge the process chamber with high-purity nitrogen for 10 s. This process is cycled 2 times to complete the preparation of the ultrathin silicon oxide.

[0175] The deposition step of the aluminum oxide layer (step S220) includes:

[0176] After the deposition of the ultrathin silicon oxide layer is completed, keep the same deposition temperature and pressure. First, introduce TMA for 10 s, then introduce nitrogen for purging for 10 s, then introduce H2O vapor for 10 s, and then introduce nitrogen for purging for 10 s. This process is cycled 25 times to complete the deposition of the aluminum oxide film.

[0177] Example 2

[0178] See Figures 1 to 2 As shown, the difference between this embodiment and Embodiment 1 is that the silicon nitride layer in this embodiment is a material layer with a single refractive index, with a thickness of 60 nm and a refractive index of 2.1.

[0179] Comparative Example 1

[0180] The difference between this comparative example and Example 1 is that the antireflection passivation composite layer in this comparative example is only provided on the first surface, that is, it does not have the second part provided on the side surface.

[0181] Comparative Example 2

[0182] The difference between this comparative example and Example 1 is that this comparative example uses a front composite layer to replace the antireflection passivation composite layer. The front composite layer is only provided on the first surface. Specifically, the front composite layer is composed of an ultrathin silicon oxide sublayer, an aluminum oxide sublayer, and a silicon nitride sublayer arranged in sequence along the direction away from the silicon substrate. Each sublayer is prepared by PECVD. The thickness of the ultrathin silicon oxide sublayer is 2 nm, the thickness of the aluminum oxide sublayer is 5 nm, the thickness of the silicon nitride sublayer is 60 nm, and the refractive index is 2.1.

[0183] Perform performance tests on the solar cells prepared in Examples 1 to 2 and Comparative Examples 1 to 2. The test results are as follows:

[0184]

[0185]

[0186] The experimental results show that, compared with Comparative Example 1 and Comparative Example 2, the conversion efficiencies of Example 1 and Example 2 are higher. Thus, it can be seen that the antireflection passivation composite layer of the present invention can effectively improve the battery conversion efficiency.

[0187] Compare the reflectivity curves of Example 1 and Example 2. From Figure 9 As can be seen from the shown reflectivity curve comparison diagram, compared with Example 2, the light reflectivities of the long wave and short wave of Example 1 are reduced by 10% - 30%. Compare the passivation PL brightness, fitting efficiency, and test efficiency of the two. The results are as follows:

[0188] Experimental group 0.1 SUN 1 SUN Ratio <![CDATA[U oc (V)]]> FF Fitted Eta (%) Example 1 3998 34198 8.55 748.94 85.40 27.03 Example 2 2981 24846 8.33 740.01 85.52 26.77

[0189] Table 1 Comparison table of passivation PL brightness and fitting efficiency

[0190] Experimental group Eta (%) <![CDATA[U oc (V)]]> <![CDATA[I sc (A)]]> FF <![CDATA[R sh (Ohm)]]> <![CDATA[R ser (Ohm)]]> Example 1 27.04 0.75 14.95 84.56 955.00 0.0002 Example 2 26.81 0.75 14.87 84.55 680.34 0.0002

[0191] Table 2 Comparison table of test efficiency

[0192] Compared with Example 2, the passivation PL brightness value of this Example 1 is increased by about 1000, the passivation effect is more obvious, the fitting efficiency is increased by 0.26%, and the test efficiency is increased by 0.23%. Thus, it can be seen that in the present invention, the silicon nitride layer is composed of sublayers with decreasing refractive indices and the same thickness, which can effectively improve the passivation effect, reduce the reflection loss, and improve the battery conversion efficiency.

[0193] In the description of this specification, the descriptions referring to terms such as "some embodiments", "exemplary", "example", or "for example" mean that the specific features, structures, materials, or characteristics described in connection with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0194] The above are only the preferred embodiments of the present invention, and do not impose any formal limitations on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the technical content prompted above within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the present invention.

Claims

1. A back-contact solar cell, characterized in that, Comprising: A silicon substrate having a first surface, a second surface, and side surfaces, the first surface and the second surface being oppositely disposed, and the side surfaces being respectively connected to the first surface and the second surface; An antireflection passivation composite layer comprising a first portion disposed on the first surface and a second portion extending from the edge of the first portion to the outside of the side surfaces; The antireflection passivation composite layer includes a ultrathin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer sequentially arranged in a direction away from the silicon substrate, and the refractive indices of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer decrease in sequence.

2. The back-contact solar cell according to claim 1, wherein The silicon nitride layer includes a first sublayer, a second sublayer, a third sublayer, and a fourth sublayer sequentially arranged in a direction away from the silicon substrate, the refractive indices of the first sublayer, the second sublayer, the third sublayer, and the fourth sublayer decrease in sequence, and the thicknesses of each sublayer are the same.

3. The back-contact solar cell according to claim 2, characterized in that, The refractive index difference between the first sublayer and the fourth sublayer is greater than or equal to 0.2, the refractive index difference between the first sublayer and the second sublayer is less than or equal to 0.3, and between the second sublayer, the third sublayer, and the fourth sublayer, the refractive index difference between adjacent sublayers is less than or equal to 0.

2.

4. The back-contact solar cell according to claim 3, characterized in that, The refractive index of the first sublayer is 2.15 - 2.35, the refractive index of the second sublayer is 2.05 - 2.15, the refractive index of the third sublayer is 1.95 - 2.05, and the refractive index of the fourth sublayer is 1.85 - 1.

95.

5. The back contact solar cell according to claim 2, characterized in that, The refractive index difference between the silicon oxynitride layer and the fourth sublayer is less than or equal to 0.2, and the refractive index difference between the silicon oxide layer and the silicon oxynitride layer is less than or equal to 0.

4.

6. The back contact solar cell according to claim 5, wherein, The refractive index of the silicon oxynitride layer is 1.75 - 1.85, and the refractive index of the silicon oxide layer is 1.45 - 1.

6.

7. The back contact solar cell according to claim 1, wherein The thickness of the ultrathin silicon oxide layer is less than 2 nm, and the thickness of the aluminum oxide layer is greater than the thickness of the ultrathin silicon oxide layer.

8. The back contact solar cell according to claim 7, characterized in that, The thickness of the ultrathin silicon oxide layer is 0.3 nm - 0.8 nm, and the thickness of the aluminum oxide layer is 3 nm - 10 nm.

9. The back-contact solar cell according to claim 1, wherein The total thickness of the silicon nitride layer is 5 nm - 30 nm, the thickness of the silicon oxynitride layer is 20 nm - 60 nm, and the thickness of the silicon oxide layer is 5 nm - 30 nm.

10. The back-contact solar cell according to claim 9, characterized in that, The thickness of the silicon oxynitride layer is greater than the total thickness of the silicon nitride layer.

11. The back-contact solar cell according to claim 1, characterized in that, The thickness of the second portion decreases in a direction from the first surface towards the second surface.

12. The back-contact solar cell according to claim 1, characterized in that, The side surfaces include a first side wall, a second side wall, a third side wall, and a fourth side wall connected in sequence, and the second portion is disposed on at least one of the first side wall, the second side wall, the third side wall, and the fourth side wall.

13. The back-contact solar cell according to claim 1, characterized in that, A doping layer is provided on the second surface, and an anti-reflection and passivation layer is provided on a side of the doping layer facing away from the silicon substrate. The anti-reflection and passivation layer on the back surface includes an ultrathin SiO2 layer, an Al2O3 layer, and a SiN layer sequentially arranged in a direction away from the silicon substrate. x layer.

14. A method for preparing a back-contact solar cell, characterized in that, Comprising: Providing a silicon substrate, the silicon substrate having a first surface, a second surface, and side surfaces, the first surface and the second surface being oppositely disposed, and the side surfaces being respectively connected to the first surface and the second surface; Depositing an antireflection passivation composite layer on the silicon substrate, the antireflection passivation composite layer comprising a first portion disposed on the first surface and a second portion extending from the edge of the first portion to the outside of the side surfaces; The step of depositing the antireflection passivation composite layer on the silicon substrate includes: Depositing an ultrathin silicon oxide layer, an aluminum oxide layer, a silicon nitride layer, a silicon oxynitride layer, and a silicon oxide layer in sequence on the first surface and outside the side surface, and making the refractive indices of the silicon nitride layer, the silicon oxynitride layer, and the silicon oxide layer decrease in sequence.

15. The method for manufacturing a back-contact solar cell according to claim 14, characterized in that, Both the ultrathin silicon oxide layer and the aluminum oxide layer are prepared by a modified ALD device, and the modified ALD device includes a process chamber and an ozone generator, and a communication pipeline is arranged between the ozone generator and the process chamber.

16. The method for preparing a back-contact solar cell according to claim 15, wherein The deposition step of the ultrathin silicon oxide layer includes: Transferring the silicon substrate into the process chamber, alternately and circularly introducing a N2 / O3 mixed gas and a purge gas into the process chamber. In the N2 / O3 mixed gas, the flow rate ratio of O3 is 5% - 50%, the deposition temperature is 50°C - 400°C, the pressure is 0.3 mbar - 0.8 mbar, and circularly introducing for N times until the thickness of the ultrathin silicon oxide layer reaches 0.3 nm - 0.8 nm; The deposition step of the aluminum oxide layer includes: After the deposition of the ultrathin silicon oxide layer is completed, maintaining the same deposition temperature and the pressure, and completing N growth cycles until the thickness of the aluminum oxide layer reaches 3 nm - 10 nm. Among them, a single growth cycle is to sequentially introduce TMA, a purge gas, H2O vapor, and a purge gas into the process chamber, and the purge gas is nitrogen.

17. The method for preparing a back-contact solar cell according to claim 14, characterized in that, The deposition step of the silicon nitride layer includes: Transferring the silicon substrate deposited with the aluminum oxide layer into a PECVD cavity, introducing ammonia gas and silane gas, and sequentially depositing a first sub-layer, a second sub-layer, a third sub-layer, and a fourth sub-layer. The refractive indices of the first sub-layer, the second sub-layer, the third sub-layer, and the fourth sub-layer decrease in sequence, and the thicknesses of each sub-layer are the same.

18. The method for manufacturing a back contact solar cell according to claim 17, characterized in that, During the deposition of the first sub-layer, the second sub-layer, the third sub-layer, and the fourth sub-layer, the flow rate ratio of ammonia gas to silane gas increases layer by layer, and the flow rate ratios of ammonia gas to silane gas of each sub-layer are 5 - 8, 8 - 11, 11 - 15, and 16 - 20 in sequence.

19. The method for preparing a back-contact solar cell according to claim 17, characterized in that, The refractive index of the first sub-layer is 2.15 - 2.35, the refractive index of the second sub-layer is 2.05 - 2.15, the refractive index of the third sub-layer is 1.95 - 2.05, and the refractive index of the fourth sub-layer is 1.85 - 1.

95.

20. The method for preparing a back-contact solar cell according to claim 14, wherein The refractive index of the silicon oxynitride layer is 1.75 - 1.85, and the refractive index of the silicon oxide layer is 1.45 - 1.

6.

21. A battery assembly, characterized in that, Including the back-contact solar cell according to any one of claims 1 to 13; or, Including the back-contact solar cell prepared by the preparation method according to any one of claims 14 to 20.

22. A photovoltaic system, characterized in that, Including the battery module according to claim 21.

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