Composite passive film layer for reducing UV absorption, back contact solar cell, cell module and photovoltaic system

Abstract

The utility model relates to the technical field of solar cells, and discloses a composite passive film layer capable of reducing UV absorption, a back contact solar cell, a cell assembly and a photovoltaic system, and the composite passive film layer is located on the front surface of the back contact solar cell; the composite passivation film layer sequentially comprises an aluminum oxide film layer, a first silicon nitride film layer, a second silicon nitride film layer and a silicon oxide film layer from bottom to top, and the refractive index of the first silicon nitride film layer is larger than that of the second silicon nitride film layer. By implementing the back contact solar cell, the passivation performance of the composite passivation film layer is improved, the light absorption efficiency is improved, the photoelectric conversion efficiency of the back contact solar cell is improved, the absorption of UV light by the composite passivation film is reduced, the performance stability of the back contact solar cell is improved, and the service life of the back contact solar cell is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, and in particular to a composite passivation film layer for reducing UV absorption, a back-contact solar cell, a battery assembly and a photovoltaic system. Background Art

[0002] Back-contact solar cells are a new type of solar cell technology. The positive and negative electrodes are both placed on the back, and the wires on the battery chip are connected on the back. No main grid is set on the front, so that light can be more fully irradiated on the battery chip, reducing the shading of the main grid and electrodes on the front, improving the efficiency and stability of the battery, and has broad application prospects.

[0003] At present, the conventional structure of the light-receiving surface of a back-contact solar cell is: a passivation layer and an anti-reflection layer are sequentially arranged on the front side of the substrate. The passivation film layer and the anti-reflection layer are arranged to reduce carrier loss, promote carrier recombination, and improve carrier lifetime. Among them, the passivation film layer mainly comprises an aluminum oxide layer. During the deposition process, the aluminum oxide reacts with the substrate to produce hydrogen, which then forms a good chemical bond with the silicon surface, saturating the dangling bonds on the silicon surface, thereby playing the role of surface hydrogen passivation, reducing the surface state density, that is, reducing the recombination centers of electrons and holes, and significantly reducing the carrier recombination rate on the surface. At the same time, the aluminum oxide generates a built-in electric field, preventing minority carriers from reaching the surface of the battery, showing a field-effect passivation effect, and further improving the surface passivation quality of the battery.

[0004] Solar cells primarily absorb and utilize visible and near-infrared light, while ultraviolet light (UV light) has higher energy. When solar cells are exposed to the sun for a long time, UV light irradiates the cell layer of the solar cell, destroying the passivation effect of the passivation layer in the solar cell, leading to photodegradation of the solar cell, thereby reducing the performance and life of the cell. Therefore, it is necessary to minimize the light-receiving surface of the solar cell and have good hydrogen passivation performance and as little UV light absorption performance as possible. However, good hydrogen passivation performance requires the use of a high content of hydrogen, which will cluster on the surface of the passivation layer, forming impurity centers and increasing defects on the surface of the passivation layer. Defects can serve as additional absorption centers, allowing more UV light to be absorbed, thereby increasing UV light absorption and reducing the efficiency of converting light energy into electrical energy. Utility Model Content

[0005] The technical problem to be solved by the present invention is to provide a composite passivation film layer, a back-contact solar cell, a battery module and a photovoltaic system that reduce UV absorption. The composite passivation film layer can have a good hydrogen passivation effect and reduce the absorption of UV light by the back-contact solar cell.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a composite passivation film layer for reducing UV absorption, wherein the composite passivation film layer is located on the front surface of a back contact solar cell;

[0007] The composite passivation film layer includes, from bottom to top, an aluminum oxide film layer, a first silicon nitride film layer, a second silicon nitride film layer, and a silicon oxide film layer, wherein the refractive index of the first silicon nitride film layer is greater than the refractive index of the second silicon nitride film layer.

[0008] As an improvement to the above solution, the refractive index of the second silicon nitride film layer is 2.01 to 2.09;

[0009] The refractive index of the first silicon nitride film layer is 2.20-2.30.

[0010] As an improvement to the above solution, the ratio of the refractive index of the first silicon nitride film layer to the refractive index of the second silicon nitride film layer is 1:(0.90-0.945).

[0011] As an improvement to the above solution, the ratio of the thickness of the first silicon nitride film layer to the thickness of the second silicon nitride film layer is 1:(3.0-5.0).

[0012] As an improvement to the above solution, the thickness of the second silicon nitride film layer is 90nm to 100nm;

[0013] The thickness of the first silicon nitride film layer is 20 nm to 30 nm.

[0014] As an improvement to the above solution, the ratio of the refractive index of the silicon oxide film layer to the refractive index of the second silicon nitride film layer is 1:(0.72-0.75).

[0015] As an improvement to the above solution, the thickness of the silicon oxide film layer is 30 nm to 40 nm.

[0016] As an improvement to the above solution, the thickness of the aluminum oxide film layer is 4 nm to 5 nm.

[0017] As an improvement to the above solution, the front surface of the back-contact solar cell has a pyramid velvet structure.

[0018] A second aspect of the present invention provides a back-contact solar cell, which includes the composite passivation film layer for reducing UV absorption.

[0019] The third aspect of the present invention provides a back-contact solar cell assembly, which includes the back-contact solar cell.

[0020] A fourth aspect of the present invention provides a photovoltaic system, which includes the back-contact solar cell assembly.

[0021] The implementation of this utility model has the following beneficial effects:

[0022] The composite passivation film layer is arranged on the front surface of the front surface of the back contact solar cell, and the composite passivation film layer includes, from bottom to top, an aluminum oxide film layer, a first silicon nitride film layer, a second silicon nitride film layer and a silicon oxide film layer, wherein the refractive index of the first silicon nitride film layer is greater than the refractive index of the second silicon nitride film layer. By adjusting the layer structure of the composite passivation film layer and the thickness and refractive index of each film layer, the passivation performance of the composite passivation film layer is improved, and the light absorption efficiency is improved, thereby improving the photoelectric conversion efficiency of the back contact solar cell, but reducing the absorption of UV light by the composite passivation film, thereby increasing the performance stability of the back contact solar cell and extending the life of the back contact solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 : A schematic structural diagram of a composite passivation film layer for reducing UV absorption in the present invention;

[0024] Figure 2 : A schematic structural diagram of the front surface of a back-contact solar cell in the present invention;

[0025] Figure 3 : A schematic structural diagram of the front surface of another back-contact solar cell in the present invention;

[0026] Figure 4 : A schematic structural diagram of another back-contact solar cell in the present invention;

[0027] Figure 5 : A schematic structural diagram of another back-contact solar cell in the present invention;

[0028] Reference numerals:

[0029] 1-aluminum oxide film layer; 2-first silicon nitride film layer; 3-second silicon nitride film layer; 4-silicon oxide film layer; 5-substrate; 6-tunneling layer; 7-N-type doped polysilicon layer; 8-P-type doped polysilicon layer; 9-isolation region; 10-passivation layer; 11-second anti-reflection layer; 12-first electrode; 13-second electrode. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail with reference to specific embodiments below.

[0031] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application. In addition, it should be understood that the specific embodiments described herein are merely used to explain the present application and are not intended to limit the present application.

[0032] In the description of this application, it should be understood that the terms "upper", "lower", "back", "front", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this application.

[0033] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0034] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0035] The disclosure below provides many different embodiments or examples for realizing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are merely examples and are not intended to limit the present application. In addition, the present application may repeat reference numbers and / or reference letters in different examples. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed. In addition, the present application provides examples of various specific processes and materials, but those skilled in the art will appreciate the application of other processes and / or the use scenarios of other materials.

[0036] References herein to "embodiments" or "implementations" mean that a particular feature, component, or characteristic described in connection with an embodiment or implementation may be included in at least one embodiment of the present application. The appearance of such phrases in various places in the specification does not necessarily refer to the same embodiment, nor do they constitute independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0037] In order to solve the above problems, the first aspect of the present invention provides a composite passivation film layer for reducing UV absorption, wherein the composite passivation film layer is located on the front surface of a back contact solar cell;

[0038] like Figure 1 As shown, the composite passivation film layer includes, from bottom to top, an aluminum oxide film layer 1, a first silicon nitride film layer 2, a second silicon nitride film layer 3 and a silicon oxide film layer 4, wherein the refractive index of the first silicon nitride film layer 2 is greater than the refractive index of the second silicon nitride film layer 3.

[0039] In the present invention, the aluminum oxide film layer 1, the first silicon nitride film layer 2, the second silicon nitride film layer 3 and the silicon oxide film layer 4 are used as composite passivation film layers. During the deposition process, they can all chemically combine with the silicon in the cell and release hydrogen. The increased atomic hydrogen can then passivate the dangling bonds on the surface of the cell substrate, achieving a good hydrogen passivation effect. Furthermore, the refractive index of the first silicon nitride film layer 2 is made greater than the refractive index of the second silicon nitride film layer 3, forming a gradient refractive index interface, which helps to more evenly distribute the light field, reduce the hot spots of light, avoid local overheating and material damage, and the first silicon nitride film layer 2 with a low refractive index is located in the upper layer to increase light absorption, and the second silicon nitride film layer 3 with a high refractive index is located in the lower layer to more effectively limit the propagation of light inside the material, reduce light escape, thereby increasing the path length of light inside the solar cell and improving light absorption efficiency.

[0040] Preferably, the ratio of the refractive index of the silicon oxide film layer 4 to the refractive index of the second silicon nitride film layer 3 is 1:(0.72-0.75). The refractive index of the silicon oxide film layer 4 is lower than the refractive index of the second silicon nitride film layer 3. While ensuring that the hydrogen passivation effect is not affected, it can promote the migration of hydrogen in the second silicon nitride film layer 3 to the silicon oxide film layer 4, allowing a certain amount of hydrogen to enter the silicon oxide film layer 4, thereby preventing a large amount of hydrogen from diffusing to the interface between the passivation composite film layer and the silicon wafer and forming clusters, which increases the number of impurity centers and further enhances the absorption of UV light. By controlling the ratio of the refractive index of the silicon oxide film layer 4 to the refractive index of the second silicon nitride film layer 3 within the range of 1:(0.72~0.75), the amount of hydrogen entering the silicon oxide film layer 4 can be controlled, so that there is an appropriate amount of hydrogen at the interface between the passivation composite film layer and the silicon wafer and inside the silicon wafer, which not only has a good hydrogen passivation effect, but also can effectively reduce the absorption of UV light. If the ratio of the refractive index of the silicon oxide film layer 4 to the refractive index of the second silicon nitride film layer 3 is greater than 1:0.75, the hydrogen entering the silicon oxide film layer 4 will be reduced, further improving the passivation effect, but will also increase the absorption capacity of UV light. If the ratio of the refractive index of the silicon oxide film layer 4 to the refractive index of the second silicon nitride film layer 3 is less than 1:0.72, the hydrogen content in the defects on the surface of the composite passivation film layer will increase, and it will be impossible to saturate the dangling bonds at the interface between the passivation composite film layer and the silicon wafer, thereby weakening the passivation effect. The ratio of the refractive index of the silicon oxide film layer 4 to the refractive index of the second silicon nitride film layer 3 is exemplarily 1:0.72, 1:0.725, 1:0.73, 1:0.735, 1:0.74, 1:0.745, and 1:0.75, but is not limited thereto.

[0041] Optionally, the refractive index of the silicon oxide film layer 4 is 1.62 to 1.67. The lower refractive index can reduce light reflection and increase light absorption, allowing more light to enter the composite passivation film layer, thereby improving light transmittance and thus improving the power generation efficiency of the back-contact solar cell.

[0042] Furthermore, the thickness of the silicon oxide film layer 4 is 30nm to 40nm, and the thickness of the silicon oxide film layer 4 is exemplarily 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, and 40nm, but is not limited thereto. Under the premise of a refractive index of 1.62 to 1.67, limiting the thickness of the silicon oxide film layer 4 to 30nm to 40nm can effectively block the penetration of impurities, reduce surface and interface defects, further improve the hydrogen passivation effect, and reduce the absorption of UV light. If the thickness of the silicon oxide film layer 4 is too thin, the hydrogen passivation effect will be deteriorated. If the thickness of the silicon oxide film layer 4 is too thick, the passivation effect will be improved, but at the same time, parasitic absorption may also be increased, affecting the optical performance of the battery.

[0043] In some embodiments, the silicon oxide film layer 4 can be obtained by deposition growth. Optionally, the silicon oxide film layer 4 is deposited and grown by plasma enhanced chemical vapor deposition (PECVD) technology. During the deposition growth process, Si source and O source are introduced into the reaction chamber and the growth temperature and growth pressure are controlled for deposition growth. In other embodiments, the silicon oxide film layer 4 can be obtained by oxidizing a silicon layer. The oxidation method can specifically be oxidation by introducing O3, or thermal oxidation by introducing O2, or oxidation of the silicon layer by concentrated nitric acid, or wet oxidation, or other low-temperature oxidation methods known in the art.

[0044] Preferably, the refractive index of the second silicon nitride film layer 3 is 2.01 to 2.09, so that the light passing through the silicon oxide film layer 4 enters the second silicon nitride film layer 3 by refraction, and the refractive index of the second silicon nitride film layer 3 is lower than the refractive index of the first silicon nitride film layer 2, so that the light entering through the second silicon nitride film layer 3 is further restricted in the propagation of light inside the material, reducing the escape of light and further improving the utilization rate of light.

[0045] Preferably, the refractive index of the first silicon nitride film layer 2 is 2.20-2.30, and the refractive index of the first silicon nitride film layer 2 is higher than the refractive index of the aluminum oxide film layer 1, which facilitates the diffusion of hydrogen from the first silicon nitride film layer 2 to the aluminum oxide film layer 1, thereby compensating for the lack of hydrogen passivation on the surface during the sintering process and reducing the impact of dangling bonds on the efficiency of solar cells.

[0046] Furthermore, the ratio of the refractive index of the first silicon nitride film layer 2 to the refractive index of the second silicon nitride film layer 3 is 1:(0.90-0.945), which can encourage as much light as possible to enter the first silicon nitride film layer 2 through the second silicon nitride film layer 3, thereby improving light absorption. At the same time, it promotes the uniform diffusion of hydrogen in the first silicon nitride film layer 2 and the second silicon nitride film layer 3, and then diffuses into the aluminum oxide film layer 1, where it is evenly distributed on the silicon wafer surface and combines with the dangling bonds of silicon atoms, further improving the passivation performance. If the ratio of the refractive index of the first silicon nitride film layer 2 to the refractive index of the second silicon nitride film layer 3 is less than 1:0.90, the diffusion pressure of hydrogen between the first silicon nitride film layer 2 and the second silicon nitride film layer 3 increases, causing more hydrogen in the second silicon nitride film layer 3 to diffuse into the silicon oxide film layer 4, resulting in high-content hydrogen clustering at the interface between the passivation composite film layer and the silicon wafer, increasing the number of impurity centers formed, and thus increasing the absorption of UV light. Exemplary ratios of the refractive index of the first silicon nitride film layer 2 to the refractive index of the second silicon nitride film layer 3 are 1:0.90, 1:0.91, 1:0.92, 1:0.93, 1:0.94, and 1:0.95, but are not limited thereto.

[0047] Furthermore, the ratio of the thickness of the first silicon nitride film layer 2 to the thickness of the second silicon nitride film layer 3 is 1:(3.0-5.0). Based on the ratio of the refractive index of the first silicon nitride film layer 2 to the refractive index of the second silicon nitride film layer 3 being 1:(0.90-0.945), adjusting the ratio of the thickness of the first silicon nitride film layer 2 to the thickness of the second silicon nitride film layer 3 can regulate the diffusion path of hydrogen in the first silicon nitride film layer 2 and the second silicon nitride film layer 3, thereby regulating the hydrogen content at the interface between the passivation composite film layer and the silicon wafer, while taking into account the hydrogen passivation effect and the low absorption of UV light, thereby improving the conversion efficiency and performance of the back-contact solar cell. If the ratio of the thickness of the first silicon nitride film layer 2 to the thickness of the second silicon nitride film layer 3 is greater than 1:5.0, the hydrogen passivation effect can be enhanced, but the absorption of UV light will be increased. If the ratio of the thickness of the first silicon nitride film layer 2 to the thickness of the second silicon nitride film layer 3 is less than 1:3.0, not only will the hydrogen passivation effect not be guaranteed, but the transmission path of the light entering the second silicon nitride film layer 3 will also be changed, causing part of the light to be reflected or absorbed, thereby reducing the utilization rate of the light, and also resulting in poor appearance color and lowering the qualified rate of the product. The ratio of the thickness of the first silicon nitride film layer 2 to the thickness of the second silicon nitride film layer 3 is exemplarily 1:3.0, 1:3.2, 1:3.4, 1:3.6, 1:3.8, 1:4.0, 1:4.2, 1:4.4, 1:4.6, 1:4.8, and 1:5.0, but is not limited thereto.

[0048] Optionally, the thickness of the first silicon nitride film layer 2 is 20 nm to 30 nm, and the thickness of the first silicon nitride film layer 2 is exemplarily 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, and 30 nm, but is not limited thereto. In some embodiments, the first silicon nitride film layer 2 can be obtained by deposition growth on the surface of the aluminum oxide film layer 1. Optionally, the first silicon nitride film layer 2 is deposited and grown by plasma enhanced chemical vapor deposition (PECVD) technology. Specifically, during the deposition growth process, Si source and N source are introduced into the reaction chamber and the growth temperature and growth pressure are controlled for deposition growth.

[0049] Optionally, the thickness of the second silicon nitride film layer 3 is 90nm to 100nm, which plays a role in locking hydrogen and resisting hydrogen. The thickness of the second silicon nitride film layer 3 is exemplarily 90nm, 91nm, 92nm, 93nm, 94nm, 95nm, 96nm, 97nm, 98nm, 99nm, and 100nm, but is not limited thereto. In some embodiments, the second silicon nitride film layer 3 can be obtained by deposition growth on the surface of the first silicon nitride film layer 2. Optionally, the second silicon nitride film layer 3 is deposited and grown by plasma enhanced chemical vapor deposition (PECVD) technology. Specifically, during the deposition growth process, Si source and N source are introduced into the reaction chamber and the growth temperature and growth pressure are controlled for deposition growth.

[0050] In some embodiments, a third silicon nitride film layer, a fourth silicon nitride film layer, or even more layers may be arranged between the first silicon nitride film layer 2 and the second silicon nitride film layer 3, but the refractive index from the first silicon nitride film layer 2 to the second silicon nitride film layer 3 shows a decreasing trend; alternatively, a third silicon nitride film layer, a fourth silicon nitride film layer, or even more layers are arranged on the upper layer of the first silicon nitride film layer 2 and / or the lower layer of the second silicon nitride film layer 3, and the refractive index of the silicon nitride film layer shows a decreasing trend from bottom to top, and the decreasing trend can be one of linear decreasing, gradient decreasing, or a combination thereof. The specific layer structure and refractive index setting of the silicon nitride film layer can be adjusted according to actual needs and are not specifically limited in this application.

[0051] Preferably, the refractive index of the aluminum oxide film layer 1 is 1.6 to 1.7. The low refractive index of the aluminum oxide film layer 1 can allow more light to undergo light conversion in the back contact solar cell substrate 5, thereby improving the photoelectric conversion efficiency of the back contact solar cell. At the same time, it is beneficial for part of the hydrogen in the first silicon nitride film layer 2 to diffuse into the aluminum oxide film layer 1, react with the surface of the back contact solar cell, saturate the dangling bonds on the surface, and allow part of the hydrogen to enter the interior of the back contact solar cell, thereby playing a role in surface hydrogen passivation.

[0052] Furthermore, the thickness of the aluminum oxide film layer 1 is 4 nm to 5 nm, which facilitates the entry of hydrogen in the first silicon nitride film layer 2. The thickness of the aluminum oxide film layer 1 is exemplarily 4 nm, 4.2 nm, 4.4 nm, 4.6 nm, 4.8 nm, and 5 nm, but is not limited thereto.

[0053] In some embodiments, the aluminum oxide film layer 1 can be obtained by deposition growth on the front surface of the back-contact solar cell. Optionally, the aluminum oxide film layer 1 is deposited and grown by plasma enhanced chemical vapor deposition (PECVD) technology. During the deposition growth process, Al source and O source are introduced into the reaction chamber and the growth temperature and growth pressure are controlled for deposition growth.

[0054] It can be understood that the film layer with a high refractive index has a relatively high density and fewer internal pores, while the film layer with a low refractive index has a relatively low density and more internal pores, that is, the film layer with a low refractive index can accommodate relatively more hydrogen, thereby affecting the distribution of hydrogen on the surface of the material. There is relatively less hydrogen in the film layer with a high refractive index, and the higher density and fewer internal voids limit the distribution of hydrogen. In this case, hydrogen may be more inclined to accumulate at lattice defects rather than be evenly distributed throughout the material.

[0055] Correspondingly, the present invention also provides a back-contact solar cell, comprising the composite passivation film layer for reducing UV absorption.

[0056] Preferably, the composite passivation film layer is located on the front surface of a back-contact solar cell, the back-contact solar cell includes the back-contact solar cell substrate 5 , and the composite passivation film layer is located on the front surface of the back-contact solar cell substrate 5 .

[0057] In some embodiments, the front surface of the back contact solar cell is a smooth surface structure, see Figure 2 .

[0058] In some other embodiments, the front surface of the back contact solar cell has a pyramid texture structure, see Figure 3 The pyramid velvet structure can increase the scattering and light trapping effects of light, thereby significantly reducing the reflectivity of the front surface of the back-contact solar cell, allowing more light energy to be absorbed by the back-contact solar cell, thereby improving the photoelectric conversion efficiency of the back-contact solar cell. Here, the front surface of the back-contact solar cell substrate 5 refers to the light-receiving surface of the back-contact solar cell substrate 5.

[0059] Preferably, the back-contact solar cell further includes a first anti-reflection layer (not shown in the figure), disposed on the upper surface of the composite passivation film layer. Optionally, the material of the first anti-reflection layer can be one of silicon nitride, silicon oxide, titanium oxide, aluminum oxide, and silicon oxynitride. The refractive index and thickness of the anti-reflection layer can be adjusted as needed and are not specifically limited in this application.

[0060] It can be understood that the back side of the back-contact solar cell is a conventional setting in the art.

[0061] In some embodiments, the back surface of the back-contact solar cell includes: a tunneling layer 6 disposed on the back surface of the substrate 5;

[0062] An N-type doped polysilicon layer 7 and a P-type doped polysilicon layer 8 are provided on the tunneling layer 6, wherein the N-type doped polysilicon layer 7 and the P-type doped polysilicon layer 8 are insulated and isolated by an isolation region 9;

[0063] a passivation layer 10 covering the N-type doped polysilicon layer 7, the P-type doped polysilicon layer 8 and the isolation region 9;

[0064] a second anti-reflection layer 11 disposed on the passivation layer 10;

[0065] A first electrode 12 and a second electrode 13 are provided on the back side of the substrate 5 . The first electrode 12 penetrates the passivation layer 10 and contacts the N-type doped polysilicon layer 7 . The second electrode 13 penetrates the passivation layer 10 and contacts the P-type doped polysilicon layer 8 .

[0066] In some embodiments, the back surface of the back contact solar cell is a smooth surface structure, and the obtained back contact solar cell can be seen in FIG. Figure 4 .

[0067] In some other embodiments, the back surface of the back contact solar cell has a pyramid texture structure, see Figure 5 The pyramid velvet structure can scatter incident light, reduce specular reflection of light, and increase the residence time of light on the back of the battery, thereby improving light utilization and photoelectric conversion efficiency.

[0068] Preferably, the material of the tunneling layer 6 can be one of silicon oxide, tantalum pentoxide, aluminum oxide, and gallium oxide. Optionally, the tunneling layer 6 includes a first tunneling layer 6 and a second tunneling layer 6 . The first tunneling layer 6 and the second tunneling layer 6 can have different thicknesses and different conductivities. The thickness and refractive index of the tunneling layer 6 can be adjusted appropriately based on actual conditions and are not specifically limited in this application.

[0069] Preferably, the doping elements of the N-type doped polysilicon layer 7 include but are not limited to P (phosphorus) and As (arsenic), and the P-type doped polysilicon layer 8 includes but is not limited to B (boron), Al (aluminum), and Ga (gallium). The thicknesses of the N-type doped polysilicon layer 7 and the P-type doped polysilicon layer 8 can be reasonably adjusted according to actual conditions and are not specifically limited in this application.

[0070] Preferably, the material of the passivation layer 10 can be one of silicon oxide, silicon oxynitride, silicon nitride, and aluminum oxide. The thickness and refractive index of the passivation layer 10 can be reasonably adjusted according to actual conditions, and this application does not make any specific restrictions.

[0071] Preferably, the material of the second anti-reflection layer 11 can be one of silicon nitride, silicon oxide, titanium oxide, aluminum oxide, and silicon oxynitride. The thickness and refractive index of the second anti-reflection layer 11 can be reasonably adjusted according to actual conditions and are not specifically limited in this application.

[0072] Preferably, the material of the first electrode 12 can be selected from multiple options, usually one of silver, copper, aluminum, nickel, tin, and cobalt; the material of the first electrode 13 can be selected from multiple options, usually one of silver, copper, aluminum, nickel, tin, and cobalt.

[0073] Correspondingly, the present invention also provides a back-contact solar cell assembly, which includes the back-contact solar cell.

[0074] It is understood that a back-contact solar cell assembly includes busbars and solder ribbons, and the back-contact solar cells are connected using the solder ribbons and busbars to form a back-contact solar cell layer. The solder ribbons can be made of a variety of materials, typically one of copper, nickel, aluminum, silver, and tin alloys; the busbars can be made of a variety of materials, typically one of copper, nickel, aluminum, silver, and tin alloys.

[0075] It is understandable that the back contact solar cell module may further include a metal frame, a back sheet, a front sheet and an adhesive film.

[0076] A front sheet, such as photovoltaic glass, can cover the adhesive film on the front surface of the back-contact solar cell. The front sheet can be made of ultra-clear glass, which has high light transmittance, high transparency, and excellent physical, mechanical, and optical properties. For example, ultra-clear glass can have a light transmittance exceeding 92%, protecting the back-contact solar cell while minimizing the impact on its efficiency. The adhesive film can also bond the front sheet and back-contact solar cell together, providing sealing, insulation, and waterproofing of the back-contact solar cell.

[0077] The backplane can be attached to the film on the back of the back-contact solar cell. The backplane can protect and support the back-contact solar cell and has reliable insulation, water resistance and aging resistance. There are multiple options for the backplane, which can usually be tempered glass, organic glass, aluminum alloy TPT composite film, KPC, CPC, etc. The specific setting can be made according to the specific situation and is not specifically limited in this application.

[0078] The whole composed of the back panel, back contact solar cell sheet, adhesive film and front panel can be set on a metal frame. The metal frame serves as the main external support structure of the entire back contact solar cell assembly and can stably support and install the back contact solar cell assembly. For example, the back contact solar cell assembly can be installed at the required installation position through the metal frame.

[0079] Correspondingly, the present invention also provides a photovoltaic system, which includes the back-contact solar cell assembly.

[0080] It is understandable that the photovoltaic system includes at least one back-contact solar cell module as described above. It is understandable that the back-contact solar cell modules can be electrically connected in parallel or in series, and the specific connection can be selected according to actual needs.

[0081] In this embodiment, the photovoltaic system can be applied to photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be applied to equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is, the photovoltaic system can be applied in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction box and an inverter. The photovoltaic array can be an array combination of multiple battery modules. For example, multiple solar cell modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter to be converted into the alternating current required by the mains power grid and then connected to the mains power network to achieve solar power supply.

[0082] The above disclosure is only a preferred embodiment of the present invention and certainly cannot be used to limit the scope of rights of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope covered by the present invention.

Claims

1. A composite passivation film layer for reducing UV absorption, characterized in that: The composite passivation film layer is located on the front surface of the back contact solar cell; The composite passivation film layer includes, from bottom to top, an aluminum oxide film layer, a first silicon nitride film layer, a second silicon nitride film layer, and a silicon oxide film layer, wherein the refractive index of the first silicon nitride film layer is greater than the refractive index of the second silicon nitride film layer.

2. The composite passivation film layer for reducing UV absorption according to claim 1, wherein: The refractive index of the second silicon nitride film layer is 2.01 to 2.09; The refractive index of the first silicon nitride film layer is 2.20-2.

30.

3. The composite passivation film layer for reducing UV absorption according to claim 2, wherein: The ratio of the refractive index of the first silicon nitride film layer to the refractive index of the second silicon nitride film layer is 1:(0.90-0.945).

4. The composite passivation film layer for reducing UV absorption according to claim 1, wherein: The ratio of the thickness of the first silicon nitride film layer to the thickness of the second silicon nitride film layer is 1:(3.0-5.0).

5. The composite passivation film layer for reducing UV absorption according to claim 1 or 4, characterized in that: The thickness of the second silicon nitride film layer is 90nm to 100nm; The thickness of the first silicon nitride film layer is 20 nm to 30 nm.

6. The composite passivation film layer for reducing UV absorption according to claim 2, characterized in that: The ratio of the refractive index of the silicon oxide film layer to the refractive index of the second silicon nitride film layer is 1:(0.72-0.75).

7. The composite passivation film layer for reducing UV absorption according to claim 1 or 6, characterized in that: The thickness of the silicon oxide film layer is 30 nm to 40 nm.

8. The composite passivation film layer for reducing UV absorption according to claim 1, wherein: The thickness of the aluminum oxide film layer is 4 nm to 5 nm.

9. The composite passivation film layer for reducing UV absorption according to claim 1, wherein: The front surface of the back contact solar cell has a pyramid texture structure.

10. A back contact solar cell, characterized in that: The composite passivation film layer for reducing UV absorption comprises the composite passivation film layer for reducing UV absorption as claimed in any one of claims 1 to 9.

11. A back contact solar cell module, characterized in that: It comprises the back-contact solar cell according to claim 10 .

12. A photovoltaic system, characterized in that: It comprises the back-contact solar cell module according to claim 11.

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