Composite passivated conductive back sheet, method of making, and photovoltaic module

Abstract

The application provides a composite passivated conductive back plate and a preparation method and a photovoltaic module, and can be widely applied to the technical field of photovoltaic modules. The composite passivated conductive back plate comprises a substrate layer, an insulating buffer layer, a composite conductive layer and a partition passivation layer which are sequentially stacked; the composite conductive layer comprises a substrate layer, a transition layer and a welding layer which are sequentially stacked; the substrate layer is located on the side close to the insulating buffer layer, and the welding layer is located on the side close to the partition passivation layer; the transition layer is a conductive nitride with a first thickness or a first alloy; the first thickness is 5-20 nm, and the first alloy comprises one or more of nickel-chromium alloy, titanium-chromium alloy, titanium-aluminum alloy and chromium-aluminum alloy. The conductive nitride improves the interface bonding between the substrate and the welding layer, improves the interface bonding force, reduces the contact resistance, and solves the problems of false welding and open circuit of the copper-aluminum composite back plate in the related art, which is beneficial to improving the conductive reliability of the battery.

Description

Technical Field

[0001] This application relates to the field of photovoltaic module technology, and more specifically, to a composite passivated conductive backsheet and its preparation method, and a photovoltaic module. Background Technology

[0002] Back-contact batteries achieve 100% light exposure on the front by transferring all electrodes to the back of the battery, significantly improving photoelectric conversion efficiency. The back side requires the simultaneous formation of isolated P-type and N-type doped regions, creating low-resistance ohmic contacts and high-quality passivation junctions. In related technologies, back-contact batteries typically use copper-aluminum composite foil backsheets. However, due to the difference in thermal expansion coefficients between copper and aluminum, and lattice mismatch leading to weak interfacial bonding, corrosion is easily formed in humid and hot environments, causing poor soldering and open-circuit faults, resulting in low conductivity reliability. Summary of the Invention

[0003] The main objective of this application is to provide a composite passivated conductive backsheet and its preparation method, as well as a photovoltaic module, so as to at least solve the problem of low conductivity reliability of batteries in related technologies.

[0004] To achieve the above objectives, according to one aspect of this application, a composite passivated conductive backsheet is provided for encapsulating a photovoltaic module, the composite passivated conductive backsheet comprising:

[0005] A substrate layer, an insulating buffer layer, a composite conductive layer, and a partitioned passivation layer are stacked sequentially.

[0006] The composite conductive layer includes a substrate layer, a transition layer, and a welding layer stacked sequentially; wherein the substrate layer is located on the side closer to the insulating buffer layer, and the welding layer is located on the side closer to the partitioned passivation layer; the transition layer is a conductive nitride or a first alloy with a thickness of a first thickness; the first thickness is 5-20 nm, and the first alloy includes one or more of nickel-chromium alloy, titanium-chromium alloy, titanium-aluminum alloy, and chromium-aluminum alloy.

[0007] This application improves the interfacial bonding between the substrate and the welding layer by using conductive nitrides, thereby enhancing the interfacial bonding force, reducing contact resistance, and alleviating the problems of poor welding and open circuits in copper-aluminum composite backplates in related technologies, which is beneficial to improving the conductivity reliability of the battery.

[0008] Optionally, the substrate layer comprises aluminum with a second thickness, and the welding layer comprises a second alloy with a third thickness, wherein the second alloy comprises a silver-copper alloy;

[0009] Wherein, the first ratio of the first thickness to the third thickness is greater than or equal to 0.001 and the first ratio is less than or equal to 0.02, and the second ratio of the second thickness to the third thickness is greater than or equal to 10 and the second ratio is less than or equal to 50.

[0010] Optionally, the second thickness is 40-130 μm, and the third thickness is 5-10 μm.

[0011] Optionally, the partitioned passivation layer includes:

[0012] The stacked structure deposited by PECVD process has contact windows at positions corresponding to the electrodes. The spacing between two adjacent contact windows of the same type of electrode is 0.8-1.5 mm, and the width of the contact window is 20-30 μm.

[0013] Optionally, the stacked structure includes a SiO2 layer with a thickness of 10-30 nm and an Al2O3 layer with a thickness of 20-50 nm stacked together;

[0014] The SiO2 layer is located on the side closer to the composite conductive layer, and the Al2O3 layer is located on the side farther away from the composite conductive layer.

[0015] The third ratio of the spacing to the electrode width is greater than 1.2 and the third ratio is less than 1.8.

[0016] Optionally, the composite passivated conductive backplate further includes:

[0017] A flame-retardant protective layer is disposed on the side of the partitioned passivation layer away from the composite conductive layer;

[0018] The flame-retardant protective layer comprises a modified polyurethane coating, the thickness of the flame-retardant protective layer is 10-20 μm, the limiting oxygen index of the flame-retardant protective layer is greater than or equal to 32%, and the adhesion is greater than or equal to 5B; wherein, the modified polyurethane coating comprises 3-5 wt% intumescent graphite and 2-3 wt% benzotriazole.

[0019] To achieve the above objectives, according to another aspect of this application, a photovoltaic module is provided, including a solar cell, the back side of which includes the aforementioned composite passivated conductive backsheet.

[0020] According to another aspect of this application, a method for preparing a composite passivated conductive backplate is provided, comprising:

[0021] The board material is pretreated to form a substrate layer;

[0022] An insulating material is coated on one side of the substrate layer to form an insulating buffer layer;

[0023] A conductive nitride or a first alloy is deposited on the side of the insulating buffer layer away from the substrate layer to form a transition layer; wherein the first thickness of the transition layer is 5-20 nm, and the first alloy includes one or more of nickel-chromium alloy, titanium-chromium alloy, titanium-aluminum alloy, and chromium-aluminum alloy.

[0024] A solder layer is deposited on the side of the transition layer away from the insulating buffer layer to form a composite conductive layer;

[0025] Deposition and etching are performed on the side of the composite conductive layer away from the transition layer to form a partitioned passivation layer, resulting in a composite passivated conductive backplane.

[0026] Optionally, the deposition of a conductive nitride or a first alloy on the side of the insulating buffer layer away from the substrate layer to form a transition layer includes:

[0027] On the side of the insulating buffer layer away from the substrate layer, a conductive nitride or a first alloy is deposited by a first magnetron sputtering, and a transition layer is formed by plasma bombardment treatment; wherein, the sputtering power of the first magnetron sputtering is 300-600W, the power of the plasma bombardment treatment is 200-300W, and the time is 1-2min;

[0028] The deposition of a solder layer on the side of the transition layer away from the insulating buffer layer includes:

[0029] A welding layer is deposited by a second magnetron sputtering on the side of the transition layer away from the insulating buffer layer; the sputtering power of the second magnetron sputtering is 500-1000W, and the substrate temperature is less than or equal to 150 degrees Celsius.

[0030] Optionally, the deposition and etching of the composite conductive layer on the side away from the transition layer to form a partitioned passivation layer includes:

[0031] A stacked structure is deposited on the side of the composite conductive layer away from the transition layer using a PECVD process, and then laser etching is performed to form a partitioned passivation layer; wherein the laser wavelength for the laser etching is 355-370nm, the energy density is 0.8-1.2J / cm², the laser spot diameter is 5-10μm, and the scanning speed is 100-300mm / s.

[0032] By applying the technical solution of this application, the present application improves the interfacial bonding between the substrate and the welding layer through conductive nitride, enhances the interfacial bonding force, reduces the contact resistance, and alleviates the problems of poor welding and open circuit in copper-aluminum composite backplates in related technologies, which is conducive to improving the conductivity reliability of the battery. Attached Figure Description

[0033] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0034] Figure 1 A schematic diagram of a composite passivated conductive backplate provided in an embodiment of this application is shown.

[0035] Figure 2 It shows Figure 1 A schematic diagram of the composite conductive layer of the composite passivated conductive backplate is shown.

[0036] Figure 3 It shows Figure 1 A schematic diagram of the partitioned passivation layer structure of the composite passivated conductive backplane is shown.

[0037] Figure 4 A schematic flowchart of a method for preparing a composite passivated conductive backplate according to an embodiment of this application is shown.

[0038] Figure 5 A schematic flowchart of another method for preparing a composite passivated conductive backplate according to an embodiment of this application is shown.

[0039] The above figures include the following reference numerals:

[0040] 10. Substrate layer; 20. Insulating buffer layer; 30. Composite conductive layer; 40. Partitioned passivation layer; 301. Substrate layer; 302. Transition layer; 303. Welding layer; 401. P-type finger electrode; 402. N-type finger electrode; 50. Flame-retardant protective layer. Detailed Implementation

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0042] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0043] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0044] Back contact (BC) cells achieve 100% light exposure on the front by transferring all electrodes to the back of the cell, significantly improving photoelectric conversion efficiency. The back of the cell needs to simultaneously set mutually isolated P-type doped regions and N-type doped regions (arranged in a finger-like cross pattern) to form a low-resistance ohmic contact and a high-quality passivation structure.

[0045] The following problems exist with back-contact batteries in related technologies: Insufficient conductivity reliability: In traditional copper-aluminum composite foil backsheets, the difference in thermal expansion coefficients and lattice mismatch between copper and aluminum materials leads to weak interfacial bonding, making them prone to corrosion in humid and hot environments, causing poor soldering and open circuit failures. Poor passivation protection synergy: When the backsheet contacts the P / N doped region on the back of the battery, it is difficult to simultaneously meet conductivity requirements and passivation protection. Existing multilayer passivation films mostly use PECVD and PE-ALD composite processes, which can improve the passivation effect, but the process is complex and has poor compatibility with the conductive layer, resulting in increased carrier recombination losses. Low process compatibility: Existing backsheet structures cannot adapt to the 0.5-2mm pitch finger-like staggered electrode layout on the back of BC batteries, requiring complex alignment processes, and the risk of grid breakage during metallization is prone to occur, resulting in low production efficiency. Insufficient environmental adaptability: There is a lack of flame-retardant and anti-oxidation protection design for the precision structure on the back of BC batteries, and performance degradation is easily caused by environmental factors during long-term use.

[0046] Therefore, there is an urgent need to develop a special backsheet for BC batteries that combines high conductivity stability, excellent passivation performance, strong process compatibility and good environmental adaptability, in order to solve the pain points of existing technologies such as structural separation, complex processes and insufficient reliability.

[0047] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0048] Figure 1 This is a schematic diagram of the structure of the composite passivated conductive backplate according to an embodiment of this application. Figure 2 This is a schematic diagram of the composite conductive layer. The composite passivated conductive backplate includes:

[0049] The substrate layer 10, the insulating buffer layer 20, the composite conductive layer 30 and the partitioned passivation layer 40 are stacked in sequence.

[0050] The composite conductive layer includes a substrate layer 301, a transition layer 302, and a welding layer 303 stacked sequentially; wherein the substrate layer is located on the side closer to the insulating buffer layer, and the welding layer is located on the side closer to the partitioned passivation layer; the transition layer is a conductive nitride or a first alloy with a thickness of 5-20 nm; the first thickness is 5-20 nm, and the first alloy includes one or more of nickel-chromium alloy, titanium-chromium alloy, titanium-aluminum alloy, and chromium-aluminum alloy.

[0051] The composite conductive layer in this application includes a substrate layer, a transition layer, and a welding layer. The transition layer, through a conductive nitride and a first alloy, increases the interfacial bonding force between the metals of the welding layer and the substrate layer, thereby improving the conductivity reliability of the battery. The conductive nitride in this application can be a highly conductive transition metal nitride or a conductive nitride with diffusion-blocking function. Exemplarily, the conductive nitride includes at least one of titanium nitride (TiN), chromium nitride (CrN), tantalum nitride (TaN), and zirconium nitride (ZrN). The first alloy includes nickel-chromium alloy (NiCr), titanium-chromium alloy (TiCr), titanium-aluminum alloy (TiAl), chromium-aluminum alloy (CrAl), and combinations thereof, used to enhance the interfacial bonding force between the substrate layer and the welding layer. In some embodiments, the substrate layer is obtained by pretreatment of modified polyolefin, and the thickness of the substrate layer is 1-2 mm. The insulating buffer layer is prepared by epoxy resin and nano-SiO2, and the thickness of the insulating buffer layer is 50-100 μm. The partitioned passivation layer is obtained by deposition and etching.

[0052] This application improves the interfacial bonding between the substrate and the welding layer by using conductive nitrides, thereby enhancing the interfacial bonding force, reducing contact resistance, and alleviating the problems of poor welding and open circuits in copper-aluminum composite backplates in related technologies, which is beneficial to improving the conductivity reliability of the battery.

[0053] Optionally, the substrate layer includes aluminum with a second thickness, and the welding layer includes a second alloy with a third thickness, the second alloy including a silver-copper alloy;

[0054] Wherein, the first ratio of the first thickness to the third thickness is greater than or equal to 0.001 and the first ratio is less than or equal to 0.02, and the second ratio of the second thickness to the third thickness is greater than or equal to 10 and the second ratio is less than or equal to 50.

[0055] In some embodiments, the aluminum purity in the substrate layer is ≥99.99%, and the tensile strength is ≥120 MPa. The transition layer is a titanium nitride or nickel-chromium alloy with a thickness of 5-20 nm (resistivity ≤30 μΩ·cm), and the weld layer is a silver-copper alloy with a thickness of 5-10 μm (Ag content 85-90 wt%). Of course, the specific composition of the substrate layer and the weld layer is merely an example, and those skilled in the art can determine the materials of the weld layer and the substrate layer according to actual needs.

[0056] Optionally, the second thickness is 40-130 μm and the third thickness is 5-10 μm.

[0057] Optionally, the partitioned passivation layer includes:

[0058] The stacked structure deposited by PECVD process has contact windows set at positions corresponding to the electrodes. The spacing between two adjacent contact windows of the same type of electrode is 0.8-1.5 mm, and the width of the contact window is 20-30 μm.

[0059] In this application, the partitioned passivation layer is deposited using a single PECVD process to create a stacked structure, fabricating electrode regions that match the electrodes and improving process compatibility. Electrodes of the same type are those with the same charge carriers, and the spacing between two adjacent contact windows within the electrode region corresponding to the same type of electrode is 0.8-1.5 mm. For example... Figure 3 As shown, the positional relationship between the P-type finger electrode 401 and the N-type finger electrode 402 is illustrated. The electrode widths of both the P-type finger electrode 401 and the N-type finger electrode 402 are set to 20 μm. Correspondingly, the contact window widths of both regions are set to 25 μm, and the spacing is set to 40 μm. In some embodiments, the P-type finger electrode 401 corresponds to the P-type electrode region (Al2O3), and the N-type finger electrode 402 corresponds to the N-type electrode region (SiO2 layer).

[0060] Optionally, the stacked structure includes a SiO2 layer with a thickness of 10-30 nm and an Al2O3 layer with a thickness of 20-50 nm stacked together;

[0061] Among them, the SiO2 layer is located on the side closer to the composite conductive layer, and the Al2O3 layer is located on the side farther away from the composite conductive layer;

[0062] The third ratio of the spacing to the electrode width is greater than 1.2 and less than 1.8.

[0063] In some embodiments, the ratio of the width of the contact window laser-etched on the backplate to the width of the finger-shaped electrode on the back of the BC battery is designed to be 1.5. Specifically, the contact window width is 25 μm, and the battery electrode width is approximately 16.67 μm, so 25 ÷ 16.67 ≈ 1.5. In practice, making the window slightly wider than the electrode ensures that the electrode can be aligned and contact the conductive layer during packaging alignment, preventing connection failure due to slight deviation, thus improving yield and reliability.

[0064] On the other hand, the different thicknesses of the SiO2 layer and Al2O3 layer in the embodiments of this application are an optimized design based on the differences in the passivation mechanism and interface characteristics of the two materials. Specifically:

[0065] The SiO2 layer is used to provide chemical passivation and interface stress buffering. A thinner layer can achieve good interface state control, while an excessively thick layer will increase series resistance and etching difficulty. The Al2O3 layer is used to focus on providing field effect passivation (high negative charge density). The passivation effect of the high interface state region on the back of the BC battery depends more on a certain thickness to ensure field effect strength and long-term reliability.

[0066] In some embodiments, this application deposits a SiO2 layer using a PECVD process at a deposition temperature of 250-300℃ and a pressure of 100-200 Pa; then deposits an Al2O3 layer at a deposition temperature of 280-320℃ and a pressure of 150-250 Pa. The different temperatures are due to the lower SiO2 deposition temperature (250–300℃): firstly, to avoid thermal damage, grain coarsening, and interfacial diffusion to the underlying composite conductive layer (metal layer); secondly, this temperature range ensures the density and uniformity of the PECVD SiO2, meeting the requirements for interfacial passivation. The slightly higher Al2O3 deposition temperature (280–320℃) is to obtain a higher quality Al2O3 film, improving its field-effect passivation effect and film density, while still keeping the temperature within a range that will not significantly degrade the underlying metal and polymer structure. The reason for the different pressures: SiO2 deposition pressure is lower (100–200 Pa): which is conducive to precursor dissociation and uniform coverage, resulting in dense, low-defect SiO2; Al2O3 deposition pressure is slightly higher (150–250 Pa): which is a process range optimized for the characteristics of Al2O3 precursor, ensuring a balance between deposition rate, film uniformity and passivation performance, while avoiding problems such as pinholes and porosity caused by excessively high / low pressure.

[0067] Optionally, the composite passivated conductive backplane also includes:

[0068] Flame-retardant protective layer 50, the flame-retardant protective layer is disposed on the side of the partitioned passivation layer away from the composite conductive layer;

[0069] The flame-retardant protective layer includes a modified polyurethane coating. The thickness of the flame-retardant protective layer is 10-20 μm. The limiting oxygen index of the flame-retardant protective layer is greater than or equal to 32%, and the adhesion is greater than or equal to 5B. The modified polyurethane coating includes 3-5 wt% intumescent graphite and 2-3 wt% benzotriazole.

[0070] In some embodiments, the flame-retardant protective layer in this application is prepared by coating modified polyurethane and a flame retardant. The water vapor transmission rate of the overall back panel is ≤0.1 g / (m²·d).

[0071] In some embodiments, the substrate layer in this application has trenches with a roughness of 0.3-0.8 μm. The substrate layer, insulating buffer layer, composite conductive layer, and partitioned passivation layer are formed into an integrated structure by hot pressing and curing. The temperature for overall pressing and curing is 120-140℃, the pressure is 0.5-1.0 MPa, and the time is 30-60 min; the insulating buffer layer is formed by mixing epoxy resin and nano-silica particles using a high-speed disperser at a mixing speed of 3000-5000 r / min.

[0072] To achieve the above objectives, according to another aspect of this application, a photovoltaic module is provided, including a solar cell, the back of which includes the aforementioned composite passivated conductive backsheet.

[0073] According to another aspect of this application, a method for preparing a composite passivated conductive backplate is provided, referring to... Figure 4 ,include:

[0074] Step S100: Pre-treat the board material to form a substrate layer;

[0075] Step S200: Coating an insulating material onto one side of the substrate layer to form an insulating buffer layer;

[0076] Step S300: Deposit a conductive nitride or a first alloy on the side of the insulating buffer layer away from the substrate layer to form a transition layer; wherein the first thickness of the transition layer is 5-20 nm, and the first alloy includes one or more of nickel-chromium alloy, titanium-chromium alloy, titanium-aluminum alloy, and chromium-aluminum alloy.

[0077] Step S400: A solder layer is deposited on the side of the transition layer away from the insulating buffer layer to form a composite conductive layer;

[0078] In step S500, deposition and etching are performed on the side of the composite conductive layer away from the transition layer to form a partitioned passivation layer, thereby obtaining a composite passivated conductive backplane.

[0079] Optionally, a conductive nitride or a first alloy is deposited on the side of the insulating buffer layer away from the substrate layer to form a transition layer, including:

[0080] Conductive nitrides or a first alloy are deposited on the side of the insulating buffer layer away from the substrate layer by first magnetron sputtering, and a transition layer is formed by plasma bombardment treatment; wherein the sputtering power of the first magnetron sputtering is 300-600W, the power of the plasma bombardment treatment is 200-300W, and the time is 1-2min.

[0081] A weld layer is deposited on the side of the transition layer away from the insulating buffer layer, including:

[0082] A second magnetron sputtering deposition layer is performed on the side of the transition layer away from the insulating buffer layer; the sputtering power of the second magnetron sputtering is 500-1000W, and the substrate temperature is less than or equal to 150 degrees Celsius.

[0083] Optionally, deposition and etching are performed on the side of the composite conductive layer away from the transition layer to form a partitioned passivation layer, including:

[0084] A stacked structure is deposited on the side of the composite conductive layer away from the transition layer using PECVD process, and then laser etching is performed to form a partitioned passivation layer. The laser wavelength for laser etching is 355-370nm, the energy density is 0.8-1.2J / cm², the laser spot diameter is 5-10μm, and the scanning speed is 100-300mm / s.

[0085] To enable those skilled in the art to better understand the technical solution of this application, the implementation process of the composite passivated conductive backplane of this application will be described in detail below with reference to specific embodiments.

[0086] This application provides a composite passivated conductive backsheet for BC batteries and its preparation method, achieving the following objectives: solving the problems of insufficient bonding force and corrosion between different metal layers, and improving conductivity reliability; synergistically achieving precise electrode contact and carrier passivation protection, reducing recombination loss; adapting to the finger-shaped staggered electrode layout on the back of BC batteries, simplifying the packaging and metallization process; enhancing the flame retardant and oxidation resistance of the backsheet, and extending the module life.

[0087] like Figure 5 As shown, the preparation method includes the following steps:

[0088] 1. Substrate pretreatment: The modified polyolefin board is placed in a vacuum plasma cleaner, and argon gas (flow rate 30-50 sccm) is introduced. The vacuum level is ≤5×10⁻⁶. -4 Under conditions of Pa and power of 400-600W, the surface is treated for 3-5 minutes to form micron-level grooves. The water contact angle of the treated surface is ≤60°.

[0089] 2. Preparation of insulating buffer layer: Epoxy resin and nano-silica particles are mixed evenly using a high-speed disperser (3000-5000 r / min), and then coated onto the surface of the substrate layer by a casting process (coating speed 1-3 m / min). The mixture is then cured at 120-150℃ for 60-90 min to form an insulating buffer layer.

[0090] 3. Preparation of composite conductive layer:

[0091] a. A transition layer is deposited on the surface of the insulating buffer layer using magnetron sputtering: target purity ≥99.995%, sputtering power 300-600W, argon flow rate 20-40sccm, deposition rate 0.5-2nm / s, followed by plasma bombardment treatment (power 200-300W, time 1-2min).

[0092] b. Deposit a welding layer on the surface of the transition layer using magnetron sputtering: target purity ≥99.99%, sputtering power 500-1000W, substrate temperature ≤150℃, deposition rate 3-8nm / s, to avoid high temperature affecting the underlying structure;

[0093] 4. Preparation of partitioned passivation layer:

[0094] a. A SiO2 layer (10-30 nm thick) is deposited on the surface of the composite conductive layer by PECVD process at a deposition temperature of 250-300℃ and a pressure of 100-200 Pa, followed by the deposition of an Al2O3 layer (20-50 nm thick) at a deposition temperature of 280-320℃ and a pressure of 150-250 Pa.

[0095] b. Use ultraviolet laser (wavelength 355-370nm) for partitioned etching, with laser spot diameter of 5-10μm, scanning speed of 100-300mm / s, and energy density controlled at 0.8-1.2J / cm², to form contact windows corresponding to the P / N electrodes of the BC battery. After etching, the verticality of the window edge is ≥85°.

[0096] 5. Preparation of flame-retardant protective layer: The modified polyurethane coating is mixed with intumescent graphite and benzotriazole, and applied to the surface of the partitioned passivation layer by spraying process (spray gun pressure 0.3-0.5MPa, spraying distance 20-30cm), and dried at 80-100℃ for 30-40min.

[0097] 6. Overall pressing and curing: Place each layer of the structure in a hot press and press for 30-60 minutes at a temperature of 120-140℃ and a pressure of 0.5-1.0MPa. After cooling to room temperature, cut and shape to obtain a composite passivated conductive backplate.

[0098] Example 1:

[0099] 1. Substrate layer: 1.5mm thick modified polyolefin board, surface roughness Ra=0.5μm after plasma treatment, water contact angle=55°;

[0100] 2. Insulating buffer layer: 60μm thick epoxy resin + 8wt% nano-silica (particle size 80nm), dielectric strength 25kV / mm, volume resistivity 5×10¹ 4 Ω·cm;

[0101] 3. Composite conductive layer: substrate layer (100μm aluminum foil, tensile strength 130MPa) + transition layer (10nm TiN, resistivity 25μΩ·cm) + solder layer (8μm silver-copper alloy, Ag content 88wt%), d1 / d2=12.5, d3 / d2=0.00125; d1 is the thickness of the substrate layer, d2 is the thickness of the solder layer, and d3 is the thickness of the transition layer;

[0102] 4. Partitioned passivation layer: SiO2 layer (20nm) + Al2O3 layer (30nm), contact window width 25μm, spacing 0.8mm, ratio of 1.5 to the width of the BC battery finger electrode;

[0103] 5. Flame-retardant protective layer: 15μm modified polyurethane + 4wt% expanded graphite + 2.5wt% benzotriazole, adhesion 5B, limiting oxygen index 34%;

[0104] 6. Preparation process: Follow the steps above, with a vacuum degree of 5×10⁻⁶. -4 Pa, sputtering power 500W, laser energy density 1.0J / cm², hot pressing temperature 130℃, pressure 0.8MPa, pressing time 45min.

[0105] Test results: Composite conductive layer bonding strength = 16.2 N / cm, contact resistance 3.2 mΩ, dielectric strength 22 kV / mm, water vapor transmission rate 0.08 g / (m²·d), module conversion efficiency 26.8% after being adapted to BC battery, no cracking after 1000 temperature cycles (-40℃~85℃), and no yellowing after 1000h UV aging.

[0106] Example 2:

[0107] The difference from Example 1 is that the transition layer uses 15nm NiCr (resistivity 28μΩ·cm), the welding layer is a 5μm silver-copper alloy (Ag content 85wt%), d1 / d2=20, the contact window width is 20μm, and the spacing is 1.2mm. Test results: composite conductive layer bonding strength = 14.5N / cm, contact resistance 4.5mΩ, module conversion efficiency 26.6%, water vapor transmission rate 0.09g / (m²·d), meeting the requirements for photovoltaic module use.

[0108] In response, the composite passivated conductive backplane and its preparation method provided in this application have achieved a significant improvement in conductivity reliability: the interface bonding between the aluminum foil substrate and the silver-copper welding layer is improved by a transition layer, the bonding force is increased by more than 40% (≥15N / cm), the contact resistance is reduced to below 5mΩ, the problem of poor soldering and open circuit of traditional copper-aluminum composite backplanes is solved, and the risk of grid breakage without main grid structure is avoided.

[0109] The composite passivated conductive backplane and its preparation method provided in this application achieve optimized photoelectric conversion efficiency: the partitioned passivation layer is designed with SiO2 / Al2O3 stacked structure for P / N electrode regions respectively, and the preparation is simplified by using a single PECVD process. In line with the passivation requirements of BC cells, the carrier recombination rate is reduced by 30%, which can increase the cell open-circuit voltage to more than 725mV, the short-circuit current density to 43mA / cm², and the module conversion efficiency to exceed 26.5%, which is better than the efficiency improvement effect of existing stacked passivation films.

[0110] The composite passivated conductive backplane and its preparation method provided in this application achieve enhanced process compatibility: the contact window spacing (0.8-1.5mm) is precisely matched with the finger electrode layout of BC battery, eliminating the need for complex alignment processes, improving packaging efficiency by 25%, reducing equipment investment costs by 15-20%, and exhibiting good compatibility with screen printing metallization processes.

[0111] The composite passivated conductive backplane and its preparation method provided in this application achieve improved environmental adaptability: the limiting oxygen index of the flame-retardant protective layer is ≥32%, the antioxidant can effectively delay the oxidation of the weld layer, and the service life is extended to more than 25 years under temperature cycling of -40℃ to 85℃ and humid heat environment of 85%RH, with a water vapor transmission rate ≤0.1g / (m²). d) To meet the requirements for long-term outdoor use of photovoltaic modules;

[0112] The composite passivated conductive backplane and its preparation method provided in this application achieve the advantages of structural integration: integrating insulation, conductivity, passivation and protection into one, replacing the traditional separate structure of "backplane + solder strip + passivation film", simplifying the component packaging process, and avoiding the complexity of PECVD and PE-ALD composite processes, thus reducing production costs.

[0113] It should be noted that the above are merely illustrative examples and do not specifically limit the methods, steps, or execution logic provided in this application.

[0114] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0115] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0116] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0117] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0118] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0119] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0121] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A composite passivated conductive backplate, characterized in that, The composite passivated conductive backsheet is used for encapsulation to form a photovoltaic module, and the composite passivated conductive backsheet includes: A substrate layer, an insulating buffer layer, a composite conductive layer, and a partitioned passivation layer are stacked sequentially. The composite conductive layer includes a substrate layer, a transition layer, and a welding layer stacked sequentially; wherein the substrate layer is located on the side closer to the insulating buffer layer, and the welding layer is located on the side closer to the partitioned passivation layer; the transition layer is a conductive nitride or a first alloy with a thickness of a first thickness; the first thickness is 5-20 nm, and the first alloy includes one or more of nickel-chromium alloy, titanium-chromium alloy, titanium-aluminum alloy, and chromium-aluminum alloy.

2. The composite passivated conductive backplane according to claim 1, characterized in that, The substrate layer includes aluminum with a second thickness, and the welding layer includes a second alloy with a third thickness, the second alloy including a silver-copper alloy; Wherein, the first ratio of the first thickness to the third thickness is greater than or equal to 0.001 and the first ratio is less than or equal to 0.02, and the second ratio of the second thickness to the third thickness is greater than or equal to 10 and the second ratio is less than or equal to 50.

3. The composite passivated conductive backplane according to claim 2, characterized in that, The second thickness is 40-130 μm, and the third thickness is 5-10 μm.

4. The composite passivated conductive backplane according to claim 1, characterized in that, The partition passivation layer includes: The stacked structure deposited by PECVD process has contact windows at positions corresponding to the electrodes. The spacing between two adjacent contact windows of the same type of electrode is 0.8-1.5 mm, and the width of the contact window is 20-30 μm.

5. The composite passivated conductive backplane according to claim 4, characterized in that, The stacked structure includes a SiO2 layer with a thickness of 10-30 nm and an Al2O3 layer with a thickness of 20-50 nm stacked together. The SiO2 layer is located on the side closer to the composite conductive layer, and the Al2O3 layer is located on the side farther away from the composite conductive layer. The third ratio of the spacing to the electrode width is greater than 1.2 and the third ratio is less than 1.

8.

6. The composite passivated conductive backplane according to claim 1, characterized in that, The composite passivated conductive backplate also includes: A flame-retardant protective layer is disposed on the side of the partitioned passivation layer away from the composite conductive layer; The flame-retardant protective layer comprises a modified polyurethane coating, the thickness of the flame-retardant protective layer is 10-20 μm, the limiting oxygen index of the flame-retardant protective layer is greater than or equal to 32%, and the adhesion is greater than or equal to 5B; wherein, the modified polyurethane coating comprises 3-5 wt% intumescent graphite and 2-3 wt% benzotriazole.

7. A photovoltaic module, characterized in that, The photovoltaic module includes a solar cell, and the back side of the solar cell includes a composite passivated conductive backsheet as described in any one of claims 1 to 6.

8. A method for preparing a composite passivated conductive backplate, characterized in that, The preparation method includes: The board material is pretreated to form a substrate layer; An insulating material is coated on one side of the substrate layer to form an insulating buffer layer; A conductive nitride or a first alloy is deposited on the side of the insulating buffer layer away from the substrate layer to form a transition layer; wherein the first thickness of the transition layer is 5-20 nm, and the first alloy includes one or more of nickel-chromium alloy, titanium-chromium alloy, titanium-aluminum alloy, and chromium-aluminum alloy. A solder layer is deposited on the side of the transition layer away from the insulating buffer layer to form a composite conductive layer; Deposition and etching are performed on the side of the composite conductive layer away from the transition layer to form a partitioned passivation layer, resulting in a composite passivated conductive backplane.

9. The method for preparing the composite passivated conductive backplate according to claim 8, characterized in that, The deposition of a conductive nitride or a first alloy on the side of the insulating buffer layer away from the substrate layer to form a transition layer includes: On the side of the insulating buffer layer away from the substrate layer, a conductive nitride or a first alloy is deposited by a first magnetron sputtering, and a transition layer is formed by plasma bombardment treatment; wherein, the sputtering power of the first magnetron sputtering is 300-600W, the power of the plasma bombardment treatment is 200-300W, and the time is 1-2min; The deposition of a solder layer on the side of the transition layer away from the insulating buffer layer includes: A welding layer is deposited by a second magnetron sputtering on the side of the transition layer away from the insulating buffer layer; the sputtering power of the second magnetron sputtering is 500-1000W, and the substrate temperature is less than or equal to 150 degrees Celsius.

10. The method for preparing the composite passivated conductive backplate according to claim 8, characterized in that, The deposition and etching process on the side of the composite conductive layer away from the transition layer to form a partitioned passivation layer includes: A stacked structure is deposited on the side of the composite conductive layer away from the transition layer using a PECVD process, and then laser etching is performed to form a partitioned passivation layer; wherein the laser wavelength for the laser etching is 355-370nm, the energy density is 0.8-1.2J / cm², the laser spot diameter is 5-10μm, and the scanning speed is 100-300mm / s.

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