High efficiency bifacial electrode solar cell

Abstract

The present application relates to the field of solar cells, in particular to a high-efficiency double-sided electrode solar cell, which comprises silver electrode, TCO film, p-type hydrogenated amorphous silicon film, intrinsic hydrogenated amorphous silicon film, n-type crystalline silicon substrate, intrinsic hydrogenated amorphous silicon film, n-type hydrogenated amorphous silicon film, TCO film and silver electrode from top to bottom. The present application adjusts PECVD process for the preparation of intrinsic hydrogenated amorphous silicon film, p-type hydrogenated amorphous silicon film and n-type hydrogenated amorphous silicon film and deposits them to appropriate thicknesses, and then prepares TCO film layer by magnetron sputtering, thereby optimizing the structure and performance of heterojunction cells, improving open-circuit voltage and enhancing the photoelectric conversion efficiency of heterojunction cells.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically to high-efficiency bifacial electrode solar cells. Background Technology

[0002] The irreplaceable role of renewable energy in energy security strategies is beyond doubt. Photovoltaics, with its advantages of abundant and readily available resources and minimal environmental impact, has become a core component of the renewable energy development strategies of major economies worldwide. For China, the contradiction between the rapid growth in electricity demand driven by economic development and the already limited environmental carrying capacity makes the application of photovoltaics even more urgent and irreplaceable. After decades of development, the photovoltaic industry has reached the conditions for large-scale application in both quality (technological maturity) and quantity (industry scale). HJT cells, with their advantages of high PID resistance, low-temperature manufacturing process, high efficiency, high light stability, and the ability to be developed into thinner designs, have become a favorite among various companies.

[0003] P-type crystalline silicon solar cells suffer from severe light-induced and photothermal-assisted degradation, while n-type crystalline silicon solar cells can effectively suppress this degradation, contributing to stable power output. Furthermore, n-type crystalline silicon offers advantages over p-type materials, including higher minority carrier lifetime and mobility, which are crucial for further improving cell efficiency. In practical applications, n-type crystalline silicon solar cells exhibit good low-light response and a low temperature coefficient, resulting in significantly higher actual power generation compared to p-type cells. Currently, HJT cells fabricated using n-type crystalline silicon generally exhibit mediocre photoelectric conversion efficiency due to limitations in manufacturing processes and their inherent structure. Therefore, we propose a high-efficiency bifacial electrode solar cell. Summary of the Invention

[0004] (i) In view of the shortcomings of the prior art, the present invention provides a high-efficiency bifacial electrode solar cell, which overcomes the shortcomings of the prior art, has a reasonable design, optimizes the structure and performance of the heterojunction cell, improves the open circuit voltage, and enhances the photoelectric conversion efficiency of the heterojunction cell.

[0005] (II) To achieve the above objectives, the present invention is implemented through the following technical solution: a high-efficiency bifacial electrode solar cell, comprising, from top to bottom, a silver electrode, a TCO thin film, a p-type hydrogenated amorphous silicon thin film, an intrinsic hydrogenated amorphous silicon thin film, an n-type crystalline silicon substrate, an intrinsic hydrogenated amorphous silicon thin film, an n-type hydrogenated amorphous silicon thin film, a TCO thin film and a silver electrode.

[0006] Preferably, the thickness of the n-type crystalline silicon substrate is 200 μm, the thickness of the p-type hydrogenated amorphous silicon film is 5 nm, the thickness of the n-type hydrogenated amorphous silicon film is 5 nm, the thickness of the intrinsic hydrogenated amorphous silicon film is 5 nm, and the thickness of the TCO film is 800 nm.

[0007] This invention also provides a method for fabricating a high-efficiency bifacial electrode solar cell, comprising the following steps:

[0008] (1) Silicon wafer selection and texturing: Select qualified n-type crystalline silicon substrates and place them into a grooved texturing equipment for etching and texturing. Control the pyramid height in the texturing surface to be between 3-5 μm to obtain a texturing substrate.

[0009] ① Select qualified n-type crystalline silicon substrates and perform inspection using existing silicon wafer feeding inspection equipment, which mainly includes thickness inspection module, line mark inspection module, hidden crack inspection module, dirt inspection module, and edge inspection module.

[0010] ② Tank-type Texturing Equipment: Modern industrial production places high demands on temperature control in the texturing process. To ensure consistent reaction conditions, temperature control accuracy must be within ±1℃. This ensures a more stable and controllable chemical reaction within the entire process tank, effectively controlling the reaction rate and evaporation of the solution, facilitating process adjustments. Considering this factor, a high-precision PT100 platinum resistance thermometer with fast response is selected as the temperature sensor within the texturing tank. Its measurement and display accuracy is 0.1℃, allowing real-time display of the solution temperature. Simultaneously, the heating system design fully considers uniformity requirements, using specially customized imported 316L stainless steel heating tubes. The discrete structure ensures that damage to a single heating tube does not affect other systems, and the threaded interface design facilitates maintenance and replacement. To prevent uneven solution temperature distribution caused by excessively high local temperatures around the heating tubes, a heat equalization baffle was installed above the heating tube area. Combined with the solution circulation system configured in the tank, the uniformity of the solution after passing through the equalization baffle was greatly enhanced. According to the actual measurement results of the process personnel, the temperature deviation of the solution in various parts of the tank does not exceed ±0.3℃.

[0011] Considering the frequent solution changes required by operators in actual production, the capacity of the heating system was carefully considered to ensure the overall production efficiency of the process line. Excessive heating power would cause large temperature fluctuations in the tank; insufficient power might result in excessively long heating times after each solution change, impacting production efficiency. Therefore, we adopted an online heating method to directly inject DI water (deionized water) at approximately 70°C during solution changes. A 12kW heating element is installed inside the tank to maintain the required process temperature. Compared to the traditional external DI water preheating tank, online heating offers advantages such as rapid heating (it can raise DI water at a flow rate of 3.5L / min from room temperature to 70°C within 3 minutes, and then maintain the outlet water temperature at approximately 70°C), smaller size (it can be installed inside the equipment, reducing the footprint of the cleanroom), and less impact on the resistivity of the DI water (online heating minimizes the resistivity decrease caused by long-term storage of DI water). This effectively reduces solution preparation time and improves production efficiency.

[0012] The tank structure's influence on solution uniformity primarily includes the uniformity of the circulation system distribution and the fineness of the N2 bubbling, significantly impacting the stability and uniformity of the silicon wafer surface texture within the process tank. The circulation system comprises a circulation inlet, circulation pump, piping system, bottom multi-channel injection pipe, and flow equalization baffles. Imported magnetic circulation pumps and imported PP fittings are used to ensure the effectiveness and cleanliness of the circulation system. The bottom multi-channel injection pipe and flow equalization baffle design ensure uniform circulation, and the circulation angle can be adjusted as needed. Actual process verification shows that after the circulation function is activated, the solution circulates smoothly in a wavy pattern. The circulation angle is comprehensive, and the flow direction is parallel to the silicon wafers. Simultaneously, the N2 bubbling function is fine, covering all areas where the silicon wafers are located. This meets the requirements for consistent surface texture on silicon wafers in batch processing processes.

[0013] (2) Textured rounding treatment: The textured substrate is subjected to thermal oxidation treatment, and then immersed in a mixed acid solution and treated at 20-25℃ for 2-4 min to remove the oxide layer, thus obtaining a pretreated substrate;

[0014] (3) Preparation of amorphous silicon thin film: an intrinsic hydrogenated amorphous silicon thin film and a p-type hydrogenated amorphous silicon thin film are deposited on one side of the pretreated substrate using PECVD (plasma-enhanced chemical vapor deposition) process, and an intrinsic hydrogenated amorphous silicon thin film and an n-type hydrogenated amorphous silicon thin film are deposited on the other side of the substrate.

[0015] (4) TCO thin film preparation: TCO thin films were prepared on p-type hydrogenated amorphous silicon thin films and n-type hydrogenated amorphous silicon thin films by magnetron sputtering to obtain the battery body;

[0016] (5) Electrode preparation: Low-temperature silver paste is printed on both sides of the battery body using screen printing process, and after drying, a high-efficiency double-sided electrode solar cell is obtained.

[0017] Preferably, in step (1), a suede surface is prepared at 75-85°C using an alkaline solution with a mass fraction of 1-2% and isopropanol accounting for 2-5% of the total mass of the alkaline solution; the alkaline solution is either sodium hydroxide or potassium hydroxide.

[0018] Preferably, in step (2), the mixed acid solution comprises 1 part nitric acid, 2 parts hydrofluoric acid, and 25 parts deionized water by weight.

[0019] Preferably, in step (3), the intrinsic hydrogenated amorphous silicon thin film processing technology has the following characteristics: electrode spacing of 1.5 cm, deposition gas pressure of 0.5 torr, frequency of 75 MHz, silane concentration of 8%, and power density of 85 mW / cm². 2 Total flow rate: 80 sccm;

[0020] p-type hydrogenated amorphous silicon thin film processing technology: electrode spacing is 1.7cm, deposition gas pressure is 1.5torr, silane concentration is 1.5%, borane concentration is 0.3%, glow discharge power is 75W, and total flow rate is 100sccm;

[0021] n-type hydrogenated amorphous silicon thin film processing technology: electrode spacing is 1.7cm, deposition gas pressure is 1.5torr, silane concentration is 1.5%, phosphine concentration is 0.4%, glow discharge power is 75W, and total flow rate is 100sccm.

[0022] Preferably, in step (4), the magnetron sputtering process is as follows: the target material is a Zn-Al alloy, the sputtering gas is a mixed gas, the sputtering pressure is 3 mtorr, and the power density is 90 mW / cm³. 2 .

[0023] Preferably, the Zn-Al alloy contains 1.5% Al by mass; the mixed gas is argon and oxygen, with an argon flow rate of 100 sccm and an oxygen flow rate of 15 sccm.

[0024] (III) This invention provides a high-efficiency bifacial electrode solar cell, which has the following beneficial effects:

[0025] This invention adjusts the PECVD process for the preparation of intrinsic hydrogenated amorphous silicon thin films, p-type hydrogenated amorphous silicon thin films, and n-type hydrogenated amorphous silicon thin films, depositing them to their respective appropriate thicknesses, and then preparing TCO thin film layers by magnetron sputtering. This optimizes the structure and performance of heterojunction solar cells, improves the open-circuit voltage, and enhances the photoelectric conversion efficiency of heterojunction solar cells.

[0026] This invention introduces hydrogenated amorphous silicon thin film layers on both sides of an n-type crystalline silicon substrate, which act as buffer layers, can adjust the bandgap, reduce the interface barrier, and passivate the dangling bonds at the a-Si / c-Si interface, thereby reducing the interface state density, reducing leakage current, and improving the overall performance of heterojunction solar cells. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the high-efficiency double-sided electrode solar cell structure of the present invention;

[0028] Figure 2 This is a flowchart illustrating the manufacturing process of the high-efficiency bifacial electrode solar cell of this invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0030] Example 1

[0031] A method for fabricating a high-efficiency bifacial electrode solar cell includes the following steps:

[0032] (1) Silicon wafer selection and texturing: Select qualified n-type crystalline silicon substrates and place them in a tank texturing equipment for etching and texturing. Control the pyramid height in the texturing surface to be between 3-5 μm to obtain a texturing substrate. Use a 1% sodium hydroxide solution and 2% isopropanol to prepare the texturing surface at 75°C.

[0033] (2) Textured surface rounding treatment: The textured substrate is subjected to thermal oxidation treatment, and then immersed in a mixed acid solution and treated at 20°C for 2 min to remove the oxide layer, thus obtaining a pretreated substrate. By weight, the mixed acid solution includes 1 part nitric acid, 2 parts hydrofluoric acid, and 25 parts deionized water.

[0034] (3) Amorphous silicon thin film preparation: Intrinsic hydrogenated amorphous silicon thin films and p-type hydrogenated amorphous silicon thin films were deposited on one side of the pretreated substrate using PECVD process, and intrinsic hydrogenated amorphous silicon thin films and n-type hydrogenated amorphous silicon thin films were deposited on the other side. Intrinsic hydrogenated amorphous silicon thin film processing parameters: electrode spacing 1.5 cm, deposition gas pressure 0.5 torr, frequency 75 MHz, silane concentration 8%, power density 85 mW / cm². 2Total flow rate 80 sccm; p-type hydrogenated amorphous silicon thin film processing: electrode spacing 1.7 cm, deposition gas pressure 1.5 torr, silane concentration 1.5%, borane concentration 0.3%, glow discharge power 75 W, total flow rate 100 sccm; n-type hydrogenated amorphous silicon thin film processing: electrode spacing 1.7 cm, deposition gas pressure 1.5 torr, silane concentration 1.5%, phosphine concentration 0.4%, glow discharge power 75 W, total flow rate 100 sccm.

[0035] (4) TCO thin film preparation: TCO thin films were prepared on p-type hydrogenated amorphous silicon thin films and n-type hydrogenated amorphous silicon thin films by magnetron sputtering to obtain the battery body. Magnetron sputtering process: The target material was Zn-Al alloy, the sputtering gas was a mixed gas, the sputtering pressure was 3 mtorr, and the power density was 90 mW / cm³. 2 The Zn-Al alloy contains 1.5% Al by mass; the mixed gas is argon and oxygen, with an argon flow rate of 100 sccm and an oxygen flow rate of 15 sccm.

[0036] (5) Electrode preparation: Low-temperature silver paste is printed on both sides of the battery body using screen printing process, and after drying, a high-efficiency double-sided electrode solar cell is obtained.

[0037] Example 2

[0038] A method for fabricating a high-efficiency bifacial electrode solar cell includes the following steps:

[0039] (1) Silicon wafer selection and texturing: Select qualified n-type crystalline silicon substrates and place them in a tank texturing equipment for etching and texturing. Control the pyramid height in the texturing surface to be between 3-5 μm to obtain a texturing substrate. Use a 2% potassium hydroxide solution and 5% isopropanol to prepare the texturing surface at 85℃.

[0040] (2) Textured surface rounding treatment: The textured substrate is subjected to thermal oxidation treatment, and then immersed in a mixed acid solution and treated at 25°C for 4 min to remove the oxide layer, thus obtaining a pretreated substrate. By weight, the mixed acid solution includes 1 part nitric acid, 2 parts hydrofluoric acid, and 25 parts deionized water.

[0041] (3) Amorphous silicon thin film preparation: Intrinsic hydrogenated amorphous silicon thin films and p-type hydrogenated amorphous silicon thin films were deposited on one side of the pretreated substrate using PECVD process, and intrinsic hydrogenated amorphous silicon thin films and n-type hydrogenated amorphous silicon thin films were deposited on the other side. Intrinsic hydrogenated amorphous silicon thin film processing parameters: electrode spacing 1.5 cm, deposition gas pressure 0.5 torr, frequency 75 MHz, silane concentration 8%, power density 85 mW / cm². 2Total flow rate 80 sccm; p-type hydrogenated amorphous silicon thin film processing: electrode spacing 1.7 cm, deposition gas pressure 1.5 torr, silane concentration 1.5%, borane concentration 0.3%, glow discharge power 75 W, total flow rate 100 sccm; n-type hydrogenated amorphous silicon thin film processing: electrode spacing 1.7 cm, deposition gas pressure 1.5 torr, silane concentration 1.5%, phosphine concentration 0.4%, glow discharge power 75 W, total flow rate 100 sccm.

[0042] (4) TCO thin film preparation: TCO thin films were prepared on p-type hydrogenated amorphous silicon thin films and n-type hydrogenated amorphous silicon thin films by magnetron sputtering to obtain the battery body. Magnetron sputtering process: The target material was Zn-Al alloy, the sputtering gas was a mixed gas, the sputtering pressure was 3 mtorr, and the power density was 90 mW / cm³. 2 The Zn-Al alloy contains 1.5% Al by mass; the mixed gas is argon and oxygen, with an argon flow rate of 100 sccm and an oxygen flow rate of 15 sccm.

[0043] (5) Electrode preparation: Low-temperature silver paste is printed on both sides of the battery body using screen printing process, and after drying, a high-efficiency double-sided electrode solar cell is obtained.

[0044] Example 3

[0045] The high-efficiency bifacial electrode solar cell prepared using the method in Example 1 comprises, from top to bottom, a silver electrode, a TCO thin film, a p-type hydrogenated amorphous silicon thin film, an intrinsic hydrogenated amorphous silicon thin film, an n-type crystalline silicon substrate, an intrinsic hydrogenated amorphous silicon thin film, an n-type hydrogenated amorphous silicon thin film, a TCO thin film, and a silver electrode. The thickness of the n-type crystalline silicon substrate is 200 μm, the thickness of the p-type hydrogenated amorphous silicon thin film is 5 nm, the thickness of the n-type hydrogenated amorphous silicon thin film is 5 nm, the thickness of the intrinsic hydrogenated amorphous silicon thin film is 5 nm, and the thickness of the TCO thin film is 800 nm.

[0046] Quality Inspection

[0047] The performance of the high-efficiency bifacial electrode solar cell in Example 3 and the commercially available heterojunction cell in the control group were tested. The specific test results are shown in the table below.

[0048] Table 1 Performance Testing

[0049]

[0050] The embodiments disclosed herein are preferred embodiments, but are not limited thereto. Those skilled in the art can readily grasp the spirit of the present invention based on the above embodiments and make different extensions and variations, but as long as they do not depart from the spirit of the present invention, they are all within the protection scope of the present invention.

Claims

1. A method for fabricating a high-efficiency bifacial electrode solar cell, characterized in that, Includes the following steps, (1) Silicon wafer selection and texturing: Select qualified n-type crystalline silicon substrates and place them into a grooved texturing equipment for etching and texturing. Control the pyramid height in the texturing surface to be between 3-5 μm to obtain a texturing substrate. The texturing tank of the trough-type texturing equipment uses a PT100 platinum resistance thermometer as a temperature sensor. The heating tube adopts a split structure and a threaded interface design. A heat equalization baffle is installed on the upper part of the heating tube area. Online heating is used to achieve fluid exchange; (2) Textured rounding treatment: The textured substrate is subjected to thermal oxidation treatment, and then immersed in a mixed acid solution and treated at 20-25℃ for 2-4 min to remove the oxide layer, thus obtaining a pretreated substrate; (3) Preparation of amorphous silicon thin film: an intrinsic hydrogenated amorphous silicon thin film and a p-type hydrogenated amorphous silicon thin film are deposited on one side of the pretreated substrate using PECVD process, and an intrinsic hydrogenated amorphous silicon thin film and an n-type hydrogenated amorphous silicon thin film are deposited on the other side. Intrinsic hydrogenated amorphous silicon thin film processing technology: electrode spacing of 1.5 cm, deposition gas pressure of 0.5 torr, frequency of 75 MHz, silane concentration of 8%, and power density of 85 mW / cm³. 2 Total flow rate: 80 sccm; p-type hydrogenated amorphous silicon thin film processing technology: electrode spacing is 1.7cm, deposition gas pressure is 1.5torr, silane concentration is 1.5%, borane concentration is 0.3%, glow discharge power is 75W, and total flow rate is 100sccm; n-type hydrogenated amorphous silicon thin film processing technology: electrode spacing is 1.7cm, deposition gas pressure is 1.5torr, silane concentration is 1.5%, phosphine concentration is 0.4%, glow discharge power is 75W, and total flow rate is 100sccm; (4) TCO thin film preparation: TCO thin films were prepared on p-type hydrogenated amorphous silicon thin films and n-type hydrogenated amorphous silicon thin films by magnetron sputtering to obtain the battery body; (5) Electrode preparation: Low-temperature silver paste is printed on both sides of the battery body using screen printing process, and after drying, a high-efficiency double-sided electrode solar cell is obtained; The high-efficiency bifacial electrode solar cell comprises, from top to bottom, a silver electrode, a TCO thin film, a p-type hydrogenated amorphous silicon thin film, an intrinsic hydrogenated amorphous silicon thin film, an n-type crystalline silicon substrate, an intrinsic hydrogenated amorphous silicon thin film, an n-type hydrogenated amorphous silicon thin film, a TCO thin film, and a silver electrode; wherein the thickness of the n-type crystalline silicon substrate is 200 μm, the thickness of the p-type hydrogenated amorphous silicon thin film is 5 nm, the thickness of the n-type hydrogenated amorphous silicon thin film is 5 nm, the thickness of the intrinsic hydrogenated amorphous silicon thin film is 5 nm, and the thickness of the TCO thin film is 800 nm.

2. The method for preparing a high-efficiency bifacial electrode solar cell as described in claim 1, characterized in that, In step (1), a velvety surface is prepared at 75-85°C using an alkaline solution with a mass fraction of 1-2% and isopropanol accounting for 2-5% of the total mass of the alkaline solution; the alkaline solution is either sodium hydroxide or potassium hydroxide.

3. The method for preparing a high-efficiency bifacial electrode solar cell as described in claim 1, characterized in that, In step (2), the mixed acid solution comprises 1 part nitric acid, 2 parts hydrofluoric acid, and 25 parts deionized water by weight.

4. The method for preparing a high-efficiency bifacial electrode solar cell as described in claim 1, characterized in that, In step (4), the magnetron sputtering process is as follows: the target material is a Zn-Al alloy, the sputtering gas is a mixed gas, the sputtering pressure is 3 mtorr, and the power density is 90 mW / cm³. 2 .

5. The method for preparing a high-efficiency bifacial electrode solar cell as described in claim 4, characterized in that, The Zn-Al alloy contains 1.5% Al by mass; the mixed gas is argon and oxygen, with an argon flow rate of 100 sccm and an oxygen flow rate of 15 sccm.

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