Topcon solar cell and manufacturing method thereof

Abstract

The invention relates to a Topcon solar cell and a manufacturing method thereof, belongs to the technical field of solar cells, and solves the problem of low photoelectric conversion efficiency of a Topcon cell in the prior art. The device comprises a silicon wafer, the silicon wafer comprises a front surface and a back surface, the front surface is a boron-diffused silicon wafer surface, and a silicon-aluminum-gallium oxide passivation film layer, a front surface passivation dielectric layer and a first conductive electrode are sequentially arranged from the front surface to the outside; a tunneling oxide layer, a phosphorus-doped silicon layer, a reverse passivation dielectric layer and a second conductive electrode are sequentially arranged from the reverse side to the outside; the chemical composition of the silicon-aluminum-gallium oxide passivation film layer is composed of oxides of silicon, aluminum and gallium, and the molar content ratio of silicon to aluminum to gallium is adjustable. The silicon-aluminum-gallium oxide passivation film layer is adopted to replace an existing aluminum oxide passivation film layer, so that the negative charge density is high, the surface passivation of the silicon wafer is good, and the photoelectric conversion efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a Topcon solar cell and a manufacturing method thereof. Background Art

[0002] Silicon-based Topcon solar cells use N-type silicon wafers as light-absorbing matrix materials, and prepare PN junctions on the textured surface of silicon wafers through high-temperature boron diffusion. On the reverse side of the cell, tunnel oxide layers, phosphorus-doped silicon layers, silicon nitride layers, and conductive electrodes are sequentially arranged from the surface of the silicon wafer to the outside; on the front side of the cell, aluminum oxide passivation film layers, silicon nitride layers, and conductive electrodes are sequentially arranged from the surface of the silicon wafer to the outside. After continuous process optimization, the world record of photoelectric conversion efficiency of the laboratory Topcon solar cells has reached 26.89%.

[0003] The uniformity of the tunneling oxide layer on the back surface of the Topcon solar cell is continuously optimized to improve the open circuit voltage of the cell. By improving the boron doping at the pn junction on the front of the Topcon solar cell, the recombination on the front of the cell is reduced, thereby improving the performance of the cell. The effect of high-temperature sintering on the passivation performance of the cell is further optimized through technologies such as laser-assisted sintering, which further improves the photoelectric conversion efficiency of the Topcon solar cell. This shows that continuous optimization and improvement of the cell process is an important means to improve the performance of Topcon solar cells. Each process improvement provides the possibility for improving the performance of solar cells.

[0004] The front of the existing Topcon cell uses a thin layer of aluminum oxide film to passivate the surface of the boron-doped silicon wafer, and then deposits a silicon nitride film on the surface of the aluminum oxide film to enhance passivation and anti-reflection. There are many methods for depositing aluminum oxide films, mainly including ALD, PECVD and PEALD. The aluminum oxide film obtained by each deposition method has slightly different structures and chemical compositions. Generally speaking, after the aluminum oxide is deposited, the film needs to be annealed to activate the passivation of the aluminum oxide film on the silicon wafer surface.

[0005] In terms of the passivation effect on the surface of the silicon wafer, the aluminum oxide film has a good chemical passivation effect. That is, during the deposition process, some oxygen atoms and some hydrogen atoms in the aluminum oxide film are combined with the silicon dangling bonds on the surface of the silicon wafer to achieve the surface chemical passivation of the silicon wafer by the film. However, after the aluminum oxide film is annealed, atomic diffusion occurs between the interface of the silicon wafer and the aluminum oxide film under higher temperature conditions, causing the atoms on the interface to be redistributed. Specifically, the hydrogen atoms in the aluminum oxide film further diffuse into the surface of the silicon wafer to further passivate the residual dangling bonds. And under high temperature annealing conditions, the silicon atoms and aluminum atoms at the interface undergo mutual exchange diffusion, specifically, the aluminum ions break away from the original aluminum oxygen network structure and enter the surface silicon oxide network to form a tetrahedral aluminum oxygen network structure. In this structure, since the film layer is an oxygen-rich structure in terms of atomic measurement, the interface is negatively charged. The aluminum oxide film on the surface of the silicon wafer is negatively charged, and the electric field formed on the surface further strengthens the passivation of the film on the surface of the silicon wafer.

[0006] From the above description, we can know that the passivation of the aluminum oxide film on the silicon wafer surface is based on good chemical passivation and negative charge of the film, where the amount of charge of the film depends on the degree of mutual diffusion of aluminum ions and silicon ions during high temperature. How to control the charge of the aluminum oxide layer so that the negative charge density of the interface is further increased and better field passivation is formed, which is the key to further improve the photoelectric conversion efficiency of Topcon cells. Summary of the invention

[0007] In view of the above analysis, the embodiments of the present invention aim to provide a Topcon solar cell and a method for manufacturing the same, so as to solve the problem that the existing Topcon cell has low photoelectric conversion efficiency.

[0008] On the one hand, the present invention provides a Topcon solar cell, including a silicon wafer, wherein the silicon wafer includes a front side and a back side, the front side is a boron-diffused silicon wafer surface, and a silicon oxide aluminum gallium passivation film layer, a front side passivation dielectric layer and a first conductive electrode are sequentially arranged from the front side outward; a tunneling oxide layer, a phosphorus-doped silicon layer, a back side passivation dielectric layer and a second conductive electrode are sequentially arranged from the back side outward; the silicon oxide aluminum gallium passivation film layer is composed of oxides of silicon, aluminum and gallium, and the molar content ratio of silicon, aluminum and gallium is adjustable.

[0009] Furthermore, in the silicon oxide aluminum gallium passivation film layer, the molar ratio of silicon atoms on the side close to the silicon wafer surface is greater than the sum of the molar ratio of aluminum atoms and the molar ratio of gallium atoms on this side, and the sum of the molar ratio of aluminum atoms and the molar ratio of gallium atoms on the side away from the silicon wafer surface is greater than the molar ratio of silicon atoms on this side.

[0010] Furthermore, in the silicon oxide aluminum gallium passivation film layer, the total molar ratio of aluminum atoms is greater than the total molar ratio of gallium atoms.

[0011] Furthermore, from the surface of the silicon wafer outward, the molar ratio of silicon atoms in the silicon oxide aluminum gallium passivation film layer gradually decreases, while the molar ratio of aluminum atoms and the molar ratio of gallium atoms gradually increase.

[0012] Furthermore, in the silicon oxide aluminum gallium passivation film layer, the total molar ratio of silicon atoms is not greater than 33%, the total molar ratio of aluminum atoms is not greater than 40%, and the total molar ratio of gallium atoms is not greater than 38%.

[0013] Furthermore, in the silicon oxide aluminum gallium passivation film layer, the total molar ratio of aluminum atoms to the total molar ratio of gallium atoms is greater than 2:1.

[0014] Furthermore, the thickness of the silicon aluminum gallium oxide passivation film layer is 1-20 nanometers, preferably 3-10 nanometers, and more preferably 4-6 nanometers.

[0015] In another aspect, the present invention provides a method for manufacturing a Topcon solar cell, which is used to manufacture the Topcon solar cell described above, comprising the following steps:

[0016] S1: Provide n-type silicon wafer as substrate and complete silicon wafer texturing and cleaning;

[0017] S2: High temperature boron diffusion on the surface of the texturing silicon wafer to prepare the PN junction;

[0018] S3: After planarizing the back surface of the silicon wafer, a tunneling oxide layer and a Poly layer are prepared;

[0019] S4: Phosphorus diffusion on the reverse Poly layer;

[0020] S5: Clean the front-side plated Poly layer, and clean the BSG and PSG layers on both sides;

[0021] S6: depositing a silicon-aluminum-gallium oxide passivation film layer on the front side of the battery;

[0022] S7: Deposition of passivation dielectric layer on both sides of the silicon wafer;

[0023] S8: Print silver paste on both sides, dry, sinter and test to complete the battery preparation.

[0024] Furthermore, in step S6, a silicon-aluminum-gallium oxide passivation film layer is deposited on the front surface by using a PECVD method;

[0025] The aluminum source of the silicon aluminum gallium oxide passivation film layer includes trimethylaluminum, trialkylaluminum, dialkylaluminum chloride, monoalkylaluminum dichloride or trialkylaluminum trichloride; the oxygen source of the silicon aluminum gallium oxide passivation film layer includes N2O, CO2 or CO; the gallium source of the silicon aluminum gallium oxide passivation film layer includes trimethylgallium; the silicon source of the silicon aluminum gallium oxide passivation film layer includes silane.

[0026] Furthermore, the aluminum-silicon-gallium oxide passivation film layer deposited on the front side by the PECVD method can also be annealed, and the required annealing conditions are: annealing time of 10-40 minutes, annealing temperature of 400-800°C, and preferably annealing temperature of 500-700°C.

[0027] Compared with the prior art, the present invention uses a silicon-aluminum-gallium oxide thin film as a passivation layer on the front of the Topcon battery to replace the existing aluminum oxide passivation film layer, which can achieve at least one of the following beneficial effects:

[0028] First, the silicon oxide aluminum gallium passivation film layer has a high negative charge density, which has good surface passivation for the silicon wafer, and the open circuit voltage of the Topcon battery is high, thereby improving the photoelectric conversion efficiency of the Topcon battery;

[0029] Secondly, the silicon oxide aluminum gallium passivation film layer can reduce the stress of the film layer on the surface of the silicon wafer by adjusting the ratio of aluminum and gallium atoms in the film layer, thereby enhancing passivation;

[0030] Thirdly, the chemical composition of the film layer can be regulated by the gas flow ratio during film formation, and the charge density of the film layer can be regulated by regulating the chemical composition of the film layer, so that gradient design can be performed.

[0031] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0033] Figure 1 A schematic diagram of the structure of a Topcon solar cell provided by the present invention;

[0034] Figure 2 This is the XPS O1s spectrum of the SiAlGaOx film layer deposited in Example 1, and the film layer contains oxygen atoms;

[0035] Figure 3 The XPS Si 2p spectrum of the SiAlGaOx film layer deposited in Example 1, the film layer contains silicon atoms;

[0036] Figure 4The Al 2p spectrum of the XPS in the SiAlGaOx film layer deposited in Example 1, the film layer contains aluminum atoms;

[0037] Figure 5 The Ga 3d spectrum of the XPS in the SiAlGaOx film layer deposited in Example 1, the film layer contains gallium atoms;

[0038] Figure 6 A comparison of the passivation effects of deposited SiAlGaOx film and aluminum oxide film on P-type silicon wafers;

[0039] Figure 7 This is a comparison chart of the effects of deposited SiAlGaOx film and aluminum oxide film on the performance of Topcon solar cells.

[0040] Reference numerals:

[0041] 1-boron diffused silicon wafer surface; 2-silicon oxide aluminum gallium passivation film layer; 3-front passivation dielectric layer; 4-first conductive electrode; 5-tunneling oxide layer; 6-phosphorus doped silicon layer; 7-reverse passivation dielectric layer. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0043] like Figure 1 As shown, the present invention provides a Topcon solar cell, including a silicon wafer, the silicon wafer including a front side and a back side, the front side (i.e., the light-receiving side) is a boron-diffused silicon wafer surface 1, and a silicon oxide aluminum gallium passivation film layer 2, a front passivation dielectric layer 3, and a first conductive electrode 4 are sequentially arranged from the front side outward; a tunneling oxide layer 5, a phosphorus-doped silicon layer 6, a back passivation dielectric layer 7, and a second conductive electrode are sequentially arranged from the back side (i.e., the backlight side) outward. The silicon oxide aluminum gallium passivation film layer 2 is composed of silicon, aluminum, and gallium oxides, and the molar content ratio of silicon, aluminum, and gallium is adjustable, wherein the molar ratio of silicon atoms is not greater than 33%, the molar ratio of aluminum atoms is not greater than 40%, and the molar ratio of gallium atoms is not greater than 38%.

[0044] The front passivation dielectric layer 3 and the back passivation dielectric layer 7 may both include silicon nitride, silicon oxynitride, or a stack of silicon nitride and silicon oxide.

[0045] Compared with the prior art, the Topcon solar cell provided by the present invention uses a silicon aluminum gallium oxide thin film as a passivation layer on the front side, replacing the existing aluminum oxide passivation film layer. The silicon aluminum gallium oxide passivation film layer 2 has a high negative charge density and good surface passivation for the silicon wafer. The open circuit voltage of the Topcon cell is high, thereby improving the photoelectric conversion efficiency of the Topcon cell.

[0046] In some preferred embodiments, in the silicon oxide aluminum gallium passivation film layer 2, the total molar ratio of aluminum atoms is greater than the total molar ratio of gallium atoms. Preferably, the molar ratio of aluminum atoms to gallium atoms is greater than 2: 1. Since the atomic radius of aluminum atoms is smaller than that of gallium atoms, the subsequent diffusion ability is strong, and such a setting can improve the passivation effect of the film layer.

[0047] In some preferred embodiments, the silicon oxide aluminum gallium passivation film layer 2 is a multi-layer structure, for example, a double-layer structure, a three-layer structure or a structure with more layers. The molar ratio of silicon atoms in the layer close to the surface of the silicon wafer is greater than the sum of the molar ratios of aluminum and gallium atoms; the sum of the molar ratios of aluminum and gallium atoms in the layer far from the surface of the silicon wafer is greater than the molar ratio of silicon atoms. The silicon-rich layer close to the surface of the silicon wafer can provide sufficient silicon-oxygen tetrahedral structure. After subsequent annealing, the cations in the outer aluminum-rich gallium-rich layer can easily diffuse into the tetrahedral oxygen structure, which is conducive to the formation of negative charge centers and enhances passivation.

[0048] In another embodiment, the silicon aluminum gallium oxide passivation film layer 2 has a gradient structure, where the molar ratio of silicon atoms in the silicon aluminum gallium oxide passivation film layer 2 gradually decreases from the surface of the silicon wafer to the outside, while the molar ratio of aluminum and gallium atoms gradually increases.

[0049] The silicon-aluminum-gallium oxide passivation film layer 2 is prepared by a PECVD method, and four source gases are introduced simultaneously during the deposition of the passivation film layer. The aluminum source in the silicon-aluminum-gallium oxide passivation film layer 2 is provided by one of trimethylaluminum, trialkylaluminum, dialkylaluminum chloride, monoalkylaluminum dichloride, and trialkylaluminum trichloride, the oxygen source is provided by one of N2O, CO2, or CO, the gallium source is provided by trimethylgallium, and the silicon source is provided by silane.

[0050] The thickness of the silicon aluminum gallium oxide passivation film layer 2 is in the range of 1-20 nanometers, preferably in the range of 3-10 nanometers, and more preferably in the range of 4-6 nanometers.

[0051] Since the aluminum-gallium-silicon oxide passivation film 2 is disposed on the front side of the silicon wafer, the film is a dielectric film. Due to the refractive index and extinction coefficient of the film, refraction and reflection will be formed on the surface of the silicon wafer, thus causing optical loss. According to experimental results, the film thickness needs to be reduced as much as possible while ensuring passivation, so as to achieve the best effect, preferably between 4-6 nanometers.

[0052] Furthermore, the silicon aluminum gallium oxide passivation film layer 2 can also be annealed, and the required annealing conditions are: annealing time is 10-40 minutes, and annealing temperature is 400-800° C. It should be noted that the silicon aluminum gallium oxide passivation film layer 2 can also be not annealed, and similar effects can be achieved in the subsequent high-temperature sintering process of the electrode.

[0053] Furthermore, the annealing temperature is preferably in the range of 500-700°C, and more preferably in the range of 550-650°C.

[0054] The experimental results show that the passivation effect of the film layer is activated after annealing, and the direct manifestation is that the minority carrier lifetime is greatly improved after annealing.

[0055] The present invention also provides a method for manufacturing a Topcon solar cell, which is used to manufacture the above-mentioned Topcon solar cell, comprising the following steps:

[0056] S1: Provide n-type silicon wafer as substrate and complete silicon wafer texturing and cleaning;

[0057] S2: High temperature boron diffusion on the surface of the texturing silicon wafer to prepare the PN junction;

[0058] S3: After planarizing the back surface of the silicon wafer, a tunneling oxide layer and a Poly layer are prepared;

[0059] S4: Phosphorus diffusion is performed on the reverse Poly layer;

[0060] S5: Clean the front-side plated Poly layer, and clean the BSG and PSG layers on both sides;

[0061] S6: depositing a silicon-aluminum-gallium oxide passivation film layer 2 on the front side of the battery;

[0062] S7: Deposition of passivation dielectric layer on both sides of the silicon wafer;

[0063] S8: Print silver paste on both sides, dry, sinter and test to complete the battery preparation.

[0064] Wherein, step S1 specifically includes the following steps:

[0065] A single crystal n-type silicon wafer is selected as the substrate, and its body resistivity is 2.5Ω·cm. A NaOH solution with a mass fraction of 6% is used to texture the surface of the silicon wafer, and the weight loss of the texture is 0.5g. The reflectivity of the silicon wafer after texture is not more than 13%.

[0066] In step S2, the textured silicon wafer is placed in a high-temperature furnace tube for boron diffusion, the diffusion temperature is 940°C, and the diffusion time is 45 minutes; after diffusion, the sheet resistance is 125 ohms, and the maximum active boron atom concentration is 3E19 atoms / cm^3.

[0067] In step S3, the back side of the silicon wafer after boron diffusion is etched with a wet etching device (with single-sided etching capability) using HF and HNO3 solutions to remove the borosilicate glass (BSG) and diffusion layer on the back surface. The front side of the silicon wafer is covered with a protective water film so that the BSG film layer on the front side is retained.

[0068] The silicon wafer was placed in the LPCVD system so that the back surface was exposed to the deposition atmosphere. Oxygen was used as the reaction gas. The oxidation temperature was 610°C and the oxidation time was 18 minutes. A tunneling silicon oxide layer with a thickness of 1.8 nanometers was prepared on the back surface.

[0069] Then, an amorphous silicon (poly) film layer is deposited on the surface of the tunnel oxide layer, using silane as a reaction gas, a reaction temperature of 620° C., and a deposition time of 36 minutes, to obtain a poly film layer with a thickness of 140 nanometers.

[0070] In step S4, poly is doped with phosphorus in a high-temperature diffusion furnace tube, the diffusion temperature is 840°C, and the diffusion time is 40 minutes; the square resistance obtained after diffusion is 40 ohms, and the concentration of active phosphorus atoms in the poly film layer is 5E20 atoms per cubic centimeter.

[0071] In step S5, a single-sided wet etching device is used to protect the back phosphosilicate glass (PSG) layer with a water film, and the front PSG layer is removed with an HF solution. In a tank cleaning machine, a NaOH alkaline solution is used to etch and remove the exposed front doped poly silicon film, while the back poly is retained due to the protection of PSG. Then, an HF solution is used to simultaneously clean and remove the front BSG film layer and the back PSG film layer.

[0072] In step S6, a silicon-aluminum-gallium oxide passivation film layer 2 is deposited on the front side of the silicon wafer.

[0073] A silicon aluminum gallium oxide passivation film layer 2 is prepared on the surface of a silicon wafer using a PECVD method. The frequency of the RF power supply used is 13.56 MHz, and the RF power range is 29 mW / cm^2. A mixed gas of TMAl, silane, TMG and nitrous oxide is used as a reaction precursor, and the flow ratio of TMAl:TMG:SiH4:N2O is 0.3:0.1:2:5. The pressure of the reaction chamber is set to 110 Pa, and a silicon aluminum gallium oxide passivation film layer 2 with a film thickness of 1-20 nm is obtained.

[0074] In some preferred embodiments, in step S6, the coated silicon wafer is annealed, and the annealing conditions are furnace annealing, the annealing temperature is 400-800° C., and the annealing time is 10-40 minutes.

[0075] In step S7, a PECVD system is used to deposit a passivation dielectric layer on both sides of the silicon wafer. The passivation dielectric layer is preferably a silicon nitride film layer. Silane and ammonia are used as reaction gases and the deposition temperature is 540°C. A 78-nanometer-thick silicon nitride film layer is deposited on the surface of the silicon aluminum gallium oxide passivation film layer. A 78-nanometer-thick silicon nitride film layer is deposited on the surface of the phosphorus-doped poly silicon on the back side.

[0076] In step S8, conductive silver paste is printed on the front and back silicon nitride surfaces of the silicon wafer, respectively, and the silver paste is dried and sintered to prepare a conductive electrode. The sintering peak temperature is 786°C.

[0077] Compared with the prior art, the beneficial effects of the method for preparing the Topcon solar cell provided by the present invention are substantially the same as the beneficial effects of the Topcon solar cell provided above, and are not described in detail herein.

[0078] Embodiment 1

[0079] In this embodiment, the aluminum-gallium silicon oxide passivation film layer is prepared by a PECVD method, and the chemical composition of the silicon film and the feasibility of the preparation method are characterized. The steps are as follows:

[0080] A. Select silicon wafer. Select a single crystal p-type silicon wafer with a bulk resistivity of 2.0 Ω·cm.

[0081] B. Polishing and cleaning of silicon wafer surface: A potassium hydroxide alkaline solution with a mass fraction of 31% is used to isotropically etch the silicon wafer to obtain a relatively flat silicon wafer surface with a reflectivity greater than 35%.

[0082] C. The aluminum-silicon-gallium oxide passivation film layer is deposited on both surfaces of the silicon wafer.

[0083] The PECVD method was used to prepare a silicon-aluminum-gallium oxide passivation film layer on the surface of a silicon wafer. The frequency of the RF power supply was 13.56 MHz, and the RF power range was 29 mW / cm^2. A mixed gas of TMAl, silane, TMG, and laughing gas was used as a reaction precursor, and the flow ratio of TMAl:TMG:SiH4:N2O was 0.3:0.1:2:5. The pressure of the reaction chamber was set to 110 Pa. A silicon-aluminum-gallium oxide passivation film layer with a film thickness of 10 nm was obtained.

[0084] D. Measure the silicon-aluminum oxide passivation film layer, such as Figure 2-Figure 5 As shown, the chemical composition of the film layer is silicon aluminum gallium oxide.

[0085] E. Anneal the coated silicon wafers under furnace annealing conditions at 660°C for 40 minutes.

[0086] F. Measure the passivation effect of silicon wafers, such as Figure 6 shown.

[0087] Comparative Example 1

[0088] In this example, a conventional aluminum oxide passivation film layer is prepared to evaluate its passivation effect, and the steps are as follows:

[0089] A. Select silicon wafer. Select a single crystal p-type silicon wafer with a bulk resistivity of 2.0 Ω·cm.

[0090] B. Polishing and cleaning of silicon wafer surface: A potassium hydroxide alkaline solution with a mass fraction of 31% is used to isotropically etch the silicon wafer to obtain a relatively flat silicon wafer surface with a reflectivity greater than 35%.

[0091] C. A 10-nanometer aluminum oxide passivation film layer is deposited on both surfaces of the silicon wafer.

[0092] D. Anneal the coated silicon wafers under furnace annealing conditions at 660°C for 40 minutes.

[0093] E. Measure the passivation effect of silicon wafers, such as Figure 6 shown.

[0094] The results show that under the condition of the same thickness, the passivation effect of the prepared silicon aluminum gallium oxide film layer is better than that of the aluminum oxide film layer, indicating that the charge density of the silicon aluminum gallium oxide film layer on the silicon wafer surface is greater than that of the corresponding aluminum oxide film layer.

[0095] Comparative Example 2

[0096] This comparative example 2 provides a method for preparing a conventional Topcon battery, and the steps are as follows:

[0097] A. Select silicon wafer. Select single crystal N-type silicon wafer with a bulk resistivity of 2.5Ω·cm.

[0098] B. Texturing of silicon wafer surface: A sodium hydroxide alkaline solution with a mass fraction of 4% was used to anisotropically etch the silicon wafer to obtain a textured silicon wafer surface with a reflectivity of 11.8%.

[0099] C. PN junction is prepared by high temperature boron diffusion on silicon wafer surface. The sheet resistance after diffusion is 130.

[0100] D. Etching and cleaning the back surface of the silicon wafer. Use a wet single-sided etching device to etch and remove the boron-doped area on the back of the silicon wafer while retaining the borosilicate glass layer on the front.

[0101] E. Growth of tunnel oxide layer and poly silicon layer on the back surface. A tunnel oxide layer with a thickness of 1.8 nanometers was grown by furnace tube thermal oxidation method, and SiH4 gas was introduced into the furnace tube to prepare a 80 nanometer poly silicon layer.

[0102] F. Use a high-temperature furnace tube to dope phosphorus into the back Poly silicon layer, wherein the concentration of active phosphorus in the Poly silicon layer reaches more than 4E20 atoms per cubic centimeter.

[0103] G. Use wet equipment to clean the Poly silicon layer plated on the front side and remove the BSG and PSG layers on the front and back sides.

[0104] H. Deposit 8 nanometers of aluminum oxide on the front to passivate the silicon wafer surface.

[0105] I. Deposit a 78 nanometer silicon nitride film on the surface of the aluminum oxide film layer.

[0106] J. Conductive silver paste is placed on the front and back surfaces of the battery respectively, and the Topcon battery is prepared after drying and sintering, and the battery performance is characterized.

[0107] Embodiment 2

[0108] This embodiment provides a method for preparing a Topcon battery using the silicon-aluminum-gallium oxide passivation film layer disclosed in the present invention, and the steps are the same as those of the comparative example 2, except that step H:

[0109] The PECVD method was used to prepare a silicon aluminum gallium oxide passivation film layer on the front surface of the silicon wafer. The frequency of the RF power supply was 13.56MHz, and the RF power range was 29mW / cm^2. A mixed gas of TMAl, TMG, silane and laughing gas was used as a reaction precursor, and the flow ratio of TMAl:TMG:SiH4:N2O was 0.3:0.1:2:5. The pressure of the reaction chamber was set to 110Pa. A silicon aluminum gallium oxide passivation film layer with a film thickness of 8nm was obtained.

[0110] The above film layer was used to prepare Topcon solar cells, and the electrical performance of the cells was tested. The results are as follows: Figure 7 As shown, the results show that under the condition of the same thickness, compared with the aluminum oxide film passivation in the prior art, the silicon oxide aluminum gallium passivation film has a better passivation effect, which is specifically manifested in the significant improvement of minority carrier lifetime and pseudo open circuit voltage. The passivation effect of the silicon oxide aluminum gallium passivation film prepared in this embodiment is better than that of the aluminum oxide film, which proves that the use of the silicon oxide aluminum gallium passivation layer in the present invention can improve the open circuit voltage and photoelectric conversion efficiency of the Topcon cell solar cell.

[0111] From the semi-quantitative analysis of XPS test, it can be obtained that the chemical composition of silicon aluminum gallium oxide is Si 0.9 Al 0.22 Ga 0.06 O2.

[0112] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A Topcon solar cell, characterized in that: The silicon wafer comprises a front side and a back side, the front side is a boron-diffused silicon wafer surface, and a silicon-aluminum-gallium oxide passivation film layer, a front side passivation dielectric layer and a first conductive electrode are sequentially arranged from the front side outwards; A tunneling oxide layer, a phosphorus-doped silicon layer, a reverse passivation dielectric layer and a second conductive electrode are sequentially arranged from the reverse surface outward; The silicon-aluminum-gallium oxide passivation film layer is composed of oxides of silicon, aluminum and gallium, and the molar content ratio of silicon, aluminum and gallium is adjustable.

2. The Topcon solar cell according to claim 1, characterized in that: In the silicon oxide aluminum gallium passivation film layer, the molar ratio of silicon atoms on the side close to the silicon wafer surface is greater than the sum of the molar ratio of aluminum atoms and the molar ratio of gallium atoms on this side, and the sum of the molar ratio of aluminum atoms and the molar ratio of gallium atoms on the side away from the silicon wafer surface is greater than the molar ratio of silicon atoms on this side.

3. The Topcon solar cell according to claim 2, characterized in that: In the silicon oxide aluminum gallium passivation film layer, the total molar ratio of aluminum atoms is greater than the total molar ratio of gallium atoms.

4. The Topcon solar cell according to any one of claims 1 to 3, characterized in that: From the surface of the silicon wafer outward, the molar ratio of silicon atoms in the silicon oxide aluminum gallium passivation film layer gradually decreases, while the molar ratio of aluminum atoms and the molar ratio of gallium atoms gradually increase.

5. The Topcon solar cell according to any one of claims 1 to 3, characterized in that: In the silicon-aluminum-gallium oxide passivation film layer, the total molar proportion of silicon atoms is not greater than 33%, the total molar proportion of aluminum atoms is not greater than 40%, and the total molar proportion of gallium atoms is not greater than 38%.

6. The Topcon solar cell according to claim 5, characterized in that: In the silicon oxide aluminum gallium passivation film layer, the total molar ratio of aluminum atoms to the total molar ratio of gallium atoms is greater than 2:

1.

7. The Topcon solar cell according to claim 1, characterized in that: The thickness of the silicon aluminum gallium oxide passivation film layer is 1-20 nanometers, preferably 3-10 nanometers.

8. A method for manufacturing a Topcon solar cell, for manufacturing a Topcon solar cell according to any one of claims 1 to 7, characterized in that: The steps include: S1: Provide n-type silicon wafer as substrate and complete silicon wafer texturing and cleaning; S2: High temperature boron diffusion on the surface of the texturing silicon wafer to prepare the PN junction; S3: After planarizing the back surface of the silicon wafer, a tunneling oxide layer and a Poly layer are prepared; S4: Phosphorus diffusion on the reverse Poly layer; S5: Clean the front-side plated Poly layer, and clean the BSG and PSG layers on both sides; S6: depositing a silicon-aluminum-gallium oxide passivation film layer on the front side; S7: Deposition of passivation dielectric layer on both sides of the silicon wafer; S8: Print silver paste on both sides, dry, sinter and test to complete the battery preparation.

9. The method for manufacturing a Topcon solar cell according to claim 8, characterized in that: Step S6: depositing a silicon-aluminum-gallium oxide passivation film layer on the front surface by using a PECVD method; The aluminum source of the silicon aluminum gallium oxide passivation film layer includes trimethylaluminum, trialkylaluminum, dialkylaluminum chloride, monoalkylaluminum dichloride or trialkylaluminum trichloride; the oxygen source of the silicon aluminum gallium oxide passivation film layer includes N2O, CO2 or CO; the gallium source of the silicon aluminum gallium oxide passivation film layer includes trimethylgallium; the silicon source of the silicon aluminum gallium oxide passivation film layer includes silane.

10. The method for manufacturing a Topcon solar cell according to claim 9, characterized in that: The aluminum-silicon-gallium oxide passivation film layer deposited on the front side by the PECVD method is annealed. The required annealing conditions are: annealing time of 10-40 minutes, annealing temperature of 400-800°C, and preferably annealing temperature of 500-700°C.

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