Solar cell and method for preparing the same

Abstract

The present application provides a solar cell and a preparation method thereof, which belongs to the field of photovoltaic technology. The solar cell comprises: a silicon wafer base layer; a boron-doped silicon layer located on the front side of the silicon wafer base layer; a tunneling oxide layer and a phosphorus-doped polycrystalline silicon carbide layer arranged in sequence on the back side of the silicon wafer base layer. Among them, the phosphorus-doped polycrystalline silicon carbide layer is doped with oxygen atoms. The solar cell provided by the present application is conducive to avoiding the film explosion phenomenon of the polycrystalline structure layer in the solar cell, and enhances the passivation performance of the solar cell; it is also conducive to improving the anti-silver paste corrosion ability of the polycrystalline structure layer, effectively reducing the metal piercing on the back side of the solar cell and the metal recombination in the solar cell, thereby effectively improving the photoelectric conversion efficiency, open circuit voltage and short circuit current of the solar cell.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a solar cell and a method for preparing the same. Background Art

[0002] TOPCon solar cell is Tunnel Oxide Passivated Contact, which was first proposed by the Frauhofer Institute for Solar Energy Research in Germany in 2013. The main structure of TOPCon solar cell is: front anti-reflection layer, front passivation layer, boron-doped silicon layer, silicon wafer substrate layer, tunnel oxide layer, phosphorus-doped polysilicon layer and back passivation layer stacked in sequence.

[0003] However, in existing TOPCon solar cells, the phosphorus-doped polysilicon layer is prone to film explosion, which will reduce the passivation performance of the solar cell, thereby reducing the open circuit voltage and photoelectric conversion efficiency of the solar cell. In addition, the phosphorus-doped polysilicon layer has poor resistance to silver paste corrosion. When silver paste is screen-printed to form a silver electrode, the phosphorus-doped polysilicon layer is prone to corrosion, causing metal to pierce through the oxide layer and enter the silicon wafer base layer; the phosphorus atom doping concentration in the area where the metal and silicon contact in the silicon wafer base layer is low, resulting in a poor field passivation effect. This area will produce a large metal complex, which will cause a loss in the open circuit voltage of the solar cell, and then cause a loss in the photoelectric conversion efficiency of the solar cell. Summary of the invention

[0004] The purpose of the present application is to provide a solar cell and a method for preparing the same, which is intended to improve the open circuit voltage and photoelectric conversion efficiency of existing TOPCon solar cells.

[0005] In a first aspect, an embodiment of the present application provides a solar cell, comprising: a silicon wafer base layer; a boron-doped silicon layer located on the front side of the silicon wafer base layer; a tunneling oxide layer and a phosphorus-doped polycrystalline silicon carbide layer disposed sequentially on the back side of the silicon wafer base layer.

[0006] The phosphorus-doped polycrystalline silicon carbide layer is doped with oxygen atoms.

[0007] In the above technical scheme, the phosphorus-doped polysilicon layer (made of phosphorus-doped silicon) in the traditional TOPCon solar cell is replaced by a phosphorus-doped polycrystalline silicon carbide layer, and the phosphorus-doped polycrystalline silicon carbide layer is doped with oxygen atoms, so that Si-O bonds are formed between the silicon atoms and the oxygen atoms in the phosphorus-doped polycrystalline silicon carbide layer; the material of the polycrystalline structure layer of the solar cell provided in the present application is mainly silicon carbide co-doped with phosphorus and oxygen, which is beneficial to improving the stability of the crystal structure of the phosphorus-doped polycrystalline silicon carbide layer, and thus is beneficial to avoiding the film bursting phenomenon of the polycrystalline structure layer in the solar cell, and enhancing the passivation performance of the solar cell; it is also beneficial to improve the anti-silver paste corrosion ability of the polycrystalline structure layer, effectively reducing the metal piercing on the back of the solar cell and the metal recombination in the solar cell, and thus can effectively improve the photoelectric conversion efficiency, open circuit voltage and short circuit current of the solar cell.

[0008] In combination with the first aspect, in an optional implementation manner of the present application, the thickness of the phosphorus-doped polycrystalline silicon carbide layer is 25-280 nm.

[0009] In the above technical solution, the thickness of the phosphorus-doped polycrystalline silicon carbide layer is 25-280 nm, which is beneficial to improving the photoelectric conversion efficiency, open circuit voltage and short circuit current of the solar cell.

[0010] In combination with the first aspect, in an optional implementation manner of the present application, the material of the tunneling oxide layer is silicon oxide, and the thickness of the tunneling oxide layer is 0.5-2 nm.

[0011] In a second aspect, the present application provides a method for preparing the solar cell provided in the first aspect, comprising:

[0012] A boron-doped silicon layer is formed on the front side of the silicon wafer base layer.

[0013] A tunnel oxide layer is formed on the back side of the silicon wafer base layer.

[0014] In an atmosphere containing oxygen, an intrinsic amorphous silicon carbide layer and a phosphorus-doped amorphous silicon carbide layer are sequentially formed on the surface of the tunnel oxide layer.

[0015] Annealing is performed so that the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer are converted into a phosphorus-doped polycrystalline silicon carbide layer.

[0016] In the above technical scheme, an intrinsic amorphous silicon carbide layer and a phosphorus-doped amorphous silicon carbide layer are formed in an atmosphere containing oxygen, so that Si-O bonds can be formed between silicon atoms and oxygen atoms in the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer; after annealing, the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer can be converted into a phosphorus-doped polycrystalline silicon carbide layer, that is, the material of the polycrystalline structure layer in the solar cell prepared in the present application is mainly silicon carbide co-doped with phosphorus and oxygen, which is beneficial to improving the stability of the crystal structure of the phosphorus-doped polycrystalline silicon carbide layer, and further helps to avoid the film explosion phenomenon of the polycrystalline structure layer in the solar cell, thereby enhancing the passivation performance of the solar cell; it is also beneficial to improve the anti-silver paste corrosion ability of the polycrystalline structure layer, effectively reduce the metal piercing on the back of the solar cell and the metal recombination in the solar cell, and further can effectively improve the photoelectric conversion efficiency, open circuit voltage and short circuit current of the solar cell.

[0017] In conjunction with the second aspect, in an optional embodiment of the present application, a method for preparing an intrinsic amorphous silicon carbide layer includes: forming an intrinsic amorphous silicon carbide layer on a surface of a tunneling oxide layer by vapor deposition in an atmosphere of a first mixed gas, wherein the first mixed gas includes O2, SiH4, CH4, and H2.

[0018] In the above technical solution, an intrinsic amorphous silicon carbide layer can be prepared and formed, and the intrinsic amorphous silicon carbide layer is doped with oxygen atoms.

[0019] Optionally, in the first mixed gas, the volume ratio of O2, SiH4, CH4 and H2 is 1:(1-10):(0.3-2):(1-10).

[0020] In the above technical solution, the ratio of O2, SiH4, CH4 and H2 is more appropriate, which is conducive to the rapid preparation of an intrinsic amorphous silicon carbide layer doped with oxygen atoms.

[0021] In combination with the second aspect, in an optional embodiment of the present application, the temperature for forming the intrinsic amorphous silicon carbide layer is 350-450°C.

[0022] In the above technical solution, it is beneficial to quickly prepare and form an intrinsic amorphous silicon carbide layer doped with oxygen atoms.

[0023] In combination with the second aspect, in an optional embodiment of the present application, a method for preparing a phosphorus-doped amorphous silicon carbide layer includes: forming a phosphorus-doped amorphous silicon carbide layer on the surface of the intrinsic amorphous silicon carbide layer by vapor deposition in an atmosphere of a second mixed gas; wherein the second mixed gas includes O2, SiH4, CH4, PH3 and H2.

[0024] In the above technical solution, a phosphorus-doped amorphous silicon carbide layer can be prepared and formed, and the phosphorus-doped amorphous silicon carbide layer is doped with oxygen atoms.

[0025] Optionally, in the second mixed gas, the volume ratio of O2, SiH4, CH4, PH3 and H2 is 1:(1-10):(0.3-2):(1-9):(1-10).

[0026] In the above technical solution, the ratio of O2, SiH4, CH4, PH3 and H2 is more appropriate, which is conducive to the rapid preparation of a phosphorus-doped amorphous silicon carbide layer doped with oxygen atoms.

[0027] In combination with the second aspect, in an optional embodiment of the present application, the temperature for forming the phosphorus-doped amorphous silicon carbide layer is 350-450°C.

[0028] In the above technical solution, it is beneficial to quickly prepare a phosphorus-doped amorphous silicon carbide layer doped with oxygen atoms.

[0029] In combination with the second aspect, in an optional implementation manner of the present application, the annealing temperature is 600-1000° C., and the annealing time is 10-60 min.

[0030] In the above technical solution, the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer can be converted into a phosphorus-doped polycrystalline silicon carbide layer, which is beneficial to improving the crystal quality of the phosphorus-doped polycrystalline silicon carbide layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A schematic diagram of the structure of a solar cell provided in an embodiment of the present application.

[0033] Figure 2 A process flow chart for preparing a solar cell according to an embodiment of the present application.

[0034] Icon: 10-solar cell; 110-silicon wafer base layer; 120-boron-doped silicon layer; 130-tunneling oxide layer; 140-phosphorus-doped polycrystalline silicon carbide layer; 150-front passivation layer; 160-front anti-reflection layer; 170-back passivation layer. DETAILED DESCRIPTION

[0035] The main structure of TOPCon solar cells is: a front anti-reflection layer, a front passivation layer, a boron-doped silicon layer, a silicon wafer base layer, a tunneling oxide layer, a phosphorus-doped polysilicon layer and a back passivation layer stacked in sequence.

[0036] The inventors have found that in existing TOPCon solar cells, the phosphorus-doped polysilicon layer is prone to film bursting, which will lead to a decrease in the passivation performance of the solar cell, thereby reducing the open circuit voltage and photoelectric conversion efficiency of the solar cell.

[0037] In addition, the inventors also found that in the existing TOPCon solar cells, the phosphorus-doped polysilicon layer has poor resistance to silver paste corrosion. When silver electrodes are formed by screen printing with silver paste, the phosphorus-doped polysilicon layer is prone to corrosion, causing metal to pierce through the oxide layer and enter the silicon wafer base layer; the phosphorus atom doping concentration in the area where the metal and silicon are in contact in the silicon wafer base layer is low, resulting in a poor field passivation effect. Larger metal composites will occur in this area, and the larger metal composites will cause a loss in the open circuit voltage of the solar cell, which in turn will cause a loss in the photoelectric conversion efficiency of the solar cell.

[0038] Therefore, the present application provides a solar cell, which can avoid the film explosion phenomenon of the polycrystalline structure layer of the TOPCon solar cell, and can also improve the anti-silver paste corrosion ability of the polycrystalline structure layer of the TOPCon solar cell, thereby improving the open circuit voltage and photoelectric conversion efficiency of the solar cell.

[0039] Figure 1 For a schematic diagram of the structure of the solar cell 10 provided in the embodiment of the present application, please refer to Figure 1 The solar cell 10 includes: a silicon wafer base layer 110; a boron-doped silicon layer 120 located on the front side of the silicon wafer base layer 110; a tunneling oxide layer 130 and a phosphorus-doped polycrystalline silicon carbide layer 140 located on the back side of the silicon wafer base layer 110.

[0040] The phosphorus-doped polycrystalline silicon carbide layer 140 is doped with oxygen atoms.

[0041] The solar cell 10 provided in the present application replaces the phosphorus-doped polycrystalline silicon layer (made of phosphorus-doped silicon) in the conventional TOPCon solar cell with a phosphorus-doped polycrystalline silicon carbide layer 140, and the phosphorus-doped polycrystalline silicon carbide layer 140 is doped with oxygen atoms, so that Si-O bonds are formed between the silicon atoms and oxygen atoms in the phosphorus-doped polycrystalline silicon carbide layer 140, generating a certain amount of SiO x .

[0042] The material of the phosphorus-doped polycrystalline silicon carbide layer 140 of the solar cell 10 provided in the present application is mainly silicon carbide co-doped with phosphorus and oxygen, which is beneficial to improving the stability of the crystal structure of the phosphorus-doped polycrystalline silicon carbide layer 140, and further helps to avoid the film bursting phenomenon of the polycrystalline structure layer (i.e., the phosphorus-doped polycrystalline silicon carbide layer 140) in the solar cell, thereby enhancing the passivation performance of the solar cell 10; it is also beneficial to improve the resistance of the polycrystalline structure layer to silver paste corrosion, effectively reducing the metal piercing on the back of the solar cell 10 and the metal recombination in the solar cell 10, and further effectively improving the photoelectric conversion efficiency, open circuit voltage and short circuit current of the solar cell 10.

[0043] In the present application, the material of the tunnel oxide layer 130 is silicon oxide (SiO x ), the thickness of the tunnel oxide layer 130 is 0.5-2nm.

[0044] By way of example, the thickness of the tunnel oxide layer 130 may be 0.5 nm, 0.7 nm, 1 nm, 1.2 nm, 1.5 nm, 1.7 nm, or 2 nm, etc.

[0045] In the present application, the thickness of the phosphorus-doped polycrystalline silicon carbide layer 140 is 25-280 nm, which is beneficial to improving the photoelectric conversion efficiency, open circuit voltage and short circuit current of the solar cell 10 .

[0046] By way of example, the thickness of the phosphorus-doped polycrystalline silicon carbide layer 140 may be 25 nm, 50 nm, 70 nm, 100 nm, 120 nm, 150 nm, 200 nm, 250 nm, 280 nm, or the like.

[0047] Furthermore, the thickness of the phosphorus-doped polycrystalline silicon carbide layer 140 is 40-150 nm, which is beneficial to improving the silver paste corrosion resistance of the polycrystalline structure layer.

[0048] In the present application, the solar cell 10 further includes a front passivation layer 150 and a front anti-reflection layer 160 which are sequentially disposed on the boron-doped silicon layer 120; the material of the front passivation layer 150 is aluminum oxide (AlO x ), the material of the front anti-reflection layer 160 is silicon nitride (SiN x ).

[0049] The solar cell 10 further includes a back passivation layer 170 disposed on the phosphorus-doped polycrystalline silicon carbide layer 140. The back passivation layer 170 is disposed on a side of the phosphorus-doped polycrystalline silicon carbide layer 140 away from the tunneling oxide layer 130. The back passivation layer 170 is made of silicon nitride (SiN x ).

[0050] The solar cell 10 further includes a front electrode (not shown) and a back electrode (not shown); illustratively, the front electrode is made of silver-aluminum material, and the back electrode is made of silver material.

[0051] The present application also provides a method for preparing a solar cell 10, comprising: forming a boron-doped silicon layer 120 on the front side of a silicon wafer base layer 110; forming a tunneling oxide layer 130 on the back side of the silicon wafer base layer 110; in an atmosphere containing oxygen, sequentially forming an intrinsic amorphous silicon carbide layer and a phosphorus-doped amorphous silicon carbide layer on the surface of the tunneling oxide layer 130; and annealing so that the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer are converted together into a phosphorus-doped polycrystalline silicon carbide layer 140.

[0052] The preparation method of the solar cell 10 provided in the present application forms an intrinsic amorphous silicon carbide layer and a phosphorus-doped amorphous silicon carbide layer in an atmosphere containing oxygen, so that Si-O bonds can be formed between silicon atoms and oxygen atoms in the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer; after annealing, the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer can be converted into a phosphorus-doped polycrystalline silicon carbide layer 140, that is, the material of the polycrystalline structure layer in the solar cell 10 prepared in the present application is mainly silicon carbide co-doped with phosphorus and oxygen, which is beneficial to improving the stability of the crystal structure of the phosphorus-doped polycrystalline silicon carbide layer 140, and further helps to avoid the film explosion phenomenon of the polycrystalline structure layer in the solar cell 10, thereby enhancing the passivation performance of the solar cell 10; it is also beneficial to improve the anti-silver paste corrosion ability of the polycrystalline structure layer, effectively reduce the metal piercing on the back of the solar cell 10 and the metal recombination in the solar cell 10, and further can effectively improve the photoelectric conversion efficiency, open circuit voltage and short circuit current of the solar cell 10.

[0053] Figure 2 For a flow chart of the preparation process of the solar cell 10 provided in the embodiment of the present application, please refer to Figure 1 and 2 , the solar cell 10 is prepared by the following steps:

[0054] S110 , forming a boron-doped silicon layer 120 on the front surface of the silicon wafer base layer 110 .

[0055] In the present application, the silicon wafer base layer 110 refers to a silicon wafer that has been subjected to a texturing treatment. The texturing treatment can form a pyramid-shaped textured surface structure on the front side of the silicon wafer, thereby playing a role in reducing reflection and limiting light.

[0056] As an example, the texturing step includes: texturing the N-type silicon wafer with 1 wt % alkali solution, and then cleaning the silicon wafer with a mixture of hydrogen peroxide and alkali to obtain the silicon wafer base layer 110 .

[0057] In the present application, the step of forming a boron-doped silicon layer 120 on the front side of the silicon wafer base layer 110 includes: using BCl3 gas to diffuse at 900-1050°C to form a pn junction, thereby obtaining a boron-doped silicon layer 120 located on the front side of the silicon wafer base layer 110.

[0058] S120, performing alkali polishing on the back side of the silicon wafer base layer 110.

[0059] In the present application, the alkali polishing treatment of the back side of the silicon wafer base layer 110 includes: using a chain HF machine to remove the borosilicate glass (BSG) with boron expansion on the back side of the silicon wafer base layer 110, and then transferring it to a tank alkali polishing machine through a robot to remove the pn junction on the back side and edge of the silicon wafer base layer 110.

[0060] S130 , forming a tunnel oxide layer 130 on the back side of the silicon wafer base layer 110 .

[0061] In the present application, a tunnel oxide layer 130 with a thickness of 0.5-2 nm is formed on the back side of the silicon wafer base layer 110 in an atmosphere of nitric oxide by plasma enhanced atomic layer deposition (PEALD) or plasma enhanced chemical vapor deposition (PECVD).

[0062] S140 , in an atmosphere containing oxygen, an intrinsic amorphous silicon carbide layer and a phosphorus-doped amorphous silicon carbide layer are sequentially formed on the surface of the tunnel oxide layer 130 .

[0063] In the present application, the method for preparing the intrinsic amorphous silicon carbide layer includes: forming the intrinsic amorphous silicon carbide layer on the surface of the tunnel oxide layer 130 by vapor deposition in an atmosphere of a first mixed gas, wherein the first mixed gas includes O2, SiH4, CH4 and H2.

[0064] The above preparation method can form an intrinsic amorphous silicon carbide layer, and the intrinsic amorphous silicon carbide layer is doped with oxygen atoms.

[0065] Furthermore, in the first mixed gas, the volume ratio of O2, SiH4, CH4 and H2 is 1:(1-10):(0.3-2):(1-10). Under the above ratio conditions, the ratio of O2, SiH4, CH4 and H2 is more appropriate, which is conducive to the rapid preparation of an intrinsic amorphous silicon carbide layer doped with oxygen atoms.

[0066] As an example, in the first mixed gas, the volume ratio of O2, SiH4, CH4 and H2 can be 1:5:0.5:5, 1:7:1:7 or 1:10:1:10, etc.

[0067] Furthermore, the temperature for forming the intrinsic amorphous silicon carbide layer is 350-450° C. Under the above temperature conditions, it is beneficial to quickly prepare and form the intrinsic amorphous silicon carbide layer doped with oxygen atoms.

[0068] As an example, the method of forming the intrinsic amorphous silicon carbide layer can be low-pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD); in the present application, the PECVD method is used to form the intrinsic amorphous silicon carbide layer, which is beneficial to reduce plating and improve the appearance and yield of the solar cell 10.

[0069] As an example, the intrinsic amorphous silicon carbide layer is formed to have a thickness of 5-80 nm.

[0070] In the present application, a method for preparing a phosphorus-doped amorphous silicon carbide layer includes: forming a phosphorus-doped amorphous silicon carbide layer on the surface of an intrinsic amorphous silicon carbide layer by vapor deposition in an atmosphere of a second mixed gas; wherein the second mixed gas includes O2, SiH4, CH4, PH3 and H2.

[0071] The above preparation method can form a phosphorus-doped amorphous silicon carbide layer, and the phosphorus-doped amorphous silicon carbide layer is doped with oxygen atoms.

[0072] Furthermore, in the second mixed gas, the volume ratio of O2, SiH4, CH4, PH3 and H2 is 1:(1-10):(0.3-2):(1-9):(1-10). Under the above ratio conditions, the ratio of O2, SiH4, CH4, PH3 and H2 is more suitable, which is conducive to the rapid preparation of the phosphorus-doped amorphous silicon carbide layer doped with oxygen atoms.

[0073] As an example, in the second mixed gas, the volume ratio of O2, SiH4, CH4, PH3 and H2 can be 1:5:1:4:5, 1:7:1:5.6:7 or 1:10:1:8:10, etc.

[0074] Furthermore, the temperature for forming the phosphorus-doped amorphous silicon carbide layer is 350-450° C. Under the above temperature conditions, it is beneficial to quickly prepare and form the phosphorus-doped amorphous silicon carbide layer doped with oxygen atoms.

[0075] As an example, the method of forming the phosphorus-doped amorphous silicon carbide layer can be low-pressure chemical vapor deposition (LPCVD) or plasma enhanced chemical vapor deposition (PECVD); in the present application, the PECVD method is used to form the phosphorus-doped amorphous silicon carbide layer, which is beneficial to reduce plating and improve the appearance and yield of the solar cell 10.

[0076] As an example, the thickness of the formed phosphorus-doped amorphous silicon carbide layer is 20-200 nm.

[0077] S150, forming a mask layer on the surface of the phosphorus-doped amorphous silicon carbide layer.

[0078] Forming a mask layer on the surface of the phosphorus-doped amorphous silicon carbide layer is beneficial to better protect the polycrystalline structure layer (i.e., the phosphorus-doped polycrystalline silicon carbide layer 140) on the back side of the silicon wafer base layer 110 from being etched and damaged during subsequent wet chemical cleaning, which is beneficial to ensuring the photoelectric conversion efficiency of the final solar cell 10.

[0079] As an example, the step of forming a mask layer on the surface of the phosphorus-doped amorphous silicon carbide layer includes: using a PECVD method, at 350-450° C., introducing a mixed gas of SiH4 and N2O to deposit a mask layer (made of SiO x , thickness is 10-50nm).

[0080] S160 , annealing, so that the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer are converted into the phosphorus-doped polycrystalline silicon carbide layer 140 .

[0081] In the present application, the annealing temperature is 600-1000°C, and the annealing time is 10-60 minutes. Under the above annealing conditions, the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer can be transformed into the phosphorus-doped polycrystalline silicon carbide layer 140, which is beneficial to improve the crystal quality of the phosphorus-doped polycrystalline silicon carbide layer 140; phosphorus atoms can also form covalent bonds with oxygen-doped amorphous silicon carbide to provide electrons to form a field passivation structure.

[0082] By way of example, the annealing temperature may be 600°C, 650°C, 700°C, 800°C, 900°C or 1000°C, etc., and the annealing time may be 10 min, 15 min, 20 min, 30 min, 45 min, 50 min or 60 min, etc.

[0083] In the present application, the annealing gas atmosphere may be nitrogen or oxygen.

[0084] S170, wet chemical cleaning is performed.

[0085] In the present application, the wet chemical cleaning steps include: first using chain hydrofluoric acid (HF) to remove the oxide layer that is plated on the front side of the silicon wafer base layer 110 in step S130, and at the same time removing the polycrystalline structure layer generated on the front side of the silicon wafer base layer 110 during the annealing process in step S160; and then transferring to an alkaline tank to remove the silicon carbide coating on the front side of the silicon wafer base layer 110 and the mask layer on the back side of the silicon wafer base layer 110.

[0086] S180 , forming a front passivation layer 150 and a front anti-reflection layer 160 in sequence on the surface of the boron-doped silicon layer 120 .

[0087] In the present application, aluminum oxide (AlO) is deposited on the surface of the boron-doped silicon layer 120 by ALD. x ) film as the front passivation layer 150; silicon nitride (SiN x ) film as the front anti-reflection layer 160.

[0088] S190 , forming a back passivation layer 170 on the surface of the phosphorus-doped polycrystalline silicon carbide layer 140 .

[0089] In the present application, silicon nitride (SiN) is deposited on the surface of the phosphorus-doped polycrystalline silicon carbide layer 140 by PECVD. x ) film, serving as a back passivation layer 170 .

[0090] S200, manufacturing a front electrode and a back electrode.

[0091] Silver paste is coated on the front and back sides of the solar cell 10 by screen printing to produce the front electrode and the back electrode.

[0092] In this application, the front electrode is made of silver-aluminum material, and the back electrode is made of silver material.

[0093] S210 , performing light injection processing, testing the photoelectric conversion efficiency of the solar cell 10 , and sorting.

[0094] As an example, the temperature of the light injection process is 700°C.

[0095] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0096] Example

[0097] This embodiment provides a method for preparing a solar cell, comprising the following steps:

[0098] (1) Texturing: An N-type silicon wafer is used and a 1 wt % sodium hydroxide solution is used for texturing; then the silicon wafer is cleaned with hydrogen peroxide and sodium hydroxide to obtain a silicon wafer base layer.

[0099] (2) Boron diffusion: Entering the boron diffusion furnace, BCl3 is diffused at 1000°C to form a pn junction, obtaining a boron-doped silicon layer located on the front side of the silicon wafer base layer.

[0100] (3) Alkali polishing: A chain HF machine is used to remove the borosilicate glass (BSG) on the back side of the silicon wafer substrate layer, and then the wafer is transferred to a tank alkali polishing machine through a robot to remove the pn junction on the back side and edge of the silicon wafer substrate layer.

[0101] (4) Formation of a tunneling oxide layer: In the PECVD device, nitric oxide gas is introduced at 400°C to form a tunneling oxide layer with a thickness of 1 nm on the back side of the silicon wafer base layer.

[0102] (5) Forming an intrinsic amorphous silicon carbide layer: In a PECVD device, O2, SiH4, CH4 and H2 with a volume ratio of 1:10:1:10 are introduced at 400°C to form an intrinsic amorphous silicon carbide layer with a thickness of 30 nm on the tunneling oxide layer.

[0103] (6) Formation of a phosphorus-doped amorphous silicon carbide layer: In a PECVD device, at 400°C, O2, SiH4, CH4, PH3 and H2 in a volume ratio of 1:10:1:8:10 are introduced to form a phosphorus-doped amorphous silicon carbide layer with a thickness of 150 nm on the intrinsic amorphous silicon carbide layer.

[0104] (7) Forming a mask layer: In a PECVD device, SiH4 and N2O with a volume ratio of 1:5 are introduced at 400°C to form a mask layer (SiO x ).

[0105] (8) Annealing: A tubular annealing furnace was used, the annealing gas atmosphere was nitrogen, the temperature was 900°C, and the time was 20 min.

[0106] (9) RCA cleaning: First, the oxide layer on the front side of the silicon wafer substrate layer that was plated in step (4) is removed through chain hydrofluoric acid (HF), and the polycrystalline structure layer generated on the front side of the silicon wafer substrate layer during the annealing process in step (8) is removed; then, the silicon carbide coating on the front side of the silicon wafer substrate layer and the mask layer on the back side of the silicon wafer substrate layer are removed in an alkaline bath.

[0107] (10) Forming a front passivation layer and a front anti-reflection layer: Aluminum oxide (AlO) is deposited on the surface of the boron-doped silicon layer by ALD. x ) film as the front passivation layer; silicon nitride (SiN x ) film as the front anti-reflection layer.

[0108] (11) Forming a back passivation layer: Silicon nitride (SiN) is deposited on the surface of the phosphorus-doped polycrystalline silicon carbide layer by PECVD. x ) film as a back passivation layer.

[0109] (12) Making the front electrode and the back electrode: coating the back of the solar cell with silver paste to make the back electrode; coating the front of the solar cell with silver-aluminum paste to make the front electrode.

[0110] (13) Light injection treatment is performed at 700°C.

[0111] Comparative Example 1

[0112] This comparative example provides a method for preparing a solar cell. The difference between this comparative example and the embodiment lies in the difference between step (5) and step (6).

[0113] Step (5): In a PECVD device, SiH4, CH4 and H2 with a volume ratio of 10:1:10 are introduced at 400°C to form an intrinsic amorphous silicon carbide layer with a thickness of 30nm on the tunneling oxide layer.

[0114] Step (6): Forming a phosphorus-doped amorphous silicon carbide layer: In a PECVD device, at 400°C, SiH4, CH4, PH3 and H2 in a volume ratio of 10:1:8:10 are introduced to form a phosphorus-doped amorphous silicon carbide layer with a thickness of 150 nm on the intrinsic amorphous silicon carbide layer.

[0115] Comparative Example 2

[0116] This comparative example provides a method for preparing a solar cell. The difference between this comparative example and the embodiment lies in the difference between step (5) and step (6).

[0117] Step (5): In a PECVD device, at 400° C., O2, SiH4 and H2 in a volume ratio of 1:10:10 are introduced to form an intrinsic amorphous silicon layer with a thickness of 30 nm on the tunneling oxide layer.

[0118] Step (6): Forming a phosphorus-doped amorphous silicon carbide layer: In a PECVD device, at 400°C, O2, SiH4, PH3 and H2 in a volume ratio of 1:10:8:10 are introduced to form a phosphorus-doped amorphous silicon layer with a thickness of 150 nm on the intrinsic amorphous silicon layer.

[0119] Comparative Example 3

[0120] This comparative example provides a method for preparing a solar cell. The difference between this comparative example and the embodiment lies in the difference between step (5) and step (6).

[0121] Step (5): In a PECVD device, SiH4 and H2 are introduced at a volume ratio of 1:1 at 400° C. to form an intrinsic amorphous silicon layer with a thickness of 30 nm on the tunneling oxide layer.

[0122] Step (6): Forming a phosphorus-doped amorphous silicon carbide layer: In a PECVD device, SiH4, PH3 and H2 with a volume ratio of 10:8:10 are introduced at 400°C to form a phosphorus-doped amorphous silicon layer with a thickness of 150nm on the intrinsic amorphous silicon layer.

[0123] Experimental Example 1

[0124] The solar cells prepared in the embodiment and comparative examples 1-3 were subjected to performance tests, and the results are shown in Table 1.

[0125] The detection method is: use the halm online IV test system to test the open circuit voltage, short circuit current and photoelectric conversion efficiency of the solar cell under the conditions of 25℃, AM1.5 and 1 standard sun.

[0126] Table 1

[0127]

[0128]

[0129] As can be seen from Table 1, the short-circuit current and open-circuit voltage of the solar cell obtained by changing the phosphorus-doped polycrystalline silicon layer to a phosphorus-doped polycrystalline silicon carbide layer, and the phosphorus-doped polycrystalline silicon carbide layer is doped with oxygen atoms, are greatly improved.

[0130] In summary, it can effectively improve the photoelectric conversion efficiency of solar cells (to more than 25.0%), open circuit voltage (increased by 2mV) and short circuit current (increased by 0.12mA / cm 2 ).

[0131] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. A solar cell, characterized in that: include: Silicon wafer base layer; a boron-doped silicon layer located on the front side of the silicon wafer substrate layer; A tunneling oxide layer and a phosphorus-doped polycrystalline silicon carbide layer are sequentially arranged on the back side of the silicon wafer substrate layer; Wherein, the phosphorus-doped polycrystalline silicon carbide layer is doped with oxygen atoms; The method for preparing the solar cell comprises: forming the boron-doped silicon layer on the front side of the silicon wafer base layer; forming the tunneling oxide layer on the back side of the silicon wafer base layer; In an atmosphere containing oxygen, sequentially forming an intrinsic amorphous silicon carbide layer and a phosphorus-doped amorphous silicon carbide layer on the surface of the tunnel oxide layer; Annealing is performed so that the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer are converted into the phosphorus-doped polycrystalline silicon carbide layer.

2. The solar cell according to claim 1, characterized in that: The thickness of the phosphorus-doped polycrystalline silicon carbide layer is 25-280 nm.

3. The solar cell according to claim 1 or 2, characterized in that: The material of the tunnel oxide layer is silicon oxide, and the thickness of the tunnel oxide layer is 0.5-2 nm.

4. A method for preparing a solar cell according to any one of claims 1 to 3, characterized in that: include: forming the boron-doped silicon layer on the front side of the silicon wafer base layer; forming the tunneling oxide layer on the back side of the silicon wafer base layer; In an atmosphere containing oxygen, sequentially forming an intrinsic amorphous silicon carbide layer and a phosphorus-doped amorphous silicon carbide layer on the surface of the tunnel oxide layer; Annealing is performed so that the intrinsic amorphous silicon carbide layer and the phosphorus-doped amorphous silicon carbide layer are converted into the phosphorus-doped polycrystalline silicon carbide layer.

5. The method for preparing a solar cell according to claim 4, characterized in that: The method for preparing the intrinsic amorphous silicon carbide layer comprises: forming the intrinsic amorphous silicon carbide layer on the surface of the tunneling oxide layer by vapor deposition in an atmosphere of a first mixed gas; Wherein, the first mixed gas includes O2, SiH4, CH4 and H2.

6. The method for preparing a solar cell according to claim 5, characterized in that: In the first mixed gas, the volume ratio of O2, SiH4, CH4 and H2 is 1:(1-10):(0.3-2):(1-10).

7. The method for preparing a solar cell according to claim 5, characterized in that: The temperature for forming the intrinsic amorphous silicon carbide layer is 350-450°C.

8. The method for preparing a solar cell according to claim 4, characterized in that: The method for preparing the phosphorus-doped amorphous silicon carbide layer comprises: forming the phosphorus-doped amorphous silicon carbide layer on the surface of the intrinsic amorphous silicon carbide layer by vapor deposition in an atmosphere of a second mixed gas; Wherein, the second mixed gas includes O2, SiH4, CH4, PH3 and H2.

9. The method for preparing a solar cell according to claim 8, characterized in that: In the second mixed gas, the volume ratio of O2, SiH4, CH4, PH3 and H2 is 1:(1-10):(0.3-2):(1-9):(1-10).

10. The method for preparing a solar cell according to claim 8, characterized in that: The temperature for forming the phosphorus-doped amorphous silicon carbide layer is 350-450°C.

11. The method for preparing a solar cell according to any one of claims 4 to 10, characterized in that: The annealing temperature is 600-1000° C., and the annealing time is 10-60 min.

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