A solar cell and a method for preparing the same

Abstract

The present application provides a solar cell and a method for preparing the same, which belongs to the technical field of solar cells. The method for preparing the solar cell includes forming a P-type doping layer on the front side of a silicon wafer by vapor deposition, and the deposition temperature is 400°C to 600°C. The method for preparing the solar cell of the present application forms a P-type doping layer on the front side of a silicon wafer by in-situ doping by vapor deposition, and because the deposition temperature is only 400°C to 600°C, the high-temperature doping process is omitted, which can reduce the carrier recombination rate on the one hand, and the saturation current density (J0) is reduced to 13fA / cm 2 ~15fA / cm 2 On the other hand, it can reduce the thermal defects formed by high temperature, and the proportion of concentric circle defects can be reduced to less than 0.5%, thereby improving the yield level of industrial production.

Description

Technical Field

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

[0002] In crystalline silicon solar cells, the metal and semiconductor contact area are seriously recombined, resulting in a large carrier recombination rate and a high saturation current density (J0), which has become an important factor restricting the efficiency development of crystalline silicon solar cells. Passivated contact cells have a higher efficiency limit, which is closest to the theoretical limit efficiency of crystalline silicon solar cells, which is 28.7%. The back of the Tunnel Oxide Passivated Contact (TOPCon) cell uses a tunnel oxide layer and n+-poly-Si for passivation contact, which can greatly reduce the recombination rate.

[0003] The existing TOPCon solar cells have already done a good job of back passivation, and there is little room for efficiency improvement. However, the front passivation only uses aluminum oxide passivation, and there is still room for further improvement of passivation performance. At the same time, the front still uses the traditional 1050℃ high-temperature boron diffusion process to form the P-type doping layer. The high temperature introduces defects, resulting in a high proportion of concentric circle defects. Summary of the invention

[0004] The embodiments of the present application provide a solar cell and a method for preparing the same, which can reduce the carrier recombination rate and the proportion of concentric circle defects.

[0005] In the first aspect, the present application provides an example of a method for preparing a solar cell, which includes: providing a silicon wafer, first forming a P-type doping layer and an N-type doping layer on the front and back of the silicon wafer, respectively, then forming a first aluminum oxide passivation layer and a second aluminum oxide passivation layer on the surface of the P-type doping layer and the N-type doping layer, respectively, then forming a first silicon nitride anti-reflection layer and a second silicon nitride anti-reflection layer on the surface of the first aluminum oxide passivation layer and the second aluminum oxide passivation layer, respectively, and finally forming an electrode by screen printing. The P-type doping layer is deposited by vapor deposition at a deposition temperature of 400°C to 600°C.

[0006] In the above technical scheme, the preparation method of the solar cell of the present application adopts the method of in-situ doping by vapor deposition to form a P-type doping layer on the front side of the silicon wafer, and because the deposition temperature is only 400°C to 600°C, the high-temperature doping process is omitted. On the one hand, the carrier recombination rate can be reduced, and the saturation current density (J0) is reduced to 13fA / cm2 to 15fA / cm2. On the other hand, the thermal defects formed by high temperature can be reduced, and the proportion of concentric circle defects is reduced to less than 0.5%, thereby improving the yield level of industrial production.

[0007] In combination with the first aspect, in an optional embodiment of the present application, the above-mentioned P-type doped layer is a boron-doped amorphous silicon layer, and the gas atmosphere for depositing the boron-doped amorphous silicon layer includes SiH4, BH3 and a carrier gas. Optionally, the volume ratio of SiH4, BH3 and the carrier gas is 1:4:4 to 1:6:6.

[0008] In combination with the first aspect, in an optional implementation manner of the present application, the thickness of the above-mentioned P-type doping layer is 400nm to 600nm.

[0009] In combination with the first aspect, in an optional embodiment of the present application, before forming the P-type doped layer, a first tunneling oxide layer is first formed on the front side of the silicon wafer, and then a P-type doped layer is formed on the surface of the first tunneling oxide layer. Optionally, a first tunneling oxide layer is formed on the front side of the silicon wafer by vapor deposition. Optionally, the deposition temperature is 300°C to 500°C. Optionally, the first tunneling oxide layer is a SiO2 layer, and the gas atmosphere for forming the first tunneling oxide layer includes N2O. Optionally, the thickness of the first tunneling oxide layer is 2nm to 4nm.

[0010] In the above example, a first tunneling oxide layer is first formed on the front side of the silicon wafer, and then a P-type doping layer is formed on the surface of the first tunneling oxide layer, which is beneficial for uniform distribution of the P-type doping layer during deposition.

[0011] In combination with the first aspect, in an optional embodiment of the present application, after forming the P-type doping layer, a first mask layer is formed on the surface of the P-type doping layer. Optionally, a first mask layer is formed on the surface of the P-type doping layer by vapor deposition. Optionally, the deposition temperature is 400°C to 600°C. Optionally, the first mask layer is a SiO2 layer, and the gas atmosphere for forming the first mask layer includes SiH4 and N2O, and the volume ratio of SiH4 to N2O is 1:6 to 1:10. Optionally, the thickness of the first mask layer is 10nm to 40nm.

[0012] In the above example, the first mask layer is used to protect the P-type doped layer from being damaged during de-plating and cleaning.

[0013] In combination with the first aspect, in an optional embodiment of the present application, the N-type doped layer is deposited by vapor deposition, and the deposition temperature is 350°C to 450°C. Optionally, the N-type doped layer is a phosphorus-doped amorphous silicon layer, and the gas atmosphere for depositing the phosphorus-doped amorphous silicon layer includes SiH4, PH3 and a carrier gas. Optionally, the volume ratio of SiH4, PH3 and carrier gas is 1:2:4 to 1:3:6. Optionally, the thickness of the N-type doped layer is 80nm to 150nm.

[0014] In combination with the first aspect, in an optional embodiment of the present application, before forming the N-type doped layer, a second tunneling oxide layer is first formed on the back of the silicon wafer, and then an N-type doped layer is formed on the surface of the second tunneling oxide layer. Optionally, a second tunneling oxide layer is formed on the back of the silicon wafer by vapor deposition. Optionally, the deposition temperature is 300°C to 400°C. Optionally, the second tunneling oxide layer is a SiO2 layer, and the gas atmosphere for forming the second tunneling oxide layer includes N2O. Optionally, the thickness of the second tunneling oxide layer is 1nm to 2nm.

[0015] In the above example, the second tunneling oxide layer is first formed on the front side of the silicon wafer, and then the N-type doping layer is formed on the surface of the second tunneling oxide layer, which is beneficial for uniform distribution of the N-type doping layer during deposition.

[0016] In combination with the first aspect, in an optional embodiment of the present application, after forming the N-type doping layer, a second mask layer is formed on the surface of the N-type doping layer. Optionally, a second mask layer is formed on the surface of the N-type doping layer by vapor deposition. Optionally, the deposition temperature is 350°C to 450°C. Optionally, the second mask layer is a SiO2 layer, and the gas atmosphere for forming the second mask layer includes SiH4 and N2O, and the volume ratio of SiH4 to N2O is 1:6 to 1:10. Optionally, the thickness of the second mask layer is 10nm to 40nm.

[0017] In the above example, the second mask layer is used to protect the N-type doped layer from being damaged during de-wrapping and cleaning.

[0018] In combination with the first aspect, in an optional embodiment of the present application, after forming a P-type doped layer and an N-type doped layer on the front and back of the silicon wafer respectively by a vapor deposition method, an annealing treatment is performed, and the annealing temperature is 900° C. to 1000° C. Optionally, the annealing time is 40 min to 60 min. Optionally, the gas atmosphere of the annealing is nitrogen or oxygen.

[0019] In the above example, the preparation method of the solar cell of the present application performs annealing treatment after forming the P-type doping layer and the N-type doping layer respectively. The P-type doping layer and the N-type doping layer can complete the crystal structure transformation at the same time. The P-type doping layer and the N-type doping layer are transformed into p+-poly-Si and n+-poly-Si respectively, which not only saves energy consumption, but also the battery cell only undergoes one annealing treatment, and basically does not increase the thermal defects formed by high temperature.

[0020] In a second aspect, the present application example provides a solar cell, which is manufactured according to the above-mentioned method for manufacturing a solar cell.

[0021] In the above technical solution, the solar cell of the present application has a lower saturation current density (J0) of 13fA / cm2 to 15fA / cm2, and a lower concentric circle defect ratio of less than 0.5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] 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.

[0023] Figure 1 This is a schematic diagram of the structure of a solar cell currently used in this application;

[0024] Figure 2 A schematic diagram of the structure of a solar cell according to an embodiment of the present application;

[0025] Figure 3 This is the EL image of the first typical concentric circle defect;

[0026] Figure 4 This is the EL image of the second typical concentric circle defect.

[0027] Icon: 10-solar cell; 111-front velvet structure; 112-first silicon nitride anti-reflection layer; 113-first aluminum oxide passivation layer; 114-P-type doping layer; 115-first tunneling oxide layer; 116-silicon layer; 117-second tunneling oxide layer; 118-N-type doping layer; 119-second aluminum oxide passivation layer; 120-second silicon nitride anti-reflection layer; 121-front electrode; 122-back electrode. DETAILED DESCRIPTION

[0028] See also Figure 1 The solar cell 10 includes, from the front to the back, a front velvet structure 111, a first silicon nitride anti-reflection layer 112, a first aluminum oxide passivation layer 113, a P-type doped layer 114, a silicon layer 116, a second tunneling oxide layer 117, an N-type doped layer 118, a second aluminum oxide passivation layer 119 and a second silicon nitride anti-reflection layer 120. A front electrode 121 and a back electrode 122 are respectively arranged on the front and back of the solar cell.

[0029] The inventors have noticed that the back passivation of existing TOPCon solar cells has been done well, and there is little room for improvement, but the front passivation only uses aluminum oxide passivation, and there is still room for further improvement of passivation performance. At the same time, the front still uses the traditional 1050℃ high-temperature boron diffusion process to form the P-type doping layer, and the high temperature introduces defects, resulting in a high proportion of concentric circle defects.

[0030] Based on the above considerations, in order to reduce the carrier recombination rate and reduce the proportion of concentric circle defects, the applicant has designed a method for preparing solar cells after in-depth research. A P-type doping layer is formed on the front side of the silicon wafer by in-situ doping using vapor deposition. Since the deposition temperature is only 400°C to 600°C, the high-temperature doping process is omitted. On the one hand, the carrier recombination rate can be reduced, and the saturation current density (J0) is reduced to 13fA / cm2 to 15fA / cm2. On the other hand, the thermal defects formed by high temperature can be reduced, and the proportion of concentric circle defects is reduced to less than 0.5%, thereby improving the yield level of industrial production.

[0031] The following is a detailed description of a solar cell and its preparation method according to an embodiment of the present application:

[0032] The present application provides a method for preparing a solar cell, which comprises the following steps:

[0033] S1, velveting;

[0034] An N-type silicon wafer is provided. A mixed solution including 2wt% hydrogen peroxide and 0.3wt% alkali is first used to clean the oil stains on the surface of the silicon wafer. Then, a 1wt% alkali solution is used for texturing. Auxiliary texturing additives are provided to slow down the reaction rate and form a pyramid-shaped front velvet structure on the surface of the silicon wafer to play a role in reducing reflection and limiting light.

[0035] S2, forming a first tunneling oxide layer, a P-type doping layer and a first mask layer on the front side;

[0036] A first tunneling oxide layer, a P-type doping layer and a first mask layer are sequentially formed on the front side of the silicon wafer by using a plasma enhanced chemical vapor deposition (PECVD) method.

[0037] First, a first tunneling oxide layer is formed on the front side of the silicon wafer, and then a P-type doping layer is formed on the surface of the first tunneling oxide layer, which is conducive to uniform distribution of the P-type doping layer during deposition. The first mask layer is used to protect the P-type doping layer from being damaged during de-plating and cleaning.

[0038] Optionally, three layers of film can be deposited in one furnace tube without breaking the vacuum.

[0039] The first tunnel oxide layer is formed by the following method:

[0040] By using a plasma enhanced chemical vapor deposition method, N2O is introduced. Under the action of a radio frequency electric field, N2O is ionized into oxygen atoms to oxidize the surface of the silicon wafer, forming a SiO2 layer to obtain a first tunneling oxide layer.

[0041] Optionally, the thickness of the first tunnel oxide layer is 2 nm to 4 nm.

[0042] Optionally, the flow rate of N2O is 8000sccm to 14000sccm.

[0043] Optionally, the deposition temperature is 300°C to 500°C.

[0044] Optionally, the deposition pressure is 100Pa-150Pa.

[0045] The P-type doped layer is formed by the following method:

[0046] A plasma enhanced chemical vapor deposition method is adopted, SiH4, BH3 and carrier gas are introduced simultaneously, and a boron-doped amorphous silicon layer is deposited on the surface of the first tunneling oxide layer to obtain a P-type doped layer.

[0047] SiH4 and BH3 are used as deposition gases and carrier gas as carrier gas, which are ionized to form plasma under the action of 200kHz-400kHz square wave or sine-cosine wave power supply to prepare boron-doped amorphous silicon layer.

[0048] Optionally, the thickness of the P-type doping layer is 400 nm to 600 nm.

[0049] As an example, the thickness of the P-type doped layer may be 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, 460nm, 470nm, 480nm, 490nm, 500nm, 510nm, 520nm, 530nm, 540nm, 550nm, 560nm, 570nm, 580nm, 590nm or 600nm.

[0050] Optionally, the volume ratio of SiH4, BH3 and carrier gas is 1:4:4 to 1:6:6.

[0051] As an example, the volume ratio of SiH4, BH3 and carrier gas can be 1:4:4, 1:5:5, 1:4:5, 1:5:4, 1:4:6, 1:6:4, 1:5:6, 1:6:5 or 1:6:6.

[0052] Optionally, the inlet flow rate of SiH4 is 2000 sccm to 5000 sccm.

[0053] Optionally, the carrier gas is Ar or H2.

[0054] Argon and hydrogen have low ionization energies and are easy to ignite, making it easier for the introduced reaction gases SiH4 and BH3 to ionize.

[0055] Optionally, the carrier gas is Ar.

[0056] The deposition temperature is 400°C to 600°C.

[0057] As an example, the deposition temperature may be 400°C, 410°C, 420°C, 430°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C, 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C or 600°C.

[0058] The first mask layer is formed by the following method:

[0059] A plasma enhanced chemical vapor deposition method is adopted to simultaneously introduce SiH4 and N2O to deposit a SiO2 layer on the surface of the P-type doped layer to obtain a first mask layer.

[0060] Optionally, the thickness of the first mask layer is 10 nm to 40 nm.

[0061] Optionally, the volume ratio of SiH4 to N2O is 1:6 to 1:10.

[0062] Optionally, the inlet flow rate of SiH4 is 1000 sccm to 4000 sccm.

[0063] Optionally, the deposition temperature is 400°C to 600°C.

[0064] It should be noted that the first tunnel oxide layer and the first mask layer may also be formed by other methods besides PECVD, which is not limited in the present application.

[0065] S3, alkali polishing;

[0066] First, a chain HF machine is used to remove the first mask layer on the back of the silicon wafer, with the volume percentage of HF being 40% to 80%. Then, the wafer is transferred to a slot-type alkali polishing machine through a robot, and a 2wt% alkali solution and alkali polishing additive are used to remove the velvet structure and edge pn junction on the back of the silicon wafer. At the same time, a small velvet structure of 0.3μm to 1μm is formed on the back of the silicon wafer.

[0067] S4, forming a second tunneling oxide layer, an N-type doping layer and a second mask layer on the back side;

[0068] A second tunneling oxide layer, an N-type doping layer and a second mask layer are sequentially formed on the back side of the silicon wafer by using a plasma enhanced chemical vapor deposition (PECVD) method.

[0069] First, a second tunneling oxide layer is formed on the back of the silicon wafer, and then an N-type doping layer is formed on the surface of the second tunneling oxide layer, which is conducive to uniform distribution of the N-type doping layer during deposition. The second mask layer is used to protect the N-type doping layer from being damaged during de-plating and cleaning.

[0070] Optionally, three layers of film can be deposited in one furnace tube without breaking the vacuum.

[0071] The second tunnel oxide layer is formed by the following method:

[0072] Using plasma enhanced chemical vapor deposition, N2O is introduced. Under the action of the radio frequency electric field, N2O is ionized into oxygen atoms to oxidize the surface of the silicon wafer, forming a SiO2 layer to obtain a second tunneling oxide layer.

[0073] Optionally, the thickness of the second tunnel oxide layer is 1 nm to 2 nm.

[0074] Optionally, the flow rate of N2O is 6000sccm to 12000sccm.

[0075] Optionally, the deposition temperature is 300°C to 400°C.

[0076] Optionally, the deposition pressure is 100Pa-150Pa.

[0077] The N-type doped layer is formed by the following method:

[0078] A plasma enhanced chemical vapor deposition method is adopted, SiH4, PH3 and carrier gas are introduced simultaneously, and a phosphorus-doped amorphous silicon layer is deposited on the surface of the second tunneling oxide layer to obtain an N-type doped layer.

[0079] Optionally, the thickness of the N-type doping layer is 80 nm to 150 nm.

[0080] Optionally, the volume ratio of SiH4, PH3 and carrier gas is 1:2:4 to 1:3:6.

[0081] Optionally, the inlet flow rate of SiH4 is 1500 sccm to 4500 sccm.

[0082] Optionally, the carrier gas is Ar or H2.

[0083] Argon and hydrogen have low ionization energies and are easy to ignite, making it easier for the introduced reaction gases SiH4 and PH3 to ionize.

[0084] Optionally, the carrier gas is H2.

[0085] Optionally, the deposition temperature is 350°C to 450°C.

[0086] The second mask layer is formed by the following method:

[0087] A plasma enhanced chemical vapor deposition method is adopted to simultaneously introduce SiH4 and N2O to deposit a SiO2 layer on the surface of the N-type doped layer to obtain a second mask layer.

[0088] Optionally, the thickness of the second mask layer is 10 nm to 40 nm.

[0089] Optionally, the volume ratio of SiH4 to N2O is 1:6 to 1:10.

[0090] Optionally, the inlet flow rate of SiH4 is 1000 sccm to 4000 sccm.

[0091] Optionally, the deposition temperature is 350°C to 450°C.

[0092] S5, annealing;

[0093] The silicon wafers on which the P-type doping layer and the N-type doping layer are respectively formed are annealed.

[0094] Optionally, the annealing temperature is 900°C to 1000°C.

[0095] As an example, the temperature of the annealing process may be 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, or 1000°C.

[0096] Optionally, the annealing treatment time is 40 min to 60 min.

[0097] As an example, the annealing treatment time may be 40 min, 45 min, 50 min, 55 min or 60 min.

[0098] Optionally, the gas atmosphere of the annealing process is nitrogen or oxygen.

[0099] Optionally, the annealing process is performed in a tubular annealing furnace.

[0100] The preparation method of the solar cell of the present application performs annealing treatment after forming a P-type doping layer and an N-type doping layer respectively. The P-type doping layer and the N-type doping layer can complete the crystal structure transformation at the same time. The P-type doping layer and the N-type doping layer are transformed into p+-poly-Si and n+-poly-Si respectively, which not only saves energy consumption, but also the battery cell only undergoes one annealing treatment, which basically does not increase the thermal defects caused by high temperature.

[0101] S6, RCA cleaning;

[0102] First, the second mask layer of the front side of the silicon wafer is removed by chain HF, the volume percentage of HF is 10% to 40%, and the SiO2 layer plated on the front side when the third mask layer is deposited in step S4, as well as the phosphorus silicon glass PSG generated during the annealing process, is removed, and then the front side poly coating is removed by the alkali tank, at which time the N-type doped layer on the back side is not damaged under the protection of the third mask layer, wherein the concentration of the alkali solution in the alkali tank is 3wt% to 6wt%. After the poly coating on the front side is completely removed, the first mask layer formed in step S2 and the second mask layer formed in step S4 are removed by the trough HF, the volume percentage of HF is 10%.

[0103] S7, deposition of aluminum oxide films on the front and back sides;

[0104] A first aluminum oxide passivation layer and a second aluminum oxide passivation layer are respectively deposited on the surfaces of the P-type doping layer and the N-type doping layer by using a Thermal ALD method.

[0105] S8, deposition of silicon nitride films on the front and back surfaces;

[0106] A first silicon nitride anti-reflection layer and a second silicon nitride anti-reflection layer are respectively deposited on the surfaces of the first aluminum oxide passivation layer and the second aluminum oxide passivation layer by plasma enhanced chemical vapor deposition. The first silicon nitride anti-reflection layer is used for anti-reflection and hydrogen passivation, and the second silicon nitride anti-reflection layer is used for back film hydrogen passivation.

[0107] S9, screen printing front and back slurry;

[0108] Electrodes are made by screen printing the front and back pastes.

[0109] S10, light injection, test efficiency and sorting.

[0110] The preparation method of the solar cell of the present application adopts the method of in-situ doping by vapor deposition to form a P-type doping layer on the front side of the silicon wafer. Since the deposition temperature is only 400℃~600℃, the high temperature doping process is omitted, which can reduce the saturation current density (J0) to 13fA / cm 2 ~15fA / cm 2 On the other hand, the proportion of concentric circle defects can be reduced to less than 0.5%, thereby improving the yield level of industrial production.

[0111] The present application also provides a solar cell, which is manufactured according to the above-mentioned method for manufacturing the solar cell.

[0112] See also Figure 2The solar cell 10 of the present application comprises, from the front to the back, a front velvet structure 111, a first silicon nitride anti-reflection layer 112, a first aluminum oxide passivation layer 113, a P-type doped layer 114, a first tunneling oxide layer 115, a silicon layer 116, a second tunneling oxide layer 117, an N-type doped layer 118, a second aluminum oxide passivation layer 119 and a second silicon nitride anti-reflection layer 120, and a front electrode 121 and a back electrode 122 are respectively arranged on the front and back of the solar cell.

[0113] The solar cell of the present application has a lower saturation current density (J0) of 13fA / cm 2 ~15fA / cm 2 , and a lower concentric circle defect ratio of less than 0.5%.

[0114] 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.

[0115] Example 1

[0116] The present invention provides a solar cell and a method for preparing the same, which comprises the following steps:

[0117] S1, velveting;

[0118] An N-type silicon wafer is provided. The oil stain on the surface of the silicon wafer is first cleaned with a mixed solution including 2wt% hydrogen peroxide and 0.3wt% alkali, and then a 1wt% alkali solution is used for texturing. An auxiliary texturing additive is provided to slow down the reaction rate and form a pyramid front velvet structure on the surface of the silicon wafer.

[0119] S2, forming a first tunneling oxide layer, a P-type doping layer and a first mask layer on the front side;

[0120] Plasma enhanced chemical vapor deposition was used to introduce 12000 sccm N2O. N2O was ionized into oxygen atoms under the action of the radio frequency electric field to oxidize the surface of the silicon wafer, forming a SiO2 layer to obtain a first tunneling oxide layer with a thickness of 2.2 nm. The deposition temperature was 450°C and the deposition pressure was 120 Pa.

[0121] Plasma enhanced chemical vapor deposition was used to simultaneously introduce 2000 sccm SiH4, 8000 sccm BH3 and 8000 ccm Ar to deposit a boron-doped amorphous silicon layer on the surface of the first tunneling oxide layer to obtain a P-type doped layer with a thickness of 500 nm. The deposition temperature was 550°C.

[0122] A plasma enhanced chemical vapor deposition method is used, and 1500 sccm SiH4 and 12000 sccm N2O are introduced simultaneously to deposit a SiO2 layer on the surface of the P-type doped layer to obtain a first mask layer with a thickness of 30 nm. The deposition temperature is 450°C.

[0123] Three layers of film are deposited in one furnace tube without breaking the vacuum.

[0124] S3, alkali polishing;

[0125] First, a chain HF machine is used to remove the first mask layer on the back of the silicon wafer, with a volume percentage of HF of 60%. Then, the wafer is transferred to a slot-type alkali polishing machine through a robot, and a 2wt% alkali solution and alkali polishing additive are used to remove the velvet structure and edge pn junction on the back of the silicon wafer. At the same time, a small velvet structure of 0.8μm is formed on the back of the silicon wafer.

[0126] S4, forming a second tunneling oxide layer, an N-type doping layer and a second mask layer on the back side;

[0127] Plasma enhanced chemical vapor deposition was used to introduce 10,000 sccm N2O. N2O was ionized into oxygen atoms under the action of the radio frequency electric field to oxidize the surface of the silicon wafer, forming a SiO2 layer to obtain a second tunneling oxide layer with a thickness of 1.5 nm. The deposition temperature was 350°C and the deposition pressure was 120 Pa.

[0128] A plasma enhanced chemical vapor deposition method is used to simultaneously introduce 2500 sccm SiH4, 5000 sccm PH3 and 10000 sccm Ar to deposit a phosphorus-doped amorphous silicon layer on the surface of the second tunneling oxide layer to obtain an N-type doped layer with a thickness of 110 nm. The deposition temperature is 400°C.

[0129] A plasma enhanced chemical vapor deposition method is used, and 1500 sccm SiH4 and 12000 sccm N2O are introduced simultaneously to deposit a SiO2 layer on the surface of the N-type doped layer to obtain a second mask layer with a thickness of 30 nm. The deposition temperature is 400°C.

[0130] Three layers of film are deposited in one furnace tube without breaking the vacuum.

[0131] S5, annealing;

[0132] The silicon wafers forming the P-type doped layer and the N-type doped layer were annealed in a tubular annealing furnace. The annealing temperature was 920° C., the annealing time was 60 min, and the gas atmosphere of the annealing was nitrogen.

[0133] S6, RCA cleaning;

[0134] First, the second mask layer of the front side of the silicon wafer is removed by chain HF, the volume percentage of HF is 30%, and the SiO2 layer plated on the front side when the third mask layer is deposited in step S4, as well as the phosphorus silicon glass PSG generated during the annealing process, is removed, and then the front poly coating is removed by the alkali tank. At this time, the N-type doped layer on the back side is not damaged under the protection of the third mask layer, and the concentration of the alkali solution in the alkali tank is 4wt%. After the poly coating on the front side is completely removed, the first mask layer formed in step S2 and the second mask layer formed in step S4 are removed by the trough HF, the volume percentage of HF is 10%.

[0135] S7, deposition of aluminum oxide films on the front and back sides;

[0136] A first aluminum oxide passivation layer and a second aluminum oxide passivation layer are respectively deposited on the surfaces of the P-type doping layer and the N-type doping layer by using a Thermal ALD method.

[0137] S8, deposition of silicon nitride films on the front and back surfaces;

[0138] A first silicon nitride anti-reflection layer and a second silicon nitride anti-reflection layer are respectively deposited on the surfaces of the first aluminum oxide passivation layer and the second aluminum oxide passivation layer by using a plasma enhanced chemical vapor deposition method.

[0139] S9, screen printing front and back slurry;

[0140] Electrodes are made by screen printing the front and back pastes.

[0141] S10, light injection, test efficiency and sorting.

[0142] Example 2

[0143] The present application provides a solar cell and a method for preparing the same. In Example 2, based on Example 1, S2 is changed, and some steps of forming the first tunneling oxide layer, the P-type doping layer and the first mask layer on the front are performed. A plasma enhanced chemical vapor deposition method is used, and 2000sccm SiH4, 10000sccm BH3 and 10000sccm Ar are introduced simultaneously to deposit a boron-doped amorphous silicon layer on the surface of the first tunneling oxide layer to obtain a P-type doping layer with a thickness of 500nm, and the deposition temperature is 550°C. Others remain unchanged.

[0144] Example 3

[0145] The present application provides a solar cell and a method for preparing the same. In Example 3, based on Example 1, S2 is changed, and some steps of forming the first tunneling oxide layer, the P-type doping layer and the first mask layer on the front are formed. A plasma enhanced chemical vapor deposition method is used, and 2000sccm SiH4, 12000sccm BH3 and 12000sccm Ar are introduced simultaneously to deposit a boron-doped amorphous silicon layer on the surface of the first tunneling oxide layer to obtain a P-type doping layer with a thickness of 500nm, and the deposition temperature is 550°C. Others remain unchanged.

[0146] Example 4

[0147] The present application provides a solar cell and a method for preparing the same. In Example 4, based on Example 1, S2 is changed, and some steps of forming the first tunneling oxide layer, the P-type doping layer and the first mask layer on the front are formed. A plasma enhanced chemical vapor deposition method is used, and 2000 sccm SiH4, 8000 sccm BH3 and 8000 sccm Ar are introduced simultaneously to deposit a boron-doped amorphous silicon layer on the surface of the first tunneling oxide layer to obtain a P-type doping layer with a thickness of 500 nm. The deposition temperature is 400° C. Others remain unchanged.

[0148] Example 5

[0149] The present application provides a solar cell and a method for preparing the same. In Example 5, based on Example 1, S2 is changed, and some steps of forming the first tunneling oxide layer, the P-type doping layer and the first mask layer on the front are formed. A plasma enhanced chemical vapor deposition method is used, and 2000sccm SiH4, 8000sccm BH3 and 8000sccm Ar are introduced simultaneously to deposit a boron-doped amorphous silicon layer on the surface of the first tunneling oxide layer to obtain a P-type doping layer with a thickness of 500nm, and the deposition temperature is 600°C. Others remain unchanged.

[0150] Example 6

[0151] The present application provides a solar cell and a method for preparing the same. In Example 6, based on Example 1, S2 is changed, and some steps of forming the first tunneling oxide layer, the P-type doping layer and the first mask layer on the front are formed. A plasma enhanced chemical vapor deposition method is used, and 2000sccm SiH4, 8000sccm BH3 and 8000sccm Ar are introduced simultaneously to deposit a boron-doped amorphous silicon layer on the surface of the first tunneling oxide layer to obtain a P-type doping layer with a thickness of 400nm. The deposition temperature is 550°C. Others remain unchanged.

[0152] Example 7

[0153] The present application provides a solar cell and a method for preparing the same. In Example 7, based on Example 1, S2 is changed, and some steps of forming the first tunneling oxide layer, the P-type doping layer and the first mask layer on the front are formed. A plasma enhanced chemical vapor deposition method is used, and 2000sccm SiH4, 8000sccm BH3 and 8000sccm Ar are introduced simultaneously to deposit a boron-doped amorphous silicon layer on the surface of the first tunneling oxide layer to obtain a P-type doping layer with a thickness of 600nm. The deposition temperature is 550°C. Others remain unchanged.

[0154] Comparative Example 1

[0155] The comparative example of the present application provides a solar cell and a method for preparing the same, which comprises the following steps:

[0156] S1, velveting;

[0157] An N-type silicon wafer is provided. The oil stain on the surface of the silicon wafer is first cleaned with a mixed solution including 2wt% hydrogen peroxide and 0.3wt% alkali, and then a 1wt% alkali solution is used for texturing. An auxiliary texturing additive is provided to slow down the reaction rate and form a pyramid front velvet structure on the surface of the silicon wafer.

[0158] S2, forming a P-type doping layer;

[0159] After cleaning and drying, the silicon wafer enters the boron diffusion furnace, and BCl3 and oxygen are diffused at 1040°C to form a P-type doped layer. The ratio of BCl3 to oxygen is 1:15, and the volume proportion of BCl3 in the furnace atmosphere is 1.4%. Through high-temperature diffusion, a 120nm borosilicate glass layer (BSG) is generated on the surface of the N-type silicon wafer, and the square resistance range is 120Ω / sq.

[0160] S3, alkali polishing;

[0161] After boron expansion, the silicon wafer is firstly treated with a chain HF machine to remove the BSG of the boron expansion on the back side, with the volume percentage of HF being 60%. Then, it is transferred to a trough-type alkaline polishing machine through a robot, and a 2% alkaline solution and alkaline polishing additive are used to remove the pn junction on the back and edge of the silicon wafer, and at the same time, a small velvet structure of 0.8μm is formed on the back side of the silicon wafer.

[0162] S4, forming a second tunneling oxide layer, an N-type doping layer and a second mask layer on the back side;

[0163] Plasma enhanced chemical vapor deposition was used to introduce 10,000 sccm N2O. N2O was ionized into oxygen atoms under the action of the radio frequency electric field to oxidize the surface of the silicon wafer, forming a SiO2 layer to obtain a second tunneling oxide layer with a thickness of 1.5 nm. The deposition temperature was 350°C and the deposition pressure was 120 Pa.

[0164] A plasma enhanced chemical vapor deposition method is used to simultaneously introduce 2500 sccm SiH4, 5000 sccm PH3 and 10000 sccm Ar to deposit a phosphorus-doped amorphous silicon layer on the surface of the second tunneling oxide layer to obtain an N-type doped layer with a thickness of 110 nm. The deposition temperature is 400°C.

[0165] A plasma enhanced chemical vapor deposition method is used, and 1500 sccm SiH4 and 12000 sccm N2O are introduced simultaneously to deposit a SiO2 layer on the surface of the N-type doped layer to obtain a second mask layer with a thickness of 30 nm. The deposition temperature is 400°C.

[0166] Three layers of film are deposited in one furnace tube without breaking the vacuum.

[0167] S5, annealing;

[0168] The silicon wafers forming the P-type doped layer and the N-type doped layer were annealed in a tubular annealing furnace. The annealing temperature was 900° C., the annealing time was 60 min, and the gas atmosphere of the annealing was nitrogen.

[0169] S6, RCA cleaning;

[0170] First, the second mask layer of the front side of the silicon wafer is removed by chain HF, the volume percentage of HF is 30%, and the SiO2 layer plated on the front side when the third mask layer is deposited in step S4, as well as the phosphorus silicon glass PSG generated during the annealing process, is removed, and then the front poly coating is removed by the alkali tank. At this time, the N-type doped layer on the back side is not damaged under the protection of the third mask layer, and the concentration of the alkali solution in the alkali tank is 4wt%. After the poly coating on the front side is completely removed, the first mask layer formed in step S2 and the second mask layer formed in step S4 are removed by the trough HF, the volume percentage of HF is 10%.

[0171] S7, deposition of aluminum oxide films on the front and back sides;

[0172] A first aluminum oxide passivation layer and a second aluminum oxide passivation layer are respectively deposited on the surfaces of the P-type doping layer and the N-type doping layer by using a Thermal ALD method.

[0173] S8, deposition of silicon nitride films on the front and back surfaces;

[0174] A first silicon nitride anti-reflection layer and a second silicon nitride anti-reflection layer are respectively deposited on the surfaces of the first aluminum oxide passivation layer and the second aluminum oxide passivation layer by using a plasma enhanced chemical vapor deposition method.

[0175] S9, screen printing front and back slurry;

[0176] Electrodes are made by screen printing the front and back pastes.

[0177] S10, light injection, test efficiency and sorting.

[0178] The structure of the solar cell is as follows: Figure 1 As shown, the solar cell 10 comprises, from the front to the back, a front velvet structure 111, a first silicon nitride anti-reflection layer 112, a first aluminum oxide passivation layer 113, a P-type doped layer 114, a silicon layer 116, a second tunneling oxide layer 117, an N-type doped layer 118, a second aluminum oxide passivation layer 119 and a second silicon nitride anti-reflection layer 120, and a front electrode 121 and a back electrode 122 are respectively arranged on the front and back of the solar cell.

[0179] Test Example 1

[0180] The solar cells prepared in Examples 1 to 7 and Comparative Example 1 were subjected to Sinton test and IV test, and their concentric circle defect ratios were detected. The results are shown in Table 1.

[0181] The concentric circle defect ratio is measured by the following method:

[0182] Electroluminescence (EL), also known as electric field luminescence, is a physical phenomenon in which an electric field is generated by applying a voltage to two electrodes, and the electrons excited by the electric field hit the luminescence center, causing the electrons to transition, change, and recombine between energy levels, resulting in luminescence. The test condition is to load a reverse biased 12V DC power supply (DC-12V) between the electrodes of the battery cell, and form an EL image through infrared camera imaging. The EL image of a typical concentric circle defect is shown below. Figures 3-4 shown.

[0183] Table 1 Sinton test results, IV test results and concentric circle defect ratios of solar cells prepared in Examples 1 to 7 and Comparative Example 1

[0184]

[0185] It can be seen from Examples 1 to 7 that the saturation current density (J0) of the solar cell prepared by the method for preparing the solar cell of the embodiment of the present application is 13 fA / cm 2 ~15fA / cm 2 , the proportion of concentric circle defects is within 0.5%.

[0186] From the comparison between Comparative Example 1 and Examples 1 to 7, it can be seen that the saturation current density (J0) of the solar cell prepared by forming the P-type doping layer using the boron diffusion high temperature process is as high as 17.8 fA / cm 2, the concentric circle defect ratio is as high as 3.8%. That is, the preparation method of the solar cell of the embodiment of the present application uses plasma enhanced chemical vapor deposition to replace the boron diffusion high temperature process to form the P-type doping layer, which reduces the carrier recombination rate and concentric circle defect ratio of the prepared solar cell. In addition, the P-type doping layer formed in Examples 1 to 7 of the present application and Comparative Example 1 is different. The P-type doping layer of Examples 1 to 7 of the present application is a layer of polycrystalline silicon (p+-poly-Si) containing boron deposited on the silicon wafer, while Comparative Example 1 is to dope boron atoms in the N-type silicon wafer, and the boron atoms form covalent bonds with the silicon atoms in the silicon wafer, which is essentially a single crystal silicon layer (p+ layer).

[0187] 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 method for preparing a solar cell, characterized in that: The preparation method of the solar cell comprises: providing a silicon wafer, first forming a P-type doping layer and an N-type doping layer on the front and back of the silicon wafer respectively, then forming a first aluminum oxide passivation layer and a second aluminum oxide passivation layer on the surface of the P-type doping layer and the surface of the N-type doping layer respectively, then forming a first silicon nitride anti-reflection layer and a second silicon nitride anti-reflection layer on the surface of the first aluminum oxide passivation layer and the surface of the second aluminum oxide passivation layer respectively, and finally forming an electrode by screen printing; The P-type doped layer is deposited by vapor deposition at a deposition temperature of 400° C. to 600° C. The P-type doped layer is a boron-doped amorphous silicon layer, and the gas atmosphere for depositing the boron-doped amorphous silicon layer includes SiH4, BH3 and a carrier gas; The N-type doped layer is deposited by vapor deposition at a deposition temperature of 350° C. to 450° C. The N-type doped layer is a phosphorus-doped amorphous silicon layer, and the gas atmosphere for depositing the phosphorus-doped amorphous silicon layer includes SiH4, PH3 and a carrier gas; After forming a P-type doping layer and an N-type doping layer on the front and back of the silicon wafer respectively by using a vapor deposition method, an annealing treatment is performed, and the temperature of the annealing treatment is 900°C to 1000°C.

2. The method for preparing a solar cell according to claim 1, characterized in that: The volume ratio of SiH4, BH3 and the carrier gas is 1:4:4 to 1:6:

6.

3. The method for preparing a solar cell according to claim 1, characterized in that: The thickness of the P-type doping layer is 400nm-600nm.

4. The method for preparing a solar cell according to claim 1, characterized in that: Before forming the P-type doping layer, a first tunneling oxide layer is formed on the front surface of the silicon wafer, and then the P-type doping layer is formed on the surface of the first tunneling oxide layer.

5. The method for preparing a solar cell according to claim 4, characterized in that: The first tunneling oxide layer is formed on the front side of the silicon wafer by using a vapor deposition method.

6. The method for preparing a solar cell according to claim 5, characterized in that: The deposition temperature is 300°C to 500°C.

7. The method for preparing a solar cell according to claim 5, characterized in that: The first tunneling oxide layer is a SiO2 layer, and the gas atmosphere for forming the first tunneling oxide layer includes N2O.

8. The method for preparing a solar cell according to claim 5, characterized in that: The thickness of the first tunnel oxide layer is 2 nm to 4 nm.

9. The method for preparing a solar cell according to claim 1, characterized in that: After the P-type doping layer is formed, a first mask layer is formed on the surface of the P-type doping layer.

10. The method for preparing a solar cell according to claim 9, characterized in that: The first mask layer is formed on the surface of the P-type doping layer by using a vapor deposition method.

11. The method for preparing a solar cell according to claim 9, characterized in that: The deposition temperature is 400°C to 600°C.

12. The method for preparing a solar cell according to claim 9, characterized in that: The first mask layer is a SiO2 layer, and the gas atmosphere forming the first mask layer includes SiH4 and N2O, and the volume ratio of SiH4 to N2O is 1:6 to 1:

10.

13. The method for preparing a solar cell according to claim 9, characterized in that: The thickness of the first mask layer is 10 nm to 40 nm.

14. The method for preparing a solar cell according to claim 1, characterized in that: The volume ratio of SiH4, PH3 and the carrier gas is 1:2:4 to 1:3:

6.

15. The method for preparing a solar cell according to claim 1, characterized in that: The thickness of the N-type doping layer is 80nm-150nm.

16. The method for preparing a solar cell according to claim 1, characterized in that: Before forming the N-type doping layer, a second tunneling oxide layer is first formed on the back side of the silicon wafer, and then the N-type doping layer is formed on the surface of the second tunneling oxide layer.

17. The method for preparing a solar cell according to claim 16, characterized in that: The second tunneling oxide layer is formed on the back side of the silicon wafer by using a vapor deposition method.

18. The method for preparing a solar cell according to claim 16, characterized in that: The deposition temperature is 300°C to 400°C.

19. The method for preparing a solar cell according to claim 16, characterized in that: The second tunneling oxide layer is a SiO2 layer, and the gas atmosphere for forming the second tunneling oxide layer includes N2O.

20. The method for preparing a solar cell according to claim 16, characterized in that: The thickness of the second tunnel oxide layer is 1 nm to 2 nm.

21. The method for preparing a solar cell according to claim 1, characterized in that: After the N-type doping layer is formed, a second mask layer is formed on the surface of the N-type doping layer.

22. The method for preparing a solar cell according to claim 21, characterized in that: The second mask layer is formed on the surface of the N-type doping layer by using a vapor deposition method.

23. The method for preparing a solar cell according to claim 21, characterized in that: The deposition temperature is 350°C to 450°C.

24. The method for preparing a solar cell according to claim 21, characterized in that: The second mask layer is a SiO2 layer, and the gas atmosphere forming the second mask layer includes SiH4 and N2O, and the volume ratio of SiH4 to N2O is 1:6 to 1:

10.

25. The method for preparing a solar cell according to claim 21, characterized in that: The thickness of the second mask layer is 10 nm to 40 nm.

26. The method for preparing a solar cell according to claim 1, characterized in that: The annealing treatment time is 40 min to 60 min.

27. The method for preparing a solar cell according to claim 1, characterized in that: The gas atmosphere of the annealing process is nitrogen or oxygen.

28. A solar cell, characterized in that: The solar cell is prepared according to the method for preparing a solar cell according to any one of claims 1 to 27.

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