Topcon battery and preparation method thereof, solar module and solar system

Abstract

The invention discloses a Topcon battery and a preparation method thereof, a solar module and a solar system, and relates to the technical field of solar cells, and the preparation method of the Topcon comprises the steps: 1, providing a substrate, and carrying out the texturing of the surface of the substrate; 2, obtaining a P + layer through boron doping and BSG removal; 3, preparing a tunneling oxide layer and a doped polycrystalline silicon layer by adopting LPCVD (Low Pressure Chemical Vapor Deposition) and high-temperature phosphorus diffusion; step 4, preparing an aluminum oxide layer on the front surface of the substrate by adopting ALD (Atomic Layer Deposition); 5, preparing a front silicon nitride layer on the front surface of the substrate by adopting PECVD (Plasma Enhanced Chemical Vapor Deposition); and 6, preparing a back silicon nitride layer on the back surface of the substrate by adopting PECVD (Plasma Enhanced Chemical Vapor Deposition), and modifying the doped polycrystalline silicon layer, so that a polycrystalline silicon layer doped with a carbon element is formed on the surface of the doped polycrystalline silicon layer. The method does not need to add extra equipment, is compatible with the existing LPCVD equipment to prepare the Topcon battery containing the polycrystalline silicon layer doped with the carbon element, is simple in operation, is low in cost, and is suitable for large-scale popularization.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to Topcon cells and preparation methods thereof, solar modules, and solar systems. Background Art

[0002] Topcon (Tunnel Oxide Passivated Contact) battery is a new type of passivated contact battery, which has gradually replaced PECR battery and become the future technology route for the new generation of N-type substrate. As industry competition intensifies, the efficiency of Topcon battery has increased from 24.5% in the early stage to 26.5%, getting closer and closer to the theoretical limit efficiency of 27.8%. The electrical performance loss analysis of each link of TOPCON battery is also used to guide the direction of subsequent technology upgrades. Companies with higher efficiency improvements will gain the greatest benefits in this technology upgrade.

[0003] According to simulation calculations, the back recombination of TOPcon cells is 1.95fA / cm 2 , accounting for 9.2% of the total composite loss of the battery. The parasitic loss of the back polysilicon layer is an important reason for the loss of battery efficiency. Therefore, improving the quality of the back polysilicon layer and reducing parasitic absorption and composite loss can significantly improve the efficiency of the battery. Studies have shown that by doping trace elements in the polysilicon layer, the quality of the back polysilicon layer can be significantly improved, the back composite loss can be improved, and the parasitic absorption can be reduced.

[0004] There are two main TOPcon battery process routes at present, PE-Poly and LP-Poly. The former uses PECVD method to deposit phosphorus-doped amorphous silicon through ionization once, and forms phosphorus-doped polysilicon through annealing. The latter uses a low-pressure deposition furnace to deposit tunnel oxide layer and amorphous silicon layer, and then dopes phosphorus atoms to form phosphorus-doped polysilicon. Trace element doping of polysilicon has only been studied in TOPcon batteries of PE-Poly route, but no related reports have been found in LP-Poly route.

[0005] As for the LP-Poly route, since the tunnel oxide layer and amorphous silicon layer grown by LPCVD are of higher quality and have a 0.5% advantage in mass production efficiency over the PE route, more and more battery cell manufacturers are planning to adopt the LP-Poly route.

[0006] Therefore, it is increasingly urgent to study on doping trace elements into the polysilicon layer in the LP-Poly route, improving the quality of the back polysilicon layer, improving the back recombination loss, and reducing parasitic absorption. Summary of the invention

[0007] The purpose of this application is to provide a Topcon cell and its preparation method, a solar module, and a solar system. The preparation method of the Topcon cell provided in this application is mainly applicable to the LP-Poly route. The method provided in this application can effectively modify the doped polysilicon layer, improve the back recombination loss, and reduce parasitic absorption.

[0008] The first aspect of the present application provides a method for preparing a Topcon battery, comprising:

[0009] Step 1: providing a substrate, and performing a texturing treatment on the surface of the substrate;

[0010] Step 2: Obtain a P+ layer by boron diffusion;

[0011] Step 3: Prepare a tunnel oxide layer and a doped polysilicon layer by LPCVD and phosphorus diffusion;

[0012] Step 4: preparing an aluminum oxide layer on the front side of the substrate by using ALD;

[0013] Step 5: preparing a front silicon nitride layer on the front side of the substrate by using PECVD;

[0014] Step 6: Prepare a back silicon nitride layer on the back side of the substrate by using PECVD, and modify the doped polysilicon layer so that a polysilicon layer doped with carbon is formed on the surface of the doped polysilicon layer.

[0015] In an optional manner, in step 6,

[0016] First, the doped polysilicon layer is modified by pretreatment; the pretreatment is to introduce methane into a PECVD furnace and excite the methane under a certain temperature, time, pressure and radio frequency power;

[0017] Subsequently, the back silicon nitride layer is prepared through at least one silicon nitride treatment stage; at least one of the silicon nitride treatment stages is to introduce ammonia and silane into a PECVD furnace and excite the ammonia and silane under a certain temperature, time, pressure and radio frequency power.

[0018] In an optional manner, during the pretreatment and each of the silicon nitride treatment stages, the substrate passes through at least one temperature zone, and in each of the temperature zones, the temperature of the pretreatment is lower than the temperature of the silicon nitride treatment stage;

[0019] Preferably, in each of the temperature zones, the temperature of the pretreatment is 10 to 40 degrees lower than the temperature of the silicon nitride treatment stage.

[0020] In an optional manner, during the pretreatment process: the gas flow rate of methane is 2000-5000 sccm, the pulse is 20-60:1000, the radio frequency power is 8000-15000 W, and the pressure is 1300-2000 mT.

[0021] In an optional manner, the back side silicon nitride layer includes four silicon nitride processing stages, wherein:

[0022] The first stage: 8000-12000sccm of ammonia, 200-3000sccm of silane, 10000-20000W of RF power, 20-60:1000 of pulse, 1600mT of pressure, and 50-300s of process time;

[0023] The second stage: introduce ammonia 4000-15000sccm, silane 1000-3000sccm, RF power 10000-20000W, pulse 20-60:1000, pressure 1600-2200mT, process time 50-300s;

[0024] The third stage: introduce ammonia 4000-15000sccm, silane 1000-3000sccm, RF power 10000-20000W, pulse 20-60:1000, pressure 1600-2200mT, process time 50-300s;

[0025] The fourth stage: introducing ammonia 2000-10000sccm, silane 500-1000sccm, RF power of 10000-20000W, pulse of 20-60:1000, pressure of 1600-2200mT, process time of 50-300s.

[0026] The second aspect of the present application provides a Topcon battery, which is prepared using the preparation method of the Topcon battery of the first aspect of the present application.

[0027] In an optional manner, the battery comprises:

[0028] A substrate, the substrate comprising a front side and a back side opposite to each other, wherein the front side is provided with a P+ layer, an aluminum oxide layer, and a front silicon nitride layer in sequence; the back side is provided with a tunneling oxide layer, a doped polysilicon layer, a polysilicon layer, and a back silicon nitride layer in sequence, wherein the polysilicon layer is doped with carbon;

[0029] Preferably, the carbon concentration in the polysilicon layer is 2×10 16 ~1×10 17 atom / cm3;

[0030] Preferably, the thickness of the doped polysilicon layer is 130-160 nm; and / or the depth of the polysilicon layer is 2-10 nm;

[0031] Preferably, the thickness of the back silicon nitride layer is 75-95 nm; and / or the refractive index of the back silicon nitride layer is 1.98-2.10.

[0032] In an optional manner, the front silicon nitride layer includes four first sub-silicon nitride layers, wherein the refractive indices of the four first sub-silicon nitride layers decrease sequentially along the front direction away from the substrate; and / or, the back silicon nitride layer includes a surface silicon nitride layer and four second sub-silicon nitride layers, wherein the refractive indices of the four second sub-silicon nitride layers decrease sequentially along the back direction away from the substrate.

[0033] The third aspect of the present application provides a solar cell assembly, comprising a Topcon cell prepared by the preparation method of the first aspect of the present application or a Topcon cell described in the second aspect of the present application.

[0034] The fourth aspect of the present application provides a solar energy system, comprising the Topcon solar energy module of the third aspect of the present application.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] (1) The method of the present application does not require the addition of additional equipment and is compatible with the equipment of the existing LP-Poly route. In the process of preparing the back silicon nitride, pretreatment is added, and radio frequency is used to excite methane gas to convert methane into carbon plasma. The high-energy plasma continuously collides with the substrate to inject carbon atoms into the doped polysilicon layer, thereby modifying the doped polysilicon layer to form a polysilicon layer doped with carbon elements, which effectively reduces the composite loss and parasitic absorption of the back polysilicon layer. The present application is simple to operate, low in cost, and suitable for mass promotion.

[0037] (2) The Topcon cell prepared in the present application forms a polycrystalline silicon layer doped with carbon on its surface by modifying the doped polycrystalline silicon layer, wherein carbon atoms can replace silicon atoms to form a substitutional solid solution, which can effectively reduce the interface state density and reduce the composite loss and parasitic absorption of the back polycrystalline silicon layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0039] Figure 1A schematic flow chart of the preparation method of the Topcon battery of the present application is shown.

[0040] Figure 2 A schematic diagram showing an embodiment of a Topcon battery of the present application.

[0041] Reference numerals:

[0042] 1-substrate; 2-P+ layer; 3-aluminum oxide layer; 4-front silicon nitride layer; 5-tunneling oxide layer; 6-doped polysilicon layer; 7-polysilicon layer; 8-back silicon nitride layer. DETAILED DESCRIPTION

[0043] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0044] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "multiple" means two or more, unless otherwise clearly and specifically defined. "Several" means one or more, unless otherwise clearly and specifically defined.

[0045] According to simulation calculations, the back recombination of TOPcon cells is 1.95fA / cm 2 , accounting for 9.2% of the total composite loss of the battery. The parasitic loss of the back polysilicon layer is an important reason for the loss of battery efficiency. Therefore, improving the quality of the back polysilicon layer and reducing parasitic absorption and composite loss can significantly improve the efficiency of the battery. Studies have shown that by doping trace elements in the polysilicon layer, the quality of the back polysilicon layer can be significantly improved, the back composite loss can be improved, and the parasitic absorption can be reduced.

[0046] There are two main TOPcon battery process routes at present, PE-Poly and LP-Poly. The former uses PECVD method to deposit phosphorus-doped amorphous silicon through ionization once, and forms phosphorus-doped polysilicon through annealing. The latter uses a low-pressure deposition furnace to deposit a tunnel oxide layer and an amorphous silicon layer, and then dopes phosphorus atoms to form phosphorus-doped polysilicon. It is necessary to dope trace elements in the polysilicon layer without introducing other impurities. The doping source of trace C, O, and N elements is usually CH 4 , CO 4 NH 3These three substances are all composed of strengthened bonds, and it is difficult to provide the required doping atoms through thermal decomposition. Therefore, in the LP-poly route, it is impossible to directly dope the doped polysilicon layer in the preparation of the doped polysilicon layer to obtain a doped polysilicon layer doped with trace elements.

[0047] To this end, the first aspect of the present application provides a method for preparing a Topcon battery, such as Figure 1 As shown, the following steps are included:

[0048] Step 1: providing a substrate, and performing a texturing process on the surface of the substrate;

[0049] Step 2: Obtain a P+ layer by boron diffusion;

[0050] Step 3: Prepare a tunnel oxide layer and a doped polysilicon layer by LPCVD and phosphorus diffusion;

[0051] Step 4: Aluminum oxide layer is prepared on the front side of the substrate by ALD;

[0052] Step 5: Prepare a front silicon nitride layer on the front side of the substrate by PECVD;

[0053] Step 6: Prepare a back silicon nitride layer on the back side of the substrate by PECVD, and modify the doped polysilicon layer so that a polysilicon layer doped with carbon is formed on the surface of the doped polysilicon layer.

[0054] The present application adds pretreatment during the preparation of back silicon nitride to introduce carbon atoms into the doped polysilicon layer, thereby modifying the doped polysilicon layer to form a polysilicon layer doped with carbon elements, thereby effectively reducing the composite loss and parasitic absorption of the back polysilicon layer. The present application does not require the addition of additional equipment, is compatible with existing LP-Poly route equipment, is simple to operate, has low cost, and is suitable for mass promotion.

[0055] Among them, in step 1, the substrate is an N-type single crystal silicon wafer, and the N-type single crystal silicon wafer includes a relative front side and a back side. By texturing the N-type single crystal silicon wafer, not only the organic dirt and metal impurities on the surface of the silicon wafer are removed; the mechanical damage layer generated by the wire cutting process of the silicon wafer can also be removed to reduce the recombination center; and at the same time, a pyramid structure is formed on the surface of the silicon wafer.

[0056] In step 2, the purpose of boron diffusion is mainly to form a PN junction on the surface of the silicon wafer, which is mainly achieved by a boron source (such as BBr 3 or BCl 3 ) is vaporized in a tube furnace and then deposited on the surface of the silicon wafer through a series of chemical reactions to obtain the appropriate doping concentration, junction depth and square resistance; a P+ layer (boron-doped layer) is formed on the front side of the silicon wafer.

[0057] In step 3, before preparing the tunnel oxide layer and the doped polysilicon layer, the BSG layer (borosilicate glass layer) on the back of the substrate needs to be removed first, and hydrofluoric acid is generally used for removal; then, alkaline polishing is performed to prepare the tunnel oxide layer and the doped polysilicon layer for the silicon wafer, and the tunnel oxide layer and the doped polysilicon layer are prepared by LPCVD and phosphorus diffusion; first, oxygen is passed through LPCVD at high temperature under low pressure conditions, and oxygen and silicon react to produce silicon oxide to form an oxide layer; silane is passed through at high temperature, and silane is thermally decomposed into silicon and hydrogen to form an amorphous silicon layer; then, phosphorus is diffused, in the presence of oxygen, POCl 3 At high temperatures, it decomposes to form phosphorus pentachloride (PCl 5 ) and phosphorus pentoxide (P 2 O 5 ), the generated P 2 O 5 Reacts with silicon at the diffusion temperature to form silicon dioxide (SiO 2 ) and phosphorus atoms, eventually forming a tunnel oxide layer and a doped polysilicon layer;

[0058] In step 4, before preparing the aluminum oxide layer, the front oxide layer and PSG layer (phosphosilicate glass layer) need to be removed. The aluminum oxide layer is mainly prepared by ALD deposition, using trimethylaluminum (TMA) as the aluminum source and vaporized water (H 2 O) or gaseous oxygen (O 2 ) as an oxygen (O) source, two or more chemical vapor precursors are alternately introduced into the reaction chamber and react on the surface of the substrate to form an aluminum oxide film.

[0059] In step 5, the substrate treated with ALD is placed in PECVD to prepare a silicon nitride layer, and a front silicon nitride layer is formed on the front side of the substrate. A layer of silicon nitride is formed on the surface of the silicon wafer, which can be used as an anti-reflection film to produce a passivation effect; and because of its dense structure, it can ensure that the silicon wafer is not oxidized; currently, the silicon nitride layer is mainly prepared by PECVD.

[0060] In step 6, after preparing the front silicon nitride layer on the front side of the substrate, PECVD is used to prepare the back side silicon nitride layer on the back side of the substrate, and the doped polysilicon layer is modified so that a polysilicon layer doped with carbon is formed on the surface of the doped polysilicon layer.

[0061] In an optional manner, in step 6,

[0062] First, the doped polysilicon layer is modified by pretreatment; the pretreatment is to introduce methane into a PECVD furnace and excite the methane under a certain temperature, time, pressure and radio frequency power;

[0063] Subsequently, a back silicon nitride layer is prepared through at least one silicon nitride treatment stage; at least one silicon nitride treatment stage is to introduce ammonia and silane into a PECVD furnace and excite the ammonia and silane under a certain temperature, time, pressure and radio frequency power.

[0064] In some specific embodiments, during the pretreatment and each silicon nitride treatment stage, the substrate passes through at least one temperature zone, and in each temperature zone, the temperature of the pretreatment is lower than the temperature of the silicon nitride treatment stage;

[0065] When the back silicon nitride layer is deposited, methane is added in the pretreatment stage, and the methane is excited by radio frequency to turn the methane into carbon plasma and hydrogen plasma. The high-energy plasma continuously collides with the substrate, and the trace carbon atoms are impacted into the doped polysilicon layer, so that the surface of the doped polysilicon layer is modified to form a polysilicon layer with carbon elements. Due to the introduction of carbon elements, the carbon elements replace silicon atoms in this polysilicon layer to form a substitutional solid solution, which passivates the polysilicon layer. The interface state density can be effectively reduced, and the composite loss and parasitic absorption of the back polysilicon layer can be reduced.

[0066] In a specific embodiment, in each temperature zone, the pretreatment temperature is 10 to 40 degrees lower than the temperature in the silicon nitride treatment stage; for example, it can be 10 degrees, 11 degrees, 12 degrees, 13 degrees, 14 degrees, 15 degrees, 16 degrees, 17 degrees, 18 degrees, 19 degrees, 20 degrees, 21 degrees, 22 degrees, 23 degrees, 24 degrees, 25 degrees, 26 degrees, 27 degrees, 28 degrees, 29 degrees, 30 degrees, 31 degrees, 32 degrees, 33 degrees, 34 degrees, 35 degrees, 36 degrees, 37 degrees, 38 degrees, 39 degrees or 40 degrees.

[0067] In some specific embodiments, during the pretreatment process, the gas flow rate of methane is 2000-5000sccm, for example, 2000sccm, 2500sccm, 3000sccm, 3500sccm, 4000sccm, 4500sccm or 5000sccm; the RF power is 8000-15000W, for example, 8000W, 9000W, 10000W, 11000W, 120 00W, 13000W, 14000W or 15000W; the pulse is 20-60:1000, for example, it can be 20:1000, 30:1000, 40:1000, 50:1000 or 60:1000; the pressure is 1300-2000mT; for example, it can be 1300mT, 1400mT, 1500mT, 1600mT, 1700mT, 1800mT, 1900mT or 2000mT.

[0068] In some specific embodiments, the preparation process of the back side silicon nitride layer includes four silicon nitride processing stages, wherein:

[0069] The first stage: introducing ammonia gas at 8000-12000sccm, for example, 8000sccm, 9000sccm, 10000sccm, 11000sccm or 12000sccm; silane at 200-3000sccm, for example, 200sccm, 500sccm, 800sccm, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm, 1600sccm, 1700sccm, 1800sccm, 1900sccm, 2000sccm, 2500sccm or 3000sccm; RF power is 10000-20 000W; for example, it can be 10000W, 11000W, 12000W, 13000W, 14000W, 15000W, 16000W, 17000W, 18000W, 19000W or 20000W; the pulse is 20-60:1000, for example, it can be 20:1000, 30:1000, 40:1000, 50:1000 or 60:1000; the pressure is 1600-2200mT, for example, it can be 1600mT, 1700mT, 1800mT, 1900mT, 2000mT, 2100mT or 2200mT; the process time is 50-300s; for example, it can be 50s, 100s, 200s or 300s.

[0070] The second stage: introducing ammonia at 4000-15000sccm, for example, 4000sccm, 5000sccm, 6000sccm, 7000sccm, 8000sccm, 9000sccm, 10000sccm, 11000sccm, 12000sccm, 13000sccm, 14000sccm or 15000sccm; silane at 1000-3000sccm, for example, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm, 1600sccm, 1700sccm, 1800sccm, 1900sccm, 2000sccm, 2500sccm or 3000sccm. 000sccm; RF power is 10000-20000W, for example, it can be 10000W, 11000W, 12000W, 13000W, 14000W, 15000W, 16000W, 17000W, 18000W, 19000W or 20000W; pulse is 20-60:1000, for example, it can be 20:1000, 3 0:1000, 40:1000, 50:1000 or 60:1000; the pressure is 1600-2200mT, for example, it can be 1600mT, 1700mT, 1800mT, 1900mT, 2000mT, 2100mT or 2200mT; the process time is 50-300s, for example, it can be 50s, 100s, 200s or 300s.

[0071] The third stage: introducing ammonia at 4000-15000sccm, for example, 4000sccm, 5000sccm, 6000sccm, 7000sccm, 8000sccm, 9000sccm, 10000sccm, 11000sccm, 12000sccm, 13000sccm, 14000sccm or 15000sccm; silane at 1000-3000sccm, 12000sccm, 13000sccm, 14000sccm or 15000sccm; silane at 1000-3000sccm, for example, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 14000sccm or 15000sccm 1900sccm, 2000sccm, 2500sccm or 3000sccm; RF power is 10000-20000W, for example, it can be 10000W, 11000W, 12000W, 13000W, 14000W, 15000W, 16000W, 17000W, 18000W, 19000W or 20000W; pulse is 20-60:1000, For example, it can be 20:1000, 30:1000, 40:1000, 50:1000 or 60:1000; the pressure is 1600-2200mT, for example, it can be 1600mT, 1700mT, 1800mT, 1900mT, 2000mT, 2100mT or 2200mT; the process time is 50-300s, for example, it can be 50s, 100s, 200s or 300s.

[0072] The fourth stage: introducing ammonia gas at 2000-10000sccm, for example, 2000sccm, 3000sccm, 4000sccm, 5000sccm, 6000sccm, 7000sccm, 8000sccm, 9000sccm or 10000sccm; silane at 500-1000sccm, for example, 500sccm, 600sccm, 700sccm, 800sccm, 900sccm or 1000sccm, and RF power at 10000-20000W, for example, 10000W, 11000W, 12000W , 13000W, 14000W, 15000W, 16000W, 17000W, 18000W, 19000W or 20000W; the pulse is 20-60:1000, for example, it can be 20:1000, 30:1000, 40:1000, 50:1000 or 60:1000; the pressure is 1600-2200mT, for example, it can be 1600mT, 1700mT, 1800mT, 1900mT, 2000mT, 2100mT or 2200mT; the process time is 50-300s, for example, it can be 50s, 100s, 200s or 300s.

[0073] In an optional manner, the method further includes:

[0074] Step 7: Prepare the Topcon battery using screen printing.

[0075] In this step, electrodes are prepared on the surface of the battery with silicon nitride layers formed on the front and back sides. The electrodes are screen-printed to print the main grid and the sub-grid on the front and back sides of the battery. After sintering and light injection, the electrodes are fixed on the surface of the battery to obtain the final product Topcon battery. Screen printing is a conventional process for preparing Topcon batteries, which will not be described here.

[0076] The second aspect of the present application provides a Topcon battery, which is prepared using the preparation method of the Topcon battery of the first aspect of the present application.

[0077] In some specific embodiments, Figure 2 As shown, the Topcon battery includes a substrate 1, which has a front side and a back side opposite to each other. The front side of the substrate is provided with a P+ layer 2, an aluminum oxide layer 3, and a front silicon nitride layer 4; the back side of the substrate is provided with a tunneling oxide layer 5, a doped polysilicon layer 6, and a back silicon nitride layer 8; the doped polysilicon layer 6 is provided with a polysilicon layer 7 on a side close to the back silicon nitride layer 8, and the polysilicon layer 7 is doped with carbon elements.

[0078] By arranging a polysilicon layer doped with carbon on the surface of the doped polysilicon layer, the carbon element can effectively act on the defect-concentrated surface layer of the polysilicon layer, thereby effectively reducing the interface state density and reducing the composite loss and parasitic absorption of the back-doped polysilicon layer.

[0079] In one embodiment, the carbon concentration in the polysilicon layer is 2×10 16 ~1×10 17 atom / cm 3 ; For example, it can be 2×10 16 atom / cm 3 , 3×10 16 atom / cm 3 , 4×10 16 atom / cm 3 , 5×10 16 atom / cm 3 , 6×10 16 atom / cm 3 ,7×10 16 atom / cm 3 , 8×10 16 atom / cm 3 ,9×10 16 atom / cm 3 or 1×10 17 atom / cm 3 .

[0080] In one embodiment, the thickness of the doped polysilicon layer is 130 to 160 nm; for example, it can be 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm or 160 nm; the depth of the polysilicon layer is 2 to 10 nm; for example, it can be 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, 5.5 nm, 6 nm, 6.5 nm, 7 nm, 22 nm, 7.5 nm, 8 nm, 8.5 nm, 9 nm, 9.5 nm or 10 nm.

[0081] In one embodiment, the thickness of the back silicon nitride layer is 75 to 95 nm; for example, it can be 75 nm, 76 nm, 77 nm, 78 nm, 79 nm, 80 nm, 81 nm, 82 nm, 83 nm, 84 nm, 85 nm, 86 nm, 87 nm, 88 nm, 89 nm, 90 nm, 91 nm, 92 nm, 93 nm, 94 nm or 95 nm.

[0082] In one practicable manner, the refractive index of the back silicon nitride layer is 1.98 to 2.10; for example, it can be 1.98, 1.99, 2, 2.01, 2.01, 2.02, 2.03, 2.04, 2.05, 2.06, 2.07, 2.08, 2.09 or 2.10.

[0083] In an operative manner, the front silicon nitride layer 4 includes four first sub-silicon nitride layers, wherein the refractive indices of the four first sub-silicon nitride layers decrease in sequence in a direction away from the front side of the substrate.

[0084] In one practicable manner, the four first silicon nitride sub-layers have different film thicknesses.

[0085] In an operative manner, the back silicon nitride layer 8 includes a surface silicon nitride layer and four second sub-silicon nitride layers, wherein the refractive indices of the four second sub-silicon nitride layers decrease in sequence in a direction away from the back side of the substrate.

[0086] In one practicable manner, the four second silicon nitride sub-layers have different film thicknesses.

[0087] The third aspect of the present application provides a solar cell assembly, comprising a Topcon cell prepared by the preparation method of the first aspect of the present application or a Topcon cell of the second aspect of the present application.

[0088] The fourth aspect of the present application provides a solar energy system, comprising the Topcon solar energy module of the third aspect of the present application.

[0089] The following describes in detail the method for preparing the photovoltaic cell disclosed in the second aspect of the present application and the photovoltaic cell disclosed in the third aspect of the present application with several specific embodiments. It is worth noting that the following description is only for illustrative purposes and is not a specific limitation of the invention.

[0090] Example 1

[0091] An N-type single crystal silicon wafer is selected, and an alkaline solution is used to texturize the N-type single crystal silicon wafer, wherein the alkaline solution is a potassium hydroxide solution;

[0092] The P+ layer is prepared using a low-pressure diffusion furnace and BCL 3 , O 2 As the reaction gas, N 2 As carrier gas, BCl 3 The flow rate is 2500sccm, O 2 The flow rate is 500~3000sccm, N 2 The flow rate is 1000~20000sccm and the doping temperature is 500~900℃.

[0093] The BSG (borosilicate glass) layer on the back and side surfaces is removed by using a 50% by volume hydrofluoric acid solution through a chain pickling device;

[0094] The back side of the substrate is subjected to alkali polishing, the temperature of the alkali bath soaking zone is 40-70°C, the concentration is 1%-5%; the alkali solution is a potassium hydroxide aqueous solution;

[0095] The tunnel oxide layer and the amorphous silicon layer are prepared by LPCVD. The tunnel oxide layer is prepared by thermal oxidation. 2 The flow rate is 10000sccm~50000sccm, the time of thermal oxygen deposition is 1min~30min; the deposition temperature of thermal oxygen is 500~700℃; when using SiH 4 Deposition of amorphous silicon, SiH 4 The gas flow rate is 1000 sccm to 2000 sccm, the deposition temperature of the amorphous silicon layer is 500 to 600° C., and the deposition time is 10 min to 30 min.

[0096] In the preparation of phosphorus doping using a tubular diffusion furnace, POCl 3 , O 2 As the reaction gas, N 2 As carrier gas, POCl 3 The flow rate is 2500sccm, O 2 The flow rate is 500~3000sccm, N 2 The flow rate is 1000-20000sccm, and the phosphorus doping temperature is 500-900°C.

[0097] The front and edge PSG layers are removed by using hydrofluoric acid and nitric acid, and then an aluminum oxide layer is prepared on the front side of the substrate by using ALD.

[0098] A front silicon nitride layer is prepared on the front side of the substrate by PECVD; wherein the PECVD process is as follows:

[0099] The first stage: 11000sccm of ammonia and 2800sccm of silane were introduced, the RF power was 15000W, the pulse was 50:900, the pressure was 1850mT, and the time was 120s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0100] The second stage: 11000sccm of ammonia and 2250sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 140s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0101] The third stage: 13000sccm of ammonia and 1700sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 160s; the temperature was 505-540 degrees; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0102] The fourth stage: 14500sccm of ammonia and 1400sccm of silane are introduced, the RF power is 16500W, the pulse is 50:900, the pressure is 1850mT, and the time is 190s; the temperature is 505-540 degrees; the temperature passes through six temperature zones, the temperature of the first temperature zone is 540, the temperature of the second temperature zone is 540, the temperature of the third temperature zone is 520, the temperature of the fourth temperature zone is 510, the temperature of the fifth temperature zone is 505, and the temperature of the sixth temperature zone is 515;

[0103] A back silicon nitride layer is prepared on the back of the substrate by PECVD and the doped polysilicon layer is modified, wherein the process is as follows:

[0104] Pretreatment stage: methane gas flow rate is 3500sccm, RF power is 10000W, pulse is 20:1000, pressure is 1500mT~2000mT, time is 100s; temperature passes through six temperature zones, the temperature of the first temperature zone is 520, the temperature of the second temperature zone is 520, the temperature of the third temperature zone is 505, the temperature of the fourth temperature zone is 500, the temperature of the fifth temperature zone is 495, and the temperature of the sixth temperature zone is 500;

[0105] The first stage: 11000sccm of ammonia and 2800sccm of silane were introduced, the RF power was 15000W, the pulse was 50:900, the pressure was 1850mT, and the time was 120s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0106] The second stage: 11000sccm of ammonia and 2250sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 140s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0107] The third stage: 13000sccm of ammonia and 1700sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 160s; the temperature was 505-540 degrees; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0108] The fourth stage: 14500sccm of ammonia and 1400sccm of silane are introduced, the RF power is 16500W, the pulse is 50:900, the pressure is 1850mT, and the time is 190s; the temperature is 505-540 degrees; the temperature passes through six temperature zones, the temperature of the first temperature zone is 540, the temperature of the second temperature zone is 540, the temperature of the third temperature zone is 520, the temperature of the fourth temperature zone is 510, the temperature of the fifth temperature zone is 505, and the temperature of the sixth temperature zone is 515;

[0109] Step 7: Print the main grid and fine grid simultaneously on the front and back sides of the substrate by screen printing, use non-burn-through silver paste, sinter at 700-850°C, and then inject light to prepare the Topcon cell.

[0110] The electrical performance data of the prepared Topcon battery was measured using a battery efficiency tester.

[0111] Example 2

[0112] The difference from Example 1 is that:

[0113] Step 6

[0114] Pretreatment stage: methane gas flow rate is 3500sccm, RF power is 9000W, pulse is 20:1000, pressure is 1500mT~2000mT, time is 100s; temperature passes through six temperature zones, the first temperature zone temperature is 510, the second temperature zone temperature is 510, the third temperature zone temperature is 500, the fourth temperature zone temperature is 495, the fifth temperature zone temperature is 490, and the sixth temperature zone temperature is 495;

[0115] The first stage: 11000sccm of ammonia and 2800sccm of silane were introduced, the RF power was 15000W, the pulse was 50:900, the pressure was 1850mT, and the time was 120s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0116] The second stage: 11000sccm of ammonia and 2250sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 140s; the temperature was 505-540 degrees; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0117] The third stage: 13000sccm of ammonia and 1700sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 160s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0118] The fourth stage: 14500sccm of ammonia and 1400sccm of silane are introduced, the RF power is 16500W, the pulse is 50:900, the pressure is 1850mT, and the time is 190s; the temperature is 505-540 degrees; the temperature passes through six temperature zones, the temperature of the first temperature zone is 540, the temperature of the second temperature zone is 540, the temperature of the third temperature zone is 520, the temperature of the fourth temperature zone is 510, the temperature of the fifth temperature zone is 505, and the temperature of the sixth temperature zone is 515;

[0119] Example 3

[0120] The difference from Example 1 is that:

[0121] Pretreatment stage: the temperature passes through six temperature zones, the temperature in the first temperature zone is 540, the temperature in the second temperature zone is 540, the temperature in the third temperature zone is 520, the temperature in the fourth temperature zone is 510, the temperature in the fifth temperature zone is 505, and the temperature in the sixth temperature zone is 515.

[0122] Example 4

[0123] The difference from Example 1 is that

[0124] Pretreatment stage: methane gas flow rate is 1500sccm;

[0125] Example 5

[0126] The difference from Example 1 is that

[0127] Pretreatment stage: methane gas flow rate is 6000sccm;

[0128] Comparative Example 1

[0129] The difference from Example 1 is that

[0130] In step 6, a back silicon nitride layer is prepared on the back side of the substrate by PECVD, and the process is as follows:

[0131] The first stage: 11000sccm of ammonia and 2800sccm of silane were introduced, the RF power was 15000W, the pulse was 50:900, the pressure was 1850mT, and the time was 120s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0132] The second stage: 11000sccm of ammonia and 2250sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 140s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0133] The third stage: 13000sccm of ammonia and 1700sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 160s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0134] The fourth stage: 14500sccm of ammonia and 1400sccm of silane were introduced, the RF power was 16500W, the pulse was 50:900, the pressure was 1850mT, and the time was 190s; the temperature passed through six temperature zones, the temperature of the first temperature zone was 540, the temperature of the second temperature zone was 540, the temperature of the third temperature zone was 520, the temperature of the fourth temperature zone was 510, the temperature of the fifth temperature zone was 505, and the temperature of the sixth temperature zone was 515;

[0135] The following table shows the test data of Examples 1 to 5 and Comparative Example 1. It can be seen from the table that (1) compared with Comparative Example 1, the efficiency Eta of Examples 1 to 5 increases significantly, and their Uoc and Isc both increase significantly; (2) compared with Examples 1-2, the efficiency of Example 3 decreases slightly because the temperature in the pretreatment is equal to the temperature in other stages; (3) compared with Examples 1-2, the methane gas flow rate of Example 4 is too small, resulting in a slight decrease in efficiency; (4) compared with Examples 1-2, the methane gas flow rate of Example 4 is too large, resulting in a slight decrease in efficiency.

[0136] Eta / % Uoc / V Isc / A FF / % Example 1 26.361 0.738 14.152 83.28 Example 2 26.341 0.738 14.154 83.25 Example 3 26.314 0.737 14.134 83.40 Example 4 26.252 0.736 14.126 83.30 Example 5 26.278 0.737 14.138 83.27 Comparative Example 1 26.210 0.7285 13.940 85.21

[0137] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art may understand and implement other changes to the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit may implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0138] Although the present application has been described in conjunction with specific features and embodiments thereof, it is obvious that various modifications and combinations may be made thereto without departing from the spirit and scope of the present application. Accordingly, this specification and the drawings are merely exemplary illustrations of the present application as defined by the appended claims, and are deemed to have covered any and all modifications, variations, combinations or equivalents within the scope of the present application. Obviously, those skilled in the art may make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A method for preparing a Topcon battery, characterized in that: The method comprises: Step 1: providing a substrate, and performing a texturing treatment on the surface of the substrate; Step 2: Obtain a P+ layer by boron diffusion; Step 3: Prepare a tunnel oxide layer and a doped polysilicon layer by LPCVD and phosphorus diffusion; Step 4: preparing an aluminum oxide layer on the front side of the substrate by using ALD; Step 5: preparing a front silicon nitride layer on the front side of the substrate by using PECVD; Step 6: Prepare a back silicon nitride layer on the back side of the substrate by using PECVD, and modify the doped polysilicon layer so that a polysilicon layer doped with carbon is formed on the surface of the doped polysilicon layer.

2. The method for preparing a Topcon battery according to claim 1, characterized in that: In step 6, First, the doped polysilicon layer is modified by pretreatment; the pretreatment is to introduce methane into a PECVD furnace and excite the methane under a certain temperature, time, pressure and radio frequency power; Subsequently, the back silicon nitride layer is prepared through at least one silicon nitride treatment stage; at least one of the silicon nitride treatment stages is to introduce ammonia and silane into a PECVD furnace and excite the ammonia and silane under a certain temperature, time, pressure and radio frequency power.

3. The method for preparing a Topcon battery according to claim 2, characterized in that: In the pretreatment and each of the silicon nitride treatment stages, the substrate passes through at least one temperature zone, and in each of the temperature zones, the temperature of the pretreatment is lower than the temperature of the silicon nitride treatment stage; Preferably, in each of the temperature zones, the temperature of the pretreatment is 10-40 degrees lower than the temperature of the silicon nitride treatment stage.

4. The method for preparing a Topcon battery according to claim 2, characterized in that: During the pretreatment process: the gas flow rate of methane is 2000-5000sccm, the radio frequency power is 8000-15000W, the pulse is 20-60:1000, and the pressure is 1300-2000mT.

5. The method for preparing a Topcon battery according to claim 2, characterized in that: The back side silicon nitride layer includes four silicon nitride processing stages, wherein: The first stage: 8000~12000sccm of ammonia, 200~3000sccm of silane, 10000~20000W of RF power, 20~60:1000 of pulse, 1600mT of pressure, and 50~300s of process time; The second stage: introduce ammonia 4000~15000sccm, silane 1000~3000sccm, RF power 10000~20000W, pulse 20~60:1000, pressure 1600~2200mT, process time 50~300s; The third stage: introduce ammonia 4000~15000sccm, silane 1000~3000sccm, RF power 10000~20000W, pulse 20~60:1000, pressure 1600~2200mT, process time 50~300s; The fourth stage: introduce ammonia 2000~10000sccm, silane 500~1000sccm, RF power is 10000~20000W, pulse is 20~60:1000, pressure is 1600~2200mT, and process time is 50~300s.

6. A Topcon battery, characterized in that: The Topcon battery is prepared by the preparation method of any one of claims 1 to 5.

7. The Topcon battery according to claim 1, characterized in that The battery comprises: A substrate, the substrate comprising a front side and a back side opposite to each other, wherein the front side is provided with a P+ layer, an aluminum oxide layer, and a front silicon nitride layer in sequence; the back side is provided with a tunneling oxide layer, a doped polysilicon layer, a polysilicon layer, and a back silicon nitride layer in sequence, wherein the polysilicon layer is doped with carbon; Preferably, the carbon concentration in the polysilicon layer is 2×10 16 ~1×10 17 atom / cm 3 ; Preferably, the thickness of the doped polysilicon layer is 130-160 nm; and / or the depth of the polysilicon layer is 2-10 nm; Preferably, the back silicon nitride layer has a thickness of 75-95 nm; and / or a refractive index of the back silicon nitride layer has a refractive index of 1.98-2.

10.

8. The Topcon battery according to claim 7, characterized in that The front silicon nitride layer includes four first sub-silicon nitride layers, wherein the refractive indices of the four first sub-silicon nitride layers decrease sequentially along the front direction away from the substrate; and / or the back silicon nitride layer includes a surface silicon nitride layer and four second sub-silicon nitride layers, wherein the refractive indices of the four second sub-silicon nitride layers decrease sequentially along the back direction away from the substrate.

9. A solar panel, characterized in that: A Topcon battery prepared by the preparation method of any one of claims 1 to 5 or a Topcon battery of any one of claims 6 to 8.

10. A solar energy system, characterized in that: A solar cell module comprising the solar cell module of claim 9.

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