Topcon cell and method of manufacturing the same, solar module, solar system

Abstract

The application 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. The preparation method of the Topcon battery comprises the following steps: step 1, providing a substrate, and performing a texturing treatment on the surface of the substrate; step 2, obtaining a P+ layer through boron doping and BSG removal; step 3, obtaining a tunneling oxide layer and a doped polysilicon layer by adopting LPCVD and high-temperature phosphorus diffusion; step 4, obtaining an aluminum oxide layer on the front surface of the substrate by adopting ALD; step 5, obtaining a front surface silicon nitride layer on the front surface of the substrate by adopting PECVD; step 6, obtaining a back surface silicon nitride layer on the back surface of the substrate by adopting PECVD, and modifying the doped polysilicon layer, so that a polysilicon layer doped with carbon elements is formed on the surface of the doped polysilicon layer. The application does not need to increase additional equipment, is compatible with the existing LPCVD equipment for preparing the Topcon battery containing the polysilicon layer doped with carbon elements, is simple to operate, low in cost and suitable for large-scale popularization.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solar cells, in particular to a Topcon cell and a preparation method thereof, a solar module and a solar system. BACKGROUND

[0002] Topcon (Tunnel Oxide Passivated Contact) cells are a new type of passivated contact cells, which have gradually replaced PECR cells and become the future technology route of new N-type substrates. With the intensification of industry competition, the efficiency of Topcon cells has been improved from 24.5% in the initial stage to 26.5% in the era, and is getting closer and closer to the theoretical limit efficiency of 27.8%. The analysis of the electrical performance loss of each link of the TOPCON cell is also used to guide the direction of subsequent technology upgrading, and the enterprises with higher efficiency improvement will obtain the greatest benefit in this technology upgrading.

[0003] According to simulation calculation, the back surface recombination of the TOPcon cell is 1.95fA / cm 2 , accounting for 9.2% of the total recombination loss of the cell. The parasitic loss of the back surface polysilicon layer is an important reason for the loss of the efficiency of the cell, so improving the quality of the back surface polysilicon layer to reduce the parasitic absorption and recombination loss can significantly improve the efficiency of the cell. Research shows that doping trace elements in the polysilicon layer can significantly improve the quality of the back surface polysilicon layer, improve the back surface recombination loss, and reduce the parasitic absorption.

[0004] There are two main process routes for the current TOPcon cell, PE-Poly and LP-Poly. The former uses PECVD to deposit phosphorus-doped amorphous silicon by ionization once, and forms phosphorus-doped polysilicon by annealing. The latter uses a low-pressure deposition furnace to deposit a tunnel oxide layer and an amorphous silicon layer, and forms phosphorus-doped polysilicon by secondary doping of phosphorus atoms. Doping trace elements in polysilicon is currently only studied in TOPcon cells using the PE-Poly route, but no relevant reports have been found in the LP-Poly route.

[0005] For the LP-Poly route, the quality of the tunnel oxide layer and the amorphous silicon layer grown by LPCVD is higher, and the production efficiency has a 0.5% advantage over the PE route. More and more cell manufacturers plan to use the LP-Poly route.

[0006] Therefore, it is increasingly urgent to study doping trace elements in the polysilicon layer in the LP-Poly route to improve the quality of the back surface polysilicon layer, improve the back surface recombination loss, and reduce the parasitic absorption. SUMMARY

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

[0008] The first aspect of the application provides a preparation method of a Topcon cell, comprising:

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

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

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

[0012] Step 4: obtaining an aluminum oxide layer on the front surface of the substrate by ALD;

[0013] Step 5: obtaining a front surface silicon nitride layer on the front surface of the substrate by PECVD;

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

[0015] In an optional mode, in the 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 at a certain temperature, time, pressure and radio frequency power;

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

[0018] In an optional mode, 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 that of the silicon nitride treatment stage;

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

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

[0021] In an alternative way, the back silicon nitride layer includes four silicon nitride processing stages, wherein,

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

[0023] In the second stage, the ammonia is 4000-15000sccm, the silane is 1000-3000sccm, the radio frequency power is 10000-20000W, the pulse is 20-60:1000, the pressure is 1600-2200mT, and the process time is 50-300s;

[0024] In the third stage, the ammonia is 4000-15000sccm, the silane is 1000-3000sccm, the radio frequency power is 10000-20000W, the pulse is 20-60:1000, the pressure is 1600-2200mT, and the process time is 50-300s;

[0025] In the fourth stage, the ammonia is 2000-10000sccm, the silane is 500-1000sccm, the radio frequency power is 10000-20000W, the pulse is 20-60:1000, the pressure is 1600-2200mT, and the process time is 50-300s.

[0026] The second aspect of the present application provides a Topcon cell prepared by the preparation method of the Topcon cell of the first aspect of the present application.

[0027] In an alternative way, the cell includes:

[0028] The substrate includes opposite front and back surfaces, wherein the front surface is sequentially provided with a P+ layer, an aluminum oxide layer, and a front silicon nitride layer; the back surface is sequentially provided with a tunneling oxide layer, a doped polysilicon layer, a polysilicon layer, and a back silicon nitride layer, wherein the polysilicon layer is doped with carbon elements.

[0029] Preferably, the concentration of carbon 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 backside silicon nitride layer is 75-95 nm; and / or, the refractive index of the backside silicon nitride layer is 1.98-2.10.

[0032] In an alternative way, the frontside silicon nitride layer comprises four layers of first sub-silicon nitride layers, wherein the refractive index of the four layers of first sub-silicon nitride layers decreases in turn along the direction away from the frontside of the substrate; and / or, the backside silicon nitride layer comprises one layer of surface silicon nitride layer and four layers of second sub-silicon nitride layers, wherein the refractive index of the four layers of second sub-silicon nitride layers decreases in turn along the direction away from the backside of the substrate.

[0033] The third aspect of the present application provides a solar module comprising the Topcon cell prepared by the method of the first aspect of the present application or the Topcon cell of the second aspect of the present application.

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

[0035] Compared with the prior art, the beneficial effects of the present application are as follows:

[0036] (1) The method of the present application does not need to add additional equipment, is compatible with the existing LP-Poly route equipment, increases the pretreatment in the process of preparing the backside silicon nitride, uses radio frequency to excite the methane gas, changes the methane into carbon plasma, and through the high-energy plasma constantly colliding with the substrate, the carbon atoms are into the doped polysilicon layer, so that the doped polysilicon layer is modified to form a polysilicon layer doped with carbon elements, which effectively reduces the recombination loss and parasitic absorption of the backside polysilicon layer. The present application is simple in operation, low in cost, and suitable for mass promotion.

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

[0038] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The schematic 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 flowchart showing the method of manufacturing the Topcon cell of the present application is shown.

[0040] Figure 2 A schematic diagram showing an embodiment of the Topcon cell of the present application is shown.

[0041] Reference Signs:

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

[0043] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely exemplary and is not intended to limit the scope of the present disclosure. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concept of the present disclosure.

[0044] Further, the terms "first", "second", etc. are used only for the purpose of description and do not imply or imply relative importance or imply the number of the technical features indicated. Thus, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified. The meaning of "several" is one or more, unless otherwise explicitly specified.

[0045] According to the simulation calculation, the backside recombination of the TOPcon cell is 1.95 fA / cm 2 , accounting for 9.2% of the total recombination loss of the cell, and the parasitic loss of the backside polysilicon layer is an important reason for the loss of the cell efficiency. Therefore, improving the quality of the backside polysilicon layer to reduce the parasitic absorption and recombination loss can significantly improve the efficiency of the cell. Research shows that doping trace elements in the polysilicon layer can significantly improve the quality of the backside polysilicon layer, improve the backside recombination loss, and reduce the parasitic absorption.

[0046] There are two major process routes for the current TOPcon cell, PE-Poly and LP-Poly. The former uses PECVD to deposit phosphorus-doped amorphous silicon by ionization, and forms phosphorus-doped polysilicon by annealing. The latter uses a low-pressure deposition furnace to deposit a tunnel oxide layer and an amorphous silicon layer, and then secondarily dopes phosphorus atoms to form phosphorus-doped polysilicon. To dope trace elements in the polysilicon layer without introducing other impurities, the common doping sources for doping trace C, O, and N elements are CH4, CO4, and NH3. These three substances are composed of strong chemical bonds, and it is difficult to provide the required doping atoms through thermal decomposition. Therefore, in the LP-poly route, it is not possible to directly dope the doped polysilicon layer with trace elements in the preparation of the doped polysilicon layer.

[0047] To this end, the first aspect of the present application provides a preparation method of a Topcon cell, as shown in the following steps: Figure 1

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

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

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

[0051] Step 4: obtaining an aluminum oxide layer on the front surface of the substrate by ALD;

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

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

[0054] The present application increases the pretreatment in the process of preparing the back surface silicon nitride layer, introduces carbon atoms into the doped polysilicon layer, modifies the doped polysilicon layer, and forms a polysilicon layer doped with carbon elements, thereby effectively reducing the recombination loss and parasitic absorption of the back surface polysilicon layer. The present application does not require additional equipment, is compatible with existing LP-Poly route equipment, is simple to operate, has low cost, and is suitable for mass production.

[0055] In step 1, the substrate is an N-type monocrystalline silicon wafer, which includes opposite front and back surfaces. By texturing the N-type monocrystalline silicon wafer, not only can the organic dirt and metal impurities on the surface of the silicon wafer be removed, but also the mechanical damage layer generated during the wire cutting process of the silicon wafer can be removed to reduce the recombination center. Meanwhile, 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. By vaporizing the boron source (such as BBr3 or BCl3) in a tube furnace and then depositing it on the surface of the silicon wafer through a series of chemical reactions, a suitable doping concentration, junction depth and sheet resistance can be obtained. A P+ layer (boron doped layer) is formed on the front surface of the silicon wafer.

[0057] ​In Step 3, before the preparation of the tunneling oxide layer and the doped polysilicon layer, the BSG layer (boron-silicon glass layer) on the back surface of the substrate needs to be removed, which is usually removed by using hydrofluoric acid; then, the substrate is subjected to alkali polishing to prepare the tunneling oxide layer and the doped polysilicon layer by using LPCVD and phosphorus diffusion. First, the LPCVD is used to form the oxide layer by passing oxygen at a high temperature under low pressure, so that the oxygen reacts with silicon to produce silicon oxide. Then, the amorphous silicon layer is formed by passing silane at a high temperature, so that the silane is thermally decomposed into silicon and hydrogen. Subsequently, the tunneling oxide layer and the doped polysilicon layer are formed by phosphorus diffusion in the presence of oxygen, so that POCl3 is decomposed into PCl5 and P2O5 at a high temperature, and the generated P2O5 reacts with silicon at the diffusion temperature to generate SiO2 and phosphorus atoms.

[0058] In Step 4, before the preparation of the aluminum oxide layer, the oxide layer and the PSG layer (phosphorus-silicon glass layer) on the front surface need to be removed. The aluminum oxide layer is mainly prepared by using the ALD method to deposit, using TMA as the aluminum source and H2O or O2 as the oxygen source. Two or more chemical vapor precursors are alternately introduced into the reaction chamber, and a reaction occurs on the surface of the substrate to form an aluminum oxide layer film.

[0059] In Step 5, the substrate after ALD treatment is placed in the PECVD for the preparation of the silicon nitride layer, so as to form a front surface silicon nitride layer on the front surface of the substrate. The silicon nitride layer formed on the surface of the silicon wafer can serve as an antireflection film and produce a passivation effect, and its dense structure ensures that the silicon wafer is not oxidized. At present, the silicon nitride layer is mainly prepared by PECVD.

[0060] In Step 6, after the preparation of the front surface silicon nitride layer on the front surface of the substrate, the back surface of the substrate is subjected to back surface silicon nitride layer preparation by PECVD, and the doped polysilicon layer is modified so that the surface of the doped polysilicon layer forms a polysilicon layer doped with carbon elements.

[0061] In an alternative way, in Step 6,

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

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

[0064] In some embodiments, the substrate passes through at least one temperature zone in each of the pre-treatment and silicon nitride treatment stages, and the temperature of the pre-treatment is lower than the temperature of the silicon nitride treatment stage in each temperature zone.

[0065] By adding methane in the pre-treatment stage and using the methane excited by radio frequency to change the methane into carbon plasma and hydrogen plasma, the trace carbon atoms are continuously impacted on the substrate by high-energy plasma to impact the doped polysilicon layer, the surface of the doped polysilicon layer is modified, and the polysilicon layer with carbon elements is formed. Due to the introduction of carbon elements, the carbon elements replace silicon atoms to form a substitutional solid solution, and the polysilicon layer is passivated. The interface state density is effectively reduced, and the recombination loss and parasitic absorption of the back polysilicon layer are reduced.

[0066] In one embodiment, the temperature of the pre-treatment is 10-40 degrees lower than the temperature of the silicon nitride treatment stage in each temperature zone; 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 embodiments, in the pre-treatment process, the gas flow of methane is 2000-5000 sccm, for example, it can be 2000 sccm, 2500 sccm, 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm or 5000 sccm; the radio frequency power is 8000-15000 W, for example, it can be 8000 W, 9000 W, 10000 W, 11000 W, 12000 W, 13000 W, 14000 W or 15000 W; 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 1300-2000 mT, for example, it can be 1300 mT, 1400 mT, 1500 mT, 1600 mT, 1700 mT, 1800 mT, 1900 mT or 2000 mT.

[0068] In some embodiments, the preparation process of the back silicon nitride layer includes four silicon nitride treatment stages, wherein,

[0069] The first stage: the ammonia gas is 8000-12000sccm, for example, it can be 8000sccm, 9000sccm, 10000sccm, 11000sccm or 12000sccm; the silane is 200-3000sccm, for example, it can be 200sccm, 500sccm, 800sccm, 1000sccm, 1100sccm, 1200sccm, 1300sccm, 1400sccm, 1500sccm, 1600sccm, 1700sccm, 1800sccm, 1900sccm, 2000sccm, 2500sccm or 3000sccm; the radio frequency power is 10000-20000W, 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: the ammonia gas is 4000-15000 sccm, for example, it can be 4000 sccm, 5000 sccm, 6000 sccm, 7000 sccm, 8000 sccm, 9000 sccm, 10000 sccm, 11000 sccm, 12000 sccm, 13000 sccm, 14000 sccm or 15000 sccm; the silane is 1000-3000 sccm, for example, it can be 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm, 1500 sccm, 1600 sccm, 1700 sccm, 1800 sccm, 1900 sccm, 2000 sccm, 2500 sccm or 3000 sccm; the radio frequency power is 10000-20000 W, for example, it can be 10000 W, 11000 W, 12000 W, 13000 W, 14000 W, 15000 W, 16000 W, 17000 W, 18000 W, 19000 W or 20000 W; 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 1600-2200 mT, for example, it can be 1600 mT, 1700 mT, 1800 mT, 1900 mT, 2000 mT, 2100 mT or 2200 mT; the process time is 50-300 s, for example, it can be 50 s, 100 s, 200 s or 300 s.

[0071] The third stage: the ammonia gas is 4000-15000 sccm, for example, it can be 4000 sccm, 5000 sccm, 6000 sccm, 7000 sccm, 8000 sccm, 9000 sccm, 10000 sccm, 11000 sccm, 12000 sccm, 13000 sccm, 14000 sccm or 15000 sccm; the silane is 1000-3000 sccm, 12000 sccm, 13000 sccm, 14000 sccm or 15000 sccm; the silane is 1000-3000 sccm, for example, it can be 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm, 1500 sccm, 1600 sccm, 1700 sccm, 1800 sccm, 1900 sccm, 2000 sccm, 2500 sccm or 3000 sccm; the radio frequency power is 10000-20000 W, for example, it can be 10000 W, 11000 W, 12000 W, 13000 W, 14000 W, 15000 W, 16000 W, 17000 W, 18000 W, 19000 W or 20000 W; 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 1600-2200 mT, for example, it can be 1600 mT, 1700 mT, 1800 mT, 1900 mT, 2000 mT, 2100 mT or 2200 mT; the process time is 50-300 s, for example, it can be 50 s, 100 s, 200 s or 300 s.

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

[0073] In an alternative way, the method further comprises:

[0074] Step 7: the Topcon cell is prepared by screen printing.

[0075] In this step, the electrodes are prepared on the surface of the cell on which the silicon nitride layers have been formed on the front side and the back side, wherein the electrodes are prepared by screen printing, the main grid and the auxiliary grid are printed on the front side and the back side of the cell, and the electrodes are fixed on the surface of the cell by sintering and light injection to obtain the final product Topcon cell. Screen printing is a conventional process for preparing Topcon cell, and thus will not be described here.

[0076] The second aspect of the present application provides a Topcon cell prepared by the method for preparing a Topcon cell according to the first aspect of the present application.

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

[0078] By setting the polycrystalline silicon layer doped with carbon element on the surface of the doped polycrystalline silicon layer, the carbon element can effectively act on the defect concentrated surface layer of the polycrystalline silicon layer, thereby effectively reducing the interface state density, reducing the recombination loss and parasitic absorption of the back doped polycrystalline silicon layer.

[0079] In an implementable manner, the concentration of carbon in the polycrystalline silicon 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 an implementable manner, the thickness of the doped polycrystalline silicon layer is 130-160nm; for example, it can be 130nm, 135nm, 140nm, 145nm, 150nm, 155nm or 160nm; the depth of the polycrystalline silicon layer is 2-10nm; for example, it can be 2nm, 2.5nm, 3nm, 3.5nm, 4nm, 4.5nm, 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 22nm, 7.5nm, 8nm, 8.5nm, 9nm, 9.5nm or 10nm.

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

[0082] In an implementable manner, the backside silicon nitride layer has a refractive index of 1.98-2.10; 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 implementable manner, the frontside silicon nitride layer 4 includes four first sub-silicon nitride layers, and the refractive index of the four first sub-silicon nitride layers decreases in turn along the direction away from the frontside of the substrate.

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

[0085] In an implementable manner, the backside silicon nitride layer 8 includes one surface silicon nitride layer and four second sub-silicon nitride layers, and the refractive index of the four second sub-silicon nitride layers decreases in turn along the direction away from the backside of the substrate.

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

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

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

[0089] The preparation method of the photovoltaic cell according to the second aspect of the present application and the photovoltaic cell according to the third aspect of the present application are described in detail below with several specific examples. It should be understood that the following description is only exemplary and is not a specific limitation on the invention.

[0090] Example 1

[0091] An N-type monocrystalline silicon wafer is selected, and an alkaline solution is used to etch the N-type monocrystalline silicon wafer, and the alkaline solution is a potassium hydroxide solution;

[0092] A low-pressure diffusion furnace is used to prepare a P+ layer, BCl3 and O2 are used as reaction gases, N2 is used as a carrier gas, the flow rate of BCl3 is 2500 sccm, the flow rate of O2 is 500-3000 sccm, and the flow rate of N2 is 1000-20000 sccm, and the doping temperature is 500-900°C.

[0093] A chain-type pickling device is used to remove the BSG (borosilicate glass) layer plated around the backside and side surface in a hydrofluoric acid solution with a volume fraction of 50%;

[0094] The back surface of the substrate is subjected to alkali etching, the temperature of the alkali tank immersion area is 40-70℃, and the concentration is 1%-5%; the alkali solution is potassium hydroxide aqueous solution;

[0095] The tunneling oxide layer and the amorphous silicon layer are prepared by LPCVD; the tunneling oxide layer is prepared by thermal oxidation, the flow rate of O2 in the thermal oxidation is 10000sccm-50000sccm, the deposition time of the thermal oxidation is 1min-30min, and the deposition temperature of the thermal oxidation is 500-700℃; the amorphous silicon is deposited by using SiH4, the gas flow rate of SiH4 is 1000sccm-2000sccm, the deposition temperature of the amorphous silicon layer is 500-600℃, and the deposition time is 10min-30min.

[0096] The phosphorus doping is prepared by using a tube diffusion furnace, POCl3 and O2 are used as the reaction gas, N2 is used as the carrier gas, the flow rate of POCl3 is 2500sccm, the flow rate of O2 is 500-3000sccm, the flow rate of N2 is 1000-20000sccm, and the phosphorus doping temperature is 500-900℃.

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

[0098] The front surface silicon nitride layer is prepared on the front surface of the substrate by using PECVD; the process of PECVD is as follows:

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

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

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

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

[0103] The back surface silicon nitride layer and the modification of the doped polysilicon layer on the substrate are prepared by PECVD, and the process is as follows:

[0104] The pretreatment stage: methane gas flow 3500sccm, radio frequency power 10000W, pulse 20:1000, pressure 1500mT-2000mT, time 100s; temperature through six temperature zones, the first temperature zone temperature is 520, the second temperature zone temperature is 520, the third temperature zone temperature is 505, the fourth temperature zone temperature is 500, the fifth temperature zone temperature is 495, the sixth temperature zone temperature is 500;

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

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

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

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

[0109] Step 7: simultaneously printing the main grid and the fine grid on the front and back of the substrate by using screen printing, using non-burn-through silver paste, and then preparing the Topcon cell by using light injection after a sintering process temperature of 700-850 degrees.

[0110] The electrical performance data of the prepared Topcon cell is measured by using a cell efficiency tester.

[0111] Example 2

[0112] The difference from example 1 is that;

[0113] In step 6

[0114] The pretreatment stage: the gas flow of methane is 3500sccm, the radio frequency power is 9000W, the pulse is 20:1000, the pressure is 1500mT-2000mT, and the time is 100s; the 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: ammonia gas 11000sccm, silane 2800sccm, radio frequency power 15000W, pulse 50:900, pressure 1850mT, time 120s; the temperature passes through six temperature zones, the first temperature zone temperature is 540, the second temperature zone temperature is 540, the third temperature zone temperature is 520, the fourth temperature zone temperature is 510, the fifth temperature zone temperature is 505, and the sixth temperature zone temperature is 515;

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

[0117] The third stage: ammonia gas 13000sccm, silane 1700sccm, radio frequency power 16500W, pulse 50:900, pressure 1850mT, time 160s; temperature through six temperature zones, the first temperature zone temperature is 540, the second temperature zone temperature is 540, the third temperature zone temperature is 520, the fourth temperature zone temperature is 510, the fifth temperature zone temperature is 505, the sixth temperature zone temperature is 515;

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

[0119] Example 3

[0120] The difference from example 1 is that;

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

[0122] Example 4

[0123] The difference from example 1 is that,

[0124] The pretreatment stage: the gas flow of methane is 1500sccm;

[0125] Example 5

[0126] The difference from example 1 is that,

[0127] The pretreatment stage: the gas flow of methane is 6000sccm;

[0128] Comparative example 1

[0129] The difference from example 1 is that,

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

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

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

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

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

[0135] The following table is the test data of Examples 1-5 and Comparative Example 1. From the table, (1) compared with Comparative Example 1, the efficiency Eta of Examples 1-5 increases significantly, and both Uoc and Isc increase significantly; (2) compared with Examples 1-2, the efficiency of Example 3 decreases slightly due to the temperature in the pretreatment being equal to the temperature in other stages; (3) compared with Examples 1-2, the efficiency of Example 4 decreases slightly due to the too small flow rate of methane gas; (4) compared with Examples 1-2, the efficiency of Example 4 decreases slightly due to the too large flow rate of methane gas.

[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 application has been described in connection with the embodiments thereof with reference to the various drawings, it will be understood that other variations and modifications of the details, and specific examples can be resorted to by those skilled in the art without departing from the spirit and scope of the application. In its broadest form, the application is directed to all new and useful processes, machines, articles of manufacture, compositions of matter, and methods that fall within the scope of the claims. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application cover the modifications and variations of this application provided they come within the scope of the appended claims and their equivalents.

[0138] Although the application has been described in connection with the embodiments thereof with reference to the various drawings, it will be understood that other variations and modifications of the details, and specific examples can be resorted to by those skilled in the art without departing from the spirit and scope of the application. In its broadest form, the application is directed to all new and useful processes, machines, articles of manufacture, compositions of matter, and methods that fall within the scope of the claims. The specification and drawings are, accordingly, to be regarded as illustrative rather than restrictive. It will be apparent to those skilled in the art that various modifications and variations can be made in the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application cover the modifications and variations of this application provided they come within the scope of the appended claims and their equivalents.

Claims

1. A method of producing a Topcon cell, characterized by, The method comprises: Step 1: providing a substrate, performing texturing on the surface of the substrate; Step 2: obtaining a P+ layer by boron diffusion; Step 3: obtaining a tunneling oxide layer and a doped polysilicon layer by LPCVD and phosphorus diffusion; Step 4: obtaining an aluminum oxide layer on the front surface of the substrate by ALD; Step 5: obtaining a front surface silicon nitride layer on the front surface of the substrate by PECVD; Step 6: obtaining a back surface silicon nitride layer on the back surface of the substrate by PECVD, and modifying the doped polysilicon layer so that a polysilicon layer doped with carbon elements is formed on the surface of the doped polysilicon layer; In step 6, first, the doped polysilicon layer is modified by pretreatment; the pretreatment is to introduce methane into the PECVD furnace and excite the methane at a certain temperature, time, pressure and radio frequency power; in the pretreatment process: the gas flow of the methane is 2000-5000sccm, the radio frequency power is 8000-15000W, the pulse is 20-60:1000, and the pressure is 1300-2000mT; Subsequently, the back surface silicon nitride layer is prepared by at least one silicon nitride treatment stage; at least one of the silicon nitride treatment stages is to introduce ammonia and silane into the PECVD furnace and excite the ammonia and the silane at a certain temperature, time, pressure and radio frequency power; 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 that of the silicon nitride treatment stage.

2. The method of claim 1, wherein the Topcon cell is prepared by a process comprising: In each of the temperature zones, the temperature of the pretreatment is 10-40 degrees lower than that of the silicon nitride treatment stage.

3. The method for preparing a Topcon battery as described in claim 1, characterized in that, The back surface silicon nitride layer comprises four silicon nitride treatment stages, wherein, In the first stage: the ammonia flow is 8000-12000sccm, the silane flow is 200-3000sccm, the radio frequency power is 10000-20000W, the pulse is 20-60:1000, the pressure is 1600mT, and the process time is 50-300s; In the second stage: the ammonia flow is 4000-15000sccm, the silane flow is 1000-3000sccm, the radio frequency power is 10000-20000W, the pulse is 20-60:1000, the pressure is 1600-2200mT, and the process time is 50-300s; In the third stage: the ammonia flow is 4000-15000sccm, the silane flow is 1000-3000sccm, the radio frequency power is 10000-20000W, the pulse is 20-60:1000, the pressure is 1600-2200mT, and the process time is 50-300s; In the fourth stage: the ammonia flow is 2000-10000sccm, the silane flow is 500-1000sccm, the radio frequency power is 10000-20000W, the pulse is 20-60:1000, the pressure is 1600-2200mT, and the process time is 50-300s.

4. A Topcon cell characterized by, The Topcon cell is prepared by the method of any one of claims 1-3.

5. The Topcon cell of claim 4, wherein, The battery comprises: a substrate comprising opposite front and back surfaces, wherein the front surface is sequentially provided with a P+ layer, an aluminum oxide layer, and a front silicon nitride layer; and the back surface is sequentially provided with a tunneling oxide layer, a doped polysilicon layer, a polysilicon layer, and a back silicon nitride layer, wherein the polysilicon layer is doped with carbon elements.

6. The Topcon cell of claim 5, wherein, The concentration of carbon in the polysilicon layer is 2 x 10 16 ~1 x 10 17 atom / cm 3 .

7. The Topcon cell of claim 5, wherein, The thickness of the doped polysilicon layer is 130-160 nm; and / or the depth of the polysilicon layer is 2-10 nm.

8. The Topcon cell of claim 5, wherein, 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.

9. The Topcon cell of claim 5, wherein, The front silicon nitride layer comprises four first sub-silicon nitride layers, wherein the refractive index of the four first sub-silicon nitride layers decreases sequentially in a direction away from the front surface of the substrate; and / or the back silicon nitride layer comprises one surface silicon nitride layer and four second sub-silicon nitride layers, wherein the refractive index of the four second sub-silicon nitride layers decreases sequentially in a direction away from the back surface of the substrate.

10. A solar module, characterized by, A Topcon battery prepared by the preparation method of any one of claims 1-3 or the Topcon battery of any one of claims 4-9.

11. A solar energy system characterized by, A solar module comprising the solar cell of claim 10.

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