Low parasitic absorption TOPCon solar cell and preparation method thereof

Abstract

The invention relates to the technical field of crystalline silicon solar cells, and particularly discloses a low parasitic absorption TOPCon solar cell which comprises an N-type silicon substrate, a boron emitter is arranged on the front surface of the N-type silicon substrate, a front passivation layer and an antireflection layer are arranged on the side face of the boron emitter, and a tunneling oxide layer is arranged on the back surface of the N-type silicon substrate. Hydrogenated lightly-doped polycrystalline silicon and hydrogenated heavily-doped polycrystalline silicon are arranged on the side surface of the tunneling oxide layer, and conductive oxide is arranged between the hydrogenated lightly-doped polycrystalline silicon and the hydrogenated heavily-doped polycrystalline silicon. According to the low parasitic absorption TOPCon solar cell provided by the invention, on the basis of a TOPCon cell, the thickened fluorine-doped tin oxide is used as the second conductive oxide layer by utilizing the transparent and conductive characteristics of the fluorine-doped tin oxide. Inward diffusion of phosphorus atoms can be effectively prevented during annealing, and inward diffusion of metal Ag can be limited during sintering. Thus, the thinned outer layer hydrogenated heavily doped Poly-Si is configured through the thickened fluorine-doped tin oxide, so that parasitic absorption is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of crystalline silicon solar cells, and in particular to a low parasitic absorption TOPCon solar cell and a preparation method thereof. Background Art

[0002] Tunneling oxide passivated contact (TOPCon) cells are a type of solar cell with a back surface passivation structure composed of tunneling oxide and heavily doped polysilicon stacks. TOPCon cells not only have excellent surface passivation and field passivation properties, but also have the function of selective carrier collection, which can effectively reduce the carrier recombination of the cell and improve the conversion efficiency of the solar cell. However, when phosphorus atoms diffuse through the tunneling oxide to the silicon substrate during annealing, they will increase the carrier recombination. In addition, polycrystalline silicon (Poly-Si) has a parasitic absorption effect, which will greatly reduce the short-circuit current of the TOPCon cell and limit the efficiency improvement of the cell. Not only that, in the screen printing process, metal ions diffuse inward during high-temperature sintering, pass through Poly-Si and enter the silicon substrate, which will also increase the metal contact recombination, which will also limit the improvement of cell efficiency.

[0003] Many strategies to improve the efficiency of TOPCon cells are aimed at improving the passivation performance of the cell, reducing the parasitic absorption of Poly-Si and reducing the metal contact recombination. The passivation performance of the cell is optimized by using a stacked tunneling oxide passivation contact structure on the back surface of the TOPCon cell, such as heavily doped polysilicon / tunneling oxide / heavily doped polysilicon / tunneling oxide, heavily doped polysilicon / tunneling oxide / lightly doped polysilicon / tunneling oxide, heavily doped polysilicon / intrinsic polysilicon / tunneling oxide and other stacked passivation structures. The parasitic absorption of Poly-Si is reduced by doping Poly-Si with elements such as C, N, and O, or by reducing the thickness. At present, how to further improve the passivation performance of TOPCon cells, reduce the parasitic absorption of Poly-Si, and reduce the metal contact recombination effect is a challenge faced in the preparation of high-efficiency TOPCon solar cells. Summary of the invention

[0004] The object of the present invention is to provide a low parasitic absorption TOPCon solar cell to solve the above-mentioned deficiencies in the prior art.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A low parasitic absorption TOPCon solar cell comprises an N-type silicon substrate, a boron emitter is arranged on the front surface of the N-type silicon substrate, a front passivation layer and an anti-reflection layer are arranged on the side of the boron emitter, a tunneling oxide layer is arranged on the back surface of the N-type silicon substrate, hydrogenated lightly doped polysilicon and hydrogenated heavily doped polysilicon are arranged on the side of the tunneling oxide layer, a conductive oxide is arranged between the hydrogenated lightly doped polysilicon and the hydrogenated heavily doped polysilicon, a rear passivation layer is arranged on the side of the hydrogenated heavily doped polysilicon, and a metal electrode Ag gate is inserted on the hydrogenated heavily doped polysilicon and the boron emitter.

[0007] Furthermore, the conductive oxide is tin oxide, and has a thickness of 1-15 nanometers.

[0008] Furthermore, the conductive oxide is fluorine-doped tin oxide.

[0009] Furthermore, the thickness of the hydrogenated lightly doped polysilicon is 5-30 nanometers, and the thickness of the hydrogenated heavily doped polysilicon is 10-130 nanometers.

[0010] Furthermore, the tunneling oxide layer is silicon oxide with a thickness of 1.2-2 nanometers, the front passivation layer is aluminum oxide with a thickness of 2-10 nanometers, and the rear passivation layer is hydrogenated silicon nitride with a thickness of 70-90 nanometers.

[0011] Furthermore, the anti-reflection layer is a stack of silicon oxide, silicon oxynitride and silicon nitride, and has a thickness of 60-80 nanometers.

[0012] A method for preparing a low parasitic absorption TOPCon solar cell, using the above-mentioned low parasitic absorption TOPCon solar cell, characterized in that it includes a fluorine-doped tin oxide preparation device, and the steps are as follows:

[0013] S1, N-type silicon substrate pretreatment: including texturing, boron diffusion, BSG removal and alkali polishing process,

[0014] S2, by PECVD, annealing, mask removal and de-wrapping processes, sequentially preparing a first layer and a second layer on the polished surface of the battery, wherein the first layer includes a tunneling oxide layer and a lightly doped polysilicon, and the second layer includes a conductive oxide layer and a heavily doped polysilicon, to form a laminated tunneling oxide passivation contact structure on the back surface of the battery,

[0015] S3, through the subsequent mass production process of TOPCon solar cells, the cells are post-processed, including ALD, front film, back film, and metallization processes to form cells.

[0016] Furthermore, the S1 performs texturing on the N-type silicon substrate to form a pyramid texture surface, and then forms a boron emitter through boron diffusion, and then forms a polished surface on the back surface of the battery through BSG removal and alkaline polishing processes.

[0017] Furthermore, the S3 deposits a front passivation layer on the front surface of the battery by ALD technology; then deposits an anti-reflection layer on the front passivation layer by PECVD technology; then, deposits a rear passivation layer on the back surface of the battery by PECVD technology; and finally forms a metal electrode Ag grid through a metallization process.

[0018] Furthermore, the specific steps of depositing fluorine-doped tin oxide using the PECVD technology in S2 are as follows:

[0019] Turn on the reduction motor, which drives the turbine blades to rotate, so that the mixed gas keeps rotating;

[0020] On the other hand, the intermittent transmission component drives the threaded rod to rotate intermittently, pushing the nitrogen into the reaction box;

[0021] In the process of pushing the nitrogen, the tin source liquid is also pushed into the atomizing nozzle, and the atomized liquid is sprayed out, so that the nitrogen and the atomized liquid enter the reaction box together;

[0022] The atomized liquid entering the reaction box rotates continuously and is evenly filled in the reaction box.

[0023] In the above technical solution, the low parasitic absorption TOPCon solar cell provided by the present invention has the following beneficial effects:

[0024] The present invention provides a low parasitic absorption TOPCon solar cell, comprising an N-type substrate, wherein the front surface of the N-type substrate is provided with a boron emitter, a front passivation layer AlO x layer and front surface SiO x / SiO y N x / SiN x The back surface of the N-type substrate is provided with a first tunneling oxide layer SiO x layer, the first layer of hydrogenated lightly doped polysilicon (n + -Poly-Si:H), the second conductive oxide layer SnO x :F layer, the second layer of hydrogenated heavily doped polysilicon (n ++ -Poly-Si:H) and post-passivation layer hydrogenated silicon nitride (SiN x :H) layer. In addition, metal electrode Ag gates are provided on the front and back surfaces of the battery. Optionally, the second layer of hydrogenated heavily doped polysilicon in the metal contact area can be selectively retained in combination with Poly-finger patterning technology.

[0025] Based on the TOPCon cell, the present invention utilizes the transparent and conductive properties of fluorine-doped tin oxide and uses thickened fluorine-doped tin oxide as the second conductive oxide layer. It can not only effectively hinder the inward diffusion of phosphorus atoms during annealing, but also limit the inward diffusion of metal Ag during sintering. Therefore, the thinned outer layer of hydrogenated heavily doped Poly-Si is configured with thickened fluorine-doped tin oxide to reduce the parasitic absorption of Poly-Si. In addition, when the Poly-finger graphic technology is applied, the thickened fluorine-doped tin oxide can be used as an alkaline etching stop layer to prepare a selectively thinned Poly-Si battery structure, which further plays a role in reducing the parasitic absorption of Poly-Si. Therefore, the present invention uses fluorine-doped tin oxide as the second conductive oxide layer to obtain a TOPCon solar cell with low parasitic absorption while optimizing the passivation performance and reducing metal contact recombination.

[0026] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

[0027] This application document provides an overview of various implementations or examples of the technology described in the present disclosure, and is not a comprehensive disclosure of the entire scope or all features of the disclosed technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0029] Figure 1 A schematic diagram of the cell structure of a low parasitic absorption TOPCon solar cell;

[0030] Figure 2 Schematic diagram of the cell structure of the TOPCon solar cell with low parasitic absorption selective Poly-Si thinning;

[0031] Figure 3 The preparation flow chart of low parasitic absorption TOPCon solar cells;

[0032] Figure 4 Flow chart of the preparation of TOPCon solar cells with selective Poly-Si thinning for low parasitic absorption;

[0033] Figure 5 This is a schematic diagram of the overall external structure of the fluorine-doped tin oxide preparation device of the present invention;

[0034] Figure 6It is a schematic structural diagram of the intermittent transmission components and gas transmission components of the fluorine-doped tin oxide preparation device of the present invention;

[0035] Figure 7 It is a schematic cross-sectional view of the gas delivery box and liquid delivery box of the fluorine-doped tin oxide preparation device of the present invention;

[0036] Figure 8 This is a schematic diagram of the internal structure of the gas delivery box and the liquid delivery box of the fluorine-doped tin oxide preparation device of the present invention;

[0037] Fig. 9 It is a partial structural schematic diagram of the pulling component of the fluorine-doped tin oxide preparation device of the present invention;

[0038] Fig.10 This is a schematic diagram of the overall structure of the pulling component of the fluorine-doped tin oxide preparation device of the present invention.

[0039] Description of reference numerals:

[0040] 1. N-type silicon substrate; 2. Boron emitter; 3. Tunneling oxide layer; 4. Hydrogenated lightly doped polysilicon; 5. Conductive oxide; 6. Hydrogenated heavily doped polysilicon; 7. Pre-passivation layer; 8. Anti-reflection layer; 9. Post-passivation layer; 10. Metal electrode Ag gate; 100. Equipment body; 101. Workbench; 102. Reaction box; 103. Gas supply box; 200. Driving component; 201. Speed ​​reducer; 202. Driving shaft; 300. Intermittent transmission component; 301. Stop wheel; 302. Paddle wheel; 303. Intermittent wheel; 304. Paddle wheel Rod; 305, pulley; 306, transmission belt; 400, gas delivery component; 401, gas delivery box; 402, threaded rod; 403, threaded sleeve; 404, air push plate; 405, gas delivery pipe; 500, infusion component; 501, infusion box; 502, partition; 503, sealing plate; 504, traction rope; 505, infusion pipe; 600, pulling component; 601, rotating frame; 602, fixed frame; 603, hose; 604, first gear; 605, adjusting screw rod; 606, second gear; 607, movable sleeve; 608, collar. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present disclosure clearer, the technical solution of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0042] See also Figure 1-9A low parasitic absorption TOPCon solar cell comprises an N-type silicon substrate 1, a boron emitter 2 is arranged on the front surface of the N-type silicon substrate 1, a front passivation layer 7 and an anti-reflection layer 8 are arranged on the side of the boron emitter 2, a tunneling oxide layer 3 is arranged on the back surface of the N-type silicon substrate 1, a hydrogenated lightly doped polysilicon 4 and a hydrogenated heavily doped polysilicon 6 are arranged on the side of the tunneling oxide layer 3, a conductive oxide 5 is arranged between the hydrogenated lightly doped polysilicon 4 and the hydrogenated heavily doped polysilicon 6, a post passivation layer 9 is arranged on the side of the hydrogenated heavily doped polysilicon 6, and a metal electrode Ag gate 10 is inserted on the hydrogenated heavily doped polysilicon 6 and the boron emitter 2.

[0043] Specifically, the conductive oxide 5 is tin oxide, and the thickness is 1-15 nanometers; the conductive oxide 5 is fluorine-doped tin oxide.

[0044] In an embodiment further provided by the present invention, the thickness of the hydrogenated lightly doped polysilicon 4 is 5-30 nanometers, and the thickness of the hydrogenated heavily doped polysilicon 6 is 10-130 nanometers.

[0045] The tunneling oxide layer 3 is silicon oxide with a thickness of 1.2-2 nanometers, the front passivation layer 7 is aluminum oxide with a thickness of 2-10 nanometers, and the rear passivation layer 9 is hydrogenated silicon nitride with a thickness of 70-90 nanometers.

[0046] The anti-reflection layer 8 is a stack of silicon oxide, silicon oxynitride and silicon nitride, and has a thickness of 60-80 nanometers.

[0047] A method for preparing a low parasitic absorption TOPCon solar cell includes a fluorine-doped tin oxide preparation device, and the steps are as follows:

[0048] S1, N-type silicon substrate 1 pre-treatment, including texturing, boron diffusion, BSG removal and alkaline polishing process, to form the polished surface of the back surface of the battery,

[0049] S2, through PECVD, annealing, mask removal and de-wrapping processes, the first layer and the second layer are sequentially prepared on the polished surface of the back surface of the battery, the first layer includes a tunneling oxide layer 3 and hydrogenated lightly doped polysilicon 4, and the second layer includes a conductive oxide layer 5 and hydrogenated heavily doped polysilicon 6, to form a laminated tunneling oxide passivation contact structure on the back surface of the battery,

[0050] S3, through the subsequent mass production process of TOPCon solar cells, the cells are post-processed, including ALD, front film, back film, and metallization processes to form cells.

[0051] (1) First, according to the existing TOPCon solar cell pre-production process, the N-type silicon substrate 1 is pre-treated, including texturing, boron diffusion, BSG removal and alkaline polishing. First, the N-type silicon substrate 1 is texturized to form a pyramid texture surface, then a boron emitter 2 is formed by boron diffusion, and then a polished surface is formed on the back surface of the cell by BSG removal and alkaline polishing.

[0052] Texturing: The N-type silicon substrate 1 is sequentially subjected to pre-cleaning, water washing, alkali texturing (KOH volume concentration 1%-20%, temperature 40-80°C, texturing additive 1-20L), water washing, post-cleaning, water washing, acid washing (volume concentration 1%-30%), water washing, slow pulling, and drying to remove mechanical damage while forming a pyramid velvet surface;

[0053] Boron diffusion: Boron chloride is used as the boron source to diffuse boron into the N-type silicon wafer after texturing under high temperature conditions, and a PN junction is formed by oxygen-free advancement (temperature 850-950°C), and then the boron advancement is continued under aerobic conditions (temperature 1000-1100°C) to form a deep PN junction and a double-sided BSG at the same time;

[0054] Remove BSG: Clean the equipment with chain hydrofluoric acid (volume concentration 1%-40%) to remove the BSG on the back of the battery and retain the BSG on the front;

[0055] Alkali polishing: After alkali polishing (KOH volume concentration 1%-20%, temperature 40-80°C, alkali polishing additive 1-20L), water washing, post-cleaning, water washing, acid washing (volume concentration 1%-30%), water washing, slow pulling, and drying, the back of the battery is polished to form a polished surface on the back of the battery.

[0056] (2) S2 is processed by PECVD, annealing, mask removal and de-wrapping to sequentially prepare the first tunnel oxide layer 3, the first hydrogenated lightly doped polysilicon 4, the second conductive oxide 5, and the second hydrogenated heavily doped polysilicon 6 on the polished surface of the battery to form the back surface of the battery. ++ -Poly-Si:H / SnO x :F / n + -Poly-Si:H / SiO x The stacked tunnel oxide passivation contact structure. First, the PECVD technology is used for a step-by-step deposition process to deposit the first layer of tunnel oxide 3, the first layer of hydrogenated lightly doped amorphous silicon (n + -a-Si:H), the second conductive oxide 5, the second hydrogenated heavily doped amorphous silicon (n ++ -a-Si:H) and mask layer SiO xThen, an annealing process is performed. Under high temperature conditions, amorphous silicon (a-Si) crystallizes to form Poly-Si, and phosphorus atoms are activated to form N-type Poly-Si. Then, the Poly-Si wrapping on the front of the battery is removed by removing the mask layer and the wrapping process. Finally, the back surface of the battery is formed. ++ -Poly-Si:H / SnO x :F / n + -Poly-Si:H / SiO x Stacked tunnel oxide passivation contact structure.

[0057] PECVD: by using PECVD step-by-step deposition technology, a first layer of tunneling oxide 3, a first layer of hydrogenated lightly doped amorphous silicon, a second layer of conductive oxide 5, a second layer of hydrogenated heavily doped amorphous silicon and a mask layer are sequentially deposited;

[0058] The first tunnel oxide deposition: using nitrous oxide (N2O) as the oxygen source, the first tunnel oxide SiO2 is deposited on the surface of the silicon wafer. x (temperature 200-600°C, pressure 50-200Torr);

[0059] The first layer of hydrogenated lightly doped amorphous silicon is deposited: SiH4 is used as the Si source, PH3 is used as the phosphorus source, and H2 is introduced at the same time to deposit the first layer of n + -a-Si:H (temperature 200-600°C, pressure 100-300 Torr);

[0060] The second conductive oxide deposition: Sn(CH3)4 is used as Sn source, O2 as oxygen source, SF6 or CF4 as F source, and the second conductive oxide SnO is deposited. x :F (temperature 200-600°C, pressure 50-200Torr);

[0061] The second layer of hydrogenated heavily doped amorphous silicon is deposited: SiH4 is used as the Si source, PH3 is used as the phosphorus source (the amount of phosphorus source is 2-5 times that of the first layer of hydrogenated lightly doped amorphous silicon), and H2 is introduced at the same time to deposit the second layer of n ++ -a-Si:H (temperature 200-600°C, pressure 100-300 Torr);

[0062] Mask layer deposition: SiH4 is used as Si source and N2O is used as oxygen source to deposit mask layer SiO x Layer (temperature 200-600°C, pressure 50-200Torr);

[0063] Annealing: Through the annealing process, a-Si is crystallized under high temperature conditions to form Poly-Si, and the phosphorus atoms in Poly-Si are activated to form N-type Poly-Si (temperature 800-1000°C, time 10-100min);

[0064] Mask removal: Clean the equipment with chain hydrofluoric acid (volume concentration 1%-40%) to remove the SiO on the front surface. x mask layer;

[0065] De-wrap plating: remove the front Poly-Si wrapping and the back surface mask layer through alkaline washing (KOH volume concentration 1%-20%, temperature 50-90°C, de-wrap plating additive 1-15L), water washing, post-cleaning, water washing, acid washing, water washing, post-cleaning, water washing, acid washing, water washing, slow pulling and drying.

[0066] (3) Through the subsequent mass production process of TOPCon solar cells, the cells are post-processed, including ALD, front film, back film, metallization process (screen printing, sintering, light injection and laser assisted sintering), to form cells. First, the front passivation layer AlO is deposited on the front surface of the cell by ALD technology. x Layer 7; then PECVD technology is used to deposit the front passivation layer AlO x The front surface SiO is deposited on layer 7. x / SiO y N x / SiN x Then, a post-passivation layer SiN is deposited on the back surface of the cell by PECVD technology. x :H layer 9; finally, a metal electrode Ag gate 10 is formed through a metallization process.

[0067] ALD: ALD technology is used to generate AlO by reacting TMA and water. x The specific process is to pass TMA, purge, pass water vapor, and purge as one cycle, and the cycle is 10-50 times to obtain the front passivation layer AlO x Layer 7 (temperature 200-300°C). TMA is Al(CH3)3;

[0068] Positive film: SiN is deposited on the front passivation layer 7 in sequence using SiH4, N2O and NH3 as source gases through PECVD step-by-step deposition technology. x 、SiO y N x and SiO x Formation of front surface SiO x / SiO y N x / SiN x Laminated anti-reflection layer 8 (temperature 400-500°C, pressure 50-150 Torr);

[0069] Back film: Through PECVD technology, SiH4 and NH3 are used as source gases to deposit the post-passivation layer SiNx :H layer (temperature 400-500°C, pressure 50-150Torr);

[0070] Metallization: A cell with a metal electrode Ag grid 10 is formed by screen printing, sintering, and light injection, and then Ag-Si alloy is formed by laser-assisted sintering technology to improve metal contact performance. Finally, a low parasitic absorption TOPCon solar cell is obtained.

[0071] The main innovation of the present invention is to use SnO x :F as the second conductive oxide layer, using SnO x :F transparent conductive properties, thickened second conductive oxide layer SnO x :F, the battery can still maintain good passivation performance and ohmic contact performance. At the same time, the second layer of hydrogenated heavily doped polysilicon is thinned to reduce the parasitic absorption of Poly-Si and increase the short-circuit current of the battery. During the sintering process, the thicker second conductive oxide layer SnO x :F will block the metal ions from diffusing inwards, thus avoiding the problem of excessive metal contact compounding caused by thinning of Poly-Si. The present invention blocks the metal from diffusing inwards by setting a thicker second conductive oxide layer to match the thinned Poly-Si, effectively reducing parasitic absorption, increasing the short-circuit current of the battery, and thus obtaining a highly efficient TOPCon battery.

[0072] In the embodiment provided by the present invention, based on a low parasitic absorption TOPCon solar cell, the Poly-finger graphic technology is added to improve the cell structure, and another low parasitic absorption selective Poly-Si thinned TOPCon solar cell and its preparation technology are obtained, and the following preparation process is adopted:

[0073] (1) The pre-sequence process of a low parasitic absorption selective Poly-Si thinned TOPCon solar cell is the same as the pre-sequence process of a low parasitic absorption TOPCon solar cell, which will not be repeated.

[0074] (2) Through PECVD, annealing, Poly-finger patterning, mask removal and de-wrapping processes, a first tunneling oxide layer 3, a first hydrogenated lightly doped polysilicon 4, a second conductive oxide layer 5, and a selectively retained second hydrogenated heavily doped polysilicon 6 are sequentially prepared on the polished surface of the battery to form a selective n ++ -Poly-Si / SnO x :F / n + -Poly-Si / SiO xThe stacked tunnel oxide passivation contact structure. First, the PECVD technology is used for a step-by-step deposition process to deposit the first tunnel oxide layer 3, the first hydrogenated lightly doped amorphous silicon, the second conductive oxide layer 5, the second hydrogenated heavily doped amorphous silicon and the mask layer SiO on the polished surface of the battery. x layer; then annealing process, under high temperature conditions, a-Si crystallizes to form Poly-Si, and phosphorus atoms are activated to form N-type Poly-Si; then Poly-finger patterning technology is used to selectively destroy the mask layer in the non-metallic contact area; then the mask layer removal / de-wrap plating process is used to clean and remove the Poly-Si wrap plating on the front of the battery. Finally, the selective n-type back surface of the battery is formed. ++ -Poly-Si:H / SnO x :F / n + -Poly-Si:H / SiO x Stacked tunnel oxide passivation contact structure.

[0075] PECVD: by using PECVD step-by-step deposition technology, a first layer of tunneling oxide 3, a first layer of hydrogenated lightly doped amorphous silicon, a second layer of conductive oxide 5, a second layer of hydrogenated heavily doped amorphous silicon and a mask layer are sequentially deposited;

[0076] The first tunnel oxide deposition: using nitrous oxide (N2O) as the oxygen source, the first tunnel oxide SiO2 is deposited on the surface of the silicon wafer. x (temperature 200-600°C, pressure 50-200Torr);

[0077] The first layer of hydrogenated lightly doped amorphous silicon is deposited: SiH4 is used as the Si source, PH3 is used as the phosphorus source, and H2 is introduced at the same time to deposit the first layer of n + -a-Si:H (temperature 200-600°C, pressure 100-300 Torr);

[0078] The second conductive oxide deposition: Sn(CH3)4 is used as Sn source, O2 as oxygen source, SF6 or CF4 as F source, and the second conductive oxide SnO is deposited. x :F (temperature 200-600°C, pressure 50-200Torr);

[0079] The second layer of hydrogenated heavily doped amorphous silicon is deposited: SiH4 is used as the Si source, PH3 is used as the phosphorus source (the amount of phosphorus source is 2-5 times that of the first layer of lightly doped hydrogenated amorphous silicon), and H2 is introduced at the same time to deposit the second layer of n ++ -a-Si:H (temperature 200-600°C, pressure 100-300 Torr);

[0080] Mask layer deposition: SiH4 is used as Si source and N2O is used as oxygen source to deposit mask layer SiO xLayer (temperature 200-600°C, pressure 50-200Torr);

[0081] Annealing: Through the annealing process, a-Si is crystallized under high temperature conditions to form Poly-Si, and the phosphorus atoms in Poly-Si are activated to form N-type Poly-Si (temperature 800-1000°C, time 10-100min);

[0082] Poly-finger patterning: Poly-finger patterning is performed on the non-metallic contact area on the back surface of the battery using a green picosecond laser (laser power 10-50W). The high energy of the laser destroys the mask layer in the non-metallic contact area, resulting in selective destruction of the mask layer.

[0083] Mask removal: Clean the equipment with chain hydrofluoric acid (volume concentration 1%-40%) to remove the SiO on the front surface. x mask layer;

[0084] De-wrap: Through alkaline washing (KOH volume concentration 1%-20%, temperature 50-90℃, de-wrap plating additive 1-15L), water washing, post-cleaning, water washing, acid washing, water washing, post-cleaning, water washing, acid washing, water washing, slow pulling and drying, the front Poly-Si dewrap is cleaned and removed, and the Poly-Si in the selectively damaged area of ​​the back mask layer is cleaned and removed, and finally the back surface mask layer is removed.

[0085] (3) The subsequent process of a low parasitic absorption selective Poly-Si thinned TOPCon solar cell is the same as the subsequent process of a low parasitic absorption TOPCon solar cell, which will not be repeated. Finally, a low parasitic absorption selective Poly-Si thinned TOPCon solar cell is obtained.

[0086] The low parasitic absorption selective Poly-Si thinned TOPCon solar cell of the present invention is similar to the low parasitic absorption TOPCon solar cell in that both have thickened SnO x :F and thinning the outer layer of Poly-Si, thus also playing a role in reducing metal contact recombination and reducing parasitic absorption. Differently, a TOPCon solar cell with low parasitic absorption selective Poly-Si thinning is combined with Poly-finger graphic technology to thicken SnO x :F acts as an alkaline etching stop layer to form a structure of selective Poly-Si thinning in the non-metallic contact area, further reducing the parasitic absorption of Poly-Si and improving battery efficiency.

[0087] In the solution further provided by the present invention, the specific steps of depositing fluorine-doped tin oxide by PECVD technology in S2 are as follows:

[0088] Turn on the reduction motor 201, which drives the turbine blades to rotate, so that the mixed gas keeps rotating;

[0089] On the other hand, the intermittent transmission component 300 drives the threaded rod 402 to intermittently rotate, pushing the nitrogen into the reaction box 102;

[0090] In the process of pushing the nitrogen, the tin source liquid is also pushed into the atomizing nozzle, and the atomized liquid is sprayed out, so that the nitrogen and the atomized liquid enter the reaction box 102 together;

[0091] The atomized liquid entering the reaction box 102 rotates continuously and is evenly filled in the reaction box 102 .

[0092] The fluorine-doped tin oxide preparation device includes an equipment body 100, which includes a workbench 101, a reaction box 102, a gas supply box 103 and a plasma source. A driving component 200 is arranged on the top of the reaction box 102. The driving component 200 includes a reduction motor 201 fixedly connected to the top of the reaction box 102, and the output end of the reduction motor 201 is fixedly connected to a driving shaft 202. An intermittent transmission component 300 is arranged on the outside of the driving shaft 202.

[0093] A gas delivery component 400 and a liquid delivery component 500 are disposed on the top of the workbench 101 .

[0094] A gas box 401 is fixedly connected to the top of the workbench 101. The interior of the gas box 401 is filled with nitrogen, which acts as an inert gas. The nitrogen is used to dilute the liquid and improve the dispersion of the gas. It can enter the reaction box 102 together with the atomized liquid to help disperse the liquid.

[0095] The inside of the gas box 401 is rotatably connected to a threaded rod 402, the external thread of the threaded rod 402 is connected to a threaded sleeve 403, the inner wall of the gas box 401 is slidably connected to an air pushing plate 404, the threaded sleeve 403 is fixedly connected to the inner wall of the air pushing plate 404, and the side end of the gas box 401 is fixedly connected to an air delivery pipe 405. When the threaded rod 402 rotates, the air pushing plate 404 moves downward, and the air delivery pipe 405 transports nitrogen.

[0096] Specifically, a limit rod is fixedly connected in the air delivery box 401, and a groove is provided on the air push plate 404, through which the air push plate 404 slides on the outer wall of the limit rod. A one-way valve is provided on the air push plate 404, and the threaded rod 402 can be rotated in the reverse direction to lift the air push plate 404 to the highest point.

[0097] An infusion box 501 is provided at the side end of the gas transmission box 401. The interior of the infusion box 501 is filled with tetramethyltin, which is liquid at room temperature. A partition 502 is fixedly connected to the inner wall of the infusion box 501. A pair of sealing plates 503 are fixedly connected to the side wall of the partition 502. A traction rope 504 is fixedly connected to the bottom of one of the sealing plates 503. An infusion tube 505 is fixedly connected to the side end of the gas transmission box 401. The infusion tube 505 is communicated with the gas transmission tube 405.

[0098] As the air push plate 404 descends, the sealing plate 503 is also pulled to move, so that the liquid is transported upward under pressure. An atomizing nozzle is provided inside the air delivery pipe 405 to atomize the liquid, thereby achieving nitrogen delivery with the atomized tetramethyltin. The two are simultaneously delivered to the reaction box 102 in a quantitative ratio to complete the subsequent gas mixing.

[0099] The intermittent transmission component 300 includes a stop wheel 301 and a toggle wheel 302 fixedly sleeved on the outer end of the driving shaft 202, the stop wheel 301 and the toggle wheel 302 fit each other, the top surface of the toggle wheel 302 is fixedly connected with a toggle lever 304, the top surface of the reaction box 102 is rotatably connected with a driven shaft, the outer end of the driven shaft is fixedly sleeved with an intermittent wheel 303, the intermittent wheel 303 is provided with a plurality of evenly distributed arc grooves and movable grooves, and the arc grooves and the movable grooves are spaced apart, when the toggle wheel 302 rotates one circle, it will enter the movable groove through the toggle lever 304, and drive the intermittent wheel 303 to rotate a set angle, for example , there are four arc grooves and movable grooves in the figure, that is, they rotate 90 degrees; pulleys 305 are fixedly sleeved on the driven shaft and the threaded rod 402, and a pair of outer walls of the pulleys 305 are connected with a transmission belt 306 for transmission. When the driven shaft rotates a set angle, the threaded rod 402 also rotates a set angle, so that the push plate 404 can also drop a set distance, pushing the gas out of the gas pipe 405 and into the reaction box 102. As the push plate 404 drops, the sealing plate 503 is also driven to drop, and the liquid is pushed up by air pressure, and atomized liquid is sprayed out from the atomizing nozzle and enters the reaction box 102 together with the gas.

[0100] Thus, the gas delivery and liquid delivery are carried out simultaneously and at intervals, ensuring that the mist liquid and the gas are mixed in the reaction box 102 for a period of time before the gas delivery and liquid delivery are carried out.

[0101] Moreover, since the amount of liquid and gas infusion each time is constant, quantitative proportioning can be carried out according to actual needs to ensure that no excess liquid or gas is wasted. At the same time, since the reaction process is relatively slow, it can be paused at any time according to the reaction effect. The structure is simple and easy to use.

[0102] The outer end of the driving shaft 202 is fixedly connected with a plurality of turbine blades. During the rotation of the turbine blades, the mixed gas can be rotated in a vortex shape, so that the atomized liquid is not easy to settle, and the atomized liquid can continue to rotate in the reaction box 102 and be evenly filled in the reaction box 102, so as to be fully mixed and reacted with the subsequently charged oxygen and fluorine source gas (SF6 or CF4), so that the reaction is more complete.

[0103] A hose 603 is also extended from the end of the gas supply pipe 405, and a pulling component 600 is provided at the bottom of the hose 603. The pulling component 600 is responsible for pulling the hose 603 to move at regular intervals so that the position of the atomized liquid and nitrogen entering the reaction box 102 can be automatically adjusted, so that the atomized liquid can be evenly filled in the reaction box 102, and the dispersion effect is better.

[0104] The pulling component 600 includes a rotating frame 601, which is in the shape of a straight slot. A mounting hole is opened on the rotating frame 601, and the hose 603 is fixedly connected to the mounting hole. The side end of the reaction box 102 is fixedly connected to the fixed frame 602. The rotating frame 601 slides inside the fixed frame 602. During the rotation of the rotating frame 601, the hose 603 can be moved up and down.

[0105] Optionally, a hydraulic rod is provided at the side end of the hose 603 . During the gas transmission process, the hydraulic rod moves slowly, so that the gas inlet position changes slowly, so that the gas is evenly dispersed into the reaction box 102 .

[0106] Optionally, a first gear 604 is also fixedly connected to the driven shaft, and an adjusting screw 605 is rotatably connected to the outside of the reaction box 102. The outer end of the adjusting screw 605 near the top is fixedly sleeved with a second gear 606. The first gear 604 and the second gear 606 have a gear ratio of 1:2-6. The outer end threaded sleeve 403 of the adjusting screw 605 is connected to a movable sleeve 607. The outer end of the movable sleeve 607 is connected to the hose 603 through a collar 608. Therefore, when the driven shaft rotates, it can slowly rotate with the adjusting screw 605 to ensure that the position of the hose 603 can be automatically moved downward without the need for other driving elements.

[0107] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A low parasitic absorption TOPCon solar cell, comprising an N-type silicon substrate (1), a boron emitter (2) being arranged on the front surface of the N-type silicon substrate (1), a front passivation layer (7) and an anti-reflection layer (8) being arranged on the side of the boron emitter (2), a tunneling oxide layer (3) being arranged on the back surface of the N-type silicon substrate (1), hydrogenated lightly doped polysilicon (4) and hydrogenated heavily doped polysilicon (6) being arranged on the side of the tunneling oxide layer (3), a conductive oxide (5) being arranged between the hydrogenated lightly doped polysilicon (4) and the hydrogenated heavily doped polysilicon (6), a rear passivation layer (9) being arranged on the side of the hydrogenated heavily doped polysilicon (6), and a metal electrode Ag gate (10) being inserted on both the hydrogenated heavily doped polysilicon (6) and the boron emitter (2).

2. The low parasitic absorption TOPCon solar cell according to claim 1, wherein the conductive oxide (5) is tin oxide and has a thickness of 1-15 nanometers.

3. The low parasitic absorption TOPCon solar cell according to claim 2, wherein the conductive oxide (5) is fluorine-doped tin oxide.

4. The low parasitic absorption TOPCon solar cell according to claim 3, wherein the hydrogenated lightly doped polysilicon (4) has a thickness of 5-30 nanometers, and the hydrogenated heavily doped polysilicon (6) has a thickness of 10-130 nanometers.

5. According to the low parasitic absorption TOPCon solar cell according to claim 4, the tunneling oxide layer (3) is silicon oxide with a thickness of 1.2-2 nanometers, the front passivation layer (7) is aluminum oxide with a thickness of 2-10 nanometers, and the rear passivation layer (9) is hydrogenated silicon nitride with a thickness of 70-90 nanometers.

6. The low parasitic absorption TOPCon solar cell according to claim 5, wherein the anti-reflection layer (8) is a stack of silicon oxide, silicon oxynitride and silicon nitride, and has a thickness of 60-80 nanometers.

7. A method for preparing a low parasitic absorption TOPCon solar cell, using the low parasitic absorption TOPCon solar cell according to any one of claims 1 to 6, comprising a fluorine-doped tin oxide preparation device, the steps of which are as follows: S1, N-type silicon substrate (1) pre-treatment: including texturing, boron diffusion, BSG removal and alkali polishing process, S2, by PECVD, annealing, mask layer removal and de-wrapping processes, sequentially preparing a first layer and a second layer on the polished surface of the battery, wherein the first layer comprises a tunneling oxide layer (3) and hydrogenated lightly doped polysilicon, and the second layer comprises a conductive oxide (5) and hydrogenated heavily doped polysilicon, to form a stacked tunneling oxide passivation contact structure on the back surface of the battery, S3, through the subsequent mass production process of TOPCon solar cells, the cells are post-processed, including ALD, front film, back film, and metallization processes to form cells.

8. According to the method for preparing a low parasitic absorption TOPCon solar cell according to claim 7, S1 performs texturing on an N-type silicon substrate (1) to form a pyramid texturing surface, then forms a boron emitter (2) by boron diffusion, and then forms a polished surface on the back surface of the cell by removing BSG and alkaline polishing.

9. According to the method for preparing a low parasitic absorption TOPCon solar cell according to claim 7, the S3 deposits a front passivation layer (7) on the front surface of the cell by ALD technology; then deposits an anti-reflection layer (8) on the front passivation layer (7) by PECVD technology; then, deposits a rear passivation layer (9) on the back surface of the cell by PECVD technology; and finally forms a metal electrode Ag grid (10) by a metallization process.

10. The method for preparing a low parasitic absorption TOPCon solar cell according to claim 7, wherein the specific steps of depositing fluorine-doped tin oxide using the PECVD technology in S2 are as follows: The reduction motor (201) is turned on, and the reduction motor (201) drives the turbine blades to rotate, so that the mixed gas is kept in a continuous rotation state; On the other hand, the intermittent transmission component (300) drives the threaded rod (402) to rotate intermittently, pushing the nitrogen into the reaction box (102); In the process of pushing the nitrogen, the tin source liquid is also pushed into the atomizing nozzle, and the atomized liquid is sprayed out, so that the nitrogen and the atomized liquid enter the reaction box (102) together; The atomized liquid entering the reaction box (102) rotates continuously and is evenly filled in the reaction box (102).

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