A low parasitic absorption topcon solar cell and a preparation method thereof

Abstract

The application 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 base, the front surface of the N-type silicon base is provided with a boron emitter, the side surface of the boron emitter is provided with a front-positioned passivation layer and an anti-reflection layer, the back surface of the N-type silicon base is provided with a tunneling oxide layer, the side surface of the tunneling oxide layer is provided with hydrogenated lightly-doped polysilicon and hydrogenated heavily-doped polysilicon, and the hydrogenated lightly-doped polysilicon and the hydrogenated heavily-doped polysilicon are provided with conductive oxide therebetween. The low parasitic absorption TOPCon solar cell provided by the application is based on a TOPCon cell, uses the transparent conductive characteristic of fluorine-doped tin oxide, and uses thickened fluorine-doped tin oxide as a second conductive oxide layer. Not only can the fluorine-doped tin oxide effectively hinder the inward diffusion of phosphorus atoms during annealing, but also can limit the inward diffusion of metal Ag during sintering. Therefore, the thickened fluorine-doped tin oxide is configured with thinned outer hydrogenated heavily-doped Poly-Si to reduce parasitic absorption.

Description

TECHNICAL FIELD

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

[0002] The tunnel oxide passivated contact (TOPCon) cell is a type of solar cell composed of a tunnel oxide and a heavily doped polysilicon stack to form a back surface passivation structure. The TOPCon cell not only has excellent surface passivation performance and field passivation performance, but also has the effect of selective collection of carriers, which can effectively reduce carrier recombination in the cell and improve the conversion efficiency of the solar cell. However, the diffusion of phosphorus atoms through the tunnel oxide to the silicon substrate during annealing increases the carrier recombination. In addition, the polysilicon (Poly-Si) has a parasitic absorption effect, which significantly reduces the short-circuit current of the TOPCon cell and limits the improvement of the cell efficiency. Moreover, during the screen printing process, metal ions diffuse inward during high-temperature sintering and penetrate into the silicon substrate through the Poly-Si, which also increases the metal contact recombination and limits the improvement of the cell efficiency.

[0003] Many strategies for improving the efficiency of the TOPCon cell are aimed at improving the passivation performance of the cell, reducing the parasitic absorption of the Poly-Si, and reducing the metal contact recombination. By using a stacked tunnel oxide passivation contact structure on the back surface of the TOPCon cell, the passivation performance of the cell can be optimized, such as: heavily doped polysilicon / tunnel oxide / heavily doped polysilicon / tunnel oxide, heavily doped polysilicon / tunnel oxide / lightly doped polysilicon / tunnel oxide, and heavily doped polysilicon / intrinsic polysilicon / tunnel oxide. By doping C, N, O, etc. in the Poly-Si, or reducing the thickness of the Poly-Si, the parasitic absorption of the Poly-Si can be reduced. Currently, how to further improve the passivation performance of the TOPCon cell, reduce the parasitic absorption of the Poly-Si, and reduce the effect of metal contact recombination is a challenge in the preparation of high-efficiency TOPCon solar cells. SUMMARY

[0004] The purpose of the present application is to provide a low parasitic absorption TOPCon solar cell to solve the above problems in the prior art.

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

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

[0007] Further, the conductive oxide is tin oxide, and the thickness is 1-15 nanometers.

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

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

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

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

[0012] A preparation method of a low parasitic absorption TOPCon solar cell, using the above low parasitic absorption TOPCon solar cell, characterized in that it comprises 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 etching process,

[0014] S2, through PECVD, annealing, mask layer removal and plating removal process, a first layer and a second layer are prepared on the polished surface of the cell in sequence, the first layer comprises a tunneling oxide layer and a lightly doped polysilicon, the second layer comprises a conductive oxide layer and a heavily doped polysilicon, and a cell back surface stack tunneling oxide passivation contact structure is formed,

[0015] S3, through the subsequent mass production process of the TOPCon solar cell, the cell is post-treated, including ALD, front film, back film, metallization process, and the cell is formed.

[0016] Further, the S1 performs texturing on the N-type silicon substrate to form a pyramid textured surface, then forms a boron emitter through boron diffusion, and then forms a polished surface on the back surface of the cell through BSG removal and alkali etching process.

[0017] Further, the S3 deposits a front passivation layer on the front surface of the battery by ALD technology; then deposits a reflection-reducing 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] Further, the specific steps of the PECVD technology in the S2 for depositing fluorine-doped tin oxide are as follows,

[0019] The speed reducer is started, and the speed reducer rotates with the turbine blade, so that the mixed gas is kept in a continuous rotating state.

[0020] On the other hand, the threaded rod is intermittently rotated through the intermittent transmission component, so that the nitrogen gas is pushed into the reaction box.

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

[0022] The atomized liquid in the reaction box is continuously rotated and uniformly filled in the reaction box.

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

[0024] The application provides a low parasitic absorption TOPCon solar cell, which comprises an N-type substrate, and the front surface of the N-type substrate is sequentially provided, from inside to outside, with a boron emitter, a front passivation layer AlO x layer, a front surface SiO x / SiO y N x / SiN x stacked reflection-reducing layer. The back surface of the N-type substrate is sequentially provided, from inside to outside, with a first layer of tunneling oxide layer SiO x layer, a first layer of hydrogenated lightly doped polysilicon (n + -Poly-Si:H), a second layer of conductive oxide layer SnO x :F layer, a second layer of hydrogenated heavily doped polysilicon (n ++ -Poly-Si:H) and a rear passivation layer of hydrogenated silicon nitride (SiN x :H) layer. Additionally, the front surface and the back surface of the battery are both provided with a metal electrode Ag grid. Optionally, the second layer of hydrogenated heavily doped polysilicon of the metal contact area can be selectively reserved by combining the Poly-finger patterning technology.

[0025] The present application is based on the TOPCon cell, using the transparent conductive characteristics of fluorine-doped tin oxide, and using thick fluorine-doped tin oxide as the second layer of conductive oxide layer. Not only can it effectively hinder the inward diffusion of phosphorus atoms during annealing, but also can limit the inward diffusion of metal Ag during sintering. Therefore, by configuring a thick fluorine-doped tin oxide with a thin outer layer of hydrogenated heavily doped Poly-Si, the parasitic absorption of Poly-Si can be reduced. In addition, when applying the Poly-finger patterning technology, the thick fluorine-doped tin oxide can be used as an alkali etching stop layer to prepare a selective Poly-Si thinned battery structure, which further reduces the parasitic absorption of Poly-Si. Therefore, the present application uses fluorine-doped tin oxide as the second layer of conductive oxide layer, which optimizes the passivation performance and reduces the metal contact recombination, and obtains a low parasitic absorption TOPCon solar cell.

[0026] It should be understood that the foregoing general description and the following detailed description are merely exemplary and explanatory, and are not intended to limit the present disclosure.

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

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0029] Figure 1 It is a battery structure schematic diagram of a low parasitic absorption TOPCon solar cell.

[0030] Figure 2 It is a battery structure schematic diagram of a low parasitic absorption TOPCon solar cell with selective Poly-Si thinning.

[0031] Figure 3 It is a preparation flow chart of a low parasitic absorption TOPCon solar cell.

[0032] Figure 4 It is a preparation flow chart of a low parasitic absorption TOPCon solar cell with selective Poly-Si thinning.

[0033] Figure 5 It is a schematic diagram of the overall external structure of the fluorine-doped tin oxide preparation device of the present application.

[0034] Figure 6The intermittent transmission part and the gas conveying part structure schematic view of the fluorine-doped tin oxide preparation device of the present application;

[0035] Figure 7 The gas conveying tank and the liquid conveying tank section structure schematic view of the fluorine-doped tin oxide preparation device of the present application;

[0036] Figure 8 The gas conveying tank and the liquid conveying tank internal structure schematic view of the fluorine-doped tin oxide preparation device of the present application;

[0037] Figure 9 The pulling part partial structure schematic view of the fluorine-doped tin oxide preparation device of the present application;

[0038] Figure 10 The pulling part overall structure schematic view of the fluorine-doped tin oxide preparation device of the present application.

[0039] Mark explanation:

[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, front passivation layer; 8, anti-reflection layer; 9, rear passivation layer; 10, metal electrode Ag gate; 100, equipment body; 101, workbench; 102, reaction box; 103, gas supply tank; 200, driving part; 201, speed reducer motor; 202, driving shaft; 300, intermittent transmission part; 301, rotation stopping wheel; 302, pushing wheel; 303, intermittent wheel; 304, pushing rod; 305, pulley; 306, transmission belt; 400, gas conveying part; 401, gas conveying tank; 402, threaded rod; 403, threaded sleeve; 404, gas pushing plate; 405, gas conveying pipe; 500, liquid conveying part; 501, liquid conveying tank; 502, partition plate; 503, sealing plate; 504, traction rope; 505, liquid conveying pipe; 600, pulling part; 601, rotating frame; 602, fixed frame; 603, hose; 604, first gear; 605, adjusting screw; 606, second gear; 607, moving sleeve; 608, collar. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical scheme and advantages of the embodiments of the present disclosure clearer, the technical scheme of the embodiments of the present disclosure will be described clearly and completely 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, rather than all the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by a person of ordinary skill in the art without any inventive effort fall within the protection scope of the present disclosure.

[0042] Please refer to Figures 1-9The low parasitic absorption TOPCon solar cell comprises an N-type silicon base 1, a boron emitter 2 arranged on the front surface of the N-type silicon base 1, a front passivation layer 7 and an anti-reflection layer 8 arranged on the side surface of the boron emitter 2, a tunneling oxide layer 3 arranged on the back surface of the N-type silicon base 1, a hydrogenated lightly doped polysilicon 4 and a hydrogenated heavily doped polysilicon 6 arranged on the side surface of the tunneling oxide layer 3, a conductive oxide 5 arranged between the hydrogenated lightly doped polysilicon 4 and the hydrogenated heavily doped polysilicon 6, a rear passivation layer 9 arranged on the side surface of the hydrogenated heavily doped polysilicon 6, and a metal electrode Ag gate 10 arranged on the hydrogenated lightly doped polysilicon 4 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 the further provided embodiment of the application, 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, the thickness is 1.2-2 nanometers, the front passivation layer 7 is aluminum oxide, the thickness is 2-10 nanometers, and the rear passivation layer 9 is hydrogenated silicon nitride, the thickness is 70-90 nanometers.

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

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

[0048] S1, N-type silicon base 1 pretreatment, including texturing, boron diffusion, BSG removal and alkali etching processes, to form a polished surface on the back surface of the cell,

[0049] S2, through PECVD, annealing, mask layer removal and plating processes, a first layer and a second layer are sequentially prepared on the polished surface of the back surface of the cell, the first layer comprises a tunneling oxide layer 3 and a hydrogenated lightly doped polysilicon 4, the second layer comprises a conductive oxide layer 5 and a hydrogenated heavily doped polysilicon 6, and a back surface stack tunneling oxide passivation contact structure of the cell is formed,

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

[0051] (1) Firstly, according to the existing TOPCon solar cell pre-production process, the N-type silicon substrate 1 is pretreated, including texturing, boron diffusion, BSG removal and alkali polishing process. Firstly, the N-type silicon substrate 1 is textured to form a pyramid texture, 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 alkali polishing process.

[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℃, texturing additive 1-20L), water washing, post-cleaning, water washing, acid washing (volume concentration 1%-30%), water washing, slow lifting and drying, to remove mechanical damage and form a pyramid texture;

[0053] Boron diffusion: using boron chloride as boron source, the N-type silicon wafer after texturing is subjected to boron diffusion under high temperature conditions, to form P-N junction by oxygen-free promotion (temperature 850-950℃), and then continue boron promotion under oxygen condition (temperature 1000-1100℃), to form P-N junction deep junction and simultaneously form double-sided BSG;

[0054] BSG removal: through chain hydrofluoric acid (volume concentration 1%-40%) cleaning equipment, the BSG on the back surface of the cell is removed, and the BSG on the front surface is retained;

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

[0056] (2) S2 is prepared by PECVD, annealing, mask layer removal and plating process, to sequentially form a first layer of tunneling oxide layer 3, a first layer of hydrogenated lightly doped polysilicon 4, a second layer of conductive oxide 5 and a second layer of hydrogenated heavily doped polysilicon 6 on the polished surface of the cell, to form an n ++ -Poly-Si:H / SnO x :F / n + -Poly-Si:H / SiO x stacked tunneling oxide passivation contact structure. Firstly, a step-by-step deposition process is carried out by PECVD technology, to sequentially deposit a first layer of tunneling oxide 3, a first layer of hydrogenated lightly doped amorphous silicon (n + -a-Si:H), a second layer of conductive oxide 5, a second layer of hydrogenated heavily doped amorphous silicon (n ++ -a-Si:H) and a mask layer SiO xlayer; then annealing process, amorphous silicon (a-Si) is crystallized to form Poly-Si under high temperature condition, and phosphorus atoms are activated to form N-type Poly-Si; then through the process of removing mask layer and stripping, the Poly-Si strip on the front surface of the cell is removed. Finally, the back surface n ++ -Poly-Si:H / SnO x :F / n + -Poly-Si:H / SiO x stacked tunnel oxide passivation contact structure.

[0057] PECVD: through PECVD step-by-step deposition technology, the first layer of tunnel oxide 3, the first layer of hydrogenated lightly doped amorphous silicon, the second layer of conductive oxide 5, the second layer of hydrogenated heavily doped amorphous silicon and the mask layer are deposited in turn;

[0058] Deposition of the first layer of tunnel oxide: with nitrous oxide (N2O) as the oxygen source, the first layer of tunnel oxide SiO x (temperature 200-600℃, pressure 50-200Torr);

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

[0060] Deposition of the second layer of conductive oxide: with Sn(CH3)4 as the Sn source, O2 as the oxygen source and SF6 or CF4 as the F source to deposit the second layer of conductive oxide SnO x :F (temperature 200-600℃, pressure 50-200Torr);

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

[0062] Deposition of the mask layer: with SiH4 as the Si source and N2O as the oxygen source to deposit the mask layer SiO x layer (temperature 200-600℃, pressure 50-200Torr);

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

[0064] Mask layer removal: The SiO2 on the previous surface is removed by cleaning with a chain-type hydrofluoric acid (volume concentration 1%-40%) cleaning device. x Mask layer;

[0065] Remove the poly-Si coating: The process involves alkaline washing (KOH volume concentration 1%-20%, temperature 50-90℃, poly-Si coating remover additive 1-15L), water washing, post-cleaning, water washing, acid washing, water washing, post-cleaning, water washing, acid washing, water washing, slow lifting, and drying to remove the poly-Si coating on the front side and the mask layer on the back surface.

[0066] (3) The cells are post-processed using the subsequent mass production process of TOPCon solar cells, including ALD, front film, back film, and metallization processes (screen printing, sintering, light injection, and laser-assisted sintering) to form the cells. First, a pre-passivation layer AlO is deposited on the front surface of the cell using ALD technology. x Layer 7; then, the AlO2 passivation layer is applied using PECVD technology. x SiO2 deposited on the surface above layer 7 x / SiO y N x / SiN x A stacked antireflection layer 8 is formed; then, a post-passivation layer SiN is deposited on the back surface of the battery using PECVD technology. x H layer 9; finally, a metal electrode Ag gate 10 is formed through a metallization process.

[0067] ALD: AlO is generated by reacting TMA and water using ALD technology. x The specific process involves a cycle of TMA flow, purging, steam flow, and purging, repeated 10-50 times to obtain the pre-passivation layer AlO. x Layer 7 (temperature 200-300℃). TMA is Al(CH3)3.

[0068] Positive film: SiN was deposited sequentially on the pre-passivation layer 7 using SiH4, N2O and NH3 as source gases via PECVD stepwise deposition technology. x SiO y N x and SiO x Formation of surface SiO x / SiO y N x / SiN x Layered antireflective layer 8 (temperature 400-500℃, pressure 50-150 Torr);

[0069] Backsheet: A passivation layer of SiN was deposited using PECVD technology with SiH4 and NH3 as source gases.x :H layer (temperature 400-500℃, pressure 50-150 Torr);

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

[0071] The main innovation of the present application is to use SnO x :F as the second layer of conductive oxide layer, and use the transparent conductive property of SnO x :F, thicken the second layer of conductive oxide layer SnO x :F, and 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 improve the short-circuit current of the battery. In the sintering process, the thicker second layer of conductive oxide layer SnO x :F will block the inward diffusion of metal ions, thereby avoiding the problem of excessive metal contact recombination caused by the thinning of Poly-Si. By setting a thicker second layer of conductive oxide layer, the present application blocks the inward diffusion of metal to match the thinned Poly-Si, effectively reduces parasitic absorption, improves the short-circuit current of the battery, and thus obtains a high-efficiency TOPCon battery.

[0072] The present application provides a low parasitic absorption TOPCon solar cell, and a preparation technology thereof. The preparation process is as follows:

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

[0074] (2) Through PECVD, annealing, Poly-finger patterning, removing the mask layer and plating process, a first layer of tunneling oxide layer 3, a first layer of hydrogenated lightly doped polysilicon 4, a second layer of conductive oxide layer 5, a selectively retained second layer of hydrogenated heavily doped polysilicon 6 are sequentially prepared on the polished surface of the battery to form a battery back surface selective n ++ -Poly-Si / SnO x :F / n + -Poly-Si / SiO xStacked tunnel oxide passivation contact structure. First, a step-by-step deposition process is performed by PECVD technology, sequentially depositing a first layer of tunnel 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 SiO x Next, an annealing process is performed, under high temperature conditions, to crystallize the a-Si into Poly-Si, and to activate the phosphorus atoms to form N-type Poly-Si. Then, a Poly-finger patterning technique is used to selectively destroy the mask layer in the non-metallic contact area. Subsequently, a de-mask / strip process is performed to clean and remove the Poly-Si strip on the front surface of the cell. Finally, a stacked tunnel oxide passivation contact structure is formed on the back surface of the cell, with the structure being n ++ -Poly-Si:H / SnO x :F / n + -Poly-Si:H / SiO x Stacked tunnel oxide passivation contact structure.

[0075] PECVD: A step-by-step deposition process is performed by PECVD technology, sequentially depositing a first layer of tunnel 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;

[0076] First layer of tunnel oxide deposition: Using nitrous oxide (N2O) as the oxygen source, a first layer of tunnel oxide SiO x (temperature 200-600°C, pressure 50-200 Torr);

[0077] First layer of hydrogenated lightly doped amorphous silicon deposition: Using SiH4 as the Si source and PH3 as the phosphorus source, while introducing H2, a first layer of n + -a-Si:H (temperature 200-600°C, pressure 100-300 Torr);

[0078] Second layer of conductive oxide deposition: Using Sn(CH3)4 as the Sn source, O2 as the oxygen source, and SF6 or CF4 as the F source, a second layer of conductive oxide SnO x :F (temperature 200-600°C, pressure 50-200 Torr);

[0079] Second layer of hydrogenated heavily doped amorphous silicon deposition: Using SiH4 as the Si source and PH3 as the phosphorus source (the amount of phosphorus source is 2-5 times that of the first layer of lightly doped hydrogenated amorphous silicon), while introducing H2, a second layer of n ++ -a-Si:H (temperature 200-600°C, pressure 100-300 Torr);

[0080] Mask layer deposition: Using SiH4 as the Si source and N2O as the oxygen source, a mask layer SiO xLayer (temperature 200-600℃, pressure 50-200Torr);

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

[0082] Poly-finger patterning: Through a green light picosecond laser (laser power 10-50W), Poly-finger patterning is performed on the non-metal contact area of the back surface of the cell. The high energy of the laser destroys the mask layer in the non-metal contact area, forming a selective destruction of the mask layer;

[0083] Remove the mask layer: Clean the equipment with chain hydrogen fluoride (volume concentration 1%-40%) to clean the SiO x Mask layer;

[0084] Remove the winding: Through alkaline washing (KOH volume concentration 1%-20%, temperature 50-90℃, winding plating additive 1-15L), water washing, post-cleaning, water washing, acid washing, water washing, post-cleaning, water washing, acid washing, water washing, slow lifting, and drying, the winding of the front Poly-Si is cleaned and removed, and at the same time, the Poly-Si in the selective destruction area of the back mask layer is cleaned and removed. Finally, the mask layer on the back surface is removed.

[0085] (3) A low parasitic absorption selective Poly-Si thinned TOPCon solar cell and a low parasitic absorption TOPCon solar cell are the same, and 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 application and the low parasitic absorption TOPCon solar cell are the same, both have the setting of thickening SnO x :F and thinning the outer Poly-Si, thus also playing a role in reducing metal contact recombination and reducing parasitic absorption. The difference is that the low parasitic absorption selective Poly-Si thinned TOPCon solar cell combines Poly-finger patterning technology to form a non-metal contact area selective Poly-Si thinned structure with thickened SnO x :F as an alkaline etching stop layer, further reducing the parasitic absorption of Poly-Si and improving the efficiency of the cell.

[0087] In the further provided scheme of the present application, the specific steps of the PECVD technology for depositing fluorine-doped tin oxide in S2 are as follows,

[0088] The reduction motor 201 is started, and the reduction motor 201 rotates the turbine blade, so that the mixed gas is kept in a continuous rotating state.

[0089] On the other hand, the reduction motor 201 rotates the turbine blade through the intermittent transmission component 300, so that the threaded rod 402 is intermittently rotated, and nitrogen gas is pushed into the reaction box 102.

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

[0091] The atomized liquid in the reaction box 102 is continuously rotated and uniformly filled in the reaction box 102.

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

[0093] The top of the workbench 101 is provided with a gas conveying component 400 and a liquid conveying component 500.

[0094] The top of the workbench 101 is fixedly connected with a gas conveying box 401, the inside of the gas conveying box 401 is filled with nitrogen gas, which acts as an inert gas, and the nitrogen gas is used for diluting the liquid and improving the dispersibility of the gas, and can enter the reaction box 102 together with the atomized liquid to help the liquid to be dispersed.

[0095] The inside of the gas conveying box 401 is rotatably connected with a threaded rod 402, the outside of the threaded rod 402 is threadedly connected with a threaded sleeve 403, the inner wall of the gas conveying box 401 is slidably connected with a gas pushing plate 404, the threaded sleeve 403 is fixedly connected to the inner wall of the gas pushing plate 404, and the side end of the gas conveying box 401 is fixedly connected with a gas conveying pipe 405.

[0096] Specifically, a limiting rod is fixedly connected in the gas conveying box 401, a groove is formed in the gas pushing plate 404, and the gas pushing plate 404 slides on the outer wall of the limiting rod through the groove. The gas pushing plate 404 is provided with a one-way valve, and the threaded rod 402 can be reversely rotated subsequently, so that the gas pushing plate 404 is lifted to the highest position.

[0097] The side end of the gas conveying box 401 is provided with a liquid conveying box 501, the inside of the liquid conveying box 501 is filled with tetramethyl tin which is liquid at room temperature, the inner wall of the liquid conveying box 501 is fixedly connected with a partition plate 502, the side wall of the partition plate 502 is fixedly connected with a pair of sealing plates 503, the bottom of one of the sealing plates 503 is fixedly connected with a traction rope 504, the side end of the gas conveying box 401 is fixedly connected with a liquid conveying pipe 505, and the liquid conveying pipe 505 and the gas conveying pipe 405 are in communication with each other.

[0098] During the descending process of the gas pushing plate 404, the sealing plate 503 is also pulled to move, so that the liquid is upwardly conveyed under pressure, the inside of the gas conveying pipe 405 is provided with an atomizing nozzle, the liquid can be atomized, so that the nitrogen gas conveying process is realized, the atomized tetramethyl tin moves, and the two are simultaneously quantitatively conveyed into the reaction box 102 according to a proportion, and the subsequent gas mixing is completed.

[0099] The intermittent transmission component 300 comprises a rotation-stopping wheel 301 and a pushing wheel 302 which are fixedly sleeved on the outer end of the driving shaft 202, the rotation-stopping wheel 301 and the pushing wheel 302 are in close contact with each other, the top surface of the pushing wheel 302 is fixedly connected with a pushing rod 304, the top surface of the reaction box 102 is rotationally connected with a driven shaft, the outer end of the driven shaft is fixedly sleeved with an intermittent wheel 303, a plurality of arc-shaped grooves and movable grooves which are uniformly distributed are formed in the intermittent wheel 303, and the arc-shaped grooves and the movable grooves are spaced apart, when the pushing wheel 302 rotates one circle, the pushing rod 304 enters the movable groove, the intermittent wheel 303 is driven to rotate a set angle, for example, there are four arc-shaped grooves and movable grooves in the drawing, that is, the rotation-stopping wheel 301 rotates 90 degrees; the driven shaft and the threaded rod 402 are both fixedly sleeved with a belt wheel 305, the outer walls of a pair of belt wheels 305 are in transmission connection with a transmission belt 306, when the driven shaft rotates a set angle, the threaded rod 402 also rotates a set angle, so that the gas pushing plate 404 can also descend a set distance, the gas is pushed out from the gas conveying pipe 405 into the reaction box 102, and because the gas pushing plate 404 descends, the sealing plate 503 also descends, the liquid is pushed upward by the gas pressure, the atomized liquid is sprayed from the atomizing nozzle, and enters the reaction box 102 together with the gas.

[0100] Therefore, the gas conveying and liquid conveying are kept to be simultaneously and intermittently carried out, and the mist liquid and the gas are kept to be linearly mixed in the reaction box 102 for a period of time before the gas conveying and liquid conveying are carried out again.

[0101] Furthermore, because the amount of liquid conveying and gas conveying is constant each time, the actual demand can be quantitatively matched, so that the liquid or gas is not wasted, and because the reaction process is relatively gentle, the reaction effect can be paused at any time, the structure is simple and convenient to use.

[0102] The outer end of the driving shaft 202 is fixedly connected with a plurality of turbine blades, in the rotating process of the turbine blades, the mixed gas can be rotated in the form of vortex, so that the atomized liquid is not easy to settle, the atomized liquid continuously rotates in the reaction box 102, is uniformly filled in the reaction box 102, and is convenient for fully mixing and reacting with the subsequent filled oxygen and fluorine source gas (SF6 or CF4), so that the reaction is more sufficient.

[0103] The end of the gas conveying pipe 405 is also provided with a hose 603, the bottom of the hose 603 is provided with a pulling component 600, the pulling component 600 is responsible for pulling the hose 603 to move every certain period of time, 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 uniformly filled in the reaction box 102, and the dispersion effect is better.

[0104] The pulling component 600 comprises a rotating frame 601, the rotating frame 601 is in the shape of a straight slot, the rotating frame 601 is provided with a mounting hole, the hose 603 is fixedly connected to the mounting hole, the side end of the reaction box 102 is fixedly connected with a fixed frame 602, the rotating frame 601 slides in the inside of the fixed frame 602, and in the rotating process of the rotating frame 601, the hose 603 can move up and down.

[0105] Optionally, the side end of the hose 603 is provided with a hydraulic rod, the hydraulic rod slowly moves in the process of conveying gas, so that the gas inlet position slowly changes, and the gas is uniformly dispersed into the reaction box 102.

[0106] Optionally, the driven shaft is also fixedly connected with a first gear 604, the outside of the reaction box 102 is rotatably connected with an adjusting lead screw 605, the outside of the adjusting lead screw 605 close to 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 outside of the adjusting lead screw 605 is threadedly sleeved with a moving sleeve 607, and the outside of the moving sleeve 607 is connected with the hose 603 through a sleeve ring 608, so that when the driven shaft rotates, the adjusting lead screw 605 can slowly rotate, and the position of the hose 603 can be automatically lowered without other driving elements.

[0107] The above only describes certain exemplary embodiments of the application in a descriptive manner, without doubt, for ordinary skilled in the art, the described embodiments can be modified in various ways without departing from the spirit and scope of the application. Therefore, the above drawings and descriptions are illustrative in nature and should not be understood as limiting the scope of protection of the claims of the application.

Claims

1. A low parasitic absorption TOPCon solar cell, comprising an N-type silicon substrate (1), a boron emitter (2) disposed on the front surface of the N-type silicon substrate (1), a front passivation layer (7) and an anti-reflection layer (8) disposed on the side of the boron emitter (2), a tunneling oxide layer (3) disposed on the back surface of the N-type silicon substrate (1), hydrogenated lightly doped polycrystalline silicon (4) and hydrogenated heavily doped polycrystalline silicon (6) disposed on the side of the tunneling oxide layer (3), a conductive oxide (5) disposed between the hydrogenated lightly doped polycrystalline silicon (4) and the hydrogenated heavily doped polycrystalline silicon (6), a rear passivation layer (9) disposed on the side of the hydrogenated heavily doped polycrystalline silicon (6), and metal electrode Ag gates (10) inserted on both the hydrogenated heavily doped polycrystalline silicon (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 with a thickness of 1-15 nanometers.

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

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

5. The low parasitic absorption TOPCon solar cell according to claim 4, wherein 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 silicon nitride with a thickness of 70-90 nanometers.

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

7. A method for fabricating a low parasitic absorption TOPCon solar cell, using the low parasitic absorption TOPCon solar cell described in any one of claims 1-6, comprising a fluorine-doped tin oxide fabrication apparatus, the steps of which are as follows: S1, N-type silicon substrate (1) pretreatment: including texturing, boron diffusion, BSG removal and alkaline polishing processes. S2, through PECVD, annealing, mask removal and decoating processes, a first layer and a second layer are sequentially prepared on the polished surface of the battery. The first layer includes a tunneling oxide layer (3) and hydrogenated lightly doped polycrystalline silicon, and the second layer includes a conductive oxide layer (5) and hydrogenated heavily doped polycrystalline silicon, forming a stacked tunneling oxide passivation contact structure on the back surface of the battery. S3 involves post-processing of the cells using the subsequent mass production process of TOPCon solar cells, including ALD, positive film, back film, and metallization processes, to form the cells.

8. The method for preparing a low parasitic absorption TOPCon solar cell according to claim 7, wherein S1 texturizes the N-type silicon substrate (1) to form a pyramid textured surface, then forms a boron emitter (2) through boron diffusion, and then forms a polished surface on the back surface of the cell through BSG removal and alkaline polishing processes.

9. The method for preparing a low parasitic absorption TOPCon solar cell according to claim 7, wherein in step S3 a pre-passivation layer (7) is deposited on the front surface of the cell by ALD technology; then an anti-reflection layer (8) is deposited on the pre-passivation layer (7) by PECVD technology; then a post-passivation layer (9) is deposited on the back surface of the cell by PECVD technology; and finally a metal electrode Ag gate (10) is formed by a metallization process.

10. The method for fabricating a low parasitic absorption TOPCon solar cell according to claim 7, wherein the specific steps of depositing fluorine-doped tin oxide using PECVD technology in step S2 are as follows: Turn on the geared motor (201), and the geared motor (201) will drive the turbine blade to rotate, so that the gas mixture will keep rotating continuously. On the other hand, the intermittent transmission component (300) drives the threaded rod (402) to rotate intermittently, pushing nitrogen into the reaction chamber (102); During the process of pushing nitrogen gas, tin source liquid is also pushed into the atomizing nozzle to spray out atomized liquid, so that nitrogen gas and atomized liquid enter the reaction chamber (102) together; The atomized liquid entering the reaction chamber (102) rotates continuously and fills the reaction chamber (102) evenly.

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