Polyfinger battery with high conductivity and preparation process

Abstract

The invention discloses a Polyfinger battery with high conductivity and a preparation process, the Polyfinger battery with high conductivity comprises a back surface structure, the back surface structure comprises a first Polyfinger structure, a second Polyfinger structure and a groove structure, the first Polyfinger structure comprises a plurality of main grids and a plurality of auxiliary grids, the second Polyfinger structure comprises a plurality of auxiliary auxiliary grids, the groove structure comprises a plurality of first conductive layers, a plurality of second conductive layers and a plurality of second conductive layers, and the first conductive layers are arranged on the back surface structure. The first Polyfinger structure and the second Polyfinger structure are connected with each other, a plurality of auxiliary grids are arranged between the plurality of auxiliary grids and the plurality of main grids, no electrode is printed on the second Polyfinger structure, the auxiliary grids are vertical to the auxiliary grids, and the auxiliary grids are 11-30 microns. The conductive performance of the cell is improved, the waste of light energy is reduced, and the conductive efficiency is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cell production, and particularly relates to a Polyfinger battery with high conductivity and a preparation process thereof. Background Art

[0002] TOPCon, full name Tunnel Oxide Passivating Contact, that is, tunneling oxide layer passivated contact, is an N-type silicon wafer battery technology that has attracted much attention since its birth in 2013. It uses N-type silicon as the substrate and realizes passivated contact through tunneling oxide layer materials, thereby improving the performance of solar cells.

[0003] Since TOPCon batteries generate electricity by light, but in the process of absorbing light, part of the light will be absorbed by the polysilicon layer and turned into heat, thus causing waste of light energy and current. And in the process of transporting current, part of the current cannot reach the polysilicon layer, thus resulting in a decrease in conductivity.

[0004] Therefore, in view of the above technical problems, it is necessary to provide a Polyfinger battery with high conductivity and a preparation process thereof.

[0005] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0006] The purpose of the present invention is to provide a Polyfinger battery with high conductivity and a preparation process thereof, which can solve the above problems.

[0007] In order to achieve the above purpose, the technical solution provided by a specific embodiment of the present invention is as follows: A Polyfinger battery with high conductivity includes single crystal silicon and a back structure. The back structure includes a first Polyfinger structure, a second Polyfinger structure and a groove structure. The first Polyfinger structure includes a plurality of main grids and a plurality of sub-grids. The second Polyfinger structure includes a plurality of auxiliary sub-grids. The first Polyfinger structure and the second Polyfinger structure are connected to each other, and a plurality of auxiliary sub-grids are arranged between the plurality of sub-grids and the plurality of main grids; Wherein, no electrode is printed on the second Polyfinger structure, and the auxiliary sub-grids are perpendicular to the sub-grids.

[0008] In one or more embodiments of the present invention, the auxiliary sub-grids are 11 - 30 microns.

[0009] In one or more embodiments of the present invention, a plurality of auxiliary sub-gates are provided per 100 microns on average between the sub-gate and the main gate.

[0010] In one or more embodiments of the present invention, the width of the auxiliary sub-gate is smaller than that of the sub-gate.

[0011] In one or more embodiments of the present invention, the first Polyfinger structure is connected with an electrode.

[0012] In one or more embodiments of the present invention, the first Polyfinger structure includes a tunneling oxide layer, a polysilicon layer, an alumina layer, a silicon nitride layer and an electrode, and the second Polyfinger structure includes a tunneling oxide layer, a polysilicon layer, an alumina layer and a silicon nitride layer.

[0013] In one or more embodiments of the present invention, a boron-doped single-crystalline silicon, a first alumina layer and a first silicon nitride layer are sequentially deposited on the top end face of the single-crystalline silicon, a tunneling oxide layer, a polysilicon layer, a second alumina layer and a second silicon nitride layer are sequentially deposited on the bottom end face of the single-crystalline silicon, a first electrode is printed on each of the boron-doped single-crystalline silicon, the first alumina layer and the first silicon nitride layer, and a second electrode is printed on each of the polysilicon layer, the second alumina layer and the second silicon nitride layer.

[0014] In one or more embodiments of the present invention, the groove structure includes an alumina layer and a silicon nitride layer.

[0015] In one or more embodiments of the present invention, a second alumina layer and a second silicon nitride layer are deposited on the bottom end face of the middle end face of the single-crystalline silicon.

[0016] A preparation process of a Polyfinger battery with high conductivity includes the following steps; S1, texturing: removing the mechanical damage layer on the surface of the silicon wafer to form a pyramid texture surface to increase the absorption of light; S2, boron diffusion: diffusing P-type impurities on the N-type substrate to form a PN junction to reach a suitable doping concentration; S3, removing BSG and alkaline polishing: removing the edge back BSG and polishing the back to improve the long-wavelength light response; S4, PE-poly: first prepare a tunneling oxide layer on the back of the battery, and then deposit a doped polysilicon layer; S5, annealing: converting the in-situ doped amorphous silicon by PECVD into a polysilicon layer by high-temperature annealing; S6, back laser: laser etching a specific area on the back of the annealed silicon wafer to remove the PSG and part of the polysilicon layer in this area; S7, RCA: After the laser-treated silicon wafer passes through PSG, RCA alkaline etching, and RCA acid etching in sequence, a back Polyfinger structure is formed. S8, ALD: A thin layer of alumina is generated to passivate the front and back sides. S9, Front and back coating: Anti-reflection and passivation are performed on the front and back sides of the battery. S10, Screen printing: Metallized electrodes are formed on the front and back sides of the battery. S11, Low-temperature sintering: The metallized electrodes are sintered using low-temperature sintering technology, and finally an ohmic contact is formed between the electrodes and the silicon wafer itself. S12, Testing and sorting: Appearance sorting, defect testing, and electrical performance sorting.

[0017] Compared with the prior art, a Polyfinger battery with high conductivity and its manufacturing process according to the present invention can improve the conductivity of the battery, reduce the waste of light energy, and effectively increase the conduction efficiency. Description of the drawings

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0019] Figure 1 It is a schematic structural diagram of a Polyfinger battery with high conductivity in an embodiment of the present invention; Figure 2 It is a schematic cross-sectional structure diagram of the Polyfinger battery cut laterally from the groove structure area; Figure 3 It is a microscopic diagram of a conventional Polyfinger battery without an additional auxiliary sub-grid; Figure 4 It is a microscopic diagram of a Polyfinger battery with an additional auxiliary sub-grid; Figure 5 It is a statistical chart of the sheet resistance of a Polyfinger battery with an auxiliary sub-grid, a Polyfinger battery without an auxiliary sub-grid, and a polysilicon region; Figure 6 It is a statistical table of the test data of a conventional Polyfinger battery and a Polyfinger battery with an additional auxiliary sub-grid.

[0020] Main reference numeral description: 1 - Monocrystalline silicon, 2 - Boron - doped monocrystalline silicon, 3 - First silicon nitride layer, 4 - First electrode, 5 - Polysilicon layer, 6 - Second silicon nitride layer, 7 - Main grid, 8 - Sub - grid, 9 - Auxiliary sub - grid, 10 - Groove structure, 11 - First alumina layer, 12 - Second alumina layer, 13 - Second electrode, 14 - Tunneling oxide layer. Detailed implementation mode

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] As Figure 1 shown, a Polyfinger battery with high conductivity and its manufacturing process in an embodiment of the present invention. A Polyfinger battery with high conductivity has a back - side structure including a first Polyfinger structure, a second Polyfinger structure, and a groove structure. The first Polyfinger structure includes a plurality of main grids 7 and a plurality of sub - grids 8, and the second Polyfinger structure includes a plurality of auxiliary sub - grids 9. This realizes reducing light source loss and improving conductivity.

[0023] Among them, the first Polyfinger structure and the second Polyfinger structure are connected to each other. A plurality of auxiliary sub - grids 9 are arranged between the plurality of sub - grids 8 and the plurality of main grids 7, and the auxiliary sub - grids 9 are perpendicular to the sub - grids 8. By setting a plurality of auxiliary sub - grids 9, the conductivity of the battery is improved, the current is introduced into the polysilicon layer 5, and the transmission performance of the battery is enhanced.

[0024] The auxiliary sub - grid 9 is 11 - 30 microns. Preferably, the grid line coverage rate is controlled at 5 - 8%.

[0025] Furthermore, on average, 1 - 4 auxiliary sub - grids 9 are provided per 100 microns between the sub - grid 8 and the main grid 7. Preferably, on average, 3 auxiliary sub - grids 9 are provided per 100 microns between the sub - grid 8 and the main grid 7.

[0026] The plurality of auxiliary sub - grids 9 are perpendicular to each other with the sub - grid 8. The width of the auxiliary sub - grid 9 is smaller than that of the sub - grid 8. This realizes that the current will not be lost during the transmission process. Since these lateral auxiliary sub - grids 9 are added, the current is guided into the polysilicon layer 5 and then transported to the electrode, realizing stronger current transmission, high current collection ability, a decrease in the internal resistance of the entire battery, and thus a significant improvement in the conduction efficiency.

[0027] The ratio of the width of the electrode region of the auxiliary gate 8 to the width of the non-electrode region is approximately 2:3.

[0028] It should be noted that no electrode is printed on the second Polyfinger structure, while an electrode is printed on the first Polyfinger structure.

[0029] As Figure 2 shown, the Polyfinger cell includes single-crystalline silicon 1. The first Polyfinger structure includes a tunneling oxide layer 14, a polysilicon layer 5, an alumina layer, a silicon nitride layer, and an electrode. That is, a boron-doped single-crystalline silicon 2, a first alumina layer 11, and a first silicon nitride layer 3 are sequentially deposited on the top end face of the single-crystalline silicon 1. A tunneling oxide layer 14, a polysilicon layer 5, a second alumina layer 12, and a second silicon nitride layer 6 are sequentially deposited on the bottom end face of the single-crystalline silicon 1. A first electrode 4 is printed on each of the boron-doped single-crystalline silicon 2, the first alumina layer 11, and the first silicon nitride layer 3. A second electrode 13 is printed on each of the polysilicon layer 5, the second alumina layer 12, and the second silicon nitride layer 6. This is the first Polyfinger structure.

[0030] The groove structure includes an alumina layer and a silicon nitride layer. That is, a second alumina layer 12 and a second silicon nitride layer 6 are deposited on the bottom end face of the middle end face of the single-crystalline silicon 1.

[0031] In addition, as Figure 1 shown, when the region of the Polyfinger cell located in the groove structure is cut transversely as a whole, the second Polyfinger structure cannot be cut and shown. Therefore Figure 2 the second Polyfinger structure is not shown.

[0032] The second Polyfinger structure includes a tunneling oxide layer, a polysilicon layer, an alumina layer, and a silicon nitride layer. That is, the second Polyfinger structure is such that a boron-doped single-crystalline silicon, an alumina layer, and a silicon nitride layer are sequentially deposited on the top end face of the single-crystalline silicon 1. A tunneling oxide layer, a polysilicon layer, an alumina layer, and a silicon nitride layer are sequentially deposited on the bottom end face of the single-crystalline silicon 1.

[0033] As Figures 3 - 5As shown in the figure, the sheet resistance of the Polyfinger battery with the auxiliary secondary grid 9 set, the Polyfinger battery without the auxiliary secondary grid 9 set, and the polysilicon region was tested. The resistance of the Polyfinger battery without the addition of the auxiliary secondary grid 9 was above 110, while the resistance of the Polyfinger battery with the addition of the auxiliary secondary grid 9 was below 80. The difference between the two was large. Therefore, it can be clearly seen that the resistance of the Polyfinger battery with the addition of the auxiliary secondary grid 9 was significantly lower than that of the Polyfinger battery without the addition of the auxiliary secondary grid 9, which proves that the Polyfinger battery with the addition of the auxiliary secondary grid 9 had a higher conduction efficiency.

[0034] As Figure 6 shown, it can be known that the battery efficiency of the improved Polyfinger battery increased by 0.06%. The key fill factor that affects the conduction performance, compared with the existing battery, because the lower the resistance, the higher the fill factor, and Figure 5 it is shown in

[0035] that the fill factor is 0.28% higher than that of the existing battery. From this, it can be concluded that the conduction performance of the Polyfinger battery in this application was effectively increased and the conduction efficiency was fast. Figure 5 Comprehensively, because the polysilicon layer in this area was etched and removed in the groove structure, and without adding the auxiliary secondary grid 9, the resistance value was as

[0036] shown, and the resistance in its area increased significantly to above 110. While after adding the auxiliary secondary grid 9 in the groove structure, the resistance value decreased significantly to below 80. Therefore, it can be proved that using the Polyfinger battery of this application can effectively improve the conduction performance of the battery. S1. Texturing: Remove the mechanical damage layer on the surface of the silicon wafer, form a clean pyramid texture on the surface of the silicon wafer, reduce the reflectivity of the silicon wafer surface to the incident sunlight, increase the absorption of sunlight by the silicon wafer, and improve the photoelectric conversion efficiency of the photovoltaic cell; S2. Boron diffusion: Deposit a boron-doped layer on the surface of the silicon wafer, use BCl3 as the diffusion source, and form a PN junction for separating photo-generated carriers, which is the core part where the solar cell can convert light energy into electrical energy; S3. Remove BSG and alkaline polishing: Remove the edge and back BSG, polish the back, and improve the long-wavelength light response; Principle of removing BSG: SiO2 + 6HF = H2SiF6 + 2H2O Principle of alkaline polishing: Si + 2NaOH + H2O = Na2SiO3 + 2H2 ↑ S4, PE-poly: First, a tunneling oxide layer 14 is prepared on the back of the battery, and then a doped polysilicon layer 5 is deposited. The two together form a passivation contact structure, providing good interface passivation for the back of the silicon wafer. This passivation structure allows electrons to tunnel into the doped polysilicon layer 5, while blocking holes and reducing the metal contact recombination current. The electrons that enter the doped polysilicon layer 5 are longitudinally collected by the back full-contact metal, so this structure has carrier selectivity.

[0037] The principle of PE-poly: Glow discharge is formed by pulsed radio frequency excitation of a heated rare gas to form a plasma. Opposite alternating voltages are applied to two corresponding graphite plates to accelerate the plasma to impact the gas between the plates, and the plasma moves to the surface of the silicon wafer to complete the film coating.

[0038] S5, Annealing: The in-situ doped amorphous silicon by PECVD is converted into a polysilicon layer 5 by high-temperature annealing.

[0039] S6, Back laser: Laser etching is performed on a specific area on the back of the annealed silicon wafer to remove the PSG and part of the polysilicon layer 5 in this area; S7, RCA: After the silicon wafer after laser treatment passes through PSG, RCA alkaline etching and RCA acid etching in sequence, a back Polyfinger structure is formed; After adjusting the laser spot overlap rate to -5 microns, a desired fine Poly grid line structure can be obtained by superimposing a 70°C RCA cleaning temperature; S8, ALD: Generate a thin alumina layer to passivate the front and back sides; The principle of ALD: 2Al(CH3)3 + 3H2O → Al2O3+ 6CH4 S9, Front and back film coating: Deposit silicon nitride on the boron diffusion surface, and antireflection and passivation are performed on the front and back sides of the battery.

[0040] S10, Screen printing: Form metallization electrodes on the front and back sides of the battery; The photo-generated carriers generated inside the battery under light irradiation are led out. The pastes on the back and front sides are printed on the photovoltaic cell in sequence and dried separately. Gas collection devices are set in the drying and printing areas to capture the organic waste gas volatilized from the paste during the printing and drying processes, and after being treated by an activated carbon absorption tower, it is discharged through the exhaust pipe. The activated carbon rods are replaced regularly to maintain the absorption efficiency of the activated carbon absorption tower.

[0041] S11. Low-temperature sintering: Sinter to form a metallized electrode using low-temperature sintering technology, and ultimately make the electrode form an ohmic contact with the silicon wafer itself.

[0042] S12. Testing and sorting: Appearance sorting, defect testing, and electrical performance sorting.

[0043] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be construed as limiting the claimed rights.

[0044] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A Polyfinger battery with high electrical conductivity, comprising single-crystalline silicon, characterized in that, It includes a back structure, and the back structure includes a first Polyfinger structure, a second Polyfinger structure and a groove structure. The first Polyfinger structure includes a plurality of main gates and a plurality of sub-gates. The second Polyfinger structure includes a plurality of auxiliary sub-gates. The first Polyfinger structure and the second Polyfinger structure are connected to each other, and a plurality of auxiliary sub-gates are arranged between the plurality of sub-gates and the plurality of main gates; Among them, no electrode is printed on the second Polyfinger structure, and the auxiliary sub-gates are perpendicular to the sub-gates.

2. The Polyfinger battery with high electrical conductivity according to claim 1, characterized in that, The auxiliary sub-gates are 11 - 30 microns.

3. The Polyfinger battery with high electrical conductivity according to claim 2, characterized in that, A plurality of auxiliary sub-gates are provided between the sub-gates and the main gates on average every 100 microns.

4. The Polyfinger battery with high electrical conductivity according to claim 2, characterized in that, The width of the auxiliary sub-gates is smaller than that of the sub-gates.

5. The Polyfinger battery with high electrical conductivity according to claim 4, characterized in that, The first Polyfinger structure is connected with an electrode.

6. The Polyfinger battery with high electrical conductivity according to claim 2 or 5, characterized in that, The first Polyfinger structure includes a tunneling oxide layer, a polysilicon layer, an alumina layer, a silicon nitride layer and an electrode; The second Polyfinger structure includes a tunneling oxide layer, a polysilicon layer, an alumina layer and a silicon nitride layer.

7. The Polyfinger battery with high electrical conductivity according to claim 2 or 5, characterized in that, On the top end face of the single-crystalline silicon, a boron-doped single-crystalline silicon, a first alumina layer and a first silicon nitride layer are sequentially deposited. On the bottom end face of the single-crystalline silicon, a tunneling oxide layer, a polysilicon layer, a second alumina layer and a second silicon nitride layer are sequentially deposited. A first electrode is printed on the boron-doped single-crystalline silicon, the first alumina layer and the first silicon nitride layer, and a second electrode is printed on the polysilicon layer, the second alumina layer and the second silicon nitride layer.

8. The Polyfinger battery with high electrical conductivity according to claim 2 or 5, characterized in that, The groove structure includes an alumina layer and a silicon nitride layer.

9. The Polyfinger battery with high electrical conductivity according to claim 8, characterized in that, A second alumina layer and a second silicon nitride layer are deposited on the bottom end face of the middle end face of the single-crystalline silicon.

10. A preparation process for the Polyfinger battery with high electrical conductivity according to any one of claims 1 - 9, characterized in that, It includes the following steps; S1. Texturing: Remove the mechanical damage layer on the surface of the silicon wafer to form a pyramid texture to increase the absorption of light; S2. Boron diffusion: Diffuse P-type impurities on the N-type substrate to form a PN junction to reach a suitable doping concentration; S3. Remove BSG and alkaline polishing: Remove the edge back BSG and polish the back to improve the long-wavelength light response; S4. PE-poly: First, prepare a tunneling oxide layer on the back of the battery, and then deposit a doped polysilicon layer; S5. Annealing: Convert the in-situ doped amorphous silicon of PECVD into a polysilicon layer by high-temperature annealing; S6. Back laser: Laser-etch a specific area on the back of the annealed silicon wafer to remove the PSG and part of the polysilicon layer in this area; S7. RCA: After the laser-treated silicon wafer passes through PSG, RCA alkaline etching and RCA acid etching in sequence, a back Polyfinger structure is formed; S8. ALD: Generate a thin alumina layer to passivate the front and back sides; S9. Front and back coating: Anti-reflection and passivation of the front and back of the battery; S10. Screen printing: Form metallization electrodes on the front and back of the battery; S11. Low-temperature sintering: Sinter into a metallization electrode by low-temperature sintering technology, and finally make the electrode form an ohmic contact with the silicon wafer itself; S12. Testing and sorting: Appearance sorting, defect testing, and electrical performance sorting.

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