Solar cell and preparation method thereof

Abstract

The invention relates to a solar cell and a preparation method thereof, and the solar cell comprises an N-type silicon wafer, and the front surface of the N-type silicon wafer is provided with a metalized region and a non-metalized region. A first tunneling oxide layer, a microcrystalline silicon layer, a second tunneling oxide layer, a front-side doped polycrystalline silicon layer, a front-side passivation anti-reflection film and a front-side metal electrode are sequentially arranged in the metallization area, and the conduction band bottom energy level of the microcrystalline silicon layer is smaller than that of the N-type silicon wafer and larger than that of the front-side doped polycrystalline silicon layer. According to the solar cell disclosed by the invention, the front passivation effect is ensured, and the permeation of doped elements into a silicon substrate under a high-temperature process can be effectively blocked, so that auger recombination is reduced; moreover, in the local passivation contact structure, the doping amount of doping elements in the front doped polycrystalline silicon layer is higher, and the thickness of the tunneling oxide layer is thinner, so that the conversion efficiency and the overall performance of the solar cell are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and particularly to a solar cell and a preparation method thereof. Background Art

[0002] The local passivation contact structure (poly finger) has passivation contacts only in the metallization region and no passivation contacts in other regions, which can avoid the parasitic absorption of sunlight by polysilicon, so that the solar cell can have a relatively high short-circuit current while maintaining a high passivation effect.

[0003] However, the conventional local passivation contact structure is a stacked design of a tunneling oxide layer and a doped polysilicon layer. During the high-temperature process after forming the front PN junction structure, it is very easy for the doping elements in the doped polysilicon layer to pass through the tunneling oxide layer into the silicon substrate too much, resulting in serious Auger recombination. To this end, the current conventional solution is to reduce the content of doping elements or increase the thickness of the tunneling oxide layer, but this will reduce the efficiency of the solar cell. Summary of the Invention

[0004] Based on this, it is necessary to provide a solar cell and a preparation method thereof for the above problems, and the solar cell has excellent passivation effect and conversion efficiency.

[0005] A solar cell includes an N-type silicon wafer. The front surface of the N-type silicon wafer has a metallization region and a non-metallization region. The metallization region is sequentially provided with a first tunneling oxide layer, a microcrystalline silicon layer, a second tunneling oxide layer, a front doped polysilicon layer, a front passivation antireflection film, and a front metal electrode. Among them, the bottom energy level of the conduction band of the microcrystalline silicon layer is less than the bottom energy level of the conduction band of the N-type silicon wafer and greater than the bottom energy level of the conduction band of the front doped polysilicon layer.

[0006] In one embodiment, the grain size of the microcrystalline silicon layer is 10 nm - 200 nm, and the conductivity of the microcrystalline silicon layer is 10 -3 S / cm - 10 3 S / cm.

[0007] In one embodiment, the thickness of the first tunneling oxide layer is 1 nm - 1.5 nm.

[0008] In one embodiment, the thickness of the microcrystalline silicon layer is 5 nm - 10 nm.

[0009] In one embodiment, the thickness of the second tunneling oxide layer is 1 nm - 1.5 nm.

[0010] In one embodiment, the thickness of the front doped polysilicon layer is 50 nm - 150 nm.

[0011] In one embodiment, the doping concentration of boron element in the front doped polysilicon layer is 10 19 atoms / cm 3 -10 20 atoms / cm 3 。

[0012] A method for manufacturing a solar cell as described above includes the following steps:

[0013] Performing boron diffusion on the textured N-type silicon wafer;

[0014] Opening a window on the side where boron diffusion is performed to form a groove, and sequentially depositing a first tunneling oxide layer, a microcrystalline silicon layer, a second tunneling oxide layer, and a front doped polysilicon layer in the groove, and then performing annealing crystallization treatment;

[0015] Depositing a front passivation and antireflection film and a back passivation and antireflection film on the front and back of the N-type silicon wafer respectively;

[0016] Preparing a front metal electrode and a back metal electrode on the front and back of the N-type silicon wafer respectively to obtain a solar cell.

[0017] In one embodiment, the microcrystalline silicon layer is deposited by plasma enhanced chemical vapor deposition method. Among them, the precursors are silane and hydrogen. The flow rate of the silane is 800 sccm - 1200 sccm, the flow rate of the hydrogen is 5000 sccm - 8000 sccm, and the deposition pressure is 300 Pa - 500 Pa.

[0018] In one embodiment, before depositing the back passivation and antireflection film, a back tunneling oxide layer and a back doped polysilicon layer are first prepared on the back.

[0019] In the solar cell of the present invention, the bottom energy level of the conduction band of the microcrystalline silicon layer is less than the bottom energy level of the conduction band of the N-type silicon wafer and greater than the bottom energy level of the conduction band of the front doped polysilicon layer, so that electrons can be transmitted in the N-type silicon wafer, the first tunneling oxide layer, the microcrystalline silicon layer, the second tunneling oxide layer, and the front doped polysilicon layer. At the same time, the conductivity of the microcrystalline silicon layer can also meet the transmission of electrons in the microcrystalline layer, so that electrons have excellent tunneling effect in the front metallization region, improving the conversion efficiency of the solar cell. In addition, the presence of the microcrystalline silicon layer is equivalent to a blocking layer, which can effectively prevent the doping elements in the front doped polysilicon layer from penetrating into the silicon substrate during the subsequent high-temperature process, thereby reducing Auger recombination.

[0020] Therefore, while ensuring the front passivation effect, the solar cell of the present invention can effectively block the penetration of doping elements into the silicon substrate during high-temperature processes, thereby reducing Auger recombination; moreover, in the local passivated contact structure, the doping amount of doping elements in the front doped polysilicon layer is higher, and the thickness of the tunneling oxide layer is thinner, thus improving the conversion efficiency and overall performance of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of a TOPCon cell with a conventional local passivated contact structure;

[0022] Figure 2 is Figure 1 a schematic energy band structure diagram of the TOPCon cell shown;

[0023] Figure 3 is a schematic structural diagram of a TOPCon cell with the local passivated contact structure of the present invention;

[0024] Figure 4 is Figure 3 a schematic energy band structure diagram of the TOPCon cell shown.

[0025] Wherein: 1, N-type silicon wafer; 2, back tunneling oxide layer; 3, back doped polysilicon layer; 4, back passivation and antireflection film; 5, back metal electrode; 6, front emitter; 7, front passivation and antireflection film; 8, front tunneling oxide layer; 81, first tunneling oxide layer; 82, second tunneling oxide layer; 9, front doped polysilicon layer; 10, front metal electrode; 11, microcrystalline silicon layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] For the convenience of understanding the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention. The optional range of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of the related listed items, and the any and all combinations include any two related listed items, any more related listed items, or all related listed items.

[0028] The poly finger technology can be applied in crystalline silicon solar cells such as TOPCon cells or PERC cells, as Figure 1 shown, a TOPCon cell with a conventional poly finger, the front metallization region of which includes a front tunneling oxide layer 8, a front doped polysilicon layer 9, a front passivation and antireflection film 7, and a front metal electrode 10. Among them, the matching of the front tunneling oxide layer 8 and the front doped polysilicon layer 9 is crucial. First of all, the front tunneling oxide layer 8 cannot be too thick and needs to maintain a good tunneling effect. Secondly, the concentration of the doping element in the front doped polysilicon layer 9 cannot be too low and needs to maintain an excellent field passivation effect. Therefore, during the subsequent high-temperature process, the boron element in the front doped polysilicon layer 9 will pass through the front tunneling oxide layer 8 too much and enter the N-type silicon wafer 1, resulting in serious Auger recombination. However, increasing the thickness of the front tunneling oxide layer 8 or reducing the boron element concentration in the front doped polysilicon layer 9 will make the passivation effect of the solar cell worse or the conversion efficiency lower.

[0029] Therefore, the present invention provides a solar cell, which can be a crystalline silicon solar cell such as a TOPCon cell or a PERC cell. The solar cell has a poly finger and the poly finger is redesigned. It can be understood that for a crystalline silicon solar cell such as a TOPCon cell or a PERC cell with a poly finger, the front non-metallization region and the back structure can refer to the prior art, and the present invention will not elaborate too much.

[0030] As Figure 3 shown, a schematic structural diagram of a TOPCon cell with the poly finger of the present invention includes an N-type silicon wafer 1. The front of the N-type silicon wafer 1 has a metallization region and a non-metallization region. The metallization region is sequentially provided with a first tunneling oxide layer 81, a microcrystalline silicon layer 11, a second tunneling oxide layer 82, a front doped polysilicon layer 9, a front passivation and antireflection film 7, and a front metal electrode 10. Among them, the bottom energy level of the conduction band of the microcrystalline silicon layer 11 is less than the bottom energy level of the conduction band of the N-type silicon wafer 1 and greater than the bottom energy level of the conduction band of the front doped polysilicon layer 9.

[0031] In the solar cell of the present invention, the energy band relationship among the microcrystalline silicon layer 11, the N-type silicon wafer 1, and the front doped polysilicon layer 9 is as Figure 4As shown, the bottom energy level of the conduction band of the microcrystalline silicon layer 11 is less than that of the N-type silicon wafer 1 and greater than that of the front-side doped polysilicon layer 9, enabling electrons to be transmitted in the N-type silicon wafer 1, the first tunneling oxide layer 81, the microcrystalline silicon layer 11, the second tunneling oxide layer 82, and the front-side doped polysilicon layer 9. At the same time, the conductivity of the microcrystalline silicon layer 11 can also meet the requirement for electron transmission in the microcrystalline layer 11, so that electrons have an excellent tunneling effect in the front-side metallization region.

[0032] In addition, the presence of the microcrystalline silicon layer 11 is equivalent to a blocking layer, which can effectively prevent the doping elements in the front-side doped polysilicon layer 9 from penetrating into the N-type silicon wafer 1 during subsequent high-temperature processes, thereby reducing Auger recombination.

[0033] Therefore, compared with Figure 2 the conventional poly finger that can ensure the tunneling effect, the solar cell of the present invention not only ensures that electrons have an excellent tunneling effect in a specific poly finger, so that it has an excellent front-side passivation effect, but also can effectively block the penetration of doping elements into the silicon substrate during high-temperature processes, thereby reducing Auger recombination; and, in the poly finger structure, the doping amount of the doping elements in the front-side doped polysilicon layer 9 is higher, and the thickness of the tunneling oxide layer is thinner, thereby improving the conversion efficiency and overall performance of the solar cell.

[0034] Optionally, the grain size in the microcrystalline silicon layer 11 is preferably 10 nm - 200 nm, so as to improve the conductivity of the microcrystalline silicon layer 11, and the conductivity of the microcrystalline silicon layer 11 is 10 -3 S / cm - 10 3 S / cm, further better meeting the requirement for electron transmission in the microcrystalline silicon layer 11.

[0035] Optionally, the thickness of the first tunneling oxide layer 81 is preferably 1 nm - 1.5 nm, the thickness of the second tunneling oxide layer 82 is preferably 1 nm - 1.5 nm, and the thickness of the first tunneling oxide layer 81 and the thickness of the second tunneling oxide layer 82 can be the same or different, and / or, the thickness of the microcrystalline silicon layer 11 is preferably 5 nm - 10 nm, which is beneficial to the tunneling of electrons in the two tunneling oxide layers and the microcrystalline silicon layer 11 with specific thicknesses, further improving the tunneling effect, and thus beneficial to improving the conversion efficiency of the solar cell.

[0036] Optionally, the thickness of the front-side doped polysilicon layer 9 is preferably 50 nm - 150 nm.

[0037] Based on the cooperation of the first tunneling oxide layer 81, the microcrystalline silicon layer 11, and the second tunneling oxide layer 82 of the present invention, boron in the front doped polysilicon layer 9 has a higher doping concentration, which is beneficial to improving the conversion efficiency of the solar cell.

[0038] Optionally, the boron doping concentration in the front doped polysilicon layer 9 is preferably 10 19 atoms / cm 3 -10 20 atoms / cm 3 , so that a suitable doping concentration is beneficial to the bottom energy level of the conduction band of the microcrystalline silicon layer 11 being greater than the bottom energy level of the conduction band of the front doped polysilicon layer 9, which is further beneficial to the tunneling of electrons therein.

[0039] Optionally, the width of the metallization region is preferably 10 μm - 100 μm.

[0040] Optionally, in the front non-metallization region of the solar cell, a front emitter 6 and a front passivation and antireflection film 7 are included, and the front passivation and antireflection film 7 in the non-metallization region and the front passivation and antireflection film 7 in the metallization region have the same laminated structure and can be prepared by the same preparation process. Preferably, the front passivation and antireflection film 7 includes an alumina and silicon nitride laminated film, and the front emitter 6 is preferably composed of a boron diffusion region on the N-type silicon wafer 1.

[0041] Optionally, the back of the solar cell includes a back tunneling oxide layer 2, a back doped polysilicon layer 3, a back passivation and antireflection film 4, and a back metal electrode 5. The back passivation and antireflection film 4 is preferably a silicon nitride thin film, and the back metal electrode 5 is preferably a silver electrode.

[0042] It can be understood that the solar cell of the present invention can also be a PERC cell, etc. When the solar cell is a PERC cell, the back of the solar cell only includes a back passivation and antireflection film 4 and a back metal electrode 5.

[0043] The present invention also provides a method for manufacturing the solar cell as described above, including the following steps:

[0044] S1, performing boron diffusion on the textured N-type silicon wafer 1;

[0045] S2, opening a window on the side where boron diffusion is performed to form a groove, and sequentially depositing a first tunneling oxide layer 81, a microcrystalline silicon layer 11, a second tunneling oxide layer 82, and a front doped polysilicon layer 9 in the groove, and then performing annealing crystallization treatment;

[0046] S3, depositing a front passivation and antireflection film 7 and a back passivation and antireflection film 4 on the front and back of the N-type silicon wafer 1 respectively;

[0047] S4. Prepare a front metal electrode 10 and a back metal electrode 5 on the front and back of the N-type silicon wafer 1 respectively to obtain a solar cell.

[0048] In step S1, the temperature of boron diffusion is preferably 1000°C - 1100°C, and the doping concentration of boron element is preferably 10 18 atoms / cm 3 -10 19 atoms / cm 3 .

[0049] In step S2, it is preferred to form a groove by laser windowing, and the width of the groove is preferably 10μm - 100μm.

[0050] Optionally, the first tunneling oxide layer 81, the microcrystalline silicon layer 11, the second tunneling oxide layer 82 and the front doped polysilicon layer 9 are deposited by plasma enhanced chemical vapor deposition (PECVD).

[0051] Optionally, in the step of depositing the first tunneling oxide layer 81, the precursor is preferably oxygen, the flow rate of oxygen is preferably 5000 sccm - 20000 sccm, and the deposition time is preferably 400 s - 1200 s.

[0052] Optionally, in the step of depositing the second tunneling oxide layer 82, the precursor is preferably oxygen, the flow rate of oxygen is preferably 5000 sccm - 20000 sccm, and the deposition time is preferably 400 s - 1200 s.

[0053] Optionally, in the step of depositing the microcrystalline silicon layer 11, the precursors are preferably silane and hydrogen, the flow rate of silane is preferably 800 sccm - 1200 sccm, the flow rate of hydrogen is preferably 5000 sccm - 8000 sccm, and the deposition pressure is preferably 300 Pa - 500 Pa. Thus, the appropriate hydrogen flow rate and deposition pressure result in a smaller grain size of the deposited microcrystalline silicon, and the grown microcrystalline silicon has better conductivity, which can better meet the electron transport in the microcrystalline silicon layer 11.

[0054] Optionally, in the step of depositing the front doped polysilicon layer 9, the precursors are preferably borane, silane and hydrogen, the flow rate of borane is preferably 500 sccm - 800 sccm, the flow rate of silane is preferably 800 sccm - 1200 sccm, the flow rate of hydrogen is preferably 3000 sccm - 5000 sccm, and the deposition pressure is preferably 100 Pa - 300 Pa, which is beneficial to increasing the doping concentration of boron element in the front doped polysilicon layer 9.

[0055] Optionally, in the step of annealing and crystallization treatment, high-temperature annealing and crystallization activate boron atoms, and the crystallization temperature is preferably 1000°C - 1100°C.

[0056] Before step S3, it also includes cleaning the stacked structure of the front non-metallized area and polishing the back surface of the N-type silicon wafer 1.

[0057] In step S3, on the front surface of the N-type silicon wafer 1, deposit the front passivation and antireflection film 7, preferably deposit a stacked film of aluminum oxide and silicon nitride to form the front passivation and antireflection film 7; on the back surface of the N-type silicon wafer 1, deposit the back passivation and antireflection film 4, preferably deposit a silicon nitride film to form the back passivation and antireflection film 4.

[0058] In step S4, in the front metallization area of the N-type silicon wafer 1, print silver-aluminum paste on the surface of the front passivation and antireflection film 7 facing away from the N-type silicon wafer 1 and sinter it at high temperature to form the front metal electrode 10, and print silver paste on the surface of the back passivation and antireflection film 4 facing away from the N-type silicon wafer 1 and sinter it at high temperature to form the back metal electrode 5.

[0059] Optionally, the back preparation process in step S3 can be specifically adjusted according to the structure of the solar cell, and the present invention does not make specific limitations. For example, when the solar cell is a PERC cell, only deposit the passivation and antireflection film 4 on the back surface of the N-type silicon wafer 1. When the solar cell is a TOPCon cell, before depositing the back passivation and antireflection film 4, deposit the back tunneling oxide layer 2 and the back doped polysilicon layer 3 on the back surface of the N-type silicon wafer 1.

[0060] In one of the embodiments, when the solar cell is a TOPCon cell, step S3 specifically includes the following steps:

[0061] (a) Deposit the back tunneling oxide layer 2 and the intrinsic amorphous silicon layer on the back surface by LPCVD, and then perform phosphorus diffusion on the intrinsic amorphous silicon layer to form a phosphorus-doped polysilicon layer;

[0062] (b) Clean the front surface for plating around;

[0063] (c) Deposit the back passivation and antireflection film 4 on the back surface.

[0064] Preferably, in step (a), the phosphorus diffusion temperature is preferably 850°C - 950°C.

[0065] Hereinafter, the solar cell and its manufacturing method will be further described through the following specific examples.

[0066] Example 1

[0067] Perform texturing and boron diffusion on the N-type silicon wafer, and perform laser window opening on the side with boron diffusion to form a groove with a width of 10 μm.

[0068] In the groove, a 1-nm first tunneling oxide layer, a 5-nm microcrystalline silicon layer, a 1-nm second tunneling oxide layer, and a 50-nm boron-doped polysilicon layer are sequentially deposited by PECVD. Among them, when depositing the first tunneling oxide layer, the precursor is oxygen, the flow rate is 5000 sccm, and the deposition time is 400 s; when depositing the second tunneling oxide layer, the precursor is oxygen, the flow rate is 5000 sccm, and the deposition time is 400 s; when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 800 sccm and hydrogen with a flow rate of 5000 sccm, and the deposition pressure is 300 Pa; when depositing the boron-doped polysilicon layer, the precursors are borane with a flow rate of 500 sccm, silane with a flow rate of 800 sccm, and hydrogen with a flow rate of 3000 sccm, the deposition pressure is 100 Pa, and the doping concentration of boron element is 10 19 atoms / cm 3 , and then anneal and crystallize at 1000 °C to activate boron atoms. The grain size of the microcrystalline silicon layer is 10 nm, and the conductivity is 10 -3 S / cm.

[0069] Use LPCVD to deposit a tunneling oxide layer and a polysilicon layer on the back of the N-type silicon wafer, then perform phosphorus diffusion on the polysilicon layer to form a phosphorus-doped polysilicon layer, deposit an alumina / silicon nitride stack on the front to form a front passivation and antireflection film, deposit a silicon nitride film on the back, and finally print and sinter silver-aluminum paste and silver paste on the front and back of the N-type silicon wafer respectively to form a front metal electrode and a back metal electrode.

[0070] The performance of the solar cell in this embodiment is shown in Table 1.

[0071] Example 2

[0072] Texturize, boron-dope the N-type silicon wafer, and perform laser window opening on the boron-doped side to form a groove with a width of 30 μm.

[0073] In the groove, a 1.2-nm first tunneling oxide layer, a 7-nm microcrystalline silicon layer, a 1.2-nm second tunneling oxide layer, and a 90-nm boron-doped polysilicon layer are sequentially deposited by PECVD. Among them, when depositing the first tunneling oxide layer, the precursor is oxygen, the flow rate is 10000 sccm, and the deposition time is 700 s; when depositing the second tunneling oxide layer, the precursor is oxygen, the flow rate is 1000 sccm, and the deposition time is 700 s; when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 900 sccm and hydrogen with a flow rate of 6000 sccm, and the deposition pressure is 350 Pa; when depositing the boron-doped polysilicon layer, the precursors are borane with a flow rate of 600 sccm, silane with a flow rate of 900 sccm, and hydrogen with a flow rate of 3500 sccm, the deposition pressure is 150 Pa, and the formed doping concentration of boron element is 3×10 19 atoms / cm3 , and then anneal and crystallize at 1030 °C to activate boron atoms. The grain size of the microcrystalline silicon layer is 50 nm, and the conductivity is 10 -1 S / cm.

[0074] Deposit a tunneling oxide layer and a polysilicon layer on the back of the N-type silicon wafer by LPCVD. Then, perform phosphorus diffusion on the polysilicon layer to form a phosphorus-doped polysilicon layer. Deposit an alumina / silicon nitride stack on the front to form a front passivation and antireflection film, deposit a silicon nitride film on the back, and finally print silver-aluminum paste and silver paste on the front and back of the N-type silicon wafer respectively and sinter them to form a front metal electrode and a back metal electrode.

[0075] The performance of the solar cell of this embodiment is shown in Table 1.

[0076] Example 3

[0077] Texturize, boron dope the N-type silicon wafer, and perform laser window opening on the boron-doped side to form a groove with a width of 70 μm.

[0078] Deposit a 1.4-nm first tunneling oxide layer, an 8-nm microcrystalline silicon layer, a 1.4-nm second tunneling oxide layer, and a 120-nm boron-doped polysilicon layer in sequence in the groove by PECVD. Among them, when depositing the first tunneling oxide layer, the precursor is oxygen, the flow rate is 15000 sccm, and the deposition time is 1000 s; when depositing the second tunneling oxide layer, the precursor is oxygen, the flow rate is 15000 sccm, and the deposition time is 1000 s; when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 1000 sccm and hydrogen with a flow rate of 7000 sccm, and the deposition pressure is 250 Pa; when depositing the boron-doped polysilicon layer, the precursors are borane with a flow rate of 700 sccm, silane with a flow rate of 1100 sccm, and hydrogen with a flow rate of 4500 sccm, the deposition pressure is 250 Pa, and the doping concentration of boron element is 8×10 19 atoms / cm 3 , and then anneal and crystallize at 1070 °C to activate boron atoms. The grain size of the microcrystalline silicon layer is 130 nm, and the conductivity is 10 S / cm.

[0079] Deposit a tunneling oxide layer and a polysilicon layer on the back of the N-type silicon wafer by LPCVD. Then, perform phosphorus diffusion on the polysilicon layer to form a phosphorus-doped polysilicon layer. Deposit an alumina / silicon nitride stack on the front to form a front passivation and antireflection film, deposit a silicon nitride film on the back, and finally print silver-aluminum paste and silver paste on the front and back of the N-type silicon wafer respectively and sinter them to form a front metal electrode and a back metal electrode.

[0080] The performance of the solar cell of this embodiment is shown in Table 1.

[0081] Example 4

[0082] The N-type silicon wafer is textured, boron-diffused, and laser windowing is performed on the boron-diffused side to form a groove with a width of 100 μm.

[0083] In the groove, a first tunneling oxide layer with a thickness of 1.5 nm, a microcrystalline silicon layer with a thickness of 10 nm, a second tunneling oxide layer with a thickness of 1.5 nm, and a boron-doped polysilicon layer with a thickness of 150 nm are sequentially deposited by PECVD. Among them, when depositing the first tunneling oxide layer, the precursor is oxygen, the flow rate is 20000 sccm, and the deposition time is 1200 s; when depositing the second tunneling oxide layer, the precursor is oxygen, the flow rate is 20000 sccm, and the deposition time is 1200 s; when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 1200 sccm and hydrogen with a flow rate of 8000 sccm, and the deposition pressure is 500 Pa; when depositing the boron-doped polysilicon layer, the precursors are borane with a flow rate of 800 sccm, silane with a flow rate of 1200 sccm, and hydrogen with a flow rate of 5000 sccm, the deposition pressure is 300 Pa, and the doping concentration of boron element is 1×10 20 atoms / cm 3 , and then annealed at 1100 °C to crystallize and activate boron atoms. The grain size of the microcrystalline silicon layer is 200, and the conductivity is 10 3 S / cm.

[0084] The tunneling oxide layer and the polysilicon layer are deposited on the back of the N-type silicon wafer by LPCVD, then phosphorus diffusion is performed on the polysilicon layer to form a phosphorus-doped polysilicon layer, an alumina / silicon nitride stack is deposited on the front to form a front passivation and antireflection film, a silicon nitride film is deposited on the back, and finally silver-aluminum paste and silver paste are printed and sintered on the front and back of the N-type silicon wafer respectively to form a front metal electrode and a back metal electrode.

[0085] The performance of the solar cell of this embodiment is shown in Table 1.

[0086] Example 5

[0087] Example 5 is different from Example 1 in that: in the groove, a first tunneling oxide layer of 0.8 nm, a microcrystalline silicon layer of 3 nm, a second tunneling oxide layer of 0.8 nm, and a boron-doped polysilicon layer of 30 nm are sequentially deposited by PECVD. Among them, when depositing the first tunneling oxide layer, the precursor is oxygen, the flow rate is 3000 sccm, and the deposition time is 200 s; when depositing the second tunneling oxide layer, the precursor is oxygen, the flow rate is 3000 sccm, and the deposition time is 200 s; when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 600 sccm and hydrogen with a flow rate of 3000 sccm, and the deposition pressure is 200 Pa; when depositing the boron-doped polysilicon layer, the precursors are borane with a flow rate of 400 sccm, silane with a flow rate of 600 sccm, and hydrogen with a flow rate of 2000 sccm, the deposition pressure is 50 Pa, and the doping concentration of boron element is 5×10 18 atoms / cm 3 , and then anneal and crystallize at 900 °C to activate boron atoms. In the microcrystalline silicon layer, the grain size of the microcrystalline silicon is 5 nm, and the conductivity is 10 -4 S / cm.

[0088] The performance of the solar cell of this example is shown in Table 1.

[0089] Example 6

[0090] Example 6 is different from Example 1 in that: in the groove, a first tunneling oxide layer of 2 nm, a microcrystalline silicon layer of 15 nm, a second tunneling oxide layer of 2 nm, and a boron-doped polysilicon layer of 200 nm are sequentially deposited by PECVD. Among them, when depositing the first tunneling oxide layer, the precursor is oxygen, the flow rate is 25000 sccm, and the deposition time is 1500 s; when depositing the second tunneling oxide layer, the precursor is oxygen, the flow rate is 25000 sccm, and the deposition time is 1500 s; when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 1400 sccm and hydrogen with a flow rate of 10000 sccm, and the deposition pressure is 800 Pa; when depositing the boron-doped polysilicon layer, the precursors are borane with a flow rate of 1000 sccm, silane with a flow rate of 1400 sccm, and hydrogen with a flow rate of 6000 sccm, the deposition pressure is 500 Pa, and the doping concentration of boron element is 5×10 20 atoms / cm 3 , and then anneal and crystallize at 1200 °C to activate boron atoms. In the microcrystalline silicon layer, the grain size of the microcrystalline silicon is 300 nm, and the conductivity is 5×10 3 S / cm.

[0091] The performance of the solar cell of this example is shown in Table 1.

[0092] Example 7

[0093] Example 7 is different from Example 1 in that when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 600 sccm and hydrogen with a flow rate of 3000 sccm, the deposition pressure is 200 Pa, the grain size of the formed microcrystalline silicon is 5 nm, and the conductivity is 10 -4 S / cm.

[0094] The performance of the solar cell of this example is shown in Table 1.

[0095] Example 8

[0096] Example 8 is different from Example 1 in that when depositing the microcrystalline silicon layer, the precursors are silane with a flow rate of 1400 sccm and hydrogen with a flow rate of 10000 sccm, the deposition pressure is 800 Pa, the grain size of the formed microcrystalline silicon is 300 nm, and the conductivity is 5×10 3 S / cm.

[0097] The performance of the solar cell of this example is shown in Table 1.

[0098] Comparative Example 1

[0099] Comparative Example 1 is different from Example 1 in that a 3-nm tunneling oxide layer and a 50-nm boron-doped polysilicon layer are sequentially deposited in the groove by PECVD. Among them, the doping concentration of boron element is 10 19 atoms / cm 3 , and then annealed at 1000 °C to crystallize and activate boron atoms.

[0100] The performance of the solar cell of this comparative example is shown in Table 1.

[0101] Comparative Example 2

[0102] Comparative Example 2 is different from Example 1 in that a 2-nm tunneling oxide layer and a 50-nm boron-doped polysilicon layer are sequentially deposited in the groove by PECVD. Among them, the doping concentration of boron element is 8×10 18 atoms / cm 3 , and then annealed at 1000 °C to crystallize and activate boron atoms.

[0103] The performance of the solar cell of this comparative example is shown in Table 1.

[0104] Table 1

[0105]

[0106] As can be seen from Table 1, the overall electrical performance of the solar cells in Examples 1-4 is excellent; in Examples 5 and 6, since the thicknesses of the first tunneling oxide layer, the microcrystalline silicon layer, the second tunneling oxide layer, and the boron-doped polysilicon layer formed are too thin or too thick, which is not conducive to electron tunneling, resulting in relatively poor overall electrical performance of the solar cells; in Example 7, the grain size of the microcrystalline silicon layer is too small and the conductivity is too small, thus affecting the contact of the solar cell, so it mainly affects the short circuit current and the fill factor; in Example 8, the grain size of the microcrystalline silicon layer is too large, mainly affecting the open circuit voltage.

[0107] Comparative Examples 1 and 2 are local passivation contact structures for preparing solar cells by conventional means, and the overall efficiency of their cells is low.

[0108] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0109] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A solar cell, comprising an N-type silicon wafer, wherein the front side of the N-type silicon wafer has a metallized region and a non-metallized region. Characterized in that The metallized region is successively provided with a first tunneling oxide layer, a microcrystalline silicon layer, a second tunneling oxide layer, a front-side doped polysilicon layer, a front-side passivation and antireflection film, and a front-side metal electrode. Among them, the bottom energy level of the conduction band of the microcrystalline silicon layer is less than the bottom energy level of the conduction band of the N-type silicon wafer and greater than the bottom energy level of the conduction band of the front-side doped polysilicon layer.

2. The solar cell according to claim 1, Characterized in that The grain size of the microcrystalline silicon layer is 10 nm - 200 nm, and the conductivity of the microcrystalline silicon layer is 10 -3 S / cm - 10 3 S / cm.

3. The solar cell according to claim 1, Characterized in that The thickness of the first tunneling oxide layer is 1 nm - 1.5 nm.

4. The solar cell according to claim 1, Characterized in that The thickness of the microcrystalline silicon layer is 5 nm - 10 nm.

5. The solar cell according to claim 1, Characterized in that The thickness of the second tunneling oxide layer is 1 nm - 1.5 nm.

6. The solar cell according to claim 1, Characterized in that The thickness of the front-side doped polysilicon layer is 50 nm - 150 nm.

7. The solar cell according to claim 1, Characterized in that The doping concentration of boron element in the front doped polysilicon layer is 10 19 atoms / cm 3 -10 20 atoms / cm 3 .

8. A method for manufacturing a solar cell according to any one of claims 1 - 7, Characterized in that Comprises the following steps: Performing boron diffusion on the textured N-type silicon wafer; Opening a window on the side where boron diffusion is performed to form a groove, and successively depositing a first tunneling oxide layer, a microcrystalline silicon layer, a second tunneling oxide layer, and a front-side doped polysilicon layer in the groove, and then performing annealing crystallization treatment; Depositing a front-side passivation and antireflection film and a back-side passivation and antireflection film on the front side and the back side of the N-type silicon wafer respectively; Preparing a front-side metal electrode and a back-side metal electrode on the front side and the back side of the N-type silicon wafer respectively to obtain a solar cell.

9. The method for manufacturing a solar cell according to claim 8, Characterized in that The microcrystalline silicon layer is deposited by plasma enhanced chemical vapor deposition. Among them, the precursors are silane and hydrogen. The flow rate of silane is 800 sccm - 1200 sccm, the flow rate of hydrogen is 5000 sccm - 8000 sccm, and the deposition pressure is 300 Pa - 500 Pa.

10. The method for manufacturing a solar cell according to claim 8, Characterized in that Before depositing the back-side passivation and antireflection film, a back-side tunneling oxide layer and a back-side doped polysilicon layer are first prepared on the back side.

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