Passivation contact structure, solar cell and preparation method thereof

Abstract

The invention discloses a passivation contact structure, a solar cell and a preparation method thereof, the passivation contact structure is used for the solar cell, the solar cell is suitable for converting light energy into electric energy, and the passivation contact structure comprises a tunneling oxide layer, a first doping layer and a second doping layer; the first doping layer comprises phosphorus-doped polycrystalline silicon or boron-doped polycrystalline silicon, and the first doping layer is suitable for being connected with an electrode of a solar cell; the second doping layer is arranged on the tunneling oxide layer and connected with the first doping layer, the second doping layer comprises phosphorus-doped polycrystalline silicon or boron-doped polycrystalline silicon, and elements of the second doping layer further comprise carbon and / or nitrogen. The solar cell using the passivation contact structure has relatively low contact resistance, relatively good passivation effect and relatively low parasitic absorption energy, so that the efficiency of the solar cell can be improved.

Description

Technical Field

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

[0002] The optimization of tunneling oxide layer and doped polysilicon is the key to realize high-efficiency solar cells. Polysilicon has a large absorption coefficient in the visible and near-infrared light range, and has large parasitic absorption losses. In actual batteries, it can only be used as the back passivation of the battery. In the structure of the solar cell on the back, doped polysilicon will still absorb part of the infrared light and cause current loss. Although parasitic absorption can be reduced by carbon and nitrogen doping of polysilicon or reducing the thickness of doped polysilicon, the contact resistance and passivation effect of the solar cell will also be affected, which will lead to a decrease in short-circuit current and open-circuit voltage respectively.

[0003] Therefore, it is difficult to achieve a balance among the contact resistance, passivation effect and parasitic absorption of the solar cell structure, which makes it difficult to further improve the efficiency of the solar cell. Summary of the invention

[0004] The purpose of the present invention is to provide a passivation contact structure, a solar cell and a method for preparing the same, so as to solve the problem that it is difficult to achieve a balance among contact resistance, passivation effect and parasitic absorption in the cell structure.

[0005] To achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a passivation contact structure for a solar cell, wherein the solar cell is suitable for converting light energy into electrical energy, comprising:

[0007] Tunneling oxide layer;

[0008] A first doped layer, comprising phosphorus-doped polysilicon or boron-doped polysilicon, wherein the first doped layer is suitable for connecting to an electrode of the solar cell;

[0009] The second doping layer is arranged on the tunneling oxide layer and connected to the first doping layer. The second doping layer includes phosphorus-doped polysilicon or boron-doped polysilicon. The elements of the second doping layer also include carbon and / or nitrogen.

[0010] In one embodiment, the first doped layer is disposed on the tunneling oxide layer, and the second doped layer at least surrounds an outer periphery of the first doped layer on a side close to the tunneling oxide layer.

[0011] In one embodiment, the elements of the tunnel oxide layer include silicon and oxygen, and also include nitrogen and / or carbon.

[0012] In one implementation, the thickness of the tunnel oxide layer is d1, satisfying: 0.5nm≤d1≤4nm.

[0013] In one embodiment, the passivation contact structure further includes a third doping layer, and the third doping layer is arranged on a surface of the first doping layer away from the tunneling oxide layer;

[0014] The third doping layer includes phosphorus-doped polysilicon or boron-doped polysilicon, and the elements of the third doping layer further include carbon and / or nitrogen.

[0015] In one embodiment, the thickness of the first doping layer is d2, which satisfies: 50nm≤d2≤200nm;

[0016] The thickness of the second doping layer is d3, which satisfies: 30nm≤d3≤150nm;

[0017] The thickness of the third doping layer is d4, which satisfies: 30nm≤d4≤150nm.

[0018] In one implementation, the following condition is also satisfied: d3 = d4.

[0019] In one implementation, the following condition is also satisfied: d2>d3.

[0020] In a second aspect, the present invention provides a solar cell, which is suitable for converting light energy into electrical energy. The solar cell includes a silicon base layer, an electrode and a passivation contact structure as described in any one of the various embodiments in the first aspect, the tunneling oxide layer is connected to the silicon base layer, and the electrode is connected to the first doping layer.

[0021] In one embodiment, the silicon base layer includes a first surface and a second surface arranged opposite to each other in a first direction, the first surface is suitable for facing the light source, at least one of the first surface and the second surface is connected to the passivation contact structure, and the first direction is the thickness direction of the solar cell.

[0022] In one embodiment, the first surface is provided with the passivation contact structure, the surface of the second doped layer away from the first surface is provided with a first anti-reflection layer, and the second surface is sequentially stacked with the tunneling oxide layer, the fourth doped layer and the second anti-reflection layer in a direction away from the first surface;

[0023] Or, the second surface is provided with the passivation contact structure, and the first surface is provided with the boron diffusion emitter layer, the aluminum oxide passivation layer and the first anti-reflection layer stacked in sequence in a direction away from the second surface;

[0024] Alternatively, both the first surface and the second surface are provided with the passivation contact structure.

[0025] In one embodiment, the first anti-reflection layer and the second anti-reflection layer include at least one of aluminum oxide, silicon oxynitride, silicon nitride, silicon oxide and magnesium fluoride;

[0026] The fourth doping layer includes phosphorus-doped polysilicon or boron-doped polysilicon, and the elements of the fourth doping layer further include carbon and / or nitrogen.

[0027] In one embodiment, the first surface is provided with the passivation contact structure, and the electrode includes a first end face and a second end face arranged opposite to each other along the first direction, the first end face protrudes from the end face of the passivation contact structure away from the silicon base layer, and there is a gap between the second end face and the tunneling oxide layer.

[0028] In a third aspect, the present invention provides a method for preparing a solar cell, comprising the following steps:

[0029] providing a silicon base layer;

[0030] Providing a passivation contact structure on the surface of the silicon base layer;

[0031] An electrode is formed on the first doped layer of the passivation contact structure to obtain a solar cell as described in any one of the various embodiments of the second aspect, wherein the solar cell includes a silicon base layer, an electrode and a passivation contact structure, wherein the tunneling oxide layer of the passivation contact structure is connected to the silicon base layer, and the electrode is arranged on the first doped layer.

[0032] In one embodiment, a passivation contact structure is provided on the surface of the silicon base layer, including:

[0033] forming a tunneling oxide layer on the surface of the silicon base layer;

[0034] Locally depositing a first doping layer on a surface of the tunneling oxide layer away from the silicon base layer;

[0035] A second doping layer and a third doping layer are deposited on surfaces of the tunneling oxide layer and the first doping layer away from the silicon base layer.

[0036] The passivation contact structure of the present invention is achieved by arranging a first doping layer and a second doping layer on a tunneling oxide layer. The passivation contact structure of the present invention uses the first doping layer at the electrode contact to achieve efficient carrier transmission and good surface passivation effect, while solving the parasitic absorption of polysilicon and the high contact resistance problem of doped polysilicon. The second doping layer is arranged at the non-electrode contact for surface passivation. The second doping layer is suitable for ensuring the surface passivation effect while reducing the parasitic absorption effect of the polysilicon layer, thereby improving the infrared response and short-circuit current of the solar cell. Therefore, through the synergistic effect of the first doping layer and the second doping layer, the solar cell using the passivation contact structure has lower contact resistance, better passivation effect and less parasitic absorption energy, thereby improving the efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 is a schematic diagram of a passivation contact structure of an embodiment;

[0039] Figure 2 is a cross-sectional view of a solar cell according to an embodiment;

[0040] Figure 3 is a cross-sectional view of a solar cell according to another embodiment;

[0041] Figure 4 is a cross-sectional view of a solar cell according to another embodiment;

[0042] Figure 5 is a flow chart of a method for preparing a solar cell according to an embodiment;

[0043] Figure 6 The present invention is a flow chart of one step in a method for preparing a solar cell according to an embodiment.

[0044] Description of reference numerals:

[0045] 100-solar cell, 10-passivation contact structure, 11-tunneling oxide layer, 12-first doping layer, 13-second doping layer, 14-third doping layer, 15-mounting groove, 20-electrode, 30-silicon base layer, 31-first surface, 32-second surface, 40-first anti-reflection layer, 50-fourth doping layer, 60-second anti-reflection layer, 70-boron diffused emitter layer, 80-aluminum oxide passivation layer, X-first direction. DETAILED DESCRIPTION

[0046] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] It should be noted that when a component is said to be "fixed to" another component, it can be directly on the other component or there can be a central component. When a component is said to be "connected to" another component, it can be directly connected to the other component or there can be a central component at the same time.

[0048] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0049] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0050] For reference Figure 1 The present invention provides a passivation contact structure 10, which is used for a solar cell 100. The solar cell 100 is suitable for converting light energy into electrical energy. The passivation contact structure 10 includes a tunneling oxide layer 11, a first doping layer 12, and a second doping layer 13. The first doping layer 12 includes phosphorus-doped polysilicon or boron-doped polysilicon, and the first doping layer 12 is suitable for connecting to an electrode 20 of the solar cell 100. The second doping layer 13 is disposed on the tunneling oxide layer 11 and connected to the first doping layer 12. The second doping layer 13 includes phosphorus-doped polysilicon or boron-doped polysilicon, and the elements of the second doping layer 13 also include carbon and / or nitrogen.

[0051] In one implementation, the first doping layer 12 is disposed on the tunneling oxide layer 11 , and the second doping layer 13 at least surrounds the periphery of the first doping layer 12 on a side close to the tunneling oxide layer 11 .

[0052] Optionally, the passivation contact structure 10 further includes a third doping layer 14, which is disposed on a surface of the first doping layer 12 away from the tunneling oxide layer 11, and a mounting groove 15 is provided on the surface of the third doping layer 14 facing away from the tunneling oxide layer 11, and the mounting groove 15 extends into the first doping layer 12, and the mounting groove 15 is suitable for accommodating an electrode 20 of the solar cell 100. The metal electrode 20 penetrates the third doping layer 14 to reach the first doping layer 12. The third doping layer 14 is phosphorus-doped polysilicon or boron-doped polysilicon, and the elements of the third doping layer 14 also include carbon and / or nitrogen. Optionally, the mounting groove 15 can be formed during the sintering process of the electrode 20, or can be formed before the passivation contact structure 10 and the electrode 20 are installed, without limitation.

[0053] The passivation contact structure 10 of the present invention uses a combination of a stacked structure of a first doping layer 12 and a third doping layer 14 at the contact point of the electrode 20 to achieve efficient carrier transport and better surface passivation effect, while solving the parasitic absorption of polysilicon and the high contact resistance problem of doped polysilicon. The third doping layer 14 is arranged on the surface of the second doping layer 13 to prevent the electrode 20 from contacting the tunneling oxide layer 11.

[0054] The tunnel oxide layer 11 serves as a channel for charge transfer in the solar cell 100 , allowing electrons to pass through. The tunnel oxide layer 11 reduces the recombination of surface charge carriers, reduces the energy loss of the solar cell 100 , and improves the efficiency of the solar cell 100 .

[0055] The positions of the first doping layer 12 and the third doping layer 14 are arranged corresponding to the electrode 20 , forming a surrounding structure in which the metal electrode 20 penetrates the first doping layer 12 and reaches the third doping layer 14 .

[0056] The passivation contact structure 10 of the present invention is achieved by setting a first doping layer 12 and a second doping layer 13 on a tunneling oxide layer 11. The passivation contact structure 10 of the present invention uses the first doping layer 12 at the contact of the electrode 20 to achieve efficient carrier transmission and good surface passivation effect, while solving the parasitic absorption of polysilicon and the high contact resistance problem of doped polysilicon. The second doping layer 13 is set at the contact of the non-electrode 20 for surface passivation. The second doping layer 13 is suitable for ensuring the surface passivation effect while reducing the parasitic absorption effect of the polysilicon layer, thereby improving the infrared response and short-circuit current of the solar cell 100. Therefore, through the synergistic effect of the first doping layer 12 and the second doping layer 13, the solar cell 100 using the passivation contact structure 10 has lower contact resistance, better passivation effect and less parasitic absorption energy, thereby improving the efficiency of the solar cell 100.

[0057] In one embodiment, the elements of the tunnel oxide layer 11 include silicon and oxygen, and also include nitrogen and / or carbon.

[0058] Optionally, the chemical composition of the tunnel oxide layer 11 includes SiaOb, SiaObNc, SiaObNcCd, etc., where a, b, c, d are positive integers representing the stoichiometric ratio of each element. Specifically, the tunnel oxide layer 11 may include silicon dioxide, silicon nitride, etc., without limitation.

[0059] The tunneling oxide layer 11 serves as a surface passivation layer in the solar cell 100 and can also satisfy the tunneling transmission of charges. The tunneling oxide layer 11 reduces the recombination of charge carriers, reduces the energy loss of the solar cell 100, and improves the efficiency of the solar cell 100.

[0060] For reference Figure 1 In one embodiment, the thickness of the tunnel oxide layer 11 is d1, which satisfies: 0.5nm≤d1≤4nm.

[0061] Optionally, d1 can be 0.5nm, 1nm, 2nm, 3nm, 4nm, etc. without limitation.

[0062] When d1 is less than 0.5nm, the tunneling oxide layer 11 is prone to problems such as excessive surface defects and charge leakage; when d1 is greater than 4nm, it is difficult to achieve electron tunneling at a lower voltage; when 0.5nm≤d1≤4nm, while achieving electron tunneling, the quality of the tunneling oxide layer 11 is good and it is not easy to have problems such as direct tunneling and charge leakage.

[0063] In one embodiment, the elements of the first doping layer 12 include silicon, phosphorus or boron; the elements of the second doping layer 13 and the third doping layer 14 include silicon, carbon and / or nitrogen, phosphorus or boron.

[0064] The doping concentration of the first doping layer 12 is greater than the doping concentrations of the second doping layer 13 and the third doping layer 14 .

[0065] Phosphorus or boron doping can form a specific energy level structure and energy band bending, realize field effect passivation and form efficient selective carrier transmission at the electrode 20, avoid electron and hole recombination, and reduce reverse saturation current. The higher doping concentration of the first doping layer 12 is conducive to better carrier transmission, while the lower doping concentration of the second doping layer 13 and the third doping layer 14 is conducive to lower parasitic absorption and fewer defect recombination centers.

[0066] Specifically, when the second doping layer 13 and the third doping layer 14 are used as electron selective contact, the passivation contact structure 10 is arranged on the side of the solar cell 100 facing away from the light source, and the second doping layer 13 and the third doping layer 14 are polysilicon co-doped with phosphorus, carbon and nitrogen; when used as hole selective contact, the passivation contact structure 10 is arranged on the side of the solar cell 100 facing the light source, and the second doping layer 13 and the third doping layer 14 are polysilicon doped with boron, carbon and nitrogen.

[0067] The second doping layer 13 and the third doping layer 14 can ensure the surface passivation effect and reduce the parasitic absorption effect of the polysilicon layer by carbon / nitrogen doping and using a lower phosphorus or boron doping concentration, thereby improving the infrared response and short-circuit current of the solar cell 100. The first doping layer 12 is suitable for improving the electron mobility and realizing the electron selective transmission at the contact of the electrode 20, and simultaneously reducing the metal composite current and contact resistance.

[0068] For reference Figure 1 In one embodiment, the thickness of the first doping layer 12 is d2, satisfying: 50nm≤d2≤200nm;

[0069] The thickness of the second doping layer 13 is d3, which satisfies: 30nm≤d3≤150nm;

[0070] The thickness of the third doping layer 14 is d4, which satisfies: 30 nm≤d4≤150 nm.

[0071] For reference Figure 1 , in one implementation, it also satisfies: d3=d4.

[0072] The second doping layer 13 and the third doping layer 14 are prepared by the same process in the preparation process, so the second doping layer 13 and the third doping layer 14 have the same thickness.

[0073] Optionally, d2 is 50nm, 100nm, 150nm, 200nm, etc., without limitation.

[0074] d3 can be 30nm, 60nm, 90nm, 120nm, 150nm, etc. without limitation.

[0075] In one embodiment, the condition d2>d3 is also satisfied. This arrangement prevents the electrode 20 from directly contacting the tunnel oxide layer 11 during the sintering process.

[0076] The stacked structure of the first doping layer 12 and the third doping layer 14 is arranged at the electrode 20 pattern, so that the tunnel oxide layer 11 can be prevented from being burned through during the sintering process of the electrode 20. The second doping layer 13 and the third doping layer 14 are relatively thin, and the surface passivation effect can be ensured by carbon / nitrogen doping and using a lower phosphorus or boron doping concentration, while reducing the parasitic absorption effect of the polysilicon layer, thereby improving the infrared response and short-circuit current of the solar cell 100.

[0077] For reference Figure 2 , Figure 3 and Figure 4The present invention provides a solar cell 100, which is suitable for converting light energy into electrical energy, including a silicon base layer 30, an electrode 20 and a passivation contact structure 10 of any of the various embodiments described above, wherein a tunneling oxide layer 11 is connected to the silicon base layer 30, and the electrode 20 is connected to the first doping layer 12.

[0078] Specifically, the electrode 20 is disposed in the stacked structure of the first doping layer 12 and the third doping layer 14 according to the grid line pattern designed for the solar cell 100 , penetrates the third doping layer 14 , and is contained in the first doping layer 12 to form a receiving structure of the electrode 20 .

[0079] The silicon substrate layer 30 may be an n-type single crystal silicon substrate, which is usually used in combination with a p-type single crystal silicon (i.e., a hole-type semiconductor) to form a pn junction, thereby achieving photoelectric conversion and carrier transport. Correspondingly, when the silicon substrate layer 30 is single crystal silicon, the solar cell 100 is a single crystal silicon solar cell 100.

[0080] Optionally, the electrode 20 is a silver grid line electrode 20, which is made of a silver wire mesh, a silver aluminum wire mesh, an electroplated wire mesh or a conductive film, and is mainly used to collect and transmit photogenerated carriers to achieve conversion of light energy into electrical energy.

[0081] The passivation contact structure 10 of the solar cell 100 of the present invention is arranged on the silicon base layer 30, and the passivation contact structure 10 is provided by arranging a first doping layer 12 and a second doping layer 13 on the tunneling oxide layer 11, and a third doping layer 14 is further provided on the surface of the second doping layer 13, and a combination of the stacked structure of the first doping layer 12 and the third doping layer 14 is used at the contact point of the electrode 20 to achieve efficient carrier transmission and good surface passivation effect, while solving the parasitic absorption of polycrystalline silicon and the high contact resistance problem of doped polycrystalline silicon, and the third doping layer 14 is arranged on the surface of the second doping layer 13 to avoid the contact between the electrode 20 and the tunneling oxide layer 11, and the second doping layer 13 is arranged at the non-electrode 20 contact point for surface passivation, and the second doping layer 13 is suitable for ensuring the surface passivation effect while reducing the parasitic absorption effect of the polycrystalline silicon layer, and therefore the solar cell 100 using the passivation contact structure 10 has lower contact resistance, better passivation effect and less parasitic absorption energy, thereby improving the efficiency, long-wave field light absorption and bifaciality of the solar cell 100.

[0082] For reference Figure 2 In one embodiment, there are multiple electrodes 20, and the passivation contact structure 10 is arranged corresponding to the electrodes 20.

[0083] A plurality of electrodes 20 are arranged at intervals or distributed in an array on the silver grid lines or thin films, and are connected and fixed to the passivation contact structure 10 by sintering.

[0084] The electrodes 20 may be arranged at intervals on a surface of the solar cell 100 facing the light source, or the electrodes 20 may be arranged at intervals on a surface of the solar cell 100 facing away from the light source.

[0085] The electrode 20 in the solar cell 100 can effectively improve the power output and efficiency of the solar cell 100 panel, and the electrode 20 is arranged corresponding to the passivation contact structure 10, which can prevent the electrode 20 from burning through the tunneling oxide layer 11 during the sintering process, affecting the performance and service life of the solar cell 100.

[0086] For reference Figure 1 In one embodiment, the silicon base layer 30 includes a first surface 31 and a second surface 32 that are arranged opposite to each other in a first direction X, the first surface 31 is suitable for facing the light source, at least one of the first surface 31 and the second surface 32 is connected to the tunneling oxide layer 11, and the first direction X is the thickness direction of the solar cell 100.

[0087] Optional, for reference Figure 2 , only the first surface 31 is provided with a passivation contact structure 10, or, reference may be made to Figure 3 , only the second surface 32 is provided with a passivation contact structure 10, or, reference may be made to Figure 4 A passivation contact structure 10 is disposed on both the first surface 31 and the second surface 32 .

[0088] The passivation contact structure 10 of the present invention has lower parasitic absorption, so the passivation contact structure 10 of the present invention can be used for the side of the solar cell 100 facing the light source to replace the diffused doped homojunction structure of the side of the traditional solar cell 100 facing the light source, to realize a double-sided solar cell 100, to solve the problem of Auger recombination loss of the boron emitter on the light source side of the traditional solar cell 100 and maintain a lower contact resistance, thereby realizing an increase in the open circuit voltage and short circuit current of the solar cell 100.

[0089] In one implementation, reference may be made to Figure 2 A passivation contact structure 10 is provided on the first surface 31, a first anti-reflection layer 40 is provided on the surface of the second doping layer 13 away from the first surface 31, and a tunneling oxide layer 11, a fourth doping layer 50 and a second anti-reflection layer 60 are stacked in sequence on the second surface 32 in a direction away from the first surface 31.

[0090] Or, you can refer to Figure 3 The second surface 32 is provided with a passivation contact structure 10 , and in a direction away from the second surface 32 , the first surface 31 is provided with a boron diffused emitter layer 70 , an aluminum oxide passivation layer 80 and a first anti-reflection layer 40 stacked in sequence.

[0091] Or, you can refer to Figure 4Both the first surface 31 and the second surface 32 are provided with a passivation contact structure 10 .

[0092] Optionally, the first anti-reflection layer 40 is disposed on the surfaces of the second doping layer 13 and the third doping layer 14 away from the first surface 31 .

[0093] Optionally, the boron diffused emitter layer 70 is a p+ emitter layer, and the boron diffused emitter layer 70 can provide injection and separation of electron-hole pairs, enhance the light absorption capacity of the solar cell 100, and guide and promote the flow of charges. Specifically, when the light source irradiates the solar cell 100, the energy of the photons will excite the electrons in the boron diffused emitter layer 70, causing them to transition to the conduction band to form free electrons. At the same time, the energy of the photons will also excite the holes in the boron diffused emitter layer 70, causing them to transition to the valence band to form free holes. The boron diffused emitter layer 70 injects electrons and holes into the pn junction. Due to the presence of the pn junction, electrons and holes will be affected by the electric field force and separated into different areas, forming a potential difference, thereby generating an electric field.

[0094] Optionally, the fourth doping layer 50 includes phosphorus-doped polysilicon or boron-doped polysilicon, and the elements of the fourth doping layer 50 further include carbon and / or nitrogen. The composition of the fourth doping layer 50 may be consistent with the composition of the second doping layer 13 .

[0095] Optionally, the first anti-reflection layer 40 and the second anti-reflection layer 60 may also be anti-reflection layers or AR layers, which are suitable for reducing the reflectivity of the light source. The first anti-reflection layer 40 and the second anti-reflection layer 60 may include at least one or any combination of aluminum oxide, silicon oxynitride, silicon nitride, silicon oxide and magnesium fluoride, etc., for reducing surface reflection and improving the absorption rate of solar light. The anti-reflection layer can also improve light absorption, enhance light transmission, suppress light energy loss, and enhance the weather resistance and corrosion resistance of the solar cell 100.

[0096] Optionally, the aluminum oxide passivation layer 80 is suitable for improving the surface passivation of the boron diffused emitter layer 70 and increasing the efficiency of the solar cell 100 .

[0097] In one embodiment, a passivation contact structure 10 is provided on the first surface 31, and the electrode 20 includes a first end face and a second end face that are arranged opposite to each other along the first direction X, the first end face protrudes from the end face of the passivation contact structure 10 away from the silicon base layer 30, and there is a gap between the second end face and the tunneling oxide layer 11. Optionally, the first end face protrudes from the end face of the third doping layer 14.

[0098] This arrangement prevents the electrode 20 from contacting the tunnel oxide layer 11 during the sintering process.

[0099] For reference Figure 5 The present invention provides a method for preparing a solar cell 100, comprising the following steps:

[0100] Step S10, providing a silicon base layer 30;

[0101] Step S20, providing a passivation contact structure 10 on the surface of the silicon base layer 30;

[0102] Step S30, forming an electrode 20 on the first doped layer 12 of the passivation contact structure 10, and obtaining a solar cell 100. The solar cell 100 includes a silicon base layer 30, an electrode 20 and a passivation contact structure 10, the tunneling oxide layer 11 is connected to the silicon base layer 30, and the electrode 20 penetrates the third doped layer 14 to reach the first doped layer 12, forming a receiving structure for the electrode 20.

[0103] Specifically, step S10 includes: cleaning the surface of the n-type single crystal silicon wafer to remove contamination and line marks, using alkaline solution to perform texturing to form a surface pyramid anti-reflection structure, performing RCA cleaning, and obtaining a silicon base layer 30.

[0104] Specifically, step S30 includes: screen printing silver paste, sintering at a high temperature of 700°C-800°C to form an electrode 20, and the printing position thereof is set corresponding to the passivation contact structure 10. The solar cell 100 prepared by the present invention is provided with a passivation contact structure 10 on a silicon base layer 30, and the first doping layer 12 and the second doping layer 13 in the passivation contact structure 10 are arranged on the tunneling oxide layer 11, and a third doping layer 14 is also arranged on the surface of the second doping layer 13. The passivation contact structure 10 of the present invention uses a combination of a stacked structure of the first doping layer 12 and the third doping layer 14 at the contact of the electrode 20 to achieve efficient carrier transport and good surface passivation effect, while solving the parasitic absorption of polycrystalline silicon and the high contact resistance of doped polycrystalline silicon. The third doping layer 14 is arranged on the surface of the second doping layer 13 to avoid the electrode 20 from contacting the tunneling oxide layer 11, and the second doping layer 13 is arranged at the non-electrode 20 contact for surface passivation. The second doping layer 13 is suitable for ensuring the surface passivation effect while reducing the parasitic absorption effect of the polycrystalline silicon layer.

[0105] For reference Figure 6 In one implementation, step S20 includes:

[0106] Step S21, forming a tunneling oxide layer 11 on the surface of the silicon base layer 30;

[0107] Step S22, locally depositing a first doping layer 12 on a surface of the tunneling oxide layer 11 away from the silicon base layer 30;

[0108] Step S23 , forming a second doping layer 13 and a third doping layer 14 by deposition on the surfaces of the tunneling oxide layer 11 and the first doping layer 12 away from the silicon base layer 30 .

[0109] Optionally, in step S21, a tunneling oxide layer 11 is formed on the surface of the silicon base layer 30, including: one of high-temperature thermal oxidation, plasma oxidation, ozone oxidation and thermal nitric acid oxidation. Specifically, the tunneling oxide layer 11 is deposited and formed using a high-temperature oxidation method in a tubular quartz furnace, the heating temperature is 500° C.-700° C., and the heating time is 10 min-30 min.

[0110] Optionally, in step S22, a first doping layer 12 is locally deposited on a surface of the tunneling oxide layer 11 away from the silicon base layer 30, and the deposition method may be a plasma enhanced chemical vapor deposition method (PECVD) or a low pressure chemical vapor deposition method (LPCVD) for mask deposition, including: a mask plate is arranged on a surface of the tunneling oxide layer 11 of the passivation contact structure 10 away from the silicon base layer 30 of the passivation contact structure 10, and the mask plate of the passivation contact structure 10 is provided with an opening;

[0111] Passing silane, passing phosphine or borane, and depositing at the opening of the mask plate of the passivation contact structure 10 to form a first transition layer;

[0112] High temperature annealing to form a first doping layer 12;

[0113] Remove the mask.

[0114] Specifically, the opening position of the mask plate corresponds to the position of the silver grid line, and the width of the opening is 50 μm-200 μm; the temperature of the high temperature annealing is 800° C.-1000° C.; when the passivation contact structure 10 is disposed on the first surface 31, when the doping element is boron, the boron doping concentration is 10 18 / cm 2 -10 21 / cm 2 , the square resistance is 30Ω / sq-150Ω / sq; when the passivation contact structure 10 is disposed on the second surface 32, when the doping element is phosphorus, the phosphorus doping concentration is 10 19 / cm 2 -10 22 / cm 2 , the square resistance is 30Ω / sq-150Ω / sq; the mask can also be formed by inkjet printing or screen printing an acid-resistant (or alkali-resistant) organic slurry at the position in contact with the gate line, and then the first doped layer 12 of the unmasked part is etched away by a mixed solution of nitric acid and hydrochloric acid (or alkaline solution); and the patterned locally doped polysilicon can also be prepared by laser etching to remove the doped first doped layer 12 outside the gate line position.

[0115] Optionally, in step S23, a second doping layer 13 and a third doping layer 14 are deposited on the surface of the tunneling oxide layer 11 and the first doping layer 12 away from the silicon base layer 30, and the deposition method may be plasma enhanced chemical vapor deposition or hot filament chemical vapor deposition (HWCVD), including:

[0116] Silane, hydrogen, nitrogen and methane are introduced, and phosphine or borane is introduced to form a second transition layer by deposition on the surface of the tunneling oxide layer 11 and the second doping layer 13 away from the silicon base layer 30;

[0117] High temperature annealing is performed to form the second doping layer 13 and the third doping layer 14 .

[0118] Specifically, the temperature of the high temperature annealing is 700° C.-950° C. When the passivation contact structure 10 is disposed on the first surface 31, the doping element is boron, and the doping concentration of the boron element is 10 18 / cm 2 -10 20 / cm 2 , square resistance is 50Ω / sq-200Ω / sq, and the doping concentration of carbon or nitrogen is 10 19 / cm 2 -10 22 / cm 2 When the passivation contact structure 10 is disposed on the second surface 32, the doping element is phosphorus, and the phosphorus doping concentration is 10 18 / cm 2 -10 20 / cm 2 , square resistance is 50Ω / sq-200Ω / sq, and the doping concentration of carbon or nitrogen is 10 19 / cm 2 -10 22 / cm 2 .

[0119] Optionally, when the passivation contact structure 10 is provided only on the second surface 32 , step S10 further includes: forming a boron diffused emitter layer 70 on the first surface 31 ; and performing back alkali polishing.

[0120] Specifically, the boron diffused emitter layer 70 is formed on the first surface 31 by high-temperature diffusion of boron diffused emitter layer 70 and borosilicate glass using boron trichloride as a boron source in a low-pressure tube furnace. The diffusion temperature is 900° C.-1100° C. for 1 h-3 h. The diffusion depth of the boron diffused emitter layer 70 finally formed is 0.5 μm-1.5 μm, and the doping concentration is 10 18 / cm 2 -10 20 / cm 2 , square resistance is 50Ω / sq-300Ω / sq.

[0121] The pickling of the first surface 31 includes removing the borosilicate glass on the second surface 32 with hydrofluoric acid or the like, and texturing and polishing the second surface 32 into a polished surface with an alkali solution.

[0122] Optionally, only when the passivation contact structure 10 is provided on the first surface 31, step S10 further includes:

[0123] A mask on the first surface 31 is formed by depositing silane and ammonia gas using PECVD on the first surface 31. The mask is a silicon nitride mask with a thickness of 200 nm and a refractive index of 1.9 to 2.2, so as to protect the velvet surface of the first surface 31 from being affected by subsequent processes.

[0124] The fourth doping layer 50 is deposited on the second surface 32. The fourth doping layer 50 can be prepared by LPCVD or PECVD. During the deposition, silane, hydrogen, phosphine, methane and ammonia are introduced to prepare phosphorus, carbon / nitrogen doped amorphous silicon, and annealed and crystallized at 600° C.-900° C. to form the doped fourth doping layer 50. The thickness of the fourth doping layer 50 is 50 nm-150 nm, and the doping concentration of phosphorus is 10 19 / cm 2 -10 21 / cm 2 , square resistance is 50Ω / sq-200Ω / sq;

[0125] Depositing a second anti-reflection layer 60 and a protective layer, using PECVD to deposit the second anti-reflection layer 60 and the protective layer on the fourth doping layer 50, the second anti-reflection layer 60 is silicon nitride, the thickness of the second anti-reflection layer 60 is 60nm-150nm, the protective layer is silicon oxide, the thickness of the protective layer is 50nm;

[0126] The mask on the first surface 31 is removed. Hydrofluoric acid is used to remove the silicon nitride mask on the first surface 31 .

[0127] Optionally, step S30 further includes: cleaning after the doping layer is deposited, the polysilicon coated on the first surface 31 may be removed by alkaline solution, the phosphosilicate glass and borosilicate glass on the first surface 31 may be removed by hydrofluoric acid, etc., and RCA cleaning may be performed to remove excess phosphosilicate glass on the second surface 32;

[0128] The preparation methods of the first anti-reflection layer 40 and the second anti-reflection layer 60 include atomic layer deposition, PECVD, thermal evaporation, physical vapor deposition, etc., without limitation. Specifically, when the anti-reflection layer is aluminum oxide, atomic layer deposition can be used, and trimethyl aluminum and water are circulated under the condition of 200°C-300°C to prepare an aluminum oxide passivation layer with a thickness of 2nm-15nm; when the anti-reflection layer contains silicon nitride, silicon oxynitride and silicon oxide, it can be prepared by PECVD, and the gas source is silane, ammonia and nitrous oxide, and the anti-reflection layer with a thickness of 50nm-150nm is deposited at 350°C-600°C.

[0129] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientation or positional relationship described in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0130] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A passivation contact structure for a solar cell, wherein the solar cell is suitable for converting light energy into electrical energy, characterized in that: include: Tunneling oxide layer; A first doped layer, comprising phosphorus-doped polysilicon or boron-doped polysilicon, wherein the first doped layer is suitable for connecting to an electrode of the solar cell; The second doping layer is arranged on the tunneling oxide layer and connected to the first doping layer. The second doping layer includes phosphorus-doped polysilicon or boron-doped polysilicon. The elements of the second doping layer also include carbon and / or nitrogen.

2. The passivation contact structure according to claim 1, characterized in that: The first doped layer is disposed on the tunneling oxide layer, and the second doped layer at least surrounds an outer periphery of the first doped layer on a side close to the tunneling oxide layer.

3. The passivation contact structure according to claim 1, characterized in that: The elements of the tunnel oxide layer include silicon and oxygen, and also include nitrogen and / or carbon.

4. The passivation contact structure according to claim 2, characterized in that: The thickness of the tunnel oxide layer is d1, which satisfies: 0.5nm≤d1≤4nm.

5. The passivation contact structure according to claim 1, characterized in that: The passivation contact structure further includes a third doping layer, and the third doping layer is arranged on a surface of the first doping layer away from the tunneling oxide layer; The third doping layer includes phosphorus-doped polysilicon or boron-doped polysilicon, and the elements of the third doping layer further include carbon and / or nitrogen.

6. The passivation contact structure according to claim 5, characterized in that: The thickness of the first doping layer is d2, which satisfies: 50nm≤d2≤200nm; The thickness of the second doping layer is d3, which satisfies: 30nm≤d3≤150nm; The thickness of the third doping layer is d4, which satisfies: 30nm≤d4≤150nm.

7. The passivation contact structure according to claim 6, characterized in that: It also satisfies: d3=d4.

8. The passivation contact structure according to claim 6, characterized in that: It also satisfies: d2>d3.

9. A solar cell, characterized in that: The solar cell is suitable for converting light energy into electrical energy, and comprises a silicon base layer, an electrode and a passivation contact structure as claimed in any one of claims 1 to 8, wherein the tunneling oxide layer is connected to the silicon base layer, and the electrode is connected to the first doping layer.

10. The solar cell according to claim 9, characterized in that: The silicon base layer includes a first surface and a second surface disposed opposite to each other in a first direction, the first surface is suitable for facing the light source, at least one of the first surface and the second surface is connected to the passivation contact structure, and the first direction is the thickness direction of the solar cell.

11. The solar cell according to claim 10, characterized in that The first surface is provided with the passivation contact structure, the surface of the second doped layer away from the first surface is provided with the first anti-reflection layer, and the second surface is sequentially stacked with the tunneling oxide layer, the fourth doped layer and the second anti-reflection layer in a direction away from the first surface; Or, the second surface is provided with the passivation contact structure, and in a direction away from the second surface, the first surface is provided with a boron diffused emitter layer, an aluminum oxide passivation layer and the first anti-reflection layer stacked in sequence; Alternatively, both the first surface and the second surface are provided with the passivation contact structure.

12. The solar cell according to claim 11, characterized in that: The first anti-reflection layer and the second anti-reflection layer include at least one of aluminum oxide, silicon oxynitride, silicon nitride, silicon oxide and magnesium fluoride; The fourth doping layer includes phosphorus-doped polysilicon or boron-doped polysilicon, and the elements of the fourth doping layer further include carbon and / or nitrogen.

13. The solar cell according to claim 11, characterized in that: The first surface is provided with the passivation contact structure, the electrode comprises a first end face and a second end face arranged opposite to each other along the first direction, the first end face protrudes from the end face of the passivation contact structure away from the silicon base layer, and there is a gap between the second end face and the tunneling oxide layer.

14. A method for preparing a solar cell, characterized in that: The steps include: providing a silicon base layer; Providing a passivation contact structure on the surface of the silicon base layer; An electrode is formed on the first doped layer of the passivation contact structure to obtain a solar cell as described in any one of claims 9 to 13, wherein the solar cell comprises a silicon base layer, an electrode and a passivation contact structure, the tunneling oxide layer of the passivation contact structure is connected to the silicon base layer, and the electrode is arranged on the first doped layer.

15. The method for preparing a solar cell according to claim 14, characterized in that: A passivation contact structure is provided on the surface of the silicon base layer, comprising: forming a tunneling oxide layer on the surface of the silicon base layer; Locally depositing a first doping layer on a surface of the tunneling oxide layer away from the silicon base layer; A second doping layer and a third doping layer are deposited on surfaces of the tunneling oxide layer and the first doping layer away from the silicon base layer.

Images