Solar cell and preparation method thereof

Abstract

The invention discloses a solar cell and a preparation method thereof. The solar cell comprises a silicon substrate, a tunneling layer, a first semiconductor layer, a second semiconductor layer and an electrode, the tunneling layer is arranged on one surface of the silicon substrate; the first semiconductor layer is arranged on one surface, far away from the silicon substrate, of the tunneling layer, the first semiconductor layer comprises a first sub-layer and a second sub-layer which are sequentially arranged from inside to outside, the first sub-layer is further doped with an oxygen element, and the second sub-layer is further doped with a carbon element and / or a nitrogen element; and the electrode is respectively in ohmic contact with the second sub-layer and the second semiconductor layer. The first sub-layer close to one side of the tunneling layer is doped with the oxygen element, so that the first sub-layer can obtain a relatively large short-circuit current gain, and meanwhile, the second sub-layer far away from one side of the tunneling layer is doped with the carbon element and / or the nitrogen element, so that the contact resistance between the second sub-layer and the electrode can be reduced; therefore, the overall conversion efficiency of the solar cell is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of photovoltaics, and in particular relates to a solar cell and a preparation method thereof. Background Art

[0002] The tunneling oxide layer passivation contact cell is referred to as TOPCon cell. It is a high-efficiency solar cell that uses an N-type silicon substrate to set a tunneling oxide layer and a doped polysilicon layer on the back of the cell. A Chinese patent application with application number 201610271978.0 discloses a tunneling oxide layer passivation contact solar cell, which discloses the following technical solution: the solar cell includes a silicon wafer, a passivation tunneling layer, and a doped thin film silicon layer. The passivation tunneling layer is between the silicon wafer and the doped thin film silicon layer. The doping concentration of the doped thin film silicon layer is uneven, and the doping concentration of the doped thin film silicon layer adjacent to the passivation tunneling layer is less than the doping concentration on the side away from the passivation tunneling layer. It can not only reduce the overall doping concentration of the doped thin film silicon layer, thereby helping to reduce the Auger recombination rate in the film, avoid the generation of silicon phosphide precipitation, increase the life of minority carriers, and thus increase the conversion efficiency of solar cells; and the polysilicon layer has a lower concentration on the side close to the silicon substrate, which can effectively reduce the probability of doped atoms diffusing into the passivation tunneling layer; the polysilicon layer has a higher concentration on the side close to the back electrode, which can reduce the contact resistance between the back electrode and the polysilicon layer. However, the doped polysilicon layer of this technical solution still has a higher parasitic absorption phenomenon, which leads to a lower current density, thereby reducing the conversion efficiency of the battery. Summary of the invention

[0003] One of the objectives of the present invention is to provide a solar cell that solves the problems raised in the above background technology.

[0004] To achieve the above object, the technical solution adopted by the present invention is: a solar cell, comprising: a silicon substrate, a tunneling layer, a first semiconductor layer, a second semiconductor layer and an electrode;

[0005] The tunneling layer is disposed on one side of the silicon substrate;

[0006] The first semiconductor layer is arranged on a side of the tunneling layer away from the silicon substrate, the first semiconductor layer comprises a first sublayer and a second sublayer arranged in sequence from the inside to the outside, the first sublayer and the second sublayer are doped with a main doping element of N-type doping or P-type doping, the first sublayer is also doped with an oxygen element, and the second sublayer is also doped with a carbon element and / or a nitrogen element;

[0007] The polarity of the second semiconductor layer is opposite to that of the first semiconductor layer;

[0008] The electrodes are in ohmic contact with the second sub-layer and the second semiconductor layer, respectively.

[0009] On the basis of the above scheme and as a preferred scheme of the above scheme, the mass concentration of oxygen element in the first sublayer is n1, the mass concentration of carbon element and / or nitrogen element in the second sublayer is n2, and n1>n2.

[0010] On the basis of the above scheme and as a preferred scheme of the above scheme, the range of n1 is 1%<n1<6%, and the range of n2 is 0.5%<n2<3%.

[0011] On the basis of the above solution and as a preferred solution of the above solution, the first semiconductor layer further includes a third sublayer, and the third sublayer is doped with a main doping element.

[0012] On the basis of the above scheme and as a preferred scheme of the above scheme, the third sublayer is doped with carbon element and / or nitrogen element, the mass concentration of carbon element and / or nitrogen element in the third sublayer is n3, and n1>n2>n3.

[0013] On the basis of the above scheme and as a preferred scheme of the above scheme, the silicon substrate is an N-type silicon substrate, the tunneling layer is arranged on the back side of the silicon substrate, the first semiconductor layer is N-type doped, the second semiconductor layer is arranged on the front side of the silicon substrate, the second semiconductor layer is P-type doped, the surface of the first semiconductor layer is provided with a back passivation layer, and the surface of the second semiconductor layer is provided with a front passivation layer.

[0014] On the basis of the above scheme and as a preferred scheme of the above scheme, the main doping element in the first sublayer, the second sublayer and the third sublayer is boron element so that the first semiconductor layer is N-type doped, and the doping concentration of the boron element in the first sublayer, the second sublayer and the third sublayer increases successively.

[0015] On the basis of the above scheme and as a preferred scheme of the above scheme, the tunneling layer includes one or more of silicon dioxide, silicon nitride, silicon oxynitride and aluminum oxide; the first semiconductor layer and the second semiconductor layer are one or more of polycrystalline silicon layers, microcrystalline silicon layers and nanocrystalline silicon layers.

[0016] On the basis of the above scheme and as a preferred scheme of the above scheme, the first semiconductor layer and the second semiconductor layer are both located on the back side of the silicon substrate, and a back passivation layer is provided between the first semiconductor layer and the second semiconductor layer, and the second semiconductor layer includes a fourth sublayer and a fifth sublayer, the fourth sublayer is doped with oxygen elements, and the fifth sublayer is doped with carbon elements and / or nitrogen elements.

[0017] A second object of the present invention is to provide a method for preparing a solar cell, comprising the following steps:

[0018] S1, forming a second semiconductor layer by sequentially performing texturing and boron diffusion on the front side of the silicon substrate;

[0019] S2, preparing a tunneling layer on the back side of the silicon substrate;

[0020] S3, sequentially preparing a first sublayer and a second sublayer on the back side of the tunneling layer, introducing an oxygen source while preparing the first sublayer to obtain the first sublayer doped with oxygen, and introducing a carbon source and / or a nitrogen source while preparing the second sublayer to obtain the second sublayer doped with carbon and / or nitrogen;

[0021] S4. Prepare electrodes on the front and back sides of the battery respectively.

[0022] The beneficial effects of the present invention are:

[0023] 1. The first sublayer close to the tunneling layer is doped with oxygen so that the first sublayer can obtain a larger short-circuit current gain. At the same time, the second sublayer away from the tunneling layer is doped with carbon and / or nitrogen to reduce the contact resistance between the second sublayer and the electrode, thereby improving the overall conversion efficiency of the solar cell.

[0024] 2. The doping concentration of oxygen in the first sublayer is greater than the doping concentration of carbon and / or nitrogen in the second sublayer, thereby reducing the concentration of the main doping element in the first sublayer and facilitating the concentration of the main doping element in the entire first semiconductor layer to increase from the inside to the outside; it can also reduce the probability of the main doping element diffusing into the tunneling layer and the silicon substrate, improve the tunneling passivation effect, reduce the parasitic absorption loss of the inner polysilicon, and increase the short-circuit current density. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0026] Figure 1 This is a schematic diagram of the structure of Example 1 of the present invention.

[0027] Figure 2 This is a schematic diagram of the structure of Example 2 of the present invention.

[0028] Figure 3 This is a schematic diagram of the structure of Example 3 of the present invention.

[0029] The reference numerals are as follows:

[0030] 1. Silicon substrate; 2. Tunneling layer; 3. First semiconductor layer; 31. First sublayer; 32. Second sublayer; 33. Third sublayer; 4. Second semiconductor layer; 41. Fourth sublayer; 42. Fifth sublayer; 5. Back passivation layer; 6. Front passivation layer; 7. Electrode. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are 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.

[0032] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "up", "down", "front", "back", "left", "right", etc. are directions or positional relationships based on the directions or positional relationships 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 device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0033] Example 1

[0034] As attached Figure 1 As shown, a solar cell comprises: a silicon substrate 1, a tunneling layer 2, a first semiconductor layer 3, a second semiconductor layer 4 and an electrode 7;

[0035] The silicon substrate 1 is an N-type silicon substrate 1,

[0036] The tunneling layer 2 is arranged on the back side of the silicon substrate 1, and the tunneling layer 2 includes one or more of silicon dioxide, silicon nitride, silicon oxynitride and aluminum oxide; the first semiconductor layer 3 and the second semiconductor layer 4 are one or more of polycrystalline silicon layer, microcrystalline silicon layer and nanocrystalline silicon layer;

[0037] The first semiconductor layer 3 is arranged on the side of the tunneling layer 2 away from the silicon substrate 1. The first semiconductor layer 3 includes a first sublayer 31 and a second sublayer 32 arranged in sequence from the inside to the outside. The first sublayer 31 and the second sublayer 32 are doped with a main doping element of N-type doping or P-type doping. When it is N-type doping, the main doping element is boron; when it is P-type doping, the main doping element is phosphorus. At the same time, the first sublayer 31 is also doped with oxygen, and the second sublayer 32 is also doped with carbon and / or nitrogen. The first sublayer close to the tunneling layer is doped with oxygen, so that the first sublayer can obtain a larger short-circuit current gain. At the same time, the second sublayer on the side away from the tunneling layer is doped with carbon and / or nitrogen, which can reduce the contact resistance between the second sublayer and the electrode, thereby improving the overall conversion efficiency of the solar cell.

[0038] The polarity of the second semiconductor layer 4 is opposite to that of the first semiconductor layer 3 ; the second semiconductor layer is disposed on the front side of the silicon substrate.

[0039] The electrode 7 is in ohmic contact with the second sub-layer 32 and the second semiconductor layer 4 , respectively.

[0040] The mass concentration of oxygen in the first sublayer 31 is n1, the mass concentration of carbon and / or nitrogen in the second sublayer 32 is n2, and n1>n2. The range of n1 is 1%<n1<6%, and the range of n2 is 0.5%<n2<3%. The doping concentration of oxygen in the first sublayer is greater than the doping concentration of carbon and / or nitrogen in the second sublayer, so that the concentration of the main doping element in the first sublayer can be reduced, which is convenient for the concentration of the main doping element in the entire first semiconductor layer to increase from the inside to the outside; it can also reduce the probability of the main doping element diffusing into the tunneling layer and the silicon substrate, improve the tunneling passivation effect, reduce the parasitic absorption loss of the inner polysilicon, and increase the short-circuit current density. The thickness of the first sublayer 31 ranges from 10nm to 100nm, and the thickness of the second sublayer 32 ranges from 5nm to 100nm.

[0041] A back passivation layer 5 is disposed on the surface of the first semiconductor layer 3 , and a front passivation layer 6 is disposed on the surface of the second semiconductor layer 4 . The back passivation layer 5 and the front passivation layer 6 can further improve the passivation effect of the battery surface.

[0042] The preparation method of this solar cell is as follows:

[0043] S1. The second semiconductor layer 4 is formed by sequentially performing texturing and boron diffusion on the front side of the silicon substrate 1.

[0044] S2 . Preparing a tunneling layer 2 on the back side of the silicon substrate 1 .

[0045] S3, sequentially prepare the first sublayer 31 and the second sublayer 32 on the back of the tunneling layer 2, and introduce an oxygen source while preparing the first sublayer 31 to obtain the first sublayer 31 doped with oxygen, and the oxygen source can be laughing gas; introduce a carbon source and / or a nitrogen source while preparing the second sublayer 32 to obtain the second sublayer 32 doped with carbon and / or nitrogen, and the carbon source can be carbon dioxide gas, and the nitrogen source can be ammonia. In order to make n1>n2, the concentration of the oxygen source introduced can be greater than the concentration of the carbon source and / or the nitrogen source introduced to achieve this.

[0046] S4. Prepare a front passivation layer and a back passivation layer on the front and back sides respectively.

[0047] S5. Prepare electrodes 7 on the front and back sides of the battery respectively.

[0048] Example 2

[0049] As attached Figure 2 As shown, a solar cell comprises: a silicon substrate 1, a tunneling layer 2, a first semiconductor layer 3, a second semiconductor layer 4 and an electrode 7;

[0050] The silicon substrate 1 is an N-type silicon substrate 1.

[0051] The tunneling layer 2 is arranged on the back side of the silicon substrate 1, and the tunneling layer 2 includes one or more of silicon dioxide, silicon nitride, silicon oxynitride and aluminum oxide; the first semiconductor layer 3 and the second semiconductor layer 4 are one or more of polycrystalline silicon layer, microcrystalline silicon layer and nanocrystalline silicon layer;

[0052] The first semiconductor layer 3 is arranged on the side of the tunneling layer 2 away from the silicon substrate 1. The first semiconductor layer 3 includes a first sublayer 31, a second sublayer 32 and a third sublayer 33 arranged in sequence from the inside to the outside. The first sublayer 31, the second sublayer 32 and the third sublayer 33 are doped with a main doping element of N-type doping or P-type doping. When it is N-type doping, the main doping element is boron; when it is P-type doping, the main doping element is phosphorus. At the same time, the first sublayer 31 is also doped with oxygen, and the second sublayer 32 and the third sublayer 33 are also doped with carbon and / or nitrogen. The first sublayer close to the tunneling layer is doped with oxygen, so that the first sublayer can obtain a larger short-circuit current gain. At the same time, the second sublayer and the third sublayer on the side away from the tunneling layer are doped with carbon and / or nitrogen, which can reduce the contact resistance between the second sublayer and the third sublayer and the electrode, thereby improving the overall conversion efficiency of the solar cell.

[0053] The polarity of the second semiconductor layer 4 is opposite to that of the first semiconductor layer 3 ; the second semiconductor layer is disposed on the front side of the silicon substrate.

[0054] The electrode 7 is in ohmic contact with the second sub-layer 32 and the second semiconductor layer 4 , respectively.

[0055] The mass concentration of oxygen in the first sublayer 31 is n1, and the range of n1 is 1%<n1<6%. The mass concentration of carbon and / or nitrogen in the second sublayer 32 is n2, and the range of n2 is 0.5%<n2<3%. The mass concentration of carbon and / or nitrogen in the third sublayer 33 is n3, and the range of n3 is 0.4<n2<2%, and n1>n2>n3. By making n1>n2>n3, the content of the main doping element in the first sublayer is further reduced, and the probability of the first sublayer blocking the main doping element from entering the tunneling layer and the silicon substrate is increased. The thickness of the first sublayer 31 is in the range of 10nm-100nm, the thickness of the second sublayer 32 is in the range of 5nm-100nm, and the thickness of the third sublayer is in the range of 5nm-100nm.

[0056] A back passivation layer 5 is disposed on the surface of the first semiconductor layer 3 , and a front passivation layer 6 is disposed on the surface of the second semiconductor layer 4 . The back passivation layer 5 and the front passivation layer 6 can further improve the passivation effect of the battery surface.

[0057] The preparation method of this solar cell is as follows:

[0058] S1. The second semiconductor layer 4 is formed by sequentially performing texturing and boron diffusion on the front side of the silicon substrate 1.

[0059] S2 . Preparing a tunneling layer 2 on the back side of the silicon substrate 1 .

[0060] S3. Prepare the first sublayer 31, the second sublayer 32 and the third sublayer 33 in sequence on the back side of the tunneling layer 2. When preparing the first sublayer 31, introduce an oxygen source to obtain the first sublayer 31 doped with oxygen. The oxygen source can be nitrous oxide. When preparing the second sublayer 32 and the third sublayer 33, introduce a carbon source and / or a nitrogen source to obtain the second sublayer 32 doped with carbon and / or nitrogen. The carbon source can be carbon dioxide gas, and the nitrogen source can be ammonia.

[0061] S4. Prepare a front passivation layer and a back passivation layer on the front and back sides respectively.

[0062] S5. Prepare electrodes 7 on the front and back sides of the battery respectively.

[0063] Example 3

[0064] As attached Figure 3 As shown, a solar cell comprises: a silicon substrate 1, a tunneling layer 2, a first semiconductor layer 3, a second semiconductor layer 4 and an electrode 7;

[0065] The silicon substrate 1 is an N-type silicon substrate 1.

[0066] The tunneling layer 2 is arranged on the back side of the silicon substrate 1, and the tunneling layer 2 includes one or more of silicon dioxide, silicon nitride, silicon oxynitride and aluminum oxide; the first semiconductor layer 3 and the second semiconductor layer 4 are one or more of polycrystalline silicon layer, microcrystalline silicon layer and nanocrystalline silicon layer;

[0067] The first semiconductor layer 3 is arranged on the side of the tunneling layer 2 away from the silicon substrate 1. The first semiconductor layer 3 includes a first sublayer 31 and a second sublayer 32 arranged in sequence from the inside to the outside. The first sublayer 31 and the second sublayer 32 are doped with a main doping element of N-type doping or P-type doping. When it is N-type doping, the main doping element is boron; when it is P-type doping, the main doping element is phosphorus. The polarity of the second semiconductor layer 4 is opposite to that of the first semiconductor layer 3; the second semiconductor layer is also arranged on the back side of the silicon substrate. A back passivation layer 5 is provided between the first semiconductor layer 3 and the second semiconductor layer 4 to prevent a short circuit between the first semiconductor layer and the second semiconductor layer, and the electrode 7 is in ohmic contact with the second sublayer 32 and the fifth sublayer 42 respectively.

[0068] The first sublayer 31 is also doped with oxygen, and the second sublayer 32 is also doped with carbon and / or nitrogen. The mass concentration of oxygen in the first sublayer 31 is n1, the mass concentration of carbon and / or nitrogen in the second sublayer 32 is n2, and n1>n2. The range of n1 is 1%<n1<6%, and the range of n2 is 0.5%<n2<3%. The second semiconductor layer 4 includes a fourth sublayer 41 and a fifth sublayer 42, the fourth sublayer 41 is doped with oxygen, and the fifth sublayer 42 is doped with carbon and / or nitrogen. The mass concentration of oxygen in the fourth sublayer 41 is n4, the mass concentration of carbon and / or nitrogen in the fifth sublayer 42 is n5, and n4>n5.

[0069] The surfaces of the first semiconductor layer 3 and the second semiconductor layer 4 are provided with a back passivation layer 5, and the surface of the silicon substrate 1 is provided with a front passivation layer 6. The back passivation layer 5 and the front passivation layer 6 can further improve the passivation effect of the battery surface.

[0070] This technical solution sets the electrodes on the back side, which reduces the blocking effect of the electrodes on the front side, and improves the utilization efficiency of sunlight. The first sublayer and the fourth sublayer on the side close to the tunneling layer are doped with oxygen elements, so that the first sublayer and the fourth sublayer can obtain a larger short-circuit current gain. At the same time, the second sublayer and the fifth sublayer on the side away from the tunneling layer are doped with carbon elements and / or nitrogen elements, which can reduce the contact resistance between the second sublayer and the fifth sublayer and the electrode, thereby improving the overall conversion efficiency of the solar cell.

[0071] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments described herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A solar cell, characterized in that: include: A silicon substrate (1), a tunneling layer (2), a first semiconductor layer (3), a second semiconductor layer (4) and an electrode (7); The tunneling layer (2) is arranged on one side of the silicon substrate (1); The first semiconductor layer (3) is arranged on a side of the tunneling layer (2) away from the silicon substrate (1), the first semiconductor layer (3) comprising a first sublayer (31) and a second sublayer (32) arranged in sequence from the inside to the outside, the first sublayer (31) and the second sublayer (32) are doped with a main doping element of N-type doping or P-type doping, the first sublayer (31) is also doped with an oxygen element, and the second sublayer (32) is also doped with a carbon element and / or a nitrogen element; The polarity of the second semiconductor layer (4) is opposite to the polarity of the first semiconductor layer (3); The electrode (7) is in ohmic contact with the second sublayer (32) and the second semiconductor layer (4), respectively.

2. A solar cell according to claim 1, characterized in that: The mass concentration of oxygen in the first sublayer (31) is n1, the mass concentration of carbon and / or nitrogen in the second sublayer (32) is n2, and n1>n2.

3. A solar cell according to claim 2, characterized in that: The range of n1 is 1%<n1<6%, and the range of n2 is 0.5%<n2<3%.

4. A solar cell according to claim 1, characterized in that: The first semiconductor layer (3) further comprises a third sublayer (33), wherein the third sublayer (33) is doped with a main doping element.

5. A solar cell according to claim 4, characterized in that: The third sublayer (33) is doped with carbon and / or nitrogen, the mass concentration of the carbon and / or nitrogen in the third sublayer (33) is n3, and n1>n2>n3.

6. A solar cell according to claim 4, characterized in that: The silicon substrate (1) is an N-type silicon substrate (1), the tunneling layer (2) is arranged on the back side of the silicon substrate (1), the first semiconductor layer (3) is N-type doped, the second semiconductor layer (4) is arranged on the front side of the silicon substrate (1), the second semiconductor layer (4) is P-type doped, a back passivation layer (5) is arranged on the surface of the first semiconductor layer (3), and a front passivation layer (6) is arranged on the surface of the second semiconductor layer (4).

7. A solar cell according to claim 6, characterized in that: The main doping element in the first sublayer (31), the second sublayer (32) and the third sublayer (33) is boron so that the first semiconductor layer (3) is N-type doped, and the doping concentration of the boron element in the first sublayer (31), the second sublayer (32) and the third sublayer (33) increases in sequence.

8. A solar cell according to claim 1, characterized in that: The tunneling layer (2) comprises one or more of silicon dioxide, silicon nitride, silicon oxynitride and aluminum oxide; the first semiconductor layer (3) and the second semiconductor layer (4) are one or more of polycrystalline silicon layers, microcrystalline silicon layers and nanocrystalline silicon layers.

9. A solar cell according to claim 1, characterized in that: The first semiconductor layer (3) and the second semiconductor layer (4) are both located on the back side of the silicon substrate (1), and a back side passivation layer (5) is provided between the first semiconductor layer (3) and the second semiconductor layer (4), the second semiconductor layer (4) comprises a fourth sublayer (41) and a fifth sublayer (42), the fourth sublayer (41) is doped with oxygen, and the fifth sublayer (42) is doped with carbon and / or nitrogen.

10. The method for preparing a solar cell according to claim 1, characterized in that: The following steps are involved: S1, sequentially performing texturing and boron diffusion on the front surface of the silicon substrate (1) to form a second semiconductor layer (4); S2, preparing a tunneling layer (2) on the back side of the silicon substrate (1); S3, sequentially preparing a first sublayer (31) and a second sublayer (32) on the back side of the tunneling layer (2), introducing an oxygen source while preparing the first sublayer (31) to obtain the first sublayer (31) doped with oxygen, and introducing a carbon source and / or a nitrogen source while preparing the second sublayer (32) to obtain the second sublayer (32) doped with carbon and / or nitrogen; S4. Prepare electrodes (7) on the front and back sides of the battery respectively.

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