A solar cell and a method of manufacturing the same

Abstract

This invention discloses a solar cell and its fabrication method. The solar cell includes a substrate, at least two sub-cells, and a contact layer stacked sequentially from bottom to top. A tunneling junction is disposed between adjacent sub-cells. The tunneling junction includes stacked n-type first doped layers, n-type second doped layers, p-type first doped layers, and p-type second doped layers. The n-type first doped layers and n-type second doped layers are adjacent, as are the p-type first doped layers and p-type second doped layers. The doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer, and the doping concentration of p-type ions in the p-type first doped layer is higher than that in the p-type second doped layer. The fabrication method is used to fabricate the aforementioned solar cell. The solar cell and fabrication method provided by this invention improve the photoelectric conversion efficiency of solar cells.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a solar cell and its fabrication method. Background Technology

[0002] Gallium arsenide solar cells have good spectral response and are commonly used in aerospace and concentrated photovoltaic power plants.

[0003] Gallium arsenide (GaAs) solar cells consist of multiple sub-cells connected in series, with each sub-cell linked by a tunneling junction. Their energy bands increase sequentially from bottom to top, each absorbing different wavelengths of light to achieve full-spectrum absorption. However, most current GaAs solar cells use gallium arsenide (GaAs) or aluminum gallium arsenide (AlGaAs) for their tunneling junctions. The light transmittance of these junctions is not ideal, resulting in less light not absorbed by the upper sub-cells reaching the lower sub-cells, leading to low photoelectric conversion efficiency.

[0004] Therefore, how to develop a solar cell that can utilize a tunnel junction with good light transmittance to improve the photoelectric conversion efficiency of the solar cell has become an important issue that the industry urgently needs to address. Summary of the Invention

[0005] To address the shortcomings of existing technologies, embodiments of the present invention provide a solar cell and a method for its fabrication.

[0006] On one hand, embodiments of the present invention propose a solar cell, comprising a substrate, at least two sub-cells, and a contact layer stacked sequentially from bottom to top, wherein a tunneling junction is disposed between two adjacent sub-cells, characterized in that the tunneling junction comprises:

[0007] An n-type first doped layer, an n-type second doped layer, a p-type first doped layer, and a p-type second doped layer are stacked together, with the n-type first doped layer and the n-type second doped layer adjacent to each other, the p-type first doped layer and the p-type second doped layer adjacent to each other, and the n-type first doped layer and the p-type first doped layer adjacent to each other; wherein the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer, and the doping concentration of p-type ions in the p-type first doped layer is higher than that in the p-type second doped layer;

[0008] Alternatively, an n-type third doped layer, an n-type fourth doped layer, and a p-type fifth doped layer may be stacked, wherein the n-type third doped layer and the n-type fourth doped layer are adjacent to each other, and the n-type fourth doped layer and the p-type fifth doped layer are adjacent to each other; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer.

[0009] Alternatively, a p-type third doped layer, a p-type fourth doped layer, and an n-type fifth doped layer may be stacked, wherein the p-type third doped layer and the p-type fourth doped layer are adjacent, and the p-type fourth doped layer and the n-type fifth doped layer are adjacent; wherein the doping concentration of p-type ions in the p-type fourth doped layer is higher than the doping concentration of p-type ions in the p-type third doped layer.

[0010] On the other hand, embodiments of the present invention provide a method for fabricating a solar cell as described in the above embodiments, including the following steps for fabricating a tunnel junction:

[0011] When the substrate is a p-type substrate, an n-type second doped layer, an n-type first doped layer, a p-type first doped layer, and a p-type second doped layer are grown sequentially from bottom to top; wherein, the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer, and the doping concentration of p-type ions in the p-type first doped layer is higher than that in the p-type second doped layer.

[0012] Alternatively, when the substrate is a p-type substrate, an n-type third doped layer, an n-type fourth doped layer, and a p-type fifth doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than the doping concentration of n-type ions in the n-type third doped layer.

[0013] Alternatively, when the substrate is a p-type substrate, the n-type fifth doped layer, the p-type fourth doped layer, and the p-type third doped layer are grown sequentially from bottom to top; wherein the doping concentration of p-type ions in the p-type fourth doped layer is higher than the doping concentration of n-type ions in the p-type third doped layer.

[0014] Alternatively, when the substrate is an n-type substrate, the p-type second doped layer, the p-type first doped layer, the n-type first doped layer, and the n-type second doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer, and the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer.

[0015] Alternatively, when the substrate is an n-type substrate, the p-type third doped layer, the p-type fourth doped layer, and the n-type fifth doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer.

[0016] Alternatively, when the substrate is an n-type substrate, the p-type fifth doped layer, the n-type fourth doped layer, and the n-type third doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer.

[0017] The solar cell and its fabrication method provided in this invention utilize a stacked n-type first doped layer, an n-type second doped layer, a p-type first doped layer, and a p-type second doped layer in the tunnel junction. The n-type first doped layer and the n-type second doped layer are adjacent to each other, the p-type first doped layer and the p-type second doped layer are adjacent to each other, and the n-type first doped layer and the p-type first doped layer are adjacent to each other. This structure facilitates current conduction between two sub-cells adjacent to the tunnel junction and improves the photoelectric conversion efficiency of the solar cell. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of a solar cell provided in the first embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the structure of a solar cell provided in the second embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the structure of a solar cell provided in the third embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the structure of a solar cell provided in the fourth embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of the structure of a solar cell provided in the fifth embodiment of the present invention;

[0024] Figure 6 This is a schematic diagram of the structure of a solar cell provided in the sixth embodiment of the present invention;

[0025] Figure 7 This is a schematic diagram of the structure of a solar cell provided in the seventh embodiment of the present invention;

[0026] Figure 8 This is a schematic diagram of the structure of a solar cell provided in the eighth embodiment of the present invention;

[0027] Figure 9This is a schematic diagram of the structure of a solar cell provided in the ninth embodiment of the present invention;

[0028] Figure 10 This is a schematic diagram of the structure of a solar cell provided in the tenth embodiment of the present invention;

[0029] Figure 11 This is a schematic flowchart of the method for preparing a solar cell according to the eleventh embodiment of the present invention;

[0030] Figure 12 This is a schematic flowchart of the method for preparing a solar cell according to the twelfth embodiment of the present invention;

[0031] Figure 13a This is a schematic diagram of the fabrication of the bottom cell of the solar cell provided in the thirteenth embodiment of the present invention;

[0032] Figure 13b This is a schematic diagram of the fabrication of the n-type second doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention;

[0033] Figure 13c This is a schematic diagram of the fabrication of the n-type first doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention;

[0034] Figure 13d This is a schematic diagram of the fabrication of the p-type first doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention;

[0035] Figure 13e This is a schematic diagram of the fabrication of the p-type second doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention;

[0036] Figure 13f This is a schematic diagram of the fabrication of the middle cell of the solar cell provided in the thirteenth embodiment of the present invention;

[0037] Figure 13g This is a schematic diagram illustrating the preparation of the tunnel junction according to the thirteenth embodiment of the present invention;

[0038] Figure 13h This is a schematic diagram of the fabrication of the top cell and contact layer of the solar cell provided in the thirteenth embodiment of the present invention;

[0039] Figure 14 This is a schematic flowchart of the method for preparing a solar cell according to the fourteenth embodiment of the present invention;

[0040] Figure 15 This is a schematic flowchart of the method for preparing a solar cell according to the fifteenth embodiment of the present invention;

[0041] Figure 16 This is a schematic flowchart of the method for preparing a solar cell according to the sixteenth embodiment of the present invention;

[0042] Figure 17 This is a schematic flowchart of the method for preparing a solar cell according to the seventeenth embodiment of the present invention. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0044] Figure 1 This is a schematic diagram of the structure of a solar cell provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the solar cell provided in this embodiment of the invention includes: a substrate 1, at least two sub-cells 2, and a contact layer 4 arranged sequentially from bottom to top; a tunneling junction 3 is disposed between two adjacent sub-cells 2; the tunneling junction 3 includes:

[0045] The n-type first doped layer 32, n-type second doped layer 31, p-type first doped layer 33, and p-type second doped layer 34 are stacked in a row. The n-type first doped layer 32 and n-type second doped layer 31 are adjacent, the p-type first doped layer 33 and p-type second doped layer 34 are adjacent, and the n-type first doped layer 32 and p-type first doped layer 33 are adjacent. The doping concentration of n-type ions in the n-type first doped layer 32 is higher than that in the n-type second doped layer 31, and the doping concentration of p-type ions in the p-type first doped layer 33 is higher than that in the p-type second doped layer 34.

[0046] Specifically, substrate 1 can be a p-type substrate or an n-type substrate. When substrate 1 is a p-type substrate, the n-type first doped layer 32, n-type second doped layer 31, p-type first doped layer 33, and p-type second doped layer 34 are stacked in the following order from bottom to top: n-type second doped layer 31, n-type first doped layer 32, p-type first doped layer 33, and p-type second doped layer 34. When substrate 1 is an n-type substrate, the n-type first doped layer 32, n-type second doped layer 31, p-type first doped layer 33, and p-type second doped layer 34 are stacked in the following order from bottom to top: p-type second doped layer 34, p-type first doped layer 33, n-type first doped layer 32, and n-type second doped layer 31. The specific structure of each sub-cell 2 and the contact layer 4 is configured according to actual needs, and this embodiment of the invention does not impose any limitations.

[0047] For example, Figure 2 This is a schematic diagram of the structure of a solar cell provided in the second embodiment of the present invention, as shown below. Figure 2As shown, the solar cell provided in this embodiment of the invention includes a substrate 21, three sub-cells: a bottom cell 22, a middle cell 23, and a top cell 24, arranged sequentially from bottom to top, and a contact layer 25. A tunnel junction 26 is provided between the bottom cell 22 and the middle cell 23, and a tunnel junction 27 is provided between the middle cell 23 and the top cell 24. The bottom cell 22 includes an emitter layer 221 and a window layer 222 arranged sequentially from bottom to top. The middle cell 23 includes an emitter layer 221 and a window layer 222 arranged sequentially from bottom to top. The top cell 24 includes a back layer 241, a base region 242, an emitter layer 243, and a window layer 244 stacked from bottom to top. The tunnel junction 26 includes an n-type second doped layer 261, an n-type first doped layer 262, a p-type first doped layer 263, and a p-type second doped layer 264 stacked from bottom to top. The tunnel junction 27 has the same structure as the tunnel junction 26, and will not be described in detail here.

[0048] In this design, substrate 21 is a p-type germanium (Ge) layer, emitter layer 221 is an n-type Ge layer, window layer 222 is an n-type gallium indium phosphide (GaInP) layer, back layer 231 is a p-type GaInP layer, base region 232 is a p-type GaAs layer, emitter layer 233 is an n-type GaAs layer, window layer 234 is an n-type aluminum gallium indium phosphide (AlGaInP) layer, back layer 241 is a p-type GaInP layer, base region 242 is a p-type GaInP layer, emitter layer 243 is an n-type GaInP layer, window layer 244 is an n-type AlGaInP layer, and contact layer 25 is an n-type GaAs layer. The n-type first doped layer 262 can be an n-type Al… 0.4 In 0.6 The p-layer and the n-type second doped layer 261 can be made of n-type Al. 0.4 In 0.6 The p-layer, the first p-type doped layer 263, can be made of Al. 0.3 In 0.7 The p-type second doped layer 264 can be made of p-type Al. 0.3 In 0.7 P layer.

[0049] For example, Figure 3 This is a schematic diagram of the structure of a solar cell provided in the third embodiment of the present invention, as shown below. Figure 3As shown, the solar cell provided in this embodiment of the invention includes a substrate 301, two sub-cells: a bottom cell 302 and a top cell 303, arranged sequentially from bottom to top, and a contact layer 304. A tunnel junction 305 is disposed between the bottom cell 302 and the top cell 303. The bottom cell 302 includes a back layer 3021, a base region 3022, an emitter layer 3023 and a window layer 3024 arranged sequentially from bottom to top. The top cell 303 includes a back layer 3031, a base region 3032, an emitter layer 3033 and a window layer 3034 arranged sequentially from bottom to top. The tunnel junction 305 includes an n-type second doped layer 3051, an n-type first doped layer 3052, a p-type first doped layer 3053 and a p-type second doped layer 3054 arranged sequentially from bottom to top.

[0050] In this design, substrate 301 is a p-type Ge layer, back layer 3021 is a p-type GaInP layer, base region 3022 is a p-type GaAs layer, emitter layer 3023 is an n-type GaAs layer, window layer 3024 is an n-type AlGaInP layer, back layer 3031 is a p-type GaInP layer, base region 3032 is a p-type GaInP layer, emitter layer 3033 is an n-type GaInP layer, window layer 3034 is an n-type AlGaInP layer, and contact layer 304 is an n-type GaAs layer. The n-type first doped layer 3052 can be an n-type Al… 0.5 In 0.5 The P-layer and the n-type second doped layer of 3051 can be made of n-type Al. 0.4 In 0.6 The p-layer and the p-type first doped layer of 3053 can be made of Al. 0.3 In 0.7 The p- and p-type second doped layer 3054 can be made of p-type Al. 0.35 In 0.65 P layer.

[0051] For example, Figure 4 This is a schematic diagram of the structure of the solar cell provided in the fourth embodiment of the present invention, as shown below. Figure 4As shown, the solar cell provided in this embodiment of the invention includes a substrate 41, four sub-cells (a first sub-cell 42, a second sub-cell 43, a third sub-cell 44, and a fourth sub-cell 45) stacked sequentially from bottom to top, and a contact layer 46. A tunnel junction 47 is formed between the first sub-cell 42 and the second sub-cell 43, a tunnel junction 48 is formed between the second sub-cell 43 and the third sub-cell 44, and a tunnel junction 49 is formed between the third sub-cell 44 and the fourth sub-cell 45. The substrate 41 can be a P-type germanium substrate. The sub-cells can be configured according to actual needs; for example, the first sub-cell 42 can be a Ge sub-cell, the second sub-cell 43 can be a GaInNAs sub-cell, the third sub-cell 44 can be a GaAs sub-cell, and the fourth sub-cell 45 can be a GaInP sub-cell. The tunnel junction 48 includes an n-type second doped layer 481, an n-type first doped layer 482, a p-type first doped layer 483, and a p-type second doped layer 484 stacked together. The n-type first doped layer 482 can be made of n-type Al. 0.5 In 0.5 The P-layer and the n-type second doped layer 481 can be made of n-type Al. 0.5 In 0.5 The p-layer and the p-type first doped layer 483 can be made of Al. 0.5 In 0.5 The p- and p-type second doped layer 484 can be made of p-type Al. 0.5 In 0.5 P layer. Tunneling junctions 47 and 49 can adopt the same structure as tunneling junction 48.

[0052] The solar cell provided in this embodiment of the invention has a structure in which the tunnel junction adopts a stacked arrangement of an n-type first doped layer, an n-type second doped layer, a p-type first doped layer, and a p-type second doped layer, with the n-type first doped layer and the n-type second doped layer adjacent to each other, the p-type first doped layer and the p-type second doped layer adjacent to each other, and the n-type first doped layer and the p-type first doped layer adjacent to each other. This structure is beneficial for current conduction between two sub-cells adjacent to the tunnel junction, thereby improving the photoelectric conversion efficiency of the solar cell.

[0053] Based on the above embodiments, the thickness of the n-type second doped layer 31 is 2-5 nm, for example 3 nm; the thickness of the n-type first doped layer 32 is 5-10 nm, for example 8 nm; the thickness of the p-type second doped layer 34 is 2-5 nm, for example 4 nm; and the thickness of the p-type first doped layer 33 is 5-10 nm, for example 7 nm.

[0054] Based on the above embodiments, the n-type second doped layer 31 is further n-type Al. x In (1-x) The P-layer and the first n-type doped layer 32 are n-type Al. yIn (1-y) The p-layer, the first p-type doped layer 33 is a p-type Al. z In (1-z) The p-layer, the second p-type doped layer 34 is a p-type Al. w In (1-w) The P-layer has the following parameters: 0.25 < x < 0.55, 0.25 < y < 0.55, 0.25 < z < 0.55, and 0.25 < w < 0.55. Aluminum indium phosphide (AlInP) material has good light transmittance, allowing more sunlight not absorbed by the upper sub-cell to enter the lower sub-cell, further improving the photoelectric conversion efficiency of the solar cell.

[0055] Based on the above embodiments, the doping concentration of n-type ions in the n-type second doped layer 31 is further 5E17 to 5E18 ions / cm³. 3 The doping concentration of n-type ions in the first n-type doped layer 32 is 2E19~2E20 ions / cm³. 3 The p-type ion doping concentration of the second p-type doped layer 34 is 5E17–5E18 ions / cm³. 3 The p-type ion doping concentration of the first p-type doped layer 33 is 2E19–2E20 ions / cm³. 3 The lower doping concentrations of the n-type second doped layer 31 and the p-type second doped layer 34 can reduce the impact on the doping concentration of adjacent sub-cells. The higher doping concentrations of the n-type first doped layer 32 and the p-type first doped layer 33 are beneficial to the current conduction between two adjacent sub-cells.

[0056] Figure 5 This is a schematic diagram of the structure of a solar cell provided in the fifth embodiment of the present invention. Figure 6 This is a schematic diagram of the structure of the solar cell provided in the sixth embodiment of the present invention, as shown below. Figure 5 and Figure 6 As shown, the solar cell provided in this embodiment of the invention includes a substrate 51, at least two sub-cells 52, and a contact layer 54 arranged sequentially from bottom to top. A tunnel junction 53 is provided between two adjacent sub-cells 52. Figure 5 As shown, tunnel junction 53 includes:

[0057] The n-type third doped layer 531, the n-type fourth doped layer 532, and the p-type fifth doped layer 533 are stacked in a row. The n-type third doped layer 531 and the n-type fourth doped layer 532 are adjacent to each other, and the n-type fourth doped layer 532 and the p-type fifth doped layer 533 are adjacent to each other. The doping concentration of n-type ions in the n-type fourth doped layer 532 is higher than that in the n-type third doped layer 531.

[0058] Specifically, substrate 1 can be a p-type substrate or an n-type substrate. When substrate 1 is a p-type substrate, the n-type third doped layer 531, n-type fourth doped layer 532, and p-type fifth doped layer 533 are stacked in the following order from bottom to top: n-type third doped layer 531, n-type fourth doped layer 532, and p-type fifth doped layer 533. When substrate 1 is an n-type substrate, the n-type third doped layer 531, n-type fourth doped layer 532, and p-type fifth doped layer 533 are stacked in the following order from bottom to top: p-type fifth doped layer 533, n-type fourth doped layer 532, and n-type third doped layer 531. The specific structure of each sub-cell 52 and the contact layer 54 is configured according to actual needs, and this embodiment of the invention does not impose limitations.

[0059] For example, Figure 7 This is a schematic diagram of the structure of the solar cell provided in the seventh embodiment of the present invention, as shown below. Figure 7 As shown, the solar cell provided in this embodiment of the invention includes a substrate 71, three sub-cells (bottom cell 72, middle cell 73, and top cell 74) stacked sequentially from bottom to top, and a contact layer 75. A tunnel junction 76 is disposed between the bottom cell 72 and the middle cell 73. The structure of the tunnel junction disposed between the middle cell 73 and the top cell 74 is the same as that of the tunnel junction 76. The bottom cell 72 can be... Figure 2 The bottom battery 22 shown in the diagram has a structure in which the middle battery 73 can be adopted. Figure 2 The structure of the middle battery 23 shown in the figure, the top battery 74 can be adopted Figure 2 The structure of the top cell 74 shown includes a tunnel junction 76 comprising an n-type third doped layer 761, an n-type fourth doped layer 762, and a p-type fifth doped layer 763 stacked sequentially from bottom to top. The n-type third doped layer 761 can be made of n-type Al. 0.4 In 0.6 The P-layer and the n-type fourth doped layer 762 can be made of n-type Al. 0.4 In 0.6 The p-layer, the fifth p-type doped layer 763, can be made of Al. 0.3 In 0.7 P.

[0060] For example, Figure 8 This is a schematic diagram of the structure of the solar cell provided in the eighth embodiment of the present invention, as shown below. Figure 8 As shown, the solar cell provided in this embodiment of the invention includes a substrate 81, two sub-cells (a bottom cell 82 and a top cell 83) stacked sequentially from bottom to top, and a contact layer 84. A tunnel junction 85 is provided between the bottom cell 82 and the top cell 83. The bottom cell 82 can be constructed using... Figure 3 The bottom battery 302 shown has a structure, and the top battery 83 can be adopted as follows: Figure 3The structure of the top cell 303 shown includes a tunnel junction 85 comprising, from bottom to top, an n-type third doped layer 851, an n-type fourth doped layer 852, and a p-type fifth doped layer 853 stacked sequentially. The substrate 301 is a p-type Ge layer, and the n-type third doped layer 851 can be an n-type Al layer. 0.5 In 0.5 The P-layer and the n-type fourth doped layer 852 can be made of n-type Al. 0.4 In 0.6 The p-layer and the p-type fifth doped layer 853 can be made of Al. 0.3 In 0.7 P.

[0061] The solar cell provided in this embodiment of the invention has a structure in which the tunnel junction adopts a stacked n-type third doped layer, an n-type fourth doped layer, and a p-type fifth doped layer, with the n-type third doped layer and the n-type fourth doped layer adjacent to each other, and the p-type fifth doped layer and the n-type fourth doped layer adjacent to each other. This structure is beneficial for current conduction between two sub-cells adjacent to the tunnel junction, thereby improving the photoelectric conversion efficiency of the solar cell.

[0062] like Figure 6 As shown, the tunnel junction 53 may include: a p-type third doped layer 534, a p-type fourth doped layer 535, and an n-type fifth doped layer 536 stacked together, with the p-type third doped layer 534 and the p-type fourth doped layer 535 adjacent to each other, and the p-type fourth doped layer 535 and the n-type fifth doped layer 536 adjacent to each other; wherein, the doping concentration of p-type ions in the p-type fourth doped layer 535 is higher than the doping concentration of p-type ions in the p-type third doped layer 534.

[0063] Specifically, substrate 1 can be a p-type substrate or an n-type substrate. When substrate 1 is a p-type substrate, the p-type third doped layer 534, p-type fourth doped layer 535, and n-type fifth doped layer 536 are stacked in the following order from bottom to top: p-type third doped layer 534, p-type fourth doped layer 535, and n-type fifth doped layer 536. When substrate 1 is an n-type substrate, the p-type third doped layer 534, p-type fourth doped layer 535, and n-type fifth doped layer 536 are stacked in the following order from bottom to top: n-type fifth doped layer 536, p-type fourth doped layer 535, and p-type third doped layer 534.

[0064] For example, Figure 9 This is a schematic diagram of the structure of the solar cell provided in the seventh embodiment of the present invention, as shown below. Figure 9As shown, the solar cell provided in this embodiment of the invention includes a substrate 71, three sub-cells (bottom cell 72, middle cell 73, and top cell 74) stacked sequentially from bottom to top, and a contact layer 75. A tunnel junction 76 is disposed between the bottom cell 72 and the middle cell 73. The structure of the tunnel junction disposed between the middle cell 73 and the top cell 74 is the same as that of the tunnel junction 76. The bottom cell 72 can be... Figure 2 The bottom battery 22 shown in the diagram has a structure in which the middle battery 73 can be adopted. Figure 2 The structure of the middle battery 23 shown in the figure, the top battery 74 can be adopted Figure 2 The structure of the top cell 74 shown includes a tunnel junction 76 comprising, from bottom to top, a p-type third doped layer 764, a p-type fourth doped layer 765, and an n-type fifth doped layer 766, which can be p-type Al. 0.4 In 0.6 The p-layer, the p-type fourth doped layer 765, can be made of p-type Al. 0.4 In 0.6 The p-layer, the n-type fifth doped layer 766 can be made of Al. 0.3 In 0.7 P.

[0065] For example, Figure 10 This is a schematic diagram of the structure of a solar cell provided in the tenth embodiment of the present invention, as shown below. Figure 10 As shown, the solar cell provided in this embodiment of the invention includes a substrate 81, two sub-cells (a bottom cell 82 and a top cell 83) stacked sequentially from bottom to top, and a contact layer 84. A tunnel junction 85 is provided between the bottom cell 82 and the top cell 83. The bottom cell 82 can be constructed using... Figure 3 The bottom battery 302 shown has a structure, and the top battery 83 can be adopted as follows: Figure 3 The structure of the top cell 303 shown includes a tunnel junction 85 comprising, from bottom to top, a p-type third doped layer 854, a p-type fourth doped layer 853, and an n-type fifth doped layer 856 stacked sequentially. The substrate 81 is a p-type Ge layer, and the p-type third doped layer 854 can be p-type Al. 0.5 In 0.5 The p-layer and the p-type fourth doped layer 855 can be made of p-type Al. 0.4 In 0.6 The P-layer and the n-type fifth doped layer 856 can be made of Al. 0.3 In 0.7 P.

[0066] The solar cell provided in this embodiment of the invention has a structure in which the tunnel junction adopts a stacked p-type third doped layer, a p-type fourth doped layer, and an n-type fifth doped layer, with the p-type third doped layer and the p-type fourth doped layer being adjacent, and the n-type fifth doped layer and the p-type fourth doped layer being adjacent. This structure is beneficial for current conduction between two sub-cells adjacent to the tunnel junction, thereby improving the photoelectric conversion efficiency of the solar cell.

[0067] Based on the above embodiments, the thickness of the n-type third doped layer 531 is 2-5 nm, for example 3 nm; the thickness of the n-type fourth doped layer 532 is 5-10 nm, for example 8 nm; and the thickness of the p-type fifth doped layer 533 is 2-5 nm, for example 4 nm.

[0068] Based on the above embodiments, the thickness of the p-type third doped layer 534 is 2-5 nm, for example 3 nm; the thickness of the p-type fourth doped layer 535 is 5-10 nm, for example 8 nm; and the thickness of the n-type fifth doped layer 536 is 2-5 nm, for example 4 nm.

[0069] Based on the above embodiments, the n-type third doped layer 531 is further n-type Al. a In (1-a) The P-layer, the fourth n-type doped layer 532 is an n-type Al. b In (1-b) The p-layer, the fifth p-type doped layer 533 is a p-type Al. c In (1-c) Layer P, where 0.25 < a < 0.55, 0.25 < b < 0.55, and 0.25 < c < 0.55;

[0070] Based on the above embodiments, the p-type third doped layer 534 is further p-type Al. d In (1-d) The p-layer, the fourth p-type doped layer 535 is a p-type Al. f In (1-f) The p-layer, the fifth n-type doped layer 536 is an n-type Al. g In (1-g) Layer P, where 0.25 < d < 0.55, 0.25 < f < 0.55, and 0.25 < g < 0.55.

[0071] Based on the above embodiments, the doping concentration of n-type ions in the n-type third doped layer 531 is further 5E17 to 5E18 ions / cm³. 3 The doping concentration of n-type ions in the fourth n-type doped layer 532 is 2E19–2E20 ions / cm³. 3 The p-type ion doping concentration of the fifth p-type doped layer 533 is 5E17–5E18 ions / cm³.3 The n-type third doped layer 531 and the p-type fifth doped layer 533 have low doping concentrations, which can reduce the impact on the doping concentration of adjacent sub-cells. The n-type fourth doped layer 532 has a high doping concentration, which is beneficial to the current conduction between two adjacent sub-cells.

[0072] Based on the above embodiments, the doping concentration of p-type ions in the p-type third doped layer 534 is further 5E17 to 5E18 ions / cm³. 3 The p-type ion doping concentration of the fourth p-type doped layer 535 is 2E19–2E20 ions / cm³. 3 The doping concentration of n-type ions in the fifth n-type doped layer 536 is 5E17–5E18 ions / cm³. 3 The n-type fifth doped layer 536 and the p-type third doped layer 534 have low doping concentrations, which can reduce the impact on the doping concentration of adjacent sub-cells. The n-type fourth doped layer 532 has a high doping concentration, which is beneficial to the current conduction between two adjacent sub-cells.

[0073] Figure 11 This is a schematic flowchart of the method for preparing a solar cell according to the eleventh embodiment of the present invention. Figure 12 This is a schematic flowchart of the method for fabricating a solar cell according to the twelfth embodiment of the present invention, as shown below. Figure 11 and Figure 12 As shown, the method for preparing a solar cell according to any of the above embodiments provided by the present invention includes, as follows: Figure 11 or Figure 12 The preparation steps of the tunnel junction are shown.

[0074] When the substrate of the solar cell is a p-type substrate, the following can be used: Figure 11 The tunnel junction fabrication steps shown involve growing an n-type second doped layer, an n-type first doped layer, a p-type first doped layer, and a p-type second doped layer sequentially from bottom to top. The specific steps are as follows:

[0075] S1101, grow an n-type second doped layer;

[0076] Specifically, when fabricating the tunnel junction between two adjacent sub-cells, an n-type second doped layer can be grown on the adjacent lower sub-cell using metal-organic chemical vapor deposition (MOCVD) with a silicon (Si) source or a tellurium (Te) source. The thickness of the n-type second doped layer can be 2–5 nm, and it can be made of n-type Al. x In (1-x)In the P-layer, 0.25 < x < 0.55, the doping concentration of n-type ions in the second n-type doped layer can be 5E17 to 5E18 ions / cm³. 3 .

[0077] S1102. An n-type first doped layer is grown on the n-type second doped layer, wherein the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer.

[0078] Specifically, after the n-type second doped layer is fabricated, an n-type first doped layer can be grown on the n-type second doped layer by introducing a Si source or a Te source using MOCVD. The doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer. The thickness of the n-type first doped layer can be 5–10 nm, and the n-type first doped layer can be n-type Al. y In (1-y) For the p-layer, 0.25 < y < 0.55, the doping concentration of n-type ions in the first n-type doped layer can be 2E19 to 2E20 ions / cm³. 3 Since the first n-type doped layer needs to obtain a high doping concentration of n-type ions, the flow rate of the introduced Si source or Te source can be increased. For example, the flow rate of the introduced Si source or Te source is 2 to 5 times that of the flow rate of the introduced Si source or Te source in step S1101.

[0079] S1103. Grow a p-type first doped layer on the n-type first doped layer;

[0080] Specifically, after the n-type first doped layer is fabricated, a p-type first doped layer can be grown on the n-type first doped layer by introducing a magnesium (Mg) source or a carbon (C) source using the MOCVD method. The thickness of the p-type first doped layer can be 5–10 nm, and the p-type first doped layer can be p-type Al. z In (1-z) For the p-layer, 0.25 < z < 0.55, the doping concentration of p-type ions in the first p-type doped layer can be 2E19 to 2E20 ions / cm³. 3 .

[0081] S1104. A p-type second doped layer is grown on the p-type first doped layer, wherein the doping concentration of p-type ions in the p-type first doped layer is higher than the doping concentration of p-type ions in the p-type second doped layer.

[0082] Specifically, after the p-type first doped layer is fabricated, a p-type second doped layer can be grown on the p-type first doped layer by introducing a Mg source or a C source using MOCVD. The doping concentration of p-type ions in the p-type first doped layer is higher than that in the p-type second doped layer. The thickness of the p-type second doped layer can be 2–5 nm, and the p-type second doped layer can be p-type Al. w In (1-w) In the p-layer, 0.25 < w < 0.55, the doping concentration of p-type ions in the second p-type doped layer is 5E17 to 5E18 ions / cm³. 3 Since the p-type second doped layer needs to obtain a low doping concentration of p-type ions, the flow rate of the introduced Mg or C source can be reduced. For example, the flow rate of the introduced Mg or C source is 50% to 80% of the flow rate of the Mg or C source introduced in step S1103. After the p-type second doped layer is fabricated, the upper sub-cell adjacent to the tunnel junction is then fabricated.

[0083] When the substrate of the solar cell is an n-type substrate, the following can be used: Figure 12 The fabrication steps of the tunnel junction shown involve growing the p-type second doped layer, the p-type first doped layer, the n-type first doped layer, and the n-type second doped layer sequentially from bottom to top. The specific steps are as follows:

[0084] S1201, Grow the p-type second doped layer;

[0085] Specifically, when fabricating the tunnel junction between two adjacent sub-cells, a p-type second doped layer can be grown on the adjacent lower sub-cell using MOCVD by introducing a Mg source or a C source. The thickness of the p-type second doped layer can be 2–5 nm, and the p-type second doped layer can be made of p-type Al. w In (1-w) In the p-layer, 0.25 < w < 0.55, the doping concentration of p-type ions in the second p-type doped layer can be 5E17 to 5E18 ions / cm³. 3 .

[0086] S1202, The p-type first doped layer is grown on the p-type second doped layer, wherein the doping concentration of p-type ions in the p-type first doped layer is higher than the doping concentration of p-type ions in the p-type second doped layer;

[0087] Specifically, after the p-type second doped layer is fabricated, a p-type first doped layer can be grown on the p-type second doped layer using MOCVD with a Mg or C source. The doping concentration of p-type ions in the p-type first doped layer is higher than that in the p-type second doped layer. The thickness of the p-type first doped layer can be 5–10 nm, and the p-type first doped layer can be p-type Al. z In (1-z) For the p-layer, 0.25 < z < 0.55, the doping concentration of p-type ions in the first p-type doped layer can be 2E19 to 2E20 ions / cm³. 3 Since the p-type first doped layer needs to obtain a high doping concentration of p-type ions, the flow rate of the introduced Mg source or C source can be increased. For example, the flow rate of the introduced Mg source or C source is 2 to 5 times that of the flow rate of the introduced Mg source or C source in step S1201.

[0088] S1203. Grow the n-type first doped layer on the p-type first doped layer;

[0089] Specifically, after the p-type first doped layer is fabricated, the n-type first doped layer can be grown on the p-type first doped layer by introducing a Si source or a Te source using MOCVD. The thickness of the n-type first doped layer can be 5–10 nm, and the n-type first doped layer can be Al. y In (1-y) For the p-layer, 0.25 < y < 0.55, the doping concentration of n-type ions in the first n-type doped layer can be 2E19 to 2E20 ions / cm³. 3 .

[0090] S1204. An n-type second doped layer is grown on the n-type first doped layer, wherein the doping concentration of n-type ions in the n-type first doped layer is higher than the doping concentration of n-type ions in the n-type second doped layer.

[0091] Specifically, after the first n-type doped layer is fabricated, an n-type second doped layer can be grown on the first n-type doped layer by introducing a Si source or a Te source using MOCVD. The doping concentration of n-type ions in the first n-type doped layer is higher than that in the second n-type doped layer. The thickness of the second n-type doped layer can be 2–5 nm, and the second n-type doped layer can be n-type Al. x In (1-x) In the P-layer, 0.25 < x < 0.55, the doping concentration of n-type ions in the second n-type doped layer is 5E17 to 5E18 ions / cm³. 3Since the n-type second doped layer needs to obtain a low doping concentration of n-type ions, the flow rate of the introduced Si or Te source can be reduced. For example, the flow rate of the introduced Si or Te source is 50% to 80% of the flow rate of the Si or Te source introduced in step S1203. After the n-type second doped layer is fabricated, the upper sub-cell adjacent to the tunnel junction is then fabricated.

[0092] It is understood that the specific fabrication processes of the substrate, individual cells, and contact layer of the solar cell are existing technologies and will not be described in detail here.

[0093] The solar cell fabrication method provided in this invention produces a tunnel junction with stacked n-type first doped layer, n-type second doped layer, p-type first doped layer, and p-type second doped layer, with the n-type first doped layer and n-type second doped layer adjacent to each other, the p-type first doped layer and p-type second doped layer adjacent to each other, and the n-type first doped layer and p-type first doped layer adjacent to each other. This structure facilitates current conduction between two sub-cells adjacent to the tunnel junction and improves the photoelectric conversion efficiency of the solar cell.

[0094] Based on the above embodiments, the solar cell fabrication method provided by the present invention further includes a growth temperature of 500-650 degrees Celsius for the n-type first doped layer and the p-type first doped layer, and a growth temperature of 700-830 degrees Celsius for the n-type second doped layer and the p-type second doped layer.

[0095] Specifically, when growing the n-type first doped layer or the p-type first doped layer, the temperature of the MOCVD reaction chamber can be set between 500 and 650 degrees Celsius to meet the growth temperature requirements of the n-type first doped layer or the p-type first doped layer. Setting the growth temperature of the n-type first doped layer or the p-type first doped layer between 500 and 650 degrees Celsius is beneficial for obtaining a higher doping concentration. When growing the n-type second doped layer or the p-type second doped layer, the temperature of the MOCVD reaction chamber can be set between 700 and 830 degrees Celsius to meet the growth temperature requirements of the n-type second doped layer or the p-type second doped layer. Setting the growth temperature of the n-type second doped layer or the p-type second doped layer between 700 and 830 degrees Celsius is beneficial for obtaining the n-type second doped layer or the p-type second doped layer with better crystal quality.

[0096] Based on the above embodiments, further, in the solar cell fabrication method provided by the present invention, the growth rate of the n-type second doped layer is 0.5–2 nm / s, the growth rate of the n-type first doped layer is 0.2–1 nm / s, the growth rate of the p-type first doped layer is 0.2–1 nm / s, and the growth rate of the p-type second doped layer is 0.5–2 nm / s. Limiting the growth rates of the n-type and p-type second doped layers to 0.5–2 nm / s ensures both production efficiency and product quality of the n-type and p-type second doped layers. Similarly, limiting the growth rates of the n-type and p-type first doped layers to 0.2–1 nm / s also ensures both production efficiency and product quality of the n-type and p-type first doped layers.

[0097] The following describes in detail the process of fabricating a solar cell comprising three solar cells and two tunnel junctions of the same structure, using the fabrication process of such a solar cell as an example.

[0098] Figure 13a This is a schematic diagram of the fabrication of the bottom cell of the solar cell provided in the thirteenth embodiment of the present invention, as shown below. Figure 13a As shown, the solar cell uses a p-type Ge substrate 131. The p-type Ge substrate 131 is placed in the MOCVD reaction chamber, and n-type phosphorus diffusion is performed on the upper surface of the p-type Ge substrate 131 to obtain the emitter layer 1321 of the bottom cell 132. Then, an n-type GaInP buffer layer is grown on the emitter layer 1321 to obtain the window layer 1322 of the bottom cell 132. The window layer 1322 plays a nucleation role.

[0099] Figure 13b This is a schematic diagram of the fabrication of the n-type second doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention, as shown below. Figure 13b As shown, the MOCVD reaction chamber temperature was set at 1350 degrees Celsius, a silicon source was introduced, and a 3nm thick layer with a doping concentration of 1E18 cells / cm was grown on the window layer 1322. 3 n-type Al 0.4 In 0.6 The P-layer is used to obtain the n-type second doped layer 1331 of the tunnel junction 133, and the growth rate of the n-type second doped layer 1331 is 1 nm / s.

[0100] Figure 13c This is a schematic diagram of the fabrication of the n-type first doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention, as shown below. Figure 13c As shown, the MOCVD reaction chamber temperature was lowered to 600 degrees Celsius, and the flow rate of the silicon source was increased to three times the original flow rate. An 8 nm thick layer with a doping concentration of 1E20 atoms / cm² was grown on the n-type second doped layer 1331.3 n-type Al 0.4 In 0.6 The p-layer is used to obtain the n-type first doped layer 1332 of the tunnel junction 133, and the growth rate of the n-type first doped layer 1332 is 0.5 nm / s.

[0101] Figure 13d This is a schematic diagram of the fabrication of the p-type first doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention, as shown below. Figure 13d As shown, while keeping the temperature of the MOCVD reaction chamber constant, a magnesium source is introduced to grow an 8 nm thick layer with a doping concentration of 1E20 atoms / cm² on the n-type first doped layer 1332. 3 n-type Al 0.4 In 0.6 The p-type first doped layer 1333 of the tunnel junction 133 is obtained by p-layer, and the growth rate of the p-type first doped layer 1333 is 0.5 nm / s.

[0102] Figure 13e This is a schematic diagram of the fabrication of the p-type second doped layer of the tunnel junction provided in the thirteenth embodiment of the present invention, as shown below. Figure 13e As shown, the temperature of the MOCVD reaction chamber was raised to 1350 degrees Celsius, and the flow rate of the magnesium source was reduced to 60% of its original flow rate. A 3 nm thick layer with a doping concentration of 1E18 atoms / cm² was grown on the p-type first doped layer 1333. 3 p-type Al 0.4 In 0.6 The p-type second doped layer 1334 of the tunnel junction 133 is obtained by p-layer, and the growth rate of the n-type second doped layer 1334 is 1 nm / s.

[0103] Figure 13f This is a schematic diagram of the fabrication of a solar cell according to the thirteenth embodiment of the present invention, as shown below. Figure 13f As shown, a p-type GaInP layer is first grown on the p-type second doped layer 1334 as the back layer 1341 of the intermediate cell 134. Next, a p-type GaAs layer is grown on the back layer 1341 as the base region 1342 of the intermediate cell 1344. Then, an n-type GaAs layer is grown on the base region 1342 as the emitter layer 1343 of the intermediate cell 1344. Finally, an n-type AlGaInP layer is grown on the emitter layer 1343 as the window layer 1344 of the intermediate cell 1344. The thicknesses of the back layer 1341, base region 1342, emitter layer 1343, and window layer 1344 of the intermediate cell 134 are set according to actual needs, and are not limited in this embodiment of the invention.

[0104] Figure 13g This is a schematic diagram illustrating the preparation of the tunnel junction provided in the thirteenth embodiment of the present invention, as shown below. Figure 13gAs shown, tunnel junction 135 and tunnel junction 133 have the same structure. The fabrication process of the n-type second doped layer 1351 of tunnel junction 135 is similar to that of the n-type second doped layer 1331 of tunnel junction 133. The fabrication process of the n-type second doped layer 1351 will not be elaborated here; it can be obtained on window layer 1344. Similarly, the fabrication process of the n-type first doped layer 1352 of tunnel junction 135 is similar to that of the n-type first doped layer 1332 of tunnel junction 133. An n-type first doped layer 1352 is obtained on the second doped layer 1351. The preparation process of the p-type first doped layer 1353 of the tunnel junction 135 is similar to that of the p-type first doped layer 1333 of the tunnel junction 133. A p-type first doped layer 1353 can be obtained on the n-type first doped layer 1351. The preparation process of the p-type second doped layer 1354 of the tunnel junction 135 is similar to that of the p-type second doped layer 1334 of the tunnel junction 133. A p-type second doped layer 1354 can be obtained on the p-type first doped layer 1353.

[0105] Figure 13h This is a schematic diagram of the fabrication of the top cell and contact layer of the solar cell provided in the thirteenth embodiment of the present invention, as shown below. Figure 13h As shown, p-type GaInP is first grown on the p-type second doped layer 1354 as the back layer 1361 of the top cell 136. Then, a p-type GaInP layer is grown on the back layer 1361 as the base region 1362 of the top cell 136. Next, an n-type GaInP layer is grown on the base region 1362 as the emitter layer 1363 of the top cell 136. Then, an n-type AlGaInP layer is grown on the emitter layer 1363 as the window layer 1364 of the top cell 136. Finally, an n-type GaAs layer is grown on the window layer 1364 as the contact layer 137, thereby completing the fabrication of the solar cell provided in this embodiment of the invention.

[0106] Figure 14 This is a schematic flowchart of the method for preparing a solar cell according to the fourteenth embodiment of the present invention. Figure 15 This is a schematic flowchart of the method for preparing a solar cell according to the fifteenth embodiment of the present invention. Figure 16 This is a schematic flowchart of the method for preparing a solar cell according to the sixteenth embodiment of the present invention. Figure 17 This is a schematic flowchart of the method for fabricating a solar cell according to the seventeenth embodiment of the present invention, as shown below. Figure 14 , Figure 15 , Figure 16 and Figure 17 As shown, the method for preparing a solar cell according to any of the above embodiments provided by the present invention includes, as follows: Figure 14 , Figure 15 , Figure 16 or Figure 17 The preparation steps of the tunnel junction are shown.

[0107] When the substrate of the solar cell is a p-type substrate, the following can be used: Figure 14 or Figure 15 The tunnel junction fabrication steps are shown. When the substrate of the solar cell is an n-type substrate, the following can be used: Figure 16 or Figure 17 The preparation steps of the tunnel junction are shown.

[0108] like Figure 14 The fabrication steps of the tunnel junction shown involve growing an n-type third doped layer, an n-type fourth doped layer, and a p-type fifth doped layer sequentially from bottom to top. The specific steps are as follows:

[0109] S1401, grow an n-type third doped layer;

[0110] Specifically, when fabricating the tunnel junction between two adjacent sub-cells, an n-type third doped layer can be grown on the adjacent lower sub-cell using MOCVD by introducing a Si or Te source. The thickness of the n-type third doped layer can be 2–5 nm, and it can be made of n-type Al. a In (1-a) In the P-layer, 0.25 < a < 0.55, the doping concentration of n-type ions in the n-type third doped layer can be 5E17 to 5E18 ions / cm³. 3 .

[0111] S1402. An n-type fourth doped layer is grown on the n-type third doped layer, wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer.

[0112] Specifically, after the n-type third doped layer is fabricated, an n-type fourth doped layer can be grown on the n-type third doped layer using MOCVD with a Si or Te source. The doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer. The thickness of the n-type fourth doped layer can be 5–10 nm, and the n-type fourth doped layer can be n-type Al. b In (1-b) For the p-layer, 0.25 < b < 0.55, the doping concentration of n-type ions in the n-type fourth doped layer can be 2E19 to 2E20 ions / cm³. 3 Since the n-type fourth doped layer needs to obtain a high doping concentration of n-type ions, the flow rate of the introduced Si source or Te source can be increased. For example, the flow rate of the introduced Si source or Te source is 2 to 5 times that of the flow rate of the introduced Si source or Te source in step S1401.

[0113] S1403. Grow a p-type fifth doped layer on the n-type fourth doped layer;

[0114] Specifically, after the n-type fourth doped layer is fabricated, a p-type fifth doped layer can be grown on the n-type fourth doped layer by introducing a Mg source or a C source using MOCVD. The thickness of the p-type fifth doped layer can be 2–5 nm, and the p-type fifth doped layer can be p-type Al. c In (1-c) In the p-layer, 0.25 < c < 0.55, the doping concentration of p-type ions in the fifth p-type doped layer is 5E17 to 5E18 ions / cm³. 3 After the p-type fifth doped layer is fabricated, the upper sub-cell adjacent to the tunnel junction is then fabricated.

[0115] like Figure 15 The fabrication steps of the tunnel junction shown involve growing the p-type fifth doped layer, the n-type fourth doped layer, and the n-type third doped layer sequentially from bottom to top. The specific steps are as follows:

[0116] 1501. Growth of the fifth n-type doped layer;

[0117] Specifically, when fabricating the tunnel junction between two adjacent sub-cells, an n-type fifth doped layer can be grown on the adjacent lower sub-cell using MOCVD by introducing a Si or Te source. The thickness of the n-type fifth doped layer can be 2–5 nm, and it can be made of n-type Al. g In (1-g) For the P-layer, 0.25 < g < 0.55, the doping concentration of n-type ions in the fifth n-type doped layer can be 5E17 to 5E18 ions / cm³. 3 .

[0118] 1502. Grow a p-type fourth doped layer on the n-type fifth doped layer;

[0119] Specifically, after the n-type fifth doped layer is fabricated, a p-type fourth doped layer can be grown on the n-type fifth doped layer by introducing a Mg source or a C source using MOCVD. The thickness of the p-type fourth doped layer can be 5–10 nm, and the p-type fourth doped layer can be p-type Al. f In (1-f) For the p-layer, 0.25 < f < 0.55, the doping concentration of p-type ions in the fourth p-type doped layer can be 2E19 to 2E20 ions / cm³. 3 .

[0120] 1503. A p-type third doped layer is grown on the p-type fourth doped layer, wherein the doping concentration of p-type ions in the p-type fourth doped layer is higher than the doping concentration of n-type ions in the p-type third doped layer.

[0121] Specifically, after the p-type fourth doped layer is fabricated, a p-type third doped layer can be grown on the p-type fourth doped layer by introducing a Mg source or a C source using MOCVD. The doping concentration of p-type ions in the p-type fourth doped layer is higher than that in the p-type third doped layer. The thickness of the p-type third doped layer can be 2–5 nm, and the p-type third doped layer can be p-type Al. d In (1-d) In the p-layer, 0.25 < d < 0.55, the doping concentration of p-type ions in the third p-type doped layer is 5E17 to 5E18 ions / cm³. 3 Since the p-type third doped layer needs to obtain a low doping concentration of p-type ions, the flow rate of the introduced Mg or C source can be reduced. For example, the flow rate of the introduced Mg or C source is 50% to 80% of the flow rate of the Mg or C source introduced in step S1502. After the p-type third doped layer is fabricated, the upper sub-cell adjacent to the tunnel junction is then fabricated.

[0122] like Figure 16 The fabrication steps of the tunnel junction shown involve growing the p-type third doped layer, the p-type fourth doped layer, and the n-type fifth doped layer sequentially from bottom to top. The specific steps are as follows:

[0123] 1601. Grow the p-type third doped layer;

[0124] Specifically, when fabricating the tunnel junction between two adjacent sub-cells, a p-type third doped layer can be grown on the adjacent lower sub-cell using MOCVD by introducing a Mg source or a C source. The thickness of the p-type third doped layer can be 2–5 nm, and the p-type third doped layer can be made of p-type Al. d In (1-d) In the p-layer, 0.25 < d < 0.55, the doping concentration of p-type ions in the third p-type doped layer can be 5E17 to 5E18 ions / cm³. 3 .

[0125] 1602. Grow the p-type fourth doped layer on the p-type third doped layer, wherein the doping concentration of p-type ions in the p-type fourth doped layer is higher than that in the p-type third doped layer;

[0126] Specifically, after the p-type third doped layer is fabricated, a p-type fourth doped layer can be grown on the p-type third doped layer using MOCVD with a Mg or C source. The doping concentration of p-type ions in the p-type fourth doped layer is higher than that in the p-type third doped layer. The thickness of the p-type fourth doped layer can be 5–10 nm, and the p-type fourth doped layer can be p-type Al. f In (1-f) For the p-layer, 0.25 < f < 0.55, the doping concentration of p-type ions in the fourth p-type doped layer can be 2E19 to 2E20 ions / cm³. 3 Since the fourth p-type doped layer needs to obtain a higher doping concentration of p-type ions, the flow rate of the introduced Mg source or C source can be increased. For example, the flow rate of the introduced Mg source or C source is 2 to 5 times that of the flow rate of the introduced Mg source or C source in step S1601.

[0127] 1603. Grow the n-type fifth doped layer on the p-type fourth doped layer;

[0128] Specifically, after the p-type fourth doped layer is fabricated, the n-type fifth doped layer can be grown on the p-type fourth doped layer by introducing a Si source or a Te source using MOCVD. The thickness of the n-type fifth doped layer can be 5–10 nm, and the n-type fifth doped layer can be Al. g In (1-g) For the P-layer, 0.25 < g < 0.55, the doping concentration of n-type ions in the fifth n-type doped layer can be 2E19 to 2E20 ions / cm³. 3 .

[0129] like Figure 17 The fabrication steps of the tunnel junction shown involve growing the p-type fifth doped layer, the n-type fourth doped layer, and the n-type third doped layer sequentially from bottom to top. The specific steps are as follows:

[0130] 1701. Growth of the fifth p-type doped layer;

[0131] Specifically, when fabricating the tunnel junction between two adjacent sub-cells, a p-type fifth doped layer can be grown on the adjacent lower sub-cell using MOCVD by introducing a Mg source or a C source. The thickness of the p-type fifth doped layer can be 2–5 nm, and the p-type fifth doped layer can be made of p-type Al. c In (1-c) In the p-layer, 0.25 < c < 0.55, the doping concentration of p-type ions in the fifth p-type doped layer can be 5E17 to 5E18 ions / cm³. 3 .

[0132] 1702. An n-type fourth doped layer is grown on the p-type fifth doped layer;

[0133] Specifically, after the p-type fifth doped layer is fabricated, the n-type fourth doped layer can be grown on the p-type fifth doped layer by introducing a Si source or a Te source using MOCVD. The thickness of the n-type fourth doped layer can be 5–10 nm, and the n-type fourth doped layer can be Al. b In (1-b) For the p-layer, 0.25 < b < 0.55, the doping concentration of n-type ions in the n-type fourth doped layer can be 2E19 to 2E20 ions / cm³. 3 .

[0134] 1703. An n-type third doped layer is grown on the n-type fourth doped layer, wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer;

[0135] Specifically, after the n-type fourth doped layer is fabricated, an n-type third doped layer can be grown on the n-type fourth doped layer by introducing a Si source or a Te source using MOCVD. The doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer. The thickness of the n-type third doped layer can be 2–5 nm, and the n-type third doped layer can be n-type Al. a In (1-a) In the P-layer, 0.25 < a < 0.55, the doping concentration of n-type ions in the n-type third doped layer is 5E17 to 5E18 ions / cm³. 3 Since the n-type third doped layer needs to obtain a low doping concentration of n-type ions, the flow rate of the introduced Si or Te source can be reduced. For example, the flow rate of the introduced Si or Te source can be 50% to 80% of the flow rate of the Si or Te source introduced in step S1702. After the n-type third doped layer is fabricated, the upper sub-cell adjacent to the tunnel junction is then fabricated.

[0136] It is understood that the specific fabrication processes of the substrate, individual cells, and contact layer of the solar cell are existing technologies and will not be described in detail here.

[0137] Based on the above embodiments, the solar cell fabrication method provided by the present invention further includes a growth temperature of 500-650 degrees Celsius for the n-type third doped layer and the p-type fifth doped layer, and a growth temperature of 700-830 degrees Celsius for the n-type fourth doped layer.

[0138] Specifically, when growing the n-type third doped layer or the p-type fifth doped layer, the temperature of the MOCVD reaction chamber can be set between 500 and 650 degrees Celsius to meet the growth temperature requirements of the n-type third doped layer or the p-type fifth doped layer. Setting the growth temperature of the n-type third doped layer or the p-type fifth doped layer between 500 and 650 degrees Celsius is beneficial for obtaining a higher doping concentration. When growing the n-type fourth doped layer, the temperature of the MOCVD reaction chamber can be set between 700 and 830 degrees Celsius to meet the growth temperature requirements of the n-type fourth doped layer. Setting the growth temperature of the n-type fourth doped layer between 700 and 830 degrees Celsius is beneficial for obtaining the n-type fourth doped layer with better crystal quality.

[0139] Based on the above embodiments, the solar cell fabrication method provided in this invention further includes a growth rate of 0.5–2 nm / s for the n-type fourth doped layer, a growth rate of 0.2–1 nm / s for the n-type third doped layer, and a growth rate of 0.2–1 nm / s for the p-type fifth doped layer. Limiting the growth rate of the n-type fourth doped layer to 0.5–2 nm / s ensures both production efficiency and product quality. Similarly, limiting the growth rates of the n-type third doped layer and the p-type fifth doped layer to 0.2–1 nm / s ensures both production efficiency and product quality.

[0140] Based on the above embodiments, the solar cell fabrication method provided by the present invention further includes a growth temperature of 500-650 degrees Celsius for the p-type third doped layer and the n-type fifth doped layer, and a growth temperature of 700-830 degrees Celsius for the p-type fourth doped layer.

[0141] Specifically, when growing the p-type third doped layer or the n-type fifth doped layer, the temperature of the MOCVD reaction chamber can be set between 500 and 650 degrees Celsius to meet the growth temperature requirements of the p-type third doped layer or the n-type fifth doped layer. Setting the growth temperature of the p-type third doped layer or the n-type fifth doped layer between 500 and 650 degrees Celsius is beneficial for obtaining a higher doping concentration. When growing the p-type fourth doped layer, the temperature of the MOCVD reaction chamber can be set between 700 and 830 degrees Celsius to meet the growth temperature requirements of the p-type fourth doped layer. Setting the growth temperature of the p-type fourth doped layer between 700 and 830 degrees Celsius is beneficial for obtaining a p-type fourth doped layer with better crystal quality.

[0142] Based on the above embodiments, the solar cell fabrication method provided in this invention further includes a p-type fourth doped layer with a growth rate of 0.5–2 nm / s, a p-type third doped layer with a growth rate of 0.2–1 nm / s, and an n-type fifth doped layer with a growth rate of 0.2–1 nm / s. Limiting the growth rate of the p-type fourth doped layer to 0.5–2 nm / s ensures both production efficiency and product quality. Similarly, limiting the growth rates of the p-type third doped layer and the n-type fifth doped layer to 0.2–1 nm / s ensures both production efficiency and product quality.

[0143] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A solar cell, comprising a substrate, at least two sub-cells, and a contact layer stacked sequentially from bottom to top, wherein a tunnel junction is disposed between two adjacent sub-cells, characterized in that, The tunnel junction includes: An n-type first doped layer, an n-type second doped layer, a p-type first doped layer, and a p-type second doped layer are stacked together, with the n-type first doped layer and the n-type second doped layer adjacent to each other, the p-type first doped layer and the p-type second doped layer adjacent to each other, and the n-type first doped layer and the p-type first doped layer adjacent to each other; wherein the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer, and the doping concentration of p-type ions in the p-type first doped layer is higher than that in the p-type second doped layer; The thickness of the n-type second doped layer is 2-5 nm, the thickness of the n-type first doped layer is 5-10 nm, the thickness of the p-type second doped layer is 2-5 nm, and the thickness of the p-type first doped layer is 5-10 nm. The n-type second doped layer is an n-type Al. x In (1-x) The p-layer, wherein the n-type first doped layer is an n-type Al. y In (1-y) The p-layer, wherein the p-type first doped layer is a p-type Al. z In (1-z) The p-layer, wherein the p-type second doped layer is a p-type Al w In (1-w) Layer P, where 0.25 < x < 0.55, 0.25 < y < 0.55, 0.25 < z < 0.55, and 0.25 < w < 0.55; The doping concentration of n-type ions in the second n-type doped layer is 5E17 to 5E18 ions / cm³. 3 The doping concentration of n-type ions in the first n-type doped layer is 2E19 to 2E20 ions / cm³. 3 The p-type ion doping concentration of the second p-type doped layer is 5E17 to 5E18 ions / cm³. 3 The doping concentration of p-type ions in the first p-type doped layer is 2E19 to 2E20 ions / cm³. 3 ; Alternatively, an n-type third doped layer, an n-type fourth doped layer, and a p-type fifth doped layer may be stacked, wherein the n-type third doped layer and the n-type fourth doped layer are adjacent to each other, and the n-type fourth doped layer and the p-type fifth doped layer are adjacent to each other; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer. The thickness of the n-type third doped layer is 2–5 nm, the thickness of the n-type fourth doped layer is 5–10 nm, and the thickness of the p-type fifth doped layer is 2–5 nm; the n-type third doped layer is n-type Al. a In (1-a) The P-layer, the n-type fourth doped layer is an n-type Al. b In (1-b) The p-layer, the fifth p-type doped layer is a p-type Al. c In (1-c) Layer P, where 0.25 < a < 0.55, 0.25 < b < 0.55, and 0.25 < c < 0.55; The doping concentration of n-type ions in the n-type third doped layer is 5E17 to 5E18 ions / cm³. 3 The doping concentration of n-type ions in the fourth n-type doped layer is 2E19 to 2E20 ions / cm³. 3 The p-type ion doping concentration of the fifth p-type doped layer is 5E17 to 5E18 ions / cm³. 3 ; Alternatively, a p-type third doped layer, a p-type fourth doped layer, and an n-type fifth doped layer may be stacked, wherein the p-type third doped layer and the p-type fourth doped layer are adjacent to each other, and the p-type fourth doped layer and the n-type fifth doped layer are adjacent to each other; wherein the doping concentration of p-type ions in the p-type fourth doped layer is higher than that in the p-type third doped layer. The thickness of the p-type third doped layer is 2-5 nm, the thickness of the p-type fourth doped layer is 5-10 nm, and the thickness of the n-type fifth doped layer is 2-5 nm. The p-type third doped layer is a p-type Al. d In (1-d) The p-layer, the fourth p-type doped layer is a p-type Al f In (1-f) The P-layer, the fifth n-type doped layer is an n-type Al. g In (1-g) Layer P, where 0.25 < d < 0.55, 0.25 < f < 0.55, 0.25 < g < 0.55; The doping concentration of p-type ions in the third p-type doped layer is 5E17 to 5E18 ions / cm³. 3 The p-type ion doping concentration of the fourth p-type doped layer is 2E19 to 2E20 ions / cm³. 3 The doping concentration of n-type ions in the fifth n-type doped layer is 5E17 to 5E18 ions / cm³. 3 .

2. A method for preparing a solar cell as described in claim 1, characterized in that, The preparation steps for the tunnel junction include the following: When the substrate is a p-type substrate, an n-type second doped layer, an n-type first doped layer, a p-type first doped layer, and a p-type second doped layer are grown sequentially from bottom to top; wherein, the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer, and the doping concentration of p-type ions in the p-type first doped layer is higher than that in the p-type second doped layer. Alternatively, when the substrate is a p-type substrate, an n-type third doped layer, an n-type fourth doped layer, and a p-type fifth doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than the doping concentration of n-type ions in the n-type third doped layer. Alternatively, when the substrate is a p-type substrate, the n-type fifth doped layer, the p-type fourth doped layer, and the p-type third doped layer are grown sequentially from bottom to top; wherein the doping concentration of p-type ions in the p-type fourth doped layer is higher than the doping concentration of n-type ions in the p-type third doped layer. Alternatively, when the substrate is an n-type substrate, the p-type second doped layer, the p-type first doped layer, the n-type first doped layer, and the n-type second doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer, and the doping concentration of n-type ions in the n-type first doped layer is higher than that in the n-type second doped layer. Alternatively, when the substrate is an n-type substrate, the p-type third doped layer, the p-type fourth doped layer, and the n-type fifth doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer. Alternatively, when the substrate is an n-type substrate, the p-type fifth doped layer, the n-type fourth doped layer, and the n-type third doped layer are grown sequentially from bottom to top; wherein the doping concentration of n-type ions in the n-type fourth doped layer is higher than that in the n-type third doped layer.

3. The preparation method according to claim 2, characterized in that, The growth temperature conditions for the n-type first doped layer and the p-type first doped layer are 500–650 degrees Celsius, and the growth temperature conditions for the n-type second doped layer and the p-type second doped layer are 700–830 degrees Celsius; or the growth temperature conditions for the n-type third doped layer and the p-type fifth doped layer are 500–650 degrees Celsius, and the growth temperature conditions for the n-type fourth doped layer are 700–830 degrees Celsius. Alternatively, the growth temperature conditions for the p-type third doped layer and the n-type fifth doped layer are 500–650 degrees Celsius, and the growth temperature conditions for the p-type fourth doped layer are 700–830 degrees Celsius.

4. The preparation method according to claim 2 or 3, characterized in that, The growth rate of the n-type second doped layer is 0.5–2 nm / s, the growth rate of the n-type first doped layer is 0.2–1 nm / s, the growth rate of the p-type first doped layer is 0.2–1 nm / s, and the growth rate of the p-type second doped layer is 0.5–2 nm / s; or the growth rate of the n-type fourth doped layer is 0.5–2 nm / s, the growth rate of the n-type third doped layer is 0.2–1 nm / s, and the growth rate of the p-type fifth doped layer is 0.2–1 nm / s; or the growth rate of the p-type fourth doped layer is 0.5–2 nm / s, the growth rate of the p-type third doped layer is 0.2–1 nm / s, and the growth rate of the n-type fifth doped layer is 0.2–1 nm / s.

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