Solar cell epitaxial wafer preparation method and solar cell epitaxial wafer

Abstract

The invention provides a preparation method of an epitaxial wafer of a solar cell and the epitaxial wafer of the solar cell, and relates to the technical field of solar cells, and the preparation method comprises the steps that a first sub-cell, a second sub-cell and a third sub-cell are sequentially formed on one side of a substrate, and the substrate is a P-type Ge substrate with the crystal orientation (100) and the monotectic orientation (111) of 15-20 degrees. The step of forming the second sub-cell comprises the substeps of forming a first base region, a first emitter region and a first window layer under the cavity pressure of 400 mbar to 600 mbar; the step of forming the third sub-cell comprises the step of forming a second base region, a second emitter region and a second window layer under the cavity pressure of 400 mbar to 600 mbar. The surface of the substrate is provided with more atomic mesas, so that base regions, emitter regions and window layers of the second sub-cell and the third sub-cell can be formed under relatively high working cavity pressure, the growth rate of the solar cell can be further improved, and the manufacturing cost of the solar cell is further effectively reduced.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a method for preparing an epitaxial wafer of a solar cell and a solar cell epitaxial wafer prepared by the preparation method. Background Art

[0002] Compared with traditional Si and GaAs single-junction solar cells, GaInP / GaInAs / Ge triple-junction solar cells have the advantages of stable structure, high reliability, long life, small size and light weight, high photoelectric conversion efficiency, and high light absorption coefficient. At present, they have become the core components of space power systems and are widely used in the power systems of spacecraft. At present, the global commercial space launch cost is between 10,000 and 20,000 US dollars per kilogram. Therefore, in view of the huge demand for commercial space, how to reduce the manufacturing cost of triple-junction solar cells for space has become an important research topic for technicians in this field. Summary of the invention

[0003] In view of this, the present application provides a method for preparing an epitaxial wafer of a solar cell and a solar cell, the scheme is as follows:

[0004] A method for preparing an epitaxial wafer of a solar cell, comprising:

[0005] A substrate is provided and placed in a working chamber; the substrate is a P-type Ge substrate with a preset deflection angle, and the preset deflection angle has a value range of 15° to 20° from the crystal direction (100) to the crystal direction (111), including end values;

[0006] A first sub-cell, a second sub-cell and a third sub-cell are sequentially formed on one side of the substrate; forming the second sub-cell comprises:

[0007] Under a first chamber pressure, a first base region, a first emitter region and a first window layer are sequentially formed, wherein the first chamber pressure has a value range of 400 mbar to 600 mbar, including end points;

[0008] Forming the third sub-cell includes:

[0009] Under a second chamber pressure, a second base region, a second emitter region and a second window layer are formed in sequence, and the second chamber pressure has a value range of 400 mbar to 600 mbar, including end points.

[0010] Optionally, forming the second sub-cell further comprises:

[0011] Under a third chamber pressure, a first source gas is introduced into the working chamber, wherein the first source gas includes trimethyl indium, trimethyl gallium, trimethyl aluminum, diethyl zinc and arsine, and a first back field layer and a third base region are formed in sequence, wherein the third base region is located between the first back field layer and the first base region, and the third base region and the first base region constitute a base region of the second sub-cell; wherein the third chamber pressure is 50 mbar, the first back field layer is a P-type AlGaAs layer, and the third base region is a Zn-doped P-type GaInAs layer;

[0012] The forming of the first base region, the first emitter region and the first window layer under the first chamber pressure comprises:

[0013] stopping the introduction of the first source gas into the working chamber;

[0014] Under the first chamber pressure, a second source gas is introduced into the working chamber, wherein the second source gas includes trimethylindium, trimethylgallium, trimethylaluminum, diethylzinc, arsine, silane and phosphine, and the first base region, the first emitter region and the first window layer are formed in sequence; wherein the first chamber pressure is 480 mbar, the first base region is a Zn-doped P-type GaInAs layer, the first emitter region is a Si-doped GaInAs layer, and the first window layer is a Si-doped AlInP layer.

[0015] Optionally, forming the third sub-cell further includes:

[0016] stopping the introduction of the second source gas into the working chamber;

[0017] Under a fourth chamber pressure, a third source gas is introduced into the working chamber, wherein the third source gas includes trimethyl indium, trimethyl gallium, trimethyl aluminum, diethyl zinc, arsine and phosphine, and a second back field layer and a fourth base region are formed in sequence, wherein the fourth base region is located between the second back field layer and the second base region, and the second base region and the fourth base region constitute a base region of the third sub-cell; wherein the fourth chamber pressure is 50 mbar, the second back field layer is a P-type AlGaInP layer, and the fourth base region is a Zn-doped P-type GaInAs layer;

[0018] The forming of the second base region, the second emitter region and the second window layer under the second chamber pressure comprises:

[0019] stopping the introduction of the third source gas into the working chamber;

[0020] Under the second chamber pressure, a fourth source gas is introduced into the working chamber, wherein the fourth source gas includes trimethylindium, trimethylgallium, trimethylaluminum, diethylzinc, arsine, phosphine and silane, and the second base region, the second emitter region and the second window layer are formed in sequence; wherein the second chamber pressure is 550 mbar, the second base region is a Zn-doped P-type GaInP layer, the second emitter region is a Si-doped N-type GaInP layer, and the second window layer is a Si-doped AlInP layer.

[0021] Optionally, the preparation method further comprises:

[0022] forming the ohmic contact layer on a side of the second window layer facing away from the substrate;

[0023] The forming of the ohmic contact layer on the side of the second window layer facing away from the substrate comprises:

[0024] stopping the introduction of the fourth source gas into the working chamber;

[0025] Under a fifth chamber pressure, introducing a fifth source gas into the working chamber, wherein the fifth source gas includes trimethylindium, trimethylgallium, arsine and silane, to form the ohmic contact layer;

[0026] The fifth chamber pressure is 50 mbar, and the ohmic contact layer is a Si-doped GaInAs layer.

[0027] Optionally, the first source gas further comprises phosphine, and forming the first sub-cell comprises:

[0028] Under the third chamber pressure, the first source gas is introduced into the working chamber, and before forming the first back field layer and the third base region, a third emitter region and a nucleation layer are sequentially formed on one side of the substrate 1;

[0029] The nucleation layer is located between the third emission region and the first back field layer. The third emission region is formed by diffusion of phosphine in the substrate. The nucleation layer is an N-type GaInP layer.

[0030] Optionally, the preparation method further comprises:

[0031] forming a first tunneling junction layer between the first sub-cell and the second sub-cell;

[0032] forming a second tunnel junction layer between the second sub-cell and the third sub-cell;

[0033] Wherein, forming a first tunnel junction layer between the first sub-cell and the second sub-cell comprises:

[0034] Under the third chamber pressure, the first source gas is introduced into the working chamber to form the first tunneling junction layer after the nucleation layer is formed and before the first back side field layer and the third base region are formed, wherein the first tunneling junction layer is located between the nucleation layer and the first back side field layer;

[0035] The forming a second tunnel junction layer between the second sub-cell and the third sub-cell comprises:

[0036] Under the fourth chamber pressure, the third source gas is introduced into the working chamber, and before forming the second back field layer and the fourth base region, the second tunnel junction layer is formed, and the second tunnel junction layer is located between the first window layer and the second back field layer.

[0037] A solar cell epitaxial wafer, comprising:

[0038] A substrate, wherein the substrate is a Ge substrate having a preset deflection angle, wherein the preset deflection angle has a value range of 15° to 20° from the crystal direction (100) to the crystal direction (111), including end value;

[0039] A first subcell, a second subcell and a third subcell are sequentially arranged on one side of the substrate, wherein the second subcell comprises a first base region, a first emitter region and a first window layer sequentially formed under a first chamber pressure, and the third subcell comprises a second base region, a second emitter region and a second window layer sequentially formed under a second chamber pressure;

[0040] The first chamber pressure has a value range of 400 mbar to 600 mbar, including the endpoint value, and the second chamber pressure has a value range of 400 mbar to 600 mbar, including the endpoint value.

[0041] Optionally, the first subcell comprises a third emission layer and a nucleation layer formed under the third cavity pressure, the nucleation layer is located between the third emission region and the first back field layer; the third emission region is formed by diffusion of phosphine in the substrate, and the nucleation layer is an N-type GaInP layer;

[0042] The second sub-cell further includes a first back field layer and a third base region sequentially formed under a third cavity pressure, wherein the third cavity pressure is 50 mbar, the third base region is located between the first back field layer and the first base region, and the third base region and the first base region constitute the base region of the second sub-cell; the first back field layer is a P-type AlGaAs layer, the third base region is a Zn-doped P-type GaInAs layer, the first base region is a Zn-doped P-type GaInAs layer, the first emitter region is a Si-doped GaInAs layer, and the first window layer is a Si-doped AlInP layer;

[0043] The third sub-cell also includes a second back field layer and a fourth base region sequentially formed under a fourth cavity pressure, the fourth cavity pressure is 50 mbar, the fourth base region is located between the second back field layer and the second base region, and the second base region and the fourth base region constitute the base region of the third sub-cell; the second back field layer is a P-type AlGaInP layer, the fourth base region is a Zn-doped P-type GaInAs layer, the second base region is a Zn-doped P-type GaInP layer, the second emitter region is a Si-doped N-type GaInP layer, and the second window layer is a Si-doped AlInP layer.

[0044] Optionally, the thickness of the third base region is 5 nm to 10 nm, including endpoint values, and the thickness of the fourth base region is 5 nm to 10 nm, including endpoint values.

[0045] Optionally, the solar cell epitaxial wafer further comprises: a first tunnel junction layer formed under the third chamber pressure, a second tunnel junction layer formed under the fourth chamber pressure, and an ohmic contact layer located on a side of the third sub-cell away from the substrate;

[0046] The first tunneling junction layer is located between the nucleation layer and the first back field layer, and the second tunneling junction layer is located between the first window layer and the second back field layer.

[0047] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0048] The preparation method comprises: forming a first subcell, a second subcell and a third subcell in sequence on one side of a substrate, wherein the substrate is a P-type Ge substrate with a preset deflection angle, and the preset deflection angle has a value range of 15° to 20° from the crystal direction (100) to the crystal direction (111), including the end value. Forming the second subcell comprises: forming a first base region, a first emitter region and a first window layer in sequence under a first chamber pressure, and the value range of the first chamber pressure is 400mbar to 600mbar, including the end value; forming the third subcell comprises: forming a second base region, a second emitter region and a second window layer in sequence under a second chamber pressure, and the value range of the second chamber pressure is 400mbar to 600mbar, including the end value. Since the substrate is a Ge substrate with a larger deflection angle between the crystal orientation (100) and the crystal orientation (111), its surface can have more atomic table surfaces, which accelerates the migration rate of Ga and In atoms, so that the first base region, the first emitter region and the first window layer of the second sub-cell can be formed under a higher working chamber pressure, and the second base region, the second emitter region and the second window layer of the third sub-cell can also be formed under a higher working chamber pressure. Therefore, the preparation method can improve the growth rate of the second sub-cell and the third sub-cell on the basis of ensuring the quality of the second sub-cell and the third sub-cell, thereby improving the growth rate of the solar cell and effectively reducing the production cost of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the related technologies, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0050] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not used to limit the conditions under which this application can be implemented, and therefore have no substantive technical significance. Any structural modification, change in proportion or adjustment of size, without affecting the effects and purposes that can be achieved by this application, should still fall within the scope of the technical contents disclosed in this application.

[0051] Figure 1 A flow chart of a method for preparing an epitaxial wafer of a solar cell provided in the present application;

[0052] Figure 2 A schematic diagram of the structure of an epitaxial wafer of a solar cell provided in this application;

[0053] Figure 3 A flow chart of another method for preparing an epitaxial wafer of a solar cell provided in the present application;

[0054] Figure 4 is a curve diagram of the cavity pressure variation of the working cavity;

[0055] Figures 5 to 8 This is a structural diagram corresponding to different steps in a method for preparing an epitaxial wafer of a solar cell provided in this application. DETAILED DESCRIPTION

[0056] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the embodiments in the present application. Obviously, the described embodiments are only embodiments of one area of ​​the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0057] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0058] As described in the background art, in view of the huge demand for commercial aerospace, how to reduce the manufacturing cost of triple-junction solar cells for space use has become an important research topic for those skilled in the art.

[0059] For solar cells, methods for reducing their cost usually include: (1) increasing the number of epitaxial wafers produced in each production cycle to reduce the cost of a single epitaxial wafer; (2) shortening the growth time of epitaxial wafers in each production cycle to reduce time costs; (3) reducing the raw material consumption of each epitaxial wafer, thereby reducing the material cost of epitaxial wafers. Any of the above three methods can effectively reduce the cost of solar cells.

[0060] As for the growth time of epitaxial wafers, relevant reports have pointed out that increasing the epitaxial growth rate can significantly shorten the growth time of epitaxial wafers, inhibit the diffusion of Zn atoms and the mixing of main group elements, and ultimately increase the carrier transport capacity of solar cells and improve the open circuit voltage of solar cells. This shows that increasing the epitaxial growth rate can lay the foundation for the efficient and low-cost epitaxial growth of multi-junction solar cells. However, further increasing the epitaxial growth rate will cause some Ga and In atoms to be covered by new atoms before reaching the target position of the lattice, resulting in a large number of vacancy defects in the formed epitaxial wafers, a decrease in carrier migration, a decrease in the minority carrier diffusion length of photogenerated carriers, and a decrease in the collection efficiency of electrons, thereby deteriorating the performance of solar cells. Therefore, the growth rate of each sub-cell in the current three-junction solar cell cannot be significantly increased and is limited to about 0.4-1.4nm / s.

[0061] In addition, the existing technology usually uses chemical vapor deposition (MOCVD) to grow solar cells. Currently, most MOCVD processes use low pressure. Reducing the working pressure can effectively suppress the flow instability caused by thermal buoyancy, increase the temperature gradient above the base, and reduce parasitic reactions, which is conducive to obtaining thin film materials with uniform thickness. However, in the actual production process, the lower the working pressure, the better. Low pressure will cause excessive consumption of raw materials and reduce the deposition rate of the film, which will lead to higher time and material costs for the existing solar cell epitaxial wafer preparation method.

[0062] Based on the above, the present application provides a method for preparing an epitaxial wafer of a solar cell, such as Figure 1 As shown, Figure 1 A flow chart of a method for preparing an epitaxial wafer of a solar cell provided in the present application, the method comprising:

[0063] S1: Figure 2 As shown, Figure 2The structural diagram of the solar cell epitaxial wafer prepared by the preparation method provided in the present application provides a substrate 1, and the substrate 1 is placed in a working chamber. The substrate 1 is a P-type Ge substrate with a preset deflection angle, and the preset deflection angle ranges from 15° to 20° in the crystal direction (100) to the crystal direction (111), including the end value. It should be noted that if the preparation method uses the MOCVD process to prepare solar cells, the substrate 1 can be placed in the MOCVD system of Aixtron, but the present application does not limit this, depending on the specific circumstances. In addition, if the preparation method adopts the MOCVD process, the initial working pressure of the MOCVD system, that is, the initial chamber pressure, can be 50 mbar, and the working temperature can be 620°C, but the present application does not limit this, depending on the specific circumstances.

[0064] S2: forming a first sub-cell 10, a second sub-cell 20 and a third sub-cell 30 in sequence on one side of the substrate 1, specifically forming a first sub-cell 10, a second sub-cell 20 and a third sub-cell 30 in a stacked arrangement in sequence on one side of the substrate 1, that is, forming a first sub-cell 1 on one side of the substrate 1, forming a second sub-cell 20 on a side of the first sub-cell 10 facing away from the substrate 1, and forming a third sub-cell 30 on a side of the second sub-cell 20 facing away from the first sub-cell 10.

[0065] For the above step S2, if Figure 3 As shown, Figure 3 The present application provides a flow chart of a method for preparing an epitaxial wafer of a solar cell, wherein forming the second sub-cell 20 includes:

[0066] S21: Under the first chamber pressure, the first base region 21, the first emitter region 22 and the first window layer 23 are sequentially formed, specifically, the first base region 21, the first emitter region 22 and the first window layer 23 are sequentially formed in a stacked arrangement along the direction away from the substrate 1, that is, the first base region 21 is formed on the side of the first sub-cell 10 away from the substrate 1, the first emitter region 22 is formed on the side of the first base region 21 away from the first sub-cell 10, and the first window layer 23 is formed on the side of the first emitter region 22 away from the first base region 21. The value range of the above-mentioned first chamber pressure is 400mbar to 600mbar, including the end value.

[0067] Forming the third sub-cell 30 includes:

[0068] S22: Under the second chamber pressure, the second base region 31, the second emitter region 32 and the second window layer 33 are sequentially formed, specifically, the second base region 31, the second emitter region 32 and the second window layer 33 are sequentially formed in a stacked arrangement on the side of the second sub-cell 20 away from the first sub-cell 10, that is, the second base region 31 is formed on the side of the second sub-cell 20 away from the first sub-cell 10, the second emitter region 32 is formed on the side of the second base region 31 away from the second sub-cell 20, and the second window layer 33 is formed on the side of the second emitter region 32 away from the second base region 31. The second chamber pressure ranges from 400 mbar to 600 mbar, including the end value.

[0069] As can be seen from the above, when the preparation method provided by the present application forms the first base region 21, the first emitter region 22 and the first window layer 23 of the second sub-cell 20 under the first chamber pressure, and the value of the first chamber pressure is between 400mbar and 600mbar, that is, in the preparation method, the first base region 21, the first emitter region 22 and the first window layer 23 of the second sub-cell 20 can be formed under a higher working chamber pressure. Since the higher working chamber pressure can reduce the gas flow rate in the working chamber, the source gas (i.e., the raw material) stays for a long time, thereby increasing the deposition rate of the first base region 21, the first emitter region 22 and the first window layer 23 of the second sub-cell 20, that is, improving the growth rate of the second sub-cell 20. At the same time, it is known that the substrate 1 is a P-type Ge substrate with a crystal orientation (100) and a crystal orientation (111) of 15° to 20°, that is, the substrate 1 is a Ge substrate with a large crystal orientation (100) and a crystal orientation (111), so that the surface of the substrate 1 can have more atomic table surfaces. In the process of forming the above-mentioned first base region 21, the first emitter region 22 and the first window layer 23, the migration rate of Ga and In atoms can be accelerated, and the problem of Ga and In atoms being covered can be effectively suppressed, thereby reducing the problem of more vacancy defects caused by the increase in deposition rate to a certain extent. It can be seen that the preparation method can improve the growth rate of the second sub-battery 20 on the basis of ensuring the quality of the second sub-battery 20. Similarly, the second base region 31, the second emitter region 32 and the second window layer 33 of the third sub-battery 30 are also formed under a higher working chamber pressure. The preparation method can also improve the growth rate of the third sub-battery 30 on the basis of ensuring the quality of the third sub-battery 30. It should be noted that, through experimental optimization, it is known that the growth rate of the second sub-cell 20 is preferably 2.9 nm / s-3.1 nm / s, and the growth rate of the third sub-cell is preferably 1.5 nm / s-1.7 nm / s.

[0070] In summary, the improved method for preparing epitaxial wafers of solar cells in the present application can improve the growth rate of the second sub-cell 20 and the third sub-cell 30 while ensuring the quality of the second sub-cell 20 and the third sub-cell 30, thereby improving the growth rate of the solar cell and effectively reducing the production cost of the solar cell.

[0071] In addition, since a higher working chamber pressure can reduce the gas flow rate in the working chamber, thereby prolonging the residence time of the source gas, compared with the related technology using a lower chamber pressure, the preparation method of the present application can achieve the same growth rate through less raw material consumption when preparing the base region, emitter region and window layer of the second sub-cell 20 and the third sub-cell 30, thereby reducing the consumption of raw materials and reducing the production cost of solar cells.

[0072] It should be noted that, for the preparation method provided in this application, the second chamber pressure can be slightly greater than the first chamber pressure, which can effectively reduce the impact of the warping problem of the epitaxial wafer on the top cell, i.e., the third sub-cell. Preferably, the first chamber pressure is 480 mbar and the second chamber pressure is 550 mbar.

[0073] Based on the above embodiments, in one embodiment of the present application, for step S2, forming the second sub-cell 20 further includes:

[0074] Under the third chamber pressure, the first source gas is introduced into the working chamber, and the first source gas includes trimethyl indium (TMIn), trimethyl gallium (TMGa), trimethyl aluminum (TMAl), diethyl zinc (DEZn) and arsine (AsH3), and a first back field layer 24 and a third base region 25 arranged in a stacked manner are formed in sequence. Specifically, the third base region 25 is located between the first back field layer 24 and the first base region 21, that is, the second sub-cell 20 includes a first back field layer 24, a third base region 25, a first base region 21, a first emitter region 22 and a first window layer 23 which are stacked in sequence and located on the side of the first sub-cell 10 away from the substrate 1. The above-mentioned first base region 21 and the third base region 25 constitute the base region of the second sub-cell 20.

[0075] The third cavity pressure is 50 mbar, the first back field layer is a P-type AlGaAs layer, and the third base region is a Zn-doped P-type GaInAs layer.

[0076] Since it takes a certain amount of time for the cavity pressure to change during the preparation of the second sub-cell 20, if the cavity pressure is increased when the first back field layer 24 is grown, defects will occur at the interface between the back field layer and the base region of the second sub-cell 20, thereby affecting the collection of photogenerated carriers. As can be seen from the above, when preparing the second sub-cell 20 in this embodiment, before the first base region 21, the first emitter region 22 and the first window layer 23 are grown at high pressure, the first back field layer 24 and the third base region 25 are formed in sequence at a lower third cavity pressure, and then the first base region 21, the first emitter region 22 and the first window layer 23 are formed by increasing the cavity pressure to the first cavity pressure, thereby effectively suppressing the defects at the interface between the back field layer and the base region of the second sub-cell 20, ensuring the collection of photogenerated carriers, and thus ensuring the performance of the second sub-cell 20.

[0077] Based on the above, in one embodiment of the present application, for step S21, under the first chamber pressure, forming the first base region 21, the first emitter region 22 and the first window layer 23 includes:

[0078] The supply of the first source gas into the working chamber is stopped.

[0079] The chamber pressure of the working chamber is increased, and under the first chamber pressure, a second source gas is introduced into the working chamber, wherein the second source gas includes trimethyl indium (TMIn), trimethyl gallium (TMGa), trimethyl aluminum (TMAl), diethyl zinc (DEZn), arsine (AsH3), silane (SiH4) and phosphine (PH3), and the first base region 21, the first emitter region 22 and the first window layer 23 are formed in sequence. Among them, the value of the first chamber pressure is 480 mbar, the first base region 21 is a Zn-doped P-type GaInAs layer, the first emitter region 22 is a Si-doped GaInAs layer, and the first window layer 23 is a Si-doped AlInP layer. It should be noted that the gas flow rate of arsine in the second source gas is greater than the gas flow rate of arsine in the first source gas. Specifically, in one embodiment of the present application, the gas flow rate of arsine in the second source gas can be 1500 sccm, but the present application does not limit this, and it depends on the specific situation.

[0080] Based on the above embodiments, in one embodiment of the present application, for step S2, forming the third sub-cell 30 further includes:

[0081] stopping the introduction of the second source gas into the working chamber;

[0082] The chamber pressure of the working chamber is adjusted, and at a fourth chamber pressure, a third source gas is introduced into the working chamber, wherein the third source gas includes trimethyl indium (TMIn), trimethyl gallium (TMGa), trimethyl aluminum (TMAl), diethyl zinc (DEZn), arsine (AsH3) and phosphine (PH3), and a second back field layer 34 and a fourth base region 35 are formed in sequence. The second base region 31 and the fourth base region 35 constitute the base region of the third sub-cell 30, and the fourth base region 35 is located between the second back field layer 34 and the second base region 31, that is, the formation of the third sub-cell 30 is specifically to form a second back field layer 34 on the side of the second sub-cell 20 away from the first sub-cell 10, to form a fourth base region 35 on the side of the second back field layer 34 away from the second sub-cell 20, to form a second base region 31 on the side of the fourth base region 35 away from the second back field layer 35, to form a second emitter region 32 on the side of the second base region 31 away from the fourth base region 35, and to form a second window layer 33 on the side of the second emitter region 32 away from the second base region 31.

[0083] The fourth chamber pressure is 50 mbar, the second back field layer 34 is a P-type AlGaInP layer, and the fourth base region 35 is a Zn-doped P-type GaInAs layer. It should be noted that the gas flow rate of phosphine in the third source gas can be 600 sccm, which is less than the gas flow rate of phosphine in the second source gas.

[0084] As can be seen from the above, in this embodiment, the value of the fourth chamber pressure is 50mbar, that is, before the second base region 31, the second emitter region 32 and the second window layer 33 are grown at high pressure, the preparation method first forms the second back field layer 34 and the fourth base region 35 in sequence at a lower fourth chamber pressure, and then forms the second base region 31, the second emitter region 32 and the second window layer 33 by increasing the chamber pressure to the second chamber pressure, which can effectively suppress the defects between the back field layer of the third sub-cell 30 and its base region interface, ensure the collection of photogenerated carriers, and further ensure the performance of the third sub-cell 30. It should be noted that the present application does not limit the specific value of the fourth chamber pressure, and the specific value depends on the situation, so that the second back field layer 34 and the fourth base region 35 can be formed at a lower chamber pressure.

[0085] Based on the above, in one embodiment of the present application, for step S22, under the second chamber pressure, forming the second base region 31, the second emitter region 32 and the second window layer 33 includes:

[0086] The supply of the third source gas into the working chamber is stopped.

[0087] The chamber pressure of the working chamber is increased, and under the second chamber pressure, a fourth source gas is introduced into the working chamber, wherein the fourth source gas includes trimethyl indium (TMIn), trimethyl gallium (TMGa), trimethyl aluminum (TMAl), diethyl zinc (DEZn), arsine (AsH3) and phosphine (PH3), and a second base region 31, a second emitter region 32 and a second window layer 33 are formed in sequence. Among them, the value of the second chamber pressure is 550 mbar, the second base region is a Zn-doped P-type GaInP layer, the second emitter region is a Si-doped N-type GaInP layer, and the second window layer is a Si-doped AlInP layer. It should be noted that the gas flow rate of phosphine in the fourth source gas is greater than the gas flow rate of phosphine in the third source gas. Specifically, in one embodiment of the present application, the value of the phosphine gas flow rate in the fourth source gas can be 1500 sccm, but the present application is not limited to this, and it depends on the specific situation.

[0088] In addition, for a Ge substrate with a large deflection angle between the crystal orientation (100) and the crystal orientation (111), when a GaInP epitaxial layer is grown thereon, the order of the GaInP epitaxial layer is better and the surface is smoother, which can effectively improve the performance of the GaInP epitaxial layer. Therefore, in the present application, the substrate 1 is a Ge substrate with a large deflection angle between the crystal orientation (100) and the crystal orientation (111), which can produce a better performance of the third sub-cell 30, thereby helping to improve the performance of the produced solar cell.

[0089] Based on the foregoing embodiments, in one embodiment of the present application, the preparation method further comprises:

[0090] S3 : forming an ohmic contact layer 40 on a side of the second window layer 33 facing away from the substrate 1 , specifically forming the ohmic contact layer 40 on a side of the second window layer 33 facing away from the second emission region 32 .

[0091] Regarding the above step S3, forming the ohmic contact layer 40 on the side of the second window layer 33 facing away from the substrate 1 includes:

[0092] The supply of the fourth source gas into the working chamber is stopped.

[0093] Under the fifth chamber pressure, the fifth source gas is introduced into the working chamber, and the fifth source gas includes trimethyl indium (TMIn), trimethyl gallium (TMGa), arsine (AsH3) and silane (SiH4) to form an ohmic contact layer 40 on the side of the second window layer 33 away from the second emission region 32, so that the prepared epitaxial wafer can be connected with other components. Among them, the value of the fifth chamber pressure is 50mbar, and the ohmic contact layer is a Si-doped GaInAs layer, that is, the ohmic contact layer 40 is formed under a relatively low chamber pressure, so that the preparation method can effectively reduce the warping problem of the epitaxial wafer, and at the same time can also inhibit the epitaxial wafer from flying out of the high-speed rotating working chamber. It should be noted that the gas flow rate of phosphine in the fifth source gas can be 600sccm, which is less than the gas flow rate of phosphine in the fourth source gas.

[0094] Based on the above embodiments, in one embodiment of the present application, the first source gas further includes phosphine (PH3), and for step S2, forming the first sub-cell 10 includes:

[0095] Under the third chamber pressure, the first source gas is introduced into the working chamber, and before forming the first back field layer 24 and the third base region 25, the third emitter region 11 and the nucleation layer 12 are sequentially formed on one side of the substrate 1. The nucleation layer 12 is located between the third emitter region 11 and the first back field layer 24, the third emitter region 11 is formed by the diffusion of phosphine in the substrate 1, and is the emitter region of the first sub-cell 1, and the nucleation layer is an N-type GaInP layer.

[0096] Based on the foregoing embodiments, in one embodiment of the present application, the preparation method further comprises:

[0097] S4: forming a first tunnel junction layer 50 between the first sub-cell 10 and the second sub-cell 20. The first tunnel junction layer 50 includes Si-doped GaAs and C-doped GaAs, which can be abbreviated as GaAs:Si / GaAs:C.

[0098] S5: forming a second tunnel junction layer 60 between the second sub-cell 20 and the third sub-cell 30. The second tunnel junction layer includes Si-doped GaAs and C-doped GaAs, which can be abbreviated as GaAs:Si / GaAs:C.

[0099] For step S4, forming a first tunnel junction layer 50 between the first sub-cell 10 and the second sub-cell 20 includes:

[0100] Under the third chamber pressure, the first source gas is introduced into the working chamber, and a first tunnel junction layer 50 is formed between the first sub-cell 10 and the second sub-cell 20 after the nucleation layer 12 is formed and before the first back field layer 24 and the third base region 25 are formed. The first tunnel junction layer 50 is located between the nucleation layer 12 and the first back field layer 24, which is equivalent to connecting the first sub-cell 10 and the second sub-cell 20 so that electrons can be transmitted between the first sub-cell 10 and the second sub-cell 20.

[0101] For step S5, forming a second tunnel junction layer 60 between the second sub-cell 20 and the third sub-cell 30 includes:

[0102] Under the fourth chamber pressure, the third source gas is introduced into the working chamber, and before the second back field layer 34 and the fourth base region 35 are formed, a second tunnel junction layer 60 is formed. The second tunnel junction layer 60 is located between the first window layer 23 and the second back field layer 34, which is equivalent to being used to connect the second sub-cell 20 and the third sub-cell 30, so that electrons can be transmitted between the second sub-cell 20 and the third sub-cell 30.

[0103] It should be noted that, in the above embodiment, the value of the third chamber pressure and the fourth chamber pressure is 50 mbar, but the present application does not limit this, and it depends on the specific situation.

[0104] In order to understand the present invention in more detail, the present invention provides a method for preparing a solar cell epitaxial wafer. Figure 4 The preparation method is described in detail. Figure 4 is the pressure change curve of the working chamber, Figure 4 The middle curve 1 represents the sequential growth of the third emitter region 11, the nucleation layer 12, the first tunnel junction layer 50, the first back field layer 24 and the third base region 25 under the third cavity pressure; the curve 2 represents the sequential growth of the first base region 21, the first emitter region 22 and the first window layer 23 under the first cavity pressure; the curve 3 represents the sequential growth of the first tunnel junction layer 50, the second back field layer 34 and the fourth base region 35 under the fourth cavity pressure; the curve 4 represents the sequential growth of the second base region 31, the second emitter region 32 and the second window layer 33 under the second cavity pressure; the curve 5 represents the growth of the ohmic contact layer 40 under the fifth cavity pressure.

[0105] Specifically, the substrate 1 is placed in a working chamber, the initial chamber pressure of the working chamber is 50 mbar, the growth temperature is 620° C. Ar is used as a carrier gas, and the first source gas is introduced into the working chamber to sequentially form the third emission region 11, the nucleation layer 12, the first tunneling junction layer 50, the first back field layer 24 and the third base region 25, as shown in curves 1 and Figure 5After that, the first source gas is stopped from being introduced into the working chamber, the chamber pressure is increased to 480 mbar, and the second source gas is introduced into the working chamber, the gas flow rate of arsine in the second source gas is 1500 sccm, and the first base region 21, the first emitter region 22 and the first window layer 23 are sequentially grown at a growth rate of 3 nm / s under a relatively high chamber pressure, as shown in curves 2 and Figure 6 shown.

[0106] Stop introducing the second source gas into the working chamber, reduce the chamber pressure to 50 mbar, and introduce the third source gas into the working chamber. The phosphine in the third source gas is reduced to 600 sccm. The first tunneling junction layer 50, the second back field layer 34 and the fourth base region 35 are grown in sequence at a lower chamber pressure, as shown in curves 3 and Figure 7 After that, the third source gas is stopped from being introduced into the working chamber, the chamber pressure is increased to 550 mbar, and the fourth source gas is introduced into the working chamber, the flow rate of the phosphine gas in the fourth source gas is increased to 1500 sccm, and the second base region 31, the second emitter region 32 and the second window layer 33 are sequentially grown at a growth rate of 1.6 nm / s under a higher chamber pressure, as shown in curves 4 and Figure 8 shown.

[0107] Finally, the fourth source gas is stopped from being introduced into the working chamber, the chamber pressure is reduced to 50 mbar, and the fifth source gas is introduced into the working chamber, the gas flow rate of phosphine in the fifth source gas is reduced to 600 sccm, and the ohmic contact layer 40 is grown at a lower chamber pressure to complete the growth of the epitaxial wafer of the solar cell, as shown in curves 5 and Figure 2 shown.

[0108] Correspondingly, the present application also provides a solar cell epitaxial wafer, which is prepared by the preparation method described in any of the above embodiments, such as Figure 2 As shown, the epitaxial wafer comprises:

[0109] Substrate 1 is a P-type Ge substrate with a preset deflection angle, wherein the preset deflection angle has a value range of 15° to 20° from the crystal direction (100) to the crystal direction (111), including the end value.

[0110] A first sub-cell 10, a second sub-cell 20 and a third sub-cell 30 are located on one side of a substrate 1. The second sub-cell 20 includes a first base region 21, a first emitter region 22 and a first window layer 23 formed in sequence under a first cavity pressure. The third sub-cell 30 includes a second base region 31, a second emitter region 32 and a second window layer 33 formed in sequence under a second cavity pressure.

[0111] The first chamber pressure has a value range of 400 mbar to 600 mbar, including the endpoint values, and the second chamber pressure has a value range of 400 mbar to 600 mbar, including the endpoint values.

[0112] As can be seen from the above, the first base region 21, the first emitter region 22 and the first window layer 23 of the second subcell 20 are formed under a relatively high working chamber pressure. Since the relatively high working chamber pressure can reduce the gas flow rate in the working chamber, the source gas (i.e., the raw material) stays for a long time, thereby increasing the deposition rate of the first base region 21, the first emitter region 22 and the first window layer 23 of the second subcell 20, i.e., increasing the growth rate of the second subcell 20. At the same time, it is known that the substrate 1 is a P-type Ge substrate with a crystal orientation (100) and a crystal orientation (111) of 15° to 20°, i.e., the substrate 1 is a Ge substrate with a relatively large crystal orientation (100) and a crystal orientation (111), so that the surface of the substrate 1 can have more atomic terraces to accelerate the migration rate of Ga and In atoms, and can effectively suppress the problem of Ga and In atoms being covered, thereby reducing the problem of more vacancy defects caused by the increased deposition rate to a certain extent. It can be seen that the second subcell 20 of the epitaxial wafer can be generated at a relatively high growth rate on the basis of ensuring its quality. Similarly, the second base region 31 , the second emitter region 32 and the second window layer 33 of the third sub-cell 30 are also formed under a higher working chamber pressure, and can also be generated at a higher growth rate while ensuring the quality of the third sub-cell 30 .

[0113] Based on the above embodiments, in one embodiment of the present application, the second subcell further includes a first back field layer 24 and a third base region 25 formed in sequence under a third chamber pressure, the value of the third chamber pressure is 50 mbar, the third base region 25 is located between the first back field layer 24 and the first base region 21, and the third base region 25 and the first base region 21 constitute the base region of the second subcell 20. The third subcell 30 further includes a second back field layer 34 and a fourth base region 35 formed in sequence under a fourth chamber pressure, the value of the fourth chamber pressure is 50 mbar, the fourth base region 35 is located between the second back field layer 34 and the second base region 31, and the second base region 31 and the fourth base region 35 constitute the base region of the third subcell 30. Among them, the first back field layer is a P-type AlGaAs layer, the third base region is a Zn-doped P-type GaInAs layer, the first base region is a Zn-doped P-type GaInAs layer, the first emitter region is a Si-doped GaInAs layer, the first window layer is a Si-doped AlInP layer, the second back field layer is a P-type AlGaInP layer, the fourth base region is a Zn-doped P-type GaInAs layer, the second base region is a Zn-doped P-type GaInP layer, the second emitter region is a Si-doped N-type GaInP layer, and the second window layer is a Si-doped AlInP layer.

[0114] As can be seen from the above, for the second subcell 20, before the first base region 21, the first emitter region 22 and the first window layer 23 are grown at high pressure, the first back field layer 24 and the third base region 25 are formed in sequence at a lower third chamber pressure, and then the first base region 21, the first emitter region 22 and the first window layer 23 are formed again when the chamber pressure is increased to the first chamber pressure, thereby effectively suppressing the defects between the back field layer and the base interface of the second subcell 20, ensuring the collection of photogenerated carriers, and thus ensuring the performance of the second subcell 20. Similarly, for the third subcell 30, the defects between the back field layer and the base interface of the third subcell 30 are also effectively suppressed, ensuring the collection of photogenerated carriers, and thus ensuring the performance of the third subcell 30.

[0115] Based on the foregoing embodiments, in one embodiment of the present application, the thickness of the third base region 25 is 5 nm to 10 nm, including endpoint values, and the thickness of the fourth base region 35 is 5 nm to 10 nm, including endpoint values.

[0116] Based on the foregoing embodiments, in one embodiment of the present application, the first sub-cell 10 includes a third emission layer 11 and a nucleation layer 12 formed under a third chamber pressure, the nucleation layer 12 is located between the third emission region 11 and the first back field layer 21, the third emission region 11 is formed by diffusion of phosphine in the substrate 1, and the nucleation layer 12 is an N-type GaInP layer.

[0117] The solar cell epitaxial wafer also includes: a first tunneling junction layer 50 formed under a third chamber pressure, a second tunneling junction layer 60 formed under a fourth chamber pressure, and an ohmic contact layer 40 located on the side of the third subcell 30 away from the substrate 1. The first tunneling junction layer 50 is located between the nucleation layer 12 and the first back field layer 21, the second tunneling junction layer 60 is located between the first window layer 23 and the second back field layer 31, and the ohmic contact layer 40 is located on the side of the second window layer 33 away from the second emission layer 32, and is a Si-doped GaInAs layer to achieve electrical connection between the epitaxial wafer and other components.

[0118] In summary, the present application provides a method for preparing an epitaxial wafer of a solar cell and an epitaxial wafer of a solar cell, the method comprising: sequentially forming a first subcell, a second subcell and a third subcell on one side of a substrate, the substrate being a P-type Ge substrate with a preset deflection angle, the preset deflection angle ranging from 15° to 20° between crystal orientation (100) and crystal orientation (111), including the end value. Forming the second subcell comprises: sequentially forming a first base region, a first emitter region and a first window layer under a first chamber pressure, the first chamber pressure ranging from 400 mbar to 600 mbar, including the end value; forming the third subcell comprises: sequentially forming a second base region, a second emitter region and a second window layer under a second chamber pressure, the second chamber pressure ranging from 400 mbar to 600 mbar, including the end value. Since the substrate is a Ge substrate with a larger deflection angle between the crystal orientation (100) and the crystal orientation (111), its surface has more atomic table surfaces, which can accelerate the migration rate of Ga and In atoms, so that the first base region, the first emitter region and the first window layer of the second sub-cell can be formed under a higher working chamber pressure, and the second base region, the second emitter region and the second window layer of the third sub-cell can also be formed under a higher working chamber pressure. Therefore, the preparation method can improve the growth rate of the second sub-cell and the third sub-cell on the basis of ensuring the quality of the second sub-cell and the third sub-cell, thereby improving the growth rate of the solar cell and effectively reducing the production cost of the solar cell.

[0119] In this specification, each embodiment is described in a progressive, parallel, or progressive and parallel manner. Each embodiment focuses on the differences from other embodiments, and the same or similar areas between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method area description.

[0120] It should be noted that in the description of the present application, it should be understood that the terms "upper", "lower", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. When a component is considered to be "connected" to another component, it may be directly connected to the other component or there may be a centrally arranged component at the same time.

[0121] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "comprising" or any other variants thereof are intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such article or device. In the absence of further restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the article or device including the above elements.

[0122] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. 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 application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an epitaxial wafer of a solar cell, characterized in that: include: Providing a substrate, and placing the substrate in a working chamber; The substrate is a P-type Ge substrate with a preset deflection angle, and the preset deflection angle has a value range of 15° to 20° from the crystal direction (100) to the crystal direction (111), including the end value; sequentially forming a first sub-cell, a second sub-cell and a third sub-cell on one side of the substrate; Forming the second sub-cell includes: Under a first chamber pressure, a first base region, a first emitter region and a first window layer are sequentially formed, wherein the first chamber pressure has a value range of 400 mbar to 600 mbar, including end points; Forming the third sub-cell includes: Under a second chamber pressure, a second base region, a second emitter region and a second window layer are formed in sequence, and the second chamber pressure has a value range of 400 mbar to 600 mbar, including end points.

2. The method for preparing an epitaxial wafer of a solar cell according to claim 1, characterized in that: The forming of the second sub-cell further comprises: Under a third chamber pressure, a first source gas is introduced into the working chamber, wherein the first source gas includes trimethyl indium, trimethyl gallium, trimethyl aluminum, diethyl zinc and arsine, and a first back field layer and a third base region are formed in sequence, wherein the third base region is located between the first back field layer and the first base region, and the third base region and the first base region constitute a base region of the second sub-cell; wherein the third chamber pressure is 50 mbar, the first back field layer is a P-type AlGaAs layer, and the third base region is a Zn-doped P-type GaInAs layer; The forming of the first base region, the first emitter region and the first window layer under the first chamber pressure comprises: stopping the introduction of the first source gas into the working chamber; Under the first chamber pressure, a second source gas is introduced into the working chamber, wherein the second source gas includes trimethylindium, trimethylgallium, trimethylaluminum, diethylzinc, arsine, silane and phosphine, and the first base region, the first emitter region and the first window layer are formed in sequence; wherein the first chamber pressure is 480 mbar, the first base region is a Zn-doped P-type GaInAs layer, the first emitter region is a Si-doped GaInAs layer, and the first window layer is a Si-doped AlInP layer.

3. The method for preparing an epitaxial wafer of a solar cell according to claim 2, characterized in that: The forming of the third sub-cell further comprises: stopping the introduction of the second source gas into the working chamber; Under a fourth chamber pressure, a third source gas is introduced into the working chamber, wherein the third source gas includes trimethyl indium, trimethyl gallium, trimethyl aluminum, diethyl zinc, arsine and phosphine, and a second back field layer and a fourth base region are formed in sequence, wherein the fourth base region is located between the second back field layer and the second base region, and the second base region and the fourth base region constitute a base region of the third sub-cell; wherein the fourth chamber pressure is 50 mbar, the second back field layer is a P-type AlGaInP layer, and the fourth base region is a Zn-doped P-type GaInAs layer; The forming of the second base region, the second emitter region and the second window layer under the second chamber pressure comprises: stopping the introduction of the third source gas into the working chamber; Under the second chamber pressure, a fourth source gas is introduced into the working chamber, wherein the fourth source gas includes trimethylindium, trimethylgallium, trimethylaluminum, diethylzinc, arsine, phosphine and silane, and the second base region, the second emitter region and the second window layer are formed in sequence; wherein the second chamber pressure is 550 mbar, the second base region is a Zn-doped P-type GaInP layer, the second emitter region is a Si-doped N-type GaInP layer, and the second window layer is a Si-doped AlInP layer.

4. The method for preparing an epitaxial wafer of a solar cell according to claim 3, characterized in that: The preparation method also includes: forming the ohmic contact layer on a side of the second window layer facing away from the substrate; The forming of the ohmic contact layer on the side of the second window layer facing away from the substrate comprises: stopping the introduction of the fourth source gas into the working chamber; Under a fifth chamber pressure, introducing a fifth source gas into the working chamber, wherein the fifth source gas includes trimethylindium, trimethylgallium, arsine and silane, to form the ohmic contact layer; The fifth chamber pressure is 50 mbar, and the ohmic contact layer is a Si-doped GaInAs layer.

5. The method for preparing an epitaxial wafer of a solar cell according to any one of claims 1 to 4, characterized in that: The first source gas further comprises phosphine, and the forming of the first sub-cell comprises: Under the third chamber pressure, the first source gas is introduced into the working chamber, and before forming the first back field layer and the third base region, a third emitter region and a nucleation layer are sequentially formed on one side of the substrate 1; The nucleation layer is located between the third emission region and the first back field layer. The third emission region is formed by diffusion of phosphine in the substrate. The nucleation layer is an N-type GaInP layer.

6. The method for preparing an epitaxial wafer of a solar cell according to claim 5, characterized in that: The preparation method also includes: forming a first tunneling junction layer between the first sub-cell and the second sub-cell; forming a second tunnel junction layer between the second sub-cell and the third sub-cell; Wherein, forming a first tunnel junction layer between the first sub-cell and the second sub-cell comprises: Under the third chamber pressure, the first source gas is introduced into the working chamber to form the first tunneling junction layer after the nucleation layer is formed and before the first back side field layer and the third base region are formed, wherein the first tunneling junction layer is located between the nucleation layer and the first back side field layer; The forming a second tunnel junction layer between the second sub-cell and the third sub-cell comprises: Under the fourth chamber pressure, the third source gas is introduced into the working chamber, and before forming the second back field layer and the fourth base region, the second tunnel junction layer is formed, and the second tunnel junction layer is located between the first window layer and the second back field layer.

7. A solar cell epitaxial wafer, characterized in that: include: A substrate, wherein the substrate is a Ge substrate having a preset deflection angle, wherein the preset deflection angle has a value range of 15° to 20° from the crystal direction (100) to the crystal direction (111), including end value; A first subcell, a second subcell and a third subcell are sequentially arranged on one side of the substrate, wherein the second subcell comprises a first base region, a first emitter region and a first window layer sequentially formed under a first chamber pressure, and the third subcell comprises a second base region, a second emitter region and a second window layer sequentially formed under a second chamber pressure; The first chamber pressure has a value range of 400 mbar to 600 mbar, including the endpoint value, and the second chamber pressure has a value range of 400 mbar to 600 mbar, including the endpoint value.

8. The solar cell epitaxial wafer according to claim 7, characterized in that: The first subcell comprises a third emission layer and a nucleation layer formed under the third cavity pressure, wherein the nucleation layer is located between the third emission region and the first back field layer; the third emission region is formed by diffusion of phosphine in the substrate, and the nucleation layer is an N-type GaInP layer; The second sub-cell further includes a first back field layer and a third base region sequentially formed under a third chamber pressure, wherein the third chamber pressure is 50 mbar, the third base region is located between the first back field layer and the first base region, and the third base region and the first base region constitute a base region of the second sub-cell; The first back field layer is a P-type AlGaAs layer, the third base region is a Zn-doped P-type GaInAs layer, the first base region is a Zn-doped P-type GaInAs layer, the first emitter region is a Si-doped GaInAs layer, and the first window layer is a Si-doped AlInP layer; The third sub-cell further includes a second back field layer and a fourth base region sequentially formed under a fourth chamber pressure, wherein the fourth chamber pressure is 50 mbar, the fourth base region is located between the second back field layer and the second base region, and the second base region and the fourth base region constitute the base region of the third sub-cell; The second back field layer is a P-type AlGaInP layer, the fourth base region is a Zn-doped P-type GaInAs layer, the second base region is a Zn-doped P-type GaInP layer, the second emitter region is a Si-doped N-type GaInP layer, and the second window layer is a Si-doped AlInP layer.

9. The solar cell epitaxial wafer according to claim 8, characterized in that: The thickness of the third base region is 5 nm to 10 nm, including the endpoint values, and the thickness of the fourth base region is 5 nm to 10 nm, including the endpoint values.

10. The solar cell epitaxial wafer according to any one of claims 7 to 9, characterized in that: The solar cell epitaxial wafer further includes: a first tunneling junction layer formed under the third chamber pressure, a second tunneling junction layer formed under the fourth chamber pressure, and an ohmic contact layer located on a side of the third sub-cell away from the substrate; The first tunneling junction layer is located between the nucleation layer and the first back field layer, and the second tunneling junction layer is located between the first window layer and the second back field layer.

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