Solar cell epitaxial structure with controlled epitaxial dislocation distribution, solar cell and manufacturing method thereof

Abstract

The invention discloses a solar cell epitaxial structure with controlled epitaxial dislocation distribution, a solar cell and a manufacturing method of the solar cell. The solar cell epitaxial structure comprises a GaAs substrate, a GaAs nucleating layer, a GaInP corrosion barrier layer, a GaAs contact layer, a GaInP top cell, a first tunnel junction, a first gradient buffer layer, a GaInAs intermediate cell, a second tunnel junction, a lattice overshoot layer, a second gradient buffer layer, a GaInAs bottom cell and a GaInAs contact layer from bottom to top in sequence. Wherein the first gradual change buffer layer is an AlGaInAs lattice gradual change buffer layer, and in the first gradual change buffer layer, the In component is increased nonlinearly from an initial layer to a target gradual change layer; the second gradual change buffer layer is an AlGaInAs lattice gradual change buffer layer, and in the second gradual change buffer layer, the In component content of the previous layer of the target gradual change layer is higher than that of the target gradual change layer in the process that the In component is increased from the initial layer to the target gradual change layer in a non-linear mode; the In component content in the lattice overshoot layer is higher than the In component content in the initial layer of the second gradient buffer layer. And the photoelectric efficiency of the solar cell can be effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of solar cells, and in particular to a solar cell epitaxial structure with controlled epitaxial dislocation distribution and a manufacturing method thereof. Background Art

[0002] In the near-space range, aircraft such as stratospheric airships and high-altitude solar drones can play an important role in meteorological observation, communication relay and information collection. Near-space aircraft, combined with satellites and ground systems, are conducive to the three-dimensional development of observation systems. Long-duration flights of aircraft in near-space require continuous energy supply, which makes solar cells the best choice for energy supply.

[0003] The long-duration work requirement limits the load and size of near-space vehicles, which places high demands on the mass-to-power ratio of solar cells. Expanding the battery area and increasing the amount of solar cells used will also increase the mass of the vehicle. Therefore, improving the photoelectric conversion efficiency of solar cells is an effective way to increase the power of the vehicle power supply and the mass-to-power ratio under the conditions of fixed battery weight and area. In addition, since the location where the solar cells of the vehicle are installed is usually a curved surface, flexible solar cells are required. In summary, flexible solar cells with high mass-to-power ratio are a very important development direction for the energy system of near-space vehicles.

[0004] Theoretically, in a triple-junction solar cell, when the bottom cell band gap is 1.0 eV, better current matching can be achieved, and higher photoelectric conversion efficiency can be achieved under the AM1.5D spectrum. Therefore, bottom cell materials with a band gap of 1.0 eV have become a hot topic in triple-junction solar cell research in recent years. 1-x In x When x=0.3, the band gap of As material is 1.0eV, but the lattice mismatch with GaAs substrate is more than 2%. The appropriate band gap combination is 1.88 / 1.42 / 1.0eV. In order to avoid the large mismatch dislocation defects of the bottom cell extending to the middle cell and top cell as much as possible, researchers first proposed the GaInAs / GaAs / GaInP reverse triple junction solar cell structure in 2004: first, lattice-matched top and neutron cells GaInP and GaAs are grown on the GaAs substrate, and then the lattice gradient buffer layer is grown to ensure the quality of the lattice-mismatched GaInAs bottom cell crystal; in 2005, the NREL laboratory in the United States took the lead in conducting experimental research on reverse triple junction cells, and the conversion efficiency of the developed cell under single-fold, AM1.5 spectrum was 31.1%. The substrate of the epitaxial thin film cell can be removed by selective wet etching process to obtain a self-supporting thin film cell, which is usually flexible. At present, the open circuit voltage of the existing flexible reverse triple-junction solar cell can reach 3.1V, and the short-circuit current density is 134mA / cm2 , the photoelectric conversion efficiency has reached 32%.

[0005] At present, in order to further improve the payload capacity of near-space vehicles, it is necessary to further improve the conversion efficiency of reverse triple-junction batteries to better provide energy for the vehicles. Summary of the invention

[0006] The purpose of the present invention is to provide a solar cell epitaxial structure with controlled epitaxial dislocation distribution in view of the technical defects existing in the prior art.

[0007] Another object of the present invention is to provide a method for manufacturing the solar cell epitaxial structure.

[0008] Another object of the present invention is to provide a solar cell based on the solar cell epitaxial structure.

[0009] The technical solution adopted to achieve the purpose of the present invention is:

[0010] A solar cell epitaxial structure with controlled epitaxial dislocation distribution, which comprises, from bottom to top, a GaAs substrate, a GaAs nucleation layer, a GaInP corrosion barrier layer, a GaAs contact layer, a GaInP top cell, a first tunnel junction, a first gradient buffer layer, a GaInAs middle cell, a second tunnel junction, a lattice overshoot layer, a second gradient buffer layer, a GaInAs bottom cell and a GaInAs contact layer;

[0011] Wherein, the first gradient buffer layer is an AlGaInAs lattice gradient buffer layer, and in the first gradient buffer layer, the In component increases nonlinearly from the initial layer to the target gradient layer;

[0012] The second gradient buffer layer is an AlGaInAs lattice gradient buffer layer. In the second gradient buffer layer, during the process of nonlinear increase of In component from the initial layer to the target gradient layer, the In component content of the previous layer of the target gradient layer is higher than that of the target gradient layer.

[0013] The In component content in the lattice overshoot layer is higher than the In component content in the initial layer of the second graded buffer layer.

[0014] In the above technical solution, the GaAs nucleation layer is n-type doped GaAs, the dopant is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 The thickness of the GaAs nucleation layer is 0.01 to 0.6 μm.

[0015] In the above technical solution, the GaInP corrosion barrier layer is an n-type doped GaInP. a In 1-aP, 0.48≤a≤0.52, dopant is Si, Se or Te, doping concentration is 1×10 17 ~1×10 19 cm -3 , thickness is 0.1~0.6μm.

[0016] In the above technical solution, the dopant in the GaAs contact layer is Si, Se or Te, and the doping concentration is 1×10 18 ~1×10 20 cm -3 , thickness is 0.2~0.8μm.

[0017] In the above technical solution, the GaInP top cell includes n-type doped n-Ga b In 1-b P emitter layer and p-type doped p-Ga b In 1-b P base layer, 0.48≤b≤0.52, n-Ga b In 1-b The dopant of the P emitter layer is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , thickness is 0.05~0.8μm, p-type doped p-Ga b In 1-b The dopant of the P base layer is Zn, Mg or C, and the doping concentration is 1×10 16 ~1×10 18 cm -3 , thickness is 0.05-0.6μm;

[0018] In the above technical solution, the first tunnel junction includes a p-type heavily doped p ++ -Al c Ga 1-c As layer and n-type heavily doped n ++ -GaAs layer, 0.1≤c≤0.7, where p ++ -Al c Ga 1-c The dopant of the As layer is Zn, Mg or C, and the doping concentration is 1×10 19 ~1×10 21 cm -3 , thickness is 0.01~0.1μm; where n ++ -GaAs layer is doped with Si, Se or Te, with a doping concentration of 1×10 19 ~1×10 21 cm -3 , thickness is 0.01~0.1μm;

[0019] In the above technical solution, the first gradient buffer layer is a multi-layer n-type doped (Al y Ga 1-y ) 1-x In x As, 0.3≤y≤0.8, its initial layer is Al y Ga 1-y As, nonlinearly changes from the initial layer to the target gradient layer, the In component changes from 0 to x1, 0.01≤x1≤0.12, and its dopant is Si, Se or Te, with a doping concentration of 1×10 17 ~1×10 19 cm -3 , each layer thickness is 0.05~0.8μm.

[0020] In the above technical solution, the intermediate cell includes n-(Al e Ga 1-e ) 1-d In d As emitter layer and p-type doped p-Ga 1-d In d As base layer, 0.01≤d≤0.12, 0.1≤e≤0.8, wherein the n-(Al e Ga 1-e ) 1-d In d The dopant of the As emitter layer is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , with a thickness of 0.01 to 0.2 μm; the p-Ga 1-d In d The dopant of the As base layer is Zn, Mg or C, and the doping concentration is 1×10 16 ~1×10 18 cm -3 , thickness is 1 to 4 μm.

[0021] In the above technical solution, the second tunnel junction includes a p-type heavily doped p ++ -(Al g Ga 1-g ) 1-f In f As layer and n-type doped n ++ -Ga 1-f In f As layer (0.01≤f≤0.12, 0.2≤g≤0.8). ++ -(Al g Ga 1-g )1-f In f The dopant of the As layer is Zn, Mg or C, and the doping concentration is 1×10 19 -1×10 21 cm -3 , with a thickness of 0.01 to 0.1 μm; wherein the n ++ -Ga 1-f In f The dopant of the As layer is Si, Sg or Tg, and the doping concentration is 1×10 19 ~1×10 21 cm -3 , thickness is 0.01~0.1μm.

[0022] In the above technical solution, the lattice overshoot layer is an n-type doped layer (Al j Ga 1-j ) 1-k In k As layer, 0.04≤k≤0.15, 0.3≤j≤0.8, f<k, its dopant is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , thickness is 0.1~1μm.

[0023] In the above technical solution, the second gradient buffer layer is an n-type doped layer (Al i Ga 1-i ) 1-h In h As layer, 0.3≤i≤0.8, dopant is Si, Se or Te, doping concentration is 1×10 17 ~1×10 19 cm -3 , the In component h from the initial layer to the target gradient layer increases nonlinearly from h1 to h2 from bottom to top, 0.01≤h1≤0.12, 0.1≤h2≤0.5, h1<k, while the In component of the previous layer of the target gradient layer is h2+z, 0.01≤z≤0.15, and the previous layer of the target gradient layer is an overshoot layer with a thickness of 0.05~0.8μm;

[0024] In the above technical solution, the GaInAs bottom cell is an n-type doped n-Ga 1-m In m As and p-type doped p-Ga 1- m In m As (0.1≤m≤0.6), wherein the n-Ga 1-m In mThe dopant of the As layer is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , with a thickness of 0.01 to 0.2 μm; wherein the p-Ga 1-m In m The dopant of the As layer is Zn, Mg or C, and the doping concentration is 1×10 16 ~1×10 18 cm -3 , thickness is 1 to 4 μm;

[0025] In the above technical solution, the GaInAs contact layer is p-type doped + -Ga 1-n In n As (0.1≤n≤0.6), dopant is Zn, Mg or C, doping concentration is 1×10 18 ~1×10 20 cm -3 , thickness is 0.2~0.8μm.

[0026] Another aspect of the present invention also includes a method for manufacturing the solar cell epitaxial structure, comprising the following steps:

[0027] Using metal organic chemical vapor deposition equipment, firstly, a GaAs nucleation layer is epitaxially grown on a GaAs substrate at a growth temperature of 560-720°C, and then a GaInP corrosion barrier layer is grown at a growth temperature of 600-720°C;

[0028] Grow GaAs contact layer at a growth temperature of 550-800°C;

[0029] Grow GaInP top cells at a growth temperature of 600-800°C;

[0030] Growing the first tunnel junction at a growth temperature of 500-700°C;

[0031] Growing a first gradient buffer layer at a growth temperature of 600-750° C.;

[0032] Grow GaInAs intermediate cells at a growth temperature of 600-800°C;

[0033] Growing a second tunnel junction at a growth temperature of 500-700° C.;

[0034] Growing a lattice overshoot layer at a growth temperature of 500-700°C;

[0035] Growing a second gradient buffer layer at a growth temperature of 600-750° C.;

[0036] Grow GaInAs bottom cells at a growth temperature of 550-700°C;

[0037] Grow a GaInAs contact layer at a growth temperature of 550-700°C.

[0038] Another aspect of the present invention also includes a solar cell prepared by the following steps:

[0039] The above epitaxial structure is taken out from MOCVD and the subsequent device process is carried out: gold, zinc, gold and silver are deposited respectively in the metal evaporation equipment to form a seed layer; then a temporary substrate is pasted, and the GaAs substrate and GaAs nucleation layer are removed by etching; followed by GaInP corrosion barrier layer etching, photolithography, gold upper electrode evaporation, GaAs contact layer etching, anti-reflection film evaporation and scribing process.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] 1. By increasing the In component of the epitaxially grown ternary compound semiconductor material, a lattice overshoot layer with a larger lattice constant is formed, and the position of the lattice overshoot layer is transferred from the traditional first lattice gradient buffer layer to above the cell in the inverted triple-junction solar cell, thereby controlling the position and degree of stress release, thereby achieving a controlled distribution of dislocations.

[0042] 2. Compared with the traditional gradient buffer layer, the first gradient buffer layer has no lattice overshoot layer, which can make the stress of the battery material incompletely released, and the dislocation density therein will be reduced accordingly, thereby improving the photoelectric conversion quantum efficiency.

[0043] 3. Compared with the traditional gradient buffer layer, the lattice overshoot layer is inserted at the bottom of the second gradient buffer layer, so that the lattice mismatch dislocations can be completely generated at the bottom of the buffer layer. These dislocations will obtain sufficient buffer layer dislocation deflection effect. In this way, the dislocations extending into the bottom battery material will be significantly reduced, thereby improving the photoelectric efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Shown is a schematic diagram of the epitaxial structure of the solar cell of the present invention.

[0045] 1-GaAs substrate, 2-GaAs nucleation layer, 3-GaInP corrosion barrier layer, 4-GaAs contact layer, 5-GaInP top cell, 6-first tunnel junction, 7-AlGaInAs overshoot-free layer lattice gradient buffer layer, 8-Ga 0.96 In 0.04 As middle cell, 9-second tunnel junction, 10-lattice overshoot layer, 11-AlGaInAs second lattice gradient buffer layer, 12-Ga 0.64 In 0.36As bottom cell, 13-GaInAs contact layer.

[0046] Figure 2 Shown is the structural diagram of the lattice graded buffer layer.

[0047] Figure 3 The IV characteristic curve of the solar cell obtained in the example. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0049] A solar cell structure with controlled epitaxial dislocation distribution, comprising, from bottom to top, a GaAs substrate 1, a GaAs nucleation layer 2, a GaInP corrosion barrier layer 3, a GaAs contact layer 4, a GaInP top cell 5, a first tunnel junction 6, an AlGaInAs non-overshoot layer lattice gradient buffer layer 7, and a Ga 0.96 In 0.04 As middle battery 8, second tunnel junction 9, lattice overshoot layer 10, AlGaInAs second lattice gradient buffer layer 11, Ga 0.64 In 0.36 As bottom cell 12 and GaInAs contact layer 13, the solar cell structure is prepared in a metal organic chemical vapor deposition (MOCVD) device by the following steps (see Figure 1 and Figure 2 ), set the reaction chamber pressure to 50 mbar:

[0050] First, an n-type doped GaAs nucleation layer 2 is epitaxially grown on a GaAs substrate 1, and its dopant is Si with a doping concentration of 2×10 18 cm -3 , growth temperature is 600℃, thickness is 0.2μm;

[0051] The GaInP corrosion barrier layer 3 is n-Ga 0.5 In 0.5 P, whose dopant is Si, and the doping concentration is 1×10 18 cm -3 , growth temperature is 650℃, thickness is 0.3μm;

[0052] n + -GaAs contact layer 4, its dopant is Si, and the doping concentration is 6×10 18 cm -3 , growth temperature is 660℃, thickness is 0.5μm;

[0053] The GaInP top cell 5 includes n-type doped n-Ga 0.5In 0.5 P emitter layer and p-type doped p-Ga 0.5 In 0.5 P base layer, where n-Ga 0.5 In 0.5 The dopant of the P layer is Si, and the doping concentration is 5×10 17 cm -3 , growth temperature is 650℃, thickness is 0.1μm; p-Ga 0.5 In 0.5 The dopant of the P layer is Zn, and the doping concentration is 1×10 18 cm -3 , growth temperature is 650℃, thickness is 0.5μm;

[0054] The first tunnel junction 6 includes a p-type heavily doped p ++ -Al 0.4 Ga 0.6 As layer and n-type heavily doped n ++ -GaAs layer, where p ++ -Al 0.4 Ga 0.6 The dopant of the As layer is C, and the doping concentration is 6×10 19 cm -3 , thickness is 0.03μm, growth temperature is 600℃; where n ++ The dopant of the GaAs layer is Te, with a doping concentration of 8×10 19 cm -3 , thickness is 0.02μm, growth temperature is 580℃;

[0055] The first gradient buffer layer is an AlGaInAs lattice gradient buffer layer 7 without overshoot layer, such as Figure 2 As shown, the In component x gradually increases and the multilayer n-type doping (Al 0.6 Ga 0.4 ) 1-x In x As, whose initial layer is Al 0.6 Ga 0.4 As, nonlinearly gradient to the target gradient layer, In component x gradient from 0 to 0.04, its dopant is Si, and the doping concentration is 1×10 18 cm -3 , the growth temperature is 670℃, and the thickness of each layer is 0.2μm;

[0056] Ga 0.96 In 0.04 As battery 8 includes n-doped n-(Al 0.5 Ga 0.5 ) 0.96 In 0.04As emitter layer and p-type doped p-Ga 0.96 In 0.04 As base layer, wherein the n-(Al 0.5 Ga 0.5 ) 0.96 In 0.04 The dopant of the As emitter layer is Si, with a doping concentration of 3×10 18 cm -3 , the growth temperature is 650°C, the thickness is 0.1μm; the p-Ga 0.96 In 0.04 The dopant of the As base layer is Zn, with a doping concentration of 3×10 17 cm -3 , growth temperature is 650℃, thickness is 3μm;

[0057] The second tunnel junction 9 includes a p-type heavily doped p ++ -(Al 0.6 Ga 0.4 ) 0.96 In 0.04 As layer and n-type doped n ++ -Ga 0.96 In 0.04 As layer. ++ -(Al 0.6 Ga 0.4 ) 0.96 In 0.04 The dopant of the As layer is C, and the doping concentration is 6×10 19 cm -3 , thickness is 0.03 μm, growth temperature is 550°C; wherein the n ++ -Ga 0.96 In 0.04 The dopant of the As layer is Te, and the doping concentration is 8×10 19 cm -3 , growth temperature is 550℃, thickness is 0.02μm;

[0058] The lattice overshoot layer 10 is as Figure 2 As shown, the In component is suddenly increased to 8% n-type doping (Al 0.6 Ga 0.4 ) 0.92 In 0.08 As layer, its dopant is Si, and the doping concentration is 9×10 17 cm -3 , growth temperature is 660℃, thickness is 0.4μm;

[0059] The second gradient buffer layer is AlGaInAs second lattice gradient buffer layer 11, which is n-type doped with gradually increasing In component h (Al0.6 Ga 0.4 ) 1-h In h As layer, such as Figure 2 As shown. The dopant is Si, and the doping concentration is 1×10 18 cm -3 , the In composition h from the initial layer to the target gradient layer changes nonlinearly from 4% to 36% from bottom to top, while the In composition of the previous layer of the target layer is 45%, which is an overshoot layer, with a growth temperature of 670℃ and a thickness of 0.2μm;

[0060] Ga 0.64 In 0.36 As bottom cell 12 is n-type doped n-Ga 0.64 In 0.36 As and p-type doped p-Ga 0.64 In 0.36 As, wherein the n-Ga 0.64 In 0.36 The dopant of the As layer is Si, and the doping concentration is 2×10 18 cm -3 , with a thickness of 0.1 μm and a growth temperature of 660°C; wherein the p-Ga 0.64 In 0.36 The dopant of the As layer is Zn, and the doping concentration is 6×10 17 cm -3 , thickness is 3μm, growth temperature is 660℃;

[0061] The GaInAs contact layer 13 is p-type doped + -Ga 0.64 In 0.36 As, the dopant is Zn, and the doping concentration is 2×10 19 cm -3 , thickness is 0.5μm, and growth temperature is 600℃.

[0062] The above epitaxial structure is taken out from MOCVD and the subsequent device process is carried out: gold, zinc, gold and silver are deposited respectively in the metal evaporation equipment to form a seed layer; then a temporary substrate is pasted; the GaAs substrate and GaAs nucleation layer are removed by corrosion; then barrier layer etching, photolithography, gold upper electrode evaporation, contact layer etching, anti-reflection film evaporation and scribing process are carried out.

[0063] The IV curve of the battery prepared by the above steps is as follows Figure 3 As shown. Its open circuit voltage is 2.91V and short circuit current is 18.1mA / cm 2 , the photoelectric conversion efficiency can reach 34%.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A solar cell epitaxial structure with controlled epitaxial dislocation distribution, characterized in that: From bottom to top, they are GaAs substrate, GaAs nucleation layer, GaInP corrosion barrier layer, GaAs contact layer, GaInP top cell, first tunnel junction, first gradient buffer layer, GaInAs middle cell, second tunnel junction, lattice overshoot layer, second gradient buffer layer, GaInAs bottom cell and GaInAs contact layer; Wherein, the first gradient buffer layer is an AlGaInAs lattice gradient buffer layer, and in the first gradient buffer layer, the In component increases nonlinearly from the initial layer to the target gradient layer; The second gradient buffer layer is an AlGaInAs lattice gradient buffer layer. In the second gradient buffer layer, during the process of nonlinear increase of In component from the initial layer to the target gradient layer, the In component content of the previous layer of the target gradient layer is higher than that of the target gradient layer. The In component content in the lattice overshoot layer is higher than the In component content in the initial layer of the second graded buffer layer.

2. The solar cell epitaxial structure according to claim 1, characterized in that: The GaAs nucleation layer is n-type doped GaAs, the dopant is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , the thickness of the GaAs nucleation layer is 0.01 to 0.6 μm; The GaInP corrosion barrier layer is an n-type doped GaInP layer. a In 1-a P, 0.48≤a≤0.52, dopant is Si, Se or Te, doping concentration is 1×10 17 ~1×10 19 cm -3 , thickness is 0.1~0.6μm; The dopant in the GaAs contact layer is Si, Se or Te, and the doping concentration is 1×10 18 ~1×10 20 cm -3 , thickness is 0.2~0.8μm.

3. The solar cell epitaxial structure according to claim 1, characterized in that: The GaInP top cell includes n-type doped n-Ga b In 1-b P emitter layer and p-type doped p-Ga b In 1-b P base layer, 0.48≤b≤0.52, n-Ga b In 1-b The dopant of the P emitter layer is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , thickness is 0.05~0.8μm, p-type doped p-Ga b In 1-b The dopant of the P base layer is Zn, Mg or C, and the doping concentration is 1×10 16 ~1×10 18 cm -3 , thickness is 0.05-0.6μm; The first tunnel junction includes a heavily p-type doped p ++ -Al c Ga 1-c As layer and n-type heavily doped n ++ -GaAs layer, 0.1≤c≤0.7, where p ++ -Al c Ga 1-c The dopant of the As layer is Zn, Mg or C, and the doping concentration is 1×10 19 ~1×10 21 cm -3 , thickness is 0.01~0.1μm; where n ++ -GaAs layer is doped with Si, Se or Te, with a doping concentration of 1×10 19 ~1×10 21 cm -3 , thickness is 0.01~0.1μm.

4. The solar cell epitaxial structure according to claim 1, characterized in that: The first graded buffer layer is a multilayer n-type doped (Al y Ga 1-y ) 1-x In x As, 0.3≤y≤0.8, its initial layer is Al y Ga 1-y As, nonlinearly changes from the initial layer to the target gradient layer, the In component changes from 0 to x1, 0.01≤x1≤0.12, and its dopant is Si, Se or Te, with a doping concentration of 1×10 17 ~1×10 19 cm -3 , each layer thickness is 0.05~0.8μm.

5. The solar cell epitaxial structure according to claim 1, characterized in that: The middle cell includes n-doped n-(Al e Ga 1-e ) 1-d In d As emitter layer and p-type doped p-Ga 1-d In d As base layer, 0.01≤d≤0.12, 0.1≤e≤0.8, wherein the n-(Al e Ga 1-e ) 1-d In d The dopant of the As emitter layer is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , with a thickness of 0.01 to 0.2 μm; the p-Ga 1-d In d The dopant of the As base layer is Zn, Mg or C, and the doping concentration is 1×10 16 ~1×10 18 cm -3 , thickness is 1 to 4 μm; The second tunnel junction includes a heavily p-type doped p ++ -(Al g Ga 1-g ) 1-f In f As layer and n-type doped n ++ -Ga 1-f In f As layer (0.01≤f≤0.12, 0.2≤g≤0.8). ++ -(Al g Ga 1-g ) 1-f In f The dopant of the As layer is Zn, Mg or C, and the doping concentration is 1×10 19 -1×10 21 cm -3 , with a thickness of 0.01 to 0.1 μm; wherein the n ++ -Ga 1-f In f The dopant of the As layer is Si, Sg or Tg, and the doping concentration is 1×10 19 ~1×10 21 cm -3 , thickness is 0.01~0.1μm.

6. The solar cell epitaxial structure according to claim 5, characterized in that: The lattice overshoot layer is an n-type doped layer with a sudden change of In composition to k (Al j Ga 1-j ) 1-k In k As layer, 0.04≤k≤0.15, 0.3≤j≤0.8, f<k, its dopant is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , thickness is 0.1~1μm.

7. The solar cell epitaxial structure according to claim 6, characterized in that: The second graded buffer layer is an n-type doped layer with a gradually increasing In content h (Al i Ga 1-i ) 1-h In h As layer, 0.3≤i≤0.8, dopant is Si, Se or Te, doping concentration is 1×10 17 ~1×10 19 cm -3 The In component h from the initial layer to the target gradient layer increases nonlinearly from h1 to h2 from bottom to top, 0.01≤h1≤0.12, 0.1≤h2≤0.5, h1<k, and the In component of the previous layer of the target gradient layer is h2+z, 0.01≤z≤0.15, and the previous layer of the target gradient layer is an overshoot layer with a thickness of 0.05~0.8μm.

8. The solar cell epitaxial structure according to claim 1, characterized in that: The GaInAs bottom cell is n-type doped n-Ga 1-m In m As and p-type doped p-Ga 1-m In m As, 0.1≤m≤0.6, wherein the n-Ga 1-m In m The dopant of the As layer is Si, Se or Te, and the doping concentration is 1×10 17 ~1×10 19 cm -3 , with a thickness of 0.01 to 0.2 μm; wherein the p-Ga 1-m In m The dopant of the As layer is Zn, Mg or C, and the doping concentration is 1×10 16 ~1×10 18 cm -3 , thickness is 1 to 4 μm; The GaInAs contact layer is p-type doped + -Ga 1-n In n As, 0.1≤n≤0.6, dopant is Zn, Mg or C, doping concentration is 1×10 18 ~1×10 20 cm -3 , thickness is 0.2~0.8μm.

9. The method for manufacturing a solar cell epitaxial structure according to any one of claims 1 to 8, characterized in that: The following steps are involved: Using metal organic chemical vapor deposition equipment, firstly, a GaAs nucleation layer is epitaxially grown on a GaAs substrate at a growth temperature of 560-720°C, and then a GaInP corrosion barrier layer is grown at a growth temperature of 600-720°C; Grow GaAs contact layer at a growth temperature of 550-800°C; Grow GaInP top cells at a growth temperature of 600-800°C; Growing the first tunnel junction at a growth temperature of 500-700°C; Growing a first gradient buffer layer at a growth temperature of 600-750° C.; Grow GaInAs intermediate cells at a growth temperature of 600-800°C; Growing a second tunnel junction at a growth temperature of 500-700° C.; Growing a lattice overshoot layer at a growth temperature of 500-700°C; Growing a second gradient buffer layer at a growth temperature of 600-750° C.; Grow GaInAs bottom cells at a growth temperature of 550-700°C; Grow a GaInAs contact layer at a growth temperature of 550-700°C.

10. A solar cell, characterized in that: The method is prepared by the following steps: taking out the solar cell epitaxial structure as described in any one of claims 1 to 8 from MOCVD and carrying out subsequent device processes: depositing gold, zinc, gold and silver respectively in a metal evaporation device to form a seed layer; then pasting a temporary substrate and removing the GaAs substrate and GaAs nucleation layer by etching; then carrying out GaInP corrosion barrier layer etching, photolithography, gold upper electrode evaporation, GaAs contact layer etching, anti-reflection film evaporation and scribing processes.

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