CN103199142B - GaInP/GaAs/InGaAs/Ge four-junction solar cell and preparation method thereof - Google Patents

Abstract

The present invention provides a GaInP/GaAs/InGaAs/Ge four-junction solar cell, the bandgap energies of which are 1.89eV, 1.42eV, 1.0eV and 0.67eV respectively; including a Ge sub-cell, a first tunnel junction, a graded transition layer, InGaAs subcell, (In)GaAs bonding layer, GaAs or GaInP bonding layer, GaAs subcell, second tunnel junction and GaInP subcell. The present invention also provides a method for preparing a GaInP/GaAs/InGaAs/Ge four-junction solar cell, which includes the steps of: 1) providing a Ge sub-cell; 2) sequentially growing a nucleation layer, a first buffer layer, and a Ge sub-cell on the surface of the Ge sub-cell. The first tunnel junction, graded transition layer, InGaAs subcell and (In)GaAs bonding layer; 3) Provide a GaAs substrate; 4) sequentially grow the second buffer layer, sacrificial layer, GaAs or GaInP bond on the GaAs substrate combined layer, GaAs sub-cell, second tunnel junction, GaInP sub-cell and GaAs contact layer; 5) peeling off the GaAs substrate; 6) bonding the (In)GaAs bonding layer to the GaAs or GaInP bonding layer.

Description

GaInP/GaAs/InGaAs/Ge four-junction solar cell and its preparation method

technical field

The invention relates to the field of solar cells, in particular to a GaInP/GaAs/InGaAs/Ge four-junction solar cell and a preparation method thereof.

Background technique

As an ideal green energy material, solar cells have become a research hotspot in various countries. In order to promote the further practical application of solar cells, improving their photoelectric conversion efficiency is an effective means to reduce the cost of power generation. The use of sub-cells with different bandgap widths in series in stacked cells can greatly improve the utilization rate of sunlight. At present, the system with more research and more mature technology is the GaInP/GaAs/Ge triple-junction cell. The highest conversion efficiency achieved so far is 32%-33%. However, the Ge-bottom cell in the triple-junction cell covers a wider spectrum, and its short-circuit current is relatively large. In order to achieve current matching with other sub-cells, the utilization rate of sunlight will inevitably be reduced. In order to further improve the conversion efficiency, it is necessary to split the bottom cell, such as inserting an InGaAsN material with a gap of 1.00eV between the GaAs and Ge cells to make a four-junction cell to achieve photocurrent matching and improve cell efficiency.

However, the currently prepared InGaAsN material has many defects and low carrier mobility, which affects the improvement of battery performance. Therefore, researchers are actively seeking other ways to obtain high-efficiency solar cells. It has been proven feasible to grow 1.0eV InGAs on GaAs substrates with a mismatch. In order to save the number of transition layers, flip-chip growth is generally used, but the device performance Compared with the formal growth, the growth has been reduced. For example, from the perspective of lattice matching, the bonding of GaInP/GaAs (1.9/1.42eV) based on GaAs substrate and InGaAsP/InGaAs (1.05/0.74eV) double junction cell on InP substrate is used. Wafer bonding cells require GaAs and InP two substrates, and the absorption coefficient of InGaAsP and InGaAs matched with the InP lattice is small, and it is necessary to grow an epitaxial layer with a thickness of nearly 6 microns, which greatly increases the production cost of the cell; how to realize a reasonable multi-junction solar cell Combining bandgap and reducing current mismatch without increasing the cost and difficulty of cell fabrication has become an urgent problem to be solved for current III-V solar cells.

Contents of the invention

The technical problem to be solved by the present invention is to provide a GaInP/GaAs/InGaAs/Ge four-junction solar cell and a preparation method thereof.

In order to solve the above problems, the present invention provides a GaInP/GaAs/InGaAs/Ge four-junction solar cell, comprising a Ge subcell, a first tunnel junction, a graded transition layer, an InGaAs subcell, (In)GaAs bonding layer, a GaAs Or a GaInP bonding layer, a GaAs subcell, a second tunnel junction and a GaInP subcell.

Further, the Ge sub-cell includes a first base region made of Ge, and a first emitter region made of Ge disposed on the first base region.

Further, the bandgap energies of the four-junction solar cells are 1.89eV, 1.42eV, 1.0eV and 0.67eV, respectively.

Further, the Ge sub-cells and the InGaAs sub-cells are sequentially disposed on the Ge substrate in a direction away from the Ge substrate to form first double-junction solar cells with bandgap energies of 1.0eV and 0.67eV respectively.

Further, the GaAs sub-cell and the GaInP sub-cell grow in a direction away from the GaAs substrate, and the GaAs substrate is peeled off to form second double-junction solar cells with bandgap energies of 1.89eV and 1.42eV, respectively.

Further, the second double-junction solar cell is bonded to the first double-junction solar cell through the (In)GaAs bonding layer and the GaAs or GaInP bonding layer.

In order to solve the above problems, the present invention also provides a method for preparing a GaInP/GaAs/InGaAs/Ge four-junction solar cell, comprising the steps of: 1) providing a Ge sub-cell; 2) sequentially growing a nucleation layer on the surface of the Ge sub-cell, The first buffer layer, the first tunnel junction, the graded transition layer, the InGaAs sub-cell and the (In)GaAs bonding layer; 3) providing a GaAs substrate; 4) growing the second buffer layer and the sacrificial layer sequentially on the GaAs substrate , a GaAs or GaInP bonding layer, a GaAs subcell, a second tunnel junction, a GaInP subcell, and a GaAs contact layer; 5) peeling off the GaAs substrate; 6) bonding the (In)GaAs bonding layer to the GaAs or GaInP Bonding layer bonding.

Further, step 6) further includes: 7) making a P electrode on the back of the cleaned Ge sub-cell, and making a grid-shaped N electrode on the surface of the cleaned GaAs contact layer to form a target solar cell.

The invention provides a GaInP/GaAs/InGaAs/Ge four-junction solar cell and a preparation method thereof, the advantages of which are:

1. The bandgap combination of the four-junction cascaded solar cell is 1.90eV, 1.42eV, ~1.00eV, 0.67eV, and the current matching of each sub-cell achieves high voltage and low current output, reducing the photoelectric conversion process. Heat energy loss improves battery efficiency;

2. The four-junction cascaded solar cell is grown by the formal growth method, which reduces the difficulty of device growth and cell technology;

3. The stripped GaAs substrate can be reused after polishing, which reduces the cost of the battery;

4. Using Ge as the supporting substrate makes full use of the good mechanical strength and thermal conductivity of Ge materials.

Description of drawings

Fig. 1 shows the structural diagram of the GaInP/GaAs/InGaAs/Ge four-junction solar cell provided by the first embodiment of the present invention;

FIG. 2 is a flow chart of the steps of the preparation method of the GaInP/GaAs/InGaAs/Ge quadruple-junction solar cell provided by the second specific embodiment of the present invention;

FIG. 3 is a structural diagram of a GaInP/GaAs/InGaAs/Ge quadruple-junction solar cell formed after step S202 according to the second specific embodiment of the present invention;

FIG. 4 is a structural view of a GaInP/GaAs/InGaAs/Ge quadruple-junction solar cell formed after step S204 according to the second embodiment of the present invention.

detailed description

The specific implementation of the GaInP/GaAs/InGaAs/Ge quadruple-junction solar cell provided by the present invention and its preparation method will be described in detail below with reference to the accompanying drawings.

First Embodiment

FIG. 1 is a structural diagram of a GaInP/GaAs/InGaAs/Ge four-junction solar cell provided in this specific embodiment.

This specific embodiment provides a GaInP/GaAs/InGaAs/Ge four-junction solar cell grown in a front-mount manner, and the bandgap combination is 1.90eV/1.42eV/~1.00eV/0.67eV. The GaInP/GaAs/InGaAs/Ge four-junction cell solar cell includes Ge sub-cells 30, InGaAs or GaInP nucleation layer 03, InGaAs buffer layer 04, first tunnel junction 31, graded transition layer 07, InGaAs sub-cells arranged in sequence. battery 32 , (In)GaAs bonding layer 12 , GaAs or GaInP bonding layer 17 , GaAs sub-cell 33 , second tunnel junction 34 , GaInP sub-cell 35 and GaAs contact layer 28 .

The Ge sub-cells 30 and the InGaAs sub-cells 32 are sequentially arranged on the Ge substrate in a direction away from the Ge substrate, forming first double-junction solar cells with bandgap energies of 1.0 eV and 0.67 eV respectively. The GaAs sub-cells 33 and GaInP sub-cells 35 grow in a direction away from the GaAs substrate 14 to form second double-junction solar cells with bandgap energies of 1.89eV and 1.42eV respectively. The GaAs substrate 14 is peeled off, and the second double-junction solar cell is bonded to the first double-junction solar cell through the (In)GaAs bonding layer 12 and the GaAs or GaInP bonding layer 17 to form a quadruple junction Solar battery.

The Ge sub-cell 30 includes a first base region 01 made of Ge, and a first emitter region 02 made of Ge disposed on the first base region 01 . Wherein, the first base region 01 is a Ge substrate.

Then grow an InGaAs or GaInP nucleation layer 03 on the surface of the Ge sub-cell 30 , and grow an InGaAs buffer layer 04 on the surface of the nucleation layer 03 . As an optional implementation manner, the bandgap of the InGaAs buffer layer 04 is greater than 0.67eV.

The first tunnel junction 31 includes a GaInP or (In)GaAs doped layer 04 and an (Al)GaAs doped layer 05 sequentially arranged in a direction gradually away from the Ge subcell 30 . Here, (In)GaAs represents InGaAs or GaAs, and (Al)GaAs represents AlGaAs or GaAs. As an optional implementation manner, the doping type of the first doped layer 05 is N type, and the doping type of the second doped layer 06 is P type.

The material of the graded transition layer 07 is _{AlyGa1 -xyInxAs or} Ga1 _{- xInxP} , which is used to realize the transition from the lattice constant of the Ge subcell 30 to the lattice constant of the InGaAs subcell 32 . Wherein the range of x in Al _y Ga _1-xy In _x As is 0-0.27, the range of y is 0-0.4; and the range of x in Ga _1-x In _x P is 0.48-0.78. The bandgap of the graded transition layer 07 is larger than 1.0eV.

The InGaAs sub-cell 32 includes a second back field layer 08 made of AlGaInAs, a second base region 09 made of InGaAs, a second emitter region 10 made of InGaAs, and a second base region 09 made of InGaAs, which are arranged in a direction gradually away from the Ge sub-cell 30. The second window layer 11, the material of the second window layer 11 is GaInP, InGaAlAs or AlInP.

The lattice constant of the (In)GaAs bonding layer 12 is the same as that of the InGaAs sub-cell 32 .

The bonding layer 17 is made of GaAs or GaInP with a thickness of 200-800nm.

The GaAs sub-cell 33 includes a third back field layer 18 made of GaInP or AlGaAs, a third base region 19 made of GaAs, and a third emitter region 20 made of GaAs, which are arranged in a direction gradually away from the Ge sub-cell 30 And the third window layer 21 made of Al(Ga)InP.

The second tunnel junction 34 includes a fifth doped layer 22 made of GaInP or GaAs, and a sixth doped layer 23 made of (Al)GaAs, which are arranged in a direction gradually away from the Ge sub-cell 30 . As an optional implementation manner, the doping type of the fifth doped layer 22 is N type, and the doping type of the sixth doped layer 23 is P type.

The GaInP sub-cell 35 includes a fourth back field layer 24 made of Al(Ga)InP, a fourth base region 25 made of GaInP, and a fourth emitter made of GaInP, which are arranged in a direction gradually away from the Ge sub-cell 30. region 26 and the fourth window layer 27 made of AlInP.

A GaAs contact layer 28 is grown on the surface of the GaInP sub-cell 35 as an ohmic contact layer. As an optional implementation manner, the doping type of the GaAs contact layer 28 is N type.

The GaInP/GaAs/InGaAs/Ge four-junction solar cell further includes an N electrode 36 and a P electrode 37 . The N electrode 36 is located on the surface of the GaAs contact layer 28 , and the P electrode 37 is located on the back of the Ge sub-cell 30 .

Second specific implementation

This specific embodiment provides a method for preparing a GaInP/GaAs/InGaAs/Ge four-junction solar cell using a front-mounting method. FIG. 2 is a flow chart of steps in the method for preparing a GaInP/GaAs/InGaAs/Ge quadruple-junction solar cell provided in this specific embodiment, and the steps shown in FIG. 2 will be described in detail next.

Step S201, providing a sub-battery.

Step S201 further includes the steps of: providing a p-type Ge substrate used as the first base region 01 of the Ge sub-cell 30; forming a first emitter region 02 of Ge by diffusion of P or As elements on the Ge substrate to form Gelatin battery 30.

Step S202 , growing an InGaAs or GaInP nucleation layer, an InGaAs buffer layer, a first tunnel junction, a graded transition layer, an InGaAs subcell, and an (In)GaAs bonding layer on the surface of the Ge subcell in sequence. The structure diagram of the GaInP/GaAs/InGaAs/Ge four-junction solar cell formed after step S202 provided in this specific embodiment is shown in FIG. 3 .

Step S202 further includes the step of: growing a first doped layer 05 made of GaInP or GaAs and a second doped layer 06 made of (Al)GaAs on the surface of the InGaAs buffer layer 04 in a direction gradually away from the Ge subcell 30, to A first tunnel junction 31 is formed. Wherein, the doping type of the first doped layer 05 is N type, and the doping type of the second doped layer 06 is P type.

In step S202, the material of the gradient transition layer 07 is _{AlyGa 1-xy} In _x As or Ga _1-x In _x P, wherein the range of x in _{AlyGa 1-xy} In _x As is 0~0.27 , the range of y is 0~0.4, while the range of x in Ga _1-x In _x P is 0.48~0.78. The bandgap of the graded transition layer 07 is larger than 1.0 eV, so as to prevent photons passing through the InGaAs cell from being absorbed by the graded transition layer 07 . The stress is released by growing the _{AlyGa1 -xyInxAs or} Ga1 _{- xInxP} graded transition layer 07 by lattice anomaly, and the transition from the Ge subcell 30 to the InGaAs subcell 32 is realized.

As an optional implementation manner, the graded transition layer 07 of _{AlyGa1 -xyInxAs or} Ga1 _{- xInxP} can be grown by a method of linear progression of In composition and Al composition, so as to release the stress. As an optional embodiment, the _{AlyGa 1-xy} In _x As or Ga _1-x In _x P graded transition layer 07 can be grown by stepping the In composition and the Al composition, and the stress can be promoted by forming multiple interfaces. The release simultaneously suppresses threading dislocations from reaching the active region. As an optional embodiment, the graded transition layer 07 of _{AlyGa 1-xy} In _x As or Ga _1-x In _x P can be grown by a combination of linear gradual and stepwise steps of In composition and Al composition to make the stress release, inhibiting threading dislocations from reaching the active region.

Step S202 further includes the step of growing a second back field layer 08 made of AlGaInAs, a second base region 09 made of InGaAs, and a second emitter made of InGaAs on the surface of the gradient transition layer 07 in a direction gradually away from the Ge subcell 30. region 10 and the second window layer 11 , wherein the material of the second window layer 11 is GaInP, InGaAlAs or AlInP, so as to form the InGaAs sub-cell 32 .

Step S203, providing a GaAs substrate.

Step S204, growing a GaAs buffer layer, an AlAs sacrificial layer, a GaAs or GaInP bonding layer, a GaAs subcell, a second tunnel junction, a GaInP subcell, and a GaAs contact layer sequentially on the GaAs substrate. The structure diagram of the GaInP/GaAs/InGaAs/Ge four-junction solar cell formed after step S204 provided in this specific embodiment is shown in FIG. 4 .

Step S204 further includes the step of growing a third back field layer 18 made of GaInP or AlGaAs, a third base region 19 made of GaAs, and a material of A third emitter region 20 made of GaAs and a third window layer 21 made of Al(Ga)InP are used to form a GaAs sub-cell 33 .

Step S204 further includes the step of: growing the fifth doped layer 22 made of GaInP or GaAs and the sixth doped layer 23 made of (Al)GaAs on the surface of the GaAs sub-cell 33 in a direction gradually away from the GaAs sub-cell 33, so as to A second tunnel junction 34 is formed.

Step S204 further includes the step of growing the fourth back field layer 24 made of Al(Ga)InP, the fourth base region 25 of GaInP, and the fourth emitter region 26 and a fourth window layer 27 of AlInP to form a GaInP sub-cell 35 .

As an optional implementation, in step S204, a GaAs buffer layer 15 and an AlAs sacrificial layer 16 are sequentially grown between the GaAs substrate 14 and the GaAs or GaInP bonding layer 17; when the GaAs substrate 14 needs to be removed, select The AlAs sacrificial layer 16 is etched by an aggressive etchant to realize the peeling off of the GaAs substrate 14 . The GaAs buffer layer 15 is a low-speed growth GaAs material with a thickness of 100-500nm; the thickness of the AlAs sacrificial layer 16 is 5-15nm; the thickness of the GaAs or GaInP bonding layer 17 is 200-800nm.

Step S205, peeling off the GaAs substrate from the GaAs or GaInP bonding layer.

Optionally, the GaAs contact layer 28 is adhered to a substrate such as Si or glass, and then the GaAs substrate 14 is removed by wet etching, for example, the AlAs sacrificial layer 16 is etched by a selective etching solution to realize the GaAs substrate 14. peel off.

Step S206, bonding the (In)GaAs bonding layer to the GaAs or GaInP bonding layer.

As an optional implementation, the method for preparing a GaInP/GaAs/InGaAs/Ge four-junction solar cell further includes the steps of manufacturing N electrodes and P electrodes, including: cleaning and removing pollutants on the surface and back of the epitaxial layer; The P electrode is made on the back of the sub-cell, and the grid-shaped N electrode is made on the surface of the GaAs contact layer to form the target solar cell, as shown in Figure 1.

The above steps are grown by MOCVD (MetalOrganicChemicalVaporDeposition, metal organic compound chemical vapor deposition) or MBE (MolecularBeamEpitaxy, molecular beam epitaxy).

If the MOCVD method is used, the N-type dopant atoms of the Ge layer are As or P, the N-type dopant atoms of the remaining layers are Si, Se, S or Te, and the P-type dopant atoms are Zn, Mg or C;

If the MBE method is used, the N-type dopant atoms of the Ge layer are As or P, the N-type dopant atoms of the remaining layers are Si, Se, S, Sn or Te, and the P-type dopant atoms are Be, Mg or C.

An example of the present invention is given next.

This embodiment provides a GaInP/GaAs/InGaAs/Ge four-junction solar cell grown by MOCVD method, as shown in Figure 3 and Figure 4, including:

(1) The P-type Ge substrate is used as the first base region 01 of the Ge sub-cell 30, and N-type doped Ge sub-cells of about 2×10 ¹⁸ cm ^-3 are formed on the surface of the P-type Ge substrate by diffusion of the P/As source. The first emitter region 02 of the battery 30, thereby forming a Ge sub-cell 30; then grow an InGaAs or GaInP nucleation layer 03 on the surface of the N-type first emitter region 02, and N-type doping about 3×10 ¹⁷ cm ^-3 , InGaAs buffer layer 04 with a thickness of 0.1 μm.

(2) On the surface of the buffer layer 04, grow a first doped layer 05 of GaInP or GaAs with an N-type doping concentration greater than 1×10 ¹⁹ cm ^-3 and a thickness of 0.015 μm, and then grow on the surface of the first doped layer 05 The second doped layer 06 of (Al)GaAs with a p-type doping concentration greater than 1×10 ¹⁹ cm ⁻³ and a thickness of 0.015 μm forms a first tunnel junction 31 .

(3) A graded transition layer of _{AlyGa 1-xy} In _x As or Ga _1-x In _x P with a P-type doping of 4×10 ¹⁷ cm ^-3 and a thickness of about 3 microns grown on the surface of the first tunnel junction 31 07. Realize the transition from the lattice constant of the Ge sub-cell 30 to the lattice constant of the InGaAs sub-cell 32 .

(4) grow an AlGaInAs layer with a P-type doping concentration of about 1×10 ¹⁸ cm ^-3 and a thickness of 0.1 micron on the surface of the gradient transition layer 07 as the second back field layer 08 of the InGaAs sub-cell 32 , and then in the second back field An InGaAs layer with a P-type doping concentration of about 3×10 ¹⁷ cm ^-3 and a thickness of 3.0 μm is grown on the surface of layer 08 as the second base region 09 of the InGaAs sub-cell 32 , and then N-type doping is grown on the surface of the second base region 09 An InGaAs layer with a concentration of about 2×10 ¹⁸ cm ^-3 and a thickness of 0.2 μm is used as the second emitter region 10 of the InGaAs sub-cell 32 , and N-type highly doped GaInP with a thickness of 0.05 μm is grown on the surface of the second emitter region 10 . The InGaAlAs or AlInP layer serves as the second window layer 11 of the InGaAs sub-cell 32 .

(5) On the surface of the second window layer 11 of the InGaAs sub-cell 32 grow an InGaAs bonding layer 12 with an N-type doping concentration of about 4×10 ¹⁸ cm ^-3 and a thickness of 0.5 μm. The lattice constant of the InGaAs bonding layer 12 is the same as The lattice constants of the InGaAs subcells 32 are the same.

(6) Grow a non-doped GaAs buffer layer 15 with a thickness of 0.3 microns on the GaAs substrate 14, and then grow a 0.01 micron AlAs sacrificial layer 16 with a P-type doping concentration of about 4×10 ¹⁸ cm ^-3 and a thickness of 0.5 microns GaAs bonding layer 17.

(7) An AlGaAs layer with a P-type doping concentration of about 1×10 ¹⁸ cm ^-3 and a thickness of 0.1 μm is grown on the surface of the GaAs bonding layer 17 as the third back field layer 18 of the GaAs sub-cell 33 , and then a P-type doping layer is grown. A GaAs layer with a dopant concentration of about 1×10 ¹⁷ cm ^-3 and a thickness of about 3 microns is used as the third base region 19 of the GaAs sub-cell 33 , and an N-type dopant concentration of about 2×10 ¹⁸ cm ^-3 is grown on the surface of the third base region 19 . ^3. A GaAs layer with a thickness of 0.15 microns is used as the third emitter region 20 of the GaAs sub-cell 33, and a layer of N-type highly doped Al(Ga)InP layer with a thickness of 0.05 microns is grown on the surface of the third emitter region 20 as the GaAs sub-cell 33 of the third window layer 21 to reduce the recombination of photogenerated carriers.

(8) A fifth doped layer 22 of GaInP or GaAs with an N-type doping concentration greater than 1×10 ¹⁹ cm ^-3 and a thickness of 0.015 μm is grown on the surface of the GaAs sub-cell 33 , and a P-type doped layer is grown on the surface of the fifth doped layer 22 Doping the sixth doped layer 23 of (Al)GaAs with a concentration greater than 1×10 ¹⁹ cm ⁻³ and a thickness of 0.015 μm, so as to form a second tunnel junction 34 ;

(9) An Al(Ga)InP layer with a P-type doping concentration of about 2×10 ¹⁸ cm ^-3 and a thickness of 0.05 μm is grown on the surface of the second tunnel junction 34 as the fourth back field layer 24 of the GaInP sub-cell 35 . A GaInP layer with a P-type doping concentration of approximately 1×10 ¹⁷ cm ^-3 and a thickness of 0.5 μm is grown on the surface of the four back field layers 24 as the fourth base region 25 of the GaInP sub-cell 35 , and N A GaInP layer with an N-type doping concentration of about 2×10 ¹⁸ cm ^-3 and a thickness of 0.2 microns is used as the fourth emitter region 26 of the GaInP sub-cell 35 , and a highly N-type doped layer with a thickness of 0.02 microns is grown on the surface of the fourth emitter region 26 . The AlInP layer serves as the fourth window layer 27 of the GaInP sub-cell 35 .

(10) Then grow a GaAs layer with an N-type doping concentration of about 6×10 ¹⁸ cm ⁻³ and a thickness of 0.5 μm on the surface of the GaInP sub-cell 35 as the contact layer 28 of the GaInP sub-cell 35 for forming an ohmic contact.

(11) Using HF acid as a selective etching solution to remove the AlAs sacrificial layer 16 to realize the peeling off of the GaAs substrate 14 ; and then bonding the InGaAs bonding layer 12 to the GaAs bonding layer 17 .

(2) Electrode preparation process

A P electrode 37 and an N electrode 36 are respectively prepared on the back of the P-type first base region 01 and the surface of the N-type GaAs contact layer 28 to obtain the required solar cell. The structure of the solar cell is shown in FIG. 1 .

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications should also be considered Be the protection scope of the present invention.

Claims (7)

1. a GaInP/GaAs/InGaAs/Ge four-junction solar cell, it is characterized in that, including Ge battery, the first tunnel knot, gradual transition layer, the sub-battery of InGaAs, (In) GaAs bonded layer, GaAs or GaInP bonded layer, the sub-battery of GaAs, the second tunnel knot and the sub-battery of GaInP, the band-gap energy of described four-junction solar cell is respectively 1.89eV, 1.42eV, 1.0eV and 0.67eV, and the thickness of described GaAs or GaInP bonded layer is 200～800nm.

GaInP/GaAs/InGaAs/Ge four-junction solar cell the most according to claim 1, it is characterised in that described Ge battery comprises the first base that material is Ge, and the first launch site that material is Ge arranged on the first base.

GaInP/GaAs/InGaAs/Ge four-junction solar cell the most according to claim 1, it is characterized in that, described Ge battery and the sub-battery of InGaAs are successively set on described Ge substrate according to the direction away from Ge substrate, form band-gap energy and are respectively first double-junction solar battery of 1.0eV, 0.67eV.

GaInP/GaAs/InGaAs/Ge four-junction solar cell the most according to claim 3, it is characterized in that, the sub-battery of described GaAs and the sub-battery of GaInP grow according to the direction away from GaAs substrate, peel off described GaAs substrate, form band-gap energy and be respectively second double-junction solar battery of 1.89eV, 1.42eV.

GaInP/GaAs/InGaAs/Ge four-junction solar cell the most according to claim 4, it is characterized in that, described second double-junction solar battery is bonded by described (In) GaAs bonded layer and GaAs or GaInP bonded layer with described first double-junction solar battery.

6. the preparation method of the GaInP/GaAs/InGaAs/Ge four-junction solar cell described in a claim 1, it is characterised in that include step:

1) a Ge battery is provided；

2) stratum nucleare, the first cushion, the first tunnel knot, gradual transition layer, the sub-battery of InGaAs and (In) GaAs bonded layer are grown into successively at Ge battery surface；

3) a GaAs substrate is provided；

4) growing the second cushion, sacrifice layer, GaAs or GaInP bonded layer, the sub-battery of GaAs, the second tunnel knot, the sub-battery of GaInP and GaAs contact layer the most successively, the thickness of described GaAs or GaInP bonded layer is 200～800nm；

5) GaAs substrate is peeled off；

6) described (In) GaAs bonded layer is bonded with described GaAs or GaInP bonded layer；

The band-gap energy of described four-junction solar cell is respectively 1.89eV, 1.42eV, 1.0eV and 0.67eV.

The preparation method of GaInP/GaAs/InGaAs/Ge four-junction solar cell the most according to claim 6, it is characterised in that step 6) also include afterwards:

7) Ge cell backside after cleaning makes P electrode, and GaAs contact layer surface after cleaning makes palisade N electrode, forms target solaode.