Flexible silicon substrate-indium phosphide solar cell and preparation method thereof

Abstract

The invention belongs to the technical field of solar cells, and discloses a flexible silicon substrate-indium phosphide solar cell and a preparation method thereof. The flexible silicon-based indium phosphide solar cell comprises a lower electrode, a flexible silicon solar cell, a first transparent conductive layer, a conductive adhesive, a second transparent conductive layer and an indium phosphide solar cell which are sequentially stacked from bottom to top, an antireflection film layer and an upper electrode are arranged on the indium phosphide solar cell; the conductive adhesive is obtained by dispersing polymethyl methacrylate microspheres coated with metal on the surface into an EVA solution. Heterogeneous integration is achieved through the transparent conductive adhesive, the two-end laminated cell is formed, the device is light, thin and flexible, the defects that a traditional four-end laminated cell is rigid, heavy, large in optical loss and the like are overcome, and the solar cell has good performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of solar cells, and particularly relates to a flexible silicon-based indium phosphide solar cell and a preparation method thereof. BACKGROUND

[0002] Energy problems are one of the major challenges facing the world today, and the development of high-efficiency solar photovoltaic technology is an important direction of modern development. Improving the efficiency of solar photovoltaic conversion and enhancing the practicality and applicability of solar cells have become urgent tasks for current research.

[0003] Currently, silicon solar cells are the most widely used photovoltaic technology due to their relatively low cost, but the theoretical limit of their photoelectric conversion efficiency is about 25%, which restricts their further development. To break through this efficiency limit, researchers have proposed a stacked cell structure combining silicon with other semiconductor materials. For example, the conversion efficiency of a silicon-based gallium arsenide three-junction cell can reach 33%, but the cost of gallium arsenide material is high.

[0004] Gallium arsenide, as a III-V semiconductor material, has a tunable band gap and is often used to build high-efficiency stacked solar cells. However, it still has certain limitations in flexible applications. In contrast, indium phosphide (InP) also belongs to III-V semiconductors and not only has a tunable band gap and high photoelectric conversion efficiency, but also exhibits excellent mechanical flexibility and material stability, making it more suitable for building flexible solar cells and providing the possibility of achieving high-efficiency and high-adaptability solar cells.

[0005] Currently, there have been some research on stacked solar cells containing indium phosphide cells. The patent application with the title of "Indium Phosphide-Perovskite Four-Terminal Stacked Solar Cell and Preparation Method Thereof" and the application number of 202211477526.X discloses a solar cell that uses indium phosphide quantum dots as the top cell and perovskite as the bottom cell, and connects the two cells optically in series through a double-sided transparent conductive glass substrate. However, this structure has obvious disadvantages: first, the intermediate connecting layer is a rigid glass substrate, making the entire device heavy and inflexible, completely unable to be applied to flexible and wearable electronic devices; second, the perovskite cell and indium phosphide quantum dot cell used in this structure have long-term stability problems, especially the perovskite material is extremely sensitive to water and oxygen, which seriously affects the service life of the device; in addition, this structure is a physically separated four-terminal device, and the upper and lower cells need to be connected through an external circuit, increasing the system complexity and energy transmission loss, and the ITO-glass-ITO connecting layer in the middle is too thick, which will cause significant optical parasitic absorption and interface reflection loss, thereby reducing the final photoelectric conversion efficiency of the cell. Therefore, there is an urgent need for a stacked solar cell structure that combines high efficiency, high stability, and good flexibility. SUMMARY

[0006] In order to overcome the shortcomings and deficiencies of the prior art, the purpose of the present application is to provide a silicon-based indium phosphide solar cell with compact structure, good stability and excellent flexibility, and a preparation method thereof. The present application heterogeneously integrates the indium phosphide solar cell and the flexible crystalline silicon cell through an ultra-thin transparent conductive adhesive to form a two-end stacked cell. This structure completely abandons the rigid glass substrate, making the overall device light and thin, and bendable, laying a foundation for realizing flexible wearable photovoltaic applications. At the same time, the present application uses the stable bulk material InP to replace the poor stability of indium phosphide quantum dots and perovskite, combined with stable and reliable crystalline silicon, which fundamentally solves the problem of short service life and poor reliability of traditional flexible stacked cells. In terms of performance, the two-end structure using TCA direct bonding avoids the complex external circuit and the optical loss caused by the over-thickness of the intermediate layer of the four-end structure, and the heterogeneously integrated way avoids the lattice mismatch problem, ensuring high interface quality and carrier transport efficiency. In addition, the preparation method of the present application successfully realizes the reliable integration of the flexible crystalline silicon cell and the indium phosphide cell, has good process compatibility, and provides a feasible technical route for preparing high-performance and high-stability flexible III-V / silicon stacked cells.

[0007] The purpose of the present application is achieved by the following technical solutions: A flexible silicon-based indium phosphide solar cell, comprising a lower electrode, a flexible silicon solar cell, a first transparent conductive layer, a conductive adhesive, a second transparent conductive layer and an indium phosphide solar cell stacked in order from bottom to top; a reflection-reducing film layer and an upper electrode are arranged on the indium phosphide solar cell; the upper electrode is arranged at both ends of the indium phosphide solar cell, and the reflection-reducing film layer is arranged on the indium phosphide solar cell not covered by the upper electrode.

[0008] The first transparent conductive layer and the second transparent conductive layer are each one of ITO, IWO and ZnO.

[0009] The thickness of each of the first transparent conductive layer and the second transparent conductive layer is 15-25 nm.

[0010] The conductive adhesive is prepared by the following method: ethylene-vinyl acetate (EVA) is prepared into a solution to obtain an EVA solution; then poly(methyl methacrylate) microspheres coated with metal on the surface are dispersed in the EVA solution to obtain the conductive adhesive; the metal in the poly(methyl methacrylate) microspheres coated with metal on the surface is one or more of gold, silver or platinum; the particle size of the microspheres is 45-55 microns.

[0011] The mass ratio of the poly(methyl methacrylate) microspheres coated with metal on the surface to EVA is 1:7-1:9.

[0012] The solvent in the EVA solution is toluene. The mass-volume ratio of EVA to toluene is 1g:(4-10)mL.

[0013] The thickness of the lower electrode is 100-150nm; The thickness of the first transparent conductive layer is 15-25nm.

[0014] The flexible silicon solar cell is a single crystal silicon solar cell.

[0015] The flexible silicon solar cell comprises a P-type silicon substrate and N-type silicon formed on the upper surface of the P-type silicon substrate by doping diffusion; the depth of the N-type silicon is 300-800nm, wherein the depth refers to the depth of the doping element in the P-type silicon substrate.

[0016] The thickness of the P-type silicon substrate is 60μm.

[0017] The lower electrode is arranged on the back surface of the P-type silicon substrate.

[0018] The first conductive layer is arranged on the N-type silicon.

[0019] The indium phosphide solar cell is a single-junction indium phosphide solar cell.

[0020] The indium phosphide solar cell comprises, from bottom to top, an n-type InP back field layer, an n-type InP base region, a P-type emitter region, and a window layer. The window layer is an AlInAs window layer.

[0021] The n-type InP back field layer is arranged on the second conductive layer.

[0022] The upper electrode is arranged on both ends or around the window layer of the indium phosphide solar cell, and the anti-reflection film layer is arranged on the window layer of the indium phosphide solar cell which is not covered by the upper electrode.

[0023] The non-window position in the window layer is sequentially provided with an etching stop layer, a contact layer, and an upper electrode.

[0024] A preparation method of a flexible silicon-based-indium phosphide solar cell, comprising the following steps: S1, doping diffusion is performed on the front surface of a P-type silicon wafer with a textured surface by high-temperature diffusion or ion implantation to form N-type silicon, and then a lower electrode is obtained by evaporating metal on the back surface of the P-type silicon wafer; the textured surface is obtained by treating the single crystal silicon with a textured solution; S2, a first transparent conductive layer is prepared on the surface of the N-type silicon by sputtering; S3, a buffer layer, a sacrificial layer, a heavily doped back field layer, a base region, an emitter region, a window layer, an etching stop layer, and a contact layer are sequentially prepared on an indium phosphide substrate by metal organic chemical vapor deposition; S4. A PVD method is used to deposit an upper electrode on the contact layer, but the upper electrode does not cover the middle of the contact layer. A chemical etching method is used to remove the sacrificial layer, the contact layer not covered by the upper electrode, and the etching stop layer covered by the contact layer not covered by the upper electrode from step S3. A second transparent conductive layer is sputtered on the back surface of the indium phosphide substrate. S5. An antireflection film is prepared on the surface of the window layer not covered by the upper electrode using PVD. S6. The first conductive layer in step S2 and the second transparent conductive layer in the battery structure after the anti-reflection film is prepared in step S5 are bonded together with an adhesive to obtain a flexible silicon-based indium phosphide solar cell.

[0025] The specific steps of step S1 are as follows: (1) Cut the silicon wafer and clean the surface of the silicon wafer; (2) Treat the cut edges of the silicon wafer with a mixture of hydrofluoric acid and nitric acid in a volume ratio of 1:8 to 1:10 for 10 to 20 minutes; (3) A textured surface is prepared by treating the silicon wafer surface with a mixed solution of potassium hydroxide and isopropanol; the concentration of potassium hydroxide in the mixed solution is 5wt%-10wt%, and the volume concentration of isopropanol is 5Vol%-10Vol%. (4) Doping diffusion is performed on the surface of P-type silicon wafers by high-temperature diffusion or ion implantation to prepare N-type silicon with a depth of 300-800 nm; (5) A lower electrode is deposited on the back surface of a P-type silicon wafer by PVD method; the lower electrode is one or more of silver, gold, titanium, and platinum, and has a thickness of 100-200 nm.

[0026] The thickness of the buffer layer in step S3 is 50-100 nm; The thickness of the sacrificial layer is 100-200 nm; The thickness of the heavily doped back field layer is 500-600 nm; The thickness of the base region is 3000 nm; The thickness of the emission region is 100-200 nm; The thickness of the window layer is 20~30nm; The thickness of the etch stop layer is 10-20 nm; The thickness of the contact layer is 100-200nm.

[0027] The upper electrode is made of one or more of gold, platinum, and nickel; the thickness of the upper electrode is 50-100 nm.

[0028] In step S4, chemical etching is used to remove the sacrificial layer, excess etch stop layer, and excess contact layer from step S3. Specific steps are as follows: 1) Use hydrofluoric acid with a volume concentration of 20%-30% to remove the sacrificial layer; 2) Use a mixed solution of H3PO4:H2O2:H2O to remove excess contact layer (contact layer not covered by the upper electrode), with a volume ratio of (3:1:40)-(5:2:40); 3) Use a mixed solution of HCl:H3PO4 to remove excess stop etching layer (etch stop layer not covered by the contact layer covered by the upper electrode), with a volume ratio of (1:3)-(1:5).

[0029] By removing excess contact layers and excess stop etch layers, the window layer is exposed, especially the window of the window layer.

[0030] The antireflective coating uses metal oxides such as Al2O3, TiO2, and ZnO as the antireflective layer material, with a thickness of 50-100 nm.

[0031] The adhesive in step S6 is prepared by EVA solution and polymethyl methacrylate microspheres with metal coating on the surface; the bonding conditions are: 100~120℃, 2~4psi or lower temperature and pressure for 8~15 minutes.

[0032] The present invention has the following advantages: This invention achieves heterogeneous integration using a transparent conductive adhesive to form a two-terminal tandem solar cell. The resulting device is thin, light, and flexible, overcoming the rigidity, bulkiness, and high optical loss inherent in traditional four-terminal tandem solar cells, thus achieving superior flexibility. The use of stable indium phosphide (IP) as the bulk material for the top cell and flexible crystalline silicon as the bottom cell improves the device's environmental stability and lifespan, surpassing that of perovskite and quantum dot-based tandem solar cells. The two-terminal structure reduces optical and electrical losses, and the mature combination of IPT and silicon materials provides a possibility for breaking through the efficiency limit of single-junction solar cells. This invention is the first to integrate a bulk IPT solar cell with a flexible crystalline silicon cell using a specific adhesive, providing a new approach to flexible and high-efficiency photovoltaic technology. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the flexible silicon-based indium phosphide solar cell of the present invention; 1: antireflective film; 2: upper electrode; 3: indium phosphide solar cell; 4: transparent conductive adhesive; 5: flexible silicon solar cell; 6: lower electrode; 7: transparent conductive layer, 7-1: first transparent conductive layer, 7-2: second transparent conductive layer; Figure 2 The following is a schematic diagram of the flexible silicon-based indium phosphide solar cell structure of the present invention: 7-1: First transparent conductive layer; 5-1: N-type silicon (i.e., silicon doped with phosphorus); 5-2: P-type silicon substrate; 6: Lower electrode; Figure 3This is a schematic diagram of the structure of the indium phosphide top cell in the flexible silicon-based indium phosphide solar cell of the present invention; 3-1: n-type InP back field layer; 3-2: n-type InP base region; 3-3: P-type emitter region; 3-4: window layer; 3-5: stop etching layer; 3-6: contact layer. Detailed Implementation

[0034] The present invention will be described in further detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0035] A schematic diagram of the flexible silicon-based indium phosphide solar cell of the present invention is shown below. Figure 1 As shown, the solar cell includes, from bottom to top, a lower electrode 6, a flexible silicon solar cell 5, a first transparent conductive layer 7-1, a conductive adhesive 4, a second transparent conductive layer 7-2, and an indium phosphide solar cell 3. The indium phosphide solar cell 3 is provided with an anti-reflection film layer 1 and an upper electrode 2. The upper electrode 2 is disposed at both ends or around the perimeter of the indium phosphide solar cell 3, and the anti-reflection film layer 1 is disposed on the indium phosphide solar cell 3 that is not covered by the upper electrode 2.

[0036] The first transparent conductive layer 7-1 and the second transparent conductive layer 7-2 are each one of ITO, IWO and ZnO.

[0037] The thickness of the first transparent conductive layer 7-1 and the second transparent conductive layer 7-2 is 15-25nm.

[0038] The thickness of the lower electrode 6 is 100-150 nm; The flexible silicon solar cell 5 is a monocrystalline silicon solar cell, and its structural schematic diagram is shown below. Figure 2 As shown.

[0039] The flexible silicon solar cell 5 includes a P-type silicon substrate 5-2 and an N-type silicon substrate 5-1 formed by doping diffusion on the upper surface of the P-type silicon substrate; the depth of the N-type silicon 5-2 is 300-800 nm, where the depth refers to the depth of doping diffusion of the doping element on the P-type silicon substrate. The doping element is P, B, etc.

[0040] The thickness of the P-type silicon substrate 5-2 is 60 μm.

[0041] The lower electrode 6 is disposed on the back side of the P-type silicon substrate 5-2.

[0042] The first conductive layer 7-1 is disposed on N-type silicon 5-1.

[0043] The indium phosphide solar cell 3 is a single-junction indium phosphide solar cell, and its structural schematic diagram is shown below. Figure 3 As shown.

[0044] The indium phosphide battery 3 comprises, from bottom to top, an n-type InP back field layer 3-1, an n-type InP base region 3-2, a P-type emitter region 3-3, a window layer 3-4, a stop etching layer 3-5, and a contact layer 3-6, stacked sequentially. The window layer 3-4 is an AlInAs window layer. The stop etching layer 3-5 and the contact layer 3-6 do not cover the window of the window layer 3-4.

[0045] The n-type InP back field layer 3-1 is disposed on the second transparent conductive layer 7-2.

[0046] The upper electrode 2 is disposed on the contact layer 3-6 of the indium phosphide solar cell 3, and the anti-reflection film layer 1 is disposed on the window layer 3-4 of the indium phosphide solar cell 3 which is not covered by the upper electrode 2, the stop etching layer 3-5 and the contact layer 3-6.

[0047] The conductive adhesive 4 is prepared by the following method: ethylene-vinyl acetate (EVA) is prepared into a solution to obtain an EVA solution; then, polymethyl methacrylate microspheres with metal coating on their surface are dispersed in the EVA solution to obtain a conductive adhesive; the metal in the polymethyl methacrylate microspheres with metal coating on their surface is one or more of gold, silver or platinum; the particle size of the microspheres is 45-55 micrometers.

[0048] The mass ratio of metal-coated polymethyl methacrylate microspheres to EVA is 1:7 to 1:9.

[0049] The solvent in the EVA solution is toluene. The mass-to-volume ratio of EVA to toluene is 1 g : (4~10) mL.

[0050] Example 1 A method for fabricating a flexible silicon-based indium phosphide tandem solar cell includes the following steps: (1) First, the 60-micron-thick P-type doped Si substrate is cut into 5×5cm pieces by mechanical cutting. 2 The size of the substrate was determined by cleaning with a mixture of alkali and hydrogen peroxide to remove the damaged layer and surface dirt. Then, the P-type silicon substrate was texturized for 30 minutes at 80°C with a mixture of 5wt% KOH and 5vol% isopropanol (water as solvent). After texturization, the silicon substrate was soaked in 36%-38% HCl to remove KOH. Then, the edges of the P-type silicon substrate were passivated with a 10% VolHF:90% VolHNO3 solution to obtain a flexible P-type silicon substrate. (2) A pn ​​junction on a P-substrate was prepared by high-temperature diffusion. POCl3 was used as the phosphorus source in a tube diffusion furnace to achieve a phosphorus concentration of 5 × 10⁻⁶ at a depth of 500 nm on the surface of the P-type silicon substrate. 19 cm -3n-type phosphorus doping (N-type silicon) yielded flexible silicon solar cells with a bandgap of 1.12 eV. (3) A transparent conductive layer ITO (first transparent conductive layer) with a thickness of 20 nm was prepared on the N-type silicon of the flexible silicon solar cell by magnetron sputtering; and a lower electrode Ag electrode with a thickness of 150 nm was prepared on the back surface of the P-type substrate by electron beam evaporation. (4) An n-type doped InP substrate with a thickness of 30 micrometers and a doping concentration of 2×10⁻⁶ is used. 18 cm -3 Using MOCVD technology, an InGaAs buffer layer, a 200 nm thick AlInAs sacrificial layer, and a 500 nm thick n-type InP heavily doped layer (doped with Si) with a doping concentration of 2 × 10⁻⁶ were sequentially grown on an n-type doped InP substrate. 18 cm -3 A 3000 nm thick n-type InP base region (doped with Si) with a doping concentration of 1 × 10⁻⁶. 17 cm -3 A 150 nm thick P-type emitter region (the emitter region is InP, and the doping element is Zn) with a doping concentration of 1 × 10⁻⁶. 18 cm -3 P-type doped Al with a thickness of 25 nm x In （1-x） As window layer (doped with Zn), doping concentration is 1.5 × 10⁻⁶. 18 cm -3 A 10 nm thick P-type InP etch stop layer (doped with Zn) with a doping concentration of 1.5 × 10⁻⁶. 18 cm -3 P-type In with a thickness of 200 nm y Ga （1-y） As contact layer, doping concentration is 2×10⁻⁶ 19 cm -3 With 0.48≤x≤0.52 and 0.48≤y≤0.52, a single-junction indium phosphide top cell can be obtained except for the electrode part; (5) An Au electrode for the battery was prepared on a portion of the contact layer on the surface of the indium phosphide top battery using an electron beam evaporation method, with a thickness of 50 nm; the middle part of the contact layer was not covered by the electrode. The AlInAs sacrificial layer in the indium phosphide battery was removed using 20% ​​HF acid. The InGaAs contact layer not covered by the electrode in the indium phosphide battery was removed using a solution of H3PO4:H2O2:H2O (volume ratio 3:1:40). The InP stop etching layer covering the removed contact layer in the indium phosphide battery was removed using an HCl:H3PO4 solution (volume ratio 1:3). A single-junction indium phosphide solar cell with a bandgap of 1.34 eV was subsequently obtained. (6) A transparent conductive layer ITO with a thickness of 20 nm was prepared on the bottom n-type InP heavily doped layer of an indium phosphide solar cell by magnetron sputtering. (7) Preparation of transparent conductive adhesive (TCA): Ethylene-vinyl acetate (EVA) and toluene are mixed at a volume ratio of 1:5 and stirred on a heating plate to form a uniform EVA solution. Then, silver-plated polymethyl methacrylate (PMMA) microspheres with a particle size of 45-55 micrometers are added. The coverage of the microspheres is controlled between 8% and 10% (the coverage here refers to the proportion of opaque microspheres to the entire transparent TCA). The mass ratio of microspheres to EVA is 1:8. The mixture is heated and stirred continuously. After the microspheres are uniformly dispersed, the transparent conductive adhesive is obtained. The transparent conductive layer on the flexible silicon solar cell and the transparent conductive layer on the indium phosphide solar cell were bonded together using a transparent conductive adhesive, and then subjected to temperature and pressure at 120°C and 3psi for 10 minutes. The thickness of the transparent conductive adhesive was 60nm. (8) A 50 nm thick aluminum oxide layer was deposited on the window layer of the tandem battery as an anti-reflection layer using electron beam evaporation.

[0051] Comparative Example 1 The transparent conductive adhesive matrix was prepared by replacing the EVA matrix in Example 1 with epoxy resin, and other conditions were the same as in Example 1.

[0052] Comparative Example 2 Remove the PMMA microspheres from the transparent conductive adhesive, and keep other conditions the same as in Example 1.

[0053] The performance test parameters of the batteries prepared in Example 1 and Comparative Examples 1-2 are shown in Table 1.

[0054] Table 1. Performance parameters of the batteries prepared in Example 1 and Comparative Examples 1-2

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A flexible silicon-based indium phosphide solar cell characterized by: The flexible silicon-based indium phosphide solar cell comprises, from bottom to top, a lower electrode, a flexible silicon solar cell, a first transparent conductive layer, a conductive adhesive, a second transparent conductive layer, and an indium phosphide solar cell; the indium phosphide solar cell is provided with an anti-reflection film layer and an upper electrode; the upper electrode is arranged on the indium phosphide solar cell and partially covers the indium phosphide solar cell, and the anti-reflection film layer is arranged on the indium phosphide solar cell not covered by the upper electrode. The conductive adhesive is prepared by the following method: ethylene-vinyl acetate is prepared into a solution to obtain an EVA solution; then poly(methyl methacrylate) microspheres coated with metal on the surface are dispersed in the EVA solution to obtain the conductive adhesive; the metal on the poly(methyl methacrylate) microspheres coated with metal is one or more of gold, silver and platinum; the particle size of the microspheres is 45-55 microns.

2. The flexible silicon-based indium phosphide solar cell according to claim 1, wherein: the flexible silicon solar cell is a single-crystal silicon solar cell; and the indium phosphide solar cell is a single-junction indium phosphide solar cell.

2. The flexible silicon-based indium phosphide solar cell according to claim 1, wherein: the flexible silicon solar cell is a single-crystal silicon solar cell; and the indium phosphide solar cell is a single-junction indium phosphide solar cell. The mass ratio of the poly(methyl methacrylate) microspheres coated with metal on the surface to EVA is 1:7-1:

9.

3. The flexible silicon-based indium phosphide solar cell according to claim 1, wherein: each of the first transparent conductive layer and the second transparent conductive layer is one of ITO, IWO and ZnO; the thickness of each of the first transparent conductive layer and the second transparent conductive layer is 15-25 nm; the thickness of the lower electrode is 100-200 nm; the thickness of the upper electrode is 50-100 nm; the lower electrode is one or more of silver, gold, titanium and platinum; the upper electrode is one or more of gold, platinum and nickel; and the anti-reflection film is one or more of Al2O3, TiO2 and ZnO, and the thickness of the anti-reflection film is 50-100 nm. The flexible silicon solar cell comprises a P-type silicon substrate and an N-type silicon formed on the upper surface of the P-type silicon substrate by doping diffusion; the depth of the N-type silicon is 300-800 nm, wherein the depth refers to the depth of the doping element in the P-type silicon substrate. The doping element is P and B; and the P-type silicon substrate is a P-type silicon substrate with a pyramidal-textured surface. The thickness of the P-type silicon substrate is 60 microns. The lower electrode is arranged on the back surface of the P-type silicon substrate. The first conductive layer is arranged on the N-type silicon.

6. The flexible silicon-based indium phosphide solar cell according to claim 1, wherein: the indium phosphide solar cell comprises, from bottom to top, an n-type InP back field layer, an n-type InP base region, a P-type emitter region and a window layer; and the window layer is a P-type doped AlInAs window layer. The window layer is sequentially provided with an etching stop layer, a contact layer and an upper electrode; the etching stop layer covers part of the window layer and the window of the window layer is not covered; and the contact layer and the upper electrode do not cover the window of the window layer.

4. The flexible Si- InP solar cell of claim 1, wherein:

7. The flexible silicon-based indium phosphide solar cell according to claim 6, wherein: the thickness of the back field layer is 500-600 nm; the thickness of the base region is 3000 nm; the thickness of the emitter region is 100-200 nm; and the thickness of the window layer is 20-30 nm.

5. The flexible Si- InP solar cell according to claim 4, wherein: ​ ​ ​ ​ ​ ​ ​ ​ n-type InP back field layer, doping concentration is (1.5~2.5) x 10 18 cm -3 ; n-type InP base region, doping concentration is (0.5~1.5) x 10 17 cm -3 ; P-type emission region, doping concentration is (0.5~1.5) x 10 18 cm -3 ; P-type doped Al x In （1-x） As window layer, doping concentration is (1~2) x 10 18 cm -3 ; 0.48≤x≤0.52; ​ ​ ​ ​ The n-type InP back field layer is arranged on the second transparent conductive layer; The etching stop layer is a P-type InP etching stop layer, and the doping concentration is (0.5-2)×10 18 cm -3 -3. y The contact layer is a P-type In （1-y） Ga 19 As contact layer, and the doping concentration is (1.5-2.5)×10 -3 cm -3. wherein 0.48≤y≤0.

52.

8. The flexible Si- InP solar cell of claim 6, wherein: The anti-reflective film layer is arranged on the window layer of the uncovered InP solar cell.

9. The method for preparing a flexible silicon-based indium phosphide solar cell according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: S1, using high-temperature diffusion or ion implantation method to dope and diffuse on the front surface of the P-type silicon wafer with a textured surface to form N-type silicon; Then, a metal is evaporated on the back surface of the P-type silicon wafer to obtain a lower electrode; the textured surface is obtained by using a single crystal silicon texturing liquid; S2, a first transparent conductive layer is prepared on the surface of the N-type silicon by sputtering; S3, a buffer layer, a sacrificial layer, a heavily doped back field layer, a base region, an emission region, a window layer, an etching stop layer and a contact layer are sequentially prepared on the InP substrate by using an organic metal chemical vapor deposition method; S4, an upper electrode is evaporated on part of the contact layer by using a PVD method; the sacrificial layer, the contact layer not covered by the upper electrode and part of the etching stop layer in step S3 are removed by using a chemical etching method, and a second transparent conductive layer is sputtered on the back surface of the InP substrate; the part of the etching stop layer refers to the etching stop layer not covered by the contact layer not covered by the upper electrode; S5, an anti-reflective film is prepared on the surface of the window layer not covered by using a PVD method; S6, the first conductive layer in step S2 and the second transparent conductive layer in the battery structure in which the anti-reflective film is prepared in step S5 are bonded by using an adhesive to obtain a flexible silicon-based InP solar cell.

10. The method of claim 9, wherein the flexible Si- InP solar cell is prepared by the steps of: In step S4, the sacrificial layer, the contact layer not covered by the upper electrode and part of the etching stop layer in step S3 are removed by using a chemical etching method, and the specific steps are as follows: ​ 1) using hydrofluoric acid with a volume concentration of 20%-30% to remove the sacrificial layer; 2) using a mixed solution of H3PO4:H2O2:H2O to remove the contact layer not covered by the upper electrode, and the volume ratio of H3PO4:H2O2:H2O is (3:1:40)-(5:2:40); 3) using a mixed solution of HCl:H3PO4 to remove part of the etching stop layer, and the volume ratio of HCl:H3PO4 is (1:3)-(1:5); The adhesive in step S6 is prepared by using an EVA solution and poly(methyl methacrylate) microspheres coated with metal on the surface; the bonding conditions are as follows: 100-120 DEG C, 2-4 psi, warm pressing for 8-15 minutes; The edge of the P-type silicon wafer with a textured surface is subjected to a passivation treatment.

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