CN114300564A

CN114300564A - Double-sided solar cell and manufacturing method thereof

Info

Publication number: CN114300564A
Application number: CN202111633668.6A
Authority: CN
Inventors: 张怡静; 陈明; 张海洋; 王冰雪; 钱富琛; 王建明; 闫大鹏
Original assignee: Wuhan Raycus Fiber Laser Technologies Co Ltd
Current assignee: Wuhan Raycus Fiber Laser Technologies Co Ltd
Priority date: 2021-12-28
Filing date: 2021-12-28
Publication date: 2022-04-08
Anticipated expiration: 2041-12-28
Also published as: CN114300564B

Abstract

The application provides a double-sided solar cell and a manufacturing method thereof, the double-sided solar cell comprises a first electrode, a first cell unit, a tunnel junction structure, a second cell unit and a second electrode which are sequentially stacked, wherein the material of the first cell unit comprises silicon; the material of the second battery cell comprises a first III-V compound semiconductor material; the material of the tunnel junction structure includes a second iii-v compound semiconductor material. The double-sided structure is realized through the first battery unit and the second battery unit, the light absorption amount is ensured to be large through double-sided light absorption, in addition, the first battery unit comprises a silicon material, the second battery unit comprises a III-V group compound semiconductor material, and the wavelength range of absorbable sunlight is ensured to be large through the integration of a Si material and the III-V group compound semiconductor material, so that the conversion of light with different wavelengths into electricity is facilitated, and the photoelectric conversion efficiency of the double-sided solar battery is ensured to be high.

Description

Double-sided solar cell and manufacturing method thereof

Technical Field

The application relates to the field of solar cells, in particular to a double-sided solar cell and a manufacturing method thereof.

Background

Common solar cells can be classified into Si solar cells, cells made of inorganic salts such as gallium arsenide iii-v group compounds, cadmium sulfide, copper indium selenide and other multi-element compounds, solar cells made of functional polymer materials, nanocrystal solar cells and the like according to their materials. Among these, the single crystal Si solar cell is the one that has been used the earliest and has the longest history. The Si atoms of the single crystal Si solar cell are arranged regularly, the conversion efficiency of the single crystal Si solar cell is the highest, the theoretical value can reach 24% -26%, and the conversion efficiency of an actual product is 15% -18%. Polycrystalline Si used in Si solar cells is formed by aggregation of single crystal Si particles. The theoretical value of the conversion efficiency of the polycrystalline Si solar cell is 20%, and the conversion efficiency of an actual product is 12% -14%. Although the conversion efficiency is slightly lower than that of a single crystal Si solar cell, the amount of the material used is dominant over that of a single crystal Si solar cell because the material is more abundant and the production is easier. The polycrystalline thin-film solar cell uses less raw materials, has high efficiency and has wider application prospect.

But it is undeniable that Si is a weak light absorber requiring an absorbing layer several hundred microns thick compared to iii-v compound materials because it is an indirect bandgap material. In addition, Si, as a photovoltaic material, has a narrow bandgap, and causes relatively large heat loss relative to the optimal solar bandgap value of 1.5 eV. The III-V group compound solar cell is made of a direct band gap semiconductor material, so that the conversion efficiency of the solar cell is high, the conversion efficiency of a unijunction solar cell is 26-28%, and the conversion efficiency of a two-junction solar cell and a three-junction solar cell can reach 35-45%. And the solar cell can be made into a thin-film solar cell, has good radiation resistance and temperature characteristics, and is suitable for concentrating power generation. In the case of a compound semiconductor solar cell, although the temperature rise does not greatly affect the characteristics of the solar cell, the resources for manufacturing the solar cell are small, the material cost is high, and the compound semiconductor solar cell is mainly used in the field of cosmic power generation at present.

In order to improve the conversion efficiency of solar cells, various approaches have been tried, such as: 1. finding a new material sensitive from near infrared to ultraviolet; 2. the novel laser processing technology is adopted to improve the solar cell processing technology innovation; 3. tracking a maximum power point; 4. the use of a light-condensing element improves conversion efficiency. These methods can improve the conversion efficiency of solar cells to various degrees, but progress is slow and has not been substantially improved further.

The above information disclosed in this background section is only for enhancement of understanding of the background of the technology described herein and, therefore, certain information may be included in the background that does not form the prior art that is already known in this country to a person of ordinary skill in the art.

Disclosure of Invention

The present disclosure provides a bifacial solar cell and a method for fabricating the same, so as to solve the problem of low photoelectric conversion efficiency of the solar cell in the prior art.

According to an aspect of an embodiment of the present invention, there is provided a bifacial solar cell including a first cell unit, a first electrode, a second cell unit, a tunnel junction structure, and a second electrode, wherein a material of the first cell unit includes silicon; the first electrode is located on a surface of the first battery cell; the second cell unit is located on a side of the first cell unit away from the first electrode, and the material of the second cell unit comprises a first III-V compound semiconductor material; the tunnel junction structure is located between the first battery cell and the second battery cell, the tunnel junction structure is in contact with the first battery cell and the second battery cell, respectively, and a material of the tunnel junction structure comprises a second III-V compound semiconductor material; the second electrode is located on a surface of the second battery cell distal from the tunnel junction structure.

Optionally, the first battery cell includes a first heavily doped layer, a first device layer, and a second heavily doped layer stacked in this order, and the doping type of the first heavily doped layer is different from that of the second heavily doped layer.

Optionally, the second battery cell includes a third heavily doped layer, a second device layer, and a fourth heavily doped layer stacked in this order, wherein the third heavily doped layer and the fourth heavily doped layer have different doping types.

Optionally, the tunnel junction structure includes a heavily doped buffer layer and a tunneling layer, where the tunneling layer is located on a surface of the heavily doped buffer layer away from the first battery cell, and the tunneling layer is bonded to the second battery cell.

Optionally, the bifacial solar cell further comprises a first transparent conductive film, a first antireflection film, a second transparent conductive film and a second antireflection film, wherein the first transparent conductive film is located between the first electrode and the first cell unit, and the first transparent conductive film is in contact with the first electrode; the first antireflection film is positioned on the surface of the first transparent conductive thin film, which is far away from the first electrode, and the first antireflection film is in contact with the first battery unit; the second transparent conductive film is positioned between the second electrode and the second battery cell, the second transparent conductive film being in contact with the second electrode; the second antireflection film is located on a surface of the second transparent conductive film away from the second electrode, and the second antireflection film is in contact with the second battery cell.

Optionally, the first III-V compound semiconductor material is Al_xGa_1-xAs, wherein X is more than 0 and less than or equal to 0.8, and the second III-V group compound semiconductor material is GaAs.

According to another aspect of the embodiments of the present invention, there is also provided a method for manufacturing a bifacial solar cell, including: providing a first battery cell, the material of the first battery cell comprising silicon; forming a tunnel junction structure on a surface of the first battery cell, a material of the tunnel junction structure comprising a second III-V compound semiconductor material; forming a second battery cell on a surface of the tunnel junction structure distal from the first battery cell, the material of the second battery cell comprising a first III-V compound semiconductor material; a first electrode is formed on a surface of the first cell unit distal from the tunnel junction structure, and a second electrode is formed on a surface of the second cell unit distal from the tunnel junction structure.

Optionally, forming a tunnel junction structure on a surface of the first battery cell comprises: growing a heavily doped buffer layer on the surface of the first battery unit by adopting a pulse laser deposition method at the reaction temperature of 600-700 ℃, wherein the thickness of the heavily doped buffer layer is 10-2000 nm, the energy of pulse laser is 0.1-1J, and the frequency of the pulse laser is 5-100 Hz; growing a tunneling layer on the surface of the heavily doped buffer layer far away from the first battery unit by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃, wherein the thickness of the tunneling layer is 1-20 nm, and the doping concentration of the tunneling layer is 1 multiplied by 10²⁰/cm³～1×10²¹/cm³。

Optionally, forming a second battery cell on a surface of the tunnel junction structure distal from the first battery cell comprises: providing a crystal bar made of the first III-V group compound semiconductor material, and performing laser cutting on the crystal bar to obtain a second prepared device layer with the thickness of 10-500 micrometers, wherein the crystal bar is obtained by adopting a crystal pulling method, and the second prepared device layer comprises a third surface and a fourth surface which are oppositely arranged; carrying out N-type or P-type doping on the third surface to form a third heavily doped layer with the doping depth of 2-10 nm, wherein the doping concentration of the third heavily doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³(ii) a Bonding the doped third surface on the surface of the tunneling layer far away from the heavily doped buffer layer by using a bonding force of 10 kN-50 kN, and keeping the bonding time for 10 s-60 s; performing P-type or N-type doping on the bonded fourth surface to form a fourth heavily doped layer with a doping depth of 2 nm-10 nm, and forming a second device layer on the remaining second preliminary device layer to obtain the second battery unit, wherein the doping concentration of the fourth heavily doped layer is 1 × 10¹⁸/cm³～1×10²¹/cm³。

Optionally, forming a second battery cell on a surface of the tunnel junction structure distal from the first battery cell comprises: growing a third heavily doped layer with the thickness of 2nm to 10nm on the surface of the tunneling layer far away from the heavily doped buffer layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600 ℃ to 1000 ℃, wherein the doping concentration of the third heavily doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³(ii) a Growing a second device layer with the thickness of 1-2 mu m on the surface of the third triple doping layer far away from the tunneling layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃; growing a fourth heavily doped layer with the thickness of 2nm to 10nm on the surface of the second device layer far away from the third heavily doped layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600 ℃ to 1000 ℃, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³And obtaining the second battery unit.

Optionally, a first battery cell is provided comprising: providing a first initial device layer; texturing the first initial device layer to obtain a first prepared device layer, wherein the first prepared device layer comprises a first surface and a second surface which are oppositely arranged; n-type or P-type doping is carried out on the first surface to form a first heavily doped layer with the doping depth of 0.1-2 mu m, P-type or N-type doping is carried out on the second surface to form a second heavily doped layer with the doping depth of 0.1-2 mu m, and the rest of the first heavily doped layer is dopedPreparing a device layer to form a first device layer, and obtaining the first battery unit, wherein the doping concentration of the first heavily doped layer is 1 x 10¹⁸/cm³～1×10²⁰/cm³The doping concentration of the second heavily doped layer is 1 x 10¹⁸/cm³～1×10²⁰/cm³。

Optionally, providing a first initial device layer comprises: providing a monocrystalline silicon wafer; polishing the double surfaces of the monocrystalline silicon wafer to obtain the first initial device layer with the thickness of 10-500 mu m; or comprises the following steps: providing a single crystal silicon rod; and cutting the silicon single crystal rod by adopting laser with the wavelength range of 300 nm-500 nm to obtain the first initial device layer with the thickness of 10 mu m-500 mu m.

Optionally, after forming a second battery cell on a surface of the tunnel junction structure remote from the first battery cell before forming a first electrode on a surface of the first battery cell remote from the tunnel junction structure and forming a second electrode on a surface of the second battery cell remote from the tunnel junction structure, the method further comprises: depositing a first predetermined material on the surface of the first battery unit far away from the tunnel junction structure by adopting a pulse laser deposition method to form a first antireflection film, and depositing the first predetermined material on the surface of the second battery unit far away from the tunnel junction structure by adopting a pulse laser deposition method to form a second antireflection film, wherein the first predetermined material comprises at least one of titanium nitride, silicon dioxide and titanium dioxide, and the thicknesses of the first antireflection film and the second antireflection film are respectively 10 nm-50 nm; depositing a second predetermined material on the surface of the first antireflection film far away from the first battery unit by adopting a pulse laser deposition method to form a first transparent conductive film, and depositing the second predetermined material on the surface of the second antireflection film far away from the second battery unit by adopting a pulse laser deposition method to form a second transparent conductive film, wherein the second predetermined material comprises indium tin oxide, and the thicknesses of the first transparent conductive film and the second transparent conductive film are respectively 10 nm-50 nm.

By applying the technical scheme of the application, the double-sided solar cell comprises a first electrode, a first cell unit, a tunnel junction structure, a second cell unit and a second electrode which are sequentially stacked, wherein the first cell unit is made of silicon; the material of the second battery cell comprises a first III-V compound semiconductor material; the material of the tunnel junction structure includes a second iii-v compound semiconductor material. Compare solar cell's among the prior art problem that photoelectric conversion efficiency is lower, this application two-sided solar cell, through first cell unit with second cell unit realizes two-sided structure, through two-sided absorbed light, has guaranteed that the absorbed light volume is great, and, first cell unit includes silicon material, second cell unit includes III-V clan compound semiconductor material, and through integrated Si material and III-V clan compound semiconductor material, it is great to have guaranteed that the wavelength range of absorbable sunlight is great, is favorable to the light conversion with different wavelength to electricity, thereby has guaranteed two-sided solar cell's photoelectric conversion efficiency is higher.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application. In the drawings:

FIG. 1 shows a schematic diagram of a bifacial solar cell structure according to one embodiment of the present application;

fig. 2 shows a schematic flow diagram of a method of fabricating a bifacial solar cell according to an embodiment of the present application;

FIG. 3 shows a schematic view of a pulsed laser deposition apparatus according to an embodiment of the present application;

FIG. 4 shows a schematic view of a pulling apparatus according to an embodiment of the present application;

fig. 5 shows a schematic view of a laser cutting device according to an embodiment of the present application.

Wherein the figures include the following reference numerals:

10. a first battery cell; 20. first, theAn electrode; 30. a second battery cell; 40. a tunnel junction structure; 50. a second electrode; 60. a first transparent conductive film; 70. a first antireflection film; 80. a second transparent conductive film; 90. a second antireflection film; 100. a first laser; 101. a first heavily doped layer; 102. a first device layer; 103. a second heavily doped layer; 110. a beam splitter; 120. a first laser beam; 130. a first reflector; 140. a first focusing mirror; 150. a second laser beam; 160. a second reflector; 170. a second focusing mirror; 180. a first laser window; 190. a second laser window; 200. a first reaction chamber; 210. a target material; 220. plasma; 230. a substrate; 240. a target material base; 250. a first rotating rod; 260. a sample stage device; 270. an air inlet; 280. an air outlet; 290. a seed holder; 300. a seed rod; 301. a third heavily doped layer; 302. a second device layer; 303. a fourth heavily doped layer; 310. seed crystal; 320. al (Al)_xGa_1-xAlloy melt; 330. as vapor; 340. an observation window; 350. a heating coil; 360. a second rotating rod; 370. a crucible; 380. a second reaction chamber; 390. a single crystal rod; 400. cutting table; 401. heavily doping the buffer layer; 402. a tunneling layer; 410. a slit; 420. a third laser beam; 430. a second laser; 440. a third reflector; 450. and a third focusing mirror.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the technical solutions better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only partial embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that the terms "first," "second," and the like in the description and claims of this application and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances such that embodiments of the application described herein may be used. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. Also, in the specification and claims, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element or "connected" to the other element through a third element.

As mentioned in the background, in order to solve the problem of low photoelectric conversion efficiency of the solar cell in the prior art, in an exemplary embodiment of the present application, a bifacial solar cell and a method for fabricating the same are provided.

According to an exemplary embodiment of the present application, there is provided a bifacial solar cell, as shown in fig. 1, including a first cell 10, a first electrode 20, a second cell 30, a tunnel junction structure 40, and a second electrode 50, wherein a material of the first cell 10 includes silicon; the first electrode 20 is located on the surface of the first battery cell 10; the second battery cell 30 is located on a side of the first battery cell 10 away from the first electrode 20, and a material of the second battery cell 30 includes a first iii-v compound semiconductor material; the tunnel junction structure 40 is located between the first battery cell 10 and the second battery cell 30, the tunnel junction structure 40 is in contact with the first battery cell 10 and the second battery cell 30, respectively, and a material of the tunnel junction structure 40 includes a second iii-v group compound semiconductor material; the second electrode 50 is located on a surface of the second battery cell 30 away from the tunnel junction structure 40.

The double-sided solar cell comprises a first electrode, a first cell unit, a tunnel junction structure, a second cell unit and a second electrode which are sequentially stacked, wherein the first cell unit is made of silicon; the material of the second battery cell includes a first III-V compound semiconductor material; the material of the tunnel junction structure includes a second iii-v compound semiconductor material. Compare the lower problem of solar cell's among the prior art photoelectric conversion efficiency, the above-mentioned two-sided solar cell of this application, realize two-sided structure through above-mentioned first battery cell and above-mentioned second battery cell, through two-sided absorption light, it is great to have guaranteed that the absorbed light volume is great, and above-mentioned first battery cell includes the silicon material, above-mentioned second battery cell includes III-V clan compound semiconductor material, through integrated Si material and III-V clan compound semiconductor material, it is great to have guaranteed that the wavelength range of absorbable sunlight is great, be favorable to converting the light of different wavelengths into electricity, thereby guaranteed that above-mentioned two-sided solar cell's photoelectric conversion efficiency is higher.

Specifically, since silicon is an indirect band gap material, silicon is a weak light absorber, and when it is applied to a solar cell, it causes relatively large heat loss with respect to an optimal solar band gap value of 1.5eV due to its narrow band gap, whereas in a iii-v group compound solar cell, since it is a direct band gap semiconductor material, the conversion efficiency of the second cell unit is high, and in a iii-v group compound semiconductor solar cell, the temperature rise has little influence on the solar cell characteristics, but the resources for manufacturing the solar cell are small, the material cost is high, and since silicon is rich in raw materials and easy to manufacture, it is ensured that the cost of the first cell unit of the silicon material is low, so that the bifacial solar cell utilizes the advantages of low cost of silicon and high photoelectric conversion efficiency of iii-v group material, the double-sided solar cell has good performance and high photoelectric conversion efficiency.

According to an embodiment of the present disclosure, as shown in fig. 1, the first battery cell 10 includes a first heavily doped layer 101, a first device layer 102, and a second heavily doped layer 103 stacked in this order, and the first heavily doped layer 101 and the second heavily doped layer 103 are doped with different types. The first heavily doped layer and the second heavily doped layer with different doping types ensure that the first battery unit can normally complete the photoelectric conversion action.

According to another embodiment of the present disclosure, as shown in fig. 1, the second battery cell 30 includes a third heavily doped layer 301, a second device layer 302, and a fourth heavily doped layer 303 stacked in this order, wherein the third heavily doped layer 301 and the fourth heavily doped layer 303 are doped with different types. The third heavily doped layer and the fourth heavily doped layer of different doping types ensure that the second battery cell can normally complete a photoelectric conversion operation.

In order to further ensure the normal operation of the bifacial solar cell, according to another embodiment of the present invention, as shown in fig. 1, the tunnel junction structure 40 includes a heavily doped buffer layer 401 and a tunneling layer 402, wherein the tunneling layer 402 is located on a surface of the heavily doped buffer layer 401 away from the first cell unit 10, and the tunneling layer 402 is bonded to the second cell unit 30. The heavily doped buffer layer can buffer the problem of lattice mismatch between the first battery unit and the second battery unit, so that the first battery unit and the second battery unit are not influenced by each other in the preparation process, and meanwhile, the tunnel junction structure has charge transmission capacity, so that the conduction of the first battery unit and the second battery unit is realized.

In order to further ensure high photoelectric conversion efficiency of the double-sided solar cell, according to an embodiment of the present disclosure, as shown in fig. 1, the double-sided solar cell further includes a first transparent conductive film 60, a first anti-reflective film 70, a second transparent conductive film 80, and a second anti-reflective film 90, wherein the first transparent conductive film 60 is located between the first electrode 20 and the first cell unit 10, and the first transparent conductive film 60 is in contact with the first electrode 20; the first antireflection film 70 is disposed on the surface of the first transparent conductive film 60 away from the first electrode 20, and the first antireflection film 70 is in contact with the first battery cell 10; the second transparent conductive film 80 is positioned between the second electrode 50 and the second battery cell 30, and the second transparent conductive film 80 is in contact with the second electrode 50; the second anti-reflective film 90 is disposed on a surface of the second transparent conductive film 80 away from the second electrode 50, and the second anti-reflective film 90 is in contact with the second battery cell 30. The first transparent conductive film and the second transparent conductive film ensure that light can penetrate through and reach the first battery unit and the second battery unit to the maximum extent, and the first antireflection film and the second antireflection film can increase light transmittance by reducing reflection of light, so that light can reach the first battery unit and the second battery unit to the maximum extent, and the photoelectric conversion efficiency of the double-sided solar battery is further ensured to be higher.

According to another embodiment of the present application, the first III-V compound semiconductor material is Al_xGa_1- _xAs, wherein X is more than 0 and less than or equal to 0.8, and the second III-V group compound semiconductor material is GaAs.

Specifically, the double-sided solar cell is prepared by mixing Si and Al_xGa_1-xAs is integrated together, the absorption range of the wavelength is expanded, and light with different wavelengths is converted into electricity, so that the photoelectric conversion efficiency of the double-sided solar cell is further ensured to be high.

According to the embodiment of the application, a manufacturing method of the double-sided solar cell is further provided.

Fig. 2 is a flow chart of a method of fabricating a bifacial solar cell according to an embodiment of the present application. As shown in fig. 2, the method comprises the steps of:

step S101, providing a first battery unit, wherein the material of the first battery unit comprises silicon;

step S102, forming a tunnel junction structure on the surface of the first battery unit, wherein the material of the tunnel junction structure comprises a second III-V group compound semiconductor material;

step S103, forming a second battery unit on the surface of the tunnel junction structure far away from the first battery unit, wherein the material of the second battery unit comprises a first III-V group compound semiconductor material;

step S104 is to form a first electrode on a surface of the first battery cell away from the tunnel junction structure, and to form a second electrode on a surface of the second battery cell away from the tunnel junction structure.

In the manufacturing method of the double-sided solar cell, firstly, a first cell unit made of silicon is provided; then, forming a tunnel junction structure of a material including a second III-V group compound semiconductor material on a surface of the first battery cell; forming a second battery unit on the surface of the tunnel junction structure far away from the first battery unit, wherein the material of the second battery unit comprises a first III-V group compound semiconductor material; finally, a first electrode is formed on a surface of the first cell unit remote from the tunnel junction structure, and a second electrode is formed on a surface of the second cell unit remote from the tunnel junction structure. Compared with the problem that the photoelectric conversion efficiency of a solar cell is low in the prior art, according to the manufacturing method of the double-sided solar cell, the double-sided structure is realized through the first cell unit and the second cell unit, the light absorption quantity is guaranteed to be large through double-sided light absorption, the first cell unit comprises a silicon material, the second cell unit comprises a III-V group compound semiconductor material, the wavelength range of absorbable sunlight is guaranteed to be large through integration of a Si material and the III-V group compound semiconductor material, light with different wavelengths is favorably converted into electricity, and therefore the photoelectric conversion efficiency of the double-sided solar cell is guaranteed to be high.

Specifically, the first electrode and the second electrode each include at least one of Ni, Au, Ti, and Al.

According to an embodiment of the present application, forming a tunnel junction structure on a surface of the first battery cell includes: growing a heavily doped buffer layer on the surface of the first battery unit by adopting a pulse laser deposition method at the reaction temperature of 600-700 ℃, wherein the thickness of the heavily doped buffer layer is 10-2000 nm, the energy of pulse laser is 0.1-1J, and the frequency of the pulse laser is 5-100 Hz; growing a tunneling layer on the surface of the heavily doped buffer layer far away from the first battery unit by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃, wherein the thickness of the tunneling layer is 1-20 nm, and the doping concentration of the tunneling layer is 1 multiplied by 10²⁰/cm³～1×10²¹/cm³. The heavily doped buffer layer can buffer the problem of lattice mismatch between the first battery unit and the second battery unit, so that the first battery unit and the second battery unit are not influenced by each other in the preparation process, and meanwhile, the tunnel junction structure has charge transmission capacity, so that the conduction of the first battery unit and the second battery unit is realized.

Specifically, the working principle of the pulsed laser deposition technology is that the laser induces the surface of the target to form high-temperature plasma, and not only can the plasma radiation spectrum be used to analyze the characteristics of the plasma, but also the plasma afterglow expansion can deposit and prepare thin films and nano materials which are the same as the target on the substrate, based on the femtosecond laser ablation characteristics and the generated plasma characteristics, the femtosecond PLD can be generally divided into the following links, as shown in fig. 3, wherein a first laser 100 emits a laser beam, the laser beam passes through a beam splitter 110, then a first laser beam 120 passes through a first reflector 130 and then is incident on a first focusing mirror 140, wherein a second laser beam 150 reflected by the beam splitter 110 reaches a second reflector 160 and then is incident on a second focusing mirror 170, and the first laser beam 120 and the second laser beam 150 respectively pass through a first laser window 180 and a second laser window 190 and then enter a first reaction chamber 200 and then reach the surface of the target 210, and interacts with the target 210 such that the surface of the target 210 is ablated and a localized high concentration plasma 220 is generated; then, the plasma 220 is transported, after the plasma 220 is formed on the surface of the target 210, isothermal expansion and adiabatic expansion emission are carried out outwards, the high-speed expansion process occurs in tens of nanoseconds, the plasma 220 has micro-explosion property and axial constraint property of emission along the normal direction of the target surface, and the plasma 220 can be transported to the substrate 230 through the characteristics; finally, the film is condensed on the surface of the substrate 230. After the plasma emitted by the expansion is transported to the substrate 230, the film is deposited on the surface of the substrate 230 and the film forming process is started. The target 210 is located on a target base 240, the target base 240 and the target 210 are driven to rotate by a first rotating rod 250, uniformity of the coating is ensured, the substrate 230 is located on a sample stage device 260, and the first reaction chamber 200 further includes an air inlet 270 and an air outlet 280. The formation and growth of the film are the final very critical links of the film prepared by the pulsed laser deposition technology, and directly influence and determine the composition, structure and performance of the film.

According to another specific embodiment of the present application, forming a second battery cell on a surface of the tunnel junction structure remote from the first battery cell includes: providing a crystal bar made of the first III-V group compound semiconductor material, and performing laser cutting on the crystal bar to obtain a second preliminary device layer with the thickness of 10-500 micrometers, wherein the crystal bar is obtained by adopting a crystal pulling method, and the second preliminary device layer comprises a third surface and a fourth surface which are oppositely arranged; doping the third surface with N-type or P-type dopant to form a third heavily doped layer with a doping depth of 2-10 nm, wherein the doping concentration of the third heavily doped layer is 1 × 10¹⁸/cm³～1×10²¹/cm³(ii) a Bonding the doped third surface on the surface of the tunneling layer far away from the heavily doped buffer layer by using a bonding force of 10 kN-50 kN, and keeping the bonding time for 10 s-60 s; forming a fourth heavily doped layer having a doping depth of 2nm to 10nm by doping the bonded fourth surface with P-type or N-type, and forming a second device layer on the remaining second preliminary device layer to obtain the second battery cell, wherein the fourth surface is doped with P-type or N-typeThe doping concentration of the heavily doped layer is 1 × 10¹⁸/cm³～1×10²¹/cm³. By doping the third surface with N-type or P-type dopant and doping the fourth surface with P-type or N-type dopant, it is ensured that the second cell unit can form electron-hole pairs, and that the second cell unit formed of the iii-v group compound semiconductor material can normally complete photoelectric conversion.

In a specific embodiment, the doping of the N-type or the P-type by diffusion or ion implantation specifically includes: to the above n-Al_xGa_1-xImplanting arsenic ions or phosphorus ions into the As single crystal wafer to form the N-type doping; bonding the doped third surface on the surface of the tunneling layer far away from the heavily doped buffer layer, and keeping the bonding time for 10-60 s, wherein the bonding force is 10-50 kN; after bonding, thinning the bonded device to 1-2 μm; and implanting boron ions into the thinned fourth surface to an implantation depth of 2-10 nm to form the P-type doping.

Specifically, there is provided an ingot made of the above-described first iii-v group compound semiconductor material, including: selecting metal Al with the purity of 99.999%, metal Ga and small As blocks, and sequentially putting the Al powder, the small Ga blocks and the small As blocks into a crucible, wherein the molar volume of the small As blocks is equal to the sum of the molar volumes of Ga and Al, and the molar volume ratio of Al to Ga is X: (1-X), wherein the value range of X is more than 0 and less than or equal to 0.8; the reaction chamber was evacuated to a high vacuum of 1X 10^-5Pa; raising the temperature in the reaction chamber to 700-800 deg.c to make the uppermost As in the crucible reach boiling point to form As vapor, filling the As vapor in the reaction chamber, and making the lower Al powder and metal Ga reach melting point to form liquid Al_xGa_1-xAlloying; rotating the crucible at a constant speed to promote uniform dissolution of the As steam and the AlGa alloy, and controlling the rotation speed of the crucible at 1-10 rpm; adding argon As inert gas into the reaction chamber to increase the pressure in the reaction chamber to 4.0 MPa-10.0 MPa and promote the As steam and the Al_xGa_1-xDissolution of the alloy to form Al_xGa_1-xPolycrystalline As; further raising the temperature to 1100-1800 ℃ when the Al is_xGa_1-xAfter the As polycrystalline material is completely melted, As shown in FIG. 4, the seed holder 290 controls the seed crystal 310 to move up and down through the seed shaft 300, the lower surface of the seed crystal 310 and the Al mentioned above_xGa_1-xThe As vapor 330 is dissolved in Al in contact with the alloy melt 320_xGa_1-xAlloy melt 320, then deposited on the lower surface of seed crystal 310; the seed crystal rod 300 controls the seed crystal 310 to move up and down at the speed of 0.1-5 mm/min, and after a certain time of reaction, Al growing on the seed crystal 310 is confirmed through the observation window 340_xGa_1-xWhen the As single crystal reaches the required length, the power supply of the heating coil 350 is turned off, and the second rotating rod 360 is controlled to stop the crucible 370 from rotating; when the temperature in the second reaction chamber 380 is naturally cooled to room temperature, the grown Al is taken out_xGa_1-xAn As single crystal rod.

In one embodiment, as shown in FIG. 5, a single crystal ingot 390 is placed on a cutting table 400, the cutting table 400 having a scale and a slit 410 below to allow a third laser beam 420 to pass through. The third laser beam 420 emitted from the second laser 430 is incident on the third focusing mirror 450 via the third reflecting mirror 440 and then focused on the single crystal rod 390. Since the diameter of the focused third laser beam 420 is small, it is approximately equal to twice the wavelength. Therefore, the cutting surface is narrow, and the single crystal ingot 390 can be cut thin.

Specifically, the heavily doped buffer layer is grown by adopting a pulse laser deposition method, then a high-quality tunneling layer is grown on the surface of the heavily doped buffer layer, which is far away from the first battery unit, by adopting a metal organic chemical vapor deposition method, and finally the second battery unit is integrated by utilizing a wafer bonding method. The preparation method less utilizes a metal organic chemical vapor deposition method to complete epitaxial growth, and ensures that the double-sided solar cell has lower manufacturing cost. In a specific embodiment, the method for manufacturing the bifacial solar cell can be used for industrial large-scale production and preparation.

In addition to the use of the aboveAccording to another embodiment of the present application, the forming a second battery cell on a surface of the tunnel junction structure away from the first battery cell includes: growing a third triple doped layer with the thickness of 2nm to 10nm on the surface of the tunneling layer far away from the heavily doped buffer layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600 ℃ to 1000 ℃, wherein the doping concentration of the third triple doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³(ii) a Growing a second device layer with the thickness of 1-2 mu m on the surface of the third triple doping layer far away from the tunneling layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃; growing a fourth heavily doped layer with the thickness of 2nm to 10nm on the surface of the second device layer far away from the third heavily doped layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600 ℃ to 1000 ℃, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³And obtaining the second battery unit.

According to a specific embodiment of the present application, there is provided a first battery cell including: providing a first initial device layer; texturing the first initial device layer to obtain a first prepared device layer, wherein the first prepared device layer comprises a first surface and a second surface which are oppositely arranged; and doping the first surface with N-type or P-type dopant to form a first heavily doped layer with a doping depth of 0.1-2 μm, doping the second surface with P-type or N-type dopant to form a second heavily doped layer with a doping depth of 0.1-2 μm, and forming a first device layer on the remaining first preliminary device layer to obtain the first battery cell, wherein the doping concentration of the first heavily doped layer is 1 × 10¹⁸/cm³～1×10²⁰/cm³The doping concentration of the second heavily doped layer is 1 × 10¹⁸/cm³～1×10²⁰/cm³. By doping the first surface with N-type or P-type dopant and doping the second surface with P-type or N-type dopantThe first battery unit is ensured to form an electron-hole pair, and the first battery unit formed by the initial device layer is ensured to normally complete the photoelectric conversion action.

In a specific embodiment, the N-type or P-type doping is performed by diffusion or ion implantation, and the doping depth of the first heavily doped layer and the second heavily doped layer is 0.1 μm to 2 μm.

Specifically, the texturing of the first initial device layer includes: placing the silicon wafer in NaOH solution with the concentration of 10 g/L-20 g/L, keeping the temperature in the solution at 70-90 ℃, adding ethanol solution with the concentration of 3 vol% -30 vol% into the NaOH solution, placing the solution for 1 min-30 min, and taking out the Si wafer. And cleaning the taken-out Si wafer with deionized water, and then blowing the Si wafer with nitrogen. The texturing process can form a pyramid-shaped textured surface on the surface of the silicon wafer, so that the silicon wafer is guaranteed to have a good light trapping effect, and the double-sided solar cell is further guaranteed to have high photoelectric conversion efficiency.

According to another specific embodiment of the present application, there is provided a first initial device layer comprising: providing a monocrystalline silicon wafer; polishing the double surfaces of the monocrystalline silicon wafer to obtain the first initial device layer with the thickness of 10-500 mu m; or comprises the following steps: providing a single crystal silicon rod; and cutting the silicon single crystal rod by adopting laser with the wavelength range of 300 nm-500 nm to obtain the first initial device layer with the thickness of 10 mu m-500 mu m.

In a specific embodiment, the double-sided solar cell is a flexible double-sided double-junction solar cell, which is obtained by cutting the single crystal silicon rod by using laser with a wavelength ranging from 300nm to 500nm to obtain the first initial device layer with a thickness ranging from 10 μm to 500 μm.

In order to further ensure high photoelectric conversion efficiency of the bifacial solar cell, according to another embodiment of the present application, after forming a second cell unit on a surface of the tunnel junction structure away from the first cell unit before forming a first electrode on a surface of the first cell unit away from the tunnel junction structure and forming a second electrode on a surface of the second cell unit away from the tunnel junction structure, the method further includes: depositing a first predetermined material on a surface of the first battery cell far away from the tunnel junction structure by using a pulse laser deposition method to form a first antireflection film, and depositing the first predetermined material on a surface of the second battery cell far away from the tunnel junction structure by using a pulse laser deposition method to form a second antireflection film, wherein the first predetermined material comprises at least one of titanium nitride, silicon dioxide and titanium dioxide, and the thicknesses of the first antireflection film and the second antireflection film are respectively 10nm to 50 nm; depositing a second predetermined material on the surface of the first antireflection film far away from the first battery unit by using a pulse laser deposition method to form a first transparent conductive film, and depositing the second predetermined material on the surface of the second antireflection film far away from the second battery unit by using a pulse laser deposition method to form a second transparent conductive film, wherein the second predetermined material comprises indium tin oxide, and the thicknesses of the first transparent conductive film and the second transparent conductive film are respectively 10nm to 50 nm. The first transparent conductive film and the second transparent conductive film ensure that light can penetrate through and reach the first battery unit and the second battery unit to the maximum extent, and the first antireflection film and the second antireflection film can increase light transmittance by reducing reflection of light, so that light can reach the first battery unit and the second battery unit to the maximum extent, and the photoelectric conversion efficiency of the double-sided solar battery is further ensured to be higher.

Specifically, for the cutting of the silicon and the single crystal rod, a short wavelength continuous laser of 300nm to 500nm may be used as the laser wavelength. In a specific embodiment, after forming the first electrode and the second electrode, the method further includes: and cutting the double-sided solar cell into required size by using laser beams, and passivating the end face to prevent light from scattering.

Example 1

Step 1:preparation of the first battery cell. Firstly, taking a piece of N-type Si with two polished surfaces, and texturing the Si piece. Placing the Si sheet in NaOH solution with the concentration of 15g/L, keeping the temperature in the solution at 80 ℃, adding ethanol solution with the concentration of 10 vol% into the NaOH solution, placing the solution for 15min, and taking out the Si sheet. And cleaning the taken-out Si wafer with deionized water, and then blowing the Si wafer with nitrogen. The Si substrate is placed on a base station in a chamber of an ion implanter, and p + and n + doping is carried out on the Si sheet. Firstly, boron ion implantation is carried out on a Si substrate, the implantation depth is 0.5 mu m, and the implantation concentration is 1 multiplied by 10²⁰/cm³Forming p + type doping. Then arsenic ion implantation is carried out on the other surface of the Si substrate, the implantation depth is 0.5 mu m, and the implantation concentration is 1 multiplied by 10²⁰/cm³And forming n + type doping. After the injection is finished, the preparation of the Si substrate battery is finished;

step 2: and preparing an n + -GaAs heavily doped buffer layer. Selecting an n + -type highly doped GaAs target material, and growing an n + -GaAs buffer layer on a p + -Si surface in the Si substrate battery by adopting a pulse laser deposition method (PLD), wherein the growth temperature is 600 ℃, the laser energy is 0.2J, the laser frequency is 10Hz, and the thickness of the buffer layer is 15 nm;

and step 3: n + -Al_0.1Ga_0.9And (4) preparing a tunneling layer. Growing n + -AlGaAs tunnel junction on the n + -GaAs buffer layer by Metal Organic Chemical Vapor Deposition (MOCVD) method at 700 deg.C and with As doping concentration of 1 × 10²⁰/cm³The growth thickness of the film is 3 nm;

and 4, step 4: n-Al_0.1Ga_0.9And (3) preparing the As single crystal rod. Selecting metal Al with the purity of 99.999 percent, metal Ga and As small blocks, putting a layer of Al powder into a crucible, then putting a layer of Ga small blocks, and then putting As blocks on the Ga small blocks. The molar volume of the As lumps is equal to the sum of the molar volumes of Ga and Al. The molar volume ratio of Al to Ga is 1: 9. after the reaction material is filled, the reaction chamber is pumped into a high vacuum state with a vacuum degree of 1 × 10^-5Pa. Then the temperature in the reaction chamber is raised to 700 ℃, the uppermost As in the crucible reaches the boiling point, and As steam is formed and filled in the reaction chamber. Meanwhile, the lower Al powder and the metal Ga reach the melting points to form liquid Al_0.1Ga_0.9And (3) alloying. At this time, the crucible was rotated at a constant speed to promote uniform dissolution of As vapor and Al0.1Ga0.9 alloy melt, and the rotation speed of the crucible was controlled at 5 revolutions/minute. Adding inert gas argon into the reaction chamber to increase the pressure in the reaction chamber to 4.0MPa and promote As steam and Al_0.1Ga_0.9Melting of the alloy melt to form Al_0.1Ga_0.9Polycrystalline As. Then the temperature is further raised to 1100 ℃ when Al is present_0.1Ga_0.9After the As polycrystalline material is completely melted. The seed crystal holder controls the seed crystal to move up and down through the seed crystal rod, and the lower surface of the seed crystal and Al are arranged on the lower surface of the seed crystal_0.1Ga_0.9The alloy melt is kept in a certain gap, and As steam is dissolved in Al_0.1Ga_0.9The alloy melt is deposited on the lower surface of the seed crystal. The seed rod controls the seed to move up and down at the speed of 0.5 mm/min. When the reaction is carried out for 5 hours, Al grows on the seed crystal_0.1Ga_0.9When the As single crystal reaches the desired length, the power supply to the heating coil is turned off to stop the rotation of the crucible. When the temperature in the reaction chamber is naturally cooled to room temperature, the grown Al is taken out_0.1Ga_0.9As single crystal rod, the apparatus is shown in FIG. 4;

and 5: n-Al_0.1Ga_0.9And (4) cutting the As single crystal rod. The single crystal bar is placed on a cutting table, the structure of which is shown in fig. 4. The cutting table is graduated and has a slit below it to allow the laser beam to pass through. Laser beams emitted by the laser are incident to the focusing mirror through the reflecting mirror and then are converged on the single crystal rod. The diameter of the laser beam spot after being converged is very small and is equal to about twice the wavelength. Therefore, the cutting surface is narrow, and the single crystal bar can be cut to be thin. The energy output by the continuous laser is 0.5J, and finally the n-Al is obtained_0.1Ga_0.9The thickness of the As single crystal wafer is 20 μm;

step 6: n-Al_0.1Ga_0.9And doping the As single crystal wafer. Placing n-AlGaAs single crystal wafer on the base station in the ion implanter chamber, and aligning to n-Al_0.1Ga_0.9As single crystal wafer is implanted with arsenic ions to an implantation depth of 2nm and an implantation concentration of 1 × 10²⁰/cm³Forming n + type doping;

and 7: bonding and thinning. The injected n + type Al_0.1Ga_0.9As single crystal wafer bonding to n + -Al_0.1Ga_0.9The As tunnel junction was applied with a bonding force of 10kN and a bonding time of 60 s. After bonding, n-Al is added_0.1Ga_0.9Thinning As to 1 μm;

and 8: p + -Al_0.1Ga_0.9And doping As. For thinned Al_0.1Ga_0.9Implanting ions of boron As with implantation depth of 2nm and implantation concentration of 1 × 10²⁰/cm³Forming p + type doping;

and step 9: and (5) preparing the antireflection film. Depositing Si on the upper and lower surfaces of the cell by PLD (pulsed laser deposition) method₃N₄A titanium thin film with a thickness of 10 nm;

step 10: and (3) preparing the transparent conductive film. Depositing indium tin oxide films on the upper and lower antireflection films by a PLD method, wherein the thickness of the indium tin oxide films is 50 nm;

step 11: preparing an electrode and scribing by laser. The preparation of a front electrode and a back electrode of the solar cell is carried out, wherein the materials of the electrodes are Ni/Au, and the thicknesses of the electrodes are respectively 100nm and 20 nm. The solar chip is then cut with a laser beam to the desired dimensions while the end faces are passivated.

Example 2

The main difference between the embodiment 2 and the embodiment 1 is that the silicon-based double-sided double-junction solar cell is prepared by directly combining PLD and MOCVD without using the technologies of wafer cutting, Czochralski method and the like, and the specific steps are as follows:

step 1: preparation of the first battery cell. Firstly, taking a piece of N-type Si with two polished surfaces, and texturing the Si piece. Placing the Si sheet in NaOH solution with the concentration of 20g/L, keeping the temperature in the solution at 80 ℃, adding ethanol solution with the concentration of 15 vol% into the NaOH solution, placing the solution for 15min, and taking out the Si sheet. And cleaning the taken-out Si wafer with deionized water, and then blowing the Si wafer with nitrogen. The Si substrate is placed on a base station in a chamber of an ion implanter, and p + and n + doping is carried out on the Si sheet. Firstly, boron ions are implanted into a Si substrate to an implantation depth of 0.4 mu mThe concentration of the mixed solution is 1 x 10²⁰/cm³Forming p + type doping. Then arsenic ion implantation is carried out on the other surface of the Si substrate, the implantation depth is 0.4 mu m, and the implantation concentration is 1 multiplied by 10²⁰/cm³And forming n + type doping. After the injection is finished, the preparation of the Si substrate battery is finished;

and step 3: n + -Al_0.1Ga_0.9And (4) preparing a tunneling layer. Growing n + -Al on the n + -GaAs buffer layer by Metal Organic Chemical Vapor Deposition (MOCVD)_0.2Ga_0.8As tunnel junction with growth temperature of 700 deg.C and As doping concentration of 1 × 10²⁰/cm³The growth thickness of the film is 3 nm;

and 4, step 4: n + -Al_0.2Ga_0.8And (5) extending the As layer. In the above n + -Al_0.2Ga_0.8Growing n + -Al on As tunnel junction by MOCVD method_0.2Ga_0.8The As device layer is grown at 700 deg.C with As doping concentration of 1 × 10²⁰/cm³The growth thickness of the film is 2 nm;

and 5: n-Al_0.3Ga_0.7And (5) extending the As layer. In the above n + -Al_0.2Ga_0.8Growing n-Al on the As layer by MOCVD method_0.3Ga_0.7The As layer grows at 750 deg.C and has As doping concentration of 1 × 10¹⁹/cm³The growth thickness of the film is 1 mu m;

step 6: p + -Al_0.6Ga_0.4And (5) extending the As layer. In the above n-Al_0.3Ga_0.7Growing p + -Al on the As layer by MOCVD method_0.6Ga_0.4The As layer grows at 800 deg.C and the doping concentration of B is 1 × 10²⁰/cm³The growth thickness of the film is 50 nm;

and 7: and (5) preparing the antireflection film. Depositing Si3N4 titanium films on the upper and lower surfaces of the cell by adopting a PLD method, wherein the growth temperature is 500 ℃, and the thickness is 20 nm;

and 8: and (3) preparing the transparent conductive film. Depositing indium tin oxide films on the upper and lower antireflection films by a PLD method, wherein the growth temperature is 500 ℃, and the thickness is 50 nm;

and step 9: preparing an electrode and scribing by laser. The preparation of a front electrode and a back electrode of the solar cell is carried out, wherein the materials of the electrodes are Ni/Au, and the thicknesses of the electrodes are respectively 100nm and 20 nm. The solar chip is then cut with a laser beam to the desired dimensions while the end faces are passivated.

Example 3

The main difference between the embodiment 3 and the embodiment 1 is that the thickness of the Si substrate is 10-50 μm by adopting a laser cutting mode, and the AlGaAs sub-battery is epitaxially grown on the Si substrate by utilizing PLD combined with MOCVD, so that the flexible double-sided double-junction solar battery can be realized, and the specific steps are as follows:

step 1: preparation of the first battery cell. Firstly, taking an N-type Si single crystal rod, placing the Si single crystal rod on a laser cutting base station, and cutting the Si single crystal rod by using laser with the wavelength of 350nm, wherein the thickness of a cut Si single crystal wafer is 20 mu m. And after cutting, texturing the Si sheet. Placing the Si sheet in NaOH solution with the concentration of 15g/L, keeping the temperature in the solution at 80 ℃, adding ethanol solution with the concentration of 20 vol% into the NaOH solution, placing the solution for 20min, and taking out the Si sheet. And cleaning the taken-out Si wafer with deionized water, and then blowing the Si wafer with nitrogen. The Si substrate is placed on a base station in a chamber of an ion implanter, and p + and n + doping is carried out on the Si sheet. Firstly, boron ion implantation is carried out on a Si substrate, the implantation depth is 0.5 mu m, and the implantation concentration is 5 multiplied by 10²⁰/cm³Forming p + type doping. Then arsenic ion implantation is carried out on the other surface of the Si substrate, the implantation depth is 0.5 mu m, and the implantation concentration is 5 multiplied by 10²⁰/cm³And forming n + type doping. After the injection is finished, the preparation of the Si substrate battery is finished;

step 2: and preparing an n + -GaAs heavily doped buffer layer. Selecting an n + -type highly doped GaAs target material, and growing an n + -GaAs buffer layer on a p + -Si surface in the Si substrate battery by adopting a pulse laser deposition method (PLD), wherein the growth temperature is 500 ℃, the laser energy is 0.2J, the laser frequency is 10Hz, and the thickness of the buffer layer is 20 nm;

and step 3: n + -Al_0.1Ga_0.9And (4) preparing a tunneling layer. Growing n + -Al on the n + -GaAs buffer layer by Metal Organic Chemical Vapor Deposition (MOCVD)_0.3Ga_0.7As tunnel junction with growth temperature of 700 deg.C and As doping concentration of 1 × 10²⁰/cm³The growth thickness of the film is 2 nm;

and 4, step 4: n + -Al_0.3Ga_0.7And (5) extending the As layer. Growing n + -Al + on the n + -Al0.3Ga0.7As tunnel junction by MOCVD method_0.3Ga_0.7The As device layer is grown at 700 deg.C and the As doping concentration is 5 × 10²⁰/cm³The growth thickness of the film is 3 nm;

and 5: n-Al_0.4Ga_0.6And (5) extending the As layer. In the above n + -Al_0.3Ga_0.7Growing n-n-Al on the As layer by MOCVD method_0.4Ga_0.6The As layer grows at 750 deg.C and has As doping concentration of 1 × 10¹⁹/cm³The growth thickness of the film is 1.5 mu m;

step 6: p + -Al_0.7Ga_0.3And (5) extending the As layer. In the above n-Al_0.4Ga_0.6Growing p + -Al on the As layer by MOCVD method_0.7Ga_0.3The As layer grows at 800 deg.C and the doping concentration of B is 1 × 10²⁰/cm³The growth thickness of the film is 60 nm;

and 7: and (5) preparing the antireflection film. Depositing Si on the upper and lower surfaces of the cell by PLD (pulsed laser deposition) method₃N₄The growth temperature of the titanium film is 500 ℃, and the thickness of the titanium film is 30 nm;

and step 9: preparing an electrode and scribing by laser. The preparation of a front electrode and a back electrode of the solar cell is carried out, the material of the electrodes is Ti/Al/Ti/Au, and the thicknesses of the electrodes are respectively 100nm, 20nm, 50nm and 20 nm. The solar chip is then cut with a laser beam to the desired dimensions while the end faces are passivated.

In the above embodiments of the present invention, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

From the above description, it can be seen that the above-described embodiments of the present application achieve the following technical effects:

1) the double-sided solar cell comprises a first electrode, a first cell unit, a tunnel junction structure, a second cell unit and a second electrode which are sequentially stacked, wherein the first cell unit is made of silicon; the material of the second battery cell includes a first III-V compound semiconductor material; the material of the tunnel junction structure includes a second iii-v compound semiconductor material. Compare the lower problem of solar cell's among the prior art photoelectric conversion efficiency, the above-mentioned two-sided solar cell of this application, realize two-sided structure through above-mentioned first battery cell and above-mentioned second battery cell, through two-sided absorption light, it is great to have guaranteed that the absorbed light volume is great, and above-mentioned first battery cell includes the silicon material, above-mentioned second battery cell includes III-V clan compound semiconductor material, through integrated Si material and III-V clan compound semiconductor material, it is great to have guaranteed that the wavelength range of absorbable sunlight is great, be favorable to converting the light of different wavelengths into electricity, thereby guaranteed that above-mentioned two-sided solar cell's photoelectric conversion efficiency is higher.

2) In the method for manufacturing the bifacial solar cell, first, a first cell unit made of silicon is provided; then, forming a tunnel junction structure of a material including a second III-V group compound semiconductor material on a surface of the first battery cell; forming a second battery unit on the surface of the tunnel junction structure far away from the first battery unit, wherein the material of the second battery unit comprises a first III-V group compound semiconductor material; finally, a first electrode is formed on a surface of the first cell unit remote from the tunnel junction structure, and a second electrode is formed on a surface of the second cell unit remote from the tunnel junction structure. Compared with the problem that the photoelectric conversion efficiency of a solar cell is low in the prior art, according to the manufacturing method of the double-sided solar cell, the double-sided structure is realized through the first cell unit and the second cell unit, the light absorption quantity is guaranteed to be large through double-sided light absorption, the first cell unit comprises a silicon material, the second cell unit comprises a III-V group compound semiconductor material, the wavelength range of absorbable sunlight is guaranteed to be large through integration of a Si material and the III-V group compound semiconductor material, light with different wavelengths is favorably converted into electricity, and therefore the photoelectric conversion efficiency of the double-sided solar cell is guaranteed to be high.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A bifacial solar cell, comprising:

a first battery cell, a material of the first battery cell comprising silicon;

a first electrode on a surface of the first battery cell;

a second cell unit located on a side of the first cell unit distal from the first electrode, the material of the second cell unit comprising a first III-V compound semiconductor material;

a tunnel junction structure between the first battery cell and the second battery cell, the tunnel junction structure in contact with the first battery cell and the second battery cell, respectively, a material of the tunnel junction structure comprising a second III-V compound semiconductor material;

a second electrode on a surface of the second battery cell distal from the tunnel junction structure.

2. The bifacial solar cell of claim 1, wherein the first cell unit comprises a first heavily doped layer, a first device layer, and a second heavily doped layer stacked in this order, the first heavily doped layer being of a different doping type than the second heavily doped layer.

3. The bifacial solar cell of claim 1, wherein the second cell unit comprises a third heavily doped layer, a second device layer, and a fourth heavily doped layer stacked in that order, wherein the third heavily doped layer is of a different doping type than the fourth heavily doped layer.

4. The bifacial solar cell of claim 1, wherein the tunnel junction structure comprises:

heavily doping the buffer layer;

and the tunneling layer is positioned on the surface of the heavy doping buffer layer far away from the first battery unit and is in bonding connection with the second battery unit.

5. The bifacial solar cell of claim 1, further comprising:

a first transparent conductive film between the first electrode and the first cell unit, the first transparent conductive film being in contact with the first electrode;

a first antireflection film on a surface of the first transparent conductive film away from the first electrode, the first antireflection film being in contact with the first battery cell;

a second transparent conductive film between the second electrode and the second cell unit, the second transparent conductive film being in contact with the second electrode;

a second antireflection film on a surface of the second transparent conductive film away from the second electrode, the second antireflection film contacting the second cell.

6. The bifacial solar cell of any one of claims 1 to 5, which isCharacterized in that the first III-V group compound semiconductor material is Al_xGa_1-xAs, wherein X is more than 0 and less than or equal to 0.8, and the second III-V group compound semiconductor material is GaAs.

7. A method of fabricating the bifacial solar cell of any one of claims 1 to 6, comprising:

providing a first battery cell, the material of the first battery cell comprising silicon;

forming a tunnel junction structure on a surface of the first battery cell, a material of the tunnel junction structure comprising a second III-V compound semiconductor material;

forming a second battery cell on a surface of the tunnel junction structure distal from the first battery cell, the material of the second battery cell comprising a first III-V compound semiconductor material;

a first electrode is formed on a surface of the first cell unit distal from the tunnel junction structure, and a second electrode is formed on a surface of the second cell unit distal from the tunnel junction structure.

8. The method of claim 7, wherein forming a tunnel junction structure on a surface of the first cell comprises:

growing a heavily doped buffer layer on the surface of the first battery unit by adopting a pulse laser deposition method at the reaction temperature of 600-700 ℃, wherein the thickness of the heavily doped buffer layer is 10-2000 nm, the energy of pulse laser is 0.1-1J, and the frequency of the pulse laser is 5-100 Hz;

growing a tunneling layer on the surface of the heavily doped buffer layer far away from the first battery unit by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃, wherein the thickness of the tunneling layer is 1-20 nm, and the doping concentration of the tunneling layer is 1 multiplied by 10²⁰/cm³～1×10²¹/cm³。

9. The method of claim 8, wherein forming a second battery cell on a surface of the tunnel junction structure distal from the first battery cell comprises:

providing a crystal bar made of the first III-V group compound semiconductor material, and performing laser cutting on the crystal bar to obtain a second prepared device layer with the thickness of 10-500 micrometers, wherein the crystal bar is obtained by adopting a crystal pulling method, and the second prepared device layer comprises a third surface and a fourth surface which are oppositely arranged;

carrying out N-type or P-type doping on the third surface to form a third heavily doped layer with the doping depth of 2-10 nm, wherein the doping concentration of the third heavily doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³；

Bonding the doped third surface on the surface of the tunneling layer far away from the heavily doped buffer layer by using a bonding force of 10 kN-50 kN, and keeping the bonding time for 10 s-60 s;

performing P-type or N-type doping on the bonded fourth surface to form a fourth heavily doped layer with a doping depth of 2 nm-10 nm, and forming a second device layer on the remaining second preliminary device layer to obtain the second battery unit, wherein the doping concentration of the fourth heavily doped layer is 1 × 10¹⁸/cm³～1×10²¹/cm³。

10. The method of claim 8, wherein forming a second battery cell on a surface of the tunnel junction structure distal from the first battery cell comprises:

growing a third heavily doped layer with the thickness of 2nm to 10nm on the surface of the tunneling layer far away from the heavily doped buffer layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600 ℃ to 1000 ℃, wherein the doping concentration of the third heavily doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³；

Growing a second device layer with the thickness of 1-2 mu m on the surface of the third triple doping layer far away from the tunneling layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃;

growing a fourth heavily doped layer with the thickness of 2nm to 10nm on the surface of the second device layer far away from the third heavily doped layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600 ℃ to 1000 ℃, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10¹⁸/cm³～1×10²¹/cm³And obtaining the second battery unit.

11. The method of claim 7, wherein providing a first battery cell comprises:

providing a first initial device layer;

texturing the first initial device layer to obtain a first prepared device layer, wherein the first prepared device layer comprises a first surface and a second surface which are oppositely arranged;

carrying out N-type or P-type doping on the first surface to form a first heavily doped layer with the doping depth of 0.1-2 mu m, carrying out P-type or N-type doping on the second surface to form a second heavily doped layer with the doping depth of 0.1-2 mu m, and forming a first device layer on the rest first preliminary device layer to obtain the first battery unit, wherein the doping concentration of the first heavily doped layer is 1 x 10¹⁸/cm³～1×10²⁰/cm³The doping concentration of the second heavily doped layer is 1 x 10¹⁸/cm³～1×10²⁰/cm³。

12. The method of claim 11, wherein providing a first initial device layer comprises:

providing a monocrystalline silicon wafer;

polishing the double surfaces of the monocrystalline silicon wafer to obtain the first initial device layer with the thickness of 10-500 mu m; or comprises the following steps:

providing a single crystal silicon rod;

and cutting the silicon single crystal rod by adopting laser with the wavelength range of 300 nm-500 nm to obtain the first initial device layer with the thickness of 10 mu m-500 mu m.

13. The method of any one of claims 7-12, wherein after forming a second cell on a surface of the tunnel junction structure distal from the first cell, before forming a first electrode on the surface of the first cell distal from the tunnel junction structure and forming a second electrode on a surface of the second cell distal from the tunnel junction structure, the method further comprises:

depositing a first predetermined material on the surface of the first battery unit far away from the tunnel junction structure by adopting a pulse laser deposition method to form a first antireflection film, and depositing the first predetermined material on the surface of the second battery unit far away from the tunnel junction structure by adopting a pulse laser deposition method to form a second antireflection film, wherein the first predetermined material comprises at least one of titanium nitride, silicon dioxide and titanium dioxide, and the thicknesses of the first antireflection film and the second antireflection film are respectively 10 nm-50 nm;

depositing a second predetermined material on the surface of the first antireflection film far away from the first battery unit by adopting a pulse laser deposition method to form a first transparent conductive film, and depositing the second predetermined material on the surface of the second antireflection film far away from the second battery unit by adopting a pulse laser deposition method to form a second transparent conductive film, wherein the second predetermined material comprises indium tin oxide, and the thicknesses of the first transparent conductive film and the second transparent conductive film are respectively 10 nm-50 nm.