CN114300564B

CN114300564B - Double-sided solar cell and manufacturing method thereof

Info

Publication number: CN114300564B
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: 2024-04-05
Anticipated expiration: 2041-12-28
Also published as: CN114300564A

Abstract

The application provides a bifacial solar cell and a manufacturing method thereof, wherein the bifacial 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 overlapped, wherein the material of the first cell unit comprises 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. The double-sided structure is realized through the first battery unit and the second battery unit, the light absorption quantity is ensured to be larger through double-sided light absorption, the first battery unit comprises a silicon material, the second battery unit comprises a III-V compound semiconductor material, the wavelength range of absorbable sunlight is ensured to be larger through integrating the Si material and the III-V compound semiconductor material, the light with different wavelengths is favorably converted into electricity, and the photoelectric conversion efficiency of the double-sided solar battery is ensured to be higher.

Description

Double-sided solar cell and manufacturing method thereof

Technical Field

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

Background

The commonly used solar cells can be classified into Si solar cells, cells using inorganic salts such as gallium arsenide III-V compounds, cadmium sulfide, copper indium selenium and other multi-element compounds as materials, solar cells prepared from functional polymer materials, nanocrystalline solar cells and the like according to the materials. Among these, single crystal Si solar cells are the earliest one used by people and have the longest history. The Si atomic arrangement of the single crystal Si solar cell is irregular, the conversion efficiency is highest in the Si solar cell, the theoretical value can reach 24% -26%, and the conversion efficiency of an actual product is 15% -18%. The poly-Si used in Si solar cells is formed by aggregation of single crystal Si particles. The theoretical value of the conversion efficiency of the poly-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 raw materials are more abundant and the manufacturing is easier, so that the use amount is more than that of a single crystal Si solar cell, which is dominant. The polycrystalline thin film solar cell has less raw materials, high efficiency and wider application prospect.

But admittedly, si is a weak light absorber, requiring an absorber layer of several hundred microns thick, because it is an indirect bandgap material, compared to group iii-v compound materials. Furthermore, si, as a photovoltaic material, causes relatively large heat loss with respect to an optimal solar spectral band gap value of 1.5eV, because it is a narrow band gap. The III-V compound solar cell has high conversion efficiency due to the direct band gap semiconductor material, the single junction solar cell has 26% -28% conversion efficiency, and the two-junction and three-junction solar cells can reach 35% -45%. But also can be made into a thin film solar cell with better radiation resistance and temperature characteristics, and is suitable for concentrating power generation. For compound semiconductor solar cells, the temperature rise has little influence on the characteristics of the solar cells, but the resources for manufacturing the solar cells are less, the material cost is higher, and the compound semiconductor solar cells are mainly used in the field of universe power generation at present.

In order to improve the conversion efficiency of solar cells, various approaches have been tried, such as: 1. searching for new materials sensitive from near infrared to ultraviolet; 2. adopting a new laser processing technology to improve the innovation of the solar cell processing technology; 3. maximum power point tracking; 4. the use of a condensing element improves the conversion efficiency. These methods can improve the conversion efficiency of solar cells to various degrees, but progress slowly, and have not been improved substantially.

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

Disclosure of Invention

The main objective of the present application is to provide a bifacial solar cell and a method for manufacturing 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, a first electrode, a second cell, a tunnel junction structure, and a second electrode, wherein a material of the first cell includes silicon; the first electrode is positioned on the surface of the first battery cell; the second battery cell is located on a side of the first battery cell remote from the first electrode, and the material of the second battery cell comprises a first iii-v compound semiconductor material; the tunnel junction structure is positioned between the first battery cell and the second battery cell, the tunnel junction structure is respectively contacted with the first battery cell and the second battery cell, and the 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 remote from the tunnel junction structure.

Optionally, the first battery unit includes a first heavily doped layer, a first device layer, and a second heavily doped layer that are stacked in order, wherein the doping types of the first heavily doped layer and the second heavily doped layer are different.

Optionally, the second battery unit includes a third heavily doped layer, a second device layer, and a fourth heavily doped layer stacked in sequence, wherein the doping type of the third heavily doped layer is different from that of the fourth heavily doped layer.

Optionally, the tunnel junction structure includes a heavily doped buffer layer and a tunneling layer, wherein 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 with 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 positioned 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 film far away from the first electrode, and the first antireflection film is in contact with the first battery cell; the second transparent conductive film is positioned between the second electrode and the second battery unit, and the second transparent conductive film is in contact with the second electrode; the second antireflection film is positioned 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 _x Ga _1-x As, 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 embodiment 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, the material of the tunnel junction structure comprising a second iii-v compound semiconductor material; forming a second cell on a surface of the tunnel junction structure remote from the first cell, the material of the second cell comprising a first iii-v compound semiconductor material; a first electrode is formed on a surface of the first cell remote from the tunnel junction structure, and a second electrode is formed on a surface of the second cell remote from the tunnel junction structure.

Optionally, 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, which is 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 10 ²⁰ /cm ³ ～1×10 ²¹ /cm ³ 。

Optionally, forming a second battery cell on a surface of the tunnel junction structure remote from the first battery cell, including: providing a crystal bar formed by the first III-V compound semiconductor material, and carrying out laser cutting on the crystal bar to obtain a second preparation device layer with the thickness of 10-500 mu m, wherein the crystal bar is obtained by adopting a crystal pulling method, and the second preparation device layer comprises a third surface and a fourth surface which are oppositely arranged; n-type or P-type doping is carried out on the third surface to form a third triple doped layer with doping depth of 2 nm-10 nm, and the doping concentration of the third triple doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ The method comprises the steps of carrying out a first treatment on the surface of the Bonding the doped third surface on the surface of the tunneling layer far away from the heavily doped buffer layer by adopting a bonding force of 10-50 kN, and keeping bonding time for 10-60 s; p-type or N-type doping is carried out on the bonded fourth surface to form a fourth heavily doped layer with doping depth of 2 nm-10 nm, the rest of the second preparation device layers form a second device layer, and the second battery unit is obtained, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ 。

Optionally, forming a second battery cell on a surface of the tunnel junction structure remote from the first battery cell, including: at 600-1000 deg.c Growing a third heavily doped layer with the thickness of 2-10 nm on the surface of the tunneling layer far from the heavily doped buffer layer by adopting a metal organic chemical vapor deposition method at a temperature, wherein the doping concentration of the third heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ The method comprises the steps of carrying out a first treatment on the surface of the Growing a second device layer with the thickness of 1-2 mu m on the surface of the third heavily doped 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 2-10 nm 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 600-1000 ℃, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ And obtaining the second battery unit.

Optionally, providing a first battery unit includes: providing a first initial device layer; texturing the first initial device layer to obtain a first preparation device layer, wherein the first preparation device layer comprises a first surface and a second surface which are oppositely arranged; performing N-type or P-type doping on the first surface to form a first heavily doped layer with doping depth of 0.1-2 mu m, performing P-type or N-type doping on the second surface to form a second heavily doped layer with doping depth of 0.1-2 mu m, and forming a first device layer on the rest of the first preparation device layers to obtain the first battery unit, wherein the doping concentration of the first heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²⁰ /cm ³ The doping concentration of the second heavily doped layer is 1×10 ¹⁸ /cm ³ ～1×10 ²⁰ /cm ³ 。

Optionally, providing a first initial device layer includes: providing a monocrystalline silicon piece; double-sided polishing is carried out on the monocrystalline silicon piece, and the first initial device layer with the thickness of 10-500 mu m is obtained; or comprises: providing a single crystal silicon rod; cutting the single crystal silicon rod by adopting laser with the wavelength range of 300-500 nm to obtain the first initial device layer with the thickness of 10-500 mu m.

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

By applying the technical scheme, the bifacial 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 overlapped, wherein the material of the first cell unit comprises silicon; the material of the second battery cell includes a first iii-v compound semiconductor material; the tunnel junction structure material includes a second III-V compound semiconductor material. Compared with the problem of lower photoelectric conversion efficiency of the solar cell in the prior art, the double-sided solar cell realizes a double-sided structure through the first cell unit and the second cell unit, light is absorbed through double sides, the light absorption quantity is ensured to be larger, the first cell unit comprises a silicon material, the second cell unit comprises a III-V compound semiconductor material, the Si material and the III-V compound semiconductor material are integrated, the absorbable sunlight is ensured to have a larger wavelength range, the light with different wavelengths is converted into electricity, and the photoelectric conversion efficiency of the double-sided solar cell is ensured to be higher.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and 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 do not constitute an undue limitation to 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 flow diagram of a method of fabricating a bifacial solar cell according to an embodiment of the application;

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

FIG. 4 shows a schematic view of a pulling device 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 above figures include the following reference numerals:

10. a first battery cell; 20. a first 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 mirror; 140. a first focusing mirror; 150. a second laser beam; 160. a second mirror; 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. a plasma; 230. a substrate; 240. a target base; 250. a first rotating lever; 260. a sample stage device; 270. an air inlet; 280. an air outlet; 290. a seed holder; 300. seed (seed) A crystal bar; 301. a third heavily doped layer; 302. a second device layer; 303. a fourth heavily doped layer; 310. seed crystal; 320. al (Al) _x Ga _1-x Alloy melt; 330. as vapors; 340. an observation window; 350. a heating coil; 360. a second rotating lever; 370. a crucible; 380. a second reaction chamber; 390. a single crystal bar; 400. a cutting table; 401. a heavily doped buffer layer; 402. a tunneling layer; 410. a slit; 420. a third laser beam; 430. a second laser; 440. a third mirror; 450. and a third focusing mirror.

Detailed Description

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The present application will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

In order to make the present application solution better understood by those skilled in the art, the following description will be made in detail and with reference to the accompanying drawings in the embodiments of the present application, it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, shall fall within the scope of the present application.

It should be noted that the terms "first," "second," and the like in the description and claims of the present application and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate in order to describe the embodiments of the present application described herein. 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. Furthermore, in the description and in the 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 described in the background art, 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 manufacturing 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, the bifacial solar cell includes a first cell 10, a first electrode 20, a second cell 30, a tunnel junction structure 40 and a second electrode 50, wherein the material of the first cell 10 includes silicon; the first electrode 20 is positioned 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 remote from the first electrode 20, and the 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 compound semiconductor material; the second electrode 50 is located on a surface of the second battery cell 30 remote 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 material of the first cell unit comprises silicon; the material of the second battery unit comprises a first III-V compound semiconductor material; the tunnel junction structure material includes a second III-V compound semiconductor material. Compared with the problem of lower photoelectric conversion efficiency of the solar cell in the prior art, the double-sided solar cell of the application realizes a double-sided structure through the first cell unit and the second cell unit, light is absorbed through double sides, the light absorption quantity is ensured to be larger, the first cell unit comprises a silicon material, the second cell unit comprises a III-V compound semiconductor material, the Si material and the III-V compound semiconductor material are integrated, the absorbable sunlight is ensured to have a larger wavelength range, and the light with different wavelengths is converted into electricity, so that the photoelectric conversion efficiency of the double-sided solar cell is ensured to be higher.

Specifically, since silicon is an indirect bandgap material, silicon is a weak light absorber, when it is applied in a solar cell, because it is a narrow bandgap, compared with an optimal solar spectrum bandgap value of 1.5eV, a relatively large heat loss is caused, whereas a iii-v compound solar cell, because it is a direct bandgap semiconductor material, the second cell has a high conversion efficiency, and for a iii-v 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 the silicon is relatively abundant due to the raw materials, and the manufacturing is relatively easy, so that the cost of the first cell of the silicon material is low, and therefore, the double-sided solar cell uses the advantages of low cost of silicon and high photoelectric conversion efficiency of the iii-v material, and ensures the performance of the double-sided solar cell is good and the photoelectric conversion efficiency is high.

According to one embodiment of the present application, 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 that are stacked in order, where the doping types of the first heavily doped layer 101 and the second heavily doped layer 103 are different. The first heavily doped layer and the second heavily doped layer with different doping types ensure that the first battery unit can normally complete photoelectric conversion action.

According to another embodiment of the present application, as shown in fig. 1, the second battery unit 30 includes a third heavily doped layer 301, a second device layer 302, and a fourth heavily doped layer 303 stacked in sequence, where the doping types of the third heavily doped layer 301 and the fourth heavily doped layer 303 are different. The third heavily doped layer and the fourth heavily doped layer with different doping types ensure that the second battery unit can normally complete photoelectric conversion action.

In order to further ensure the normal operation of the bifacial solar cell, according to yet another embodiment of the present application, 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 10, and the tunneling layer 402 is bonded to the second cell 30. The heavily doped buffer layer can buffer the lattice mismatch problem between the first battery unit and the second battery unit, so that the first battery unit and the second battery unit are not affected by each other in the preparation process, and meanwhile, the tunnel junction structure has charge transmission capability, and the conduction between the first battery unit and the second battery unit is realized.

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

According to another embodiment of the present application, the first III-V compound semiconductor material is Al _x Ga _1- _x As, 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 bifacial solar cell is formed by mixing Si and Al _x Ga _1-x As is integrated together to expand the absorption range of the wavelength, which is favorable for converting light with different wavelengths into electricity, thereby further ensuring higher photoelectric conversion efficiency of the double-sided solar cell.

According to the embodiment of the application, a manufacturing method of the bifacial solar cell is also provided.

Fig. 2 is a flow chart of a method of fabricating a bifacial solar cell according to an embodiment of the 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 compound semiconductor material;

step S103, forming a second cell unit on a surface of the tunnel junction structure, which is far away from the first cell unit, wherein a material of the second cell unit comprises a first iii-v compound semiconductor material;

Step S104, forming a first electrode on a surface of the first battery cell away from the tunnel junction structure, and forming a second electrode on a surface of the second battery cell away from the tunnel junction structure.

In the method for manufacturing the bifacial solar cell, first, a first cell unit is provided, wherein the material of the first cell unit comprises silicon; then forming a tunnel junction structure comprising a material of a second III-V compound semiconductor material on a surface of the first battery cell; thereafter, forming a second cell on a surface of the tunnel junction structure remote from the first cell, the material of the second cell comprising a first iii-v compound semiconductor material; finally, a first electrode is formed on a surface of the first battery cell remote from the tunnel junction structure, and a second electrode is formed on a surface of the second battery cell remote from the tunnel junction structure. Compared with the problem of lower photoelectric conversion efficiency of the solar cell in the prior art, the manufacturing method of the double-sided solar cell realizes a double-sided structure through the first cell unit and the second cell unit, ensures that the absorbed light quantity is larger through double-sided light absorption, and ensures that the photoelectric conversion efficiency of the double-sided solar cell is higher through the first cell unit comprising a silicon material and the second cell unit comprising a III-V compound semiconductor material and integrating a Si material and a III-V compound semiconductor material.

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

According to a specific 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, which is 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 10 ²⁰ /cm ³ ～1×10 ²¹ /cm ³ . The heavily doped buffer layer can buffer the lattice mismatch problem between the first battery unit and the second battery unit, so that the first battery unit and the second battery unit are not affected by each other in the preparation process, and meanwhile, the tunnel junction structure has charge transmission capability, and the conduction between the first battery unit and the second battery unit is realized.

Specifically, the working principle of the pulse laser deposition technology is that the laser induces the target surface to form high-temperature plasma, so that the characteristic of the plasma can be analyzed through a plasma radiation spectrum, meanwhile, the plasma afterglow expansion can deposit and prepare a film and a nano material which are the same as the target on a substrate, based on the characteristic of femtosecond laser ablation and the generated plasma characteristic, the femtosecond PLD can be generally divided into the following links, as shown in fig. 3, a first laser 100 emits a laser beam, the first laser beam 120 after passing through a beam splitter 110 is incident on a first focusing mirror 140 through a first reflecting mirror 130, wherein a second laser beam 150 reflected by the beam splitter 110 reaches a second reflecting mirror 160 and is incident on a second focusing mirror 170, the first laser beam 120 and the second laser beam 150 respectively enter the first laser window 180 and the second laser window 190 and then reach the surface of the target 210, and the interaction with the target 210 causes the surface of the target 210 to be ablated and generate localized high concentration 220; then, after the plasma 220 is formed on the surface of the target 210, isothermal expansion and adiabatic expansion emission are performed outwards, and the high-speed expansion process occurs in the moment of tens of nanoseconds, so that the plasma 220 can be transported to the substrate 230 through the characteristics, and the micro-explosion property and the axial restraint of the emission along the normal direction of the target surface are provided; finally, a film is formed on the surface of the substrate 230 by condensation. After the expanding and emitted plasma is transported to the substrate 230, it is deposited on the surface of the substrate 230 and the film forming process is started. Wherein, the target 210 is disposed on the target base 240, the first rotating rod 250 drives the target base 240 and the target 210 to rotate, so as to ensure uniformity of the plating film, the substrate 230 is disposed on the 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 last key links of the pulse laser deposition technology for preparing the film, and directly influence and determine the composition, structure and performance of the film.

According to another 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 formed by the first III-V compound semiconductor material, and performing laser cutting on the crystal bar to obtain a second preparation device layer with the thickness of 10-500 mu m, wherein the crystal bar is obtained by adopting a crystal pulling method, and the second preparation device layer comprises a third surface and a fourth surface which are oppositely arranged; n-type or P-type doping is performed on the third surface to form a third heavily doped layer with a doping depth of 2 nm-10 nm, wherein the doping concentration of the third heavily doped layer is 1×10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ The method comprises the steps of carrying out a first treatment on the surface of the Bonding the doped third surface on the surface of the tunneling layer far away from the heavily doped buffer layer by adopting a bonding force of 10-50 kN, and keeping bonding time for 10-60 s; p-type or N-type doping is carried out on the bonded fourth surface to form a fourth heavily doped layer with doping depth of 2 nm-10 nm, the rest of the second preparation device layers form a second device layer, and the second battery unit is obtained, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ . By performing N-type or P-type doping on the third surface and P-type or N-type doping on the fourth surface, it is ensured that the second battery cell can form electron-hole pairs, and it is ensured that the second battery cell formed of the iii-v compound semiconductor material can normally complete photoelectric conversion actions.

In a specific embodiment, the N-type or P-type doping is performed by diffusion or ion implantation, which specifically includes: to the above n-Al _x Ga _1-x Carrying out arsenic ion or phosphorus ion implantation on the As single crystal wafer to form the N-type doping; bonding the doped third surface to the tunneling layerThe bonding time is kept for 10 s-60 s, and the bonding force is 10 kN-50 kN; after bonding is finished, thinning the bonded device to 1-2 mu m; and carrying out boron ion implantation on the thinned fourth surface, wherein the implantation depth is 2-10 nm, and forming the P-type doping.

Specifically, provided is a crystal rod composed of the first III-V compound semiconductor material, comprising: selecting metal Al with the purity of 99.999%, metal Ga and As small blocks, and sequentially putting the Al powder, the Ga small blocks and the As small blocks into a crucible, wherein the molar volume of the As small blocks is equal to the sum of the molar volumes of Ga and Al, and the molar volume ratio of the Al to the Ga is X: (1-X), wherein X is more than 0 and less than or equal to 0.8; the reaction chamber is pumped into a high vacuum state with the vacuum degree of 1 multiplied by 10 ^-5 Pa; the temperature in the reaction chamber is raised to 700 ℃ to 800 ℃, the As at the uppermost layer in the crucible reaches the boiling point to form As steam, the As steam is filled in the reaction chamber, and simultaneously, the Al powder and the metal Ga at the lower part also reach the melting point to form liquid Al _x Ga _1-x An alloy; the crucible is rotated at a constant speed, so that the As steam and the AlGa alloy are promoted to be uniformly dissolved, and the rotation speed of the crucible is controlled to be 1-10 revolutions per minute; adding inert gas argon into the reaction chamber to increase the pressure in the reaction chamber to 4.0-10.0 MPa, and promoting the As steam and the Al _x Ga _1-x Dissolution of the alloy to form Al _x Ga _1-x As polycrystal; further raising the temperature to 1100-1800 ℃ when the Al is _x Ga _1-x After 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 by the seed rod 300, and the lower surface of the seed crystal 310 is connected with the Al _x Ga _1-x Alloy melt 320 is contacted, and As vapor 330 is dissolved in Al _x Ga _1-x Alloy melt 320 is then deposited on the lower surface of seed crystal 310; the seed rod 300 controls the seed crystal 310 to move up and down at a speed of 0.1 to 5mm/min, and confirms Al grown on the seed crystal 310 through the observation window 340 after a certain time has elapsed from the reaction _x Ga _1-x When the As single crystal reaches the required length, the power supply of the heating coil 350 is turned off to control The second rotating rod 360 is made to stop the rotation of the crucible 370; when the temperature in the second reaction chamber 380 is naturally cooled to room temperature, taking out the grown Al _x Ga _1-x As single crystal rod.

In a specific embodiment, as shown in FIG. 5, the single crystal ingot 390 is placed on a cutting table 400, the cutting table 400 has graduations thereon, and a slit 410 is provided 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 through the third reflecting mirror 440 and then converged on the single crystal rod 390. Since the spot diameter of the third laser beam 420 after focusing is small, it is approximately equal to twice the wavelength. The cutting surface is narrow, and thus the single crystal ingot 390 can be cut thin.

Specifically, the heavily doped buffer layer is grown by 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 a metal organic chemical vapor deposition method, and finally the second battery unit is integrated by a wafer bonding method. The preparation method utilizes the metal organic chemical vapor deposition method to finish epitaxial growth less, and ensures that the manufacturing cost of the double-sided solar cell is lower. In a specific embodiment, the manufacturing method of the bifacial solar cell can be used for industrialized mass production and preparation.

In addition to the techniques of preparing the crystal bar by using the wafer cutting and pulling method, the second battery unit may be prepared by other methods, and according to another embodiment of the present application, the forming a second battery unit on a surface of the tunnel junction structure, which is far from the first battery unit, includes: growing a third heavily doped layer with the thickness of 2-10 nm on the surface of the tunneling layer far from the heavily doped buffer layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃, wherein the doping concentration of the third heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ The method comprises the steps of carrying out a first treatment on the surface of the At 600-1000 deg.C, on the surface of the third doped layer far from the tunneling layer a metal organic chemical vapor deposition method is adopted to grow the film with a thickness of 1 muA second device layer of m-2 μm; growing a fourth heavily doped layer with the thickness of 2-10 nm on the surface of the second device layer far from the third heavily doped layer by adopting a metal organic chemical vapor deposition method at the reaction temperature of 600-1000 ℃, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ The second battery cell described above is obtained.

According to a specific embodiment of the present application, there is provided a first battery cell comprising: providing a first initial device layer; texturing the first initial device layer to obtain a first preparation device layer, wherein the first preparation device layer comprises a first surface and a second surface which are oppositely arranged; the first surface is doped with N type or P type to form a first heavily doped layer with doping depth of 0.1 μm-2 μm, the second surface is doped with P type or N type to form a second heavily doped layer with doping depth of 0.1 μm-2 μm, the rest of the first preparation device layer forms a first device layer to obtain the first battery unit, wherein the doping concentration of the first heavily doped layer is 1×10 ¹⁸ /cm ³ ～1×10 ²⁰ /cm ³ The doping concentration of the second heavily doped layer is 1×10 ¹⁸ /cm ³ ～1×10 ²⁰ /cm ³ . By carrying out N-type or P-type doping on the first surface and carrying out P-type or N-type doping on the second surface, the first battery unit is ensured to form electron-hole pairs, and the first battery unit formed by the initial device layer is ensured to normally complete photoelectric conversion actions.

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 first initial device layer is subjected to texturing, which comprises the following steps: placing the silicon chip 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 3-30 vol% into the NaOH solution, and taking out the Si chip after placing in the solution for 1-30 min. The Si sheet taken out was rinsed with deionized water and then dried with nitrogen. The surface of the silicon wafer can form pyramid-shaped suede in the texturing process, so that the silicon wafer is guaranteed to have good light trapping effect, and the photoelectric conversion efficiency of the double-sided solar cell is further guaranteed to be high.

According to another specific embodiment of the present application, there is provided a first initial device layer comprising: providing a monocrystalline silicon piece; double-sided polishing is carried out on the monocrystalline silicon piece, and the first initial device layer with the thickness of 10-500 mu m is obtained; or comprises: providing a single crystal silicon rod; cutting the single crystal silicon rod by using laser with the wavelength ranging from 300nm to 500nm to obtain the first initial device layer with the thickness ranging from 10 mu m to 500 mu m.

In a specific embodiment, the single crystal silicon rod is cut by using a 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, so that the manufactured double-sided solar cell is a flexible double-sided double-junction solar cell.

In order to further ensure that the photovoltaic conversion efficiency of the bifacial solar cell is high, according to a further specific embodiment of the present application, after forming a first electrode on a surface of the first cell away from the tunnel junction structure and before forming a second electrode on a surface of the second cell away from the tunnel junction structure, the method further comprises, after forming a second cell on a surface of the tunnel junction structure away from the first cell: depositing a first preset 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 preset 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 preset 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 10-50 nm; depositing a second preset material on the surface of the first antireflection film, which is 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 preset material on the surface of the second antireflection film, which is far away from the second battery unit, by adopting a pulse laser deposition method to form a second transparent conductive film, wherein the second preset material comprises indium tin oxide, and the thicknesses of the first transparent conductive film and the second transparent conductive film are respectively 10-50 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 greatest extent, and the first antireflection film and the second antireflection film can increase light transmittance by reducing reflection of the light, so that the light can reach the first battery unit and the second battery unit to the greatest extent, and the photoelectric conversion efficiency of the double-sided solar cell is further ensured to be higher.

Specifically, for the cutting of the silicon and the single crystal rod, a short wave continuous laser with the wavelength of 300-500 nm can be adopted. 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 a required size by using a laser beam, and passivating the end face to prevent light from being emitted.

Example 1

Step 1: preparation of the first battery cell. Firstly, taking a double-side polished N-type Si sheet, and texturing the Si sheet. The Si piece was placed in a NaOH solution having a concentration of 15g/L, the temperature in the solution was maintained at 80 ℃, an ethanol solution having a concentration of 10vol% was added to the NaOH solution, and after the Si piece was placed in the solution for 15 minutes, the Si piece was taken out. The Si sheet taken out was rinsed with deionized water and then dried with nitrogen. The Si substrate was placed on a pedestal within the chamber of the ion implanter and p+ and n+ doping was performed on the Si wafer. Firstly, performing boron ion implantation on Si substrate with implantation depth of 0.5 μm and implantation concentration of 1×10 ²⁰ /cm ³ A p + type doping is formed. 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 10 ²⁰ /cm ³ An n + type doping is formed.After the injection is finished, the preparation of the Si substrate battery is finished;

step 2: and (3) preparing an n+ -GaAs heavily doped buffer layer. An n+ type high doped GaAs target material is selected, a pulse laser deposition method (PLD) is adopted to grow an n+ -GaAs buffer layer on a p+ -Si surface in the Si substrate battery, the growth temperature is 600 ℃, the laser energy is 0.2J, the laser frequency is 10Hz, and the thickness of the buffer layer is 15nm;

step 3: n+ -Al _0.1 Ga _0.9 Preparation of the tunneling layer. Growing n+ -AlGaAs tunnel junction on the n+ -GaAs buffer layer by Metal Organic Chemical Vapor Deposition (MOCVD) method at 700deg.C with As doping concentration of 1×10 ²⁰ /cm ³ The film growth thickness is 3nm;

step 4: n-Al _0.1 Ga _0.9 And (5) preparing an As single crystal rod. Selecting metal Al, metal Ga and As small blocks with purity of 99.999%, putting a layer of Al powder into a crucible, then putting a layer of Ga small blocks, and then putting an As block on the Ga small blocks. The molar volume of the As block 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, and the vacuum degree is 1 multiplied by 10 ^-5 Pa. 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. At the same time, the lower Al powder and metal Ga reach the melting point to form liquid Al _0.1 Ga _0.9 And (3) alloy. 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 rpm. 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 _0.1 Ga _0.9 Dissolving the alloy melt to form Al _0.1 Ga _0.9 As is polycrystalline. Then the temperature is further raised to 1100 ℃ when Al _0.1 Ga _0.9 The As polycrystalline material is completely melted. The seed crystal holder controls the seed crystal to move up and down through the seed rod, and the lower surface of the seed crystal is connected with Al _0.1 Ga _0.9 The alloy melt keeps a certain gap, and As vapor is dissolved in Al _0.1 Ga _0.9 In the alloy melt, then deposited on the lower surface of the seed crystal.The seed rod controls the seed crystal to move up and down, and the speed is 0.5mm/min. After 5 hours of reaction, al grows on the seed crystal _0.1 Ga _0.9 When the As single crystal reaches the required length, the power supply of the heating coil is turned off, and the crucible stops rotating. When the temperature in the reaction chamber is naturally cooled to room temperature, taking out the grown Al _0.1 Ga _0.9 As single crystal rod, the device is shown in figure 4;

step 5: n-Al _0.1 Ga _0.9 Cutting the As single crystal rod. The single crystal rod was placed on a cutting table having a structure as shown in FIG. 4. The cutting table has graduations thereon and a slit below to allow the laser beam to pass through. The laser beam emitted by the laser is incident to the focusing mirror through the reflecting mirror and then converged on the single crystal rod. Since the spot diameter of the converged laser beam is small, it is approximately equal to twice the wavelength. Therefore, the cutting surface is narrow, and the single crystal rod can be cut thin. The energy output by the continuous laser is 0.5J, and finally n-Al is obtained _0.1 Ga _0.9 The thickness of As single crystal wafer is 20 μm;

step 6: n-Al _0.1 Ga _0.9 Doping of As single crystal wafers. Placing an n-AlGaAs single crystal wafer on a base station in a chamber of an ion implanter to n-Al _0.1 Ga _0.9 Arsenic ion implantation is carried out on the As single crystal wafer, the implantation depth is 2nm, and the implantation concentration is 1 multiplied by 10 ²⁰ /cm ³ Forming n+ type doping;

step 7: bonding and thinning. N+ type Al after injection _0.1 Ga _0.9 As single crystal wafer bonded to n+ -Al _0.1 Ga _0.9 On an As tunnel junction, a bonding force of 10kN was applied with a bonding time of 60s. After bonding is completed, n-Al is added _0.1 Ga _0.9 As is thinned to a thickness of 1 mu m;

step 8: p+ -Al _0.1 Ga _0.9 Doping of As. For Al after thinning _0.1 Ga _0.9 Ion implantation of As is carried out, the implanted ions are boron ions, the implantation depth is 2nm, and the implantation concentration is 1 multiplied by 10 ²⁰ /cm ³ Forming p+ type doping;

step 9: and (3) preparing an antireflection film. Depositing Si on the upper and lower surfaces of the battery by PLD method ₃ N ₄ Titanium film with thickness of 10nm;

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

step 11: electrode preparation and laser scribing. And preparing a front electrode and a back electrode of the solar cell, wherein the electrode is made of Ni/Au, and the thickness of the electrode is 100nm and 20nm respectively. Then the solar chip is cut by laser beam, cut into the required size and the end face is passivated.

Example 2

The main difference between example 2 and example 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, pulling method and the like, and the specific steps are as follows:

step 1: preparation of the first battery cell. Firstly, taking a double-side polished N-type Si sheet, and texturing the Si sheet. The Si piece was placed in a NaOH solution having a concentration of 20g/L, the temperature in the solution was maintained at 80 ℃, an ethanol solution having a concentration of 15vol% was added to the NaOH solution, and after the Si piece was placed in the solution for 15 minutes, the Si piece was taken out. The Si sheet taken out was rinsed with deionized water and then dried with nitrogen. The Si substrate was placed on a pedestal within the chamber of the ion implanter and p+ and n+ doping was performed on the Si wafer. Firstly, performing boron ion implantation on Si substrate with implantation depth of 0.4 μm and implantation concentration of 1×10 ²⁰ /cm ³ A p + type doping is formed. 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 10 ²⁰ /cm ³ An n + type doping is formed. After the injection is finished, the preparation of the Si substrate battery is finished;

Step 3: n+ -Al _0.1 Ga _0.9 Preparation of the tunneling layer. The metal organic chemical vapor phase is adopted on the n+ -GaAs buffer layerDeposition (MOCVD) process for growing n+ -Al _0.2 Ga _0.8 As tunnel junction with growth temperature of 700 deg.C and doping concentration of As of 1×10 ²⁰ /cm ³ The film growth thickness is 3nm;

step 4: n+ -Al _0.2 Ga _0.8 Epitaxy of the As layer. Above n+ -Al _0.2 Ga _0.8 MOCVD method is adopted to grow n+ -Al on As tunnel junction _0.2 Ga _0.8 As device layer with growth temperature of 700 deg.C and doping concentration of As of 1×10 ²⁰ /cm ³ The film growth thickness is 2nm;

step 5: n-Al _0.3 Ga _0.7 Epitaxy of the As layer. Above n+ -Al _0.2 Ga _0.8 Growing n-Al on As layer by MOCVD method _0.3 Ga _0.7 As layer, growth temperature of 750 ℃, doping concentration of As of 1×10 ¹⁹ /cm ³ The film growth thickness is 1 μm;

step 6: p+ -Al _0.6 Ga _0.4 Epitaxy of the As layer. The above n-Al _0.3 Ga _0.7 The P+ -Al is grown on the As layer by MOCVD method _0.6 Ga _0.4 As layer, growth temperature of 800 deg.C, doping concentration of B of 1×10 ²⁰ /cm ³ The film growth thickness is 50nm;

step 7: and (3) preparing an antireflection film. Depositing Si3N4 titanium films on the upper and lower surfaces of the battery by adopting a PLD method, wherein the growth temperature is 500 ℃, and the thickness is 20nm;

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

step 9: electrode preparation and laser scribing. And preparing a front electrode and a back electrode of the solar cell, wherein the electrode is made of Ni/Au, and the thickness of the electrode is 100nm and 20nm respectively. Then the solar chip is cut by laser beam, cut into the required size and the end face is passivated.

Example 3

The main difference between example 3 and example 1 is that by using a laser cutting method to achieve a thickness of 10 μm to 50 μm of the Si substrate, a flexible double-sided double-junction solar cell can be achieved by using PLD in combination with MOCVD to epitaxially grow AlGaAs subcells on the Si substrate, which comprises the following specific steps:

step 1: preparation of the first battery cell. Firstly, an N-type Si single crystal rod is taken, the Si single crystal rod is placed on a laser cutting base, the Si single crystal rod is cut by utilizing laser with the wavelength of 350nm, and the thickness of a cut Si single crystal wafer is 20 mu m. After cutting, the Si sheet is subjected to texturing. The Si pieces were placed in a NaOH solution having a concentration of 15g/L, the temperature in the solution was maintained at 80 ℃, an ethanol solution having a concentration of 20vol% was added to the NaOH solution, and after placing in the solution for 20 minutes, the Si pieces were taken out. The Si sheet taken out was rinsed with deionized water and then dried with nitrogen. The Si substrate was placed on a pedestal within the chamber of the ion implanter and p+ and n+ doping was performed on the Si wafer. Firstly, performing boron ion implantation on Si substrate with implantation depth of 0.5 μm and implantation concentration of 5×10 ²⁰ /cm ³ A p + type doping is formed. 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 10 ²⁰ /cm ³ An n + type doping is formed. After the injection is finished, the preparation of the Si substrate battery is finished;

step 2: and (3) preparing an n+ -GaAs heavily doped buffer layer. An n+ type high doped GaAs target material is selected, a pulse laser deposition method (PLD) is adopted to grow an n+ -GaAs buffer layer on a p+ -Si surface in the Si substrate battery, the growth temperature is 500 ℃, the laser energy is 0.2J, the laser frequency is 10Hz, and the thickness of the buffer layer is 20nm;

step 3: n+ -Al _0.1 Ga _0.9 Preparation of the tunneling layer. Growing n+ -Al on the n+ -GaAs buffer layer by Metal Organic Chemical Vapor Deposition (MOCVD) _0.3 Ga _0.7 As tunnel junction with growth temperature of 700 deg.C and doping concentration of As of 1×10 ²⁰ /cm ³ The film growth thickness is 2nm;

step 4: n+ -Al _0.3 Ga _0.7 Epitaxy of the As layer. Growing n+ -Al on the n+ -Al0.3Ga0.7As tunnel junction by MOCVD method _0.3 Ga _0.7 As device layer with growth temperature of 700 deg.C and doping concentration of As of 5×10 ²⁰ /cm ³ The film growth thickness is 3nm;

step 5: n-Al _0.4 Ga _0.6 Epitaxy of the As layer. Above n+ -Al _0.3 Ga _0.7 Growing n-n-Al on As layer by MOCVD method _0.4 Ga _0.6 As layer, growth temperature of 750 ℃, doping concentration of As of 1×10 ¹⁹ /cm ³ The film growth thickness is 1.5 μm;

step 6: p+ -Al _0.7 Ga _0.3 Epitaxy of the As layer. The above n-Al _0.4 Ga _0.6 The P+ -Al is grown on the As layer by MOCVD method _0.7 Ga _0.3 As layer, growth temperature of 800 deg.C, doping concentration of B of 1×10 ²⁰ /cm ³ The film growth thickness is 60nm;

step 7: and (3) preparing an antireflection film. Depositing Si on the upper and lower surfaces of the battery by PLD method ₃ N ₄ The growth temperature of the titanium film is 500 ℃, and the thickness of the titanium film is 30nm;

step 9: electrode preparation and laser scribing. The front electrode and the back electrode of the solar cell are prepared, the materials of the electrodes are Ti/Al/Ti/Au, and the thicknesses of the electrodes are 100nm, 20nm, 50nm and 20nm respectively. Then the solar chip is cut by laser beam, cut into the required size and the end face is passivated.

In the foregoing embodiments of the present invention, the descriptions of the embodiments are emphasized, and for a portion of this disclosure that is not described in detail in this embodiment, reference is made to the related descriptions of other embodiments.

From the above description, it can be seen that the above 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 material of the first cell unit comprises silicon; the material of the second battery unit comprises a first III-V compound semiconductor material; the tunnel junction structure material includes a second III-V compound semiconductor material. Compared with the problem of lower photoelectric conversion efficiency of the solar cell in the prior art, the double-sided solar cell of the application realizes a double-sided structure through the first cell unit and the second cell unit, light is absorbed through double sides, the light absorption quantity is ensured to be larger, the first cell unit comprises a silicon material, the second cell unit comprises a III-V compound semiconductor material, the Si material and the III-V compound semiconductor material are integrated, the absorbable sunlight is ensured to have a larger wavelength range, and the light with different wavelengths is converted into electricity, so that the photoelectric conversion efficiency of the double-sided solar cell is ensured to be 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 comprising a material of a second III-V compound semiconductor material on a surface of the first battery cell; thereafter, forming a second cell on a surface of the tunnel junction structure remote from the first cell, the material of the second cell comprising a first iii-v compound semiconductor material; finally, a first electrode is formed on a surface of the first battery cell remote from the tunnel junction structure, and a second electrode is formed on a surface of the second battery cell remote from the tunnel junction structure. Compared with the problem of lower photoelectric conversion efficiency of the solar cell in the prior art, the manufacturing method of the double-sided solar cell realizes a double-sided structure through the first cell unit and the second cell unit, ensures that the absorbed light quantity is larger through double-sided light absorption, and ensures that the photoelectric conversion efficiency of the double-sided solar cell is higher through the first cell unit comprising a silicon material and the second cell unit comprising a III-V compound semiconductor material and integrating a Si material and a III-V compound semiconductor material.

The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for manufacturing a double-sided solar cell is characterized in that,

the bifacial solar cell includes:

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

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

a second battery cell located on a side of the first battery cell remote from the first electrode, the material of the second battery cell comprising a first iii-v compound semiconductor material;

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

a second electrode located on a surface of the second battery cell remote from the tunnel junction structure

The method comprises the following steps:

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, the material of the tunnel junction structure comprising a second iii-v compound semiconductor material;

forming a second cell on a surface of the tunnel junction structure remote from the first cell, the material of the second cell comprising a first iii-v compound semiconductor material;

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,

forming a tunnel junction structure on a surface of the first battery cell, comprising:

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, which is 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 10 ²⁰ /cm ³ ～1×10 ²¹ /cm ³ ，

Forming a second cell on a surface of the tunnel junction structure remote from the first cell, comprising:

providing a crystal bar formed by the first III-V compound semiconductor material, and carrying out laser cutting on the crystal bar to obtain a second preparation device layer with the thickness of 10-500 mu m, wherein the crystal bar is obtained by adopting a crystal pulling method, and the second preparation device layer comprises a third surface and a fourth surface which are oppositely arranged;

n-type or P-type doping is carried out on the third surface to form a third triple doped layer with doping depth of 2 nm-10 nm, and the doping concentration of the third triple doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ ；

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

p-type or N-type doping is carried out on the bonded fourth surface to form a fourth heavily doped layer with doping depth of 2 nm-10 nm, the rest of the second preparation device layers form a second device layer, and the second battery unit is obtained, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ 。

2. The method of claim 1, wherein the first battery cell comprises a first heavily doped layer, a first device layer, and a second heavily doped layer stacked in sequence, the first heavily doped layer being of a different doping type than the second heavily doped layer.

3. The method of claim 1, wherein the second battery cell comprises a third heavily doped layer, a second device layer, and a fourth heavily doped layer stacked in sequence, wherein the doping type of the third heavily doped layer is different from the doping type of the fourth heavily doped layer.

4. The method of claim 1, wherein the tunnel junction structure comprises:

a heavily doped buffer layer;

and the tunneling layer is positioned on the surface, far away from the first battery unit, of the heavily doped buffer layer, and the tunneling layer is connected with the second battery unit in a bonding way.

5. The method of claim 1, wherein the bifacial solar cell further comprises:

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

And the second antireflection film is positioned on the surface, far away from the second electrode, of the second transparent conductive film, and the second antireflection film is in contact with the second battery unit.

6. According to claimThe method of any one of claims 1 to 5, wherein the first group iii-v compound semiconductor material is Al _x Ga _1-x As, 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. The method of claim 1, wherein forming a second cell on a surface of the tunnel junction structure remote from the first cell comprises:

growing a third heavily doped layer with the thickness of 2-10 nm 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 600-1000 ℃, wherein the doping concentration of the third heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ ；

Growing a second device layer with the thickness of 1-2 mu m on the surface of the third heavily doped 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 2-10 nm 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 600-1000 ℃, wherein the doping concentration of the fourth heavily doped layer is 1 multiplied by 10 ¹⁸ /cm ³ ～1×10 ²¹ /cm ³ And obtaining the second battery unit.

8. The method of claim 1, wherein providing a first battery cell comprises:

providing a first initial device layer;

texturing the first initial device layer to obtain a first preparation device layer, wherein the first preparation 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 doping depth of 0.1-2 mu m, and P-type or N-type doping is carried out on the second surface to form a heavily doped layer with doping depth of 0A second heavily doped layer with a thickness of 1-2 μm, and the rest of the first preparation device layer forms a first device layer to obtain the first battery unit, wherein the doping concentration of the first heavily doped layer is 1×10 ¹⁸ /cm ³ ～1×10 ²⁰ /cm ³ The doping concentration of the second heavily doped layer is 1×10 ¹⁸ /cm ³ ～1×10 ²⁰ /cm ³ 。

9. The method of claim 8, wherein providing a first initial device layer comprises:

providing a monocrystalline silicon piece;

double-sided polishing is carried out on the monocrystalline silicon piece, and the first initial device layer with the thickness of 10-500 mu m is obtained;

or comprises:

providing a single crystal silicon rod;

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

10. The method of any one of claims 1, 7 to 9, wherein a first electrode is formed on a surface of the first cell remote from the tunnel junction structure, and wherein after forming a second cell on a surface of the tunnel junction structure remote from the first cell, before forming a second electrode on a surface of the second cell remote from the tunnel junction structure, the method further comprises:

depositing a first preset 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 preset 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 preset 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 10-50 nm;

depositing a second predetermined material on a surface of the first antireflection film, which is far from the first battery cell, using a pulse laser deposition method to form a first transparent conductive film, and depositing the second predetermined material on a surface of the second antireflection film, which is far from the second battery cell, using a pulse laser deposition method to form a second transparent conductive film,

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.