Solar cell and method for preparing solar cell

Abstract

This disclosure provides a solar cell and its fabrication method, comprising: a solar cell substrate, a transparent conductive film, a first copper seed layer, a second copper seed layer, and grid electrodes; the transparent conductive film is prepared by annealing, the annealing being carried out in an annealing atmosphere including a protective gas and maintaining a constant annealing temperature; the first copper seed layer is prepared by vapor deposition, and the second copper seed layer is prepared by sputtering. By combining the annealing of the transparent conductive film with the vapor deposition of the first copper seed layer, damage to the transparent conductive film during the copper seed layer fabrication process can be minimized, reducing the number of voids generated on the transparent conductive film, thereby improving the electrical contact performance and transmittance degradation of the transparent conductive film during the copper seed layer fabrication process, and increasing the conversion efficiency of the solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a solar cell and a method for preparing the solar cell. Background Art

[0002] Solar energy is a completely clean energy source. Large-scale utilization of solar energy will help reduce the demand for fossil energy and meet the requirements of current sustainable development. Solar cells can convert solar energy into electrical energy and are considered an effective way to utilize solar energy.

[0003] The grid electrode is used to conduct the photocurrent in the solar cell to the external circuit and is an important part of the solar cell. Taking the heterojunction solar cell (Heterojunction with Intrinsic Thinfilm, HJT) as an example, the preparation process of the grid electrode in the heterojunction solar cell usually includes double-sided screen printing of silver paste. This preparation method consumes a large amount of silver paste, which obviously leads to a high production cost of heterojunction solar cells.

[0004] In order to reduce production costs, many current studies have gradually turned to the preparation of copper grid electrodes through processes such as copper electroplating. The preparation process of copper grid electrodes usually includes the preparation of a copper seed layer and the electroplating of copper on the copper seed layer. The copper seed layer is usually prepared by magnetron sputtering. This preparation method has the following problems. On the one hand, during the preparation of the copper seed layer, the sputtered copper atoms have high energy and will collide and form tiny holes on the transparent conductive film below. These holes will not only increase the reflection of light, but also deteriorate the electrical contact performance between the copper seed layer and the transparent conductive film. On the other hand, the magnetron sputtering method will also produce copper ions with higher energy. These copper ions can be injected into the transparent conductive film, resulting in the deterioration of the transmittance of the transparent conductive film. The combined effect of the above factors ultimately leads to a significant reduction in the efficiency of solar cells. Summary of the invention

[0005] In view of this, in order to improve the conversion efficiency of solar cells, it is necessary to provide a solar cell.

[0006] An embodiment of the present disclosure provides a solar cell, comprising: a solar cell substrate, a transparent conductive film, a first copper seed layer, a second copper seed layer and a gate electrode, wherein the transparent conductive film, the first copper seed layer, the second copper seed layer and the gate electrode are sequentially stacked on at least one side surface of the solar cell substrate;

[0007] The transparent conductive film is a transparent conductive film prepared after annealing treatment, and the annealing treatment is carried out in a vacuum environment and the annealing temperature is kept constant; the first copper seed layer is prepared by evaporation, and the second copper seed layer is prepared by sputtering.

[0008] In some embodiments of the present disclosure, the carrier concentration of the transparent conductive film prepared after annealing is 10 21 / cm 3 above.

[0009] Furthermore, the present disclosure also provides a method for preparing the solar cell of the above embodiment, which comprises the following steps:

[0010] Providing the solar cell substrate, on which a transparent conductive film precursor is stacked;

[0011] Placing the transparent conductive film precursor in a vacuum environment, performing annealing treatment on the transparent conductive film precursor, maintaining the annealing temperature constant, and forming the transparent conductive film;

[0012] Depositing the first copper seed layer on the transparent conductive film by evaporation;

[0013] depositing the second copper seed layer on the first copper seed layer by sputtering;

[0014] A gate line electrode is formed on the second copper seed layer.

[0015] In some examples of this embodiment, in the step of annealing the transparent conductive film, hydrogen and a protective gas are continuously introduced into the annealing chamber, and the protective gas is selected from one or more of nitrogen, argon, helium and neon; and / or,

[0016] In the step of annealing the transparent conductive film, the annealing temperature is controlled to be 100° C. to 200° C.

[0017] In some examples of this embodiment, in the step of depositing the first copper seed layer, hydrogen and protective gas are introduced into a deposition chamber to form an ion flow, and the ion flow bombards the copper target to generate copper atoms, and the generated copper atoms diffuse onto the transparent conductive film to form the first copper seed layer.

[0018] In some examples of this embodiment, in the step of depositing the first copper seed layer, the deposition temperature is controlled to be above 1600° C.

[0019] In some examples of this embodiment, the thickness of the prepared first copper seed layer is controlled to be 20 nm to 100 nm.

[0020] In some examples of this embodiment, in the step of depositing the first copper seed layer, the deposition rate is controlled to be 0.1 nm / s to 3.0 nm / s; and / or

[0021] Control the evaporation power to ≤10kW.

[0022] In some examples of this embodiment, the thickness of the prepared second copper seed layer is controlled to be 100 nm to 200 nm.

[0023] In some examples of this embodiment, in the step of depositing the second copper seed layer, the deposition temperature is controlled to be 20° C. to 60° C.

[0024] The solar cell provided in the present disclosure includes a solar cell substrate, a transparent conductive film, a first copper seed layer, a second copper seed layer and a gate electrode. The transparent conductive film is a transparent conductive film prepared after annealing treatment, the annealing treatment is carried out in an annealing atmosphere including a protective gas and the annealing temperature is kept constant; the first copper seed layer is prepared by evaporation, and the second copper seed layer is prepared by sputtering.

[0025] The copper seed layer in the conventional technology is usually directly prepared on the transparent conductive film by magnetron sputtering. Compared with the conventional technology, the solar cell has at least the following beneficial effects: the crystallinity and density of the transparent conductive film after annealing can be significantly improved, so it has a higher surface resistance, and the energy of the copper atoms produced by evaporation is lower. By matching the annealed transparent conductive film and the evaporated first copper seed layer, the damage to the transparent conductive film during the preparation of the copper seed layer can be reduced as much as possible, and the holes generated on the transparent conductive film can be reduced, thereby improving the problem of electrical contact performance and permeability degradation of the transparent conductive film during the preparation of the copper seed layer, and improving the conversion efficiency of the solar cell. Furthermore, the combination of the first copper seed layer and the second copper seed layer ensures the adhesion and conductivity of the overall copper seed layer, and makes it suitable for further forming a gate electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A method for preparing a solar cell in one embodiment of the present disclosure is shown;

[0027] Figure 2 Shows Figure 1 A schematic diagram of the structure of the solar cell substrate provided in step S1 of the preparation method;

[0028] Figure 3 Shows Figure 1 Schematic diagram of the device structure prepared in step S2 of the preparation method;

[0029] Figure 4Shows Figure 1 Schematic diagram of the device structure prepared in step S3 of the preparation method;

[0030] Figure 5 Shows Figure 1 Schematic diagram of the device structure prepared in step S4 of the preparation method;

[0031] Figure 6 Shows Figure 1 A schematic diagram of the structure of a solar cell prepared by the preparation method;

[0032] The reference numerals and their meanings are as follows:

[0033] 100, substrate; 111, front intrinsic amorphous silicon layer; 112, front doped amorphous silicon layer; 113, front transparent conductive film; 1130, front transparent conductive film precursor; 114, front first copper seed layer; 115, front second copper seed layer; 116, front gate electrode; 121, back intrinsic amorphous silicon layer; 122, back doped amorphous silicon layer; 123, back transparent conductive film; 1230, back transparent conductive film precursor; 124, back first copper seed layer; 115, back second copper seed layer; 116, back gate electrode. DETAILED DESCRIPTION

[0034] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items, and "more" used herein includes two or more items.

[0036] In the present invention, unless otherwise stated, the sum of the parts of each component in the composition can be 100 parts by weight. Unless otherwise specified, the basis of the percentages (including weight percentages) of the present invention is the total weight of the composition. In addition, "wt%" herein means mass percentage, and "at%" means atomic percentage.

[0037] In this article, unless otherwise stated, each reaction step may be carried out in the order described herein or may not be carried out in the order described herein. For example, other steps may be included between each reaction step, and the order of the reaction steps may also be appropriately swapped. This can be determined by the technician based on common knowledge and experience. Preferably, the reaction method herein is carried out sequentially.

[0038] An embodiment of the present disclosure provides a solar cell, which includes: a solar cell substrate, a transparent conductive film, a first copper seed layer, a second copper seed layer and a gate electrode, wherein the transparent conductive film, the first copper seed layer, the second copper seed layer and the gate electrode are sequentially stacked on at least one side surface of the solar cell substrate; the transparent conductive film is a transparent conductive film prepared after annealing treatment, the annealing treatment is carried out in a vacuum environment and the annealing temperature is kept constant; the first copper seed layer is prepared by evaporation, and the second copper seed layer is prepared by sputtering.

[0039] It is understood that in addition to the photovoltaic effect functional structure located in the inner layer, the solar cell also has a transparent conductive film and a grid electrode located on the outer side. The solar cell substrate refers to a semi-finished solar cell with a transparent conductive film but no grid electrode located on the surface. The source of the solar cell substrate can be a commercially available semi-finished product that has not yet been prepared with a grid electrode, or a semi-finished solar cell prepared in a previous process.

[0040] It can be understood that when the transparent conductive film on the solar cell substrate is annealed, the transparent conductive film needs to be heated to a preset annealing temperature to improve the crystal structure inside the transparent conductive film.

[0041] It can be understood that when the first copper seed layer is deposited, it is prepared by evaporation. Evaporation refers to a process method in which the material to be coated is vaporized and the particles diffuse to the surface of the substrate to be coated to form a coating. Among them, the method of vaporizing the material to be coated is usually heating evaporation, and the heating evaporation methods include resistance heating and electron beam heating. Radio frequency induction heating, arc heating and laser heating, etc. When the second copper seed layer is deposited, it is prepared by sputtering. Sputtering refers to a process method in which charged particles bombard a target material, the accelerated particles collide with the atoms on the surface of the target material, and transfer energy and momentum, so that the atoms on the surface of the target material escape and bombard the surface of the substrate to be coated to form a coating. Among them, sputtering methods include DC sputtering, AC sputtering, reactive sputtering and magnetron sputtering. Compared with the evaporation method, the copper seed layer prepared by sputtering is denser and has better conductivity, and its bonding with the transparent conductive film is also more firmly. Therefore, in traditional technology, sputtering is generally used to directly prepare the copper seed layer on the transparent conductive film, and then the gate line electrode is electroplated on the copper seed layer.

[0042] The solar cell provided in the present disclosure includes a solar cell substrate, a transparent conductive film, a first copper seed layer, a second copper seed layer and a gate electrode. The transparent conductive film is a transparent conductive film prepared after annealing treatment, the annealing treatment is carried out in an annealing atmosphere including a protective gas and the annealing temperature is kept constant; the first copper seed layer is prepared by evaporation, and the second copper seed layer is prepared by sputtering.

[0043] The copper seed layer in the conventional technology is usually directly prepared on the transparent conductive film by magnetron sputtering. Compared with the conventional technology, the solar cell has at least the following beneficial effects: the crystallinity and density of the transparent conductive film after annealing can be significantly improved, so it has a higher surface resistance, and the energy of the copper atoms produced by evaporation is lower. By matching the annealed transparent conductive film and the evaporated first copper seed layer, the damage to the transparent conductive film during the preparation of the copper seed layer can be reduced as much as possible, and the holes generated on the transparent conductive film can be reduced, thereby improving the problem of electrical contact performance and permeability degradation of the transparent conductive film during the preparation of the copper seed layer, and improving the conversion efficiency of the solar cell. Furthermore, the combination of the first copper seed layer and the second copper seed layer ensures the adhesion and conductivity of the overall copper seed layer, and makes it suitable for further forming a gate electrode.

[0044] Annealing can significantly improve the compactness and carrier concentration of the transparent conductive film. In some examples of this embodiment, the carrier concentration of the transparent conductive film prepared after annealing is 10 21 / cm 3 This doping concentration is greater than the critical concentration (7.1×10 18 / cm 3 ), so the low energy states in its conduction band are filled with electrons, which increases the optical width of the transparent conductive film and blue-shifts the actual spectral absorption limit wavelength.

[0045] The present disclosure further provides a method for preparing a solar cell, which comprises the following steps:

[0046] Providing a solar cell substrate, on which a transparent conductive film precursor is stacked;

[0047] placing the transparent conductive film precursor in a vacuum environment, performing annealing treatment on the transparent conductive film precursor, maintaining the annealing temperature constant, and forming a transparent conductive film;

[0048] Depositing a first copper seed layer on the transparent conductive film by evaporation;

[0049] depositing a second copper seed layer on the first copper seed layer by sputtering;

[0050] A gate line electrode is formed on the second copper seed layer.

[0051] In order to facilitate understanding of the method for preparing a solar cell provided by the present disclosure, the present disclosure provides Figure 1 , which shows a specific implementation of a method for preparing a solar cell, the method for preparing a solar cell includes steps S1 to S5.

[0052] Step S1, refer to Figure 2 As shown, a solar cell substrate is provided.

[0053] In some examples of this embodiment, the solar cell substrate includes a substrate 100, a front intrinsic amorphous silicon layer 111, a front doped amorphous silicon layer 112, a back intrinsic amorphous silicon layer 121 and a back doped amorphous silicon layer 122, the front intrinsic amorphous silicon layer 111 is arranged on the front of the substrate 100, the front doped amorphous silicon layer 112 is arranged on the front intrinsic amorphous silicon layer 111, the back intrinsic amorphous silicon layer 121 is arranged on the back of the substrate 100, and the back doped amorphous silicon layer 122 is arranged on the back intrinsic amorphous silicon layer 121. Two transparent conductive films are arranged on the solar cell substrate, namely, a front transparent conductive film precursor 1130 and a back transparent conductive film precursor 1230, the front transparent conductive film precursor 1130 is arranged on the front doped amorphous silicon, and the back transparent conductive film precursor 1230 is arranged on the back doped amorphous silicon. It can be understood that the solar cell substrate is a substrate of a heterojunction solar cell. The transparent conductive film precursor can be a transparent conductive material directly deposited on the solar cell substrate without annealing. The transparent conductive material can be selected from one or more of indium tin oxide, aluminum zinc oxide and fluorine-doped tin oxide. Further optionally, the transparent conductive material is an indium tin oxide film layer.

[0054] Optionally, the solar cell substrate may include a silicon solar cell substrate. A silicon solar cell substrate refers to a cell substrate having a photovoltaic effect and made of single crystal silicon, polycrystalline silicon or amorphous silicon as a base material.

[0055] In some other embodiments, the transparent conductive film precursor on the solar cell substrate may also be disposed only on the front-side doped amorphous silicon or the back-side doped amorphous silicon.

[0056] In some examples of this embodiment, the substrate 100 in the solar cell substrate is a silicon substrate.

[0057] In some examples of this embodiment, the substrate 100 in the solar cell substrate has a velvet surface with a pyramid-shaped structure.

[0058] Step S2, annealing the transparent conductive film precursor.

[0059] The step of annealing the transparent conductive film precursor in the solar cell substrate includes: placing the transparent conductive film precursor in a vacuum environment, annealing the transparent conductive film precursor, and maintaining the annealing temperature constant to form a transparent conductive film. The role of annealing the transparent conductive film precursor is to improve its crystallization degree and density, and also to improve the conductivity of the transparent conductive film.

[0060] Reference Figure 3 As shown, it shows the Figure 2 After the annealing treatment, the front transparent conductive film precursor 1130 is transformed into the front transparent conductive film 113, and the back transparent conductive film precursor 1230 is transformed into the back transparent conductive film 123.

[0061] In some examples of this embodiment, in the step of annealing the transparent conductive film precursor, the solar cell substrate is placed in an annealing chamber, and the annealing temperature is controlled to be 100° C. to 200° C. For example, optionally, the annealing temperature is controlled to be 100° C., 120° C., 140° C., 160° C., 180° C., 200° C., or a range between the above annealing temperatures.

[0062] Among them, controlling the annealing temperature within this range can improve the crystallinity, density and carrier concentration of the transparent conductive film precursor, and improve the electrical contact performance of the transparent conductive film. For example, the carrier concentration in the transparent conductive film formed after annealing is generally 10 21 / cm 3 Above, it is considered as heavily doped, which is greater than the critical concentration (7.1×10 18 / cm 3 ), so the low energy states in the conduction band of the transparent conductive film are filled with electrons, the optical bandwidth of the transparent conductive film is increased, and the actual spectral absorption limit wavelength is blue-shifted.

[0063] In some examples of this embodiment, in the step of annealing the transparent conductive film precursor, the solar cell substrate is placed in an annealing chamber, and hydrogen and protective gas are introduced into the annealing chamber. Under the action of hydrogen and protective gas, the transparent conductive film can be protected from further oxidation and generation of new impurities during the annealing process. In addition, the introduced hydrogen can cause hydrogen ions to adhere to the transparent conductive film, which can prevent copper ions from being injected into the transparent conductive film during the subsequent preparation of the copper seed layer, thereby improving the injection of copper ions into the transparent conductive film.

[0064] Optionally, the protective gas should be selected from gases that do not substantially react with the transparent conductive film, for example, it may include one or more of nitrogen, argon, helium and neon.

[0065] In some specific examples of this embodiment, gas is continuously introduced into the annealing chamber, and the annealing chamber is evacuated.

[0066] In some examples of this embodiment, the flow rate of the introduced gas is 100 sccm to 1000 sccm.

[0067] Step S3, preparing a first copper seed layer on the transparent conductive film by evaporation.

[0068] Reference Figure 4 As shown, it shows that Figure 3 Schematic diagram of the structure of preparing the first copper seed layer on the structure shown in FIG. Figure 3 On the basis of the solar cell substrate shown, a front first copper seed layer 114 and a back first copper seed layer 124 are further provided.

[0069] Among them, the evaporation method refers to evaporation by heating so that the atoms on the copper target escape and diffuse and adsorb onto the substrate. Compared with the sputtering method, the kinetic energy of copper atoms generated by the evaporation method is lower. The transparent conductive film is first annealed, and then the first copper seed layer is prepared on the transparent conductive film by evaporation. During the diffusion and adsorption film formation process of the copper seed layer, there is basically no bombardment damage to the transparent conductive film, thereby reducing the generation of small holes on the transparent conductive film.

[0070] In some examples of this embodiment, in the step of depositing the first copper seed layer, the deposition temperature is controlled to be above 1600° C.

[0071] In some examples of this embodiment, in the step of depositing the first copper seed layer, the thickness of the first copper seed layer can be controlled to be 20nm to 100nm. Optionally, in the step of depositing the first copper seed layer, the thickness of the first copper seed layer can be controlled to be 50nm to 70nm. For example, the thickness of the first copper seed layer is 50nm, 55nm, 60nm, 65nm, 70nm, or a range between the thicknesses. On the one hand, the thickness of the first copper seed layer in this example will not be too thin, so that the bombardment of copper atoms on the transparent conductive film during the subsequent sputtering preparation of the second copper seed layer can be prevented; on the other hand, the thickness will not be too thick, which can minimize the negative effects of the first copper seed layer prepared by evaporation on adhesion, density and electrical contact performance.

[0072] In some examples of this embodiment, in the step of depositing the first copper seed layer, hydrogen and protective gas are introduced into the deposition chamber and the hydrogen and protective gas are formed into an ion flow, and the copper target is bombarded by the ion flow, and local high temperature is generated on the surface of the copper target so that the copper atoms on the surface of the film material evaporate, and finally diffuse and adsorb to the surface of the solar cell substrate to form the first copper seed layer. Wherein, under the action of the ion flow, not only evaporated copper atoms can be generated, but some of the copper atoms will also be ionized, and finally form ionized gas masses, which are easy to adsorb on the surface of the solar cell substrate to form the first copper seed layer. Wherein, the introduced hydrogen can generate a large number of hydrogen ions on the surface of the transparent conductive film, and its activity is greater than that of copper ions, which can prevent copper ions from being injected into the transparent conductive film and improve the injection of copper ions into the transparent conductive film.

[0073] In some examples of this embodiment, the flow rates of the hydrogen gas and the protective gas are controlled to be 100 sccm to 1200 sccm.

[0074] In some examples of this embodiment, the deposition rate may be controlled to be 0.1 nm / s to 3 nm / s to obtain a first copper seed layer with better quality.

[0075] In some examples of this embodiment, the deposition pressure is controlled to be 0.5Pa-2.0Pa.

[0076] In some examples of this embodiment, the evaporation power is controlled to be ≤10 kW. For example, optionally, the evaporation power is controlled to be 100 W, 1 kW, 3 kW, 5 kW, 7 kW, 9 kW, 10 kW, or a range therebetween.

[0077] It can be understood that in other examples of this embodiment, the process parameters of evaporation can also be configured according to the default settings on the evaporation machine.

[0078] Through steps S2 to S3, the first copper seed layer can be deposited on the surface of the transparent conductive film without damaging the transparent conductive film as much as possible. However, the first copper seed layer prepared by evaporation has poor conductivity and adhesion properties and is difficult to be directly used as the copper seed layer required for the subsequent preparation of copper grid electrodes. Therefore, in this embodiment, a second copper seed layer is also prepared in step S4. The first copper seed layer is directly attached to the surface of the transparent conductive film, and plays the role of spacing the second copper seed layer prepared by subsequent sputtering, and blocks the bombardment of copper atoms on the transparent conductive film during the sputtering process.

[0079] Step S4, preparing a second copper seed layer on the first copper seed layer by sputtering.

[0080] Reference Figure 5 As shown, it shows that Figure 4Schematic diagram of the structure of preparing the second copper seed layer on the structure shown in FIG. Figure 4 On the basis of the device structure shown, a front second copper seed layer 115 located on the front first copper seed layer 114 and a back second copper seed layer 115 located on the back first copper seed layer 124 are further provided.

[0081] Among them, the sputtering method refers to the generation of high-speed particles by bombarding the target material with charged particles, and the high-speed particles bombard the surface of the material to deposit. The second copper seed layer prepared by the sputtering method has significantly higher density and adhesion performance, and has better conductivity, which is suitable for the preparation of subsequent copper grid line electrodes.

[0082] In some examples of this embodiment, in the step of depositing the second copper seed layer, the deposition temperature is controlled to be 20° C. to 60° C.

[0083] In some examples of this embodiment, the thickness of the second copper seed layer is thicker than the thickness of the first copper seed layer. Optionally, the thickness of the second copper seed layer is more than twice the thickness of the first copper seed layer. The second copper seed layer is used as a major part for subsequent gate line electrode growth, and a thicker second copper seed layer is prepared.

[0084] In some examples of this embodiment, in the step of depositing the second copper seed layer, the thickness of the second copper seed layer can be controlled to be 100nm to 200nm. Optionally, in the step of depositing the second copper seed layer, the thickness of the second copper seed layer can be controlled to be 100nm, 110nm, 120nm, 140nm, 150nm, 170nm, 180nm, 200nm, or a range between the thicknesses.

[0085] In some examples of this embodiment, in the step of depositing the second copper seed layer, the sputtering power may be controlled to be 100 W to 2000 W. Optionally, in the step of depositing the second copper seed layer, the sputtering power may be controlled to be 100 W, 300 W, 500 W, 700 W, 1000 W, 1200 W, 1500 W, 1800 W, 2000 W, or a range between the sputtering powers.

[0086] In some examples of this embodiment, in the step of depositing the second copper seed layer, the deposition rate of the second copper seed layer is controlled to be 0.4 nm / s to 1.0 nm / s to obtain a second copper seed layer with better quality.

[0087] In some examples of this embodiment, in the step of depositing the second copper seed layer, a protective gas is introduced into the deposition chamber. Optionally, the protective gas is selected from gases that do not react with copper, such as one or more of nitrogen, argon, helium and neon.

[0088] In some examples of this embodiment, in the step of depositing the second copper seed layer, the gas flow rate introduced into the deposition chamber is 100 sccm to 1200 sccm.

[0089] In some examples of this embodiment, during the step of depositing the second copper seed layer, the deposition chamber is continuously evacuated to control the vacuum level in the deposition chamber to be in a suitable deposition condition.

[0090] The second copper seed layer is prepared by step S4. The film layer of the prepared second copper seed layer is denser than that of the first copper seed layer, the film layers are closely connected, and rapid and mass production can be achieved.

[0091] Step S5, preparing a gate line electrode on the second copper seed layer.

[0092] In some examples of this embodiment, the method of preparing the gate line electrode may be electroplating. Optionally, the material of the gate line electrode includes copper.

[0093] It can be understood that the gate electrode is used to conduct the current generated by the solar cell during operation to the electrical appliance. After the gate electrode is prepared on the solar cell substrate, the preparation process of the solar cell can be completed. The solar cell can also be packaged and tested later to be put into actual use.

[0094] Furthermore, the present disclosure also provides a solar cell, which can be prepared by the above-mentioned method for preparing a solar cell.

[0095] Reference Figure 6 As shown, in an embodiment of a solar cell provided by the present disclosure, the solar cell includes a solar cell substrate, a transparent conductive film, a first copper seed layer, a second copper seed layer and a gate electrode, wherein the transparent conductive film, the first copper seed layer, the second copper seed layer and the gate electrode are sequentially stacked on at least one side surface of the solar cell substrate; the transparent conductive film is a transparent conductive film prepared after annealing treatment, wherein the annealing treatment is carried out in an annealing atmosphere including a protective gas and the annealing temperature is kept constant; the first copper seed layer is prepared by evaporation, and the second copper seed layer is prepared by sputtering.

[0096] exist Figure 6In the illustrated embodiment, a transparent conductive film, a first copper seed layer, a second copper seed layer, and a gate electrode are disposed on the opposite front and back sides of the solar cell substrate. The transparent conductive film includes a front transparent conductive film 113 and a back transparent conductive film 123, the first copper seed layer includes a front first copper seed layer 114 and a back first copper seed layer 124, the second copper seed layer includes a front second copper seed layer 115 and a back second copper seed layer 115, and the gate electrode includes a front gate electrode 116 and a back gate electrode 116. The front first copper seed layer 114, the front second copper seed layer 115, and the front gate electrode 116 are sequentially stacked on the front transparent conductive film 113, and the back first copper seed layer 124, the back second copper seed layer 115, and the back gate electrode 116 are sequentially stacked on the back transparent conductive film 123.

[0097] In order to make it easier to understand and implement the present invention, the following relatively easy to implement, more specific and detailed test examples and comparative examples are provided as reference. Through the description and performance results of the following specific test examples and comparative examples, the embodiments of the present invention and their advantages will also be apparent. In the following test examples and comparative examples,

[0098] Unless otherwise specified, the raw materials used in the following examples and comparative examples can be purchased from the market.

[0099] The solar cell substrate used in the following embodiments and comparative examples is a heterojunction solar cell substrate, which includes an N-type silicon substrate with a thickness of 150 μm, a front intrinsic amorphous silicon layer, an N-type doped amorphous silicon layer, and a front transparent conductive film stacked in sequence on the front side of the N-type silicon substrate, and a back intrinsic amorphous silicon layer, a P-type doped amorphous silicon layer, and a back transparent conductive film stacked in sequence on the back side of the N-type silicon substrate, wherein the front transparent conductive film and the back transparent conductive film are both 110 nm thick indium tin oxide film layers.

[0100] Example 1

[0101] Provide heterojunction solar cell substrates;

[0102] The transparent conductive film on the heterojunction solar cell substrate is annealed at a temperature of 150° C., and a mixed gas of argon and hydrogen is introduced at a flow rate of 800 sccm;

[0103] The heterojunction solar cell substrate is placed in a deposition chamber of a reactive plasma deposition process (RPD), and a first copper seed layer is prepared by evaporation. During the evaporation process, the evaporation power is controlled to be 100 W, the argon gas flow rate is 1000 sccm, the deposition rate is 2 nm / s, the process time is 30 s, the deposition pressure is 0.7 Pa, the deposition temperature is 100° C., and the thickness of the prepared first copper seed layer is 60 nm;

[0104] The heterojunction solar cell substrate was transferred to a deposition chamber of a magnetron sputtering process, and a second copper seed layer was prepared by sputtering. During the sputtering process, the evaporation power was controlled to be 200 W, the argon gas flow rate was 1000 sccm, the deposition rate was controlled to be 0.5 nm / s, the process time was 200 s, the deposition pressure was 0.5 Pa, the deposition temperature was 40°C, and the thickness of the prepared second seed layer was 100 nm.

[0105] The heterojunction solar cell substrate is transferred to an electroplating tank and copper grid electrodes are prepared by electroplating.

[0106] Example 2

[0107] Provide heterojunction solar cell substrates;

[0108] The transparent conductive film on the heterojunction solar cell substrate is annealed at a temperature of 150° C., and a mixed gas of argon and hydrogen is introduced at a flow rate of 800 sccm;

[0109] The heterojunction solar cell substrate is placed in a deposition chamber of a reactive plasma deposition process (RPD), and a first copper seed layer is prepared by evaporation. During the evaporation process, the evaporation power is controlled to be 100 W, the argon gas flow rate is 1000 sccm, the deposition rate is 2 nm / s, the process time is 20 s, the deposition pressure is 0.7 Pa, the deposition temperature is 100° C., and the thickness of the prepared first copper seed layer is 40 nm;

[0110] The heterojunction solar cell substrate was transferred to a deposition chamber of a magnetron sputtering process, and a second copper seed layer was prepared by sputtering. During the sputtering process, the evaporation power was controlled to be 200 W, the argon gas flow rate was 1000 sccm, the deposition rate was controlled to be 0.5 nm / s, the process time was 240 s, the deposition pressure was 0.5 Pa, the deposition temperature was 40°C, and the thickness of the prepared second seed layer was 120 nm.

[0111] The heterojunction solar cell substrate is transferred to an electroplating tank and copper grid electrodes are prepared by electroplating.

[0112] Comparative Example 1

[0113] Provide heterojunction solar cell substrates;

[0114] The heterojunction solar cell substrate was transferred to a deposition chamber of a magnetron sputtering process, and a second copper seed layer was prepared by sputtering. During the sputtering process, the evaporation power was controlled to be 200 W, the argon gas flow rate was 1000 sccm, the deposition rate was controlled to be 0.5 nm / s, the process time was 320 s, the deposition pressure was 0.5 Pa, the deposition temperature was 40°C, and the thickness of the prepared second seed layer was 160 nm.

[0115] The heterojunction solar cell substrate is transferred to an electroplating tank and copper grid electrodes are prepared by electroplating.

[0116] Comparative Example 2

[0117] Provide heterojunction solar cell substrates;

[0118] The transparent conductive film on the heterojunction solar cell substrate is annealed at a temperature of 150° C., and a mixed gas of argon and hydrogen is introduced at a flow rate of 800 sccm;

[0119] The heterojunction solar cell substrate was transferred to a deposition chamber of a magnetron sputtering process, and a second copper seed layer was prepared by sputtering. During the sputtering process, the evaporation power was controlled to be 200 W, the argon gas flow rate was 1000 sccm, the deposition rate was controlled to be 0.5 nm / s, the process time was 320 s, the deposition pressure was 0.5 Pa, the deposition temperature was 40°C, and the thickness of the prepared second seed layer was 160 nm.

[0120] The heterojunction solar cell substrate is transferred to an electroplating tank and copper grid electrodes are prepared by electroplating.

[0121] Comparative Example 3

[0122] Provide heterojunction solar cell substrates;

[0123] The transparent conductive film on the heterojunction solar cell substrate is annealed at a temperature of 150° C., and a mixed gas of argon and hydrogen is introduced at a flow rate of 800 sccm;

[0124] The heterojunction solar cell substrate is placed in a deposition chamber of a reactive plasma deposition process (RPD), and a first copper seed layer is prepared by evaporation. During the evaporation process, the evaporation power is controlled to be 100 W, the argon gas flow rate is 1000 sccm, the deposition rate is 2 nm / s, the process time is 80 s, the deposition pressure is 0.7 Pa, and the deposition temperature is 100° C. The thickness of the prepared first copper seed layer is 160 nm;

[0125] The heterojunction solar cell substrate is transferred to an electroplating tank and copper grid electrodes are prepared by electroplating.

[0126] Test: Test the electrical properties of the solar cell electrodes and the tensile force of the grid electrode prepared in the above embodiments and comparative examples. The electrical properties of the solar cell electrodes include the conversion efficiency E ff , open circuit voltage V oc , short circuit current I sc , fill factor FF, series resistance R s And the parallel resistor R shFor the convenience of comparison, the electrical properties and tensile force of comparative example 1 are taken as 100%, and the electrical properties and tensile forces of other embodiments and comparative examples are normalized. The results can be seen in Table 1.

[0127] Table 1. Electrical properties and tensile test results of each embodiment and comparative example after normalization

[0128] <![CDATA[E ff ]]> <![CDATA[V oc ]]> <![CDATA[I sc ]]> FF <![CDATA[R s ]]> <![CDATA[R sh ]]> pull Comparative Example 1 100.00％ 100.00％ 100.00％ 100.00％ 100.00％ 100.00％ 100.00％ Example 1 100.21％ 100.00％ 100.37％ 100.05％ 99.15％ 100.20％ 100.03％ Example 2 100.10％ 100.00％ 100.28％ 100.04％ 99.37％ 101.49％ 100.09％ Comparative Example 2 100.01％ 100.01％ 100.04％ 99.99％ 99.54％ 100.09％ 100.03％ Comparative Example 3 100.02％ 100.01％ 100.03％ 100.00％ 99.75％ 100.21％ 100.02％

[0129] As shown in Table 1, in both Example 1 and Example 2, the transparent conductive film was annealed, and the first copper seed layer was prepared by evaporation. The conversion efficiency (E ff ) were increased by 0.21% and 0.1% respectively compared with Comparative Example 1. Although Comparative Example 2 was annealed, the second copper seed layer was directly sputtered and deposited afterwards, and the conversion efficiency of its solar cell was not significantly improved. This may be mainly because the sputtered second copper seed layer still caused relatively obvious damage to the transparent conductive film after annealing. Although Comparative Example 3 was annealed, only the first copper seed layer was evaporated and deposited afterwards, and the conversion efficiency of its solar cell was not significantly improved. This may be mainly because the quality of the evaporated first copper seed layer was poor, resulting in poor electrical contact between the gate electrode and the solar cell substrate, which in turn resulted in no significant improvement in the conversion efficiency of the solar cell.

[0130] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0131] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A solar cell, characterized in that: include: A solar cell substrate, a transparent conductive film, a first copper seed layer, a second copper seed layer and a gate electrode, wherein the transparent conductive film, the first copper seed layer, the second copper seed layer and the gate electrode are sequentially stacked on at least one side surface of the solar cell substrate; The transparent conductive film is a transparent conductive film prepared after annealing treatment, and the annealing treatment is performed in a vacuum environment and the annealing temperature is kept constant; the first copper seed layer is prepared by evaporation, and in the step of depositing the first copper seed layer, hydrogen and protective gas are introduced into a deposition chamber to form an ion flow, and the ion flow bombards a copper target material to generate copper atoms, and the generated copper atoms diffuse onto the transparent conductive film to form the first copper seed layer; The second copper seed layer is prepared by sputtering.

2. The solar cell according to claim 1, characterized in that: The carrier concentration of the transparent conductive film prepared after annealing is 10 21 / cm 3 above.

3. The method for preparing a solar cell according to any one of claims 1 to 2, characterized in that: The steps include: Providing the solar cell substrate, on which a transparent conductive film precursor is stacked; Placing the transparent conductive film precursor in a vacuum environment, performing annealing treatment on the transparent conductive film precursor, maintaining the annealing temperature constant, and forming the transparent conductive film; Depositing the first copper seed layer on the transparent conductive film by evaporation, in the step of depositing the first copper seed layer, introducing hydrogen and protective gas into a deposition chamber to form an ion flow, bombarding a copper target material with the ion flow to generate copper atoms, and the generated copper atoms diffuse onto the transparent conductive film to form the first copper seed layer; depositing the second copper seed layer on the first copper seed layer by sputtering; A gate line electrode is formed on the second copper seed layer.

4. The method for preparing a solar cell according to claim 3, characterized in that: In the step of annealing the transparent conductive film, hydrogen and protective gas are continuously introduced into the annealing chamber; and / or, In the step of annealing the transparent conductive film, the annealing temperature is controlled to be 100° C. to 200° C.

5. The method for preparing a solar cell according to any one of claims 3 to 4, characterized in that: In the step of depositing the first copper seed layer, the deposition temperature is controlled to be above 1600° C.

6. The method for preparing a solar cell according to any one of claims 3 to 4, characterized in that: The thickness of the prepared first copper seed layer is controlled to be 20 nm to 100 nm.

7. The method for preparing a solar cell according to any one of claims 3 to 4, characterized in that: In the step of depositing the first copper seed layer, controlling the deposition rate to be 0.1 nm / s to 3.0 nm / s; and / or Control the evaporation power to ≤10kW.

8. The method for preparing a solar cell according to any one of claims 3 to 4, characterized in that: The thickness of the prepared second copper seed layer is controlled to be 100 nm to 200 nm.

9. The method for preparing a solar cell according to any one of claims 3 to 4, characterized in that: In the step of depositing the second copper seed layer, the deposition temperature is controlled to be 20° C. to 60° C.

10. The method for preparing a solar cell according to any one of claims 3 to 4, characterized in that: In the step of depositing the second copper seed layer, the sputtering power is controlled to be 100W-2000W.

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