A solar cell, a preparation method thereof, a stacked cell, and a photovoltaic module

Abstract

The application relates to a solar cell and a preparation method thereof, a laminated cell and a photovoltaic module. The preparation method of the solar cell comprises the following steps: providing a substrate; preparing a titanium chalcogenide compound by using a solid-phase synthesis method; performing ultrasonic treatment on a mixture of the titanium chalcogenide compound and an oxidizing agent to obtain a titanium dioxide amorphous precursor solution; coating the titanium dioxide amorphous precursor solution on the surface of the substrate and performing first heat treatment to obtain an electron transport layer; forming a perovskite layer on the surface of the electron transport layer; forming a hole transport layer on the surface of the perovskite light-absorbing layer; and forming an electrode layer on the surface of the hole transport layer. The solid-phase method is combined with ultrasonic treatment to prepare an amorphous sol with low viscosity, good fluidity and uniform dispersion, and then a uniform wet film with high wettability and stable performance is prepared, so that the film thickness is uniform, the film solution can be quickly and uniformly spread on the surface of the substrate, and the method is suitable for large-area preparation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic cells, in particular to a solar cell, a preparation method thereof, a stacked cell and a photovoltaic module. BACKGROUND

[0002] Solar energy has the advantages of safety, no pollution, and no geographical condition limitation, and is the most widely used and most promising renewable energy. Among various technologies for effectively utilizing solar energy, photovoltaic power generation is undoubtedly one of the most promising directions. Among various new solar cells, perovskite solar cells have excellent photoelectric conversion performance, and the required raw materials are abundant, so they are one of the most promising solar cells.

[0003] The perovskite solar cell includes a substrate, an electron transport layer, a perovskite layer, a hole transport layer and an electrode layer. The common material for the electron transport layer is metal oxide. How to provide a metal oxide electron transport layer with simple preparation process and high uniformity is a problem urgently to be solved in the field. SUMMARY

[0004] In view of this, the present application provides a solar cell, a preparation method thereof, a stacked cell and a photovoltaic module. The preparation method of the present application is simple and easy to operate, suitable for large-area preparation, and can prepare a high-quality titanium dioxide electron transport layer.

[0005] In a first aspect, the present application provides a preparation method of a solar cell, including the following steps:

[0006] providing a substrate;

[0007] preparing a titanium chalcogenide compound by a solid-phase synthesis method;

[0008] ultrasonically treating a mixture of the titanium chalcogenide compound and an oxidizing agent to obtain a titanium dioxide amorphous precursor solution;

[0009] coating the titanium dioxide amorphous precursor solution on a surface of the substrate and performing a first heat treatment to obtain an electron transport layer;

[0010] forming a perovskite layer on a surface of the electron transport layer;

[0011] forming a hole transport layer on a surface of the perovskite light-absorbing layer;

[0012] forming an electrode layer on a surface of the hole transport layer.

[0013] In a second aspect, the embodiments of the present application provide a solar cell, comprising: a substrate, an electron transport layer, a perovskite layer, a hole transport layer and an electrode layer, the electron transport layer is between the substrate and the perovskite layer, the hole transport layer is between the perovskite layer and the electrode layer, the electron transport layer comprises a plurality of titanium dioxide crystals, and the plurality of titanium dioxide crystals are stacked to form a dendritic structure.

[0014] In a third aspect, the embodiments of the present application provide a stacked cell, comprising: a bottom cell, a composite layer and a top cell stacked in sequence along a preset direction; wherein the top cell is a solar cell formed by the preparation method of the solar cell of the first aspect or the solar cell of the second aspect.

[0015] In a fourth aspect, the embodiments of the present application provide a photovoltaic module, comprising:

[0016] a cell string, the cell string is connected by a plurality of solar cells formed by the preparation method of the first aspect or the solar cell of the second aspect;

[0017] an encapsulation layer, the encapsulation layer covers the surface of the cell string;

[0018] a cover plate, the cover plate is used to cover the surface of the encapsulation layer away from the cell string.

[0019] The technical solutions of the present application have at least the following beneficial effects:

[0020] The titanium chalcogenide compound is obtained by a solid phase synthesis method, and then a mixture of the titanium chalcogenide compound and an oxidizing agent is subjected to ultrasonic treatment, so that a low-viscosity, good-flowing and uniformly dispersed titanium dioxide amorphous sol can be prepared, and no impurity functional groups are introduced. The particle size of the titanium dioxide can be accurately adjusted by controlling the added mass of the titanium chalcogenide compound and the oxidizing agent. Finally, the titanium dioxide amorphous precursor solution is coated on the surface of the substrate, so that a uniform wet film with high wettability and stable performance can be obtained, and a uniform and dense titanium dioxide film is prepared by first heat treatment. The crystal in the titanium dioxide film is in a dendritic structure, which has a unique three-dimensional branched structure, can effectively shorten the electron diffusion distance, and the titanium dioxide crystal in the dendritic structure can increase the contact area with the perovskite layer and the substrate, provide more charge extraction sites, so that the electrons generated in the perovskite layer can be quickly captured and transmitted, thereby enhancing the light capture performance. The preparation method of the present application uses a solid phase method combined with ultrasonic treatment to prepare a low-viscosity, good-flowing and uniformly dispersed amorphous sol, and then a uniform wet film with high wettability and stable performance is prepared, which can ensure uniform film thickness, and the film solution can quickly and uniformly spread on the surface of the substrate, reducing defects such as "edge shrinkage" and "pinholes". The preparation method of the present application is simple and easy to operate, suitable for large-area preparation, and can prepare a highly uniform large-area titanium dioxide crystal film. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0022] Figure 1 The preparation flow chart of the solar cell provided by the embodiment of the present application;

[0023] Figure 2 The structure schematic diagram of the solar cell provided by the embodiment of the present application;

[0024] Figure 3 The structure schematic diagram of the photovoltaic module provided by the embodiment of the present application;

[0025] Figure 4 The XRD diagram of TiS2 prepared in Example 1 of the present application;

[0026] Figure 5 The XRD diagram of amorphous silicon dioxide in the amorphous silicon dioxide precursor solution prepared by the embodiment of the present application;

[0027] Figure 6XRD pattern of the silicon dioxide crystal in the silicon dioxide electron transport layer prepared for Example 1 of the present application;

[0028] Figure 7 XRD pattern of the crystallization of the amorphous silicon dioxide prepared in the present application at different temperatures.

[0029] Reference signs:

[0030] 1000 - photovoltaic module

[0031] 100 - solar cell

[0032] 1 - substrate

[0033] 2 - electron transport layer

[0034] 3 - perovskite layer

[0035] 4 - hole transport layer

[0036] 5 - electrode layer

[0037] 200 - first cover plate

[0038] 300 - first encapsulation adhesive layer

[0039] 400 - second encapsulation adhesive layer

[0040] 500 - second cover plate DETAILED DESCRIPTION

[0041] In order to better understand the technical solutions of the present application, the embodiments of the present application are described in detail below in combination with the drawings.

[0042] It should be clear that the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0043] The terms used in the embodiments of the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0044] It should be understood that the term "and / or" used herein is only to describe the association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of A alone, A and B together, and B alone. In addition, the character " / " in this paper generally represents that the front and rear associated objects are a "or" relationship.

[0045] The structure of the perovskite solar cell includes a substrate, an electron transport layer, a perovskite layer, a hole transport layer and an electrode layer. A metal oxide such as titanium dioxide is commonly used as the material of the electron transport layer for collecting and transporting photo-generated carriers. In the preparation process of the electron transport layer, “large-area preparation” is a key process feature and technical direction.

[0046] In the related art, the sol-gel method is commonly used to prepare the titanium dioxide electron transport layer. The sol-gel method uses a titanium precursor (such as tetrabutyl titanate, tetraisopropyl titanate, etc.) to form a sol through hydrolysis-polycondensation, forms a film through spin coating or drop coating, and then obtains a titanium dioxide film through solidification. Due to the low film forming efficiency of the sol prepared by the above preparation process, the poor stability of the sol, and the insufficient performance of the film layer after low-temperature solidification, it is difficult to prepare the sol in a large area, which limits the application of metal oxides in perovskite solar cells.

[0047] In view of this, the present application provides a preparation method of a solar cell, Figure 1 The preparation flowchart of the solar cell of the present application is shown as follows: Figure 1 As shown in the figure, the preparation method of the solar cell includes the following steps:

[0048] providing a substrate;

[0049] preparing a titanium chalcogenide compound by a solid-phase synthesis method;

[0050] ultrasonic treatment of the mixture of the titanium chalcogenide compound and the oxidizing agent to obtain a titanium dioxide amorphous precursor solution;

[0051] coating the titanium dioxide amorphous precursor solution on the surface of the substrate and performing a first heat treatment to obtain an electron transport layer;

[0052] forming a perovskite layer on the surface of the electron transport layer;

[0053] forming a hole transport layer on the surface of the perovskite light-absorbing layer;

[0054] forming an electrode layer on the surface of the hole transport layer.

[0055] In the above scheme, the titanium chalcogenide compound is first prepared by a solid phase synthesis method, and then the mixture of the titanium chalcogenide compound and the oxidizing agent is subjected to ultrasonic treatment, so that a low-viscosity, good-flowing and uniformly dispersed titanium dioxide amorphous sol can be prepared, and no impurity functional groups are introduced, and the particle size of the titanium dioxide can be accurately adjusted by controlling the added mass of the titanium chalcogenide compound and the oxidizing agent; finally, the titanium dioxide amorphous precursor solution is coated on the surface of the substrate, so that a uniform wet film with high wettability and stable performance can be obtained, and a uniform and dense titanium dioxide film can be prepared by the first heat treatment. The crystal in the titanium dioxide film is in a dendritic structure, which has a unique three-dimensional branched structure, can effectively shorten the electron diffusion distance, and the dendritic titanium dioxide crystal can increase the contact area with the perovskite layer and the substrate, so as to provide more charge extraction sites, so that the electrons generated in the perovskite layer can be quickly captured and transmitted, thereby enhancing the light capture performance. The preparation method of the present application uses a solid phase method combined with ultrasonic treatment to prepare a low-viscosity, good-flowing and uniformly dispersed amorphous sol, and then a uniform wet film with high wettability and stable performance is prepared, so that the film thickness can be uniform, and the film solution can be quickly and uniformly spread on the surface of the substrate, reducing defects such as "edge shrinkage" and "pinholes". The preparation method of the present application is simple and easy to operate, suitable for large-area preparation, and can prepare a highly uniform large-area titanium dioxide crystal film.

[0056] Compared with the titanium dioxide amorphous sol prepared by using traditional organic titanium precursor (such as tetrabutyl titanate, tetraisopropyl titanate, etc.), solvent and catalyst as raw materials, the titanium chalcogenide compound prepared by the solid phase synthesis method of the present application is used as the raw material for preparing the titanium dioxide amorphous precursor solution, without adding solvent and catalyst, avoiding the influence of impurity functional groups on the quality of the titanium dioxide film, and the influence of external temperature, humidity and air flow on the preparation of the wet film is small (the hydrolysis of tetrabutyl titanate is extremely sensitive to temperature, humidity, water content and reaction speed), which is beneficial to improve the quality of the prepared electron transport layer, enhance the extraction of photo-generated electrons in the electron transport layer, and further improve the efficiency of the prepared solar cell.

[0057] The preparation method of the solar cell of the present application will be described in detail below.

[0058] S100, providing a substrate.

[0059] In some embodiments, the substrate includes a rigid substrate or a flexible substrate, and the preparation method of the present application is suitable for both rigid substrates and flexible substrates. For example, the rigid substrate includes at least one of indium tin oxide, indium tin oxide, aluminum-doped zinc oxide, antimony-doped tin oxide, etc. The flexible substrate includes at least one of polyethylene terephthalate, polyimide and polyethylene naphthalate.

[0060] In some embodiments, the thickness of the substrate is 80 nm to 200 nm, and can be specifically 80 nm, 90 nm, 100 nm, 120 nm, 130 nm, 150 nm, 160 nm, 180 nm, 190 nm, 200 nm, or a range between any two of the above values. Controlling the thickness of the substrate within the above range can balance the conductivity and light transmittance.

[0061] In some embodiments, after the substrate is provided, the method further includes sequentially ultrasonic cleaning the substrate with deionized water, acetone and ethanol for 15 minutes to 30 minutes.

[0062] S200, forming a titanium dioxide electron transport layer on the surface of the substrate.

[0063] S201, preparing a titanium chalcogenide compound by a solid phase synthesis method.

[0064] Specifically, the preparation of the titanium chalcogenide compound by the solid phase synthesis method includes: mixing titanium simple substance and chalcogen simple substance in a molar ratio of 1: (2.0-2.2) and then performing a second heat treatment to obtain the titanium chalcogenide compound.

[0065] In some embodiments, the molar ratio of the titanium simple substance to the chalcogen simple substance is 1: (2.0-2.2), and can be specifically 1:2.0, 1:2.05, 1:2.1, 1:2.15, 1:2.2, or a range between any two of the above values. Controlling the molar ratio of the titanium simple substance to the chalcogen simple substance within the above range can pre-compensate for sulfur volatilization during the second heat treatment, which is conducive to obtaining a titanium sulfide with high purity. Depending on the selection of the chalcogen simple substance, the titanium sulfide is at least one of titanium disulfide, titanium diselenide and titanium ditelluride.

[0066] It can be understood that the purity of the titanium simple substance is greater than or equal to 99%, and the purity of the chalcogen simple substance is greater than or equal to 99% to avoid impurities in the product.

[0067] In some embodiments, the chalcogen simple substance includes at least one of simple sulfur, simple selenium and simple tellurium. The application uses the chalcogen simple substance as a raw material for reaction with the titanium simple substance, which is low in raw material cost, direct in reaction path and more environmentally friendly. In particular, in industrial large-scale production, the high cost and process complexity of traditional organic titanium precursors (such as tetrabutyl titanate) can be avoided, and high-efficiency conversion can be achieved by using the high reactivity of titanium sulfide. The following will be described by taking the chalcogen simple substance including simple sulfur as an example.

[0068] In some embodiments, the mixing is performed in a ball mill, and the titanium simple substance and the chalcogen simple substance are fully mixed and uniformized by ball milling.

[0069] In some embodiments, the temperature of the second heat treatment is 700-1200℃, specifically 700℃, 800℃, 900℃, 1000℃, 1100℃, 1200℃ or a range between any two of the aforementioned values. Controlling the temperature of the second heat treatment within the aforementioned range facilitates sufficient combination of the atoms of the chalcogen elemental substance and the titanium elemental substance, and facilitates the generation of titanium disulfide with high purity.

[0070] Preferably, the second heat treatment is a segmented temperature increase treatment, first increasing the temperature to 400-600℃, holding for 1-10h, then increasing the temperature to 700-1200℃, holding for 15-24h, and slowly cooling to room temperature after the holding. The segmented temperature increase treatment at 400-600℃ can avoid rapid volatilization of the chalcogen elemental substance due to local overheating, and simultaneously remove water and volatile impurities in the raw material. The treatment at 700-1200℃ can promote sufficient combination of the chalcogen elemental substance and the titanium elemental substance, and facilitate full growth of the product crystal grains.

[0071] In some embodiments, the temperature increase rate of the second heat treatment is 1-10℃ / min, specifically 1℃ / min, 3℃ / min, 5℃ / min, 7℃ / min, 9℃ / min, 10℃ / min or a range between any two of the aforementioned values. Controlling the temperature increase rate of the second heat treatment within the aforementioned range facilitates slow temperature increase of the second heat treatment, which makes the heat received by the raw material particles uniform, and avoids local overheating leading to adhesion between the raw material particles. Preferably, the temperature increase rate of the second heat treatment is 5-10℃ / min.

[0072] In some embodiments, the holding time of the second heat treatment is 20-48h, specifically 20h, 24h, 28h, 30h, 32h, 36h, 40h, 44h, 48h or a range between any two of the aforementioned values. Controlling the holding time of the second heat treatment within the aforementioned range ensures complete reaction of the raw materials, reduces the residual unreacted raw materials, and facilitates full growth of the product crystal grains and improves the crystallinity.

[0073] S202, ultrasonic treatment is performed on the mixture of the titanium chalcogen compound and the oxidizing agent to obtain a titanium dioxide amorphous precursor solution.

[0074] Specifically, the titanium chalcogen compound and the solution containing the oxidizing agent are mixed to obtain a premix, and the premix is ultrasonically treated in an oxygen atmosphere and centrifuged.

[0075] The titanium chalcogen compound and the solution containing the oxidizing agent are mixed first, and then are subjected to ultrasonic treatment in an oxygen atmosphere. The ultrasonic treatment not only promotes the uniform dispersion of the components and the sufficient mixing of the titanium chalcogen compound and the oxidizing agent, but also promotes the reaction of the titanium chalcogen compound and the oxidizing agent by the heat generated by the ultrasonic treatment. Moreover, the ultrasonic treatment is performed in an oxygen atmosphere, which provides an oxygen-rich environment for the reaction of the titanium chalcogen compound, promotes the uniform dispersion of the titanium sulfide and the contact reaction with the oxidizing agent, and enhances the redox capacity of the oxidizing agent, thereby facilitating the obtaining of high-purity titanium dioxide. The oxidizing agent and the oxygen atmosphere together provide an oxygen source, ensuring the sufficient oxidation of the titanium chalcogen compound and the generation of high-purity titanium dioxide amorphous precursor liquid.

[0076] In some embodiments, the oxidizing agent comprises hydrogen peroxide. Taking sulfur as an example, the hydrogen peroxide can deeply oxidize the sulfur ions to form sulfate, and the titanium ions form unstable titanium peroxide complexes with the hydrogen peroxide, which are finally converted into titanium dioxide.

[0077] In some embodiments, the solvent in the solution containing the oxidizing agent comprises at least one of deionized water and ethanol. The addition of the solvent promotes the sufficient mixing of the titanium chalcogen compound and the oxidizing agent, and the solvent of the present application is environmentally friendly.

[0078] In some embodiments, the mass ratio of the titanium chalcogen compound to the oxidizing agent is 1: (5-20), specifically 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, or a range formed by any two of the above values. Controlling the mass ratio of the titanium chalcogen compound to the oxidizing agent within the above range is conducive to the sufficient oxidation of the titanium ions to form high-purity titanium dioxide.

[0079] The present application does not limit the flow rate of the oxygen atmosphere, as long as the ultrasonic treatment is performed in the oxygen atmosphere.

[0080] In some embodiments, the power of the ultrasonic treatment is 500-1000 W, specifically 500 W, 600 W, 700 W, 800 W, 900 W, 1000 W, or a range formed by any two of the above values. The time of the ultrasonic treatment is 1-3 min, specifically 1 min, 1.5 min, 2 min, 2.5 min, 3 min, or a range formed by any two of the above values. The present application controls the power and time of the ultrasonic treatment to provide a strong activation reaction interface for the reaction, promote the sufficient reaction of the titanium chalcogen compound and the oxidizing agent at a lower temperature, and improve the uniformity of the reaction product.

[0081] In some embodiments, the ultrasonic treatment is followed by a step of mixing the ultrasonic treatment product with a hydrolysis solution, the hydrolysis solution promoting further hydrolysis-polycondensation of the ultrasonic treatment product to form an amorphous film solution, i.e. a titanium dioxide amorphous precursor solution. The viscosity of the titanium dioxide amorphous precursor solution is easy to control, and the titanium dioxide amorphous precursor solution can be uniformly spread on the surface of the substrate during coating. The titanium dioxide amorphous precursor solution can be subsequently formed into a film by a low-temperature process, without the need for high-temperature annealing, thus avoiding the heat resistance limit of flexible substrates and being suitable for the preparation of an electron transport layer on a flexible substrate.

[0082] In some embodiments, the hydrolysis solution comprises at least one of deionized water and an alcohol compound.

[0083] In some embodiments, the volume ratio of the ultrasonic treatment product to the hydrolysis solution is 1: (0.2-1), specifically 1:0.2, 1:0.4, 1:0.5, 1:0.6, 1:0.8, 1:1, or a range defined by any two of the above values.

[0084] The present application discards the conventional solution preparation process, and uses a solid-phase synthesis method as the first step of preparing raw materials. The addition amount of titanium and chalcogen elements can be accurately controlled to prepare high-purity titanium chalcogen compounds. The titanium and chalcogen elements can be accurately weighed, and the titanium chalcogen compound and the solution containing the oxidizing agent are mixed and subjected to ultrasonic treatment to obtain a titanium dioxide amorphous precursor solution. During the preparation of the titanium dioxide amorphous precursor solution, the temperature and humidity of the environment do not have a great impact on the purity of the product. The preparation method of the present application has low requirements for equipment, does not require the use of organic solvents, and does not have the problem of waste liquid treatment. At the same time, the influence of solvent volatilization on the prepared wet film is avoided, which is conducive to the preparation of a low-viscosity, good-flowing, and uniformly dispersed film solution.

[0085] S203, coating the titanium dioxide amorphous precursor solution on the surface of the substrate and performing a first heat treatment to obtain an electron transport layer.

[0086] In some embodiments, the coating comprises spin coating. The low-viscosity, good-flowing, and uniformly dispersed titanium dioxide amorphous precursor solution prepared by the present application can be spin-coated on the surface of the substrate to achieve large-area preparation of a titanium dioxide electron transport layer.

[0087] In some embodiments, the spin coating speed is 3000 rpm-6000 rpm, specifically 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm, 5000 rpm, 5500 rpm, 6000 rpm, or a range defined by any two of the above values.

[0088] In some embodiments, the spin coating time is 10s-50s, specifically, 10s, 20s, 25s, 30s, 35s, 40s, 45s, 50s or a range between any two of the above values. Preferably, the spin coating time is 20s-35s.

[0089] In some embodiments, the temperature of the first heat treatment is greater than or equal to 200℃, specifically, 200℃, 250℃, 300℃, 350℃, 400℃, 500℃, 600℃ or a range between any two of the above values. The titanium dioxide amorphous precursor solution of the present application can be crystallized at a lower temperature (300℃ and below) and can also be crystallized at a higher temperature (300℃ and above), which can match the preparation of titanium dioxide electron transport layers with different requirements.

[0090] In some embodiments, the time of the first heat treatment is 1min-3min, specifically, 1min, 1.5min, 2min, 2.5min, 3min or a range between any two of the above values.

[0091] In some embodiments, the heating rate of the first heat treatment is 1℃ / min-10℃ / min, specifically, 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or a range between any two of the above values.

[0092] In some embodiments, the thickness of the electron transport layer is 100nm-300nm, specifically, 100nm, 150nm, 200nm, 250nm, 300nm or a range between any two of the above values. The electron transport layer of the present application has an appropriate thickness, so that the electron transport layer and the perovskite layer can be in close contact, effectively improving the extraction of photo-generated electrons.

[0093] S300, forming a perovskite layer on the surface of the electron transport layer.

[0094] Specifically: coating a perovskite precursor solution on the surface of the electron transport layer, spin coating at a speed of 3000rpm-5000rpm for 20s-30s, and then annealing at 90℃-100℃ for 10min to obtain the perovskite layer. The solute of the perovskite precursor solution is 3-bromo-benzyl ammonium iodide or 3-chloro-benzyl ammonium iodide, methyl ammonium chloride and lead iodide. The solvent of the perovskite precursor solution is N-dimethylformamide and dimethyl sulfoxide.

[0095] In some embodiments, the perovskite layer has a thickness of 300 nm to 800 nm, and specifically, the thickness of the perovskite layer can be 300 nm, 350 nm, 420 nm, 480 nm, 500 nm, 600 nm, 630 nm, 700 nm, 720 nm, 750 nm, 800 nm, or a range between any two of the above values. Controlling the thickness of the perovskite layer within the above range is conducive to light absorption and inhibiting carrier recombination.

[0096] S400, forming a hole transport layer on the surface of the perovskite light-absorbing layer.

[0097] Specifically, an organic material containing at least one of 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and poly-3-hexylthiophene, or an inorganic material containing at least one of CuI, CuSCN, TiO2, and SnO2 is dissolved in a solvent (e.g., chlorobenzene) to obtain a mixed solution, the mixed solution is coated on the surface of the perovskite layer, and after spin coating at a speed of 4000 rpm to 5000 rpm for 20 s to 30 s, annealing at 90°C to 100°C for 10 min is performed to obtain the hole transport layer.

[0098] In some embodiments, the hole transport layer has a thickness of 1 nm to 200 nm, and specifically, the thickness of the hole transport layer can be 1 nm, 10 nm, 20 nm, 50 nm, 100 nm, 120 nm, 156 nm, 170 nm, 180 nm, 195 nm, 200 nm, or a range between any two of the above values. Controlling the thickness of the hole transport layer within the above range is conducive to improving the open-circuit voltage and the fill factor.

[0099] S500, forming an electrode layer on the surface of the hole transport layer.

[0100] Specifically, the product obtained in S400 is placed in a vacuum evaporation box, and a metal material (e.g., at least one of gold, silver, copper, aluminum, and chromium) is evaporated on the surface of the hole transport layer to obtain the electrode layer.

[0101] Based on the same inventive concept, the embodiments of the present application also provide a solar cell prepared by the above preparation method, Figure 2 A structural schematic diagram of the solar cell provided by the present application is shown in FIG. 1. Figure 2 As shown in FIG. 1, the solar cell includes a substrate 1, an electron transport layer 2, a perovskite layer 3, a hole transport layer 4, and an electrode layer 5. The electron transport layer 2 is located between the substrate 1 and the perovskite layer 3, and the hole transport layer 4 is located between the perovskite layer 3 and the electrode layer 5. The electron transport layer 2 includes a plurality of titanium dioxide crystals stacked to form a dendritic structure.

[0102] In the above scheme, the electron transport layer 2 of the present application comprises titanium dioxide crystals with dendritic structure, which has a unique three-dimensional branched structure and can effectively shorten the electron diffusion distance. Moreover, the titanium dioxide crystals with dendritic structure can increase the contact area with the perovskite layer 3, provide more charge extraction sites, enable the electrons generated in the perovskite layer 3 to be quickly captured and transported, and thus enhance the light capture performance. The solar cell of the present application has excellent charge separation efficiency and charge transport efficiency, and significantly improves the photoelectric conversion efficiency and long-term stability of the solar cell.

[0103] In some embodiments, the thickness of the electron transport layer 2 is 100 nm to 300 nm, and can be specifically 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, or a range between any two of the above values. The electron transport layer 2 of the present application has a suitable thickness, so that the electron transport layer 2 can be in close contact with the perovskite layer 3 and the substrate 1, respectively, and effectively improve the extraction of photo-generated electrons.

[0104] In some embodiments, the particle size of the titanium dioxide crystals is 100 nm to 2 μm, and can be specifically 100 nm, 300 nm, 500 nm, 800 nm, 1 μm, 1.5 μm, 2 μm, or a range between any two of the above values. The particle size of the titanium dioxide crystals of the present application is nanoscale and / or micrometer scale, so that the electron transport layer 2 has a high specific surface area and at the same time has good structural stability, which can synergistically improve the charge extraction efficiency of the solar cell and the long-term reliability of the device.

[0105] In some embodiments, the titanium dioxide crystals are of rutile type or anatase type.

[0106] It can be understood that the solar cell prepared by the above preparation method of the present application is a formal perovskite solar cell, and the formal perovskite solar cell has a structure from top to bottom as substrate, electron transport layer, perovskite layer, hole transport layer and electrode layer. On the premise of the concept of the present application, those skilled in the art can also prepare a reverse perovskite solar cell, and the reverse perovskite solar cell has a structure from bottom to top as substrate, hole transport layer, perovskite layer, electron transport layer and electrode layer.

[0107] Based on the same inventive concept, the embodiments of the present application also provide a stacked cell, comprising: a bottom cell, a composite layer and a top cell stacked in sequence along a predetermined direction; wherein the top cell is a solar cell prepared by the above preparation method, which can endow the stacked cell with higher photoelectric conversion performance.

[0108] It can be understood that the stacked battery includes but is not limited to a two-terminal stacked battery, a three-terminal stacked battery, and a four-terminal stacked battery. Further, the stacked battery includes but is not limited to a perovskite battery stacked with a crystalline silicon battery, a perovskite battery stacked with a perovskite battery, and a perovskite battery stacked with a thin-film battery. The thin-film battery includes but is not limited to a perovskite solar thin-film battery, a copper-indium-selenium solar thin-film battery, a gallium arsenide solar thin-film battery, and a cadmium sulfide solar thin-film battery. The crystalline silicon battery includes but is not limited to a PERC battery (passivated emitter and rear cell), an IBC battery (interdigitated back contact cell), a TOPCon battery (tunnel oxide passivated contact cell), an HJT battery (heterojunction cell), and an HBC battery (heterojunction with intrinsic thin layer cell).

[0109] Based on the same inventive concept, the embodiments of the present application also provide a photovoltaic module, which comprises:

[0110] A cell string is connected by a plurality of solar cells prepared by the above preparation method;

[0111] An encapsulation layer covers the surface of the cell string;

[0112] A cover plate is used to cover the surface of the encapsulation layer away from the cell string.

[0113] Specifically, referring to Figure 3 , the photovoltaic module 1000 comprises a first cover plate 200, a first encapsulation adhesive layer 300, a solar cell string, a second encapsulation adhesive layer 400, and a second cover plate 500.

[0114] In some embodiments, the solar cell string comprises a plurality of solar cells 100 as described above connected by a conductive ribbon, and the connection between the solar cells 100 can be partially stacked or spliced.

[0115] In some embodiments, the first cover plate 200 and the second cover plate 500 can be transparent or opaque cover plates, such as glass cover plates or plastic cover plates.

[0116] The two sides of the first encapsulation adhesive layer 300 are in contact with the first cover plate 200 and the cell string, respectively, and the two sides of the second encapsulation adhesive layer 400 are in contact with the second cover plate 500 and the cell string, respectively. The first encapsulation adhesive layer 300 and the second encapsulation adhesive layer 400 can be ethylene-vinyl acetate copolymer (EVA) adhesive film, polyethylene octene elastomer (POE) adhesive film, or polyethylene terephthalate (PET) adhesive film, respectively.

[0117] The photovoltaic module 1000 can also be fully encapsulated on the side edges, that is, the encapsulation adhesive tape is used to completely encapsulate the side edges of the photovoltaic module 1000 to prevent the phenomenon of lamination deviation of the photovoltaic module 1000 during the lamination process.

[0118] The photovoltaic module 1000 further comprises an edge sealing component which fixes the part of the edge encapsulated in the photovoltaic module 1000. The edge sealing component can fix the edge close to the corner encapsulated on the photovoltaic module 1000. The edge sealing component can be a high-temperature-resistant adhesive tape. The high-temperature-resistant adhesive tape has excellent high-temperature-resistant characteristics and will not decompose or fall off during the lamination process, thereby ensuring reliable encapsulation of the photovoltaic module 1000. The two ends of the high-temperature-resistant adhesive tape are fixed to the second cover plate 500 and the first cover plate 200, respectively. The two ends of the high-temperature-resistant adhesive tape can be bonded to the second cover plate 500 and the first cover plate 200, respectively, and the middle part can limit the side edge of the photovoltaic module 1000 to prevent the photovoltaic module 1000 from being offset during the lamination process.

[0119] The embodiments of the present application are further described below in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the protection scope, appropriate changes can be made.

[0120] Embodiment 1

[0121] (1) High-purity titanium elements (purity greater than or equal to 99.9%) and high-purity sulfur elements (purity greater than or equal to 99.9%) with a molar ratio of 1:2.2 were placed in a ball mill for mixing for 5h-6h. After mixing, the obtained material was placed in a vacuum sintering furnace and heated to 1000℃ at a rate of 5℃ / min, and kept for 24h to obtain titanium disulfide.

[0122] (2) The titanium disulfide, hydrogen peroxide, and deionized water were mixed and then placed in an oxygen atmosphere for ultrasonic treatment for 2min. The ultrasonic power was 800W, the mass ratio of TiS2 to hydrogen peroxide was 1:8, and the mass ratio of hydrogen peroxide to deionized water was 1:1. The ultrasonic product was placed in deionized water for hydrolysis for 1h to obtain a titanium dioxide amorphous precursor solution.

[0123] (3) The ITO glass sheet was sequentially ultrasonically cleaned with deionized water, acetone, and ethanol for 15min-20min, and then dried.

[0124] (4) The titanium dioxide amorphous precursor solution obtained in step (2) was spin-coated on the ITO glass sheet at a speed of 3000rpm for 20s, and then placed in a vacuum sintering furnace and heated to 500℃ at a rate of 5℃ / min for sintering for 3min to obtain a white anatase-type titanium dioxide electron transport layer with a thickness of 170nm.

[0125] (5) The product obtained in step (4) is cooled to room temperature, preheated at 130°C for 3-5 min, 50 μL of perovskite solution (3-chlorobenzylammonium iodide, methylammonium chloride, lead iodide mixed in N,N-dimethylformamide and dimethyl sulfoxide) is spin-coated on the surface of the electron transport layer of the product obtained in step (4) at a speed of 4000 rpm for 20 s, and then annealed at 90°C for 10 min to prepare a perovskite layer.

[0126] (6) 10 mg of poly-3-hexylthiophene is dissolved in 1 mL of a mixed solution of chlorobenzene, and then dropped onto the surface of the perovskite layer, spin-coated on the surface of the perovskite layer at a speed of 4000 rpm for 20 s, and then annealed at 90°C for 10 min to prepare a hole transport layer.

[0127] (7) The product obtained in step (6) is placed in a vacuum evaporation box, and copper is evaporated on the hole transport layer to obtain a solar cell.

[0128] Figure 4 The XRD pattern of the titanium disulfide prepared in step (1) is shown in FIG. 1. Figure 4 It can be seen that the titanium disulfide obtained in the present application is in a pure phase.

[0129] Figure 5 The SEM pattern of the titanium dioxide amorphous precursor solution in step (2) is shown in FIG. 2. Figure 5 It can be seen that the titanium dioxide in the titanium dioxide amorphous precursor solution is in a nanosheet structure.

[0130] Figure 6 The SEM pattern of the titanium dioxide electron transport layer prepared in step (4) is shown in FIG. 3. Figure 6 It can be seen that the titanium dioxide is in a nanobranch crystal structure, and the texture is uniform, indicating that a large-area distributed titanium dioxide electron transport layer is prepared in the present application.

[0131] Example 2

[0132] Different from example 1, (4) the titanium dioxide amorphous precursor solution obtained in step (2) is spin-coated on an ITO glass sheet at a speed of 4500 rpm for 25 s, and then placed in a vacuum sintering furnace and heated to 500°C at a rate of 5°C / min for sintering for 3 min to obtain a white anatase-type titanium dioxide electron transport layer with a thickness of 230 nm.

[0133] Example 3

[0134] Different from example 1, the titanium dioxide amorphous precursor solution obtained in step (2) is spin-coated on an ITO glass sheet at a speed of 4500 rpm for 35 s, and then placed in a vacuum sintering furnace and heated to 500°C at a rate of 5°C / min for sintering for 3 min to obtain a white anatase-type titanium dioxide electron transport layer with a thickness of 250 nm.

[0135] The solar cells prepared in Examples 1-3 were subjected to photovoltaic conversion efficiency (PCE), open-circuit voltage (Voc), short-circuit current density (Jsc) and fill factor (FF) determination, and the determination results are shown in Table 1.

[0136] Table 1. Performance of solar cells prepared in Examples 1-3

[0137]

[0138] As can be seen from Table 1, the solar cell composed of the electron transport layer prepared by the preparation method of the present application has a higher photovoltaic conversion efficiency.

[0139] By changing the sintering temperature in the vacuum sintering furnace of step (4) of Example 1, the crystallization of the titanium dioxide amorphous precursor liquid prepared by the present application was observed, Figure 7 The crystallization of titanium dioxide under the conditions of sintering temperature in the vacuum sintering furnace of step (4) being 25℃, 50℃, 100℃, 200℃, 300℃, 400℃ and 500℃, respectively, is shown, and Figure 7 It can be seen that the amorphous titanium dioxide obtained by the preparation method of the present application begins to crystallize at 200℃, and exhibits the characteristic peaks of anatase titanium dioxide, and is completely crystallized at 400℃-500℃. Therefore, the crystallization of titanium dioxide can be achieved at a relatively wide heat treatment temperature, and different heat treatment temperatures can be selected according to the type of the selected substrate, and a large-area titanium dioxide electron transport layer can be prepared.

[0140] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a solar cell, characterized in that, Includes the following steps: Provide a base; Titanium disulfide was prepared by solid-state synthesis. The mixture of titanium disulfide and hydrogen peroxide was subjected to ultrasonic treatment to obtain an amorphous titanium dioxide precursor solution. The amorphous titanium dioxide precursor liquid is coated on the surface of the substrate and subjected to a first heat treatment to obtain an electron transport layer. A perovskite layer is formed on the surface of the electron transport layer; A hole transport layer is formed on the surface of the perovskite layer; An electrode layer is formed on the surface of the hole transport layer.

2. The preparation method according to claim 1, characterized in that, The preparation of titanium disulfide using the solid-state synthesis method includes: Titanium and sulfur in a molar ratio of 1:(2.0~2.2) were mixed and then subjected to a second heat treatment.

3. The preparation method according to claim 2, characterized in that, Prior to the second heat treatment, the process further includes a step of ball milling the mixture of elemental titanium and elemental sulfur.

4. The preparation method according to claim 2, characterized in that, The temperature of the second heat treatment is 700℃~1200℃, the heating rate of the second heat treatment is 1℃ / min~10℃ / min, and the holding time of the second heat treatment is 20h~48h.

5. The preparation method according to claim 1, characterized in that, The ultrasonic treatment of the mixture of titanium disulfide and hydrogen peroxide includes: The titanium disulfide is mixed with a solution containing hydrogen peroxide to obtain a premix, which is then subjected to ultrasonic treatment in an oxygen atmosphere. The ultrasonic treatment is followed by a centrifugation step.

6. The preparation method according to claim 5, characterized in that, The ultrasonic treatment power is 500W~1000W, and the ultrasonic treatment time is 1min~3min; The solvent in the hydrogen peroxide-containing solution includes at least one of deionized water and ethanol; The mass ratio of titanium disulfide to hydrogen peroxide is 1:(5~20).

7. The preparation method according to claim 1, characterized in that, The ultrasonic treatment of the mixture of titanium disulfide and hydrogen peroxide further includes: The step of mixing the product obtained from the ultrasonic treatment with a hydrolysate, wherein the hydrolysate comprises at least one of deionized water and an alcohol compound.

8. The preparation method according to claim 1, characterized in that, The coating includes spin coating, the coating rotation speed is 3000rpm~6000rpm, and the coating time is 10s~50s; The temperature of the first heat treatment is greater than or equal to 200℃, the time of the first heat treatment is 1 min to 3 min, and the heating rate of the first heat treatment is 1℃ / min to 10℃ / min.

9. A solar cell, characterized in that, The solar cell is fabricated using the solar cell fabrication method according to any one of claims 1 to 8. The solar cell comprises: a substrate, an electron transport layer, a perovskite layer, a hole transport layer, and an electrode layer. The electron transport layer is located between the substrate and the perovskite layer, and the hole transport layer is located between the perovskite layer and the electrode layer. The electron transport layer comprises a plurality of titanium dioxide crystals, and the plurality of titanium dioxide crystals are stacked to form a dendritic structure.

10. The solar cell according to claim 9, characterized in that, The thickness of the electron transport layer is 100nm~300nm.

11. The solar cell according to claim 9, characterized in that, The titanium dioxide crystals have a particle size of 100 nm to 2 μm.

12. The solar cell according to claim 9, characterized in that, The titanium dioxide crystals are rutile or anatase.

13. A stacked battery, characterized in that, include: A bottom cell, a composite layer, and a top cell are stacked sequentially along a predetermined direction; wherein the top cell is a solar cell formed by the method for preparing a solar cell as described in any one of claims 1 to 8 or a solar cell as described in any one of claims 9 to 12.

14. A photovoltaic module, characterized in that, The photovoltaic module includes: A battery string, wherein the battery string is formed by connecting a plurality of solar cells formed by the preparation method according to any one of claims 1 to 8 or solar cells according to any one of claims 9 to 12; An encapsulation layer that covers the surface of the battery string; A cover plate for covering the surface of the encapsulation layer away from the battery string.

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