Organic electron transport material, preparation method thereof and perovskite solar cell

Abstract

The invention discloses an organic electron transport material, a preparation method thereof and a perovskite solar cell, and relates to the technical field of organic photoelectric materials. The organic electron transport material has a structural formula shown as a formula (I), and R1 and R2 are independently selected from any one of C3-C20 cycloalkyl, C2-C20 straight chain or branched chain alkenyl, C2-C20 straight chain or branched chain aliphatic amide, C2-C20 straight chain or branched chain aliphatic isocyanate and substituent formed by interrupting the C3-C20 cycloalkyl by at least one-O-. The organic electron transport material provided by the invention can greatly improve the photo-thermal stability and environmental stability of the perovskite solar cell on the premise of not sacrificing the photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of organic photoelectric materials, and in particular to an organic electron transport material and a preparation method thereof, and a perovskite solar cell. Background Art

[0002] While the photoelectric conversion efficiency of photovoltaic materials, such as silicon-based solar cells, has rapidly improved, it still struggles to meet the demands of commercial applications. For example, silicon-based solar cells are expensive to produce, and in industrial-scale production, photogenerated electrons are prone to recombination during transmission, significantly impacting cell efficiency. Industrial-grade solar cells, on the other hand, place extremely high demands on material stability and photoelectric efficiency. Therefore, the development of low-cost, high-photoelectric-efficiency photovoltaic materials is crucial. Perovskite solar cells, in particular, have garnered widespread attention due to their high efficiency, low cost, ease of large-scale production, and environmental friendliness.

[0003] Perovskite solar cells typically consist of a conductive glass layer, an electron transport layer (ETL), a perovskite layer, a hole transport layer (HTL), and a metal electrode layer. The electron transport layer (ETL) is a crucial component for charge separation and transport. It not only separates photogenerated carriers in the perovskite and transfers electrons to the HTL, but also influences the crystal quality and film morphology of the perovskite layer. Therefore, the performance of the ETL is crucial to the photoelectric conversion efficiency of perovskite solar cells. Currently, the ETL materials used in perovskite solar cells are primarily inorganic and organic small molecule materials. Inorganic materials, for example, can be tin oxide. However, tin oxide has small crystal size and low crystallinity, making it susceptible to oxidation or hydrolysis under conditions of light and high temperature, resulting in poor photothermal stability in practical applications. Similar to tin oxide, organic small molecule materials also face performance degradation under conditions of light and high temperature. Furthermore, in the presence of moisture and oxygen, these molecules easily penetrate the ETL into the perovskite layer. Perovskite materials are extremely sensitive to moisture and oxygen, significantly reducing the stability and photoelectric conversion efficiency of perovskite solar cells. The above problems directly affect the long-term stability and reliability of perovskite solar cells. Summary of the Invention

[0004] The main purpose of the present invention is to provide an organic electron transport material and a preparation method thereof, and a perovskite solar cell, so as to solve the problem in the prior art that perovskite solar cells are difficult to balance photoelectric conversion efficiency and environmental stability due to the poor photothermal stability of electron transport materials.

[0005] In order to achieve the above object, according to one aspect of the present invention, an organic electron transport material is provided. The organic electron transport material has the structural formula shown in formula (I):

[0006]

[0007] Wherein, R1 and R2 are each independently selected from C3 to C 20 Cycloalkyl, C2~C 20 Straight or branched alkenyl, C2~C 20 Straight-chain or branched aliphatic amide groups, C2~C 20 Straight-chain or branched aliphatic isocyanate group, C3~C 20 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

[0008] Furthermore, R1 and R2 are each independently selected from C3 to C 10 Cycloalkyl, C2~C 15 Straight or branched alkenyl, C2~C 15 Straight-chain or branched aliphatic amide groups, C2~C 10 Straight-chain or branched aliphatic isocyanate group, C3~C 10 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

[0009] Furthermore, R1 and R2 are each independently selected from C3 to C 12 A straight or branched alkenyl group, a C3-C 15 Any one of a straight-chain or branched aliphatic amide group, a C2-C6 straight-chain or branched aliphatic isocyanate group, and a C3-C6 cycloalkyl group interrupted by one -O-.

[0010] Furthermore, R1 and R2 are the same.

[0011] Further, R1 and R2 are each independently selected from Any one of .

[0012] The second aspect of the present invention provides a method for preparing the organic electron transport material of the first aspect, comprising the following steps: mixing 1,4,5,8-naphthalenetetracarboxylic anhydride, an amino compound containing R1 and R2 with an organic solvent under a protective atmosphere, and performing an amidation reaction to obtain an organic electron transport material; wherein R1 and R2 are each independently selected from C3 to C 20 Cycloalkyl, C2~C 20 Straight or branched alkenyl, C2~C 20 Straight-chain or branched aliphatic amide groups, C2~C 20 Straight-chain or branched aliphatic isocyanate group, C3~C 20Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

[0013] Furthermore, R1 and R2 are each independently selected from C3 to C 10 Cycloalkyl, C2~C 15 Straight or branched alkenyl, C2~C 15 Straight-chain or branched aliphatic amide groups, C2~C 10 Straight-chain or branched aliphatic isocyanate group, C3~C 10 Any one of the substituents formed by the cycloalkyl group being interrupted by at least one -O-;

[0014] Preferably, R1 and R2 are each independently selected from C3 to C 12 A straight or branched alkenyl group, a C3-C 15 Any one of a straight-chain or branched aliphatic amide group, a C2-C6 straight-chain or branched aliphatic isocyanate group, and a C3-C6 cycloalkyl group interrupted by a -O-;

[0015] More preferably, R1 and R2 are the same.

[0016] Furthermore, the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(1-10);

[0017] Preferably, the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(2-5);

[0018] More preferably, the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(2-3);

[0019] The temperature of the amidation reaction is 80°C to 120°C, and the time of the amidation reaction is 12h to 24h;

[0020] Preferably, the amidation reaction temperature is 90°C to 110°C, and the amidation reaction time is 15h to 20h;

[0021] More preferably, the amidation reaction temperature is 100° C. to 110° C., and the amidation reaction time is 16 h to 18 h;

[0022] Preferably, the organic solvent comprises N,N-dimethylformamide.

[0023] Furthermore, after the amidation reaction is completed, the method further includes: naturally cooling the amidation reaction product to room temperature, washing with water to obtain a washed product; extracting the washed product with a first extractant, and collecting an organic phase; drying and purifying the organic phase in sequence to obtain the organic electron transport material; wherein the first extractant includes dichloromethane; the second extractant used in the purification process includes a mixture of petroleum ether and dichloromethane, and the volume ratio of the petroleum ether to the dichloromethane is (1 to 2): (1 to 2).

[0024] The third aspect of the present invention provides a perovskite solar cell, comprising a conductive glass layer, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer stacked in sequence, wherein the electron transport layer comprises the organic electron transport material of the first aspect or the organic electron transport material prepared by the preparation method of the second aspect.

[0025] The technical solution of the present invention is applied. The organic electron transport material provided by the present invention includes a conjugated aromatic skeleton and a thermally cross-linked side chain group R1 and R2 connected to the conjugated aromatic skeleton. Due to the presence of the thermally cross-linked side chain group, the organic electron transport material molecule can spontaneously undergo a cross-linking reaction during heating to form a three-dimensional network structure. This three-dimensional network structure enhances the intermolecular force, so that the electron transport layer maintains good performance under light and high temperature conditions, is not prone to decomposition or structural changes, and greatly improves the mechanical strength and stability of the perovskite solar cell. At the same time, this three-dimensional network structure can effectively block moisture and oxygen in the environment from penetrating into the perovskite layer, reducing the risk of moisture and oxygen erosion of the perovskite material, and improving the water and oxygen resistance of the perovskite solar cell. In addition, the electron transport layer formed by the organic electron transport material can optimize its interface contact and energy level matching with the perovskite layer, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. Therefore, the organic electron transport material of the present invention can significantly improve the photothermal stability and environmental stability of the perovskite solar cell without sacrificing the photoelectric conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic structural diagram of a perovskite solar cell according to one embodiment of the present invention;

[0027] Figure 2 The electrostatic potential and electron orbital arrangement diagram of the organic electron transport material in Example 1 of the present invention;

[0028] Figure 3 The electrostatic potential and electron orbital arrangement diagram of the organic electron transport material in Example 2 of the present invention;

[0029] Figure 4Steady-state fluorescence spectra (PL) of buried interfaces of perovskite solar cells in Example 3, Example 4, and Comparative Example 2 of the present invention;

[0030] Figure 5 The buried interface transient photon spectrum (TRPL) of the perovskite solar cell in Example 3, Example 4 and Comparative Example 2 of the present invention is shown;

[0031] Figure 6 X-ray diffraction patterns of the organic electron transport materials of Examples 1 and 2 of the present invention and the electron transport material of Comparative Example 1, as well as the X-ray diffraction patterns after working at 85° C. for 7 days;

[0032] Figure 7 The conductivity test curves of the organic electron transport materials of Examples 1 and 2 of the present invention and the electron transport material of Comparative Example 1, as well as the conductivity test curves after working at 85° C. for 7 days;

[0033] Figure 8 Graphs showing the current-voltage (JV) characteristics of the perovskite solar cells in Example 3, Example 4, and Comparative Example 2 of the present invention;

[0034] Figure 9 The organic electron transport material in Example 1 of the present invention 1 HNMR spectrum;

[0035] Figure 10 The organic electron transport material in Example 1 of the present invention 13 CNMR spectrum;

[0036] Figure 11 The organic electron transport material in Example 2 of the present invention 1 HNMR spectrum;

[0037] Figure 12 The organic electron transport material in Example 2 of the present invention 13 CNMR spectrum.

[0038] Description of reference numerals:

[0039] 1-conductive glass layer; 101-glass substrate; 102-ITO film; 2-electron transport layer; 3-perovskite layer; 4-hole transport layer; 5-metal electrode layer. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0041] As described in the background of the present invention, in the prior art, due to the poor photothermal stability of electron transport materials, perovskite solar cells have difficulty in achieving both photoelectric conversion efficiency and environmental stability. To address the above problems, in a typical embodiment of the present invention, an organic electron transport material is provided, wherein the organic electron transport material has the structural formula shown in formula (I):

[0042]

[0043] Wherein, R1 and R2 are each independently selected from C3 to C 20 Cycloalkyl, C2~C 20 Straight or branched alkenyl, C2~C 20 Straight-chain or branched aliphatic amide groups, C2~C 20 Straight-chain or branched aliphatic isocyanate group, C3~C 20 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

[0044] The organic electron transport material of the present invention has a conjugated aromatic structure, specifically a naphthalene diimide (NDI) skeleton, which is formed by replacing two carbon atoms on the naphthalene ring with an imide group (-N(C=O)-). In the NDI skeleton, the π electron system of the naphthalene ring and the π electron system of the imide group are connected to each other through conjugation, forming an extended conjugated π electron system with a high electron affinity, which makes it perform well in the application of electron transport materials and is particularly suitable for use as an electron transport layer material in perovskite solar cells. At the same time, the rigid structure of the aromatic ring also helps to maintain the stability of the organic electron transport material, so that it exhibits excellent performance in the application of perovskite solar cells.

[0045] The organic electron transport material of the present invention not only improves the electron transport performance of the organic electron transport material by introducing thermally cross-linked side chain groups on the NDI skeleton, but also significantly improves its photothermal stability and water and oxygen resistance. The organic electron transport material is applied as an electron transport layer in perovskite solar cells, which can greatly improve the photothermal stability and environmental stability of the perovskite solar cell without sacrificing the photoelectric conversion efficiency.

[0046] R1 and R2 are thermal cross-linking side chain groups connected to the NDI skeleton, and R1 and R2 can be the same or different. R1 and R2 independently include but are not limited to C3 to C 20 Cycloalkyl, C2~C 20 Straight or branched alkenyl, C2~C 20 Straight-chain or branched aliphatic amide groups, C2~C 20Straight-chain or branched aliphatic isocyanate group, C3~C 20 Any of the substituents formed by interrupting a cycloalkyl group with at least one -O- group. On the one hand, these thermally crosslinked side chain groups, under appropriate heat treatment conditions, form a three-dimensional network structure through chemical reactions between themselves and other molecules. This three-dimensional network structure can enhance intermolecular forces, helping to improve the overall mechanical strength and stability of the organic electron transport material, reducing its potential for degradation during temperature fluctuations or prolonged use. This allows the organic electron transport material to maintain its structure and electron transport properties even at elevated temperatures, resulting in high thermal stability and contributing to the stable operation of perovskite solar cells under conditions of light and high temperature. On the other hand, the stable chemical chains formed by this three-dimensional network structure can resist oxidation reactions, helping the organic electron transport material maintain its structural integrity and electron transport properties in an aerobic environment. Furthermore, perovskite materials are highly sensitive to moisture and easily degrade in humid environments. These thermally crosslinked side chain groups possess a certain degree of hydrophobicity, which can enhance the water resistance of the organic electron transport material, effectively preventing moisture and oxygen from penetrating into the perovskite layer, reducing the risk of moisture and oxygen corrosion of the perovskite material and improving the water and oxygen resistance of the perovskite solar cell.

[0047] In addition, by controlling the group types of R1 and R2, on the one hand, the presence of thermally cross-linked side chain groups can optimize the contact with the perovskite layer and improve the interface stability by changing the surface properties of the organic electron transport material. For example, it can enhance wettability, promote the formation of a more uniform perovskite film, improve the charge transfer efficiency at the interface, and reduce non-radiative recombination; on the other hand, it helps to adjust the energy level of the organic electron transport material so that it more closely matches the electronic structure of the perovskite layer. The optimization of the energy level helps to improve the electron injection efficiency and reduce energy loss, thereby improving the overall photoelectric conversion efficiency and stability.

[0048] Therefore, by introducing thermally crosslinked side chain groups into the NDI backbone, not only can the photothermal and environmental stability of the organic electron transport material be enhanced by forming a stable crosslinked network structure, but the performance of the perovskite solar cell can also be improved by improving the interfacial interaction and energy level matching with the perovskite layer. The organic electron transport material of the present invention can significantly improve the photothermal and environmental stability of the perovskite solar cell without sacrificing the photoelectric conversion efficiency.

[0049] In order to further improve the photothermal stability and environmental stability of organic electron transport materials, in some embodiments, R1 and R2 are each independently selected from C3 to C 10 Cycloalkyl, C2~C 15 Straight or branched alkenyl, C2~C 15 Straight-chain or branched aliphatic amide groups, C2~C10 Straight-chain or branched aliphatic isocyanate group, C3~C 10 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

[0050] In some embodiments, R1 and R2 are each independently selected from C3 to C 12 A straight or branched alkenyl group, a C3-C 15 Any of the following substituents: a linear or branched aliphatic amide group, a C2-C6 linear or branched aliphatic isocyanate group, or a C3-C6 cycloalkyl group interrupted by an -O-. The use of these groups not only improves the conductivity of the electron transport layer but also improves the interface between it and the perovskite layer, reducing non-radiative recombination at the interface and further enhancing the photoelectric conversion efficiency of perovskite solar cells.

[0051] In some embodiments, R1 and R2 are the same. When R1 and R2 are the same, the molecular structure of the organic electron transport material is more symmetrical, which helps to form a more ordered crystal structure, thereby improving the electron mobility of the electron transport layer, reducing scattering during electron transport, and further improving the electron transport efficiency of the perovskite solar cell.

[0052] In some embodiments, R1 and R2 are selected from Any of the above substituents. All of the above substituents are thermally cross-linkable groups. By controlling the R1 and R2 substituents to meet the above specific structures, the electron transport performance of the organic electron transport material can be further optimized, while enhancing its compatibility with the perovskite layer, reducing interface defects, and improving the stability and life of the perovskite solar cell.

[0053] It should be noted that “*” represents the connection site.

[0054] The second aspect of the present invention provides a method for preparing an organic electron transport material, comprising the following steps: mixing 1,4,5,8-naphthalenetetracarboxylic anhydride, an amino compound containing R1 and R2 with an organic solvent under a protective atmosphere, and performing an amidation reaction to obtain the organic electron transport material; wherein R1 and R2 are each independently selected from C3 to C 20 Cycloalkyl, C2~C 20 Straight or branched alkenyl, C2~C 20 Straight-chain or branched aliphatic amide groups, C2~C 20 Straight-chain or branched aliphatic isocyanate group, C3~C 20 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

[0055] Specifically, conducting the reaction under the protection of an inert gas such as nitrogen or argon effectively eliminates the adverse effects of oxygen and moisture on the reaction, ensuring the purity and efficiency of the synthesis process. 1,4,5,8-naphthalenetetracarboxylic anhydride and an amino compound containing R1 and R2 groups are added to an organic solvent that can dissolve the reactants and promote the reaction. At an appropriate temperature, the anhydride group of 1,4,5,8-naphthalenetetracarboxylic anhydride reacts with the amino group of the amino compound to form an amide bond (-CONH-). During the amidation reaction, R1 and R2 are introduced as side chains onto the NDI backbone to form an organic electron transport material.

[0056] In some embodiments, the organic solvent is divided into a first part of organic solvent and a second part of organic solvent; 1,4,5,8-naphthalenetetracarboxylic anhydride is mixed with the first part of organic solvent, the temperature is raised to 80°C to 100°C and stirred for a certain time to obtain a first reaction liquid; an amino compound containing R1 and R2 groups is mixed with the second part of organic solvent to obtain a second reaction liquid; the first reaction liquid and the second reaction liquid are mixed to obtain a first reaction system; the first reaction system is heated to reflux state and maintained for a certain time to perform an amidation reaction to obtain an organic electron transport material.

[0057] In some embodiments, R1 and R2 are each independently selected from C3 to C 10 Cycloalkyl, C2~C 15 Straight or branched alkenyl, C2~C 15 Straight-chain or branched aliphatic amide groups, C2~C 10 Straight-chain or branched aliphatic isocyanate group, C3~C 10 Any one of the substituents formed by the cycloalkyl group being interrupted by at least one -O-;

[0058] In some embodiments, R1 and R2 are each independently selected from C3 to C 12 A straight or branched alkenyl group, a C3-C 15 Any one of a straight-chain or branched aliphatic amide group, a C2-C6 straight-chain or branched aliphatic isocyanate group, and a C3-C6 cycloalkyl group interrupted by one -O-.

[0059] In some embodiments, R1 and R2 are the same. By controlling R1 and R2 to be the same, not only is the electron transport performance of the prepared organic electron transport material guaranteed, but its physical and chemical properties are also optimized, resulting in excellent performance in perovskite solar cells, while also helping to reduce production costs.

[0060] When R1 and R2 are the same, the amino compound can be R-NH2, where R refers to the same R1 and R2. In this case, R can be any of the following groups: This helps to prepare organic electron transport materials with excellent comprehensive performance.

[0061] When R1 and R2 are the same and the amino compound is R-NH2, 1,4,5,8-naphthalenetetracarboxylic anhydride, R-NH2 and an organic solvent are mixed to carry out an amidation reaction, specifically the following reaction occurs:

[0062]

[0063] By controlling the reaction conditions, the structure and properties of the prepared organic electron transport material can be precisely adjusted to make it more suitable as a material for the electron transport layer. At the same time, the high yield and high purity of the reaction are guaranteed, which is conducive to the industrial production of the material. In some embodiments, the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1: (1 to 10). The molar ratio of the reaction raw materials is a key parameter affecting the reaction yield, product purity and final material properties. By controlling the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound within the above range, the complete reaction of 1,4,5,8-naphthalenetetracarboxylic anhydride is ensured, and the unreacted raw materials in the product are avoided.

[0064] In some preferred embodiments, the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(2-5). This molar ratio range comprehensively considers the reaction efficiency, product purity and cost-effectiveness, while promoting the complete reaction and reducing the residual raw materials. At the same time, it avoids side reactions and unnecessary post-treatments, which helps to prepare high-purity products while maintaining a high reaction yield.

[0065] In some preferred embodiments, the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(2-3). By controlling the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound within the above range, it is helpful to prepare a more uniform and pure target product, while minimizing the generation of by-products, further ensuring the efficient synthesis and performance of the product.

[0066] Specifically, the molar ratio of 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10 or a range consisting of any two thereof.

[0067] In some embodiments, the amidation reaction temperature is 80°C to 120°C, and the amidation reaction time is 12 hours to 24 hours. By controlling the amidation reaction temperature, a basic thermodynamic environment for the reaction is provided, accelerating the reaction rate while promoting effective contact and reaction between the raw materials. By controlling the amidation reaction time, sufficient reaction progress is ensured, thereby improving the yield and purity of the prepared organic electron transport material.

[0068] In some embodiments, the amidation reaction temperature is 90° C. to 110° C., and the amidation reaction time is 15 to 20 hours. By controlling the amidation reaction temperature and time, the reaction efficiency and product quality are further optimized, which helps to reduce side reactions and improve the stability and purity of the prepared organic electron transport material.

[0069] To more precisely control the reaction and obtain the highest quality and highest yield of organic electron transport materials, in some embodiments, the amidation reaction temperature is 100°C to 110°C, and the amidation reaction time is 16 hours to 18 hours. Reaction under these conditions avoids the potential decomposition of the raw materials and products under high temperature or prolonged heating, ensuring the purity of the prepared organic electron transport material and the controllability of the reaction.

[0070] Specifically, the temperature of the amidation reaction can be 80°C, 90°C, 100°C, 110°C, 120°C or a range consisting of any two thereof, and the time of the amidation reaction can be 12h, 14h, 16h, 18h, 20h, 22h, 24h or a range consisting of any two thereof.

[0071] In some embodiments, the organic solvent includes N,N-dimethylformamide (DMF), which helps to uniformly disperse the reaction raw materials in the reaction system, promotes the reaction between the anhydride and the amino group, accelerates the formation of the amide bond, and promotes the efficient conduct of the amidation reaction. At the same time, DMF has good chemical stability at high temperatures and is not easy to decompose, reducing the possibility of side reactions. In addition, its high dielectric constant is conducive to the separation of charges and the interaction of reactants, thereby improving the reaction yield and product purity.

[0072] In the process of preparing organic electron transport materials, the amidation reaction also includes a post-processing step, which includes cooling, water washing, extraction, drying, and purification. In some embodiments, after the amidation reaction is completed, the following steps are further included: naturally cooling the amidation reaction product to room temperature, washing it with water to obtain a washed product; extracting the washed product with a first extractant and collecting the organic phase; drying and purifying the organic phase in sequence to obtain an organic electron transport material; wherein the first extractant includes dichloromethane; the second extractant used in the purification process includes a mixture of petroleum ether and dichloromethane, and the volume ratio of petroleum ether to dichloromethane is (1-2): (1-2). These post-processing steps ensure the purity and stability of the final product, thereby improving its performance in applications such as perovskite solar cells.

[0073] Specifically, after the reaction is completed, the reaction mixture is naturally cooled to room temperature (e.g., 20 to 30° C.). Cooling helps to stabilize the product by reducing molecular motion and avoids side reactions in subsequent treatments. The cooled product is washed with water. The main purpose is to remove water-soluble by-products generated in the reaction, such as unreacted raw materials or acidic by-products, to improve the purity of the product and obtain a washed product. The washed product is extracted with a first extractant to separate and collect the target product in the organic phase. The organic phase needs to be dried, and a desiccant such as anhydrous magnesium sulfate (MgSO4) is generally used to remove the moisture therein to prevent the influence of moisture on the product in the subsequent purification step. The second extractant is then used for purification. In the purification process, a mixture of petroleum ether and dichloromethane is used as the second extractant. The difference in solubility of the two for different compounds can be utilized to perform more precise separation and purification by methods such as column chromatography, thereby further improving the purity of the target product.

[0074] In some embodiments, the first extractant includes dichloromethane, which has good solubility and separation properties from the aqueous phase and can effectively extract the organic product from the aqueous solution. This step usually requires multiple extractions to ensure that as much product as possible is recovered.

[0075] In some embodiments, the volume ratio of petroleum ether to dichloromethane is (1-2): (1-2), for example, 1:2, 1:1.5, 1:1, 1.5:1, 2:1 or a range consisting of any two of them. The use of such a mixed solvent can find the best balance between solubility and selectivity to optimize the purification effect.

[0076] The second aspect of the present invention provides a perovskite solar cell, comprising a conductive glass layer, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer stacked in sequence, wherein the electron transport layer comprises the organic electron transport material provided in the first aspect or the organic electron transport material prepared by the preparation method provided in the second aspect.

[0077] The use of the organic electron transport material provided by the present invention as the electron transport layer can significantly improve the photoelectric conversion efficiency and stability of perovskite solar cells. Its unique chemical structure and optimized physical properties enable perovskite solar cells to maintain high-efficiency operation under various environmental conditions.

[0078] Specifically, the conductive glass layer usually uses a glass substrate doped with indium tin oxide (ITO) as the transparent conductive layer of the perovskite solar cell, providing support and allowing light to enter. Specifically, the conductive glass layer is an ITO glass substrate, including a stacked glass substrate and an ITO film; the ITO film is a transparent conductive film composed of indium oxide (In2O3) and tin oxide (SnO2), usually coated on the glass surface by sputtering deposition and other methods to form an ITO glass substrate. ITO has good visible light transmittance, which makes it suitable as a transparent electrode in solar cells, allowing sunlight to penetrate while collecting current, without affecting the cell efficiency due to blocking light.

[0079] The electron transport layer (ETL) adopts the organic electron transport material provided by the present invention. Compared with traditional inorganic materials such as SnO2, this organic electron transport material can significantly enhance the stability of the device while maintaining good electron transport performance, reduce the negative impact of water and oxygen on material performance, and improve the surface wettability and crystallization quality of the perovskite layer.

[0080] The perovskite layer acts as a light-absorbing layer. Perovskite materials possess unique photoelectric properties, enabling efficient conversion of light energy into electrical energy. In this invention, the synergistic effect of the perovskite layer and the electron transport layer further enhances light absorption efficiency and carrier transport, which is key to improving the efficiency of perovskite solar cells.

[0081] The hole transport layer (HTL), located between the perovskite layer and the metal electrode layer, is responsible for extracting and transporting holes. Common materials include 2,7-bis(9,9-dimethyl-9H-fluorenyl)-9,9-dimethyl-9H-fluorene (also known as Spiro-OMeTAD). Working together with the electron transport layer, it optimizes charge separation and transport, reduces non-radiative recombination, and improves fill factor (FF) and short-circuit current (Jsc).

[0082] The metal electrode layer usually uses metal materials such as silver (Ag) or gold (Au) as the electrical contact of the perovskite solar cell to collect and conduct charges.

[0083] The stacked structure perovskite solar cell provided by the present invention not only improves the photoelectric conversion efficiency to more than 23% through the special electron transport layer material, but also significantly enhances the long-term stability and environmental adaptability of the device. In particular, by introducing the organic electron transport material of the present invention into the upright structure perovskite solar cell, the problem of performance degradation of existing SnO2-based devices in humidity and oxygen environments, as well as the stability problem under high temperature conditions, is solved, which helps to realize the industrial production of perovskite solar cells.

[0084] The present application is further described in detail below with reference to specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0085] Example 1

[0086] The organic electron transport material of this embodiment is NDI-O, which has the structure shown in Formula S-1:

[0087]

[0088] The preparation route of the organic electron transport material NDI-O of this embodiment is as follows:

[0089]

[0090] The preparation method of the organic electron transport material NDI-O of this embodiment includes the following steps:

[0091] Under a nitrogen atmosphere, 1,4,5,8-naphthalenetetracarboxylic anhydride (0.7 g, 2.61 mmol) was dissolved in DMF (15 mL), the temperature was raised to 90 ° C and stirred for 30 min to obtain a first reaction solution; 3-methyl-3-aminomethyl-1-oxetane (0.55 g, 5.48 mmol) was dissolved in DMF (10 mL) to obtain a second reaction solution; the second reaction solution was slowly added dropwise to the above-mentioned turbid first reaction solution, and after the addition was complete, a first reaction system was obtained; the first reaction system was heated to reflux and maintained for 24 h. After the reaction was completed, it was cooled to 25 ° C, extracted with dichloromethane, and the organic phase was collected; the organic phase was dried using MgSO4, and the solvent was removed under reduced pressure to obtain a crude product; the crude product was purified by column chromatography with petroleum ether / dichloromethane (1:1, v / v) as the eluent to obtain 0.87 g of a white solid product (yield 53%), which is the organic electron transport material of this embodiment.

[0092] The organic electron transport material of this embodiment 1 HNMR images Figure 9 As shown, 1HNMR (500MHz, Chloroform-d) δ8.78 (s, 4H), 4.80 (d, J = 6.2 Hz, 4H), 4.39 (s, 4H), 4.32 (d, J = 6.2 Hz, 4H), 1.44 (s, 6H); organic electron transport materials 13 CNMR image Figure 10 As shown, 13 CNMR(126MHz,Chloroform-d)δ163.58,131.49,126.86,126.64,81.30,46.20,40.93,22.66.

[0093] Example 2

[0094] The organic electron transport material of this embodiment is NDI-3X, which has the structure shown in Formula S-2:

[0095]

[0096] The preparation route of the organic electron transport material NDI-3X of this embodiment is as follows:

[0097]

[0098] The preparation method of the organic electron transport material NDI-O of this embodiment includes the following steps:

[0099] Under a nitrogen atmosphere, the raw material 1,4,5,8-naphthalenetetracarboxylic anhydride (0.7 g, 2.61 mmol) was dissolved in DMF (15 mL), the temperature was raised to 90 ° C and stirred for 30 min to obtain a first reaction solution; 2,2,2-triallylethylamine (0.95 g, 5.74 mmol) was dissolved in DMF (10 mL) to obtain a second reaction solution; the second reaction solution was slowly added dropwise to the above-mentioned turbid first reaction solution, and after the addition was complete, a first reaction system was obtained; the first reaction system was heated to reflux and maintained for 24 h. After the reaction was completed, it was cooled to 25 ° C, extracted with dichloromethane, and the organic phase was collected; the organic phase was dried using MgSO4, and the solvent was removed under reduced pressure to obtain a crude product; the crude product was purified by column chromatography with petroleum ether / dichloromethane (1:3, v / v) as the eluent to obtain 0.81 g of a white solid product (yield 55%), which is the organic electron transport material of this embodiment.

[0100] The organic electron transport material in Example 1 1 HNMR images Figure 11 As shown, 1HNMR (500MHz, Chloroform-d) δ8.73 (s, 4H), 5.96 (m, J = 17.2, 10.1, 7.2 Hz, 6H), 5.13–4.91 (m, 12H), 4.30 (s, 4H), 2.20 (d, J = 7.2 Hz, 12H); The organic electron transport material in Example 1 13 CNMR image Figure 12 As shown, 13 CNMR(126MHz,Chloroform-d)δ163.97,134.32,131.19,126.67,126.53,118.11,46.15,41.24,41.18.

[0101] Example 3

[0102] like Figure 1 As shown, the perovskite solar cell of this embodiment includes a conductive glass layer 1, an electron transport layer 2, a perovskite layer 3, a hole transport layer 4, and a metal electrode layer 5 stacked in sequence, wherein the conductive glass layer 1 includes a glass substrate 101 and an ITO film 102. The specific preparation method includes the following steps:

[0103] S1, ultrasonically cleaning a glass substrate coated with an ITO film using a glass cleaning solution, deionized water, acetone, and isopropyl alcohol for 15 minutes each, then drying it with dry compressed air, and then treating it with ultraviolet ozone for 15 minutes to improve its wettability, thereby obtaining a treated ITO glass substrate;

[0104] S2, mixing the organic electron transport material of Example 1 with chlorobenzene to prepare an organic electron transport material solution with a concentration of 0.3 mg / mL;

[0105] S3, spin-coating the organic electron transport material solution in S2 on the ITO glass substrate treated in S1 at a speed of 3000 rpm for 30 seconds to form an electron transport layer;

[0106] S4, in a glove box, the perovskite solution was stirred overnight, filtered through a 0.22 μm polytetrafluoroethylene (PTFE) filter membrane, and then deposited with ethyl acetate as an anti-solvent to obtain a perovskite film. After the perovskite film was annealed, a perovskite layer was formed; the Spiro-OMeTAD solution was spin-coated on the surface of the perovskite layer at a speed of 3000 rpm for 30 seconds to deposit a Spiro-OMeTAD film on the perovskite layer as a hole transport layer; finally, the perovskite film was heated under high vacuum (less than 10 -5 Under the conditions of 400 nm Pa, a Ag thin film with a thickness of 80 nm was evaporated as a metal electrode layer by thermal evaporation to obtain the perovskite solar cell of this embodiment.

[0107] Example 4

[0108] The difference from Example 3 is that in S2, the organic electron transport material of Example 1 is replaced by the organic electron transport material of Example 2.

[0109] Example 5

[0110] The difference from Example 3 is that in S2 and S3, the concentration of the organic electron transport material solution is 0.5 mg / mL.

[0111] Under nitrogen protection and room temperature, the perovskite solar cell of Example 5 achieved a championship efficiency of 25.23% under one standard sunlight.

[0112] Example 6

[0113] The difference from Example 4 is that in S2 and S3, the concentration of the organic electron transport material solution is 0.5 mg / mL.

[0114] Under nitrogen protection and room temperature, the perovskite solar cell of Example 6 achieved a championship efficiency of 24.33% under one standard sunlight.

[0115] Comparative Example 1

[0116] The electron transport material in this comparative example is SnO2 material, which is produced by Xi'an Baolait.

[0117] Comparative Example 2

[0118] The difference from Example 3 is that in the perovskite solar cell of this comparative example, S2, the SnO2 material is mixed with water to prepare a SnO2 solution with a concentration of 0.3 mg / mL; S3, the SnO2 solution in S2 is spin-coated on the treated ITO glass substrate at a speed of 3000 rpm for 30s to form an electron transport layer, and the other steps remain unchanged to obtain the perovskite solar cell of this comparative example.

[0119] Test example

[0120] 1. Electrostatic potential and electron orbital arrangement diagram;

[0121] The organic electron transport material was prepared into a thin film sample, and density functional theory (DFT) calculations were performed using Gaussian 09 software to explore the molecular configuration, molecular orbital energy level, charge density distribution and dipole moment.

[0122] Please refer to the electrostatic potential and electron orbital arrangement diagram of the organic electron transport material in Example 1 and Example 2. Figure 2 and Figure 3 .

[0123] 2. Steady-state fluorescence spectrum (PL) and transient fluorescence spectrum (TRPL) of buried interface;

[0124] The buried interface steady-state fluorescence spectrum (PL) and buried interface transient fluorescence spectrum (TRPL) are used to evaluate the photoelectric performance of the interface between the electron transport layer and the perovskite layer in perovskite solar cells.

[0125] The specific test method for steady-state fluorescence spectroscopy (PL) is as follows: using a fluorescence spectrometer, the perovskite solar cell is placed on the test platform, and a laser with a wavelength of 200nm to 900nm is selected as the excitation source (the HSD signal does not exceed 500,000cps, and the MCP signal does not exceed 300,000cps); turning on the laser, and using a spectrometer to collect the steady-state fluorescence spectrum data emitted by the sample; analyzing the steady-state fluorescence spectrum data using Fluoracle software to determine the steady-state fluorescence spectrum diagram of its buried interface.

[0126] The specific test method for transient fluorescence spectroscopy (TRPL) is as follows: Use a fluorescence spectrometer to place the perovskite solar cell on a test platform, select a laser with a wavelength of 200nm to 900nm as the excitation source (HSD signal does not exceed 500,000cps, and MCP signal does not exceed 300,000cps); turn on the laser and use a spectrometer to collect transient fluorescence spectrum data emitted by the sample; analyze the transient fluorescence spectrum data using Fluoracle software to determine the transient fluorescence spectrum of its buried interface.

[0127] The steady-state fluorescence spectra and transient spectra of the buried interface of the perovskite solar cell in Example 3, Example 4 and Comparative Example 2 are shown in Figure 2. Figure 4 and Figure 5 .

[0128] 3. Conductivity and conductivity test curve after working at 85℃ for 7 days

[0129] The specific test method for the electrical conductivity and the electrical conductivity after working at 85°C for 7 days is as follows: Place the organic electron transport material on the test platform using an RTS-7 two-probe tester, set the voltage parameter to -2V to 2V, and collect its current data while increasing the voltage to obtain its voltage-current graph. The electrical conductivity test results of the organic electron transport materials of Examples 1 and 2 and the electron transport material in Comparative Example 1 are shown in Figure 7 .

[0130] 4. Current-voltage (JV) characteristic curve of perovskite solar cell

[0131] The specific test method of the current-voltage (JV) characteristic curve of the perovskite solar cell is as follows: using a Keithley 2400 current-voltage source and an EnliTech SS-X5-3A solar simulator at 100mW / cm 2 , under the simulated illumination condition of AM 1.5G, the current density of the electronic device in the space charge limited current (SCLC) analysis is measured as a function of voltage. The test results of the perovskite solar cell in Example 3, Example 4 and Comparative Example 2 are shown in Figure 8 .

[0132] 5. Organic electron transport materials NDI-O and NDI-X 1 HNMR spectrum and 13 CNMR spectrum

[0133] Organic electron transport materials NDI-O and NDI-X 1 HNMR spectrum and 13 The specific test method of CNMR spectrum is as follows: NDI-O and NDI-X are dissolved in deuterated chloroform (CDCl3) and transferred to nuclear magnetic resonance tubes, which are then placed on the test platform of 500MHz fully digital nuclear magnetic resonance spectrometer. 1 H and 13 C one-dimensional liquid nuclear magnetic spectrum test, after the test is completed, the NMR spectrum data is analyzed by MestReNova software to determine its 1 HNMR spectrum and 13 CNMR spectrum.

[0134] Organic electron transport materials of Example 1 and Example 2 1 HNMR spectrum and 13 The test results of CNMR spectrum are shown in Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 .

[0135] according to Figure 4 It can be seen that compared with Comparative Example 2, the carrier transfer speed in the perovskite solar cells of Example 3 and Example 4 is fast and the non-radiative recombination is low, which is conducive to obtaining a higher short-circuit current J SC It is shown that the organic electron transport materials of Examples 1 and 2 are helpful to increase the carrier transport speed and reduce non-radiative recombination. Figure 5It can be seen from the TRPL spectrum that when the organic electron transport material of Example 1 is used as an electron transport layer, the time for the carriers to be excited to a higher energy state is 172.37 ns (nanoseconds); when the organic electron transport material of Example 2 is used as an electron transport layer, the time for the carriers to be excited to a higher energy state is 225.73 ns (nanoseconds), and when the electron transport material of Comparative Example 1 is used as an electron transport layer, the time for the carriers to be excited to a higher energy state is 339.33 ns (nanoseconds), which further verifies that when the organic electron transport materials of Examples 1 and 2 are used as electron transport layers, the efficient transmission of carriers at the interface helps to extend the carrier lifetime, which helps to improve the photoelectric conversion efficiency and stability of perovskite solar cells.

[0136] according to Figure 6 and Figure 7 It can be seen that compared with the electron transport material of Comparative Example 1, the organic electron transport materials of Examples 1 and 2 still maintain excellent performance after working at 85° C. for one week, indicating that the organic electron transport material has excellent stability. Figure 6 NDO, NDX, and SnO2 refer to the organic electron transport materials of Example 1, Example 2, and the electron transport material of Comparative Example 1, respectively.

[0137] according to Figure 8 It can be seen that the perovskite solar cell of Example 3 satisfies the following conditions: open circuit voltage V oc When the short-circuit current is 1.147V, the short-circuit current J SC 26.32 mA / cm 2 , the fill factor FF is 83.59%, the photoelectric conversion efficiency is 25.23%; the open circuit voltage V OC When the short-circuit current is 1.124V, the short-circuit current J SC 26.23 mA / cm 2 , the fill factor FF is 83.38%, and the photoelectric conversion efficiency is 24.64%. The perovskite solar cell of Example 4 meets the following requirements: open circuit voltage V OC When the short-circuit current is 1.140V, the short-circuit current J SC 25.67 mA / cm 2 , the fill factor FF is 83.16%, the photoelectric conversion efficiency is 24.33%; the open circuit voltage V OC When the short-circuit current is 1.123V, the short-circuit current J sc 25.42 mA / cm 2 , the fill factor FF is 81.98%, and the photoelectric conversion efficiency is 23.40%. Under the same conditions, the perovskite solar cell of Comparative Example 2 meets the following requirements: open circuit voltage V OC When the short-circuit current is 1.101V, the short-circuit current J SC 22.77 mA / cm 2, the fill factor FF is 82.58%, and the photoelectric conversion efficiency is only 20.71%; the open circuit voltage V OC When the short-circuit current J is 1.092V, SC 22.53 mA / cm 2 , the filling factor FF is 80.37%, and the photoelectric conversion efficiency is only 19.77%. It can be seen from this that the perovskite solar cell of Example 3 performs best, especially the photoelectric conversion efficiency reaches 25.23%. Although the performance of Example 4 is slightly lower, it is still within the range of high-efficiency cells, indicating that the organic electron transport material of the specific structure of the present invention used in Examples 3 and 4 helps to promote the growth of high-quality perovskite films, reduce interface defects and improve the transmission efficiency of electrons and holes. The introduction of organic electron transport materials helps to improve the overall performance of perovskite solar cells, especially in improving the photoelectric conversion efficiency. In contrast, the perovskite solar cell of Comparative Example 2 has poor performance, especially in terms of short-circuit current J SC In terms of photoelectric conversion efficiency, this is because the electron transport layer material used in Comparative Example 2 has a low efficiency in carrier extraction and transmission, as well as a high non-radiative recombination loss.

[0138] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An organic electron transport material, characterized in that The organic electron transport material has the structural formula shown in formula (I): Wherein, R1 and R2 are each independently selected from C3 to C 20 Cycloalkyl, C2~C 20 Straight or branched alkenyl, C2~C 20 Straight-chain or branched aliphatic amide groups, C2~C 20 Straight-chain or branched aliphatic isocyanate group, C3~C 20 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

2. The organic electron transport material according to claim 1, characterized in that R1 and R2 are each independently selected from C3 to C 10 Cycloalkyl, C2~C 15 Straight or branched alkenyl, C2~C 15 Straight-chain or branched aliphatic amide groups, C2~C 10 Straight-chain or branched aliphatic isocyanate group, C3~C 10 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

3. The organic electron transport material according to claim 2, characterized in that R1 and R2 are each independently selected from C3 to C 12 A straight or branched alkenyl group, a C3-C 15 Any one of a straight-chain or branched aliphatic amide group, a C2-C6 straight-chain or branched aliphatic isocyanate group, and a C3-C6 cycloalkyl group interrupted by one -O-.

4. The organic electron transport material according to any one of claims 1 to 3, characterized in that R1 and R2 are the same.

5. The organic electron transport material according to any one of claims 1 to 4, characterized in that R1 and R2 are each independently selected from Any one of .

6. A method for preparing the organic electron transport material according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: mixing 1,4,5,8-naphthalenetetracarboxylic anhydride, an amino compound containing R1 and R2 and an organic solvent under a protective atmosphere, and performing an amidation reaction to obtain the organic electron transport material; Wherein, R1 and R2 are each independently selected from C3 to C 20 Cycloalkyl, C2~C 20 Straight or branched alkenyl, C2~C 20 Straight-chain or branched aliphatic amide groups, C2~C 20 Straight-chain or branched aliphatic isocyanate group, C3~C 20 Any of the substituents wherein the cycloalkyl group is interrupted by at least one -O-.

7. The preparation method according to claim 6, characterized in that R1 and R2 are each independently selected from C3 to C 10 Cycloalkyl, C2~C 15 Straight or branched alkenyl, C2~C 15 Straight-chain or branched aliphatic amide groups, C2~C 10 Straight-chain or branched aliphatic isocyanate group, C3~C 10 Any one of the substituents formed by the cycloalkyl group being interrupted by at least one -O-; Preferably, R1 and R2 are each independently selected from C3 to C 12 A straight or branched alkenyl group, a C3-C 15 Any one of a straight-chain or branched aliphatic amide group, a C2-C6 straight-chain or branched aliphatic isocyanate group, and a C3-C6 cycloalkyl group interrupted by a -O-; More preferably, R1 and R2 are the same.

8. The preparation method according to claim 6 or 7, characterized in that The molar ratio of the 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(1-10); Preferably, the molar ratio of the 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(2-5); More preferably, the molar ratio of the 1,4,5,8-naphthalenetetracarboxylic anhydride to the amino compound is 1:(2-3); The temperature of the amidation reaction is 80°C to 120°C, and the time of the amidation reaction is 12h to 24h; Preferably, the temperature of the amidation reaction is 90° C. to 110° C., and the time of the amidation reaction is 15 h to 20 h; More preferably, the temperature of the amidation reaction is 100° C. to 110° C., and the time of the amidation reaction is 16 h to 18 h; Preferably, the organic solvent comprises N,N-dimethylformamide.

9. The preparation method according to claim 6 or 7, characterized in that: After the amidation reaction is completed, the method further comprises: The amidation reaction product is naturally cooled to room temperature and washed with water to obtain a washed product; the washed product is extracted with a first extractant, and an organic phase is collected; the organic phase is dried and purified in sequence to obtain the organic electron transport material; wherein the first extractant includes dichloromethane; the second extractant used in the purification process includes a mixture of petroleum ether and dichloromethane, and the volume ratio of the petroleum ether to the dichloromethane is (1-2): (1～2)。 10. A perovskite solar cell, characterized in that: The invention comprises a conductive glass layer, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer stacked in sequence, wherein the electron transport layer comprises the organic electron transport material according to any one of claims 1 to 5 or the organic electron transport material prepared by the preparation method according to any one of claims 6 to 9.

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