An organic electron transport material and use thereof, perovskite solar cell and preparation method thereof

Abstract

This invention provides an organic electron transport material and its applications, a perovskite solar cell and its preparation method. The structural formula of the organic electron transport material is shown in formula (I), where R1 is selected from C. 1～10 Alkyl group; R2 is selected from C 1～10 Alkylene, C 6～11 aryl or C 7～16 The perovskite solar cell of this invention uses a self-assembled organic electron transport material based on NDI as the core and with anchoring groups (acidic groups, such as phosphate, carboxyl, mercapto, or borate groups) introduced on one side to prepare the electron transport layer. The resulting perovskite solar cell exhibits significantly improved photoelectric conversion efficiency and other performance characteristics.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, specifically to an organic electron transport material and its applications, and a perovskite solar cell and its preparation method. Background Technology

[0002] Among numerous renewable energy sources, solar energy has attracted much attention due to its advantages such as abundant resources and lack of geographical limitations. In the new generation of photovoltaic cells, emerging perovskite solar cells (PSCs) have achieved a single-junction efficiency exceeding 26.1%, possessing power conversion efficiency comparable to commercial crystalline silicon cells.

[0003] Commonly used nip perovskite solar cells (NPSCs) consist of a conductive glass substrate, an electron transport layer, a perovskite layer, a hole transport layer, and metal electrodes. As a crucial component of PSCs, the electron transport layer (ETL) plays a vital role in extracting and transporting electrons, significantly contributing to improved device efficiency and stability. It also significantly influences the crystal quality and thin film morphology of the perovskite (PVK) layer. The commonly used electron transport material, tin oxide (SnO2), suffers from numerous defects at the interface with the perovskite light-absorbing layer, leading to reduced device stability and limiting the development of nip perovskite solar cells.

[0004] In recent years, researchers have developed many types of charge transport layer materials in hopes of obtaining low-cost, high-performance perovskite solar cells. Self-assembled monolayers (SAMs) have begun to be widely used in perovskite solar cells due to their advantages such as low material cost, compatibility with flexible substrates, tunable bandgap, high transmittance, and green solvent processing. Unfortunately, most of the various types of SAMs developed in recent years have been used as hole transport layers or modification layers, with limited research on electron transport layers. Furthermore, current high-efficiency perovskite solar cells (PSCs) employ a layer-by-layer spin-coating method to prepare the electron transport layer, which not only complicates the fabrication process but also wastes significant time and solvent, increasing industrialization costs. In addition, using layer-by-layer spin-coated SAMs makes it difficult to achieve uniform and dense electron transport layer films over large areas, making the fabrication of highly crystalline and defect-free perovskite films on large-area substrates challenging. Therefore, finding a high-efficiency, low-cost electron transport layer SAM and a simpler device fabrication process are urgent technical problems to be solved. Summary of the Invention

[0005] To address the above problems, this invention provides an organic electron transport material and its applications, a perovskite solar cell and its preparation method.

[0006] In a first aspect, the present invention provides an organic electron transport material, the structural formula of which is shown in formula (I):

[0007]

[0008] Among them, R1 is selected from C 1～10 alkyl;

[0009] R2 is selected from C 1～10 Alkylene, C 6～11 aryl or C 7～16 arylene alkyl groups;

[0010] R3 is selected from acidic groups.

[0011] Secondly, the present invention provides the use of the above-mentioned organic electron transport material as an electron transport material for perovskite solar cells.

[0012] Thirdly, the present invention also provides a perovskite solar cell, comprising a conductive substrate, an electron transport layer, a perovskite material layer, a hole transport layer, and a metal electrode, wherein the electron transport layer comprises the aforementioned organic electron transport material.

[0013] Fourthly, the present invention provides another perovskite solar cell, comprising a conductive substrate, a self-assembled electron transport layer, a perovskite hybrid layer, a hole transport layer, and a metal electrode, wherein the self-assembled electron transport layer comprises the aforementioned organic electron transport material, and the perovskite hybrid layer comprises a perovskite material and the aforementioned organic electron transport material.

[0014] Fifthly, the present invention provides a method for preparing the perovskite solar cell described in the third aspect, comprising:

[0015] An electron transport layer is formed on a conductive substrate using the organic electron transport material described in the first aspect, and then a perovskite material layer, a hole transport layer, and a metal electrode are fabricated on the electron transport layer to obtain the perovskite solar cell.

[0016] In a sixth aspect, the present invention provides a method for preparing the perovskite solar cell described in the fourth aspect, comprising the following steps:

[0017] (1) Prepare a perovskite precursor mixed solution containing the organic electron transport material described in the first aspect, and then coat it onto a conductive substrate to form a self-assembled electron transport layer and a perovskite mixed layer.

[0018] (2) A hole transport layer and a metal electrode are prepared on the perovskite mixed layer to obtain the perovskite solar cell.

[0019] Beneficial effects:

[0020] (1) The perovskite solar cell of the present invention uses a self-assembled organic electron transport material based on NDI as the core and unilaterally introduced anchoring groups (acidic groups such as phosphate groups, carboxyl groups, mercapto groups or borate groups, etc.) to prepare the electron transport layer, and the resulting perovskite solar cell has significantly improved performance such as photoelectric conversion efficiency (PCE).

[0021] (2) The electron transport layer constructed by the self-assembled organic electron transport material of the present invention has wide applicability, and the large-area perovskite devices and flexible perovskite devices prepared thereon have excellent performance.

[0022] (3) Based on self-assembled organic electron transport materials, perovskite solar cells can be prepared by in-situ blending, which can further improve the photoelectric conversion efficiency and other performance of the device. Attached Figure Description

[0023] Figure 1 The current-voltage curves (JV curves) of positively positioned PSCs devices for ETL prepared based on NDI-PA, NDI-CA and NDI-C4 in Embodiment 1, Embodiment 2 and Comparative Example 1 of the present invention are shown.

[0024] Figure 2 This is a process flow diagram of the in-situ blending method for preparing organic-inorganic lead halide perovskite solar cells according to the present invention.

[0025] Figure 3 The ultraviolet-visible absorption spectra of the perovskite films prepared in Examples 1, 3, and Comparative Example 2 of this invention are shown below.

[0026] Figure 4 The cross-sectional elemental distribution map of the PSCs device prepared in Example 3 of the present invention was determined by time-of-flight secondary ion mass spectrometry (TOP-SIMS).

[0027] Figure 5 This is a schematic diagram showing the changes after a perovskite precursor mixed solution containing organic electron transport materials in Example 3 of the present invention is spin-coated onto an ITO substrate.

[0028] Figure 6 The JV curves are for the perovskite solar cell prepared in Example 3 of the present invention and the ETL-free perovskite solar cell (ITO / PVK) prepared in Comparative Example 2.

[0029] Figure 7The external quantum efficiency (EQE) curves of the perovskite solar cells prepared in Example 3 and Comparative Example 2 of this invention are shown.

[0030] Figure 8 JV curves of the flexible perovskite solar cell prepared in Example 4 of the present invention and the ETL-free flexible perovskite solar cell prepared in Comparative Example 3.

[0031] Figure 9 The JV curves are for the large-area perovskite solar cell prepared in Example 5 of the present invention and the large-area perovskite solar cell without ETL prepared in Comparative Example 4. Detailed Implementation

[0032] The present application will now be described in further detail with reference to the accompanying drawings and embodiments. Through these descriptions, the features and advantages of the present application will become clearer and more apparent.

[0033] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments. Although various aspects of embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated otherwise.

[0034] In this invention, the term "NDI" represents a group with the following structure:

[0035]

[0036] The term "DMSO" stands for dimethyl sulfoxide;

[0037] The term "DMF" stands for N,N-dimethylformamide;

[0038] The term "DMP" stands for dimethyl phthalate;

[0039] The term "DMSO-d6" refers to dimethyl sulfoxide-d6;

[0040] The term "D2O" refers to heavy water;

[0041] The term "PE" stands for petroleum ether;

[0042] The term "DCM" stands for dichloromethane;

[0043] The term "MA" represents CH3NH3 + ;

[0044] The term "FA" represents HC(NH2)2 + .

[0045] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0046] In a first aspect, the present invention provides an organic electron transport material, the structural formula of which is shown in formula (I):

[0047]

[0048] Among them, R1 is selected from C 1～10 alkyl;

[0049] R2 is selected from C 1～10 Alkylene, C 6～11 aryl or C 7～16 arylene alkyl groups;

[0050] R3 is selected from acidic groups.

[0051] It should be noted that the acidic group selected from R3 can be a group formed by removing -OH or -H from an acid molecule, and can be an acidic group containing P, C, S, or B elements. The organic electron transport material of this invention uses NDI as its core, with a C atom bonded to an N atom in NDI. 1～10 Alkyl (R) 11 The other N is connected sequentially to R2 and R3. The resulting organic electron transport material can better extract and transport electrons. The efficiency and stability of perovskite devices constructed based on the organic electron transport material can be significantly improved.

[0052] In one embodiment of the organic electron transport material of the present invention, the acidic group is selected from phosphate, carboxyl, mercapto, or borate groups; and / or

[0053] R1 is selected from C 2～6 Straight-chain alkyl groups, preferably -CH2CH2CH3 or -CH2CH2CH2CH3; and / or

[0054] R2 is selected from C 2～5 Straight-chain alkylene groups, preferably -CH2CH2CH2- or -CH2CH2CH2CH2-; or

[0055] R2 is selected from C 7～9 arylene alkyl groups, preferably

[0056] It should be noted that the phosphate group is the group formed after the removal of one -OH group from phosphate. The carboxyl group is -COOH, i.e. The mercapto group is -SH, and the borate group is the group formed after boric acid loses one -OH group. In the organic electron transport material of the present invention, by selecting the above-mentioned R1, R2 and acidic groups (R3), the organic electron transport material can better exert its function and further improve the performance of perovskite devices.

[0057] In another embodiment of the organic electron transport material of the present invention, the organic electron transport material is selected from the following compounds and combinations thereof:

[0058]

[0059] It should be noted that, as a preferred embodiment, the photoelectric conversion efficiency of the perovskite solar cell constructed based on the above-mentioned compound as an organic electron transport material is further improved.

[0060] Furthermore, the present invention may also provide a method for preparing the above-mentioned organic electron transport material, which may include the following steps:

[0061] (S1) makes It reacts with R1-NH2 to produce

[0062] (S2) makes It reacts with H2N-R2-R3 to produce

[0063] Among them, R1 is selected from C 1～10 Alkyl group; R2 is selected from C 1～10 Alkylene, C 6～11 aryl or C 7～16 Aromatic alkyl group; R3 is selected from acidic groups.

[0064] More preferably, the acidic group is selected from phosphate, carboxyl, mercapto, or borate groups; and / or

[0065] R1 is selected from C 2～6 Straight-chain alkyl groups, preferably -CH2CH2CH3 or -CH2CH2CH2CH3; and / or

[0066] R2 is selected from C 2～5 Straight-chain alkylene groups, preferably -CH2CH2CH2- or -CH2CH2CH2CH2-; or

[0067] R2 is selected from C 7～9 arylene alkyl groups, preferably

[0068] Taking the phosphate-anchored self-assembled molecule (3-(7-butyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2(1H)-yl)propyl)phosphonic acid (NDI-PA) as an example, its synthesis method is as follows:

[0069] (S1) Under the action of potassium hydroxide aqueous solution, the raw material 1,4,5,8-naphthalenetetracarboxylic anhydride is completely dissolved in an appropriate amount of deionized water. Then, phosphoric acid solution is added dropwise to adjust the pH value to 6-7, specifically 6.4, and the mixture is stirred thoroughly. n-Butylamine is slowly added dropwise, and after stirring, phosphoric acid solution is added again to adjust the pH value to 6-7, specifically 6.4. Under nitrogen protection, the temperature is raised to 100-120℃, specifically 110℃, and refluxed overnight. After the reaction is complete, the solution is cooled to room temperature, the insoluble matter is filtered out, and then an appropriate amount of acetic acid is added dropwise. The product precipitates out, and is further filtered, washed, and vacuum dried to finally obtain 7-butyl-1H-isocyaneno[6,5,4-def]isoquinoline-1,3,6,8(7H)-tetraone (NDA-1C4).

[0070]

[0071] (S2) Under nitrogen conditions, NDA-1C4 reacts with 3-aminopropane-1-phosphoric acid and imidazole to generate (3-(7-butyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2(1H)-yl)propyl)phosphonic acid (NDI-PA).

[0072]

[0073] Preferably, in step (S1), the molar equivalent of the n-butylamine raw material relative to 1,4,5,8-naphthalenetetracarboxylic anhydride can be 0.8 to 1.2 eq., more preferably 1.0 to 1.2 eq., and the concentration of potassium hydroxide and phosphoric acid aqueous solution can be 0.8 to 1.2 M, for example, both can be 1 M.

[0074] Preferably, in step (S1), when the reaction temperature is 110°C, the reaction time can be 10 to 36 hours, more preferably 12 to 24 hours, and even more preferably 18 to 24 hours.

[0075] Preferably, in step (S1), after the reaction is completed, post-processing is performed. The specific method is as follows: naturally cool to room temperature, filter insoluble impurities to obtain a clear yellow solution; further slowly add anhydrous acetic acid, and a white product quickly precipitates in the solution. After thorough stirring, filter the product again, wash with ethanol, and vacuum dry to finally obtain a white solid powder product.

[0076] Preferably, in step (S2), the molar equivalent of 3-aminopropane-1-phosphoric acid relative to NDA-1C4 is 1–3 eq., more preferably 1–2 eq., and even more preferably 1.5–2 eq. The molar equivalent of imidazole relative to NDA-1C4 is 30–100 eq., more preferably 40–50 eq. In this step, imidazole is dissolved at high temperature as a reaction solvent.

[0077] Preferably, in step (S2), the reaction temperature can be 120-140°C, and when the reaction temperature is 130°C, the reaction time can be 2-24 hours, more preferably 6-18 hours, and even more preferably 6-12 hours.

[0078] Preferably, in step (S2), after the reaction is completed, a post-processing is performed, specifically as follows: naturally cool to room temperature, reduce the reaction to a powder state; add 2M HCl / ethanol (2:1, v / v) mixture and stir vigorously for 30 min, filter insoluble matter, wash with ethanol, and vacuum dry to obtain a light pink solid product.

[0079] The method for preparing organic electron transport materials according to the present invention has simple synthesis steps, low overall preparation cost, and can achieve large-scale synthesis of materials.

[0080] Secondly, the present invention provides the use of the above-mentioned organic electron transport material as an electron transport material for perovskite solar cells.

[0081] It should be noted that the aforementioned organic electron transport materials exhibit good solubility in perovskite precursor solutions, and their relatively large molecular size prevents them from entering the crystal lattice during perovskite crystallization. Using these organic electron transport materials as electron transport materials in perovskite solar cells significantly improves their performance.

[0082] Thirdly, the present invention also provides a perovskite solar cell, comprising a conductive substrate, an electron transport layer, a perovskite material layer, a hole transport layer, and a metal electrode, wherein the electron transport layer comprises the aforementioned organic electron transport material.

[0083] It should be noted that the electron transport layer in the perovskite solar cell of the present invention comprises the aforementioned organic electron transport material, which uses NDI as its core, with a C atom connected to an N atom in NDI. 1～10 An alkyl group (R1), with R2 and R3 sequentially connected to another N group, forms an organic electron transport material that acts as an electron transport layer, allowing it to perform its function better. This results in perovskite solar cells exhibiting high short-circuit current J. SC It has high photoelectric conversion efficiency and excellent performance.

[0084] In one embodiment of the perovskite solar cell according to the third aspect of the present invention, the thickness of the electron transport layer is 20–50 nm; and / or

[0085] The thickness of the perovskite material layer is 400–600 nm; and / or

[0086] The hole transport layer has a thickness of 20–100 nm; and / or

[0087] The thickness of the metal electrode is 50–100 nm.

[0088] It should be noted that controlling the thickness of the electron transport layer formed by the aforementioned organic electron transport material as described above, and controlling the thickness of other layers as described above, can further improve the photoelectric conversion efficiency and other performance of the perovskite solar cell, resulting in excellent overall performance of the cell.

[0089] Fourthly, the present invention provides another perovskite solar cell, comprising a conductive substrate, a self-assembled electron transport layer, a perovskite hybrid layer, a hole transport layer, and a metal electrode, wherein the self-assembled electron transport layer comprises the aforementioned organic electron transport material, and the perovskite hybrid layer comprises a perovskite material and the aforementioned organic electron transport material.

[0090] In this preferred perovskite solar cell of the present invention, the aforementioned organic electron transport material exists in two parts. The first part forms a self-assembled electron transport layer located between the conductive substrate and the perovskite hybrid layer. The other part, a small amount of organic electron transport material, together with the perovskite material, forms a perovskite hybrid layer located between the self-assembled electron transport layer and the hole transport layer. The organic electron transport material in the perovskite hybrid layer can be mainly located on the upper surface of the perovskite material, i.e., near the surface of the hole transport layer. In this preferred perovskite solar cell, the organic electron transport material not only effectively performs its electron transport function but also better synergizes with the perovskite material, further significantly improving the cell's photoelectric conversion efficiency and other performance parameters.

[0091] In one embodiment of the perovskite solar cell according to the fourth aspect of the present invention, the thickness of the self-assembled electron transport layer is 1–5 nm, and the thickness of the perovskite mixed layer is 400–600 nm; and / or

[0092] The mass ratio of perovskite material to organic electron transport material in the perovskite hybrid layer is (500–2000):1; and / or

[0093] The hole transport layer has a thickness of 20–100 nm; and / or

[0094] The thickness of the metal electrode is 50–100 nm.

[0095] In the above-mentioned preferred perovskite solar cells, by controlling the thickness of the self-assembled electron transport layer, the thickness of the perovskite mixed layer, and the mass ratio of perovskite material to organic electron transport material in the perovskite mixed layer as described above, the short-circuit current J of the cell is... SC The photoelectric conversion efficiency can be further improved.

[0096] In one embodiment of the perovskite solar cell described in the third or fourth aspect of the present invention, the conductive substrate is selected from ITO or PEN / ITO; and / or

[0097] The perovskite material is ABX3, where A is selected from CH3NH3. + HC(NH2)2 + Ca 2+ Cs + and Rb + and its combinations; B is selected from Pb 2+ Sn 2+ and Ti 4+ and combinations thereof; X is selected from halide ions and halide-like ions and combinations thereof; and / or

[0098] The material of the hole transport layer is selected from 2,2′,7,7′-tetratetra(N,N-di-p-methoxyphenylamine)-9,9′-spirodifluorene (Spiro-OMeTAD), cuprous iodide (CuI), cuprous thiocyanate (CuSCN), metal phthalocyanine compounds, poly(3-hexylthiophene) (P3HT), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and combinations thereof; and / or

[0099] The metal electrode is selected from Ag electrode, Au electrode or Cu electrode.

[0100] Furthermore, perovskite materials can specifically be MA 0.03 Cs 0.07 FA 0.9 Pb(I 0.92 Br 0.08 )3, etc. The perovskite solar cell constructed based on the above-mentioned organic electron transport material has a wide range of applicability. When the above-mentioned conductive substrate, perovskite material layer, hole transport layer and metal electrode are selected, the cell has excellent comprehensive performance.

[0101] Fifthly, the present invention provides a method for preparing the perovskite solar cell described in the third aspect, comprising:

[0102] An electron transport layer is formed on a conductive substrate using the organic electron transport material described in the first aspect, and then a perovskite material layer, a hole transport layer, and a metal electrode are fabricated on the electron transport layer to obtain the perovskite solar cell.

[0103] It should be noted that the above method is a layer-by-layer spin coating method. The organic electron transport material of the present invention can be well dissolved in a solvent to obtain a solution, therefore perovskite solar cells can be prepared by layer-by-layer spin coating. Based on NDI as the core, where a C atom is connected to an N atom in NDI. 1～10 An organic electron transport material with an alkyl group (R1) and R2 and R3 connected sequentially to another N group forms an electron transport layer, which improves the electron extraction and transport process and significantly enhances device efficiency and stability.

[0104] In a sixth aspect, the present invention provides a method for preparing the perovskite solar cell described in the fourth aspect, comprising the following steps:

[0105] (1) Prepare a perovskite precursor mixed solution containing the organic electron transport material described in the first aspect, and then coat it onto a conductive substrate to form a self-assembled electron transport layer and a perovskite mixed layer.

[0106] (2) A hole transport layer and a metal electrode are prepared on the perovskite mixed layer to obtain the perovskite solar cell.

[0107] It should be noted that when a perovskite precursor mixed solution containing organic electron transport materials and perovskite precursors is coated onto a conductive substrate, the organic electron transport materials, due to their unique structure, will automatically migrate towards the conductive substrate and form a self-assembled electron transport layer on the surface of the conductive substrate. A small amount of organic electron transport materials that fail to migrate to the surface of the conductive substrate in time can form a perovskite mixed layer together with the perovskite material. This in-situ blending method of self-assembled small molecules is a preferred preparation method. By adding self-assembled small molecules containing anchoring groups (phosphate groups, carboxyl groups, mercapto groups, borate groups, etc.) to the perovskite precursor solution, the self-assembled electron transport layer and the perovskite mixed layer can be prepared simultaneously in one step. This method helps to eliminate a large number of defects at the interface, enabling the fabrication of more efficient perovskite devices. It has important reference value for simplifying device processes and improving the efficiency and stability of upright perovskite photovoltaic cells.

[0108] By directly incorporating self-assembled small-molecule organic electron transport materials into a perovskite precursor solution, a one-step spin-coating process is employed to prepare a self-assembled electron transport layer and a perovskite hybrid layer, thus solving the problem of poor surface wettability of the electron transport layer (ETL) during layer-by-layer spin-coating. The upright perovskite device fabricated using this in-situ blending method achieves a photoelectric conversion efficiency of 22.13%. This significantly improves the photoelectric conversion efficiency and stability of upright PSCs, while simplifying the device fabrication process, reducing costs, and further advancing the commercialization of perovskite devices.

[0109] In one embodiment of the method described in the fifth or sixth aspect of the present invention, the method further includes a preprocessing step:

[0110] The conductive substrate is cleaned and then subjected to ultraviolet ozone treatment.

[0111] The ultraviolet ozone treatment time is 10-30 minutes, preferably 15-20 minutes.

[0112] In the above-mentioned layer-by-layer spin coating method, cleaning the conductive substrate and performing ultraviolet ozone treatment as described above can effectively improve its wettability. Then, the electron transport layer, perovskite material layer, hole transport layer and metal electrode are prepared by layer-by-layer spin coating. The organic electron transport material can form a more stable and uniform electron transport layer on the conductive substrate, and the final perovskite device has better performance.

[0113] In the above-mentioned in-situ blending method, the conductive substrate is first treated with ultraviolet ozone to improve its wettability, and then a self-assembled electron transport layer and a perovskite hybrid layer are prepared by in-situ blending. The organic electron transport material can form a stable and uniform self-assembled electron transport layer on the conductive substrate, and the resulting perovskite device has better performance.

[0114] In one embodiment of the method described in the fifth aspect of the present invention, the method for forming an electron transport layer on a conductive substrate using the organic electron transport material includes:

[0115] The organic electron transport material is mixed with an organic solvent to form a solution, then spin-coated onto the conductive substrate, and then annealed.

[0116] The organic solvent is selected from one or more of DMF, DMSO and DMP;

[0117] The organic electron transport material is mixed with the organic solvent at a ratio of (0.1–3) mg: 1 mL;

[0118] The solution formed by mixing the organic electron transport material with the organic solvent is applied to the conductive substrate by spin coating at a speed of 3000-6000 rpm for 15-60 seconds, and then annealed at 90-110°C to form the electron transport layer.

[0119] In the above-mentioned spin-coating method, the organic solvent is selected and the mixing ratio of organic electron transport material and organic solvent is controlled as above. At the same time, the electron transport layer is prepared under the above-mentioned control conditions so that the organic electron transport material can better form an electron transport layer on the conductive substrate, so as to more effectively play the role of electron extraction and transport, and thus better improve the performance of the prepared perovskite solar cell.

[0120] In one embodiment of the method described in the sixth aspect of the present invention, the method for preparing the perovskite precursor mixed solution in step (1) includes:

[0121] The organic electron transport material is mixed with a perovskite precursor solution at a ratio of (0.1-2) mg: 1 mL to obtain the perovskite precursor mixed solution.

[0122] The concentration of the perovskite precursor solution is 1–2 M;

[0123] The method of coating onto the conductive substrate in step (1) includes:

[0124] The perovskite precursor mixture solution is spin-coated at a speed of 800-1200 rpm for 5-15 seconds, and then spin-coated at a speed of 3000-5000 rpm for 20-40 seconds.

[0125] Step (1) also includes the following steps after the coating is applied to the conductive substrate:

[0126] Add the antisolvent dropwise, and then anneal at 80–120°C for 30–50 min to form the self-assembled electron transport layer and the perovskite mixed layer.

[0127] In this in-situ blending method, the solvent for the perovskite precursor solution can be a mixture of DMF and DMSO. A perovskite precursor mixed solution is obtained by uniformly mixing the organic electron transport material with the perovskite precursor solution; the concentration of the organic electron transport material is preferably 0.5–1 mg / mL. The perovskite precursor mixed solution is prepared according to the above ratio, and a self-assembled electron transport layer and a perovskite mixed layer are prepared under the above controlled conditions, using NDI as the core, with a C atom attached to a nitrogen atom in NDI. 1～10 Organic electron transport materials with alkyl groups (R1) and R2 and R3 connected sequentially to another N group can better synergize with perovskite materials, significantly improving the photoelectric conversion efficiency of perovskite solar cells.

[0128] The present invention will be further described in detail below through examples, but these examples are not intended to limit the invention. In the following examples, unless otherwise specified, the experimental instruments and raw materials involved are all commercially available products.

[0129] Preparation Example 1

[0130] Step a:

[0131] Synthesis of 7-butyl-1H-isocyaneno[6,5,4-def]isoquinoline-1,3,6,8(7H)-tetraone (NDA-1C4)

[0132]

[0133] In a 500 mL double-necked flask, 1,4,5,8-naphthalenetetracarboxylic anhydride (1.0 g, 3.73 mmol), deionized water (175 mL), and 1 M potassium hydroxide solution (17.5 mL) were added and stirred thoroughly until the solution became clear. The pH was adjusted to 6.4 by slowly adding 1 M phosphoric acid solution. After stirring for 10 min, n-butylamine (0.37 mL, 3.76 mmol, 1.0 eq.) was added, and stirring continued for another 10 min. The pH was then adjusted to 6.4 again by adding 1 M phosphoric acid solution. Nitrogen gas was purged three times using a double-row tube, and the temperature was raised to 100 °C. The reaction was refluxed overnight under nitrogen. After the reaction was completely cooled to room temperature, the insoluble matter was filtered off, and then anhydrous acetic acid was slowly added dropwise. The product was observed to precipitate in the flask, further filtered, washed, and dried under vacuum to obtain a white powder. NMR data. 1 H NMR(500MHz,DMSO-d6)δ8.52(d,J=7.5,1.4Hz,2H),8.11(d,J=7.5Hz,2H),4.04(t, J=7.4Hz,2H),1.62(m,J=6.8Hz,2H),1.37(m,J=7.4Hz,2H),0.93(t,J=7.3Hz,3H). 13 C NMR(125MHz,DMSO-d6)δ169.26,163.30,138.16,130.54,129.33,128.96,125.94,124.65,40.07,30.01,20.25,14.18.MALDI-TOF(m / z):[M] + Calculated value C 18 H 13 NO5: 323.0794, Measured value: 323.0770.

[0134] Step b:

[0135] Synthesis of (3-(7-butyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2(1H)-yl)propyl)phosphonic acid (NDI-PA)

[0136]

[0137] Under nitrogen atmosphere, the raw material NDA-1C4 (0.5 g, 1.55 mmol) prepared in step a was added to a 250 mL reaction tube along with 3-aminopropane-1-phosphoric acid (0.32 g, 2.32 mmol, 1.5 eq.) and imidazole (5.26 g, 77.33 mmol, 50.0 eq.). The temperature was raised to 130 °C, and the reaction system changed from a solid powder to a molten salt and finally to a solution. The reaction was carried out overnight. After the reaction was completed, the mixture was thoroughly cooled to a solid powder, and then 60 mL of a mixture of 2 M HCl and ethanol (2:1, v / v) was added. The mixture was stirred vigorously for 30 min, and the solid was filtered off. The filter cake was washed with a large amount of ethanol, and the product was recrystallized using a mixture of dichloromethane and ethanol. The product was filtered again and dried under vacuum to obtain a pale yellow powder (0.45 g, 65%). NMR data 1 H NMR (500MHz, DMSO-d6): 8.56 (s, 4H), 4.00 (m, J = 6.2Hz, 4H), 1.85 (m, J = 8.6Hz, 2H), 1.60 (m, J=17.2, 8.8Hz, 4H), 1.37 (m, J=7.4Hz, 2H), 0.94 (t, J=7.4Hz, 3H). 13 C NMR(125MHz,DMSO-d6):162.49,162.43,130.40,126.17,126.01,29.53,21.70,19.79,13.70.MALDI-TOF(m / z):[MH] - Calculated value C 21 H 20 N2O7P, 443.1014; Measured value: 443.1018.

[0138] Preparation Example 2

[0139] Synthesis of 4-(7-Butyl-1,3,6,8-tetraoxo-3,6,7,8-tetrahydrobenzo[lmn][3,8]phenoxylin-2(1H)-yl)butyric acid (NDI-CA)

[0140]

[0141] Under a nitrogen atmosphere, the raw materials NDA-1C4 (0.4 g, 1.24 mmol), 4-aminobutyric acid (0.26 g, 2.48 mmol, 2.2 eq.), and anhydrous acetic acid (20 mL) prepared in step a of Example 1 were added to a reaction flask, and the mixture was heated to 110 °C for 12 h. After the reaction was complete, the mixture was cooled to room temperature, and the product precipitated. 50 mL of ice water was added to the reaction flask, and the mixture was stirred vigorously for 30 min. The solid product was filtered, recrystallized from the product with ethanol and petroleum ether, filtered through a membrane, and dried under vacuum to obtain a pale pink solid product (0.34 g, 67%). NMR data1 H NMR (500MHz, DMSO-d6): 12.06 (s, 1H), 8.63 (s, 4H), 4.08 (m, J = 26.1, 7.2Hz, 4H), 2.35 (t, J = 7.3Hz ,2H),1.92(m,J=7.1Hz,2H),1.64(m,J=7.4Hz,2H),1.38(m,J=7.4Hz,2H),0.94(t,J=7.3Hz,3H). 13 C NMR(125MHz,DMSO-d6)δ174.44,162.81,162.61,130.73,130.70,126.36,126 .17,126.04,40.28,31.71,29.93,23.30,20.28,14.15.MALDI-TOF(m / z):[MH] - Calculated value C 22 H 19 N2O6: 407.1249, Measured value: 407.1248.

[0142] Preparation Example 3

[0143] Synthesis of 2,7-dibutylbenzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone (NDI-C4)

[0144]

[0145] Under a nitrogen atmosphere, 1,4,5,8-naphthalenetetracarboxylic anhydride (1.0 g, 3.73 mmol) was dissolved in DMF (15 mL), heated to 90 °C, and stirred for 30 min. n-Butylamine (0.60 g, 8.20 mmol, 2.2 eq.) was dissolved in DMF (10 mL) and then slowly added dropwise to the turbid starting solution using a titration funnel. The reaction mixture was stirred and refluxed at 110 °C for 24 h, and the reaction was monitored by TLC. After the reaction was complete, the mixture was extracted with DCM and deionized water, and the organic phase was dried over anhydrous MgSO4 and the solvent was removed under reduced pressure. The crude product was purified by column chromatography using PE / DCM (1:2, v / v) as the eluent to give a pale pink solid product NDI-C4 (0.84 g, 60%). NMR data. 1 H NMR (500MHz, CDCl3): 8.75 (s, 4H), 4.22-4.17 (m, 4H), 1.76-1.69 (m, 4H), 1.45 (m, J = 14.9, 7.5Hz, 4H), 0.99 (t, J = 7.4Hz, 6H). 13C NMR(125MHz, CDCl3):162.96,131.06,126.79,126.76,40.91,30.32,20.51,13.98.MALDI-TOF(m / z):[M+Na] + Calculated value C 22 H 22 N2O4, 401.1472; Measured value: 401.1474.

[0146] Preparation Example 4

[0147] Synthesis of ((1,3,6,8-tetraoxo-1,3,6,8-tetrahydrobenzo[lmn][3,8]phenanthroline-2,7-diyl)bis(propane-3,1-diyl))bis(phosphonic acid)(NDI-2PA).

[0148]

[0149] A mixture of 1,4,5,8-naphthalenetetracarboxylic anhydride (1.02 g, 3.73 mmol), 3-aminopropylphosphonic acid (1.24 g, 8.95 mmol, 2.4 eq.), and imidazole (5 g) was heated overnight at 130 °C. After the reaction was complete, the mixture was cooled thoroughly to a solid powder, and 60 mL of a mixture of 2 M HCl and ethanol (2:1, v / v) was added. The mixture was stirred vigorously for 2 h and then filtered. The resulting solid was washed with ethanol (30 mL × 3) to give a white solid NDI-2PA (1.12 g, 59%). NMR data 1 H NMR (500MHz, disodium salt, D2O): 7.42 (d, J = 6.2Hz, 4H), 3.00 (d, J = 7.4Hz, 4H), 1.43 (m, J = 16.9, 8.2Hz, 4H), 1.10 (m, J = 16.9, 7.8Hz, 4H). 13 C NMR(125MHz, disodium salt,D2O):175.98,175.85,172.01,171.87,139.97,138.57,136.40,135.03,127.61,12 7.49,127.16,126.81,126.46,41.50,41.35,27.38,26.34,23.81.MALDI-TOF(m / z):[MH] - Calculated value C 20 H 19 N2O 10 P2, 509.0593; Measured value: 509.0578.

[0150] Example 1

[0151] Layer-by-layer spin coating process for fabrication of ITO / ETL / perovskite / Spiro-OMeTAD / Ag electrodes

[0152] The ITO glass substrate was cleaned for 15 min each with glass cleaning solution, deionized water, acetone, and isopropanol, and then dried with compressed air. The cleaned ITO glass was then treated with ultraviolet ozone for 15 min to improve wettability. NDI-PA obtained from Preparation Example 1 was mixed with DMSO to prepare a solution with a concentration of 0.75 mg / mL. This solution was then spin-coated onto the ITO substrate at 4000 rpm for 30 s, followed by annealing at 100 °C to obtain an electron transport layer (ETL). 12.8 mg MAI, 27.1 mg FABr, 49.2 mg CsI, 63.8 mg MACl, 79.2 mg PbBr2, 380.8 mg FAI, and 591.2 mg PbI2 were mixed in 1 mL of DMSO / DMF (4:1, v / v) and stirred overnight. After filtration through a 0.22 μm polytetrafluoroethylene (PTFE) filter, a MACl solution with a concentration of approximately 1.5 M was obtained. 0.03 Cs 0.07 FA 0.9 Pb(I 0.92 Br 0.08 3. Precursor Solution. 40 μL of perovskite precursor solution was transferred and added dropwise onto an ETL plate, then spin-coated at 1000 rpm for 10 s, followed by spin-coating at 4000 rpm for 30 s. 20 s before the end of spin-coating, 260 μL of ethyl acetate antisolvent was rapidly added dropwise to the center of the perovskite film. The prepared layer-by-layer spin-coated sample was then immediately placed on a preheated hot plate and annealed at 100 °C for 40 min. After annealing, a Spiro-OMeTAD precursor solution was prepared by dissolving 72.5 mg Spiro-OMeTAD, 28.8 μL of tributyl phosphate (tBP), and 17.5 μL of LiTFSI in 1 mL of chlorobenzene, and then spin-coated onto the perovskite film at 3000 rpm for 30 s. The sample was then exposed to air for 24 h to ensure sufficient oxidation of the hole transport layer (HTL). Finally, an 80 nm thick Ag film was thermally evaporated as the contact electrode to obtain the perovskite solar cell. Ultimately, the perovskite solar cell achieved a photoelectric conversion efficiency of 20.90%.

[0153] In the perovskite solar cell prepared in this embodiment, the thickness of the electron transport layer is 30 nm, the thickness of the perovskite material layer is 550 nm, and the thickness of the hole transport layer is 70 nm.

[0154] Example 2

[0155] Perovskite solar cells were fabricated according to the process in Example 1, with the following differences:

[0156] The NDI-PA was replaced with NDI-CA obtained from Preparation Example 2 to prepare the electron transport layer, and finally a perovskite solar cell with a photoelectric conversion efficiency of 19.75% was obtained.

[0157] Comparative Example 1

[0158] Perovskite solar cells were fabricated according to the process in Example 1, with the following differences:

[0159] The NDI-PA was replaced with NDI-C4 obtained from Preparation Example 3 to prepare the electron transport layer, and finally a perovskite solar cell with a photoelectric conversion efficiency of 14.51% was obtained.

[0160] Test Example 1

[0161] In a nitrogen atmosphere, AM 1.5 (100mW cm⁻¹) -2 Under simulated light irradiation, the perovskite solar cells prepared in Examples 1, 2, and 1 (Comparative Example 1) were tested, and the resulting current-voltage curves (JV curves) are shown below. Figure 1 As shown.

[0162] In Examples 1, 2, and Comparative Example 1, NDI-PA, NDI-CA, and NDI-C4 were used as electron transport layers in spin-coated devices to compare photoelectric conversion efficiencies and investigate the influence of different anchoring groups on device efficiency. Figure 1 It is clear that the conventional device based on NDI-PA achieved the best efficiency of 20.90%, which is higher than the 19.75% of the NDI-CA-based device and far higher than the 14.51% of the NDI-C4-based device. By comparing the photoelectric conversion efficiency of upright perovskite solar cells based on NDI-PA, NDI-CA, and NDI-C4 as ETLs, it can be seen that devices based on NDI as the core ETL, and those based on NDI-PA or NDI-CA with anchoring groups, have superior performance. Furthermore, the phosphate groups in NDI-PA have a stronger anchoring ability and a stronger boosting effect than the carboxylic acid groups.

[0163] Based on the self-assembly properties of SAMs, we attempted to fabricate devices using an in-situ blending method. Figure 2 Organic preparation of small molecules based on NDI-PA self-assembly using a one-step spin-coating process The process flow diagram of inorganic lead halide perovskite solar cells shows that the one-step spin-coating process involves spin-coating a perovskite solution containing NDI-PA self-assembled small molecules onto an ITO substrate to form a perovskite mixed layer (containing a small amount of NDI-PA) and an electron transport layer composed of NDI-PA self-assembled small molecules. The final structure of the perovskite solar cell is: ITO / NDI-PA+PVK / Spiro-OMeTAD / Ag.

[0164] Example 3

[0165] In-situ blending process for preparing ITO / NDI-PA+PVK / Spiro-OMeTAD / Ag electrodes

[0166] ITO cleaning: The ITO substrate was ultrasonically cleaned sequentially with deionized water, glass cleaner, acetone, and isopropanol, and then dried with dry compressed air. The cleaned ITO substrate was then treated with UV-ozone for 15 min to improve its wettability.

[0167] Self-assembled electron transport layer, NDI-PA blended MA 0.03 Cs 0.07 FA 0.9 Pb(I 0.92 Br 0.08 3. Perovskite Mixed Layer: To prepare the perovskite PVK precursor solution, 12.8 mg MAI, 27.1 mg FABr, 49.2 mg CsI, 63.8 mg MACl, 79.2 mg PbBr2, 380.8 mg FAI, and 591.2 mg PbI2 were added to 1 mL of DMF / DMSO (1:4, v / v) solution and stirred overnight to obtain MA at a concentration of approximately 1.5 M. 0.03 Cs 0.07 FA 0.9 Pb(I 0.92 Br 0.083. Precursor Solution. Then, NDI-PA was added to a 1.5 M perovskite precursor solution at an optimal concentration of 0.75 mg / mL. 40 μL of the perovskite precursor solution containing NDI-PA was spin-coated onto an ITO substrate. The process involved spin-coating at 1000 rpm for 10 s, followed by spin-coating at 4000 rpm for 30 s. 20 s before the end of the second spin-coating, 260 μL of ethyl acetate antisolvent was rapidly added to the perovskite film. The prepared ITO / NDI-PA+PVK film was then transferred to a preheated hot plate and annealed at 100 °C for 40 min. The thickness of the self-assembled electron transport layer formed by NDI-PA was 2 nm, and the thickness of the perovskite mixed layer formed by the perovskite material containing a small amount of NDI-PA was 550 nm. The mass ratio of perovskite material to NDI-PA in the perovskite mixed layer was approximately 1500 times.

[0168] Fabrication of the HTL / Ag electrode: Finally, a 70 nm thick Spiro-OMeTAD electrode and an 80 nm thick Ag electrode were sequentially deposited onto the prepared perovskite film (perovskite mixed layer). The effective area of ​​the device is 0.04 cm². 2 .

[0169] Ultimately, a perovskite solar cell with a photoelectric conversion efficiency of 22.13% was obtained.

[0170] To demonstrate the universality of the NDI-PA in-situ blending method, we further applied it to flexible devices (0.04 cm²). 2 ) and large area (1cm) 2 In the device.

[0171] Example 4: Fabrication of Flexible Devices

[0172] Perovskite solar cells were prepared according to the process in Example 3, with the following differences:

[0173] By replacing the ITO substrate with a PEN / ITO substrate, a flexible device PEN / ITO / NDI-PA+PVK is obtained.

[0174] Example 5: Fabrication of large-area devices

[0175] Perovskite solar cells were prepared according to the process in Example 3, with the following differences:

[0176] At 1cm 2 A shadow mask was used, and an 80nm thick Ag film was thermally evaporated as a contact electrode to obtain a large-area device ITO / NDI-PA+PVK.

[0177] Comparative Example 2

[0178] Perovskite solar cells were prepared according to the process in Example 3, with the following differences:

[0179] Without adding NDI-PA to the perovskite precursor solution, an in-situ blended upright perovskite solar cell (ITO / PVK) without ETL was obtained. Ultimately, the device achieved a power conversion efficiency of only 19.70%.

[0180] Comparative Example 3: Fabrication of Flexible Devices

[0181] Perovskite solar cells were prepared according to the method in Example 4, with the following differences:

[0182] By not adding NDI-PA to the perovskite precursor solution, a flexible, ETL-free perovskite solar cell device, PEN / ITO / PVK, is obtained.

[0183] Comparative Example 4: Fabrication of Large-Area Devices

[0184] Perovskite solar cells were prepared according to the method in Example 5, with the following difference:

[0185] By not adding NDI-PA to the perovskite precursor solution, a large-area ETL-free device, ITO / PVK, is obtained.

[0186] Experiments showed that the NDI-2PA molecule prepared in Preparation Example 4 was insoluble in solvents such as DMF, DMSO, and isopropanol, making it difficult to independently spin-coat an electron transport layer or to perform in-situ blending with a perovskite precursor. This indicates that NDI-PA containing only one phosphate functional group can better balance the requirements of molecular solubility and self-assembly functionality. Furthermore, the NDI-C4 prepared in Preparation Example 3 lacked an anchoring group and could not be in-situ blended.

[0187] Test Example 2

[0188] The perovskite films obtained by spin-coating layer by layer in Example 1 (ITO / NDI-PA / PVK), the perovskite films obtained by in-situ blending in Example 3 (ITO / NDI-PA+PVK), and the ETL-free perovskite films prepared in Comparative Example 2 (ITO / PVK) were tested using a UV-Vis spectrophotometer (Shimadzu UV-2550). The UV-Vis absorption spectra of the three perovskite films are as follows: Figure 3 As shown, the perovskite film (ITO / NDI-PA+PVK) obtained by in-situ blending in Example 3 exhibits higher absorption intensity across the entire wavelength range, which is beneficial for obtaining a higher short-circuit current J. SC .

[0189] Test Example 3

[0190] To verify that NDI-PA added to the perovskite precursor solution can spontaneously form an ETL after spin coating, we used time-of-flight secondary ion mass spectrometry (TOP-SIMS) to analyze the cross-sectional elements of the device prepared in Example 3. PO3 was selected. - As a characteristic signal of NDI-PA, PbI3 - and In2O2 - These serve as characteristic signals for the perovskite layer and the ITO substrate, respectively. Figure 4 As shown, in the in-situ blended device based on NDI-PA, PO3 - Primarily distributed between the ITO and perovskite layers, indicating the spontaneous formation of an intermediate ETL. Notably, PO3... - The curve shows a high peak in the initial stage, indicating that a small portion of NDI-PA remains on the surface of the perovskite active layer. PO3 - The three-dimensional distribution map also confirms this, showing that a small amount of NDI-PA did not have time to deposit downwards and remained on the upper surface after the perovskite crystallized into a film. This confirms that the self-assembled small molecule NDI-PA in the solution automatically migrated to ITO during spin coating, such as... Figure 5 As shown, the NDI-PA component is anchored to the ITO surface through coordination with hydroxyl groups, and after uniform arrangement, it becomes an electron transport layer. This illustrates that in the device prepared in Example 3, the NDI-PA portion in the perovskite precursor mixed solution forms a self-assembled electron transport layer connected to the ITO substrate, while the other portion forms a perovskite mixed layer with the perovskite material.

[0191] Test Example 4

[0192] The perovskite solar cells (ITO / NDI-PA+PVK) obtained by in-situ blending in Example 3 and the ETL-free perovskite solar cells (ITO / PVK) prepared in Comparative Example 2 were tested using a Keithley 2400 current and voltage source. The current-voltage curves (JV curves) of the obtained solar cell devices are shown below. Figure 6 As shown, the open-circuit voltage V of the device fabricated based on NDI-PA in-situ blending is... OC The voltage is 1.146V, and the short-circuit current is J. SC 23.91 mA / cm 2 The fill factor FF is 80.73% and the photoelectric conversion efficiency is 22.13%, which is far superior to the photoelectric conversion efficiency of 19.70% of ITO / PVK devices.

[0193] Further comparison of the external quantum efficiency (EQE) curves of ITO / PVK and ITO / NDI-PA+PVK perovskite devices yields the following results: Figure 7 As shown, it is demonstrated that the device based on the in-situ blending method exhibits a significant enhancement in photon response across the entire wavelength range.

[0194] Test Example 5

[0195] In a nitrogen atmosphere, AM 1.5 (100mW cm⁻¹) -2 The flexible perovskite devices prepared in Example 4 and Comparative Example 3 were tested under simulated light irradiation, and the obtained current-voltage (JV) characteristic curves are shown below. Figure 8 Similarly, the large-area perovskite solar cells prepared in Example 5 and Comparative Example 4 were tested, and the obtained current-voltage (JV) characteristic curves were obtained. Figure 9 As shown.

[0196] Satisfactorily, Examples 4 and 5 are based on MA 0.03 Cs 0.07 FA 0.9 Pb(I 0.92 Br 0.08 The flexible device PEN / ITO / NDI-PA+PVK and the large-area device ITO / NDI-PA+PVK based on perovskite precursor 3 achieved high photoelectric conversion efficiencies of 21.01% and 19.19%, respectively. Both are superior to the flexible device PEN / ITO / PVK (photoelectric conversion efficiency 18.10%) prepared in Comparative Example 3 and the large-area device ITO / PVK (photoelectric conversion efficiency 16.07%) prepared in Comparative Example 4. This indicates that the in-situ blending method based on NDI-PA has good adaptability to different devices.

[0197] The present application has been described above with reference to preferred embodiments; however, these embodiments are merely exemplary and illustrative. Various substitutions and modifications can be made to the present application based on these embodiments, all of which fall within the protection scope of the present application.

Claims

1. An organic electron transport material, the structural formula of which is shown in formula (I): Equation (I) in, R1 is selected from C 1~10 alkyl; R2 is selected from C 1~10 Alkylene; R3 is selected from phosphate and carboxyl groups.

2. The organic electron transport material according to claim 1, wherein, R1 is selected from C 2~6 Straight-chain alkyl groups; and / or R2 is selected from C 2~5 Straight-chain alkylene groups.

3. The organic electron transport material according to claim 1 or 2, wherein, The organic electron transport material is selected from the following compounds and combinations thereof: 。 4. The organic electron transport material according to claim 2, wherein, R1 is -CH2CH2-CH3 or -CH2CH2CH2CH3; and / or R2 is -CH2CH2CH2- or -CH2CH2CH2CH2-.

5. Use of the organic electron transport material according to any one of claims 1 to 4 as an electron transport material for perovskite solar cells.

6. A perovskite solar cell, comprising a conductive substrate, an electron transport layer, a perovskite material layer, a hole transport layer, and a metal electrode, wherein, The electron transport layer comprises the organic electron transport material according to any one of claims 1 to 4.

7. The perovskite solar cell according to claim 6, wherein, The thickness of the electron transport layer is 20~50 nm; and / or The thickness of the perovskite material layer is 400~600 nm; and / or The hole transport layer has a thickness of 20~100 nm; and / or The thickness of the metal electrode is 50~100 nm.

8. A perovskite solar cell, comprising a conductive substrate, a self-assembled electron transport layer, a perovskite hybrid layer, a hole transport layer, and a metal electrode, wherein, The self-assembled electron transport layer comprises the organic electron transport material according to any one of claims 1 to 4, and the perovskite hybrid layer comprises a perovskite material and the organic electron transport material according to any one of claims 1 to 4.

9. The perovskite solar cell according to claim 8, wherein, The thickness of the self-assembled electron transport layer is 1-5 nm, and the thickness of the perovskite hybrid layer is 400-600 nm; and / or The mass ratio of perovskite material to organic electron transport material in the perovskite hybrid layer is (500~2000):1; and / or The hole transport layer has a thickness of 20~100 nm; and / or The thickness of the metal electrode is 50~100 nm.

10. The perovskite solar cell according to claim 6 or 8, wherein, The conductive substrate is selected from ITO or PEN / ITO; and / or The perovskite material in the perovskite material layer or the perovskite mixed layer is independently ABX3, wherein A is selected from CH3NH3. + HC(NH2)2 + Ca 2+ Cs + and Rb + and its combinations; B is selected from Pb 2+ Sn 2+ and Ti 4+ and combinations thereof; X is selected from halide ions and halide-like ions and combinations thereof; and / or The material of the hole transport layer is selected from 2,2′,7,7′-quadratic ( N , N 1,9′-spirodifluorene (Spiro-OMeTAD), cuprous iodide (CuI), cuprous thiocyanate (CuSCN), metal phthalocyanine compounds, poly(3-hexylthiophene) (P3HT), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) and combinations thereof; and / or The metal electrode is selected from Ag electrode, Au electrode or Cu electrode.

11. A method for preparing the perovskite solar cell of claim 6 or 7, wherein, include: An electron transport layer is formed on a conductive substrate using the organic electron transport material as described in any one of claims 1 to 4, and then a perovskite material layer, a hole transport layer, and a metal electrode are prepared on the electron transport layer to obtain the perovskite solar cell.

12. The method according to claim 11, wherein, The method further includes a preprocessing step: The conductive substrate is cleaned and then subjected to ultraviolet ozone treatment. The ultraviolet ozone treatment time is 10~30 min.

13. The method of claim 12, wherein, The ultraviolet ozone treatment time is 15-20 minutes.

14. The method according to claim 11, wherein, The method for forming an electron transport layer on a conductive substrate using the organic electron transport material includes: The organic electron transport material is mixed with an organic solvent to form a solution, then spin-coated onto the conductive substrate, and then annealed. The organic solvent is selected from one or more of DMF, DMSO and DMP; The organic electron transport material is mixed with the organic solvent at a ratio of (0.1~3) mg: 1 mL; The solution formed by mixing the organic electron transport material with the organic solvent is applied to the conductive substrate by spin coating at a speed of 3000~6000 rpm for 15~60 s, and then annealed at 90~110℃ to form the electron transport layer.

15. A method for preparing the perovskite solar cell of claim 8 or 9, wherein, Includes the following steps: (1) Prepare a perovskite precursor mixed solution containing the organic electron transport material according to any one of claims 1 to 4, and then coat it onto a conductive substrate to form a self-assembled electron transport layer and a perovskite mixed layer. (2) A hole transport layer and a metal electrode are prepared on the perovskite mixed layer to obtain the perovskite solar cell.

16. The method according to claim 15, wherein, The method further includes a preprocessing step: The conductive substrate is cleaned and then subjected to ultraviolet ozone treatment. The ultraviolet ozone treatment time is 10~30 min.

17. The method according to claim 15, wherein, The method for preparing the perovskite precursor mixed solution in step (1) includes: The organic electron transport material is mixed with the perovskite precursor solution at a ratio of (0.1~2) mg:1 mL to obtain the perovskite precursor mixed solution; The concentration of the perovskite precursor solution is 1~2 M; The method of coating onto the conductive substrate in step (1) includes: The perovskite precursor mixture solution is spin-coated at a speed of 800-1200 rpm for 5-15 s, and then spin-coated at a speed of 3000-5000 rpm for 20-40 s. Step (1) also includes the following steps after the coating is applied to the conductive substrate: Add the antisolvent dropwise, and then anneal at 80~120℃ for 30~50 min to form the self-assembled electron transport layer and the perovskite mixed layer.

18. The method of claim 16, wherein, The ultraviolet ozone treatment time is 15-20 minutes.

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