Perovskite precursor solution, preparation method and application thereof

Abstract

The application discloses a perovskite precursor solution and a preparation method and application thereof. The perovskite precursor solution comprises a perovskite precursor, a solvent and an additive, and a general structure of the additive is shown as formula I: in the formula I, R1 and R2 are independently selected from any one of hydrogen, C1-C 10 alkyl, C3-C 10 cycloalkyl, C6-C 10 aryl, C7-C 10 aralkyl; R1 and R2 are not hydrogen at the same time. The additive in the perovskite precursor solution of the application belongs to a hydantoin derivative, and a substituent is designed at a specific position of the hydantoin heterocycle, so that the additive can realize efficient defect passivation and inhibit the induced FA ＋ deprotonation degradation path, thereby solving the problem that the passivation effect and long-term stability of the additive are difficult to coordinate.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, and particularly to a perovskite precursor solution, its preparation method, and its application. Background Technology

[0002] Perovskite solar cells, with their outstanding technological advantages such as excellent photoelectric conversion efficiency, low manufacturing cost, and flexible fabrication capabilities, have become a core research and development focus and industrialization direction in the field of third-generation photovoltaic technology, and the industry's industrialization process is accelerating. In the overall fabrication process of perovskite photovoltaic modules, the crystal quality, defect density, and long-term structural stability of the perovskite light-absorbing layer directly determine the photoelectric conversion efficiency and service life of the photovoltaic device, and are the core factors restricting the overall performance and industrial application of the device. Molecular additive engineering, as a core process for regulating the microstructure and performance parameters of the perovskite light-absorbing layer, can effectively optimize the crystallization state of the perovskite thin film, reduce the internal defect density of the film, and improve the operational stability of the device, making it an indispensable key technology in the perovskite cell fabrication process.

[0003] Currently, the mainstream molecular additives used in the industry primarily employ modified molecules that are heterocyclic compounds containing active functional groups such as carbonyl and amino groups. The core modification principle of these additives is: through pre-designed active functional groups in the molecular structure, they interact with lead ions (Pb) within the perovskite lattice. 2+ ), formamidin (FA) + Organic cations such as hydrogen cations form non-covalent interactions such as coordination and hydrogen bonding, thereby passivating surface and bulk defects in perovskite films, regulating film crystallization behavior, reducing non-radiative recombination centers inside the device, and ultimately improving the initial photoelectric conversion efficiency of perovskite solar cells.

[0004] However, existing molecular additives suffer from a serious trade-off between passivation and degradation, making it difficult to ensure a synergistic optimization of efficiency and stability. While most conventional molecular additives can interact with FA in perovskite systems... + Hydrogen bonding can be formed to achieve short-term defect passivation, optimize device photoelectric performance, improve the initial crystal quality of perovskite films, reduce initial defect density, and enhance initial photoelectric conversion efficiency. However, during long-term operation, molecular additives can induce new perovskite degradation pathways, such as inducing formamidinium cations (FACs) in the crystal lattice. + The deprotonation reaction occurs, transforming the original passivated functional structure into a degradation inducer, continuously destroying the perovskite lattice structure, accelerating the overall performance degradation of the device, resulting in extremely poor long-term operational stability of the battery, and failing to meet the core requirements of industrialization for device lifespan. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, an object of the present invention is to provide a perovskite precursor solution. A second object of the present invention is to provide a method for preparing this perovskite precursor solution. A third object of the present invention is to provide applications of this perovskite precursor solution.

[0006] The inventive concept of this invention is as follows: This invention introduces a novel additive into a perovskite precursor solution. This additive is a hydantoin derivative with substituents designed at specific positions on the hydantoin heterocycle, enabling it to achieve efficient defect passivation while suppressing induced fatty acid (FA). ＋ The deprotonation degradation pathway solves the problem of the difficulty in synergistically achieving the passivation effect and long-term stability of additives.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a perovskite precursor solution, comprising a perovskite precursor, a solvent, and an additive, wherein the additive has the general structural formula shown in Formula I: ; In Equation I, R1 and R2 are independently selected from hydrogen, C1-C, and C2, respectively. 10 Alkyl, C3-C 10 cycloalkyl, C6-C 10 Aryl, C7-C 10 Any of the aralkyl groups; R1 and R2 are not both hydrogen.

[0008] The heterocyclic structure of the additive in the perovskite precursor solution of this invention contains two carbonyl (C=O) active sites and one imino (NH) active site, exhibiting multi-site coordination ability. The carbonyl groups can interact with divalent cations in the perovskite precursor (such as Pb). 2+ ) Form coordination bonds, passivating vacancy defects; imino groups react with organic cations (such as FA) in the perovskite precursor. + The substituents R1 and R2 form hydrogen bonds, stabilizing organic cations and inhibiting deprotonation degradation. These substituents enhance the electron cloud density and electron-donating ability of the carbonyl group, improving the stability of the imino structure. Increased imino stability makes it less prone to dissociation of hydrogen atoms. + This blocks the degradation pathway of organic cations and inhibits deprotonation degradation. Therefore, R1 and R2 enhance the passivation effect of the carbonyl group in the heterocycle and the stability of the imino group, improving the ability to inhibit the deprotonation of organic cations. This allows the additives of the present invention to achieve synergistic passivation and stabilization, improving the photoelectric performance and long-term operational stability of perovskite solar cell devices.

[0009] In some embodiments of the present invention, R1 is selected from hydrogen, and the general structural formula of the additive is shown in Formula II: ; The additive of this invention has only R2 attached to the carbon atom of the heterocycle. In this case, the additive molecule exhibits a non-planar configuration, enabling bidentate coordination (one C=O simultaneously interacts with two divalent cations). This significantly enhances the electron-donating ability of the carbonyl group and the stability of the imino structure in the heterocycle, thus giving the additive a core advantage in inhibiting degradation. In contrast, when the heterocycle structure lacks both R1 and R2 (i.e., hydantoin) or R2 is hydrogen, the additive molecule has a planar or near-planar configuration, with no electronic effect or the electronic effect limited to the vicinity of the nitrogen atom, resulting in a smaller impact on the electron cloud density of the carbonyl group. Furthermore, when R1 is hydrogen, it does not inhibit or counteract the deprotonation-inhibiting degradation effect produced by R2.

[0010] The mechanism by which R2 significantly enhances the electron-donating ability of the carbonyl group and improves the stability of the imino (NH) structure is as follows: 1. Hyperconjugation effect: CH bond of R2 (C1-C) 10 Alkyl, C3-C 10 cycloalkyl, C7-C 10 Aryl groups form σ-π hyperconjugation with heterocycles, affecting the electron cloud distribution of the entire heterocycle, enhancing the electron-donating ability of the carbonyl group and stabilizing the NH structure.

[0011] 2. Electron-shell induction effect: The σ bond in R2 can "push" the electron cloud toward the heterocycle, increasing the electron density of the entire heterocycle (including NH), thereby reducing the acidity of NH, making it less likely to lose protons, and enhancing the stability of NH.

[0012] 3. Physical shielding effect: When R2 is a sterically hindered group (such as C6-C...) 10 Aryl and tert-butyl compounds, being large in size and suspended on heterocyclic rings (hydantoin), physically hinder external nucleophiles or nearby organic cations (such as FA) from entering the ring. ＋ The protons are located near the NH site. Even if the NH has a tendency to dissociate protons, the space is too crowded, making it difficult for the protons to be successfully "captured" by external bases (such as FA molecules). This kinetic barrier enables the additive to achieve the purpose of "inhibiting deprotonation".

[0013] 4. Regulation of molecular stacking and interfacial environment: At the perovskite grain boundary, when R2 is a sterically hindered group, the additive forces the molecules to adopt a specific arrangement, so that the active NH group is wrapped in a hydrophobic environment or a densely stacked layer. This change in physical environment indirectly protects the NH bond from attack and improves the stability of NH.

[0014] 5. Energy level modulation: R2 is an electron-withdrawing substituent (such as C6-C). 10When aryl groups are used, they can regulate the molecular energy levels of additives, optimize the energy level arrangement between the perovskite layer and the adjacent carrier transport layer, and reduce interfacial nonradiative recombination losses. In addition, they can also change the work function of the perovskite surface and improve the selective extraction efficiency of carriers.

[0015] Preferably, the additive comprises at least one selected from 1-methylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-n-propylhydantoin, 5-isopropylhydantoin, 5-n-butylhydantoin, 5-isobutylhydantoin, 5-n-octylhydantoin, 5-cyclopropylhydantoin, 5-cyclopentylhydantoin, 5-cyclohexylhydantoin, 5-phenylhydantoin, 5-p-methylphenylhydantoin, 5-naphthylhydantoin, 5-benzylhydantoin, 5-phenylethylhydantoin, and 5-phenylpropylhydantoin.

[0016] Preferably, the additive is 5-methylhydantoin. When the additive is 5-methylhydantoin, R1 is hydrogen and R2 is methyl. The intensity of the hyperconjugation effect between R2 and the heterocycle is positively correlated with the number of hydrogen atoms on the α-C (i.e., the carbon atom directly attached to the heterocycle). Therefore, the hyperconjugation effect is strongest when the additive is 5-methylhydantoin. Furthermore, 5-methylhydantoin has good solubility in the perovskite precursor solution and will not affect the final uniformity of its dispersion in the perovskite film.

[0017] Preferably, the perovskite precursor comprises an ABX3 structure, wherein A is an organic cation and / or an alkali metal cation, B is a divalent cation, and X is a halide anion.

[0018] Preferably, the organic cation includes methylammonium cation (MA). + ) or formamidinium cation (FA + ).

[0019] Preferably, the alkali metal cation includes cesium ions (Cs). + ( ), at least one of rubidium ions, potassium ions, and sodium ions.

[0020] Preferably, the divalent cation includes lead ions (Pb). 2+ ), tin ions (Sn) 2+ At least one of germanium ions and zinc ions. Preferably, the halide anion includes chloride ions (Cl... - ), bromide ions (Br) - ), iodide ions (I - At least one of the following.

[0021] Preferably, the perovskite precursor comprises FA 0.95 Cs 0.05 PbI3, FA0.8 Cs 0.2 PbI3, FA 0.5 Cs 0.5 PbI 3、 (CsPbI3) 0.085 (FAPbI3) 0.9 (CsPbBr3) 0.015 MAPbI3, MA 0.5 Cs 0.5 PbI 3、 MA 0.8 Cs 0.2 At least one of PbI3.

[0022] Preferably, the concentration of the additive in the perovskite precursor solution is 0.5~2.0 mg / mL; more preferably, the concentration of the additive in the perovskite precursor solution is 0.6~1.6 mg / mL; even more preferably, the concentration of the additive in the perovskite precursor solution is 0.8~1.2 mg / mL.

[0023] Preferably, the concentration of the perovskite precursor in the perovskite precursor solution is 0.5~1.5M; more preferably, the concentration of the perovskite precursor in the perovskite precursor solution is 0.6~1.2M; even more preferably, the concentration of the perovskite precursor in the perovskite precursor solution is 0.7~1.0M.

[0024] Preferably, the solvent includes at least one of dimethylformamide (DMF), dimethyl sulfoxide (DMSO), methylpyrrolidone (NMP), γ-butyrolactone, acetonitrile, methanol, and ethanol; more preferably, the solvent is a mixed solution of DMF and NMP; and even more preferably, the volume ratio of DMF to NMP in the mixed solution is (8~18):1.

[0025] Preferably, the perovskite precursor solution further includes auxiliary materials; more preferably, the auxiliary materials include at least one of methylammonium chloride (MACl), methylammonium iodide (MAI), methylammonium bromide (MABr), and ethylammonium chloride (EACl).

[0026] Preferably, the auxiliary material accounts for 20% to 40% of the molar percentage of the perovskite precursor; more preferably, the auxiliary material accounts for 22% to 38% of the molar percentage of the perovskite precursor; and even more preferably, the auxiliary material accounts for 25% to 35% of the molar percentage of the perovskite precursor.

[0027] In a second aspect, the present invention provides a method for preparing the perovskite precursor solution described in the first aspect, comprising the following steps: mixing the perovskite precursor, additives and solvent to obtain the perovskite precursor solution.

[0028] In some embodiments of the present invention, the perovskite precursor solution further includes auxiliary materials, and the preparation method is to mix the perovskite precursor, additives, auxiliary materials and solvent to obtain the perovskite precursor solution.

[0029] Thirdly, the present invention provides a perovskite light-absorbing layer, wherein the perovskite light-absorbing layer is formed from the perovskite precursor solution described in the first aspect.

[0030] Preferably, the thickness of the perovskite light-absorbing layer is 350~800 nm; more preferably, the thickness of the perovskite light-absorbing layer is 400 nm~600 nm; and even more preferably, the thickness of the perovskite light-absorbing layer is 450 nm~550 nm.

[0031] Fourthly, the present invention provides a method for preparing a perovskite light-absorbing layer, comprising the following steps: coating a perovskite precursor solution described in the first aspect onto a substrate to obtain a perovskite precursor wet film, followed by vacuum flash evaporation and annealing to obtain the perovskite light-absorbing layer.

[0032] Preferably, the coating method includes spin coating or application coating.

[0033] Preferably, the vacuum degree of the vacuum flash evaporation is 3~10 Pa; more preferably, the vacuum degree of the vacuum flash evaporation is 4~8 Pa; and even more preferably, the vacuum degree of the vacuum flash evaporation is 4.5~6 Pa.

[0034] Preferably, the vacuum flash evaporation time is 10-50 s; more preferably, the vacuum flash evaporation time is 15-45 s; and even more preferably, the vacuum flash evaporation time is 20-40 s.

[0035] Preferably, the annealing method includes furnace annealing.

[0036] Preferably, the annealing temperature is 100~150℃; more preferably, the annealing temperature is 110~140℃; and even more preferably, the annealing temperature is 125~135℃.

[0037] Preferably, the annealing time is 3 to 8 minutes; more preferably, the annealing time is 4 to 6 minutes.

[0038] Fifthly, the present invention provides a perovskite solar cell, which, from bottom to top, comprises a conductive substrate, a hole transport layer, the perovskite light-absorbing layer described in the third aspect, a passivation layer, an electron transport layer, and an electrode layer.

[0039] Preferably, the conductive substrate includes at least one of fluorine-doped tin oxide (FTO) conductive glass and indium tin oxide (ITO) conductive glass.

[0040] Preferably, the thickness of the conductive substrate is 10nm~100nm; more preferably, the thickness of the conductive substrate is 10nm~80nm; even more preferably, the thickness of the conductive substrate is 15nm~70nm; even more preferably, the thickness of the conductive substrate is 20nm~60nm.

[0041] Preferably, the material of the hole transport layer includes at least one of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), (2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl)phosphonic acid (MeO-2PACz), [4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz), MeOF-4PACz, (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid (Me-4PACz), 2-(3,6-dimethyl-9H-carbazole-9-yl)ethylphosphonic acid (Me-2PACz), poly(2-(9H-carbazole-9-yl)ethyl)phosphonic acid (Poly-2PACz), and poly[4-(9H-carbazole-9-yl)butyl]phosphonic acid (Poly-4PACz).

[0042] Preferably, the material of the passivation layer includes at least one of phenylethyl ammonium iodide (PEAI), piperazine monoiodide (PipI), propane-1,3-diammonium iodide (PDAI2), ethylenediamine diiodide (EDAI2), polymethyl methacrylate (PMMA), and cesium bromide (CsBr).

[0043] Preferably, the material of the electron transport layer includes titanium dioxide (TiO2), tin dioxide (SnO2), zinc oxide (ZnO), tungsten trioxide (WO3), niobium pentoxide (Nb2O5), and C. 60 One of [6,6]-phenyl-C61-butyrate methyl ester (PCBM), naphthalimide (NDI), and their derivatives; more preferably, the material of the electron transport layer includes SnO2 and C 60 .

[0044] Preferably, the thickness of the electron transport layer is 50-70 nm; more preferably, the thickness of the electron transport layer is 52-68 nm. Even more preferably, the thickness of the electron transport layer is 55-65 nm.

[0045] Preferably, the material of the electrode layer includes at least one of silver, gold, copper, and bismuth.

[0046] Preferably, the thickness of the electrode layer is 100~150nm; more preferably, the thickness of the electrode layer is 110~130nm.

[0047] Sixthly, the present invention provides a method for preparing a perovskite solar cell, comprising the following steps: S1: Prepare a hole transport layer on a conductive substrate; S2: Coat the perovskite precursor solution described in the first aspect onto the hole transport layer, and then anneal it after vacuum flash evaporation to obtain a perovskite light-absorbing layer. S3: An electron transport layer is prepared on the perovskite light-absorbing layer; S4: Prepare a passivation layer on the electron transport layer; S4: An electrode layer is prepared on the passivation layer to obtain the perovskite solar cell.

[0048] The beneficial effects of this invention are: (1) The additive in the perovskite precursor solution of the present invention solves the inherent contradiction of the "passivation-degradation" trade-off in traditional multi-active-site additives. The heterocycle of the additive of the present invention contains two carbonyl (C=O) active sites and one imino (NH) active site, which has multi-site coordination ability. Among them, the carbonyl group can react with divalent cations (such as Pb) in the perovskite precursor. 2 + ) Form coordination bonds, passivating vacancy defects; imino groups react with organic cations (such as FA) in the perovskite precursor. + The substituents R1 and R2 form hydrogen bonds, stabilizing organic cations and inhibiting deprotonation degradation. These substituents enhance the electron cloud density and electron-donating ability of the carbonyl group, improving the stability of the imino structure. Increased imino stability makes it less prone to dissociation of hydrogen atoms. + This blocks the degradation pathway of organic cations and inhibits deprotonation degradation. Therefore, R1 and R2 enhance the passivation effect of the carbonyl group in the heterocycle and the stability of the imino group, improving the ability to inhibit the deprotonation of organic cations. This allows the additives of the present invention to achieve synergistic passivation and stabilization, improving the photoelectric performance and long-term operational stability of perovskite solar cell devices.

[0049] (2) This invention reveals the differentiated regulatory mechanism of perovskite degradation pathways by hydantoin derivatives with different substitution positions, filling the gap in the understanding of the structure-activity relationship between microstructure and additive reactivity in this field. In N-substituted (i.e., when R2 is hydrogen) hydantoin derivatives, R1 is attached to a nitrogen atom, and the molecule maintains a planar or near-planar configuration. Due to the participation of the lone pair electrons of the nitrogen atom in the conjugation of the heterocycle (n-π conjugation), the electronic effect of the substituent is limited to the vicinity of the nitrogen atom and cannot form σ-π hyperconjugation. Compared with N-substituted hydantoin derivatives, C-substituted hydantoin derivatives (Formula II) exhibit stronger coordination ability and hydrogen bond stability due to their non-planar configuration and the hyperconjugation effect of the substituents. The discovery of the isomerism effect of different substituent positions for hydantoin derivatives provides a new theoretical guidance for the rational design of perovskite additives.

[0050] (3) This invention has good process compatibility and is applicable to perovskite precursor materials with different compositions (such as formamidinium lead iodide, cesium-doped perovskite, etc.) and different structural components (formal structure, trans structure). The preparation of the perovskite precursor solution of this invention does not require additional process steps, does not change the existing preparation process, and is easy to implement quickly on existing production lines, and has good prospects for industrialization and promotion.

[0051] (4) This invention achieves comprehensive optimization of the crystal quality, defect density, and interface characteristics of the perovskite light-absorbing layer. The additives in the perovskite precursor solution can effectively reduce the defect state density of the perovskite light-absorbing layer, prolong carrier lifetime, and improve the photoelectric conversion efficiency of the device. At the same time, by inhibiting the deprotonation of organic cations and the degradation of the Pb-I framework, the performance degradation of perovskite solar cell devices under environmental stresses such as heat, light, and humidity is significantly delayed, enabling the device to maintain excellent stability during long-term operation. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the perovskite solar cell structure in Example 1; Figure 2 The JV characteristic curves of the perovskite solar cells in Example 1, Example 2 and Comparative Example 1 are shown. Figure 3 PCE box plots of perovskite solar cells in Examples 1, 2, and Comparative Example 1; Figure 4 The graph shows the stability data of the perovskite solar cells of Example 1, Example 2, and Comparative Example 1. Detailed Implementation

[0053] To enable those skilled in the art to better understand this application, the present invention will be further described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims.

[0054] In the description of this invention, it should be noted that unless specific conditions are specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available products. Furthermore, to better illustrate this invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that this invention can be practiced even without certain specific details. In some embodiments, raw materials, methods, and means well known to those skilled in the art are not described in detail in order to highlight the main points of this invention.

[0055] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0056] The additive used in Example 1 of this invention is 5-methylhydantoin (5-MH), with the structural formula as follows: ; The additive used in Example 2 of this invention is 1-methylhydantoin (1-MH), with the structural formula as follows: .

[0057] In the perovskite solar cell of the present invention, the thickness of the hole transport layer and the passivation layer can be less than 10 nm, and the present invention does not impose any special limitation.

[0058] Example 1 This embodiment provides a perovskite solar cell, which is prepared using the following method: (1) Select a 30cm×30cm ITO conductive glass substrate, scribble P1 with a laser, and then clean and dry it; (2) Dissolve Me-4PACz in anhydrous ethanol to prepare a hole transport layer solution with a concentration of 0.5 mg / mL. Spin-coat the hole transport layer solution onto a conductive substrate. After vacuum flash evaporation at 5 Pa for 30 s, anneal at 100 °C for 5 minutes in an annealing furnace to obtain the hole transport layer. (3) Weigh out lead iodide (PbI2), cesium iodide (CsI), cesium bromide (CsBr) and formamidine iodide (FAI) respectively and dissolve them in a mixed solvent (DMF to NMP volume ratio of 15:1) to prepare (CsPbI3) with a concentration of 0.8M. 0.085 (FAPbI3) 0.9(CsPbBr3) 0.015 A perovskite precursor solution was prepared by adding MACl (0.24 M) to the solution, followed by the addition of 5-methylhydantoin (1.0 mg / mL). The perovskite precursor solution was then spin-coated onto a hole transport layer to obtain a wet perovskite precursor film. This wet film was then flash-evaporated under vacuum at 5 Pa for 40 s, followed by annealing at 130 °C for 20 minutes to obtain a perovskite light-absorbing layer with a thickness of 500 nm. (4) A passivation layer solution (PEAI isopropanol solution with a concentration of 0.2 mg / mL) was spin-coated onto the perovskite light-absorbing layer, and then annealed in an annealing furnace at 60 °C for 5 minutes to obtain the passivation layer; (5) Vacuum evaporation of C on the passivation layer 60 After atomic deposition of SnO2, an electron transport layer with a total thickness of 60 nm is formed; (6) Draw lines on electron transport layer P2 and deposit copper electrodes with a thickness of 120 nm to obtain electrode layer; then draw lines on P3 and encapsulate to obtain the perovskite solar cell.

[0059] Example 2 This embodiment provides a perovskite solar cell. The difference between this embodiment and embodiment 1 is that the additive used in step (3) is 1-methylhydantoin, while the rest is the same as in embodiment 1.

[0060] Comparative Example 1 This embodiment provides a perovskite solar cell. The difference between this comparative example and Example 1 is that 5-methylhydantoin is not added in step (3), while the rest is the same as Example 1.

[0061] Performance testing: Under standard test conditions (AM1.5, 25℃, 1000W / m) 2 The short-circuit current density (Jsc), open-circuit voltage (Voc), power conversion efficiency (PCE), and fill factor (FF) of the perovskite solar cells in Examples 1, 2, and Comparative Example 1 were tested. The test results are shown in Table 1 and 2. Figure 2 As shown.

[0062] Table 1. Performance data of perovskite solar cells in Examples 1, 2 and Comparative Example 1

[0063] Figure 2 The graphs show the JV characteristics of the perovskite solar cells in Examples 1, 2, and 1 (Comparative Example 1).

[0064] From Table 1 and Figure 2It can be seen that, compared with Comparative Example 1 without any additives, the additive 5-methylhydantoin in Example 1 and the additive 1-methylhydantoin in Example 2 can significantly improve the FF and PCE of the device. This is because the heterocyclic structure of the additives introduced into the perovskite precursor solution in Examples 1 and 2 contains two carbonyl (C=O) active sites and one imino (NH) active site, wherein the carbonyl (C=O) interacts with the uncoordinated Pb in the perovskite. 2+ Formation of coordination bonds, passivating lead vacancy defects; imino (NH) and formamidinium ions (FA) + The N atom of FA forms a stable hydrogen bond, making FA + The protons are "anchored" and not easily detached, thus avoiding FA. + →FA+H + This occurs, thereby inhibiting FA. + Deprotonation. Furthermore, the methyl group at the C position in the additive 5-methylhydantoin of Example 1 and the methyl group at the N position in the additive 1-methylhydantoin of Example 2 can further enhance the passivation effect of the carbonyl group in the heterocycle and the stability of the imino group, thereby improving the photoelectric performance of the device.

[0065] Compared to Example 2, Example 1 exhibits superior photoelectric properties. This is because the additive in Example 2 is 1-methylhydantoin, while the additive in Example 1 is 5-methylhydantoin, with the methyl group having a different substitution position in the heterocycle. The 5-methylhydantoin molecule with the methyl group at the C position in the heterocycle has a non-planar configuration, enabling bidentate coordination (one C=O interacts with two Pb groups simultaneously), while the 5-methylhydantoin molecule has a near-planar configuration and cannot achieve this effect. Furthermore, the CH bond of the methyl group on the 5-methylhydantoin exhibits a hyperconjugation effect with the π system of the heterocycle, pushing the electron cloud density across the entire heterocycle and significantly enhancing the electron density of the NH bond. This makes the NH bond more stable and less prone to breakage, and the enhanced NH stability prevents the provision of excess H. + The decatalytic reaction was eliminated, inhibiting the formation of PbI2 and Pb. In 1-methylhydantoin, the methyl group is attached to nitrogen, limiting the electronic effect to the vicinity of the nitrogen atom. This prevents the NH group from stabilizing through hyperconjugation, resulting in weaker stability of NH compared to Example 1. Therefore, Example 1 exhibits superior photoelectric properties.

[0066] Figure 3 The PCE box plots for the perovskite solar cells of Examples 1, 2, and Comparative Example 1 are shown, with a sample size of 20. Figure 3 It can be seen that the device of Example 1 exhibits the highest average photoelectric conversion efficiency and has the smallest data dispersion. The device of Example 1 has excellent repeatability and stability.

[0067] This invention further evaluated the stability of the perovskite solar cells of Example 1, Example 2, and Comparative Example 1. The perovskite solar cell devices of Example 1, Example 2, and Comparative Example 1 were tested under isothermal conditions of 100±5℃ using an AM1.5G solar simulator (100 mW / cm²). 2 Accelerated thermal aging for 1000 hours (MPPT) was performed. The test results are as follows: Figure 4 As shown.

[0068] Figure 4 The graph shows the stability data of the perovskite solar cells in Examples 1, 2, and Comparative Example 1. Figure 4 It can be seen that after 1000 hours of thermal aging, the PCE of Comparative Example 1 is approximately 52% of the initial PCE. The stability of both Examples 1 and 2 is improved. The PCE of the device in Example 2 after 1000 hours of thermal aging remains at 80% of the initial PCE, while the PCE of the device in Example 1 after 1000 hours of thermal aging reaches as high as 95% of the initial PCE. The device in Example 1 exhibits excellent stability. Furthermore, the PCE of the device in Example 1 after 1000 hours of thermal aging is superior to the initial PCE of the device in Comparative Example 1. The perovskite solar cell of Example 1 exhibits excellent photoelectric performance and stability.

[0069] Furthermore, this invention introduces an additive (bulk phase doping) into the perovskite precursor solution, rather than using the additive as a passivation layer material for interface passivation. The two have different mechanisms of action and ranges of action. This invention uses 5-methylhydantoin as the additive for illustration, as shown in Table 2.

[0070] Table 2. Differences between 5-methylhydantoin bulk doping and its use as an interfacial passivation layer

[0071] As shown in Table 2, the introduction of additives (bulk doping) into the perovskite precursor solution in this invention yields significantly better results than interface passivation. Specifically: (1) More comprehensive defect passivation: Bulk doping can make the additives evenly distributed inside the grains, grain boundaries and surface of the perovskite film, and can passivate bulk defects, grain boundary defects and interface defects at the same time; while interface passivation can only passivate the interface defects between the perovskite light-absorbing layer and the electron transport layer, and cannot reach the perovskite bulk and grain boundary defects. A large number of grain boundaries still exist inside the perovskite film as degradation channels.

[0072] (2) Crystallization regulation: Through bulk doping, the additive participates in the nucleation and crystal growth process in the precursor solution. The C=O and Pb² groups in the additive... +Coordination can slow down the crystallization rate, resulting in larger grains and fewer grain boundaries. However, interface passivation is done by coating the perovskite after it has crystallized, which cannot improve grain size, crystallization orientation, or grain boundary density, and therefore does not have a crystallization control effect.

[0073] (3) Suppress FA + Deprotonation: Bulk doping methods involving NH groups and FA in additives. + Formation of stable hydrogen bonds, inhibiting FA + →FA + H + The deprotonation reaction, FA + The deprotonation reaction is a key factor in the thermal degradation of perovskites, so bulk doping can significantly improve the stability of perovskite devices. However, with interfacial passivation, the additives exist in the passivation layer, which cannot protect the fatty acids (FAs) in the bulk phase. + .

[0074] (4) Uniformity and coverage: In bulk doping, additives can achieve molecular-level uniform distribution through solution mixing. However, interface passivation may have problems such as incomplete coverage, uneven thickness, and pinholes, and may also cause uncontrollable interfacial reactions with perovskite.

[0075] In summary, the additives 1-methylhydantoin or 5-methylhydantoin introduced into the perovskite precursor solution in this invention resolve the inherent contradiction of the "passivation-degradation" trade-off inherent in traditional multi-active-site additives. The heterocyclic structure of 1-methylhydantoin or 5-methylhydantoin contains two carbonyl (C=O) active sites and one imino (NH) active site, exhibiting multi-site coordination ability. The carbonyl groups can interact with divalent cations (such as Pb) in the perovskite precursor. 2+ ) Form coordination bonds, passivating vacancy defects; imino groups react with organic cations (such as FA) in the perovskite precursor. + The additives form hydrogen bonds, stabilize organic cations, and inhibit deprotonation degradation. The additives in Examples 1 and 2 of this invention effectively reduce the defect state density of the perovskite light-absorbing layer, extend carrier lifetime, and improve the photoelectric conversion efficiency of the device. By inhibiting the deprotonation of organic cations and the degradation of the Pb-I framework, they significantly delay the performance degradation of perovskite solar cell devices under environmental stresses such as heat, light, and humidity, enabling the devices to maintain excellent stability during long-term operation.

[0076] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A perovskite precursor solution, characterized in that, It includes a perovskite precursor, a solvent, and an additive, the general structural formula of which is shown in Formula I: ； In Equation I, R1 and R2 are independently selected from hydrogen, C1-C, and C2, respectively. 10 Alkyl, C3-C 10 cycloalkyl, C6-C 10 Aryl, C7-C 10 Any of the aralkyl groups; R1 and R2 are not both hydrogen.

2. The perovskite precursor solution according to claim 1, characterized in that, R1 is selected from hydrogen.

3. The perovskite precursor solution according to claim 1, characterized in that, The additive includes at least one selected from 1-methylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-n-propylhydantoin, 5-isopropylhydantoin, 5-n-butylhydantoin, 5-isobutylhydantoin, 5-n-octylhydantoin, 5-cyclopropylhydantoin, 5-cyclopentylhydantoin, 5-cyclohexylhydantoin, 5-phenylhydantoin, 5-p-methylphenylhydantoin, 5-naphthylhydantoin, 5-benzylhydantoin, 5-phenylethylhydantoin, and 5-phenylpropylhydantoin.

4. The perovskite precursor solution according to claim 1, characterized in that, The perovskite precursor includes an ABX3 structure, wherein A is an organic cation and / or an alkali metal cation, B is a divalent cation, and X is a halide anion; And / or, the solvent includes at least one of dimethylformamide, dimethyl sulfoxide, methylpyrrolidone, γ-butyrolactone, acetonitrile, methanol, and ethanol.

5. The perovskite precursor solution according to claim 1, characterized in that, In the perovskite precursor solution, the concentration of the perovskite precursor is 0.5~1.5M; And / or, the concentration of the additive is 0.5~2.0 mg / mL.

6. A method for preparing the perovskite precursor solution according to any one of claims 1 to 5, characterized in that, Includes the following steps: The perovskite precursor, additives, and solvent are mixed to obtain the perovskite precursor solution.

7. A perovskite light-absorbing layer, characterized in that, The perovskite light-absorbing layer is formed from the perovskite precursor solution according to any one of claims 1 to 5.

8. A method for preparing a perovskite light-absorbing layer, characterized in that, Includes the following steps: The perovskite precursor solution according to any one of claims 1 to 5 is coated on a substrate to obtain a perovskite precursor wet film, which is then annealed after vacuum flash evaporation to obtain the perovskite light-absorbing layer.

9. A perovskite solar cell, characterized in that, The perovskite solar cell comprises, from bottom to top, a conductive substrate, a hole transport layer, a perovskite light-absorbing layer as described in claim 7, a passivation layer, an electron transport layer, and an electrode layer.

10. A method for preparing a perovskite solar cell, characterized in that, Includes the following steps: S1: Prepare a hole transport layer on a conductive substrate; S2: Coat the perovskite precursor solution according to any one of claims 1 to 5 onto the hole transport layer, and anneal it after vacuum flash evaporation to obtain a perovskite light-absorbing layer. S3: An electron transport layer is prepared on the perovskite light-absorbing layer; S4: Prepare a passivation layer on the electron transport layer; S4: An electrode layer is prepared on the passivation layer to obtain the perovskite solar cell.

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