Ionic liquid additive for perovskite solar cells and method of making the same

Abstract

This invention relates to the field of optoelectronic materials and photovoltaic device fabrication technology, and discloses an ionic liquid additive for perovskite solar cells and its preparation method. The additive is composed of 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium acetate, thioacetamide, and lead iodide. This invention employs a stepwise thermal induction process under dry conditions to construct a supramolecular eutectic system with a dual anion competition mechanism, and achieves in-situ pre-anchoring of metal ions. A multiple hydrogen bond network is used to convert the volatile thioacetamide into a thermally stable homogeneous liquid component, solving the problem of its loss during high-temperature annealing. Simultaneously, the in-situ formed lead coordination clusters act as active seed crystals, effectively reducing the nucleation barrier and inducing preferential grain growth. This invention improves the thin film crystallization quality and enhances the photoelectric conversion efficiency and environmental stability of the battery by achieving hierarchical release of functional molecules and deep passivation of grain boundary defects.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic materials and photovoltaic device fabrication technology, specifically to ionic liquid additives for perovskite solar cells and their preparation methods. Background Technology

[0002] Organic-inorganic hybrid perovskite solar cells, especially those based on formamidinium lead iodine (... Photovoltaic cells, due to their excellent photoelectric conversion efficiency and low manufacturing cost, have become a research hotspot in the photovoltaic field. However, Thin film preparation typically requires annealing at high temperatures to achieve the desired effect from non-photoactive... Phase photoactivity The phase transformation process places extremely high demands on the composition control and crystallization kinetics of the precursor solution.

[0003] Currently, to passivate defects in perovskite films and improve crystallinity, researchers often introduce sulfur- or oxygen-containing Lewis bases as additives into the precursor solution, such as sulfur-coordinating molecules like thioacetamide. These small organic molecule additives are typically solid and possess high saturated vapor pressures. In the preparation of... Thin film required In high-temperature annealing processes, free-state solid additives are highly susceptible to thermal volatilization. This rapid loss of additives not only prevents them from continuously performing their passivation function during grain boundary formation but also causes an imbalance in the stoichiometry of the film surface components, leading to an increase in defect density and a decrease in device thermal stability.

[0004] Furthermore, existing additive strategies often employ single-solvent or single-anion ionic liquid systems to regulate the crystallization process. In a single system, the interaction force between the additive and the perovskite precursor component is constant. If the interaction force is too weak, it cannot effectively suppress the rapid precipitation of the precursor; if the interaction force is too strong, it will lead to an overly stable adduct, hindering the normal formation of the perovskite lattice. This single and fixed interaction mode makes it difficult to simultaneously address colloidal regulation during the film formation stage and defect repair during the annealing stage, resulting in difficulties in obtaining perovskite films with high phase purity and few defects.

[0005] On the other hand, in the solution-based preparation of perovskite thin films, crystallization nucleation typically faces a high Gibbs free energy barrier. In the absence of effective heterogeneous nucleation sites, the precursor solution tends to undergo random, homogeneous nucleation. This nucleation method is often difficult to control, easily leading to an excessive number of nuclei and uneven growth rates, ultimately resulting in thin films with small grain sizes and high grain boundary density. Numerous grain boundaries are not only the primary sites for nonradiative recombination of charge carriers but also channels for water and oxygen intrusion, severely limiting the photoelectric conversion efficiency and environmental stability of the battery, and exacerbating the current and voltage hysteresis effects of the device. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an ionic liquid additive for perovskite solar cells and its preparation method, which solves the problems in existing technologies such as the easy volatilization and failure of solid additives during high-temperature annealing, the difficulty of controlling the crystallization process by a single interaction system, and the lack of effective nucleation sites leading to small film grain size and high grain boundary defect density.

[0007] To address the above problems, the present invention provides the following technical solution: In a first aspect, the present invention provides an ionic liquid additive for perovskite solar cells, employing the following technical solution: An ionic liquid additive for perovskite solar cells, said ionic liquid additive being made from raw materials comprising the following molar ratios: Component A1 is specifically 1-ethyl-3-methylimidazolium tetrafluoroborate; Component A2 is specifically 1-ethyl-3-methylimidazolium acetate; Component B is specifically thioacetamide; Component C, specifically lead iodide; The molar ratio of component A1 to component A2 is 8:1 to 12:1; The total molar amount of components A1 and A2 to the molar ratio of component B is 1:0.8 to 1:1.2; The amount of component C added is 0.2% to 0.5% of the total amount of substance in the current system.

[0008] By adopting the above technical solution, the present invention achieves the following technical effects by utilizing the chemical interactions between the components: First, by constructing a thermally stable liquid supramolecular eutectic system, the volatilization of functional components was suppressed. Component B (thioacetamide) acts as a hydrogen bond donor, forming a multiple hydrogen bond network with the anions and imidazole cations in components A1 and A2. This interaction alters the lattice energy of thioacetamide, causing it to transform into a homogeneous liquid state at room temperature. This eutectic structure lowers the saturated vapor pressure of thioacetamide, enabling it to be stably retained within the perovskite film or at grain boundaries during high-temperature annealing at 150°C, thus avoiding passivation failure caused by high-temperature volatilization.

[0009] Second, the hierarchical release of functional molecules is achieved using a dual anion competition mechanism. The system simultaneously contains acetate ions with strong coordinating ability (…). ) and tetrafluoroborate with weak coordination ability ( Thioacetamide binds differently to these two anions: during the low-temperature film-forming stage, it binds more strongly to... The weaker thioacetamide is preferentially released to modulate the colloidal properties of the precursor; during the high-temperature annealing stage, it is combined with... The strong thioacetamide is released upon heating and plays a chemical passivation role during grain boundary formation, repairing uncoordinated lead ion defects.

[0010] Third, the nucleation barrier is lowered through in-situ metal ion pre-anchoring. Component C (lead iodide) dissolves in the ligand-rich eutectic fluid during preparation, forming lead-containing coordination clusters. When this additive is added to the perovskite precursor, these pre-formed clusters act as heterogeneous nucleation sites, inducing... Mutually Growth along preferred orientation, suppressing non-photoactive The formation of the phase results in a dense film with large grains.

[0011] Preferably, the water content of component A1 is ≤500ppm and the water content of component A2 is ≤1000ppm.

[0012] By adopting the above technical solution, the low water content control avoids the hydrolysis reaction of thioacetamide during heating to generate ammonium acetate and hydrogen sulfide, thus ensuring the chemical stability of the eutectic system; at the same time, it prevents water molecules from inducing phase decomposition of the perovskite film, ensuring the long-term stability of the device.

[0013] Preferably, component B is vacuum dried before use to remove adsorbed water.

[0014] By adopting the above technical solution, the interference of adsorbed water on the raw material surface on the co-crystallization reaction is further eliminated, ensuring the effective construction of the hydrogen bond network between component B and the ionic liquid.

[0015] Preferably, the ionic liquid additive is a single-phase transparent viscous liquid at room temperature, and its color is light yellow or amber.

[0016] By employing the above technical solution, the physical state indicates that a homogeneous deep eutectic solvent has been formed among the components, rather than a physical suspension. The single-phase liquid characteristic ensures that the additives can be rapidly and uniformly dispersed after being added to the precursor solution, avoiding microscopic defects caused by localized oversaturation.

[0017] Secondly, the present invention provides a method for preparing an ionic liquid additive for perovskite solar cells, employing the following technical solution: A method for preparing an ionic liquid additive for perovskite solar cells includes the following steps: S1. Mix component A1 and component A2 and homogenize them under heating and stirring conditions to obtain a colorless and transparent homogeneous liquid. S2. While maintaining stirring, add component B to the homogeneous liquid obtained in S1, raise the temperature to carry out a thermally induced reaction until the solid powder disappears and a single-phase fluid is formed. S3. While maintaining heating and stirring, add component C to the fluid obtained in S2, continue the reaction until the powder is completely dissolved, stop heating and cool to room temperature to obtain the ionic liquid additive.

[0018] By adopting the above technical solution, the present invention achieves the orderly transformation of each component through a step-by-step process, the specific principle of which is as follows: First, a bi-anion substrate was constructed using the S1 step. A homogeneous substrate was then established by mixing the two ionic liquids through a heating homogenization process. and An anionic environment provides a basis for subsequent acceptance of hydrogen bond donors.

[0019] Secondly, the S2 step achieves in-situ liquidization of solid organic molecules. Under specific temperature conditions and with stirring, the energy provided by the system enables component B (thioacetamide) to overcome lattice energy and establish hydrogen bonds by embedding amino groups into the bi-anion network. This process transforms component B into a deep eutectic solvent precursor, solving its problems of easy precipitation at room temperature and easy volatilization at high temperatures.

[0020] Finally, step S3 completes the in-situ pre-assembly of the metal complex. In a fluid rich in strong coordinating groups, component C (lead iodide) dissociates, and lead ions are coordinated by the surrounding high concentration of ligands, forming coordination clusters in situ. These clusters remain stable in the ionic liquid medium after cooling, becoming the nucleation cores for subsequent perovskite film growth.

[0021] Preferably, the entire preparation process is carried out in a dry environment with a relative humidity of ≤20%.

[0022] By adopting the above technical solution, the dry environment blocks the side reaction pathways of acetate hygroscopicity and thioacetamide hydrolysis to generate gas, thus ensuring the chemical purity of the final product.

[0023] Preferably, the specific process parameters for step S1 are: heating temperature of 40-50℃, stirring speed of 400-500 rpm, and stirring time of 15-20 minutes.

[0024] By adopting the above technical solution, this temperature range is sufficient to reduce the viscosity of ionic liquids and promote molecular-level miscibility, while avoiding thermal degradation of raw materials.

[0025] Preferably, the specific process parameters for step S2 are: thermal induction reaction temperature of 68-72°C, stirring speed of 600-800 rpm, and reaction time of 30-45 minutes.

[0026] By employing the above technical solution, this temperature is higher than the activation energy threshold for eutectic formation, ensuring that solid component B rapidly enters the liquid phase network, and is lower than the thermal decomposition temperature of component B. The higher stirring speed provides shear force, accelerating the mass transfer process.

[0027] Preferably, the specific process parameters for step S3 are: the reaction temperature is maintained at 68-72°C, and the reaction time is 30-40 minutes.

[0028] By employing the above technical solution, maintaining this temperature ensures the system's low viscosity, which is beneficial for the diffusion and dissolution of component C. Sufficient reaction time ensures that the metal coordination reaction reaches equilibrium, avoiding the residue of unreacted particles.

[0029] Preferably, in step S2, component B is added slowly in powder form; in step S3, component C is added in powder form, and the reaction endpoint is determined by the absence of visible particulate matter.

[0030] By adopting the above technical solution, slow feeding avoids local agglomeration, and the endpoint is set with no particulate matter visible to the naked eye, which intuitively indicates that the system has been completely transformed into a homogeneous liquid.

[0031] This invention provides an ionic liquid additive for perovskite solar cells and a method for its preparation. It offers the following advantages: 1. This invention utilizes a thermally induced eutectic process to transform volatile solid thioacetamide into a thermally stable liquid supramolecular eutectic system. By leveraging the multiple hydrogen bond network formed between thioacetamide and the dianionic liquid, the saturated vapor pressure of thioacetamide is reduced, allowing it to remain within the perovskite film during high-temperature annealing and crystallization. This property solves the problem of traditional solid additives failing due to volatilization during annealing, ensuring continuous passivation of grain boundary defects by the functional components and improving the thermal stability of the device.

[0032] 2. This invention achieves the hierarchical release of functional molecules by constructing a dual-anion competition system based on strongly coordinated acetate and weakly coordinated tetrafluoroborate. During film formation, molecules bound to weak hydrogen bond acceptors are preferentially released to regulate the colloidal properties of the precursor, while molecules bound to strong hydrogen bond acceptors are released during the high-temperature annealing stage to repair grain boundary defects. This synergistic mechanism avoids the problem of excessively strong or weak binding of additives by a single solvent system, achieving kinetic control throughout the entire process from film formation to crystallization, and suppressing the formation of non-photoactive phases.

[0033] 3. This invention introduces an in-situ metal ion pre-anchoring strategy to pre-form lead-containing coordination clusters in an ionic liquid medium. These clusters, after being added to the perovskite precursor, act as heterogeneous nucleation seeds, reducing the... The nucleation barrier of the perovskite phase induces grain growth along a preferred orientation. This technique improves the crystallinity quality of the thin film, increases grain size, and reduces grain boundary density, thereby reducing nonradiative recombination losses of charge carriers during transport, improving the photoelectric conversion efficiency of the device, and suppressing hysteresis. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to comparative examples and test cases. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Preparation Examples 1-3: Preparation Example 1: This preparation example provides an ionic liquid additive for perovskite solar cells, the preparation process of which is carried out in a dry environment with a relative humidity ≤20%, and includes the following steps: Construction of a bi-anionic mixed substrate: 100 mmol of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 10 mmol of 1-ethyl-3-methylimidazolium acetate (EMIMAc) were mixed (molar ratio 10:1), placed in a glass container, and magnetically stirred at 500 rpm for 20 minutes at 45 °C until a colorless and transparent homogeneous liquid was obtained. Thermally induced supramolecular cocrystallization: While maintaining the above liquid under stirring, slowly add 110 mmol of thioacetamide (TAA) powder (i.e., the total ionic liquid to TAA molar ratio is 1:1), raise the system temperature to 70°C, increase the stirring speed to 800 rpm, and continue the reaction for 40 minutes until the solid powder completely disappears, forming a single-phase transparent viscous fluid; the thioacetamide (TAA) is dried in a vacuum drying oven at room temperature for 24 hours before use; In-situ metal ion pre-anchoring: Maintaining a constant temperature of 70°C and stirring, add 0.77 mmol of lead iodide to the above fluid. Add the powder (0.35% of the total amount of the current system) and stir continuously for 40 minutes until the powder is completely dissolved. Stop heating and let it cool naturally to room temperature to obtain a clear amber liquid with a water content of ≤500ppm, which is the ionic liquid additive A1.

[0036] Preparation Example 2: This preparation example provides an ionic liquid additive for perovskite solar cells, the preparation process of which is carried out in a dry environment with a relative humidity ≤20%, and includes the following steps: Construction of a bi-anionic mixed substrate: 80 mmol of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 10 mmol of 1-ethyl-3-methylimidazolium acetate (EMIMAc) were mixed (molar ratio 8:1), placed in a glass container, and magnetically stirred at 400 rpm for 15 minutes at 45 °C until a colorless and transparent homogeneous liquid was obtained. Thermally induced supramolecular cocrystallization: While maintaining the above liquid under stirring, slowly add 72 mmol of thioacetamide (TAA) powder (i.e., the total ionic liquid to TAA molar ratio is 1:0.8), raise the system temperature to 70°C, increase the stirring speed to 600 rpm, and continue the reaction for 30 minutes until the solid powder completely disappears, forming a single-phase transparent viscous fluid; the thioacetamide (TAA) should be dried in a vacuum drying oven at room temperature for 24 hours before use; In-situ metal ion pre-anchoring: Maintaining a constant temperature of 70°C and stirring, add 0.324 mmol of lead iodide to the above fluid. Add the powder (0.2% of the total amount of the current system) and stir continuously for 30 minutes until the powder is completely dissolved. Stop heating and let it cool naturally to room temperature to obtain a clear, light yellow liquid with a water content ≤1000ppm, which is the ionic liquid additive A2.

[0037] Preparation Example 3: This preparation example provides an ionic liquid additive for perovskite solar cells, the preparation process of which is carried out in a dry environment with a relative humidity ≤20%, and includes the following steps: Construction of a bi-anionic mixed substrate: 120 mmol of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 10 mmol of 1-ethyl-3-methylimidazolium acetate (EMIMAc) were mixed (molar ratio 12:1), placed in a glass container, and magnetically stirred at 500 rpm for 20 minutes at 45 °C until a colorless and transparent homogeneous liquid was obtained. Thermally induced supramolecular cocrystallization: While maintaining the above liquid under stirring, slowly add 156 mmol of thioacetamide (TAA) powder (i.e., the total ionic liquid to TAA molar ratio is 1:1.2), raise the system temperature to 70°C, increase the stirring speed to 800 rpm, and continue the reaction for 40 minutes until the solid powder completely disappears, forming a single-phase transparent viscous fluid; the thioacetamide (TAA) should be dried in a vacuum drying oven at room temperature for 24 hours before use; In-situ metal ion pre-anchoring: Maintaining a constant temperature of 70°C and stirring, add 1.43 mmol of lead iodide to the above fluid. Add the powder (0.5% of the total amount of the current system) and stir continuously for 40 minutes until the powder is completely dissolved. Stop heating and let it cool naturally to room temperature to obtain a clear, dark amber liquid, which is the ionic liquid additive A3.

[0038] Examples 1-3: Example 1: This embodiment provides a perovskite solar cell prepared using the above-mentioned ionic liquid additive, the structure of which is as follows: The specific preparation method is carried out at a relative humidity (RH) of The process is carried out in an air environment and includes the following steps: Substrate cleaning and electron transport layer fabrication: The etched ITO conductive glass was ultrasonically cleaned sequentially with deionized water, acetone, and isopropanol for 15 minutes each, then treated with ultraviolet ozone (UV-Ozone) for 15 minutes, and finally spin-coated with tin dioxide. The colloidal dispersion was annealed at 3000 rpm for 30 seconds in air at 150°C for 30 minutes, and then naturally cooled to room temperature to obtain the desired product. Electron transport layer substrate.

[0039] Preparation of modified perovskite precursor solution: 258 mg of formamidin hydroiodide (FAI) and 691.5 mg of lead iodide ( Dissolve in 1 mL of mixed solvent ( In a volume ratio of 1.5 M, a concentration of 1.5 M was obtained. Basic precursor solution. Subsequently, using a pipette, ionic liquid additive A1 obtained in Preparation Example 1 was added at a volume ratio of 2.0 vol% (i.e., 20 mL of the basic precursor per 1 mL of solution). Additive A1 was added dropwise to the above base solution, vortexed for 30 seconds and allowed to stand to remove bubbles, to obtain the modified precursor solution.

[0040] Deposition of perovskite thin films: The modified precursor solution was added dropwise to... On the substrate, a one-step spin-coating method was used to form a film: first, spin-coating was performed at 1000 rpm for 10 seconds, followed immediately by spin-coating at 5000 rpm for 20 seconds; 15 seconds before the end of the second stage of spin-coating, 150 μL of film was rapidly added dropwise. Chlorobenzene was used as the antisolvent. After spin coating, the wet film was immediately placed on a hot plate at 150°C for annealing for 20 minutes. The film changed from dark brown to glossy dark black, resulting in a modified perovskite film.

[0041] Hole transport layer and electrode fabrication: Spiro-OMeTAD solution (72.3 mg dissolved in 1 mL chlorobenzene, with 28.8 mg added) was spin-coated onto a perovskite film. TBP and 17.5 Li-TFSI / acetonitrile solution), spin-coated at 3000 rpm for 30 seconds. Finally, vacuum thermal evaporation was used... A perovskite solar cell device D1 was fabricated by depositing an 80 nm thick silver (Ag) electrode under vacuum.

[0042] Example 2: This embodiment provides a perovskite solar cell prepared using the aforementioned ionic liquid additive. The specific preparation method is carried out at a relative humidity (RH) of [missing information]. The process is carried out in an air environment and includes the following steps: Substrate cleaning and electron transport layer fabrication: The process steps and parameters are exactly the same as in Example 1.

[0043] Preparation of modified perovskite precursor solution: Prepare 1.5M The basic precursor solution (solvent to solute ratio as in Example 1) was prepared. Then, using a pipette, ionic liquid additive A2 obtained in Preparation Example 2 was added at a volume ratio of 1.5 vol% (i.e., 15 vol% per 1 mL of basic precursor). Additive A2 was added dropwise to the base solution, vortexed for 30 seconds and allowed to stand to remove bubbles, thus obtaining the modified precursor solution.

[0044] Deposition of perovskite thin films: The modified precursor solution from step (2) was added dropwise to... On the substrate, the same spin-coating procedure and antisolvent drop-addition steps as in Example 1 were performed. After spin-coating, the wet film was annealed on a hot plate at 150°C for 20 minutes to obtain the modified perovskite film.

[0045] Hole transport layer and electrode fabrication: The process steps and parameters are exactly the same as in Example 1, and the perovskite solar cell device D2 is obtained.

[0046] Example 3: This embodiment provides a perovskite solar cell prepared using the aforementioned ionic liquid additive. The specific preparation method is carried out at a relative humidity (RH) of [missing information]. The process is carried out in an air environment and includes the following steps: Substrate cleaning and electron transport layer fabrication: The process steps and parameters are exactly the same as in Example 1.

[0047] Preparation of modified perovskite precursor solution: Prepare 1.5M The basic precursor solution (solvent to solute ratio as in Example 1) was prepared. Subsequently, the ionic liquid additive A3 obtained in Preparation Example 3 was pipetted and added at a volume ratio of 3.0 vol% (i.e., 30 mL of the basic precursor per 1 mL of solution). Additive A3 was added dropwise to the base solution, vortexed for 30 seconds and allowed to stand to remove bubbles, thus obtaining the modified precursor solution.

[0048] Deposition of perovskite thin films: The modified precursor solution was added dropwise to... On the substrate, the same spin-coating procedure and antisolvent drop-addition steps as in Example 1 were performed. After spin-coating, the wet film was annealed on a hot plate at 150°C for 20 minutes to obtain the modified perovskite film.

[0049] Hole transport layer and electrode fabrication: The process steps and parameters are exactly the same as in Example 1, and the perovskite solar cell device D3 is obtained.

[0050] Comparative Examples 1-5: Comparative Example 1 (Blank Control Group): Compared with Example 1, the only difference is that no ionic liquid additive A1 is added when preparing the modified perovskite precursor solution. Only the basic precursor solution is used for spin coating to form a film. All other steps and parameters are the same.

[0051] Comparative Example 2 (Physical Mixing / Non-eutectic Group): Compared with Example 1, the only difference is that instead of preparing liquid additive A1 in advance, solid thioacetamide (TAA) powder, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF4) and 1-ethyl-3-methylimidazolium acetate (EMIMAc) in the same amount as in Example 1 are directly added to the basic precursor solution. After being stirred and dissolved for a long time, spin coating is performed. All other steps and parameters are the same.

[0052] (Design objective: To demonstrate that the "liquid supramolecular eutectic" structure of this invention is superior to the simple physical superposition of the components, and to verify the inhibitory effect of eutectic locking on TAA volatilization) Comparative Example 3 (Single Anion Group): Compared with Example 1, the only difference is that in the preparation process of the ionic liquid additive, component A2 (EMIMAc) is not added, but is replaced by an equimolar amount of component A1 (EMIMBF4), that is, only a single anion substrate is constructed, and the remaining preparation steps and battery preparation parameters are the same.

[0053] (Design objective: To demonstrate the key role of the strong coordinating anion (Ac-) in the "bi-anion competition mechanism" for staged release and defect passivation) Comparative Example 4 (Metal-free Pre-anchored Group): Compared with Example 1, the only difference is that in the preparation process of the ionic liquid additive, the "in-situ metal ion pre-anchoring" is omitted, that is, component C is not added. The same preparation steps and battery preparation parameters were used to prepare a eutectic ionic liquid without metal clusters.

[0054] (Design objective: To demonstrate the effect of active seed crystals introduced by "in-situ metal ion pre-anchoring" on reducing the nucleation barrier and promoting grain growth) Comparative Example 5 (Cold Mix / Unreacted Group): Compared with Example 1, the only difference is that in the preparation of the ionic liquid additive, all raw materials were simply physically stirred at room temperature (25°C) after mixing, without undergoing a thermally induced co-crystallization reaction at 70°C, and a stable supramolecular network was not formed. All other battery preparation parameters were the same.

[0055] (Design objective: to demonstrate the necessity of the "thermally induced eutectic process" for forming a homogeneous stable fluid and locking the chemical potential).

[0056] Test Examples 1-6: Test Example 1: Thermal Stability Test of Additives This test case aims to investigate the mass loss behavior of ionic liquid additives at simulated perovskite film annealing temperatures and to verify the thermal lock-in effect of the supramolecular eutectic structure on the volatile component thioacetamide (TAA).

[0057] Experimental methods: Pure thioacetamide powder (denoted as pure TAA), the physical mixture prepared in Comparative Example 2 (denoted as sample D-2), and the pre-nucleated bi-anionic supramolecular eutectic ionic liquid additive prepared in Example 1 (denoted as sample S-1) were selected as test objects.

[0058] Thermogravimetric analysis (TGA) was used for testing. 5-8 mg of each of the above samples were placed in an alumina crucible. The testing environment was a high-purity nitrogen gas flow (50 mL / min) to prevent sample oxidation from interfering with the determination of mass changes.

[0059] The heating program is set as follows: (1) Increase the temperature from room temperature to 150℃ at a rate of 10℃ / min; (2) Keep at a constant temperature of 150℃ for 60 minutes.

[0060] Real-time recording of sample mass changes over time and temperature, with a focus on examining the mass residue rate during the isothermal stage.

[0061] Experimental data: The mass residue data of different samples during the isothermal stage at 150℃ are shown in Table 1.

[0062] Table 1. Data record of mass residual rate of each sample during the isothermal process at 150℃ Note: The mass residual rate is calculated based on the normalized initial mass before entering the constant temperature zone.

[0063] Results Analysis and Conclusions: Based on the data in Table 1 and the technical mechanism proposed in this invention, the following analytical conclusions are drawn: The melting point of pure TAA is approximately 113℃. At an annealing temperature of 150℃, it remains liquid and rapidly evaporates. Data shows that the residual mass of pure TAA decreased to 18.63% after 30 minutes of isothermal treatment, and it was almost completely evaporated after 60 minutes. This indicates that during the annealing process of conventional perovskite thin film preparation, without effective restraint, TAA molecules can easily escape from the film, resulting in their inability to effectively passivate grain boundary defects.

[0064] The mass residue of sample D-2 (physical mixing group) at the end of the isothermal treatment was 61.23%. Considering that the ionic liquid components (EMIMBF4 and EMIMAc) in the formulation have good thermal stability at 150°C and do not volatilize, this mass loss (approximately 38%) is mainly attributed to the volatilization of the TAA component in the mixture. This indicates that simple physical mixing did not change the chemical potential of TAA, and TAA molecules still maintain a high degree of freedom in the mixture, and will still detach from the system upon heating.

[0065] Sample S-1 (an embodiment of the present invention) maintained a mass retention rate of 97.58% after being kept at 150°C for 60 minutes, demonstrating good thermal stability. The extremely low mass loss indicates that the vast majority of TAA molecules in the system were effectively retained.

[0066] This result confirms the formation mechanism of the dianion supramolecular eutectic system: First, this invention utilizes a thermally induced process to form a multiple hydrogen bond network between the amino group in the TAA molecule and the acetate group (strong hydrogen bond acceptor) in EMIMAc and the tetrafluoroborate group (weak hydrogen bond acceptor) in EMIMBF4. This intermolecular interaction reduces the saturated vapor pressure of TAA.

[0067] Second, the lead ions introduced in situ form coordination clusters with TAA and acetate ions, which further increases the escape energy barrier of TAA molecules.

[0068] Third, the deep eutectic solvent structure formed by homogenization of the system has high viscosity and cohesive energy, which restricts the thermal motion of the internal components.

[0069] In summary, the ionic liquid additive prepared in this invention transforms a volatile solid additive into a thermally stable liquid component through the dual effects of chemical bonding and physical structure. During the deposition and annealing of perovskite thin films, this additive ensures that the functional molecule TAA remains inside the film, thereby exerting the expected defect passivation and crystallization control effects, and solving the technical problem of traditional solid additives failing in high-temperature annealing processes.

[0070] Test Example 2: Photovoltaic Performance and Hysteresis Test of Perovskite Solar Cells This test case aims to evaluate the effects of different additive regimens on... The impact of perovskite solar cell device photoelectric conversion efficiency (PCE) and operational stability was investigated by obtaining key photovoltaic parameters through current density-voltage (JV) scanning curves, verifying the actual effect of the technical solution of this invention in improving device performance.

[0071] Experimental methods: Unencapsulated perovskite solar cell devices prepared in Examples 1-3 and Comparative Examples 1-5 were selected as test objects.

[0072] The test was conducted under standard atmospheric quality AM1.5G illumination conditions, using a Class A solar simulator equipped with filters, and the light intensity was calibrated to [value missing]. (Calibrated using a standard silicon reference cell).

[0073] The testing steps are as follows: (1) The effective illumination area of ​​the battery is limited by a metal mask plate. This is to eliminate measurement errors caused by edge effects.

[0074] (2) Use a Keithley 2400 digital source table to collect JV scan data. The scan range is set to... .

[0075] (3) Perform reverse scanning (RS, from open-circuit voltage to short-circuit current) and forward scanning (FS, from short-circuit current to open-circuit voltage) respectively, with the scanning rate set to [value missing]. .

[0076] (4) Record the open-circuit voltage ( ), short-circuit current density ( ), fill factor (FF) and photoelectric conversion efficiency (PCE).

[0077] (5) Calculate the hysteresis index (HI). The formula is as follows: .

[0078] Experimental data: Table 2 shows the photovoltaic performance parameters and hysteresis index of each group of devices under reverse scanning. The data is the average of 5 devices in the same batch, and significant digits are retained to reflect the actual experimental fluctuations.

[0079] Table 2. Photovoltaic performance parameters of perovskite solar cell devices in different experimental groups Results Analysis and Conclusions: Based on the test data in Table 2, and considering the mechanism of action of the pre-nucleated bi-anion supramolecular eutectic ionic liquid additive of this invention, the following analysis is conducted: Overall performance improvement analysis: Compared to Comparative Example 1 (blank group, PCE 22.93%), the device efficiencies of Examples 1-3 were significantly improved, with Example 1 reaching 24.89%. This indicates that the introduction of ionic liquid additives effectively improved the efficiency of the devices. The crystallinity quality of the thin film. Specifically, The increase from 1.148V to 1.165V demonstrates that the TAA and imidazole cations in the additive effectively passivated the non-radiative recombination centers at the grain boundaries. The improvement in FF is attributed to the enhanced carrier transport capability and the reduction in series resistance.

[0080] Advantages of the dual anion system (compared to D-Comp3): Comparative Example 3, using only a single anion (EMIMBF4), prepared an additive with a PCE of 23.64%, significantly lower than Example 1. This is because it lacks a strong hydrogen bond acceptor site provided by acetate (Ac-). In Example 1, Ac- and BF4- constructed a competitive binding environment, allowing the functional molecule TAA to be released in stages during annealing. The system lacking Ac- has a single and weak binding force on TAA, causing some TAA to volatilize prematurely before the film crystallization is complete, failing to fully exert its passivating effect, resulting in… And the decrease of FF.

[0081] The role of metal ion pre-anchoring (compared to D-Comp4): Comparative Example 4 did not introduce additives during preparation. Pre-anchoring was performed, and its PCE was 23.87%. Although the physical properties were better than the blank group, they were lower than those of Example 1. The main differences were in the FF and hysteresis index. Example 1 introduced uniformly distributed heterogeneous nucleation sites in the precursor solution through in-situ formed lead-sulfur coordination clusters, which lowered the nucleation barrier and induced larger and denser perovskite grains. Comparative Example 4, which lacked this mechanism, had uneven grain size distribution and relatively high grain boundary density, resulting in hindered carrier transport and a more obvious hysteresis effect (HI=0.032).

[0082] The difference between eutectic process and physical mixing (comparison of D-Comp2 and D-Comp5): The PCE values ​​for Comparative Example 2 (physical mixing) and Comparative Example 5 (cold mixing) were 23.27% and 23.07%, respectively, with no significant improvement in FF (80.55% and 80.20%). This indicates that simple physical superposition of components cannot achieve the expected synergistic effect. The thermally induced eutectic process (step 2) used in this invention transforms each component into a thermodynamically stable single liquid phase, ensuring the uniformity of the additives at the microscale. In physically mixed or cold-mixed samples, the lack of sufficient chemical potential locking between components leads to uneven component distribution during spin coating, and even local phase separation, severely affecting the homogeneity of the film and the repeatability of the final device.

[0083] In summary, the optimal photovoltaic performance (highest efficiency and lowest hysteresis) demonstrated in Example 1 confirms that the present invention achieves precise control of perovskite crystallization kinetics and effective passivation of defects through a dual mechanism of "dual anion competitive locking" and "metal pre-anchoring nucleation".

[0084] Test Example 3: Device Environmental Stability Test This test case aims to examine the long-term storage stability of unencapsulated perovskite solar cell devices in a natural air environment, with a focus on verifying the effect of the ionic liquid additive of this invention on... The ability to maintain the stability of the black phase and its barrier effect against water and oxygen erosion.

[0085] Experimental methods: Battery devices prepared in Examples 1-3 and Comparative Examples 1-5 were selected, and three parallel samples were selected in each group. The average value of the test results was taken and normalized to reflect the degradation trend.

[0086] The test conditions are set as follows: (1) Environment: Dark state, air atmosphere.

[0087] (2) Relative humidity (RH): .

[0088] (3) Temperature: .

[0089] (4) Duration: Continuous monitoring for 500 hours.

[0090] Test process: First, the initial photoelectric conversion efficiency of each device was measured at 0 hours. The device was then placed in the aforementioned environment for static aging. Approximately every 100 hours, the device was removed and subjected to a JV scan under standard AM1.5G illumination, and the photoelectric conversion efficiency was recorded for each scan. ).

[0091] Data processing uses normalized PCE as its representation, i.e. .

[0092] Experimental data: The normalized photoelectric conversion efficiency changes of each group of devices during the 500-hour aging cycle are shown in Table 3.

[0093] Table 3. Long-term stability test data of unpackaged devices in air environment (RH40%) (normalized PCE) Results Analysis and Conclusions: Table 3 shows the monitoring data that reveals the impact of different modification strategies on the environmental stability of the device, which is analyzed in conjunction with the material microstructure as follows: Phase stability and water-oxygen barrier properties: After 500 hours of exposure to air, the normalized efficiency of the blank control group (D-Comp1) was only 0.052, indicating near device failure. Visual observation revealed that the film color changed from black to yellow, confirming the failure. Moisture-induced transformation to non-photoactive Phase transition. In contrast, Example 1 (D-Ex1) maintained an initial efficiency of 0.928 under the same conditions. This is mainly attributed to the protective effect of the hydrophobic properties of the ionic liquid additive. The bi-anionic supramolecular eutectic structure constructed in this invention resides at the grain boundaries after annealing, with the hydrophobic alkyl imidazole cation and fluoride anion (BF4)... - This forms a physical barrier, cutting off the channels for water molecules to penetrate into the perovskite lattice.

[0094] Structural integrity and defect density: The final retention rates of Comparative Example 2 (physical mixing group) and Comparative Example 5 (cold mixing group) were 0.615 and 0.658, respectively, with significantly faster decay rates than the examples. This indicates that if a stable eutectic fluid is not formed, the uneven distribution of components during film formation leads to microscopic pores or incomplete coverage areas in the film, and these defects become entry points for water and oxygen erosion. The thermally induced eutectic process of this invention ensures the continuous distribution of additives at grain boundaries, minimizing exposed interfaces.

[0095] Chemical anchoring of the crystal lattice by two anions: Comparing D-Comp3 (monoanion group, retention rate 0.741) and D-Ex1 (dianion group, retention rate 0.928), the introduction of acetate ( This improves stability. It has more than BF4 - Stronger coordination ability, enabling it to coordinate with uncoordinated surfaces. This forms a stable chemical bond. This chemical anchoring effect not only passivates surface defects but also inhibits ion migration and increases the rigidity of the crystal structure, thereby slowing down the degradation process induced by environmental factors.

[0096] The effect of prenucleation on grain quality: D-Ex1 outperformed D-Comp4 (the group without metal anchoring, with a retention rate of 0.765%). The metal clusters introduced through the pre-anchoring process promoted the formation of dense, large grains and reduced grain boundary density. Since grain boundaries are the main water and oxygen diffusion channels in perovskite films, the reduction in grain boundary density directly slowed down the erosion rate of the film interior by the external environment.

[0097] In summary, the ionic liquid additives provided by this invention synergistically improve the operational stability of perovskite solar cells in humid air environments by constructing a dense hydrophobic physical barrier, enhancing the chemical anchoring effect at the surface and interface, and optimizing the microstructure of the thin film.

[0098] Test Example 4: Thin Film Defect Density and Carrier Dynamics Test This test case aims to quantitatively characterize the defect state density and recombination lifetime of photogenerated carriers inside perovskite thin films, and to verify the suppression of nonradiative recombination through steady-state photoluminescence spectroscopy. From the perspective of microscopic carrier dynamics, it verifies the chemical passivation effect of ionic liquid additives on grain boundary defects and their role in improving crystal quality.

[0099] Experimental methods: Perovskite thin film samples prepared in Examples 1-3 and Comparative Examples 1-5 were selected for testing.

[0100] Steady-state photoluminescence (PL) spectroscopy testing: Perovskite films were directly deposited on a quartz glass substrate (excluding the transport layer). Steady-state PL spectra were acquired using a fluorescence spectrometer with the excitation wavelength set to 470 nm, and the intensity and position changes of the emission peaks were recorded.

[0101] Defect density test (SCLC method): Fabrication of a single-electron transport device (Electron-Only Device) with the following structure: IV curves were tested using an electrochemical workstation under dark conditions. The trap-filled limit voltage was identified in the curves. According to the formula Calculate the defect density of the thin film .in The vacuum permittivity, The relative permittivity of perovskite is 46.9. For elementary charge, The thickness is the thin film thickness.

[0102] Carrier lifetime testing (TRPL method): Sample preparation was the same as for PL testing. Testing was performed using a time-resolved fluorescence spectrometer with an excitation wavelength set to 470 nm. The acquired time-resolved photoluminescence (TRPL) decay curves were fitted using a double exponential function to calculate the average carrier lifetime.

[0103] Experimental data: The trap filling limit voltage, calculated defect density, and average carrier lifetime data for each group of samples are shown in Table 4.

[0104] Table 4. Defect density and carrier dynamics parameters of perovskite thin films. Results Analysis and Conclusions: Table 4 shows the test data and spectral analysis, reflecting the electronic quality of perovskite films under different preparation processes. The analysis, combined with the technical solution of this invention, is as follows: Suppression of nonradiative recombination (PL analysis): Steady-state PL spectra show that while the blank control group (D-Comp1) exhibits a certain luminescence intensity, indicating acceptable basic crystal quality, the PL peak intensity of Example 1 (D-Ex1) is approximately twice that of the blank group, and the luminescence peak position shows a slight blue shift. This enhanced PL intensity directly confirms the reduction in the density of non-radiative recombination centers (deep-level defects) within the thin film, indicating that photogenerated carriers are more prone to radiative recombination. This is consistent with the device open-circuit voltage (V0). OC The improvement is highly consistent.

[0105] Reduction in defect density: Blank control group (D-Comp1) Up to 0.58V, corresponding to a defect density of This indicates that even with advanced basic processes, the thin film still retains a certain amount of deep-level defects, which mainly originate from coordination unsaturation at grain boundaries. And iodine vacancies. The defect density of Example 1 (D-Ex1) was significantly reduced to This decrease confirms the presence of thioacetamide (TAA) and acetate in the ionic liquid additive. Through Lewis acid-base interactions, charged defect sites at grain boundaries are effectively filled.

[0106] Verification of the dual anion synergistic passivation mechanism: Comparison of D-Ex1 and D-Comp3 (mono-anion group, defect density) ), introducing auxiliary anions Subsequently, the defect density decreased further by approximately 60%. This indicates that... With its strong coordination ability, it can specifically repair BF4. - Deep defects that cannot be passivated; at the same time, the graded release characteristics of the bi-anionic eutectic system ensure that the passivating agent can play a role in all stages of crystal growth, avoiding surface passivation failure caused by annealing volatilization.

[0107] The contribution of pre-nucleation process to crystallization quality: Average carrier lifetime is a key indicator for measuring the nonradiative recombination rate of thin films. The average lifetime of D-Ex1 reached 1386.4 ns, significantly higher than the 1050.8 ns of the metal-free anchored group (D-Comp4). Although D-Comp4 exhibited good fundamental performance with a lifetime exceeding 1 microsecond, its grain growth was limited due to the lack of pre-nucleated clusters, resulting in a larger total grain boundary area and an increased overall nonradiative recombination probability. Example 1 induced the growth of large-sized grains through in-situ formed metal clusters, reducing the number of grain boundaries and further extending the carrier lifetime.

[0108] In summary, the SCLC, TRPL, and steady-state PL test results consistently demonstrate that the ionic liquid additive prepared in this invention can further reduce the defect state density of perovskite films and suppress non-radiative recombination based on existing high-level preparation processes. The mechanism stems from the efficient chemical passivation of the dual anion system and the improvement of crystal growth quality by the pre-nucleation mechanism.

[0109] Test Example 5: Analysis of Thin Film Crystal Structure and Phase Purity This test case utilizes X-ray diffraction (XRD) combined with field emission scanning electron microscopy (SEM) to characterize the crystal structure of the perovskite thin film. By analyzing the parameters of characteristic diffraction peaks, grain size, and grain boundary state, the test verifies the effect of the "in-situ metal pre-anchoring" strategy in the ionic liquid additive on... - The effects of inducing crystal growth, promoting grain coarsening, and stabilizing phases.

[0110] Experimental methods: Perovskite thin film samples prepared in Examples 1-3 and Comparative Examples 1-5 were selected (deposited on glass substrates, without spin-coated hole transport layers).

[0111] 1. Crystal structure analysis: The test was conducted using an X-ray diffractometer, with the radiation source being... ray( The tube voltage is 40kV and the tube current is 40mA. The scanning mode is... Linked scanning, scanning range ( ) set as The scanning step size is .

[0112] 2. Microscopic morphology analysis: The surface morphology of the perovskite film was observed using field emission scanning electron microscopy (SEM) at an accelerating voltage of 5 kV, and the average grain size was statistically analyzed based on the SEM images.

[0113] Data processing focuses on the following parameters: Main characteristic peak (100) crystal plane (approximately The diffraction intensity of ) (100) Full width at half maximum (FWHM) of the crystal plane, which is inversely proportional to the grain size; δ phase (non-photoactive yellow phase) characteristic peak (approximately) )or Residual peak ( The existence of ); Average grain size measured by SEM images.

[0114] Experimental data: The statistical analysis of the XRD pattern characteristic parameters of each group of samples is shown in Table 5.

[0115] Table 5. Statistical table of characteristic diffraction peak parameters of perovskite thin films XRD Results Analysis and Conclusions: XRD patterns and SEM images together reveal the effects of different process conditions on... The influence of thin film crystallization kinetics and phase transition behavior, combined with the technical mechanism analysis, is as follows: Improvement in crystal orientation and grain size: SEM images clearly show that, under high-level basic processes, the blank group (D-Comp1) film, although with good coverage, has grain sizes mainly distributed in the 600-700 nm range (average 0.65 μm) and contains many obvious grain boundaries. In contrast, Example 1 (D-Ex1) exhibits significant grain coarsening, with the average grain size increasing to 1.25 μm, blurred grain boundaries, and high fusion, with no abnormal new crystal precipitation observed. In the corresponding XRD data, the (100) main peak FWHM of D-Ex1 narrows to 0.124°. This confirms that the pre-anchored lead ligand clusters in the additive of this invention act as heterogeneous nucleation centers, effectively reducing the nucleation density, promoting secondary grain growth, and eliminating fine grains that are detrimental to carrier transport.

[0116] The regulation of nucleation density by pre-anchoring mechanisms: Although the metal-free anchored group (D-Comp4) contained the same chemical ligands, its grain size (0.88 μm), while superior to the blank group, was still significantly smaller than that of Example 1. This indicates that in the absence of pre-anchored clusters, the nucleation process mainly relies on homogeneous nucleation induced by solvent evaporation, with random nucleation sites and a high nucleation barrier, resulting in a limited final grain size. This result directly verifies the effectiveness of the "in-situ metal ion pre-anchoring" process in thermodynamically reducing the nucleation barrier and kinetically promoting grain coarsening.

[0117] Analysis of phase purity and new crystal formation: Regarding phase purity, the blank group (D-Comp1) showed a very weak δ-phase characteristic peak at 11.8°, indicating that the basic process had controlled the phase transition well, but still did not achieve perfect pure phase. In contrast, the XRD patterns of the example group showed no detectable δ-phase or... Residual peaks were observed, and no new adduct phase was found. This indicates that the ionic liquid additive did not precipitate as an impurity, but rather stabilized the black perovskite phase entirely through a dual action: firstly, the acetate group ( )and The strong hydrogen bonding between the crystals leads to a reduction in lattice distortion energy; secondly, the large volume of imidazole cations is enriched at the grain boundaries and surfaces, effectively reducing the surface energy (Gibbs free energy) of the crystal, thereby thermodynamically stabilizing the α-phase structure and inhibiting its spontaneous transformation to the δ-phase.

[0118] Advantages of homogeneous eutectic systems: Although the grain size of the physical hybrid group (D-Comp2) was slightly increased, trace amounts were detected in XRD. The residual peak (12.7°) indicates that uneven distribution of additives led to local component imbalance. The thermally induced eutectic process of this invention ensures the uniform effect of the regulator throughout the film formation process, avoiding the formation of impurity phases, thereby obtaining a high-purity, large-grained homogeneous pure-phase film.

[0119] In summary, XRD and SEM analyses confirm that the ionic liquid additive provided in this invention promotes ionic liquid formation through a pre-nucleation mechanism. The preferential growth of large grains eliminates trace impurities, ensuring high efficiency and high stability of the device from the perspectives of crystal structure and micromorphology.

[0120] Test Example 6: Electrochemical Impedance Spectroscopy (EIS) Test This test case analyzes the charge transport dynamics and interfacial recombination behavior inside the battery device using electrochemical impedance spectroscopy. By comparing the changes in series resistance (Rs) and recombination resistance (Rrec), the effect of ionic liquid additives on improving the electrical losses of the device is verified.

[0121] Experimental methods: Perovskite solar cell devices prepared in Examples 1-3 and Comparative Examples 1-5 were selected. Under dark conditions, the devices were tested using an electrochemical workstation (Zahner) with a bias voltage of 0.9V. The frequency scan range was set from 1MHz to 1Hz, and the AC perturbation signal amplitude was 20mV. The obtained Nyquist spectra were fitted and analyzed using an equivalent circuit model (including series resistance Rs, composite resistance Rrec, and constant phase angle element CPE).

[0122] Experimental data: The EIS fitting parameters for each group of samples are shown in Table 6.

[0123] Table 6. Statistical table of electrochemical impedance spectroscopy parameters of devices in different experimental groups Results Analysis and Conclusions: EIS test data reveals the regulation mechanism of different additive schemes on the carrier transport and recombination process inside the device. The analysis, combined with the technical solution of this invention and the aforementioned photovoltaic performance data, is as follows: The correlation between optimization of series resistance (Rs) and improvement of fill factor: Table 6 shows that the series resistance Rs of the blank control group (D-Comp1) is 21.15 ohms cm. 2 This indicates that even with advanced basic processes, the device still exhibits a certain degree of ohmic loss. The Rs of Example 1 (D-Ex1) decreased to 12.43 ohm cm⁻¹. 2 This reduction in internal resistance directly corresponds to the experimental result of increasing the device fill factor (FF) from 79.85% to 81.40%. The reasons for this can be attributed to two main factors: Firstly, the aforementioned SEM test confirmed that Example 1 formed large-sized grains at the micrometer scale, which reduced the number of grain boundaries and thus reduced the grain boundary scattering resistance when charge carriers are transported in the polycrystalline thin film. Secondly, the functionalized ionic liquid additives improved the interfacial contact quality between the perovskite layer and the charge transport layer, reducing the contact resistance. Compared to the metal-free anchoring group (D-Comp4, Rs = 15.89 ohm cm⁻¹), this resulted in a lower contact resistance. 2 The lower Rs in Example 1 confirms that the pre-anchored nucleation mechanism effectively improves the overall conductivity of the thin film by enhancing crystal continuity.

[0124] The correlation between an increase in the combined resistance (Rrec) and an increase in open-circuit voltage: The recombination resistance Rrec reflects the ease with which charge carriers undergo nonradiative recombination within a device; a higher Rrec value indicates a lower recombination rate. In Example 1, the Rrec reached 4625.3 ohms / cm. 2Compared to the blank group (1845.6 ohm cm) 2 It increased by about 2.5 times.

[0125] This difference explains why the open-circuit voltage (Voc) of Example 1 reached 1.172V in the JV test. The Rrec of D-Comp3 (mono-anion group) is 3120.4 ohm cm⁻¹. 2 Although superior to the blank group, it is still significantly lower than Example 1. This further verifies the synergistic passivation mechanism of the dual anion system of the present invention: acetate (Ac-) and thioacetamide (TAA) chemically modify defect energy levels at different depths, and the graded release achieved by the thermally induced eutectic process eliminates recombination centers at grain boundaries to the greatest extent, thereby significantly extending carrier lifetime and improving recombination resistance.

[0126] In summary, EIS impedance analysis confirms from an electrical perspective that the additive provided by this invention synergistically improves the photoelectric conversion efficiency of the device by reducing the series resistance and significantly increasing the composite resistance, which corroborates the aforementioned conclusions on crystal structure optimization and defect density reduction.

Claims

1. An ionic liquid additive for use in perovskite solar cells, characterized in that, The ionic liquid additive is made from raw materials comprising the following molar ratios: Component A1 is specifically 1-ethyl-3-methylimidazolium tetrafluoroborate; Component A2 is specifically 1-ethyl-3-methylimidazolium acetate; Component B is specifically thioacetamide; Component C, specifically lead iodide; The molar ratio of component A1 to component A2 is 8:1 to 12:1; The total molar amount of components A1 and A2 to the molar ratio of component B is 1:0.8 to 1:1.2; The amount of component C added is 0.2% to 0.5% of the total amount of substance in the current system.

2. The ionic liquid additive for perovskite solar cells according to claim 1, characterized in that, The water content of component A1 is ≤500ppm, and the water content of component A2 is ≤1000ppm.

3. The ionic liquid additive for perovskite solar cells according to claim 1, characterized in that, Component B is vacuum dried before use to remove adsorbed water.

4. The ionic liquid additive for perovskite solar cells according to claim 1, characterized in that, The ionic liquid additive is a single-phase transparent viscous liquid at room temperature, and its color is light yellow or amber.

5. A method for preparing ionic liquid additives for perovskite solar cells, characterized in that, The ionic liquid additive used in any one of claims 1-4 for perovskite solar cells comprises the following steps: S1. Mix component A1 and component A2 and homogenize them under heating and stirring conditions to obtain a colorless and transparent homogeneous liquid. S2. While maintaining stirring, add component B to the homogeneous liquid, raise the temperature to carry out a thermally induced reaction until the solid powder disappears and a single-phase fluid is formed; S3. While maintaining heating and stirring, add component C to the fluid and continue the reaction until the powder is completely dissolved. Stop heating and cool to room temperature to obtain the ionic liquid additive.

6. The method for preparing the ionic liquid additive for perovskite solar cells according to claim 5, characterized in that, The entire preparation process is carried out in a dry environment with a relative humidity of ≤20%.

7. The method for preparing the ionic liquid additive for perovskite solar cells according to claim 5, characterized in that, The specific process parameters for step S1 are as follows: The heating temperature is 40-50℃, the stirring speed is 400-500 rpm, and the stirring time is 15-20 minutes.

8. The method for preparing the ionic liquid additive for perovskite solar cells according to claim 5, characterized in that, The specific process parameters for step S2 are as follows: The thermally induced reaction temperature is 68–72℃, the stirring speed is 600–800 rpm, and the reaction time is 30–45 minutes.

9. The method for preparing the ionic liquid additive for perovskite solar cells according to claim 5, characterized in that, The specific process parameters for step S3 are as follows: The reaction temperature is maintained at 68–72℃, and the reaction time is 30–40 minutes.

10. The method for preparing the ionic liquid additive for perovskite solar cells according to claim 5, characterized in that, In step S2, component B is added slowly in powder form; In step S3, component C is added in powder form, and the reaction endpoint is determined by the absence of visible particulate matter.

Images