Perovskite solar cell based on imidazolyl ionic liquid additive and preparation method thereof

Abstract

The invention belongs to the technical field of perovskite solar cells, and discloses a perovskite solar cell based on an imidazolyl ionic liquid additive and a preparation method of the perovskite solar cell. The perovskite absorption layer comprises imidazolyl ionic liquid, the structural general formula of the imidazolyl ionic liquid is shown in the specification, R1 and R2 are independently H, C1-C18 alkyl, alkenyl or aryl, R3 is CHnY3-n, Y is at least one of H, F, Cl, Br and I, n is more than or equal to 0 and less than or equal to 3, and m is equal to 0 or 1. The ionic liquid is added to regulate and control the crystallization process of the perovskite layer, and the photoelectric efficiency and the stability are improved. Under the condition of no interface passivation, the power conversion efficiency of the MT and PIT improved perovskite solar device can reach 24.97% and 25.14%. At the room temperature of a nitrogen environment, the initial efficiency of a PIT improved device is far higher than that of a device without an additive, wherein the initial efficiency of the PIT improved device is 97% or above within 2000h.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, and in particular to perovskite solar cells. Background Technology

[0002] Over the past few decades, solar cells have been considered one of the most promising alternatives to traditional fossil fuels. Among various photovoltaic devices, perovskite solar cells (PSCs) have seen the fastest growth in power conversion efficiency (PCE) in recent years. The perovskite light-absorbing layer in a perovskite solar cell is the site of photoexciton separation, and the quality of the perovskite thin film significantly affects the photoelectric performance of the perovskite solar cell.

[0003] The soft ionic bonds and weak Coulomb interactions in the inverted organic-inorganic hybrid perovskite (PSC) lattice inevitably lead to a large number of defects in the perovskite film both within the bulk and at the interface during high-temperature annealing and rapid crystallization. This exacerbates nonradiative recombination and reduces the efficiency and stability of PSCs. To date, strategies such as solvent engineering, interface passivation engineering, and additive engineering have been proposed to improve the performance of PSCs.

[0004] Existing technologies for preparing perovskite precursor solutions exhibit poor wettability due to the influence of the hole transport layer, leading to uneven coverage and poor crystal quality during perovskite crystallization. Furthermore, the rapid crystallization rate results in small grains and numerous grain boundaries, making the perovskite more susceptible to humidity and oxygen, thus reducing device stability. While passivation layers mitigate defects, they also increase the complexity of the device fabrication process, as the perovskite dissolution and recrystallization process is somewhat uncontrollable. Introducing organic molecular additives into the perovskite precursor can achieve good coverage of the precursor solution on the FTO surface, while simultaneously enhancing the interaction between the precursor solution and molecules within the perovskite precursor, raising the nucleation energy barrier, releasing residual stress, and improving stability. However, most of these additive molecules are expensive and toxic; therefore, developing non-toxic, moderately priced materials that slow down crystallization and provide good passivation is crucial.

[0005] Imidazole-based ionic liquids can be used as additives in perovskite precursors. The introduction of imidazole-based ionic liquids, through coordination bonds and π-π interactions, slows the release of cations and anions during perovskite annealing, leading to an increase in the energy barrier for perovskite nucleation, increasing grain size, and thus effectively reducing defect formation. However, not all of these have positive effects. For example, the p-benzenesulfonic acid anion in 1-methylimidazolium p-toluenesulfonate is bulky and its embedding within the crystal lattice causes severe distortion, resulting in lattice aberrations, defects, and nonradiative recombination. Furthermore, its introduction unintentionally alters the Fermi level, valence band top, or conduction band bottom positions of the perovskite active layer, causing energy level mismatch at the interface. Existing technology CN117545336A discloses the application of imidazole-based ionic liquids, perovskite solar cells, and their fabrication methods. The disclosed ionic liquid additives are limited to halogen anions, such as chloride ions. However, their low electronegativity and small radius result in insufficient binding strength with Pb and organic cations in the perovskite precursor solution, failing to suppress the formation of corresponding defects. In summary, the limitations of ionic liquid additives in improving PSC performance include their single molecular design dimension and lack of multiple stabilization mechanisms. Summary of the Invention

[0006] To address the current limitations of ionic liquid additives in terms of insufficient anionic activity and limited passivation sites, which leads to decreased perovskite film quality and increased ion migration, resulting in reduced device efficiency and severely compromised long-term stability, this invention proposes a perovskite solar cell based on imidazole-based ionic liquid additives and its fabrication method.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] A perovskite absorber layer based on an imidazole-based ionic liquid additive includes a perovskite absorber layer material and an imidazole-based ionic liquid; wherein the general structural formula of the imidazole-based ionic liquid is as follows: Among them, R1 and R2 are independently H and C1-C, respectively. 18 Alkyl, alkenyl, or aryl, R3 is CH n Y 3-n Y is selected from at least one of H, F, Cl, Br, and I, 0≤n≤3, and m=0 or 1.

[0009] sulfonic acid group (–SO3) - It possesses strong electronegativity and proton donor capability, and can react with Pb. 2+ or Cs + When metal cations form coordination bonds, they effectively passivate iodine vacancies and Pb. 0Defects, etc.; the lone pair electrons of the imidazole cation can form weak hydrogen bonds or electrostatic shielding with the halide anion, inhibiting halide vacancies and ion migration; the two "one anion and one cation" form a dual-site passivation, which significantly reduces the non-radiative recombination loss of the film and improves Voc.

[0010] Furthermore, the aforementioned imidazole-based ionic liquid is a trifluoromethanesulfonate. The strong electron-withdrawing group in trifluoromethanesulfonate is sulfonic acid (-SO3). - ) and trifluoromethyl (-CF3) can bind to uncoordinated Pb on the perovskite surface 2+ Combination. By selectively adsorbing onto specific crystal planes (such as the (110) plane), the surface energy is reduced, inducing the perovskite to preferentially grow along the

[001] direction, thereby reducing the grain boundary density.

[0011] Furthermore, the aforementioned imidazole-based ionic liquid is one or more of 1-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, 1-octyl-3-methylimidazolium trifluoromethanesulfonate, 1-vinyl-3-methylimidazolium trifluoromethanesulfonate, and 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate.

[0012] More preferably, the imidazole-based ionic liquid is 1-methylimidazolium trifluoromethanesulfonate (MT) or 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate (PIT).

[0013] In both ionic liquids, the CF and sulfonic acid groups in the trifluorosulfonic acid anion effectively passivate deep-level defects of lead vacancies. The two cations, due to their different structures, also play different roles. The 1-methylimidazolium cation has a small structure and low steric hindrance, exhibiting a larger binding energy with the perovskite itself and existing iodine and lead vacancies. Compared to the phenylimidazolium cation, it can bind to defects more effectively, passivating them. The phenylimidazolium cation has a large structure and high steric hindrance, effectively slowing down the crystallization rate of the perovskite layer, increasing grain size while releasing residual stress in the perovskite film. The sulfonic acid group, CF bond, imidazolium, and phenyl group in the molecular structure effectively passivate iodine and lead vacancy defects, and compared to the 1-methylimidazolium cation, the energy levels are more matched. This constructs a stable and normal interfacial charge transport channel, resulting in higher device efficiency and nitrogen stability.

[0014] The crystal structure of the perovskite absorber layer material described above is of the ABX3 type, wherein A is at least one of an organic cation and / or a Group 1 metal cation, and B is Pb. 2+ Sn 2+ Bi 2+ 、Ge 2+ One or more of the following, where X is one or more of the halide ions.

[0015] Furthermore, the aforementioned organic cation is FA. + and MA + At least one of the following; a Group 1 metal cation such as Cs + wait.

[0016] Furthermore, the general structural formula of the above-mentioned perovskite absorber layer material is Cs. a MA b FA 1-a-b PbX3, where 0 ≤ a < 1, 0 ≤ b ≤ 1, and X is one or more halide ions. When X is two or more halide ions, the sum of the coefficients is 1.

[0017] Furthermore, the perovskite absorber layer material mentioned above is Cs. 0.05 MA 0.1 FA 0.85 PbI3, Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 PbI3 and (FA) 0.95 MA 0.05 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.05 Any one of the three.

[0018] The solid content of the imidazole-based ionic liquid in the perovskite absorber layer is 0.1-15 wt%, and the thickness of the perovskite absorber layer is 100-2000 nm.

[0019] More preferably, the solid content of the imidazole-based ionic liquid in the perovskite absorber layer is 1.5-2.5 wt%.

[0020] The above-described application of the perovskite absorber layer modified with imidazole-based ionic liquid additives in perovskite solar cells. The perovskite solar cell can be a single-junction or multi-junction perovskite solar cell; this invention does not impose specific limitations on the specific type of perovskite cell.

[0021] For example, a perovskite solar cell (single junction) based on imidazole-based ionic liquid additives according to the present invention includes a conductive substrate, a hole transport layer / electron transport layer, the perovskite absorber layer based on imidazole-based ionic liquid additives, the electron transport layer / hole transport layer and the top electrode layer stacked sequentially from bottom to top.

[0022] Furthermore, the aforementioned conductive substrate (transparent conductive substrate) is made of FTO glass, ITO glass, ITO / PET, ITO / PEN, or ITO / PI.

[0023] The hole transport layer is made of at least one of nickel oxide, SAM, PEDOT:PSS, PTAA, or CuSCN, and its thickness is 10-400 nm; the electron transport layer is made of SnO2, TiO2, Nb2O5, or PC. 61 At least one of BM or C60 layers, with the electron transport layer having a thickness of 10-500 nm.

[0024] Furthermore, the aforementioned SAM includes at least one of 2PACz, MeO-4PACz, and Me-4PACz.

[0025] Furthermore, the perovskite solar cell described above also includes an interface buffer layer located between the electron transport layer / hole transport layer and the top electrode layer, which is made of copper bath (BPC), tin oxide, zinc oxide, yttrium oxide, cerium oxide, titanium oxide or niobium oxide, with a thickness of 1-100 nm; the top electrode layer is made of any one of Cu, Ag, Au and C, with a thickness of 10-1200 nm.

[0026] The fabrication method of the above-mentioned perovskite solar cell includes the following steps:

[0027] (1) Hole transport layer / electron transport layer is prepared by spin coating on a conductive substrate;

[0028] (2) Disperse and dissolve the perovskite precursor and imidazole ionic liquid in an organic solvent to prepare a perovskite precursor solution; spin-coat the perovskite precursor solution onto the hole transport layer / electron transport layer prepared in step (1), and add antisolvent dropwise in the later stage of spin coating, and after annealing, obtain a perovskite absorption layer based on imidazole ionic liquid additive.

[0029] (3) The surface of the perovskite absorber layer prepared in step (2) is vapor-deposited to obtain an electron transport layer / hole transport layer, an interface buffer layer and a top electrode layer in sequence.

[0030] Furthermore, in step (2) above, the organic solvent is one or more of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL), N-methyl-2-pyrrolidone (NMP), and N,N'-dimethylacrylurea (DMPU); the antisolvent is one or more of anisole (AS), chlorobenzene (CB), toluene (TL), ethyl acetate (EA), and diethyl ether; the annealing temperature is 50-300℃, and the time is 3-30min.

[0031] For example, a multi-junction perovskite solar cell based on imidazole-based ionic liquid additives includes, from bottom to top, a conductive substrate, a hole transport layer / electron transport layer, a narrow bandgap active layer, an electron transport layer / hole transport layer, and a top electrode layer; or a hole transport layer / electron transport layer, a wide bandgap active layer, an electron transport layer / hole transport layer, and a top electrode layer.

[0032] Furthermore, at least one of the narrow bandgap active layer and the wide bandgap active layer is the perovskite absorber layer based on the imidazole-based ionic liquid additive of the present invention. The specific configuration depends on the material of the perovskite absorber layer and will not be specifically described in the present invention.

[0033] Specifically, when one of the narrow bandgap active layer and the wide bandgap active layer is the perovskite absorber layer based on imidazole-based ionic liquid additives of the present invention, the other layer can be any one of the perovskite absorber layer based on imidazole-based ionic liquid additives, monocrystalline silicon active layer, copper indium gallium selenide, and organic photovoltaic active layer of the present invention.

[0034] The beneficial effects of this invention are:

[0035] (1) This invention utilizes sulfonic acid groups and imidazole to achieve both defect passivation and crystallization regulation, effectively improving the efficiency of perovskite devices. Due to differences in molecular structure, the passivation and crystallization regulation effects vary. The strong electron-withdrawing group in trifluoromethanesulfonate: sulfonic acid (-SO3) - ) and trifluoromethyl (-CF3) can bind to uncoordinated Pb on the perovskite surface 2+ Combining. By selectively adsorbing onto specific crystal planes (such as the (110) plane), the surface energy is reduced, inducing preferential growth of perovskite along the

[001] direction, reducing grain boundary density, thereby improving crystal quality, reducing interface defects, reducing non-radiative recombination, and further improving device efficiency. The N lone pair electrons on the imidazole cation can form weak hydrogen bonds with halide anions, inhibiting the formation of halide vacancies and ion migration, reducing residual stress inside the lattice, and improving the stability of the perovskite layer.

[0036] (2) In the 1-methylimidazolium trifluoromethanesulfonate or 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate proposed in this invention, the CF group in the trifluorosulfonic acid anion and the sulfonic acid group effectively passivate the deep-level defects of lead vacancies. The two cations also play different roles due to their different structures. The methylimidazolium cation has a small structure and low steric hindrance, exhibiting a larger binding energy with the perovskite itself and existing iodine and lead vacancies. Compared with the phenylimidazolium cation, it can better bind to defects and passivate them. The phenylimidazolium cation has a large structure and high steric hindrance, effectively slowing down the crystallization rate of the perovskite layer, increasing the grain size while releasing residual stress in the perovskite film. The sulfonic acid group, CF bond, and imidazolium group in the molecular structure effectively passivate lead and iodine vacancies, and compared with the 1-methylimidazolium cation, it has better energy level matching. A stable and normal interfacial charge transport channel is constructed, resulting in higher device efficiency. Under conditions without interface passivation, the power conversion efficiencies of the MT and PIT-improved perovskite solar devices reached 24.97% and 25.14%, respectively. Simultaneously, stability tests were conducted on the perovskite devices at room temperature in a nitrogen atmosphere. The device in Comparative Example 1 had already degraded to 94% of its initial efficiency after 700 hours, the MT-improved device had degraded to 96% of its initial efficiency after 1600 hours, while the PIT-improved device still maintained an initial efficiency of over 97% after 2000 hours. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 The current density-voltage curve of the perovskite solar cell prepared in Example 1 is shown.

[0039] Figure 2 The current density-voltage curve of the perovskite solar cell prepared in Example 2 is shown.

[0040] Figure 3 The current density-voltage curve of the perovskite solar cell prepared in Example 3 is shown.

[0041] Figure 4 The current density-voltage curve of the perovskite solar cell prepared in Example 4 is shown.

[0042] Figure 5 The current density-voltage curve of the perovskite solar cell prepared in Example 5 is shown.

[0043] Figure 6 The current density-voltage curve of the perovskite solar cell prepared for Comparative Example 1 is shown.

[0044] Figure 7 The current density-voltage curve of the perovskite solar cell prepared for Comparative Example 2 is shown.

[0045] Figure 8 The current density-voltage curve of the perovskite solar cell prepared for Comparative Example 3 is shown.

[0046] Figure 9 The efficiency degradation diagrams of the perovskite solar cells prepared in Comparative Example 1 and Examples 1 and 2 under nitrogen atmosphere are shown. Detailed Implementation

[0047] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0048] Example 1

[0049] This embodiment of the perovskite solar cell based on an imidazole-based ionic liquid additive includes, from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer (635 nm thick) based on an imidazole-based ionic liquid additive, an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein, the imidazole-based ionic liquid is 1-methylimidazolium trifluoromethanesulfonate (MT), and the material of the perovskite absorber layer is Cs. 0.05 MA 0.1 FA 0.85 The solid content of 1-methylimidazolium trifluoromethanesulfonate in the PbI3 perovskite absorber layer is 1.5 wt%.

[0050] The fabrication method of the perovskite solar cell based on imidazole-based ionic liquid additives in this embodiment includes the following steps:

[0051] (1) Preparation of hole transport layer

[0052] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0053] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0054] (2) Preparation of perovskite absorber layer

[0055] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), cesium iodide (CsI), formamidinium iodide (FAI), and methylamine iodide (MAI) in a molar ratio of 10:0.5:8.5:1 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 900 μL, volume ratio 149:31) to prepare a mixed solution. Then, imidazole ionic liquid MT was added to the mixed solution to prepare the perovskite precursor solution. The concentration of lead iodide was 3.15 mol / mL, and the concentration of MT in the perovskite precursor solution was 1.5 mg / mL.

[0056] b. Spin-coat the above-mentioned perovskite precursor solution (100 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain a perovskite absorber layer containing an imidazole-based ionic liquid additive. The spin-coating process parameters are: 1000 rpm for 10 s, 5000 rpm for 35 s; and anisole, the antisolvent, is added dropwise 15 s before the end of the spin-coating process.

[0057] (3) Fabrication of electron transport layer and top electrode layer

[0058] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0059] Example 2

[0060] This embodiment of the perovskite solar cell based on an imidazole-based ionic liquid additive includes, from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer (665 nm thick) containing an imidazole-based ionic liquid additive, an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein the imidazole-based ionic liquid is 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate (PIT), and the material of the perovskite absorber layer is Cs. 0.05 MA 0.1 FA 0.85 The solid content of 1-phenyl-1H-imidazol-3-onium trifluoromethanesulfonate in the PbI3 perovskite absorber layer is 2.5 wt%.

[0061] The fabrication method of the perovskite solar cell based on imidazole-based ionic liquid additives in this embodiment includes the following steps:

[0062] (1) Preparation of hole transport layer

[0063] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0064] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0065] (2) Preparation of perovskite absorber layer

[0066] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), cesium iodide (CsI), formamidinium iodide (FAI), and methylamine iodide (MAI) in a molar ratio of 10:0.5:8.5:1 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 900 μL, volume ratio 149:31) to prepare a mixed solution. Then, the imidazole ionic liquid PIT was added to the mixed solution to prepare the perovskite precursor solution. The concentration of lead iodide was 3.15 mol / mL, and the concentration of PIT in the perovskite precursor solution was 2.5 mg / mL.

[0067] b. Spin-coat the above-mentioned perovskite precursor solution (100 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain a perovskite absorber layer containing an imidazole-based ionic liquid additive. The spin-coating process parameters are: 1000 rpm for 10 s, 5000 rpm for 35 s; and anisole, the antisolvent, is added dropwise 15 s before the end of the spin-coating process.

[0068] (3) Fabrication of electron transport layer and top electrode layer

[0069] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0070] Example 3

[0071] This embodiment of the perovskite solar cell based on an imidazole-based ionic liquid additive includes, from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer (665 nm thick) containing an imidazole-based ionic liquid additive, an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein the imidazole-based ionic liquid is 1-vinyl-3-methylimidazolium trifluoromethanesulfonate (VMIm), and the material of the perovskite absorber layer is Cs. 0.05 MA 0.1FA 0.85 The solid content of 1-vinyl-3-methylimidazolium trifluoromethanesulfonate in the PbI3 perovskite absorber layer is 2.5 wt%.

[0072] The fabrication method of the perovskite solar cell based on imidazole-based ionic liquid additives in this embodiment includes the following steps:

[0073] (1) Preparation of hole transport layer

[0074] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0075] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0076] (2) Preparation of perovskite absorber layer

[0077] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), cesium iodide (CsI), formamidinium iodide (FAI), and methylamine iodide (MAI) in a molar ratio of 10:0.5:8.5:1 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 900 μL, volume ratio 149:31) to prepare a mixed solution. Then, the imidazole ionic liquid PIT was added to the mixed solution to prepare the perovskite precursor solution. The concentration of lead iodide was 3.15 mol / mL, and the concentration of VMIm in the perovskite precursor solution was 2.5 mg / mL.

[0078] b. Spin-coat the above-mentioned perovskite precursor solution (100 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain a perovskite absorber layer containing an imidazole-based ionic liquid additive. The spin-coating process parameters are: 1000 rpm for 10 s, 5000 rpm for 35 s; and anisole, the antisolvent, is added dropwise 15 s before the end of the spin-coating process.

[0079] (3) Fabrication of electron transport layer and top electrode layer

[0080] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0081] Example 4

[0082] This embodiment of the perovskite solar cell based on an imidazole-based ionic liquid additive includes, from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer (665 nm thick) containing an imidazole-based ionic liquid additive, an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein the imidazole-based ionic liquid is 1-butyl-3-methylimidazolium trifluoromethanesulfonate, and the material of the perovskite absorber layer is Cs. 0.05 (FA 0.98 MA 0.02 ) 0.95 The solid content of 1-butyl-3-methylimidazolium trifluoromethanesulfonate in the PbI3 perovskite absorber layer is 2.5 wt%.

[0083] The fabrication method of the perovskite solar cell based on imidazole-based ionic liquid additives in this embodiment includes the following steps:

[0084] (1) Preparation of hole transport layer

[0085] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0086] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0087] (2) Preparation of perovskite absorber layer

[0088] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), cesium iodide (CsI), formamidinium iodide (FAI), and methylamine iodide (MAI) in a molar ratio of 1:0.05:0.931:0.019 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 1000 μL, volume ratio of DMF to DMSO 4:1) to prepare a mixed solution. Then, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, an imidazolium-based ionic liquid, was added to the mixed solution to prepare the perovskite precursor solution. The concentration of lead iodide was 0.75 mol / mL, and the concentration of 1-butyl-3-methylimidazolium trifluoromethanesulfonate in the perovskite precursor solution was 2.5 mg / mL.

[0089] b. Spin-coat the above-mentioned perovskite precursor solution (150 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain a perovskite absorber layer containing an imidazole-based ionic liquid additive. The spin-coating process parameters are: 2000 rpm for 25 s, 5000 rpm for 30 s; and add the anti-solvent chlorobenzene dropwise 10 s before the end of the spin-coating process.

[0090] (3) Fabrication of electron transport layer and top electrode layer

[0091] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0092] Example 5

[0093] This embodiment of the perovskite solar cell based on an imidazole-based ionic liquid additive includes, from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer (665 nm thick) containing an imidazole-based ionic liquid additive, an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein the imidazole-based ionic liquid is 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate (PIT), and the material of the perovskite absorber layer is (FA... 0.95 MA 0.05 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.05 )3. The solid content of 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate (PIT) in the perovskite absorber layer is 2.5 wt%.

[0094] The fabrication method of the perovskite solar cell based on imidazole-based ionic liquid additives in this embodiment includes the following steps:

[0095] (1) Preparation of hole transport layer

[0096] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0097] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0098] (2) Preparation of perovskite absorber layer

[0099] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), lead bromide (PbBr₂), formamidine iodide (FAI), cesium iodide (CsI), and methyl bromide (MABr) in a molar ratio of 1.423:0.077:1.32:0.09:0.08 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 1000 μL, volume ratio 4:1) to prepare a mixed solution. Then, imidazole-based ionic liquid 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate (PIT) was added to the mixed solution to prepare the perovskite precursor solution. The concentration of lead iodide was 0.75 mol / mL, and the concentration of 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate (PIT) in the perovskite precursor solution was 2.5 mg / mL.

[0100] b. Spin-coat the above-mentioned perovskite precursor solution (150 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain a perovskite absorber layer containing an imidazole-based ionic liquid additive. The spin-coating process parameters are: 1000 rpm for 10 s, 4000 rpm for 30 s; and add the anti-solvent chlorobenzene dropwise 10 s before the end of the spin-coating process.

[0101] (3) Fabrication of electron transport layer and top electrode layer

[0102] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0103] Comparative Example 1

[0104] This comparative perovskite solar cell includes, from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer (635 nm thick) without imidazole-based ionic liquid, an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein, the material of the perovskite absorber layer is Cs. 0.05 MA 0.1 FA 0.85 PbI3.

[0105] The fabrication method of the perovskite solar cell in this comparative example includes the following steps:

[0106] (1) Preparation of hole transport layer

[0107] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0108] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0109] (2) Preparation of perovskite absorber layer

[0110] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), cesium iodide (CsI), formamidinium iodide (FAI), and methylamine iodide (MAI) in a molar ratio of 10:0.5:8.5:1 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 900 μL, volume ratio 149:31) to prepare a mixed solution, i.e., the perovskite precursor solution. The concentration of lead iodide was 3.15 mol / mL.

[0111] b. Spin-coat the above-mentioned perovskite precursor solution (100 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain the perovskite absorber layer. The spin-coating process parameters are: 1000 r spin-coating for 10 s, 5000 r spin-coating for 35 s; and add the anti-solvent anisole dropwise 15 s before the end of the spin-coating process.

[0112] (3) Fabrication of electron transport layer and top electrode layer

[0113] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0114] Comparative Example 2

[0115] This comparative example of a perovskite solar cell based on 1-ethyl-3-methylimidazolium chloride additive includes, in order from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer (635 nm thick) containing an imidazolium-based ionic liquid additive, an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein, the imidazolium-based ionic liquid is 1-ethyl-3-methylimidazolium chloride ([EMIM]Cl), and the material of the perovskite layer is Cs. 0.05 MA 0.1 FA 0.85 The solid content of 1-ethyl-3-methylimidazolium chloride in the PbI3 perovskite layer is 2.5 wt%.

[0116] The preparation method of the perovskite solar cell based on 1-ethyl-3-methylimidazolium chloride additive in this comparative example includes the following steps:

[0117] (1) Preparation of hole transport layer

[0118] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0119] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0120] (2) Preparation of perovskite absorber layer

[0121] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), cesium iodide (CsI), formamidinium iodide (FAI), and methylamine iodide (MAI) in a molar ratio of 10:0.5:8.5:1 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 900 μL, volume ratio 149:31) to prepare a mixed solution. Then, the imidazole ionic liquid [EMIM]Cl was added to the mixed solution to prepare the perovskite precursor solution. The concentration of lead iodide was 3.15 mol / mL, and the concentration of [EMIM]Cl in the perovskite precursor solution was 2.5 mg / mL.

[0122] b. Spin-coat the above-mentioned perovskite precursor solution (100 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain a perovskite absorber layer containing an imidazole-based ionic liquid additive. The spin-coating process parameters are: 1000 rpm for 10 s, 5000 rpm for 35 s; and anisole, the antisolvent, is added dropwise 15 s before the end of the spin-coating process.

[0123] (3) Fabrication of electron transport layer and top electrode layer

[0124] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0125] Comparative Example 3

[0126] This comparative example of a perovskite solar cell based on 1-butyl-3-methylimidazolium thiocyanate additive includes, from bottom to top, a conductive substrate, a hole transport layer (20 nm thick), a perovskite absorber layer containing an imidazolium-based ionic liquid (635 nm thick), an electron transport layer (35 nm C60 layer), and a top electrode layer (100 nm); wherein the imidazolium-based ionic liquid is 1-butyl-3-methylimidazolium thiocyanate (BMIT), and the material of the perovskite absorber layer is Cs. 0.05 MA 0.1 FA 0.85 The solid content of 1-butyl-3-methylimidazolium thiocyanate in the PbI3 perovskite absorber layer is 2.5 wt%.

[0127] The preparation method of the perovskite solar cell based on 1-butyl-3-methylimidazolium thiocyanate additive in this comparative example includes the following steps:

[0128] (1) Preparation of hole transport layer

[0129] a. Preparation of SAM solution: Dissolve Me-4PACz in ethanol to obtain a Me-4PACz solution with a concentration of 0.5 mg / mL.

[0130] b. In a glove box, 35 μL of the prepared Me-4PACz solution was statically added to an FTO substrate, and a hole transport layer was prepared by spin coating. The spin coating parameters were 3000 rpm for 30 s.

[0131] (2) Preparation of perovskite absorber layer

[0132] a. Preparation of perovskite precursor solution: Lead iodide (PbI₂), cesium iodide (CsI), formamidinium iodide (FAI), and methylamine iodide (MAI) in a molar ratio of 10:0.5:8.5:1 were added to a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (total volume 900 μL, volume ratio 149:31) to prepare a mixed solution. Then, the imidazole ionic liquid BMIT was added to the mixed solution to prepare the perovskite precursor solution. The concentration of lead iodide was 3.15 mol / mL, and the concentration of BMIT in the perovskite precursor solution was 2.5 mg / mL.

[0133] b. Spin-coat the above-mentioned perovskite precursor solution (100 μL) onto the surface of the hole transport layer, and anneal at 120 °C for 10 min to obtain a perovskite absorber layer containing an imidazole-based ionic liquid additive. The spin-coating process parameters are: 1000 rpm for 10 s, 5000 rpm for 35 s; and anisole, the antisolvent, is added dropwise 15 s before the end of the spin-coating process.

[0134] (3) Fabrication of electron transport layer and top electrode layer

[0135] An electron transport layer and a top electrode layer were sequentially fabricated using a vapor deposition process. The electron transport layer was deposited on the surface of the perovskite absorber layer, first with a 35 nm C60 layer, followed by an 8 nm BCP layer (interface buffer layer). The top electrode layer was formed by vapor deposition of Ag on the surface of the electron transport layer, with a thickness of 100 nm.

[0136] Implementation Results Example

[0137] The performance of the perovskite solar cells prepared in Examples 1-5 and Comparative Examples 1-3 of this invention was tested. The specific testing process is as follows: The performance of the perovskite solar cells under one solar illumination (AM 1.5G, 100mW cm⁻¹) was measured using a Keithley 2400 source measurement device solar simulator. -2 The JV data curve is shown below, where the light source is a 100W xenon arc lamp. The results are as follows: Figure 1-8 As shown.

[0138] from Figure 1-8 As can be seen, the addition of MPT reduces the initial fill power of the perovskite device, thus decreasing efficiency. While the addition of BMIT lowers the open-circuit voltage, it effectively passivates defects and improves fill power, thereby increasing device efficiency. The addition of MT and PIT effectively increases the open-circuit voltage from 1.091 eV to 1.122 eV and 1.124 eV, respectively, and the fill power from 82.41% to 85.73% and 85.97%, respectively.

[0139] The perovskite solar cells prepared in Examples 1-5 and Comparative Examples 1-3 of this invention were tested for their open-circuit voltage, short-circuit current density, fill factor, and device efficiency. The data obtained are shown in Table 1.

[0140] Table 1

[0141] PCE / (%) <![CDATA[J SC / mA cm -2 ]]> <![CDATA[V OC / V]]> FF / (%) Comparative Example 1 23.05 25.60 1.091 82.41 Comparative Example 2 23.37 25.60 1.100 82.75 Comparative Example 3 23.67 26.10 1.075 84.21 Example 1 24.97 25.97 1.122 85.73 Example 2 25.14 25.89 1.124 85.97 Example 3 24.65 25.94 1.116 85.13 Example 4 24.86 26.18 1.120 84.76 Example 5 24.64 25.88 1.144 83.20

[0142] Table 1 shows that, based on the comparison between Examples 1-5 and Comparative Examples 1-3, the perovskite solar cells prepared by adding 1-methylimidazolium trifluoromethanesulfonate (MT) and 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate (PIT) to the perovskite precursor solution exhibit significantly improved cell performance.

[0143] In 1-methylimidazolium trifluoromethanesulfonate, the lone pair electrons of the 1-methylimidazolium cation passivate Pb. 2+Compared to the MT cation, the 1-phenyl-1H-imidazolium-3-onium cation exhibits superior conductivity, good planarity, and a tendency for self-aggregation within its benzene ring. The properties of the benzene ring further enhance the FF-boosting effect of PIT compared to MT. Furthermore, π electrons can coordinate with lead atoms in the perovskite lattice, and the large steric hindrance restricts the crystallization rate of the perovskite. Trifluoromethanesulfonic acid anions diffuse into the lower perovskite layer, passivating mismatched Pb with deep-level defects. 2+ This suppresses non-radiative recombination. The fluorine group binds to FA via hydrogen bonds. + The interaction enhances the phase stability of FAPbI3 perovskite. The addition of MT and PIT simultaneously optimizes the energy level structure between PSC layers, promoting charge transfer. Specifically, the addition of PIT results in a more matched energy level between perovskite film layers, thus exhibiting a higher Vt. OC Under conditions without interface passivation, the PCE of perovskite solar devices improved by MT and PIT can reach 24.97% and 25.14%, respectively, far exceeding the 23.05% of those without additives. The imidazole cation in [EMIM]Cl can passivate anionic defects and fix the migration of iodide ions, exhibiting a certain passivation effect. Its anionic structure is simple, with a small molecular size, which can fill migrating iodine vacancies. However, its passivation effect is not as good as PIT due to its overly simple structure. The BMIT cation, compared to methylimidazolium, has a larger volume, reducing grain boundary penetration and preventing it from reaching the defect core, thus limiting its anionic passivation ability and its potential for improvement.

[0144] The stability of perovskite solar cells was determined under nitrogen atmosphere at room temperature, and the results are as follows: Figure 9 As shown, the device of Comparative Example 1 has degraded to 94% of its initial efficiency after 700 hours, the device improved by MT has degraded to 96% of its initial efficiency after 1600 hours, while the device improved by PIT still has an initial efficiency of over 97% after 2000 hours.

[0145] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A perovskite absorber layer based on an imidazole-based ionic liquid additive, comprising a perovskite absorber layer material and an imidazole-based ionic liquid, characterized in that, The general structural formula of the imidazole-based ionic liquid is: Among them, R1 and R2 are independently H and C1-C, respectively. 18 Alkyl, alkenyl, or aryl, R3 is CH n Y 3-n Y is selected from at least one of H, F, Cl, Br, and I, 0≤n≤3, and m=0 or 1.

2. The perovskite absorber layer based on imidazole-based ionic liquid additives according to claim 1, characterized in that, The imidazole-based ionic liquid is one or more of 1-methylimidazolium trifluoromethanesulfonate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-hexyl-3-methylimidazolium trifluoromethanesulfonate, 1-octyl-3-methylimidazolium trifluoromethanesulfonate, 1-vinyl-3-methylimidazolium trifluoromethanesulfonate, and 1-phenyl-1H-imidazolium-3-onium trifluoromethanesulfonate.

3. The perovskite absorber layer based on imidazole-based ionic liquid additives according to claim 2, characterized in that, The perovskite absorber layer material has an ABX3 crystal structure, where A is at least one of an organic cation and / or a Group 1 metal cation, and B is Pb. 2+ Sn 2+ Bi 2+ 、Ge 2+ One or more of the following, where X is one or more of the halide ions.

4. The perovskite absorber layer based on imidazole-based ionic liquid additives according to claim 3, characterized in that, The organic cation is FA. + and MA + At least one of them.

5. The perovskite absorber layer based on imidazole-based ionic liquid additives according to any one of claims 1-4, characterized in that, The general structural formula of the perovskite absorber layer material is Cs. a MA b FA 1-a-b PbX3, where 0≤a<1, 0≤b≤1, and X is one or more of the halide ions.

6. The perovskite absorber layer based on imidazole-based ionic liquid additives according to claim 5, characterized in that, The solid content of the imidazole-based ionic liquid in the perovskite absorber layer is 0.1-15 wt%.

7. The application of the perovskite absorber layer based on imidazole-based ionic liquid additives as described in any one of claims 1-4 or 6 in perovskite solar cells.

8. A perovskite solar cell, characterized in that, It includes a conductive substrate, a hole transport layer / electron transport layer, a perovskite absorption layer based on imidazole-based ionic liquid additives as described in claim 1, an electron transport layer / hole transport layer, and a top electrode layer, which are stacked sequentially from bottom to top.

9. The perovskite solar cell according to claim 8, characterized in that, The perovskite solar cell further includes an interface buffer layer located between the electron transport layer / hole transport layer and the top electrode layer, which is made of copper oxide, tin oxide, zinc oxide, yttrium oxide, cerium oxide, titanium oxide, or niobium oxide; the material of the top electrode layer is any one of Cu, Ag, Au, and C.

10. The method for preparing the perovskite solar cell according to claim 9, characterized in that, The steps are as follows: (1) Hole transport layer / electron transport layer is prepared by spin coating on a conductive substrate; (2) Spin-coat a perovskite precursor solution containing imidazole-based ionic liquid additives onto the hole transport layer / electron transport layer prepared in step (1), and add antisolvent dropwise in the later stage of spin coating, and after annealing, obtain a perovskite absorber layer based on imidazole-based ionic liquid additives. (3) The surface of the perovskite absorber layer prepared in step (2) is vapor-deposited to obtain an electron transport layer / hole transport layer, an interface buffer layer and a top electrode layer in sequence.

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