3D / 2D perovskite solar cell

Abstract

The present invention relates to a 2D passivation layer having significant electronic and spatial effects on the performance of a 3D / 2D perovskite solar cell.

Description

Technical Field

[0001] The present invention relates to 2D passivation layers, which have significant electronic and steric effects on the performance of 3D / 2D perovskite solar cells. Background Art

[0002] The ever-increasing demand for energy is driving researchers to explore alternative, clean, and sustainable energy sources. Among renewable energy sources such as wind, tidal, solar, hydrothermal, and geothermal, solar energy holds the greatest potential due to its abundant reserves and ability to meet extremely high energy demands. To this end, photovoltaic (PV) solar cells were invented to convert sunlight into electricity.

[0003] In 1954, a breakthrough in solar cells was achieved when scientists at Bell Labs developed the world's first practical silicon solar cell with a 6% efficiency. This marked the beginning of the first generation of solar cells based on crystalline silicon. Subsequently, researchers continuously developed additional materials to produce low-cost solar cells, which gave rise to the second generation of solar cells. These cells were primarily based on III-V semiconductors, such as gallium arsenide and indium phosphide. Due to the scarcity and toxicity of these materials, the third generation of solar cells emerged, including dye-sensitized solar cells and organic photovoltaics (OPVs). Among these third-generation solar cells, perovskite solar cells (PSCs) have become the most promising due to their excellent photovoltaic performance, abundance, ease of processing, and low cost.

[0004] In 1839, Gustav Ross discovered a naturally occurring mineral, calcium titanate (CaTiO3). This mineral was named after the Russian mineralogist Lev Perovsky. A perovskite structure refers to any substance with the same crystal structure as CaTiO3. Typically, perovskites have an ABX3 structure, where "A" is a monovalent cation, "B" is a divalent cation, and "X" is an anion that combines with both. For perovskite solar cells, "A" is typically methylamine (MA, CH3NH 3+ ) or formamidine (FA, CH(NH2) 2+ ), "B" is usually lead (Pb 2+ ), "X" is usually a halide, such as iodine (I - ), bromine (Br - ) or chlorine (Cl - ).

[0005] Low-dimensional perovskites have attracted much attention due to their unique optoelectronic properties and excellent stability. Low-dimensional perovskites can be obtained by introducing long alkyl chain A-position spacer cations into three-dimensional (3D) perovskites. Since the spacer cations have a large ionic radius, their introduction results in a tolerance factor greater than 1. Low-dimensional perovskites are usually expressed using the formula (A') m An-1 B n X 3n+1 denoted by , where A' can be a divalent (m = 1) or monovalent (m = 2) cation. In this formula, n is the number of metal layers sandwiched between the organic layers, and band gap and quantum confinement can be manipulated by varying n. When n = 1, a pure two-dimensional (2D) layer is formed, while when n = ∞, a pure 3D perovskite layer is formed.

[0006] Perovskites offer numerous advantages. By varying the A, B, and X ions, they can form a wide variety of structures, resulting in a vast family of perovskites. This gives perovskites a remarkable property: their band gap can be tuned by varying the A, B, and X compounds. Due to their unique properties, such as a direct band gap, high absorption coefficient, low exciton binding energy, and large dielectric constant, perovskites are used in a variety of optoelectronic applications, including lasers, light-emitting diodes, transistors, and solar cells. Perovskite solar cells function similarly to solid-state pn junction solar cells. When a perovskite solar cell is exposed to light, the perovskite layer absorbs photons of a wavelength that matches its band gap. Upon photon absorption, electrons are excited into the perovskite's conduction band, leaving behind holes, or charge carriers, in the valence band. These electrons and holes are collected by an electron transport layer (ETL) and a hole transport layer (HTL), respectively. Free electrons travel from the perovskite layer into the ETL and then into a transparent conductive oxide (TCO), typically indium tin oxide (ITO) or fluorine-doped tin dioxide (FTO). At the same time, the holes move to the HTL and reach the metal electrode. Connecting the TCO to the metal electrode allows electrons to flow through an external circuit to generate photocurrent, ultimately causing the electrons and holes to recombine.

[0007] PSCs can be fabricated in either mesoporous or planar configurations. In a mesoporous structure, the perovskite material is attached to a mesoporous metal oxide scaffold layer. This scaffold facilitates the transport of photogenerated electrons to the extracellular layer (ETL). Mesoporous structures require high-temperature processing during fabrication. While mesoporous device structures were often used in early research, planar structures have attracted greater attention in recent years due to their simplicity. A typical planar device structure consists of a perovskite absorber layer, a TCO, and a metal electrode sandwiched between a high-transmitter layer (HTL) and an extracellular layer (ETL). Planar structures can have two different configurations. In the conventional (nip) planar structure, an n-type ETL is coated on top of the TCO, allowing light to reach the ETL first. In the inverted (pin) structure, a p-type high-transmitter layer (HTL) is coated on top of the TCO, allowing light to reach the HTL first. Device performance is closely related to the choice of transport layer. A transport layer with efficient charge extraction and good transport properties enables high-performance cells. A good transport layer must possess the following characteristics: a band alignment that matches the perovskite, high transmittance in the visible light region, high carrier mobility, high stability, ease of processing, and low cost. The ETL extracts photogenerated electrons from the perovskite and transfers them to the TCO or metal electrode while blocking hole transport. Furthermore, the ETL plays a role in surface modification and charge recombination mitigation in perovskite films. The ETL must have energy levels compatible with the perovskite to facilitate electron transport and enhance the built-in potential. The most commonly used ETLs are titanium dioxide (TiO2) and tin dioxide (SnO2) for nip structures, and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) for pin structures. In addition to these materials, fullerenes and their derivatives, metal oxides, organic small molecules, and polymers can also be used as ETLs. The electron extraction and transport properties of the ETL can be further improved through doping, passivation, and the use of additives or nanoparticles. The HTL transfers photogenerated holes from the perovskite to the metal electrode or TCO while blocking electron transport. This reduces charge recombination, thereby increasing contact selectivity and enhancing the open-circuit voltage. Furthermore, the HTL can act as a moisture barrier or metal ion diffusion barrier to suppress cell performance degradation. Moreover, HTL also helps to better cover the perovskite layer. The most commonly used HTL materials are 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD) and poly[bis(4-phenyl)-(2,5,6-trimethylphenyl)amine] (PTAA) for nip structures, and poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) for pin structures. In addition to these materials, small molecules, polymers, and inorganic molecules can also be used as HTL. Over the past decade, perovskite-based photovoltaic devices have had problems with cell instability caused by internal and external factors. In the process of scaling up from the cell level to the module level, reasonable strategies must be adopted to fundamentally eliminate the influence of these two factors.Utilizing a passivation layer is the simplest, most accessible, and most promising strategy for enhancing the crystallinity of the perovskite bulk phase and reducing interfacial losses through interface manipulation. Passivation engineering can achieve better band alignment, enhance carrier transport, reduce surface defects, and block external stimuli (such as heat, oxygen, and moisture). Furthermore, reducing interfacial losses can improve PSC efficiency, while suppressing performance degradation can enhance PSC stability. Furthermore, the advantage of passivation engineering lies in its simple spin-coating process, enabling its application to large-area PSCs for commercialization. Understanding the underlying principles of extrinsic degradation mechanisms and their interplay with intrinsic degradation factors is crucial, as these interactions are closely linked to the methodology for PSC performance. Well-known conventional approaches, such as placing UV filters and encapsulating constructed devices, appear to be able to protect PSCs from external environmental factors. For example, while illumination is known to be the primary trigger for photovoltaic device operation, it can also cause perovskite molecular decomposition and, by creating carrier recombination centers, degrade the performance of perovskite-based solar devices. Therefore, finding permanent solutions to these internal cell issues should be a primary focus for researchers, as these external factors can also trigger intrinsic degradation in PSCs. The intrinsic instability is mainly caused by deep-level defect states, for example, due to Pb-I bonds and Pb. 2+ Due to the soft properties of ions, the lead (Pb) element at the B site in PSC will degrade under light and high temperature, resulting in Pb 2+ The ions are reduced to Pb atoms and generate deep energy level defect states, which have a negative impact on the interface connection and the transport of photogenerated carriers.

[0008] To address these issues, the addition of a protective passivation layer (also known as an interfacial layer) between the TCO / CTL (where CTL refers to ETL or HTL), CTL / perovskite interface, or CTL / metal electrode interface in PSCs is the most widely used and effective strategy. Passivation engineering is mainly used to reduce interfacial defects that stimulate perovskite degradation. Passivation engineering can reduce non-radiative recombination by passivating surface defects in charge transport materials and perovskite materials, improve charge carrier transport through band alignment, and improve cell stability due to the hydrophobicity of the protective interfacial materials used in PSCs. To this end, researchers have tried a variety of commercial and novel organic (fullerene-based and non-fullerene-based) and polymer passivators and introduced them into PSCs to compare the device performance of PSCs with and without passivation layers. Based on the long-term stability results obtained, adding a protective passivation layer between the charge transport layer and the perovskite light absorption layer remains the best strategy.

[0009] Defects within the battery and defects caused by corrosion due to long-term contact with metals are also not conducive to the long-term stability of the battery. Currently, a variety of methods have been proven to solve these problems, among which 2D perovskite is considered to be one of the most promising materials due to its higher stability than its 3D counterpart.

[0010] Phenethylammonium iodide (PEAI) and butylammonium iodide (BAI) are widely reported as 2D cations in the literature, although many other 2D cations also exist. In recent studies, halogenated PEAI salts have been used for passivation on top of 3D perovskites to form pure 2D Ruddlesden-Popper (RP) layered perovskites or interfacial protective layers. In the prior art, 2D layers formed by 2-(o-fluorophenyl)ethylammonium iodide (oFPEAI), 2-(m-fluorophenyl)ethylammonium iodide (mFPEAI) and 2-(p-fluorophenyl)ethylammonium iodide (pFPEAI) were introduced on top of their 3D perovskites and reported to have a power conversion efficiency (PCE) exceeding 20% ​​under 1440h of continuous illumination with improved stability.

[0011] Attached photos

[0012] Figure 1 :(a) Schematic diagram of molecular structure, (b) table of possible molecules.

[0013] Figure 2 : Schematic diagram of ion substitutes.

[0014] Figure 3 : Monosubstituted phenethylammonium salt.

[0015] Figure 4 : Disubstituted phenethylammonium salt.

[0016] Figure 5 : Trisubstituted phenethylammonium salt.

[0017] Figure 6 : Tetrasubstituted phenethylammonium salt.

[0018] Figure 7 : Pentasubstituted phenethylammonium salts, wherein R is not hydrogen.

[0019] Figure 8 :

[0020] A. Schematic diagram of solar cell structure.

[0021] Schematic diagram of the structures of Bo-OMe-PEAI, m-OMe-PEAI and p-OMe-PEAI.

[0022] C. X-ray diffraction (XRD) patterns of the control (ref.) 3D perovskite and the perovskites treated with methoxy-substituted salts (o-OMe-PEAI, m-OMe-PEAI, and p-OMe-PEAI). Peaks 002, 040, and 001 represent the diffraction peaks of 2D (n=1), quasi-2D (n=2), and PbI2 (001), respectively.

[0023] D. Grazing-incidence wide-angle X-ray scattering (GIWAXS) image of 3D perovskite.

[0024] E. GIWAXS image of 3D / 2D perovskite film.

[0025] Figure 9 : XRD spectra of pure 2D films (n=1) of o-OMe-PEAI, m-OMe-PEAI and p-OMe-PEAI.

[0026] Figure 10 .XRD spectrum of o-OMe-PEAI quasi-2D film (n=2).

[0027] Figure 11 .GIWAXS spectra of pure 2D films (n=1) of o-OMe-PEAI, m-OMe-PEAI and p-OMe-PEAI.

[0028] Figure 12 : Thin film characterization;

[0029] AD. Scanning electron microscopy (SEM) top view and cross-sectional images of 3D films (A) and 3D / 2D films containing o-OMe-PEAI (B), m-OMe-PEAI (C), and p-OMe-PEAI (D).

[0030] E. Steady-state photoluminescence (PL) spectra.

[0031] F. Time-resolved PL (TRPL) trajectories.

[0032] G. Absorption spectra of 3D films and 3D films treated with OMe-PEAI.

[0033] Figure 13 : PL spectra of pure 2D films (n=1) of o-OMe-PEAI, m-OMe-PEAI, and p-OMe-PEAI.

[0034] Figure 14 .Device parameters and molecular dynamics;

[0035] AD. (A) Open-circuit voltage (VOC), (B) short-circuit current (JSC), (C) fill factor (FF), and (D) PCE statistics for the control sample (3D) and 3D / 2D solar cells (five devices total). Boxplot details: The bottom and top edges of the boxplot represent the 25th and 75th percentiles, respectively. The center horizontal line of the boxplot represents the median, with the whiskers extending to the extreme data points. The mean is represented by the open symbol.

[0036] E. Current density-voltage (JV) curves of the best control sample and 3D / 2D solar cells.

[0037] F. External quantum efficiency (EQE) spectra of the best control sample and 3D / 2D solar cells.

[0038] Figure 15 .ad) Statistics of the control sample and 3D / 2D films; e) JV curves of the original device and the halogenated PEAI-treated device simulated under single-sun illumination; f) EQE spectra and calculated photocurrent values.

[0039] Figure 16 a) Steady-state photoluminescence spectra, (b) time-resolved PL traces, and (c) transmission spectra of the control sample and the meta-halide PEAI salt-treated 3D perovskite films. Summary of the Invention

[0040] The formation of 2D perovskites is due to the presence of large ammonium salts whose sizes exceed the tolerance factor of the inorganic lattice, preventing the continuity of the 3D framework and resulting in the formation of well-defined 2D fragments. Despite the excellent stability of 2D perovskites, their high exciton binding energy, poor charge separation characteristics and large band gap have been shown to be detrimental to device performance in terms of efficiency. Studies have been conducted to modify 3D perovskites with their 2D counterparts (3D / 2D) to improve stability without compromising efficiency. Various organic ammonium salts have been used to produce efficient 3D / 2D solar cells, but research has mainly focused on halogenated analogs of PEAI salts. The influence of functional group position on the aromatic groups of PEAI-based salts has also been studied.

[0041] Strong electron-releasing group substitutions are widely used in the design of hole transport materials due to their ability to stabilize holes and passivate defects through uncoordinated lone pairs of electrons. Considering these advantages, electron-donating groups are also preferred in the design of large organic ammonium salts of 2D / 3D perovskites because they have the potential to enhance hole extraction and to bind to uncoordinated Pb on the surface of 3D perovskites. 2+ions form favorable interaction sites. To date, methoxyl (OMe)-substituted organic ammonium salts have not been used in 3D / 2D perovskite solar cells. The influence of the -OMe substitution position (ortho, meta, and para) on 2D PEAI salts and their impact on the performance and long-term stability of 3D / 2D PSCs has not been studied in the prior art.

[0042] Figure 1-7 Possible, but not limiting, alternatives to ammonium salts for the growth of 2D perovskite layers are presented.

[0043] R is a halogen, an aromatic group, an alkoxy group, an alkyl group, a thiol group, an amino group or hydrogen, but cannot be all hydrogen;

[0044] X is iodide, bromide or chloride, acetate, triflate, nitrate, alkyl sulfate, alkyl phosphate, amino acid, tetracyanoborate, dicyanamide, tricyanomethane, carboxylate, hexafluorophosphate, tetrafluoroborate, tetrafluoromethylacetate, bis(trifluoromethanesulfonyl)imide;

[0045] The present invention uses a simple and direct synthesis method to synthesize three methoxy-substituted organic ammonium salts, namely 2-methoxy-PEAI (o-OMe-PEAI), 3-methoxy-PEAI (m-OMe-PEAI), and 4-methoxy-PEAI (p-OMe-PEAI), and uses them together with the (Cs0.04FA0.85MA0.11)Pb(I0.96Br0.01Cl0.03)3 trication perovskite in 3D / 2D PSCs. The present invention clarifies the influence of the position of the methoxy-substituted ammonium salt on the device performance and stability of the 3D / 2D PSC. X-ray diffraction (XRD) and grazing-incidence wide-angle X-ray scattering (GIWAXS) results show that the 2D layer formed on the 3D perovskite is independent of the -OMe position. Photoluminescence (PL) and time-resolved PL (TRPL) analysis show that the film treated with the methoxy-substituted salt significantly reduces the trap density and prolongs the carrier lifetime. All salt treatments significantly improved PCE, with o-OMe-PEAI showing the strongest performance (21.35%-23.34%). Drift-diffusion simulations explained the improvements in fill factor (FF) and open-circuit voltage (VOC) after salt treatment. Density functional theory (DFT) analysis revealed that films treated with o-OMe-PEAI exhibited the lowest formation energy, forming an ultrastable interface, thereby enhancing device performance and long-term stability.

[0046] In another embodiment of the present invention, a group of halogenated PEA+ cations (x-XPEA+, where x: ortho (o), meta (m), para (p), X: F, Cl, Br) were synthesized by a robust and facile method and deposited on top of 3D perovskites. Regardless of the nature and position of the halogen, XRD and GIWAXS analysis of all cations confirmed the formation of a 2D perovskite layer. DFT analysis showed that the meta-substituted cations have lower formation energy and higher interfacial dipole moment compared to their ortho and para counterparts, which is responsible for their enhanced performance. The device treated with m-BrPEAI exhibited the highest efficiency of 23.42%, a VOC of 1.13 V, and a FF of 81.2%. This comprehensive study provides guidance for understanding the phenomena behind the interaction of large cations with 3D perovskites and their impact on performance and stability. DETAILED DESCRIPTION

[0047] OMe-PEAI two-dimensional passivation layer

[0048] Device structure:

[0049] The structure of the solar cell is FTO / cp-TiO2 / mp-TiO2 / SnO2 / perovskite / OMe-PEAI / Spiro-OMeTAD / Au, e.g. Figure 8 shown.

[0050] A 3D trication perovskite absorber layer was used, and an isopropyl alcohol (IPA) solution of methoxy-substituted salt was coated on its surface by spin coating to form a 3D / 2D perovskite structure.

[0051] FTO glass substrates (Nippon Sheet Glass, TEC9AX) were cleaned with Hellmanex, deionized water, acetone, and IPA for 15 minutes, respectively. The substrates were then treated with UV-ozone for 15 minutes. A TiO2 solution was prepared by diluting a bis(acetylacetonato)diisopropoxytitanium solution with IPA in a volume ratio of 1:15. A dense layer (c-TiO2) was deposited on the FTO substrate by spray pyrolysis at 450°C and then annealed in situ for 30 minutes. A mesoporous TiO2 (m-TiO2) solution was prepared by dissolving 1 g of TiO2 slurry in 10.5 mL of ethanol and stirring overnight. The m-TiO2 layer was then deposited at 4,500 rpm for 20 seconds. After annealing at 125°C for 30 minutes, the m-TiO2 film was gradually heated to 500°C in air and then annealed at 500°C for 20 minutes. The SnO2 layer was prepared by spin-coating a 0.1M SnCl4 solution at 3,000 rpm for 20 seconds. The substrate was then annealed at 150°C for 10 minutes and 190°C for 1 hour. Before use, the FTO / c-TiO2 / m-TiO2 / SnO2 substrate was treated with UV-ozone for 30 minutes.

[0052] A precursor solution was prepared by dissolving PbI2 (1.35 M), CsI (0.05 M), FAI (1.12 M), MABr (0.05 M), and MACl (0.10 M) in a 4:1 (volume ratio) DMF:DMSO mixture. 25 mL of the perovskite precursor was then spin-coated onto an FTO / c-TiO2 / m-TiO2 / SnO2 substrate (approximately 1.4 cm wide × 3 cm high × 2.4 cm long). The coating process was performed in a two-step procedure, running at 1,000 rpm for 12 seconds and 4,000 rpm for 25 seconds. In the second step (11 seconds), 750 mL of chlorobenzene was rapidly injected onto the substrate as an antisolvent. The film was then annealed at 100°C for 45 minutes. After cooling to room temperature, a 10 mg / mL solution of x-OMe-PEAI in IPA was spin-coated onto the substrate at 4,000 rpm for 15 seconds. Next, a HTM solution was prepared by mixing a chlorobenzene stock solution of spiro-OMeTAD with an acetonitrile solution of 4-tert-butylpyridine, lithium bistrifluoromethanesulfonimide (Li[TFSI]), and Co[t-BuPyPz]3[TFSI]3 (FK209, Dyesol) at a molar ratio of spiro-OMeTAD:FK209:Li[TFSI]:4-tert-butylpyridine (TBP) = 1:0.03:0.5:3.3. 40 mL of the spiro-OMeTAD solution was deposited onto the perovskite film at 3,500 rpm for 20 seconds to serve as a hole transport layer. Finally, a 70 nm thick gold layer was evaporated as the counter electrode to complete the device fabrication.

[0053] Compound synthesis

[0054]

[0055] Scheme 1. Synthesis of o-OMe-PEAI, m-OMe-PEAI, and p-OMe-PEAI. Phenethylammonium substituted with ortho, meta, and para methoxy groups (o-OMe-PEA, m-OMe-PEA, and p-OMe-PEA) were successfully synthesized. The resulting material (7.2 mmol) was dissolved in ethanol (7 mL), and the reaction was cooled to 0°C. HI (7.9 mmol, 57 wt.% aqueous solution) was slowly added, and the reaction mixture was stirred at this temperature for 2 h. The reaction mixture was concentrated under reduced pressure, and cold ether (50 mL) was added to precipitate the product. The crude product was dissolved in a small amount of ethanol and precipitated with cold ether to obtain the target salt with high purity.

[0056] 2-(2-Methoxyphenyl)ethyl-1-ammonium iodide (o-OMe-PEAI), yield 63%. White solid. 1H NMR (400 MHz, DMSO): δ 7.75 (s, 3H), 7.30-7.11 (m, 2H), 7.03-6.84 (m, 2H), 3.80 (m, 3H), 3.03-2.91 (m, 2H), 2.86-2.81 (m, 2H); 13C NMR (100 MHz, DMSO): δ 157.6, 130.6, 128.8, 125.3, 120.9, 111.3, 55.9, 28.5.

[0057] 2-(3-Methoxyphenyl)ethyl-1-ammonium iodide (m-OMe-PEAI), yield 65%. White solid. 1H NMR (400 MHz, DMSO): δ 7.76 (s, 3H), 7.25 (t, J = 8.0 Hz, 1H), 6.82 (d, J = 7.5 Hz, 3H), 3.74 (s, 3H), 3.07 (d, J = 7.1 Hz, 2H), 2.84-2.79 (m, 2H); 13C NMR (100 MHz, DMSO): δ 159.4, 138.7, 129.7, 120.8, 114.3, 112.2.

[0058] 2-(4-Methoxyphenyl)ethyl-1-ammonium iodide (p-OMe-PEAI), yield 32%. White solid. 1H NMR (400 MHz, DMSO): δ 7.74 (s, 3H), 7.17 (d, J = 8.5 Hz, 2H), 6.89 (d, J = 8.6 Hz, 2H), 3.72 (s, 3H), 3.05-2.95 (m, 2H), 2.84-2.68 (m, 2H); 13C NMR (100 MHz, DMSO): δ 158.1, 129.7, 128.9, 114.0, 55.1, 32.1.

[0059] Preparation of 2D perovskite films

[0060] To prepare pure 2D films, x-OMe-PEAI salt was mixed with PbI2 in a 2:1 molar ratio and dissolved in a DMF:DMSO mixture (4:1 volume ratio). For quasi-2D perovskite films, o-OMe-PEAI (2M), MAI (1M), and PbI2 (2M) were mixed and dissolved in a 4:1 volume ratio of DMF:DMSO. All ETLs were then coated on the substrate at speeds of 1,000 and 4,000 rpm for coating times of 12 and 25 seconds, respectively. The films were annealed at 100°C for 45 minutes.

[0061] Crystallographic characteristics

[0062] XRD spectra show that all the peaks of 3D / 2D films are below 10°, which is attributed to the formation of a low-dimensional top perovskite layer. For the salt-treated 3D perovskite, peaks at 2θ = 4.92°, 4.97°, and 4.90° are observed ( Figure 8 C) are consistent with the peaks of pure (OMe-PEAI)2PbI4 2D perovskite (n=1) (4.97°, 4.91° and 4.94°), but with a slight (<0.06°) shift ( Figure 9 ). In addition, a significant decrease in the PbI2 peak intensity (2θ = 12.7°) was observed for the films treated with OMe-PEAI, indicating that the organic ammonium salt interacts with the excess PbI2 on the 3D perovskite surface, providing further strong evidence for the formation of a 2D layer. The additional peak observed for o-OMe-PEAI at 2θ = 7.55° ((040) orientation) originates from the quasi-2D perovskite structure with n = 2 ( Figure 10 ).

[0063] Since the crystal orientation can affect the optoelectronic performance and overall stability of the device, GIWAXS measurements were performed at an incident angle of 0.2° to reveal the crystal orientation of the perovskite component. The strong scattering rings at the 3D perovskite belong to the (110) oriented crystal plane and the (001) oriented PbI2 crystal plane ( Figure 8 D) After the o-OMe-PEAI salt is inserted into the 3D perovskite, the scattering ring of PbI2 gradually decreases. A new spot appears ( Figure 8 E). Pure two-dimensional o-OMe-PEAI film ((OMe-PEAI)2PbI4) in q z =0.3 and There are also strong spots nearby, which confirms the formation of a 2D layer ( Figure 11 ).

[0064] Film properties

[0065] like Figure 12 The top view scanning electron microscopy (SEM) image of A-12D shows that the surface morphology of the film changes after being treated with -OMe salt. Figure 12 A) has a higher contrast, and bright grain sites are observed, indicating the presence of excess PbI2 on the surface. In contrast, the perovskite film treated with methoxy-substituted salts has fewer bright grains on the surface, indicating that the OMe-PEAI salt reacts with the excess PbI2 on the 3D perovskite surface. It should be noted that since the 2D layer is very thin, it cannot be distinguished in the cross-sectional SEM ( Figure 12B-12D). All 3D / 2D perovskites exhibit higher PL intensities compared to the 3D control film ( Figure 12 E) and longer PL decay time ( Figure 12 F; Table 1), which indicates that the OMe-PEAI salt suppresses non-radiative recombination and reduces the defect density in the perovskite layer and / or grain boundaries.

[0066] Table 1: Fitting parameters of TRPL spectra of control and OMe-PEAI treated membranes. A1 and A2 are the fractions of the two decay processes, and T1 and T2 are the shorter and longer lifetimes, respectively.

[0067]

[0068] It is particularly noteworthy that the PL intensity and lifetime of the film treated with o-OMe-PEAI salt increased significantly, which means that the ortho-salt has a better passivation effect than the ammonium salts substituted with meta- and para-methoxy groups. Due to the low salt concentration in the solution, no PL signal was detected at a shorter wavelength for the corresponding high-bandgap two-dimensional perovskite, resulting in a very thin two-dimensional perovskite layer. The absorption spectrum shows that the absorption of the 3D / 2D film does not change significantly compared with the 3D film, indicating that the 2D material is not incorporated into the 3D perovskite body, which is consistent with the results of XRD and GIWAXS analysis. The spectrum of the pure 2D film is shown in Figure 2. Figure 13 shown.

[0069] Photovoltaic performance and DFT calculations

[0070] The VOC and FF of the 3D films treated with OMe-PEAI salt were significantly improved ( Figure 14 A and 14C), which is consistent with the results of steady-state PL and TRPL studies, respectively, indicating excellent charge transport properties. In addition, a slight increase in short-circuit current (JSC) was also observed in 3D / 2D solar cells ( Figure 14 B). The average efficiencies of control, o-OMe-PEAI, m-OMe-PEAI, and p-OMe-PEA IPSCs were 20.86%, 23.08%, 21.79%, and 22.25%, respectively ( Figure 14 D). All device parameters of all solar cells fabricated in this study showed limited deviations, demonstrating the reproducibility of the device fabrication process (Table 2).

[0071] Table 2: V of control sample (3D) and 3D / 2D solar cells oc 、J sc , FF and PCE statistics

[0072]

[0073] The highest PCEs of 3D perovskite PSCs treated with o-OMe-PEAI, m-OMe-PEAI, and p-OMe-PEAI were 23.34%, 22.25%, and 22.62%, respectively, while the highest PCE of the control sample was 21.35%. Figure 14 E) All 3D / 2D PSCs treated with methoxy-substituted salts exhibit lower hysteresis than the control solar cells, indicating that the migration and accumulation of ions are suppressed by passivating the defects on the perovskite surface. Figure 14 As shown in Figures E and 14F, the JSC values ​​obtained from the current-voltage (JV) curves and external quantum efficiency (EQE) spectra are in good agreement.

[0074] Finally, DFT calculations confirmed that o-OMe-PEA has the highest iodine vacancy formation energy among the three tested interfaces, which is consistent with the hypothesis of a reduced trap state concentration (Table 3). The order of iodine vacancy formation energy correlates with device performance, supporting the above hypothesis.

[0075] Table 3. Formation energies of neutral iodine vacancies at various interfaces.

[0076] interface <![CDATA[Δ f TO vac I,eV]]> o-OMe-PEAI 3.83 m-OMe-PEAI 3.03 p-OMe-PEAI 3.41

[0077] The ionization energies of the control sample and the 3D / 2D film were extracted using ultraviolet photoelectron spectroscopy (UPS), and the ionization energies of the control sample, o-OMe-PEAI, m-OMe-PEAI, and p-OMe-PEAI were -5.49, -6.03, -6.19, and -6.03 eV, respectively. The highest occupied molecular orbital (HOMO) energy level of the 3D / 2D film was lower than that of the control sample, which improved the performance of the solar cell despite the greater mismatch with the transport layer. These observations may be explained in two ways: (1) the lower energy level means that the n-type characteristics are weakened after salt treatment and band bending occurs, thereby improving the charge transport performance; and / or (2) holes tunnel through the 2D layer to reach the hole transport layer, which is confirmed by the increase in VOC and FF. The study shows that inserting a very thin uniform insulating layer into the PSC can improve the device performance by extending the carrier lifetime and increasing FF.

[0078] Two-dimensional passivation layer of x-RPEAI salt

[0079] The second group of compounds of the present invention is a series of large sterically hindered organic cations based on the phenylethylammonium (PEA) skeleton, which have three different halogens (-F, -Cl and -Br) on the aromatic benzene ring of the corresponding x-RPEAI salts, located at the ortho (-o), meta (-m) and para (-p) positions, respectively.

[0080] A large number of studies on PEAI-type salts have been conducted in the existing literature, exploring the influence of substituents or their positions on the PSC performance. However, detailed systematic analysis is still needed, and efforts are needed to fundamentally understand the influence of the nature and position of the substituents of 2D-forming salts on the performance of 3D / 2DPSCs. A simple and direct method was used to synthesize phenylethylammonium (PEA) skeletons, in which three different halogens (-F, -Cl and -Br) were located at the ortho (-o), meta (-m) and para (-p) positions of the aromatic benzene ring of the corresponding x-RPEAI salts, and they were used as 2D perovskite layers on the surface of CsFAMA-based 3D trication perovskite. X-ray diffraction (XRD) and grazing-incidence wide-angle X-ray scattering (GIWAXS) analysis confirmed that all nine salts formed 2D layers. In addition, by studying photoluminescence (PL) and time-resolved photoluminescence (TRPL) spectroscopy techniques, it was found that the 2D perovskite layer based on m-XPEA2PbI4 deposited on the 3D perovskite was more effective in suppressing non-radiative carrier recombination than the control sample and its -ortho and -para analogs. Among these nine different 2D perovskites, m-XPEA2PbI4 has a stronger interface dipole effect and lower formation energy on the 3D perovskite surface, which has been confirmed by detailed DFT analysis. Combining experimental and theoretical studies, the halogen substituents on the meta-phenyl ring of the 2D PEAI salt were studied, and higher V oc (1.13V) and FF (over 81%), thereby achieving an energy conversion efficiency of over 23%.

[0081] The developed robust and facile method was used to synthesize ortho-, meta-, and para-halogenated phenylethylammonium cations (x-XPEA) in high yield. + ), (average yield over 85%). To the best of our knowledge, this is the first time that such a simple and direct three-step synthetic scheme has been used to prepare bulky organic cations using widely available aromatic aldehyde derivatives as starting materials. Three different bulky organic cations (o-ClPEA + 、m-ClPEA + and m-BrPEA + ) has not been tested in PSCs and can be prepared by the simple and direct method described above. All device architectures are based on (Cs 0.04 FA 0.85 MA 0.11 )Pb(I 0.96 Br 0.01 Cl 0.03 )3) and deposited the triple-cation 3D perovskite composite material by conventional spin coating. The synthesized x-RPEAI salt was coated on the 3D perovskite, and a 3D / 2D hybrid structure was constructed using the same method.

[0082] Synthesis of ortho-, meta-, and para-halogenated nitrovinylbenzene (x-RNVB, where x: o, m, p, R: F, Cl, Br) skeletons

[0083] The systematic synthesis of the target o-, m-, and p-halonitrovinylbenzene scaffolds (x-RB-CH=CH-NO2 or x-RNVB, where x: o, m, p, and X: F, Cl, Br) was performed by Henry reaction, starting from their technical-grade benzaldehyde form (x-RB-CH=O or x-RBA), according to the literature with slight modifications. Empty, dry reaction flasks of appropriate size were evacuated and filled with an inert gas (i.e., argon (Ar) or nitrogen (N2)) three times. Ammonium acetate (NH4OAc, 2.0 eq.) was then added to these reaction flasks and dissolved in acetic acid (AcOH, 10 eq.). Nitromethane (CH3NO2, 5.0 eq.), dried over molecular sieves for several days, was then transferred to the resulting solution. x-RBA (1.0 eq.) was added dropwise to these solutions. The reaction mixture was stirred at 90°C under an inert atmosphere in the dark. The reaction progress of each experiment was monitored using thin layer chromatography (TLC) technology. Generally, 3 hours was sufficient for the starting material (x-RBA) to disappear and a very wide dominant spot to appear, which belonged to the target nitroaldol condensation product (x-RNVB). After the reaction was completed, AcOH and CH3NO2 in the reaction mixture were evaporated under reduced pressure, and then water was poured into the remaining residue. The resulting suspension was extracted three times with dichloromethane (DCM or CH2Cl2). The combined organic phases were dried over anhydrous sodium sulfate (Na2SO4), filtered through filter paper, and then evaporated under reduced pressure. The residual mixture was purified by silica gel column chromatography using a suitable solvent system. The purified halogenated nitroaldol skeleton (x-RNVB) was collected in a glass vial and vacuum dried at room temperature for at least 30 minutes. The isolated target x-RNVB materials were obtained in different colors and stored in vials filled with argon or nitrogen for use in the next step.

[0084] o-Fluoronitrovinylbenzene (o-FNVB). Yield 89%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ8.06 (d, J=13.8Hz, 1H), 7.74 (d, J=13.8Hz, 1H), 7.59-7.44 (m, 2H), 7.26 (t, J=7.5Hz, 1H), 7.23-7.14 (m, 1H); 13 C NMR (100MHz, CDCl3): δ163.0, 160.5, 139.3, 139.1, 133.7, 133.6, 132.4, 131.3, 125.0, 124.9, 118.3, 118.2, 116.6, 116.4.

[0085] m-Fluoronitrovinylbenzene (m-FNVB). Yield 92%. Yellow solid.1 H NMR (400MHz, CDCl3): δ7.97 (d, J=13.7Hz, 1H), 7.57 (d, J=13.7Hz, 1H), 7.45 (q, J=7.8Hz, 1H), 7.35 (d, J=7.7Hz, 1H), 7.29-7.14 (m, 2H); 13 C NMR (100MHz, CDCl3): δ164.1, 161.6, 138.0, 137.6, 132.1, 132.0, 131.0, 130.9, 125.1, 125.0, 119.1, 118.8, 115.4, 115.2.

[0086] p-Fluoronitrovinylbenzene (p-FNVB). Yield 86%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ7.98 (d, J=13.7Hz, 1H), 7.64-7.47 (m, 3H), 7.15 (t, J=8.5Hz, 2H); 13 C NMR (100MHz, CDCl3): δ166.1, 163.5, 137.8, 136.7, 131.3, 131.2, 126.2, 126.2, 116.8, 116.6.

[0087] o-Chloronitrovinylbenzene (o-ClNVB). Yield 86%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ8.41 (d, J=13.7Hz, 1H), 7.66-7.56 (m, 2H), 7.50 (d, J=1.4Hz, 1H), 7.43 (t, J=1.7Hz, 1H), 7.34 (t, J=1.2Hz, 1H); 13 C NMR (100MHz, CDCl3): δ138.7, 135.9, 135.0, 132.8, 130.6, 128.5, 128.3, 127.4.

[0088] m-Chloronitrovinylbenzene (m-ClNVB). Yield 89%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ7.94 (d, J=13.7Hz, 1H), 7.59 (s, 1H), 7.54-7.52 (m, 1H), 7.51-7.46 (m, 1H), 7.45 (s, 1H), 7.44-7.41 (m, 1H); 13C NMR (100MHz, CDCl3): δ137.9, 137.4, 135.3, 131.9, 131.7, 130.6, 128.7, 127.2.

[0089] p-Chloronitrovinylbenzene (p-ClNVB). Yield 86%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ7.96 (d, J=13.7Hz, 1H), 7.62-7.55 (m, 1H), 7.55-7.40 (m, 4H); 13 C NMR (100MHz, CDCl3): δ138.4, 137.8, 137.5, 130.4, 129.9, 128.7.

[0090] o-Bronitrovinylbenzene (o-BrNVB). Yield 88%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ8.40 (d, J=13.7Hz, 1H), 7.69 (dd, J=7.6, 1.7Hz, 1H), 7.58 (dd, J=6.4, 1.2Hz, 1H), 7.54 (d, J=13.8Hz, 1H), 7.43-7.29 (m, 2H); 13 C NMR (100MHz, CDCl3): δ138.7, 137.5, 133.9, 132.9, 130.2, 128.4, 128.1, 126.3.

[0091] m-Bronitrovinylbenzene (m-BrNVB). Yield 91%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ7.93 (d, J=13.7Hz, 1H), 7.69 (s, 1H), 7.62 (d, J=7.2Hz, 1H), 7.56 (d, J=13.7Hz, 1H), 7.48 (d, J=7.8Hz, 1H), 7.34 (t, J=7.9Hz, 1H); 13 C NMR (100MHz, CDCl3): δ138.1, 137.4, 134.9, 132.1, 131.7, 130.9, 127.7, 123.4.

[0092] p-Bronitrovinylbenzene (p-BrNVB). Yield 94%. Yellow solid. 1 H NMR (400MHz, CDCl3): δ7.94 (d, J=13.7Hz, 1H), 7.65-7.52 (m, 3H), 7.42 (d, J=8.5Hz, 2H); 13C NMR (100MHz, CDCl3): δ137.8, 137.5, 132.8, 130.4, 128.9, 126.8.

[0093] Synthesis of ortho-, meta-, and para-halogenated phenylethylammonium (x-RPEA, where x: o, m, p, R: F, Cl, Br) skeletons Target - The systematic synthesis of m- and p-halogenated phenylethylammonium scaffolds (x-RB-CH2CH2-NH2 or x-RPEA, where x: o, m, p and R: F, Cl, Br) was carried out with reference to the literature and slight modifications. - The system synthesizes x-RNVB) as a raw material and uses LiAlH4 for reduction reaction. Empty, dry reaction flasks of appropriate size are evacuated and filled with inert gas (i.e., argon (Ar), nitrogen (N2)) three times. Then, lithium aluminum hydride (LAH or LiAlH4, x g, 4.0 eq.) is carefully transferred to these flasks at room temperature, and then the appropriate anhydrous ether (Et2O) is added dropwise at 0°C. The corresponding x-RNVB molecule (2.0 g, 1.0 eq.) is transferred to different empty flasks (all of which have been thoroughly dried and filled with the selected inert gas) and then dissolved in the selected reaction solvent (Et2O) to prepare the precursor. If the solubility of x-RNVB in the solvent is poor, use a heat gun while stirring. To avoid explosion caused by highly volatile organic vapors, additional protective measures are taken by providing an output to the system. The prepared precursor was slowly added to the corresponding reaction flask at 0°C, which contained a reducing suspension (LiAlH4 / reaction solvent: Et2O). Then, under an argon atmosphere, the mixture was stirred at a temperature close to the reflux temperature of the reaction solvent for 3 hours. After the reaction was completed, the reaction temperature was cooled to 0°C. The subsequent mixture was diluted with Et2O and then quenched by slowly adding water (x mL), 15% NaOH aqueous solution (x mL) and water (3xmL). The resulting mixture was dried over Mg2SO4 and filtered with filter paper. The resulting residue was washed excessively with Et2O. The combined organic phases were evaporated under reduced pressure. The crude halogenated aromatic phenethylammonium skeleton (x-RPEA) was obtained as a liquid with a unique color and was directly used in the next reaction without further purification.

[0094] o-Fluorophenethylammonium (o-FPEA). Yield 72%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.26-7.11 (m, 2H), 7.11-6.94 (m, 2H), 3.08-2.85 (m, 2H), 2.82 (t, J=6.7Hz, 2H), 2.60 (s, 2H); 13CNMR (100MHz, CDCl3): δ162.5, 160.1, 131.1, 131.1, 128.0, 127.9, 126.6, 126.4, 124.0, 124.0, 115.4, 115.2, 42.2, 33.3.

[0095] m-Fluorophenethylammonium (m-FPEA). Yield 84%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.35-7.21 (m, 1H), 7.01 (d, J=7.6Hz, 1H), 6.95 (d, J=9.1Hz, 2H), 3.00 (t, J=6.9Hz, 2H), 2.78 (t, J=6.8Hz, 2H), 1.69 (s, 2H); 13 C NMR (100 MHz, CDCl3): δ 162.8, 160.3, 141.1, 141.0, 128.6, 128.5, 123.1, 123.1, 114.3, 114.1, 111.6, 41.8, 38.2. p-Fluorophenethylammonium (p-FPEA). Yield 72%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.22-7.03 (m, 2H), 6.95 (t, J = 8.7Hz, 2H), 2.91 (t, J = 6.9Hz, 2H), 2.69 (t, J = 6.9Hz, 2H), 1.83 (s, 2H); 13 C NMR (100MHz, CDCl3): δ162.7, 160.3, 135.3, 135.3, 130.2, 130.1, 115.1, 43.5, 39.0.

[0096] o-Chlorophenethylammonium (o-ClPEA). Yield 77%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.17-7.06 (m, 3H), 6.97 (d, J=6.9Hz, 1H), 2.85 (t, J=6.9Hz, 2H), 2.63 (t, J=6.9Hz, 2H), 2.57 (s, 2H); 13 C NMR (100MHz, CDCl3): δ141.6, 134.2, 129.7, 128.9, 127.0, 126.5, 43.0, 39.1.

[0097] m-Chlorophenethylammonium (m-ClPEA). Yield 88%. Pale yellow liquid. 1H NMR (400MHz, CDCl3): δ7.34 (d, J=7.5Hz, 1H), 7.24-7.12 (m, 3H), 3.02-2.90 (m, 2H), 2.88 (t, J=6.7Hz, 2H), 2.03 (s, 2H); 13 C NMR (100MHz, CDCl3): δ137.3, 134.2, 131.0, 129.6, 127.7, 126.8, 41.9, 37.7.

[0098] p-Chlorophenethylammonium (p-ClPEA). Yield 83%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.25(d,

[0099] J=7.8Hz, 2H), 7.11 (d, J=8.1Hz, 2H), 2.93 (t, J=6.9Hz, 2H), 2.70 (t, J=7.0Hz, 2H), 1.75 (s, 2H); 13 C NMR (100MHz, CDCl3): δ138.2, 132.0, 130.2, 128.6, 43.3, 39.2.

[0100] o-Bromophenethylammonium (o-BrPEA). Yield 80%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.53(d,

[0101] J=7.8Hz, 1H), 7.26-7.17(m, 2H), 7.10-7.02(m, 1H), 2.99-2.92(m, 2H), 2.88(t,

[0102] J=6.3Hz, 2H), 1.64 (s, 2H); 13 C NMR (100MHz, CDCl3): δ139.0, 132.9, 130.9,

[0103] 128.0, 127.4, 124.7, 42.1, 40.3.

[0104] m-Bromophenethylammonium (m-BrPEA). Yield 85%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.51-7.28 (m, 1H), 7.23-6.98 (m, 3H), 2.86 (t, J=6.9Hz, 2H), 2.63 (t, J=6.9Hz, 2H), 1.78 (s, 2H); 13C NMR (100MHz, CDCl3): δ142.1, 131.8, 130.0, 129.3, 127.5, 122.5, 43.2, 39.6.

[0105] p-BrPEA. Yield: 74%. Pale yellow liquid. 1 H NMR (400MHz, CDCl3): δ7.40(d,

[0106] J=8.3Hz, 2H), 7.06 (d, J=8.3Hz, 2H), 2.92 (t, J=6.9Hz, 2H), 2.68 (t, J=6.9Hz, 2H), 1.51 (s, 2H); 13 C NMR (100MHz, CDCl3): δ138.8, 131.5, 130.6, 120.0, 43.4, 39.4.

[0107] Synthesis of ortho-, meta- and para-halogenated phenethylammonium iodide (x-RPEAI, where x: o, m, p, R: F, Cl, Br) salts become

[0108] A systematic synthesis of the target aromatic o-, m-, and p-halogenated phenethylammonium iodide scaffolds (x-XB-CH2CH2-NH3I or x-RPEAI, where x represents o, m, p and R represents F, Cl, or Br) was performed. Following a literature review with minor modifications, a previously synthesized aromatic phenethylammonium molecule (x-XPEA) was used as the starting material and treated with hydrochloric acid (HI) (57 wt.% aqueous solution). Each x-XPEA molecule (1.0 eq.) was added to an empty reaction flask (50 mL) and dissolved in ethanol (EtOH, 5.0 mL). Hydroiodic acid (HI, 1.05 eq., 57.0 wt.% aqueous solution) was then slowly added to the resulting solution under an ice bath. The reaction mixture was stirred at 0°C for 1 h under argon atmosphere, then the ice bath was removed and allowed to warm to room temperature. The reaction solvent and excess HI were then evaporated under reduced pressure at 60°C. The resulting brown solid was washed thoroughly with Et2O until a color change was observed. If it is realized that a large amount of Et2O is needed to purify the crude salt, the washing procedure is stopped and the precipitation procedure is continued. This procedure is applied by refrigerating the unpurified salt in Et2O for at least one day to slow down and control the precipitation of pure salt. The pure precipitate obtained is filtered with filter paper and washed again with Et2O. Additional purification is also carried out by recrystallization with EtOH. After the recrystallization is completed, the ultrapure crystals are filtered with filter paper and washed for the last time with Et2O. These pure salt crystals are transferred to glass vials, first dried in the open air, and then further dried in vacuum at room temperature. The isolated target aromatic halogenated phenethylammonium iodide (x-RPEAI) salt is presented in a single color and stored in a glove box filled with N2 for PSC studies.

[0109] o-Fluorophenethylammonium iodide (o-FPEAI). Yield 85%. Yellow solid. 1 H NMR (400MHz, DMSO-d6): δ7.83 (s, 3H), 7.38-7.29 (m, 2H), 7.24-7.14 (m, 2H), 3.08-2.98 (m, 2H), 2.94-2.85 (m, 2H); 13 CNMR (100MHz, CDCl3): δ161.7, 159.3, 131.1, 131.1, 129.1, 129.0, 124.7, 124.6, 123.8, 123.7, 115.4, 115.2, 26.4, 26.4.

[0110] m-Fluorophenethylammonium iodide (m-FPEAI). Yield 91%. Pale yellow solid. 1 H NMR (400MHz, DMSO-d6): δ7.78 (s, 3H), 7.42-7.35 (m, 1H), 7.19-7.03 (m, 3H), 3.14-3.02 (m, 2H), 2.93-2.83 (m, 2H); 13 CNMR (100MHz, CDCl3): δ163.4, 161.0, 140.0, 139.9, 130.5, 130.5, 124.9, 124.9, 115.6, 115.4, 113.7, 113.5, 32.5, 32.5.

[0111] p-Fluorophenethylammonium iodide (p-FPEAI). Yield: 84%. Pale yellow solid. 1 H NMR (400 MHz, DMSO-d6):

[0112] δ7.77(s, 3H), 7.41-7.21(m, 2H), 7.20-7.00(m, 2H), 3.16-2.93(m, 2H), 2.93-2.72(m, 2H); 13 C NMR (100MHz, CDCl3): δ162.7, 160.3, 133.6, 133.6, 131.0, 130.9, 115.8, 115.6, 32.4.

[0113] o-Chlorophenethylammonium iodide (o-ClPEAI). Yield 86%. Bright yellow solid. 1 H NMR (400 MHz, DMSO-d6): δ

[0114] 7.85 (s, 3H), 7.46 (d, J=7.6Hz, 1H), 7.39 (d, J=6.9Hz, 1H), 7.38-7.27 (m, 2H), 3.01 (td, J=12.9, 8.6Hz, 4H); 13 C NMR (100MHz, CDCl3): δ134.6, 133.0, 131.0, 129.4, 128.9, 127.6, 38.3, 30.7;

[0115] HRMS (ESI; Figure S43, Supporting Information) m / z: [M+H] + Calculated value: C8H 11 ClIN, 156.0580; Found, 156.0585. m-Chlorophenethylammonium iodide (m-ClPEAI). Yield 87%. Yellow crystalline solid. 1 H NMR (400MHz, DMSO-d6): δ7.77 (s, 3H), 7.43-7.33 (m, 2H), 7.31 (d, J=8.1Hz, 1H), 7.24 (d, J=7.3Hz, 1H), 3.18-3.00 (m, 2H), 2.94-2.79 (m, 2H); 13 C NMR (100 MHz, CDCl3): δ 139.7, 133.1, 130.4, 128.6, 127.5, 126.8, 39.5, 32.5; HRMS (ESI; Figure S44, Supporting Information) m / z: [M+H] + C8H 11 Calculated ClIN: 156.0580; Found: 156.0567.

[0116] p-Chlorophenethylammonium iodide (p-ClPEAI). Yield 86%. Brown solid. 1 H NMR (400MHz, DMSO-d6): δ7.75 (s, 3H), 7.39 (d, J=8.3Hz, 2H), 7.30 (d, J=8.4Hz, 2H), 3.21-2.88 (m, 2H), 3.01-2.73 (m, 2H); 13 C NMR (100MHz, CDCl3): δ136.2, 131.4, 130.6, 128.5, 32.2.

[0117] o-Bromophenethylammonium iodide (o-BrPEAI). Yield 90%. Brown solid. 1H NMR (400MHz, DMSO-d6): δ7.86 (s, 3H), 7.63 (d, J=8.0Hz, 1H), 7.38 (d, J=4.1Hz, 2H), 7.27-7.18 (m, 1H), 3.12-2.94 (m, 4H); 13 C NMR (100MHz, DMSO-d6): δ136.3, 132.7, 131.0, 129.1, 128.2, 123.8, 38.4, 33.2.

[0118] m-Bromophenethylammonium iodide (m-BrPEAI). Yield 88%. Pale yellow crystalline solid. 1 H NMR (400MHz, DMSO-d6): δ7.76 (s, 3H), 7.51 (s, 1H), 7.46 (d, J=6.8Hz, 1H), 7.30 (d, J=6.9Hz, 2H), 3.17-2.99 (m, 2H), 2.86 (t, J=7.7Hz, 2H); 13 C NMR (100MHz, CDCl3): δ140.0, 131.5, 130.7, 129.7, 127.9, 121.8, 39.6, 32.4;

[0119] HRMS (ESI; Figure S45, Supporting Information) m / z: [M+H] + , calculated value is C8H 11 BrIN, 200.0075; measured value: 200.0075.

[0120] p-BrPEAI (p-BrPEAI). Yield: 84%. Yellow solid. 1 H NMR (400MHz, DMSO-d6): δ7.75 (s, 3H), 7.53 (d, J = 8.3Hz, 2H), 7.24 (d, J = 8.3Hz, 2H), 3.14-2.93 (m, 2H), 2.91-2.76 (m, 2H); 13 C NMR (100MHz, CDCl3): δ136.6, 131.4, 131.0, 119.9, 32.3.

[0121] Perovskite solar cells with and without 2D layers were fabricated and characterized under single-sun illumination. Figure 15 a and Figure 15 b) V was observed in salt-treated 3D perovskite films. OC The significant improvement of FF and NPs indicates the excellent surface passivation effect and enhanced hole extraction, respectively. SC Increase( Figure 15c) may be associated with enhanced V OC and FF, which leads to enhanced PCE ( Figure 15 d), and the extremely thin 2D film does not increase the absorption in the 3D perovskite. The 2D passivation film shows lower hysteresis than the control film, which indicates reduced ion migration and enhanced charge extraction. The control 3D device shows the highest PCE of 20.80% and the open circuit voltage (V OC ) is 1.09V, the short-circuit current (J SC ) is 24.54 mA / cm 2 , the fill factor (FF) is 79.7%. By introducing a 2D layer on the 3D perovskite film, the device performance is significantly improved. The average V OC The integrated J obtained by external quantum efficiency (EQE) measurement is about 1.13 V, which means that the 2D layer formed by the x-RPEAI salt effectively passivates the recombination center. Better device parameters can be observed by inserting the m-RPEAI 2D layer (PCE>23%), which is consistent with the results of PL and TRPL studies. SC and Figure 15 J obtained from the current density-voltage (JV) curves in e and f SC consistent.

[0122] The optical properties of the control and x-RPEAI treated perovskite films were investigated by PL, TRPL and UV-visible absorption (UV-Vis) spectroscopy. Figure 16 ac). PL measurements were performed from the film side using 450nm excitation light. Compared to the control film, the 2D-treated 3D film showed higher PL intensity at 812nm, which is generally associated with reduced non-radiative recombination. Due to the low concentration of the 2D precursor solution, the 2D perovskite has no PL emission at shorter wavelengths; therefore, extremely thin films ( Figure 16 a) Relatedly, the PL spectra of all salt-treated films show enhanced PL intensity for all halogen substituents at the -meta position. This indicates that RPEAI derivatives substituted with -meta halogens have a better suppression effect on non-radiative carrier recombination. Figure 16 As shown in Figure 2b, the average carrier lifetime in the 3D / 2D perovskite film is significantly longer than that in the control device. It is foreseeable that the 2D perovskite film can reduce the defect density, thereby reducing non-radiative recombination. All halide 2D salts have longer carrier lifetimes than the control film, confirming the suppression of non-radiative recombination and the enhanced effect of defect passivation, thereby improving V OC Among the nine salts, the meta-halogenated derivatives exhibited longer lifetimes than their ortho- and para-position counterparts. According to the transmission spectra, the insertion of a 2D layer on top of the 3D perovskite did not affect the transmittance of the 3D / 2D hybrid structure ( Figure 16c) In summary, for strong electron-donating groups such as -OMe that can coordinate with the iodine or lead centers in perovskites, the ortho position is the preferred substitution position to improve performance and stability.

[0123] Halogens have a weaker tendency to form the above interactions and are more suitable for substituting at the meta position because they can produce enhanced and correctly oriented dipole moments at the meso position in 2D perovskites.

Claims

1. A perovskite solar cell, characterized in that A 2D passivation layer comprising the following compounds: in; R is halogen, aromatic group, alkoxy group, alkyl group, thiol, amino group or hydrogen; X is iodide, bromide, chloride, acetate, triflate, nitrate, alkyl sulfate, alkyl phosphate, amino acid, tetracyanoborate, dicyanamide, tricyanomethane, carboxylate, hexafluorophosphate, tetrafluoroborate, tetrafluoromethylacetate or bis(trifluoromethanesulfonyl)imide, Wherein, all R cannot be hydrogen.

2. The perovskite solar cell according to claim 1, characterized in that The compound is o-methoxyphenethylammonium iodide.

3. The perovskite solar cell according to claim 1, wherein The compound is m-methoxyphenethylammonium iodide.

4. The perovskite solar cell according to claim 1, wherein The compound is p-methoxyphenethylammonium iodide.

5. The perovskite solar cell according to claim 1, wherein The compound has one of the following structures; 6. The perovskite solar cell according to claim 1, characterized in that The compound has one of the following structures; 7. The perovskite solar cell according to claim 1, wherein The compound has one of the following structures; 8. The perovskite solar cell according to claim 1, wherein The compound has one of the following structures; 9. The perovskite solar cell according to claim 1, wherein The compound has one of the following structures; Wherein, R is not hydrogen.

10. The perovskite solar cell according to claim 1, wherein The compound is ortho-, meta- or para-halogenated phenethylammonium iodide, wherein R is Cl, Br or F, and X is iodide.

11. The perovskite solar cell according to claim 1, characterized in that The substitution position of the strong electron-donating group is the ortho position.

12. The perovskite solar cell according to claim 1, wherein The substitution position of halogen is meta.

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