Preparation method of co-self-assembly monolayer with high stability and hole selectivity

Abstract

This invention discloses a method for preparing a highly stable and hole-selective co-self-assembled monolayer. The method involves dissolving both a host solute and a guest solute in a solvent, then spin-coating the mixed solution directly onto a conductive substrate, followed by thermal annealing to obtain the co-self-assembled monolayer. The phosphonic acid groups in both solutes synergistically anchor on the conductive substrate surface, enhancing interfacial bonding strength and passivating defects at the perovskite buried substrate interface. Therefore, perovskite solar cells prepared based on this co-self-assembled monolayer exhibit significantly improved stability under high temperature, illumination, and bending stress, possessing both high hole selectivity and low interfacial charge recombination efficiency, providing a reliable interfacial solution for the fabrication of efficient and stable flexible devices.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials technology, specifically relating to a method for preparing a highly stable and hole-selective co-self-assembled monolayer. Background Technology

[0002] Perovskite solar cells, as a representative of the next generation of thin-film photovoltaic technology, have become a research frontier in the photovoltaic field. However, in practical applications, flexible perovskite devices still face challenges such as poor stability and severe interfacial recombination losses. Self-assembled monolayers (SAMs), as a novel interfacial material, show broad application prospects due to their advantages such as strong designability of molecular structure, simple film formation process, and low material consumption.

[0003] 4-(3,6-dimethyl-9H-carbazole-9-yl)butylphosphonic acid (Me-4PACz) is one of the most widely used hole-selective host SAMs in inverted perovskite solar cells. Its molecule consists of a phosphonic acid anchoring group, a butyl linker, and a 3,6-dimethylcarbazole functional end group. However, the steric hindrance effect of the carbazole group leads to easy aggregation and uneven coverage of the molecule on the substrate, resulting in nanoscale voids. The strong hydrophobicity of the molecular layer surface causes poor wettability of the perovskite precursor solution, generating numerous micropores and crystal defects at the buried interface. These microscale defects and inhomogeneities at the Me-4PACz / perovskite interface have become key bottlenecks restricting device efficiency and stability. These defects, acting as deep-level traps, capture photogenerated carriers, leading to severe nonradiative recombination losses. Simultaneously, the flexible alkyl chain, acting as an insulating spacer, hinders charge transport along the intermolecular direction to some extent, limiting the overall conductivity and hole mobility of the SAM layer and affecting efficient hole extraction. These factors severely limit the open-circuit voltage and fill factor performance of the final device. Furthermore, Me-4PACz exhibits slow degradation and molecular desorption under practical operating conditions such as continuous bending, illumination, and thermal stress, and its long-term operational stability still needs improvement. Therefore, it is urgent to develop novel co-self-assembly strategies to overcome the inherent limitations of Me-4PACz and achieve the fabrication of highly efficient and stable flexible perovskite solar cells. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a highly stable and hole-selective co-self-assembled monolayer and its application in the field of solar cells.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: One of the objectives of this invention is to protect a method for preparing a highly stable and hole-selective co-assembled monolayer, which involves dissolving both the host solute and the guest solute in a solvent, then spin-coating the mixed solution directly onto a conductive substrate, followed by thermal annealing.

[0006] Further, the main solute is 4-(3,6-dimethyl-9H-carbazole-9-yl)butylphosphonic acid (Me-4PACz), 4-(9H-carbazole-9-yl)butylphosphonic acid (4PACz), (4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl)phosphonic acid (MeO-4PACz), 2-(9H-carbazole-9-yl)ethylphosphonic acid (2PACz), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz), (2-(3,6-bis(2-phenylthiophen-5-yl)-9H-carbazole-9-yl)ethyl)phosphonic acid (PhT-2PACz). One or more of Me-4PACz, (4-(9H-carbazole-9-yl)phenyl)phosphonic acid (pPhPACz), (4-(diphenylamino)phenylethyl)phosphonic acid (2PATPA), (3-((9-ethyl-9H-carbazole-3-yl)oxy)propyl)phosphonic acid (HTL201), 4-(7-(4-(bis(4-methoxyphenyl)amino)phenyl)benzo[c][1,2,5]thiadiazole-4-yl)-2-fluorobenzoic acid (TBT-FBA), and 5-(7-(4-(bis(4-methoxyphenyl)amino)phenyl)benzo[c][1,2,5]thiadiazole-4-yl)isophthalic acid (TBT-DBA). Preferably, the main solute is Me-4PACz.

[0007] Further, the guest solute is diethyl (4-iodobenzyl)phosphonate, diethyl (4-bromobenzyl)phosphonate, diethyl (4-cyanobenzyl)phosphonate, diethyl (4-isopropylbenzyl)phosphonate, benzylphosphonic acid, diethyl benzylphosphonate, diethyl 4-(nitrobenzyl)phosphonate, diethyl (4-chlorobenzyl)phosphonate, diethyl (4-fluorobenzyl)phosphonate, diethyl iodomethylphosphonate, diethyl (3-methylbenzyl)phosphonate, etc. One or more of the following: diethyl 3-nitrobenzylphosphonate, diethyl (2-chlorobenzyl)phosphonate, diethyl 3-bromobenzylphosphonate, diethyl 3,5-dimethoxybenzylphosphonate, diethyl (3-methoxybenzyl)phosphonate, diethyl 4-(bromophenyl)phosphonate, diethyl (aminomethyl)phosphonate, diethyl bromomethylphosphonate, phenylphosphonic acid, (4-aminophenyl)phosphonic acid, (4-hydroxyphenyl)phosphonic acid, and (4-bromophenyl)phosphonic acid. Preferably, the guest solute is diethyl (4-iodobenzyl)phosphonate (4-IBPA-DE).

[0008] Further, the solvent is one or more of ethanol, distilled water, 2-cyclohexylethanol, deuterated ethanol, methanol, isopropanol, n-propanol, n-butanol, acetone, acetonitrile, ethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether.

[0009] Furthermore, the concentration of the guest solute in the mixed solution is 0.01~10.0 mg / ml, and the concentration of the host solute is 0.01~10.0 mg / ml.

[0010] Furthermore, after the main solute, guest solute and solvent are mixed, the mixture is stirred at 200-500 rpm for 0.5-3 hours at room temperature.

[0011] Furthermore, the spin coating speed is 2000~5000 rpm, the time is 10~35s, and the coating amount is 40~200 μL / cm. 2 .

[0012] Furthermore, the conductive substrate is polyethylene terephthalate (ITO-PET) etched with indium tin oxide.

[0013] Furthermore, the heat annealing temperature is 90~130 ℃ and the time is 5~60 min.

[0014] Furthermore, the preparation process is carried out in a glove box, where the water content is <1 ppm and the oxygen content is <1 ppm.

[0015] The second objective of this invention is to protect the highly stable and hole-selective co-assembled monolayer obtained by the preparation method.

[0016] A third objective of this invention is to protect the application of the highly stable and hole-selective co-assembled monolayer in the fabrication of perovskite solar cells.

[0017] Furthermore, the application method involves sequentially depositing a perovskite photoactive layer, an electron transport layer, and a metal electrode on a conductive substrate coated with the aforementioned self-assembled monolayer, thereby forming the perovskite solar cell.

[0018] Furthermore, the perovskite photoactive layer is made of formamidinium lead iodine.

[0019] Furthermore, the electron transport layer is a PCBM.

[0020] Furthermore, the metal electrode is vacuum-deposited silver.

[0021] Guest solutes such as diethyl (4-iodobenzyl)phosphonate (4-IBPA-DE) have small molecular volumes, and their planar benzene ring structure allows them to anchor more compactly to the gaps between host solute molecules such as Me-4PACz, effectively filling uncovered substrate sites and forming a dense and nearly continuous co-self-assembled monolayer (Co-SAM). Simultaneously, the two molecules form multi-point anchorages on the substrate through their respective phosphonic acid groups, avoiding overall interfacial failure caused by desorption from a single anchoring point. Furthermore, the iodobenzene ring in 4-IBPA-DE exhibits superior thermal stability compared to conventional alkyl groups, further enhancing the conformational retention of Co-SAM under sustained thermal stress.

[0022] Beneficial effects of this invention: (1) This invention employs a novel method for preparing a co-self-assembled monolayer. The molecular structure of the introduced guest solute 4-IBPA-DE comprises three key parts: an iodine atom at the para position of the benzene ring as a functional group, a benzyl group as a linker arm, and diethyl phosphonate as an anchoring group. In solution, the diethyl phosphonate group can undergo hydrolysis to transform into a free phosphonic acid group, which can chemically bond with the hydroxyl groups on the substrate surface, achieving a firm anchoring of the SAM molecule and thus enhancing the interfacial bonding strength. The rigid structure of the benzene ring endows the molecule with a certain skeletal stability, while the terminal iodine atom has strong polarization characteristics and can establish connections with cations and halide ions in the perovskite layer through non-covalent interactions such as halogen bonds, providing passivation sites for interfacial defects. In addition, the iodine atom in the iodobenzene ring can absorb some ultraviolet light energy and dissipate it in the form of heat, providing a certain ultraviolet shielding protection for the SAM layer. Therefore, the optimized interfacial energy level arrangement of 4-IBPA-DE can reduce the hole extraction barrier, reduce the residence time and accumulation of photogenerated holes at the interface, and alleviate interfacial photochemical corrosion.

[0023] (2) This invention discloses a flexible perovskite solar cell based on a novel high-stability Co-SAM, which can achieve a photoelectric conversion efficiency of 23.6% and exhibit excellent multi-factor stability: 4-IBPA-DE guest molecules effectively fill the covering gap of Me-4PACz to form a nearly pinhole-free dense SAM layer, which provides a template effect for the growth of the upper perovskite crystal, promotes the crystallization of the perovskite film in a favorable orientation, and reduces lattice defects and residual tensile stress; when external bending stress is applied, the uniform and dense Co-SAM interface helps to uniformly transfer and disperse the stress, avoids the stress concentration at local defects and the initiation and propagation of interface cracks, thereby significantly improving the bending resistance of the flexible device. Attached Figure Description

[0024] Figure 1 The diagram shows the process of preparing the self-assembled layer and perovskite thin film in Example 1 and Comparative Example 1, as well as a comparison of the physical perovskite thin films obtained.

[0025] Figure 2 The current density-voltage (JV) test curves (including forward and reverse scans) of the perovskite solar cells prepared in Examples 1-3 and Comparative Example 1 are shown.

[0026] Figure 3 The image shows a comparison of the contact angles of the self-assembled layers prepared in Example 1 and Comparative Example 1 with water and N,N-dimethylformamide (DMF).

[0027] Figure 4 X-ray photoelectron spectroscopy (XPS) of the self-assembled layers prepared for Example 1 and Comparative Example 1.

[0028] Figure 5 Energy dispersive X-ray spectra (EDS) of the self-assembled layers prepared in Example 1 and Comparative Example 1.

[0029] Figure 6 Scanning electron microscope (SEM) images of the surface and cross-section of the perovskite thin films prepared in Example 1 and Comparative Example 1.

[0030] Figure 7 The normalized power conversion efficiency of the flexible perovskite solar cells prepared for Example 1 and Comparative Example 1 is compared after exposure to a high temperature environment of 85 °C for 300 hours (a), continuous illumination of AM1.5G for 300 hours (b), and bending 1000 times with a bending radius of 5 mm (c).

[0031] Figure 8 The reverse scan JV test curves are for the perovskite solar cells prepared in Comparative Examples 2 and 3. Detailed Implementation

[0032] A highly stable and hole-selective co-assembled monolayer is obtained by adding both a host solute and a guest solute to a solvent and stirring at 200–500 rpm for 0.5–3 h at room temperature to obtain a mixed solution containing 0.01–10.0 mg / ml of guest solute and 0.01–10.0 mg / ml of host solute. This mixed solution is then directly spin-coated onto an ITO-PET conductive substrate (spin-coating speed 2000–5000 rpm, time 10–35 s, spin-coating amount 40–200 μL / cm). 2 The product is then annealed at 90-130℃ for 5-60 minutes.

[0033] The main solute is one or more of Me-4PACz, 4PACz, MeO-4PACz, 2PACz, MeO-2PACz, PhT-2PACz, pPhPACz, 2PATPA, HTL201, TBT-FBA, and TBT-DBA.

[0034] The guest solute is diethyl (4-iodobenzyl)phosphonate, diethyl (4-bromobenzyl)phosphonate, diethyl (4-cyanobenzyl)phosphonate, diethyl (4-isopropylbenzyl)phosphonate, benzylphosphonic acid, diethyl benzylphosphonate, diethyl 4-(nitrobenzyl)phosphonate, diethyl (4-chlorobenzyl)phosphonate, diethyl (4-fluorobenzyl)phosphonate, diethyl iodomethylphosphonate, diethyl (3-methylbenzyl)phosphonate, 3-nitrobenzyl... The solvent is one or more of the following: diethyl methylbenzylphosphonate, diethyl (2-chlorobenzyl)phosphonate, diethyl 3-bromobenzylphosphonate, diethyl 3,5-dimethoxybenzylphosphonate, diethyl (3-methoxybenzyl)phosphonate, diethyl 4-(bromophenyl)phosphonate, diethyl (aminomethyl)phosphonate, diethyl bromomethylphosphonate, phenylphosphonic acid, (4-aminophenyl)phosphonic acid, (4-hydroxyphenyl)phosphonic acid, and (4-bromophenyl)phosphonic acid. Further, the solvent is one or more of the following: ethanol, distilled water, 2-cyclohexylethanol, deuterated ethanol, methanol, isopropanol, n-propanol, n-butanol, acetone, acetonitrile, ethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0036] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0037] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0038] Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this invention are commercially available. See Table 1 for details.

[0039] Table 1 Raw materials used in the examples and comparative examples Example 1

[0040] This embodiment provides a device for a flexible solar cell fabricated based on a highly stable and hole-selective co-self-assembled monolayer, the structure of which is: PET / ITO / Co-SAM / FAPbI3 / PCBM / Ag.

[0041] The anode is ITO, the hole transport layer is Co-SAM, the perovskite photoactive layer is FAPbI3, the electron transport layer is PCBM, and the cathode is Ag.

[0042] The following are the steps of a method for fabricating a high-stability and hole-selective co-self-assembled monolayer and its solar cell: (1) Preparation of Co-SAM solution: Accurately weigh 0.15 mg 4-IBPA-DE and 0.3 mg Me-4PACz, dissolve them together in 1.0 mL of ethanol solvent, stir at 300 rpm at room temperature for 1 h to fully dissolve and mix them.

[0043] (2) Preparation of perovskite precursor solution: Weigh 172 mg FAI and 461 mg PbI2, dissolve them in 1.0 mL of a mixed solvent of DMF and DMSO (volume ratio 4:1), stir at 60 °C for 1 h, and store at 60 °C for later use.

[0044] (3) Preparation of PCBM solution: Weigh 20.0 mg PCBM powder, add 1.0 mL chlorobenzene solvent, and stir at room temperature for 1 h until fully dissolved.

[0045] (4) Cleaning of PET substrate: The flexible PET substrate etched by ITO is ultrasonically treated with acetone and ethanol for 15 minutes each, then placed on a 100 ℃ heating table to dry fully, then polyimide high temperature resistant tape is pasted on, and then cleaned by UVO cleaning machine for 15 minutes to completely remove organic residual impurities on the ITO surface.

[0046] (5) Spin-coating preparation of Co-SAM self-assembled layer: The Co-SAM solution prepared in step (1) was spin-coated onto a clean ITO surface at a speed of 4000 rpm for 30 s, with a spin-coating amount of 100 μL / cm. 2 After spin coating, the substrate is heat-treated at 100 ℃ for 10 min to form a self-assembled layer.

[0047] (6) Spin-coating preparation of perovskite layer: The perovskite precursor solution was spin-coated onto the surface of the prepared Co-SAM self-assembled layer at a speed of 4000 rpm for 30 s (ethyl acetate was added dropwise as an antisolvent to assist perovskite grain crystallization at about 15 s of spin-coating), and the spin-coating amount was 100 μL / cm. 2After spin coating, the substrate is thermally annealed at 150 °C for 30 min to form a perovskite film.

[0048] (7) Spin-coating preparation of PCBM layer: Spin-coating PCBM solution onto the perovskite layer surface at 3000 rpm for 30 s, with a coating amount of 100 μL / cm. 2 The PCBM layer was then annealed at 80 °C for 0.5 h to form the PCBM layer.

[0049] (8) Tape peeling: Remove the polyimide high-temperature resistant tape that was pasted on the substrate surface in step (4).

[0050] (9) A layer with a thickness of approximately 85 nm and an effective area of ​​0.1 cm was deposited on the top by vacuum thermal evaporation. 2 Flexible solar cells were fabricated using metallic silver as the counter electrode. Example 2

[0051] The difference from Example 1 is that the 4-IBPA-DE used in step (1) is replaced with diethyl benzylphosphonate. Example 3

[0052] The difference from Example 1 is that the 4-IBPA-DE used in step (1) is replaced with diethyl 3-nitrobenzylphosphonate. Comparative Example 1

[0053] The difference from Example 1 is that the 4-IBPA-DE used in step (1) is replaced with phenylphosphonic acid. Comparative Example 2

[0054] The difference from Example 1 is that the 4-IBPA-DE used in step (1) is replaced with diethyl (4-bromobenzyl)phosphonate. Comparative Example 3

[0055] The difference from Example 1 is that the 4-IBPA-DE used in step (1) is replaced with (4-iodophenyl)phosphonic acid.

[0056] Figure 1 The figures show schematic diagrams of the processes for preparing self-assembled layers and perovskite films in Example 1 and Comparative Example 1, as well as comparative images of the resulting perovskite films. As can be seen from the figures, the perovskite film prepared in Comparative Example 1 has incomplete coverage. The introduction of 4-IBPA-DE effectively solves the problem of uneven film formation during spin-coating of the Me-4PACz solution, enabling the perovskite film formed on top to achieve nearly 100% coverage.

[0057] Figure 2The JV curves of the perovskite solar cells prepared in Examples 1-3 and Comparative Example 1 under forward and reverse scanning are shown in Table 2. The corresponding photovoltaic parameters are listed in Table 2. As can be seen from the figure, the PCE of the device modified with 4-IBPA-DE guest can reach 23.60%, and the hysteresis index is as low as 0.019, which is significantly better than that of Comparative Example 1.

[0058] Table 2. Main performance parameters of the flexible solar cells prepared in Examples 1-3 and Comparative Example 1

[0059] Figure 3 The figure shows a comparison of the contact angles of the self-assembled layers prepared in Example 1 and Comparative Example 1 with water and DMF. As can be seen from the figure, the water contact angle of the self-assembled layer prepared in Comparative Example 1 is approximately 90.1°, and the DMF contact angle is approximately 43.9°, exhibiting hydrophobicity. In contrast, the water contact angle of the Co-SAM self-assembled layer in Example 1 decreases to 69.6°, and the DMF contact angle decreases to 40.0°. This indicates that the modification with 4-IBPA-DE effectively improves the chemical environment of the film surface, fills interfacial vacancies, and forms a dense functionalized interfacial layer, significantly enhancing the hydrophilicity of the film. This effectively promotes the uniform spreading of the perovskite precursor solution on the hole transport layer surface, laying a crucial foundation for improving the optoelectronic performance and environmental stability of the device.

[0060] Figure 4 XPS images of the self-assembled layers prepared in Example 1 and Comparative Example 1 are shown. As can be seen from the figures, the 4-IBPA-DE molecule contains a para-iodine-substituted benzyl ring and a benzyl (-CH2) spacer group. The C1s binding energy of its benzyl ring carbon is similar to that of the aromatic carbon in carbazole, which can enhance the signal intensity in the aromatic carbon region. The introduction of the benzyl group increases the proportion of the CC / CH component, broadening the peak shape in this region and causing a slight shift in the peak position (a, b). After hydrolysis, 4-IBPA-DE generates (4-iodobenzyl)phosphonic acid (4-IBPA), whose P-OH condenses with the hydroxyl groups on the ITO substrate surface to form an In-OP bond. Furthermore, unlike the anchoring mode in Comparative Example 1, the benzylphosphonic acid skeleton of 4-IBPA has greater conformational freedom, allowing for more favorable anchoring geometries. The differences in the chemical environment around the oxygen atom under different anchoring modes are directly reflected in the changes in the O 1s binding energy (c, d). Furthermore, the P 2p binding energy of phosphorus in phosphonates is close to but not entirely identical to that of Me-4PACz. The superposition of the P 2p signals from the two phosphorus chemical states leads to a shift or asymmetric broadening of the P 2p peak, and its area also increases accordingly (e, f). Therefore, 4-IBPA-DE provides an excellent guest molecule selection strategy with halogen bond guidance, conformational adaptation, and electronic regulation.

[0061] Figure 5The figures show the EDS images of the self-assembled layers prepared in Example 1 and Comparative Example 1. As can be seen from the figures, compared with the system in Comparative Example 1, in the 4-IBPA-DE modified system, the characteristic signal intensities of indium (In) and tin (Sn), which are the core components of the indium tin oxide (ITO) substrate, show a weakening trend, while the elemental signals of phosphorus (P) and nitrogen (N), which represent the characteristics of Me-4PACz molecules, show an enhanced trend. This indicates that the ITO substrate surface is more completely covered, and the exposed pore area is significantly reduced, which also confirms that 4-IBPA-DE has a significant advantage in enhancing interfacial adsorption stability.

[0062] Figure 6 The images show SEM images of the surface and cross-section of the perovskite films prepared in Example 1 and Comparative Example 1. The surface SEM images reveal that the perovskite film obtained in Example 1 has a larger grain size and a more flat and dense overall surface. The cross-sectional SEM images further illustrate that the buried interface of the perovskite film formed on the substrate of Example 1 has a tighter contact, with no obvious voids, thus improving the interface performance of the device.

[0063] Figure 7 The graph shows a comparison of the normalized power conversion efficiency of the flexible perovskite solar cells prepared in Example 1 and Comparative Example 1. As can be seen from the graph, after exposing the flexible perovskite solar cell prepared in Comparative Example 1 to a high-temperature environment of 85 °C for 300 hours, its efficiency was reduced to only 20.13% of the initial value, while the efficiency of the flexible perovskite solar cell prepared in Example 1 remained above 80% (a). Furthermore, after 300 hours of continuous AM1.5G illumination, the efficiency of the flexible perovskite solar cell prepared in Comparative Example 1 showed a significant decrease, while the efficiency of the flexible perovskite solar cell prepared in Example 1 remained above 50% (b). In addition, after being bent 1000 times with a bending radius of 5 mm, the efficiency of the flexible perovskite solar cell prepared in Comparative Example 1 was reduced to only about 18%, while the efficiency of the flexible perovskite solar cell prepared in Example 1 remained above 80% (c). These results demonstrate that 4-IBPA-DE can improve the orderliness of the Co-SAM layer on the ITO substrate surface, thereby slowing down the performance aging of the device under high temperature, continuous illumination and bending conditions, and enhancing its stability.

[0064] Figure 8 The reverse scan JV test curves of the perovskite solar cells prepared in Comparative Examples 2 and 3 are shown in Table 3. The corresponding photovoltaic parameters are detailed in Table 3. A comparison with Figure 2 and Table 2 shows that the Jsc and PCE of the perovskite solar cells prepared in Comparative Examples 2 and 3 are significantly lower than those of the perovskite solar cell prepared in Example 1.

[0065] Table 3. Main performance parameters of the perovskite solar cells prepared in Comparative Examples 2 and 3

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a highly stable and hole-selective co-self-assembled monolayer, characterized in that: The co-self-assembled monolayer is prepared by dissolving both the host solute and the guest solute in a solvent, then spin-coating the mixed solution directly onto a conductive substrate, followed by thermal annealing.

2. The preparation method according to claim 1, characterized in that: The main solute is one or more of Me-4PACz, 4PACz, MeO-4PACz, 2PACz, MeO-2PACz, PhT-2PACz, pPhPACz, 2PATPA, HTL201, TBT-FBA, and TBT-DBA.

3. The preparation method according to claim 1, characterized in that: The guest solute is diethyl (4-iodobenzyl)phosphonate, diethyl (4-bromobenzyl)phosphonate, diethyl (4-cyanobenzyl)phosphonate, diethyl (4-isopropylbenzyl)phosphonate, benzylphosphonic acid, diethyl benzylphosphonate, diethyl 4-(nitrobenzyl)phosphonate, diethyl (4-chlorobenzyl)phosphonate, diethyl (4-fluorobenzyl)phosphonate, diethyl iodomethylphosphonate, diethyl (3-methylbenzyl)phosphonate, 3-nitrobenzyl... Diethyl methylbenzylphosphonate, (2-chlorobenzyl)phosphonate, 3-bromobenzylphosphonate, 3,5-dimethoxybenzylphosphonate, (3-methoxybenzyl)phosphonate, 4-(bromophenyl)phosphonate, (aminomethyl)phosphonate, bromomethylphosphonate, phenylphosphonic acid, (4-aminophenyl)phosphonic acid, (4-hydroxyphenyl)phosphonic acid, and (4-bromophenyl)phosphonic acid are among one or more of these.

4. The preparation method according to claim 1, characterized in that: The solvent is one or more of ethanol, distilled water, 2-cyclohexylethanol, deuterated ethanol, methanol, isopropanol, n-propanol, n-butanol, acetone, acetonitrile, ethylene glycol monobutyl ether, and dipropylene glycol monomethyl ether.

5. The preparation method according to claim 1, characterized in that: The concentration of the guest solute in the mixed solution is 0.01~10.0 mg / ml, and the concentration of the host solute is 0.01~10.0 mg / ml.

6. The preparation method according to claim 1, characterized in that: The spin coating process involves a rotation speed of 2000–5000 rpm, a time of 10–35 s, and a coating volume of 40–200 μL / cm. 2 .

7. The preparation method according to claim 1, characterized in that: The conductive substrate is ITO-PET.

8. The preparation method according to claim 1, characterized in that: The heat annealing temperature is 90~130 ℃, and the time is 5~60 min.

9. A highly stable and hole-selective co-assembled monolayer prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the highly stable and hole-selective co-self-assembled monolayer as described in claim 9 in the fabrication of perovskite solar cells.

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