Perovskite solar cell and method of manufacturing the same

Abstract

The application provides a perovskite solar cell and a preparation method thereof, and relates to the technical field of solar cells. The perovskite solar cell comprises: a transparent conductive layer arranged on a glass substrate and used for collecting photo-generated holes; a hole transport material layer arranged on the transparent conductive layer and used for selectively extracting photo-generated holes and regulating interface energy levels, wherein the material of the hole transport material layer comprises a benzene bridged double (R-substituted benzene [c] carbazole)-cyano vinyl phosphonic acid self-assembled monolayer material; the self-assembled monolayer material takes a benzene group as a bridging unit, the benzene group is connected to two substituted benzene [c] carbazole units, a nitrogen atom of each substituted benzene [c] carbazole unit is connected to a substituted phenyl group, and the substituted phenyl group is anchored to the transparent conductive layer through a cyano vinyl phosphonic acid group to form stable chemical adsorption; and a perovskite layer arranged on the hole transport material layer and used for absorbing photons to generate electron-hole pairs.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and more specifically, to a perovskite solar cell and its fabrication method. Background Technology

[0002] Perovskite solar cells have attracted widespread attention in recent years due to their advantages such as high photoelectric conversion efficiency, solution-processability, low-temperature fabrication, and applicability to tandem photovoltaic devices. Among them, inverted pin-structured perovskite solar cells are considered to have high industrialization potential due to their smaller hysteresis effect, lower fabrication temperature, and ease of integration with silicon solar cells or other photovoltaic absorber layers.

[0003] In inverted perovskite solar cells, the buried interface between the transparent conductive layer and the perovskite light-absorbing layer has a significant impact on hole extraction, interfacial recombination, thin film crystal quality, and long-term stability. Traditional hole transport materials typically require the introduction of lithium salts, organic bases, or other dopants to improve conductivity. However, these dopants may be hygroscopic or migratory, easily causing interface degradation, perovskite decomposition, and decreased device stability.

[0004] Self-assembled monolayers (SAMs) can chemically bond with the surface of transparent conductive oxides through anchoring groups such as phosphonic acids and carboxylic acids, achieving hole-selective contact at extremely thin thicknesses. These materials typically do not require dopants, which helps reduce parasitic absorption, minimize interface defects, and improve device stability. However, existing self-assembled monolayer materials still have room for improvement in terms of molecular energy level modulation, interfacial dipole construction, perovskite nucleation induction, and the diversity of aromatic framework structures. Most mononuclear molecules struggle to form highly ordered, close-packed structures, and their highest occupied molecular orbital (HOMO) energy levels have limited matching with wide-bandgap perovskites. Summary of the Invention

[0005] In view of the above, the present invention provides a perovskite solar cell and a method for preparing the same, in order to at least partially solve at least one of the above-mentioned technical problems.

[0006] One aspect of the present invention provides a perovskite solar cell, comprising: a glass substrate; a transparent conductive layer disposed on the glass substrate for collecting photogenerated holes; and a hole transport material layer disposed on the transparent conductive layer for selectively extracting photogenerated holes and modulating interface energy levels, wherein the hole transport material layer comprises a phenylene-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material, wherein the self-assembled monolayer material uses phenylene groups as bridging units, the phenylene groups connecting two substituted benzo[c]carbazole units, the nitrogen atom of each substituted benzo[c]carbazole unit being connected to a substituted phenyl group, the substituted phenyl group being anchored to the transparent conductive layer through a cyanovinylphosphonic acid group to form a stable chemisorption; and a perovskite layer disposed on the hole transport material layer for absorbing photons to generate electron-hole pairs.

[0007] According to embodiments of the present invention, a self-assembled monolayer material is configured to have the following general formula: Ph-BCzPA-R, wherein the substituent R is selected from one of methyl, methoxy, chlorine, bromine, or fluorine; when the substituent R is methyl, the self-assembled monolayer material is a Ph-BCzPA-Me compound; when the substituent R is methoxy, the self-assembled monolayer material is a Ph-BCzPA-MeO compound; when the substituent R is a chlorine atom, the self-assembled monolayer material is a Ph-BCzPA-Cl compound; when the substituent R is a bromine atom, the self-assembled monolayer material is a Ph-BCzPA-Br compound; and when the substituent R is a fluorine atom, the self-assembled monolayer material is a Ph-BCzPA-F compound.

[0008] According to an embodiment of the present invention, the phosphonic acid groups in the hole transport material layer are bonded to the surface of the transparent conductive layer through P–O–M chemical bonds to form a dense self-assembled monolayer, wherein M represents a metal atom in the transparent conductive layer.

[0009] According to an embodiment of the present invention, the core framework of the self-assembled monolayer material constitutes a rigid extended conjugate plane and extends toward the perovskite layer to improve the compatibility of the buried interface and induce perovskite orientation crystallization.

[0010] According to an embodiment of the present invention, the perovskite layer is configured to have an ABX3 crystal structure, and the band gap of the perovskite layer is in the range of 1.50 eV to 1.80 eV; wherein, A is at least one of ammonium methyl ion, formamidine ion, cesium ion and rubidium ion; B is lead, tin or lead-tin mixed metal; and X is one of iodide ion, bromide ion and chloride ion.

[0011] According to an embodiment of the present invention, the perovskite solar cell further includes: an electron transport layer disposed on the perovskite layer for selectively collecting photogenerated electrons while blocking holes; a buffer layer disposed on the electron transport layer for optimizing interface energy level matching and stability; a metal electrode layer disposed on the buffer layer for collecting electrons to form an external circuit closure and provide current output; and an anti-reflection layer disposed on the metal electrode layer for reducing light reflection.

[0012] According to embodiments of the present invention, the material of the electron transport layer includes one of C60, C60 derivatives, SnO2 and PCBM; the material of the buffer layer includes 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline; the material of the metal electrode layer includes one of silver, copper, aluminum or gold; and the material of the antireflection layer includes at least one of lithium fluoride and magnesium fluoride.

[0013] Another aspect of the present invention provides a method for fabricating a perovskite solar cell, comprising: obtaining a glass substrate and forming a transparent conductive layer on the glass substrate; forming a hole transport material layer on the transparent conductive layer, wherein the hole transport material layer comprises the aforementioned benzo[c]carbazole-cyanovinylphosphonic acid-based self-assembled monolayer material; forming a perovskite layer on the hole transport material layer; and sequentially depositing an electron transport layer, a buffer layer, a metal electrode layer, and an antireflection layer on the perovskite layer.

[0014] According to an embodiment of the present invention, forming a hole transport material layer on a transparent conductive layer includes: dissolving a benzo[c]carbazole-cyanovinylphosphonic acid-based self-assembled monolayer material in an organic solvent to obtain a hole transport material solution; depositing the hole transport material solution onto the transparent conductive layer by spin coating, dip coating, blade coating or spray coating; and annealing at 80°C to 150°C for 5 to 30 minutes to form a self-assembled monolayer.

[0015] According to embodiments of the present invention, a method for preparing a benzo[c]carbazole-cyanovinylphosphonic acid-based self-assembled monolayer material comprises: obtaining R-substituted bromobenzo[c]carbazole and 4-fluorobenzaldehyde, and subjecting R-substituted bromobenzo[c]carbazole and 4-fluorobenzaldehyde to an N-arylation reaction to obtain an aldehyde intermediate AR; reacting the aldehyde intermediate AR with diethyl cyanomethylphosphonate in a Horner-Wadsworth-Emmons reaction to obtain a diethyl cyanovinylphosphonate intermediate BR; and reacting the diethyl cyanovinylphosphonate intermediate BR with pinacol 1,4-phenylenediol ester in a Suzuki reaction. A coupling reaction was performed to construct a benzo[c]carbazole-bridged bisbenzo[c]carbazole skeleton, yielding a protected benzo[c]carbazole dimer 2c-R. The protected benzo[c]carbazole dimer 2c-R was reacted with trimethylbromosilane, followed by methanol hydrolysis and purification to obtain the target benzo[c]carbazole-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material Ph-BCzPA-R.

[0016] The perovskite solar cells and their fabrication methods provided in this invention have at least the following beneficial effects:

[0017] (1) The perovskite solar cell and its preparation method provided in the embodiments of the present invention use a benzene-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material as the hole transport material layer, and use phosphonic acid groups as anchoring groups to form stable chemical adsorption with the transparent conductive layer to construct an ultrathin, stable hole transport material layer without dopants, thereby reducing the stability problems caused by the moisture absorption and migration of dopants in traditional doped hole transport materials.

[0018] (2) The perovskite solar cell and its preparation method provided in the embodiments of the present invention introduce different substituents R, including Me, MeO, Cl, Br or F, on the benzo[c]carbazole core, and use the electron-donating or electron-withdrawing effect of the substituents to precisely control the highest occupied molecular orbital energy level, so as to achieve a good match with the top of the perovskite valence band and suppress the accumulation of interfacial charge.

[0019] (3) The perovskite solar cell and its preparation method provided in the embodiments of the present invention use benzene-bridged bisbenzo[c]carbazole as the hole transport framework. Its extended rigid conjugated structure helps to improve the hole transport capability and can regulate the properties of the buried interface through molecular polarization, thereby promoting the orderly accumulation of molecules on the surface of the transparent conductive layer.

[0020] (4) The perovskite solar cell and its preparation method provided in the embodiments of the present invention introduce a cyanovinylphosphonic acid structure. The cyano and phosphonic acid groups can synergistically regulate the interface dipole and energy level arrangement, which is beneficial to reduce the hole extraction barrier, suppress non-radiative recombination at the interface and improve the photoelectric conversion efficiency.

[0021] (5) The perovskite solar cell and its preparation method provided in the embodiments of the present invention have extremely thin self-assembled monolayers, which can reduce parasitic light absorption and series resistance. In addition, the Suzuki coupling route has relatively mild conditions, readily available raw materials, and adjustable structure, which is beneficial to improving the photoelectric conversion efficiency and long-term operational stability of the perovskite solar cell. Attached Figure Description

[0022] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0023] Figure 1 A schematic diagram of a perovskite solar cell according to an embodiment of the present invention is shown.

[0024] Figure 2 A flowchart illustrating a method for fabricating a perovskite solar cell according to an embodiment of the present invention is shown schematically.

[0025] Figure 3 The flowchart illustrates a method for preparing a benzo[c]carbazole-cyanovinylphosphonic acid-based self-assembled monolayer material according to an embodiment of the present invention.

[0026] Figure label:

[0027] 1-Glass substrate; 2-Transparent conductive layer; 3-Hole transport material layer; 4-Perovskite layer; 5-Electron transport layer; 6-Buffer layer; 7-Metal electrode layer; 8-Antireflection layer. Detailed Implementation

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0031] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0032] In the embodiments of this invention, the collection, updating, analysis, processing, use, transmission, provision, disclosure, and storage of data (e.g., including but not limited to user personal information) comply with relevant laws and regulations, are used for legitimate purposes, and do not violate public order and good morals. In particular, necessary measures have been taken to prevent unauthorized access to user personal information data and to maintain the security of user personal information and network security.

[0033] Benzo[c]carbazole possesses a rigid fused-ring structure, strong hole transport capability, and excellent electron donor properties. Bridging two benzo[c]carbazole units with a benzene strut can significantly extend the molecular π-conjugated system, improving molecular rigidity and charge delocalization ability. Introducing different substituents R into the benzo[c]carbazole skeleton can adjust the highest occupied molecular orbital energy level, interfacial dipole, molecular stacking, and wettability. Combining a para-phenyl linker with a cyanovinylphosphonic acid anchoring unit can construct novel self-assembled monolayer materials with strong interfacial dipoles, high chemical stability, and excellent nucleation induction capabilities.

[0034] Based on this concept, embodiments of the present invention provide a perovskite solar cell based on benzo[c]carbazole-cyanovinylphosphonic acid material.

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0036] Figure 1 A schematic diagram of a perovskite solar cell according to an embodiment of the present invention is shown.

[0037] like Figure 1 As shown, the structure of this perovskite solar cell may include, for example, a glass substrate 1, a transparent conductive layer 2, a hole transport material layer 3, and a perovskite layer 4.

[0038] The glass substrate 1 is used to provide mechanical support.

[0039] For example, in this embodiment, the glass substrate 1 can be disposed at the bottom layer to provide a flat and stable support for the battery, while allowing visible light to pass through and enter the light-absorbing layer (such as the perovskite layer 4) to ensure the photoelectric conversion efficiency of the device.

[0040] A transparent conductive layer 2 is disposed on the glass substrate 1 and is used to collect photogenerated holes.

[0041] For example, in this embodiment, the transparent conductive layer 2 can be stacked on the glass substrate 1, allowing visible light to penetrate to the perovskite layer 4, while simultaneously acting as an electrode to collect holes extracted from the hole transport material layer 3. The transparent conductive layer 2 can be fluorine-doped tin oxide (FTO) or indium tin oxide (ITO), and its thickness can be from 80 nm to 300 nm.

[0042] Hole transport material layer 3 is disposed on transparent conductive layer 2 and is used to selectively extract photogenerated holes and modulate the interface energy level. The material of hole transport material layer 3 includes phenylene-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material. The self-assembled monolayer material uses phenylene groups as bridging units, and the phenylene groups connect two substituted benzo[c]carbazole units. The nitrogen atom of each substituted benzo[c]carbazole unit is connected to a substituted phenyl group. The substituted phenyl group is anchored to the transparent conductive layer through the cyanovinylphosphonic acid group to form a stable chemisorption.

[0043] For example, in this embodiment, the hole transport material layer 3 comprises a benzo[c]carbazole-cyanovinylphosphonic acid self-assembled monolayer material, the core molecular framework of which is composed of two benzo[c]carbazole units connected by benzo[c]carbazole units, wherein the nitrogen atom of each benzo[c]carbazole unit is connected to a para-substituted phenyl group, and the para-position of the phenyl group is connected to a phosphonic acid anchoring group through a cyanovinyl group.

[0044] The coupling site on the benzo[c]carbazole unit is connected to the benzo[c] bridging unit, and another aromatic ring site is connected to a substituent.

[0045] The substituent is used to regulate the highest occupied molecular orbital energy level, interfacial dipole, molecular stacking and surface wettability of the molecule. The cyanovinyl structure is used to construct interfacial dipoles, enhance hole extraction and suppress interfacial nonradiative recombination.

[0046] The perovskite layer 4 is disposed on the hole transport material layer 3 and is used to absorb photons to generate electron-hole pairs.

[0047] For example, in this embodiment, the perovskite layer 4 serves as the light-absorbing layer of the battery, responsible for absorbing incident photons and generating photogenerated electron-hole pairs.

[0048] The perovskite solar cell provided in this invention uses a phenyl-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material as the hole transport material layer. The phosphonic acid group is used as an anchoring group to form a stable chemical adsorption with the transparent conductive layer, thereby constructing an ultrathin, stable hole transport material layer without dopants. This reduces the stability problems caused by dopant hygroscopicity and migration in traditional doped hole transport materials.

[0049] According to embodiments of the present invention, a self-assembled monolayer material (referring to a benzene-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material) is configured to have the following general formula:

[0050] Ph-BCzPA-R

[0051] The substituent R is selected from one of methyl, methoxy, chlorine, bromine or fluorine.

[0052] When the substituent R is methyl, the self-assembled monolayer material is a Ph-BCzPA-Me compound; when the substituent R is methoxy, the self-assembled monolayer material is a Ph-BCzPA-MeO compound; when the substituent R is a chlorine atom, the self-assembled monolayer material is a Ph-BCzPA-Cl compound; when the substituent R is a bromine atom, the self-assembled monolayer material is a Ph-BCzPA-Br compound; and when the substituent R is a fluorine atom, the self-assembled monolayer material is a Ph-BCzPA-F compound.

[0053] For example, in this embodiment, the substituent R can be selected from any one of methyl (Me), methoxy (MeO), chlorine (Cl), bromine (Br), or fluorine (F), which means that the self-assembled monolayer material can include at least one of the following compounds:

[0054] Ph-BCzPA-Me, where R is a methyl group.

[0055] Ph-BCzPA-MeO, where R is a methoxy group.

[0056] Ph-BCzPA-Cl, where R is a chlorine atom.

[0057] Ph-BCzPA-Br, where R is a bromine atom.

[0058] Ph-BCzPA-F, where R is a fluorine atom.

[0059] The perovskite solar cell provided in this invention introduces different substituents R, including Me, MeO, Cl, Br or F, onto the benzo[c]carbazole core. By utilizing the electron-donating or electron-withdrawing effects of the substituents, the energy level of the highest occupied molecular orbital is precisely controlled, achieving a good match with the top of the perovskite valence band and suppressing the accumulation of interfacial charge.

[0060] According to an embodiment of the present invention, the phosphonic acid groups in the hole transport material layer 3 are bonded to the surface of the transparent conductive layer through P–O–M chemical bonds to form a dense self-assembled monolayer, wherein M represents a metal atom in the transparent conductive layer.

[0061] According to an embodiment of the present invention, the core framework of the self-assembled monolayer material forms a rigid extended conjugate plane that extends toward the perovskite layer to improve the compatibility of the buried interface and induce perovskite orientation crystallization.

[0062] For example, in this embodiment, the benzo[c]carbazole core and phenyl linking group are oriented towards the side of the perovskite layer 4, which is beneficial to improving the wetting and nucleation behavior of the perovskite precursor at the bottom interface.

[0063] The perovskite solar cell provided in this embodiment of the invention uses benzene-bridged bisbenzo[c]carbazole as the hole transport framework. Its extended rigid conjugated structure helps to improve the hole transport capability and can regulate the properties of the buried interface through molecular polarization, promoting the orderly accumulation of molecules on the surface of the transparent conductive layer.

[0064] In this embodiment, the cyanovinyl structure has strong dipole characteristics and can be used to adjust the interfacial dipole and energy level arrangement.

[0065] The perovskite solar cell provided in this invention introduces a cyanovinylphosphonic acid structure. The cyano and phosphonic acid groups can synergistically regulate the interfacial dipole and energy level arrangement, which is beneficial for reducing the hole extraction barrier, suppressing interfacial nonradiative recombination, and improving photoelectric conversion efficiency.

[0066] According to an embodiment of the present invention, the perovskite layer 4 is configured to have an ABX3 crystal structure, and the band gap of the perovskite layer is in the range of 1.50 eV to 1.80 eV.

[0067] Wherein, A is at least one of methylammonium ion, formamidinium ion, cesium ion and rubidium ion (for example, A can be methylammonium ion, formamidinium ion, cesium ion, rubidium ion or a mixture thereof); B is lead, tin or a lead-tin mixture metal; X is one of iodide ion, bromide ion and chloride ion.

[0068] In this embodiment, the thickness of the perovskite layer 4 can be from 300 nm to 1000 nm.

[0069] According to an embodiment of the present invention, the structure of the perovskite solar cell may further include, for example, an electron transport layer 5, a buffer layer 6, a metal electrode layer 7, and an antireflection layer 8.

[0070] The electron transport layer 5 is disposed on the perovskite layer 4 and is used to selectively collect photogenerated electrons while blocking holes.

[0071] In this embodiment, the electron transport layer 5 is made of one of C60, C60 derivatives, SnO2, and PCBM. The thickness of the electron transport layer 5 is 10 nm to 50 nm.

[0072] The buffer layer 6 is disposed on the electron transport layer 5 and is used to optimize the interface energy level matching and stability between the electron transport layer 5 and the metal electrode layer 7.

[0073] In this embodiment, the material of the buffer layer 6 includes 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline (BCP). The thickness of the buffer layer 6 is 2 nm to 15 nm.

[0074] The metal electrode layer 7 is disposed on the buffer layer 6 and is used to collect electrons to form an external circuit closure and provide current output.

[0075] In this embodiment, the material of the metal electrode layer 7 includes one of silver, copper, aluminum, or gold. The thickness of the metal electrode layer 7 is 50 nm to 200 nm.

[0076] An antireflection layer 8 is disposed on the metal electrode layer 7 to reduce light reflection.

[0077] In this embodiment, the antireflective layer 8 is made of at least one of lithium fluoride and magnesium fluoride (e.g., lithium fluoride, magnesium fluoride, or a combination thereof). The thickness of the antireflective layer 8 is from 0.5 nm to 10 nm.

[0078] This invention also provides a method for preparing perovskite solar cells based on benzo[c]carbazole-cyanovinylphosphonic acid material.

[0079] Figure 2 A flowchart illustrating a method for fabricating a perovskite solar cell according to an embodiment of the present invention is shown.

[0080] like Figure 2 As shown, the method for preparing this perovskite solar cell may include steps S210-S240, for example.

[0081] S210, obtain a glass substrate 1 and form a transparent conductive layer 2 on the glass substrate.

[0082] For example, in this embodiment, a glass substrate 1 can be provided first, and a transparent conductive layer 2 can be formed on the glass substrate 1. The transparent conductive layer 2 can be obtained by magnetron sputtering, chemical vapor deposition, sol-gel method, or by directly using commercially available transparent conductive glass, and the thickness is preferably 80 nm to 300 nm. Before deposition, the surface of the transparent conductive layer 2 can be treated with ultraviolet ozone or oxygen plasma to improve the surface hydroxyl density and wettability.

[0083] S220, a hole transport material layer 3 is formed on the transparent conductive layer 2, wherein the hole transport material layer 3 includes the above-mentioned benzo-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material.

[0084] In this embodiment, a hole transport material layer 3 is formed on the transparent conductive layer 2, which may specifically include:

[0085] A hole transport material solution was obtained by dissolving a benzo[c]carbazole-cyanovinylphosphonic acid-based self-assembled monolayer material in an organic solvent. The hole transport material solution was then deposited onto a transparent conductive layer by spin coating, dip coating, blade coating, or spray coating. The self-assembled monolayer was then annealed at 80°C to 150°C for 5 to 30 minutes.

[0086] For example, in this embodiment, a self-assembled monolayer material Ph-BCzPA-R (R being Me, MeO, Cl, Br, or F) of benzo[c]carbazole-cyanovinylphosphonic acid can be dissolved in anhydrous ethanol, isopropanol, chlorobenzene, toluene, or N,N-dimethylformamide or a mixture thereof to prepare a deposition solution with a concentration of 0.1 mg / mL to 5.0 mg / mL. Subsequently, the deposition solution is uniformly coated onto the surface of the transparent conductive layer 2 by spin coating, dip coating, blade coating, or spray coating. After coating, the layer is annealed at 80°C to 150°C for 5 to 30 minutes to promote the formation of dense P–O–M chemical adsorption bonds between the phosphonic acid groups and the surface of the transparent conductive oxide, thus self-assembling into an ordered monolayer with a thickness of 0.5 nm to 10 nm.

[0087] S230, a perovskite layer 4 is formed on the hole transport material layer 3.

[0088] For example, in this embodiment, a one-step anti-solvent method, a two-step sequential method, or a vacuum evaporation method can be used to deposit a perovskite precursor solution onto the surface of SAMs. Subsequently, the perovskite precursor is annealed at 80°C to 150°C for 5 to 30 minutes to induce the perovskite precursor to nucleate and grow epitaxially on the molecular template, forming a dense, large-grained perovskite polycrystalline thin film with a thickness of 300 nm to 1000 nm.

[0089] S240, an electron transport layer 5, a buffer layer 6, a metal electrode layer 7, and an antireflection layer 8 are sequentially deposited on the perovskite layer 4.

[0090] For example, in this embodiment, a vacuum level better than 5×10⁻⁶ can be used. -4 In the cavity of Pa, C60 is deposited sequentially as an electron transport layer 5 with a thickness of 10 nm to 50 nm by vacuum thermal evaporation; BCP is deposited as a buffer layer 6 with a thickness of 2 nm to 15 nm; Ag, Cu, Al or Au is deposited as a metal electrode layer 7 with a thickness of 50 nm to 200 nm; and LiF or MgF2 is deposited as an antireflection layer 8 with a thickness of 0.5 nm to 10 nm.

[0091] According to embodiments of the present invention, a method for preparing the benzo[c]carbazole-based bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material is also provided, as detailed in the following figures. Figure 3 As shown.

[0092] Figure 3 The flowchart illustrates a method for preparing a benzo[c]carbazole-cyanovinylphosphonic acid-based self-assembled monolayer material according to an embodiment of the present invention.

[0093] like Figure 3 As shown, the preparation method of the benzo[c]carbazole-cyanovinylphosphonic acid self-assembled monolayer material may include, for example, steps S310-S340.

[0094] S310, obtain R-substituted bromobenzo[c]carbazole and 4-fluorobenzaldehyde, and then subject R-substituted bromobenzo[c]carbazole and 4-fluorobenzaldehyde to N-arylation reaction to obtain aldehyde intermediate AR.

[0095] For example, in this embodiment, N-arylation is first performed: that is, R-substituted bromobenzo[c]carbazole is reacted with 4-fluorobenzaldehyde under alkaline conditions and in a polar solvent at 100°C to 120°C to obtain the aldehyde intermediate AR.

[0096] S320, the aldehyde intermediate AR is reacted with diethyl cyanomethylphosphonate via a Horner-Wadsworth-Emmons reaction to obtain diethyl cyanovinylphosphonate intermediate BR.

[0097] For example, in this embodiment, the Horner-Wadsworth-Emmons reaction is carried out again: that is, the aldehyde intermediate AR obtained in the previous step is reacted with diethyl cyanomethylphosphonate under alkaline conditions in THF to obtain diethyl cyanovinylphosphonate intermediate BR.

[0098] S330, the intermediate BR of cyanovinylphosphonate was subjected to a Suzuki coupling reaction with pinacol 1,4-benzyl diboronic acid to construct a benzo[c]carbazole skeleton and obtain the protected benzo[c]carbazole dimer 2c-R.

[0099] For example, in this embodiment, Suzuki coupling is further performed: that is, the diethyl cyanovinylphosphonate intermediate BR obtained in the previous step is reacted with pinacol ester of 1,4-phenyldiboronic acid under palladium catalyst and alkaline conditions in toluene or toluene / water mixed solvent to construct a benzo[c]carbazole skeleton and obtain the protected benzo[c]carbazole dimer 2c-R.

[0100] S340, the protected benzo[c]carbazole-bridged dimer 2c-R was reacted with bromotrimethylsilane, followed by methanol hydrolysis and purification to obtain the target benzo[c]carbazole-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material Ph-BCzPA-R.

[0101] For example, in this embodiment, the final step is to perform deprotection and hydrolysis: that is, after deprotection and hydrolysis of the protected benzo[c]carbazole dimer 2c-R obtained in the previous step, the target benzo[c]carbazole bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material Ph-BCzPA-R is finally obtained.

[0102] In this embodiment, a four-step core route of "phosphonate coupling followed by deprotection hydrolysis" was adopted to prepare Ph-BCzPA-R. This route can avoid the coordination interference of free phosphonate groups on the palladium-catalyzed Suzuki coupling system, thereby improving the dimer construction efficiency, reaction selectivity, and final product purity.

[0103] The following will provide a more detailed explanation of these four core steps:

[0104] (1) Preparation of aldehyde intermediate AR by N-arylation reaction:

[0105] R-substituted bromobenzo[c]carbazole, 4-fluorobenzaldehyde, an inorganic base, and a polar solvent were added to a dry reaction flask and the reaction was stirred under nitrogen or argon protection.

[0106] The inorganic base can be K2CO3 or Cs2CO3, and the polar solvent can be anhydrous DMF or DMSO. The reaction temperature is 100℃ to 120℃, and the reaction time is 12 hours to 24 hours.

[0107] After the reaction was completed, the mixture was cooled to room temperature, quenched in deionized water, and extracted with dichloromethane or ethyl acetate. The organic phase was dried over anhydrous Na2SO4, concentrated under reduced pressure, and then purified by silica gel column chromatography to obtain the 4-formylphenyl-substituted benzo[c]carbazole aldehyde intermediate AR, wherein R is methyl, methoxy, chlorine, bromine, or fluorine.

[0108] (2) Preparation of phosphonate intermediate BR by Horner-Wadsworth-Emmons reaction:

[0109] Intermediate AR was dissolved in anhydrous THF, and sodium hydride was added in portions under an inert atmosphere, followed by dropwise addition of diethylcyanomethylphosphonate. The reaction system was stirred at room temperature to 65°C for 6 to 24 hours to allow the aldehyde group to react with diethylcyanomethylphosphonate to form diethyl cyanovinylphosphonate intermediate BR.

[0110] After the reaction was completed, the mixture was quenched with saturated NH4Cl solution, extracted with ethyl acetate or dichloromethane, and the organic phase was dried, concentrated, and purified by column chromatography to obtain the intermediate BR containing the following structural units:

[0111] Ar–CH=C(CN)–P(O)(OEt)2

[0112] This intermediate is a protected phosphonate ester structure, suitable for direct use in subsequent Suzuki coupling reactions.

[0113] (3) Construction of the 2c-R benzene-bridged dimer framework by Suzuki coupling reaction:

[0114] Intermediate BR and pinacol ester of 1,4-phenyldiborate were added to a dry reaction flask in stoichiometric ratio. A palladium catalyst and a base were then added, along with toluene or a toluene / water mixture. The palladium catalyst could be Pd(PPh3)4, Pd2(dba)3, or Pd(dppf)Cl2; the base could be K2CO3, Cs2CO3, or Na2CO3.

[0115] Under nitrogen or argon protection, the reaction system was heated to 100°C to 120°C and reacted for 12 to 24 hours. After cooling, the reaction solution was filtered through diatomaceous earth to remove palladium black and inorganic salts. The filtrate was concentrated under reduced pressure and purified by silica gel column chromatography, recrystallization, or precipitation to obtain the benzo[c]carbazole phosphonate diethyl ester dimer intermediate 2c-R.

[0116] In this step, two R-substituted benzo[c]carbazole units are connected by a central benzo[c]carbazole bridging unit to form a benzo[c]carbazole conjugated framework for the target material.

[0117] (4) Preparation of the target product Ph-BCzPA-R by TMSBr deprotection and hydrolysis:

[0118] Intermediate 2c-R was dissolved in anhydrous dichloromethane or 1,4-dioxane, and trimethylbromosilane was slowly added dropwise at room temperature for 12 to 24 hours to remove the ethyl protecting group from the phosphonate. Subsequently, anhydrous methanol was slowly added to hydrolyze the silanized intermediate for 30 to 60 minutes.

[0119] After the reaction was completed, the solvent was removed by vacuum evaporation. The residue was repeatedly washed with water, ether or methanol, filtered, and dried under vacuum at 40°C to 60°C to obtain the target benzo[c]carbazole-cyanovinylphosphonic acid self-assembled monolayer material Ph-BCzPA-R.

[0120] When R is a methyl group, we get Ph-BCzPA-Me:

[0121]

[0122] When R is a methoxy group, Ph-BCzPA-MeO is obtained:

[0123]

[0124] When R is chlorine, we get Ph-BCzPA-Cl:

[0125]

[0126] When R is bromine, we get Ph-BCzPA-Br:

[0127]

[0128] When R is fluorine, we get Ph-BCzPA-F:

[0129]

[0130] To make the objectives, technical solutions, and advantages of the present invention clearer, the preparation (synthesis) method of Ph-BCzPA-R of the present invention will be further described in detail below with reference to two specific embodiments (Example 1 and Example 2).

[0131] Example 1, Preparation of Ph-BCzPA-Cl:

[0132] Taking R=Cl as an example, chloro-substituted bromobenzo[c]carbazole was used as the starting material and reacted with 4-fluorobenzaldehyde in a K2CO3 / DMF system at 120℃ to prepare the aldehyde intermediate A-Cl. Subsequently, intermediate A-Cl reacted with diethyl cyanomethylphosphonate under NaH / THF conditions to obtain diethyl cyanovinylphosphonate intermediate B-Cl. Then, B-Cl reacted with pinacol ester of 1,4-phenyldiboronic acid in a Pd(PPh3)4 / K2CO3 / toluene system at 120℃ to construct a benzene-bridged bisbenzo[c]carbazole skeleton, yielding the protected dimer 2c-Cl. Finally, 2c-Cl was deprotected by TMSBr and hydrolyzed with methanol, and after washing, filtration, and vacuum drying, the target product Ph-BCzPA-Cl was obtained.

[0133] Example 2: General preparation of a series of substituent derivatives:

[0134] Using the same synthesis strategy as in Example 1, Ph-BCzPA-Me, Ph-BCzPA-MeO, Ph-BCzPA-Br and Ph-BCzPA-F can be prepared by simply replacing the R-substituted bromobenzo[c]carbazole starting material in step 1.

[0135] When R is a methyl group, Ph-BCzPA-Me is obtained.

[0136] When R is a methoxy group, Ph-BCzPA-MeO is obtained.

[0137] When R is bromine, Ph-BCzPA-Br is obtained.

[0138] When R is fluorine, Ph-BCzPA-F is obtained.

[0139] The above synthetic route features mild conditions, clear steps, and tunable structure. The obtained Ph-BCzPA-R molecule can be confirmed in structure and purity by 1H NMR spectroscopy, 1P NMR spectroscopy, mass spectrometry, elemental analysis, and high-performance liquid chromatography (HPLC). This material meets the application requirements of self-assembled monolayer hole transport materials in perovskite solar cells. Those skilled in the art can perform conventional optimizations on the solvent system, reaction temperature, catalyst type, catalyst dosage, feed ratio, and purification method without departing from the spirit of this invention; all such optimizations should fall within the scope of protection of this invention.

[0140] The perovskite solar cell fabrication method provided in this invention produces a self-assembled monolayer with an extremely thin thickness, which can reduce parasitic light absorption and series resistance. Furthermore, the Suzuki coupling route has relatively mild conditions, readily available raw materials, and a tunable structure, which is beneficial for improving the photoelectric conversion efficiency and long-term operational stability of perovskite solar cells.

[0141] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A perovskite solar cell, characterized in that, include: Glass substrate; A transparent conductive layer is disposed on the glass substrate for collecting photogenerated holes; A hole transport material layer, disposed on the transparent conductive layer, is used to selectively extract the photogenerated holes and modulate the interface energy level. The hole transport material layer comprises a phenylene-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material. The self-assembled monolayer material uses phenylene groups as bridging units, and the phenylene groups connect two substituted benzo[c]carbazole units. The nitrogen atom of each substituted benzo[c]carbazole unit is connected to a substituted phenyl group. The substituted phenyl group is anchored to the transparent conductive layer through the cyanovinylphosphonic acid group to form a stable chemisorption. A perovskite layer, disposed on the hole transport material layer, is used to absorb photons and generate electron-hole pairs.

2. The perovskite solar cell according to claim 1, characterized in that, The self-assembled monolayer material is configured to have the following general formula: Ph-BCzPA-R Wherein, the substituent R is selected from one of methyl, methoxy, chlorine, bromine or fluorine; When the substituent R is methyl, the self-assembled monolayer material is a Ph-BCzPA-Me compound; When the substituent R is methoxy, the self-assembled monolayer material is a Ph-BCzPA-MeO compound; When the substituent R is a chlorine atom, the self-assembled monolayer material is a Ph-BCzPA-Cl compound; When the substituent R is a bromine atom, the self-assembled monolayer material is a Ph-BCzPA-Br compound; When the substituent R is a fluorine atom, the self-assembled monolayer material is a Ph-BCzPA-F compound.

3. The perovskite solar cell according to claim 1, characterized in that, The phosphonic acid groups in the hole transport material layer are bonded to the surface of the transparent conductive layer through P–O–M chemical bonds to form a dense self-assembled monolayer, wherein M represents a metal atom in the transparent conductive layer.

4. The perovskite solar cell according to claim 1, characterized in that, The core framework of the self-assembled monolayer material forms a rigid extended conjugate plane that extends toward the perovskite layer to improve the compatibility of the buried interface and induce perovskite orientation crystallization.

5. The perovskite solar cell according to claim 4, characterized in that, The perovskite layer is configured to have an ABX3 crystal structure, and the band gap of the perovskite layer is in the range of 1.50 eV to 1.80 eV; Wherein, A is at least one of methylammonium ion, formamidine ion, cesium ion and rubidium ion; B is lead, tin or a lead-tin mixture metal; X is one of iodide ion, bromide ion and chloride ion.

6. The perovskite solar cell according to claim 1, characterized in that, Also includes: An electron transport layer, disposed on the perovskite layer, is used to selectively collect photogenerated electrons while blocking holes; A buffer layer, disposed on the electron transport layer, is used to optimize interface energy level matching and stability; A metal electrode layer is disposed on the buffer layer to collect electrons to form an external circuit closure and provide current output; An antireflection layer is disposed on the metal electrode layer to reduce light reflection.

7. The perovskite solar cell according to claim 6, characterized in that, The electron transport layer is made of one of C60, C60 derivatives, SnO2, and PCBM. The material of the buffer layer includes 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline; The material of the metal electrode layer includes one of silver, copper, aluminum or gold; The antireflective layer is made of at least one of lithium fluoride and magnesium fluoride.

8. A method for fabricating a perovskite solar cell, characterized in that, include: Obtain a glass substrate and form a transparent conductive layer on the glass substrate; A hole transport material layer is formed on the transparent conductive layer, wherein the hole transport material layer comprises a benzo-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material as described in any one of claims 1 to 7; A perovskite layer is formed on the hole transport material layer; An electron transport layer, a buffer layer, a metal electrode layer, and an antireflection layer are sequentially deposited on the perovskite layer.

9. The method for preparing a perovskite solar cell according to claim 8, characterized in that, The formation of a hole transport material layer on the transparent conductive layer includes: The benzo-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material was dissolved in an organic solvent to obtain a hole transport material solution; The hole transport material solution is deposited onto the transparent conductive layer by spin coating, dip coating, blade coating or spray coating. Annealing at 80°C to 150°C for 5 to 30 minutes forms a self-assembled monolayer.

10. The method for preparing a perovskite solar cell according to claim 8, characterized in that, The preparation method of the benzo[c]carbazole-cyanovinylphosphonic acid-based self-assembled monolayer material includes: R-substituted bromobenzo[c]carbazole and 4-fluorobenzaldehyde were obtained, and the R-substituted bromobenzo[c]carbazole and 4-fluorobenzaldehyde were subjected to N-arylation reaction to obtain aldehyde intermediate AR. The aldehyde intermediate AR was reacted with diethyl cyanomethylphosphonate via a Horner-Wadsworth-Emmons reaction to obtain diethyl cyanovinylphosphonate intermediate BR. The diethyl cyanovinylphosphonate intermediate BR was subjected to a Suzuki coupling reaction with pinacol 1,4-benzyl diboronic acid to construct a benzo[c]carbazole skeleton, thereby obtaining the protected benzo[c]carbazole dimer 2c-R. The protected benzo-bridged dimer 2c-R was reacted with trimethylbromosilane, followed by methanol hydrolysis and purification to obtain the target benzo-bridged bis(R-substituted benzo[c]carbazole)-cyanovinylphosphonic acid self-assembled monolayer material Ph-BCzPA-R.

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