Self-assembled single-layer perovskite solar cell and preparation method thereof

Abstract

The invention belongs to the field of solar cells, and particularly discloses a self-assembled single-layer perovskite solar cell and a preparation method thereof. The self-assembled monolayer of the present invention comprises a first self-assembled monolayer molecule which is a compound of formula I and a second self-assembled monolayer molecule which is a compound of formula II wherein i, n, m, p, q, R1-R5 are as defined herein. When the self-assembled monolayer is used as a hole transport layer in a perovskite solar cell, effective electron / charge delocalization can be realized, charge transfer can be improved, energy level matching can be realized, hole transport capability can be improved, and stability and efficiency of a cell assembly can be improved. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the field of solar cells, and in particular relates to a self-assembled monolayer perovskite solar cell and a preparation method thereof. Background Art

[0002] Perovskite solar cells (PSCs) are considered to be strong competitors for thin-film solar cells due to their excellent optoelectronic performance and low manufacturing cost. According to the deposition order of the functional layers, PSCs can be divided into two main types: standard structure (sequential deposition of electron transport layer (ETL) / perovskite (PVK) / hole transport layer (HTL)) and inverted structure (sequential deposition of hole transport layer (HTL) / perovskite (PVK) / electron transport layer (ETL)). At present, the power conversion efficiency (PCE) certification rate of both inverted and formal structure PSCs exceeds 25%. In this field, device stability, manufacturing cost and convenience of manufacturing process have become the focus of research. Compared with formal structure cells, inverted structure PSCs show better stability, lower manufacturing cost and broader application prospects. They can even be combined with traditional solar cells to form a series structure to improve the overall performance.

[0003] In contrast to the classic and widely used HTLs, self-assembled monolayers (SAMs) have emerged as HTLs and have recently shown promising applications in high-performance single-junction and multi-junction PSCs. SAM molecules include [4-(3,6-dimethyl-9h-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz), [2-(9h-carbazol-9-yl)ethyl]phosphonic acid (2PACz), and [2-(3,6-dimethoxy-9h-carbazol-9-yl)ethyl]phosphonic acid (MeO-2PACz). HTLs prepared using SAMs not only exhibit negligible parasitic absorption, low material consumption, and stable adhesion, but also possess an inherent passivation effect on the underlying defects of PVKs. Unfortunately, similar to the aggregation behavior of molecules, solution-prepared SAMs on substrates are prone to aggregation and poor uniformity, resulting in severe energy loss at the SAM / PVK interface and insufficient charge extraction. The poor hydrophilicity of SAMs is also an obstacle to the preparation of high-performance and high-yield PSCs, especially when Me-4PACz and 2PACz are used as HTLs. Furthermore, it is worth noting that the unevenness of the SAM-based bottom interface region makes the device susceptible to external factors and accelerates the degradation of device performance, which is mainly due to the presence of a large number of defect sites and unsatisfactory morphology at the bottom of the PVK film with a low crystallization barrier.

[0004] Recently, Park et al. found that introducing 3-mercaptopropionic acid (3-MPA) into SAMs (2PACz) effectively inhibited the aggregation of 2PACz molecules, resulting in a more uniform HTL and a certified PCE of 24.8% for inverted PSCs. Furthermore, Al-Ashouri et al. achieved promising results by using a hybrid Me-4PACz (with 1,6-hexanediphosphonic acid as an additive) as an HTL to enhance the hydrophilicity of the SAM. Jiang et al. found that the HTL prepared using the hybrid material (i.e., MeO-2PACz + Me-4PACz) exhibited excellent hydrophilicity and good interfacial stability, thereby achieving excellent and stable inverted PSCs. However, SAM molecules using alkyl chain-linked carbazoles generally suffer from poor stability due to electron / charge localization, which affects the stability of the cell device. Furthermore, the application of carbazole-based SAMs in perovskite solar cells is hindered by poor surface wettability with the perovskite precursor solution, which limits their application in certain perovskite solar cells. Summary of the Invention

[0005] In response to the above-mentioned problems existing in the prior art, the present invention proposes a hybrid self-assembled monomolecular material to improve its interface stability and photoelectric properties, thereby improving the performance and stability of perovskite solar cells, and providing a new solution for the preparation of large-area commercial perovskite solar cells.

[0006] Specifically, one aspect of the present invention provides a self-assembled monolayer comprising a first self-assembled monolayer molecule and a second self-assembled monolayer molecule;

[0007] The first self-assembled monolayer molecule is a compound of formula I:

[0008]

[0009] In Formula I, R1 is selected from a hydrogen atom, a C1-C4 alkyl group, and a C1-C4 alkoxy group, each R2 is independently selected from a C1-C4 alkyl group and a C1-C4 alkoxy group, n is 0, 1, 2, 3, 4, or 5, each R3 is independently selected from a C1-C4 alkyl group and a C1-C4 alkoxy group, and m is 0, 1, 2, 3, 4, or 5;

[0010] The second self-assembled monolayer molecule is a compound of formula II:

[0011]

[0012] In formula II, each R4 is independently selected from C1-C4 alkyl and C1-C4 alkoxy, p is 0, 1, 2, 3 or 4, each R5 is independently selected from C1-C4 alkyl and C1-C4 alkoxy, q is 0, 1, 2, 3 or 4, and i is 1, 2, 3, 4, 5 or 6.

[0013] In one or more embodiments, the mass fraction of the first self-assembled monolayer molecules in the self-assembled monolayer is 40%-70%.

[0014] In one or more embodiments, the mass fraction of the second self-assembled monolayer molecules in the self-assembled monolayer is 30%-60%.

[0015] In one or more embodiments, the molar ratio of the first self-assembled monolayer molecules to the second self-assembled monolayer molecules is 1:2-3:1.

[0016] In one or more embodiments, the first self-assembled monolayer molecule is (4-(3,6-bis(2,4-dimethoxyphenyl)-9H-carbazole-9-yl)phenyl)phosphonic acid, and the second self-assembled monolayer molecule is selected from [2-(9H-carbazole-9-yl)ethyl]phosphonic acid, [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid or [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid.

[0017] In one or more embodiments, the self-assembled monolayer has a thickness of 2-5 nm.

[0018] Another aspect of the present invention provides a method for preparing the self-assembled monolayer described in any embodiment of the present invention, the method comprising dispersing the first self-assembled monolayer molecules and the second self-assembled monolayer molecules in a solvent to obtain a self-assembled monolayer solution, coating the self-assembled monolayer solution, and then annealing to obtain a self-assembled monolayer.

[0019] In one or more embodiments, in the self-assembled monolayer solution, the mass of the first self-assembled monolayer molecules is 0.25-0.4 mg per milliliter of solvent.

[0020] In one or more embodiments, in the self-assembled monolayer solution, the mass of the second self-assembled monolayer molecules is 0.1-0.25 mg per milliliter of solvent.

[0021] In one or more embodiments, the solvent is one or both selected from ethanol and isopropanol.

[0022] In one or more embodiments, the coating is one or more selected from spin coating, knife coating, spray coating, spray pyrolysis, and slot coating.

[0023] In one or more embodiments, the annealing temperature is 90-120°C.

[0024] In one or more embodiments, the annealing time is 15-30 minutes.

[0025] Another aspect of the present invention provides a self-assembled monolayer prepared by the method described in any embodiment of the present invention.

[0026] Another aspect of the present invention further provides a perovskite solar cell comprising the self-assembled monolayer described in any embodiment of the present invention, wherein the self-assembled monolayer serves as a hole transport layer in the perovskite solar cell.

[0027] In one or more embodiments, the perovskite solar cell comprises a conductive substrate, a hole transport layer, a perovskite light absorbing layer, an electron transport layer and a back electrode in sequence.

[0028] 1. In the hybrid self-assembled monomolecular material of the present invention, the conjugated structure of the benzene ring can effectively achieve electron / charge delocalization and enhance the intrinsic stability of the molecule. This improvement in stability is crucial for the long-term operation of the device.

[0029] 2. The conjugated structure of self-assembled single molecules helps to improve the hole transport ability, which is crucial to improving the performance of perovskite solar cells.

[0030] 3. The hole transport layer prepared by self-assembled monomolecules containing benzene substituents exhibits better conductivity and hydrophilicity, which is very beneficial for the preparation of high-coverage perovskite films and helps in the preparation of large-area perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of a perovskite solar cell in some embodiments of the present invention. DETAILED DESCRIPTION

[0032] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used herein. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0033] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0034] Herein, “comprising,” “including,” “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of,” for example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to have been disclosed herein.

[0035] Throughout this document, all features, such as values, amounts, amounts, and concentrations, specified in numerical ranges or percentage ranges are provided for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to encompass and specifically disclose all possible subranges and individual values within those ranges (including integers and fractions).

[0036] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0037] Herein, when describing embodiments or examples, it should be understood that they are not intended to limit the present invention to these embodiments or examples. On the contrary, all substitutes, modifications and equivalents of the methods and materials described herein are within the scope defined by the present invention.

[0038] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0039] The self-assembled monolayer of the present invention comprises a first self-assembled monolayer molecule and a second self-assembled monolayer molecule;

[0040] The first self-assembled monolayer molecule is a compound of formula I

[0041] In Formula I,

[0042] R1 is selected from hydrogen atom, C1-C4 alkyl and C1-C4 alkoxy, each R2 is independently selected from C1-C4 alkyl and C1-C4 alkoxy, n is 0, 1, 2, 3, 4 or 5, each R3 is independently selected from: C1-C4 alkyl and C1-C4 alkoxy, m is 0, 1, 2, 3, 4 or 5;

[0043] The second self-assembled monolayer molecule is a compound of formula II

[0044] In Formula II,

[0045] Each R4 is independently selected from C1-C4 alkyl and C1-C4 alkoxy, p is 0, 1, 2, 3 or 4, each R5 is independently selected from: C1-C4 alkyl and C1-C4 alkoxy, q is 0, 1, 2, 3 or 4; i is 1, 2, 3, 4, 5 or 6.

[0046] In some preferred embodiments, in Formula I, R1 is selected from a hydrogen atom; R2 is selected from a methyl group, an ethyl group, a methoxy group or an ethoxy group, and n is 1 or 2; R3 is selected from a methyl group, an ethyl group, a methoxy group or an ethoxy group, and m is 1 or 2.

[0047] In some preferred embodiments, the compound of formula I is

[0048] In some preferred embodiments, in Formula II, R4 is selected from methyl, ethyl, methoxy or ethoxy, p is 1 or 2; R5 is selected from methyl, ethyl, methoxy or ethoxy, q is 1 or 2; i is 1, 2, 3, 4, 5 or 6.

[0049] In some preferred embodiments, in Formula II, R4 is selected from methyl, ethyl, methoxy or ethoxy, p is 1 or 2; R5 is selected from methyl, ethyl, methoxy or ethoxy, q is 1 or 2; i is 2 or 4.

[0050] In some preferred embodiments, the compound of formula II is

[0051] In some preferred embodiments, the compound of formula II is

[0052] The mass fraction of the first self-assembled monolayer molecules of the present invention in the self-assembled monolayer is 40%-70%, for example, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%; the mass fraction of the second self-assembled monolayer molecules in the self-assembled monolayer is 30%-60%, for example, 32%, 34%, 36%, 38%, 40%, 42%, the molar ratio of the first self-assembled monolayer molecules to the second self-assembled monolayer molecules is 1:2-3:1, for example, 1:1.8, 1:1.6, 1:1.4, 1:1.2, 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1.

[0053] The thickness of the self-assembled monolayer of the present invention is 2-5 nm, for example, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm.

[0054] The self-assembled monolayer of the present invention can be prepared by the following method: dispersing the first self-assembled monolayer molecules and the second self-assembled monolayer molecules in a solvent to obtain a self-assembled monolayer solution, coating the self-assembled monolayer solution, and then annealing to obtain a self-assembled monolayer.

[0055] In the self-assembled monolayer solution, the mass of the first self-assembled monolayer molecules per milliliter of solvent is 0.25-0.4 mg, for example, 0.26 mg, 0.27 mg, 0.28 mg, 0.29 mg, 0.3 mg, 0.32 mg, 0.34 mg, 0.36 mg, and 0.38 mg.

[0056] In the self-assembled monolayer solution, the mass of the second self-assembled monolayer molecules per milliliter of solvent is 0.1-0.25 mg, for example, 0.12 mg, 0.14 mg, 0.16 mg, 0.18 mg, 0.2 mg, 0.21 mg, 0.22 mg, 0.23 mg, and 0.24 mg.

[0057] The annealing temperature is 90-120°C, for example, 95°C, 100°C, 105°C, 110°C, 115°C.

[0058] The annealing time is 15-30 min, for example, 16 min, 17 min, 18 min, 19 min, 20 min, 22 min, 24 min, 26 min, and 28 min.

[0059] In some embodiments, the perovskite solar cell has an inverse structure of pin, that is, a hole transport layer, a perovskite layer, and an electron transport layer are sequentially deposited on a substrate.

[0060] In the present invention, the transparent conductive oxide layer used for the conductive substrate can be selected from ITO, FTO, ICO, NiO X , Al2O3, CuO2, CuO, CuAlO2, CuCrO2, WO3, MoO X 、V2O5、VO X and CrO X One or more of .

[0061] In the present invention, the hole transport layer is a self-assembled monolayer, and the self-assembled monolayer molecular material is a mixture of two self-assembled monolayer molecules with different structures, namely a first self-assembled monolayer molecule containing a benzene ring as a connecting group and a second self-assembled monolayer molecule containing an alkyl group as a connecting group.

[0062] In the present invention, the chemical formula of the perovskite structure material is ABX3; the A ion can be one or more selected from methylamine ion, formamidine ion, cesium ion and rubidium ion; the B ion can be one or more selected from lead ion, tin ion, copper ion, zinc ion, gallium ion, tin ion and calcium ion; the X ion can be one or more selected from F - , I - Br - 、Cl - and SCN - One or more of .

[0063] The solvent used in the perovskite precursor solution of the present invention can be one or more selected from N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), acetonitrile, methoxyethanol and ionic liquid.

[0064] The perovskite film of the present invention is preferably prepared by an antisolvent method:

[0065] The first stage: spin-coating the perovskite precursor on a conductive substrate at a speed of 1000-2000 r / min (e.g., 1200 r / min, 1400 r / min, 1600 r / min, 1800 r / min) for 5-15 s (e.g., 6 s, 7 s, 8 s, 9 s, 10 s, 11 s, 12 s, 13 s, 14 s);

[0066] The second stage: spin coating is performed at a speed of 2500-4000 r / min (e.g., 2800 r / min, 3000 r / min, 3200 r / min, 3400 r / min, 3600 r / min, 3800 r / min) for 30-50 s (e.g., 32 s, 34 s, 36 s, 38 s, 40 s, 42 s, 44 s, 46 s, 48 s), and then 90-150 mL (e.g., 100 mL, 110 mL, 120 mL, 130 mL, 140 mL) of chlorobenzene or ethyl acetate is dripped onto the substrate as an antisolvent.

[0067] The third stage: after the spin coating is completed, it is transferred to a hot plate at 90-120°C (for example, 95°C, 100°C, 105°C, 110°C, 115°C) and annealed for 10-20 minutes (for example, 12 minutes, 14 minutes, 16 minutes, 18 minutes) to obtain a perovskite light-absorbing layer.

[0068] In the present invention, the thickness of the perovskite film can be 0.6-1.5 μm, for example, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, and 1.4 μm.

[0069] In the present invention, the material of the electron transport layer can be selected from TiO2, SnO2, ZnO, ZrO2, GZO, IZO, FTO, ITO, BaSnO3, TiSnO x 、SnZnO x , one or more of fullerenes (such as C60 and C70) and fullerene derivatives (such as PCBM).

[0070] In the present invention, the thickness of the electron transport layer may be 30-50 nm, for example, 32 nm, 34 nm, 36 nm, 38 nm, 40 nm, 42 nm, 44 nm, 46 nm, or 48 nm.

[0071] The electrode material of the present invention can be one or more selected from Au, Ag, Al, Cu, graphene, TCO materials and nanocrystalline silicon, and the electrode preparation method includes but is not limited to one or more of spin coating, blade coating, evaporation, printing, spraying, spray pyrolysis and slit coating.

[0072] The present invention will be described below by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the present invention. The methods, reagents, and materials used in the examples are, unless otherwise stated, conventional methods, reagents, and materials in the art. The compounds in the examples can all be purchased from commercial sources.

[0073] Example 1

[0074] like Figure 1 As shown in FIG, an inverted perovskite solar cell is prepared in the order of a conductive substrate, a hole transport layer, a perovskite light absorbing layer, an electron transport layer, and a back electrode. The specific steps are as follows:

[0075] Preparation of perovskite precursor solution: Cesium iodide (CsI), rubidium iodide (RbI), iodomethane (FAI), lead iodide (PbI2), lead bromide (PbBr2) and methylammonium bromide (MABr) were mixed according to the stoichiometric molar ratio, added to a mixed solvent of N,N-dimethylformamide: dimethyl sulfoxide = 4:1 (v / v) for dissolution, and filtered using a 0.45μm oil filter to obtain Rb with a concentration of 1.2mol / L. 0.05 Cs 0.05 MA 0.05 FA 0.85 Pb(I 0.95 Br 0.05 )3 perovskite precursor solution;

[0076] (1) Conductive substrate pretreatment: Provide an ITO glass substrate with a thickness of 0.7 mm and a size of 2.5 cm*2.5 cm. After cleaning and drying, treat with UV-ozone for 20 min to obtain a clean conductive substrate.

[0077] (2) Preparation of a hole transport layer: (4-(3,6-bis(2,4-dimethoxyphenyl)-9H-carbazole-9-yl)phenyl)phosphonic acid and Me-4PACz were dispersed in ethanol solvent to obtain a self-assembled monolayer solution (in the self-assembled monolayer solution, the mass of (4-(3,6-bis(2,4-dimethoxyphenyl)-9H-carbazole-9-yl)phenyl)phosphonic acid was 0.391 mg per milliliter of solvent; the mass of Me-4PACz was 0.109 mg per milliliter of solvent). After standing for 25 seconds, the self-assembled monolayer solution was spin-coated on a conductive substrate at a speed of 4000 r / min for 15 seconds in a nitrogen glove box. After the spin coating, the substrate was transferred to a hot plate at 100°C and annealed for 10 minutes to obtain a self-assembled monolayer with a thickness of 2.5 nm as a hole transport layer.

[0078] (3) Preparation of perovskite layer:

[0079] Preparation of a perovskite light-absorbing layer: In a nitrogen glove box, in the first stage, the perovskite precursor solution was spin-coated on a conductive substrate at a speed of 500 rpm for 5 seconds. In the second stage, the perovskite precursor solution was spin-coated on the conductive substrate at a speed of 4000 rpm for 50 seconds. During the 40-second coating period in the second stage, 150 μL of chlorobenzene antisolvent was added to the surface of the conductive substrate coated with the perovskite precursor solution. Finally, after the spin coating was completed, the substrate was transferred to a hot plate at 120°C and annealed for 20 minutes to obtain a perovskite light-absorbing layer with a thickness of 700 nm.

[0080] Preparation of perovskite passivation layer: 70 μL of 0.5 mg / mL 1,3-propylenediamine iodide (PDADI) in isopropanol was added dropwise to the surface of the perovskite light-absorbing layer. The layer was then spin-coated at 4000 rpm for 30 seconds. After the spin coating, the layer was transferred to a hot plate at 100°C and annealed for 2 minutes to obtain a 6 nm thick perovskite passivation layer.

[0081] (4) Preparation of electron transport layer: a C60 layer with a thickness of 30 nm and a BCP layer with a thickness of 6 nm are sequentially deposited on the perovskite light absorption layer by thermal evaporation. The C60 layer and the BCP layer together constitute the electron transport layer;

[0082] (5) Preparation of back electrode: Ag with a thickness of 180 nm was deposited on the electron transport layer by thermal evaporation to obtain a back electrode, thereby obtaining the inverted perovskite solar cell module of this embodiment.

[0083] Example 2

[0084] Example 2 An inverse perovskite solar cell module was prepared according to a method similar to Example 1, except that Me-4PACz was replaced by 2PACz of equal mass.

[0085] Example 3

[0086] Example 3 An inverse perovskite solar cell module was prepared according to a method similar to Example 1, except that Me-4PACz was replaced by MeO-2PACz of equal mass.

[0087] Comparative Example 1

[0088] The wide bandgap perovskite solar cell of Comparative Example 1 was prepared by a method similar to that of Example 1, except that: in step (2), MeO-2PACz was dispersed in the solvent ethanol to obtain a self-assembled monolayer solution (in the self-assembled monolayer solution, the mass of MeO-2PACz per milliliter of solvent was 0.5 mg), and after standing for 25 seconds, the self-assembled monolayer solution was spin-coated on a conductive substrate at a speed of 3000 r / min for 30 seconds in a nitrogen glove box, and then after the spin coating was completed, it was transferred to a hot plate at 100° C. and annealed for 10 minutes to obtain a self-assembled monolayer with a thickness of 1.6 nm as a hole transport layer.

[0089] Comparative Example 2

[0090] The wide bandgap perovskite solar cell of Comparative Example 2 was prepared by a method similar to that of Example 1, except that: in step (2), MeO-2PACz and Me-4PACz were dispersed in ethanol solvent to obtain a self-assembled monolayer solution (in the self-assembled monolayer solution, the mass of MeO-2PACz phosphonic acid was 0.5 mg per milliliter of solvent; the mass of Me-4PACz was 0.5 mg per milliliter of solvent). After standing for 25 seconds, the self-assembled monolayer solution was spin-coated on a conductive substrate at a speed of 3000 r / min for 30 seconds in a nitrogen glove box, and then transferred to a hot plate at 100° C. for annealing for 10 minutes to obtain a self-assembled monolayer with a thickness of 2.2 nm as a hole transport layer.

[0091] Test Case

[0092] At 25°C, AM1.5G standard solar spectrum, light intensity of 100mW / cm 2 The performance (open circuit voltage, short circuit current density, fill factor and photoelectric conversion efficiency) of the solar cell modules in Examples 1-3 and Comparative Examples 1-2 was measured using a solar simulator with a voltage range of -0.3 to 1.3 V. The performance (open circuit voltage, short circuit current density, fill factor and photoelectric conversion efficiency) of the solar cell modules in Examples 1-3 and Comparative Examples 1-2 was measured at 25°C, AM1.5G standard solar spectrum and a light intensity of 100 mW / cm 2Under the conditions of aging, a solar simulator was used with the voltage range set to -0.3 to 1.3 V to measure the performance (open circuit voltage, short circuit current density, fill factor and photoelectric conversion efficiency) of the solar cell modules in Examples 1-3 and Comparative Examples 1-2. The aging conditions were as follows: the cells were placed in an environment of 85°C for 1000 hours. The specific test results are shown in Table 1.

[0093] (1) Open circuit voltage (Voc): The voltage value corresponding to the current being zero.

[0094] (2) Short-circuit current density (Jsc): The current value when the voltage is zero is the short-circuit current (Isc), and the current per unit battery surface area is the short-circuit current density.

[0095] (3) Fill factor (FF): The ratio of the maximum output power (Pmax) of the battery to the product of the open circuit voltage and the short circuit current. The calculation formula is (Pmax / Voc*Isc), where the maximum power point is the point where the battery output power reaches its maximum value.

[0096] (4) Photoelectric conversion efficiency (PCE): Photoelectric conversion efficiency refers to the ratio of maximum output power to incident light power (Pin), and the calculation formula is (Pmax / Pin)*100%.

[0097] Table 1: Photovoltaic performance test results of the solar cell modules of Example 1 and Comparative Examples 1-2 and their aging

[0098]

[0099]

[0100] As can be seen from Table 1, the perovskite cell prepared with the mixed SAMs of the present invention as the hole transport layer has excellent efficiency and stability, especially after aging, it still maintains a high fill factor and photoelectric conversion efficiency.

Claims

1. A self-assembled monolayer, characterized in that The self-assembled monolayer comprises a first self-assembled monolayer molecule and a second self-assembled monolayer molecule; The first self-assembled monolayer molecule is a compound of formula I: In Formula I, R1 is selected from a hydrogen atom, a C1-C4 alkyl group, and a C1-C4 alkoxy group, each R2 is independently selected from a C1-C4 alkyl group and a C1-C4 alkoxy group, n is 0, 1, 2, 3, 4, or 5, each R3 is independently selected from a C1-C4 alkyl group and a C1-C4 alkoxy group, and m is 0, 1, 2, 3, 4, or 5; The second self-assembled monolayer molecule is a compound of formula II: In formula II, each R4 is independently selected from C1-C4 alkyl and C1-C4 alkoxy, p is 0, 1, 2, 3 or 4, each R5 is independently selected from C1-C4 alkyl and C1-C4 alkoxy, q is 0, 1, 2, 3 or 4, and i is 1, 2, 3, 4, 5 or 6.

2. The self-assembled monolayer according to claim 1, wherein The mass fraction of the first self-assembled monolayer molecules in the self-assembled monolayer is 40%-70%; The mass fraction of the second self-assembled monolayer molecules in the self-assembled monolayer is 30%-60%; The molar ratio of the first self-assembled monolayer molecules to the second self-assembled monolayer molecules is 1:2-3:

1.

3. The self-assembled monolayer according to claim 1, wherein The first self-assembled monolayer molecule is (4-(3,6-bis(2,4-dimethoxyphenyl)-9H-carbazol-9-yl)phenyl)phosphonic acid, The second self-assembled monolayer molecules are selected from [2-(9H-carbazol-9-yl)ethyl]phosphonic acid, [2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid or [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid.

4. The self-assembled monolayer according to claim 1, wherein The thickness of the self-assembled monolayer is 2-5 nm.

5. A method for preparing the self-assembled monolayer according to any one of claims 1 to 4, characterized in that: The method comprises dispersing first self-assembled monolayer molecules and second self-assembled monolayer molecules in a solvent to obtain a self-assembled monolayer solution, coating the self-assembled monolayer solution, and then annealing to obtain a self-assembled monolayer.

6. The method according to claim 5, wherein The method has one or more of the following characteristics: In the self-assembled monolayer solution, the mass of the first self-assembled monolayer molecules is 0.25-0.4 mg per milliliter of solvent; In the self-assembled monolayer solution, the mass of the second self-assembled monolayer molecules is 0.1-0.25 mg per milliliter of solvent; The solvent is one or two selected from ethanol and isopropanol.

7. The method according to claim 5, wherein The method has one or more of the following characteristics: The coating is one or more selected from spin coating, blade coating, spray coating, spray pyrolysis and slot coating; The annealing temperature is 90-120° C. The annealing time is 15-30 minutes.

8. A self-assembled monolayer prepared by the method according to any one of claims 5 to 7.

9. A perovskite solar cell comprising the self-assembled monolayer according to any one of claims 1 to 4 and 8, characterized in that The self-assembled monolayer serves as a hole transport layer in perovskite solar cells.

10. The perovskite solar cell according to claim 9, wherein The perovskite solar cell comprises a conductive substrate, a hole transport layer, a perovskite light absorbing layer, an electron transport layer and a back electrode in sequence.

Images