Small organic molecule hole transport material with indolocarbazole as conjugate core as well as preparation method and application of small organic molecule hole transport material

Abstract

The invention discloses a small organic molecule hole transport material with indolocarbazole as a conjugated core and a preparation method and application thereof.According to the small organic molecule hole transport material with indolocarbazole as the conjugated core, indolocarbazole serves as a terminal group, the group is modified in a modification mode that a long carbon chain and benzene ring bromine are substituted and combined, and the chemical name is ((2, 3, 4, 5, 6-tetramethyl-3-piperidine-2-yl) carbazole). The invention relates to a 2, 9-dibromo indolo [3, 2-a] carbazole-5, 12-diyl) bis (butane-4, 1-diyl)) bis (phosphonic acid). The hole transport material is introduced into a solar cell system, so that on one hand, the energy level arrangement in the cell can be reasonably optimized, the charge transport efficiency is effectively improved, the energy loss is reduced, and the photoelectric conversion efficiency of the cell is remarkably improved; and on the other hand, the application of the functional material further verifies the effectiveness of the multi-anchor point strategy in the aspects of realizing upward orientation of the material surface and improving the comprehensive performance of the perovskite solar cell.

Description

Technical Field

[0001] This invention relates to the field of organic small molecule hole transport materials technology, and in particular to an organic small molecule hole transport material with indole-carbazole as a conjugated core, its preparation method and application. Background Technology

[0002] Photovoltaic technology, as a core means of efficient solar energy utilization, can directly convert solar energy into electrical energy. Among them, inverted perovskite solar cells (i-PSCs), with their unique structure of "substrate / transparent electrode / hole transport layer (HTL) / perovskite active layer / electron transport layer (ETL) / metal electrode," have shown significant advantages in suppressing ion migration, improving interface stability, and being compatible with flexible substrates, and have become one of the mainstream research directions in the field of perovskite photovoltaics. In the structural design of inverted perovskite cells, the hole transport layer (HTL), as a key functional layer adjacent to the transparent electrode and the perovskite active layer, directly determines the interface energy level matching degree, charge extraction efficiency, and device stability. On the one hand, it is necessary to achieve efficient hole transport from the perovskite valence band (VB) to the electrode; on the other hand, it is necessary to block direct contact between the electrode and the perovskite to suppress interface reactions.

[0003] Since the advent of the inverted structure, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) has become the most widely used HTL material due to its simple preparation by spin coating of aqueous solution and low contact resistance with ITO electrodes, which has driven the rapid improvement of the efficiency of inverted perovskite solar cells. However, PEDOT:PSS has three major drawbacks: First, its sulfonic acid groups (-SO3H) are strongly acidic and will undergo protonation with perovskite, accelerating the degradation of the active layer; second, its inherent hygroscopicity causes the device's efficiency to decrease by more than 50% after 1000 hours in a humid and hot environment (such as 40℃ / 60% RH); third, its high surface roughness (up to 6.04nm) easily causes uneven perovskite film formation, leading to non-radiative recombination at the buried layer interface, resulting in an open-circuit voltage (Voc) loss of more than 0.35V, which seriously restricts the performance limit and long-term stability of the inverted battery [Joule 2024, 8, 1324-1338; Adv. Mater. 2024, 36, 2309124.].

[0004] To address the application bottlenecks of PEDOT:PSS, the scientific community has conducted research on several alternatives to HTL: one type is p-type organic polymers (such as PTB7-Th and PBDTTT-ET), which, although possessing high hole mobility, are difficult to control in terms of molecular chain and have poor solubility, making them unsuitable for large-area solution preparation; the other type is inorganic metal oxides (such as NiOx and CuI), which, although exhibiting excellent stability, require high-temperature annealing (>300℃), are incompatible with flexible substrates, and suffer from significant energy level mismatch issues at the perovskite interface [Nat. Energy 2023, 8, 789-801; Adv. Energy Mater. 2023, 13, 2204156.]. In contrast, pure organic small molecule HTL has three major advantages: First, the molecular structure can be precisely modified (such as by introducing functional groups such as hydroxyl and amino groups), and can achieve a perfect match with perovskite through energy level engineering; second, it has good solution film-forming properties, can be prepared at low temperatures (<100℃), and is compatible with flexible and large-area processes; third, it has no acidic groups or hygroscopic components, which can significantly improve interfacial stability.

[0005] Therefore, developing novel organic small molecule hole transport materials (HTMs) with low acidity, low hygroscopicity, low Voc loss, and high photoelectric conversion efficiency, in response to the structural characteristics and performance requirements of inverted perovskite solar cells, is of vital technical significance for overcoming the application limitations of PEDOT:PSS and further improving the photoelectric conversion efficiency and industrial adaptability of inverted perovskite solar cells. Summary of the Invention

[0006] The main objective of this invention is to provide an indole-carbazole-based conjugated core organic small molecule hole transport material, its preparation method, and its application, aiming to solve at least one of the aforementioned technical problems.

[0007] To achieve the above objectives, this invention provides an indole-carbazole-based conjugated core organic small molecule hole transport material, the chemical structural formula of which is shown below: .

[0008] This invention relates to an organic small molecule hole transport material with indolocarbazole as the conjugated core. The indolocarbazole is used as the terminal group, and the group is modified by a combination of long carbon chain and bromine substitution of benzene ring. The chemical name is: ((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonic acid), hereinafter referred to as 2KaBr.

[0009] This invention also provides a method for preparing the above-mentioned indolocarbazole-based conjugated core organic small molecule hole transport material. Specifically, the synthetic route is as follows:

[0010] .

[0011] Furthermore, the preparation method of the indolocarbazole-based conjugated core organic small molecule hole transport material includes the following steps: Step B1: Anhydrous N,N-dimethylformamide was added to 5,12-dihydroindolo[3,2-a]carbazole, and after stirring to dissolve, sodium hydride was added and reacted for 0.5 h; then 1,4-dibromobutane was added and stirred at room temperature for 2 h; the resulting reaction mixture was extracted with dichloromethane, the organic phases were combined, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product; the crude product was separated by silica gel mobile phase column chromatography using a mixed solution of n-hexane and dichloromethane as eluent to obtain compound 5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole; Step B2: Compound 5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole was dissolved in anhydrous tetrahydrofuran, and N-bromosuccinimide was added and reacted in an ice-water bath for 2 h; the resulting reaction mixture was extracted with dichloromethane, the organic phases were combined, dried with anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product; the crude product was separated by silica gel mobile phase column chromatography using a mixed solution of n-hexane and dichloromethane as eluent to obtain compound 2,9-dibromo-5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole; Step B3: The compound 2,9-dibromo-5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole was dissolved in triethyl phosphite and stirred under reflux at 150°C for 20 h. The resulting reaction mixture was extracted with dichloromethane, the organic phases were combined, dried with anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was separated by silica gel mobile phase chromatography using a mixed solution of dichloromethane and methanol as the eluent to obtain the compound tetraethyl((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonate). Step B4: The compound tetraethyl((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonate) was dissolved in dichloromethane; then trimethylbromosilane was added and the mixture was stirred at room temperature for 14 h; the solvent was removed from the reaction mixture under reduced pressure, and the solid residue was reprecipitated using a mixture of water and methanol; the precipitate was collected by filtration and washed with dichloromethane to obtain the target compound ((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonic acid), that is, the indolocarbazole is a conjugated core organic small molecule hole transport material.

[0012] Further, in step B1, the volume ratio of n-hexane to dichloromethane in the mixed solution of n-hexane and dichloromethane is 2:5; in step B2, the volume ratio of n-hexane to dichloromethane in the mixed solution of n-hexane and dichloromethane is 1:10; and in step B3, the volume ratio of dichloromethane to methanol in the mixed solution of dichloromethane and methanol is 15:1.

[0013] This invention also provides an application of the above-mentioned indolocarbazole-based conjugated core organic small molecule hole transport material in perovskite solar cells.

[0014] The present invention also provides a perovskite solar cell comprising the above-mentioned indobenzocarbazole as a conjugated core organic small molecule hole transport material.

[0015] The present invention also provides a method for preparing the above-mentioned perovskite solar cell, comprising the following steps: Step S1: Prepare a nickel oxide solution and a solution of the above-mentioned indole-carbazole as a conjugated core organic small molecule hole transport material; Step S2: Pre-treat the transparent conductive substrate ITO; Step S3: Spin-coat the nickel oxide solution onto the pretreated transparent conductive substrate ITO at 3000 rpm for 30 s, and anneal at 100°C for 10 min. Step S4: Spin-coat the hole transport material solution onto the spin-coated layer obtained in step S3 at a speed of 4000 rpm for 25 s, and then anneal at 100°C for 10 min; Step S5: Spin coat the perovskite solution onto the spin coating obtained in step S4. The spin coating process is first spin coated at 1000 rpm for 10 seconds, and then spin coated at 5000 rpm for 30 seconds. During the spin coating process, the anti-solvent anisole is added at 25 seconds. After the spin coating is completed, anneal at 100°C for 20 minutes. Step S6: Mix the isopropanol solution of 1 mg / ml ethylenediamine dihydroiodide and the isopropanol solution of 2 mg / ml phenylethyl ammonium iodide at a volume ratio of 1:1, spin coat the mixture on the spin coating obtained in step S5 at 5000 rpm for 30 s, and then anneal at 90 °C for 15 min. Step S7: Spin-coat a chlorobenzene solution of 20 mg / mL [6,6]-phenyl-C61-butyrate methyl ester onto the spin coating obtained in step S6 for 40 s at a speed of 2500 rpm, and then let it stand for 10 min. Step S8: Spin-coat a 0.5 mg / mL dimethyl-4,7-diphenyl-1,10-phenanthroline isopropanol solution onto the spin-coated layer obtained in step S7 for 30 s at a speed of 500 rpm. Step S9: Using vacuum evaporation, deposit 20 nm of Ag at a rate of 0.1 Å / s and then deposit 80 nm of Ag at a rate of 1 Å / s on the spin coating obtained in step S8 as the electrode of the device.

[0016] The beneficial effects of this invention are reflected in: This invention relates to indolocarbazole as a conjugated core organic small molecule hole transport material. With indolocarbazole as the conjugated core and phosphonic acid groups as anchoring functional groups, it can be used as a hole transport material. The invention also provides a preparation method and application scenarios for this type of material. This material uses indolocarbazole as the terminal group and is modified by a combination of long carbon chains and bromine substitution of the benzene ring.

[0017] From the perspective of performance advantages, introducing indolofaradazole as a conjugate core functional material into the battery system can, on the one hand, rationally optimize the internal energy level arrangement of the battery, effectively improve charge transport efficiency, reduce energy loss, and thus significantly improve the photoelectric conversion efficiency of the battery; on the other hand, the application of this functional material further verifies the effectiveness of the multi-anchor point strategy in achieving material orientation and improving the overall performance of perovskite solar cells.

[0018] Device performance tests show that the perovskite solar cell fabricated using 2KaBr as the hole transport material has higher photoelectric conversion efficiency and open-circuit voltage than the control device without hole transport material, and the photoelectric performance of the device is substantially improved. Attached Figure Description

[0019] Figure 1 This is a structural diagram of a perovskite solar cell based on indole-carbazole as a conjugated core organic small molecule hole transport material, according to the present invention.

[0020] Figure 2 This is the energy level arrangement diagram of the perovskite solar cell based on an organic small molecule hole transport material layer with indole-carbazole as the conjugated core, as described in this invention.

[0021] Figure 3 The JV curves are for the perovskite solar cells prepared in Example 1 and Comparative Examples 2 and 4. Detailed Implementation

[0022] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0023] Unless otherwise specified, the raw materials, reagents or devices used in the following embodiments can be obtained from conventional commercial sources or by existing known methods; unless otherwise specified, the methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0024] Example 1 Preparation of 2KaBr, a small organic molecule hole transport material with indolocarbazole as the conjugated core. The chemical structural formula of 2KaBr is shown in Formula I:

[0025] Formula I The synthetic route and preparation process of 2KaBr are as follows:

[0026]

[0027] Step B1: At room temperature, the two-necked flask was first evacuated and purged with N2 three times. Then, 5,12-dihydroindolo[3,2-a]carbazole (2 g, 7.8 mmol), compound 1, was added. Next, 25 mL of anhydrous DMF (N,N-dimethylformamide) was added, and the mixture was stirred for 10 min until dissolved. Then, NaH (sodium hydride) (1.12 g, 46.8 mmol) was added, and the reaction was allowed to proceed for 0.5 h. Subsequently, 1,4-dibromobutane (3.37 g, 15.6 mmol) was slowly added using a syringe, and the reaction was continued with stirring at room temperature for 2 h. After the reaction was complete, the mixture was cooled to room temperature, and the resulting reaction mixture was transferred to a 500 mL pear-shaped separatory funnel and extracted with dichloromethane. The dichloromethane layers were combined, dried with anhydrous sodium sulfate, and then the solvent was removed by rotary evaporation to obtain the crude product. The crude product was obtained by mixing n-hexane and dichloromethane (2:5). Using a mixed solution of v / v as eluent, the compound was separated by silica gel mobile phase column chromatography to obtain compound 5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole (2.80 g, yield approximately 68%), namely compound 2; Step B2: First, evacuate the two-necked flask, then purge with N2 three times. Dissolve compound 2 in 30 mL of anhydrous tetrahydrofuran, and then slowly add NBS (N-bromosuccinimide) (1.94 g, 10.9 mmol) in portions. React in an ice-water bath for 2 h. After the reaction is complete, cool to room temperature and transfer the resulting reaction mixture into a 500 mL pear-shaped separatory funnel for extraction with dichloromethane. Combine the dichloromethane layers, dry with anhydrous magnesium sulfate, and then remove the solvent by rotary evaporation to obtain the crude product. Use a mixed solution of n-hexane and dichloromethane (1:10, v / v) as the eluent and separate the crude product by silica gel mobile phase chromatography to obtain compound 2,9-dibromo-5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole (2.24 g, yield approximately 60%), i.e., compound 3. Step B3: First, evacuate the three-necked flask, purge with N2 three times, then dissolve compound 3 in 22 mL of triethyl phosphite. The mixture is stirred and refluxed at 150 °C for 20 h. After the reaction is complete, cool to room temperature, transfer the resulting reaction mixture to a 500 mL pear-shaped separatory funnel, extract with dichloromethane, combine the dichloromethane layers, dry with anhydrous magnesium sulfate, and then remove the solvent by rotary evaporation to obtain the crude product. The crude product is separated by silica gel mobile phase chromatography using a mixed solution of dichloromethane and methanol (15:1, v / v) as the eluent to obtain compound tetraethyl((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonate) (1.31 g, yield approximately 50%), and compound 4. Step B4: First, evacuate the two-necked flask, then purge with N2 three times. Dissolve compound 4 in 25 mL of dry dichloromethane. Next, add 2.1 mL of bromotrimethylsilane (16.4 mmol), and stir the mixture at room temperature for 14 h. After the reaction, remove the solvent from the reaction mixture under reduced pressure, and then reprecipitate the solid residue using a mixture of water and methanol (5:1, v / v). Note that methanol should be added first to dissolve the residue before adding water. The precipitate is then collected by filtration and washed with dichloromethane to obtain the target compound ((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonic acid), i.e., 2KaBr (675 mg, yield approximately 60%).

[0028] 2KaBr 1H NMR spectral data: 1 H NMR (300 MHz, Chloroform-d) δ 8.84 (s,2H), 8.19 – 8.10 (m, 1H), 7.57 – 7.39 (m, 2H), 4.19 (td, J = 6.9, 4.2 Hz,2H), 1.96 – 1.86 (m, 2H), 1.86 – 1.78 (m, 3H), 1.78 – 1.62 (m, 2H). The structural formula of 2KaBr was confirmed as shown in Formula I.

[0029] Example 2 Fabrication of perovskite solar cells based on 2KaBr Step S1: Prepare solutions related to perovskite solar cells, including NiO (nickel oxide) solution (concentration 5 mg / mL, solvent is H2O / IPA (3:1, v / v)) and 2KaBr solution (concentration 1 mg / mL, solvent is N,N-dimethylformamide). Step S2: Pre-treat the transparent conductive substrate ITO; The transparent conductive substrate ITO was ultrasonically cleaned sequentially with deionized water, acetone, and isopropanol for 30 min, dried, and then treated with oxygen plasma for 10 min to remove any remaining organic residues. Step S3: In a fume hood, spin-coat the NiO solution onto the pretreated transparent conductive substrate ITO at 3000 rpm for 30 s, and anneal at 100 ℃ for 10 min. Step S4: In a glove box, spin-coat the 2KaBr solution onto the spin-coated layer obtained in step S3 at a speed of 4000 rpm for 25 s, and anneal at 100°C for 10 min. Step S5: Prepare a 1.5M perovskite solution, the perovskite being FA. 0.88 Cs 0.12 PbI3 was prepared using a mixed solution of DMF (N,N-dimethylformamide) and DMSO (dimethyl sulfoxide) in a volume ratio of 1:4. The perovskite solution was spin-coated onto the spin-coated layer obtained in step S4 inside a glove box. The spin-coating process was first performed at a speed of 1000 rpm for 10 s, and then at a speed of 5000 rpm for 30 s. At the 25th second of the spin-coating process, 150 μL of anisole (anti-solvent) was rapidly added dropwise. After the spin-coating was completed, the mixture was annealed at 100°C for 20 min. Step S6: Dissolve EDAI2 (ethylenediamine dihydroiodide) in IPA (isopropanol) to prepare a concentration of 1 mg / ml, and dissolve PEAI (phenylethyl ammonium iodide) in IPA (isopropanol) to prepare a concentration of 2 mg / ml. Mix the two in a volume ratio of 1:1 and spin coat the mixture onto the spin coating obtained in step S5 at 5000 rpm for 30 s. Then anneal at 90 ℃ for 15 min in a glove box. Step S7: Dissolve PCBM ([6,6]-phenyl-C61-butyrate methyl ester) in CB (chlorobenzene) to prepare a concentration of 20 mg / mL, and then spin coat it onto the spin coating obtained in step S6 at a speed of 2500 rpm for 40 s, and let it stand for 10 min. Step S8: Dissolve BCP (dimethyl-4,7-diphenyl-1,10-phenanthroline) in IPA (isopropanol) to prepare a concentration of 0.5 mg / mL, and then spin coat it onto the spin coating obtained in step S7 at 500 rpm for 30 s. Step S9: Using vacuum evaporation, deposit 20 nm of Ag at a rate of 0.1 Å / s on the spin coating obtained in step S8, and then deposit 80 nm of Ag at a rate of 1 Å / s as the electrode of the device.

[0030] Comparative Example 1 Preparation of 2Ka of Indobenzocarbazole as a Conjugated Core Organic Small Molecule Hole Transport Material The chemical structural formula of 2Ka is shown in Formula II:

[0031] Formula II The synthetic route and preparation process of 2Ka are as follows:

[0032] .

[0033] Step A1: At room temperature, first evacuate the two-necked flask, then purge with N2 three times. Add 5,12-dihydroindolo[3,2-a]carbazole (2 g, 7.8 mmol), compound 1, followed by 25 mL of anhydrous DMF (N,N-dimethylformamide). Stir for 10 min until dissolved, then add NaH (sodium hydride) (1.12 g, 46.8 mmol) and react for 0.5 h. Then, slowly add 1,4-dibromobutane (3.37 g, 15.6 mmol) using a syringe, and continue stirring at room temperature for 2 h. After the reaction is complete, cool to room temperature, and transfer the resulting reaction mixture to a 500 mL aerator. Extracted with dichloromethane in a pear-shaped separatory funnel; the organic phases were combined, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product; the crude product was separated by silica gel mobile phase column chromatography using a mixed solution of n-hexane and dichloromethane (2:5, v / v) as eluent to obtain compound 5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole (2.87 g, yield approximately 70%), i.e., compound 2; Step A2: First, evacuate the three-necked flask, purge with N2 three times, then dissolve compound 2 in 20 mL of triethyl phosphite. The mixture is stirred and refluxed at 150 °C for 20 h. After the reaction is complete, cool to room temperature, transfer the resulting reaction mixture to a 500 mL pear-shaped separatory funnel, extract with dichloromethane, combine the organic phases, dry with anhydrous magnesium sulfate, and then remove the solvent by rotary evaporation to obtain the crude product. The crude product is separated by silica gel mobile phase column chromatography using a mixed solution of dichloromethane and methanol (10:1, v / v) as the eluent to obtain compound tetraethyl(indolo[3,2-a]carbazole-5,12-diylbis(butane-4,1-diyl))bis(phosphonate) (2.45 g, yield approximately 50%), i.e., compound 3. Step A3: First, evacuate the two-necked flask, then purge with N2 three times. Dissolve compound 3 in 25 mL of dry dichloromethane. Next, add 4.9 mL of trimethylbromosilane (38.2 mmol), and stir the mixture at room temperature for 14 h. After the reaction, remove the solvent from the reaction mixture under reduced pressure, and then reprecipitate the solid residue using a mixture of water and methanol (5:1, v / v). Note that methanol should be added first to dissolve the residue before adding water. The precipitate is then collected by filtration and washed with dichloromethane to obtain the target compound (indo[3,2-a]carbazole-5,12-diylbis(butane-4,1-diyl))bis(phosphonic acid), i.e., 2Ka (1.2 g, yield approximately 60%). 2Ka 1H NMR data: 1 H NMR (300 MHz, Chloroform-d) δ 8.84 (s, 4H),8.03 – 7.92 (m, 2H), 7.85 – 7.76 (m, 1H), 7.59 – 7.48 (m, 1H), 7.48 – 7.40(m, 2H), 7.40 – 7.19 (m, 4H), 4.19 (td, J = 6.9, 4.2 Hz, 4H), 1.96 – 1.74 (m,8H), 1.78 – 1.62 (m, 4H). The structural formula of 2Ka is confirmed as shown in Equation II.

[0034] Comparative Example 2 Fabrication of 2Ka-based perovskite solar cells The preparation method is the same as in Example 2, except that 2Ka is used instead of 2KaBr.

[0035] Comparative Example 3 Comparison of perovskite solar cell fabrication The preparation method is the same as in Example 2, except that step S4 is omitted.

[0036] Experimental Example 1 Performance Testing of Perovskite Solar Cells Based on Indolocarbazole as a Conjugated Core Organic Small Molecule Hole Transport Material Figure 1 The diagram shows the structure of a perovskite solar cell based on indole-carbazole as the conjugated core organic small molecule hole transport material. The inverted perovskite solar cells prepared in Example 1 and Comparative Example 1 have an ITO / NiO structure. x / 2Ka or2KaBr / PVK / EDAI:PEAI / PCBM / BCP / Ag.

[0037] Figure 2The diagram shows the energy level arrangement of the perovskite solar cells prepared in Example 1 and Comparative Example 1. As can be seen from the diagram, the indole-carbazole organic small molecules 2Ka or 2KaBr interact with the basic hole transport layer (i.e., NiO). x This material constitutes a hybrid hole transport material, which not only forms a perovskite / organic material heterojunction, but also further enhances the internal electric field strength of the device through the precise matching of its HOMO energy level with the perovskite valence band, while reducing the interface charge transport barrier and significantly improving the interface charge extraction efficiency.

[0038] Figure 3 The figure shows the JV curves of the perovskite solar cells prepared in Example 1 and Comparative Examples 1 and 2. As can be seen from the figure, the perovskite solar cell based on 2Ka (denoted as NiOx+2Ka in the figure) and the perovskite solar cell based on 2KaBr (denoted as NiOx+2KaBr in the figure) achieved power conversion efficiencies (PCE) of 22.43% and 23.25%, respectively. The comparative perovskite solar cell prepared in Comparative Example 3 (denoted as NiOx in the figure), i.e., pure NiO... x The battery achieved only 20.89% PCE. Due to the benzene ring bromine substitution modification, 2KaBr's highest occupied molecular orbital (HOMO) more precisely matches the perovskite valence band, reducing energy level losses and increasing open-circuit voltage (Voc). Simultaneously, the combined effect of the long carbon chain's hydrophobicity and the adsorption defects of the benzene ring bromine optimizes the series / parallel resistance (Rs / Rsh) to improve the fill factor (FF). Compared to inorganic NiO... X 2Ka and 2KaBr-type organic small molecule HTLs have advantages in energy level tuning flexibility and interface defect passivation ability. Ultimately, synergistic optimization of Voc, FF, and short-circuit current density (Jsc) was achieved in 2KaBr devices, resulting in a photoelectric conversion efficiency (PCE) that is significantly higher than that of 2Ka and pure NiO. x Device.

[0039] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. Indolocarbazole is a conjugated core organic small molecule hole transport material, characterized in that... Its chemical structural formula is shown below: 。 2. The preparation method of the indolocarbazole-based conjugated core organic small molecule hole transport material as described in claim 1, characterized in that, The synthesis route is as follows: 。 3. The preparation method of the indolocarbazole-based conjugated core organic small molecule hole transport material as described in claim 2, characterized in that, Includes the following steps: Step B1: Anhydrous N,N-dimethylformamide was added to 5,12-dihydroindolo[3,2-a]carbazole, and after stirring to dissolve, sodium hydride was added and reacted for 0.5 h; then 1,4-dibromobutane was added and stirred at room temperature for 2 h; the resulting reaction mixture was extracted with dichloromethane, the organic phases were combined, dried with anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product; the crude product was separated by silica gel mobile phase column chromatography using a mixed solution of n-hexane and dichloromethane as eluent to obtain compound 5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole; Step B2: Compound 5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole was dissolved in anhydrous tetrahydrofuran, and N-bromosuccinimide was added and reacted in an ice-water bath for 2 h; the resulting reaction mixture was extracted with dichloromethane, the organic phases were combined, dried with anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product; the crude product was separated by silica gel mobile phase column chromatography using a mixed solution of n-hexane and dichloromethane as eluent to obtain compound 2,9-dibromo-5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole; Step B3: The compound 2,9-dibromo-5,12-bis(4-bromobutyl)-5,12-dihydroindolo[3,2-a]carbazole was dissolved in triethyl phosphite and stirred under reflux at 150°C for 20 h. The resulting reaction mixture was extracted with dichloromethane, the organic phases were combined, dried with anhydrous magnesium sulfate, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was separated by silica gel mobile phase chromatography using a mixed solution of dichloromethane and methanol as the eluent to obtain the compound tetraethyl((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonate). Step B4: The compound tetraethyl((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonate) was dissolved in dichloromethane; then trimethylbromosilane was added and the mixture was stirred at room temperature for 14 h; the solvent was removed from the reaction mixture under reduced pressure, and the solid residue was reprecipitated using a mixture of water and methanol; the precipitate was collected by filtration and washed with dichloromethane to obtain the target compound ((2,9-dibromoindolo[3,2-a]carbazole-5,12-diyl)bis(butane-4,1-diyl))bis(phosphonic acid), that is, the indolocarbazole is a conjugated core organic small molecule hole transport material.

4. The preparation method of the indolocarbazole-based conjugated core organic small molecule hole transport material as described in claim 3, characterized in that, In step B1, the volume ratio of n-hexane to dichloromethane in the mixed solution of n-hexane and dichloromethane is 2:5; in step B2, the volume ratio of n-hexane to dichloromethane in the mixed solution of n-hexane and dichloromethane is 1:10; in step B3, the volume ratio of dichloromethane to methanol in the mixed solution of dichloromethane and methanol is 15:

1.

5. The application of the indolocarbazole-as-conjugated core organic small molecule hole transport material as described in claim 1 in perovskite solar cells.

6. A perovskite solar cell, characterized in that, Includes indole-carbazole as described in claim 1, which is a conjugated core organic small molecule hole transport material.

7. The method for preparing a perovskite solar cell as described in claim 6, characterized in that, Includes the following steps: Step S1: Prepare a nickel oxide solution and a solution of indole-carbazole as the conjugated core organic small molecule hole transport material as described in claim 1; Step S2: Pre-treat the transparent conductive substrate ITO; Step S3: Spin-coat the nickel oxide solution onto the pretreated transparent conductive substrate ITO at 3000 rpm for 30 s, and anneal at 100℃ for 10 min. Step S4: Spin-coat the hole transport material solution onto the spin-coated layer obtained in step S3 at a speed of 4000 rpm for 25 s, and then anneal at 100°C for 10 min; Step S5: Spin coat the perovskite solution onto the spin coating obtained in step S4. The spin coating process is first spin coated at 1000 rpm for 10 seconds, and then spin coated at 5000 rpm for 30 seconds. During the spin coating process, the anti-solvent anisole is added at 25 seconds. After the spin coating is completed, anneal at 100°C for 20 minutes. Step S6: Mix the isopropanol solution of 1 mg / ml ethylenediamine dihydroiodide and the isopropanol solution of 2 mg / ml phenylethyl ammonium iodide at a volume ratio of 1:1, spin coat the mixture on the spin coating obtained in step S5 at 5000 rpm for 30 s, and then anneal at 90 °C for 15 min. Step S7: Spin-coat a chlorobenzene solution of 20 mg / mL [6,6]-phenyl-C61-butyrate methyl ester onto the spin coating obtained in step S6 for 40 s at a speed of 2500 rpm, and then let it stand for 10 min. Step S8: Spin-coat a 0.5 mg / mL dimethyl-4,7-diphenyl-1,10-phenanthroline isopropanol solution onto the spin-coated layer obtained in step S7 for 30 s at a speed of 500 rpm. Step S9: Using vacuum evaporation, deposit 20 nm of Ag at a rate of 0.1 Å / s and then deposit 80 nm of Ag at a rate of 1 Å / s on the spin coating obtained in step S8 as the electrode of the device.

Images