Benzimidazole n-type dopant containing julolidine substitution and preparation method and application thereof

Abstract

The present invention relates to a benzimidazole n-type dopant containing a juloridine substitution, and its preparation method and application. The molecular structure of the dopant is as follows: #imgabs0# wherein R1, R2, and R3 are selected from at least one of hydrogen, a substituted or unsubstituted C1-C10 straight-chain alkyl group, and a substituted or unsubstituted C3-C20 branched-chain alkyl group, preferably R1 is a methyl group, R2 is a hydrogen or alkoxy group, and R3 is a hydrogen group. When used, the dopant and the n-type organic semiconductor material are directly added to an organic solvent for blending, or a component prepared using the n-type organic semiconductor material is soaked in an organic solvent containing the dopant, thereby achieving doping of the n-type organic semiconductor and improving its performance. Practical results have shown that the doping efficiency of the dopant is high, the performance of the doped n-type organic semiconductor material is better, and it has good application prospects in perovskite solar cells and other aspects.

Description

Technical Field

[0001] The present invention relates to the technical field of functional materials and organic semiconductor devices, and in particular to a julolidine-substituted benzimidazole n-type dopant, a preparation method and an application thereof. Background Art

[0002] Organic semiconductor devices, including organic thermoelectric devices, organic light-emitting diodes, organic photovoltaic cells, organic field-effect transistors, organic lasers, and organic biosensors, have been widely developed and applied due to their advantages such as light weight, portability, flexibility, and ease of solution processing for large-scale production. However, compared with inorganic semiconductor materials, organic semiconductor materials have relatively low performance in electrical properties such as conductivity due to the constraints of their intrinsic properties. This limits further improvement in the performance of organic semiconductor devices, and how to improve the performance of organic semiconductor materials has become a pain point in the current development of organic semiconductor devices.

[0003] Doping organic semiconductor materials is an effective method for regulating their electrical properties, including energy level structure and conductivity. Doping generates additional charge carriers (holes or electrons) in organic semiconductor materials, significantly increasing their carrier concentration and conductivity. It also reduces ohmic losses at interfaces between the doped organic semiconductor layer and other materials (such as metal electrode layers and perovskite layers), significantly improving the performance of organic semiconductor devices.

[0004] Organic semiconductor devices often utilize both p-type and n-type organic semiconductor materials. For example, in perovskite solar cells, p-type and n-type organic semiconductor materials can serve as the hole and electron transport layers, respectively. In organic thermoelectric devices, the thermoelectric arm must be composed of p-type and n-type organic semiconductor materials, respectively. Compared to the rapid advancements in the performance of p-type-doped organic semiconductor materials, the development of n-type-doped organic semiconductor materials has been relatively slow in recent years, significantly hindering further improvements in the performance of these devices. This is due, firstly, to the scarcity of n-type organic semiconductors with high carrier mobility, resulting in a relatively limited selection of materials. Secondly, for these existing n-type organic semiconductors, efficient n-type dopants are still relatively scarce. These dopants must be well miscible with the n-type organic semiconductor, achieve effective n-type doping, and have high doping efficiency. This sluggish development of efficient n-type dopants has resulted in the underdevelopment of existing n-type-doped organic semiconductors, far from achieving their optimal performance. Furthermore, n-type dopants need to have good solubility to meet the conditions for solution processing, thereby enabling large-scale, low-cost production of organic semiconductor devices. Therefore, the development of new n-type dopants with excellent solubility and high doping efficiency is of great significance for improving the performance of organic semiconductor devices and reducing their production costs.

[0005] As the current mainstream n-type dopant, 1H-benzimidazole molecules have poor miscibility with mainstream n-type organic semiconductor materials and limited doping efficiency. This results in the doped n-type organic semiconductor materials being unable to meet the ever-increasing performance requirements when used as functional building blocks in organic semiconductor devices, severely restricting the development of organic semiconductor devices. Therefore, the development of new n-type dopants and their application in the manufacture of organic semiconductor devices is particularly important. Summary of the Invention

[0006] The present invention provides a julolidine-substituted benzimidazole n-type dopant, which exhibits good compatibility with currently mainstream n-type organic semiconductor materials and achieves efficient n-type doping, effectively improving the conductivity and other properties of n-type doped organic semiconductor materials. To achieve the above objectives, the technical solutions employed by the present invention are as follows:

[0007] A benzimidazole n-type dopant containing julolidine substitution has a molecular structure as shown below:

[0008]

[0009] Wherein R1, R2, and R3 are all selected from at least one of hydrogen, substituted or unsubstituted C1-C10 straight-chain alkyl, and substituted or unsubstituted C3-C20 branched-chain alkyl.

[0010] Furthermore, when R1, R2, and R3 are selected from substituted straight-chain or branched alkyl groups, the substituted group is specifically one or more (i.e., more than two) non-adjacent methylene groups -CH2-, and the substituent group is selected from at least one of -O-, -S-, -NH-, -CO-, -COO-, -COOH-, -OCO-, -OCO-O-, -SO2-, -S-CO-, -CO-S-, -CH=CH-, -C≡C-, aryl, and heteroaryl.

[0011] Preferably, R1 is specifically methyl, R2 is specifically hydrogen or alkoxy, and R3 is specifically hydrogen.

[0012] The present invention also provides a method for preparing the julolidine-substituted benzimidazole n-type dopant, which mainly comprises the following steps: dissolving reactant I and reactant II in a solvent, adding an acid reagent and heating to perform a microwave reaction, and finally separating and purifying to obtain the target product. The specific process is as follows:

[0013]

[0014] Furthermore, the solvent is selected from at least one of methanol, ethanol, isopropanol, and dichloromethane, the acid reagent is specifically acetic acid, and the microwave reaction temperature is 40-80°C.

[0015] Furthermore, the process of separating and purifying the product is as follows: after the reaction is completed, the mixture is transferred to a low temperature (such as below 10° C.) environment for refrigeration, and after the precipitate is fully precipitated, it is filtered, and the obtained filter residue is recrystallized with a solvent.

[0016] The present invention also provides the use of the julolidine-substituted benzimidazole n-type dopant in n-type organic semiconductors and related devices (such as perovskite solar cells).

[0017] Furthermore, the application process is specifically as follows: directly adding the dopant and n-type organic semiconductor material into an organic solvent and blending them together, or soaking a component prepared using n-type organic semiconductor material with an organic solvent containing the dopant, thereby achieving doping of the n-type organic semiconductor.

[0018] Furthermore, the n-type organic semiconductor material is selected from [6,6]-phenyl-C61-butyric acid isomethyl ester (PC 61 BM), [6,6]-phenyl-C71-butyric acid isomethyl ester (PC 71 BM), 2′-[4-[2-[2-(2-ethoxyethoxy)ethoxy]ethoxy]phenyl]-1′,5′-dihydro-1′-methyl-2′H-[5,6]fullerenyl-C 60 -I h -[1,9-c]pyrrole (PTEG-1), 1′,5′-dihydro-1′-[4-[2-(2-methoxyethoxy)ethoxy]phenyl]-1′-methyl-2′H-[5,6]fullerenyl-C 60 -I h-[1,9-c]pyrrole (PDEG-1), poly(2,7-bis(2-octyldodecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8(2H,7H)-tetraone-4,9-diyl)([2,2']dithienyl-5,5'-diyl)(N2200), poly[3,7-dicyano-5,5',6,6-tetrahydro-5,5'-bis(2- Octyldodecyl)-4,4′,6,6′-tetraoxo[2,2′-bis-4H-dithieno[3,2-c:2′,3′-e]azepine]-8,8′-diyl] (PCNI-BTI), poly[[1,2-dihydro-1-(4-octadecyldodecyl)-2-oxo-3H-indol-6-yl-3-ylidene]-(1E)-1,2-ethylenediyl[1,2 -dihydro-1-(4-octadecyldodecyl)-2-oxo-3H-indol-6-yl-3-ylidene](2,6-dioxybenzo[1,2-b:4,5-b′]difuran-3,7(2H,6H)-diylidene)] (BDPPV), poly[[4,5-dihydro-4-(4-octadecyldodecyl)-5-dihydro-6H-thieno[3,2-b]pyrrole-2 -yl-6-ylidene]-(1E)-1,2-ethylenediyl[4,5-dihydro-4-(4-octadecyldodecyl)-5-oxo-6H-thieno[3,2-b]pyrrol-2-yl-6-ylidene](2,6-dioxybenzo[1,2-b:4,5-b′]difuran-3,7(2H,6H)-ylidene)](TBDPPV) (specific chemical structure as shown in FIG. Figure 1 As shown), the organic solvent is selected from at least one of chloroform, chlorobenzene, o-dichlorobenzene and toluene.

[0019] Furthermore, the doping molar percentage of the dopant does not exceed 50%, preferably 10%-35%.

[0020] The innovation of the present invention lies in the introduction of the N-heterocyclic aromatic hydrocarbon unit julolidine into the benzimidazole molecule. The benzene ring in the chemical structure of julolidine fuses two six-membered cycloalkanes that share the same nitrogen atom, which gives the benzimidazole dopant stronger lipophilicity and increases its affinity with alkylated n-type organic semiconductors. It can effectively enhance the miscibility of such dopants with organic semiconductor materials, help improve the doping efficiency between the two, and thus improve the performance of the doped semiconductor material.

[0021] Compared with existing similar technologies, the beneficial effects of the present invention are mainly reflected in the following aspects: (1) The preparation method of the dopant is relatively simple and easy to implement, and does not require reaction conditions such as high temperature and high pressure, as well as expensive and sophisticated reaction equipment, and does not involve complicated reaction steps and separation and purification methods; (2) The dopant includes a series of compounds, so the selection range is relatively wide, and it can be used alone or in combination; (3) Practical results show that the doping efficiency of the dopant is high, and the obtained n-type organic semiconductor material has better performance, which has good application prospects in organic semiconductor devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the chemical structure of various n-type organic semiconductors described in the present invention;

[0023] Figure 2 n-type organic semiconductor PC 61 BM, schematic diagram of the chemical structures of the two dopants;

[0024] Figure 3 n-type organic semiconductor PC 61 Relationship between conductivity and doping concentration before and after BM doping;

[0025] Figure 4 n-type organic semiconductor PC before and after doping 61 Schematic diagram of the structure of a perovskite solar cell with BM as the electron transport layer;

[0026] Figure 5 n-type organic semiconductor PC before and after doping 61 Current density-voltage diagram of perovskite solar cells with BM as electron transport layer. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to fully understand the technical solutions and beneficial effects of the present invention, further description will be given below in conjunction with specific embodiments.

[0028] The chemical structural formula of the julolidine-substituted benzimidazole n-type dopant of the present invention is as follows:

[0029]

[0030] Wherein, R1, R2, and R3 are each independently hydrogen, substituted or unsubstituted C1-C10 straight chain or C3-C20 branched alkyl, and one or more non-adjacent methylene groups -CH2- can be independently substituted by -O-, -S-, -NH-, -CO-, -COO-, -COOH-, -OCO-, -OCO-O-, -SO2-, -S-CO-, -CO-S-, -CH=CH-, -C≡C- and the like, or substituted by aryl or heteroaryl groups.

[0031] In one embodiment, R1 in the dopant is one of methyl, ethyl, and propyl, and R2 and R3 are any one of methyl, ethyl, propyl, methoxy, and acetoxy. The specific preparation method is as follows:

[0032]

[0033] The specific steps of the above reaction are: adding the reactants into a microwave reaction vessel and dissolving them with methanol, then dropping a small amount of glacial acetic acid, then stirring the mixture and heating it to about 60°C, reacting under the assistance of microwaves, and after the reaction, transferring the mixture to a low temperature place for refrigeration to allow the crude product to fully precipitate, collecting the crude product after filtration and re-crystallizing and purifying it with methanol as a solvent to obtain the target product.

[0034] In another embodiment, R1 in the dopant is methyl, R2 is any one of hydrogen, alkoxy, and acyloxy hydrocarbon, and R3 is hydrogen. The specific preparation method is as follows:

[0035]

[0036] The specific steps of the above reaction are the same as the reaction process in the previous embodiment.

[0037] In the above embodiments, when R1 is methyl and R2 and R3 are both hydrogen, the performance of the dopant is better. The corresponding new dopant is systematically named 9-(1,3-dimethyl-2,3-dihydro-1H-benzimidazol-2-yl)-julolide (JLBI), and its molecular formula is as follows: Figure 2 As shown in the middle figure.

[0038] The present invention uses the most representative n-type organic semiconductor material [6,6]-phenyl-C61-butyric acid isomethyl ester PC 61 BM (chemical structure as Figure 2 As shown in the figure above, PC is doped by JLBI. 61The specific process and analytical test results of BM prove the advantages and beneficial effects of the new dopant provided by the present invention. For comparison, the present invention uses the most representative benzimidazole dopant 4-(2,3-dihydro-1,3-dimethyl-1H-benzimidazole-2-yl)-N,N-dimethylaniline (N-DMBI, such as Figure 2 As shown in the figure below) as a reference, PC was carried out under the same conditions. 61 BM doping experiment.

[0039] 1. PC with different doping concentrations 61 BM conductivity changes

[0040] PC with different doping concentrations 61 The device structure of BM conductivity test is glass substrate / PC 61 BM or doped PC 61 BM film / silver electrode (glass / PC 61 BM or doped PC 61 BM / Ag), the preparation method of which is as follows:

[0041] (1) The glass substrate was cleaned with deionized water, acetone, and isopropanol ultrasonically in sequence, then purged with nitrogen to make it fully dry, and finally treated with ozone and placed in a glove box.

[0042] (2) Dissolve JLBI dopant in chloroform and add PC 61 BM was dissolved to obtain a series of PC with different doping concentrations (0, 10, 15, 20, 25, 30, 35 mol%). 61 BM solution, and PC in this solution 61 The concentration of BM was 10 mg mL -1 Wherein the doping molar concentration percentage = the amount of dopant material ÷ (the amount of dopant material + PC 61 amount of BM material).

[0043] (3) In a glove box filled with nitrogen, the prepared PC 61 The BM solution was dropped onto the rotating pre-treated glass substrate (rotation speed: 500-600 rpm), and the PC was controlled by controlling the amount of droplets. 61 The thickness of the BM film is about 100nm, and then the PC 61 The BM film was annealed at 125°C for 60 minutes to obtain PC films with different doping concentrations. 61 BM film.

[0044] (4) Cover the sample with a mask and fix it in the mold, transfer the mold containing the sample into the vacuum evaporation chamber, and 61Parallel silver electrodes are deposited on the BM film. The thickness of the silver electrodes is 80 nanometers, the width of the silver electrodes is 8 millimeters, and the distance between the silver electrodes is 2 millimeters.

[0045] (5) The current-voltage relationship of the device was tested by the four-probe method, and the conductivity σ of the film was calculated. The calculation formula is σ = w / (RLd), where w is the distance between the silver electrodes, R is the resistance of the test area, L is the width of the electrode itself, and d is the PC after annealing. 61 BM film thickness.

[0046] PC with different doping concentrations 61 The relationship between the conductivity and doping concentration of BM is as follows: Figure 3 As shown in the figure, when the doping concentration of JLBI is 0, PC 61 The electrical conductivity of the BM film is 8.1×10 -8 S·m -1 ; With the increase of JLBI doping concentration, PC 61 The conductivity of BM film increases gradually; when the doping concentration of JLBI is 30%, PC 61 The conductivity of BM film is the largest, and then the PC 61 The above results show that the conductivity of BM film decreases. 61 N-type doping of BM can significantly improve its conductivity.

[0047] Further research found that when JLBI was doped with PC 61 BM and under the optimal doping molar percentage (30%), the doping efficiency is 20%, PC 61 The conductivity of the BM film was increased from 8×10 -8 S·m -1 Increased to 0.79S·m after doping -1 As a comparison, under the same conditions, N-DMBI was doped into PC. 61 BM, when the doping molar percentage is 30%, the doping efficiency is <1%, and the PC after doping 61 The electrical conductivity of the BM film is only 0.01 S·m -1 (Adv.Mater.,2017,29,1701641). This shows that at the same doping concentration, JLBI has a 61 The improvement in BM film conductivity is superior to that of N-DMBI. The doping efficiency in this embodiment is calculated as follows: doping efficiency E = carrier concentration n / number of dopant molecules per unit volume r, where carrier concentration n can be directly measured and number of dopant molecules per unit volume r = fRρ / M, where f is the doping molar percentage and R is Avogadro's constant (6.02×1023 ), ρ is the dopant density, and M is the molar mass of the dopant.

[0048] 2. PC 61 Preparation and performance study of perovskite solar cells with BM as electron transport layer

[0049] PC before and after doping 61 BM films are used as electron transport layers in Figure 4 The perovskite solar cell shown has the following structure: glass / indium tin oxide / (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl)phosphonic acid / perovskite layer / PC 61 BM or doped PC 61 BM / silver(glass / ITO / MeO-2PACz / Cs 0.05 FA 0.79 MA 0.16 PbBr 0.51 I 2.49 / PC 61 BM or dopedPC 61 BM / Ag). The preparation and assembly steps of each functional layer of the perovskite solar cell are as follows:

[0050] (1) ITO glass pretreatment: The glass substrate with patterned ITO electrodes was ultrasonically cleaned with deionized water, acetone, and isopropyl alcohol in sequence, dried with nitrogen purge, and then transferred into a glove box after ozone treatment.

[0051] (2) Preparation of MeO-2PACz thin film on pretreated ITO glass: MeO-2PACz was dissolved in ethanol to a concentration of 0.1×10 -3 mol·L -1 A MeO-2PACz solution was prepared and dropped onto a rotating ITO glass (6000 rpm) for 20 seconds. The ITO glass with the MeO-2PACz film was annealed on a 100°C hotplate for 30 minutes. The annealed sample was then transferred to an argon-filled glove box for subsequent preparation of the perovskite layer and electron transport layer.

[0052] (3) 548.6 mg of lead iodide (PbI2), 190.06 mg of formamidine hydroiodide (FAI), 77.07 mg of lead bromide (PbBr2), and 21.84 mg of methylamine bromide (MABr) were dissolved in 1.0 mL of a mixed solvent of anhydrous DMF and DMSO (the volume ratio of the two was 4:1), and then 30 μL of cesium iodide (CsI)-DMSO solution (concentration of 2 mol·L -1 ), thereby obtaining Cs 0.05 FA0.79 MA 0.16 PbBr 0.51 I 2.49 A peroxide solution was prepared. After stirring at room temperature for 10 minutes, an appropriate amount of the solution was dripped directly onto the ITO glass coated with the MeO-2PACz thin film. The spin coating was performed at a speed of 6000 rpm, an acceleration of 1000 rpm / s, and a spin coating time of 30 seconds. Five seconds before the end of spin coating, 120 μL of ethyl acetate (EA) antisolvent was added to the sample surface. The resulting sample was then annealed on a 120°C hot plate for 45 minutes.

[0053] (4) In an argon atmosphere glove box, prepare a concentration of 10 mg mL -1 Pure PC 61 BM chloroform solution. PC with a dopant molar fraction (i.e. doping concentration) of 0.25% was prepared using the above method. 61 BM chloroform solution (PC in solution 61 The concentration of BM was controlled at 10 mg mL -1 ). 61 BM solution and doped PC 61 The BM solution was drop-coated onto the perovskite layer at a spin speed of 1500 rpm for 30 seconds. The sample was then annealed on a hot plate at 125°C for 20 minutes to form the electron transport layer.

[0054] (5) Cover the sample with a mask and secure it in a mold. Transfer the mold containing the sample to the chamber of a vacuum evaporator and evaporate Ag to a thickness of approximately 100 nm as the top electrode. This completes the fabrication of the perovskite solar cell.

[0055] The current density-voltage test of the perovskite solar cell was completed by Keithley 2400. The test conditions were: the cell active area was 16mm 2 , the simulated sunlight intensity is 100mW·cm -2 (AM 1.5G), the test results are as follows Figure 5 shown. Figure 5 The results showed that JLBI doped PC 61 When the optimal molar percentage of BM is 0.25%, the device current density of the battery is 20.8 mA·cm -2 Increased to 22.6 mA·cm -2 , the device photoelectric conversion efficiency increased from 16.9% to 17.3%. This shows that the JLBI provided by this application has a significant effect on PC 61 After doping, BM can be used as an electron transport layer and can effectively improve the performance of perovskite solar cell devices.

[0056] The present invention combines a benzimidazole n-type dopant (such as JLBI) containing julolidine substitution with an n-type organic semiconductor (such as PC 61 Doping of n-type organic semiconductors is achieved by directly blending the n-type organic semiconductor material with a julolidine-substituted benzimidazole (BM) in an organic solvent, or by impregnating a component made of n-type organic semiconductor material with an organic solvent containing the dopant. During the doping process, this julolidine-substituted benzimidazole n-type dopant exhibits higher doping efficiency, and the doped organic semiconductor material exhibits improved performance. When doped at a low molar ratio, the n-type organic semiconductor material exhibits excellent performance in related device applications.

Claims

1. A benzimidazole n-type dopant containing julolidine substitution, characterized in that The molecular structure of this dopant is shown below: Wherein R1 is methyl, R2 is hydrogen, and R3 is hydrogen.

2. The method for preparing the julolidine-substituted benzimidazole n-type dopant according to claim 1, characterized in that The method comprises the following steps: dissolving reactant I and reactant II in a solvent, adding an acid reagent and heating to perform microwave reaction, and finally separating and purifying to obtain the target product. The specific process is as follows: 。 3. The method according to claim 2, wherein: The solvent is selected from at least one of methanol, ethanol, isopropanol, and dichloromethane; the acid reagent is specifically acetic acid; and the microwave reaction temperature is 40-80°C.

4. The method according to claim 2, wherein The process of separating and purifying the product is as follows: after the reaction is completed, the mixture is transferred to a low-temperature environment for refrigeration, and after the precipitate is fully precipitated, it is filtered, and the obtained filter residue is dissolved in a solvent and then recrystallized.

5. Use of the julolidine-substituted benzimidazole n-type dopant according to claim 1 in n-type organic semiconductors and related devices.

6. The use according to claim 5, characterized in that The specific process of this application is as follows: directly adding the dopant and n-type organic semiconductor material into an organic solvent and blending them together, or soaking a component prepared using n-type organic semiconductor material with an organic solvent containing the dopant, thereby achieving doping of the n-type organic semiconductor.

7. The use according to claim 6, characterized in that: The n-type organic semiconductor material is selected from PC 61 BM, PC 71 At least one of BM, PTEG-1, PDEG-1, N2200, PCNI-BTI, BDPPV, and TBDPPV, and the organic solvent is at least one of chloroform, chlorobenzene, o-dichlorobenzene, and toluene.

8. The use according to claim 5, characterized in that: The doping mole percentage of the dopant does not exceed 50%.

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