Naphtho-imidazoline n-type molecular dopant as well as preparation method and application thereof

Abstract

The invention relates to a naphtho-imidazoline n-type molecular dopant as well as a preparation method and application thereof. The naphtho-imidazoline compound taking naphtho-imidazole as a core unit is designed and optimized from molecular engineering, can be used as an n-type molecular dopant, and can obtain a good doping effect when being doped with fullerene and conjugated polymer organic semiconductor materials; various properties of organic electronic devices are effectively improved, good stability is shown, and popularization and application of doped organic semiconductor materials and devices are facilitated.

Description

Technical Field

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

[0002] With the rapid development of modern miniaturized and integrated electronic technologies and related wearable electronic devices, organic semiconductor materials, which are softer, lighter, and more amenable to low-cost, large-area printing production than inorganic semiconductor materials, have attracted increasing attention. Organic semiconductor electronic devices, represented by organic light-emitting diodes (OLEDs), organic photovoltaic cells (OPVs), organic thermoelectric (OTE) devices, and biosensors, are achieving breakthroughs in key areas such as display technology, energy, sensing, environmental monitoring, and biomedical diagnostics.

[0003] Compared to inorganic semiconductors, intrinsic organic semiconductors have relatively poor electrical conductivity, so doping is necessary to improve their electrical properties. Early research typically used inorganic dopants such as halides and alkali metals to achieve organic semiconductor doping. However, these inorganic dopants are unable to form covalent bonds with the organic host material and exhibit a strong diffusion tendency within the organic host material, leading to performance instability in the doped organic injection layer or pn junction used for ohmic contact under operating conditions.

[0004] To address this issue, molecular doping has gradually developed in recent years and has become an effective doping strategy for organic semiconductor materials. In the molecular doping process, organic electron acceptors or donors are used as p-type or n-type dopants. Numerous current cases have confirmed that molecular doping can adjust the conductivity of organic semiconductor materials over a range of several orders of magnitude. In addition, molecular doping can also reduce ohmic losses in the charge transport layer and injection barriers at the electrode interface, meeting today's high performance standards for related devices.

[0005] The two effects of reducing ohmic losses in the charge transport layer and the injection barrier at the electrode interface have been very successfully applied in pin multilayer structure devices. For example, p-doped hole and n-doped organic electron transport layer materials have been widely used in organic semiconductor devices such as organic light-emitting diodes, organic solar cells, perovskite solar cells and organic thermoelectric devices. Driven by the continuous expansion of application scenarios, the performance improvement of doped organic semiconductor materials has made significant progress in recent years. However, it is worth noting that p-type doped organic electronic materials, such as poly (3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) and its composite materials with Bi2Te3, exhibit excellent thermoelectric properties at room temperature with an electrical conductivity (σ) of 4000 S·cm-1 , which is close to the level of inorganic semiconductor materials. However, unlike the excellent performance of p-type conjugated polymers, only a few n-type conjugated polymer materials have a conductivity higher than 1000 S·cm -1 , the conductivity of some materials is between 100 and 1 S·cm -1 The conductivity of most materials is between 1 S·cm -1 For organic electronic devices constructed with both p-type and n-type materials, the imbalance in performance between the two hinders their efficient collaboration, hindering the development of high-performance devices. Therefore, the development of high-performance n-type organic semiconductor materials and n-type dopant materials is of vital importance.

[0006] Among current n-type dopants, benzimidazole derivatives, represented by N-DMBI, have attracted significant attention due to their unique electronic structure and tunable molecular orbital energy levels. These compounds possess high electron affinity (EA), making them highly efficient n-type dopants. They can also effectively lower the electron injection barrier of n-type organic semiconductors, demonstrating their potential for applications in organic field-effect transistors (OFETs), organic photovoltaics (OPVs), and organic thermoelectrics (OTEs). The inventor's research team previously developed a julolidine-substituted benzimidazole n-type dopant (Chinese Patent CN116903618A), achieving excellent doping results.

[0007] To further enhance the performance of these dopants, researchers have tailored their chemical structures through molecular engineering, focusing on improving doping efficiency (i.e., the number of free carriers provided per dopant molecule), environmental stability (including tolerance to oxygen and moisture), processability (involving properties such as solubility and film-forming properties), and compatibility with host materials. The coordinated optimization of these performance metrics is crucial for improving the performance of n-type organic semiconductor materials and fabricating high-performance organic electronic devices. Unfortunately, existing benzimidazole derivatives remain susceptible to degradation due to water and oxygen (their poor stability in air), making them unable to meet the current demand for further development of organic doped materials and devices with air-stable service environments. Furthermore, the n-type doping mechanism of benzimidazole derivatives remains largely unexplained. Summary of the Invention

[0008] The present invention addresses the aforementioned issues with existing n-type dopants by designing and optimizing a naphthoimidazole-based compound using molecular engineering techniques. This novel naphthoimidazole-based compound can be used as an n-type molecular dopant, achieving excellent doping effects when doping fullerenes and conjugated polymer organic semiconductor materials. This not only effectively improves the electrical performance of the device but also exhibits excellent performance stability. To achieve the aforementioned objectives, the present invention employs the following technical solutions: A naphthoimidazole compound can be used as an n-type molecular dopant for organic semiconductor materials. The chemical structure of the compound includes the following three: or or .

[0009] In the above scheme, the side chains R1, R2, and R3 are each selected from hydrogen, a substituted or unsubstituted C1-C6 straight chain or branched alkyl group.

[0010] As a preferred embodiment, in the naphthoimidazoline compound, R1 is methyl, R2 and R3 are both hydrogen, and the corresponding chemical structure is: or or .

[0011] The present invention also provides a method for preparing the naphthoimidazoline compound, comprising: mixing reactant I with reactant II, reactant III, or reactant IV in an acidic solution to react to obtain a naphthoimidazoline compound of the corresponding chemical structure. The specific reaction process is as follows: .

[0012] In the above solution, the acidic solution is specifically a mixture of an acid reagent and a solvent, and the volume ratio of the two is 0.005-0.03:1.

[0013] In the above scheme, the acid reagent is specifically an organic acid, including formic acid, acetic acid, and propionic acid.

[0014] In the above scheme, the solvent is specifically an organic solvent, including methanol, ethanol, isopropanol, acetonitrile, ethyl acetate, and n-hexane.

[0015] In the above scheme, microwaves are used to heat the mixture during the reaction process, and the microwave reaction temperature is 40-80°C. Microwaves can heat the reaction system evenly. Compared with direct heating, microwaves heat the mixture faster, which can significantly shorten the time required for the reaction to complete.

[0016] In the above scheme, after the reaction, the mixture is transferred to a low temperature (<5°C) environment for refrigeration to precipitate, and after filtration, the solid crude product is mixed with the reaction solvent for recrystallization, thereby achieving product purification.

[0017] The third object of the present invention is to provide the use of the naphthiazoline compounds as n-type molecular dopants in organic semiconductor materials and devices.

[0018] In the above scheme, the application process is specifically as follows: an organic semiconductor solution and a dopant solution are prepared separately, and then the two solutions are mixed in proportion to obtain a mixed solution, and the mixed solution is used to form a film on a substrate to obtain a doped organic semiconductor material, thereby preparing high-performance organic electronic devices.

[0019] In the above scheme, the organic semiconductor materials used to prepare the organic semiconductor solution include n-type fullerene materials (such as PTEG-1, PTEG-2, etc.) and conjugated polymer materials (such as ThDPP-CNBTz, N2200, P(DPP-DCNPz), BDPPV, etc.).

[0020] In the above solution, the organic solvent used to prepare the organic semiconductor solution and the dopant solution is at least one selected from chloroform, chlorobenzene, and o-dichlorobenzene.

[0021] In the above solution, the doping molar percentage concentration does not exceed 60%.

[0022] In the above scheme, the organic semiconductor solution and the dopant solution need to be heated and stirred after being mixed. The heating temperature is 20-200° C. and the stirring time is 20-120 minutes.

[0023] In the above solution, the mixed solution is formed into a film on the substrate by spin coating, and the spin coating speed is 400-2000 rpm.

[0024] This invention, starting with molecular structural design, uses naphthimidazole as the parent nucleus. By selecting different substituent units (dimethylaniline, julolidine, and morpholine) and adjusting the chemical structure with different side chain combinations, a series of novel naphthimidazole n-type molecular dopants with different chemical structures were prepared. These dopants are compatible with the energy levels of currently mainstream n-type organic semiconductor materials, exhibiting good doping capacity and efficiency. The doped organic semiconductor materials not only have good stability but also significantly improve electrical conductivity.

[0025] Compared with existing similar products or technologies, the beneficial effects of the present invention are mainly reflected in the following aspects: (1) The preparation and purification process of the dopant is relatively simple, without the need for complex reaction equipment and harsh reaction conditions. The solvent can be recycled and reused, so the cost of the entire preparation process is relatively low and easy to implement.

[0026] (2) The prepared imidazoline n-type molecular dopant has outstanding performance, including significant improvements in doping efficiency, environmental stability, processing performance, and compatibility with the host material, which will contribute to the promotion and application of doped organic semiconductor materials and devices.

[0027] (3) The prepared naphthoimidazole-based n-type molecular dopants have diverse chemical structures. This diverse structural feature provides a wider range of options for their use in different application scenarios. On the one hand, the dopant can be used alone with its unique chemical structure and performance characteristics to fully exert its specific functions and advantages; on the other hand, the dopant can also be reasonably mixed and compounded with other materials to meet the diverse requirements of material performance in different fields and application scenarios through optimized combination. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 These are the molecular structural formulas of several organic semiconductor materials and imidazoline-based n-type molecular dopants involved in the present invention.

[0029] Figure 2 The conductivity curves of PTEG-2 and ThDPP-CNBTz at different dopant concentrations.

[0030] Figure 3 This is the stability test result of JLNI-doped ThDPP-CNBTz thin film sample in an inert gas environment.

[0031] Figure 4 This is a schematic structural diagram of the organic thermoelectric device prepared in the present invention. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to fully understand the technical solutions and beneficial effects of the present invention, the following is further described in detail with reference to specific embodiments and accompanying drawings. It should be emphasized that the following embodiments are only preferred embodiments of the present invention and do not constitute any limitation of the present invention. On this basis, the present invention may have many other embodiments, all of which will fall within the scope of protection of the present invention.

[0033] Currently, the development of n-type organic thermoelectric (OTE) materials faces two major challenges: low doping efficiency and poor air stability. Low doping efficiency results in low conductivity, while higher dopant concentrations can affect molecular stacking and, in turn, the device structure. Improving doping efficiency is difficult due to the poor compatibility between commonly used dopants and the host material. Currently, there are relatively few well-compatible host material and dopant combinations, making it crucial to address compatibility issues between dopants and host materials. Furthermore, existing dopants have poor stability in air, hindering the application of doped organic semiconductor devices.

[0034] This invention aims to improve the doping efficiency and air stability of n-type dopants by modifying their energy levels while simultaneously improving their compatibility with the host material through novel molecular structural design. The invention also uses various characterization techniques to delve into the interplay between molecular structure, aggregated structure, and device performance, providing guidance for the subsequent development and design of dopant molecules.

[0035] The chemical structures of the three types of naphthiazoline n-type molecular dopants developed by the present invention are shown below: , The side chains R1, R2 and R3 are each selected from hydrogen, a substituted or unsubstituted C1-C6 straight chain or branched alkyl group.

[0036] The present invention starts with molecular engineering, for the problems existing in existing n-type dopants, designs and optimizes the naphthoimidazole-based compounds with naphthoimidazole as core unit. On the one hand, in view of the fact that the contribution of the HOMO energy level of benzimidazole derivatives mainly comes from the o-aryl diamine structural unit, the contribution of the LUMO energy level mainly comes from the electron-donating structural unit connected by sp3-C, the naphthalene unit with relatively strong electron-withdrawing ability is used to replace the original benzene ring structure in the o-phenylenediamine structural unit, thereby reducing the HOMO energy level of the target dopant molecule. In addition, the relatively larger conjugated plane of naphthalene atoms makes it show better miscibility when doping some materials with larger conjugated scales. On the other hand, the present invention attempts to regulate the electron-donating structural unit connected by sp3-C, introduces dimethylaniline, julolidine, phenylmorpholine structural units respectively, while optimizing its miscibility as a dopant and a host material, regulates the LUMO energy level of the target molecule, and then improves the stability of the corresponding cation after its use as a dopant, and finally improves the air stability of the doped organic semiconductor material.

[0037] Example 1 The naphthoimidazoline n-type molecular dopant prepared in this embodiment is systematically named 4-(4-(1,3-dimethyl-2,3-dihydro-1H-naphtho[2,3-d]imidazol-2-yl)phenyl)morpholine, abbreviated as MNI, and its chemical structure is shown in the attached figure. Figure 1 As shown, the specific synthesis steps are as follows:

[0038] Step 1: Synthesis of N,N'-(naphthalene-2,3-diyl)bis(4-methylbenzenesulfonamide) (i.e. compound 1-1) Naphthalene-2,3-diamine (5.53 g, 35 mmol) and p-toluenesulfonyl chloride (13.5 g, 70 mmol) were dissolved in 70 mL of pyridine, and the resulting mixture was stirred at 30°C for 22 hours. A 2 M aqueous HCl solution was slowly added to the mixture using a pipette until no further solid precipitate formed. The precipitate was filtered and dissolved in ethanol. The mixture was heated under reflux for 4 hours and cooled thoroughly to precipitate a large amount of white crystals. Filtering afforded 12.2 g (85% yield) of compound 1-1.

[0039] Compound 1-1 1 The test results of H NMR (500 MHz, CDCl3) are: δ 7.60 (d, J = 8.1 Hz, 6H), 7.42 (s, 4H), 7.19 (d, J = 8.1 Hz, 4H), 7.04 (s, 2H), 2.37 (s, 6H).

[0040] Step 2: Synthesis of N,N'-(naphthalene-2,3-diyl)bis(N,4-dimethylbenzenesulfonamide) (i.e. compound 1-2) Compound 1-1 (12.2 g, 26.2 mmol) synthesized in the previous step was dissolved in 20 mL of DMF. K₂CO₃ (16.5 g, 119 mmol) was added and stirred at room temperature for 1 hour. Methyl iodide (5.5 mL, 88 mmol) was then slowly added dropwise to the mixture at 0°C. The mixture was then heated under reflux at 110°C for 13 hours. After the reaction, the mixture was cooled to room temperature, 500 mL of deionized water was added, and the mixture was extracted with dichloromethane, washed with saturated brine, dried over anhydrous magnesium sulfate, and filtered. The filtrate was concentrated in vacuo to obtain a crude solid product. The crude solid product was recrystallized from ethanol and filtered to obtain 11.7 g of compound 1-2 (90% yield).

[0041] Compound 1-2 1 H NMR (500 MHz, CDCl3) test results are: δ 7.75 (t, J= 7.5 Hz, 4H), 7.64 (s, 2H), 7.49 (s, 2H), 7.35 (d, J = 5.3 Hz, 6H), 3.32 (d, J = 7.9 Hz, 6H), 2.47 (d, J = 5.6 Hz, 6H).

[0042] Step 3: N2,N3-dimethylnaphthalene-2,3-diamine (ie compound 1-3) Compound 1-2 (0.494 g, 1 mmol) synthesized in the previous step was dissolved in 90% by mass H₂SO₄ solution (1 mL). The resulting mixture was stirred at 85°C for 4-5 hours, cooled, poured into ice water, and 0.25 mol / L NaOH solution was slowly added to adjust the pH of the mixture to 11. The resulting mixture was extracted with dichloromethane, washed with saturated brine, and dried over anhydrous magnesium sulfate. After filtration, the filtrate was concentrated by vacuum distillation to obtain 0.11 g of compound 1-3 (yield 60%).

[0043] Since N2,N3-dimethylnaphthalene-2,3-diamine is easily deteriorated when left in the air for a long time, it can be directly used for the subsequent reaction without further purification.

[0044] Step 4: Synthesis of 4-(4-(1,3-dimethyl-2,3-dihydro-1H-naphtho[2,3-d]imidazol-2-yl)phenyl)morpholine (MNI) To a 25 mL microwave reaction vial, N2,N3-dimethylnaphthalene-2,3-diamine (0.27 g, 1.47 mmol), 4-(4-morpholinyl)benzaldehyde (0.281 g, 1.47 mmol), and 3 mL of methanol were added, followed by a drop of glacial acetic acid. Once the mixed solution turned green, the microwave reaction vial was placed in a microwave reactor. The reaction temperature was set to 80°C, the heating time was 2 minutes, and the reaction was maintained at this temperature for 120 minutes. After removal from the microwave reaction vial and cooling to room temperature, the mixture was transferred to a low-temperature reagent cabinet (0°C) and refrigerated for 12 hours to fully precipitate a solid. The solid was collected by filtration under reduced pressure, recrystallized from methanol, and dried under vacuum to yield the product, MNI (0.21 g, 40% yield), as pale yellow crystals.

[0045] Product MNI 1 The test results of H NMR (500 MHz, CDCl3) are: δ 7.53 (s, 2H), 7.42 (d, J = 8.4Hz, 2H), 7.15 (s, 2H), 6.94 (d, J= 8.4 Hz, 2H), 6.51 (s, 2H), 5.17 (s, 1H), 3.88 (s, 4H), 3.22 (s, 4H), 2.67 (s, 6H).

[0046] Example 2 The naphthoimidazoline n-type molecular dopant prepared in this embodiment is systematically named 1,3-dimethyl-2-(2,3,6,7-tetrahydro-1H,5H-pyridin[3,2,1-ij]quinolin-9-yl)-2,3-dihydro-1H-naphtho[2,3-d]imidazole, abbreviated as JLNI. Its chemical structure is shown in the attached figure. Figure 1 As shown, the specific synthesis steps are as follows:

[0047] Step 1: Synthesize N2,N3-dimethylnaphthalene-2,3-diamine (ie, compound 1-3) by referring to the method in Example 1.

[0048] Step 2: To a 25 mL microwave reaction vial, add N2,N3-dimethylnaphthalene-2,3-diamine (0.27 g, 1.47 mmol), 2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinoline-9-carbaldehyde (0.295 g, 1.47 mmol), and 3 mL of methanol. Then, add one drop of glacial acetic acid. Once the mixed solution turns green, place the microwave reaction vial in a microwave reactor. The reaction temperature is set to 80°C, with a ramp time of 2 minutes. After incubation for 120 minutes, remove the microwave reaction vial and cool to room temperature. The mixture is then transferred to a cold reagent cabinet (0°C) and refrigerated for 12 hours to allow the solid precipitate to precipitate. The solid is collected by filtration under reduced pressure, recrystallized from methanol, and dried under vacuum to yield the product, JLNI, as pale yellow crystals (0.21 g, 40% yield).

[0049] Products of JLNI 1 The results of H NMR (500 MHz, CDCl3) were: δ 7.58-7.43 (m, 2H), 7.19-7.08 (m, 2H), 6.89 (s, 2H), 6.49 (s, 2H), 5.02 (s, 1H), 3.23-3.10 (m, 4H), 2.77 (t, J = 6.6Hz, 4H), 2.68 (s, 6H), 2.03-1.93 (m, 4H).

[0050] Example 3 The naphthoimidazoline type n-type molecular dopant prepared in this embodiment is systematically named 4-(1,3-dimethyl-2,3-dihydro-1H-naphtho[2,3-d]imidazol-2-yl)-N,N-dimethylaniline, abbreviated as N-DMNI, and its chemical structure is shown in the attached figure. Figure 1 As shown, the specific synthesis steps are as follows:

[0051] Step 1: Synthesize N2,N3-dimethylnaphthalene-2,3-diamine (i.e., compound 1-3) by referring to the method in Example 1.

[0052] Step 2: To a 25 mL microwave reaction vial, add N2,N3-dimethylnaphthalene-2,3-diamine (0.27 g, 1.47 mmol), 4-(dimethylamino)benzaldehyde (0.219 g, 1.47 mmol), and 3 mL of methanol. Then, add one drop of glacial acetic acid. Once the mixed solution turns green, place the microwave reaction vial in a microwave reactor. Set the reaction temperature to 80°C, ramp for 2 minutes, and maintain the reaction for 120 minutes. After removal from the microwave reaction vial and cooling to room temperature, the mixture is transferred to a cold reagent cabinet (0°C) and refrigerated for 12 hours to allow the solid precipitate to precipitate. The solid is collected by vacuum filtration, recrystallized from methanol, and dried under vacuum to yield the product, N-DMNI (0.21 g, 45% yield), as pale yellow crystals.

[0053] Product N-DMNI 1 The results of H NMR (500 MHz, CDCl3) were: δ 7.60 – 7.49 (m, 2H), 7.38 (d, J = 7.3 Hz, 2H), 7.15 (dd, J = 6.1, 3.2 Hz, 2H), 6.76 (d, J = 8.9 Hz, 2H), 6.51 (s, 2H), 5.16 (s, 1H), 3.00 (s, 6H), 2.67 (s, 6H).

[0054] In order to fully understand the doping effects of the three naphthoimidazoline n-type molecular dopants MNI, JLNI, and N-DMNI prepared in Examples 1-3 of the present invention, the representative n-type fullerene material PTEG-2 and the conjugated polymer ThDPP-CNBTz (chemical structure as shown in FIG. Figure 1 As shown in the figure, the conductivity evolution of PTEG-2 and ThDPP-CNBTz was characterized when they were doped with different concentrations of MNI, JLNI, and N-DMNI. At the same time, the existing high-performance dopant JLBI (chemical structure as shown in the figure) was used to characterize the conductivity evolution of PTEG-2 and ThDPP-CNBTz when they were doped with different concentrations of MNI, JLNI, and N-DMNI. Figure 1The experimental process is as follows: (1) A certain amount of PTEG-2 or ThDPP-CNBTz was weighed and added to chloroform. The resulting mixture was heated to 60 °C and stirred for 30 min to completely dissolve the raw materials. The mixture was then cooled to room temperature to obtain an organic semiconductor solution.

[0055] (2) Weigh an appropriate amount of MNI, JLNI, N-DMNI, or JLBI dopant and add it to chloroform. Heat the resulting mixture to 30°C and stir for 10 minutes to completely dissolve the raw materials. Then cool it to room temperature to obtain a dopant solution.

[0056] (3) According to the set doping ratio, the dopant solution is added to the organic semiconductor solution, and the resulting mixture is stirred evenly at room temperature to obtain a series of spin coating solutions with different doping concentrations (doping percentage molar concentration = amount of dopant substance ÷ amount of organic semiconductor substance). The prepared spin coating solution is evenly coated on a glass substrate that has been pretreated (such as cleaning, drying, etc.) using a spin coater. The amount of spin coating solution added is 30 μL, the spin coating speed is 1000 rpm, the spin coating time is 1 min, and the thickness of the film obtained by spin coating is 60 nm. After spin coating, the wet film is placed in a nitrogen environment at 25°C to dry, and a series of thin film samples to be tested are obtained, which are respectively recorded as PTEG-2 / JLBI, PTEG-2 / MNI, PTEG-2 / JLNI, ThDPP-CNBTz / MNI, ThDPP-CNBTz / JLNI, and ThDPP-CNBTz / N-DMNI. The " / " before represents the type of organic semiconductor material, and the " / " after represents the type of dopant.

[0057] (4) The prepared thin film sample is fixed in a suitable mold and covered with a mask. The mold containing the sample is transferred to the chamber of a vacuum evaporator and the chamber door is closed and evacuated to a vacuum state. Two parallel rectangular silver electrodes are prepared on the thin film sample by evaporation. The silver electrodes are generally 60 nm thick, 8 mm long, and 2 mm wide.

[0058] (5) After the evaporation is completed, the sample is removed and then annealed in a glove box at 125°C for 1.5 hours. After the device cools down, its resistance is measured using the four-probe method (i.e., the relationship between current and voltage, Ohm's law), and the conductivity σ of the film is calculated. The conductivity calculation formula is: σ = w / (RLd) in w is the width of the silver electrode, R To test the area resistance, L is the length of the electrode itself, d is the thickness of the film sample after annealing.

[0059] The test results are as follows Figure 2 As shown. Figure 2 As can be seen in a, when PTEG-2 is doped with JLBI, the conductivity of the thin film sample reaches a maximum of 0.93 S·cm at a doping concentration of 30 mol%. -1 When PTEG-2 is doped with JLNI, the conductivity of the thin film sample reaches a maximum of 3.0 S·cm when the doping concentration is 15 mol%. -1 When PTEG-2 is doped with MNI, the conductivity of the thin film sample reaches a maximum of 3.5 S·cm at a doping concentration of 20 mol%. -1 , which is nearly 4 times higher than that of JLBI-doped PTEG-2. This result shows that the naphthiazoline-based n-type molecular dopant provided by the present invention can achieve better conductivity performance at a lower doping concentration.

[0060] from Figure 2 As can be seen in b, when ThDPP-CNBTz is doped with MNI, the conductivity of the film sample reaches a maximum of 17 S·cm when the doping concentration is 40 mol%. -1 When ThDPP-CNBTz is doped with N-DMNI, the conductivity of the film sample reaches a maximum of 29 S·cm when the doping concentration is 40 mol%. -1 When JLNI doped ThDPP-CNBTz, the conductivity of the film sample reached a maximum of 32 S·cm when the doping concentration was 40 mol%. -1 , which is 6.4×10 6 times.

[0061] In order to fully understand the stability of organic semiconductor materials doped with different naphthoimidazoline n-type molecular dopants, ThDPP-CNBTz / JLNI thin film samples were tested according to the following method: The evaporated ThDPP-CNBTz / JLNI film sample (device structure as shown in Figure 4 ) in a glove box and annealed at 125°C for 1.5 hours. After cooling, the film sample's resistance was measured using the same method at different time points. The time after the film sample annealed and cooled for 10 minutes was marked as 0h (the start time). The resistance of the ThDPP-CNBTz / JLNI film sample in the glove box was measured over 17 days: 0h, 50h, 100h, 150h, 200h, 250h, 300h, 350h, and 400h. This was used to calculate the film's conductivity, σ.

[0062] The test results are as follows Figure 3As shown in the figure, the conductivity of the thin film sample obtained by JLNI doping ThDPP-CNBTz remained basically unchanged within 14 days under an inert atmosphere (N2), and the conductivity after 14 days only decreased by about 10%. This result shows that it has good stability.

[0063] In order to verify the performance of doped organic semiconductor materials based on naphthiazoline n-type molecular dopants in specific application scenarios, Figure 4 The device configuration shown was used to characterize the thermoelectric properties of JLNI-doped ThDPP-CNBTz thin film samples to observe the performance of such materials in thermoelectric scenarios.

[0064] The preparation process of this device is consistent with the preparation of the ThDPP-CNBTz / JLNI thin film sample mentioned above. The Seebeck coefficient of the sample was measured using a Cryoall CTA-35 (Beijing Cryoall) instrument. The specific test process is as follows: First, ThDPP-CNBTz / JLNI film samples with doping concentrations of 10%, 20%, 30%, 40%, 50%, and 60% were placed in the Seebeck tester respectively, and the films were fixed with clamps; then the film was vacuumed and then filled with helium, and this was done three times, followed by annealing at 125°C in the chamber for 1.5 hours; after annealing, the film was cooled to room temperature and the room-temperature Seebeck coefficient of each film sample was tested, with three points measured on each film and three films measured for each concentration. Finally, the test result took the average value of the 9 Seebeck coefficients.

[0065] The Seebeck coefficient and power factor curves of the device at different doping concentrations are shown in Table 1 below.

[0066] Table 1 Comparison of Seebeck coefficient and power factor of devices at different doping concentrations

[0067] It can be seen from the table that with the increase of doping concentration, the absolute value of Seebeck coefficient gradually decreases, and the power factor reaches the maximum when the doping concentration is 40mol%, which is PF=30.71 μW·m -1 K -2 The above results show that the device has good thermoelectric conversion capability and can be used in the development of organic thermoelectric devices in conjunction with corresponding p-type organic semiconductor materials.

[0068] The novel naphthiazoline compounds provided by the present invention can achieve good doping effects and effectively improve the electrical properties when used to dope fullerene and conjugated polymer organic semiconductor materials. They also have good performance stability, providing a new solution for the development of flexible devices based on organic semiconductors.

Claims

1. A naphthiazoline-based n-type molecular dopant, characterized in that: The chemical structure of the dopant is: or or , The side chains R1, R2, and R3 are independently selected from any one of hydrogen, substituted or unsubstituted C1-C6 straight chain or branched alkyl.

2. The naphthiazoline-based n-type molecular dopant according to claim 1, wherein: The chemical structure of the dopant is: or or .

3. A method for preparing a naphthiazoline-based n-type molecular dopant, characterized in that The method comprises: mixing reactant I with reactant II or reactant III or reactant IV in an acidic solution to react and obtain a naphthiazoline-based n-type molecular dopant. The specific reaction process is as follows: 。 4. The method according to claim 3, wherein: The acidic solution is a mixture of an acid reagent and a solvent. The acid reagent is specifically an organic acid, and the solvent is specifically an organic solvent.

5. The method according to claim 3, wherein: During the reaction process, the mixed material is heated by microwave, and the microwave reaction temperature is 40-80°C.

6. The method according to claim 3, wherein: After the reaction is completed, the mixture is placed in a low temperature environment for refrigeration to precipitate, and then filtered and recrystallized.

7. Use of the naphthoimidazoline-based n-type molecular dopant according to any one of claims 1 to 2 in organic semiconductor materials and organic semiconductor devices.

8. The use according to claim 7, characterized in that The specific application process is: mixing an organic semiconductor solution and a dopant solution in proportion to obtain a mixed solution, forming a film on a substrate using the mixed solution to obtain a doped organic semiconductor material, and preparing an organic semiconductor device using the organic semiconductor material.

9. The use according to claim 8, characterized in that: Organic semiconductor materials include n-type fullerene materials and conjugated polymer materials.

10. The use according to claim 8, characterized in that: The doping molar percentage concentration does not exceed 60%.

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