A polymer with alternating perylene diimide and naphthalene diimide, and its preparation method and application

Abstract

The present invention belongs to the technical field of semiconductor materials, and discloses a polymer with alternating arrangement of perylene diimide and naphthalene diimide, and its preparation method and application. The preparation method of the polymer includes the following steps: mixing naphthalic anhydride, alkanolamine and an organic solvent, and reacting to obtain naphthalene diimide-diol; mixing naphthalene diimide-diol, bromoacetic acid, 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and an organic solvent, and reacting to obtain naphthalene diimide-dibromide; mixing naphthalene diimide-dibromide, perylene diimide-diamine and an organic solvent, and reacting to obtain the polymer. The present invention takes naphthalene diimide and perylene diimide as the core structures, and through design and synthesis, obtains a polymer with good water and alcohol solubility. This polymer can integrate the physical and chemical properties of the above two structural units, providing a guarantee for its application as an electron transport layer material in solar cells.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor materials, and particularly relates to a polymer with alternating perylene diimide and naphthalene diimide, and a preparation method and application thereof. Background Art

[0002] Organic solar cells have the advantages of low cost, light weight, solution processability, etc., and have great application potential in the fields of smart glass, wearable devices, Internet of Things, etc. In recent years, with the continuous enrichment of organic semiconductor materials and the optimization of device processes, the photoelectric conversion efficiency of single-junction organic solar cells has exceeded 19%. Electron transport layer materials play a crucial role in improving the efficiency of battery devices, such as optimizing the contact between the light-absorbing layer and the electrode, reducing carrier recombination, improving the morphology of the active layer, and isolating water and oxygen. In the past decade or so, small molecule and polymer electron transport layer materials based on perylene diimide (Angew. Chem. Int. Edit. 2018, 57, 9675; Nat Commun 2020, 11, 2726) and naphthalene diimide (Joule 3, 227; Angew. Chem. Int. Edit. 2020, 59, 18131) have been relatively well developed, and their physical and chemical properties and application effects have their own advantages and disadvantages, such as differences in solubility, electron transport ability, ultraviolet-visible absorption spectrum, and work function regulation ability.

[0003] At present, how to simultaneously take into account the electron transport layer materials with these two structural properties remains to be studied. Summary of the Invention

[0004] The purpose of the present invention is to provide a polymer with alternating perylene diimide and naphthalene diimide, and a preparation method and application thereof, so as to solve the problems existing in the prior art.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a polymer with alternating perylene diimide and naphthalene diimide, and the structural formula of the polymer NDIN-PDIN-P with alternating perylene diimide and naphthalene diimide is as follows:

[0007]

[0008] Wherein,

[0009] R 1 、R 2 are independently a hydrogen atom, a fluorine atom, a chlorine atom or a bromine atom;

[0010] m and n are independently integers from 1 to 8, and z is an integer from 2 to 2000.

[0011] The present invention also provides a method for preparing a polymer with alternating perylene diimide and naphthalene diimide, comprising the following steps:

[0012] (1) Mix naphthalic anhydride, alkanolamine and an organic solvent, and carry out a reaction to obtain naphthalene diimide-diol;

[0013] Or mix naphthalic anhydride and alkanolamine, and carry out a reaction to obtain naphthalene diimide-diol;

[0014] (2) Mix naphthalene diimide-diol, bromoacetic acid, 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and an organic solvent, and carry out a reaction to obtain naphthalene diimide-dibromo;

[0015] (3) Mix naphthalene diimide-dibromo, perylene diimide-diamine and an organic solvent, and carry out a reaction to obtain the polymer NDIN-PDIN-P.

[0016] Preferably, in the above method for preparing a polymer with alternating perylene diimide and naphthalene diimide, in step (1), the molar ratio of the naphthalic anhydride to the alkanolamine is 0.5-1.5:2-4;

[0017] The molar volume ratio of the naphthalic anhydride to the organic solvent in step (1) is 0.5-1.5 mmol:8-15 mL.

[0018] Preferably, in the above method for preparing a polymer with alternating perylene diimide and naphthalene diimide, in step (1), the temperature of the reaction is 50-110 °C, and the reaction time is 3-24 h.

[0019] Preferably, in the above method for preparing a polymer with alternating perylene diimide and naphthalene diimide, in step (2), the molar volume ratio of the naphthalene diimide-diol, bromoacetic acid, 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and the organic solvent is 3-8 mmol:10-20 mmol:0.3-1 mmol:10-20 mmol:40-80 mL.

[0020] Preferably, in the above method for preparing a polymer with alternating perylene diimide and naphthalene diimide, in step (2), the temperature of the reaction is 70-110 °C, and the reaction time is 12-48 h.

[0021] Preferably, in the above method for preparing a polymer with alternating perylene diimide and naphthalene diimide, in step (3), the molar volume ratio of the naphthalene diimide-dibromo, perylene diimide-diamine and organic solvent is 0.5 to 1.5 mmol: 0.5 to 1.5 mmol: 3 to 15 mL.

[0022] Preferably, in the above method for preparing a polymer with alternating perylene diimide and naphthalene diimide, in step (3), the temperature of the reaction is 50 to 80 °C, and the reaction time is 1 to 10 h.

[0023] Preferably, in the above method for preparing a polymer with alternating perylene diimide and naphthalene diimide, in step (1), the organic solvent is ethanol, N,N-dimethylformamide or acetonitrile;

[0024] In step (2), the organic solvent is one or more of chloroform, N,N-dimethylformamide, 2,2,2-trifluoroethanol and hexafluoroisopropanol;

[0025] In step (3), the organic solvent is dichloromethane, 1,2-dichloroethane, N,N-dimethylformamide or tetrahydrofuran.

[0026] The present invention also provides an application of a polymer with alternating perylene diimide and naphthalene diimide in the electron transport layer material of a solar cell.

[0027] Through the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention uses naphthalene diimide and perylene diimide as the core structures. Through design and synthesis, a polymer with alternating perylene diimide and naphthalene diimide with good water and alcohol solubility is obtained. This polymer can combine the physical and chemical properties of the above two structural units, providing guarantee for its core application as an electron transport layer material of a solar cell.

[0029] (2) The synthesis method of this material is simple and efficient, with good stability and repeatability, low cost, universality, and is easy to scale up production. Description of the Drawings

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art.

[0031] Figure 1 1H NMR spectrum of naphthalene diimide-dibromo in Example 1;

[0032] Figure 2 13C NMR spectrum of naphthalene diimide-dibromo in Example 1;

[0033] Figure 3 It is the ultraviolet-visible absorption spectrum diagram of the polymer NDIN-PDIN-P in Example 1;

[0034] Figure 4 It is the performance test and morphology characterization diagram of the polymer NDIN-PDIN-P in Example 1; among them, a is the work function diagram, b is the conductivity diagram, and c and d are atomic force microscope diagrams;

[0035] Figure 5 It is the J-V curve and external quantum efficiency diagram of the battery device in Application Example 1; among them, a is the J-V curve diagram, and b is the external quantum efficiency diagram;

[0036] Figure 6 It is the J-V curve and external quantum efficiency diagram of the battery device in Application Example 2; among them, a is the J-V curve diagram, and b is the external quantum efficiency diagram. Detailed implementation manners

[0037] The present invention provides a polymer with alternating perylene diimide and naphthalene diimide. The structural formula of the polymer NDIN-PDIN-P with alternating perylene diimide and naphthalene diimide is as follows:

[0038]

[0039] Among them,

[0040] R 1 、R 2 are independently preferably a hydrogen atom, a fluorine atom, a chlorine atom or a bromine atom, more preferably a hydrogen atom, a fluorine atom or a chlorine atom, and even more preferably a hydrogen atom or a fluorine atom;

[0041] m and n are independently preferably integers from 1 to 8, more preferably integers from 2 to 6, and even more preferably integers from 3 to 5; z is preferably an integer from 2 to 2000, more preferably an integer from 150 to 1600, and even more preferably an integer from 500 to 1200.

[0042] The present invention also provides a preparation method of a polymer with alternating perylene diimide and naphthalene diimide, comprising the following steps:

[0043] (1) Mix naphthalic anhydride, alkanolamine and an organic solvent, and carry out a reaction to obtain naphthalene diimide-diol;

[0044] Or mix naphthalic anhydride and alkanolamine, and carry out a reaction to obtain naphthalene diimide-diol;

[0045] (2) Mix naphthalenediimide - diol, bromoacetic acid, 4 - dimethylaminopyridine, 1 - (3 - dimethylaminopropyl)-3 - ethylcarbodiimide hydrochloride and an organic solvent, and conduct a reaction to obtain naphthalenediimide - dibromo;

[0046] (3) Mix naphthalenediimide - dibromo, perylene diimide - diamine and an organic solvent, and conduct a reaction to obtain the polymer NDIN - PDIN - P.

[0047] In the present invention, the reaction formula for the preparation method of the polymer with alternating perylene diimide and naphthalenediimide is as follows:

[0048]

[0049] In the present invention, the molar ratio of the naphthalic anhydride to the alkanolamine in step (1) is preferably 0.5 - 1.5:2 - 4, more preferably 0.8 - 1.3:2.3 - 3.5, and still more preferably 1 - 1.2:2.5 - 3;

[0050] The molar volume ratio of the naphthalic anhydride to the organic solvent in step (1) is preferably 0.5 - 1.5 mmol:8 - 15 mL, more preferably 0.8 - 1.2 mmol:9 - 13 mL, and still more preferably 0.95 - 1 mmol:10 - 12 mL.

[0051] In the present invention, the organic solvent in step (1) is preferably ethanol, N,N - dimethylformamide or acetonitrile, more preferably ethanol or N,N - dimethylformamide, and still more preferably ethanol.

[0052] In the present invention, the reaction temperature in step (1) is preferably 50 - 110 °C, more preferably 60 - 95 °C, and still more preferably 75 - 80 °C; the reaction time is preferably 3 - 24 h, more preferably 5 - 20 h, and still more preferably 12 - 15 h.

[0053] In the present invention, the specific method of the reaction in step (1) is: heating under reflux.

[0054] In the present invention, after the reaction in step (1), it further includes:

[0055] The obtained product precipitates in solid form, and after filtration, washing and drying, naphthalenediimide - diol is obtained;

[0056] The washing is preferably carried out with ethanol, and more preferably with ethanol three times.

[0057] In the present invention, the organic solvent in step (2) is preferably one or more of chloroform, N,N-dimethylformamide, 2,2,2-trifluoroethanol, and hexafluoroisopropanol, more preferably one or more of chloroform, N,N-dimethylformamide, and 2,2,2-trifluoroethanol, and still more preferably one or two of chloroform or N,N-dimethylformamide.

[0058] In the present invention, the molar volume ratio of the naphthalenediimide-diol, bromoacetic acid, 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, and the organic solvent in step (2) is preferably 3-8 mmol: 10-20 mmol: 0.3-1 mmol: 10-20 mmol: 40-80 mL, more preferably 4-7 mmol: 12-18 mmol: 0.5-0.9 mmol: 12-18 mmol: 45-70 mL, and still more preferably 5-6 mmol: 15-16 mmol: 0.6-0.8 mmol: 14-16 mmol: 55-60 mL.

[0059] In the present invention, the temperature of the reaction in step (2) is preferably 70-110 °C, more preferably 80-100 °C, and still more preferably 85-95 °C; the reaction time is preferably 12-48 h, more preferably 15-40 h, and still more preferably 20-30 h.

[0060] In the present invention, after the reaction in step (2), it further includes:

[0061] Adding a solvent to the obtained product to precipitate the product in solid form, and obtaining naphthalenediimide-dibromide through filtration, washing, and drying;

[0062] The solvent is preferably ether, tetrahydrofuran, or toluene, more preferably ether or tetrahydrofuran, and still more preferably tetrahydrofuran;

[0063] The washing is preferably carried out by washing successively with ethanol and chloroform.

[0064] In the present invention, when m = 2 in the perylene diimide-diamine in step (3), it is consistent with the preparation method of PDIN described in Patent CN 114507232B; when m is other integers from 1 to 8, the preparation method of the perylene diimide-diamine is consistent with the preparation method of PDIN described in Patent CN 114507232B. The only difference is that when m = 1, 3, 4, 5, 6, 7, 8, N,N-dimethyl-1,3-diaminopropane is respectively replaced by N,N-dimethyl-1,2-diaminoethane, N,N-dimethyl-1,4-diaminobutane, N,N-dimethyl-1,5-diaminopentane, N,N-dimethyl-1,6-diaminohexane, N,N-dimethyl-1,7-diaminoheptane, N,N-dimethyl-1,8-diaminooctane, N,N-dimethyl-1,9-diaminononane.

[0065] In the present invention, the organic solvent described in step (3) is preferably dichloromethane, 1,2-dichloroethane, N,N-dimethylformamide or tetrahydrofuran, more preferably dichloromethane, 1,2-dichloroethane or N,N-dimethylformamide, and still more preferably dichloromethane or 1,2-dichloroethane.

[0066] In the present invention, the molar volume ratio of the naphthalene diimide-dibromo, perylene diimide-diamine and organic solvent in step (3) is preferably 0.5 - 1.5 mmol: 0.5 - 1.5 mmol: 3 - 15 mL, more preferably 0.8 - 1.2 mmol: 0.6 - 1.0 mmol: 5 - 12 mL, and still more preferably 0.9 - 1 mmol: 0.7 - 0.8 mmol: 8 - 10 mL.

[0067] In the present invention, the temperature of the reaction in step (3) is preferably 50 - 80 °C, more preferably 55 - 75 °C, and still more preferably 60 - 65 °C; the reaction time is preferably 1 - 10 h, more preferably 4 - 8 h, and still more preferably 5 - 6 h.

[0068] In the present invention, the specific method of the reaction in step (3) is: the reaction is carried out in an oil bath.

[0069] In the present invention, after the reaction in step (3) is completed, it further includes:

[0070] Adding a solvent to the obtained product, filtering, washing, then subjecting to Soxhlet extraction and dialysis for purification, and then removing water to obtain the polymer NDIN-PDIN-P;

[0071] The solvent is preferably water, ethanol or ether, more preferably water or ether, and still more preferably ether;

[0072] The time of the Soxhlet extraction is preferably 24 h;

[0073] The specific method of dialysis:

[0074] After drying the product extracted by Soxhlet extraction, it was dissolved in trifluoroethanol and dialyzed in water for 3 days using a dialysis bag with a molecular weight cut-off of 3500.

[0075] The present invention also provides an application of a polymer with alternating perylene diimide and naphthalene diimide in the material of the electron transport layer of a solar cell.

[0076] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0077] Example 1

[0078] (1) 1,4,5,8-Naphthalenetetracarboxylic dianhydride (R 1 =H, 10 mmol, 2.68 g), ethanolamine (n = 1, 30 mmol, 1.83 g) were placed in a 250 mL single-necked round-bottom flask, 120 mL of ethanol was added as a solvent, and the reaction was carried out at 85 °C for 24 hours under heating and reflux. After the reaction, the product precipitated in solid form, was filtered, washed 3 times with ethanol and then dried to obtain the product naphthalene diimide-diol as a light brown solid, without purification, and the yield was 80%;

[0079] (2) Naphthalene diimide-diol (R 1 =H, n = 1, 5 mmol, 1.77 g), bromoacetic acid (15 mmol, 2.07 g), 4-dimethylaminopyridine (DMAP, 0.5 mmol, 61 mg) were placed in a dry 100 mL round-bottom flask, 50 mL of anhydrous N,N-dimethylformamide was added as a solvent, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDCI, 12 mmol, 2.3 g) was added at room temperature, and the system was heated to 80 °C and reacted for 12 hours. After the reaction, it was cooled to room temperature, and tetrahydrofuran was added to precipitate the product solid. After filtration, it was washed successively with ethanol and chloroform and then dried to obtain naphthalene diimide-dibromo as a light yellow solid, and the yield was 70%.

[0080] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum of the above-prepared naphthalene diimide-dibromo are respectively as shown in Figure 1 、 2 shown. From Figure 1 、 2 it can be seen that 11H NMR (400 MHz, CDCl3) δ (ppm) = 7.74 (s, 4H), 3.59 (t, J = 5.20 Hz, 4H), 3.49 (t, J = 5.20 Hz, 4H), 3.45 (s, 4H); 13 13C NMR (100 MHz, CDCl3) δ (ppm) = 167.8, 163.0, 131.0, 126.5, 126.4, 41.5, 39.1;

[0081] (3) Weigh naphthalenediimide - dibromo (R 1 = H, n = 1; 1 mmol, 596 mg), perylenediimide - diamine (R 2 = H, m = 2; 1 mmol, 560 mg) into a 20 mL pressure - resistant reaction tube, add 5 mL of 2,2,2 - trifluoroethanol as the solvent, and place the reaction tube in an 80 °C oil bath for reaction for 48 hours. After the reaction is completed, cool it to room temperature, add 100 mL of tetrahydrofuran, and the product precipitates as a red solid. After filtration, the crude product is obtained. The solid is subjected to Soxhlet extraction with chloroform for 24 hours, dried and dissolved in 10 mL of trifluoroethanol. Using a dialysis bag with a molecular weight cut - off of 3500, dialysis is carried out in distilled water for 3 days, during which the water is changed 5 times. After dialysis, the distilled water is removed by freeze - drying to obtain the polymer NDIN - PDIN - P as a dark - black solid with a yield of 70%; among them, the preparation method of the perylenediimide - diamine is the same as that of PDIN in Patent CN 114507232B.

[0082] The ultraviolet - visible absorption spectrum of the polymer NDIN - PDIN - P prepared above is as Figure 3 shown. As Figure 3 can be seen, the absorption peaks at 310 - 400 nm are the characteristic absorption peaks of naphthalenediimide, and the absorption peaks at 420 - 600 nm are the characteristic absorption peaks of perylenediimide, proving that this material contains both of the above - mentioned two units.

[0083] The gel permeation chromatography of the polymer NDIN - PDIN - P prepared above is shown in Table 1. As can be seen from Table 1, the average molecular weight of the polymer NDIN - PDIN - P is 12786.

[0084] Table 1 Gel permeation chromatography results of polymer NDIN - PDIN - P

[0085]

[0086]

[0087] Characterize the physical and chemical properties and morphology of the polymer NDIN - PDIN - P prepared in Example 1, and the results are as Figure 4As shown. From Figure 4 it can be seen that ultraviolet photoelectron spectroscopy was used to test the material NDIN-PDIN-P. The results show that NDIN-PDIN-P can significantly reduce the work function of the metal silver electrode (WF(NDIN-PDIN-P) = 4.20 eV; WF(Ag) = 4.60 eV, Figure 4 a); the conductivity test result is 1.08×10 -6 S / cm( Figure 4 b); the surface of the thin film was observed by atomic force microscopy ( Figure 4 c, d), showing that the thin film is flat and has a low roughness (RMS = 0.974 nm).

[0088] Application Example 1

[0089] The polymer NDIN-PDIN-P is used as an electron transport layer material in an organic solar cell device:

[0090] Among them, the donor material used in the battery device is PM6, and the acceptor material is L8-BO. Its structure is as follows:

[0091]

[0092] The washed and dried ITO glass substrate was treated with Plasma for 15 minutes. After filtering the PEODT:PSS aqueous solution with a water-soluble filter head, it was spin-coated on the ITO substrate at a speed of 6000 revolutions per minute and annealed at 150 °C for 15 minutes to form a uniform thin film; then a chloroform (CF) solution with a mass ratio of PM6 to L8-BO of 1:1.2 (15 mg / mL, the total concentration of PM6 and L8-BO) (DBCl + CF = 12 mg / mL, DBCl is 1,3-dibromo-5-chlorobenzene) was uniformly spin-coated on top of PEDOT:PSS, and then annealed at 80 °C for 5 minutes (the thickness is about 90 nm), and then a 2,2,2-trifluoroethanol solution of NDIN-PDIN-P with a concentration of 1 mg / mL was spin-coated at a speed of 3500 revolutions per minute as the electron transport layer (the thickness is 5 nm), and finally a 100 nm Ag electrode was evaporated.

[0093] Under the optimal conditions of the device (the test area is 0.04 cm 2 ), the J-V curve and external quantum efficiency were measured as follows Figure 5 As shown. From Figure 5 it can be seen that the open-circuit voltage is 0.89 V, the short-circuit current density is 25.76 mA / cm 2 , the fill factor is 80.3%, the photoelectric conversion efficiency is 18.42%, and the corrected current is 24.51 mA / cm 2, which proves that the material has potential application value in organic solar cells.

[0094] Application Example 2

[0095] The polymer NDIN-PDIN-P is used as an electron transport layer material in an organic solar cell device:

[0096] Among them, the donor material used in the battery device is PM6, which has the same structure as PM6 in Application Example 1; the acceptor material is BTP-4Cl, and its structure is as follows:

[0097]

[0098] The cleaned and dried ITO glass substrate was treated with Plasma for 15 minutes. After filtering the PEODT:PSS aqueous solution with a water-soluble filter head, it was spin-coated on the ITO substrate at a speed of 6000 revolutions per minute and annealed at 150 °C for 15 minutes to form a uniform thin film. Subsequently, a chlorobenzene solution with a mass ratio of PM6:BTP-4Cl of 1:1.2 (10 mg / mL, based on PM6) (added with 0.5% of 1,8-diiodooctane) was uniformly spin-coated on top of PEDOT:PSS and annealed at 80 °C for 10 minutes (thickness about 90 nm), and then a 2,2,2-trifluoroethanol solution of NDIN-PDIN-P with a concentration of 1 mg / mL was spin-coated at a speed of 3500 revolutions per minute as the electron transport layer (thickness about 5 nm). Finally, a 100-nm Ag electrode was evaporated.

[0099] Under the optimal conditions of the device (test area is 0.04 cm 2 ), the J-V curve and external quantum efficiency are as follows Figure 6 shown. From Figure 6 it can be seen that the open-circuit voltage is 0.844 V, the short-circuit current density is 27.18 mA / cm 2 , the fill factor is 78.4%, the photoelectric conversion efficiency is 18.01%, the corrected current is 26.1 mA / cm 2 , and the J-V curve and external quantum efficiency are as follows Figure 6 shown;

[0100] Application Example 3

[0101] The preparation method of the battery device described in Application Example 2 is the same, and the only difference is that the thickness of the electron transport layer is different. Electron devices with electron transport layer thicknesses of 10 nm, 20 nm, 25 nm, and 40 nm were prepared using 2,2,2-trifluoroethanol solutions of NDIN-PDIN-P with concentrations of 2 mg / mL, 4 mg / mL, 6 mg / mL, and 8 mg / mL, respectively.

[0102] The performance of the battery devices prepared in Application Example 2 and Application Example 3 was tested, and the results are shown in Table 2. It can be seen from Table 2 that under the condition that the film thickness of NDIN-PDIN-P is 40 nm, the photoelectric conversion efficiency of the device is still 15.58%, reaching 86% of the optimal photoelectric conversion efficiency, which proves that this material has potential application value in organic solar cells.

[0103] Table 2 Performance test results of the battery devices in Application Example 2 and Application Example 3

[0104] <![CDATA[V oc / V]]> <![CDATA[J sc / mA / cm 2 > FF / % PCE / % Thickness / nm 1 mg / mL 0.844 27.18 78.4 18.01 5 2 mg / mL 0.842 26.88 78.7 17.82 10 4 mg / mL 0.842 26.30 78.4 17.37 20 6 mg / mL 0.841 25.56 77.6 16.68 25 8 mg / mL 0.837 24.26 76.7 15.58 40

[0105] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A polymer with an alternating arrangement of perylene diimide and naphthalene diimide, characterized in that, The structural formula of the polymer NDIN-PDIN-P with alternating perylene diimide and naphthalene diimide is as follows: Among them, R 1 、R 2 independently is a hydrogen atom, a fluorine atom, a chlorine atom or a bromine atom; m and n are independently integers from 1 to 8, and z is an integer from 2 to 2000.

2. The preparation method of the polymer with alternating perylene diimide and naphthalene diimide, characterized in that, It includes the following steps: (1) Mix phthalic anhydride, alkanolamine and an organic solvent and react to obtain naphthalene diimide-diol; Or mix phthalic anhydride and alkanolamine and react to obtain naphthalene diimide-diol; (2) Mix naphthalene diimide-diol, bromoacetic acid, 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and an organic solvent and react to obtain naphthalene diimide-dibromide; (3) Mix naphthalene diimide-dibromide, perylene diimide-diamine and an organic solvent and react to obtain the polymer NDIN-PDIN-P.

3. The preparation method of the polymer with alternating perylene diimide and naphthalene diimide according to claim 2, characterized in that In step (1), the molar ratio of the phthalic anhydride to the alkanolamine is 0.5-1.5:2-4; In step (1), the molar volume ratio of the phthalic anhydride to the organic solvent is 0.5-1.5 mmol:8-15 mL.

4. The method for preparing a polymer with alternating perylene diimide and naphthalene diimide according to claim 2 or 3, characterized in that, In step (1), the temperature of the reaction is 50-110 °C, and the reaction time is 3-24 h.

5. The preparation method of the polymer with alternating perylene diimide and naphthalene diimide according to claim 4, characterized in that In step (2), the molar volume ratio of the naphthalene diimide-diol, bromoacetic acid, 4-dimethylaminopyridine, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride and the organic solvent is 3-8 mmol:10-20 mmol:0.3-1 mmol:10-20 mmol:40-80 mL.

6. The preparation method of the polymer with alternating perylene diimide and naphthalene diimide as claimed in claim 5, characterized in that, In step (2), the temperature of the reaction is 70-110 °C, and the reaction time is 12-48 h.

7. The preparation method of the polymer with alternating perylene diimide and naphthalene diimide according to claim 5 or 6, characterized in that In step (3), the molar volume ratio of the naphthalene diimide-dibromide, perylene diimide-diamine and the organic solvent is 0.5-1.5 mmol:0.5-1.5 mmol:3-15 mL.

8. The preparation method of the polymer with alternating perylene diimide and naphthalene diimide as claimed in claim 5 or 6, characterized in that, In step (3), the temperature of the reaction is 50-80 °C, and the reaction time is 1-10 h.

9. The preparation method of the polymer with alternating perylene diimide and naphthalene diimide according to claim 8, characterized in that In step (1), the organic solvent is ethanol, N,N-dimethylformamide or acetonitrile; In step (2), the organic solvent is one or more of chloroform, N,N-dimethylformamide, 2,2,2-trifluoroethanol and hexafluoroisopropanol; In step (3), the organic solvent is dichloromethane, 1,2-dichloroethane, N,N-dimethylformamide or tetrahydrofuran.

10. Application of the polymer with alternating perylene diimide and naphthalene diimide described in claim 1 in the electron transport layer material of a solar cell.

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