Naphthalimide cathode interface layer material containing benzoheterocyclic side chain and preparation method of naphthalimide cathode interface layer material

Abstract

The invention belongs to the technical field of organic photoelectric materials, and particularly relates to an electron transport layer material based on a naphthalimide derivative and a preparation method and application thereof. The material has a chemical structural general formula as shown in a formula I, wherein R substituent groups are selected from specific aryl functional groups as shown in a formula II. Naphthalimide is used as an electron transmission core skeleton, and multi-function optimization is realized through structural modification: (1) a naphthalimide conjugated system and an active layer are complementary in light absorption wavelength, so that photon energy loss is reduced; (2) the LUMO energy level is remarkably improved by introducing an electron withdrawing group, a proper energy level gradient is formed with a common acceptor material, and the electron injection driving force is enhanced; and (3) modification of side chain polar groups endows the material with excellent alcohol-soluble characteristics. In addition, a Suzuki coupling reaction one-step method is adopted for preparation, the process is simple and efficient, good stability and repeatability are achieved, the cost is low, and large-scale industrial production is easy.

Description

Technical Field

[0001] The present invention relates to the technical field of organic photoelectric materials, in particular to a naphthalimide cathode interface layer material containing a benzoheterocyclic side chain and a preparation method thereof. Background Art

[0002] As a representative of the new generation of photovoltaic technology, organic solar cells have attracted much attention in the field of clean energy due to their outstanding advantages such as light weight, flexibility, environmental friendliness, and solution processability. After scientific research, their photoelectric conversion efficiency has leapt from less than 1% in the initial stage to more than 20% at present. The interface engineering system of organic solar cells is mainly composed of electron transport layer (ETL) and hole transport layer (HTL). Its core functions can be summarized as follows: 1) optimizing the energy level gradient by regulating the physical and chemical properties of the interface, thereby reducing the Schottky barrier between the electrode and the active layer; 2) inducing the active layer to form a vertical phase separation structure, thereby increasing the electron / hole mobility ratio; 3) constructing a physical barrier to isolate external water and oxygen, thereby improving device stability; 4) improving the morphology of the active layer and improving the carrier transport efficiency.

[0003] The current electron transport layer material system is showing a diversified development trend. According to the intrinsic properties of the materials, it can be divided into two categories: inorganic and organic. The inorganic system mainly includes low work function metals (such as Ca, Ba), metal salts (LiF, CsF) and transition metal oxides (ZnO X 、TiO X 、SnO X ) are divided into three categories. Organic systems mainly include n-type conjugated semiconductors (fullerene derivatives, perylene imide materials), ionic polyelectrolytes (polyfluorene electrolytes, polythiophene electrolytes, etc.) and non-conjugated neutral polymers (PEI, PEO, etc.). Among them, organic electron transport materials represented by PFN-Br and PDIN have become standardized components in organic photovoltaic devices and have commercial application prospects due to their solution processability and interface modification capabilities. However, existing interface materials generally have problems such as complex synthesis routes, high raw material costs or the involvement of high-risk reagents. Therefore, the development of new electron transport materials with simple synthesis processes, environmentally friendly properties and excellent device compatibility has become one of the key research directions to promote breakthroughs in the industrialization of organic photovoltaic technology. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a naphthalimide cathode interface layer material containing benzoheterocyclic side chains and its preparation and application. Specifically, a benzoheterocyclic functional unit and its specific substituent group are introduced into the side chain of the core skeleton through a molecular engineering strategy. The introduction of a large planar benzene ring regulates the molecular stacking pattern through a steric effect, which not only suppresses the excessive aggregation of the rigid skeleton, but also promotes the orderly arrangement of the side groups; secondly, the polar substituents form a three-dimensional network structure through intermolecular interactions, significantly improving the crystallinity of the film and reducing the surface roughness. Finally, the synthesis method is simple and efficient, with good stability and easy to produce on a large scale.

[0005] In a first aspect of the present invention, a naphthalimide cathode interface layer material containing a benzoheterocyclic side chain is provided, the structural formula of which is shown in Formula I;

[0006]

[0007] Wherein, R is any one of the following structures:

[0008]

[0009] Optionally, the molecular structure of the naphthalimide cathode interface layer material containing a benzoheterocyclic ring in the side chain is:

[0010]

[0011] The second aspect of the present invention provides a photovoltaic device comprising the naphthaleneimide cathode interface layer material containing a benzoheterocyclic side chain as described in the first aspect.

[0012] Optionally, the photovoltaic device structure includes, in sequence: a substrate, an anode interface layer, an active layer, a cathode interface layer and a metal electrode.

[0013] Optionally, the substrate includes transparent glass and a transparent conductive film.

[0014] Optionally, the anode interface layer is selected from any one of PEDOT:PSS and MoO3.

[0015] Optionally, the cathode interface layer is selected from any one of NDI-SZ and NDI-BI.

[0016] Optionally, the thickness of the anode interface layer is 20 to 50 nm.

[0017] Optionally, the cathode interface layer has a thickness of 5 to 15 nm.

[0018] Optionally, the active layer has a thickness of 80 to 150 nm.

[0019] Optionally, the metal electrode is selected from any one of silver and aluminum.

[0020] Optionally, the photovoltaic device is a polymer solar cell.

[0021] Here, polymer solar cells refer to active layers in which the donor is a polymer and the acceptor is a small molecule.

[0022] In a third aspect of the present invention, a method for preparing the naphthalimide cathode interface layer material containing a benzoheterocyclic side chain according to the first aspect is provided, comprising mixing raw materials and reacting to obtain the naphthalimide cathode interface layer material containing a benzoheterocyclic side chain, wherein the raw materials include: 4,9-dibromoisochromeno[6,5,4-DEF]isochromene-1,3,6,8-tetraketone, 3-dimethylaminopropylamine, and benzoheterocyclic borate. The molecular structure of the naphthalimide cathode interface layer material containing a benzoheterocyclic side chain is shown below:

[0023]

[0024] Wherein, R is any one of the following structures:

[0025]

[0026] Optionally, in the molecular structure of the naphthalimide cathode interface layer material containing a benzoheterocyclic side chain, R can be any one of the following structures:

[0027]

[0028] Optionally, the preparation method of the naphthalimide cathode interface layer material containing benzoheterocyclic side chains comprises the following steps:

[0029] (1) adding 4,9-dibromoisochromeno[6,5,4-DEF]isochromene-1,3,6,8-tetraone and 3-dimethylaminopropylamine to a reaction solvent to obtain NDI-2Br after reaction;

[0030] (2) mixing NDI-2Br, benzoheterocyclic borate, solvent, and catalyst to react to obtain the cathode interface layer material;

[0031] The reaction scheme is as follows:

[0032]

[0033] Optionally, in step (1), the molar ratio of 4,9-dibromoisochromeno[6,5,4-DEF]isochromene-1,3,6,8-tetraone to 3-dimethylaminopropylamine is 1:2 to 1:6;

[0034] Optionally, in step (1), the solvent is selected from at least one of acetic acid, n-butanol, and toluene;

[0035] Optionally, in step (1), the reaction temperature is 80-100° C., and the reaction time is 10-24 h;

[0036] Optionally, in step (1), after the reaction is completed, the system is cooled to room temperature, poured into ice water, and then 4N sodium hydroxide solution is added to adjust the pH to 7-9, extracted with dichloromethane, and the organic phase is concentrated, followed by column chromatography (the column is filled with 300-400 mesh silica gel, and the eluent is dichloromethane and methanol in a volume ratio of 20:1) for purification, and finally dried and concentrated to obtain the product NDI-2Br;

[0037] Optionally, in step (2), the molar ratio of NDI-2Br to benzoheterocyclic borate is 1:2 to 1:6;

[0038] Optionally, in step (2), the solvent is selected from at least one of toluene, xylene, and 1,4-dioxane;

[0039] Optionally, in step (2), the catalyst is selected from at least one of tetrakis(triphenylphosphine)palladium, trisdibenzylideneacetone dipalladium, and 1,1'-bis(diphenylphosphinodiphenylphosphinodiphenylphosphine)palladium dichloride;

[0040] Optionally, in step (2), the reaction temperature is 100-120° C., and the reaction time is 18-36 h;

[0041] Optionally, in step (2), after the reaction is completed, the system is cooled to room temperature, the reaction solution is decompressed to remove the solvent, and the cathode interface layer material is separated by silica gel column chromatography (the column is filled with 300-400 mesh silica gel, and the eluent is dichloromethane and methanol in a volume ratio of 5:1).

[0042] The present invention has the following beneficial effects:

[0043] This invention uses naphthaleneimide as the core structure and successfully synthesizes a new material with excellent alcohol solubility through a coupling reaction with benzoheterocyclic borate. Due to its good solubility, this material provides a key guarantee for its application as an electron transport layer in solar cells. The unique visible light absorption characteristics of the naphthaleneimide structure complement the spectral response of the solar cell active layer, effectively broadening the light absorption range; at the same time, its high LUMO energy level significantly improves the conductivity of the electron transport layer, thereby enhancing the open-circuit voltage and short-circuit current density of the device, ultimately achieving higher photoelectric conversion efficiency, and providing an innovative solution for the research and development of high-efficiency solar cell materials.

[0044] The synthesis process of the present invention is ingeniously designed and simple to operate. By optimizing reaction conditions and raw material ratios, an efficient and controllable material preparation process is achieved. This method exhibits excellent stability and high reproducibility, significantly reducing synthesis costs. It also has broad material applicability and can be flexibly applied to the synthesis of derivatives with different structures. Its modular design is particularly well-suited to industrial production needs, laying a solid technical foundation for the large-scale commercial preparation of high-performance electron transport layer materials, balancing the dual value of scientific research innovation and industrial implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0046] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of NDI-SZ prepared in Example 1 of the present invention;

[0047] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of NDI-BI prepared in Example 2 of the present invention;

[0048] Figure 3 When the donor material is PM6 and the acceptor material is L8-BO, the photoelectric conversion efficiency of the organic solar cell device using NDI-SZ prepared in Example 3 of the present invention as the electron transport layer material;

[0049] Figure 4 When the donor material is PM6 and the acceptor material is L8-BO, the external quantum efficiency of the organic solar cell device using NDI-SZ prepared in Example 3 of the present invention as the electron transport layer material is shown;

[0050] Figure 5 When the donor material is PM6 and the acceptor material is L8-BO, the photoelectric conversion efficiency of the organic solar cell device using NDI-BI prepared in Example 4 of the present invention as the electron transport layer material;

[0051] Figure 6 When the donor material is PM6 and the acceptor material is L8-BO, the external quantum efficiency of the organic solar cell device using NDI-BI prepared in Example 4 of the present invention as the electron transport layer material is shown; DETAILED DESCRIPTION

[0052] The following descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise indicated, all technical and scientific terms used in this application have the same meanings as those commonly understood by those of ordinary skill in the art to which this application belongs. The reagents used in this example do not have the manufacturer indicated and are all conventional products available on the market.

[0053] Example 1:

[0054] 1. Synthesis of NDI-2Br compound. The synthesis method is as follows:

[0055]

[0056] The specific synthesis steps are:

[0057] 4,9-Dibromoisochromeno[6,5,4-DEF]isochromene-1,3,6,8-tetraone (5 g, 11.75 mmol) was weighed into a 50 mL dry two-necked flask. 50 mL of acetic acid (AcOH) was added as the reaction solvent. 3-Dimethylaminopropylamine (47 mmol) was then added to the flask. The mixture was heated to 90°C in an oil bath and stirred for 10 hours. After the reaction, the mixture was cooled to room temperature and poured into ice water (50 mL). The pH was adjusted to 7-9 with 4N sodium hydroxide solution. The mixture was extracted with dichloromethane three times (3 times with 100 mL). The organic phase was concentrated and purified by column chromatography (packed with 300-400 mesh silica gel and eluent: dichloromethane:methanol in a 20:1 volume ratio). Finally, the mixture was dried and concentrated to afford NDI-2Br as a gray-green solid in approximately 85% yield. Characterization data of NDI-2Br: 1H NMR (400 MHz, Chloroform-d) δ 8.99 (s, 2H), 4.30–4.24 (m, 4H), 2.44 (t, J = 7.2 Hz, 4H), 2.23 (s, 12H), 1.96–1.88 (m, 4H).

[0058] 2. Synthesis of naphthaleneimide derivative NDI-SZ. The synthesis method is as follows:

[0059]

[0060] The specific synthesis steps are:

[0061] NDI-2Br (0.594 g, 1 mmol), benzothiazole borate ester 2a (0.9 g, 3 mmol), potassium carbonate (2.77 g, 20 mmol), tetrakis(triphenylphosphine)palladium (57.8 mg, 0.05 mmol), and toluene (20 mL) were added to a 100 mL Schlenk reaction tube. The mixture was heated to 100°C in an oil bath and stirred for 18 hours. After the reaction, the mixture was cooled to room temperature and concentrated to obtain the crude product. The crude product was then purified by column chromatography (packed with 300-400 mesh silica gel and eluent: dichloromethane:methanol in a volume ratio of 5:1). Finally, the product was dried and concentrated to obtain NDI-SZ as a red solid in approximately 80% yield. Characterization data of NDI-SZ: 1H NMR(400MHz,Chloroform-d)δ8.72(s,2H),8.00–7.93(m,4H),7.40(m,2H),4.17–4. 09(m,4H),2.89(s,6H),2.35(t,J=7.2Hz,4H),2.19(s,12H),1.83(t,J=7.2Hz,4H).

[0062] The H NMR spectrum of NDI-SZ is as follows Figure 1 shown.

[0063] Example 2:

[0064] The synthesis of the naphthalene imide derivative NDI-BI is shown in the figure below:

[0065]

[0066] The specific synthesis steps are:

[0067] NDI-2Br (0.594 g, 1 mmol), benzimidazole borate ester 2b (0.955 g, 3 mmol), potassium carbonate (2.77 g, 20 mmol), tetrakis(triphenylphosphine)palladium (57.8 mg, 0.05 mmol), and toluene (20 mL) were added to a 100 mL Schlenk reaction tube. The mixture was heated to 100°C in an oil bath and stirred for 18 hours. After the reaction, the mixture was cooled to room temperature and concentrated to obtain a crude product. The product was then purified by column chromatography (packed with 300-400 mesh silica gel and eluent: dichloromethane:methanol in a volume ratio of 5:1). Finally, the product was dried and concentrated to obtain a red solid, NDI-BI, in an approximately 85% yield. Characterization data of NDI-BI: 1 HNMR(400MHz,Chloroform-d)δ8.71(s,2H),7.37–7.30(m,2H),7.00–6.92(m,2H),4.71(m,2H),4.14(t ,J=7.6Hz,4H),2.70(s,6H),2.40(d,J=7.2Hz,4H),2.23(s,12H),1.87(t,J=7.2Hz,4H),1.65(s,12H).

[0068] The H NMR spectrum of NDI-BI is as follows Figure 2 shown.

[0069] Example 3:

[0070] Organic solar cell devices using naphthaleneimide derivative NDI-SZ as electron transport layer material:

[0071] Among them, the donor material used in the battery device is PM6, and the acceptor material is L8-BO. ​​Its structure is shown in the figure below:

[0072]

[0073] (1) Ultrasonic cleaning of the ITO glass was performed for 10 min using detergent, deionized water, acetone, and isopropyl alcohol, respectively. After drying, the ITO glass was placed in a UV-ozone cleaning machine for 20 min. All subsequent steps were performed in a glove box.

[0074] (2) Use DIB as an additive and dissolve it in chloroform at a concentration of 12 mg / mL.

[0075] (3) PM6 and L8-BO were used as the donor material and acceptor material of the active layer, respectively, with a mass ratio of 1:1.2, and were dissolved in the above DIB chloroform solution to a total concentration of 15 mg / mL.

[0076] (4) Static coating of hole transport layer: 2PACz was dissolved in ethanol to prepare a 0.27 mg / mL solution, and the solution was spin-coated on the ITO glass at a speed of 3000 rpm, and then annealed at 100 °C for 10 min.

[0077] (5) Spin coating the active layer: The mixed solution was spin-coated on the surface of the hole transport layer at a speed of 3000 rpm, and then annealed at 100 °C for 10 min.

[0078] (6) Spin coating of electron transport layer: The product NDI-SZ prepared in Example 1 was dissolved in methanol at a concentration of 1.5 mg / mL, and then the solution was spin-coated on the active layer at a speed of 3000 rpm to obtain a cathode interface layer.

[0079] (7) Vacuum evaporation metal cathode: 100 nm of Ag was evaporated as the cathode using a vacuum evaporation system. The effective area of ​​the device was 0.04 cm 2 Under the optimal conditions of the device, the parameters are measured as shown in Table 1:

[0080] Table 1: Photoelectric performance of OSCs based on NDI-SZ cathode interface layer in PM6:L8-BO system

[0081]

[0082] Example 4:

[0083] Organic solar cell devices using naphthaleneimide derivative NDI-BI as electron transport layer material:

[0084] (1) Ultrasonic cleaning of the ITO glass was performed for 10 min using detergent, deionized water, acetone, and isopropyl alcohol, respectively. After drying, the ITO glass was placed in a UV-ozone cleaning machine for 20 min. All subsequent steps were performed in a glove box.

[0085] (2) Use DIB as an additive and dissolve it in chloroform at a concentration of 12 mg / mL.

[0086] (3) PM6 and L8-BO were used as the donor material and acceptor material of the active layer, respectively, with a mass ratio of 1:1.2, and were dissolved in the above DIB chloroform solution to a total concentration of 15 mg / mL.

[0087] (4) Static coating of hole transport layer: 2PACz was dissolved in ethanol to prepare a 0.27 mg / mL solution, and the solution was spin-coated on the ITO glass at a speed of 3000 rpm, and then annealed at 100 °C for 10 min.

[0088] (5) Spin coating the active layer: The mixed solution was spin-coated on the surface of the hole transport layer at a speed of 3000 rpm, and then annealed at 100 °C for 10 min.

[0089] (6) Spin coating of electron transport layer: The product NDI-BI prepared in Example 2 was dissolved in methanol at a concentration of 1.5 mg / mL, and then the solution was spin-coated on the active layer at a speed of 3000 rpm to obtain a cathode interface layer.

[0090] (7) Vacuum evaporation metal cathode: 100 nm of Ag was evaporated as the cathode using a vacuum evaporation system. The effective area of ​​the device was 0.04 cm 2 Under the optimal conditions of the device, the parameters are measured as shown in Table 2:

[0091] Table 2: Photoelectric performance of OSCs based on NDI-BI cathode interface layer in PM6:L8-BO system

[0092]

Claims

1. A naphthalimide-based solar cell cathode interface layer material containing a benzoheterocyclic side chain, characterized in that: The structure of the naphthalimide-based solar cell cathode interface layer material containing a benzoheterocyclic side chain is shown in Formula I: Wherein, R is any one of the following formula II structures:

2. The naphthaleneimide-based solar cell cathode interface layer material containing a benzoheterocyclic side chain according to claim 1, characterized in that: Its molecular structure is:

3. The method for preparing a naphthalimide cathode interface layer material containing a benzoheterocyclic side chain according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) adding 4,9-dibromoisochromeno[6,5,4-DEF]isochromene-1,3,6,8-tetraone and 3-dimethylaminopropylamine to a reaction solvent to obtain NDI-2Br after reaction. The structural formula of the NDI-2Br is shown in Formula III; (2) mixing NDI-2Br, benzoheterocyclic borate, solvent, and catalyst to react to obtain the cathode interface layer material; The reaction scheme is as follows:

4. The preparation method according to claim 3, wherein The molar ratio of the 4,9-dibromoisochromeno[6,5,4-DEF]isochromene-1,3,6,8-tetraone to 3-dimethylaminopropylamine is 1:2 to 1:6; In the step (1), the solvent is selected from at least one of acetic acid, n-butanol, and toluene; In the step (1), the reaction temperature is 80-100° C. and the reaction time is 10-24 h; In the step (1), after the reaction is completed, the system is cooled to room temperature, poured into ice water, and then 4N sodium hydroxide solution is added to adjust the pH to 7-9, extracted with dichloromethane, and the organic phase is concentrated, followed by column chromatography (the column is filled with 300-400 mesh silica gel, and the eluent is dichloromethane and methanol in a volume ratio of 20:1) for purification, and finally dried and concentrated to obtain the product NDI-2Br; In the step (2), the molar ratio of NDI-2Br to benzoheterocyclic borate is 1:2 to 1:6; In the step (2), the solvent is selected from at least one of toluene, xylene, and 1,4-dioxane; In the step (2), the catalyst is selected from at least one of tetrakis(triphenylphosphine)palladium, trisdibenzylideneacetone dipalladium, and 1,1'-bis(diphenylphosphinodiphenylphosphino)ferrocenepalladium dichloride; In the step (2), the reaction temperature is 100-120° C., and the reaction time is 18-36 h; In the step (2), after the reaction is completed, the system is cooled to room temperature, the solvent is evaporated off from the reaction solution under reduced pressure, and the cathode interface layer material is obtained by separation using silica gel column chromatography.

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