A naphthalimide-substituted quinoxaline conjugated polymer and its use in the preparation of organic photovoltaic devices

Abstract

The application relates to the technical field of photovoltaic materials, and particularly discloses a novel structure of a quinoline conjugated polymer containing naphthalimide substitution; the quinoline conjugated polymer containing naphthalimide substitution contains any structure shown in P1-P6. The quinoline conjugated polymer containing naphthalimide substitution has high energy conversion efficiency (PCE), high short-circuit current density (Jsc), open-circuit voltage (Voc) and filling factor (FF) when used as an active layer material in a polymer solar cell.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic materials technology, specifically to a naphthalimide-substituted quinoxaline conjugated polymer and its application in the preparation of organic photovoltaic devices. Background Technology

[0002] Polymer solar cells (PSCs) use π-conjugated organic semiconductors as the light-absorbing layer. They can be fabricated into lightweight, low-cost, and flexible devices through solution processing, and large-area devices can also be fabricated through high-speed roll-to-roll printing. This has led to their great application potential in wearable / portable electronics, color-changing windows, building-integrated photovoltaics, and other fields, attracting widespread attention. At the same time, organic semiconductor materials can be precisely controlled through changes in their chemical structure, such as optical absorption, electronic energy levels, crystallinity, and carrier mobility, enabling the diversified development of material systems.

[0003] In recent years, researchers both domestically and internationally have become increasingly active in this field, focusing on the design and development of novel light-absorbing layer materials. For example, Chinese invention patent CN107903278A discloses an organic small molecule material containing benzodithiophene, its preparation method, and its applications. The preparation of this material includes the following steps: synthesizing a monomer containing acetylene silane and aldehyde groups with benzodithiophene as the core through a coupling reaction; obtaining an intermediate containing terminal alkyne active groups by removing the alkyl silane groups from the monomer; performing a Sonogashira coupling reaction between the intermediate containing terminal alkyne active groups and Al containing halogenated groups to obtain an organic small molecule material containing aldehyde functional groups; and performing a Knoevenagel condensation reaction between the organic small molecule material containing aldehyde functional groups and Al under alkaline catalysis to obtain the target small molecule material. This material exhibits broader and stronger absorption and good thermal stability, making it suitable for use in organic photovoltaic devices. However, its maximum energy conversion efficiency is only 6.25%, requiring further improvement. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, the present invention provides a naphthalimide-substituted quinoxaline conjugated polymer.

[0005] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0006] This invention first provides a naphthalimide-substituted quinoxaline conjugated polymer, wherein the naphthalimide-substituted quinoxaline conjugated polymer contains any of the structures shown in P1-P6:

[0007]

[0008] Preferably, n>1 in the structures shown in P1-P6.

[0009] More preferably, 6 ≤ n ≤ 30.

[0010] Preferably, R in the structures shown in P1-P6 is selected from alkyl groups.

[0011] More preferably, R in the structures shown in P1-P6 is selected from C. 20-30 alkyl.

[0012] Preferably, the Donor in the structures shown in P1-P6 is selected from any of the following structures:

[0013] Donor:

[0014] Preferably, in the Donor structure, R is selected from alkyl groups; X is selected from H, F, or Cl.

[0015] Preferably, the naphthalimide-substituted quinoxaline conjugated polymer has the following structure:

[0016]

[0017] Preferably, X in the naphthalimide-substituted quinoxaline conjugated polymer structure is selected from H, F, or Cl.

[0018] Preferably, n>1 in the structure of the naphthalimide-substituted quinoxaline conjugated polymer.

[0019] This invention also provides the application of a naphthalimide-substituted quinoxaline conjugated polymer in the preparation of organic photovoltaic devices.

[0020] Beneficial effects: This invention provides a novel naphthaleneimide-substituted quinoxaline conjugated polymer. When used as an active layer material in polymer solar cells, this naphthaleneimide-substituted quinoxaline conjugated polymer exhibits high power conversion efficiency (PCE), as well as high short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF). Its PCE is significantly higher than that of the benzo[a]thiophene-containing small molecule organic material disclosed in prior art CN107903278A. Furthermore, its short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) are also significantly higher than those of the benzo[a]thiophene-containing small molecule organic material disclosed in prior art CN107903278A. Attached Figure Description

[0021] Figure 1 Thermogravimetric curves of the polymer donors obtained from polymers PDNB and PDNB-2F in the present invention are shown.

[0022] Figure 2 The diagram shows the redox potential curves of the polymer donors obtained from polymers PDNB and PDNB-2F in the embodiments of the present invention.

[0023] Figure 3 The UV-Vis absorption spectra of the polymer donors obtained from polymers PDNB and PDNB-2F in this invention are shown.

[0024] Figure 4 The device performance spectra of polymer donors obtained from polymers PDNB and PDNB-2F in this invention are shown. Detailed Implementation

[0025] The present invention will be further explained below with reference to the embodiments, but the embodiments do not limit the present invention in any way.

[0026] The raw materials used in the following examples are all conventional raw materials that can be purchased by those skilled in the art or prepared by conventional methods; the reaction conditions not specified in detail in the following examples are all conventional conditions well known to those skilled in the art.

[0027] The synthetic routes for the naphthalimide-substituted quinoxaline conjugated polymers in the following examples are as follows:

[0028]

[0029] Example 1: Naphthalimide-substituted quinoxaline conjugated polymer

[0030] The naphthalimide-substituted quinoxaline conjugated polymer in this embodiment has the following structure:

[0031] Where n = 21.

[0032] As shown in the above synthetic route, the preparation method of the naphthaleneimide-substituted quinoxaline conjugated polymer is as follows:

[0033] (1) An acetic acid solution of compound M1 reacted with compound M2 at 120°C for 12 h to give compound M3;

[0034] (2) Compound M3 and compound M4 were coupled by Stille coupling reaction for 12 h at a reaction temperature of 120 °C in N,N-dimethylformamide as solvent and tetra-triphenylphosphine palladium as catalyst to obtain compound M5.

[0035] (3) Compound M5 was reacted with NBS at room temperature for 8 hours in tetrahydrofuran as solvent to obtain compound M6;

[0036] (4) Compound M6 was polymerized with compound M7 at 120°C for 48 h in chlorobenzene solvent and palladium catalyst to obtain a naphthalimide-substituted quinoxaline conjugated polymer (abbreviated as PDNB).

[0037] In steps (1)-(4), the molar ratio of the reactants in each step is 1:1.

[0038] The molecular weight and elemental analysis data of PDNB are as follows:

[0039] Mn=35.99kDa, Mw=87.62kDa, PDI=2.43.Anal.Calcd for C 104 H 135 F2N3O2S6:C,73.93;H,8.05;N,2.49.Found:C,73.41;H,8.03;N,2.38.

[0040] Example 2: Naphthalimide-substituted quinoxaline conjugated polymer

[0041] The naphthalimide-substituted quinoxaline conjugated polymer in this embodiment has the following structure:

[0042] Where n = 22.

[0043] As shown in the above synthetic route, the preparation method of the naphthaleneimide-substituted quinoxaline conjugated polymer is as follows:

[0044] (1) An acetic acid solution of compound M1 reacted with compound M2 at 120°C for 12 h to give compound M3;

[0045] (2) Compound M3 and compound M4 were coupled by Stille coupling reaction for 12 h at a reaction temperature of 120 °C in N,N-dimethylformamide as solvent and tetra-triphenylphosphine palladium as catalyst to obtain compound M5.

[0046] (3) Compound M5 was reacted with NBS at room temperature for 8 hours in tetrahydrofuran as solvent to obtain compound M6;

[0047] (4) Compound M6 was polymerized with compound M8 at 120°C for 48 h in chlorobenzene solvent and palladium catalyst to obtain a naphthalimide-substituted quinoxaline conjugated polymer (abbreviated as PDNB-2F).

[0048] In steps (1)-(4), the molar ratio of the reactants in each step is 1:1.

[0049] The molecular weight and elemental analysis data of PDNB-2F are as follows:

[0050] Mn=39.31kDa, Mw=106.43kDa, PDI=2.71.Anal.Calcd for C 104 H 133 F4N3O2S6:C,72.39;H,7.77;N,2.44.Found:C,72.18;H,7.68;N,2.36.

[0051] Experimental Example 1

[0052] Using the naphthaleneimide-substituted quinoxaline conjugated polymers described in Examples 1 and 2 as the active layer material, organic solar cell devices were fabricated according to the method in "Zhang Bo et al. Design, synthesis and photovoltaic application of wide-bandgap conjugated polymers based on 3,4-dicyanothiophene [J]. Acta Polymerica Sinica. 2020, 6(51):620-631."; and their photovoltaic performance, such as power conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF), was tested; the test results are shown in Table 1.

[0053] Table 1. Photovoltaic performance test results of the naphthalimide-substituted quinoxaline conjugated polymer of the present invention.

[0054]

[0055] As can be seen from the experimental results in Table 1, when the naphthalimide-substituted quinoxaline conjugated polymer prepared in Example 1 is used as an active layer material in organic solar cell devices, its power conversion efficiency (PCE) reaches 8.83%, which is significantly higher than that of the benzodithiophene-containing organic small molecule material disclosed in the prior art CN107903278A. In addition, its photovoltaic performance, such as short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF), is also significantly higher than that of the benzodithiophene-containing organic small molecule material disclosed in the prior art CN107903278A.

[0056] Furthermore, the experimental results in Table 1 also show that when the naphthaleneimide-substituted quinoxaline conjugated polymer prepared in Example 2 is used as an active layer material in organic solar cell devices, its power conversion efficiency (PCE) reaches 12.18%, which is significantly higher than that of the naphthaleneimide-substituted quinoxaline conjugated polymer prepared in Example 1. In addition, its short-circuit current density (Jsc) is also significantly higher than that of the naphthaleneimide-substituted quinoxaline conjugated polymer prepared in Example 1. This indicates that in the naphthaleneimide-substituted quinoxaline conjugated polymers of the structure described in this invention, the PCE of the naphthaleneimide-substituted quinoxaline conjugated polymer after X is substituted by F is significantly higher than that of the naphthaleneimide-substituted quinoxaline conjugated polymer after X is substituted by H; simultaneously, the short-circuit current density (Jsc) of the naphthaleneimide-substituted quinoxaline conjugated polymer after X is substituted by F is also significantly higher than that of the naphthaleneimide-substituted quinoxaline conjugated polymer after X is substituted by H.

Claims

1. A naphthalimide-substituted quinoxaline conjugated polymer, characterized in that, The aforementioned naphthalimide-substituted quinoxaline conjugated polymer has the following structure: ； In the structure of the naphthalimide-substituted quinoxaline conjugated polymer, X is selected from H, F, or Cl; The n>1 in the structure of the naphthalimide-substituted quinoxaline conjugated polymer.

2. The application of the naphthalimide-substituted quinoxaline conjugated polymer according to claim 1 in the preparation of organic photovoltaic devices.

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