Application of imide-based large dipole moment volatile solid additive in bulk heterojunction organic solar cell

Abstract

The invention discloses application of an imide-based large-dipole-moment volatile solid additive in a bulk heterojunction organic solar cell, and belongs to the technical field of solar cell solid additives. The large-dipole-moment additive can better act on donor and acceptor molecules, the morphology of an active layer is improved, exciton dissociation and charge transfer are optimized, and finally the energy conversion efficiency of the organic solar cell is enhanced. The good volatility can prevent the additive from continuously influencing the morphology of the active layer and damaging the long-term stability of the organic solar cell. The development of the imide type additive also widens the variety of additives. More importantly, the imide type additive can induce a receptor to nucleate and then grow, so that a receptor domain with a uniform size is formed, and carrier transport is optimized.

Description

Technical Field

[0001] The present invention relates to the field of organic solar cells, and in particular to the application of a class of imide-based large dipole moment volatile solid additives in bulk heterojunction organic solar cells. Background Art

[0002] Organic solar cells have been widely studied due to their advantages such as lightness, flexibility, and solution processing. In bulk heterojunction organic solar cells, the active layer, which is a blend of donor and acceptor materials, is an important part of photoelectric conversion, and its photoelectric conversion efficiency is highly dependent on the morphology of the active layer. Solid additives are an important morphology adjustment strategy (Chinese patents, publication numbers: CN110518120A, CN119277880A, CN118890906A).

[0003] Currently, most solid additives are aromatic ring derivatives based on benzene or thiophene, which usually have small dipole moments and limited interactions with donor and acceptor molecules. Large dipole moment additives have strong intermolecular interactions and can act more effectively on donor and acceptor molecules, optimize their stacking behavior, improve the morphology of organic solar cells, and enhance the photoelectric performance. However, large dipole moment additives often have strong intermolecular interactions and are generally difficult to remove after the solar cell is prepared, which will have a negative impact on the stability of organic solar cells (OSCs). Therefore, it is extremely challenging to develop solid additives that have both large dipole moments and volatility. Summary of the invention

[0004] In view of the current research status of solid additives for organic solar cells, the purpose of the present invention is to develop a class of solid additives with large dipole moment and good removability to improve the performance of organic solar cell devices, and to achieve the volatility of large dipole moment additives by regulating the intermolecular interaction by adjusting the imide dihedral angle.

[0005] The technical solution adopted by the present invention is: application of a type of imide-based large dipole moment volatile solid additive, wherein the solid additive has the following general structural formula:

[0006]

[0007] Where Ar1 is ; R1, R2, R3, R4, R5 are each independently F, Cl, Br, I or H.

[0008] Ar2 is ; R9, R10, R11, R12 are each independently F, Cl, Br, I or H.

[0009] And R1, R2, R3, R4, R5, R9, R10, R11, and R12 are not H at the same time.

[0010] The solid additive is used as a solid additive for bulk heterojunction organic solar cells.

[0011] Furthermore, in the above simultaneous structure, R1, R2, R3, R4, and R5 are not H at the same time, and R9, R10, R11, and R12 can be H at the same time.

[0012] Furthermore, the solid additive is used in a photoactive layer of a bulk heterojunction organic solar cell.

[0013] Furthermore, the solid additive is used in the photoactive layer of PM6:BTP-eC9 bulk heterojunction organic solar cell.

[0014] Furthermore, the photoactive layer of the PM6:BTP-eC9 bulk heterojunction organic solar cell includes a donor, an acceptor and a solid additive, and the mass of the solid additive is 3-30% of the mass of the donor.

[0015] The present invention provides a method for preparing a type of imide-based large dipole moment volatile solid additive.

[0016]

[0017] The compound (I) and the compound (II) react in a solution to obtain the above solid additive.

[0018] Specifically, compound I and compound II are prepared in a molar ratio of 1:1-20, the reaction temperature is 150-160° C., the reaction time is 2-8 h, and the solvent is N,N-dimethylformamide.

[0019] Beneficial effects of the present invention:

[0020] 1. Additives with large dipole moments can better interact with donors and acceptors, and have a better regulatory effect on molecular stacking and active layer morphology.

[0021] 2. The large dipole moment additive of the present invention has good volatility and can be completely removed by annealing, which is beneficial to enhancing the morphology stability of the active layer.

[0022] 3. At present, most solid additives are based on benzene ring and thiophene derivatives. The development of imide-type additives is conducive to expanding the types of additives.

[0023] 4. The large dipole moment additives described in the present invention can induce the receptor to nucleate first and then grow, which is beneficial to the formation of receptor domains of uniform size and improves exciton dissociation and charge transfer.

[0024] 5. Thanks to the strong intermolecular interaction of large dipole moment additives, the proportion of the additives used in bulk heterojunction organic solar cells is only 3%-30% of the donor mass, which is much lower than the 150% of the commonly used commercial additive 1,4-diiodobenzene, which is conducive to reducing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Fourier transform infrared spectra of the additive pClPA, the mixture PM6:BTP-eC9 and PM6:BTP-eC9:pClPA before and after annealing.

[0026] Figure 2 In situ UV-visible absorption spectra of the active layer solution (PM6:BTP-eC9) with and without the additive pClPA treatment, showing the change of the maximum absorption peak position of the donor and acceptor over time.

[0027] Figure 3 Current density-voltage curves of PM6:BTP-eC9 bulk heterojunction organic solar cell devices treated without additives, treated with the commercially available common additive 1,4-diiodobenzene, and treated with the additive pClPA described in Example 1.

[0028] Figure 4 The current density-voltage curves of PM6:BTP-eC9 bulk heterojunction organic solar cell devices without additive treatment and with the additives pFPA, pBrPA, pIPA, 3FPA, 3FPA-1, and 5FPA described in the present invention.

[0029] Figure 5 It is the dihedral angle of the additive oClPA, mClPA and pClPA described in the present invention. DETAILED DESCRIPTION

[0030] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0031] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0032] The technical scheme of the present invention is further described in detail below through specific embodiments. It should be understood that the implementation of the present invention is not limited to the following embodiments, and any formal modifications or changes made to the present invention will fall within the scope of protection of the present invention. In the present invention, unless otherwise specified, all parts and percentages are units of substance quantity, and the equipment and raw materials used can be purchased from the market or are commonly used in the art.

[0033] The following description is given in the embodiments:

[0034] Example 1

[0035]

[0036] Add 500 mg of phthalic anhydride and 430 mg of 4-chloroaniline to a 25 mL reaction bottle and use 7 mL of N,N-dimethylformamide as solvent. Under argon protection, react at 150°C for 2.5 h. After the reaction is completed, cool to room temperature, pour the reaction solution into ice water, and filter to collect the solid. Purify by column separation and recrystallization with methanol and chloroform to obtain white crystals pClPA (796 mg, 91.60%). The product was identified by mass spectrometry. HRMS (MALDI-TOF) Calcd for C 14 H 8 ClNO 2 Exact Mass:257.0244, found:257.0187(M + ).

[0037] Example 2

[0038]

[0039] Add 500 mg of phthalic anhydride and 497 mg of 3,4,5-trifluoroaniline to a 25 mL reaction bottle and use 7 mL of N,N-dimethylformamide as solvent. Under argon protection, react at 150°C for 3.5 h. After the reaction is completed, cool to room temperature, pour the reaction solution into ice water, and filter to collect the solid. Purify by column separation and recrystallization with methanol and chloroform to obtain white crystals 3FPA (872 mg, 93.20%). The product was identified by mass spectrometry. HRMS (MALDI-TOF) Calcd for C 14 H 6 F 3 NO 2 Exact Mass:277.0351, found:277.0255(M + ).

[0040] Example 3

[0041]

[0042] Add 500 mg of 4-chlorophthalic anhydride and 419 mg of 4-chloroaniline to a 25 mL reaction bottle and use 7 mL of N,N-dimethylformamide as solvent. Under argon protection, react at 150°C for 4 h. After the reaction is completed, cool to room temperature, pour the reaction solution into ice water, and filter to collect the solid. Purify by column separation and recrystallization with methanol and chloroform to obtain white crystals pClPACl (700 mg, 87.52%). The product was identified by mass spectrometry. HRMS (MALDI-TOF) Calcd for C14 H 7 Cl 2 NO 2 Exact Mass:290.9854, found:290.9754(M+).

[0043] The following imide additives were synthesized by referring to the method of the above examples, and the product structures were identified by mass spectrometry.

[0044]

[0045] Example 4

[0046] The solid additive pClPA synthesized in Example 1 and the commercially available common additive 1,4-diiodobenzene were applied to PM6:BTP-eC9 bulk heterojunction organic solar cells. The specific steps are as follows: First, the conductive ITO substrate was cleaned. It was placed in deionized water, acetone and isopropanol for ultrasonic cleaning for 30 min, and then the dried ITO substrate was placed in a plasma cleaner for cleaning for 3 min to completely remove the surface organic matter. Then, PEDOT:PSS was spin-coated on the treated ITO substrate. PEDOT:PSS was evenly spin-coated on the surface of the ITO substrate at a speed of 4000 rpm. After the spin coating was completed, it was annealed at 150°C for 18 min, and then the ITO substrate was transferred to a glove box. The donor PM6 and the acceptor BTP-eC9 were dissolved in chloroform at a mass ratio of 1:1.2 to prepare a solution with a total concentration of 15.4 mg / mL. Add 15% of the mass of the donor additive pClPA to the solution to prepare an active layer solution treated with the additive pClPA; add 150% of the mass of the donor additive DIB to the solution to prepare an active layer solution treated with the additive DIB. The prepared active layer solution needs to be stirred at 40°C for 3 h in advance. Spin coat the active layer solution on the surface of PEDOT:PSS at 4000 rpm, and then anneal at 100°C for 10 min. Subsequently, spin coat a 0.5 mg / mL methanol solution of PNDIT-F3N on the surface of the active layer at 3000 rpm. Finally, at about 10⁻ 4 Pa, a silver electrode was evaporated on the surface of PNDIT-F3N with a thickness of about 80 nm to obtain an organic solar cell device.

[0047] Among them, PM6, BTP-eC9 and PNDIT-F3N were purchased from Solarmer; 1,4-diiodobenzene was purchased from TCI; chloroform and methanol were purchased from J&K Technologies; and PEDOT:PSS was purchased from Heraeus.

[0048] In filling N 2A AAA solar simulator AM 1.5 G (100 mW / cm 2 ) The open circuit voltage, short circuit current, fill factor and energy conversion efficiency of the prepared photovoltaic devices were tested, as shown in Table 1 and Figure 3 As shown. The additive pClPA can effectively improve the short-circuit current (J SC ) and fill factor (FF), the energy conversion efficiency increased from 16.13% to 18.58%, higher than 17.74% of 1,4-diiodobenzene. This is attributed to the larger dipole moment of the additive pClPA. Compared with 1,4-diiodobenzene, pClPA has stronger intermolecular interactions with donors and acceptors, which is more conducive to improving the morphology of the active layer.

[0049] Table 1 Photovoltaic device test data

[0050]

[0051] Example 5

[0052] PM6:BTP-eC9 bulk heterojunction organic solar cell devices treated with additives pFPA, pBrPA, pIPA, 3FPA, 3FPA-1, and 5FPA were prepared according to the method of Example 4, and the open circuit voltage, short circuit current, fill factor, and energy conversion efficiency of the prepared photovoltaic devices were tested, as shown in Table 2 and Figure 4 shown.

[0053] Table 2 Photovoltaic device test data

[0054]

[0055] Thanks to the strong intermolecular interaction of large dipole moment additives, the proportion of the additives used in the bulk heterojunction organic solar cells is only 3%-30% of the donor mass, which is much lower than 150% of the commonly used commercial additive 1,4-diiodobenzene, which is conducive to reducing costs.

[0056] Example 6

[0057] Fourier transform infrared spectrometer was used to verify the volatility of the additive pClPA in Example 1. Figure 1 As shown, the additive pClPA has a peak at 1713 cm -1 , 824 cm -1 and 716 cm -1 The characteristic peaks of almost completely disappeared after annealing at 100 °C for 10 min, indicating that the additive pClPA can be removed by annealing. Figure 5As shown, the dihedral angles of the additives oClPA, mClPA, and pClPA of the present invention are 37.8°, 37.9°, and 68.4°, respectively, which helps to reduce the planarity of the additive molecules, control the intermolecular interactions, and enhance the volatility of the additives.

[0058] Example 7

[0059] The effect of the additive pClPA in Example 1 on the film-forming kinetics of the donor and acceptor was investigated by in situ UV-visible absorption spectroscopy. Figure 2 As shown in the figure, the maximum absorption peak position of the donor acceptor changes with time. Compared with the donor, the additive pClPA has a more significant effect on the acceptor. As the solvent evaporates, the entire film-forming process can be simply divided into three stages: the first stage, the solution state, at which the maximum absorption peak position remains almost unchanged; the second stage, the crystallization and growth stage, the maximum absorption peak rapidly red-shifts; the third stage, the film state, the maximum absorption peak position tends to be stable again. The crystallization and growth stage of the acceptor is 12 s, and the red shift is kept at a uniform rate, which indicates that the nucleation and crystal growth of the acceptor are carried out simultaneously, which may generate receptor domains with uneven sizes and limit charge transfer. The crystallization and growth stage of the acceptor treated with the additive pClPA is extended to 22 s, which is conducive to the formation of ordered intermolecular stacking. In addition, the crystallization and growth stage of the acceptor is divided into three parts, which indicates that the additive pClPA can induce the acceptor to nucleate first and then grow, which is conducive to the generation of receptor domains with uniform sizes.

[0060] Finally, it should be emphasized that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various changes and modifications. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of a class of imide-type large dipole moment volatile solid additives, characterized in that: The solid additive has the following general structural formula: ； Where Ar1 is ; R1, R2, R3, R4, R5 are each independently F, Cl, Br, I or H; Ar2 is ; R9, R10, R11, R12 are each independently F, Cl, Br, I or H; and R1, R2, R3, R4, R5, R9, R10, R11, and R12 are not H at the same time; The solid additive is used for bulk heterojunction organic solar cells.

2. The use of an imide-type large dipole moment volatile solid additive according to claim 1, characterized in that: The solid additive has the following general structural formula: ； Where Ar1 is ; R1, R2, R3, R4, R5 are each independently F, Cl, Br, I or H; and R1, R2, R3, R4, and R5 are not H at the same time; Ar2 is ; R9, R10, R11, R12 are each independently F, Cl, Br, I or H; The solid additive is used as a solid additive for bulk heterojunction organic solar cells.

3. The use of an imide-type large dipole moment volatile solid additive according to claim 1 or 2, characterized in that: The solid additive is used in a photoactive layer of a bulk heterojunction organic solar cell.

4. The use of an imide-type large dipole moment volatile solid additive according to claim 3, characterized in that: The solid additive is used in the photoactive layer of PM6:BTP-eC9 bulk heterojunction organic solar cell.

5. The use of an imide-type large dipole moment volatile solid additive according to claim 4, characterized in that: The photoactive layer of the PM6:BTP-eC9 bulk heterojunction organic solar cell includes a donor, an acceptor and a solid additive, wherein the mass of the solid additive is 3-30% of the mass of the donor.

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