A completely non-condensed ring electron acceptor material and its preparation method and application

Abstract

The present invention discloses a completely non-condensed ring electron acceptor material and its preparation method and application, wherein the core group is a fluoroboron dipyrrole unit, each of the four α sites of the core skeleton has a methyl substituent, the end group is a halogen-substituted 3-(dicyanomethylene)indene-1-ketone unit, and the π bridge between the end group and the core is an alkyl-substituted thiophene unit. Based on the inherent strong extinction characteristics of the fluoroboron dipyrrole core itself, supplemented by the additional push-pull electron effect of the thiophene electron-donating group on the 10th position of the core and the fluoroboron dipyrrole, and the strong intramolecular charge transfer characteristics promoted by the molecular A-D-A'-D-A configuration, the acceptor material of the present invention can achieve a relatively ideal light absorption capacity under the premise of a limited degree of conjugation, which is conducive to improving the performance of photovoltaic devices. The four methyl units on the core group can provide a certain steric hindrance, promote the formation of a spatial torsion between the skeleton core and the thiophene π bridge, break the planarity of the entire molecule, and solve the problem of weak light absorption and difficult morphology control of completely non-condensed ring acceptors.

Description

Technical Field

[0001] The invention belongs to the field of organic photovoltaic materials and relates to an electron acceptor material, in particular to a completely non-condensed ring electron acceptor material and a preparation method and application thereof. Background Art

[0002] Organic photovoltaics, also known as organic solar cells, is a new generation of solar energy utilization technology with great potential. Different from inorganic silicon-based solar cells, organic solar cells have the advantages of light weight, flexibility, large-area printing, and semi-transparent preparation, and have received widespread attention in academia and industry. Organic solar cells generally have a "sandwich" device structure with positive and negative electrodes sandwiching an active layer. The active layer is a mixture of p-type electron donor (referred to as donor) materials and n-type electron acceptor (referred to as acceptor) materials. Its photoelectric conversion process usually goes through the following four steps. First, the active layer absorbs sunlight and converts photons into excitons (bound pairs of holes and electrons); then, the excitons diffuse to the donor and acceptor contact interface in the active layer and dissociate into free charges; then, under the action of the built-in electric field, holes and electrons migrate along the donor phase and the acceptor phase respectively; finally, the free charges are collected by the corresponding electrodes to form current. In recent years, organic photovoltaics have achieved rapid development with continuous breakthroughs in materials science and device engineering, and its energy conversion efficiency has made great progress.

[0003] The core of organic solar cells is the active layer formed by a blend of donor and acceptor materials. Therefore, the development of new and efficient donor and acceptor materials is the key to improving the photovoltaic performance of organic solar cells. At present, donor materials are usually dominated by p-type polymers. In terms of acceptors, n-type small molecule semiconductors that can be easily blended with p-type polymers to form an ideal active layer morphology are the mainstream of the current development of acceptor materials. Small molecule acceptors have the advantages of easy synthesis, easy chemical structure modification, and batch stability. In particular, condensed ring electron acceptors with rigid condensed ring cores have been fully developed in the past decade or so, which has greatly driven the continuous breakthroughs in the efficiency of organic photovoltaics. For example, most of the high-efficiency organic photovoltaic devices reported in academia are prepared based on a blend system of polymer donors and condensed ring acceptors.

[0004] However, the synthesis and preparation of condensed ring electron acceptors is often complicated. The synthesis of the core large rigid multi-ring condensed structure often requires tedious reaction steps. The conditions of some chemical reactions are very harsh, and the reaction yield of multi-site simultaneous ring closure is low, and there are many by-products, which also brings difficulties to subsequent purification. Therefore, considering the loss and difficulty of chemical reactions, the synthesis cost of large condensed ring electron acceptors is relatively high, which reduces the cost-effectiveness of this type of photovoltaic material and limits its large-scale commercial application to a certain extent.

[0005] In response to the above problems of fused ring receptors, the design strategy of non-fused ring electron receptors has been developed in recent years. Small fused rings or single aromatic rings are connected together through carbon-carbon single bonds, and the planarity of the linked ring structure is maintained through the non-covalent bond interaction of heteroatoms on adjacent rings. Such non-fused ring receptors can achieve photovoltaic performance comparable to that of large fused ring receptors, which has become the mainstream design idea of ​​non-fused ring receptors. However, in such molecular designs, several small fused ring structures are still used, such as cyclopentadithiophene (CPDT), indacenodithiophene (IDT) and other fused rings and their derivatives. We can call such molecular designs partial non-fused ring receptors. The synthesis of these small fused rings also undergoes more complicated reactions and purification steps, which increases the preparation cost of the materials to a certain extent. In addition, in such molecular designs, CPDT or IDT groups are often used, which also limits the diversity of material design and the selectivity of molecular building blocks, thereby creating barriers in molecular design.

[0006] Therefore, from the perspective of further reducing the cost of material preparation and enriching the diversity of molecular design, the design of the above-mentioned partially non-condensed ring receptor can be further simplified. Thus, completely non-condensed ring receptors came into being. Different from condensed ring electron receptors and partially non-condensed ring electron receptors, except for the end groups on both sides of the molecule, the skeleton of completely non-condensed ring receptors is composed entirely of single aromatic rings connected by carbon-carbon single bonds. Single aromatic rings are cheap and easy to obtain, and there are many methods for constructing carbon-carbon single bonds between aromatic rings. The reaction is mature, the conditions are mild, and the yield is high. Therefore, this molecular design strategy can greatly reduce the cost of material synthesis, which is of great significance for achieving cost-effective organic photovoltaic technology.

[0007] However, the only drawback is that designing completely non-condensed ring receptors will cause the following two major problems. These two disadvantages limit the development of completely non-condensed ring receptors and the improvement of photovoltaic performance. First, large rigid condensed rings, or small condensed ring structures that maintain planarity through non-covalent bonds, have a large degree of conjugation, which is beneficial to improve the light absorption capacity of the receptor material. Sufficient light capture is a necessary prerequisite for achieving high efficiency of organic photovoltaic devices. Therefore, completely non-condensed ring receptors that abandon condensed ring structures in the molecular skeleton will face the problem of insufficient conjugation, which in turn affects the light absorption capacity of the material. Second, in the current mainstream design of some non-condensed ring receptors, the small condensed ring structures in their skeletons, such as sp on CPDT and IDT, are not suitable for the design of completely non-condensed ring receptors. 3The alkyl side chains substituted on the hybrid carbon atoms are beneficial to inhibit the rigid receptor molecules from producing too strong intermolecular interactions in the active layer, thereby weakening the receptor's excessive crystallization and promoting a good miscible morphology with the donor material. Therefore, if a single aromatic ring is used to replace the condensed ring structure to construct a completely non-condensed ring receptor, the above strategy for adjusting the morphology of the active layer will no longer apply. It is necessary to consider how to alleviate the excessive intermolecular stacking caused by the rigid structure of the receptor material in the molecular design, so as to ensure the ideal miscible morphological characteristics of the donor and receptor. Summary of the invention

[0008] Purpose of the invention: The technical problem to be solved by the present invention is to provide a new type of completely non-condensed ring electron acceptor material in view of the deficiencies of the prior art, to make up for the performance disadvantages of the completely non-condensed ring acceptor material and to further improve its photovoltaic performance.

[0009] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A completely non-condensed ring electron acceptor material, the core group of which is a fluoroborane dipyrrole unit, each of the four α sites of the core skeleton has a methyl substituent, the end group is a 3-(dicyanomethylene)inden-1-one unit substituted with a fluorine or chlorine atom, and the π bridge between the end group and the core group is an alkyl-substituted thiophene unit.

[0011] Specifically, its chemical structure is as follows:

[0012]

[0013] Wherein, X is a halogen atom such as fluorine or chlorine.

[0014] The central unit of the molecular skeleton of the present invention is tetramethyl fluoroborane dipyrrole (5,5-difluoro-1,3,7,9-tetramethyl-5H-4λ 4 ,5λ 4-dipyrrolo[1,2-c:2',1'-f][1,3,2]diazacyclohexaborane, hereinafter referred to as TMBDP group). This structure is a derivative of the star dye BODIPY (boron dipyrromethene) and has unique optical properties. The unit has a strong light absorption capacity and a high molar extinction coefficient. In addition, 2-(2-ethylhexyl)thiophene is substituted at position 10 of the TMBDP skeleton, which promotes the push-pull electron effect inside the core unit, enhances the charge transfer within the molecule, and is conducive to further enhancing the absorption. Therefore, the strong light absorption characteristics of the core group itself are used to enhance the ability of the entire acceptor material to capture sunlight. In addition, the TMBDP group has a certain electron-pulling (electron-accepting, A) ability, which is suitable as an acceptor core unit to promote the charge transfer of the entire molecular skeleton. On both sides of the core unit are electron-donating (electron-donating, D) π bridge groups 3-hexylthiophene. The hexyl side chain helps to enhance the solubility of the material and provides the necessary conditions for the subsequent solution-processed organic photovoltaic device preparation. Finally, on both sides of the alkylthiophene π bridge, halogenated 3-(dicyanomethylene)inden-1-one was used as the terminal electron-withdrawing group substitution, and the entire completely non-condensed ring receptor formed an AD-A'-DA type molecular configuration, further enhancing the charge transfer within the molecule and improving the light absorption ability of the material.

[0015] Furthermore, the present invention also provides a method for preparing the above-mentioned completely non-condensed ring electron acceptor material, comprising the following steps:

[0016] (1) The compound tetramethylfluoroborane dipyrrole (5,5-difluoro-1,3,7,9-tetramethyl-5H-4λ 4 ,5λ 4 -dipyrrolo[1,2-c:2',1'-f][1,3,2]diazacyclohexaborane) is coupled with the compound 4-hexyl-5-boric acid pinacol ester-2-carboxaldehyde shown in formula 2 to obtain the compound shown in formula 3;

[0017]

[0018] (2) reacting the compound of formula 3 obtained in step (1) with the compound of formula 4, 3-(dicyanomethylene)inden-1-one halide, to carry out dehydration condensation to obtain;

[0019]

[0020] Wherein, X is a halogen atom such as fluorine or chlorine.

[0021] In the synthesis steps of the present invention, all molecular building blocks can be purchased from commercial channels and have the characteristics of wide sources, easy synthesis and simple structure. This type of receptor molecule can be prepared from commercial raw materials in only two steps. In addition, these two steps are well-known and mature chemical reactions with mild conditions and high yields, which reduce the loss of materials during the synthesis process and ensure low preparation costs.

[0022] The small molecule receptor material obtained by the present invention has a completely non-condensed ring molecular skeleton. The central TMBDP unit is a "quasi-tricyclic" condensed ring structure constructed by a coordination reaction between dipyrromethene and a boron nitrogen bridge bond, which has a similar condensed ring property to a certain extent, and can make up for the disadvantage of insufficient conjugation degree of completely non-condensed ring small molecules. And the synthesis of this unit, that is, the formation of a boron nitrogen coordination bridge bond, is simpler and easier than the ring-closing reaction of a condensed ring structure, and the preparation cost is low. In addition, based on the inherent strong extinction characteristics of the TMBDP core itself, supplemented by the additional push-pull electron effect of the thiophene electron-donating group at the 10th position of the core and the TMBDP, and the strong intramolecular charge transfer characteristics promoted by the AD-A'-DA configuration of the entire molecule, the completely non-condensed ring small molecule receptor involved in the present invention can achieve a relatively ideal light absorption capacity on the basis of a limited degree of conjugation, thereby helping to improve the performance of photovoltaic devices. In addition, the four methyl units on the TMBDP core can provide a certain amount of steric hindrance, prompting the skeleton core and the thiophene π bridge to form a spatial twist, so that the planarity of the entire molecule is broken. Based on this conformation, the strong intermolecular interaction of the receptor material itself is suppressed, and it is expected that a pure receptor phase of appropriate size will be formed in the active layer of the donor and receptor blend, and an ideal miscible morphology will be formed with the donor. Therefore, the present invention has the effect of "killing two birds with one stone", and at the same time solves the problem of weak light absorption and difficult morphology control of completely non-condensed ring receptors.

[0023] Furthermore, in step (1), the compound represented by formula 1 and the compound represented by formula 2 are coupled via a one-step palladium-catalyzed Suzuki-Miyaura reaction.

[0024] Furthermore, in step (1), the compound represented by formula 1 and the compound represented by formula 2 are mixed with anhydrous potassium carbonate, trisdibenzylideneacetone dipalladium, and tri(o-methylphenyl)phosphine, and then a reaction solvent is added, and the mixture is reacted at 85 to 95° C. for 36 to 48 hours under a nitrogen atmosphere; after the reaction is completed, the mixture is cooled to room temperature, separated by extraction, and purified by column chromatography to obtain a compound represented by formula 3.

[0025] Furthermore, in step (1), the molar ratio of the compound represented by formula 1, the compound represented by formula 2, anhydrous potassium carbonate, trisdibenzylideneacetone dipalladium, and tri(o-methylphenyl)phosphine is 1:(2.5-3.5):(8-12):(0.1-0.15):(0.1-0.15), preferably 1:2.5:10:0.15:0.15; the reaction solvent is a mixed solvent of toluene, water, and ethanol in a volume ratio of 1:(0.2-0.25):(0.25-0.4) (preferably 1:0.2:0.4).

[0026] Furthermore, in step (2), the compound represented by formula 3 and the compound represented by formula 4 are subjected to dehydration condensation by Vilsmeier-Haack reaction.

[0027] Furthermore, in step (2), the compound represented by formula 3 and the compound represented by formula 4 are mixed, a reaction solvent is added, and a nitrogen atmosphere is added to 60-65° C. under light-proof conditions for reaction for 6-12 hours. After the reaction is completed, the mixture is cooled to room temperature, separated by extraction, and purified by column chromatography to obtain the obtained mixture.

[0028] Furthermore, in step (2), the molar ratio of the compound represented by formula 3 to the compound represented by formula 4 is 1:2.5 to 1:5, preferably 1:4; and the reaction solvent is a pyridine-trichloromethane mixed solvent with a volume ratio of 1:10 to 1:15 (preferably 1:10).

[0029] Furthermore, the present invention also claims to protect the use of the above-mentioned completely non-condensed ring electron acceptor material in the preparation of organic solar cells.

[0030] Beneficial effects:

[0031] In line with the original intention of developing low-cost and cost-effective electron acceptor materials, the present invention provides a new design idea for completely non-condensed ring acceptors in view of the disadvantages of completely non-condensed ring acceptor materials, and designs and synthesizes completely non-condensed ring acceptor materials based on this idea. Furthermore, the completely non-condensed ring acceptors with 5,6-difluoro-3-(dicyanomethylene)indene-1-one and 5,6-dichloro-3-(dicyanomethylene)indene-1-one as end groups are named GMB1-F and GMB1-Cl respectively (chemical structure as shown in Figure 1 The receptor material has a simple structure, and its π bridge is a single thiophene ring, presenting a completely non-condensed ring configuration. It can be prepared based on simple molecular building blocks through simple chemical reactions. The clever thing is that its core is a "quasi-triple ring" structure formed by a boron-nitrogen coordination bridge. The construction method is simple but has the advantages of comparable small condensed rings.

[0032] With fluoroborane dipyrrole derivatives as the core, using their own high extinction, strong absorption characteristics, and "quasi-tricyclic" molecular structure, it is expected to make up for the weak light absorption ability of completely non-condensed ring receptors due to insufficient conjugation. Based on this, the receptor material's ability to capture sunlight is enhanced, which is conducive to improving the short-circuit current density of organic photovoltaic devices.

[0033] In addition, the four methyl groups attached to the core unit of the receptor are steric groups. The steric hindrance effect is used to regulate the planarity of the molecule, so that the molecule presents a twisted conformation, which in turn affects its rigidity and crystallinity in the solution-processed active layer. This provides a prerequisite for the formation of an ideal active layer morphology, and also provides ideas for the design of small molecule receptor materials with spatial structures. Based on the appropriate active layer morphology, the receptor material helps organic photovoltaic devices achieve a higher fill factor.

[0034] In summary, the completely non-condensed ring receptor provided by the present invention fully demonstrates the advantages of completely non-condensed ring receptors in streamlining molecular structure, simplifying synthesis process and reducing preparation cost. At the same time, the use of fluoroboron dipyrrole core units not only makes up for the disadvantage of weak light absorption of completely non-condensed ring receptors due to insufficient conjugation, but also provides a novel method for regulating the rigidity of completely non-condensed ring receptors by introducing steric hindrance. Organic photovoltaic devices prepared based on such receptors can achieve an energy conversion efficiency of about 3.5%. Taking into account the chemical structure of the material, the preparation cost and the device efficiency, this type of receptor is a class of cost-effective organic photovoltaic materials. In addition, the fluoroboron dipyrrole unit is a group that has been widely used in many organic optoelectronic fields such as bioimaging, fluorescent probes and photodynamic therapy. Its application in the field of organic photovoltaics has not yet been carried out, and there are very few related studies. The receptor material of the present invention is a preliminary attempt of the fluoroboron dipyrrole unit in the field of completely non-condensed ring receptors in organic photovoltaics, which can provide reference and reference for the subsequent development of such materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.

[0036] Figure 1 The present invention provides a molecular structure of a completely non-fused ring receptor.

[0037] Figure 2 The chemical structure of the polymer donor PBDB-T in the present invention that is paired with a completely non-fused ring acceptor.

[0038] Figure 3 Schematic diagram of the structure of the organic photovoltaic device prepared based on a completely non-condensed ring receptor in the present invention.

[0039] Figure 4This is the H NMR spectrum of the intermediate compound 3.

[0040] Figure 5 This is the H NMR spectrum of the completely non-fused ring receptor GMB1-F.

[0041] Figure 6 This is the mass spectrum of the completely non-fused ring receptor GMB1-F.

[0042] Figure 7 This is the molar extinction coefficient spectrum of the completely non-fused ring receptor GMB1-F.

[0043] Figure 8 This is the current density-voltage (JV) characteristic curve of the GMB1-F acceptor device.

[0044] Fig. 9 This is the H NMR spectrum of the completely non-fused ring receptor GMB1-Cl.

[0045] Fig.10 This is the mass spectrum of the completely non-fused ring receptor GMB1-Cl.

[0046] Fig.11 This is the molar extinction coefficient spectrum of the completely non-fused ring receptor GMB1-Cl.

[0047] Fig.12 This is the current density-voltage (JV) characteristic curve of the device with GMB1-Cl as the acceptor. DETAILED DESCRIPTION

[0048] The present invention can be better understood with reference to the following examples.

[0049] The solvents involved in the material synthesis process are all commercially available products and have not been purified by other means before use. Fluoroboron dipyrrole molecular building blocks, namely 2,8-dibromo-10-(5-(2-ethylhexyl)thienyl-2-yl)-5,5-difluoro-1,3,7,9-tetramethyl-5H-4λ 4 ,5λ 4 -Dipyrrolo[1,2-c:2',1'-f][1,3,2]diazaborolidine was purchased from Wuhan WuXi AppTec New Drug Development Co., Ltd. 4-Hexyl-5-boronic acid pinacol ester-2-carboxaldehyde, 5,6-difluoro-3-(dicyanomethylene)indene-1-one and 5,6-dichloro-3-(dicyanomethylene)indene-1-one were purchased from Suzhou Nakai Technology Co., Ltd.

[0050] In a specific embodiment, the photovoltaic performance of the material is characterized by preparing an organic solar cell device. The electron donor material used in combination with the synthesized electron acceptor is PBDB-T (chemical structure: Figure 2 The device structure used is as shown in Figure 2. Figure 3 As shown, it is ITO / PEDOT:PSS / active layer / PDINO / Al (indium tin oxide / poly (3,4-ethylenedioxythiophene): polystyrene sulfonate / active layer / 3,3'-(1,3,8,10-tetraanthrone [2,1,9-def:6,5,10-d'e'f'] diisoquinoline-2,9 (1H,3H,8H,10H)-diyl) bis (N,N-dimethylpropane-1-amine oxide / aluminum). Among them, ITO is the positive electrode, PEDOT:PSS is the hole transport layer, PDINO is the electron transport layer, and metal Al is the negative electrode. The current density-voltage (JV) curve of the device is at AM 1.5G, 100mW cm -2 Measured under simulated sunlight.

[0051] Example 1: A completely non-fused ring receptor based on a fluoroborylpyrrole core with 5,6-difluoro-3-(dicyanomethylidene)inden-1-one as the terminal group.

[0052] (1) Starting from the commercially available dibromo TMBDP core group (compound shown in Formula 1), a one-step palladium-catalyzed Suzuki-Miyaura reaction is carried out to couple with 4-hexyl-5-boronic acid pinacol ester-2-carboxaldehyde (compound shown in Formula 2) to obtain a compound shown in Formula 3:

[0053]

[0054] Weigh compound 1 (1 part, molar ratio), compound 2 (2.5 parts), anhydrous potassium carbonate (10 parts), tris dibenzylideneacetone palladium (Pd 2 (dba) 3 , 0.15 parts), tri(o-methylphenyl)phosphine (P(o-tolyl) 3 , 0.15 parts) were added to two round-bottom flasks in turn, and a mixed solvent of toluene, water and ethanol was added in a volume ratio of 1:0.2:0.4, and the nitrogen was replaced three times. The reaction was carried out at 95°C for 48 hours. After the reaction was completed, it was cooled to room temperature, extracted with saturated sodium chloride and dichloromethane until the organic phase was colorless, dried with anhydrous magnesium sulfate, and filtered. The crude product can be purified by column chromatography, and the eluent is a mixed solvent of dichloromethane and petroleum ether (volume ratio of 3:1). The product is a red viscous liquid (yield is about 90%). The hydrogen nuclear magnetic resonance spectrum of the product 3 ( 1 H NMR) Figure 4 shown.

[0055] 1 H NMR (400 MHz, CDCl 3,δppm):9.86(s,2H),7.67(d,J=1.2Hz,2H),6.85(q,J=3.2Hz,2H),2.81(d,J=6.8Hz,2H),2.46(s,6H) ,2.35(dd,J=16,8Hz,4H),1.62(d,J=3.9Hz,1H),1.55(s,6H),1.27-1.20(m,21H),0.89-0.83(m,15H).

[0056] (2) Compound 3 and the compound 5,6-difluoro-3-(dicyanomethylene)inden-1-one shown in formula 4 are subjected to dehydration condensation by Vilsmeier-Haack reaction to obtain the final product, a completely non-condensed ring small molecule receptor GMB1-F, such as Figure 1 shown.

[0057]

[0058] Weigh compound 3 (1 part, molar ratio) and compound 4 (4 parts) and add them to two round-bottom flasks, add anhydrous chloroform as the reaction solvent, replace nitrogen three times, and add pyridine (volume ratio with chloroform is 1:10). React at 65°C for 12 hours under light-proof conditions. After the reaction is completed, cool to room temperature, extract the organic phase, dry it over anhydrous magnesium sulfate, and filter to obtain a crude product. The crude product can be purified by column chromatography, and the eluent is a mixed solvent of dichloromethane and petroleum ether (volume ratio of 3:1). The GMB1-F product is a dark green powder solid (yield of approximately 85%). The chemical structure of the product is confirmed by nuclear magnetic resonance hydrogen spectrum, mass spectrometry (MS) and elemental analysis. The nuclear magnetic resonance hydrogen spectrum of the product is as follows Figure 5 As shown, the mass spectrum Figure 6 shown.

[0059] 1 H NMR (400 MHz, CDCl 3 ,δppm):8.85(d,J=1.6Hz,2H),8.56(q,J=8Hz,2H),7.80(d,J=2.3Hz,2H),7.72-7.67(m,2H),6.85(dd,J=25.7,4.1Hz,2H),2.82( d,J=6.7Hz,2H),2.52(s,6H),2.40(m,4H),1.58(d,J=21.2Hz,10H),1.25(m,21H),0.87(m,12H).MS(MALDI-TOF)(m / z):Calcd.for C 71 H 65 BF 6 N 6 O 2 S 3[M+]:1254.43; found:1253.86.Anal.Calcd.for C 71 H 65 BF 6 N 6 O 2 S 3 :C 67.93, H 5.22, B 0.86, F 9.08, N 6.69, O2.55, S 7.66; found: C 67.59, H 5.77, N 6.25, S 7.70.

[0060] It can be seen that starting from commercial raw materials, the molecule can be prepared in two simple and high-yield steps. The molar extinction coefficient spectrum of the material is shown in Figure 7 This type of receptor achieves wide absorption covering the spectral range of 300-700nm, and the maximum molar extinction coefficient at the absorption peak can be as high as 1.12×10 5 M -1 cm -1 , which is comparable to many non-condensed-ring small molecule receptors and even some condensed-ring electron receptors.

[0061] Then, PBDB-T was used as the polymer donor material and GMB1-F as the electron acceptor material to prepare an organic solar cell device. The JV characteristic curve of the device is shown in Figure 8 In addition, Table 1 lists the performance of the solar cell device of Example 1. The average energy conversion efficiency is taken from at least 10 independent photovoltaic devices.

[0062] Table 1 Performance of photovoltaic devices using GMB1-F as acceptor material in Example 1

[0063]

[0064] Example 2: A completely non-fused ring receptor based on a fluoroboryl pyrrole core with 5,6-dichloro-3-(dicyanomethylidene)inden-1-one as the terminal group.

[0065] (1) Starting from the commercially available dibromo TMBDP core group (compound shown in Formula 1), a one-step palladium-catalyzed Suzuki-Miyaura reaction is carried out to couple with 4-hexyl-5-boronic acid pinacol ester-2-carboxaldehyde (compound shown in Formula 2) to obtain a compound shown in Formula 3:

[0066]

[0067] Weigh compound 1 (1 part, molar ratio), compound 2 (2.5 parts), anhydrous potassium carbonate (10 parts), tris dibenzylideneacetone palladium (Pd 2 (dba) 3, 0.15 parts), tri(o-methylphenyl)phosphine (P(o-tolyl) 3 , 0.15 parts) are added to two round-bottom flasks in turn, and a mixed solvent of toluene, water and ethanol is added in a volume ratio of 1:0.2:0.4, and nitrogen is replaced three times. The reaction is carried out at 95°C for 48 hours. After the reaction is completed, it is cooled to room temperature, extracted with saturated sodium chloride and dichloromethane until the organic phase is colorless, dried with anhydrous magnesium sulfate, and filtered. The crude product can be purified by column chromatography, and the eluent is a mixed solvent of dichloromethane and petroleum ether (volume ratio is 3:1). The product is a red viscous liquid (yield is about 90%). Its structure is confirmed in the same way as in Example (1).

[0068] (2) Compound 3 and the compound 5,6-dichloro-3-(dicyanomethylene)inden-1-one shown in formula 4 are subjected to dehydration condensation by Vilsmeier-Haack reaction to obtain the final product, a completely non-condensed ring small molecule receptor GMB1-Cl, such as Figure 1 shown.

[0069]

[0070] Weigh compound 3 (1 part, molar ratio) and compound 4 (4 parts) and add them to two round-bottom flasks, add anhydrous chloroform as the reaction solvent, replace nitrogen three times, and add pyridine (volume ratio with chloroform is 1:10). React at 65°C for 12 hours under light-proof conditions. After the reaction is completed, cool to room temperature, extract the organic phase, dry it over anhydrous magnesium sulfate, and filter to obtain a crude product. The crude product can be purified by column chromatography, and the eluent is a mixed solvent of dichloromethane and petroleum ether (volume ratio of 3:1). The GMB1-Cl product is a purple-black powder solid (yield of approximately 85%). The chemical structure of the product was confirmed by nuclear magnetic resonance hydrogen spectrum, mass spectrometry and elemental analysis. The nuclear magnetic resonance hydrogen spectrum of the product is as follows Fig. 9 As shown, the mass spectrum Fig.10 shown.

[0071] 1 H NMR (400 MHz, CDCl 3 ,δppm)8.87(d,J=1.6Hz,2H),8.79(s,2H),7.96(d,J=3.9Hz,2H),7.81(d,J=2.5Hz,2H),6.88(dd,J=28,4.6Hz,2H),2.82(d,J =6.2Hz,2H),2.52(s,6H),2.40(m,4H),1.58(d,J=21.5Hz,10H),1.24(s,21H),0.87(m,12H).MS(MALDI-TOF)(m / z):Calcd.for C 71 H 65 BCl 4F 2 N 6 O 2 S 3 [M+]:1318.31; found:1319.73.Anal.Calcd.forC 71 H 65 BCl 4 F 2 N 6 O 2 S 3 :C 64.55, H 4.96, B 0.82, Cl 10.73, F 2.88, N 6.36, O 2.42, S 7.28; found: C 64.71, H 4.82, N 6.07, S 7.03.

[0072] The molar extinction coefficient spectrum of GMB1-Cl is as follows Fig.11 As shown, it can be seen that the material also exhibits considerable light absorption in the visible light region. Then, PBDB-T was used as the polymer donor material and GMB1-Cl as the electron acceptor material to construct an organic solar cell device. The device JV characteristic curve is shown in Fig.12 In addition, Table 2 lists the performance of the solar cell device of Example 2. The average energy conversion efficiency is taken from at least 10 independent photovoltaic devices.

[0073] Table 2 Performance of photovoltaic devices using GMB1-Cl as acceptor material in Example 2

[0074]

[0075] Combining the device data of Example 1 and Example 2, we can find that the photovoltaic device based on the blended PBDB-T and the completely non-condensed ring receptor material developed by the present invention as the active layer exhibits an energy conversion efficiency of about 3.5%, thereby proving that the molecular design strategy provided by the present invention is effective. Based on the completely non-condensed ring core skeleton of the fluoroboron dipyrrole core and the single thiophene ring π bridge, a completely non-condensed ring receptor can be constructed and a relatively ideal device performance can be achieved. At the same time, considering the difficulty of material synthesis, structural complexity, preparation cost and photovoltaic performance, the completely non-condensed ring receptor designed by the present invention is a class of cost-effective photovoltaic receptor materials. In addition, the present invention is the first attempt and application of the fluoroboron dipyrrole unit as the core unit and the strategy of introducing steric hindrance effect to regulate molecular rigidity in the design of completely non-condensed ring receptor materials. Based on this novel design strategy, the disadvantage of the weak light absorption ability of the completely non-condensed ring receptor is compensated, and the problem of the difficulty in regulating the morphology of the active layer of the completely non-condensed ring receptor is solved simultaneously. This "killing two birds with one stone" strategy also reflects the creativity of the design ideas and material molecular structure of the present invention.

[0076] In summary, focusing on the scientific problem of how to construct cost-effective photovoltaic acceptor materials, with the goal of designing and synthesizing efficient and low-cost completely non-condensed ring acceptors, the present invention has developed a novel and efficient molecular design strategy to address the existing performance defects of completely non-condensed ring acceptors, and synthesized two new completely non-condensed ring electron acceptor materials. By analyzing their chemical structures and linking their physical properties and photovoltaic performance, this type of acceptor material has the following obvious characteristics:

[0077] First, the center of the molecule is the fluoroboron dipyrrole structural unit. The fluoroboron dipyrrole unit is a "cold" group in the design of organic photovoltaic electron acceptor materials. By utilizing the high extinction characteristics of the fluoroboron dipyrrole unit and the "quasi-tricyclic" structure formed based on the boron-nitrogen coordination bridge, the disadvantage of the poor light absorption ability of the completely non-condensed ring electron acceptor due to insufficient conjugation is compensated. In addition, it is the first time to design a completely non-condensed ring electron acceptor with a fluoroboron dipyrrole core.

[0078] Second, the methyl units at the four α sites on the fluoroborane dipyrrole skeleton produce a steric effect, causing a twist between the π bridge and the core unit. Therefore, the planar rigidity of the receptor molecule is broken, thereby inducing moderate crystallinity and forming an ideal active layer morphology. According to sufficient literature research, the strategy of introducing steric groups into the core of a completely non-condensed ring receptor to twist the molecular skeleton and optimize the morphology has not yet been reported.

[0079] Third, the two material molecules present a completely non-condensed ring skeleton. The completely non-condensed ring skeleton is easy to construct. The two molecules designed by the present invention can be realized based on commercially available molecular building blocks in only two steps. The reaction process is simple, the conditions are mature, and the yield is high. And these commercially available building blocks are also easy to synthesize and prepare. Based on this, the receptor material developed by the present invention has the characteristics of easy synthesis and low cost.

[0080] Combining the above three points, it can be seen that on the basis of retaining the easy synthesis and low-cost characteristics of completely non-condensed ring receptor materials, the molecular design ideas developed by the present invention have compensated for the performance disadvantages of this type of material to a certain extent, and are innovative and advanced. In addition, there are very few reports on the construction of receptor units based on fluoroboron dipyrrole units. This patent is the first to use this unit as the core to construct a completely non-condensed ring receptor. In addition, there are no reports on the construction of a completely non-condensed ring receptor skeleton with a torsional configuration using the steric effect on the core. Therefore, the molecular design ideas of this patent and the corresponding material molecular structure are also novel. In summary, the design ideas developed by this patent have a positive role in promoting and application value for further developing new low-cost and high-efficiency electron receptor materials, and then realizing cost-effective organic photovoltaic technology.

[0081] The present invention provides a completely non-condensed ring electron acceptor material and its preparation method and application ideas and methods. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented by existing technologies.

Claims

1. A completely non-condensed ring electron acceptor material, characterized in that: The core group is a fluoroborane dipyrrole unit, and its skeleton has four α Each site has a methyl substituent, the terminal group is a 3-(dicyanomethylene)inden-1-one unit substituted with a fluorine or chlorine atom, and the π bridge between the terminal group and the core group is an alkyl-substituted thiophene unit; The chemical structure of the completely non-condensed ring electron acceptor material is as follows: ； Wherein, X is a halogen atom such as fluorine or chlorine.

2. The method for preparing the completely non-condensed ring electron acceptor material according to claim 1, characterized in that: The steps include: (1) The compound tetramethyl boron dipyrrole (5,5-difluoro-1,3,7,9-tetramethyl-5 H -4 λ 4 ,5 λ 4 -dipyrrolo[1,2- c :2',1'- f [1,3,2]diazacyclohexylborane), coupled with the compound of formula 2, 4-hexyl-5-boric acid pinacol ester-2-carboxaldehyde, to obtain the compound of formula 3; ； (2) reacting the compound of formula 3 obtained in step (1) with the halide of 3-(dicyanomethylene)inden-1-one of formula 4 to carry out dehydration condensation to obtain; ； Wherein, X is a halogen atom such as fluorine or chlorine.

3. The method for preparing a completely non-condensed ring electron acceptor material according to claim 2, characterized in that: In step (1), the compound represented by formula 1 and the compound represented by formula 2 are coupled by a one-step palladium-catalyzed Suzuki-Miyaura reaction.

4. The method for preparing a completely non-condensed ring electron acceptor material according to claim 3, characterized in that: In step (1), the compound represented by formula 1 and the compound represented by formula 2 are mixed with anhydrous potassium carbonate, tris dibenzylideneacetone dipalladium, and tri(o-methylphenyl)phosphine, and then a reaction solvent is added. o C for 36 to 48 hours; after the reaction is completed, cool to room temperature, separate by extraction, and purify by column chromatography to obtain the compound shown in formula 3.

5. The method for preparing a completely non-condensed ring electron acceptor material according to claim 4, characterized in that: In step (1), the molar ratio of the compound represented by formula 1, the compound represented by formula 2, anhydrous potassium carbonate, trisdibenzylideneacetone dipalladium, and tri(o-methylphenyl)phosphine is 1:(2.5-3.5):(8-12):(0.1-0.15):(0.1-0.15); the reaction solvent is a mixed solvent of toluene, water, and ethanol in a volume ratio of 1:(0.2-0.25):(0.25-0.4).

6. The method for preparing a completely non-condensed ring electron acceptor material according to claim 2, characterized in that: In step (2), the compound represented by formula 3 and the compound represented by formula 4 are subjected to dehydration condensation by Vilsmeier-Haack reaction.

7. The method for preparing a completely non-condensed ring electron acceptor material according to claim 6, characterized in that: In step (2), the compound represented by formula 3 and the compound represented by formula 4 are mixed, a reaction solvent is added, and a nitrogen atmosphere is added to 60-65° C. o C for 6 to 12 hours, and after the reaction is completed, cooled to room temperature, separated by extraction, and purified by column chromatography to obtain the product.

8. The method for preparing a completely non-condensed ring electron acceptor material according to claim 7, characterized in that: In step (2), the molar ratio of the compound represented by formula 3 and the compound represented by formula 4 is 1:2.5 to 1:5; and the reaction solvent is a pyridine-trichloromethane mixed solvent with a volume ratio of 1:10 to 1:

15.

9. Use of the completely non-condensed ring electron acceptor material according to claim 1 in preparing organic solar cells.

Images