A Class of Medium-Bandgap Non-Fused-Ring Dimeric Acceptor Materials and Their Applications in Organic Solar Cells

Abstract

This invention discloses a type of medium-bandgap non-fused-ring dimer acceptor material and its application in organic solar cells, belonging to the field of organic semiconductor materials technology. The medium-bandgap non-fused-ring dimer acceptor material has the structure shown in formula (1). This type of acceptor material possesses the technical advantages of simple molecular structure, easy synthesis, and precise controllability of molecular structure. By adjusting units A and B, the optical bandgap of this type of material can be controllably adjusted within the range of 1.5~1.7 eV. This type of material can be combined with most donor materials. When the donor material is polymer D18, its binary OSC device energy conversion efficiency reaches 14.59%. When added as a third component to the D18:L8-BO system, the device efficiency can be increased to 19.49%. This invention provides a new approach for the design of indoor photovoltaic and tandem organic solar cell materials.

Description

Technical Field

[0001] This invention relates to the field of organic solar energy technology, specifically to a class of medium bandgap non-fused ring dimer acceptor materials and their application in organic solar cells. Background Technology

[0002] Organic solar cells (OSCs), as a new generation of photovoltaic technology, have shown significant potential in the field of renewable energy due to their advantages such as wide availability of materials, lightweight nature, and flexible processing. In recent years, the rapid development of non-fullerene fused-ring electron acceptor materials, represented by Y6, has greatly promoted the power conversion efficiency (PCE) of single-junction organic solar cells to exceed 20%, laying a solid foundation for commercial applications.

[0003] Current development of acceptor materials mainly focuses on three directions: small molecules, dimers, and polymers. Small molecule acceptor materials are prone to self-aggregation and migration under long-term storage or photothermal aging conditions, leading to deterioration of the active layer morphology and disruption of charge transport channels. Polymer acceptor materials suffer from difficulties in precisely controlling the polymerization reaction, resulting in variations in molecular weight distribution and end-group structures between different batches, directly affecting the reproducibility of device performance. To address these challenges, researchers have proposed a small molecule acceptor dimerization strategy. Dimeric acceptors, which connect two acceptor units via covalent bonds, offer advantages such as well-defined molecular structures, relatively simple synthesis, and good batch-to-batch reproducibility, making them a current research hotspot.

[0004] Currently, highly efficient dimerizing acceptor materials include those based on fused-ring electron acceptors and those based on non-fused-ring acceptors. Dimeric acceptor materials constructed from fused-ring electron acceptor units typically exhibit narrow optical band gaps. For example, CN119751483A discloses a material using 3,4-ethylenedioxythiophene as a bridging unit. This material achieves a high open-circuit voltage of 1.02 eV and a binary device efficiency of 15.1% by introducing alkoxy side chains into the outer chain to weaken the intramolecular charge transfer effect. Other literature has also reported dimerization strategies based on Y-series fused-ring acceptors, which maintain high photovoltaic performance while improving device stability. Although dimerizing acceptor materials based on fused-ring electron acceptors exhibit excellent photovoltaic performance and stability, their complex synthetic routes and high costs remain significant challenges. The construction of fused-ring structures usually requires multi-step cyclization reactions and meticulous intermediate modifications, with harsh reaction conditions and unstable yields, severely limiting their large-scale preparation and commercial application. Furthermore, fused-ring acceptor materials typically possess narrow optical band gaps (≤1.35 eV), with absorption spectra concentrated in the near-infrared region and weak absorption in the visible light range. This limits their applicability in specific scenarios such as indoor photovoltaics and semi-transparent devices. Research on non-fused-ring dimer acceptors is relatively scarce. The paper "High-efficiency and stable organic solar cells based on non-fused-ring dimer acceptors as a third component" (Acta Phys.-Chim. Sin. 2026) reported narrow-bandgap dimer acceptors D-2BTH2F-H and D-2BTH2F-F derived from the non-fused-ring small molecule acceptor 2BTh-2F. However, the efficiencies of binary devices based on D18 donors were only 7.74% and 6.95%, respectively, far below the current mainstream levels, limiting their application potential as main acceptor materials.

[0005] In summary, the existing technologies have the following main problems: (1) The synthesis of dimer receptors based on fused ring structures is complex and costly, making it difficult to meet the needs of large-scale preparation; (2) When the reported non-fused ring dimer receptors are used as main receptor materials, the efficiency of binary devices is low, which limits their practicality. Summary of the Invention

[0006] To address the shortcomings of existing fused-ring dimer acceptor materials, such as complex synthesis, high cost, and narrow band gap, this invention organically combines the cost advantages of non-fused rings with the stability advantages and performance advantages of dimers with medium band gaps. It provides a class of medium-bandgap non-fused-ring dimer acceptor materials and their applications. This material exhibits excellent photoelectric properties, with an optical band gap between 1.5 and 1.7 eV. It overcomes the deficiencies of existing non-fused-ring dimer acceptor materials in terms of energy level matching, open-circuit voltage optimization, and application scenario expansion. Binary or ternary organic solar cells based on this medium-bandgap non-fused-ring dimer acceptor material have achieved high PCE, further expanding the application of dimer acceptor materials in indoor photovoltaics, flexible electronics, and tandem organic solar cells.

[0007] To achieve the above objectives, the present invention provides a class of medium-bandgap non-fused ring dimer acceptor materials, the molecular structure of which is shown in formula (1): Equation (1)

[0008] The A group mentioned in the formula is independently selected from one of the electron-withdrawing unit structures shown in formula (2), where the dashed lines in formula (2) represent double bond connection positions. Equation (2) ; In formula (2), X is a H, F or Cl atom; R1 is selected from a straight chain with C2 or C6 atoms; more preferably, R1 is a straight-chain alkyl group with C6 atoms.

[0009] More preferably, the A unit is independently selected from one of the structures shown in equation (3): Equation (3) .

[0010] The non-fused ring intermediate band gap dimer acceptor material is characterized in that the B unit is independently selected from one of the structures shown in formula (4): Equation (4) ; According to the present invention, in order to obtain a receptor material with superior performance, preferably, the medium band gap non-fused ring dimer receptor material has the chemical structure shown in formula (5): Equation (5) .

[0011] Secondly, the present invention provides the application of the above-mentioned medium bandgap non-fused ring dimer acceptor material in organic solar cells.

[0012] Preferably, the organic solar cell has a layered structure, comprising, from bottom to top, an anode, a hole transport layer, a photoactive layer, an electron transport layer, and a cathode.

[0013] Preferably, the medium bandgap non-fused ring dimer acceptor material is used in the photoactive layer of an organic solar cell.

[0014] More preferably, the anode is indium tin oxide, the hole transport layer is PEDOT:PSS, the electron transport layer is PNDIT-F3N, and the cathode is Ag.

[0015] Preferably, the medium-bandgap non-fused ring dimer acceptor material is blended with the polymer donor material to form the photoactive layer of the binary bulk heterojunction organic solar cell, wherein the weight ratio of the polymer donor to the acceptor is 1:1 to 1:1.4, and the thickness of the active layer is 80 to 200 nm.

[0016] Preferably, the polymer donor material is D18, with a chemical structure as shown in formula (6): Equation (6)

[0017] Preferably, the medium bandgap non-fused ring dimer acceptor material is used as the third component in the photoactive layer of an organic solar cell in a D18:L8-BO organic solar cell, wherein the mass ratio of D18:L8-BO is 1:1.2, and the mass ratio of D18:medium bandgap non-fused ring dimer acceptor material is 1:0.05 to 1:0.1.

[0018] More preferably, the chemical structure of the L8-BO is shown in formula (7): Equation (7)

[0019] The medium-bandgap non-fused-ring dimer acceptor material provided by this invention has the following characteristics compared with the currently reported fused-ring dimer acceptor materials: (1) The synthesis does not require complex fused-ring reactions (such as Friedel-Crafts cyclization, transition metal-catalyzed intramolecular cyclization, etc.), but only simple electrophilic substitution and coupling reactions (such as Suzuki and Stille coupling), which simplifies the complexity of the molecular structure and thus reduces the production cost; (2) The absorption spectrum, energy level and molecular stacking mode of the dimer acceptor can be finely adjusted by electron-withdrawing A units and bridging B units; (3) This type of material can be combined with most donor materials. When the donor material is polymer D18, the energy conversion efficiency of its binary OSCs device is as high as 14.59%. When it is added as a third component to the D18:L8-BO system, the device efficiency can be increased to 19.49%. This invention provides new ideas for the design of materials for indoor photovoltaic and tandem organic solar cells; (4) The medium band gap expands the application of dimer acceptor materials in indoor photovoltaic, flexible electronics and tandem organic solar cells, while achieving the goals of high efficiency, high stability, low cost and wide applicability, and promoting the commercial application of organic solar cells. Attached Figure Description

[0020] Figure 1 The UV-Vis absorption spectrum of the dimer receptor DNFA1 in Example 1; Figure 2 The UV-Vis absorption spectrum of the dimer acceptor DNFA2 in Example 2; Figure 3 The UV-Vis absorption spectrum of the dimer acceptor DNFA3 in Example 3; Figure 4 The UV-Vis absorption spectrum of the dimer acceptor DNFA1 in Example 4; Figure 5 The cyclic voltammetry curves for the dimer acceptor DNFA1 in Example 1 are shown below. Figure 6 The cyclic voltammetry curve of the dimer acceptor DNFA2 in Example 2; Figure 7 The cyclic voltammetry curve of the dimer acceptor DNFA3 in Example 3; Figure 8 The cyclic voltammetry curve of the dimer acceptor DNFA4 in Example 4; Figure 9 The JV curve of the DNFA1 binary organic solar cell device in Example 1 is shown. Figure 10 The JV curve of the DNFA2 binary organic solar cell device in Example 2; Figure 11 The JV curve of the DNFA3 binary organic solar cell device in Example 3; Figure 12 The JV curve of the DNFA4 binary organic solar cell device in Example 4; Figure 13 The JV curve of the DNFA2 ternary organic solar cell device in Example 2; Figure 14 The JV curve is shown for the DNFA3 ternary organic solar cell device in Example 3. Detailed Implementation

[0021] To further understand the purpose, content, and advantages of this invention, specific embodiments of the invention are described in detail below. However, these embodiments are not limited to the examples described below and should be freely combined according to actual circumstances. The endpoints and values ​​of the ranges disclosed herein are not limited to the precise ranges and values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0022] The present invention will be further described in detail below with reference to the embodiments: Unless otherwise specified, the reagents and materials used in each embodiment can be commercially available. For ease of description, some compounds in the synthetic route equations of each embodiment are numbered, and these numbers will be used to represent the compounds in certain positions. The structural formulas of the donor materials used in the embodiments are as described in the Summary of the Invention section.

[0023] Example 1

[0024] Synthesis of the non-fused-ring dimer acceptor material DNFA1

[0025] This embodiment illustrates the preparation process of the medium-bandgap non-fused-ring dimer acceptor material DNFA1. The synthetic route is shown below:

[0026] 1.1 Synthesis of Compound 3

[0027] In a 50 mL double-necked round-bottom flask, compound 1 (2 g, 7.5 mmol), compound 2 (3.6 g, 18.5 mmol), and K₂CO₃ (3.1 g, 22.5 mmol) were dissolved in 20 mL DMF. The mixture was stirred at 100 °C for 12 h under nitrogen protection. After cooling to room temperature, the reaction mixture was extracted three times with ethyl acetate, dried over anhydrous MgSO₄, and concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether) to give a colorless liquid (2.9 g, 80% yield).

[0028] 1 H NMR (400 MHz, CDCl3) δ 7.08 (s, 2H), 3.83 (d, J = 5.6 Hz, 4H), 1.75(s, 2H), 1.49 (s, 4H), 1.32 (d, J = 3.6 Hz, 12H), 0.94 – 0.89 (m, 12H).

[0029] 1.2 Synthesis of Compound 5

[0030] In a 50 mL double-necked round-bottom flask, compound 3 (1 g, 2.0 mmol), compound 4 (2.2 g, 4.1 mmol), Pd2(dba)3 (92.9 mg, 0.1 mmol), and p-( o -tol)3 (123.6 mg, 0.4 mmol) was dissolved in 15 mL of toluene, and the reaction was carried out under nitrogen protection at 110 °C with stirring for 8 h. After cooling the reaction solution to room temperature, the toluene was removed by concentration under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether) to give a pale yellow liquid (1.6 g, yield 60%).

[0031] 1 H NMR (400 MHz, CD2Cl2) δ 9.95 (s, 2H), 7.44 (s, 2H), 7.23 (s, 2H), 3.96 (d, J = 5.4 Hz, 4H), 2.82 (d, J = 7.2 Hz, 4H), 1.79 (p, J = 6.0 Hz, 2H),1.67 (s, 2H), 1.46 (dd, J = 20.6, 6.7 Hz, 4H), 1.32 – 1.12 (m, 44H), 0.89 (t, J = 7.4 Hz, 6H), 0.80 (dt, J = 14.3, 7.0 Hz, 18H).

[0032] 1.3 Synthesis of Compound 6

[0033] In a 50 mL double-necked round-bottom flask, POCl3 (0.15 mL, 1.79 mmol) was added under nitrogen protection. The reaction system was cooled to 0 °C, and anhydrous DMF (0.14 mL, 1.79 mmol) was added dropwise, with stirring at 0 °C for 1 h. Subsequently, a solution of compound 5 (1 g, 1.19 mmol) in 1,2-dichloroethane (10 mL) was slowly added dropwise to the generated Wiesmeer reagent. After the addition was complete, the mixture was stirred at 0 °C for 30 min, then heated to 40 °C and reacted for another 5 h. The reaction solution was cooled to room temperature, and a saturated sodium bicarbonate solution was slowly added, with stirring continued for 1 h. The mixture was extracted three times with dichloromethane, the organic phases were combined, washed with saturated brine, dried over anhydrous MgSO4, and concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, v:v = 3:1) to give a yellow liquid (698 mg, yield 68%).

[0034] 1 H NMR (400 MHz, CDCl3) δ 10.02 (s, 1H), 7.46 (s, 1H), 7.40 (s, 1H), 7.23 (s, 2H), 6.93 (s, 1H), 4.01 (d, J = 5.4 Hz, 2H), 3.97 (d, J = 5.4 Hz, 2H), 2.88 (d, J = 7.2 Hz, 2H), 2.57 (d, J = 6.8 Hz, 2H), 1.84 (q, J = 6.0 Hz,2H), 1.64 – 1.41 (m, 6H), 1.40 – 1.19 (m, 44H), 1.02 – 0.97 (d, J = 6.4 Hz, 6H), 0.91 – 0.83 (m, 18H).

[0035] 1.4 Synthesis of Compound 8

[0036] In a 50 mL double-necked round-bottom flask, compound 6 (600 mg, 0.69 mmol), compound 7 (379 mg, 1.39 mmol), pyridine (0.1 mL), and chloroform (10 mL) were added. The mixture was stirred at 65 °C for 12 h under nitrogen protection. After cooling, the reaction mixture was slowly added dropwise to 50 mL of methanol to precipitate. The precipitate was collected by filtration, and the crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, v:v = 3:1) to give a blue viscous liquid (524 mg, yield 68%).

[0037] 1 H NMR (400 MHz, CH2Cl2) δ 8.99 (s, 1H), 8.51 (d, J = 8.6 Hz, 1H),7.98 (s, 1H), 7.84 (d, J = 6.6 Hz, 1H), 7.66 (s, 1H), 7.49 (s, 1H), 7.37 (s,1H), 7.31 (s, 1H), 7.00 (s, 1H), 4.11 (d, J = 5.4 Hz, 2H), 4.06 (d, J = 5.3Hz, 2H), 2.95 (d, J = 7.3 Hz, 2H), 2.59 (d, J = 6.9 Hz, 2H), 2.09 – 1.99 (m,1H), 1.93 – 1.84 (m, 1H), 1.67 – 1.52 (m, 6H), 1.42 – 1.21 (m, 44H), 0.99 (q, J = 7.1 Hz, 6H), 0.94 – 0.79 (m, 18H).

[0038] 1.5 Synthesis of Compound 9

[0039] In a 50 mL double-necked round-bottom flask, POCl3 (0.13 mL, 1.40 mmol) was added under nitrogen protection. The reaction system was cooled to 0 °C, and anhydrous DMF (0.11 mL, 1.40 mmol) was slowly added dropwise while stirring at 0 °C for 1 h to prepare the Wiesmere reagent. Subsequently, a solution of compound 8 (524 mg, 0.47 mmol) in 1,2-dichloroethane (10 mL) was slowly added dropwise to the above reagent. After the addition was complete, the mixture was stirred at 0 °C for 30 min, then heated to 40 °C and reacted for another 12 h. The reaction solution was cooled to room temperature, and a saturated sodium bicarbonate solution was slowly added while stirring for another 1 h. The mixture was extracted three times with dichloromethane, the organic phases were combined, washed with saturated brine, dried over anhydrous MgSO4, and concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, v:v = 2:1) to give a dark purple solid (431 mg, yield 80%).

[0040] 1 H NMR (400 MHz, CDCl3) δ 10.05 (s, 1H), 9.00 (s, 1H), 8.52 (d, J =8.5 Hz, 1H), 7.99 (s, 1H), 7.81 (d, J = 6.5 Hz, 1H), 7.65 (s, 1H), 7.53 (s,1H), 7.36 (s, 1H), 7.30 (s, 1H), 4.08 (d, J = 5.4 Hz, 4H), 2.92 (d, J = 6.1Hz, 4H), 2.03 – 1.98 (m, 1H), 1.90 – 1.86 (m, 1H), 1.65 – 1.52 (m, 6H), 1.38– 1.23 (m, 44H), 1.00 (t, J = 7.4 Hz, 6H), 0.93 – 0.82 (m, 18H).

[0041] 1.6 Synthesis of Compound 11

[0042] In a 25 mL double-necked round-bottom flask, compound 9 (430 mg, 0.37 mmol), compound 10 (102 mg, 0.17 mmol), Pd2(dba)3 (7.78 mg, 0.008 mmol), and p-( o-tol)3 (10.33 mg, 0.03 mmol) was dissolved in 10 mL of toluene. The reaction mixture was stirred at 110 °C for 6 h under nitrogen protection. After cooling to room temperature, the toluene was removed by concentration under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, v:v = 2:1) to give a deep blue solid (185 mg, 52% yield).

[0043] 1 H NMR (400 MHz, CDCl3) δ 10.05 (s, 2H), 9.01 (s, 2H), 8.70 (d, J =8.3 Hz, 2H), 8.02 (s, 2H), 7.84 (d, J = 8.3 Hz, 2H), 7.67 (s, 2H), 7.53 (s,2H), 7.40 (s, 2H), 7.38 (s, 2H), 7.31 (s, 2H), 4.09 (d, J = 5.0 Hz, 8H), 2.96(d, J = 7.3 Hz, 4H), 2.90 (d, J = 7.2 Hz, 4H), 2.06 – 1.97 (m, 2H), 1.93 –1.85 (m, 2H), 1.77 – 1.73 (m, 4H), 1.65 – 1.53 (m, 8H), 1.33 – 1.24 (m, 88H), 1.02 (q, J = 8.0 Hz, 12H), 0.93 – 0.83 (m, 36H).

[0044] 1.7 Synthesis of product DNFA1

[0045] In a 25 mL single-necked round-bottom flask, compound 11 (180 mg, 0.08 mmol), compound 12 (32 mg, 0.13 mmol), Ac₂O (0.15 mL), and BF₃·OEt₂ (0.15 mL) were added sequentially, followed by the addition of 15 mL of toluene to dissolve and mix. The mixture was stirred at room temperature for 50 min under nitrogen protection. After the reaction was complete, the reaction solution was slowly added dropwise to 30 mL of methanol to settle, and the solid was collected by filtration. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, v:v = 1:1) to give a blue-black solid (116 mg, yield 58%).

[0046] 1H NMR (400 MHz, CDCl3) δ 8.92 (s, 2H), 8.59 (d, J = 8.2 Hz, 2H), 8.15(s, 2H), 7.91 (s, 2H), 7.70 (d, J = 16.6 Hz, 6H), 7.52 (s, 2H), 7.36 (s, 2H), 7.30 (s, 2H), 4.30 (d, J = 7.3 Hz, 4H), 4.17 (s, 8H), 2.94 (d, J = 7.2 Hz, 4H), 2.77 (d, J = 7.1 Hz, 4H), 2.07– 2.00 (m, 4H), 1.75– 1.69 (m, 4H), 1.67 –1.56 (m, 8H), 1.40 – 1.25 (m, 104H), 1.01 (q, J = 7.2 Hz, 12H), 0.92 – 0.85(m, 42H).

[0047] Example 2

[0048] Synthesis of the non-fused-ring dimer acceptor material DNFA2

[0049] The preparation of DNFA2 follows the same procedure as DNFA1, except that the starting material 2-(3-ethyl-4-oxothiazolidine-2-yl)malononitrile is replaced with (5,6-difluoro-1,3-bis(dicyanomethylene)inden-1-one). The synthetic route is shown below:

[0050] In a 25 mL single-necked round-bottom flask, compound 11 (130 mg, 0.06 mmol), compound 13 (31 mg, 0.14 mmol), Ac₂O (0.15 mL), and BF₃·OEt₂ (0.15 mL) were added sequentially, followed by the addition of 15 mL of toluene to dissolve and mix. The mixture was stirred at room temperature for 50 min under nitrogen protection. After the reaction was complete, the reaction solution was slowly added dropwise to 30 mL of methanol to settle, and the solid was collected by filtration. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, v:v = 1:1) to give a blue-black solid (80 mg, yield 52%).

[0051] 1H NMR (400 MHz, CDCl3) δ 8.83 (s, 2H), 8.81 (s, 2H), 8.48 (s, 2H), 8.35 (s, 2H), 7.80 (s, 2H), 7.67 (d, J = 9.8 Hz, 4H), 7.59 (s, 2H), 7.49 (s,2H), 7.29 (d, J = 3.5 Hz, 4H), 7.17 (s, 2H), 4.23 (s, 8H), 2.97 (d, J = 7.3Hz, 4H), 2.92 (dd, J = 35.1, 7.4 Hz, 4H), 2.14 – 2.10 (m, 4H), 1.41 – 1.12(m, 12H), 1.30 – 1.21 (m, 88H), 0.98 (dd, J = 11.0, 6.8 Hz, 12H), 0.90 – 0.82(m, 36H).

[0052] Example 3

[0053] Synthesis of the non-fused-ring dimer acceptor material DNFA3

[0054] The preparation of DNFA3 follows the same procedure as DNFA1, except that the starting material 2-(3-ethyl-4-oxothiazolidine-2-yl)malonadionitrile is replaced with 5,6-dichloro-1,3-bis(dicyanomethylene)inden-1-one. The synthetic route is shown below:

[0055] The product is a blue-black solid.

[0056] 1 H NMR (400 MHz, CDCl3) δ 8.82 – 8.80 (m, 4H), 8.50 (s, 4H), 7.76 (s,2H), 7.65 (d, J = 8.2 Hz, 6H), 7.58 (d, J = 8.3 Hz, 2H), 7.31 (s, 2H), 7.28(s, 2H), 7.15 (s, 2H), 4.27 (s, 8H), 2.98 (d, J = 6.4 Hz, 4H), 2.89 (d, J=7.2 Hz, 4H), 2.14 (s, 4H), 1.76 (s, 4H), 1.48 (d, J = 7.2 Hz, 8H), 1.31 –1.22 (m, 88H), 0.99 (d, J = 6.4 Hz, 12H), 0.91 – 0.84 (m, 36H).

[0057] Example 4

[0058] Synthesis of the non-fused-ring dimer acceptor material DNFA4

[0059] The preparation of DNFA4 is the same as that of DNFA1, except that compound 10 is replaced with compound 4,7-bis(4,4,5,5-tetramethyl-1,3,2-dioxoborocyclo-2-yl)benzo[c][1,2,5]thiadiazole by the following synthetic steps.

[0060]

[0061] In a 50 mL double-necked round-bottom flask, compound 9 (500 mg, 0.44 mmol), compound 15 (81 mg, 0.21 mmol), Cs₂CO₃ (195 mg, 0.62 mmol), and Pd(PPh₃)₄ (12.10 mg, 0.01 mmol) were added sequentially, along with a 6:1 mixture of toluene and DMF. Under nitrogen protection, the reaction mixture was stirred at 110 °C for 7 h. After cooling to room temperature, the reaction mixture was poured into water and extracted three times with dichloromethane. The combined organic phases were dried over anhydrous MgSO₄ and concentrated under reduced pressure to remove the solvent. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane, v:v = 2:1) to give a blue-black solid (82 mg, 40% yield).

[0062] 1 H NMR (400 MHz, CDCl3) δ 10.05 (s, 2H), 9.09 (s, 2H), 8.88 (s, 2H), 8.60 (s, 2H), 8.45 (d, J = 6.4 Hz, 2H), 8.03 (s, 2H), 7.69 (s, 2H), 7.53 (s,2H), 7.38 (s, 2H), 7.31 (s, 2H), 4.09 (s, 8H), 2.98 (s, 4H), 2.89 (s, 4H),1.98 (d, J = 6.2 Hz, 2H), 1.89 (d,J = 6.1 Hz, 2H), 1.66 – 1.61 (m, 12H), 1.29 (s, 88H), 1.00 (d, J = 7.0 Hz, 12H), 0.89 – 0.87 (m, 36H).

[0063] Comparative Example 1

[0064] Non-fused ring small molecule acceptor material TBT-4F

[0065] The molecular structure of the non-fused-ring small molecule acceptor material TBT-4F is shown below, and is used to compare its photovoltaic performance with that of Examples DNFA1~DNFA4.

[0066]

[0067] Example 5

[0068] Photophysical properties testing of non-fused-ring dimer acceptors

[0069] The ultraviolet-visible absorption spectra were measured using a Shimadzu UV-2600 ultraviolet-visible spectrophotometer. Figure 1 The figures show the UV-Vis absorption spectra of DNFA1 to DNFA4 in chloroform solution and thin film. As can be seen, they exhibit broad and strong absorption in both solution and thin film, displaying two distinct characteristic absorption peaks in the 400-900 nm range. The short-wavelength absorption is attributed to the π-π bonds in the molecular backbone. The transition, with long-wavelength absorption peaks attributed to intramolecular charge transfer (ICT) from donor to acceptor units. The thin film exhibits a significant redshift in absorption compared to solution, along with vibrational shoulders, due to enhanced molecular packing in the solid state. This is based on the formula for calculating the optical band gap. E g =1240 / λ (where E g (where λ is the optical band gap and λ is the maximum absorption sideband value of the thin film), the optical band gaps of DNFA1 to DNFA4 are obtained, as shown in Table 1 below.

[0070] Table 1 Absorption Boundary Values ​​and Optical Band Gap of DNFA1~DNFA4

[0071] As can be seen from Table 1, the optical band gaps of the non-fused ring dimer acceptors DNFA1 to DNFA4 prepared in the above embodiments are between 1.5 and 1.7 eV, which belong to medium band gap acceptor materials.

[0072] Example 6

[0073] Electrochemical performance testing of non-fused-ring dimer acceptors

[0074] Cyclic voltammetry curves of DNFA1–DNFA4 were measured using a CHI630E electrochemical analyzer. 0.1 M tetrabutylammonium hexafluorophosphate was used as the electrolyte in acetonitrile solution. Platinum disk electrode, Ag / AgCl electrode, and platinum wire were used as the working, reference, and counter electrodes, respectively, with ferrocene as the internal standard. The sample was prepared as a 3 mg / mL chloroform solution, uniformly coated onto the platinum disk electrode, dried, and then placed in acetonitrile solution. The circuit was connected, and the oxidation and reduction potentials of the sample were measured at room temperature and under nitrogen protection. The instrument scan rate was 0.05 V / s. Cyclic voltammetry curves of DNFA1–DNFA4 in solid films are shown below. Figure 2 As shown, according to the calculation formula E HOMO =-( E ox +4.80)eV and E LUMO =-( E red +4.80)eV, the HOMO and LUMO energy levels of DNFA1~DNFA4 were obtained, as shown in Table 2 below.

[0075] Table 2 HOMO and LUMO energy levels of DNFA1~DNFA4

[0076] Example 7

[0077] Fabrication and Performance Testing of Binary Organic Solar Cell Devices Based on Non-Fused Ring Dimeric Acceptor Materials

[0078] Commercially available D18 (CAS No.: 2433725-54-1) was used as the active layer donor material for organic solar cells. DNFA1~DNFA4 synthesized in Examples 1-4 were used as active layer acceptor materials. Organic solar cell devices were fabricated using a bulk heterojunction device structure: ITO / PEDOT:PSS (20nm) / D18:DNFA1~DNFA4 (1:1.2, CF, 100nm) / PNDIT-F3N (5nm) / Ag (100 nm). Simulated sunlight (100mW / cm²) was used. 2 Under irradiation, the organic solar cell was measured. J – V Curves, such as Figures 9-12 As shown in Table 3, the performance of the two components is as follows.

[0079] Table 3 Performance of Two-Element Solar Cell Devices

[0080] As shown in the table above, the PCE of binary devices based on non-fused-ring dimer receptors DNFA2~DNFA4 are 14.59%, 11.08% and 11.02%, respectively, all higher than the PCE of 10.71% for the non-fused-ring small molecule receptor TBT-4F, proving that the dimerization strategy is an effective method to improve the PCE of OSCs devices.

[0081] Example 8

[0082] Fabrication and Performance Testing of Organic Solar Cell Ternary Devices Based on Non-Fused Ring Dimeric Acceptor Materials

[0083] Commercially available D18 (CAS No.: 2433725-54-1) and L8-BO (CAS No.: 2668341-40-8) were used as the donor and acceptor host materials for the active layer of organic solar cells, respectively. DNFA2 and DNFA3, synthesized in Examples 2 and 3, were used as the third component of the active layer. Organic solar cell devices were fabricated using a bulk heterojunction device structure: ITO / PEDOT:PSS (20nm) / D18:L8-BO:non-fused-ring dimer acceptor material (CF, 0.5% DIB, 100nm) / PNDIT-F3N (5nm) / Ag (100 nm), with a mass ratio of D18:L8-BO:non-fused-ring dimer acceptor material of 1:1:0.05. Simulated sunlight (100 mW / cm²) was used. 2 Under irradiation, the organic solar cell was measured. J – V Curves, such as Figures 13-14 As shown in Table 4, the performance of the three components is as follows.

[0084] Table 4 Performance of Three-Element Solar Cells

[0085] As can be seen from the table above, since the absorption regions of the medium bandgap non-fused ring dimer acceptor and the narrow bandgap acceptor material L8-BO have complementary effects, the short-circuit current of the device is improved after adding DNFA2 or DNFA3, thereby increasing the device PCE from 18.77% of D18:L8-BO to 19.49% and 19.21%, respectively.

[0086] Although the invention has been described in conjunction with preferred embodiments, the invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the invention. Guided by the inventive concept, those skilled in the art should recognize that any modifications made to the various embodiments of the invention will be covered by the spirit and scope of the claims.

Claims

1. A class of medium-bandgap non-fused-ring dimer acceptor materials, characterized in that, It has the chemical structure shown in formula (1): Equation (1) ; The A group is independently selected from one of the electron-withdrawing unit structures shown in formula (2), where the dashed lines in formula (2) represent double bond connection positions. Equation (2) ; In formula (2), X is an H, F or Cl atom; R1 is selected from a straight chain with C2 or C6 atoms; Group B is selected from one of the structures shown in formula (3): Equation (3) .

2. The medium-bandgap non-fused-ring dimer acceptor material according to claim 1, characterized in that, The A unit is independently selected from one of the structures shown in equation (4): Equation (4) .

3. The medium bandgap non-fused ring dimer acceptor material according to claims 1-2, characterized in that, The medium-bandgap non-fused-ring dimer acceptor material has the chemical structure shown in formula (5): Equation (5) .

4. The application of the medium-bandgap non-fused-ring dimer acceptor material according to any one of claims 1 to 3, characterized in that, The medium-bandgap non-fused-ring dimer acceptor material is used as an acceptor material for the photoactive layer of organic solar cells.

5. The application of the medium-bandgap non-fused-ring dimer acceptor material according to claim 4, characterized in that, The organic solar cell has a layered structure, comprising, from bottom to top, an indium tin oxide conductive glass anode, a hole transport layer, a photoactive layer, an electron transport layer, and a cathode.

6. The application of the medium bandgap non-fused ring dimer acceptor material according to claim 4, characterized in that, The process includes the following steps: blending the medium bandgap non-fused ring dimer acceptor material with a polymer donor material to form a binary bulk heterojunction organic solar cell photoactive layer, wherein the weight ratio of the polymer donor to the photoactive layer acceptor material is 1:1 to 1:1.4, and the thickness of the photoactive layer is 80 to 200 nm.

7. The application of the medium bandgap non-fused ring dimer acceptor material according to claim 6, characterized in that, The polymer donor material is D18, and the photoactive layer acceptor material is the medium-bandgap non-fused ring dimer acceptor material. Alternatively, the polymer donor material is D18, and the photoactive layer acceptor material is the medium-bandgap non-fused-ring dimer acceptor material and L8-BO, with a D18:L8-BO mass ratio of 1:1.2 and a D18:medium-bandgap non-fused-ring dimer acceptor material mass ratio of 1:0.05 to 1:0.

1.

8. The method for preparing the medium-bandgap non-fused-ring dimer acceptor material as described in claim 1, comprising the following steps: using compound 9 as a raw material, the medium-bandgap non-fused-ring dimer acceptor material is obtained through coupling and condensation reactions; the preparation route of compound 9 is as follows: 。

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