A class of asymmetric medium-bandgap fused-ring acceptor materials and their photovoltaic applications

Abstract

The present invention relates to a class of asymmetric medium-bandgap fused ring acceptor materials and their photovoltaic applications. The general structural formula of the fused ring acceptor molecule is shown in Formula I, wherein Ar1 is an aromatic unit, R1, R2, and R3 are linear, branched, or alkyl-substituted aromatic side chains, and Weak A is a different weak electron-withdrawing group. The material has an asymmetric fused ring structure, and this material also has the advantages of good solubility and easy film processing. When it is used as an acceptor material in combination with p-type semiconductor materials in organic solar cells, not only can excellent device performance be obtained, but also the device can have high open circuit voltage, short circuit current, and fill factor. In addition, this type of material can be applied to stacked organic solar cells and indoor organic photovoltaic devices to obtain excellent device performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic solar cell material preparation, relates to a class of organic solar cell receptor materials, specifically to a class of medium-bandgap fused-ring receptor materials containing an asymmetric fused-ring structure, and also relates to applications in stacked organic solar cells and indoor photovoltaic devices. Background Art

[0002] As energy issues become increasingly serious, the development of new energy sources is urgent. Solar energy has great development prospects due to its many advantages, such as being clean, pollution-free, inexhaustible, and inexhaustible. How to better utilize solar energy is an effective solution to the energy crisis. Over the past three decades, organic solar cells (OSCs) have attracted much attention due to their low manufacturing cost, good mechanical flexibility, and light weight. The rapid development of organic solar cells is mainly due to the continuous innovation of donor and acceptor materials in recent years. Currently, the power conversion efficiency of single-junction devices and tandem devices exceeds 19% and 20%, respectively (Adv. Mater., 2021, 33, e2102420; Joule., 2022, 6, 171-184). However, compared with commercial silicon-based solar cells and high-efficiency perovskite solar cells, the device efficiency of OSCs still needs to be further improved.

[0003] To further improve the efficiency of OSCs, the development of tandem solar cells (composed of a front cell with a wide-bandgap absorption and a rear cell with a narrow-bandgap absorption) is urgently needed. Acceptor materials with narrow-bandgap absorption characteristics have been extensively studied, and device efficiencies have exceeded 19%. However, research on medium-bandgap acceptor materials for the preparation of high-efficiency front cells is still lagging behind, and there is an urgent need to develop excellent medium-bandgap acceptor materials to improve the performance of the front cell.

[0004] Currently, research on medium-bandgap acceptor materials has received insufficient attention. Literature research reveals only a few reports of such materials (Adv. Mater. 2017, 29, 1700254; Chem. Mater. 2019, 31, 3941-3947; Joule. 2021, 5, 1231-1245; Adv. Mater. 2022, 34, e2108090). Therefore, the development of more efficient medium-bandgap acceptor materials is crucial. Our research has shown that modifying the classic A-DA′DA fused ring structure with oxygen-containing alkyl side chains, combined with weak electron-withdrawing end groups, can effectively modulate the absorption of the material, resulting in medium-bandgap acceptors. However, molecules with symmetrical structures generally exhibit strong crystallinity, making device morphology difficult to effectively control. Asymmetric strategies offer an effective means of manipulating molecular properties. In acceptor molecules, altering structural symmetry not only influences the spectrum and energy levels but also enhances the molecular dipole and charge transport capabilities. Furthermore, structural changes can regulate the molecular stacking and crystallinity of the material, ultimately improving the compatibility of the donor and acceptor. Therefore, in order to promote the efficiency improvement and commercial application of organic solar cells, we invented a class of asymmetric medium-bandgap fused-ring acceptors, achieving high-efficiency tandem organic solar cells and indoor photovoltaic devices. Summary of the Invention

[0005] The purpose of the present invention is to prepare a class of asymmetric medium band gap (E g ≈1.55–2.00 eV) fused-ring acceptor materials can serve as acceptors in the active layer of OSCs. These materials offer advantages such as a high lowest unoccupied molecular orbital (LUMO) energy level, absorption from the near-ultraviolet to the visible region, and high device open-circuit voltage. When used as acceptor materials in tandem organic solar cells and indoor photovoltaic devices, they demonstrate excellent device performance, with high open-circuit voltage, short-circuit current, and fill factor. Therefore, these materials hold great promise for application in tandem organic solar cells and indoor photovoltaic devices.

[0006] The technical solution adopted by the present invention is to provide a medium band gap acceptor material having an asymmetric fused ring structure containing an alkoxy side chain and a weak electron-withdrawing end group structure. The structural feature of the fused ring central core is that a thiophene unit containing an alkoxy side chain and a thiophene unit containing an alkoxy side chain are used as π bridges, respectively, to form a fused ring center with a conjugated structure containing a benzene ring. The two sides of the central core are connected to weak electron-withdrawing end groups. The general structural formula is shown in Formula I:

[0007]

[0008] in:

[0009] In the structural formula, R1, R2, and R3 are independently selected from linear, branched, or alkyl-substituted aryl side chains having 1 to 40 carbon atoms;

[0010] Weak A units are selected from any one of the following structural formulas:

[0011]

[0012] in:

[0013] The dotted line in the Weak A structure indicates the connection site to the Weak A unit.

[0014] Preferably, the Ar1 unit is selected from any one of the following structural formulas:

[0015]

[0016] Wherein, R4 in the Ar1 structural formula is independently selected from H, a linear or branched alkyl group having 1 to 20 carbon atoms, and the dotted line in the Ar1 structural formula represents the connection site with other units.

[0017] The preparation method of the compound comprises the following steps:

[0018] Its synthetic route is as follows:

[0019]

[0020] In the structural formula, R1, R2, and R3 are all straight-chain, branched, or alkyl-substituted aryl side chains having 1 to 40 carbon atoms.

[0021] (1) Compound A, Compound B, and Compound C are added to 80-100 mL of toluene, and then the catalyst, tetrakis(triphenylphosphine)palladium, is added. The mixture is reacted at 80-90°C for 10-12 hours to obtain Compound D through a Stille coupling reaction.

[0022] (2) Under nitrogen protection, compound D and triphenylphosphine were added to o-dichlorobenzene, and the system was heated to 160-180°C for 16-18 hours to obtain compound E;

[0023] (3) Under nitrogen protection, compound E, halogenated alkane R3Br, potassium carbonate, and potassium iodide were added to N,N-dimethylformamide and reacted at 80-85°C for 10-12 hours to obtain compound F;

[0024] (4) This reaction is a Vilsmeier-Haack reaction. Compound F is dissolved in 1,2-dichloroethane and then added dropwise to the formylation reagent phosphorus oxychloride at low temperature. The molar ratio of compound 6 to phosphorus oxychloride is 1:10 to 1:30. After reacting at low temperature for 1 to 2 hours, the system is heated to 80 to 100°C and reacted for 8 to 12 hours to obtain compound G.

[0025] (5) This reaction is a Knoevenagel condensation reaction. Under nitrogen protection, compound G, Weak A and pyridine are reacted at 60°C for 5-8 hours to obtain compound H.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] (1) The present invention is the first to simultaneously utilize thiophene structures modified with alkoxy side chains and thiophene structures modified with alkoxy side chains as π bridge units of fused ring acceptors in collaboration with weak electron-withdrawing end groups to obtain an asymmetric medium band gap (E) with a high absorption coefficient. g ≈1.55–2.00 eV) fused-ring acceptor materials. Their absorption range is in the near-ultraviolet and visible regions, significantly blue-shifted compared to common narrow-bandgap acceptor materials.

[0028] (2) Compared with symmetrical alkoxy side chains and strong electron-withdrawing end groups, these materials have higher LUMO energy levels, which can significantly improve the open-circuit voltage of photovoltaic devices. Moreover, the change in symmetry effectively regulates the crystallinity of the material, enhances the dipole and charge transport capabilities, and enables the device to have a higher short-circuit current density and fill factor.

[0029] (3) The light absorption range of this type of material is complementary to that of the narrow-bandgap acceptor material and can provide a higher open-circuit voltage. When used as a front cell, it can achieve good light absorption complementarity and voltage superposition with the rear cell made of the narrow-bandgap acceptor material, thereby realizing a high-efficiency stacked organic solar cell (efficiency exceeding 20%).

[0030] (4) The absorption range of this type of material has a good match with the emission spectrum of indoor lighting sources. Photovoltaic devices based on this type of receptor material exhibit excellent open-circuit voltage and energy conversion efficiency (efficiency exceeds 32%) under indoor light irradiation, and have important applications in indoor photovoltaic devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the thin film absorption spectrum of the acceptor molecule ABTP-S.

[0032] Figure 2 This is the thin film absorption spectrum of the acceptor molecule ABTP-SCl.

[0033] Figure 3This is the thin film absorption spectrum of the acceptor molecule ABTP-4Cl.

[0034] Figure 4 This is the thin film absorption spectrum of the receptor molecule ABTP-4F.

[0035] Figure 5 This is the thin film absorption spectrum of the receptor molecule ABNP-S.

[0036] Figure 6 This is the thin film absorption spectrum of the acceptor molecule ABSeP-S.

[0037] Figure 7 This is the thin film absorption spectrum of the acceptor molecule ABQP-S.

[0038] Figure 8 J–V characteristic curves with PBDB-T as donor and ABTP-S and ABNP-S as acceptors.

[0039] Figure 9 EQE characteristic curves with PBDB-T as donor and ABTP-S and ABNP-S as acceptors.

[0040] Figure 10 The J–V characteristic curves of the stacked cells prepared with PM6:Y6-O / BZ4F-O-1 and PBDB-T:ABTP-S / ABNP-S as front cells and PTTzF:Y6:

[70] PCBM as back cells, respectively.

[0041] Figure 11 J–V characteristic curves of single-junction devices based on PM6:Y6-O / BZ4F-O-1 and PBDB-T:ABTP-S / ABNP-S under indoor lighting conditions. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the following further describes the specific implementation of the present invention with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that if there are any processes not specifically described below, they can be implemented or understood by those skilled in the art with reference to the existing technology.

[0043] The practice of the present invention can employ conventional techniques of organic synthetic chemistry and organic photovoltaic device preparation. In the following examples, efforts have been made to ensure the accuracy of the numbers used (including mass, temperature, time, etc.), but some experimental errors and deviations should be taken into account. The temperatures used in the following examples are expressed in ° C. and the pressures are atmospheric pressure or near atmospheric pressure. The solvents used are all analytical or chromatographically pure, all reactions are carried out in an inert gas atmosphere, and device preparation is carried out in a nitrogen glove box. Unless otherwise noted, all reagents are obtained from commercial channels.

[0044] Example 1

[0045]

[0046] (1) Raw materials or intermediate reactants

[0047] Triphenylphosphine (PPh3), tetrakistriphenylphosphine palladium (Pd(PPh3)4), 5-(bromomethyl)heptane, potassium carbonate (K2CO3), potassium iodide (KI), pyridine, N,N-dimethylformamide (DMF), 1,2-dichloroethane, tetrahydrofuran (THF), toluene, 1,2-dichlorobenzene, and chloroform were purchased from companies such as Anage, J&K, and Suzhou Nakai.

[0048] (2) Preparation of Compound 4

[0049] Compound 1 (4,7-dibromo-5,6-dinitrobenzo[c][1,2,5]thiadiazole) (3.82 g, 10 mmol), compound 2 (6.02 g, 12 mmol), compound 3 (7.03 g, 12 mmol), and Pd(PPh3)4 (346.2 mg, 0.3 mmol) were added to a toluene (60 mL) solution under nitrogen. The reaction mixture was heated to reflux and stirred for 12 hours. After the reaction solution was cooled to room temperature, the reaction was quenched with water and extracted with dichloromethane. The organic phase was concentrated under reduced pressure to obtain a crude product, which was further purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 2:1) as the eluent to obtain compound 4 (2.18 g as a red solid, yield = 29.8%).

[0050] (3) Synthesis of compound 5

[0051] Under a nitrogen atmosphere, compound 4 (1.46 g, 2 mmol) and PPh3 (5.24 g, 20 mmol) were added to 20 mL of o-dichlorobenzene (o-DCB). The reaction system was heated to 160°C and refluxed for 16 h. After completion of the reaction, the mixture was cooled to room temperature, the solvent was removed by distillation under reduced pressure, and the mixture was precipitated with 100 mL of methanol. The crude product was filtered and used directly in the next reaction. The crude product, 5-(bromomethyl)heptane (1.78 g, 10 mmol), KI (0.55 g, 3.33 mmol), and K2CO3 (1.92 g, 12.92 mmol) were added to 50 mL of DMF. The reaction was stirred at 80°C under nitrogen for 24 h. After cooling to room temperature, water was added and the mixture was extracted three times with dichloromethane. The combined organic phases were further washed with water, dried over MgSO4, filtered, and concentrated under reduced pressure. The product was purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V=4:1) as eluent to obtain compound 5 (0.93 g as a yellow oily liquid, yield=52.2%).

[0052] (4) Synthesis of Compound 6

[0053] Under a nitrogen atmosphere, POCl3 (3.06 g, 20 mmol) was slowly added to ultra-dry DMF (1.1 g, 15 mmol) at 0°C for 2 h. Compound 5 (0.89 g, 1 mmol) in 25 mL of 1,2-dichloroethane was slowly added dropwise to the reaction mixture. The reaction was continued at 0°C for 1 h, then the temperature was raised to 90°C for 12 h. After completion of the reaction, the mixture was cooled to room temperature and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4, filtered, and the organic solvent removed to obtain the crude product. Column chromatography using a mixture of petroleum ether and dichloromethane (V / V = 1:2) as the eluent afforded compound 6 (0.83 g, yellow solid, yield = 87.7%).

[0054] (5) Compound ABTP-S

[0055] Under a nitrogen atmosphere, compound 6 (300 mg, 0.317 mmol), compound 7 (300 mg, 1.5 mmol), and 30 mL of chloroform were added sequentially to a 100 mL two-necked flask. 1 mL of pyridine was added, and the mixture was stirred at 65°C for 12 h. After the reaction solution was cooled to room temperature, it was precipitated with methanol and filtered to collect the precipitate. The crude product was separated by column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 1:1) as the eluent to obtain ABTP-S (353.5 mg as a black solid, yield = 85.2%).

[0056] Example 2

[0057]

[0058] (1) Raw materials or intermediate reactants

[0059] Triphenylphosphine (PPh3), tetrakistriphenylphosphine palladium (Pd(PPh3)4), 5-(bromomethyl)heptane, potassium carbonate (K2CO3), potassium iodide (KI), pyridine, N,N-dimethylformamide (DMF), 1,2-dichloroethane, tetrahydrofuran (THF), toluene, 1,2-dichlorobenzene, and chloroform were purchased from companies such as Anage, J&K, and Suzhou Nakai.

[0060] (2) The preparation of compound 4, compound 5 and compound 6 was the same as that of ABTP-S.

[0061] (3) Compound ABTP-SCl

[0062] Under a nitrogen atmosphere, compound 6 (300 mg, 0.317 mmol), compound 8 (350 mg, 1.5 mmol), and 30 mL of chloroform were added sequentially to a 100 mL two-necked flask. 1 mL of pyridine was added, and the mixture was stirred at 65°C for 12 h. After the reaction solution was cooled to room temperature, it was precipitated with methanol and filtered to collect the precipitate. The crude product was separated by column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 1:1) as the eluent to obtain ABTP-SCl (384.6 mg of a black solid, yield = 83.2%).

[0063] Example 3

[0064]

[0065] (1) Raw materials or intermediate reactants

[0066] Triphenylphosphine (PPh3), tetrakistriphenylphosphine palladium (Pd(PPh3)4), 5-(bromomethyl)heptane, potassium carbonate (K2CO3), potassium iodide (KI), pyridine, N,N-dimethylformamide (DMF), 1,2-dichloroethane, tetrahydrofuran (THF), toluene, 1,2-dichlorobenzene, and chloroform were purchased from companies such as Anage, J&K, and Suzhou Nakai.

[0067] (2) The preparation of compound 4, compound 5 and compound 6 was the same as that of ABTP-S.

[0068] (3) Compound ABTP-4Cl

[0069] Under a nitrogen atmosphere, compound 6 (300 mg, 0.317 mmol), compound 9 (423 mg, 1.5 mmol), and 30 mL of chloroform were added sequentially to a 100 mL two-necked flask. 1 mL of pyridine was added, and the mixture was stirred at 65°C for 12 h. After the reaction solution was cooled to room temperature, it was precipitated with methanol and filtered to collect the precipitate. The crude product was separated by column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 2:1) as the eluent to obtain ABTP-4Cl (379.4 mg black solid, yield = 81.2%).

[0070] Example 4

[0071]

[0072] (1) Raw materials or intermediate reactants

[0073] Triphenylphosphine (PPh3), tetrakistriphenylphosphine palladium (Pd(PPh3)4), 5-(bromomethyl)heptane, potassium carbonate (K2CO3), potassium iodide (KI), pyridine, N,N-dimethylformamide (DMF), 1,2-dichloroethane, tetrahydrofuran (THF), toluene, 1,2-dichlorobenzene, and chloroform were purchased from companies such as Anage, J&K, and Suzhou Nakai.

[0074] (2) The preparation of compound 4, compound 5 and compound 6 was the same as that of ABTP-S.

[0075] (3) Compound ABTP-4F

[0076] Under a nitrogen atmosphere, compound 6 (300 mg, 0.317 mmol), compound 10 (327 mg, 1.5 mmol), and 30 mL of chloroform were added sequentially to a 100 mL two-necked flask. 1 mL of pyridine was added, and the mixture was stirred at 65°C for 12 h. After the reaction solution was cooled to room temperature, it was precipitated with methanol and filtered to collect the precipitate. The crude product was separated by column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 2:1) as the eluent to obtain ABTP-4F (352.4 mg black solid, yield = 82.6%).

[0077] Example 5

[0078]

[0079] (1) Raw materials or intermediate reactants

[0080] Triphenylphosphine (PPh3), tetrakistriphenylphosphine palladium (Pd(PPh3)4), 5-(bromomethyl)heptane, potassium carbonate (K2CO3), potassium iodide (KI), pyridine, N,N-dimethylformamide (DMF), 1,2-dichloroethane, tetrahydrofuran (THF), toluene, 1,2-dichlorobenzene, and chloroform were purchased from companies such as Anage, J&K, and Suzhou Nakai.

[0081] (2) Preparation of Compound 12

[0082] Compound 11 (4,7-dibromo-2-(2-ethylhexyl)-5,6-dinitro-2H-benzo[D][1,2,3]triazole) (4.77 g, 10 mmol), compound 2 (6.02 g, 12 mmol), compound 3 (7.03 g, 12 mmol) and Pd(PPh3)4 (346.2 mg, 0.3 mmol) were added to a toluene (60 mL) solution under nitrogen. The reaction mixture was heated to reflux and stirred for 15 h. After the reaction solution was cooled to room temperature, the reaction was quenched with water and extracted with dichloromethane. The organic phase was concentrated under reduced pressure to obtain a crude product, which was further purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 2:1) as eluent to obtain compound 12 (2.17 g of red solid, yield = 26.3%).

[0083] (3) Synthesis of Compound 13

[0084] Under a nitrogen atmosphere, compound 12 (1.65 g, 2 mmol) and PPh3 (5.24 g, 20 mmol) were added to 20 mL of o-dichlorobenzene (o-DCB). The reaction system was heated to 160°C and refluxed for 16 h. After completion of the reaction, the mixture was cooled to room temperature. The solvent was removed by distillation under reduced pressure, and the mixture was precipitated with 100 mL of methanol. The crude product was filtered and used directly in the next reaction. The crude product, 5-(bromomethyl)heptane (1.78 g, 10 mmol), KI (0.55 g, 3.33 mmol), and K2CO3 (1.92 g, 12.92 mmol) were added to 50 mL of DMF. The reaction was stirred at 80°C under nitrogen for 24 h. After cooling to room temperature, water was added and the mixture was extracted three times with dichloromethane. The combined organic phases were further washed with water, dried over MgSO4, filtered, and concentrated under reduced pressure. The product was purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V=3:1) as eluent to obtain compound 13 (0.87 g yellow oily liquid, yield=44.3%).

[0085] (4) Synthesis of Compound 14

[0086] Under a nitrogen atmosphere, POCl3 (3.06 g, 20 mmol) was slowly added to ultra-dry DMF (1.1 g, 15 mmol) at 0°C for 2 h. Compound 13 (0.98 g, 1 mmol) in 25 mL of 1,2-dichloroethane was slowly added dropwise to the reaction mixture. The mixture was allowed to react at 0°C for 1 h, then heated to 90°C for 12 h. After completion of the reaction, the system was cooled to room temperature and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4, filtered, and the solvent removed to obtain the crude product. Column chromatography using a mixture of petroleum ether and dichloromethane (V / V = 1:2) as the eluent afforded compound 14 (0.87 g, yellow solid, yield = 83.7%).

[0087] (5) Compound ABNP-S

[0088] Under a nitrogen atmosphere, compound 14 (300 mg, 0.288 mmol), compound 7 (280 mg, 1.4 mmol), and 30 mL of chloroform were added sequentially to a 100 mL two-necked flask. 1 mL of pyridine was added, and the mixture was stirred at 65°C for 12 h. After the reaction solution was cooled to room temperature, it was precipitated with methanol and filtered to collect the precipitate. The crude product was separated by column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 1:1) as eluent to obtain ABNP-S (333.1 mg black solid, yield = 82.3%).

[0089] Example 6

[0090]

[0091] (1) Raw materials or intermediate reactants

[0092] Triphenylphosphine (PPh3), tetrakistriphenylphosphine palladium (Pd(PPh3)4), 5-(bromomethyl)heptane, potassium carbonate (K2CO3), potassium iodide (KI), pyridine, N,N-dimethylformamide (DMF), 1,2-dichloroethane, tetrahydrofuran (THF), toluene, 1,2-dichlorobenzene, and chloroform were purchased from companies such as Anage, J&K, and Suzhou Nakai.

[0093] (2) Preparation of Compound 16

[0094] Compound 15 (4,7-dibromo-5,6-dinitrobenzo[c][1,2,5]selenadiazole) (4.30 g, 10 mmol), compound 2 (6.02 g, 12 mmol), compound 3 (7.03 g, 12 mmol), and Pd(PPh3)4 (346.2 mg, 0.3 mmol) were added to a toluene (60 mL) solution under nitrogen. The reaction mixture was heated to reflux and stirred for 12 h. After the reaction solution was cooled to room temperature, the reaction was quenched with water and extracted with dichloromethane. The organic phase was concentrated under reduced pressure to obtain a crude product, which was further purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 2:1) as the eluent to obtain compound 16 (2.14 g as a red solid, yield = 27.5%).

[0095] (3) Synthesis of Compound 17

[0096] Under a nitrogen atmosphere, compound 16 (1.56 g, 2 mmol) and PPh3 (5.24 g, 20 mmol) were added to 20 mL of o-dichlorobenzene (o-DCB). The reaction system was heated to 160°C and refluxed for 16 h. After completion of the reaction, the system was cooled to room temperature, the solvent was removed by distillation under reduced pressure, and the mixture was precipitated with 100 mL of methanol. The crude product was filtered and used directly in the next reaction. The crude product, 5-(bromomethyl)heptane (1.78 g, 10 mmol), KI (0.55 g, 3.33 mmol), and K2CO3 (1.92 g, 12.92 mmol) were added to 50 mL of DMF. The reaction was stirred at 80°C under nitrogen for 24 h. After cooling to room temperature, water was added and the mixture was extracted three times with dichloromethane. The combined organic phases were further washed with water, dried over MgSO4, filtered, and concentrated under reduced pressure. The product was purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V=3:1) as eluent to obtain compound 17 (0.94 g yellow oily liquid, yield=50.2%).

[0097] (4) Synthesis of Compound 18

[0098] Under a nitrogen atmosphere, POCl3 (3.06 g, 20 mmol) was slowly added to ultra-dry DMF (1.1 g, 15 mmol) at 0°C for 2 h. Compound 5 (0.94 g, 1 mmol) in 25 mL of 1,2-dichloroethane was slowly added dropwise to the reaction mixture. The reaction was continued at 0°C for 1 h, then the temperature was raised to 90°C for 12 h. After completion of the reaction, the mixture was cooled to room temperature and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4, filtered, and the organic solvent removed to obtain the crude product. Column chromatography using a mixture of petroleum ether and dichloromethane (V / V = 1:2) as the eluent afforded compound 18 (0.84 g yellow solid, yield = 84.6%).

[0099] (5) Compound ABSeP-S

[0100] Under a nitrogen atmosphere, compound 18 (300 mg, 0.302 mmol), compound 7 (300 mg, 1.5 mmol), and 30 mL of chloroform were added sequentially to a 100 mL two-necked flask. 1 mL of pyridine was added, and the mixture was stirred at 65°C for 12 h. After the reaction solution was cooled to room temperature, it was precipitated with methanol and filtered to collect the precipitate. The crude product was separated by column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 1:1) as eluent to obtain ABSeP-S (329.0 mg black solid, yield = 80.2%).

[0101] Example 7

[0102]

[0103] (1) Raw materials or intermediate reactants

[0104] Triphenylphosphine (PPh3), tetrakistriphenylphosphine palladium (Pd(PPh3)4), 5-(bromomethyl)heptane, potassium carbonate (K2CO3), potassium iodide (KI), pyridine, N,N-dimethylformamide (DMF), 1,2-dichloroethane, tetrahydrofuran (THF), toluene, 1,2-dichlorobenzene, and chloroform were purchased from companies such as Anage, J&K, and Suzhou Nakai.

[0105] (2) Preparation of Compound 20

[0106] Compound 19 (5,8-dibromo-6,7-dinitroquinoxaline) (3.76 g, 10 mmol), compound 2 (6.02 g, 12 mmol), compound 3 (7.03 g, 12 mmol), and Pd(PPh3)4 (346.2 mg, 0.3 mmol) were added to a toluene (60 mL) solution under nitrogen. The reaction mixture was heated to reflux and stirred for 12 h. After the reaction solution was cooled to room temperature, the reaction was quenched with water and extracted with dichloromethane. The organic phase was concentrated under reduced pressure to obtain a crude product, which was further purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 3:2) as eluent to obtain compound 20 (1.62 g of a red solid, yield = 22.4%).

[0107] (3) Synthesis of Compound 21

[0108] Under a nitrogen atmosphere, compound 20 (1.45 g, 2 mmol) and PPh3 (5.24 g, 20 mmol) were added to 20 mL of o-dichlorobenzene (o-DCB). The reaction system was heated to 160°C and refluxed for 16 h. After completion of the reaction, the mixture was cooled to room temperature, the solvent was removed by distillation under reduced pressure, and the mixture was precipitated with 100 mL of methanol. The crude product was filtered and used directly in the next reaction. The crude product, 5-(bromomethyl)heptane (1.78 g, 10 mmol), KI (0.55 g, 3.33 mmol), and K2CO3 (1.92 g, 12.92 mmol) were added to 50 mL of DMF. The reaction was stirred at 80°C under nitrogen for 24 h. After cooling to room temperature, water was added and the mixture was extracted three times with dichloromethane. The combined organic phases were further washed with water, dried over MgSO4, filtered, and concentrated under reduced pressure. The product was purified by silica gel column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 4:1) as eluent to obtain compound 21 (0.85 g as a yellow oily liquid, yield = 48.3%).

[0109] (4) Synthesis of Compound 22

[0110] Under a nitrogen atmosphere, POCl3 (3.06 g, 20 mmol) was slowly added to ultra-dry DMF (1.1 g, 15 mmol) at 0°C for 2 h. Compound 21 (0.88 g, 1 mmol) in 25 mL of 1,2-dichloroethane was slowly added dropwise to the reaction mixture. The reaction was continued at 0°C for 1 h, then the temperature was raised to 90°C for 12 h. After completion of the reaction, the mixture was cooled to room temperature and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4, filtered, and the organic solvent removed to obtain a crude product. Column chromatography using a mixture of petroleum ether and dichloromethane (V / V = 1:1) as the eluent afforded compound 22 (0.78 g, yellow solid, yield = 83.5%).

[0111] (5) Compound ABQP-S

[0112] Under a nitrogen atmosphere, compound 22 (300 mg, 0.319 mmol), compound 7 (320 mg, 1.6 mmol), and 30 mL of chloroform were added sequentially to a 100 mL two-necked flask. 1 mL of pyridine was added, and the mixture was stirred at 65°C for 12 h. After the reaction solution was cooled to room temperature, it was precipitated with methanol and filtered to collect the precipitate. The crude product was separated by column chromatography using a mixed solvent of petroleum ether and dichloromethane (V / V = 1:1) as eluent to obtain ABQP-S (340 mg black solid, yield = 81.7%).

[0113] Figure 1 This is the UV-visible absorption spectrum of the compound ABTP-S film. In the range of 300-900 nm, the absorption peak of the compound ABTP-S is located at 705 nm, the optical absorption edge is 740 nm, and the corresponding optical band gap is 1.68 eV.

[0114] Figure 2 This is the UV-visible absorption spectrum of the compound ABTP-SCl film. In the range of 300-900 nm, the absorption peak of the compound ABTP-SCl is located at 713 nm, the optical absorption edge is 750 nm, and the corresponding optical band gap is 1.65 eV.

[0115] Figure 3 This is the UV-visible absorption spectrum of the compound ABTP-4Cl film. In the range of 300-900 nm, the absorption peak of the compound ABTP-4Cl is located at 686 nm, the optical absorption edge is 735 nm, and the corresponding optical band gap is 1.69 eV.

[0116] Figure 4This is the UV-visible absorption spectrum of the compound ABTP-4F film. In the range of 300-900 nm, the absorption peak of the compound ABTP-4F is located at 696 nm, the optical absorption edge is 725 nm, and the corresponding optical band gap is 1.71 eV.

[0117] Figure 5 This is the UV-visible absorption spectrum of the compound ABNP-S film. In the range of 300-900 nm, the absorption peak of the compound ABNP-S is located at 715 nm, the optical absorption edge is 765 nm, and the corresponding optical band gap is 1.62 eV.

[0118] Figure 6 This is the UV-visible absorption spectrum of the compound ABSeP-S film. In the range of 300-900 nm, the absorption peak of the compound ABSeP-S is located at 717 nm, the optical absorption edge is 750 nm, and the corresponding optical band gap is 1.65 eV.

[0119] Figure 7 This is the UV-visible absorption spectrum of the compound ABQP-S film. In the range of 300-900 nm, the absorption peak of the compound ABQP-S is located at 697 nm, the optical absorption edge is 730 nm, and the corresponding optical band gap is 1.70 eV.

[0120] Figure 8 JV curves for organic solar cell devices based on PBDB-T:ABTP-S and PBDB-T:ABNP-S are shown. The PBDB-T:ABTP-S device exhibits an open-circuit voltage of 1.10 V, a short-circuit current of 16.95 mA / cm², and a fill factor of 78.03%. Ultimately, it achieves an efficiency of 14.55%. The PBDB-T:ABNP-S device exhibits an open-circuit voltage of 1.08 V, a short-circuit current of 17.24 mA / cm², and a fill factor of 77.28%. Ultimately, it achieves an efficiency of 14.39%.

[0121] Figure 9 The following are the EQE curves for organic solar cell devices based on PBDB-T:ABTP-S and PBDB-T:ABNP-S. Both devices demonstrate excellent photoresponse within the 300-740nm spectral range. The PBDB-T:ABTP-S device exhibits an EQE exceeding 70% within the 400-690nm range, while the PBDB-T:ABNP-S device exhibits an EQE exceeding 70% within the 400-700nm range. Therefore, both devices demonstrate excellent performance.

[0122] Figure 10The J–V characteristic curves of stacked cells prepared with PM6:Y6-O / BZ4F-O-1 and PBDB-T:ABTP-S / ABNP-S as front cells and PTTzF:Y6:

[70] PCBM as back cells were presented. The PM6:Y6-O device exhibited an open circuit voltage of 1.75 V, a short circuit current of 14.30 mA / cm², and a fill factor of 77.25%. Finally, an efficiency of 19.33% was achieved. The PM6:BZ4F-O-1 device exhibited an open circuit voltage of 1.74 V, a short circuit current of 14.10 mA / cm², and a fill factor of 74.89%. Finally, an efficiency of 18.37% was achieved. The PBDB-T:ABTP-S device exhibited an open circuit voltage of 1.92 V, a short circuit current of 13.86 mA / cm², and a fill factor of 78.12%. Finally, an efficiency of 20.79% was achieved. The PBDB-T:ABNP-S device exhibited an open-circuit voltage of 1.90 V and a short-circuit current of 13.85 mA / cm², along with a fill factor of 77.00%. Ultimately, an efficiency of 20.26% was achieved.

[0123] Figure 11 J–V curves of single-junction cells with PM6:Y6-O / BZ4F-O-1 and PBDB-T:ABTP-S / ABNP-S as active layers under indoor lighting conditions are shown. The PM6:Y6-O device exhibited an open-circuit voltage of 0.86 V, a short-circuit current of 126.32 μA / cm², and a fill factor of 80.02%. Ultimately, an efficiency of 30.61% was achieved. The PM6:BZ4F-O-1 device exhibited an open-circuit voltage of 0.79 V, a short-circuit current of 123.87 μA / cm², and a fill factor of 75.37%. Ultimately, an efficiency of 25.97% was achieved. The PBDB-T:ABTP-S device exhibited an open-circuit voltage of 0.97 V, a short-circuit current of 119.76 μA / cm², and a fill factor of 79.26%. Ultimately, an efficiency of 32.42% was achieved. The PBDB-T:ABNP-S device exhibited an open-circuit voltage of 0.95 V and a short-circuit current of 122.39 μA / cm², along with a fill factor of 74.28%. Ultimately, an efficiency of 30.41% was achieved.

[0124] Example 8

[0125] The materials obtained in Examples 1 and 5 (ABTP-S, ABNP-S) are used as examples to illustrate the application of the asymmetric medium-bandgap fused-ring acceptor materials of the present invention in organic solar cells and indoor photovoltaic devices, but the present invention is not limited to the examples given.

[0126] The specific preparation process of the device is as follows:

[0127] (1) Single junction device preparation

[0128] The device was fabricated by spin-coating a 40nm thick hole-transport layer (PEDOT:PSS) onto ITO glass, followed by a 100nm thick photoactive layer of a blend of donor and acceptor materials. A 5nm thick layer of PFN-Br was then applied as the cathode interface layer, followed by a 100nm thick Ag electrode. The device was then tested under both a standard solar simulator and an indoor light simulator.

[0129] (2) Preparation of stacked devices

[0130] The stacked device uses the following structure: ITO / PEDOT:PSS / front-cell active layer / connector layer / back-cell active layer / PDINO / Ag. The front-cell active layer preparation process is the same as for the single-cell device. The connection layer (ZnO / PEDOT:PSS / PMA) is prepared by spin-coating a ZnO nanoparticle layer (approximately 20 nm) on the front-cell active layer. PEDOT:PSS (diluted in deionized water at a ratio of 1:2.5) is then spin-coated on the ZnO layer (approximately 15 nm). The substrate is thermally annealed at 100°C for 5 minutes, and then approximately 5 nm of phosphomolybdic acid (PMA) is spin-coated on the PEDOT:PSS. The back-cell active layer preparation method is the same as for the single-cell device. After the front-cell, connection layer, and back-cell active layer are prepared, the electron transport layer, PDINO, is spin-coated (3000 rpm). Finally, a Ag electrode is deposited by high vacuum evaporation to produce the stacked device.

[0131] Table 1. Device performance parameters of ITO / PEDOT:PSS / PBDB-T:Acceptor / PFN-Br / Ag (AM1.5G)

[0132]

[0133] Table 2. Performance parameters of stacked solar cells fabricated with ITO / PEDOT:PSS / PBDB-T:Acceptor / PFN-Br / Ag as the front cell and ITO / PEDOT:PSS / PTTzF:Y6:

[70] PCBM / PDINO / Ag as the back cell (AM1.5G)

[0134]

[0135] Table 3. Performance parameters of tandem solar cells (AM1.5G) using ITO / PEDOT:PSS / PBDB-T:ABTP-S / PFN-Br / Ag as the front cell, PTTzF:Y6:

[70] PCBM, PTB7-Th:O6T-4F, and PM6:BTP-eC9 as the back cells, and a device structure of ITO / PEDOT:PSS / active layer / PDINO / Ag.

[0136]

[0137] Table 4. Performance parameters of ITO / PEDOT:PSS / PBDB-T:Acceptor / PFN-Br / Ag devices under indoor lighting (1000 Lux, input power (P in ) is 284 microwatts per square centimeter)

[0138]

[0139] As shown in Table 1, the single-junction devices prepared with PBDB-T as the donor and ABTP-S and ABNP-S as the acceptors all exhibited an open circuit voltage close to 1.1 V, a high fill factor, and good device efficiency. The corresponding JV curves and EQE curves are shown in the attached Figure 8 and 9 , which shows that this type of material has great application potential. The front cells were prepared with PBDB-T:ABTP-S and PBDB-T:ABNP-S as the active layer, and the back cells were prepared with PTTzF:Y6:

[70] PCBM as the active layer. The performance of the tandem solar cell device is shown in Table 2. Since the medium-bandgap material and the narrow-bandgap material have good complementary absorption, and the front cell has excellent photovoltaic performance, the efficiency of the above-mentioned tandem solar cell devices exceeds 20%. In particular, the efficiency of the tandem cell device based on ABTP-S reached 20.79%. In addition, in order to study the universality of medium-bandgap materials in tandem cells, the front cell with PBDB-T:ABTP-S as the active layer was matched with different back cells, and the device data are shown in Table 3. It can be found that the precell based on the medium-bandgap acceptor not only matches well with PTTzF:Y6:

[70] PCBM, but also achieves tandem device efficiencies of 17.54% and 20.21% with PTB7-Th:O6T-4F and PM6:BTP-eC9, respectively. These results demonstrate that the medium-bandgap acceptor material of the present invention not only exhibits good device efficiency in single-junction devices but also exhibits excellent performance and universality in tandem cell devices. This suggests that asymmetric medium-bandgap acceptors are a highly promising class of precell materials.

[0140] The absorption spectra of the medium-bandgap acceptors ABTP-S and ABNP-S closely match the emission spectra of indoor light sources. Therefore, single-junction devices based on PBDB-T:ABTP-S and PBDB-T:ABNP-S were prepared. The device performance under indoor lighting conditions is shown in Table 4. The ABTP-S and ABNP-S-based devices exhibited excellent device efficiencies of 32.42% and 31.63%, respectively. These results demonstrate the promising application of the medium-bandgap acceptors of this invention in the field of indoor photovoltaics.

[0141] Comparative Example

[0142]

[0143] In order to further illustrate that the asymmetric medium band gap receptor involved in the present invention has unique advantages in OSCs, taking the embodiments ABTP-S and ABNP-S involved in the present invention as examples, receptors with similar structures and symmetrical structures are selected for comparison (Comparative Example 1 and Comparative Example 2). Both Y6-O and BZ4F-O-1 contain alkoxy side chains and strong electron-withdrawing end groups. The difference is that Y6-O is a symmetrical seven-ring receptor with benzothiadiazole as the core unit, which forms a sharp contrast with the ABTP-S molecule in terms of molecular symmetry. BZ4F-O-1 is a symmetrical five-ring receptor with benzotriazole as the core, which forms a sharp contrast with the ABNP-S molecule in terms of molecular symmetry. Under the same conditions, single-junction devices and stacked devices were prepared using the above four materials as receptors, and the single-junction devices were tested under standard sunlight and indoor light environments respectively. The relevant device data are shown in Tables 5-7.

[0144] Table 5. Device parameters of single-junction organic solar cells based on PM6:Y6-O / BZ4F-O-1 and PBDB-T:ABTP-S / ABNP-S under standard sunlight conditions (AM1.5G)

[0145]

[0146] It can be found from the single junction device data (Table 5) that compared with Comparative Examples 1 and 2, due to the use of weak electron-withdrawing end groups in ABTP-S and ABNP-S, they exhibit better medium band gap absorption and high LUMO energy levels, so the open circuit voltage of the ABTP-S and ABNP-S devices is also significantly improved. Not only that, the presence of the asymmetric structure can promote charge transfer and reduce material crystallization. The fill factor of the ABTP-S and ABNP-S devices is improved. Finally, the devices based on ABTP-S and ABNP-S exhibit high open circuit voltage and good device performance.

[0147] Table 6. Device parameters of tandem organic solar cells prepared using PM6:Y6-O / BZ4F-O-1 and PBDB-T:ABTP-S / ABNP-S as front cells and PTTzF:Y6:

[70] PCBM as back cells under standard sunlight conditions (AM1.5G)

[0148]

[0149] Front cells were prepared using ABTP-S, ABNP-S and two comparative materials as acceptors, and back cells were prepared using PTTzF:Y6:

[70] PCBM as the active layer to obtain stacked solar cell devices. The device performance is shown in Table 6. Since the single-junction device of PBDB-T:ABTP-S / ABNP-S has a higher open circuit voltage than the PM6:Y6-O / BZ4F-O-1 device, the open circuit voltage of the stacked device based on ABTP-S and ABNP-S is significantly higher than that of the two comparative materials. Since the fill factor of the device of comparative example 2 is low, which limits the fill factor of the stacked device, the device efficiency is only 18.37%. Thanks to the high open circuit voltage and better device performance of the PBDB-T:ABTP-S / ABNP-S device, the stacked device based on ABTP-S and ABNP-S achieved device efficiencies of 20.79% and 20.26%, respectively, which are higher than the two comparative examples. This further illustrates that the medium-bandgap asymmetric acceptor reported in the present invention is a good front cell material.

[0150] Table 7. Device parameters of single-junction devices based on PM6:Y6-O / BZ4F-O-1 and PBDB-T:ABTP-S / ABNP-S under indoor light conditions (1000 Lux, input power (P in ) is 284 microwatts per square centimeter).

[0151]

[0152] Table 7 shows the device performance of single-junction devices based on the four aforementioned acceptor materials under room lighting conditions. Due to the high LUMO energy levels of ABTP-S and ABNP-S, the PBDB-T:ABTP-S / ABNP-S device exhibits a higher open-circuit voltage than the PM6:Y6-O / BZ4F-O-1 device. Furthermore, the asymmetric structure facilitates charge transfer and reduces material crystallization, resulting in improved short-circuit current and fill factor. Ultimately, the PBDB-T:ABTP-S device achieved the best device efficiency of 32.42% under room lighting.

[0153] The above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention and are not intended to limit the embodiments of the present invention. Those skilled in the art will appreciate that other variations or modifications may be made based on the above description. It is not necessary and impossible to enumerate all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention are intended to be included within the scope of protection of the claims of the present invention.

Claims

1. A class of asymmetric medium-band-gap fused-ring receptor materials, the general structure of which is shown in Formula I: in: In the structural formula, R1, R2, and R3 are independently selected from linear, branched, or alkyl-substituted aryl side chains having 1 to 40 carbon atoms; Weak A units are selected from any one of the following structural formulas: in: The dotted line in the Weak A structure indicates the connection site with the Weak A unit; the Ar1 unit is selected from any one of the following structures: Wherein, R4 in the Ar1 structural formula is independently selected from H, a linear or branched alkyl group having 1 to 20 carbon atoms, and the dotted line in the Ar1 structural formula represents the connection site with other units.

2. The method for preparing the asymmetric medium band gap fused ring receptor material according to claim 1, comprising the following steps: Its synthetic route is as follows: In the structural formula, R1, R2, and R3 are independently selected from linear, branched, or alkyl-substituted aryl side chains having 1 to 40 carbon atoms.

3. The preparation method according to claim 2, characterized in that The steps include: (1) Compound A, Compound B, and Compound C are added to 80-100 mL of toluene, and then a catalyst, tetrakis(triphenylphosphine)palladium, is added; and a Stille coupling reaction is performed to obtain Compound D; (2) Under nitrogen protection, compound D and triphenylphosphine are added to o-dichlorobenzene, and the system is heated to react to obtain compound E; (3) Under nitrogen protection, compound E, alkyl halide R3Br, potassium carbonate and potassium iodide are added to N,N-dimethylformamide to react to obtain compound F; (4) This reaction is a Vilsmeier-Haack reaction. Compound F is dissolved in 1,2-dichloroethane and then added dropwise to the formylation reagent phosphorus oxychloride at -10 to 0°C. After reacting at low temperature for 1 to 2 hours, the system is heated to 80 to 100°C and reacted for 8 to 12 hours to obtain compound G. (5) This reaction is a Knoevenagel condensation reaction. Under nitrogen protection, compound G is reacted with Weak A and pyridine to obtain compound H.

4. The preparation method according to claim 3, characterized in that In step (1), the reaction conditions of the Stille coupling reaction are: reaction at 80-90° C. for 10-12 h.

5. The preparation method according to claim 3, characterized in that: In step (2), the reaction is carried out at 160-180° C. for 16-18 hours.

6. The preparation method according to claim 3, characterized in that: In step (3), the reaction is carried out at 80-85° C. for 10-12 hours.

7. The preparation method according to claim 3, characterized in that: In step (4), the molar ratio of compound F to phosphorus oxychloride is 1:10 to 1:

30.

8. The preparation method according to claim 3, characterized in that: In step (5), the reaction is carried out at 60° C. for 5 to 8 hours.

9. The asymmetric medium-bandgap fused-ring acceptor material according to claim 1 is used in the fields of tandem organic solar cells and indoor photovoltaic devices.

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