A quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells, its preparation method and application

Abstract

A quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells, its preparation method, and its application are disclosed. The method includes step 1: reacting compound 1 through two heating reactions, hydrolysis, decarboxylation, strong base tert-butyllithium hydrogenation with tin oxide, and Stille coupling to obtain the final reaction product, compound 6; step 2: reacting compound 6, anhydrous o-dichlorobenzene, triethyl phosphite, 2-butyliodooctane, potassium carbonate, and anhydrous N,N-dimethylformamide to obtain BTOR; step 3: preparing QxO1 in a two-necked flask; step 4: reacting QxO1, anhydrous 1,2-dichloroethane, Vilsmerier reagent, sodium acetate aqueous solution, and dichloromethane to obtain QxO1-CHO; step 5: adding QxO1-CHO, fluorocyanoindanone, and anhydrous trichloromethane to react to obtain QxO-1. QxO-1 is applied to the fabrication of solar cell devices. This invention provides a simple two-step method to obtain thiophene[3,2-b]thiophene units with alkoxy chains substituted at the 3-position without post-processing, greatly reducing the reaction steps and corresponding post-processing purification.

Description

Technical Field

[0001] This invention belongs to the field of solar cell materials technology, specifically relating to a quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells, its preparation method, and its application. Background Technology

[0002] Organic photovoltaics (OPVs) offer advantages such as low cost, flexibility, and solution processing, making them promising for various applications including wearable devices and building-integrated photovoltaics (BIPV). They can complement traditional silicon-based photovoltaic devices effectively. With the rapid development of the Internet of Things (IoT), the market demand for low-energy indoor optoelectronic devices is increasing, such as sensors, Bluetooth devices, and other wearable or smart electronic devices. Traditional silicon-based solar cells have an absorption range that doesn't match indoor light (such as fluorescent lamps and LEDs), and their rigidity and opacity limit their deployment in the indoor photovoltaic field. On the other hand, the numerous advantages of organic photovoltaics (OPVs) allow for good compatibility with indoor optoelectronic devices. Thanks to continuous innovation in active layer materials, especially non-fullerene acceptor materials, device efficiencies have reached 25%-30% under indoor LED illumination (200-1000 lux, 3000K). Indoor organic photovoltaics (IOPV) are demonstrating tremendous growth momentum and broad application prospects.

[0003] Most indoor lighting resources have a light response range concentrated in the visible light range of 400-750nm. Besides indoor light sources whose spectral range is concentrated in the visible light range, their illuminance is typically less than 1mW cm⁻¹. -2 Generally, it is more than a standard ray of sunlight (AM 1.5G, 100mW cm⁻¹). -2 The light intensity is 100-1000 times lower, which leads to a significant reduction in the carrier density of indoor photovoltaic devices and easily results in substantial energy loss (E). loss The recombination effect of trap-assisted charges is a significant concern. Therefore, designing active layer materials that simultaneously possess a spectral response range matching indoor light, low device energy loss, and reduced trap-assisted charge recombination is crucial for improving the efficiency of indoor photovoltaic devices and promoting their large-scale application.

[0004] Currently, the absorption range of most donor materials can meet the requirements for indoor light absorption (optical band gap E). g optWhile wide-bandgap acceptors (~2 eV) are widely used in OPV, suitable wide-bandgap acceptors for high-efficiency indoor photovoltaic (IOPV) devices are relatively scarce. In OPV, the light absorption characteristics of the acceptor material have a decisive influence on the cutoff absorption range of the blend film. Therefore, designing wide-bandgap acceptor materials with suitable absorption ranges is an important strategy for solving the spectral mismatch in OPV systems. Benefiting from the unique electronic structure and molecular packing properties of non-fullerene acceptor (NFA) materials, chemical modification of NFA materials has become a mainstream research direction in the OPV field in recent years, greatly promoting the improvement of photovoltaic device efficiency. However, wide-bandgap acceptor materials with cutoff absorption wavelengths less than 750 nm and low energy loss (E0.05) are still relatively scarce. loss Research on IOPV devices with voltages <0.6V is insufficient. Therefore, due to the mismatch between the active layer absorption spectrum and the indoor LED spectrum, the device's E... loss High leakage current or other factors that limit the efficiency improvement of IOPV devices are the main challenges.

[0005] With innovations in active layer materials, especially non-fullerene acceptor materials, the performance of organic solar cells has achieved continuous breakthroughs, particularly in single-junction photovoltaic devices based on Y6 and its derivative acceptor materials, where efficiencies have exceeded 19%. However, these materials exhibit a relatively red-shifted absorption spectrum (with a cutoff absorption wavelength greater than 900 nm), making them unsuitable for indoor organic photovoltaic applications. Literature review revealed that by modulating the alkyl side chains at both ends of the Y6 material's central core (e.g., the Y6O molecule), a significant blue shift (~100 nm) in the absorption spectrum can be achieved. When the electron-deficient benzothiadiazole (BT) in the Y6 molecule's central core is replaced with a quinoxaline structure with weaker electron-withdrawing ability, the absorption spectrum of the material exhibits a blue shift of ~50 nm compared to the Y6 molecule. Furthermore, the acceptor molecule CH6, employing a fluoroquinoxaline central core, achieves a high open-circuit voltage (V0.875). oc Based on this, the present invention utilizes a synergistic strategy of intermediate core and side chain modulation to achieve a further blue shift in the absorption spectrum of the material, thereby obtaining a wide-bandgap acceptor material that is more compatible with indoor spectra, which has important application value in the field of indoor lighting. Summary of the Invention

[0006] To comprehensively address the aforementioned problems, this invention provides a quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells, its preparation method, and its applications. Studies have shown that introducing an electron-deficient nucleus with relatively weak electron-withdrawing ability into the intermediate core of the popular small-molecule acceptor Y6 molecule causes a blue shift in the material's absorption spectrum. Furthermore, replacing the alkyl side chains at both ends of the intermediate core with alkoxy side chains results in a blue shift of nearly 100 nm. Currently, well-developed Y6 and its derivative acceptor materials exhibit excellent three-dimensional molecular packing, low exciton dissociation driving force, and low energy loss. Therefore, while fully utilizing the excellent photoelectric properties of these materials, achieving a blue shift in the absorption spectrum to match indoor spectra is a crucial design strategy for constructing highly efficient wide-bandgap acceptors.

[0007] Based on this, this invention utilizes a synergistic regulation strategy involving the intermediate core, side chains, and terminals to design and construct a series of wide-bandgap small molecule receptors with tightly ordered molecular structures using conventional synthetic techniques. Simultaneously, by matching suitable donor materials and precisely controlling the morphology of the active layer, it is expected to reduce E... loss And achieve high efficiency in IOPV.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells, with the molecular formula:

[0010]

[0011] A method for preparing a quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells includes:

[0012] Step 1: Compound 1 is subjected to two heating reactions, hydrolysis reaction, decarboxylation reaction, strong base tert-butyllithium dehydrogenation to form tin oxide and Stille coupling reaction to obtain the final reaction product, namely compound 6;

[0013] Step 2: Compound 6, anhydrous o-dichlorobenzene, triethyl phosphite, 2-butyliodooctane, potassium carbonate, and anhydrous N,N-dimethylformamide were reacted and further processed to obtain BTOR;

[0014] Step 3: Add compound BTOR and lithium aluminum hydride in THF solution to a two-necked flask to react and obtain crude product. Then, add dichlorodicyanobenzoquinone and anhydrous chloroform to the crude product and react for 5 minutes. Then add 4,5-difluoro-1,2-phenylenediamine to prepare QxO1.

[0015] Step 4: Combine QxO1 prepared in Step 3, anhydrous 1,2-dichloroethane, Vilsmerier reagent, sodium acetate aqueous solution, and dichloromethane to prepare QxO1-CHO;

[0016] Step 5: Add the intermediate QxO1-CHO prepared in Step 4, fluorocyanoindanone, and anhydrous chloroform to react and prepare QxO-1, namely the quinoxaline fused ring wide bandgap acceptor material.

[0017] Preferably, step 2 includes:

[0018] Step 2.1: Add compound 6 prepared in step 1 to a 100 mL single-necked flask, and replace the gas 3 times under a nitrogen atmosphere;

[0019] Step 2.2: Continue adding anhydrous o-dichlorobenzene and triethyl phosphite, heat the mixture at 160°C for 12 hours, then distill off o-dichlorobenzene and excess triethyl phosphite under reduced pressure. Add 2-butyliodooctane and potassium carbonate, purge the gas three times under a nitrogen atmosphere, add 15 mL of anhydrous N,N-dimethylformamide under nitrogen atmosphere, and heat the mixture at 100°C for 12 hours.

[0020] Step 2.3: The reaction progress was monitored by TLC. The reaction was stopped when the starting material disappeared. The organic phase was extracted three times with ethyl acetate, dried with anhydrous magnesium sulfate for 2 hours, and the organic phase was removed under reduced pressure. At the same time, hexane was used as the eluent. The orange-yellow transparent oily product BTOR was obtained by layer chromatography.

[0021] Preferably, step 3 includes:

[0022] Step 3.1: Add compound BTOR to a two-necked flask, add anhydrous THF under a nitrogen atmosphere, and then add a THF solution of lithium aluminum hydride dropwise using a constant pressure dropping funnel under an ice bath. After the addition is complete, remove the ice bath and reflux the reaction at 65°C for 4 hours.

[0023] Step 3.2: Monitor the reaction progress by TLC. Stop the reaction when the starting material disappears. Extract the organic phase three times with ethyl acetate, dry the organic phase with anhydrous magnesium sulfate, remove the organic phase under reduced pressure, and proceed directly to the next reaction without post-treatment.

[0024] Step 3.3: Dichlorodicyanobenzoquinone was added to the crude product from Step 3.2, followed by anhydrous chloroform. After reacting for 5 minutes, 4,5-difluoro-1,2-phenylenediamine was added, and the mixture was stirred at room temperature for 6 hours. The reaction progress was monitored by TLC, and the reaction was stopped when the starting material disappeared. The organic phase was removed under reduced pressure, and hexane and dichloromethane were used as eluents. The brownish-red solid QxO1 was obtained by layer-by-layer chromatography.

[0025] Preferably, step 4 includes:

[0026] Step 4.1: Under nitrogen protection, add intermediate QxO1 to a 250mL two-necked flask, purge the gas three times, add anhydrous 1,2-dichloroethane using a syringe, and add Vilsmerier reagent dropwise to the reaction system under argon protection. Stir the reaction at room temperature for 1h, and then heat the reaction at 85℃ for 12h.

[0027] Step 4.2: Monitor the reaction progress by TLC. Stop the reaction when the starting material disappears. Pour the reaction solution into a saturated sodium acetate aqueous solution, add dichloromethane and extract the reaction solution with distilled water. Dry the organic phase with anhydrous sodium sulfate, filter and remove the solvent under reduced pressure. Column chromatography yields a reddish-black solid QxO1-CHO.

[0028] Preferably, step 5 includes:

[0029] Step 5.1: Add intermediate QxO1-CHO and fluorocyanoindanone to a two-necked flask, purge the gas three times, add anhydrous chloroform, and stir the mixture at room temperature in the dark for 12 hours.

[0030] Step 5.2: The reaction progress was monitored by TLC. The reaction was stopped when the raw materials disappeared. Trichloromethane was added and the reaction solution was extracted with distilled water. The organic phases were combined and dried with anhydrous sodium sulfate for 2 hours. The solution was filtered and the solvent was removed under reduced pressure. The green solid QxO-1, i.e., quinoxaline fused ring wide band gap acceptor material, was obtained by column chromatography using a mixture of trichloromethane and PE as the eluent.

[0031] Preferably, compound 6 is:

[0032] An application of a quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells, applied to the fabrication of organic solar cells.

[0033] Compared with the prior art, the beneficial effects of the present invention are:

[0034] 1. In terms of raw material synthesis, this invention can obtain thiophene[3,2-b]thiophene units with alkoxy chain substitution at position 3 through a simple two-step method without post-processing. Compared with the multi-step alkyl chain conversion reaction of the prior art, this invention greatly reduces the reaction steps and corresponding post-processing purification.

[0035] 2. In terms of material design strategy, compared with existing literature which only regulates through the intermediate core or side chain, this invention can achieve a significant blue shift in the absorption spectrum of the material by synergistically utilizing the intermediate core and side chain regulation strategy, thereby obtaining a wide bandgap acceptor material suitable for indoor photovoltaics.

[0036] 3. Indoor photovoltaic devices were fabricated based on wide bandgap acceptor materials. During device testing, a 2700K LED light source (500 lux) simulator was used, and a PCE of 22.26% was obtained without any post-processing. This further demonstrates that the wide bandgap material prepared in this invention has excellent performance when applied to indoor photoorganic photovoltaic devices. Attached Figure Description

[0037] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof.

[0038] In the attached diagram:

[0039] Figure 1 This is a flowchart illustrating the material synthesis process of the present invention.

[0040] Figure 2 This is a schematic diagram of the material absorption spectrum of the present invention;

[0041] Figure 3 This is a standard JV test curve under sunlight irradiation according to the present invention;

[0042] Figure 4 This is the JV test curve under indoor LED light illumination according to the present invention;

[0043] Figure 5 This is a flowchart of the method of the present invention. Detailed Implementation

[0044] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0045] A quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells, with the molecular formula:

[0046]

[0047] A method for preparing a quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells includes:

[0048] Step 1: Compound 1 is subjected to two heating reactions, a hydrolysis reaction, a decarboxylation reaction, a strong base tert-butyllithium hydrogenation to form a tin compound, and a Stille coupling reaction to obtain the final reaction product, compound 6. Specifically:

[0049] Step 1.1: Add compound 1 to a 250ml two-necked flask (5 g, 19.21 mmol), anhydrous sodium methoxide (1.56 g, 28.82 mmol), and the mixture was purged three times under a nitrogen atmosphere. 100 mL of anhydrous methanol was added, and the mixture was heated to reflux at 70 °C for 12 hours. The organic phase was removed under reduced pressure. 1-Bromodecane (4.67 g, 21.131 mmol) and 30 mL of anhydrous N,N-dimethylformamide were added under an argon atmosphere, and the mixture was purged three times under a nitrogen atmosphere. The mixture was heated to 80 °C for 12 hours. The reaction was detected by thin-layer chromatography (TLC). The reaction was stopped when the starting material disappeared. The organic phase was extracted three times with ethyl acetate (150 mL × 3), and dried over anhydrous magnesium sulfate for 2 hours. A colorless, transparent oily compound 2 was obtained by layer-by-layer chromatography using dichloromethane:n-hexane (1:3) as the eluent. Yield: 3.54g, yield: 52%;

[0050] 1 H NMR (300MHz, CDCl3) δ7.57(d,J=5.3Hz,1H),7.22(d,J=5.3Hz,1H),4.40(t,J=5.6Hz,2H),3.89(s,3H),1.29–1.26(m,16H),0.89–

[0051] 0.88(m, 3H).

[0052] Step 1.2: Add compound 2 to a 100ml two-necked flask. (3 g, 8.46 mmol), lithium hydroxide monohydrate (710 mg, 16.92 mmol), and the mixture was purged three times under a nitrogen atmosphere. 30 mL of anhydrous tetrahydrofuran (THF) and 10 mL of distilled water were added. The reaction mixture was refluxed at 65 °C for 12 h. The organic phase was removed under reduced pressure, and the mixture was neutralized to a weakly acidic state with 15% hydrochloric acid. The organic phase was extracted three times with ethyl acetate (150 mL × 3). The organic phase was dried over anhydrous magnesium sulfate for 2 h, and the organic phase was removed under reduced pressure. The compound was recrystallized from n-hexane.

[0053] 3 2.74g, yield 95%.

[0054] 1 H NMR (400MHz, CDCl3) δ7.64(d,J=5.3Hz,1H),7.29(d,J=1.4Hz,1H),7.28(s,1H),5.33(s ,1H),4.54(d,J=7.5Hz,2H),1.91–1.80(m,2H),1.63–1.26(m,11H),1.03–0.92(m,6H).

[0055] Step 1.3: Add compound 3 to a 100ml two-necked flask. (2.5 g, 7.34 mmol), silver carbonate (81.1 mg, 0.294 mmol), glacial acetic acid (0.34 mL, 0.0587 mmol), and the mixture was purged three times under a nitrogen atmosphere. 15 mL of dimethyl sulfoxide (DMSO) was added. The reaction solution was heated at 130 °C for 12 h. Thin-layer chromatography (TLC) was used to detect the reaction; upon observation of the disappearance of the starting material, the reaction was stopped. The organic phase was extracted three times with ethyl acetate (150 mL × 3), dried over anhydrous magnesium sulfate for 2 h, and the organic phase was removed under reduced pressure using n-hexane as the eluent. Layer-by-layer chromatography yielded a colorless, transparent oily compound 4. Yield: 2g, yield: 92%.

[0056] 1 H NMR(400MHz, CDCl3) δ7.38(dd,J=5.1,1.5Hz,1H),7.19(d,J=5.1Hz,1H),6.29(d,J=1.5Hz,1H),4.0 9(t,J=6.6Hz,2H),1.90–1.81(m,2H),1.52–1.45(m,2H),1.37–1.27(m,14H),0.90(t,J=6.8Hz,3H).

[0057] Step 1.4: Add compound 4 to a 100ml two-necked flask. (2 g, 6.75 mmol) was added, and the gas was purged three times under a nitrogen atmosphere. 20 mL of anhydrous tetrahydrofuran (THF) and 20 mL of anhydrous diethyl ether were added. The reaction mixture was cooled to -65 °C for 30 minutes, and then 5.18 mL of tert-butyllithium reagent (1.3 M) was added dropwise at -65 °C. The reaction was continued at -65 °C for 2 h. Subsequently, 2.01 mL of tributyltin chloride (7.425 mmol) was added at -65 °C, and the reaction was continued at room temperature for 12 h. The reaction was quenched with 4 mL of saturated ammonium chloride aqueous solution, and the organic phase was extracted three times with ethyl acetate (150 mL × 3). The organic phase was dried over anhydrous magnesium sulfate for 2 h, and the organic phase was removed under reduced pressure to give compound 5. Without any prior treatment, it can be directly applied to the next reaction step.

[0058] Step 1.5: Compound 5 The mixture was transferred to a 100 mL two-necked flask, and 4,7-dibromo-5,6-dinitrobenzo[c][1,2,5]thiadiazole (1.037 g, 2.7 mmol), tris(dibenzylacetone)palladium (Pd2(dba)3) (99 mg, 0.108 mmol), and tri-o-methylphosphine (66 mg, 0.216 mmol) were added. The mixture was purged three times under a nitrogen atmosphere, and 20 mL of anhydrous toluene was added. The reaction mixture was heated at 85 °C for 12 h. The reaction was monitored by TLC, and the reaction was stopped when the starting material disappeared. The reaction mixture was poured into 200 mL of anhydrous methanol, yielding a brownish-red solid precipitate. The filter cake was eluented with dichloromethane:n-hexane (1:4), and the brownish-red compound 6 was obtained by layer-by-layer chromatography. Yield: 990g, yield: 45%.

[0059] 1 H NMR (400MHz, CDCl3) δ7.61 (s, 2H), 6.44 (s, 2H), 4.00 (t, J = 4.7Hz, 4H), 1.8 4–1.73(m,2H),1.55–1.41(m,8H),1.40–1.25(m,12H),1.01–0.69(m,16H).

[0060] Step 2: Compound 6 BTOR is obtained by reacting anhydrous o-dichlorobenzene, triethyl phosphite, 2-butyliodooctane, potassium carbonate, and anhydrous N,N-dimethylformamide, followed by further treatment. This includes:

[0061] Step 2.1: Add compound 6 prepared in step 1 to a 100 mL single-necked flask. (900mg, 1.104mmol), gas was replaced 3 times under a nitrogen atmosphere;

[0062] Step 2.2: Continue to add 6 mL of anhydrous o-dichlorobenzene and triethyl phosphite (3.67 g, 22.08 mmol). Heat the reaction at 160 °C for 12 h. Distill off o-dichlorobenzene and excess triethyl phosphite under reduced pressure. Add 2-butyliodooctane (1.64 g, 5.52 mmol) and potassium carbonate (763 mg, 5.52 mmol). Replace the gas three times under a nitrogen atmosphere. Add 15 mL of anhydrous N,N-dimethylformamide (DMF) under nitrogen atmosphere and heat the reaction at 100 °C for 12 h.

[0063] Step 2.3: The reaction progress was monitored by TLC. The reaction was stopped when the starting material disappeared. The organic phase was extracted three times with ethyl acetate (150 mL × 3). The organic phase was dried with anhydrous magnesium sulfate for 2 h. The organic phase was removed under reduced pressure. Hexane was used as the eluent. The colorless and transparent oily product BTOR 744 mg was obtained by layer chromatography with a yield of 62%. The structural formula of BTOR is:

[0064] 1 H NMR (400MHz, CDCl3) δ6.30 (s, 2H), 4.54 (d, J = 7.2Hz, 4H), 4.16 (t, J = 6.5Hz, 4H), 2.08–2.0 1(m,2H),1.93–1.86(m,4H),1.36–1.24(m,34H),0.94–0.81(m,26H),0.70–0.57(m,18H).

[0065] Step 3: Compound BTOR and lithium aluminum hydride in THF solution were added to two two-necked flasks to react and obtain crude products. Then, dichlorodicyanobenzoquinone, anhydrous chloroform, and 4,5-difluoro-1,2-phenylenediamine were added to one two-necked flask to prepare QxO1. This includes:

[0066] Step 3.1: Add compound BTOR (360 mg, 0.331 mmol) to a 100 mL two-necked flask, add anhydrous THF under a nitrogen atmosphere, and then add a THF solution of lithium aluminum hydride (126 mg, 3.31 mmol) dropwise using a constant pressure dropping funnel under ice bath conditions. After the addition is complete, remove the ice bath and reflux the reaction at 65 °C for 4 h.

[0067] Step 3.2: Monitor the reaction progress by TLC. If the starting material disappears, stop the reaction and extract the organic phase three times with ethyl acetate (150 mL × 3). Dry the organic phase with anhydrous magnesium sulfate for 2 hours. Remove the organic phase under reduced pressure. The reaction can be directly added to the next step without post-treatment.

[0068] Step 3.3: Dichlorocyanobenzoquinone (376 mg, 1.655 mmol) was added to the crude product from Step 3.2, followed by 20 mL of anhydrous chloroform. After reacting for 5 minutes, 4,5-difluoro-1,2-phenylenediamine (143 mg, 0.993 mmol) was added, and the mixture was stirred at room temperature for 6 hours. The reaction was monitored by TLC, and upon observation of the disappearance of the starting material, the reaction was stopped. The organic phase was removed under reduced pressure, and a hexane:dichloromethane (1:10) was used as the eluent. Layer-by-layer chromatography yielded a brownish-red solid QxO1 (155 mg, 40% yield), with the following structural formula:

[0069] 1H NMR (300MHz, CDCl3) δ8.13(t,J=9.6Hz,2H),6.31(s,2H),4.60(d,J=7.7Hz,4H),4.18(t,J=6.4Hz,4H ),2.18–2.09(m,2H),1.95–1.88(m,4H),1.37–1.24(m,34H),0.97–0.80(m,30H),0.68–0.57(m,14H).

[0070] Step 4: Combine the QxO1 prepared in Step 3, anhydrous 1,2-dichloroethane, Vilsmerier reagent, sodium acetate aqueous solution, and dichloromethane to prepare QxO1-CHO. This includes:

[0071] Step 4.1: Under nitrogen protection, add intermediate (QxO1) (150 mg) to a 250 mL two-necked flask, purge the gas three times, and add 20 mL of anhydrous 1,2-dichloroethane using a syringe. Under argon protection, add the pre-prepared Vilsmerier reagent dropwise to the reaction system, stir the reaction at room temperature for 1 h, and then heat the reaction at 85 °C for 12 h.

[0072] Step 4.2: The reaction was monitored by TLC. Upon detection of the disappearance of the starting material, the reaction was stopped. The reaction solution was poured into 30 mL of saturated sodium acetate aqueous solution, and 80 mL of dichloromethane was added. The reaction solution was extracted three times with distilled water (100 × 3). The organic phase was dried over anhydrous sodium sulfate for 2 h. The solvent was removed by filtration and reduced pressure. Column chromatography yielded a reddish-black solid QxO1-CHO in 75% yield. The structural formula is:

[0073]

[0074] 1 H NMR (300MHz, CDCl3) δ10.14(s,2H),8.19(t,J=9.5Hz,2H),4.78(t,J=6.4Hz,4H),3.51(d,J =5.3Hz,4H),2.15–2.08(m,2H),2.05–1.97(m,4H),1.37–1.28(m,24H),1.00–0.86(m,54H).

[0075] Step 5: Add the intermediate QxO1-CHO prepared in Step 4, fluorocyanoindanone, and anhydrous chloroform to react and prepare QxO-1. This includes:

[0076] Step 5.1: Add intermediate QxO1-CHO (100mg, 0.082mmol) and fluorocyanoindanone (94mg, 0.409mmol) to a 100mL two-necked flask, purge the gas three times, add 30mL of anhydrous chloroform, and stir the mixture at room temperature in the dark for 12h.

[0077] Step 5.2: TLC was used to monitor the reaction progress. Upon detection of the disappearance of the starting material, the reaction was stopped. 50 mL of chloroform was added, and the reaction solution was extracted three times with distilled water (100 × 3). The organic phases were combined and dried over anhydrous sodium sulfate for 2 hours. The mixture was filtered, and the solvent was removed under reduced pressure. Column chromatography with chloroform (CF) / PE = 1:1 as eluent yielded the green solid QxO-1, i.e., the quinoxaline fused-ring wide-bandgap acceptor material, with a yield of 88%. The structural formula of QxO-1 is:

[0078] 1 H NMR (400MHz, CDCl3) δ9.35(s,2H),8.56(dd,J=10.0,6.5Hz,2H),8.24(t,J=9.2Hz,2H),7.67(t,J=7.7Hz,2H),5.37(t,J=4 .7Hz,4H),4.81(d,4H),2.21–2.16(m,2H),2.06–2.01(m,4H),1.28–1.27(m,18H),1.11–0.88(m,46H),0.76–0.63(m,14H).

[0079] A quinoxaline fused-ring wide-bandgap acceptor material for organic solar cells is applied to the fabrication of organic solar cell devices.

[0080] Experimental verification:

[0081] 1. Absorption spectroscopy and electrochemical cyclic voltammetry:

[0082] The absorption spectra of QxO-1 material in dilute chloroform solution and thin film were measured using a UV-Vis spectrophotometer. Figure 2 As shown, the corresponding data are summarized in Table 1. Among them, the maximum absorption peak (λ) of QxO-1 in solution is... max The maximum absorption peak is located at 712 nm. When in the thin film state, its maximum absorption peak is red-shifted to 761 nm, indicating that there is obvious π-π stacking in the solid state, which is beneficial to obtaining good charge transport properties.

[0083] This invention utilizes electrochemical cyclic voltammetry. The electrochemical energy levels of QxO-1 material in the solid state were tested. The highest occupied orbital (HOMO) and lowest unoccupied orbital (LUMO) energy levels of QxO-1 were -5.68 and -3.84 eV, respectively, showing good absorption spectrum complementarity and energy level matching with the polymer donor D18.

[0084] Table 1 Electrochemical energy levels of QxO-1 material in solid state

[0085]

[0086] 2. Fabrication and performance characterization of photovoltaic devices:

[0087] The prepared organic photoacceptor compound QxO-1 was used as an electron acceptor in the fabrication of solar cell devices: the forward device structure was ITO / PEDOT:PSS / donor material:acceptor material.

[0088] The device fabrication process is as follows: First, the ITO (indium tin oxide) conductive glass is pretreated. The specific steps are as follows: First, the ITO glass is ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol solvents for 20 minutes each. After removal, it is dried with a nitrogen gun and treated with ultraviolet-ozone for 20 minutes. Then, a layer of PEDOT:PSS solution is spin-coated onto the pretreated ITO glass, and it is heated at 150°C for 10 minutes on a hot plate, then transferred to a vacuum glove box. A chloroform solution of the mixture of compound QxO-1 prepared in the example and the donor material is spin-coated onto the substrate surface as an active layer (100 nm). Subsequently, a 6 nm layer of PNDIT-F3N is spin-coated onto the active layer surface as an electron transport layer. Finally, a 70 nm thick metal electrode Ag is deposited by vapor deposition. During the vapor deposition process, the vacuum level is maintained below 2 × 10⁻⁴ Pa. The device performance was tested under standard sunlight (AM 1.5G) irradiation conditions using a computer-controlled Keithley 2400 digital source meter.

[0089] A comparison of the performance of solar cells fabricated using organic photoelectric compound QxO-1 as the acceptor material and D18 as the donor material (light intensity 100 mW / cm²). 2 (Measured under M1.5G irradiation conditions), the device structure is ITO / ZnO / PFN-Br / donor material:acceptor material / MoOx / Ag, and its current density-voltage (JV) test curve is shown below. Figure 3As shown, the relevant parameters are listed in Table 2. Among them, the photovoltaic device based on D18:QxO-1 achieves an open-circuit voltage greater than 1V, making it a very suitable material for indoor wide-bandgap acceptors. Although the initial device efficiency is relatively low, further optimization of the device process and control of the active layer morphology are expected to yield a high-efficiency, low-energy-loss wide-bandgap acceptor with improved efficiency.

[0090] Table 2. Parameters of JV test curves based on QxO-1 devices

[0091]

[0092] 3. Fabrication of indoor photovoltaic devices:

[0093] The fabrication process of the indoor photovoltaic device is as described above under standard sunlight. During device testing, a 2700K LED light source (500 lux) simulator was used, and a PCE of 22.26% was obtained without any post-processing. This indicates that the design of this type of wide-bandgap material is very suitable for indoor organic photovoltaic applications. Further improvements in the efficiency of indoor organic photovoltaic devices can be achieved through detailed device process optimization and active layer morphology control. Specific photovoltaic parameters are summarized in Table 3, and the corresponding indoor JV curves are shown below. Figure 4 As shown.

[0094] Table 3 Indoor photovoltaic parameters under indoor lighting (LED 500 lux) conditions

[0095]

[0096] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a quinoxaline fused ring wide band gap acceptor material for organic solar cells, characterized by: Comprising the following steps: Step 1: Compound 1 is reacted by twice heating reaction, hydrolysis reaction, decarboxylation reaction, strong base tert-butyllithium dehydrogenation stannide and Stille coupling reaction to obtain the final reaction product, i.e. compound 6; Step 2: Compound 6, anhydrous o-dichlorobenzene, triethyl phosphite, 2-butyl iodide octane and potassium carbonate and anhydrous N,N-dimethylformamide are reacted to further process to obtain BTOR; Step 3: Two-mouth bottles are added with compound BTOR and THF solution of lithium aluminum hydride to react to reduce to obtain a crude product, then 2,3-dichloro-5,6-dicyano-1,4-benzoquinone, anhydrous chloroform are added to the above crude product to react for 5 minutes, and then 4,5-difluoro-1,2-phenylenediamine is added to react to obtain QxO1; Step 4: QxO1 prepared in step 3, anhydrous 1,2-dichloroethane, Vilsmerier reagent, aqueous sodium acetate and dichloromethane are added to prepare QxO1-CHO; Step 5: Intermediate QxO1-CHO prepared in step 4, fluorinated cyano indanone and anhydrous chloroform are added to react to obtain QxO-1, i.e. quinoxaline fused ring wide band gap acceptor material; 。 2. The method for preparing quinoxaline fused ring wide band gap acceptor material for organic solar cells according to claim 1, characterized in that: Step 2 comprises: Step 2.1: In a 100 mL single-mouth bottle, compound 6 prepared in step 1 is added, and the gas is replaced for 3 times under nitrogen atmosphere; Step 2.2: Anhydrous o-dichlorobenzene and triethyl phosphite are continuously added, and the reaction is heated at 160 DEG C for 12 hours, then o-dichlorobenzene and excess triethyl phosphite are distilled out under reduced pressure, and 2-butyl iodide octane and potassium carbonate are added, the gas is replaced for 3 times under nitrogen atmosphere, and anhydrous N,N-dimethylformamide 15 mL is added under nitrogen atmosphere, and the reaction is heated at 100 DEG C for 12 hours, Step 2.3: The reaction process is detected by TLC, and the reaction is stopped when the raw material disappears, and the organic phase is extracted with ethyl acetate for 3 times, the organic phase is dried with anhydrous magnesium sulfate for 2 hours, and the organic phase is removed under reduced pressure, and the product BTOR in orange transparent oil is obtained by layer-by-layer chromatography with n-hexane as eluent.

3. The method according to claim 2, characterized in that: Step 3 comprises: Step 3.1: In two-mouth bottles, compound BTOR is added, anhydrous THF is added under nitrogen atmosphere, and THF solution of lithium aluminum hydride is added dropwise through a constant pressure dropping funnel under ice bath, the ice bath is removed after the dropwise addition is completed, and the reaction is refluxed at 65 DEG C for 4 hours, Step 3.2: The reaction process is detected by TLC, and the reaction is stopped when the raw material disappears, and the organic phase is extracted with ethyl acetate for 3 times, the organic phase is dried with anhydrous magnesium sulfate, and the organic phase is removed under reduced pressure, and the crude product can be directly used in the next step without further treatment; Step 3.3: 2,3-dichloro-5,6-dicyano-1,4-benzoquinone is added in the crude product of step 3.2, anhydrous chloroform is added, 4,5-difluoro-1,2-phenylenediamine is added after 5 minutes of reaction, and the reaction is stirred at room temperature for 6 hours; the reaction process is detected by TLC, and the reaction is stopped when the raw material disappears, the organic phase is removed under reduced pressure, and QxO1 in brown red solid is obtained by layer-by-layer chromatography with n-hexane and dichloromethane as eluent.

4. The method according to claim 3, characterized in that: Step 4 comprises: Step 4.1: In a 250 mL two-necked flask, under nitrogen protection, add intermediate QxO1, pump in and out gas for 3 times, and then add anhydrous 1,2-dichloroethane with a syringe, and then add Vilsmerier reagent drop by drop under argon protection, and stir the reaction at room temperature for 1 h, and then heat the reaction at 85 ℃ for 12 h; Step 4.2: TLC is used to detect the progress of the reaction, and the reaction is stopped when the raw material disappears, and then the reaction liquid is poured into saturated aqueous sodium acetate solution, dichloromethane is added, and the reaction liquid is extracted with distilled water, the organic phase is dried over anhydrous sodium sulfate, filtered and the solvent is removed under reduced pressure, and column chromatography is used to obtain red-black solid QxO1-CHO.

5. The method according to claim 4, characterized in that: Step 5 comprises: Step 5.1: In a two-necked flask, add intermediate QxO1-CHO and fluorinated cyanoinde ketone, pump in and out gas for 3 times, add anhydrous chloroform, stir the reaction at room temperature in the dark for 12 h; Step 5.2: TLC is used to detect the progress of the reaction, and the reaction is stopped when the raw material disappears, then add chloroform and extract the reaction liquid with distilled water, combine the organic phases, dry the organic phase over anhydrous sodium sulfate for 2 h, filter and remove the solvent under reduced pressure, and column chromatography is used with a mixture of chloroform and PE as the eluent to obtain green solid QxO-1, which is a quinoxaline fused ring wide band gap acceptor material.

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