Ternary organic solar cell based on high dielectric constant non-fullerene receptor and preparation method thereof

Abstract

The invention discloses a ternary organic solar cell based on a high-dielectric-constant non-fullerene receptor and a preparation method of the ternary organic solar cell, and belongs to the technical field of organic photoelectric materials and devices. The acceptor material L8-BO-FO is synthesized by introducing a polar side chain containing five ether oxygen units into an L8-BO molecule, and the dielectric constant (epsilon r) of the film is as high as 7.41. A small amount (0.5 wt%) of L8-BO-FO is introduced into a PM6: L8-BO binary system as an object to form a ternary active layer, and the dielectric property, exciton kinetics, charge transfer and active layer morphology of the system can be synergistically optimized. The efficiency of the obtained three-element device reaches up to 21.0% under the thickness of 110 nm, more importantly, the efficiency can still be kept at 19.1% under a film with the thickness of 300 nm, the unprecedented thickness insensitivity is shown, and the industrialization process of organic solar cells is greatly promoted.

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronic materials and devices, specifically relating to a novel high-dielectric-constant non-fullerene small molecule acceptor material, its preparation method, and ternary organic solar cells (OSCs) containing this material as a guest component. This solar cell device exhibits high photoelectric conversion efficiency and excellent insensitivity to active layer thickness. Background Technology

[0002] Organic solar cells (OSCs) have become a promising green energy technology due to their outstanding advantages such as light weight, flexibility, semi-transparency, and the ability to be fabricated over large areas using solution methods. In recent years, with the rapid development of non-fullerene acceptors (NFAs), the photoelectric conversion efficiency (PCE) of single-junction OSCs has exceeded 20%, demonstrating enormous commercial potential.

[0003] However, compared to inorganic solar cells (such as silicon-based and perovskite cells), OSCs still lag behind in performance. One of their core bottlenecks lies in the inherently low dielectric constant (ε) of organic semiconductor materials. r ≈ 3-5). The low dielectric constant leads to enhanced Coulomb interactions, resulting in a high binding energy (E0). b The presence of Frenkel excitons (300-1000 meV) significantly increases the energy barrier for exciton dissociation, exacerbates charge recombination, and ultimately limits charge extraction efficiency and overall device performance.

[0004] To overcome this challenge, researchers have explored various strategies to improve the dielectric constant of the active layer. For example, by substituting diselenium onto the outermost thiophene ring of L8-BO, the acceptor T9SBO-F was prepared, and its ε... r The efficiency was improved from 3.96 to 5.04, and the PCE of the ternary device was increased to 19.0%. For example, C60-Y was prepared by functionalizing fullerene C60 onto the core of the Y-series acceptor Me-Y, and its ε-coefficient was further improved. r The dielectric constant was increased from 2.79 to 3.95, and the efficiency of the three-element components was improved to 19.22%. This work demonstrates that dielectric constant engineering is an effective strategy for improving the performance of OSCs.

[0005] Furthermore, the thickness insensitivity of devices is crucial for achieving large-scale, high-throughput roll-to-roll printing. In thick-film devices, charge extraction is more difficult, and bimolecular recombination is more severe, making the dielectric constant particularly critical. Developing novel material systems that can improve efficiency while ensuring thick-film performance is a key issue that urgently needs to be addressed to promote the industrialization of OSCs. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a ternary organic solar cell based on a high dielectric constant non-fullerene acceptor and its preparation method, with the following objectives:

[0007] The primary objective of this invention is to provide a novel non-fullerene acceptor material, L8-BO-FO, with a high dielectric constant.

[0008] Another object of the present invention is to provide a method for preparing the above-mentioned receptor material.

[0009] Another object of the present invention is to provide a ternary organic solar cell containing L8-BO-FO as a guest acceptor, which has both high conversion efficiency and excellent insensitivity to active layer thickness.

[0010] The final object of the present invention is to provide a method for preparing the above-described organic solar cell.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] In a first aspect, the present invention provides a non-fullerene acceptor material L8-BO-FO, the molecular formula of which is C 90 H 102 F4N8O 12 S5, with a molecular weight of 1723.12 g / mol, is a material derived from the classic acceptor L8-BO by replacing the terminal branched alkyl side chain (2-butyloctyl) with a flexible polar side chain (FO side chain) containing five ethylene glycol ether units. The introduction of this side chain significantly increases the polarity and dipole moment of the molecule (6.63D calculated by DFT), resulting in a film dielectric constant of 7.41 (1 kHz), far exceeding the 4.57 of L8-BO.

[0013] Secondly, the present invention provides a method for preparing the L8-BO-FO. This method uses the compound 3,9-bis(2-butyloctyl)-12,13-dihydro-[1,2,5]thiadiazo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole as the starting material, and synthesizes it through three steps:

[0014] Nucleophilic substitution reaction: Compound 3,9-bis(2-butyloctyl)-12,13-dihydro-[1,2,5]thiadiazo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole reacted with excess 16-bromo-2,5,8,11,14-pentahexadecane in DMF solvent at 90 °C under K2CO3 / KI catalysis, introducing an ether chain side chain to give compound 1.

[0015] Vilsmeier formylation reaction: Compound 1 reacts with the POCl3 / DMF system in 1,2-dichloroethane to introduce formyl groups (-CHO) at both ends of the molecule, yielding compound 2.

[0016] Knoevenagel condensation reaction: Compound 2 reacts with IC-2F in chloroform under pyridine catalysis, ultimately condensing to give the target product L8-BO-FO. Each product can be purified by silica gel column chromatography.

[0017] Thirdly, the present invention provides an organic solar cell. The cell comprises, in sequence, an anode, a hole transport layer, an active layer, an electron transport layer, and a cathode. The active layer is a ternary blend system, comprising:

[0018] Donor (D): Polymer PM6;

[0019] Host Acceptor (HA): L8-BO;

[0020] Guest Acceptor (GA): L8-BO-FO as described in this invention.

[0021] The doping ratio (mass fraction) of L8-BO-FO is from 0.1wt% to 10wt%, with the most preferred ratio being 0.5wt%. At this ratio, the dielectric constant of the active layer is optimized, which can effectively promote exciton dissociation, suppress charge recombination, balance carrier transport, and optimize the morphology of the active layer.

[0022] Fourthly, this invention provides a method for fabricating the aforementioned organic solar cell. A conventional "positive" device structure (ITO / HTL / ActiveLayer / ETL / Ag) is employed, wherein the active layer is prepared using a solution spin-coating method. The key lies in dissolving PM6, L8-BO, and L8-BO-FO in an optimized ratio in a solvent such as chloroform to form a homogeneous blend solution, which is then spin-coated into a film.

[0023] Specifically, the technical solution adopted in this invention is as follows:

[0024] A non-fullerene acceptor material, the molecular structure of which is shown in general formula I:

[0025]

[0026] Where n is an integer between 4 and 6.

[0027] Furthermore, the structure of the receptor material is as follows:

[0028]

[0029] It is named L8-BO-FO. Furthermore, the relative permittivity ε of the material in the thin film state... r The value is 6.5 to 8.0 in the frequency range of 100 Hz to 1 MHz, and preferably 7.41 at 1 kHz.

[0030] A method for providing the non-fullerene acceptor material L8-BO-FO includes the following steps:

[0031]

[0032] (a) Compound Y6-NH (i.e., compound 3,9-bis(2-butyloctyl)-12,13-dihydro-[1,2,5]thiadiazo[3,4-e]thieno[2'',3'':4',5']pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole) was subjected to a nucleophilic substitution reaction with 16-bromo-2,5,8,11,14-pentahexadecane under basic conditions in a polar aprotic solvent to give intermediate compound 1;

[0033] (b) Compound 1 was reacted with Vilsmeier-Haack reagent to formylate, giving intermediate compound 2;

[0034] (c) Compound 2 and compound IC-2F were subjected to Knoevenagel condensation reaction in the presence of an organic base, and the final product L8-BO-FO was obtained after purification.

[0035] Furthermore, in step (a):

[0036] (1) The alkaline conditions are provided by potassium carbonate;

[0037] (2) The polar aprotic solvent is N,N-dimethylformamide (DMF).

[0038] (3) The reaction is carried out under the protection of an inert gas, the reaction temperature is 85-95 ℃, and the reaction time is 8-12 hours.

[0039] An organic solar cell includes an anode, a hole transport layer, an active layer, an electron transport layer, and a cathode stacked sequentially. The active layer comprises a donor material and an acceptor material, and the acceptor material comprises a host acceptor and the guest acceptor L8-BO-FO.

[0040] Furthermore, the donor material is polymer PM6, and the host acceptor is L8-BO.

[0041] Furthermore, the total mass ratio of donor material to acceptor material in the active layer is 1:1 to 1:1.5, preferably 1:1.2; the mass of the guest acceptor L8-BO-FO accounts for 0.1% to 10% of the total mass of donor material and host acceptor material, preferably 0.2% to 2%, more preferably 0.5%.

[0042] Furthermore, the thickness of the active layer is 80 nm to 400 nm; when the thickness of the active layer is 110 ± 20 nm, the power conversion efficiency (PCE) of the solar cell is not less than 20.0%; when the thickness of the active layer is 300 ± 20 nm, the power conversion efficiency (PCE) of the solar cell is not less than 19.0%.

[0043] A method for preparing the organic solar cell includes the following steps:

[0044] (1) Provide an anode substrate;

[0045] (2) A hole transport layer is prepared on the anode;

[0046] (3) A mixed solution containing donor material, host acceptor and guest acceptor L8-BO-FO is spin-coated onto the hole transport layer to form an active layer;

[0047] (4) An electron transport layer is prepared on the active layer;

[0048] (5) Fabricate a cathode on the electron transport layer.

[0049] Furthermore, the solvent of the mixed solution in step (3) is chloroform and / or chlorobenzene, and the solution concentration is 10-20 mg / mL; the spin coating speed is 2000-4000 rpm.

[0050] Compared with the prior art, the present invention has the following significant advantages:

[0051] Material innovation: This invention is the first to design and synthesize a high dipole moment and high dielectric constant acceptor, L8-BO-FO (6.63 / 7.41), which incorporates an odd number (5) of ether oxygen units in its side chain. Both DFT calculations and experiments demonstrate that its dipole moment and dielectric constant are significantly higher than those of L8-BO (3.08 / 4.57).

[0052] High device efficiency: Introducing only 0.5wt% of L8-BO-FO into the PM6:L8-BO binary system can significantly improve the PCE of ternary devices from 19.1% to 21.0% (certified efficiency 20.43%).

[0053] Excellent thickness insensitivity: The ternary device of this invention exhibits extremely excellent thickness tolerance. When the active layer thickness increases from 110 nm to 300 nm, the efficiency of the binary device drops sharply to 16.5%, while the ternary device can still maintain a high efficiency of 19.1%, which was the highest record for 300 nm thick OSCs at that time, greatly promoting the industrial application of OSCs.

[0054] Through systematic device physics and morphology characterization, this invention reveals the intrinsic mechanism of performance improvement: the introduction of L8-BO-FO increases the dielectric constant, enhances the dielectric shielding effect, reduces the exciton binding energy, accelerates exciton dissociation and charge transport, suppresses nonradiative recombination, and optimizes the morphology and vertical phase distribution of the blend film, ultimately achieving high efficiency and high thickness tolerance in a synergistic manner. Attached Figure Description

[0055] Figure 1 The following are characterization diagrams of the basic properties of the materials: (a) chemical structures of PM6, L8-BO, and L8-BO-FO; (b) frequency-varying dielectric constants of L8-BO and L8-BO-FO films; (c) UV-Vis absorption spectra of the films; and (d) energy level diagrams.

[0056] Figure 2 The photovoltaic performance diagrams of the devices are as follows: (a) JV curves of the devices at different L8-BO-FO doping concentrations; (b) Statistical variation of PCE with doping concentration; (c) Certified JV curve of the optimal device; (d) EQE spectrum; (e) Energy loss analysis; (f) EL-EQE spectrum; (g) MD simulation of PM6:L8-BO:L8-BO-FO ternary blends (blue: PM6; red: L8-BO; yellow: L8-BO-FO); (h) MD simulation of the nonradiative recombination rate k of PM6:L8-BO and PM6:L8-BO:L8-BO-FO blends. nr (i) Non-radiative voltage loss ΔV nr With the considered quantum mechanical recombination energy λ qm The functional relationship.

[0057] Figure 3The following are the morphological characterization diagrams of the binary and ternary active layers: (ac) AFM height map; (df) 2D GIWAXS plot; (g) 1D line cut spectrum; (h) GISAXS spectrum; (ik) Radial distribution function (RDF) plot of MD simulation. Detailed Implementation

[0058] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited thereto.

[0059] Example 1: Synthesis of compound L8-BO-FO

[0060]

[0061] Step 1: Synthesis of Compound 1

[0062] Under nitrogen protection, 3,9-bis(2-butyloctyl)-12,13-dihydro-[1,2,5]thiadiazo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole (1 g, 1.29 mmol), 16-bromo-2,5,8,11,14-pentahexadecane (3.25 g, 10.32 mmol), potassium carbonate (K₂CO₃, 1.43 g, 10.32 mmol), and potassium iodide (KI, 0.17 g, 1.03 mmol) were dissolved in 30 mL of anhydrous DMF. The reaction mixture was stirred at 90 °C for 12 hours. After the reaction was complete, the mixture was cooled to room temperature and extracted with dichloromethane. The organic phase was dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography to give compound 1 as a yellow solid (1.2 g, 75% yield). 1 HNMR (400 MHz, CDCl3) δ 6.98 (s, 2H), 4.95 (s, 4H), 3.85 (s, 4H), 3.66 (s, 10H), 3.49 (s, 8H), 3.33 (s, 12H), 3.26 (s, 8H), 2.74 (d, 4H), 1.26 (s, 40H), 0.88 (s, 6H); 13CNMR (101 MHz, CDCl3) δ 150.86, 138.43, 130.67, 126.66, 121.65, 121.26, 77.44, 77.12, 76.81, 71.91, 70.57, 70.51, 7 0.39, 70.06, 66.73, 59.06, 51.83, 39.49, 31.63, 29.10, 29.02, 26.41, 22.59, 22.26, 14.09; MS (MALDI-TOF) calcd forC 64 H 98 N4O 10 S5[M] + : 1242.5886, found 1242.5868.

[0063] Step 2: Synthesis of Compound 2

[0064] Vilsmeier's reagent was prepared by slowly adding POCl3 (2 mL) dropwise to anhydrous DMF (3 mL) under an ice bath at 0 °C and stirring for 1 hour. In another reaction flask, compound 1 (1.2 g, ~1 mmol) was dissolved in 30 mL of 1,2-dichloroethane. Under nitrogen protection, the Vilsmeier reagent was slowly added dropwise to the solution of compound 1. After the addition was complete, the reaction system was heated to 90 °C and stirred for 12 hours. After the reaction was complete, the mixture was cooled to 0 °C, slowly quenched in ice water, and stirred for 4 hours. Extraction was performed with dichloromethane, and the organic phase was dried, filtered, and concentrated. The crude product was purified by silica gel column chromatography to give compound 2 as an orange solid (700 mg, yield 67%). 1 HNMR (500 MHz, CDCl3) δ 10.10 (s, 2H), 5.03 (t, J = 5.6 Hz, 4H), 3.94 (t, J = 5.7 Hz, 4H), 3.67-3.64 (m, 6H), 3.57–3.52 (m, 10H), 3.49 (dd, 8H), 3.33 (s, 6H), 3.27 (dt, 8H), 2.04 (t, 4H), 1.25 (s, 34H), 0.88 (d, 6H), 0.87 (s, 6H); 13CNMR (101 MHz, CDCl3) δ 181.91, 147.38, 146.32, 143.49, 137.61, 136.51, 132.85, 129.17, 127.41, 112.63, 77.24, 77.03, 76.81, 71.89, 70.88, 70.47 MS (MALDI-TOF) calcd for C 66 H 98 N4O 12 S5[M] + : 1298.5785, found 1299.5835.

[0065] Step 3: Synthesis of L8-BO-FO

[0066] Under nitrogen protection, compound 2 (700 mg, 0.54 mmol), IC-2F (495 mg, 2.15 mmol), and pyridine (1 mL) were dissolved in 19 mL of chloroform. The reaction mixture was stirred at 65 °C for 12 hours. After the reaction was complete, the reaction solution was cooled to room temperature and then poured into methanol to precipitate a solid. The solid was collected by filtration and further purified by silica gel column chromatography to give the final product L8-BO-FO as a purple-black solid (600 mg, yield 64%). 1 HNMR (500 MHz, CDCl3)δ 8.90 (s, 2H), 8.50 (dd, J = 9.9, 6.5 Hz, 2H), 7.65 (t, J = 7.5 Hz, 2H), 5.15–5.11 (m, 4H), 4.08 (t, 4H), 3.54–3.45 (m, 22H), 3.40–3.32 (m, 10H), 3.30 (s, 6H), 2.02 (dd, 4H), 1.87 (td, 6H), 1.73–1.70 (m, 8H), 1.43 (s, 32H); 13CNMR (101 MHz, CDCl3) δ186.09, 150.86, 138.43, 130.67, 126.66, 121.65, 121.26, 77.44, 77.12, 76.81, 71.91, 70.57, 70. 51, 70.39, 70.06, 66.73, 59.06, 51.83, 39.49, 31.63, 29.10, 29.02, 26.41, 22.59, 22.26, 14.09; MS (MALDI-TOF) calcd for C 90 H 102 F4N8O 12 S5[M] + : 1722.6157, found1723.6163.

[0067] Example 2: Photophysical properties

[0068] Figure 1 Figure b shows the frequency-varying dielectric constants of L8-BO and L8-BO-FO films. As can be seen from the figure, compared to the L8-BO film (4.57), the L8-BO-FO film exhibits a higher ε... r The value was (7.41). Therefore, we chose to introduce L8-BO-FO molecules as guest components into the PM6:L8-BO host binary blend system. Furthermore, the ε-value of the blend films with different L8-BO-FO doping ratios was tested. r Value. ε of the blend film. r The value increases monotonically with increasing doping ratio. Figure 1 Figure c shows the UV-Vis absorption spectra of PM6, L8-BO, and L8-BO-FO thin films. The pure PM6 film exhibits an absorption window in the 400-700 nm range, with its peak and shoulder peaks located at 580 nm and 620 nm, respectively. The absorption spectra of L8-BO and L8-BO-FO show significant absorption in the 600-900 nm range, with their maximum absorption peaks located at 805 nm and 807 nm, respectively. Furthermore, the energy levels of the corresponding materials were determined using electrochemical cyclic voltammetry (CV). Figure 1 (d). The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PM6, L8-BO, and L8-BO-FO are -5.49 / -3.47 eV, -5.72 / -3.93 eV, and -5.30 / -3.94 eV, respectively.

[0069] Example 3: Fabrication and Performance Testing of Organic Solar Cells

[0070] 1. Solution preparation:

[0071] Preparation of hole transport layer solution: Dissolve 2PACz in ethanol to a concentration of 0.5 mg / mL.

[0072] Preparation of the active layer solution: Weigh the donor PM6 and the host receptor L8-BO at a mass ratio of 1:1.2, then add guest receptor L8-BO-FO at concentrations of 0%, 0.5%, 1%, 2%, and 4% of the total receptor mass, and dissolve them together in chloroform to a total concentration of 16 mg / mL. Heat and stir at 50 °C for at least 6 hours to ensure complete dissolution.

[0073] Preparation of electron transport layer solution: Dissolve PNDIT-F3N in methanol to a concentration of 0.5 mg / mL.

[0074] 2. Device fabrication:

[0075] Anodizing: The patterned ITO glass substrate was ultrasonically cleaned for 15 minutes each with detergent, deionized water, acetone and isopropanol, then dried with nitrogen and treated with UV-ozone for 15 minutes.

[0076] Spin-coating hole transport layer: Spin-coat 2PACz solution onto ITO surface at 3000 rpm for 30 seconds, then anneal at 100°C for 10 minutes.

[0077] Spin-coating the active layer: In a glove box under nitrogen atmosphere, the active layer solution was spin-coated at 3500 rpm for 30 seconds to form a film approximately 110 nm thick. It was then annealed at 100 °C for 10 minutes.

[0078] Spin-coating electron transport layer: Spin-coat PNDIT-F3N solution at 3000 rpm for 30 seconds.

[0079] Cathode deposition: The substrate is transferred to a vacuum deposition chamber, and deposition is carried out at a temperature of < 5 × 10⁻⁶. -4 A silver (Ag) electrode with a thickness of approximately 100 nm was thermally evaporated under a vacuum of Pa.

[0080] 3. Performance Testing:

[0081] Devices with L8-BO-FO content of 0%, 0.5%, 1%, 2%, and 4% were tested using a Keithley 2400 source meter under standard AM 1.5G spectrum and 100 mW / cm² light intensity. The JV curves of these devices were measured. Figure 2 As shown in Figure a. Figure 2 b represents the statistical variation of the PCE guest acceptor L8-BO-FO with doping concentration; Figure 2 In the figures a and b, it is indicated that the performance is optimal when the doping concentration of the guest acceptor L8-BO-FO is 0.5%. The performance parameters of the optimal device are: V oc = 0.906 V, Jsc = 27.93 mA / cm², FF = 82.76%, PCE = 21.0%. This result was certified by the South China National Metrology and Testing Center. Figure 2 (c) The authentication value is 20.43%.

[0082] 4. External quantum efficiency and energy loss

[0083] Simultaneously, we measured the external quantum efficiency (EQE) spectra of the relevant binary (PM6:L8-BO, i.e., the device with a 0% L8-BO-FO ratio) and ternary (PM6:L8-BO:L8-BO-FO) devices (e.g., ...). Figure 2 (d) to verify J in the JV curve SC The difference. J calculated from EQE spectra. SC The deviation from the measured JV value is within 5%, which is within the acceptable error range. Compared with PM6:L8-BO binary devices, all ternary devices with different doping ratios of L8-BO-FO exhibit stronger EQE responses in the 420-780 nm range, which corresponds to the JV value of the ternary device. SC The improvement.

[0084] Figure 2 In the diagram, e and f represent the energy loss analysis and EL-EQE spectra of the two-element and optimal three-element devices, respectively. The effect of L8-BO-FO on energy loss (E0) was investigated using Fourier transform photocurrent external quantum efficiency (FTPS-EQE) and electroluminescence external quantum efficiency (EL-EQE) measurements. loss The impact of ). Indicates radiation loss above the band gap, Indicates radiation below the band gap and This represents non-radiative energy loss. The E of a three-element device... loss It is 0.547 eV, lower than the 0.550 eV of the main binary device. The binary and optimal ternary OSCs are... and There is almost no difference; E loss The reduction is mainly due to The reduction in efficiency was further confirmed by measuring the EL quantum efficiency of the relevant OSC. Experiment It can be calculated using the following formula: The EL-EQE Gundam of the Tri-Element OSC ,correspond =0.229 eV, which is better than the 0.236 eV of the PM6:L8-BO binary device, and is consistent with the above results. It is worth noting that E loss The decrease can also be attributed to the ε of the ternary blend film. r The enhancement.

[0085] At the same time, we performed molecular dynamics (MD) simulations ( Figure 2 The average CT state energy was calculated using DFT and analyzed using the Marcus-Levich-Jortner model. Introducing L8-BO-FO increased the average CT state energy from 1.625 eV to 1.646 eV, which helps reduce the exciton binding energy. Due to the increased coupling energy, the nonradiative recombination rates of the two systems are almost identical. Figure 2 The increased dipole moment during the transition from the excited state to the ground state increases the radiative recombination rate, thereby slightly reducing the non-radiative voltage loss (h). Figure 2 (i), consistent with experimental results.

[0086] Example 4: Fabrication and Performance of Thick-Film Devices

[0087] The concentration of the active layer solution was adjusted to 22 mg / mL, the spin-coating speed was reduced to 2000 rpm, and other steps were the same as in Example 2, resulting in a device with an active layer thickness of approximately 300 nm. The performance parameters of this thick-film device are: V oc = 0.893 V, J sc =27.62 mA / cm², FF = 78.62%, PCE = 19.1%.

[0088] Comparative Example 1: Binary components without L8-BO-FO

[0089] Without adding L8-BO-FO, using only PM6:L8-BO (1:1.2) to fabricate binary devices, the PCE of a 110 nm thick device is 19.1%, and the PCE of a 300 nm thick device is reduced to 16.50%.

[0090] Comparative Example 2: Devices with a high proportion of L8-BO-FO doping

[0091] Ternary devices were fabricated by increasing the doping ratio of L8-BO-FO to 4 wt%. The PCE of the 110 nm thick device decreased to 19.2%, indicating the existence of an optimal doping window. Excessive doping can damage the morphology and negatively impact performance.

[0092] Introducing only 0.5 wt% L8-BO-FO into the PM6:L8-BO binary system can significantly improve the PCE of the ternary device from 19.1% to 21.0% (certification efficiency 20.43%). The specific OSCs parameters are shown in Table 1 below:

[0093] Table 1

[0094]

[0095] a Integral short-circuit current density derived from the external quantum efficiency curve;

[0096] b The average value derived from 10 standard devices;

[0097] c Efficiency certified by the South China National Metrology and Testing Center.

[0098] Example 5: Morphology characterization of binary and ternary active layers

[0099] Binary active layer: The donor PM6 and the host acceptor L8-BO were weighed at a mass ratio of 1:1.2 and dissolved in chloroform to a total concentration of 16 mg / mL. The mixture was heated and stirred at 50 °C for at least 6 hours to ensure complete dissolution; the PM6:L8-BO film (i.e., the host binary film) was obtained by spin coating.

[0100] Donor PM6 and guest acceptor L8-BO-FO were weighed at a mass ratio of 1:1.2 and dissolved in chloroform to a total concentration of 16 mg / mL. The solution was heated and stirred at 50 °C for at least 6 hours to ensure complete dissolution; a PM6:L8-BO-FO film was obtained by spin-coating.

[0101] Ternary active layer: Donor PM6 and host receptor L8-BO were weighed at a mass ratio of 1:1.2, and guest receptor L8-BO-FO (0.5% of the total receptor mass) was added. All were dissolved in chloroform to a total concentration of 16 mg / mL. The mixture was heated and stirred at 50 °C for at least 6 hours to ensure complete dissolution. The PM6:L8-BO:L8-BO-FO film (i.e., ternary film) was obtained by spin-coating.

[0102] Besides improving dielectric properties through L8-BO-FO doping, the morphological changes induced by L8-BO-FO in the active layer also affect charge transport and recombination. Therefore, we conducted a series of morphological characterization studies, including atomic force microscopy (AFM), grazing incidence wide-angle X-ray scattering (GIWAXS), and grazing incidence small-angle X-ray scattering (GISAXS), to systematically investigate the influence of L8-BO-FO on morphological characteristics.

[0103] Figure 3 AFM results for samples a, b, and c show that in the two binary systems, the PM6:L8-BO-FO film has a rougher surface due to the higher crystallinity of L8-BO-FO, with a root mean square roughness (RMS) of 1.18 nm, while the RMS of the host binary PM6:L8-BO film is only 0.99 nm. Introducing L8-BO-FO into the host reduces the RMS of the ternary film (PM6:L8-BO:L8-BO-FO) to 0.957 nm and reveals a clearer fibrous network, which is beneficial for charge transport and inhibits recombination.

[0104] Further utilize GIWAXS ( Figure 3 The effects of L8-BO-FO on crystallization and molecular stacking were investigated using df and MD simulations. Two-dimensional GIWAXS patterns and corresponding out-of-plane (OOP) line-cut curves showed that all films were predominantly face-on stacked, with obvious (010) π-π stacking peaks appearing in the OOP direction. The (010) peak positions for PM6:L8-BO, PM6:L8-BO-FO, and the ternary film (PM6:L8-BO:L8-BO-FO) were 1.659, 1.695, and 1.667, respectively. The corresponding π-π spacing d π-π The values ​​are 3.79, 3.71, and 3.77 respectively. The coherence lengths (CCLs) are 13.50, 22.26, and 14.73, respectively. Compared to the main binary thin film, the ternary thin film d π-π The shrinkage and increase of CCL indicate that L8-BO-FO doping promotes more ordered molecular stacking, which is beneficial for charge transport.

[0105] To analyze the local morphological changes, we performed radial distribution function (RDF) analysis on the system after MD equilibrium. Figure 3 (Ik). RDF reflects the relative density of atoms at a distance r centered on the reference atom, and the local density ρ. local =ρ global g(r). It can be seen that, compared to the binary system PM6:L8-BO, the main peak of g(r) for PM6-PM6 in the ternary system PM6:L8-BO:L8-BO-FO shifts to the right (4.450 → 4.650). ), while PM6-L8-BO (4.450 → 4.350) ) and L8-BO-L8-BO (4.375 → 4.325 The leftward shift of the main peak indicates that the introduction of L8-BO-FO enhances the ordered arrangement of L8-BO molecules. Further normalization based on the extracted π-π packing pairs yields an average packing distance of 4.419 for the entire system. (PM6:L8-BO) and 4.375 (PM6:L8-BO:L8-BO-FO) confirms that the ternary system has a more compact packing, consistent with the GIWAXS results.

[0106] GISAXS was used to quantitatively characterize the phase separation structure within the active layer. One-dimensional GISAXS curves fitted with the Debye–Anderson–Brumberger model yielded average sizes ζ of the interdiffused phase regions of 24.5 nm (PM6:L8-BO), 27.8 nm (PM6:L8-BO-FO), and 25.3 nm (PM6:L8-BO:L8-BO-FO). The ternary system exhibits a suitable phase separation scale, consistent with the AFM morphology.

[0107] The results above show that the introduction of L8-BO-FO can effectively optimize phase separation and molecular stacking, improving charge transport capability while reducing recombination loss.

[0108] The above embodiments fully demonstrate that the L8-BO-FO material described in this invention and its application in ternary organic solar cells can significantly improve the photoelectric conversion efficiency of the device and endow the device with excellent insensitivity to active layer thickness, showing good application prospects.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A non-fullerene acceptor material characterized in that, The molecular structure is shown in general formula I: ； Wherein, n is an integer of 4-6.

2. The non-fullerene acceptor material according to claim 1, characterized in that, The structure of the acceptor material is: 。 3. The non-fullerene acceptor material according to claim 1, characterized in that, The relative dielectric constant ε of the material in the thin film state in the frequency range from 100 Hz to 1 MHz is r 6.5 to 8.

0.

4. A method for preparing the non-fullerene acceptor material L8-BO-FO according to claim 2, characterized in that, The method comprises the following steps: ； (a) carrying out a nucleophilic substitution reaction of compound Y6-NH and 16-bromo-2, 5, 8, 11, 14-pentaoxahexadecane under alkaline conditions in a polar aprotic solvent to obtain intermediate compound 1; (b) reacting intermediate compound 1 with Vilsmeier-Haack reagent to carry out formylation to obtain intermediate compound 2; (c) carrying out a Knoevenagel condensation reaction of intermediate compound 2 and compound IC-2F in the presence of an organic base to obtain the final product L8-BO-FO after purification.

5. The method of claim 4, wherein, In step (a): (1) the alkaline conditions are provided by potassium carbonate; (2) the polar aprotic solvent is N, N-dimethylformamide; (3) the reaction is carried out under inert gas protection, the reaction temperature is 85-95 DEG C, and the reaction time is 8-12 hours.

6. An organic solar cell comprising, in this order, an anode, a hole-transporting layer, an active layer, an electron-transporting layer, and a cathode, characterized in that, The active layer comprises a donor material and an acceptor material, the acceptor material comprises a host acceptor and a guest acceptor, and the guest acceptor is the acceptor material according to any one of claims 1-3.

7. The organic solar cell according to claim 6, characterized in that The donor material is a polymer PM6, the host acceptor is L8-BO, and the guest acceptor is L8-BO-FO.

8. The organic solar cell according to claim 7, characterized in that The total mass ratio of the donor material to the acceptor material in the active layer is 1:1 to 1:1.5; and the mass of the guest acceptor L8-BO-FO accounts for 0.1% to 10% of the total mass of the donor material and the host acceptor material.

9. The organic solar cell according to claim 6, characterized in that The thickness of the active layer is 80 nm to 400 nm; when the thickness of the active layer is 110 ± 20 nm, the energy conversion efficiency of the solar cell is not less than 20.0%; and when the thickness of the active layer is 300 ± 20 nm, the energy conversion efficiency of the solar cell is not less than 19.0%.

10. A method of producing an organic solar cell as claimed in any one of claims 6-9, characterized in that, The method comprises the following steps: (1) providing an anode substrate; (2) preparing a hole transport layer on the anode; (3) spin-coating a mixed solution comprising a donor material, a host acceptor and a guest acceptor on the hole transport layer to form an active layer; (4) preparing an electron transport layer on the active layer; (5) preparing a cathode on the electron transport layer; The solvent of the mixed solution in step (3) is chloroform and / or chlorobenzene, the total concentration of the mixed solution is 10-20 mg / mL, and the spin-coating speed is 2000-4000 rpm.

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