Dithiophene-cyclohexanedione two-armed oligomer donor materials, methods of making and use thereof

Abstract

This invention relates to the field of organic solar cell technology, specifically to a dithienocyclohexanedione-based two-arm oligomer donor material, its preparation method, and its applications. This donor material has an A(B-A')2 structure, with dithienocyclohexanedione (BDD) as the central charge-withdrawing (A) unit, a simple triple monocyclic aromatic hydrocarbon as the arm (B) unit, and an alkylcyanorhodanine as the terminal charge-withdrawing (A') unit. This type of two-arm oligomer donor material is simple to synthesize, with controllable reaction conditions, making it suitable for large-scale production. When used as a third component in organic solar cell systems, it can significantly improve the photovoltaic performance of the device. The preferred PM6:BTP-eC9 organic solar cell shows an increase in photoelectric conversion efficiency from 18.68% to 19.75%, indicating broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of organic solar cell technology, specifically to a dithiophenecyclohexanedione double-arm oligomer donor material, its preparation method, and its application. Background Technology

[0002] Organic solar cells (OSCs) possess advantages such as light weight, low cost, solution-processability, and good mechanical flexibility, and are considered one of the most promising renewable energy technologies. In recent years, thanks to innovations in high-performance photovoltaic materials and optimizations in advanced device engineering, particularly the significant progress in Y-series non-fullerene acceptors (NFAs), the power conversion efficiency (PCE) of single-junction OSC devices has been continuously improved. Currently, OSC devices containing simple non-fused-ring small-molecule donor materials have achieved an efficiency of 19.3%. However, there are relatively few reports on high-performance small-molecule donor materials, which severely restricts the stability of OSC device performance and its commercial application.

[0003] Small molecule donor (SMD) materials have become a hot topic in current organic photovoltaic research due to their advantages such as tunable energy level structure and absorption characteristics, and controllable ordered molecular stacking. At present, SMD materials and their OSCs devices have made some progress, but most of the research focuses on benzodithiophene (BDT) derivatives, and the PCE of their ternary devices has exceeded 19%. However, BDT-based SMD materials still have shortcomings in terms of light absorption, electron transport and morphological stability. The main problems restricting the development of BDT-based SMD materials are: (1) With the BDT unit with electron-donating characteristics as the core structure, the energy level is difficult to control and is prone to energy level mismatch with small molecule acceptors; (2) The rigidity and planarity of the BDT unit are too strong, which easily leads to high crystallinity of the material, making it difficult to form an ideal donor-acceptor (D / A) phase separation morphology and ordered molecular stacking, which is not conducive to improving carrier migration performance. Therefore, there is an urgent need to develop oligomer donor materials with novel structural units as the core, controllable structure, energy level matching, and simple synthesis, which also have mid-bandgap light absorption, high carrier mobility and excellent morphology control capabilities, in order to meet the urgent need of ternary OSCs devices for multifunctional third component materials. Summary of the Invention

[0004] This invention aims to address the shortage of existing high-performance small molecule donor materials. A class of A(D-A')2 type dithienylcyclohexanedione oligomer donor materials was designed and synthesized, and a preparation method for this type of oligomer donor material and its application in organic solar cells are provided. The oligomer donor material provided by this invention has an A(D-A')2 type structure, with dithienylcyclohexanedione (BDD) as the conjugated bridging center electron-withdrawing (A) unit, a triple monocyclic aromatic hydrocarbon as the arm (B) unit, and an alkylcyanorhodanine as the terminal electron-withdrawing (A') group. The chemical structure of this type of two-arm oligomer donor material is shown in formula (1):

[0005]

[0006] Equation (1)

[0007] in, for , or Isoelectron-deficient monocyclic aromatic hydrocarbons, with long-chain alkyl groups R having a C20 value. n H 2n+1 (n = 8, 10, 12, 16, 20); short-chain alkyl group R1 is C n H 2n+1 (n = 2, 4, 6).

[0008] Preferred for R is C8H 17 Isooctyl, R1 is C2H5 ethyl, and the preferred two-arm oligomer donor material has the chemical structure shown in formula (2).

[0009]

[0010] Equation (2)

[0011] Compared with existing donor materials, the double-arm oligomer donor material of this invention has advantages such as simple structure, mild preparation conditions, and excellent film-forming properties. This type of material is entirely composed of non-fused-ring structural units, without a complex fused-ring skeleton, making its synthesis and purification processes simple. Its molecular core uses an electron-deficient dithiophene-cyclohexanedione unit, which can effectively control the electrical properties and carrier transport properties of the donor material.

[0012] The A(D-A')2 type dithiophenecyclohexanedione oligomer donor material provided by this invention has the following outstanding advantages in molecular structure:

[0013] (1) The dithiophenecyclohexanedione unit has a rigid plane, which endows the material with excellent crystallinity, charge transport characteristics and ideal absorption spectrum, which is conducive to achieving efficient photon capture in a wide spectral range;

[0014] (2) The moderate electron-withdrawing ability of the dithiophenecyclohexanedione unit endows the material with a deeper HOMO energy level, which is conducive to the formation of cascade energy levels with the host system donor and acceptor materials and promotes hole transfer.

[0015] (3) The dithiophenecyclohexanedione unit has a typical quinone structure, which makes the material molecule present an A'-BAB-A' type structure, which is conducive to generating a stronger intramolecular charge transfer (ICT) effect.

[0016] (4) The strong polarity of the dithiophenecyclohexanedione unit gives the material a higher dielectric constant, which is beneficial to exciton dissociation and reduces bimolecular recombination;

[0017] (5) The triple monocyclic aromatic hydrocarbon arm structure can form intramolecular non-covalent bond interactions such as sulfur-fluorine and nitrogen-hydrogen, which can improve molecular planarity and thus optimize molecular stacking and film morphology.

[0018] These A(D-A')2 type dithiophenecyclohexanedione oligomer donor materials have excellent photoelectric properties. When used as a third component in organic solar cells as an active layer, they can significantly improve the photovoltaic performance and stability of the device.

[0019] The organic solar cell device has an ITO / PEDOT:PSS / active layer / PDINN / Ag structure; the host donor material of the active layer is the polymer donor material PM6, the guest donor material is the dithiophenecyclohexanedione double-arm oligomer donor material BDD-Rh, and the host acceptor material is the small molecule acceptor material Y6, BTP-eC9, or L8-BO.

[0020] The doping ratio of oligomer donor material in the active layer is 5 wt%-20 wt% of the mass of the host donor material; the mass ratio of host donor material to host acceptor material in the active layer is 1:1 to 1.5.

[0021] The A(D-A')2 type dithiophenecyclohexanedione oligomer donor material provided by the present invention is synthesized through a simple and mild Stille coupling reaction, tinning reaction, acylation reaction, and condensation reaction.

[0022] The A(D-A')2 type dithiophenecyclohexanedione oligomer donor material of this invention, used as a third component in traditional binary OSCs systems, can significantly improve the photovoltaic performance of OSCs devices. When the oligomer donor material is BDD-Rh-1 and the host donor:acceptor material is preferably PM6:BTP-eC9, the photovoltaic performance of the device is comprehensively improved with the increase of the BDD-Rh-1 doping ratio (from 0 to 5%): the short-circuit current of the device (J) SCThe open-circuit voltage (V) increased from 27.77 mA / cm² to 28.81 mA / cm². OC The voltage was increased from 0.843 V to 0.855 V, and the fill factor (FF) was increased from 79.81% to 80.13%. The PCE of the device was as high as 19.75%, which is significantly better than the 18.68% of the binary system.

[0023] The preferred structural formulas of the host donor and acceptor materials are as follows:

[0024]

[0025] Compared with the prior art, the technical advantages of the present invention are as follows:

[0026] (1) The oligomer donor material is composed of non-fused ring structural units with a simple molecular structure. Its molecular central core adopts an electron-deficient dithiophene-cyclohexanedione unit, which can effectively control the electrical properties and carrier transport properties of the donor material.

[0027] (2) The synthesis route of oligomer donor materials is simple, the reaction conditions are mild and controllable, the purification process is simple, and it is suitable for large-scale preparation and production;

[0028] (3) The oligomer donor material is a medium-wide bandgap donor material, which can broaden the light absorption range, optimize the energy level matching of the device, and significantly improve the photovoltaic performance of the device;

[0029] (4) Using it as a third component in ternary blend OSCs can further optimize the morphology of the blend film and significantly improve the photoelectric conversion efficiency of the device, with excellent application performance and good industrialization prospects.

[0030] To more clearly illustrate the present invention, the following description, in conjunction with embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific details described below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention. Attached Figure Description

[0031] Figure 1 The photon NMR spectrum of the oligomer donor material BDD-Rh-1 prepared in Example 1 of this invention is shown.

[0032] Figure 2 The image shows the UV performance of the oligomer donor material BDD-Rh-1 prepared in Example 1 of this invention.

[0033] Figure 3 This is a theoretical calculation diagram of the oligomer donor material BDD-Rh-1 prepared in Example 1 of the present invention.

[0034] Figure 4The image shows the CV performance of the oligomer donor material BDD-Rh-1 prepared in Example 1 of this invention.

[0035] Figure 5 The thermogravimetric analysis (TG) diagram of the oligomer donor material BDD-Rh-1 prepared in Example 1 of this invention.

[0036] Figure 6 UV diagram and energy level diagram for the PM6:BTP-eC9:BDD-Rh-1 ternary system.

[0037] Figure 7 shows the current-voltage (JV) curves of PM6:BTP-eC9:BDD-Rh-1 ternary organic solar cells: a) PEDOT:PSS is the hole transport material, b) 2PACZ is the hole transport material. Detailed Implementation

[0038] This invention provides, on the one hand, a method for the molecular construction and preparation of A(D-A')2 type BDD oligomer donor materials. A(D-A')2 type BDD oligomer donor material BDD-Rh is prepared through simple and mild Stille coupling, tinning, acylation, and condensation reactions. On the other hand, it provides the application of A(D-A')2 type BDD oligomer donor materials in ternary OSCs. Using BDD-Rh as a third component in traditional high-efficiency binary OSCs, ternary OSC devices with significantly improved photovoltaic performance are obtained. The preferred OSC device structure is ITO / PEDOT:PSS (30 nm) / active layer (100 nm) / PDINN (10 nm) / Ag (100 nm).

[0039] In the active layer of the device, the dithiophenecyclohexanedione donor material BDD-Rh serves as the third component guest donor material. In traditional high-efficiency binary OSCs devices, the donor and acceptor materials are respectively the host donor and host acceptor materials of the ternary active layer. The preferred doping concentration of BDD-Rh in the active layer is 5 wt% of the host donor material, and the active layer blend is dissolved in chloroform solvent.

[0040] The thicknesses of the hole injection layer and active layer were measured using a probe-type surface profilometer (Dektak-XT). The electron transport layer material PDINN and the cathode material Ag were deposited using a vacuum evaporation apparatus (ZD-400), and their thicknesses and deposition rates were measured using a thin film deposition controller (SQC-310C). Except for ITO and PEDOT:PSS, the operation of the other functional layers was performed in a nitrogen-filled glove box. The current-voltage (JV) characteristic curves of the device were obtained using a semiconductor current-voltage source (Keithley-2420) at an analog light source intensity of AM 1.5 G, 100 mW / cm².2 (Newport, 100 Mw / cm) -2 The external quantum efficiency (EQE) of the device was obtained under a nitrogen atmosphere (with silicon-based cell correction); the external quantum efficiency (EQE) of the device was obtained using the solar cell spectral response measurement system QE-R3011 (Enli-Technology).

[0041] The specific fabrication process steps for the above-mentioned organic solar cell devices are as follows:

[0042] Step 1: Clean the indium tin oxide (ITO) conductive glass (substrate) with ITO cleaning solution, deionized water, acetone and isopropanol in sequence for 20 min, and then dry it in a vacuum drying oven at 80℃.

[0043] Step 2: Perform a 15-minute ultraviolet ozone plasma surface treatment on the substrate treated in Step 1. This treatment method utilizes the strong oxidizing properties of ozone generated under microwaves to clean residual organic matter on the ITO surface. At the same time, it can increase the oxygen vacancies on the ITO surface and improve the work function of the ITO surface.

[0044] Step 3: Spin-coat PEDOT:PSS aqueous solution onto the substrate treated in Step 2 at a speed of 2000-4000 rpm / min, preferably 3000 rpm / min, for 30 s, and anneal at 150°C for 15 min to a thickness of 30 nm.

[0045] Step 4: Spin-coat the active layer solution onto the substrate treated in Step 3. Dissolve the host donor material (D1), the third component guest donor material (D2), and the host acceptor material (A) in chloroform at a mass ratio of D1:D2:A of 1:0.05:1 (w / w). The total concentration of PM6 in the host donor material is 7 mg / mL. -1 The mixture was stirred at room temperature for 3 h. 0.25% of 1,8-diiodooctane (DIO) was added 30 min before spin-coating the active layer. The active layer solution was added dropwise at a speed of 1500–3000 rpm / min, preferably 2000 rpm / min, and spin-coated for 30 s to prepare an active layer blend film with a thickness of 100 nm.

[0046] Step 5: Spin-coat the cathode buffer layer solution onto the substrate treated in Step 4, with a concentration of 1.0–3.0 mg / mL. -1 A PDINN methanol solution, preferably 1.0 mg / mL. -1A PDINN methanol solution was added dropwise at a rotation speed of 2000–4000 rpm / min, preferably 3000 rpm / min, and deposited on the active layer for 30 s to a thickness of 10 nm.

[0047] Step 6: Place the substrate treated in Step 5 onto the mask template and evacuate it to 3×10⁻⁶ in the vacuum chamber. -4 Pa, vapor-deposited cathode Ag, with a thickness of 100 nm.

[0048] In this invention, the preparation methods are all conventional unless otherwise specified. Unless otherwise specified, the raw materials used can be obtained from publicly available commercial sources.

[0049] Example 1: Preparation of dithiophenecyclohexanedione donor material BDD-Rh-1

[0050] The synthetic route of the thienocyclohexanedione donor material BDD-Rh-1 of this invention is as follows:

[0051] Synthesis of Compound 3

[0052] In a 100 mL double-necked round-bottom flask, compound 1 (1 g, 1.66 mmol), compound 2 (1.49 g, 4.15 mmol), Pd2(dba)3 (75 mg, 0.08 mmol), tris(o-tolyl)phosphine (100 mg, 0.33 mmol), and toluene (20 mL) were added. A nitrogen gas reservoir was connected, and the reaction mixture was evacuated to remove air from the flask. The mixture was then stirred under reflux for 1 h under N2 protection. After cooling, the reaction mixture was poured into water (150 mL) and extracted three times with CH2Cl2 (40 mL). The organic phases were combined, dried, and filtered off the desiccant. The organic solvent was removed under reduced pressure, and the residue was purified by column chromatography using PE as the eluent to give 1.20 g of a yellow oily substance containing compound 3, with a yield of 87%. 1 H NMR (500 MHz, CDCl3) δ 7.21 (d, J = 1.6Hz, 1H), 6.59 (d, J = 1.8 Hz, 1H), 2.85–2.71 (m, 2H), 2.60 (dd, J = 7.9, 2.0Hz, 2H), 1.78–1.67 (m, 2H), 1.42–1.24 (m, 16H), 0.90 (t, J = 7.1 Hz, 12H).

[0053] Synthesis of Compound 4

[0054] In a 100 mL double-necked round-bottom flask, compound 3 (1 g, 1.20 mmol) was added and dissolved in 15 mL of anhydrous THF. A nitrogen gas bag was connected, and the flask was evacuated to remove air. The flask was then cooled to -78°C in a cryogenic bath. LDA (1.50 mL, 2 M) was slowly added to the flask, and the mixture was stirred for 2 h. Then, Me3SnCl (3.60 mL, 1 M) was added, and the mixture was allowed to rise to room temperature for another 10 h. The reaction was quenched by injecting 10 mL of water into the flask, and the reaction mixture was poured into 150 mL of water. The mixture was extracted three times with CH2Cl2 (40 mL), and the organic phases were combined, dried, filtered, and the organic solvent was removed under reduced pressure to obtain 1.25 g of a yellow viscous liquid containing compound 4, with a yield of 90%, requiring no further purification. 1 H NMR (500 MHz, CDCl3) δ 2.86-2.71 (m, 1H), 1.78-1.64 (m, 1H), 1.41-1.33 (m, 1H), 1.35-1.31 (m, 1H), 1.31(s, 1H), 1.31 (d, J = 3.1 Hz, 2H), 1.31-1.25 (m, 1H), 0.93-0.85 (m, 8H).

[0055] Synthesis of Compound 7

[0056] In a 100 mL double-necked round-bottom flask, compound 5 (500 mg, 1.85 mmol), compound 6 (1.14 g, 4.63 mmol), Pd2(dba)3 (85 mg, 0.09 mmol), tris(o-tolyl)phosphine (109 mg, 0.36 mmol), and toluene (15 mL) were added. A nitrogen gas reservoir was connected, and the reaction mixture was evacuated to remove air from the flask. The mixture was then refluxed and stirred for 2 h under N2 protection. After cooling, the reaction mixture was poured into water (150 mL) and extracted three times with CH2Cl2 (40 mL). The combined and dried organic phases were filtered off. The organic solvent was removed under reduced pressure, and the mixture was purified by column chromatography using PE as the eluent to give compound 7 as a white solid, 473 mg, with a yield of 92%. 1 H NMR (500 MHz, CDCl3) δ 7.45 (dd, J = 5.0, 1.7 Hz,1H), 7.37 (dd, J = 8.0, 5.0 Hz, 1H), 7.34-7.29 (m, 1H), 7.11 (dd, J = 6.1,5.0 Hz, 1H).

[0057] Synthesis of Compound 8

[0058] Compound 7 (450 mg, 1.62 mmol) was added to a 100 mL double-necked round-bottom flask and dissolved in 15 mL of anhydrous THF. A nitrogen gas reservoir was connected, and the flask was evacuated to remove air. The flask was then cooled to -78°C in a cryogenic bath. n-BuLi (0.97 mL, 2.5 M) was slowly added to the flask, and the mixture was stirred for 1 h. Then, DMF (220 mg, 0.30 mmol) was added, and the mixture was allowed to rise to room temperature for another 10 h. The reaction was quenched by injecting 10 mL of water into the flask, and the reaction solution was poured into 150 mL of water. After reacting for 15 min, the reaction solution was poured into water, acidified with concentrated HCl (5 mL), and extracted three times with CH2Cl2 (40 mL). The combined and dried organic phases were filtered off, the desiccant was removed under reduced pressure, and the organic solvent was removed. The mixture was purified by column chromatography to obtain 406 mg of compound 4 as a brown solid, with a yield of 82%. 1 H NMR (500 MHz, CDCl3) δ 9.88 (s, 1H), 7.79 (d,J = 6.5 Hz, 1H), 7.45 (dd, J = 5.0, 1.7 Hz, 1H), 7.44-7.39 (m, 2H), 7.37 (dd,J = 8.0, 5.0 Hz, 1H), 7.34-7.29 (m, 1H), 7.11 (dd, J = 6.1, 5.0 Hz, 1H).

[0059] Synthesis of Compound 9

[0060] In a 100 mL double-necked round-bottom flask, compound 8 (400 mg, 1.31 mmol) and THF (15 mL) were added. The mixture was cooled to 0°C, protected from light, and stirred. NBS (256 mg, 1.44 mmol) was then added. The mixture was stirred overnight at room temperature. The reaction solution was extracted three times with CH2Cl2 (40 mL). The extracts were combined, the organic phases were dried, and the desiccant was filtered off. The organic solvent was removed under reduced pressure, and the mixture was purified by column chromatography to give 480 mg of compound 9 as a dark brown solid, with a yield of 95%. 1 H NMR (500 MHz, CDCl3) δ 9.88 (s, 1H), 7.79 (d, J = 6.5 Hz, 1H), 7.44-7.37 (m, 3H), 7.14 (d, J = 6.8 Hz, 1H), 7.05 (dd, J = 6.8, 2.0 Hz, 1H).

[0061] Synthesis of Compound 10

[0062] In a 100 mL double-necked round-bottom flask, compound 4 (645 mg, 0.56 mmol), compound 9 (450 mg, 1.17 mmol), Pd2(dba)3 (27 mg, 0.03 mmol), tris(o-tolyl)phosphine (36 mg, 0.12 mmol), and toluene (20 mL) were added. A nitrogen gas reservoir was connected, and the reaction mixture was evacuated to purge the air from the flask. The mixture was then stirred under reflux for 2 h under N2 protection. After cooling, the reaction mixture was poured into water (150 mL) and extracted three times with CH2Cl2 (40 mL). The combined and dried organic phases were filtered off. The organic solvent was removed under reduced pressure, and the mixture was purified by column chromatography to give 702 mg of compound 10 as a red solid, with a yield of 87%. 1 H NMR (500 MHz, CDCl3) δ 9.88 (s, 1H), 7.79 (d, J = 6.6 Hz,1H), 7.45- 7.34 (m, 3H), 7.23-7.04 (m, 3H), 2.88-2.60 (m, 4H), 1.76-1.67 (m,2H), 1.39-1.25 (m, 16H), 0.90 (t, J = 7.1 Hz, 12H).

[0063] Synthesis of BDD-Rh-1

[0064] In a 100 mL double-necked round-bottom flask, compound 10 (300 mg, 0.208 mmol), compound 11 (1.0 g, 5.20 mmol), triethylamine (211 mg, 2.08 mmol), and 15 mL of chloroform were added. A nitrogen atmosphere was connected, and the reaction was carried out at 60°C under nitrogen protection for 12 h. After cooling, the reaction mixture was poured into anhydrous MeOH (200 mL), forming a purple-red solid precipitate. The precipitate was filtered, and then purified by column chromatography using CH₂Cl₂ as the eluent to obtain 242 mg of the purple-red solid BDD-Rh-1, with a yield of 65%. 1H NMR (500 MHz, CDCl3) δ 7.85 (s, 1H), 7.45-7.38 (m, 2H), 7.38 (dd,J = 8.0, 5.0 Hz, 1H), 7.29 (dd, J = 6.8, 2.0 Hz, 1H), 7.21 (dd, J = 6.4, 2.0Hz, 1H), 7.08 (d, J = 6.4 Hz, 1H), 3.92 (q, J = 8.0 Hz, 2H), 2.83 (dd, J =14.7, 7.0 Hz, 1H), 2.75 (dd, J = 14.7, 7.1 Hz, 1H), 2.67 (d, J = 7.8 Hz, 1H),1.78-1.65 (m, 2H), 1.40-1.24 (m, 19H), 0.93-0.87 (m, 12H).

[0065] The product's 1H NMR spectrum is as follows Figure 1 As shown.

[0066] Example 2: Theoretical calculations for the dithiophenecyclohexanedione donor material BDD-Rh-1

[0067] Using Gaussian 09W software with B3LYP / 6-31G* as the basis set, density functional theory (DFT) simulations were performed to calculate the optimal molecular configuration, frontier orbital energy levels, and surface electrostatic potential of BDD-Rh-1. The calculation results are as follows: Figure 2 As shown, the BDD-Rh-1 molecular units exhibit a small twist angle, displaying a nearly linear side view and good planarity. This planarity is conducive to ordered molecular stacking and π-conjugation extension through the molecular skeleton, enhancing the planarity of the aggregated state and the tightness of molecular packing, thereby strengthening intramolecular charge transport and photostability. Geometric optimization yielded a near-planar structure of the small molecule, and the dipole moment of BDD-Rh-1 was calculated to be 1.66 D. The magnitude of the dipole moment reflects the strength of the interaction between adjacent molecules, indicating that BDD-Rh-1 has strong intermolecular interactions and readily forms tight intermolecular packing. From the electron cloud distribution of the frontier molecular orbitals (HOMO and LUMO), it can be seen that the HOMO of BDD-Rh-1 is mainly distributed on the thiophene ring and the BDD group, while the LUMO is uniformly distributed on the trunk and ends, indicating that the HOMO energy level of BDD-Rh-1 is mainly regulated by the central electron-withdrawing unit.

[0068] Example 3: UV-Vis absorption spectrum of dithiophenecyclohexanedione donor material BDD-Rh-1

[0069] Figure 3The donor material BDD-Rh-1 in Example 1 is shown in a dilute chloroform solution (10). -5 The normalized UV absorption spectra of the BDD-Rh-1 film in its thin film state and in relation to the normalized UV absorption spectra of PM6 and BTP-eC9 films in the ternary system were compared. The maximum absorption peak (560 nm) of the BDD-Rh-1 film showed a significant redshift compared to its solution absorption peak (496 nm), indicating strong π-π interactions in the thin film state. Figure 7a It is known that BDD-Rh-1 has an absorption range in the visible light region (450-700 nm), which is complementary to the PM6:BTP-eC9 system and helps to enhance the light absorption capacity of the photoactive layer.

[0070] Example 4: Electrochemical performance analysis of BDD-Rh-1, a dithiophenecyclohexanedione donor material

[0071] The dithiophenecyclohexanedione donor material BDD-Rh-1 from Example 1 was dissolved in dichloromethane. Cyclic voltammetry (CV) was performed using a CHI 620 voltammeter with a platinum wire as the working electrode, Ag / AgCl as the reference electrode, tetrabutylammonium hexafluorophosphonate (nBu4NPF6) acetonitrile solution (0.1 M) as the electrolyte, and ferrocene / ferrocene cations (Fc / Fc) as the electrolyte. + Using the redox couple as a reference, the cyclic voltammetry performance was tested at a scan rate of 50 mV / s. Figure 4 It can be seen that the measured ferrocene / ferrocene cation (Fc / Fc) + The oxidation potential of BDD-Rh-1 is 0.48 eV, and the calculated HOMO level is 5.26 eV, while the LUMO level is 3.57 eV. Figure 7b It can be seen that the energy levels of BDD-Rh-1 and PM6:BTP-eC9 system form a good cascade match.

[0072] Example 5: Thermogravimetric analysis of dithiophenecyclohexanedione donor material BDD-Rh-1

[0073] The dithiophenecyclohexanedione donor material BDD-Rh-1 from Example 1 was heated at a rate of 20 °C / min within the range of 30–600 °C under N2 protection, and its thermogravimetric curve was measured. Figure 5 It can be seen that the temperature at which BDD-Rh-1 loses 5 wt% of thermal decomposition is 382℃, indicating that the material has high thermal stability.

[0074] Example 6: Performance of organic solar cell devices using dithiophenecyclohexanedione donor material BDD-Rh-1

[0075] The dithiophenecyclohexanedione donor material BDD-Rh-1 from Example 1 was blended with PM6:BTP-eC9 in different proportions (mass ratio 1:1.2:X, X = 0, 0.05, 0.1). The active layer was prepared by spin coating with chloroform as solvent, and the resulting device had the structure ITO / PEDOT:PSS (30 nm) / PM6: BDD-Rh-1(X wt%):BTP-eC9 (100 nm) / PDINN (10 nm) / Ag (100 nm).

[0076] Table 1. Photovoltaic performance parameters of BDD-Rh-1 devices under different D / A ratios.

[0077] PM6:BDD-Rh-1:BTP-eC9 <![CDATA[V OC (V)]]> <![CDATA[J SC (mA cm -2 )]]> FF(%) PCE (%) 1:0:1.2 0.855 27.05 77.26 17.87 0.95:0.05:1.2 0.865 26.99 77.48 18.10 1:0.05:1.2 0.856 27.99 77.01 18.45 1.0:0.1:1.2 0.859 28.02 75.93 18.29

[0078] As shown in Table 1, the photovoltaic performance of the device reaches its optimal level when the BDD-Rh-1 doping ratio is X=0.05, and the open-circuit voltage (V) of the ternary device is [value missing]. OC ), short-circuit current density (J SC The fill factor (FF) and photoelectric conversion efficiency (PCE) of the system were significantly higher than those of the binary control system.

[0079] Based on this, morphology of the active layer was optimized by adding 0.25% 1,8-diiodooctane (DIO) as an additive. The current density-voltage (JV) curves and corresponding photovoltaic parameters of the device under optimal conditions are summarized in […]. Figure 7a And in Table 2. Under standard test conditions (AM 1.5, 100 mW / cm²), 2 The photovoltaic performance of the optimal PM6:BDD-Rh binary device prepared by testing is: V OC = 0.843 V, J SC = 27.77 mA / cm 2 FF = 79.81%, PCE = 18.68%. The photovoltaic performance of the optimal PM6:BDD-Rh:BTP-eC9 ternary device prepared by testing is: V OC = 0.849 V, J SC = 28.34 mA / cm 2 FF = 80.04%, PCE = 19.26%. Further optimization of the device performance was achieved by replacing PEDOT:PSS with 2PACZ as the hole transport material. The photovoltaic performance of the optimal PM6:BDD-Rh:BTP-eC9 ternary device was tested and found to be: V OC = 0.855 V, J SC =28.81 mA / cm 2, FF = 80.13%, PCE =19.75%.

[0080] Table 2. Photovoltaic performance parameters of binary and ternary devices under optimal conditions.

[0081] active layer <![CDATA[V OC (V)]]> <![CDATA[J SC (mA cm -2 )]]> FF(%) PCE (%) <![CDATA[ a) PM6:BTP-eC9]]> 0.843 27.77 79.81 18.68 <![CDATA[ a) PM6:BDD-Rh-1:BTP-eC9]]> 0.849 28.34 80.04 19.26 <![CDATA[ b) PM6:BDD-Rh-1:BTP-eC9]]> 0.855 28.81 80.13 19.75

[0082] a) PEDOT:PSS is a hole transport material; b) 2PACZ is a hole transport material.

[0083] Although the invention has been described in conjunction with preferred embodiments, the invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the invention. Guided by the inventive concept, those skilled in the art should recognize that any modifications made to the various embodiments of the invention will be covered by the spirit and scope of the claims.

Claims

1. A dithiophene-cyclohexanedione-based two-arm oligomer donor material, characterized in that, The oligomer donor material is constructed with dithiophenecyclohexanedione as the conjugated bridging center electron-withdrawing A unit, a triple monocyclic aromatic hydrocarbon as the arm B unit, and an alkylcyanorhodanine as the terminal electron-withdrawing A' unit, and has an A(B-A')2 type double-arm structure.

2. The dithiophene-cyclohexanedione double-arm oligomer donor material according to claim 1, characterized in that, The chemical structure of the A(B-A')2 type double-arm oligomer donor material is shown in formula (1): Equation (1) in, for , or Electron-deficient monocyclic aromatic hydrocarbons, with long-chain alkyl groups R having a C20 value. n H 2n+1 n = 8, 10, 12, 16, 20; short-chain alkyl group R1 is C n H 2n+1 n = 2, 4, 6.

3. The dithiophenecyclohexanedione-based two-arm oligomer donor material according to claim 1, characterized in that, The chemical structure of the A(B-A')2 type double-arm oligomer donor material is shown in formula (2): Equation (2).

4. The dithiophenecyclohexanedione double-arm oligomer donor material according to claim 1 or 2, characterized in that, The donor material was prepared and synthesized through Stille coupling reaction, tinning reaction, acylation reaction and condensation reaction.

5. The application of a dithiophenecyclohexanedione-based two-arm oligomer donor material according to claim 1 or 2, characterized in that, The donor material is used as the third component of the active layer to prepare an organic solar cell.

6. The application of the dithiophene-cyclohexanedione double-arm oligomer donor material according to claim 5, characterized in that, The organic solar cell device has an ITO / PEDOT:PSS / active layer / PDINN / Ag structure.

7. The application of the dithiophene-cyclohexanedione double-arm oligomer donor material according to claim 5, characterized in that, The host donor material of the active layer is the polymer donor material PM6, the guest donor material is the dithiophenecyclohexanedione two-arm oligomer donor material BDD-Rh according to claim 1 or 2, and the host acceptor material is the small molecule acceptor material Y6, BTP-eC9 or L8-BO.

8. The application of the dithiophene-cyclohexanedione double-arm oligomer donor material according to claim 7, characterized in that, The doping ratio of oligomer donor material in the active layer is 5 wt%-20 wt% of the mass of the host donor material.

9. The application of the dithiophene-cyclohexanedione double-arm oligomer donor material according to claim 7, characterized in that, The mass ratio of the host donor material to the host acceptor material in the active layer is 1:1 to 1.5.

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