A class of flexible single-component block polymer materials, their preparation methods, and applications

Abstract

A class of flexible single-component block polymer materials, their preparation methods, and applications are disclosed. The molecular structure of the polymer material is as follows: First, a BDT-type polymer donor fragment and a polymer acceptor material PYHT fragment are synthesized; then, the polymer donor material PM6 fragment is transferred to the polymer acceptor material PYHT fragment using a syringe for further polymerization to obtain the material. The material of this invention, as a photoactive layer material, can achieve highly efficient photoelectric conversion in devices while simultaneously improving the mechanical properties of the active layer material.

Description

Technical Field

[0001] This invention belongs to the field of organic solar cell technology, and specifically relates to the synthesis of a class of flexible single-component block polymer materials with BDT-type polymer donors and Y-series acceptors and their application in organic solar cell devices. Background Technology

[0002] Organic photovoltaics (OPV) is an emerging technology with the feasibility of large-scale roll-to-roll manufacturing and advantages such as light weight, high flexibility, and low cost. Simultaneously, it has the potential for flexible wearable applications, enabling wider application in various scenarios including daily life and industrial production. In particular, the donor and acceptor in single-component organic solar cell materials are covalently linked, which can suppress gradual demixing between the donor and acceptor, providing a long-term stable nanophase morphology and showing great application potential. However, current single-component block polymer organic solar cell materials, due to their rigid polymer chains, lack good mechanical properties, often making it difficult to maintain stability under external forces. Therefore, solving the problem of rigid polymer chains is a crucial step towards industrialization and functionalization. The team led by Professor Yuan Jianyu from Soochow University, published in *Advanced Materials*, reported that *Enhanced Intramolecular Hole Transfer in Block Copolymer Enables >15% and Operational Stable Single-Material–Organic Solar Cells* represent the highest photoelectric conversion efficiency (PCE) of single-component block polymers to date, with a PCE of 15.02%. The team led by Professor Yan Han from Xi'an Jiaotong University, published in *Energy & Environmental Science*, reported that *Towards efficient and stable organic solar cells: fixing the morphology problem in block copolymer active layers with synergistic strategies supported by interpretable machine learning*, achieved a PCE of 15.9% by adding small-molecule additives to single-component block polymers. Currently, regardless of whether additives are added or not, the rigidity and poor mechanical flexibility of block polymers pose a significant obstacle to industrial applications. Summary of the Invention

[0003] The purpose of this invention is to address the problems existing in the prior art by providing a class of flexible single-component block polymer materials, their preparation methods, and applications. This class of materials consists of flexible single-component block polymer materials with BDT-type polymer donors and Y-series acceptors. Specifically, flexible chains are introduced into the acceptor portion of the single-component material, replacing the rigid thiophene units. This improves the tensile properties of the polymer chains, solving the problem of easy breakage under external force due to rigid connections. Furthermore, high-efficiency organic solar cells can be obtained through simple solution processing.

[0004] The present invention describes a class of flexible single-component block polymer materials having the following molecular structure:

[0005]

[0006] Where X is a H atom or a halogen atom, R1 and R2 are alkyl chains, and a represents the length of the flexible chain.

[0007] The flexible single-component block polymer material described in this invention also includes its derivatives.

[0008] The preparation method of a class of flexible single-component block polymer materials described in this invention comprises the following steps (taking PM6-b-PYHT as an example):

[0009] (1) Synthesis of BDT-type polymer donor fragments: The raw materials BDT-2F and BDD-2Br were polymerized in toluene to obtain the polymer donor fragment PM6.

[0010] (2) Synthesis of polymer receptor material PYHT fragment: The raw materials 2,5-bis(trimethyltinyl)thiophene, 1,6-bis(5-(trimethyltinyl)thiophene)hexyl and Y5-2Br were polymerized in toluene to obtain the polymer receptor PYHT fragment.

[0011] (3) Synthesis of flexible single-component block polymer material PM6-b-PYHT: The obtained polymer donor material PM6 fragment was transferred to the reaction tube of polymer acceptor material PYHT fragment using a syringe, and polymerization was continued to initially obtain flexible single-component block polymer material PM6-b-PYHT. The mixture was precipitated with methanol, filtered, and extracted successively with solvents n-hexane, acetone, dichloromethane, and trichloromethane. Then, it was filtered through a silica gel column, concentrated, precipitated, and filtered to obtain the final product, flexible single-component block polymer material PM6-b-PYHT.

[0012] Its molecular structure is as follows:

[0013]

[0014] The present invention describes the application of a type of flexible single-component block polymer material as a photoactive layer material in the fabrication of polymer single-component organic solar energy devices.

[0015] Furthermore, the polymer single-component organic solar cell device of the present invention includes an indium tin oxide (ITO) conductive glass anode, an anode modification layer, a photoactive layer, a cathode modification layer, and a cathode. The anode modification layer is PEDOT / PSS (30 nm); the cathode modification layer is PF3N (30 nm); the cathode is an Ag (100 nm) deposition layer; and the active layer material is the flexible single-component material described in this invention.

[0016] This invention improves tensile properties by modifying the connecting units of the polymer chain. Flexible chains replace thiophene units in the material, achieving a transformation from rigid to flexible connections. Since only the acceptor portion is affected, the bulk material remains largely unchanged, and the synthesis process is not overly complex. Simultaneously, the covalent bonds within the material enhance stability and electrical conductivity. Most importantly, the introduction of flexible groups significantly improves the material's mechanical properties, providing better resistance to external forces, which is of great practical significance for achieving large-area wearable applications. The introduction of flexible chain connections results in better mechanical flexibility than the original rigid thiophene group connections.

[0017] Compared with currently reported materials, the flexible single-component block polymer material of this invention has the following characteristics: (1) It connects the polymer donor material and the polymer acceptor material through covalent bonds, achieving effective exciton dissociation and charge generation; (2) The covalent connection of the donor and acceptor parts into one material makes the processing of organic solar energy devices simpler; (3) Due to the covalent connection of the donor and acceptor parts, it can better resist the deterioration of the active layer morphology during device aging, resulting in better device stability; (4) The acceptance part introduces flexible groups, and the single-component material has better mechanical properties than the original rigid material, making it better suited for the fabrication of wearable organic solar cells. Therefore, this type of material is a single-component organic solar energy material with great development prospects and application potential.

[0018] The flexible single-component block polymer material described in this invention is used as a photoactive layer material to prepare single-component organic solar energy devices, thereby achieving efficient photoelectric conversion of the devices and improving the mechanical properties of the active layer material. Attached Figure Description

[0019] Figure 1 The UV-Vis absorption spectrum of the PM6-b-PYIT solid film is shown.

[0020] Figure 2 This is the UV-Vis absorption spectrum of the PM6-b-PYHT solid film of the present invention.

[0021] Figure 3 The cyclic voltammetry curves for the PM6-b-PYIT solid membrane are shown.

[0022] Figure 4 This is the cyclic voltammetry curve of the PM6-b-PYHT solid membrane of the present invention.

[0023] Figure 5 The JV curve is for a PM6-b-PYIT monocomponent solar cell device.

[0024] Figure 6 This is the JV curve of the PM6-b-PYHT single-component solar cell device of the present invention.

[0025] Figure 7 The tensile stress-strain curve of PM6-b-PYIT film.

[0026] Figure 8 This is the tensile stress-strain curve of the PM6-b-PYHT film of the present invention. Detailed Implementation

[0027] The present invention will be further described below through specific embodiments, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0028] Example 1

[0029] Taking PM6-b-PYHT as an example, the preparation method of a type of flexible single-component block polymer material described in this embodiment is as follows.

[0030] 1.1 Synthesis of flexible polymer receptor fragments.

[0031] In a 25 mL reaction tube, Y5-2Br (60 mg, 0.0320 mmol), 2,5-bis(trimethyltinyl)thiophene (11.8 mg, 0.0288 mmol), 1,6-bis(5-(trimethyltinyl)thiophene)hexyl (1.8 mg, 0.0032 mmol), tris(dibenzylacetone)palladium (0.59 mg, 0.00064 mmol), tris(o-methylphenyl)phosphine (0.78 g, 0.00256 mmol), and toluene (2 mL) were added sequentially. The mixture was stirred and refluxed in an oil bath at 110 °C for 5 h under nitrogen protection.

[0032] The synthesis route is as follows:

[0033]

[0034] 1.2 Synthesis of polymer donor fragments.

[0035] In a 10 mL reaction tube, BDT-2F (27.1 mg, 0.0288 mmol), BDD-2Br (22.1 mg, 0.0288 mmol), tetrakis(triphenylphosphine)palladium (3.7 g, 0.00317 mmol), and toluene (3 mL) were added sequentially. The mixture was stirred and refluxed in an oil bath at 110 °C for 3 h under nitrogen protection.

[0036] The synthesis route is as follows:

[0037]

[0038] 1.3 Synthesis of flexible single components.

[0039] After the synthesis of the donor and acceptor fragments, the donor fragment was aspirated and injected into the polymer acceptor reaction tube using a syringe. The reaction was then continued under stirring and reflux in an oil bath at 110 °C for 24 h. After the reaction was completed, the polymer was injected into methanol for precipitation, filtered, and extracted successively with n-hexane, acetone, and dichloromethane, and finally with chloroform. The chloroform extract was collected, and most of the solvent was evaporated under reduced pressure.

[0040] The molecular structure of the product is as follows:

[0041]

[0042] Example 2

[0043] Performance characterization of flexible single-component materials and fabrication and testing of photovoltaic devices.

[0044] The UV-Vis absorption spectra of the flexible single-component material were measured using an HP-8453 UV-Vis spectrometer.

[0045] Organic solar cell devices based on flexible single-component materials include: an indium tin oxide (ITO) conductive glass anode, an anode modification layer, a photoactive layer, a cathode modification layer, and a cathode. The anode modification layer is PEDOT / PSS (30 nm); the cathode modification layer is PF3N (30 nm); and the cathode is an Ag (100 nm) deposition layer. The active layer material is PM6-b-PYIT or the flexible single-component block polymer material PM6-b-PYHT described in this invention.

[0046] Example 3

[0047] Photophysical properties of PM6-b-PYHT and performance testing of its single-component organic solar cell device.

[0048] The UV absorption spectrum of PM6-b-PYIT in a solid hybrid film is as follows: Figure 1As shown, the absorption of PM6-b-PYIT is mainly distributed between 400 nm-660 nm and 700 nm-830 nm, with a donor absorption peak at 625 nm and an acceptor absorption peak at 808 nm. The UV absorption spectrum of PM6-b-PYHT in solid films is shown below. Figure 2 As shown, the absorption of PM6-b-PYHT is mainly distributed between 400-660 nm and 700-830 nm, with a donor absorption peak at 626 nm and an acceptor absorption peak at 806 nm.

[0049] The cyclic voltammetric curve of PM6-b-PYIT in a solid membrane is shown below. Figure 3 As shown, reversible oxidation and reduction peaks are observed, according to the calculation formula E. HOMO = -(E ox + 4.40) eV, yielding its HOMO energy level of -5.61 eV; according to the calculation formula E LUMO = - (E red From the given information, we can derive their LUMO energy levels as -3.51 eV. Therefore, the electrochemical band gap of PM6-b-PYIT is calculated to be 2.10 eV.

[0050] The cyclic voltammetry curve of PM6-b-PYHT in a solid membrane is shown below. Figure 4 As shown, reversible oxidation and reduction peaks are observed, according to the calculation formula E. HOMO = -(E ox + 4.40) eV, yielding its HOMO energy level of -5.62 eV; according to the calculation formula E LUMO = - (E red +4.40) eV, yielding their LUMO energy levels of -3.54 eV. Based on this, the electrochemical band gap of PM6-b-PYHT is calculated to be 2.08 eV, which is similar to that of PM6-b-PYIT.

[0051] The JV curve of the PM6-b-PYIT photovoltaic device is as follows: Figure 5 As shown, the PM6-b-PYIT device exhibits good photovoltaic performance, with an open-circuit voltage of 0.921 V and a short-circuit current of 23.77 mA cm⁻¹. -2 The fill factor is 66.20%, and the photoelectric conversion efficiency (PCE) is 14.51%. The JV curve of the PM6-b-PYHT photovoltaic device is shown below. Figure 6 As shown, the PM6-b-PYHT device exhibits good photovoltaic performance, with an open-circuit voltage of 0.920 V and a short-circuit current of 24.29 mA cm⁻¹. -2The fill factor is 63.82%, and the photoelectric conversion efficiency (PCE) is 14.26%.

[0052] The tensile stress-strain curve of PM6-b-PYIT film is shown below. Figure 7 As shown, the PM6-b-PYIT film fractured when the deformation reached 8.53% under tensile stress, while the PM6-b-PYHT film fractured when the deformation reached 14.56% (as shown in the figure). Figure 8 Fracture only occurred when (as shown in the image). This demonstrates that replacing rigid units with flexible units significantly improves the mechanical tensile properties of single-component organic solar cell materials.

[0053] 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 embodiments of the invention will be covered by the spirit and scope of the claims.

Claims

1. A class of flexible single component block polymer materials characterized by It has the following molecular structure: Where X is a H atom or a halogen atom, R1 and R2 are alkyl chains, a represents the length of the flexible chain, m≠0, n≠1.

2. A method of making a class of flexible, single-component block polymer materials, characterized by Follow these steps: (1) Synthesis of BDT-based polymer donor fragments: The raw materials BDT-2F and BDD-2Br were polymerized in toluene to obtain the polymer donor fragment PM6; (2) Synthesis of polymer receptor material PYHT fragment: 2,5-bis(trimethyltinyl)thiophene, 1,6-bis(5-(trimethyltinyl)thiophene)hexyl and Y5-2Br were polymerized in toluene to obtain polymer receptor PYHT fragment; (3) Synthesis of flexible single-component block polymer material PM6-b-PYHT: The obtained polymer donor PM6 fragment was transferred to the reaction tube of polymer acceptor PYHT fragment using a syringe, and polymerization was continued to initially obtain flexible single-component block polymer material PM6-b-PYHT; it was precipitated with methanol, filtered, and extracted successively with solvents n-hexane, acetone, dichloromethane, and trichloromethane, then passed through a silica gel column, and finally concentrated, precipitated, and filtered to obtain flexible single-component block polymer material PM6-b-PYHT, the molecular structure of which is as follows: Where m≠0, n≠0.

3. The application of the flexible single-component block polymer material described in claim 1 as a photoactive layer material in the fabrication of polymer single-component organic solar energy devices.

4. Use according to claim 3, characterized in that The polymer-based single-component organic solar energy device includes an indium tin oxide conductive glass anode, an anode modification layer, a photoactive layer, a cathode modification layer, and a cathode. The anode modification layer is PEDOT / PSS; the cathode modification layer is PF3N; the cathode is an Ag deposition layer; and the active layer material is the flexible single-component block polymer material described above.

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