A low melting temperature solid additive containing mesogens and its preparation method and application

Abstract

The present invention belongs to the field of semiconductor material technology, and specifically relates to a low melting temperature solid additive containing a mesogen, and its preparation method and application. The present invention uses a derivative of biphenol and 1,8-dibromooctane as the main raw materials, and obtains a solid additive material with a low melting temperature through organic synthesis, and is applied in high-efficiency organic solar cell devices. Experiments show that the low melting temperature solid additive provided by the present invention can significantly improve device performance in organic solar cell devices, achieving a photoelectric conversion efficiency far exceeding that of additive-free binary organic solar cells, and the device stability is also significantly improved, with broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor materials, and in particular relates to a low melting temperature solid additive containing mesogens, a preparation method and an application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Organic solar cells (OSCs) are considered one of the most promising photovoltaic technologies due to their unique properties, such as lightweight, semitransparency, and flexibility, demonstrating enormous potential for practical applications. Advances in materials design and device engineering have enabled single-junction organic solar cell devices to achieve power conversion efficiencies (PCEs) exceeding 19%. The nanoscale morphology of binary or multi-element active layers, composed of polymer donors and non-fullerene small molecule acceptors, plays a crucial role in charge generation and transport, as well as in suppressing charge recombination. To achieve the desired active layer morphology with appropriate domain size and molecular orientation, adding a small amount of a suitable solvent additive, such as 1,8-diiodooctane (DIO), diphenyl ether (DPE), and 1-chloronaphthalene (1-CN), to the main solvent is considered one of the most effective approaches. Solvent additives, with higher boiling points than the main solvent, can promote precise distribution and separation of donor and acceptor materials, facilitating optimal phase separation during film formation. However, due to the high boiling points of solvent additives, even small amounts of residual additives can disrupt the desired morphology of the photoactive layer, leading to additional recombination energy losses and reducing device fabrication reproducibility and long-term stability. Therefore, it is crucial and urgent to address the above shortcomings while ensuring optimal morphology control.

[0004] Liquid crystal molecules possess the properties of both crystals and liquids, exhibiting the fluidity of liquids while maintaining anisotropy and ordered aggregation. Below the phase transition temperature, they exhibit strong self-assembly properties. For example, the BTR series of small molecule donor materials contain benzodithiophene, terthiophene, and rhodamine, and when used as the third component in the preparation of ternary devices, they are widely considered to be highly efficient nematic liquid crystals. However, it should be noted that the phase transition temperature of BTR is generally too high (approximately 160-230°C, much higher than the thermal annealing temperature of the active layer), which limits some of its key liquid crystal properties.

[0005] Therefore, how to synthesize a solid additive with a low melting temperature so that it exhibits the characteristics of a liquid additive during processing while maintaining a solid state during device operation, thereby achieving the dual goals of optimizing the active layer morphology and improving device stability, is an urgent problem to be solved by technical personnel in this field. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention provides a low-melting-temperature solid additive containing mesogens, a preparation method thereof, and an application thereof. The additive material prepared by the present invention is simple to synthesize, low in cost, and has a low melting temperature. It is applied to organic solar cell devices. By adjusting the incorporation ratio, a photoelectric conversion efficiency of 18.3% can be achieved, and the ideal photoelectric conversion efficiency can still be maintained after a long period of storage.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The first aspect of the present invention provides a compound having a structure represented by Formula I or a pharmaceutically acceptable salt, solvate, or hydrate thereof:

[0009] Formula I;

[0010] Wherein, R is selected from one of cyano, alkoxy and formate groups.

[0011] The second aspect of the present invention provides a low melting temperature solid additive containing a mesogen, wherein the low melting temperature solid additive comprises the compound described in the first aspect.

[0012] The third aspect of the present invention provides a method for preparing the compound described in the first aspect, specifically comprising: mixing 1,8-dibromooctane, compound 1 and potassium carbonate in an organic solvent, and heating the mixture to react.

[0013] Preferably, the molar ratio of the 1,8-dibromooctane, compound 1 and potassium carbonate is 7-9:1:7-9; preferably 8:1:8; the compound 1 is , R is selected from one of cyano, alkoxy and formate groups.

[0014] Preferably, the organic solvent is selected from one or more of acetone and N,N-dimethylformamide, preferably acetone.

[0015] Preferably, the temperature of the heating reaction is 50-70° C., and the time is 8-12 h; further preferably, the temperature of the heating reaction is 60° C., and the time is 10 h.

[0016] Preferably, the heating reaction is carried out under an inert atmosphere; further preferably, the inert atmosphere is selected from one or more of hydrogen, argon and nitrogen.

[0017] Preferably, after the heating reaction is completed, the mixture is washed with saturated brine, extracted with an organic solvent, and then the organic solvent is removed by rotary evaporation. The product is then purified using a gel chromatography column to obtain a low melting temperature solid additive containing mesogenic units.

[0018] Further preferably, the organic solvent used in the extraction is selected from one of dichloromethane, ethyl acetate and chloroform, preferably dichloromethane; and the eluent used in the gel chromatography column purification is a petroleum ether / dichloromethane elution system with a volume ratio of 3:1.

[0019] The fourth aspect of the present invention provides a use of the compound described in the first aspect, the low melting temperature solid additive containing mesogens described in the second aspect, and / or the compound prepared by the preparation method described in the third aspect in an organic solar cell.

[0020] A fifth aspect of the present invention provides a method for preparing a photoactive layer of an organic solar cell, comprising: mixing the compound described in the first aspect, the low melting temperature solid additive containing mesogens described in the second aspect, and / or the compound prepared by the preparation method described in the third aspect with an electron donor material, an electron acceptor material, and a solvent to obtain a blend; and using the blend to prepare the photoactive layer of the organic solar cell.

[0021] Preferably, the mass ratio of the compound to the electron acceptor material is 0.1-0.3:1, preferably 0.2:1; the mass ratio of the electron donor material to the electron acceptor material is 1:1-2, preferably 1:1.2.

[0022] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0023] (1) The present invention uses a biphenol derivative and 1,8-dibromooctane as the main raw materials, and through organic synthesis, obtains a solid additive material with a low melting temperature, which is applied in high-efficiency organic solar cell devices. Experiments show that the low melting temperature solid additive provided by the present invention can significantly improve the device performance in organic solar cell devices, achieving a photoelectric conversion efficiency far exceeding that of additive-free binary organic solar cells, and the device stability is also significantly improved.

[0024] (2) The synthesis method of the present invention is simple, efficient, reproducible, low-cost, universal, and easy to scale up for production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a hydrogen nuclear magnetic resonance spectrum of the low melting temperature solid additive material CB8-Br prepared in Example 1 of the present invention;

[0027] Figure 2 These are performance test diagrams of the organic solar cell device prepared in Experimental Example 1 of the present invention, wherein (a) is a JV curve diagram and (b) is an external quantum efficiency diagram;

[0028] Figure 3 Performance test graphs of organic solar cell devices containing different amounts of additive CB8-Br prepared in Experimental Examples 1 to 3 of the present invention, wherein (a) is a JV curve graph and (b) is a device stability test curve;

[0029] Figure 4 These are performance test diagrams of the organic solar cell device prepared in Experimental Example 4 of the present invention, wherein (a) is a JV curve diagram and (b) is an external quantum efficiency diagram;

[0030] Figure 5 These are analysis graphs of the optical and electrical properties of the low-melting-temperature solid additive material CB8-Br prepared in Example 1 of the present invention; wherein, (a) is a UV-visible absorption comparison spectrum of the CB8-Br solution and the film, (b) is a UV-visible absorption comparison spectrum before and after the addition of the additive to the active layer of an organic solar cell, (c) is a cyclic voltammetry curve of CB8-Br, and (d) is a differential scanning calorimetry analysis curve of CB8-Br. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0032] The first typical embodiment of the present invention provides a compound having a structure represented by Formula I or a pharmaceutically acceptable salt, solvate, and hydrate thereof:

[0033] Formula I;

[0034] Wherein, R is selected from one of cyano, alkoxy and formate groups.

[0035] A second typical embodiment of the present invention provides a low melting temperature solid additive containing a mesogen, wherein the low melting temperature solid additive comprises the above-mentioned compound.

[0036] A third typical embodiment of the present invention provides a method for preparing the above-mentioned compound, specifically comprising: mixing 1,8-dibromooctane, compound 1 and potassium carbonate in an organic solvent, and heating the mixture to react to obtain the compound.

[0037] In one or more examples of this embodiment, the molar ratio of 1,8-dibromooctane, compound 1 and potassium carbonate is 7-9:1:7-9; preferably 8:1:8; the compound 1 is , R is selected from one of cyano, alkoxy and formate groups.

[0038] In one or more examples of this embodiment, the organic solvent is selected from one or more of acetone and N,N-dimethylformamide, preferably acetone.

[0039] In one or more examples of this embodiment, the temperature of the heating reaction is 50-70° C., and the time is 8-12 h; more preferably, the temperature of the heating reaction is 60° C., and the time is 10 h.

[0040] In one or more examples of this embodiment, the heating reaction is carried out under an inert atmosphere; further preferably, the inert atmosphere is selected from one or more of hydrogen, argon, and nitrogen.

[0041] In one or more examples of this embodiment, after the heating reaction is completed, the product is washed with saturated brine, extracted with an organic solvent, and then the organic solvent is removed by rotary evaporation. The product is then purified using a gel chromatography column to obtain a low melting temperature solid additive containing a mesogenic unit.

[0042] In one or more examples of this embodiment, the organic solvent used for the extraction is selected from one of dichloromethane, ethyl acetate and chloroform, preferably dichloromethane; and the eluent used for the gel chromatography column purification is a petroleum ether / dichloromethane elution system with a volume ratio of 3:1.

[0043] A fourth typical embodiment of the present invention provides use of the above-mentioned compound, the low melting temperature solid additive containing a mesogen, and / or the compound prepared by the above-mentioned preparation method in an organic solar cell.

[0044] A fifth typical embodiment of the present invention provides a method for preparing a photoactive layer of an organic solar cell, comprising: mixing the above-mentioned compound, a low melting temperature solid additive containing a mesogen and / or a compound prepared by the above-mentioned preparation method with an electron donor material, an electron acceptor material and a solvent to obtain a blend; and using the blend to prepare the photoactive layer of the organic solar cell.

[0045] In one or more examples of this embodiment, the mass ratio of the compound to the electron acceptor material is 0.1-0.3:1, preferably 0.2:1; the mass ratio of the electron donor material to the electron acceptor material is 1:1-2, preferably 1:1.2.

[0046] The present invention will be further described in detail below with reference to specific embodiments. It should be noted that the specific embodiments are intended to explain the present invention rather than to limit it.

[0047] Example 1 :This embodiment provides a low melting temperature solid additive material CB8-Br

[0048] The synthesis method is as follows:

[0049]

[0050] Specifically comprising the following synthesis steps:

[0051] 4'-Cyano-4-hydroxybiphenyl (0.5 g, 2.56 mmol, 1.0 eq) and 1,8-dibromooctane (5.57 g, 20.48 mmol, 8.0 eq) were added sequentially to a two-necked reaction flask. Potassium carbonate (2.83 g, 20.48 mmol, 8.0 eq) was added to provide an alkaline environment. Ultra-dry acetone was used as the solvent and the reaction was heated under reflux at 60°C under nitrogen for 10 h. After completion of the reaction, the mixture was washed with saturated brine and extracted three times with dichloromethane. The organic phases were combined, dried over anhydrous sodium sulfate, filtered, and the solvent was removed by rotary evaporation. The product was then separated and purified by column chromatography (petroleum ether:dichloromethane = 3:1) to obtain 0.86 g of the additive CB8-Br as a pale yellow solid in an 86.9% yield. 1 H NMR (400 MHz, CDCl3) δ 7.66 (dd, J = 21.0, 8.6 Hz, 4H), 7.53 (d, J = 8.8 Hz, 2H), 6.99 (d, J = 8.8 Hz, 2H), 4.01 (t, J = 6.5 Hz, 2H), 3.41 (t, J = 6.8 Hz, 2H), 1.92-1.77 (m, 4H), 1.52-1.34 (m, 8H). The specific H NMR spectrum is shown in Figure 2. Figure 1 shown.

[0052] Test Example 1 This experimental example provides the application of low melting temperature solid additive material CB8-Br in the preparation of organic solar cells

[0053] This experimental example uses a single-layer device structure of ITO / PEDO:PSS / photoactive layer / HPDIN-B02 / Ag, where ITO is a transparent conductive electrode, PEDOT:PSS is a hole transport layer, HPDIN-B02 is an electron transport layer, and the photoactive layer is composed of a blend of electron donor PM6 and electron acceptor L8-BO. ​​The additive CB8-Br is used in the preparation process of the photoactive layer film.

[0054] The structure of the donor material being PM6 and the acceptor material being L8-BO is shown below:

[0055]

[0056] The process of preparing organic solar cells using low melting temperature solid additive materials is as follows:

[0057] The device substrate, an ITO glass substrate, was cleaned and dried, then treated in a UV cleaner for 15 minutes before use. The hole transport layer (PEDOT:PSS) was then spin-coated onto the ITO substrate at 4000 rpm and annealed at 200°C for 15 minutes to form a uniform film. After annealing, the sample was transferred to a nitrogen glove box and the prepared photoactive layer solution was spin-coated onto the hole transport layer. The photoactive layer solution consisted of a blend of CB8-Br, PM6, and L8-BO dissolved in chloroform to a concentration of 15 mg / mL (PM6:L8-BO = 1:1.2, mass ratio). The CB8-Br additive was used at a concentration of 20% of the receptor mass. The spin coater was operated at 3000 rpm / min for 30 seconds, resulting in a photoactive layer thickness of 90 nm. The photoactive layer was annealed at 80°C for 5 minutes, and then an electron transport layer solution, HPDIN-B02 (2 mg / mL), was spin-coated at 3500 rpm. Finally, a 100 nm thick Ag electrode was evaporated to form an organic solar cell. Simultaneously, a control organic solar cell was prepared in parallel without adding solid additives when preparing the donor and acceptor blend solution.

[0058] In a nitrogen-filled glove box, a AAA-class solar simulator (AM 1.5G, 100 mW cm -2 ) irradiated on the prepared organic solar cell under the optimal conditions of the device (test area is 0.0289 cm 2 ) was used to test the voltage-current curve (JV curve of the device), and the parameters were measured as shown in Table 1.

[0059] Table 1

[0060]

[0061] As shown in Table 1, the photoelectric conversion efficiency of a single-cell organic solar cell device using PM6 and L8-BO as the photoactive layer is generally 16.59% without the use of additives. However, after the present invention uses CB8-Br as an additive, the photoelectric conversion efficiency of the organic solar cell device is 18.12%, reaching the world's leading level in this field, proving that this material has potential application value in organic solar cells.

[0062] Depend on Figure 2 As can be seen in Figure (a), compared with the PM6:L8-BO binary device without additives, after adding CB8-Br, although the open circuit voltage is reduced to a certain extent, the short circuit current density and fill factor are significantly improved, and the device efficiency is increased from 16.59% to 18.12%. In the external quantum efficiency diagram, the error between the short circuit current density value corrected by EQE and the device short circuit current value is within 95%, which also confirms the reliability of the short circuit current density (such as Figure 2 (as shown in Figure (b)).

[0063] Test Example 2 This experimental example provides the application of low melting temperature solid additive material CB8-Br in the preparation of organic solar cells

[0064] This experiment differs from Experiment 1 in that the additive CB8-Br is added at a concentration of 10% of the receptor mass. All other experimental conditions and testing procedures remain the same. Device test results show that the addition of 10% CB8-Br significantly increases the device's short-circuit current density and fill factor, as well as its photoelectric conversion efficiency. The measured parameters are shown in Table 2.

[0065] Table 2

[0066]

[0067] Test Example 3 This experimental example provides the application of low melting temperature solid additive material CB8-Br in the preparation of organic solar cells

[0068] This experiment differs from Experiment 1 in that the amount of the CB8-Br additive used is 40% of the acceptor mass. Other experimental conditions and testing procedures remain the same. Device test results show that after the addition of 40% CB8-Br, all device parameters drop sharply, with the photoelectric conversion efficiency dropping to less than 1%, indicating that the additive dosage exceeds the maximum value for device preparation. The measured parameters are shown in Table 3.

[0069] Table 3

[0070]

[0071] Test Example 4:This test example compares the performance of the organic solar cell devices prepared in Test Examples 1 to 3

[0072] from Figure 3 As can be seen in Figure (a), by adjusting the amount of additive CB8-Br added, gradually increasing it from 10% to 30% relative to the mass of the electron acceptor material, the photoelectric conversion efficiency of the device has a significant increase followed by a decrease, and the best photoelectric conversion efficiency is achieved when the introduction amount is 20%. Therefore, effective regulation of the performance of organic solar cell devices can be achieved.

[0073] from Figure 3 As can be seen from Figure (b), the battery device using CB8-Br (the amount of CB8-Br added is 20% of the acceptor mass) can still maintain more than 96% of the initial photoelectric conversion efficiency after more than 900 hours, showing excellent device stability.

[0074] Test Example 5 This experimental example provides the application of low melting temperature solid additive material CB8-Br in the preparation of organic solar cells

[0075] This experimental example uses a single-layer device structure of ITO / PEDO:PSS / photoactive layer / HPDIN-B02 / Ag, where ITO is a transparent conductive electrode, PEDOT:PSS is a hole transport layer, HPDIN-B02 is an electron transport layer, and the photoactive layer is composed of a blend of electron donor PM6 and electron acceptor BTP-eC9. The additive CB8-Br is used in the preparation process of the photoactive layer film.

[0076] Among them, the receptor material is BTP-eC9, and its structure is shown below:

[0077]

[0078] The process of preparing organic solar cells using low melting temperature solid additive materials is as follows:

[0079] The device substrate, ITO glass, was cleaned and dried, then treated in a UV cleaner for 15 minutes before use. The hole transport layer (PEDOT:PSS) was spin-coated onto the ITO substrate using a spin coater at 4000 rpm and annealed at 200°C for 15 minutes to form a uniform film. After annealing, the sample was transferred to a nitrogen glove box and the prepared photoactive layer solution was spin-coated onto the hole transport layer. The photoactive layer solution consisted of a blend of CB8-Br, PM6, and BTP-eC9 dissolved in chloroform to a concentration of 15 mg / mL (PM6:BTP-eC9 = 1:1.2, mass ratio). The amount of CB8-Br additive was 20% of the receptor mass. The spin coat was performed at 3500 rpm / min for 30 seconds, resulting in an active layer thickness of 90 nm. The active layer was annealed at 80°C for 5 minutes, followed by spin coating of the electron transport layer solution HPDIN-B02 (2 mg / mL) at 3500 rpm. Finally, a 100 nm thick Ag electrode was evaporated. Simultaneously, a control organic solar cell was prepared in parallel without adding solid additives when preparing the donor and acceptor blend solution.

[0080] In a nitrogen-filled glove box, a AAA-class solar simulator (AM 1.5G, 100 mW cm -2 ) irradiated on the prepared organic solar cell under the optimal conditions of the device (test area is 0.0289 cm 2 ) to test the voltage-current curve, and the measured parameters are shown in Table 4.

[0081] Table 4

[0082]

[0083] As shown in Table 4, the photoelectric conversion efficiency of a single-cell organic solar cell device with PM6 and BTP-eC9 as the photoactive layer is 17.18% without using additives. However, after using CB8-Br as an additive in the present invention, the photoelectric conversion efficiency of the organic solar cell device is 18.38%, reaching the world's leading level in this field.

[0084] Depend on Figure 4 As can be seen in Figure (a), compared with the PM6:BTP-eC9 binary device without additives, after adding CB8-Br, although the open circuit voltage is reduced to a certain extent, the short circuit current density and fill factor are significantly improved, and the device efficiency is increased from 17.18% to 18.38%. In the external quantum efficiency diagram, the error between the short circuit current density value corrected by EQE and the device short circuit current value is within 95%, which also confirms the reliability of the short circuit current density (such as Figure 4 (as shown in Figure (b)).

[0085] Test Example 6 :This experiment tests the optical and electrochemical properties of CB8-Br and PM6 and L8-BO blend films.

[0086] Depend on Figure 5 As can be seen from Figure (a), the absorption spectrum of CB8-Br solution is distributed in 250-340 nm, with the highest absorption peak at 298 nm, while its film absorption is red-shifted, with the maximum absorption peak at 308 nm (film preparation: using chloroform as solvent, a 15 mg / mL solution is prepared, and the solution is spin-coated on a quartz substrate at a rotation speed of 1500 rpm / min).

[0087] Depend on Figure 5 As can be seen in Figure (b), by comparing the UV-visible absorption spectra before and after the addition of the additive CB8-Br to the active layer of the organic solar cell, it can be found that after the addition of CB8-Br (the amount of CB8-Br added is 20% of the acceptor mass), the absorption of the photoactive layer film undergoes a significant overall red shift, and the absorption coefficient of the acceptor part also increases to a certain extent (650~900 nm). These are all conducive to the device obtaining a higher short-circuit current density and ultimately improving the photoelectric conversion efficiency (preparation of the photoactive layer film: using chloroform as the solvent, a 12 mg / mL solution is prepared, and it is spin-coated on a quartz substrate at a rotation speed of 2500 rpm / min).

[0088] Depend on Figure 5 As can be seen in Figure (c), the cyclic voltammetry curve shows that the highest unoccupied molecular orbital (HOMO) of CB8-Br is -5.93 eV, while the lowest occupied molecular orbital (LUMO) is -3.61 eV.

[0089] Depend on Figure 5 As can be seen from Figure (d) in the figure, the melting temperature of CB8-Br is 80.1℃ from the differential scanning calorimetry test analysis.

[0090] Currently, the active layer annealing temperature of most high-efficiency organic solar cells ranges from 80-100°C. In particular, the PM6:L8-BO and PM6:BTP-eC9 systems, which achieve PCEs exceeding 19%, have an annealing temperature of precisely 80°C. This means that during annealing, the CB8-Br-containing active layer optimizes the active layer morphology in liquid form. However, during normal device operation, the CB8-Br remains in the active layer as a solid, maintaining a stable active layer morphology and thus improving device stability.

[0091] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. Application of a compound in an organic solar cell, wherein the compound is The compound is used as a low melting temperature solid additive for organic solar cells.

2. A method for preparing a photoactive layer of an organic solar cell, characterized in that: The compound according to claim 1 is mixed with an electron donor material, an electron acceptor material and a solvent to obtain a blend; and the organic solar cell photoactive layer is prepared using the blend.

3. The method according to claim 2, characterized in that The mass ratio of the compound to the electron acceptor material is 0.1-0.3:1; the mass ratio of the electron donor material to the electron acceptor material is 1:1-2.

4. The method according to claim 3, characterized in that The mass ratio of the compound to the electron acceptor material is 0.2:1; the mass ratio of the electron donor material to the electron acceptor material is 1:1.2.

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