An inorganic hole transport material based on vanadium-based complex and its preparation method and application

Abstract

The present invention relates to the field of organic photovoltaic materials, specifically to an inorganic hole transport material based on a vanadium-based complex, its preparation method, and its application. The inorganic hole transport material based on a vanadium-based complex provided by the present invention has a work function of -5.52eV, matching the HOMO energy level of the donor material PM6 of -5.6eV. This material improves the exciton relaxation time, reduces the non-radiative recombination of excitons, and achieves high transmittance, thereby increasing short-circuit current and, in turn, improving photoelectric conversion efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of organic photovoltaic materials, and in particular to an inorganic hole transport material based on a vanadium-based complex, and a preparation method and 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] Solar cells can directly convert solar energy into electrical energy and are an important clean energy generation technology. With the rapid development of this field, photovoltaic technology has evolved from commercial silicon-based solar cells and inorganic thin-film solar cells to the third generation of new solar cells, including dye-sensitized solar cells, perovskite solar cells and quantum dot solar cells. These devices can achieve a high power conversion efficiency (PCE), but their widespread application is restricted by factors such as high cost, poor stability, and the presence of harmful components. As one of the important representatives of new solar cells, organic solar cells (OSC), also known as organic photovoltaic (OPV) devices, also have good application prospects. They are easy to achieve low-cost, large-area solution processing, and can be made into semi-transparent devices or flexible devices, but their relatively low photoelectric conversion efficiency and poor stability are the main challenges restricting the practical application of OSC devices.

[0004] Electrode interface layers, located between the organic photovoltaic active layer and the electrodes, play a crucial role in reducing interfacial barriers and facilitating the capture and transport of charge carriers. Therefore, interface engineering is an effective method for improving device performance. Electrode interface layers primarily consist of a hole-transporting anode interface layer and an electron-transporting cathode interface layer. The fundamental function of the hole-transport layer is to increase the rate of hole transport within the device and effectively trap electrons within the light-emitting layer, maximizing carrier recombination. Furthermore, the hole-transport layer reduces the energy barrier during hole injection, improving its injection efficiency and thereby enhancing device brightness, efficiency, and lifetime.

[0005] Hole transport materials are divided into organic hole transport materials and inorganic hole transport materials. Organic hole transport materials can be divided into organic small molecules and polymer hole transport materials according to their molecular structure. The most widely used organic small molecule hole transport material is the self-assembled monolayer (SAM) material, but it is often difficult to achieve the ideal coverage when used. Although OSCs based on SAM materials are highly efficient, their preparation process is relatively complicated and the device stability is poor. PEDOT:PSS is one of the commonly used polymer hole transport materials in organic solar cells. The advantage of PEDOT:PSS is that it can form a film from a solution, which is especially suitable for flexible substrates, but the stability of organic photovoltaic cells will be affected by the acidity of PEDOT:PSS. Inorganic hole transport materials are generally metal oxides, such as V2O5, Co3O4, NiO x However, since the processing temperature of metal oxides is generally high and the processing time is long, there is a certain damage to the indium tin oxide (ITO) electrode.

[0006] Therefore, designing and synthesizing new hole transport materials is urgent and necessary to improve the device efficiency, stability and life of organic solar cells and realize the commercialization of high-performance organic solar cells. Summary of the Invention

[0007] In order to overcome the above problems, the present invention provides an inorganic hole transport material based on a vanadium-based complex, and a preparation method and application thereof.

[0008] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0009] In a first aspect of the present invention, there is provided an inorganic hole transport material based on a vanadium-based complex, wherein the structural formula of the vanadium-based complex is as shown in Formula I, Formula II or Formula III.

[0010]

[0011]

[0012] The second aspect of the present invention provides a method for preparing a vanadium-based complex represented by Formula I, Formula II or Formula III, comprising:

[0013] (1) 1,3,5-benzenetricarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-BTC shown in formula I;

[0014] (2) 1,3-Benzenedicarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-mBDC shown in formula II;

[0015] (3) 1,4-Benzenedicarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-pBDC shown in formula III.

[0016] The third aspect of the present invention provides the use of the above-mentioned inorganic hole transport material based on the vanadium-based complex in an organic solar cell.

[0017] A fourth aspect of the present invention provides an organic solar cell comprising a substrate, a bottom electrode, a hole transport layer, an organic photovoltaic active layer, an electron transport layer, and a top electrode;

[0018] The hole transport layer includes the above-mentioned inorganic hole transport material based on the vanadium-based complex.

[0019] The beneficial effects of the present invention are:

[0020] (1) The work function of the inorganic hole transport material based on the vanadium-based complex provided by the present invention is -5.52 eV, which matches the HOMO energy level of the donor material PM6 of -5.6 eV, thereby increasing the exciton relaxation time, reducing the non-radiative recombination of excitons, and improving the short-circuit current by high transmittance, thereby improving the photoelectric conversion efficiency.

[0021] (2) Conventional vanadium oxides, when used in the preparation of solar cell devices, typically require high temperature and ultraviolet light treatment to load the vanadium oxide onto the bottom electrode, thus limiting their application in flexible solar cell devices. The vanadium-based complex provided in the present invention, however, can complete molecular self-assembly at low temperatures and then form a well-formed molecular self-assembled film through spin coating and thermal annealing, without the need for high temperature treatment. Therefore, it can be used as a hole transport layer material in flexible solar cell devices.

[0022] (3) The present invention provides a simple method for preparing an inorganic hole transport material based on a vanadium-based complex, with mild reaction conditions, short reaction time, and relatively stable products. Using it as an anode interface layer material for organic solar cells offers low cost and high device fabrication operability. Its photoelectric conversion efficiency in high-efficiency systems can reach 19.27%, 18.70%, and 18.50%, compared to 18.20% achieved with conventional PEDOT:PSS as a hole transport layer material for the same device. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Figure 1 IR spectrum of the vanadium-based complex V-BTC synthesized in Example 1;

[0025] Figure 2 The transmittance of the vanadium-based complex V-BTC and PEDOT:PSS synthesized in Example 1, which were spin-coated on clean ITO glass treated with UV ozone using the same spin-coating method;

[0026] Figure 3 Schematic diagram of the structure of an organic solar cell;

[0027] Figure 4 1 is the current density-voltage characteristic curve of V-BTC used as a hole-forming material in an organic solar cell in Example 1;

[0028] Figure 5 The current density-voltage characteristic curve of an organic solar cell in which the vanadium-based complex V-mBDC in Example 2 is used as a hole transport layer material;

[0029] Figure 6 The current density-voltage characteristic curve of an organic solar cell in which the vanadium-based complex V-pBDC in Example 3 is used as a hole transport layer material;

[0030] Figure 7 The current density-voltage characteristic curve of organic solar cells based on PEDOT:PSS;

[0031] Figure 8 Transient photovoltage test curves of an organic solar cell based on the vanadium-based complex V-BTC in Example 1 and an organic solar cell based on PEDOT:PSS;

[0032] Figure 9 The UV photoelectron spectrum of the organic solar cell based on the vanadium-based complex V-BTC in Example 1;

[0033] Figure 10 This is the external quantum efficiency curve of the organic solar cell based on the vanadium-based complex V-BTC in Example 1. DETAILED DESCRIPTION

[0034] 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.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0036] A first typical embodiment of the present invention provides an inorganic hole transport material based on a vanadium-based complex, wherein the structural formula of the vanadium-based complex is as shown in Formula I, Formula II or Formula III.

[0037]

[0038] A second typical embodiment of the present invention provides a method for preparing a vanadium-based complex represented by Formula I, Formula II or Formula III, comprising:

[0039] (1) 1,3,5-benzenetricarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-BTC shown in formula I;

[0040] (2) 1,3-Benzenedicarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-mBDC shown in formula II;

[0041] (3) 1,4-Benzenedicarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-pBDC shown in formula III.

[0042] In one or more embodiments, in (1), the molar ratio of 1,3,5-benzenetricarboxylic acid to vanadium trichloride is 0.8 to 1.2:5, preferably 1:5.

[0043] In one or more embodiments, in (1), the concentration of 1,3,5-benzenetricarboxylic acid in methanol is 0.02 to 0.03 mol / L, preferably 0.02 to 0.03 mol / L.

[0044] In one or more embodiments, in (1), the heating reaction temperature is 60 to 180° C., preferably 60° C.; the reaction time is 2 to 12 hours, preferably 2 hours.

[0045] In one or more embodiments, in (2), the molar ratio of 1,3-benzenedicarboxylic acid to vanadium trichloride is 0.8 to 1.2:5, preferably 1:5.

[0046] In one or more embodiments, in (2), the concentration of 1,3-benzenedicarboxylic acid in methanol is 0.02 to 0.03 mol / L, preferably 0.02 to 0.03 mol / L.

[0047] In one or more embodiments, in (2), the heating reaction temperature is 60 to 180° C., preferably 60° C.; the reaction time is 2 to 12 h, preferably 2 h.

[0048] In one or more embodiments, in (3), the molar ratio of 1,4-benzenedicarboxylic acid to vanadium trichloride is 0.8 to 1.2:5, preferably 1:5.

[0049] In one or more embodiments, in (3), the concentration of 1,4-benzenedicarboxylic acid in methanol is 0.02 to 0.03 mol / L, preferably 0.02 to 0.03 mol / L.

[0050] In one or more embodiments, in (3), the heating reaction temperature is 60 to 180° C., preferably 60° C.; the reaction time is 2 to 12 h, preferably 2 h.

[0051] A third typical embodiment of the present invention provides the use of the above-mentioned inorganic hole transport material based on the vanadium-based complex in an organic solar cell.

[0052] A fourth typical embodiment of the present invention provides an organic solar cell comprising a substrate, a bottom electrode, a hole transport layer, an organic photovoltaic active layer, an electron transport layer, and a top electrode;

[0053] The hole transport layer includes the above-mentioned inorganic hole transport material based on the vanadium-based complex.

[0054] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0055] Example 1

[0056] 1,3,5-Benzenetricarboxylic acid (53.5 mg, 0.25 mmol) was dispersed in methanol (40 mL) and ultrasonicated for 10 min. Vanadium trichloride (197 mg, 1.25 mmol) was then added and heated under reflux at 60 °C for 2 h. The mixture was then naturally cooled to room temperature to produce the vanadium-based complex V-BTC shown in Formula I.

[0057] Figure 1 The infrared spectrum of the vanadium-based complex V-BTC synthesized in this embodiment is as follows: Figure 1 It can be seen that V-BTC is at 1000cm -1The increase in the intensity of the left and right C=O vibrations is conducive to broadening its absorption of photons.

[0058] Take 55 μL of the vanadium-based complex V-BTC solution with a concentration of 4.6 mg / mL after cooling in this embodiment, and spin-coat it on a clean ITO glass treated with UV ozone. The spin-coating parameters are 4000 rpm and the coating time is 30 s. The sample is annealed in an oven at 100 ° C for 20 minutes, and its transmittance is tested. For comparison, a PEDOT:PSS solution (PEDOT:PSS to water ratio of 5:1) is spin-coated on a clean ITO glass treated with UV ozone using the same spin-coating method, and its transmittance is tested. The thickness of the HTL formed by the vanadium-based complex and PEDOT:PSS is 10 nm. The results are shown in Figure 2. Figure 2 As shown, from Figure 2 It can be seen from the figure that the vanadium-based complex V-BTC synthesized in this embodiment has good transmittance.

[0059] Example 2

[0060] 1,3-Benzenedicarboxylic acid (41.5 mg, 0.25 mmol) was dispersed in methanol (40 mL) and ultrasonicated for 10 min. Vanadium trichloride (197 mg, 1.25 mmol) was then added and the mixture was heated under reflux at 60 °C for 2 h. The mixture was then naturally cooled to room temperature to synthesize the vanadium-based complex V-mBDC shown in formula II.

[0061] Example 3

[0062] 1,4-Benzenedicarboxylic acid (41.5 mg, 0.25 mmol) was dispersed in methanol (40 mL) and ultrasonicated for 10 min. Vanadium trichloride (197 mg, 1.25 mmol) was then added and the mixture was heated under reflux at 60 °C for 2 h. The mixture was then naturally cooled to room temperature to synthesize the vanadium-based complex V-pBDC shown in formula III.

[0063] Experimental Example 4

[0064] Preparation of organic solar cells:

[0065] The vanadium-based complexes prepared in Examples 1 to 3 and PEDOT:PSS were used as hole transport layer materials to synthesize the following Figure 3 The organic solar cell shown.

[0066] The specific method is:

[0067] The cooled vanadium-based complex solution (concentration of 4.6 mg / mL) and the PEDOT:PSS solution (PEDOT:PSS to water ratio of 5:1) in Examples 1 to 3 were spin-coated on clean ITO glass treated with UV ozone at a speed of 4000 r / min for 30 s. The annealing temperature of the vanadium-based complex was 100° C. for 20 min; the annealing temperature of PEDOT:PSS was 150° C. for 15 min. The thickness of the vanadium-based complex and PEDOT:PSS coatings were both 10 nm.

[0068] The light-absorbing layer material includes the donor PM6 and the acceptor L8-BO, which are mixed at a mass ratio of 1:1.2 and dissolved in chloroform solvent to a total concentration of 13 mg / mL. The chloroform solvent also contains 16 mg / mL of 1,3-dibromo-5-chlorobenzene. The light-absorbing layer material is spin-coated on the hole transport layer to a thickness of about 90 nm. The electron transport layer is spin-coated with a 1 mg / mL solution of PDINN in 2,2,2-trifluoroethanol to a thickness of about 10 nm. Finally, a 90 nm Ag electrode is vacuum-evaporated, as shown in FIG. Figure 3 shown.

[0069] Each organic solar cell was tested under standard AM 1.5 simulated sunlight, and the results are as follows Figures 4 to 7 As shown. Figure 4 As shown, the organic solar cell based on the vanadium-based complex V-BTC in Example 1 has an open circuit voltage V oc is 0.889V, short-circuit current density J sc 27.12 mA·cm -2 , the filling factor FF is 79.92%, and the energy conversion efficiency is 19.27%, proving that this material can be used as a hole transport material for organic solar cells.

[0070] like Figure 5 As shown, the organic solar cell based on the vanadium-based complex V-mBDC in Example 2 has an open circuit voltage V oc is 0.888V, short-circuit current density J sc 26.74 mA·cm -2 , the filling factor FF is 78.73% and the energy conversion efficiency is 18.70%.

[0071] like Figure 6 As shown, the organic solar cell based on the vanadium-based complex V-pBDC in Example 3 has an open circuit voltage V oc is 0.884V, short-circuit current density J sc 26.66 mA·cm -2 , the filling factor FF is 78.51% and the energy conversion efficiency is 18.50%.

[0072] In comparison, the open circuit voltage V oc =0.882V, short-circuit current J sc =26.70mA·cm -2 , fill factor FF = 77.26%, and the energy conversion efficiency is only 18.20%, which is much lower than the performance of solar cell devices prepared by V-BTC under the same conditions, such as Figure 7 shown.

[0073] The organic solar cell based on the vanadium-based complex V-BTC in Example 1 and the organic solar cell based on PEDOT:PSS were subjected to transient photovoltage tests. The results are as follows: Figure 8 As shown, the TPV of the organic solar cell using the vanadium-based complex V-BTC in Example 1 was found to be 10.71 μs, while that of the PEDOT:PSS-based complex was 3.10 μs. This result demonstrates that V-BTC can achieve a longer exciton relaxation time as a hole transport layer, demonstrating its superior performance as an organic solar cell.

[0074] The organic solar cell based on the vanadium-based complex V-BTC in Example 1 was further analyzed by ultraviolet photoelectron spectroscopy. The work function was 5.52 eV, while the HOMO energy level of PM6 is usually 5.6 eV. The two are relatively close, which is beneficial to improving the transport of carriers and reducing the non-radiative recombination of materials, thereby increasing the voltage of the device. Figure 9 shown.

[0075] The external quantum efficiency of the organic solar cell based on the vanadium-based complex V-BTC in Example 1 was also tested. It was found that its absorption in the long wavelength band of 800-850 nm was higher, and the integrated current was 25.91 mA cm -2 ,like Figure 10 It is shown to be a good hole transport material.

[0076] 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 shall be included within the scope of protection of the present invention.

Claims

1. Application of an inorganic hole transport material based on a vanadium-based complex in an organic solar cell, characterized in that: The structural formula of the vanadium-based complex is shown in Formula I, Formula II or Formula III. Formula I; Formula II Formula III.

2. The use according to claim 1, characterized in that The preparation method of an inorganic hole transport material based on a vanadium-based complex comprises: (1) 1,3,5-benzenetricarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-BTC shown in formula I; (2) Dispersing 1,3-benzenedicarboxylic acid in methanol solvent, adding vanadium trichloride, stirring and heating to synthesize the vanadium-based complex V-mBDC shown in formula II; (3) 1,4-Benzenedicarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-pBDC shown in formula III.

3. The use according to claim 2, characterized in that In (1), the molar ratio of 1,3,5-benzenetricarboxylic acid to vanadium trichloride is 0.8~1.2:5; Alternatively, the concentration of 1,3,5-benzenetricarboxylic acid in methanol is 0.02~0.03mol / L.

4. The use according to claim 3, characterized in that The molar ratio of 1,3,5-benzenetricarboxylic acid to vanadium trichloride is 1:

5.

5. The use according to claim 2, characterized in that In (1), the heating reaction temperature is 60~180℃; the reaction time is 2~12 h.

6. The use according to claim 5, characterized in that The heating temperature of the reaction was 60°C.

7. The use according to claim 5, characterized in that The reaction time is 2 h.

8. The use according to claim 2, characterized in that (2), the molar ratio of 1,3-benzenedicarboxylic acid to vanadium trichloride is 0.8~1.2:5; Alternatively, in (2), the concentration of 1,3-benzenedicarboxylic acid in methanol is 0.02~0.03mol / L.

9. The use according to claim 8, characterized in that The molar ratio of 1,3-phthalic acid to vanadium trichloride is 1:

5.

10. The use according to claim 2, characterized in that In (2), the heating reaction temperature is 60~180℃; the reaction time is 2~12h.

11. The use according to claim 10, characterized in that The heating temperature of the reaction was 60°C.

12. The use according to claim 10, characterized in that The reaction time is 2 h.

13. The use according to claim 2, characterized in that (3), the molar ratio of 1,4-benzenedicarboxylic acid to vanadium trichloride is 0.8~1.2:5; Alternatively, in (3), the concentration of 1,4-benzenedicarboxylic acid in methanol is 0.02–0.03 mol / L.

14. The use according to claim 13, characterized in that The molar ratio of 1,4-phthalic acid to vanadium trichloride is 1:

5.

15. The use according to claim 2, characterized in that The heating reaction temperature is 60~180℃; the reaction time is 2~12 hours.

16. The use according to claim 15, characterized in that The heating temperature of the reaction was 60°C.

17. The use according to claim 15, characterized in that The reaction time is 2 h.

18. An organic solar cell, characterized in that: It includes a substrate, a bottom electrode, a hole transport layer, an organic photovoltaic active layer, an electron transport layer, and a top electrode; The hole transport layer includes an inorganic hole transport material based on a vanadium-based complex; the structural formula of the vanadium-based complex is shown in Formula I, Formula II or Formula III, Formula I; Formula II Formula III.

19. The organic solar cell according to claim 18, wherein The preparation method of an inorganic hole transport material based on a vanadium-based complex comprises: (1) 1,3,5-benzenetricarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-BTC shown in formula I; (2) Dispersing 1,3-benzenedicarboxylic acid in methanol solvent, adding vanadium trichloride, stirring and heating to synthesize the vanadium-based complex V-mBDC shown in formula II; (3) 1,4-Benzenedicarboxylic acid is dispersed in methanol solvent, and then vanadium trichloride is added, stirred and heated to synthesize the vanadium-based complex V-pBDC shown in formula III.

20. The organic solar cell according to claim 19, wherein In (1), the molar ratio of 1,3,5-benzenetricarboxylic acid to vanadium trichloride is 0.8~1.2:5; Alternatively, the concentration of 1,3,5-benzenetricarboxylic acid in methanol is 0.02~0.03mol / L.

21. The organic solar cell according to claim 20, wherein The molar ratio of 1,3,5-benzenetricarboxylic acid to vanadium trichloride is 1:

5.

22. The organic solar cell according to claim 19, wherein In (1), the heating reaction temperature is 60~180℃; the reaction time is 2~12 h.

23. The organic solar cell according to claim 22, wherein The heating temperature of the reaction was 60°C.

24. The organic solar cell according to claim 22, wherein The reaction time is 2 h.

25. The organic solar cell according to claim 19, wherein (2), the molar ratio of 1,3-benzenedicarboxylic acid to vanadium trichloride is 0.8~1.2:5; Alternatively, in (2), the concentration of 1,3-benzenedicarboxylic acid in methanol is 0.02~0.03mol / L.

26. The organic solar cell according to claim 25, wherein The molar ratio of 1,3-phthalic acid to vanadium trichloride is 1:

5.

27. The organic solar cell according to claim 19, wherein In (2), the heating reaction temperature is 60~180℃; the reaction time is 2~12h.

28. The organic solar cell according to claim 27, wherein The heating temperature of the reaction was 60°C.

29. The organic solar cell according to claim 27, wherein The reaction time is 2 h.

30. The organic solar cell according to claim 19, wherein (3), the molar ratio of 1,4-benzenedicarboxylic acid to vanadium trichloride is 0.8~1.2:5; Alternatively, in (3), the concentration of 1,4-benzenedicarboxylic acid in methanol is 0.02–0.03 mol / L.

31. The organic solar cell according to claim 30, wherein The molar ratio of 1,4-phthalic acid to vanadium trichloride is 1:

5.

32. The organic solar cell according to claim 19, wherein The heating reaction temperature is 60~180℃; the reaction time is 2~12 hours.

33. The organic solar cell according to claim 32, wherein The heating temperature of the reaction was 60°C.

34. The organic solar cell according to claim 32, wherein The reaction time is 2 h.

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