An organic solar cell active layer and a method for preparing the same

Abstract

The present application relates to an organic solar cell active layer, which comprises a donor material, an acceptor material and a specific additive having the following structure: wherein X is independently selected from a hydrogen atom or a halogen. After adding the dibromothiophene-based additive with a specific structure to the active layer, it is surprisingly found that the photoelectric conversion efficiency of the active layer material (such as the currently highest efficient PM6:Y6 blended active layer material) can be significantly improved. This effect is more ideal than adding conventional additives.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of optoelectronic materials, and particularly relates to an active layer of an organic solar cell and a preparation method thereof. BACKGROUND

[0002] In today's world, energy is the basis for the survival and development of human society. With the development of science and technology and the growth of population, people's demand for energy consumption is increasing, and finding renewable energy has become a challenge for scientists. Among many green renewable energies, such as wind energy, water energy, solar energy, and tidal energy, solar energy is inexhaustible, widely distributed, and as a technology that directly converts light energy into electrical energy, it has been the focus of scientists' research. Organic solar cells have attracted widespread attention as a new generation of clean energy technology due to their light weight, low cost, large-area printing, flexibility, and other advantages.

[0003] In recent years, the rapid development of organic polymer materials and non-fullerene small molecule acceptor materials has shown great potential for development, with the efficiency of polymer photovoltaic devices exceeding 19% in the current literature. With the continuous development of photovoltaic cell materials and the continuous improvement of preparation processes, polymer solar cells are expected to be commercialized and industrialized in the near future. However, the current defects of polymer photovoltaic devices restrict their commercial application, so the focus of improvement at this stage is how to improve the energy conversion efficiency, device working life, and stability.

[0004] Currently, adding additives to the active layer of a solar cell can improve the blending morphology of the donor material and the acceptor material in the active layer, which is an indisputable fact. In the prior art, commonly used additives include diiodooctane or organic additives containing cyano groups, with an addition amount ranging from 0.1 to 1 wt%.

[0005] However, finding a new type of additive that can significantly improve the photoelectric effect of solar cells compared to the above additives is a problem that has been studied in this industry. SUMMARY

[0006] Based on the above problems, the present application proposes a new type of organic solar cell containing a specific structure of additive in the active layer. The active layer after film formation is applied to an organic solar cell device, and tests show that the addition of the additive greatly improves the efficiency of the organic solar cell. Through external quantum efficiency spectrum analysis, it is found that the device containing the additive has a strong optical response in the range of 300-900 nm, indicating that more photons and excitons can be obtained, thereby improving the device current and the efficiency of the entire device. This technical solution is conducive to the further development of the field of organic solar cells.

[0007] It is an object of the present application to provide an organic solar cell active layer, comprising a donor material, an acceptor material and a specific additive having the following structure:

[0008]

[0009] wherein X is independently selected from a hydrogen atom or a halogen.

[0010] Further, the content of the specific additive is 0.1-0.5wt% of the active layer.

[0011] Further, the donor material is selected from a P-type organic semiconductor based on specific unit 1, and the acceptor material is selected from an N-type organic semiconductor based on specific unit 2; wherein the specific unit 1 is selected from one or more of the following structures:

[0012]

[0013] The specific unit 2 is selected from one or more of the following structures:

[0014]

[0015] wherein R1-R6 are independently selected from an alkyl group having 1-40 carbon atoms, or an alkyl derivative having 1-40 carbon atoms;

[0016] one or more carbon atoms on the alkyl derivative are substituted by one or more of a hydrogen atom, an oxygen atom, an alkenyl group, an alkynyl group, an aryl group, a hydroxyl group, an amino group, a carbonyl group, a carboxyl group, an ester group, a cyano group, a nitro group;

[0017] and / or,

[0018] one or more hydrogen atoms on the alkyl derivative are substituted by one or more of a fluorine atom, a chlorine atom, a bromine atom, an iodine atom;

[0019] X1-X6 are independently selected from one or more of a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group.

[0020] Further, the acceptor material is a non-fullerene small molecule material.

[0021] Further, the acceptor material is selected from one or more of Y6, Y6-BO, BTP-EC9, LB-BO.

[0022] It is another object of the present application to provide a preparation method of the above-mentioned organic solar cell active layer, comprising the following steps:

[0023] The donor material and the acceptor material are dissolved in a solvent, and then the specific additive is added to the solution, and finally a film is formed on the device by spin coating.

[0024] Further, the step further comprises annealing the film after spin coating.

[0025] Further, the solvent is selected from one or more of chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, trimethylbenzene.

[0026] Another object of the present application is to provide an organic solar cell containing the above-mentioned organic solar cell active layer.

[0027] Further, the organic solar cell further comprises at least one of an electron transport layer and a hole transport layer.

[0028] The present application has the following beneficial effects:

[0029] The present inventors have found that, by adding a dibromothiophene-based additive with a specific structure to the active layer, the photoelectric conversion efficiency of the active layer material (such as the currently highest-efficiency PM6:Y6 blended active layer material) can be surprisingly improved. This effect is more ideal than adding conventional cyano-based additives. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 (a) shows the structure of the organic solar cell involved in the examples, and the structure of PM6 and Y6;

[0031] Figure 1 (b) shows the structure of 2PACZ and PDINN involved in the examples;

[0032] Figure 2 J-V curves of Examples 1-2, Comparative Examples 1-5 and a blank sample are shown;

[0033] Figure 3 EQE graphs of Examples 1-2, Comparative Examples 1-5 and a blank sample are shown. DETAILED DESCRIPTION

[0034] In order to more clearly illustrate the technical solutions of the present application, the following examples are listed. The raw materials, reactions and post-treatment methods appearing in the examples are all common raw materials on the market, and are well-known technical means to those skilled in the art, unless otherwise stated.

[0035] In the examples of the present application,

[0036] PM6 is purchased from a commercial resource Solliant Organic Optoelectronic Technology (Beijing) Co., Ltd.

[0037] Y6 is purchased from the commercial resource Solon Organic Optoelectronic Technology (Beijing) Co., Ltd.

[0038] 2PACZ is purchased from the commercial resource TCL Co., Ltd.

[0039] PDINN is purchased from the commercial resource TCL Co., Ltd.

[0040] Example 1

[0041] An organic solar cell device, the device structure of which is ITO (135 nm) / 2PACZ (40 nm) / active layer (100 nm) (PM6:Y6 = 1:1.2, m / m, 0.5wt% of the specific additive 2F in the active layer) / PDINN (40 nm) / Ag (100 nm) from bottom to top.

[0042] The structure of the specific additive is as follows:

[0043]

[0044] The synthesis route of the above 2F is described in the reference (S. Liu, Y. Firdaus, S. Thomas, et al. Angewandte Chemie International Edition, 2018, 57(2): 531-535.).

[0045] The preparation method of the above organic solar cell device adopts the conventional preparation method well known to those skilled in the art, unless otherwise specified. Among them, the preparation method of the active layer of the organic solar cell is as follows:

[0046] Chloroform is used as the solvent, PM6:Y6 is dissolved in chloroform at a ratio of 1:1.2, and the total concentration of the solute is ensured to be 12 mg / ml. Then 0.5wt% of the specific additive 2F is added to the solute, stirred uniformly, then spin-coated on 2PACZ, then heat annealed at 80°C, and film is formed.

[0047] Example 2

[0048] An organic solar cell device, the device structure of which is ITO (135 nm) / 2PACZ (40 nm) / active layer (100 nm) (PM6:Y6 = 1:1.2, m / m, 0.5wt% of the specific additive 2Br in the active layer) / PDINN (40 nm) / Ag (100 nm) from bottom to top. The structure of the specific additive is as follows:

[0049]

[0050] The above 2Br is purchased from the commercial resource Maklin Co., Ltd.

[0051] The preparation methods of the above-mentioned organic solar cell devices all adopt conventional preparation methods well known to those skilled in the art, unless otherwise specified. Among them, the preparation method of the active layer of the organic solar cell is as follows:

[0052] PM6:Y6 is dissolved in chloroform at a ratio of 1:1.2 with chloroform as the solvent, and the total concentration of the solute is ensured to be 12 mg / ml. Then 0.5wt% of the specific additive 2Br is added to the solute, stirred uniformly, spin-coated onto the 2PACZ, then heat annealed at 80°C, and formed into a film.

[0053] Comparative Example 1

[0054] The device structure, materials used and preparation method of Comparative Example 1 are all the same as those of Example 1, the only difference being that in Comparative Example 1, the specific additive 2F is replaced with an equal amount of chloronaphthalene.

[0055] Comparative Example 2

[0056] The device structure, materials used and preparation method of Comparative Example 2 are all the same as those of Example 1, the only difference being that in Comparative Example 2, the specific additive 2F is replaced with an equal amount of trifluorotoluene.

[0057] Comparative Example 3

[0058] The device structure, materials used and preparation method of Comparative Example 3 are all the same as those of Example 1, the only difference being that in Comparative Example 3, the specific additive 2F is replaced with an equal amount of trifluorobenzene.

[0059] Comparative Example 4

[0060] The device structure, materials used and preparation method of Comparative Example 4 are all the same as those of Example 1, the only difference being that in Comparative Example 4, the specific additive 2F is replaced with an equal amount of difluorobenzene.

[0061] Blank Sample

[0062] The device structure, materials used and preparation method of the blank sample are all the same as those of Example 1, the only difference being that in the blank sample, the specific additive 2F is removed and no other additive is added.

[0063] Figure 1 (a) shows the structure of the organic solar cell structure involved in the examples, and the structural formula of PM6 and Y6; Figure 1 (b) shows the structural formula of 2PACZ and PDINN involved in the examples.

[0064] Test Example

[0065] Photovoltaic performance tests were conducted on the organic solar cell devices in Examples 1-2 and Comparative Examples 1-5 above. The test conditions were: the main photovoltaic material polymer donor PM6: small molecule acceptor Y6 (1:1.2, m / m). PM6 and Y6 were readily available and acquired from commercial resource Shuolun Organic Optoelectronic Technology (Beijing) Co., Ltd. Prior to testing the BHJ solar cells, basic characteristics such as energy levels and absorption spectra of the materials were measured using air photoelectron spectroscopy (PESA) and ultraviolet-visible absorption spectroscopy (UV-vis). Figure 1 As shown, the device structure is ITO / 2PACZ / PM6:Y6 / PDINN / Ag (device area with mask, 0.04cm). 2 ), where 2PACZ and PDINN are the hole transport layer and electron transport layer, respectively.

[0066] The detailed preparation method of the organic solar cell device is as follows: First, the ITO-coated glass slides are engraved and numbered, and then ultrasonically cleaned for 15 minutes each time. The cleaning steps are: cleaning once in isopropanol, once in detergent, three times in deionized water, and once in isopropanol. After cleaning, the slides are dried in a 70°C oven for at least 3 hours. Then, the ITO glass is treated in an oxygen plasma treatment instrument for 15 minutes, and then transferred to a glove box under a nitrogen atmosphere. 2PACZ is dissolved in anhydrous ethanol (concentration of 0.27 mg / mL), and then spin-coated at 3000 rpm for 30 seconds on a spin coater, followed by heating on a 100°C heating stage for 10 minutes to obtain a 2PACZ film with a thickness of approximately 40 nm. Then, PM6:Y6 (1:1.2, m / m) is dissolved in chloroform, and 0.5 wt% of different additives (as shown in Examples 1-2 and Comparative Examples 1-4) are added. The total concentration of the blend solution was 16 mg / mL. The mixture was stirred at 50°C for at least 1 hour on a heated stirrer to ensure complete dissolution. Then, it was spin-coated onto a pre-sprayed 2 PACZ ITO glass substrate at 4000 rpm for 30 seconds to obtain a blend film with a thickness of approximately 100 nm (measured using a step-by-step instrument). The spin-coated active layer containing the additive was placed in a vacuum environment for at least 30 minutes to remove any residual additives. Next, the film was annealed at 80°C for 10 minutes on a heating stage. After cooling, a PDINN film approximately 5 mm thick (PDINN concentration 1 mg / mL dissolved in methanol, spin-coated at 3000 rpm for 15 seconds) was coated onto the film. Finally, the prepared film was placed on a custom-made photomask, with an effective area of ​​0.04 × 0.04 cm². 2 In a vacuum evaporation chamber, at a concentration of less than 5 × 10⁻⁶ -4 A 100nm thick Ag film is thermally deposited under pressure of pa to finally obtain a complete battery device.

[0067] The current-voltage (J-V) curves obtained from the experiment were operated by a computer-controlled Keithley 2400 sourcemeter program at 100 mW cm -2 The test was performed under AM 1.5G spectrum (1 sun, calibrated by a standard silicon solar cell before the test, manufactured by San-EI Electric Co, Ltd, Japan), and a mold with a square light aperture was used, with an accurate area of 0.04 cm 2 to define the effective area of the device before obtaining the PCE. The external quantum efficiency (EQE) measurement was performed by a QE-C system (Entitech, Taiwan). The EQE system was calibrated by a silicon photodiode before the measurement.

[0068] The results obtained are shown in Table 1.

[0069] Table 1 Photovoltaic performance parameters of organic solar cell devices in Examples 1-2, Comparative Examples 1-5 and the blank sample

[0070]

[0071] As can be seen from Table 1, in Examples 1 and 2, due to the use of the specific additive based on dibromothiophene, the final PCE details obtained are superior to the photovoltaic performance of similar devices (such as comparative examples and blank samples) with other additives.

[0072] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be carried out in other specific forms without departing from the spirit or essential characteristics of the present application. Accordingly, no matter from which point of view, the examples should be considered as exemplary and non-limiting, and the scope of the present application is defined by the appended claims, not by the foregoing description, and therefore all changes falling within the meaning and range of equivalency of the essential elements of the claims are intended to be embraced therein.

[0073] Furthermore, it should be understood that although the present specification is described in terms of embodiments, not every implementation embodies an independent technical solution, and the present specification is described in this way only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. An active layer for an organic solar cell, characterized in that, The active layer of the organic solar cell includes a donor material, an acceptor material, and a specific additive, wherein the specific additive has the following structure: ； in, The content of the specific additive is 0.1-0.5 wt% of the active layer; The donor material is selected from PM6, and the acceptor material is selected from Y6.

2. The method for preparing the active layer of an organic solar cell as described in claim 1, characterized in that, The method for preparing the active layer of the organic solar cell includes the following steps: The donor and acceptor materials are dissolved in a solvent, and then the specific additives are added to the solvent. Finally, the mixture is spin-coated onto the device to form a film.

3. The method for preparing the active layer of an organic solar cell according to claim 2, characterized in that, The steps also include annealing the film after spin coating.

4. The method for preparing the active layer of an organic solar cell according to claim 2, characterized in that, The solvent is selected from one or more of chloroform, chlorobenzene, dichlorobenzene, trichlorobenzene, toluene, xylene, and trimethylbenzene.

5. An organic solar cell comprising the organic solar cell active layer as described in claim 1.

6. The organic solar cell according to claim 5, characterized in that, The organic solar cell further includes at least one electron transport layer and a hole transport layer.

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