A fully solution-processed solar cell

Abstract

The present invention relates to a fully solution-processed solar cell comprising an organic electron transport layer 1 and an organic electron transport layer 2, wherein the organic electron transport layer 1 and the organic electron transport layer 2 are disposed adjacent to each other. The present invention has the following beneficial effects: the dual organic electron transport layer can effectively improve the selectivity and charge transport characteristics of mainstream device structures, enhance electron transport and extraction, block hole reverse transport, reduce carrier recombination, and lower series resistance, thereby increasing the photovoltaic conversion efficiency of the solar cell. This invention is conducive to achieving further breakthroughs in the performance of organic solar cells and perovskite solar cells, and has a significant role in promoting their commercialization.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric devices, in particular to a fully solution-processed solar cell. Background Art

[0002] As energy shortages and ecological pollution become increasingly severe, the research and application of solar cells, a sustainable and clean energy technology, has become increasingly urgent. Currently, solar cells have advanced to the third generation—thin-film solar cells, primarily organic solar cells and perovskite solar cells. Compared to traditional silicon-based solar cells, third-generation thin-film solar cells offer distinct advantages such as solution processability, lightweight construction, and low cost. They hold enormous commercial value and market competitiveness in the distributed photovoltaic power generation sector.

[0003] The electron transport layer (ETL) is a crucial functional layer in the structure of third-generation thin-film solar cells, significantly impacting the device's charge transfer efficiency and, consequently, its photovoltaic performance. Currently, solution processing is the preferred method for fabricating ETLs. The advantages of this device fabrication process include low energy consumption, environmental friendliness, and simplified fabrication.

[0004] In order to achieve full solution processing, both organic solar cells and perovskite solar cells currently use orthogonal solvent processing methods to achieve multi-layer solution deposition preparation of the device structure. Therefore, solution-processable electron transport layer materials are widely used. For example, the electron transport layer used in organic solar cell devices is mainly a water-alcohol soluble material because its active layer is insoluble in water-alcohol solvents. Among the many water-alcohol soluble electron transport layer materials, water-alcohol soluble conjugated polymers are widely used because of their significant effects. For example, the current high-efficiency organic solar cells have achieved a performance record of 19%, and the devices used are such materials (AdvancedMaterials.2021,33,2102420). However, in organic solar cell devices, water-alcohol soluble conjugated polymers are more used in organic solar cells with a single-layer electron transport layer structure. In the existing technology, there are also some organic solar cells based on inorganic-organic double-layer electron transport layer structures (Energy & Environmental Science. 2012, 5, 8208; ACS Applied Energy Materials. 2021, 4, 4489), but their disadvantages are that the inorganic materials themselves are prone to photocatalysis, and are prone to cause surface defects, as well as poor compatibility with organic materials.

[0005] Therefore, how to more efficiently utilize the electron transport layer structure so that it can contribute more significantly to the photoelectric conversion efficiency of organic solar cells is an urgent problem to be solved. Summary of the Invention

[0006] By summarizing the experience of predecessors, we found that narrow-bandgap conjugated polymer materials have good electron transport properties, but their hole blocking ability is limited. Wide-bandgap conjugated polymers have strong hole blocking ability, but poor electron transport performance. The present invention proposes a fully solution-processed organic solar cell structure, which is composed of a double-layer organic electron transport layer material, and the two are arranged adjacent to each other. This setting can produce a good synergistic effect between the organic electron transport layer 1 and the organic electron transport layer 2, that is, it can further improve the electron transport efficiency of the mainstream device structure on the existing device structure, and can also achieve the effect of blocking the reverse transmission of holes while achieving the improvement of electron transmission and extraction capabilities, thereby achieving the selective transmission of photogenerated charges in solar cells, reducing interface carrier recombination, and reducing series resistance, thereby improving the photoelectric conversion efficiency of solar cells.

[0007] The technical solution of the present invention is achieved through the following technical means:

[0008] A fully solution-processed solar cell comprises an organic electron transport layer 1 and an organic electron transport layer 2, wherein the organic electron transport layer 1 and the organic electron transport layer 2 are arranged adjacent to each other.

[0009] Furthermore, the fully solution-processed solar cell comprises, from bottom to top, a conductive substrate, a hole transport layer, an active layer, an organic electron transport layer 1, an organic electron transport layer 2 and a metal electrode.

[0010] Furthermore, the optical band gap of the material in the organic electron transport layer 1 is 1.5-2.5 eV; the optical band gap of the material in the organic electron transport layer 2 is 2.5-4 eV.

[0011] The specific value of the optical band gap described in the present invention is calculated by dividing 1240 by the cutoff wavelength of the absorption edge of the semiconductor material.

[0012] Furthermore, the material in the active layer is selected from organic photovoltaic materials or perovskite photovoltaic materials.

[0013] Furthermore, when the active layer of the present invention is an organic photovoltaic material, it is a bulk heterojunction composed of a polymer donor material and a non-fullerene acceptor material. Preferably, the organic photovoltaic material is a PM6:Y7 bulk heterojunction or a PM6:Y6 bulk heterojunction, and the blend ratio of the two is preferably 1:1-1.2 (m / m).

[0014] When the active layer of the present invention is a perovskite photovoltaic material, it has an ABX3 structure or an A2A ’ n-1 B n X 3n+1The perovskite material has a structure in which the A ion is at least one of the following compounds: methylamine, formamidine, cesium, phenylethylamine, and n-butylamine; the B ion is at least one of the following compounds: lead, tin, and germanium; and the X ion is at least one of the following compounds: iodine, chlorine, and bromine.

[0015] Furthermore, the material in the organic electron transport layer 1 and the material in the organic electron transport layer 2 essentially embody the characteristics of n-type materials and are selected from one or more of phthalocyanines, perylene derivatives, naphthalene derivatives, acene derivatives, oligothiophenes, and polyparaphenylenes.

[0016] Furthermore, the material in the organic electron transport layer 1 is a narrow bandgap material selected from PC 61 BM, PC 71 BM, PNDIT-F3N, PNDIT-F3N-Br, PNDIT-F8, PDIN, PDINO, PDINN, or derivatives thereof.

[0017] Furthermore, the material in the organic electron transport layer 2 is a wide bandgap material, which is a material based on 1,10-phenanthroline and its derivatives.

[0018] The 1,10-phenanthroline of the present invention has the following structure:

[0019]

[0020] Its derivatives mean that other substituents may be attached to any one or more sites on any one or more benzene rings in the above molecular structure. The substituents include but are not limited to alkyl groups, alkoxy groups, alkylthio groups, aromatic groups, ester groups, alkynyl groups, alkenyl groups, nitro groups, amino groups, carboxyl groups, halogen atoms, etc.

[0021] Specific materials based on 1,10-phenanthroline and its derivatives include, but are not limited to, Phen-NaDPO, Phen-m-PhDPO, Phen-DFP, BCP, Bphen, DMPP, and their derivatives.

[0022] PC of the present invention 61 BM, PC 71 For the specific structure of BM, please refer to the literature Advanced Materials.2018,30,1705706. The optical band gaps of BM were tested in this experiment and were 2.1eV and 1.8eV respectively.

[0023] The specific structures of PNDIT-F3N, PNDIT-F3N-Br, and PNDIT-F8 described in the present invention can be found in the Journal of The American Chemical Society, 2016, 138, 2004. Their optical band gaps, as measured in this experiment, are 1.64 eV, 1.29 eV, and 1.74 eV, respectively.

[0024] The specific structure of PDIN described in the present invention can be found in the literature Energy & Environmental Science 2014, 7, 1966. Its optical band gap was tested in this experiment and was found to be 2.33 eV.

[0025] For the specific structures of PDINO and PDINN described in the present invention, please refer to the literature Nature Communications.2020,11,2726. Their optical band gaps were tested in this experiment and were 2.58eV and 2.24eV respectively;

[0026] The specific structure of Phen-NaDPO described in the present invention can be found in the literature Advanced Functional Materials.2014, 24, 6540. Its optical band gap was tested in this experiment and was 3.4 eV.

[0027] For the specific structure of Phen-m-NaDPO described in the present invention, please refer to the literature Science Bulletin.2020,65,2033. Its optical band gap was tested in this experiment and was 3.49 eV;

[0028] The specific structure of Phen-DFP described in the present invention can be found in the Journal of Materials Chemistry C. 2017, 5, 2329. The optical band gap of Phen-DFP was tested in this experiment and was found to be 3.6 eV.

[0029] For the specific structures of BCP, Bphen, and DMPP described in the present invention, please refer to the literature Dyes and Pigments.2013,97,258. The optical band gaps thereof were tested in this experiment and were 3.5 eV, 3.7 eV, and 3.7 eV, respectively.

[0030] Furthermore, the hole transport layer is selected from one or more of PEDOT:PSS, PTAA or MoO3.

[0031] Furthermore, the metal electrode is selected from a gold electrode, a silver electrode, a copper electrode, an aluminum electrode, a platinum electrode, and an alloy electrode;

[0032] Wherein, the alloy is a mixture of two or more metals mentioned above.

[0033] Preferably, the metal electrode in the present invention is a silver electrode or an aluminum electrode.

[0034] Furthermore, the conductive substrate is selected from a rigid conductive substrate, a flexible conductive substrate, or a metal film.

[0035] The rigid conductive substrate of the present invention includes but is not limited to indium tin oxide conductive glass (ITO), tin dioxide doped fluorine conductive glass (FTO), zinc oxide doped aluminum conductive glass (AZO), etc.; the flexible conductive substrate includes but is not limited to indium tin oxide conductive polyethylene terephthalate (ITO-PET conductive plastic sheet), PEDOT conductive polymer (PH1000 conductive film), etc.; the metal film includes but is not limited to silver film, aluminum film, gold film, platinum film, magnesium film, and alloy films of the above metals, etc.

[0036] Preferably, the conductive substrate in the present invention is ITO glass.

[0037] The preparation method of the fully solution-processed solar cell of the present invention is as follows:

[0038] S1: Select a suitable conductive substrate, clean it and dry it;

[0039] S2: preparing a hole transport layer on the surface of a conductive substrate;

[0040] S3: preparing an active layer on the hole transport layer;

[0041] S4: depositing an organic electron transport layer 1 onto the active layer by a solution method;

[0042] S5: depositing an organic electron transport layer 2 onto the organic electron transport layer 1 by a solution method;

[0043] S6: depositing metal on the organic electron transport layer 2 by vacuum evaporation.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The technical solution of the present invention uses a layer-by-layer solution deposition method to construct a dual organic electron transport layer on top of the active layer, forming an NN-type homogeneous heterojunction. Its main features are: this dual organic electron transport layer can effectively improve the selectivity and charge transfer characteristics of mainstream device structures, enhance electron transport and extraction, block hole reverse transport, reduce carrier recombination, and lower series resistance, thereby improving the photovoltaic conversion efficiency of solar cells. This invention is conducive to achieving further breakthroughs in the performance of organic solar cells and perovskite solar cells, overcoming the inherent shortcomings of single electron transport layers and inorganic-organic dual electron transport layer device structures, and has a significant role in promoting commercialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 An SEM image of a cross section of a fully solution-processed solar cell in Example 1 is shown.

[0047] Figure 2 The device structures of the fully solution-processed solar cells of Examples 1-3 are shown.

[0048] Figure 3 JV curves of the perovskite solar cells and organic solar cells obtained in Examples 1-3 and Comparative Examples 1-5 are shown. DETAILED DESCRIPTION

[0049] In order to more clearly illustrate the technical solution of the present invention, the following preparation examples and examples are listed. Unless otherwise stated, the raw materials, reactions and post-treatment methods shown in the preparation examples and examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0050] The raw materials in the examples of the present invention, PM6 and PFN-Br, were purchased from Beijing Shuolun Organic Photoelectric Technology Co., Ltd.

[0051] Y7 is purchased from Shenzhen Ruixun Optoelectronic Material Technology Co., Ltd.

[0052] Y6 and PDNIT-F3N were purchased from Dongguan Fuan Optoelectronics Technology Co., Ltd.

[0053] Phen-NaDPO and BCP were prepared according to the literature (Advanced Functional Materials.2014,24,6540 and Dyes and Pigments.2013,97,258);

[0054] PEDOT:PSS was purchased from Xi'an Baolait Optoelectronics Technology Co., Ltd.;

[0055] Phenylethylamine iodine, lead iodide, lead chloride, methylamine iodide, PC 61 BM, PC 71 BM was purchased from Xi'an Baolait;

[0056] ITO is purchased from Liaoning Youxuan New Energy Technology Co., Ltd.

[0057] (PEA)2MA3Pb4I in the embodiment of the present invention 13 The structure is synthesized by configuring phenylethylamine iodine, methylamine iodide, lead iodide and lead chloride in a molar ratio of 2:3:4:0.2, and can be prepared with reference to the literature (Advanced Energy Materials. 2018, 8, 1800185).

[0058] Example 1

[0059] A fully solution-processed solar cell with the following structure from bottom to top: ITO (150nm) / PEDOT:PSS (20nm) / (PEA)2MA3Pb4I 13 (350nm) / Organic electron transport layer 1(PC 61 BM) (100 nm) / organic electron transport layer 2 (Phen-NaDPO) (5 nm) / silver electrode (80 nm).

[0060] The preparation method of the above-mentioned all-solution processed solar cell is as follows:

[0061] S1. Ultrasonic cleaning of ITO glass was performed in acetone, ethanol, high-efficiency detergent, deionized water, and ethanol for 10-15 minutes, respectively. The cleaned ITO glass was dried with nitrogen before use.

[0062] S2. PEDOT:PSS was spin-coated on the ITO at a speed of 4000 rpm and thermally annealed at 140°C for 15 min to form a hole transport layer;

[0063] S3.(PEA)2MA3Pb4I 13 Dissolved in a mixed solution of DMF and DMSO (16:1, v / v), the lead ion concentration in the precursor solution was 1 mol / L, and the solution was spin-coated on the above PEDOT:PSS at a speed of 4000 rpm, and thermally annealed at 100°C for 10 min to form an active layer;

[0064] S4. PC 61 BM was dissolved in chlorobenzene to form a solution with a concentration of 15 mg / mL. The solution was spin-coated on the active layer at a speed of 3000 rpm and thermally annealed at 60°C for 2 min to form an organic electron transport layer 1.

[0065] S5. Phen-NaDPO was dissolved in methanol to form a solution at a concentration of 1 mg / mL, and the solution was spin-coated at a speed of 2000 rpm and deposited on the organic electron transport layer 1 to form an organic electron transport layer 2;

[0066] S6. Deposit an 80 nm silver electrode on the organic electron transport layer 2 by vacuum thermal evaporation with a vacuum degree of 3×10 - 4 Pa.

[0067] Figure 1 The SEM image of the cross section of the fully solution-processed solar cell in Example 1 is shown. As can be seen from the image, the device structure has a double-layer organic electron transport layer structure.

[0068] Example 2

[0069] A fully solution-processed solar cell, whose structure from bottom to top is ITO (150nm) / PEDOT:PSS (40nm) / PM6:Y7 (1:1.2m / m) (100nm) / organic electron transport layer 1 (PNDIT-F3N) (5nm) / organic electron transport layer 2 (Phen-NaDPO) (5nm) / silver electrode (100nm).

[0070] The preparation method of the above-mentioned all-solution processed solar cell is as follows:

[0071] S1. Ultrasonic cleaning of ITO glass was performed in acetone, ethanol, high-efficiency detergent, deionized water, and ethanol for 10-15 minutes, respectively. The cleaned ITO glass was dried with nitrogen before use.

[0072] S2. PEDOT:PSS was spin-coated on the ITO at a speed of 5000 rpm and thermally annealed at 140°C for 15 min to form a hole transport layer;

[0073] S3. A solution of PM6:Y7 (1:1.2 m / m) was dissolved in chlorobenzene to form a solution, and 0.3 wt % of chloronaphthalene was added to form a solute concentration of 0.3 mg / mL. The solution was spin-coated at 3000 rpm onto the PEDOT:PSS film and thermally annealed at 100°C for 10 min to form an active layer.

[0074] S4. PNDIT-F3N was dissolved in ethanol to form a solution at a concentration of 1 mg / mL. The solution was spin-coated on the active layer at a speed of 4000 rpm and thermally annealed at 60°C for 2 min to form an organic electron transport layer 1.

[0075] S5. Phen-NaDPO was dissolved in methanol to form a solution at a concentration of 1 mg / mL, and the solution was spin-coated at a speed of 4000 rpm and deposited on the organic electron transport layer 1 to form an organic electron transport layer 2;

[0076] S6. Deposit a 100 nm silver electrode on the organic electron transport layer 2 by vacuum thermal evaporation with a vacuum degree of 3×10 -4 Pa.

[0077] Example 3

[0078] A fully solution-processed solar cell, whose structure from bottom to top is ITO (150nm) / MoO3 (10nm) / PM6:Y6 (1:1.2m / m) (100nm) / organic electron transport layer 1 (PNDIT-F3N) (5nm) / organic electron transport layer 2 (BCP) (5nm) / silver electrode (100nm).

[0079] The preparation method of the above-mentioned all-solution processed solar cell is as follows:

[0080] S1. Ultrasonic cleaning of ITO glass was performed in acetone, ethanol, high-efficiency detergent, deionized water, and ethanol for 10-15 minutes, respectively. The cleaned ITO glass was dried with nitrogen before use.

[0081] S2. MoO3 was spin-coated on the ITO at a speed of 3000 rpm and thermally annealed at 140°C for 15 min to form a hole transport layer;

[0082] S3. A PM6:Y6 solution (1:1.2 m / m) was dissolved in chloroform to form a solution, and 0.5 wt% of chloronaphthalene was added to form a solute concentration of 16 mg / mL. The solution was spin-coated at 3000 rpm onto the PEDOT:PSS film and thermally annealed at 100°C for 10 min to form an active layer.

[0083] S4. PNDIT-F3N was dissolved in ethanol to form a solution at a concentration of 1 mg / mL, and the solution was spin-coated at a speed of 4000 rpm and deposited on the active layer to form an organic electron transport layer 1;

[0084] S5. BCP was dissolved in methanol to form a solution at a concentration of 1 mg / mL, and the solution was spin-coated and deposited on the organic electron transport layer 1 at a speed of 4000 rpm to form an organic electron transport layer 2;

[0085] S6. Deposit a 100 nm silver electrode on the organic electron transport layer 2 by vacuum thermal evaporation with a vacuum degree of 3×10 -4 Pa.

[0086] Figure 2 The device structures of the fully solution-processed solar cells of Examples 1-3 are shown.

[0087] Comparative Example 1

[0088] The device structure and materials used in Comparative Example 1 are the same as those in Example 3, with the only difference being that Comparative Example 1 is a single electron transport layer structure, and the electron transport layer is ZnO (40 nm).

[0089] Comparative Example 2

[0090] The device structure and materials used in Comparative Example 2 are the same as those in Example 3, with the only difference being that Comparative Example 2 is a single electron transport layer structure, and the electron transport layer is PFN-Br (5 nm).

[0091] Comparative Example 3

[0092] The device structure and materials used in Comparative Example 3 are the same as those in Example 3. The only difference is that Comparative Example 3 is a single electron transport layer structure, and the electron transport layer is: inorganic electron transport layer 1 (ZnO) (40 nm) / organic electron transport layer 2 (PFN-Br) (5 nm).

[0093] Comparative Example 4

[0094] The device structure and materials used in Comparative Example 4 are the same as those in Example 3, with the only difference being that Comparative Example 4 is a single electron transport layer structure, and the electron transport layer is PNDIT-F3N (10 nm).

[0095] Comparative Example 5

[0096] The device structure and materials used in Comparative Example 5 are the same as those in Example 3, with the only difference being that Comparative Example 5 is a single electron transport layer structure, and the electron transport layer is BCP (10 nm).

[0097] Test Case

[0098] The solar cell performance tests and characterizations were performed on the devices obtained in Examples 1-3 and Comparative Examples 1-5. The test conditions were 100 mW / cm 2 AM = 1.5G sunlight. Figure 3 The JV curves of the solar cells of the devices obtained in Examples 1 to 3 and Comparative Examples 1 to 5 are shown. The obtained data results are shown in Table 1.

[0099] Table 1 Solar cell performance data of devices obtained in Examples 1-3 and Comparative Examples 1-5

[0100] sample Voc(V) <![CDATA[Jsc(mA / cm 2 )]]> FF(%) PCE (%) Example 1 1.17 15.99 78.8 14.74 Example 2 0.87 26.27 74.4 17.08 Example 3 0.86 26.16 72.5 16.48 Comparative Example 1 0.83 22.71 67.7 12.79 Comparative Example 2 0.84 23.94 70.8 14.21 Comparative Example 3 0.86 24.27 70.0 14.45 Comparative Example 4 0.86 26.12 69.3 15.48 Comparative Example 5 0.64 25.13 55.2 8.85

[0101] As can be seen from Table 1, the fully solution-processed solar cell of the present invention has a double-layer organic electron transport layer structure, which has a significantly improved photoelectric conversion efficiency compared to solar cells with a single-layer organic electron transport layer structure and solar cells with an inorganic-organic double-layer electron transport layer structure.

[0102] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the invention can be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0103] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A fully solution-processed solar cell, characterized in that: The fully solution-processed solar cell comprises an organic electron transport layer 1 and an organic electron transport layer 2, wherein the organic electron transport layer 1 and the organic electron transport layer 2 are arranged adjacent to each other; The material of the organic electron transport layer 1 is PNDIT-F3N; The material in the organic electron transport layer 2 is a material based on 1,10-phenanthroline and its derivatives; Also included: an active layer; The material in the active layer is selected from organic photovoltaic materials.

2. The fully solution-processed solar cell according to claim 1, characterized in that: The fully solution-processed solar cell comprises, from bottom to top, a conductive substrate, a hole transport layer, an active layer, an organic electron transport layer 1, an organic electron transport layer 2, and a metal electrode.

3. The fully solution-processed solar cell according to claim 1, characterized in that: The optical band gap of the material in the organic electron transport layer 1 is 1.5-2.5 eV; the optical band gap of the material in the organic electron transport layer 2 is 2.5-4 eV.

4. The fully solution-processed solar cell according to claim 2, characterized in that: The hole transport layer is selected from one or more of PEDOT:PSS, PTAA or MoO3.

5. The fully solution-processed solar cell according to claim 2, characterized in that: The metal electrode is selected from a gold electrode, a silver electrode, a copper electrode, an aluminum electrode, a platinum electrode, and an alloy electrode; Wherein, the alloy is a mixture of two or more metals mentioned above.

6. The fully solution-processed solar cell according to claim 2, characterized in that: The conductive substrate is selected from a rigid conductive substrate, a flexible conductive substrate, or a metal film.

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