A hole transport layer, a preparation method thereof, a transverse perovskite solar cell and application thereof

Abstract

This invention discloses a hole transport layer and its preparation method, an inverted perovskite solar cell, and its application. The hole transport layer comprises bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II. The structural formulas of bisphosphonic acid self-assembled monomolecule material I and II are shown below: The structural formulas of bisphosphonic acid self-assembled monomolecule material II are shown below: This invention selects bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II as the materials for the hole transport layer. Their synergistic effect effectively increases device lifetime, induces high-quality crystal growth, and significantly improves photoelectric conversion efficiency when preparing inverted perovskite solar cells.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a hole transport layer and its preparation method, an inverted perovskite solar cell and its application. Background Technology

[0002] In the early stages of the development of inverted perovskite solar cells, PEDOT:PSS was the first widely used hole transport film, laying the foundation for inverted devices. With technological advancements, hole transport layer materials have included hydrophobic polymers and inorganic metal oxides, as well as self-assembled monolayers of phosphonic acids. However, these materials currently have shortcomings. For example, PEDOT:PSS possesses inherent defects such as strong acidity and extreme water absorption. This not only corrodes the underlying transparent conductive substrate but also accelerates the hydrolysis and degradation of the upper perovskite material, severely shortening the device's lifespan. For instance, monolayers represented by 2PACz can only form bidentate coordination with the metal oxide surface due to limited bond energy, failing to establish a sufficiently dense density of stable anchoring sites on the substrate surface. This inherent structural defect of weak binding affinity makes it prone to desorption, leading to deep-level traps and limiting long-term operational stability.

[0003] Therefore, the above-mentioned defects indicate that existing hole transport layers have problems such as low film density, unsatisfactory crystalline substrate, and incomplete defect passivation. It is necessary to develop a hole transport layer that simultaneously achieves efficient charge extraction, deep defect passivation, and stability. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, a first aspect of this invention proposes a hole transport layer with excellent coverage and uniformity, capable of simultaneously achieving efficient charge extraction, deep defect passivation, and stability. This can improve the photoelectric conversion efficiency and lifetime of inverted perovskite solar cells.

[0005] A second aspect of the present invention also provides a method for preparing a hole transport layer.

[0006] A third aspect of the present invention also provides an inverted perovskite solar cell.

[0007] A fourth aspect of the present invention also provides an application.

[0008] According to a first aspect of the present invention, a hole transport layer is provided, comprising bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II; The structural formula of the bisphosphonic acid self-assembled monomolecule material I is shown below: ; The structural formula of the bisphosphonic acid self-assembled monomolecule material II is shown below: .

[0009] According to a preferred embodiment of the present invention, the mass ratio of the bisphosphonic acid self-assembled monomolecule II to the bisphosphonic acid self-assembled monomolecule I is 1:(0.05~5). For example, it includes sub-ranges such as 1:0.05, 1:0.11, 1:0.15, 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.33, 1:3.0, 1:3.5, 1:4, 1:4.5, 1:5, or any two of the above values.

[0010] According to a preferred embodiment of the present invention, the mass ratio of the bisphosphonic acid self-assembled monomolecule II to the bisphosphonic acid self-assembled monomolecule I is 1:(0.11~2.33). For example, it includes 1:0.11, 1:0.15, 1:0.2, 1:0.5, 1:1, 1:1.5, 1:2, 1:2.33 or any subrange consisting of two of the above values.

[0011] The hole transport layer according to embodiments of the present invention has at least the following beneficial effects: This invention selects bisphosphonic acid self-assembled single-molecule material I and bisphosphonic acid self-assembled single-molecule material II as the hole transport layer materials. The two work synergistically to effectively increase the device lifetime, induce high-quality crystal growth, and improve the photoelectric conversion efficiency when preparing inverted perovskite solar cells.

[0012] Furthermore, bisphosphonic acid self-assembled monomolecule materials I and II can first improve the coverage and uniformity of the hole transport layer. By using small-volume non-fluorinated molecules as "structural fillers," they fill the gaps caused by steric hindrance during the self-assembly of large-volume fluorinated molecules, achieving high-coverage interface engineering. This reduces the steric hindrance of monomolecules, promoting high-density anchoring of bisphosphonic acid groups to the substrate, and significantly enhancing interfacial adhesion and uniformity.

[0013] Furthermore, the hole transport layer of the present invention has the characteristics of low HOMO energy level and high work function, achieving excellent low barrier energy level alignment with the perovskite layer, and possessing efficient hole extraction and electron blocking capabilities.

[0014] Furthermore, the strong hydrogen bonds and electrostatic coordination between the hole transport layer and the perovskite layer of the present invention effectively passivate lattice defects in situ, minimize nonradiative recombination losses, and significantly extend carrier lifetime.

[0015] Furthermore, the hole transport layer of this invention provides strong "blue-shifted hydrogen bonds" and electrostatic interactions through fluorine atoms, deeply passivating lattice defects on the perovskite substrate in situ. Additionally, it improves wettability, suppresses disordered nucleation, and induces the growth of high-quality perovskite crystals. This enhances the photoelectric conversion efficiency of the device, resulting in excellent anti-degradation stability.

[0016] According to a second aspect of the present invention, a method for preparing a hole transport layer is provided, comprising the following steps: S1. Dissolve bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II in ethanol, mix them evenly to obtain a mixture; S2. The mixture is applied to the substrate surface and annealed to obtain a hole transport layer.

[0017] According to a preferred embodiment of the present invention, the annealing temperature is 100~120°C. For example, the temperature includes 100°C, 105°C, 110°C, 115°C, 120°C, or any sub-range consisting of any two of the above values.

[0018] According to a preferred embodiment of the present invention, the annealing time is 5 to 20 minutes. For example, it includes 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, or any sub-range consisting of two of the above values.

[0019] According to a preferred embodiment of the present invention, in step S2, the mixture is coated by spin coating.

[0020] According to a preferred embodiment of the present invention, the rotation speed of the spin coating method is 3000~5000 rpm. For example, it includes 3000 rpm, 3500 rpm, 4000 rpm, 4500 rpm, 5000 rpm, or any sub-range composed of two of the above values.

[0021] According to a preferred embodiment of the present invention, the rotation time of the spin coating method is 20 to 40 seconds. For example, it includes 20 seconds, 25 seconds, 28 seconds, 30 seconds, 33 seconds, 35 seconds, 38 seconds, 40 seconds, or any sub-range composed of two of the above values.

[0022] According to a preferred embodiment of the present invention, in step S1, the concentrations of bisphosphonic acid self-assembled monomolecule I and bisphosphonic acid self-assembled monomolecule II in the mixture are independently selected from 0.5 to 1 mg / mL. For example, it includes 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL, 1 mg / mL, or any sub-range consisting of any two of the above values.

[0023] According to a preferred embodiment of the present invention, the substrate includes at least one of ITO conductive glass, FTO conductive glass, and PET flexible conductive substrate.

[0024] According to a preferred embodiment of the present invention, the substrate needs to be cleaned and activated before use.

[0025] According to a preferred embodiment of the present invention, the cleaning and activation methods include the following: The substrate was first ultrasonically cleaned with deionized water, acetone and ethanol, and then irradiated in a UV-Ozone cleaner.

[0026] A third aspect of the present invention provides an inverted perovskite solar cell, comprising the hole transport layer described in the first aspect of the present invention.

[0027] It is understood that the inverted perovskite solar cell prepared by the hole transport layer of the present invention can further improve the device lifetime and significantly improve the photoelectric conversion efficiency.

[0028] The fourth aspect of this invention provides a hole transport layer as described above for use in the fabrication of single-junction perovskite solar cells, perovskite tandem solar cells, or perovskite solar cells. Applications in organic tandem batteries.

[0029] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0030] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 These are Kelvin probe force microscopy (KPFM) images of the hole transport layer in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention. Figure 2 These are water contact angle diagrams of the hole transport layer in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 3 These are X-ray photoelectron spectroscopy (XPS) images of the hole transport layer in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 4 These are scanning electron microscope (SEM) images of the hole transport layer in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 5 These are X-ray diffraction (XRD) patterns of the hole transport layer in Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention; Figure 6This is an ultra-long stability aging tracking line graph of devices fabricated from the hole transport layers of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention, with a duration of up to 1000 hours. Detailed Implementation

[0031] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0032] Unless otherwise specified, the reagents, methods and equipment used in this invention are all conventional reagents, methods and equipment in this technical field.

[0033] Example 1 This example provides a hole transport layer comprising bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II; the mass ratio of bisphosphonic acid self-assembled monomolecule material II to bisphosphonic acid self-assembled monomolecule material I is 1:0.11.

[0034] The structural formula of bisphosphonic acid self-assembled monomolecule material I is shown below: ; The structural formula of bisphosphonic acid self-assembled monomolecule material II is shown below: .

[0035] The method for preparing the hole transport layer is as follows: Substrate cleaning and activation: ITO conductive glass with a sheet resistance of 7 Ω / sq was selected. The substrate was sequentially treated with a special detergent, deionized water, acetone, and ethanol in a 40 kHz ultrasonic cleaner for 30 minutes each. After drying with high-purity nitrogen, it was irradiated in a UV-Ozone cleaner for 20 minutes.

[0036] S1. In a glove box, bisphosphonic acid self-assembled monomolecular material II (3-BPIC-F) and bisphosphonic acid self-assembled monomolecular material I (3-BPIC) powders were separately dissolved in anhydrous ethanol to prepare independent stock solutions of 0.9 mg / mL. The solutions were magnetically stirred for 3 hours and sonicated for 10 minutes. Subsequently, the two stock solutions were mixed at a volume ratio of 1:0.11 and filtered using a 0.22-micron polytetrafluoroethylene filter.

[0037] S2. Pipette 40 μL of the mixture onto an ITO substrate, let it stand for 10 seconds, then spin coat at 4000 rpm for 30 seconds. After spin coating, immediately transfer to a 100°C hot plate for annealing for 10 minutes. After annealing and cooling, spin coat with a small amount of pure anhydrous ethanol at 4000 rpm for 30 seconds to remove all physically adsorbed excess molecules, obtaining the hole transport layer.

[0038] Example 2 This example provides a hole transport layer, which uses the same raw materials and preparation method as in Example 1. The difference is that the mass ratio of bisphosphonic acid self-assembled monomolecule material II (3-BPIC-F) to bisphosphonic acid self-assembled monomolecule material I (3-BPIC) powder is 1:0.428.

[0039] Example 3 This example provides a hole transport layer with the same raw materials and preparation method as in Example 1. The difference is that the mass ratio of bisphosphonic acid self-assembled monomolecule material II (3-BPIC-F) and bisphosphonic acid self-assembled monomolecule material I (3-BPIC) powder is 1:1.

[0040] Example 4 This example provides a hole transport layer, which uses the same raw materials and preparation method as in Example 1. The difference is that the mass ratio of bisphosphonic acid self-assembled monomolecule material II (3-BPIC-F) to bisphosphonic acid self-assembled monomolecule material I (3-BPIC) powder is 1:2.33.

[0041] Comparative Example 1 This example provides a hole transport layer, which is prepared in the same way as in Example 1. The difference is that only one raw material, bisphosphonic acid self-assembled monomolecule material II (3-BPIC), is used.

[0042] Comparative Example 2 This example provides a hole transport layer, which is prepared in the same way as in Example 1. The difference is that only one raw material, bisphosphonic acid, is used to self-assemble a single-molecule material I (3-BPIC-F).

[0043] First, the hole transport layers of Examples 1, 1, and 2 of this invention were tested using Kelvin probe force microscopy (KPFM). KPFM is an advanced non-destructive characterization technique capable of mapping the contact potential difference (CPD) of material surfaces at the nanoscale. The distribution of CPD directly reflects the local work function and charge distribution state of the surface. In the interface engineering of perovskite solar cells, if there are drastic fluctuations in surface potential (i.e., a large half-width at half-maximum (FWHM) of the CPD histogram), it indicates the presence of chemical heterogeneity, molecular aggregation, or localized defect states on the surface. These regions of potential fluctuation are the fatal carrier recombination centers. Therefore, the core scientific standard for evaluating the quality of an interface is: the smaller the FWHM of the CPD peak distribution, the more uniform the surface potential, and the more perfect the interface quality. The results of this invention are as follows: Figure 1 As shown, the size of FWHM is: Example 1 (Co-SAMs) > Comparative Example 1 (3-BPIC-F) > Comparative Example 2 (3-BPIC).

[0044] Furthermore, the hole transport layers of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention were subjected to water contact angle tests, and the results are as follows: Figure 2 As shown, the hole transport layer in Embodiment 1 of the present invention is at a moderate level of hydrophobicity, which is beneficial for high-quality film growth.

[0045] Furthermore, the hole transport layers of Examples 1, 1, and 2 of this invention were subjected to X-ray photoelectron spectroscopy (XPS) testing. X-ray photoelectron spectroscopy (XPS), by measuring the binding energy of inner-shell electrons, can extremely sensitively capture minute changes in the chemical environment and electron cloud density surrounding atoms. When SAM molecules chemically bond or strongly electrostatically interact with the perovskite layer or the underlying ITO, the characteristic peaks of the relevant elements show a significant shift in binding energy. The presence and magnitude of this shift are criteria for measuring whether effective chemical anchoring has been achieved at the interface. The results of this invention are as follows... Figure 3 As shown, the hole transport layer in Example 1 of the present invention exhibits a more significant shift, indicating that the synergistic effect of the bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II of the present invention provides a better anchoring effect compared to Comparative Example 1 and Comparative Example 2.

[0046] Furthermore, the hole transport layers of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention were subjected to SEM testing, and the results are as follows: Figure 4 As shown, the hole transport layer in Embodiment 1 of the present invention has a larger grain size and fewer grain boundaries, indicating that the film quality is higher.

[0047] Furthermore, XRD tests were performed on the hole transport layers of Embodiment 1, Comparative Example 1, and Comparative Example 2 of the present invention. X-ray diffraction (XRD) reflects the long-range order, crystal orientation, and microscopic residual stress within the crystal through Bragg's diffraction law. Since the grain boundaries of perovskites are channels for water intrusion and regions highly enriched with deep-level traps, the absolute physical standard for evaluating the quality of the light absorption layer is: the sharper and higher the intensity of the XRD diffraction peaks, the better. The results of the present invention are as follows: Figure 5 As shown, the diffraction peaks of the hole transport layer in Embodiment 1 of the present invention are sharp and have high intensity.

[0048] Performance testing The hole transport layers of Examples 1-4 and Comparative Examples 1-2 of the present invention were respectively fabricated into devices according to the following methods: 1. Prepare a 1.66 mol / L mixed cationic perovskite precursor solution (dissolve PbI2, FAI, MAI, CsI, and passivating agent MACl in a DMF / DMSO solvent at a volume ratio of 8:2). Drop 50 μL of this solution onto the substrate and spin-coat at 4000 rpm for 40 seconds. At the 32-second countdown, rapidly and in one drop, add 120 μL of ethyl acetate antisolvent containing F-PEAI (0.133 mg / mL) to initiate a transient burst nucleation. Then transfer the film to a 100°C hot plate for annealing for 30 minutes.

[0049] 2. After the crystals have cooled, take 0.3 mg / mL piperazine iodine (PI) isopropanol polar passivation solution and spin-coat it onto the perovskite surface at 5000 rpm for 30 seconds, and then briefly anneal it at 100 degrees Celsius for 10 minutes.

[0050] 3. Transfer the above-mentioned devices to a high-vacuum thermal evaporation system (vacuum degree <1*10). -5 Torr). By precisely controlling the evaporation rate, the following layers are deposited sequentially: a 1 nm thick lithium fluoride (LiF, work function modified layer), a 24 nm thick fullerene (C60, electron transport layer), a 4.7 nm thick copper bath (BCP, hole blocking buffer layer), and finally a 130 nm thick silver electrode, thus completing the assembly of the entire device.

[0051] The photoelectric performance of the fabricated devices was tested using an experimental instrument including a solar simulator equipped with a 450 W xenon lamp, a digital source meter (Keithley), and an external quantum efficiency testing system (Newport-Oriel IQE200). The tests were conducted at room temperature in a glovebox filled with high-purity nitrogen. The illumination conditions were standard AM 1.5G simulated sunlight, and the light intensity was precisely calibrated to 100 mW / cm² using a calibrated standard silicon reference cell before testing. 2 To avoid edge effects causing overestimation of current, a metal mask was strictly used during testing to fix the effective light-receiving area of ​​the device at 0.0465 cm². 2 .

[0052] The results are shown in Table 1: Table 1

[0053] As shown in Table 1, the present invention selects bisphosphonic acid self-assembled single-molecule material I and bisphosphonic acid self-assembled single-molecule material II as the hole transport layer materials. The two work synergistically to effectively increase the device lifetime, induce high-quality crystal growth, and improve the photoelectric conversion efficiency when preparing inverted perovskite solar cells.

[0054] Furthermore, the devices fabricated using the hole transport layers of Embodiment 1, Comparative Example 1, and Comparative Example 2 of this invention were subjected to an aging test. The photoelectric conversion efficiency, measured under standard AM1.5G sunlight simulation for up to 1000 hours, was as follows: Figure 6 As shown, the device of Embodiment 1 of the present invention has better aging resistance and stability.

[0055] The present invention has been described in detail above with reference to the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A hole transport layer, characterized in that, Including bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II; The structural formula of the bisphosphonic acid self-assembled monomolecule material I is shown below: ； The structural formula of the bisphosphonic acid self-assembled monomolecule material II is shown below: 。 2. The hole transport layer according to claim 1, characterized in that, The mass ratio of the bisphosphonic acid self-assembled monomolecule material II to the bisphosphonic acid self-assembled monomolecule material I is 1:(0.05~5).

3. The hole transport layer according to claim 1 or 2, characterized in that, The mass ratio of the bisphosphonic acid self-assembled monomolecule material II to the bisphosphonic acid self-assembled monomolecule material I is 1:(0.11~2.33).

4. A method for preparing a hole transport layer as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Dissolve bisphosphonic acid self-assembled monomolecule material I and bisphosphonic acid self-assembled monomolecule material II in ethanol, mix them evenly to obtain a mixture; S2. The mixture is applied to the substrate surface and annealed to obtain a hole transport layer.

5. The preparation method according to claim 4, characterized in that, The annealing temperature is 100~120℃.

6. The preparation method according to claim 4, characterized in that, The annealing time is 5 to 20 minutes.

7. The preparation method according to claim 4, characterized in that, In step S2, the mixture is coated by spin coating, and / or the spin coating speed is 3000~5000 rpm; And / or, the rotation time of the spin coating method is 20~40s.

8. The preparation method according to claim 4, characterized in that, In step S1, the concentrations of bisphosphonic acid self-assembled monomolecule I and bisphosphonic acid self-assembled monomolecule II in the mixture are independently selected from 0.5 to 1 mg / mL.

9. A reverse perovskite solar cell, characterized in that, Includes the hole transport layer as described in any one of claims 1 to 3.

10. The hole transport layer according to any one of claims 1 to 3 in the fabrication of single-junction perovskite solar cells, perovskite tandem solar cells, or perovskite... Applications in organic tandem batteries.

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