Hole transport layer and preparation method thereof, and solar cell comprising hole transport layer

Abstract

The invention provides a hole transport layer, a preparation method thereof and a solar cell comprising the hole transport layer, and the preparation method of the hole transport layer comprises the following steps: dissolving a monophosphate material Me-4PACz and a bisphosphate material 3-BPIC-F in an organic solvent according to a certain mass ratio to obtain a hole transport layer precursor solution; depositing on the surface of a substrate by a solution method process; after deposition, annealing treatment is carried out to promote self-assembly and ordered arrangement of molecules so as to obtain a hole transport layer with the thickness of 1-2 nm; the hole transport layer obtained by the method is a mixed self-assembly monomolecular layer system based on Me-4PACz and 3-BPIC-F, and through the synergistic effect of the two materials, the interface performance of a photoelectric device is optimized, so that the photoelectric conversion efficiency and long-term stability of the device are remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a hole transport layer and its preparation method, and a solar cell containing the hole transport layer. Background Technology

[0002] Perovskite solar cells have attracted widespread attention due to their high photoelectric conversion efficiency, low material cost and simple process. Their laboratory efficiency has exceeded 27%, approaching the level of crystalline silicon devices.

[0003] Among interface modification materials, Me-4PACz ((4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid) with a monophosphonate structure and 3-BPIC-F (a fluorinated aromatic molecule substituted with bisphosphonate) with a bisphosphonate structure exhibit significant advantages due to their unique structural characteristics: the carbazole group of Me-4PACz possesses excellent conjugation properties, and its monophosphonic acid group can react with Pb on the perovskite surface. 2+ Precise combination achieves efficient defect passivation; 3-BPIC-F relies on the axisymmetric structure of bisphosphonates to form higher adsorption energy, shorter interfacial spacing and more uniform surface coverage on ITO substrates. At the same time, the introduction of fluorine atoms increases the molecular dipole moment, which can not only efficiently regulate the substrate work function, but also enhance the hole extraction capability. Both perform outstandingly in a single functional dimension.

[0004] However, the inherent defects of single SAM materials have become the core bottleneck restricting the performance breakthrough and industrial application of perovskite solar cells, specifically in three aspects:

[0005] 1. Lack of functional balance: Although Me-4PACz can effectively passivate perovskite surface defects, the monophosphonate molecules are prone to uneven stacking during self-assembly, and the carbazole group has low intrinsic conductivity, which directly limits the charge transport efficiency; although 3-BPIC-F achieves excellent hole extraction through the synergistic effect of bisphosphonate and fluorine atoms, its molecular structure has a much weaker passivation ability for deep perovskite defects than Me-4PACz, and cannot simultaneously meet the dual core requirements of "defect passivation-charge transport".

[0006] 2. Insufficient interface compatibility: The monophosphonate surface of Me-4PACz is highly hydrophobic and has poor wettability with perovskite precursor solutions, which can easily lead to grain boundary defects during the crystallization of the photoactive layer; Although 3-BPIC-F has excellent compatibility with the active layer interface, the anchoring stability of bisphosphonates to the substrate is still lacking when used alone, and the risk of interface peeling is likely to occur during long-term operation.

[0007] 3. Limited stability improvement: Whether it is the monophosphonate Me-4PACz or the bisphosphonate 3-BPIC-F, the SAM interface barrier formed by a single molecule is insufficient to block water and oxygen erosion, and cannot effectively inhibit the hydrolysis and oxidation of perovskite materials, resulting in significant performance degradation of the device under long-term light exposure or humid heat environment.

[0008] The aforementioned shortcomings indicate that existing single SAM materials cannot simultaneously meet the requirements of efficient defect passivation, stable charge transport, and long-term environmental tolerance, necessitating the development of novel interface modification systems. Summary of the Invention

[0009] To address the shortcomings of existing technologies where a single SAM material cannot simultaneously achieve efficient charge extraction, deep defect passivation, and interface stability, the present invention aims to provide a hole transport layer and its preparation method, as well as a solar cell containing the hole transport layer. The hole transport layer is a hybrid self-assembled monolayer system based on Me-4PACz and 3-BPIC-F. Through the synergistic effect of the two materials, the interface performance of the optoelectronic device is optimized, thereby significantly improving the photoelectric conversion efficiency and long-term stability of the device.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] The first aspect of this invention is to provide a method for preparing a hole transport layer, comprising the following steps:

[0012] (1) Dissolve Me-4PACz and 3-BPIC-F in an organic solvent at a mass ratio of (1:5) to (5:1) to form a homogeneous mixed solution; the total concentration of Me-4PACz and 3-BPIC-F in the mixed solution is 0.1 to 5 mg / mL;

[0013] (2) The homogeneous mixed solution obtained in step (1) is deposited on the substrate surface using a solution method.

[0014] (3) After deposition, annealing is performed to promote the orderly arrangement of molecular self-assembly, resulting in a hole transport layer with a thickness of 1-2 nm.

[0015] Furthermore, the organic solvent in step (1) includes at least one of anhydrous ethanol and DMF.

[0016] Preferably, in step (1), the mass ratio of Me-4PACz to 3-BPIC-F is (1:3) to (3:1).

[0017] Furthermore, in step (2), the solution method is selected from one of the spin coating, immersion, or spray coating processes.

[0018] Furthermore, in step (2), the solution method is a spin coating process with a spin coating speed of 1000-5000 rpm and a time of 20-30 s.

[0019] Furthermore, in step (2), the solution method is an immersion process with an immersion time of 10 to 600 seconds.

[0020] Furthermore, in step (3), the annealing temperature is 60-120°C and the time is 5-30 min.

[0021] A second aspect of the present invention is to provide a hole transport layer, which is prepared by the above-described preparation method.

[0022] A third aspect of the present invention is to provide a solar cell comprising the aforementioned hole transport layer, wherein the solar cell is a perovskite solar cell or an organic solar cell.

[0023] Compared with the prior art, the present invention has at least the following beneficial effects:

[0024] 1. More comprehensive defect passivation: Me-4PACz anchors surface Pb through phosphonic acid groups. 2+ 3-BPIC-F blocks grain boundary ion vacancies through fluorinated and carboxylic acid groups, doubly suppressing nonradiative recombination and forming a "surface-grain boundary" dual passivation network; this synergistic effect increases the open-circuit voltage (V) by reducing nonradiative recombination losses. oc This makes a key contribution to achieving higher photoelectric conversion efficiency (PCE).

[0025] 2. Enhanced interface stability: The methoxy group (-OCH3) of Me-4PACz and the fluorinated group (-F) of 3-BPIC-F form a dense hydrophobic barrier, effectively blocking water and oxygen corrosion. At the same time, the conjugated benzene ring in the 3-BPIC-F molecule and the carbazole group of Me-4PACz form strong interlayer adhesion through π-π stacking, extending device life.

[0026] 3. Better process adaptability: 3-BPIC-F improves the wettability of Me-4PACz, and Me-4PACz assists 3-BPIC-F in orderly film formation, reducing crystallization defects and improving the consistency of large-area preparation. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell provided in an embodiment of this application.

[0028] Figure 2 This is a schematic diagram of the static water contact angle of the hole transport layer in Embodiment 2 of this application.

[0029] Figure 3This is a schematic diagram of the static water contact angle of the hole transport layer in Comparative Example 1 of this application.

[0030] Figure 4 This is a schematic diagram of the static water contact angle of the hole transport layer in Comparative Example 2 of this application.

[0031] Figure 5 These are images showing the appearance of the perovskite films in Examples 2, 1, and 2 of this application.

[0032] Figure 6 This is a SEM image of the perovskite thin film in Example 2 of this application.

[0033] Figure 7 This is a SEM image of the perovskite thin film in Comparative Example 1 of this application.

[0034] Figure 8 This is a SEM image of the perovskite thin film in Comparative Example 2 of this application.

[0035] Figure 9 The stability of the devices in Example 2 (C2), Comparative Example 1 (T1), and Comparative Example 2 (T2) at 85°C and 85% RH (relative humidity) is measured.

[0036] In the figure: 1-Transparent conductive substrate; 2-Hole transport layer; 3-Perovskite thin film; 4-Electron transport layer; 5-Back electrode layer. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0038] This invention first provides a method for preparing a hole transport layer, comprising the following steps:

[0039] (1) Dissolve Me-4PACz and 3-BPIC-F in an organic solvent at a mass ratio of (1:5) to (5:1) to form a homogeneous mixed solution; the total concentration of Me-4PACz and 3-BPIC-F in the mixed solution is 0.1 to 5 mg / mL;

[0040] (2) The homogeneous mixed solution obtained in step (1) is deposited on the substrate surface using a solution method.

[0041] (3) After deposition, annealing is performed to promote the orderly self-assembly of molecules, resulting in a hole transport layer with a thickness of 1–2 nm; wherein, the structural formula of Me-4PACz is:

[0042]

[0043] The structural formula of 3-BPIC-F is:

[0044]

[0045] The hole transport layer preparation method of this invention involves blending monophosphate material Me-4PACz and diphosphate material 3-BPIC-F at a certain mass ratio to form a hybrid SAMs hole transport layer. Through the complementary and synergistic effects of the structural advantages of the two materials (Me-4PACz and 3-BPIC-F) (Me-4PACz has excellent defect passivation ability, while 3-BPIC-F has more uniform surface coverage and dipole moment), it can achieve efficient passivation of perovskite defects at both deep and shallow layers using the monophosphonate of Me-4PACz, and optimize the interfacial charge extraction efficiency by relying on the diphosphonate and fluorine atoms of 3-BPIC-F. Simultaneously, the interface wettability of the hybrid system can be controlled. By anchoring stability to the substrate and constructing a denser water and oxygen barrier, multi-dimensional performance optimization of "defect passivation-charge transport-interface stability" is ultimately achieved, providing key technical support for the high performance and industrial application of perovskite solar cells. Among them, the thickness of the prepared hole transport layer is 1-2 nm, which can ensure complete molecular coverage to effectively exert the role of SAMs, while maintaining its molecular-level order and uniformity, reducing resistance, avoiding grain boundary defects, improving film stability and performance consistency, and preventing molecular shedding and aggregation. If the thickness is too thin (less than 1 nm), it may lead to incomplete molecular coverage and a large number of exposed areas on the substrate surface, which cannot effectively exert the interface regulation, passivation or functionalization role of SAMs. For example, in perovskite solar cells, excessively thin SAMs cannot adequately passivate perovskite surface defects, increasing the probability of carrier recombination and reducing device efficiency. If the thickness is too thick (greater than 2 nm), SAMs may transform from an ordered monolayer into a multilayer stack or a disordered structure, destroying their molecular-level order and uniformity. Furthermore, excessively thick SAMs introduce additional resistance, affecting charge transport efficiency. They are also prone to grain boundaries or defects, reducing the stability and performance consistency of the film, and may also lead to an imbalance in intermolecular forces, causing problems such as SAMs shedding and agglomeration in subsequent processes.

[0046] The hole transport layer and its preparation method of the present invention are applicable to the interface modification of optoelectronic devices such as perovskite solar cells and organic solar cells. The preparation process is compatible with both flexible and rigid substrates and can be seamlessly integrated with existing device preparation processes. The process can be achieved at low temperature using a solution method and can form a film in air, which is beneficial for large-scale production and cost control. At the same time, the solution method process can be seamlessly integrated with the perovskite layer deposition process, which is convenient for industrial scale-up.

[0047] Furthermore, the organic solvent in step (1) includes at least one of anhydrous ethanol and DMF.

[0048] Preferably, the mass ratio of Me-4PACz to 3-BPIC-F in step (1) is (1:3) to (3:1).

[0049] Hole transport layers were prepared by mixing 3-BPIC-F and Me-4PACz at a mass ratio of (1:3) to (3:1). This process can better optimize the interface energy level matching, making the HOMO energy level more accurately match the perovskite valence band, reducing the hole extraction energy barrier, enhancing carrier transport dynamics, forming a more continuous hole transport network, improving mobility, and synergistically passivating perovskite surface / deep defects. Different functional groups were used to specifically passivate iodine vacancies, lead vacancies, etc., and the perovskite grain morphology was controlled to make the grains larger and more uniform with fewer grain boundaries. This reduced carrier recombination, improved charge transport efficiency and thin film stability, and ultimately improved the performance of perovskite solar cell devices.

[0050] Furthermore, in step (2), the solution method is selected from one of the spin coating, immersion, or spray coating processes.

[0051] Furthermore, in step (2), the solution method is a spin coating process with a spin coating speed of 1000-5000 rpm and a time of 20-30 s.

[0052] Furthermore, in step (2), the solution method is an immersion process with an immersion time of 10 to 600 seconds.

[0053] Furthermore, in step (3), the annealing temperature is 60-120°C and the time is 5-30 min.

[0054] A second aspect of the present invention is to provide a hole transport layer, which is prepared by the above-described preparation method.

[0055] A third aspect of the present invention is to provide a perovskite solar cell, see [link to previous document]. Figure 1 The perovskite solar cell comprises, from bottom to top, a transparent conductive substrate 1, the aforementioned hole transport layer 2, a perovskite thin film 3, an electron transport layer 4, and a back electrode layer 5.

[0056] The transparent conductive substrate 1 includes, but is not limited to, glass, polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), and polycarbonate (PC) combined with one or more of ITO, IWO, FTO, and AZO; the perovskite thin film 3 includes a perovskite material and a surface modifier, wherein the perovskite material is a mixed cationic perovskite and the surface modifier is an organic halide material; the electron transport layer 4 includes an n-type inorganic semiconductor material or an n-type organic semiconductor material, tin oxide (SnO). xTitanium oxide (TiO2), zinc oxide (ZnO), fullerene (C60), [6,6]-phenyl C 61 Methyl butyrate (PCBM) and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) or a combination of at least two of them; the back electrode 5 includes, but is not limited to, any one of a metal electrode, a transparent conductive oxide or a carbon electrode.

[0057] The present invention will be described in detail below with reference to specific embodiments, but this does not limit the present invention.

[0058] The materials and reagents used in the following examples are all commercially available products.

[0059] Example 1

[0060] The fabrication of the perovskite solar cell in this embodiment includes the following steps:

[0061] S1. Cleaning of transparent conductive substrate 1: A large area (50mm×50mm) ITO transparent conductive substrate 1 was ultrasonically treated with acetone and isopropanol for 25min respectively, and the surface was dried with nitrogen; then it was treated with ultraviolet ozone for 10min; the ultrasonic cleaning power was 100Hz and the time was 15min.

[0062] S2. Preparation of hole transport layer 2: Me-4PACz and 3-BPIC-F in a mass ratio of 5:1 were dissolved in ethanol and sonicated for 15 min to obtain a homogeneous mixed solution with a concentration of 0.5 mg / mL. The mixed solution was deposited on the upper surface of the transparent conductive substrate 1 by spin coating. The spin coating parameters were 5000 rpm for 30 s. After spin coating, the substrate was annealed at 100℃ for 10 min to obtain hole transport layer 2.

[0063] S3. Preparation of perovskite film 3: 668.45 mg of lead iodide (PbI2), 236.89 mg of formamidinium iodide (FAI), and 18.84 mg of cesium iodide (CsI) were weighed and placed in a solvent (volume ratio DMF:DMSO = 4:1), stirred until completely dissolved, and a mixed cation perovskite concentration of 1.5 M was prepared. Then, the solution was filtered three times using a 0.22 μm filter to obtain a perovskite precursor solution (clear yellow liquid). The obtained perovskite precursor solution was spin-coated onto hole transport layer 2 at 4000 rpm for 40 s, and annealed at 100 °C for 30 min to obtain a perovskite film. 2-phenylethylamine hydroiodate was spin-coated onto the perovskite surface for surface passivation at a concentration of 1.0 mg / ml at 4000 rpm for 40 s, and annealed at 100 °C for 10 min to obtain perovskite film 3.

[0064] S4. Fabrication of electron transport layer 4: A 30 nm thick C layer was deposited on the perovskite film 3 by vacuum evaporation. 60 The resulting components are then placed in a vacuum coating machine and coated in C... 60 A layer of SnO was deposited on top. x Thus, an electron transport layer is obtained;

[0065] S5. Preparation of back electrode layer 5: The component obtained in step S4 is placed in a vacuum coating machine, and a 100nm metal Cu electrode is deposited on the buffer layer 5 by thermal evaporation to obtain a perovskite solar cell, denoted as C1.

[0066] Example 2

[0067] The fabrication of the perovskite solar cell in this embodiment differs from that in Example 1 only in that the mass ratio of Me-4PACz to 3-BPIC-F in step S2 is 5:3.

[0068] The resulting perovskite solar cell is denoted as C2.

[0069] Example 3

[0070] The fabrication of the perovskite solar cell in this embodiment differs from that in Example 1 only in that the mass ratio of Me-4PACz to 3-BPIC-F is 1:1.

[0071] The resulting perovskite solar cell is designated C3.

[0072] Example 4

[0073] The only difference between the preparation of the perovskite solar cell in this embodiment and that in Example 1 is that the mass ratio of Me-4PACz to 3-BPIC-F in step S2 is 1:2.

[0074] The resulting perovskite solar cell is designated C4.

[0075] Comparative Example 1

[0076] The preparation of the perovskite solar cell in this comparative example differs from that in Example 1 only in that: step S2 is as follows: Me-4PACz is dissolved in ethanol and sonicated for 15 min to obtain a uniform solution with a concentration of 0.5 mg / mL. The solution is then deposited on the upper surface of the transparent conductive substrate 1 by spin coating. The spin coater parameters are 5000 rpm for 30 s. After spin coating, the substrate is annealed at 100°C for 10 min to obtain the hole transport layer 2.

[0077] The resulting perovskite solar cell is denoted as T1.

[0078] Comparative Example 2

[0079] The preparation of the perovskite solar cell in this comparative example differs from that in Example 1 only in that: step S2 is as follows: 3-BPIC-F is dissolved in ethanol, and after sonication for 15 min, a uniform solution with a concentration of 0.5 mg / mL is obtained. The solution is then deposited on the upper surface of the transparent conductive substrate 1 by spin coating. The spin coater parameters are 5000 rpm for 30 s. After spin coating, the substrate is annealed at 100°C for 10 min to obtain the hole transport layer 2.

[0080] The resulting perovskite solar cell is denoted as T2.

[0081] JV tests were performed on C1–C4 and T1–T2: a standard solar intensity calibration was performed using a solar simulator, and the calibration was applied to an area of ​​10.5 cm². 2 The above C1~C4 and T1~T2 were subjected to JV testing, including photoelectric conversion efficiency (PCE), fill factor (FF), and open-circuit voltage (V). oc ) and short-circuit current (J sc The test was conducted with a starting voltage of 8.5V, a cutoff voltage of -0.1V, and a test step size of 0.2V. The test results are shown in Table 1.

[0082] Table 1. JV test results for C1~C4 and T1~T2

[0083] Devices Voc(V) <![CDATA[Jsc(mA / cm 2 )]]> FF (%) PCE (%) C1 7.93 3.22 82.92 21.17 C2 8.41 3.26 82.53 22.50 C3 8.29 3.20 81.60 21.62 C4 8.13 3.21 82.23 21.46 T1 7.63 3.24 82.66 20.45 T2 7.54 3.22 82.11 19.91

[0084] As shown in Table 1, the perovskite solar cell based on the Me-4PACz and 3-BPIC-F hybrid hole transport layer of the present invention exhibits significantly improved device performance compared to the Me-4PACz-based perovskite solar cell (Comparative Example 1) and the 3-BPIC-F-based perovskite solar cell (Comparative Example 2). The optimal ratio is 5:3 (Example 2), with a PCE improvement of over 2%. This improvement mainly comes from V. oc V oc An increase of over 10.2%.

[0085] The hole transport layers obtained in step S2 of Examples 2 and Comparative Examples 1-2 were subjected to hydrophilicity tests, and their contact angles were measured using a contact angle tester.

[0086] In Comparative Example 1, the hole transport layer (containing only Me-4PACz) obtained in step S2 has a static water contact angle of 82.058°, exhibiting a hydrophobic surface (such as...). Figure 3 As shown); the static water contact angle of the hole transport layer (containing only 3-BPIC-F) obtained in step S2 of Comparative Example 2 is 13.292°, exhibiting a strongly hydrophilic surface (as shown). Figure 4As shown); the static water contact angle of the hybrid hole transport layer (a mixture of Me-4PACz and 3-BPIC-F) obtained in step S2 of Example 2 is 30.413°, exhibiting moderate hydrophilicity (as shown). Figure 2 (As shown); The above data indicate that mixing Me-4PACz with 3-BPIC-F significantly alters the surface properties of the resulting hybrid hole transport layer. Its wettability falls between that of the two single components, shifting from hydrophobicity to moderate hydrophilicity. Furthermore, the film quality is optimized. This optimized surface property facilitates the spreading and nucleation of the perovskite precursor solution on the transport layer, thus laying the foundation for forming high-quality, uniform perovskite films and ultimately positively impacting device performance. See [link to relevant documentation] Figure 9 , Figure 9 The stability of devices C2 in Example 2, T1 in Comparative Example 1, and T2 in Comparative Example 2 under the test conditions of 85°C and 85% RH (relative humidity) is compared. It can be seen that device C2 in Example 2 (a perovskite solar cell based on a hybrid hole transport layer of Me-4PACz and 3-BPIC-F) exhibits the best stability, maintaining an efficiency of over 80% of its initial efficiency after more than 1000 hours, with extremely gradual degradation. In contrast, device T1 in Comparative Example 1 (a Me-4PACz-based perovskite solar cell) only maintains about 60% of its initial efficiency after more than 1000 hours. Device T2 in Comparative Example 2 (a 3-BPIC-F-based perovskite solar cell) shows the fastest efficiency degradation, with its efficiency dropping to only 30% of its initial efficiency after more than 1000 hours. Clearly, the hole transport layer obtained by mixing the two materials in a certain proportion can significantly enhance the stability of the battery under high humidity and high temperature conditions.

[0087] Figure 5These are images showing the film appearance of the perovskite films in Examples 2, 1, and 2 of this application. From the film appearance, when the perovskite film is formed on a Me-4PACz-based hole transport layer (Comparative Example 1), the resulting perovskite film 3 exhibits obvious pores and discontinuous defects; when formed on a 3-BPIC-F-based hole transport layer (Comparative Example 2), the resulting perovskite film 3 is uniform and dense; when formed on a mixed hole transport layer (a mixture of Me-4PACz and 3-BPIC-F) (Example 2), the resulting perovskite film is a uniform film without obvious defects. 3-BPIC-F, due to its excellent film formation characteristics, through π-π stacking... Intermolecular forces such as overlapping and polar interactions effectively suppress phase separation and molecular aggregation problems that easily occur when Me-4PACz forms films alone. Simultaneously, it optimizes the film-forming kinetics and process adaptability of the mixed system, compensating for the inherent shortcomings of Me-4PACz, such as insufficient fluidity and poor film continuity. Ultimately, the resulting perovskite film 3 exhibits a uniform, dense appearance with no obvious pores or discontinuous regions. Furthermore, the perovskite films 3 obtained in step S3 of Example 2, Comparative Example 1, and Comparative Example 2 were characterized using scanning electron microscopy. The SEM images of the perovskite films 3 obtained in step S3 of Example 2 and Comparative Examples 1-2 are shown below. Figures 6-8 As shown, Figures 6-8 As can be seen from the data: When Me-4PACz is used as the hole transport layer, the perovskite film 3 exhibits obvious pores, blurred grain boundaries, and inhomogeneity. This type of structure is prone to generating many defects (such as carrier recombination centers at grain boundaries), which may affect the carrier transport efficiency and stability of perovskite devices. When 3-BPIC-F is used as the hole transport layer, the perovskite film 3 exhibits uniform grain size, clear boundaries, and no obvious pores. It can provide a uniform interface for perovskite nucleation and growth, promoting orderly grain growth. However, it should be noted that there is a certain amount of lead iodide (PbI2) residue on its film surface, and PbI2 can easily become carrier recombination centers and accelerate perovskite decomposition. When Me-4PACz and 3-BPIC-F are mixed as the hole transport layer, the perovskite film has better grain uniformity, no obvious pores, and the grain size is between the former two and the distribution is relatively uniform. Furthermore, Me-4PACz can react with PbI2 through active groups (such as phosphonic acid groups) in its molecules. 2+Strong coordination occurs, effectively reducing the potential PbI2 residue caused by 3-BPIC-F and significantly reducing defect sites. This indicates that the perovskite film prepared on the mixed hole transport layer (a mixture of Me-4PACz and 3-BPIC-F) has significantly reduced crystallization defects and significantly improved structural quality. It can also synergistically suppress nonradiative recombination induced by PbI2, and significantly improve the consistency of large-area preparation. This structure is beneficial to reducing carrier recombination at grain boundaries and improving carrier transport efficiency. At the same time, the denser and more uniform grain structure can enhance the stability of the perovskite film and reduce the erosion of the external environment (such as water and oxygen) and the degradation caused by PbI2.

[0088] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent transformations or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a hole transport layer, characterized in that, Includes the following steps: (1) Dissolve Me-4PACz and 3-BPIC-F in an organic solvent at a mass ratio of (1:5) to (5:1) to form a homogeneous mixed solution; the total concentration of Me-4PACz and 3-BPIC-F in the mixed solution is 0.1 to 5 mg / mL; (2) The homogeneous mixed solution obtained in step (1) is deposited on the substrate surface using a solution method. (3) After deposition, annealing is performed to promote the orderly arrangement of molecular self-assembly, resulting in a hole transport layer with a thickness of 1-2 nm.

2. The preparation method according to claim 1, characterized in that, The organic solvent in step (1) includes at least one of anhydrous ethanol and DMF.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of Me-4PACz to 3-BPIC-F is (1:3) to (3:1).

4. The preparation method according to claim 1, characterized in that, In step (2), the solution method is selected from one of the spin coating, immersion, or spray coating processes.

5. The preparation method according to claim 1, characterized in that, In step (2), the solution method is a spin coating process with a spin coating speed of 1000-5000 rpm and a time of 20-30 s.

6. The preparation method according to claim 1, characterized in that, In step (2), the solution method is an immersion process with an immersion time of 10 to 600 seconds.

7. The preparation method according to claim 1, characterized in that, In step (3), the annealing temperature is 60-120℃ and the time is 5-30min.

8. A hole transport layer, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. A solar cell, characterized in that, It includes a hole transport layer, wherein the hole transport layer is the hole transport layer of claim 8 or is prepared by any one of the preparation methods of claims 1 to 7.

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