Carbazole polymer hole transport material applied to trans-perovskite solar cell

Abstract

The invention belongs to the field of organic photoelectric polymer materials, and discloses a carbazole polymer hole transport material applied to a trans-perovskite solar cell, and the carbazole polymer has a chemical structure as shown in a general formula (A). The chemical structure of the polymer is improved, carbazole and thiophene are used as main chain frameworks, a certain proportion of thiophene units containing alkyl sodium sulfonate side chains and substituted carbazole units containing diphenyl phosphinoxyl side chains are introduced into the structure, and the random quadripolymer with the ionic characteristics as shown in the general formula (A) is constructed. According to the invention, by covalently introducing a diphenyl phosphine oxide group and a sodium sulfonate functional group into a polymer chain, the polymer material has excellent hole transport performance and good film forming quality at the same time. General formula (A).

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronic polymer materials, and more specifically, relates to a carbazole polymer hole transport material for use in inverted perovskite solar cells. Background Technology

[0002] Since their inception in 2009, perovskite solar cells (PVSCs) have demonstrated enormous commercial potential due to their excellent light absorption performance, long carrier diffusion length, and low-cost fabrication. Among various device structures, inverted (p-i-n type) perovskite solar cells have become a key research and application area due to their advantages such as simple fabrication process, high interface stability, low hysteresis effect, and suitability for constructing flexible and tandem photovoltaic devices. In inverted perovskite solar cells, the hole transport layer not only performs the functions of hole extraction and transport but also plays a crucial role in regulating the nucleation, crystallization, and interface energy level matching of the perovskite thin film, thus having a decisive impact on the efficiency and stability of the device.

[0003] The most widely used high-performance hole transport material is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA). While this material exhibits excellent energy level matching and hole migration properties, it suffers from significant drawbacks. Its strong intrinsic hydrophobicity hinders the wetting and uniform film formation of perovskite precursor solutions, easily leading to uneven perovskite layer morphology. Therefore, developing a polymer hole transport material with good solution processability, improved interfacial interactions, and promotion of perovskite crystallization is crucial for realizing high-efficiency inverted perovskite solar cells. Summary of the Invention

[0004] To address the issue of strong hydrophobicity in existing hole transport materials such as PTAA, this invention aims to provide a carbazole-based polymer hole transport material for inverted perovskite solar cells. This material is produced by modifying the chemical structure of the polymer, using carbazole and thiophene as the main chain backbone. A certain proportion of thiophene units containing alkyl sulfonate side chains and substituted carbazole units containing diphenylphosphoxy side chains are introduced into the structure, resulting in a random quaternary copolymer with ionic properties as shown in general formula (A). This invention covalently introduces diphenylphosphoxy and sodium sulfonate functional groups into the polymer chain, enabling the polymer material to possess both excellent hole transport performance and good film formation quality. Applying this quaternary copolymer as a hole transport layer in inverted perovskite solar cells can significantly improve the crystal quality (i.e., perovskite crystal quality) and interfacial energy level matching of the perovskite film, thereby effectively improving the energy conversion efficiency of the device and solving the technical problem of low efficiency in existing inverted perovskite solar cells.

[0005] To achieve the above object, according to one aspect of the present invention, there is provided a carbazole-based polymer, characterized in that the carbazole-based polymer has a chemical structure as shown in the general formula (A):

[0006] General formula (A) In the formula, both a and b are greater than 0, and 0 < a + b < 1, and n is an integer from 10 to 30.

[0007] As a further preference of the present invention, in the general formula (A), a = 0.1 and b = 0.1; correspondingly, the carbazole-based polymer has a structural general formula as shown in the formula PCz-10S10P:

[0008] PCz-10S10P.

[0009] As a further preference of the present invention, the molecular weight of the carbazole-based polymer is 15,000 - 30,000 g / mol.

[0010] According to another aspect of the present invention, the present invention provides an application of the above carbazole-based polymer in a perovskite solar cell.

[0011] As a further preference of the present invention, the carbazole-based polymer is used as a hole transport material.

[0012] As a further preference of the present invention, the perovskite in the perovskite solar cell contains Pb element and / or I element.

[0013] As a further preference of the present invention, the perovskite solar cell is preferably a perovskite solar cell with a trans-planar structure.

[0014] Through the above technical solutions conceived by the present invention, compared with the prior art, the following beneficial effects can be achieved: (1) By introducing a sodium alkyl sulfonate side chain with ionic properties into the polymer of the carbazole and thiophene main chain structure, the present invention significantly improves the solution processing performance of the material, making it have good solubility in conventional solvents. This design effectively improves the surface wettability of the polymer film and is expected to improve the perovskite growth quality.

[0015] (2) The diphenylphosphine oxide group introduced into the polymer side chain by the present invention has good electron donor-acceptor regulation ability. Taking the case where the B position in the perovskite material ABX3 is Pb element and the X position contains I element, this polymer can coordinate with the uncoordinated Pb 2+ ions or I -The vacancies interact, effectively passivating interface defect states and reducing nonradiative recombination of charge carriers at the interface. Furthermore, the strong polarity of the phosphoxy group improves the energy level arrangement of the polymer, making hole injection more efficient and charge transport smoother, thereby lowering the interface energy barrier and increasing the open-circuit voltage and fill factor of the device.

[0016] The carbazole polymer PCz-10S10P exemplified in the later embodiments of this invention, when used as a hole transport material in perovskite solar cells, exhibits performance at a light intensity of 100 mW / cm². -2 Under simulated AM 1.5 G sunlight irradiation conditions, the highest photoelectric conversion efficiency can reach 24.0%.

[0017] In summary, this invention uses carbazole and thiophene as the polymer backbone structure, and introduces sodium alkyl sulfonate and diphenylphosphine oxide into the side chains to control the hydrophobic properties and passivation ability of the material. The resulting carbazole-based polymer hole transport material exhibits excellent solution processing performance and interface control capabilities, and can achieve dense and flat film morphologies under conventional solution processing, significantly improving the crystallinity and photoelectric performance of the perovskite layer. The inverted perovskite solar cell prepared using this material achieves a maximum power conversion efficiency of 24%, demonstrating excellent photoelectric performance. Attached Figure Description

[0018] Figure 1 The synthesis route for PCz-10S10P in Example 1 is shown below.

[0019] Figure 2 The 1H NMR spectrum of PCz-10S10P in Example 1 is shown.

[0020] Figure 3 The UV-Vis absorption spectrum of PCz-10S10P in Example 2 is shown.

[0021] Figure 4 The cyclic voltammetry curves for PCz-10S10P in Example 2 are shown.

[0022] Figure 5 The contact angles of the PCz-10S10P film and the conventional PTAA film with water droplets in Example 3 are shown.

[0023] Figure 6 This is an example of a small-area inverse planar perovskite solar cell (0.08 cm²) using conventional PTAA and PCz-10S10P as hole transport materials, as described in Example 3. 2 ) optimal device JV curve. Detailed Implementation

[0024] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0025] The carbazole polymer in the present invention may have a chemical structure such as that shown in the general formula (A):

[0026] General formula (A) In the formula, 0 < a + b < 1, and n is an integer from 10 to 30.

[0027] When a = 0.1 and b = 0.1, the carbazole polymer has a structural general formula shown as PCz-10S10P:

[0028] PCz-10S10P The following are specific embodiments: Example 1 Synthesis of compound PCz-10S10P: The synthesis route is as Figure 1 shown, Compound 1 (150 mg, 0.23 mmol), compound 2 (12.6 mg, 23 μmol), compound 3 (10.6 mg, 23 μmol), compound 4 (103 mg, 0.18 mmol), anhydrous Na2CO3 (242 mg, 2.3 mmol), Pd2(dba)3 (21 mg, 23 μmol), P( o -tol)3 (33 mg, 0.11 mmol), 2 drops of Aliquat 336, 10 mL of dry toluene and 5 mL of deionized water were added to a 50 mL dry Schlenk flask. Under N2 conditions, three freeze-pump-thaw cycles were performed to remove oxygen, and then it was heated to 90 °C and reacted for 72 h. After cooling, water and dichloromethane were added for extraction, drying, and the solvent was evaporated to obtain a light yellow solid. It was dissolved in a small amount of chloroform and then reprecipitated in methanol, and filtered. The obtained precipitate was loaded into a Soxhlet extractor and extracted successively with 50 - 60 mL of methanol, acetone, and n-hexane for 24 - 30 h each to remove small molecules and catalysts, obtaining 0.10 g of a black solid, denoted as PCz-10S10P, with a yield of 94%. M n = 26.1 kDa and = 1.32. 1 H NMR (600 MHz, Chloroform- d ) δ 8.35 – 8.17 (m, 2H), 7.93 (s, 1H), 7.84 (s), 7.75(s, 1H), 7.63 (s, 2H), 4.77 (s, 1H), 4.25 (s,), 2.48 (d, J = 16.1 Hz, 2H), 2.06 (s, 2H), 1.58 (s, 6H), 1.36 – 1.13 (m, 25H), 0.81 (t, J = 6.9 Hz, 7H). The polymerization reaction of PCz-10S10P is inherently uncontrollable, but under the above conditions, the molecular weight can be stabilized at 15000-30000 g / mol, corresponding to n of 10-30 in the general structural formula of PCz-10S10P, with good reproducibility (this invention underwent multiple synthesis verifications during the experimental process). The 1H NMR spectrum of the product PCz-10S10P is as follows: Figure 2 As shown.

[0029] In addition, the raw materials compound 1, compound 3, and compound 4 used in the above preparation process were all commercially available, and compound 2 was synthesized according to the method in the relevant literature ( Eur. J. Org. Chem. 2025, 28 , e202500229).

[0030] Example 2 The PCz-10S10P material obtained in Example 1 was tested, and the basic photophysical properties of PCz-10S10P were obtained: The UV-Vis absorption spectra of the polymer PCz-10S10P film were measured using a Shimadzu UV-3600 UV-Vis spectrophotometer. The film was obtained by spin-coating a PCz-10S10P chlorobenzene solution (2 mg / mL) at 6000 rpm for 30 s, followed by annealing at 100 °C for 10 min. The results are as follows: Figure 3 As shown. The highest occupied molecular orbital (HOMO) energy levels of the polymer PCz-10S10P were determined by cyclic voltammetry (CV), and the test results are shown in [Figure number missing]. Figure 4 The HOMO level of the polymer was calculated to be -5.57 eV based on the oxidation initiation potential. Combined with the optical band gap determined by the ultraviolet absorption spectrum, its lowest unoccupied molecular orbital (LUMO) level was further calculated to be -2.65 eV.

[0031] Example 3 For the PCz-10S10P material obtained in Example 1, the device performance of PCz-10S10P as a hole transport layer in a perovskite solar cell was tested: First, we tested the contact angles of PTAA and PCz-10S10P films with water, and the results are as follows: Figure 5 As shown, the contact angle of the PCz-10S10P film is 100°, significantly smaller than that of the PTAA film (107°). This result indicates that the introduction of the sodium alkyl sulfonate side chain reduces the hydrophobicity of the polymer, which helps to solve the problem of poor perovskite quality in large-area devices due to strong hydrophobicity. The PTAA and PCz-10S10P film samples were prepared by first dissolving PTAA and PCz-10S10P in chlorobenzene to form PTAA and PCz-10S10P solutions, respectively, with a concentration of 2 mg / mL. Then, the prepared PTAA and PCz-10S10P solutions were spin-coated onto an ITO substrate at 6000 rpm for 30 seconds, followed by annealing at 100 °C for 10 minutes.

[0032] The polymer PCz-10S10P was used as a hole transport material in the fabrication of an inverted planar perovskite solar cell. The specific device structure was ITO / HTM / perovskite / C 60 / Bathocuproine (BCP) / Ag, using (FA) 0.92 MA 0.08 ) 0.9 Cs 0.1 Pb(I 0.92 Br 0.08 )3(FA: NH=CHNH3 + MA: CH3NH3 + PCz-10S10P was used as the perovskite layer material. Simultaneously, PCz-10S10P was used as the hole transport material (i.e., HTM). For comparison, PTAA was used instead of PCz-10S10P as the HTM to prepare inverted planar perovskite solar cell samples. Specifically: Glass / ITO substrate (15 Ω sq) -1The glass / ITO substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol, each step lasting 20 minutes. Subsequently, the cleaned glass / ITO substrate was dried in an oven at 100 °C and subjected to oxygen plasma treatment for 10 minutes. Finally, it was transferred to a nitrogen-filled glove box for later use. PTAA and PCz-10S10P were dissolved in chlorobenzene to form PTAA and PCz-10S10P solutions, respectively, with a concentration of 0.2 mg / mL. The prepared PTAA and PCz-10S10P solutions were spin-coated onto the ITO substrate at 6000 rpm for 30 seconds, followed by annealing at 100 °C for 10 minutes. The resulting glass / ITO / HTL was used as the substrate for subsequent processes such as perovskite deposition. The perovskite precursor solution was prepared by dissolving 32.48 mg CsI, 177.99 mg FAI, 10.08 mg MABr, 534.78 mg PbI2, and 33.03 mg PbBr2 in 1 mL of a mixed solvent of DMF:DMSO (volume ratio 5:1). The resulting chemical formula is (FA... 0.92 MA 0.08 ) 0.9 Cs 0.1 Pb(I 0.92 Br 0.08 3. Then, 10 mol% MACl was added to the precursor solution. The perovskite solution was spin-coated onto a glass / ITO / HTL substrate at 5000 rpm for 30 seconds. 12 seconds before the end of the spin-coating, 150 μL of chlorobenzene was slowly added dropwise to the center of the film. The resulting perovskite film was then heated on a hot plate at 65 °C for 5 minutes, followed by heating at 100 °C for 15 minutes. All spin-coating processes were performed at room temperature. Finally, the film was heated under high vacuum conditions (<4 × 10⁻⁶). -6 Torr) sequentially thermally evaporates 20 nm of C. 60 A 6 nm BCP and a 100 nm silver electrode were used. The effective area of ​​each device was defined and measured to be 0.08 cm² using a metal mask. 2 .

[0033] The device was subjected to a light intensity of 100 mW / cm². -2 Under simulated AM1.5G sunlight irradiation conditions, PATT and polymer PCz-10S10P were used as undoped hole transport materials in small-area solar cell devices (0.08 cm²). 2 )of JV Curves Figure 6As shown, for the device using PCz-10S10P as the HTM, the PCE can reach up to 24.0%, which is significantly higher than 21.1% of the PTAA device. It is worth noting that, in order to more clearly show the influence of different HTMs on the growth behavior of perovskite films, passivation materials (such as phenethylammonium iodide) were deliberately not used between the perovskite layer and the electron transport layer during the device preparation process. Therefore, although the efficiency of this device is lower than the highest efficiency value reported currently, it can be clearly seen that the performance of the device prepared with PCz-10S10P is significantly better than that of the device using PTAA, fully demonstrating the potential and advantages of PCz-10S10P in improving device performance. Subsequently, the device efficiency can be further improved by using a passivation layer.

[0034] It can be seen that when the compound PCz-10S10P is used as a hole transport material in a transversely planar perovskite solar cell, the efficiency of the solar cell is significantly improved compared with PTAA. This is due to the optimization of the hydrophobic property, which can improve the growth quality of perovskite.

[0035] In addition, the above embodiments are only examples. For example, in addition to reacting at 90 °C for 72 h used in Example 1, as Figure 1 shown, the reaction temperature for generating the target polymer can be flexibly selected within the range of 80 - 100 °C, and the reaction time can also be flexibly selected within the range of 72 - 80 h. Another example is that the contents of thiophene and diphenylphosphine oxide side chains substituting carbazole in the carbazole polymer can be regulated (in the corresponding general formula A, 0 < a + b < 1). The introduction of the sodium alkyl sulfonate side chain can regulate the hydrophobicity of the material, and diphenylphosphine oxide provides an effective passivation effect to precisely regulate the properties of the material, but does not change the hole transport property of the material. Therefore, it can be inferred that polymers with different contents can also be used as hole transport materials in perovskite solar cells like the PCz-10S10P of the present invention.

[0036] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A carbazole polymer, characterized in that, The carbazole-based polymer has a chemical structure as shown in the general formula (A): General formula (A) In the formula, both a and b are greater than 0, and 0 < a + b < 1, and n is an integer from 10 to 30.

2. The carbazole polymer as described in claim 1, characterized in that, In the general formula (A), a = 0.1 and b = 0.1; correspondingly, the carbazole-based polymer has a structural general formula as shown in the formula PCz-10S10P: PCz-10S10P 3. The carbazole polymer as described in claim 2, characterized in that, The molecular weight of the carbazole-based polymer is 15,000 - 30,000 g / mol.

4. Use of the carbazole-based polymer according to any one of claims 1 - 3 in a perovskite solar cell.

5. The application as described in claim 4, characterized in that, The carbazole-based polymer is used as a hole transporting material.

6. The application as described in claim 4, characterized in that, The perovskite in the perovskite solar cell contains Pb element and / or I element.

7. The application as described in claim 4, characterized in that, The perovskite solar cell is preferably a perovskite solar cell with a reverse planar structure.

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