A passivation layer for passivating the interface of a perovskite thin film and a preparation method and use thereof

Abstract

The application belongs to the technical field of perovskite, and provides a passivation layer for passivating the interface of a perovskite film, and a preparation method and application thereof. The passivation layer is arranged at least at the lower interface of the perovskite layer, and the passivation layer adopts a self-assembled molecular material. The basic structural unit of the self-assembly is a compound with a specific structure. The compound has a biphenyl structure, a plurality of alkyl or halogenated alkyl groups are connected to one of the benzene rings, and a dicyclohexyl phosphine group is connected to the other benzene ring. The passivation layer can passivate the upper interface and / or the lower interface of the perovskite film, so as to improve the energy barrier at the interface and reduce the energy loss caused by non-radiative recombination.

Description

Technical Field

[0001] This invention belongs to the field of perovskite technology, and relates to a passivation layer for passivating the interface of perovskite thin films, its preparation method and application. Background Technology

[0002] Environmental pollution and energy development are issues of common concern worldwide, and also important issues for China's economic development. Social development is inseparable from the emergence of high-quality energy and the use of advanced energy technologies.

[0003] Today, traditional energy sources such as coal and oil not only face the gradual depletion of resources, but are also heavily criticized for the unavoidable pollution caused during their use. Further technological and social development cannot be separated from the development and use of higher-quality energy sources and more advanced energy technologies. Therefore, solar energy, as an important renewable and clean energy source, is playing an increasingly prominent role in the energy sector.

[0004] In the field of solar cells, perovskite solar cells are gaining increasing attention due to their excellent photoelectric properties, such as long carrier diffusion length, tunable bandgap, and high absorption coefficient. When metal halide perovskites were first used as light-absorbing materials in solar cells in 2009, their energy conversion efficiency was only 3.8%. After more than a decade of development, the efficiency of inverted perovskite solar cells has now reached 26.9%, comparable to mature commercial silicon-based solar cells. Moreover, compared to perovskite solar cells, there is still considerable room for improvement in efficiency (the theoretical efficiency is 33%), and given their ease of low-cost manufacturing, they will inevitably be promoted for large-scale production and application.

[0005] However, several challenges remain in the development of perovskite solar cells to ensure optimal performance. For instance, high-density defects at the perovskite film interface often lead to the formation of non-radiative recombination centers, causing unnecessary energy loss. This is often related to the low fill factor and leakage current issues in perovskite solar cells. Therefore, selecting suitable interface engineering materials to passivate energy level defects at the perovskite interface is becoming increasingly important.

[0006] Previous studies have shown that self-assembled monolayers (SAMs) can effectively improve the power conversion efficiency and stability of perovskite solar cells, attracting significant research interest. SAM-based interface passivation materials are two-dimensional nanomaterials, one or several molecules thick, formed by molecules with specific functional properties through chemical bonds or supramolecular interactions. The interaction between the passivation layer and the perovskite layer can significantly affect the crystal growth, morphology, and work function of the perovskite layer. Furthermore, SAMs with passivation groups such as carbazole, phenothiazine, triphenylamine, amine, or thiol can effectively passivate defects at the perovskite film interface.

[0007] Therefore, a new passivation layer is proposed to improve the energy loss problem caused by the interface between the upper and lower perovskite layers. Summary of the Invention

[0008] In view of the problems existing in the prior art, the purpose of this invention is to provide a passivation layer for passivating the interface of a perovskite thin film, its preparation method, and its application. The passivation layer is at least disposed at the lower interface of the perovskite layer, and the passivation layer is made of a self-assembling molecular material. The basic structural unit for self-assembly is a compound with a specific structure, having a biphenyl structure, with multiple alkyl or haloalkyl groups attached to one benzene ring and a dicyclohexylphosphine group attached to the other benzene ring. This passivation layer can passivate the upper and / or lower interfaces of the perovskite thin film, thereby improving the energy barrier at the interface and reducing energy loss caused by non-radiative recombination.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a passivation layer for passivating the interface of a perovskite thin film, wherein the passivation layer is at least disposed at the lower interface of the perovskite layer, and the passivation layer is made of a self-assembling molecular material, wherein the basic structural unit for self-assembly includes a compound having the structure shown in Formula I:

[0011]

[0012] Wherein, R is selected from any one of C1 to C6 alkyl or haloalkyl. C1 alkyl is methyl, C2 alkyl is ethyl, C3 alkyl includes n-propyl and isopropyl, C4 alkyl includes n-butyl and its isomers, C5 alkyl includes n-pentyl and its isomers, and C6 alkyl includes n-hexyl and its isomers; at least one hydrogen site in the C1 to C6 haloalkyl is substituted with a halogen.

[0013] To improve the energy conversion efficiency and stability of perovskite devices and components, nonradiative recombination caused by defects at the upper and lower interfaces of the perovskite thin film needs to be comprehensively considered. The lower interface (the side of the perovskite thin film facing the hole transport layer, or the buried interface) may be rich in deep-level trapped states from both the hole transport layer and the perovskite thin film. Band imbalance at the buried interface can adversely affect effective charge transport, leading to unnecessary charge recombination. Simultaneously, at the upper interface of the perovskite (the side of the perovskite thin film facing the electron transport layer), it is also necessary to reduce trap-assisted recombination at the interface between the perovskite thin film and the electron transport layer.

[0014] However, when existing solutions address issues such as defect passivation at the perovskite interface, the same interface passivation material is rarely used to treat defects and energy loss at the upper and lower interfaces of the perovskite.

[0015] The compound of Formula I described in this invention contains numerous alkyl units. Due to the σ-π hyperconjugation effect between these alkyl units and the benzene ring, it possesses a strong electron-donating ability and can act as a Lewis base to passivate trap defects on the perovskite surface. The electron-donating ability of the alkyl group can be achieved through interaction with B-site ions in the perovskite, such as Pb. 2+ The formation of stronger coordination bonds promotes the formation of high-quality perovskite films, modulates the energy barrier at the interface, facilitates efficient carrier transport, and suppresses the formation of non-radiative recombination centers caused by defects. In summary, the passivation layer described in this invention, placed at the upper and lower interfaces, minimizes the energy barrier (potential barrier) at the interface between the perovskite film and the electron transport layer and / or between the perovskite film and the hole transport layer, thereby promoting efficient charge carrier transport.

[0016] Furthermore, the coverage, nucleation, and growth of perovskite thin films during preparation are highly dependent on the characteristics of the substrate (referring to the hole transport layer). Currently, the commonly used hole transport layer at the lower interface uses functional molecules such as Me-4pacz, 2pacz, or Lewis acids and Lewis bases as passivation materials at the interface. Surface engineering techniques for the upper interface include treating the perovskite thin film with functional molecules via solution methods, or depositing inorganic modified molecules such as LiF onto the perovskite thin film surface via physical vapor deposition. These methods do not have a significant impact on or ability to regulate the coverage, crystallinity, and grain size of the perovskite thin film.

[0017] To address this issue, the passivation layer described in this invention effectively improves the wettability of the perovskite deposition substrate, promoting perovskite crystallization and efficient carrier transport. Furthermore, the passivation layer effectively reduces trap-assisted recombination at the interface. Due to its inherent hydrophobicity, the passivation layer prevents the entry of moisture, oxygen, etc. (especially on the back electrode side) from affecting the perovskite, thereby enhancing device stability. More importantly, it improves the wettability of the perovskite, promoting its crystallization and increasing grain size, which also effectively reduces interface defects to some extent.

[0018] Meanwhile, when the passivation layer is used to passivate both the upper and lower interfaces of the perovskite film, the application of the same material can effectively reduce manufacturing costs and further promote the development of large-area industrialization.

[0019] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0020] As a preferred embodiment of the present invention, R is selected from any one of methyl, ethyl, propyl, butyl, or trifluoromethyl.

[0021] As a preferred embodiment of the present invention, the compound having the structure shown in Formula I is selected from at least one of the following compounds:

[0022]

[0023] As a preferred technical solution of the present invention, the compound having the structure shown in Formula I is preferably compound IA, with the Chinese name 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl, abbreviated as X-PHOS, and CAS number 564483-18-7.

[0024] As a preferred embodiment of the present invention, the thickness of the passivation layer is 1 to 5 nm, such as 1 nm, 2 nm, 3 nm, 4 nm or 5 nm.

[0025] In a second aspect, the present invention provides a method for preparing a passivation layer at the interface of a passivated perovskite thin film as described in the first aspect. The preparation method includes: preparing a passivation solution by a compound having the structure shown in Formula I, coating it on a substrate and annealing it to obtain a passivation layer, wherein the substrate is a hole transport layer or a perovskite layer.

[0026] As a preferred embodiment of the present invention, the concentration of the passivation solution is 0.01–0.3 mg / mL, for example, 0.01 mg / mL, 0.03 mg / mL, 0.05 mg / mL, 0.08 mg / mL, 0.1 mg / mL, 0.13 mg / mL, 0.15 mg / mL, 0.18 mg / mL, 0.2 mg / mL, 0.22 mg / mL, 0.25 mg / mL, 0.28 mg / mL, or 0.3 mg / mL. The dosage is 0.2–0.35 μL / cm³. 2 For example, 0.2 μL / cm 2 0.25μL / cm 2 0.27 μL / cm 2 0.3 μL / cm 2 Or 0.35 μL / cm 2 wait.

[0027] As a preferred technical solution of the present invention, the coating volume of the passivation solution and the coating volume of the perovskite precursor solution are (0.8 to 1.2):1, for example, 0.8:1, 0.9:1, 1:1, 1.1:1 or 1.2:1, etc.

[0028] As a preferred embodiment of the present invention, the concentration of the perovskite precursor solution is 0.8–1.3 mol / L. For example, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.3 mol / L, etc.

[0029] As a preferred embodiment of the present invention, the annealing temperature is 60-80℃, such as 60℃, 63℃, 65℃, 68℃, 70℃, 72℃, 75℃, 78℃ or 80℃, and the time is 5-15min, such as 5min, 6min, 7min, 8min, 9min, 10min, 11min, 12min, 13min, 14min or 15min.

[0030] Thirdly, the present invention provides a perovskite solar cell, wherein the perovskite solar cell contains a passivation layer at the perovskite thin film interface as described in the first aspect.

[0031] As a preferred technical solution of the present invention, the passivation layer of the passivated perovskite film interface is disposed between the hole transport layer and the perovskite film, and / or disposed on the film surface of the perovskite film, that is, in direct contact with the perovskite film.

[0032] As a preferred technical solution of the present invention, the perovskite solar cell includes a substrate, a transparent electrode layer, a hole transport layer, a lower interface passivation layer, a perovskite layer, an upper interface passivation layer, an electron transport layer, and a back electrode layer, which are stacked sequentially.

[0033] This invention does not limit the manufacturing method of the perovskite solar cell, especially the manufacturing method of the layer structure other than the passivation layer. Exemplarily, the manufacturing method of the perovskite solar cell includes:

[0034] Step 1: Clean the transparent conductive glass in sequence with dish soap water, pure water, acetone, and anhydrous ethanol, then dry it for later use.

[0035] Step 2: A hole transport layer with a thickness of approximately 15–25 nm is prepared on transparent conductive glass using magnetron sputtering equipment;

[0036] Step 3: Prepare a passivation layer on the hole transport layer according to the preparation method described in the second aspect;

[0037] Step 4: Prepare a perovskite precursor solution, spin-coat it onto the substrate on the formed passivation layer and anneal it to complete the formation and growth of perovskite nuclei and form a perovskite thin film.

[0038] Step 5: After the perovskite thin film is completed, a passivation layer is prepared on it according to the preparation method described in the second aspect;

[0039] Step 6: Then, using a vacuum apparatus, an electron transport layer with a thickness of approximately 15–25 nm is prepared on the second passivation layer;

[0040] Step 7: Finally, electrodes are fabricated on the obtained electron transport layer using a magnetron sputtering device to obtain a perovskite solar cell.

[0041] It should also be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0042] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0043] This invention effectively reduces energy loss at the upper and lower interfaces of perovskite thin films by setting a specific passivation layer. Furthermore, the passivation layer at the lower interface serves as a substrate to improve the crystallinity of the perovskite film, effectively increasing the grain size of the perovskite, reducing interface energy loss caused by non-radiative recombination, and promoting efficient carrier transport. The passivation layer at the upper interface effectively modulates the energy barrier at the interface, reducing trap-assisted recombination, thereby significantly improving the efficiency and stability of the device. Attached Figure Description

[0044] Figure 1 This is a SEM image of the interface of the perovskite thin film in battery C7 in Application Example 1.

[0045] Figure 2This is a SEM image of the interface of the perovskite thin film in battery D1 of Comparative Example 1.

[0046] Figure 3 The diagram shows the structure and carrier transport of battery C7 in Application Example 1. In the diagram, 1-transparent conductive glass, 2-hole transport layer, 3-passivation layer, 4-perovskite thin film, 5-electron transport layer, and 6-electrode. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0048] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0049] Example 1

[0050] This embodiment provides a passivation layer for passivating the interface of a perovskite thin film. The passivation layer is in contact with the perovskite thin film, and the basic structural unit in the passivation layer that undergoes self-assembly is a compound with the structure shown in Formula IA.

[0051]

[0052] Compound IA, Chinese name 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl, abbreviation X-PHOS, CAS number 564483-18-7.

[0053] This embodiment provides a method for preparing a passivation layer at the interface of a perovskite thin film, the method comprising:

[0054] X-PHOS was prepared into a passivation solution with a concentration of 0.05 mg / mL, and the dosage was 0.27 μL / cm³. 2 The passivation solution was spin-coated at 1600 rpm for 20 s, and then annealed at 70 °C for 10 min to obtain the passivation layer.

[0055] Examples 2 to 13

[0056] Examples 2 to 13 are all based on the scheme of Example 1, with adjustments made to at least one of the basic structural units in the passivation layer, the concentration of the passivation solution (the thickness of the passivation layer), and the annealing temperature, as shown in Table 1.

[0057] Table 1

[0058]

[0059] Application Example 1

[0060] This application example provides a perovskite solar cell, the manufacturing method of which is as follows:

[0061] Step 1: Clean the 5cm*5cm FTO transparent conductive glass with detergent, pure water, acetone, and anhydrous ethanol, then dry it for later use.

[0062] Step 2: Prepare NiO with a thickness of approximately 20 nm on FTO using magnetron sputtering equipment. x Hole transport layer;

[0063] Step 3: As needed, according to the preparation method provided in any of Examples 1-13, the passivation solution is used at a volume of 0.27 μL / cm³. 2 In NiO x The first passivation layer is fabricated on the hole transport layer.

[0064] Step 4: Prepare a perovskite precursor solution of the CsFAMA ternary system. Take 1.2M of the perovskite precursor solution, spin-coat it on the first passivation layer and anneal it to complete the formation and growth of perovskite nuclei and form a perovskite film with a thickness of 500nm.

[0065] Step 5: After the perovskite film is completed, according to the preparation method provided in any one of Examples 1-13, the passivation solution is used at a rate of 0.27 μL / cm². 2 A second passivation layer is prepared on the perovskite film;

[0066] Step 6: Subsequently, C was prepared sequentially on the second passivation layer using a vacuum apparatus. 60 The layer and SnO2 layer serve as electron transport layers, with a total thickness of approximately 20 nm.

[0067] Step 7: Finally, a composite electrode ITO / Cu was prepared on the SnO2 layer on the outer side of the electron transport layer using a magnetron sputtering device to obtain perovskite solar cells numbered C1 to C19.

[0068] Application Comparative Example 1

[0069] This application example provides a perovskite solar cell whose manufacturing method omits steps 3 and 5, and is otherwise identical to Application Example 1.

[0070] The individual battery records are shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] Note: In Table 2, PCE is in % (%), Voc is in V (V), and Isc is in mA / cm². 2 The theoretical range of FF is ≤1.

[0075] As can be seen from Table 2:

[0076] By comparing all the batteries obtained in Application Example 1 with battery D1 obtained in Comparative Example 1, it was found that setting a specific passivation layer at the upper and lower interfaces of the perovskite thin film is beneficial to a significant improvement in the overall performance of the battery.

[0077] Figure 1 and Figure 2 The images show SEM images of the perovskite film surfaces in batteries C7 and D1, respectively. As can be seen from the two images... Figure 1 Perovskites are relatively large and uniform in size, and have good crystallinity. This is due to the passivation layer altering the wettability of the crystalline substrate, which facilitates the nucleation and growth of perovskite crystals.

[0078] A comparison of cells C1 to C5 revealed that, for the lower interface of the perovskite film (hole transport layer side), the optimal concentration of the passivation solution for the passivation layer is 0.15 mg / mL, which corresponds to the passivation layer of Example 3. Furthermore, cells C6 to C10 showed that, for the upper interface of the perovskite film (electron transport layer side), the optimal concentration of the passivation solution for the passivation layer is 0.1 mg / mL, which corresponds to the passivation layer of Example 2.

[0079] By comparing batteries C3 with C7 and C19, it was found that setting passivation layers at both the upper and lower interfaces of the perovskite thin film can achieve the best optimization effect, and battery C7 has the best performance. Figure 3 The diagram shows the structure and carrier transport of battery C7. Battery C7 includes a transparent conductive glass 1, a hole transport layer 2, a first passivation layer 3, a perovskite thin film 4, a second passivation layer 3, an electron transport layer 5, and an electrode 6, which are stacked in sequence. The photogenerated holes and electrons generated by the perovskite thin film 4 are transported to one side of the first passivation layer 3 and the other side of the second passivation layer 3, respectively.

[0080] The performance differences of other batteries compared to C7, such as C11, C12, C15, C16, C13, C14, C17, and C18, are due to variations in the annealing temperature and materials used in the passivation layer. Annealing temperature affects the film formation of the passivation material; for lower interface passivation, it further affects the wettability of the perovskite substrate, thus impacting the overall battery performance. Simultaneously, the annealing temperature during surface treatment can influence the already crystallized perovskite film to some extent. Different passivation materials can cause issues with the overall bandgap matching, changes in surface potential, and the ability to passivate defects. For X-PHOS, its passivation layer can act as a tunneling layer, allowing carrier passage; lateral comparisons reveal that it is more conducive to passivating trapped states and surface dangling bonds.

[0081] In summary, the above demonstrates that the present invention can effectively reduce energy loss at the upper and lower interfaces of perovskite thin films by setting a specific passivation layer. Furthermore, the passivation layer at the lower interface serves as a substrate to improve the crystallinity of the perovskite thin film, effectively increasing the grain size of the perovskite, reducing interface energy loss caused by non-radiative recombination, and promoting efficient carrier transport. The passivation layer at the upper interface effectively modulates the energy barrier at the interface, reducing trap-assisted recombination, thereby significantly improving the efficiency and stability of the device.

[0082] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0083] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0084] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A passivation layer for passivating perovskite thin film interfaces, characterized in that, The passivation layer is disposed at least at the lower interface of the perovskite layer, and the passivation layer is made of a self-assembling molecular material. The basic structural unit for self-assembly includes compounds having the structure shown in Formula I: R is selected from any one of C1 to C6 alkyl or haloalkyl.

2. The passivation layer at the perovskite thin film interface according to claim 1, characterized in that, The R is selected from any one of methyl, ethyl, propyl, butyl, or trifluoromethyl.

3. The passivation layer at the perovskite thin film interface according to claim 1 or 2, characterized in that, Compounds having the structure shown in Formula I are selected from at least one of the following compounds:

4. The passivation layer for the perovskite thin film interface according to any one of claims 1-3, characterized in that, The thickness of the passivation layer is 1–5 nm.

5. A method for preparing a passivation layer at the interface of a perovskite thin film according to any one of claims 1-4, characterized in that, The preparation method includes: A passivation solution is prepared by a compound having the structure shown in Formula I. After coating and annealing on a substrate, a passivation layer is obtained. The substrate is a hole transport layer or a perovskite layer.

6. The method for preparing a passivation layer at the interface of a perovskite thin film according to claim 5, characterized in that, The concentration of the passivation solution is 0.01–0.3 mg / mL, and the volume used is 0.2–0.35 μL / cm³. 2 .

7. The method for preparing a passivation layer at the perovskite thin film interface according to claim 5, characterized in that, The annealing temperature is 60–80°C, and the time is 5–15 minutes.

8. A perovskite battery, characterized in that, The perovskite solar cell contains a passivation layer for the perovskite thin film interface as described in any one of claims 1-4.

9. The perovskite solar cell according to claim 8, characterized in that, The passivation layer is disposed between the hole transport layer and the perovskite film, and / or disposed on the surface of the perovskite film, and is in direct contact with the perovskite film.

10. The perovskite solar cell according to claim 8 or 9, characterized in that, The perovskite solar cell comprises a substrate, a transparent electrode layer, a hole transport layer, a lower interface passivation layer, a perovskite layer, an upper interface passivation layer, an electron transport layer, and a back electrode layer, which are stacked sequentially.

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