Titanate self-assembled monolayer passivation layer, and preparation method and application thereof

Abstract

The application discloses a titanate self-assembled monomolecular passivation layer and a preparation method and application thereof, and belongs to the technical field of photovoltaic cells. A stable molecular buffer interface is constructed between an oxidized nickel film and a perovskite light-absorbing layer by introducing a diisopropyl titanate di(triethanolamine) self-assembled molecular layer on the surface of the oxidized nickel film. The titanate molecules can be coordinated or condensed with the hydroxyl groups on the surface of the oxidized nickel, and interact with unsaturated nickel sites through a multidentate triethanolamine structure, so as to simultaneously inhibit the chemical activity of surface hydroxyl defects and high-valence nickel ions, significantly reduce the interface defect state density and non-radiative recombination loss. The passivation layer can be formed under mild conditions, and the process is simple and highly compatible with the preparation process of a trans device. The passivation layer can realize the synchronous improvement of the photoelectric conversion efficiency and long-term operation stability of the trans perovskite solar cell without increasing the complexity of the device structure.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell technology, and in particular to a titanate self-assembled monomolecular passivation layer, its preparation method, and its application. Background Technology

[0002] Organic-inorganic hybrid perovskite materials are widely considered a class of highly promising photovoltaic absorbers due to their excellent photoelectric properties, including high optical extinction coefficients, low exciton binding energies, and long carrier lifetimes. Perovskite solar cells constructed using these materials have achieved photoelectric conversion efficiencies exceeding 26% on a laboratory scale, surpassing the performance of traditional silicon-based solar cells. Furthermore, perovskite solar cells offer significant advantages such as relatively simplified fabrication processes and the ability to achieve lightweight and flexible devices, making them a promising candidate for next-generation commercial photovoltaic technology.

[0003] The high efficiency of perovskite solar cells stems not only from the excellent electrical and optical properties of the hybrid perovskite materials themselves, but also from the rational selection of materials for each functional layer and the control of interfaces within the device. Among these, nickel oxide (NiO) is particularly important. x Nickel oxide (NiO) is a commonly used hole transport layer material in inverted (pin) perovskite solar cells. It has attracted widespread attention from academia and industry due to its good energy level matching with the perovskite valence band, high chemical stability, low raw material cost, and suitability for solution-based or low-temperature processing. However, NiO hole transport layers still have significant limitations in practical applications. While NiO with an ideal stoichiometric ratio of 1:1 is intrinsically a Mott insulator, to obtain sufficient hole conductivity, the actual prepared NiO... x Thin films typically introduce a high concentration of nickel vacancy defects, thereby inducing the formation of Ni. 3+ Ni 4+ High-valence nickel ions. These high-valence nickel species are highly chemically reactive and readily react with organic cations in perovskite materials (such as methylamine ions, MA). + Formamidinium ion (FA) + Deprotonation reactions (such as those involving NiO deposited via solution deposition) accelerate interfacial chemical degradation, thereby introducing additional device failure risks. x Thin film surfaces often contain a large number of reactive hydroxyl groups (derived from NiOOH and Ni(OH)2, etc.). These surface hydroxyl groups act as negative charge centers electrically, which not only further intensifies the deprotonation reaction of organic cations in the perovskite layer, but also easily acts as carrier trapping centers during hole transport, significantly increasing the probability of nonradiative recombination, thus adversely affecting the photovoltaic performance and long-term stability of perovskite solar cells.

[0004] Therefore, there is an urgent need for an effective chemical and electrical passivation method for the surface of nickel oxide hole transport layer to suppress interfacial reactions, reduce recombination losses, and improve the efficiency of carrier extraction and transport. Summary of the Invention

[0005] The purpose of this invention is to provide a self-assembled monomolecular passivation layer of titanate, its preparation method and application. By using diisopropyl titanate (di(triethanolamine) titanate) as a passivation material, a stable molecular-level buffer interface is constructed between the nickel oxide hole transport layer and the perovskite active layer, overcoming the problems of high surface defect density, insufficient chemical stability and severe interfacial recombination that are common in the nickel oxide hole transport layer of existing inverted perovskite solar cells.

[0006] To achieve the above objectives, the present invention provides a self-assembled monomolecular passivation layer of titanate ester, which is formed by the self-assembly of titanate ester compounds on the substrate surface through chemical bonding.

[0007] Preferably, the titanate compound is diisopropyl di(triethanolamine) titanate (C 18 H 42 N2O8Ti).

[0008] Preferably, the diisopropyl di(triethanolamine) titanate molecule is bonded to the active group on the substrate surface through the titanate group and coordinated through its triethanolamine group via polydentate coordination.

[0009] Preferably, the substrate is a nickel oxide hole transport layer.

[0010] Preferably, a titanate self-assembled monomolecular passivation layer is disposed between the nickel oxide hole transport layer and the perovskite light-absorbing layer of the inverted perovskite solar cell.

[0011] Preferably, the thickness of the titanate self-assembled monomolecular passivation layer is 2-6 nm.

[0012] This invention also provides a method for preparing the above-mentioned titanate self-assembled monomolecular passivation layer, comprising the following steps:

[0013] S1. Provide a substrate to complete the fabrication of the nickel oxide hole transport layer for inverted solar cells;

[0014] S2. Dissolve the titanate compound in a solvent to prepare a precursor solution;

[0015] S3. Spin-coat or scrap-coat the precursor solution onto the substrate surface;

[0016] S4. Through heat treatment, titanate compounds are self-assembled on the substrate surface to form a monomolecular passivation layer.

[0017] Preferably, the titanate compound is diisopropyl di(triethanolamine)titanate; the solvent is ethanol or isopropanol, and the concentration of diisopropyl di(triethanolamine)titanate in the precursor solution is 1-5 μL / mL.

[0018] Preferably, in step S4, the heat treatment temperature is 60-80°C and the time is 2-5 minutes to evaporate the ethanol / isopropanol organic solvent.

[0019] The titanate self-assembled monomolecular passivation layer provided by this invention is applied in inverted perovskite solar cells to modify the interface between the hole transport layer and the light-absorbing active layer.

[0020] Preferably, the hole transport layer is a nickel oxide thin film, and the light-absorbing active layer is a perovskite thin film, wherein the perovskite thin film is ABX3, and A is Cs. + CH3NH3 + CH(NH2)2 + Or a mixture of A sites; B is Pb 2+ Sn 2+ Or a mixed B site; X is Cl - ,Br - I - Or a mixed X-bit.

[0021] Therefore, the present invention has the following beneficial effects:

[0022] 1. The titanate groups in diisopropyl di(triethanolamine)titanate can coordinate or condense with hydroxyl groups on the nickel oxide film surface, achieving stable anchoring of the nickel oxide surface and effectively consuming surface-active hydroxyl groups, thus reducing the interface defect density. Simultaneously, the abundant polydentate coordination sites in the triethanolamine structure facilitate interaction with unsaturated metal sites on the nickel oxide surface, further suppressing the chemical activity of high-valence nickel ions. Compared to conventional passivation methods relying on single functional groups, this multi-functional group synergistic mechanism results in a more robust and stable bond with nickel oxide. Furthermore, this molecular passivation process can be spontaneously completed under mild conditions, requiring no additional high temperatures or complex post-processing, which simplifies the process and improves compatibility with flexible devices and low-temperature process routes.

[0023] 2. Diisopropyl di(triethanolamine)titanate forms a dense monomolecular buffer interface between the nickel oxide and perovskite layers, physically preventing direct contact between the two and reducing chemical reactions and structural damage at the interface. Simultaneously, the polar functional groups in diisopropyl di(triethanolamine)titanate can synergistically passivate defect states at the buried interface of the perovskite active layer, effectively suppressing nonradiative recombination at the interface and promoting efficient carrier extraction and transport.

[0024] 3. Through the dual passivation effect of chemical and electrical processes described above, this invention synergistically optimizes the physical contact, chemical stability, and electrical performance of the nickel oxide / perovskite interface at the molecular level, thereby achieving a simultaneous improvement in the photoelectric conversion efficiency and working life of inverted perovskite solar cells, which has significant application prospects.

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of an inverse perovskite solar cell in an application example;

[0027] Figure 2 This is a schematic diagram of an inverse perovskite solar cell in the comparative example.

[0028] Figure 3 For application examples and comparative examples of inverted perovskite solar cells at 1000 W / m 2 Current-voltage characteristic curve under illumination conditions;

[0029] Figure 4 The short-term steady-state power output curves of the inverted perovskite solar cells in the application examples and comparative examples are shown under the same light intensity.

[0030] Figure 5 Transient photovoltage decay spectra of inverted perovskite solar cells in application examples and comparative examples;

[0031] Figure 6 Normalized transient photocurrent decay spectrum of inverted perovskite solar cells in application examples and comparative examples.

[0032] Figure 7 The results of the 666-hour stability test of the inverted perovskite solar cells in the application examples and comparative examples under continuous illumination are shown. Detailed Implementation

[0033] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0035] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that can be understood by those skilled in the art. These other embodiments are also covered within the scope of protection of this invention.

[0036] Example 1

[0037] This embodiment provides a titanate self-assembled monomolecular passivation layer disposed between the nickel oxide hole transport layer and the perovskite light-absorbing layer of an inverted perovskite solar cell. The preparation method includes the following steps:

[0038] (1) Prepare a nickel oxide thin film as a nickel oxide hole transport layer.

[0039] (2) Take diisopropyl di(triethanolamine)titanate (C 18 H 42 N2O8Ti) was dissolved in ethanol and stirred until homogeneous to obtain a precursor solution with a concentration of 2 μL / mL.

[0040] (3) Spin-coat the precursor solution onto the surface of the nickel oxide film at a speed of 6000 rpm.

[0041] (4) Anneal at 70°C for 2 minutes to obtain a 2nm thick di(triethanolamine) titanate diisopropyl ester self-assembled molecular layer on the surface of nickel oxide film.

[0042] Example 2

[0043] This embodiment provides a titanate self-assembled monomolecular passivation layer disposed between the nickel oxide hole transport layer and the perovskite light-absorbing layer of an inverted perovskite solar cell. The preparation method includes the following steps:

[0044] (1) Prepare a nickel oxide thin film as a nickel oxide hole transport layer.

[0045] (2) Take diisopropyl di(triethanolamine)titanate (C 18 H 42 N2O8Ti) was dissolved in ethanol and stirred until homogeneous to obtain a precursor solution with a concentration of 2 μL / mL.

[0046] (3) Spin-coat the precursor solution onto the surface of the nickel oxide film at a speed of 2000 rpm.

[0047] (4) Anneal at 70°C for 2 minutes to obtain a self-assembled molecular layer of di(triethanolamine) titanate with a thickness of 6 nm on the surface of nickel oxide film.

[0048] Example 3

[0049] This embodiment provides a titanate self-assembled monomolecular passivation layer disposed between the nickel oxide hole transport layer and the perovskite light-absorbing layer of an inverted perovskite solar cell. The preparation method includes the following steps:

[0050] (1) Prepare a nickel oxide thin film as a nickel oxide hole transport layer.

[0051] (2) Take diisopropyl di(triethanolamine)titanate (C 18 H 42 N2O8Ti) was dissolved in isopropanol and stirred until homogeneous to obtain a precursor solution with a concentration of 3 μL / mL.

[0052] (3) Spin-coat the precursor solution onto the surface of the nickel oxide film at a speed of 2000 rpm.

[0053] (4) Anneal at 60°C for 3 minutes to obtain an 8 nm self-assembled molecular layer of di(triethanolamine) titanate on the surface of the nickel oxide film.

[0054] Application examples

[0055] This application example provides a trans-perovskite solar cell, such as Figure 1 As shown, this inverted perovskite solar cell comprises, from bottom to top, a conductive substrate, a hole transport layer, a titanate self-assembled monomolecular passivation layer prepared in Example 1, a perovskite active layer, an electron transport layer, an electrode buffer layer, and a top electrode, stacked sequentially. The fabrication method is as follows:

[0056] (1) Substrate cleaning: The conductive ITO substrate was ultrasonically cleaned in deionized water, acetone and ethanol for 15 minutes each, and then dried by heating. Before use, the ITO surface was further treated with ultraviolet ozone for 15 minutes.

[0057] (2) Preparation of nickel oxide hole transport layer: Nickel oxide nanoparticles were dispersed in deionized water at a concentration of 20 mg / ml, and then spin-coated onto a conductive substrate at a spin coating rate of 3000 rpm for 30 seconds. After spin coating, the nanoparticles were annealed at 130℃ for 15 minutes, and the thickness of the nickel oxide hole transport layer was 25 nm.

[0058] (3) Preparation of self-assembled passivation layer: This step is the same as the preparation method in Example 1.

[0059] (4) Preparation of the perovskite active layer: A perovskite film was deposited onto a passivated nickel oxide film using a spin-coating method. The perovskite layer composition was FA. 0.83 Cs 0.07 MA 0.13 PbI 2.90 Br 0.13 (MA) + CH3NH3 + ;FA + CH(NH2)2 + The film thickness is 650 nm.

[0060] (5) Preparation of electron transport layer: Methyl [6,6]-phenyl-C61-butyrate (PC) 61BM is dissolved in a solvent and deposited on the surface of a perovskite film with a thickness of 40 nm by spin coating.

[0061] (6) Preparation of electrode buffer layer: 4,7-diphenyl-1,10-o-diazaphenanthroline (Bphen) was dissolved in a solvent and deposited on the surface of electron transport layer by spin coating, with a thickness of 1 nm.

[0062] (7) Preparation of the top electrode: Place the above sample in the thermal evaporation chamber and evacuate to 5×10⁻⁶. -4 Below Pa, Ag metal particles were placed in a tungsten boat and metal electrodes were deposited at a rate of 0.05-0.15 nm / s, with an electrode thickness of 100 nm.

[0063] Comparative Example

[0064] This comparative example provides a trans-perovskite solar cell, such as Figure 2 As shown, this inverted perovskite solar cell comprises, from bottom to top, a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, an electrode buffer layer, and a top electrode. The fabrication method is as follows:

[0065] The preparation method is as follows:

[0066] (1) Substrate cleaning: The conductive ITO substrate was ultrasonically cleaned in deionized water, acetone and ethanol for 15 minutes each, and then dried by heating. Before use, the ITO surface was further treated with ultraviolet ozone for 15 minutes.

[0067] (2) Preparation of nickel oxide hole transport layer: Nickel oxide nanoparticles were dispersed in deionized water at a concentration of 20 mg / ml, and then spin-coated onto a conductive substrate at a spin coating rate of 3000 rpm for 30 seconds. After spin coating, the nanoparticles were annealed at 130℃ for 15 minutes, and the thickness of the nickel oxide hole transport layer was 25 nm.

[0068] (3) Preparation of the perovskite active layer: A perovskite film was deposited onto a nickel oxide film using a spin-coating method. The perovskite layer composition was FA. 0.83 Cs 0.07 MA 0.13 PbI 2.90 Br 0.13 (MA) + CH3NH3 + ;FA + CH(NH2)2 + The film thickness is 650 nm.

[0069] (4) Preparation of electron transport layer: Methyl [6,6]-phenyl-C61-butyrate (PC61BM) was dissolved in a solvent and deposited on the surface of a perovskite film by spin coating, with a thickness of 40 nm.

[0070] (5) Preparation of the interface barrier layer: 4,7-diphenyl-1,10-o-diazaphenanthroline (Bphen) was dissolved in a solvent and deposited on the surface of the electron transport layer by spin coating, with a thickness of 1 nm.

[0071] (6) Preparation of the top electrode: Place the above sample in the thermal evaporation chamber and evacuate to 5×10⁻⁶. -4 Below Pa, Ag metal particles were placed in a tungsten boat and metal electrodes were deposited at a rate of 0.05-0.15 nm / s, with an electrode thickness of 100 nm.

[0072] Under standard test conditions (AM 1.5G spectrum, 100 mW / cm²), 2 The current density-voltage (JV) characteristic curves of the inverse perovskite solar cell measured under illumination intensity are shown in Table 1. Figure 3 As shown:

[0073] Table 1 Test Results

[0074]

[0075] The results show that the photoelectric conversion efficiency of perovskite solar cells is significantly improved by introducing diisopropyl di(triethanolamine)titanate as a passivation layer, from 19.9% ​​to 24.1%.

[0076] To test the steady-state output performance of the inverse perovskite solar cells in the application examples and comparative examples, standard test conditions (AM 1.5G, 100 mW / cm²) were applied. 2 Under these conditions, a fixed bias tracking method was used at the device's maximum power point voltage, and the change in current density over time was continuously measured. The data acquisition interval was 1 second, thus obtaining the short-term steady-state power output curve. The results are as follows: Figure 4 As shown, the comparative model provides an initial current density of approximately 20 mA / cm² for the battery. 2 As the voltage increases, the current density remains relatively stable with no significant degradation. The application example provides an initial current density of approximately 25 mA / cm². 2 It remained at a high level throughout the process without significant fluctuations, demonstrating superior stability.

[0077] The transient photovoltage decay spectrum of the inverse perovskite solar cell in the application examples and comparative examples is as follows: Figure 5 As shown, the normalized transient photocurrent decay spectrum is as follows: Figure 6As shown, the application example device passivated with diisopropyl titanate (DIT) exhibits a slower decay rate in the transient photovoltage decay spectrum, indicating a significant extension of carrier lifetime and effective suppression of interfacial recombination. In the normalized transient photocurrent decay spectrum, it shows a faster current rise and a smoother decay, reflecting an improvement in carrier transport and extraction efficiency. Together, these findings verify that the passivator can reduce interfacial defects by optimizing the interfacial performance of the nickel oxide hole transport layer.

[0078] The inverted perovskite solar cells in the application examples and comparative examples were subjected to experiments under AM 1.5 solar simulator illumination at 45°C, i.e., standard illumination (100 mW / cm²). 2 Under these conditions, the stability test was conducted continuously for 666 hours, with one efficiency data point collected every 6 minutes (0.1 hours). The results of the 666-hour stability test are as follows: Figure 7 As shown, the device current density in the application example remains stable at 1.0 mA / cm². 2 Near the same location, there is almost no attenuation; while the comparative device exhibits significant efficiency degradation, with the current density decreasing from approximately 0.9 mA / cm² initially. 2 Gradually decreased to 0.2 mA / cm 2 The following demonstrates that the device in the application example exhibits superior stability, confirming that the diisopropyl di(triethanolamine)titanate passivation layer can block the adverse interactions between the nickel oxide layer and the perovskite layer, thereby improving the long-term operational stability of the device.

[0079] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A self-assembled monomolecular passivation layer of titanate, characterized in that, It is formed by the self-assembly of titanate compounds on the substrate surface through chemical bonding; The titanate compound is diisopropyl di(triethanolamine) titanate; Diisopropyl di(triethanolamine) titanate molecules are bonded to the active groups on the substrate surface through titanate groups and coordinated through their triethanolamine groups. The substrate is a nickel oxide hole transport layer.

2. The titanate self-assembled monomolecular passivation layer according to claim 1, characterized in that, A titanate self-assembled monomolecular passivation layer is disposed between the nickel oxide hole transport layer and the perovskite active layer of an inverted perovskite solar cell.

3. A method for preparing a self-assembled monomolecular passivation layer of titanate as described in any one of claims 1-2, characterized in that, Includes the following steps: S1, Provide the substrate; S2. Dissolve the titanate compound in a solvent to prepare a precursor solution; S3. Spin-coat or scrap-coat the precursor solution onto the substrate surface; S4. Through heat treatment, titanate compounds are self-assembled on the substrate surface to form a monomolecular passivation layer.

4. The method for preparing a self-assembled monomolecular passivation layer of titanate according to claim 3, characterized in that, The solvent for the precursor solution is ethanol or isopropanol, and the concentration of diisopropyl di(triethanolamine)titanate in the precursor solution is 1-5 μL / mL.

5. The method for preparing a self-assembled monomolecular passivation layer of titanate according to claim 3, characterized in that, In step S4, the heat treatment temperature is 60-80℃ and the time is 2-5 minutes.

6. An application of a self-assembled monomolecular passivation layer of titanate as described in any one of claims 1-2, characterized in that, Titanate self-assembled monomolecular passivation layers are used in inverted perovskite solar cells to modify the interface between the hole transport layer and the perovskite active layer.

7. The application of the titanate self-assembled monomolecular passivation layer according to claim 6, characterized in that, The hole transport layer is a nickel oxide thin film, and the perovskite active layer is a perovskite thin film, wherein the perovskite thin film is ABX3, and A is Cs. + CH3NH3 + CH(NH2)2 + Or a mixture of A sites; B is Pb 2+ Sn 2+ Or a mixed B site; X is Cl - ,Br - I - Or a mixed X-bit.

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