Electron transport layer, solar cell and preparation method

Abstract

The invention relates to an electron transport layer, a solar cell and a preparation method, an atomic layer deposition technology is adopted, and a mixed oxygen source composed of H2O and O3 is used, the preparation method comprises the following steps: step 1, providing a substrate, and placing the substrate in an atomic layer deposition reaction chamber; step 2, stabilizing the temperature of the reaction chamber between 80 DEG C and 120 DEG C; and step 3, carrying out a plurality of atomic layer deposition cycles until the SnO2 film reaches a preset thickness. The mixed oxygen source composed of H2O and O3 generates a synergistic enhancement effect at a low temperature, and promotes full reaction and decomposition of a precursor, so that the compactness of the SnOx film is remarkably improved, and the defect density in the SnOx film is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of perovskite solar cells, and in particular to an electron transport layer, a solar cell and a preparation method. BACKGROUND

[0002] In recent years, perovskite solar cells have been widely considered as one of the most promising candidates for next-generation photovoltaic technology due to their flexible preparation process, wide light absorption range, large carrier diffusion length, and long carrier lifetime, and have attracted continuous attention from the research community. According to recent reports, the energy conversion efficiency of small-area laboratory perovskite cells has broken through 26%, and large-area modules (such as 1m x 2m specifications) have also achieved a conversion efficiency of over 18%.

[0003] Atomic layer deposition (ALD) is a derivative technology of chemical vapor deposition (CVD), and its core principle is to alternately and self-limitingly introduce gas-phase precursors into the reaction chamber, so that sequential chemical reactions occur on the substrate surface, thereby forming a uniform and dense thin film layer by layer. Due to its excellent film formation quality and consistency, this technology has been widely used in the manufacturing process of perovskite solar cells, especially in the deposition of tin oxide (SnO2) electron transport layers.

[0004] The structure of a perovskite solar cell (PSC) is similar to a sandwich structure, and is composed of a layer of thin films. In a transverse perovskite solar module, the order of device preparation is: conductive glass substrate → P1 scribe line → hole transport layer → perovskite absorber layer → electron transport layer → P2 scribe line → electrode → P3, P4 scribe line.

[0005] In the development of perovskite solar cells, the performance and quality of SnO2 thin films in the electron transport layer (ETL) have an important influence on the efficiency of perovskite cells. The oxygen source reacting with the Sn source affects the performance and quality of the oxide thin film. When SnO x When a thin film is prepared using atomic layer deposition technology, the deposition temperature is low, and H2O with weak oxidizing properties is used as the oxygen source. The limited reactivity of the oxygen source will restrict the full decomposition and surface reaction of the precursor. This will result in a deposition rate and density of the thin film that does not meet the theoretical expectations, and may introduce a large number of defects such as oxygen vacancies, ultimately degrading the electrical properties (such as carrier mobility and conductivity) of the thin film, making it difficult to meet the application requirements of a high-efficiency electron transport layer.

[0006] Brief summary of the defects of the prior art: The surface reaction with the tin precursor cannot be fully carried out, resulting in the presence of carbon impurities, which destroys the chemical purity of the thin film.

[0007] The thin film has poor density and high defect density.

[0008] Tin price state out of control.

[0009] In view of the above defects, the present design person actively researches and innovates, so as to create an electron transport layer, a solar cell and a preparation method, so that it has more industrial use value. SUMMARY

[0010] To solve the above technical problems, the purpose of the present application is to provide an electron transport layer, a solar cell and a preparation method.

[0011] To achieve the above purpose, the present application adopts the following technical solutions: One of the purposes of the present application is: A preparation method of an electron transport layer, which adopts atomic layer deposition technology and uses a mixed oxygen source composed of H2O and O3, and the preparation method comprises the following steps: Step 1: providing a substrate and placing it in an atomic layer deposition reaction chamber; Step 2: stabilizing the temperature of the reaction chamber at 80-120℃; Step 3: performing a plurality of atomic layer deposition cycles until the SnO2 film reaches a preset thickness, each atomic layer deposition cycle comprising the following steps in turn: Step 31: introducing a tin-containing precursor into the reaction chamber to cause self-limiting chemical adsorption on the surface of the substrate; Step 32: introducing a purge gas to remove unreacted tin-containing precursors and gas-phase byproducts in the reaction chamber; Step 33: introducing a mixed oxygen source composed of H2O and O3 into the reaction chamber to cause a surface reaction with the chemisorbed tin-containing precursor; Step 34: introducing a purge gas to remove unreacted mixed oxygen source and gas-phase byproducts in the reaction chamber; Wherein the mixed volume ratio of H2O and O3 is 1:1 to 3:1.

[0012] As a further improvement of the present application, the mixed volume ratio of H2O and O3 in the mixed oxygen source is 2:1.

[0013] As a further improvement of the present application, the tin-containing precursor is tetrakisdimethylamino tin.

[0014] As a further improvement of the present application, the number of atomic layer deposition cycles is 70-90, and the preset thickness of the SnO2 film is 18-22nm.

[0015] As a further improvement of the present application, in step 33, the mixed oxygen source composed of H2O and O3 is adopted in a sequential pulse mode, that is, H2O is first introduced and then O3 is introduced; wherein the pulse duration of H2O is 0.1-0.5 seconds, the pulse duration of O3 is 0.5-2.0 seconds, and there is no purging interval between the two.

[0016] The second object of the present application is: An electron transport layer for a perovskite solar cell, which is prepared by the preparation method described above.

[0017] The third object of the present application is: A preparation method of a solar cell, which comprises the following steps in sequence: Step 1: providing a conductive glass substrate and performing P1 laser scribing; Step 2: preparing a hole transport layer on the scribed substrate; Step 3: preparing a perovskite absorption layer on the hole transport layer; Step 4: sequentially preparing an interface modification layer, a first electron transport layer and a second electron transport layer on the perovskite absorption layer; The second electron transport layer is a SnO2 film, which is prepared by an atomic layer deposition process, the deposition temperature is 80-120 DEG C, the oxygen precursor used is a mixed oxygen source of H2O and O3, and the tin precursor is a tin-containing organic compound. Step 5: performing P2 laser scribing to expose the conductive glass substrate; Step 6: performing P3 laser scribing and preparing a metal top electrode.

[0018] As a further improvement of the present application, in step 4, the mixed volume ratio of H2O and O3 in the mixed oxygen source is 2:1.

[0019] As a further improvement of the present application, in step 4, the thickness of the SnO2 film is controlled to be 18-22 nm by controlling the number of cycles of the atomic layer deposition.

[0020] The fourth object of the present application is: A solar cell prepared by the preparation method described above.

[0021] By the above-mentioned scheme, the present application has at least the following advantages: 1. The quality of the thin film is significantly improved: the mixed oxygen source composed of H2O and O3 produces a synergistic effect at low temperature, which promotes the full reaction and decomposition of the precursor, thereby significantly improving the quality of the SnO2 film. x The density of the thin film is improved, and the internal defect density is effectively reduced.

[0022] 2. Interface band precise optimization: this method can precisely regulate the Fermi level of SnO x thin film and stabilize the valence state of tin element, so as to realize the optimal matching of energy level between the conductive band of perovskite layer and the Fermi level, thereby significantly reducing the charge transport energy barrier at the interface.

[0023] 3. Comprehensive enhancement of device performance: based on the above two points, the charge extraction efficiency and transport capacity of the device are greatly improved, which finally contributes to the higher photoelectric conversion efficiency of perovskite solar module.

[0024] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, and can be implemented according to the content of the specification, the following is the preferred embodiment of the present application and is described in detail with the help of the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0026] Figure 1 is a flowchart of a preparation method of an electron transport layer of the present application; Figure 2 is a flowchart of a preparation method of a solar cell of the present application; Figure 3 is an AFM two-dimensional height topography of SnO2 thin film prepared in the experimental example of the present application; Figure 4 is an AFM three-dimensional height topography of SnO2 thin film prepared in the experimental example of the present application; Figure 5 is a surface potential distribution diagram of SnO2 thin film prepared in the experimental example of the present application; Figure 6 is an AFM two-dimensional height topography of SnO2 thin film prepared in the comparative example of the present application; Figure 7 is an AFM three-dimensional height topography of SnO2 thin film prepared in the comparative example of the present application; Figure 8 is a surface potential distribution diagram of SnO2 thin film prepared in the comparative example of the present application. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application will be further described in detail below in combination with the drawings and examples. The following examples are used to illustrate the present application, but not to limit the scope of the present application.

[0028] In order to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be described clearly and completely below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0029] The first embodiment of the present application: The present embodiment aims to overcome the shortcomings of the prior art, and provides a perovskite solar module based on an atomic layer deposition mixed oxygen process and a preparation scheme thereof. The core of the scheme is that when SnO2 thin films are prepared by using the atomic layer deposition technology, a mixed oxygen source composed of H2O and strong oxidizing ozone (O3) in a specific ratio is introduced. The mixed oxygen process can synergistically promote the full reaction and decomposition of the precursor at low temperature, so as to obtain high-quality SnO2 thin films with high compactness and low defect density. At the same time, the method can accurately control the Fermi level of SnO2 and stabilize the valence state of tin, so that it can realize optimal matching with the conduction band bottom of the perovskite layer, significantly reduce the interface energy barrier, and thus improve the charge extraction efficiency and performance of the device. x x x

[0030] A preparation method of an electron transport layer, which adopts the atomic layer deposition technology and uses a mixed oxygen source composed of H2O and O3. The preparation method comprises the following steps: Step 1: providing a substrate and placing it in an atomic layer deposition reaction chamber.

[0031] Step 2: stabilizing the temperature of the reaction chamber at 80-120℃.

[0032] Step 3: performing a plurality of atomic layer deposition cycles (70-90 cycles) until the SnO2 thin film reaches a preset thickness (18-22 nm), each atomic layer deposition cycle comprising the following steps in sequence: Step 31: introducing a tin-containing precursor (tetra-dimethylamino tin) into the reaction chamber so that it undergoes self-limiting chemical adsorption on the surface of the substrate.

[0033] Step 32: introducing a purge gas to remove unreacted tin-containing precursor and gas-phase by-products in the reaction chamber.

[0034] ​​​Step 33: Introduce a mixed oxygen source composed of H2O and O3 into the reaction chamber to react with the chemisorbed tin-containing precursor.

[0035] The mixture of H2O and O3 has a volume ratio of 1:1 to 3:1.

[0036] O3 is generally considered too strong an oxidizer and may over-oxidize the interface or damage the organic underlayer, so a single, mild oxygen source is preferred. However, experiments have shown that within the specified low-temperature window (80-120°C), H2O and O3 in the above ratio range can produce a synergistic effect: H2O ensures a mild start and uniformity over a large area, while the appropriate amount of O3 effectively promotes the complete decomposition of the precursor, eliminates carbon impurities, and stabilizes the tin valence without negative effects.

[0037] This ratio range is the key to achieving a balance between "high density" and "low damage". If the ratio is less than 1:1, O3 is too high, increasing the cost and potentially causing potential risks to the underlayer; if the ratio is greater than 3:1, the enhancing effect of O3 is weakened, and it cannot effectively solve the inherent defects of a single H2O oxygen source. Therefore, this range is an optimized process window that has been repeatedly verified to produce high-quality films, and is not common knowledge in the field.

[0038] In addition, in step 33, the mixed oxygen source composed of H2O and O3 is introduced in a sequential pulse manner, i.e., H2O is introduced first and then O3 is introduced; the pulse duration of H2O is 0.1-0.5 seconds, and the pulse duration of O3 is 0.5-2.0 seconds, with no purge interval between the two.

[0039] First step (H2O pulse): H2O molecules first undergo hydrolysis reaction with the surface TDMASn ligand, forming a preliminary Sn-OH structure to prepare for the subsequent reaction.

[0040] Second step (O3 pulse, no interval): The subsequent O3, as a highly active oxygen source, can efficiently remove the remaining C and H impurities in Sn-OH and deeply oxidize them into ideal SnO2 films, while effectively filling the oxygen vacancies left by the single H2O reaction.

[0041] This pulse strategy, compared to simple mixed pulses, can more accurately regulate the surface chemical reaction path, thereby more effectively reducing carbon impurity residues and oxygen vacancy density, which is the core of obtaining a high-performance electron transport layer. The specific timing parameters of this step are the result of extensive experimental optimization, constituting a non-obvious, efficient process combination.

[0042] Step 34: Introduce a purge gas to remove unreacted mixed oxygen source and gas-phase byproducts in the reaction chamber.

[0043] The specific details of the above steps are as follows: Substrate preparation and loading: clean 5cm 5cm glass substrate is placed in the reaction chamber of the atomic layer deposition device; Atomic layer deposition device reaction chamber temperature rise and stabilization: set the temperature of the reaction chamber to a process window of 80℃-120℃, and make it fully stable; SnO2 thin film deposition cycle: the following deposition cycle is executed in sequence until the target thickness of the thin film is reached: a. Tin source pulse and saturation: sufficient tin source tetrakisdimethylamino tin (TDMASn) is introduced into the reaction chamber to complete self-limiting chemical adsorption on the substrate surface.

[0044] b. Purge: high-purity nitrogen is introduced to remove residual tin source precursors and gas-phase byproducts in the reaction chamber.

[0045] c. Mixed oxygen source pulse and reaction: a mixed oxygen source composed of H2O and O3 in a volume ratio of 2:1 is introduced to react with the chemisorbed tin source precursor.

[0046] d. Purge: high-purity nitrogen is introduced again to remove residual mixed oxygen source and reaction byproducts.

[0047] Deposition termination and sample removal: when the SnO2 thin film thickness reaches 20nm by controlling the number of cycles, deposition is stopped and the deposited sample is removed.

[0048] Second embodiment of the present application: An electron transport layer for a perovskite solar cell, the electron transport layer being prepared by the preparation method described above.

[0049] Third embodiment of the present application: A preparation method of a solar cell, the preparation method comprising the following steps in sequence: Step 1: provide a conductive glass substrate and perform P1 laser scribing.

[0050] Step 2: prepare a hole transport layer on the scribed substrate.

[0051] Step 3: prepare a perovskite absorption layer on the hole transport layer.

[0052] Step 4: sequentially prepare an interface modification layer, a first electron transport layer and a second electron transport layer on the perovskite absorption layer.

[0053] In step 4, the mixed volume ratio of H2O and O3 in the mixed oxygen source is 2:1.

[0054] In step 4, the thickness of the SnO2 film is 18-22 nm by controlling the number of cycles of atomic layer deposition.

[0055] The second electron transport layer is a SnO2 film prepared by an atomic layer deposition process, the deposition temperature is 80-120°C, the oxygen precursor used is a mixed oxygen source of H2O and O3, and the tin precursor is a tin-containing organic compound.

[0056] Step 5: P2 laser scribing is performed to expose the conductive glass substrate.

[0057] Step 6: P3 laser scribing is performed, and a metal top electrode is prepared.

[0058] A fourth embodiment of the present application: A solar cell prepared by the preparation method described above.

[0059] Experimental examples of the present application: A preparation method of a solar cell, the preparation method sequentially includes the following steps: 1. Substrate preparation: take a 5cm x 5cm ITO glass substrate, clean and dry, and then perform P1 laser scribing.

[0060] 2. Hole transport layer deposition: spin-coat PTAA solution (1 mg / mL in CB) on the scribed ITO substrate at a speed of 5000 rpm for 30 seconds, and then anneal at 100°C for 10 minutes.

[0061] 3. Perovskite layer deposition: use a doctor blade to coat FA 0.83 Cs 0.17 PbI 2.8 Cl 0.2 The perovskite precursor solution (1.5M) is coated on the substrate at a rate of 4cm / s, followed by vacuum flash treatment for 18 seconds, and annealing at 150°C for 15 minutes to form a perovskite film.

[0062] The above steps 1-3 lay the foundation for a high-quality electron transport layer: P1 scribing first defines the cell unit, ensuring that all subsequent functional layers (hole transport layer PTAA, perovskite layer) are accurately prepared only in the effective area. This provides a clean, flat, and non-cross-contaminated perovskite surface for ALD deposition of SnO2 electron transport layer in step 5, which is a prerequisite for obtaining a uniform and high-performance interface. This sequence is a specific and necessary process for preparing trans (p-i-n) structure devices in the art.

[0063] 4. Interface modification and electron transport layer deposition: spin-coat PEAI solution (4mg / mL) and anneal. Then deposit 30nm thick C60 Layer as electron transport layer.

[0064] Step 4: First spin-coat PEAI (interface passivation) on perovskite layer, then evaporate C 60 The order is crucial.

[0065] PEAI passivation: First passivate perovskite surface defects, reduce recombination.

[0066] C 60 Function: As an organic protective layer, protect perovskite from potential erosion by H2O / O3 plasma or strong oxidizing gas during subsequent ALD deposition; at the same time, as a nucleation layer, provide an ideal substrate for the ALD growth of inorganic SnO2.

[0067] Synergy with Step 5: This design allows the subsequent mixed-oxygen ALD process to be safe and efficient on the C 60 surface, realizing the combination of the advantages of high interface quality of organic ETL and high bulk quality of inorganic ETL.

[0068] 5. Deposition of SnO2 using mixed oxygen as oxygen source: ALD process is adopted, with TDMASn as tin precursor at 80℃ cavity temperature; mixed oxygen composed of H2O and O3 in a ratio of 2:1 as oxygen precursor, 80 cycles are performed to deposit a SnO2 film about 20nm thick.

[0069] Step 5: ALD deposition at low temperature of 80℃ using TDMASn and H2O / O3 (2:1) mixed oxygen source, is the core of this solution.

[0070] Necessity of low temperature: protect the underlying temperature-sensitive materials (perovskite, C 60 , PTAA).

[0071] Synergy of mixed oxygen: H2O: Take advantage of its small molecule and good diffusion characteristics, first react with the organic ligand of TDMASn through hydrolysis, achieving mild and uniform nucleation.

[0072] O3: As a strong oxidizing agent, it follows or simultaneously, deeply oxidizes the precursor, effectively eliminates carbon and hydrogen impurities, and fills oxygen vacancies, ensuring the chemical purity of the SnO2 film.

[0073] This synergy effect is particularly critical and unexpected in the low temperature window of 80-120℃, as it solves the problem of single oxygen source not being able to balance reaction completeness and film quality at low temperature.

[0074] 6. P2 scribe: P2 laser scribing is performed to expose the bottom ITO electrode.

[0075] 7、 P3 scribe and electrode preparation: P3 laser scribing was performed, and finally a metal top electrode was deposited to complete the module preparation.

[0076] Steps 6 and 7: P2 scribe (exposing the bottom ITO) first, then P3 scribe and top electrode evaporation, which ensures that the top electrode and the bottom ITO form a series connection through the P2 scribe channel, and is a key step in standardizing the construction of high-efficiency modules. All previous thin film preparation is finally integrated into a solar cell device.

[0077] Effect test: The obtained module was tested for JV, and the initial efficiency was 20.73%, and the fill factor (FF) of the device was improved to 80.58%.

[0078] The AFM characterization of the SnO2 thin film prepared in the experimental example is shown in Figures 3-5 .

[0079] Comparative example of the present application: A group of perovskite module samples were prepared using only H2O as the oxygen source for SnO2, and the other steps were the same. The initial efficiency was 17.80%, and the fill factor of the device was 72.07%.

[0080] The AFM characterization of the SnO2 thin film prepared in the comparative example is shown in Figures 6-8 .

[0081] As shown in Figures 3-8 , it can be seen that: The surface roughness of the experimental example was 0.26 nm, and the surface was flat; while the surface roughness of the comparative example was 0.28 nm, and the surface was slightly undulating. Therefore, the surface of the thin film of the experimental example is more flat and has lower roughness, reduces interface defects, improves the uniformity of contact with the perovskite layer, and reduces interface carrier recombination.

[0082] The potential color distribution of the experimental example was uniform and had small fluctuations; while the potential color gradient of the comparative example was obvious and had large fluctuations. Therefore, the surface potential uniformity of the experimental example is more optimal, the carrier transport is more stable, the charge recombination loss is reduced, and the charge transport efficiency is improved.

[0083] The above results show that compared with the SnO2 thin film using H2O as the oxygen source, the mixed oxygen SnO2 thin film prepared by the present application has advantages in quality and performance, significantly improves the device performance, and lays the foundation for its application value in high-performance perovskite solar modules.

[0084] In the description of the present application, it is to be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance or implying the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified and limited, the term "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0085] In the description of the present application, it is to be understood that the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrally connected, it can be mechanically connected, or it can be electrically connected, it can be directly connected, or it can be indirectly connected through an intermediate medium, it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0086] The above is only the preferred embodiment of the present application, and is not used to limit the present application, it should be pointed out that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, these improvements and modifications should be considered as the protection scope of the present application.

Claims

1. A method for preparing an electron transport layer, characterized in that, The preparation method, employing atomic layer deposition (ALD) technology and using a mixed oxygen source consisting of H2O and O3, includes the following steps: Step 1: Provide a substrate and place it in the atomic layer deposition reaction chamber; Step 2: Stabilize the temperature of the reaction chamber between 80°C and 120°C; Step 3: Perform several atomic layer deposition cycles until the SnO2 film reaches the preset thickness. Each atomic layer deposition cycle includes the following steps: Step 31: Introduce a tin-containing precursor into the reaction chamber to induce self-limiting chemisorption on the substrate surface; Step 32: Introduce purge gas to remove unreacted tin-containing precursors and gaseous byproducts from the reaction chamber; Step 33: Introduce a mixed oxygen source consisting of H2O and O3 into the reaction chamber to allow it to react with the chemisorbed tin-containing precursor on its surface. Step 34: Introduce purge gas to remove unreacted mixed oxygen sources and gaseous byproducts from the reaction chamber; The volume ratio of H2O to O3 is 1:1 to 3:

1.

2. The method for preparing an electron transport layer as described in claim 1, characterized in that, The volume ratio of H2O to O3 in the mixed oxygen source is 2:

1.

3. The method for preparing an electron transport layer as described in claim 1, characterized in that, The tin-containing precursor is tetradimethylaminotin.

4. The method for preparing an electron transport layer as described in claim 1, characterized in that, The atomic layer deposition cycle is 70-90 times, and the preset thickness of the SnO2 thin film is 18-22 nm.

5. The method for preparing an electron transport layer as described in claim 1, characterized in that, In step 33, the mixed oxygen source composed of H2O and O3 is introduced in a sequential pulse mode, that is, H2O is introduced first and then O3 is introduced; wherein, the pulse duration of H2O is 0.1~0.5 seconds and the pulse duration of O3 is 0.5~2.0 seconds, with no purging interval between them.

6. An electron transport layer for use in a perovskite solar cell, characterized in that, The electron transport layer is prepared by any one of claims 1 to 5.

7. A method for preparing a solar cell, characterized in that, The preparation method includes the following steps in sequence: Step 1: Provide a conductive glass substrate and perform P1 laser scribing; Step 2: Prepare a hole transport layer on the scribing substrate; Step 3: Prepare a perovskite absorber layer on the hole transport layer; Step 4: Sequentially prepare an interface modification layer, a first electron transport layer, and a second electron transport layer on the perovskite absorber layer; The second electron transport layer is a SnO2 thin film, which is prepared by atomic layer deposition process at a deposition temperature of 80°C to 120°C. The oxygen precursor used is a mixed oxygen source of H2O and O3, and the tin precursor is a tin-containing organic compound. Step 5: Perform P2 laser scribing to expose the conductive glass substrate; Step 6: Perform P3 laser scribing and fabricate the metal top electrode.

8. The method for preparing a solar cell as described in claim 7, characterized in that, In step 4, the volume ratio of H2O and O3 in the mixed oxygen source is 2:

1.

9. The method for preparing a solar cell as described in claim 7, characterized in that, In step 4, the thickness of the SnO2 film is made to be 18~22nm by controlling the number of atomic layer deposition cycles.

10. A solar cell, characterized in that, The solar cell is prepared by the method described in any one of claims 7 to 9.

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