Tin oxide film and preparation method and application thereof

Abstract

The invention provides a tin oxide thin film and a preparation method and application thereof, relates to the technical field of solar cells, and can improve the proportion of tetravalent tin in the tin oxide thin film and enable the energy level of the tin oxide thin film to be better matched with perovskite, thereby improving the performance of a device. According to the preparation method of the tin oxide thin film, the tin oxide thin film is deposited on a substrate through an atomic layer deposition technology, and in the deposition process, a first oxygen source and a second oxygen source are continuously used as oxygen sources to react with a tin metal organic source, the first oxygen source is selected from one or more of water, hydrogen peroxide and oxygen, the process temperature of the reaction between the second oxygen source and the tin metal organic source is less than 100 DEG C, the oxidation intensity of the second oxygen source to tin metal is greater than that of the first oxygen source, and the generated product is tetravalent tin oxide.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a tin oxide thin film and a preparation method and application thereof. Background Art

[0002] Organic-inorganic hybrid perovskites, with their excellent properties such as high absorption coefficient, low exciton binding energy, long carrier diffusion length, and high carrier mobility, have attracted widespread attention as ideal photovoltaic absorber materials. Perovskite solar cells are suitable for combining with traditional solar cells (such as silicon-based cells and copper indium gallium selenide) to produce stacked devices, and are receiving increasing attention.

[0003] In perovskite single-junction cells, perovskite / perovskite tandem cells, or perovskite / crystalline silicon tandem cells (collectively referred to as perovskite cells in this application), tin oxide is a commonly used buffer layer and electron transport layer. Tetrakis(dimethylamino)tin (TDMASn) and deionized water are generally used as precursors to prepare tin oxide films by atomic layer deposition (ALD). However, the process has the following problems:

[0004] Since TDMASn will react with perovskite at temperatures above 95°C, only low-temperature processes can be used, and the process temperature is between 80-95°C. Moreover, since perovskite is sensitive to strong oxides, water is generally used as the oxide of TDMASn. Under low-temperature process conditions, the reaction between TDMASn and water is not sufficient and it cannot be fully oxidized, resulting in the final formation of SnO x It is a mixed film of SnO and SnO2, in which a large amount of Sn is in divalent state. SnO is a p-type semiconductor, and SnO2 is an n-type semiconductor, so the energy level of the mixture does not match well with the perovskite and transport layer, resulting in low device filling. Summary of the Invention

[0005] The purpose of the present invention is to provide a tin oxide film and a preparation method and application thereof, which can increase the proportion of tetravalent tin in the tin oxide film, thereby improving device performance.

[0006] The object of the present invention is to provide a method for preparing a tin oxide thin film, wherein the tin oxide thin film is deposited on a substrate by atomic layer deposition technology, wherein the deposition process includes the steps of continuously using a first oxygen source and a second oxygen source as oxygen sources to react with a tin metal organic source, wherein the first oxygen source is selected from one or more of water, hydrogen peroxide and oxygen, the process temperature for the reaction of the second oxygen source with the tin metal organic source is less than 100°C, the oxidation strength of the second oxygen source on tin metal is greater than that of the first oxygen source, and the generated product is tetravalent tin oxide.

[0007] Optionally, the first oxygen source is water, the second oxygen source is iodine vapor or bromine vapor, or a mixed gas containing iodine vapor and / or bromine vapor.

[0008] Optionally, the tin metal organic source is selected from one or more of alkyl tin, tin alcohol salt, and Sn(NR1R2)4, where R1 and R2 are each independently selected from C1-C4 alkyl groups.

[0009] Optionally, the tin metal organic source is tin bis(dimethylamide).

[0010] Optionally, the step of continuously using the first oxygen source and the second oxygen source as oxygen sources to react with the tin metal organic source includes multiple following cycles:

[0011] Introduce the tin metal organic source, and then clean the chamber;

[0012] Introduce the first oxygen source to react with the tin metal organic source to form a tin oxide thin film;

[0013] Introduce the second oxygen source to perform secondary oxidation on the tin oxide thin film to increase the proportion of tetravalent tin in the thin film, and then clean the chamber.

[0014] Optionally, after introducing the first oxygen source to react with the tin metal organic source, first clean the chamber, and then introduce the second oxygen source to perform secondary oxidation on the tin oxide thin film.

[0015] Optionally, the time for introducing the first oxygen source is 5-15 seconds; the time for introducing the second oxygen source is 0.5-2 seconds.

[0016] Optionally, the number of the cycles is 50-300, preferably 80-150.

[0017] Optionally, the cleaning of the chamber includes: purging the chamber with an inert gas.

[0018] Optionally, the thickness of the tin oxide thin film is 5-30 nm, preferably 8-15 nm.

[0019] Optionally, before the step of continuously using the first oxygen source and the second oxygen source as oxygen sources to react with the tin metal organic source, it further includes: a first stage of using the first oxygen source as an oxygen source to react with the tin metal organic source.

[0020] Another object of the present invention is to provide another method for preparing a tin oxide thin film. The tin oxide thin film is deposited on a substrate by atomic layer deposition technology. During the deposition process, it includes a first stage in which a first oxygen source is used as an oxygen source to react with a tin metal organic source, and a second stage in which a second oxygen source is used as an oxygen source to react with the tin metal organic source. Wherein, the oxidation intensity of the second oxygen source for tin metal is greater than that of the first oxygen source, and the product formed is tin tetraoxide.

[0021] Optionally, the first oxygen source is water and the second oxygen source is ozone.

[0022] Optionally, the first stage includes the following cycles: introducing the tin metal organic source, and then cleaning the chamber; introducing the first oxygen source to react with the tin metal organic source to form a tin oxide thin film;

[0023] The second stage includes the following cycles: introducing the tin metal organic source, and then cleaning the chamber; introducing the second oxygen source to react with the tin metal organic source to form a tin tetraoxide thin film.

[0024] Optionally, the number of cycles in the first stage is 30 - 100; the number of cycles in the second stage is 20 - 270.

[0025] Another object of the present invention is to provide a tin oxide electron transport layer or a tin oxide buffer layer, which is prepared by the preparation method described in any one of the above.

[0026] Another object of the present invention is also to provide a perovskite solar cell, which includes the tin oxide electron transport layer and / or the tin oxide buffer layer described above.

[0027] The perovskite solar cell includes a perovskite thin film. A second electron transport layer is further provided between the perovskite thin film and the tin oxide electron transport layer or the tin oxide buffer layer. The second electron transport layer is one of C60, C70, and PCBM.

[0028] The present invention provides a tin oxide thin film, its preparation method and application. During the process of depositing a tin oxide thin film on a substrate by atomic layer deposition technology, a first oxygen source and a second oxygen source are continuously used as oxygen sources to react with a tin metal organic source. That is, on the basis of the oxidation by the first oxygen source, a second oxygen source with a greater oxidation intensity is further introduced to perform secondary oxidation on the tin oxide thin film. The purpose is to increase the proportion of tin tetravalent in the thin film, make the energy level of the tin oxide thin film more matched with the perovskite, and thus improve the device performance. Description of the Drawings

[0029] Figure 1 It is a comparative XPS characterization diagram of the perovskite solar cells provided in the examples and comparative examples of this application;

[0030] Figure 2 A comparison chart of the fill factors of the perovskite solar cells provided in the examples and comparative examples of the present application;

[0031] Figure 3 A comparison chart of the device efficiency of the perovskite solar cells provided in the examples and comparative examples of the present application.

[0032] Abbreviations and key terms used in this description

[0033] Perovskite

[0034] The perovskite material of the present application is a material with a chemical structural formula of ABX3, wherein A + and B 2+ Represents cations of different radius sizes, X — Cation A is an anion that forms a bond with both cations. + The radius has a certain size, such as Cs + 、(CH3NH3) + cation B 2+ Generally inorganic cations, such as Pb 2+ Sn 2+ , whose atomic size is large and plays a supporting role in the unit cell; the anion X — Generally, they are inorganic anions with strong bonding ability, such as halogen ions.

[0035] Atomic layer deposition

[0036] Atomic layer deposition (ALD) is a method of forming a deposition film by alternately pulsing gaseous precursors into a reactor and chemically adsorbing and reacting them on a deposition substrate, and it is a method that can deposit substances layer by layer in the form of a single atomic film on the surface of a substrate. During atomic layer deposition, the chemical reaction of a new atomic film layer is directly associated with the previous layer, and this way enables each reaction to deposit only one atomic layer. Conventional ALD equipment may include a reactor chamber, a substrate holder, a gas flow system including gas inlets for supplying precursors and reactants to the substrate surface, and an exhaust system for removing the gases used. The thin film growth mechanism relies on the adsorption of precursors on the active sites of the substrate, and preferably maintains conditions such that no more than a monolayer is formed on the substrate. Exposing the substrate to a first precursor is typically followed by a purge stage or other removal process (e.g., evacuation or "pumping") to remove any excess first precursor and any reaction by-products from the reaction chamber. Then a second reactant or precursor is introduced into the reaction chamber, where it reacts with the first precursor, and this reaction produces the desired film on the substrate. When all available first precursors adsorbed on the substrate have reacted with the second precursor and the reaction terminates, a second purge or other removal stage is performed to remove any remaining second precursor and possible reaction by-products in the reaction chamber. This cycle can be repeated to grow the film to the desired thickness. Detailed Description

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0038] As used herein, a "substrate" may refer to any one or more underlying materials on which a device, circuit, or film can be used or formed.

[0039] As used herein, a "film" may refer to any continuous or discontinuous structure, material, or materials deposited by the methods disclosed herein.

[0040] As used herein, an "electron transport layer" refers to a layer through which electrons can flow easily and which generally reflects holes.

[0041] In this article, the "buffer layer" refers to a layer that plays an interface regulating role. It can be located between the electron transport layer and the electrode, or between the electron transport layer and the light absorption layer. On the one hand, it can make the energy levels on the electron transport path more matched, accelerate electron extraction and transmission, passivate interface defect states, and reduce interface recombination current; on the other hand, it can also protect the perovskite absorption layer, thereby improving battery stability.

[0042] The object of the present invention is to provide a method for preparing a tin oxide thin film. In the process of depositing the tin oxide thin film on a substrate by atomic layer deposition technology, the method includes the steps of continuously using a first oxygen source and a second oxygen source as oxygen sources to react with a tin metal organic source, wherein the first oxygen source is selected from one or more of water, hydrogen peroxide and oxygen, the process temperature for the reaction of the second oxygen source with the tin metal organic source is less than 100°C, the oxidation strength of the second oxygen source on tin metal is greater than that of the first oxygen source, and the generated product is tetravalent tin oxide.

[0043] Currently, tin oxide thin films are deposited using atomic layer deposition (ALD). Water is typically used as the oxide, but the reaction between the tin metal organic source and water is incomplete under low-temperature process conditions, preventing full oxidation and leaving a significant amount of Sn in a divalent state. As is well known, SnO is a p-type semiconductor, while SnO2 is an n-type semiconductor. Therefore, the energy levels of the mixture do not match well with the perovskite and transport layers, resulting in low device fill.

[0044] To address the above issues, the solution provided in this application involves introducing a tin metal organic source into a chamber and adsorbing it onto a substrate. A first oxygen source is then introduced to react with the tin metal organic source on the substrate to form tin oxide (containing a large amount of divalent tin). A second oxygen source is then introduced to further oxidize the tin oxide, converting all or at least a large portion of the divalent tin into tetravalent tin oxide, thereby increasing the proportion of tetravalent tin in the film and resulting in the resulting tin oxide film exhibiting an n-type semiconductor or a near-n-type semiconductor. The first oxygen source can be one or more selected from water, hydrogen peroxide, and oxygen; the second oxygen source has a greater oxidizing strength for tin metal than the first oxygen source, and the resulting product is tetravalent tin oxide. The second oxygen source can be, for example, iodine vapor or bromine vapor.

[0045] The above-mentioned tin metal-organic source can be one or more selected from alkyl tin, alcohol tin salts, and Sn(NR1R2)4, where R1 and R2 are each independently selected from C1-C4 alkyl groups. C1-C4 alkyl groups include the following: methyl (CH3) with only one carbon atom, ethyl (C2H5) with two carbon atoms, propyl (C3H7) with three carbon atoms and two isomers: n-propyl (CH3CH2CH2) and isopropyl (CH3CH(CH3)), butyl (C4H9) with four carbon atoms and four isomers: n-butyl (CH3CH2CH2CH3), isobutyl (CH3CH(CH3)CH3), sec-butyl (CH3CH(CH3)CH2), and tert-butyl (C(CH3)3).

[0046] Exemplarily, the tin metal-organic source is tin bis(dimethylamide); the first oxygen source is water, the second oxygen source is iodine vapor or bromine vapor, or a mixed gas containing iodine vapor and / or bromine vapor. When the first oxygen source is water and the second oxygen source is iodine vapor, the product generated in the first stage is a mixed thin film of SnO and SnO2 (SnO is in the majority), and the product generated in the second stage is SnO2 and SnI4 (or SnBr4), and the reaction formula is Sn 2+ +I2→Sn 4+ +2I - .

[0047] The atomic layer deposition tin oxide scheme provided by the present application, after the first oxygen source reacts with the tin metal-organic source adsorbed on the substrate, a second oxygen source with stronger oxidizing property and capable of generating tetravalent tin oxide is continuously introduced to perform secondary oxidation on the thin film on the substrate, so as to increase the proportion of tetravalent tin in the thin film. The finally generated tin oxide thin film exhibits an n-type semiconductor and can be widely applied in the semiconductor field, especially in the field of solar cells.

[0048] Specifically, the preparation method for preparing a tin oxide thin film by atomic layer deposition provided by the present application includes multiple cycles of the following steps:

[0049] Step 1: Introduce the tin metal-organic source;

[0050] Step 2: Clean the cavity;

[0051] Step 3: Introduce the first oxygen source to react with the tin metal-organic source to generate a tin oxide thin film (single-layer or multi-layer tin oxide);

[0052] Step 4: Introduce the second oxygen source to perform secondary oxidation on the tin oxide thin film to increase the proportion of tetravalent tin in the thin film;

[0053] Step 5: Then clean the cavity.

[0054] The number of cycles can be set according to the preset thickness of the tin oxide thin film. Optionally, the number of times of cyclically executing the above steps one to five can be 50 - 300 times, preferably 80 - 150 times.

[0055] Optionally, in another embodiment, after introducing the first oxygen source to react with the tin metal organic source, the chamber is first cleaned, and then the second oxygen source is introduced to perform secondary oxidation on the tin oxide thin film. Cleaning the chamber before introducing the second oxygen source can avoid the residual first oxygen source from affecting the effect of secondary oxidation. The above method of cleaning the chamber is not specifically limited, as long as it can remove the reactants in the chamber, including but not limited to: purging the chamber with an inert gas.

[0056] Optionally, the time for introducing the first oxygen source can be 5 - 15 seconds; the time for introducing the second oxygen source can be 0.5 - 2 seconds.

[0057] The tin metal organic source, the first oxygen source, and the second oxygen source can use an inert gas as a carrier gas or can be directly introduced, depending on the specific situation. Exemplarily, the tin metal organic source tetrakis(dimethylamino)tin can be introduced using an inert gas as a carrier gas, and the introduction time is 0.1 - 1 s; the first oxygen source water can also be introduced using an inert gas as a carrier gas, and the introduction time is 5 - 15 s; the second oxygen source iodine vapor can be directly introduced, and the introduction time is 0.5 - 1.5 s.

[0058] Optionally, the thickness of the tin oxide thin film is 5 - 30 nm, preferably 8 - 15 nm.

[0059] The embodiments of the present application also provide a tin oxide electron transport layer or a tin oxide buffer layer, which is prepared by the preparation method described in any one of the above. The tin oxide electron transport layer or the tin oxide buffer layer provided by the embodiments of the present application, due to the existence of a secondary oxidation stage in the preparation process, with tetravalent tin oxide as the main body, the film layer presents a p-type semiconductor, is suitable for being used as an electron transport layer or a buffer layer, and is particularly suitable for being used as the electron transport layer of a perovskite battery.

[0060] Another preparation method of a tin oxide thin film according to the embodiments of the present invention further includes: a first stage of using the first oxygen source as the oxygen source to react with the tin metal organic source before the step of continuously using the first oxygen source and the second oxygen source as the oxygen source to react with the tin metal organic source. In this solution, in the first stage, the first oxygen source with relatively weak oxidizing property and low erosion to perovskite is used. After forming a certain tin oxide thin film protection, in the second stage, the first and second oxygen sources are alternately used to continue the preparation, ensuring that the subsequent generated film layer contains a higher proportion of tetravalent tin.

[0061] An embodiment of the present invention provides another method for preparing a tin oxide thin film, which deposits the tin oxide thin film on a substrate using atomic layer deposition technology, wherein the deposition process includes a first stage using a first oxygen source as an oxygen source to react with a tin metal organic source, and a second stage using a second oxygen source as an oxygen source to react with the tin metal organic source, wherein the second oxygen source has a greater oxidizing strength for tin metal than the first oxygen source, and the generated product is tetravalent tin oxide.

[0062] When depositing a tin oxide film on a substrate using atomic layer deposition technology, this solution uses a first oxygen source with weak oxidizing properties and low corrosiveness to perovskite in the first stage to form a certain degree of tin oxide film protection. In the second stage, a second oxygen source with stronger oxidizing properties and high corrosiveness is used to continue the preparation, ensuring that the subsequently generated film layer contains a higher proportion of tetravalent tin, so that the energy level of the overall tin oxide film is more matched with the perovskite, thereby improving device performance.

[0063] For example, optionally, the first oxygen source is water, and the second oxygen source is ozone.

[0064] Optionally, the first stage includes several cycles of: introducing the tin metal organic source and then cleaning the chamber; introducing the first oxygen source to react with the tin metal organic source to form a tin oxide film;

[0065] The second stage includes the following cycles: introducing the tin metal organic source, then cleaning the chamber; introducing the second oxygen source to react with the tin metal organic source to form a tetravalent tin oxide film. Optionally, the first stage has 30-100 cycles; the second stage has 20-270 cycles.

[0066] An embodiment of the present application further provides a perovskite solar cell comprising the above-mentioned tin oxide electron transport layer and / or tin oxide buffer layer.

[0067] Preferably, when using ALD to prepare a tin oxide film, water is used as an oxygen source to react with tetrakis(dimethylamino)tin, and iodine vapor is then used as an oxygen source to further oxidize the reaction product, and the above steps are repeated to reach a preset film thickness. The resulting tin oxide film has a high SnO2 content, and the film behaves as an n-type semiconductor, which is well matched with the perovskite energy band, and the resulting battery has good electrical parameters. Due to the presence of a large amount of iodine ions in the perovskite, the use of iodine vapor as an oxide does not negatively affect the stability and efficiency of the device.

[0068] The tin oxide film of the present application can be used in perovskite cells, perovskite / perovskite tandem cells, perovskite / crystalline silicon tandem cells, perovskite / perovskite / perovskite tandem cells, and perovskite / perovskite / crystalline silicon tandem cells.

[0069] Exemplarily, the perovskite device structure provided by the present application is ITO glass / NiO x / perovskite / C60 / SnO x / Cu electrode. The perovskite / perovskite tandem device structure provided by the present application is ITO glass / NiO x / wide-bandgap perovskite / C60 / SnO x / ITO / PEDOT:PSS / narrow-bandgap perovskite / C60 / SnO x / Cu electrode. The crystalline silicon / perovskite tandem device structure provided by the present application is silicon bottom cell / NiO x / wide-bandgap perovskite / C60 / SnO x / ITO / Cu electrode. Another exemplary tandem device structure is silicon bottom cell / HTL / wide-bandgap perovskite / C60 (ETL is mainly C60) / SnO x / TCO / metal electrode.

[0070] In some other embodiments, a second electron transport layer is further disposed between the perovskite thin film and the tin oxide electron transport layer or the tin oxide buffer layer, and the second electron transport layer is one of C60, C70, and PCBM.

[0071] In some embodiments, the present application further provides a perovskite tandem solar cell, which includes a crystalline silicon bottom cell, an intermediate composite layer, and a perovskite top cell stacked in sequence, wherein the perovskite top cell is the perovskite solar cell described in any one of the above. The perovskite solar cell may include any one of the following perovskite thin films: FACsPbIBrCl, FAMACsPbIBrCl, FACsDMAPbIBrCl, CsDMAPbIBrCl, FACsPbIBr, FAMACsPbIBr, FACsDMAPbIBr, CsDMAPbIBr, FACsPbI, FAMACsPbI, FACsDMAPbI, CsDMAPbI, FACsPbSnI, FAMACsPbSnI, and FACsDMAPbSnI and CsDMAPbSnI. The crystalline silicon bottom cell is selected from one of TOPCon cells, HJT cells, IBC cells, PERC cells, and HBC cells.

[0072] The perovskite solar cell may also be provided with other functional layers as needed, such as an electron blocking layer, which does not belong to the improvement points of the present application and will not be further limited.

[0073] The present application improves the proportion of tetravalent tin in the film and simultaneously improves the device performance by performing secondary oxidation on the SnO x film in the ALD process. The following will be described in combination with specific test examples.

[0074] Comparative Example:

[0075] In the ALD process, the following steps were repeated 100 times.

[0076] The first step is to introduce TDMASn precursor for 50ms; the second step is to clean the chamber for 10s; the third step is to introduce H2O precursor for 10s (first step oxidation); and the fourth step is to clean the chamber for 10s.

[0077] Embodiment 1:

[0078] In the ALD process, the following steps were repeated 100 times.

[0079] The first step is to introduce TDMASn precursor for 50ms; the second step is to clean the cavity for 10s; the third step is to introduce H2O precursor for 10s (first step oxidation); the fourth step is to clean the cavity for 10s; the fifth step is to introduce I2 precursor for 1s; the sixth step is to clean the cavity for 10s.

[0080] Example 2:

[0081] In the ALD process, the following steps were repeated 100 times.

[0082] The first step is to introduce TDMASn precursor for 50ms; the second step is to clean the chamber for 10s; the third step is to introduce H2O precursor for 10s (first step oxidation); the fourth step is to introduce I2 precursor for 1s; the fifth step is to clean the chamber for 10s.

[0083] In the comparative example, water was used as the sole oxidation source. In Examples 1 and 2, an iodine vapor oxidation step was added after the H2O oxidation. Figure 1 The XPS characterization shown in the figure shows that the Sn 3d peak of the secondary oxidized tin oxide film shifts to a higher energy compared to the primary oxidized film, indicating that the Sn 4+ The proportion of increased.

[0084] like Figure 2 and Figure 3 As shown, the perovskite cells prepared in Examples 1 and 2 have significantly improved fill factors due to a better match between the energy levels of the tin oxide film, the perovskite, and the electron transport layer, resulting in better device conversion efficiency. The perovskite cell prepared in Comparative Example 1 has a fill factor of 82.5% and a device efficiency of 21.1%. The perovskite cells prepared in Examples 1 and 2 have a fill factor of 85.2% and a device efficiency of 21.6%.

[0085] Figure 1 and Figure 2 TDMASn-H2O represents the sample prepared using water as the sole oxygen source, and TDMASn-H2O-I2 represents the sample prepared using water as the first oxygen source and I2 as the second oxygen source.

[0086] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a tin oxide thin film, characterized in that, Deposit a tin oxide thin film on a substrate by atomic layer deposition technology, wherein during the deposition process, it includes steps of continuously using a first oxygen source and a second oxygen source as oxygen sources to react with a tin metal organic source. Among them, the first oxygen source is selected from one or more of water, hydrogen peroxide, and oxygen. The process temperature for the second oxygen source to react with the tin metal organic source is less than 100 °C. The oxidation intensity of the second oxygen source on tin metal is greater than that of the first oxygen source, and the resulting product is tin(IV) oxide.

2. The preparation method according to claim 1, characterized in that, The first oxygen source is water, and the second oxygen source is iodine vapor or bromine vapor, or a mixed gas containing iodine vapor and / or bromine vapor.

3. The preparation method according to claim 1, characterized in that, The tin metal organic source is selected from one or more of alkyltin, alcohol tin salts, and Sn(NR1R2)4, where R1 and R2 are each independently selected from C1-C4 alkyl groups.

4. The preparation method according to claim 1, characterized in that, The tin metal organic source is tin(IV) bis(dimethylamino).

5. The preparation method according to claim 1, characterized in that, The step of continuously using the first oxygen source and the second oxygen source as oxygen sources to react with the tin metal organic source includes multiple following cycles: Introduce the tin metal organic source, and then clean the chamber; Introduce the first oxygen source to react with the tin metal organic source to form a tin oxide thin film; Introduce the second oxygen source to perform secondary oxidation on the tin oxide thin film to increase the proportion of tin(IV) in the thin film, and then clean the chamber.

6. The preparation method according to claim 5, characterized in that, After introducing the first oxygen source to react with the tin metal organic source, first clean the chamber, and then introduce the second oxygen source to perform secondary oxidation on the tin oxide thin film.

7. The preparation method according to claim 5 or 6, characterized in that, The time for introducing the first oxygen source is 5 - 15 seconds; the time for introducing the second oxygen source is 0.5 - 2 seconds.

8. The preparation method according to claim 5 or 6, characterized in that, The number of the cycles is 50 - 300, preferably 80 - 150.

9. The preparation method according to claim 1, characterized in that, The thickness of the tin oxide thin film is 5 - 30 nm, preferably 8 - 15 nm.

10. The preparation method according to any one of claims 1-6 and 9, characterized in that, Before the step of continuously using the first oxygen source and the second oxygen source as oxygen sources to react with the tin metal organic source, it further includes: a first stage of using the first oxygen source as an oxygen source to react with the tin metal organic source.

11. A method for preparing a tin oxide thin film, characterized in that, Deposit a tin oxide electron transport layer or a tin oxide buffer layer on a substrate by atomic layer deposition technology, wherein during the deposition process, it includes a first stage of using the first oxygen source as an oxygen source to react with the tin metal organic source, and a second stage of using the second oxygen source as an oxygen source to react with the tin metal organic source. Among them, the oxidation intensity of the second oxygen source on tin metal is greater than that of the first oxygen source, and the resulting product is tin(IV) oxide.

12. The preparation method according to claim 11, wherein The first oxygen source is water, and the second oxygen source is ozone.

13. The preparation method according to claim 11 or 12, characterized in that, The first stage includes the following cycles: introduce the tin metal organic source, and then clean the chamber; introduce the first oxygen source to react with the tin metal organic source to form a tin oxide thin film; The second stage includes the following cycles: introduce the tin metal organic source, and then clean the chamber; introduce the second oxygen source to react with the tin metal organic source to form a tin(IV) oxide thin film.

14. The preparation method according to claim 13, characterized in that, The number of cycles in the first stage is 30 - 100; the number of cycles in the second stage is 20 - 270.

15. A tin oxide electron transport layer or a tin oxide buffer layer, which is prepared by the preparation method according to any one of claims 1 - 14.

16. A perovskite solar cell, which comprises the tin oxide electron transport layer and / or tin oxide buffer layer described in claim 15.

17. The perovskite solar cell according to claim 16, characterized in that, It includes a perovskite thin film, and a second electron transport layer is further disposed between the perovskite thin film and the tin oxide electron transport layer or the tin oxide buffer layer, and the second electron transport layer is one of C60, C70, and PCBM.

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