A post-processing method for ALD-SnO2 thin films and the prepared tin oxide thin films and their applications

Abstract

This invention belongs to the field of photovoltaic technology and discloses a post-processing method for ALD-SnO2 thin films, including the following steps: immersing the ALD-SnO2 thin film in water or a DMPS aqueous solution, heating, cleaning, and annealing to obtain a water-treated or DMPS aqueous solution-treated ALD-SnO2 thin film, respectively denoted as W-SnO2 thin film or D-SnO2 thin film. This invention uses immersion water bath or DMPS aqueous solution bath treatment to solve the problems of poor performance of ALD-SnO2 thin films and subsequent perovskite film formation. Specifically, the organic residues on the surface of the W-SnO2 thin film are almost completely removed; however, with prolonged water bath time, the film morphology gradually transforms into an island-like distribution, and the density is impaired. The DMPS aqueous solution bath treatment optimizes the surface groups and energy level structure of the film without destroying the initial morphology and density.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic technology, specifically relating to a post-processing method for ALD-SnO2 thin films and the tin oxide thin films prepared therefrom and their applications. Background Technology

[0002] Most existing n–i–p perovskite solar cells (PSCs) use tin oxide (SnO2) as the electron transport layer (ETL) due to its high electron mobility and optimal energy levels. Generally, an ideal SnO2 ETL should simultaneously meet several stringent criteria, such as conformal film morphology on the substrate, non-pinhole film coverage, high electron mobility, energy levels aligned with the perovskite layer, strongly chelating surface functional groups for defect passivation, and being as thin as possible to minimize resistance. SnO2 ETLs are typically prepared using solution methods, including colloidal nanocrystalline coating deposition or chemical bath deposition (CBD). However, these solution methods require thicker film stacks to ensure complete SnO2 film coverage and effectively block pores, resulting in typically high film thicknesses. To reduce film thickness while maintaining SnO2 film coverage, atomic layer deposition (ALD) is the optimal choice. It utilizes in-situ surface reactions to achieve wafer-scale monolayer films, offering unparalleled conformality and density. However, the highest efficiency of PSCs based on monolayer ALD-SnO2 is only 22.86%, far lower than that of PSCs based on solution-processed SnO2. Therefore, identifying the root cause of this difference is crucial for improving the performance of nip PSCs.

[0003] Currently, in the ALD process of SnO2 thin films, tetratetra(dicarboxamido)tin(IV) (TDMASn) is commonly used as the Sn source, while H2O, O3, and O2 plasmas are typically used as oxygen sources. However, precisely controlling the valence state of Sn in a closed-environment reaction is inherently difficult, and the optimal energy level window is usually very narrow, making precise ALD-SnO2 energy level engineering a significant challenge. Incomplete reactions of the Sn precursor leave residual organic ligands that act as electron traps, resulting in organic residues in the bulk phase and surface of the film. This reduces carrier mobility and consequently affects device performance, which is one of the main obstacles hindering the widespread application of ALD-SnO2 layers in devices. Furthermore, the surface functional groups on SnO2 play an important role in regulating perovskite nucleation, crystal quality, interfacial charge transport dynamics, and nonradiative recombination pathways.

[0004] Therefore, altering the surface morphology and crystallinity of SnO2 films is an effective way to improve device performance. Maintaining the inherent conformability and density of the ALD process while eliminating organic residues in the bulk and surface of the SnO2 film, adjusting energy levels, and optimizing surface functional groups are key challenges in transforming the morphological advantages of this technology into high-efficiency nip devices. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a post-processing method for ALD-SnO2 thin films, the prepared tin oxide thin films, and their applications. The post-processing method removes organic residues from the bulk phase and surface of the ALD-SnO2 thin film using an immersion water bath or DMPS aqueous solution bath strategy. This optimizes the surface functional groups and energy level structure without altering the morphology and density, thereby preparing high-quality SnO2 thin films and improving the photoelectric performance of perovskite solar cells.

[0006] The inventive concept of this invention is as follows: This invention proposes a post-treatment method for ALD-SnO2 thin films, employing an immersion water bath or a DMPS aqueous solution bath to remove organic residues from the surface and bulk phase of the ALD-SnO2 thin film. This addresses the poor performance of the ALD-SnO2 thin film and subsequent perovskite film formation issues, allowing the prepared SnO2 thin film to maintain its initial morphology and density, thereby improving the photovoltaic performance of the device. Specifically, the ALD-SnO2 thin film undergoes water bath treatment to fully remove residual organic matter. However, the film (W-SnO2 thin film) after water bath treatment still suffers from uneven morphology and poor coverage. Further, sodium 2,3-dimercapto-1-propanesulfonate (DMPS), containing mercapto and sulfonic acid functional groups, is introduced into the water bath, allowing the mercapto / sulfonic acid groups (-SH / -SO3H) to simultaneously graft onto the bulk phase and surface of the film. DMPS can effectively suppress the morphological evolution of SnO2 films, allowing post-treated films (D-SnO2 films) to maintain the initial coverage and conformal morphology of ALD-SnO2 films, and can improve the surface functional groups and energy level structure of the films. Therefore, PSCs and their components (PSMs) prepared based on W-SnO2 or D-SnO2 films have improved photoelectric conversion efficiency (PCE) and operational stability.

[0007] To address the aforementioned technical problems, the first aspect of the present invention provides a post-processing method for ALD-SnO2 thin films, comprising the following steps: ALD-SnO2 films are prepared by immersing them in water or DMPS aqueous solution, heating them, and then cleaning and annealing them. These are referred to as W-SnO2 films or D-SnO2 films, respectively.

[0008] In some embodiments of the present invention, the water is deionized water or distilled water.

[0009] In some embodiments of the present invention, the molar concentration of the DMPS aqueous solution is 20-80 mmol / L, and the DMPS aqueous solution needs to be sealed and stored in an oxygen-free environment before use.

[0010] In some embodiments of the present invention, the molar concentration of the DMPS aqueous solution is 40-60 mmol / L.

[0011] In some embodiments of the present invention, the heating temperature is 80-95°C.

[0012] In some embodiments of the present invention, the heating temperature is 85-95°C.

[0013] In some embodiments of the present invention, the heating time is 10-60 min. The heating time is related to the thickness of the ALD-SnO2 film. The greater the thickness of the film, the longer the heating time.

[0014] In some embodiments of the present invention, the heating time is 15-45 minutes.

[0015] In some embodiments of the present invention, the heating time is 25-35 minutes.

[0016] In some embodiments of the present invention, the annealing temperature is 120-180°C.

[0017] In some embodiments of the present invention, the annealing temperature is 140-160°C.

[0018] In some embodiments of the present invention, the annealing time is 30-90 minutes.

[0019] In some embodiments of the present invention, the annealing time is 40-80 minutes.

[0020] In some embodiments of the present invention, the cleaning is performed using deionized water or distilled water.

[0021] In some embodiments of the present invention, the preparation process of the ALD-SnO2 thin film includes the following steps: A conductive substrate is placed in an ALD device and preheated; then a tin source, an oxygen source, and an inert gas are introduced to deposit SnO2 on the surface of the conductive substrate to obtain the ALD-SnO2 thin film.

[0022] In some embodiments of the present invention, the conductive substrate is a fluorine-doped tin oxide (FTO) rigid conductive glass treated with laser etching and ultraviolet ozone (UVO).

[0023] In some embodiments of the present invention, the UVO treatment time is 10-20 min.

[0024] In some embodiments of the present invention, the preheating is performed by heating at a temperature of 100-150°C for 5-20 minutes.

[0025] In some embodiments of the present invention, the tin source comprises tetra(dicarboxamido)tin (IV) (TDMASn).

[0026] In some embodiments of the present invention, the oxygen source is selected from at least one of H2O, O2 plasma, and O3.

[0027] In some embodiments of the present invention, the inert gas is selected from at least one of argon and nitrogen.

[0028] In some embodiments of the present invention, the pressure in the ALD device is less than 4 × 10⁻⁶. 1 torr.

[0029] In some embodiments of the present invention, an ALD-SnO2 thin film is deposited with an inert gas flow rate of 20-40 sccm. During the deposition process, the temperatures of the tin source, oxygen source, and conductive substrate are 60-80°C, room temperature, and 120-180°C, respectively. The circulating atmosphere and time of the inert gas during the deposition process are as follows: the circulating atmosphere is introduced sequentially in the order of 0.01-0.5s for the tin source, 1-15s for the inert gas, 0.01-1s for the oxygen source, and 1-15s for the inert gas.

[0030] In some embodiments of the present invention, the thickness of the ALD-SnO2 thin film is 2-10 nm.

[0031] A second aspect of the present invention provides a tin oxide thin film, which is prepared by the post-processing method for ALD-SnO2 thin films described in the first aspect of the present invention.

[0032] A third aspect of the present invention provides a photovoltaic device comprising the tin oxide thin film described in the second aspect of the present invention.

[0033] In some embodiments of the present invention, the photovoltaic device is a perovskite solar cell or a component thereof.

[0034] In some embodiments of the present invention, the tin oxide thin film serves as the electron transport layer of a photovoltaic device.

[0035] Compared with the prior art, the above-described technical solution of the present invention has at least the following technical effects or advantages: (1) The post-treatment method for ALD-SnO2 thin films provided by this invention employs immersion water bath or DMPS aqueous solution bath treatment to remove organic residues on the surface and bulk phase of the ALD-SnO2 thin film, thereby solving the problems of poor performance of ALD-SnO2 thin films and subsequent perovskite film formation. Specifically, the organic residues on the surface of the W-SnO2 thin film treated by water bath are almost completely removed. However, as the water bath time increases, the morphology of the film gradually transforms into an island-like distribution, and the density is impaired. This degraded morphology demonstrates the negative impact of water bath treatment on the morphology and density of SnO2 thin films, providing a reference for water bath post-treatment in the field of inorganic semiconductors. DMPS aqueous solution bath treatment achieves the removal of organic residues in the bulk phase and surface of the film while suppressing the morphology degradation of the SnO2 thin film during the water bath process. Without destroying the initial morphology and density, it optimizes the surface groups and energy level structure of the film.

[0036] (2) Using the D-SnO2 thin film prepared in this invention as the electron transport layer of perovskite solar cells, small-area PSCs and large-area PSMs with excellent photovoltaic performance were obtained, achieving a small area (0.1486 cm²) 2 The PCE of PSCs reached 25.26%, with a large area (12.5cm) 2 The PCE of PSMs reached 22.42%.

[0037] (3) The post-processing method for ALD-SnO2 thin films provided by this invention can be applied to the preparation and optimization of industrial electron transport layers. At the same time, the synergistic modification method of the bulk phase and surface of this invention has the advantages of low cost, high repeatability and simple operation, and has excellent industrial application value and prospects. Attached Figure Description

[0038] Figure 1 A schematic diagram illustrating the mechanism for preparing Comparative Example 1 and Examples 1-6; Figure 2 SEM images of tin oxide films prepared by FTO, Comparative Example 1, Examples 2-3 and Examples 5-6; Figure 3 The CV curve of the tin oxide thin film prepared in Comparative Example 1 is shown. Figure 4 The CV curves are for the tin oxide films prepared in Examples 1-6. Figure 5 A schematic diagram of the energy level structure of the tin oxide thin films prepared by FTO, Comparative Example 1, Example 2 and Example 5; Figure 6The photoelectron spectra of the tin oxide thin films prepared in Comparative Examples 1, 2, and 5 are shown. Figure 7 To compare the small-area perovskite solar cells fabricated in Application Example 1 and Application Example 3 JV Line graph; Figure 8 To compare the large-area perovskite solar cell modules prepared in Application Example 2 and Application Example 4 J- V Line graph. Detailed Implementation

[0039] The present invention will now be described in detail with reference to embodiments to facilitate understanding of the invention by those skilled in the art. It is particularly important to note that the embodiments are merely illustrative of the invention and should not be construed as limiting the scope of protection of the invention. Non-essential improvements and adjustments made to the invention by those skilled in the art based on the above description should still fall within the scope of protection of the invention. Furthermore, all raw materials mentioned below, unless otherwise specified, are commercially available products; all process steps or preparation methods not mentioned in detail are process steps or preparation methods known to those skilled in the art.

[0040] Comparative Example 1 A method for preparing an ALD-SnO2 thin film includes the following steps: (1) A 10cm×10cm FTO rigid conductive substrate was etched by a femtosecond laser (FemtoYL, 1030nm). P1 was etched according to the drawing of a small area perovskite solar cell. The conductive substrate was placed in a container containing isopropanol (IPA) and sonicated for 15 minutes to ensure that the substrate surface was clean and free of stains. Then, the substrate surface was dried with a nitrogen gas gun and placed in an ultraviolet ozone cleaner for 15 minutes before use to obtain a UVO-treated FTO conductive substrate.

[0041] (2) Preparation of ALD-SnO2 thin film: The FTO substrate was pre-treated in UVO for 15 min. In the ALD system (Veeco-Fiji G2), at 4×10 1 ALD-SnO2 thin films were deposited under a pressure of 30 sccm of argon (Ar) gas. During the deposition process, the TDMASn source, deionized water source, and conductive substrate were maintained at 70 °C, room temperature, and 150 °C, respectively. After preheating for 10 min, a circulating atmosphere was introduced sequentially in the order of 0.1 s TDMASn, 8 s Ar, 0.06 s H2O, and 10 s Ar to obtain the ALD-SnO2 thin film of this comparative example.

[0042] Example 1 A method for preparing a W-SnO2 thin film includes the following steps: The ALD-SnO2 film prepared in Comparative Example 1 was immersed in deionized water, heated at 90°C for 15 min, rinsed with deionized water, dried under N2 flow, and then annealed at 150°C for 60 min to obtain the W-SnO2 film of this comparative example.

[0043] Example 2 Following the preparation method of Example 1, the heating time at 90°C was changed to 30 min to obtain the W-SnO2 thin film of this comparative example.

[0044] Example 3 Following the preparation method of Example 1, the heating time at 90°C was changed to 45 min to obtain the W-SnO2 thin film of this comparative example.

[0045] Example 4 A method for preparing a D-SnO2 thin film includes the following steps: The W-SnO2 film prepared in Comparative Example 3 was immersed in a DMPS aqueous solution (concentration of 50 mmol / L), heated at 90°C for 15 min, rinsed with deionized water, dried under N2 flow, and then annealed at 150°C for 60 min to obtain the D-SnO2 film of this embodiment.

[0046] Example 5 Following the preparation method of Example 1, the heating time at 90°C was changed to 30 min to obtain the D-SnO2 thin film of this example.

[0047] Example 6 Following the preparation method of Example 1, the heating time at 90°C was changed to 45 min to obtain the D-SnO2 thin film of this example.

[0048] Comparative Application Example 1 A method for fabricating a small-area perovskite solar cell includes the following steps: (1) Preparation of perovskite layer: The prepared FAPbI3 perovskite precursor solution [1.53 mmol lead iodide, 1.4 mmol formamidin hydroiodate, 0.5 mmol methylamine hydrochloride, 0.8 mL N,N-dimethylformamide (DMF) and 0.1 mL dimethyl sulfoxide (DMSO)] was shaken for 1 hour for later use; the 10 cm × 10 cm ALD-SnO2 film substrate prepared in Comparative Example 1 was cut into 2 cm × 2 cm square pieces and subjected to UVO treatment for 15 min; the perovskite film was prepared by spin coating, and the entire spin coating process was carried out in a nitrogen glove box. The spin coating parameters were a rotation speed of 6000 rpm and an acceleration of 2000 rpm, and the entire process lasted for 30 s. 100 µL of ethyl acetate (EA) was added dropwise 25 s after the start of spin coating. The prepared film was annealed on a hot plate at 100 °C for 1 hour.

[0049] (2) Preparation of 2D layer: Dissolve 2 mg of butylamine iodide (iBAI) in 1 mL of isopropanol; after the substrate cools, spin-coat 30 μL of iBAI solution onto the FAPbI3 perovskite film, spin-coat at 5000 rpm for 10 s, and then anneal at 100 °C for 10 min.

[0050] (3) Preparation of the hole transport layer: First, 0.091 g of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD) powder, 1 mL of chlorobenzene, 36.5 µL of 4-tert-butylpyridine, 23.5 µL of acetonitrile solution of lithium bis(trifluoromethanesulfonylimide) (520 g / L), and 11 µL of acetonitrile solution of FK209 cobalt salt (300 g / L) were mixed to prepare the Spiro-OMeTAD solution; 80 µL of the solution was dropped onto the perovskite light-absorbing layer, and the spin coating parameters were set at a speed of 3000 rpm for 30 s to obtain the Spiro-OMeTAD hole transport layer. The prepared film was placed in a drying cabinet with a relative humidity of less than 20% for 10-15 hours to ensure that the chlorobenzene completely evaporated.

[0051] (4) Fabrication of the gold electrode layer: After spin-coating Spiro-OMeTAD, the functional layer films of the positive and negative electrodes are etched by laser to expose the conductive electrodes. A gold evaporation mask is attached to leave the gold evaporation area; gold with a thickness of 80-100 nm is deposited on the hole transport layer of Spiro-OMeTAD by vacuum evaporation to form a gold counter electrode, thus obtaining the small-area perovskite solar cell of this comparative application example.

[0052] Comparative Application Example 2 A method for fabricating a large-area perovskite solar cell includes the following steps: (1) Preparation of perovskite layer: Referring to the preparation method of Comparative Example 1, the etching P1 was changed from the pattern of small area perovskite solar cell to the pattern of large area perovskite solar cell module to obtain ALD-SnO2 thin film. The prepared FAPbI3 perovskite precursor solution (1.53 mmol lead iodide, 1.4 mmol formamidin hydroiodate, 0.5 mmol methylamine hydrochloride, 0.8 mL DMF and 0.1 mL DMSO) was shaken for 1 hour for later use; the ALD-SnO2 thin film substrate with a size of 10 cm × 10 cm was cut into 5 cm × 5 cm square pieces and subjected to UVO treatment for 15 min; the perovskite thin film was prepared by spin coating, and the entire spin coating process was carried out in a nitrogen glove box. The spin coating parameters were 6000 rpm and 2000 rpm, with the entire process lasting 30 seconds. 240 µL of EA was added 25 seconds after the start of spin coating. The resulting film was annealed on a hot plate at 100 °C for 1 hour.

[0053] (2) Preparation of 2D layer: Dissolve 2 mg of iBAI in 1 mL of isopropanol; after the substrate cools, spin-coat 100 μL of iBAI solution onto the FAPbI3 perovskite film, spin-coat at 5000 rpm for 10 s, and then anneal at 100 °C for 10 min.

[0054] (3) Preparation of the hole transport layer: First, 0.091 g of Spiro-OMeTAD powder, 1 mL of chlorobenzene, 36.5 µL of 4-tert-butylpyridine, 23.5 µL of acetonitrile solution of lithium bis(trifluoromethanesulfonylimide) (520 g / L), and 11 µL of acetonitrile solution of FK209 cobalt salt (300 g / L) were mixed to prepare the Spiro-OMeTAD solution. 300 µL of the solution was dropped onto the perovskite light-absorbing layer, and the spin coating parameters were set at a speed of 3000 rpm for 30 s to obtain the Spiro-OMeTAD hole transport layer. The prepared film was placed in a drying cabinet with a relative humidity of less than 20% for 10-15 hours to ensure that the chlorobenzene completely evaporated. Subsequently, a picosecond laser (GS-PGN30) was used to etch the P2 etching line parallel to P1 and offset 30 µm towards the positive electrode to remove the functional layer and retain FTO.

[0055] (4) Fabrication of the gold electrode layer: After spin-coating Spiro-OMeTAD, the functional layer films of the positive and negative electrodes were etched by laser to expose the conductive electrodes. A gold vapor deposition mask was attached, and gold with a thickness of 80-100 nm was deposited on the hole transport layer of Spiro-OMeTAD by vacuum evaporation to form the gold counter electrode. Subsequently, a picosecond laser (GS-PGN30) was used to etch P3 parallel to P2 and offset 20 µm towards the positive electrode to obtain P3, thus obtaining the large-area perovskite solar cell of this comparative application example.

[0056] Application Example 1 Referring to the preparation method of Comparative Application Example 1, the ALD-SnO2 film was changed to the W-SnO2 film prepared in Example 2, and a small-area perovskite solar cell of this Comparative Application Example was obtained.

[0057] Application Example 2 Referring to the preparation method of Comparative Application Example 2, the ALD-SnO2 film was changed to the W-SnO2 film prepared in Example 2, and a large-area perovskite solar cell of this Comparative Application Example was obtained.

[0058] Application Example 3 Referring to the preparation method of Comparative Application Example 1, the ALD-SnO2 film was changed to the D-SnO2 film prepared in Example 5 to obtain the small-area perovskite solar cell of this application example.

[0059] Application Example 4 Referring to the preparation method of Comparative Application Example 2, the ALD-SnO2 film was changed to the D-SnO2 film prepared in Example 5, and a large-area perovskite solar cell of this application example was obtained.

[0060] Performance testing 1. Principle Analysis of Tin Oxide Film Formation Process Figure 1 The schematic diagrams of the mechanisms used in Comparative Example 1 and Examples 1-6 are shown below, in which: Figure 1 Part a ( Figure 1 a) A schematic diagram of the preparation of ALD-SnO2 (Fabrication of ALD-SnO2) by sequentially introducing TDMASn, argon, water and argon in a circulating atmosphere for Comparative Example 1. Figure 1 Part b ( Figure 1 (i)-(iii) in b) are schematic diagrams of the preparation of W-SnO2 by water bath treatment under different post-treatment times in Examples 1-3; Figure 1 Part C ( Figure 1 c) (i)-(iii) are schematic diagrams of D-SnO2 prepared by DMPS solution bath treatment at different post-treatment times in Examples 4-6.

[0061] Depend on Figure 1As shown in Figure a, during the nth cycle, TDMASn is adsorbed onto the surface of the FTO conductive substrate, and excess TDMASn atmosphere is blown away by N2. During the (n+1)th cycle, deionized water reacts with the thin layer of TDMASn adsorbed on the FTO conductive substrate surface to generate SnO2. In the figure, the "gray spheres" represent fully reacted SnO2, and the "pink spheres" represent areas uniformly distributed on the film surface and in the bulk phase where the reaction is incomplete.

[0062] Depend on Figure 1 b and Figure 1 As can be seen from c, short-term deionized water bath or DMPS solution bath post-treatment only affects the shallow surface layer of the ALD-SnO2 film and cannot remove organic impurities in the deeper bulk phase. With extended treatment time, the solution gradually penetrates into the film layer (Penetrating solution). When the penetration depth reaches exactly the interface between ALD-SnO2 and FTO, the film exhibits significantly reduced conductivity while maintaining good density. Figure 1 (i of b and i of 1c). After annealing, the SnO2 film recrystallized, and its conductivity recovered and even exceeded the initial value of the ALD-SnO2 film. This is because the organic residues in the film layer were sufficiently removed. Up to this stage, both groups of films exhibited sufficient density. However, the grain size of the W-SnO2 film increased significantly ( Figure 1 b of ii), while the morphology of the D-SnO2 film is still very close to that of ALD-SnO2 ( Figure 1 c(ii). This is because, under continuous deionized water bath conditions, SnO2 undergoes hydroxylation to form SnO. α (OH) β Its volume expands, causing the W-SnO2 film to tend to exhibit an uneven island distribution, and it gradually detaches over time. Figure 1 (b of iii). In contrast, the morphological degradation of the SnO2 film was significantly suppressed after the introduction of DMPS, which is attributed to the interaction between DMPS and SnO2 through the -SH / -SO3H groups in its molecule. α (OH) β Strong chelation between crystal lattices. However, with continued extension of the reaction time, the DMPS water bath still leads to the appearance of a small number of poorly observable microcracks in the D-SnO2 film, ultimately causing the film to lose its good density. Figure 1 (ciii). This confirms that DMPS can effectively delay morphological degradation. By selecting an appropriate DMPS solution bath treatment time, D-SnO2 films with conformal growth, density, and bulk / surface co-modification can be obtained.

[0063] 2. Microstructure of tin oxide thin films Figure 2 The af part (i.e. Figure 2 a- Figure 2 f) Surface morphology images of tin oxide films prepared by FTO, Comparative Example 1, Examples 2-3, and Examples 5-6, respectively. Figure 2 In b, the ALD-SnO2 film exhibits a dense and uniformly distributed fine particle structure, which is consistent with... Figure 2 The original morphology of FTO in a is similar, indicating its good coverage and conformal growth characteristics. Although CV results indicate that the W-SnO2 surface remains dense after 30 min of deionized water bath treatment, its SEM morphology shows that the W-SnO2 grains have significantly coarsened. Figure 2 c). Extending the post-treatment time to 45 min, the W-SnO2 film surface exhibited a morphology of visible pores and island-like distribution. Figure 2 d). This indicates that the deionized water bath gradually degrades the originally dense, conformal morphology of the ALD-SnO2 film, ultimately leading to localized detachment of the SnO2 layer. After treatment with the DMPS solution bath, the morphology of the D-SnO2 film did not show significant changes after 30 minutes. Figure 2 e). Furthermore, even with only a slight increase in grain size at 45 min, the film exhibits a uniform, pore-free surface morphology. Figure 2 f). Therefore, it can be inferred that the leakage current detected in the D-SnO2 film during CV testing at 45 min is due to microcracks on the film surface below the SEM resolution limit. These results further confirm that DMPS can suppress the islanding distribution and large-area detachment of SnO2 films after a water bath. A suitable DMPS solvent bath post-treatment time can effectively remove organic matter from the bulk phase of the film without affecting the film's density and conformal growth characteristics.

[0064] 3. Density of tin oxide thin films Figure 3 and Figure 4 The af part (i.e. Figure 4 a- Figure 4 f) are cyclic voltammetry (CV) curves of the tin oxide films prepared in Comparative Example 1 and Examples 1-6, respectively. The horizontal axis represents voltage and the vertical axis represents current. Figure 4 In the text, "w / o annealing" indicates that the water bath treatment was not performed, while "annealing" indicates that the water bath treatment was performed. Figure 3 The CV curve in the image did not show a duckbill-shaped characteristic peak, indicating that the ALD-SnO2 film has good density. Figure 4It can be seen that different post-treatment times have an effect on the density of ALD-SnO2 films. After 15 min of deionized water bath or DMPS aqueous solution bath, neither W-SnO2 nor D-SnO2 films, whether annealed or not, showed duckbill-shaped characteristic peaks. The current values ​​at 0.5V and +1.2V are also very close to those of the ALD-SnO2 thin film. Figure 4 a and Figure 4 d). Furthermore, the CV curves of unannealed W-SnO2 and D-SnO2 films were significantly better than those of annealed films. A broader SnO2 characteristic peak was observed near 0.5V. This suggests that the 15-minute post-treatment has an effect on the coverage and conductivity of the ALD-SnO2 film, but the effect is limited. Extending the post-treatment time to 30 minutes revealed that both W-SnO2 and D-SnO2 films maintained good density properties regardless of annealing. However, the two unannealed film groups showed... The current value at 0.5V is significantly lower than that of the initial ALD-SnO2 thin film. Figure 4 b and Figure 4 e). After annealing and dehydration, the current values ​​of both groups of films recovered and exceeded the original ALD-SnO2 values. This indicates that after the reaction, the surface layer of the unannealed film transformed into a less conductive SnO2 hydrate (SnO2 hydrate). α (OH) β After annealing and dehydration, the conductivity of the film surpassed that of ALD-SnO2, indicating that the organic matter within the film participating in the reaction was effectively removed. Extending the deionized water bath time to 45 min, different intensities of "duckbill" characteristic peaks were detected in the CV curves of both groups of films, with the peak intensity of W-SnO2 being significantly greater than that of D-SnO2. Figure 4 c and Figure 4 f). This indicates that 45 minutes is sufficient to act on the entire film layer, and DMPS can inhibit film detachment.

[0065] 4. Energy level structure of tin oxide thin films Figure 5 This is a schematic diagram of the energy level structure of the tin oxide thin films prepared by FTO, Comparative Example 1, Example 2, and Example 5. Figure 5 The conduction band bottom (CBM) of W-SnO2 was shown to be... 3.97 eV, close to the CBM of ALD-SnO2 ( (4.00 eV), indicating that deionized water post-treatment has almost no effect on the energy level structure of SnO2. In contrast, under DMPS modification, the CBM of D-SnO2 shifts downward to... The 4.30 eV allows for a better match between the CBM of the thin film and the perovskite layer, thereby reducing the driving force for interfacial carrier recombination and thus increasing the open-circuit voltage of the device.

[0066] 5. Surface functional groups of tin oxide films Figure 6 The af part (i.e. Figure 6 a- Figure 6 f) shows the photoelectron spectra of the tin oxide films prepared in Comparative Examples 1, 2, and 5. The horizontal axis represents binding energy, and the vertical axis represents binding strength. Figure 6 As shown in Figure a, the ALD-SnO2 film surface exhibits a significant CN signal, indicating that the TDMASn precursor was not completely decomposed. This suggests that unreacted organic matter also exists in the bulk phase. To remove organic residues from the surface and bulk phase, the ALD-SnO2 film was post-treated using a deionized water bath or a DMPS aqueous solution bath. After 30 minutes of deionized water bath post-treatment, the intensity of the CN characteristic peak in the W-SnO2 film significantly decreased. Figure 6 (b) This confirms that post-treatment with deionized water effectively removes organic residues from the film surface. Furthermore, after 30 minutes of post-treatment with a DMPS aqueous solution bath, the peak intensity of the CN characteristic peak in the D-SnO2 film also significantly decreased. Figure 6 c). By Figure 6 d- Figure 6 As shown in f, CS, -SO3H, and -SH peaks appeared only on the surface of the D-SnO2 film, indicating that DMPS was adsorbed on the SnO2 surface. This only confirms that the water bath treatment has a significant effect on the functional groups on the surface of the ALD-SnO2 film, but it still cannot determine whether it will penetrate into the interior of the film.

[0067] 6. Photovoltaic performance of perovskite solar cells The perovskite solar cells and modules prepared in Comparative Application Examples 1-2 and 1-4 were tested respectively, with the light intensity measured at one solar radiation (AM 1.5G, 100mW / cm²). 2 The standard silicon cell calibration was used, and the test area for the small-area cell was 0.1486 cm². 2 The test area for large-area components is 12.5cm². 2 The results of reverse (RS) and forward (FS) scans are shown in Table 1 and Figure 7-8 As shown.

[0068] Table 1:

[0069] Figure 7The current density-voltage (DC) data of the best-performing perovskite solar cells fabricated based on ALD-SnO2, W-SnO2, and D-SnO2ETL are shown. JV The specific parameters are shown in Table 1. Among them, the highest PCE of the monolayer ALD-SnO2-based device is only 20.48%, which is significantly lower than the performance of high-efficiency devices. In contrast, the PCE of the best-performing W-SnO2-based device is significantly improved to 24.10%, while the best PCE of the D-SnO2-based device continues to improve to 25.26%. The post-treatment with deionized water bath or DMPS aqueous solution bath mainly affects the photoelectric performance of the device by significantly increasing the open-circuit voltage (…). V OC ) and fill factor (FF), while slightly increasing short-circuit current density ( J SC For the three groups of devices fabricated based on ALD-SnO2, W-SnO2, and D-SnO2 ETL, V OC As the voltage increased from 1.042V to 1.143V and then to 1.167V, the FF (force factor) improved from 77.09% to 81.41% and then to 83.47%, respectively. This performance improvement is attributed to the synergistic optimization of the D-SnO2 layer, the PVK layer, and the D-SnO2 / PVK buried substrate.

[0070] Figure 8 The current density-voltage (V / V) ratio of the best-performing perovskite solar cell modules based on ALD-SnO2, W-SnO2, and D-SnO2ETL is shown. JV The PCE curves are shown in Table 1, with specific parameters. Among them, the component with the best performance based on D-SnO2 has a PCE of 22.42% (…). V OC = 7.018V, J SC = 4.145mA / cm 2 (FF = 77.07%), which is also significantly better than the best-performing component based on ALD-SnO2 (PCE = 17.12%). V OC = 6.347V, J SC = 4.122mA / cm 2 ,FF = 65.44%) and W-SnO2-based devices (PCE = 19.55%, V OC = 6.672V, J SC = 4.135mA / cm 2(FF = 70.86%). In contrast, D-SnO2-based components show almost no open-circuit voltage loss compared to small-area PSCs. The DMPS aqueous bath posttreatment suppresses the negative effects of morphology degradation while improving the functional groups and energy level structure on the SnO2 film surface, which facilitates the preparation of efficient large-area PSMs.

[0071] For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of this invention, without requiring creative effort. Therefore, any simple improvements made to this invention by those skilled in the art based on the disclosure of this invention should be within the scope of protection of this invention. The above embodiments are preferred embodiments of this invention, and all processes similar to this invention and equivalent changes should fall within the scope of protection of this invention.

Claims

1. A post-processing method for ALD-SnO2 thin films, characterized in that, Includes the following steps: ALD-SnO2 films are prepared by immersing them in water or DMPS aqueous solution, heating them, and then cleaning and annealing them. These are referred to as W-SnO2 films or D-SnO2 films, respectively.

2. The post-processing method for ALD-SnO2 thin films according to claim 1, characterized in that, The water is deionized water or distilled water.

3. The post-processing method for ALD-SnO2 thin films according to claim 1, characterized in that, The molar concentration of the DMPS aqueous solution is 20-80 mmol / L.

4. The post-processing method for ALD-SnO2 thin films according to claim 1, characterized in that, The heating temperature is 80-95℃; and / or the heating time is 10-60 min.

5. The post-processing method for ALD-SnO2 thin films according to claim 1, characterized in that, The annealing temperature is 120-180℃; and / or the annealing time is 30-90 min.

6. The post-processing method for ALD-SnO2 thin films according to claim 1, characterized in that, The preparation process of the ALD-SnO2 thin film includes the following steps: A conductive substrate is placed in an ALD device and preheated; then a tin source, an oxygen source, and an inert gas are introduced to deposit SnO2 on the surface of the conductive substrate to obtain the ALD-SnO2 thin film.

7. The post-processing method for ALD-SnO2 thin films according to claim 6, characterized in that, The preheating is performed at a temperature of 100-150°C for 5-20 minutes; and / or, the tin source includes TDMASn; and / or, the oxygen source is selected from at least one of H2O, O2 plasma, and O3.

8. The post-processing method for ALD-SnO2 thin films according to any one of claims 1-7, characterized in that, The thickness of the ALD-SnO2 film is 2-10 nm.

9. A tin oxide thin film, characterized in that, The ALD-SnO2 thin film was prepared using the post-processing method described in any one of claims 1-8.

10. A photovoltaic device, characterized in that, Includes the tin oxide thin film as described in claim 9.

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