Sn-based perovskite thin film based on stress regulation and preparation method thereof, and optoelectronic device

Abstract

The application discloses a tin-based perovskite film based on stress regulation, a preparation method thereof and a photoelectric device, wherein the preparation method comprises the following steps: placing a tin-based perovskite liquid film and a ligand solution in a same chamber, stopping air extraction after the chamber is vacuumized to be lower than 1000 Pa through air extraction, wherein the ligand solution is a solution containing an amine group or a mercapto functional group; maintaining a closed state of the chamber, tin-based perovskite is complexed with a solvent to form an intermediate phase solid film with heat stress impact resistance, and the ligand solution continuously volatilizes to fill the chamber to form a ligand atmosphere, the ligand is combined with uncoordinated tin in the intermediate phase solid film to reduce surface defects; and taking out the intermediate phase solid film and then annealing. Through two-step regulation of stress impact and grasping the opportunity of defect treatment, the ligand is combined with uncoordinated tin in the intermediate phase solid film in vacuum drying, and dangling bonds and defects on the surface of the perovskite are weakened. Then, annealing treatment is performed, lattice distortion caused during annealing is reduced, and finally the quality of the tin-based perovskite film is improved.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic technology, and more specifically, relates to a stress-controlled tin-based perovskite thin film, its preparation method, and optoelectronic devices. Background Technology

[0002] Compared to traditional lead-based perovskites, tin-based perovskites possess superior optoelectronic properties, such as a narrower optical bandgap and better optical and thermal stability, making them the most promising perovskite materials for achieving high efficiency, stability, and low toxicity. Obtaining uniform, dense, and high-quality perovskite thin films is crucial for fabricating high-performance perovskite optoelectronic devices. However, the low Young's modulus of perovskites makes them more susceptible to lattice distortion caused by external light and heat. The perovskite thin film fabrication process includes an annealing step, which leads to lattice tensile strain and distortion. These distorted regions become defect centers, enhancing nonradiative recombination of charge carriers and degrading the performance of tin-based perovskite optoelectronic devices. Therefore, finding a process method to reduce defects in tin-based perovskites is of great significance for improving the optoelectronic performance of these devices. Summary of the Invention

[0003] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a stress-controlled tin-based perovskite thin film, its preparation method and optoelectronic device, the purpose of which is to solve the technical problem of many defects in tin-based perovskites.

[0004] To achieve the above objectives, according to one aspect of the present invention, a method for preparing stress-controlled tin-based perovskite thin films is provided, comprising:

[0005] A tin-based perovskite solution is coated onto the substrate surface to form a tin-based perovskite liquid film;

[0006] The tin-based perovskite liquid film and the ligand solution are placed in the same chamber and the chamber is evacuated to a vacuum level of less than 1000 Pa before the evacuation is stopped. The ligand solution is a solution containing amine or mercapto functional groups.

[0007] Maintaining the chamber in a sealed state allows some of the solvent in the tin-based perovskite liquid film to evaporate, and the tin-based perovskite to complex with the solvent to form an intermediate phase solid film that can resist thermal stress. Meanwhile, the ligand solution continues to evaporate, filling the chamber to form a ligand atmosphere. The evaporated ligands combine with the uncoordinated tin in the intermediate solid phase film to reduce surface defects.

[0008] The intermediate solid phase film was removed and annealed at a temperature of 45°C to 110°C.

[0009] In one embodiment, the volume of the ligand solution is 10 μL to 50 μL, the vacuum degree is 100 Pa to 1000 Pa, and the duration of maintaining the chamber in a sealed state is 60 s to 180 s.

[0010] In one embodiment, the evacuation time for reducing the chamber vacuum to below 1000 Pa does not exceed 10 seconds.

[0011] In one embodiment, the low-temperature annealing time is 3 min to 5 min, and the high-temperature annealing time is 5 min to 15 min.

[0012] In one embodiment, during annealing, a low-temperature annealing at 45°C to 50°C is performed first, followed by a high-temperature annealing at 90°C to 110°C.

[0013] In one embodiment, the ligand solution is any one or a mixture of several of methylamine, dimethylamine, ethylamine, diethylamine, ethylenediamine, dipropylamine, 2-phenylethylthiol, ethylthiol, and ethyl-1,2-dithiolphenol.

[0014] In one embodiment, the solvent in the tin-based perovskite solution is any one or a mixture of dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, γ-butyrolactone, and N-methylpyrrolidone.

[0015] In one embodiment, the solute in the tin-based perovskite solution is one or more of the following: methylamine tin iodide, formamidinium tin iodide, methylamine tin iodide bromide, formamidinium tin iodide bromide, cesium tin iodide, cesium tin iodide bromide, phenethylamine tin iodide, n-butylamine tin iodide, isobutylamine tin iodide, or phenylenediamine tin iodide.

[0016] According to another aspect of the present invention, a tin-based perovskite thin film is provided, which is prepared by any of the stress-controlled tin-based perovskite thin film preparation methods described above.

[0017] According to another aspect of the present invention, an optoelectronic device is provided, which comprises the above-described tin-based perovskite thin film.

[0018] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0019] After obtaining the perovskite liquid film, the present invention processes it in two stages: the first stage is vacuum drying and forming a ligand atmosphere during the vacuum drying process, and the second stage is annealing.

[0020] First, this invention employs vacuum drying to obtain an intermediate phase solid film formed by the complexation of tin-based perovskite and solvent, reducing the impact of thermal stress on the film's crystal structure during subsequent annealing. Vacuum-assisted fabrication technology is used to control the uniformity of strain distribution in the perovskite film, thereby reducing ion migration and facilitating the fabrication of highly efficient and stable tin-based perovskite solar cells. Simultaneously, by reducing ambient pressure and accelerating solvent evaporation at room temperature, the solution quickly achieves high supersaturation, enabling rapid nucleation of a large amount of solute on the substrate and improving growth during subsequent annealing. This results in a dense, high-quality perovskite film that effectively suppresses leakage current caused by pinholes on the perovskite film surface, improving the device's photoelectric conversion efficiency.

[0021] Secondly, this invention creates a ligand atmosphere during vacuum drying, weakening defects through ligands, followed by gradual annealing to obtain a high-quality tin-based perovskite film. By timing the defect treatment, the solvent is initially evaporated under vacuum, causing the perovskite in the liquid perovskite film to complex with the solvent to form an intermediate solid film. At this time, uncoordinated tin exists on the surface of the intermediate solid film, resulting in dangling bonds and defects. This invention, by creating a ligand atmosphere, allows the volatilized ligands to combine with the uncoordinated tin in the intermediate solid film, weakening the dangling bonds and defects on the perovskite surface, thereby suppressing charge carrier recombination. The intermediate solid film is then annealed. Since the defects in the intermediate solid film itself have been weakened before annealing, the lattice distortion caused during annealing is reduced, resulting in a high-quality tin-based perovskite film. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating the steps of a method for preparing a stress-controlled tin-based perovskite thin film according to one embodiment.

[0023] Figure 2 SEM morphology of the tin-based perovskite film provided for Comparative Example 1;

[0024] Figure 3 SEM morphology image of the tin-based perovskite thin film provided in Example 1;

[0025] Figure 4 Comparison of performance tests of perovskite solar cells fabricated from perovskite films with and without ligand treatment;

[0026] Figure 5 A comparison of the performance of perovskite solar cells fabricated from perovskite films after direct annealing and after ligand treatment during vacuum.

[0027] Figure 6 This is a comparison chart showing the performance of perovskite solar cells fabricated from perovskite thin films prepared by direct high-temperature annealing and pre-annealing followed by high-temperature annealing, as described in one embodiment. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] like Figure 1 The diagram shows a flowchart of a method for preparing a stress-controlled tin-based perovskite thin film in one embodiment, which mainly includes the following steps:

[0030] Step S100: Apply the tin-based perovskite solution to the substrate surface to form a tin-based perovskite liquid film.

[0031] First, a tin-based perovskite solution needs to be prepared, which can be done using traditional methods. Specifically, the solute in the tin-based perovskite solution can be one or more of the following: methylamine tin iodide, formamidinium tin iodide, methylamine tin iodide bromide, formamidinium tin iodide bromide, cesium tin iodide, cesium tin iodide bromide, phenethylamine tin iodide, n-butylamine tin iodide, isobutylamine tin iodide, or phenylenediamine tin iodide. The solvent can be any one or more of dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, γ-butyrolactone, and N-methylpyrrolidone. The solute and solvent are mixed in a specific ratio to obtain the desired tin-based perovskite solution.

[0032] Secondly, a tin-based perovskite solution is applied to the substrate surface to form a tin-based perovskite liquid film. Specifically, any one of the following processes can be used for coating: spin coating, spray coating, immersion coating, blade coating, or roller coating.

[0033] Step S200: Place the tin-based perovskite liquid film and the ligand solution in the same chamber and stop pumping the air to make the vacuum level of the chamber lower than 1000 Pa. The ligand solution is a solution containing amine or mercapto functional groups.

[0034] Specifically, the vacuum level can be selected from 100 Pa to 1000 Pa, as the solvent and ligand solutions in the tin-based perovskite liquid film will evaporate rapidly under vacuum. The vacuuming time should be as short as possible to allow the solution to quickly reach a supersaturated state and reduce lattice defects. Specifically, the vacuuming time should be controlled within 10 seconds.

[0035] The ligand solution is selected from solutions containing amino or thiol functional groups, which can bind uncoordinated tin in subsequent steps. Specifically, the ligand solution can be any one or a mixture of several of methylamine, dimethylamine, ethylamine, diethylamine, ethylenediamine, dipropylamine, 2-phenylethanethiol, ethanethiol, and ethyl-1,2-dithiolphenol.

[0036] Step S300: Maintain the chamber in a sealed state, allowing some of the solvent in the tin-based perovskite liquid film to evaporate, and the tin-based perovskite to complex with the solvent to form an intermediate phase solid film that can resist thermal stress impact. The ligand solution continues to evaporate, filling the chamber to form a ligand atmosphere. The evaporated ligands combine with the uncoordinated tin in the intermediate phase solid film to reduce surface defects.

[0037] After evacuation is stopped, the chamber is sealed and maintained for a period of time to allow the internal reagents to react. During this process, under vacuum, the solvent and ligand solvent in the tin-based perovskite liquid film rapidly reach supersaturation and evaporate. Part of the solvent in the tin-based perovskite liquid film evaporates, and the tin-based perovskite complexes with the remaining solvent to form an intermediate phase solid film. The intermediate phase consists of a metal salt and a complex SnX2·Y, where X is a halogen and Y is the complexed solvent, such as DMSO. After the tin-based perovskite and the remaining solvent form the intermediate phase solid film, uncoordinated tin exists on the surface of the intermediate phase solid film, leading to dangling bonds and defects. At this point, the evaporated ligands combine with the uncoordinated tin, weakening the dangling bonds and defects on the perovskite surface, thereby suppressing charge carrier recombination.

[0038] In one embodiment, the degree of reaction between the ligand and the mesophase solid film is controlled by adjusting the amount of ligand solution and the reaction time. If the reaction is too strong, it can damage the structure of the mesophase solid film itself; conversely, if the reaction is too weak, it will not effectively weaken dangling bonds and defects. Therefore, in this embodiment, the amount of ligand solution is selected to be 10 μL to 50 μL, and the time for maintaining the chamber in a sealed state at a vacuum of 100 Pa to 1000 Pa is 60 s to 180 s. The effect is better within this parameter range.

[0039] Step S400: Take out the intermediate phase solid film and anneal it at a temperature of 45℃~110℃.

[0040] The mesophase solid film, after defect treatment, is then annealed. Since a mesophase solid film with thermal stress resistance has already formed in the vacuum chamber and has undergone defect treatment, annealing reduces distortion, resulting in a higher quality film. In one embodiment, a low-temperature annealing at 45°C–50°C followed by a high-temperature annealing at 90°C–110°C can be performed. Direct high-temperature annealing causes a rapid phase transformation of the tin-based perovskite mesophase solid film, resulting in numerous pinholes and severe thermal stress, leading to the re-formation of defects and non-radiative recombination centers. Low-temperature pre-annealing promotes further fusion and growth of mesophase grains, forming smooth and complete grains. In one embodiment, the low-temperature annealing time is controlled to be 3–5 minutes, and the high-temperature annealing time is 5–15 minutes. This controlled annealing time ensures both the fusion and growth of mesophase grains and the smooth transformation of the mesophase into a perovskite structure while removing residual solvent.

[0041] Accordingly, the present invention also relates to a high-quality tin-based perovskite thin film prepared by the above preparation method and an optoelectronic device comprising the high-quality tin-based perovskite thin film. The optoelectronic device may specifically be a solar cell, a light-emitting diode, a sensor, a transistor, or a laser.

[0042] The effects of the present invention will be illustrated below with specific comparative examples and embodiments.

[0043] Comparative Example 1

[0044] A perovskite precursor solution with a solute composition of CsSnI3 was prepared using a mixed solvent of DMF:DMSO = 1:0.25. Tin-based perovskite films were prepared by spin coating followed by direct annealing at 90°C for 10 minutes. The surface SEM images of the resulting films are shown below. Figure 2 It can be seen that there are pores on the surface of the thin film, indicating incomplete coverage. The device fabricated from the obtained tin-based perovskite thin film has an open-circuit voltage of 0.31V and an energy conversion efficiency of 3.75%.

[0045] Comparative Example 2

[0046] A tin-based perovskite thin film was prepared using a mixed solvent with a DMF:DMSO ratio of 1:0.25 and a perovskite precursor solution containing CsSnI₂Br as the solute, and then prepared by spin coating followed by direct annealing at 90°C for 10 minutes. The device fabricated from the obtained tin-based perovskite thin film exhibited an open-circuit voltage of 0.32V and a power conversion efficiency of 3.88%.

[0047] Comparative Example 3

[0048] A perovskite precursor solution with a solute component of CsSnI3 was prepared using a mixed solvent with a composition of DMF:DMSO = 1:0.25 and a spin coating process was used to obtain a light yellow perovskite liquid film.

[0049] A tin-based perovskite liquid film was placed in a vacuum chamber and rapidly evacuated to 1000 Pa within 5 seconds. The vacuum was then maintained at 1000 Pa for 90 seconds to obtain an intermediate phase solid film.

[0050] After removing the mesophase solid film, it was directly placed on a hot plate at 90°C for 10 minutes for heat treatment. The open-circuit voltage of the device prepared by the tin-based perovskite thin film was 0.34V and the energy conversion efficiency was 4.36%.

[0051] Comparative Example 4

[0052] A perovskite precursor solution with a CsSnI3 solute was prepared using a mixed solvent of DMF:DMSO (1:0.25). The solution was then spin-coated followed by direct annealing at 90°C for 10 minutes, and subsequently subjected to defect treatment in an ethylenediamine ligand atmosphere. The resulting tin-based perovskite thin film produced a device with an open-circuit voltage of 0.33V and a power conversion efficiency of 3.93%.

[0053] Example 1

[0054] A perovskite precursor solution with a solute component of CsSnI3 was prepared using a mixed solvent with a composition of DMF:DMSO = 1:0.25 and a spin coating process was used to obtain a light yellow perovskite liquid film.

[0055] A tin-based perovskite liquid film and an ethylenediamine solution were placed together in a vacuum chamber, and a vacuum was rapidly drawn to 1000 Pa within 5 seconds. Then, the ligand surface was treated under a vacuum of 1000 Pa for 90 seconds to obtain an intermediate phase solid film.

[0056] After removing the mesophase solid film, it was directly placed on a hot plate at 90°C for 10 minutes for heat treatment. The surface SEM image of the resulting film is shown below. Figure 3 The device fabricated from the obtained tin-based perovskite thin film has an open-circuit voltage of 0.41V and an energy conversion efficiency of 5.69%.

[0057] Example 2

[0058] The difference from the preparation method in Example 1 is that:

[0059] The solute component is CsSnI2Br.

[0060] Example 3

[0061] The difference from the preparation method in Example 1 is that:

[0062] After removing the mesophase solid film, it was first pre-annealed at 45℃ for 5 min, and then annealed at 90℃ for 10 min. The open-circuit voltage of the device prepared by the obtained tin-based perovskite thin film was 0.45V and the power conversion efficiency was 5.95%.

[0063] Table 1 below shows the comparative data of the above comparative examples and embodiments.

[0064] Table 1 Comparison of data from various comparative examples and embodiments.

[0065]

[0066] First, compare Figure 2 and Figure 3 Comparison shows that the CsSnI3 film obtained by direct annealing has pores on its surface and is not fully covered, while the film prepared by the present invention is uniform and dense with high coverage of the substrate. Under high magnification, it can be observed that the surface of the perovskite film is free of pores and fully covers the substrate.

[0067] Furthermore, comparing Comparative Example 1, Comparative Example 3, and Example 1, the vacuum drying + annealing process, compared to direct high-temperature annealing, can improve the open-circuit voltage. Combined with... Figure 4 The current-voltage curves shown are as follows: the dashed line represents the current-voltage curve of the device when no ligand atmosphere is formed in the vacuum chamber, and the solid line represents the current-voltage curve of the device when a ligand atmosphere is formed in the vacuum chamber. By comparison, it can be seen that the photoelectric performance of the device is further improved after a ligand atmosphere is formed during vacuum drying.

[0068] Comparing Comparative Example 4 and Example 1, in combination Figure 5 The current-voltage curves shown are as follows: the dashed line represents the current-voltage curve of the device obtained after direct annealing followed by ligand treatment, and the solid line represents the current-voltage curve of the device obtained when a ligand atmosphere is formed in a vacuum chamber. By comparison, it can be seen that even if defect treatment is performed in a ligand atmosphere after annealing, the improvement on the thin film performance is not significant. However, the photoelectric performance of the device obtained by forming a ligand atmosphere during vacuum drying in this invention is significantly improved.

[0069] Comparing Example 1 and Example 3, in conjunction with the appendix Figure 6 The current-voltage curves shown are as follows: the dashed line represents the current-voltage curve of the device formed by direct high-temperature annealing after vacuum drying, and the solid line represents the current-voltage curve of the device obtained by pre-annealing and then high-temperature annealing after vacuum drying. By comparison, it can be seen that performing low-temperature pre-annealing before high-temperature annealing during annealing can further improve the device performance.

[0070] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing stress-controlled tin-based perovskite thin films, characterized in that, include: A tin-based perovskite solution is coated onto the substrate surface to form a tin-based perovskite liquid film; The tin-based perovskite liquid film and the ligand solution are placed in the same chamber and the chamber is evacuated to a vacuum level of less than 1000 Pa. The evacuation time does not exceed 10 seconds. The ligand solution is a solution containing amine or thiol functional groups. Maintaining the chamber in a sealed state allows some of the solvent in the tin-based perovskite liquid film to evaporate, and the tin-based perovskite complexes with the solvent to form an intermediate solid phase film that can resist thermal stress. Meanwhile, the ligand solution continues to evaporate, filling the chamber to form a ligand atmosphere. The evaporated ligands combine with the uncoordinated tin in the intermediate solid phase film to reduce surface defects. The intermediate solid phase film is removed and annealed at a temperature of 45℃~110℃.

2. The method for preparing stress-controlled tin-based perovskite thin films as described in claim 1, characterized in that, The volume of the ligand solution is 10 μL to 50 μL, the vacuum degree is 100 Pa to 1000 Pa, and the duration of maintaining the chamber in a sealed state is 60 s to 180 s.

3. The method for preparing stress-controlled tin-based perovskite thin films as described in claim 1, characterized in that, First, perform low-temperature annealing at 45℃~50℃ for 3min~5min, then perform high-temperature annealing at 90℃~110℃ for 5min~15min.

4. The method for preparing stress-controlled tin-based perovskite thin films as described in claim 1, characterized in that, The ligand solution is any one or a mixture of several of the following: methylamine, dimethylamine, ethylamine, diethylamine, ethylenediamine, dipropylamine, 2-phenylethylthiol, ethylthiol, and ethyl-1,2-dithiol phenol.

5. The method for preparing stress-controlled tin-based perovskite thin films as described in claim 1, characterized in that, The solvent in the tin-based perovskite solution is any one or a mixture of dimethylformamide, dimethyl sulfoxide, N,N-dimethylacetamide, γ-butyrolactone, and N-methylpyrrolidone.

6. The method for preparing stress-controlled tin-based perovskite thin films as described in claim 1, characterized in that, The solute in the tin-based perovskite solution is one or more of the following: methylamine tin iodide, formamidinium tin iodide, methylamine tin iodide bromide, formamidinium tin iodide bromide, cesium tin iodide, cesium tin iodide bromide, phenethylamine tin iodide, n-butylamine tin iodide, isobutylamine tin iodide, or phenylenediamine tin iodide.

7. A tin-based perovskite thin film, characterized in that, It is prepared by the stress-controlled tin-based perovskite thin film preparation method according to any one of claims 1 to 6.

8. An optoelectronic device, characterized in that, It includes the tin-based perovskite thin film as described in claim 7.

Images