High-fluorescence quantum yield all-inorganic perovskite thin film, preparation method and application thereof

Abstract

This invention discloses a high-fluorescence quantum yield all-inorganic perovskite thin film, its preparation method, and its applications, belonging to the field of lead-free perovskite optoelectronic device technology. The thin film preparation method includes the following steps: dissolving tin dibromide and cesium bromide in an organic solvent to obtain a precursor solution; adding N-(diphenylphosphino)-P,P-diphenylphosphineamide; coating the obtained perovskite precursor solution onto a substrate; and then annealing to obtain a high-fluorescence quantum yield all-inorganic perovskite thin film, which is a CsSnBr3 perovskite thin film. The CsSnBr3 perovskite thin film prepared using the method of this invention exhibits a high fluorescence quantum yield and improved film coverage. The high-fluorescence quantum yield CsSnBr3 perovskite thin film prepared by this invention can be applied to perovskite light-emitting devices, perovskite solar cells, perovskite photodetectors, and other fields.

Description

Technical Field

[0001] This invention belongs to the field of lead-free perovskite optoelectronic device technology, and particularly relates to a high fluorescence quantum yield all-inorganic perovskite thin film, its preparation method and application. Background Technology

[0002] In the current development of high-performance lead-free perovskite materials, CsSnBr3 has attracted research attention due to its excellent light absorption and carrier transport properties. However, its application in device fabrication is limited by insufficient thin film quality and luminous efficiency. Studies have shown that the main reason for the performance limitations of this material lies in the Sn... 2+ It is easily oxidized during preparation and subsequent processes, transforming into Sn. 4+ This oxidation process causes two problems simultaneously: first, it generates high concentrations of Sn vacancies and other defects, which, as non-radiative recombination centers, significantly reduce the fluorescence quantum yield of the material; second, the rapid crystallization process results in poor crystal integrity and low surface coverage of the obtained film, which is not conducive to obtaining high-performance devices.

[0003] Therefore, development can inhibit Sn 2+ Finding a method for oxidizing and preparing CsSnBr3 films with high coverage and low defect density is a key issue that needs to be addressed to advance this material toward practical applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a high-fluorescence quantum yield all-inorganic perovskite thin film, its preparation method, and its applications. The all-inorganic perovskite thin film prepared by this invention is a CsSnBr3 perovskite thin film. This invention prepares a high-fluorescence quantum yield CsSnBr3 perovskite thin film, with a simple and low-cost preparation method that is conducive to large-scale production, and can improve the fluorescence quantum yield of CsSnBr3 perovskite thin films.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing an all-inorganic perovskite thin film with high fluorescence quantum yield, comprising the following steps: Cesium bromide and tin dibromide were dissolved in an organic solvent to obtain a precursor solution; N-(diphenylphospho)-P,P-diphenylphosphine amide was added to the precursor solution to obtain a perovskite precursor solution. The perovskite precursor solution was stirred and then coated onto a substrate. After annealing, the high fluorescence quantum yield all-inorganic perovskite film, which is a CsSnBr3 perovskite film, was obtained.

[0006] The principle of this invention: The reason why N-(diphenylphosphino)-P,P-diphenylphosphineamide can significantly improve the performance of CsSnBr3 perovskite films is mainly due to its unique molecular structure—containing both P=O (phosphorus-oxygen double bond) and PN (phosphorus-nitrogen bond) functional groups, it plays a dual role as a ligand and antioxidant in the system. The core feature of N-(diphenylphosphino)-P,P-diphenylphosphineamide lies in its P=O group, on which the oxygen atom carries a lone pair of electrons, exhibiting strong Lewis basicity (electron-donating ability). In the perovskite precursor solution, it can react with the Lewis acid with an empty orbital—divalent tin ion (Sn... 2+ Strong coordination interactions occur. Furthermore, the PN bonds in the molecule provide the structural basis for its chelation with metal ions. The core challenge facing tin-based perovskites is Sn... 2+ It is easily oxidized to Sn 4+ This not only disrupts the crystal structure of perovskite but also introduces numerous defects. The addition of N-(diphenylphosphino)-P,P-diphenylphosphineamide inhibits oxidation through the following pathway: Physical barrier: The N-(diphenylphosphino)-P,P-diphenylphosphineamide molecule interacts with Sn through the P=O group. 2+ Coordination, as in Sn 2+ The surface is covered with a protective shell, which effectively blocks oxygen in the air from affecting Sn. 2+ Contact and attack. Chemical reducing environment: N-(diphenylphosphino)-P,P-diphenylphosphine amide has certain reducing properties and can consume dissolved oxygen or oxidizing substances in solution, thus providing Sn. 2+ Create a stable chemical environment.

[0007] During the rapid crystallization process of perovskite films, a large number of uncoordinated Sn molecules are generated on the surface and at the grain boundaries. 2+ These (i.e., dangling bonds) are nonradiative recombination centers that trap charge carriers, severely reducing fluorescence quantum yield. The P=O group of N-(diphenylphospho)-P,P-diphenylphosphine amide, acting as a Lewis base, can "stitch together" these uncoordinated Sn bonds through coordinate bonds. 2+ Defect sites. This defect passivation reduces nonradiative recombination, thereby significantly improving the fluorescence quantum yield and carrier lifetime of the film. This is due to the interaction between N-(diphenylphospho)-P,P-diphenylphosphine amide and Sn. 2+ The strong coordination effect of N-(diphenylphosphino)-P,P-diphenylphosphine amide temporarily "locks in" part of the precursor, slowing down the excessively rapid crystallization rate. This is beneficial for forming a more uniform, denser perovskite film with fewer defects. Through surface coordination, N-(diphenylphosphino)-P,P-diphenylphosphine amide helps stabilize the target crystal phase of CsSnBr3 and prevents it from undergoing a phase transformation during annealing.

[0008] Furthermore, the molar ratio of cesium bromide to tin dibromide is (1-2.5):1.

[0009] Furthermore, the organic solvent is dimethyl sulfoxide.

[0010] Furthermore, the concentration of tin ions in the precursor solution is 0.01-2 mmol / mL.

[0011] Furthermore, in the perovskite precursor solution, the concentration of N-(diphenylphospho)-P,P-diphenylphosphine amide is 3 mg / mL.

[0012] Furthermore, when stirring the perovskite precursor solution, the temperature is from room temperature to 150°C, and the stirring time is 6-12 hours.

[0013] Furthermore, the annealing temperature is 80-200℃, and the time is 3-10 minutes.

[0014] The present invention also provides a CsSnBr3 perovskite thin film with high fluorescence quantum yield prepared according to the above method, which has a fluorescence quantum yield of 15±0.2%.

[0015] The present invention also provides an application of the above-mentioned high fluorescence quantum yield CsSnBr3 perovskite thin film in perovskite light-emitting devices, perovskite solar cells and perovskite photodetectors.

[0016] For example, the perovskite light-emitting device is a perovskite light-emitting diode.

[0017] Compared with existing technologies, the preparation method of this invention has many significant advantages. It is simple to operate, low in cost, operates under mild conditions, and has low toxicity, making it highly suitable for large-scale production. More importantly, this preparation method can significantly improve the fluorescence quantum yield of CsSnBr3 perovskite films and effectively enhance the efficiency of perovskite light-emitting diodes prepared using tin-based halide perovskite films. Specifically, its benefits are mainly reflected in the following aspects: First, the preparation method of the present invention successfully improves the oxidation resistance of divalent tin, significantly reduces the defect state density of tin-based perovskite films, improves carrier lifetime, and greatly improves the overall stability of devices and films.

[0018] Secondly, the raw materials used in the preparation method of the present invention are inexpensive, and the preparation process is simple and intuitive, making it very suitable for large-scale production.

[0019] Furthermore, the preparation method of the present invention significantly improves the external quantum efficiency of perovskite light-emitting diodes.

[0020] Finally, the lead-free, high-efficiency, and stable tin-based halide perovskite thin films prepared by this invention have broad application prospects. They can be applied not only to perovskite light-emitting diodes and solar cells, but also extended to detectors, fluorescent thin films, phosphors, and semiconductor transistors, providing entirely new possibilities for related industries. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The fluorescence of the CsSnBr3 perovskite films prepared in Example 1 and Comparative Example 1 is shown (where Target represents Example 1 and Control represents Comparative Example 1). Figure 2 The PLQY test results of CsSnBr3 perovskite thin films prepared in Example 1 and Comparative Example 1 under varying power are shown (where Control represents Comparative Example 1 and Target represents Example 1). Figure 3 SEM image (μm) of the CsSnBr3 perovskite film prepared in Comparative Example 1. Figure 4 SEM image (μm) of the CsSnBr3 perovskite thin film prepared in Example 1. Figure 5 The brightness-current density test results of perovskite light-emitting diodes prepared using CsSnBr3 perovskite thin films obtained in Example 1 and Comparative Example 1 (where Control represents Comparative Example 1 and Target represents Example 1). Figure 6 The external quantum efficiency-current density test results of perovskite light-emitting diodes prepared using CsSnBr3 perovskite thin films obtained in Example 1 and Comparative Example 1 are shown (where Control represents Comparative Example 1 and Target represents Example 1). Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] An embodiment of the present invention provides a method for preparing an all-inorganic perovskite thin film with high fluorescence quantum yield, comprising the following steps: Cesium bromide and tin dibromide were dissolved in an organic solvent to obtain a precursor solution; N-(diphenylphospho)-P,P-diphenylphosphine amide was added to the precursor solution to obtain a perovskite precursor solution. The perovskite precursor solution was stirred and then coated onto a substrate. After annealing, a high fluorescence quantum yield all-inorganic perovskite film, namely CsSnBr3 perovskite film, was obtained.

[0028] In this invention, N-(diphenylphosphino)-P,P-diphenylphosphineamide, through its P=O functional group as a Lewis base coordination site, acts as a "multifunctional ligand" in the tin-based perovskite system. It interacts with Sn... 2+ The strong coordination effect simultaneously inhibits Sn. 2+The three main functions of oxidation (improving stability), passivation of defect sites (improving fluorescence efficiency), and regulation of the crystallization process (improving film quality) comprehensively enhance the performance of CsSnBr3 perovskite thin films and their optoelectronic devices.

[0029] In a preferred embodiment of the present invention, the molar ratio of cesium bromide to tin dibromide is (1-2.5):1, preferably 1:1.

[0030] In a preferred embodiment of the present invention, the organic solvent is dimethyl sulfoxide.

[0031] In a preferred embodiment of the present invention, the concentration of tin (Sn) ions in the precursor solution is 0.01-2 mmol / mL, preferably 0.3 mmol / mL.

[0032] In a preferred embodiment of the present invention, the concentration of N-(diphenylphospho)-P,P-diphenylphosphine amide in the perovskite precursor solution is 3 mg / mL.

[0033] In a preferred embodiment of the present invention, when stirring the perovskite precursor solution, the temperature is from room temperature to 150°C, and the stirring time is 6-12 hours; preferably, it is stirred for 12 hours at room temperature.

[0034] In a preferred embodiment of the present invention, the annealing temperature is 80-200°C and the time is 3-10 min; preferably, the annealing treatment is performed at 80°C for 5 min.

[0035] For example, the substrate is a PEDOT:PSS substrate.

[0036] This invention does not limit the method of coating the perovskite precursor solution onto the substrate; any method commonly used in the art (such as spin coating, blade coating, or spray coating) that can form a uniform thin film on the substrate surface is acceptable. In the following embodiments of this invention, spin coating is used as an example, with a spin coating speed of 5000 rpm.

[0037] An embodiment of the present invention also provides a CsSnBr3 perovskite thin film with high fluorescence quantum yield prepared according to the above method, which has a fluorescence quantum yield of 15±0.2%.

[0038] Embodiments of the present invention also provide an application of the above-mentioned high fluorescence quantum yield CsSnBr3 perovskite thin film in perovskite light-emitting devices, perovskite solar cells, and perovskite photodetectors.

[0039] For example, a perovskite light-emitting device is a perovskite light-emitting diode.

[0040] PEDOT:PSS stands for poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, which is an aqueous solution of a high molecular weight polymer with electrical conductivity, optical transparency, and solution processing properties.

[0041] Compared to patent CN118613126A, the material in this patent has a quasi-two-dimensional structure. These amines are typically bulky organic ammonium cations, such as PEA. + TEA + BA + These organic amine cations participate in lattice construction and are an indispensable part of the stoichiometry of quasi-two-dimensional perovskites. Through electrostatic interactions and hydrogen bonds, these cations spatially "separate" the three-dimensional perovskite layers, forming a natural multi-quantum-well structure that determines the material's dimensionality (n-value) and exciton binding energy. The organic amines within the lattice are part of the perovskite composition itself and are subject to strict stoichiometry in use. If the amount added to the precursor solution deviates from the required ratio for the target n-value (e.g., n=5 corresponds to 20% organic amine), it will lead to phase imbalance or the formation of an n=1 phase / pure three-dimensional impurity phase.

[0042] This invention is a completely inorganic three-dimensional system. The N-(diphenylphospho)-P,P-diphenylphosphineamide (small molecule amine) used in this invention is a Lewis base, which does not participate in lattice construction and mainly acts as a passivating agent and crystallization regulator. Their role is to regulate the crystallization rate and fill defects (such as uncoordinated tin ions) during film formation. They do not enter the crystal lattice, but only regulate crystallization, existing at grain boundaries. Typically, Lewis bases are used in a non-stoichiometric manner, and the amount used is often very small (the molar ratio relative to tin salts is usually 0.1%~5%).

[0043] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0044] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0045] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0046] The technical solution of the present invention will be further illustrated by the following embodiments.

[0047] Example 1 A method for preparing CsSnBr3 perovskite thin films with high fluorescence quantum yield, comprising the following steps: (1) Cesium bromide and tin dibromide were dissolved in 1 mL of DMSO (dimethyl sulfoxide) solvent at a molar ratio of 1:1 to obtain a precursor solution, wherein the concentration of Sn ions was 0.3 mmol / mL.

[0048] (2) Add 3 mg of N-(diphenylphospho)-P,P-diphenylphosphineamide (DPPA) to the above precursor solution to obtain a clear perovskite precursor solution.

[0049] (3) Stir the perovskite precursor solution obtained in step (2) at room temperature for 12 h; filter the stirred perovskite precursor solution and spin-coat it onto the PEDOT:PSS substrate at a speed of 5000 rpm, and anneal it at 80℃ for 5 min to obtain CsSnBr3 perovskite film with a fluorescence quantum yield of 15%.

[0050] Comparative Example 1 A method for preparing CsSnBr3 perovskite thin films, comprising the following steps: (1) Cesium bromide and tin dibromide were dissolved in 1 mL of DMSO solvent at a molar ratio of 1:1 to obtain a precursor solution, wherein the concentration of Sn ions was 0.3 mmol / mL.

[0051] (2) Stir the precursor solution obtained in step (1) at room temperature for 12 hours; filter the stirred precursor solution and spin coat it onto the PEDOT:PSS substrate at 5000 rpm, and anneal it at 80°C for 5 minutes to obtain CsSnBr3 perovskite film.

[0052] Test Example 1 The fluorescence of the CsSnBr3 perovskite films prepared in Example 1 and Comparative Example 1 was tested. The fluorescence images showing the changes over time are shown in the figure. Figure 1 .

[0053] Figure 1 The images show the fluorescence of both films in air (Target represents Example 1, and Control represents Comparative Example 1). The comparison reveals that the CsSnBr3 perovskite film with added DPPA exhibits brighter red light emission and better stability; after being stored in air for 1 hour, the luminescence intensity showed no significant change. This indicates that the addition of DPPA not only improves the fluorescence quantum yield of the film but also enhances its stability in air, resulting in better overall stability.

[0054] The fluorescence quantum yields of the CsSnBr3 perovskite films prepared in Example 1 and Comparative Example 1 were measured at room temperature and in air. Figure 2 The PLQY test results for CsSnBr3 perovskite thin films prepared in Example 1 and Comparative Example 1 under varying power are shown (where Control represents Comparative Example 1 and Target represents Example 1). Figure 2It can be seen that the PLQY of the film obtained by adding DPPA is significantly higher than that of the control sample, which means that the CsSnBr3 perovskite film prepared by adding DPPA can effectively passivate the defect state density of the film and improve the radiative recombination efficiency.

[0055] Figure 3 The image shows a SEM image of the CsSnBr3 perovskite thin film prepared in Comparative Example 1. As can be seen from the SEM image, the surface coverage of the thin film obtained in Comparative Example 1 is low, and there are a large number of pores in the film, which is not conducive to obtaining high-performance devices.

[0056] Figure 4 The image shows a SEM image of the CsSnBr3 perovskite film prepared in Example 1. As can be seen from the SEM image, the film obtained in Example 1 has a higher surface coverage and is more flat and dense. This means that the CsSnBr3 perovskite film prepared with DPPA has a tighter contact with the electron transport layer, which is beneficial to reducing device leakage current.

[0057] Based on the above experimental results, it can be seen that the addition of DPPA in Example 1 not only improved the fluorescence quantum yield of the CsSnBr3 film and reduced the defect state density in the film, but also improved the stability of the film, resulting in a denser CsSnBr3 perovskite film.

[0058] Application Example 1 Perovskite light-emitting diodes (LEDs) were fabricated using the CsSnBr3 perovskite thin films prepared in Example 1 and Comparative Example 1, respectively. The specific fabrication process was as follows: an electron transport layer (40 nm thick), lithium fluoride (1 nm thick), and an aluminum metal electrode (100 nm thick) were sequentially deposited on the surface of the CsSnBr3 perovskite thin films prepared in Example 1 and Comparative Example 1, respectively, thus obtaining two types of perovskite LED devices (these two devices were identical except for the different preparation methods of the CsSnBr3 perovskite thin films). The luminance and electroluminescent efficiency (EQE) of these two perovskite LED devices were measured using a CS2000 luminance meter and a Keithley 2450 source meter. The luminance-current density test results are shown below. Figure 5 As shown, the external quantum efficiency-current density test results are as follows: Figure 6 As shown, by Figure 5 and Figure 6 As can be seen (where Control represents Comparative Example 1 and Target represents Example 1), the perovskite light-emitting diode device obtained using the CsSnBr3 perovskite thin film of Example 1 exhibits higher brightness and the external quantum efficiency is increased from 0.39% to 0.81%, which can be attributed to the improved morphology of the CsSnBr3 perovskite thin film and the higher fluorescence quantum yield.

[0059] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an all-inorganic perovskite thin film with high fluorescence quantum yield, characterized in that, Includes the following steps: Cesium bromide and tin dibromide were dissolved in an organic solvent to obtain a precursor solution; N-(diphenylphospho)-P,P-diphenylphosphine amide was added to the precursor solution to obtain a perovskite precursor solution. The perovskite precursor solution was stirred, then coated onto a substrate, and annealed to obtain the all-inorganic perovskite film with high fluorescence quantum yield.

2. The method for preparing a high fluorescence quantum yield all-inorganic perovskite thin film according to claim 1, characterized in that, The molar ratio of cesium bromide to tin dibromide is (1-2.5):

1.

3. The method for preparing a high fluorescence quantum yield all-inorganic perovskite thin film according to claim 1, characterized in that, The organic solvent is dimethyl sulfoxide.

4. The method for preparing a high fluorescence quantum yield all-inorganic perovskite thin film according to claim 1, characterized in that, The concentration of tin ions in the precursor solution is 0.01-2 mmol / mL.

5. The method for preparing a high fluorescence quantum yield all-inorganic perovskite thin film according to claim 1, characterized in that, In the perovskite precursor solution, the concentration of N-(diphenylphospho)-P,P-diphenylphosphine amide is 3 mg / mL.

6. The method for preparing a high fluorescence quantum yield all-inorganic perovskite thin film according to claim 1, characterized in that, When stirring the perovskite precursor solution, the temperature is between room temperature and 150°C, and the stirring time is 6-12 hours.

7. The method for preparing a high fluorescence quantum yield all-inorganic perovskite thin film according to claim 1, characterized in that, The annealing temperature is 80-200℃ and the time is 3-10 minutes.

8. A high-fluorescence quantum yield all-inorganic perovskite thin film, characterized in that, The fluorescence quantum yield is 15 ± 0.2% obtained by the preparation method according to any one of claims 1-7.

9. The application of the all-inorganic perovskite thin film with high fluorescence quantum yield as described in claim 8 in perovskite light-emitting devices, perovskite solar cells, and perovskite photodetectors.

10. The application according to claim 9, characterized in that, The perovskite light-emitting device is a perovskite light-emitting diode.

Images