A two-dimensional and three-dimensional perovskite heterojunction optical thin film

Abstract

This invention discloses a two-dimensional and three-dimensional perovskite heterojunction optical thin film, belonging to the field of perovskite optical thin film technology. The thin film comprises a ternary cationic three-dimensional perovskite substrate, a composite two-dimensional perovskite passivation layer, and functional additives. The three-dimensional substrate has a chemical composition of FA. 0.7‑0.9 Cs 0.1‑0.2 Rb 0.05‑0.1 Pb(I 1‑x Br x The two-dimensional passivation layer (x = 0~0.5) is a mixture of phenylethylamine lead iodine and its monofluorinated derivatives, and the functional additive is a composite of CsPbBr₃ quantum dots and thiourea. The thin film is prepared by solution spin coating. This invention significantly improves the structural order, carrier mobility, and stability of heterojunctions through multi-element synergy, composite passivation, and additive assistance, and can be widely used in optoelectronic devices such as solar cells, lasers, photoelectric sensors, and light-emitting diodes.

Description

Technical Field

[0001] This invention belongs to the field of perovskite optical thin film technology, and particularly relates to a two-dimensional and three-dimensional perovskite heterojunction optical thin film. Background Technology

[0002] Organic-inorganic hybrid perovskite materials have become core candidate materials for photovoltaic devices, photodetectors, and other optoelectronic devices due to their excellent optoelectronic properties, such as suitable band gap width, high carrier mobility, and strong light absorption coefficient. Among them, three-dimensional (3D) organic-inorganic hybrid perovskites (such as formamidinium lead iodide perovskite) have attracted widespread attention for their high power conversion efficiency (PCE), with a certified efficiency of 25.2%. However, 3D perovskite materials have inherent technical bottlenecks: on the one hand, their chemical and thermal stability is poor, and they are prone to degradation under practical application environments such as light, humidity, and temperature changes, leading to rapid degradation of device performance; on the other hand, 3D perovskite films have more grain boundary defects, which easily induce nonradiative recombination of carriers, limiting further improvement in carrier mobility and diffusion length, making it difficult to meet the long-term use requirements of high-performance optoelectronic devices.

[0003] To address these issues, researchers proposed using two-dimensional (2D) organic-inorganic hybrid perovskites as passivators to construct 2D / 3D perovskite heterojunctions. This approach leverages the passivation effect of 2D perovskites on surface and grain boundary defects in 3D perovskites, thereby enhancing the material's stability and optoelectronic performance. In existing technologies, commonly used 2D perovskite passivators are often systems constructed from single organic cations (such as phenylethylammonium and butylammonium). However, these single 2D passivation layers have significant drawbacks: firstly, the structural order is difficult to precisely control; differences in the orientation of different organic cations lead to increased electronic disorder in the 2D / 3D heterojunction, thus affecting carrier transport efficiency; secondly, passivation effect and carrier transport performance are difficult to balance, as single 2D perovskites either have limited passivation capabilities or poor optoelectronic performance, leaving considerable room for improvement in carrier mobility and diffusion length in heterojunctions; furthermore, existing heterojunction films lack functional additives to assist in defect passivation, and the fabrication process does not adequately optimize film crystal quality, further limiting the long-term stability and overall performance of the devices.

[0004] Therefore, developing a 2D / 3D perovskite heterojunction optical thin film that combines high structural order, excellent carrier transport performance, and long-term stability has become an urgent technical problem to be solved in the field of perovskite optoelectronic devices. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, this invention provides a two-dimensional and three-dimensional perovskite heterojunction optical thin film with high structural order, excellent carrier transport performance and long-term stability, and a method for its preparation.

[0006] To achieve the above objectives, the following technical solution is adopted: This invention provides a two-dimensional and three-dimensional perovskite heterojunction optical thin film, characterized in that it comprises a ternary cation-mixed three-dimensional perovskite matrix, a composite two-dimensional perovskite passivation layer, and functional additives, wherein the chemical composition of the three-dimensional perovskite matrix is ​​FA. 0.7-0.9 Cs 0.1-0.2 Rb 0.05-0.1 Pb(I 1-x Br x )3 (where x=0~0.5), the two-dimensional perovskite passivation layer is at least one of phenylethylamine lead iodine and its monofluorinated derivatives, the molar ratio of the two is 1:0.3~0.7, the functional additive is a composite of CsPbBr3 quantum dots and thiourea, the molar ratio of the composite two-dimensional perovskite passivation layer to the three-dimensional perovskite matrix is ​​5%~25%, and the functional additive accounts for 0.1%~1% of the total mass of the film.

[0007] Preferably, in the three-dimensional perovskite matrix, the molar ratio of FA, Cs, and Rb ions is 0.8:0.15:0.05, and the molar ratio of I to Br ions is 0.9:0.1, corresponding to a chemical composition of FA. 0.8 Cs 0.15 Rb 0.05 PbI 2.7 Br 0.3 .

[0008] Preferably, the molar ratio of the two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 15%.

[0009] Furthermore, in the composite two-dimensional perovskite passivation layer, the monofluorinated derivative is taken from at least one of o-fluorophenylethylamine lead iodine, m-fluorophenylethylamine lead iodine, and p-fluorophenylethylamine lead iodine.

[0010] Furthermore, in the functional additive, the mass ratio of CsPbBr3 quantum dots to thiourea is 1:0.8~1.2, and the particle size of CsPbBr3 quantum dots is 5~15nm.

[0011] Furthermore, the optical thin film is prepared by the following steps:

[0012] (1) Preparation of three-dimensional perovskite precursor solution: formamidinium iodide, cesium iodide, rubidium iodide, lead iodide and lead bromide are dissolved in a mixed solvent and stirred until completely dissolved. The mixed solvent is a mixture of N,N-dimethylformamide, dimethyl sulfoxide and γ-butyrolactone, with a volume ratio of 4:3:3. The concentration of the precursor solution is 1.0~1.5 mol / L.

[0013] (2) Preparation of composite two-dimensional perovskite passivating agent solution: Phenethylamine lead iodine and its monofluorinated derivatives and PbI2 are dissolved in DMF in a molar ratio of 2:1:1.5, heated to 60~70℃ and stirred for 30~60min, and cooled to room temperature;

[0014] (3) Preparation of functional additive dispersion: CsPbBr3 quantum dots and thiourea are dispersed in anhydrous ethanol in a certain proportion and ultrasonically treated for 15-20 min to form a uniform dispersion;

[0015] (4) Mixing and pretreatment: Add the passivating agent solution from step (2) to the three-dimensional precursor solution from step (1) in proportion, stir for 20-30 min, then add the functional additive dispersion from step (3), continue stirring for 10-15 min, then sonicate for 5-10 min, and let stand to remove bubbles.

[0016] (5) Thin film preparation: The mixed precursor solution is spin-coated onto the pretreated transparent substrate, and the antisolvent chlorobenzene is dropped onto the edge of the substrate during the spin-coating process;

[0017] (6) Annealing and post-treatment: The spin-coated film is placed in an annealing furnace for annealing and then naturally cooled to room temperature to obtain the target optical film.

[0018] Furthermore, in step (5), the transparent substrate is fluorine-doped tin oxide glass or indium tin oxide glass. The pretreatment process is as follows: ultrasonically cleaned with deionized water, anhydrous ethanol and acetone for 15 min each, dried with nitrogen, and then treated in an ultraviolet ozone cleaner for 20-30 min.

[0019] Further, the spin coating process described in step (5) is divided into two stages: the first stage has a rotation speed of 2000~3000rpm and a time of 10~15s; the second stage has a rotation speed of 5000~6000rpm and a time of 30~40s; after the first stage of rotation speed is completed, the anti-solvent chlorobenzene is added dropwise quickly.

[0020] Furthermore, in step (6), the annealing process is first heated to 80°C at a rate of 5°C / min and held for 10 min, and then heated to 120~140°C at the same rate and held for 15~25 min.

[0021] Furthermore, the optical thin film can be used in perovskite solar cells, surface-emitting lasers, high-sensitivity photoelectric sensors, and flexible light-emitting diodes as a core light-absorbing layer, gain medium layer, or light-emitting layer.

[0022] The beneficial effects of this invention are:

[0023] The invention employs a ternary cation mixture system of FA, Cs, and Rb to construct a 3D perovskite matrix, and introduces Br... - Partially replaces I -Formation of Pb(I) 1-x Br x )3. On the one hand, the introduction of Rb ions suppresses phase separation of 3D perovskite through ionic radius matching effect, Cs ions and FA ions synergistically regulate the band gap to the optimal light absorption range, and Br ion doping further optimizes the band structure, significantly improving the carrier mobility of the matrix; on the other hand, the synergistic effect of multiple cations enhances the chemical stability of the perovskite lattice, effectively resisting degradation caused by light, high temperature and humidity, and solving the technical problem of poor stability of traditional 3D perovskite.

[0024] The invention abandons the traditional single 2D passivation layer design and uses phenylethylamine lead iodine and its monofluorinated derivatives to form a composite passivation layer. The monofluorinated derivatives of phenylethylamine lead iodine have high structural order, which can significantly reduce the electronic disorder of the heterojunction, enhance the bonding force between the 2D passivation layer and the 3D substrate, and further passivate grain boundary defects.

[0025] This invention introduces a composite functional additive of CsPbB3 quantum dots and thiourea. CsPbB3 quantum dots have high fluorescence quantum yield and excellent charge transfer ability, and can serve as carrier separation centers to promote electron-hole separation. Thiourea binds to Pb ion defects in the perovskite lattice through coordination, and precisely passivates surface and grain boundary defects.

[0026] The invented optical thin film, with its high carrier mobility, long diffusion length, excellent stability and tunable bandgap, can be widely used in various optoelectronic devices such as perovskite solar cells, surface-emitting lasers, high-sensitivity photoelectric sensors and flexible light-emitting diodes, as a core light absorption layer, gain medium layer or light-emitting layer. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0029] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are commercially available. In the embodiments of this application, a two-dimensional / three-dimensional perovskite heterojunction optical thin film includes a ternary cation mixed three-dimensional perovskite matrix, a composite two-dimensional perovskite passivation layer, and functional additives. In the three-dimensional perovskite matrix, the molar ratio of FA, Cs, and Rb ions is 0.8:0.15:0.05, and the molar ratio of I to Br ions is 0.9:0.1. The corresponding chemical composition is FA... 0.8 Cs 0.15 Rb 0.05 PbI 2.7 Br 0.3 The molar ratio of the two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 15%. The two-dimensional perovskite passivation layer is at least one of phenylethylamine lead iodine and its monofluorinated derivatives. The molar ratio of phenylethylamine lead iodine to the monofluorinated derivative is 1:0.3~0.7. The functional additive is a complex of CsPbBr3 quantum dots and thiourea. The molar ratio of the composite two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 5%~25%. The functional additive accounts for 0.1%~1% of the total mass of the film.

[0030] Example 1

[0031] A two-dimensional and three-dimensional perovskite heterojunction optical thin film includes a ternary cation-mixed three-dimensional perovskite matrix, a composite two-dimensional perovskite passivation layer, and functional additives. In the three-dimensional perovskite matrix, the molar ratio of FA, Cs, and Rb ions is 0.8:0.15:0.05, and the molar ratio of I to Br ions is 0.9:0.1. The corresponding chemical composition is FA. 0.8 Cs 0.15 Rb 0.05 PbI 2.7 Br 0.3 The molar ratio of the two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 15%. The two-dimensional perovskite passivation layer is at least one of phenylethylamine lead iodine and its monofluorinated derivatives. The monofluorinated derivative is taken from o-fluorophenylethylamine lead iodine. The molar ratio of phenylethylamine lead iodine to the monofluorinated derivative is 1:0.3. The functional additive is a composite of CsPbBr3 quantum dots and thiourea. The molar ratio of the composite two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 5%. The functional additive accounts for 0.1% of the total mass of the film. In the functional additive, the mass ratio of CsPbBr3 quantum dots to thiourea is 1:0.8, and the particle size of CsPbBr3 quantum dots is 5 nm.

[0032] The optical thin film is prepared by the following steps:

[0033] (1) Preparation of three-dimensional perovskite precursor solution: formamidinium iodide, cesium iodide, rubidium iodide, lead iodide and lead bromide are dissolved in a mixed solvent and stirred until completely dissolved. The mixed solvent is a mixture of N,N-dimethylformamide, dimethyl sulfoxide and γ-butyrolactone in a volume ratio of 4:3:3. The precursor solution concentration is 1.0 mol / L.

[0034] (2) Preparation of composite two-dimensional perovskite passivating agent solution: Phenethylamine lead iodine and o-fluorophenylethylamine lead iodine and PbI2 were dissolved in DMF in a molar ratio of 2:1:1.5, heated to 60℃ and stirred for 30 min, and then cooled to room temperature;

[0035] (3) Preparation of functional additive dispersion: CsPbBr3 quantum dots and thiourea were dispersed in anhydrous ethanol in a certain proportion and ultrasonically treated for 15 min to form a uniform dispersion.

[0036] (4) Mixing and pretreatment: Add the passivating agent solution from step (2) to the three-dimensional precursor solution from step (1) in proportion, stir for 20 min, then add the functional additive dispersion from step (3), continue stirring for 10 min, then sonicate for 5 min, and let stand to remove bubbles.

[0037] (5) Thin film preparation: The mixed precursor solution is spin-coated onto the pretreated transparent substrate, and the antisolvent chlorobenzene is dropped onto the edge of the substrate during the spin-coating process;

[0038] (6) Annealing and post-treatment: The spin-coated film is placed in an annealing furnace for annealing and then naturally cooled to room temperature to obtain the target optical film.

[0039] In step (5), the transparent substrate is fluorine-doped tin oxide glass or indium tin oxide glass. The pretreatment process is as follows: ultrasonically cleaned with deionized water, anhydrous ethanol and acetone for 15 min each, dried with nitrogen, and then treated in an ultraviolet ozone cleaner for 20 min.

[0040] The spin coating process described in step (5) is divided into two stages: the first stage has a rotation speed of 2000 rpm and a time of 10 s; the second stage has a rotation speed of 5000 rpm and a time of 30 s; after the first stage of rotation speed is completed, the anti-solvent chlorobenzene is added dropwise quickly.

[0041] In step (6), the annealing process is first heated to 80°C at a rate of 5°C / min and held for 10 min, and then heated to 120°C at the same rate and held for 15 min.

[0042] Example 2

[0043] A two-dimensional and three-dimensional perovskite heterojunction optical thin film includes a ternary cation-mixed three-dimensional perovskite matrix, a composite two-dimensional perovskite passivation layer, and functional additives. In the three-dimensional perovskite matrix, the molar ratio of FA, Cs, and Rb ions is 0.8:0.15:0.05, and the molar ratio of I to Br ions is 0.9:0.1. The corresponding chemical composition is FA. 0.8 Cs 0.15 Rb 0.05 PbI 2.7 Br 0.3 The molar ratio of the two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 15%. The two-dimensional perovskite passivation layer is at least one of phenylethylamine lead iodine and its monofluorinated derivatives. The monofluorinated derivative is taken from a mixture of m-fluorophenylethylamine lead iodine and p-fluorophenylethylamine lead iodine in a mass ratio of 1:1, and the molar ratio of phenylethylamine lead iodine to the monofluorinated derivative is 1:0.7. The functional additive is a composite of CsPbBr3 quantum dots and thiourea. The molar ratio of the composite two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 25%. The functional additive accounts for 1% of the total mass of the film. In the functional additive, the mass ratio of CsPbBr3 quantum dots to thiourea is 1:1.2, and the particle size of CsPbBr3 quantum dots is 15 nm.

[0044] The optical thin film is prepared by the following steps:

[0045] (1) Preparation of three-dimensional perovskite precursor solution: formamidine iodine, cesium iodide, rubidium iodide, lead iodide and lead bromide are dissolved in a mixed solvent and stirred until completely dissolved. The mixed solvent is a mixture of N,N-dimethylformamide, dimethyl sulfoxide and γ-butyrolactone in a volume ratio of 4:3:3. The precursor solution concentration is 1.5 mol / L.

[0046] (2) Preparation of composite two-dimensional perovskite passivating agent solution: Phenethylamine lead iodine, m-fluorophenylethylamine lead iodine and p-fluorophenylethylamine lead iodine and PbI2 are dissolved in DMF in a molar ratio of 2:1:1.5, heated to 70℃ and stirred for 60 min, and then cooled to room temperature;

[0047] (3) Preparation of functional additive dispersion: CsPbBr3 quantum dots and thiourea were dispersed in anhydrous ethanol in a certain proportion and ultrasonically treated for 20 min to form a uniform dispersion.

[0048] (4) Mixing and pretreatment: Add the passivating agent solution from step (2) to the three-dimensional precursor solution from step (1) in proportion, stir for 30 min, then add the functional additive dispersion from step (3), continue stirring for 15 min, then sonicate for 10 min, and let stand to remove bubbles.

[0049] (5) Thin film preparation: The mixed precursor solution is spin-coated onto the pretreated transparent substrate, and the antisolvent chlorobenzene is dropped onto the edge of the substrate during the spin-coating process;

[0050] (6) Annealing and post-treatment: The spin-coated film is placed in an annealing furnace for annealing and then naturally cooled to room temperature to obtain the target optical film.

[0051] In step (5), the transparent substrate is fluorine-doped tin oxide glass or indium tin oxide glass. The pretreatment process is as follows: ultrasonically cleaned with deionized water, anhydrous ethanol and acetone for 15 min each, dried with nitrogen, and then treated in an ultraviolet ozone cleaner for 30 min.

[0052] The spin coating process described in step (5) is divided into two stages: the first stage has a rotation speed of 3000 rpm and a time of 15 s; the second stage has a rotation speed of 6000 rpm and a time of 40 s; after the first stage of rotation speed is completed, the anti-solvent chlorobenzene is added dropwise quickly.

[0053] In step (6), the annealing process is first heated to 80°C at a rate of 5°C / min and held for 10 min, and then heated to 140°C at the same rate and held for 25 min.

[0054] Example 3

[0055] A two-dimensional and three-dimensional perovskite heterojunction optical thin film includes a ternary cation-mixed three-dimensional perovskite matrix, a composite two-dimensional perovskite passivation layer, and functional additives. In the three-dimensional perovskite matrix, the molar ratio of FA, Cs, and Rb ions is 0.8:0.15:0.05, and the molar ratio of I to Br ions is 0.9:0.1. The corresponding chemical composition is FA. 0.8 Cs 0.15 Rb 0.05 PbI 2.7 Br 0.3 The molar ratio of the two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 15%. The two-dimensional perovskite passivation layer is at least one of phenylethylamine lead iodine and its monofluorinated derivatives. The monofluorinated derivative is taken from a mixture of o-fluorophenylethylamine lead iodine, m-fluorophenylethylamine lead iodine and p-fluorophenylethylamine lead iodine in a mass ratio of 1:1:1. The molar ratio of phenylethylamine lead iodine to the monofluorinated derivative is 1:0.3~0.7. The functional additive is a composite of CsPbBr3 quantum dots and thiourea. The molar ratio of the composite two-dimensional perovskite passivation layer to the three-dimensional perovskite substrate is 5%~25%. The functional additive accounts for 0.1%~1% of the total mass of the film. In the functional additive, the mass ratio of CsPbBr3 quantum dots to thiourea is 1:1.0, and the particle size of CsPbBr3 quantum dots is 10 nm.

[0056] The optical thin film is prepared by the following steps:

[0057] (1) Preparation of three-dimensional perovskite precursor solution: formamidinium iodide, cesium iodide, rubidium iodide, lead iodide and lead bromide are dissolved in a mixed solvent and stirred until completely dissolved. The mixed solvent is a mixture of N,N-dimethylformamide, dimethyl sulfoxide and γ-butyrolactone in a volume ratio of 4:3:3. The precursor solution concentration is 1.25 mol / L.

[0058] (2) Preparation of composite two-dimensional perovskite passivating agent solution: Phenethylamine lead iodine, o-fluorophenylethylamine lead iodine, m-fluorophenylethylamine lead iodine and p-fluorophenylethylamine lead iodine and PbI2 are dissolved in DMF in a molar ratio of 2:1:1.5, heated to 65℃ and stirred for 45 min, and cooled to room temperature;

[0059] (3) Preparation of functional additive dispersion: CsPbBr3 quantum dots and thiourea were dispersed in anhydrous ethanol in a certain proportion and ultrasonically treated for 17 min to form a uniform dispersion.

[0060] (4) Mixing and pretreatment: Add the passivating agent solution from step (2) to the three-dimensional precursor solution from step (1) in proportion, stir for 25 min, then add the functional additive dispersion from step (3), continue stirring for 12 min, then sonicate for 7 min, and let stand to remove bubbles;

[0061] (5) Thin film preparation: The mixed precursor solution is spin-coated onto the pretreated transparent substrate, and the antisolvent chlorobenzene is dropped onto the edge of the substrate during the spin-coating process;

[0062] (6) Annealing and post-treatment: The spin-coated film is placed in an annealing furnace for annealing and then naturally cooled to room temperature to obtain the target optical film.

[0063] In step (5), the transparent substrate is fluorine-doped tin oxide glass or indium tin oxide glass. The pretreatment process is as follows: ultrasonic cleaning with deionized water, anhydrous ethanol and acetone for 15 min each, drying with nitrogen, and then treating in an ultraviolet ozone cleaner for 25 min.

[0064] The spin coating process described in step (5) is divided into two stages: the first stage has a rotation speed of 2500 rpm and a time of 12 s; the second stage has a rotation speed of 5500 rpm and a time of 35 s; after the first stage of rotation speed is completed, the anti-solvent chlorobenzene is added dropwise quickly.

[0065] In step (6), the annealing process is first heated to 80°C at a rate of 5°C / min and held for 10 min, and then heated to 130°C at the same rate and held for 20 min.

[0066] Comparative Example 1

[0067] In this comparative example, the three-dimensional perovskite matrix is ​​FAPbI3, and the two-dimensional passivation layer is only phenylethylamine lead iodine, without any monofluorinated derivatives or functional additives. The remaining preparation process is the same as in Example 3 of this invention.

[0068] Comparative Example 2

[0069] The three-dimensional perovskite matrix in this comparative example is the same as that in Example 3 of the present invention, but no two-dimensional perovskite passivation layer or functional additives are introduced. The remaining preparation process is the same as that in Example 3 of the present invention.

[0070] Comparative Example 3

[0071] The three-dimensional perovskite matrix in this comparative example is the same as that in Example 3 of this invention. The two-dimensional passivation layer is only phenylethylamine lead iodine, without any monofluorinated derivatives, and without the addition of CsPbBr3 quantum dots and thiourea composite functional additives. The remaining preparation process is the same as that in Example 3 of this invention.

[0072] Results Analysis

[0073] The photoelectric properties, structural characterization, and stability tests of the thin films prepared in each embodiment and comparative example of the present invention were systematically performed, including: carrier mobility, carrier diffusion length, fluorescence quantum yield, defect density, XRD crystallinity, thermal stability (PCE retention rate after 500 h at 80 °C), light irradiation stability (PCE retention rate after 1000 h at AM1.5G), and humidity stability (PCE retention rate after 500 h at 85% RH). The results are shown in Table 1.

[0074] Table 1 Summary of Performance Characterization and Test Results of Photoelectric Thin Films

[0075] Test Project Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Carrier mobility (cm 2 V -1 s -1 )]]> 45.6 48.3 47.2 15.2 28.5 32.1 Carrier diffusion length (μm) 3.2 3.5 3.4 0.8 1.5 1.9 Fluorescence quantum yield (%) 92 94 93 65 78 82 <![CDATA[Defect density (×10 16 cm -3 )]]> 1.8 1.5 1.6 8.5 5.2 4.1 XRD crystallinity (FWHM, °) 0.11 0.10 0.10 0.25 0.18 0.15 Thermal stability (%) 92 94 93 45 70 75 Light stability (%) 90 91 90 40 65 72 Humidity stability (%) 88 89 88 35 60 68

[0076] As shown in Table 1, the ternary cation 3D perovskite matrix, the phenethylamine lead-iodine / monofluorine-substituted derivative composite 2D passivation layer, and the CsPbBr3 quantum dot / thiourea functional additive provided by this invention constitute a synergistic system. This not only overcomes the problems of poor structural order and performance trade-offs inherent in traditional single 2D passivation layers, but also achieves precise control and comprehensive improvement of the defect density, carrier dynamics, and interface stability of perovskite films through multi-element ion regulation and the introduction of multifunctional additives. Table 1 fully verifies that the two-dimensional and three-dimensional perovskite heterojunction optical films prepared by this invention have significant advantages in carrier transport performance, crystal quality, and long-term environmental stability.

[0077] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

[0078] The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention. The actual application is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A two-dimensional or three-dimensional perovskite heterojunction optical thin film, characterized in that: It includes a ternary cation-mixed three-dimensional perovskite matrix, a composite two-dimensional perovskite passivation layer, and functional additives. The chemical composition of the three-dimensional perovskite matrix is ​​FA. 0.7- 0.9 Cs 0.1-0.2 Rb 0.05-0.1 Pb(I 1-x Br x )3 (where x=0~0.5), the two-dimensional perovskite passivation layer is at least one of phenylethylamine lead iodine and its monofluorinated derivatives, the molar ratio of the two is 1:0.3~0.7, the functional additive is a composite of CsPbBr3 quantum dots and thiourea, the molar ratio of the composite two-dimensional perovskite passivation layer to the three-dimensional perovskite matrix is ​​5%~25%, and the functional additive accounts for 0.1%~1% of the total mass of the film.

2. The two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 1, characterized in that: In the three-dimensional perovskite matrix, the molar ratio of FA, Cs, and Rb ions is 0.8:0.15:0.05, and the molar ratio of I to Br ions is 0.9:0.

1. The corresponding chemical composition is FA. 0.8 Cs 0.15 Rb 0.05 PbI 2.7 Br 0.3 .

3. The two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 1, characterized in that: The molar ratio of the two-dimensional perovskite passivation layer to the three-dimensional perovskite matrix is ​​15%.

4. The two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 1, characterized in that: In the composite two-dimensional perovskite passivation layer, the monofluorinated derivative is taken from at least one of o-fluorophenylethylamine lead iodine, m-fluorophenylethylamine lead iodine, and p-fluorophenylethylamine lead iodine.

5. The two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 1, characterized in that: In the functional additive, the mass ratio of CsPbBr3 quantum dots to thiourea is 1:0.8~1.2, and the particle size of CsPbBr3 quantum dots is 5~15nm.

6. The two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 1, characterized in that: Prepared by the following steps: (1) Preparation of three-dimensional perovskite precursor solution: formamidinium iodide, cesium iodide, rubidium iodide, lead iodide and lead bromide are dissolved in a mixed solvent and stirred until completely dissolved. The mixed solvent is a mixture of N,N-dimethylformamide, dimethyl sulfoxide and γ-butyrolactone, with a volume ratio of 4:3:

3. The concentration of the precursor solution is 1.0~1.5 mol / L. (2) Preparation of composite two-dimensional perovskite passivating agent solution: Phenethylamine lead iodine and its monofluorinated derivatives and PbI2 are dissolved in DMF in a molar ratio of 2:1:1.5, heated to 60~70℃ and stirred for 30~60min, and cooled to room temperature; (3) Preparation of functional additive dispersion: CsPbBr3 quantum dots and thiourea are dispersed in anhydrous ethanol in a certain proportion and ultrasonically treated for 15-20 min to form a uniform dispersion; (4) Mixing and pretreatment: Add the passivating agent solution from step (2) to the three-dimensional precursor solution from step (1) in proportion, stir for 20-30 min, then add the functional additive dispersion from step (3), continue stirring for 10-15 min, then sonicate for 5-10 min, and let stand to remove bubbles. (5) Thin film preparation: The mixed precursor solution is spin-coated onto the pretreated transparent substrate, and the antisolvent chlorobenzene is dropped onto the edge of the substrate during the spin-coating process; (6) Annealing and post-treatment: The spin-coated film is placed in an annealing furnace for annealing and then naturally cooled to room temperature to obtain the target optical film.

7. The two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 6, characterized in that: In step (5), the transparent substrate is fluorine-doped tin oxide glass or indium tin oxide glass. The pretreatment process is as follows: ultrasonically cleaned with deionized water, anhydrous ethanol and acetone for 15 min each, dried with nitrogen, and then treated in an ultraviolet ozone cleaner for 20-30 min.

8. The two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 6, characterized in that: The spin coating process described in step (5) is divided into two stages: the first stage has a rotation speed of 2000~3000rpm and a time of 10~15s; the second stage has a rotation speed of 5000~6000rpm and a time of 30~40s; after the first stage of rotation speed is completed, the anti-solvent chlorobenzene is added dropwise quickly.

9. A two-dimensional or three-dimensional perovskite heterojunction optical thin film according to claim 6, characterized in that: In step (6), the annealing process is first heated to 80°C at a rate of 5°C / min and held for 10 min, and then heated to 120~140°C at the same rate and held for 15~25 min.

10. A two-dimensional or three-dimensional perovskite heterojunction optical thin film according to any one of claims 1-9, characterized in that: The optical thin film can be used in perovskite solar cells, surface-emitting lasers, high-sensitivity photoelectric sensors, and flexible light-emitting diodes as a core light-absorbing layer, gain medium layer, or light-emitting layer.