Chiral quasi-two-dimensional perovskite material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of photoelectric information technologies, in particular to a chiral quasi-two-dimensional perovskite material and a preparation method and application thereof, n phases of different dimensions in the chiral quasi-two-dimensional perovskite material are in vertical phase distribution, large n phases are distributed at the bottom end, and small n phases are distributed at the top end. The n phases with different dimensions have vertical phase distribution, the large n phase is distributed at the bottom end, the small n phase is distributed at the top end, after the spin light emitting diode device is assembled, the small n phase is regulated to be close to the electron transport layer, the large n phase is regulated to be close to the hole transport layer, spin polarized electrons are transmitted to the large n phase to be compounded with holes by utilizing the CISS effect of the small n phase, and the self-luminous efficiency of the spin light emitting diode device is improved. On the premise of not sacrificing excellent luminescence performance and electrical performance of the large n phase, circular polarization luminescence with high asymmetric factors and excellent device brightness and external quantum efficiency are realized at the same time. A new thought is provided for realizing a high-performance spin light-emitting diode device, and the regulation and control process is relatively easy.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic information technology, and particularly relates to a chiral quasi-two-dimensional perovskite material, a preparation method thereof, and an application thereof. Background Art

[0002] Circularly polarized light (CPL) has attracted extensive attention due to its potential applications in fields such as new display technologies, quantum computing, optical communication, and bioimaging. Currently, circularly polarized light is usually generated by passing unpolarized light through a polarizer, which results in brightness loss and a more complex and bulky device structure when applied to devices. Therefore, efforts are being made in the research field to develop circularly polarized electroluminescent devices based on chiral luminescent materials, which can provide a simple and efficient way to directly generate circularly polarized light.

[0003] Chiral perovskite materials have a series of excellent optoelectronic properties and can be used to control spin, light, and charge. They have large spin-orbit coupling and also exhibit long spin coherence lifetimes. By using different types of chiral ligands to regulate the distortion degree and properties of octahedra in the structure, excellent circular dichroism absorption (CD) and circularly polarized light emission properties can be obtained. In addition, chiral perovskite materials also have narrow emission spectra, ultra-high color purity, high photoluminescence quantum yields, and wide emission wavelength tunability, meeting the requirements of circularly polarized light technology. However, many chiral perovskites with excellent circularly polarized photoluminescence properties are usually two-dimensional, one-dimensional, and zero-dimensional materials, and their ultra-wide band gaps and electrical insulation properties make it difficult to directly use them in the emission layer of spin light-emitting diodes. Therefore, how to obtain chiral perovskite materials with excellent electrical properties and circularly polarized luminescence properties is of great significance for their practical applications in spin light-emitting diodes. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a chiral quasi-two-dimensional perovskite material. By regulating the vertical phase distribution of different n-phases in the thin film, the small n-phase near the cathode has a stronger chiral-induced spin selectivity (CISS) effect, which can inject spin-direction-polarized electrons into the large n-phase, ultimately realizing circularly polarized luminescence. This result has achieved excellent circularly polarized electroluminescence asymmetry factors, brightness, and external quantum efficiency (EQE) when applied to spin light-emitting diode devices.

[0005] Another purpose of the present invention is to provide a preparation method of a chiral quasi-two-dimensional perovskite material, which can regulate the vertical phase distribution of different n-phases in the thin film by dropwise adding different volumes of antisolvent during the spin-coating process, thereby realizing a quasi-two-dimensional chiral perovskite material with excellent electrical properties and circularly polarized luminescence performance.

[0006] The third purpose of the present invention is to provide an application of a chiral quasi-two-dimensional perovskite material.

[0007] One of the solutions adopted by the present invention to achieve its purpose is: a chiral quasi-two-dimensional perovskite material, in which the n phases of different dimensions in the chiral quasi-two-dimensional perovskite material have a vertical phase distribution. Among them, the large n phase, that is, the phase with more perovskite octahedral cage layers in the crystal structure, is distributed at the bottom, and the small n phase, that is, the phase with fewer perovskite octahedral cage layers in the crystal structure, is distributed at the top.

[0008] The different n phases represent the number of metal halide octahedral cages between organic ligand layers in the perovskite structure. As the n value increases, the material transitions from two-dimensional to three-dimensional, and its bandgap gradually narrows, and properties such as light absorption and carrier mobility also change.

[0009] By regulating the vertical phase distribution of different n phases in the thin film, the small n phase near the cathode has a stronger chiral-induced spin selectivity (CISS) effect, which can inject spin-direction-polarized electrons into the large n phase, and finally achieve circularly polarized luminescence. When this result is applied to spin light-emitting diode devices, excellent circularly polarized electroluminescence asymmetry factors, brightness, and external quantum efficiency (EQE) are obtained.

[0010] Preferably, the general structural formula of the chiral quasi-two-dimensional perovskite material is L 2 A n-1 B n X 3n+1 , where L is any one or more of R / S-(+)-α-methylbenzylamine (R / S-MBA), R / S-(+)-α-phenylethylamine (R / S-PEA), R / S-β-methylphenethylamine (R / S-MPEA), R / S-(+)-1-phenylpropylamine (R / S-PPA), R / S-(+)-1-1-naphthylethylamine (R / S-1-1-NEA), R / S-(-)-1-2-naphthylethylamine (R / S-1-2-NEA), R / S-1-(2-bromophenyl)-ethylamine (R / S-2BrMBA), R / S-1-(3-bromophenyl)-ethylamine (R / S-3BrMBA), R / S-1-(4-bromophenyl)-ethylamine (R / S-4BrMBA), R / S-2-octylamine (R / S-OAm), A is MA + 、FA + 、Cs + One or more of them, B is Pb 2+ , X is any one or a combination of Cl, Br, I, and the value range of n is 1 < n < 10.

[0011] Where L is a chiral organic cation.

[0012] Another solution adopted by the present invention to achieve its purpose is: a preparation method of the chiral quasi-two-dimensional perovskite material described above, including the following steps:

[0013] Step 1: Dissolve one or more monovalent cation halides, one or more monovalent chiral ammonium halides, and a lead salt in a solvent to form a chiral quasi-two-dimensional perovskite precursor solution;

[0014] Step 2: Deposit the precursor solution on the surface of a substrate in an inert gas environment, and add an anti-solvent during the deposition process for crystallization to obtain a quasi-two-dimensional chiral perovskite thin film;

[0015] Step 3: After standing for a certain period of time, perform thermal annealing on the quasi-two-dimensional chiral perovskite thin film to obtain a chiral quasi-two-dimensional perovskite material with a vertical phase distribution.

[0016] Preferably, in Step 1, the molar ratio of the monovalent cation halide, the chiral ammonium halide, and the lead element is 2:2:3, and the concentration of the lead element is 0.2 - 0.5 M.

[0017] Preferably, in Step 1, the monovalent cation is MA + , FA + , Cs + or one or more of them, and the lead salt is at least one of lead halide, lead acetate, lead nitrate, and lead oleate.

[0018] Preferably, in Step 1, the monovalent chiral ammonium halide is R / S-(+)-α-methylbenzylammonium halide (R / S-MBAX), R / S-(+)-α-phenethylammonium halide (R / S-PEAX), R / S-β-methylphenethylammonium halide (R / S-MPEAX), R / S-(+)-1-phenylpropylammonium halide (R / S-PPAX), R / S-(+)-1-1-naphthylethylammonium halide (R / S-1-1-NEAX), R / S-(-)-1-2-naphthylethylammonium halide (R / S-1-2-NEAX), R / S-1-(2-bromophenyl)-ethylammonium halide (R / S-2BrMBAX), R / S-1-(3-bromophenyl)-ethylammonium halide (R / S-3BrMBAX), R / S-1-(4-bromophenyl)-ethylammonium halide (R / S-4BrMBAX), R / S-2-octylammonium halide (R / S-OAmX) (where X = Cl, Br, I), or any one or more of them.

[0019] Preferably, in Step 1, the solvent is a mixed solvent of DMSO and DMF with a volume ratio of 1:4 - 1:0.

[0020] In Step 1, the concentration of the lead element is 0.1 - 0.5 M, and the ratio of the DMSO and DMF mixed solvent is DMSO:DMF = 1:0, 4:1, 2:1, 1:1, 1:2, and 1:4.

[0021] Preferably, in step 2, the antisolvent is at least one of toluene, chlorobenzene, ethyl acetate, and chloroform. The crystallization time of different n-phase perovskites is regulated by adding the antisolvent. Specifically, 120 - 200 μL of the antisolvent is added when spin-coating for 10 - 20 s, and different n-phase perovskites start to crystallize 1 - 10 s after adding the antisolvent.

[0022] Preferably, in step 3, the sample after spin-coating is left standing for 20 - 60 min and then thermally annealed at 80 - 100 °C to regulate the self-assembly of the quasi-two-dimensional chiral perovskite film and the dynamic process of the diffusion distribution between different phases in the vertical space.

[0023] The solution adopted to achieve the third object of the present invention is: an application of the chiral quasi-two-dimensional perovskite material, using the chiral quasi-two-dimensional perovskite material as a light-emitting layer to prepare a chiral perovskite spin light-emitting diode device.

[0024] A chiral perovskite spin light-emitting diode device, whose structure includes a transparent conductive substrate, a hole transport layer, a chiral quasi-two-dimensional perovskite light-emitting layer, an electron transport layer, and a metal electrode.

[0025] Further, the transparent conductive substrate is ITO glass, FTO glass, or a PET-ITO flexible substrate, with a sheet resistance of 10 - 100 Ω and a thickness of 1 - 3 mm.

[0026] Further, the hole transport layer is one of PEDOT:PSS, PEDOT:PSS / PVK, NiOx / PVK, PVK / TFB, PVK / Poly-TPD, NiOx / PVK / TFB, with a thickness of 45 - 60 nm.

[0027] Further, the thickness of the quasi-two-dimensional chiral perovskite light-emitting layer is 60 - 120 nm.

[0028] Further, the electron transport layer is one of TPBi, ZnO-NP, CBP, or TmPyPb, with a thickness of 35 - 60 nm.

[0029] Further, the electrode material is one of Al, LiF / Al, LiQ / Al, with a thickness of 100 - 120 nm.

[0030] The present invention has the following advantages and beneficial effects:

[0031] In the chiral quasi-two-dimensional perovskite material of the present invention, the n phases of different dimensions have a vertical phase distribution, where the large n phase is distributed at the bottom and the small n phase is distributed at the top. After assembling into a spin light-emitting diode device, the small n phase is regulated to be close to the electron transport layer, and the large n phase is regulated to be close to the hole transport layer. The CISS effect of the small n phase is utilized to transfer spin-polarized electrons into the large n phase for recombination with holes, achieving circularly polarized luminescence with a high asymmetry factor, excellent device brightness, and external quantum efficiency simultaneously without sacrificing the excellent luminescence performance and electrical properties of the large n phase. It provides a new idea for realizing a high-performance spin light-emitting diode device, and the regulation process is relatively easy.

[0032] The preparation method of the present invention controls the spatial distribution of different phases in the vertical space of the entire film by adding an antisolvent to control the crystallization time of different phases, thereby regulating the vertical phase distribution of the chiral quasi-two-dimensional perovskite film, and regulating the vertical spatial charge transfer direction between different n phases to promote the radiative recombination of spin-polarized carriers in the light-emitting region. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 XRD diffraction pattern of quasi-two-dimensional chiral perovskite R-MBA prepared by dropping different amounts of toluene antisolvent according to the present invention 2 (CsPbBr 3 ) 2 PbBr 4 ;

[0034] Figure 2 Circularly polarized emission spectrum of quasi-two-dimensional chiral perovskite R-MBA prepared by dropping 200 μL of toluene antisolvent according to the present invention 2 (CsPbBr 3 ) 2 PbBr 4 ;

[0035] Figure 3 Schematic diagram of the structure of a green light spin light-emitting diode device prepared based on R-MBA 2 (CsPbBr 3 ) 2 PbBr 4 according to the present invention;

[0036] Figure 4 Current density-voltage-brightness curve of a green light spin light-emitting diode device prepared based on R-MBA 2 (CsPbBr 3 ) 2 PbBr 4 prepared according to the present invention;

[0037] Figure 5 Based on R-MBA prepared according to the present invention2 (CsPbBr 3 ) 2 PbBr 4 Circularly polarized electroluminescence spectrum and device working diagram of the green light spin light emitting diode device prepared;

[0038] Figure 6 Based on R-3BrMBA prepared by the present invention 2 (CsPbBr 3 ) 2 PbBr 4 Current density-voltage-brightness curve of the green light spin light emitting diode device prepared;

[0039] Figure 7 Based on R-NEA prepared by the present invention 2 (CsPbBr 3 ) 2 PbBr 4 Current density-voltage-brightness curve of the green light spin light emitting diode device prepared. Specific embodiments

[0040] For a better understanding of the present invention, the following examples are further descriptions of the present invention, but the content of the present invention is not limited to the following examples only.

[0041] Example 1

[0042] A preparation method of a chiral quasi-two-dimensional perovskite material, comprising the following steps:

[0043] Step 1: Dissolve 0.13 - 0.27 mmol CsBr, 0.13 - 0.27 mmol R-MBA:Br, and 0.2 - 0.4 mmol PbBr 2 in 250 μL of ultradry DMF and 750 μL of ultradry DMSO, place it in an inert gas atmosphere, and stir overnight at 60 °C to form a chiral quasi-two-dimensional perovskite precursor solution. Optionally, the volume ratio of DMSO to DMF can be 1:0, 4:1, 2:1, 1:1, 1:2, and 1:4.

[0044] Step 2: Cool the precursor solution prepared in Step 1 to 40 °C, and filter it with a nylon filter head with a pore size of 0.22 μm for standby.

[0045] Step 3: Use a pipette to take 60 - 100 μL of the precursor solution in Step 2 and drop-coat it on the surface of the substrate, and spin-coat it at a speed of 4000 rpm for 60 s. When the spin-coating program reaches the 20th s, add 60 μL of toluene as an anti-solvent to obtain a sample with a small n phase below and a large n phase above; add 120 - 200 μL or more of toluene as an anti-solvent to obtain a sample with a small n phase above and a large n phase below. ByFigure 1 , it can be seen that only the diffraction peaks of cubic phase CsPbBr3 are present on the surface of the sample with 50 μL of toluene added dropwise, indicating that the surface of the sample is mainly a three-dimensional perovskite structure with a large n-phase. In addition to the diffraction peaks of cubic phase CsPbBr with relatively low diffraction intensity in the XRD diffraction of the sample prepared by adding 120 μL of toluene dropwise 3 , there are also other miscellaneous peaks, indicating that there are other perovskite structures with different small n-phases on the surface of the sample. As Figure 2 shown, due to the presence of chiral perovskite structures with other small n-phases in the sample prepared with 200 μL of toluene, it exhibits obvious circularly polarized emission under 365 nm ultraviolet light irradiation. To obtain the sample with the best vertical phase distribution, 120 - 200 μL of toluene was selected as the antisolvent in the subsequent steps.

[0046] Step 4: After spin coating is completed, place the sample under an inert gas condition and let it stand for 20 Min. Subsequently, place the sample on a hot stage at 80 °C and anneal it for 10 Min to obtain a chiral quasi-two-dimensional perovskite thin film with a thickness of 60 - 100 nm and obvious green fluorescence.

[0047] Example 2

[0048] A preparation method of a chiral quasi-two-dimensional perovskite material, which is different from Example 1 in that the chiral ammonium halide is replaced from R-MBA:Br to R-3BrMBA:Br.

[0049] Example 3

[0050] A preparation method of a chiral quasi-two-dimensional perovskite material, which is different from Example 1 in that the chiral ammonium halide is replaced from R-MBA:Br to R-NEA:Br.

[0051] Example 4:

[0052] In this example, a green light spin-emitting diode device based on (R-MBA) 2 (CsPbBr 3 ) 2 PbBr 4 was prepared. The specific steps are as follows:

[0053] (1) Pretreatment of the transparent conductive substrate ITO glass

[0054] Step 1: Ultrasonically clean the etched ITO glass 3 times with ultrapure water and detergent, and ultrasonically clean it more than 3 times with isopropyl alcohol for standby.

[0055] Step 2: Blow off the residual solvent on the surface with a nitrogen gun, bake it in an oven at 100 °C for more than 20 Min, and then perform UVO treatment for 20 Min.

[0056] (2) Preparation of the hole transport layer

[0057] Step 1: Spin-coat PEDOT:PSS Al 4083 on the ITO glass treated with UVO in air at a spin-coating speed of 4000 rpm for 40 s. Immediately after spin-coating, place it in an oven at 150 °C for annealing for 15 min.

[0058] Step 2: Immediately transfer the ITO glass on which PEDOT:PSS spin-coating is completed in Step 1 to an inert gas atmosphere. After cooling to room temperature, deposit a PVK solution dissolved in chlorobenzene with a concentration of 4 mg / mL on the upper layer of PEDOT:PSS at a speed of 2000 rpm for a spin-coating time of 40 s, and anneal it on a hot stage at 150 °C for 10 min.

[0059] (3) Preparation of chiral quasi-two-dimensional perovskite light-emitting layer

[0060] Prepared by the preparation method of Example 1.

[0061] (4) Preparation of electron transport layer

[0062] Specific steps: Under a vacuum condition with a pressure of 3×10 -4 -1×10 -5 Pa, evaporate and deposit an electron transport layer TPBi with a thickness of 50 - 60 nm, and the evaporation rate is

[0063] (5) Preparation of electron injection layer

[0064] Specific steps: Under a vacuum condition with a pressure of 3×10 -4 -1×10 -5 Pa, evaporate and deposit an electron injection layer LiF with a thickness of 0.8 - 1.0 nm, and the evaporation rate is

[0065] (6) Preparation of metal electrode

[0066] Specific steps: Under a vacuum condition with a pressure of 3×10 -4 -1×10 -5 Pa, evaporate and deposit a metal electrode Al with a thickness of 100 - 120 nm, and the evaporation rate is

[0067] (7) Device encapsulation

[0068] Specific steps: Under an inert gas atmosphere condition, uniformly coat the ultraviolet curable glue around the active area of the device, then add a glass cover plate, and irradiate it under a 365 nm ultraviolet lamp for 30 s.

[0069] According to Figure 3 The performance of the device prepared with the device structure in Figure 4As shown, its peak brightness is 7381 cd / m2. In addition, the device Figure 5 shows significantly different left- and right-handed circularly polarized luminescence.

[0070] Example 5

[0071] A chiral perovskite-based spin light-emitting diode and its preparation method. The difference from Example 4 is that the chiral quasi-two-dimensional perovskite light-emitting layer is prepared by the method of Example 2.

[0072] Its device performance is as Figure 6 shown, and the peak brightness is 1651 cd / m 2 .

[0073] Example 6

[0074] A chiral perovskite-based spin light-emitting diode and its preparation method. The difference from Example 4 is that the chiral quasi-two-dimensional perovskite light-emitting layer is prepared by the method of Example 3.

[0075] Its device performance is as Figure 7 shown, and the peak brightness is 2700 cd / m 2 .

[0076] The above are the preferred embodiments of the present invention. Of course, the scope of the rights of the present invention cannot be limited thereby. It should be pointed out that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and changes can still be made, and these improvements and changes are also regarded as the protection scope of the present invention.

Claims

1. A chiral quasi-two-dimensional perovskite material, characterized in that: The n phases of different dimensions in the chiral quasi-two-dimensional perovskite material are vertically distributed, wherein the large n phase is distributed at the bottom and the small n phase is distributed at the top.

2. The chiral quasi-two-dimensional perovskite material according to claim 1, characterized in that: The chiral quasi-two-dimensional perovskite material has the general structural formula L2A n-1 B n X 3n+1 , L is any one or more of R / S-(+)-α-methylbenzylamine, R / S-(+)-α-phenylethylamine, R / S-β-methylphenylethylamine, R / S-(+)-1-phenylpropylamine, R / S-(+)-1-1-naphthylethylamine, R / S-(-)-1-2-naphthylethylamine, R / S-1-(2-bromophenyl)-ethylamine, R / S-1-(3-bromophenyl)-ethylamine, R / S-1-(4-bromophenyl)-ethylamine, and R / S-2-octylamine, and A is MA + , FA + , Cs + One or more of the following, B is Pb 2+ , X is any one or a combination of Cl, Br, I, and n is in the range of 1 <n<10。 3. A method for preparing a chiral quasi-two-dimensional perovskite material according to claim 1 or 2, characterized in that: The following steps are involved: Step 1: dissolving one or more monovalent cation halides, one or more monovalent chiral ammonium halides and lead salts in a solvent to form a chiral quasi-two-dimensional perovskite precursor solution; Step 2: In an inert gas environment, the precursor solution is deposited on the substrate surface, and an anti-solvent is added during the deposition process for crystallization to obtain a quasi-two-dimensional chiral perovskite film; Step 3: After standing for a certain period of time, the quasi-two-dimensional chiral perovskite film is thermally annealed to obtain a chiral quasi-two-dimensional perovskite material with a vertical phase distribution.

4. The method for preparing a chiral quasi-two-dimensional perovskite material according to claim 3, characterized in that: In the step 1, the molar ratio of the monovalent cationic halide, the chiral ammonium halide and the lead element is 2:2:3, wherein the concentration of the lead element is 0.2-0.5M.

5. The method for preparing a chiral quasi-two-dimensional perovskite material according to claim 3, characterized in that: In step 1, the monovalent cation is MA + , FA + , Cs + One or more of the above, wherein the lead salt is at least one of lead halide, lead acetate, lead nitrate and lead oleate.

6. The method for preparing a chiral quasi-two-dimensional perovskite material according to claim 3, characterized in that: In the step 1, the monovalent chiral ammonium halide is R / S-(+)-α-methylbenzyl ammonium halide (R / S-MBAX), R / S-(+)-α-phenylethyl ammonium halide (R / S-PEAX), R / S-β-methylphenylethyl ammonium halide (R / S-MPEAX), R / S-(+)-1-phenylpropyl ammonium halide (R / S-PPAX), R / S-(+)-1-1-naphthylethyl ammonium halide (R / S-1-1-NEAX), R / S-(-)- 1-2-naphthylethylammonium (R / S-1-2-NEAX), R / S-1-(2-bromophenyl)ethylammonium halides (R / S-2BrMBAX), R / S-1-(3-bromophenyl)ethylammonium halides (R / S-3BrMBAX), R / S-1-(4-bromophenyl)ethylammonium halides (R / S-4BrMBAX), and R / S-2-octanium halides (R / S-OAmX) (wherein X = Cl, Br, I).

7. The method for preparing a chiral quasi-two-dimensional perovskite material according to claim 3, characterized in that: In the step 1, the solvent is a mixed solvent of DMSO and DMF in a volume ratio of 1:4-1:

0.

8. The method for preparing a chiral quasi-two-dimensional perovskite material according to claim 3, characterized in that: In step 2, the anti-solvent is at least one of toluene, chlorobenzene, ethyl acetate, and chloroform, and the crystallization time of different n-phase perovskites is regulated by adding the anti-solvent. Specifically, 120-200 μL of the anti-solvent is added when the spin coating is 10-20 s to regulate the crystallization of the perovskites of different n-phases 1-10 s after the anti-solvent is added.

9. The method for preparing a chiral quasi-two-dimensional perovskite material according to claim 3, characterized in that: In step 3, the sample after spin coating is allowed to stand for 20-60 minutes and then thermally annealed at 80-100° C. to regulate the dynamic process of self-assembly of the quasi-two-dimensional chiral perovskite film and diffusion distribution between different phases in the vertical space.

10. An application of the chiral quasi-two-dimensional perovskite material according to claim 1 or 2, characterized in that: The chiral quasi-two-dimensional perovskite material is used as a light-emitting layer to prepare a chiral perovskite-based spin light-emitting diode device.

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