Light emitting diode containing chiral quasi-two-dimensional perovskite, preparation method and application thereof

Abstract

The invention belongs to the field of spin polarization luminescent materials, and particularly relates to a light-emitting diode containing chiral quasi-two-dimensional perovskite, a preparation method of the light-emitting diode and application of the light-emitting diode in circular polarization electroluminescent imaging, information encryption, quantum communication and spin electronic devices. According to the invention, a quasi-two-dimensional perovskite structure is used as a light-emitting layer of the light-emitting diode, and organic cations in the quasi-two-dimensional perovskite structure are chiral enantiomers with levorotation or dextrorotation optical activity, so that the formed chiral perovskite structure can correspondingly generate levorotation and dextrorotation circularly polarized light. Chiral quasi-two-dimensional perovskite is adopted as the light emitting layer, circularly polarized light emission can be directly achieved only through one layer of structure, and an extra transmission layer for controlling carrier spin injection is not needed. Therefore, the invention provides the light-emitting diode which can directly emit high-efficiency circularly polarized light under the condition of room temperature without an external magnetic field or a ferromagnetic material, and the light-emitting diode can be used for preparing a device which is simple in structure and can obtain higher performance.

Description

Technical Field

[0001] The present invention belongs to the field of spin-polarized luminescent materials. More specifically, the present invention relates to a light-emitting diode comprising a chiral quasi-two-dimensional (2D) perovskite, a method for preparing the same, and its uses in circularly polarized electroluminescence imaging, information encryption, quantum communication, and spintronic devices. Background Art

[0002] Metal halide perovskites have excellent properties such as adjustable bandgap, high photoluminescence quantum yield, and solution processability, and thus have great application potential in the field of light-emitting diodes (LEDs). In the past few years, great progress has been made in the electroluminescence (EL) efficiency of perovskite light-emitting diodes. However, in traditional spin light-emitting diodes, the key challenge is to control the spin-polarized electron density through the unbalanced spin distribution at the interface, which makes it difficult to directly emit polarized light from perovskite LEDs at room temperature without a magnetic field.

[0003] Therefore, based on the problems existing in the prior art, there is an urgent need in the art for a light-emitting diode comprising a light-emitting layer of chiral quasi-two-dimensional perovskite, which can directly achieve circularly polarized electroluminescence (CPEL) at room temperature through a single-layer structure of the chiral perovskite light-emitting layer without an additional transport layer for controlling carrier spin injection, nor the application of an external magnetic field or ferromagnetic material. Summary of the Invention

[0004] In view of this, in a first aspect, the present invention provides a light-emitting diode comprising: a light-emitting layer comprising a quasi-two-dimensional perovskite of the general formula C2A n- 1B n X 3n+1 wherein C comprises a chiral molecule in R-configuration or S-configuration, A is a first cation, B is a second cation, X is an anion, and n represents the number of layers of the quasi-two-dimensional perovskite.

[0005] In one embodiment, the quasi-two-dimensional perovskite comprises an R-configuration chiral molecule, and the R-configuration chiral molecule comprises at least one of the following:

[0006]

[0007] wherein R1 comprises a first carbon chain having 1-10 carbon atoms, R2 comprises a second carbon chain having 1-10 carbon atoms or at least one of a hydrogen atom, a halogen atom, an alkoxy group, or a carboxylic acid group, and R3 comprises a third carbon chain having 1-10 carbon atoms.

[0008] In one embodiment, the chiral molecule comprises at least one of the following compounds in the R-configuration or S-configuration: 1-(1-naphthyl)-ethylammonium (NEA), 1-(2-naphthyl)-ethylammonium, β-methylphenylethylammonium (MPEA), methylbenzylammonium (MBA), 4-methoxy-α-methylbenzylammonium, 3-methoxy-α-methylbenzylammonium, 2-methoxy-α-methylbenzylammonium, 4-bromo-α-methylbenzylammonium, 3-bromo-α-methylbenzylammonium, 2-bromo-α-methylbenzylammonium, 1-methyl-3-phenylpropylammonium, 2-amino-5-methylhexane, 4-fluoro-α-methylbenzylammonium, 3-fluoro-α-methylbenzylammonium, 2-fluoro-α-methylbenzylammonium alanine, 2-octylammonium, sec-butylammonium, 2-amino-3-methylbutane, 3,3-dimethyl-2-butylammonium, 1-cyclohexylethylammonium, ethylbenzylammonium, 1,2,3,4-tetrahydro-1-naphthylammonium, 3-amino-1-BOC-piperidine, 1-(4-bromophenyl)ethylammonium, 1-(2-fluorophenyl)ethylammonium, 1-amino-2-(methoxymethyl)pyrrolidine, borneolammonium, 1-m-tolylethylammonium or 1-methoxy-2-propylammonium. Preferably, the chiral molecule is 1-(1-naphthyl)-ethylammonium in the R-configuration or S-configuration.

[0009] In one embodiment, A comprises at least one of cesium (Cs), methylammonium (MA), and formamidinium (FA). Preferably, A is cesium and / or formamidinium.

[0010] In one embodiment, B comprises at least one of lead (Pb), tin (Sn), copper (Cu), or germanium (Ge). Preferably, B is lead.

[0011] In one embodiment, X comprises at least one of fluorine, chlorine, bromine, and iodine. Preferably, X is bromine.

[0012] In one embodiment, at least 50% of the chiral molecules are the same enantiomer.

[0013] In one embodiment, the quasi-two-dimensional perovskite is prepared by a solution processing method.

[0014] In one embodiment, the quasi-two-dimensional perovskite is a film with an average thickness less than or equal to 50 nm.

[0015] In one embodiment, the light-emitting diode further comprises a substrate, an anode, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and a cathode.

[0016] In one embodiment, the light-emitting diode does not include a ferroelectric electrode or a spin-filtering layer.

[0017] In one embodiment, the substrate comprises one of glass, quartz, polyimide, polyethylene terephthalate, metal, alloy, and stainless steel. Preferably, the substrate is glass.

[0018] In one embodiment, the anode comprises one of indium tin oxide (ITO), gold (Au), silver (Ag), fluorine-doped tin oxide (FTO), indium gallium zinc oxide (IZGO), and graphite. Preferably, the anode is indium tin oxide.

[0019] In one embodiment, the hole injection layer comprises one of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), nickel oxide, copper phthalocyanine, molybdenum oxide, tungsten oxide, and vanadium pentoxide. Preferably, the hole injection layer is nickel oxide.

[0020] In one embodiment, the hole transport layer comprises one of poly(9-vinylcarbazole) (PVK), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD). Preferably, the hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] or poly(9-vinylcarbazole).

[0021] In one embodiment, the electron transport layer comprises one of 1,3,5-tris(1-phenyl-1H-benzoimidazol-2-yl)benzene (TPBi), 4,7-diphenyl-1,10-phenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T), 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PYMPM), 1,3,5-tris(pyridin-3-yl-phenyl)benzene (TpPyPB), and poly[(9,9-bis(3-((N,N-dimethyl)-N-ethylamine)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (PFN-Br). Preferably, the electron transport layer is 1,3,5-tris(1-phenyl-1H-benzoimidazol-2-yl)benzene.

[0022] In one embodiment, the electron injection layer comprises one of lithium fluoride (LiF), lithium octafluoride (Liq), cesium carbonate (Cs2CO3), and lithium carbonate (Li2CO3). Preferably, the electron injection layer is lithium fluoride.

[0023] In one embodiment, the cathode comprises one of aluminum (Al), gold (Au), silver (Ag), and copper (Cu). Preferably, the cathode is aluminum.

[0024] In a second aspect, the present invention provides a method for preparing the light-emitting diode described in the first aspect of the present invention, which comprises the following steps:

[0025] 1) According to the general formula C2A n-1 B n X 3n+1 , dissolve R / S-CX, AX, and BX in a solvent in a required molar ratio to prepare a perovskite precursor solution, wherein the molar concentration of BX is maintained at 0.1 M to 1 M;

[0026] 2) Spin-coat the hole injection layer and the hole transport layer sequentially on the surface of the conductive substrate, and then spin-coat the perovskite precursor solution obtained in 1) on the surface of the hole transport layer to obtain a quasi-two-dimensional perovskite film;

[0027] 3) Deposit an electron transport layer, an electron injection layer, and a cathode sequentially on the surface of the quasi-two-dimensional perovskite film by thermal evaporation.

[0028] Those skilled in the art can understand that the descriptions related to the light-emitting diode in the first aspect of the present invention above are all applicable to the second aspect of the present invention, and thus will not be repeated here.

[0029] In a third aspect, the present invention provides the application of the light-emitting diode described in the first aspect of the present invention in circularly polarized electroluminescence imaging, information encryption, quantum communication, and spintronic devices.

[0030] The light-emitting diode of the present invention can directly achieve circularly polarized electroluminescence at room temperature through a light-emitting layer containing chiral quasi-two-dimensional perovskite without an additional transport layer for controlling the spin injection of carriers, nor the application of an external magnetic field or ferromagnetic material. Among them, the chiral perovskite can simultaneously regulate the spin injection of electrons and serve as a light-emitting layer, and only one layer structure is required to achieve efficient and direct circularly polarized light emission. Therefore, a device with a simple structure and higher performance can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other implementation schemes can also be obtained based on these drawings.

[0032] Figure 1A Shows based on R- / S-NEA2(FAx Cs 1-x ) n-1 Pb n Br 3n+1 (n = 1 to ∞) of the composition of quasi-2D perovskites.

[0033] Figure 1B Shows the absorption spectra and photoluminescence (PL) spectra of R-NEA2FA2Pb3Br 10 , R-NEA2(FA 0.92 Cs 0.08 )2PbBr4 and R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 Absorption spectra and photoluminescence (PL) spectra of chiral perovskite films.

[0034] Figure 1C Shows the absorption spectra and PL spectra of S-NEA2FA2Pb3Br 10 , S-NEA2(FA 0.92 Cs 0.08 )2PbBr4 and S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 Absorption spectra and PL spectra of chiral perovskite films.

[0035] Figure 1D Shows the absorption spectra and PL spectra of rac-NEA2FA2Pb3Br 10 , rac-NEA2(FA 0.92 Cs 0.08 )2PbBr4 and rac-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 Absorption spectra and PL spectra of chiral perovskite films.

[0036] Figure 2A Shows the absorption spectra of R-NEA2FA2Pb3Br 10 , R-NEA2(FA 0.92 Cs 0.08 )2PbBr4, R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 , Powder X-ray diffraction (PXRD) patterns of R-NEA2PbBr4 and FAPbBr3 films.

[0037] Figure 2B Shows the absorption spectra of R-NEA2FA2Pb3Br 10 , R-NEA2(FA 0.92 Cs 0.08 )2PbBr4, R-NEA2(FA0.85 Cs 0.15 )2Pb3Br 10 Time-resolved photoluminescence (TRPL) decay curves of R-NEA2PbBr4 and FAPbBr3 films.

[0038] Figure 2C Shows the photoluminescence quantum yield (PLQY) of R-NEA2FA2Pb3Br 10 、R-NEA2(FA 0.92 Cs 0.08 )2PbBr4 and R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 films.

[0039] Figure 3A Shows the scanning electron microscope (SEM) image of R-NEA2FA2Pb3Br 10 film.

[0040] Figure 3B Displays the scanning electron microscope (SEM) image of R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 film.

[0041] Figure 3C Shows the atomic force microscope (AFM) image of R-NEA2FA2Pb3Br 10 film.

[0042] Figure 3D Shows the atomic force microscope (AFM) image of R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 film.

[0043] Figure 4A Shows the circular dichroism (CD) spectra of R-, S- and rac-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 films.

[0044] Figure 4B - Figure 4D Shows the R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 ( Figure 4B ) / S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 ( Figure 4C ) / rac-NEA2(FA0.85 Cs 0.15 )2Pb3Br 10 ( Figure 4D ) film's left-handed (σ + ) and right-handed (σ - ) circularly polarized luminescence (CPL) spectra.

[0045] Figure 4E Shows the extracted CPL spectra of R- / S- / rac-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 film.

[0046] Figure 4F Shows the calculated g 0.85 Cs 0.15 )2Pb3Br 10 values of the film. lum

[0047] Figure 5A - Figure 5B Shows the left-handed (σ 0.92 Cs 0.08 )2Pb3Br 10 ( Figure 5A ) / S-NEA2(FA 0.92 Cs 0.08 )2Pb3Br 10 ( Figure 5B ) film and right-handed (σ + ) CPL spectra. -

[0048] Figure 5C Shows the extracted CPL spectra of R- / S-NEA2(FA 0.92 Cs 0.08 )2Pb3Br 10 film.

[0049] Figure 5D Illustrates the calculated g 0.92 Cs 0.08 )2Pb3Br 10 values of the film. lum

[0050] Figure 6A - Figure 6B Shows the left-handed (σ 10 ( Figure 6A ) / S-NEA2FA2Pb3Br 10 ( Figure 6B ) film and right-handed (σ + ) CPL spectra. - ​

[0051] Figure 6C Shows the extracted CPL spectra of the R- / S-NEA2FA2Pb3Br 10 film.

[0052] Figure 6D Shows the calculated g 10 values of the R- / S-NEA2FA2Pb3Br lum film.

[0053] Figure 7 Shows the PLQY and g 10 as a function of the CsBr ratio doped in the R-NEA2FA2Pb3Br lum perovskite.

[0054] Figure 8 Shows the g lum of the R-NEA2FA2Pb3Br10 film at different temperatures.

[0055] Figure 9A - Figure 9L Shows the left-handed (σ 10 ) and right-handed (σ + ) CPL spectra of the R-NEA2FA2Pb3Br - film from 80 to 300 K.

[0056] Figure 10A Shows the transient absorption (TA) spectra of the R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 film.

[0057] Figure 10B Shows the TA kinetics (395 nm) probed at the exciton bleaching in the n = 1 phase in the first 10 ps.

[0058] Figure 10C Shows the TA kinetics (538 nm) probed at the exciton bleaching in the 3D phase.

[0059] Figure 10D Shows the fitted initial decay time constants of 2D and quasi-2D (dots) (probed at 395 nm) and the initial rise time constants of 3D and quasi-2D (squares) (probed at 538 nm).

[0060] Figure 10E Shows the energy and spin funneling processes for the transfer of spin-polarized excitons from the 2D phase to the 3D phase.

[0061] Figure 11A - Figure 11C Shows the n = 1 R-NEA2PbBr4 ( Figure 11A)、R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 ( Figure 11B ) and TA spectra of 3D FAPbBr3( Figure 11C ).

[0062] Figure 11D - Figure 11F Shows n = 1 R-NEA2PbBr4( Figure 11D )、R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 ( Figure 11E ) and TA kinetics of 3D FAPbBr3( Figure 11F ).

[0063] Figure 12A - Figure 12C Shows the device structure of a spin LED based on R- / S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 as the emitting layer (EML) ( Figure 12A ), energy bandgap diagrams of different layers ( Figure 12B ), and cross-sectional scanning electron microscope (SEM) images ( Figure 12C ).

[0064] Figure 12D - Figure 12H Shows the current density-luminance-voltage (J-L-V) curve ( Figure 12D ); EQE-luminance curve, (inset shows a photo of the device operating at 4 V) ( Figure 12E ); left-(σ+) and right-(σ-) CPEL spectra of spin LEDs based on R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 ( Figure 12F ) and S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 ( Figure 12G ); CPEL spectra of spin LEDs based on R- / S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 and g Figure 12H ). EL ( Figure 12I ).

[0065] Figure 12J Illustrates the summary of g EL and EQE in the spin LEDs of the literature and the present invention.

[0066] Figure 13A - Figure 13G shows R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 and S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 histograms of the peak EQE of perovskite LEDs( Figure 13A ), current efficiency (CE)-luminance curves( Figure 13B ), power efficiency (PE)-luminance curves( Figure 13C ), and EL spectra at different voltages( Figure 13D - Figure 13E ); EL spectra( 0.85 Cs 0.15 )2Pb3Br 10 and the International Commission on Illumination (CIE) coordinates( Figure 13F ) of spin LEDs based on Figure 13G .

[0067] Figure 14A - Figure 14H shows the device structures( 10 )( Figure 14F ) of R-NEA2FA2Pb3Br 0.92 Cs 0.08 )2Pb3Br 10 perovskite LEDs, EQE-luminance curves( Figure 14A ), CE-luminance curves( Figure 14B ), PE-luminance curves( Figure 14C ), J-L-V curves( Figure 14D ), and EL spectra at different voltages( Figure 14E ); EL spectra( Figure 14F - Figure 14G ) of spin LEDs based on R-NEA2FA2Pb3Br 10 and R-NEA2(FA 0.92 Cs 0.08 )2Pb3Br 10 at 5 V. Figure 14H )

[0068] Figure 15 is an exemplary schematic diagram of the perovskite light-emitting diode 100 of the present invention. The structure of the perovskite light-emitting diode 100 from top to bottom is a cathode layer 110, an electron injection layer 120, an electron transport layer 130, a perovskite light-emitting layer 140, a hole transport layer 150, a hole injection layer 160, an anode layer 170, and a substrate 180 in sequence. Detailed implementation manners

[0069] ​The present invention will be described clearly and completely in conjunction with the embodiments and drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments that can be obtained by those of ordinary skill in the art based on the embodiments in the present invention fall within the scope of protection of the present invention.

[0070] References in the specification to "one embodiment", "an exemplary embodiment", and "some embodiments", etc., mean that the described embodiments may include specific features, structures, or characteristics, but each embodiment does not necessarily include the specific features, structures, or characteristics. In addition, such phrases do not necessarily refer to the same embodiment. And when a specific feature, structure, or characteristic is described in connection with an embodiment, it should be considered that it is within the knowledge of those skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0071] As used herein, unless otherwise specified, the following terms shall be understood to have the following meanings. Unless otherwise defined herein, technical terms used in connection with the disclosed and / or claimed inventive concepts shall have the meanings commonly understood by those of ordinary skill in the art. In addition, unless the context otherwise requires, singular terms shall include the plural, and plural terms shall include the singular.

[0072] The singular forms of the indefinite and definite articles include the plural referents, unless the context clearly dictates otherwise or the context of the reference clearly implies the contrary. As used herein, the words "comprising", "having", "including", or "containing" are inclusive or open-ended and do not exclude additional, unrecited elements or method steps.

[0073] As used herein, the term "substantially" is used to indicate that an exact value may not be obtained. For example, those skilled in the art will understand that in some chemical reactions, 100% conversion of reactants is possible but not likely to occur. Most of the reactants can be converted into products, and the conversion rate of the reactants can approach 100%. Thus, although from a practical perspective, 100% of the reactants are converted, from a technical perspective, there is still a small and sometimes difficult-to-determine amount of reactants remaining. For this example of chemical reactants, this amount can be relatively easily determined by the detection limit of the instrument used to test it. However, in many cases, this amount may be difficult to determine, and thus the term "substantially" is used. In some embodiments of the present invention, the term "substantially" is defined as within 20%, 15%, 10%, 5% or 1% of a specific value or target. In further embodiments of the present invention, the term "substantially" is defined as within the range of 1%, 0.9%, 0.8%, 0.7%, 0.6%, 0.5%, 0.4%, 0.3%, 0.2% or 0.1% of a specific value or target.

[0074] Except as otherwise indicated in any operating instance or otherwise specified, numbers (representing, for example, the amounts of ingredients used in the specification and claims) should be understood to be modified in all instances by the term "about". The numerical parameters set forth in the specification and the appended claims are approximations, which may vary depending on the desired properties sought to be obtained in the practice of the present invention.

[0075] As used herein, the term "about" is used to indicate that an exact value may not be achieved. Thus, the term "about" is used to represent this limit of uncertainty. In some embodiments of the present invention, the term "about" is used to represent a limit of uncertainty of ±20%, ±15%, ±10%, ±5% or ±1% less than or equal to a specific value or target. In some embodiments of the present invention, the term "about" is used to indicate a limit of uncertainty of ±1%, ±0.9%, ±0.8%, ±0.7%, ±0.6%, ±0.5%, ±0.4%, 0.3%, 0.2% or 0.1% less than or equal to a specific value or target.

[0076] As described in the background section, in a conventional spin light-emitting diode, spin-polarized electrons are injected into a common light-emitting diode through a spin injection terminal, and the spin-polarized electrons recombine with unpolarized holes to emit circularly polarized light. In this process, controlling spin, charge, and light requires the simultaneous use of an electric field and a magnetic field. Usually, carriers are injected under the application of an electric field, and spin polarization is achieved by applying a magnetic field or a polarized ferromagnetic contact. In currently reported conventional quasi-two-dimensional perovskite organic light-emitting diodes, in the quasi-two-dimensional perovskite structure C2A n-1 B n X 3n+1Among them, a non-chiral organic small molecule is used as the organic cation (C). US Patent Application US2022251443A1 uses chiral two-dimensional perovskite as the transport layer of a light-emitting diode to achieve spin-polarized carrier injection. Among them, the light-emitting layer is a perovskite nanocrystal material, which results in at least two-layer structures of a transport layer and a light-emitting layer being required to achieve circularly polarized electroluminescence.

[0077] The object of the present invention is to provide a light-emitting diode that can directly achieve circularly polarized electroluminescence through only one structure of a chiral perovskite light-emitting layer at room temperature without controlling the spin injection of carriers in the transport layer, nor applying an external magnetic field or ferromagnetic material.

[0078] Therefore, in a first aspect, the present invention provides a light-emitting diode comprising: a light-emitting layer comprising a quasi-two-dimensional perovskite of the general formula C2A n- 1B n X 3n+1 wherein C includes a chiral molecule in the R-configuration or S-configuration, A is a first cation, B is a second cation, X is an anion, and n represents the number of layers of the quasi-two-dimensional perovskite.

[0079] Those skilled in the art know that the term "perovskite" refers to a class of ceramic oxides with a cubic crystal form. Such oxides were first discovered in the calcium titanate (CaTiO3) compound present in perovskite ore, and thus got this name. Thereafter, "perovskite" or "perovskite structure" generally refers to a large class of compounds with a crystal structure similar to that of CaTiO3 and a molecular general formula of ABX3. In this general formula, A and B are two cations with very different sizes. Usually, A represents a monovalent organic cation (formamidinium, methylammonium) or an inorganic cation (cesium ion, rubidium ion), B represents a divalent metal cation, such as a lead ion, a tin ion, a copper ion, a germanium ion, etc., and X represents an anion combined with the above cations, usually a halogen anion, such as a bromide ion, an iodide ion, a chloride ion, etc., and n represents the number of layers of the quasi-two-dimensional perovskite. Preferably, the range of n is 2-9, and more preferably n is 3.

[0080] Perovskites can generally be classified according to the crystal structure type into: three-dimensional perovskites, which are formed by the alternating combination of organic and inorganic components in three-dimensional space and usually exhibit high photoelectric conversion efficiency and electron mobility but poor stability; two-dimensional perovskites, which are sheet-like structures formed by the alternating formation of two components. Although they show better stability, their photoelectric conversion efficiency and electron mobility are weak; and quasi-two-dimensional perovskites, a new type of crystal structure type, which is a structure composed of an alternating arrangement of a layer of oxide octahedra and a layer of metal ion hexahedra. This structure is regarded as a chemical variant of the three-dimensional perovskite structure. In the quasi-two-dimensional perovskite structure, the oxide octahedra and metal ion hexahedra are connected by oxygen atoms respectively to form a two-dimensional layer composed of oxygen ions, and the metal ions are distributed on both sides of this two-dimensional layer. This arrangement makes the quasi-two-dimensional perovskite structure have good electron transport performance and photoelectric conversion performance, so it is widely used in optoelectronic devices, catalysts, batteries and other fields.

[0081] The term "chiral molecule" refers to a molecule with a certain configuration or conformation that is not the same as its mirror image and cannot be superimposed on each other. All chiral molecules have optical activity, and at the same time, the molecules of all compounds with optical activity are chiral molecules. Chiral molecules include asymmetric molecules that do not have any symmetry elements and dissymmetric molecules that have a simple axis of symmetry but no other symmetry elements.

[0082] In this article, the term "chiral perovskite" refers to a group of molecules specially prepared to have the same chirality, such as non-racemic perovskites. For example, chiral cations can include cations with at least 75%, 80%, 85%, 90%, 95%, 99% or optionally 99.9% of the same chirality or enantiomer. In one embodiment, at least 50% of the chiral molecules are the same enantiomer.

[0083] In one embodiment, the quasi-2D perovskite contained in the light-emitting diode of the present invention has the property of the average anisotropy factor of circular dichroism (gCD). In the spin-polarized light-emitting diode, the chiral molecule serves as the cation in the quasi-2D perovskite to produce circularly polarized electroluminescence higher than 1×10 -3 . During the circularly polarized electroluminescence process, the initial spin-polarized excitons are generated in the chiral 2D phase of the quasi-2D perovskite. The spin-polarized excitons transfer from the chiral 2D phase to the 3D phase on an ultrafast time scale of less than 1 ps, and finally emit CPEL in the 3D phase of the quasi-2D perovskite. In one embodiment, the light-emitting diode produces CPEL at room temperature (25 °C).

[0084] In one embodiment, the light-emitting diode further includes a substrate, an anode, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and a cathode.Figure 15 An exemplary schematic diagram of the light-emitting diode 100 described herein is shown. The chiral perovskite layer 140 includes chiral cations, for example, the R- / S-forms of 1-(1-naphthyl)-ethylammonium, which affect electron spin and enable CPEL. The substrate 180 may include one of glass, quartz, polyimide, polyethylene terephthalate, metal, alloy, and stainless steel. The anode layer 170 may include one of indium tin oxide (ITO), gold (Au), silver (Ag), fluorine-doped tin oxide (FTO), indium gallium zinc oxide (IZGO), and graphite. The hole injection layer 160 may include one of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), nickel oxide, copper phthalocyanine, molybdenum oxide, tungsten oxide, and vanadium pentoxide. The hole transport layer 150 may include one of poly(9-vinylcarbazole) (PVK), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB), and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine] (poly-TPD). The electron transport layer 130 may include one of 1,3,5-tris(1-phenyl-1H-benzoimidazol-2-yl)benzene (TPBi), 4,7-diphenyl-1,10-phenanthroline (BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T), 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PYMPM), 1,3,5-tris(p-pyridin-3-yl-phenyl)benzene (TpPyPB), and poly[(9,9-bis(3-((N,N-dimethyl)-N-ethylamine)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (PFN-Br). The electron injection layer 120 may include one of lithium fluoride (LiF), lithium octylquinolate (LiQ), cesium carbonate (Cs2CO3), and lithium carbonate (Li2CO3). The cathode layer 110 may include one of aluminum (Al), gold (Au), silver (Ag), and copper (Cu). In one embodiment, the light-emitting diode does not include a ferroelectric electrode or a spin filtering layer.

[0085] In one embodiment, the quasi-two-dimensional perovskite is solution-processed. The term "solution-processed" refers to the use of methods known in the art to generate perovskite materials with high efficiency and low cost. Solution processing can be carried out at low temperatures, such as below 200 °C, below 150 °C, below 100 °C, or optionally at room temperature (e.g., about 25 °C). Solution processing can produce various perovskite materials (e.g., polycrystalline films, colloidal NCs, single crystals, etc.).

[0086] The present invention will be further described in detail below in conjunction with specific embodiments.

[0087] Example

[0088] Materials and methods

[0089] (1) Synthesis of R / S-NEABr:

[0090] Disperse 2 ml of R / S-NEA in 6 ml of ethanol, and then add 4 ml of concentrated hydrobromic acid solution (HBr, 48% by weight, aqueous solution). After stirring in an ice bath for 2 hours, remove the solvent under vacuum at 50 °C. The solid product is further dissolved in ethanol and recrystallized 5 times with ether. Collect the obtained white precipitate R / S-NEABr and dry it in an oven at 120 °C for 2 hours.

[0091] (2) Preparation of perovskite precursor solution:

[0092] Prepare the perovskite precursor solution by dissolving R / S-NEABr, FABr, CsBr, and PbBr2 in DMSO in the required molar ratios. And the concentration of PbBr2 is maintained at 0.3 M. Before spin-coating, stir the obtained solution at 50 °C for 2 hours.

[0093] (3) Device fabrication:

[0094] All devices are fabricated on glass substrates patterned with indium tin oxide (ITO) (sheet resistance of 8 Ω per square). The substrates are cleaned with detergent and deionized water in an ultrasonic bath, dried in an oven at 120 °C, and treated with O2 plasma for 10 minutes. Spin-coat the nickel oxide precursor on the ITO substrate at 3000 rpm (30 seconds), and anneal it in air at 370 °C for 1 hour. After cooling to room temperature, transfer the substrates to a glove box. Then, spin-coat with a 8 mg / mL solution of PTAA in chlorobenzene at 4000 rpm (30 seconds), followed by annealing at 170 °C for 20 minutes. Thereafter, spin-coat a thin PVK layer onto the PTAA-coated substrate at 4000 rpm (30 seconds), and anneal it at 170 °C for 30 minutes. Prepare the perovskite film by spin-coating the perovskite precursor solution at 4000 rpm (60 seconds), and during the spin-coating process, quickly drop 300 μL of ethyl acetate onto the surface at the 45th second. The perovskite film is annealed at 80 °C for 10 minutes. Finally, load the obtained sample into a thermal evaporator for thin film deposition. Without breaking the vacuum, deposit the electron transport layer (TPBi, 40 nm), electron injection layer (LiF, 1 nm), and cathode (Al, 100 nm) onto the perovskite film at 4 × 10 -5 Pa. The light-emitting area of the device is 8 mm 2, which is determined by the overlapping area of the ITO anode and the Al cathode.

[0095] Experimental results

[0096] Figure 1A show the quasi-2D perovskite structures with different layer thicknesses from n = 1 to n = ∞, i.e., the light-emitting layer 140, i.e., R- / S-NEA2(FA x Cs 1-x ) n-1 Pb n Br 3n+1 , where R- / S-NEA is a chiral molecule, FA is formamidine, Cs is cesium, Pb is lead, Br is bromine, and n is the thickness. NEA2FA2Pb3Br with R-form, S-form, and rac-form 10 , NEA2(FA 0.92 Cs 0.08 )2PbBr4, and NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 films' absorption spectra and PL spectra ( Figure 1B - Figure 1D ) show characteristic exciton peaks at 390 nm and 530 nm, corresponding to n = 1 (R- / S- / rac-NEA2PbBr4) and 3d phase (FAPbBr3 or CsPbBr3), respectively, and show a PL peak at 535 nm.

[0097] Powder X-ray diffraction (PXRD) in Figure 2A shows the characteristic peaks of NEA2PbBr4 and FAPbBr3 in NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 . The addition of CsBr broadens these peaks and enhances the intensity. Time-resolved photoluminescence spectra of quasi-2D perovskites with different CsBr contents ( Figure 2B ), and the results are well fitted by a tri-exponential function. In the quasi-2D perovskites, the amplitude-averaged PL lifetime constants increase from 135 ns to 246 ns and 277 ns, and the PLQY ( Figure 2C ) increases from 67.5% to 82.7% and 91.0%, corresponding to 0%, 8%, and 15% CsBr contents in the quasi-2D perovskites, respectively.

[0098] Scanning electron microscopy (SEM) is used to determine the morphology of the perovskite film ( Figure 3A - Figure 3B ). The R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 film shows a more uniform morphology than R-NEA2FA2Pb3Br 10Smaller perovskite grain size. Atomic force microscopy (AFM) was used to determine the morphology and roughness of the quasi-2D perovskite film ( Figure 3C - Figure 3D ). The root mean square (RMS) roughness decreased from 7.96 nm (0% CsBr) to 1.96 nm (15% CsBr). The smoother the perovskite film, the smaller the perovskite grain size, which is more conducive to obtaining a higher PLQY.

[0099] The circular dichroism (CD) of the film was also observable from Figure 4A . Strong CD signals at 390 nm related to the n = 12D chiral (R- / S-NEA)2PbBr4 phase and small CD signals at 450 nm related to the n = 2 2D perovskite were observed in both R-type and S-type perovskite films, indicating chiral transfer to the n = 2 phase and potential other intermediate states. The CPL signal was measured by using a quarter-wave plate, followed by a linear polarizer and a spectrometer to split the emitted light into left-circularly polarized and right-circularly polarized components. We calculated the degree of circular polarization by using the following luminescence asymmetry factor (g lum ):

[0100]

[0101] where I R and I L represent the right CPL intensity and the left CPL intensity, respectively. Figure 4B - Figure 4D Shows the left-handed (σ 0.85 Cs 0.15 )2Pb3Br 10 and right-handed (σ + ) CPL spectra of (FA - )2Pb3Br Figure 4E - Figure 4F Gives the CPL and calculated g lum of the chiral perovskite film. The calculated g 0.85 Cs 0.15 )2Pb3Br 10 films of R- and S-NEA2(FA lum are 7.2×10 -2 and -6.6×10 -2 , respectively. Figure 5A - Figure 5B And Figure 6A - Figure 6B also obtained the CPL spectra of R- / S-NEA2(FA 0.92 Cs 0.08 )2PbBr4 and R- / S-NEA2FA2Pb3Br 10 , and the calculated g lum is 7.6×10 -2 (R-, 8% CsBr) and 7.2×10 -2(S-, 8% CsBr) and 8.6×10 -2 (0% CsBr) and 7.7×10 -2 (S-, 0% CsBr)( Figure 5A - Figure 5B and Figure 6A - Figure 6B ). The relationship between PLQY, g lum value and CsBr ratio is summarized in Fig. 7A, which shows that the PLQY shows an upward trend while the g lum value shows a downward trend.

[0102] To further study the g lum properties of chiral perovskite films, we measured the temperature-dependent CPL ( Figure 8 , Figure 9A - Figure 9L ), and the g 10 of R-NEA2FA2Pb3Br lum thin films monotonically decreases as the temperature increases from 80 K to 300 K, indicating that the chiral transfer from 2D perovskite to 3D perovskite decreases with increasing temperature.

[0103] The femtosecond transient absorption (TA) spectra of chiral quasi-2D perovskite films were carried out in Figure 10A . For R-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 films, at different time delays with an excitation energy of 3.81 eV, the spectra are mainly composed of two photo-bleaching signals centered at 538 nm and 394 nm, originating from the excitons of the 3D and n = 1 2D phases respectively ( Figure 11A - Figure 11C ). The ultrafast dynamics at the 2D / 3D interface can be probed by the kinetics of the recovery of exciton bleaching in the 2D and 3D phases ( Figure 10B - Figure 10C ). The exciton bleaching recovery kinetics of the n = 1 R-NEA2PbBr4 film can be fitted by a triple-exponential function, including sub-picosecond 0.23 ps, 186 ps, and 1726 ps components ( Figure 11D - Figure 11F ). The n = 1 exciton decay curve of the chiral quasi-2D perovskite film shows a new sub-picosecond (about 0.20 ps) decay component faster than trap-mediated recombination, resulting in a 60% reduction in the absolute amplitude of exciton bleaching ( Figure 10B ). The lifetime decay of 3D perovskite exciton bleaching from 0.12 ps to 0.18 ps ( Figure 10C ) further supports the energy transfer process. The TA kinetic fitting results of different films are summarized in Table 1. The initial decay of n = 1 exciton bleaching and the rise of 3D bleaching coincide with each other ( Figure 10D ), indicating that the initial excitons transfer from the 2D phase to the 3D phase. The energy transfer process is faster than the spin-flip process, and the initial spin-polarized excitons in the chiral 2D phase can transfer the spin state to the 3D phase to generate CPL from the 3D phase.Figure 10E )。

[0104] Table 1. TA kinetic fitting results of different films.

[0105]

[0106]

[0107] Describes an exemplary spin LED based on the following structure ( Figure 12A ): Glass / Indium Tin Oxide (ITO) / Nickel Oxide (NiO x ) / Poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) / Poly(9-vinylcarbazole) (PVK) / R- / S- quasi-2D perovskite / 1,3,5-tris(1-phenyl-1H-benzoimidazol-2-yl)benzene (TPBi) (40 nm) / Lithium Fluoride (LiF) (1 nm) / Aluminum (Al) (100 nm). ITO and Al are used as the anode and cathode. NiO x and LiF are used as the hole injection layer and the electron injection layer, respectively. PTAA and PVK are used as hole transport layers, while TPBi is used as an electron transport layer. R- / S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 is the emitting layer (EML), which is prepared by spin-coating a precursor solution in dimethyl sulfoxide (DMSO). The energy band diagram ( Figure 12B ) ensures that charge carriers are injected from the electrodes and effectively transported to the EML. Cross-sectional scanning electron microscopy (SEM) images (Figure 12c) show the interfaces of the different layers. The optimized spin LED exhibits a low turn-on voltage of 2.8 V and a maximum brightness of 1084 cd / m 2 ([[]] Figure 12D ). Based on R- / S-NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 perovskite, the maximum EQEs are 12.9% and 13.5% respectively ( Figure 12E ). Figure 13A - Figure 13C The statistical maximum EQE, power efficiency, and current efficiency are shown in

[0108]

[0109] where I R and I L represent the right CPL intensity and the left CPL intensity, respectively.

[0110] Based on R- / S-NEA2(FA0.85 Cs 0.15 )2Pb3Br 10 's spin LED shows a significant intensity difference between right - hand circularly polarized emission and left - hand circularly polarized emission in the EL spectrum, directly generating CPEL in the chiral perovskite layer ( Figure 12F - Figure 12G ). The maximum g EL is estimated to be 7.8×10 -2 and - 7.0×10 -2 ( Figure 12H - Figure 12I ). The g EL value is higher than the g EL values of the reported perovskite spin LEDs ( Figure 12J ). The EL spectrum presents a narrow full - width at half - maximum of 20 nm, with emission peaks at 528 nm (R - ) and 530 nm (S - ), and remains stable at different voltages ( Figure 13D - Figure 13G ), and the CIE coordinates of our green device are (0.19, 0.75), closer to the green primary color specified by Rec.2020. The spin LED based on a lower concentration of CsBr results in relatively poor EL performance, and the EQEs for the perovskites of R - NEA2FA2Pb3Br 10 and R - NEA2(FA 0.92 Cs 0.08 )2PbBr4 are 3.4% and 6.4% respectively (Figures 14a - 14e). The EL spectrum is also stable at different voltages ( Figure 14F - Figure 14H ). The EL performance is summarized in Table 2.

[0111] Table 2. EL performance of spin LEDs based on R - NEA2FA2Pb3Br 10 , R - NEA2(FA 0.92 Cs 0.08 )2Pb3Br 10 and R - NEA2(FA 0.85 Cs 0.15 )2Pb3Br 10 .

[0112]

[0113] In summary, this paper describes high - performance green spin LEDs based on chiral quasi - 2D perovskites as the emitting layer, which have a maximum EQE of over 13% and a high CPEL of 7.8×10 -2 at room temperature. The chiral 2D phase in the chiral quasi - 2D perovskite first generates spin - polarized excitons, and then their energy and spin are transferred to the higher n - phase within 0.2 ps and finally to the 3D phase. This process is faster than the spin - flip process in halide perovskites, generating spin - unbalanced excitons in the 3D phase, thus producing CPL in the 3D phase.

Claims

1. A light emitting diode, comprising: Contains the general formula C2A n-1 B n X 3n+1 A light-emitting layer of a quasi-two-dimensional perovskite, wherein C includes a chiral molecule of R-configuration or S-configuration, A is a first cation, B is a second cation, X is an anion, and n represents the number of layers of the quasi-two-dimensional perovskite.

2. The light-emitting diode according to claim 1, wherein the quasi-two-dimensional perovskite comprises an R-configuration chiral molecule, and the R-configuration chiral molecule comprises at least one of the following: in, R1 comprises a first carbon chain having 1-10 carbon atoms, R2 comprises a second carbon chain having 1-10 carbon atoms or at least one of a hydrogen atom, a halogen atom, an alkoxy group or a carboxylic acid group, and R3 comprises a third carbon chain having 1-10 carbon atoms.

3. The light-emitting diode according to claim 1, wherein the chiral molecule comprises at least one of the following compounds of R-configuration or S-configuration: 1-(1-naphthyl)-ethylammonium, 1-(2-naphthyl)-ethylammonium, β-methylphenylethylammonium, methylbenzylammonium, 4-methoxy-α-methylbenzylammonium, 3-methoxy-α-methylbenzylammonium, 2-methoxy-α-methylbenzylammonium, 4-bromo-α-methylbenzylammonium, 3-bromo-α-methylbenzylammonium, 2-bromo-α-methylbenzylammonium, 1-methyl-3-phenylpropylammonium, 2-amino-5-methylhexane, 4-fluoro-α-methylbenzylammonium, ammonium, 3-fluoro-α-methylbenzyl ammonium, 2-fluoro-α-methylbenzyl ammonium alanine, 2-octylammonium, sec-butylammonium, 2-amino-3-methylbutane, 3,3-dimethyl-2-butylammonium, 1-cyclohexylethylammonium, ethylbenzyl ammonium, 1,2,3,4-tetrahydro-1-naphthyl ammonium, 3-amino-1-BOC-piperidine, 1-(4-bromophenyl)ethylammonium, 1-(2-fluorophenyl)ethylammonium, 1-amino-2-(methoxymethyl)pyrrolidine, bornyl ammonium, 1-m-tolylethylammonium or 1-methoxy-2-propylammonium, preferably, the chiral molecule is 1-(1-naphthyl)-ethylammonium of R-configuration or S-configuration. 4 . The light emitting diode according to claim 1 , wherein A comprises at least one of cesium, methylammonium and formamidine, and preferably, A is cesium and / or formamidine. 5 . The light emitting diode according to claim 1 , wherein B comprises at least one of lead, tin, copper or germanium, and preferably, B is lead. 6 . The light emitting diode according to claim 1 , wherein X comprises at least one of fluorine, chlorine, bromine and iodine, and preferably, X is bromine.

7. A light-emitting diode according to any one of claims 1 to 6, wherein at least 50% of the chiral molecules are the same enantiomer.

8. The light-emitting diode according to any one of claims 1 to 7, wherein the quasi-two-dimensional perovskite is prepared by a solution processing method. 9 . The light-emitting diode according to claim 1 , wherein the quasi-two-dimensional perovskite is a thin film with an average thickness less than or equal to 50 nm. 10 . The light-emitting diode according to claim 1 , wherein the light-emitting diode further comprises a substrate, an anode, a hole injection layer, a hole transport layer, an electron transport layer, an electron injection layer, and a cathode.

11. The light-emitting diode according to any one of claims 1 to 10, wherein the light-emitting diode does not comprise a ferroelectric electrode or a filter layer for spin screening. 12 . The light emitting diode according to claim 10 , wherein the substrate comprises one of glass, quartz, polyimide, polyethylene terephthalate, metal, alloy and stainless steel, and preferably, the substrate is glass. 13 . The light emitting diode according to claim 10 , wherein the anode comprises one of indium tin oxide, gold, silver, fluorine-doped tin oxide, indium gallium zinc oxide and graphite, and preferably, the anode is indium tin oxide. 14 . The light-emitting diode according to claim 10 , wherein the hole injection layer comprises one of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, nickel oxide, copper phthalocyanine, molybdenum oxide, tungsten oxide and vanadium pentoxide, preferably, the preferred material is nickel oxide.

15. The light-emitting diode according to claim 10, wherein the hole transport layer comprises one of poly(9-vinylcarbazole), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine], preferably, the hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] or poly(9-vinylcarbazole).

16. The light-emitting diode according to claim 10, wherein the electron transport layer comprises 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2,4,6-tris(biphenyl-3- 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine, One of 1,3,5-tri(p-pyridin-3-yl-phenyl)benzene and poly[(9,9-bis(3-((N,N-dimethyl)-N-ethylamino)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide, preferably, the electron transport layer is 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene. 17 . The light emitting diode according to claim 10 , wherein the electron injection layer comprises one of lithium fluoride, lithium octahydroxyquinoline, cesium carbonate and lithium carbonate, and preferably, the electron injection layer is lithium fluoride.

18. The light emitting diode according to claim 10, wherein the cathode comprises one of aluminum, gold, silver and copper, and preferably, the cathode is aluminum.

19. The method for preparing a light emitting diode according to claims 1 to 18, comprising the following steps: 1) According to the general formula C2A n-1 B n X 3n+1 , dissolving R / S-CX, AX and BX in a solvent at a desired molar ratio to prepare a perovskite precursor solution, wherein the molar concentration of BX is maintained at 0.1 M to 1 M; 2) depositing a hole injection layer and a hole transport layer on the surface of a conductive substrate in sequence by spin coating, and then spin coating the perovskite precursor solution obtained in 1) on the surface of the hole transport layer to obtain a quasi-two-dimensional perovskite film; 3) Depositing an electron transport layer, an electron injection layer and a cathode in sequence on the surface of the quasi-two-dimensional perovskite film by thermal evaporation.

20. The method for preparing a light-emitting diode according to claim 19, wherein the chiral molecule comprises at least one of the following compounds in R-configuration or S-configuration: 1-(1-naphthyl)-ethylammonium, 1-(2-naphthyl)-ethylammonium, β-methylphenylethylammonium, methylbenzylammonium, 4-methoxy-α-methylbenzylammonium, 3-methoxy-α-methylbenzylammonium, 2-methoxy-α-methylbenzylammonium, 4-bromo-α-methylbenzylammonium, 3 -Bromo-α-methylbenzylammonium, 2-bromo-α-methylbenzylammonium, 1-methyl-3-phenylpropylammonium, 2-amino-5-methylhexane, 4-fluoro-α-methylbenzylammonium, 3-fluoro-α-methylbenzylammonium, 2-fluoro-α-methylbenzylammonium alanine, 2-octyl ammonium, sec-butyl ammonium, 2-amino-3-methylbutane, 3,3-dimethyl-2-butylammonium, 1-cyclohexylethylammonium, ethylbenzylammonium, 1,2,3,4-tetrahydro-1-naphthyl ammonium, 3-amino -1-BOC-piperidine, 1-(4-bromophenyl)ethylammonium, 1-(2-fluorophenyl)ethylammonium, 1-amino -2-(methoxymethyl)pyrrolidine, bornyl ammonium, 1-m-tolylethylammonium or 1-methoxy -2-propylammonium, preferably, the chiral molecule is 1-(1-naphthyl)-ethylammonium of R-configuration or S-configuration.

21. The method for preparing a light-emitting diode according to claims 19-20, wherein A comprises at least one of cesium, methylammonium and formamidine, and preferably, A is cesium and / or formamidine.

22. The method for preparing a light-emitting diode according to any one of claims 19 to 21, wherein B comprises at least one of lead, tin, copper or germanium, and preferably, B is lead.

23. The method for preparing a light emitting diode according to any one of claims 19 to 22, wherein X comprises at least one of fluorine, chlorine, bromine and iodine, and preferably, X is bromine. 24 . The method for preparing a light emitting diode according to claim 19 , wherein the substrate comprises one of glass, quartz, polyimide, polyethylene terephthalate, metal, alloy and stainless steel, and preferably, the substrate is glass. 25 . The method for preparing a light emitting diode according to claim 19 , wherein the anode comprises one of indium tin oxide, gold, silver, fluorine-doped tin oxide, indium gallium zinc oxide and graphite, and preferably, the anode is indium tin oxide.

26. The method for preparing a light-emitting diode according to any one of claims 19 to 25, wherein the hole injection layer comprises one of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, nickel oxide, copper phthalocyanine, molybdenum oxide, tungsten oxide and vanadium pentoxide, preferably, the preferred material is nickel oxide.

27. The method for preparing a light-emitting diode according to any one of claims 19 to 26, wherein the hole transport layer comprises one of poly(9-vinylcarbazole), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) and poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)-benzidine], preferably, the hole transport layer is poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] or poly(9-vinylcarbazole).

28. The method for preparing a light-emitting diode according to any one of claims 19 to 27, wherein the electron transport layer comprises 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, 4,7-diphenyl-1,10-phenanthroline, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine, 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine, 1,3,5-tris(p-pyridin-3-yl-phenyl)benzene and poly[(9,9-dimethyl-1,10-phenanthroline)]. (3-((N,N-dimethyl)-N-ethylamine)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide, preferably, the electron transport layer is 1,3,5-tri(1-phenyl-1H-benzimidazol-2-yl)benzene.

29. The method for preparing a light-emitting diode according to any one of claims 19 to 28, wherein the electron injection layer comprises one of lithium fluoride, lithium octahydroxyquinoline, cesium carbonate and lithium carbonate, and preferably, the electron injection layer is lithium fluoride. 30 . The method for preparing a light emitting diode according to claim 19 , wherein the cathode comprises one of aluminum, gold, silver and copper, and preferably, the cathode is aluminum.

31. Application of the light-emitting diodes as described in claims 1 to 18 in circularly polarized electroluminescent imaging, information encryption, quantum communication and spintronic devices.

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