Perovskite polycrystalline film microcavity exciton polariton laser device and preparation method thereof

Abstract

The invention belongs to the technical field of nonlinear optical materials and devices, and particularly relates to a perovskite polycrystalline film microcavity exciton polariton laser device and a preparation method thereof. The laser device sequentially comprises a transparent substrate, a lower-layer distributed Bragg reflector, a perovskite active layer and an upper-layer distributed Bragg reflector from bottom to top. Wherein the perovskite active layer comprises a perovskite polycrystalline material, and the perovskite polycrystalline material comprises a perovskite phase capable of being strongly coupled with cavity photons and a perovskite phase capable of being weakly coupled with calcium of the cavity photons. According to the invention, a perovskite phase which is strongly coupled with cavity photons and a perovskite phase which is weakly coupled with the cavity photons are combined, and the perovskite phase which is weakly coupled with the cavity photons is utilized to construct a channel which is used for intra-cavity radiation pumping assistance and relaxes towards the lower support bottom of polaritons, so that the polariton polariton laser is realized in the perovskite polycrystalline film micro-cavity.

Description

Technical Field

[0001] The present invention belongs to the technical field of nonlinear optical materials and devices, and in particular relates to a perovskite polycrystalline thin film microcavity exciton-polariton laser device and a preparation method thereof. Background Art

[0002] Laser devices, which emit coherent photons, have important applications in high-quality displays, optical communications, and other fields. Exciton-polaritons, formed by strongly coupled excitons and cavity photons, can undergo Bose-Einstein condensation, exhibiting novel quantum phenomena such as superfluidity and vortices, as well as photonic functions such as lasers and switches. These devices have the potential to achieve coherent photon emission without the need for population inversion, helping to lower the laser emission threshold.

[0003] Metal halide perovskites, as a new type of optoelectronic material, have been used in the study of room-temperature exciton-polaritons due to their diverse structures, high luminescence efficiency, small Stokes shift, excellent optical gain, and solution processability. However, there are no reports of perovskite polycrystalline thin-film microcavity devices capable of achieving room-temperature exciton-polariton lasing.

[0004] For exciton-polariton devices, the concentration of the exciton reservoir is a crucial factor influencing the relaxation of the polaritons toward the lower branch and the realization of lasing. In common perovskite polycrystalline films, carrier recombination behavior depends on their concentration. Exciton recombination typically occurs when the carrier concentration is below 10 to the power of 17 per cubic centimeter, which cannot provide a high-density exciton reservoir and thus limits exciton-polariton lasing.

[0005] Intracavity pump-assisted promotion of exciton-polariton lasing has been demonstrated in organic systems. Currently, intracavity radiative pump-assisted polariton luminescence has been used to overcome the bottleneck effect of perovskite exciton-polariton luminescence. However, further research is needed to further optimize the phase distribution of perovskite polycrystalline films to achieve intracavity pump-assisted exciton-polariton lasing. Summary of the Invention

[0006] In order to improve the deficiencies of the prior art, the purpose of the present invention is to provide a perovskite polycrystalline thin film microcavity exciton polariton laser device and a preparation method thereof, wherein the perovskite polycrystalline thin film comprises both a perovskite phase that can strongly couple with cavity photons and a perovskite phase that weakly couples with cavity photons.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] In a first aspect, the present invention provides an exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity, which comprises, from bottom to top, a transparent substrate, a lower distributed Bragg reflector, a perovskite active layer, and an upper distributed Bragg reflector;

[0009] The perovskite active layer comprises a perovskite polycrystalline material, and the perovskite polycrystalline material comprises a perovskite phase capable of strongly coupling with cavity photons and a perovskite phase capable of weakly coupling with cavity photons.

[0010] According to an embodiment of the present application, the perovskite polycrystalline material is a mixture of multiple perovskite phases (at least including one perovskite phase capable of strongly coupling with cavity photons and one perovskite phase capable of weakly coupling with cavity photons), and the perovskite polycrystalline material is formed by spin-coating a precursor solution corresponding to a perovskite of an average molecular formula of A2’A n-1 B n X 3n+1 , and wherein A, A’ are different, the ionic radius of A’ is greater than A, A’ is selected from any one of phenethylamine, naphthylmethylamine, butylamine, and A is selected from any one or more of formamidinium ion, methylamine ion, cesium ion, potassium ion, sodium ion, rubidium ion, amine ion; B is one or more of lead ion, tin ion, germanium ion; and X is one or more of iodine ion, bromine ion, chlorine ion.

[0011] According to an embodiment of the present application, the average molecular formula of the perovskite polycrystalline material is determined according to the molecular formula of the perovskite phase corresponding to the stoichiometric ratio of each component, and in particular, is determined according to all the perovskite phases obtained and the stoichiometric ratio thereof under the current stoichiometric ratio condition.

[0012] According to an embodiment of the present application, when n is infinite, the structure of A2’A n-1 B n X 3n+1 is equivalent to ABX3.

[0013] According to an embodiment of the present application, in the solution for preparing the perovskite polycrystalline material, the value of n is in the range of 3≤n≤10, preferably 5≤n≤10, and more preferably 8≤n≤10, for example, 8 or 10.

[0014] According to an embodiment of the present application, when n≥8 in the solution for preparing the perovskite polycrystalline material, the perovskite polycrystalline material not only includes the perovskite phase A2’A n-1 B n X 3n+1 capable of strongly coupling with cavity photons, but also contains a small amount of the perovskite phase ABX3 capable of weakly coupling with cavity photons.

[0015] According to an embodiment of the present application, the perovskite active layer is formed by a perovskite precursor solution; and the perovskite precursor solution comprises a perovskite material and a polar solvent.

[0016] According to an embodiment of the present invention, the perovskite material includes an organic ammonium halide salt with a large cation radius, BX2 and an organic ammonium halide salt with a small cation radius, wherein the molar ratio of the organic ammonium halide salt with a large cation radius, BX2 and the organic ammonium halide salt with a small cation radius is 2:n:n-1, 1≤n≤∞.

[0017] According to an embodiment of the present invention, the organic large cationic radius ammonium halide salt is selected from at least one of PEABr, NMABr, PEAI, and NMAI.

[0018] According to an embodiment of the present invention, the organic small cationic radius ammonium halide salt is selected from at least one of CsBr, MABr, FABr, MAI, and FAI.

[0019] According to an embodiment of the present invention, the BX2 is selected from at least one of PbBr2, PbI2, and SnI2, for example, PbBr2.

[0020] According to an embodiment of the present invention, the polar solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone and N-methylpyrrolidone.

[0021] According to an embodiment of the present invention, the perovskite polycrystalline material is selected from a precursor solution with a larger component ratio n value, such as PEA2FA4Pb5Br 16 、PEA2FA7Pb8Br 25 、PEA2FA9Pb 10 I 31 、PEA2FA8Pb9I 28 、NMA2FA7Pb8I 25 、NMA2FA9Pb 10 I 31 One or more of the .

[0022] According to an embodiment of the present invention, the concentration of the perovskite precursor solution is 0.3 to 1.2 mol / L, preferably the concentration of the perovskite precursor solution is 0.5 to 1.0 mol / L, for example, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.85 mol / L, or 0.9 mol / L.

[0023] According to an embodiment of the present invention, the upper distributed Bragg reflector includes alternating high-refractive-index material layers and low-refractive-index material layers, wherein the high-refractive-index material layer is a layer structure formed by one of tantalum pentoxide, zinc sulfide, etc., for example, a tantalum pentoxide layer; the low-refractive-index material layer is a layer structure formed by one of silicon dioxide, magnesium fluoride, etc., for example, a silicon dioxide layer.

[0024] According to an embodiment of the present invention, the lower distributed Bragg reflector includes alternating high-refractive-index material layers and low-refractive-index material layers, wherein the high-refractive-index material layer is a layer structure formed by one of tantalum pentoxide, zinc sulfide, etc., for example, a tantalum pentoxide layer; the low-refractive-index material layer is a layer structure formed by one of silicon dioxide, magnesium fluoride, etc., for example, a silicon dioxide layer.

[0025] As an example, the laser device includes a transparent substrate, on which a lower distributed Bragg reflector, a perovskite active layer and an upper distributed Bragg reflector are arranged from bottom to top, wherein the upper distributed Bragg reflector includes several layers of silicon dioxide layers and tantalum pentoxide layers arranged alternately, and the lower distributed Bragg reflector includes several layers of silicon dioxide layers and tantalum pentoxide layers arranged alternately, a layer of the upper distributed Bragg reflector in contact with the perovskite active layer is a silicon dioxide layer, and a layer of the lower distributed Bragg reflector in contact with the perovskite active layer is a silicon dioxide layer.

[0026] According to an embodiment of the present invention, the thickness of the perovskite active layer is 90 to 180 nanometers, preferably the thickness of the perovskite active layer is 100 to 150 nanometers, for example, 131 nanometers, 133 nanometers, or 133.5 nanometers.

[0027] According to an embodiment of the present invention, the lower distributed Bragg reflector includes 12.5 pairs of alternately arranged silicon dioxide layers and tantalum pentoxide layers; the upper distributed Bragg reflector includes 9.5 pairs of alternately arranged silicon dioxide layers and tantalum pentoxide layers.

[0028] According to an embodiment of the present invention, the transparent substrate is quartz or ordinary glass.

[0029] According to an embodiment of the present invention, the perovskite active layer has substantially the following Figure 2 、 Figure 6 Photoluminescence spectra are shown.

[0030] According to an embodiment of the present invention, the laser device has substantially the following Figure 3 、 Figure 7 The luminous intensity-excitation power density curve.

[0031] According to an embodiment of the present invention, the laser device has substantially the following Figure 4 、 Figure 8 or Figure 11 The luminescence spectrum-excitation power density curve is shown.

[0032] According to an embodiment of the present invention, the laser device has substantially the following Figure 9 or Figure 12Angle-resolved luminescence spectra before the laser threshold power density are shown.

[0033] According to an embodiment of the present invention, the laser device has substantially the following Figure 10 or Figure 13 Angle-resolved luminescence spectra after the laser threshold power density is shown.

[0034] In a second aspect, the present invention provides a method for preparing the above-mentioned perovskite polycrystalline thin film microcavity exciton polariton device, comprising the following preparation steps:

[0035] (1) alternately forming a high refractive index material layer and a low refractive index material layer on a transparent substrate to obtain a lower distributed Bragg reflector;

[0036] (2) spin-coating the perovskite precursor solution onto the lower distributed Bragg reflector obtained in step (1), rapidly adding an anti-solvent during the spin-coating process, and obtaining a perovskite active layer after annealing;

[0037] (3) Alternately forming a high refractive index material layer and a low refractive index material layer on the perovskite active layer to obtain an upper distributed Bragg reflector, that is, a perovskite thin film microcavity device.

[0038] According to an embodiment of the present invention, before step (1), the method further comprises the following step: pre-treating the transparent substrate by ultraviolet ozone for 10 to 30 minutes.

[0039] According to an embodiment of the present invention, the high refractive index material and the low refractive index material have the definitions described above.

[0040] According to an embodiment of the present invention, the concentration of the perovskite precursor solution described in step (2) is 0.3 to 1.2 mol per liter, and preferably the concentration of the perovskite precursor solution described in step (2) is 0.5 to 1.0 mol per liter, for example, 0.6 mol per liter, 0.7 mol per liter, 0.8 mol per liter, 0.85 mol per liter, or 0.9 mol per liter.

[0041] According to an embodiment of the present invention, the spin coating speed in step (2) is 1500 to 8500 rpm, the spin coating acceleration is 1000 to 8000 rpm / s, and the total spin coating time is 20 to 120 seconds.

[0042] According to an embodiment of the present invention, the annealing temperature in step (2) is 24 to 150° C., and the annealing time is 1 to 120 minutes.

[0043] According to an embodiment of the present invention, the anti-solvent in step (2) is one or more of ethyl acetate, chlorobenzene, toluene, chloroform, etc.

[0044] Preferably, the thickness of the perovskite active layer thin film in step (2) has the definition as described above.

[0045] Preferably, the vacuum degree of the vacuum deposition process in steps (1) and (3) is 2x10 -4 ~ 2x10 -6 Pascals.

[0046] Advantages

[0047] 1. The present application combines the perovskite phase strongly coupled with cavity photons and the perovskite phase weakly coupled with cavity photons, uses the perovskite phase weakly coupled with cavity photons to construct a channel for polariton relaxation under the lower branch, and realizes polariton laser in a perovskite polycrystalline thin film microcavity.

[0048] 2. The present application takes full advantage of the characteristics of the perovskite polycrystalline thin film multiphase distribution, and realizes wavelength-tunable laser emission in a low-quality factor thin film microcavity. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 The structure diagram of the perovskite polycrystalline thin film microcavity polariton device prepared for the embodiment 1 of the present application.

[0050] Figure 2 The photoluminescence spectrum of the perovskite active layer of the perovskite polariton light-emitting device without using the in-cavity pump-assisted polariton relaxation mechanism under the lower branch for the embodiment 1 of the present application.

[0051] Figure 3 The light-emitting intensity-excitation power density curve of the perovskite polariton light-emitting device without using the in-cavity pump-assisted polariton relaxation mechanism under the lower branch for the embodiment 1 of the present application.

[0052] Figure 4 The light-emitting spectrum-excitation power density curve of the perovskite polariton light-emitting device without using the in-cavity pump-assisted polariton relaxation mechanism under the lower branch for the embodiment 1 of the present application.

[0053] Figure 5 The angle-resolved photoluminescence spectrum of the perovskite polariton light-emitting device without using the in-cavity pump-assisted polariton relaxation mechanism under the lower branch for the embodiment 1 of the present application.

[0054] Figure 6 The photoluminescence spectrum of the perovskite active layer of the perovskite polariton laser device using the in-cavity pump-assisted polariton relaxation mechanism under the lower branch for the embodiment 2 of the present application.

[0055] Figure 7This is a luminescence intensity-excitation power density curve of the perovskite exciton-polariton laser device using the intracavity pump-assisted polariton bottom-branch relaxation mechanism according to Example 2 of the present invention.

[0056] Figure 8 This is the luminescence spectrum-excitation power density curve of the perovskite exciton-polariton laser device using the intracavity pump-assisted polariton bottom-branch relaxation mechanism according to Example 2 of the present invention.

[0057] Figure 9 This is the angle-resolved luminescence spectrum before the laser threshold power density of the perovskite exciton-polariton laser device using the intracavity pump-assisted polariton bottom-branch relaxation mechanism in Example 2 of the present invention.

[0058] Figure 10 This is the angle-resolved luminescence spectrum after the laser threshold power density of the perovskite exciton-polariton laser device using the intracavity pump-assisted polariton bottom-branch relaxation mechanism in Example 2 of the present invention.

[0059] Figure 11 This is the luminescence spectrum-excitation power density curve of the perovskite exciton-polariton laser device using the intracavity pump-assisted polariton lower branch relaxation mechanism according to Example 3 of the present invention.

[0060] Figure 12 This is the angle-resolved luminescence spectrum before the laser threshold power density of the perovskite exciton-polariton laser device using the intracavity pump-assisted polariton lower-branch relaxation mechanism in Example 3 of the present invention.

[0061] Figure 13 This is the angle-resolved luminescence spectrum after the laser threshold power density of the perovskite exciton-polariton laser device using the intracavity pump-assisted polariton bottom-branch relaxation mechanism in Example 3 of the present invention. DETAILED DESCRIPTION

[0062] The following text further describes the laser device, its preparation method, and its applications in conjunction with specific embodiments. It should be understood that the following embodiments are merely illustrative and illustrative of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above-mentioned disclosure are encompassed within the scope of protection intended by the present invention.

[0063] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0064] In the following examples, the perovskite precursor solution is prepared by dissolving organic halide ammonium salts phenethylammonium bromide (PEABr), methyl ether bromide (FABr), and lead bromide (PbBr2) in a polar solvent N-N dimethylformamide (DMF).

[0065] The anti-solvent is toluene.

[0066] The transparent substrate quartz is obtained by the following treatment method:

[0067] A quartz substrate with a size of 1.5 cm×1.5 cm was used, and deionized water, acetone, and ethanol were ultrasonically treated for half an hour in sequence, and then placed in an oven for drying for 15 minutes to obtain a quartz substrate.

[0068] Example 1

[0069] This embodiment provides a perovskite polycrystalline thin film microcavity exciton-polariton light-emitting device that does not use an intracavity pump-assisted polariton bottom-branch relaxation mechanism. The preparation method is as follows:

[0070] (1) Place the quartz substrate in a vacuum of 2×10 -5 In Pa's vacuum chamber, electron beams were used to alternately deposit 15.5 pairs of silicon dioxide and tantalum pentoxide to obtain the lower distributed Bragg reflector; wherein, the thickness of each silicon dioxide layer was 91.8 nanometers, and the thickness of each tantalum pentoxide layer was 65.6 nanometers.

[0071] (2) The perovskite precursor solution was prepared according to the concentrations of PEABr at 0.16 mol / l, FABr at 0.32 mol / l, and PbBr2 at 0.4 mol / l. The corresponding perovskite is A'2A n-1 B n X 3n+1 , wherein n is 5, that is, the stoichiometric ratio of PEABr:FABr:PbBr2=2:4:5 is n=5, and the solvent used is DMF.

[0072] (3) The perovskite precursor solution prepared in step (2) was spin-coated on the lower distributed Bragg reflector prepared in step (1) at a rotation speed of 2000 rpm. The total spin-coating time was 40 seconds. At the 11th second, 155 microliters of toluene antisolvent was quickly added to the perovskite wet film. After the spin-coating was completed, the film was annealed at 85 degrees for 10 minutes and at 95 degrees for 5 minutes to obtain a polycrystalline thin film of the perovskite active layer. The luminescent phase of the perovskite active layer was mainly a perovskite phase with n greater than or equal to 5.

[0073] (4) The perovskite active layer film obtained in step (3) is placed in a vacuum of 2×10 -5 In Pa's vacuum chamber, 9.5 pairs of silicon dioxide and tantalum pentoxide were alternately deposited using an electron beam to obtain the upper distributed Bragg reflector; the thickness of the single layer of silicon dioxide was 91.8 nanometers and the thickness of the single layer of tantalum pentoxide was 65.6 nanometers.

[0074] The structural diagram of the prepared perovskite polycrystalline thin film microcavity exciton polariton device is shown inFigure 1 As shown, a lower distributed Bragg reflector, a perovskite active layer and an upper distributed Bragg reflector are arranged on a transparent substrate from bottom to top, wherein the lower distributed Bragg reflector includes several layers of silicon dioxide and tantalum pentoxide arranged alternately, wherein a layer of the upper distributed Bragg reflector in contact with the perovskite active layer is silicon dioxide, and a layer of the lower distributed Bragg reflector in contact with the perovskite active layer is silicon dioxide.

[0075] The thickness of the perovskite active layer is 100-150 nm. In this embodiment, the thickness of the perovskite active layer is 131 nm.

[0076] The lower distributed Bragg reflector includes 12.5 pairs of alternately arranged silicon dioxide layers and tantalum pentoxide layers; the upper distributed Bragg reflector includes 9.5 pairs of alternately arranged silicon dioxide layers and tantalum pentoxide layers.

[0077] The photoluminescence spectrum of the perovskite active layer polycrystalline film is as follows Figure 2 As shown, according to Figure 2 It can be seen that the luminescence of the perovskite active layer film mainly comes from the high-order perovskite phase (n≥5).

[0078] The luminescence intensity-excitation power density curve of perovskite polycrystalline thin film microcavity device is as follows: Figure 3 , the luminescence spectrum-excitation power density curve is as follows Figure 4 , angle-resolved luminescence spectrum such as Figure 5 ,according to Figure 3 、 Figure 4 、 Figure 5 It can be seen that with the increase of excitation power, the luminescence intensity only shows a linear increase, so no laser emission is achieved. The luminescence of the perovskite polycrystalline thin film microcavity exciton polariton device comes from the lower branch of the polariton, and there is no laser emission. Figure 5 As shown, the emission peak of the dispersion curve of the perovskite polycrystalline thin film microcavity device is located between the exciton energy and the photon mode energy, and red-shifts with the coupling intensity, which is consistent with the LPB (lower branch) characteristics.

[0079] Example 2

[0080] This embodiment provides a structure and preparation method of a perovskite polycrystalline thin film microcavity exciton polariton device using an intracavity pump-assisted polariton lower branch relaxation mechanism. The method of this embodiment is basically the same as that of Example 1, except that the perovskite precursor solution of this embodiment is configured with a concentration of 0.10 mol / l PEABr, 0.35 mol / l FABr and 0.40 mol / l PbBr2, that is, the stoichiometric ratio is n=8, and the perovskite material in the perovskite active layer includes at least a perovskite phase with n greater than or equal to 8 and a perovskite phase with a FAPbBr3 structure. The thickness of the perovskite active layer prepared in this embodiment is approximately 133 nanometers.

[0081] The photoluminescence spectrum of the perovskite active layer prepared in this example is as follows Figure 6 ,according to Figure 6 There is a shoulder peak at 541 nm in the luminescence peak of the perovskite. It can be seen that in addition to the luminescence from the high-order perovskite phase (n≥8), there is also luminescence from the n→∞ perovskite. That is, compared with the luminescence from only the high-order perovskite phase (n≥5) in Example 1, the perovskite phase of the FAPbBr3 structure with n→∞ can provide additional conditions for establishing intracavity pumping.

[0082] The luminescence intensity-excitation power density curve of the perovskite polycrystalline thin film microcavity exciton polariton device prepared in this embodiment is shown in FIG. Figure 7 , the luminescence spectrum-excitation power density curve is as follows Figure 8 , the angle-resolved luminescence spectrum before the laser threshold power density is as follows Figure 9 The angle-resolved luminescence spectrum after the laser threshold power density is as follows: Figure 10 ,according to Figure 7 and Figure 8 It can be seen that the luminescence of the perovskite polycrystalline thin film microcavity device shows a nonlinear increase in intensity and a narrowed half-peak width, which proves the effectiveness of the exciton laser emission. Figure 9 and Figure 10 It can be seen that the laser emission of the perovskite polycrystalline thin film microcavity device comes from the exciton polariton.

[0083] Example 3

[0084] This embodiment provides a structure and preparation method of a perovskite polycrystalline thin film microcavity exciton polariton device using an intracavity pump-assisted polariton bottom-branch relaxation mechanism, which is basically the same as Example 2, except that the concentration of PbBr2 in the perovskite precursor solution of this embodiment is 0.420 mol / l, and the concentrations of PEABr and FABr are increased proportionally, that is, the ratio of PEABr, FABr and PbBr2 is kept unchanged. The thickness of the perovskite active layer prepared in this embodiment is approximately 133.5 nanometers.

[0085] The luminescence spectrum-excitation power density curve of the perovskite polycrystalline thin film microcavity exciton polariton device prepared in this embodiment is shown in FIG. Figure 11 , the angle-resolved luminescence spectrum before the laser threshold power density is as follows Figure 12 The angle-resolved luminescence spectrum after the laser threshold power density is as follows: Figure 13 ,according to Figure 11 It can be seen that the perovskite polycrystalline thin film microcavity device can achieve laser emission. Figure 12 and Figure 13 It can be seen that the laser emission from the perovskite polycrystalline thin-film microcavity device originates from the exciton-polariton. Compared with Example 2, the polariton lower branch bottom red-shifts to 544 nanometers, and the corresponding laser emission wavelength red-shifts to 541 nanometers. This indicates that changes in the perovskite precursor solution concentration affect the thickness of the active layer film, which in turn changes the microcavity detuning and affects the position of the polariton lower branch. However, polariton laser emission can still be obtained, demonstrating the effectiveness of the strategy of using the intracavity radiation pumping mechanism to obtain exciton-polariton laser emission in the present invention.

[0086] The above examples illustrate the specific embodiments of the present invention. However, the scope of protection of the present invention is not limited to the above-mentioned exemplary embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art within the spirit and principles of the present invention shall be included in the scope of protection of the claims of the present invention.

Claims

1. An exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity, characterized in that: The laser device includes, from bottom to top, a transparent substrate, a lower distributed Bragg reflector, a perovskite active layer and an upper distributed Bragg reflector; wherein, the perovskite active layer includes a perovskite polycrystalline material, and the perovskite polycrystalline material includes a perovskite phase that can strongly couple with cavity photons and a perovskite phase that weakly couples with cavity photons.

2. The exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity according to claim 1, characterized in that: The perovskite polycrystalline material is a mixture of multiple perovskite phases, and the mixture includes at least one perovskite phase that can strongly couple with cavity photons and one perovskite phase that can weakly couple with cavity photons. The perovskite polycrystalline material is composed of an average molecular formula of A2'A n-1 B n X 3n+1 The perovskite is spin-coated from a precursor solution corresponding to the perovskite, wherein 3≤n≤10, and wherein A and A' are different, the ionic radius of A' is larger than that of A, A' is selected from any one of phenylethylamine, naphthylmethylamine, and butylamine, and A is selected from any one or more of formamidinium ion, methylamine ion, cesium ion, potassium ion, sodium ion, rubidium ion, and amine ion; B is one or more of lead ion, tin ion, and germanium ion; and X is one or more of iodide ion, bromide ion, and chloride ion.

3. The exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity according to claim 1, characterized in that: When n is infinite, A2'A n-1 B n X 3n+1 The structural equivalent is ABX3.

4. The exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity according to claim 1, characterized in that: When n≥8, the perovskite material includes the strong coupling perovskite phase A2'A n-1 B n X 3n+1 and the weakly coupled perovskite phase ABX3.

5. The exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity according to any one of claims 1 to 4, characterized in that: The perovskite polycrystalline material includes an organic ammonium halide salt with a large cation radius, BX2 and an organic ammonium halide salt with a small cation radius, wherein the molar ratio of the organic ammonium halide salt with a large cation radius, BX2 and the organic ammonium halide salt with a small cation radius is 2:n:n-1, 1≤n≤∞.

6. The exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity according to any one of claims 1 to 4, characterized in that: The upper distributed Bragg reflector includes alternating high-refractive index material layers and low-refractive index material layers; the lower distributed Bragg reflector includes alternating high-refractive index material layers and low-refractive index material layers.

7. The exciton-polariton laser device based on a perovskite polycrystalline thin film microcavity according to any one of claims 1 to 4, characterized in that: The thickness of the perovskite active layer is 90 to 180 nanometers.

8. A method for preparing the perovskite polycrystalline thin film microcavity exciton polariton device according to any one of claims 1 to 7, characterized in that: The method comprises the following preparation steps: (1) alternately forming a high refractive index material layer and a low refractive index material layer on a transparent substrate to obtain a lower distributed Bragg reflector; (2) spin-coating the perovskite precursor solution onto the lower distributed Bragg reflector obtained in step (1), rapidly adding an anti-solvent during the spin-coating process, and obtaining a perovskite active layer after annealing; (3) Alternately forming a high refractive index material layer and a low refractive index material layer on the perovskite active layer to obtain an upper distributed Bragg reflector, that is, a perovskite polycrystalline thin film microcavity device.

9. The preparation method according to claim 8, characterized in that The spin coating speed in step (2) is 1500 to 8500 rpm, the spin coating acceleration is 1000 to 8000 rpm / s, and the total spin coating time is 20 to 120 seconds.

10. The preparation method according to claim 9, characterized in that The annealing temperature in step (2) is 24-150° C., and the annealing time is 1-120 minutes; the anti-solvent in step (2) is one or more of ethyl acetate, chlorobenzene, toluene, chloroform, etc.

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