Perovskite thin film heterostructure with low ASE threshold value, preparation method thereof and laser
By setting or doping colloidal quantum dots on perovskite thin films to form heterostructures, the high threshold problem caused by hot carriers in perovskite lasers is solved, achieving low ASE threshold and high-stability gain laser output.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-31
AI Technical Summary
In perovskite lasers, the long lifetime of hot carriers leads to competition between thermal emission and non-radiative recombination and stimulated emission, which increases the gain threshold of the laser and may even cause quenching of the outgoing light.
Colloidal quantum dots are set or doped on perovskite thin films to form heterostructures. The emission wavelength of colloidal quantum dots is located between the emission wavelength of pump laser and perovskite. Charge carriers are injected into perovskite through energy level gradient, which promotes the amplification of spontaneous emission process.
It lowers the threshold for perovskite to generate gain lasers, improves luminescence intensity and stability, promotes stimulated emission, and reduces the adverse effects of hot carriers on laser output.
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Figure CN121769657A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of perovskite laser technology, and more particularly to a perovskite thin film heterostructure with a low ASE threshold, its preparation method, and a laser. Background Technology
[0002] Metal halide perovskites are represented by the chemical formula ABX3 or A2BX4, where A represents a monovalent cation, such as Cs. + Methylamine (MA) + ), formamidin (FA) + ), phenylethylamine (PEA) + ), Butylammonium (BA) + ), etc., where B is a divalent metal cation, such as Pb. 2+ or Sn 2+ X represents a halide anion, such as I. - Cl - or Br - By alloying different A-site cations and X-site anions, the absorption and emission wavelengths of perovskites can be continuously tuned across the entire visible and near-infrared spectral range. Metal halide perovskites possess excellent optical gain properties, including high photoluminescence quantum efficiency, large optical gain coefficient, and easily tunable bandgap, and exhibit large absorption coefficients in the visible and near-infrared spectral ranges. Benefiting from these superior properties, perovskite lasers using metal halide perovskites as gain media have immeasurable prospects in applications such as optical storage, optical interconnects, high-quality displays, and on-chip photonic communication.
[0003] However, perovskite materials have long hot carrier lifetimes and slow relaxation rates. In laser applications, the long-lived hot carriers can lead to competition between thermoluminescence, nonradiative recombination, and stimulated emission, which can increase the threshold for perovskite to generate gain lasers and may even cause the emitted light to quench. Summary of the Invention
[0004] This invention provides a perovskite thin film heterostructure with a low ASE threshold, which aims to reduce the threshold for perovskite lasers to generate gain laser light.
[0005] The perovskite thin film heterostructure with low ASE threshold provided by this invention includes:
[0006] A perovskite thin film; the colloidal quantum dots are disposed on the perovskite thin film or doped in the perovskite thin film; the perovskite thin film can generate a gain laser of a second preset wavelength under the excitation of a pump laser of a first preset wavelength;
[0007] Colloidal quantum dots are disposed on the perovskite film; the emission wavelength of the colloidal quantum dots is located between the first preset wavelength and the second preset wavelength.
[0008] Optionally, the material of the perovskite thin film includes perovskite with the chemical formula ABX3 or A2BX4, wherein A is Cs. + MA + FA + BA + PEA + At least one of them, B is a divalent metal cation, and X is I. - Cl - ,Br - At least one of them.
[0009] Optionally, the light emission wavelength of the colloidal quantum dots is located in the red or green light band.
[0010] Optionally, the colloidal quantum dots are at least one of CdSe, CdZnS, CdZnSe, ZnSe, ZnTe, ZnSeTe, PbS, and PbSe.
[0011] The method for preparing a perovskite thin film heterostructure with a low ASE threshold provided by the present invention includes the following steps:
[0012] S1, a perovskite thin film is prepared on a substrate; the perovskite thin film can generate a gain laser of a second preset wavelength when excited by a pump laser of a first preset wavelength.
[0013] S2, depositing colloidal quantum dots on the perovskite film; the emission wavelength of the colloidal quantum dots is located between the first preset wavelength and the second preset wavelength.
[0014] Optionally, the perovskite film is an FAPbI3 film; the FAPbI3 film is prepared by the following steps:
[0015] S11, FAI powder and PbI2 powder are mixed in a molar ratio of 1:1 and dissolved in a mixed solvent composed of DMF and DMSO to obtain FAPbI3 precursor solution;
[0016] S12, spin-coating the FAPbI3 precursor solution onto the substrate at a preset rotation speed, and spin-coating chlorobenzene onto the substrate within a preset time after spin-coating the FAPbI3 precursor solution;
[0017] S13, the spin-coated sample is annealed to obtain a crystalline FAPbI3 perovskite film.
[0018] Optionally, the colloidal quantum dots are CdSe quantum dots; the CdSe quantum dots are prepared through the following steps:
[0019] A mixture of CdO, oleic acid, and octadecane was heated to a first preset temperature under a nitrogen atmosphere to obtain a cadmium precursor solution; a mixture of Se powder and trioctylphosphine was heated to a second preset temperature to obtain a selenium precursor solution.
[0020] The cadmium precursor solution is heated to a third preset temperature, and then the selenium precursor solution is added to the cadmium precursor solution for a preset reaction time. After the reaction, the mixed solution is lowered to a fourth preset temperature, and a preset amount of Cd(OA)2 and S-TOP solution is added to the mixed solution for a preset reaction time. After the reaction is completed, the reactants are lowered to a fifth preset temperature for washing and purification to obtain core-shell structured CdSe quantum dots.
[0021] Optionally, the colloidal quantum dots are CdSe quantum dots, and the deposition of colloidal quantum dots on the perovskite film specifically includes the following steps:
[0022] A CdSe quantum dot solution with a concentration of 50 g / ml was spin-coated onto the perovskite film at a speed of 2000 rpm.
[0023] The sample after spin-coating with CdSe quantum dot solution was annealed at 90℃ for 5 min.
[0024] Optionally, the method for preparing a perovskite thin film heterostructure with a low ASE threshold further includes step S3, which involves hot-pressing the sample deposited with colloidal quantum dots at a preset pressure and a preset temperature.
[0025] The present invention also proposes a laser comprising the perovskite thin film heterostructure with low ASE threshold described above or the perovskite thin film heterostructure with low ASE threshold prepared by the above preparation method.
[0026] The present invention has the following beneficial effects:
[0027] The perovskite thin film heterostructure proposed in this invention includes a perovskite thin film and colloidal quantum dots disposed on or doped therein. The perovskite serves as the gain medium for a laser, undergoing amplified spontaneous emission under pump laser excitation to generate a gain laser. The emission wavelength of the colloidal quantum dots lies between the pump laser wavelength and the perovskite emission wavelength, thus creating an energy level gradient between the colloidal quantum dots and the perovskite. When the colloidal quantum dots are excited by the pump laser, they generate a large number of charge carriers. This energy level gradient drives the charge carriers in the colloidal quantum dots to be injected into the perovskite through a funnel effect (via Forster resonance energy transfer, charge transfer, etc.). This energy transfer process is faster than the stimulated emission process of the perovskite and can be considered as part of the population inversion of the perovskite, promoting amplified spontaneous emission and ultimately achieving the particle inversion conditions required for lasing. Compared to schemes that rely solely on the perovskite itself to generate charge carriers (the hot charge carriers generated by the perovskite itself have a long lifetime and a slow relaxation rate), this invention provides the perovskite with additional charge carriers through colloidal quantum dots, which can be used to achieve the conditions for amplified spontaneous emission, thus promoting the stimulated emission process of the perovskite and lowering the threshold for the perovskite to generate gain lasers. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0029] Figure 1 These are schematic diagrams of some embodiments of the perovskite thin film heterostructure with low ASE threshold proposed in this invention.
[0030] Figure 2 This is a schematic diagram illustrating the principle of the low ASE threshold perovskite thin film heterostructure proposed in this invention.
[0031] Figure 3 The ASE emission spectra of the samples in the embodiments and comparative examples of this invention are shown below.
[0032] Figure 4 The figure shows a comparison of the luminescence intensity statistics of the sample and the comparative sample under different pump laser energy densities (a), and a statistical graph of ASE luminescence intensity and spectral linewidth (b).
[0033] Figure 5 The images show the ASE emission spectra of the sample and the comparative sample of the present invention under different pump laser energy densities.
[0034] Figure 6The ASE emission spectra of the sample and the comparative sample of the present invention after being irradiated by laser in air for 24 hours are shown.
[0035] Figure 7 This is a statistical graph showing the change in ASE emission intensity over time after the sample of this embodiment of the invention was irradiated by laser in air for 24 hours.
[0036] Explanation of reference numerals in the attached figures: 1. Substrate; 2. Perovskite film; 3. Colloidal quantum dots; 4. Transparent encapsulation layer. Detailed Implementation
[0037] To make the objectives, features, and advantages of this invention more apparent and understandable, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described below are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0038] The terms "first," "second," "third," "fourth," etc. (if present) in the specification and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.
[0039] Experimental methods in the embodiments of this invention that do not specify specific conditions are generally performed under conventional conditions and conditions described in the manual, or under conditions recommended by the manufacturer; the general equipment, materials, reagents, etc. used are commercially available unless otherwise specified.
[0040] The technical terms are explained below:
[0041] Perovskite laser: A laser device that uses perovskite material as the gain medium and achieves optical amplification through stimulated emission.
[0042] FAPbI3 perovskite: ABX3 type formamidinium lead iodide perovskite (chemical formula CH(NH2)2PbI3), with a band gap of approximately 1.48 eV, is a commonly used material for near-infrared perovskite light-emitting devices.
[0043] Colloidal quantum dots (CQDs): Colloidal quantum dots are semiconductor nanostructures that can bind excitons in three spatial directions, and their band gap width is adjustable with size.
[0044] Amplified spontaneous emission (ASE): When the excitation intensity exceeds the threshold, the photons spontaneously emitted in the material are amplified by the gain and output a narrow bandwidth, highly directional beam (without a strict resonant cavity). Whether amplified spontaneous emission can be generated is the key basis for judging whether a material has laser gain capability.
[0045] Hot carriers and hot carrier relaxation: Hot carriers refer to carriers with energy higher than the Fermi level, which are in a non-thermal equilibrium state; hot carrier relaxation refers to hot carriers gradually releasing excess energy through interaction with the lattice and other carriers, eventually returning to a thermal equilibrium state.
[0046] Thermoluminescence effect: When a material is excited by light, the hot carriers undergo radiative recombination before sufficient thermal relaxation, resulting in a phenomenon where the energy is higher than that of band-edge emission, competing with amplified spontaneous emission.
[0047] Radiative recombination and non-radiative recombination: Radiative recombination refers to the recombination of electrons and holes, which releases a photon; non-radiative recombination refers to the recombination of electrons and holes, which does not emit a photon, but instead converts energy into other forms, such as heat (phonons), vibration, defect trapping, etc.
[0048] Funnel effect: The physical phenomenon in which charge carriers, under the influence of a concentration gradient or a built-in electric field, are directionally accumulated and rapidly transported to a specific region, much like water flowing through a funnel. For heterojunctions, the band gap difference leads to the formation of a continuous energy level gradient between the two layers of material, and the diffusion driving force of the energy level gradient leads to the formation of the funnel effect.
[0049] Transient fluorescence spectroscopy (TRPL) is a characterization technique that uses short-pulse lasers to excite materials and record the curve of photoluminescence intensity decaying over time, thereby analyzing parameters such as carrier lifetime and recombination ratio. It is used to evaluate the quality of perovskite materials and device performance.
[0050] Unless otherwise specified, the perovskite in this invention refers to metal halide perovskite with the chemical formula ABX3.
[0051] Perovskite materials have a long hot carrier lifetime and a slow relaxation rate. In the field of solar cells, the photoelectric conversion efficiency is mainly determined by the band gap energy of the absorbing material. The absorbing material needs to have a relatively slow hot carrier relaxation or cooling rate so that it can maintain a relatively high energy level for a long time and ensure that the hot carrier extraction process can be carried out efficiently. Therefore, the long hot carrier lifetime makes perovskite materials suitable for solar cells. However, in laser applications, the long hot carrier lifetime can lead to competition between thermoluminescence, stimulated emission and non-radiative recombination, which can increase the threshold for perovskite to generate gain laser and even cause the emitted light to quench.
[0052] To address the problems encountered by perovskites in laser applications, this invention provides a perovskite thin film heterostructure with a low ASE threshold.
[0053] The low ASE threshold perovskite thin film heterostructure provided in this embodiment of the invention includes a perovskite thin film and colloidal quantum dots; wherein, the perovskite thin film can generate a gain laser of a second preset wavelength under the excitation of a pump laser of a first preset wavelength; the emission wavelength of the colloidal quantum dots is located between the first preset wavelength and the second preset wavelength.
[0054] See Figure 1 In some embodiments, the perovskite thin film 2 is disposed on the substrate 1, such as... Figure 1 As shown in (a), colloidal quantum dots 3 are disposed on the perovskite thin film 2 in the form of a layer; in other embodiments, such as Figure 1 As shown in (b), colloidal quantum dots 3 can also be doped into perovskite thin film 2; both of these bonding morphologies are common morphologies of heterostructures. It is understood that in this invention, the doping morphology of colloidal quantum dots and the layered heterostructure morphology have similar functional properties and can achieve the same or similar beneficial effects. The following embodiments use the layered heterostructure morphology to illustrate the technical solution of this invention in detail.
[0055] Perovskite thin films exhibit amplified spontaneous emission under pump laser excitation. The core condition for amplified spontaneous emission is population inversion, which requires the pump laser to increase the number of high-energy carriers in the perovskite film to a greater number of low-energy carriers, ensuring that stimulated emission exceeds stimulated absorption. However, due to the long lifetime and slow relaxation rate of the hot carriers generated by the perovskite film itself, competition arises between thermoluminescence, nonradiative recombination, and stimulated emission. This reduces the number of high-energy carriers available for stimulated emission, delays the achievement of the population inversion condition, and increases the threshold for amplified spontaneous emission. In other words, a higher pump laser energy is required to generate a sufficient number of high-energy carriers to achieve the population inversion condition.
[0056] The perovskite thin film heterostructure proposed in this invention includes a perovskite thin film and colloidal quantum dots disposed thereon or doped therein; wherein, the perovskite serves as the gain medium of a laser, undergoing amplified spontaneous emission under the excitation of a pump laser, thereby generating a gain laser; the emission wavelength of the colloidal quantum dots is located between the pump laser wavelength and the emission wavelength of the perovskite, thus forming an energy level gradient between the colloidal quantum dots and the perovskite, and the energy transfer process is described in [reference needed]. Figure 2 In (a), the band gap of colloidal quantum dots is larger than that of perovskites (having a lower valence band top and a higher conduction band bottom). Colloidal quantum dots, acting as energy transfer mediators, will absorb the pump laser energy (E). pumping The energy is naturally released into the perovskite with a narrower band gap through the energy level gradient ∆E, and the perovskite then emits light through spontaneous emission. Figure 2E in emission (Process); specifically, see [link to relevant documentation]. Figure 2 In (b), when colloidal quantum dots are excited by a pump laser, a large number of charge carriers are generated. Figure 2 As shown in (a), the energy level gradient drives the carriers in the colloidal quantum dot to be injected into the perovskite through the funnel effect. The diffusion process of these carriers is faster than the stimulated emission process of the perovskite.
[0057] The charge carriers diffused into the perovskite by the colloidal quantum dot layer can serve as part of the population inversion quantity of the perovskite, promoting the achievement of the particle inversion condition required for amplified spontaneous emission. Compared with the scheme that relies solely on the perovskite itself to generate charge carriers, the embodiments of the present invention provide the perovskite with additional charge carriers that can be used to achieve the amplified spontaneous emission condition through colloidal quantum dots, promoting the stimulated emission process of the perovskite, thereby reducing the threshold for the perovskite to generate gain laser.
[0058] In embodiments of the present invention, the perovskite used to generate gain laser light includes, but is not limited to, three-dimensional perovskite and two-dimensional perovskite; wherein, the chemical formula of three-dimensional perovskite can be represented as ABX3, and the chemical formula of two-dimensional perovskite can be represented as A2BX4, where A can be selected from Cs. + MA + FA + PEA + One or more of the following, where B is a divalent metal cation and X is I. - Cl - ,Br - At least one of the following, some typical perovskite materials such as CsPbCl3, CsPbBr3, MAPbBr3, (PEA)2PbBr4, CsPbBr 3-x Cl x (BA)2PbB4, CsPbI 3-x Br x MASnI3, FA 0.75 Cs 0.25 Sn 0.5 Pb 0.5 I3 and other materials can be used as perovskite thin film materials in this invention. In addition, some quasi-two-dimensional perovskites, or inorganic perovskites and organic-inorganic hybrid perovskites not mentioned in the above examples, as long as the perovskite material can generate gain laser under the action of a pump laser of a certain wavelength, are all suitable for the technical solution of this invention.
[0059] In some preferred embodiments, the perovskite film is a FAPbI3 film; currently, in perovskite near-infrared laser applications, FAPbI3 is a gain medium with excellent overall performance in the 850nm wavelength window.
[0060] In some preferred embodiments, colloidal quantum dots in the red or green light bands are selected for perovskite near-infrared laser applications; the fabrication process of colloidal quantum dots in the red and green light regions is more mature, and the device stability and repeatability are also higher.
[0061] In this embodiment of the invention, the emission wavelength of the colloidal quantum dots is located between the pump laser wavelength and the gain laser wavelength emitted by the perovskite. The colloidal quantum dots include, but are not limited to, CdSe system quantum dots, Zn-based quantum dots, Pb-based quantum dots, etc., such as one or more of CdSe, CdZnS, CdZnSe, ZnSe, ZnTe, ZnSeTe, PbS, PbSe, etc., or heterojunctions. The structural types of quantum dot materials include, but are not limited to, alloy type, doped type, special assembly structure (e.g., core-shell structure), etc.
[0062] In some preferred embodiments, the colloidal quantum dots can be CdSe quantum dots; the optical properties of CdSe quantum dots are precisely controllable, their preparation and processing are convenient, and their stability can be improved through structural optimization.
[0063] In some preferred embodiments, see [reference] Figure 1 The perovskite film heterostructure with a low ASE threshold also includes a transparent encapsulation layer 4, which is disposed on the perovskite film 2 and the colloidal quantum dot 3. The transparent encapsulation layer 4 is used to isolate water and oxygen and improve the stability of the perovskite film heterostructure. The material of the transparent encapsulation layer 4 is preferably polymethyl methacrylate (PMMA).
[0064] In some embodiments, perovskite thin film heterostructures with low ASE thresholds can be prepared by the following steps:
[0065] S1, a perovskite thin film is prepared on the substrate; the perovskite thin film can generate a gain laser of a second preset wavelength when excited by a pump laser of a first preset wavelength.
[0066] S2, depositing colloidal quantum dots on a perovskite film; the emission wavelength of the colloidal quantum dots is between a first preset wavelength and a second preset wavelength.
[0067] For embodiments where the perovskite film is a FAPbI3 film, in some preferred embodiments, the FAPbI3 film can be prepared by the following steps:
[0068] S11, FAI (formamidinium iodide, used to provide formamidinium cations for perovskite structures) powder and PbI2 powder are mixed in a molar ratio of 1:1 and dissolved in a mixed solvent composed of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) to obtain FAPbI3 precursor solution;
[0069] S12, spin-coat the FAPbI3 precursor solution onto the substrate at a preset rotation speed, and spin-coat chlorobenzene onto the substrate within a preset time after spin-coating the FAPbI3 precursor solution; chlorobenzene, as an anti-solvent, can reduce the solubility of the solvent in the perovskite precursor, induce rapid nucleation and crystallization of the perovskite, which helps to generate a uniform and dense thin film structure.
[0070] S13, anneal the spin-coated sample to obtain a crystalline FAPbI3 perovskite film; preferably, a temperature gradient progressive annealing method can be used to improve the film density.
[0071] The precursor solution concentration, spin coating speed, spin coating time for chlorobenzene, and annealing temperature can be optimized according to actual experimental / production conditions.
[0072] For embodiments where the colloidal quantum dots are CdSe quantum dots, in some preferred embodiments, the CdSe quantum dots can be prepared by the following steps:
[0073] A mixture of CdO, oleic acid (OA), and octadecane was heated to a first preset temperature under a nitrogen atmosphere. CdO reacted with oleic acid to generate cadmium oleate (Cd(OA)2). Octadecane served as a high-boiling-point non-coordinating solvent to provide a stable high-temperature reaction environment, and the reaction yielded a cadmium precursor solution. A mixture of Se powder and trioctylphosphine (TOP) was heated to a second preset temperature. Trioctylphosphine served as a coordinating solvent to coordinate with Se, yielding a selenium precursor solution (Se-TOP).
[0074] The cadmium precursor solution was heated to a third preset temperature, and then a selenium precursor solution was added to the cadmium precursor solution for a preset reaction time. Se-TOP reacted with (Cd(OA)2) to generate CdSe crystal nuclei. After the reaction, the mixed solution was lowered to a fourth preset temperature, and a preset amount of Cd(OA)2 and S-TOP solution (a complex formed by S and trioctylphosphine) were added to the mixed solution for a preset reaction time. Cd(OA)2 and S-TOP reacted to generate CdS, and CdS covered the surface of the CdSe crystal nuclei to form a shell. After the reaction was completed, the reactants were lowered to a fifth preset temperature for washing and purification to obtain core-shell structured CdSe quantum dots.
[0075] The concentrations of cadmium precursor solution, selenium precursor solution, preset amounts of Cd(OA)2 and S-TOP solutions used to form the CdS shell, first preset temperature, second preset temperature, third preset temperature, fourth preset temperature, and fifth preset temperature can be optimized according to actual experimental / production conditions.
[0076] For embodiments where the colloidal quantum dots are CdSe quantum dots, in some preferred embodiments, the deposition of colloidal quantum dots on a perovskite film specifically includes the following steps: spin-coating a CdSe quantum dot solution with a concentration of 50 g / ml onto the perovskite film at a rotation speed of 2000 rpm; annealing the sample after spin-coating the CdSe quantum dot solution at 90°C for 5 min; under these experimental conditions, CdSe quantum dots can be uniformly covered on the perovskite film, achieving a good film formation effect.
[0077] Furthermore, in some preferred embodiments, after depositing colloidal quantum dots on the perovskite film, the process may further include: hot-pressing the sample with deposited colloidal quantum dots at a preset pressure and a preset temperature. The hot-pressing method allows for recrystallization of the perovskite, resulting in a denser film with a smoother morphology and lower surface roughness, thereby reducing scattering within the film, enhancing photoluminescence intensity, and improving the stability of perovskite luminescence. In some specific embodiments, after depositing colloidal quantum dots on the perovskite film, a transparent encapsulation layer is first spin-coated onto the sample surface to prepare the transparent encapsulation layer before hot-pressing the sample.
[0078] Based on the above embodiments, in order to more clearly illustrate the implementation and beneficial effects of the technical solution of the present invention, the present invention also proposes the following specific embodiments. It should be noted that the following specific embodiments are merely exemplary and do not constitute any limitation on the scope of protection of the present invention.
[0079] Example 1
[0080] Prepare a quartz substrate-perovskite-CQD-PMMA structure.
[0081] Step 1, Preparation of FAPbI3 thin film:
[0082] FAI powder and lead iodide (PbI2) powder were mixed in a molar ratio of 1:1, and then the mixed powder was added to a solvent of DMF:DMSO = 8:1 to obtain a FAPbI3 precursor solution with a concentration of 300 mg / ml.
[0083] The FAPbI3 precursor solution was spin-coated onto a quartz substrate at a speed of 3000 rpm. Within 30 seconds after spin-coating the FAPbI3 precursor solution, chlorobenzene was spin-coated onto the quartz substrate as an anti-solvent. The anti-solvent can reduce the solubility of the solvent in the perovskite precursor, induce rapid nucleation and crystallization of perovskite, and help generate a uniform and dense thin film structure.
[0084] The spin-coated samples were subjected to progressive annealing at 110 / 130 / 150℃ to eventually form a smooth and dense black crystalline FAPbI3 perovskite film.
[0085] Step 2, Preparation of CdSe colloidal quantum dots:
[0086] A mixture of CdO, oleic acid, and octadecane was heated to 210°C under a nitrogen atmosphere to react and obtain a cadmium precursor solution; Se powder was heated to 150°C to react and obtain a selenium precursor solution.
[0087] The cadmium precursor solution was heated to 280°C, and then the selenium precursor solution was injected into the cadmium precursor solution. After reacting for about 1 hour, the temperature of the reaction system was lowered to 260°C, and a small amount of Cd(OA)2 and S-TOP solution was slowly added to form a CdSe / CdS core / shell structure.
[0088] After the reaction was completed, the reaction system was cooled to about 80°C. The resulting reaction product was purified by washing with hexane / ethanol, and then the washed product was redispersed in chlorobenzene to form a CdSe colloidal quantum dot solution with a concentration of about 50 mg / mL. The resulting CdSe colloidal quantum dot solution was transparent red, and the emission peak of the CdSe colloidal quantum dots was located in the red light band, exhibiting high luminescence efficiency and good dispersion stability. Using chlorobenzene as a dispersion solvent can improve the compatibility of quantum dots with perovskite precursors and the uniformity of film formation.
[0089] This step can be completed before or after step 1, and the prepared CdSe colloidal quantum dot solution is ready for use.
[0090] Step 3: Spin-coat the CdSe colloidal quantum dot solution onto the FAPbI3 thin film:
[0091] A CdSe quantum dot solution with a concentration of 50 g / ml was spin-coated onto a perovskite film at a speed of 2000 rpm; the sample after spin-coating the CdSe quantum dot solution was annealed at 90 °C for 5 min.
[0092] Step 4, Prepare the PMMA encapsulation layer:
[0093] PMMA solution was spin-coated onto the surface of a sample with a CdSe colloidal quantum dot layer, and then dried to form a PMMA encapsulation layer.
[0094] Step 5, hot pressing treatment:
[0095] With a size of 14.7×14.7mm 2 Taking the sample area as an example, a pressure of about 69 bar is applied to the sample surface, and the sample is hot-pressed at this pressure for 5 minutes at an imprinting temperature of 140°C, finally obtaining a sample with a quartz substrate-perovskite-CQD-PMMA structure.
[0096] Comparative Example 1
[0097] Prepare a quartz substrate-perovskite-PMMA structure.
[0098] This comparative example is based on Example 1, except that instead of spin-coating CdSe colloidal quantum dots onto the FAPbI3 film, PMMA is directly spin-coated for encapsulation, resulting in a sample with a quartz substrate-perovskite-PMMA structure.
[0099] Transient fluorescence spectroscopy was performed on the samples from Example 1 and Comparative Example 1. The samples were pumped using a 532 nm nanosecond laser and a 355 nm quasi-nanosecond laser, respectively. At high pump energy densities, the emission spectra of the samples are shown below. Figure 3 As shown (horizontal axis is wavelength, vertical axis is photoluminescence (PL) intensity), where the red line represents the example (with QD) and the black line represents the comparative example (without QD). The ASE emission wavelength of perovskite is λ = 820 nm. Figure 3 The results show that at λ=820nm, the ASE luminescence intensity of the example sample is significantly higher than that of the comparative sample, regardless of whether the pump laser is 532nm or 355nm. This indicates that the introduction of the colloidal quantum dot layer enhances the ASE luminescence intensity of the perovskite film.
[0100] Furthermore, the threshold can be determined by the nonlinear inflection point of the sudden increase in spectral intensity and the sudden decrease in linewidth. Similar to laser emission, when the gain exceeds the loss, that is, when the pump intensity exceeds the threshold, the emitted light intensity will suddenly increase, forming a nonlinear inflection point at the threshold, and at the same time, the spectral linewidth will suddenly decrease.
[0101] By varying the energy density of the pump laser, the luminescence intensity data of the example sample (wQD) and the comparative sample (woQD) at wavelengths of 800 nm and 820 nm were statistically analyzed. The results are as follows: Figure 4 As shown in (a) (the left ordinate represents photoluminescence (PL) intensity, and the right ordinate represents the ratio of luminescence intensity of the example sample to the comparative sample (P_w.QD / P_wo QD)), the luminescence intensity of the example sample and the comparative sample at 800 nm wavelength is essentially zero and does not change with pump laser energy, indicating that 800 nm is not the ASE emission wavelength of perovskite; the pump laser energy density of the example sample and the comparative sample is close to 40 μJ·cm. -2 The pump laser began generating 820nm light, and the higher the energy of the pump laser, the greater the luminescence intensity. After ASE emission was generated, the 820nm luminescence intensity of the example sample was consistently higher than that of the comparative sample, with a ratio greater than 1. This is consistent with... Figure 3 The results are consistent, indicating that the introduction of the colloidal quantum dot layer enhances the ASE luminescence intensity of the perovskite film.
[0102] By varying the energy density of the pump laser, the luminescence intensity and spectral linewidth of the example sample (w.QD) and the comparative sample (wo.QD) were statistically analyzed. The results are as follows: Figure 4 As shown in (b) (the left ordinate is the photoluminescence (PL) intensity, and the right ordinate is the full width at half maximum (FVHM)), the sample of the example produced an inflection point in the output light intensity and linewidth at a lower pump laser energy density, indicating that the introduction of the colloidal quantum dot layer reduced the threshold for the perovskite film to generate gain laser.
[0103] Figure 5 The specific spectra of sample emission under different pump laser energy densities are shown. Figure 5 (a) in the figure is the spectrum of the comparative sample, with an emission threshold of approximately 34 μJ·cm⁻¹. -2 , Figure 5 (b) in the figure is the spectrum of the sample in the example, with an emission threshold of approximately 30 μJ·cm. -2 This further illustrates that the introduction of the colloidal quantum dot layer lowers the threshold for gain lasing generation in perovskite films. Figure 5 (b) also shows the emission wavelength of CdSe quantum dots at around 630 nm (red band), but the overall energy shifts to the near-infrared peak at around 820 nm. The energy in the red band does not increase with the increase of pump energy density.
[0104] Furthermore, the stability of the example samples and comparative samples was analyzed. Both groups of samples were placed in air and at room temperature, and then irradiated with a laser for 24 hours. After 24 hours, transient fluorescence spectroscopy was performed on the samples, and the results are as follows. Figure 6 As shown; Figure 6 (a) shows the emission spectrum of the comparative sample. The results indicate that after being placed in air for 24 hours, the threshold for gain laser emission of the comparative sample decreased from 34 μJ·cm⁻¹. -2 Increased to 43.7 μJ·cm -2 The increase reached 9.7 μJ·cm -2 ; Figure 6 (b) shows the emission spectrum of the example sample. The results indicate that after being placed in air for 24 hours, the threshold for generating gain laser light in the example sample decreased from 30 μJ·cm⁻¹. -2 Increased to 34.4 μJ·cm -2 It only increased by 4.4 μJ·cm -2 The increase was significantly lower than that of the comparative sample, indicating that the introduction of the colloidal quantum dot layer improved the stability of the luminescence threshold of the perovskite film.
[0105] In addition, the luminescence intensity stability test was performed on the example samples after being placed in air for 24 hours. During the test, the emission intensity at a fixed wavelength was monitored. The experiment showed that as the pump laser irradiation time increased, the emission peak of the example samples gradually blue-shifted from approximately 819.5 nm to 816.5 nm. This may be because the migration of iodine ions or slight iodine loss in the perovskite film under long-term excitation caused lattice contraction, resulting in an increase in the effective band gap of the material. The results of the emission intensity change over time are as follows: Figure 7 As shown, due to the blue shift of the emission peak causing a mismatch between the monitoring wavelength and the actual peak value, the monitoring wavelength needs to be changed in the experiment. For ease of display, the change in monitoring wavelength when the blue shift occurs is shown in... Figure 7 The horizontal axis is broken in half. Figure 7 The results showed that as the duration of pump laser irradiation increased, the emission intensity of the sample gradually decreased, and after 24 hours it still had 15% of the initial intensity.
[0106] In summary, by introducing a colloidal quantum dot layer onto the perovskite thin film, the embodiments of the present invention not only effectively reduce the threshold for gain laser generation of the perovskite thin film, but also improve the ASE luminescence intensity and luminescence stability of the perovskite thin film to a certain extent, which is of great value for the application of perovskite lasers.
[0107] The perovskite laser with the low ASE threshold perovskite thin film heterostructure proposed in this invention is suitable for many application fields, including but not limited to novel micro laser displays, virtual reality / augmented reality optical engines, gas / environmental monitoring, medical diagnostics, optical computing, and on-chip integrated laser arrays.
[0108] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.
Claims
1. A low ASE threshold perovskite thin film heterostructure, characterized in that, The application relates to a perovskite film heterostructure with a low ASE threshold. The perovskite film can generate gain laser of a second preset wavelength under the excitation of pump laser of a first preset wavelength. The colloidal quantum dots are arranged on the perovskite film or doped in the perovskite film, and the light-emitting wavelength of the colloidal quantum dots is between the first preset wavelength and the second preset wavelength. The light-emitting wavelength of the colloidal quantum dots is in the red light or green light band.
2. The low ASE threshold perovskite thin film heterostructure of claim 1, wherein, The material of the perovskite thin film includes a perovskite of a chemical formula of ABX3 or A2BX4, wherein A is at least one of Cs + , MA + , FA + , BA + , PEA + , B is a divalent metal cation, and X is at least one of I - , Cl - , Br - .
3. The low ASE threshold perovskite thin film heterostructure of claim 1, wherein, The colloidal quantum dots are at least one of CdSe, CdZnS, CdZnSe, ZnSe, ZnTe, ZnSeTe, PbS and PbSe.
4. The low ASE threshold perovskite thin film heterostructure of claim 1, wherein, The application further relates to a preparation method of the perovskite film heterostructure.
5. A method for preparing a perovskite thin film heterostructure with a low ASE threshold, characterized in that, S1, preparing a perovskite film on a substrate; the perovskite film can generate gain laser of a second preset wavelength under the excitation of pump laser of a first preset wavelength; S2, depositing colloidal quantum dots on the perovskite film; the light-emitting wavelength of the colloidal quantum dots is between the first preset wavelength and the second preset wavelength. The perovskite film is an FAPbI3 film; the FAPbI3 film is prepared by the following steps.
6. The method of claim 5, wherein the method further comprises: S11, mixing FAI powder and PbI2 powder in a molar ratio of 1:1 and dissolving the mixture in a mixed solvent composed of DMF and DMSO to obtain an FAPbI3 precursor solution; S12, spin coating the FAPbI3 precursor solution on a substrate at a preset rotating speed, and spin coating chlorobenzene on the substrate within a preset time after spin coating the FAPbI3 precursor solution; S13, annealing the sample after spin coating to obtain a crystallized FAPbI3 perovskite film. The colloidal quantum dots are CdSe quantum dots; the CdSe quantum dots are prepared by the following steps.
7. The method of claim 5, wherein the method further comprises: A mixture of CdO, oleic acid and octadecane is heated to a first preset temperature under a nitrogen atmosphere to obtain a cadmium precursor solution; a mixture of Se powder and trioctylphosphine is heated to a second preset temperature to obtain a selenium precursor solution; The cadmium precursor solution is heated to a third preset temperature, then the selenium precursor solution is added to the cadmium precursor solution to react for a preset time, after the reaction, the mixed solution is reduced to a fourth preset temperature, a preset amount of Cd(OA)2 and S-TOP solution is added to the mixed solution to react for a preset time, after the reaction, the reactants are reduced to a fifth preset temperature for washing and purification to obtain CdSe quantum dots with a core-shell structure. The colloidal quantum dots are CdSe quantum dots; depositing colloidal quantum dots on the perovskite film specifically includes the following steps.
8. The method for preparing a perovskite thin film heterostructure with a low ASE threshold according to claim 5, characterized in that, CdSe quantum dot solution with a concentration of 50 g / ml is spin coated on the perovskite film at a rotating speed of 2000 rpm; The sample after spin coating the CdSe quantum dot solution is annealed at 90 DEG C for 5 min. The application further relates to a preparation method of the perovskite film heterostructure.
9. The method of claim 5, wherein the method further comprises: The application relates to a perovskite film heterostructure with a low ASE threshold. 10. A laser characterized by,