An erbium / ytterbium co-doped perovskite near-infrared light-emitting thin film and its light-emitting diode

Abstract

The present invention discloses an erbium / ytterbium co-doped perovskite near-infrared luminescent thin film and a light-emitting diode thereof. By using rare-earth erbium, ytterbium and cesium acetates to replace the corresponding chlorides as the erbium, ytterbium and cesium sources respectively, the problem that lead dichloride precipitates in the dimethyl sulfoxide solution and ytterbium ions precipitate in the methanol solution due to the increase of chloride ions during the preparation of the erbium / ytterbium co-doped perovskite thin film by the solution method is solved. The effective doping of erbium / ytterbium ions replacing the lead ion lattice positions is realized, the doping amount of erbium ions is increased, the film-forming quality is improved, the defect density and its non-radiative recombination probability are reduced, and the luminescence performance of the erbium-doped perovskite near-infrared luminescence at 1.54 microns is significantly improved.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of novel electronic components, and particularly relates to an erbium / ytterbium co-doped perovskite near-infrared light-emitting thin film and a light-emitting diode thereof. Background Art

[0002] Pure inorganic perovskite CsPbX 3 (X = Cl, Br, I) materials have excellent optoelectronic properties, including tunable luminescence, high photoluminescence quantum efficiency, high carrier mobility, simple preparation, low cost, solution processability, etc. In recent years, significant progress has also been made in the research on 1.54-μm photoluminescence of erbium-doped perovskite:

[0003] In terms of the solution method: In 2021, Miyasaka et al. in Japan used perchlorometal salts as the sources of chloride ions and various metal ions to prepare an erbium-doped perovskite thin film Er / Yb:CsPbX 3 , and the external quantum efficiency of its 1.54-μm photoluminescence reached 12.6%, which was the highest value reported at that time.

[0004] In terms of the quantum dot method: Artizzu et al. prepared an erbium / ytterbium co-doped perovskite 1.54-μm photoluminescence material by using rare earth acetates, and its external quantum efficiency reached 6%; however, both of these two methods stopped at the aspect of photoluminescence and did not further achieve 1.54-μm near-infrared electroluminescence of erbium. The reasons are:

[0005] First: The counter anions used in the solution method are all chloride ions. Since the solubility of the chlorides formed between chloride ions and the cations (lead, cesium) in the system is very low, in the case of high rare earth ion doping, a small amount of metal chlorides precipitate out in the prepared thin film and currently cannot be effectively overcome, which seriously hinders the transport of carriers inside the light-emitting layer.

[0006] Second: There are literature reports on using metal acetates as metal sources in the quantum dot method. The prepared erbium-doped perovskite thin film effectively solves the problem of precipitation and significantly improves its film-forming quality. However, in order to maintain the stability of the quantum dots, ligand coating is required. The polarity of common ligands such as oleic acid and oleylamine is weak, and the presence of a large amount of ligands severely restricts the transport of charges inside the light-emitting layer.

[0007] Therefore, both of the above two methods significantly affect the effective transport of carriers inside the light-emitting layer, resulting in the inability to achieve 1.54-μm near-infrared electroluminescence of erbium-doped perovskite.

[0008] There are also literatures that disclose the combined use of acetate (Ac - ) and thiocyanate (SCN -) Reports on the preparation of highly efficient and uniform perovskite-based solar cell devices. Solar cells and light-emitting diodes are two processes with similar basic structures but completely opposite functions. Summary of the Invention

[0009] The object of the present invention is to provide an erbium / ytterbium co-doped perovskite near-infrared light-emitting thin film and a light-emitting diode thereof.

[0010] The innovation of the present invention lies in that this method overcomes the precipitation of metal chlorides caused by high-concentration rare-earth doping in the current solution method and the adverse effects of the presence of weakly polar organic ligands on the carrier transport performance in the quantum dot method, realizes the effective doping of erbium / ytterbium ions substituting for lead ion lattice sites, increases the doping amount of erbium ions, improves the film-forming quality, reduces the defect density and its non-radiative recombination probability, significantly enhances the luminescence performance of erbium-doped perovskite near-infrared luminescence at 1.54 microns, with a photoluminescence efficiency of 30.12%, which is 2.4 times the highest value reported internationally at present, and for the first time realizes the near-infrared electroluminescence of erbium-doped perovskite at 1.54 microns. The external quantum efficiency of its near-infrared light-emitting diode is 0.37%, which is 336 times that of erbium-based organic electroluminescent devices (OLEDs).

[0011] To achieve the above-mentioned invention object, the technical solution of the present invention is as follows:

[0012] An erbium / ytterbium co-doped perovskite near-infrared light-emitting thin film, and a preparation method of the erbium / ytterbium co-doped perovskite near-infrared light-emitting thin film, comprising the following steps:

[0013] (1) Add ytterbium(III) acetate tetrahydrate [Yb(CH 3 COO) 3 ·4H 2 O], erbium(III) acetate tetrahydrate [Er(CH 3 COO) 3 ·4H 2 O] and lead dichloride (PbCl 2 ) to dimethyl sulfoxide (DMSO) solvent, heat and stir until completely dissolved, and obtain solution A after filtration;

[0014] (2) Add ytterbium(III) chloride hexahydrate (YbCl 3 ·6H 2 O) and cesium acetate (CH 3 COOCs) to methanol solvent, stir and heat under reflux until clear to obtain solution B;

[0015] (3) Dropwise add and spin-coat solution A on a substrate, then heat and anneal, and then spin-coat solution B thereon and heat and anneal to obtain a fully crystallized erbium / ytterbium co-doped perovskite thin film;

[0016] The lead dichloride used in step (1) needs to be fully dried;

[0017] The ytterbium(III) chloride hexahydrate used in step (2) needs to be fully dried;

[0018] The structure of the perovskite obtained in step (3) is one of the CsPbX 3 type and Cs 4 PbX 6 among them.

[0019] Furthermore, the specific process of step (1) is as follows: Prepare a mixed solution containing 0.8 M lead dichloride and ytterbium(III) acetate tetrahydrate and erbium(III) acetate tetrahydrate with different molar concentration ratios; among them, the sum of the molar concentrations of Yb 3+ and Er 3+ is 0.9 M, and the change range of Er 3+ is 0 - 0.9 M, with a change interval of 0.1 M; Heat the mixed solution to 70 °C and continuously stir until completely dissolved; Filter the prepared solution through a polytetrafluoroethylene filter with a pore size of 0.22 μm to obtain solution A.

[0020] Furthermore, the concentration of Yb 3+ in step (2) is 0.1 M - 0.2 M, and the concentration of Cs + is 0.1 M - 0.3 M.

[0021] Furthermore, the specific process of step (3) is as follows: Preheat the substrate on a hot plate to 70 °C and fix it on a spin coater. Use a pipette to suck 150 μL of solution A and drop it at the center of the substrate, spin coat at a speed of 4000 - 6000 revolutions per minute for 40 - 60 seconds, and transfer it to a hot plate at a temperature of 60 - 100 °C for annealing for 10 - 15 minutes; Then use a pipette to suck 150 - 200 μL of solution B and drop it at the center of the film containing Pb 2+ , Er 3+ and Yb 3+ ions, spin coat at a speed of 4000 - 6000 revolutions per minute for 40 - 60 seconds, and anneal at 250 °C for 10 minutes to obtain an erbium / ytterbium co-doped perovskite film.

[0022] A light-emitting diode containing an erbium / ytterbium co-doped perovskite near-infrared light-emitting film; from bottom to top, it includes a transparent conductive glass substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport and hole blocking layer, a buffer layer, and a metal cathode layer; the perovskite light-emitting layer is an erbium / ytterbium co-doped perovskite near-infrared light-emitting film layer.

[0023] Furthermore, the material used for the hole injection layer is one of PEDOT / PSS or MoO3.

[0024] Further, the material used for the hole transport layer is one of PVK, Poly-TPD or NiOx.

[0025] Further, the material used for the electron transport and hole blocking layer is one of TPBi or BmPyPhB.

[0026] Further, the metal cathode layer is a composite cathode composed of LiF and a metal, and the metal is one of Ag, Al or Au.

[0027] Further, when a forward voltage is applied between the positive and negative electrodes of the light-emitting diode, near-infrared characteristic fluorescence of erbium ions at 1.54 μm is emitted.

[0028] The beneficial effects of the present invention are as follows:

[0029] This method eliminates the adverse effects of the precipitation of metal chlorides in the current solution method and the presence of weakly polar organic ligands in the quantum dot method on the carrier transport performance. By using acetates of rare earth elements erbium, ytterbium and cesium to replace the corresponding chlorides as the erbium, ytterbium and cesium sources respectively, it solves the problem of the precipitation of lead dichloride in dimethyl sulfoxide solution and ytterbium ions in methanol solution caused by the increase of chloride ions during the preparation of erbium / ytterbium co-doped perovskite thin films by the current solution method, realizes the effective doping of erbium / ytterbium ions replacing lead ion lattice sites, increases the doping amount of erbium ions, improves the film-forming quality, reduces the defect density and its non-radiative recombination probability, significantly enhances the luminescence performance of erbium-doped perovskite near-infrared luminescence at 1.54 μm, with its photoluminescence efficiency reaching 30.12%, which is 2.4 times the highest value reported internationally at present, significantly improves the carrier transport efficiency of perovskite as the emission layer, and for the first time realizes the near-infrared electroluminescence of erbium-doped perovskite at 1.54 μm. The external quantum efficiency of its near-infrared light-emitting diode is 0.37%, which is 336 times that of erbium-based organic light-emitting devices (OLEDs). Description of the Drawings

[0030] Figure 1 Scanning electron microscope image of the erbium / ytterbium co-doped perovskite (Er x :Yb 0.9-x :CsPbCl 3 ) thin film prepared by the present invention.

[0031] Figure 2 It is a schematic structural diagram of the light-emitting diode device provided by the present invention.

[0032] Figure 3 It is the photoluminescence and electroluminescence spectra diagram of the light-emitting diode device provided by the present invention.

[0033] Figure 4It is the voltage-current density-near infrared luminescence intensity characteristic curve of the light-emitting diode device provided by the present invention.

[0034] Figure 5 It is the current density-power density characteristic curve of the light-emitting diode device provided by the present invention.

[0035] Figure 6 It is the current density-external quantum efficiency curve of the light-emitting diode device provided by the present invention.

[0036] In the figure: 1 is a transparent conductive glass substrate, 2 is a hole injection layer, 3 is a hole transport layer, 4 is a perovskite light-emitting layer, 5 is an electron transport and hole blocking layer, 6 is a buffer layer, and 7 is a metal cathode layer. Specific Embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings.

[0038] An erbium / ytterbium co-doped perovskite near-infrared luminescent thin film, and a preparation method of the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film, comprising the following steps:

[0039] (1) Adding ytterbium(III) acetate tetrahydrate [Yb(CH 3 COO) 3 ·4H 2 O], erbium(III) acetate tetrahydrate [Er(CH 3 COO) 3 ·4H 2 O] and lead dichloride (PbCl 2 ) to a dimethyl sulfoxide (DMSO) solvent, heating and stirring until completely dissolved, and filtering to obtain solution A;

[0040] (2) Adding ytterbium(III) chloride hexahydrate (YbCl 3 ·6H 2 O) and cesium acetate (CH 3 COOCs) to a methanol solvent, stirring and heating under reflux until clear to obtain solution B;

[0041] (3) Dropwise adding and spin-coating solution A on a substrate, heating and annealing, and then spin-coating solution B thereon and heating and annealing to obtain a fully crystallized erbium / ytterbium co-doped perovskite thin film;

[0042] The lead dichloride used in step (1) needs to be fully dried; the process is to put the lead dichloride powder into a vacuum drying oven and dry it for 24 hours to remove the adsorbed water molecules.

[0043] In step (2), the ytterbium(III) chloride hexahydrate needs to be fully dried. The process is to put the ytterbium(III) chloride hexahydrate powder into a vacuum drying oven and dry it for 24 hours to remove the adsorbed water molecules.

[0044] The structure of the perovskite obtained in step (3) is one of CsPbX 3 type and Cs 4 PbX 6 . Referring to Figure 1 , it can be seen from the figure that the erbium / ytterbium co-doped perovskite thin film has high density and uniformity.

[0045] Furthermore, the specific process of step (1) is as follows: Prepare a mixed solution containing 0.8M lead dichloride and ytterbium(III) acetate tetrahydrate and erbium(III) acetate tetrahydrate with different molar concentration ratios; the sum of the molar concentrations of Yb 3+ and Er 3+ is 0.9M, and the change range of Er 3+ is 0 - 0.9M with a change interval of 0.1M; heat the mixed solution to 70°C and continuously stir until completely dissolved; filter the prepared solution through a polytetrafluoroethylene filter with a pore size of 0.22μm to obtain solution A.

[0046] Furthermore, in step (2), the concentration of Yb 3+ is 0.1M - 0.2M, and the concentration of Cs + is 0.1M - 0.3M.

[0047] Furthermore, the specific process of step (3) is as follows: Preheat the substrate on a hot plate to 70°C and fix it on a spin coater. Use a pipette to suck 150μL of solution A and drop it on the center of the substrate, and spin coat it at a speed of 4000 - 6000 revolutions per minute for 40 - 60 seconds, then transfer it to a hot plate at a temperature of 60 - 100°C and anneal it for 10 - 15 minutes; then use a pipette to suck 150 - 200μL of solution B and drop it on the center of the film containing Pb 2+ , Er 3+ and Yb 3+ ions, spin coat it at a speed of 4000 - 6000 revolutions per minute for 40 - 60 seconds, and anneal it at 250°C for 10 minutes to obtain an erbium / ytterbium co-doped perovskite thin film.

[0048] A light-emitting diode containing an erbium / ytterbium co-doped perovskite near-infrared light-emitting thin film; from bottom to top, it includes a transparent conductive glass substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport and hole blocking layer, a buffer layer, and a metal cathode layer; the perovskite light-emitting layer is an erbium / ytterbium co-doped perovskite thin film layer, and the thickness of the perovskite light-emitting layer is 80 - 120 nanometers. For the specific structure, refer to Figure 2 .

[0049] Further, the material used for the hole injection layer is one of PEDOT / PSS or MoO 3 ; the thickness of the hole injection layer is 2 to 10 nanometers.

[0050] Further, the material used for the hole transport layer is one of PVK, Poly-TPD or NiOx, and the thickness of the hole transport layer is 40 to 50 nanometers.

[0051] Further, the material used for the electron transport and hole blocking layer is one of TPBi or BmPyPhB, and the thickness of the electron transport and hole blocking layer is 40 to 50 nanometers.

[0052] Further, the metal cathode layer is a composite cathode composed of LiF and a metal, and the metal is one of Ag, Al or Au.

[0053] Further, when a forward voltage is applied between the positive and negative electrodes of the light-emitting diode, the 1.54-micron near-infrared characteristic fluorescence of erbium ions is emitted. Refer to Figure 3 , as can be seen from the figure, the device emits a characteristic emission peak of erbium with a main peak at 1532 nm, and its electroluminescence spectrum is almost completely consistent with the photoluminescence spectrum.

[0054] Figure 4 is the voltage-current density-near-infrared luminescence intensity characteristic curve of the light-emitting diode device provided by the present invention. It can be seen that the near-infrared luminescence intensity increases with the increase of the current density, and the turn-on voltage of the device is 1.25 volts.

[0055] Figure 5 is the current density-power density characteristic curve of the light-emitting diode device provided by the present invention. It can be seen that in the initial stage, as the current density gradually increases, the power density rapidly increases, and gradually slows down at 90 mA / cm 2 and starts to slowly decrease at 170 mA / cm 2 .

[0056] Figure 6 is the current density-external quantum efficiency curve of the light-emitting diode device provided by the present invention. It can be seen that the highest external quantum efficiency of this light-emitting diode device reaches 0.37%, which is 336 times that of erbium-based organic light-emitting devices (OLEDs), and the light-emitting diode of erbium-doped perovskite is realized for the first time.

[0057] Preparation method of this light-emitting diode:

[0058] Etch thin strip electrodes on a transparent conductive glass substrate, and then spin-coat a hole injection layer and a hole transport layer in sequence; then prepare an erbium / ytterbium co-doped perovskite (Er x :Yb 0.9-x :CsPbCl 3 ) thin film using the method disclosed above; after completion, transfer it to an organic evaporation chamber, and when the vacuum degree reaches 2 - 3×10 -5 Pa, evaporate an electron transport and hole blocking layer, and control the evaporation rate at 0.05 - 0.1 nm / s; then evaporate a metal cathode layer in sequence under a vacuum atmosphere, where the evaporation rate of lithium fluoride (LiF) is controlled at 0.05 - 0.01 nm / s, and the evaporation rate of silver (Ag) is controlled at 0.3 - 0.6 nm / s.

[0059] The described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

Claims

1. An erbium / ytterbium co-doped perovskite near-infrared luminescent thin film, Characterized in that: The preparation method of the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film includes the following steps: (1) Add ytterbium(III) acetate tetrahydrate [Yb(CH 3 COO) 3 ·4H 2 O], erbium(III) acetate tetrahydrate [Er(CH 3 COO) 3 ·4H 2 O] and lead(II) chloride (PbCl 2 ) to dimethyl sulfoxide (DMSO) solvent, heat and stir until completely dissolved, and obtain solution A after filtration; (2) Add ytterbium(III) chloride hexahydrate (YbCl 3 ·6H 2 O) and cesium acetate (CH 3 COOCs) into a methanol solvent, stir and heat under reflux until clear to obtain solution B; (3) Drop and spin-coat solution A on the substrate and then heat and anneal it. Then spin-coat solution B on it and heat and anneal to obtain a fully crystallized erbium / ytterbium co-doped perovskite thin film; The lead dichloride used in step (1) needs to be fully dried; The ytterbium(III) chloride hexahydrate used in step (2) needs to be fully dried; The structure of the perovskite obtained in step (3) is one of CsPbX 3 type and Cs 4 PbX 6 in one of them.

2. The erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to the claim, Characterized in that: The specific process of the step (1) is as follows: Prepare a mixed solution containing 0.8 M lead dichloride and ytterbium(III) tetrahydrate and erbium(III) tetrahydrate with different molar concentration ratios; wherein the sum of the molar concentrations of Yb 3+ and Er 3+ is 0.9 M, and the change range of Er 3+ is 0 - 0.9 M, with a change interval of 0.1 M; Heat the mixed solution to 70 °C and continuously stir until completely dissolved; Filter the prepared solution through a polytetrafluoroethylene filter with a pore size of 0.22 μm to obtain the solution A.

3. The erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to the claim, Characterized in that: In step (2), the concentration of Yb 3+ is 0.1 M - 0.2 M, and the concentration of Cs + is 0.1 M - 0.3 M.

4. The erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to the claim, Characterized in that: The specific process of step (3) is as follows: Preheat the substrate to 70 °C on a hot plate and fix it on a spin coater. Use a pipette to suck 150 μL of solution A and drop it on the center of the substrate. Spin-coat it at a speed of 4000 - 6000 revolutions per minute for 40 - 60 seconds, and transfer it to a hot plate at a temperature of 60 - 100 °C for annealing for 10 - 15 minutes; Then, use a pipette to aspirate 150 - 200 μL of Solution B and drop it onto the center of the film containing Pb 2+ , Er 3+ and Yb 3+ ions, spin - coat at a speed of 4000 - 6000 revolutions per minute for 40 - 60 seconds, and anneal at 250 °C for 10 minutes to obtain an erbium / ytterbium co - doped perovskite film.

5. A light-emitting diode containing the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to any one of claims 1 - 4, Characterized in that: It includes a transparent conductive glass substrate, a hole injection layer, a hole transport layer, a perovskite light-emitting layer, an electron transport and hole blocking layer, a buffer layer, and a metal cathode layer from bottom to top; the perovskite light-emitting layer is an erbium / ytterbium co-doped perovskite near-infrared luminescent thin film layer.

6. The light-emitting diode containing the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to claim 5, Characterized in that: The material used for the hole injection layer is one of PEDOT / PSS or MoO 3 in the following.

7. The light-emitting diode containing the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to claim 5, Characterized in that: The material used for the hole transport layer is one of PVK, Poly-TPD, or NiOx.

8. The light-emitting diode containing the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to claim 5, Characterized in that: The material used for the electron transport and hole blocking layer is one of TPBi or BmPyPhB.

9. The light-emitting diode containing the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to claim 5, Characterized in that: The metal cathode layer is a composite cathode composed of LiF and a metal, and the metal is one of Ag, Al, or Au.

10. The light-emitting diode containing the erbium / ytterbium co-doped perovskite near-infrared luminescent thin film according to claim 5, Characterized in that: When a forward voltage is applied between the positive and negative electrodes of the light-emitting diode, it emits the 1.54-μm near-infrared characteristic fluorescence of erbium ions.

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