An erbium / ytterbium co-doped perovskite near-infrared luminescent film and light-emitting diode thereof

Abstract

The invention discloses an erbium / ytterbium co-doped perovskite near-infrared luminescent film and a light-emitting diode thereof. Acetates of rare earth erbium, ytterbium and cesium are used instead of corresponding chlorides as erbium, ytterbium and cesium sources respectively, thereby solving the problem of precipitation of lead dichloride in a dimethyl sulfoxide solution and ytterbium ions in a methanol solution caused by an increase in chloride ions in the current solution method for preparing the erbium / ytterbium co-doped perovskite film, achieving effective doping of erbium / ytterbium ions replacing lead ion sites, increasing the doping amount of erbium ions, improving film quality, reducing defect density and non-radiative recombination probability, and significantly improving the luminescent performance of the erbium-doped perovskite 1.54-micron near-infrared luminescence.

Description

Technical Field

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

[0002] Pure inorganic perovskite CsPbX3 (X=C1, Br, I) materials have excellent optoelectronic properties, including tunable luminescence and high photoluminescence quantum efficiency, high carrier mobility, simple preparation, low cost, solution processing, etc. In recent years, the research on erbium-doped perovskite 1.54 micron photoluminescence has also made significant progress:

[0003] In terms of solution method: In 2021, Miyasaka et al. from Japan used perchlorometallic salts as sources of chloride ions and various metal ions to prepare erbium-doped perovskite film Er / Yb:CsPbX3, whose external quantum efficiency of photoluminescence at 1.54 microns reached 12.6%, which was the highest value reported at the time.

[0004] In the quantum dot method: Artizzu et al. prepared erbium / ytterbium co-doped perovskite 1.54 micron photoluminescent material by using rare earth acetate, and its external quantum efficiency reached 6%; but both methods stopped at photoluminescence and did not further realize erbium 1.54 micron near-infrared electroluminescence, the reason is:

[0005] First, the counter anions used in the solution method are all chloride ions. Since the solubility of chloride salts generated between chloride ions and cations (lead, cesium) in the system is very low, in the case of high rare earth ion doping, a small amount of metal chloride salts precipitate in the prepared film in the form of precipitation, and it is currently impossible to effectively overcome this problem, which seriously hinders the transport of carriers within the light-emitting layer.

[0006] Second: There are literature reports on the use of metal acetate as a metal source in the quantum dot method. The prepared erbium-doped perovskite film effectively solves the problem of precipitation and significantly improves its film quality. However, in order to maintain the stability of the quantum dots, they need to be coated with ligands. Commonly used ligands such as oleic acid and oleylamine have weak polarity. The presence of a large number of ligands severely limits the transfer of charges within the light-emitting layer.

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

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

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

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

[0011] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention is:

[0012] An erbium / ytterbium co-doped perovskite near-infrared luminescent film, and a method for preparing the erbium / ytterbium co-doped perovskite near-infrared luminescent film, comprising the following steps:

[0013] (1) adding ytterbium (III) acetate tetrahydrate [Yb(CH3COO)3·4H2O], erbium (III) acetate tetrahydrate [Er(CH3COO)3·4H2O] and lead dichloride (PbCl2) to a dimethyl sulfoxide (DMSO) solvent, heating and stirring until all the mixture is dissolved, and filtering to obtain a solution A;

[0014] (2) adding ytterbium (III) chloride hexahydrate (YbCl3·6H2O) and cesium acetate (CH3COOCs) into methanol solvent, stirring and heating under reflux until the solution becomes clear to obtain solution B;

[0015] (3) adding solution A dropwise and spin-coating the solution onto the substrate, followed by heating and annealing, and then spin-coating solution B thereon and heating and annealing to obtain a fully crystallized erbium / ytterbium co-doped perovskite film;

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

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

[0018] The structure of the perovskite obtained in step (3) is one of CsPbX3 and Cs4PbX6.

[0019] Furthermore, the specific process of step (1) is: preparing a mixed solution containing 0.8M lead dichloride and ytterbium (III) acetate tetrahydrate and erbium (III) acetate tetrahydrate in different molar concentration ratios; wherein Yb 3+ With Er 3+ The sum of the molar concentrations of Er is 0.9M. 3+ The range of change is 0-0.9M, and the change interval is 0.1M; the mixed solution is heated to 70°C and continuously stirred until it is completely dissolved; the prepared solution is filtered using a polytetrafluoroethylene filter with a pore size of 0.22 μm to obtain the solution A.

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

[0021] Further, the specific process of step (3) is as follows: preheat the substrate to 70°C on a heating plate and fix it on a spin coater, use a pipette to draw 150 μL of solution A and drop it on the center of the substrate, spin coat it at a speed of 4000-6000 rpm for 40-60 seconds, transfer it to a heating plate at a temperature of 60-100°C for annealing for 10-15 minutes; then use a pipette to draw 150-200 μL of solution B and drop it on the substrate containing Pb 2+ , Er 3+ and Yb 3+ The center of the ion film is spin-coated at a speed of 4000-6000 rpm for 40-60 seconds, and annealed 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 luminescent film; from bottom to top, it comprises a transparent conductive glass substrate, a hole injection layer, a hole transport layer, a perovskite luminescent layer, an electron transport and hole blocking layer, a buffer layer, and a metal cathode layer; the perovskite luminescent layer is an erbium / ytterbium co-doped perovskite near-infrared luminescent film layer.

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

[0024] Furthermore, the hole transport layer is made of a material selected from the group consisting of PVK, Poly-TPD and NiOx.

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

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

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

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

[0029] The 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, and uses acetates of rare earth erbium, ytterbium and cesium to replace the corresponding chlorides as erbium, ytterbium and cesium sources, respectively, to solve the problem of precipitation of lead dichloride in dimethyl sulfoxide solution and ytterbium ions in methanol solution caused by the increase of chloride ions in the current solution method for preparing erbium / ytterbium co-doped perovskite films, and realizes the effective doping of erbium / ytterbium ions replacing lead ion sites, thereby increasing the doping amount of erbium ions. The film formation quality has been improved, the defect density and its non-radiative recombination probability have been reduced, and the luminescence performance of erbium-doped perovskite at 1.54 microns near-infrared luminescence has been significantly improved. Its photoluminescence efficiency has reached 30.12%, which is 2.4 times the highest value currently reported internationally. It has significantly improved the carrier transfer efficiency of perovskite as an emission layer, and achieved the first 1.54-micron near-infrared electroluminescence of erbium-doped perovskite. 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). BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The erbium / ytterbium co-doped perovskite (Er x :Yb 0.9-x :SEM image of CsPbCl3) film.

[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 a photoluminescence and electroluminescence spectrum diagram of the light emitting diode device provided by the present invention.

[0033] Figure 4 It is a voltage-current density-near-infrared luminous 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 6It 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. DETAILED DESCRIPTION

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

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

[0039] (1) adding ytterbium (III) acetate tetrahydrate [Yb(CH3COO)3·4H2O], erbium (III) acetate tetrahydrate [Er(CH3COO)3·4H2O] and lead dichloride (PbCl2) to a dimethyl sulfoxide (DMSO) solvent, heating and stirring until all the mixture is dissolved, and filtering to obtain a solution A;

[0040] (2) adding ytterbium (III) chloride hexahydrate (YbCl3·6H2O) and cesium acetate (CH3COOCs) into methanol solvent, stirring and heating under reflux until the solution becomes clear to obtain solution B;

[0041] (3) adding solution A dropwise and spin-coating the solution onto the substrate, followed by heating and annealing, and then spin-coating solution B thereon and heating and annealing to obtain a fully crystallized erbium / ytterbium co-doped perovskite 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] The ytterbium (III) chloride hexahydrate in step (2) 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 CsPbX3 and Cs4PbX6. Figure 1 It can be seen from the figure that the erbium / ytterbium co-doped perovskite film has a highly dense and uniform structure.

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

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

[0047] Further, the specific process of step (3) is as follows: preheat the substrate to 70°C on a heating plate and fix it on a spin coater, use a pipette to draw 150 μL of solution A and drop it on the center of the substrate, spin coat it at a speed of 4000-6000 rpm for 40-60 seconds, transfer it to a heating plate at a temperature of 60-100°C for annealing for 10-15 minutes; then use a pipette to draw 150-200 μL of solution B and drop it on the substrate containing Pb 2+ , Er 3+ and Yb 3+ The center of the ion film is spin-coated at a speed of 4000-6000 rpm for 40-60 seconds and annealed at 250° C. for 10 minutes to obtain an erbium / ytterbium co-doped perovskite film.

[0048] A light-emitting diode containing an erbium / ytterbium co-doped perovskite near-infrared light-emitting film; from bottom to top, it comprises 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 film layer, the thickness of the perovskite light-emitting layer is 80-120 nanometers, and the specific structure is referenced Figure 2 .

[0049] Furthermore, the hole injection layer is made of a material selected from PEDOT / PSS or MoO3; and the hole injection layer has a thickness of 2 to 10 nanometers.

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

[0051] Furthermore, 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] Furthermore, the metal cathode layer is a composite cathode composed of LiF and metal, and the metal is one of Ag, Al or Au.

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

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

[0055] Figure 5 This is the current density-power density characteristic curve of the light emitting diode device provided by the present invention. It can be seen that at the beginning, as the current density gradually increases, the power density increases rapidly. 2 The value gradually slowed down to 170mA / cm 2 Start to slowly decrease.

[0056] Figure 6 This 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 maximum external quantum efficiency of the light-emitting diode device reaches 0.37%, which is 336 times that of the erbium-based organic electroluminescent device (OLED), and it is the first time that an erbium-doped perovskite light-emitting diode has been realized.

[0057] The light emitting diode preparation method:

[0058] A thin strip electrode is etched on a transparent conductive glass substrate, and then a hole injection layer and a hole transport layer are sequentially spin-coated; then, the erbium / ytterbium co-doped perovskite (Er x :Yb 0.9-x :CsPbCl3) film; after completion, transfer it to the organic evaporation chamber and wait until the vacuum degree reaches 2-3×10 -5 Pa, evaporate the electron transport and hole blocking layer, and the evaporation rate is controlled at 0.05-0.1 nm / s; then evaporate the metal cathode layer in a vacuum atmosphere, wherein 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 some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. An erbium / ytterbium co-doped perovskite near-infrared luminescent film, characterized in that: The method for preparing the erbium / ytterbium co-doped perovskite near-infrared luminescent film comprises the following steps: (1) adding ytterbium (III) acetate tetrahydrate [Yb(CH3COO)3·4H2O], erbium (III) acetate tetrahydrate [Er(CH3COO)3·4H2O] and lead dichloride (PbCl2) to a dimethyl sulfoxide (DMSO) solvent, heating and stirring until all the mixture is dissolved, and filtering to obtain a solution A; (2) adding ytterbium (III) chloride hexahydrate (YbCl3·6H2O) and cesium acetate (CH3COOCs) into methanol solvent, stirring and heating under reflux until the solution becomes clear to obtain solution B; (3) adding solution A dropwise and spin-coating the solution onto the substrate, followed by heating and annealing, and then spin-coating solution B thereon and heating and annealing to obtain a fully crystallized erbium / ytterbium co-doped perovskite film; The lead dichloride used in step (1) needs to be fully dried; The ytterbium (III) chloride hexahydrate in step (2) needs to be fully dried; The structure of the perovskite obtained in step (3) is one of CsPbX3 and Cs4PbX6.

2. The erbium / ytterbium co-doped perovskite near-infrared luminescent film according to claim 1, characterized in that: The specific process of step (1) is: preparing a mixed solution containing 0.8M lead dichloride and ytterbium (III) acetate tetrahydrate and erbium (III) acetate tetrahydrate in different molar concentration ratios; wherein Yb 3+ With Er 3+ The sum of the molar concentrations of Er is 0.9M. 3+ The range of change is 0-0.9M, and the change interval is 0.1M; the mixed solution is heated to 70°C and continuously stirred until it is completely dissolved; the prepared solution is filtered using 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 film according to claim 1, characterized in that: In the step (2), Yb 3+ The concentration of Cs is 0.1M-0.2M. + The concentration is 0.1M-0.3M.

4. The erbium / ytterbium co-doped perovskite near-infrared luminescent film according to claim 1, characterized in that: The specific process of step (3) is as follows: preheat the substrate to 70°C on a heating plate and fix it on a spin coater, use a pipette to draw 150 μL of solution A and drop it on the center of the substrate, spin coat it at a speed of 4000-6000 rpm for 40-60 seconds, and transfer it to a heating plate at a temperature of 60-100°C for annealing for 10-15 minutes; Then use a pipette to draw 150-200 μL of solution B and drop it on the 2+ , Er 3+ and Yb 3+ The center of the ion film is spin-coated at a speed of 4000-6000 rpm for 40-60 seconds, and annealed at 250° C. for 10 minutes to obtain an erbium / ytterbium co-doped perovskite film.

5. A light-emitting diode comprising the erbium / ytterbium co-doped perovskite near-infrared light-emitting film according to any one of claims 1 to 4, characterized in that: 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 thin film layer.

6. The light-emitting diode containing erbium / ytterbium co-doped perovskite near-infrared light-emitting film according to claim 5, characterized in that: The hole injection layer is made of a material selected from PEDOT / PSS and MoO3.

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

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

9. The light-emitting diode containing erbium / ytterbium co-doped perovskite near-infrared light-emitting film according to claim 5, characterized in that: The metal cathode layer is a composite cathode composed of LiF and 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 light-emitting 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, the light emitting diode emits 1.54 micron near-infrared characteristic fluorescence of erbium ions.

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