An Optimization Method for CsPbI3 Red Perovskite Nanocrystalline LED Devices

Abstract

The application relates to the technical field of light-emitting materials, and discloses an optimization method of a CsPbI3 red light perovskite nanocrystal LED device to solve the problem of poor photoelectric properties of existing light-emitting devices taking perovskite nanocrystal materials as light-emitting layers. The photoelectric properties and stability of the CsPbI3 perovskite nanocrystal are optimized, the photoluminescence quantum yield of the CsPbI3 nanocrystal is improved, the charge transport capacity of the nanocrystal is enhanced, ion migration is greatly inhibited, the peak brightness of 2731 cd / m 2 (TPP) and 3188 cd / m 2 (DPB) and the maximum external quantum efficiency of 19.2% (TPP) and 21.6% (DPB) are achieved, and the stability of the device is improved by nearly ten times compared with that of the unoptimized device.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and in particular to an optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device. Background Technology

[0002] Metal halide perovskite nanocrystals hold great promise for applications in light-emitting diodes (LEDs) and displays due to their high photoluminescence quantum yield, tunable optical bandgap, excellent color purity, and low-cost solution processability. However, the photoelectric properties of LEDs using perovskite nanocrystals as the emitting layer are still far inferior to those of state-of-the-art organic light-emitting diodes (OLEDs). This is partly due to defects on the surface of perovskite nanocrystals leading to a lower photoluminescence quantum yield, and the insulating properties of long-chain oleylamine oleic acid suppressing conductivity, resulting in lower device efficiency. Furthermore, the low activation energy of halide ions makes them susceptible to migration under external stress, causing degradation of the nanocrystals and reducing device stability, severely hindering the industrial application of perovskite nanocrystals and related devices. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by proposing an optimized method for CsPbI3 red-light perovskite nanocrystalline LED devices.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] An optimization method for CsPbI3 red-light perovskite nanocrystal LED devices utilizes triphenylphosphine (TPP) and its derivative, (diphenylphosphino)-biphenyl (DPB), to optimize the photoelectric properties of CsPbI3 perovskite nanocrystals. The method specifically includes the following steps:

[0006] Step 1: Place octadecene, oleic acid and cesium acetate in a container, heat and degas under vacuum, then heat and stir under an inert gas atmosphere until the solution dissolves to obtain a cesium oleate solution.

[0007] Step 2: Pour lead iodide, oleic acid, oleylamine and TPP or DPB into a container containing octadecene, heat and degas under vacuum, then heat under an inert gas atmosphere and inject cesium oleate solution. After the reaction is complete, cool the solution to room temperature in a water bath.

[0008] Step 3: Centrifuge and purify the reaction product from Step 2. Disperse the precipitate after centrifugation in a mixed solvent of toluene and ethyl acetate, and then continue to centrifuge and purify. Finally, disperse the precipitate after centrifugation in toluene to obtain CsPbI3 nanocrystals treated with TPP or DPB.

[0009] Step 4: Preliminary preparation of CsPbI3 nanocrystalline LEDs based on TPP or DPB;

[0010] The ITO substrate was cleaned with deionized water, ethanol, chloroform, acetone and isopropanol respectively, and then cleaned with a UV ozone generator.

[0011] ZnO was spin-coated onto an ITO substrate and then annealed. The substrate was then transferred to a glove box filled with N2 gas, and polyethyleneimine (PEI) was spin-coated onto the ZnO film to form a ZnO / PEI layer. After annealing, the ZnO / PEI layer was used as an electron transport layer and a modification layer.

[0012] The TPP or DPB-treated CsPbI3 nanocrystal solution prepared in step 3 was spin-coated onto the ZnO / PEI layer as a light-emitting layer.

[0013] Step 5: The product obtained in Step 4 is transferred to a vacuum chamber and TCTA, TAPC, MoO3 and Au layers are deposited sequentially by thermal evaporation. The TCTA and TAPC layers serve as hole transport layers and electron blocking layers, respectively, and the MoO3 and Au layers serve as top electrodes. This yields a CsPbI3 nanocrystalline LED based on TPP or DPB treatment.

[0014] Preferably, in steps 1 and 2, the inert gas introduced is nitrogen.

[0015] Preferably, in step 2, the volume ratio of octadecene, oleic acid and oleylamine is 10:1:1.

[0016] Preferably, in step 3, the centrifugal speed is 5000-10000 r / min.

[0017] Preferably, in step 4, the spin coating speed of ZnO is 1000 r / min, the spin coating speed of polyethyleneimine is 3000 r / min, and the spin coating speed of nanocrystals on the ZnO / PEI layer is 1000 r / min.

[0018] Preferably, in step 4, the annealing treatment of ZnO is specifically annealing at 150°C for 10 minutes, and the annealing treatment of polyethyleneimine is specifically annealing at 125°C for 10 minutes.

[0019] Preferably, in step 4, the ITO substrate is cleaned with deionized water, ethanol, chloroform, acetone and isopropanol for 15 minutes each; and cleaned with an ultraviolet ozone generator for 20 minutes.

[0020] This invention optimizes the photoelectric properties and stability of CsPbI3 perovskite nanocrystals using triphenylphosphine (TPP) and its derivative 2-(diphenylphosphino)-biphenyl (DPB), improving the photoluminescence quantum yield of CsPbI3 nanocrystals, enhancing the charge transport capability of the nanocrystals, and significantly suppressing ion migration, achieving a yield of 2731 cd / m³. 2 (TPP) and 3188cd / m 2 The peak luminance (DPB) and maximum external quantum efficiency of 19.2% (TPP) and 21.6% (DPB) are achieved, and the stability of the device is nearly ten times better than that of the unoptimized one. Attached Figure Description

[0021] Figure 1 This is a comparison diagram of the photoluminescence performance of CsPbI3 nanocrystals before and after experimental optimization in the embodiments of the invention;

[0022] Figure 2 This is a comparison diagram of the lifetime of CsPbI3 nanocrystals before and after experimental optimization in the embodiments of the invention;

[0023] Figure 3 The X-ray photoelectron spectra of CsPbI3 nanocrystals before and after experimental optimization in the embodiments of the invention are shown.

[0024] Figure 4 The X-ray diffraction patterns of CsPbI3 nanocrystals placed in air for different times before and after experimental optimization in the embodiments of the invention.

[0025] Figure 5 This is a comparison of the carrier mobility of CsPbI3 nanocrystalline thin films before and after experimental optimization in the embodiments of the invention.

[0026] Figure 6 The current density-voltage curves of CsPbI3 nanocrystalline LEDs before and after experimental optimization are shown in the embodiments of the invention.

[0027] Figure 7 The current density-brightness curves of CsPbI3 nanocrystalline LEDs before and after experimental optimization are shown in the embodiments of the invention.

[0028] Figure 8 The current density-external quantum efficiency curves of CsPbI3 nanocrystalline LEDs before and after experimental optimization in the embodiments of the invention are shown.

[0029] Figure 9 The current density-voltage curves of CsPbI3 nanocrystalline LEDs before and after experimental optimization in the embodiments of the invention are shown in the forward and reverse voltage scans (the arrows indicate the direction of the scan voltage).

[0030] Figure 10The stability curves of CsPbI3 nanocrystalline LEDs before and after experimental optimization in the embodiments of the invention are shown. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] Example:

[0033] 1) First, put 0.96g of cesium acetate, 5mL of oleic acid and 30mL of octadecene into a 100mL three-necked flask, and degas and dry the mixture under vacuum at 120℃ until a clear solution is formed, which is the precursor solution.

[0034] 2) Next, 0.173g of lead iodide, 0.3g of TPP (or 0.0276g of DPB), 1mL of oleylamine, 1mL of oleic acid, and 10mL of octadecene were placed into a 50mL three-necked flask. The solution was first degassed and dried under vacuum at 120℃ for 1h. Then, under a nitrogen atmosphere, the solution was heated to 170℃ and 0.8mL of precursor solution was injected. After reacting for 5s, the solution was quickly cooled to room temperature in a water bath.

[0035] 3) Finally, the reaction product is purified by centrifugation. The precipitate after centrifugation is dispersed in a mixed solvent of toluene and ethyl acetate, and then centrifuged and purified again. Finally, the precipitate after centrifugation is dispersed in toluene to obtain CsPbI3 nanocrystals treated with TPP or DPB.

[0036] 4) Fabrication of CsPbI3 nanocrystalline LEDs based on TPP or DPB treatment

[0037] First, the ITO substrate was cleaned for 15 minutes each with deionized water, ethanol, chloroform, acetone and isopropanol, and then cleaned with a UV ozone generator for 20 minutes.

[0038] ZnO was spin-coated onto an ITO substrate at 1000 rpm for 30 seconds, followed by annealing at 150 °C for 10 minutes. The substrate was then transferred to a glove box filled with N2 gas, and polyethyleneimine (PEI) (dissolved in 2-methoxyethanol solution, mass fraction 0.2%) was spin-coated onto the ZnO film at 3000 rpm for 50 seconds, followed by annealing at 125 °C for 10 minutes. The ZnO / PEI layer served as both an electron transport layer and a modification layer.

[0039] The CsPbI3 nanocrystal solution prepared in step 3) after TPP or DPB treatment was spin-coated onto the ZnO / PEI layer at a speed of 1000 r / min as a light-emitting layer.

[0040] 5) The product obtained in step 4) is finally transferred into a vacuum chamber, and TCTA, TAPC, MoO3 and Au layers are deposited sequentially by thermal evaporation, wherein the TCTA and TAPC layers serve as hole transport layers and electron blocking layers, and the MoO3 and Au layers serve as top electrodes; thereby obtaining CsPbI3 nanocrystalline LEDs based on TPP or DPB treatment.

[0041] like Figure 1 As shown, the addition of TPP and DPB can improve the luminescence intensity of CsPbI3 nanocrystals, and DPB is more effective than TPP in improving the luminescence intensity. Furthermore, as... Figure 2 As shown, the fluorescence lifetime of CsPbI3 nanocrystals treated with TPP and DPB increased, indicating that TPP and DPB passivated defects on the nanocrystal surface, suppressed nonradiative recombination, and thus improved luminescence efficiency. Figure 3 As shown, in CsPbI3 nanocrystals treated with TPP or DPB, the binding energy of Pb shifts towards higher energies, while the binding energy of I shifts towards lower energies. This indicates that TPP and DPB can coordinate with both Pb and I, with DPB exhibiting stronger coordination ability. This results in better passivation of defects and suppression of ion migration, significantly improving the stability of the material. Figure 4 As shown, CsPbI3 nanocrystals treated with TPP or DPB exhibited excellent water and oxygen stability. Furthermore, as... Figure 5 As shown in Figure 6, the delocalization properties of TPP and DPB enhance carrier mobility. LEDs were fabricated using CsPbI3 nanocrystals treated with TPP or DPB as the light-emitting layer. Figure 7 As shown in Figure 8, this LED achieves 2731 cd / m². 2 (TPP) and 3188cd / m 2 The peak luminance (DPB) and maximum external quantum efficiency of 19.2% (TPP) and 21.6% (DPB) are shown. Figure 9 As shown, migration was significantly suppressed in CsPbI3 nanocrystalline LEDs treated with TPP or DPB. Furthermore, as... Figure 10 As shown, the stability of LEDs has been greatly improved.

[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device, characterized in that, The photoelectric properties of CsPbI3 perovskite nanocrystals were optimized using triphenylphosphine (TPP) and its derivative, (diphenylphosphino)-biphenyl (DPB), specifically including the following steps: Step 1: Place octadecene, oleic acid and cesium acetate in a container, heat and degas under vacuum, then heat and stir under an inert gas atmosphere until the solution dissolves to obtain a cesium oleate solution. Step 2: Pour lead iodide, oleic acid, oleylamine and the optimizer into a container containing octadecene. Heat and degas the container under vacuum. Then heat the container under an inert gas atmosphere and inject cesium oleate solution. After the reaction is complete, cool the solution to room temperature in a water bath. Step 3: Centrifuge and purify the reaction product from Step 2. Disperse the precipitate after centrifugation in a mixed solvent of toluene and ethyl acetate, and then continue to centrifuge and purify. Finally, disperse the precipitate after centrifugation in toluene to obtain the CsPbI3 nanocrystals treated with the optimization agent. Step 4: Preliminary preparation of CsPbI3 nanocrystalline LEDs based on the optimizing agent; The ITO substrate was cleaned with deionized water, ethanol, chloroform, acetone and isopropanol respectively, and then cleaned with a UV ozone generator. ZnO was spin-coated onto an ITO substrate and then annealed. The substrate was then transferred to a glove box filled with N2 gas, and polyethyleneimine (PEI) was spin-coated onto the ZnO film to form a ZnO / PEI layer. After annealing, the ZnO / PEI layer was used as an electron transport layer and a modification layer. The CsPbI3 nanocrystal solution prepared in step 3 and treated with the optimizer was spin-coated onto the ZnO / PEI layer as a light-emitting layer. Step 5: The product obtained in Step 4 is transferred to a vacuum chamber and TCTA, TAPC, MoO3 and Au layers are deposited sequentially by thermal evaporation. The TCTA and TAPC layers serve as hole transport layers and electron blocking layers, respectively, and the MoO3 and Au layers serve as top electrodes. This yields a CsPbI3 nanocrystalline LED based on the optimizer treatment. The optimizing agent in step 2 is TPP or DPB.

2. The optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device according to claim 1, characterized in that, In steps 1 and 2, the inert gas introduced is nitrogen.

3. The optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device according to claim 1, characterized in that, In step 2, the volume ratio of octadecene, oleic acid, and oleylamine is 10:1:

1.

4. The optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device according to claim 1, characterized in that, In step 3, the centrifugal speed is 5000-10000 r / min.

5. The optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device according to claim 1, characterized in that, In step 4, the spin coating speed of ZnO is 1000 r / min, the spin coating speed of polyethyleneimine is 3000 r / min, and the spin coating speed of nanocrystals on the ZnO / PEI layer is 1000 r / min.

6. The optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device according to claim 1, characterized in that, In step 4, the annealing treatment of ZnO is specifically annealing at 150°C for 10 minutes, and the annealing treatment of polyethyleneimine is specifically annealing at 125°C for 10 minutes.

7. The optimization method for a CsPbI3 red-light perovskite nanocrystalline LED device according to claim 1, characterized in that, In step 4, the ITO substrate is cleaned with deionized water, ethanol, chloroform, acetone and isopropanol for 15 minutes each; and then cleaned with a UV ozone generator for 20 minutes.

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