High-color purity large-size perovskite nanocrystal, manufacturing method for light-emitting diode, and light-emitting diode
Patent Information
- Application Number
- PCT/CN2025/085898
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-03-28
- Publication Date
- 2026-10-01
Smart Images
Figure CN2025085898_01102026_PF_FP_ABST
Abstract
Description
High color purity large-size perovskite nanocrystals, methods for fabricating light-emitting diodes and light-emitting diodes Technical Field
[0001] This invention relates to the field of optoelectronic materials technology, and in particular to a high color purity large-size perovskite nanocrystal, a method for preparing a light-emitting diode, and the light-emitting diode itself. Background Technology
[0002] Perovskite quantum dots (nanocrystalline) are a new generation of luminescent materials, possessing advantages such as narrow emission spectra and high fluorescence quantum efficiency (approaching 100%), showing great potential in light-emitting diodes (LEDs), display technology, and photovoltaics. Nanocrystalline materials typically exhibit a quantum confinement effect within the Bohr exciton diameter, making the emission peak position highly dependent on the nanocrystalline particle size. This can easily lead to a broadening of the emission peak linewidth, thereby reducing the color purity of the fabricated perovskite nanocrystalline LEDs. Improving the color purity of perovskite nanocrystalline LEDs is one of the keys to realizing full-color displays and solid-state lighting.
[0003] To achieve high color purity perovskite nanocrystals, existing technologies mainly employ size control and mixed halogen methods. Size control adjusts the emission color by reducing the size of the perovskite nanocrystal. However, the resulting perovskite nanocrystals, due to their smaller size, have more surface defects, poor stability, and high carrier transport resistance, requiring higher driving voltages. Furthermore, since the size of perovskite is influenced by various factors, size control is difficult to precisely regulate, resulting in low color purity. The mixed halogen method adjusts the halogen ratio of the perovskite nanocrystals to control the emission wavelength. This technique requires strict control of the halogen ratio and is easily affected by the degree of reaction, resulting in insufficient color purity. Moreover, the mixed halogen system is prone to halide segregation, leading to broadening or peak shifting of the emission peak, resulting in poor performance of the fabricated perovskite LED devices. Summary of the Invention
[0004] To address the aforementioned shortcomings, this invention proposes a method for fabricating high-color-purity, large-size perovskite nanocrystals and light-emitting diodes, as well as the light-emitting diode itself.
[0005] The technical solution adopted in this invention is a method for preparing high-color-purity, large-size perovskite nanocrystals, the method comprising:
[0006] S100, prepare TBPO-xMBr2, TBPO-xMI2 or TBPO-xMCl2 solutions, where M is a divalent metal and x is the molar ratio;
[0007] S200: Lead oxide, 2-bromoacetophenone, oleic acid, and octadecene are mixed and then injected with diphenyl phosphate and oleylamine at 200-240°C. The mixture is kept at this temperature for 15-30 minutes. After cooling, cesium oleate is injected and kept at this temperature to terminate the reaction and obtain the initial nanocrystals.
[0008] S300: Add the TBPO-xMBr2 solution prepared in S100 to the initial nanocrystals obtained in S200 to obtain cesium lead bromine green perovskite nanocrystals; or
[0009] The TBPO-xMI2 solution prepared by S100 is added to the initial nanocrystals prepared by S200 to obtain iodine-bromine mixed halogen pure red perovskite nanocrystals; or
[0010] The TBPO-xMCl2 solution prepared by S100 is added to the initial nanocrystals prepared by S200 to obtain chlorobromine mixed halogen pure blue perovskite nanocrystals.
[0011] Preferably, M is one of zinc, manganese or calcium.
[0012] Preferably, 0 < x < 0.6.
[0013] Preferably, the step of injecting cesium oleate after cooling and maintaining the temperature in step S200 specifically includes: cooling to 140-200°C, injecting cesium oleate, and maintaining the temperature.
[0014] Preferably, the step of injecting cesium oleate after cooling and maintaining the temperature in step S200 specifically includes: injecting cesium oleate after cooling and maintaining the temperature for 2 to 20 minutes.
[0015] This invention also discloses a method for fabricating high color purity, large-size perovskite nanocrystalline light-emitting diodes, the method comprising:
[0016] S100, Cleaning the ITO glass substrate;
[0017] S200: A hole transport layer is prepared on the ITO glass substrate, wherein the hole transport layer is made of PTAA material and a PEABr / F-PEABr / PEAI / F-PEAI modification layer;
[0018] S300. When the hole transport layer is modified with a PEABr / F-PEABr layer, the aforementioned cesium lead bromine green perovskite nanocrystals or chlorobromine mixed halogen pure blue perovskite nanocrystals are spin-coated onto the surface of the hole transport layer; or
[0019] When the hole transport layer is modified with PEAI / F-PEAI, the aforementioned iodine-bromine mixed halogen pure red perovskite nanocrystals are spin-coated onto the surface of the hole transport layer.
[0020] S400: An electron transport layer is prepared on the perovskite nanocrystalline layer;
[0021] S500, Electrodes are fabricated on the electron transport layer.
[0022] The present invention also discloses a high color purity large-size perovskite nanocrystal light-emitting diode, which is prepared by the above-described preparation method.
[0023] Compared with the prior art, the present invention has the following beneficial effects:
[0024] 1. This invention synthesizes large-size cesium lead-bromine green perovskite nanocrystals. Furthermore, halide ion exchange is performed on these large-size cesium lead-bromine perovskite nanocrystals to obtain large-size iodine-bromine mixed halogen pure red perovskite nanocrystals and large-size chloro-bromine mixed halogen pure blue perovskite nanocrystals. These large-size perovskite nanocrystals reduce the sensitivity of the emission peak to the nanocrystal size distribution, thereby achieving high color purity green light and pure red and pure blue perovskite nanocrystals. Since large-size perovskite nanocrystals can effectively reduce the total number of nanocrystals in a given volume of emitting layer, the device can have a lower turn-on voltage. Simultaneously, compared to small-size nanocrystals, large-size perovskite nanocrystals have fewer surface defects and surface organic ligands, resulting in better carrier transport capability in the large-size perovskite nano-emitting layer, achieving efficient and stable perovskite nanocrystal LEDs.
[0025] 2. This invention develops ligand-assisted halide ion exchange for perovskite nanocrystals, which makes the spectrum of the mixed halide perovskite nanocrystals obtained by halide ion exchange more stable and suppresses halide segregation. This is also the key to developing high-performance mixed halide perovskite nanocrystal LED devices.
[0026] 3. This invention uses high-color-purity, large-size cesium lead bromide perovskite nanocrystals and mixed halide perovskite nanocrystals to prepare electroluminescent LED devices, achieving an efficiency of 16.03% (half-width at half maximum) for a green LED with an emission peak at 520nm, an efficiency of 19.70% (half-width at half maximum) for a pure red LED with an emission peak at 633nm, and an efficiency of 6.60% (half-width at half maximum) for a pure blue LED with an emission peak at 469nm. Attached Figure Description
[0027] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:
[0028] Figure 1 is a flowchart of the technical solution of the present invention;
[0029] Figure 2 is a schematic diagram of the structure of a perovskite nanocrystalline LED;
[0030] Figure 3 shows the UV-Vis absorption spectra (dashed lines) and fluorescence spectra (solid lines) of large-sized cesium lead bromide perovskite nanocrystals before surface passivation (DPP NCs) and after surface passivation (DPP+T-Br NCs).
[0031] Figure 4 shows the time-resolved fluorescence spectra of large-sized cesium lead bromide perovskite nanocrystals before and after surface passivation (DPP NCs) and after surface passivation (DPP+T-Br NCs).
[0032] Figure 5 shows the X-ray diffraction patterns of large-sized cesium lead bromide perovskite nanocrystals before and after surface passivation (DPP NCs) and the standard XRD ICSD 97851.
[0033] Figure 6 shows the Fourier transform infrared spectra of large-sized cesium lead bromide perovskite nanocrystals before and after surface passivation (DPP NCs) and after surface passivation (DPP+T-Br NCs).
[0034] Figure 7 shows the UV-Vis absorption spectrum (dashed line) and fluorescence spectrum (solid line) of large-size iodine-bromine mixed perovskite nanocrystals after halide ion exchange.
[0035] Figure 8 shows the X-ray diffraction patterns of large-size iodine-bromine mixed perovskite nanocrystals with different emission wavelengths after halide ion exchange.
[0036] Figure 9 shows the UV-Vis absorption spectrum (dashed line) and fluorescence spectrum (solid line) of large-sized chlorobromine mixed perovskite nanocrystals after halide ion exchange.
[0037] Figure 10 shows the X-ray diffraction patterns of large-size chlorobromine mixed perovskite nanocrystals with different emission wavelengths after halide ion exchange.
[0038] Figure 11 shows transmission electron microscopy images of large-sized cesium lead bromide perovskite nanocrystals (DPP+T-Br), large-sized iodine bromide mixed perovskite nanocrystals (DPP+TI), and large-sized chloro bromide mixed perovskite nanocrystals (DPP+T-C1).
[0039] Figure 12 shows the photothermal stability of large-size cesium lead bromide perovskite nanocrystals (DPP+T-Br), large-size iodine bromide mixed perovskite nanocrystals (DPP+TI), and large-size chloro bromide mixed perovskite nanocrystals (DPP+T-Cl).
[0040] Figure 13 shows the performance test results of LED devices prepared using large-size cesium lead bromide perovskite nanocrystals.
[0041] Figure 14 shows the performance test results of the LED device prepared by large-size iodine-bromine mixed perovskite nanocrystals (DPP+TI).
[0042] Figure 15 shows the performance test results of LED devices prepared from large-size chlorobromine mixed perovskite nanocrystals (DPP+T-Cl). Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0044] In one embodiment, a method for preparing high-color-purity, large-size perovskite nanocrystals, as shown in Figure 1, includes:
[0045] S100. Prepare TBPO-xMBr2 solution, where M is a divalent metal and x is the molar ratio.
[0046] Specifically, M can be zinc. Tributylphosphine oxide, zinc bromide, and toluene are mixed in a certain proportion and ultrasonically treated at room temperature for 30 minutes to obtain a clear tributylphosphine oxide-zinc bromide solution.
[0047] S200: Lead oxide, 2-bromoacetophenone, oleic acid, and octadecene are mixed and then injected with diphenyl phosphate and oleylamine at 200–240°C for 15–30 minutes. After cooling, cesium oleate is injected and kept at the same temperature to terminate the reaction, thus obtaining the initial nanocrystals. Cesium oleate can be prepared by the method described in the following examples, or it can be obtained directly.
[0048] Specifically, lead oxide, 2-bromoacetophenone, oleic acid, and octadecene were added to a reaction flask in a specific ratio. The flask was then connected to a double-row tube, and the mixture was stirred and dehydrated and deoxygenated. The reaction temperature was then raised to 200–240°C, with 220°C being optimal. A certain amount of diphenyl phosphate and oleylamine were injected, and the temperature was maintained for 15–30 minutes. The mixture was then cooled, and a certain amount of pre-prepared cesium oleate was injected and maintained for a period of time. Finally, the reaction flask was placed in an ice bath to cool and terminate the reaction. The product was then purified to obtain initial nanocrystals.
[0049] Lead oxide (PbO) provides Pb. 2+ 2-Bromoacetophenone (C8H7BrO) provides Br -Oleic acid (OA) and diphenyl phosphate (DPP) are used as ligands, and octadecene (ODE) is used as a solvent. Injecting oleylamine (OAm) at 200-240°C and holding for 15-30 minutes promotes the release of Br- from 2-bromoacetophenone. Cesium oleate (Cs-oleate) provides Cs+, and this hot-injection method promotes crystal growth, resulting in large-sized initial nanocrystals, i.e., large-sized cesium lead bromide perovskite nanocrystals.
[0050] S300: The TBPO-xMBr2 solution prepared in S100 is added to the initial nanocrystals prepared in S200 to obtain cesium lead bromine green perovskite nanocrystals.
[0051] Specifically, a large-size initial nanocrystal solution and toluene were mixed in a certain proportion, and then a certain amount of tributylphosphine oxide-zinc bromide solution was added to passivate the surface of cesium lead bromine nanocrystals (initial nanocrystals). The product was then purified and dispersed in n-hexane.
[0052] TBPO (tributylphosphine oxide) acts as a ligand, interacting with Pb on the perovskite surface via the P=O group. 2+ Coordination covers over 90% of surface defects, forming a protective layer and extending fluorescence lifetime. MBr2 provides divalent metal ions, which are doped into the perovskite lattice to compensate for defects, adjust the band gap, and improve crystallinity.
[0053] The method for preparing high color purity large-size perovskite nanocrystals in this embodiment increases the holding time after cesium oleate injection to form large-size nanocrystals. The large-size nanocrystals themselves reduce the sensitivity of the emission peak to the nanocrystal size distribution. Combined with the passivation effect of TBPO-xMBr2 solution on the halogen vacancies on the nanocrystal surface, surface defects are reduced, making the emission of nanocrystals more concentrated, thereby improving color purity.
[0054] Modifying the nanocrystal surface with TBPO-xMBr2 solution reduces surface organic long-chain ligands and defects, thereby decreasing the resistance to carrier transport and improving its transport capability. This contributes to achieving highly efficient and stable perovskite nanocrystal LEDs, reducing device turn-on voltage, and improving luminous efficiency. The organic ligand diphenyl phosphate can strongly coordinate with Pb2+ and anchor halide ions through hydrogen bonds. Furthermore, the passivation layer formed on the nanocrystal surface by TBPO-xMBr2 solution can suppress halide segregation and other problems, improving the stability of nanocrystals under different environments and extending their lifespan.
[0055] In one embodiment, a method for preparing high-color-purity, large-size perovskite nanocrystals, as shown in Figure 1, includes:
[0056] S100. Prepare TBPO-xMI2 solution, where M is a divalent metal and x is the molar ratio.
[0057] Specifically, M can be zinc. Tributylphosphine oxide, zinc iodide, and toluene are mixed in a certain proportion and ultrasonically treated at room temperature for 30 minutes to obtain a clear tributylphosphine oxide-zinc iodide solution.
[0058] S200: Lead oxide, 2-bromoacetophenone, oleic acid, and octadecene are mixed and then injected with diphenyl phosphate and oleylamine at 200–240°C for 15–30 minutes. After cooling, cesium oleate is injected and kept at the same temperature to terminate the reaction, thus obtaining the initial nanocrystals, i.e., large-size cesium lead bromide perovskite nanocrystals. This step is the same as in the previous example.
[0059] S300: Add the TBPO-xMI2 obtained in S100 to the initial nanocrystals obtained in S200 to obtain iodine-bromine mixed halogen pure red perovskite nanocrystals.
[0060] Specifically, a large-size initial nanocrystal solution and toluene are mixed in a certain proportion, followed by the addition of a certain amount of tributylphosphine oxide-zinc iodide solution until the resulting large-size iodine-bromine mixed halogen pure red perovskite nanocrystals exhibit pure red luminescence under ultraviolet light. The product is then purified and dispersed in n-hexane.
[0061] In one embodiment, a method for preparing high-color-purity, large-size perovskite nanocrystals, as shown in Figure 1, includes:
[0062] S100. Prepare TBPO-xMCl2 solution, where M is a divalent metal and x is the molar ratio.
[0063] Specifically, M can be zinc. Tributylphosphine oxide, zinc chloride, and toluene are mixed in a certain proportion and ultrasonically treated at room temperature for 30 minutes to obtain a clear tributylphosphine oxide-zinc chloride solution.
[0064] S200: Lead oxide, 2-bromoacetophenone, oleic acid, and octadecene are mixed and then injected with diphenyl phosphate and oleylamine at 200–240°C for 15–30 minutes. After cooling, cesium oleate is injected and kept at the same temperature to terminate the reaction, thus obtaining the initial nanocrystals, i.e., large-size cesium lead bromide perovskite nanocrystals. This step is the same as in the previous example.
[0065] S300: The TBPO-xMCl2 solution prepared in S100 is added to the initial nanocrystals prepared in S200 to obtain chlorobromine mixed halogen pure blue perovskite nanocrystals.
[0066] Specifically, a large-size initial nanocrystal solution and toluene are mixed in a certain proportion, followed by the addition of a certain amount of tributylphosphine oxide-zinc chloride solution until the resulting large-size chlorobromine mixed halogen pure blue perovskite nanocrystals exhibit pure blue luminescence under ultraviolet light. The product is then purified and dispersed in n-hexane.
[0067] In the three embodiments described above, ligand-assisted halide ion exchange of perovskite nanocrystals was developed, which made the spectrum of the mixed halide perovskite nanocrystals obtained by halide ion exchange more stable and suppressed halide segregation. This is also the key to developing high-performance mixed halide perovskite nanocrystal LED devices.
[0068] In the three embodiments described above, M can be zinc, manganese, calcium, magnesium, etc., wherein Zn 2+ Mn can be incorporated into the perovskite lattice to compensate for defects and adjust the band gap; 2+ Carrier mobility can be enhanced through spin-orbit coupling; Ca 2+ With Pb 2+ When radii are close, lattice stress can be reduced. Within the range of 0 < x < 0.6, metal salts such as ZnBr2, ZnI2, and ZnCl2 can dissolve in a toluene solution of tributylphosphine oxide, resulting in a passivation layer with ideal thickness and quality, effectively reducing surface defects and the number of non-radiative recombination centers.
[0069] When preparing tributylphosphine oxide-zinc bromide / tributylphosphine oxide-manganese bromide / tributylphosphine oxide-calcium bromide solutions (TBPO-xZnBr2 / TBPO-xMnBr2 / TBPO-xCaBr2), such as TBPO-0.4ZnBr2 / TBPO-0.4MnBr2 / TBPO-0.4CaBr2, different bromides and bromide contents (x) will affect the passivation effect and stability of cesium lead bromide perovskite nanocrystals.
[0070] For example, tributylphosphine oxide-zinc iodide / tributylphosphine oxide-manganese iodide / tributylphosphine oxide-calcium iodide solutions (TBPO-xZnI2 / TBPO-xMnI2 / TBPO-xCaI2) and TBPO-0.4ZnI2 / TBPO-0.4MnI2 / TBPO-0.4CaI2 can be prepared. Different iodides affect the stability of iodine-bromine mixed perovskite nanocrystals, and the content (x) of different iodides affects the amount of tributylphosphine oxide-iodide used in the halide ion exchange process.
[0071] For example, tributylphosphine oxide-zinc chloride / tributylphosphine oxide-manganese chloride / tributylphosphine oxide-calcium chloride solutions (TBPO-xZnCl2 / TBPO-xMnCl2 / TBPO-xCaCl2), such as TBPO-0.4ZnCl2 / TBPO-0.4MnCl2 / TBPO-0.4CaCl2. Different chlorides affect the stability of chlorobromine mixed perovskite nanocrystals, and the content (x) of different chlorides affects the amount of tributylphosphine oxide-chloride used in the halide ion exchange process.
[0072] In the above three embodiments, step S200 can be performed before S100, or the two can be performed simultaneously.
[0073] In one embodiment, the method further includes the following steps prior to step S200:
[0074] Preparation of cesium oleate. Cesium carbonate, oleic acid, and octadecene were added to a reaction flask in a certain proportion. The reaction flask was connected to a double-row tube and stirred and dehydrated and deoxygenated at 120 degrees Celsius for 1 hour. Then, nitrogen gas was introduced into the reaction flask and the temperature was raised to 150 degrees Celsius until all the cesium carbonate dissolved.
[0075] In one embodiment, the step S200, which involves cooling down, injecting cesium oleate, and holding the temperature, specifically includes: cooling to 140–200°C, injecting cesium oleate, and holding the temperature. Different reaction temperatures affect the final size of the perovskite nanocrystals obtained. With a fixed holding time, the higher the reaction temperature, the larger the nanocrystals. When the temperature is between 140 and 200°C, the energy of the reaction system is moderate. After the cesium oleate is injected, the crystal growth is neither too rapid, resulting in excessively large and unevenly distributed crystals, nor too slow, affecting production efficiency, and thus yields relatively large nanocrystals.
[0076] In one embodiment, the step S200, which involves cooling down, injecting cesium oleate, and holding the solution at that temperature, specifically includes: injecting cesium oleate after cooling and holding the solution at that temperature for 2–20 minutes. Different holding times affect the final size of the perovskite nanocrystals obtained. At a fixed reaction temperature, the longer the holding time, the larger the nanocrystals. A holding time of 2–20 minutes can effectively control the growth process of the perovskite nanocrystals, resulting in larger nanocrystals.
[0077] In one specific embodiment, large-size cesium lead bromine green perovskite nanocrystals were synthesized.
[0078] Step 1: Preparation of cesium oleate. Add 390.8 mg of cesium carbonate, 2 mL of oleic acid, and 18 mL of octadecene to a reaction flask. Connect the reaction flask to a double-row tube and stir and dehydrate and deoxygenate at 120°C for 1 hour. Then, purge the reaction flask with nitrogen and raise the temperature to 150°C until all the cesium carbonate dissolves.
[0079] Step 2: Preparation of tributylphosphine oxide-zinc bromide solution. 218.3 mg of tributylphosphine oxide, 45.0 mg of zinc bromide, and 1 mL of toluene were mixed and sonicated at room temperature for 30 minutes to obtain a clear tributylphosphine oxide-zinc bromide solution.
[0080] Step 3: Preparation of large-size cesium lead bromide perovskite nanocrystals. 89.2 mg lead oxide, 238.8 mg 2-bromoacetophenone, 2 mL oleic acid, and 10 mL octadecene were added to a reaction flask. The flask was connected to a double-row tube and heated to 80°C with stirring to remove water and oxygen. The reaction temperature was then raised to 220°C, and 0.4 mL diphenyl phosphate and 1 mL oleylamine were injected sequentially and held at this temperature for 15 minutes. Subsequently, the temperature was lowered to 180°C, and 1 mL of the prepared cesium oleate was injected and held at this temperature for 2 minutes. Finally, the reaction flask was placed in an ice bath to cool and terminate the reaction. The product was purified and dispersed in 5 mL n-hexane.
[0081] Step 4: Mix the solution of large-sized cesium lead bromide perovskite nanocrystals and toluene at a volume ratio of 10:1. Then, add a certain amount of tributylphosphine oxide-zinc bromide solution to passivate the surface of the cesium lead bromide nanocrystals. Purify the product and disperse it in n-hexane to obtain large-sized cesium lead bromide green light perovskite nanocrystals.
[0082] The large-size cesium lead bromide green perovskite nanocrystals synthesized in this invention have a narrower emission spectrum half-width (FWHM) (15.5 nm) and higher color purity compared to previously reported cesium lead bromide perovskite nanocrystals.
[0083] In one specific embodiment, the synthesis of large-size iodine-bromine mixed halogen pure red perovskite nanocrystals was carried out.
[0084] Step 1: Preparation of tributylphosphine oxide-zinc iodide solution. 218.3 mg of tributylphosphine oxide, 63.8 mg of zinc iodide, and 1 mL of toluene were mixed and sonicated at room temperature for 30 minutes to obtain a clear tributylphosphine oxide-zinc iodide solution.
[0085] Step 2: Preparation of large-size iodine-bromine mixed halogen pure red perovskite nanocrystals. A solution of large-size cesium lead-bromine perovskite nanocrystals (obtained in Step 3 of the previous embodiment) and toluene were mixed at a volume ratio of 10:1. Tributylphosphine oxide-zinc iodide solution was then added dropwise until the resulting large-size iodine-bromine mixed halogen pure red perovskite nanocrystals exhibited pure red fluorescence under ultraviolet light. The product was then purified and dispersed in n-hexane.
[0086] In one specific embodiment, the synthesis of large-size chlorobromine mixed halogen pure blue perovskite nanocrystals.
[0087] Step 1: Preparation of tributylphosphine oxide-zinc chloride solution. 218.3 mg of tributylphosphine oxide, 27.3 mg of zinc chloride, and 1 mL of toluene were mixed and sonicated at room temperature for 30 minutes to obtain a clear tributylphosphine oxide-zinc chloride solution.
[0088] Step 2: Preparation of large-size chlorobromine mixed halogen pure blue perovskite nanocrystals. A solution of large-size cesium lead bromide perovskite nanocrystals (prepared using the same method as in the previous example) and toluene were mixed at a volume ratio of 10:1. Tributylphosphine oxide-zinc chloride solution was then added dropwise until the resulting large-size chlorobromine mixed halogen pure blue perovskite nanocrystals exhibited pure blue luminescence under ultraviolet light. The product was then purified and dispersed in n-hexane.
[0089] The large-size iodine-bromine mixed halogen pure red perovskite nanocrystals (and large-size chlorobromine mixed halogen pure blue perovskite nanocrystals) synthesized in this invention exhibit better stability, more uniform nanocrystal size distribution, narrower emission spectrum full width at half maximum (FWHM), and higher color purity compared to small-size iodine-bromine mixed halogen perovskite nanocrystals. Specifically, the large-size iodine-bromine mixed halogen pure red perovskite nanocrystals have a FWHM of 27.6 nm (emission peak at 622 nm); the large-size chlorobromine mixed halogen pure blue perovskite nanocrystals have a FWHM of 13.2 nm (emission peak at 459 nm).
[0090] This invention also provides a method for fabricating a high color purity, large-size perovskite nanocrystalline light-emitting diode (LED), the method comprising:
[0091] S100, Clean the ITO glass substrate.
[0092] S200. A hole transport layer is prepared on the ITO glass substrate. The hole transport layer is made of PTAA material and modified with PEABr / F-PEABr / PEAI / F-PEAI.
[0093] S300. When the hole transport layer is a PEABr / F-PEABr modified layer, the cesium lead bromine green perovskite nanocrystals or chlorobromine mixed halogen pure blue perovskite nanocrystals prepared in the aforementioned embodiments are spin-coated onto the surface of the hole transport layer; or
[0094] When the hole transport layer is modified with PEAI / F-PEAI, the iodine-bromine mixed halogen pure red perovskite nanocrystals prepared in the aforementioned embodiments are spin-coated onto the surface of the hole transport layer.
[0095] S400. An electron transport layer is prepared on the perovskite nanocrystalline layer.
[0096] S500, Electrodes are fabricated on the electron transport layer.
[0097] In a more specific embodiment, a green perovskite nanocrystal LED is fabricated.
[0098] Step 1: Clean the indium tin oxide (ITO) glass substrate. The ITO glass substrate is ultrasonically cleaned sequentially with deionized water, acetone, and isopropanol. After drying, the surface of the ITO glass substrate is cleaned with ultraviolet ozone for 15 minutes.
[0099] Step 2: Preparation of the hole transport layer. Poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS) was spin-coated onto the ITO glass surface at 4000 rpm and annealed at 150°C for 15 minutes. Subsequently, a chlorobenzene solution (5 mg / mL) of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) was spin-coated onto the PEDOT:PSS layer at 2000 rpm and annealed at 120°C for 20 minutes. Finally, a solution (10 mg / mL) of N,N-dimethylformamide (DMF) of brominated phenethylamine (PEABr) was spin-coated onto the PTAA layer at 4000 rpm and annealed at 80°C for 10 minutes.
[0100] Step 3: Preparation of perovskite nanocrystal layer. The prepared 5 mg / mL green perovskite nanocrystal solution was spin-coated onto the surface of the hole transport layer at 2000 rpm.
[0101] Step 4: Fabrication of the electron transport layer. Under a vacuum of 4 × 10⁻⁶... -4 A 40 nm electron transport layer of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi) was deposited in a vacuum environment below Pa.
[0102] Step 5: Electrode fabrication. Under a vacuum of 4 × 10⁻⁶. -4 1 nanometer lithium fluoride and 100 nanometer aluminum are sequentially vapor-deposited in a vacuum environment below Pa.
[0103] The green perovskite nanocrystalline LED prepared by this invention has excellent color purity (electroluminescence peak of 520nm and full width at half maximum of 16.6nm), which is one of the best properties among this type of material.
[0104] In a more specific embodiment, a pure red perovskite nanocrystal LED is prepared.
[0105] Step 1: Clean the indium tin oxide (ITO) glass substrate. The ITO glass substrate is ultrasonically cleaned sequentially with deionized water, acetone, and isopropanol. After drying, the surface of the ITO glass substrate is cleaned with ultraviolet ozone for 15 minutes.
[0106] Step 2: Preparation of the hole transport layer. PEDOT:PSS was spin-coated onto the ITO glass surface at 4000 rpm and annealed at 150°C for 15 minutes. Then, a chlorobenzene solution of PTAA (5 mg / mL) was spin-coated onto the PEDOT:PSS layer at 2000 rpm and annealed at 120°C for 20 minutes. Finally, a DMF solution of phenylethylamine iodide (PEAI) (10 mg / mL) was spin-coated onto the PTAA layer at 4000 rpm and annealed at 80°C for 10 minutes.
[0107] Step 3: Preparation of perovskite nanocrystal layer. The prepared 5 mg / mL red light perovskite nanocrystal solution was spin-coated onto the surface of the hole transport layer at 2000 rpm.
[0108] Step 4: Fabrication of the electron transport layer. Under a vacuum of 4 × 10⁻⁶... -4 A 40 nm TPBi electron transport layer was deposited in a vacuum environment below Pa.
[0109] Step 5: Electrode fabrication. Under a vacuum of 4 × 10⁻⁶. -4 1 nanometer lithium fluoride and 100 nanometer aluminum are sequentially vapor-deposited in a vacuum environment below Pa.
[0110] The pure red perovskite nanocrystal LED prepared by this invention has excellent color purity (electroluminescence peak of 633nm and full width at half maximum of 29.2nm), which is one of the best properties among this type of material.
[0111] In a more specific embodiment, a pure blue perovskite nanocrystal LED is prepared.
[0112] Step 1: Clean the indium tin oxide (ITO) glass substrate. The ITO glass substrate is ultrasonically cleaned sequentially with deionized water, acetone, and isopropanol. After drying, the surface of the ITO glass substrate is cleaned with ultraviolet ozone for 15 minutes.
[0113] Step 2: Preparation of the hole transport layer. PEDOT:PSS was spin-coated onto the ITO glass surface at 4000 rpm and annealed at 150°C for 15 minutes. Then, a chlorobenzene solution of PTAA (5 mg / mL) was spin-coated onto the PEDOT:PSS layer at 2000 rpm and annealed at 120°C for 20 minutes. Finally, a DMF solution of PEABr (10 mg / mL) was spin-coated onto the PTAA layer at 4000 rpm and annealed at 80°C for 10 minutes.
[0114] Step 3: Preparation of perovskite nanocrystal layer. The prepared 5 mg / mL blue light perovskite nanocrystal solution was spin-coated onto the surface of the hole transport layer at 2000 rpm.
[0115] Step 4: Fabrication of the electron transport layer. Under a vacuum of 4 × 10⁻⁶... -4A 40 nm TPBi electron transport layer was deposited in a vacuum environment below Pa.
[0116] Step 5: Electrode fabrication. Under a vacuum of 4 × 10⁻⁶. -4 1 nanometer lithium fluoride and 100 nanometer aluminum are sequentially vapor-deposited in a vacuum environment below Pa.
[0117] The pure blue perovskite nanocrystal LED prepared by this invention has excellent color purity (electroluminescence peak at 469 nm and full width at half maximum at 15.2 nm), which is one of the best properties among this type of material.
[0118] In a specific embodiment, the characterization and results are described.
[0119] The prepared large-size perovskite nanocrystals and their LEDs were tested and characterized.
[0120] (1) UV-Vis absorption and fluorescence spectra: The UV-Vis absorption and photoluminescence spectra of the large-size perovskite nanocrystal solution were characterized. Figure 3 shows the UV-Vis absorption (dashed line) and fluorescence (solid line) spectra of the large-size cesium lead bromide perovskite nanocrystals before surface passivation (DPP NCs) and after surface passivation (DPP+T-Br NCs). The emission peak of DPP NCs is 519 nm with a half-width at half-maximum (WHM) of 15.8 nm; the emission peak of DPP+T-Br NCs is 520 nm with a WHM of 15.5 nm.
[0121] Figure 7 shows the UV-Vis absorption spectrum (dashed line) and fluorescence spectrum (solid line) of large-size iodine-bromine mixed perovskite nanocrystals after halide ion exchange. The figure shows that perovskite nanocrystals with different emission wavelengths within the pure red emission range can be achieved through halide ion exchange. Specifically, the emission peak is at 640 nm with a half-width at half-maximum (HWHM) of 28.4 nm; the emission peak is at 635 nm with a HWHM of 28.2 nm; and the emission peak is at 622 nm with a HWHM of 27.6 nm.
[0122] Figure 9 shows the UV-Vis absorption spectrum (dashed line) and fluorescence spectrum (solid line) of large-size chlorobromine mixed perovskite nanocrystals after halide ion exchange. As can be seen from the figure, perovskite nanocrystals with different emission wavelengths within the pure blue emission range can be achieved through halide ion exchange. Specifically, the emission peak is at 468 nm with a half-width at half-maximum (HWHM) of 13.8 nm; the emission peak is at 464 nm with a HWHM of 13.6 nm; and the emission peak is at 459 nm with a HWHM of 13.2 nm.
[0123] (2) TRPL: The fluorescence lifetime of large-sized cesium lead bromide perovskite nanocrystals was characterized, and the influence of the introduction of ligands on the fluorescence lifetime of nanocrystals was analyzed.
[0124] Figure 4 shows the time-resolved fluorescence spectra of large-sized cesium lead bromide perovskite nanocrystals before and after surface passivation (DPP NCs) and after surface passivation (DPP+T-Br NCs). It can be seen that the fluorescence lifetime of DPP+T-Br NCs is longer than that of DPP NCs, indicating that further surface passivation can effectively improve the fluorescence lifetime of perovskite nanocrystals.
[0125] (3) XRD: X-ray diffraction characterization of large-sized perovskite nanocrystals. See Figures 5, 8 and 10.
[0126] Figure 5 shows that the synthesized cesium lead bromide perovskite nanocrystals (DPP NCs) and the passivated cesium lead bromide perovskite nanocrystals (DPP+T-Br NCs) both conform to the standard XRD ICSD97851 and belong to the orthorhombic crystal system.
[0127] Figure 8 shows that the large-sized iodine-bromine mixed perovskite nanocrystals after iodine ion exchange also belong to the orthorhombic crystal system, and as the number of iodine ions exchanged increases (the emission peak becomes more red-shifted), the characteristic peak shifts to a lower angle due to the lattice expansion effect.
[0128] Figure 10 shows that the large-sized chlorobromine mixed perovskite nanocrystals after chloride ion exchange also belong to the orthorhombic crystal system, and as more chloride ions are exchanged (the emission peaks shift more blue), the characteristic peaks shift to higher angles due to the lattice contraction effect.
[0129] (4) FTIR: The surface ligands of large-size perovskite nanocrystals are characterized, and the functional groups in the ligands are characterized.
[0130] Figure 6 shows the Fourier transform infrared spectra of large-sized cesium lead bromide perovskite nanocrystals before and after surface passivation (DPP NCs) and after surface passivation (DPP+T-Br NCs). A 1130 cm⁻¹ depth can be observed in the spectra. -1 The characteristic peak of the P=O bond at the location indicates that the ligand DPP is effectively introduced into the surface of the perovskite nanocrystals.
[0131] (5) Photothermal stability test: Under continuous illumination of 405nm and continuous heating of 80 degrees Celsius, the change in luminescence intensity of large-size perovskite nanocrystals was tested.
[0132] Figure 12 shows the photothermal stability of large-size cesium lead bromide perovskite nanocrystals (DPP+T-Br), large-size iodine bromide mixed perovskite nanocrystals (DPP+TI), and large-size chloro bromide mixed perovskite nanocrystals (DPP+T-Cl). The test conditions were continuous illumination at 405 nm and continuous heating at 80 degrees Celsius. All three nanocrystals (DPP+T-Br, DPP+TI, and DPP+T-Cl) exhibited excellent photothermal stability.
[0133] (6) TEM: The large-sized perovskite nanocrystals were characterized by transmission electron microscopy to analyze their size.
[0134] Figure 11 shows transmission electron microscopy (TEM) images of large-size cesium lead bromide perovskite nanocrystals (DPP+T-Br), large-size iodine bromide mixed perovskite nanocrystals (DPP+TI), and large-size chloro bromide mixed perovskite nanocrystals (DPP+T-Cl). The DPP+T-Br nanocrystals are approximately 15.61 nm in size, the DPP+TI nanocrystals are approximately 16.03 nm in size, and the DPP+T-Cl nanocrystals are approximately 14.43 nm in size.
[0135] (7) LED device testing: The prepared red, green and blue perovskite nanocrystalline LEDs were tested. The main test parameters were electroluminescence peak, current density, external quantum efficiency, and luminous brightness. See Figure 13-15.
[0136] Figure 13 shows the performance test results of the LED device fabricated using large-size cesium lead bromide perovskite nanocrystals. Figure 13(a) shows the JVL curve, indicating that the device has a start-up voltage of 2.7V and a maximum luminance of 11201 cd / m². 2 Figure 13(b) shows the external quantum efficiency-current density curve, indicating that the highest efficiency of the device is 16.03%. Figure 13(c) shows the electroluminescence spectrum, indicating that the emission peak of the device is 520 nm with a full width at half maximum (FWHM) of 16.6 nm. Figure 13(d) shows the spectrum of the green LED device at different voltages, demonstrating that the device has good spectral stability.
[0137] Figure 14 shows the performance test results of the LED device fabricated from large-size iodine-bromine mixed perovskite nanocrystals (DPP+TI). Figure 14(a) shows the JVL curve, indicating that the device has a turn-on voltage of 3.0V and a maximum luminance of 717 cd / m². 2 Figure 13(b) shows the external quantum efficiency-current density curve, indicating that the highest efficiency of the device is 19.70%. Figure 14(c) shows the electroluminescence spectrum, indicating that the emission peak of the device is 633 nm and the full width at half maximum (FWHM) is 29.2 nm. Figure 14(d) shows the spectrum of the red LED device at different voltages, demonstrating that the device has good spectral stability.
[0138] Figure 15 shows the performance test results of the LED device prepared from large-size chlorobromine mixed perovskite nanocrystals (DPP+T-Cl). Figure 15(a) shows the JVL curve, indicating that the device has a turn-on voltage of 3.3V and a maximum luminance of 762 cd / m². 2Figure 15(b) shows the external quantum efficiency-current density curve, indicating that the highest efficiency of the device is 6.60%. Figure 15(c) shows the electroluminescence spectrum, indicating that the emission peak of the device is 469 nm with a full width at half maximum (FWHM) of 15.2 nm. Figure 15(d) shows the spectrum of the blue LED device at different voltages, demonstrating that the device has good spectral stability.
[0139] In one embodiment, the present invention also discloses a high color purity large-size perovskite nanocrystal light-emitting diode, which is prepared by the above-described preparation method. A schematic diagram of the perovskite nanocrystal LED structure is shown in Figure 2. The present invention prepares an electroluminescent LED using high color purity large-size cesium lead bromide perovskite nanocrystals and mixed halogen perovskite nanocrystals. This achieves an efficiency of 16.03% (half-width at half maximum) for a green LED with an emission peak at 520 nm, an efficiency of 19.70% (half-width at half maximum) for a pure red LED with an emission peak at 633 nm, and an efficiency of 6.60% (half-width at half maximum) for a pure blue LED with an emission peak at 469 nm.
[0140] In the description of this specification, the use of terms such as "Embodiment 1," "this embodiment," or "in one embodiment" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in one or more embodiments or examples.
[0141] In the description of this specification, the terms "connection," "installation," "fixing," "setting," and "having" are interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.
[0142] In the description of this specification, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0143] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the technology of this invention. Those skilled in the art can easily make various modifications to these examples and apply the general principles described herein to other embodiments without creative effort. Therefore, this invention is not limited to the above embodiments. Modifications in the following situations should be within the scope of protection of this invention: ① New technical solutions implemented based on the technical solution of this invention and combined with existing common knowledge, where the technical effects of the new technical solution do not exceed the technical effects of this invention; ② Equivalent substitutions of some features of the technical solution of this invention using known technology, resulting in the same technical effects as those of this invention; ③ Extendable technical solutions based on the technical solution of this invention, where the substantive content of the extended technical solution does not exceed the technical solution of this invention; ④ Equivalent transformations made using the content of this specification and drawings, directly or indirectly applied to other related technical fields.
Claims
1. A method for preparing high-color-purity, large-size perovskite nanocrystals, characterized in that, The method includes: S100, prepare TBPO-xMBr2, TBPO-xMI2 or TBPO-xMCl2 solutions, where M is a divalent metal and x is the molar ratio; S200: Lead oxide, 2-bromoacetophenone, oleic acid, and octadecene are mixed and then injected with diphenyl phosphate and oleylamine at 200-240°C. The mixture is kept at this temperature for 15-30 minutes. After cooling, cesium oleate is injected and kept at this temperature to terminate the reaction and obtain the initial nanocrystals. S300: Add the TBPO-xMBr2 solution prepared in S100 to the initial nanocrystals obtained in S200 to obtain cesium lead bromine green perovskite nanocrystals; or The TBPO-xMI2 solution prepared by S100 is added to the initial nanocrystals prepared by S200 to obtain iodine-bromine mixed halogen pure red perovskite nanocrystals; or The TBPO-xMCl2 solution prepared by S100 is added to the initial nanocrystals prepared by S200 to obtain chlorobromine mixed halogen pure blue perovskite nanocrystals.
2. The preparation method according to claim 1, characterized in that, M is one of zinc, manganese, or calcium.
3. The preparation method according to claim 1, characterized in that, 0＜x＜0.6。 4. The preparation method according to claim 1, characterized in that, The process of injecting cesium oleate after cooling in S200 and then maintaining the temperature specifically includes: cooling to 140-200°C, injecting cesium oleate, and maintaining the temperature.
5. The preparation method according to claim 1, characterized in that, The process of injecting cesium oleate after cooling in S200 and maintaining the temperature specifically includes: injecting cesium oleate after cooling and maintaining the temperature for 2 to 20 minutes.
6. A method for fabricating a high color purity, large-size perovskite nanocrystalline light-emitting diode, characterized in that, The method includes: S100, Cleaning the ITO glass substrate; S200: A hole transport layer is prepared on the ITO glass substrate, wherein the hole transport layer is made of PTAA material and a PEABr / F-PEABr / PEAI / F-PEAI modification layer; S300. When the hole transport layer is a PEABr / F-PEABr modified layer, the cesium lead bromine green perovskite nanocrystals or chlorobromine mixed halogen pure blue perovskite nanocrystals prepared according to any one of claims 1-5 are spin-coated onto the surface of the hole transport layer; or When the hole transport layer is modified with PEAI / F-PEAI, the iodine-bromine mixed halogen pure red perovskite nanocrystals prepared according to any one of claims 1-5 are spin-coated onto the surface of the hole transport layer. S400: An electron transport layer is prepared on the perovskite nanocrystalline layer; S500, Electrodes are fabricated on the electron transport layer.
7. A high color purity, large-size perovskite nanocrystal light-emitting diode, characterized in that, It is prepared by the preparation method described in claim 6.