Perovskite light-emitting device and preparation method and application thereof

Abstract

The invention belongs to the technical field of light-emitting devices, and particularly relates to a perovskite light-emitting device and a preparation method and application thereof. The perovskite light-emitting device comprises a substrate, an anode, a hole transport-phosphorescence sensitization layer, a perovskite light-emitting layer, a phosphorescence ultrathin layer, an electron transport layer, an electron injection layer and a cathode which are stacked in sequence. According to the perovskite light-emitting device, the hole transport-phosphorescence sensitization layer and the phosphorescence ultra-thin layer are combined, efficient charge transport and energy transfer are achieved by reasonably regulating and controlling the concentration of a doped material in the sensitization layer and the thickness of the ultra-thin layer, and the performance of the perovskite light-emitting device is remarkably improved; according to the structural design, the synergistic effect of the sensitization layer and the ultrathin layer is fully utilized, and a new thought is provided for development of an efficient perovskite light-emitting device.

Description

Technical Field

[0001] The present invention belongs to the technical field of light-emitting devices, and in particular relates to a perovskite light-emitting device and a preparation method and application thereof. Background Art

[0002] Perovskite light-emitting devices are a new type of light-emitting device that uses perovskite materials as the light-emitting layer. In recent years, the external quantum efficiency (EQE) of perovskite light-emitting devices in the green, red and near-infrared bands has exceeded 20%, showing broad application potential in ultra-high-definition display, solid-state lighting and optical communications.

[0003] However, blue perovskite luminescent materials still have significant spectral stability issues. Due to the influence of ion migration, phase separation and surface defects, their emission peaks are prone to red shift or spectrum broadening during device operation, making it difficult to meet the strict requirements for precise color control in practical applications.

[0004] Since blue light perovskite has a shorter wavelength and a higher band gap energy, it is more susceptible to external influences, resulting in prominent problems with the stability of its chemical properties. In addition, blue light perovskite light-emitting devices usually experience efficiency roll-off at high current density, which is related to the fact that perovskite materials are more likely to produce non-radiative recombination, Auger recombination, and carrier localization in a highly excited state, thus limiting their luminous efficiency at high brightness.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a perovskite light-emitting device and a preparation method thereof; the perovskite light-emitting device adopts a perovskite light-emitting layer combined with a hole transport-phosphorescence sensitization layer and a phosphorescent ultra-thin layer structure, which improves the efficiency roll-off of the perovskite light-emitting device, improves the overall stability of the device, and significantly extends the service life of the device.

[0007] In order to overcome the deficiencies of the prior art, the present invention provides the following technical solutions: A perovskite light-emitting device comprises a substrate, an anode, a hole transport-phosphorescence sensitization layer, a perovskite light-emitting layer, a phosphorescent ultra-thin layer, an electron transport layer, an electron injection layer and a cathode which are stacked in sequence.

[0008] Furthermore, the hole transport-phosphorescence sensitization layer is composed of a hole transport material doped with a phosphorescent material and a fluorescent material; the molar concentration of the phosphorescent material in the hole transport-phosphorescence sensitization layer is 5-15%, and the molar concentration of the fluorescent material in the hole transport-phosphorescence sensitization layer is 0.1-3%.

[0009] Furthermore, the emission wavelength of the phosphorescent material is shorter than that of the fluorescent material; the emission wavelength of the phosphorescent material and the absorption wavelength of the fluorescent material overlap; and the difference between the HOMO energy level of the phosphorescent material and the HOMO energy level of the fluorescent material is greater than 0.2 eV.

[0010] Furthermore, the phosphorescent material is Fir6; and / or the fluorescent material is 4TCzBN.

[0011] Further, the hole transport material is poly-9-vinyl carbazole or poly-3,4-ethylenedioxythiophene / polystyrene sulfonate; And / or, the material of the phosphorescent ultra-thin layer is Fir6; And / or, the material of the perovskite light-emitting layer is selected from a two-dimensional crystal structure or a three-dimensional crystal structure, or a combination thereof.

[0012] Furthermore, the thickness of the hole transport-phosphorescence sensitization layer is 15-20 nm; and / or the thickness of the phosphorescent ultra-thin layer is 0.01-1 nm; and / or the thickness of the perovskite light-emitting layer is 10-25 nm.

[0013] In addition, the present invention also provides a method for preparing the above-mentioned perovskite light-emitting device, comprising the following steps: S1, mixing the phosphorescent material, fluorescent material and hole transport material in proportion, filtering through a microporous filter membrane, spin coating on an ITO glass substrate under an atmospheric environment, and annealing to obtain a hole transport-phosphorescence sensitization layer; S2, preparing a perovskite precursor solution; then filtering the perovskite precursor solution through a microporous filter membrane, spin coating it on the substrate obtained in step S1 in a glove box filled with nitrogen, and annealing to obtain a perovskite light-emitting layer; S3, on the substrate obtained in step S2, sequentially evaporating a phosphorescent ultra-thin layer and an electron transport layer by vacuum evaporation method; S4. On the substrate obtained in step S3, an electron injection layer and a metal cathode are sequentially deposited by vacuum evaporation to obtain the perovskite light-emitting device.

[0014] Further, in step S1, the spin coating conditions are: spin coating speed 3500 rpm, spin coating acceleration 1000 rpm / s, and spin coating time 40 s; And / or, in step S1, the annealing condition is: annealing on a hot plate at 165° C. for 25 minutes; And / or, in step S1, the microporous filter membrane is a polytetrafluoroethylene microporous filter membrane with a pore size of 0.22 μm.

[0015] Further, in step S2, the spin coating conditions are: spin coating at 6500 rpm for 90 seconds; And / or, in step S2, the annealing condition is: keeping warm at 65° C. for 5 minutes.

[0016] And / or, in step S3, the vacuum degree of the evaporation is controlled at 3×10 -5 Below Pa; And / or, in step S3, the phosphorescent material is heated to 185° C. and then vapor deposited; the film forming rate is 0.2 nm / s; And / or, in step S4, the vacuum degree of the evaporation is controlled at 3×10 -4 Below Pa, the film formation rate is 0.2nm / s.

[0017] In addition, the present invention also provides the use of the above-mentioned perovskite light-emitting device in display and lighting products.

[0018] Compared with the prior art, the technical solution of the present invention has at least the following technical effects: The present invention designs a perovskite light-emitting device based on a hole transport-phosphorescence sensitization layer combined with a phosphorescent ultra-thin layer. The hole transport-phosphorescence sensitization layer and the phosphorescent ultra-thin layer are combined. By rationally regulating the concentration of the doping material in the sensitization layer and the thickness of the ultra-thin layer, efficient charge transfer and energy transfer are achieved, and the performance of the perovskite light-emitting device is significantly improved; this structural design makes full use of the synergistic effect of the sensitization layer and the ultra-thin layer, and provides a new idea for the development of efficient perovskite light-emitting devices. Specifically, using the principle of phosphorescence sensitization, phosphorescent materials and fluorescent materials are co-doped into the hole transport layer, and carriers are easily captured preferentially by the phosphorescent material. The singlet excitons formed can transfer energy to the singlet excitons of the fluorescent material through FET (Förster energy transfer), which greatly increases the utilization rate of the excitons and also improves the emission energy of the fluorescent material. The phosphorescent ultra-thin layer can reuse the excitons formed by some holes passing through the perovskite light-emitting layer to the electron transport layer and then transfer energy to the perovskite light-emitting layer. The present invention improves the efficiency roll-off of the perovskite light-emitting device by combining a hole transport-phosphorescence sensitization layer with a phosphorescence ultra-thin layer, improves the overall stability of the device, and significantly prolongs the service life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. Among them: Figure 1 It is a schematic structural diagram of the perovskite light-emitting device of the present invention; Figure 2 The external quantum efficiency-brightness characteristic curves of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 of the present invention; Figure 3 The normalized electroluminescence spectra of Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 of the present invention are shown. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0021] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0022] According to a first aspect of the present invention, a perovskite light emitting device is provided, such as Figure 1 As shown, its structure includes a substrate, an anode, a hole transport-phosphorescence sensitization layer, a perovskite light-emitting layer, a phosphorescent ultra-thin layer, an electron transport layer, an electron injection layer and a cathode stacked in sequence.

[0023] The internal quantum efficiency of traditional fluorescent materials is limited by the proportion of singlet excitons (25%), which makes it difficult to further improve the luminous efficiency. To overcome this problem, phosphorescence-sensitized fluorescence technology has gradually received attention. By introducing phosphorescent materials as sensitizing layers in the device and utilizing their higher triplet exciton utilization rate, energy transfer from phosphorescent materials to fluorescent materials is promoted, thereby effectively improving the exciton utilization efficiency. The present invention dopes phosphorescent materials and fluorescent materials into the hole transport layer to form a hole transport-phosphorescence sensitization layer. The hole transport layer is doped with phosphorescence sensitizers, which can significantly improve the film quality of the hole transport layer. The perovskite light-emitting layer is directly spin-coated on the hole transport layer, and its film quality directly affects the performance of the perovskite layer. If the film quality of the hole transport layer is poor, the defect density of the perovskite will be large, thereby reducing the luminescence efficiency. By improving the film quality of hole transport, the defects in the perovskite are reduced, and the luminescence efficiency is improved. At the same time, the phosphorescent material is doped in the hole transport layer, and the carriers are easily captured by the phosphorescent material to form excitons. The singlet excitons of the phosphorescent material can be converted to triplet excitons through intersystem crossing, and the accumulation of a large number of triplet excitons will lead to the annihilation of triplet excitons. By introducing fluorescent materials, both the singlet excitons and triplet excitons of the phosphorescent material can be transferred to the singlet state of the fluorescent material through FET (Förster energy transfer). Dexter energy transfer is suppressed, the annihilation of triplet excitons is weakened, and the utilization rate of excitons is improved.

[0024] Advantages of the phosphorescent ultra-thin layer: some holes can pass through the perovskite light-emitting layer to the electron transport layer and form excitons with electrons for reuse, thereby transferring energy to the perovskite light-emitting layer. In addition, the ultra-thin layer preparation process is simple, providing an effective strategy for the commercial application of perovskite light-emitting devices.

[0025] Energy transfer process of perovskite light-emitting layer: When an external voltage is applied to the perovskite film, electrons and holes combine through Coulomb force to form excitons. The energy released by the exciton recombination is emitted in the form of photons, forming the luminescence of the perovskite material. When excitons and energy leakage occur, the hole transport-phosphorescence sensitization layer and the phosphorescence ultra-thin layer can be transferred to the perovskite light-emitting layer through the FET process, further improving the emission of energy of the perovskite material, thereby improving device performance.

[0026] In the perovskite light-emitting device of the above scheme, as a preferred embodiment, the hole transport-phosphorescence sensitization layer 3 is composed of a hole transport material doped with a phosphorescent material and a fluorescent material; wherein, in order to ensure efficient energy transfer between the hole transport-phosphorescence sensitization layer and the perovskite light-emitting layer, the molar concentration of the phosphorescent material doped in the hole transport-phosphorescence sensitization layer is preferably 5-15% (for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%), and the molar concentration of the fluorescent material doped in the hole transport-phosphorescence sensitization layer is preferably 0.1-3% (for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%).

[0027] In order to ensure that the phosphorescent material can successfully sensitize the fluorescent material, the emission wavelength of the phosphorescent material is shorter than the emission wavelength of the fluorescent material; the emission wavelength of the phosphorescent material and the absorption wavelength of the fluorescent material overlap. In order to ensure that phosphorescence can effectively capture carriers, the difference between the HOMO energy level of the phosphorescent material and the HOMO energy level of the fluorescent material is greater than 0.2 eV.

[0028] In the perovskite light-emitting device of the above scheme, as a preferred embodiment, the phosphorescent material is Fir6; optionally, the fluorescent material is 4TCzBN. The emission wavelength of Fir6 is shorter than that of 4TCzBN, and the emission wavelength of Fir6 overlaps with the absorption wavelength of 4TCzBN.

[0029] In the perovskite light-emitting device of the above scheme, as a preferred embodiment, the hole transport material is poly-9-vinyl carbazole or poly-3,4-ethylenedioxythiophene / polystyrene sulfonate; In order to ensure the wide applicability of the present invention, the material of the phosphorescent ultra-thin layer and the phosphorescent material in the hole transport-phosphorescent sensitization layer may be the same or different. Preferably, the material of the phosphorescent ultra-thin layer is Fir6.

[0030] In the perovskite light-emitting device of the above scheme, as a preferred implementation mode, the thickness of the hole transport-phosphorescence sensitization layer is 15~20nm (for example, 15nm, 16nm, 17nm, 18nm, 19nm, 20nm); optionally, in order to ensure efficient energy transfer between the phosphorescent ultra-thin layer and the perovskite light-emitting layer, the thickness of the phosphorescent ultra-thin layer is preferably 0.01~1nm (for example, 0.01nm, 0.1nm, 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm); optionally, the thickness of the perovskite light-emitting layer is 10~15nm (for example, 10 nm, 11 nm, 12 nm, 13nm, 14 nm, 15 nm).

[0031] The material of the perovskite light-emitting layer is selected from a two-dimensional crystal structure or a three-dimensional crystal structure, or a combination thereof, or others, such as ABX 3 The compound has a structure of type 2; the A position is a positive monovalent organic cation or an inorganic metal cation with a larger radius. The B position is a positive divalent metal cation with a smaller radius. The X position is a negative monovalent halogen element. The A, B, and X positions can all be composed of one or more components.

[0032] According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned perovskite light-emitting device, comprising the following steps: S1, mixing the phosphorescent material, fluorescent material and hole transport material in proportion, filtering through a microporous filter membrane, spin coating on an ITO glass substrate under an atmospheric environment, and annealing to obtain a hole transport-phosphorescence sensitization layer; S2, preparing a perovskite precursor solution; then filtering the perovskite precursor solution through a microporous filter membrane, spin coating it on the substrate obtained in step S1 in a glove box filled with nitrogen, and annealing to obtain a perovskite light-emitting layer; S3, on the substrate obtained in step S2, sequentially evaporating a phosphorescent ultra-thin layer and an electron transport layer by vacuum evaporation method; S4. On the substrate obtained in step S3, an electron injection layer and a metal cathode are sequentially deposited by vacuum evaporation to obtain the perovskite light-emitting device.

[0033] In the above preparation method, as a preferred embodiment, in step S1, the spin coating conditions are: spin coating speed is 3500 rpm, spin coating acceleration is 1000 rpm / s, and spin coating time is 40 s.

[0034] Optionally, in step S1, the annealing condition is: annealing on a hot plate at 165°C for 25 minutes.

[0035] Optionally, in step S1, the microporous filter membrane is a polytetrafluoroethylene microporous filter membrane with a pore size of 0.22 μm.

[0036] In the above preparation method, as a preferred embodiment, the phenylethylamine cesium lead chloride bromine (PEACsPb (Cl / Br)) mixed quasi-two-dimensional perovskite prepared by spin coating method, which has been widely studied, is used as an example to briefly describe the basic content of the scheme of the present invention. The preparation method of the perovskite precursor solution comprises: PEABr, CsBr, (PbCl 2 +PbBr 2 ) was added to DMSO (dimethyl sulfoxide) at a molar ratio of 0.8:1:0.95, and the molar concentration of CsBr was maintained at 1.2 mmol / ml. The solution was added to a magnetic stirrer and stirred at 200 rpm for 2 hours; before use, the perovskite precursor solution was filtered with a 0.22μm polytetrafluoroethylene filter.

[0037] Optionally, in step S2, the spin coating condition is: spin coating at 6500 rpm for 90 seconds; Optionally, in step S2, the annealing condition is: keeping warm at 65°C for 5 minutes.

[0038] In the above preparation method, as a preferred embodiment, in step S3, the vacuum degree of the evaporation is controlled at 3×10 -5 Below Pa; Optionally, in step S3, the phosphorescent material is heated to 185° C. and then vapor deposition is started; the film forming rate is 0.2 nm / s; Optionally, in step S4, the vacuum degree of the evaporation is controlled at 3×10 -4 Below Pa, the film formation rate is 0.2nm / s.

[0039] According to a third aspect of the present invention, there is provided application of the above-mentioned perovskite light-emitting device in display and lighting products.

[0040] The present invention will be described in detail below in conjunction with embodiments of the present invention, and each example is provided by way of explanation of the present invention without limiting the present invention. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present invention without departing from the scope or spirit of the present invention. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desired that the present invention includes such modifications and variations within the scope of the appended claims and their equivalents.

[0041] In the embodiments of the present invention, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0042] It should be noted that the meanings of the abbreviations in the present invention are as follows: ITO: Indium Tin Oxide, used as a transparent anode; PEDOT:PSS: poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate, as the hole transport material in the hole transport-phosphorescence sensitizing layer; Fir6: iridium(III) bis(2,4-difluorophenylpyrido)tetra(1-pyrazolyl)borate, as the phosphorescent material for sensitizing fluorescence in the hole transport-phosphorescent sensitizing layer; 4TCzBN: 2,3,5,6-tetrakis[3,6-bis(1,1-dimethylethyl)-9H-carbazole-9-yl]benzonitrile, which is used as a fluorescent material sensitized by the phosphorescent material in the hole transport-phosphorescence sensitization layer and transfers energy to the perovskite material; PEACsPb(Cl / Br): phenylethylamine cesium lead chloride-bromine mixed quasi-two-dimensional perovskite, used as the light-emitting material in the perovskite light-emitting layer; TmPyPB: 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bipyridine, thickness 35 nm, electron transport material, conducive to the transmission of electrons; Liq: 8-hydroxyquinoline-lithium, thickness 1 nm, electron injection layer material, conducive to electron injection; Al: Aluminum, 100 nm thick, used as cathode.

[0043] Embodiment 1: This embodiment provides a method for preparing a perovskite light-emitting device, and the specific steps are as follows: Step 1: Clean the ITO glass with acetone, anhydrous ethanol, and deionized water in turn, and ultrasonically clean it in a constant temperature water bath at 50°C for 15 minutes. Rinse with deionized water before each cleaning step, and then blow dry with high-purity nitrogen. Then move the substrate rack with the ITO glass slide into the OLED-V organic multifunctional high vacuum film forming equipment, place it in the pretreatment chamber, and pretreat it with oxygen plasma for 10 minutes to increase the work function of ITO and improve the hole injection ability.

[0044] Step 2: After cooling the substrate for 15 min, take out the PEDOT:PSS aqueous solution from the refrigerator (3-5 ℃). Mix the phosphorescent material Fir6 and the fluorescent material 4TCzBN with the PEDOT:PSS aqueous solution at a doping concentration of 8% and 2%, where the doping percentage refers to the molar ratio of the hole transport material to the dopant. The phosphorescent material in this structure can sensitize the fluorescent material and enhance the emission energy of the fluorescent material, so that the sensitized fluorescent material transfers higher energy to the perovskite light-emitting layer. Shake the mixed solution thoroughly and filter it with a 0.22 μm polytetrafluoroethylene filter. Start spin coating the PEDOT:PSS doped solution as a hole transport-phosphorescence sensitization layer in an atmospheric environment. The doping solution was spread on the surface of the anode glass, and the PEDOT:PSS doping solution was spin-coated using a coating machine at a speed of 3500 rpm, a spin-coating acceleration of 1000 rpm / s, and a spin-coating time of 40 s. After the spin-coating, the substrate was placed on a hot plate at 165 °C for annealing for 25 minutes to obtain a hole transport doping layer. Subsequently, the film was cooled for 20 min.

[0045] Step 3: When preparing the light-emitting layer, the prepared hole transport doping layer film is transferred to a glove box filled with nitrogen, and the perovskite light-emitting layer precursor solution is prepared in the glove box filled with nitrogen.

[0046] Preparation of perovskite light-emitting layer precursor solution: PEABr, CsBr, (PbCl 2 +PbBr 2 ) was added to DMSO in a certain molar ratio of 0.8:1:0.95 to prepare the perovskite precursor solution. The molar concentration of CsBr was maintained at 1.2 mmol / ml. The solution was added to a magnetic stirrer and stirred at 200 rpm for 2 hours. Before use, the perovskite precursor solution was filtered with a 0.22 μm polytetrafluoroethylene filter.

[0047] In a glove box filled with nitrogen, the filtered perovskite precursor solution was evenly spread on the surface of the cooled hole transport doping layer, and the perovskite film was spin-coated at 6500 rpm for 90 seconds using a spin coater, and then treated at 65°C for 5 minutes to obtain a perovskite light-emitting layer.

[0048] Step 4: Move the substrate into the organic thin film evaporation chamber to sequentially evaporate the phosphorescent ultra-thin layer and the electron transport layer. The vacuum degree of evaporation is controlled at 3×10 -5 Pa or less. Among them, phosphor material powder and electron transport material powder are placed in an organic heating source, and metal particles are placed in a metal heating source. The phosphor material placed in the organic source is gradually heated to 185°C. When the rate monitored by the quartz crystal oscillator is 0.2 nm / s, the large baffle is opened to start evaporating the ultra-thin layer until the quartz crystal oscillator monitors the film thickness to be 0.5nm. The large baffle is closed to complete the evaporation of the ultra-thin layer. After the organic functional layer is prepared, a 1nm thick electron injection layer Liq and a 100nm thick metal cathode Al are then evaporated. The vacuum degree of evaporation is controlled at 3×10 -4 Pa, the film formation rate is 0.2 nm / s, and the film formation rate and thickness are monitored in real time by a quartz crystal oscillator during the entire evaporation process. After the evaporation is completed, the prepared device is taken out for scraping, and the electroluminescent efficiency, electroluminescent spectrum, current density-voltage-brightness and other photoelectric properties are measured.

[0049] The structure of the perovskite light-emitting device prepared in this embodiment is: ITO / PEDOT:PSS:Fir6 (8%): ​​4TCzBN (2%) (15nm) / PEACsPb (Cl / Br) (15nm) / Fir6 (0.5 nm) / TmPyPB (35 nm) / Liq (1nm) / Al (100 nm).

[0050] Comparative Example 1: This comparative example provides a method for preparing a perovskite light-emitting device with a single ultra-thin phosphorescent layer. The remaining step parameters are the same as those in Example 1, except that: PEDOT:PSS was taken out of the refrigerator without treatment. After being fully shaken, it was filtered through a 0.22 μm polytetrafluoroethylene filter and used directly. The structure of the single phosphorescent ultra-thin layer perovskite light-emitting device prepared in this comparative example was: ITO / PEDOT:PSS (15nm) / PEACsPb(Cl / Br) (15nm) / Fir6 (0.5nm) / TmPyPB (35 nm) / Liq (1nm) / Al (100 nm).

[0051] Comparative Example 2: This comparative example provides a perovskite light-emitting device with a single undoped hole transport layer. The remaining step parameters are the same as those of Example 1, except that: No hole transport-phosphorescence sensitization layer and phosphorescence ultra-thin layer were set, only one hole transport layer and perovskite layer were set. PEDOT:PSS was taken out of the refrigerator without treatment. After being fully shaken, it was directly used after filtering with a 0.22 μm polytetrafluoroethylene filter. The specific device structure was: ITO / PEDOT:PSS (15 nm) / PEACsPb(Cl / Br) (15 nm) / TmPyPB (35 nm) / Liq (1 nm) / Al (100 nm).

[0052] Comparative Example 3: This comparative example provides a perovskite light-emitting device combining a hole transport-phosphorescent doping layer and a phosphorescent ultra-thin layer. The remaining step parameters are the same as those of Example 1, except that: In this comparative example, the phosphorescent material used in the hole transport-phosphorescent doping layer is Firpic (bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)iridium III), and the fluorescent material is Bepp2 (bis[2-(2-pyridyl)phenol]beryllium).

[0053] The phosphorescent materials Firpic and Bepp2 were mixed with the PEDOT:PSS solution at molar concentrations of 8% and 2%. Since the phosphorescent material in this structure cannot sensitize the fluorescent material, there is no process in which the sensitized fluorescent material achieves energy enhancement and transfers energy to the perovskite light-emitting layer. Since the emission wavelength of the fluorescent material is smaller than that of the phosphorescent material, the singlet excitons of the fluorescent material can be transferred to the singlet excitons of the phosphorescent material through the Förster energy transfer (FET) mechanism. The singlet excitons of the phosphorescent material are further converted into triplet excitons through intersystem crossing, thereby inducing the annihilation of triplet excitons and causing a decrease in device performance.

[0054] The specific device structure is ITO / PEDOT:PSS:Firpic (8%):Bepp2(2%) (15 nm) / PEACsPb (Cl / Br) (15 nm) / Fir6 (0.5 nm) / TmPyPB (35 nm) / Liq(1 nm) / Al(100nm).

[0055] Comparative Example 4: This comparative example provides a light-emitting device combining a perovskite-doped sensitizing layer with a phosphorescent ultra-thin layer. The remaining step parameters are the same as those of Example 1, except that: In this comparative example, PEDOT:PSS was taken out of the refrigerator without treatment, and was directly used after being fully shaken and filtered with a 0.22 μm polytetrafluoroethylene filter. The PEDOT:PSS doping solution was spin-coated using a gel coater at a speed of 3500 rpm, a spin-coating acceleration of 1000 rpm / s, and a spin-coating time of 40 s. After the spin coating, the substrate was placed on a hot plate at 165°C for annealing for 25 minutes to obtain a hole transport layer; Preparation of perovskite light-emitting layer precursor solution: PEABr, CsBr, (PbCl 2 +PbBr 2 ) was added to DMSO in a certain molar ratio of 0.8:1:0.95 to prepare a perovskite precursor solution. Then, Fir6 and 4TCzBN with molar concentrations of 8% and 2%, respectively, were doped into the perovskite precursor solution. The doping percentage refers to the ratio of dopant and Cs + The molar ratio of CsBr was maintained at 1.2 mmol / ml. The solution was added to a magnetic stirrer and stirred at 200 rpm for 2 hours. Before use, the perovskite precursor solution was filtered with a 0.22 μm polytetrafluoroethylene filter. The filtered perovskite precursor solution was evenly spread on the surface of the cooled hole transport doping layer, and the perovskite film was spin-coated at 6500 rp for 90 seconds using a spin coater, and then treated at 65°C for 5 minutes to obtain a perovskite light-emitting layer.

[0056] In this structure, the phosphorescent material and the fluorescent material are mixed with the perovskite precursor solution, which cannot change the film quality of the hole transport layer. Since the film quality of the hole transport layer cannot be improved, the defect density of the perovskite light-emitting layer increases, which reduces the light-emitting performance of the device.

[0057] The specific device structure is: ITO / PEDOT:PSS (15 nm) / PEACsPb (Cl / Br):8% Fir6:2%4TCzBN (15 nm) / Fir6 (0.5 nm) / TmPyPB (35 nm) / Liq (1 nm) / Al (100 nm).

[0058] Comparative Example 5: This comparative example provides a perovskite light-emitting device with a single hole transport-phosphorescence sensitization layer. The remaining step parameters are the same as those of Example 1, except that: The substrate is moved into an organic thin film evaporation chamber to evaporate only the electron transport layer, electron injection layer and metal cathode Al, without the phosphorescent ultra-thin layer. Since the device has a hole transport-phosphorescent sensitization layer, the performance of the device is improved compared to the performance of the single perovskite light-emitting layer in comparative example 2.

[0059] This structure does not have a phosphorescent ultra-thin layer. The specific device structure is: ITO / PEDOT: PSS: 8% Fir6: 2% 4TCzBN ( (15 nm) / PEACsPb (Cl / Br) (15 nm) / TmPyPB (35 nm) / Liq (1 nm) / Al (100 nm).

[0060] from Figure 2 , 3 It can be seen that by combining the hole transport-phosphorescence sensitization layer with the phosphorescent ultra-thin layer, energy is transferred to the perovskite light-emitting layer to prepare a sky blue perovskite light-emitting device with high efficiency, low roll-off and spectrally stable. From the electroluminescence spectrum, Example 1, Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5 all show the luminescence peak of sky blue perovskite. The maximum external quantum efficiencies of the six are 8.0%, 3.7%, 2.7%, 3.6%, 5.3%, and 4.9%, respectively. Compared with Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4, and Comparative Example 5, the external quantum efficiency of Example 1 has been significantly improved. It is proved that the hole transport-phosphorescence sensitization layer used in the present invention is combined with the phosphorescent ultra-thin layer, and then the method of realizing high-quality energy transfer of fluorescent materials and phosphorescent ultra-thin layers to perovskites is used to prepare high-efficiency perovskite light-emitting devices with superior performance and potential application prospects. The device obtained by the present invention can be applied to display and lighting fields.

[0061] The above describes and evaluates the efficacy of some embodiments of the present invention. It should be understood that the present invention is not limited to the above specific implementations. Any technician familiar with the art can use the above disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention still falls within the scope of protection of the technical solutions of the present invention.

Claims

1. A perovskite light-emitting device, characterized in that: The invention comprises a substrate, an anode, a hole transport-phosphorescence sensitization layer, a perovskite light-emitting layer, a phosphorescence ultra-thin layer, an electron transport layer, an electron injection layer and a cathode which are stacked in sequence.

2. The perovskite light-emitting device according to claim 1, characterized in that: The hole transport-phosphorescence sensitization layer is composed of a hole transport material doped with a phosphorescent material and a fluorescent material; the molar concentration of the phosphorescent material in the hole transport-phosphorescence sensitization layer is 5-15%, and the molar concentration of the fluorescent material in the hole transport-phosphorescence sensitization layer is 0.1-3%.

3. The perovskite light-emitting device according to claim 2, characterized in that: The emission wavelength of the phosphorescent material is shorter than that of the fluorescent material; the emission wavelength of the phosphorescent material and the absorption wavelength of the fluorescent material overlap; the difference between the HOMO energy level of the phosphorescent material and the HOMO energy level of the fluorescent material is greater than 0.2 eV.

4. The perovskite light-emitting device according to claim 3, characterized in that: The phosphorescent material is Fir6; and / or the fluorescent material is 4TCzBN.

5. The perovskite light-emitting device according to claim 4, characterized in that: The hole transport material is poly-9-vinyl carbazole or poly-3,4-ethylenedioxythiophene / polystyrene sulfonate; And / or, the material of the phosphorescent ultra-thin layer is Fir6; And / or, the material of the perovskite light-emitting layer is selected from a two-dimensional crystal structure or a three-dimensional crystal structure, or a combination thereof.

6. The perovskite light-emitting device according to claim 1, characterized in that: The thickness of the hole transport-phosphorescence sensitization layer is 15-20 nm; and / or the thickness of the phosphorescent ultra-thin layer is 0.01-1 nm; and / or the thickness of the perovskite light-emitting layer is 10-25 nm.

7. A method for preparing a perovskite light-emitting device according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, mixing the phosphorescent material, fluorescent material and hole transport material in proportion, filtering through a microporous filter membrane, spin coating on an ITO glass substrate under an atmospheric environment, and annealing to obtain a hole transport-phosphorescence sensitization layer; S2, preparing a perovskite precursor solution; Then, the perovskite precursor solution is filtered through a microporous filter membrane, and then spin-coated on the substrate obtained in step S1 in a glove box filled with nitrogen, and annealed to obtain a perovskite light-emitting layer; S3, on the substrate obtained in step S2, sequentially evaporating a phosphorescent ultra-thin layer and an electron transport layer by vacuum evaporation method; S4. On the substrate obtained in step S3, an electron injection layer and a metal cathode are sequentially deposited by vacuum evaporation to obtain the perovskite light-emitting device.

8. The preparation method according to claim 7, characterized in that: In step S1, the spin coating conditions are: spin coating speed 3500 rpm, spin coating acceleration 1000 rpm / s, and spin coating time 40 s; And / or, in step S1, the annealing condition is: annealing on a hot plate at 165° C. for 25 minutes; And / or, in step S1, the microporous filter membrane is a polytetrafluoroethylene microporous filter membrane with a pore size of 0.22 μm.

9. The preparation method according to claim 7, characterized in that: In step S2, the spin coating conditions are: spin coating at 6500 rpm for 90 seconds; And / or, in step S2, the annealing condition is: keeping warm at 65° C. for 5 minutes; And / or, in step S3, the vacuum degree of the evaporation is controlled at 3×10 -5 Below Pa; And / or, in step S3, the phosphorescent material is heated to 185° C. and then vapor deposited; the film forming rate is 0.2 nm / s; And / or, in step S4, the vacuum degree of the evaporation is controlled at 3×10 -4 Below Pa, the film formation rate is 0.2nm / s.

10. Application of the perovskite light-emitting device according to any one of claims 1 to 6 in display and lighting products.

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