WO2022217600A1 - 有机电致发光器件和显示装置 - Google Patents

有机电致发光器件和显示装置 Download PDF

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WO2022217600A1
WO2022217600A1 PCT/CN2021/087868 CN2021087868W WO2022217600A1 WO 2022217600 A1 WO2022217600 A1 WO 2022217600A1 CN 2021087868 W CN2021087868 W CN 2021087868W WO 2022217600 A1 WO2022217600 A1 WO 2022217600A1
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emitting layer
homo
fluorescent guest
light
host material
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PCT/CN2021/087868
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English (en)
French (fr)
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张晓晋
杨绘耘
吴勇
王丹
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京东方科技集团股份有限公司
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Priority to US17/635,705 priority Critical patent/US20230345752A1/en
Priority to PCT/CN2021/087868 priority patent/WO2022217600A1/zh
Priority to CN202180000812.4A priority patent/CN115669264A/zh
Publication of WO2022217600A1 publication Critical patent/WO2022217600A1/zh

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/125—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light
    • H10K50/13—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers specially adapted for multicolour light emission, e.g. for emitting white light comprising stacked EL layers within one EL unit
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/12—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants
    • H10K50/121—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising dopants for assisting energy transfer, e.g. sensitization
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/10—OLED displays
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/20—Delayed fluorescence emission
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/20—Delayed fluorescence emission
    • H10K2101/25—Delayed fluorescence emission using exciplex
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/30—Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/90—Multiple hosts in the emissive layer
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
    • H10K2102/301—Details of OLEDs
    • H10K2102/351—Thickness
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/30—Coordination compounds
    • H10K85/311—Phthalocyanine
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K85/00—Organic materials used in the body or electrodes of devices covered by this subclass
    • H10K85/60—Organic compounds having low molecular weight
    • H10K85/649—Aromatic compounds comprising a hetero atom
    • H10K85/657—Polycyclic condensed heteroaromatic hydrocarbons
    • H10K85/6572—Polycyclic condensed heteroaromatic hydrocarbons comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole

Definitions

  • the embodiments of the present disclosure relate to, but are not limited to, the field of display technology, and in particular, relate to an organic electroluminescence device and a display device.
  • Thermally activated delayed fluorescence (TADF) materials are the third generation of organic light-emitting materials developed after organic fluorescent materials and organic phosphorescent materials. In recent years, they have developed rapidly and have good application potential in organic light-emitting diode (OLED) technology.
  • the super-fluorescence technology based on TADF sensitizer is considered to be the solution of TADF materials with application value in OLED technology, but at present, OLED devices using TADF materials face many problems, such as high device operating voltage and low efficiency , shorter lifespan, etc.
  • Embodiments of the present disclosure provide an organic electroluminescence device, comprising an anode, a cathode, a light-emitting layer disposed between the anode and the cathode, and an auxiliary light-emitting layer located on a side of the light-emitting layer facing the anode;
  • the auxiliary light-emitting layer includes a first host material and a first fluorescent guest material;
  • the light-emitting layer includes a second host material, a TADF material and a second fluorescent guest material;
  • the first host material and the first fluorescent guest material satisfy:
  • the lowest singlet energy of the first host material is S1(B)
  • the lowest triplet energy is T1(B)
  • the lowest singlet energy of the first fluorescent guest material is S1(C)
  • the lowest The triplet energy is T1(C)
  • the highest occupied molecular orbital energy level of the first host material is HOMO(B)
  • the lowest unoccupied molecular orbital energy level of the first fluorescent guest material is LUMO(C).
  • An embodiment of the present disclosure further provides a display device, including the organic electroluminescence device described in any one of the embodiments.
  • 1 is a spectrogram of a TADF material and a fluorescent guest material of a light-emitting layer in an organic electroluminescent device of some exemplary embodiments;
  • FIG. 2 is a schematic structural diagram of an organic electroluminescent device of some exemplary embodiments.
  • TADF material is the third-generation organic light-emitting material developed after organic fluorescent material and organic phosphorescent material. It has developed rapidly in recent years and has good application potential in OLED technology. TADF materials have a small lowest singlet state-lowest triplet energy difference ( ⁇ E ST ), and the lowest triplet state (T1) excitons can be transformed into the lowest singlet state (S1) through inverse intersystem crossing (abbreviated as RISC) The excitons further realize fluorescence emission through the radiative transition of the lowest singlet state (S1) excitons to the ground state (S0), so that a theoretical 100% internal quantum efficiency can be achieved.
  • RISC inverse intersystem crossing
  • the super-fluorescence technology based on TADF sensitizer is considered to be the realization solution of TADF materials with application value in OLED technology.
  • OLED devices using TADF materials face many problems, which hinder their practical use, such as: (1) In order to prevent the diffusion of triplet excitons in the light-emitting layer, high T1 hole-blocking layer materials and electron-blocking layer materials are used on both sides of the light-emitting layer, which limits the selection of the corresponding film materials and reduces the complexity of device design. Flexibility; (2) There are charge traps in the light-emitting layer, resulting in higher operating voltage and higher power consumption of the device.
  • Embodiments of the present disclosure provide an organic electroluminescence device, comprising an anode, a cathode, a light-emitting layer disposed between the anode and the cathode, and an auxiliary light-emitting layer located on a side of the light-emitting layer facing the anode;
  • the auxiliary light-emitting layer includes a first host material and a first fluorescent guest material;
  • the light-emitting layer includes a second host material, a TADF material and a second fluorescent guest material.
  • an auxiliary light-emitting layer is disposed on the side of the light-emitting layer facing the anode.
  • the auxiliary light-emitting layer may be disposed between the electron blocking layer and the light-emitting layer,
  • the first host material in the auxiliary light-emitting layer can be set to have higher hole transport ability and the ability to block leakage of triplet excitons in the light-emitting layer, so that the electron blocking layer material is not required to have higher triplet energy
  • the flexibility of material selection of the electron blocking layer can be improved.
  • the hole transport ability of the second host material in the light-emitting layer is stronger than that of the TADF material.
  • the doping concentration of the material, or the material with TADF properties contained in the auxiliary light-emitting layer (which can be a mass percentage) is less than the doping concentration of the TADF material in the light-emitting layer, so that the gap between the electron blocking layer and the light-emitting layer can be reduced.
  • the high hole transport resistance can better transport holes to the light-emitting layer, thereby reducing the operating voltage of the device.
  • the first host material may be referred to as material B
  • the first fluorescent guest material may be referred to as material C
  • the second host material may be referred to as material D
  • the TADF material may be referred to as material E
  • the second fluorescent guest material may be referred to as material F for short.
  • the highest occupied molecular orbital energy level of a material is referred to as the HOMO energy level, and the lowest unoccupied molecular orbital energy level is referred to as the LUMO energy level.
  • the lowest singlet energy of a material is referred to as S1 energy, and the lowest triplet energy is referred to as T1 energy.
  • the lowest singlet energy of the first host material is S1(B), the lowest triplet energy is T1(B); the lowest singlet energy of the first fluorescent guest material is S1(C), the lowest triplet energy is S1(C), the lowest triplet energy is The energy is T1(C); the lowest singlet energy of the second host material is S1(D), the lowest triplet energy is T1(D); the lowest singlet energy of the TADF material is S1(E) , the lowest triplet energy is T1(E); the lowest singlet energy of the second fluorescent guest material is S1(F), and the lowest triplet energy is T1(F).
  • the HOMO energy level of the first host material is HOMO(B), and the LUMO energy level is LUMO(B); the HOMO energy level of the first fluorescent guest material is HOMO(C), and the LUMO energy level is LUMO(C) ;
  • the HOMO energy level of the second host material is HOMO (D), and the LUMO energy level is LUMO (D);
  • the HOMO energy level of the TADF material is HOMO (E), and the LUMO energy level is LUMO (E);
  • the HOMO energy level of the second fluorescent guest material is HOMO(F), and the LUMO energy level is LUMO(F).
  • the electroluminescence spectrum of the material refers to the luminescence spectrum obtained when the material is doped into the host material in a certain proportion (eg, 20%) to prepare an OLED device, and the luminescence spectrum is obtained in an electrified state.
  • the description of S1 and T1 of the host material refers to S1 and T1 of the exciplex if the host material is in the form of an exciplex containing two components.
  • the first host material in the auxiliary light-emitting layer, may be a hole-type material, and the hole mobility of the first host material may be at least ten times higher than the electron mobility.
  • the first host material may be a carbazole-based material.
  • the first host material does not have TADF properties, that is, the first host material satisfies: S1(B)-T1(B)>0.2eV.
  • the first fluorescent guest material may be a common fluorescent material, such as anthracene, fluorene, pyrene, pyrrole, or a boron-containing material with multiple resonance effects.
  • the doping concentration of the first fluorescent guest material may be 0.5% to 10%, that is, the mass percentage of the first fluorescent guest material in the auxiliary light-emitting layer is 0.5% to 10%.
  • the first host material and the first fluorescent guest material satisfy:
  • the auxiliary light-emitting layer satisfies the above conditions, and the first host material in the auxiliary light-emitting layer can play the role of dispersing the first fluorescent guest material, the role of hole transport, and the role of blocking triplet excitons in the light-emitting layer
  • the material of the electron blocking layer does not need to have higher triplet energy to block triplet excitons in the light-emitting layer, which can improve the flexibility of material selection of the electron blocking layer.
  • excitons are mainly generated in the TADF material of the light-emitting layer, and the first host material does not have TADF properties, so that the first host material will not compete with the light-emitting layer for excitons, and will not lose the blocking triplet state The role of excitons.
  • the first host material and the first fluorescent guest material will not form an excimer complex, so that the electric charges in the light-emitting layer will not be consumed in large quantities, so that the device efficiency will not be affected and the luminescent color of the device will not be red-shifted.
  • the auxiliary light-emitting layer may be composed of two components of the first host material and the first fluorescent guest material.
  • the auxiliary light-emitting layer may not contain a material with TADF properties; or, the auxiliary light-emitting layer may contain a material with TADF properties, and the doping concentration of the material with TADF properties contained in the auxiliary light-emitting layer (may be is less than the doping concentration of the TADF material in the light-emitting layer.
  • the auxiliary light-emitting layer can be formed by dual-source co-evaporation.
  • the thickness of the auxiliary light-emitting layer may be 1 nm to 10 nm, for example, the thickness may be 8 nm.
  • the second host material in the light-emitting layer, may be a single-component material (such as carbazole), or a mixed material with exciplex properties (such as "carbazole+ Triazine", “carbazole + pyridine” or “carbazole + oxadiazole", etc.).
  • the second host material when the second host material is a single-component material, the second host material may satisfy: S1(D)-T1(D)>0.2eV, and the hole mobility of the second host material may be higher than the electron mobility rate at least ten times.
  • the materials that can be selected for the TADF material include, but are not limited to, triazines, pyridines, ketones, quinones, and the like with smaller ⁇ E ST .
  • the proportion of the TADF material in the light-emitting layer (which can be a mass percentage) is X, 5% ⁇ X ⁇ 50%, such as 15% ⁇ X ⁇ 40%.
  • the second fluorescent guest material may be a common fluorescent material, such as anthracene, fluorene, pyrene or pyrrole.
  • the second fluorescent guest material is a boron-containing material with multiple resonance TADF properties, and S1(F)-T1(F) ⁇ 0.2 eV.
  • the doping concentration of the second fluorescent guest material may be 0.5% to 5%, that is, the mass percentage of the second fluorescent guest material in the light-emitting layer is 0.5% to 5%, which is beneficial to reduce the second fluorescent guest material.
  • the probability of the material trapping excitons favors the formation of excitons mainly in the TADF material.
  • the second host material, TADF material and second fluorescent guest material may satisfy:
  • the absorption spectrum of the second fluorescent guest material and the emission spectrum (which can be an electroluminescence spectrum) of the TADF material may have a large overlap. Under normalized conditions, the absorption spectrum of the second fluorescent guest material is the same as the The overlapping area of the emission spectrum of the TADF material may not be less than 70% of the absorption spectrum area of the second fluorescent guest material. The peak position difference between the lowest energy absorption peak of the absorption spectrum of the second fluorescent guest material and the highest energy emission peak of the emission spectrum of the TADF material may be no greater than 20 nm. In this way, the larger the overlapping area of the absorption spectrum of the second fluorescent guest material and the emission spectrum of the TADF material, the more favorable the TADF material is to transfer energy to the second fluorescent guest material through the Forster energy transfer method. glow.
  • the light-emitting layer satisfies the above conditions, the holes in the second host material can be better transferred to the TADF material, and the TADF material acts as an electron trap of the second host material, which helps excitons mainly form in the TADF material, And it can be ensured that the TADF material can transfer energy to the second fluorescent guest material after generating excitons, so that the second fluorescent guest material emits light.
  • the TADF material is a sensitizer for the second fluorescent guest material.
  • the second host material does not form an exciplex with the TADF material.
  • the second host material, the TADF material and the second fluorescent guest material may also satisfy: ⁇ (D)> ⁇ (E)> ⁇ (F ), where ⁇ (D) represents the wavelength of the strongest emission peak of the second host material, ⁇ (E) represents the wavelength of the strongest emission peak of the TADF material, and ⁇ (F) represents the second fluorescent guest material the wavelength of the strongest emission peak.
  • ⁇ (D) represents the wavelength of the strongest emission peak of the second host material
  • ⁇ (E) represents the wavelength of the strongest emission peak of the TADF material
  • ⁇ (F) represents the second fluorescent guest material the wavelength of the strongest emission peak.
  • the first host material in the auxiliary light-emitting layer and the second host material in the light-emitting layer may be the same or different, and the first fluorescent guest material in the auxiliary light-emitting layer is different from that in the light-emitting layer.
  • the second fluorescent guest materials may be the same or different.
  • the first host material is different from the second host material and meets the above conditions, so that holes can enter the light-emitting layer more efficiently from the first host material, and the first host material can effectively block The role of triplet excitons.
  • the first host material in the auxiliary light-emitting layer and the TADF material in the light-emitting layer do not form an exciplex, which can prevent competition with the light-emitting layer for excitons.
  • the emission spectrum of the first fluorescent guest material is close to the emission spectrum of the second fluorescent guest material, and the peak position difference may be less than 5 nm; the normalization condition
  • the overlapping area of the emission spectrum of the first fluorescent guest material and the emission spectrum of the second fluorescent guest material may be greater than 90% of the area of the emission spectrum of the first fluorescent guest material, and may be greater than 90% of the emission spectrum of the second fluorescent guest material. 90% of the area.
  • the absorption spectrum of the first fluorescent guest material and the emission spectrum (which can be an electroluminescence spectrum) of the TADF material in the light-emitting layer may have a large overlap, and under normalized conditions, the overlapping area of the spectrum may not be smaller than that of the first fluorescent guest 70% of the absorption spectral area of the material.
  • the TADF material in the light-emitting layer can better transmit energy to the first fluorescent guest material and the second fluorescent guest material by means of Forster energy transfer, so that the first fluorescent guest material and the second fluorescent guest material emit light.
  • the TADF material is a sensitizer for the second fluorescent guest material and a sensitizer for the first fluorescent guest material.
  • the emission spectra of the first fluorescent guest material and the second fluorescent guest material have a high degree of coincidence, so that the purity of the luminescent color of the device can be ensured.
  • the first fluorescent guest material participates in luminescence and is located in a different layer from the TADF material, so that the physical separation of the exciton recombination center and the luminescence center can be achieved, which is beneficial to improve the performance of the device.
  • the emission color of the first fluorescent guest material and the second fluorescent guest material can be any color, such as red, green or blue.
  • the light-emitting layer may be composed of the second host material, the TADF material, and the second fluorescent guest material.
  • the light-emitting layer may be formed by co-evaporation from multiple sources.
  • the light emitting layer may have a thickness of 10 nm to 30 nm.
  • the thickness of the light-emitting layer is at least twice the thickness of the auxiliary light-emitting layer, that is, the ratio of the thickness of the light-emitting layer to the thickness of the auxiliary light-emitting layer is greater than 2:1.
  • the organic electroluminescent device may further include an electron blocking layer disposed on a side of the auxiliary light emitting layer facing the anode.
  • the material of the electron blocking layer and the material of the first host may satisfy:
  • HOMO(A) represents the highest occupied molecular orbital energy level of the material of the electron blocking layer
  • LUMO(A) represents the lowest unoccupied molecular orbital energy level of the material of the electron blocking layer.
  • the organic electroluminescent device may further include a hole blocking layer disposed on a side of the light emitting layer facing the cathode.
  • the T1 energy of the material of the hole blocking layer may be greater than the T1 energy of the TADF material in the light-emitting layer, and the difference between the two may be greater than 0.2 eV, so that the hole blocking layer can play a role in The effect of blocking triplet exciton leakage in the light-emitting layer.
  • the absolute value of the HOMO energy level of the material of the hole blocking layer may be greater than the absolute value of the HOMO energy level of the second host material in the light emitting layer by 0.2 eV or more.
  • the hole blocking layer may have a thickness of 5 nm to 30 nm, and the hole blocking layer may be formed by an evaporation process.
  • the organic electroluminescent device may further include a hole injection layer and a hole transport layer disposed between the anode and the electron blocking layer.
  • the hole injection layer, the hole transport layer and the electron blocking layer may be stacked on the anode in sequence.
  • the hole transport layer may be formed of a material with good hole transport capability, such as an aromatic amine or carbazole material.
  • the absolute value of the HOMO energy level difference between the material of the hole transport layer and the material of the electron blocking layer may be no greater than 0.2 eV.
  • the thickness of the hole transport layer may be 1 nm to 200 nm, and the hole transport layer may be formed through an evaporation process.
  • the hole injection layer can be made of CuPc (copper phthalocyanine), HATCN (2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazabenzene) and phenanthrene) or MnO 3 (manganic anhydride) or other materials, or p-type doping in hole transport materials.
  • the hole injection layer may have a thickness of 1 nm to 30 nm, and may be formed by evaporation.
  • the organic electroluminescent device may further include an electron injection layer and an electron transport layer disposed between the cathode and the hole blocking layer.
  • the electron transport layer and the electron injection layer may be sequentially stacked on the hole blocking layer.
  • the electron transport layer may be formed by vapor deposition of an electron transport material with good electron transport capability, or an electron transport material doped with LIQ 3 , Li (lithium), Ca (calcium), etc. material formation.
  • the thickness of the electron transport layer may be 10 nm to 70 nm.
  • the electron injection layer can be formed by using a low work function metal such as Li, Ca or Yb (ytterbium), or can be formed by using a metal salt material such as LiF (lithium fluoride) or LiQ 3 through evaporation.
  • the thickness of the electron injection layer may be 0.5 nm to 2 nm.
  • the cathode may be formed using a lower work function metal such as Al, Ag, Mg, or an alloy containing a low work function metal material.
  • the thickness of the cathode can be greater than 80 nm to ensure good reflectivity (for example, the reflectivity for light with a wavelength of 550 nm can be greater than 85%).
  • the thickness of the cathode can be 10 nm to 20 nm to ensure a certain transmittance (for example, the transmittance for light with a wavelength of 550 nm can be greater than 45%).
  • the organic electroluminescent device may further include an optical cover layer (CPL for short) disposed on the surface of the cathode facing away from the light-emitting layer to improve the optical output.
  • the CPL can be formed by vapor deposition of an organic small molecule material with a refractive index greater than 1.8, and the thickness of the CPL can be 50 nm to 100 nm.
  • the anode may be a material with a high work function.
  • the anode may be made of a transparent oxide material, such as indium tin oxide (ITO) or indium zinc oxide (IZO), and the thickness may be 80 nm to 200 nm.
  • the anode can be a composite structure of metal and transparent oxide, such as Ag/ITO, Ag/IZO, Al/ITO, Al/IZO or ITO/Ag/ITO, etc., which can ensure good reflectivity , the thickness of the metal layer in the anode may be 10 nm to 100 nm, and the thickness of the oxide layer may be 5 nm to 20 nm.
  • the organic electroluminescent device may include an anode 2 , a hole injection layer (HIL) 3 , and a hole transport layer (HTL) stacked on the substrate 1 in sequence. 4. Electron Blocking Layer (EBL) 5, Assistant Luminescent Layer (ALL) 6, Light Emitting Layer (EML) 7, Hole Blocking Layer (HBL) 8, Electron Transport Layer (ETL) 9, Electron Injection Layer (EIL) 10 and cathode 11.
  • the organic electroluminescent device may further include an encapsulation layer 12 disposed on the side of the cathode 11 away from the substrate 1 , and the encapsulation layer 12 plays a protective role.
  • the organic electroluminescence device can be a top emission device, and the thickness of the organic layer between the cathode and the anode can be designed to meet the optical path requirement of the optical micro-resonator, so as to obtain better light extraction intensity and desired color.
  • the internal optical path length of the top-emitting device can be adjusted by changing the thickness of the hole transport layer or the thickness of the electron blocking layer.
  • device 1 and device 2 are devices of the comparative example
  • device 3, device 4 and device 5 are devices of three exemplary embodiments of the present disclosure.
  • TM is the auxiliary light-emitting layer and the host material in the light-emitting layer (that is, the first host material of the auxiliary light-emitting layer and the second host material of the light-emitting layer are both TM)
  • TH is two different materials with TADF properties (two kinds of materials) The materials can all have TADF properties)
  • RD is a common red fluorescent guest material
  • EBL-1 and EBL-2 are two different hole-transporting materials, respectively.
  • the thickness of the auxiliary light-emitting layer is 3 nm
  • the doping concentration of RD in the auxiliary light-emitting layer is 1%
  • the thickness of the light-emitting layer is 22 nm
  • the proportions of TM, TH, and RD in the light-emitting layer are 70 %, 29.3%, 0.7%.
  • the molecular energy orbitals and excited state information of the above materials are shown in Table 1.
  • the emission spectrum of TH, and the absorption spectrum and emission spectrum of RD are shown in Figure 1.
  • curve a represents the electroluminescence spectrum of TH
  • curve b represents the absorption spectrum of RD
  • curve c represents the electroluminescence spectrum of RD.
  • the performance of the above five devices is shown in Table 2.
  • the LT95 lifetime of device 2 to device 5 (referring to the light-emitting time required for the brightness of the light emitted by the device to decay to 95% of the initial brightness) is based on the LT95 of device 1.
  • the lifetime is the benchmark, the ratio of the LT95 lifetime of each device in Device 2 to Device 5 to the LT95 lifetime of Device 1.
  • the device structures of the device 1 and the device 2 are both common super-fluorescent bottom-emitting devices, the difference between the two is the material of the electron blocking layer, and the rest are the same. It can be seen from Table 1 and Table 2 that EBL-1 and EBL-2 have similar HOMO energy level and LUMO energy level, but the T1 of EBL-2 is smaller, which is easy to cause leakage of triplet excitons in the light-emitting layer, Therefore, the efficiency of device 2 is significantly reduced relative to that of device 1.
  • the lifetime of device 2 is improved, mainly because EBL-2 has a shallower HOMO level than EBL-1, so that the potential barrier formed near the interface between the electron blocking layer and the light-emitting layer It helps to slow down the injection of holes into the light-emitting layer, thereby forming a better carrier balance.
  • the device 3 the device 4 and the device 5 of the embodiments of the present disclosure, the device 3, the device 4 and the device 5 all include an auxiliary light-emitting layer and a light-emitting layer. It can be seen from Table 1 and Table 2 that:
  • device 3 includes an auxiliary light-emitting layer. Because the auxiliary light-emitting layer can block triplet excitons in the light-emitting layer, the efficiency of device 3 is not sensitive to the T1 of the electron blocking layer. EBL-2 with lower T1, but still maintains good efficiency and lifespan, and device 3 is provided with an auxiliary light-emitting layer, so the hole transport resistance between the electron blocking layer and the light-emitting layer can be reduced. The holes are better transported to the light-emitting layer and, therefore, the voltage of device 3 is significantly reduced.
  • device 4 and device 5 are provided with auxiliary light-emitting layers, so the hole transport resistance between the electron blocking layer and the light-emitting layer can be reduced, and holes can be better transported to the light-emitting layer. Therefore, device 4 And device 5 has a lower operating voltage and maintains better efficiency.
  • the thickness of the auxiliary light-emitting layer was increased from 3 nm to 6 nm, the lifetime of the device decreased.
  • the organic electroluminescent device of the exemplary embodiments of the present disclosure by arranging an auxiliary light-emitting layer on the side of the light-emitting layer facing the anode, and performing reasonable material selection and material energy level matching for the auxiliary light-emitting layer and the light-emitting layer, Compared with the device with a single light-emitting layer structure, the organic electroluminescent device of the embodiment of the present disclosure can achieve a lower operating voltage under the condition of ensuring better efficiency and life, and the selection of the electron blocking layer material has advantages. Greater flexibility.
  • An embodiment of the present disclosure further provides a display substrate, including the organic electroluminescence device described in any of the foregoing embodiments.
  • the display substrate includes a display area including a plurality of organic electroluminescent devices arranged in an array.
  • the display substrate may include a driving circuit layer disposed on the substrate, a light emitting structure layer disposed on the side of the driving circuit layer away from the substrate, and an encapsulation structure disposed on the side of the light emitting structure layer away from the substrate Floor.
  • the driving circuit layer includes a pixel driving circuit, and the pixel driving circuit includes a thin film transistor and a storage capacitor.
  • the light emitting structure layer includes a plurality of organic electroluminescence devices, and the anode of each organic electroluminescence device is connected to the drain electrode of the thin film transistor of the corresponding pixel driving circuit.
  • the encapsulation structure layer may adopt UV glue encapsulation or thin film encapsulation. Inorganic materials are used, organic materials can be used for the second encapsulation layer, and the encapsulation structure layer can ensure that outside water vapor cannot enter the display area.
  • the substrate can be a flexible substrate or a rigid substrate, such as polyimide, glass, sapphire, or silicon wafer, etc. If a bottom-emitting device is designed, the transmittance of the substrate to light with a wavelength of 550 nm can be greater than 85%.
  • the display substrate may also include other film layers, such as spacer columns, etc., which are not limited in the present disclosure.
  • An embodiment of the present disclosure further provides a display device, including the organic electroluminescence device described in any of the foregoing embodiments.
  • the display device can be any product or component with a display function, such as a mobile phone, a tablet computer, a TV, a monitor, a notebook computer, a digital photo frame, a navigator, a car monitor, a smart watch or a smart bracelet.

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Abstract

一种有机电致发光器件，包括阳极（2）、阴极（11）、设于阳极（2）和阴极（11）之间的发光层（7），以及位于发光层（7）朝向阳极（2）一侧的辅助发光层（6）；辅助发光层（6）包括第一主体材料和第一荧光客体材料；发光层（7）包括第二主体材料、TADF材料和第二荧光客体材料；第一主体材料和第一荧光客体材料满足：S1(B)-T1(B)>0.2eV；S1(B)>S1(C)；T1(B)>T1(C)；||HOMO(B)-LUMO(C)|-S1(C)|≤0.2eV；其中，第一主体材料的最低单重态能量为S1(B)，最低三重态能量为T1(B)；第一荧光客体材料的最低单重态能量为S1(C)，最低三重态能量为T1(C)；第一主体材料的最高占据分子轨道能级为HOMO(B)；第一荧光客体材料的最低未占分子轨道能级为LUMO(C)。

Description

有机电致发光器件和显示装置 技术领域
本公开实施例涉及但不限于显示技术领域，具体涉及一种有机电致发光器件和显示装置。
背景技术
热活化延迟荧光(TADF)材料是继有机荧光材料和有机磷光材料之后发展的第三代有机发光材料，近年来获得较快发展，在有机发光二极管(OLED)技术中具有较好应用潜力。基于TADF敏化剂的超荧光技术，被认为是具有应用价值的TADF材料在OLED技术中的实现方案，但目前，应用TADF材料的OLED器件面临诸多问题，例如器件工作电压较高、效率不高、寿命较短等。
发明内容
以下是对本文详细描述的主题的概述。本概述并非是为了限制权利要求的保护范围。
本公开实施例提供一种有机电致发光器件，包括阳极、阴极、设于所述阳极和所述阴极之间发光层，以及位于所述发光层的朝向所述阳极一侧的辅助发光层；所述辅助发光层包括第一主体材料和第一荧光客体材料；所述发光层包括第二主体材料、TADF材料和第二荧光客体材料；
所述第一主体材料和所述第一荧光客体材料满足：
S1(B)-T1(B)>0.2eV；
S1(B)>S1(C)；
T1(B)>T1(C)；
||HOMO(B)-LUMO(C)|-S1(C)|≤0.2eV；
其中，所述第一主体材料的最低单重态能量为S1(B)，最低三重态能量为T1(B)；所述第一荧光客体材料的最低单重态能量为S1(C)，最低三重态能 量为T1(C)；所述第一主体材料的最高占据分子轨道能级为HOMO(B)；所述第一荧光客体材料的最低未占分子轨道能级为LUMO(C)。
本公开实施例还提供一种显示装置，包括任一实施例所述的有机电致发光器件。
在阅读并理解了附图和详细描述后，可以明白其他方面。
附图说明
附图用来提供对本公开技术方案的进一步理解，并且构成说明书的一部分，与本公开的实施例一起用于解释本公开的技术方案，并不构成对本公开技术方案的限制。附图中部件的形状和大小不反映真实比例，目的只是示意说明本公开内容。
图1为一些示例性实施例的有机电致发光器件中发光层的TADF材料和荧光客体材料的光谱图；
图2为一些示例性实施例的有机电致发光器件的结构示意图。
具体实施方式
本领域的普通技术人员应当理解，可以对本公开实施例的技术方案进行修改或者等同替换，而不脱离本公开实施例技术方案的精神和范围，均应涵盖在本公开的权利要求范围当中。
在附图中，有时为了明确起见，夸大表示了构成要素的大小、层的厚度或区域。因此，本公开的实施方式并不一定限定于该尺寸，附图中每个部件的形状和大小不反映真实比例。此外，附图示意性地示出了一些例子，本公开的实施方式不局限于附图所示的形状或数值。
TADF材料是继有机荧光材料和有机磷光材料之后发展的第三代有机发光材料，近年来获得较快发展，在OLED技术中具有较好应用潜力。TADF材料具有较小的最低单重态-最低三重态能量差(△E ST)，最低三重态(T1)激子可以通过反系间窜越(简称RISC)转变成最低单重态(S1)激子，进一步通过最低单重态(S1)激子到基态(S0)的辐射跃迁实现荧光发射，从 而可实现理论上100％的内量子效率。基于TADF敏化剂的超荧光技术，被认为是具有应用价值的TADF材料在OLED技术中的实现方案，但目前，应用TADF材料的OLED器件面临诸多问题，阻碍其走向实用，如：(1)为了防止发光层中三重态激子的扩散，会在发光层两侧搭配高T1的空穴阻挡层材料和电子阻挡层材料，这对相应膜层材料的选择造成局限性，降低了器件设计的灵活性；(2)发光层存在电荷陷阱，导致器件工作电压较高，功耗较大。
本公开实施例提供一种有机电致发光器件，包括阳极、阴极、设于所述阳极和所述阴极之间发光层，以及位于所述发光层的朝向所述阳极一侧的辅助发光层；所述辅助发光层包括第一主体材料和第一荧光客体材料；所述发光层包括第二主体材料、TADF材料和第二荧光客体材料。
本公开实施例的有机电致发光器件，在发光层的朝向阳极一侧设置辅助发光层，如此，在一些可能的实施方式中，辅助发光层可以设置为位于电子阻挡层和发光层之间，辅助发光层中的第一主体材料可以设置为具有较高的空穴传输能力和阻挡发光层中的三重态激子泄漏的能力，这样，可不必要求电子阻挡层材料具有较高的三重态能量以阻挡发光层中的三重态激子泄漏，可以提高电子阻挡层材料选择的灵活性。此外，由于发光层为超荧光体系，发光层中第二主体材料的空穴传输能力强于TADF材料的空穴传输能力，设置辅助发光层后，辅助发光层可以设置为不含有具有TADF性质的材料，或者辅助发光层中含有的具有TADF性质的材料的掺杂浓度(可为质量百分比)小于发光层中的所述TADF材料的掺杂浓度，如此，可降低电子阻挡层和发光层之间的空穴传输阻抗，可使空穴更好地传输至发光层，从而可降低器件的工作电压。
本文中，为便于描述，所述第一主体材料可简称材料B，所述第一荧光客体材料可简称材料C，所述第二主体材料可简称材料D，所述TADF材料可简称材料E，所述第二荧光客体材料可简称材料F。
材料的最高占据分子轨道能级简称HOMO能级，最低未占分子轨道能级简称LUMO能级。材料的最低单重态能量简称S1能量，最低三重态能量简称T1能量。
所述第一主体材料的最低单重态能量为S1(B)，最低三重态能量为T1(B)；所述第一荧光客体材料的最低单重态能量为S1(C)，最低三重态能量为T1(C)；所述第二主体材料的最低单重态能量为S1(D)，最低三重态能量为T1(D)；所述TADF材料的最低单重态能量为S1(E)，最低三重态能量为T1(E)；所述第二荧光客体材料的最低单重态能量为S1(F)，最低三重态能量为T1(F)。
所述第一主体材料的HOMO能级为HOMO(B)，LUMO能级为LUMO(B)；所述第一荧光客体材料的HOMO能级为HOMO(C)，LUMO能级为LUMO(C)；所述第二主体材料的HOMO能级为HOMO(D)，LUMO能级为LUMO(D)；所述TADF材料的HOMO能级为HOMO(E)，LUMO能级为LUMO(E)；所述第二荧光客体材料的HOMO能级为HOMO(F)，LUMO能级为LUMO(F)。
本文中，材料的电致发射光谱，是指将材料以某比例(如20％)掺入主体材料中，制备OLED器件，通电状态下获得的发光光谱。对主体材料的S1及T1的描述，如果主体材料为含有两种组分的激基复合物形式，则指激基复合物的S1和T1。对主体材料的HOMO、LUMO的描述，如果主体材料为激基复合物形式，则分别指形成激基复合物的两种组分的绝对值较小的HOMO和绝对值较大的LUMO。
在一些示例性实施例中，所述辅助发光层中，所述第一主体材料可以为空穴型材料，所述第一主体材料的空穴迁移率可高于电子迁移率至少十倍。比如，所述第一主体材料可以为咔唑类材料。所述第一主体材料不具有TADF性质，即，第一主体材料满足：S1(B)-T1(B)>0.2eV。
所述第一荧光客体材料可以是普通荧光材料，如蒽类、芴类、芘类、吡咯类或者是具有多重共振效应的含硼类材料。所述第一荧光客体材料的掺杂浓度可以为0.5％至10％，即第一荧光客体材料在辅助发光层中的质量百分比为0.5％至10％。
所述第一主体材料和所述第一荧光客体材料满足：
S1(B)>S1(C)；
T1(B)>T1(C)；
||HOMO(B)-LUMO(C)|-S1(C)|≤0.2eV。
本实施例中，辅助发光层满足上述条件，辅助发光层中的第一主体材料可以起到分散第一荧光客体材料的作用、空穴传输作用，以及阻挡发光层中的三重态激子的作用，这样，在器件还包括电子阻挡层的情况下，可不必要求电子阻挡层材料具有较高的三重态能量以阻挡发光层中的三重态激子，可以提高电子阻挡层材料选择的灵活性。此外，本公开实施例中，激子主要产生于发光层的TADF材料，第一主体材料不具有TADF性质，这样，第一主体材料不会与发光层争夺激子，并且不会丧失阻挡三重态激子的作用。此外，第一主体材料和第一荧光客体材料不会形成激基复合物，这样不会大量消耗发光层中的电荷，从而不会影响器件效率和不会造成器件发光颜色红移。
在一些示例性实施例中，所述辅助发光层可以由所述第一主体材料和所述第一荧光客体材料两种组分组成。所述辅助发光层中可以不含有具有TADF性质的材料；或者，所述辅助发光层中含有具有TADF性质的材料，且所述辅助发光层中含有的具有TADF性质的材料的掺杂浓度(可以为质量百分比)小于所述发光层中的所述TADF材料的掺杂浓度。所述辅助发光层可通过双源共同蒸镀形成。所述辅助发光层的厚度可以为1nm至10nm，比如，厚度可以为8nm。
在一些示例性实施例中，所述发光层中，所述第二主体材料可以为单一组分材料(如咔唑类)，或者为具有激基复合物性质的混合材料(如“咔唑+三嗪”、“咔唑+吡啶”或“咔唑+恶二唑”等)。当第二主体材料为单一组分材料时，所述第二主体材料可满足：S1(D)-T1(D)>0.2eV，所述第二主体材料的空穴迁移率可高于电子迁移率至少十倍。
所述TADF材料满足：△E ST(E)＝S1(E)-T1(E)<0.2eV。所述TADF材料可以选择的材料包括但不限于△E ST较小的三嗪类、吡啶类、酮类、醌类等。所述TADF材料在发光层中所占的比例(可为质量百分比)为X，5％<X<50％，比如15％<X<40％。
所述第二荧光客体材料可以是普通荧光材料，如蒽类、芴类、芘类或吡咯类。或者，第二荧光客体材料是具有多重共振TADF性质的含硼类材料，S1(F)-T1(F)<0.2eV。所述第二荧光客体材料的掺杂浓度可以为0.5％至5％， 即第二荧光客体材料在发光层中所占的质量百分比为0.5％至5％，这样，有利于降低第二荧光客体材料俘获激子的几率，有利于激子主要形成于所述TADF材料。
所述第二主体材料、TADF材料和第二荧光客体材料可满足：
S1(D)>S1(E)>S1(F)；
T1(D)>T1(E)>T1(F)；
|HOMO(D)-HOMO(E)|<0.2eV；
|LUMO(D)-LUMO(E)|>0.3eV；
||HOMO(D)-LUMO(E)|-S1(E)|≤0.2eV；
||HOMO(D)-LUMO(E)|-T1(E)|≤0.2eV。
所述第二荧光客体材料的吸收光谱与所述TADF材料的发射光谱(可为电致发射光谱)可以有较大重叠，归一化条件下，所述第二荧光客体材料的吸收光谱与所述TADF材料的发射光谱的重叠面积可不小于第二荧光客体材料的吸收光谱面积的70％。第二荧光客体材料的吸收光谱的能量最低吸收峰与所述TADF材料的发射光谱的能量最高发射峰的峰位差可以不大于20nm。这样，所述第二荧光客体材料的吸收光谱与所述TADF材料的发射光谱重叠面积越大，越有利于TADF材料通过Forster能量传递方式将能量传递给第二荧光客体材料使第二荧光客体材料发光。
本实施例中，发光层满足上述条件，第二主体材料中的空穴能够更好地传递至TADF材料，TADF材料作为第二主体材料的电子陷阱，有助于激子主要形成在TADF材料，并且可以保证TADF材料在产生激子后能够将能量传递给第二荧光客体材料，使第二荧光客体材料发光。可理解为TADF材料是第二荧光客体材料的敏化剂。此外，第二主体材料与TADF材料不会形成激基复合物。
在一些示例性实施例中，所述发光层中，所述第二主体材料、所述TADF材料和所述第二荧光客体材料还可以满足：λ(D)>λ(E)>λ(F)，其中，λ(D)代表所述第二主体材料的最强发射峰波长，λ(E)代表所述TADF材料的最强发射峰波长，λ(F)代表所述第二荧光客体材料的最强发射峰波长。这样，有 利于发光层中能量传递的方向是流向第二荧光客体材料，有利于提高器件效率。
在一些示例性实施例中，所述辅助发光层中的第一主体材料与发光层中的第二主体材料可以相同或者不同，所述辅助发光层中的第一荧光客体材料与发光层中的第二荧光客体材料可以相同或者不同。
当第一主体材料与第二主体材料不同时，则满足以下条件：
|HOMO(B)-HOMO(D)|<0.2eV；
|HOMO(B)-HOMO(E)|<0.2eV；
T1(B)>T1(E)，比如T1(B)-T1(E)>0.2eV；
||HOMO(B)-LUMO(E)|-S1(E)|≤0.2eV；
||HOMO(B)-LUMO(E)|-T1(E)|≤0.2eV。
本实施例中，第一主体材料与第二主体材料不同，且满足上述条件，这样，可以保证空穴能够从第一主体材料更高效地进入发光层，以及第一主体材料起到良好的阻挡三重态激子的作用。此外，辅助发光层中的第一主体材料与发光层中的所述TADF材料不会形成激基复合物，可防止与发光层争夺激子。
当第一荧光客体材料与第二荧光客体材料不同时，可以满足以下条件：第一荧光客体材料的发射光谱与第二荧光客体材料的发射光谱接近，峰位差可小于5nm；归一化条件下，第一荧光客体材料的发射光谱与第二荧光客体材料的发射光谱的重叠面积可大于第一荧光客体材料的发射光谱的面积的90％，并可大于第二荧光客体材料的发射光谱的面积的90％。第一荧光客体材料的吸收光谱与发光层中的所述TADF材料的发射光谱(可为电致发射光谱)可以有较大重叠，归一化条件下，光谱的重叠面积可不小于第一荧光客体材料的吸收光谱面积的70％。这样，发光层中的TADF材料可以更好地通过Forster能量传递方式将能量传递给第一荧光客体材料和第二荧光客体材料，使第一荧光客体材料和第二荧光客体材料发光。可理解为TADF材料是第二荧光客体材料的敏化剂，且是第一荧光客体材料的敏化剂。第一荧光客体材料与第二荧光客体材料的发射光谱重合度高，这样可以确保器件发光颜 色的纯度。此外，第一荧光客体材料参与发光且与所述TADF材料位于不同层，这样可实现激子复合中心与发光中心在物理上的分离，有利于提高器件性能。第一荧光客体材料与第二荧光客体材料的发光颜色可以是任意颜色，比如红色、绿色或蓝色等。
在一些示例性实施例中，所述发光层可以由所述第二主体材料、所述TADF材料和所述第二荧光客体材料组成。所述发光层可通过多源共同蒸镀形成。
在一些示例性实施例中，所述发光层的厚度可以为10nm至30nm。发光层的厚度至少大于辅助发光层的厚度的两倍，即发光层厚度与辅助发光层厚度的比大于2：1。
在一些示例性实施例中，所述有机电致发光器件还可以包括设于所述辅助发光层的朝向所述阳极一侧的电子阻挡层。
本实施例的一个示例中，所述电子阻挡层的材料与所述第一主体材料可满足：|HOMO(A)-HOMO(B)|≤0.2eV，|LUMO(B)|-|LUMO(A)|>0.2eV，其中，HOMO(A)代表电子阻挡层的材料的最高占据分子轨道能级，LUMO(A)代表电子阻挡层的材料的最低未占分子轨道能级。这样，可使空穴更好地从电子阻挡层传递至辅助发光层，并可抑制电子传递。
在一些示例性实施例中，所述有机电致发光器件还可以包括设于所述发光层的朝向所述阴极一侧的空穴阻挡层。
本实施例的一个示例中，所述空穴阻挡层的材料的T1能量可以大于发光层中所述TADF材料的T1能量，两者差值可大于0.2eV，这样，空穴阻挡层可起到阻挡发光层中的三重态激子泄漏的作用。空穴阻挡层的材料的HOMO能级的绝对值可以比发光层中第二主体材料的HOMO能级的绝对值大0.2eV以上。所述空穴阻挡层的厚度可以为5nm至30nm，空穴阻挡层可通过蒸镀工艺形成。
在一些示例性实施例中，所述有机电致发光器件还可以包括设于所述阳极和所述电子阻挡层之间的空穴注入层和空穴传输层。所述空穴注入层、空穴传输层和电子阻挡层可依次叠设于所述阳极上。
本实施例的一个示例中，所述空穴传输层可以是具有良好空穴传输能力的材料形成，比如芳胺类或者咔唑类材料。所述空穴传输层的材料与所述电子阻挡层的材料的HOMO能级差的绝对值可不大于0.2eV。空穴传输层的厚度可以为1nm至200nm，空穴传输层可通过蒸镀工艺形成。
所述空穴注入层可以是采用CuPc(酞菁铜)、HATCN(2,3,6,7,10,11-六氰基-1,4,5,8,9,12-六氮杂苯并菲)或MnO 3(锰酸酐)等材料形成，或者是在空穴传输材料中进行p型掺杂形成。空穴注入层的厚度可为1nm至30nm，可通过蒸镀形成。
在一些示例性实施例中，所述有机电致发光器件还可以包括设于阴极和所述空穴阻挡层之间的电子注入层和电子传输层。所述电子传输层和所述电子注入层可依次叠设于所述空穴阻挡层上。
本实施例的一个示例中，所述电子传输层可以是具有良好电子传输能力的电子传输型材料蒸镀形成，或者是电子传输型材料掺杂LIQ 3、Li(锂)、Ca(钙)等材料形成。电子传输层的厚度可以为10nm至70nm。
所述电子注入层可采用Li、Ca或Yb(镱)等低功函数金属形成，或是采用LiF(氟化锂)或LiQ 3等金属盐材料通过蒸镀形成。电子注入层的厚度可以为0.5nm至2nm。
在一些示例性实施例中，所述阴极可以采用Al、Ag、Mg等较低功函数的金属形成，或采用含有低功函数金属材料的合金形成。有机电致发光器件为底发射器件时，阴极的厚度可大于80nm，以保证良好的反射率(比如，对波长为550nm的光的反射率可大于85％)。有机电致发光器件为顶发射器件时，阴极的厚度可以为10nm至20nm，以保证一定的透过率(比如，对波长为550nm的光的透过率可大于45％)。
在一些示例性实施例中，所述有机电致发光器件还可以包括设于阴极的背离发光层的表面上的光学覆盖层(简称CPL)，以提高光学输出。CPL可为折射率大于1.8的有机小分子材料蒸镀形成，CPL的厚度可为50nm至100nm。
在一些示例性实施例中，所述阳极可以为具有高功函数的材料。示例性 地，对于底发射型器件，阳极可以采用透明氧化物材料，如氧化铟锡(ITO)或氧化铟锌(IZO)等，厚度可以为80nm至200nm。或者，对于顶发射型器件，阳极可以采用金属和透明氧化物的复合结构，如Ag/ITO、Ag/IZO、Al/ITO、Al/IZO或者ITO/Ag/ITO等，可保证良好的反射率，阳极中金属层的厚度可为10nm至100nm，氧化物层的厚度可为5nm至20nm。
在一些示例性实施例中，如图2所示，所述有机电致发光器件可以包括依次叠设于基底1上的阳极2、空穴注入层(HIL)3、空穴传输层(HTL)4、电子阻挡层(EBL)5、辅助发光层(Assistant Luminescent layer，简称ALL)6、发光层(EML)7、空穴阻挡层(HBL)8、电子传输层(ETL)9、电子注入层(EIL)10和阴极11。所述有机电致发光器件还可以包括设于所述阴极11的背离所述基底1一侧的封装层12，封装层12起到保护作用。
在一些示例性实施例中，所述有机电致发光器件可为顶发射器件，阴极和阳极之间的有机层的厚度可设计为满足光学微谐振腔的光程要求，从而获得较优的出光强度和所需的颜色。可通过改变空穴传输层的厚度或电子阻挡层的厚度来对顶发射器件内部光程进行调节。
下面对本公开的一些示例性实施例的有机电致发光器件的性能进行测试和比较。
器件1(比较例)：Ag(100nm)/ITO(8nm)/HIL/HTL/EBL-1/TM:TH:RD(25nm,70％:29.3％:0.7％)/HBL/ETL/EIL(1nm)/Mg:Ag(15nm)/CPL
器件2(比较例)：Ag(100nm)/ITO(8nm)/HIL/HTL/EBL-2/TM:TH:RD(25nm,70％:29.3％:0.7％)/HBL/ETL/EIL(1nm)/Mg:Ag(15nm)/CPL
器件3(实施例)：Ag(100nm)/ITO(8nm)/HIL/HTL/EBL-2/TM:RD(3nm,1％)/TM:TH:RD(22nm,70％:29.3％:0.7％)/HBL/ETL/EIL(1nm)/Mg:Ag(15nm)/CPL
器件4(实施例)：Ag(100nm)/ITO(8nm)/HIL/HTL/EBL-1/TM:RD(3nm,1％)/TM:TH:RD(22nm,70％:29.3％:0.7％)/HBL/ETL/EIL(1nm)/Mg:Ag(15nm)/CPL
器件5(实施例)：Ag(100nm)/ITO(8nm)/HIL/HTL/EBL-1/TM:RD(6nm, 1％)/TM:TH:RD(19nm,70％:29.3％:0.7％)/HBL/ETL/EIL(1nm)/Mg:Ag(15nm)/CPL
上述五个器件中，器件1和器件2为比较例的器件，器件3、器件4和器件5为本公开的三个示例性实施例的器件。其中，TM为辅助发光层和发光层中的主体材料(即辅助发光层的第一主体材料和发光层的第二主体材料均为TM)；TH为具有TADF性质的两种不同材料(两种材料可以均具有TADF性质)；RD为普通红色荧光客体材料；EBL-1和EBL-2分别是两种不同的空穴传输型材料。以器件3为例说明，辅助发光层的厚度为3nm，辅助发光层中RD的掺杂浓度为1％；发光层的厚度为22nm，发光层中TM、TH、RD所占的比例分别为70％、29.3％、0.7％。上述材料的分子能轨及激发态信息见表1。TH的发射光谱，以及RD的吸收光谱和发射光谱见图1，图1中，曲线a代表TH的电致发射光谱，曲线b代表RD的吸收光谱，曲线c代表RD的电致发射光谱。上述五个器件的性能见表2，表2中，器件2至器件5的LT95寿命(是指器件发出的光的亮度衰减至初始亮度的95％所需的发光时长)是以器件1的LT95寿命为基准，器件2至器件5中每个器件的LT95寿命与器件1的LT95寿命的比值。
表1材料分子能轨及激发态
  HOMO(eV) LUMO(eV) T1(eV) S1(eV)
TM -5.8 -2.6 2.70 3.48
TH -5.9 -3.6 2.35 2.43
RD -5.6 -3.6 未检出 2.03
EBL-1 -5.7 -2.5 2.61 /
EBL-2 -5.6 -2.3 2.53 /
表2器件的性能
Figure PCTCN2021087868-appb-000001
关于比较例的器件1和器件2，器件1和器件2的器件结构均为普通的超荧光底发射器件，两者的不同为电子阻挡层的材料不同，其余相同。从表1和表2可以看出：EBL-1和EBL-2具有相似的HOMO能级和LUMO能级，但EBL-2的T1较小，这样容易造成发光层中三重态激子的泄漏，因此器件2相对于器件1，效率明显下降。器件2相对于器件1，器件2的寿命有所提高，主要是由于EBL-2具有相对于EBL-1更浅的HOMO能级，这样，在电子阻挡层与发光层的界面附近形成的势垒有助于减缓空穴向发光层的注入，从而形成了更好的载流子平衡。
关于本公开实施例的器件3、器件4和器件5，器件3、器件4和器件5均包括辅助发光层和发光层。从表1和表2可以看出：
相对于器件1，器件3包括辅助发光层，因辅助发光层可以对发光层中的三重态激子进行阻挡，因此，器件3的效率对电子阻挡层的T1并不敏感，器件3虽然使用了T1较低的EBL-2，但仍然保持了较好的效率和寿命，并且，器件3由于设置了辅助发光层，因此可降低电子阻挡层和发光层之间的空穴传输阻抗，可使空穴更好地传输至发光层，因此，器件3的电压明显降低。
相对于器件1，器件4和器件5由于均设置了辅助发光层，因此可降低电子阻挡层和发光层之间的空穴传输阻抗，可使空穴更好地传输至发光层，因此器件4和器件5具有更低的工作电压，并保持了较好的效率。此外，当辅助发光层的厚度从3nm提高到6nm时，器件的寿命有所下降。
综上，本公开的示例性实施例的有机电致发光器件，通过在发光层的朝向阳极一侧设置辅助发光层，并对辅助发光层和发光层进行合理的材料选择及材料能级搭配，使得本公开实施例的有机电致发光器件相对于单发光层结构的器件来讲，可在保证较好效率和寿命的条件下，实现更低的工作电压，并且对电子阻挡层材料的选择具有较大的灵活性。
本公开实施例还提供一种显示基板，包括前文任一实施例所述的有机电致发光器件。
在一些示例性实施例中，所述显示基板包括显示区域，显示区域包括阵列排布的多个有机电致发光器件。在垂直于显示基板的方向上，显示基板可 以包括设置在基底上的驱动电路层、设置在驱动电路层远离基底一侧的发光结构层，以及设置在发光结构层的远离基底一侧的封装结构层。驱动电路层包括像素驱动电路，像素驱动电路包括薄膜晶体管和存储电容。发光结构层包括多个有机电致发光器件，每个有机电致发光器件的阳极与对应的像素驱动电路的薄膜晶体管的漏电极连接。封装结构层可以采用UV胶封装或薄膜封装等方式，比如，封装结构层可以包括依次叠设的第一封装层、第二封装层和第三封装层，第一封装层和第三封装层可采用无机材料，第二封装层可采用有机材料，封装结构层可以保证外界水汽无法进入显示区域。所述基底可以是柔性基底或者刚性基底，比如聚酰亚胺、玻璃、蓝宝石或硅片等，如果设计底发射器件，基底对于波长为550nm的光的透过率可大于85％。所述显示基板还可以包括其它膜层，如隔垫柱等，本公开在此不做限定。
本公开实施例还提供一种显示装置，包括前文任一实施例所述的有机电致发光器件。显示装置可以为手机、平板电脑、电视机、显示器、笔记本电脑、数码相框、导航仪、车载显示器、智能手表或智能手环等任何具有显示功能的产品或部件。
虽然本公开所揭露的实施方式如上，但所述的内容仅为便于理解本公开而采用的实施方式，并非用以限定本公开。任何所属领域内的技术人员，在不脱离本公开所揭露的精神和范围的前提下，可以在实施的形式及细节上进行任何的修改与变化，但本申请的专利保护范围，仍须以所附的权利要求书所界定的范围为准。

Claims (20)

  1. 一种有机电致发光器件，包括阳极、阴极、设于所述阳极和所述阴极之间发光层，以及位于所述发光层的朝向所述阳极一侧的辅助发光层；所述辅助发光层包括第一主体材料和第一荧光客体材料；所述发光层包括第二主体材料、TADF材料和第二荧光客体材料；
    所述第一主体材料和所述第一荧光客体材料满足：
    S1(B)-T1(B)>0.2eV；
    S1(B)>S1(C)；
    T1(B)>T1(C)；
    ||HOMO(B)-LUMO(C)|-S1(C)|≤0.2eV；
    其中，所述第一主体材料的最低单重态能量为S1(B)，最低三重态能量为T1(B)；所述第一荧光客体材料的最低单重态能量为S1(C)，最低三重态能量为T1(C)；所述第一主体材料的最高占据分子轨道能级为HOMO(B)；所述第一荧光客体材料的最低未占分子轨道能级为LUMO(C)。
  2. 如权利要求1所述的有机电致发光器件，其中，所述第一主体材料为空穴型材料，所述第一主体材料的空穴迁移率高于电子迁移率至少十倍。
  3. 如权利要求1所述的有机电致发光器件，其中，所述辅助发光层中不含有具有TADF性质的材料。
  4. 如权利要求1所述的有机电致发光器件，其中，所述第二主体材料、所述TADF材料和所述第二荧光客体材料满足：
    S1(E)-T1(E)<0.2eV；
    S1(D)>S1(E)>S1(F)；
    T1(D)>T1(E)>T1(F)；
    |HOMO(D)-HOMO(E)|<0.2eV；
    |LUMO(D)-LUMO(E)|>0.3eV；
    ||HOMO(D)-LUMO(E)|-S1(E)|≤0.2eV；
    ||HOMO(D)-LUMO(E)|-T1(E)|≤0.2eV；
    其中，所述第二主体材料的最低单重态能量为S1(D)，最低三重态能量为T1(D)；所述TADF材料的最低单重态能量为S1(E)，最低三重态能量为T1(E)；所述第二荧光客体材料的最低单重态能量为S1(F)，最低三重态能量为T1(F)；所述第二主体材料的最高占据分子轨道能级为HOMO(D)，最低未占分子轨道能级为LUMO(D)；所述TADF材料的最高占据分子轨道能级为HOMO(E)，最低未占分子轨道能级为LUMO(E)。
  5. 如权利要求4所述的有机电致发光器件，其中，所述第二荧光客体材料的吸收光谱与所述TADF材料的发射光谱的重叠面积不小于所述第二荧光客体材料的吸收光谱面积的70％；
    所述第二荧光客体材料的吸收光谱的能量最低吸收峰与所述TADF材料的发射光谱的能量最高发射峰的峰位差不大于20nm。
  6. 如权利要求4所述的有机电致发光器件，其中，所述第二主体材料为单一组分材料，或者为具有激基复合物性质的混合材料；
    当所述第二主体材料为单一组分材料时，所述第二主体材料满足：S1(D)-T1(D)>0.2eV，且所述第二主体材料的空穴迁移率高于电子迁移率至少十倍。
  7. 如权利要求4所述的有机电致发光器件，其中，所述第二主体材料、所述TADF材料和所述第二荧光客体材料还满足：λ(D)>λ(E)>λ(F)；
    其中，λ(D)代表所述第二主体材料的最强发射峰波长，λ(E)代表所述TADF材料的最强发射峰波长，λ(F)代表所述第二荧光客体材料的最强发射峰波长。
  8. 如权利要求4所述的有机电致发光器件，其中，所述发光层由所述第二主体材料、所述TADF材料和所述第二荧光客体材料组成。
  9. 如权利要求1所述的有机电致发光器件，其中，所述第一主体材料与所述第二主体材料相同或者不同；
    当所述第一主体材料与所述第二主体材料不同时，满足以下条件：
    |HOMO(B)-HOMO(D)|<0.2eV；
    |HOMO(B)-HOMO(E)|<0.2eV；
    T1(B)>T1(E)；
    ||HOMO(B)-LUMO(E)|-S1(E)|≤0.2eV；
    ||HOMO(B)-LUMO(E)|-T1(E)|≤0.2eV；
    其中，所述第一主体材料的最高占据分子轨道能级为HOMO(B)；所述第二主体材料的最高占据分子轨道能级为HOMO(D)；所述TADF材料的最高占据分子轨道能级为HOMO(E)，最低未占分子轨道能级为LUMO(E)；所述第一主体材料的最低三重态能量为T1(B)；所述TADF材料的最低单重态能量为S1(E)，最低三重态能量为T1(E)。
  10. 如权利要求1所述的有机电致发光器件，其中，所述第一荧光客体材料与所述第二荧光客体材料相同或者不同；
    当所述第一荧光客体材料与所述第二荧光客体材料不同时，满足以下条件：所述第一荧光客体材料的发射光谱与所述第二荧光客体材料的发射光谱的重叠面积大于第一荧光客体材料的发射光谱的面积的90％，并大于所述第二荧光客体材料的发射光谱的面积的90％；所述第一荧光客体材料的吸收光谱与所述TADF材料的发射光谱的重叠面积不小于所述第一荧光客体材料的吸收光谱面积的70％。
  11. 如权利要求1所述的有机电致发光器件，还包括设于所述辅助发光层的朝向所述阳极一侧的电子阻挡层；
    所述电子阻挡层的材料与所述第一主体材料满足以下条件：
    |HOMO(A)-HOMO(B)|≤0.2eV，|LUMO(B)|-|LUMO(A)|>0.2eV，其中，HOMO(A)代表电子阻挡层的材料的最高占据分子轨道能级，LUMO(A)代表电子阻挡层的材料的最低未占分子轨道能级。
  12. 如权利要求11所述的有机电致发光器件，还包括设于所述阳极和所述电子阻挡层之间的空穴注入层和空穴传输层。
  13. 如权利要求1所述的有机电致发光器件，还包括设于所述发光层的朝向所述阴极一侧的空穴阻挡层；
    所述空穴阻挡层的材料的最低三重态能量大于所述TADF材料的最低三重态能量，所述空穴阻挡层的材料的最高占据分子轨道能级的绝对值比所述 第二主体材料的最高占据分子轨道能级的绝对值大0.2eV以上。
  14. 如权利要求13所述的有机电致发光器件，还包括设于所述阴极和所述空穴阻挡层之间的电子注入层和电子传输层。
  15. 如权利要求1所述的有机电致发光器件，其中，所述TADF材料在所述发光层中所占的质量百分比为X，5％<X<50％。
  16. 如权利要求1所述的有机电致发光器件，其中，所述第二荧光客体材料在所述发光层中所占的质量百分比为0.5％至5％。
  17. 如权利要求1所述的有机电致发光器件，其中，所述发光层的厚度至少大于所述辅助发光层的厚度的两倍。
  18. 如权利要求1所述的有机电致发光器件，其中，所述发光层的厚度为10nm至30nm。
  19. 如权利要求1所述的有机电致发光器件，其中，所述辅助发光层的厚度为1nm至10nm。
  20. 一种显示装置，包括权利要求1至19任一项所述的有机电致发光器件。
PCT/CN2021/087868 2021-04-16 2021-04-16 有机电致发光器件和显示装置 WO2022217600A1 (zh)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109599493A (zh) * 2017-09-30 2019-04-09 昆山国显光电有限公司 一种有机电致发光器件
CN111653679A (zh) * 2020-06-18 2020-09-11 京东方科技集团股份有限公司 有机发光器件及其制备方法、显示面板和显示装置
CN112234150A (zh) * 2020-10-16 2021-01-15 京东方科技集团股份有限公司 发光器件、显示基板
CN112447921A (zh) * 2019-09-04 2021-03-05 乐金显示有限公司 有机发光二极管和具有该二极管的有机发光装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109599493A (zh) * 2017-09-30 2019-04-09 昆山国显光电有限公司 一种有机电致发光器件
CN112447921A (zh) * 2019-09-04 2021-03-05 乐金显示有限公司 有机发光二极管和具有该二极管的有机发光装置
CN111653679A (zh) * 2020-06-18 2020-09-11 京东方科技集团股份有限公司 有机发光器件及其制备方法、显示面板和显示装置
CN112234150A (zh) * 2020-10-16 2021-01-15 京东方科技集团股份有限公司 发光器件、显示基板

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