Electroluminescent devices having sensitizer and fluorescent emitter

Patent metadata

Field	Value
Publication number	US-12484440-B2
Application number	US-201917276060-A
Country	US
Kind code	B2
Filing date	Sep 12, 2019
Priority date	Sep 12, 2018
Publication date	Nov 25, 2025
Grant date	Nov 25, 2025

Abstract

The present invention describes electronic devices and compositions that can be used in electronic devices, the electronic devices including a sensitizer and a fluorescent emitter, wherein the sensitizer is a phosphorescent compound and wherein at least one of the two following conditions (I) or (II) must be satisfied, it being preferable when condition (I) is satisfied:

S 1 K (FE)− S 1 K ( S )≥ X   (I)

S 1 max (FE)− S 1 max ( S )≤ Y   (II)

wherein, e.g., X, Y are each −0.5 eV; S 1 K (FE) is the energy of the first excited singlet state of the fluorescent emitter; S 1 K (S) is the energy of the first excited state of the sensitizer; S 1 max (FE) is the energy of the first excited singlet state of the fluorescent emitter; S 1 max (S) is the energy of the first excited state of the sensitizer; and wherein the photoluminescence spectra of the sensitizer and of the fluorescent emitter are determined at room temperature.

First claim

The invention claimed is:

1 . A fluorescent electronic device comprising at least one layer, a sensitizer and a fluorescent emitter, wherein both the sensitizer and the fluorescent emitter are deposited by co-evaporation in the same one of at least one layer as a mixture, and wherein the sensitizer is a phosphorescent compound and wherein at least one of the two following conditions (I) or (II) must be satisfied:
S 1 K (FE)− S 1 K ( S )≥ X   (I)
S 1 max (FE)− S 1 max ( S )≤ Y   (II)
where the parameters used are as follows: X, Y are each −0.5 eV or are each −0.4 eV, S 1 K (FE) is an energy of a first excited singlet state of the fluorescent emitter which is ascertained from an edge of a first maximum on a short-wavelength side of a normalized photoluminescence spectrum of the fluorescent emitter; S 1 K (S) is an energy of a first excited state of the sensitizer which is ascertained from an edge of a first maximum on a short-wavelength side of a normalized photoluminescence spectrum of the sensitizer; S 1 max (FE) is the energy of the first excited singlet state of the fluorescent emitter which is ascertained from a location of the first maximum at short wavelengths of a photoluminescence spectrum of the fluorescent emitter; S 1 max (S) is the energy of the first excited state of the sensitizer which is ascertained from a location of the first maximum at short wavelengths of a photoluminescence spectrum of the sensitizer; wherein the photoluminescence spectra of the sensitizer and of the fluorescent emitter are determined from solution at a concentration of 1 mg in 100 ml of toluene at room temperature, wherein the fluorescent emitter is a sterically shielded compound having a shielding factor (SF) of not less than 0.5; wherein the photoluminescence emission spectrum of the sensitizer overlaps with an absorption spectrum of the fluorescent emitter; and wherein the Forster radius is not more than 3 nm.

2 . The device according to claim 1 , wherein both conditions (I) and (II) are satisfied.

3 . The device according to claim 1 , wherein excitation energy is transferred from the sensitizer to the fluorescent emitter and the fluorescent emitter emits excitation energy absorbed by the sensitizer by fluorescence.

4 . The device according to claim 1 , wherein a metal-to-ligand charge transfer (MLCT) band of the photoluminescence spectrum of the sensitizer overlaps with an absorption spectrum of the fluorescent emitter.

5 . The device according to claim 1 , wherein a magnitude of a triplet metal-to-ligand charge transfer ( 3 MLCT) band of the photoluminescence spectrum of the sensitizer and an absorption maximum of the fluorescent emitter satisfies the following condition (III):
|λ em 3 MLCT ( S )−λ abs max (FE)|≤ V   (III)
where V is 0.5 eV; and where λ em 3 MLCT (S) is the triplet metal-to-ligand charge transfer ( 3 MLCT) band of the photoluminescence spectrum of the sensitizer and is found from an edge in a photoluminescence spectrum of the sensitizer and λ abs max (FE) is a peak absorption wavelength of a first maximum at long wavelengths of the fluorescent emitter, where the values are each calculated in electron volts.

6 . The device according to claim 1 , wherein the following condition (IV) is satisfied
λ em 3 MLCT ( S )−λ abs max (FE)≤ W   (IV)
where W is 0.5 eV; and where λ em 3 MLCT (S) is a triplet metal-to-ligand charge transfer ( 3 MLCT) band of a photoluminescence spectrum of the sensitizer and is found from an edge in the photoluminescence spectrum of the sensitizer and λ abs max (FE) is a peak absorption wavelength of a first maximum at long wavelengths of the fluorescent emitter, where λ em 3 MLCT (S) and λ abs max (FE) are each calculated in electron volts.

7 . The device according to claim 1 , wherein the sensitizer is a phosphorescent compound comprising an organometallic complex.

8 . The device according to claim 1 , wherein the sensitizer is a phosphorescent compound from a group of organometallic complexes containing Cu, Ir, Pt, Rh, Ru, Os or Pd.

9 . The device according to claim 1 , wherein the fluorescent emitter is a purely organic compound devoid of metals or metal ions.

10 . The device according to claim 1 , wherein the fluorescent emitter is a purely organic compound devoid of metals or metal ions, selected from a group consisting of fused aromatics having 6 to 60 aromatic ring atoms.

11 . The device according to claim 1 , wherein the fluorescent emitter is a purely organic compound devoid of metals or metal ions, selected from a group consisting of the pyrenes, perylenes, anthracenes, fluorenes and indenofluorenes.

12 . The device according to claim 1 , wherein the fluorescent emitter is a purely organic compound devoid of metals or metal ions, with aromatic groups in substituted form.

13 . The device according to claim 1 , comprising an emission layer, and wherein the sensitizer and the fluorescent emitter are in the emission layer.

14 . The device according to claim 1 , wherein the layer in which the sensitizer and the fluorescent emitter are present contains a further material selected from a group consisting of electron transport materials, hole conductor materials, quantum materials, bipolar hosts, wide band gap materials, phosphorescent emitters, fluorescent emitters, and materials having delayed fluorescence.

15 . The device according to claim 1 , wherein the at least one layer in which the sensitizer and the fluorescent emitter are present does not contain any further material.

16 . A composition comprising at least one sensitizer and at least one fluorescent emitter, wherein both the at least one sensitizer and the at least one fluorescent emitter are deposited by co-evaporation in the same one of at least one layer as a mixture, wherein the at least one sensitizer is a phosphorescent compound and wherein at least one of the two following conditions (I) and (II) must be satisfied:
S 1 K (FE)− S 1 K ( S )≥ X   (I)
S 1 max (FE)− S 1 max ( S )≤ Y   (II),
where the parameters used are as follows: X, Y are each −0.5 eV or are each −0.4 eV, S 1 K (FE) is an energy of a first excited singlet state of the at least one fluorescent emitter which is ascertained from an edge of a first maximum on a short-wavelength side of a normalized photoluminescence spectrum of the at least one fluorescent emitter; S 1 K (S) is an energy of a first excited state of the at least one sensitizer which is ascertained from an edge of a first maximum on a short-wavelength side of a normalized photoluminescence spectrum of the at least one sensitizer; S 1 max (FE) is the energy of the first excited singlet state of the at least one fluorescent emitter which is ascertained from a location of the first maximum at short wavelengths of a photoluminescence spectrum of the at least one fluorescent emitter; S 1 max (S) is the energy of the first excited state of the at least one sensitizer which is ascertained from a location of the first maximum at short wavelengths of a photoluminescence spectrum of the at least one sensitizer, wherein the fluorescent emitter is a sterically shielded compound having a shielding factor (SF) of not less than 0.5, wherein the photoluminescence emission spectrum of the at least one sensitizer overlaps with an absorption spectrum of the at least one fluorescent emitter, and wherein the Forster radius is not more than 3 nm.

17 . The composition according to claim 16

Assignees

• Merck Patent Gmbh

Inventors

• Stengel Ilona
• Horn Antonia
• May Falk
• Lackner Aaron
• Pflumm Christof
• Mekic Amel
• Haase Nils

Classifications

• H10K2101/40

  Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers · CPC title

• H10K2101/30

  Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values · CPC title

• H10K2101/10

  Triplet emission · CPC title

• H10K50/121 Primary

  for assisting energy transfer, e.g. sensitization · CPC title

• H10K50/11

  characterised by the electroluminescent [EL] layers · CPC title