Organic electroluminescent device with thermally activated delayed fluorescence material

• US 10,069,079 B2
• Filed: 03/18/2014
• Issued: 09/04/2018
• Est. Priority Date: 04/08/2013
• Status: Active Grant

• Current Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Original Assignee: Merck Patent GmbH (Merck & Co., Inc.)
• Inventors: Stoessel, Philipp, Parham, Amir Hossain, Pflumm, Christof, Jatsch, Anja, Kaiser, Joachim
• Primary Examiner(s): Clark, Gregory D
• Application Number:
  US14/782,974
• Publication Number:
  US 20160315268A1
• Time in Patent Office: 1,631 Days
• Field of Search: None
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 2101/20 Delayed fluorescence emission
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 2101/40 Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/16 Electron transporting layers
• CPC Class Codes: H10K 50/18 Carrier blocking layers
• CPC Class Codes: H10K 71/00 Manufacture or treatment specially adapted for the organic devices covered by this subclass
• CPC Class Codes: H10K 71/12 using liquid deposition, e.g. spin coating
• CPC Class Codes: H10K 71/13 using printing techniques, e.g. ink-jet printing or screen printing
• CPC Class Codes: H10K 85/30 Coordination compounds
• CPC Class Codes: H10K 85/60 Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence
• CPC Class Codes: H10K 85/624 containing six or more rings
• CPC Class Codes: H10K 85/626 containing more than one polycyclic condensed aromatic rings, e.g. bis-anthracene
• CPC Class Codes: H10K 85/633 comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/654 comprising only nitrogen as heteroatom H10K85/652 takes precedence
• CPC Class Codes: H10K 85/6572 comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole

Abstract

The present invention relates to organic electroluminescent devices which comprise mixtures of at least one electron-conducting material and an emitting material which has a small singlet-triplet separation.

Claims

1. An organic electroluminescent device comprising cathode, anode and an emitting layer, which comprises the following compounds:

(A) electron-transporting compound which has an LUMO≤

−

2.5 eV; and

(B) a luminescent organic compound which has a separation between the lowest triplet state T₁ and the first excited singlet state S₁ of ≤

0.15 eV (TADF compound).

2. The organic electroluminescent device according to claim 1, wherein the TADF compound in a layer in a mixture with the electron-transporting compound has a luminescence quantum efficiency of at least 40%.

3. The organic electroluminescent device according to claim 1, wherein the separation between S₁ and T₁ of the TADF compound is <

0.10 eV.

4. The organic electroluminescent device according to claim 1, wherein the separation between S₁ and T₁ of the TADF compound is <

0.05 eV.

5. The organic electroluminescent device according to claim 1, wherein the TADF compound is an aromatic compound which has both donor and also acceptor substituents.

6. The organic electroluminescent device according to claim 1, wherein the following applies to the LUMO of the TADF compound LUMO(TADF) and the HOMO of the electron-transporting matrix HOMO(matrix):

LUMO(TADF)−

HOMO(matrix)>

S₁(TADF)−

0.4 eV,

where S₁(TADF) is the first excited singlet state S₁ of the TADF compound.

7. The organic electroluminescent device according to claim 1, wherein the electron-transporting compound has an LUMO≤

−

2.60 eV.

8. The organic electroluminescent device according to claim 1, wherein the lowest triplet energy of the electron-transporting compound is a maximum of 0.1 eV lower than the triplet energy of the TADF compound.

9. The organic electroluminescent device according to claim 1, wherein the electron-transporting compound is selected from the substance classes of the triazines, the pyrimidines, the lactams, the metal complexes, the aromatic ketones, the aromatic phosphine oxides, the azaphospholes, the azaboroles, which are substituted by at least one electron-conducting substituent, and the quinoxalines.

10. The organic electroluminescent device according to claim 1, wherein the electron-transporting compound is selected from the substance classes of the triazines, the pyrimidines, the lactams, Be complexes, Zn complexes, Al complexes, the aromatic ketones, the aromatic phosphine oxides, the azaphospholes, the azaboroles, which are substituted by at least one electron-conducting substituent, and the quinoxalines.

11. The organic electroluminescent device according to claim 1, wherein the electron-transporting compound is selected from the compounds of the following formulae (1) and (2),

12. The organic electroluminescent device according to claim 1, wherein the electron-transporting compound is selected from the compounds of the following formulae (1a) and (2a) to (2d),

13. The organic electroluminescent device according to claim 12, wherein at least one radical R is selected, identically or differently on each occurrence, from the group consisting of benzene, ortho-, meta- or para-biphenyl, ortho-, meta-, para- or branched terphenyl, ortho-, meta-, para- or branched quaterphenyl, 1-, 2-, 3- or 4-fluorenyl, 1-, 2-, 3- or 4-spirobifluorenyl, 1- or 2-naphthyl, pyrrole, furan, thiophene, indole, benzofuran, benzothiophene, 1-, 2- or 3-carbazole, 1-, 2- or 3-dibenzofuran, 1-, 2- or 3-dibenzothiophene, indenocarbazole, indolocarbazole, 2-, 3- or 4-pyridine, 2-, 4- or 5-pyrimidine, pyrazine, pyridazine, triazine, anthracene, phenanthrene, triphenylene, pyrene, benzanthracene or combinations of two or three of these groups, each of which is optionally substituted by one or more radicals R¹, or from the structures of the following formulae (3) to (44),

14. The organic electroluminescent device according to claim 13, wherein X is on each occurrence, identically or differently, CR¹ or N, and where a maximum of 2 symbols X per ring stand for N.

15. The organic electroluminescent device according to claim 1, wherein the electron-transporting compound material is selected from the compounds of the formulae (45) and (46),

16. The organic electroluminescent device according to claim 15, wherein the group Ar¹ stands for a group of the following formula (47), (48), (49) or (50),

17. The organic electroluminescent device according to claim 10, wherein the electron-transporting compound is selected from the compounds of the formulae (70) and (71),

18. The organic electroluminescent device according to claim 17, wherein Ar⁴ is selected, identically or differently on each occurrence, from phenyl, 2-, 3- or 4-tolyl, 3- or 4-o-xylyl, 2- or 4-m-xylyl, 2-p-xylyl, o-, m- or p-tert-butylphenyl, o-, m- or p-fluorophenyl, benzophenone, 1-, 2- or 3-phenylmethanone, 2-, 3- or 4-biphenyl, 2-, 3- or 4-o-terphenyl, 2-, 3- or 4-m-terphenyl, 2-, 3- or 4-p-terphenyl, 2′

-p-terphenyl, 2′

-, 4′

- or 5′

-m-terphenyl, 3′

- or 4′

-o-terphenyl, p-, m,p-, o,p-, m,m-, o,m- or o,o-quaterphenyl, quinquephenyl, sexiphenyl, 1-, 2-, 3- or 4-fluorenyl, 2-, 3- or 4-spiro-9,9′

-bifluorenyl, 1-, 2-, 3- or 4-(9,10-dihydro)phenanthrenyl, 1- or 2-naphthyl, 2-, 3-, 4-, 5-, 6-, 7- or 8-quinolinyl, 1-, 3-, 4-, 5-, 6-, 7- or 8-isoquinolinyl, 1- or 2-(4-methylnaphthyl), 1- or 2-(4-phenylnaphthyl), 1- or 2-(4-naphthylnaphthyl), 1-, 2- or 3-(4-naphthylphenyl), 2-, 3- or 4-pyridyl, 2-, 4- or 5-pyrimidinyl, 2- or 3-pyrazinyl, 3- or 4-pyridanzinyl, 2-(1,3,5-triazin)yl-, 2-, 3- or 4-(phenylpyridyl), 3-, 4-, 5- or 6-(2,2′

-bipyridyl), 2-, 4-, 5- or 6-(3,3′

-bipyridyl), 2- or 3-(4,4′

-bipyridyl), and combinations of one or more of these radicals, which is optionally substituted by one or more radicals R.

19. A process for the production of the organic electroluminescent device as claimed in claim 1, which comprises applying at least one layer by means of a sublimation process and/or in that at least one layer is applied by means of an OVPD (organic vapour phase deposition) process or with the aid of carrier-gas sublimation and/or in that at least one layer is applied from solution, by spin coating or by means of a printing process.

20. A process for the production of an organic electroluminescent device according to claim 1, which comprises applying at least one layer by means of a sublimation process and/or in that at least one layer is applied by means of an OVPD (organic vapour phase deposition) process or with the aid of carrier-gas sublimation and/or in that at least one layer is applied from solution, by spin coating or by means of a printing process.

21. The organic electroluminescent device according to claim 1, wherein LUMO is determined by using the quantum-chemical calculations and wherein LUMO in electron volts is determined by the following equation:

LUMO(eV)=((LEh*27.212)−

2.0041)/1.385

wherein LEh is the energy level in hartree units, which is obtained by the energy calculation of the quantum-chemical calculations.