Metal-assisted delayed fluorescent materials as co-host materials for fluorescent OLEDS

• US 10,294,417 B2
• Filed: 03/19/2018
• Issued: 05/21/2019
• Est. Priority Date: 08/22/2014
• Status: Active Grant

• Current Assignee: Arizona Board of Regents (University of Arizona)
• Original Assignee: Arizona Board of Regents (University of Arizona)
• Inventors: Li, Jian
• Primary Examiner(s): Tobergte, Nicholas J
• Application Number:
  US15/925,203
• Publication Number:
  US 20180312750A1
• Time in Patent Office: 428 Days
• CPC Class Codes: C09K 11/06 containing organic luminescent materials
• CPC Class Codes: C09K 2211/185 of the platinum group, i.e. Os, Ir, Pt, Ru, Rh or Pd
• CPC Class Codes: C09K 2211/187 of the iron group metals, i.e. Fe, Co or Ni
• CPC Class Codes: C09K 2211/188 of other metals not provided for in one of the previous groups
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/13 comprising stacked EL layers within one EL unit
• CPC Class Codes: H10K 85/331 Metal complexes comprising an iron-series metal, e.g. Fe, Co, Ni
• CPC Class Codes: H10K 85/341 Transition metal complexes, e.g. Ru(II)polypyridine complexes H10K85/331 takes precedence
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/346 comprising platinum
• CPC Class Codes: H10K 85/371 Metal complexes comprising a group IB metal element, e.g. comprising copper, gold or silver
• CPC Class Codes: H10K 85/381 Metal complexes comprising a group IIB metal element, e.g. comprising cadmium, mercury or zinc
• CPC Class Codes: H10K 85/60 Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: H10K 85/622 containing four rings, e.g. pyrene
• CPC Class Codes: H10K 85/649 Aromatic compounds comprising a hetero atom
• CPC Class Codes: H10K 85/653 comprising only oxygen as heteroatom
• CPC Class Codes: H10K 85/654 comprising only nitrogen as heteroatom H10K85/652 takes precedence
• CPC Class Codes: H10K 85/655 comprising only sulfur as heteroatom
• CPC Class Codes: H10K 85/656 comprising two or more different heteroatoms per ring H10K85/652 takes precedence
• CPC Class Codes: H10K 85/657 : Polycyclic condensed heteroaromatic hydrocarbons
• CPC Class Codes: H10K 85/6572 : comprising only nitrogen in the heteroaromatic polycondensed ring system, e.g. phenanthroline or carbazole
• CPC Class Codes: H10K 85/6574 : comprising only oxygen in the heteroaromatic polycondensed ring system, e.g. cumarine dyes
• CPC Class Codes: H10K 85/6576 : comprising only sulfur in the heteroaromatic polycondensed ring system, e.g. benzothiophene

Abstract

A light emitting device includes a first electrode, a hole transporting layer in contact with the first electrode, a second electrode, an electron transporting layer in contact with the second electrode; and an emissive layer between the hole transporting layer and the electron transporting layer. The emissive layer includes a metal-assisted delayed fluorescent (MADF) emitter, a fluorescent emitter, and a host, and the MADF emitter harvests electrogenerated excitons and transfers energy to the fluorescent emitter.

Claims

1. A light emitting device comprising:

a first electrode;

a hole transporting layer in contact with the first electrode;

a second electrode;

an electron transporting layer in contact with the second electrode; and

an emissive layer between the hole transporting layer and the electron transporting layer, wherein the emissive layer comprises a donor, an acceptor, and a host,

wherein;

the donor is a metal-assisted delayed fluorescent (MADF) emitter that demonstrates an emission spectrum consisting of dual emission characteristics from delayed fluorescence and phosphorescence,

the acceptor is a fluorescent emitter,

the delayed fluorescence emission energy of the donor is greater than the emission energy of the acceptor and the phosphorescence emission energy of the donor is greater than or less than the emission energy of the acceptor, such that an emission spectrum of the donor partially overlaps in wavelength with an absorption spectrum of the acceptor, and

dipole coupling between the donor in an excited state and the acceptor in a ground state allows a transfer of energy from the donor to the acceptor.

2. The light emitting device of claim 1, wherein the transfer of energy from the donor to the acceptor is a transfer of energy from an allowed relaxation transition of the donor to an allowed excitation transition of the acceptor.

3. The light emitting device of claim 1, wherein the transfer of energy occurs between mixed singlet/triplet excitons of the donor and singlet excitons of the acceptor.

4. The light emitting device of claim 1, wherein the transfer of energy occurs between a triplet exciton of the donor and a singlet exciton of the acceptor.

5. The light-emitting device of claim 1, wherein the donor, in a triplet state, is less stable than the acceptor, in a singlet state.

6. The light-emitting device of claim 1, wherein a dopant concentration of the acceptor is reasonably small, i.e. 3 weight percent or less, to encourage Foster energy transfer and suppress Dexter energy transfer between donor and acceptor.

7. The light-emitting device of claim 1, wherein light emission from the light-emitting device is primarily from the acceptor.

8. The light emitting device of claim 1, wherein the donor is a compound of structure (a) or (b):

9. The light emitting device of claim 8, wherein a² is absent.

10. The light emitting device of claim 8, wherein a² and b² are absent.

11. The light emitting device of claim 8, wherein X is N.

12. The light emitting device of claim 8, wherein A is

13. The light emitting device of claim 8, wherein C in structure (a) or (b) is

14. The light emitting device of claim 8, wherein N in structure (a) or (b) is

15. The light emitting device of claim 8, wherein M is palladium (II).

16. The light emitting device of claim 8, wherein the donor is one of the following:

17. The light emitting device of claim 8, wherein the donor is a compound of General Formula A:

18. The light emitting device of claim 17, wherein Y^2b is C;

Y^2c, Y^3b and Y^4b are N; and

M is Ir or Rh.

19. The light emitting device of claim 8, wherein the MADF emitter is a compound of General Formula B:

20. The light emitting device of claim 19, wherein M is Pt or Pd, Y^2b and Y^2c are C, Y^3b and Y^4b are N, each of Y^1a and Y^1b is independently O, NR³, CR³R⁴, S, AsR³, BR³, PR³, P(O)R³, or SiR³R⁴, or a combination thereof, wherein each of R³ and R⁴ is independently hydrogen, halogen, hydroxyl, thiol, or substituted or unsubstituted alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkane, cycloalkane, heterocyclyl, amino, alkoxy, haloalkyl, arylalkane, arylalkene, or R³ and R⁴ together form C═

O, wherein each of R³ and R⁴ is independently optionally linked to an adjacent ring structure, thereby forming a cyclic structure.

21. The light emitting device of claim 19, wherein M is Au, Y^2b Y^2c and Y^4b are C, Y^3b is N, each of Y^1a and Y^1b is independently O, NR³, CR³R⁴, S, AsR³, BR³, PR³, P(O)R³, or SiR³R⁴, or a combination thereof, wherein each of R³ and R⁴ is independently hydrogen, halogen, hydroxyl, thiol, or substituted or unsubstituted alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkane, cycloalkane, heterocyclyl, amino, alkoxy, haloalkyl, arylalkane, arylalkene, or R³ and R⁴ together form C═

O, wherein each of R³ and R⁴ is independently optionally linked to an adjacent ring structure, thereby forming a cyclic structure.

22. The light emitting device of claim 8, wherein the donor is a compound of General Formula C:

23. The light emitting device of claim 8, wherein the donor is a compound of General Formula D:

24. The light emitting device of claim 8, wherein the donor is a compound of General Formula E:

25. The light emitting device of claim 8, wherein the donor has an energy of the singlet excited state(s) no more than 0.2 eV greater than the energy of the lowest triplet state, and the MADF emitter emits simultaneously from the lowest triplet state and the singlet excited state(s) at room temperature or elevated temperature.

26. The light emitting device of claim 25, wherein the donor harvests electrogenerated singlet and triplet excitons.

27. The light emitting device of claim 24, wherein each of Fl¹, Fl², Fl³, Fl⁴, if present, has one of the following structures:

1. Aromatic Hydrocarbons and Their Derivatives

28. The light emitting device of claim 1, wherein the acceptor comprises one of the following compounds: