Efficient organic light-emitting diodes and fabrication of the same

• US 9,853,220 B2
• Filed: 09/11/2012
• Issued: 12/26/2017
• Est. Priority Date: 09/12/2011
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Ma, Liping
• Primary Examiner(s): Leeser, Erich A
• Application Number:
  US14/344,300
• Publication Number:
  US 20150041780A1
• Time in Patent Office: 1,932 Days
• CPC Class Codes: C09B 57/00 Other synthetic dyes of known constitution
• CPC Class Codes: C09B 57/008 Triarylamine dyes containing no other chromophores
• CPC Class Codes: H10K 2101/27 Combination of fluorescent and phosphorescent emission
• CPC Class Codes: H10K 50/13 comprising stacked EL layers within one EL unit
• CPC Class Codes: H10K 50/131 with spacer layers between the electroluminescent layers
• CPC Class Codes: H10K 50/155 comprising dopants
• CPC Class Codes: H10K 50/156 comprising a multilayered structure
• CPC Class Codes: H10K 50/157 between the light-emitting layer and the cathode
• CPC Class Codes: H10K 50/171 Electron injection layers
• CPC Class Codes: H10K 50/19 Tandem OLEDs
• CPC Class Codes: H10K 50/818 Reflective anodes, e.g. ITO combined with thick metallic layers
• CPC Class Codes: H10K 50/852 comprising a resonant cavity structure, e.g. Bragg reflector pair
• CPC Class Codes: H10K 50/854 comprising scattering means
• CPC Class Codes: H10K 85/342 comprising iridium
• CPC Class Codes: H10K 85/615 Polycyclic condensed aromatic hydrocarbons, e.g. anthracene
• CPC Class Codes: H10K 85/631 Amine compounds having at least two aryl rest on at least one amine-nitrogen atom, e.g. triphenylamine
• CPC Class Codes: H10K 85/633 comprising polycyclic condensed aromatic hydrocarbons as substituents on the nitrogen atom
• CPC Class Codes: H10K 85/636 comprising heteroaromatic 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 85/656 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

Abstract

Light-emitting devices comprising light-emitting diodes are described herein. These devices may include a substrate, a reflective anode, a hole-injection layer, a hole-transport layer, an emissive component, an electron-transport layer, a cathode, an enhancement layer, and a light-scattering layer. The emissive component may include first and second fluorescent light-emitting layers with an intervening phosphorescent light-emitting layer or first and second phosphorescent light-emitting layers with an intervening fluorescent light-emitting layer.

Claims

1. A light-emitting device comprising:

a substrate;

a reflective anode over the substrate;

a hole-injection layer over the reflective anode;

a hole-transport layer over the hole-injection layer;

an emissive component over the hole-transport layer, wherein the emissive component comprises;

a first fluorescent light-emitting layer;

a second fluorescent light-emitting layer; and

an intervening phosphorescent light-emitting layer disposed between the first fluorescent light-emitting layer and the second fluorescent light-emitting layer;

or wherein the emissive component comprises;

a first phosphorescent light-emitting layer;

a second phosphorescent light-emitting layer; and

an intervening fluorescent light-emitting layer disposed between the first phosphorescent light-emitting layer and the second phosphorescent light-emitting layer;

an electron-transport layer over the emissive component;

a semi-transparent or transparent cathode over the electron-transport layer;

an enhancement layer over the semi-transparent or transparent cathode; and

a light-scattering layer over the enhancement layer;

wherein the first fluorescent light-emitting layer, the second fluorescent light-emitting layer, and the intervening fluorescent light-emitting layer each comprises a fluorescent ambipolar host material selected from the group consisting of;

2. The light-emitting device of claim 1, wherein the reflective anode comprises a first anode sublayer and a second anode sublayer, wherein the first anode sublayer comprises a material selected from the group consisting of Al, Ag, Ni, and combinations thereof, and wherein the second anode sublayer comprises a material selected from the group consisting of Ag, Al, Au, and combinations thereof.

3. The light-emitting device of claim 1, wherein the hole-injection layer comprises a high work function material.

4. The light-emitting device of claim 1, wherein the hole-transport layer comprises 4,4′

-bis[N-(naphthyl)-N-phenyl-amino]biphenyl.

5. The light-emitting device of claim 4, wherein the hole-transport layer further comprises a MoO₃ dopant.

6. The light-emitting device of claim 1, wherein the hole-transport layer comprises:

a first hole-transport sublayer comprising 4,4′

-bis[N-(naphthyl)-N-phenyl-amino]biphenyl and a dopant, wherein the dopant is MoO₃; and

a second hole-transport sublayer comprising 4,4′

-bis[N-(naphthyl)-N-phenyl-amino]biphenyl, wherein the second hole-transport sublayer is substantially free of MoO₃.

7. The light-emitting device of claim 1, wherein the fluorescent ambipolar host material has a peak emission in the range of about 430 nm to about 500 nm.

8. The light-emitting device of claim 1, wherein the first phosphorescent light-emitting layer and the second phosphorescent light-emitting layer each comprises a host and a phosphorescent dopant material, or the intervening phosphorescent light-emitting layer comprises the host and the phosphorescent dopant material, wherein the phosphorescent dopant material has a peak emission in the range of about 570 nm to about 650 nm.

9. The light-emitting device of claim 1, wherein the first phosphorescent light-emitting layer and the second phosphorescent light-emitting layer each comprises a host, or the intervening phosphorescent light-emitting layer comprises the host, wherein the host comprises:

10. The light-emitting device of claim 1, wherein the first phosphorescent light-emitting layer and the second phosphorescent light-emitting layer each comprises two phosphorescent emitters, or the intervening phosphorescent light-emitting layer comprises two phosphorescent emitters, wherein each phosphorescent emitter emits visible light having a peak emission in the red to green range.

11. The light-emitting device of claim 1, wherein the electron-transport layer comprises 1,3,5-tris[2-N-phenylbenzimidazol-z-yl]benzene.

12. The light-emitting device of claim 1, wherein the semi-transparent or transparent cathode comprises a first cathode sublayer comprising materials selected from Mg, Ca, Mg/Ag, LiF/Al, CsF, CsF/Al or alloys thereof and a second cathode sublayer comprising materials selected from Al, Ag, Au, Cu, Mg/Ag, or alloys thereof.

13. The light-emitting device of claim 1, wherein the enhancement layer comprises a visible light substantially transparent material having refractive index higher than about 1.5.

14. The light-emitting device of claim 1, wherein the light-scattering layer comprises one or more of the compounds, each selected from the group consisting of:

15. The light-emitting device of claim 1, wherein the light-scattering layer comprises voids having a volume that is at least about 50% of the volume of the light-scattering layer.

16. The light-emitting device of claim 1, wherein the light-scattering layer has a thickness in the range of about 0.1 μ

m to about 10 μ

m.

17. The light-emitting claim 1, wherein at least a portion of the first fluorescent light-emitting layer and at least a portion of the intervening phosphorescent light-emitting layer directly contact one another.

18. The light-emitting device claim 17, wherein at least a portion of the second fluorescent light-emitting layer and at least a portion of the intervening phosphorescent light-emitting layer directly contact one another.

19. The light-emitting device claim 1, wherein at least a portion of the first phosphorescent light-emitting layer and at least a portion of the intervening fluorescent light-emitting layer directly contact one another.

20. The light-emitting device claim 19, wherein at least a portion of the second phosphorescent light-emitting layer and at least a portion of the intervening fluorescent light-emitting layer directly contact one another.

21. The light-emitting device of claim 1, wherein:

the first fluorescent light-emitting layer is undoped;

the intervening phosphorescent light-emitting layer comprises a fluorescent host material of the first fluorescent light-emitting layer; and

the second fluorescent light-emitting layer is undoped, or the second fluorescent light-emitting layer comprises the fluorescent host material of the first fluorescent light-emitting layer.