White organic light emitting device (OLED)

• US 20090226757A1
• Filed: 06/18/2008
• Published: 09/10/2009
• Est. Priority Date: 03/04/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Song, Jung_Bae, Kim, Sang-Yeol, Kim, Mu-Gyeom, Lee, Sung-Hun
• Granted Patent: US 8,119,258 B2
• Time in Patent Office: Days
• US Class Current: 428/690
• CPC Class Codes: H10K 2101/30 Highest occupied molecular orbital [HOMO], lowest unoccupied molecular orbital [LUMO] or Fermi energy values
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 50/171 Electron injection layers
• CPC Class Codes: H10K 85/1135 Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
• CPC Class Codes: Y10S 428/917 Electroluminescent

Abstract

A white Organic Light Emitting Device (OLED) includes: an anode and cathode spaced apart from each other; first, second, and third light emitting layers sequentially stacked between the anode and the cathode; and an electron injection induction layer, arranged between the second light emitting layer and the third light emitting layer, to induce the electron to flow into the second light emitting layer from the third light emitting layer. A difference between a Lowest Occupied Molecular Orbital (LUMO) energy level of the electron injection induction layer and the LUMO energy level of a dopant existing in the second light emitting layer is 0.4 eV or below.

Claims

1. A white Organic Light Emitting Device (OLED) comprising:

an anode and cathode spaced apart from each other;

first, second, and third light emitting layers sequentially stacked between the anode and the cathode; and

an electron injection induction layer, arranged between the second light emitting layer and the third light emitting layer, to induce electrons to flow into the second light emitting layer from the third light emitting layer;

wherein a difference between a Lowest Occupied Molecular Orbital (LUMO) energy level of the electron injection induction layer and the LUMO energy level of a dopant in the second light emitting layer is 0.4 eV or below.

2. The white OLED of claim 1, wherein the electron injection induction layer comprises a material having an excellent hole transporting property and electron transporting property.

3. The white OLED of claim 1, wherein the electron injection induction layer comprises a carbazole compound.

4. The white OLED of claim 3, wherein the carbazole compound comprises 4,4-N,N′

-dicarbazole-biphenyl (CBP), a CBP derivative, N,N′

-dicarbazolyl-3,5-benzene (mCP), or a mCP derivative.

5. The white OLED of claim 1, wherein the electron injection induction layer has a thickness in a range of 1-10 nm.

6. The white OLED of claim 1, wherein the first, second, and third light emitting layers respectively comprise red, green, and blue light emitting layers.

7. The white OLED of claim 1, wherein the first and second light emitting layers comprise a host material having a better hole transporting property than an electron transporting property.

8. The white OLED of claim 1, wherein the first light emitting layer comprises a host material of a triphenylamine derivative.

9. The white OLED of claim 8, wherein the triphenylamine derivative comprises N,N′

-diphenyl-N,N′

-bis(3-methylphenyl)-1,1′

-bi-phenyl-4,4′

-diamine (TPD) or N,N′

-di(naphthalen-1-yl)-N,N′

-diphenyl-benzidine (NPB).

10. The white OLED of claim 1, wherein the second light emitting layer comprises a host material of a triphenylamine derivative or a carbazole compound.

11. The white OLED of claim 1, wherein the third light emitting layer comprises a fluorescent host material having an excellent hole transporting property and electron transporting property or a phosphorescent host material having a better electron transporting property than a hole transporting property.

12. The white OLED of claim 1, wherein the first, second, and third light emitting layers each have a thickness in a range of 1-20 nm.

13. The white OLED of claim 1, further comprising a Hole Transporting Layer (HTL) arranged between the anode and the first light emitting layer and an Electron Transporting Layer (ETL) arranged between the cathode and the third light emitting layer.

14. The white OLED of claim 13, wherein the HTL comprises N,N′

-diphenyl-N,N′

-bis(3-methylphenyl)-1,1′

-bi-phenyl-4,4′

-diamine (TPD) or N,N′

-di(naphthalen-1-yl)-N,N′

-diphenyl-benzidine (NPB).

15. The white OLED of claim 13, wherein the ETL comprises an aryl compound.

16. The white OLED of claim 15, wherein the aryl compound comprises oxadiazole, triazole, phenanthroline, benzoxazole, or benzthiazole.

17. The white OLED of claim 13, further comprising a Hole Injecting Layer (HIL) arranged between the anode and the HTL and an Electron Injecting Layer (EIL) arranged between the cathode and the ETL.

18. The white OLED of claim 17, wherein the HIL comprises 4,4′

,4″

-tris(3-methylphenylphenylamino)triphenylamine (MTDATA), copper phthalocyanine (CuPc), or poly(3,4-ethylenedioxythiphene, polystyrene sulfonated (PEDOT/PSS).

19. The white OLED of claim 17, wherein the EIL comprises Lithium Fluoride (LIF) or Lithium Quinolate (LiQ).

20. The white OLED of claim 1, wherein the anode comprises a material having a work function of 4.7 eV or above.

21. The white OLED of claim 1, wherein the anode comprises Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), SnO₂, or ZnO.

22. The white OLED of claim 1, wherein the cathode comprises at least one metal selected from the group consisting of aluminum (Al), silver (Ag), magnesium (Mg), Lithium (Li), or Calcium (Ca).