Light emitting element and light emitting device

• US 7,943,925 B2
• Filed: 03/08/2004
• Issued: 05/17/2011
• Est. Priority Date: 03/17/2003
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Hiroko
• Primary Examiner(s): Jackson, Jr.; Jerome
• Assistant Examiner(s): Chen; Yu
• Application Number:
  US10/793,861
• Publication Number:
  US 20040183082A1
• Time in Patent Office: 2,626 Days
• Field of Search: 257/40, 257/E51.01, 257/E51.018, 257/E51.013, 257/E51.022, 257/E51.043, 257101-103, 257/E51.026, 257/E51.044, 257/E31.041, 313/500, 313503-506, 427/64, 427/68, 428/690, 428/917
• US Class Current: 257/40
• CPC Class Codes: H10K 2101/10 Triplet emission
• CPC Class Codes: H10K 50/11 characterised by the electroluminescent [EL] layers
• CPC Class Codes: H10K 50/125 specially adapted for multicolour light emission, e.g. for emitting white light
• CPC Class Codes: H10K 85/113 Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: H10K 85/1135 Polyethylene dioxythiophene [PEDOT]; Derivatives thereof
• CPC Class Codes: H10K 85/30 Coordination compounds
• CPC Class Codes: H10K 85/311 Phthalocyanine
• CPC Class Codes: H10K 85/324 comprising aluminium, e.g. Alq3
• 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 85/60 Organic compounds having low molecular weight H10K85/10 - H10K85/50 take precedence
• 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 85/649 Aromatic compounds comprising a hetero atom

Abstract

A high efficient white emission light emitting element having peak intensity in each wavelength region of red, green, and blue is provided. Specifically, a white emission light emitting element having an emission spectrum that is independent of current density is provided. A first light emitting layer 312 exhibiting blue emission and a second light emitting layer 313 containing a phosphorescent material that generates simultaneously phosphorescent emission and excimer emission are combined. In order to derive excimer emission from the phosphorescent material, it is effective to disperse a phosphorescent material 323 having a high planarity structure such as platinum complex at a high concentration of at least 10 wt % to a host material 322. Further, the first light emitting layer 312 is provided to be in contact with the second light emitting layer 313 at the side of an anode. Ionization potential of the second light emitting layer 313 is preferably larger by 0.4 eV than that of the first light emitting layer 312.

Claims

1. A light emitting element comprising:

an anode and a cathode;

a hole injection layer over the anode;

a first light emitting layer between the anode and the cathode, the first light emitting layer exhibiting blue emission and comprising a first host material and a guest material; and

a second light emitting layer between the anode and the cathode, the second light emitting layer containing a second host material and a phosphorescent material,

wherein the first light emitting layer is nearer to the anode than the second light emitting layer,

wherein the phosphorescent material is an organic metal complex with platinum as a central metal and including a platinum-carbon bond,

wherein the phosphorescent material is dispersed to the second host material at a concentration of at least 15 wt%, and

wherein the light emitting element emits white light.

2. A light emitting element according to claim 1, wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm.

3. A light emitting element according to claim 1, wherein the phosphorescent material has an emission spectrum with at least two intensity peaks at a wavelength region of at least 500 nm and at most 700 nm, and at least one of the intensity peaks corresponds to excimer emission.

4. A light emitting element according to claim 1, wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm, the phosphorescent material has an emission spectrum with at least two intensity peaks at a wavelength region of at least 500 nm and at most 700 nm, and at least one of the intensity peaks in the emission spectrum of the phosphorescent material corresponds to excimer emission.

5. A light emitting element according to claim 1,

wherein the phosphorescent material is selected from

6. A light emitting element according to claim 1,

wherein the light emitting element is incorporated into an electronic device selected from the group consisting of a display device, a laptop computer, a mobile computer, an image reproduction device, a goggle type display, a video camera, and a cellular phone.

7. A light emitting element according to claim 1, wherein the second light emitting layer is capable of simultaneously generating phosphorescent emission from the phosphorescent material and excimer emission from the phosphorescent material.

8. A light emitting element according to claim 1,

wherein the guest material is capable of exhibiting blue emission.

9. A light emitting element according to claim 1, wherein the hole injection layer is formed of polyvinyl carbazole or vanadium pentoxide.

10. A light emitting element comprising:

a first electrode;

a hole injection layer over the first electrode;

a first light emitting layer over the hole injection layer, the first light emitting layer comprising a first host material and a guest material;

a second light emitting layer formed over the first light emitting layer, the second light emitting layer consisting of containing a second host material and a phosphorescent material, and

a second electrode formed over the second light emitting layer,

wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm,

wherein the second light emitting layer has an emission spectrum with at least two intensity peaks in a wavelength region of at least 500 nm and at most 700 nm,

wherein the phosphorescent material is an organic metal complex with platinum as a central metal and including a platinum-carbon bond,

wherein the phosphorescent material is dispersed to the second host material at a concentration of at least 15 wt%, and

wherein the light emitting element emits white light.

11. A light emitting element according to claim 10,

wherein at least one of the intensity peaks corresponds to excimer emission.

12. A light emitting element according to claim 10,

wherein the phosphorescent material is selected from

13. A light emitting element according to claim 10,

wherein the light emitting element is incorporated into an electronic device selected from the group consisting of a display device, a laptop computer, a mobile computer, an image reproduction device, a goggle type display, a video camera, and a cellular phone.

14. A light emitting element according to claim 10, wherein the second light emitting layer is capable of simultaneously generating phosphorescent emission from the phosphorescent material and excimer emission from the phosphorescent material.

15. A light emitting element according to claim 10,

wherein the guest material is capable of exhibiting blue emission.

16. A light emitting element according to claim 10, wherein the hole injection layer is formed of polyvinyl carbazole or vanadium pentoxide.

17. A light emitting element comprising:

a first electrode;

a hole injection layer over the first electrode;

a first light emitting layer over the hole injection layer, the first light emitting layer comprising a first host material and a guest material;

a second light emitting layer formed over the first light emitting layer, the second light emitting layer containing a second host material and a phosphorescent material, and

a second electrode formed over the second light emitting layer,

wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm,

wherein the second light emitting layer has an emission spectrum with at least two intensity peaks in a wavelength region of at least 500 nm and at most 700 nm,

wherein the phosphorescent material is an organic metal complex with platinum as a central metal and including a platinum-carbon bond,

wherein the second light emitting layer is capable of simultaneously generating phosphorescent emission from the phosphorescent material and excimer emission from the phosphorescent material,

wherein the phosphorescent material is dispersed to the second host material at a concentration of at least 15 wt%, and

wherein the light emitting element emits white light.

18. A light emitting element according to claim 17,

wherein at least one of the intensity peaks corresponds to excimer emission.

19. A light emitting element according to claim 17,

wherein the phosphorescent material is selected from

20. A light emitting element according to claim 17,

wherein the light emitting element is incorporated into an electronic device selected from the group consisting of a display device, a laptop computer, a mobile computer, an image reproduction device, a goggle type display, a video camera, and a cellular phone.

21. A light emitting element according to claim 17,

wherein the guest material is capable of exhibiting blue emission.

22. A light emitting element according to claim 17, wherein the hole injection layer is formed of polyvinyl carbazole or vanadium pentoxide.

23. A light emitting element comprising:

an anode;

a hole injection layer over the anode;

a first light emitting layer over the hole injection layer, the first light emitting layer comprising a first host material and a guest material;

a second light emitting layer formed over the first light emitting layer, the second light emitting layer containing a second host material and a phosphorescent material;

an electron transporting layer over the second light emitting layer;

an electron injection layer over the electron transporting layer; and

a cathode formed over the electron injection layer,

wherein the first light emitting layer exhibits blue emission,

wherein the phosphorescent material is an organic metal complex with platinum as a central metal and including a platinum-carbon bond, wherein the phosphorescent material is dispersed to the second host material at a concentration of at least 15 wt%, and

wherein the light emitting element emits white light.

24. A light emitting element according to claim 23, wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm.

25. A light emitting element according to claim 23, wherein the phosphorescent material has an emission spectrum with at least two intensity peaks at a wavelength region of at least 500 nm and at most 700 nm, and at least one of the intensity peaks corresponds to excimer emission.

26. A light emitting element according to claim 23, wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm, the phosphorescent material has an emission spectrum with at least two intensity peaks at a wavelength region of at least 500 nm and at most 700 nm, and at least one of the two intensity peaks in the emission spectrum of the phosphorescent material corresponds to excimer emission.

27. A light emitting element according to claim 23,

wherein the phosphorescent material is selected from

28. A light emitting element according to claim 23,

wherein the light emitting element is incorporated into an electronic device selected from the group consisting of a display device, a laptop computer, a mobile computer, an image reproduction device, a goggle type display, a video camera, and a cellular phone.

29. A light emitting element according to claim 23, wherein the second light emitting layer is capable of simultaneously generating phosphorescent emission from the phosphorescent material and excimer emission from the phosphorescent material.

30. A light emitting element according to claim 23,

wherein the guest material is capable of exhibiting blue emission.

31. A light emitting element according to claim 23, wherein the hole injection layer is formed of polyvinyl carbazole or vanadium pentoxide.

32. A light emitting element comprising:

a first electrode;

a hole injection layer over the first electrode;

a first light emitting layer over the hole injection layer, the first light emitting layer comprising a first host material and a guest material;

a second light emitting layer containing a second host material and a phosphorescent material over the first light emitting layer;

an electron transporting layer over the second light emitting layer;

an electron injection layer over the electron transporting layer, and

a cathode formed over the electron injection layer,

wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm,

wherein the second light emitting layer has an emission spectrum with at least two intensity peaks in a wavelength region of at least 500 nm and at most 700 nm,

wherein the phosphorescent material is an organic metal complex with platinum as a central metal and including a platinum-carbon bond, wherein the phosphorescent material is dispersed to the second host material at a concentration of at least 15 wt%, and

wherein the light emitting element emits white light.

33. A light emitting element according to claim 32,

wherein at least one of the intensity peaks corresponds to excimer emission.

34. A light emitting element according to claim 32,

wherein the phosphorescent material is selected from

35. A light emitting element according to claim 32,

wherein the light emitting element is incorporated into an electronic device selected from the group consisting of a display device, a laptop computer, a mobile computer, an image reproduction device, a goggle type display, a video camera, and a cellular phone.

36. A light emitting element according to claim 32, wherein the second light emitting layer is capable of simultaneously generating phosphorescent emission from the phosphorescent material and excimer emission from the phosphorescent material.

37. A light emitting element according to claim 32,

wherein the guest material is capable of exhibiting blue emission.

38. A light emitting element according to claim 32, wherein the hole injection layer is formed of polyvinyl carbazole or vanadium pentoxide.

39. A semiconductor device comprising:

a first electrode formed over a substrate;

a hole injection layer over the first electrode;

a first light emitting layer formed over the hole injection layer, the first light emitting layer exhibiting blue emission and comprising a first host material and a guest material;

a second light emitting layer formed over the first light emitting layer, the second light emitting layer containing a second host material and a phosphorescent material;

a second electrode formed over the second light emitting layer; and

a color filter formed over the second electrode,

wherein the phosphorescent material is an organic metal complex with platinum as a central metal and including a platinum-carbon bond, wherein the phosphorescent material is dispersed to the second host material at a concentration of at least 15 wt%, and

wherein the second light emitting layer is capable of simultaneously generating phosphorescent emission from the phosphorescent material and excimer emission from the phosphorescent material.

40. A semiconductor device according to claim 39,

wherein the color filter comprises a coloring layer and a light shielding layer.

41. A semiconductor device according to claim 39,

wherein the phosphorescent material is selected from

42. A semiconductor device according to claim 39, wherein the guest material is capable of exhibiting blue emission.

43. A semiconductor device according to claim 39, wherein the hole injection layer is formed of polyvinyl carbazole or vanadium pentoxide.

44. A semiconductor device comprising:

a first electrode formed over a substrate;

a hole injection layer over the first electrode;

a first light emitting layer formed over the hole injection layer, the first light emitting layer comprising a first host material and a guest material;

a second light emitting layer formed over the first light emitting layer, the second light emitting layer containing a second host material and a phosphorescent material,

a second electrode formed over the second light emitting layer; and

a color filter formed over the second electrode,

wherein the first light emitting layer has an emission spectrum with maximum intensity in a wavelength region of at least 400 nm and at most 500 nm,

wherein the second light emitting layer has an emission spectrum with at least two intensity peaks in a wavelength region of at least 500 nm and at most 700 nm,

wherein the phosphorescent material is an organic metal complex with platinum as a central metal and including a platinum-carbon bond, wherein the phosphorescent material is dispersed to the second host material at a concentration of at least 15 wt%, and

wherein the second light emitting layer is capable of simultaneously generating phosphorescent emission from the phosphorescent material and excimer emission from the phosphorescent material.

45. A semiconductor device according to claim 44,

wherein the color filter comprises a coloring layer and a light shielding layer.

46. A semiconductor device according to claim 44,

wherein the phosphorescent material is selected from

47. A semiconductor device according to claim 44, wherein the guest material is capable of exhibiting blue emission.

48. A semiconductor device according to claim 44, wherein the hole injection layer is formed of polyvinyl carbazole or vanadium pentoxide.