Organic electroluminescent element
View Patent ↗The present invention proposes a white organic electroluminescent element which is a multiunit element capable of emitting high intensity light that is important to a light source for lighting use, and can have an extended lifetime while suppressing deterioration in luminance. The organic electroluminescent element includes: a transparent electrode; and a first light-emitting unit including a blue fluorescent light-emitting layer containing a blue fluorescent light-emitting material; an intermediate layer; and a second light-emitting unit including a red phosphorescent light-emitting layer containing a red phosphorescent light-emitting material and a green phosphorescent light-emitting layer containing a green phosphorescent light-emitting material; and a reflecting electrode, wherein: the first and second light-emitting units are stacked having the intermediate layer interposed therebetween; and a film thickness (tR) of the red phosphorescent light-emitting layer and a film thickness (tG) of the green phosphorescent light-emitting layer satisfy a relation of 5*tR≦tG.
1. An organic electroluminescent element, comprising:
a transparent electrode;
a first light-emitting unit including a blue fluorescent light-emitting layer containing a blue fluorescent light-emitting material;
an intermediate layer;
a second light-emitting unit including a red phosphorescent light-emitting layer containing a red phosphorescent light-emitting material and a green phosphorescent light-emitting layer containing a green phosphorescent light-emitting material; and
a reflecting electrode,
wherein:
the first light-emitting unit and the second light-emitting unit are stacked such that the intermediate layer is interposed between the first light-emitting unit and the second light-emitting unit; and
a film thickness (tR) of the red phosphorescent light-emitting layer and a film thickness (tG) of the green phosphorescent light-emitting layer satisfy a relation of 7*tR≦tG.
2. The organic electroluminescent element according to claim 1 , wherein
the film thickness (tR) of the red phosphorescent light-emitting layer is 5 nm or less.
3. The organic electroluminescent element according to claim 1 , wherein:
each of the red phosphorescent light-emitting layer and the green phosphorescent light-emitting layer contains an electron transporting material as a host material;
the red phosphorescent light-emitting layer is disposed closer to the transparent electrode; than the green phosphorescent light-emitting layer; and
the green phosphorescent light-emitting layer is disposed closer to the reflecting electrode than the red phosphorescent light-emitting layer.
4. The organic electroluminescent element according to claim 1 , wherein:
each of the red phosphorescent light-emitting layer and the green phosphorescent light-emitting layer contains a hole transport material as a host material;
the red phosphorescent light-emitting layer is disposed closer to the reflecting electrode; than the green phosphorescent light-emitting layer; and
the green phosphorescent light-emitting layer is disposed closer to the transparent electrode than the red phosphorescent light-emitting layer.
5. The organic electroluminescent element according to claim 1 , wherein:
the first light-emitting unit is disposed closer to the transparent electrode than the second light-emitting unit; and
the second light-emitting unit is disposed closer to the reflecting electrode than the first light-emitting unit.
6. The organic electroluminescent element according to claim 1 , wherein
the film thickness (tR) of the red phosphorescent light-emitting layer and the film thickness (tG) of the green phosphorescent light-emitting layer satisfy the relation of 10*tR<tG.
7. The organic electroluminescent element according to claim 1 , wherein
the film thickness (tR) of the red phosphorescent light-emitting layer and the film thickness (tG) of the green phosphorescent light-emitting layer satisfy the relation of 80*tR>tG.
8. The organic electroluminescent element according to claim 1 , wherein
the film thickness (tR) of the red phosphorescent light-emitting layer is at most 3 nm.
9. The organic electroluminescent element according to claim 1 , wherein
a film thickness of the second light-emitting unit is at least 20 nm.
10. The organic electroluminescent element according to claim 9 , wherein
the film thickness of the second light-emitting unit is at most 80 nm.
11. The organic electroluminescent element according to claim 1 , wherein
the first light-emitting unit includes a green fluorescent light-emitting layer containing a green fluorescent light-emitting material.
12. The organic electroluminescent element according to claim 11 , wherein:
each of the red phosphorescent light-emitting layer and the green phosphorescent light-emitting layer contains an electron transporting material as a host material;
the red phosphorescent light-emitting layer is disposed closer to the transparent electrode than the green phosphorescent light-emitting layer;
the green phosphorescent light-emitting layer is disposed closer to the reflecting electrode than the red phosphorescent light-emitting layer;
the blue fluorescent light-emitting layer is disposed closer to the transparent electrode than the green fluorescent light-emitting layer; and
the green fluorescent light-emitting layer is disposed closer to the reflecting electrode than the blue fluorescent light-emitting layer.
13. The organic electroluminescent element according to claim 11 , wherein:
each of the red phosphorescent light-emitting layer and the green phosphorescent light-emitting layer contains a hole transport material as a host material;
the red phosphorescent light-emitting layer is disposed closer to the reflecting electrode than the green phosphorescent light-emitting layer; and
the green phosphorescent light-emitting layer is disposed closer to the transparent electrode than the red phosphorescent light-emitting layer;
the blue fluorescent light-emitting layer is disposed closer to the transparent electrode than the green fluorescent light-emitting layer; and
the green fluorescent light-emitting layer is disposed closer to the reflecting electrode than the blue fluorescent light-emitting layer.
14. The organic electroluminescent element according to claim 1 , wherein
the film thickness (tR) of the red phosphorescent light-emitting layer and the film thickness (tG) of the green phosphorescent light-emitting layer are set such that an emission color is configured to change into an intended color due to a continuous drive of the organic electroluminescent element.
15. A method of manufacturing an organic electroluminescent element, comprising:
forming a transparent electrode;
forming a first light-emitting unit above the transparent electrode, the first light-emitting unit including a blue fluorescent light-emitting layer containing a blue fluorescent light-emitting material;
forming an intermediate layer above the first light-emitting unit;
forming a second light-emitting unit above the intermediate layer, the second light-emitting unit including a red phosphorescent light-emitting layer containing a red phosphorescent light-emitting material and a green phosphorescent light-emitting layer containing a green phosphorescent light-emitting material; and
forming a reflecting electrode above the second light-emitting unit,
wherein:
the first light-emitting unit and the second light-emitting unit are stacked such that the intermediate layer is interposed between the first light-emitting unit and the second light-emitting unit; and
in the forming of the second light-emitting unit, a film thickness (tR) of the red phosphorescent light-emitting layer and a film thickness (tG) of the green phosphorescent light-emitting layer satisfy a relation of 7*tR<tG.
16. The method of manufacturing the organic electroluminescent element according to claim 15 , further comprising:
driving the organic electroluminescent element to shift an emission zone with respect to the second light-emitting unit and change an emission color into an intended color.