Organic electroluminescence device and organic electroluminescence display

1. An organic electroluminescence device, comprising:

an anode;

a cathode formed above said anode;

a light-emitting layer containing an organic light-emitting material that is formed between said anode and the cathode;

a hole-injecting layer on the anode that includes a hole-transporting material and an acceptor;

an electron-transporting suppressing stack between the hole-injecting layer and the light-emitting layer;

wherein the electron-transporting suppressing stack consists of a plurality of carrier-transporting layers, and forms energy barriers relative to electrons flowing from the light-emitting layer to the hole-injecting layer, and

wherein said electron-transporting suppressing stack has arranged a first carrier-transporting layer bordering the anode side of the light-emitting layer and a second carrier-transporting layer bordering the anode side of said first carrier-transporting layer alternating repeatedly in said sequential order, and

wherein an electron affinity of the first carrier-transporting layer and an electron affinity of the second carrier-transporting layer have a relationship in an equation (1) represented as

E aHT1 >E aHT2   (1)

where in the equation (1) E aHT1 is the electron affinity of the first carrier-transporting layer and E aHT2 is the electron affinity of the second carrier-transporting layer.

2. The organic electroluminescence device as claimed in claim 1 ,

wherein the electron affinity of the first carrier-transporting layer and an electron affinity of the light-emitting layer have a relationship in an equation (2) represented as

E aHT1 <E aEM   (2)

where in the equation (2) E aHT1 is the electron affinity of the first carrier-transporting layer and E aEM is the electron affinity of the light-emitting layer.

3. The organic electroluminescence device as claimed in claim 1 ,

wherein the electron affinity of the first carrier-transporting layer or the second carrier-transporting layer that faces the cathode side of said hole-injecting layer, and an electron affinity of the hole-injecting layer have a relationship in an equation (3) represented as

E aHT >E aHI   (3)

where in the equation (3) E aHT is the electron affinity of the first or the second carrier-transporting layer that faces the cathode side of said hole-injecting layer and E aHI is the electron affinity of the hole-injecting layer.

4. The organic electroluminescence device as claimed in claim 1 , further comprising an electron-transporting layer between said light-emitting layer and the cathode,

wherein an ionizing potential of said electron-transporting layer and an ionizing potential of said light-emitting layer have a relationship in an equation (4) represented as

I pEM <I pET   (4)

where in the equation (4) I pEM is the ionizing potential of the light-emitting layer and I pET is the ionizing potential of the electron-transporting layer.

5. The organic electroluminescence device as claimed in claim 1 ,

wherein the first carrier-transporting layer is as thick as or thicker than the second carrier-transporting layer.

6. The organic electroluminescence device as claimed in claim 1 ,

wherein a thickness of the first carrier-transporting layer and a thickness of the second carrier-transporting layer are in a range of 2 nm to 50 nm.

7. The organic electroluminescence device as claimed in claim 1 ,

wherein a content of the acceptor in the hole-injecting layer is in a range of 0.05 vol. % to 2 vol. %.

8. The organic electroluminescence device as claimed in claim 1 ,

wherein either one of said first carrier-transporting layer and said second carrier-transporting layer is made of the same material as the hole-transporting material of said hole-injecting layer.

9. The organic electroluminescence device as claimed in claim 1 ,

wherein said electron-transporting suppressing stack further includes a third carrier-transporting layer,

and has arranged the first carrier-transporting layer, the second carrier-transporting layer, and the third carrier-transporting layer repeating systematically.

10. The organic electroluminescence device as claimed in claim 9 ,

wherein said electron-transporting suppressing stack has arranged the first carrier-transporting layer bordering the anode side of the light-emitting layer, the second carrier-transporting layer bordering the anode side of said first carrier-transporting layer, the third carrier-transporting layer bordering the anode side of said second carrier-transporting layer, and a further first carrier-transporting layer bordering the anode side of said third carrier-transporting layer,

and wherein an electron affinity of said first carrier-transporting layer and said further first carrier-transporting layer, an electron affinity of said second carrier-transporting layer, and an electron affinity of said third carrier-transporting layer have a relationship in an equation (5) represented as

E aHT1 >E aHT2 >E aHT3   (5)

where in the equation (5) E aHT1 is the electron affinity of said first carrier-transporting layer, and said further first carrier-transporting layer, E aHT2 is the electron affinity of said second carrier-transporting layer, and E aHT3 is the electron affinity of said third carrier-transporting layer.

11. The organic electroluminescence device as claimed in claim 1 , further comprising a further hole-injecting layer between said anode and the hole-injecting layer,

wherein said further hole-injecting layer is made of a hole-transporting material.

12. An organic electroluminescence display, comprising the electroluminescence device as claimed in claim 1 .