Organic electroluminescent element

1 . An organic electroluminescent element comprising a cathode, an electron injection promoting layer, a luminescent layer, and an anode in that order, wherein the luminescent layer is adjacent to the electron injection promoting layer and contains a luminescent material, the electron injection promoting layer contains an electron transport material and has a thickness of 3 nm or less, and the electron affinity of the electron transport material is equal to or higher than the electron affinity of the luminescent material.

2 . The organic electroluminescent element of claim 1 , wherein the luminescent layer contains a host material, and the electron affinity of the electron transport material is equal to or higher than the electron affinity of the host material.

3 . The organic electroluminescent element of claim 1 , wherein the luminescent material is a phosphorescent material.

4 . The organic electroluminescent element of claim 2 , wherein the luminescent material is a phosphorescent material.

5 . The organic electroluminescent element of claim 1 , wherein the electron affinity of the electron transport material contained in the electron injection promoting layer is 2.7 eV or higher.

6 . The organic electroluminescent element of claim 2 , wherein the electron affinity of the electron transport material contained in the electron injection promoting layer is 2.7 eV or higher.

7 . The organic electroluminescent element of claim 1 , wherein the film thickness of the electron injection promoting layer is from 0.1 to 2 nm.

8 . The organic electroluminescent element of claim 2 , wherein the film thickness of the electron injection promoting layer is from 0.1 to 2 nm.

9 . The organic electroluminescent element of claim 1 , wherein the electron transport material contained in the electron injection promoting layer is represented by the following formula (A-1) or (B-1):

wherein formula (A-1), Z A1 represents an atomic group required for formation of a nitrogen-containing heterocyclic group, L A1 represents a linking group, and n A1 represents an integer of 2 or more:

wherein formula (B-1), Z B1 represents an atomic group required for formation of an aromatic hydrocarbon ring or a heterocyclic group, L B1 represents a linking group, and n B1 represents an integer of 2 or more.

10 . The organic electroluminescent element of claim 1 , wherein the electron transport material contained in the electron injection promoting layer is represented by the following formula (A-1) or (B-1):

wherein formula (A-1), Z A1 represents an atomic group required for formation of a nitrogen-containing heterocyclic group, L A1 represents a linking group, and n A1 represents an integer of 2 or more, and

wherein formula (B-1), Z B1 represents an atomic group required for formation of an aromatic hydrocarbon ring or a heterocyclic group, L B1 represents a linking group, and n B1 represents an integer of 2 or more.

11 . The organic electroluminescent element of claim 1 , wherein the electron transport material contained in the electron injection promoting layer contains three or more nitrogen atoms.

12 . The organic electroluminescent element of claim 2 , wherein the electron transport material contained in the electron injection promoting layer contains three or more nitrogen atoms.

13 . The organic electroluminescent element of claim 2 , wherein the host material has a carbazole group.

14 . The organic electroluminescent element of claim 3 , wherein the host material has a carbazole group.

15 . The organic electroluminescent element of claim 1 , wherein an electron transport layer containing a compound represented by the following formula (C) is provided between the cathode and the electron injection promoting layer and adjacent to the electron injection promoting layer:

wherein at least one of R 1 to R 6 represents a substitute, and the remaining represent a hydrogen atom, M represents aluminum, gallium or indium, and Y represents an aromatic group or silyl group that may have a substituent.

16 . The organic electroluminescent element of claim 2 , wherein an electron transport layer containing a compound represented by the following formula (C) is provided between the cathode and the electron injection promoting layer and adjacent to the electron injection promoting layer:

wherein at least one of R 1 to R 6 represents a substitute, and the remaining represent a hydrogen atom, M represents aluminum, gallium or indium, and Y represents an aromatic group or silyl group that may have a substituent.