Organic electroluminescent element and display device or light emitting device equipped with the same
It is an object of the present invention to provide an organic electroluminescent element having a longer lifetime. In order to accomplish the object, an organic electroluminescent element adapted to comprise a light emitting layer including an organic material between an anode and a cathode is provided with a hole transport layer for transporting holes injected from the anode toward the light emitting layer. Along with the hole transport layer, an intermediate layer having an energy level of a lowest unoccupied molecular orbital lower than those of the hole transport layer and the light emitting layer is provided therebetween.
1. An organic electroluminescent element comprising a light emitting layer including an organic material between an anode and a cathode, comprising:
a hole transport layer provided between the anode and the light emitting layer;
an intermediate layer provided between the hole transport layer and the light emitting layer, wherein the intermediate layer has an energy level of a lowest unoccupied molecular orbital lower than energy levels of lowest unoccupied molecular orbitals of the hole transport layer and the light emitting layer;
wherein the intermediate layer has an energy level of a highest occupied molecular orbital lower than energy levels of highest occupied molecular orbitals of the hole transport layer and the light emitting layer;
wherein a difference between an energy level of a highest occupied molecular orbital of the light emitting layer and the energy level of the lowest unoccupied molecular orbital of the intermediate layer is approximately 1.5 eV or less;
wherein the hole transport layer and the intermediate layer contact each other and the intermediate layer and light emitting layer contact each other; and
further comprising a hole injection layer between the anode and the hole transport layer, wherein a difference between an energy level of a highest occupied molecular orbital of the hole transport layer and an energy level of a lowest unoccupied molecular orbital of the hole injection layer is approximately 1.5 eV or less;
wherein the intermediate layer and the hole injection layer are comprised of a same material.
2. An organic electroluminescent element comprising:
an anode;
a hole transport layer including an amine derivative;
a light emitting layer;
an electron transport layer; and
an intermediate layer provided between the hole transport layer and the light emitting layer; wherein
the intermediate layer at least includes a pyrazine derivative having a molecular structure shown by formula (1):
wherein a difference between an energy level of a highest occupied molecular orbital of the light emitting layer and the energy level of the lowest unoccupied molecular orbital of the intermediate layer is approximately 1.5 eV or less, and
wherein the hole transport layer and the intermediate layer contact each other and the intermediate layer and light emitting layer contact each other.
3. The organic electroluminescent element according to claim 2 , wherein the pyrazine derivative at least includes a material having a molecular structure shown by formula (2):
4. The organic electroluminescent element according to claim 2 , wherein the organic electroluminescent element is included in a device selected from a group consisting of: a display device and a light emitting device.
5. The organic electroluminescent element according to claim 2 , further comprising a hole injection layer between the anode and the hole transport layer, wherein a difference between an energy level of a highest occupied molecular orbital of the hole transport layer and an energy level of a lowest unoccupied molecular orbital of the hole injection layer is approximately 1.5 eV or less.
6. The organic electroluminescent element according to claim 5 , wherein the intermediate layer and the hole injection layer are comprised of a same material.
7. An organic electroluminescent element comprising:
an anode;
a hole transport layer including an amine derivative;
a light emitting layer;
an electron transport layer; and
an intermediate layer provided between the hole transport layer and the light emitting layer; wherein
the intermediate layer at least includes a material having a molecular structure shown by formula (3):
8. The organic electroluminescent element according to claim 7 , wherein the organic electroluminescent element is included in a device selected from a group consisting of: a display device and a light emitting device.
9. The device according to claim 7 , wherein a difference between an energy level of a highest occupied molecular orbital of the light emitting layer and an energy level of a lowest unoccupied molecular orbital of the intermediate layer is approximately 1.5 eV or less.
10. The organic electroluminescent element according to claim 7 , wherein the intermediate layer and a hole injection layer are comprised of a same material.