Organic electroluminescent device and display apparatus

1. An organic electroluminescent device for emitting red light comprising:

an anode;

a cathode; and

an organic layer comprising (i) a light emitting layer comprising a red fluorescent light-emitting guest material and a first host material, the first host material comprising a polycyclic aromatic hydrocarbon compound having a skeleton with a 4 to 7 membered ring, and (ii) a photosensitizing layer comprising a blue light-emitting guest material and a second host material,

wherein,

the light-emitting layer is provided between the anode and the cathode,

the photosensitizing layer is provided adjacent to and in contact with the light-emitting layer,

the photosensitizing layer transfers energy to the light emitting layer,

blue light emitted from the photosensitizing layer is not extracted from the anode or the cathode or from the device,

the device does not comprise a filter for producing red light from an emission of white light; and

only red light generated in the light emitting layer is extracted from the device.

2. The organic electroluminescent device according to claim 1 , wherein the polycyclic aromatic hydrocarbon compound is selected from the group consisting of pyrene, benzopyrene, chrysene, naphthacene, benzonaphthacene, dibenzonaphthacene, perylene and coronene.

3. The organic electroluminescent device according to claim 1 , wherein a compound represented by the following general formula (1) is used as the host material of the light-emitting layer:

wherein R 1 to R 8 each independently represents hydrogen, a halogen, a hydroxyl group, a substituted or unsubstituted carbonyl group having not more than 20 carbon atoms, a substituted or unsubstituted carbonyl ester group having not more than 20 carbon atoms, a substituted or unsubstituted alkyl group having not more than 20 carbon atoms, a substituted or unsubstituted alkenyl group having not more than 20 carbon atoms, a substituted or unsubstituted alkoxyl group having not more than 20 carbon atoms, a cyano group, a nitro group, a substituted or unsubstituted silyl group having not more than 30 carbon atoms, a substituted or unsubstituted aryl group having not more than 30 carbon atoms, a substituted or unsubstituted heterocyclic group having not more than 30 carbon atoms or a substituted or unsubstituted amino group having not more than 30 carbon atoms.

4. The organic electroluminescent device according to claim 1 , wherein the photosensitizing layer is provided adjacent to the light-emitting layer and between the light-emitting layer and the cathode.

5. The organic electroluminescent device according to claim 1 , wherein red light generated in the light-emitting layer is multiply resonated in any layer between the anode and the cathode and extracted from any one side of the anode or the cathode.

6. The organic electroluminescent device according to claim 1 , wherein a perylene derivative, a diketopyrrolopyrrole derivative, a pyromethene derivative, a pyran derivative or a styryl derivative is used as the red light-emitting guest material.

7. The organic electroluminescent device according to claim 1 , wherein a hole transport layer provided adjacent to the light-emitting layer has a multilayer structure comprising a first hole transport layer and a second hole transport layer each of which has different materials from each other, the second hole transport layer is adjacent to the light-emitting layer, and the second hole transport layer includes an organic material represented by the following general formula (2):

wherein A 1 to A 3 each independently represents an aryl group or a heterocyclic group.

8. The organic electroluminescent device according to claim 1 , wherein a hole transport layer provided adjacent to the light-emitting layer has a multilayer structure comprising a first hole transport layer and a second hole transport layer each of which has different materials from each other, the second hole transport layer is adjacent to the light-emitting layer, and the second hole transport layer includes an organic material represented by the following general formula (3):

wherein

A 1 to A 4 , Z 1 and Z 2 each independently represents hydrogen, a halogen, a hydroxyl group, a carbonyl group, a carbonyl ester group, an alkyl group, an alkenyl group, an alkoxyl group, a cyano group, a nitro group or an amino group,

A 1 to A 4 may constitute a cyclic structure in a site adjacent to each other,

Ar 1 and Ar 2 each independently represents an aryl group or a heterocyclic group, and

B 1 and B 2 each represents hydrogen, an alkyl group, an aryl group or a heterocyclic group.

9. The organic electroluminescent device according to claim 1 , wherein a hole transport layer provided adjacent to the light-emitting layer has a multilayer structure comprising a first hole transport layer and a second hole transport layer each of which has different materials from each other, the second hole transport layer is adjacent to the light-emitting layer, and the second hole transport layer includes an organic material represented by the following general formula (4):

wherein

Ar 1 and Ar 2 each independently represents an aryl group or a heterocyclic group,

R 1 to R 8 each independently represents hydrogen, a halogen, an alkyl group, an aralkyl group, an alkenyl group, a cyano group, an amino group, an acyl group, an alkoxycarbonyl group, a carboxyl group, an alkoxy group, an aryloxy group, an alkylsulfonyl group, a hydroxyl group, an amide group, an aryl group or a heterocyclic group and may constitute a cyclic structure in a site adjacent to each other, and

X represents a divalent aromatic ring group.

10. A display apparatus comprising a substrate having thereon a plural number of red light-emitting, organic electroluminescent devices comprising

an anode;

a cathode; and

an organic layer,

wherein,

the organic layer comprises (i) a light emitting layer comprising a red fluorescent light-emitting guest material and a first host material, the first host material comprising a polycyclic aromatic hydrocarbon compound having a skeleton with a 4 to 7 membered ring, and (ii) a photosensitizing layer comprising a blue light-emitting guest material and a second host material,

the light-emitting layer is provided between the anode and the cathode of the red light-emitting, organic electroluminescent devices,

the photosensitizing layer is provided adjacent to and in contact with the light-emitting layer of the red light-emitting, organic electroluminescent devices,

the photosensitizing layer transfers energy to the light emitting layer of the red light-emitting, organic electroluminescent devices,

blue light emitted from the photosensitizing layer is not extracted from the anode or the cathode of the red light-emitting, organic electroluminescent devices or from the red light-emitting, organic electroluminescent devices,

the plural number of red light-emitting, organic electroluminescent devices do not comprise a filter for producing red light from an emission of white light; and

only red light generated in the light emitting layer is extracted from the plural number of red light-emitting, organic electroluminescent devices.

11. The display apparatus according to claim 10 , wherein the organic electroluminescent device is provided as a red light-emitting device in a part of plural pixels.

12. The display apparatus according to claim 11 , wherein the photosensitizing layer of the organic electroluminescent device covers a plurality of pixels so as to function as a common light-emitting layer.

13. The display apparatus according to claim 11 , wherein an organic electroluminescent device for emitting blue light and an organic electroluminescent device for emitting green light are provided together with the red light-emitting device.