Organic electroluminescent device
View Patent ↗An organic electroluminescent device comprising two electrodes and at least one organic compound layer disposed between the electrodes, wherein a luminescent layer is included in the organic compound layers, the luminescent layer includes a fluorescent compound, at least one of the organic compound layers comprises an amplifying agent, the fluorescent compound emits fluorescent light upon application of voltage, the amplifying agent is capable of amplifying a number of singlet excitons and of amplifying luminescence intensity, and an amount of the amplifying agent is such an amount that at least 51% of light components emitted by the device upon the application of voltage is fluorescent light, wherein the fluorescent compound is selected from the group consisting of a distyryl arylene derivative, an oligoarylene derivative, an nitrogen-containing aromatic heterocyclic compound, a sulfur-containing heterocyclic compound, a metal complex, an oxo-substituted heterocyclic compound, an organosilicon compound and a triaryl amine derivative.
1. An organic electroluminescent device comprising two electrodes and at least one organic compound layer disposed between the electrodes,
wherein a luminescent layer comprising a laminated construction comprising at least two alternating layers in total where one layer includes a fluorescent compound and the other layer includes an amplifying agent, is included in the organic compound layers, at least one of the organic compound layers comprises the amplifying agent, the fluorescent compound emits fluorescent light upon application of voltage, the amplifying agent is capable of amplifying a number of singlet excitons formed upon the application of voltage and of amplifying luminescence intensity upon the application of voltage, and an amount of the amplifying agent is such an amount that at least 51% of light components emitted by the device upon the application of voltage is fluorescent light,
wherein the fluorescent compound is a compound represented by the following formula (7):
wherein in Formula (7), R 71 and R 72 bond to one another to form a benzene ring resulting a coumarin skeleton that is further substituted with a dialkylamino group at the 7-position of the coumarin skeleton, R 73 represents a hydrogen atom, and R 74 represents a five membered heterocyclic ring as follows:
wherein X is S;
wherein a host material is contained in both the layer including the fluorescent compound and the layer including the amplifying agent, and
wherein the laminated construction comprises at least four alternating layers.
2. The organic electroluminescent device according to claim 1 , wherein a concentration of the fluorescent compound in the luminescent layer is 0.1% to 10% by weight.
3. The organic electroluminescent device according to claim 1 , wherein a fluorescence quantum yield of the fluorescent compound is 70% or higher.
4. The organic electroluminescent device according to claim 1 , wherein an emission spectrum of the amplifying agent overlaps an absorption spectrum of the fluorescent compound.
5. The organic electroluminescent device according to claim 1 , wherein a phosphorescence quantum yield of the amplifying agent is 50% or higher.
6. The organic electroluminescent device according to claim 1 , wherein a phosphorescence life of the amplifying agent is 10 μs or shorter.
7. The organic electroluminescent device according to claim 1 , wherein one of the organic compound layers contacts an anode-side surface of the luminescent layer and the organic compound layer has a lowest excited triplet state energy of 209.2 kJ/mol to 377.1 kJ/mol.
8. The organic electroluminescent device according to claim 1 , wherein one of the organic compound layers contacts a cathode-side surface of the luminescent layer and the organic compound layer has a lowest excited triplet state energy of 209.2 kJ/mol to 377.1 kJ/mol.
9. The organic electroluminescent device according to claim 1 , wherein the device emits white light.
10. The organic electroluminescent device according to claim 1 , wherein the number of laminated layers in the laminated construction is 6 to 20.
11. The organic electroluminescent device according to claim 1 , wherein the thickness of each of the at least four alternating layers is from 0.5 nm to 10 nm.
12. The organic electroluminescent device according to claim 1 , wherein the thickness of each of the at least four alternating layers is from 1 nm to 5 nm.
13. The organic electroluminescent device according to claim 1 , wherein the organic electroluminescent device is used in combination with a singlet blue luminescent device.