Organic electroluminescence device
An organic EL device includes a pair of electrodes and an organic compound layer between pair of electrodes. The organic compound layer includes an emitting layer including a first material and a second material. The second material is a fluorescent material. Singlet energy EgS(H) of the first material and singlet energy EgS(D) of the second material satisfy a relationship of the following formula (1). The first material satisfies a relationship of the following formula (2) in terms of a difference ΔST(H) between the singlet energy EgS(H) and an energy gap Eg 77K (H) at 77K. EgS( H )>EgS( D ) (1) Δ ST ( H )=EgS( H )−Eg 77K ( H )<0.3 (eV) (2)
1. An organic electroluminescence device, comprising a pair of electrodes and an organic compound layer between the pair of electrodes, the organic compound layer comprising an emitting layer comprising a first material and a second material,
wherein:
the second material is a fluorescent material;
the first material is a compound comprising at least one donor element and only one acceptor element bonded together by single bond(s);
one of the at least one donor element is an unsubstituted carbazole structure;
the acceptor element is a cyano-substituted aromatic ring;
singlet energy EgS(H) of the first material and singlet energy EgS(D) of the second material satisfy a relationship of a formula (1):
EgS( H )>EgS( D ) (1); and
the emitting layer is not a phosphorescent emitting layer.
2. The organic electroluminescence device according to claim 1 , wherein the organic electroluminescence device exhibits a ratio of the luminous intensity due to delayed fluorescence relative to the total luminous intensity of larger than 37.5%.
3. The organic electroluminescence device according to claim 1 , wherein the organic electroluminescence device exhibits a residual intensity ratio larger than 36.0% after the elapse of 1 μs after voltage removal in a transitional EL measurement, the residual intensity ratio being a ratio of the luminous intensity due to delayed fluorescence relative to the total luminous intensity after the elapse of 1 μs.
4. The organic electroluminescence device according to claim 1 , wherein a half bandwidth of a photoluminescence spectrum of the first material is 50 nm or more.
5. The organic electroluminescence device according to claim 1 , wherein a half bandwidth of a photoluminescence spectrum of the first material is 75 nm or more.
6. The organic electroluminescence device according to claim 1 , wherein a difference ΔT between the energy gap Eg 77K (H) at 77K of the first material and an energy gap Eg 77K (D) at 77K of the second material satisfies a relationship of a formula (3):
66 T =Eg 77K ( H )−Eg 77K ( D )≥0.6 (eV) (3).
7. The organic electroluminescence device according to claim 1 , wherein the second material is selected from the group consisting of bisarylamino naphthalene derivative, an aryl-substituted naphthalene derivative, a bisarylamino anthracene derivative, an aryl-substituted anthracene derivative, a bisarylamino pyrene derivative, an aryl-substituted pyrene derivative, a bisarylamino chrysene derivative, an aryl-substituted chrysene derivative, a bisarylamino fluoranthene derivative, an aryl-substituted fluoranthene derivative, an indenoperylene derivative, a pyrromethene boron complex compound, a compound having a pyrromethene skeleton or a metal complex thereof, a diketopyrrolopyrrole derivative, and a perylene derivative.
8. The organic electroluminescence device according to claim 1 , wherein the first material is not an acridine derivative.
9. The organic electroluminescence device according to claim 1 , wherein a second donor element is a substituted carbazole and the substituent of the carbazole structure is an aryl group having 6 to 40 carbon atoms.
10. The organic electroluminescence device according to claim 1 , wherein the cyano-substituted aromatic ring has a substituent that is not a heterocyclic group having 2 to 40 carbon atoms.
11. The organic electroluminescence device according to claim 10 , wherein the substituent of the cyano-substituted aromatic ring is an aryl group having 6 to 40 carbon atoms.
12. The organic electroluminescence device according to claim 1 , wherein the acceptor element is not an azine ring.
13. The organic electroluminescence device according to claim 1 , wherein the first material is not a pyrazine derivative, a pyrimidine derivative or a triazine derivative.
14. The organic electroluminescence device according to claim 1 , wherein the donor element consists of an unsubstituted carbazolyl group.
15. The organic electroluminescence device according to claim 1 , wherein the cyano-substituted aromatic ring is not substituted by a substituent other than the cyano group(s).