Material for organic electroluminescent elements, and organic electroluminescent element using same
The present invention discloses an organic electroluminescent (EL) device having improved luminous efficiency, sufficiently secured driving stability, and a simple construction. The organic EL device of the present invention includes, between an anode and a cathode laminated on a substrate, an organic layer including a material for a luminescent device, in which the material for a luminescent device includes a carborane compound. The carborane compound includes a branched carborane compound in which three or more carborane rings bonded to one another through an aromatic group are present, at least one dibenzothiophene ring is present, and the at least one dibenzothiophene ring is bonded to the carborane ring.
1. A material for an organic electroluminescent device, comprising a carborane compound represented by the general formula (1):
where
a ring A represents a divalent carborane group C2B10H10 represented by the formula (1a) or the formula (1b), and when a plurality of rings A are present in a molecule thereof, the rings may be identical to or different from each other;
s and t each represent a number of repetitions and represent an integer of from 1 to 4;
L 1 represents a trivalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a trivalent substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or a trivalent linked aromatic group formed by linking 2 to 6 of the substituted or unsubstituted aromatic hydrocarbon groups or the substituted or unsubstituted aromatic heterocyclic groups, and when L 1 represents the linked aromatic group, the group may be linear or branched, and aromatic rings to be linked may be identical to or different from each other;
L 2 and L 3 each represent a single bond, a divalent substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a divalent substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, or a divalent linked aromatic group formed by linking 2 to 6 of the substituted or unsubstituted aromatic hydrocarbon groups or the substituted or unsubstituted aromatic heterocyclic groups, terminal L 2 and L 3 may each represent an alkyl group having 1 to 12 carbon atoms or an alkoxy group having 1 to 12 carbon atoms, when L 2 and L 3 each represent the linked aromatic group, the group may be linear or branched, and aromatic rings to be linked may be identical to or different from each other, and when a plurality of each of L 2 's and L 3 's are present in the molecule, the plurality of each of L 2 's and L 3 's may be identical to or different from each other.
L 4 represents a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 30 carbon atoms, a linked aromatic group formed by linking 2 to 6 aromatic groups selected from the substituted or unsubstituted aromatic hydrocarbon groups and the substituted or unsubstituted aromatic heterocyclic groups, an alkyl group having 1 to 12 carbon atoms, or an alkoxy group having 1 to 12 carbon atoms, and when L 4 represents the linked aromatic group, the group may be linear or branched, and aromatic rings to be linked may be identical to or different from each other; and
when the aromatic group in each of L 1 to L 4 has a substituent, the substituent is an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an acetyl group, the aromatic group may have a plurality of substituents, and the plurality of substituents may be identical to or different from each other.
2. A material for an organic electroluminescent device according to claim 1 , wherein the carborane compound represented by the general formula (1) comprises a carborane compound represented by the general formula (2) or (3):
where the ring A, s, t, L 1 , L 2 , L 3 , and L 4 have the same meanings as in the general formula (1).
3. A material for an organic electroluminescent device according to claim 1 , wherein in the general formula (1), the ring A represents a divalent carborane group C2B10H10 represented by the formula (1a).
4. A material for an organic electroluminescent device according to claim 2 , wherein in the general formula (2) or (3), the ring A represents a divalent carborane group C 2 B 10 H 10 represented by the formula (1a).
5. A material for an organic electroluminescent device according to claim 1 , wherein in the general formula (1), L 1 to L 4 each independently represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 18 carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 6 aromatic groups selected from the aromatic hydrocarbon groups and the aromatic heterocyclic groups.
6. A material for an organic electroluminescent device according to claim 1 , wherein in the general formula (1), L 1 to L 4 each independently represent a substituted or unsubstituted aromatic heterocyclic group having 3 to 17 carbon atoms, or a linked aromatic group formed by linking 2 to 6 aromatic groups selected from the aromatic heterocyclic groups.
7. A material for an organic electroluminescent device according to claim 1 , wherein in the general formula (1), s and t each represent an integer of 1.
8. An organic electroluminescent device having a structure in which an anode, an organic layer, and a cathode are laminated on a substrate, wherein the organic layer comprises an organic layer containing the material for an organic electroluminescent device of claim 1 .
9. An organic electroluminescent device according to claim 8 , wherein the organic layer containing the material for an organic electroluminescent device comprises at least one layer selected from the group consisting of a light-emitting layer, an electron-transporting layer, and a hole-blocking layer.
10. An organic electroluminescent device according to claim 9 , wherein the organic layer containing the material for an organic electroluminescent device comprises a light-emitting layer containing a phosphorescent light-emitting dopant.
11. An organic electroluminescent device according to claim 10 , wherein an emission wavelength of the phosphorescent light-emitting dopant has an emission maximum wavelength at 550 nm or less.