Patent ID: 8426042

Claim:
A material for an organic electroluminescence device comprising at least a phosphorescent metal complex A and a phosphorescent metal complex B, wherein the phosphorescent metal complex A comprises a partial structure represented by the following formula (1), and the phosphorescent metal complex B has the same structure with the phosphorescent metal complex A except that, in at least one substituent of R 1 and R 2 in the formula (1), one or more atoms directly bonding to Q 1 or Q 2 are substituted with an atom belonging to the same group as in the one or more atoms and having a greater atomic weight than the one or more atoms, and a ratio of the content of the phosphorescent metal complex B to a content of the phosphorescent metal complex A is 0.005% by mass or more and 2% by mass or less: wherein each of R 1 and R 2 independently represents a substituent; when a plurality of R 1 's are present, the R 1 's may be the same with or different from each other; when a plurality of R 2 's are present, the R 2 ′s may be the same with or different from each other; and the R 1 's and the R 2 's may be bonded to each other to form a ring; M represents a metal having an atomic weight of 40 or more; each of X 1 , X 2 and X 3 independently represents a carbon atom or a nitrogen atom, provided that all of X 1 , X 2 and X 3 do not represent a nitrogen atom; Q 1 represents a 5- or 6-membered aromatic heterocyclic ring; Q 2 represents a 5- or 6-membered aromatic hydrocarbon ring or aromatic heterocyclic ring; each of n1 and n2 independently represents an integer of 0 to 4, but there is no case where the sum of n1 and n2 is 0; the bidentate ligand including Q 1 and Q 2 may form a tridentate or higher multidentate ligand by bonding to other ligands, and Q 1 and Q 2 may be linked via a linking group to form a ring.