Tridentate platinum, palladium, and gold complexes of Formulas A-I and A-II and tridentate iridium and rhodium compounds of Formulas B-I, B-II, and B-III suitable for delayed fluorescent and phosphorescent or phosphorescent emitters in display and lighting applications. ##STR00001## ##STR00002##

A polycyclic compound according to an embodiment of the inventive concept is represented by the following Formula 1:

##STR00001##

In Formula 1, Ar.sub.1 and Ar.sub.2 are each independently substituted or unsubstituted aryl group having 6 to 30 carbon atoms for forming a ring, or substituted or unsubstituted heteroaryl group having 2 to 30 carbon atoms for forming a ring, where Ar.sub.1 and Ar.sub.2 may combine with each other to form a ring, and A is represented by the following Formula 2-1 or 2-2:

##STR00002##

A condensed cyclic compound and an organic light-emitting device including the same are provided. The condensed cyclic compound may have a structure shown below:

##STR00001## wherein details about the possible constituents are provided in detail in the disclosure.

A dual host system for OLEDs that contains hole-transporting indolocarbazole and electron-transporting indolocarbazole exhibiting superior performance in the OLEDs is disclosed.

A novel organometallic complex is provided. An organometallic complex emitting green to blue phosphorescence is provided. An organometallic complex having a deep LUMO level and emitting green to blue phosphorescence is provided. A light-emitting element with high emission efficiency is provided. A light-emitting element emitting green to blue phosphorescence and having low drive voltage is provided. A light-emitting device with low power consumption is provided. The organometallic complex includes iridium and a ligand having a triazole skeleton. The triazole skeleton has a group including a pyridine ring or a group including a pyrimidine ring and an aryl group. One of nitrogen atoms included in the triazole skeleton is coordinated to the iridium. The aryl group is bonded to the iridium at the ortho position of the aryl group.

An organometallic compound represented by Formula 1:
M(L.sub.1).sub.n1(L.sub.2).sub.n2  Formula 1 wherein in Formula 1, M, L.sub.1, L.sub.2, n.sub.1, and n.sub.2 are the same as described in the specification.

The present invention relates to a compound of a formula (I) or (II), to the use of this compound in an electronic device, and to an electronic device comprising one or more compounds of the formula (I) or (II). The invention furthermore relates to the preparation of the compound of the formula (I) or (II) and to a formulation comprising one or more compounds of the formula (I) or (II).

The present invention relates to organic light emitting elements, comprising thermally activated delayed fluorescence (TADF) emitters and/or hosts on basis of phthalimide and naphthalimide materials, which have a sufficiently small energy gap between S.sub.1 and T.sub.1 (ΔE.sub.ST) to enable up-conversion of the triplet exciton from T.sub.1 to S.sub.1. The organic light emitting elements show high electroluminescent efficiency.

The present invention relates to a novel indole-based compound having excellent hole injection and transport capabilities, light-emission, and other properties, and to an organic electroluminescent device the luminous efficiency, driving voltage, service life, and other characteristics of which are improved due to containing the compound in one or more organic material layers.

A heterocyclic compound represented by Formula 1 and an organic light-emitting device including the same. ##STR00001##
The heterocyclic compound represented by Formula 1 has excellent light emitting characteristics and high charge transporting capabilities.