An organometallic compound, represented by Formula 1:

M.sub.1(Ln.sub.1).sub.n1(Ln.sub.2).sub.n2  Formula 1

wherein, in Formula 1, M.sub.1 is a transition metal, Ln.sub.1 is a ligand represented by Formula 1A, Ln.sub.2 is a ligand represented by Formula 1B, n1 is 1 or 2, and n2 is 1 or 2:

##STR00001##

wherein the substituents of Formulae 1A and 1B are as provided herein in the detailed description.

A composition including a first compound and a second compound, wherein the first compound is an organometallic compound represented by Formula 1, the second compound is an organometallic compound represented by Formula 2, the first compound and the second compound are different from each other, the first compound and the second compound are each not tris[2-phenylpyridine]iridium, and |λP(Ir1)-λP(Ir2)| is in a range of 0 nm to about 30 nm, and at least one of Expressions 1 to 4 presented in the specification is satisfied,

Ir(L.sub.11).sub.n11(L.sub.12).sub.n12(L.sub.13).sub.n13  Formula 1

Ir(L.sub.21).sub.n21(L.sub.22).sub.n22(L.sub.23).sub.n23  Formula 2

wherein L.sub.11 to L.sub.13, L.sub.21 to L.sub.23, n11 to n13, and n21 to n23 are as provided herein.

A light emitting device in which: a) an absolute value of a lowest unoccupied molecular orbital (LUMO) energy level of a first electron transporting compound (ET-1) is smaller than an absolute value of a LUMO energy level of a host compound (H-1), b) an absolute value of a LUMO energy level of a second electron transporting compound (ET-2) is smaller than an absolute value of a LUMO energy level of a third electron transporting compound (ET-3), c) and an absolute value of a LUMO energy level of the second electron transporting compound (ET-2) is smaller than an absolute value of a LUMO energy level of the first electron transporting compound (ET-1).

Disclosed is an organometallic compound represented by a following Chemical Formula 1. The organometallic compound acts as a dopant of a light-emitting layer of an organic light-emitting diode. Thus, operation voltage of the diode is lowered, and luminous efficiency and lifespan thereof are improved:

Ir(L.sub.A).sub.m(L.sub.B).sub.n  [Chemical Formula 1] where in the Chemical Formula 1, L.sub.A represents a main ligand having an imidazole or benzimidazole group, and includes one selected from a group consisting of following Chemical Formula 2-1, Chemical Formula 2-2, Chemical Formula 2-3, Chemical Formula 2-4, Chemical Formula 2-5, Chemical Formula 2-6, Chemical Formula 2-7 and Chemical Formula 2-8, L.sub.B denotes an ancillary ligand represented by a following Chemical Formula 3, each of m and n denotes a number of the ligands bound to Ir (iridium), and m is 1, 2 or 3, and n is 0, 1 or 2, and a sum of m and n is 3

The present invention provides a nitrogen-containing fused heterocyclic compound and applications thereof. When the nitrogen-containing fused heterocyclic compound of the present invention is used as a host material of an emitting layer of an organic light-emitting element, the organic light-emitting element has a lower driving voltage (4.3 V or lower), a higher current efficiency (16 Cd/A or higher) and a longer service life (230 h or higher).

The present invention provides a nitrogen-containing fused heterocyclic compound and applications thereof. When the nitrogen-containing fused heterocyclic compound of the present invention is used as a host material of an emitting layer of an organic light-emitting element, the organic light-emitting element has a lower driving voltage (3.8 V to 4.1 V), a higher current efficiency (15 Cd/A to 23 Cd/A or higher) and a longer service life (273 h or higher).

A light-emitting device includes a first electrode, a second electrode facing the first electrode, and an interlayer disposed between the first electrode and the second electrode, wherein the interlayer includes an emission layer, and the emission layer includes a condensed cyclic compound. An electronic apparatus includes the light-emitting device. The condensed cyclic compound is represented by Formula 1, wherein the detailed description of Formula 1 is the same as described in the specification:

##STR00001##

A light-emitting device including an organometallic compound represented by Formula 1, an electronic apparatus including the light-emitting device, and the organometallic compound represented by Formula 1 are provided:

##STR00001## wherein in Formula 1, M is platinum (Pt), palladium (Pd), nickel (Ni), copper (Cu), silver (Ag), gold (Au), rhodium (Rh), iridium (Ir), ruthenium (Ru), or osmium (Os).

A light-emitting device including: m emitting units located between a first electrode and a second electrode; and m−1 charge generation units, each located between two neighboring emitting units among the m emitting units and including an n-type charge generation layer and a p-type charge generation layer. The m emitting units may each include an emission layer, at least one of the m emission layers comprises a first emission layer and a second emission layer that are in contact with each other, the first emission layer includes a first host, a second host, and a first dopant, the second emission layer includes a third host, a fourth host, and a second dopant, the first host and the second host form a first exciplex, the third host and the fourth host form a second exciplex, and the first dopant is a delayed fluorescence dopant, and the second dopant is a phosphorescent dopant.

A metal compound including a first ligand L.sub.A having the Formula: ##STR00001##
is disclosed. The metal compounds are useful in the emissive layer in organic light emitting devices.