A composition is disclosed that includes a first compound capable of functioning as a host in an emissive layer of an OLED at room temperature; and a second compound that includes a ligand L.sub.A of Formula III ##STR00001##
where ring A is a 5-membered or 6-membered carbocyclic or heterocyclic ring; where R represents two adjacent substituents that are joined together to form a ring that is fused to ring B, and R has a structure of Formula IV ##STR00002##
or Formula V ##STR00003##
disclosed herein.

Provided are an organometallic compound represented by Formula 1 and an organic light-emitting device including the same. The organic light-emitting device includes a first electrode; a second electrode facing the first electrode; an organic layer between the first electrode and the second electrode and including an emission layer; and at least one organometallic compound represented by Formula 1.

An organometallic compound represented by Formula 1:

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

wherein, M is a transition metal, L.sub.1 and L.sub.2 are ligands as provided herein, n1 and n2 are each independently 1 or 2, the sum of n1 and n2 is 2 or 3, and L.sub.1 is different from L.sub.2.

Provided are organometallic compounds including a ligand L.sub.A of Formula I ##STR00001##

Provided are organometallic compounds comprising a first ligand L.sub.A comprising a multicyclic fused ring system wherein ligand L.sub.A is coordinated to a metal M; and wherein M is selected from the group consisting of Os, Ir, Pd, Pt, Cu, Ag, and Au. Also provided are formulations comprising these compounds. Further provided are OLEDs and related consumer products that utilize these compounds.

An iridium complex which has a phenylpyridine bidentate ligand containing a group represented by the following general formula (A):

##STR00001##

(In the general formula (A), X represents a cyano group or a halogenated alkyl group. L represents a single bond or a divalent linking group. R represents a substituent. n represents an integer of 0 to 4. * represents a binding site to a phenylpyridine bidentate ligand.)

An organic light-emitting diode and a preparation method therefore, a display panel and a display device. The organic light-emitting diode comprises an anode (300); a light-emitting layer (200); and a cathode (100), wherein the light-emitting layer (200) is internally provided with a doping material and at least two types of host materials, and a horizontal alignment factor of the light-emitting layer (200) is not less than 65%.

To provide a light-emitting element with an improved reliability, a light-emitting element with a high current efficiency (or a high quantum efficiency), and a novel dibenzo[f,h]quinoxaline derivative that is favorably used in a light-emitting element which is one embodiment of the present invention. A light-emitting element includes an EL layer between an anode and a cathode. The EL layer includes a light-emitting layer; the light-emitting layer contains a first organic compound having an electron-transport property and a hole-transport property, a second organic compound having a hole-transport property, and a light-emitting substance; the combination of the first organic compound and the second organic compound forms an exciplex; the HOMO level of the first organic compound is lower than the HOMO level of the second organic compound; and a difference between the HOMO level of the first organic compound and the HOMO level of the second organic compound is less than or equal to 0.4 eV.

Provided are a compound for an organic optoelectronic device represented by a combination of Chemical Formula 1 and Chemical Formula 2, a composition for an organic optoelectronic device including the same, an organic optoelectronic device, and a display device. Details for Chemical Formula 1 and Chemical Formula 2 are as defined in the specification.

An organic compound and an organic light emitting device including the same are disclosed. For example, an organic compound is represented by the following chemical formula in which one of X1 and X2 is N, and the other one of X1 and X2 is O or S. The organic light emitting diode and the organic light emitting device each includes the organic compound.

##STR00001##