An light emitting device of the present embodiments includes oppositely disposed first electrode and second electrode, and a plurality of organic layers disposed between the first electrode and the second electrode, wherein at least one among the plurality of organic layers includes a fused polycyclic compound represented by Formula 1 below, thereby showing improved emission efficiency:

##STR00001##

An light emitting device of the present embodiments includes oppositely disposed first electrode and second electrode, and a plurality of organic layers disposed between the first electrode and the second electrode, wherein at least one among the plurality of organic layers includes a fused polycyclic compound represented by Formula 1 below, thereby showing improved emission efficiency:

##STR00001##

A metal-organic chalcogenolate (MOC) includes silver phenylselenolate functionalized with at least one functional group. The functional group may be methyl (CH.sub.3), dimethylamine (N(CH.sub.3).sub.2), thiomethyl (SCH.sub.3), fluoro (F) trifluoromethyl (CF.sub.3), cyanide (CN), carboxy (COOH), nitrito (NO.sub.2), or alkoxy (OC.sub.xH.sub.y). The MOC can be in the form of a single crystal consisting essentially of a nanocluster (0D), a nanotube (1D), or a single monolayer (2D).

An organic electroluminescence device of an embodiment includes a first electrode, a hole transport region on the first electrode, an emission layer on the hole transport region, an electron transport region on the emission layer, and a second electrode on the electron transport region, wherein the emission layer includes a first host compound represented by Formula 1, a second host compound represented by Formula 2, and a dopant compound comprising an organometallic complex including Pt, Au, or Cu as a central metal element, and may show improved life characteristics.

An organometallic compound represented by Formula 1:

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

wherein 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 ring CY.sub.1, ring CY.sub.2, ring CY.sub.3, X.sub.1, X.sub.2, X.sub.41, X.sub.42, R.sub.1 to R.sub.6, R.sub.10, R.sub.20, R.sub.30, R.sub.40, b10, b20, b30, and b40 are as described in the detailed description, and * and *′ each indicate a binding site to M.sub.1.

A light emitting element includes a first electrode, a second electrode disposed on the first electrode, and an emission layer disposed between the first electrode and the second electrode. The emission layer may include a hole transporting host, an electron transporting host, a phosphorescent sensitizer, and a delayed fluorescent dopant. The delayed fluorescent dopant may have a greater absolute value of the HOMO energy level than the hole transporting host. Accordingly, the light emitting element including the delayed fluorescent dopant in an embodiment may exhibit long lifespan.

A condensed cyclic compound represented by Formula 1:

##STR00001## wherein in Formula 1, Ar and R.sub.1 to R.sub.8 are the same as described in the specification.

According to an aspect of the present disclosure, a compound having a metal planar tetradentate coordination configuration is disclosed. In the compounds, the metal M is Pt or Pd; the four coordinating atoms are Z.sup.1, Z.sup.2, Z.sup.3, and Z.sup.4 and are each selected from N, C, and O. The compound includes a substituent R, and atoms M, Z.sup.1, Z.sup.2, Z.sup.3, and Z.sup.4 are used to define a first plane that passes through the metal M and is positioned to have a minimum sum of shortest distances with Z.sup.1, Z.sup.2, Z.sup.3, and Z.sup.4. At least one non-hydrogen atom in R falls within a distal circle of a cylinder extending perpendicular to the first plane, where the distal circle of the cylinder is a height h from the base circle and the height h ranges from 3.3 Å to 4.8 Å.

A ligand for metal complexes are disclosed, in which an imidazole ring is fused to an aromatic ring as a substituent or an imidazole ring is fused to a six-member ring of the original ligand. The features of these elements within the ligand afford a better device performance in general OLED device.

An organic light-emitting device having improved efficiency and lifespan includes: a first electrode, a second electrode, and an organic layer between the first electrode and the second electrode, wherein the organic layer includes an emission layer, the emission layer includes a first compound, a second compound, a third compound, and a fourth compound, the first compound, the second compound, the third compound, and the fourth compound are different from each other, the third compound includes a metal element having an atomic number of 40 or more, the fourth compound includes boron (B), the third compound and the fourth compound each satisfy Conditions 1-1 and 1-2 below, and the fourth compound satisfies Condition 2 or 3:

T.sub.1(C3).sub.onset≥S.sub.1(C4).sub.onset  Condition 1-1

T.sub.1(C3).sub.max≥S.sub.1(C4).sub.max  Condition 1-2

K.sub.RISC(C4)≥10.sup.3 S.sup.−1  Condition 2

f(C4)≥0.1.  Condition 3