Compounds comprising a ligand L.sub.A selected from the group consisting of Formula I and Formula II may be useful as blue phosphorescent materials in OLED devices. The materials were determined computationally to have appropriate triplet energies for use as blue emitters and to possess sufficient chemical stability for use in devices. ##STR00001##

The present disclosure relates to a plurality of host materials, an organic electroluminescent compound, and an organic electroluminescent device comprising the same. By comprising a specific combination of host compounds and/or an organic electroluminescent compound according to the present disclosure as an organic electroluminescent material, an organic electroluminescent device having low driving voltage and/or high luminous efficiency and/or long lifespan characteristics can be provided.

Embodiments provide a light emitting element that includes a first electrode, a second electrode facing the first electrode, and an emission layer disposed between the first electrode and the second electrode, wherein the emission layer includes a polycyclic compound represented by Formula 1, which is explained in the specification:

##STR00001##

A heteroaromatic compound which can be used as the fluorescent guest material in the light emitting layer of the organic electroluminescence device is disclosed. The organic electroluminescence device employing the heteroaromatic compound of the present invention can operate under reduced driving voltage, increase current efficiency, and prolong half-life time.

A compound represented by the general formula (1) is useful as a light emitting material. In the general formula (1), Ar.sup.1 to Ar.sup.3 represent an aryl group, provided that Ar.sup.2 and Ar.sup.3 are the same as each other, and at least one of Ar.sup.1 to Ar.sup.3 represents an aryl group substituted with a group represented by the general formula (2). In the general formula (2), R.sup.1 to R.sup.8 represent a hydrogen atom or a substituent; Z represents O, S, R.sup.9N, (R.sup.10) (R.sup.11)C, or (R.sup.12) (R.sup.13)Si; and R.sup.9 to R.sup.13 each independently represent a hydrogen atom or a substituent. ##STR00001##

Disclosed are polycyclic aromatic compounds that can be employed in various organic layers of organic electroluminescent devices. Also disclosed are organic electroluminescent devices including the polycyclic aromatic compounds. The organic electroluminescent devices are highly efficient and long lasting and have greatly improved luminous efficiency.

Provided is an organic electroluminescent element which has improved driving voltage and improved current efficiency. An organic electroluminescent element having the above-mentioned improved characteristics is provided by using, as a material for organic electroluminescent elements, a polycyclic aromatic compound in which a nitrogen atom and another heteroatom or a metal atom (X) are adjacent to each other in a non-aromatic ring.

An organic light-emitting element which emits delayed fluorescence comprising specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives or 1,2,4-thiadiazole derivatives in the light-emitting layer, a light-emitting layer comprising the specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives or 1,2,4-thiadiazole derivatives, specific specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives and 1,2,4-thiadiazole derivatives and an organic light emitting element comprising the specific 1,2,4-azole derivatives as well as a light emitting layer comprising the specific 1,2,4-azole derivatives; the use of the specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives and 1,2,4-thiadiazole derivatives for electrophotographic photoreceptors, photoelectric converters, sensors, dye lasers, solar cell devices and organic light emitting elements, and the use of the specifically substituted 1,2,4-triazole derivatives, 1,2,4-oxadiazole derivatives and 1,2,4-thiadiazole derivatives for generating delayed fluorescence emission.

Provided are a polycyclic compound and an organic electroluminescence device including the same. The polycyclic compound according to an exemplary embodiment of the present disclosure is represented by the following formula 1. ##STR00001## In Formula 1, X is O, SiRR, S, or BAr.sub.1. At least one of R.sub.1 to R.sub.8 is an aryl amine-containing electron donor. When X is O, SiRR, or S, the aryl amine-containing electron donor further includes a Si.

Alkaline phosphatase chemiluminescent substrate formulations are provided exhibiting rapid incubation periods and improved stability for use in immunoassays.