A light-emitting element including a fluorescent material as a light-emitting material and having high emission efficiency is provided. The light-emitting element includes a pair of electrodes and an EL layer provided between the pair of electrodes. The EL layer includes a host material and a guest material. The host material is capable of exhibiting thermally activated delayed fluorescence at room temperature. The guest material is capable of exhibiting fluorescence. The second triplet excitation energy level of the guest material is higher than or equal to the lowest singlet excitation energy level of the guest material.

An object of one embodiment of the present invention is to provide a multicolor light-emitting element that utilizes fluorescence and phosphorescence and is advantageous for practical application. The light-emitting element has a stacked-layer structure of a first light-emitting layer containing a host material and a fluorescent substance, a separation layer containing a substance having a hole-transport property and a substance having an electron-transport property, and a second light-emitting layer containing two kinds of organic compounds that form an exciplex and a substance that can convert triplet excitation energy into luminescence. Note that a light-emitting element in which light emitted from the first light-emitting layer has an emission spectrum peak on the shorter wavelength side than an emission spectrum peak of the second light-emitting layer is more effective.

A composition for an organic optoelectronic device, an organic optoelectronic device, and a display device, the composition including a first compound represented by Chemical Formula 1 and a second compound represented by a combination of Chemical Formula 2 and Chemical Formula 3: ##STR00001##

A compound of Formula I: ##STR00001## wherein ring A is a 5-membered or 6-membered aromatic ring; wherein R.sup.A, R.sup.B, and R.sup.C each independently represent mono to the maximum allowable substitution, or no substitution; wherein Y.sup.1 is absent or present, and when present is selected from the group consisting of a direct bond, O, S, Se, CRR, NR, SiRR, and BR; wherein each X.sup.1-X.sup.3 is N or CR; wherein at least one of X.sup.1-X.sup.3 is N; wherein each A.sup.1-A.sup.5 is independently C or N; wherein the maximum number of N atoms that can connect to each other within each ring is two; wherein each R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently selected from the group consisting of alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, aryl, heteroaryl, and combinations thereof; wherein each R, R, R.sup.A, R.sup.B, and R.sup.C is independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein any two substituents may be joined or fused together to form a ring.

Disclosed is an OLED configuration that although comprises an exciplex that has an emission spectrum that is redder than the emission spectrum of the emitter, the emission from the exciplex is suppressed so that the overall OLED emission spectrum is still dominated by the emission of the emitter.

The present disclosure relates to a plurality of host materials comprising a compound represented by formula 1 and a compound represented by formula 2, and an organic electroluminescent device comprising the same. By comprising the plurality of host materials comprising a specific combination of compounds, it is possible to provide an organic electroluminescent device having long lifespan characteristics.

An organic light-emitting device includes a first electrode; a second electrode facing the first electrode; and an organic layer between the first electrode and the second electrode, the organic layer including an emission layer. The emission layer includes at least one heterocyclic compound of Formula 1. The heterocyclic compound may be a host or a delayed fluorescent dopant. The organic light-emitting device including the heterocyclic compound may have a low driving voltage, high efficiency, high luminance, and a long lifespan.

An organic light-emitting device including 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 first material not including an electron transport moiety, a second material including at least one electron transport moiety, a third material having reorganization energy of about 0.4 eV or more, and a light-emitting material, wherein the first material, the second material, the third material, and the light-emitting material are different from one another, and wherein a ratio of a light-emitting component emitted from the light-emitting material to a total of light-emitting components emitted from the emission layer is about 90% or more.

The present disclosure relates to an organic electroluminescent compound, an organic electroluminescent material comprising the same, and an organic electroluminescent device. By comprising the organic electroluminescent compound according to the present disclosure, an organic electroluminescent device having low driving voltage and/or high luminous efficiency and/or long lifespan can be provided.

Provided is a compound of Chemical Formula 1: ##STR00001## wherein: X.sub.1 to X.sub.6 are each independently CH or N, provided that at least one of X.sub.1 to X.sub.6 is N; Ar.sub.1 to Ar.sub.4 are each independently a substituted or unsubstituted: C.sub.6-60 aryl or C.sub.2-60 heteroaryl containing one or more of N, O, and S, provided that at least one of Ar.sub.1 to Ar.sub.4 is any one of: ##STR00002## R.sub.2 is hydrogen, deuterium, or a substituted or unsubstituted: C.sub.6-60 aryl or C.sub.2-60 heteroaryl containing one or more of N, O and S; each R.sub.3 is independently hydrogen, deuterium, or a substituted or unsubstituted: C.sub.6-60 aryl or C.sub.2-60 heteroaryl containing one or more of N, O, and S; each R.sub.1 is independently hydrogen, deuterium, or a substituted or unsubstituted: C.sub.6-60 aryl or C.sub.2-60 heteroaryl containing one or more of N, O and S; and n is an integer of 0 to 8, and organic light emitting devices including the same.