The present invention relates to a light emitting device including a light emitting layer having a stacked structure of two or more layers in which the light emitting layer is alternately disposed with a first light emitting material layer and a second light emitting material layer. In addition, the light-emitting material layer is a perovskite layer or an organic material layer, the first light-emitting material layer and the second light-emitting material layer are characterized in that they have different band gaps. By alternately disposing the first light emitting material layer and the second light emitting material layer to have a stacked structure and by controlling the energy level, there is an advantage in that the electroluminescence efficiency can be improved by controlling the electron-hole recombination region of the light emitting device. In addition, there is an advantage that a white light emitting device can be manufactured by controlling the energy levels of the first light emitting material layer and the second light emitting material layer.

An organic electroluminescence device includes two or more emitting units disposed between an anode and a cathode, and an intermediate layer, in which the intermediate layer contains a phenanthroline compound, the laminated emitting unit includes a first emitting layer containing a first host material and a second emitting layer containing a second host material, and a triplet energy T.sub.1(H1) of the first host material and a triplet energy T.sub.1(H2) of the second host material satisfy a relationship of a numerical formula (Numerical Formula 3),

T.sub.1(H1)>T.sub.1(H2)  (Numerical Formula 3).

Compounds of Formula I,

##STR00001##

and Formula IIa,

##STR00002##

Formula IIb,

##STR00003##

are provided. In these structures, M is Pt or Pd; each of X.sup.1 to X.sup.6, X.sup.9 to X.sup.12, and Z.sup.1 to Z.sup.3 is C or N; each of L.sup.1, L.sup.2, L.sup.3, and L.sup.4 is a direct bond or a linker; at least three of L.sup.1, L.sup.2, L.sup.3, and L.sup.4 are present; each K.sup.1, K.sup.2, and K.sup.3 is a bond, O, or S; when Z.sup.1 is N, ring A in Formula I is not a pyridine or pyrazole; L.sup.5 is a bond or an organic linker; Y is selected from the group consisting of amino, alkoxy, aryloxy, or SiR.sup.1R.sup.2R.sup.3; when Y is SiR.sup.1R.sup.2R.sup.3, L.sup.2 is not BR. Devices, consumer products, and formulations containing these compounds are also disclosed.

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.

Organic light emitting devices (OLEDs) with emissive layers containing both phosphorescent Pt complexes and fluorescent emitters, are described. The devices presented employ both fluorescent and phosphorescent Pt complexes in order to redistribute the excited states to primarily reside on known stable fluorescent emitters to achieve high device operational stability but maintain the high efficiency characteristic of phosphorescent OLEDs.

Disclosed is an organic light emitting diode (OLED) includes a first emitting material layer, which includes a first compound and a second compound, and a second emitting material layer, which includes a third compound and a fourth compound, wherein a HOMO energy level of the first compound is higher than a HOMO energy level of the second compound and a HOMO energy level of the third compound is lower than a HOMO energy level of the fourth compound, and an organic light emitting device having the OLED. The OLED and the organic light emitting device disclosed have enhanced luminous efficiency, color purity and luminous life span as well as low driving voltage by applying the emitting material layer.

Provided is a light-emitting element with high external quantum efficiency and a low drive voltage. The light-emitting element includes a light-emitting layer which contains a phosphorescent compound and a material exhibiting thermally activated delayed fluorescence between a pair of electrodes, wherein a peak of a fluorescence spectrum and/or a peak of a phosphorescence spectrum of the material exhibiting thermally activated delayed fluorescence overlap(s) with a lowest-energy-side absorption band in an absorption spectrum of the phosphorescent compound, and wherein the phosphorescent compound exhibits phosphorescence in the light-emitting layer by voltage application between the pair of electrodes.

Provided is a light-emitting element with high external quantum efficiency and a low drive voltage. The light-emitting element includes a light-emitting layer which contains a phosphorescent compound and a material exhibiting thermally activated delayed fluorescence between a pair of electrodes, wherein a peak of a fluorescence spectrum and/or a peak of a phosphorescence spectrum of the material exhibiting thermally activated delayed fluorescence overlap(s) with a lowest-energy-side absorption band in an absorption spectrum of the phosphorescent compound, and wherein the phosphorescent compound exhibits phosphorescence in the light-emitting layer by voltage application between the pair of electrodes.

Provided is a light-emitting element including a fluorescence-emitting material with high emission efficiency. The light-emitting element includes a pair of electrodes and an EL layer between the pair of electrodes. The EL layer includes a first organic compound, a second organic compound, and a guest material. The first organic compound has a function of emitting a thermally activated delayed fluorescence at room temperature. The guest material has a function of emitting fluorescence. A HOMO level of the first organic compound higher than or equal to a HOMO level of the second organic compound. A LUMO level of the first organic compound is lower than or equal to a LUMO level of the second organic compound.

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.