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.

To increase emission efficiency of a fluorescent light-emitting element by efficiently utilizing a triplet exciton generated in a light-emitting layer. The light-emitting layer of the light-emitting element includes at least a host material and a guest material. The triplet exciton generated from the host material in the light-emitting layer is changed to a singlet exciton by triplet-triplet annihilation (TTA). The guest material (fluorescent dopant) is made to emit light by energy transfer from the singlet exciton. Thus, the emission efficiency of the light-emitting element is improved.

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 organic electroluminescent device and a display apparatus. The organic electroluminescent device includes a first electrode, a second electrode and an organic layer located between the first electrode and the second electrode. The organic layer includes a light-emitting layer. The light-emitting layer contains a host material, a thermally activated delayed fluorescence sensitizer and a fluorescent dye. The energy level relationship between the host material and the thermally activated delayed fluorescence sensitizer is LUMO.sub.host≥LUMO.sub.sensitizer, while HOMO.sub.sensitizer≥HOMO.sub.host.

An organic electroluminescent device and a display apparatus. The organic electroluminescent device includes a first electrode, a second electrode and at least two organic electroluminescent units located between the first electrode and the second electrode. The at least two organic electroluminescent units are arranged in a stacked manner. The at least two organic electroluminescent units include a first organic electroluminescent unit. The first organic electroluminescent unit includes a first light-emitting layer. The first light-emitting layer contains a first host material, a thermally activated delayed fluorescence sensitizer and a first fluorescent dye.

A light emitting material containing an adjustment compound N in addition to a donor compound D and an acceptor compound A that form an exciplex and satisfying HOMO(D)>HOMO(N)>HOMO(A), LUMO(D)>LUMO(N)+0.1 eV and LUMO(N)>LUMO(A) has improved luminous efficiency or emission lifetime.

The present disclosure belongs to the technical field of organic light-emitting diods (OLEDs), and provides a compound used as an electron transmission material of OLEDs. Molecules of the compounds include an aromatic ring (or aromatic fused ring) and a phenanthroline group that are connected to each other. In an embodiment, the compound according to the present disclosure includes two types of groups, i.e., an aromatic ring (or aromatic fused ring) and a phenanthroline (or benzoquinoline) group. These two groups not only have good electron accepting ability, but also can be well doped with metals. The planarity of the two groups is conducive to the stacking of molecules, which facilitates the combination of holes and electrons and generates excitons, thereby increasing the electron mobility of the material and improving efficiency of device.

A novel light-emitting device that is highly convenient, useful, or reliable is provided. The light-emitting device includes a first electrode, a second electrode, a unit, and a first layer. The second electrode includes a region overlapping with the first electrode. The unit includes a region positioned between the first electrode and the second electrode. The unit includes a second layer and a third layer. The second layer includes a region where the third layer is positioned between the second layer and the first electrode. The second layer contains a light-emitting material. The first layer includes a region positioned between the third layer and the first electrode. The first layer contains a material having an acceptor property and a first material. The first layer includes a first region and a second region. The first region includes a region positioned between the second region and the first electrode. The first region contains the material having an acceptor property at a first concentration. The second region contains the material having an acceptor property at a second concentration. Note that the second concentration is higher than zero and lower than the first concentration.

An electroluminescent device and a display device including the same. The electroluminescent device includes a first electrode and a second electrode facing each other; a light emitting layer disposed between the first electrode and the second electrode, the light emitting layer including a quantum dot; a hole transport layer disposed between the light emitting layer and the first electrode; and an electron transport layer disposed between the light emitting layer and the second electrode, wherein the hole transport layer, the light emitting layer, or a combination thereof includes thermally activated delayed fluorescence material, and the thermally activated delayed fluorescence material is present in an amount of greater than or equal to about 0.01 wt % and less than about 10 weight percent (wt %), based on 100 wt % of the hole transport layer, the light emitting layer, or the combination thereof including the thermally activated delayed fluorescence material.

Provided are a heterocyclic compound represented by Formula 1-1 or 1-2, an organic light-emitting device including the heterocyclic compound, and an electronic apparatus including the organic light-emitting device:

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Formulae 1-1 and 1-2 may each be understood by referring to the descriptions of Formulae 1-1 and 1-2 provided herein.