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.

The present disclosure relates to compounds capable of emitting delayed fluorescence, and uses of these compounds in organic light-emitting diodes.

An organic light emitting device having a light emitting layer that contains first to fourth organic compounds satisfying the following formulae has a long emission lifetime and is stable. The second organic compound is a delayed fluorescent material, and the amount of light emission from the fourth organic compound is the maximum. E.sub.S1 is a lowest excited singlet energy, E.sub.T1 is a lowest excited triplet energy. E.sub.S1(1)>E.sub.S1(4)>E.sub.S1(2)>E.sub.S1(3), E.sub.T1(1)>E.sub.T1(2)>E.sub.T1(3)>E.sub.T1(4).

A light-emitting device including an organometallic compound represented by Formula 1, an electronic apparatus including the light-emitting device, and the organometallic compound represented by Formula 1 are provided.

##STR00001##

Provided is a light emitting element includes a polycyclic compound in which an electron donor substituent, which may increase the photoluminescence quantum yield (PLQY) and oscillator strength (f), is introduced at the para-position of a boron atom, thereby exhibiting high efficiency and long service life characteristics.

The invention relates to an organic molecule, in particular for use in organic optoelectronic devices. According to the invention, the organic molecule has one first chemical moiety with a structure of formula I, ##STR00001## and one second chemical moiety with a structure of formula II, ##STR00002## wherein the first chemical moiety is linked to the second chemical moiety via a single bond.

Embodiments provide an organometallic compound, a light-emitting device including the organometallic compound, and an electronic apparatus including the light-emitting device. The light-emitting device includes a first electrode, a second electrode facing the first electrode, an interlayer between the first electrode and the second electrode and including an emission layer, and the organometallic compound, which is represented by Formula 1.

##STR00001##

The description of Formula 1 is provided in the specification.

Provided is an organic electroluminescent device. The organic electroluminescent device is a blue delayed fluorescent device including an anode, a cathode, an emissive layer disposed between the anode and the cathode and a hole blocking layer disposed between the emissive layer and the cathode, where the hole blocking layer comprises a hole blocking material having a structure of Formula 1, and the emissive layer comprises a first host material, a second host material and a blue delayed fluorescent material having a structure of Formula 3. The blue delayed fluorescent device exhibits excellent overall device performance, such as higher efficiency and longer lifetime. Further provided are a light-emitting device comprising a blue delayed fluorescent unit, a green phosphorescent unit and a red phosphorescent unit and a display assembly comprising the blue delayed fluorescent device and the light-emitting device.

A thermally activated delayed fluorescent molecular material, a synthesizing method therefor, and an electroluminescent device are provided. The thermally activated delayed fluorescent molecular containing an indenobenzoselenoheteroaromatic ring donor is synthesized, so that an electron donating ability of the donor is increased, and an non-radiative transition rate is effectively inhibited, thereby increasing photo-luminescence quantum yield (PLQY) of the molecule; and increasing the twist angle between the electron donor and the electron acceptor. Meanwhile, electron cloud overlapping between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) is reduced, thereby obtaining a smaller ΔE.sub.ST value. The organic electroluminescent device adopts the thermally activated delayed fluorescent molecular material prepared according to the synthesizing method, and thus has high luminous efficiency and long service life.

The purpose of the present invention is to provide: a π-conjugated compound exhibiting excellent light emission characteristics; an organic electroluminescent element using same; a display device; and an illumination device. Accordingly, this organic electroluminescent element is provided with: a positive electrode; a negative electrode; and at least one organic layer which is sandwiched between the positive electrode and the negative electrode, and which includes a light emission layer. The light emission layer includes a π-conjugated compound having a structure represented by any of general formulae (1)-(3) ##STR00001##
(in general formulae (1)-(3), at least one among R1-R4, R5-R8, and R9-R16 represents a group represented by general formula (4) ##STR00002##
(in general formula (4): Ar1 and Ar2 represent substituted or unsubstituted aryl groups; L1 represents a single bond or a substituted or unsubstituted arylene group; and # represents a bond to general formulae (1)-(3))).