Disclosed herein are organic light emitting diode (OLED) devices and methods of use thereof. In one embodiment, an organic light emitting diode (OLED) device includes an emitting layer including: a host and an emitter, wherein the host exhibits triplet-triplet annihilation up-conversion, wherein the emitter has a band gap and exhibits triplet-triplet annihilation up-conversion, wherein the host and the emitter are different, and wherein the emitter has a concentration of 5% or more in the emitting layer.

A novel light-emitting device is provided. Alternatively, a light-emitting device having a long driving lifetime at high temperature is provided. The light-emitting device includes an anode, a cathode, and an EL layer positioned between the anode and the cathode. The EL layer includes a first layer, a second layer, a third layer, and a light-emitting layer in this order from the anode side. The first layer includes a first organic compound and a second organic compound. The second layer includes a third organic compound. The third layer includes a fourth organic compound. The light-emitting layer includes a fifth organic compound and an emission center substance. The first organic compound exhibits an electron-accepting property with respect to the second organic compound. A difference between HOMO levels of the fourth organic compound and the fifth organic compound is less than or equal to 0.24 eV.

An organic electroluminescent device having an anode, a cathode, and a light emitting layer between the anode and the cathode, in which the light emitting layer contains a first organic compound, a second organic compound, and a third organic compound that satisfy the following expression (A), the second organic compound is a delayed fluorescent material, and the third organic compound is a light emitting material, is capable of enhancing the light emission efficiency. E.sub.S1(A), E.sub.S1(B) and E.sub.S1(C) represent a lowest, singlet excitation energy level of the first, second and third organic compound, respectively.
E.sub.S1(A)>E.sub.S1(B)>E.sub.S1(C)(A)

A copolymer including a structural unit represented by Chemical Formula 1 ##STR00001##
wherein the copolymer is capable of improving luminous efficiency and durability, particularly, an improvement in luminescence life-span, of an electroluminescence device, particularly a quantum dot electroluminescence device.

A light-emitting device with high emission efficiency and reliability is provided. The light-emitting device includes a fluorescent light-emitting layer and a phosphorescent light-emitting layer. A host material used in the fluorescent light-emitting layer has a function of converting triplet excitation energy into light emission and a guest material used in the fluorescent light-emitting layer emits fluorescence. The guest material has a molecular structure including a luminophore and a protecting group, and one molecule of the guest material includes five or more protecting groups. The introduction of the protecting groups into the molecule inhibits transfer of triplet excitation energy from the host material to the guest material by the Dexter mechanism. An alkyl group or a branched-chain alkyl group is used as the protecting group. The longest wavelength absorption band in the absorption spectrum of the guest material in the phosphorescent light-emitting layer has an overlap with the emission spectrum of the host material in the phosphorescent light-emitting layer.

Organic luminescent material, includes: host material, TADF sensitizer, and fluorescent-luminescent material; wherein absolute value of difference between LUMO level of the host material and LUMO level of the TADF sensitizer is not more than 0.4 eV, and absolute-value of difference between HOMO level of the host material and HOMO level of the TADF sensitizer is not more than 0.4 eV; absolute-value of LUMO level of the fluorescent-luminescent material is not more than absolute-value of the LUMO level of the host material and the LUMO level of the TADF sensitizer, and/or absolute-value of HOMO level of the fluorescent-luminescent material is not less than an absolute-value of the HOMO level of the host material and absolute-value of the HOMO level of the TADF sensitizer; and emission-spectrum of the host material overlaps an absorption-spectrum of the TADF sensitizer, and emission-spectrum of the TADF sensitizer overlaps absorption-spectrum of the fluorescent-luminescent material.

Disclosed are a light-emitting device and a display device including the same. An emissive layer is formed so as to have a dual-layer structure, the triplet energy level of a dopant of a first emissive layer adjacent to a hole transport layer is greater than the triplet energy level of a first host in the first emissive layer, and the triplet energy level of the first host is greater than the triplet energy level of a second host of a second emissive layer, whereby triplet excitons generated in the first emissive layer are recycled to the second emissive layer so as to be reused for light emission.

A quantum dot light-emitting device including first electrode and a second electrode, a quantum dot layer between the first electrode and the second electrode, a first electron transport layer and a second electron layer disposed between the quantum dot layer and the second electrode. The second electron transport layer is disposed between the quantum dot layer and the first electron transport layer, wherein each of the first electron transport layer and the second electron transport layer includes an inorganic material. A lowest unoccupied molecular orbital energy level of the second electron transport layer is shallower than a lowest unoccupied molecular orbital energy level of the first electron transport layer, and a lowest unoccupied molecular orbital energy level of the quantum dot layer is shallower than a lowest unoccupied molecular orbital energy level of the second electron transport layer. An electronic device including the quantum dot light-emitting device.

Disclosed is an organic light-emitting device including an emission layer that includes a compound satisfying conditions 5 and 6 below:
0 eV<E.sub.ST20.1 eVCondition 1:
E.sub.ST>0.2 eVCondition 6:

An organic light-emitting diode display device is provided, including an anode layer, a cathode layer, a first light-emitting layer, and a second light-emitting layer disposed between the anode layer and the cathode layer, wherein the first light-emitting layer comprises a first light-emitting part, a second light-emitting part, and a third light-emitting part arranged side-by-side, the second light-emitting layer is configured to emit light of a same color as light emitted from the first light-emitting part, and the organic light-emitting diode display device further includes a charge generating layer disposed between the second light-emitting layer and the first light-emitting part.