The present application relates to a light-emitting device, comprising an anode, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode, which are stacked in sequence, wherein the light-emitting layer comprises N stacked light-emitting units; each light-emitting unit comprises a thermal activation delayed fluorescent material layer and a quantum dot material layer; the light emitted from the thermal activation delayed fluorescent material layer and the light emitted from the quantum dot material layer are synthesized into white light.

Provided are a backlight unit, a down-conversion medium including the same, and a display device including the down-conversion medium. The backlight unit includes a light source configured to generate blue light; and an optical film configured to absorb a portion of the blue light generated from the light source to generate red light and green light, wherein the optical film includes a quantum dot matrix in which semi-metal element oxide is embedded.

Provided are a backlight unit, a down-conversion medium including the same, and a display device including the down-conversion medium. The backlight unit includes a light source configured to generate blue light; and an optical film configured to absorb a portion of the blue light generated from the light source to generate red light and green light, wherein the optical film includes a quantum dot matrix in which semi-metal element oxide is embedded.

A light-emitting element whose degree of deterioration with driving time is improved and of which emission colors are easily controlled. A light-emitting emitting element having a first electrode, a second electrode, and a layer containing an organic compound located between the first electrode and the second electrode, in which the layer containing the organic compound at least has, from the second electrode side, a light-emitting layer in which a first layer, a second layer, and a third layer are stacked, and a hole-transporting layer provided in contact with the third layer; the first layer contains a first organic compound and a second organic compound; the second layer contains a third organic compound and a fourth organic compound; and the third layer contains the first organic compound and a fifth organic compound.

A method of depositing a cathode on an organic light emitting diode (OLED) stack is provided. The method includes providing a substrate having at least a partial organic light emitting diode (OLED) stack disposed on a surface of the substrate. The method further includes depositing, on top of the partial OLED stack, a solution comprising a metal compound. The method further includes forming a conductive solid layer from the metal compound in the solution to form a cathode for the partial OLED stack.

A compound has, in a molecule, a cyclic structure represented by a formula (1) below; and at least one cyclic structure selected from the group consisting of a cyclic structure represented by a formula (10) below and a cyclic structure represented by a formula (11) below. In the formula (1): R.sub.1 to R.sub.16 are each independently a hydrogen atom, an alkyl group or the like; and R.sub.X and R.sub.Y are each independently an alkyl group.

##STR00001##

A compound has, in a molecule, a cyclic structure represented by a formula (1) below; and at least one cyclic structure selected from the group consisting of a cyclic structure represented by a formula (10) below and a cyclic structure represented by a formula (11) below. In the formula (1): R.sub.1 to R.sub.16 are each independently a hydrogen atom, an alkyl group or the like; and R.sub.X and R.sub.Y are each independently an alkyl group.

##STR00001##

A light receiving element includes a first electrode, a hole transport region disposed on the first electrode, a light receiving layer disposed on the hole transport region and converting incident light to an electrical signal, an electron transport region disposed on the light receiving layer, and a second electrode disposed on the electron transport region. The light receiving layer includes a p-dopant compound, a donor compound, and an acceptor compound.

A light receiving element includes a first electrode, a hole transport region disposed on the first electrode, a light receiving layer disposed on the hole transport region and converting incident light to an electrical signal, an electron transport region disposed on the light receiving layer, and a second electrode disposed on the electron transport region. The light receiving layer includes a p-dopant compound, a donor compound, and an acceptor compound.

A light-emitting element includes an anode electrode and a cathode electrode, and is provided with a first hole transport layer, a second hole transport layer, a light-emitting layer, a first electron transport layer, and a second electron transport layer. At a HOMO level, an energy level difference between the second hole transport layer and the light-emitting layer on the second hole transport layer side is from 0.0 eV to 0.15 eV, and at a LUMO level, an energy level difference between the first electron transport layer and the light-emitting layer on the first electron transport layer side is from 0.0 eV to 0.15 eV. The second electron transport layer is a mixed layer that includes an organic material having electron transport properties and an electron-accepting material and contains the electron-accepting material in an amount greater than 50 mass %.