A display device, includes: a first light-emitting element emitting a first light having a first wavelength; and a second light-emitting element emitting a second light having a second wavelength, the first light and the second light being released in a first direction; a first optical layer formed in a second direction with respect to the first light-emitting element, and positioned to coincide with the first light-emitting element in the second direction, the first optical layer being transparent to the light having the second wavelength and reflective or absorptive of the light having the first wavelength; and a second optical layer formed in the second direction with respect to the second light-emitting element, and positioned to coincide with the second light-emitting element in the second direction, the second optical layer being transparent to the light having the first wavelength and reflective or absorptive of the light having the second wavelength.

A light-emitting device includes a light-emitting part. The light-emitting part contains a quantum dot. The quantum dot has a core and a shell. The shell is located outside the core. Each of the core and the shell has a hexagonal structure. The lattice constant of the core is larger than the lattice constant of the shell.

A display apparatus with high display quality is provided. A high-resolution display apparatus is provided. The display apparatus includes a plurality of pixels, and the pixels each include a light-emitting device, a first transistor, a second transistor, a third transistor, a fourth transistor, and a first capacitor. One electrode of the light-emitting device is electrically connected to one of a source and a drain of the first transistor, one of a source and a drain of the second transistor, and one electrode of the first capacitor. A gate of the second transistor is electrically connected to the other electrode of the first capacitor, one of a source and a drain of the third transistor, and one of a source and a drain of the fourth transistor. One frame period of each of the pixels includes a period in which the first transistor and the fourth transistor are each in a conduction state.

The present disclosure provides a blue organic electroluminescence device, a display panel, and a display apparatus. A blue organic electroluminescence device includes a light-emitting layer having a matrix material and a blue fluorescent doping material doped in the matrix material, where dipole moments of the matrix material and the blue fluorescent doping material are both 0 to 1 D, which can ensure higher energy transfer efficiency and charge balance, ensure that an emission spectrum is a narrow spectrum, and thus have better color purity and higher external quantum Efficiency (EQE) to obtain the blue organic electroluminescence devices with high color purity and high luminous efficiency.

The present disclosure provides a blue organic electroluminescence device, a display panel, and a display apparatus. A blue organic electroluminescence device includes a light-emitting layer having a matrix material and a blue fluorescent doping material doped in the matrix material, where dipole moments of the matrix material and the blue fluorescent doping material are both 0 to 1 D, which can ensure higher energy transfer efficiency and charge balance, ensure that an emission spectrum is a narrow spectrum, and thus have better color purity and higher external quantum Efficiency (EQE) to obtain the blue organic electroluminescence devices with high color purity and high luminous efficiency.

Provided are an ultraviolet emitting optical device and an operating method thereof. The ultraviolet emitting optical device includes a substrate, a first encapsulation layer, an active layer and a second encapsulation layer sequentially stacked on the substrate, a first electrode layer between the first encapsulation layer and the active layer, a second electrode layer between the active layer and the second encapsulation layer, and color centers provided in the active layer, wherein the active layer includes hexagonal boron nitride (hBN), wherein the color centers are configured to emit light in an ultraviolet wavelength range.

A compound having a Pt tetradentate structure of Formula 1, ##STR00001##
is provided. In the structure of Formula 1, rings C and D each independently represent 5- or 6-membered carbocyclic or heterocyclic ring; L.sup.1, L.sup.2, and L.sup.3 are each independently a direct bond, BR, NR, PR, O, S, Se, C═O, S═O, SO.sub.2, SiRR′, GeRR′, alkyl, cycloalkyl, or a combination thereof; the sum of n1 and n2 is 1 or 2; X is selected from NR.sup.E, O, S, and Se; X.sup.3 and X.sup.4 each independently carbon or nitrogen; and one of Q.sup.1, Q.sup.3, and Q.sup.4 is oxygen, and the remaining two of Q.sup.1, Q.sup.3, and Q.sup.4 each represents a direct bond. Formulations and devices, such as an OLEDs, that include the compound of Formula 1 are also described.

A compound having a Pt tetradentate structure of Formula 1, ##STR00001##
is provided. In the structure of Formula 1, rings C and D each independently represent 5- or 6-membered carbocyclic or heterocyclic ring; L.sup.1, L.sup.2, and L.sup.3 are each independently a direct bond, BR, NR, PR, O, S, Se, C═O, S═O, SO.sub.2, SiRR′, GeRR′, alkyl, cycloalkyl, or a combination thereof; the sum of n1 and n2 is 1 or 2; X is selected from NR.sup.E, O, S, and Se; X.sup.3 and X.sup.4 each independently carbon or nitrogen; and one of Q.sup.1, Q.sup.3, and Q.sup.4 is oxygen, and the remaining two of Q.sup.1, Q.sup.3, and Q.sup.4 each represents a direct bond. Formulations and devices, such as an OLEDs, that include the compound of Formula 1 are also described.

Provided are an organic electroluminescence device, which shows high luminous efficiency, is free of any pixel defect, and has a long lifetime, and a material for an organic electroluminescence device for realizing the device. The material for an organic electroluminescence device is a compound having a π-conjugated heteroacene skeleton crosslinked with a carbon atom, nitrogen atom, oxygen atom, or sulfur atom. The organic electroluminescence device has one or more organic thin film layers including a light emitting layer between a cathode and an anode, and at least one layer of the organic thin film layers contains the material for an organic electroluminescence device.

Provided are an organic electroluminescence device, which shows high luminous efficiency, is free of any pixel defect, and has a long lifetime, and a material for an organic electroluminescence device for realizing the device. The material for an organic electroluminescence device is a compound having a π-conjugated heteroacene skeleton crosslinked with a carbon atom, nitrogen atom, oxygen atom, or sulfur atom. The organic electroluminescence device has one or more organic thin film layers including a light emitting layer between a cathode and an anode, and at least one layer of the organic thin film layers contains the material for an organic electroluminescence device.