Disclosed are a light emitting device that includes an additional layer adjacent to a light emitting layer and thus is capable of utilizing, in light emission, holes not used in the light emitting layer, to improve efficiency and lifespan, and a light emitting display device including the same. The light emitting device includes a first electrode and a second electrode facing each other, and an unit comprising a hole transport layer, a light emitting layer, an efficiency-improving layer, and an electron transport layer sequentially stacked between the first electrode and the second electrode, wherein the light emitting layer includes a first host comprising an anthracene derivative and a first blue light emitting dopant, and the efficiency-improving layer includes a second host having bipolarity and a second blue light emitting dopant.

Disclosed are a light emitting element and a display device including the same, wherein a hole generation layer is further provided between a hole transport layer and an emission layer, in addition to an electron blocking layer, in order to control the speed of electrons and holes introduced into the emission layer, whereby it is possible to prevent accumulation of carriers at the electron blocking layer or the hole transport layer, and therefore it is possible to reduce turn-on voltage, to maintain uniform efficiency irrespective of change in current density, to prevent defects at specific gradation, and to increase lifetime.

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.

A light-emitting device includes an electron transport region including a first electron transport layer and a second electron transport layer. The first electron transport layer includes a first compound, the second electron transport layer includes a second compound, the first compound includes a pyrimidine group, the second compound includes a triazine group, and an absolute value of a lowest unoccupied molecular orbital (LUMO) energy of the first compound (E.sub.LUMO_E1) is less than an absolute value of a LUMO energy of the second compound (E.sub.LUMO_E2). An electronic apparatus including the light-emitting device.

Disclosed is a device that includes an emissive material or region including a host that is doped with a first material as an emitter that is an acceptor and a phosphorescent-capable second material as a sensitizer. The first material and the second material each has a first singlet state and a first triplet state. The first triplet state of the second material is not lower than the first triplet state of the first material. The second material transfers excitons to the first material and the excitons that transition to the first triplet state of the first material can be activated to the first singlet state of the first material through a thermal activation process.

An organic light-emitting device including a first electrode; a second electrode facing the first electrode; an emission layer between the first electrode and the second electrode; a hole transport region between the first electrode and the emission layer; and an electron transport region between the emission layer and the second electrode, wherein: the emission layer includes a first compound, at least one of the hole transport region and the electron transport region includes a second compound, the first compound is represented by Formula 1A or 1B, and the second compound is represented by Formula 2A or 2B: ##STR00001##

An organic light emitting device includes: a first electrode; a second electrode facing the first electrode; and an organic layer between the first electrode and the second electrode, the organic layer including an emission layer, wherein the organic layer includes a first compound, a second compound, a third compound, and a fourth compound, and the first compound to the fourth compound satisfy Equations 1 to 8:
E.sub.1,LUMO≥E.sub.2,LUMO+0.15 electron volts (eV)  Equation 1
E.sub.1,HOMO≥E.sub.2,HOMO+0.15 eV  Equation 2
E.sub.1,T1≥E.sub.4,T1  Equation 3
E.sub.2,T1≥E.sub.4,T1  Equation 4
E.sub.3,T1≥E.sub.4,T1  Equation 5
E.sub.3,LUMO≥E.sub.2,LUMO+0.1 eV  Equation 6
−5.6 eV≥E.sub.3,HOMO  Equation 7
E.sub.gap1≥E.sub.gap3.  Equation 8

An organic light-emitting device including a first electrode, a second electrode, an emission layer disposed between the first electrode and the second electrode, a hole transport region disposed between the first electrode and the emission layer, and an electron transport region disposed between the emission layer and the second electrode, wherein the emission layer includes a host and a dopant, wherein the dopant is an iridium-free organometallic compound, and wherein a dopant concentration profile of the emission layer satisfies predetermined parameters disclosed in the specification.

The present disclosure provides an organic emitting compound of the following Formula, and an organic light emitting diode, which includes a first electrode; a second electrode facing the first electrode; and a first emitting material layer positioned between the first electrode and the second electrode and including a first host and the organic emitting compound, and an organic light emitting display device including the organic light emitting diode. ##STR00001##

An organometallic compound is represented by Formula 1. An organic light-emitting device includes a first electrode, a second electrode, and an organic layer including an emission layer between the first electrode and the second electrode, wherein the organic layer includes at least one of the organometallic compound represented by Formula 1. An apparatus includes the organic light-emitting device.