A novel light-emitting element is provided. A light-emitting element with a long lifetime is provided. A light-emitting element with high emission efficiency is provided. In the light-emitting element, an EL layer includes a hole-injection layer, a first hole-transport layer, a second hole-transport layer, a third hole-transport layer, a light-emitting layer, a first electron-transport layer, and a second electron-transport layer in this order; the hole-injection layer includes an organic acceptor; the LUMO level of the host material is higher than that of the first electron-transport layer; the LUMO level of the second electron-transport layer is higher than that of the first electron-transport layer; the host material is a substance including a condensed aromatic ring skeleton; and the first and second electron-transport layers each include a substance having a heteroaromatic ring skeleton.

The present invention relates to iridium complexes suitable for use in organic electroluminescent devices, especially as emitters.

A metal tetradentate complex is disclosed in which an imidazole moiety is used as a linker in the ligand. The complex is useful as an emitter or other functional roles in an OLED device.

A compound having a formula: ##STR00001##
Formula I useful as emitters in OLEDs is disclosed.

An organometallic compound represented by Formula 1:
M(L.sub.1).sub.n1(L.sub.2).sub.n2(L.sub.3).sub.n3  Formula 1 wherein M, L.sub.1, L.sub.2, L.sub.3, n1, n2, and n3 are the same as described in the specification.

An organic electroluminescence device includes a first electrode, an organic layer disposed on the first electrode, and a second electrode disposed on the organic layer. The organic layer includes an organometallic compound represented by Formula 1 below. ##STR00001##
where R.sub.1 to R.sub.4, X.sub.1 to X.sub.4, Ar.sub.1 to Ar.sub.3, M, Q, m1 to m4, and n are as defined in the specification.

An organic light-emitting device including a predetermined host and a thermally activated delayed fluorescence emitter.

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. The emission layer includes at least one organometallic compound of Formula 1, and at least one selected from a second compound and a third compound, where the organometallic compound, the second compound, and the third compound are different from each other. When the emission layer comprises both the second compound and the third compound, the second compound and the third compound form an exciplex, and the organometallic compound and the second compound and/or the third compound do not form an exciplex:
M(L.sub.1).sub.n1(L.sub.2).sub.n2,  Formula 1
wherein in Formula 1, L.sub.1 is represented by Formula 2-1: ##STR00001##

An organic light-emitting device includes: a first pixel electrode on a first emission region, a second pixel electrode on a second emission region, and a third pixel electrode on a third emission region; a counter electrode facing each of the first pixel electrode, the second pixel electrode, and the third pixel electrode; and an interlayer between the counter electrode and each of the first pixel electrode, the second pixel electrode, and the third pixel electrode. The interlayer includes an emission layer, and a hole transport region between the emission layer and each of the first pixel electrode, the second pixel electrode, and the third pixel electrode, the hole transport region includes a planarization layer that includes an amine-based compound represented by Formula 1, Formula 2A, or Formula 2B, and the amine-based compound has a crystallization peak having a noise-to-peak ratio of 1.75 or more in an X-ray diffraction (XRD) spectrum.

A compound for an organic optoelectronic device, an organic optoelectronic device including the same, and a display device, the compound being represented by Chemical Formula 1: ##STR00001##