An organic light emitting diode (OLED) architecture in which efficient operation is achieved without requiring a blocking layer by locating the recombination zone close to the hole transport side of the emissive layer. Aryl-based hosts and Ir-based dopants with suitable concentrations result in an efficient phosphorescent OLED structure. Previously, blocking layer utilization in phosphorescent OLED architectures was considered essential to avoid exciton and hole leakage from the emissive layer, and thus keep the recombination zone inside the emissive layer to provide high device efficiency and a pure emission spectrum.

An organic light emitting device including: a substrate; a first electrode; a second electrode; and an organic layer interposed between the first electrode and the second electrode and including an emission layer, wherein one of the first electrode and the second electrode is a reflective electrode and the other is a semitransparent or transparent electrode, and wherein the organic layer includes a layer having at least one of the compounds having at least one carbazole group, and a flat panel display device including the organic light emitting device. The organic light emitting device has low driving voltage, excellent current density, high brightness, excellent color purity, high efficiency, and long lifetime.

Organometallic compounds comprising an imidazole carbene ligand having a N-containing ring fused to the imidazole ring are provided. In particular, the N-containing ring fused to the imidazole ring may contain one nitrogen atom or more than one nitrogen atom. These compounds may demonstrate high photoluminescent (PL) efficiency, Gaussian emission spectra, and/or short excited state lifetimes. These materials may be especially useful as blue phosphorescent emitters.

An organic light emitting device including: a substrate; a first electrode; a second electrode; and an organic layer interposed between the first electrode and the second electrode and including an emission layer, wherein one of the first electrode and the second electrode is a reflective electrode and the other is a semitransparent or transparent electrode, and wherein the organic layer includes a layer having at least one of the compounds having at least one carbazole group, and a flat panel display device including the organic light emitting device. The organic light emitting device has low driving voltage, excellent current density, high brightness, excellent color purity, high efficiency, and long lifetime.

An organic light emitting diode (OLED) architecture in which efficient operation is achieved without requiring a blocking layer by locating the recombination zone close to the hole transport side of the emissive layer. Aryl-based hosts and Ir-based dopants with suitable concentrations result in an efficient phosphorescent OLED structure. Previously, blocking layer utilization in phosphorescent OLED architectures was considered essential to avoid exciton and hole leakage from the emissive layer, and thus keep the recombination zone inside the emissive layer to provide high device efficiency and a pure emission spectrum.

A triarylamine derivative represented by a general formula (G1) given below is provided. Note that in the formula, Ar represents either a substituted or unsubstituted phenyl group or a substituted or unsubstituted biphenyl group; α represents a substituted or unsubstituted naphthyl group; β represents either hydrogen or a substituted or unsubstituted naphthyl group; n and m each independently represent 1 or 2; and R.sup.1 to R.sup.8 each independently represent any of hydrogen, an alkyl group having 1 to 6 carbon atoms, or a phenyl group. ##STR00001##

Objects are to provide the following: a substance that facilitates hole injection and has high triplet excitation energy; a light-emitting element having high emission efficiency using the substance that facilitates hole injection and has high triplet excitation energy; a light-emitting element having low driving voltage; and a light-emitting device, an electronic device, and a lighting device having low power consumption. Provided is a triazole derivative in which a dibenzothiophen-4-yl or dibenzofuran-4-yl group represented by General Formula (G2) is bonded to any one of Ar.sup.1 to Ar.sup.3 of a triazole derivative represented by General Formula (G1). In the formulas, A represents oxygen or sulfur, Ar.sup.1 to Ar.sup.3 separately represent a substituted or unsubstituted aryl group having 6 to 13 carbon atoms, and R.sup.1 to R.sup.7 separately represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 13 carbon atoms. ##STR00001##

Organic light emitting devices are described wherein the emissive layer comprises a host material containing an emissive molecule, which molecule is adapted to luminesce when a voltage is applied across the heterostructure, and the emissive molecule is selected from the group of phosphorescent organometallic complexes, including cyclometallated platinum, iridium and osmium complexes. The organic light emitting devices optionally contain an exciton blocking layer. Furthermore, improved electroluminescent efficiency in organic light emitting devices is obtained with an emitter layer comprising organometallic complexes of transition metals of formula L.sub.2MX, wherein L and X are distinct bidentate ligands. Compounds of this formula can be synthesized more facilely than in previous approaches and synthetic options allow insertion of fluorescent molecules into a phosphorescent complex, ligands to fine tune the color of emission, and ligands to trap carriers.

A carbazole derivative represented by the general formula (1) is provided. In the formula, Ar.sup.1 represents a substituted or unsubstituted aryl group having 6 to 10 carbon atoms which form a ring; α and β independently represent a substituted or unsubstituted arylene group having 6 to 12 carbon atoms which form a ring; R.sup.1 represents an alkyl group having 1 to 4 carbon atoms or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms which form a ring; and R.sup.11 to R.sup.17 and R.sup.21 to R.sup.28 independently represent hydrogen, an alkyl group having 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms which form a ring. ##STR00001##

An organic electroluminescence device having a layer of an organic light emitting medium which comprises (A) a specific arylamine compound and (B) at least one compound selected from specific anthracene derivatives, spirofluorene derivatives, compounds having condensed rings and metal complex compounds and is disposed between a pair of electrodes and an organic light emitting medium comprising the above components (A) and (B) are provided. The organic electroluminescence device exhibits a high purity of color, has excellent heat resistance and a long life and efficiently emits bluish to yellowish light. The organic light emitting medium can be advantageously used for the organic electroluminescence device.