Light-emitting element
First Claim
1. A light-emitting element comprising:
- a first electrode;
a first EL layer over the first electrode;
a charge-generation layer over the first EL layer;
a second EL layer over the charge-generation layer, anda second electrode over the second EL layer,wherein at least one of the first EL layer and the second EL layer comprises;
a first layer containing a first organic compound;
a second layer containing a second organic compound; and
a light-emitting layer interposed between the first layer and the second layer, the light-emitting layer containing a phosphorescent compound, the first organic compound, and the second organic compound, andwherein the first organic compound and the second organic compound are selected so that an exciplex is formed therebetween, andwherein the phosphorescent compound is an organometallic complex whose absorption originating from a triplet metal-to-ligand charge transfer transition overlaps with an emission of the exciplex.
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Abstract
A light-emitting element having extremely high efficiency of approximately 25% is provided. The light-emitting element includes a light-emitting layer which contains a phosphorescent guest, an n-type host, and a p-type host, where the light-emitting layer is interposed between an n-type layer including the n-type host and a p-type layer including the p-type host, and where the n-type host and the p-type host are able to form an exciplex in the light-emitting layer. The light-emitting element exhibits an extremely high emission efficiency (power efficiency of 74.3 lm/W, external quantum efficiency of 24.5%, energy efficiency of 19.3%) at a low driving voltage (2.6 V) at which luminance of 1200 cd/m2 is attainable.
81 Citations
15 Claims
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1. A light-emitting element comprising:
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a first electrode; a first EL layer over the first electrode; a charge-generation layer over the first EL layer; a second EL layer over the charge-generation layer, and a second electrode over the second EL layer, wherein at least one of the first EL layer and the second EL layer comprises; a first layer containing a first organic compound; a second layer containing a second organic compound; and a light-emitting layer interposed between the first layer and the second layer, the light-emitting layer containing a phosphorescent compound, the first organic compound, and the second organic compound, and wherein the first organic compound and the second organic compound are selected so that an exciplex is formed therebetween, and wherein the phosphorescent compound is an organometallic complex whose absorption originating from a triplet metal-to-ligand charge transfer transition overlaps with an emission of the exciplex. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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Specification