Light-Emitting Element, Light-Emitting Device, and Lighting Device

Abstract

Disclosed is a light-emitting element with a microcavity structure which is capable of amplifying a plurality of wavelengths to give emission of a desired color. The light-emitting element includes a pair of electrodes and an EL layer having a light-emitting substance interposed between the pair of electrodes. One of the pair of electrodes gives a reflective surface and the other electrode gives a semi-reflective surface. The light-emitting element is arranged so that the emission of the light-emitting substance covers at least two wavelengths λ and an optical path length L between the reflective surface and the semi-reflective surface satisfies an equation L=nλ/2 where n is an integer greater than or equal to 2.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . A light-emitting element comprising:
 a first substrate;   a first metal electrode over the first substrate;   a conductive metal oxide layer over and in contact with the first metal electrode, the conductive metal oxide layer comprising indium and tin;   a first light-emitting layer over the conductive metal oxide layer;   a second light-emitting layer over the first light-emitting layer; and   a second metal electrode over the second light-emitting layer,   wherein the first light-emitting layer and the second light-emitting layer are provided between the first metal electrode and the second metal electrode,   wherein the first metal electrode is configured to function as an anode,   wherein the first light-emitting layer and the second light-emitting layer are different in emission color from each other, and   wherein an optical path length L between a bottom surface of the conductive metal oxide layer and a bottom surface of the second metal electrode is between 650 nm and 1500 nm.   
     
     
         3 . The light-emitting element according to  claim 2 , further comprising a third light-emitting layer between the first light-emitting layer and the second light-emitting layer. 
     
     
         4 . The light-emitting element according to  claim 3 , wherein the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are different in emission color from each other. 
     
     
         5 . The light-emitting element according to  claim 3 , wherein the third light-emitting layer has an emission peak at a wavelength of 495 nm to 560 nm. 
     
     
         6 . The light-emitting element according to  claim 2 , further comprising a charge generation layer between the first light-emitting layer and the second light-emitting layer. 
     
     
         7 . The light-emitting element according to  claim 2 ,
 wherein the second metal electrode comprises at least one of silver and magnesium.   
     
     
         8 . The light-emitting element according to  claim 2 ,
 wherein the first light-emitting layer and the second light-emitting layer overlap with the first metal electrode.   
     
     
         9 . The light-emitting element according to  claim 2 , further comprising a layer between the conductive metal oxide layer and the first light-emitting layer,
 wherein the layer comprises a material having a hole-transport property.   
     
     
         10 . The light-emitting element according to  claim 2 , wherein the optical path length is 1200 nm to 1400 nm. 
     
     
         11 . The light-emitting element according to  claim 2 , further comprising a second substrate over the second metal electrode,
 wherein a space between the second metal electrode and the second substrate is filled with a solid.   
     
     
         12 . A lighting device comprising the light-emitting element according to  claim 2 . 
     
     
         13 . A light-emitting element comprising:
 a first substrate;   a first metal electrode over the first substrate;   a conductive metal oxide layer over and in contact with the first metal electrode, the conductive metal oxide layer comprising indium and tin;   a first light-emitting layer over the conductive metal oxide layer;   a second light-emitting layer over the first light-emitting layer; and   a second metal electrode over the second light-emitting layer,   wherein the first light-emitting layer and the second light-emitting layer are provided between the first metal electrode and the second metal electrode,   wherein the first metal electrode is configured to function as an anode,   wherein the first light-emitting layer and the second light-emitting layer are different in emission color from each other,   wherein the first light-emitting layer has an emission peak at a wavelength of 430 nm to 495 nm, and   wherein an optical path length L between a bottom surface of the conductive metal oxide layer and a bottom surface of the second metal electrode is between 650 nm and 1500 nm.   
     
     
         14 . The light-emitting element according to  claim 13 , further comprising a third light-emitting layer between the first light-emitting layer and the second light-emitting layer. 
     
     
         15 . The light-emitting element according to  claim 14 , wherein the first light-emitting layer, the second light-emitting layer, and the third light-emitting layer are different in emission color from each other. 
     
     
         16 . The light-emitting element according to  claim 14 , wherein the third light-emitting layer has an emission peak at a wavelength of 495 nm to 560 nm. 
     
     
         17 . The light-emitting element according to  claim 13 , further comprising a charge generation layer between the first light-emitting layer and the second light-emitting layer. 
     
     
         18 . The light-emitting element according to  claim 13 ,
 wherein the second metal electrode comprises at least one of silver and magnesium.   
     
     
         19 . The light-emitting element according to  claim 13 ,
 wherein the first light-emitting layer and the second light-emitting layer overlap with the first metal electrode.   
     
     
         20 . The light-emitting element according to  claim 13 , further comprising a layer between the conductive metal oxide layer and the first light-emitting layer,
 wherein the layer comprises a material having a hole-transport property.   
     
     
         21 . The light-emitting element according to  claim 13 , wherein the optical path length is 1200 nm to 1400 nm. 
     
     
         22 . The light-emitting element according to  claim 13 , further comprising a second substrate over the second metal electrode,
 wherein a space between the second metal electrode and the second substrate is filled with a solid.   
     
     
         23 . A lighting device comprising the light-emitting element according to  claim 13 .