Light emitting device

Abstract

It is an object of the invention to provide a light emitting device which can display a superior image in which luminescent color from each light emitting layer is beautifully displayed and power consumption is lowered in a light emitting element in which light emitting layers are stacked. One feature of the invention is that, in a light emitting element which comprises light emitting layers stacked between electrodes, each distance between each light emitting layer and an electrode is approximately oddly multiplied ¼ wavelength by controlling a thickness of a layer provided therebetween to enhance luminous output efficiency. Another feature of the invention is that a drive voltage is lowered using a high conductive material for the layer compared with a conventional element.

1 . A light emitting device comprising: 
 a plurality of light emitting layers which are stacked between a first electrode and a second electrode; and    a layer comprising an organic compound and a metal oxide between one of the plurality of light emitting layers and the first electrode,    wherein at least one distance from one of the plurality of light emitting layers to the first electrode is in a range of oddly multiplied ¼ wavelength ±10%.    
     
     
         2 . A light emitting device comprising: 
 a plurality of light emitting layers each emitting a color different from each other which are stacked between a first electrode and a second electrode; and    a layer comprising an organic compound and a metal oxide between one of the plurality of light emitting layers and the first electrode,    wherein at least one distance from one of the plurality of light emitting layers to the first electrode is in a range of oddly multiplied ¼ wavelength ±10%.    
     
     
         3 . A light emitting device comprising: 
 a plurality of light emitting layers emitting a color which are stacked between a first electrode and a second electrode; and    a layer comprising an organic compound and a metal oxide between one of the plurality of light emitting layers and the first electrode,    wherein at least one distance from one of the plurality of light emitting layers to the first electrode is in a range of oddly multiplied ¼ wavelength ±10%.    
     
     
         4 . A light emitting device comprising: 
 a stacked layer type light emitting element in which a plurality of light emitting layers are stacked between a first electrode and a second electrode; and    a single-layer type light emitting element having one light emitting layer between a third electrode and a fourth electrode,    wherein at least one distance from one of the plurality of light emitting layers to the first electrode is in a range of oddly multiplied ¼ wavelength ±10%.    
     
     
         5 . A light emitting device comprising: 
 a stacked layer type light emitting element in which a plurality of light emitting layers emitting a color are stacked between a first electrode and a second electrode; and    a single-layer type light emitting element having one light emitting layer between a third electrode and a fourth electrode,    wherein at least one distance from one of the plurality of light emitting layers to the first electrode is in a range of oddly multiplied  1 / 4  wavelength + 10 %.    
     
     
         6 . The light emitting device according to claims  4  or  5 , 
 wherein a distance from the light emitting layer to the third electrode is in a range of oddly multiplied ¼ wavelength ±10%.    
     
     
         7 . The light emitting device according to any one of  claims 1  to  5 , 
 wherein the metal oxide is a vanadium oxide, a molybdenum oxide, a niobium oxide, a rhenium oxide, a tungsten oxide, a ruthenium oxide, a titanium oxide, a chromium oxide, a zirconium oxide, a hafnium oxide, or a tantalum oxide.    
     
     
         8 . The light emitting device according to any one of  claims 1  to  5 , 
 wherein the organic compound is a hole transporting material.    
     
     
         9 . The light emitting device according to any one of  claims 1  to  5 , 
 wherein the metal oxide exhibits an electron accepting property to the organic compound.    
     
     
         10 . The light emitting device according to any one of  claims 1  to  5 , 
 wherein each of the plurality of light emitting layers exhibits red, blue or green.