Stable Blue Phosphorescent Organic Light Emitting Devices

Abstract

Novel combination of materials and device architectures for organic light emitting devices is provided. An organic light emitting device, is provided, having an anode, a cathode, and an emissive layer disposed between the anode and the cathode. The emissive layer includes a host and a phosphorescent emissive dopant having a peak emissive wavelength less than 500 nm, and a radiative phosphorescent lifetime less than 1 microsecond. Preferably, the phosphorescent emissive dopant includes a ligand having a carbazole group.

What is claimed is: 
     
         1 . An organic light emitting device, comprising:
 an anode,   a cathode,   an emissive layer disposed between the anode and the cathode, the emissive, layer further comprising a host and a phosphorescent emissive dopant having a peak emissive wavelength less than 500 nm, and a radiative phosphorescent lifetime less than 1 microsecond.   
     
     
         2 . The device of  claim 1 , wherein the phosphorescent emissive dopant includes a carbazole group. 
     
     
         3 . The device of  claim 2 , wherein the phosphorescent emissive dopant comprises a structure selected from the group consisting of: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         where R 1 -R 4  are independently selected from the group consisting of: H, aryl and alkyl, where the aryl and alkyl may be further substituted, 
         Ar is an aryl that may be further substituted, and 
         M is a metal having an atomic weight greater than 40. 
       
     
     
         4 . The device of  claim 3 , wherein M is iridium. 
     
     
         5 . The device of  claim 3 , wherein additional ligands are coordinated to the metal M. 
     
     
         6 . The device of  claim 4 , wherein three identical ligands are coordinated to the metal M. 
     
     
         7 . The device of  claim 1 , wherein the device has a graded interface. 
     
     
         8 . An organic light emitting device, comprising:
 an anode,   a cathode,
 an emissive layer disposed between the anode and the cathode, the emissive layer further comprising: 
 an phosphorescent emissive dopant including a steric bulky spacer group having a size of at least 10 angstroms. 
   
     
     
         9 . The device of  claim 8 , wherein the phosphorescent emissive dopant has a peak emissive wavelength less than 500 nm. 
     
     
         10 . The device of  claim 8 , wherein the steric bulky spacer group is selected from the group consisting of dendrimers and alkane chains.