Phosphorescent oled with mixed electron transport materials

Abstract

An OLED device comprises, in sequence, an anode, a light-emitting layer that comprises a phosphorescent light-emitting organometallic compound, a hole-blocking layer, and a cathode, and between the hole-blocking layer and the cathode, a further layer containing: a) a first compound that has the lowest LUMO value of the compounds in the layer, the amount being greater than or equal to 10% by volume and less than 100% by volume of the layer; b) at least one second compound that is a low voltage electron transport material, exhibiting a higher LUMO value than the first compound, the total amount of said compound(s) being less than or equal to 90% by volume and more than 0% by volume of the layer. Such a device provides improved drive voltage.

1 . An OLED device comprising, in sequence, an anode, a light-emitting layer that comprises a phosphorescent light-emitting organometallic compound, a hole-blocking layer, and a cathode, and between the hole-blocking layer and the cathode, a further layer containing: 
 a) a first compound that has the lowest LUMO value of the compounds in the layer, the amount being greater than or equal to 10% by volume and less than 100% by volume of the layer;    b) at least one second compound that is a low voltage electron transport material, exhibiting a higher LUMO value than the first compound, the total amount of said compound(s) being less than or equal to 90% by volume and more than 0% by volume of the layer.    
   
   
       2 . The OLED device of  claim 1  wherein said further layer is adjacent to an electron-injecting layer, which is adjacent to the cathode.  
   
   
       3 . The OLED device of  claim 1  wherein said further layer is adjacent to the cathode.  
   
   
       4 . The OLED device of  claim 1  comprising a first compound and two second compounds.  
   
   
       5 . The OLED device of  claim 1  wherein said further layer is a non-emitting layer.  
   
   
       6 . The OLED device of  claim 1  wherein the first compound is present in an amount of 40% to 90% by volume.  
   
   
       7 . The OLED device of  claim 1  wherein the first compound is present in an amount of 50% to 80% by volume.  
   
   
       8 . The OLED device of  claim 1  wherein the first compound has a LUMO value of −2.30 eV or lower.  
   
   
       9 . The OLED device of  claim 1  wherein the first compound has a LUMO value of −2.50 eV or lower.  
   
   
       10 . The OLED device of  claim 1  wherein the first compound has a LUMO value of −2.70 eV or lower.  
   
   
       11 . The OLED device of  claim 1  wherein the first compound is a polycyclic aromatic hydrocarbon.  
   
   
       12 . The OLED device of  claim 1  wherein the first compound is represented by Formula V:  
     
       
         
         
             
             
         
       
     
     wherein: 
 R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , R 8 , R 9 , R 10 , R 11 , and R 12  are independently selected as hydrogen or substituents;  
 provided that any of the indicated substituents may join to form further fused rings.  
 
   
   
       13 . The OLED device of  claim 12  wherein R 1 , R 3 , R 4 , R 7 , R 9 , R 10 , represent hydrogen; R 2  and R 8  represent hydrogen or independently selected alkyl groups; R 5 , R 6 , R 11 , and R 12  represent independently selected aryl groups.  
   
   
       14 . The OLED device of  claim 1  wherein the first compound is represented by Formula VI:  
     
       
         
         
             
             
         
       
     
     wherein: 
 R 13 , R 14 , R 15  and R 16  represent hydrogen or one or more substituents selected from the following groups:  
 Group 1: hydrogen, alkyl and alkoxy groups typically having from 1 to 24 carbon atoms;  
 Group 2: a ring group, typically having from 6 to 20 carbon atoms;  
 Group 3: the atoms necessary to complete a carbocyclic fused ring group such as naphthyl, anthracenyl, pyrenyl, and perylenyl groups, typically having from 6 to 30 carbon atoms;  
 Group 4: the atoms necessary to complete a heterocyclic fused ring group such as furyl, thienyl, pyridyl, and quinolinyl groups, typically having from 5 to 24 carbon atoms;  
 Group 5: an alkoxylamino, alkylamino, and arylamino group typically having from 1 to 24 carbon atoms; and  
 Group 6: fluorine, chlorine, bromine and cyano radicals.  
 
   
   
       15 . The OLED device of  claim 1  wherein the second compound as a test voltage no more than 50% higher than Alq.  
   
   
       16 . The OLED device of  claim 1  wherein the second compound has a test voltage no more than 25% higher than Alq.  
   
   
       17 . The OLED device of  claim 1  wherein the second compound is represented by Formula I:  
     
       
         
         
             
             
         
       
     
     wherein 
 M represents a metal;  
 n is an integer of from 1 to 4; and  
 Z independently in each occurrence represents the atoms completing a nucleus having at least two fused aromatic rings.  
 
   
   
       18 . The OLED device of  claim 1  wherein the second compound is represented by Formula II:  
       (R S -Q) 2 -M-O-L   Formula II  
     wherein 
 M is a metal or non-metal;  
 Q in each occurrence represents a substituted 8-quinolinolato ligand;  
 R S  represents an 8-quinolinolato ring substituent chosen to block sterically the attachment of more than two substituted 8-quinolinolato ligands to M; and  
 L is a phenyl or aromatic fused ring moiety, which can be substituted with hydrocarbon groups such that L has from 6 to 24 carbon atoms.  
 
   
   
       19 . The OLED device of  claim 1  wherein the second compound is represented by Formula VII:  
     
       
         
         
             
             
         
       
     
     wherein 
 R 17 , R 18 , R 19 , R 20 , R 21 , R 22 , R 23  and R 24  are hydrogen or substituents; and  
 provided that any of the indicated substituents may join to form further fused rings.  
 
   
   
       20 . The OLED device of  claim 1  wherein the first compound is a polycyclic aromatic hydrocarbon and the second compound is an organometallic compound.  
   
   
       21 . The OLED device of  claim 1  wherein the first compound is a polycyclic aromatic hydrocarbon having at least 3 fused rings and the second compound is tris(8-quinolinolato)aluminum (III) (Alq).  
   
   
       22 . The OLED device of  claim 1  wherein the first and second compounds are selected from metal and non-metal chelated oxinoids, anthracenes, bipyridyls, butadienes, imidazoles, phenanthrenes, phenanthrolines, styrylarylenes, benzazoles, buckministerfullerene-C 60  (also known as buckyball or fullerene-C 60 ), tetracenes, xanthenes, perylenes, coumarins, rhodamines, quinacridones, dicyanomethylenepyrans, thiopyrans, polymethines, pyrylliums, fluoranthenes, periflanthrenes, silacyclopentadienes or siloles, thiapyrylliums, triazines, carbostyryls, metal and non-metal chelated bis(azinyl)amines, metal and non-metal chelated bis(azinyl)methenes.  
   
   
       23 . The OLED device of  claim 1  wherein the phosphorescent light-emitting material comprises an organometallic complex comprising a metal and at least one ligand, wherein the metal is selected from the group consisting of Ir, Rh, Ru, Pt, and Pd.  
   
   
       24 . The device of  claim 23  wherein the metal is Ir.  
   
   
       25 . The device of  claim 23  wherein at least one ligand comprises a 2-phenylpyridine group, a 1-phenylisoquinoline group, a 3-phenylisoquinoline group, a 1-phenylimidazo[1,2-a]pyridine, a thiazole ring group that is fused with at least one aromatic ring group, or an oxazole ring group that is fused with at least one aromatic ring group.  
   
   
       26 . The device of  claim 1  wherein the hole-blocking layer comprises bathocuproine (BCP) or bis(2-methyl-8-quinolinolato)(4-phenylphenolato)Aluminum(III) (Balq).  
   
   
       27 . The OLED device of  claim 1  wherein at least one additional compound comprising a metallic material based on a metal having a work function less than 4.2 eV, is present in said further layer.  
   
   
       28 . The device of  claim 27  wherein the metallic material comprises Li metal.  
   
   
       29 . The device of  claim 27  wherein the metallic material is present at a level of 1 to 5% of the layer.  
   
   
       30 . The device of  claim 1  wherein the first compound is selected from the group consisting of:  
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
   
   
       31 . The device of  claim 1  wherein the second compound is selected from the group consisting of:  
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
   
   
       32 . The device of  claim 1  wherein the first compound is selected from the group consisting of:  
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     and the second compound is selected from the group consisting of: