Iridium complex, light-emitting element, display device, electronic device, and lighting device

Abstract

Provided is a light-emitting element with high emission efficiency. The light-emitting element includes a first organic compound, a second organic compound, and a guest material. The LUMO level of the first organic compound is lower than that of the second organic compound, and the HOMO level of the first organic compound is lower than that of the second organic compound. The LUMO level of a guest material is higher than that of the first organic compound, and the HOMO level of the guest material is lower than that of the second organic compound. The guest material has a function of converting triplet excitation energy into light emission. The first organic compound and the second organic compound form an exciplex.

1 . A light-emitting element comprising:
 a first organic compound;   a second organic compound; and   a guest material,   wherein a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound,   wherein a HOMO level of the first organic compound is lower than a HOMO level of the second organic compound,   wherein a LUMO level of the guest material is higher than the LUMO level of the first organic compound,   wherein a HOMO level of the guest material is lower than the HOMO level of the second organic compound,   wherein the guest material is configured to convert triplet excitation energy into light emission, and   wherein the first organic compound and the second organic compound form an exciplex.   
     
     
         2 . The light-emitting element according to  claim 1 ,
 wherein an energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound is larger than or equal to transition energy obtained from an absorption edge of the guest material.   
     
     
         3 . The light-emitting element according to  claim 1 ,
 wherein an energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound is larger than or equal to light emission energy of the guest material.   
     
     
         4 . The light-emitting element according to  claim 1 ,
 wherein an energy difference between the LUMO level of the guest material and the HOMO level of the guest material is larger than a transition energy obtained from an absorption edge of the guest material by 0.4 eV or more.   
     
     
         5 . The light-emitting element according to  claim 1 ,
 wherein an energy difference between the LUMO level of the guest material and the HOMO level of the guest material is larger than the light emission energy of the guest material by 0.4 eV or more.   
     
     
         6 . The light-emitting element according to  claim 1 ,
 wherein an emission spectrum of the guest material has at least one peak in a wavelength region of greater than or equal to 400 nm and less than 505 nm.   
     
     
         7 . The light-emitting element according to  claim 1 ,
 wherein the exciplex is configured to transfer excitation energy to the guest material.   
     
     
         8 . The light-emitting element according to  claim 1 ,
 wherein an emission spectrum of the exciplex has a region overlapping an absorption band on the lowest energy side of the guest material.   
     
     
         9 . The light-emitting element according to  claim 1 ,
 wherein the guest material includes iridium.   
     
     
         10 . The light-emitting element according to  claim 9 ,
 wherein the guest material includes a ligand coordinated to the iridium, and   wherein the ligand includes a nitrogen-containing five-membered heterocyclic skeleton.   
     
     
         11 . The light-emitting element according to  claim 10 ,
 wherein the ligand includes a triazole skeleton or an imidazole skeleton.   
     
     
         12 . The light-emitting element according to  claim 1 ,
 wherein the first organic compound is configured to transport an electron, and   wherein the second organic compound is configured to transport a hole.   
     
     
         13 . The light-emitting element according to  claim 1 ,
 wherein the first organic compound includes a t-electron deficient heteroaromatic ring skeleton, and   wherein the second organic compound includes at least one of a t-electron rich heteroaromatic ring skeleton and an aromatic amine skeleton.   
     
     
         14 . An iridium complex represented by General Formula (G1): 
       
         
           
           
               
               
           
         
         wherein Ar 1  represents a substituted or unsubstituted first aryl group having 6 to 13 carbon atoms, 
         wherein Ar 2  represents a substituted or unsubstituted second aryl group having 6 to 13 carbon atoms, 
         wherein each of Q 1  and Q 2  independently represents N or C—R, 
         wherein R included in the C—R represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted third aryl group having 6 to 13 carbon atoms, 
         wherein at least one of Q 1  and Q 2  represents the C—R, and 
         wherein at least one of the first aryl group to the third aryl group comprises a cyano group. 
       
     
     
         15 . An iridium complex represented by General Formula (G2): 
       
         
           
           
               
               
           
         
         wherein Ar 1  represents a substituted or unsubstituted first aryl group having 6 to 13 carbon atoms, 
         wherein each of R 1  to R 4  independently represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted fourth aryl group having 6 to 13 carbon atoms, and a cyano group, 
         wherein each of Q 1  and Q 2  independently represents N or C—R, 
         wherein R included in the C—R represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted third aryl group having 6 to 13 carbon atoms, 
         wherein at least one of Q 1  and Q 2  represents the C—R, and 
         wherein at least one of the first aryl group, the third aryl group, the fourth aryl group, and the R 1  to the R 4  comprises a cyano group. 
       
     
     
         16 . The iridium complex according to  claim 15 , wherein the iridium complex is represented by General Formula (G3): 
       
         
           
           
               
               
           
         
         wherein R 5  represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted third aryl group having 6 to 13 carbon atoms. 
       
     
     
         17 . The iridium complex according to  claim 15 , wherein the iridium complex is represented by General Formula (G4): 
       
         
           
           
               
               
           
         
         wherein each of R 5  and R 6  independently represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted third aryl group having 6 to 13 carbon atoms. 
       
     
     
         18 . The iridium complex according to  claim 15 ,
 wherein Ar 1  represents a substituted or unsubstituted phenyl group, and   wherein the phenyl group comprises a cyano group.   
     
     
         19 . The iridium complex according to  claim 15 , wherein the iridium complex is represented by General Formula (G5): 
       
         
           
           
               
               
           
         
         wherein R 5  represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 13 carbon atoms, 
         wherein each of R 7  and R 11  represents an alkyl group having 1 to 6 carbon atoms, 
         wherein R 7  and R 11  have the same structure, 
         wherein each of R 8  to R 10  independently represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted phenyl group, and a cyano group, and 
         wherein at least one of the R 8  to the R 10  comprises a cyano group. 
       
     
     
         20 . The iridium complex according to  claim 15 , wherein the iridium complex is represented by General Formula (G6): 
       
         
           
           
               
               
           
         
         wherein each of R 5  and R 6  independently represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 13 carbon atoms, 
         wherein each of R 7  and R 11  represents an alkyl group having 1 to 6 carbon atoms, 
         wherein R 7  and R 11  have the same structure, 
         wherein each of R 8  to R 10  independently represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted phenyl group, and a cyano group, and 
         wherein at least one of the R 8  to the R 10  comprises a cyano group. 
       
     
     
         21 . The iridium complex according to  claim 15 , wherein the iridium complex is represented by General Formula (G7): 
       
         
           
           
               
               
           
         
         wherein R 6  represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted third aryl group having 6 to 13 carbon atoms. 
       
     
     
         22 . The iridium complex according to  claim 15 , wherein the iridium complex is represented by General Formula (G8): 
       
         
           
           
               
               
           
         
         wherein R 6  represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted aryl group having 6 to 13 carbon atoms, 
         wherein each of R 7  and R 11  represents an alkyl group having 1 to 6 carbon atoms, 
         wherein R 7  and R 11  have the same structure, 
         wherein each of R 8  to R 10  independently represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 6 carbon atoms, a substituted or unsubstituted phenyl group, and a cyano group, and 
         wherein at least one of the R 8  to the R 10  comprises a cyano group. 
       
     
     
         23 . A light-emitting element comprising the iridium complex according to  claim 15 . 
     
     
         24 . A light-emitting element comprising:
 an iridium complex;   a first organic compound; and   a second organic compound;   wherein a LUMO level of the first organic compound is lower than a LUMO level of the second organic compound,   wherein a HOMO level of the first organic compound is lower than a HOMO level of the second organic compound,   wherein a LUMO level of the iridium complex is higher than the LUMO level of the first organic compound,   wherein a HOMO level of the iridium complex is lower than the HOMO level of the second organic compound,   wherein the first organic compound and the second organic compound form an exciplex,   wherein the iridium complex is represented by General Formula (G1):   
       
         
           
           
               
               
           
         
         wherein Ar 1  represents a substituted or unsubstituted first aryl group having 6 to 13 carbon atoms, 
         wherein Ar 2  represents a substituted or unsubstituted second aryl group having 6 to 13 carbon atoms, 
         wherein each of Q 1  and Q 2  independently represents N or C—R, 
         wherein R included in the C—R represents any of hydrogen, an alkyl group having 1 to 6 carbon atoms, a haloalkyl group having 1 to 6 carbon atoms, and a substituted or unsubstituted third aryl group having 6 to 13 carbon atoms, 
         wherein at least one of Q 1  and Q 2  represents the C—R, and 
         wherein at least one of the first aryl group to the third aryl group comprises a cyano group. 
       
     
     
         25 . The light-emitting element according to  claim 24 ,
 wherein an energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound is larger than or equal to transition energy obtained from an absorption edge of the iridium complex.   
     
     
         26 . The light-emitting element according to  claim 24 ,
 wherein an energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound is larger than or equal to light emission energy of the iridium complex.   
     
     
         27 . The light-emitting element according to  claim 24 ,
 wherein the exciplex is configured to transfer excitation energy to the iridium complex.   
     
     
         28 . The light-emitting element according to  claim 24   wherein an emission spectrum of the exciplex has a region overlapping an absorption band on the lowest energy side of the iridium complex.   
     
     
         29 . The light-emitting element according to  claim 24 ,
 wherein the first organic compound is configured to transport an electron, and   wherein the second organic compound is configured to transport a hole.   
     
     
         30 . The light-emitting element according to  claim 24 ,
 wherein the first organic compound includes a π-electron deficient heteroaromatic ring skeleton, and   wherein the second organic compound includes at least one of a π-electron rich heteroaromatic ring skeleton and an aromatic amine skeleton.   
     
     
         31 . A display device comprising:
 the light-emitting element according to  claim 24 ; and   at least one of a color filter and a transistor.   
     
     
         32 . An electronic device comprising:
 the display device according to  claim 31 ; and   at least one of a housing and a touch sensor.   
     
     
         33 . A lighting device comprising:
 the light-emitting element according to  claim 24 ; and   at least one of a housing and a touch sensor.