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 . (canceled) 
     
     
         2 . A light-emitting device 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,   wherein the first organic compound and the second organic compound form an exciplex, and   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 a transition energy obtained from an absorption edge of the guest material.   
     
     
         3 . A light-emitting device 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,   wherein the first organic compound and the second organic compound form an exciplex, and   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.   
     
     
         4 . A light-emitting device 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,   wherein the first organic compound and the second organic compound form an exciplex, and   wherein an energy difference between the LUMO level of the guest material and the HOMO level of the guest material is larger than an energy difference between the LUMO level of the first organic compound and the HOMO level of the second organic compound.   
     
     
         5 . The light-emitting device according to  claim 2 , 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. 
     
     
         6 . The light-emitting device according to  claim 3 , 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 device according to  claim 4 , 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. 
     
     
         8 . The light-emitting device according to  claim 2 , wherein the HOMO level of the guest material is higher than the HOMO level of the first organic compound. 
     
     
         9 . The light-emitting device according to  claim 3 , wherein the HOMO level of the guest material is higher than the HOMO level of the first organic compound. 
     
     
         10 . The light-emitting device according to  claim 4 , wherein the HOMO level of the guest material is higher than the HOMO level of the first organic compound. 
     
     
         11 . The light-emitting device according to  claim 2 ,
 wherein the guest material comprises a ligand coordinated to the iridium, and   wherein the ligand comprises a nitrogen-containing five-membered heterocyclic skeleton and a cyano group.   
     
     
         12 . The light-emitting device according to  claim 11 , wherein the nitrogen-containing five-membered heterocyclic skeleton is a triazole skeleton. 
     
     
         13 . The light-emitting device according to  claim 3 ,
 wherein the guest material comprises a ligand coordinated to the iridium, and   wherein the ligand comprises a nitrogen-containing five-membered heterocyclic skeleton and a cyano group.   
     
     
         14 . The light-emitting device according to  claim 13 , wherein the nitrogen-containing five-membered heterocyclic skeleton is a triazole skeleton. 
     
     
         15 . The light-emitting device according to  claim 4 ,
 wherein the guest material comprises a ligand coordinated to the iridium, and   wherein the ligand comprises a nitrogen-containing five-membered heterocyclic skeleton and a cyano group.   
     
     
         16 . The light-emitting device according to  claim 15 , wherein the nitrogen-containing five-membered heterocyclic skeleton is a triazole skeleton. 
     
     
         17 . The light-emitting device according to  claim 2 ,
 wherein the first organic compound comprises 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.   
     
     
         18 . The light-emitting device according to  claim 3 ,
 wherein the first organic compound comprises 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.   
     
     
         19 . The light-emitting device according to  claim 4 ,
 wherein the first organic compound comprises 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.