Host materials for electroluminescent devices

1. A composition comprising:

a first compound capable of functioning as a host in an emissive layer of an organic light emitting device at room temperature; and

a second compound comprising a ligand L A of Formula III

 wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclic ring;

wherein R represents two adjacent substituents that are joined together to form a ring that is fused to ring B, and R has a structure of Formula IV

 or Formula V

wherein the wavy lines indicate bonds to ring B;

wherein R A represents two substitutions to a maximum possible number of substitutions on a ring carbon the substituents are attached thereto;

wherein R B represents no substitution to a maximum possible number of substitutions on a ring carbon the substituents are attached thereto;

wherein R A and R B are each independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein two adjacent R A are joined to form a ring;

wherein A 1 , A 2 , A 3 , and A 4 are each independently CR C or N;

wherein Z 1 , Z 2 , Z 3 , and Z 4 are each independently C or N;

wherein at least two adjacent of Z 1 , Z 2 , Z 3 , and Z 4 are C and fuse to R;

wherein when R is Formula V, at least one of A 1 , A 2 , A 3 , A 4 , Z 1 , Z 2 , Z 3 , and Z 4 is N;

wherein Y is selected from the group consisting of BR′, NR′, PR′, O, S, Se, C—O, S—O, SO 2 , CR′R″, SiR′R″, and GeR′R″;

wherein R C , R 13 , R 14 , R′, and R″ are each independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein any two adjacent substituents are optionally joined to form into a ring;

wherein the ligand L A is coordinated to a metal M;

wherein M is Ir or Pt;

wherein the ligand L A is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and

wherein M is optionally coordinated to other ligands; and

wherein at least one of the following two conditions is true:

(i) the highest occupied molecular orbital of the first compound has an energy level equal to or less than −5.1 eV; and

(ii) the difference in energy between the highest occupied molecular orbital of the first compound and the highest occupied molecular orbital of the second compound is less than 0.3 eV.

2. The composition of claim 1 , wherein at least one of R 13 and R 14 comprises a chemical group selected from the group consisting of alkyl, cycloalkyl, partially fluorinated alkyl, partially fluorinated cycloalkyl, and combinations thereof.

3. The composition of claim 1 , wherein R 13 and R 14 are joined to form a ring.

4. The composition of claim 1 , wherein R 13 and R 14 are not hydrogen.

5. The composition of claim 1 , wherein one of R 13 and R 14 comprises a ring structure and the other of R 13 and R 14 comprises alkyl.

6. The composition of claim 5 , wherein the ring structure can be cycloalkyl, heterocycloalkyl, cycloalkenyl, aryl, heteroaryl, and combinations thereof.

7. The compound of claim 1 , wherein two adjacent R C are joined to form a ring.

8. The composition of claim 1 , wherein R A is a substituent selected from the group consisting of fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof;

wherein R B is a hydrogen or a substituent selected from the group consisting of deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof; and

R C , R 13 , R 14 , R′, and R″ are each independently selected from the group consisting of hydrogen, deuterium, fluorine, alkyl, cycloalkyl, heteroalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, aryl, heteroaryl, nitrile, isonitrile, sulfanyl, and combinations thereof.

9. The composition of claim 1 , wherein the second compound has a formula of M(L A ) 2 L 2 , wherein L 2 is an unsubstituted or substituted acetylacetonate ligand.

10. The composition of claim 1 , wherein the second compound emits light with a peak emission wavelength equal to or greater than 600 nm, wherein at least one of the following two conditions is true:

( 111 the highest occupied molecular orbital of the second compound has an energy level equal to or less than −5.3 eV; and

(iv) the difference in energy between the highest occupied molecular orbital of the first compound and the highest occupied molecular orbital of the second compound is less than 0.1 eV.

11. The composition of claim 1 , wherein the second compound is selected from the group consisting of:

12. The composition of claim 1 , wherein the first compound is a compound of Formula I

wherein ring A is fused to a structure of Formula II:

wherein each Ar 1 , Ar 2 , and Ar 3 is independently a substituted or unsubstituted six-membered aromatic ring; and

the second compound is capable of functioning as a phosphorescent emitter at room temperature; wherein the second compound emits light with a peak emission wavelength equal to or greater than 550 nm;

wherein at least one of the following two conditions is true:

(i) the highest occupied molecular orbital of the second compound has an energy level equal to or less than −5.1 eV; and

(ii) the difference in energy between the highest occupied molecular orbital of the first compound and the highest occupied molecular orbital of the second compound is less than 0.3 eV.

13. The composition of claim 12 , wherein Ar 1 , Ar 2 , and Ar 3 are phenyl rings.

14. The composition of claim 12 , wherein at least one of Ar 1 , Ar 2 , and Ar 3 comprises a fused carbocyclic or heterocyclic ring.

15. The composition of claim 1 , wherein the composition comprises a third compound, which serves as a co-host.

16. An organic light emitting device (OLED) comprising:

a cathode;

an anode; and

an emissive layer, disposed between the anode and cathode;

wherein the emissive layer comprises a composition comprising:

a first compound capable of functioning as a host in an emissive layer of the OLED at room temperature; and

a second compound comprising a ligand L A of Formula III

 wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclic ring;

wherein R represents two adjacent substituents that are joined together to form a ring that is fused to ring B, and R has a structure of Formula IV

 or Formula V

wherein the wavy lines indicate bonds to ring B;

wherein R A represents two substitutions to a maximum possible number of substitutions on a ring carbon the substituents are attached thereto;

wherein R B represents no substitution to a maximum possible number of substitutions on a ring carbon the substituents are attached thereto;

wherein R A and R B are each independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein two adjacent R A are joined to form a ring;

wherein A 1 , A 2 , A 3 , and A 4 are each independently CR C or N;

wherein Z 1 , Z 2 , Z 3 , and Z 4 are each independently C or N;

wherein at least two adjacent of Z 1 , Z 2 , Z 3 , and Z 4 are C and fuse to R;

wherein when R is Formula V, at least one of A 1 , A 2 , A 3 , A 4 , Z 1 , Z 2 , Z 3 , and Z 4 is N;

wherein Y is selected from the group consisting of BR′, NR′, PR′, O, S, Se, C—O, S═O, SO 2 , CR′R″, SiR′R″, and GeR′R″;

wherein R C , R 13 , R 14 , R′, and R″ are each independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein any two adjacent substituents are optionally joined to form into a ring;

wherein the ligand L A is coordinated to a metal M;

wherein M is Ir or Pt;

wherein the ligand L A is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and

wherein M is optionally coordinated to other ligands; and

wherein at least one of the following two conditions is true:

(i) the highest occupied molecular orbital of the first compound has an energy level equal to or less than −5.1 eV; and

(ii) the difference in energy between the highest occupied molecular orbital of the first compound and the highest occupied molecular orbital of the second compound is less than 0.3 eV.

17. The OLED of claim 16 , wherein at least one of R 13 and R 14 comprises a chemical group selected from the group consisting of alkyl, cycloalkyl, partially fluorinated alkyl, partially fluorinated cycloalkyl, and combinations thereof.

18. A consumer product comprising an organic light-emitting device (OLED) comprising:

an anode;

a cathode; and

an emissive layer, disposed between the anode and cathode;

wherein the emissive layer comprises a composition comprising:

a first compound capable of functioning as a host in an emissive layer of the OLED at room temperature; and

a second compound comprising a ligand L A of Formula III

 wherein ring A is a 5-membered or 6-membered carbocyclic or heterocyclic ring;

wherein R represents two adjacent substituents that are joined together to form a ring that is fused to ring B, and R has a structure of Formula IV

 or Formula V

wherein the wavy lines indicate bonds to ring B;

wherein R A represents two substitutions to a maximum possible number of substitutions on a ring carbon the substituents are attached thereto;

wherein R B represents no substitution to a maximum possible number of substitutions on a ring carbon the substituents are attached thereto;

wherein R A and R B are each independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein two adjacent R A are joined to form a ring;

wherein A 1 , A 2 , A 3 , and A 4 are each independently CR C or N;

wherein Z 1 , Z 2 , Z 3 , and Z 4 are each independently C or N;

wherein at least two adjacent of Z 1 , Z 2 , Z 3 , and Z 4 are C and fuse to R;

wherein when R is Formula V, at least one of A 1 , A 2 , A 3 , A 4 , Z 1 , Z 2 , Z 3 , and Z 4 is N;

wherein Y is selected from the group consisting of BR′, NR′, PR′, O, S, Se, C—O, S═O, SO 2 , CR′R″, SiR′R″, and GeR′R″;

wherein R C , R 13 , R 14 , R′, and R″ are each independently selected from the group consisting of hydrogen, deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein any two adjacent substituents are optionally joined to form into a ring;

wherein the ligand L A is coordinated to a metal M;

wherein M is Ir or Pt;

wherein the ligand L A is optionally linked with other ligands to comprise a tridentate, tetradentate, pentadentate, or hexadentate ligand; and

wherein M is optionally coordinated to other ligands; and

wherein at least one of the following two conditions is true:

(i) the highest occupied molecular orbital of the first compound has an energy level equal to or less than −5.1 eV; and

(ii) the difference in energy between the highest occupied molecular orbital of the first compound and the highest occupied molecular orbital of the second compound is less than 0.3 eV.

19. The consumer product of claim 18 , wherein at least one of R 13 and R 14 comprises a chemical group selected from the group consisting of alkyl, cycloalkyl, partially fluorinated alkyl, partially fluorinated cycloalkyl, and combinations thereof.

20. The composition of claim 1 , wherein the second compound is a transition metal complex comprising at least one ligand selected from the group consisting of:

wherein R 1 and R 2 represent mono to a maximum possible number of substitutions, or no substitution; wherein each R 1 and R 2 is independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and

wherein any two substituents may be joined or fused together to form a ring.