Organic electroluminescent materials and devices

A compound of formula Ir(LA)m(LB)n(LC)o;

• wherein:
• m and n are each independently 1 or 2, o is 0 r 1, and m+n+o=3;
• LA has a structure of Formula I,
• LB has Formula II, RE
• LC is a bidentate ligand;
• moieties A and D are each independently a 5-membered or 6-membered carbocyclic or heterocyclic ring or a polycyclic ring system comprising two or more 5-membered and/or 6-membered carbocyclic or heterocyclic rings;
• one of moiety A and moiety D is coordinated to Ir by a 5-membered carbocyclic or heterocyclic ring, and the other one of moiety A and moiety D is coordinated to Ir by a 6-membered carbocyclic or heterocyclic ring;
• each of X and X1 to X12 is independently C or N;
• the one of X5 to X8 bonded to moiety A is C;
• Y is selected from the group consisting of the group consisting of BR, BRR′, NR, PR, P(O)R, O, S, Se, C═O, C═S, C═Se, C═NR′, C═CRR, S═O, SO2, CRR′, SiRR′, and GeRR′;
• RA, RB, RC, RD, and RE each independently represent mono to the maximum allowable substitution, or no substitution;
• each R, R′, RA, RB, RC, RD, and RE is independently a hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, germyl, boryl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, selenyl, and combinations thereof;
• LA is complexed to Ir forming a 5-membered chelate ring;
• at least one RD or RE substituent comprises an electron-withdrawing group, or an aryl or heteroaryl substituted with an electron-withdrawing group;
• and
• any two adjacent substituents can be joined or fused to form a ring,
• with the proviso that when moiety A is coordinated to Ir by a 5-membered ring and moiety D is coordinated to Irby a 6-membered ring, when moiety D is a 3-silyl-pyridine group and only one RE is an electron-withdrawing group, then RE is not F on X9, and
• with the proviso that the compound is not