Organic electroluminescent materials and devices

A compound of Formula of Ir(LA)n(LB)m(LC)o, wherein ligand LA has a structure of Formula I,

• ligand LB has a structure of Formula II,
• and LC is a bidentate ligand;
• and wherein n is 1, or 2;
• m is 1, or 2;
• o is 0, or 1;
• and n+m+o=3;
• wherein moiety A is selected from the group consisting of alkyl, heteroalkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, silyl, germyl, and combinations thereof;
• each of X1 to X19 is independently C or N;
• Y is selected from the group consisting of BR, BRR′, NR, PR, P(O)R, O, S, Se, C═O, C═S, C═Se, C═NR′, C═CR′R″, S═O, SO2, CRR′, SiRR′, and GeRR′;
• RA, RB, RC, RD, and RE each independently represent mono to the maximum number of substitutions, or no substitutions;
• wherein 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;
• at least one RD or RE comprises an electron-withdrawing group, or an aryl or heteroaryl substituted with an electron-withdrawing group;
• any two R, R′, RA, RB, RC, RD, and RE can be joined or fused to form a ring, subject to the following seven provisos:
• (1) moiety A is not an adamantyl group;
• (2) moiety A and RA do not form a fused 5-membered pyrrole ring comprising X11;
• (3) if RD at X17 is a trimethylsilyl group, then at least one RE is not hydrogen or fluorine;
• (4) an RB and an RC substituent are not joined to form a ring;
• (5) if X1 is N, then moiety A is not an alkyl group;
• (6) RD is not a partially fluorinated alkyl, a partially fluorinated aryl, or a partially fluorinated arylalkyl group;
• and
• (7) moiety A is not a para-tolyl group.