Organic electroluminescent materials and devices

An organic light emitting device (OLED) comprising:

• an anode;
• a cathode;
• and
• an emissive region disposed between the anode and the cathode, wherein the emissive region comprises a compound comprising a structure of Formula I:
• wherein:
• each of X1, X2, X3, X4, X1′, X2′, X3′, X4′, X5, X6, X7, X8, X9, X10, X8′, X9′, and X10′ is independently C or N;
• each of X1, X2, X3, X4, X1′, X2′, X3′, X4′, X3, X6, X7, X8, X9, X10, X8′, X9′, and X10′ are C if connected to an RA, RB, RC, RD, or RE;
• wherein when R3 is H, then R4 is not N,
• wherein when R5 is H, then R6 is not N,
• at least one of the following conditions is true:
• (1) at least one RA or RB has a structure of Formula II,
• or Formula III,
• with the proviso that if the structure of Formula II or Formula III is attached to X2 or X2′, and at least one of R3, R4, R5, or R6 is phenyl, phenyl-d5, or 4-tert-butyl-phenyl, then R1 and R2 are not hydrogen or deuterium;
• (2) R3 and R4 are different, and R5 and R6 are different;
• (3) at least one of R3, R4, R5 and R6 comprises a silyl group, a germyl group, or boryl group;
• (4) at least one RA or RB comprises an electron-withdrawing group;
• (5) exactly one of R3, R4, R5 and R6 is H or D;
• or
• (6) exactly one of R3 or R4 is hydrogen or deuterium and the other is not phenyl, phenyl-d5, 4-tert-butyl-phenyl, or NR2, and exactly one of R5 and R6 is hydrogen or deuterium and the other is not phenyl, phenyl-d5, 4-tert-butyl-phenyl, or —NR2;
• wherein each of RA, RB, RC, RD, RE, RF, and RG independently represents mono to the maximum allowable substitutions, or no substitutions;
• each R1, R2, R3, R4, R5, R6, RA, RB, RC, RD, RE, RE, and RG is independently hydrogen or a substituent selected from the group consisting of deuterium, halogen, alkyl, cycloalkyl, heteroalkyl, heterocycloalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, germyl, boryl, selenyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carboxylic acid, ether, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof;
• and any two RA, RB, RC, RD, RE, RF, and RG may be joined or fused to form a ring.