Full Definitions:    Ar1-Ar3=6-60C aryl optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 1-20C alkoxy, 1-20C alkylamine, 1-20C alkylthiophene, 6-20C arylthiophene, 2-20C alkenyl, 2-20C alkynyl, 3-20C cycloalkyl, 6-60C aryl (optionally substituted by deuterium, 8-20C arylalkenyl, silane, boron, germanium, 5-20C heterocyclyl), 5-60C heteroaryl (optionally substituted by deuterium, halo, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 8-20C arylamine, 6-60C aryl, 6-20C aryl substituted by deuterium, 8-20C arylalkyl, 8-20C arylalkenyl, 5-20C heterocyclyl, nitrile or acetylene), 1-30C alkoxy (optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 2-30C heterocycloalkyl, 6-60C aryl, 6-20C aryl substituted by deuterium, 3-60C heteroaryl), 6-30C aryloxy or 6-60C arylamine (both optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl group, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 2-30C heterocycloalkyl, 6-60C aryl, 6-20C aryl substituted by deuterium or 3-60C heteroaryl), 1-50C alkyl (optionally substituted by 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 6-20C aryl optionally substituted by deuterium, 8-20C arylalkyl, 8-20C arylalkenyl, 5-20C heterocyclyl, nitrile or acetylene), at least one of Ar1-Ar3 contains deuterium;    R1,R2=H, deuterium, halo, nitro, nitrile, amino, 6-60C aryl (optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 1-20C alkoxy, 1-20C alkylamine, 1-20C alkylthiophene, 6-20C arylthiophene, 2-20C alkenyl, 2-20C alkynyl, 3-20C cycloalkyl, 6-60C aryl, 6-20C aryl substituted by deuterium, 8-20C arylalkenyl, silane, boron, germanium or 5-20C heterocyclyl), 5-60C heteroaryl (optionally substituted by deuterium, halo, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 8-20C arylamine, 6-60C aryl, 6-20C aryl substituted by deuterium, 8-20C arylalkyl, 8-20C arylalkenyl, 5-20C heterocyclyl, nitrile or acetylene) containing O, N or S, 1-30C alkoxy (optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 2-30C heterocycloalkyl, 6-60C aryl, 6-20C aryl substituted by deuterium, or 3-60C heteroaryl), 6-30C aryloxy (optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 2-30C heterocycloalkyl, 6-60C aryl, 6-20C aryl substituted by deuterium or 3-60C heteroaryl), or 1-50C alkyl (optionally substituted by 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 6-20C aryl, 6-20C aryl substituted by deuterium, 8-20C arylalkyl, 8-20C arylalkenyl, 5-20C heterocyclyl, nitrile or acetylene);    or R1+R2+adjacent group=optionally saturated aliphatic ring or hetero ring;    L=6-60C arylene or 5-60C heteroarylene (both optionally substituted by nitro, nitrile, halo, alkyl, alkoxy or amino);    a=0-4;    b=0-3;and    c=0-2.    SPECIFIC COMPOUNDS - 132 compounds (I) are specifically claimed, e.g. 2,3,4,5,6-pentadeutero-N-(4-(2,3,4,5,6-pentadeuterophenyl)phenyl)-N-(4-(9-phenyl-9H-carbazol-3-yl)phenyl)aniline of formula (A), N-(2,3,4,5,6-pentadeuterophenyl)-N-phenyl-5-(9-phenyl-9H-carbazol-3-yl)naphthalen-1-amine, 2,3,4,5,6-pentadeutero-N-(4-(9-(naphthalen-1-yl)-9H-carbazol-3-yl)phenyl)-N-phenylaniline, N-(4-(9-(naphthalen-2-yl)-9H-carbazol-3-yl)phenyl)-N-(2,3,4,5,6-pentadeuterophenyl)naphthalen-1-amine and N-(2,3,4,5,6-pentadeuterophenyl)-N-(4-(9-(4-phenylphenyl)-9H-carbazol-3-yl)phenyl)naphthalen-2-amine.