TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The phenanthrene-containing compound (I) is of formula (II)-(VII). Full Definitions:    ring A=6-60C monocyclic or polycyclic aromatic or heterocyclic system;    Y'=direct bond, H, deuterium, halo, nitrile, nitro, -L-N(Ar1)(Ar2), 2-60C heterocyclic group comprising at least one heteroatom chosen from O, N, S, Si and P, and optionally substituted by deuterium, halo, -N(Ar1)(Ar2), 1-20C alkyl, 7-20C arylalkyl, 2-20C alkenyl, 8-20C arylalkenyl, 1-20C alkoxy, 6-60C aryl, 6-20C aryl substituted with deuterium, nitrile or acetylene, 1-30C alkoxy or 6-30C aryloxy optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 6-60C aryl, 6-20C aryl substituted with deuterium or 2-60C heterocyclic group, 1-50C alkyl optionally substituted by 2-20C alkenyl, 1-20C alkoxy, 6-20C aryl, 6-20C aryl substituted with deuterium, 7-20C arylalkyl, 8-20C arylalkenyl, 2-20C heterocyclic group, nitrile or acetylene, or bivalent substituent chosen from 6-60C arylene, fluorenyl, ring with 6-60C aromatic ring and 3-60C aliphatic fused ring, 2-60C heterocyclic group, or divalent aliphatic hydrocarbyl, or 6-60C aryl or fluorenyl (both optionally substituted by deuterium, halo, silane, boron, germanium, 1-20C alkylthio, 6-20C arylthio, 1-20C alkoxy, -N(Ar1)(Ar2), 1-20C alkyl, 7-20C arylalkyl, 2-20C alkenyl, 8-20C arylalkenyl, 2-20C alkynyl, 3-20C cycloalkyl, 6-20C aryl substituted by deuterium or 2-20C heterocyclic group);    n=1 or 2;    R1-R11=H, deuterium, halo, nitrile, nitro, -L-N(Ar1)(Ar2), 2-60C heterocyclic group comprising at least one heteroatom chosen from O, N, S, Si and P, and optionally substituted by deuterium, halo, -N(Ar1)(Ar2), 1-20C alkyl, 7-20C arylalkyl, 2-20C alkenyl, 8-20C arylalkenyl, 1-20C alkoxy, 6-60C aryl, 6-20C aryl substituted with deuterium, nitrile or acetylene, 1-30C alkoxy or 6-30C aryloxy optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 6-60C aryl, 6-20C aryl substituted with deuterium or 2-60C heterocyclic group, or 1-50C alkyl optionally substituted by 2-20C alkenyl, 1-20C alkoxy, 6-20C aryl, 6-20C aryl substituted with deuterium, 7-20C arylalkyl, 8-20C arylalkenyl, 2-20C heterocyclic group, nitrile or acetylene, or 6-60C aryl or fluorenyl (both optionally substituted by deuterium, halo, silane, boron, germanium, 1-20C alkylthio, 6-20C arylthio, 1-20C alkoxy, -N(Ar1)(Ar2), 1-20C alkyl, 7-20C arylalkyl, 2-20C alkenyl, 8-20C arylalkenyl, 2-20C alkynyl, 3-20C cycloalkyl, 6-20C aryl substituted by deuterium or 2-20C heterocyclic group);    X=S, SO or SO2;    L=direct bond, 6-60C arylene, fluorenyl, ring in which 6-60C aromatic ring and 3-60C aliphatic fused ring, 2-60C heterocyclic group comprising at least one heteroatom chosen from O, N, S, Si and P, and optionally substituted by deuterium, halo, -N(Ar1)(Ar2), 1-20C alkyl, 7-20C arylalkyl, 2-20C alkenyl, 8-20C arylalkenyl, 1-20C alkoxy, 6-60C aryl, 6-20C aryl substituted with deuterium, nitrile or acetylene, or divalent aliphatic hydrocarbyl;and    Ar1,Ar2=2-60C heterocyclic group comprising at least one heteroatom chosen from O, N, S, Si and P, and optionally substituted by deuterium, halo, -N(Ar1)(Ar2), 1-20C alkyl, 7-20C arylalkyl, 2-20C alkenyl, 8-20C arylalkenyl, 1-20C alkoxy, 6-60C aryl, 6-20C aryl substituted with deuterium, nitrile or acetylene, 1-30C alkoxy or 6-30C aryloxy optionally substituted by deuterium, halo, amino, nitrile, nitro, 1-20C alkyl, 2-20C alkenyl, 1-20C alkoxy, 3-30C cycloalkyl, 6-60C aryl, 6-20C aryl substituted with deuterium or 2-60C heterocyclic group, or 1-50C alkyl optionally substituted by 2-20C alkenyl, 1-20C alkoxy, 6-20C aryl, 6-20C aryl substituted with deuterium, 7-20C arylalkyl, 8-20C arylalkenyl, 2-20C heterocyclic group, nitrile or acetylene, or 6-60C aryl or fluorenyl (both optionally substituted by deuterium, halo, silane, boron, germanium, 1-20C alkylthio, 6-20C arylthio, 1-20C alkoxy, -N(Ar1)(Ar2), 1-20C alkyl, 7-20C arylalkyl, 2-20C alkenyl, 8-20C arylalkenyl, 2-20C alkynyl, 3-20C cycloalkyl, 6-20C aryl substituted by deuterium or 2-20C heterocyclic group).    SPECIFIC COMPOUNDS - 145 Phenanthrene-containing compounds are specifically claimed e.g. 12-phenyl-13-thia-indeno(1,2-l)phenanthrene of formula (Ia), 12-naphthalen-1-yl-13-thia-indeno(1,2-l)phenanthrene, 12-naphthalen-2-yl-13-thia-indeno(1,2-l)phenanthrene, 12-phenanthren-1-yl-13-thia-indeno(1,2-l)phenanthrene and 12-phenanthren-1-yl-13-thia-indeno(1,2-l)phenanthrene.