NOVELTY - Aromatic heterocyclic polymeric organic semiconductor compounds (I) are new.    USE - (I) are useful in organic electronic device, preferably organic solar cell and organic thin film transistor (all claimed).    ADVANTAGE - (I): exhibiting low band-gap can be prepared by extending pi - pi stacking by using sulfur and thiophene containing comonomers in copolymerization; exhibit high solubility and high thermal stability and excellent electrical properties; and can be combined with fullerene derivatives to provide photoactive layer of organic electronic device with high efficiency.    DETAILED DESCRIPTION - Aromatic heterocyclic polymeric organic semiconductor compounds of formula (I) are new.    A = 6-30C aryl or B, N, O, S, P (=O), Si and/or P containing 3-30C heteroaryl (all optionally substituted by G) or does not exist, preferably aromatic heterocyclic moieties of formulae (II)-(IX);    C1, D1 = 6-30C aryl or 3-30C heteroaryl (all optionally substituted by G), preferably (II)-(IX);    G = 1-30C alkyl, 1-30C alkoxy, 3-30C cycloalkyl or -NR101R102;    R101, R102 = H, OH, 1-30C alkyl, 1-30C alkoxy, 3-30C cycloalkyl or 6-30C aryl;    B1 = quinoxalin-5,8-diyl or nitrogen containing fused heteroarylene moieties of formulae (X)-(XII);    ring E1, ring F1 = 6-30C aromatic ring or N, O and/or S containing 3-30C heteroaromatic ring (all optionally substituted by 1-30C alkyl, 1-30C alkoxy, 3-30C cycloalkyl or -NR103R104), preferably 1,2-phenylene, phenanthren-9,10-diyl, (1,2,5)thiadiazol-3,4-diyl, furazan-3,4-diyl, (1,2,5)selenadiazol-3,4-diyl or substituted naphthalen-1,2-diyl group of formula (XIII);    R103, R104 = H, OH, 1-30C alkyl, 1-30C alkoxy, 3-30C cycloalkyl or 6-30C aryl;    o = 1-2000;    p, q = 0-2000;    R1-R19 = H, 1-30C alkyl, 1-30C alkoxy, 3-30C cycloalkyl, 6-30C aryl (optionally substituted by G) or B, N, O, S, P(=O), Si and/or P containing 3-30C heteroaryl (optionally substituted by G);    T = -CR105R106 or -NR107;    R105-R107 = H, 1-30C alkyl, 1-30C alkoxy or 3-30C cycloalkyl;    Z = S, Se or O;    a, b = 1-3;    c = 1-2; and    e = 1-4.    INDEPENDENT CLAIMS are also included for:    (1) preparing (I); and    (2) an organic electronic device including (I).    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of organic solar cell.