NOVELTY - Organic semiconductor compound comprising at least one poly(substituted thiophene)-poly(substituted nitrogen containing fused ring) structural unit (I), is new.    USE - (I) is useful in a transistor and an electronic device, which is a solar cell (all claimed).    ADVANTAGE - (I): has low band gap; has excellent and/or improved charge mobility, coplanarity, miscibility with carbon nanotube, fullerene or graphene; and exhibits good and/or improved semiconductor characteristics.    DETAILED DESCRIPTION - Organic semiconductor compound comprising at least one poly(substituted thiophene)-poly(substituted nitrogen containing fused ring) structural unit of formula (I), is new.    R1, R2 = 1-20C alkyl, 1-20C alkoxy (both linear or branched), 3-20C cycloalkyl, 3-20C cycloalkyloxy, 6-30C aryl, 6-30C aryloxy or 2-30C heteroaryl (all optionally substituted), H and/or halo, where if R1 is not H, one of CH2 and many non-adjacent CH2 groups are optionally substituted with -O-, -S-, -S(O)2-, -CO-, -OCO-, -C(O)O-, -CR51=CR52-, -CC- or -SiR53R54;    R51-R54 = 1-15C alkyl (linear or branched), 3-15C cycloalkyl, 1-15C alkoxy, 6-15C aryl or 2-15C heteroaryl (all optionally substituted) and/or H;    X = -CR3=N-, -N=N-, -CR4=CR5-, -O-, -S-, -Se- or -NR6;    Y1 = -CR7=CR8-, -O-, -S-, -Se- or -NR9-; either    R3-R9 = 1-20C alkyl, 1-20C alkoxy (both linear or branched), 3-20C cycloalkyl, 3-20C cycloalkyloxy, 6-30C aryl, 6-30C aryloxy or 2-30C heteroaryl (all optionally substituted), H and/or halo, where one of CH2 and many non-adjacent CH2 groups are optionally substituted with -O-, -S-, -S(O)2-, -CO-, -OCO-, -C(O)O-, -CR51=CR52-, -CC- or -SiR53R54; or    R4R5 = fused ring (when X is -CR4=CR5); or    R7R8 = fused ring (when Y1 is -CR7=CR8);    Z = 1-40C arylene, 4-14C heteroaromatic ring or 6-30C condensed polycyclic group including a heteroaromatic ring (all optionally substituted); and    p, q = a mole ratio of each structural unit and p/(p+q) is 0.5-0.95.    An INDEPENDENT CLAIM is also included for a transistor (10) comprising (I).    DESCRIPTION OF DRAWING(S) - The figure shows schematic cross-sectional diagram illustrating transistor.    Transistor (10)    Substrate (12)    Gate electrode (14)    Insulation layer (16)    Active layer (18)