NOVELTY - Organic compound which has a polymer structure comprising a repeating unit (I), is new.    USE - The organic compound is useful as organic semiconductor and in solar cell (all claimed).    ADVANTAGE - The organic compound exhibits excellent photoelectric conversion efficiency.    DETAILED DESCRIPTION - Organic compound which has a polymer structure comprising a repeating unit of formula -(A-D1)- (I), is new.    A = substituted dibenzo(a,c)phenazine moiety of formula (Ia), where (A) includes two or more different repeating units;    D1 = substituted fused heterocyclic moiety of formula (IIa-IIc), thiophene, selenophene, oligothiophene, oligoselenophene, alkoxybenzene, tolan, thienothiophene, carbazole, fluorene, 3,4-ethylenedioxythiophene, cyclopentadithiophene, dithienothiophene, heptadecanylcarbazole, phosphafluorene, thiazolothiazole, pyridine, phenylthiophene, phenanthroline, phenanthrene, thiadiazole, crown ether, arylamine, diketo-pyrrolopyrrole, thiophene-benzene-thiophene unit or their derivative, where D1 comprises benzothiophene skeleton;    R1 = straight or branched-chain alkyl or straight-chain or branched-chain alkoxy (both optionally substituted) or H, preferably perfluoroalkyl;    R2 = straight or branched-chain alkyl, straight-chain or branched-chain alkoxy, phenyl, thienyl or selenophene (all optionally substituted);    m = 0-4;    X = O, S, Se, Te or N;    Z = H or halo;    W1 = straight-chain or branched-chain alkyl or straight-chain or branched-chain alkoxy (both optionally substituted), ketone or ester (substituted with optionally substituted straight-chain or branched-chain alkyl);    V1 = -CR32-, -SiR32- or -NR3-; and    R3 = straight-chain or branched- chain alkyl (optionally substituted).    An INDEPENDENT CLAIM is also included for a solar cell comprising an active layer (13) which contains an n-type semiconductor and the organic compound.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic sectional view of an organic thin-film solar cell.    Substrate (10)    Anode (11)    Cathode (12)    Active layer (13)    Hole transport layer (14)