NOVELTY - Polymer (I) comprising heterocyclic compounds (AA), is new    USE - (I) is useful as semiconductors or charge transport materials, as thin-film transistors (TFTs), or in semiconductor components for organic light-emitting diodes (OLEDs), for photovoltaic components or in sensors, as an electrode material in batteries, as optical waveguides or for electrophotography applications (claimed).    ADVANTAGE - (I): is easy to synthesize; has high mobilities and good oxidation stability; can be processed readily; and provides highly regioregular polythiophenes.    DETAILED DESCRIPTION - Polymer (I) comprising heterocyclic compounds of formula (AA), is new.    R1-R4 = H, halo, -CN, -NO2, oxo, -OH, =C(R5)2, 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 1-20C alkoxy, 1-20C alkylthio, 1-20C haloalkyl, -Y1-3-10C cycloalkyl, -Y1-6-14C aryl, -Y1-3-12C membered cycloheteroalkyl, or -Y1-5-14C membered heteroaryl, where each of 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 3-10C cycloalkyl, 6-14C aryl, 3-12 membered cycloheteroalkyl or 5-14 membered heteroaryl (all optionally substituted with 1-4 R5 groups);    R2R3 = cyclic moiety;    R5 = halo, -CN, -NO2, oxo, -OH, -NH2, -NH(1-20C alkyl), -N(1-20C alkyl)2, -N(1-20C alkyl)-6-14C aryl, -N(6-14C aryl)2, -S(O)mH, -S(O)m-1-20C alkyl, -S(O)2OH, -S(O)m-O-1-20C alkyl, -S(O)m-O-6-14C aryl, -CHO, -C(O)-1-20C alkyl, -C(O)-6-14C aryl, -C(O)OH, -C(O)-O-1-20C alkyl, -C(O)-O-6-14C aryl, -C(O)NH2, -C(O)NH-1-20C alkyl, -C(O)N(1-20C alkyl)2, -C(O)NH-6-14C aryl, -C(O)N(1-20C alkyl)-6-14C aryl, -C(O)N(6-14C aryl)2, -C(S)NH2, -C(S)NH-1-20C alkyl, -C(S)N(1-20C alkyl)2, -C(S)N(6-14C aryl)2, -C(S)N(1-20C alkyl)-6-14C aryl, -C(S)NH-6-14C aryl, -S(O)mNH2, -S(O)mNH(1-20C alkyl), -S(O)mN(1-20C alkyl)2, -S(O)mNH(6-14C aryl), -S(O)mN(1-20C alkyl)-6-14c aryl, -S(O)mN(6-14C aryl)2, -SiH3, -SiH(1-20C alkyl)2, -SiH2(1-20C alkyl), -Si(1-20C alkyl)3, 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 1-20C alkoxy, 1-20C alkylthio, 1-20C haloalkyl, 3-10C cycloalkyl, 1-14C aryl, haloaryl, 3-12 membered cycloheteroalkyl or 5-14 membered heteroaryl;    Y1 = divalent 1-6C alkyl, divalent 1-6C haloalkyl, or covalent bond;    m = 0-2;    X = O, S, Se, NR10, PR10, PR10R11R12, SiR10R11 or CR10R11;    R10-R12 = H, 1-30C alkyl, 2-30C alkenyl, 1-30C haloalkyl, -L-Ar1, -L-Ar1-Ar1, - L-Ar1-R13, or -L-Ar1-Ar1-R13;    R13 = 1-20C alkyl, 2-20C alkenyl, 1-20C haloalkyl, 1-20C alkoxy, -L1-Ar2, -L1-Ar2-Ar2, -L1-Ar2-R15, or -L1-Ar2-Ar2-R15;    L = -O-, -Y1-O-Y1-, -S-, -S(O)-, -Y1-S-Y1-, -C(O)-, -NR14C(O)-, -NR14-, -SiR142- , -Y1-(SiR142)-Y1-, divalent 1-30C alkyl, divalent 1-30C alkenyl, divalent 1-30C haloalkyl, or covalent bond;    L1 = -O-, -Y1-O-Y1-, -S-, -S(O)-, -Y1-S-Y1-, -C(O)-, -NR14C(O)-, -NR14- , -SiR142, -Y1-(SiR142)-Y1-, divalent 1-20C alkyl, divalent 1-20C alkenyl, divalent 1-20C haloalkyl, or covalent bond;    Ar1, Ar2 = 6-14C aryl or 5-14 membered heteroaryl (both optionally substituted with 1-5 substituents comprising halo, -CN, 1-6C alkyl, 1-6C alkoxy, or 1-6C haloalkyl);    R14 = H, 1-6C alkyl, or -Y1-6-14C aryl; and    R15 = 1-20C alkyl, 2-20C alkenyl, 1-20C haloalkyl, or 1-20C alkoxy.    INDEPENDENT CLAIMS are included for:    (1) a thin film semiconductor comprising (I); and    (2) a composite comprising a substrate and the thin film semiconductor deposited on the substrate;    (3) a process for preparation of the composite comprising dissolving (I) in a liquid medium to form a solution, depositing the solution on a substrate, and removing the solvent to form a thin film semiconductor on the substrate;    (4) a field effect transistor device comprising the thin film semiconductor or the composite;    (5) a photovoltaic device comprising the thin film semiconductor or the composite; and    (6) an organic light emitting diode device comprising the thin film semiconductor or the composite.