NOVELTY - Fused bithiophene-vinylene polymers (Ia) comprising repeating units (A) and optionally repeating units (B1), is new.    USE - The polymers are useful in an electronic device, an optical device, and an optoelectronic device; and a thin film semiconductor. The thin film semiconductor is useful in a field effect transistor device having a structure including top-gate bottom-contact structure, bottom-gate topcontact structure, top-gate top-contact structure, and bottom-gate bottom-contact structure; a photovoltaic device; and an organic light emitting device (all claimed).    ADVANTAGE - The polymers exhibit semiconductor behavior such as high carrier mobility and/or good current modulation characteristics in a field-effect device, and light absorption/charge separation in a photovoltaic device. The polymers possess solution-processability high mobility and/or a wide absorption spectrum.    DETAILED DESCRIPTION - Fused bithiophene-vinylene polymers (Ia) comprising repeating units of formula (A) and optionally repeating units of formula (-(-W1x-R3C=CR4-)4-)(B1), is new.    Z = S, Se, N-R or O;    X = R5-C-R6, N-R5, R5-N+-R6, B-R5, R5-B--R6, R5-Si-R6, O, Se, R5-HC=CH-R6, R6-CH(R5)-CH(R6)-R5, C=D1, -C(=D1)-C(=D1)-, pyrrolidine-2,5-dione moiety of formula (a), benzene moiety of formula (b), pyrazine moiety of formula (c) or heterocyclic moieties formulae (d)-(j);    D1 = O, C(CN)2 or CR4R5;    E = CR4R5, NR4, O or S;    R = H, CN, 1-30C alkyl, 2-30C alkenyl or 1-30C haloalkyl;    X1 = R5-C-R6, N-R5, R5-N+-R6, B-R5, R5-B--R6, R5-Si-R6, O, S, Se, R5-HC=CH-R6, R6-CH(R5)-CH(R6)-R5, C=D1, -C(=D1)-C(=D1)- or (a);    W1 = a monocyclic or polycylic moiety optionally substituted with 1-4 R1a groups;    R1a = 1-20C alkyl, 2-20C alkenyl, 2-20C alkynyl, 1-20C alkoxy, a 1-20C alkylthio, 1-20C haloalkyl, -Y1-3-10C cycloalkyl, -Y1-6-14C aryl, -Y1-3-12 membered cycloheteroalkyl group or -Y1-5-14 membered heteroaryl group (all optionally substituted with 1-4 R1b groups), halo, -CN, -NO2, oxo, -OH or =C(R1b)2;    R1b = 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, 6-14C aryl or haloaryl, a 3-12 membered cycloheteroalkyl or a 5-14 membered heteroaryl group;    Y1 = a divalent 1-6C alkyl, a divalent 1-6C haloalkyl or a covalent bond;    m = 0-2;    R1, R2, R5, R6 = H, CN, 1-30C alkyl, 2-30C alkenyl, 1-30C haloalkyl, -L-Ar1, -L-Ar1-Ar1, -L-Ar1-R7 or -L-Ar1-Ar1-R7;    L = -O-, -Y1-O-Y1-, -S-, -S(O)-, -Y1-S-Y1-, -C(O)-, -NR1cC(O)-, -NR1c-, -Si(R1c)2, -Y1-(Si(R1c)2)-Y1-, a divalent 1-30C alkyl, a divalent 1-30C alkenyl, a divalent 1-30C haloalkyl or a covalent bond;    R1c = H, 1-20C alkyl or -Y1-6-14C aryl;    Ar1 = 6-14C aryl or a 5-14 membered heteroaryl group (both optionally substituted with 1-5 substituents of halo, -CN, 1-6C alkyl, 1-6C alkoxy or 1-6C haloalkyl);    R7 = 1-20C alkyl, 2-20C alkenyl, 1-20C haloalkyl, 1-20C alkoxy, -L1-Ar2, -L1-Ar2-Ar2, -L1-Ar2-R8 or -L1-Ar2-Ar2-R8;    L1 = -O- , -Y1-O-Y1-, -S-, -S(O)-, -Y1-S-Y1-, -C(O)-, -NR1cC(O)-, -NR1c-, -Si(R1c)2, -Y1-(Si(R1c)2)-Y1-, a divalent 1-20C alkyl, divalent 1-20C alkenyl, divalent 1-20C haloalkyl or a covalent bond;    Ar2 = 6-14C aryl or a 5-14 membered heteroaryl group (both optionally substituted with 1-5 substituents of halo, -CN, 1-6C alkyl, 1-6C alkoxy or 1-6C haloalkyl);    R8 = 1-20C alkyl, 2-20C alkenyl, 1-20C haloalkyl or 1-20C alkoxy;    R3, R4 = H, CN, 1-30C alkyl, 2-30C alkenyl, 1-30C haloalkyl or -L-R9;    R9 = 1-20C alkyl, 2-20C alkenyl or 1-20C haloalkyl;    x = 1-6; and    n = 2-5000.    INDEPENDENT CLAIMS are included for:    (1) a composition comprising (Ia) dissolved or dispersed in to a liquid medium;    (2) a thin film semiconductor comprising (Ia); and    (3) a field effect transistor device comprising the thin film semiconductor.