NOVELTY - 3-Substituted tellurophene compounds (I) are new.    USE - (I) are useful in an oligomeric or polymeric compound, and a conjugated polymer which is useful: in a film that is used in an electrode, where the electrode is installed in contact with the film and is useful in a solar cell; and a composite material that is useful in an optoelectronic device including a diode, a LED, a transistor, a solar cell, a photodiode or a light-emitting transistor (all claimed).    ADVANTAGE - (I) provide the polymer which provides the film having a thickness of 1-10000 nm, preferably 10-500 nm (claimed), and exhibits excellent stability.    DETAILED DESCRIPTION - 3-Substituted tellurophene compounds of formula (I) and their salts are new.    R1a=monovalent organic group;    X1a=halo, H, Li, Na, MgX2a, B(OR2b) 2, B(OH) 2, or SnR2c 3, where if one X1a is H, then the other X1a is not H;    X2a=Cl or Br;    R2b=1-10C alkyl or optionally substituted 1-10C alkylene bridging the O-atoms bound to B;    R2c=1-10C alkyl; and    n=greater than 1.    INDEPENDENT CLAIMS are also included for:    (1) substituted tellurophene compounds of formula (I-b);    (2) substituted tellurophene compounds of formula (I-c);    (3) substituted tellurophene compounds of formula (I-d);    (4) an oligomeric or polymeric compound comprising at least two tellurophene-2,5-diyl groups covalently linked to each other at one or the other of the 2- and 5-positions of each tellurophene ring, where each of the tellurophene rings is substituted at its 3- or 4-position;    (5) a conjugated polymer comprising (I), where the polymer has a number average molecular weight of at least 2000 when measured by gel permeation chromatography relative to polystyrene standards;    (6) a film comprising the polymer;    (7) a composite material comprising a polymer layer comprising the polymer, and a support disposed on at least one side of the polymer layer;    (8) a semiconductor composite material comprising the polymer in combination with an electron acceptor material;    (9) preparing a polytellurophene compound, comprising exposing (I-c) (where X1a is iodide) to an electrochemical potential of 0.1-3 V for a period of time sufficient to form the polytellurophene compound;    (10) preparing (I);    (11) preparing 2-chloro-acetyl of formula (R1a-C(=O)-CH 2-Cl) (II) comprising coupling 2-chloro-acetyl of formula (L1a-C(=O)-CH 2-Cl) (a1) and an organometallic salt of formula (R1a -Z1a +) (a2);    (12) preparing 1-chloromethyl-1-hydroxy-prop-2-ynyl of formula (III) comprising coupling (II) and an organometallic salt of formula (HCC -Z1a +) (a3); and    (13) preparing (I-b) comprising either mixing (III) with a mixture of a tellurium salt and a reducing agent, or coupling (a1) with the organometallic salt (a2) to form (II), coupling (II) with (a3) to form (III), and mixing (III) with a mixture of a tellurium salt and a reducing agent.    L1a=leaving group, preferably -N(OH)R1w;    R1w=alkyl; and    Z1a=not defined.