NOVELTY - New polymer (P1) comprises: substituted tricyclic repeating units, and has a degree of polymerization of 3-10000.    USE - As polymeric semiconductor component for electronic, optical or optoelectronic device; such as organic photovoltaic device (preferably bulk heterojunction photovoltaic device) (all claimed) and organic light-emitting transistors (OLETs), such as thin film semiconductors, photodetectors, and other organic light emitting devices.    ADVANTAGE - The polymer provides organic semiconductor material that is active component for organic photovoltaics (OPVs) and organic light-emitting transistors (OLETs) such that they are commercially relevant i.e. can be processable in cost-effective manner. The compounds exhibit properties such as optimized optical absorption, good charge transport characteristics and chemical stability in ambient conditions, low-temperature processability, large solubility in common solvents, and processing versatility (e.g. via various solution processes). As a result, optoelectronic devices such as solar cells that incorporate greater than or equal to 1 of the compounds as photoactive layer can exhibit high performance in ambient conditions e.g. greater than or equal to 1 of low band-gap, high fill factor, high open circuit voltage, and high power conversion efficiency. Similarly, other organic semiconductor-based devices such as organic light-emitting transistors (OLETs) can be fabricated efficiently using the organic semiconductor materials. The polymeric compounds can exhibit semiconductor behavior such as optimized light absorption/charge separation in photovoltaic device; charge transport/recombination/light emission in light-emitting device; and/or high carrier mobility and/or good current modulation characteristics in field-effect device. In addition, the compounds can possess certain processing advantages such as solution-processability and/or good stability (e.g. air stability) in ambient conditions, and operation advantages in fabrication and/or use of the devices. The compounds can be used to prepare either p-type (donor or hole-transporting), n-type (acceptor or electron-transporting), or ambipolar semiconductor materials, which in turn can be used to fabricate various organic or hybrid optoelectronic articles, structures and devices, including organic photovoltaic devices and OLETs. In optical or optoelectronic device i.e. solar cell, particularly, bulk heterojunction solar cell, the compounds exhibit broad optical absorption and/or tuned redox properties and bulk carrier mobilities. The obtained bulk heterojunction solar cells can incorporate blend material (e.g. blended film) including the polymer compound as donor material and acceptor material as photoactive layer. While in most state-of-the-art devices, thickness of blended film often is limited to less than or equal to 100 nm (to obtain good device performance), comparable performance with films prepared from the copolymers in broad thickness range can be obtained, specifically, with thin films having thickness of less than or equal to 100 nm, as well as films having thickness greater than 200 nm.    DETAILED DESCRIPTION - New polymer (P1) comprises: a substituted tricyclic repeating unit (M1a) of formula (Ia) or (Ib), or a substituted tricyclic repeating unit (M1b) of formula (Ic) or (Id), and has a degree of polymerization of 3-10000.    Ar1 and Ar2=6-14C aryl or 5-14 membered heteroaryl (both optionally substituted) (preferably Ar1+5-membered ring attached to Ar1 containing S-CH=CH and Ar2+5-membered ring attached to Ar2 containing S-CH=CH are selected from 12 groups as given in the specification e.g. groups of formulae (ia), (ib), (ic), (id) and (Ie) (all having any carbon optionally substituted by F, Cl, CN or L2-R'));    L2=-O-, -S-, -Se-, -C(O)-, -OC(O)-, -C(O)O-, or covalent bond;    Ar3 and Ar4=phenyl or 5 or 6-membered heteroaryl (both optionally substituted);    L'=-O-, -S-, -Se-, -OC(O)-, -C(O)O-, divalent 1-20C (halo)alkyl, or covalent bond;    L1=-O-, -S-, -Se-, -OC(O)-, -C(O)O-, or divalent 1-20C (halo)alkyl;    U'1 and U'=-O-, -S-, or -Se-;    V'1 and V'=-CR'1= or -N=;    W'1=-O-, -S-, or -Se-;    W'=-CR'1= or -N=;    R'1=H, F, Cl, CN, or L'1R';    L'1=-O-, -S-, -Se-, -C(O)-, -OC(O)-, -C(O)O-, or covalent bond;    R'=1-40C (halo)alkyl, 2-40C alkenyl, or 2-40C alkynyl.    An INDEPENDENT CLAIM is included for an electronic, optical or optoelectronic device comprising a polymeric semiconductor component comprising the polymer (P1).    DESCRIPTION OF DRAWING(S) - The figure shows structure of the bulk-heterojunction organic solar cell incorporating greater than or equal to 1 polymer compound (P1) as donor material.    Substrate (20)    Anode (22)    Photoactive layer incorporating polymer compound (P1) (24)    Cathode (26)