NOVELTY - Polymer comprising electron-acceptor unit (A) and an electron-donor unit (D1) is new, where (A) comprises a bithiopheneimide moiety (I).    USE - The polymer is useful in electronic, optical or optoelectronic device comprising organic photovoltaic device (all claimed), LED, light emitting transistors, thin film semiconductors, solar cells, photodiodes, bulk hetero junction solar cells and FET.    ADVANTAGE - The polymer: exhibits improved device performance (high power conversion efficiency, low band-gap, high fill factor, high open circuit voltage, field-effect mobility, on or off current ratios, and/or air stability), good solubility in common solvents thus enabling device fabrication via solution processes, optimized optical absorption or charge separation, high carrier mobility, good current modulation, good charge transport characteristics and chemical stability in ambient conditions, low-temperature processability, p-type semiconductor activity, ambipolar activity, light absorption, light emission, tuned redox properties and processing versatility.    DETAILED DESCRIPTION - Polymer comprising electron-acceptor unit (A) and an electron-donor unit (D1) is new, where (A) comprises a bithiopheneimide moiety of formula (I).    L = -O-, -S-, -Se-, -OC(O)-, -C(O)O-, divalent 1-20C alkyl, divalent 1-20C haloalkyl or covalent bond; and    Ar1 = 6-20C aryl or 5-20 membered heteroaryl (both optionally substituted).    INDEPENDENT CLAIMS are also included for:    (1) an electronic, optical or optoelectronic device comprising a polymeric semiconductor component that comprises the polymer; and    (2) an organic photovoltaic device comprising an anode (22), a cathode (26), optionally at least one anode interlayer, optionally at least one cathode interlayer, and the polymeric semiconductor component in between the anode and cathode.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the organic photovoltaic device which can incorporate the polymer in its photoactive layer.    Substrate (20)    Anode (22)    Photoactive layer (24)    Cathode (26)