NOVELTY - A conjugated polymer (P1) comprising carbonyl substituted thieno (3,4-b) thiophene units, is new.    USE - As photovoltaic material in photovoltaic devices, where the photovoltaic devices are polymer solar cell devices or photodetector devices; and as active layer material in electronic devices, where the electronic devices are field effect transistors, light emitting devices, and sensors, electrochromic devices and capacitors (all claimed).    ADVANTAGE - The conjugated polymer possesses high mobility, good harvest of sunlight, good processibility, and proper molecular energy level; has a good solar cell material; and also shows excellent photovoltaic properties, especially in obtaining higher open circuit voltage, and as a result, a power conversion efficiency of 7.7% with an open circuit of 0.78V and a short circuit current of 15mA.    DETAILED DESCRIPTION - A conjugated polymer (P1) comprsing carbonyl substituted thieno (3,4-b) thiophene units of formulae (I)-(IV), is new.    R1 and R2=proton, halo, optionally substituted alkyls, amino, N-substituted amino groups or optionally substituted aryls;    Ar'=ethenylene, or ethynylene, or monocyclic, bicyclic and polycyclic arylenes, or monocyclic, bicyclic and polycyclic heteroarylenes, or unit being comprised of at least two compounds choosing from ethenylene, ethynylene, or monocyclic, bicyclic and polycyclic arylene, or monocyclic, bicyclic and polycyclic heteroarylenes;    R'1=proton, optionally substituted alkyls or optionally substituted aryls;    R'2, and R3-R6=proton, optionally substituted alkyls, optionally substituted alkoxyls, halo or optionally substituted aryls;    R'1a=proton, optionally substituted alkyls or optionally substituted aryls;    R'2a and R'3-R'6=proton, optionally substituted alkyls, optionally substituted alkoxyls, halo or optionally substituted aryls;    R'1b, R'3a and R'4a=proton, optionally substituted alkyls or optionally substituted aryls;    R'2b=proton, optionally substituted alkyls, optionally substituted alkoxyls, halo or optionally substituted aryls;    X=carbon, silicon or germanium;    n=not defined.