NOVELTY - Device comprises at least one cathode; at least one anode; and at least one photovoltaic active layer disposed between the cathode and anode and comprising at least one p-type material and at least one n-type material, where the p-type material comprises at least one polymer comprising a polymer backbone moiety.    USE - The device is useful as organic photovoltaic device.    ADVANTAGE - In the invention, good photovoltaic efficiency and lifetime can be achieved. The R group can provide solubility, environmental stability, and fine tuning of spectroscopic and/or electronic properties. Different polymer microstructures can be prepared which encourage multiple band gaps and broad and strong absorptions. The carbonyl can interact with adjacent thiophene rings to provide backbone with rigidity, induce planarity, and reduce and/or eliminate intramolecular chain twisting defects.    DETAILED DESCRIPTION - Device comprises at least one cathode; at least one anode; and at least one photovoltaic active layer disposed between the cathode and anode and comprising at least one p-type material and at least one n-type material, where the p-type material comprises at least one polymer comprising a polymer backbone moiety comprising any of formulae I, V, VI, VII, VIII, VIII-B, where moiety (I) is directly covalently linked through the thiophene ring to at least one fused ring structure, where the moiety V is bivalently linked to the polymer backbone via the R1 and R2 groups.    A1 and A2=each independently comprise a fused ring system comprising at least two fused rings directly covalently linked to cyclic polymer substructure of formula IX, or each independently do not comprise an unfused thiophene or unfused benzene ring directly covalently linked to cyclic polymer substructure of formula IX;    A=a heteroatom, where in formula VII, the two illustrated thiophene rings independently are each part of a fused ring system;    R's=form a ring; and    R1 and R2 groups=form a ring, where the ring is directly, covalently linked to at least one fused ring structure.    INDEPENDENT CLAIMS are:    (1) a composition comprising an oligomer or a polymer having a donor-acceptor structure, where the donor comprises a fused ring system which is directly and covalently linked to an acceptor structure comprising diketopyrrolopyrrole structure; or a composition comprising an oligomer or a polymer having a donor-acceptor structure, where the acceptor comprises a diketopyrrolopyrrole structure which is not directly and covalently linked to a donor structure by an unfused thiophene or an unfused benzene ring; or a composition comprising at least one polymer comprising a polymer backbone moiety of formula VIII; or composition comprising at least one oligomer comprising an oligomer backbone moiety of formula VIII, where the oligomer comprises at least two polymerizable groups; or a composition comprising at least one moiety of formula VIII, where at least one of A1 or A2 comprises an arylamine moiety directly, covalently linked to cyclic polymer substructure of formula IX; and    (2) a method comprising preparing polymer backbone moiety comprising formula VIII; modifying the compound so that A1 and A2 each comprise at least one polymerizable group.