Synthesis of homopolymer containing diphenyl end-capped oligothiophene co-oligomer unit in the side chain. 
[reaction: see text] A new polymer with the diphenyl end-capped oligothiophene co-oligomer unit in the side chain was obtained by the ROMP method.  The polymer showed good photophysical characteristics, thermal stability, and film-forming properties.  A photovoltaic cell fabricated from this polymer showed relatively large open-circuit voltage (V(OC) = 0.7 V), moderate short-circuit current (I(SC) = 0.7 microA/cm(2)), and excellent device stability under ambient conditions.