A series of polymers based on 8,8'-biindeno[2,1-b] thiophenylidene for use in photovoltaic devices and field-effect transistors are reported. These structurally twisted olefins are effective building blocks for preparation of low bandgap polymers with optical bandgaps of 1.2-1.5 eV. Device performance, such as V-oc and J(sc), in solar cell devices could be successfully modulated by incorporation of a variety of comonomers. Ambipolar properties in field-effect transistors using Au electrodes were also studied, with PtBTPDPP exhibiting balanced charge transport properties with hole and electron mobilities of 0.09 and 0.12 cm(2).V-1.s(-1), respectively. (C) 2015 Wiley Periodicals, Inc.