The invention relates to novel organic semiconducting polymers containing one or more monomers derived from s-indacene fused symmetrically on each terminus with dithieno[3,2-b;2′,3′-d]thiophene (IDDTT), cyclopenta[2,1-b;3,4-b′]dithiophene (IDCDT), or derivatives thereof, to methods for their preparation and educts or intermediates used therein, to polymer blends, mixtures and formulations containing them, to the use of the polymers, polymer blends, mixtures and formulations as semiconductors in organic electronic (OE) devices, especially in organic photovoltaic (OPV) devices and organic photodetectors (OPD), and to OE, OPV and OPD devices comprising these polymers, polymer blends, mixtures or formulations.