The present invention relates to polymers comprising one or more (repeating) unit(s) of the formula A polymer, comprising (repeating) unit(s) of the formula (1) and (2), wherein A is a repeating unit of the formula (I), and —COM1- is a repeating unit of formula (3), or (4), and their use as organic semiconductor in organic devices, especially in organic photovoltaics (solar cells) and photodiodes, or in a device containing a diode and/or an organic field effect transistor. The polymers according to the invention have excellent solubility in organic solvents and excellent film-forming properties. In addition, high efficiency of energy conversion, excellent field-effect mobility, good on/off current ratios and/or excellent stability can be observed, when the polymers according to the invention are used in organic field effect transistors, organic photovoltaics (solar cells) and photodiodes.