The present invention relates to 1,4-diketopyrrolo[3,4-c]pyrrole (DPP) derivatives of the below formula to their manufacture; to their use as organic semiconductors, e.g. in semiconductor devices, especially a sensor, a diode, a photodiode, an organic field effect transistor, a transistor for flexible displays, and/or a solar cell (photovoltaic cell); to such semiconductor devices comprising diketopyrrolopyrrol derivatives of the formula I as a semiconducting effective means, and to devices containing said semiconductor devices. The compounds of the formula I have excellent solubility in organic solvents. High efficiency of energy conversion, excellent field-effect mobility, good on/off current ratios and/or excellent stability can be observed, when said compounds are used in semiconductor devices or organic photovoltaic (PV) devices.