The invention relates to a blend containing an electron acceptor and an electron donor, the acceptor being an n-type semiconductor which is a small molecule that does not contain a fullerene moiety, the electron donor being a p-type semiconductor which is a conjugated polymer comprising donor and acceptor units in random sequence, to a formulation containing such a blend, to the use of the blend in organic electronic (OE) devices, especially organic photovoltaic (OPV) devices, perovskite-based solar cell (PSC) devices, organic photodetectors (OPD) and organic light emitting diodes (OLED), and to OE, OPV, PSC, OPD and OLED devices comprising the blend.