OLEDs are attractive and distinctive light sources because of they are very thin, emit over an area and can be flexible. These features also make them very interesting for medical applications as compact, lightweight sources can enable ambulatory treatment. In photodynamic therapy (PDT), light in combination with a photosensitiser leads to the generation of reactive oxygen species that can kill nearby cells. We report the development of improved OLEDs for PDT. In particular, we show their use for antimicrobial PDT i.e. for killing bacteria, parasites and fungi in vitro.