The current work investigates two fundamental problems of small molecule organic solar cells (OSC): transparent top contacts and alternative donor materials. Transparent top contacts are a prerequisite for inverted, i.e. top-illuminated OSC on opaque substrates. This work documents that transparent, ultra-thin metal films are a possible solution to this challenge. It is shown that silver or gold layers with thicknesses Three diindenoperylene derivatives are introduced as green donor materials. Although these experiments are still at a very early stage, OSC...