In view of climate change and the needs of the energy reform, it has become particularly important to significantly increase the efficiency of organic solar cells. In a process known as ‘singlet fission’, one photon simultaneously excites two electrons. If this effect can be exploited, it may well be possible to dramatically increase the power generated by solar cells. Physicists and chemists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) collaborating in an international joint project with Northwestern University in the USA have successfully worked out all the decisive intermediate phases in the singlet fission process and have managed to describe the mechanism in detail for the first time. The results have been published in the leading specialist journal Nature Communications.