Singlet fission, a process in which a singlet exciton in an organic solid forms a singlet biexciton which then splits into two independent triplet excitons, promises a route for circumventing the Shockley-Queisser limit to the efficiency of single-junction solar cells. Unfortunately, even for the most suitable chromophores other processes often intervene. Only very few materials are known to provide a triplet quantum yield close to 200% and they appear impractical for other reasons. In an effort