Singlet exciton fission in a linear tetracene tetramer

A novel covalently linked tetracene tetramer was synthesized for the first time. Intramolecular singlet fission (iSF) can be conducted efficiently within this tetramer with the triplet state quantum yield as high as 128% and a lifetime >100 mu s in solution. This is the highest iSF yield achieved so far in a tetracene compound in solution, and it is also the only case with a triplet quantum yield exceeding 100%. The unexpected long lifetime for the triplet state formed via iSF in this tetramer is favorable for the application of iSF in solar cells. This remarkably promoted iSF efficiency in comparison with that of the tetracene trimer with similar molecular structure can be attributed to the enhanced delocalization of singlet excitons in this molecule.