Efficient singlet fission in an orthogonal anthracene dimer film

Developing efficient singlet fission (SF) materials with high triplet energy and good stability for practical applications is still a challenge. Anthracene is stable and can carry out SF but with less efficiency, because its SF is strongly endothermic. Herein, using time-resolved fluorescence and transient absorption spectroscopy, we found for the first time an efficient SF material (phi(T) = 164%) based on an anthracene dimer, with high triplet energy (1.51 eV) and good stability simultaneously. This is attributed to its orthogonal dimeric structure and the nearly perpendicular intermolecular conformation in its solid film that could decrease its triplet energy moderately to make SF thermodynamically isoergic. This result suggests that a covalently linked anthracene dimer might be an ideal structure skeleton to develop new SF materials with high efficiencies and good stability.