Sensitized Singlet Fission in Pentacene-Subphthalocyanine Conjugates

The goal of harnessing the theoretical potential of singlet fission (SF), a process in which one singlet excited state is split into two triplet excited states, has become a central challenge in solar energy research. Covalently-linked dimers provide crucial models for understanding the role of chromophore arrangement and coupling in SF. Sensitizers can be integrated into these systems to expand the absorption bandwidth through which singlet fission can be accessed. Here, we define the role of the sensitizer-chromophore geometry in sensitized singlet fission model systems. To this end, several conjugates have been synthesized consisting of a pentacene dimer (SF motif) connected via a rigid alkynyl bridge to subphthalocyanines (the sensitizer motif). Steady-state and time-resolved photophysical measurements are used to confirm that both conjugates operate as per design, displaying near unity energy transfer efficiencies and high triplet quantum yields from SF.