Acceptor-Type Singlet Fission Material Based on Strong Absorption Tetracyanothienoquinoid Skeleton

The practical efficiency of singlet fission (SF)-based photovoltaic devices is still far from satisfactory due to the limited scope of SF materials suitable for device application and the scarcity of schemes available for triplet utilization. Most SF materials identified to date are typically electron donors while acceptor-type SF materials remain largely unexplored. Basically, the combination of a conventional electron donor and SF-active electron acceptor could circumvent the competitive energy transfer channel and better play the unique advantages of the SF process, which might be an adequate alternative for practical application. In this work, we presented a new acceptor-type SF material based on a tetracyanothienoquinoid skeleton. Such a quinoid skeleton exhibited strong absorption, ultrafast SF process, and excellent stability. Using transient spectroscopy and multireference calculations (XDWCASPT2), the SF dynamics were examined featuring the rapid generation and subsequent annihilation and/or partial dissociation of multiexciton states. Therefore, our results not only provide a robust acceptor-type SF material but also suggest an adequate donor-acceptor alternative for SF-based solar cells, which could pave the way for the practical application of such a potential process.