Tailoring Molecular Architectures for Intramolecular Charge Separation of the Multiexciton State Generated by Singlet Fission

Harvesting multiexcitons generated by singlet fission (SF) holds promise for advancing optoelectronic devices and photochemistry. Conventional approaches focus on interfacial exciton or charge transfer after dephasing the triplet-pair [T1T1] to low-energy free triplets. However, the high potential [T1T1] state possesses a unique characteristic multi-reference wavefunction, opening new opportunities for advancing underexplored multiexciton-driven photochemical processes. Here, we report a functional multicomponent system with covalently integrated electron-rich moieties to direct multiexciton charge transfer specifically from the [T1T1] state to a charge separated (CS) state. We elucidate the design rules of these second generation [G2] SF chromophores that favor multiexciton-driven charge separation prior to dephasing into free triplets. Our spectroscopic studies reveal how the same SF system can mediate either generation of free triplets or CS formation from [T1T1] by modulating the local dielectric environment. These findings provide fundamental insights into multiexciton dynamics and lay the foundation for unconventional multiexciton-driven energy conversion systems.