Singlet fission as a polarized spin generator for biological nuclear hyperpolarization

Singlet fission (SF), converting a singlet excited state into a spin-correlated triplet-pair state, is the sole way to generate a spin quintet state in organic materials. Although its application to photovoltaics as an exciton multiplier has been extensively studied, use of its unique spin degree of freedom is largely unexplored. Here, we demonstrate that the spin polarization of the quintet multiexcitons generated by SF improves the sensitivity of biological magnetic resonance through dynamic nuclear polarization (DNP). We form supramolecular assemblies of a few pentacene chromophores and use SF-born quintet spins to achieve DNP of water-glycerol, the most basic biological matrix, at lower microwave intensities than for conventional triplet-based DNP. Our demonstration opens a new use of SF as a “polarized spin generator” in bio-quantum technology.