Singlet fission can overcome efficiency limits in solar cells by converting one photon into two triplet excitons. But even the most efficient singlet fission organic chromophores like pentacene do not possess triplet energies, E(T₁), compatible with the band gaps, E_g, of commonly used Si- and GaAs-based photovoltaic devices. Peropyrene fulfills these energetic requirements, but unsubstituted peropyrene fails to efficiently undergo singlet fission because of excimer formation. We solve this problem by bending peropyrene to enable favorable packing in the solid-state without perturbing the electronic structure of the chromophore itself.

Bending of shorter and longer homologs of peropyrene has previously been achieved through several strategies. None of these methodologies, however, are transferable to the peropyrene scaffold, leaving the route to progressive bending in peropyrene inaccessible. We address this limitation by employing π-radical cascade reactions^[1], a versatile synthetic platform that enables progressive bending of the peropyrene framework, providing a series that allows a systematic evaluation of how molecular curvature suppresses excimer formation in the solid state and ultimately enhances the efficiency of singlet fission.

[1] P. L. Widmer, L. Valenta, M. Mayländer, J. Hutter, F. J. Carta, S. Jurt, O. Blacque, L. Bigler, S. Richert, T. Šolomek and M. Juríček Angewandte Chemie International Edition 2026, e6610209.