Cibalackrot-type compounds: Stable singlet fission materials with aromatic ground state and excited state

Singlet fission is a multiexciton generation process, where one singlet exciton is absorbed and two triplet excitons are produced. The potential of more efficient photovoltaic devices utilizing singlet fission materials has attracted wide interests for tuneable, stable organic chromophores with suitable excited-state ordering. The strict energetic requirements hinder the exploration of novel organic materials, and most well-known singlet fission materials, linear acenes, are considered to be unstable in their excited states. To solve the stability issue, excited-state aromaticity provides a feasible research option, from which a few chromophores have been designed and studied. This review describes indolonaphthyridine (IND) derivative chromophores and discusses their ability to undergo singlet fission with superior ambient stability. Deepened theoretical analysis taking into account the excited-state Huckel-aromatic and diradical characters rationalizes the special properties of these chromophores. Moreover, the improved understanding of the aromatic character enables us to outline a feasible design strategy suitable for other scaffolds undergo singlet fission and excited-state aromaticity. Hopefully, this review can light a fire on the way toward various novel singlet fission chromophores designed based on the excited-state aromatic view.

Automated summary

This review focuses on indolonaphthyridine (IND) derivative chromophores and their ability to undergo singlet fission with superior ambient stability. The research explores the excited-state Huckel-aromatic and diradical characters and provides a feasible design strategy for other scaffolds to undergo singlet fission and excited-state aromaticity.