Designing potentially singlet fission materials with an anti-Kasha behaviour

Singlet fission (SF) compounds offer a promising avenue for improving the performance of solar cells. Using TD-DFT methods, anti-Kasha azulene derivatives that could carry out SF have been designed. For this purpose, substituted azulenes with a donor (–OH) and/or an acceptor group (–CN) have been systematically studied using the S₂ ≥ 2T₁ formula. We have found that –CN (–OH) substituents on electrophilic (nucleophilic) carbons result in improved SF properties when compared to azulene.