Tuning Intermolecular Singlet Fission Efficiencies of Perylenediimide Derivatives through Bay Aromatic Substitution

Comprehensive SummarySinglet fission (SF) has potential applications in high-efficiency photo-energy harvesting applications, but its practical application is hindered by the limited number of materials. In this work, we explored the bay aromatic substitution strategy for the design of new perylenediimide (PDI) based SF materials. A series of PDI derivatives with biphenyl or naphthalene units substituted at the bay positions were designed and synthesized to investigate the effects of aromatic substitutes on their photodynamic behaviours. The bay substitutions do not shift the energy level of the PDI core significantly but give rise to different intermolecular coupling strengths in the thin films and affect the intermolecular SF efficiency. Femtosecond transient absorption (fsTA) spectroscopy reveals that appropriate spacing configuration from the bay aromatic substitution groups enhances the SF yields by promoting the interaction of neighbouring PDI cores. Triplet exciton yields of up to 183% have been obtained from these new PDI derivatives, making them potential candidates in future SF-based optoelectronics.