Regulation of the Helical Organic Co-crystal for Room-Temperature Phosphorescence via External Heavy-Atom and Polarity Effects

The development of phosphorescent materials, in particular those with room-temperature phosphorescence (RTP), has attracted a great deal of attention due to their great potential in optoelectronics, sensing, and bioelectronics. In this study, we present an organic co-crystal with RTP behavior, prepared via a solution self-assembly strategy using benzo[b]naphtho[1,2-d]thiophene (BNT) as the electron donor and octafluoronaphthalene (OFN) as the electron acceptor. The organic co-crystals can achieve RTP upon introduction of a heavy-atom-containing solvent with a high polarity to regulate the radiative decay pathway. The heavy-atom effect and high orbital coupling constant between the S₂ and T₁ excited states were the crucial factors for phosphorescence activation. In addition, the co-crystals exhibit unique supramolecular chirality driven by polarity with helical morphologies and tunable colors. Our findings provide valuable insights into the design of RTP organic co-crystals and colorful helices.