Boosting ultralong organic phosphorescence performance by synergistic heavy-atom effect and multiple intermolecular interactions in molecular crystal

Ultralong organic phosphorescent (UOP) luminogens are of great practical importance in the field of optoelectronics, however, it remains a significant challenge to construct materials with high phosphorescent yields (Phi(ph)) and long lifetimes simultaneously. We herein present a feasible molecular engineering strategy to boost the Phi(ph) and lifetime via a synergistic heavy-atom effect and methylation approach used to adjust the intrinsic photophysical processes and solid packing. As expected, efficient UOP with an enhanced Phi(ph) of 11.1% and an improved lifetime of 391 ms is obtained for BrMOPP consisting of one methyl moiety and bromine atom in the 5,5-dioxide phenothiazine skeleton, which is much better than that of reference luminogen without functional units (0.5%, 185 ms). Dense network packing formed through multiple intramolecular interactions along with a, b, and c axis directions provides the rigid molecular alignment in the three-dimensional framework, suppressing the nonradiative relaxation pathway. Combining with the efficient intersystem crossing induced by the bromine atom, the resulting phosphors with excellent Phi(ph) and long lifetime are achieved, and are successfully applied to anti-counterfeiting and data encryption. This study will provide a reasonable approach for further optimizing the UOP performance from the molecular level.

Automated summary

By utilizing a molecular engineering strategy involving a heavy-atom effect and methylation approach, the study achieved significant improvements in the phosphorescent yield and lifetime of ultralong organic phosphorescent luminogens. The resulting phosphors demonstrated excellent performance and were successfully applied to anti-counterfeiting and data encryption.