Molecular Engineering via Controlling Structural Deformation for Highly Efficient Ultralong Organic Phosphorescence

It is an enormous challenge to achieve the highly efficient organic room-temperature phosphorescence (RTP) with long lifetime. Here we demonstrated that by bridging the carbazole and halogenated phenyl ring with methylene linker, a type of RTP phosphors CzBX (X = Cl, Br) shows high phosphorescence efficiency ( Ф Ph ), up to 38% for CzBBr with a lifetime of 220 ms, which is much higher than that of compounds CzPX (X = Cl, Br) with C-N bond as a linker ( Ф Ph < 1%). Single crystal analysis and theoretical calculations revealed that, in the crystal phase, the intermolecular π-Br interaction accelerates the intersystem crossing process, while tetrahedron-like structure induced by sp 3 methylene linker restrains the nonradiative decay channel, leading to the high phosphorescence efficiency in CzBBr. This research not only paves a new road for achieving highly efficient and long-lived RTP materials but also expands the applications in anti-counterfeiting or data encryption.