Highly Efficient Persistent Room‐Temperature Phosphorescence from Heavy Atom‐Free Molecules Triggered by Hidden Long Phosphorescent Antenna

Abstract Persistent (lifetime > 100 ms) room‐temperature phosphorescence ( p RTP) is important for state‐of‐the‐art security and bioimaging applications. An unclear relationship between chromophores and physical parameters relating to p RTP has prevented obtaining an RTP yield of over 50% and a lifetime over 1 s. Here highly efficient p RTP is reported under ambient conditions from heavy atom‐free chromophores. A heavy atom‐free aromatic core substituted with a long‐conjugated amino group considerably accelerates the phosphorescence rate independent of the intramolecular vibration‐based nonradiative rate from the lowest excited triplet state. One of the designed heavy atom‐free dopant chromophores presents an RTP yield of 50% with a lifetime of 1 s under ambient conditions. The afterglow brightness under strong excitation is at least 10 4 times stronger than that of conventional long‐persistent luminescence emitters. Here it is shown that highly efficient p RTP materials allow for high‐resolution gated emission with a size of the diffraction limit using small‐scale and low‐cost photodetectors.