Realize efficient organic afterglow from simple halogenated acridan derivatives

• A new group of efficient RTP emitters was proposed. • Rational design improved ISC efficiency and restrained non-radiative decay. • Br-DMAc realized high RTP efficiency up to 3.2% with lifetime about 372 ms. • Applications in information encryption and fingerprint detection are showcased. Organic molecules with persistent room-temperature phosphorescence (RTP) have attracted considerable attention due to their broad applications, but typically suffered from low emission intensity and short lifetime. In this contribution, a twisted donor-acceptor (D-A) system by simple conjugation of acridan and aryl halide is proposed to construct efficient and ultralong RTP luminogens. The photophysical measurements and theoretical predictions demonstrate the halogenation renders simultaneous realization of large spin-orbital coupling (SOC), small energy gap between singlet/triplet excited states, and restrained non-radiative decay channel, which benefit for RTP properties. Correspondingly, the acridan derivatives realized phosphorescence quantum efficiency up to 3.2% with lifetime up to 372 ms in its crystalline state, and also exhibited distinct afterglow in heavily grinded samples. To demonstrate the potential applications, these materials were furtherly explored in information encryption and fingerprint identification. This study not only provides rare examples of efficient and long-lived phosphors based on acridan building block, but also sheds light on the inherent photophysical mechanism of RTP materials and paves a way to design highly promising RTP luminogens with a simplified structure.