Developing stable organic radical anions to achieve long persistent luminescence for afterglow lighting

The exploration of stable organic radical anions plays a vital role in acquiring efficient exciplex-based organic long persistent luminescence (OLPL) systems with ultralong duration but still remains a formidable challenge. Hereof, we developed an effective exciplex-based OLPL system by improving the stability of radical anions and slowing down the recombination rate of radical intermediates formed from the charge separation of exciplex. The resulting exciplex system exhibits the state-of-the-art ultralong green OLPL with a duration surpassing 180 min. Time-dependent electron spin resonance measurements demonstrate that stable radical anions formed in the developed acceptors and slow radical ion recombination rate should be responsible for this remarkable OLPL emission. More interestingly, using the light-emitting diode containing the prepared OLPL materials, an intelligent afterglow lighting device was established, with which the words can be recognized even 180 s after turning off the voltage. The current study not only provides valuable insights into developing acceptors for achieving high-performance OLPL materials but also sheds light on their applications in energy-saving afterglow lighting.