Achieving trap-depth-tunable organic persistent luminescence through host energy-level engineering

Recent studies have indicated that traps play a crucial role in determining characteristics of organic persistent luminescence, yet constructing traps with controllable depth remains highly challenging. Herein, we propose a host energy-level engineering strategy, which enables precise control of trap depth. Using the Randall-Wilkins method, the trap depth can be tuned from 0.38 to 0.72 eV without altering emission wavelength and the result aligns well with density functional theory calculations. Specifically, a host-guest material namely CPND@DPEPO, which has a deep trap of ~ 0.72 eV, exhibits deep-blue persistent luminescence lasting for 27 hours and efficient energy storage over 14 days at room temperature. By utilizing these trap-containing materials as the emission layer in organic light-emitting diodes, we develop a pixel-programmable information storage device. This work establishes a fundamental principle for designing organic materials with controllable trap depth, potentially expanding their applications in night tracing, military communication and biological imaging. Zhan et al. report a host energy level engineering strategy to modulate trap depth in organic host-guest systems, achieving persistent luminescence up to 27 hours and energy storage for 14 days. 4×4 electroluminescent arrays based on the host-guest system demonstrate pixel-programmable information storage capabilities.