Stimuli‐Responsive and Tunable Host–Guest Ultralong Organic Phosphorescence: Design Strategies and Multifunctional Applications

ABSTRACT Ultralong organic phosphorescent (UOP) materials have emerged as a transformative class of luminescent systems exhibiting prolonged afterglow under ambient conditions. In recent years, extensive efforts have been put on molecular design and aggregation control toward efficient UOP systems, with a growing focus on host–guest systems. Stimuli‐responsive UOP materials have been a vibrant and promising research direction in smart luminescent materials. This review summarizes recent progress in organic UOP materials that respond to external stimuli (heat, light, and mechanical force) as well as internal chemical cues (solvent polarity, acid/base conditions, and humidity). The basic luminescent mechanisms of UOP are first introduced, followed by a detailed summary of molecular designing principles and strategies for the construction of efficient and tunable stimuli‐responsive UOP materials. Various practical applications of these materials, such as bioimaging, sensing, anti‐counterfeiting, data encryption, and 3D printing, are overviewed. Finally, current challenges and future research directions are discussed to highlight the key opportunities and focus for the advancement of the next‐generation UOP systems.