Advances in AIE-based solid-state fluorescent photoswitches

Photoswitchable molecules exhibit remarkable advantages, including rapid response, reversibility, and fatigue resistance, and hold tremendous potential for applications in fields such as anti-counterfeiting, super-resolution imaging, optical information storage, and sensing. Compared to their solution-state counterparts, solid-state fluorescent photoswitches offer advantages such as enhanced stability and ease of processing/integration, representing a more desirable form for practical applications. However, the restricted molecular packing in the solid state often hinders the photoisomerization of the photochromic units, leading to compromised photochromic performance. The integration of aggregation-induced emission (AIE) motifs with fluorescent photoswitches is an effective strategy for achieving high-performance solid-state fluorescent photoswitches. The twisted conformations of AIE luminogens (AIEgens) provide the necessary spatial freedom for the photoisomerization of the photochromic units in the solid state, thereby successfully overcoming the limitations imposed by molecular packing and enabling efficient solid-state fluorescent photoswitching. This review summarizes the representative types of solid-state fluorescent photoswitchable molecular systems developed in recent years based on this strategy, along with their applications. It aims to provide guidance for the design of novel solid-state photoswitchable systems and is significant for deepening the understanding of their stimulus-responsive mechanisms, developing new materials, and expanding their application scope.