Ultralong excimer phosphorescence by the self‐assembly and confinement of terpyridine derivatives in polymeric matrices

Ultralong organic room temperature phosphorescence (RTP) is attracting increasing attention due to its fascinating optical phenomena and wide applications. Among various RTP, excimer phosphorescence is of fundamental significance, but it remains a considerable challenge to achieve flexible, multicolor and large‐area excimer RTP materials, which should greatly advance the understanding and development of organic light‐emitting devices. Herein, we present ultralong excimer RTP films by the self‐assembly and confinement of terpyridine (Tpy) derivatives in polymeric matrices. Strikingly, the self‐assembly of Tpy derivatives induces the formation of excimer complexes, thus immensely minimizing singlet‐triplet splitting energy (ΔEST) to promote the intersystem crossing process. Furthermore, the confinement by multiple hydrogen bonding interactions as well as the compact aggregation of phosphors jointly suppresses the nonradiative transitions, leading to long‐lived excimer RTP (τ = 543.9 ms, 19,000‐fold improvements over the powder). On account of the outstanding afterglow performance and color‐tunability of RTP materials, flexible and large‐area films were fabricated for intelligent display, anticounterfeiting, and time‐resolved information encryption. Ultralong excimer RTP is successfully realized by the aggregation and confinement of terpyridine derivatives in polymeric matrices. Experimental results and theoretical calculations jointly unveil that the ultralong RTP originates from triplet excimer emission. Taking advantage of the outstanding afterglow performance and color‐tunability of RTP materials, flexible, and large‐area films are fabricated for intelligent display, anticounterfeiting, and time‐resolved information encryption.