Triplet Exciplex Mediated Multi‐Color Ultra‐Long Afterglow Mate‐rials.

Organic long‐lived phosphorescent materials demonstrating ultra‐long photoluminescence have practical advantages owing to their flexible design and easy processability. However, the exact photophysical process underpinning the persistent‐luminescent continues to elude full understanding, and the principles governing the compatibility of hosts and guests remain elusive. In this work, a new type of nonradiative energy transfer mechanism is proposed for the bi‐component RTP system. Different from Förster resonance energy transfer or Dexter‐type energy transfer, this energy transfer mechanism primarily relies on a triplet exciplex to exchange the electron. This facilitates the formation of triplet excitons that are otherwise difficult to excite directly. An evaluation methodology is devised to gauge the potential of a specific dopant‐host combination toward generating pronounced afterglow. According to this framework, the enhancement of the afterglow is proportional to the decrease in the activation energy (ΔG≠) associated with the electron transfer reaction between the dopant and the host. Notably, when the ΔG≠ too larger, no observable afterglow occurs, as higher ΔG≠ values significantly impede the electron transfer reaction between the two components. Furthermore, the remarkable dependence of afterglow intensity on the dopant concentration renders the bi‐component RTP system highly promising for applications requiring ultra‐high sensitivity and broad‐spectrum detection capabilities. [ABSTRACT FROM AUTHOR]