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.