Enhanced Ultra-Long Room Temperature Phosphorescence by Intermolecular Donor-Acceptor Interaction in Polymer Network

Ultra-long room temperature phosphorescence (URTP) is an attractive phenomenon in organic photonics. However, most of the reported strategies for enhancing URTP require complicated synthesis processes. Herein, a novel strategy is reported, two birds with one stone, for enhancing URTP by doping the ground-state intermolecular donor-acceptor complexes into a dense polymer network: i) The dense network ensures the formation of intermolecular donor-acceptor complexes, which provide a smaller singlet-triplet energy difference (Delta EST) and more intersystem crossing (ISC) channels than the individual donor or acceptor molecules; ii) The dense network adequately suppresses the non-radiative relaxation caused by molecular vibrations and oxygen quenching. The URTP intensities of the intermolecular donor-acceptor complexes doped film are 20 times higher than that of the film only doped with acceptor molecules, and the phosphorescence lifetime is up to 200 ms. The theoretical calculation reveals the electronic interaction between donor and acceptor and the increased ISC channel, which elucidates the photophysical mechanism of the strategy and confirms its rationality. An advanced encryption application is developed based on enhanced URTP films. This work opens a new direction for URTP materials through the intermolecular donor-acceptor interaction.

Automated summary

A novel strategy for enhancing ultra-long room temperature phosphorescence (URTP) is reported by doping ground-state intermolecular donor-acceptor complexes into a dense polymer network. This strategy increases URTP by ensuring formation of intermolecular donor-acceptor complexes and suppressing non-radiative relaxation. The URTP intensity and phosphorescence lifetime of the doped film are significantly improved compared to the film doped with acceptor molecules only. The photophysical mechanism and rationality of the strategy are confirmed by theoretical calculations, and an advanced encryption application based on enhanced URTP films is developed.