Thermal-Annealing Enhanced Room-Temperature Phosphorescence of Polymer-Based Organic Materials

Polymer-based organic room-temperature phosphorescent (RTP) materials have recently attracted significant attention. In most of the previous works, 'chemical approaches' were applied to improve the performance of RTP materials, such as designing certain phosphors or selecting specific polymeric matrixes. However, enhancing triplet emission through facile 'physical approaches' is rarely reported. In this study, enhanced RTP emissions of phosphor-doped polymers are reported by thermal annealing. By doping a difluoroboron beta-diketonate derivative into poly(diacetone acrylamide) (PDAAM), green RTP emissions can be obtained. After thermal annealing at 125 degrees C for 5 min, the afterglow duration of RTP increases from 2.6 to 5.3 s and also the brightness of RTP emission exhibits a threefold increase. Such post-treatment is applicable for various polymeric matrixes. The mechanism underlying thermal-annealing enhanced RTP is investigated. Moreover, it demonstrates that controlled RTP by thermal annealing can be used in information encryption and anti-counterfeiting. This work provides new insight into the development of organic RTP materials with tunable emissions. Lifetimes and intensities of room-temperature phosphorescence (RTP) emissions of phosphor-doped polymers can be enhanced by a facile physical post-treatment, i.e., thermal annealing. Such 'thermal-annealing enhanced RTP' is due to the increased packing density of polymer chains after thermal annealing (physical aging), which suppresses non-radiative decay and improves the oxygen barrier of matrixes.image