Tunable High-Temperature Afterglow through Recombination of Thermally Released Excitons

Developing smart materials with tunable high-temperature afterglow (HTA) luminescence remains a formidable challenge. This study presents a metal-free doping system using boric acid as matrix and polycyclic aromatic hydrocarbons as dopants. This composition achieves dynamically tunable afterglow combining a bright blue HTA lasting for over ten seconds even at 150℃ and an ultra-long yellow room-temperature phosphorescence (RTP) below 110℃. The observed HTA is attributed to the electron-hole recombination within the dopant molecules. Heating stimuli release the trapped electrons from oxygen vacancies formed by boric acid. The planarity of dopants is investigated playing a pivotal role in modulating Dexter electron transfer (ET) for capturing released electrons by dopants and thereby affecting the overall performance of tunable HTA. This work provides an efficient and universal doping strategy to engineer tunable HTA through the synergistic action of thermally releasing electrons, Dexter ET and electron-hole recombination.