Gel Displays Heating-Activated Wavelength-Tunable High-Temperature Phosphorescence

Organic room-temperature phosphorescence materials are valuable for information storage, encryption, and sensing. In most systems, heating accelerates non-radiative decay, leading to monotonic weakening and loss of phosphorescence. High-temperature tolerance, tunable color, and heating-activated emission are seldom combined in one system. A triphenylamine derivative is doped into a calcium polyacrylate matrix to construct a material in which heating activates phosphorescence. The hydrated network shows no phosphorescence at room temperature. Heating induces a phase separation that initiates and intensifies the emission, which is opposite to typical thermal quenching. Continued heating removes water and locks the rigid microenvironment, yielding a phosphorescent xerogel. In this xerogel, emission is reversibly tuned from 505 nm to 450 nm, a visible afterglow persists to 473 K, and a lifetime of about 9 ms remains detectable at 573 K. Mechanistic studies attribute this behavior to multi-force synergy within the matrix: hydrogen bonding provides baseline rigidity for triplet stabilization, Ca²⁺-COO^- coordination imparts thermal stability and triggers phase separation, and the resulting phase-separated domains form the confined microenvironment responsible for phosphorescence. These results demonstrate that thermally induced phase separation can build molecular rigidity on demand, so that heat acts as an activator rather than a quencher of phosphorescence.