Investigating the Long-Term stability of photoluminescence lifetimes in PMMA films doped with β-Diketonate europium complexes based on bipyridine derivatives

In this work, two β-diketonate ligands: dibenzoylmethane (DBM) and Hexafluoroacetone (hfac) have been selected to synthesize a series of β-diketonate europium complexes based on bipyridine and terpyridine derivatives. These complexes were then incorporated into PMMA films to comprehensively investigate their thermal and long-term photoluminescence stability. Comparatively, Eu(hfac)L1-5 demonstrated higher heat resistance than Eu(DBM)L1-5, as indicated by their respective initial decomposition temperatures. Various aspects including absorbance, excitation, and emission were examined in solution, powder, and within the PMMA-doped films. Notably, the complexes exhibited a remarkable red emission peak at 613 nm and a high photoluminescence quantum yield. To assess their stability, the films were subjected to light, indoor, and dark storage conditions for 720 h, with photoluminescence measurements recorded at both 0 h and 720 h. The results revealed that the hfac-based europium complexes (Eu(hfac)3L1-5) demonstrated good stability under light, indoor, and dark conditions compared to the DBM-based europium complexes (Eu(DBM)3L1-5). This study highlights the direct impact of the β-diketonate ligand structure on the stability of such complexes in films, thus showcasing their potential for future applications in stable optoelectronic devices.