PMMA and PVDF luminescent films containing Eu(III) and Tb(III) tetrakis complexes as candidates for phosphor-converted UV LED application

In the search for lighting devices application, the aim of this study was the synthesis and characterization of films via the drop-casting method based on tetra substituted complexes of europium(III) with dibenzoylmetanate (Hdbm), for red emission, and terbium(III) with acetylacetonate (Hacac), for green one, using the polymers polymethyl-methacrylate (PMMA) and polyvinylidene fluoride (PVDF). The tetrakis complexes Q1[Eu(dbm)4], where Q1 = Didodecyldimethylammonium (C26H56N+) and Na[Tb(acac)4] were successfully obtained without water molecules in the coordination sphere, having their molecular properties and structural (FTIR, TGA, MALDI-TOF, elemental analysis) and optical (UV-Vis and photoluminescence) fully elucidated. In the case of the Q1[Eu(dbm)4] complex, films supported on PMMA or PVDF, in concentrations of 0.1%, 0.25%, 0.5%, 0.75%, 1%, 2% and 5% were produced. As for the Na[Tb(acac)4] complex, for both PMMA and PVDF films, the concentrations used were 0.5%, 0.75%, 1%, 2% and 5%. All films had their luminescent properties evaluated and it was observed that the concentration of the complexes embedded in the two polymers modifies the analyzed photophysical parameters (lifetime, intrinsic quantum yield and absolute quantum yield), but not uniformly, as at high complexes concentrations tend to form clusters. Among the series of red-emitting polymeric films, both in PVDF and in PMMA, those with a concentration of 1% of the Eu(III) complex were considered the most promising candidates for manufacturing LED prototypes. In the case of green-emitting films, the 5% concentration of terbium(III) tetrakis complex results in a more suitable system to be used in the production of lighting devices. Therefore, the red and green luminescent films produced can be used to produce phosphor-converted UV LED devices.