Electrically tunable polarized luminescence from guest–host composites via interaction between rare earth complexes and liquid crystals

Polarized luminescence has many applications in energy saving, displays, communication and other fields. Here, electrically tunable polarized luminescence of aligned Eu(tta)₃phen/E7 composites is successfully obtained based on the interaction between liquid crystal (LC) hosts and rare earth (RE) complex guests. The generation mechanism of the polarization effect is thoroughly explored from three different aspects. The polarized luminescence of Eu(tta)₃phen/E7 composites is closely related to the polarized energy absorption of incident light, the site symmetry of Eu³⁺ ions for oriented Eu(tta)₃phen complex molecules, and the polarized energy transfer from E7 to Eu(tta)₃phen. The convenient control of the well-aligned Eu(tta)₃phen complex by simply embedding the Eu(III) complex guest in the E7 host and utilizing small-magnitude electric field forces is explicitly confirmed. The E7 host not only provides the orientation condition for the electrically tunable polarized luminescence but also promotes the degree of polarization through polarized energy transfer. The polarized spectral properties and the symmetry of the Eu³⁺ site of the aligned Eu(tta)₃phen complexes are described in detail. The analysis of the generation mechanism of polarized luminescence supplements the research content in the field of RE/LC composites and paves the way for exciting novel advances in the field of polarized emission.