The luminescence features of new europium-based PEO electrolytes where the lanthanide ion is encapsulated into a ligand structure cage (eg Eu3+-picrate complexes with trans-1,4-dithiane-1,4-dioxide, TDTD) were reported. The complexes are non-hygroscopic and strongly luminescent in the temperature range of 10 to 300 K. The emission spectra were recorded in this temperature range and the corresponding lines assigned to the D-5(0.1)-->F-7(0-4) transitions. The measured line widths, which are of the same order of magnitude of the one observed in crystals (1-2 Angstrom), are approximately,two orders of magnitude sharper than the ones observed in glasses and other Eu3+ based polymeric materials. The Stark components of the F-7(0.4), D-5(0) levels and the corresponding barycenters were calculated;and modeled by the superposition of the free ion Hamiltonian with a local-field perturbation. The average cation-nearest ligand distance was determined for the PEO-Eu(pic)(3)TDTD1.5 complexes and the results obtained, (-)(R)=2.45 A, agree very well with the X-ray average ion-nearest ligands distances measured for the picrate salt, (-)(R)=2.448 Angstrom.