Résumé:
In this work, nanocrystalline ZnO: Eu3. powders and thin films co doped with Li. were successfully synthesized by the sol gel method. Co doping with Li. was found to significantly influence the structural, morphological, and luminescent properties of ZnO: Eu3. materials. X ray diffraction (XRD) and Raman spectroscopy confirmed the formation of a wurtzite hexagonal structure with crystallite sizes ranging between 27 and 31 nm. Morphological analysis by FE-SEM revealed that the introduction of Li. and Eu3. modifies the particle and grain shapes, evolving from quasi spherical, randomly packed morphologies to more block like structures. Photoluminescence (PL) studies demonstrated strong red emission arising from the .D. ¨ .F. (J = 0.4) intra 4f transitions of Eu3. ions under both charge transfer (O2. ¨ Eu3.) and .D. excitations. The emission intensity was found to depend on the excitation wavelength, with an optimum at 7% Li. under 465 nm excitation and at 10% under 258 nm excitation. In particular, under 258 nm excitation, Li. concentrations of 5 and 10% enhanced red emission due to more efficient energy transfer from ZnO defect centres to Eu3. ions, as further confirmed by the variation of the .D. lifetime with Li content. Local field effect analysis indicated that 5 % Li. yields the highest bulk radiative lifetime values (ƒÑB = 3.004 ms for the real cavity model and ƒÑB = 6.042 ms for the virtual cavity model). Finally, the combined structural and optical results demonstrate that Li. co doped ZnO: Eu3. powders and thin films are promising candidates for optoelectronic applications, particularly in display and lighting technologies.
