Electronic and optical properties of Er-doped Y₂O₂S phosphors

In this paper, we report a detailed computational and experimental investigation of the structural, electronic and dynamic properties of undoped and Er³⁺-doped Y₂O₂S phosphors by using computational crystal field (CF) calculations and electronic density of states by density functional theory (DFT), combined with optical measurements including excitation spectra, emission spectra from X-ray, ultraviolet and near infrared (NIR) excitations, and quantum yield determination under ultraviolet and NIR excitations. Emission decays and quantum yields of the visible and NIR bands were measured for different Er³⁺ doping concentrations in the Er³⁺-doped Y₂O₂S phosphors. Results show that green (550 nm) and red (667 nm) emission intensity and the respective ratio of these emission intensities depend on both the excitation wavelength and the Er³⁺ doping concentration. Although the total emission efficiency does not appreciably depend on the excitation wavelength, the excitation wavelength that provided the highest efficiency was found to be 250 nm in these Er³⁺-doped Y₂O₂S phosphors with both 1% and 10% Er doping concentrations.