LUMINESCENCE AND ELECTRON-PARAMAGNETIC-RESONANCE STUDIES OF WHITE-LIGHT EMITTING SRS-PR,F THIN-FILM ELECTROLUMINESCENT DEVICES

The fluorescence emission and excitation spectra of white-light emitting SrS: Pr, F thin film electroluminescent devices have been investigated. It was determined from the results obtained that the dominant electroluminescence mechanism was that the ionization of Pr3+ centers occurs first, then subsequently recombination with electrons occurs, and finally Pr3+ center transitions give rise to luminescence. The emission mechanism of SrS: Pr, F seems to be the same as that of a SrS: Pr, K electroluminescent device, except for the appearance of strong peaks around 610-670 nm. The impurity excitation peak in the lower excitation energy, longer-wavelength region in the FL spectrum may be an important factor for the selection of an effective white-light emitting EL material. The electron paramagnetic resonance experiment of SrS: Pr, F was performed on powder and thin film specimens. The hyperfine structure of an isolated Mn2+ ion was observed in this SrS: Pr, F thin film. This Mn center which was substituted for Sr, seems to contribute to the strong red emission in the white EL spectrum.