Luminescence properties of thin-film SrS:Cu phosphors for electroluminescent displays

The origin of the electronic fine structure in thin-film SrS:Cu has been interpreted in terms of the several possible perturbations including spin-obit coupling, the Jahn-Teller effect and low symmetry splittings. Photoluminescence excitation measurements showed that the peak position of the excitation bands were independent of temperature suggesting that the electronic fine structure in our system was not due to the Jahn-Teller effect. Selective excitation measurements revealed that no peak shift occurs with changing excitation wavelength, indicating that Cu+ pairs or aggregates and Cu+-defect coupled centers were not existent in our system Finally, several models were proposed for off-center displacements of Cu in SrS, since a rigorous treatment of these displacements is difficult. Both the tetragonal and trigonal distortion models for a [111] displacement yielded reasonable distortions parameters of 0.16 Angstrom and 0.11 Angstrom, respectively. However, crystal field analysis showed that a [110] displacement was more likely since the energy level splitting scheme more closely resembled the observed data.