Luminescent properties of Eu'+ or Ce3+ doped Sffia~S4 powder samples are investigated over the temperature range 30 to 300 K. Up to 300 K the lifetime remains constant (TO = 480 and 24 ns for Eu '+ and Ce3+, respectively) showing that the probability of non-radiative transitions is negligible at room temperature. The decay of thin films prepared by reactive radio-frequency magnetron sputtering deviates strongly from an exponential one as a consequence of energy transfer to defects. Codoping of Ce3' with Na+ considerably increases the luminescence efficiency.Les proprittts luminescentes de poudres de SrGazS4 doptes au Eu2+ et au Ce3+ sont ttudites pour des temptratures variant de 30 h 300 K. Jusqu'h 300 K, les durkes de vie restent invariantes (zo = 480 et 24 ns pour Eu2+ et Ce3+ respectivement). Ceci montre que les probabilitts de transitions non-radiatives sont ntgligeables h la tempkrature ambiante. Le dtclin de couches minces prtpartes par pulvtrisation cathodique radio-frtquence est beaucoup plus rapide et montre la prbsence d'un transfert d'tnergie vers des dtfauts. Le codopage de SrGazS4 : Ce3+ avec du Na+ ambliore fortment le rendement de luminescence.
In ac-coupled ZnS:Mn thin-film electroluminescent devices, the excitation efficiency ηexc depends on the insulator/ZnS interfaces and the excitation level. For optimized devices which are used in industrial production, ηexc does not depend on the transferred charge as long as the excitation level is below the saturation range. In the saturation range, ηexc decreases with increasing charge transfer. Hence the decrease of the total efficiency η at high excitation levels is partly due to the behavior of the excitation efficiency and not entirely to the decrease of the radiative efficiency ηlum. In devices with shallow insulator/ZnS interface states, however, charge injection starts at lower fields and ηexc increases strongly with the transferred charge and the applied voltage.
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