Field quenching effects in polycrystalline SrS:Pb and SrS:Ce,Pb thin films for electroluminescence devices

• Published in: Journal of applied physics 1996-09, Vol.80 (6), p.3526-3531
• Main Authors: Oberacker, T. A., Schlotterbeck, G., Bilger, G., Braunger, D., Schock, H.-W.
• Format: Article
• Language: English
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.363225

The luminescence properties of lead ions and their sensitizing effect on cerium activators in strontium sulfide thin-film electroluminescence (TFEL) devices have been investigated. Polycrystalline SrS:Pb and SrS:Ce,Pb thin active layers for such TFEL devices have been prepared by multi-source deposition. Emission spectroscopy under application of a high electric field (EL), under e-beam excitation [cathodoluminescence (CL)], and under CL conditions with additional EL drive has been carried out. It has been found that the luminescence of SrS:Pb under EL drive is very weak, while the CL signal is considerably higher. This CL signal has shown strong quenching effects upon application of an additional ac voltage. The Pb2+ emission dropped to some 5% at an applied voltage of 100 V0p, being roughly 40 V below EL threshold. More than half of this drop occurred between 0 and 30 V0p. A remarkably lower quenching effect on the Ce3+ activator luminescence has been observed. Such luminescence quenching is attributed to the field induced ionization of the luminescent ions. From the obtained results it is concluded that the optical energy transfer from Pb2+ sensitizers to Ce2+ activators in SrS TFEL devices is low.