TRAILING-EDGE PHENOMENA IN SRS-CECL3 THIN-FILM ELECTROLUMINESCENT DEVICES

SrS:CeCI3 based thin film electroluminescent devices in conventional a nd multilayer structures have been investigated by means of time and v oltage dependant photoluminescence (PL) measurements after laser excit ation of the Ce3+ ions. It turned out that a significant photo-induced transferred charge as well as photo-induced electroluminescence (PEL) occurs at voltage levels far below the actual EL threshold, mainly in the trailing edge of the voltage pulse. Furthermore, a reduction of t he PL intensity by increasing the applied voltage is observed. At EL t hreshold voltage, the PL intensity is as low as 65-75% of the zero vol tage value. These observations are independent of the device structure . The PEL can be described as a partial regain of the quenched PL, bei ng more pronounced in the multilayer case due to a higher mean electri c field strength in the SrS:CeCl3 layers. To explain the experimental findings, a quenching caused by weakly accelerated electrons is propos ed.