White light emission from Y2SiO5:Ce, Tb films excited by electroluminescence

In this work, we propose a simple electroluminescent device that emits white light from a single composition luminescent layer. The Y2SiO5:Ce, Tb phosphor film is produced by pulsed laser deposition and sandwiched between two electrodes to fabricate the electroluminescent device. The heterostructure consists basically of a ZnO:Ga layer (as the transparent electrode), a Y2SiO5:Ce-0.0075, Tb-0.04 phosphor film grown on BaTiO3 ceramics and silver as the back electrode. Electroluminescence spectra from Y2SiO5:Ce show the characteristic blue (broad band) emission centered at lambda(em) = 440 nm (5d -> F-7(5/2) electronic transition) while a well-defined green emission located at lambda(em) = 544 nm (D-5(4) -> F-7(5) electronic transition) is obtained from Y2SiO5:Tb. Moreover, in the Y2SiO5:Ce, Tb system a white emission is generated. From electro-optical measurements, we found threshold voltages of V-th similar to 50 V for the Y2SiO5:Tb and V-th similar to 100 V for the Y2SiO5:Ce phosphors. For the combined system (Y2SiO5:Ce, Tb), the green emission (from Tb ions) initiates at 150 V while the blue component (Ce ions) starts at V > 400 V, yielding white light emission in an energy transfer mechanism between Cc and Tb. (c) 2006 Elsevier B.V. All rights reserved.