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:Ce0.0075, Tb0.04 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 λem = 440 nm (5d → 7F5/2 electronic transition) while a well-defined green emission located at λem = 544 nm (5D4 → 7F5 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 Vth ∼ 50 V for the Y2SiO5:Tb and Vth ∼ 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 Ce and Tb.