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 Y 2 SiO 5 :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 Y 2 SiO 5 :Ce 0.0075 , Tb 0.04 phosphor film grown on BaTiO 3 ceramics and silver as the back electrode. Electroluminescence spectra from Y 2 SiO 5 :Ce show the characteristic blue (broad band) emission centered at λ em = 440 nm (5d → 7 F 5/2 electronic transition) while a well-defined green emission located at λ em = 544 nm ( 5 D 4 → 7 F 5 electronic transition) is obtained from Y 2 SiO 5 :Tb. Moreover, in the Y 2 SiO 5 :Ce, Tb system a white emission is generated. From electro-optical measurements, we found threshold voltages of V th ∼ 50 V for the Y 2 SiO 5 :Tb and V th ∼ 100 V for the Y 2 SiO 5 :Ce phosphors. For the combined system (Y 2 SiO 5 :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.