White Light Generation in Rare-Earth-Doped Amorphous Films Produced by Ultrasonic Spray Pyrolysis

Abstract

Aluminium and hafnium oxide films doped with CeCl3/TbCl3/MnCl2 were deposited at 300 °C by ultrasonic spray pyrolysis. The films analysed by X-Ray diffraction exhibit a very broad band typical of amorphous materials. Non-radiative energy transfer from Ce3+ to Tb3+ and Mn2+ is observed upon UV excitation at 280 nm (peak emission wavelength of AlGaN-based LEDs). Such energy transfer gives place to a simultaneous emission of the donor and acceptor ions in the blue, green, yellow and red regions, resulting in cold white light emission, with chromaticity coordinates and colour temperatures: (0.30,0.32) and 7300 K (AOCTM film), and (0.32,0.37) and 6400 K (HOCTM film). Thus, this type of thin films might contribute to the development of efficient AlGaN-based LEDs pumped phosphors for cold white light generation.