Blue-green-red luminescence from CeCl₃- and MnCl ₂-doped hafnium oxide layers prepared by ultrasonic spray pyrolysis

Hafnium oxide films doped with CeCl₃ and/or MnCl₂, and deposited at 300 °C by an ultrasonic spray pyrolysis process, were characterized using x-ray diffraction (XRD), energy-dispersive spectroscopy and photoluminescence. The XRD results revealed that the films are predominantly amorphous. The weak green-red emission of Mn²⁺ is enhanced through an efficient energy transfer from Ce³⁺ to Mn²⁺ ions. Spectroscopic data revealed that the energy transfer is nonradiative in nature and it could occur in Ce³⁺ and Mn²⁺ clusters through a short-range interaction mechanism. The efficiency of this transfer increases with the Mn²⁺ ion concentration, so that an efficiency of about 78% is attained for a 5at.% of MnCl₂ concentration, which makes these films interesting phosphors for the design of luminescent layers with blue, green and red emissions.