Thin-Film Oxide Phosphors as Electroluminescent Materials

Abstract

ABSTRACTIn this paper, we introduce rare earth- or transition metal-activated oxide phosphor thin films prepared by magnetron sputtering and dip-coated solution deposition. Thin-film electroluminescent (TFEL) devices using these oxide phosphor thin films as the emitting layer were investigated with a single insulating layer device structure using a thick ceramic sheet insulating layer. High-luminance multicolor emissions and high luminous efficiencies were obtained in TFEL devices using various oxide phosphors: binary compound, Ga2O3; ternary compound, Zn2SiO4, CaGa2O4 and ZnGa2O4; and multicomponent oxide, Zn2SiO4-Zn2GeO4 system. Luminances above 2000 cd/m2were obtained in CaGa2O4:Mn and Zn2Si1-XGeXO4:Mn TFEL devices driven at 1 kHz. Maximum luminous efficiencies of 2.53, 1.7 and 1.2 Im/W were obtained in Zn2Si0.7Ge0.3O4:Mn, Ga2O3:Mn and ZnGa2O4:Mn TFEL devices, respectively. Stable long-term operation was obtained in dip-coated and sputtered Ga2O3:Mn phosphor TFEL devices even when driven at 10 kHz. Various thin-film oxide phosphors activated with transition metals are suitable for the emitting layer of full-color electroluminescent displays (ELD) without the use of color filters. In particular, Ga2O3 is very promising as a phosphor host material for ELDs.