Oxide thin-film electroluminescent devices and materials

Abstract

This report reviews newly developed oxide phosphors shown to be promising as the emitting layer of thin-film electroluminescent (TFEL) devices. Since the first report of a high-luminance TFEL device using a Mn-activated Zn 2SiO 4 (Zn 2SiO 4:Mn) phosphor, high-luminance multicolor-emitting TFEL devices have been fabricated using various oxide phosphors activated with Eu or Mn. In addition, many oxides that consist of binary and ternary compounds and multicomponent oxides have been developed and shown to be promising as a host material for TFEL phosphors. This report focuses on Mn-activated Y 2O 3-based oxide phosphors: a binary compound and various ternary compounds and multicomponent oxides, composed of Y 2O 3 in combination with another binary compound such as Ga 2O 3 or GeO 2. TFEL devices of which every constituent was an oxide material were fabricated using oxide phosphor thin films deposited by r.f. magnetron sputtering, pulsed laser deposition or a sol–gel process. High luminances and luminous efficiencies comparable to those of TFEL devices using ZnS:Mn sulfide phosphor were realized using Mn-activated Y 2O 3-based oxide phosphors. Luminances above 7000 cd/m 2 (1 kHz-driving voltage) and luminous efficiencies of approximately 10 lm/W (60 Hz driving voltage) were obtained in yellow emitting TFEL devices fabricated using a Y 2O 3:Mn, a ((Y 2O 3) 0.6–(GeO 2) 0.4):Mn or a ((Y 2O 3) 0.5–(Ga 2O 3) 0.5):Mn thin film and driven by an ac sinusoidal wave voltage. Also, a high luminance above 1000 cd/m 2 for green emission was obtained in a ((Y 2O 3) 0.3–(Ga 2O 3) 0.7):Mn TFEL device driven at 1 kHz.