Preparation of Mn-activated yttrium germanate phosphor thin films for electroluminescent devices

Abstract

Manganese (Mn)-activated yttrium germanate phosphor thin films were prepared by conventional r.f. magnetron sputtering. The phosphor thin films prepared with a Y 2O 3 content of 33, 50 and 67 mol.% and postannealed above approximately 950 °C were crystallized and identified as Y 2Ge 2O 7, Y 2GeO 5 and Y 4GeO 8, respectively, whereas all as-deposited thin films were found to be amorphous. Thin-film electroluminescent (TFEL) devices were fabricated using the postannealed phosphor thin films. The obtainable electroluminescent (EL) characteristics were considerably affected by the Mn content and the postannealing temperature of the phosphor thin-film emitting layers. High luminances for yellow photoluminescence and EL emissions were obtained in TFEL devices using these ternary compound phosphors activated with Mn and postannealed at 1020–1045 °C. Maximum luminance of 2590, 3020 and 2500 cd/m 2 were obtained in 1 kHz-driven TFEL devices using Y 2Ge 2O 7:Mn, Y 2GeO 5:Mn and Y 4GeO 8:Mn thin-film emitting layers, respectively.