In this paper, new multicomponent oxides are shown to be promising as a host material for the phosphor thin-film emitting layer of thin-film electroluminescent (TFEL) devices. Mn-activated (Y 2O 3–GeO 2) multicomponent oxide phosphor thin films were prepared by r.f. magnetron sputtering and used as the emitting layer of TFEL devices. High luminance multicolor emissions were obtained in TFEL devices using (Y 2O 3–GeO 2):Mn thin films prepared with a GeO 2 content of 0–100 mol.%. In a yellow emitting TFEL device fabricated using a Y 2GeO 5 phosphor thin film prepared with a GeO 2 content of approximately 50 mol.%, a high luminance of 758 cd/m 2 and a luminous efficiency of 1.4 lm/W were obtained when driven by a sinusoidal wave voltage at 1 kHz.