Luminescence Saturation Effects in Y₂O₂S: Eu Phosphor

Abstract

The saturation effects of Eu3+ luminescence in Y2O2S have been investigated using a pulsed nitrogen laser at room temperature and at 80 K, and also under pulsed cathode-ray excitation at room temperature. Interaction between excited-state Eu3+ ions gives rise to a predominant energy-loss mechanism causing saturation. One of the two Eu3+ ions in the charge transfer state (CTS) is forced to relax nonradiatively to the 7F state by dipole-dipole interaction, and the other is promoted to a higher bound exciton state, or eventually dissociated to a free hole and a bound electron. Interaction between a Eu3+ ion in the 5D state and a CTS-Eu3+ ion also causes nonradiative relaxation of the 5D state, which causes differences in the saturation behavior of different emitting states and brings about excitation intensity dependence in the luminescence decay curves.