Photoconductivity and luminescence in lanthanum oxysulfide

Rare-earth doped crystals of lanthanum oxysulfide were found to exhibit strong photoconductivity which increases rapidly with temperature. Correlation of photoconductivity to luminescence spectra of La2O2S : Eu shows that thermal quenching of the luminous emission from 5D states leads to the production of photocarriers, the majority of which are most likely holes. Special features of La2O2S : Eu photoconductivity indicate the important role which the charge-transfer states play in the luminescence mechanisms.