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.