Temperature-dependent brightening and darkening of photoluminescence from PbS quantum dots in glasses

The authors report that the darkening and brightening of photoluminescence from PbS quantum dots can be controlled by adjusting the temperature and excitation intensity. Intensity of the photoluminescence from PbS quantum dots increased with time (photobrightening) when temperature was below 150K. On the other hand, darkening was observed at temperatures above 150K. It was also possible to make a reversible change between photobrightening and photodarkening from the same specimen through the careful control of the temperature and excitation intensity.