Charge propagation dynamics in temperature quenching of sm-doped tio2: Impedance spectroscopy of release processes of trapped charges determining luminescence intensity

The mechanism of the temperature quenching of luminescence in samarium-doped titanium dioxide (TiO2:Sm) was investigated with electrical measurement techniques. Because electrical measurements are sensitive to charge dynamics, the indirect excitation processes of the Sm dopants, i.e., trapping and recombination of injected charges into the host TiO2, can be clarified. Complex impedance spectroscopy between 100 and 300 K revealed a correlation between the temperature quenching of TiO2:Sm and the trapping and recombination processes. Analyses using equivalent circuits revealed that the main factor determining the temperature quenching properties was delocalization of the trapped charges and decoupling of free charges in TiO2 from trapped charges. The delocalization and decoupling parameters were evaluated from the equivalent circuit constants, and a numerical model incorporating the determined values reproduced the experimentally observed temperature quenching of photoluminescence. © 2013 The Japan Society of Applied Physics.