Validated Approach to Measure Thermal Quenching in the Presence of Trapping Defects

Thermal quenching (TQ) is the gradual loss of quantum efficiency when the temperature exceeds a certain threshold. As such, the TQ behavior can make or break a luminescent material or phosphor. In addition to the impact of an undesired TQ on the phosphor’s application potential, accurate measurements of the TQ can also provide insights into the nature of the underlying (thermally induced) nonradiative pathways, which is helpful for further optimization of phosphors. Performing reliable TQ measurements is, however, less straightforward as might be anticipated. In this work, we discuss the considerable impact of the presence of charge trapping defects and of the resulting thermal and optical detrapping of trapped charges on the shape of the recorded TQ curves. Experimental approaches to minimize this impact are validated to establish the underlying TQ profile. In the case of persistent phosphors, we demonstrate that with an accurate measurement of the TQ profile, the degree of nonradiative losses for the trapping and detrapping processes can be straightforwardly quantified. In the case of Sr 2 MgSi 2 O 7:Eu 2+,Dy 3+, the contribution of fading over the course of 12 h is negligible when kept at room temperature. Finally, guidelines for the accurate and reliable determination of TQ profiles and TQ-corrected TL glow curves are formulated.