High partial thermal conductivity of luminescence sites: a crucial factor for reducing the heat-induced lowering of the luminescence efficiency

The good thermal stability of a phosphor is crucial for its practical applications. Unfortunately, in the past decades, only Gurney-Mott equation was available to describe the relation between the luminescence property of a phosphor and temperature, which is, however, phenomenological and not precise. In this work, we introduced a hypothesis that the lowering of the luminescence efficiency of a phosphor is caused by the heat generated during the luminescence process and can be reduced if the luminescence site dissipates the heat away. We verified this hypothesis by evaluating the thermal conductivities κ of their luminescent sites, the Eu atoms, in the three phosphors, SrLiAl3N4:Eu2+, Sr2Si5N8:Eu2+ and SrSiN2:Eu2+ as well as those of the Sr atoms in their hosts SrLiAl3N4, Sr2Si5N8 and SrSiN2. It is suggested that our new approach can be employed as a practical criterion to search for phosphor materials with efficient luminescence property.