The Interpretation of the Dependence of Luminescent Efficiency on Activator Concentration

The previously published analysis (see reference 1) of the dependence of efficiency of substitutionally activated inorganic phosphors on activator concentration is generalized to include a wide variety of inorganic phosphors under various types of excitation. In addition to the optical excitation of the activator, the creation of conduction electrons and excitons, and the transfer of their energy to the luminescent and non-luminescent activator ions and to other impurities and lattice defects are included in the formulation. The dependence of efficiency on activator concentration of ZnF2:Mn under c.r., x-ray, vacuum u.v. and near u.v. has been measured and interpreted on the basis of the theory. Preliminary photo-conductivity measurements clarify the role of the conduction band in the luminescence of ZnF2:Mn. Also the dependence of the efficiency vs. activator concentration of both ZnF2:Mn and KCl:Tl on temperature has been measured and interpreted on the basis of the variation in activation energy for competing radiationless processes with distance between activator ions. In addition, other efficiency vs. activator concentration data previously published by other authors (see reference 8) on a variety of phosphors and at various temperatures can be correlated and explained with the general theory.