How far are luminescence properties predictable?

Abstract

Our knowledge of the luminescence of isolators has increased considerably during the past decade. As a consequence it has become possible to understand the luminescence of technically important phosphors and even to predict efficient luminescent materials. We first illustrate how emission spectra of a given activator can be varied by changing the host lattice. Second we consider the factors influencing the luminescent efficiency. Using a single-configurational coordinate model, we have performed calculations on a model system. These illustrate which factors are important for efficiency. Some clear results are reported. Finally, we discuss the mobility of excitation energy. In some phosphors the excitation is highly mobile even at low temperatures. As a consequence emission originates from centers which trap the excitation energy. In other phosphors this mobility is low, and at low temperatures emission occurs from the regular luminescence centers. At higher temperatures the excitation energy can become mobile because of thermal activation