Design of sustainable luminescent materials - from basics to real applications

Speaker: Jun-Prof. Markus Suta, Heinrich Heine University Düsseldorf

Host: on invitation of Prof. Dierk Raabe

Luminescent materials are ever important for various applications such as sustainable LED phosphors, upconversion nanocrystals, or luminescent thermometers to mention just a few. For all of these applications, a firm understanding of the interplay between the radiative and non-radiative decay pathways is crucial for targeted design. Within this tutorial lecture, I will demonstrate that for the case of two luminescent materials classes. In the first part, an overview of the requirements for phosphors for both phosphor-converted white-light LEDs and displays will be given. Narrow-band emitting UCr₄C₄-type phosphors based on the rare-earth ions Eu²⁺ or Ce³⁺ fulfill many of the desired requirements suited for these applications. Despite this success, however, our economic dependence on few global export players for the rare-earth elements demands a more sustainable resource strategy. I will show how the more abundant transition metal ions Mn²⁺ and Cr³⁺ can be made competitive alternative activators.

Another emerging materials class are luminescent Boltzmann thermometers. They essentially rely on non-interacting emitting centers with two thermally coupled and radiatively emitting states. The luminescence intensity ratio then follows Boltzmann’s law. Trivalent lanthanoids with their narrow line 4fⁿ-4fⁿ luminescence embedded into micro- or nanocrystalline compounds have emerged here. The ultimate desire to design such thermometers for the application of interest (e.g. catalysis, biothermal imaging) requires, however, a careful understanding of both thermodynamic and kinetic concepts of their performance. It will be demonstrated that precise temperature measurements with these thermometers are fundamentally limited to only a small temperature window and what are strategies to overcome this obstacle. As it turns out, this approach has a much deeper connection to a fundamental understanding of the nature and control of non-radiative transition rates , which could open a whole new perspective on the sustainable control of the efficiency of inorganic phosphors quite generally.

Registration: https://plan.events.mpg.de/event/430/

The colloquia series is organized by of the International Max Planck Research School on Sustainable Metallurgy (IMPRS SusMet)