Rare earth doped luminescent materials

Re-doped materials are investigated intensively world wide for a wide range of application such as Displays, LED lighting, IR-markers, detectors, up en down converters for PV-devices. In many of these materials a strong absorption followed by intense luminescence is desired. One possibility to achieve that is by strong absorption in the host lattice of the luminescent material followed by energy efficient transfer to the Re- ions. Although materials absorb strongly above their bandgap energy, Re-ion luminescence efficiencies are usually low because of the many possible alternative relaxation routes like charge trapping or the formation of excitonic species with subsequent radiative or non-radiative relaxation.

In this project you will use a femto second laser system and a state-of-the-art streak camera system to study the dynamical behavior of electrons, holes and excitons that follow after excitation of the host lattice and learn about possible energy transfer routes to the Re-ions. The transfer should reveal itself in the form of delayed luminescence evidenced by a risetime profile of the luminescence intensity after pulsed femto second laser excitation. In this project you will measure the risetime profiles as a function of temperature, and Re-ion concentration and excitation energy. The project also involves the modeling of results for example using rate equations.