PhD n°2
Eligibility:
EU mobility rules apply. In principle, applicants can have any nationality and any current residence (although immigration rules apply, favoring
EU applicants). Candidates who have already been awarded a PhD degree are not eligible. In addition, candidates who have already spent more than 12 months in the Czech Republic within the last 3 years are not eligible (unless as part of a procedure for obtaining refugee status under the Geneva Convention).
Objectives:
the main scientific objective of this combined theoretical and experimental work is to gain insight into the physical mechanisms that influence the efficiency and thermal quenching of materials used for phosphor-converted LEDs. We will analyse temperature dependent trends in the electronic
properties and their signatures in various spectroscopies when chemical types, concentrations and geometrical arrangements of the dopants and of the ligands are varied.
Therefore, the following tasks will be addressed:
- The Researcher will implement ML for displacements (provided by UL) and combine it with one- step model of photoemission.
- ML supported study of thermal quenching and its impact on the quantum efficiency of luminescent materials by alloy analogy model.
- Analyzing the results in terms of their trends with chemical composition, concentration and geometrical arrangements of dopants and ligands.
- Experimentally identify signatures and analyze ML predicted thermal quenching behavior by valence band photoemission spectroscopy of several lanthanide-doped silico-oxo-nitrides.
Expected Results:
- Description of the role of exchange-splitting and spin-orbit coupling for electronic transitions localized lose to the lanthanide dopant (WP3).
- Understanding the role of electronic correlations and disorder in lanthanide-doped phosphors.
- Developing new and improving existing schemes for description of excited states of dopants, with emphasis on electron-hole interaction (WP1).
- Study of structure related properties around lanthanide impurities and the impact on the quantum efficiency of the luminescent materials. Description of thermal quenching by means of alloy analogy model and experimental identification the markers of vibrations in photoemission and XAS spectra (WP2, WP1).
- Development of the interface between ML for displacements and spectroscopic modules of the KKR package (WP1).
Planned secondment(s): 9 months
- AALTO: P. Rinke, M12-M13; understanding of deep learning models and setting up database for pcLED relevant materials (WP2)
- UL: M. Verstraete, M22-23; implement ML for displacements and apply thermal property calculations to the emission quenching (WP1, WP2).
- CNRS: D. Sébilleau, M30-M31; use of complementary spectroscopy methods (EELS) and photoelectron diffraction (PED) developed in the MsSpec package (WP1).
- Intersectoral: RVM: R. Varga, M16-M18; Contact with experimental and theoretical tools in an industrial setting for disordered materials screening
Enrolment in Doctoral degree(s):
University of West Bohemia
Contact:
Jan Minar
jminar@ntc.zcu.cz