Center for Molecular Modeling - J.J. Joos

Exploring lanthanide doping in UiO-66: a combined experimental and computational study of the electronic structure

kurt — Fri, 23 Feb 2018 19:50:21 +0000

K. Hendrickx, J.J. Joos, A. De Vos, D. Poelman, P. F. Smet, V. Van Speybroeck, P. Van der Voort, K. Lejaeghere

Inorganic Chemistry

57, 5463-5474

2018

DOI

http://dx.doi.org/10.1021/acs.inorgchem.8b00425

Private attachment

Hendrickx_2018_InorgChem_lanthanide-UiO-electronic.pdf

Manuscript.pdf

Charge transfer induced energy storage in CaZnOS:Mn - insight from experimental and computational spectroscopy

kurt — Sat, 24 Sep 2016 09:46:09 +0000

J.J. Joos, K. Lejaeghere, K. Korthout, A. Feng, D. Poelman, P. F. Smet

Physical Chemistry Chemical Physics (PCCP)

19 (13), 9075-9085

2017

Abstract

CaZnOS:Mn2+ is a rare-earth-free luminescent compound with an orange broadband emission at 612 nm, featuring pressure sensing capabilities, often explained by defect levels where energy can be stored. Despite recent efforts from experimental and theoretical points of view, the underlying luminescence mechanisms in this phosphor still lack a profound understanding. By the evaluation of thermoluminescence as a function of the charging wavelength, we probe the defect levels allowing energy storage. Multiple trap depths and trapping routes are found, suggesting predominantly local trapping close to Mn2+ impurities. We demonstrate that this phosphor shows mechanoluminescence which is unexpectedly stable at high temperature (up to 200 °C), allowing pressure sensing in a wide temperature range. Next, we correlate the spectroscopic results with a theoretical study of the electronic structure and stability of the Mn defects in CaZnOS. DFT calculations at the PBE+U level indicate that Mn impurities are incorporated on the Zn site in a divalent charge state, which is confirmed by X-ray absorption spectroscopy (XAS). Ligand-to-metal charge transfer (LMCT) is predicted from the location of the Mn impurity levels, obtained from the calculated defect formation energies. This LMCT proves to be a very efficient pathway for energy storage. The excited state landscape of the Mn2+ 3d5 electron configuration is assessed through the spin-correlated crystal field and a good correspondence with the emission and excitation spectra is found. In conclusion, studying phosphors at both a single-particle level (i.e. via calculation of defect formation energies) and a many-particle level (i.e. by accurately localizing the excited states) is necessary to obtain a complete picture of luminescent defects, as demonstrated in the case of CaZnOS:Mn2+.

Open Access version available at UGent repository

Gold Open Access

DOI

http://dx.doi.org/10.1039/C7CP00285H

Private attachment

c7cp00285h.pdf

First-principles study of antisite defect configurations in ZnGa2O4:Cr persistent phosphors

kurt — Wed, 27 Jan 2016 11:24:02 +0000

A. De Vos, K. Lejaeghere, D.E.P. Vanpoucke, J.J. Joos, P.F. Smet, K. Hemelsoet

Inorganic Chemistry

55 (5), 2402–2412

2016

Abstract

Poster

Conference / event / venue

IAP Annual meeting

Hasselt

Friday, 11 September, 2015

Abstract (private)

Abstract_Poster.pdf

Combined theoretical-experimental study of chromium doped zinc gallate phosphor

arthur — Wed, 09 Sep 2015 10:59:45 +0000

A. De Vos, K. Lejaeghere, D.E.P. Vanpoucke, J.J. Joos, P.F. Smet, K. Hemelsoet

ISBN/ISSN:

Poster

Conference / event / venue

XVIITH INTERNATIONAL KRUTYN SUMMER SCHOOL 2015

Krutyń, Poland

Sunday, 14 June, 2015 to Saturday, 20 June, 2015

Abstract (private)

Abstract_Poster.pdf