Experimental and numerical analysis of Tm2+excited-states dynamics and luminescence in Ca X2(X= Cl, Br, I)

M P Plokker; I C van der Knijff; A V de Wit; B Voet; T Woudstra; V Khanin; P Dorenbos; E van der Kolk

doi:10.1088/1361-648X/abfa5d

Experimental and numerical analysis of Tm²⁺excited-states dynamics and luminescence in Ca X₂(X= Cl, Br, I)

J Phys Condens Matter. 2021 May 21;33(25). doi: 10.1088/1361-648X/abfa5d.

Authors

M P Plokker¹, I C van der Knijff¹, A V de Wit¹, B Voet¹, T Woudstra¹, V Khanin¹, P Dorenbos¹, E van der Kolk¹

Affiliation

¹ Luminescence Materials Research Group, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands.

PMID: 33882460
DOI: 10.1088/1361-648X/abfa5d

Abstract

The prospect of using Tm²⁺-doped halides for luminescence solar concentrators (LSCs) requires a thorough understanding of the temperature dependent Tm²⁺excited states dynamics that determines the internal quantum efficiency (QE) and thereby the efficiency of the LSC. In this study we investigated the dynamics in CaX₂:Tm²⁺(X= Cl, Br, I) by temperature- and time-resolved measurements. At 20 K up to four distinct Tm²⁺emissions can be observed. Most of these emissions undergo quenching via multi-phonon relaxation below 100 K. At higher temperatures, only the lowest energy 5d-4f emission and the 4f-4f emission remain. Fitting a numerical rate equation model to the data shows that the subsequent quenching of the 5d-4f emission is likely to occur initially via multi-phonon relaxation, whereas at higher temperatures additional quenching via interband crossing becomes thermally activated. At room temperature only the 4f-4f emission remains and the related QE becomes close to 30%. Possible reasons for the quantum efficiency not reaching 100% are provided.

Keywords: CaCl2:Tm2+ CaBr2:Tm2+ CaI2:Tm2+; Tm2+ doped halides; Tm2+ excited states dynamics; luminescence quenching; photoluminescence; rate equations modelling.

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