Photoluminescence and excited states dynamics of Tm 2+ -doped CsCa(Cl/Br) 3 and CsCa(Br/I) 3 perovskites

Plokker, M P; Biner, D A; Dusoswa, N; Dorenbos, P; Krämer, K W; Van Der Kolk, E (2021). Photoluminescence and excited states dynamics of Tm 2+ -doped CsCa(Cl/Br) 3 and CsCa(Br/I) 3 perovskites. Journal of physics: materials, 4(4), 045004. IOP Publishing 10.1088/2515-7639/ac24ed

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In this study, we systematically vary the Cl/Br and Br/I ratios in CsCaX3:Tm2+ (X = Cl, Br, I) and hereby gradually shift the positions of the Tm2+ 4f125d1-levels as relative to the two 4f13 levels. At low temperatures up to five distinct Tm2+ 4f125d1→4f13 emissions and the 4f13→4f13 emission can be observed. As the temperature increases, most of the 4f125d1→4f13 emissions undergo quenching via multi-phonon relaxation (MPR) and at room temperature only the lowest energy 4f125d1→4f13 and the 4f13→4f13 emission remains. For all compositions a 4f13→4f13 risetime phenomenon is then observed whose duration matches the 4f125d1→4f13 decay time. It shows the feeding of the 4f13 state after 4f125d1 excitation. Surprisingly, the feeding time becomes longer from Cl→Br→I, while the related 4f125d1-4f13 energy gap becomes smaller. The temperature dependence of the 4f125d1→4f13 and 4f13→4f13 emission intensity shows a anticorrelation as earlier observed in other systems and confirms that the feeding process is thermally stimulated. However, the thermally stimulated activation energies that control the feeding process, increase from Cl→Br→I despite our observation that the 4f125d1-4f13 energy gap becomes smaller. An analysis reveals that the unexpected behaviour in risetime and activation energy, as a function of composition, cannot be explained by 4f125d1→4f13 feeding via interband crossing, but more likely via MPR where the electron–phonon coupling strength decreases from Cl→Br→I. No strong relation was found between composition and the quantum efficiency (QE) of the 4f13→4f13 emission, due to the presence of fluctuations that are likely caused by intrinsic differences in sample quality. Nevertheless, a 4f13→4f13 QE of up to 70% has been observed and the materials can therefore be used in luminescence solar concentrators.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Department of Chemistry, Biochemistry and Pharmaceutical Sciences (DCBP)

UniBE Contributor:

Biner, Daniel and Krämer, Karl

Subjects:

500 Science > 530 Physics
500 Science > 540 Chemistry

ISSN:

2515-7639

Publisher:

IOP Publishing

Language:

English

Submitter:

Karl Krämer

Date Deposited:

28 Dec 2021 11:54

Last Modified:

05 Dec 2022 15:55

Publisher DOI:

10.1088/2515-7639/ac24ed

BORIS DOI:

10.48350/161872

URI:

https://boris.unibe.ch/id/eprint/161872

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