TY - JOUR
T1 - Concentration and temperature dependent luminescence properties of the SrI2-TmI2 system
AU - Plokker, M. P.
AU - Hoogsteen, W.
AU - Abellon, R. D.
AU - Krämer, K. W.
AU - van der Kolk, E.
N1 - Accepted Author Manuscript
PY - 2020
Y1 - 2020
N2 - The concentration dependent luminescence of the SrI2-TmI2 system was investigated. For Tm2+ concentrations up to 5 mol %, the quantum efficiency (QE) of the 2F5/2→2F7/2 emission exhibits a constant value above 50%. The QE drops for higher Tm2+ concentrations, partly due to concentration quenching, as evidenced by a decreasing luminescence lifetime of the 2F5/2→2F7/2 emission, and partly due to the formation of a second crystal phase with CdCl2 structure, in which the 2F5/2→2F7/2 emission is quenched. The temperature and time dependent relaxation dynamics were studied to identify the origin of the limited QE for Tm2+-doping levels below 5 mol %. An anti-correlation between the 5d-4f (3H6,t2g)S=3/2→2F7/2 and 4f-4f 2F5/2→2F7/2 emission intensities was found and rationalised by non-radiative, thermally stimulated, inter-configurational 5d-4f relaxation to the emitting 2F5/2 level of Tm2+. Both, the rise time of the 4f-4f and the decay time of the 5d-4f emission become shorter with increasing temperature. We suggest a similar non-radiative relaxation from the 5d level towards the 2F7/2 ground state to limit the QE below unity. This route becomes more efficient when the 5d (3H6,t2g)S=3/2 state moves closer to the 4f 2F5/2 and 2F7/2 states, which is the case for the CdCl2 phase with a QE close to zero.
AB - The concentration dependent luminescence of the SrI2-TmI2 system was investigated. For Tm2+ concentrations up to 5 mol %, the quantum efficiency (QE) of the 2F5/2→2F7/2 emission exhibits a constant value above 50%. The QE drops for higher Tm2+ concentrations, partly due to concentration quenching, as evidenced by a decreasing luminescence lifetime of the 2F5/2→2F7/2 emission, and partly due to the formation of a second crystal phase with CdCl2 structure, in which the 2F5/2→2F7/2 emission is quenched. The temperature and time dependent relaxation dynamics were studied to identify the origin of the limited QE for Tm2+-doping levels below 5 mol %. An anti-correlation between the 5d-4f (3H6,t2g)S=3/2→2F7/2 and 4f-4f 2F5/2→2F7/2 emission intensities was found and rationalised by non-radiative, thermally stimulated, inter-configurational 5d-4f relaxation to the emitting 2F5/2 level of Tm2+. Both, the rise time of the 4f-4f and the decay time of the 5d-4f emission become shorter with increasing temperature. We suggest a similar non-radiative relaxation from the 5d level towards the 2F7/2 ground state to limit the QE below unity. This route becomes more efficient when the 5d (3H6,t2g)S=3/2 state moves closer to the 4f 2F5/2 and 2F7/2 states, which is the case for the CdCl2 phase with a QE close to zero.
UR - http://www.scopus.com/inward/record.url?scp=85084409029&partnerID=8YFLogxK
U2 - 10.1016/j.jlumin.2020.117327
DO - 10.1016/j.jlumin.2020.117327
M3 - Article
AN - SCOPUS:85084409029
VL - 225
JO - Journal of Luminescence
JF - Journal of Luminescence
SN - 0022-2313
M1 - 117327
ER -