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| VOLUME 123 (2026) | ISSUE 6 | PAGE 425 |
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Delayed photoluminescence blinking of single semiconductor quantum dots: novel experiments and modeling1)
M. A. Kniazeva+, A. O. Tarasevich+, A. V. Naumov+*×, I. Yu. Eremchev*× 2)
+Lebedev Physical Institute of the Russian Academy of Sciences, Troitsk Branch, 108840 Troitsk, Moscow, Russia *Institute of Spectroscopy of the Russian Academy of Sciences, 108840 Troitsk, Moscow, Russia ×Moscow Pedagogical State University, 119435 Moscow, Russia
Abstract
The photoluminescence (PL) kinetics of semiconductor nanocrystals (quantum dots, QDs) includes a surprisingly wide range of times. The presence of shallow metastable trap states leads to the appearance of a long tail on the PL decay curve, the so-called delayed PL, at times ranging from hundreds of nanoseconds to microseconds. Surprisingly, intensity and lifetime of the delayed PL from a single QD notably fluctuate in time. In this work, delayed PL of single colloidal core/shell CdSeS/ZnS QDs was in depth studied by time-gated PL traces analysis. Observed delayed PL blinking allowed us to study the shallow trap states. We show that single QD PL in active trap state is characterized by mono or bi-exponential decays with times altering from 60 ns to 600 ns, that is much exceed exciton lifetime in bright state  30 ns.
Simulation allowed us to conclude that the absence of an
exciton component in the kinetics of delayed PL can be explained by the fast
( 100 ps) charge carrier Auger trapping process on
a shallow trap state. We associate this state with a localized defect at the
inner core/shell QD interface. Also, we demonstrate that
the variation in the lifetimes and delayed PL decay shapes can be described entirely
by a change in the thermal de-trapping rate.
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