The excited state dynamics of ligand-passivated PbBr2 molecular clusters (MCs) in
solution have been investigated for the first time using femtosecond transient absorption
spectroscopy. The results uncover a transient bleach (TB) feature peaked around 404 nm,
matching the ground state electronic absorption band peaked at 404 nm. The TB recovery signal
can be fitted with a triple exponential with fast (10 ps), medium (350 ps), and long (1.8 ns) time
constants. The medium and long time constants are very similar to those observed in the timeresolved
photoluminescence (TRPL) decay monitored at 412 nm. The TB fast component is
attributed to vibrational relaxation in the excited electronic state while the medium component
with dominant amplitude is attributed to recombination between the relaxed electron and hole.
The small amplitude slow component is assigned to electrons in a relatively long-lived excited
electronic state, e.g., triplet state, or shallow trap state due to defects. This study provides new
insights into the excited state dynamics of metal halide MCs.
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Ultrafast Exciton Dynamics of CH 3 NH 3 PbBr 3 Perovskite Nanoclusters
Exciton dynamics o perovskite nanoclusters has been investigated or the rst
time using emtosecond transient absorption (TA) and time-resolved photoluminescence
(TRPL) spectroscopy. The TA results show two photoinduced absorption signals at 420 and
461 nm and a photoinduced bleach (PB) signal at 448 nm. The analysis o the PB recovery
kinetic decay and kinetic model uncovered multiple processes contributing to electron−hole
recombination. The ast component (∼8 ps) is attributed to vibrational relaxation within the
initial excited state, and the medium component (∼60 ps) is attributed to shallow carrier
trapping. The slow component is attributed to deep carrier trapping rom the initial
conduction band edge (∼666 ps) and the shallow trap state (∼40 ps). The TRPL reveals
longer time dynamics, with modeled lietimes o 6.6 and 93 ns attributed to recombination
through the deep trap state and direct band edge recombination, respectively. The signicant
role o exciton trapping processes in the dynamics indicates that these highly conned
nanoclusters have deect-rich suraces.
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- Award ID(s):
- 2203633
- PAR ID:
- 10537506
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry Letters
- Volume:
- 15
- Issue:
- 19
- ISSN:
- 1948-7185
- Page Range / eLocation ID:
- 5177 to 5182
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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