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Creators/Authors contains: "Zhang, Jin Z"

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  1. ; ; ; ; ; ; ; ; ( , The Journal of Physical Chemistry Letters)
    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 lietimes o 6.6 and 93 ns attributed to recombination through the deep trap state and direct band edge recombination, respectively. The signicant role o exciton trapping processes in the dynamics indicates that these highly conned nanoclusters have deect-rich suraces. 
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    Free, publicly-accessible full text available May 16, 2025
  2. ; ( , The Journal of Physical Chemistry Letters)
    We have synthesized inherently chiral cesium lead halide perovskite magic-sized clusters (PMSCs) and ligand-assisted metal halide molecular clusters (MHMCs) using the achiral ligands octanoic acid (OCA) and octylamine (OCAm). UV–vis electronic absorption was used to confirm characteristic absorption bands while circular dichroism (CD) spectroscopy was utilized to determine their chiroptical activity in the 412–419 and 395–405 nm regions, respectively. In contrast, the larger sized counterpart of PMSCs, namely, perovskite quantum dots (PQDs), do not show chirality. The inherent chirality of the clusters is tentatively attributed to a twisted chiral layered structure, defect-induced chiral structure, or twisted Pb–Br octahedra 
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  3. ; ; ( , The Journal of Physical Chemistry Letters)
    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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  4. ; ; ; ( , The Journal of Physical Chemistry Letters)
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  5. ; ; ; ; ( , The Journal of Physical Chemistry Letters)
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  6. ; ; ; ; ; ( , The Journal of Physical Chemistry C)
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  7. ; ; ( , Journal of the Chinese Chemical Society)
    Abstract Background

    Research into perovskite nanocrystals (PNCs) has uncovered interesting properties compared to their bulk counterparts, including tunable optical properties due to size‐dependent quantum confinement effect (QCE). More recently, smaller PNCs with even stronger QCE have been discovered, such as perovskite magic sized clusters (PMSCs) and ligand passivated PbX2metal halide molecular clusters (MHMCs) analogous to perovskites.

     Objective

    This review aims to present recent data comparing and contrasting the optical and structural properties of PQDs, PMSCs, and MHMCs, where CsPbBr3PQDs have first excitonic absorption around 520 nm, the corresponding PMSCS have absorption around 420 nm, and ligand passivated MHMCs absorb around 400 nm.

     Results

    Compared to normal perovskite quantum dots (PQDs), these clusters exhibit both a much bluer optical absorption and emission and larger surface‐to‐volume (S/V) ratio. Due to their larger S/V ratio, the clusters tend to have more surface defects that require more effective passivation for stability.

     Conclusion

    Recent study of novel clusters has led to better understanding of their properties. The sharper optical bands of clusters indicate relatively narrow or single size distribution, which, in conjunction with their blue absorption and emission, makes them potentially attractive for applications in fields such as blue single photon emission.

     
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  8. ; ; ; ; ( , The Journal of Physical Chemistry Letters)
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  9. ; ; ; ; ; ; ( , The Journal of Physical Chemistry Letters)
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  10. ; ; ; ; ; ; ( , The Journal of Physical Chemistry C)
    null (Ed.)
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