Area- and Thickness-Dependent Biexciton Auger Recombination in Colloidal CdSe Nanoplatelets: Breaking the “Universal Volume Scaling Law”

Li, Qiuyang; Lian, Tianquan

doi:10.1021/acs.nanolett.7b00587

Cited by 132 publications

(244 citation statements)

References 57 publications

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“…20 Alongside the structural effects mentioned above, the reaction conditions have proven to have a significant impact on the photocatalytic efficiencies of such nanosystems. 21−24 High-excitation fluences lead to the generation of multiple excitons (MX) on the semiconductor segment, as was reported previously for spherical, 25−27 rod, 28−30 and platelets 31 nanostructures. The formation of excess charge carriers that can be transferred to the catalytic site may lead to enhanced photocatalytic efficiency, especially in multielectron reactions such as hydrogen generation via water reduction or CO 2 reduction.…”

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confidence: 69%

Charge Carrier Dynamics in Photocatalytic Hybrid Semiconductor–Metal Nanorods: Crossover from Auger Recombination to Charge Transfer

et al. 2018

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Hybrid semiconductor-metal nanoparticles (HNPs) manifest unique, synergistic electronic and optical properties as a result of combining semiconductor and metal physics via a controlled interface. These structures can exhibit spatial charge separation across the semiconductor-metal junction upon light absorption, enabling their use as photocatalysts. The combination of the photocatalytic activity of the metal domain with the ability to generate and accommodate multiple excitons in the semiconducting domain can lead to improved photocatalytic performance because injecting multiple charge carriers into the active catalytic sites can increase the quantum yield. Herein, we show a significant metal domain size dependence of the charge carrier dynamics as well as the photocatalytic hydrogen generation efficiencies under nonlinear excitation conditions. An understanding of this size dependence allows one to control the charge carrier dynamics following the absorption of light. Using a model hybrid semiconductor-metal CdS-Au nanorod system and combining transient absorption and hydrogen evolution kinetics, we reveal faster and more efficient charge separation and transfer under multiexciton excitation conditions for large metal domains compared to small ones. Theoretical modeling uncovers a competition between the kinetics of Auger recombination and charge separation. A crossover in the dominant process from Auger recombination to charge separation as the metal domain size increases allows for effective multiexciton dissociation and harvesting in large metal domain HNPs. This was also found to lead to relative improvement of their photocatalytic activity under nonlinear excitation conditions.

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confidence: 69%

Charge Carrier Dynamics in Photocatalytic Hybrid Semiconductor–Metal Nanorods: Crossover from Auger Recombination to Charge Transfer

et al. 2018

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“…3D confinement of QDs increases the uncertainty in momentum which boosts Auger recombination strictly obeying universal volume scaling law . Owing to 1D confinement in NPLs, momentum conservation is more pronounced and Auger recombination rate is significantly diminished . In addition to suppressed Auger recombination, large absorption cross‐section and giant oscillator strength of NPLs resulted in exceptional low amplified spontaneous emission (ASE) threshold values reaching 6 µJ cm −2 .…”

Section: Resultsmentioning

confidence: 99%

Highly Stable, Near‐Unity Efficiency Atomically Flat Semiconductor Nanocrystals of CdSe/ZnS Hetero‐Nanoplatelets Enabled by ZnS‐Shell Hot‐Injection Growth

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Quliyeva

Gungor

et al. 2019

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Colloidal semiconductor nanoplatelets (NPLs) offer important benefits in nanocrystal optoelectronics with their unique excitonic properties. For NPLs, colloidal atomic layer deposition (c‐ALD) provides the ability to produce their core/shell heterostructures. However, as c‐ALD takes place at room temperature, this technique allows for only limited stability and low quantum yield. Here, highly stable, near‐unity efficiency CdSe/ZnS NPLs are shown using hot‐injection (HI) shell growth performed at 573 K, enabling routinely reproducible quantum yields up to 98%. These CdSe/ZnS HI‐shell hetero‐NPLs fully recover their initial photoluminescence (PL) intensity in solution after a heating cycle from 300 to 525 K under inert gas atmosphere, and their solid films exhibit 100% recovery of their initial PL intensity after a heating cycle up to 400 K under ambient atmosphere, by far outperforming the control group of c‐ALD shell‐coated CdSe/ZnS NPLs, which can sustain only 20% of their PL. In optical gain measurements, these core/HI‐shell NPLs exhibit ultralow gain thresholds reaching ≈7 µJ cm−2. Despite being annealed at 500 K, these ZnS‐HI‐shell NPLs possess low gain thresholds as small as 25 µJ cm−2. These findings indicate that the proposed 573 K HI‐shell‐grown CdSe/ZnS NPLs hold great promise for extraordinarily high performance in nanocrystal optoelectronics.

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“…The increased energy offset barrier between core and shell limits the extension of electron and hole wave functions into the shell, and this decreases the impact of the surface traps and increases the overlap of electron and hole wave functions. 42,43 We show pump-fluence-dependent ASE for the x = 0.75 in Figure 2e,f for 1PA and 2PA, respectively. All of the curves show red-shifted ASE with respect to the PL peaks due to multiexciton interaction in type-I nanocrystals.…”

Section: Acs Nanomentioning

confidence: 99%

Giant Alloyed Hot Injection Shells Enable Ultralow Optical Gain Threshold in Colloidal Quantum Wells

et al. 2019

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As an attractive materials system for highperformance optoelectronics, colloidal nanoplatelets (NPLs) benefit from atomic-level precision in thickness, minimizing emission inhomogeneous broadening. Much progress has been made to enhance their photoluminescence quantum yield (PLQY) and photostability. However, to date, layer-by-layer growth of shells at room temperature has resulted in defects that limit PLQY and thus curtail the performance of NPLs as an optical gain medium. Here, we introduce a hot-injection method growing giant alloyed shells using an approach that reduces core/shell lattice mismatch and suppresses Auger recombination. Near-unity PLQY is achieved with a narrow full-width-at-half-maximum (20 nm), accompanied by emission tunability (from 610 to 650 nm). The biexciton lifetime exceeds 1 ns, an order of magnitude longer than in conventional colloidal quantum dots (CQDs). Reduced Auger recombination enables record-low amplified spontaneous emission threshold of 2.4 μJ cm −2 under one-photon pumping. This is lower by a factor of 2.5 than the best previously reported value in nanocrystals (6 μJ cm −2 for CdSe/CdS NPLs). Here, we also report single-mode lasing operation with a 0.55 mJ cm −2 threshold under twophotoexcitation, which is also the best among nanocrystals (compared to 0.76 mJ cm −2 from CdSe/CdS CQDs in the Fabry−Peŕot cavity). These findings indicate that hot-injection growth of thick alloyed shells makes ultrahigh performance NPLs.

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Area- and Thickness-Dependent Biexciton Auger Recombination in Colloidal CdSe Nanoplatelets: Breaking the “Universal Volume Scaling Law”

Cited by 132 publications

References 57 publications

Charge Carrier Dynamics in Photocatalytic Hybrid Semiconductor–Metal Nanorods: Crossover from Auger Recombination to Charge Transfer

Charge Carrier Dynamics in Photocatalytic Hybrid Semiconductor–Metal Nanorods: Crossover from Auger Recombination to Charge Transfer

Highly Stable, Near‐Unity Efficiency Atomically Flat Semiconductor Nanocrystals of CdSe/ZnS Hetero‐Nanoplatelets Enabled by ZnS‐Shell Hot‐Injection Growth

Giant Alloyed Hot Injection Shells Enable Ultralow Optical Gain Threshold in Colloidal Quantum Wells

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