Controlling photoinduced electron transfer from PbS@CdS core@shell quantum dots to metal oxide nanostructured thin films

Zhao, Haiguang; Fan, Zhiyuan; Liang, Hongyan; Selopal, Gurpreet Singh; Gonfa, Belete Atomsa; Liu, Jin; Soudi, Afsoon; Cui, Daling; Enrichi, Francesco; Natile, Marta Maria; Concina, Isabella; Ma, Dongling; Govorov, Alexander O.; Rosei, Federico; Vomiero, Alberto

doi:10.1039/c4nr01562b

Cited by 81 publications

(84 citation statements)

References 35 publications

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“…In the present case, the threshold size for charge injection from PbS QDs to TiO 2 is around 8 nm, which is not in agreement with our previous estimate (5.2 nm), based on measurements of photoluminescence lifetime . The main reason for this discrepancy is that here we take the absolute position of the CB for TiO 2 and the work function of HOPG from the literature (respectively 4.25 and 4.6 eV), while it is subject to significant variations, depending on the environmental conditions.…”

Section: Resultscontrasting

confidence: 99%

Direct Measurement of Electronic Band Structure in Single Quantum Dots of Metal Chalcogenide Composites

Benetti

Cui

Zhao

et al. 2018

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Metal chalcogenide quantum dots (QDs) are among the most promising materials as light harvesters in all‐inorganic systems for applications in solar cells and production of solar fuels. The electronic band structure of composite QDs formed by lead and cadmium chalcogenides directly grafted on highly oriented pyrolytic graphite surfaces through successive ionic layer absorption and reaction is investigated. Atomic force microscopy and Kelvin probe force microscopy (KPFM) are applied to investigate PbS, CdS, and PbS/CdS QD systems. The variation of the surface potential of individual QDs is measured, investigating the evolution of the electronic band structure as a function of QD size and composition. A shift of the Fermi level toward more negative values occurs when QD size is increased. The shift is more pronounced in CdS than in PbS, while the composite PbS/CdS exhibits an intermediate behavior. The calculated shift is in good agreement with the experiments. These results highlight the ability of KPFM to directly measure the electronic band structure in individual QDs of metal chalcogenide composites. This feature regulates charge dynamics in composite systems, thereby affecting device performance. This work provides valuable insights for applications in several fields, in which charge injection plays a major role.

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Section: Resultscontrasting

confidence: 99%

Direct Measurement of Electronic Band Structure in Single Quantum Dots of Metal Chalcogenide Composites

Benetti

Cui

Zhao

et al. 2018

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“…19,[22][23][24][25] The optoelectronic properties of such QD solids can also be tailored by choosing their surface-ligands, which control the inter-QD separation-dependent degree of electronic coupling.…”

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Temperature-Dependent Optical Properties of PbS/CdS Core/Shell Quantum Dot Thin Films: Probing the Wave Function Delocalization

et al. 2015

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Colloidal semiconductor quantum dots (QDs) are extraordinarily appealing for the development of cheap and large area solar cells due to high absorption efficiency, tunable bandgap energies, and solution processability. Understanding and controlling electronic wave function delocalization in QD thin films is therefore pivotal for realizing efficient optoelectronic devices. Here, a detailed study of the exciton recombination dynamics in PbS/CdS core/shell films as a function of temperature and surface chemistry is reported. By decreasing the temperature from 295 to 5.4 K, electronic wave function delocalization from the PbS core to the monolayer CdS shell is observed, demonstrating a reduction of the conduction band offset at low temperature and the formation of a quasi-type II band alignment. Interestingly, films made with core−shell particles, where the shell is thicker than a monolayer, display type I alignment also at low temperature.

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“…6,14,17 They are particularly relevant because charge generation dynamics are intimately connected to the PCE of an operating device. For this reason, the combined investigation of the ultrafast optical response and functional characterization of solar cells allows one to correlate the fundamental physical/chemical processes that occur in the operating device and the light-to-electric power conversion.…”

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confidence: 99%

Modulating Exciton Dynamics in Composite Nanocrystals for Excitonic Solar Cells

Concina

Manzoni

Grancini

et al. 2015

J. Phys. Chem. Lett.

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Quantum dots (QDs) represent one of the most promising materials for third-generation solar cells due to their potential to boost the photoconversion efficiency beyond the Shockley-Queisser limit. Composite nanocrystals can challenge the current scenario by combining broad spectral response and tailored energy levels to favor charge extraction and reduce energy and charge recombination. We synthesized PbS/CdS QDs with different compositions at the surface of TiO2 nanoparticles assembled in a mesoporous film. The ultrafast photoinduced dynamics and the charge injection processes were investigated by pump-probe spectroscopy. We demonstrated good injection of photogenerated electrons from QDs to TiO2 in the PbS/CdS blend and used the QDs to fabricate solar cells. The fine-tuning of chemical composition and size of lead and cadmium chalcogenide QDs led to highly efficient PV devices (3% maximum photoconversion efficiency). This combined study paves the way to the full exploitation of QDs in next-generation photovoltaic (PV) devices.

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Controlling photoinduced electron transfer from PbS@CdS core@shell quantum dots to metal oxide nanostructured thin films

Cited by 81 publications

References 35 publications

Direct Measurement of Electronic Band Structure in Single Quantum Dots of Metal Chalcogenide Composites

Direct Measurement of Electronic Band Structure in Single Quantum Dots of Metal Chalcogenide Composites

Temperature-Dependent Optical Properties of PbS/CdS Core/Shell Quantum Dot Thin Films: Probing the Wave Function Delocalization

Modulating Exciton Dynamics in Composite Nanocrystals for Excitonic Solar Cells

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