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Comparing Halide Ligands in PbS Colloidal Quantum Dots for Field-Effect Transistors and Solar Cells.

ABSTRACT: Capping colloidal quantum dots (CQDs) with atomic ligands is a powerful approach to tune their properties and improve the charge carrier transport in CQD solids. Efficient passivation of the CQD surface, which can be achieved with halide ligands, is crucial for application in optoelectronic devices. Heavier halides, i.e., I- and Br-, have been thoroughly studied as capping ligands in the last years, but passivation with fluoride ions has not received sufficient consideration. In this work, effective coating of PbS CQDs with fluoride ligands is demonstrated and compared to the results obtained with other halides. The electron mobility in field-effect transistors of PbS CQDs treated with different halides shows an increase with the size of the atomic ligand (from 3.9 × 10-4 cm2/(V s) for fluoride-treated to 2.1 × 10-2 cm2/(V s) for iodide-treated), whereas the hole mobility remains unchanged in the range between 1 × 10-5 cm2/(V s) and 10-4cm2/(V s). This leads to a relatively more pronounced p-type behavior of the fluoride- and chloride-treated films compared to the iodide-treated ones. Cl-- and F--capped PbS CQDs solids were then implemented as p-type layer in solar cells; these devices showed similar performance to those prepared with 1,2-ethanedithiol in the same function. The relatively stronger p-type character of the fluoride- and chloride-treated PbS CQD films broadens the utility of such materials in optoelectronic devices.

SUBMITTER: Bederak D

PROVIDER: S-EPMC6317010 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

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Comparing Halide Ligands in PbS Colloidal Quantum Dots for Field-Effect Transistors and Solar Cells.

Bederak Dmytro D Balazs Daniel M DM Sukharevska Nataliia V NV Shulga Artem G AG Abdu-Aguye Mustapha M Dirin Dmitry N DN Kovalenko Maksym V MV Loi Maria A MA

ACS applied nano materials 20181109 12

Capping colloidal quantum dots (CQDs) with atomic ligands is a powerful approach to tune their properties and improve the charge carrier transport in CQD solids. Efficient passivation of the CQD surface, which can be achieved with halide ligands, is crucial for application in optoelectronic devices. Heavier halides, i.e., I<sup>-</sup> and Br<sup>-</sup>, have been thoroughly studied as capping ligands in the last years, but passivation with fluoride ions has not received sufficient consideratio ...[more]

PMID: 30613830

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Project description:Pairs of coupled quantum dots with controlled coupling between the two potential wells serve as an extremely rich system, exhibiting a plethora of optical phenomena that do not exist in each of the isolated constituent dots. Over the past decade, coupled quantum systems have been under extensive study in the context of epitaxially grown quantum dots (QDs), but only a handful of examples have been reported with colloidal QDs. This is mostly due to the difficulties in controllably growing nanoparticles that encapsulate within them two dots separated by an energetic barrier via colloidal synthesis methods. Recent advances in colloidal synthesis methods have enabled the first clear demonstrations of colloidal double quantum dots and allowed for the first exploratory studies into their optical properties. Nevertheless, colloidal double QDs can offer an extended level of structural manipulation that allows not only for a broader range of materials to be used as compared with epitaxially grown counterparts but also for more complex control over the coupling mechanisms and coupling strength between two spatially separated quantum dots. The photophysics of these nanostructures is governed by the balance between two coupling mechanisms. The first is via dipole-dipole interactions between the two constituent components, leading to energy transfer between them. The second is associated with overlap of excited carrier wave functions, leading to charge transfer and multicarrier interactions between the two components. The magnitude of the coupling between the two subcomponents is determined by the detailed potential landscape within the nanocrystals (NCs). One of the hallmarks of double QDs is the observation of dual-color emission from a single nanoparticle, which allows for detailed spectroscopy of their properties down to the single particle level. Furthermore, rational design of the two coupled subsystems enables one to tune the emission statistics from single photon emission to classical emission. Dual emission also provides these NCs with more advanced functionalities than the isolated components. The ability to better tailor the emission spectrum can be advantageous for color designed LEDs in lighting and display applications. The different response of the two emission colors to external stimuli enables ratiometric sensing. Control over hot carrier dynamics within such structures allows for photoluminescence upconversion. This Account first provides a description of the main hurdles toward the synthesis of colloidal double QDs and an overview of the growing library of synthetic pathways toward constructing them. The main discoveries regarding their photophysical properties are then described in detail, followed by an overview of potential applications taking advantage of the double-dot structure. Finally, a perspective and outlook for their future development is provided.

Dataset Information

Comparing Halide Ligands in PbS Colloidal Quantum Dots for Field-Effect Transistors and Solar Cells.

Publications

Comparing Halide Ligands in PbS Colloidal Quantum Dots for Field-Effect Transistors and Solar Cells.

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