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Special Issue "Colloidal Quantum Dots"

A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: 31 December 2017

Special Issue Editor

Guest Editor
Dr. David Binks

School of Physics and Astronomy, University of Manchester, UK
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Special Issue Information

Dear Colleagues,

Colloidal quantum dots (CQDs), semiconductor nanocrystals synthesised by solvent-based chemistry, have been studied intensively over the last three decades. Their small scale, typically a few nanometres, results in an optical band gap that is size-tunable by the quantum confinement effect. This property, coupled with their photo-stability and the low-cost and facile methods by which they can be produced and processed, has prompted their study as the light absorbing or emitting species for a number of important applications, including lighting and displays, third generation solar cells, lasers and image processing.

CQDs can be produced as homogeneous crystals of single materials and alloys, or as more complex structures. A shell or shells of different material can be grown around the original nanocrystal subsequent to its synthesis to produce a core/shell CQD. This spherical heterostructure enables the engineering of carrier wavefunctions, and hence of the photo-physical properties of the CQD. By choice of core and shell material with a suitable band alignment, and by control of the core size and shell thickness during growth, heterostructures can be produced that, for instance, localise electrons and holes in different regions, thus allowing control over the rate of radiative recombination, or maximise photoluminescence quantum yield (PLQY) by reducing the interaction of carriers with surface traps.

Indeed, it is becoming clear that the role of surface traps is key to the performance of CQDs for many applications. The nanoscale of CQDs means that a large fraction of the constituent atoms lie on the surface, where they may be under-coordinated. The resulting dangling bonds can lead to the formation of mid-gap states that trap carriers and act as a channel for non-radiative recombination, as well producing phenomenon such as photoluminescence intermittency, sometimes referred to as ‘blinking’. Such traps can be passivated to an extent by organic surface ligands, but steric hindrance can prevent these often bulky molecules from accessing every surface site. As described above, the growth of a suitable a shell can reduce the interaction of carriers with surface traps, but it can also reduce the efficiency with which they can be extracted to, for instance, contribute to the output of a CQD-based solar cell. However, in recent years the use of compact halide ions for surface passivation has proved particularly effective, resulting in near-unity PLQY and solar cell efficiencies in excess of 10%.

It is my pleasure to invite you to submit a manuscript for this Special Issue. Full papers, communications, and reviews are all welcome.

Dr. David Binks
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • colloidal quantum dot
  • nanoparticle
  • nano crystal

Published Papers (1 paper)

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Review

Open AccessFeature PaperReview Carrier Multiplication Mechanisms and Competing Processes in Colloidal Semiconductor Nanostructures
Materials 2017, 10(9), 1095; doi:10.3390/ma10091095
Received: 28 August 2017 / Revised: 10 September 2017 / Accepted: 14 September 2017 / Published: 18 September 2017
PDF Full-text (6127 KB) | HTML Full-text | XML Full-text
Abstract
Quantum confined semiconductor nanoparticles, such as colloidal quantum dots, nanorods and nanoplatelets have broad extended absorption spectra at energies above their bandgaps. This means that they can absorb light at high photon energies leading to the formation of hot excitons with finite excited
[...] Read more.
Quantum confined semiconductor nanoparticles, such as colloidal quantum dots, nanorods and nanoplatelets have broad extended absorption spectra at energies above their bandgaps. This means that they can absorb light at high photon energies leading to the formation of hot excitons with finite excited state lifetimes. During their existence, the hot electron and hole that comprise the exciton may start to cool as they relax to the band edge by phonon mediated or Auger cooling processes or a combination of these. Alongside these cooling processes, there is the possibility that the hot exciton may split into two or more lower energy excitons in what is termed carrier multiplication (CM). The fission of the hot exciton to form lower energy multiexcitons is in direct competition with the cooling processes, with the timescales for multiplication and cooling often overlapping strongly in many materials. Once CM has been achieved, the next challenge is to preserve the multiexcitons long enough to make use of the bonus carriers in the face of another competing process, non-radiative Auger recombination. However, it has been found that Auger recombination and the several possible cooling processes can be manipulated and usefully suppressed or retarded by engineering the nanoparticle shape, size or composition and by the use of heterostructures, along with different choices of surface treatments. This review surveys some of the work that has led to an understanding of the rich carrier dynamics in semiconductor nanoparticles, and that has started to guide materials researchers to nanostructures that can tilt the balance in favour of efficient CM with sustained multiexciton lifetimes. Full article
(This article belongs to the Special Issue Colloidal Quantum Dots)
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