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      Surface Traps in Colloidal Quantum Dots: A Combined Experimental and Theoretical Perspective

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      The Journal of Physical Chemistry Letters
      American Chemical Society

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          Abstract

          Surface traps are ubiquitous to nanoscopic semiconductor materials. Understanding their atomistic origin and manipulating them chemically have capital importance to design defect-free colloidal quantum dots and make a leap forward in the development of efficient optoelectronic devices. Recent advances in computing power established computational chemistry as a powerful tool to describe accurately complex chemical species and nowadays it became conceivable to model colloidal quantum dots with realistic sizes and shapes. In this Perspective, we combine the knowledge gathered in recent experimental findings with the computation of quantum dot electronic structures. We analyze three different systems: namely, CdSe, PbS, and CsPbI 3 as benchmark semiconductor nanocrystals showing how different types of trap states can form at their surface. In addition, we suggest experimental healing of such traps according to their chemical origin and nanocrystal composition.

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          Most cited references47

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          Generalized Gradient Approximation Made Simple.

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            cp2k:atomistic simulations of condensed matter systems

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              Highly Dynamic Ligand Binding and Light Absorption Coefficient of Cesium Lead Bromide Perovskite Nanocrystals.

              Lead halide perovskite materials have attracted significant attention in the context of photovoltaics and other optoelectronic applications, and recently, research efforts have been directed to nanostructured lead halide perovskites. Collodial nanocrystals (NCs) of cesium lead halides (CsPbX3, X = Cl, Br, I) exhibit bright photoluminescence, with emission tunable over the entire visible spectral region. However, previous studies on CsPbX3 NCs did not address key aspects of their chemistry and photophysics such as surface chemistry and quantitative light absorption. Here, we elaborate on the synthesis of CsPbBr3 NCs and their surface chemistry. In addition, the intrinsic absorption coefficient was determined experimentally by combining elemental analysis with accurate optical absorption measurements. (1)H solution nuclear magnetic resonance spectroscopy was used to characterize sample purity, elucidate the surface chemistry, and evaluate the influence of purification methods on the surface composition. We find that ligand binding to the NC surface is highly dynamic, and therefore, ligands are easily lost during the isolation and purification procedures. However, when a small amount of both oleic acid and oleylamine is added, the NCs can be purified, maintaining optical, colloidal, and material integrity. In addition, we find that a high amine content in the ligand shell increases the quantum yield due to the improved binding of the carboxylic acid.
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                Author and article information

                Journal
                J Phys Chem Lett
                J Phys Chem Lett
                jz
                jpclcd
                The Journal of Physical Chemistry Letters
                American Chemical Society
                1948-7185
                03 October 2017
                19 October 2017
                : 8
                : 20
                : 5209-5215
                Affiliations
                []Dipartimento di Matematica e Fisica ‘E. De Giorgi’, Università del Salento , via per Arnesano, 73100 Lecce, Italy
                []NANOTEC−CNR Istituto di Nanotecnologia, via per Arnesano, 73100 Lecce, Italy
                [§ ]Department of Theoretical Chemistry, Faculty of Science, Vrije Universiteit Amsterdam , de Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
                Author notes
                Article
                10.1021/acs.jpclett.7b02193
                5651579
                28972763
                e995ec87-374d-40a0-a224-e738838d8e40
                Copyright © 2017 American Chemical Society

                This is an open access article published under a Creative Commons Attribution (CC-BY) License, which permits unrestricted use, distribution and reproduction in any medium, provided the author and source are cited.

                History
                : 19 August 2017
                : 03 October 2017
                Categories
                Perspective
                Custom metadata
                jz7b02193
                jz-2017-02193q

                Physical chemistry
                Physical chemistry

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