Download or read book Semiconducting Nanocrystals Synthesis Colloidal Stability and Charge Carrier Dynamics written by Shuai Chen and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal nanocrystals (NCs) with controllable morphologies and sizes are at the core of nanomaterials research. Among different NCs (zero-dimensional quantum dots, one-dimensional nanorods, etc.), two-dimensional cadmium selenide (CdSe) nanoplatelets (NPLs) with lateral extension of over 100 nm2 and atomically precise thickness are one of the most promising semiconductors for optoelectronic applications. However, several issues remain for implementing CdSe NPLs for applications, including: (1) containing toxic and heavy elements, and (2) lacking a fundamental understanding of the colloidal stability and the process of charge carrier generation in solids. This thesis aims to synthesize environmentally friendly alternatives, such as indium phosphide (InP) NCs with varied shapes, and shed light on colloidal stability and charge carrier generation and dynamics using conventional CdSe NPLs as the model system. The introductory Chapter 1 briefly presents an overview of nanomaterials and nanotechnology, including quantum confinement in NCs, quantum dots, InP NCs, the synthesis status of CdSe NPLs, colloidal NCs stabilization in dispersion, photophysics of CdSe NPLs, ligand exchange method, and the thermal annealing method. In Chapter 2, we introduce terahertz (THz) spectroscopy basics, including the generation and detection mechanism, experimental setups, and the conductivity models for data analysis to infer charge transport properties in materials of interest. Chapters 3-5 present the key results of this thesis. In Chapter 3, we synthesize InP NCs with different shapes and sizes by utilizing triphenyl phosphite as the phosphorus source. We show that InP NCs can be synthesized and formed from In2O3 NCs. Our findings open new synthetic possibilities by utilizing a cost-effective, non-pyrophoric, and non-toxic phosphorus precursor. In Chapter 4, we combine THz photoconductivity measurements with simulations to study the colloidal stability and aggregation process in CdSe NPL dispersion. We demonstrate that increasing the facet area of NPLs and the solvent length can reduce the critical concentration at which NPLs start aggregating. Our simulation attributes the effect to the solvation force-dominated colloidal stability for the NPL system; the solvation force is enhanced by increasing the NPL lateral area and the length of solvent molecules. In Chapter 5, we report that thermal annealing constitutes an effective strategy to control the optical absorption and electrical properties of CdSe NPLs by tuning the inter-NPL distance. We observe a direct correlation between the temperature-dependent ligand decomposition and the NPL-NPL distance shortening (by TEM). This leads to a strong red-shift in the absorption band edge (by UV-vis studies) and enhanced electrical transport Abstract in NPL films. Our results illustrate a straightforward manner to control the interfacial electronic coupling strength for developing functional optoelectronics through thermal treatments.
Download or read book Semiconductor and Metal Nanocrystals written by Victor I. Klimov and published by CRC Press. This book was released on 2003-11-07 with total page 505 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast technological potential of nanocrystalline materials, as well as current intense interest in the physics and chemistry of nanoscale phenomena, has led to explosive growth in research on semiconductor nanocrystals, also known as nanocrystal quantum dots, and metal nanoparticles. Semiconductor and Metal Nanocrystals addresses current topics impacting the field including synthesis and assembly of nanocrystals, theory and spectroscopy of interband and intraband optical transitions, single-nanocrystal optical and tunneling spectroscopies, electrical transport in nanocrystal assemblies, and physical and engineering aspects of nanocrystal-based devices. Written by experts who have contributed pioneering research, this reference comprises key advances in the field of semiconductor nanocrystal quantum dots and metal nanoparticles over the past several years. Focusing specifically on nanocrystals generated through chemical techniques, Semiconductor and Metal Nanocrystals Merges investigative frontiers in physics, chemistry, and engineering Documents advances in nanocrystal synthesis and assembly Explores the theory of electronic excitations in nanoscale particles Presents comprehensive information on optical spectroscopy of interband and intraband optical transitions Reviews data on single-nanocrystal optical and tunneling spectroscopies Weighs controversies related to carrier relaxation dynamics in ultrasmall nanoparticles Discusses charge carrier transport in nanocrystal assemblies Provides examples of lasing and photovoltaic nanocrystal-based devices Semiconductor and Metal Nanocrystals is a must read for scientists, engineers, and upper-level undergraduate and graduate students interested in the physics and chemistry of nanoscale semiconductor and metal particles, as well as general nanoscale science.
Download or read book Colloidal Semiconductor Nanocrystals Synthesis Properties and Applications written by Vladimir Lesnyak and published by Frontiers Media SA. This book was released on 2020-01-06 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Semiconductor Nanocrystals written by Alexander L. Efros and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: A physics book that covers the optical properties of quantum-confined semiconductor nanostructures from both the theoretical and experimental points of view together with technological applications. Topics to be reviewed include quantum confinement effects in semiconductors, optical adsorption and emission properties of group IV, III-V, II-VI semiconductors, deep-etched and self assembled quantum dots, nanoclusters, and laser applications in optoelectronics.
Download or read book Semiconductor Nanocrystal Quantum Dots written by Andrey Rogach and published by Springer Science & Business Media. This book was released on 2008-09-02 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first book to specifically focus on semiconductor nanocrystals, and address their synthesis and assembly, optical properties and spectroscopy, and potential areas of nanocrystal-based devices. The enormous potential of nanoscience to impact on industrial output is now clear. Over the next two decades, much of the science will transfer into new products and processes. One emerging area where this challenge will be very successfully met is the field of semiconductor nanocrystals. Also known as colloidal quantum dots, their unique properties have attracted much attention in the last twenty years.
Download or read book Photoactive Semiconductor Nanocrystal Quantum Dots written by Alberto Credi and published by Springer. This book was released on 2017-01-20 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: The series Topics in Current Chemistry Collections presents critical reviews from the journal Topics in Current Chemistry organized in topical volumes. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science. The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience. Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.
Download or read book Quantum Confined Semiconductor Nanocrystals written by Wesley Chiang and published by American Chemical Society. This book was released on 2023-09-26 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today, the fascinating story of colloidal quantum dots has no series finale yet. Instead, there continue to be advancements in our understanding of the fundamental properties of these nanocrystals, each of these advancements catalyzing a spin-off into a new journey toward potential applications. These remarkable advancements include improving the synthesis techniques, characterizing nanocrystals at the single-particle level, and tailoring their properties for specific applications. The quantum-confined colloidal semiconductor nanocrystals field has witnessed a remarkable convergence of nanoscience, materials chemistry, and spectroscopy, resulting in unprecedented control over their properties. With ongoing research efforts, the potential of semiconductor nanocrystals continues to unfold. Scientists are exploring new materials, developing scalable synthesis methods, and pushing the boundaries of their applications in fields such as quantum computing, energy storage, and biological sensing. The authors take the reader into quantum confinement and quantum dots. While the contents of this primer are rather expansive, they merely scratch the surface of the complex voyage that quantum dot sciences have undergone. The authors have identified vital terminology, valuable concepts, techniques, and applications.
Download or read book Colloidal Quantum Dot Optoelectronics and Photovoltaics written by Gerasimos Konstantatos and published by Cambridge University Press. This book was released on 2013-11-07 with total page 329 pages. Available in PDF, EPUB and Kindle. Book excerpt: Captures the most up-to-date research in the field, written in an accessible style by the world's leading experts.
Download or read book Nanocrystal Quantum Dots written by and published by . This book was released on 2010 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metal and Semiconductor Nanocrystals written by Jing Zhao and published by Frontiers Media SA. This book was released on 2020-01-14 with total page 91 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stabilizing Degenerate Dopants in Colloidal Semiconductor Nanocrystals written by Kimberly H. Hartstein and published by . This book was released on 2018 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt: Semiconductor nanocrystals possessing excess delocalized charge carriers are garnering considerable attention for their applications in a wide range of emerging technologies. In order to realize their incorporation into practical devices, a detailed understanding of their electronic structural properties is essential. Precise control over the introduction and removal of degenerate dopants from semiconductor nanostructures presents exciting opportunities for careful study of their electronic structures and associated capabilities. This thesis explores the careful incorporation and characterization of the stability of degenerate dopants in semiconductor nanomaterials. Chapter 1 provides an introduction to degenerately doped semiconductor nanocrystals, briefly describing methods to incorporate and confirm the presence of excess charge carriers. We explore factors that influence charge carrier stability in a variety of semiconductor nanocrystal lattices, and consider what limits the extent of stable carrier incorporation. Chapter 2 investigates the stability of degenerate dopants in n-doped CdSe/CdS core/shell quantum dots and explores their luminescent signatures. These studies reveal that CdS shell deposition greatly slows electron trapping, and we characterize the luminescence from a photogenerated four-carrier negative tetron (three electrons and one hole). Chapter 3 applies in situ spectroelectrochemical potentiometry to quantify the Fermi-level energy in p-doped plasmonic copper-sulfide nanocrystals. We reversibly tune the plasmon absorption band using redox chemistry, and demonstrate identical absorption bands in low-chalcocite copper-sulfide nanocrystals with and without cation vacancies. This work demonstrates that cation vacancies internal to the nanocrystal lattice are far more effective at stabilizing free carriers than anions at the nanocrystal surfaces. Chapter 4 applies magnetic circular dichroism (MCD) spectroscopy to identify classical cyclotron splittings in plasmonic semiconductor nanocrystals, and compares their magnetic signatures with those exhibited by plasmonic metal nanoparticles. We demonstrate that the sign of the MCD signal is sensitive to the sign of the carriers (n or p), and that the magnitude of the cyclotron splitting reflects the carrier effective masses for the delocalized carriers. Overall, this work focuses on stable incorporation of degenerate dopants into semiconductor nanocrystals as a method to improve our understanding of the fundamental electronic structural properties of these materials to work toward their implementation into practical device architectures.
Download or read book Nanocrystals written by Sudheer Neralla and published by BoD – Books on Demand. This book was released on 2012-08-29 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystals research has been an area of significant interest lately, due to the wide variety of potential applications in semiconductor, optical and biomedical fields. This book consists of a collection of research work on nanocrystals processing and characterization of their structural, optical, electronic, magnetic and mechanical properties. Various methods for nanocrystals synthesis are discussed in the book. Size-dependent properties such as quantum confinement, superparamagnetism have been observed in semiconductor and magnetic nanoparticles. Nanocrystals incorporated into different material systems have proven to possess improved properties. A review of the exciting outcomes nanoparticles study has provided indicates further accomplishments in the near future.
Download or read book Synthesis and Characterization of Semiconductor Nanomaterials written by Fanxin Wu and published by . This book was released on 2004 with total page 392 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Nanocrystal Quantum Dots written by Victor I. Klimov and published by CRC Press. This book was released on 2017-12-19 with total page 485 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of recent advancements in colloidal nanocrystals and quantum-confined nanostructures, Nanocrystal Quantum Dots is the second edition of Semiconductor and Metal Nanocrystals: Synthesis and Electronic and Optical Properties, originally published in 2003. This new title reflects the book’s altered focus on semiconductor nanocrystals. Gathering contributions from leading researchers, this book contains new chapters on carrier multiplication (generation of multiexcitons by single photons), doping of semiconductor nanocrystals, and applications of nanocrystals in biology. Other updates include: New insights regarding the underlying mechanisms supporting colloidal nanocrystal growth A revised general overview of multiexciton phenomena, including spectral and dynamical signatures of multiexcitons in transient absorption and photoluminescence Analysis of nanocrystal-specific features of multiexciton recombination A review of the status of new field of carrier multiplication Expanded coverage of theory, covering the regime of high-charge densities New results on quantum dots of lead chalcogenides, with a focus studies of carrier multiplication and the latest results regarding Schottky junction solar cells Presents useful examples to illustrate applications of nanocrystals in biological labeling, imaging, and diagnostics The book also includes a review of recent progress made in biological applications of colloidal nanocrystals, as well as a comparative analysis of the advantages and limitations of techniques for preparing biocompatible quantum dots. The authors summarize the latest developments in the synthesis and understanding of magnetically doped semiconductor nanocrystals, and they present a detailed discussion of issues related to the synthesis, magneto-optics, and photoluminescence of doped colloidal nanocrystals as well. A valuable addition to the pantheon of literature in the field of nanoscience, this book presents pioneering research from experts whose work has led to the numerous advances of the past several years.
Download or read book Ultrafast Charge Carrier Dynamics in Bare and Surface modified Semiconductor Nanoparticles written by Jameel Abdul-Hadi Hasan and published by . This book was released on 2015 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Charge-carrier relaxation dynamics in semiconductor nanoparticles has been in the forefront of research for last three decades both for their fundamental nature as well as for applications in light-harvesting, luminescent labels, light-emitting diodes and nonlinear optics. Significant research has focused on II-VI semiconductors with emphasis on CdS and CdSe that are toxic. On the other hand, ZnO and TiO2 semiconductor nanoparticles are less toxic and have enormous applications in photo-catalysis, water splitting, solar cells and optical sensors. However, the investigations of charge-carrier dynamics in these semiconductor nanomaterials compared to II-VI semiconductor quantum dots are quite limited. The knowledge of charge-carrier relaxation is essential to realize their optical applications. In this dissertation, efforts were made to probe ultrafast charge-carrier dynamics in bare ZnO and surface-modified TiO2 nanoparticles with combined femtosecond fluorescence upconversion and transient absorption measurements. Quantum-sized ZnO semiconductor nanoparticles show two luminescence bands corresponding to band-edge and trap-state luminescence where the dynamics of band-edge luminescence was not well understood. In this dissertation, studies were carried out to probe the ultrafast band-edge luminescence dynamics in bare ZnO nanoparticles as a function of size. The measurements have shown interesting role of rate of trapping in the band-edge luminescence dynamics and conclusively shown that trapping dynamics dominates the charge-carrier relaxation. Along similar lines, ultrafast interfacial charge-transfer emission was monitored in small molecule-modified TiO2 nanoparticles and have shown that small molecules create inter band-gap charge-transfer excitons that delocalize relatively fast into the conduction band of TiO2 leading to efficient charge separation. In this study, results revealed that increasing the strength of donor leads to better charge separation. Ultrafast measurements on chromophore-surface modified TiO2 nanoparticles have shown the role of localized charge-transfer excitons in charge separation and their use in dye solar cells. The results have shed light on heterogeneous interfacial charge-carrier relaxation dynamics in dye functionalized semiconductor nanoparticles. Finally, interesting trap-state luminescence of ZnO nanoparticles was used to develop turn-on luminescent dissolved oxygen (DO) sensors. Further, the sensitivity of ZnO nanoparticles towards DO was improved by preparing ZnO/graphene oxide nanocomposites that have shown additional ratiometric sensing capabilities for DO.
Download or read book A NOVEL APPROACH FOR THE FABRICATION OF ALL INORGANIC NANOCRYSTAL SOLIDS written by Pavel Moroz and published by . This book was released on 2015 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: Growing fossil fuels consumption compels researchers to find new alternative pathways to produce energy. Along with new materials for the conversion of different types of energy into electricity innovative methods for efficient processing of energy sources are also introduced. The main criteria for the success of such materials and methods are the low cost and compelling performance. Among different types of materials semiconductor nanocrystals are considered as promising candidates for the role of the efficient and cheap absorbers for solar energy applications. In addition to the anticipated cost reduction, the integration of nanocrystals (NC) into device architectures is inspired by the possibility of tuning the energy of electrical charges in NCs via nanoparticle size. However, the stability of nanocrystals in photovoltaic devices is limited by the stability of organic ligands which passivate the surface of semiconductors to preserve quantum confinement. The present work introduces a new strategy for low-temperature processing of colloidal nanocrystals into all-inorganic films: semiconductor matrix encapsulated nanocrystal arrays (SMENA). This methodology goes beyond the traditional ligand-interlinking scheme and relies on the encapsulation of morphologically-defined nanocrystal arrays into a matrix of a wide-band gap semiconductor, which preserves optoelectronic properties of individual nanoparticles. Fabricated solids exhibit excellent thermal stability, which is attributed to the heteroepitaxial structure of nanocrystal-matrix interfaces. The main characteristics and properties of these solids were investigated and compared with ones of traditionally fabricated nanocrystal films using standard spectroscopic, optoelectronic and electronic techniques. As a proof of concept, we successfully fabricated an all-inorganic depleted-heterojunction solar cell prototype which shows a promising 4.0% power conversion efficiency. We also characterized electron transport phenomena in different types of nanocrystal films using all-optical approach. By measuring excited carrier lifetimes in either ligand-linked or matrix-encapsulated PbS nanocrystal films containing a tunable fraction of insulating ZnS domains, we uniquely distinguish the dynamics of charge scattering on defects from other processes of exciton dissociation. The measured times are subsequently used to estimate the diffusion length and the carrier mobility for each film type within hopping transport regime. It is demonstrated that nanocrystal films encapsulated into semiconductor matrices exhibit a lower probability of charge scattering than nanocrystal solids cross-linked with either 3-mercaptopropionic acid or 1,2-ethanedithiol molecular linkers. The suppression of carrier scattering in matrix-encapsulated nanocrystal films is attributed to a relatively low density of surface defects at nanocrystal/matrix interfaces. High stability and low density of defects made it possible to fabricate infrared-emitting nanocrystal solids. Presently, an important challenge facing the development of nanocrystal infrared emitters concerns the fact that both the emission quantum yield and the stability of colloidal nanoparticles become compromised when nanoparticle solutions are processed into solids. Here, we address this issue by developing an assembly technique that encapsulates infrared-emitting PbS NCs into crystalline CdS matrices, designed to preserve NC emission characteristics upon film processing. Here, the morphology of these matrices was designed to suppress the nonradiative carrier decay, whereby increasing the exciton lifetime up to 1 æs, and boosting the emission quantum yield to an unprecedented 3.7% for inorganically encapsulated PbS NC solids.
Download or read book Semiconductor and Metal Nanocrystals written by Victor I. Klimov and published by CRC Press. This book was released on 2003-11-07 with total page 479 pages. Available in PDF, EPUB and Kindle. Book excerpt: The vast technological potential of nanocrystalline materials, as well as current intense interest in the physics and chemistry of nanoscale phenomena, has led to explosive growth in research on semiconductor nanocrystals, also known as nanocrystal quantum dots, and metal nanoparticles. Semiconductor and Metal Nanocrystals addresses current topics impacting the field including synthesis and assembly of nanocrystals, theory and spectroscopy of interband and intraband optical transitions, single-nanocrystal optical and tunneling spectroscopies, electrical transport in nanocrystal assemblies, and physical and engineering aspects of nanocrystal-based devices. Written by experts who have contributed pioneering research, this reference comprises key advances in the field of semiconductor nanocrystal quantum dots and metal nanoparticles over the past several years. Focusing specifically on nanocrystals generated through chemical techniques, Semiconductor and Metal Nanocrystals Merges investigative frontiers in physics, chemistry, and engineering Documents advances in nanocrystal synthesis and assembly Explores the theory of electronic excitations in nanoscale particles Presents comprehensive information on optical spectroscopy of interband and intraband optical transitions Reviews data on single-nanocrystal optical and tunneling spectroscopies Weighs controversies related to carrier relaxation dynamics in ultrasmall nanoparticles Discusses charge carrier transport in nanocrystal assemblies Provides examples of lasing and photovoltaic nanocrystal-based devices Semiconductor and Metal Nanocrystals is a must read for scientists, engineers, and upper-level undergraduate and graduate students interested in the physics and chemistry of nanoscale semiconductor and metal particles, as well as general nanoscale science. About the Editor: VICTOR I. KLIMOV is Team Leader, Softmatter Nanotechnology and Advanced Spectroscopy Team, Chemistry Division, Los Alamos National Laboratory, New Mexico. The recipient of the Los Alamos Fellows Prize (2000), he is a Fellow of the Alexander von Humboldt Foundation, leader of the Nanophotonics and Nanoelectronics Thrust of the Center for Integrated Nanotechnologies (U.S. Department of Energy), a member of the Los Alamos Board of Governors of the Institute for Complex Adaptive Matter, and a member of the Steering Committee for the Los Alamos Quantum Institute. He received the M.S. (1978), Ph.D. (1981), and Dr. Sci. (1993) degrees from Moscow State University, Russia.
