[PDF] Study Of Colloidal Lead Sulfide Quantum Dot Light Emitting Diodes With Inorganic Charge Injection Layers And Ligand Exchanges eBook

Author : Gerasimos Konstantatos
Publisher : Cambridge University Press
Page : 478 pages
File Size : 21,46 MB
Release : 2013-11-07
Category : Technology & Engineering
ISBN : 1107469368

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Capturing the most up-to-date research in colloidal quantum dot (CQD) devices, this book is written in an accessible style by the world's leading experts. The application of CQDs in solar cells, photodetectors and light-emitting diodes (LEDs) has developed rapidly over recent years, promising to transform the future of clean energy, communications, and displays. This complete guide to the field provides researchers, students and practitioners alike with everything they need to understand these developments and begin contributing to future applications. Introductory chapters summarise the fundamental physics and chemistry, whilst later chapters review the developments that have propelled the field forwards, systematically working through key device advances. The science of CQD films is explained through the latest physical models of semiconductor transport, trapping and recombination, whilst the engineering of organic and inorganic multilayered materials is shown to have enabled major advances in the brightness and efficiency of CQD LEDs.

Author : Victor I. Klimov
Publisher : CRC Press
Page : 485 pages
File Size : 36,70 MB
Release : 2017-12-19
Category : Technology & Engineering
ISBN : 1420079271

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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.

Author : Rachel Hoffman Gilmore
Publisher :
Page : 117 pages
File Size : 41,55 MB
Release : 2017
Category :
ISBN :

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Quantum dots, also called semiconductor nanocrystals, are an interesting class of materials because their band gap is a function of the quantum dot size. Their optical properties are not determined solely by the atomic composition, but may be engineered. Advances in quantum dot synthesis have enabled control of the ensemble size dispersity and the creation of monodisperse quantum dot ensembles with size variations of less than one atomic layer. Quantum dots have been used in a variety of applications including solar cells, light-emitting diodes, photodetectors, and thermoelectrics. In many of these applications, understanding charge transport in quantum dot solids is crucial to optimizing efficient devices. We examine charge transport in monodisperse, coupled quantum dot solids using spectroscopic techniques explained by hopping transport models that provide a complementary picture to device measurements. In our monodisperse quantum dot solids, the site-to-site energetic disorder that comes from size dispersity and the size-dependent band gap is very small and spatial disorder in the quantum dot superlattice often has a greater impact on charge transport. In Chapter 2, we show that improved structural order from self-assembly in monodisperse quantum dots reduces the interparticle spacing and has a greater impact than reduced energetic disorder on increasing charge carrier hopping rates. In Chapter 3, we present temperature-dependent transport measurements that demonstrate again that when energetic disorder is very low, structural changes will dominate the dynamics. We find increasing mobility with decreasing temperature that can be explained by a 1-2 Å contraction in the edge-to-edge nearest neighbor quantum dot spacing. In Chapter 4, we study optical states that are 100-200 meV lower in energy than the band gap. Because we work with monodisperse quantum dots, we are able to resolve this trap state separately from the band edge state and study its optical properties. We identify the trap state as dimers that form during synthesis and ligand exchange when two bare quantum dot surfaces fuse. The findings of this thesis point to the importance of minimizing the structural disorder of the coupled quantum dot solid in addition to the energetic disorder to optimize charge carrier transport.

Author : Morteza Sasani Ghamsari
Publisher : BoD – Books on Demand
Page : 171 pages
File Size : 26,21 MB
Release : 2017-10-25
Category : Technology & Engineering
ISBN : 9535135759

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Quantum dot-based light emitting diodes were assigned to bringing together the latest and most important progresses in light emitting diode (LED) technologies. In addition, they were dedicated to gain the perspective of LED technology for all of its advancements and innovations due to the employment of semiconductor nanocrystals. Highly selective, the primary aim was to provide a visual source for high-urgency work that will define the future directions relating to the organic light emitting diode (OLED), with the expectation for lasting scientific and technological impact. The editor hopes that the chapters verify the realization of the mentioned aims that have been considered for editing of this book. Due to the rapidly growing OLED technology, we wish this book to be useful for any progress that can be achieved in future.

Author : Vanessa Claire Wood
Publisher :
Page : 89 pages
File Size : 45,63 MB
Release : 2007
Category :
ISBN :

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This thesis presents the first colloidal quantum dot light emitting devices (QD-LEDs) with metal oxide charge transport layers. Colloidally synthesized quantum dots (QDs) have shown promise as the active material in optoelectronic devices because of their tunable, narrow band emission. To date, the most efficient QD-LEDs involve a monolayer of closely packed QDs sandwiched between organic charge transport layers. However, these organic materials are subject to degradation due to atmospheric oxygen and water vapor. In contrast, metal-oxide films used in this work are chemically and morphologically stable in air and can withstand numerous organic solvents, which increases the flexibility of device processing. Furthermore, they can sustain higher carrier injection rates needed to realize an electrically pumped colloidal QD laser. This thesis details the characterization techniques, such as Atomic Force Microscopy, photoluminescence spectroscopy, Hall Effect measurements, X-Ray Diffraction, and Ultraviolet Photoelectron Spectroscopy, used to design efficient QD-LEDs. It reviews the steps used to optimize device performance and obtain a transparent device architecture with external quantum efficiency of 0.15% and a peak luminance of 7000 Cd/m2. This manifests a 100-fold improvement in efficiency over any previously reported all inorganic QD-LED structure.

Author : John Donegan
Publisher : CRC Press
Page : 244 pages
File Size : 26,99 MB
Release : 2016-04-19
Category : Science
ISBN : 9814316091

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In the last two decades, semiconductor quantum dots-small colloidal nanoparticles-have garnered a great deal of scientific interest because of their unique properties. Among nanomaterials, CdTe holds special technological importance as the only known II-VI material that can form conventional p-n junctions. This makes CdTe very important for the dev

Author : Vanessa Claire Wood
Publisher :
Page : 172 pages
File Size : 16,15 MB
Release : 2010
Category :
ISBN :

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This thesis develops methods for integrating colloidally synthesized quantum dots (QDs) and metal oxides in optoelectronic devices, presents three distinct light emitting devices (LEDs) with metal oxides surrounding a QD active layer, and uses these novel metal oxide based QD-LEDs to study mechanisms for electrical excitation of QDs. QD-LEDs have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with high color rendering index. This work demonstrates that air-stable metal oxides can be used to achieve QD-LEDs that have long shelf lives and operate at constant luminance in ambient conditions, unpackaged. Because metal oxides range from conductors to dielectrics, they can be used to develop a variety of different device architectures to explore mechanisms for electrical excitation of QDs. We report the first all-inorganic QD-LEDs with n- and p-type metal oxide charge transport layers and present design rules to enable systematic improvement of device efficiency. To shift away from direct charge injection as a means for electroluminescence (EL) in inorganic-based QD-LED structures, we develop a unipolar device architecture that presents the first evidence of field driven EL in QDs. To further explore this field driven excitation mechanism, we develop a structure that situates QDs between two insulating metal oxide layers. By eliminating the need for energy band alignment, these devices enable EL from QDs with emission peaks from 450 nm-1500 nm as well as from novel nanoparticles, such as phosphor doped-core/shell nanocrystals.

Author : Whitney Rochelle Hess
Publisher :
Page : 161 pages
File Size : 27,51 MB
Release : 2017
Category :
ISBN :

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Solution processability and optoelectronic tunability makes lead sulfide quantum dots (PbS QDs) promising candidates for low-temperature, solution-processed thin film solar cells. Central to this thesis is the crucial role of QD surface chemistry and leveraging surface modification to prepare QDs suitable for optoelectronic device applications. The work presented here explores the versatility of PbS QDs integrated into two main device architectures, where the primary role of the QD is unique in each case. In p-i-n planar perovskite solar cells, efforts to utilize PbS QDs as a hole transport material and the effects of size tuning and surface passivation with cadmium on device characteristics are discussed. A combination of QD size reduction and minimal cadmium-to-lead cation exchange is found to improve the open circuit voltage and hole extraction into the PbS QD layer. In ZnO/PbS QD heterojunction solar cells, the feasibility of preparing fully inorganic, halometallate-passivated PbS QD inks for use as the absorber layer is discussed. A modified biphasic ligand exchange strategy is presented and in order to further elucidate electronic passivation in these QD ink systems, optical properties were investigated with steady state and time-resolved photoluminescence. Significantly, PbS QDs exhibit comparable quantum yields in solution before and after ligand exchange and no significant trap state emission was observed in solution and in film. Ink devices were fabricated with one- and two-layer depositions, which significantly reduce fabrication time compared to traditional layer-by-layer deposition, and devices exhibit anomalous efficiency improvement throughout storage in air.