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Design And Optimization Of Colloidal Quantum Dot Solids For Enhanced Charge Transport And Photovoltaics
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Book Synopsis Design and Optimization of Colloidal Quantum Dot Solids for Enhanced Charge Transport and Photovoltaics by : Sangjin Lee (Ph. D.)
Download or read book Design and Optimization of Colloidal Quantum Dot Solids for Enhanced Charge Transport and Photovoltaics written by Sangjin Lee (Ph. D.) and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal quantum dots (CQDs) have attracted much attention due to their distinctive optical properties such as wide spectral responses and tunable absorption spectra with simple size control. These properties, together with the advantages of solution processing and superior robustness to organic materials, have motivated the recent investigation of CQD-based solar cells, which have seen rapid growth in power conversion efficiency in just the last 10 years, to a current record of over 10%. However, in order to continue to push the efficiencies higher, a better understanding of the charge transport phenomena in CQD films is needed. While the carrier transport mechanisms between isolated molecules have been explored theoretically and the device-scale mobility of CQD layers has been characterized using experimental measurements such as time-of-flight analysis and field-effect-transistor measurements, a systematic study of the connection between these two distinct scales is required in order to provide crucial information regarding how CQD layers with higher charge carrier mobility can be achieved. While a few strategies such as ligand exchanges, band-like transport, and trap-state-mediated transport have been suggested to enhance the charge carrier mobility, inhomogeneity in CQD solids has been considered a source of the mobility degradation because the electronic properties in individual CQDs may have dispersions introduced in the synthesis and/or in the deposition process, leading to the deviations of the localized energy states from the regular positions or the average energy levels. Here, we suggest that control over such design factors in CQD solids can provide important pathways for improvements in device efficiencies as well as the charge carrier mobility. In particular, we have focused on the polydispersity in CQDs, which normally lies in the range of 5-15%. The effect of size-dispersion in CQD solids on the charge carrier mobility was computed using charge hopping transport models. The experimental film deposition processes were replicated using a molecular dynamics simulation where the equilibrium positions of CQDs with a given radii distribution were determined under a granular potential. The radii and positions of the CQDs were then used in the charge hopping transport simulator where the carrier mobility was estimated. We observed large decreases (up to 70%) in electron mobility for typical experimental polydispersity (about 10%) in CQD films. These large degradations in hopping charge transport were investigated using transport vector analysis with which we suggested that the site energy differences raised the portion of the off-axis rate of charge transport to the electric field direction. Furthermore, we have shown that controlling the size distribution remarkably impacts the charge carrier mobility and we suggested that tailored and potentially experimentally achievable re-arrangement of the CQD size ensemble can mediate the mobility drops even in highly dispersive cases, and presents an avenue towards improved charge transport. We then studied the degradation in CQD solar cells with respect to the polydispersity and how these enhanced charge transport from re-design of CQD solids can boost the photovoltaic performances. In addition, we estimated the potential in the binary CQD solids in terms of their improved charge transport and efficient light absorption. Combined with the accurate size-dependent optical absorption model for CQDs, our hopping model confirmed that the inclusion of smaller CQDs could enhance both the charge transport and the solar light absorption, leading to the enhanced average charge generation rates and solar cell performance.
Book Synopsis Quantum Dot Heterojunction Solar Cells by : Rachelle Ihly
Download or read book Quantum Dot Heterojunction Solar Cells written by Rachelle Ihly and published by . This book was released on 2014 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis explores the understanding of the chemistry and physics of colloidal quantum dots for practical solar energy photoconversion. Solar cell devices that make use of PbS quantum dots generally rely on constant and unchanged optical properties such that band gap energies remain tuned within the device. The design and development of unique experiments to ascertain mechanisms of optical band gap shifts occurring in PbS quantum dot thin-films exposed to air are discussed. The systematic study of the absorption properties of PbS quantum dot films exposed to air, heat, and UV illumination as a function of quantum dot size has been described. A method to improve the air-stability of films with atomic layer deposition of alumina is demonstrated. Encapsulation of quantum dot films using a protective layer of alumina results in quantum dot solids that maintain tuned absorption for 1000 hours. This thesis focuses on the use of atomic force microscopy and electrical variants thereof to study the physical and electrical characteristics of quantum dot arrays. These types of studies have broad implications in understanding charge transport mechanisms and solar cell device operation, with a particular emphasis on quantum dot transistors and solar cells. Imaging the channel potential of a PbSe quantum dot thin-film in a transistor showed a uniform distribution of charge coinciding with the transistor current voltage characteristics. In a second study, solar cell device operation of ZnO/PbS heterojunction solar cells was investigated by scanning active cross-sections with Kelvin probe microscopy as a function of applied bias, illumination and device architecture. This technique directly provides operating potential and electric field profiles to characterize drift and diffusion currents occurring in the device. SKPM established a field-free region occurring in the quantum dot layer, indicative of diffusion-limited transport. These results provide the path to optimization of future architectures that may employ drift-based transport in the quantum dot layer for enhanced charge extraction and power conversion efficiency.
Book Synopsis Colloidal Quantum Dot Optoelectronics and Photovoltaics by : Gerasimos Konstantatos
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.
Book Synopsis A Surface Chemistry Approach to Enhancing Colloidal Quantum Dot Solids for Photovoltaics by : Graham Hamilton Carey
Download or read book A Surface Chemistry Approach to Enhancing Colloidal Quantum Dot Solids for Photovoltaics written by Graham Hamilton Carey and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Colloidal Quantum Dot Optoelectronics and Photovoltaics by : Gerasimos Konstantatos
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 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Engineering of Doping and Transport for Enhanced Colloidal Quantum Dot Photovoltaics by : David Zhitomirsky
Download or read book Engineering of Doping and Transport for Enhanced Colloidal Quantum Dot Photovoltaics written by David Zhitomirsky and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Nanocrystal Quantum Dots by : Victor I. Klimov
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.
Book Synopsis Designing Quantum Dot Solids for Optoelectronic Devices Through Matrix Engineering by : Jason Tolentino
Download or read book Designing Quantum Dot Solids for Optoelectronic Devices Through Matrix Engineering written by Jason Tolentino and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Colloidal quantum dot (CQD) solids represent a class of materials that allows one to control the optical and electronic properties due to their unique size-dependent properties with special electronic and optoelectronic device applications. Unfortunately, integration of these materials into high performing devices such as transistors and solar cells have been challenging due to: 1) uncontrolled environmental stability 2) lack of accurate control over charge carrier type and mobility 3) poor device operational stability and 4) limited experimental methods to probe the density of states in these materials in order to understand fundamental electronic and optical properties. In this thesis, we demonstrate the ability to stabilize and improve the environmental stability of these materials with amorphous Al2O3 (a-alumina). More importantly, we can accurately engineer the carrier type and mobility by varying the thickness of the alumina. Through a combination of small, compact inorganic ligands and the ability to passivate surface electronic traps, air-stable, high electron mobility PbSe QD field-effect transistors (FET) are obtained. We then show that we can also improve transistor device operational stability through an in-vacuo ligand exchange with H2S gas introduced in an atomic layer deposition (ALD) chamber. We find that this method is universal when volatile ligands are used. Possible mechanisms for device instability will be discussed such as proton migration and trap passivation. Using an optimized film preparation, this work will be the first demonstration of a QD FET with an electron mobility greater than 10 cm2 V-1 s-1 that is also operationally stable. Finally, we introduce a unique transmission spectroscopy technique of field-effect transistors to electrostatically probe induced charge carriers in PbSe QD films. With this technique we resolve occupation of quantized states of the quantum dots rather than the matrix or interfacial states. This platform is used to test fundamental transport models as it relates to disordered semiconductors such as QDs. From this technique, we can draw important conclusions about charge transport at room temperature. This novel experimental method can be extended to other experimental setups such as photoluminescence and photoconductivity in order to understand how to rationally improve the electronic properties of QD films.
Book Synopsis Quantum Dot Solar Cells by : Jiang Wu
Download or read book Quantum Dot Solar Cells written by Jiang Wu and published by Springer Science & Business Media. This book was released on 2013-09-28 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: The third generation of solar cells includes those based on semiconductor quantum dots. This sophisticated technology applies nanotechnology and quantum mechanics theory to enhance the performance of ordinary solar cells. Although a practical application of quantum dot solar cells has yet to be achieved, a large number of theoretical calculations and experimental studies have confirmed the potential for meeting the requirement for ultra-high conversion efficiency. In this book, high-profile scientists have contributed tutorial chapters that outline the methods used in and the results of various quantum dot solar cell designs, including quantum dot intermediate band solar cells, hot electron quantum dot solar cells, quantum-dot sensitized solar cells, colloidal quantum dot solar cells, hybrid polymer-quantum dot solar cells, and MEG quantum dot solar cells. Both theoretical and experimental approaches are described. Quantum Dot Solar Cells helps to connect the fundamental laws of physics and the chemistry of materials with advances in device design and performance. The book can be recommended for a broad audience of chemists, electrical engineers, and materials scientists, and is suitable for use in courses on materials and device design for advanced and future optoelectronics.
Book Synopsis Colloidal Quantum Dots for Solar Energy Conversion by : Mengxia Liu
Download or read book Colloidal Quantum Dots for Solar Energy Conversion written by Mengxia Liu and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing global energy demand requires the development of clean energy sources that will help reduce the consumption of fossil fuels. Solar energy, the most abundant renewable source, is converted to electricity using photovoltaic devices. The photovoltaics market has witnessed rapid growth in the past decade, and today many photovoltaic strategies aim at low-cost, solution-processed manufacture. Colloidal quantum dots (CQDs), an emerging semiconductor material, have attracted attention in view of their spectral tunability. The bandgap of CQDs is readily tuned to harvest infrared solar energy. This could enable both full-spectrum devices and also tandem solar cells that can be integrated with wider-bandgap semiconductors. Unfortunately, a high density of surface-associated trap states, low carrier mobilities, and an inhomogeneous energy landscape have previously limited CQD photovoltaic performance. I introduce three strategies to address these problems. Through new materials processing approaches, I succeeded in increasing charge extraction, reducing bandtail states, and lowering the barrier to carrier hopping in CQD solids. The benefits from enhanced charge extraction were demonstrated in a double-sided junction architecture enabled by the engineering of an electron-accepting layer. This architecture resulted in an increase in the width of the carrier depletion region and a resultant decrease in recombination. I elucidated the effect of bandtail states on carrier transport and designed a solution-phase ligand-exchange method to create CQD inks that can be deposited as an active layer in a single step. The resulting CQD films exhibited a flattened energy landscape that increased the carrier diffusion length and contributed to solar cells having certified solar power conversion efficiencies of 11.3%. I then explored the translation of this strategy to small-bandgap infrared CQDs. Through management of surface ligands, I improved CQD passivation while reducing CQD fusion. I conclude with a new strategy for the design of a hybrid material system that combined CQDs with epitaxially-grown inorganic metal halide perovskites. The matrix-passivated CQD films showcased a two-fold increase in carrier mobility and superior thermal stability compared to pristine CQDs. This work provides promising pathways to achieve more fully the potential of CQD solids, and to showcase these advances in improved performance for CQD solar cells.
Book Synopsis Nanoscale Interfaces in Colloidal Quantum Dot Solar Cells by : Kyle Kemp
Download or read book Nanoscale Interfaces in Colloidal Quantum Dot Solar Cells written by Kyle Kemp and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quantum Dot Photodetectors by : Xin Tong
Download or read book Quantum Dot Photodetectors written by Xin Tong and published by Springer Nature. This book was released on 2021-09-17 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of state-of-the-art quantum dot photodetectors, including device fabrication technologies, optical engineering/manipulation strategies, and emerging photodetectors with building blocks of novel quantum dots (e.g. perovskite) as well as their hybrid structured (e.g. 0D/2D) materials. Semiconductor quantum dots have attracted much attention due to their unique quantum confinement effect, which allows for the facile tuning of optical properties that are promising for next-generation optoelectronic applications. Among these remarkable properties are large absorption coefficient, high photosensitivity, and tunable optical spectrum from ultraviolet/visible to infrared region, all of which are very attractive and favorable for photodetection applications. The book covers both fundamental and frontier research in order to stimulate readers' interests in developing novel ideas for semiconductor photodetectors at the center of future developments in materials science, nanofabrication technology and device commercialization. The book provides a knowledge sharing platform and can be used as a reference for researchers working in the fields of photonics, materials science, and nanodevices.
Book Synopsis Charge Carrier Dynamics in Lead Sulfide Quantum Dot Solids by : Rachel Hoffman Gilmore
Download or read book Charge Carrier Dynamics in Lead Sulfide Quantum Dot Solids written by Rachel Hoffman Gilmore and published by . This book was released on 2017 with total page 117 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Book Synopsis Charge Transport in Colloidal Quantum Dot Solids by : Jihye Kim
Download or read book Charge Transport in Colloidal Quantum Dot Solids written by Jihye Kim and published by . This book was released on 2013 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Handbook of Photovoltaic Science and Engineering by : Antonio Luque
Download or read book Handbook of Photovoltaic Science and Engineering written by Antonio Luque and published by John Wiley & Sons. This book was released on 2011-01-31 with total page 1172 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most comprehensive, authoritative and widely cited reference on photovoltaic solar energy Fully revised and updated, the Handbook of Photovoltaic Science and Engineering, Second Edition incorporates the substantial technological advances and research developments in photovoltaics since its previous release. All topics relating to the photovoltaic (PV) industry are discussed with contributions by distinguished international experts in the field. Significant new coverage includes: three completely new chapters and six chapters with new authors device structures, processing, and manufacturing options for the three major thin film PV technologies high performance approaches for multijunction, concentrator, and space applications new types of organic polymer and dye-sensitized solar cells economic analysis of various policy options to stimulate PV growth including effect of public and private investment Detailed treatment covers: scientific basis of the photovoltaic effect and solar cell operation the production of solar silicon and of silicon-based solar cells and modules how choice of semiconductor materials and their production influence costs and performance making measurements on solar cells and modules and how to relate results under standardised test conditions to real outdoor performance photovoltaic system installation and operation of components such as inverters and batteries. architectural applications of building-integrated PV Each chapter is structured to be partially accessible to beginners while providing detailed information of the physics and technology for experts. Encompassing a review of past work and the fundamentals in solar electric science, this is a leading reference and invaluable resource for all practitioners, consultants, researchers and students in the PV industry.
Book Synopsis Semiconductor Nanocrystals by : Alexander L. Efros
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.
Book Synopsis Electron Transport in Quantum Dots by : Jonathan P. Bird
Download or read book Electron Transport in Quantum Dots written by Jonathan P. Bird and published by Springer Science & Business Media. This book was released on 2013-11-27 with total page 481 pages. Available in PDF, EPUB and Kindle. Book excerpt: When I was contacted by Kluwer Academic Publishers in the Fall of 200 I, inviting me to edit a volume of papers on the issue of electron transport in quantum dots, I was excited by what I saw as an ideal opportunity to provide an overview of a field of research that has made significant contributions in recent years, both to our understanding of fundamental physics, and to the development of novel nanoelectronic technologies. The need for such a volume seemed to be made more pressing by the fact that few comprehensive reviews of this topic have appeared in the literature, in spite of the vast activity in this area over the course of the last decade or so. With this motivation, I set out to try to compile a volume that would fairly reflect the wide range of opinions that has emerged in the study of electron transport in quantum dots. Indeed, there has been no effort on my part to ensure any consistency between the different chapters, since I would prefer that this volume instead serve as a useful forum for the debate of critical issues in this still developing field. In this matter, I have been assisted greatly by the excellent series of articles provided by the different authors, who are widely recognized as some of the leaders in this vital area of research.
