Download or read book Growth and Optical Characterization of Zinc Oxide Nanowires for Anti reflection Coatings for Solar Cells written by Martha Coakley and published by . This book was released on 2011 with total page 86 pages. Available in PDF, EPUB and Kindle. Book excerpt: The optical properties of solar cells greatly affect their efficiencies. Decreasing the broadband and directional reflectance of solar cells increases the solar irradiance transmitted and absorbed by the cell, thereby increasing the production of electron-hole pairs. Traditional optical enhancements such as light trapping and anti-reflection coatings reduce the reflectance of silicon at an optimized wavelength and angle of incidence. They do not perform as well at high angles of incidence or over the broadband solar spectrum. Theoretical studies suggest that layers with a suitable gradient-index of refraction can create both a broadband and directional anti-reflective coating. Through their variations in height and tapered growth, Zinc oxide (ZnO) nanowires can create a gradient index anti-reflection coating. ZnO is a wide-band gap semiconductor that is non-absorbing over most of the solar spectrum. With low cost, low temperature techniques, ZnO nanowires can be grown with a variety of morphologies. ZnO nanowires were grown by aqueous chemical growth and by electrodeposition on silicon to create a gradient-index anti-reflective coating for solar cell applications. The nanowire arrays were characterized using SEM images, goniometer scattering measurements, and integrating sphere total reflectance measurements. ZnO nanowires grown by aqueous chemical growth on silicon had average diameters between 60 nm and 100 nm and average lengths between 800 nm and 1100 nm. The nanowires had vertical alignment. They exhibited relatively small diffuse reflectivities and relatively large specular reflectivities. ZnO nanowires grown by electrodeposition had greater variances in length and diameter, with average diameters between 85 nm and 180 nm and average lengths between 500 nm and 1200 nm. Electrodeposited ZnO nanowires were randomly arrayed and exhibited relatively large diffuse reflectivities and relatively small specular reflectivities. Total reflectance measurements showed that all nanowire arrays reduced the broadband reflectance of silicon. Smaller nanowire arrays outperformed the larger crystal growths. A five-fold decrease in the broadband reflectance of silicon was obtained from both vertical and randomly oriented nanowire arrays. The reflectances were constant for angles of incident below 35°. Measurements at angles of incidence greater than 35° are required to determine whether ZnO nanowires can perform as directional anti-reflective coatings and whether the morphology of the nanowires affects the directional reflectances.
Download or read book Growth and Optical Electrical and Mechanical Characterization of Zinc Oxide Nanowires written by Martial Duchamp and published by . This book was released on 2010 with total page 178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis of Zinc Oxide by Sol Gel Method for Photoelectrochemical Cells written by Siti Salwa Alias and published by Springer Science & Business Media. This book was released on 2013-11-20 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the study of synthesized ZnO powder using Zn(CH3COO)2∙2H2O precursor, methanol (as solvent), and sodium hydroxide (NaOH) to vary the pH. The successfully synthesized ZnO powder from the sol-gel centrifugation and sol-gel storage methods were characterized and investigated by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, UV–visible spectroscopy, and photoluminescence test to compare the properties of the nanoparticles. The best characteristic of the ZnO powder from both methods was observed when the powders were coated on an ITO glass to fabricate a PEC. The current density–voltage performances of both PECs were investigated under luminescent and dark conditions.
Download or read book Zinc Oxide Nanostructures Synthesis and Characterization written by Sotirios Baskoutas and published by MDPI. This book was released on 2018-12-04 with total page 303 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Zinc Oxide Nanostructures: Synthesis and Characterization" that was published in Materials
Download or read book Optical Characterization of ZnO Nanowires as a Function of the Growth Conditions written by Sergio Roso Casares and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: [ANGLÈS] In the present work we have grown ZnO nanowires over different substrates by the vapour-liquid-solid growth method, changing several growth parameters, such as the Au sputtered thin layer, temperature, pressure and gas flow. We have characterized their optical properties measuring the optical absorption and photoluminescence spectra at room temperature. The near-band edge and defect-related emission bands have been discussed as a function of the growth conditions.
Download or read book Optical Characterization of Doped Zinc Oxide Nanowires written by Faezeh Mohammadbeigi and published by . This book was released on 2017 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO is a promising semiconductor material with a direct band gap energy of 3.3 eV which makes it a good candidate for UV and visible range light emitting devices. Metalorganic chemical vapour epitaxy (MOVPE) provides the possibility of industrial scale growth of ZnO, with very fine control of impurity dopants. Despite the vast recent literature on ZnO, there are very few studies of systematic intentional doping. ZnO nanowires (NWs) can be grown easily on various substrates with high crystalline quality and low defect densities and tend to exhibit reduced substrate induced strain. This enables us to perform careful spectroscopic analysis of impurity related optical transitions and identify the physical nature of various dopant species. A detailed study of low temperature photoluminescence (PL) transitions in doped ZnO NWs, thin films, and bulk crystals grown by MOVPE and chemical vapour transport (CVT) methods is presented. The standard group III donors were first investigated. Donor bound exciton (D0X) transitions previously assigned to Ga, Al, and In were confirmed in intentionally doped samples. Group IV dopants such as carbon, and tin are interesting since they can act in principle as double donors or double acceptors. We report four new shallow D0X transitions (Z-lines), at 3360.8 (Z1), 3361.2 (Z2), 3361.7 (Z3) and 3361.9 (Z4) meV, which can be greatly enhanced by co-doping with carbon tetrachloride and hydrogen. These shallow donors appear to be due to carbon impurities complexed with other unknown defects in four distinct configurations. Carbon-doped samples also exhibit two distinct acceptors with binding energies of 133 ± 5 and 181 ± 5 meV. Doping concentration and temperature dependent PL studies of unintentionally doped and Sn-doped ZnO single crystals confirmed emission from the I10 D0X transition which was recently proven to contain Sn on a Zn site. Sb-doped ZnO NWs were grown in an attempt to produce p-type material as reported by some groups. Our PL studies including Magneto PL, have shown that rather than p-doped material, the addition of small amounts of Sb-dopant resulted in a new PL transition at 3364.3 meV, which turns out to be the shallowest D0X transition so far observed in ZnO.
Download or read book Low Dimensional ZnO Nanostructures written by Hsin-Ming Cheng and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc oxide nanostructure has a wide bandgap energy of 3.37 eV and a large exciton binding energy of 60 meV at room temperature. It is certainly a promising material for photonic devices in the ultraviolet to blue wavelength range. ZnO-related materials are also expected to construct the exciton as well as polariton lasers owing to their excitonic-stimulated emission and laser behavior under optically pumping can be obtained at ambient temperature. Because of the optical losses, including not only nonradiative recombination centers but also traps of excitons, the high quality of ZnO becomes even more imperative in the excitonic lasing processes. In the present chapter, ZnO nanowire structures via a low-pressure vapor-phase deposition and a simple solvothermal method will be presented. The one-dimensional ZnO nanowires could afford a direct conduction pathway to significantly enhance the overall efficiency of the dye-sensitized solar cells. Furthermore, this content will demonstrate how to employ the hierarchical structure of the ZnO nanoparticles, fabricated from sol-gel method, which could promote light scattering, thus, enhancing photon absorption and the overall solar conversion efficiency. The aim of this chapter is to present the correlation between the fundamental properties of ZnO nanostructures and their photovoltaics performances.
Download or read book Zinc Oxide Bulk Thin Films and Nanostructures written by Chennupati Jagadish and published by Elsevier. This book was released on 2011-10-10 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: With an in-depth exploration of the following topics, this book covers the broad uses of zinc oxide within the fields of materials science and engineering:- Recent advances in bulk , thin film and nanowire growth of ZnO (including MBE, MOCVD and PLD), - The characterization of the resulting material (including the related ternary systems ZgMgO and ZnCdO), - Improvements in device processing modules (including ion implantation for doping and isolation ,Ohmic and Schottky contacts , wet and dry etching), - The role of impurities and defects on materials properties - Applications of ZnO in UV light emitters/detectors, gas, biological and chemical-sensing, transparent electronics, spintronics and thin film
Download or read book Growth and Characterization of Zinc Oxide ZnO Nanostructures for Photovotaic Applications written by Basma El Zein and published by . This book was released on 2012 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt: We identified that the growth parameters are vital to control the crystallinity, morphology and the defect levels in the synthesized ZnO nanowires. SEM, XRD, TEM, HRTEM analysis show that the nanostructures are highly crystalline and are vertically oriented. We also report the in-situ growth of PbS nanoparticles without linker on the surface of well -oriented ZnO NWs by (SILAR) technique. The PbS Nanoparticles are packed tightly on the surface of the ZnO Nanowires with different sizes and densities, without insulating nature organic ligands, which might affect both the electronic structure at the interface and the electron - transfer rate. The SEM, TEM, HRTEM, PL and XRD analysis, confirm the attachment of the spherical shape polycrystalline PbS nanoparticles. We propose at the end of the thesis the p-PbS /n-ZnO hetero-junction with its future applications in solar cells.
Download or read book Nanoengineering of ZnO Electrical and Optical Characteristics by Controlling Its Morphology and Defects Via Reaction Kinetics Fluid Dynamics and Stoichiometry in Low pressure CVD Synthesis written by Taehoon Lim and published by . This book was released on 2016 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: LPCVD synthesis and characterization of ZnO with diverse morphology for semiconducting applications are studied and discussed in this dissertation. Because nanoscale ZnO shows variant characteristics depending on its physical dimensions, morphology, and impurity concentration, the focus of this work is to control the structure and composition of ZnO by adjusting synthesis parameters and methods. In Chapter 2, the synthesis of ZnO with optimized concentration of oxygen vacancies and physical dimensions are discussed. Opaqueness of ZnO is derived from scattering due to its physical dimensions, but visible transparency for the photocatalytic application of ZnO for solar cell devices is required. By controlling the concentration of oxygen vacancies and physical dimensions, fluorescent and transparent ZnO is successfully synthesized. In Chapter 3, a method to stabilize precursor supply and to lower the reaction temperature is discussed. In CVD synthesis, the stable and continuous growth of ZnO is inhibited by the premature oxidation of Zn, and the formation of a zinc oxide layer that blocks the evaporation of Zn precursor. By controlling the fluid dynamics of precursor vapors, a low temperature synthesis method with higher product uniformity is developed. Using this method, a stable synthesis technique for producing high quality ZnO under low temperature is successfully achieved. In Chapter 4, the synthesis of ZnO under relatively low temperature is discussed. During LPCVD synthesis it is observed that as the distance from the source increases, the partial vapor pressure of Zn near the surface of the deposition substrate is drastically decreased (along the axis of gas flow), forming a dimensional gradient on a single substrate. The changing reactant ratio near the surface drives the non-uniformity of product in terms of morphology, physical dimensions, and impurity concentration. In Chapter 5, a novel template-free self-catalyzed synthesis technique for achieving ultra-thin ZnO nanowires is discussed. From the tip of synthesized hexagonal cone ZnO, ultra-thin ZnO nanowires are grown by self-catalysis.
Download or read book One dimensional Zinc Oxide Nanomaterials written by Benjamin A. Weintraub and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As humanly engineered materials systems approach the atomic scale, top-down manufacturing approaches breakdown and following nature's example, bottom-up or self-assembly methods have the potential to emerge as the dominant paradigm. Synthesis of one-dimensional nanomaterials takes advantage of such self-assembly manufacturing techniques, but until now most efforts have relied on high temperature vapor phase schemes which are limited in scalability and compatibility with organic materials. The solution-phase approach is an attractive low temperature alternative to overcome these shortcomings. To this end, this thesis is a study of the rationale solution-phase synthesis of ZnO nanowires and applications in photovoltaics. The following thesis goals have been achieved: rationale synthesis of a single ZnO nanowire on a polymer substrate without seeding, design of a wafer-scale technique to control ZnO nanowire array density using layer-by-layer polymers, determination of optimal nanowire field emitter density to maximize the field enhancement factor, design of bridged nanowires across metal electrodes to order to circumvent post-synthesis manipulation steps, electrical characterization of bridged nanowires, rationale solution-phase synthesis of long ZnO nanowires on optical fibers, fabrication of ZnO nanowire dye-sensitized solar cells on optical fibers, electrical and optical characterization of solar cell devices, comparison studies of 2-D versus 3-D nanowire dye-sensitized solar cell devices, and achievement of 6-fold solar cell power conversion efficiency enhancement using a 3-D approach. The thesis results have implications in nanomanufacturing scale-up and next generation photovoltaics.
Download or read book Zinc Oxide and Related Materials Volume 957 written by Jürgen H. Christen and published by . This book was released on 2007-04-05 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: The MRS Symposium Proceeding series is an internationally recognised reference suitable for researchers and practitioners. The topics covered in this volume, first published in 2007, include devices, defects, spintronics and magnetism, growth, optical properties and nanostructures, and doping and processing TFTs.
Download or read book Nanowires written by Luke J. Wilson and published by Nova Science Publishers. This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc Oxide (ZnO) is a metal oxide semiconductor of group II-IV whose nature resides at the borderline between covalent and ionic semiconductors. In the last decade it has raised several attention in the research field since it possesses promising catalytic, electrical, electronic and optical properties. It can be easily prepared in different shapes and sizes at both the micrometric and nanometric scale, including the forms of micro- and nanowires, nanobelts, nanotubes, micro- and nanoparticles, multipods, tetrapods, and flower-like microstructures. This different variety of morphologies has thus attracted considerable attention for potential application in solar cells, nanogenerators, field effect transistors, gas sensors and other electronic micro- and nanodevices. This book discusses the synthesis and the electrical properties of ZnO nanowires. It also discusses rough silver nanowires, nanobuds and nanoparticle substrates; the synthesis and properties of Ni nanowires in porous silicon templates; and phonon scattering and elastic energy propagation in nanowires.
Download or read book Nanocrystalline Zinc Oxide Thin Films for Solar Cell written by Akbar I. Inamdar and published by LAP Lambert Academic Publishing. This book was released on 2010-12 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc oxide has attracted considerable attention due to its good optical, electrical, and piezoelectric properties and its potential applications in diverse areas. The novel functions of ZnO nanostructures arrays have been revealed successfully in the solar cells, gas sensors, piezoelectric, photodetectcors, LED, field emitters and so on. Films with well-aligned ZnO nanorods or nanowires may exhibit much larger surface areas than ZnO films prepared from randomly oriented nanoparticles. A plethora of physical and chemical methods have been used for the synthesis of ZnO nanostructures including physical and chemical techniques. Electrodeposition is of particular interest due to low cost, environmental friendly, and feasibility of room temperature growth. The central idea of this work is to test the applicability of simple and inexpensive electrodeposition technique as an update on previously studied methods for the synthesis of nanocrystalline ZnO thin films for solar cell. In this direction the attempts were made to fabricate zinc oxide nanocrystalline thin films by varying various process parameters and by using novel approaches, as well.
Download or read book Electrochemical Growth and Characterization of ZnO Nanowires written by Lilei Hu and published by . This book was released on 2014 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO semiconductor materials, especially nanostructured materials, have potential applications in large-area electronics, photonics and optoelectronics due to their unique electrical and optical properties. ZnO nanowires have advantages of high surface area to volume ratio, with the prospective for nanoscale control of doping the electrical properties for 1-D nanoelectronic devices. Many techniques have been tried to achieve high quality ZnO nanowires in large scale with low cost and simple fabrication. However, most of these techniques require high temperatures that exclude applications in flexible electronics. P-type conductivity is another impediment for fully realizing ZnO materials for electronic device application; and this limitation has prevented advances in optoelectronic and integrated circuit applications for ZnO. To overcome the problems, this study investigated the synthesis and doping of ZnO nanowires at low temperature through a rapid electrochemical deposition growth technique. Material properties were studied using scanning electron microscopy (SEM), photoluminescence spectroscopy (PL), Raman spectroscopy, X-ray diffraction (XRD), ultraviolet to visible (UV-Vis) transmission spectroscopy, and electrical current-voltage measurements. ZnO nanowire doping was investigated using Al for n-type doping and for p-type doping, Ag/Al (co-doping) and Li. Al and Ag have significant influences on ZnO nanowire structures, while Li was found to improve the nanowire structure quality. The mechanisms for electrochemical deposition were studied through characterization of the chemical reactions, interface science and semiconductor/solution interface. It was found that the low temperature grown nanowires had high oxygen vacancy condition induced donor defect states, while, incorporation of Li dopants contributed to trap states (deep acceptor states), rather than shallow acceptor states in the band gap. Shown by XRD and PL, oxygen assisted post-growth annealing was found to promote recrystallization of ZnO and elimination of oxygen vacancies for better crystal quality and photoluminescence emission. Cr, Al or Au metals were used as contacts to Li-doped ZnO nanowires to examine electrical properties of the doped nanowires, turning out high ideal factor were obtained because of the poor contact quality due to significant surface and interface states in ZnO nanowires. At last, mechanisms of surface states related tunneling current at the metal-semiconductor interface were discussed.
Download or read book Zinc Oxide Nanowire Array based Optoelectronic Devices written by Guoping Wang and published by . This book was released on 2011 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt: ZnO nanowire array-based optoelectronic devices are discussed in this dissertation. ZnO has a wide band gap of 3.37 eV and a large exciton binding energy of 60 meV at room temperature, which make it a promising candidate for optoelectronic devices such as blue-light emitting diodes, ultraviolet laser diodes and photodiodes. Recently, there have been tremendous interests in ZnO nanowire arrays. It is well known that one of the biggest challenges toward good ZnO-based optoelectronic devices is the difficulty of reliably fabricating p-type ZnO due to the self-compensating effect from native defects (for example, oxygen vacancy V o and zinc interstitial Zni) and/or H incorporation. There has already been a great deal of efforts on the fabrication of p-type ZnO films by doping group I (Na, Ag) and group V elements (N, P, As, Sb) as p-type dopants. In contrast, there have been only a few reports on p-type ZnO nanowires (doped with N, P and Na). Recently, researchers are interested in developing optoelectronic devices based on ZnO nanowires such as biosensors, ultraviolet detectors, ultraviolet light emitting diodes and electrically driven nanowire lasers. The growth of p-type ZnO nanowires with good stability will be an essential step for the applications of nanowires in nanoelectronics and optoelectronics. In this dissertation, first, n-type ZnO nanowire array and its application have been discussed. ZnO has very high electronic carrier mobility and electron affinity, making it a very possible candidate as an effective dye-sensitized solar cell (DSSC) semiconductor. The great properties of vertically aligned ZnO-nanowire array, such as large surface area and fast electron-transport rate, make it a very promising option for the photoanode of DSSCs. Nanowires provide electrons injected from optically excited dye a direct effective path to collecting electrode via the semiconductor conduction band, offering the potential for much faster charge transport than nanoparticle cells. In order to make homojunctional devices based on ZnO nanowire, a great deal of efforts has been made on the growth of p-type ZnO nanowire. Ag, a group Ib element, was predicted to be an acceptor in ZnO when incorporated into substitutional Zn sites and researchers experimentally demonstrated reliable fabrication of p-type ZnO thin films doped with Ag on sapphire substrate and also demonstrated the possibility of achieving Ag-doped p-type ZnO nanowires. Also Sb as an effective dopant for reproducible p-type ZnO thin films has been shown in our group. In chapter 3 of this dissertation, the synthesis and characterization of single-crystalline Ag-doped p-type ZnO nanowires and also Sb-doped p-type ZnO nanowire arrays have been discussed. In chapter 4 of this dissertation, ZnO homojunction photodiodes based on Sb-doped p-type nanowire array have been discussed. In chapter 5 of this dissertation, LED devices based on Sb-doped p-type nanowire array have been discussed. In chapter 6 of this dissertation, electrically pumped ZnO nanowirewaveguided lasing based on Sb-doped p-type nanowire array has been discussed. In chapter 7, the gain calculation for ZnO has been made and a brief discussion about the comparison between the calculation results and the experimental results has also been made. In chapter 8, Lists of conclusions are made for this dissertation.
Download or read book Transparent Conductive Zinc Oxide written by Klaus Ellmer and published by Springer. This book was released on 2010-11-30 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zinc oxide (ZnO) belongs to the class of transparent conducting oxides that can be used as transparent electrodes in electronic devices or heated windows. In this book the material properties of, the deposition technologies for, and applications of zinc oxide in thin film solar cells are described in a comprehensive manner. Structural, morphological, optical and electronic properties of ZnO are treated in this review.
