Bandstructure Engineering of Indium Arsenide Quantum Dots in Gallium Arsenide Antimonide Barriers for Photovoltaic Applications PDF Download
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Author: Jonathan Boyle Publisher: ISBN: Category : Indium arsenide Languages : en Pages : 0
Book Description
Increasing the efficiency of solar cell technology is one of the current research aims being under taken in order to help supply growing global energy demands. The research presented in this thesis contributes to the current materials hunt for suitable candidates for an Intermediate Band Solar Cell (IBSC). A background on other "third generation" photovoltaic concepts along with details about the IBSC concept is also presented. The research presented in this thesis contains theoretical and experimental work on a quantum dot (QD) nanostructure. The structure contains a GaAs substrate, followed by a 10 nm GaAs 1-x Sb x barrier, a single layer of InAs QDs, followed by another 10 nm GaAs 1-x Sb x barrier and then capped by a thick GaAs layer. Theoretical calculations that accounted for strain were performed for a range of Sb compositions (x=0.04, 0.12, 0.14, 0.18, 0.22, 0.26, 0.30), for a QD of modeled size of 40 nm x 40 nm x 5 nm (WxLxH) at 4.4 K. Three samples containing the above structure were also studied by time integrated- and time resolved-photoluminescence. The samples had a 12% Sb concentration, but varied by their GaAs 1-x Sb x barrier thicknesses. Sample A had symmetric Sb barriers of 20 nm for the bottom and 20 nm for the top. Sample B had symmetric barriers of 10 nm for the bottom and 10 nm for the top, while sample C had asymmetric barriers of 30 nm for the bottom and 10 nm for the top. The samples were studied for temperature dependence for the range of 4.4 K to 300 K, and for excitation dependence from ~3 W/cm 2 -225 W/cm 2.
Author: Jonathan Boyle Publisher: ISBN: Category : Indium arsenide Languages : en Pages : 0
Book Description
Increasing the efficiency of solar cell technology is one of the current research aims being under taken in order to help supply growing global energy demands. The research presented in this thesis contributes to the current materials hunt for suitable candidates for an Intermediate Band Solar Cell (IBSC). A background on other "third generation" photovoltaic concepts along with details about the IBSC concept is also presented. The research presented in this thesis contains theoretical and experimental work on a quantum dot (QD) nanostructure. The structure contains a GaAs substrate, followed by a 10 nm GaAs 1-x Sb x barrier, a single layer of InAs QDs, followed by another 10 nm GaAs 1-x Sb x barrier and then capped by a thick GaAs layer. Theoretical calculations that accounted for strain were performed for a range of Sb compositions (x=0.04, 0.12, 0.14, 0.18, 0.22, 0.26, 0.30), for a QD of modeled size of 40 nm x 40 nm x 5 nm (WxLxH) at 4.4 K. Three samples containing the above structure were also studied by time integrated- and time resolved-photoluminescence. The samples had a 12% Sb concentration, but varied by their GaAs 1-x Sb x barrier thicknesses. Sample A had symmetric Sb barriers of 20 nm for the bottom and 20 nm for the top. Sample B had symmetric barriers of 10 nm for the bottom and 10 nm for the top, while sample C had asymmetric barriers of 30 nm for the bottom and 10 nm for the top. The samples were studied for temperature dependence for the range of 4.4 K to 300 K, and for excitation dependence from ~3 W/cm 2 -225 W/cm 2.
Author: Anup Pancholi Publisher: ProQuest ISBN: 9780549924562 Category : Gallium arsenide Languages : en Pages :
Book Description
The last few years have seen rapid advances in nanoscience and nanotechnology, allowing unprecedented manipulation of nanostructures controlling solar energy capture, conversion, and storage. Quantum confined nanostructures, such as quantum wells (QWs) and quantum dots (QDs) have been projected as potential candidates for the implementation of some high efficiency photovoltaic device concepts, including the intermediate band solar cell (IBSC). In this dissertation research, we investigated multiple inter-related themes, with the main objective of providing a deeper understanding of the physical and optical properties of QD structures relevant to the IBSC concept. These themes are: (i) Quantum engineering and control of energy levels in QDs, via a detailed study of the electronic coupling in multilayer QD structures; (ii) Controlled synthesis of well-organized, good quality, high volume density, and uniform-size QD arrays, in order to maximize the absorption efficiency and to ensure the coupling between the dots and the formation of the minibands; and (iii) Characterization of carrier dynamics and development of techniques to enhance the charge transport and efficient light harvesting. A major issue in a QD-based IBSC is the occurrence of charge trapping, followed by recombination in the dots, which results in fewer carriers being collected and hence low quantum efficiency. In order to collect most of the light-generated carriers, long radiative lifetimes, higher mobilities, and a lower probability of non-radiative recombination events in the solar cell would be desirable. QD size-dependent radiative lifetime and electronic coupling in multilayer QD structures were studied using photoluminescence (PL) and time-resolved photoluminescence (TRPL). For the uncoupled QD structures with thick barriers between the adjacent QD layers, the radiative lifetime was found to increase with the QD size, which was attributed to increased oscillator strength in smaller size dots. On the other hand, in the sample with thin barrier and electronically coupled QDs, the radiative lifetime increases and later decreases with the dot size. This is due to the enhancement of the oscillator strength in the larger size, coherently coupled QDs. In order to improve the quality of multi-layer QD structures, strain compensated barriers were introduced between the QD layers grown on off-oriented GaAs (311)B substrate. The QD shape anisotropy resulted from the growth on off-oriented substrate was studied using polarization-dependent PL measurements both on the surface and the edge of the samples. The transverse electric mode of the edge-emitted PL showed about 5° deviation from the sample surface for the dots grown on (311)B GaAs, which was attributed to the tilted vertical alignment and the shape asymmetry of dots resulted from the substrate orientation. Significant structural quality improvements were attained by introducing strain compensated barriers, i.e., reduction of misfit dislocations and uniform dot size formation. Longer lifetime (~1 ns) and enhanced PL intensity at room temperature were obtained, compared to those in conventional multilayer (In, Ga)As/GaAs QD structures. A significant increase in the open circuit voltage (V oc) was observed for the solar cell devices fabricated with the strain compensated structures. A major issue in a QD IBSC is the occurrence of charge trapping, followed by recombination in the dots, which results in fewer carriers being collected, and hence low quantum efficiency. We proposed and studied a novel structure, in which InAs QDs were sandwiched between GaAsSb (12% Sb) strain-reducing layers (SRLs) with various thicknesses. Both short (~1 ns) and long (~4-6 ns) radiative lifetimes were measured in the dots and were attributed to type-I and type-II transitions, respectively, which were induced by the band alignment modifications at the QD/barrier interface in the structures analyzed, due to the quantum confinement effect resulting from different GaAsSb barrier thicknesses. Based on our findings, a structure with type-II QD/barrier interface with relatively long radiative recombination lifetime may be a viable candidate in designing IBSC.
Author: R. K. Sharma Publisher: Springer ISBN: 3319976044 Category : Technology & Engineering Languages : en Pages : 1260
Book Description
This book disseminates the current knowledge of semiconductor physics and its applications across the scientific community. It is based on a biennial workshop that provides the participating research groups with a stimulating platform for interaction and collaboration with colleagues from the same scientific community. The book discusses the latest developments in the field of III-nitrides; materials & devices, compound semiconductors, VLSI technology, optoelectronics, sensors, photovoltaics, crystal growth, epitaxy and characterization, graphene and other 2D materials and organic semiconductors.
Author: Antonio Luque Publisher: John Wiley & Sons ISBN: 0470721693 Category : Technology & Engineering Languages : en Pages : 1172
Book Description
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.
Author: Jonathan Boyle
Author: Jonathan Boyle
Author: Anup Pancholi
Author: P. Bhattacharya
Author: Suryanarayanan Ganesan
Author: Abu Syed Mahajumi
Author: Syed Hassan Shah
Author: 
Author: B. E. Anspaugh
Author: R. K. Sharma
Author: Antonio Luque