Download or read book Development of III Sb Quantum Dot Systems for High Efficiency Intermediate Band Solar Cells written by and published by . This book was released on 2015 with total page 36 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project aimed to develop solar cells that can help reduce cost per watt. This work focused on developing solar cells that utilize quantum dot (QD) nanomaterials to provide multijunction solar cell efficiency at the cost of single junction solar cell. We focused on a novel concept known as intermediate band solar cells (IBSC) where an additional energy band is inserted in a single solar cell to accommodate sub-bandgap photons absorption which otherwise are lost through transmission. The additional energy band can be achieved by growing QDs within a solar cell p-n junction. Though numerous studies have been conducted to develop such QD systems, very small improvements in solar energy conversion efficiency have been reported. This is mainly due to non-optimal material parameters such as band gap, band offset etc. In this work, we identified and developed a novel QD material system that meets the requirements of IBSC more closely than the current state-of-the-art technology. To achieve these goals, we focused on three important areas of solar cell design: band structure calculations of new materials, efficient device design for high efficiency, and development of new semiconductor materials. In this project, we focused on III-Sb materials as they possess a wide range of energy bandgaps from 0.2 eV to 2eV. Despite the difficulty involved in realizing these materials, we were successfully developed these materials through a systematic approach. Materials studied in this work are AlAsSb (Aluminum Arsenide Antimonide), InAlAs (Indium Aluminum Arsenide) and InAs (Indium Arsenide). InAs was used to develop QD layers within AlAsSb and InAlAs p-n junctions. As the QDs have very small volume, up to 30 QD layers been inserted into the p-n junction to enhance light absorption. These QD multi-stack devices helped in understanding the challenges associated with the development of quantum dot solar cells. The results from this work show that the quantum dot solar cells indeed improve the efficiency via sub-bandgap photon absorption but much lower than the expected theoretical efficiencies. Yet, these devices serve as a proof of concept and the results provide vital information for future IBSC work. With further understanding of the operation of intermediate band solar cells and the identification of less expensive materials can substantially improve the solar cell efficiency and drastically cut the cell cost thereby reducing the dollar/watt cost.
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.
Download or read book Fabrication and Investigation of III V Quantum Structured Solar Cells with Fabry P rot Cavity and Nanophotonics in Order to Explore High efficiency Photovoltaic Concepts written by Benoît Behaghel and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past decade, photovoltaics (PV) has become a key player for the future of worldwide energy generation. Innovation in PV is likely to rely on high efficiency PV with flexible and lightweight thin films to enable PV deployement for mobile applications. In the framework of the Japanese-French laboratory “NextPV”, this thesis investigates the development of III-V quantum structured solar cells to explore high-efficiency photovoltaic concepts especially intermediate band solar cells (IBSC). Quantum structured IBSC have proven to be limited by thermal escape at room temperature and by low subbandgap light absorption. Following a consistent approach, we evaluate the topology, thermal escape mechanism, quantum structure and optical absorption of In(Ga)As quantum dots in a wide gap Al0.2GaAs host material. We also characterize quantitatively the device operation and improve the optical design. For a high irradiation, we evidence a hot carrier population in the quantum dots. At the same time, sequential two-photon absorption (S-TPA) is demonstrated both optically and electrically. We also show that S-TPA for both subbandgap transitions can be enhanced by a factor x5-10 with light management techniques, for example by implementation of Fabry-Perot cavities with the different epitaxial transfer methods that we developed. More advanced periodical nanostructures were also fabricated in the case of multi-quantum well solar cells using nanoimprint lithography techniques. Overall we discuss the possibility of realizing intermediate-band-assisted hotcarrier solar cells with light management to open the path for high-efficiency quantum structured IBSC.
Download or read book Quantum Dots for Intermediate Band in Solar Cells written by Shadi Dashmiz and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Self Assembled Quantum Dots written by Zhiming M Wang and published by Springer Science & Business Media. This book was released on 2007-11-29 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: This multidisciplinary book provides up-to-date coverage of carrier and spin dynamics and energy transfer and structural interaction among nanostructures. Coverage also includes current device applications such as quantum dot lasers and detectors, as well as future applications to quantum information processing. The book will serve as a reference for anyone working with or planning to work with quantum dots.
Download or read book Quantum Dot Intermediate Band Solar Cells written by Steven Evans Jenks and published by . This book was released on 2012 with total page 516 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advisor: Robert Gilmore.
Download or read book Developing High efficiency Compound Semiconductor III V Quantum Dot Solar Cells written by P.-M. Lam and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Developing High efficiency Compound Semiconductor III V Quantum Dot Solar Cells written by Phu-Minh Lam and published by . This book was released on 2016 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Role of Quantum Dot Size on the Performance of Intermediate Band Solar Cells written by Najla A. Alnami and published by . This book was released on 2014 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this thesis is to understand possible mechanisms for the reported decrease of the open circuit voltage and solar cell efficiency in quantum dot (QD) intermediate band solar cells (IBSCs). More specifically, the effect of indium arsenide (InAs) QD height on the open circuit voltage and solar cell efficiency was studied in a systematic way. To explore this effect in QD solar cells, several solar cells (SCs) were grown with varying InAs QD heights. All experimental characteristics of the QD solar cells were compared to a reference structure without QDs. All samples were grown by Molecular Beam Epitaxy (MBE), and self-assembled InAs QDs were formed using the Stranski-Krastanov (SK) growth method. Using a QD truncation technique, the height of the QDs was accurately varied between 2 nm and 5 nm, while maintaining both lateral size and areal density of the QDs. The intermediate band (IB) of each solar cell was constructed from 10 layers of InAs QDs of the same size and density. All samples were fabricated as solar cell devices using standard optical photolithography, for electrical characterization and solar cell efficiency studies. Optical and structural characterization was done for all samples. The following characterizations were performed: Transmission Electron Microscopy (TEM), Low Temperature Photoluminescence (PL), Power Dependent PL, External Quantum Efficiency (EQE), Temperature Dependent Solar Power Conversion Efficiency, and Current-Voltage measurements. The efficiency measurements demonstrate the critical role of QD size on the performance of QD IBSCs. The EQE measurement indicates a change in the position of the band edge, due to carrier confinement, consistent with a QD size variation as verified by TEM and PL. Measurements demonstrate that the EQE in the NIR range of the spectrum is enhanced in the QD IBSCs devices due to light absorption by the QDs. This work also demonstrates that open circuit voltage (Voc) decreases with an increase of the QD height, which leads to significant degradation of the solar cell conversion efficiency for QD sizes above 3 nm. In addition, for samples with QD heights of 4 nm and above, the EQE spectra in the GaAs region decreases, indicating a loss of photocurrent, most likely due to traps introduced by the large QDs. These experimental results suggest that the open circuit voltage in QD IBSCs degrades with the increase of QD height as a result of (i) a decrease of the effective band gap of the absorber media and (ii) enhanced Shockley-Read-Hall recombination in the presence of traps in the solar cell space charge region.
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.
Download or read book Growth and Characterization of Self assembled Quantum Dots for Intermediate Band Solar Cells written by Meng Sun and published by . This book was released on 2013 with total page 33 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, Molecular Beam Epitaxy technology is presented in detail and several powerful characterization techniques such as XRD, AFM, TEM, PL are also reviewed. SAQDs are discussed to be applied in IBSCs application due to the formation of intermediate band which helps to absorb sub-band gap photons. We investigate how the structural and optical properties of InAs self-assembled quantum dots buried in AlAs0.56Sb0.44 barriers can be controlled through the use of thin GaAs1xSbx cladding layers. Structural and optical properties of the SAQDs are studied, and the characteristics we demonstrate for this quantum dot system show great potential for application in intermediate band solar cells.
Download or read book Solar Technologies for the 21st Century written by Anco S. Blazev and published by CRC Press. This book was released on 2021-01-07 with total page 726 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book examines solar technologies, describes their properties, and evaluates the technological potential of each. It also reviews the logistics of deploying solar energy as a viable and sustainable way to solve urgent energy, environmental, and socio-economic problems. Topics discussed include solar power generation, today’s solar technologies, solar thermal, silicon PV, thin PV, 3-D solar cells, nano-PV, organic solar cells, solar successes and failures, solar power fields, finance and regulations, solar markets and solar energy and the environment.
Download or read book Quantum Dot Enhanced Epitaxial Lift off Solar Cells written by Mitchell F. Bennett and published by . This book was released on 2013 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Embedded nanostructures such as quantum dots (QDs) have been studied for many applications in solar cells including enhanced mini-band absorption in intermediate-band solar cells and current matching in multi junction cells. The major drawbacks of using such techniques to decrease intrinsic solar cell loss mechanisms are twofold: first, it is difficult to maintain partially populated states using QDs due to a quick thermal extraction of carriers; second, QDs have a weak absorption which necessitates a near-perfect control of QD growth mechanisms to carefully ensure a balance between dot size and density. One avenue for improving absorption into QDs is to utilize a thin cell with a back surface reflector in order to increase the effective optical path length (OPL) of light through the QD region, which has the potential to increase absorption into QD states. One method for the processing of thin solar cells that has been experimentally demonstrated on large 4-6" wafers is epitaxial lift-off, which takes advantage of an inverted growth and a wet chemical etch of a sacrificial release layer to remove the substrate. In this thesis, 0.25 cm2 InAs/GaAs QD cells were grown on 4" wafers, fabricated, and processed by epitaxial lift off, creating thin and flexible devices. Materials and optical characterization techniques such as atomic force microscopy and photoluminescence were used on test structures prior to and following ELO, and analysis indicated that QD optical coherence and material quality after ELO processing were preserved, although non-uniform. This was concluded to be caused by the radial thermal profile of the growth reactor, through which spatial dependence led to local variations in QD quality and size across the 4" wafer, indicative of the high temperature sensitivity of QDs. Transmission electron microscopy measurements were used to investigate defects and dislocations throughout the QD device structure that would impact performance, and showed a higher concentration of defects in regions of the wafer subject to a higher temperature during growth. A similar pattern of radial dependence was observed in solar cell devices by electrical characterization. Current-voltage measurements under one-sun AM0 illumination were taken on several cells around the wafer, showing a statistical variation in solar cell device metrics dependent on wafer position. Spectral responsivity measurements show an established cavity mode pattern in sub-host bandgap wavelengths, which is discussed as an enhancement due to the thinning of the device. Integrated external quantum efficiency shows a QD contribution to the short circuit current density of 0.23 mA/cm2. In addition to optical, materials, and electrical characterization, QD and baseline ELO devices were exposed to alpha radiation to gauge the effects of a harmful environment on cell performance. The QD device exhibited a remaining factor increase of 2 % (absolute) in conversion efficiency over the baseline device at an end of life alpha particle fluence of 5x109[alpha]/cm2/s. In addition, linear temperature coefficients for solar cell figures of merit were extracted as a function of increasing [alpha] fluence. At a fluence of 5x108[alpha]/cm2/s, the QD device showed an efficiency temperature coefficient 0.2 %/°C higher (absolute) than the baseline, indicating that the inclusion of QDs could improve the radiation and temperature tolerance of solar cell devices used for space applications."--Abstract.
Download or read book Intermediate Band Solar Cells Based on InAs Quantum Dots Embedded in InGaAs Quantum Well written by Ramesh Vasan and published by . This book was released on 2013 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intermediate band solar cells based on quantum dots and quantum wells with anti-reflection coating are investigated in this thesis. The demand for high efficient solar cells as an alternate source of energy is the main motivation for this research project. Intermediate band solar cells based on quantum dots were the subject of intensive research in recent years. High power conversion efficiency was predicted from InAs/GaAs intermediate band solar cells as the presence of InAs quantum dots increased the absorption below the band gap of the host material. In this thesis, an attempt has been made to further increase the absorption of GaAs solar cells by embedding InAs quantum dots in InxGa 1-xAs quantum wells. The quantum efficiency and spectral response measurements of quantum dots embedded in quantum well devices exhibit an extended response till 1280 nm in the near infrared region of the electromagnetic spectrum. The interband transition peaks associated with the InxGa 1-xAs quantum well exhibit a red shift as In mole fraction (x) in In xGa1-xAs quantum well is increased above 0%. The short circuit current density increased, while open circuit voltage decreased, as x is increased. In addition, the use of inexpensive anti-reflection coating (ARC) on these intermediate band solar cells has been studied. Anti-reflection coating based on Zinc oxide (ZnO) has significantly improved the power conversion efficiency of the solar cells. The ZnO synthesized using sol-gel technique was spin coated on the solar cells and subsequently annealed. The short circuit current density was significantly increased after the deposition of the ARC. Enhancement of the order of 42 % in the power conversion efficiency was obtained. Around 43% enhancement in quantum efficiency and 44% enhancement in spectral response measurements were also observed.
Download or read book Calculation of the Band Properties of a Quantum Dot Intermediate Band Solar Cell with Centrally Located Hydrogenic Impurities written by Michael Levy and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the quantum dot implementation of an intermediate band solar cell presented in this thesis, the offset of the intermediate band with respect to the conduction band is approximated by the ground state energy of a single electron in a single quantum dot heterojunction. The ground state energy is calculated with the radial Schrodinger equation with a Hamiltonian whose potential is composed from the step-like conduction band offset of the quantum dot heterojunction and the 1/r electrostatic potential of the hydrogenic impurity. The position of the intermediate band is tuned by adjusting the radius of the quantum dots. By assuming that the centrally located impurities are ionized, the location of the Fermi energy is guaranteed to be within the intermediate band. An intermediate band solar cell contains three bands: a conduction band, a valence band; and an intermediate band. The addition of an intermediate band augments the photogeneration of carriers. These additional carriers allow for an increased theoretical efficiency as compared to a conventional homojunction solar cell. The challenges in implementing an intermediate band solar cell involve centering the intermediate band at an energy level matched to the solar spectrum and aligning the Fermi energy within the intermediate band. The latter is necessary to ensure both a supply of electrons capable of photon induced transition to the conduction band as well as a large population of holes that allow photon induced electrons to transition from the valence band to the intermediate band. This thesis presents a novel material system, InPAs quantum dots enveloped in AlGaAs barriers grown on GaAs substrates, with which to implement an optimized QD-IBSC. This novel material system is selected based upon a refined set of design rules that include a requirement that the quantum dot/barrier pair offer a negligible valence band offset. With such a design rule the existence of hole levels is avoided, thus reducing bandgap narrowing at the valence band edge and the existence of minibands below the intermediate band.
Download or read book Basic Research of Self Organized Quantum Dots and Their Potential In Solar Cells and Novel Devices Applications Phase 4 written by and published by . This book was released on 2006 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the research output from our AOARD-supported work on basic investigation of self-assembled quantum dots and their potential applications during 2006. The research project is the fourth year of AOARD-support following the previous ones in 2003 2004 and 2005. During the past year, 6 international journal publications on self-assembled quantum dots and quantum dot molecules, heterostructure solar cells and quantum dot solar cells were published. There were technical papers on different growth techniques for different patterns of quantum dot molecules, e.g. bi-quantum dot molecules, long chain quantum dot molecules, quantum dot rings presented at 14th International Conference on Molecular Beam Epitaxy (MBE 2006), 32nd International Conference on Micro-and Nano- Engineering (MNE 2006), Electronic Material Conference (EMC 2006) and ECTI-CON 2006. Three papers on quantum dot molecule solar cells and their potential applications at high concentrated sunlight were also presented at major international solar cell conferences, i.e. 4th World Conference on Photovoltaic Energy Conversion (WCPEC-4), 21st European PVSEC and at MRS (Material Research Society) Fall Meeting 2006. All our journal and technical papers (17 in total) acknowledge financial supports from AOARD and Thailand Research Fund (TRF). Research work on quantum dot molecules based on InAs and InP materials will be investigated and their applications for high efficiency solar cells will be presented in the upcoming 2nd IEEE-NEMs (Nano/Micro Engineered and Molecular Systems) in 2007. Challenge of 30 % up efficiency quantum dot molecular solar cells will be our target of our research in 2007 and 2008.
