Download or read book Optimization Design and Performance Analysis of Light Trapping Structures in Thin Film Solar Cells written by Shima Hajimirza and published by . This book was released on 2013 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar cells are at the frontier of renewable energy technologies. Photovoltaic energy is clean, reusable, can be used anywhere in our solar system and can be very well integrated with power distribution grids and advanced technological systems. Thin film solar cells are a class of solar cells that offer low material cost, efficient fabrication process and compatibility with advanced electronics. However, as of now, the conversion efficiency of thin film solar cells is inferior to that of thick crystalline cells. Research efforts to improve the performance bottlenecks of thin film solar cells are highly motivated. A class of techniques towards this goal is called light trapping methods, which aims at improving the spectral absorptivity of a thin film cell by using surface texturing. The precise mathematical and physical characterization of these techniques is very challenging. This dissertation proposes a numerical and computational framework to optimize, design, and fabricate efficient light trapping structures in thin film solar cells, as well as methods to verify the fabricated designs. The numerical framework is based on the important "inverse optimization" technique, which is very is widely applicable to engineering design problems. An overview of the state-of-the-art thin film technology and light trapping techniques is presented in this thesis. The inverse problem is described in details with numerous examples in engineering applications, and is then applied to light trapping optimization. The proposed designs are studied for sensitivity analysis and fabrication error, as other aspects of the proposed computational framework. At the end, reports of fabrication, measurement and verification of some of the proposed designs are presented.

Download or read book Introduction to Light Trapping in Solar Cell and Photo detector Devices written by Stephen J. Fonash and published by Elsevier. This book was released on 2014-09-15 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: New Approaches to Light Trapping in Solar Cell Devices discusses in detail the use of photonic and plasmonic effects for light trapping in solar cells. It compares and contrasts texturing, the current method of light-trapping design in solar cells, with emerging approaches employing photonic and plasmonic phenomena. These new light trapping methods reduce the amount of absorber required in a solar cell, promising significant cost reduction and efficiency. This book highlights potential advantages of photonics and plasmonics and describes design optimization using computer modeling of these approaches. Its discussion of ultimate efficiency possibilities in solar cells is grounded in a review of the Shockley-Queisser analysis; this includes an in-depth examination of recent analyses building on that seminal work.

Download or read book Thin film Silicon Solar Cells written by Xing Sheng (Ph. D.) and published by . This book was released on 2012 with total page 159 pages. Available in PDF, EPUB and Kindle. Book excerpt: The photovoltaic technology has been attracting widespread attention because of its effective energy harvest by directly converting solar energy into electricity. Thin-film silicon solar cells are believed to be a promising candidate for further scaled-up production and cost reduction while maintaining the advantages of bulk silicon. The efficiency of thin-film Si solar cells critically depends on optical absorption in the silicon layer since silicon has low absorption coefficient in the red and near-infrared (IR) wavelength ranges due to its indirect bandgap nature. This thesis aims at understanding, designing, and fabricating novel photonic structures for efficiency enhancement in thin-film Si solar cells. We have explored a previously reported a photonic crystal (PC) based structure to improve light absorption in thin-film Si solar cells. The PC structure combines a dielectric grating layer and a distributed Bragg reflector (DBR) for effcient light scattering and reflection, increasing light path length in the thin-film cell. We have understood the operation principles for this design by using photonic band theories and electromagnetic wave simulations. we discover that this DBR with gratings exhibit unusual light trapping in a way different from metal reflectors and photonic crystals. The light trapping effects for the DBR with and without reflector are numerically investigated. The self-assembled anodic aluminum oxide (AAO) technique is introduced to non- lithographically fabricate the grating structure. We adjust the AAO structural parameters by using different anodization voltages, times and electrolytes. Two-step anodization is employed to obtain nearly hexagonal AAO pattern. The interpore periods of the fabricated AAO are calculated by fast Fourier transform (FFT) analysis. We have also demonstrated the fabrication of ordered patterns made of other materials like amorphous Si (a-Si) and silver by using the AAO membrane as a deposition mask. Numerical simulations predict that the fabricated AAO pattern exhibits light trapping performance comparable to the perfectly periodic grating layer. We have implemented the light trapping concepts combining the self-assembled AAO layer and the DBR in the backside of crystalline Si wafers. Photoconductivity measurements suggest that the light absorption is improved in the near-IR spectral range near the band edge of Si. Furthermore, different types of thin-film Si solar cells, including a-Si, mi- crocrystalline Si ([mu]-Si) and micromorph Si solar cells, are investigated. For demonstration, the designed structure is integrated into a 1:5 [mu]m thick [mu]c-Si solar cell. We use numerical simulations to obtain the optimal structure parameters for the grating and the DBR, and then we fabricate the optimized structures using the AAO membrane as a template. The prototype devices integrating our proposed backside structure yield a 21% improvement in efficiency. This is further verified by quantum efficiency measurements, which clearly indicate stronger light absorption in the red and near-IR spectral ranges. Lastly, we have explored the fundamental light trapping limits for thin-film Si solar cells in the wave optics regime. We develop a deterministic method to optimize periodic textures for light trapping. Deep and high-index-contrast textures exhibit strong anisotropic scattering that is outside the regime of validity of the Lambertian models commonly used to describe texture-induced absorption enhancement for normal incidence. In the weak ab- sorption regime, our optimized surface texture in two dimensions (2D) enhances absorption by a factor of 2.7[pi]n, considerably larger than the classical [pi]n Lambertian result and exceeding by almost 50% a recent generalization of Lambertian model for periodic structures in finite spectral range. Since the [pi]n Lambertian limit still applies for isotropic incident light, our optimization methodology can be thought of optimizing the angle/enhancement tradeoff for periodic textures. Based on a modified Shockley-Queisser theory, we conclude that it is possible to achieve more than 20% efficiency in a 1:5 [mu]m thick crystalline Si cell if advanced light trapping schemes can be realized.

Download or read book Plasmonic and Photonic Designs for Light Trapping in Thin Film Solar Cells written by Liming Ji and published by . This book was released on 2012 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin film solar cells are promising to realize cheap solar energy. Compared to conventional wafer cells, they can reduce the use of semiconductor material by 90%. The efficiency of thin film solar cells, however, is limited due to insufficient light absorption. Sufficient light absorption at the bandgap of semiconductor requires a light path more than 10x the thickness of the semiconductor. Advanced designs for light trapping are necessary for solar cells to absorb sufficient light within a limited volume of semiconductor. The goal is to convert the incident light into a trapped mode in the semiconductor layer. In this dissertation, a critical review of currently used methods for light trapping in solar cells is presented. The disadvantage of each design is pointed out including insufficient enhancement, undesired optical loss and undesired loss in carrier transport. The focus of the dissertation is light trapping by plasmonic and photonic structures in thin film Si solar cells. The performance of light trapping by plasmonic structures is dependent on the efficiency of photon radiation from plasmonic structures. The theory of antenna radiation is used to study the radiation by plasmonic structures. In order to achieve efficient photon radiation at a plasmonic resonance, a proper distribution of surface charges is necessary. The planar fishnet structure is proposed as a substitution for plasmonic particles. Large particles are required in order to resonate at the bandgap of semiconductor material. Hence, the resulting overall thickness of solar cells with large particles is large. Instead, the resonance of fishnet structure can be tuned without affecting the overall cell thickness. Numerical simulation shows that the enhancement of light absorption in the active layer is over 10x compared to the same cell without fishnet. Photons radiated from the resonating fishnet structure travel in multiple directions within the semiconductor layer. There is enhanced field localization due to interference. The short circuit current was enhanced by 13.29%. Photonic structures such as nanodomes and gratings are studied. Compared to existing designs, photonic structures studied in this dissertation exhibited further improvements in light absorption and carrier transport. The nanodome geometry was combined with conductive charge collectors in order to perform simultaneous enhancement in optics and carrier transport. Despite the increased volume of semiconductor material, the collection length for carriers is less than the diffusion length for minority carriers. The nanodome geometry can be used in the back end and the front end of solar cells. A blazed grating structure made of transparent conductive oxide serves as the back passivation layer while enhancing light absorption. The surface area of the absorber is increased by only 15%, indicating a limited increase in surface recombination. The resulting short circuit current is enhanced by over 20%. The designs presented in the dissertation have demonstrated enhancement in Si thin film solar cells. The enhancement is achieved without hurting carrier transport in solar cells. As a result, the enhancement in light absorption can efficiently convert to the enhancement in cell efficiency. The fabrication of the proposed designs in this dissertation involves expensive process such as electron beam lithography. Future work is focused on optical designs that are feasible for cheap fabrication process. The designs studied in this dissertation can serve as prototype designs for future work.

Download or read book High Efficiency III V Thin Film Solar Cells written by Xiaohan Li (Ph. D.) and published by . This book was released on 2015 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photon management via submicron and subwavelength nanostructures has been extensively studied over the last decade, and has become one of the most important approaches of boosting the energy conversion efficiency for thin-film photovoltaic devices. The incorporation of low dimensional nanostructures, such as GaAs/InGaAs quantum wells, into typical GaAs single-junction cells will extend the cell absorption further into the sub-GaAs bandgap region but usually results in reduced cell open-circuit voltage. As a consequence, various bandgap engineering techniques for improving the energy conversion efficiency for quantum well solar cells have been reported. This dissertation will describe studies of light trapping in multiple GaAs/InGaAs quantum well solar cells via nanostructured front side dielectric coating and back side metal/dielectric contacts, photovoltaic performance enhancement for bulk and flexible thin-film GaAs solar cells through subwavelength nanostructured antireflection coating, and bandgap engineering techniques for GaAs/InGaAs multiple quantum well solar cells. In the study of nanostructured dielectric antireflection coatings, a 5.8% increase in short-circuit current density is observed for the GaAs/In0.3Ga0.7As multiple quantum well cell coated with TiO2 nanostructured coating compared to the cell coated with conventional Si3N4 single-layer antireflection coating even in the presence of high surface recombination. Numerical simulation shows that as high as 13% increase in short-circuit current density can be achieved without surface recombination. In the study of GaAs/In0.3Ga0.7As multiple quantum well solar cells integrated with nanostructured back side metal/dielectric contacts, as high as 2.9% per quantum well external quantum efficiency is achieved, significantly surpassing the 1% per quantum well external quantum efficiency typically observed in quantum well solar cells. In both studies, two major mechanisms contributing to the increased longer wavelength quantum well absorption have been elucidated: Fabry-Perot resonances and scattering into guided optical modes. In application of subwavelength-scale optical nanostructures on bulk and flexible epitaxial lift-off GaAs solar cells for broadband, omnidirectional improvement of photovoltaic performance, 1.1× increase in short-circuit current density is observed for the bulk GaAs cell fully integrated with optical nanostructures compared to the unpatterned cell (1.09× increase in short-circuit current density for flexible epitaxial lift-off GaAs cell) at normal incidence, while 1.67× increase in short-circuit current density is observed (1.52× increase in short-circuit current density is observed for flexible epitaxial lift-off GaAs cell) at 80° angle of incidence. In the study of bandgap engineering strategies for improving the photovoltaic performance for GaAs/InGaAs multiple quantum well solar cells, a quantum well solar cell with graded quantum well depths, which has an average 18% indium concentration in quantum wells, is shown to yield improvements in both open-circuit voltage and short-circuit current density compared to a GaAs/In0.18Ga0.82As quantum well solar cell with constant quantum well depths across the intrinsic region. The results of this study suggest that such an approach can also be implemented in quantum well solar cells with more complex quantum well structures, such as ternary or quaternary quantum wells, where the conduction and valence band offsets of each quantum well can be simultaneously engineered.

Download or read book Light Trapping in Thin Film Crystalline Silicon Solar Cells written by Javaneh Boroumand Azad and published by . This book was released on 2017 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents numerical and experimental studies of a unified light trapping approach that is extremely important for all practical solar cells. A 2D hexagonal Bravais lattice diffractive pattern is studied in conjunction with the verification of the reflection mechanisms of single and double layer anti-reflective coatings in the broad range of wavelength 400 nm - 1100 nm. By varying thickness and conformity, we obtained the optimal parameters which minimize the broadband reflection from the nanostructured crystalline silicon surface over a wide range of angle 0°-65°. While the analytical design of broadband, angle independent anti-reflection coatings on nanostructured surfaces remains a scientific challenge, numerical optimization proves a viable alternative, paving the path towards practical implementation of the light trapping solar cells. A 3 [micrometer] thick light trapping solar cell is modeled in order to predict and maximize combined electron-photon harvesting in ultrathin crystalline silicon solar cells. It is shown that the higher charge carrier generation and collection in this design compensates the absorption and recombination losses and ultimately results in an increase in energy conversion efficiency. Further, 20 [micrometer] and 100 [micrometer] thick functional solar cells with the light trapping scheme are studied. The efficiency improvement is observed numerically and experimentally due to photon absorption enhancement in the light trapping cells with respect to a bare cell of same thickness.

Download or read book Anti reflection and Light Trapping in c Si Solar Cells written by Chetan Singh Solanki and published by Springer. This book was released on 2017-06-30 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers essential insights into c-Si based solar cells and fundamentals of reflection, refraction, and light trapping. The basic physics and technology for light trapping in c-Si based solar cells are covered, from traditional to advanced light trapping structures. Further, the book discusses the latest developments in plasmonics for c-Si solar cell applications, along with their future scope and the requirements for further research. The book offers a valuable guide for graduate students, researchers and professionals interested in the latest trends in solar cell technologies.

Download or read book High Efficiency Thin Film Silicon Solar Cells with Novel Light Trapping written by Lirong Zeng (Ph. D.) and published by . This book was released on 2008 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: (Cont.) To prove the theory on the intended application, top-contacted thin film Si solar cells integrated with the TPC back reflector are successfully fabricated using Si-on-insulator material through an active layer transfer technique. All cells exhibit strong absorption enhancement, similar to that predicted by simulation. The 5 [mu]m thick cells gained 19% short circuit current density improvement, despite machine problems during fabrication. The textured photonic crystal back reflector design can be applied directly to single and poly-crystalline Si solar cells, and its principle is broadly applicable to other materials systems.

Download or read book Ultrathin Crystalline Silicon Solar Cells Incorporating Advanced Light trapping Structures written by Matthew S. Branham and published by . This book was released on 2015 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Solar photovoltaics, which convert the energy potential of photons from the sun directly into electrical power, hold immense promise as a cornerstone of a clean energy future. Yet their cost remains greater than that of conventional energy sources in most markets and a barrier to large-scale adoption. Crystalline silicon modules, with a 90% share of the worldwide photovoltaic market, have witnessed a precipitous drop in price over the last decade. But going forward, further evolutionary cost reduction will be difficult given the significant cost of the silicon wafer alone - roughly 35% of the module. Dramatically reducing the thickness of silicon used to make a solar cell from the current 350 [mu]m could rewrite the economics of photovoltaics. For thin-film crystalline silicon solar cells to deliver the anticipated cost benefits of reduced material requirements, it is essential that they also yield power conversion efficiencies comparable to commercial solar cells. A significant hurdle to realizing elevated efficiency in crystalline silicon films thinner than 20 [mu]m is the loss of current resulting from reduced photon absorption. A range of light management structures have been proposed in the literature to address this issue and many have been demonstrated to provide high absorption across the spectral range relevant to crystalline silicon, but their promise has yet to be realized in an active photovoltaic device. The focus of this thesis is the development of an experimental platform and fabrication process to evaluate the effectiveness of theoretically-designed light-trapping structures in functional photovoltaic devices. The experimental effort yielded 10-pm-thick crystalline silicon solar cells with a peak short-circuit current of 34.5 mA cm-2 and power conversion efficiency of 15.7%. The record performance for a crystalline silicon photovoltaic of such thinness is enabled by an advanced light-trapping design incorporating a 2D photonic crystal and a rear dielectric/reflector stack. A parallel line of questioning addressed in this thesis is whether periodic wavelength-scale optical structures are superior to periodic or random structures with geometric-optics-scale features. Through the synthesis of experimental and theoretical evidence, the case is constructed that wavelength-scale light-trapping structures are in fact comparable to conventional random pyramid surface structures for broad-spectrum absorption in silicon solar cells as thin as 5 [mu]m. These results have important implications for the design of cost-effective and manufacturable light-trapping structures for ultrathin crystalline silicon solar cells.

Download or read book Light Trapping in Thin film Solar Cells Using Dielectric and Metallic Nanostructures written by and published by . This book was released on 2014 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Photovoltaics (PV) is a sustainable and clean source of energy and the sun provides more than enough energy to make PV a major electricity source. To make PV fully competitive with conventional energy sources, a reduction of the cost per watt is required. This can be achieved by increasing the conversion efficiency of the modules or by decreasing manufacturing cost. Thin-film solar cells offer the potential for lower manufacturing costs. They can also serve as top cells in high-efficiency tandem solar cells. A major problem with thin-film solar cells is the incomplete absorption of the solar spectrum, which leads to a drastic reduction of the efficiency. To enhance the absorption of light in thin-film solar cells light trapping is required, in which nanostructures are integrated in the cell to enhance the path length of the light in the absorber layer. In this thesis we present new insights in light trapping in thin-film hydrogenated amorphous Si (a-Si:H) and Cu(In,Ga)Se2 (CIGSe) solar cells. We experimentally study arrays of metallic and dielectric resonant scatterers at the front and at the back side of thin-film solar cells, and demonstrate efficient light trapping without deterioration of the electrical properties of the devices. We emphasize the relevance of minimizing optical losses in the light trapping patterns. We compare periodic and random scattering patterns and demonstrate the importance of the spatial frequency distribution in the scattering patterns. We present an optimization of the spatial frequency distribution of light trapping patterns that is applicable to all thin-film solar cell types."-Samenvatting auteur.

Download or read book Thin Film Silicon Solar Cells written by Arvind Victor Shah and published by CRC Press. This book was released on 2010-08-19 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photovoltaic technology has now developed to the extent that it is close to fulfilling the vision of a "solar-energy world," as devices based on this technology are becoming efficient, low-cost and durable. This book provides a comprehensive treatment of thin-film silicon, a prevalent PV material, in terms of its semiconductor nature, startin

Download or read book Thin Film Crystalline Silicon Solar Cells written by Rolf Brendel and published by John Wiley & Sons. This book was released on 2011-02-15 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: This introduction to the physics of silicon solar cells focuses on thin cells, while reviewing and discussing the current status of the important technology. An analysis of the spectral quantum efficiency of thin solar cells is given as well as a full set of analytical models. This is the first comprehensive treatment of light trapping techniques for the enhancement of the optical absorption in thin silicon films.

Download or read book Photon Management in Solar Cells written by Ralf B. Wehrspohn and published by John Wiley & Sons. This book was released on 2015-06-08 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by renowned experts in the field of photon management in solar cells, this one-stop reference gives an introduction to the physics of light management in solar cells, and discusses the different concepts and methods of applying photon management. The authors cover the physics, principles, concepts, technologies, and methods used, explaining how to increase the efficiency of solar cells by splitting or modifying the solar spectrum before they absorb the sunlight. In so doing, they present novel concepts and materials allowing for the cheaper, more flexible manufacture of solar cells and systems. For educational purposes, the authors have split the reasons for photon management into spatial and spectral light management. Bridging the gap between the photonics and the photovoltaics communities, this is an invaluable reference for materials scientists, physicists in industry, experimental physicists, lecturers in physics, Ph.D. students in physics and material sciences, engineers in power technology, applied and surface physicists.

Download or read book High Efficiency Amorphous Silicon Thin Film Solar Cells written by Nowshad Amin and published by LAP Lambert Academic Publishing. This book was released on 2014-06-11 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: The conversion efficiency of a solar cell can substantially be increased by improved material properties and associated designs. In this book, it has been shown that how the parametric optimization can lead to successful design of amorphous silicon thin film solar cells by using a software called AMPS-1D (Analysis of Microelectronic and Photonic Structures) prior to fabrication. Solar cells of single junction based on hydrogenated amorphous (a-Si: H) have been analyzed by using AMPS-1D simulator. The efficiency of single junction a-Si: H can be achieved as high as over 19% after parametric optimization in the simulation. Therefore, the numerically designed and optimized a-SiC: H/a-SiC: H-buffer/a-Si: H/a-Si: H solar cells have been fabricated by using PECVD (plasma enhanced chemical vapor deposition) where the best initial conversion efficiency of 10.02% has been achieved (Voc= 0.88 V, Jsc= 15.57 mA/cm2 and FF= 0.73) as one of the highest recorded efficiency to

Download or read book Towards Lightweight and Flexible High Performance Nanocrystalline Silicon Solar Cells Through Light Trapping and Transport Layers written by Zachary Gray and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates ways to enhance the efficiency of thin film solar cells through the application of both novel nano-element array light trapping architectures and nickel oxide hole transport/electron blocking layers. Experimental results independently demonstrate a 22% enhancement in short circuit current density (JSC) resulting from a nano-element array light trapping architecture and a ~23% enhancement in fill factor (FF) and ~16% enhancement in open circuit voltage (VOC) resulting from a nickel oxide transport layer. In each case, the overall efficiency of the device employing the light trapping or transport layer was superior to that of the corresponding control device. Since the efficiency of a solar cell scales with the product of JSC, FF, and VOC, it follows that the results of this thesis suggest high performance thin film solar cells can be realized in the event light trapping architectures and transport layers can be simultaneously optimized. The realizations of these performance enhancements stem from extensive process optimization for numerous light trapping and transport layer fabrication approaches. These approaches were guided by numerical modeling techniques which will also be discussed. Key developments in this thesis include (1) the fabrication of nano-element topographies conducive to light trapping using various fabrication approaches, (2) the deposition of defect free nc-Si:H onto structured topographies by switching from SiH4 to SiF4 PECVD gas chemistry, and (3) the development of the atomic layer deposition (ALD) growth conditions for NiO.

Download or read book Silicon Based Thin Film Solar Cells written by Roberto Murri and published by Bentham Science Publishers. This book was released on 2013-03-20 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicon Based Thin Film Solar Cells explains concepts related to technologies for silicon (Si) based photovoltaic applications. Topics in this book focus on ‘new concept’ solar cells. These kinds of cells can make photovoltaic power production an economically viable option in comparison to the bulk crystalline semiconductor technology industry. A transition from bulk crystalline Si solar cells toward thin-film technologies reduces usage of active material and introduces new concepts based on nanotechnologies. Despite its importance, the scientific development and understanding of new solar cells is not very advanced, and educational resources for specialized engineers and scientists are required. This textbook presents the fundamental scientific aspects of Si thin films growth technology, together with a clear understanding of the properties of the material and how this is employed in new generation photovoltaic solar cells. The textbook is a valuable resource for graduate students working on their theses, young researchers and all people approaching problems and fundamental aspects of advanced photovoltaic conversion.

Download or read book Enhancement of Thin film Solar Cell Efficiency by Light Trapping written by Takumi Yoshida and published by . This book was released on 1998 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: