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Languages : en
Pages : 4
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Book Description
Sub-wavelength periodic texturing (gratings) of crystalline-silicon (c-Si) surfaces for solar cell applications can be designed for maximizing optical absorption in thin c-Si films. We have investigated c-Si grating structures using rigorous modeling, hemispherical reflectance, and internal quantum efficiency measurements. Model calculations predict almost (approximately)100% energy coupling into obliquely propagating diffraction orders. By fabrication and optical characterization of a wide range of 1D & 2D c-Si grating structures, we have achieved broad-band, low ((approximately) 5%) reflectance without an anti-reflection film. By integrating grating structures into conventional solar cell designs, we have demonstrated short-circuit current density enhancements of 3.4 and 4.1 mA/cm2 for rectangular and triangular 1D grating structures compared to planar controls. The effective path length enhancements due to these gratings were 2.2 and 1.7, respectively. Optimized 2D gratings are expected to have even better performance.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 4
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Book Description
Sub-wavelength periodic texturing (gratings) of crystalline-silicon (c-Si) surfaces for solar cell applications can be designed for maximizing optical absorption in thin c-Si films. We have investigated c-Si grating structures using rigorous modeling, hemispherical reflectance, and internal quantum efficiency measurements. Model calculations predict almost (approximately)100% energy coupling into obliquely propagating diffraction orders. By fabrication and optical characterization of a wide range of 1D & 2D c-Si grating structures, we have achieved broad-band, low ((approximately) 5%) reflectance without an anti-reflection film. By integrating grating structures into conventional solar cell designs, we have demonstrated short-circuit current density enhancements of 3.4 and 4.1 mA/cm2 for rectangular and triangular 1D grating structures compared to planar controls. The effective path length enhancements due to these gratings were 2.2 and 1.7, respectively. Optimized 2D gratings are expected to have even better performance.
Author: Xianqin Meng
Publisher:
ISBN:
Category :
Languages : en
Pages : 132
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Book Description
Gratings are considered. The goal is to integrate such structures into ultra-thin film silicon photovoltaic solar cells, with a view to improve their conversion efficiency. First, a PCs assisted ultra-thin film crystalline silicon (c-Si) solar cell is designed optimized by using the Finite Different Time Domain (FDTD) approach. An increase over50% is achieved for the absorption, as integrated over the whole spectral range, by patterning a 2D PCs in the active Si layer. This enhancement is achieved by combining Slow Bloch modes and Fabry-Perot modes. In order to fabricate such solar cells, we developed a process based on Laser Holographic Lithography, Reactive Ion Etching and Inductivity Coupled Plasma etching. We have investigated the influence of the parameters taking part in these processes on the obtained patterns. Finally the optical and electrical properties of the devices have been characterized by our co-workers at IMEC, Belgium. Absorption measurements are in good agreement with the theoretical simulations. Moreover, the integrated absorption is tolerant with regard to the sunlight angle of incidence. The final fabricated 2D PCs patterned solar cell exhibits a 20% higher short circuit current (Jsc = 15mA/cm2) than the reference. Additionally, a more complex thin film c-Si solar cells integrating front and back diffraction gratings has been designed. Long wavelength absorption is increased thanks to the long period (750 nm) back grating, while the incident light reflection is reduced by using a short period (250 nm) front grating. A short-circuit current increase up to 30 mA/cm2 is predicted for this device, far above the 18 mA/cm2 value for the unpatterned reference These are first steps towards the development of a future generation of PC and diffraction grating assisted solar cells.
Author: Ralf B. Wehrspohn
Publisher: John Wiley & Sons
ISBN: 3527665692
Category : Science
Languages : en
Pages : 376
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Book Description
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.
Author: Samuel Turner
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A light trapping structure can improve the efficiency of a photovoltaic device by increasing the path length for weakly absorbed light, and hence reduce the cost of solar electricity. With a broad scope for their application to photovoltaic devices of varied design and composition, the study of light trapping structures holds promise for a photovoltaic industry undergoing rapid growth. Wavelength-scale dielectric diffraction gratings have recently received significant attention as light trapping structures whose theoretical upper limits for path length enhancement exceed the Lambertian light trapping limit conventionally applied to wafer-based devices. Metallic diffraction gratings suffer from losses that place constraints on their structural parameters, limiting their light trapping efficiency. This work investigates the light trapping properties of wavelength-scale TiO2 diffraction gratings, exploring a range of designs and drawing direct comparisons with optimum silver diffraction gratings and the Lambertian light trapping limit. InGaAs/GaAs quantum well solar cells (QWSC) form the material system which facilitates this study, wherein the wavelengths longer than the bandgap of GaAs (873 nm), that are weakly absorbed by the quantum wells (QWs), are studied. Ultimately however, the theoretical and experimental investigations of this study aim to provide insights that can be considered more generally across a broad range of devices and material systems. Finite-difference time-domain (FDTD) simulations are used to study wavelength-scale TiO2 diffraction gratings for light trapping in InGaAs/GaAs QWSCs. The designs investigated include symmetric rectangular strip, symmetric square pillar and asymmetric skewed pyramid diffraction gratings. The ratio of this enhancement to the maximum achievable enhancement - that is, without transmission losses - is 33 %, 77 % and 75 % for the optimum TiO2 rectangular strip, square pillar and skewed pyramid diffraction gratings, respectively. The optimum TiO2 square pillar and skewed pyramid diffraction gratings perform comparably with relative enhancements greater than that of the optimum TiO2 rectangular strip diffraction grating and nearest that of the Lambertian light trapping limit (97 %). All three optimum designs outperform an optimum silver square pillar diffraction grating whose relative enhancement is 28 %. Experimentally, an InGaAs/GaAs QWSC structure is grown through metal organic chemical vapour deposition on a semi-insulating (SI) GaAs substrate. TiO2 and silver square pillar diffraction gratings are fabricated on the rear of InGaAs/GaAs QWSCs using a single layer, positive resist lithographic lift-off process with the techniques of electron beam lithography and electron beam evaporation. The structural parameters of the silver square pillar diffraction grating are optimal (50 nm in height), whereas those of the TiO2 square pillar diffraction grating (83 +/- 5 nm in height) represent a compromise between performance and what is practicably achievable with respect to the optimum height of approximately 500 nm that is calculated through FDTD simulations. The TiO2 and silver square pillar diffraction gratings generate enhancements in short-circuit current density of 0.2 mAcm-2 and 0.6 mAcm-2, respectively. For the TiO2 square pillar diffraction grating to provide enhancement that surpasses not only that of the silver square pillar diffraction grating but approaches the theoretical ideal defined through FDTD simulations new strategies for fabrication are required and discussed.
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Publisher:
ISBN:
Category : Photovoltaic cells
Languages : en
Pages : 0
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Book Description
Author: Ralf B. Wehrspohn
Publisher: John Wiley & Sons
ISBN: 3527411755
Category : Science
Languages : en
Pages : 376
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Book Description
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.
Author: Christian Stefano Schuster
Publisher: Springer
ISBN: 3319442783
Category : Science
Languages : en
Pages : 129
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Book Description
This thesis introduces a figure of merit for light trapping with photonic nanostructures and shows how different light trapping methods compare, irrespective of material, absorber thickness or type of nanostructure. It provides an overview of the essential aspects of light trapping, offering a solid basis for future designs. Light trapping with photonic nanostructures is a powerful method of increasing the absorption in thin film solar cells. Many light trapping methods have been studied, but to date there has been no comprehensive figure of merit to compare these different methods quantitatively. This comparison allows us to establish important design rules for highly performing structures; one such rule is the structuring of the absorber layer from both sides, for which the authors introduce a novel and simple layer-transfer technique. A closely related issue is the question of plasmonic vs. dielectric nanostructures; the authors present an experimental demonstration, aided by a detailed theoretical assessment, highlighting the importance of considering the multipass nature of light trapping in a thin film, which is an essential effect that has been neglected in previous work and which allows us to quantify the parasitic losses.
Author: Jahangir Hossain
Publisher: Springer Science & Business Media
ISBN: 9814585300
Category : Technology & Engineering
Languages : en
Pages : 459
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Book Description
This book focuses on the issues of integrating large-scale renewable power generation into existing grids. The issues covered in this book include different types of renewable power generation along with their transmission and distribution, storage and protection. It also contains the development of medium voltage converters for step-up-transformer-less direct grid integration of renewable generation units, grid codes and resiliency analysis for large-scale renewable power generation, active power and frequency control and HVDC transmission. The emerging SMES technology for controlling and integrating large-scale renewable power systems is also discussed. Since the protection issues with large-scale distributed renewable power systems are different compared to the existing protection system for one way power flow, this book includes a new protection technique for renewable generators along with the inclusion of current status of smart grid. This book is a good reference for the researchers who are working the area of renewable power generation and smart grids.
Author: Deborah M. Kane
Publisher: Pan Stanford Publishing
ISBN: 9814310026
Category : History
Languages : en
Pages : 463
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Book Description
This book reports current nanotechnology research from Australia, in addition to being the first trial of a new workshop program for the professional development of early career researchers (ECRs, including research students). It showcases the professional talents and high-quality writing of ECRs and also describes the workshop program, organized under the auspices of the Australian Research Council Nanotechnology Network, designed to facilitate this. The nanotechnology research topics include plasmonics, the building blocks of plasmonic circuits; the use of metal nanoparticles to improve infrared light trapping in solar cell applications; methods for the bulk synthesis of graphene; synthesis of nanorods of vanadium compounds for energy storage; nanodiamonds, superparamagnetic nanoparticles and synthesis of hollow nanostructured silica, along with a discussion of their applications; molecular dynamics modelling of self-cleaning coatings; metal nanostructure-enhanced fluorescence and its biological applications; luminescent nano-bioprobes for bioassays and bioimaging; biomimicry leading to olfactory nano-biosensors; and superparamagnetic nanoparticles as MRI contrast agents.
Author: Narottam Das
Publisher: BoD – Books on Demand
ISBN: 953512935X
Category : Technology & Engineering
Languages : en
Pages : 316
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Book Description
Nanostructured solar cells are very important in renewable energy sector as well as in environmental aspects, because it is environment friendly. The nano-grating structures (such as triangular or conical shaped) have a gradual change in refractive index which acts as a multilayer antireflective coating that is leading to reduced light reflection losses over broadband ranges of wavelength and angle of incidence. There are different types of losses in solar cells that always reduce the conversion efficiency, but the light reflection loss is the most important factor that decreases the conversion efficiency of solar cells significantly. The antireflective coating is an optical coating which is applied to the surface of lenses or any optical devices to reduce the light reflection losses. This coating assists for the light trapping capturing capacity or improves the efficiency of optical devices, such as lenses or solar cells. Hence, the multilayer antireflective coatings can reduce the light reflection losses and increases the conversion efficiency of nanostructured solar cells.
