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Author: Inès Massiot
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Reducing the absorber thickness is an attractive solution to decrease the production cost of solar cells. Furthermore, it allows to reduce the amount of material needed and improve the current collection in the cell. This thesis has been focused on the design of nanostructures to enhance light absorption in very small semiconductor volumes in order to achieve efficient ultra-thin solar cells. First, we have proposed an original light-trapping concept for ultra-thin amorphous silicon (a-Si:H) solar cells. A one-dimensional metallic grating is patterned on the front surface of the cell deposited on a metallic mirror. Broadband multi-resonant absorption has been demonstrated for both light polarizations. The metallic grating is also used as an alternative transparent electrode in order to reduce optical losses in the front contact. A detailed analysis of the multi-resonant absorption mechanism has been carried out through numerical calculations. The fabrication and optical characterization of ultra-thin a-Si:H solar cells with metallic gratings have validated the multi-resonant approach.Second, we have proposed a design with a two-dimensional metallic grid as a resonant front contact for very thin (25 nm) gallium arsenide (GaAs) layers. We have shown through the design and fabrication of a proof-of-concept structure the potential of metallic nanogrids to confine efficiently light absorption with an ultra-thin GaAs layer.Finally, advanced light-trapping structures could also allow a thickness reduction of crystalline silicon wafers of a factor 20 to 100 with respect to state-of-the-art cells. We have developed a process to transfer micron-thick epitaxial crystalline silicon (c-Si) layers onto a low-cost host substrate. Inverted nanopyramids have also been fabricated in crystalline silicon in order to achieve a broadband anti-reflection effect. It opens promising perspectives towards the realization of double-sided nanopatterned ultra-thin c-Si cells.
Author: Inès Massiot
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Reducing the absorber thickness is an attractive solution to decrease the production cost of solar cells. Furthermore, it allows to reduce the amount of material needed and improve the current collection in the cell. This thesis has been focused on the design of nanostructures to enhance light absorption in very small semiconductor volumes in order to achieve efficient ultra-thin solar cells. First, we have proposed an original light-trapping concept for ultra-thin amorphous silicon (a-Si:H) solar cells. A one-dimensional metallic grating is patterned on the front surface of the cell deposited on a metallic mirror. Broadband multi-resonant absorption has been demonstrated for both light polarizations. The metallic grating is also used as an alternative transparent electrode in order to reduce optical losses in the front contact. A detailed analysis of the multi-resonant absorption mechanism has been carried out through numerical calculations. The fabrication and optical characterization of ultra-thin a-Si:H solar cells with metallic gratings have validated the multi-resonant approach.Second, we have proposed a design with a two-dimensional metallic grid as a resonant front contact for very thin (25 nm) gallium arsenide (GaAs) layers. We have shown through the design and fabrication of a proof-of-concept structure the potential of metallic nanogrids to confine efficiently light absorption with an ultra-thin GaAs layer.Finally, advanced light-trapping structures could also allow a thickness reduction of crystalline silicon wafers of a factor 20 to 100 with respect to state-of-the-art cells. We have developed a process to transfer micron-thick epitaxial crystalline silicon (c-Si) layers onto a low-cost host substrate. Inverted nanopyramids have also been fabricated in crystalline silicon in order to achieve a broadband anti-reflection effect. It opens promising perspectives towards the realization of double-sided nanopatterned ultra-thin c-Si cells.
Author: Shrestha Basu Mallick
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
This work is about nano-structuring of semiconductor devices for the improvement of their optical properties. The phenomenon of guided resonances in photonic crystal (PC) slabs will be introduced and ways of engineering these guided resonances for a variety of applications such as improved reflectivity in micro-electro-mechanical (MEMS) mirrors and increased absorption in thin-film solar cells will be discussed. The first part of the work focuses on the application of PCs in MEMS. A new process (GOPHER) that was developed to make low stress PCs out of monolithic silicon will be discussed. The advantage and ease of making multilayer PCs with Gopher will be illustrated and experimental results showing Gopher structures having spectra with broadband reflectivity (suitable for mirror applications) as well as sharp peaks (suitable for sensors) will be presented. Other applications of Gopher such as making waveguides etc., will be briefly discussed. The integration of a high quality PC mirror with a 1D resonant MEMS scanner will be demonstrated. Finally, the results of fabrication of a prototype wafer-scale encapsulated optical device will be shown. The Gopher process has a lot of potential for facilitating the integration of micro- and nano-scale photonics with CMOS circuitry. The second part of the work focuses on the application of PCs for light-trapping in solar cells. Thin-film photovoltaics has the potential to reduce cost by reducing the amount of photoactive material required and allowing for the use of material of poorer quality. Crystalline Silicon (c-Si) is an attractive material for photovoltaic cells due to its natural abundance, nearly ideal band gap, and leverage of existing process and materials knowledge. However, the poor optical absorption in the near-infrared spectral range requires the use of very efficient light trapping techniques. One such technique that is explored is to pattern the active layer into a 2D PC. Electromagnetic simulations are performed to show that an enhancement in integrated short-circuit current by a factor of 3 is possible when compared to a planar slab of equivalent volume. This is because the PC supports guided resonances into which incident radiation can couple which increases the absorption. Finally, the fabrication of an ultrathin c-Si solar cell where the active material is patterned into a square-lattice 2D PC is demonstrated. Both short-circuit current and external quantum efficiency measurements show an enhancement in optical absorption, especially at longer wavelengths. Scanning photocurrent maps confirm the improved optical absorption in the photonic structure over an unpatterned reference. Future applications of nanostructuring to thin-film cells that can be commercially realized is discussed.
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: Clément Colin
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
One of the natural tendencies of photovoltaic technologies is the systematic reduction of the thickness of the solar cells in order to reduce the cost, to save rare or toxic elements or to limit recombination. So far, crystalline thin-film (GaAs) and poly-crystalline (CIGS) technology are reaching optimum conversion efficiency for thicknesses around 1 or 2 microns. Typically, this thickness range does not require new solutions of optical trappings as it is the case for amorphous silicon. However, if we want to reduce these thicknesses by a factor of 10 or even 100 to study new concepts of collections and conversions (GaAs or GaSb) or reduce the use of indium (CIGS), new needs for efficient light absorption are necessary for these technologies. This manuscript is focused on the design, simulation and realization of innovative nanophotonic solutions for future ultra-thin crystalline solar cells.As a first step, we were engaged in an approach at odds with the usual design of solar cells to trap light in a ultra-thin (≤100 nm) layer of material (GaAs, GaSb and CIGS). We propose an array of metal nanostructure placed in front of the cell, transferred on a metal mirror in order to obtain a high, multi-resonant absorption independent of the angle of incidence and polarization. Numerical analysis of the resonant mechanisms involved was conducted as well as the fabrication and optical characterization of demonstrators. The results of this study are motivating for future work on the ultra-thin devices, involving new concepts of collection (ballistic transport) or conversion (hot carrier solar cells).On the other hand, we studied the possibility of integrating a rear gold nanostructured back contact (200-400 nm) in thin CIGS solar cells to potentially increase the current of short circuit and open circuit voltage. We have proposed an innovative process to achieve this structure and the optical trapping for CIGS solar cells. Numerical study, manufacture of demonstrators and first measurements are presented.
Author: Jef Poortmans
Publisher: John Wiley & Sons
ISBN: 0470091266
Category : Science
Languages : en
Pages : 504
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Book Description
Thin-film solar cells are either emerging or about to emerge from the research laboratory to become commercially available devices finding practical various applications. Currently no textbook outlining the basic theoretical background, methods of fabrication and applications currently exist. Thus, this book aims to present for the first time an in-depth overview of this topic covering a broad range of thin-film solar cell technologies including both organic and inorganic materials, presented in a systematic fashion, by the scientific leaders in the respective domains. It covers a broad range of related topics, from physical principles to design, fabrication, characterization, and applications of novel photovoltaic devices.
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.
Author: Nicolas Vandamme
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The thickness reduction of solar cells is motivated by the reduction of production costs and the enhancement of conversion efficiencies. However, for thicknesses below a few hundreds of nanometers, new light trapping strategies are required. We propose to introduce nanophotonics and plasmonics concepts to absorb light on a wide spectral range in ultrathin GaAs layers. We conceive and fabricate multi-resonant structures made of arrays of metal nanostructures. First, we design a super-absorber made of a 25 nm-thick GaAs slab transferred on a back metallic mirror with a top metal nanogrid that can serve as an alternative front electrode. We analyze numerically the resonance mechanisms that result in an average light absorption of 80% over the 450nm-850nm spectral range. The results are validated by the fabrication and characterization of these multi-resonant super-absorbers made of ultrathin GaAs. Second, we use a similar strategy for GaAs solar cells with thicknesses 10 times thinner than record single-junction photovoltaic devices. A silver nanostructured back mirror is used to enhance the absorption efficiency by the excitation of various resonant modes (Fabry-Perot, guided modes,...). It is combined with localized ohmic contacts in order to enhance the absorption efficiency and to optimize the collection of photogenerated carriers. According to numerical calculations, the short-circuit current densities (Jsc) can reach 22.4 mA/cm2 and 26.0 mA/cm2 for absorber thicknesses of t=120 nm and t=220 nm, respectively. We have developed a fabrication process based on nano-imprint lithography and on the transfer of the active layers. Measurements exhibit record short-circuit currents up to 17.5 mA/cm2 (t=120 nm) and 22.8 mA/cm2 (t=220 nm). These results pave the way toward conversion efficiencies above 20% with single junction solar cells made of absorbers thinner than 200 nm.
Author:
Publisher:
ISBN: 9789077209851
Category :
Languages : en
Pages : 143
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Book Description
"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.
Author: Atul Tiwari
Publisher: Wiley-Scrivener
ISBN: 9781118686256
Category : Technology & Engineering
Languages : en
Pages : 0
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Book Description
Focusing on the cutting-edge technologies available in the field of photovoltaics, Solar Cell Nanotechnology explores the latest research and development activities related to organic, inorganic, and hybrid materials being used in solar cell manufacturing. Several chapters are dedicated to explaining the fundamentals of photovoltaics and nanomaterials utilized in the manufacturing of solar cells. Other essential subjects, such as microcontact printing, plasmonic light trapping, outdoor and indoor efficiency, luminescent solar concentrators, and photon management in photovoltaics, are comprehensively reviewed. Written for a broad audience, this is an essential book for engineers, nanotechnologists, and materials scientists.
Author:
Publisher:
ISBN: 9789077209769
Category :
Languages : en
Pages : 145
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Book Description
"Photovoltaics is a sustainable and environmentally clean source of energy that has the potential to become a major source of energy for our society. In order for this to happen, photovoltaics needs to be economically competitive with other conventional energy sources. This can be achieved by reducing the production costs of solar panels and by improving their photovoltaic conversion efficiency. For Si solar cells, both challenges can be achieved by reducing the thickness of the solar cell. However, major optical losses occur when the thickness of Si solar cell is reduced, due to incomplete absorption of light. In this thesis, we investigate new ways of enhancing light absorption in Si solar cells by using nanostructures that show resonant interaction with light. We study the fundamental aspects of resonant scattering of light by metallic and dielectric nanoparticles placed on top of thick and thin dielectric substrates. If optimally designed these nanostructures can lead to efficient light coupling and trapping in solar cells. This allows the realization of novel solar cell architectures with higher efficiency that can be made at lower costs."--Samenvatting auteur.
