Fabrication of Ultra Thin CdS/CdTe Solar Cells by Magnetron Sputtering PDF Download
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Author: Victor Plotnikov
Publisher:
ISBN:
Category : Magnetrons
Languages : en
Pages : 212
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Book Description
CdTe is a nearly perfect absorber material for second generation polycrystalline solar cells because the bandgap closely matches the peak of the solar spectrum, relatively high absorption coefficient and good electronic properties in the polycrystalline phase. Fabricating high-efficiency CdS/CdTe solar cells with an ultra-thin absorber layer is a challenging yet highly desirable step in improving CdTe technology. Most of today's CdTe solar cells utilize an absorber layer which is about 2.5 microns to 8 microns thick. Thinning this layer down typically results in poorer cell performance due to shunting, incomplete photon absorption, fully depleted CdTe layer or interference between the main and the back contact junction when the CdTe layer thickness approaches a certain limit. While some of these losses are fundamental, others can be minimized by careful optimization of the fabrication steps. In this dissertation I present the results of such optimization. Magnetron sputtered CdS/CdTe solar cells with the absorber layer thicknesses from 2.6 microns to 0.3 microns were studied. The deposition process itself and all the post-deposition parameters such as the CdCl2 treatment, thickness of the Cu layer in the thermally evaporated Cu/Au back contact, and the back contact thermal activation/diffusion time for a given CdTe layer thickness were optimized to achieve the top performance for the cell of a given thickness. 13.5 % efficiency cells with 2.5 microns CdTe, 12% cells with 1 microns CdTe, 9.7% cells with 0.5 microns CdTe and 6.7% with 0.3 microns CdTe were fabricated.
Author: Victor Plotnikov
Publisher:
ISBN:
Category : Magnetrons
Languages : en
Pages : 212
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Book Description
CdTe is a nearly perfect absorber material for second generation polycrystalline solar cells because the bandgap closely matches the peak of the solar spectrum, relatively high absorption coefficient and good electronic properties in the polycrystalline phase. Fabricating high-efficiency CdS/CdTe solar cells with an ultra-thin absorber layer is a challenging yet highly desirable step in improving CdTe technology. Most of today's CdTe solar cells utilize an absorber layer which is about 2.5 microns to 8 microns thick. Thinning this layer down typically results in poorer cell performance due to shunting, incomplete photon absorption, fully depleted CdTe layer or interference between the main and the back contact junction when the CdTe layer thickness approaches a certain limit. While some of these losses are fundamental, others can be minimized by careful optimization of the fabrication steps. In this dissertation I present the results of such optimization. Magnetron sputtered CdS/CdTe solar cells with the absorber layer thicknesses from 2.6 microns to 0.3 microns were studied. The deposition process itself and all the post-deposition parameters such as the CdCl2 treatment, thickness of the Cu layer in the thermally evaporated Cu/Au back contact, and the back contact thermal activation/diffusion time for a given CdTe layer thickness were optimized to achieve the top performance for the cell of a given thickness. 13.5 % efficiency cells with 2.5 microns CdTe, 12% cells with 1 microns CdTe, 9.7% cells with 0.5 microns CdTe and 6.7% with 0.3 microns CdTe were fabricated.
Author:
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ISBN:
Category : Cadmium sulfide
Languages : en
Pages : 6
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Book Description
A CdSxTe1-x layer forms by interdiffusion of CdS and CdTe during the fabrication of thin-film CdTe photovoltaic (PV) devices. The CdSxTe1-x layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work has indicated that the electrical junction is located in this interdiffused CdSxTe1-x region. Further understanding, however, is essential to predict the role of this CdSxTe1-x layer in the operation of CdS/CdTe devices. In this study, CdSxTe1-x alloy films were deposited by RF magnetron sputtering and co-evaporation from CdTe and CdS sources. Both radio-frequency-magnetron-sputtered and co-evaporated CdSxTe1-x films of lower S content (x
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
A CdSxTe1-x layer forms by interdiffusion of CdS and CdTe during the fabrication of thin-film CdTe photovoltaic (PV) devices. The CdSxTe1-x layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work [1] has indicated that the electrical junction is located in thisinterdiffused CdSxTe1-x region. Further understanding, however, is essential to predict the role of this CdSxTe1-x layer in the operation of CdS/CdTe devices. In this study, CdSxTe1-x alloy films were deposited by RF magnetron sputtering and co-evaporation from CdTe and CdS sources. Both radio-frequency-magnetron-sputtered and co-evaporated CdSxTe1-x films of lower S content (x
Author:
Publisher:
ISBN:
Category : Cadmium sulfide
Languages : en
Pages : 6
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Book Description
A CdSxTe1-x layer forms by interdiffusion of CdS and CdTe during the fabrication of thin-film CdTe photovoltaic (PV) devices. The CdSxTe1-x layer is thought to be important because it relieves strain at the CdS/CdTe interface that would otherwise exist due to the 10% lattice mismatch between these two materials. Our previous work [1] has indicated that the electrical junction is located in this interdiffused CdSxTe1-x region. Further understanding, however, is essential to predict the role of this CdSxTe1-x layer in the operation of CdS/CdTe devices. In this study, CdSxTe1-x alloy films were deposited by radio-frequency (RF) magnetron sputtering and co-evaporation from CdTe and CdS sources. Both RF-magnetron-sputtered and co-evaporated CdSxTe1-x films of lower S content (x
Author: Arvind Shah
Publisher: Springer Nature
ISBN: 3030464873
Category : Science
Languages : en
Pages : 357
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Book Description
This book gives a comprehensive introduction to the field of photovoltaic (PV) solar cells and modules. In thirteen chapters, it addresses a wide range of topics including the spectrum of light received by PV devices, the basic functioning of a solar cell, and the physical factors limiting the efficiency of solar cells. It places particular emphasis on crystalline silicon solar cells and modules, which constitute today more than 90 % of all modules sold worldwide. Describing in great detail both the manufacturing process and resulting module performance, the book also touches on the newest developments in this sector, such as Tunnel Oxide Passivated Contact (TOPCON) and heterojunction modules, while dedicating a major chapter to general questions of module design and fabrication. Overall, it presents the essential theoretical and practical concepts of PV solar cells and modules in an easy-to-understand manner and discusses current challenges facing the global research and development community.
Author: Alvin D. Compaan
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
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: Adam Lee Sanford
Publisher:
ISBN:
Category :
Languages : en
Pages : 154
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Book Description
The n-CdS/p-CdTe solar cell has been researched for many years now. Research groups use a variety of processes to fabricate thin-film CdS/CdTe cells, including physical vapor deposition, chemical vapor deposition, and RIF diode sputtering. One of the central areas of investigation concerning CdS/CdTe cells is the problem of a Schottky barrier at the back contact. Even cells fabricated with ohmic back contacts degrade into Schottky barriers as the devices are used. This severely degrades power generation. One possible solution is to use p-ZnTe as an interlayer between CdTe and the back contact. ZnTe is easily doped with Cu to be p-type. However, even contacts with this ZnTe interlayer degrade over time, because Cu is highly mobile and diffuses away from the contact towards the CdS/CdTe junction. Another possibility is to dope ZnTe with N. It has been demonstrated using molecular beam epitaxy and RF diode sputtering. In this study, CdTe films are fabricated using a variation of RF diode sputtering called triode sputtering. This technique allows for control of ion bombardment to the substrate during deposition. Also, a higher plasma density near the target is achieved allowing depositions at lower pressures. These films are characterized structurally to show the effects of the various deposition parameters. N-doped ZnTe films are also fabricated using this technique. These films are characterized electrically to show the effects of the various deposition parameters. Also, the effects of post-deposition annealing are observed. It is found that annealing at the right temperature can increase the conductivity of the films by a factor of 3 or more. However, annealing at higher temperatures decreases the conductivity to as low as 12% of the initial conductivity. Finally, RF triode sputtered N-doped ZnTe films are used as an interlayer at the back contact of a CdS/CdTe solar cell. The effects of annealing the device before and after contact deposition are observed. Annealing before depositing contacts results in an increase in V[Subscript oc] of 20mV. Annealing after contact deposition results in a degradation of fill factor over time.
Author: Sivashankar Krishnamoorthy
Publisher: Springer Nature
ISBN: 3031427009
Category :
Languages : en
Pages : 391
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Book Description
Author: Wei Xia
Publisher:
ISBN:
Category :
Languages : en
Pages : 173
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Book Description
"This thesis is an investigation of the fabrication, characterization and performance of high-efficiency and ultra-thin CdTe solar cells with an aim of reducing the material usage and cell manufacturing cost. Several approaches have been successfully carried out to directly or indirectly improve the device performance. Major achievements are listed below: 1) A close-spaced sublimation (CSS) process with an improved control of the deposition temperature-time profile was developed to fabricate high-quality ultra-thin CdTe films. Three key factors in the CSS process including oxygen pressure, substrate temperature and thermal etch duration were optimized. 2) A two-stage post-deposition treatment including a high temperature annealing (HTA) followed by a vaporous cadmium chloride treatment (VCC) was developed and optimized for the growth of high-quality CdTe films. The effects of HTA and VCC on ultra-thin CdTe solar cells were revealed by a combination of characterization techniques, including photoluminescence. 3) In a collaborative effort two new back contact buffers, MoOx and Te/Cu, were identified and applied in ultra-thin CdTe solar cells. Substitution of a conventional acid etching method with the new back contact buffers was found to enhance the cell efficiency from ~10% to ~13.5%. Moreover, the new buffers improved the reproducibility of cell fabrication. A low-resistance electrical back contact based on the Te/Cu buffer and Ni as electrode was developed. A thermal activation process was found necessary to promote ohmic contact formation. Cu diffusion into the Te layer and CdTe bulk layer occurred during the thermal activation process and must be controlled to prevent excessive diffusion into the CdS/CdTe junction. The effects of Cu concentration and Te thickness on device performance and cell stability were systematically investigated and a cell efficiency as high as ~15% with good stability has been achieved using an optimized Te/Cu buffer. 4) A novel vaporous zinc chloride treatment was developed for the formation of Cd1xZnxS from CdS films. Compared with conventional fabrication methods, the VZC method features simple setup and operation and is capable of producing Cd1xZnxS films with a homogenous structure. The Zn to Cd doping ratio in Cd1−xZnxS can be easily controlled by adjusting the process parameters. By replacing CdS with a more transparent Cd1−xZnxS as the window layer, CdTe solar cells with a higher (12-14%) short-circuit current, Jsc, have been demonstrated"--Page v-vi.
