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Development Of High Performance Transparent Conducting Oxides And Their Impact On The Performance In Cds Cdte Solar Cells
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Book Synopsis Development of High-performance Transparent Conducting Oxides and Their Impact on the Performance in CdS/CdTe Solar Cells by : Timothy J. Coutts
Download or read book Development of High-performance Transparent Conducting Oxides and Their Impact on the Performance in CdS/CdTe Solar Cells written by Timothy J. Coutts and published by . This book was released on 1998 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of High-performance Transparent Conducting Oxides and Their Impact on the Performance in CdS/CdTe Solar Cells by :
Download or read book Development of High-performance Transparent Conducting Oxides and Their Impact on the Performance in CdS/CdTe Solar Cells written by and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Issues in the Development of All-sputtered ZnO/CdS/CdTe Flexible Solar Cells by : Anthony Clark Vasko
Download or read book Issues in the Development of All-sputtered ZnO/CdS/CdTe Flexible Solar Cells written by Anthony Clark Vasko and published by . This book was released on 2009 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cadmium telluride (CdTe) solar cells are traditionally made on glass in a superstrate configuration, taking advantage of the transparency and mechanical rigidity of glass, as well as the ability to form the back contact last. However, there are advantages to fabricating solar cells on flexible substrates such as plastic sheets. Advantages include high specific powers (power generated per mass of the device) for low weight applications, the possibility for continuous roll-to-roll manufacturing suitable for industry, and the opportunity to place solar devices on objects and structures that are not necessarily flat. We have fabricated various flexible CdTe devices through sputter deposition, using aluminum doped zinc oxide (AZO) as a transparent conducting oxide (TCO) top contact. Early devices, made by naively applying fabrication techniques used with glass cells, had poor performance. This inspired several investigations. Traditional simple heuristic analysis of solar cell current-voltage curves assumes the cell is reasonably performing and that series and shunt resistance losses are small. This was not true for our early cells, inspiring us to derive a simple model for very poor cells. Early cells showed significant losses due to both series and shunt resistance. Series resistance losses in flexible cells inspired us to investigate more deeply series resistance losses in general, resulting in a fairly simple model that relates fill factor losses, in dot cells made in a typical geometry, to TCO sheet resistance. This model was confirmed by experiment. Series resistance losses also led to futher investigation of AZO properties. We have found that AZO sheet resistance increases during cell fabrication, but a model that is supported by experiment indicates that the resistivity change is limited to a finite thickness of material. This allows fabrication of AZO which remains of good sheet resistance throughout the fabrication process. Shunt resistance losses inspired a study of highly resistive and transparent (HRT) zinc oxide made by reactive sputtering with oxygen, which can be used as a buffer for shunts. Data on resisitivity as a function of oxygen in the sputter gas is given when using doped and undoped zinc oxygen sputter targets. Calculations on theoretical effects of such buffer layers are also presented. A high temperature cadmium chloride (CdCl2) treatment is needed to create high efficiency CdTe cells. This can be a difficult step for flexible cells, as it can lead to CdTe film delamination. We have optimized a treatment for flexible cells and found that conditions, different from those which are optimal for cells on glass, allows high performance with no delamination. Understanding of these issues allowed progress in the performance of our cells fabricated on flexible substrates. Ultimately, we have fabricated a flexible CdTe cell with efficiency of 10.5%. This efficiency is, to our knowledge, the best of any flexible CdTe cell which uses zinc oxide as a transparent conducting oxide. The performance of these cells also compares favorably to the best overall flexible CdTe cells.
Book Synopsis Advanced Processing of CdTe- and CuIn[subscript 1-x]Ga[subscript x]Se2-Based Solar Cells: Final Technical Report, 26 May 1998-22 December 2001 by : Don Louis Morel
Download or read book Advanced Processing of CdTe- and CuIn[subscript 1-x]Ga[subscript x]Se2-Based Solar Cells: Final Technical Report, 26 May 1998-22 December 2001 written by Don Louis Morel and published by DIANE Publishing. This book was released on 2003 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis CdTe Solar Cells by : Mohammed Alturkestani
Download or read book CdTe Solar Cells written by Mohammed Alturkestani and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents various studies into the effects of both growth and processing conditions on a) the electrical properties of interfaces of the CdTe solar cell, and b) the photovoltaic (PV) performance. Annealing of the CdS/TCO (transparent conductive oxide) bilayer in both oxidising and reducing ambients was investigated in order to study changes in the electrical properties of the In/CdS/TCO structure. It was found that post-growth oxidising changed the current?voltage (J-V) characteristics from Ohmic to rectifying, which was attributed to the creation of a CdO-n+/CdS-n junction, as an oxygen-rich layer was revealed by Auger electron spectroscopy (AES) on the CdS surface. A new method of testing pinholing of the CdS film was used, which gave confidence that the observed Ohmic behaviour was genuine. Annealing CdS (in various ambients) was further investigated by studying its effect on full devices, but the effect on PV performance was insignificant. This study was paired with an investigation into a rapid screening method of optimising CdTe/CdS cell PV performance, which reduced the number of the required samples by a factor of ~ 30. This was achieved by varying the CdTe thickness by chemically bevelling the cells in a Br2/methanol solution. The best performance was obtained at a CdTe thickness of ~ 3?m, for which the CdCl2 treatment used was optimum. Both the uniformity and roughness of the cell layers are vital to obtaining high quality results using this methodology. The electrical current transport mechanism in the CdTe/CdS heterojunction was investigated as a function of a) growth technique by which devices were fabricated, and b) window layer type. Data were collected by recording J-V-T measurements in different light intensities (including dark), with temperature being varied in the range of 200? 300 K. The transport mechanism was found to be dependent only on the window material under forward bias condition in the dark, but was independent of both the window layer and growth technique in a) forward bias in the light, and b) reverse bias in the dark. A new method was used to determine the diode ideality factor in the light, and therefore identify the transport mechanism. The back contact of the CdTe/CdS cell was investigated by measuring its barrier height (?b). In a preliminary study, two methods of?b measurement were compared, with the most applicable method being used to study Au, Sb2Te3 and As2Te3 contacts, with the CdTe back surface being either a) as-grown, b) nitric/phosphoric acid etched or c) plasma etched. The value of the barrier height for each contact and its impact on the cell performance are presented and discussed.
Book Synopsis Influence of a Front Buffer Layer on the Performance of Flexible CdS/CdTe Solar Cells by : Hasitha Padmika Mahabaduge
Download or read book Influence of a Front Buffer Layer on the Performance of Flexible CdS/CdTe Solar Cells written by Hasitha Padmika Mahabaduge and published by . This book was released on 2013 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cadmium telluride (CdTe) solar cells have been developing as a promising candidate for large-scale application of photovoltaic energy conversion and have become the most commercially successful polycrystalline thin-film solar module material. In scaling up from small cells to large-area modules, inevitably non-uniformities across the large area will limit the performance of the large cell or module. The effects of these non-uniformities can be reduced by introducing a thin, high-resistivity transparent buffer layer between the conductive electrodes and the semiconductor diode. ZnO is explored in this dissertation as a high-resistivity transparent buffer layer for sputtered CdTe solar cells and efficiencies over 15% have been achieved on commercially available Pilkington TEC15M glass substrates. The highest open-circuit voltage of 0.858V achieved using the optimized ZnO buffer layer is among the best reported in the literature. The properties of ZnO:Al as a buffer are also investigated. We have shown that ZnO:Al can serve both as a transparent conducting oxide layer as well as a high-resistivity transparent layer for CdTe solar cells. ZnO:Al reactively sputtered with oxygen can give the necessary resistivities that allow it to be used as a high-resistivity transparent layer. Glass is the most common choice as the substrate for solar cells fabricated in the superstrate configuration due to its transparency and mechanical rigidity. However flexible substrates offer the advantages of light weight, high flexibility, ease of integrability and higher throughput through roll-to-roll processing over glass. This dissertation presents significant improvements made to flexible CdTe solar cells reporting an efficiency of 14% on clear Kapton® flexible polyimide substrates. Our efficiency of 14% is, to our knowledge, the best for any flexible CdTe cell reported in literature.
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 818 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Fundamentals Of Solar Cells by : Alan Fahrenbruch
Download or read book Fundamentals Of Solar Cells written by Alan Fahrenbruch and published by Elsevier. This book was released on 2012-12-02 with total page 580 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Solar Cells: Photovoltaic Solar Energy Conversion provides an introduction to the fundamental physical principles of solar cells. It aims to promote the expansion of solar photovoltaics from relatively small and specialized use to a large-scale contribution to energy supply. The book begins with a review of basic concepts such as the source of energy, the role of photovoltaic conversion, the development of photovoltaic cells, and sequence of phenomena involved in solar power generation. This is followed by separate chapters on each of the processes that take place in solar cell. These include solar input; properties of semiconductors; recombination and the flow of photogenerated carriers; charge separation and the characteristics of junction barriers; and calculation of solar efficiency. Subsequent chapters deal with the operation of specific solar cell devices such as a single-crystal homojunction (Si); a single-crystal-heterojunction/buried-homojunction (AlGaAs/GaAs); and a polycrystalline, thin-film cell (CuxS/CdS). This book is intended for upper-level graduate students who have a reasonably good understanding of solid state physics and for scientists and engineers involved in research and development of solar cells.
Book Synopsis Applications of Cd2SnO4 Transparent Conducting Oxides in CdS/CdTe Thin-Film Devices by : X. Wu
Download or read book Applications of Cd2SnO4 Transparent Conducting Oxides in CdS/CdTe Thin-Film Devices written by X. Wu and published by . This book was released on 1997 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: An unusual processing scheme has been developed for preparing single-phase cadmium stannate (Cd2SnO4 or CTO) films. Cd2SnO4 transparent conducting oxide (TCO) films have several significant advantages over conventional TCOs when applied to CdS/CdTe thin-film devices. They are more conductive, more transparent, have lower surface roughness, are patternable, and are exceptionally stable. Cd2SnO4-based CdS/CdTe polycrystalline thin-film solar cells with efficiencies of 14% have been fabricated. Preliminary cell results have demonstrated that device performance can be enhanced by replacing the SnO2 layer with a Cd2SnO4 TCO film.
Book Synopsis Approaches to Fabricating High-efficiency Ultra-thin CdTe Solar Cells by : Wei Xia
Download or read book Approaches to Fabricating High-efficiency Ultra-thin CdTe Solar Cells written by Wei Xia and published by . This book was released on 2012 with total page 173 pages. Available in PDF, EPUB and Kindle. Book excerpt: "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.
Book Synopsis CdTe Solar Cells by : Jonathan Major
Download or read book CdTe Solar Cells written by Jonathan Major and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A systematic study is presented on the control of CdTe and CdS layers during their growth, with the understanding gained being implemented in the production of solar cells with enhanced performance. In particular the growth mechanisms for close space sublimation (CSS)? grown CdTe were evaluated as a function of processing gas (N2, 02 and H2) and nitrogen pressure. Films were shown to form via the Volmer-Weber growth mode with films deposited under nitrogen showing well defined crystal facets. Inclusion of oxygen in the deposition ambient produced islands of a rounded morphology, reduced size and increased number density, whilst hydrogen was shown to increase the island number density and the level of substrate coverage. Growth mechanisms were deduced from the morphologies observed at different stages of growth by ex-situ AFM and SEM and by comparison with growth literature, especially the work of P. Barna. Nucleation density, step flow and impurity incorporation are all invoked in the discussion. Factors influencing the cell performance were evaluated with the aid of a optical beam induced current (OBIC) and external quantum efficiency (EQE) system built as part of this work and having the capacity to measure EQE or OBIC maps with a resolution of 12.5pm. The system was used to evaluate the photovoltaic response of CdTe/CdS devices as a function of wavelength with the impact of the nitric-phosphoric acid (NP) etch on the back surface, the uniformity of CdTe/CdS devices deposited by different methods and the effect of absorber layer thickness of PV uniformity being assessed. The performance of CdTe/CdS devices was evaluated as a function of variables that could be influenced by growth of the CdTe and CdS layers. The use of lower substrate temperature and the incorporation oxygen in CdS increased V? from 0.51 to 0.65V is discussed. Oxygen in the CdTe was also shown to influence the junction position and hence efficiency, while oxygen in the CdS layer was also shown to be vital for the formation of hetero-junctions. The CdTe grain size was shown to be significantly increased for deposition under higher nitrogen pressures (Grain diameter = [0.027P + 0.9]gm, where P is the pressure in Torr), with the average grain diameters being 0.94pm at 2Torr and 5.63pm at 200Torr. Device performance was improved as a result with the peak device efficiency being increased from 2.1% at 2Torr to 14.1% at 100Torr. The series resistance was shown to be minimised for larger grain size, owing to the reduced contribution of grain boundaries. Suggestions for the fabrication of high efficiency solar cells are given with reference to the efficiency limiting factor.
Book Synopsis Improved Transparent Conducting Oxides Boost Performance of Thin-Film Solar Cells (Fact Sheet) by :
Download or read book Improved Transparent Conducting Oxides Boost Performance of Thin-Film Solar Cells (Fact Sheet) written by and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Today?s thin-film solar cells could not function without transparent conducting oxides (TCOs). TCOs act as a window, both protecting the cell and allowing light to pass through to the cell?s active layers. Until recently, TCOs were seen as a necessary, but static, layer of a thin-film photovoltaic (PV) cell. But a group of researchers at the National Renewable Energy Laboratory (NREL) hasidentified a pathway to producing improved TCO films that demonstrate higher infrared transparency. To do so, they have modified the TCOs in ways that did not seem possible a few years ago.
Book Synopsis Dissertation Abstracts International by :
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2003 with total page 768 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synerjy written by and published by . This book was released on 1996 with total page 618 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Advanced Processing of CdTe- and CuInxGa{sub 1-x}Se2-Based Solar Cells; Phase I Report by :
Download or read book Advanced Processing of CdTe- and CuInxGa{sub 1-x}Se2-Based Solar Cells; Phase I Report written by and published by . This book was released on 2000 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main tasks of the cadmium telluride portion of this project include the development of simplified processing for fabricating high-efficiency CdTe solar cells, studies on the long-term stability of CdTe devices, and the development of alternative transparent conducting oxides, window layers, and back contacts. The second portion of this project focused on CIGS solar cells. The main tasks include the development of a manufacturable process for CIGS devices and the development of high-band-gap alloys for use in tandem cell structures. Additional objectives include development of improved junction formation processing and contributing to the overall understanding of these materials and devices. Because the processing is manufacturing-driven, the authors use an all solid-state, simplified two-step process that relaxes the level of deposition control required.
Book Synopsis Organic Nanostructured Thin Film Devices and Coatings for Clean Energy by : Sam Zhang
Download or read book Organic Nanostructured Thin Film Devices and Coatings for Clean Energy written by Sam Zhang and published by CRC Press. This book was released on 2010-06-18 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Authored by leading experts from around the world, the three-volume Handbook of Nanostructured Thin Films and Coatings gives scientific researchers and product engineers a resource as dynamic and flexible as the field itself. The first two volumes cover the latest research and application of the mechanical and functional properties of thin films an
Book Synopsis Electrical & Electronics Abstracts by :
Download or read book Electrical & Electronics Abstracts written by and published by . This book was released on 1997 with total page 2240 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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