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Development Of Transparent And Conducting Back Contacts On Cds Cdte Solar Cells For Photoelectrochemical Application
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Book Synopsis Development of Transparent and Conducting Back Contacts on CdS/CdTe Solar Cells for Photoelectrochemical Application by : Upendra Avachat
Download or read book Development of Transparent and Conducting Back Contacts on CdS/CdTe Solar Cells for Photoelectrochemical Application written by Upendra Avachat and published by . This book was released on 2005 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research work focuses on developing various back contacts with good transparency in the infrared region (~750 - 1150 nm) for a CdS/CdTe solar cell. CdS/CdTe solar cells were prepared with three different configurations, Glass/SnO2:F/CdS/CdTe/ZnTe:Cu/ITO/Ni-Al (series 1), Glass/SnO2:F/CdS/CdTe/Cu2Te/ITO/Ni-Al (series 2), Glass/SnO2:F/CdS/CdTe/Br-Me etching/Cu/ITO/Ni-Al (series 3).
Book Synopsis Development of Back Contacts for CdTe Thin Films Solar Cells by : Fadhil Khalaf Dahash Alfadhili
Download or read book Development of Back Contacts for CdTe Thin Films Solar Cells written by Fadhil Khalaf Dahash Alfadhili and published by . This book was released on 2020 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin film solar cells based on polycrystalline p-type cadmium telluride (CdTe) represent one of these the most promising photovoltaic (PV) device due to high efficiency and low-cost production. Currently, CdTe solar cells provide the lowest cost electricity generation in utility-scale applications, which is a cost-competitive with the traditional power source, fossil fuel. CdTe thin film PV has attained 22.1 % of power conversion efficiency for small area scale and 18.6 % for modules scale. However, the high efficiency of CdTe devices has been achieved by increasing the photo-generated current by changing the traditional window layer (CdS) of CdTe to a wider bandgap material with better band alignment. The open-circuit voltage (VOC) remains below the theoretical limit due to a barrier at the back of the device due to the deep valence band edge of CdTe (-5.9 eV). Voc can be increased by adding a buffer layer between CdTe and the back electrode to decrease band banding and reducing carrier recombination at the back interface. In this thesis, several materials were investigated as a back-buffer layer, such as single-wall carbon nanotube (SWCNT), zinc telluride (ZnTe), tellurium (Te), and cadmium zinc telluride (CZT) to minimize the bend bending at CdTe/back-buffer layer interface. An alternative method to reduce the carrier recombination at the rear surface, the use of aluminum oxide (Al2O3) layer as a passivation layer was also demonstrated. Finally, an effective method of CdCl2 treatment for CZT thin film was investigated. This method shows that zinc (Zn) can be maintained during the heat treatment.
Book Synopsis Studies of ZnTe Back Contacts to CdS/CdTe Solar Cells by :
Download or read book Studies of ZnTe Back Contacts to CdS/CdTe Solar Cells written by and published by . This book was released on 1997 with total page 0 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 Development and Application of Transparent P-type Back Contact Layers for Bifacial CdTe Solar Cells by : Kamala Khanal Subedi
Download or read book Development and Application of Transparent P-type Back Contact Layers for Bifacial CdTe Solar Cells written by Kamala Khanal Subedi and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Development of CdTe Thin Film Solar Cells on Flexible Foil Substrates by : Deidra Ranel Hodges
Download or read book Development of CdTe Thin Film Solar Cells on Flexible Foil Substrates written by Deidra Ranel Hodges and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Cadmium telluride (CdTe) is a leading thin film photovoltaic (PV) material due to its near ideal band gap of 1.45 eV, its high optical absorption coefficient and availability of various device fabrication methods. Superstrate CdTe solar cells fabricated on glass have to-date exhibited efficiencies of 16.5%. Work on substrate devices has been limited due to difficulties associated with the formation of an ohmic back contact with CdTe. The most promising approach used to-date is based on the use of an interlayer between the CdTe and a metal electrode, an approach that is believed to yield a pseudo-ohmic contact. This research investigates the use of ZnTe and Sb2Te3 as the interlayer, in the development of efficient back contacts. Excellent adhesion and minimum stress are also required of a CdTe thin film solar cell device on a flexible stainless steel (SS) foil substrate. Foil substrate curvature, flaking, delamination and adhesion as a result of compressive strain due to the coefficient of thermal expansion (CTE) mismatch between the flexible SS foil substrate and the solar cell films have been studied. A potential problem with the use of a SS foil as the substrate is the diffusion of iron (Fe), chromium (Cr) and other elemental impurities into the layers of the solar cell device structure during high temperature processing. A diffusion barrier limiting the out diffusion of these substrate elements is being investigated in this study. Silicon nitride (Si3N4) films deposited on SS foils are being investigated as the barrier layer, to reduce or inhibit the diffusion of substrate impurities into the solar cell. Thin film CdTe solar cells have been fabricated and characterized by AFM, XRD, SEM, ASTM D3359-08 tape test, current-voltage (I-V) and spectral measurements. My individual contributions to this work include the Molybdenum (Mo) development, the adhesion studies, the silicon nitride (Si3N4) barrier studies, and EDS and SEM lines measurements and analysis of substrate out-diffused impurities. The rest of my colleagues focused on the development of CdTe, CdS, ZnTe, the CdCl2 heat treatment, and other back contact interlayer materials.
Book Synopsis Electrical Characterization of Thin Film CdTe Solar Cells by : Darshini Desai
Download or read book Electrical Characterization of Thin Film CdTe Solar Cells written by Darshini Desai and published by . This book was released on 2007 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: Photovoltaic device modeling results obtained using AMPS (Analysis of microelectronic and photonic structures) suggest that the dominant recombination mechanism is the SRH recombination through midgap states.
Download or read book ZnTe written by and published by . This book was released on 2003 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ability to produce high-performance CdS/CdTe photovoltaic (PV) devices that incorporate high-transparency back contacts for multijunction thin-film PV applications will require an even greater level of understanding than has been required for single-junction devices. This study reports some of our initial investigations at NREL to modify the ZnTe:Cu contact process previously developed for single-junction applications for optimal use as a transparent back contact. We have succeeded in producing devices incorporating a transparent ZnTe:Cu/ITO/metal-grid contact that demonstrates nominally identical light I-V (LIV) performance to the ZnTe:Cu/Ti contact used in single-junction devices. However, we have determined that the transparent conducting oxide (TCO), CdS, CdTe, and ZnTe:Cu layers are all factors in the optical absorption within the device. Finally, we have concluded that optimizing the transparent ZnTe:Cu contact for use with NREL-produced device material will require a more detailed understanding of the evolution of the junction region during the contact process.
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 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 RF Sputtered Back Contacts for CdS/CdTe Thin Film Solar Cells by : Vijay Viswanathan
Download or read book RF Sputtered Back Contacts for CdS/CdTe Thin Film Solar Cells written by Vijay Viswanathan and published by . This book was released on 1997 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Development of ZnTe written by and published by . This book was released on 2012 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main focus of the work at NREL was on the development of Cu-doped ZnTe contacts to CdTe solar cells in the substrate configuration. The work performed under the CRADA utilized the substrate device structure used at NREL previously. All fabrication was performed at NREL. We worked on the development of Cu-doped ZnTe as well as variety of other contacts such as Sb-doped ZnTe, CuxTe, and MoSe2. We were able to optimize the contacts to improve device parameters. The improvement was obtained primarily through increasing the open-circuit voltage, to values as high as 760 mV, leading to device efficiencies of 7%.
Book Synopsis Study Of Cu Free Back Contacts to Thin Film CdTe Solar Cells by : Vijay Viswanathan
Download or read book Study Of Cu Free Back Contacts to Thin Film CdTe Solar Cells written by Vijay Viswanathan and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: The effect of etching ambient, pressure, plasma power and etch time on contact performance will be studied.
Book Synopsis Development of ZnTe:Cu Contacts for CdTe Solar Cells: Cooperative Research and Development Final Report, CRADA Number CRD-08-320 by :
Download or read book Development of ZnTe:Cu Contacts for CdTe Solar Cells: Cooperative Research and Development Final Report, CRADA Number CRD-08-320 written by and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main focus of the work at NREL was on the development of Cu-doped ZnTe contacts to CdTe solar cells in the substrate configuration. The work performed under the CRADA utilized the substrate device structure used at NREL previously. All fabrication was performed at NREL. We worked on the development of Cu-doped ZnTe as well as variety of other contacts such as Sb-doped ZnTe, CuxTe, and MoSe2.We were able to optimize the contacts to improve device parameters. The improvement was obtained primarily through increasing the open-circuit voltage, to values as high as 760 mV, leading to device efficiencies of 7%.
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 Transparent Indium Tin Oxide Contacts to CdTe in Thin Film CdTe-CdS Solar Cells by : Jung-Hsin Chao
Download or read book Transparent Indium Tin Oxide Contacts to CdTe in Thin Film CdTe-CdS Solar Cells written by Jung-Hsin Chao and published by . This book was released on 1996 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
