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Nickel-metal hydride (NiMH) is a commercially important rechargeable battery technology for both consumer and industrial applications due to design flexibility, excellent energy and power, environmental acceptability and cost. [1] From the initial product introduction in 1991 of cylindrical cells having an energy of 54 Wh kg −1 , today's small consumer cells have a specific energy over 100 Wh kg −1 . Numerous licensed manufacturers produce a myriad of NiMH products ranging from 30 mAh button cells to a wide variety of consumer cylindrical products, prismatic cells up to 250 Ah for electric buses and 6 Ah multicell modules for hybrid electric vehicles. Power has increased from under 200 to 1200 W kg −1 commercially and up to 2000 W kg −1 at a development level [2] . Early NiMH batteries had limited operating temperatures while today's batteries can provide excellent power at cold temperatures of −30 °C and provide over 90% capacity at 70 °C. Many of these product performance advances are a result of innovations to the metal hydride and nickel hydroxide materials. We will report on some of these key material advances which provide today's NiMH performance and new materials to allow higher energy, power and significant cost reduction.

Multielement, multiphase disordered metal hydride alloys have enabled the widespread commercialization of NiMH batteries by allowing high capacity and good kinetics while overcoming the crucial barrier of unstable oxidation/corrosion behavior to obtain long cycle life. Atomic engineering is used to promote a high concentration of active hydrogen storage sites vital for raising NiMH specific energy to 100 Wh kg−1 by utilizing metal hydride materials having in excess of 440 mAh g−1 specific capacity. New commercial applications demand fundamentally higher specific power and discharge rate kinetics. Disorder at the metal/electrolyte interface has enabled a surface oxide with metallic nickel alloy inclusions having a diameter less than 70 A embedded within the oxide, which provide exceptional catalytic activity to the metal hydride electrode surface and allowed NiMH specific power exceeding 1000 W kg−1.

While Ovonic NiMH batteries are already in high volume commercial production for portable applications, advances in materials technology have enabled performance improvements in specific energy (100 Wh/kg), specific power (600-1000 W/kg), high temperature operation, charge retention, and voltage stability. Concurrent with technology advances, Ovonic NiMH batteries have established performance and commercial milestones in electric vehicles, hybrid electric vehicles, as well as scooter, motorcycle and bicycle applications. As important as these advances, significant manufacturing cost reductions have also occurred which allow continued growth of NiMH technology. In this paper, advances in performance, applications and cost reduction are discussed with particular emphasis on the improved proprietary metal hydride and nickel hydroxide materials that make such advances possible.

With their impressive energy performance and their outstanding power capability, Ni-MH batteries are equally suitable for use in pure and hybrid electric vehicles. This is due to the basic nickel-metal hydride technology. For one thing, hydrogen can be stored in metal-hydride alloys at very high volumetric densities, comparable to the density in liquid hydrogen, leading to the superior energy density of metal-hydride batteries. The operating principles of the Ni-MH battery are described as is their construction and manufacture. The on-road performance of Ni-MH batteries and hybrid electric vehicle batteries are discussed.

Nickel/metal hydride batteries today represent the fastest growing market segment for rechargeable batteries due to the high energy density and more environmentally acceptable chemistry offered by this technology. The high energy density of nickel/metal hydride batteries coupled with high power density and long cycle life make this battery chemistry a key enabling technology for practical electric vehicles, including cars, vans, trucks, and other forms of transportation such as scooters, bicycles, and three-wheelers. This paper provides a review of Ovonic technology and up-dates recent developments in materials and cell development for both consumer electronic and EV applications, and highlights areas for future development.

Although GeTe-${\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}$ (GST) alloys are widely used in data storage, many fundamental issues are still under debate. Here, we demonstrate that the presence of vacancies in the crystalline phase has far-reaching consequences, namely, a triad of twofold coordinated Te atoms with lone-pair electrons generated around the vacancy enables the formation of soft three-center four-electron bonds, whose properties provide an explanation for the unusual characteristics of GST, in particular, the increase in local disorder upon crystallization, the co-existence of a very fast switching rate with a large property contrast, the possibility of a solid-solid amorphization process that excludes conventional melting, and the drastic difference in crystallization behavior between GST and the ideal binary GeTe. Anisotropy of the three-center bonds may serve as an additional degree of freedom for information recording and provide a unified explanation for a variety of unique effects observed in lone-pair semiconductors.

The crystallization of amorphous carbon films, under inert atmospheres, occurs at annealing temperatures above 800 °C. In this work we have found that when the annealing of carbon films is performed under atmospheric conditions, crystallization occurs at temperatures as low as 200 °C. The catalytic effect of oxygen in the crystallization process is understood in terms of the generation of a porous structure in the carbon film due to the vaporization of carbon oxides.

Neutral and ionic gas temperatures (Tn and Ti) are crucial parameters in the plasma processing of materials (etching and film deposition). Here we evaluate a method used for obtaining the temperatures, i.e., the Doppler broadening, of emission lines. We focus on Ar lines from microwave electron cyclotron resonance plasmas. We use the same technique for both ions and neutrals. Three factors are important in achieving accuracy: (1) knowing the correct instrument width at the central wavelength of each ion and neutral line, (2) understanding the noise‐dependent variation in the measured widths, and (3) knowing how the magnetic field affects the spectra. We find that T can be determined to within ∼100 °C. Ti and Tn are typically found to be ∼0.5 and

Amorphous thin film tetrahedrally based alloys have recently achieved an efficiency which permits them in volume production to become competitive to fossil fuels. In this paper, the next stage of development which is to raise stabilized efficiencies to 18% is discussed. It is shown how the scientific and technological problems can be viewed and understood and point to means of solution.

We report the effect that thermal annealing in inert and oxidizing atmospheres, and with and without encapsulating layers, has on the structure of tungsten/carbon [W/C] multilayer thin films. This study focuses on the tungsten component and deals mainly with multilayers where the ratio of thickness of tungsten layers is equal to or greater than for the carbon layers (that is, γ ≤ 0.5). This is in contrast to prior studies where the tungsten layer thickness was generally held constant and the carbon layer was varied. Thermal annealing in inert atmospheres produces reactions and other structural changes in the tungsten and carbide layers which depend on the as-deposited multilayer structure which depends, in turn, on the thickness of the tungsten layer. In samples where both the tungsten and carbide fractions of the multilayer are completely amorphous as deposited, which is the case for thin tungsten layers (thickness of tungsten (tw)4 nm/period), the reactions in the tungsten layer forming crystalline tungsten and tungsten carbide occur at annealing temperatures above 900°C. The layer pair spacing, or period, (d), in this group shows an expansion of up to 10-15% of the original value as has been reported in the past. Changes in both the tungsten and carbide layers, and their interfaces, contribute to changes in d spacing and relative thickness of the high and low Z components. When the tungsten layer thickness exceeds 4 nm per period the tungsten is partially crystallized in as-prepared samples. In such multilayers interfacial reactions, producing an oriented partially crystalline W2C/C superlattice, occur at temperatures of 600°C and below. The fact that W2C crystallites in one period can form a structure which is correlated to W2C crystallites in neighboring layers is somewhat surprising, since layers are presumably still separated by amorphous carbon which is still visible via Raman. The expansion of the layer pair spacing is relatively small (5%) in this group and, more importantly, mostly involves increases in the thickness of the high Z components. Samples annealed in air at temperatures below 300°C are progressively destroyed by the oxidation of both tungsten and carbide layers. Encapsulation of similar multilayers with a thin (30 nm) dielectric layer of any of several types can retard oxidation to 600°C. The silicon-containing encapsulants generally perform better. Failure at this temperature is seen to occur from pinhole formation.

Widespread use of electric vehicles can have significant impact on urban air quality, national energy independence, and international balance of trade. An efficient battery is the key technological element to the development of practical electric vehicles. The science and technology of a nickel metal hydride battery, which stores hydrogen in the solid hydride phase and has high energy density, high power, long life, tolerance to abuse, a wide range of operating temperature, quick-charge capability, and totally sealed maintenance-free operation, is described. A broad range of multi-element metal hydride materials that use structural and compositional disorder on several scales of length has been engineered for use as the negative electrode in this battery. The battery operates at ambient temperature, is made of nontoxic materials, and is recyclable. Demonstration of the manufacturing technology has been achieved.

We describe a pairing mechanism that is based on changes in the O-Cu-O bonds and orbital configurations that occur in the mixed valence planar superconducting ceramics. We discuss the mobility of these spin-zero bosons and their distinctive differences from other proposed real-space bosons.

High-quality epitaxial YBa 2 Cu 3 O 7−δ (F) films were grown directly on r-plane (1 1 02) sapphire by a pulsed laser deposition technique using a multiphase fluorinated target. X-ray diffraction data showed that the film is highly c -axis oriented and in-plane aligned. The c -axis and in-plane mosaic spread are 1.1° and 2.4°, respectively. The microwave surface resistance measured by a con-focal resonator configuration is 56 mΩ at 94.1 GHz at 77 K which is the best reported value for a YBCO film on sapphire. The improved film quality is attributed to the fluorine which is transported from the target to the growing surface of the film where it acts as an etching and/or catalytic agent to preferentially remove defects and second phase impurities and to promote better in-plane epitaxy.

High quality epitaxial YBa 2 Cu 3 O 7-δ (F) films were grown directly on r -plane (1102) sapphire by a pulsed laser deposition technique using a multiphase fluorinated target. X-ray diffraction data showed that the film is highly c -axis oriented and in-plane aligned. The c -axis and in-plane mosaic spread are 1.1° and 2.4°, respectively. The film has a Tc(R=) of 89K with a transition width less than 0.25K. The microwave surface resistance R s measured by a con-focal resonator configuration is 56mΩ at 94.1 GHz at 77K which is the best reported value for a YBCO film on sapphire. The magnetization critical current density is as high as 3x10 7 A/cm 2 at 5K and 2x10 6 A/cm 2 at 77K. A bandpass filter which is centered at 8.1 GHz is fabricated. A very low insertion loss (

The environmental advantages of ovonic NiH/sub 2/ batteries, due to the nontoxicity of ovonic alloys, are briefly discussed, and their general performance is described. Commercial progress in their development is summarized. Their use in electric vehicles is examined. >

Paul Davies, a highly respected theoretical physicist recently stated that "the essence of life is information." 1 I will describe how the essence of information is plasticity, that information is encoded energy requiring what neurophysiologists call plasticity. Plasticity is the ability of neurons through their synapses to have memory, learn, adapt and evolve in response to their environment. I will show that Ovonic memories, both optical and electrical, have rich and deep new physics that make them cognitive devices and therefore open up a huge new field of chalcogenide-based intelligent computers, intelligence that works in a similar manner to the brain. We have shown that the plasticity necessary for an intelligent opto-electronic computer is a function of energy pulses, whether electrical or optical.

Among the various alternative fuels, hydrogen is the only fuel, which is clean and sustainable. More importantly, if hydrogen is produced from renewable resources, virtually no CO 2 emissions are produced. Texaco Ovonic Hydrogen Systems (TOHS) has converted a gasoline internal combustion engine (ICE) hybrid vehicle to a hydrogen vehicle using its advanced metal hydride storage. Compared to its gasoline counterpart, the converted vehiole demonstrated a reduction in CO 2 tailpipe emission of 220 grams per mile. Ovonic metal hydride hydrogen storage systems consist of three critical elements: (1) an advanced metal hydride alloy, (2) an efficient heat exchanger and (3) a lightweight fiber wrapped pressure container. A 50 liter Ovonic metal hydride storage vessel installed in the vehicle provides a storage capacity of 3 kg hydrogen and a driving range of 130-150 miles.

The development of Ovonic nickel-metal hydride (Ni-MH) batteries developed by Ovonic Battery Company, a Subsidiary of Energy Conversion Devices, has led to the introduction of the first commercial hybrid electric vehicles (HEVs), the Toyota Prius and the Honda Insight. All three American domestic automakers have also announced plans to produce HEV sport utility vehicles, more suited to the American market, and with an even greater positive impact on fuel conservation and environmental emissions. Novel water-cooled Ovonic Ni-MH BEV batteries aimed at these applications have been developed with a specific power in excess of 1000 W/kg. Full systems development has provided for production prototype battery packs complete with mechanical packaging, thermal management, electrical power interconnects, and electronic controls meeting vehicle manufacturer requirements. Our manufacturing joint venture with Chevron Texaco, Texaco Ovonic Battery Systems, is expanding its production facilities to meet the market needs for hybrid electric vehicles in North America.

This paper describes a basic new scientific and technological approach for information and computing use. It is based on Ovonic cognitive devices that utilize an atomically engineered Ovonic chalcogenide material as the active medium. We demonstrate how such a device possesses many unique functions including an intrinsic neurosynaptic functionality that permits the processing of information in a manner analogous to that of biological neurons and synapses. Our Ovonic cognitive devices can not only accomplish conventional binary computing, but are capable of non-binary generation of information, storage, encryption, higher mathematics, modular arithmetic and factoring. Uniquely, almost all of these functions can be accomplished in a single nanosized device. These devices and systems are robust at room temperature (and above). They are non-volatile and also can include other volatile devices such as the Ovonic Threshold Switch and Ovonic multi-terminal threshold and memory devices that can replace transistors.

Hydrogen is called the “ultimate fuel.” It is also the ultimate element. It was born in the Big Bang and almost all of known matter is composed of it. Its condensation into a star, our sun, through fusion, provides us the energy and the photons which power our earth and which we can utilize in the form of photovoltaics to break apart water and generate hydrogen as an energy source on earth.The hydrogen economy is here. It has been initiated by the electric and hybrid vehicles which depend upon it for their operation through nickel metal hydride batteries and hydrogen as a fuel for the internal combustion engine and by outwitting the Carnot cycle for use as a fuel cell.I will discuss the complete system needed for the hydrogen economy from generation to storage to infrastructure and use. Any one part of this loop is necessary but not sufficient.Our global economy is based upon energy and the societal needs for a nonpolluting, non-climate change fuel which does not require strategic military defense as does oil. The transition from fossil fuels to hydrogen is of revolutionary import not only for its societal impact but also for the new materials science that it absolutely requires in all of its aspects. New science and new technologies build much needed new industries, which provide not only jobs but also feedback on our educational system.Recall that the ages of civilization are known by their materials. Truly, the presentage will be known by the materials that make up the twin pillars of our global economy – energy and information. Therefore, I will address the new science, technology and atomic engineering of the materials so necessary to make positive, realistic and productive this revolutionary transition of energy from its fossil fuel beginnings to the present.

Energy Conversion Devices, Inc. (ECD) and United Solar Systems Corp. (United Solar) are developing lightweight, flexible photovoltaic modules that can replace conventional roofing materials and be economically and aesthetically integrated into residential and commercial buildings. The modules will be fabricated from high-efficiency multi-junction a-Si alloy solar cells developed by ECD and United Solar. These cells are produced on thin, flexible, stainless steel substrates. Two types of products, 1 ft by 10 ft overlapping PV shingles and 1.3 ft by 20 ft PV roof panels are being developed by United Solar and ECD, respectively. United Solar's shingle type design uses a roof mounting procedures similar to those used with conventional asphalt shingles, while ECD's PV panel uses mounting procedures conforming to metal roof systems. Thus, they can be installed on roof sheathings, replacing ordinary shingles or metal roofing panels, on a standard wood roof construction.

The authors have investigated variations in the a-Si deposition process to achieve a high V/sub oc/ a-Si solar cell to be used as the top cell of a triple-junction stacked solar cell. In this investigation, a-Si n-i-p solar cells were deposited on stainless steel substrates in a multichamber RF PECVD deposition system. Different deposition conditions were explored for the intrinsic a-Si layer with the goal of obtaining high V/sub oc/. After process optimization, the authors have achieved a V/sub oc/ of 1.04 V for a-Si n-i-p solar cells with the intrinsic layer deposited at 150/spl deg/C at high hydrogen dilution. This V/sub oc/ is higher than any V/sub oc/ achieved for a single-junction solar cell using a-SiC as the intrinsic layer. This high V/sub oc/ a-Si material is a better choice for the top cell i layer of a triple-junction a-Si alloy solar cell than high bandgap a-SiC alloys.

In order to improve further the economies of scale which are inherent in continuous roll-to-roll amorphous silicon alloy solar cell manufacturing processes, the authors have developed a concept for a serpentine web plasma CVD deposition process to maximize throughput while keeping the size of the deposition chambers small. When this technique is incorporated into a continuous roll-to-roll PV manufacturing process, it will maximize the throughput for a high volume production plant, reduce the machine cost, improve gas utilization, reduce power consumption, and improve the solar cell stability. To demonstrate the serpentine web deposition concept, the authors have constructed a single loop serpentine deposition chamber to deposit an a-Si for n-i-p structure solar cells. During the initial process of optimization, the authors have produced single-junction a-Si solar cells with an 8.6% efficiency, and triple-junction a-Si solar cells with a 9.5% initial efficiency, where the top cell intrinsic layer was deposited in the serpentine deposition chamber.

The engineering principles used to make >20-A-s/sup -1/ intrinsic layers of good-photovoltaic-quality amorphous silicon over large areas are addressed. Deposition equipment was designed and installed in a plasma-assisted CVD (chemical vapor deposition) roll-to-roll processor. Films were made in this machine with gas mixtures containing silane. Same-bandgap tandem solar cells using this material had 8.2% (average) to 8.6% (best cell) conversion efficiencies. >

The V-Ti-Zr-Ni-Cr alloy system has been developed for Ni-MH batteries. The authors discuss alloy characteristics, implications for cell construction, and advances in cycle life performance for a variety of practical conditions. These alloys have high hydrogen storage capacity, low cost, excellent mechanical and chemical properties, and are easy to manufacture. General performance characteristics of these Ni-MH batteries allow drop-in replacement for Ni-Cd batteries. Cycle life has been established at over 400 cycles under aggressive 100% depth of discharge conditions and under several test conditions emphasizing overcharge and deep discharge. Advanced cell designs have achieved over 700 cycles under 100% DOD conditions, with projections that 1000 cycles may be possible. >

Microcrystalline Si p-layers have been widely used in a-Si solar cell technology to achieve high efficiency. To improve the solar cell performance further, the authors have studied the deposition of high quality /spl mu/c-Si p-layer material using a modified VHF plasma enhanced CVD process and consequently have improved the solar cell current. This improvement was primarily in the blue response which leads to a 6-10% improvement in the overall solar cell efficiency. In addition, they have explored the deposition of a-Si at high rates using VHF plasma and compared these VHF i-layers with RF plasma deposited i-layers. With improved deposition conditions, VHF intrinsic layers deposited at a rate up to 15 /spl Aring//s show similar device performance and light stability to VHF and RF i-layers deposited at low rates and show higher stability than RF i-layers deposited at high rates in the same deposition system. A 10.9% efficient single-junction solar cell was fabricated using a VHF deposited i-layer.

The successful introduction of hydrogen for transportation, consumer and military applications will require the simultaneous introduction of small scale hydrogen production-storage and distribution systems for central depot and residential use. These systems will have to be flexible, safe and economical. An integrated photovoltaic-electrolyzer-metal hydride system will meet these requirements. The system makes use of high efficiency, low cost amorphous silicon photovoltaic panels coupled to alkaline electrolysis cell stacks. The produced hydrogen is in turn stored as a metal hydride. The system can be scaled from a few watts to several kilowatts and installed in virtually any location. Metal hydride hydrogen storage is an inherently safe, low-pressure storage method. The system can be designed to be coupled directly to the application device or used to refill other storage containers. It will therefore be applicable to virtually all hydrogen applications such as fuel cells, combustion and chemical processes. The development of economical, small-scale hydrogen production-storage systems, especially utilizing renewable energy sources, will enable the successful introduction of hydrogen applications in the marketplace. This paper addresses the conceptual design, integration and sizing of the system components.

Nickel-metal hydride batteries are in high volume commercial production for mass market portable applications due to an excellent cost to performance ratio, application to a versatile product mix and environmental acceptability. Ovonic Battery Company Inc. (OBC) a subsidiary of Energy Conversion Devices Inc. (ECD) has established the dominant position in Ni-MH batteries by establishing a fundamental patent portfolio, a network of licensees and business affiliates, and continued product improvement based upon its atomic engineering approach. The largest opportunities for Ni-MH market growth are portable power tools, EV, HEV and fuel cell electric vehicles. These applications benefit from improvements in specific energy, cycle life, high temperature performance, activation/formation, and in particular specific power. Advances in materials technology have enabled performance improvements in specific energy (100 Wh/kg), specific power (1000 W/kg), high temperature operation, charge retention, cycle life and voltage stability. While electrode configuration and packaging are important factors in cell design, at the core of next generation Ni-MH technology are the continuing fundamental improvements to the metal hydride and nickel hydroxide active materials. In this paper, advances in performance, applications and cost reduction are discussed with particular emphasis on the improved proprietary metal hydride and nickel hydroxide materials that make such advances possible.

Performance data for batteries based on multicomponent hydrogen storage alloys using the principles of atomic engineering are presented. In particular, the successful scale-up of this technology for electric vehicle applications is shown. >

Hydrogen $({\mathrm{H}}_{2})$ dilution of the source gas is known to be a key factor in producing hydrogenated amorphous silicon films that demonstrate a high degree of optoelectronic stability. In this work, we investigate, using Raman spectroscopy and high-resolution transmission electron microscopy (TEM), whether microstructural differences exist between such films and those made with no ${\mathrm{H}}_{2}$ dilution (i.e., that have greater instabilities). The key variable is the ${\mathrm{H}}_{2}$ dilution, which ranges from none to very high levels, producing amorphous and microcrystalline silicon films. The TEM results show that embedded within the amorphous matrix are chainlike objects (CLO's) having \ensuremath{\sim}3 nm widths, \ensuremath{\sim}30 nm lengths, and showing a high degree of order along their length. Such order implies vanishing levels of bond-angle distortion (BAD). These CLO's are present in all samples investigated, but their density increases with the level of ${\mathrm{H}}_{2}$ dilution. The Raman spectra show a TO band centered at $490 {\mathrm{cm}}^{\ensuremath{-}1}$ $(37\ifmmode\pm\else\textpm\fi{}3{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ full width). Quantitative analysis shows this band to exist in all samples investigated, but increases in magnitude with increasing ${\mathrm{H}}_{2}$ dilution. In the highest dilutions when microcrystallites are observed, the band is distinctly evident. Its position and width are also consistent with very low (crystallinelike) levels of BAD \ensuremath{\sim}0\ifmmode^\circ\else\textdegree\fi{}. It is thus likely the $490 {\mathrm{cm}}^{\ensuremath{-}1}$ Raman band is a signature of the intermediate ordered CLO's.

Phase change technology has progressed from the original invention of Ovshinsky to become the leading choice for rewritable optical disks. ECD's early work in phase change materials and methods for operating in a direct overwrite fashion were crucial to the successes that have been achieved. Since the introduction of the first rewritable phase change products in 1991, the market has expanded from CD-RW into rewritable DVD with creative work going on worldwide. Phase change technology is ideally suited to address the continuous demand for increased storage capacity. First, laser beams can be focused to ever-smaller spot sizes using shorter wavelength lasers and higher performance optics. Blue lasers are now commercially viable and high numerical aperture and near field lenses have been demonstrated. Second, multilevel approaches can be used to increase capacity by a factor of three or more with concomitant increases in data transfer rate. In addition, ECD has decreased manufacturing costs through the use of innovative production technology. These factors combine to accelerate the widespread use of phase change technology. As in all our technologies, such as thin film photovoltaics, nickel metal hydride batteries, hydrogen storage systems, fuel cells, electrical memory, etc., we have invented the materials, the products, the production machines and the production processes for high rate, low-cost manufacture.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The structures of Ovonic multi-element, multi-phase Zr-based transition metal alloys for hydrogen storage are studied. The alloys are designed to be multi-phase materials. The hexagonal and diamond cubic structures, known as C14 and C15 Laves structures respectively, are the two major hydrogen storage phases in the alloys. In both C14 and C 15 structures, Zr and Ti are the elements typically occupying the hydride former (A) sites and V, Cr, Mn, Fe, Co and Ni the catalytic (B) sites. Based on the application of Ovshinsky's design principles for disordered materials, both A and B sites are compositionally disordered by the corresponding elements in cubic (C15) structure. However, the hexagonal (C14) structure has two distinct B sites, B(I) and B(Il) with a 1:3 ratio. Preliminary neutron diffraction studies indicate that the B(I) sites are predominantly occupied by Ni and the B(ll) sites are randomly mixed with V, Cr, Mn, Fe, and Ni. It is then proposed that the formula of the hexagonal structure should become A2B(I)IB(II) 3 in the current multi-element Zr-based alloys. Minor phases close to the structures of Zr7Ni10, Zr9Ni11, and ZrO2 are also present in some alloys. The average electron concentration factor (e/a) derived from the alloy composition dictates the alloy structures. The alloys with higher electron concentration factor (> 7.1) favor the diamond cubic structure. On the other hand, the hexagonal structure is associated with the alloys with lower electron concentration factor (< 6.5). The alloys having electron concentration factors in between are mixtures of the diamond cubic and hexagonal structures.

Under the PVMat 2A Program, Energy Conversion Devices, Inc. (ECD) has performed manufacturing technology development work utilizing its proprietary continuous roll-to-roll triple-junction a-Si alloy solar cell production line. Among the accomplishments achieved under this program, ECD demonstrated the production of the world’s first 4 ft2 PV modules utilizing triple-junction two-bandgap solar cells manufactured in a commercial, continuous roll-to-roll production line. These 4 ft2 modules had 9.5% initial efficiency and 8% stable module efficiency. ECD has recently designed and constructed a 5 MW continuous roll-to-roll a-Si solar cell processor for its U.S. joint venture, United Solar Systems Corp. (United Solar). The state-of-the-art processor incorporates major advances in solar cell design and manufacturing processes achieved by United Solar and ECD, with support from DOE/NREL. The advanced continuous roll-to-roll triple-junction a-Si module production technology will reduce module production costs, in...

Microcrystalline silicon (μc-Si) p-layers have been widely used in amorphous silicon (a-Si) solar cell research and manufacturing to achieve record high solar cell efficiency. In order to further improve the solar cell performance and achieve wider parameter windows for the process conditions, we studied the deposition of high quality μc-Si p-layer material using a very high frequency (VHF) plasma enhanced CVD process. A design of experiment (DOE) approach was used for the exploration and optimization of deposition parameters. The usage of DOE leads to a quick optimization of the deposition process within a short time frame. In addition, by using a modified VHF deposition process, we have improved the solar cell blue response which leads to a 6–10% improvement in the solar cell efficiency. Such an improvement is likely due to an improved microcrystalline formation in the p-layer.

Significant progress has been made recently at ECD (Energy Conversion Devices, Inc.), in developing new manufacturing technologies for a‐Si (amorphous silicon) photovoltaics. In a 2 MW continuous roll‐to‐roll a‐Si PV (photovoltaics) manufacturing plant, designed and constructed by ECD, we have advanced ECD’s PV technology and demonstrated the manufacturing of 4 ft2 PV modules with 9.5% initial and 8% stable efficiencies. In addition, high subcell yield up to 99.7% has been demonstrated in 600 m long (about 15 kWp) production runs with high uniformity and consistency. ECD has recently designed and constructed an additional pilot manufacturing machine to develop new technologies including high throughput serpentine web continuous roll‐to‐roll deposition of a‐Si alloy materials. When it is incorporated into a large‐scale production line, serpentine technology can maximize the throughput for a high volume production plant, reduce the machine cost, improve the gas utilization, reduce power consumption, and improve the material stability. Using a single loop serpentine chamber to deposit the top i layer, we have demonstrated triple‐junction triple‐bandgap solar cells with 95% initial efficiency.

Energy Conversion Devices, Inc. (ECD) has developed a building integrated PV (BIPV) metal roofing module under the DOE/NREL PV:BONUS program. The module has been designed to be aesthetically and mechanically integrated into residential and commercial buildings. The module is an exact replacement for a metal roofing "pan" manufactured by ATAS International, requires no electrical feedthroughs or additional fasteners, and uses standard metal roofing materials and installation techniques already in use in the metal roofing industry. Consequently this PV roofing retains the watertight features of the best 30 year roofing systems and can be installed by metal roofing contractors with no additional specialized training. The modules are fabricated from multi-junction a-Si alloy solar cells produced on a thin, flexible stainless steel substrate. The polymer encapsulated modules are large-area (typically up to 22 ft long and 1.5 ft wide), lightweight, and flexible. This paper summarizes: the PV module and demonstration array design; the installation procedure; the demonstration program; and the projected cost.

We report the results of production start-up efforts at the 2 MW Sovlux photovoltaic production line. Triple-junction solar cells with higher than 10% initial efficiency were produced in this production line with subcell yield up to 96%. The production process demonstrated high reproducibility and consistency from run to run. 2 ft/sup 2/ and 4 ft/sup 2/ modules assembled in the Sovlux plant using these solar cell material have demonstrated an initial efficiency of 9.4%. The solar cell material produced in Sovlux was also shipped to ECD to assemble large area 1.3 ft. by 20 ft. rooftop modules. Lightweight, flexible rooftop modules with initial efficiency up to 9.3% were produced at a high yield.

Proprietary, multicomponent hydrogen storage materials have been developed making use of the principles of disorder by atomic engineering of the short-range and intermediate -range order. These materials form the basis for Ovonic Nickel-Metal Hydride batteries which have emerged as the leading battery technology for electric vehicle applications. Ovonic Batteries have the highest volumetric energy density available extending the practical range of electric vehicles from under 100 miles to over 200 miles.

Energy Conversion Devices, Inc. (ECD) has designed and constructed a 2 Megawatt (mW) manufacturing line that produces triple‐junction spectrum‐splitting a‐Si alloy solar cells in a continuous roll‐to‐roll process. This manufacturing line has reliably and consistently produced high efficiency solar cells. We have demonstrated the production of 4ft 2 triple‐junction two band‐gap a‐Si alloy PV production modules with 8% stable aperture area efficiency. The production line has successfully incorporated: 1) a band‐gap profiled a‐Si‐Ge narrow band‐gap solar cell deposited in a continuous roll‐to‐roll process using a proprietary gas distribution manifold and cathode configuration; and 2) a textured Ag/ZnO back‐reflector deposited in a continuous roll‐to‐roll sputtering machine with production subcell yields greater than 99%.

Tungsten/carbon (W/C) multilayer thin films prepared by sputtering on unheated Si(100) substrates were encapsulated with various types of layer having low x-ray absorption. Isochronal annealings for 1 hr in the temperature range from 300 to 600 degree(s)C and isothermal annealings at 300 and 400 degree(s)C were carried out under ambient conditions (in air) on coated and uncoated multilayers. The encapsulated layers are: SiN x and SiO 2 prepared by plasma enhanced chemical vapor deposition (PECVD) and SiC, Al 2 O 3 , C and B 4 C prepared by sputtering techniques. Previous studies have shown that unprotected W/C multilayers annealed in air exhibit oxidation at relatively low temperatures (approximately 300 degree(s)C). In the present study, we have used Raman scattering (RS), Auger depth profiling and scanning electron microscopy (SEM) to investigate the effects of thermal treatments on the encapsulated W/C multilayers. The results indicate that oxidation of both W and C layers takes place during annealing at temperatures which depend on the type of protective layer. For example, in the isochronal annealing experiments, multilayers coated with C, Al 2 O 3 and B 4 C suffer oxidation during annealing at 400 degree(s)C, whereas multilayers coated with the other three types of protective films prevent multilayers from oxidation at annealing temperatures as high as 600 degree(s)C. SEM micrographs show that the formation of pinholes through the protective layer occurred during annealing at the temperatures for which oxidation was first detected. Auger profiling shows the loss of compositional modulation in the region reached by oxygen. A WO 3 phase is identified by RS in the oxidized region, and the loss of the C layers is most likely due to the formation of carbon oxide vapors.

Tungsten/carbon (W/C) multilayer thin films with a nominal d spacing varying from 2.5 to 14 nm were prepared by magnetron sputtering technique. The thicknesses of the W and C layers were varied from 0.5 to 12 nm. The multilayers were subjected to isochronal anneals in a quartz tube furnace in the range of 300 to 1000 C under high purity Ar flow conditions. X-ray diffraction, Raman scattering and Auger depth profiling were used to characterize the structure of the as-prepared and annealed films. It is found that an overcoat layer of silicon nitride (30-50 nm) prevents the multilayers from oxidation during the 1 hr heat treatment at temperatures as high as 1000 C in Ar flow. In all studied W/C multilayers, the carbon layers are amorphous (up to 12 nm). The tungsten layers are also amorphous when their thicknesses are less than 5 nm. Tungsten layers thicker than 5 nm show crystalline W peaks in addition to the amorphous W feature. Annealing of samples with a silicon nitride protective layer results in several structural changes which depend on annealing temperature, d spacing, the as-deposited W layer structure and the layer thickness ratio of W to C. For W layer thicker than C layer and W layer thickness > 4 nm and/or C layer thickness < 1 nm, the multilayers show the initial crystal formation of microcrystalline W2C occurring at C-W interfaces (that interface in which C was deposited on W) after 600 C anneal, followed by a second crystallization of a-W or a-W and WC at W-C interfaces (W was deposited on C) at the annealing temperature of 900 C. They reveal a relatively small (< 5 %) or essentially no layer expansion. For those multilayers having thin W layers (2 nm) and the same or thicker C layer thicknesses, the initial crystallization takes place at both W-C and C-W interfaces at 900 C or higher. The crystal formed is a-W or a-W and WC. The layer pair period of the multilayers in this group increases monotonically with increasing annealing temperature. Expansion is up to 16 % of the original d spacing and occurs in both W and C layers at approximately equal rates. The expansion in all multilayers is interpreted to be associated mainly with the structural ordering processes in the amorphous W and C layers.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report on evidence that fluorine, properly incorporated into a-Si, replaces weakly bonded hydrogen and improves the material stability under light soaking. Our fluorinated amorphous silicon (a-Si:H:F) is made by if glow discharge at high deposition temperatures up to 430 C from a gas mixture of SiH4 or Si2H6 and F2. These a-Si:H:F films show much lower density of states in the light soaking saturated state than device quality a-Si:H prepared in the same deposition system. It is evident from our results that fluorine incorporated into the network at such high deposition temperature makes for a new configuration which minimizes dangling bonds and other defects.