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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.

Parathyroid hormone-related protein (PTHrP) immunoreactivity has been detected in the bladder and increases in response to dilatation secondary to obstruction. The hypothesis that PTHrP could be increased solely by stretch rather than other possible in vivo variables was tested by stretching cultured bladder smooth muscle cells and analyzing the culture medium for this protein. In response to mechanical stretch, PTHrP was increased in smooth muscle cell cultures. Immunoradiometric assay revealed maximal rates of secretion for the first eight hours. Comparison of percent change in PTHrP secretion of flexed cells for the various flex parameters revealed a difference (p = .006) when the degree of stretch (i.e. percent elongation) was altered. The protein synthesis inhibitor cycloheximide inhibited basal and stretch-induced PTHrP secretion.PTHrP (1-100 nM) relaxed carbachol-contracted bladder body and base by 15% and 45% respectively. PTHrP did not affect bladder contractions induced by potassium (124...

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.

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.

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. >

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.

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 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 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.

The thermal activation energy, AE, of the conductivity in amorphous chalcogenide semiconductors is usually about half of the optical gap energy E. This is commonly interpreted as (intrinsic) conduction at the mobility edge by carriers whose concentration is governed by the Fermi energy EF which is pinned near the gap center. Small changes in glass composition and the presence of impurities usually have little effect on the properties except for small changes in EO and AE with composition. The insensitivity to impurities is ascribed to the fact that in a material lacking long-range order each foreign atom can satisfy its valency requirement,(1) and, thus, will not act as an electrically active center. The origin of the various states in the gap (DECs) (2,3) and the pinning of EF is attributed to those DECs which are inherent valence alternation defect centers.

The relationship between electronic conduction and stereochemical local bonding arrangements is illustrated by four examples: the unusual high conductance ON-state of the Ovonic Threshold Switch resulting from nonequilibrium excitation processes the high conductivity connected with the oxidation states of the Ovitron, the chemical modification of electronic transport in amorphous semiconductors and insulators, and the high temperature copper oxide ceramic superconductors. We discuss the effect of fluorination on raising the superconducting transition temperature to Tc=155K or higher, on eliminating oxygen diffusion and on orienting the crystallites in the YBaCuO superconductors.

The position of the Department of Energy (DoE) reiterated specifically at this meeting (1) is that photovoltaic solar energy conversion will not begin to make a large-scale contribution to our overall energy production until 1986 at the earliest, and more probably the year 2000. It is the theme of this paper that the basic materials problems which have led to such pessimistic projections have already been solved and that, given an intensive program of development, economically competitive photovoltaic cells can be mass produced in the near future.

The US Department of Energy is probably the best known body to have claimed that photovoltaic conversion devices cannot compete with fossil tuels or uranium until at the earliest 1986, or more likely 2000. Such statements are based on the known current technological problems of three types of silicon—single crystal, polycrystalline, and amorphous. With amorphous silicon the chief difficulty has been the high density of states (as explained by Taylor on p 672) which restricts the necessary current flow.

Photovoltaic devices based on amorphous alloys of silicon with H and/or F have recently generated substantial interest in the photovoltaic community and the larger solid state physics and electronics communities as well. These developments have been reviewed recently by D. Carlson of RCA Labs(1). It was Carlson’s early collaboration with C. Wronski(2) which served to rekindle scientific and technological interest in a-Si:H produced by the glow discharge induced decomposition of SiH4 gas and the deposition of Si-rich fragments of this gas onto substrates held at 200–300°C(3–5).

There are three key issues that challenge amorphous photovoltaics, namely, efficiency, stability, and production. In this paper we will review the current status of our amorphous photovoltaics at ECD in terms of these three issues and demonstrate how we have broken the efficiency-stability-production barrier.

It is difficult to do justice to the scientific and technological impact of the recent discoveries in high Tc superconducting ceramic oxides. It is now clear that the oxides that were the basis of the lanthanum copper oxide ceramics which moved the superconducting temperature from 23 to 30 to 40K (1) have been around for some time.(2,3)

It is well known in crystalline tetrahedral semiconductors that conventional incorporation of atoms by substitutional doping increases the electrical conductivity by many orders of magnitude. Such doping is the basis of the crystalline semiconducting industry and has recently been extended to amorphous silicon and germanium, with hydrogen appearing to play an important compensating role.(1–3)

An important difference between crystalline and amorphous structures is that while in crystals the local environment is the same everywhere, in amorphous materials one finds a large spectrum of 3-dimensionally varying spatial and bonding relationships. This gives rise to unique energy interactions, orbital overlaps and bonding configurations of the lone pair electrons associated with the group VI chalcogen atoms which do not occur in crystals. We present the ‘ball and spoke’ models we have built to test out the concepts of lone pair relationships discussed earlier (Ovshinsky 1972, Ovshinsky 1973, Ovshinsky and Fritzsche 1973).

There is a need for alternative energy sources. Photovoltaics are an attractive possibility, but their application has been limited by economic considerations in single-crystal materials, and for physical reasons such as grain boundaries in poly-crystalline materials. Amorphous semiconductors are especially attractive in this regard because they are basically much less expensive than their crystalline counterparts and because they possess a direct band gap with a high value for the optical absorption coefficient. We report here the development of a new alloy that eliminates the physical problems associated with the silicon-hydrogen alloys.

A working model is offered to explain the mechanism of high temperature superconductivity in ceramic materials. In this model there are several interdependent, subtly balanced processes which combine to create new and unique phenomena due to the stereochemical nature of these materials.

A positive electrode material comprising particles (1) including at least one electrochemically active hydroxide and a substantially continuous, uniform encapsulant layer (4) surrounding the particles of positive electrode material. The encapsulant layer is formed from a material which, upon oxidation during processing or charging of the electrode, is convertible to a highly conductive form and upon subsequent discharging of the electrode does not revert to its previous form. Preferably, the electrochemically active hydroxide includes at least nickel hydroxide. The encapsulant layer is preferably formed from at least cobalt hydroxide or cobalt oxyhydroxide and is formed by precipitation from a cobalt salt solution, which can be a cobalt sulfate solution. Electrodes which include the electrochemically active material as well as a precipitation process for forming the material are disclosed.

Amorphous Si:F:H with desirable properties for photovoltaic applications can be fabricated by the glow discharge of SiF4 and H2. The preparation conditions influence the properties of the resultant alloy. For instance, altering the ratio of SiF4 to H2 from 80 to 5 can alter the localized state density from 1019cm−3eV−1 to ≃ 1016cm−3eV-1, respectively. The conduction mechanisms are altered and there are vast changes in the photoconductivity as the density of recombination centers is decreased. The lower density of states achieved in the a-Si:F:H alloy reflects in the ease of doping. In addition, the lower density of states in a-Si:F:H alloy should result in a wider depletion region than reported for the a-Si:H alloy when fabricated within the device configuration. Results of C-V measurements using Au Schottky barrier devices confirm this.

We have grown amorphous silicon-germanium alloys by rf glow discharge decomposition of disilane, germane, silicon tetrafluoride and hydrogen. Films with an optical band gap in the range of 1.72 to 1.2e V have been made. The optimized films show the following properties: 1) incorporation of germanium is uniform across the length of the sample; 2) hydrogen is bonded to silicon and germanium uniformly without any preference; 3) the slope of the valence band tail remains constant as the optical gap is lowered down to 1.25eV and 4) use of silicon tetrafluoride in the gas mixture improves the quality of the material. Photothermal deflection spectroscopy and space charge limited conduction were used to obtain information about the deep states. Even for the lowest band gap material, the density of states at the Fermi level is about 10 17 cm −3 eV −1 which demonstrates the high quality of the material.

Platelets are an active element in the generation of thrombus and may influence rates of thrombolysis during the administration of plasminogen activators. To assess the potential importance of platelet aggregation in the thrombolytic response to plasminogen activators, we measured rates of thrombolysis induced by tissue plasminogen activator in the presence and absence of a coinfusion of prostaglandin E1 in a rabbit jugular vein model of thrombosis. Rates of lysis were quantified by measuring the half-time for lysis of the thrombus. At all concentrations of tissue plasminogen activator used, prostaglandin E1 markedly reduced the half-time for clot lysis and enhanced somewhat the overall extent of thrombolysis, without affecting significantly either the degree of fibrinogen depletion or the animals' mean arterial pressures. These effects on thrombolytic efficacy were accompanied by ex vivo evidence of platelet inhibition. These data suggest that the antiplatelet prostaglandin E1 may be a very useful adjunctive agent in thrombolytic therapy primarily by virtue of the significant improvement in the rate of thrombolysis that its use affords.

Previously we have shown that amorphous silicon-based alloys containing F and H (1–7) possess desirable properties for photovoltaic application. Amorphous tetrahedral semiconductors ordinarily possess a very large density of states which act as traps leading to low values for drift mobility and low recombination lifetimes of free carriers. However, Spear and his group (8–10) reported that a-Si decomposed from SiH4 gas by r.f. glow discharge and deposited on a heated substrate produces a film which has a comparatively low density of states. However, materials prepared in this way possess a large concentration of H.(11) Because of the relatively low density of states, these types of films can be doped n type, albeit using relatively large concentration of the dopant. However, p-type doping using B2H6 is generally accompanied with the decrease in the band gap, indicating alloying action rather than conventional doping.(9) Furthermore, the material has apparently a sufficiently large carrier lifetime that efficiencies of photovoltaic devices exceeding 5% have been reported.(12)

THE AMORPHOUS-CRYSTALLINE transition in a-Si and a-Ge has been studied for many years [1,2]. However, unlike electrical and optical properties, no substantial modifications on the RDF (radial distribution function) for the amorphous phases have been reported for different methods of preparation or annealing conditions short of crystallization. More recently, Barna et al. [3] have found a small shift of the second peak in the RDF towards smaller r, and a more pronounced peak at 5 A for the a-Si: H prepared by glow discharge technique. These authors concluded that a higher degree of local order is present in the glow discharge a-Si: H although they stated that there exist only minor differences in amorphous silicon samples with different preparations. Earlier Raman measurements [4] have not been shown to be sensitive to preparation conditions, however, recent results indicated that Raman measurements can indeed differentiate various types of amorphous silicon samples. Tsu et al.

Since the publication of the paper announcing the discovery of reversible switching phenomena in certain types of chalcogenide glasses [1], much effort has been devoted towards the characterization, improvement, and understanding of the properties of these materials [2]. This interest has been stimulated both by the basic scientific questions that have to be answered in order to understand the structures and properties of these alloys, and by their obvious potential as reversible threshold and memory switching elements in a wide variety of electronic devices [2,3].

A roll-to-roll plasma deposition machine for depositing multilayered amorphous alloys has been developed. The plasma deposition machine has multiple deposition areas and processes a stainless steel substrate 16 in wide continuously. Amorphous photovoltaic thin films (less than 1 μm thick) with a six-layer structure (p-i-n-p-i-n) are deposited continuously in a single pass onto a roll of stainless steel substrate 16 in wide and 1000 ft long. Mass production of low cost tandem solar cells utilizing roll-to-roll processes is now possible. A commercial plant utilizing this plasma deposition machine for manufacturing tandem amorphous silicon alloy solar cells is now in operation.

Photovoltaic quality films of a-Si:F:H prepared by the plasma-induced reaction of, for example, SiF4 and H2 appear to contain unusual bonding configurations involving the intimate association of silicon with both fluorine and hydrogen atoms.(1) The creation of radical sub-fluorides of silicon has been suggested as a mechanism for the deposition of such films.(2) Indeed, the presence of various excited-state neutral and ionic silicon radical species has been demonstrated in the optical emission of plasmas containing SiH4, SiF4 and H2,(3,4) and the silylene radical, SiH2, has been proposed to play a dominant role in the deposition of a-Si:H from the H0M0CVD of SiH4.(5)

As glow discharge amorphous silicon alloys become more important for commercial production of photovoltaic, xerographic, optical sensing, and microelectronic devices, economic considerations have motivated considerable research aimed at increasing deposition rate and gas utilization efficiency. Recently, a low pressure microwave glow discharge process was reported (1) which produces good quality a-Si:F:H films, with essentially 100% gas utilization at deposition rates > 100A/sec.

Description of a double-injection space-charge process which can account for the principal features of amorphous threshold switching, and discussion of its applicability to chalcogenide glasses under various operating conditions.

We describe here a rapid and reversible transition between a highly resistive and a conductive state effected by an electric field which we have observed in various types of disordered materials, particularly amorphous semiconductors1,2 covering a wide range of compositions. These include oxide- and boron-based glasses and materials which contain the elements tellurium and/or arsenic combined with other elements such as those of groups III, IV, and VI.

Differential thermal analysis (DTA) and differential calorimeter (DCA) measurements were performed between 300 and 800°K on chalcogenide alloy glasses of various compositions. Fast and slow cooling cycles were used to determine the rates of structure formation. After each thermal cycle the electrical conductivity was determined. These studies were supplemented by thermal expansion measurements. The calorimetric studies distinguish between materials (i) which show no memory effect but only ovonic switching action and (ii) those which show switching effect with memory action. The memory materials (ii) show an exothermic reaction at a temperature T1 between 200–300°C and an endothermic reaction at a higher temperature. The bistable resistance state of these materials is associated with the formation near T1. The other materials (i) do not show any reaction and remain highly resistive even after slow cooling from the melt.

The need for continuous monitoring of species like H/sub 2/S and CH/sub 3/SH in the atmosphere is obvious because of their toxic nature and is particularly important in synfuel production and geothermal energy utilization. Chemiluminescence under the right conditions is an extremely sensitive method, with the possibility of obtaining one photon for each molecule of interest. It is apparent that a selective detector should be based on emission from a species related chemically to the analyte rather than the reagent. ClO/sub 2/ is an interesting reagent in that it reacts, vide infra, with H/sub 2/S and CH/sub 3/SH to produce sulfur atoms, which recombine to form electronically excited S/sub 2/ and in turn result in fluorescence. To minimize the effects of quenching, one must keep the reaction zone at reduced pressures. To maximize sensitivity despite the high-order reaction, one must keep the volume of the reaction zone small, and the reagent gas (ClO/sub 2/) must be in excess to produce complete reaction in a pseudo-first-order regime. A successful on-line chemiluminescence detector is therefore dependent on meeting these various design parameters and is reported here.

We have developed an amorphous silicon alloy based solar cell with a novel structure in which the optical gap of the intrinsic layer changes in a substantial portion of the bulk. Computer simulation studies show that for a given short circuit current, it is possible with this structure to obtain higher open circuit voltage and fill factor than in a conventional cell design. Experimental cell structures have been made and confirm the theoretical prediction. The new cell design shows a considerable improvement in efficiency. Incorporation of this structure in the bottom cell of a triple device has resulted in the achievement of 13.7% efficiency under global AM1.5 illumination.

A process is described which provides a simple, automatic means for quickly reducing the deleterious effects of shunts in completed thin‐film solar cells. The method has been used to passivate current shunting defects in large area, mass produced solar cells made from amorphous silicon alloys. In the passivation process, photovoltaic devices are exposed to an electrochemical bath which selectively converts the top surface conducting oxide to a lesser conducting state at the vicinity of shunts. The process and its utility in repairing defects will be described.

The development of a photovoltaic power generating module is presented. The module is a tandem cell solar generator made using roll-to-roll amorphous silicon alloy thin-film deposition technology. This product is a large-area (1 ft*4 ft) single solar cell that eliminates the distinction between a cell and a module. Device series connections occur externally at the module level, resulting in substantial reductions in fabrication costs. >

We have achieved 13% efficient amorphous silicon solar cells in the laboratory and in the 8–9% range in production. We will describe how we have solved the problems of efficiency, stability, and continuous-web production of large-area thin-film amorphous silicon photovoltaic devices.

When I first began to study amorphous materials in the mid 1950’s, the field appeared to be as mysterious as hieroglyphics had been to renaissance scholars. While it was taken for granted that amorphous materials had no real significance scientifically or technologically, it was clear to me, even then, that this was a rich, unexplored, and important area of science [for early references see 1–5]. Until then its major thrust was in the ancient art of glass making, and glass meetings devoted inordinate amounts of time to discussing “What is glass?”

We have used molecular-beam deposition (MBD) with a base pressure of 10–10 torr to prepare a-Si and a-Ge at relatively low substrate temperatures. The films contain voids which can adsorb gases such as H2, F2, SiF4, GeF4, O2, etc. Due to the high reactivity of the dangling bonds present, these molecules are broken down to their atomic constituents, thereby passivating the dangling bonds. Further annealing is required to form proper chemisorption and drive the passivating agents into smaller or isolated voids. Typically a decrease of dark conductivity by as much as 8 orders of magnitude is observed accompanied by the appearance of few decades of photocurrent above the dark current under (Air Mass 1) AM1. For a-Ge, using a similar procedure, fluorine is more effective as a passivating agent than hydrogen.

A roll-to-roll plasma deposition machine for depositing multi-layered amorphous alloys has been developed. The plasma deposition machine (approximately 35 ft. long) has multiple deposition areas and processes 16-inch wide stainless steel substrate continuously. Amorphous photovoltaic thin films (less than 1pm) having a six layered structure (PINPIN) are deposited on a roll of 16-inch wide 1000 ft. long stainless steel substrate, continu-ously, in a single pass. Mass production of low-cost tandem amorphous solar cells utilizing roll-to-roll processes is now possible. A commercial plant utilizing this plasma deposition machine for manufacturing tandem amorphous silicon alloy solar cells is now in operation. At Energy Conversion Devices, Inc. (ECD), one of the major tasks of the photovoltaic group has been the scale-up of the plasma deposition process for the production of amorphous silicon alloy solar cells. Our object has been to develop the most cost effective way of producing amorphous silicon alloy solar cells having the highest efficiency. The amorphous silicon alloy solar cell which we produce has the following layer structure: 1. Thin steel substrate. 2. Multi-layered photovoltaic amorphous silicon alloy layers (approximately 1pm thick; tandem cells have six layers). 3. ITO. 4. Grid pattern. 5. Encapsulant. The deposition of the amorphous layer is technologically the key process. It was clear to us from the beginning of this scale-up program that amorphous silicon alloy solar cells produced in wide width, continuous roll-to-roll production process would be ultimate lowest cost solar cells according to the following reasons. First of all, the material cost of our solar cells is low because: (1) the total thickness of active material is less than 1pm, and the material usage is very small; (2) silicon, fluorine, hydrogen, and other materials used in the device are abundant and low cost; (3) thin, low-cost substrate is used; and (4) product yield is high. In addition, the development of high efficiency cells in future time will further reduce the material cost. Secondly, the labor cost associated with the production of our solar cells is low because our process utilizes simple, high production rate, highly automated processing for the complete fabrication of photovoltaic modules. Specifically, six layers of tandem amorphous silicon alloy solar cell are plasma-deposited on a roll of wide stainless steel substrate, continuously in a single pass. Over one order of magnitude increase in the line speed is straightforward from an engineering point of view. Other downstream process steps for the fabrication of photovoltaic modules also utilize simple, high production rate, highly automated machineries.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Tellurium-based chalcogenide alloys, which are used for electronic switch materials, also have the appropriate optical and thermal properties for reversible optical data recording. One of the major concerns encountered with this type of phase change material is that there can be two contradictory characteristics of the material, i.e., the amorphous phase thermal stability and the crystallization rate are involved. We have demonstrated, in this paper, that this problem can be solved. We report that certain transition metal elements added to Te alloy films can substantially improve the rate of crystallization without any reduction of the amorphous phase stability.

A manufacturing plant for producing thin-film amorphous silicon alloy based solar cells using roll-to-toll deposition is being operated by Sovonics Solar Systems in Troy, Michigan, USA. The authors detail the performance of solar cells produced at this plant. Roll-to-roll deposition on stainless steel has been shown to be a viable method of producing high-quality thin-film solar cell materials. Various thin-film depositions are made on 1000-foot-long rolls of 14-inch-wide, thin stainless steel in the deposition facility. The rolls are then cut into appropriate sizes for module fabrication. Quality analysis, in situ deposition monitoring, and post deposition measurements have enabled a detailed analysis of production run data, including such parameters as layer thickness, adhesion, conversion efficiency, yield, etc. These and other properties of the photovoltaic materials and devices have been monitored and studied in order to optimize the roll-to-roll deposition process. >

The authors have developed an amorphous silicon alloy-based solar cell with a novel structure. Computer simulation studies show that for a given short-circuit current, it is possible to obtain a higher open-circuit voltage and fill factor than in a conventional cell design. For a nominal 1.5 eV a-SiGe alloy, the fill factor under red illumination can be improved from 0.55 to 0.64 for the same short-circuit current. Experimental cell structures confirm the theoretical prediction. The novel cell design shows a considerable improvement in efficiency. Dynamic internal collection efficiency measurements show reduced recombination in these cells, which gives rise to the observed higher fill factors. Incorporation of this structure in the bottom cell of a triple device has resulted in the achievement of 13.7% efficiency under global AM1.5 illumination. >

The solid-state revolution, which began in 1947 with the invention of the transistor, was made possible by the ability to make crystalline materials (at that time germanium) sufficiently free of defects that substitutional dopants could overcome the background noise of other defects and control the electronic transport properties of the semiconductor. Since the early 1930’s Bloch, Wilson, and others had laid a sufficient theoretical groundwork in semiconductors so that transistor action could be predicted, demonstrated, and understood even though the point contact transistor had many mysteries associated with it. Figure 1 shows that historical lever that moved the world, the first transistor.

The use of fundamental chemical bonding considerations in the determination of the structures and properties of a wide variety of glasses with predominantly covalent bonding is reviewed. Simple considerations based on chemical ordering, coordination numbers and bond energies, can often be used to obtain information concerning the nature of the average local order around any given type of central atom in such an alloy glass. This information enables the explanation and prediction of various physical, chemical and electrical properties. Examples of these procedures are given by examining some chalcogenide glasses of interest due to their reversible threshold switching (Si18Ge7As35Te40) and memory switching (Ge15Te81Sb2S2 and Ge24Te72Sb2S2) properties.