Monolithic Series Research Articles

Monolithic Blue LED Series Arrays for High-Voltage AC Operation

Design and fabrication of monolithic blue LED series arrays that can be operated under high ac voltage are described. Several LEDs, such as 3, 7, and 20, are connected in series and in parallel to meet ac operation. The chip size of a single device is 150 μm × 120 μm and the total size is 1.1 mm × 1 mm for a 40 (20 + 20) LED array. Deep dry etching was performed as device isolation. Two-layer interconnection and air bridge are utilized to connect the devices in an array. The monolithic series array exhibit the expected operation function under dc and ac bias. The output power and forward voltage are almost proportional to LED numbers connected in series. On-wafer measurement shows that the output power is 40 mW for 40 (20 + 20) LED array under ac 72 V.

Microcrystalline silicon and the impact on micromorph tandem solar cells

Intrinsic microcrystalline silicon opens up new ways for silicon thin-film multi-junction solar cells, the most promising being the tandem concept. The microstructure of entirely microcrystalline p-i-n solar cells is investigated by transmission electron microscopy. By applying low pressure chemical vapor deposition ZnO as front TCO in p-i-n configurated micromorph tandems, a remarkable reduction of the microcrystalline bottom cell thickness is achieved. Micromorph tandem cells with high open circuit voltages of 1.413 V could be accomplished. A stabilized efficiency of around 11% is estimated for micromorph tandems consisting of 2 μm thick bottom cells. Applying the monolithic series connection, a micromorph module (23.3 cm2) of 9.1% stabilized efficiency could be obtained. © 2002 Elsevier Science B.V. All rights reserved.

Optical properties of silicon-based thin-film solar cells in substrate and superstrate configuration

Abstract The optical properties of microcrystalline silicon substrate-type solar cells with a front ZnO thickness of 500–1000 nm as required for monolithic series connection in PV-modules are investigated. The surface texture of the front ZnO was varied to study the possibility to reduce reflection losses and to improve light trapping. Before encapsulation, certain textures of the front ZnO exhibit improved light coupling for substrate solar cells. For substrate solar cells encapsulated with EVA and a glass cover, however, additional texture of the front ZnO has hardly any effect. Encapsulation also removes the antireflection conditions in case that the front ZnO was originally designed as ARC. So far, the quantum efficiency of encapsulated substrate solar cells does not show the high level as observed in superstrate solar cells possibly due to parasitic absorption in the front and back contact and the not optimized texture of the reflector (substrate).

The influence of monolithic series connection on the efficiency of GaAs photovoltaic converters for monochromatic illumination

This paper presents a theoretical study of the performance and optimization of monolithically series connected GaAs photovoltaic converters under homogeneous monochromatic illumination. The effects of base resistance, perimeter recombination, and isolation trench optical losses on device efficiency are especially highlighted. All the calculations are made for values of the number of individual photovoltaic converters connected in series, n, of 1 (such is the case of a conventional GaAs photovoltaic converter without monolithic connection) 2, 3, and 6. The results show that the losses in monolithic connection can be minimized by means of an increase in device area together with the inclusion of a highly doped lateral conduction layer, and that monolithic connection does not lead to a greater immunity from high series resistance relative to a conventional photovoltaic converter (as stated in literature). The maximum efficiencies predicted are 60.2, 58.9, 58.5, and 57.5% for n=1, 2, 3, and 6, respectively, for an illumination power density of between 10 and 20 W/cm/sup 2/ and a wavelength of 830 nm. Nevertheless, if a dc-dc converter is considered to boost the voltage of an n=1 GaAs photovoltaic converter (with losses associated to this circuit usually of 20%), its maximum efficiency drops to 48.2%.

Microcrystalline/micromorph silicon thin-film solar cells prepared by VHF-GD technique

Hydrogenated microcrystalline silicon prepared at low temperatures by the glow discharge technique is examined here with respect to its role as a new thin-film photovoltaic absorber material. XRD and TEM characterisations reveal that microcrystalline silicon is a semiconductor with a very complex morphology. Microcrystalline p–i–n cells with open-circuit voltages of up to 560–580 mV could be prepared. “Micromorph” tandem solar cells show under outdoor conditions higher short-circuit currents due to the enhanced blue spectra of real sun light and therefore higher efficiencies than under AM1.5 solar simulator conditions. Furthermore, a weak air mass dependence of the short-circuit current density could be observed for such micromorph tandem solar cells. By applying the monolithic series connection based on laser patterning a first micromorph mini-module (total area of 23.6 cm 2) with 9% cell conversion efficiency could be fabricated.

Progress in monolithic series connection of wafer-based crystalline silicon solar cells by the novel ‘HighVo’ (High Voltage) cell concept

Progress in the development of the new HighVo cell concept for monolithic series connection of wafer-based crystalline silicon solar cells is presented. HighVo cells have been produced using standard low-cost silicon wafer technology without any photo lithographic masking step. The cells obtained with a total area of 21 cm 2 exhibited a voltage at the maximum power point V MPP of 2.8 V and a conversion efficiency η of 11.4 %. To our knowledge this is the highest conversion efficiency reported so far for monolithically integrated non-thin-film silicon solar cells.

00/02741 Three-layer organic solar cell with high-power conversion efficiency of 3.5%

A new type of photovoltaic module based on monolithically series connected dye sensitized photoelectrochemical cells is described. Each solar cell element consists of three porous layers on a transparent conducting substrate, namely a photoelectrode of dye sensitized nanocrystalline TiO2 (anatase), a spacer of electrically insulating, light reflecting particles of TiO2 (rutile), and a counterelectrode of graphite powder and carbon black. The pores of these layers are filled with a redox electrolyte containing iodide for hole transport between photo- and counterelectrode. The monolithic series connection on the transparent conducting substrate, e.g., SnO2 coated glass, is achieved by simple overlap of each carbon counterelectrode with the back contact of the adjacent photoelectrode. Such modules may be produced in a continuous non-vacuum process by simple printing techniques. In this paper we present the first results on energy conversion efficiency and long term stability obtained with this new type of solar cell.

Novel Amorphous Silicon Solar Cell using a Manufacturing Procedure with a Temporary Superstrate

AbstractWe developed a novel temporary-superstrate concept for SnO2/p-i-n amorphous silicon solar cells. This concept combines roll-to-roll manufacturability, the utilization of light scattering, the conductive properties of SnO2:F, and the possibility of monolithic series connection. To this purpose, the deposition of high quality textured SnO2:F layers on aluminum foil has been developed using APCVD. Layers have been obtained with a transmission of 80 % and a sheet resistance of 12 Ω/□. After definition of the entire p-i-n cell structure including the back contact, the cell is laminated with a permanent carrier foil. By removing the aluminum foil, light can enter the cell through the textured TCO layer. A wide variety of transparent encapsulants can be used to finalize the (flexible or preshaped) product. Preliminary cells made according to this scheme have an efficiency of 6 %.

5593901 Monolithic series and parallel connected photovoltaic module : Oswald Robert; Mongon John; Weiss Peggy Newtown, PA, United States assigned to Amoco/Enron Solar

5593901 Monolithic series and parallel connected photovoltaic module : Oswald Robert; Mongon John; Weiss Peggy Newtown, PA, United States assigned to Amoco/Enron Solar

Induced superconductivity in InAs quantum wells with superconducting contacts

Modulation-doped InAs quantum wells with AlSb barriers and superconducting Nb electrodes form a model system for semiconductor-coupled superconducting weak links in the ballistic (‘clean’) limit. A tutorial outline of their general physics is presented, followed by a discussion of selected properties of monolithic series arrays of such links, especially the puzzling temperature dependence of their current–voltage characteristics.

Low cost photovoltaic modules based on dye sensitized nanocrystalline titanium dioxide and carbon powder

A new type of photovoltaic module based on monolithically series connected dye sensitized photoelectrochemical cells is described. Each solar cell element consists of three porous layers on a transparent conducting substrate, namely a photoelectrode of dye sensitized nanocrystalline TiO 2 (anatase), a spacer of electrically insulating, light reflecting particles of TiO 2 (rutile), and a counterelectrode of graphite powder and carbon black. The pores of these layers are filled with a redox electrolyte containing iodide for hole transport between photo- and counterelectrode. The monolithic series connection on the transparent conducting substrate, e.g., SnO 2 coated glass, is achieved by simple overlap of each carbon counterelectrode with the back contact of the adjacent photoelectrode. Such modules may be produced in a continuous non-vacuum process by simple printing techniques. In this paper we present the first results on energy conversion efficiency and long term stability obtained with this new type of solar cell.

Treatment of hypertension: the place of angiotensin-converting enzyme inhibitors in the nineties.

The past decade has seen a shift in the strategy for hypertension treatment from stepped therapy--a highly structured monolithic series of steps--to recommendations for a more individualized selection of treatment. Severe hypertension is a clear indicator to bypass traditional steps. Demographic factors, such as age, gender, and race, are often cited, but have proved to be less helpful. Concomitant medical conditions and problems are very common and are more often the crucial determinants in the selection of antihypertensive therapy. Coronary artery disease, diabetes mellitus, heart failure, azotemia, asthma, and chronic obstructive pulmonary artery disease, anxiety, and depression are all common, and each has implications for the selection of antihypertensive therapy. Blood pressure reduction is a surrogate for reduction of cardiovascular risk, and therefore, consideration of concomitant medical problems has extended to left ventricular hypertrophy, obesity, mild hyperlipidemia, and insulin resistance, as additional risk factors in hypertension. Consideration of all these factors makes it possible to individualize antihypertensive therapy in most patients today.

Reconstruction of local landscape development in the post-atlantic based on palaeoecological investigations at carrownaglogh prehistoric field system, County Mayo, Ireland

Palaeoecological investigations were carried out at a late Bronze Age site situated at Carrownaglogh, northeast Co. Mayo, with a view to reconstructing environmental conditions prior to and following blanket bog growth, which served to preserve the site. The main feature of the excavated area consisted of a stone wall enclosure (2.2 ha) sited on a small knoll at 150 m O.D. Well-defined cultivation ridges, 14C dated to the 9th century B.C., filled the area within the enclosure. Outside the enclosure, the ground is ridged or levelled and stone cleared. Soil profile descriptions, chemical and mechanical analyses of fossil soils and pollen analysis of a series of short monoliths, which included mineral soil and overlying peat, were carried out. To facilitate interpretation of the pollen analytical results surface samples from poorly fertilised arable land, where chemical weed control was minimal, were pollen-analytically investigated. A pollen diagram from the adjoining basin, spanning the period from c. 3600 yr B.P. to recent times, permits the results of the above investigations to be placed in the context of the regional vegetational history. Three distinct phases of extensive woodland clearance associated with arable and pastural farming are identified, dating to 2750, 1950 and 1000 yr B.P. The first of these, which emerges with particular clarity in the concentration pollen diagram, is equated with the farming phase which resulted in the ridge formation on the knoll.

Disposal of hazardous elemental wastes

A low-cost permanent geological method for the disposal of hazardous wastes is presented. The RUMOD (regional underground monolith disposal) system processes wastes into a granular form, transports it in bulk to a regional disposal site, mixes it with special cement-based grouts, and pumps it into large caverns 300-2000m underground. The final waste form is a series of monoliths composed of waste and a cement-based grout, with dimensions up to 25 m wide, 60 m high, and several hundred meters long. This approach has not been seriously considered in the past because of projected high costs. But recent technical developments suggest that it may now be possible. The disposal site, underground cavern construction, regional treatment facilities, as well as economic factors of the system are discussed. The major technologies required for RUMOD are in commercial use, but they have not been integrated for use as waste disposal systems.

A monolithic high-power series voltage regulator

A complete series voltage regulator circuit capable of delivering /SUP 1///SUB 2/ ampere of current has been built on a single 63/spl times/66-mil die using the conventional all- diffused processing technology. Improved performance has been achieved by using an internal low-power voltage regulator to supply the desired dc output voltage reference directly to a second main regulator. This permits the dc and ac characteristics of the regulator to be separately optimized with the result that excellent transient characteristics are realized simultaneously with low drift and excellent regulation.