Showing papers on "Solar cell published in 1976"

Computer-aided numerical analysis of silicon solar cells

Abstract: The application of a proven semiconductor device analysis computer code to the study of silicon solar cells is described. The code, which simultaneously solves Poisson's equation and the hole and electron continuity equations in one dimension, provides an effective analysis capability for solar cells that does not require limiting assumptions or approximations. Numerical solutions of the carrier transport problem in the illuminated solar cell illustrate where and how improvements in cell design can be achieved. The reliability of the analyses is demonstrated through a simulation of the conventional silicon solar cell. Results of this analysis are examined, and most practical design modifications to effect improvements in cell performance are identified and evaluated. This systematic technique is used with succeeding computer-aided analyses to identify the post-process silicon characteristics required to achieve a power-conversion efficiency greater than 20%.

MIS‐Schottky theory under conditions of optical carrier generation in solar cells

Abstract: The theory of MIS‐Schottky barriers and their electrical characteristics is examined for its application to solar cells. It is found that the interface behavior of contacts forward‐biased by illumination is qualitatively different from that of the same contacts biased in the dark by an applied forward voltage. Observed increases due to the interfacial layer in the open‐circuit voltage of the solar cell cannot therefore be associated with increases in the ’’n value’’ measured for the dark current, but rather are due to the different effects of this layer on the transport properties of majority and minority carriers. The theory predicts an optimum thickness for the interfacial layer above which the short‐circuit (minority‐carrier) current decreases, and the efficiency (fill factor) is degraded.

Semiconductor p-n junction solar cell and method of manufacture

Abstract: There is described efficient semiconductor p-n junction solar cells which can be made from defect-rich semiconductor material. The solar cells include an extended electric field surrounding the p-n junction for extracting the photo-generated carriers in the presence of defects which would otherwise reduce the efficiency of the cell. There is also described a method of fabricating efficient semiconductor p-n junction solar cells.

Photoelectrolysis of water with TiO2‐covered solar‐cell electrodes

Abstract: A TiO2–solar‐cell hybrid structure has been used successfully as the anode electrode in the photoelectrolysis of water. The TiO2 films have been fabricated by chemical vapor deposition. Conversion efficiency of solar energy of about 0.1% has been attained in the preliminary experiment.

High-intensity, solid-state-solar cell device

Abstract: A semiconductor solar cell capable of converting incident radiation to electrical energy at high efficiency includes a plurality of series-connected unit solar cells formed on a common wafer of semiconductor material. The unit solar cells each include a semiconductor substrate of one conductivity type and a p-n junction formed in the substrate. The light-receiving surface of the cell may have an opaque member thereon, and incident light is directed onto the portion of that surface not covered by the opaque member. A variety of embodiments illustrates the invention.

MIS solar cell—General theory and new experimental results for silicon

Abstract: The metal–thin‐insulator–semiconductor structure recently has been shown to have potential as a simple efficient solar cell. A general theory of these solar cells as well as experimental results for silicon devices optimized on the basis of this theory are described. The experimental devices have exceptionally good open‐circuit voltages. Under illumination resulting in a short‐circuit current density of 32 mA/cm2, an open‐circuit voltage of 618 mV and a fill factor of 0.6 were obtained.

Solar cell electric and heating system

Abstract: A system for converting solar energy into electric energy at reduced cost makes use of an array of light sensitive, voltage producing solar cells of the flat disc silicon type. To increase power, while using fewer costly cells, each cell of the array has a truncated conical shell mounted on legs at a spaced distance thereover, the shell having a mirror-like reflective inner surface. Thus, sunlight is received in the large end and reflected through the small end to the cell. A sealed, weather-tight enclosure for the array, has fluid inlets and outlets for producing heat, the heat conductive shells absorbing and radiating heat.

Combined solar cell and hot air collector apparatus

Abstract: A solar collector having at least one solar cell, an air retaining plate located parallel to and immediately behind the unlit side of the cell. A plate is spaced from the back of the cell to permit passage of substantially all the air that is to be treated by the cell, the retaining plate being in communication with the portion of the collector through which the air is withdrawn.

Evaluation of the CdS/CdTe heterojunction solar cell

Abstract: A variety of CdS/CdTe heterojunction solar cells have been prepared by the vacuum evaporation of n‐CdS films onto single‐crystal p‐CdTe substrates. Comparisons have been made between cells prepared using different substrate resistivities, substrate surface preparations, and CdS film resistivities. The mechanisms controlling the dark junction current, photocarrier collection, and photovoltaic properties with junction interface states present are modeled. A solar efficiency of 7.9% under 85 mW/cm2 of solar simulator illumination was measured on a cell with an indium‐tin‐oxide coating and a glycerol antireflection coating.

On the Power-Characteristics of Electrochemical Solar Cells

Abstract: The output-power-characteristics of an electrochemical solar cell are analysed. Up to 9.5% efficiency with reference to the spectrum of a Xenon lamp has been reached with a CdS/[Fe(CN)6]3-/4--electrolyte cell which is equivalent to 5.5% efficiency for solar radiation. It is shown that the polarisation of the inert counter electrode and the semiconductor electrode has a critical influence on the efficiency and can lead to great losses. Die Leistungscharakteristik einer elektrochemischen Sonnenzelle wurde untersucht. Bezogen auf das Spektrum einer Xenon-Lampe konnte mit einer CdS/[Fe(CN)6]3-/4--Redox-Elektrolytzelle eine maximale Energiewandlung von 9,5% erreicht werden. Das entspricht einer Ausbeute von 5,5% fur das Sonnenspektrum. Es wird gezeigt, das die Polarisation der Gegenelektrode und der Halbleiterelektrode einen kritischen Einflus auf die Leistungsfahigkeit hat. Bei hoher Polarisierbarkeit der Elektroden entstehen an den Phasengrenzen grose Verluste.

Theoretical analysis of Al x Ga 1-x As-GaAs graded band-gap solar cell

Abstract: A practical theoretical analysis of an n/p graded band-gap Al(x)Ga(1-x)As-GaAs solar cell indicates that the presence of a built-in electric field acting on holes in the surface layer increases the hole collection efficiency of a nearly optimum cell to a maximum of 97.8%. The electric field is created by the band-gap gradient and serves to reduce the surface hole recombination by 97% and reduce the bulk hole recombination by 80%, compared to a similar GaAs cell. These reduced losses increase cell response substantially for wavelengths less than 0.59 micron and yield a maximum air-mass-zero efficiency of 17.7% (not corrected for a 13% front-surface contact). The model includes an optimized antireflection coating, series resistance, and junction-recombination current.

Solar cell package

Abstract: A solar cell package includes a plurality of solar cells within a space formed by a support member and a transparent cover member. A first conductor is positioned between the support member and the solar cells and makes electrical contact to a first surface of each of the solar cells. A second conductor is essentially coplanar with the first conductor and makes electrical contacts to a second surface of each of the solar cells. The output terminals of the solar cell package are connected to the first and second conductors. The first and second conductors are electrically isolated from each other and are also insulated from the support member and from the solar cells insulative means which is electrically insulated but thermally conductive to facilitate dissipation of thermal power dissipated in the solar cells.

High‐performance solar cell material: n‐AlAs/p‐GaAs prepared by vapor phase epitaxy

Abstract: Solar cells with measured sea level sunlight power conversion efficiencies of 13–18% and areas of several cm2 have been prepared by vapor phase epitaxial growth of n‐AlAs on p‐GaAs substrates. The cells are provided with an antireflective passivating anodically grown coating and have much improved stability in the laboratory atmosphere.

Method of making encapsulated solar cell modules

Abstract: Electrical connections to solar cells in a module are made at the same time the cells are encapsulated for protection. The encapsulating material is embossed to facilitate the positioning of the cells during assembly.

Photovoltaic system including a lens structure

Abstract: A photovoltaic or solar cell generator includes a plurality of unit solar cells each having one or more p-n junctions. An optical light-focusing system, which includes an array of lens elements, focuses the incoming radiation into a series of preferably narrow beams that are incident on the surfaces of the unit solar cells at locations lying immediately adjacent but spaced from the p-n junctions.

Polycrystalline thin‐film InP/CdS solar cell

Abstract: We report the preparation of a polycrystalline thin‐film InP/CdS solar cell of area 0.52 mm2 having a power conversion efficiency of 2.8% under AM1 conditions. Based on the current‐voltage characteristics, we estimate that development of an improved contact to the p‐type InP would result in substantially higher efficiencies without any further improvement in the InP/CdS interface.

Solar cell converting light into electric power - has light concentrator with fluorescent centres in transparent layer with specified refractive index

Abstract: The solar light radiation energy is converted into electric power by a device, in which the solar radiation (2) is collected in a transparent layer. The latter refractive index is higher than that of the surrounding medium. The layer, intended for concentration of the solar radiation, has fluorescence centres. The concentrated light is applied to a known solar cell (7). Pref. the surface of the concentrator layer (1) is 10-2000 times greater than that of the solar cell. The solar cell may be of semiconductor type and may be tuned to the wavelength, emitted by the fluorescence centres, in relation to the depth of its pn-junction, doping profile, its anti-reflection layer and width of the blocked band.

Operation of ITO/Si heterojunction solar cells

Abstract: We have fabricated solar cells consisting of transparent conducting films of indium‐tin oxide (ITO) rf sputtered onto wafers of single‐crystalline Si. A model quantitatively explaining the experimental data for this MOS‐type solar cell is presented.

Semiconductor Electrodes VI . A Photoelectrochemical Solar Cell Employing a Anode and Oxygen Cathode

Abstract: A photoelectrochemical cell for conversion of light to electrical energy based on the photosensitized oxidation of water at a chemically vapor deposited, thin film, n-type TiO/sub 2/ anode and the reduction of oxygen at a fuel cell-type cathode is described. The effect of load resistance on the current, cell voltage, and power was studied, and quantum and power efficiencies under short-circuit conditions for monochromatic light of about 365 nm was estimated as 26 percent and 1-2 percent, respectively. Open-circuit cell voltages of 0.89V were obtained. The cell is simple to construct and is capable of continuous operation with no apparent deterioration in performance. (auth)

A model for Schottky‐barrier solar cell analysis

Abstract: A general model for the analysis of metal‐semiconductor solar cells is presented. The model takes into account the cell optical properties, carrier recombination effects, semiconductor minority‐carrier properties, series resistance, cell thickness, and active surface area. Numerical methods are used to solve the appropriate continuity equations and hence compute the photocurrent density under AMO conditions. The operation of the model is demonstrated using p‐ and n‐type Si and GaAs with Au being taken as the barrier metal. Calculations are presented showing the effect on solar energy conversion efficiency of surface recombination velocity, barrier height, minority‐carrier lifetime, barrier metal thickness, collecting grid configuration, and cell thickness. A comparison of practical and computed data for the Au/n‐GaAs system yields good agreement.

Continuous process for fabricating solar cells and the product produced thereby

Abstract: The process comprises the following steps: (1) forming a glass sheet which defines a substrate layer for the solar cell product; (2) forming a diffusion barrier layer on at least one surface of the substrate; (3) forming a first electrically-conductive layer on the diffusion barrier, the first electrically-conductive layer being a first electrode in the solar cell product; (4) depositing small-grain polycrystalline silicon in a thin film, i.e., 10-100 micrometers, on the first electrode layer; (5) recrystallizing, typically by heating, the deposited polycrystalline silicon until it reforms into large-grain polycrystalline or single-crystal silicon; (6) forming a PN junction in the recrystallized silicon layer; and (7) forming a second electrically-conductive layer on the recrystallized silicon layer, the second electrically-conductive layer being a second electrode in the solar cell product. The solar cell product produced by the above-process may be fabricated in large surface area configurations, suitable for terrestrial as well as extra-terrestrial use, at relatively low cost.

Process for fabricating polycrystalline inp-cds solar cells

Abstract: The specification describes a compound semiconductor solar cell and fabrication process therefor wherein both the P and N-type layers of the cell are polycrystalline semiconducting material and have large crystallites with grain boundaries of similar dimensions and spacings. These grain boundaries are spaced apart by a distance substantially greater than the optical absorption length, Λ, in one of the layers and by an amount sufficient to permit substantial numbers of photon-generated carriers in that one layer to cross the PN junction between the layers. Thus, substantial power is generated without the requirement for using expensive monocrystalline semiconductive materials.

Solar cell array design handbook, volume 1

Abstract: Twelve chapters discuss the following: historical developments, the environment and its effects, solar cells, solar cell filters and covers, solar cell and other electrical interconnections, blocking and shunt diodes, substrates and deployment mechanisms, material properties, design synthesis and optimization, design analysis, procurement, production and cost aspects, evaluation and test, orbital performance, and illustrative design examples. A comprehensive index permits rapid locating of desired topics. The handbook consists of two volumes: Volume 1 is of an expository nature while Volume 2 contains detailed design data in an appendix-like fashion. Volume 2 includes solar cell performance data, applicable unit conversion factors and physical constants, and mechanical, electrical, thermal optical, magnetic, and outgassing material properties. Extensive references are provided.

Polycrystalline silicon solar cells on metallurgical silicon substrates

Abstract: The use of a polycrystalline silicon p - n junction structure deposited on low-cost substrates is a promising approach for the fabrication of low-cost solar cells. Metallurgical-grade silicon, with a purity of about 98% and a cost of about $1/kg, was cast into plates in a boron nitride container and used as substrates for the deposition of solar cell structures. The substrates were polycrystalline with millimeter size crystallites. Solar cells of the configurations n > + -silicon/p-silicon/metallurgical silicon and n + -silicon/p + -silicon/metallurgical silicon were prepared by the thermal decomposition of silane and the thermal reduction of trichlorosilane containing appropriate dopants. The AMO efficiencies of n + -silicon/ p -silicon/metallurgical silicon solar cells were up to 2.8% (with no anti-reflection coatings) and were limited by the grain boundaries in the p -layer. The grain boundary effects were reduced by increasing the dopant concentration in the p -layer, and AMO efficiencies of about 3.5% were obtained from n + -silicon/p + -silicon/metallurgi silicon solar cells.

Theoretical analysis of graded-band-gap gallium-aluminum arsenide/gallium arsenide p-Ga1t̄xAlxAs/p-GaAs/n-GaAs solar cells

Abstract: Graded-band-gap p- Ga 1 t x Al x A s/p- GaAs /n- GaAs solar cell structures are analyzed as a function of the drift field in the surface layer and thickness of the p-GaAs layer. Such cells allow conversion efficiencies higher than conventional GaAs cells due to the reduction of the surface recombination effect. The p-type GaAs is preferable, because the electron diffusion length is several times larger than the hole diffusion length. The optimum thickness of the p-GaAs layer is calculated for AMO (6000 K blackbody radiation) and with typical parameters assumed. The efficiency strongly depends on the drift field E, and the maximum energy conversion efficiency approaches 20% at E = −3000 V/cm.

Induced junction solar cell and method of fabrication

Abstract: An induced junction solar cell is fabricated on a p-type silicon substrate by first diffusing a grid of criss-crossed current collecting n + stripes and thermally growing a thin SiO 2 film, and then, using silicon-rich chemical vapor deposition (CVD), producing a layer of SiO 2 having inherent defects, such as silicon interstices, which function as deep traps for spontaneous positive charges. Ion implantation increases the stable positive charge distribution for a greater inversion layer in the p-type silicon near the surface. After etching through the oxide, to parallel collecting stripes, a pattern of metal is produced consisting of a set of contact stripes over the exposed collecting stripes and a diamond shaped pattern which functions as a current collection bus. Then the reverse side is metallized.

Tubular solar cell and method of making same

Abstract: High efficiency, low cost solar energy conversation is facilitated by using tubular photovoltaic solar cells situated at the focus of a line-generated paraboloidal reflector. Advantageously each solar cell comprises a pair of concentric glass tubes that are hermetically sealed at the ends. A photovoltaic junction is formed over the entire inside surface of one of the concentric tubes. For example, this may comprise an inner electrically conductive film, contiguous layers of Cu2 S and CdS forming a heterojunction, and an outer film of optically transparent but electrically conductive material. The conductive films provide electrical connection to the junction via external contacts that are symmetrically disposed at the ends of the tubular cell. In other embodiments the photovoltaic junction is formed in a crystalline silicon layer that is grown in situ on one of the glass tubes. Techniques for promoting oriented semiconductor crystalline growth are disclosed. These include providing minute crystalline islands in a metal matrix to serve as growth centers, surface alignment using a wavy layer deposited at an actue angle onto the glass substrate, surface seeding and normalization growth atop a fluid-like thin film deposition substrate.

Theoretical optimization and parametric study of n-on-p Al/x/Ga/1-x/As-GaAs graded band-gap solar cell

Abstract: A comprehensive theoretical model of the graded band-gap Al(x)Ga(1-x)As-GaAs solar cell is used to optimize the n-on-p cell. The model includes power losses due to surface, bulk, and junction minority-carrier recombination, series resistance, and photon reflection from an SiO antireflection coating of optimum thickness. The optimized cell has a junction depth/graded band-gap layer thickness of 1.0 micron, respective donor and acceptor concentrations of 4 x 10 to the 17th power and 2 x 10 to the 17th power per cu cm, and a surface AlAs mode fraction of x = 0.35. The optimized graded band-gap cell has an air-mass-zero efficiency of 17.7% (not corrected for a 13% front surface contact area) and is shown to be less sensitive than a similar n-on-p GaAs cell to material degradation in the form of decreased minority-carrier diffusion lengths and increased surface-recombination velocity